Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘I’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘I’
IACS – It means ‘International annealed copper standard is a measure of electrical conductivity agreed in 1913 with ‘pure’ copper set as 100 %. Advances in copper refining mean that now the pure Copper can attain 103 % IACS. The minimum requirement for high conductivity copper now is 101% IACS. IACS is a standard reference used in reporting electrical conductivity. The conductivity of a material, in % IACS, is equal to 1724.1 divided by the electrical resistivity of the material in nsigma·m.
I-beam – It is a structural steel shape with ‘I’ cross-section. I-beams are typically made of structural steel and serve a wide variety of construction uses. The horizontal elements of the I-beam are called flanges, and the vertical element is known as the ‘web’. The web resists shear forces, while the flanges resist most of the bending moment experienced by the beam. The Euler–Bernoulli beam equation shows that the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion, for which hollow structural sections are frequently preferred.
Icephobic coatings -These are specialized surface treatments designed to minimize ice adhesion and prevent ice formation on surfaces, particularly in environments where temperatures are near freezing. These coatings frequently utilize hierarchical roughness to achieve low ice adhesion and improve water repellency.
Ice point – It is the temperature at which liquid and solid water are in equilibrium under atmospheric pressure. The ice point is by far the most important ‘fixed point’ for defining temperature scales and for calibrating thermometers. It is 0-degre C or 273.15 K.
Ice thermal storage – It is a system which utilizes the latent heat of water to achieve high densities of cooling energy, allowing for the shifting of cooling loads to off-peak periods to reduce costs.
Icing protection – It refers to systems and techniques designed to prevent or mitigate the formation of ice on wind turbine blades, which can include coatings, heating elements, and chemical agents, frequently needing a combination of methods for effective performance in cold climates.
Icing salts – These are substances, such as calcium chloride and sodium chloride, which are used to lower the freezing point of water, resulting in their application for de-icing surfaces, which can lead to physical deterioration of materials like concrete because of temperature changes and osmotic pressure effects.
Icosahedral symmetry -It refers to a high-order, non-crystallographic symmetry, characterized by 20 triangular faces, 12 vertices, and 30 edges. It represents a specific type of rotational symmetry (five-fold, three-fold, and two-fold axes) which is common in atomic clusters and quasi-crystals, where the atomic structure shows long-range order without translational periodicity.
Ideal crack – It is a simplified model of a crack which is used in elastic-stress analysis. In a stress-free body, the crack has two smooth surfaces which are coincident and join within the body along a smooth curve called the crack front. In two-dimensional representations, the crack front is called the crack tip.
Ideal-crack-tip stress field – It is the singular stress field, which is infinitesimally close to the crack front, that results from the dominant influence of an ideal crack in an elastic body which is deformed. In a linear-elastic homogeneous body, the significant stress components vary inversely as the square root of the distance from the crack tip. In a linear-elastic body, the crack-tip stress field can be regarded as the superposition of three component stress fields called modes.
Ideal critical diameter – Under an ideal quench condition, the bar diameter which has 50 % martensite at the centre of the bar when the surface is cooled at an infinitely rapid rate (i.e., when H = infinity, where ‘H’ is the quench severity factor or Grossmann number).
Ideal current source – It is a component which drives a certain current strength through any connected load, irrespective of the voltage required to do so.
Ideal cycle – It is a theoretical, reversible thermodynamic cycle used to analyze and set maximum performance benchmarks for engines and power plants. It assumes frictionless processes, no heat loss to surroundings, and perfect working fluids (e.g., air-standard cycles), typically ignoring practical losses to determine maximum potential efficiency.
Ideal cycle efficiency – It is the maximum theoretical ratio of network output to heat input (Wnet/Qin) for a thermodynamic cycle, assuming reversible processes, no heat losses, and, for air-standard cycles, ideal gas behaviour. It acts as a benchmark, frequently determined by peak temperature and pressure ratios (e.g., 1-Tc/Te for Carnot).
Ideal design – It is a theoretical, optimized solution that achieves maximum functionality, efficiency, and reliability while eliminating or minimizing trade-offs and constraints. It represents the perfect, most desirable outcome, frequently used as a target for innovation, which balances user needs with technical feasibility and sustainability.
Ideal elastomer – It is a theoretically perfect, cross-linked amorphous polymer which shows high elasticity, returning instantly to its original shape without energy loss (hysteresis) after substantial deformation. It is characterized by zero inter-molecular attractions (excluding cross-links), with retraction force solely driven by entropy, molecular chains moving from ordered to random coiled states.
Ideal entropy – It represents a benchmark, typically defined by the isentropic process (adiabatic and reversible) where entropy remains constant, serving as a model of maximum efficiency, or as the theoretical configurational entropy arising from mixing components, which is based on the number of possible permutations during ideal interchanges.
Ideal filter – It is a filter which precisely passes signals at certain frequency sets while completely rejecting all other frequencies. It ideally possesses a flat magnitude characteristic and a linear phase characteristic over its passband.
Ideal gas – It is a theoretical gas composed of several randomly moving point particles which are not subject to interparticle interactions. The ideal gas concept is useful since it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics. The requirement of zero interaction frequently can be relaxed if, e.g., the interaction is perfectly elastic or regarded as point-like collisions. Under different conditions of temperature and pressure, several real gases behave qualitatively like an ideal gas where the gas molecules (or atoms for monatomic gas) play the role of the ideal particles. Several gases such as nitrogen, oxygen, hydrogen, noble gases, some heavier gases like carbon di-oxide and mixtures such as air, can be treated as ideal gases within reasonable tolerances over a considerable parameter range around standard temperature and pressure. Normally, a gas behaves more like an ideal gas at higher temperature and lower pressure, since the potential energy because of the inter-molecular forces becomes less significant compared with the kinetic energy of the particles, and the size of the molecules becomes less significant compared to the empty space between them. One mole of an ideal gas has a volume of 22.71095464… litres at standard temperature and pressure (a temperature of 273.15 K and an absolute pressure of exactly 0.1 MPa).
Ideal gas constant (R) – It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature increment per quantity of substance, rather than energy per temperature increment per particle. The constant is also a combination of the constants from Boyle’s law, Charles’s law, Avogadro’s law, and Gay-Lussac’s law.
Ideal gas equation (PV = nRT) – It is a foundational thermodynamic equation modeling the state of a hypothetical ideal gas by relating absolute pressure (P), volume (V), quantity in moles (n), and absolute temperature (T) using the universal gas constant (R = 8.314 Joule/mol. K). It accurately approximates real gases at high temperatures and low pressures, combining Boyle’s, Charles’s, and Avogadro’s laws.
Ideal gas law – It is the equation of state of a hypothetical ideal gas. It is a good approximation of the behaviour of several gases under several conditions, although it has several limitations. The ideal gas law is frequently written in an empirical form PV = nRT, where ‘P’, ‘V’, and ‘T’ are the pressure, volume, and temperature respectively, ‘n’ is the quantity of substance, and ‘R’ is the ideal gas constant.
Ideal image – It is a reproduction of an object which is indistinguishable from the original, replicating the light properties such as intensity, wavelength, and spatial distribution of color and relative intensity at each point.
Ideality factor – It is an important parameter which characterizes the carrier recombination process in diodes, typically ranging from 1 to 2. It indicates the influence of diffusion and recombination on carrier transport, with values approaching 1 signifying diffusion dominance and values near 2 indicating substantial recombination effects.
Ideal machine – It refers to a hypothetical mechanical system in which energy and power are not lost or dissipated through friction, deformation, wear, or other inefficiencies. Ideal machines have the theoretical maximum performance, and hence are used as a baseline for evaluating the performance of real machine systems. A simple machine, such as a lever, pulley, or gear train, is ‘ideal’ if the power input is equal to the power output of the device, which means there are no losses. In this case, the mechanical efficiency is 100 %.
Ideal mechanical advantage (IMA) -It is the mechanical advantage of a device with the assumption that its components do not flex, there is no friction, and there is no wear. It is calculated using the physical dimensions of the device and defines the maximum performance the device can achieve.
Ideal membrane – it is one which has well-defined particle or solute rejection characteristics, is resistant to variations in temperature, pH, and operating pressure, allows high rates of filtration, possesses high mechanical strength, and is easy and economical to produce.
Ideal plasticity – It is a material model in which the material does not support any additional stress after reaching the yield stress, indicating that it behaves perfectly plastically without hardening or strain hardening
Ideal quench – It is a theoretical, instantaneous, and uniform cooling process which reduces the surface temperature of an austenitized steel part to the temperature of the quenching medium immediately. It is a bench-marking concept, frequently used in hardenability calculations (ideal diameter, D1) to represent the maximum possible hardening capability of a steel alloy without regard to distortion or cracking.
Ideal randomness source – It is a component, system, or process which produces a sequence of bits that are completely unpredictable, unbiased (uniform distribution), and independent of any previous or future outputs. In an ideal scenario, each bit has an equal probability of being 0 or 1, and the sequence contains a maximum quantity of entropy, meaning it cannot be predicted better than a random guess, regardless of the observer’s knowledge of the system.
Ideal refrigerant – It is a material which is nontoxic, noncorrosive, has compatible physical properties with system needs, and possesses a high latent heat of vapourization, allowing it to vapourize and condense at reasonable pressures at desired temperature levels.
Ideal solution – It is a solution which shows thermodynamic properties analogous to those of a mixture of ideal gases. The enthalpy of mixing is zero, as is the volume change on mixing. The vapour pressures of all components obey Raoult’s law across the entire range of concentrations, and the activity coefficient (which measures deviation from ideality) is equal to one for each component. The concept of an ideal solution is fundamental to both thermodynamics and chemical thermodynamics and their applications, such as the explanation of colligative properties.
Ideal transformer – It is a system consisting of two resistance-less coils which share a common magnetic circuit with infinite permeability and zero core loss, allowing complete linkage of magnetic flux between the coils. It operates under the conditions which the voltage and current ratios are proportional to the turns-ratio of the coils.
Ideal work – It is that work which is needed to bring about homogeneous deformation in producing the shape change of the metal. In practice, it is not possible to achieve a situation of ideal or homogeneous deformation in extrusion because of the contributions of inhomogeneous (or redundant) deformation and friction.
Identifiable person – Iin data privacy, security, and systems design, an identifiable person (frequently referred to as a ‘data subject’) is any living individual who can be distinguished from others, directly or indirectly, through the use of identifiers. This definition is foundational for compliance with regulations like GDPR (general data protection regulation) and security frameworks, which need systems to protect ‘personally identifiable information’ (PII).
Identification – It is the marking / labeling of steel so that different customer products can be distinguished from one another after the product manufacture.
Identification cross reference drawing – It is an administrative type drawing which assigns unique identifiers which are compatible with automated data processing systems, item identification specifications, and provides a cross reference to the original incompatible identifier. It does not specify any engineering or design requirements beyond those already contained in the drawings, and specification etc. governing the original item.
Identification etching – It is the etching to expose particular micro-constituents with all others remain unaffected.
Identification product code – It is a unique identifier, assigned to each finished / manufactured product which is ready, to be marketed or for sale. A bar code is a type of the identification product code. Identification tag (label) – It is for identifying quality/ dimension of the product as well as distinguishing between prime and defective products. Identification tags (labels) can be embedded into almost any material – textile, paper, plastic, etc. They can be directly incorporated into goods, their labels, or in the coatings during the manufacturing process.
Identified project – An identified project is a project associated with a known source.
Identified resource – It is the Resource whose location, grade, quality, and quantity are known or estimated from specific geological evidence. Identified resources include economic, marginally economic, and sub-economic components. To reflect varying degrees of geological certainty, these economic divisions can be sub-divided into measured, indicated, and inferred.
Idiomorphic crystal – It is an individual crystal which has grown without restraint so that the habit planes are clearly developed.
Idiomorphic cubic crystals – These are well-formed crystalline solids which show their characteristic, symmetric geometric shape (specifically that of a cube, octahedron, or dodecahedron) without being obstructed by surrounding grains during growth.
Idlers, belt conveyor – Idlers of belt conveyor are the rollers which are used at certain spacing for supporting the active as well as return side of the conveyor belt. Accurately made, rigidly installed and well-maintained idlers are very important for smooth and efficient running of a belt conveyor. Important requirements for idlers are proper support and protection for the belt and proper support for the load being conveyed. They are designed to incorporate rolls with different diameters. The rolls are fitted with antifriction bearings and seals, and are mounted on shafts. Frictional resistance of the idler roll influences belt tension and, hence, the power requirement. Roll diameter, bearing design, and seal requirements constitute the major components affecting frictional resistance. Selection of the proper roll diameter and size of bearing and shaft is based on the type of service, load carried, belt speed and operating condition.
Idler spacing – It is the distance between two idlers. Factors to be considered when selecting idler spacing are belt weight, material weight, idler load rating, belt sag, idler life, belt rating, belt tension, and radius in vertical curves. More complex issues (such as belt flap or vibration stability in wind, and power usage from belt indentation, material tramping, and rolling resistance) are affected less by idler spacing.
Idle speed control – It is a system which prevents engine stall during idle by maintaining a low but stable engine RPM (revolutions per minute), adjusting the throttle bypass valve to compensate for power-consuming accessories. This control activates when the throttle is fully closed and the engine RPM drops below a minimum threshold, frequently while the vehicle is stationary.
Ignitability – It refers to a material’s ability to ignite under specific thermal exposure conditions, which is influenced by different factors including geometry, environmental conditions, and the material’s thermophysical properties. It involves a sequence of events including inert heating, thermal decomposition, and gas-phase reactions leading to sustained combustion.
Igneous intrusion – It is a body of igneous rock formed from magma solidifying beneath the earth’s surface, creating underground features like dikes, sills, and plutons. These intrusions are important since they alter surrounding rock (country rock), influence resource deposits (like oil cracking), and create resistant rock formations that impact large-scale civil engineering projects, mining, and tunneling.
Igneous iron ores -These iron ore deposits are formed by crystallization from liquid rock materials, either as layered type deposits that possibly are the result of crystals of heavy iron bearing minerals settling as they crystallize to form iron rich concentrations, or as deposits which show intrusive relationship with their wall rocks. These ore deposits are either tabular or irregular and are composed largely of magnetite with varying quantities of hematite. Igneous ores are normally high in iron content and are often high in phosphorus or titanium content.
Igneous rocks – These are the rocks formed by the solidification of molten material from far below the earth’s surface.
Ignition – It is the initiation of a rapid, high-temperature combustion reaction from a slower reaction, caused by adding sufficient activation energy to a fuel-air mixture. It represents the interaction between heat release, heat loss, and chemical kinetics, transitioning a mixture into a self-sustaining fire, necessary for engine combustion or industrial processes.
Ignition engines – These are internal combustion engines which rely on the controlled ignition of an air-fuel mixture, typically initiated by a spark plug, to produce power through a cyclic thermodynamic process. The combustion process needs precise timing and conditions to prevent issues such as engine knock, which occurs when autoignition disrupts uniform flame propagation.
Ignition fuel – it focuses on optimizing the initiation of combustion in engines, using spark ignition (fast-burning fuels like gasoline) or compression ignition (slower-burning fuels like diesel). It involves managing spark timing, energy transfer, and fuel properties to maximize efficiency, reduce emissions, and prevent engine knock. Key techniques include optimizing octane numbers / cetane numbers, improving spark plug reliability, and using advanced modeling.
Ignition furnace, ignition hood – It is the furnace, where raw mix is ignited by burner flame, Burner uses a mixture of coke oven gas, blast furnace gas and sometimes natural gas as the fuel. The calorific value of the mixture and the set hood temperature are controlled. A separate control system is provided to maintain a fixed hood pressure by adjusting the wind-box dampers immediately under the ignition hood.
Ignition loss – It is the difference in weight before and after burning. As with glass, it is the burning off of the binder or size.
Ignition point – It focuses on managing the minimum temperature or energy needed for a substance to spontaneously ignite in an oxidizing atmosphere, important for safety and combustion performance. It involves optimizing factors like fuel type, oxygen levels, and heating methods to prevent premature ignition or improve combustion in engines, burners, and materials, with key aspects including ignition delay, spark energy, and flame location optimization.
Ignition quality – It focuses on the characteristics of fuel which determine its readiness to burn, specifically its ignition delay time under different engine temperatures and pressures. It is a critical aspect of internal combustion engine performance, directly impacting engine efficiency, noise, and pollutant emissions.
Ignition source – It involves identifying, evaluating, and mitigating potential energy sources, such as electrical sparks, hot surfaces, static electricity, or open flames, capable of igniting flammable materials in industrial processes. It focuses on fire prevention by ensuring hazardous energy levels do not contact fuel-air mixtures.
Ignition system – It involves designing electrical subsystems which transform low battery voltage (12 volts) into high-voltage (8 kilovolts to 40 kilovolts) pulses, igniting air-fuel mixtures in internal combustion engines. Key components include ignition coils, spark plugs, and electronic controls, ensuring precise timing for optimal performance, fuel efficiency, and emissions control.
Ignition temperature – It is the lowest temperature of a fuel at which combustion becomes self-sustaining.
Ignition time – It is also known as ignition delay time. It is the time needed for the ignition of the upper layer of the feedstock, from the moment when the fluidized bed with the fuel is moved below the heated furnace and main air is supplied.
Ignition timing – It involves determining the precise moment a spark plug fires or fuel ignites relative to piston position (top dead centre) to optimize combustion, engine power, and fuel efficiency. It balances advancing timing for pressure against retarding it to reduce emissions and engine knock. Modern systems use ECU (electronic control unit) computers to map this based on load and speed.
Ignition voltage – It is the lowest voltage needed to initiate a normal glow discharge in a gas, occurring at a specific pressure and interelectrode distance, where the discharge begins to cover the cathode surface.
Ignition zone – It involves designing and optimizing the specific, localized area within a combustion chamber where the spark plug, ignition coil, and electron circuits create a high-energy discharge to initiate fuel-air mixture combustion. This field focuses on controlling the spark, timing, and energy release to ensure rapid flame propagation, prevent engine knock, and maintain stable combustion.
III-nitride materials – These are a class of wide-bandgap semiconductor compounds (aluminum nitride, AlN, gallium nitride, GaN, indium nitride, InN and their alloys) featuring high chemical / thermal stability, high dielectric breakdown, and direct bandgaps covering the ultraviolet to infrared spectrum. They are engineered for high-efficiency light emitting diodes, lasers, high-frequency /power transistors, and opto-electronics. They are comprised of Group-III elements (aluminum, gallium, indium) combined with nitrogen.
Illite – It is a common, non-expanding clay mineral. It is normally represented by chemical formula [(K,H3O)(Al,Mg,Fe)2(Si,Al)4O₁10[(OH)2, (H2O)]. It has a mica-like structure. It is important in soil mechanics, ceramics, and petroleum geology for its stability, variable plasticity, and role in reservoir quality, frequently forming in shales or as a product of feldspar / mica alteration, influencing fluid flow and wellbore stability.
Illuminance – It is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. illuminance is measured in lux (lx), or equivalently in lumens per square meter.
Illuminant – It is a theoretical light source defined by its specific spectral power distribution (SPD) — the relative energy emitted at each wave-length across the visible and near-ultra-violet spectrum. Unlike a physical light source, an illuminant is a mathematical model used to standardize color measurement, imaging, and lighting design.
Illuminants – It is the light oil or coal compounds which readily burn with a luminous flame, such as ethylene, propylene, and benzene.
Illumination – It is the intensity of light falling at a given place on a lighted surface i.e., the luminous flux incident per unit area, expressed in lumens per unit of area. Different types of illumination which are used in metallographical analysis are bright-field illumination, dark-field illumination, differential interference contrast illumination, and polarized light illumination.
Ilmenite – It is a titanium-iron oxide mineral with the idealized formula FeTiO3. It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing inks, fabrics, and plastics etc. Ilmenite is a heavy (specific gravity 4.7), moderately hard (Mohs hardness 5.6 to 6), opaque black mineral with a submetallic lustre. It is almost always massive, with thick tabular crystals being quite rare. It shows no discernible cleavage, breaking instead with a conchoidal to uneven fracture.
Image – It is a representation of an object produced by radiation, normally with a lens or mirror system.
Image alignment – It is the process of accurately aligning corresponding regions in images, which is complicated by non-linear distortions and artifacts introduced by different microscopy techniques. It frequently involves using image similarity measures, fiducial markers, or model-based approaches to enhance alignment accuracy.
Image analysis – This is improvement to metallographical microscope observation (MMO) which improves on eye evaluation by using high-speed computer evaluation of video-scanned microscope images to distinguish dark and light regions based on a gray scale cutoff. This method can easily evaluate larger areas and greater inclusion numbers than metallographical microscope observation, but is subject to errors such as mistaking scratches, pitting, and stains for non-metallic inclusions.
Image analysis system – It is a software package which allows users to display, manipulate, and analyze images captured from cameras or retrieved from storage, utilizing different algorithms and tools for image processing. These systems frequently include features for immediate result visualization and options to undo changes, facilitating user interaction and learning.
Image analyzer – It is a system or software which automatically processes digital images to extract quantitative, meaningful data, going beyond simple improvement (image processing) to perform tasks like object detection, measurement, classification, and pattern recognition for objective analysis and decision-making in different fields such as from manufacturing. It uses computer vision, signal processing, and AI (artificial intelligence) to turn visual information into numerical insights, identifying features, shapes, sizes, or defects for quality control, research, and automation.
Image brightness – It is the level of brightness at a specific location within an image, which can be represented as a spatial array of brightness levels in either film images, determined by silver crystal density, or digital images, defined by pixel values on a grid.
Image communication – It refers to the transfer of image records, which can occur in either physical forms (such as photographic negatives or prints) or electronic transmission of digitized imagery. It is necessary in the imaging chain and frequently needs image compression, especially in low bandwidth scenarios.
Image contrast – It is a measure of the degree of detectable difference in intensity within an image.
Image impedance – It is a parameter which is used in design of electrical networks such as filters.
Image interpretation – It is a higher-level process which utilizes diffefrent methods, including sensing, preprocessing, segmentation, description, and recognition, to extract useful information from a scene under diverse viewing conditions. This process can be complicated by factors such as variations in illumination, viewing geometry, and occlusion of objects.
Image noise – It is the random variation in brightness within an image which introduces distortion and manifests as a grainy or mottled texture, frequently resulting from factors such as quantum noise, grain and structure noise, Poisson noise, speckle noise, and electronic or thermal noise in imaging procedures.
Image noise reduction – It is a technique which is used to reduce interfering effects in processing of an image.
Image processing – It is the electronic recording, storage, alteration and reproduction of pictures.
Image processing methods – These refer to sophisticated computer techniques used to manipulate and enhance digital images by altering aspects such as contrast and highlighting desired features.
Image quality indicator (IQI) – It is one of the methods of controlling the quality of a radiograph. It is also referred to as penetrameters. It provides a means of visually informing the film interpreter of the contrast sensitivity and definition of the radiograph. The image quality indicator indicates that a specified quantity of change in material thickness is detectable in the radiograph, and that the radiograph has a certain level of definition so that the density changes are not lost because of the unsharpness. Without such a reference point, consistency and quality cannot be maintained and defects can go undetected.
Image resolution – It refers to the quantity of visible detail in a digital image, expressed in pixel dimensions (e.g., 640 pixels by 480 pixels), and can also be measured in terms of pixels per inch (ppi) or dots per inch (dpi). It determines the clarity and sharpness of images produced by cameras, monitors, and printers.
Image rotation – In electron optics, it is the angular shift of the electron image of an object around the optic axis induced by the tangential component of force exerted on the electrons perpendicular to the direction of motion in the field of a magnetic lens.
Image zoom – It is a geometric operation which magnifies or minifies an input image using mapping functions, adjusting the image size by specified factors along vertical and horizontal directions. It frequently uses interpolation methods, such as nearest neighbour or bilinear interpolation, to improve image quality while maintaining the original information.
Imaging – It is the multidisciplinary process of creating visual representations of objects or phenomena, frequently invisible to the naked eye, using technologies like ultrasound, X-rays, magnetism (magnetic resonance imaging, MRI), or light to capture, process, and analyze data for diagnostics, monitoring, and design. Imaging engineering specifically involves designing, building, maintaining, and applying these specialized systems, integrating physics, mathematic, and software for different applications like industrial inspection, enabling detailed insights for informed decision-making.
Imaging concentrators -These are devices which focus rays from a light source onto a focal point, creating an image of the light source, and need high accuracy tracking to achieve high concentration. Examples include parabolic troughs for 2D concentration and parabolic dishes for 3D concentration.
Immediate predecessors – In a network diagram, these are the activities which are to be completed by no later than the start time of the given activity.
Immediate successor – In a network diagram, given the immediate predecessor of an activity, this activity becomes the immediate successor of each of these immediate predecessors. If an immediate successor has a multiple of immediate predecessors, then all are to be finished before the activity can begin.
Immersed-electrode furnace – It is a furnace which is used for liquid carburizing of parts by heating molten salt baths with the use of electrodes immersed in the liquid.
Immersed membrane bio-reactor – It is a wastewater treatment system where filtration membranes (hollow fibre or flat sheet) are placed directly inside the bio-reactor tank. It combines suspended growth activated sludge with low-pressure membrane filtration, reducing footprint by replacing secondary clarifiers and utilizing air scouring to minimize fouling.
Immersed thermocouple – It is a robust temperature sensor designed for direct insertion into liquids, gases, or molten metals to measure process temperatures. It typically features a protective sheath (thermowell) shielding the sensor junction from corrosion and mechanical damage, ensuring accurate, fast-response readings in harsh industrial environments.
Immersed transformers – It refer to a type of transformer in which the coil and core are completely immersed in insulating oil, which facilitates heat dissipation and provides electrical insulation, preventing breakdown or damage to the components.
Immersion cleaning – It is the cleaning in which the work is immersed in a liquid solution.
Immersion coating – It is a coating produced in a solution by chemical or electro-chemical action without the use of external current.
Immersion cooling technology – It encompasses systems in which electronic components are directly exposed to and interact with dielectric fluids for cooling purposes. This includes systems using single-phase or two-phase dielectric liquids, leveraging their thermal capabilities to manage and dissipate heat generated by electronic components. Heat is removed from the system by putting the coolant in direct contact with hot components, and circulating the heated liquid through heat exchangers. This practice is highly effective as liquid coolants can absorb more heat from the system than air. Immersion cooling has several benefits, including but not limited to: sustainability, performance, reliability, and cost.
Immersion etching – It is the method in which a micro-section is dipped face up into etching solution and is moved around during etching. This is the most common etching method.
immersion lens, immersion objective – It is an objective in which a medium of high refractive index is used in the object space to increase the numerical aperture and hence the resolving power of the lens.
Immersion objective (electron optics) – It is a lens system in which the object space is at a potential or in a medium of index of refraction different from that of the image space.
Immersion plate – It is a metallic deposit produced by a displacement reaction in which one metal displaces another from solution, for example: Fe + Cu2+ = Cu + Fe2+.
Immersion plating – It means depositing of a metallic coating on a metal immersed in a liquid solution, without the aid of an external electric current. It is also called dip plating.
Immersion quenching – It is a heat treatment process where a heated metal object is rapidly cooled by submerging it in a liquid medium, such as water, oil, or polymer solution. This process is used to modify the microstructure and mechanical properties of the material, frequently to increase hardness and strength.
Immersion silver plating – It is a surface finishing process used in electronics manufacturing, particularly for printed circuit boards (PCBs). It involves depositing a thin layer of silver onto a copper surface through a chemical displacement reaction, where silver ions in solution replace copper atoms on the board. This process protects the copper from oxidation and enhances solderability. The core of the process is a chemical reaction where silver ions in a solution (e.g., a solution containing silver nitrate) gain electrons and are reduced to metallic silver, while copper atoms on the printed circuit board surface lose electrons and are oxidized, dissolving into the solution.
Immersion testing – It is a method which is used to evaluate the performance of materials or products when submerged in a liquid, particularly to assess their resistance to corrosion, water ingress, or other environmental factors.
Immersion time – It refers to the duration the component spends submerged in the quenching medium. The needed time is determined by the need to cool the entire cross-section of the part (not just the surface) below the martensite start temperature (Ms) to ensure full martensitic transformation.
Immiscible gas injection – It is an enhanced oil recovery (EOR) technique where gases (e.g., carbon di-oxide, nitrogen, or natural gas) are injected below the minimum miscibility pressure (MMP) into an oil reservoir. The injected gas does not mix with the oil, instead displacing it towards production wells through pressure maintenance, expansion, and gravitational forces.
Immiscible liquids -These are liquids which do not mix or dissolve in each other because of the differences in their molecular structures and intermolecular interactions, such as the case with water and oil. This phenomenon is important in applications like solvent extraction and separation processes.
Immiscible substances – Substances are said to be immiscible if the mixture does not form a solution for certain proportions. For example, oil is not soluble in water, so these two solvents are immiscible. Another example is butanone (methyl ethyl ketone) which is considerably soluble in water, but these two solvents are also immiscible since in some proportions the mixture separates into two phases.
Immobile dislocation – It is a line defect in a crystal lattice which cannot easily move (glide) under applied stress, frequently formed by the interaction or pinning of mobile dislocations, hindering plastic flow and contributing to material hardening, unlike mobile (glissile) dislocations which allow for deformation. These sessile dislocations form when two moving dislocations meet, creating a new dislocation with a Burgers vector outside the original slip system, making them ‘stuck’ and important for work hardening and fatigue.
Immobilized metal affinity chromatography – It is a technique which utilizes a stationary phase with covalently connected chelating groups to form strong coordinative complexes with transition metals, allowing for the retention and separation of analytes which form stable complexes with the metal. The elution of analytes can be achieved by altering the pH or using competing ligands in the mobile phase.
Immunity – It is a state of resistance to corrosion or anodic dissolution of a metal caused by thermo-dynamic stability of the metal.
Impact – In crushing terminology, impact refers to the sharp, instantaneous collision of one moving object against another. Both objects can be moving, or one object can be motionless. There are two variations of impact, namely (i) gravity impact, and (ii) dynamic impact. Material dropped onto a hard surface such as a steel plate is an example of gravity impact. Gravity impact is most often used when it is necessary to separate two materials which have relatively different friability. The more friable material is broken, while the less friable material remains unbroken. Separation can then be done by screening. Material dropping in front of a moving hammer (both objects in motion), illustrates dynamic impact. When crushed by gravity impact, the free-falling material is momentarily stopped by the stationary object. But when crushed by dynamic impact, the material is unsupported and the force of impact accelerates movement of the reduced particles toward breaker blocks and / or other hammers. Dynamic impact has definite advantages for the reduction of several materials.
Impact angle – It is the angle formed between the trajectory of an incoming particle, object, or fluid, and the surface it strikes. It is normally measured relative to the surface plane (0-degree is tangential, 90-degree is normal) and is critical for determining damage severity, erosion, or bonding efficiency.
Impact assessment – It is the practice of identifying and evaluating the detrimental and beneficial consequences of climate change on natural and human systems is known as impact assessment.
Impact behaviour – It refers to the mechanical response, deformation, and damage mechanisms of materials or structures subjected to high-rate, transient loading (impacts). It characterizes a material’s ability to absorb / dissipate energy through elastic-plastic deformation or fracture, normally measured by toughness and resistance to damage.
Impact compaction – It is a ground improvement engineering technique which increases the density, stiffness, and bearing capacity of loose, granular soils by using a heavy hammer to repeatedly strike an impact plate on the ground surface, forcing soil particles into a tighter formation. It is normally used for shallow,, rapid stabilization (up to 3 meter to 7 meter depth) of sand, gravel, and fills, reducing future liquefaction and settlement.
Impact crusher – Impact crushers make use of impact rather than compression to crush material. The material is contained within a cage, with openings of the desired size at the bottom, end, or side to allow crushed material to escape. There are two types of impact crushers namely (i) horizontal shaft impact crusher, and (ii) vertical shaft impact crusher. Impact crushers are frequently used with materials, which are soft or which are easily cleaving from the surface. The crusher consists of a fast-spinning rotor and beaters attached to the rotor. Feed is entering to the crusher from the top and crushing starts immediately when the feed is impacted with beaters towards the crusher’s inner surface. Impact crusher can also be equipped with a bottom screen, which prevents material leaving the crusher until it is fine enough to pass through the screen. This type of crusher is normally used for soft and non-abrasive materials. In case of environment management, impact means the detrimental and beneficial consequence of climate change on natural and human systems is known as impact.
Impact cut-off machines – These are normally referred to as abrasive cut-off machines or metallographic cutters. These are precision instruments designed to slice through metal, ceramic, or composite samples for microstructural examination. They are designed to minimize deformation and heat damage during the cutting process, ensuring the sample’s microstructure remains intact.
Impact damage – It refers to the structural or material degradation caused by a high-force, short-duration collision between two or more bodies. It results from impulsive loading (such as dropped tools, bird strikes, or debris impact) producing defects ranging from superficial coating damage to critical failures like delamination, fibre breakage, or perforation.
Impact / cut resistant conveyor belt – This type of belt minimizes damages to belt carcass from sharp objects or strong impact, and prevents belts from being cut or broken by damage.
Impacted structure -It is a component or system subjected to sudden, high-intensity, and short-duration dynamic loads, such as collisions, explosions, or dropped objects. These events cause significant deformation, energy absorption, and potential structural damage. The structure absorbs impact energy, often resulting in inelastic deformation, local indentation, or internal, often hidden, damage, particularly in composites.
Impact energy – It is the quantity of energy, normally given in joules, needed to fracture a material. It is normally measured by means of an Izod test or Charpy test. The type of the sample and test conditions affect the values and hence are to be specified.
Impact extrusion – It is the process (or resultant product) in which a punch strikes a slug (normally unheated) in a confining die. The metal flow can be either between punch and die or through another opening. The impact extrusion of unheated slugs is frequently called cold extrusion.
Impact fatigue – It refers to the phenomenon where materials, particularly steels, experience degradation and failure because of the cyclic impacts, with their strength being influenced by factors such as impact stress and loading time. Different phenomenological models are used to analyze impact fatigue behaviour, distinguishing between high-cycle and low-cycle fatigue based on empirical relationships.
Impact height – It refers to the vertical distance from which a mass is dropped to generate impact energy during testing, with specific heights increased until a visible crack is detected in the sample.
Impact idler – It is a belt idler having a resilient roll covering, resilient molded elastomer rings, springs or other means of absorbing impact energy at the place where material falls onto the belt.
Impaction ratio – It is the cross-sectional area of undisturbed fluid containing particles which ultimately impinges on a given solid surface, divided by the projected area of the solid surface.
Impact level – It defines how significantly a sudden force or event affects a system, ranging from material properties (impact strength, toughness) measured by energy absorption (Charpy tests / Izod tests) to structural safety (impact loads from collisions, blasts) and software / system risk (low, moderate, high levels for data compromise). It quantifies resistance to shock, assesses structural failure potential, and informs safety design, ensuring components can absorb energy without catastrophic failure.
Impact line – It is a blemish on a drawn metal part caused by a slight change in metal thickness. The mark is called an impact line when it results from the impact of the punch on the blank. It is called a recoil line when it results from transfer of the blank from the die to the punch during forming, or from a reaction to the blank being pulled sharply through the draw ring.
Impact load – It is especially severe shock load such as that caused by instantaneous arrest of a falling mass, by shock meeting of two parts (e.g., in a mechanical hammer), or by explosive impact, in which there can be an exceptionally rapid buildup of stress.
Impact localization – It is the process of determining the location of an impact based on sensor data, which can be approached using either sparse or dense sensor arrays. Methods for sparse arrays include time difference and reference database methods, while dense arrays utilize techniques such as beam-forming and multiple signal classification.
Impact pads – These pads, which range from simple rectangular plates to complex shapes with lips for reducing the energy of the impact stream, are inserted on the tundish bottom immediately below the ladle shroud region. Impact pads have been developed to cushion the tundish bottom from the ladle stream impact. Without such a pad, the impact energy can eventually work through the spray lining and result in steel penetration into the back-up shapes. Like dams, weirs and baffles, these high-alumina refractory plates are installed on the back-up lining and are anchored using the spray lining. Within the recent past, large quantity of work has been done to turn the simple impact pad into a turbulence-inhibiting device and a true flow modifying device. The working principle of these high-tech impact pads is to revert the impact stream onto itself, hence using own energy of the stream for dampening it.
Impact parts – It refers to components specifically designed to withstand, initiate, or absorb high-velocity collisions, sudden shock loading, or repetitive percussive forces. These parts are engineered to manage energy dissipation to prevent structural failure or to perform work, such as in mining, automotive crash safety, or fastening tools.
Impact point – it is also called point of impact. It is the precise, initial location on a target surface where a moving object (impactor or projectile) makes first contact. It is a fundamental concept in collision mechanics, safety testing, and ballistics, used to analyze localized damage, energy transfer, and structural response.
Impact prediction – It is a way of mapping the environmental consequences of the significant aspects of the project and its alternatives. Since the environmental impact cannot be predicted with absolute certainty, hence, it is necessary that all the possible factors are considered and all the possible precautions for reducing the degree of uncertainty are taken.
Impact pressure – It is the pressure exerted by a fluid in motion when it is brought to rest (decelerated to zero velocity) against a surface. It represents the difference between the total stagnation pressure (Pt) and the static pressure (Ps), frequently defined by the dynamic pressure equation ‘delta P =1/2 p x v square’, and is important for calculating flow velocity and structural loads.
Impact properties – These define a material’s ability to absorb energy and resist fracture from sudden, high-force loads (shock or impacts), basically measuring its toughness, unlike static strength. Quantified by tests like Charpy or Izod, these properties determine if a material shatters (brittle) or deform without breaking (tough), important for applications like safety gear.
Impact resistance – It is the ability to avoid damage because of the contact with a forceful motion or object. Galvanized coating’s uppermost, pure zinc Eta layer is relatively soft and absorbs impact shock, protecting the underlying alloy layers. In conveyors, impact resistance is the relative ability of a conveyor belt assembly to absorb impact loading without damage to the belt.
Impact sintering – It is an instantaneous sintering process during high energy rate compacting which causes localized heating, welding, or fusion at the particle contacts.
Impact roller – It is a specialized engineering component, used either for soil compaction or in conveyor systems, designed to absorb high-impact energy. In construction, it is a non-cylindrical, multi-sided drum (3 sides to 5 sides) used to impart high-energy, deep-compaction impact forces to soil. In conveying, it is a rubber-disc-covered roller positioned in loading zones to protect belts from damage by falling material.
Impact speed drop compensation – It is a part of rolling mill automation. The system speeds up the stand during the head threading, reducing the speed drop when the material impacts the rolls. Once the bar is inside the stand, the control changes back to the mills cascade speed reference.
Impact strength – It is a measure of the resiliency or toughness of a solid. The maximum force or energy of a blow (given by a fixed procedure) which can be withstood without fracture, as opposed to fracture strength under a steady applied force.
Impact test – It is a test for determining the energy absorbed in fracturing a test piece at high velocity, as distinct from static test. The test can be carried out in tension, bending, or torsion, and the test bar can be notched or unnotched. Several types of impact tests have been used to evaluate the notch toughness of metals, plastics, and ceramics. The types of impact tests can be normally classified in terms of loading method (pendulum stroke or drop weight loading) and the type of notched sample (e.g., Charpy V-notch, Charpy U-notch, or Izod).
Impact transition temperature – It is the temperature in which the material changes its behaviour from ductile to a brittle. It is also known as the brittle to ductile transition temperature.
Impact troughing idler – It is a type of conveyor idler designed to support the conveyor belt at loading points, absorbing the impact of falling material and preventing damage to the belt. They feature resilient rubber discs or rings on the rollers to cushion the impact. Impact idlers are crucial at loading zones where materials are dropped onto the conveyor belt, as this is where the belt experiences the most significant impact and potential damage. They are typically configured as a series of rollers mounted on a frame, with the rollers fitted with rubber rings or discs to absorb the impact.
Impact toughness – It is a material’s ability to absorb energy and deform plastically without fracturing when subjected to a sudden, sharp blow or impact load, important for components in dynamic environments to prevent brittle failure. It is measured by tests like Charpy and Izod, which quantify the energy absorbed during the fracture of a notched specimen, indicating how well a material can withstand shocks without breaking.
Impact tube – It is also known as Pitot tube. It is an instrument which measures the stagnation pressure of a flowing fluid, consisting of an open tube pointing into the fluid and connected to a pressure-indicating device.
Impact value – It measures a material’s resistance to sudden shock or impact, frequently determined by how much finer material is produced after a standardized drop-hammer test, with lower values indicating tougher, more durable aggregates suitable for roads and concrete, as opposed to slow compression resistance. The specific test, like the ‘aggregate impact value test’, quantifies this by crushing aggregates and measuring the percentage of fine powder generated, revealing their suitability for heavy-load applications like pavements.
Impact velocity – It is the relative velocity between the surface of a solid body and an impacting liquid or solid particle. For describing this velocity completely, it is necessary to specify the direction of motion of the particle relative to the solid surface in addition to the magnitude of the velocity. The related terms which are also in use are (i) absolute impact velocity which is the magnitude of the impact velocity, and (ii) normal impact velocity which is the component of the impact velocity that is perpendicular to the surface of the test solid at the point of impact.
Impact wear – It is the wear of a solid surface resulting from repeated collisions between that surface and another solid body. The term erosion is preferred in the case of multiple impacts and when the impacting body or bodies are very small relative to the surface being impacted.
Impedance – It is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage. Impedance extends the concept of resistance to alternating current circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
Impedance function – It is the dynamic impedance matrix which describes the force-displacement relationships of a foundation subjected to time-harmonic loads, representing the response of the foundation in relation to its movements and the applied forces.
Impedance levels – These refer to the values of electrical impedance measured at different frequencies, which provide a comprehensive electrical representation of a device. These levels are characterized by both magnitude and phase, and they can be visualized through impedance spectra, typically represented in Bode or Cole-Cole plots.
Impedance parameters (Z-parameters) – These are a set of four electrical, complex-valued coefficients (Z11, Z12, Z21, and Z22) which characterize the voltage-current relationship of a linear, two-port network under open-circuit conditions. They define how input and output voltages (V1, V2) depend on input and output currents (I1, I2) using V = Z x I.
Impedance tube – It is also called Kundt tube, It is a specialized, hollow laboratory apparatus used in acoustic engineering to measure material properties like sound absorption, reflection coefficients, and transmission loss. It consists of a tube, a sound source (speaker), and microphones, allowing for the precise measurement of sound waves at normal incidence.
Impedance tube method – It is a technique used to measure the normal incidence sound absorption and transmission loss of materials. It uses a speaker at one end to generate plane waves in a rigid tube, with microphones measuring sound pressure to determine acoustic impedance.
Impeller – It, is a driven rotor which is used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
Impeller blade – It is a specialized, shaped vane attached to a rotating impeller hub which transfers mechanical energy from a motor to a fluid (liquid or gas). By rotating at high speeds, these blades increase the fluid’s velocity and pressure, directing it from the eye toward the outlet in pumps, compressors, and agitators.
Impeller design – It refers to the process of creating impellers that meet specific performance criteria, such as achieving a desired pressure ratio and flow characteristics, while considering aerodynamic performance and mechanical integrity. It involves optimizing parameters like outlet diameter and rotational speed to enhance efficiency within defined design spaces for centrifugal compressors.
Impeller inlet – It is the entry point of fluid into the impeller, where flow recirculation can occur, potentially inducing pre-swirl and affecting the performance of the pump. Proper design features, such as swirl-breaking elements, are essential to mitigate these effects.
Impeller outlet – It is the location on a centrifugal pump where fluid is discharged from the rim of the impeller after receiving energy from its rotation, resulting in an increase in both pressure and velocity.
Impeller region – It refers to the critical, high-shear, and rotational zone surrounding an impeller, encompassing the fluid dynamics and geometry from the inlet (eye) through the blade passages to the discharge. It controls energy transfer (fluid acceleration), flow recirculation, and pressure generation, where precise geometry is essential for performance. It is the area surrounding the impeller within a pump, where flow characteristics such as recirculation and pressure dynamics considerably influence the pump’s performance and efficiency.
Impeller Reynolds Number (Rei or Nre) – It is a dimensionless parameter, defined as the ratio of inertial forces to viscous forces in a stirred vessel. It determines if the mixing flow is laminar (Rei is less than 10), transitional, or turbulent (Rei is higher than 10,000). The formula is ‘Rei = (N x Di square x d)/m’ where ‘N’ is impeller speed, ‘Di’ diameter, ‘d’ density, and ‘m’ viscosity.
Impeller rotational speed – It refers to the rate at which an impeller rotates within a stirred vessel, measured in revolutions per minute (rpm), which influences the mixing efficiency and spatial concentration distributions of components in the fluid.
Impeller shaft – it is a mechanical component which transmits power from an electric motor to the impeller within a process vessel, and it can need support from bearings to minimize friction and vibration.
Impeller size – It refers to the dimensions of the impeller in a pump, which can considerably affect pump efficiency and is characterized by its diameter and shape.
Impeller speed – It normally refers to the rotational speed (N) of an impeller, measured in revolutions per minute (RPM), which drives mixing efficiency or pumping action. In contrast, impeller tip speed is the linear velocity at the outer edge, important for predicting wear and shear rates.
Impeller tip speed – It is the linear velocity of the outer edge of an impeller, typically expressed in meters per second, and is influenced by the impeller speed and diameter.
Impeller vane – It is a curved or straight blade attached to the hub of an impeller, acting as the main component in rotating machinery (pumps, compressors, mixers) to impart kinetic energy to fluids. Vanes spin to generate centrifugal force, forcing fluid from the eye (inlet) to the outlet, increasing velocity and pressure.
Impeller zone – It is the critical, high-shear region immediately surrounding a rotating impeller in mixing tanks, pumps, or compressors. It is defined by intense energy dissipation, high-velocity fluid flow, and active turbulence, where macroscopic flow patterns (axial or radial) are generated, considerably influencing overall mixing efficiency and pressure generation.
Impenetrability condition – It states that two distinct material bodies cannot occupy the same spatial location simultaneously. It ensures that contact surfaces maintain integrity, preventing material interpenetration during deformation or collision. When two bodies are in contact, they are either to maintain that contact or to separate, without passing through one another.
Imperceptibility – It is the quality of an image obtained after data embedding which shows minimal distortion, assessed through both subjective and objective tests comparing the original and watermarked images. It is characterized by high fidelity and quality metrics indicating a high degree of perceptual imperceptibility even with substantial data payloads.
Imperfect information – It refers to situations where decision-makers, system designers, or operators lack complete, accurate, or timely data regarding system states, component reliability, or environmental conditions. This incompleteness introduces risk, uncertainty, and potential for sub-optimal performance, frequently leading to increased costs or, in game theory, inability to observe others’ actions.
Imperfect interface – It refers to the modeling of non-ideal boundaries between materials in composites or joints, accounting for discontinuities in displacement, traction, temperature, or heat flux caused by defects like cracks, voids, or thin interphases. These models replace thin, complex adhesive layers with mathematical conditions which describe physical behaviour, necessary for accurate structural analysis.
Imperfection – It is a deviation from ideality. An imperfection may or may not be a defect, may or may not be addressed by a specification, and may or may not be related to a failure. All defects are imperfections. Imperfections may be geometric, metallurgical, and cosmetic. In crystallography, it is a deviation from an ideal space lattice.
Imperfection amplitude – It defines the maximum magnitude of geometric, structural, or material deviations (e.g., bowing, sway) from a perfect, ideal shape. It is a critical parameter for buckling, non-linear stability, and finite element analysis (FEA), frequently scaled to values like L/1,000 or L/150 for structural member design.
Imperfection shape – It refers to modeling the minor, unavoidable deviations from perfect geometry (e.g., bowing, denting, or non-straightness) which structural elements possess after fabrication, which considerably influence buckling strength. These shapes are normally defined as initial imperfections in finite element analysis (FEA) by scaling buckling modes or using specific, prescribed geometric deviations (such as parabolic or sinusoidal shapes) to predict real-world structural stability.
Imperfect plate – It is a structural plate with initial, unintentional deviations from its ideal flat geometry (e.g., waviness, curvature, or boundary irregularities). These imperfections, frequently induced by manufacturing processes like cold-forming, considerably affect non-linear buckling behaviour and normally reduce the load-bearing capacity.
Imperfect shell – it is a thin-walled structural element (cylindrical, spherical, or conical) containing small, unintentional geometric deviations from its ideal shape, frequently caused by fabrication, welding, or material curing, which considerably reduce its load-bearing capacity, particularly buckling strength. These deviations, or imperfections, make the structure highly sensitive to buckling, frequently needing the use of empirical ‘knock-down factors’ in design to account for reduced performance.
Imperfect structure – It refers to a structural system which deviates from its ideal, theoretical, or designed geometry or material properties, typically arising from fabrication, construction tolerances, or material irregularities. These deviations, such as out-of-straightness or misalignment, are critical to analyze since they considerably influence stability, buckling loads, and dynamic behaviours like vibration.
Imperial gallon – It is a unit of volume defined as exactly 4.54609 litres (around 277.42 cubic inches). Engineered around the mass of water, it represents the volume of 10 avoirdupois pounds of distilled water weighed in air at 16.7 deg C with a 30-inch (762 millimeters) mercury barometer. It is about 20 % larger than the United States liquid gallon.
Impermeable rock – It is a geological material with negligible permeability, preventing the flow of fluids (water, oil, gas) because of absent, extremely fine, or unconnected pore spaces. These low-permeability materials (e.g., shale, granite, clay, or salt) act as important seals, caprocks, or structural barriers in, for instance, sub-surface reservoirs.
Impermeable surface – It is a solid, human-made material (such as concrete, asphalt, or rooftops) which prevents water from infiltrating into the soil, causing rapid surface runoff. These surfaces are central to storm-water management, as they reduce ground-water recharge and increase flood risks by directing rain directly into drainage systems.
Impervious cover – It is a ground cover which does not allow water to pass through it to the soil below such as blacktop, brick, cobble, or bluestone, increasing storm water runoff and resulting in non-point source pollution.
Impervious layer – It is a dense, low-permeability material layer (like clay, shale, asphalt, or concrete) which restricts or prevents the passage of liquids, such as water or landfill leachate. These layers are important for containment in landfill liners, dam cores, and preventing surface runoff or groundwater contamination.
Impervious surface – It is solid surface which does not allow water to penetrate, forcing it to run off.
Impingement – It is a process resulting in a continuing succession of impacts between liquid or solid particles and a solid surface.
Impingement attack – It is the ‘form of erosion corrosion in aqueous liquids under high velocity or turbulent flow conditions associated on the metal surface causing repetitive disruption of protective films leading to accelerated localised corrosion’. It is the corrosion associated with turbulent flow of liquid. It can be accelerated by entrained gas bubbles.
Impingement corrosion – It is a form of erosion-corrosion normally associated with the local impingement of a high-velocity, flowing fluid against a solid surface.
Impingement erosion – It is the loss of material from a solid surface because of the liquid impingement.
Impingement umbrella – It is the partial screening of the surface of a solid sample subjected to solid impingement which sometimes occurs when some of the solid particles rebound from the surface and impede the motion of other impinging particles.
Implementation – It is the critical process of transforming a design, concept, or technical specification into a functional, tangible system, component, or product. It bridges the gap between theoretical planning (system definition / architecture) and operational reality. It is frequently described as the ‘doing’ stage, involving fabrication, coding, installation, and testing to produce the final, usable system.
Implementation complexity – It refers to the measure of effort, resources, and difficulty needed to turn a design, plan, or algorithm into a functional system or product. It encompasses the intricacy of code, hardware, and structural dependencies, frequently measured by metrics like code readability, component coupling, and the number of logical paths (e.g., cyclomatic complexity).
Implementation guidance – It refers to the documented, structured instructions, best practices, and procedures designed to translate a designed system (or ‘the what’) into a functional, working reality (‘the how’). It serves as the bridge between technical design (architecture, blueprints) and operational reality, detailing the steps, tools, and, in some cases, ‘rules’ which are to be followed for successful deployment, ensuring fidelity to the original design while adapting to local constraints.
Implementation of change – It is the structured process of executing, integrating, and sustaining new processes, technologies, or behaviours within an organization to achieve specific goals. It involves moving from a current state to a desired future state by applying a planned, systematic approach which minimizes disruption and resistance.
Implementation process – It is the structured, action-oriented phase of turning a plan, idea, strategy, or design into reality, involving defined steps, resource allocation, and execution to achieve specific goals, focusing on the ‘how’ after the ‘what’ has been decided. It bridges the gap between concept and actual operation, needing tasks like team assembly, budget deployment, and risk management to ensure successful adoption and results.
Implicit approach – It is a, frequently iterative, process which relies on indirect, automatic, or holistic mechanisms rather than direct, step-by-step, or conscious instructions. It needs solving equations by considering both current and previous states simultaneously for stability.
Implicit feedback – It refers to data collected from user interactions with a system, such as clicks, purchase history, viewing time, or search queries, which implicitly indicate user preferences without them explicitly providing ratings. Unlike explicit feedback (e.g., 5-star ratings or thumbs-up), which directly states a preference, implicit feedback is inferred from behaviour.
Implicit function – It is a function in the form F(x, y, z) = c, where ‘c’ is an arbitrary constant. It is used to describe geometric shapes, separate 3D space into regions, and convert positions into scalar values.
Implicit integration method – It is a numerical technique which calculates the new response value for a time step based on current and previous response values, and is characterized by its unconditional stability compared to explicit methods. It frequently needs iterative correction and can involve the evaluation of tangent stiffness, making it more reliable and superior for certain applications.
Implicit solver – It is a computational method which determines current quantities such as displacement, velocity, or acceleration at a future time step by utilizing values from a previous time step, while maintaining global equilibrium through the formation and inversion of a global stiffness matrix. This method is characterized by unconditionally stable solutions and typically requires fewer time steps for accurate results, despite being computationally intensive because of the matrix operations involved.
Import – It means bringing goods, materials, or data from another country for use, sale, or integration, frequently because of the local unavailability, cost benefits, or superior quality / technology, encompassing physical items (like steel, machinery) and digital data (like software components), important for economic growth but needing navigating customs and logistics.
Importance sampling – It is a variance reduction technique which focuses on sampling only in the region of interest, using a weighted average of random samples drawn from an alternative distribution. It is used to approximate expectations with respect to a target density function, particularly in scenarios involving low probability events.
Import substitution industrialization – It is a trade and economic policy which advocates replacing foreign imports with domestic production. It is based on the premise that a country is required to attempt to reduce its foreign dependency through the local production of industrialized products.
Imposed strain – It is the total, deliberate, or boundary-driven deformation forced upon a material or structural system, frequently used in failure analysis, high-pressure torsion (HPT), and rheological studies. It represents the prescribed displacement or changes in shape, distinguishing it from stress-induced deformation.
Impoverishment – it is the loss of any constituent from an alloy or from localized areas of an alloy by oxidation, liquidation, volatilization, or changes in the solid state. The term depletion is also used, particularly in referring to the lowering of the concentration of solute in a solid solution, around particles precipitated from solid solution.
Impregnate – In reinforced plastics, it means to saturate the reinforcement with a resin.
Impregnated carbon – It is a specialized form of activated carbon, processed to have its internal surface pores infused with specific chemicals, metals, or metal oxides (e.g., silver, iodine, caustic soda). This modification improves its adsorption capacity and adds catalytic properties to remove specific, hard-to-adsorb pollutants from air and water.
Impregnated fabric – It is a fabric impregnated with a synthetic resin.
Impregnation – It is the treatment of porous castings with a sealing medium to stop pressure leaks. It is also the process of filling the pores of a sintered compact, normally with a liquid such as a lubricant. It is also the process of mixing particles of a non-metallic substance in a cemented carbide matrix, as in the diamond impregnated tools.
Impregnation resins – These are liquid resins, frequently polymers, which are used to fill the pores or voids within a porous material, improving its properties. This process, known as resin impregnation, improves the material’s structural integrity, electrical insulation, and resistance to environmental factors.
Impressed current – It is the direct current supplied by a device employing a power source external to the electrode system of a cathodic protection installation.
Impressed current cathodic protection – It is a technique which is widely used for the protection of buried pipelines and the hulls of ships immersed in seawater. A direct current electrical circuit is used to apply an electric current to the metallic structure. The negative terminal of the current source is connected to the metal needing protection. The positive terminal is connected to an auxiliary anode immersed in the same medium to complete the circuit. The electric current charges the structure with excess electrons and hence changes the electrode potential in the negative direction until the immunity region is reached. Impressed current cathodic protection is a specialized technology and can be very effective if correctly designed and operated. Typical materials used for anodes are graphite, silicon, titanium, and niobium plated with platinum.
Impressed current corrosion – It is the electro-chemical corrosion because of the action of an external source of electric current.
Impressed current systems – These are cathodic protection systems utilized in high power demand applications, such as large water storage tanks, where they maintain protective potentials by adjusting current density needs through automatic potential control rectifiers.
Impression – It refers to a measurable, distinct instance of a system, component, or content being displayed, loaded, or physically stamped. In mechanical, materials, or manufacturing engineering, an impression is a physical indentation. In electron microscopy, it is the reproduction of the surface contours of a sample formed in a plastic material after the application of pressure, heat, or both. In hardness testing, it is the imprint or dent made in the sample by the indenter of a hardness-measuring device. In software engineering, web development, and digital marketing analytics, an impression is a unit of measure for digital content visibility.
Impression-die forging – It is a forging which is formed to the needed shape and size by machined impressions in specially prepared dies which exert three-dimensional control on the work-piece.
Impression replica – It is a surface replica made by impression. A replica is a reproduction of a surface in a material. It is normally accomplished by depositing a thin film of suitable material, such as plastic, onto the sample surface. This film is subsequently extracted and examined by transmission electron microscopy.
Imprint lithography – it is a micro-moulding process where the topography of a template dictates the patterns formed on a substrate, with different methods classified under nano-imprint lithography (NIL) for nano-scale applications.
Improve corrosion resistance – It refers to improving the ability of materials, particularly steel, to withstand oxidation and degradation in corrosive environments, mainly through the addition of elements like chromium, silicon, manganese, and tungsten, which contribute to the formation and stability of protective layers and reduce material loss.
Improve light extraction – It refers to methods used to improve the efficiency of light emitted from LEDs (light emitting diodes) by overcoming Fresnel reflection loss at the surface / air interface, frequently through techniques like random surface texturing or photonic crystal patterning, which redirect trapped photons into the extraction cone.
Improvement factor – It is a metric which quantifies the ratio of performance, efficiency, or quality after a change, modification, or process compared to the baseline or original state. It is widely used in engineering to measure enhancements, such as radar signal-to-clutter ratio, material strength, or imaging contrast, and in economics for labour productivity.
Improvement maintenance – It is the combination of all technical, administrative and managerial actions, intended to ameliorate the intrinsic reliability and / or maintainability and / or safety of an object, without changing the original function.
Improvement strategies – These are structured, ongoing approaches designed to enhance performance, processes, and efficiency across different sectors. These strategies constitute a ‘factor’ in organizational success since they act as the driving force for sustainable growth, competitiveness, and adaptation to change, rather than being a one-time initiative.
Improve phase – It is the stage in a process where ideas are developed to eliminate sources of variation, involving the testing and standardization of potential solutions while optimizing critical inputs to reduce defects. This phase includes identifying causes of variation, verifying critical inputs, and establishing operating parameters.
Impulse blading – It is a type of turbine blade design where the rotating blades are driven solely by the impact of a high-velocity fluid jet, rather than relying on pressure changes as the fluid passes through the blades. It is one of two normal methods for extracting kinetic energy from steam in a turbine. In the stationary blades, steam is accelerated to a velocity around twice that of the moving blades. Velocity is achieved at the expense of pressure. The moving blades extract kinetic energy from the fast-moving steam, so that it leaves with essentially no tangential component of velocity. In passing through one row of fixed blades and one row of moving blades, called a stage, the quantity of energy transferred to the rotor is proportional to the change in absolute steam velocity.
Impulsive force – It is a large force acting over a very short time interval, causing a substantial change in an object’s momentum. It is mathematically defined as the product of the average force and the time it acts (J = Favg x delta t), and it equals the change in momentum (delta p), making its SI (International System of Units) unit Newton-seconds or kilogram.meter/second.
Impulse function – It is a very short pulse, theoretically infinitely short, which is used to evaluate system dynamics and determine a system’s response to any input through convolution.
Impulse input – It is a very high pulse applied to a system over a very short time, where the magnitude approaches infinity while the time approaches zero. An example of an impulse input is a hammer striking a bell, delivering a finite quantity of energy to the system.
Impulse invariant method – It is a technique for designing digital filters where the impulse response of the digital filter is a sampled version of the impulse response of a corresponding analog filter. This method preserves the shape of the impulse response but can result in an aliased frequency response, necessitating careful consideration of the sampling rate to minimize errors introduced by aliasing.
Impulse line – It is a small-bore pipe or tube which connects a process pipeline’s tapping point to a pressure-sensing instrument (like a transmitter or gauge) in industrial systems, serving as a pathway to transmit pressure signals for measurement without exposing the instrument to the main process fluid, protecting it from heat, vibration, or contaminants. These lines are important for accurate flow, pressure, and level measurement, frequently used in conjunction with devices like orifice plates and venturi meters.
Impulse noise – It is a type of sudden, short-duration, high-amplitude sound or signal disturbance, like a sharp bang, click, or spike, frequently caused by physical impacts (explosions, gunfire) or electrical events (voltage spikes, lightning). It is characterized by rapid changes in sound pressure or signal level and can cause substantial damage (hearing loss, data corruption) because of its intensity and abrupt onset, frequently exceeding the ear’s or system’s ability to adapt.
Impulse pumps – These pumps use pressure created by gas (normally air). In some impulse pumps the gas trapped in the liquid (normally water), is released and accumulated somewhere in the pump, creating a pressure which can push part of the liquid upwards. Conventional impulse pumps include (i) hydraulic ram pumps, (ii) pulser pumps, and (iii) airlift pumps. Instead of a gas accumulation and releasing cycle, the pressure can be created by burning of hydrocarbons. Such combustion driven pumps directly transmit the impulse from a combustion event through the actuation membrane to the pump fluid. In order to allow this direct transmission, the pump needs to be almost entirely made of an elastomer (e.g., silicone rubber). Hence, the combustion causes the membrane to expand and thereby pumps the fluid out of the adjacent pumping chamber.
Impulse, resistance welding – it is a group of pulses which are occurring on a regular and which are separated only by an inter-pulse time.
Impulse response, impulse response function (IRF) – Impulse response function of a dynamic system is its output when presented with a brief input signal, called an impulse. Normally, an impulse response is the reaction of any dynamic system in response to some external change. In both cases, the impulse response describes the reaction of the system as a function of time (or possibly as a function of some other independent variable which parameterizes the dynamic behaviour of the system).
Impulse sequence – It is denoted as delta [n], is a fundamental discrete-time signal in digital signal processing, defined as having a value of 1 at n = 0 and a value of 0 for all other integer values of ‘n’. It serves as a, ideal test signal used to characterize linear time-invariant (LTI) systems.
Impulse signal – It is also known as the Dirac delta function [delta (t)]. It is an idealized, infinitesimally short pulse with infinite amplitude but a finite, unit area (integral of 1). It is zero everywhere except at time t = 0, where it is infinite, making it a crucial tool in signal processing and systems analysis to represent instantaneous events and understand system behaviour by containing all frequencies.
Impulse train – It is a sequence of impulses (delta functions) which are uniformly spaced apart by a specific time interval, denoted as ‘To’. It is normally used in the ideal sampling process.
Impulse turbine – An impulse turbine has fixed nozzles which orient the steam flow into high-speed jets. These jets contain considerable kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage. As the steam flows through the nozzle, its pressure falls from the inlet pressure to the exit pressure (atmospheric pressure, or more normally, the condenser vacuum). Because of this higher ratio of expansion of steam in the nozzle, the steam leaves the nozzle with a very high velocity. The steam leaving the moving blades has a large portion of the maximum velocity of the steam when leaving the nozzle. The loss of energy because of this higher exit velocity is normally called the ‘carry over velocity’ or ‘leaving loss’. In the impulse turbine, the fixed blades are quite different in shape from the moving ones since their job is to accelerate the steam until its velocity in the direction of rotation is around twice that of the moving blades. The moving blades are designed to absorb this impulse and to transfer it to the rotor in the form of kinetic energy. In this arrangement, majority of the pressure drop in each complete stage takes place in the fixed blades; the pressure drop through the moving blades is only sufficient to maintain the forward flow of steam. The quantity of energy transferred to the rotor in each stage is proportional to the change in absolute steam velocity in the direction of rotation.
Impurities -These are elements or compounds whose presence in a material is undesirable. In a chemical or material, it is minor constituent(s) or component(s) which is not included deliberately. It is normally to some degree or above some level, undesirable.
Impurity content – It is the measured quantity, concentration, or percentage of unwanted, foreign substances present within a material, product, or mixture. It represents any component other than the intended chemical entity, such as raw materials, by-products, or contaminants. This metric ensures quality, safety, and performance standards. It is frequently defined as the mass of impurities divided by the total mass of the mixture, typically expressed as a percentage [J = (A/B) x 100 %].
Impurity level – It refers to the concentration of unwanted or foreign substances within a material, frequently dictating its purity, quality, and performance. This quantifies contaminants (organic, inorganic, or solvents). In semiconductors, it represents dopant atoms which modify electrical properties.
Impurity limit – It is the maximum permissible concentration of unwanted elements (such as iron, nickel, copper, or sulphur) allowed in a metal or alloy before it negatively affects the material’s intended properties, such as corrosion resistance, ductility, or mechanical strength. These limits are important for defining high-purity materials and ensuring that performance (especially corrosion resistance) is not considerably accelerated by low-solubility elements.
Inactive film binders – An inactive film binder is typically a liquid solution which uses surface tension to pull the material’s particle together. It can also be a dry solid which is mixed thoroughly with the material to be briquetted before a solvent such as water or alcohol is added. In this case, the solid acts as both lubricant and glue, forming a solid bridge between particles when the solvent dries. Examples of inactive binders are water, alcohol, oils, wheat flour, molasses, starches, casein, glucose, dextrin, alginates, and gum arabic.
Inactive matrix binders – An inactive matrix binder embeds the material to be briquetted in a matrix (or framework) of the binder. Some inactive matrix binders such as coal tar pitch need to be heated to reduce their viscosity during the briquetting process but it sets hard when allowed to cool. Examples of inactive matrix binders are petroleum asphalt, carnauba wax, paraffin, wood tar, colloidal alumina, and metal stearate.
Inactive node – It is a component, device, or computational point which is powered on or exists within a system but is not currently participating in active operations, processing, or network traffic. They are used to represent excluded zones in simulations, define standby hardware in clusters, or identify dead sensors.
INBA slag granulation process – It is a process developed by Paul Wurth. It is a method for efficiently processing blast furnace slag by quenching it with water. This process rapidly cools the molten slag, converting it into a granular material, frequently referred to as granulated slag, which can be used in several applications like cement production. It is a popular and effective method, and has INBA dewatering drum is a key component. The process involves pouring molten slag from the blast furnace into a granulation tank where it is met with high-pressure water jets.
Incandescent light bulb – It is a device which uses a fine wire filament heated by an electric current to make light and heat.
Incandescent lamp – It is an electric light which produces illumination by heating a thin wire, called a filament (normally tungsten), until it glows white-hot, relying on the principle of incandescence, where heat creates light. Encased in a glass bulb (either vacuum or filled with inert gas like argon / nitrogen to prevent oxidation), it is a simple, inexpensive light source but inefficient, converting most energy to heat rather than light, resulting in a warm, yellowish glow and a relatively short lifespan.
Incentive mechanism – It is a structured system of rules, rewards, and penalties designed to motivate participants (like engineers, contractors, or users) to behave in ways that align with specific project, organizational, or system goals, ensuring efficiency, quality, cooperation, and better outcomes, frequently by linking performance metrics (cost, safety, innovation) to tangible benefits or consequences.
Incentives – They are anything that persuade a person or organization to alter their behavior to produce the desired outcome. The laws of economists and of behaviour state that higher incentives quantity to higher levels of effort and hence higher levels of performance. For comparison, a disincentive is something that discourages from certain actions.
Incentive system – The primary purpose of an incentive system is to build a workforce of the employees in the organization which is not only motivated but also effective, efficient and accountable as well. Employees in the organization are geared to take up challenging tasks besides giving a healthy output. Besides this primary purpose, incentive system results into the improvements in the work culture of the organization by (i) creating a positive work environment, (ii) motivating higher performance, (iii) reinforcing desired behaviour, (iv) creating a culture of recognition, (v) increasing the employees’ morale, (vi) supporting the organization’s mission and values, (vii) increasing retention of the employees and decreasing their turnover, and (viii) encouraging loyalty and identification of the employees with the organization.
Incentive wages – These consist of the extra-compensation paid to an employee for production over a specified magnitude which stems from exercise of more than the normal skill, effort, or concentration when accomplished in a pre-determined way involving standard tools, facilities and materials.
Inch-ton – It is a unit of energy or work, defined as the quantity of work done when a force of one ton is raised or moved a distance of one inch against the force of gravity.
Incidence angle – It is the angle between an incoming wave (like light or sound) or particle and the normal, an imaginary line perpendicular (at 90-degree) to a surface at the point where the wave hits it. It is a fundamental concept in optics, determining how light reflects (angle of incidence equals angle of reflection) or refracts (bends) as it interacts with different mediums or surfaces.
Incidence rate – Incidence rate is the total number of accidents multiplied by 1,000 and divided by the number of persons employed during the period
Incident – It is an unintended event, including operating errors, equipment failures, initiating events, accident precursors, near misses or other mishaps, or unauthorized act, malicious or non-malicious, the consequences or potential consequences of which are not negligible from the point of view of protection and safety. It is an unwanted event which, in different circumstances, can have resulted in harm to people, damage to property or loss to a process.
Incident bar – It is an important component in a ‘split Hopkinson pressure bar’ (SHPB) (or Kolsky) apparatus, used to study material behaviour under high strain rate loading. It is a long, elastic bar which receives an impact from a striker bar, creating a compressive stress wave that propagates to a sample placed between the incident and transmitting bars.
Incident beam – It is also called incident ray. It is a stream of energy, like light, particles, or waves, which travels towards and strikes a surface or interface, originating from a source and before it reflects, refracts, or is absorbed. It is the initial beam hitting something, important for understanding phenomena like reflections (mirrors), refractions (lenses), and diffraction (X-rays on crystals).
Incident energy – It is the thermal energy from an electrical arc flash that strikes a surface, measured in calories per square centimeter, quantifying the heat exposure (like a burn risk) and helping determine necessary personal protective equipment (PPE) and safe working distances, with 1.2 calories per square centimeter being the threshold for second-degree burns. It depends on fault current, voltage, arc duration, and distance, with longer duration and higher current increasing the hazard.
Incident field – It refers to the electro-magnetic field which illuminates a surface, which can be characterized by its ensemble of realizations and is used to calculate the resulting speckle pattern produced by scattering.
Incident handling – It is the comprehensive, structured process which an organization uses to manage the full lifecycle of an incident interruption, i.e., from the moment a potential threat or failure is detected until after the organization has recovered and learned from the event. It combines proactive planning (preparation) with reactive actions (detection, containment, eradication, and recovery) to minimize operational, financial, and reputational damage.
Incident intensity – It refers to the quantity of energy or power a wave (typically light, electro-magnetic, or sound) delivers per unit time per unit area onto a surface, before any transmission, reflection, or absorption occurs. It is measured in watts per square meter. It is the power (P) distributed over a given area (A), represented by the formula I = P/A. In the context of the photoelectric effect, a higher incident intensity corresponds to a higher number of emitted electrons.
Incident irradiance – It is the total quantity of radiant power (energy per unit time) falling upon a specific, defined surface area from all directions, typically measured in watts per square meter. It represents the power density of electro-magnetic radiation, such as solar energy or light, arriving at a surface, rather than what is emitted or reflected.
Incident photon – It is a particle of light or electro-magnetic radiation (E = h x v) which strikes or collides with a material, surface, or atom. It acts as the incoming, main energy source which triggers interactions such as photoelectric absorption, Compton scattering, or pair production, transferring energy to electrons.
Incident-photon-to-current efficiency (IPCE) – It is frequently synonymous with ‘external quantum efficiency (EQE). It is the ratio of the number of charge carriers (electrons) collected in an external circuit to the number of incident photons on a photoactive device (like a solar cell or photoelectrode) at a specific wavelength. It measures the efficiency with which a device converts incident light of a given wavelength into electrical current. It is defined as IPCE (lambda) = Nelectron / Nphotons.
Incident plane – It is defined in optics as the plane containing both the incident ray (or wave propagation vector) and the normal vector to the surface at the point of incidence. It serves as the reference plane for describing reflection and refraction, with the reflected and refracted rays also lying within this plane.
Incident point – It the specific location where an incoming ray (like light, or even a potential security issue) strikes a surface or boundary, marking the start of an interaction such as reflection, refraction, or absorption. It is an important concept in optics, to define angles of incidence and reflection, and in security for identifying potential threats.
Incident polarization – It refers to the orientation of the electric field vector of a light wave or electro-magnetic radiation before it interacts with a boundary, surface, or optical element. It defines whether the wave’s electric field oscillates parallel (p-polarization) or perpendicular (s-polarization) to the plane of incidence. It is the polarization state of the light beam ‘incident’ upon a material or surface.
Incident radiant power – It is frequently referred to as radiant flux. It is the total quantity of electro-magnetic energy (radiant energy) which strikes a specific surface or detector per unit time. Measured in Watts or Joules per second, it represents the rate at which radiant energy flows onto a target.
Incident ray – It is the incoming ray of light which strikes a surface or boundary between two different media (like air and glass), while the point where it hits is the point of incidence, forming an angle with the ‘normal’ (a line perpendicular to the surface). This ray is fundamental in understanding reflection (bouncing off) and refraction (bending through) of light, defining the angle of incidence (with the normal) and leading to reflected or refracted rays.
Incident response – It is a structured, systematic, and planned approach which organizations use to detect, manage, and recover from incidents occurring at the work-place. It is designed to minimize damage, reduce recovery time and costs, and prevent future incidents. It focuses on the technical execution of containment, eradication, and recovery, such as patching, restoring systems from backups, and changing access configurations.
Incident response plan – It is a documented, structured strategy for handling security incidents (failures) by defining procedures, roles, and communication to rapidly detect, contain, eradicate, recover, and learn from threats, minimizing damage, downtime, and costs while ensuring operational continuity and compliance. It moves organizations from reactive chaos to a controlled, efficient response, frequently following phases like preparation, identification, containment, eradication, recovery, and lessons learned.
Incident investigation – It is the process of systematically gathering and analyzing information about an incident. This is done for the purposes of identifying causes and making recommendations to prevent the incident from happening again.
Incineration – It is a waste treatment process which involves the combustion of substances contained in waste materials. Industrial plants for waste incineration are commonly referred to as waste-to-energy facilities. Incineration and other high-temperature waste treatment systems are described as ‘thermal treatment’. Incineration of waste materials converts the waste into ash, flue gas and heat. The ash is mostly formed by the inorganic constituents of the waste and can take the form of solid lumps or particulates carried by the flue gas. The flue gases are to be cleaned of gaseous and particulate pollutants before they are dispersed into the atmosphere. In some cases, the heat that is generated by incineration can be used to generate electric power.
Incineration plant – It is a specialized industrial facility designed to treat waste materials through high-temperature combustion (typically 850 deg C to 1,000 deg C), reducing waste volume by up to 95 %. These plants convert solid waste into ash, flue gas, and heat, frequently operating as ‘waste-to-energy’ (WTE) plants to generate electricity or steam.
Incinerator – It is a specialized, high-temperature furnace or vessel designed for the controlled combustion and thermal treatment of solid, liquid, or gaseous waste materials. Its main purpose is to oxidize organic compounds, reduce waste volume by up to 95 %, and destroy toxic or hazardous materials.
Incipient cavitation – It is the formation of cavities or bubbles in the liquid flow which begins when the pressure first dips below the vapour pressure. It is identified by a deviation from the quadratic relationship between volumetric flow rate and pressure drop and by an increased noise emission.
Incipient crack – It is an extremely small, initial flaw or micro-crack which forms in a material, frequently at a surface defect or stress concentration point (like a pit or notch), marking the very beginning of fatigue or fracture, frequently undetectable by the naked eye but critical for structural integrity as it grows. These tiny cracks can stop growing (arrest) or, under sufficient stress and favourable conditions (like hydrogen presence or specific material properties), can grow into larger, detectable defects, representing the first stage of material failure.
Incipient melting – It consists of heating of material into a two-phase liquid-solid region on the phase diagram so that some liquid is formed.
Inclinable press – It is a press which can be inclined to facilitate handling of the formed parts.
Inclination – It refers to the angle a line makes with the positive x-axis, measured counterclockwise, while slope is the ratio of the vertical change to the horizontal change between any two points on the line. A steeper line has a larger angle of inclination.
Inclination angle – It is the angle a line or surface makes with the horizontal, typically measured counter-clockwise from the positive x-axis in coordinate geometry, representing slope or tilt, It is used for ramps / forces differing from the angle of elevation, which is from an observer to an object above.
Incline conveyor – It is a conveyor system which is specifically designed with an upward slope to facilitate the efficient transport of materials. Periodic inspections are necessary for ensuring proper alignment, maintaining optimal belt tension, and upholding overall functionality. This type of conveyor is also known as an extendible or flexing conveyor.
Incline conveyor length -It is determined by evaluating the elevation change from the infeed to discharge points in relation to the degree of incline. Understanding and measuring this length is crucial for proper conveyor system design and performance.
Inclined jet – It is a fluid stream (liquid or gas) discharged from a nozzle at an angle relative to a surface or the horizontal plane. It is used to improve material removal in machining, improve dilution of buoyant discharges, or optimize convective heat transfer, frequently characterized by its discharge angle (theta).
Inclined plane – It is also known as a ramp. It is a flat supporting surface tilted at an angle from the vertical direction, with one end higher than the other, used as an aid for raising or lowering a load. The inclined plane is one of the six classical simple machines, It is used to move heavy loads over. Inclined position – It is the position of a pipe joint in which the axis of the pipe is at an angle of around 45-degree to the horizontal, and the pipe is not rotated during welding.
Inclined position with restriction ring – It is the position of a pipe joint in which the axis of the pipe is at an angle of around 45-degree to the horizontal, and a restriction ring is located near the joint. The pipe is not rotated during welding.
Inclined wall – It is also called slanted wall or sloped wall. It is a vertical structural or architectural element tilted at an angle other than 90 degrees from the horizontal plane. These walls are used to create non-vertical surfaces, frequently in, but not limited to, attics, modern facades, or retaining structures. They need specific construction techniques to ensure stability.
Inclinometer – It is an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity’s direction. It is also known as a tilt indicator, tilt sensor, tilt meter, slope alert, slope gauge, gradient meter, gradiometer, level gauge, level meter, declinometer, and pitch and roll indicator. It measures both inclines and declines using three different units of measure namely degrees percentage points, and topos.
Included angle – It is a non-standard term for groove angle which is the total included angle of the groove between the work pieces.
Inclusion – Inclusions are non-metallic compounds and precipitates which form in steel during its production and processing and hence are the by-products of steelmaking which arise from different chemistries and processes. Inclusions can vary widely in size and composition, giving rise to a corresponding wide range of effects and mandating sophisticated analytical equipment for characterization. Inclusions are constituted by glass-ceramic phases embedded in steel metal matrix. Inclusion control is to promote the removal of inclusions from steel and to reduce their harmful effects on the quality and the processing of steel. It is an important aspect of the steelmaking practice. However, the presence of certain inclusion types can also yield beneficial effects in the steel. Inclusion is a physical and mechanical discontinuity occurring within a material or part, normally consisting of solid, encapsulated foreign material. Inclusions are frequently capable of transmitting some structural stresses and energy fields, but to a noticeably different degree than from the parent material. Inclusion is also the particles of foreign material in a metallic matrix. The particles are normally compounds, such as oxides, sulphides, or silicates, but can be of any substance which is foreign to (and essentially insoluble in) the matrix.
Inclusion agglomeration and clogging – The agglomeration of solid inclusions can occur on any surface aided by surface tension effects, including on refractory and bubble surfaces. The high contact angle of alumina in liquid steel (134-degree to 146-degree) encourages an inclusion to attach itself to refractory in order to minimize contact with steel. High temperatures of 1,530 deg C enable sintering of alumina to occur. Large contact angle and larger inclusion size favour the agglomeration of inclusions. Because of the collision and agglomeration, inclusions in steel tend to grow with increasing time and temperature. Inclusion growth by collision, agglomeration, and coagulation in ingot has been the subject of various studies, in which the numerical simulation of inclusion nucleation starting from deoxidant addition and growth by collision and diffusion from nano-size to micro-size is reported.
Inclusion assessment – It is the systematic process of identifying, quantifying, and characterizing non-metallic, solid-phase impurities (inclusions) trapped within a metal matrix (normally steel). This process determines the cleanliness of the metal by analyzing the inclusion population’s type, quantity, size distribution, composition, and morphology.
Inclusion count – It is the determination of the number, kind, size, and distribution of non-metallic inclusions in metals.
Inclusion engineering – The term ‘inclusions engineering’ means the design of the inclusions so as to alleviate their harmful effects on the product properties. Inclusion engineering does not refer to removal of inclusions but it refers to modify them either in terms of chemical composition or shape so that harmful effects of the inclusions can be converted to improve the steel properties. Inclusion engineering also involves distribution of inclusion uniformly in the matrix, so that composite properties can be generated in the product. In some cases, deliberate attempts are made to form very fine inclusions (e.g. nitrides, and carbo-nitrides inclusions in hardening steel). Such inclusion can form by reaction between tungsten, titanium, aluminum with oxygen, nitrogen, sulphur, or carbon.
Inclusion principle – It states that fragments (inclusions) within a rock are older than the rock which contains them (host rock), a key concept for relative dating, explaining that the fragments have been formed first before being incorporated into the younger, surrounding material. For example, pebbles in a conglomerate or xenoliths (foreign fragments) in igneous rock are always older than the sediment or magma which solidified around them.
Inclusion, stringer – It is an impurity, metallic or non-metallic, which is trapped in the ingot and elongated subsequently in the direction of working. It can be revealed during working or finishing as a narrow streak parallel to the direction of working.
Inclusion type – Inclusion types include oxides, sulphides, silicates, and slag, categorized as internal (endogenous, like deoxidation products) or external (exogenous, from surroundings). Inclusions can be detrimental (causing cracks) or beneficial (controlling grain size).
Incoherence – It refers to a lack of logical connection, consistency, or structure within a system, process, or data set, leading to misalignment of goals, contradictory needs, or, in physics / signal processing, waves which are not in phase. It denotes a state of disorganization or internal contradiction which hinders functionality.
Incoherent particles – These are distinct second-phase precipitate particles with crystal structures and lattice planes which are discontinuous and not aligned with the surrounding matrix. They form in the final stage of age-hardening, acting as effective barriers to dislocation movement (strengthening) because of their well-defined, separate interfaces.
Incoherent scattering – It is the deflection of electrons by electrons or atoms which results in a loss of kinetic energy by the incident electron.
Incombustible gases – These are substances which do not ignite, burn, or support combustion when exposed to air, oxygen, or high temperatures, serving as critical safety, shielding, or extinguishing agents in engineering applications. Examples include nitrogen, carbon di-oxide, and noble gases like argon.
Incoming exergy – It is the total useful work potential (availability) accompanying mass, fuel, or heat streams entering a system, defined relative to a specific reference environment. It represents the maximum theoretical work obtainable as these streams reach equilibrium with the surroundings, calculated using parameters like enthalpy, entropy, and temperature.
Incoming light – It is also called incident light. It refers to light rays, waves, or photons traveling toward a surface, interface, or optical component before interaction occurs. It is a fundamental concept in optics, optoelectronics, and imaging, defining the energy input which is subsequently reflected, absorbed, or transmitted.
Incoming medium – It refers to the abrasive material which is drawn into the extrusion chamber of a one-way abrasive flow machining machine, allowing it to be directed towards the internal features of the work-piece for machining.
Incoming optical signal – It is a modulated light wave (typically infrared) carrying data, which travels through an optical fibre channel to a receiver. It represents the final, frequently attenuated, light-based information arriving at a photodetector to be converted back into an electrical signal.
Incoming photons – These are defined as quanta of electro-magnetic radiation, elementary particles with no charge or rest mass traveling at the speed of light, which strike, interact with, or are absorbed by a material, such as a semi-conductor or metal surface. These photons transfer energy, causing phenomena like photoelectric absorption, Compton scattering, or pair production.
Incoming signal – It is a time-varying physical quantity, such as voltage, current, or electro-magnetic wave, originating from an external source and detected by a device, receiver, or system. It acts as an input which conveys information (data, audio, or video) to be processed, demodulated, or measured.
Incomplete annealing – In process of incomplete annealing, the steel is heated to around upper basic temperature. Both the hypo-eutectic steel or hyper-eutectic steel are given this treatment. The heat treatment process is obtained by slow cooling after thermal insulation. It is largely performed to get spherical pearlite for the hyper-eutectic steel, to remove the internal stress, to decrease the hardness, and to increase the machinability.
Incomplete combustion – It is the partial burning of fuel because of insufficient oxygen, leading to less energy release and the production of harmful byproducts like carbon mono-oxide, soot (unburnt carbon), and water, instead of the ideal carbon di-oxide and water from complete combustion. This process creates toxic gases and particulate matter, posing substantial health and environmental risks, and occurs when oxygen supply is limited.
Incomplete fusion – Itis a welding defect where the filler metal fails to properly melt and bond with the base metal or preceding weld beads. It creates a weak joint with gaps, often caused by low heat input, fast travel speed, or poor technique. It appears as elongated dark lines on radiographs.
Incomplete seam – It is the junction line of metal which has passed through a die forming a hollow profile (shape), separated and not completely rejoined. Flare testing is a method of evaluating weld integrity.
Incomplete surface coverage – It refers to a state where an applied substance (like a coating, film, or mono-layer) or a physical structure fails to fully cover a target area, leaving gaps, voids, or pinholes. It indicates partial, rather than total, occupation of a surface, frequently reducing efficacy, stability, or protection.
Incompressible flow – It is a fluid dynamics approximation where the fluid’s density (d) is considered constant, meaning it does not considerably change with pressure or time, which mathematically translates to the velocity field’s divergence being zero. This assumption simplifies analysis, especially for liquids like water and gases (like air) at low speeds (Mach number less than 0.3), as density variations become negligible, making it ideal for modeling everyday flows in pipes.
Incompressible fluid – It is a fluid whose volume or density does not change with pressure, typically assumed in certain cases to simplify flow equations.
Incompressible inviscid fluid – It refers to a fluid whose density is constant (normalized to unity) and has no viscosity, meaning it experiences no internal friction, allowing it to flow without energy loss. This type of fluid motion is governed by the Euler equations, which describe the velocity and pressure distribution in space.
Incompressible limit – It is the mathematical transformation of compressible fluid equations into incompressible ones as the Mach number (M = u/c) approaches zero. It signifies the state where density variations become negligible, causing the flow to become divergence-free, transforming compressible Navier-Stokes equations into incompressible Navier-Stokes equations.
Incompressible liquid – It is a fluid whose density remains constant regardless of pressure changes, allowing for simplified flow calculations in scenarios such as liquid flow through a feed line.
Incompressible material – It is a type of material whose volume does not change under applied deformation, analogous to a linear elastic material with a Poisson’s ratio of 0.5.
Incompressible viscous fluid – It is a fluid whose density remains constant during motion and is characterized by equations which govern its continuity, motion, and energy, which together form a closed system for analyzing viscous flow dynamics.
Inconel – It is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant.
Inconel alloys – These are a family of austenitic nickel-chromium-based superalloys known for exceptional high-temperature strength, superior corrosion resistance, and oxidation resistance. Developed for extreme environments, they rely on solid-solution strengthening or precipitation hardening to maintain structural integrity under high pressure and thermal stress.
Inco pressure carbonyl process – It is a sophisticated vapometallurgical technique used to extract and refine nickel, cobalt, and iron from different feed materials (such as matte, sulphide ores, or alloys) by reacting them with carbon mono-oxide (CO) at high temperatures (150 deg C to 220 deg C) and high pressures (e.g., 7 mega-pascals or higher). It is a highly selective method which produces exceptionally high-purity (frequently higher than 99.99 %) nickel powders or pellets.
Incorporating carbon – It refers to the addition of carbon into semi-conductor materials to suppress donor diffusion and improve shallow junction formation by trapping impurities and reducing their mobility.
Incorporating mechanisms – It refers to the integration of fundamental, underlying processes into models or systems to improve their accuracy, predictive power, and understanding of causality. This approach shifts, for example, agent-based models from purely data-driven to mechanistically driven, improving simulation of multi-scale, dynamic phenomena.
Incoterms – It is an abbreviation for the international commercial terms and is the registered trademark name given to these terms by International Chamber of Commerce (ICC). They are a series of three-letter trade terms related to common contractual sales practices. The Incoterms rules are intended mainly to clearly communicate the tasks, costs, and risks associated with the transportation and delivery of goods. They are published by the International Chamber of Commerce and are widely used in international commercial transactions. Incoterms are a set of rules which define the responsibilities of sellers and buyers for the delivery of goods under sales contracts for domestic and international trade. They apportion transportation costs and responsibilities associated with the delivery of goods between buyers (importers) and sellers (exporters) and reflect modern day transportation practices. Incoterms significantly reduce misunderstandings among trading parties and thereby minimize trade disputes and litigation.
Increased draft – It refers to a higher-than-average reduction in the thickness of a work-piece as it passes between rolls.
Increase tool life – It refers to the improvement of the durability and longevity of cutting tools, achieved through methods such as heat-assisted machining, which reduces cutting forces, decreases wear rates, and suppresses chatter, ultimately leading to longer operational periods for the tools.
Increasing deformation – It refers to the process where strain applied to a material is raised, causing flow stress to initially rise rapidly before peaking and gradually stabilizing due to dynamic softening mechanisms overcoming hardening effects. This process is influenced by factors such as deformation temperature, strain rate, and hydrogen content.
Increasing fly ash – It refers to the practice of incorporating higher quantities of pulverized fuel ash, a by-product of coal combustion, into concrete mixtures, typically exceeding 30 %, to improve durability, workability, and pozzolanic activity. It acts as a sustainable, cementitious material which improves compressive strength over time and lowers water demand.
Increasing moisture content – It refers to the rise in water mass per unit mass of material, which improves the cohesive strength of particulate substances and can lead to issues such as bridging and blocking feeding systems.
Increasing nitrogen content – It refers to the rise in the quantity of nitrogen present in fuel, which is associated with higher emissions of nitrogen oxides (NOx) and nitrous oxide (N2O) during combustion processes.
Increasing omega – It refers to the process of slowly raising the forcing frequency in a system, typically starting just below a natural frequency, to observe changes in the system’s response and identify regions where transitions or jumps to different operating conditions can occur.
Increasing pH – It refers to a decrease in the concentration of hydrogen ions (H+) in a solution, making it less acidic and more basic or alkaline. On the 0 to 14 scale, a higher pH value signifies lower acidity, moving closer to or exceeding 7 (neutral) towards 14 (strongly basic).
Increasing shear rate – It refers to a rise in the velocity gradient between adjacent layers of a fluid, signifying that the fluid is experiencing faster deformation (deformation rate or strain rate), typically measured in reciprocal seconds (per second). As the shear rate increases, the shear stress increases, causing a reduction in viscosity for shear-thinning (non-Newtonian) fluids.
Increasing shear stress – It refers to a rise in the frictional, tangential force (t) acting parallel to a surface, per unit area (A), defined by t = F/A. It occurs in materials when parallel forces cause internal layers to slide over each other or in fluids when velocity gradients increase. It triggers deformation / fracture in solid.
Increasing substrate temperature – It refers to the elevation of the temperature at which a substrate is maintained during the growth of diamond in chemical vapour deposition (CVD), considerably influencing growth rates, crystallite size, and the quality of the diamond films produced. Substrate temperatures typically range from 600 deg C to 1,000 deg C, with optimum growth occurring around 800 deg C to 1,000 deg C.
Increasing surface area – It refers to expanding the total exposed, outermost boundary of a solid substance, typically by grinding, crushing, or breaking it into smaller particles or by increasing its porosity. This process raises the ratio of surface area to volume, leading to higher chemical reactivity, faster reaction rates, and improved adsorption or filtration capabilities.
Increasing titanium (Ti) content – It refers to the metallurgical process or compositional change of raising the weight percentage or atomic percentage of titanium within an alloy system (such as steel, nickel-based superalloys, or high-entropy alloys). This, in turn, influences the microstructure, phase composition, and resulting physical or mechanical properties of the material.
Increment – It is an individual portion of material collected by a single operation of a sampling device from parts of a lot separated in time or space. Increments can be tested individually or combined (composited) and tested as a unit.
Incremental erosion – It is the gradual depletion of material because of the factors like friction and abrasion, needing systematic inspections and maintenance to prevent equipment failure and ensure prolonged functionality.
Incremental forging – It is a closed die forging process in which only a portion of the work piece is shaped during each of a series of press strokes. The process is similar to open die forging (cogging) of ingots, billets, thick plates, and shafts. In contrast to such operations, however, impression dies (not flat or V-shaped tooling) are utilized. The main applications of the technique are very large plan-area components of high temperature alloys for which die pressures can easily equal or exceed 140 MPa to 280 MPa. In such instances, part plan area is limited to around several thousands of square centimeters for the very large presses (50,000 tons). By forging, only a portion of the part at a time, however, reduces the press requirements.
Incremental forming – It is a class of forming processes characterized by the gradual deformation of small areas of a product, where only a limited portion is formed at any given time, while the area of local deformation moves across the entire product.
Incremental hole-drilling method – It is a semi-destructive technique to measure subsurface residual stresses by drilling a small, incremental hole in a material and monitoring the surface deformation, which is then used with calibration coefficients (frequently from ‘finite element analysis’) to calculate the original stress profile as the hole deepens. This popular method, also known as the ‘hole-drilling strain-gauge method’, is valued for its relative simplicity and effectiveness in analyzing stresses near surfaces in various materials and components.
Incremental isotropy – It is a specialized concept used to describe the deformation behaviour of materials during plastic forming processes, particularly when a material which has been initially isotropic becomes anisotropic because of the deformation history (such as rolling, drawing, or bending). It is a state where, at any specific moment or ‘increment’ of loading, the material properties (specifically the relationship between the increment of plastic strain and the current stress) are considered isotropic, even if the material has developed preferred orientations (textures) from previous, accumulated strain.
Incremental seat test – It is the leakage testing of valve seats in an assembled valve by increasing the applied pressure in prescribed pressure steps.
incremental shaft encoder – It is an electro-mechanical sensor that converts the rotational motion or position of a shaft into a series of digital pulses. By counting these pulses, devices measure speed, distance, and direction. They typically utilize a rotating disk with optical or magnetic sensors to produce signals, which are lost when power is removed.
Incremental step test – It is a technique which has been proposed as a time-saving method to determine the cyclic stress strain (CSS) curve with one sample is the incremental step test (IST). In each block the amplitude is first increased linearly with time up to a maximum amplitude, then decreased to zero (or a minimum amplitude value). This loading sequence (block) is applied repeatedly until a stabilized behaviour is established. Then the cyclic stress strain curve is obtained simply by connecting the load reversal points in the stress-strain course. It appears very doubtful that this test procedure gives a cyclic stress strain curve identical to that determined in single-step tests at different amplitudes. As described above, each amplitude leads to a characteristic dislocation distribution and arrangement that cannot be expected to exist at each single cycle of the incremental step test.
Incremental testing – It is a strategy where a system is built and tested in small, growing parts (increments) rather than all at once, integrating and verifying modules sequentially to find defects early and ensure smooth working of the system.
Increment function – It increases a numerical value by a specific, predefined quantity, typically by 1 in programming contexts, frequently denoted by the ++ operator. It fetches a variable’s current value, adds the increment, and stores the result back, acting as a concise operation to update counters or pointers, such as i++ or ++i.
Incubation period – It is a period prior to the detection of corrosion while the metal is in contact with a corrodent. In cavitation and impingement erosion, it is the initial stage of the erosion rate-time pattern during which the erosion rate is zero or negligible compared to later stages. In cavitation and impingement erosion, it is the exposure duration associated with the initial stage of the erosion rate-time pattern during which the erosion rate is zero or negligible compared to later stages. Quantitatively, incubation period is sometimes defined as the intercept on the time or exposure axis, of a straight-line extension of the maximum slope portion of the cumulative erosion-time curve.
Incumbent supplier – It is organization which currently provides goods or services to a customer, holding the existing contract and frequently possessing substantial advantages like established relationships, deep knowledge, and economies of scale over new competitors (challenger suppliers). In procurement, they are the existing provider whose contract is being re-evaluated, offering them a strong position to retain the business but also facing competition from others trying to displace them.
Indefinite chill iron rolls – These are alloy iron rolls and are cast in chill moulds. After casting the hard top chill layer is cut off and the remaining part of the roll has hardness practically constant up to a great depth. In fact, drop in hardness from the surface to the core of the roll is gradual up to 100 millimeters to 125 millimeters depth compared to chill roll where the drop in hardness is sharp. With this type of roll, there is a very thin clearly defined white graphite-free chill and no intermediate mix zone. The surface layers contain very small particles of graphite and the structure changes smoothly into the grey core. These rolls can be heat treated to toughen them against shock loadings. An example of this type is the Adamite indefinite chill. These rolls can be heat treated and are resistant to spalling and fire cracking. Indefinite chill rolls are normally used in the intermediate and finishing stands of section mills where deep grooves are required to be cut to make the needed profiles for the sections to be rolled. These rolls have better resistance to fire cracking and spalling than the chill rolls and also better strength. They are reasonably tough with good wearing properties.
Indefinite delivery / indefinite quantity – It is a flexible contract type for procuring undefined quantities of supplies or services over a set period, allowing agencies to order as needed within minimum / maximum limits, streamlining projects where exact needs are not known upfront. It defines a fixed contract duration (e.g., 5 years) but not the precise quantities or delivery times, using task orders or delivery orders for specific needs.
Indentation – It is imperfection which can occur during the moulding or firing process of a brick or a block.
Indentation curve – It is also called load-displacement curve. It is a plot of the force applied by a probe against the depth of penetration into a material, used to determine mechanical properties like hardness and stiffness. It consists of a loading phase, representing elastic / plastic deformation, and an unloading phase, allowing calculation of Young’s modulus and plastic work.
Indentation hardness – It is the resistance of a material to indentation. It is the normal type of hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. It is also the resistance of a solid surface to the penetration of a second, normally harder, body under prescribed conditions. Numerical values used to express indentation hardness are not absolute physical quantities, but depend on the hardness scale used to express hardness. Examples of indentation hardness are Brinell hardness, Knoop hardness, nano-hardness, Rockwell hardness, and Vickers hardness.
Indentation method -It is a material characterization technique which determines mechanical properties, such as hardness, elastic modulus, and plastic deformation, by forcing a probe of known geometry into a material’s surface while recording load-displacement data. It is used to measure hardness, stiffness, and creep behavior, frequently utilizing micro-indentation or nano-indentation tools.
Indentation rolling resistance – It is a force which resists the motion of a rolling object, specifically when a viscoelastic material (like a conveyor belt) is indented by a rigid object (like an idler roll). This resistance arises from energy loss due to the deformation of the viscoelastic material as it is compressed and then relaxes during rolling. It is a major factor in the total resistance to motion in systems like belt conveyors, and understanding it is important for optimizing energy efficiency.
Indentation tests – These tests measure a material’s mechanical properties, mainly hardness, by pressing a hard indenter (like diamond or steel) into its surface and analyzing the resulting permanent impression or load-displacement curve, revealing resistance to localized plastic deformation, stiffness, and other properties like elastic modulus, yield strength, and creep behaviour, applicable from macro-scale to nano-scale. Common methods include Brinell, Rockwell, Vickers, and nano-indentation, offering fewer invasive ways to characterize materials compared to traditional tensile tests.
Indentation testing – It is a mechanical test method used for evaluating the hardness and other mechanical properties of materials by pressing a hard object (indenter) into the sample and measuring the resulting indentation. It is a versatile technique applicable to different materials and scales, from macro- to nano-indentation.
Indenter – In hardness testing, it is a solid body of prescribed geometry, normally chosen for its high hardness, which is used to determine the resistance of a solid surface to penetration.
Independent component analysis – It is a statistical method used to identify hidden factors of random variables. It is a linear generative model which assumes the observed variables are a linear mixture of unknown non-Gaussian and mutually independent variables. The aim of independent component analysis is to find those variables without making any assumptions about the mixing system.
Independent events – These refer to occurrences where the probability of one event does not affect the probability of another, such that the joint probability is the product of their individual probabilities: P(A and B) = P(A) x P(B). Hence, the information obtained from two independent events can be expressed as the sum of the information from each event: i(A and B) = i(A) + i(B).
Independent Gaussian – It refers to a set of random variables that are distributed according to Gaussian distributions and are statistically independent from one another. In the context of ‘independent component analysis (ICA), the presence of independent Gaussian components results in a situation where the mixing matrix cannot be identified, as the uncorrelatedness of jointly Gaussian variables implies independence.
Independent increments – These refer to a property of a stochastic process where the change in the process value (the increment) over any non-overlapping time interval is statistically independent of the changes over other disjoint time intervals. It signifies that past behaviour does not influence future changes.
Independent measurement – It refers to a data point collected in a way which is not influenced by, or correlated with, other measurements in the same study or system. It ensures that each observation provides new, unique information, frequently used in experiments to avoid bias or to establish causality.
Independent node – It is a specific, important junction where the voltage is unknown and needs a distinct Kirchhoff’s current law (KCL) equation. The number of independent nodes equals the total number of nodes (N) minus one reference (ground) node. These nodes are used to solve for voltages in nodal analysis.
Independent qualified reviewer – Independent qualified reviewer is an individual or organization, external to the organizational design team, who conducts an objective, documented, and systematic evaluation of engineering designs, calculations, or technical processes to ensure safety, code compliance, and quality.
Independent regulatory agency – it is a government body with autonomy from political influence, tasked with creating, enforcing, and overseeing technical standards, safety protocols, and fair practices in specific industries to protect public interest, ensure fair markets, and manage complex systems, operating with technical expertise and accountability to the legislature. They depoliticize decision-making by focusing on techno-commercial principles, ensuring compliance through inspections, audits, and imposing penalties for violations.
Independent system operator – It is an entity responsible for maintaining grid reliability by balancing energy production and demand, facilitating market interactions between energy producers and utility distributors, and managing energy reserves to prevent shortfalls.
Independent tanks – These are self-contained, freestanding structures made of materials such as aluminum alloy or 9 % nickel steel, designed to hold liquefied gases without contributing to the hull strength of a ship. They include different types based on design pressure, notably Type A, Type B, and Type C tanks, with Type B being specifically designed without general assumptions used in other types. Independent t-test – It isa statistical procedure for comparing measurements of mean scores in two different groups or samples. It is also called the independent samples t-test.
Independent variables – These are variables which are not seen as depending on any other variable in the scope of the experiment in question. In this sense, some common independent variables are time, space, density, mass, fluid flow rate, and previous values of some observed value of interest to predict future values (the dependent variable).
Independent voltage source – It is a circuit element where the voltage across its terminals is independent of any other variables in the circuit.
Index – It is a statistical measure of change in a representative group of individual data points. These data can be derived from any number of sources, including organizational performance, prices, productivity, and employment.
Indexing – It is the process of separating a designated quantity of products from a larger group, typically achieved with a singulation-specific indexer conveyor. This ensures precise control and organization of materials during the conveying process.
Indexing data – It refers to the construction of data indices to enhance the efficiency of data query responses, with the choice of index being determined by the characteristics of the data being queried.
Index function – It retrieves a value or reference from a table or range at a specific row and column position, acting like a lookup tool that pinpoints data based on numeric coordinates, frequently combined with the match function for powerful, flexible data retrieval in spreadsheets like Excel. It returns the content of a cell at the intersection of a given row and column number within a selected array.
Index number – It is a data figure reflecting quantity compared with a standard or base value. It is normally expressed as 100 times the ratio to the base value.
Index of refraction – It is the ratio of the phase velocity of mono-chromatic light in a vacuum to that in a specified medium. Index of refraction is normally a function of wave length and temperature.
Index polymer optical fibre – It is also called plastic optical fibre. It is a data transmission or illumination medium crafted from transparent polymers, typically poly-methyl methacrylate (PMMA) or fluorinated polymers, consisting of a high-refractive-index core surrounded by a lower-refractive-index cladding. These fibres utilize ‘total internal reflection’ (TIR) at the core-cladding boundary to guide light. They are highly flexible, durable, cost-effective, and easy to install, making them ideal for short-range, high-speed data links, automotive networks, and illumination applications.
Index profile – It is specifically a refractive index profile. It is the mapping or distribution of the refractive index across the cross-section of an optical fibre, typically covering the core and cladding. It defines how the light-guiding material’s index changes radially, determining key properties like light propagation, numerical aperture, and signal dispersion.
Indicated mean effective pressure – It is a crucial engine performance metric representing the hypothetical constant pressure acting on a piston throughout the power stroke which produces the same network as the actual, varying gas pressures in the cylinder, serving as a measure of the work output from combustion before mechanical losses. It is calculated from the engine’s pressure-volume (P-V) diagram, reflecting the gross power generated within the cylinders and offering a speed-independent way to compare engine thermodynamics.
Indicated mineral resource – An indicated mineral resource is that part of a mineral resource for which quantity, grade (or quality), densities, shape, and physical characteristics are estimated with sufficient confidence to allow the application of modifying factors in sufficient detail to support mine planning and evaluation of the economic viability of the deposit. Geological evidence is derived from adequately detailed and reliable exploration, sampling, and testing gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes, and is sufficient to assume geological and grade (quality) continuity between points of observation where data and samples are gathered. An indicated mineral resource has a lower level of confidence than that applying to a measured mineral resource and can only be converted to a probable ore reserve.
Indicated thermal efficiency – It measures how effectively an engine converts fuel’s chemical energy into useful work inside the cylinders, defined as the ratio of indicated power (IP) to the heat energy supplied by the fuel per second (fuel power). It shows the efficiency of the combustion process itself, before accounting for mechanical losses like friction, by comparing the power generated in the cylinder to the total energy from the fuel.
Indications and warnings – It refer to the systematic process of detecting, analyzing, and reporting pre-event indicators, such as activities, anomalies, or system behaviours, which suggest an imminent threat, providing sufficient time for decision-makers to implement defensive measures. It transforms raw data into actionable intelligence to avoid strategic surprise, moving from reactive to proactive risk management.
Indicating instruments – These are those instruments which indicate the magnitude of a quantity being measured. These instruments generally make use of a dial and a pointer for this purpose. Examples are ordinary voltmeters, ammeters, and watt-meters. The analog indicating instruments can be further divided into two groups consisting of (i) electro-mechanical instruments, and (ii) electronic instruments. Electronic instruments are constructed by addition of electronic circuits to electro-magnetic indicators in order to increase the sensitivity and input impedance.
Indicator – It is a direct or indirect measurement of some valued component or quality in a system, including an ecosystem or organization.
Indicator crack method – It is a technique for detecting surface or near-surface discontinuities in ferro-magnetic materials. It relies on creating a magnetic flux leakage field at a crack, which is then made visible by applying ferro-magnetic particles (the indicator).
Indicator diagram – It is a PV diagram which shows the pressure and volume changes occurring inside an engine cylinder, allowing for the determination of the work done by the engine and the assessment of its power and efficiency.
Indicator function – It is also called characteristic function. It is a mathematical function which returns 1 if an element belongs to a specific set or condition is met, and 0 otherwise, acting as a binary switch for set membership or event occurrence. It is fundamental in probability (as indicator random variables) to define events, in set theory to represent subsets, and in statistics (dummy variables) for data analysis.
Indicator lamp – It is a small, typically coloured, illuminated signaling device used on machinery, control panels, and vehicles to visually convey the status (e.g., power on, operating, faulty) of a system or circuit. It is also known as a pilot light, it provides immediate, visual feedback to users, frequently using colour-coding.
Indicator light – It is a small, coloured signal on devices which visually communicates status, like power (green for on, red for off / warning), operation (blue for active), or issues (yellow for caution, red for critical), helping users quickly to understand if equipment is working, needs attention, or has a fault. ,
Indicator, pH – It is a halochromic chemical compound added in small quantities to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and / or emission properties. Hence, a pH indicator is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Arrhenius model. Normally, the indicator causes the colour of the solution to change depending on the pH. Indicators can also show change in other physical properties, e.g., olfactory indicators show change in their odour.
Indicators – These are quantitative or qualitative parameters that provide a simple and reliable basis for assessing change. Indicators are alternative measures which are used to identify the status of a concern when for technical or financial reasons the concern cannot be measured. In case of chemical wet analysis, indicators are substances whose solutions change color due to changes in pH. These are called acid-base indicators. They are normally weak acids or bases, but their conjugate base or acid forms have different colors due to differences in their absorption spectra.
Indices, Miller-Bravais – These are the indices which are used for the hexagonal system. They involve use of a fourth axis, a3, coplanar with and at 120-degree to a1 and a2.
Indices, Miller (for lattice planes) – These are the reciprocals of the fractional intercepts which a plane makes on the three axes. The symbols are (hkl).
Indigenous – It means originating or occurring naturally in a particular place.
Indigenous fuel – It refers to energy sources produced or sourced domestically within a country, excluding imports. These resources, such as coal, natural gas, biomass, or biofuels, are utilized to improve energy security, reduce import bills, and promote self-reliance. It normally implies a focus on local availability to support national energy independence.
Indigenous inclusion – It occurs within the liquid steel, precipitating out during cooling and solidification. The inclusions belonging to this class result from additives to the steel. They are deoxidation products or precipitated inclusions during cooling and solidification of steel. Alumina inclusions in low carbon aluminum killed (LCAK) steel, and silica inclusions in silicon-killed steel are generated by the reaction between the dissolved oxygen and the added aluminum and silicon deoxidants are typical deoxidation inclusions. Indigenous inclusion is an inclusion which is native, innate, or inherent in the molten metal treatment. Indigenous inclusions include sulphides, nitrides, and oxides derived from the chemical reaction of the molten metal with the local environment. Such inclusions are small and need microscopic magnification for identification.
Indirect-arc furnace – It is an electric arc furnace in which the metallic charge is not one of the poles of the arc. It is an electric furnace in which the arc is struck between two horizontal electrodes, heating the metal charge by radiation.
Indirect cold extrusion – It is frequently referred to as backward or reverse extrusion. It is a metal forming process where a cold metal billet (slug) is placed in a closed-ended container and deformed at room temperature by a punch (ram) which forces the metal to flow in the opposite direction of the punch movement. Since the billet does not move relative to the container wall, this method considerably reduces friction, lowers the needed extrusion force, and allows for the creation of more complex or precise shapes, particularly in softer metals like aluminum, copper, and some steels.
Indirect contact condensation recovery – Indirect contact condensation recovery units cool gases to around 40 deg C. In this range, the water vapour in gases condenses almost completely. Indirect contact exchangers consist of a shell and tube heat exchangers. They can be designed with stainless steel, glass, Teflon, or other advanced materials.
Indirect conversion – It is a two-step imaging or energy transformation process where an initial signal (typically X-rays) is first converted into visible light through a scintillator (e.g., cesium iodide), and then into an electrical charge by a photodiode. It is commonly used in flat-panel detectors for digital radiography to produce images by converting light to charge, which is then read out by a thin-film transistor (TFT) array.
Indirect costs – It is the cost which is not directly associated with the production of identifiable goods or services. It is also called burden costs or overhead costs. Indirect costs are expenses which are not directly linked to a specific product, service, or project, but are necessary for the overall operation of an organization.
Indirect effect – It occurs when an action, event, or variable influences another entity not directly, but through one or more intermediate, mediating factors, processes, or species. It represents a secondary, chain-reaction consequence that propagates through a system, rather than a direct, immediate, or linear cause-and-effect relationship.
Indirect extrusion – It is also called backward extrusion. It is the extrusion, in which the die is at the ram end of the stock and the product travels in the direction opposite that of the ram, either around the ram (as in the impact extrusion of cylinders such as cases for dry cell batteries), or up through the centre of a hollow ram.
Indirect heating system – It is a method where a primary energy source (like a boiler or heater) heats a transfer fluid (water, glycol, or air), which is then circulated through a heat exchanger to heat a separate, final medium. This process ensures the heat source does not directly contact the material, space, or fluid being heated.
Indirect injection diesel engine – It is a compression-ignition engine where fuel is injected into an auxiliary compartment, a pre-combustion or swirl chamber, rather than directly into the main cylinder. Combustion begins in this chamber, allowing for better fuel-air mixing, quieter, smoother operation, and higher engine speeds, though it results in lower efficiency because of the heat loss.
Indirect liquefaction – It is a two-step thermo-chemical process which converts carbon-based feedstocks (coal, biomass, or natural gas) into liquid fuels or chemicals. It first gasifies the feedstock into synthesis gas (syngas, hydrogen + carbon mono-oxide), which is then converted into synthetic liquid hydrocarbons or alcohols using catalysts, very frequently through the Fischer-Tropsch (FT) synthesis.
Indirect rapid tooling -It creates moulds or dies in a multi-step process. A rapid prototyping (RP) technique first builds a master pattern or model (e.g., from polymer), which then serves as the basis for creating the actual tool, frequently using casting or other pattern-based methods with materials like epoxy, silicone, or metal, enabling cost-effective low-volume production of parts before final hard tooling is made.
Indirect semiconductor – It is a material where the maximum energy of the valence band and the minimum energy of the conduction band occur at different momentum values (k-vectors). Because of this misalignment, electrons transitioning between bands need a change in both energy and momentum, typically involving a phonon (lattice vibration). Common examples are Silicon (Si) and Germanium (Ge), which have low light-emission efficiency.
Indirect sintering – It is a process whereby the heat needed for sintering is generated outside the body and transferred to the compact by conduction, convection, and radiation etc.
Indirect solar gain – It is a passive solar heating technique where sunlight is captured and absorbed by a thermal mass (such as a masonry wall, water tank, or greenhouse) located between the sun and the living space. This stored heat is later transferred into the interior through conduction, convection, or radiation, often after a time delay, providing a steady heat source.
Indirect steam generation – It is a process which produces steam by transferring heat from a primary medium, such as hot thermal oil, high-temperature water, or existing industrial steam, to feedwater through a heat exchanger, rather than direct combustion. This method avoids direct contact between the heating source and the generated steam, ensuring high-purity or ‘clean steam production.
Indirect tensile test – It is a laboratory method for determining the tensile strength of brittle materials (like concrete, rock, or ceramics) by applying a compressive load along the diameter of a cylindrical sample. This compressive load induces tensile stress perpendicular to the loading plane, causing the sample to split.
Indirect tube extrusion – It is backward extrusion. It is a metal forming process where a hollow or solid billet remains stationary within a container while a hollow ram (equipped with a die and mandrel) moves to force metal backward through the die opening. This method eliminates friction between the billet and container walls, resulting in lower extrusion forces, higher speeds, better material uniformity, and reduced defects compared to direct methods.
Indirect water heating systems – These are systems which circulate a heat transfer fluid through a closed collector loop to a heat exchanger, where potable water is heated. These systems can use different heat transfer fluids, including water / ethylene glycol solutions, and can need protection devices to manage pressure and temperature.
Indium – Its symbol is ‘In,’ and atomic number 49. It is a soft, silvery-white post-transition metal. It has a low melting point (156.6 deg C) and is primarily used as indium tin oxide in liquid-crystal displays (LCDs), solar panels, and in specialized low-temperature soldering. Indium is found in zinc ores.
Indium gallium arsenide (InGaAs) – It is an alloy of indium arsenide (InAs) and gallium arsenide (GaAs) normally used as a substrate material in image sensors for near-infrared applications, covering a spectral range of 900 nano-meters to 1,700 nano-meters.
Indium tin oxide – It is a conductive and transparent oxide used mainly as an electrode material because of its high stability, optical transparency, and compatibility with micro-fabrication processes. Its properties enable the integration of electro-chemical and optical measurement techniques in different sensing applications.
Individual – It refers to a single person (an engineer) applying science, math, and creativity to design / build things, or to a specific, separate component / system being worked on, highlighting unique aspects like design, function, or differences from others in a group. It emphasizes problem-solving for one person / item, distinct from collective efforts, or characteristics that set one engineer apart from another.
Individual accountability – It means that each person owns his / her tasks, decisions, and outcomes, answering for them transparently to build trust and improve projects, rather than just shifting blame. It fosters learning from mistakes and ensures commitment through clear roles, visible progress, and an environment where raising concerns is encouraged for better collective results and safety.
Individual anode – It is a specific unit of anode material which produces a certain current output, used in galvanic protection systems to meet the needed current demand for a designated area.
Individual carbon nano-tubes – These are hollow, cylindrical nano-structures made of a single or multiple layers of graphene (atomically thin carbon sheets) rolled into tubes, typically 1 nano-meter to 3 nano-meters in diameter. They possess unique, high-aspect-ratio geometries, with lengths reaching micro-meters to milli-meters. These, also known as ‘buckytubes’, possess extraordinary electrical, mechanical, and thermal properties which differ from bulk carbon.
Individual components – These refer to the distinct elements within a system which are described by their behaviour and parameters, which can occur multiple times and are later combined to form a modular overall system.
Individual decisions – These are taken by a single person, normally the head of the organization, with or without consulting others affected. These are taken in the context of routine programmed decisions where the analysis of different alternatives is simple and for which broad policy manuals are provided. Sometimes, important non-programmed decisions are also taken by individuals.
Individual fibres – These refer to discrete strands which can be produced in different geometric forms and configurations, including different cross-sectional shapes and structures, which are designed for improved mechanical interaction with binders during manufacturing processes.
Individual grains – These grains refer to the distinct crystalline regions within poly-crystalline materials, whose growth kinetics and behaviour can vary from grain to grain during processes like recrystallization and grain growth, as observed through advanced experimental techniques.
Individual macerals – These are defined as specific types of organic particles classified within the broader maceral groups, vitrinite, liptinite (exinite), and inertinite, based on their vegetal matter origin, morphology, and chemical composition.
Individual ply – It is a single, distinct layer or sheet of material which is stacked or combined with other similar layers to form a thicker, more rigid, or stronger component, such as in plywood, laminated composites, or fabric.
Individual power constraints – These refer to the specific limits on the power which each relay can utilize in a single-user multi-relay network, which are to be adhered to during the relay beam-forming design process.
Individual process – It is a distinct, non-overlapping operation combined with others to achieve specific tasks within a broader scope of work. These processes are distinct operations within a broader scope of work, ideally without overlapping or duplicating the functions of other processes. In organizational behaviour, these processes are psychological mechanisms, such as perception, motivation, decision-making, and emotion, which influence how a person behaves and interacts within their work environment. These processes include personality, perception, attitudes, learning, and motivation, forming the foundation of employee behaviour and performance.
individual pump – It is also called single pump unit. It is a standalone configuration comprising one glanded pump paired with its own dedicated driver, such as an electric motor or engine, designed to move fluid independently. It is not integrated with other pumps in a shared casing or manifold system. These units are normally used for fluid transport.
Individual resistance – It means a person’s capacity to oppose external pressures, maintain personal beliefs, or reject changes, frequently rooted in self-interest, fear, or misunderstanding, but it can also refer technically to the electrical opposition of a single component in a circuit. In social contexts, it is about defying conformity and standing up for oneself, while in electric circuits, it is about how one part of a circuit resists current flow compared to others.
Individuals – Individuals are the conceivable constituent parts of a population.
individual sensor – It is a device, module, or subsystem designed to detect, measure, and respond to specific physical, or chemical properties in its surrounding environment. It functions as a transducer, converting environmental input, such as light, heat, pressure, motion, or moisture, into a readable output signal, typically an electrical, analog, or digital signal, which is then sent to a processor for monitoring or control purposes.
Individual voxels – These refer to the smallest distinguishable units of three-dimensional space in imaging analysis, which can reveal local heterogeneities in tissue, such as hyper-permeable or hyper-vascular areas. Each voxel contains a series of values for several parameters, allowing for detailed assessment of features.
Individual zones – These refer to groups of devices within a network which are either located close to one another or share common security requirements, allowing for logical segmentation based on different functional criteria.
Indoor air – It refers to the air present within confined spaces. It encompasses the physical, chemical, and biological characteristics of this environment, which directly affect the health and comfort of occupants, frequently containing pollutants at concentrations higher than outdoor air.
Indoor air pollution – It is the contamination of air inside buildings by harmful substances like gases (carbon mono-oxide, radon), particulate matter, mold, pesticides, and VOCs (volatile organic compounds) from sources such as cooking fuels, cleaning products, furniture, and outdoor pollutants, frequently becoming more concentrated indoors because of poor ventilation and energy-efficient, airtight homes, posing serious health risks.
Indoor air purification – It is the process of removing contaminants, such as dust, pollen, viruses, bacteria, and volatile organic compounds (VOCs), from enclosed spaces to improve air quality and health. It utilizes technologies like HEPA (high efficiency particulate air) filters, activated carbon, and ultra-violet light to sanitize air, distinct from mere ventilation.
Indoor air quality – It refers to the quality of air within and around buildings and structures, especially as it relates to the health and comfort of building occupants. It’s influenced by various factors, including pollutants, temperature, humidity, and ventilation.
Indoor temperature difference – It refers to the temperature variation between the indoor environment and an adjacent space, which influences the rate of heat transfer through building elements such as partitions, ceilings, and floors.
Induced bending moment – It is the internal reaction moment developed within a structural element (like a beam) to counteract external loads, such as weight, causing the material to bend. It acts as a resistant force to keep the structure in equilibrium, varying in magnitude across the length of the element.
Induced charge – It is the separation of positive and negative charges within a neutral object when a charged object is brought near it, causing the free electrons to redistribute, creating a temporary opposite charge on the near side and a like charge on the far side, all without direct physical contact. This process, called electrostatic induction, allows an object to become charged by attracting or repelling these induced charges, frequently by grounding it while the charged object is nearby.
Induced convection – It is frequently referred to as forced convection. It is a heat transfer mechanism where fluid movement (liquid or gas) is generated by external, artificial means rather than natural buoyancy forces. It uses devices like fans, pumps, or stirrers to increase fluid velocity, improving considerably heat transfer rates.
Induced corrosion – It refers to the accelerated deterioration of materials, typically metals, triggered by specific, external, or environmental factors which initiate or speed up electro-chemical reactions, frequently leading to premature, localized failure. Common types include micro-biologically influenced corrosion (MIC) caused by bacteria, chloride-induced corrosion, and carbonation-induced corrosion in concrete.
Induced cracking – It is also referred to as hydrogen-induced cracking (HIC). It is the degradation and failure of materials, particularly steel, caused by the diffusion of atomic hydrogen into the metal structure, creating internal pressure that leads to cracking. It frequently occurs in, but is not limited to, corrosive environments (wet hydrogen sulphide, H2S) or through hydrogen introduced during manufacturing / welding.
Induced current – It is the electric current which flows in a conductor when it is exposed to a changing magnetic field, a phenomenon called electro-magnetic induction, where a varying magnetic flux through a closed circuit generates an electromotive force (EMF) causing charge carriers (like electrons) to move. This current is produced by altering the magnetic field’s strength, moving the conductor in the field, changing the loop’s area, or changing the distance between magnet and conductor, and its strength is governed by Faraday’s Law and direction by Lenz’s Law, forming the basis for generators and transformers.
Induced damage – It means harm caused indirectly by a main event or force, rather than direct impact, frequently resulting from the shock, stress, or secondary actions of a collision, misuse, or external factor, and normally seen as damage to machine vehicle parts not directly hit in a crash, or electronic failures from misuse like spills, excluded from standard warranties.
Induced deformation – It refers to a change in the shape, volume, or position of a material, structure, or ground, caused by external factors rather than innate properties. These alterations can result from mechanical, physical, or chemical influences like seismic activity, moisture changes, electric fields, or swelling.
Induced degradation effect – It refers to the deterioration of solar modules caused by high electrical potential differences between the module frame and solar cells, resulting in leakage currents which drive cations, particularly sodium, from the glass into the solar cell and associated coatings. This effect can lead to substantial power losses and is characterized by improved recombination, shunt formation, and potential damage to module components.
Induced delamination – It is the intentional or unintentional separation of layers within a composite, laminate, or coated material, frequently occurring at the interface because of the stresses. It is a critical failure mode in engineering, frequently caused by impact, mechanical loading, or environmental factors (moisture, heat), leading to reduced structural stiffness and strength.
Induced dipole – It is a temporary separation of positive and negative charge that forms in a nonpolar atom or molecule when it is near an external electric field from a charged ion or a polar molecule, causing its electron cloud to distort, creating a weak, fleeting dipole which leads to attraction (like in dipole-induced dipole forces).
Induced draft – It is a ventilation method using a fan, typically at the outlet of a system like a boiler or cooling tower, to pull air or exhaust gases out, creating a negative pressure (vacuum) which draws fresh air in and ensures the safe, efficient discharge of hot gases through a chimney or stack. It is used in industrial settings to control combustion, improve heat transfer, and manage emissions by creating a steady airflow, unlike forced draft which pushes air in.
Induced draft cooling tower – It is a mechanical draft system which uses top-mounted fans to draw air upward through the tower, cooling hot water which is sprayed downward. By locating fans at the air discharge point, it induces a low-pressure air flow, maximizing thermal efficiency, preventing recirculation of hot, moist air, and creating a strong counterflow with descending water.
Induced draft fan – It is a fan exhausting hot gases from the heat absorbing equipment. It is an important industrial component which pulls hot flue gases from boilers, furnaces, and combustion chambers, creating negative pressure to ensure they are efficiently exhausted through a chimney or stack, hence maintaining proper airflow, improving combustion, and controlling emissions.
Induced electric field – it is a non-electrostatic electric field generated by a changing magnetic field, forming closed loops and existing even without a conductor, as described by Faraday’s law of induction. Unlike static electric fields from charges, induced electric fields are non-conservative, meaning they do work to move charges in a closed path (like driving current in a wire), and are important for phenomena like electromagnetic induction and eddy currents.
Induced embrittlement – It is the reduction of a material’s ductility and fracture toughness because of the environmental interactions or internal structural changes, typically resulting in sudden, brittle failure. It occurs when materials are exposed to specific factors, such as liquid metals, hydrogen, or radiation—frequently under tensile stress.
Induced failure – It refers to the degradation or breakage of materials and components caused directly by external, operational, or environmental stressors rather than inherent design flaws. These, such as vibration-induced, thermally induced, or fatigue-induced failures, arise when excessive, repetitive, or rapid changes in force or temperature exceed a material’s tolerance.
Induced fatigue – It is a result of the fluctuation of the nominal primary stresses, i.e. the stress range induced by the applied loads. It is the progressive, localized, and permanent structural damage caused by fluctuating or cyclic stresses, frequently below the yield strength. It occurs in three stages, namely crack initiation, propagation, and final fracture. It is typically caused by service loads, vibration, or stress concentrations at sharp corners or welding defects.
Induced fission – It is a nuclear engineering process where a heavy nucleus (e.g., 235U) absorbs a neutron, becoming unstable and splitting into smaller fission fragments, while releasing substantial kinetic energy, radiation, and additional neutrons. It is the fundamental, controllable chain reaction mechanism used in nuclear reactors for power generation.
Induced flow rate – It refers to the volumetric flow rate of fluid generated by the movement of channel walls or boundary motions, calculated by integrating the induced axial velocity across the cross-sectional area of the conduit. It represents fluid motion driven by external or boundary forces rather than solely by pressure differences, frequently analyzed over time as a time-averaged flow rate.
Induced graft polymerization – It is a surface modification technique which uses activation energy, such as high-energy radiation, ultra-violet light, or plasma, to create reactive radical sites on a polymer. These sites initiate covalent bonding with monomers, forming side chains which improve material properties like wettability, adhesion, or biocompatibility without changing bulk properties.
Induced ground deformations – These refer to permanent shifts in the ground caused by processes such as soil liquefaction during seismic events, which can result in lateral movements and subsidence because of the loss of shear strength in saturated soils. These deformations can occur immediately or be delayed following the seismic shaking.
Induced heating – It refers to the process of generating heat within a material through the creation of an electro-magnetic field and the formation of eddy currents, which result in Joule’s heating. This method is characterized by its energy efficiency, minimal emissions, and its application in different sustainable material processing technologies.
Induced hydrophilicity – It refers to the temporary or permanent alteration of a material’s surface to increase its affinity for water (wettability), typically lowering the water contact angle to less than 90-degree, or less than 5-degree for superhydrophilicity. This is achieved through engineering techniques like ultra-violet induced photocatalysis (e.g., titanium di-oxide coatings), plasma treatment, or chemical modifications, causing water to spread into a uniform film rather than beads.
Induced loads – These are structural forces generated internally or indirectly by external environmental factors, dynamic pressures, or operational activities rather than direct, static weight. Examples include wind-induced vibrations, water current shear forces, thermal expansion stresses, and structural deformations caused by foundation settlement.
Induced martensitic transformation – It is a process where a metastable phase (typically austenite) transforms into martensite because of the applied mechanical stress or plastic strain rather than cooling. This shear-driven, diffusion-less transformation improves material properties like strength, ductility, and fracture toughness, frequently utilized in TRIP (transformation induced plasticity) steels and shape memory alloys.
Induced noise – It refers to unwanted electrical, acoustic, or mechanical energy transferred from a source to a receiver, degrading system performance or causing malfunctions. It normally arises from electro-magnetic fields, fluid flow (flow-induced), or mechanical vibrations (e.g., coil whine) acting on a component.
Induced oxidation – It is a degradation process, particularly in polymers and metals, where external factors like metal ions (e.g., cobalt), light, or specific environments catalyze material oxidation, causing increased brittleness, cracking, and structural failure, even without mechanical stress. It is frequently a catalyzed, rapid, and destructive chemical reaction.
Induced periodic surface structures – These surface structures are laser induced. These surface structures are frequently referred to as ripples, are self-organized, quasi-periodic micro-structures or nano-structures (typically 10 nano-meters to 100 nano-meters high) formed on material surfaces (metals, semi-conductors, di-electrics) when irradiated with polarized laser pulses, normally below the ablation threshold. They are classified as LSFL (low spatial frequency, higher than lambda/2) or HSFL (high spatial frequency, less than lambda/2) based on their periodicity.
Induced phase modulation – It is a nonlinear optical process where the phase of a weak probe pulse is modulated by an intense pump pulse, both traveling through a X-cube nonlinear medium (e.g., optical fibre). It results in spectral broadening and frequency chirping of the probe pulse caused by the time-varying refractive index induced by the pump’s intensity.
Induced plasticity – It is specifically referred as ‘transformation-induced plasticity, or TRIP. It refers to a material’s capacity for improved plastic deformation and high work-hardening during stress-induced phase transformations, frequently occurring below the conventional yield stress. It occurs because of the microscopic stresses arising from volume changes during phase shifts (e.g., austenite to martensite).
Induced polarization – It is a method of ground geophysical surveying using an electrical current to determine indications of mineralization.
Induced polarization surveys – These are conducted along grid lines with readings taken at receiving electrodes planted in the earth and moved from station to station. The electrodes are connected to a receiver and measure the chargeability (the capacity for various minerals to build up a charge of electricity) and resistivity effects on current forced into the ground and bedrock.
Induced power penalty – It is the increase in received optical power (measured in decibel, dB) needed to maintain a specific, desired bit error rate (BER) or signal quality in the presence of specific impairments or degrading. It represents the extra ‘penalty’ in power which is to be added to a system to compensate for signal degradation, such as noise, crosstalk, dispersion, or timing jitter. to achieve the same performance as an ideal, unimpaired system.
Induced precipitation – It refers to the intentional formation of a solid phase from a liquid solution or within a solid matrix, driven by external factors such as strain, additives, or biological agents. Key types include ‘strain-induced precipitation hardening’ (SIPH) in metals (e.g., niobium carbide, NbC, titanium carbide, TiC in steel), ‘solvent-induced precipitation’ in chemical processing, and ‘micro-biologically induced calcite precipitation’ (MICP) for soil stabilization.
Induced refractive index change – It is the alteration of a material’s optical refractive index, typically in glass or polymers, caused by external stimuli like laser irradiation (photo-induced), mechanical stress, or temperature shifts. This process modifies material density or structure to create wave-guides, gratings, or lenses for photonics, enabling precise control over light propagation.
Induced residual stress – It is the internal, ‘locked-in’ stress remaining within a solid material after all external loads, thermal gradients, or manufacturing constraints are removed. Caused by non-uniform plastic deformation, thermal cycles, or phase changes during processes like welding, machining, or heat treating, these stresses can be tensile (frequently harmful) or compressive (frequently beneficial).
Induced roll magnetic separator – It uses electromagnetic fields to generate high-intensity magnetic fields. These magnetic fields enable the separation of weak and para-magnetic minerals (e.g. mica, iron-coated silica, etc.) from non-metallic minerals (e.g. feldspar, silica sand, zircon, etc.) in a dry state. Induced roll magnetic separators are widely used to treat beach sands, wolframite and tin ores, glass sands, and phosphate rock.
Induced roughness – It refers to surface irregularities intentionally or inadvertently created on a material, which cause localized asperity contact, increased friction, or modified surface texture. This phenomenon influences component performance, such as improving seal lubrication through micro-wedges or affecting crack propagation.
Induced separation – It refers to the process of phase separation in a polymer solution which can be triggered by different mechanisms, including thermally induced separation, which reduces polymer solubility through temperature decrease or freezing, resulting in high and low concentration regions within the solution. In fluid Dynamics it means the forcing of boundary-layer separation from a surface, frequently caused by shock waves or adverse pressure gradients.
Induced settlement – It refers to ground displacement, subsidence, or downward movement of soil and structures caused by human-made activities rather than natural consolidation. These activities alter the stress state, groundwater levels, or physical density of the ground, leading to vertical displacement.
Induced stress – It refers to internal resisting forces (newton per square meter or pascal) developed within a material, structure, or soil mass in response to applied external loads (e.g., foundations, machinery) or disturbances, such as excavation. It acts to resist deformation, calculated as force divided by cross-sectional area (s = F/A).
Induced shift – It normally refers to an unwanted or artificial displacement, error, or change in a measurement, material, or system behaviour caused by external factors, tools, or physical processes.
Induced surface – It refers to a topographically altered or modified surface layer on a material produced by an external stimulus (mechanical, laser, or electrical) rather than being part of the bulk material’s inherent structure. Key types include ‘laser-induced periodic surface structures (LIPSS) (self-organized ripples), deformation-induced surface roughening, and ion beam-induced surface modification. These surfaces are engineered to alter functional performance, such as improving lubrication, changing wettability, or improving fatigue life, and are analyzed in terms of surface integrity.
Induced tilt – It refers to an unintended or secondary inclination (angle) of a component, system, or structure that arises as a consequence of another action, process, or environmental effect, rather than being intentionally designed into the system. It is a critical factor in structural, geotechnical, optical, and mechanical engineering, where it frequently leads to operational, stability, or performance issues.
Induced transformation – It refers to a phase change, typically from austenite to martensite or bainitic ferrite, triggered by applied stress or plastic strain (frequently called transformation induced plasticity effect or strain-induced martensite). This phenomenon improves mechanical properties, specifically increasing ductility, strength, and fatigue resistance, by altering the microstructure under deformation.
Induced velocity – It is the additional, localized velocity imparted to a fluid (air or water) by a lifting body, such as a rotor blade, as it generates lift. It is key to calculating wake behaviour, induced drag, and rotor performance, frequently representing the downward velocity (downwash) or inflow velocity which dictates lift, thrust, and power requirements.
Induced vibration – It refers to structural oscillations triggered by an external, dynamic source, normally fluid flow (liquids or gases) or, less frequently, electro-magnetic forces. These vibrations arise when fluid interaction causes boundary layer separation, turbulent mixing, or vortex shedding, leading to potential resonance, fatigue, and structural failure, particularly at high flow velocities.
Induced voltage – It is the electrical potential (voltage) created in a conductor when it experiences a change in magnetic flux, a phenomenon known as electro-magnetic induction, described by Faraday’s law. This voltage is generated when a conductor moves through a magnetic field, or when the magnetic field itself changes, and it is what drives induced electric currents, important for generators, transformers, and motors.
Induced volume – It refers to the increase in a material’s unit cell volume caused by the accumulation of point defects, micro-structural changes, or radiation exposure, leading to macroscopic swelling. This volume change represents a structural deformation or expansion, frequently studied to predict material durability and integrity.
Inductance calculation – It is the process of determining the ability of a conductor or coil to store magnetic energy and oppose changes in current, measured in h(H). It is defined as the ratio of induced voltage (v) to the rate of change of current (di/dt), expressed by L =v/(di/dt), and depends on geometry and core material.
Inductance-resistance-capacitance (LRC) circuit – it is also known as an RLC circuit or resonant circuit. It is an electrical circuit consisting of an inductor (L), a resistor (R), and a capacitor (C), connected in series or parallel. These circuits are fundamental components in several electronic systems, particularly those involving filtering, oscillation, and signal processing.
Inductance value – It is the property of a coil which causes it to induce a back electromotive force (EMF) in response to a change in current, measured in henries (H). A circuit has an inductance of one henry when the induced back EMF is 1 volt for a current change of 1 ampere per second.
Induction – It refers to a rapid, non-contact heating process which uses electro-magnetic induction to generate heat directly within an electrically conductive material. It is widely used in manufacturing for heat treatment, melting, welding, and brazing since it is clean, efficient, and highly controllable.
Induction bonding – It is a secondary joining process for thermoplastic composite parts in which a metallic susceptor is placed in the bond line and an induction coil is used to heat the joint above the melt temperature of the thermoplastic matrix.
Induction brazing – It is a brazing process in which the heat needed is got from the resistance of the work-pieces to induced electric current.
Induction coil – It is a type of electrical transformer, which is used to produce high-voltage pulses from a low-voltage direct current supply. To create the flux changes it is necessary to induce voltage in the secondary coil, the direct current in the primary coil is repeatedly interrupted by a vibrating mechanical contact called an interrupter.
Induction factor (alpha) – It is a dimensionless parameter measuring the reduction in wind speed as it passes through a rotor, defined as the ratio of velocity drop to free-stream velocity: alpha = (Vfreestream – Vrotor)/ Vfreestream. It is important for determining blade twist and designing efficient turbines, typically ranging from 0 to 1.
Induction furnace – Induction furnace consists basically of a crucible, inductor coil, and shell, cooling system and tilting mechanism. The crucible is formed from refractory material, which the furnace coils is lined with. This crucible holds the charge material and subsequently the melt. The choice of refractory material depends on the type of the charge and basically consist of either acidic, basic or neutral refractories. Induction furnace is an alternating current electric furnace in which the main conductor is coiled and generates, by electro-magnetic induction, a secondary current which develops heat within the metal charge.
Induction generator – It is a type of generator where the rotating field winding is excited by induction from the stationary armature winding.
Induction-hardened steels – These are ferrous components surface-hardened by rapid electro-magnetic heating and immediate quenching, transforming the surface micro-structure to martensite. This metallurgical process increases surface hardness and wear resistance while maintaining a ductile, tough core. It is highly localized, allowing for specific area hardening.
Induction hardening – It is a surface-hardening process in which only the surface layer of a suitable ferrous work-piece is heated by electro-magnetic induction to above the upper critical temperature and immediately quenched.
Induction heating – It is the heating by combined electrical resistance and hysteresis losses induced by subjecting a metal to the varying magnetic field surrounding a coil carrying alternating current.
Induction heating coil – It is also called inductor. It is an electrical component, typically made of copper tubing, which produces a high-frequency, time-varying magnetic field when alternating current (AC) passes through it. This magnetic field induces eddy currents within an electrically conductive work-piece, heating it directly through Joule heating (resistance) without direct contact.
Induction heating – surface quenching – It is a metallurgical heat treatment process which uses electro-magnetic induction to rapidly heat the surface layer of a conductive metal part above its transformation temperature (austenite range). The part is immediately quenched, normally with water, oil, or polymer, to produce a hard, wear-resistant surface (martensite) while maintaining a tough, ductile core.
Induction melting – It is the melting in an induction furnace.
Induction logging – It is an electro-magnetic borehole surveying method used to measure the electrical conductivity (and resistivity) of geological formations. It utilizes a transmitter coil to induce alternating eddy currents in the formation, which are then measured by receiver coils to determine subsurface hydrocarbon saturation, especially in non-conductive (oil-based or empty) muds.
Induction machine – It is an asynchronous alternating current (AC) electrical machine which converts electrical energy into mechanical energy (motor) or vice-versa (generator) using electro-magnetic induction. The stator winding, when excited by AC, creates a rotating magnetic field which induces rotor current, causing the rotor to spin at a speed less than the synchronous speed.
Induction motor – It is a type of motor where the rotating field winding is excited by induction from the stationary armature winding. The induction motor is an alternating current motor which differs in several ways from the direct current motor, but works on the same principle. Analysis indicates that the stator flux and the rotor flux rotate in synchronism in the air gap, and the two flux distributions are displaced from each other by a torque-producing displacement angle. The torque is produced because of the tendency of the two flux distributions to align with each other. It is highlighted at the outset that alternating current motors are not fundamentally different from direct current motors. Their construction details are different, but the same fundamental principles underlie their operation. The induction motor is the most rugged and the most widely used motor in the industry. Like the direct current motor, the induction motor has a stator and a rotor mounted on bearings and separated from the stator by an air gap. However, in the induction motor, both stator winding and rotor winding carry alternating current. The alternating current is supplied to the stator winding directly and to the rotor winding by induction, hence the name induction motor. In induction motor, the stator windings serve as both armature windings and field windings. When the stator windings are connected to an alternating current supply, flux is produced in the air gap and revolves at a fixed speed known as synchronous speed. This revolving flux induces voltage in the stator windings as well as in the rotor windings. If the rotor circuit is closed, current flows in the rotor winding and reacts with the revolving flux to produce torque. The steady-state speed of the rotor is very close to the synchronous speed. The rotor can have a winding similar to the stator or a cage-type winding. The latter is formed by placing aluminum or copper bars in the rotor slots and shorting them at the ends by means of rings.
Induction period – It is the time which elapses between achieving super-saturation and the first detection of a precipitate, influenced by factors such as temperature, mixing intensity, and impurities. It consists of three components namely the time to reach a quasi-steady-state distribution of embryos, the time needed to form nuclei, and the time required for nuclei to grow to detectable sizes.
Induction phase – It normally refers to the initial, preparatory, or lag period before a primary action occurs, such as in chemical reactions (time before substantial reaction) or the startup of an induction motor. It specifically refers to the creation of an electromotive force (EMF) through a magnetic field.
Induction pressure welding – It is a solid -welding, obtained by the use of high frequency induction heating and by simultaneous application of pressure. Oxidation is avoided by purging with hydrogen gas. The surfaces to be joined are heated by induction current produced by an inductor in series with two capacitors, powered by a transformer with two high frequency alternators. The induced current flows in a longitudinal loop along the edges to be welded, heating them uniformly through their thickness over a certain length. Forging rolls, then weld together the fused lips, leaving a slight external flash, which is removed afterwards. The normal speed of welding depends on the power supplied. Induction pressure welding is extensively used in joining boiler grade chromium-molybdenum steel tubes.
Induction regulator – It is a kind of variable transformer which provides stepless control of the output by changing the coupling between two coils.
Induction sintering – It is the sintering in which the needed heat is generated by subjecting the compact to electro-magnetic conduction.
Induction skull melting – It is also known as cold crucible induction melting (CCIM). It is a specialized technique for melting metals, particularly reactive metals like titanium, zirconium, and their alloys. It utilizes a water-cooled copper crucible divided into segments, with an induction coil placed around it. The process involves creating a ‘skull’ layer of solidified metal between the molten metal and the crucible, preventing contamination of the melt.
Induction soldering – It is a soldering process in which the heat needed is got from the resistance of the work-pieces to induced electric current.
Induction tempering – It is the tempering of steel using low-frequency electrical induction heating.
Induction time – It is the lag phase between the initiation of a process (e.g., mixing reactants, setting environmental conditions) and the first detectable appearance of a product, change in system properties, or start of a rapid reaction. It represents a metastable state where significant, accelerated transformations have not yet occurred.
Induction turbine – This is the turbine in which low pressure steam is introduced at an intermediate stage for the production of additional power.
Induction unit – It is an HVAC (heating, ventilation, and air conditioning) terminal device which uses high-velocity primary air (supplied from a central plant) to induce, mix, and circulate a larger volume of room (secondary) air over a heating / cooling coil for localized climate control. Normally installed under windows, these units provide efficient, quiet, and individualized temperature regulation without needing fans within the unit itself.
Induction welding – It is a welding process which produces coalescence of metals by the heat got from the resistance of the work-pieces to the flow of induced high-frequency welding current with or without the application of pressure. The effect of the high-frequency welding current is to concentrate the welding heat at the desired location.
Induction work coil – It is the inductor used in the processes of induction heating and melting as well as induction welding, brazing, and soldering.
Inductive charger – it is a device which transfers electrical energy to electric vehicles (EVs) through magnetic induction, utilizing a main winding in the charger and a secondary winding in the vehicle inlet, enabling contactless charging with high efficiency and safety in different weather conditions.
Inductive coupling – It is a method of wireless energy or signal transfer between two circuits through a shared alternating magnetic field, created by mutual inductance (M). It occurs when changing current in one coil induces a voltage in a nearby coil, normally applied in transformers, RFID (Radio-Frequency Identification) systems, and contactless charging.
Inductive effect – It is a permanent, distance-dependent phenomenon in chemistry where electron density shifts along a chain of atoms (sigma-bonds) because of the electro-negativity difference between atoms or groups. It causes polarization, inducing partial positive (delta plus) or negative (delta negative) charges on neighbouring atoms, important for determining molecular stability, reactivity, and physical properties.
Inductive heating – It is defined as a technique where electrically conductive materials are heated by being placed in a variable magnetic field generated by an inductor, which induces eddy currents which dissipate heat because of the Joule effect.
Inductive load – It is an AC electrical component or device containing coils (inductors) which uses electro-magnetic fields to function, causing the current waveform to lag behind the voltage waveform. These loads, such as motors, transformers, and solenoids, consume both real and reactive power, resulting in a lagging power factor.
Inductively coupled plasma (ICP) – It is an argon plasma excitation source for atomic emission spectroscopy or mass spectroscopy. It is operated at atmospheric pressure and sustained by inductive coupling to a radio-frequency electromagnetic field.
Inductively coupled plasma (ICP) spectroscopy – It is a powerful analytical technique which uses an extremely hot argon plasma (around 10,000 K) to atomize and excite elements in a metal sample, allowing for the precise identification and quantification of metallic and non-metallic elements, including trace impurities, by measuring the specific light wave-lengths (Inductively coupled plasma – optical emission spectrometry, ICP-OES) or ion masses (Inductively coupled plasma – mass spectrometry, ICP-MS) they emit or form as they return to a ground state, important for quality control, alloy development, and understanding material composition.
Inductively coupled plasma atomic emission spectrometry (ICP/AES) – It is an analytical technique used for the detection of trace elements. It uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic at wavelengths characteristic of a particular element. The intensity of this emission is indicative of the concentration of the element within the sample. Inductively coupled plasma atomic emission spectrometer consists of two parts namely (i) the inductively coupled plasma, and (ii) the optical spectrometer. The inductively coupled plasma torch consists of 3 concentric quartz glass tubes. The output of the radio frequency generator surrounds part of this quartz torch. Argon gas is typically used to create the plasma. The radio frequency generated and maintained argon plasma, portions of which are as hot as 10,000 deg K, excites the electrons. The plasma is used to atomize and ionize the elements in the sample. When the electrons return to ground state at a certain spatial position in the plasma, they emit energy at the specific wave-lengths peculiar to the elemental composition of the sample. Light emitted from the plasma is focused through a lens and passed through an entrance slit into the spectrometer. There are two types of spectrometers used in the inductively coupled plasma atomic emission spectrometer analysis. These are namely (i) sequential (mono-chromator), and (ii) simultaneous (poly-chromator). Inductively coupled plasma mass spectrometry (ICP-MS) is a very powerful tool for trace (ppb, parts per billion-ppm) and ultra-trace (parts per quadrillion -parts per billion) elemental analysis.
Inductively coupled plasma – mass spectrometry – It is a powerful analytical technique which uses an extremely hot argon plasma (around 6,000 K to 10,000 K) to atomize and ionize a liquid sample, then separates and detects these ions by their mass-to-charge ratio, allowing for precise quantification of most elements, even at ultra-trace (parts per trillion or lower) concentrations. It is necessary for environmental monitoring, and geo-chemistry, offering high sensitivity, multi-element detection, and isotopic analysis capabilities.
Inductively coupled plasma – optical emission spectrometry – It is a powerful analytical technique which uses a superheated argon plasma (6,000 K to 10,000 K) to excite atoms in a liquid sample, causing them to emit light at specific wave-lengths, which a spectrometer measures to determine the concentration of elements present, ideal for multi-element analysis in environmental, and material science.
Inductive power transfer – It is a method of transferring electrical energy wirelessly from a transmitter to a receiver using a magnetic field, normally operating within 10 kilo-hertz to 250 kilo hertz. It uses magnetically coupled coils (a loosely coupled transformer) without direct contact, relying on Faraday’s law of induction to move power across an air gap.
Inductive power transmission – It is a method of transferring power wirelessly from a source to a receiver using electromagnetic induction. It has been utilized in different applications, particularly for electric vehicle charging, allowing for contactless power transfer across different power levels.
Inductive output tube – It is a high power, high frequency amplifier tube, which in some forms is capable of megawatt pulses at hundreds of mega-hertz.
Inductive reactance (Xl) – It is the opposition an inductor presents to a change in alternating current (AC), measured in ohms, acting like resistance but varying with frequency (f) and inductance (L) through the formula ‘Xl = 2pi F x L’, where higher frequency or inductance means higher opposition, causing current to lag voltage by 90 degrees in a purely inductive circuit.
Inductor – It is a device consisting of one or more associated windings, with or without a magnetic core, for introducing inductance into an electric circuit.
Inductor design – It is the systematic process of creating a passive magnetic component which stores energy or limits alternating current, involving the selection of magnetic core materials (ferrite, iron), shapes, sizes, and winding configurations to meet specific inductance, current, and frequency requirements based on electromagnetic principles.
Induration – During the induration, heat hardening of green pellets is carried out. Induration of green pellets consists of three main steps namely (i) drying of green pellets, (ii) firing of pellets at around 1300 deg C to sinter the iron oxide particles, and (iii) cooling of hot pellets before discharging.
Industrial accident – It is an unintended event due to an unsafe act or unsafe condition or a combination of both, which may or may not result in property damage, personal injury, work interruption, product damage or a combination of these.
Industrial air conditioning – It is an engineering system designed to control temperature, humidity, air quality, and air purity in manufacturing plants, data centres, and industrial facilities. It focuses on enabling precise production processes and equipment reliability rather than human comfort, frequently operating 24/7 with high-capacity, heavy-duty equipment.
Industrial applications – These refer to the use of systems and technologies in different sectors such as process control, manufacturing automation, and energy management, frequently involving advanced methods for controlling processes and operations in different industries.
Industrial ashes – These are defined as the residues produced from the combustion of traditional and renewable fuels in energy power plants, which include coal ashes, biomass ashes, and solid waste ashes. Their management is important because of the potential environmental hazards, toxicity, and the need for sustainable disposal or conversion into valuable products.
Industrial atmosphere – It is an atmosphere in an area of heavy industry with soot, fly ash, and sulphur compounds as the principal constituents.
Industrial automation – It is the general practice of automatic control applied to industrial operations.
Industrial automation and control systems – These are integrated systems of hardware (sensors, programmable logic controller, PLCs), software, and personnel which use feedback loops and data to monitor, control, and optimize industrial processes automatically, minimizing human intervention for higher efficiency, quality, safety, and consistency in production. Industrial automation and control systems manage everything from simple tasks to complex plant-wide operations, acting as the ‘brains’ and ‘nervous system’ for modern manufacturing and utilities.
Industrial batteries – These are heavy-duty, rechargeable, or main electro-chemical devices engineered for high-capacity energy storage, designed to withstand rigorous, continuous, or standby use in demanding environments (e.g., forklifts, uninterruptible power supply systems). They are characterized by long lifespans, high energy density, and structural durability against vibrations and temperature extremes.
Industrial boiler – It is an enclosed pressure vessel which uses fuel combustion (gas, oil, coal, biomass) or electricity to heat water or generate steam for industrial processes, power generation, and heating. Engineered for high-pressure and high-temperature operations, they function as heat exchangers, separating hot combustion gases from water to produce high-pressure steam or hot water.
Industrial buildings – These are specialized, large-scale structures designed to house manufacturing, production, assembly, and warehousing activities. Engineered for heavy loads, efficiency, and safety, they feature high ceilings, open floor plans, and durable materials, serving as critical infrastructure for industrial operations.
Industrial chromium plating – It is produced by electro-deposition from a solution containing chromic acid (CrO3) and a catalytic anion in proper proportion. The metal so produced is extremely hard and corrosion resistant. The process is used for applications where excellent wear and / or corrosion resistance is needed. This includes products such as piston rings, shock absorbers, struts, brake pistons, engine valve stems, cylinder liners, and hydraulic rods. Other applications are for aircraft landing gears, textile and gravure rolls, plastic rolls, and dies and moulds.
Industrial cluster – It is a geographic concentration of interconnected organizations, specialized suppliers, service providers, and associated institutions (like universities or trade associations) in a particular field, designed to improve productivity, innovation, and competitiveness. They leverage proximity for shared infrastructure, labour pools, and knowledge spillovers.
Industrial complex – It is an integrated network of functionally related industrial organizations, production units, and infrastructure located in a specific, concentrated area. These complexes optimize production through close, frequently symbiotic, input-output links, such as refineries, pipelines, and supply chains, to improve efficiency, reduce costs, and facilitate large-scale manufacturing.
Industrial computed tomography – It is, in a general sense, is an imaging technique which generates an image of a thin, cross-sectional slice of a test piece. The computed tomography imaging technique differs from other imaging methods in that the energy beam and the detector array in computed tomography systems lie in the same plane as the surface being imaged. This is unlike typical imaging techniques, in which the energy beam path is perpendicular to the surface being imaged. Moreover, since the plane of a computed tomography image is parallel with the energy beam and detector scan path, computed tomography systems need a computing procedure to calculate, locate, and display the point-by-point relative attenuation of the energy beam passing through the structures within the thin, cross-sectional slice of the test piece.
Industrial conditions – These refer to the specific, frequently harsh, operational environments, parameters, and mechanical states (e.g., temperature, pressure, lubrication, vibration) within manufacturing or processing settings. These factors are critical to monitor as they directly influence equipment reliability, material degradation, process efficiency, and product quality.
Industrial control – It refers to the use of integrated hardware, software, and networking components (such as programmable logic controllers, supervisory control and data acquisition, and distributed control system) to monitor, automate, and manage physical industrial processes, manufacturing, or critical infrastructure. Engineering these systems ensures safe, efficient, and precise operation by connecting sensors to control elements.
Industrial control panel enclosures – These are robust, protective cabinets which serve as a centralized location for housing various electrical components. These include, but are not limited to switches, drives etc.
Industrial control system – It is an electronic control system and associated instrumentation which is used for industrial process control. Control systems can range in size from a few modular panel-mounted controllers to large interconnected and interactive distributed control systems with several thousands of field connections. Control systems receive data from remote sensors measuring process variables, compare the collected data with desired set-points, and derive command functions that are used to control a process through the final control elements, such as control valves.
Industrial crystallization – it is a unit operation and separation technology which produces pure solid crystals from a liquid solution or melt by creating a super-saturated state. It is widely used in different industries to achieve specific product quality metrics, including crystal size distribution, shape, structure, and purity.
Industrial data – It refers to the specialized process of structuring, standardizing, and providing context to the vast, heterogeneous, and frequently chaotic data generated by industrial machinery, sensors, and operational systems. It is a critical subset of industrial data engineering which transforms raw data, such as temperature, pressure, or vibration readings, into a meaningful, actionable format, frequently creating a ‘digital twin’ of physical assets.
Industrial design – It is the first broadly functional description of a product with emphasis on visual and aesthetic features (shape, colour, texture).
Industrial design engineering – It is a multidisciplinary field merging engineering, design thinking, and user experience to develop mass-produced products which are functional, ergonomic, aesthetically pleasing, and manufacturable. It transforms concepts into, sustainable, and efficient, market-ready solutions by combining technical analysis with user-focused innovation.
Industrial designer – Industrial designer is a professional who blends artistic creativity with technical engineering principles to develop functional, aesthetic, and mass-producible products. They bridge the gap between user needs and manufacturing feasibility, focusing on form, ergonomics, materials, and user experience. These designers collaborate with engineers to ensure products are both visually appealing and structurally sound.
Industrial development – It is the strategic process of increasing manufacturing capacity, productivity, and infrastructure through technological advancement. It involves optimizing integrated systems, people, materials, information, equipment, and energy, to create efficient, sustainable, and high-quality production systems, mainly aimed at economic growth.
Industrial discharge – It refers to the release of liquid, solid, or gaseous waste products, pollutants, and contaminants from manufacturing or processing facilities into the environment (water, air, or soil). Engineered systems treat these effluents to remove heavy metals, toxic chemicals, and suspended solids before disposal.
Industrial ecology – It is an engineering and systems-based approach which studies material and energy flows through industrial processes, aiming to minimize environmental impact by mimicking natural ecosystems. It seeks to create closed-loop systems, where waste becomes raw material, to optimize resource use, reduce emissions, and promote sustainable industrial development.
Industrial ecology concept – It is an approach to industrial design and manufacturing which promotes environmental sustainability by optimizing the total materials cycle, from raw material extraction to waste disposal, while minimizing material waste and pollutants.
Industrial electrical control panels – These panels are a special type of assembly which contains at least two power circuits, control circuits, or any combination of power and control circuit components. These panels are factory-based wired assemblies of industrial control equipment, such as motor controllers, switches, relays, and auxiliary devices which control equipment in the industrial environment. These types of industrial control panels can include a means of disconnecting that which it is powering, as well as a protective device of the branch-circuit. Industrial control panels are intended for general-use industrial applications for the control of industrial machineries, lighting, motors, or pump loads or a combination of these loads, and are intended for installation in ordinary locations.
Industrial electronics – It is a specialized branch of engineering which applies electronic devices, circuits, and systems to control, automate, and optimize industrial processes and machinery. It focuses on robust, high-power, and high-reliability systems, encompassing power electronics, motor drives, sensors, and programmable logic controllers to improve productivity and efficiency in manufacturing, energy, and, mining sectors.
Industrial energy conservation – It consists of the strategic, technical process of reducing energy consumption per unit of output without sacrificing production volume or quality. It involves optimizing systems, such as motors, boilers, and furnaces, through efficiency improvements, waste minimization, and technology upgrades to reduce costs and environmental impact.
Industrial energy consumption – It refers to the total thermal and kinetic energy needed by the manufacturing, mining, and construction sectors for production, processing, and assembly. It represents the energy used for heating, cooling, mechanical power, and raw material feedstock. This important metric quantifies the intensity of energy usage relative to output to drive efficiency and lower carbon emissions.
Industrial energy efficiency – It is the engineering practice of minimizing energy input needed to produce a unit of output (e.g., giga-joules per ton) by optimizing processes, equipment performance, and system design, while maintaining productivity. It involves utilizing advanced technologies, such as waste heat recovery and high-efficiency motors, to reduce energy costs and emissions.
Industrial energy systems – These are structured engineering frameworks designed for the generation, distribution, and utilization of energy within manufacturing plants and industrial facilities. They integrate primary energy sources, conversion processes, and end-user demands, focusing on optimizing efficiency, reliability, and cost-effectiveness. These systems, including electrical, steam, and thermal, frequently involve complex, large-scale networks tailored to specific industrial processes.
Industrial engineer – Industrial engineer is a professional who optimizes complex processes, systems, or organizations by integrating people, money, knowledge, information, equipment, energy, and materials. They focus on increasing efficiency, reducing waste, and improving productivity and quality across manufacturing, safety and healthcare, logistics, and service industries.
Industrial engineering – It is an engineering discipline which is concerned with the optimization of complex processes, systems, or organizations by developing, improving and implementing integrated systems of people, money, knowledge, information and equipment. It is central to manufacturing operations. Industrial engineering personnel use specialized knowledge and skills in the mathematical, physical, and social sciences, together with engineering analysis and design principles and methods, to specify, predict, and evaluate the results obtained from systems and processes.
Industrial environment – It is a specialized, frequently harsh, operational setting, such as manufacturing plants, warehouses, or processing facilities, characterized by extreme conditions like high heat, humidity, vibration, and chemical exposure. It involves integrated systems of people, materials, equipment, and energy, focusing on production, safety, and regulatory compliance.
Industrial equipment – It refers to heavy-duty, durable machinery, tools, and systems designed for manufacturing, processing, extracting, or constructing products and materials. These, including machine tools, and specialized apparatus, are engineered for efficiency, speed, and precision in industrial, or utility settings.
Industrial ergonomics – It is a sub-field of engineering. It is the scientific discipline of designing industrial work-places, tools, tasks, and environments to fit the physical and cognitive capabilities of workers. It focuses on optimizing human well-being, reducing physical strain, and preventing work-related musculoskeletal disorders (WMSDs) by minimizing risks like awkward postures and repetitive motions.
Industrial estate – It is a specially planned, zoned tract of land designed for, and developed to accommodate, a cluster of industrial organizations. It offers standardized, pre-built factory buildings, necessary infrastructure (power, water, transportation), and shared services to promote economic growth, efficiency, and environmental management.
Industrial experiment – It is a structured, purposeful investigation conducted within an organization, frequently directly on production systems, to evaluate, optimize, or improve processes and product quality. Utilizing techniques like ‘design of experiments’ (DOE), these trials manipulate input variables to analyze their impact on output performance, replacing traditional trial-and-error methods.
Industrial exposure – It refers to the practical, hands-on experience a trainee / apprentice gains by directly engaging with real-world industrial environments, processes, and technologies outside the classroom. It bridges the gap between theoretical academic knowledge and industry standards, fostering technical, soft, and managerial skills necessary for a successful engineering career.
Industrial fans and blowers – These are machines, whose primary function is to provide a large flow of air or gas to various processes. This is achieved by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine. The flow rates of these fans range from around 5.7 cubic meter per minute to 57,000 cubic meter per minute. A blower is another name for a fan which operates where the resistance to the flow is primarily on the downstream side of the fan.
Industrial furnace – It is an engineered, high-temperature thermal processing unit used to heat, melt, or treat materials, typically above 400 deg C to 650 deg C, through fuel combustion or electrical energy. Important for metallurgy, ceramics, and chemical processing, these units consist of a refractory-lined chamber, heating source, and control systems to ensure uniform, large-scale heating.
Industrial gases – The term ‘Industrial gas’ is referred to a group of gases which are specifically produced for use in a variety of industrial processes. They are distinct from the fuel gases. However, acetylene is sometimes considered as industrial gas. Speciality gases such as neon, krypton, xenon and helium are sometimes considered under the category of industrial gases. Industrial gases are produced and supplied in both gas and liquid form and transported in cylinder, as bulk liquid or in pipelines as gas. Common industrial gases normally used in industry are oxygen, nitrogen, argon, and hydrogen.
Industrial gas turbine – It is a rotary internal combustion engine which converts fuel chemical energy into continuous mechanical shaft power or electrical energy, typically for power generation or industrial processes. It operates on the Brayton cycle, comprising a compressor, combustor, and turbine, frequently running on natural gas with efficiencies up to 60 % in combined cycles.
Industrial heat process – It refers to the deliberate application of thermal energy, generated from fuel combustion or electricity, to raw materials for manufacturing, treating, or modifying goods. It covers diverse operations like drying, melting, curing, and steaming across sectors such as steel, and chemicals production. These processes typically fall into low ( less than 400 dg C), medium (400 deg C to 1,150 deg C), and high (higher than 1,150 deg C) temperature ranges.
Industrial heat treatment – It is a controlled process of heating metal components to specific, pre-determined temperatures (frequently up to 1315 deg C) for steel), holding them at that temperature to achieve a desired, uniform metallurgical microstructure (soaking), and then cooling at controlled rates to alter physical / mechanical properties.
Industrial hygiene – It deals with work-place conditions to prevent workers from injury or illness. Chemical hazards, especially toxic hazards, are one of the main health concerns in the work-place. Hazardous chemicals in the work-place are to be accordingly identified, evaluated, and controlled to ensure safety and health in the work-place. Chemicals can be hazardous because of their toxic (health), physical, and environmental properties.
Industrial injury – An injury arising from an industrial accident which occurs whilst a person is working for the organization or on the organization’s premises for purposes in connection with or arising out of and in the course of the person’s work, but which may not necessarily result in absence from work.
Industrial instruments – These are specialized devices, sensors, and systems used in engineering to measure, monitor, and control physical process variables, such as pressure, temperature, level, and flow, within industrial environments. They act as the “nervous system” of manufacturing plants, ensuring safe, efficient, and consistent operation. Key components include sensors, transmitters, controllers, and final control elements like valves.
Industrial Internet of Things – It refers to the application of Internet of Things (IoT) technologies in industrial settings, focusing on connecting machines, devices, and systems to improve efficiency, productivity, and safety. It is basically a network of interconnected devices within industrial operations that gather and exchange data to optimize processes, predict maintenance needs, and improve overall performance.
Industrial laboratories – These are specialized facilities within engineering and manufacturing sectors designed for research, development, testing, and quality control of products and processes. Staffed by engineers and scientists, they bridge bench-top innovation with commercial production, focusing on optimizing materials, improving efficiency, ensuring safety compliance, and solving technical problems.
Industrial lasers – These are high-power, precision optical devices used in manufacturing for material processing, specifically cutting, welding, marking, drilling, and cleaning. They operate on stimulated emission principles, providing non-contact, high-speed, and automated precision, considerably improving efficiency in different industries.
Industrial machinery – It refers to heavy, specialized mechanical equipment, tools, and automated systems used for manufacturing, processing, power generation, and construction. Engineered for high durability, efficiency, and safety, these devices are designed to transform raw materials into finished products.
Industrial minerals – These are non-metallic, non-fuel minerals used in the chemical and manufacturing industries. Examples are asbestos, gypsum, salt, graphite, mica, gravel, building stone, and talc etc.
Industrial network – It is the specialized communication infrastructure linking sensors, controllers, and machinery within industrial environments (e.g., factories) to enable real-time automation, data exchange, and control. It acts as the backbone for process automation, designed to withstand harsh, high-interference environments while ensuring reliability, safety, and interoperability between multi-vendor devices.
Industrial park – It is a master-planned area of land, engineered to support manufacturing, logistics, and, research, or service activities by grouping firms within a common, serviced, and secured infrastructure ecosystem. It features, specialized, pre-developed, or ready-built factory plots equipped with necessary utilities, power, water, waste management, and digital connectivity, designed to improve operational efficiency, reduce costs, and, ensure regulatory compliance.
Industrial power system – It is a specialized electrical network designed to generate, distribute, and utilize electrical energy within factories, plants, and large facilities. Engineered for high reliability, efficiency, and heavy-duty loads, these systems typically utilize three-phase alternating current power, incorporating transformers, switchgear, motors, and backup power to ensure continuous operation.
Industrial process heat system – It is an engineered assembly of equipment designed to generate, transfer, and apply thermal energy for transforming raw materials into finished products. These systems operate through combustion (fuels), electrical resistance, or steam to facilitate processes like melting, drying, and chemical reactions, focusing on maximizing efficiency and temperature control.
Industrial processing – It is the large-scale, systematic transformation of raw materials into finished products through chemical, physical, mechanical, or electrical procedures. It focuses on improving efficiency, optimizing production, and ensuring quality, spanning from raw material acquisition to final inventory storage.
Industrial production – It is the systematic process of manufacturing goods on a large scale by transforming raw materials into finished products using automated machinery, robots, and computers. It focuses on optimizing material, energy, and information flows to improve productivity, quality, and cost-efficiency.
Industrial research – It is the planned, systematic investigation aimed at acquiring new knowledge or skills to develop or considerably improve products, processes, or services. It focuses on practical applications to meet organizational goals by creating prototypes, pilot lines, or testing new technologies.
Industrial robot – It is an automatically controlled, reprogrammable, multipurpose manipulator with three or more axes, designed to perform tasks such as material handling, welding, painting, and assembly in industrial environments. These machines are defined by their high speed, precision, and repeatability, and can be fixed or mobile.
Industrial scrap – It refers to leftover, unusable, or defective material generated during manufacturing, cutting, and shaping processes, which can be reused as raw material for new products, distinguishing it from general waste because of its inherent material value, frequently categorized as ‘prompt’ (new) or ‘obsolete’ (old) scrap, like metal shavings, offcuts, or rejected parts.
Industrial situation – It refers to the circumstances, conditions, or context within an industrial environment, frequently relating to operational, safety, or labour-related matters. It can signify a state, such as a potential hazard needing preventive action, or a specific, contextual, environment characterized by complex machinery, manufacturing, or stringent safety protocols.
Industrial solid waste treatment – It is the systematic process of collecting, handling, processing, recycling, and disposing of solid by-products generated by manufacturing, or mining activities. It aims to reduce waste volume and toxicity, mitigate environmental pollution, protect human health, and, when possible, convert waste into usable materials.
Industrial spray coatings – These are normally referred to as thermal spraying or metallizing. These are a group of surface coating processes which involve depositing heated or molten materials (metals, alloys, ceramics, or cermets) onto a substrate (base material) to form a protective or functional layer. These coatings are used to improve surface properties such as corrosion resistance, wear resistance, erosion protection, heat resistance, and electrical conductivity, or to restore dimensions on worn or damaged components.
Industrial steam turbine – It is a rotary engine which converts thermal energy from high-pressure, high-temperature steam into rotational mechanical energy. Acting as a prime mover, it drives equipment like generators, pumps, and compressors for power generation, and industrial processes. It operates using impulse or reaction principles to spin a rotor, making it a critical component for driving industrial machinery and utility-scale electricity production.
Industrial symbiosis – It is a systems-oriented concept which stems from the view that industrial systems are not to be designed in isolation from their surroundings but in relation to all the systems in the surrounding as well as the environment. It promotes the exchange of resources, materials, and energy through a network of industries resulting in closed-loop inter-dependent relationships between systems, and transforms systems toward replicating the self-sustaining capability of nature. The main objective of this method is to mimic the cyclic transformation of materials as in ecological systems as opposed to linear transformation of materials which takes place through the economy. It also promotes some key aspects like driving technological innovation as a means to solve environmental challenges, adopting a life cycle perspective to avoid overlooking key aspects of design and promotes dematerialization and eco-efficiency to reduce consumption of resources. These approaches also aim to shift the focus from minimizing wastes of individual facilities (pollution prevention) to minimizing wastes produced by the system as a whole. Industrial symbiosis pathways can include utilization of wastes and by-products as feedstocks for other industries, closed-loop recovery of metals and scraps, conversion of wastes to energy and recycling post-consumer waste.
Industrial system – It is an organized, integrated network consisting of inputs, processes, and outputs which converts raw materials, labour, and infrastructure into finished products. These systems, common in manufacturing, utilize technology, energy, and machinery to transform resources into goods while aiming for optimal quality, safety, and efficiency.
Industrial trial – It is a large-scale, real-world simulation or test conducted within a manufacturing environment to evaluate the feasibility, performance, and scalability of a new product or process. These trials use actual production equipment and resources to validate recipes, ensure product consistency, and verify operational efficiencies before full-scale commercialization.
Industrial user – It is a non-domestic entity, such as a factory, organization, or facility, which discharges wastewater, pollutants, or processed materials into a public sewer system, frequently involved in manufacturing, mining, or, in some cases, services. They are typically defined by their non-residential, high-volume, or hazardous waste output and are to comply with specific national, state, and local environmental pre-treatment standards.
Industrial ventilation – It is a mechanical system designed to move, supply, and exhaust air to control work-place environments by removing contaminants like dust, fumes, vapors, and gases. It protects workers by maintaining safe air quality, controlling heat and humidity, and preventing fires or explosions. It includes local exhaust (capturing at source) and dilution ventilation.
Industrial waste – It refers to any unwanted or unusable material resulting from industrial processes, activities, or production, which can be solid, liquid, or gaseous.
Industrial waste heat – It is the thermal energy generated as a by-product of industrial processes (such as manufacturing, fuel combustion, and chemical reactions) which is not utilized and is typically rejected into the environment through exhaust gases, cooling water, or radiation. It represents untapped energy which, if recovered, can improve energy efficiency, reduce operating costs, and decrease carbon emissions.
Industrial waste heat recovery – It is the process of capturing and reusing thermal energy released as a by-product from industrial processes, such as exhaust gases, cooling water, or heated products, which otherwise is wasted into the atmosphere. It boosts energy efficiency, reduces carbon di-oxide emissions, and lowers costs.
Industrial waste incinerator – It is a specialized, high-temperature thermal oxidation system designed to destroy, reduce, or detoxify solid, liquid, or gaseous waste streams generated from manufacturing and processing operations. Unlike municipal waste incinerators, these units are frequently customized to handle specific, sometimes hazardous, industrial byproducts (such as contaminated solvents, sludge, or oily waste) while operating under strict regulatory standards for combustion efficiency (frequently exceeding 99.99 % destruction efficiency).
Industrial wastewater – Industrial wastewater also sometimes called effluent is the aqueous discard which results after the water is used for the industrial purposes. Industrial wastewater is the result of different substances which get dissolved or suspended in water during its used. Industrial wastewater means the water or liquid which carries waste from industrial processes. It can result from any process or activity of industry which uses water as a reactant or for transportation of heat or materials. Industrial wastewater frequently presents physico-chemical characteristics which need treatment before its release to the environment or the sewer system. Further, a number of different industrial activities contribute to emissions of heavy metals, with the majority of industrial releases originating from metal processing facilities (iron and steel, and non-ferrous metals production).
Industrial wastewater treatment – It refers to the systematic processes used to remove harmful contaminants, toxins, and pollutants from by-product water (effluent) generated by manufacturing, mining, and other industrial activities. The objective is to purify wastewater to meet environmental regulations, protect ecosystems, and enable water reuse or safe discharge into sewers or water bodies.
Industrial water treatment – It is the process of managing, purifying, and conditioning water used in industrial activities, including raw intake, process water, and wastewater. It utilizes physical, chemical, and biological methods to remove contaminants, ensuring compliance with environmental discharge regulations, enabling water reuse, and preventing damage to equipment like boilers and cooling towers.
Industrial water use – It refers to water consumed by industries for manufacturing, processing, cooling, sanitation, and transporting products, encompassing both self-supplied withdrawals and public-supply deliveries. It includes water used in mining, energy generation, and manufacturing, frequently resulting in substantial consumption for, or pollution during, production operations.
Industrial worker – Industrial worker is an individual employed in manufacturing, mining, construction, or production units, frequently in a manual, skilled, or unskilled capacity to produce or process goods. They work directly in manufacturing processes or related, incidental tasks, such as handling, cleaning, or repairing machinery, typically within factories, and are normally not part of management.
Industry consensus standard – It is a voluntary, non-government guideline developed through a collaborative, balanced process involving stakeholders (industry experts, consumers, government) to establish best practices for product, process, or service quality and safety. While voluntary, they are frequently used by regulatory agencies to define industry standards.
Industry restructuring – It is the strategic, large-scale reorganization of an economic sector to improve efficiency, competitiveness, or adapt to changes like new technology or regulations. It involves shifting resources, altering production methods, or changing corporate structures to address under-performance, declining productivity, or market shifts.
Industry sector – It consists of distinct categories of economic activity which influence project development and implementation strategies, characterized by unique cultures, historical developments, and applicable codes and standards. Examples include oil and gas, water / wastewater, mining, metal, power generation, and infrastructure.
Industry stakeholders – Industry stakeholders are any individuals, groups, or organizations which have a vested interest in or are affected by an organization’s or industry’s activities, decisions, and outcomes, including customers, employees, investors, suppliers, communities, governments, and regulators. They can influence or be influenced by the organization’s success, performance, and profitability, with interests ranging from financial returns to social and environmental impacts.
Industry standard – It is a widely accepted benchmark, guideline, or requirement for products, practices, or processes within a specific field, ensuring quality, consistency, safety, and interoperability, frequently developed by industry experts and followed voluntarily, though sometimes mandatory. It acts as a common framework, setting expectations for performance, functionality, and professional conduct, from technical specifications to operational procedures.
Ineffective length – It is the characteristic, relatively short length of a fibre in a composite material near a break where the fibre’s stress is considerably reduced or zero because of the stress redistribution to surrounding fibres. It represents the segment of fiber which cannot carry maximum load, typically defining the distance from a break point where stress builds back up to 95 % of its maximum value.
Inelastic electron scatter – It is the deflection of electrons by electrons or atoms which results in a loss of kinetic energy by the incident electron.
Inelastic electron tunneling spectroscopy – It is a highly sensitive analytical technique used to get vibrational spectra of molecules, typically in monolayer or sub-monolayer quantities, trapped within a metal-insulator-metal junction. It works by detecting small energy losses (eV = hw) in the tunneling current which correspond to specific molecular vibrations.
Inelastic materials – These are substances which do not return to their original shape, size, or structure after a deforming force (stress) is removed, resulting in permanent or plastic deformation. They show non-linear stress-strain behaviour, frequently characterized by molecules flowing, material ‘necking’ (thinning), or fracturing.
Inelastic response – It refers to the nonlinear, permanent deformation of a structure or material when subjected to loads exceeding its elastic limit, resulting in energy dissipation, yielding, and residual displacement. Unlike elastic behaviour, the system does not return to its original shape after the load is removed, often characterized by stiffness degradation.
Inelastic scattering – It is a collision or interaction which changes the energy of an incident particle.
Inelastic straining – It refers to the permanent deformation of materials, such as prestressing steels, which occurs under long-term static tensile loading, even at stress levels lower than those experienced during short-term loading. This phenomenon is influenced by factors including the applied stress value, temperature, and time.
Inelastic strain range – It is the total permanent (non-recoverable) deformation a material experiences during a loading-unloading cycle, calculated by subtracting the elastic strain component from the total strain range (delta Ein = Etotal – delta Eel). It is critical for calculating low-cycle fatigue, as it represents the plastic or creep deformation.
Inelastic strain rate – It is the time rate of change of the non-recoverable (permanent) component of deformation in a material. Unlike elastic strain, which is fully reversible upon unloading, inelastic strain represents deformation which remains after the load is removed, encompassing plastic flow, creep, and other time-dependent viscous behaviours.
Inequality constraint – It is a technical, physical, or chemical boundary condition which limits a process parameter to a specific range (e.g., ‘x’ is equal to or less than ‘y’ or ‘x’ is equal to or higher than ‘y’) to ensure the final product meets metallurgical, mechanical, or quality specifications. Unlike equality constraints (e.g., exact stoichiometry), inequality constraints provide a ‘feasible region’ or ‘operating window’ rather than a single set point, normally applied in alloy composition, heat treatment, or, refining.
Inert – The term is used to describe a substance which is not chemically reactive. From a thermodynamic perspective, a substance is inert, if it is thermodynamically unstable (positive standard Gibbs free energy of formation) yet decomposes at a slow, or negligible rate.
Inert anode – It is an anode which is insoluble in the electrolyte under the conditions prevailing in the electrolysis. It is a non-consumable, non-reactive electrode, which is used in electrolysis which does not chemically react with the electrolyte or consume itself during the process. Unlike traditional consumable carbon anodes, inert anodes (frequently made of ceramic or metallic materials) are designed to maintain their shape and mechanical integrity, with a main purpose of evolving oxygen (O2) instead of carbon di-oxide (CO2).
Inert filler – It is a material added to a plastic to alter the end-item properties through physical rather than chemical means.
Inert gas – It is a gas, such as helium, argon, or nitrogen, which is stable, does not support combustion, and does not form reaction products with other materials. In welding, it is a gas which does not normally combine chemically with the base metal or filler metal.
Inert gas arc welding – It is a non-standard term for gas metal arc welding. It is an arc welding in which coalescence of metals is produced by heating them with an arc between a continuous filler metal electrode and the work-pieces. Shielding is achieved entirely from an externally supplied inert gas.
Inert gas atomization – It is a specialized technique used to produce metal powders with a high degree of purity and uniformity. It involves the conversion of molten metal into droplets and their subsequent solidification into fine particles under the influence of an inert gas, such as nitrogen or argon.
Inert gaseous constituent – It is the incombustible gases such as nitrogen which can be present in a fuel.
Inert gas fusion – It is an analytical technique for determining the concentrations of oxygen, hydrogen, and nitrogen in a sample. The sample is melted in a graphite crucible in an inert gas atmosphere and individual component concentrations are detected by infrared or thermal conductive methods.
Inert gas purging – It is the industrial process of removing hazardous, flammable, or undesirable gases (like oxygen or hydro-carbons) from pipes, tanks, and vessels by displacing them with a non-reactive gas, typically nitrogen or carbon di-oxide. It ensures safety by eliminating ignition risks and preventing oxidation during startup, shutdown, or maintenance.
Inert gas system – It is an important safety mechanism on tankers which prevents explosions by filling empty cargo tank spaces with inert ga, normally containing less than 8 % oxygen, which displaces flammable hydrocarbon vapours. By keeping oxygen levels below the threshold for combustion, it secures the tank’s atmosphere, typically using cooled and cleaned boiler flue gas or nitrogen.
Inert gas tungsten arc welding – It is a non-standard term for gas tungsten arc welding. It is an arc welding coalescence of metals is produced by heating them with an arc between a tungsten (non-consumable) electrode and the work. Shielding is achieved from an inert gas or inert gas mixture. Pressure and filler metal may or may not be used.
Inert gas welding – It refers to an electric arc welding process which uses a dedicated tungsten electrode to create an arc across the work-piece, with a separate filler rod introduced into the weld pool, all protected by an inert gas shield.
Inertia – It a property of matter by which it remains at rest or in uniform motion in the same straight line unless acted upon by some external force. It is the natural tendency of an object in motion to stay in motion and object at rest to stay at rest, unless a force causes its velocity to change.
Inertia block in equipment foundation – It is used for small moving blocks, and equipments etc. In this situation, small dynamic equipments are normally designed with a supporting inertia block to alter natural frequencies away from equipment operating speeds and resist amplitudes by increasing the resisting inertia force.
Inertial collection – In this system, dust particles strike the fabrics placed perpendicular to the gas flow direction instead of changing direction with the gas stream.
Inertial force – It also called a fictitious, or pseudo force. It is an apparent force which acts on all mass-possessing bodies when observed from a non-inertial (accelerating or rotating) frame of reference. It acts in the opposite direction of the frame’s acceleration, calculated as the product of mass and acceleration (F = -m x a), allowing Newton’s laws of motion to be applied in that frame.
Inertial frame of reference – It is a viewpoint (coordinate system) which is either at rest or moving at a constant velocity in a straight line, where Newton’s laws of motion hold true without needing extra ‘fictitious’ forces. In such a frame, an object’s motion only changes if an external force acts on it, meaning it stays at rest or moves at a steady speed and direction unless pushed or pulled. Earth is frequently considered an approximate inertial frame for short-term, local events, but technically it is non-inertial because of its rotation and orbit, needing corrections for high-precision work.
Inertial impaction – It is a mechanism where particles collide with droplets because of their mass and velocity, leading to particle collection in gas streams, particularly effective for larger particles and smaller droplet sizes. The efficiency of this process increases with particle diameter and relative velocity between particles and droplets. It is a particle capture mechanism where larger, heavier particles in a gas stream cannot follow sharp turns in the airflow because of their inertia, causing them to fly off the streamlines and collide with nearby surfaces and get trapped.
Inertial mass – It is a fundamental property of matter which quantifies an object’s resistance to changes in its motion (inertia). The more inertial mass an object has, the harder it is to accelerate or decelerate, measured by applying a force and observing the resulting acceleration (m = F/a), distinct from gravitational mass but experimentally found to be equivalent.
Inertial measurement unit – It is a sensor system using accelerometers and gyroscopes (and frequently magnetometers) to measure an object’s 3D motion, including linear acceleration (force) and angular rate (rotation), enabling precise tracking of orientation (pitch, roll, yaw), velocity, and position for applications in robotics, navigation, autonomous vehicles, and wearables. Inertial measurement units are crucial for inertial navigation, calculating movement from an initial point, but suffer from accumulated error (drift) over time, frequently needing fusion with other sensors like ‘global positioning system’ (GPS) for accuracy.
Inertial navigation system – It is a location identification technology which utilizes inertial measuring units (IMUs) such as accelerometers and gyroscopes to determine the position and angular motion of objects relative to an initial starting point, angle, and velocity. It is effective for both indoor and outdoor applications, though it is subject to drift and cumulative error, which can be mitigated using filtering methods like Kalman filtering.
Inertial sensors – These are devices which detect an object’s location relative to a starting point by measuring motion and orientation, utilizing components such as accelerometers, gyroscopes, pressure sensors, and magnetometers. They provide relative position estimations, which can be improved in accuracy when combined with other technologies.
Inertia coefficient – It is a dimensionless number which quantifies the added inertia experienced by a body in a fluid, frequently calculated theoretically but typically measured in practice, especially for irregular shapes and under specific flow conditions. It quantifies the total inertial force, comprising added mass and Froude-Krylov forces, acting on a body moving through a fluid.
Inertia force – It is not a fundamental force like gravity, but rather a fictitious force (or pseudo-force) which an observer invokes in an accelerating (non-inertial) frame to explain an object’s resistance to changes in its motion (its inertia), appearing as an outward push, like centrifugal force in a rotating system or the force felt when a car brakes. It quantifies the effort needed to overcome an object’s inherent tendency (inertia) to stay at rest or keep moving uniformly, directly related to its mass.
Inertia matrix – It is also called inertia tensor. It is a symmetric 3 x 3 matrix defining a rigid body’s resistance to rotational acceleration about three orthogonal axes. It relates angular momentum to angular velocity (L = Iw), with diagonal elements representing moments of inertia and off-diagonal elements representing products of inertia.
Inertia welding – It is also known as inertia friction welding. It is a solid-state welding process which joins materials by friction. It involves rotating one part and then forcing it against a stationary part, generating heat at the interface because of friction. This heat softens the material, and the subsequent application of force forges the two parts together.
Inertinite – It refers to a group of partially oxidized organic (mainly plant) materials or fossilized charcoals, all sharing the characteristic that they typically are inert (i.e., not altered) when heated in the absence of oxygen. Inertinite is a common maceral in most types of coal. The main inertinite sub-macerals are fusinite, semi-fusinite, micrinite, macrinite, and funginite, with semi-fusinite being the most common. From the perspective of coal combustion, inertinite can be burned to yield heat but does not yield substantial volatile fractions during the coking.
Inertinite macerals – These are a group of coal components, including fusinite, semi-fusinite, macrinite, and micrinite, derived from highly oxidized or charred plant matter. They are characterized by high reflectance (bright appearance under microscopes), high carbon content, and low volatile matter. Inertinite normally remains inert, or unreactive, during industrial carbonization.
Inert macerals – These are the components of coking coal which do not undergo fluidization during the carbonization process because of their limited thermoplastic properties and volatile content, hence retaining their shape and morphology after heating.
Inexpensive carbon sources – These are abundant, low-cost organic materials, such as crude glycerol, agricultural residues, or industrial waste, used in bio-processing to fuel microbial growth and produce compounds like biofuels or bioplastics. These materials reduce considerably production costs compared to refined substrates.
Infeasible design – It is an engineering or optimization concept defining a solution which fails to meet one or more specified constraints, requirements, or functional criteria. While potentially physically constructible or operational, an infeasible design does not satisfy the needed performance, safety, or geometric limitations, making it unacceptable for the intended application.
Infeed conveyor – It is a conveyor which is responsible for introducing materials into a production or processing line, demanding regular checks for consistent material flow and proper alignment.
Infeed end – It is the end of a conveyor system located closest to the loading point, where materials are introduced onto the conveyor. Regular inspections are necessary to maintain efficient material transfer.
Infeed rolling – It is also known as plunge rolling. It is a thread rolling process where the dies plunge into the work-piece without significant axial movement. This method is used for general rolling, including threads with shoulders or heads, and is known for its speed and efficiency in producing discrete lengths of rolled geometry.
Inference – Inference is the process of deducing properties of the underlying distribution or population, by analysis of data. It is the process of making generalizations from the sample to a population.
Inference process – It is the method of mapping membership values from input variables through a rule-base to output variables, frequently using techniques such as the maximum-minimum reasoning approach.
Inferential analyzing method – It uses a small sample to conclude a bigger population. It means, data from a subject sample of the world is used to test a general theory about its nature. The types of data sets which can be used in this method are observational, retrospective data set, and cross-sectional time study.
Inferential sensor – It is also known as a soft sensor, virtual sensor, or proxy sensor. It is a computer-based predictive model used in industrial processes to calculate or estimate key, hard-to-measure, or infrequently measured, product quality variables (e.g., composition, purity, viscosity) using other easily measured, high-frequency process data (e.g., temperature, pressure, flow rate). These sensors act as a mathematical alternative to physical hardware sensors, providing real-time, online estimates to enable improved process monitoring, control, and optimization.
Inferential statistics – The body of statistical techniques concerned with making inferences about a population based on drawing a sample from it.
Inferred mineral resource – An inferred mineral resource is that part of a mineral resource for which quantity and grade (or quality) are estimated on the basis of limited geological evidence and sampling. Geological evidence is sufficient to imply but not verify geological and grade (or quality) continuity. It is based on exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes. An inferred mineral resource has a lower level of confidence than that applying to an indicated mineral resource and is not to be converted to an ore reserve. It is reasonably expected that the majority of Inferred mineral resources can be upgraded to Indicated mineral resources with continued exploration.
Infilled frames – These frames refer to structural systems where frame members and infill panels interact to develop combined resistance to in-plane loading, resulting in increased rigidity and strength beyond the individual contributions of the frame and infill.
In-fill drilling – It is a method of drilling intervals between existing holes, which is used to provide greater geological detail and to help establish reserve estimates.
Infill wall – It is a non-load-bearing panel built within a building’s structural frame (like concrete or steel) to partition spaces, support cladding, and provide thermal insulation / acoustic insulation, rather than carrying floor loads. While frequently considered non-structural, these walls considerably affect the building’s overall stiffness and seismic performance by acting like diagonal struts, which can be beneficial but also cause complex interactions during events like earthquakes.
Infiltrant – It is the material used to infiltrate a porous sinter. The Infiltrant as positioned on the compact is called a slug.
Infiltration – It is the process of filling the pores of a sintered or unsintered compact with a metal or alloy of lower melting temperature.
Infiltration method – It is a liquid state process for producing functionally graded materials (FGMs) by soaking a molten matrix into the space between a preformed dispersed phase, such as ceramic particles, either without pressure through capillary action or with pressure. This method enables the formation of FG (functionally graded) structures with improved microstructure and electrical properties.
Infiltration pressure – It is the external force (gas, mechanical, or vacuum) applied to drive a liquid metal into a porous preform of particles, overcoming surface tension in non-wetting systems. It is an important parameter in metal matrix composite manufacturing, frequently determined by the capillary force of the porous network.
InfiniBand – It is a point-to-point interconnect which enables direct data transfer between sender and receiver memory using features such as zero-copy and remote direct memory access (RDMA), hence reducing processor overhead.
Infinite acting radial flow – It refers to the main flow regime occurring after the initial wellbore response and before any boundary effects, characterized by a reservoir behaving as if it is infinite. During Infinite acting radial flow, pressure response is proportional to the logarithm of time, and this relationship is used to determine average reservoir permeability and skin factor through different semi-log methods.
Infinite-acting reservoir – It is a reservoir where the pressure disturbance spreads without being influenced by reservoir boundaries or the shape of the drainage area, resulting in a transient state flow characterized by a pressure drop which is a function of dimensionless time.
Infinite crack -It is frequently a semi-infinite crack. It refers to a theoretical, sharp, 2D crack edge that extends infinitely in one direction within an infinite or semi-infinite medium. It is used to analyze crack tip stress fields and crack propagation dynamics under loading without boundary interference.
Infinite cylinder – It is a geometric shape which extends infinitely in both length and width. It can be detected by determining the intersection between a plane and the cylinder, based on the distance between them and the radius of the cylinder. It is a modeling simplification used to represent a long, cylindrical object (such as a rod, wire, pipe, or continuously cast billet) where the heat flow or stress along the axis is negligible compared to the heat flow or stress in the radial direction.
Infinite dilution – It is a theoretical state where solute concentration approaches zero, meaning each solute molecule is surrounded only by solvent molecules, eliminating solute-solute interactions. It represents an ideal scenario used in thermodynamics, chemical separation, and adsorption to evaluate activity coefficients, molecular interactions, and solute behaviour.
Infinite-dimensional optimization – It is the process of solving optimization problems which involve functions over infinite-dimensional spaces, frequently needing discretization techniques to approximate the solutions in finite-dimensional settings. These problems typically involve a large number of variables and constraints, making them complex and challenging to solve.
Infinite domain – It refers to a problem space where physical phenomena, such as heat transfer, electromagnetic radiation, or stress fields, extend indefinitely, with effects typically fading at infinity. To avoid inaccurate results from artificial boundaries, engineers use infinite elements or specialized boundary techniques to model these open systems.
Infinite element – It is a specialized numerical tool in finite element analysis (FEA) designed to model unbounded, open, or infinite domains (e.g., far-field soil in foundation problems or exterior acoustic radiation). They prevent boundary reflection by using specialized shape functions which simulate decay, allowing for accurate simulation of far-field conditions without needing massive, impractical mesh extensions.
Infinite impulse response – It is a filter which, mathematically, never gets to a zero effect of an impulse at its input, though practically the response can become negligible after a definite time.
Infinite input impedance – It is an ideal condition in electrical engineering where a circuit, typically an operational amplifier or measuring device, draws zero current from the source (Iin = 0) regardless of the applied voltage (Vin). It signifies an open circuit at the input terminals, preventing loading effects, ensuring maximum voltage transfer, and maintaining source signal integrity.
Infinite interval – It defines a range of values or temporal domain which extends without bound toward positive or negative infinity. Represented using interval notation, these intervals are important for modeling systems with unbounded parameters, such as infinite time frames, infinite boundary value problems in PDEs (partial differential equations), or infinite integration limits in signal analysis.
Infinite loss – It normally refers to a theoretical state where a system, component, or signal experiences maximum attenuation, complete blocking, or zero transmission of power. It is an idealization used to model perfect isolation or disconnection.
Infinite plane – It is a theoretical, two-dimensional surface extending indefinitely in all directions with zero thickness, used to simplify models by neglecting edge effects. It acts as an idealized boundary, such as a uniform charge sheet (electric field E = sigma/2eo) or a ground plane, representing large, flat surfaces where boundary conditions are uniform. It assumes the boundary is so far away that it does not affect the local solution, allowing for, constant, uniform field strengths (e.g., in electro-magnetics or fluid dynamics).
Infinite plate – It is a two-dimensional, isotropic material structure which extends indefinitely in all directions and can be subjected to external forces, such as constant in-plane tension, as exemplified by models involving circular holes. It is a theoretical, two-dimensional model of a material structure which extends indefinitely in its planar (length and width) directions. It is characterized by its thickness being very small relative to its surface area, frequently having no boundaries in the analysis, meaning boundary conditions at the edges are disregarded.
Infinite resistance – It is an idealized engineering condition where a circuit element, such as an open switch or broken wire, prohibits all electrical current (I = 0) regardless of the voltage applied. It represents an open circuit, characterized by a complete lack of conductivity and an infinitely high impediment to electron flow.
Infinite series – It refers to a sum of an infinite sequence of real numbers which converges to a limit. The sum of the infinite series is called the sum of the series, and the individual sums of the sequence up to a certain point are known as partial sums.
Infinite series solution – It represents functions, such as solutions to complex differential equations, as a sum of an infinite sequence of terms (e.g., Fourier series). It provides a way to approximate or express behaviour in fields like signal processing or heat transfer, where partial sums approach a specific value (convergence).
Infinitesimal – It is an infinitely small quantity (dx, dy, e) that is larger than zero but smaller than any measurable, standard positive number. It represents a value approaching zero that, in practical calculation, allows high-order terms (like dx square) to be neglected, enabling accurate modelling of continuous, non-linear physical phenomena.
Infinitesimal control volume – It is a vanishingly small, fixed region in space (dx x dy x dz) used for differential analysis of fluid flow or heat transfer. It enables the derivation of governing differential equations (e.g., Navier-Stokes) by assuming properties are uniform within the tiny volume.
Infinitesimal perturbations– These refer to small deviations or disturbances added to a known solution of a system, used in linear stability analysis to evaluate the sensitivity of the flow to these minor changes.
Infinitesimal strain theory – it is a framework used to analyze deformation in materials under the assumption of small strains, which simplifies the general physical laws formulated in finite strain theory.
Infinite span – It is a two-dimensional (2-D) flow condition where fluid motion occurs strictly perpendicular to the span, ignoring tip effects. It is frequently simulated in wind tunnels, it models an aero-foil of infinite length to focus on sectional characteristics rather than 3-D finite span effects.
Infinite zero – It refers to a system matrix T(z) having a zero of order ‘k’ at infinity, analyzed by substituting z = 1/w and examining the zero at w = 0. It represents a specific, invariant structure in control systems important for decoupling, model following, and analyzing system behaviour at high frequencies.
Infinity – It is not a conventional number, but a concept representing a value or quantity that is unbounded, endless, or limitless. It is used in processes where variables increase without bound, such as in control systems, electromagnetic fields, and asymptotic analysis in materials science.
Inflating roll method (variable crown roll method) – In case of the work roll with a longer roll barrel length, the effect of work roll bending (WRB) is less likely to transmit to the strip width central region in work roll bending shape control. The strip shape control effect can be maintained by combining the work roll bending method with the method by which a back-up-roll is partially inflated in the roll barrel direction for shape control. If the shape control performance can be maintained by using an inflating roll as a back-up roll, it is possible to eliminate the need to process the work roll to form a convex-curved shape in strip centre region. This type of roll reduces the chance of sharp uneven contact between the strip and the work roll, and is effective especially when the quality of the strip surface needs to always be superior.
Inflation – It is the action of inflating something or the condition of being inflated. It also means that the prices of goods and services normally increase over time, meaning the money buys less than it used to.
Inflection point – It is a specific location on a curve, such as a beam’s bending moment diagram, stress-strain curve, or process graph, where the concavity changes from upward to downward (or vice versa). It signifies a shift in curvature, where the second derivative of the function f”(x) = 0. It is the position on a curved line, such as a phase boundary, at which the direction of curvature is reversed.
Inflow – It is the movement of liquid or air into a place.
Inflow angle – It is the angle at which fluid (liquid or gas) approaches a component, surface, or system, such as a turbine blade, airfoil, or vessel wall, typically measured relative to a reference axis, chord line, or plane of rotation. It is important for determining lift, drag, turbulence, and pressure distribution.
Inflow boundary – It is a computational domain edge where fluid enters, needing predefined physical variables like velocity, pressure, or mass flow. It sets necessary input parameters, such as velocity profiles or thermal conditions, which drive the simulation’s downstream behaviour, acting as a virtual upstream channel to define flow characteristics.
Inflow factor – It is a dimensionless parameter used to quantify the velocity or volume of fluid entering a system relative to a reference condition, normally used in aerodynamics (wind turbines) and, less frequently, in geotechnical or hydraulic applications (tunneling).
Inflow performance relationship – It defines the mathematical and graphical relationship between a well’s fluid (gas, oil, water) production rate (q) and its flowing bottom-hole pressure (Pwf), indicating the reservoir’s ability to deliver fluids. It models the pressure drawdown needed to drive production, normally used to optimize production systems.
Inflow performance relationship – It is a fundamental engineering tool defining the relationship between a well’s production rate (q) and its flowing bottom-hole pressure (Pwf) under specific reservoir conditions. It shows the reservoir’s capacity to deliver fluids to the wellbore, used for designing completions, optimizing artificial lift, and nodal analysis.
Inflow temperature – It is the temperature of a working fluid (liquid or gas) as it enters a system or component (e.g., heat exchanger, reactor, turbine). It is an important parameter for defining system efficiency, heat transfer performance, and thermal safety limits, normally measured at the inlet boundary.
Influence coefficient – It defines the response (displacement, rotation, or force) at a specific location ‘i’ caused by a unit load or displacement applied at another location ‘j’ in a structure. It quantifies how loads or movements affect different parts of a system, important for analyzing structural flexibility, stiffness, and vibration.
Influence coefficient method – It is a technique used to quantify how a unit force, displacement, or vibration input at one location (J) affects the response (e.g., deflection, stress, vibration amplitude) at another location (i). It is a linear, superposition-based method frequently used in structural analysis, vibration, and rotor balancing.
Influence diagram – It is a compact, graphical, and mathematical representation of a decision-making problem under uncertainty, normally used in engineering and project management to map dependencies between variables. It acts as a Bayesian decision network (or decision diagram) which visualizes how specific decisions, uncertainties, and objective outcomes influence one another to optimize utility.
Influence variability – It refers to how variations in inputs (e.g., materials, environmental conditions, user behaviour) affect system performance, quality, and reliability, necessitating robust design to mitigate risks. It is defined as the extent to which data points differ from the average, acting as an important performance index in manufacturing.
Influence zone – It is the surrounding soil, rock, or structural area affected by excavation, construction, or loading, characterized by substantial changes in stress and deformation. Typically extending 2 to 3 times the tunnel diameter or at a 45-degree angle from foundations, this zone needs careful analysis to ensure structural stability.
Influencing factors – These are variables, conditions, or elements, such as material properties, environmental loads, or human actions, which directly affect the design, performance, reliability, and outcome of a system or process. These factors are identified and analyzed to control, predict, and optimize engineering outputs.
Influencing parameters – These are also called influencing drivers. These are measurable, controllable, or uncontrollable factors which directly impact a system’s performance, behaviour, or output. These variables define, constrain, or optimize engineering designs and processes, such as temperature, pressure, or material properties, to ensure desired, high-quality outcomes.
Influent flow – It refers to the untreated or contaminated water flowing into the waste water treatment plant ready for processing.
Informal communication – It is the spontaneous, unofficial exchange of technical ideas, project updates, or feedback through casual channels like chats, emails, or hallway conversations, bypassing formal hierarchies to quickly share knowledge, build camaraderie, solve problems, and foster innovation, complementing structured methods like formal reports. It is the ‘grapevine’ which lets junior engineers quickly ask senior ones for advice or teams’ bond over a shared technical challenge outside official meetings, crucial for building relationships and a collaborative culture.
Informal methods – These are flexible, experience-based, and frequently qualitative processes used for designing, verifying, and validating systems, relying on expert judgment rather than strict mathematical or rigid, formal, rule-based methodologies. They allow for rapid iteration and communication, utilizing tools like natural language, sketches, or prototypes, particularly during early development.
Informal standards – These standards are by SDOs (standards development organizations) such as American Society for Testing and Materials (ASTM), American Society of Mechanical Engineers (ASME), Institute of Electrical and Electronics Engineers (IEEE), and Society of Automobile Engineers (SAE) etc.
Information and communications technology – It is an extensional term for information technology (IT) which stresses the role of unified communications and the integration of tele-communication (telephone lines and wireless signals) and computers, as well as necessary enterprise software, middleware, storage, and audio-visual, which enable users to access, store, transmit, understand and manipulate information. Information and communications technology is also used to refer to the convergence of audiovisuals and telephone networks with computer networks through a single cabling or link system.
Information appliance – Conceptually, it is an embedded computer system with a specialized user interface designed to simplify one task, such as e-mail or photos, A modern smart phone approaches this concept.
Information axiom – In axiomatic design, it is a principle stating that the optimal design is the one with the lowest information content, which maximizes the probability of success in satisfying functional requirements. It aims to minimize the uncertainty of achieving design goals by selecting the design with the highest probability of meeting specifications.
Information construct – It refers to the organized and structured representations of building-related information which facilitate sharing, collaboration, and management throughout the lifecycle of a construction project. It enables effective communication among stakeholders and support optimized decision-making in project planning and execution.
Information content – It is the measure of data conveyed by an event, inversely related to its probability, where rare events carry higher information value. It quantifies uncertainty, typically in bits’, and is defined as I(x) = log2[1/P(x), necessary for efficient coding, communication systems, and reducing signal redundancy. The information content. I(x) of an event ‘x’ is given by the logarithmic formula I(x) = -log2[1/P(x)], where P(x) is the probability of the event’s occurrence.
Information distribution – It is the channels used to provide stakeholders with timely information and updates regarding the organizational activities.
Information engineering – It applies engineering principles to develop robust, efficient information systems, focusing on the lifecycle of data and knowledge, i.e., its generation, distribution, analysis, and use to meet organizational goals, integrating tech like AI (artificial intelligence), software, hardware, and networks for decision support and operations. It is a systematic discipline for building complex systems, combining software engineering with data management, analysis, and enterprise architecture, ensuring data flows efficiently for strategic objectives.
Information exchange i- It is the formal or systematic sharing of data, knowledge, and specifications between different systems, teams, or stages using defined formats and protocols, ensuring consistency for collaboration, design, and analysis, frequently through electronic means, facilitating processes lie routing network data.
Information field – It is a conceptual or mathematical model representing the distribution, intensity, and dynamics of data within a system, such as a manufacturing shop floor, mapping state spaces to value ranges. It quantifies uncertainty, complex relationships, and information flow to optimize performance and manage cognitive loads or machine states.
Information flow control – It is the process of managing and restricting how data moves within a system, ensuring sensitive information stays confidential and is not misused, preventing leaks, and maintaining integrity, frequently by tracking data propagation and enforcing security policies beyond simple access controls. It is important for data security in complex systems like online platforms, ensuring data flows only to authorized destinations as per defined rules.
Information leakage – It refers to the unauthorized, unintentional, or accidental transmission or exposure of sensitive, confidential, or proprietary data from within an organization to an external or untrusted environment. It represents a critical security failure, frequently stemming from human error, misconfigured systems, or security vulnerabilities.
Information life cycle – It is the journey data takes from its creation / collection to its eventual disposal / archiving, encompassing stages like storage, usage, distribution, and maintenance, with the goal of managing data effectively for security, compliance, and optimization.
Information management – It is the process of systematically collecting, organizing, storing, retrieving, and distributing information within an organization to support its operations and decision-making. It encompasses the entire lifecycle of information, from creation to disposal, and involves both technology and people.
Information / measurement standards – Such standards describe test and measurement methods for describing, quantifying and evaluating product attributes such as materials, processes and functions.
Information network – It is a structured system of interconnected computing devices, software, and transmission media designed to store, process, and transmit data between users, centres, and applications. It forms the backbone of modern information technology (IT) infrastructure, utilizing protocols and hardware like routers, switches, and satellites to facilitate information exchange.
Information processing approach – It is a cognitive framework which models human thinking and, by analogy, system design as a series of stages, input, encoding, storage, and output, similar to a computer. It focuses on how information is acquired, processed in working memory, and retrieved from long-term memory. In engineering, this approach helps analyze, simulate, and design complex systems (like intelligent tutoring systems) by mimicking human cognitive processes, including attention and decision-making, in artificial systems.
Information repository – In information technology, it is a central place in which an aggregation of data is kept and maintained in an organized way, usually in computer storage. It can be just the aggregation of data itself into some accessible place of storage or it can also imply some ability to selectively extract data.
Information resource management – It is the strategic approach of treating information (data, text, voice, image) as a valuable organizational asset, applying standard management principles (planning, organizing, controlling) to its lifecycle. i.e., from creation / collection to use, storage, and disposal, to support goals, link needs to system solutions, and improve efficiency, integrating people, technology, and processes.
Information signal – It is a time-varying physical quantity, such as voltage, current, or electro-magnetic waves, which represents and conveys data, measurements, or messages between components, devices, or systems. It acts as a measurable, functional representation of information (e.g., audio, video, sensor data) and is distinguished from noise, allowing for communication or control.
Information system – It is an integrated collection of components (hardware, software, data, people, and processes) which work together to collect, process, store, and distribute data, transforming it into useful information to support decision-making, coordination, control, and analysis within an organization. Basically, it is a socio-technical system which uses technology to manage information flow, helping organizations run operations, interact with customers, and gain a competitive edge.
Information technology – It is a set of related fields that encompass computer systems, software, programming languages, and data and information processing, and storage. Information technology forms part of information and communications technology (ICT).
Information technology system – It is normally an information system, a communications system, or, more specifically speaking, a computer system, including all hardware, software, and peripheral equipment which is operated by a limited group of users. Information technology systems play an important role in facilitating efficient data management, improving communication networks, and supporting organizational processes across different industries.
Information type – It defines a category for organizing and managing data, like personal data, financial records, or operational data, each with specific security, privacy, and access rules. It helps classify information for effective governance, ensuring appropriate handling, such as defining ‘personally identifiable information’ (PII) against ‘confidential operational data’, frequently based on organizational policies or legal requirements.
Infrared – It is the part of the electro-magnetic spectrum between the visible light range and the radar range. Radiant heat is in this range, and infrared heaters are frequently used in the thermoforming and curing of plastics and composites. Infrared analysis is used for identification of polymer constituents.
Infrared absorption – It is the process where molecules absorb specific infrared radiation frequencies, matching their natural molecular vibrational modes (stretching / bending). This phenomenon is used to identify molecular structures, measure gas concentrations, and monitor materials, typically by identifying spectral fingerprints.
Infrared analyzer – It is an atmosphere-monitoring device which measures a gas (normally carbon mono-oxide, carbon di-oxide, and methane) presence based on specific wave-length absorption of infrared energy.
Infrared brazing – It is a brazing process in which the heat needed is furnished by infrared radiation.
Infrared diode laser – It is a compact, semiconductor-based opto-electronic device which produces coherent, mono-chromatic infrared light (typically 0.7 micro-meters to higher than 30 micro-meters) through stimulated emission within a p-n junction. Engineered for high efficiency, these lasers are critical for fibre-optic communication, barcode scanning, and precision industrial marking.
Infrared dryer – It uses invisible infrared (IR) electro-magnetic radiation to directly heat and evaporate moisture or solvents from materials, offering faster, more energy-efficient drying than conventional methods by delivering energy directly to the product rather than the surrounding air. These systems feature precisely controlled emitters, frequently tailored to material absorption spectra, allowing for high heat flux, rapid drying, precise temperature management, and compact designs, ideal for industries like foundry for core or mould drying, plastics, and coatings.
Infrared drying – It is an engineering, non-contact thermal process which utilizes electro-magnetic radiation (typically 0.78 micro-meters to 1,000 micro-meters) to directly heat and remove moisture from materials. By penetrating the surface to generate localized, internal heat, it offers faster, more energy-efficient drying, frequently with improved product quality compared to conventional convection.
Infrared emissions – These emissions refer to the release of energy in the form of electro-magnetic radiation with wave-lengths longer than visible light but shorter than micro-waves, frequently perceived as heat.
Infrared fibres – These are specialized optical wave-guides engineered to transmit light in the infrared spectrum, typically at wavelengths higher than 2 micro-meters, where traditional silica fibres are opaque. Engineered using materials like chalcogenide glasses, tellurides, fluorides, or hollow waveguides, they are vital for high-power laser delivery (carbon di-oxide, erbium-doped yttrium aluminium garnet), spectroscopic sensing, and thermal imaging.
Infrared lamp – It is an electrical, incandescent-type device engineered to emit electro-magnetic radiation mainly in the infrared spectrum (0.7 micro-meters to 400 micro-meters) for heating or, less commonly, signaling purposes. Designed to operate at lower filament temperatures than standard lighting, these lamps maximize radiant energy output, converting electrical energy into efficient, directional heat for industrial drying, and thermo-forming applications.
Infrared laser – It is an engineering-grade light source emitting electro-magnetic radiation with wave-lengths longer than visible light (typically 0.78 micro-meters to 200 micro-meters), operating within the near-infrared, mid-infrared, or far-infrared spectrum. These lasers are important for high-precision molecular spectroscopy, industrial cutting, and free-space communication because of their ability to target specific material absorption lines and penetrate materials like silicon.
Infrared light – It is a form of electro-magnetic radiation with wave-lengths longer than visible light (higher than 700 nano-meters to 780 nano-meters) and shorter than micro-waves, extending up to 1 milli-meter. Engineering defines it by its thermal properties (heat transfer) and its application in technologies like telecommunications, night vision, spectroscopy, and sensing.
Infrared light absorption – It is the process where materials capture infrared radiation, causing molecular bond vibrations (stretching / bending) when the incident frequency matches the material’s natural resonance. It is used to convert light to heat or identify materials through spectra analysis, especially for identifying chemical functional groups.
Infrared pyrometer – It is a non-contact, passive sensor which measures an object’s surface temperature by detecting the intensity of infrared radiation it emits. It ius used widely for high-temperature or inaccessible applications, these devices convert thermal radiation into electrical signals based on the Stefan-Boltzmann law.
Infrared radiation – It is electro-magnetic radiation (EMR) with wave-lengths longer than those of visible light but shorter than microwaves. The infrared spectral band begins with waves which are just longer than those of red light (the longest waves in the visible spectrum), so infrared is invisible to the human eye. Infrared normally understood to include wave-lengths from around 750 nano-meters (400 tera-hertz) to 1 millimeter (300 giga-hertz). Infrared is normally divided between longer-wavelength thermal infrared, emitted from terrestrial sources, and shorter-wavelength infrared or near-infrared, part of the solar spectrum. Longer infrared wave-lengths (30 micrometers to 100 micrometers) are sometimes included as part of the tera-hertz radiation band. Almost all black-body radiation from objects near room temperature is in the infrared band. As a form of electro-magnetic radiation, infrared carries energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon.
Infrared radiation pyrometer – It is also called infrared thermometer / infrared pyrometer. It is a non-contact instrument which measures an object’s temperature by detecting the infrared (thermal) radiation it emits, translating this energy into an electrical signal for display, important for high-temperature, moving, or inaccessible industrial applications where physical contact is impossible or unsafe. It works by capturing thermal energy (infrared light) with an optical system, converting it to an electrical signal through a detector (like a thermocouple), and processing it to determine temperature, frequently using principles from the Stefan-Boltzmann law.
Infrared (IR) rays – These are electro-magnetic waves longer than visible light (around 700 nano-meters to 1 millimeter), invisible but felt as heat, used for thermal imaging, remote controls, fibre optics, and industrial heating, leveraging their heat emission from objects and interaction with materials for sensing, communication, and processing, categorized into ‘near’ (NIR), ‘mid’ (MIR), and ‘far’ (FIR) infrared for specific applications like night vision, spectroscopy, or material curing.
Infrared region – It is the band of electro-magnetic radiation located between visible light and micro-waves, with wave-lengths ranging from around 700 nano-meters to 1 milli-meter (780 nano-meters to 1 milli-meter is also commonly used). It is frequently used for thermal imaging, remote controls, fibre optic communication, and molecular spectroscopy.
Infrared soldering – It is a soldering process in which the heat needed is furnished by infrared radiation.
Infrared spectrometer – It is a device which is used to measure the amplitude of electro-magnetic radiation of wave-lengths between visible light and micro-waves.
Infrared spectroscopy – It is the study of the interaction of material systems with electro-magnetic radiation in the infrared region of the spectrum. The technique is useful for determining the molecular structure of organic and inorganic compounds by identifying the rotational and vibrational energy levels associated with the different molecules.
Infrared spectrum – It the range of wave-lengths of infrared radiation. It is also a display or graph of the intensity of infrared radiation emitted or absorbed by a material as a function of wave-length or some related parameter.
Infrared thermography – It is a maintenance technique utilizing infrared technology to detect and monitor temperature variations in equipment components, needing periodic assessments for identifying potential issues.
Infrared thermometer – It is a non-contact radiant energy detector. The amount of radiant energy emitted is proportional to the temperature of the object. Non-contact thermometers measure the intensity of the radiant energy and produce a signal proportional to the target temperature. The physics behind this broadcasting of energy is called Planck’s law of thermal radiation. This radiated energy covers a wide spectrum of frequencies, but the infrared spectrum is normally used for temperature measurement. IR thermometers capture the invisible infrared energy which is naturally emitted from all objects warmer than absolute zero (0 Kelvin). Infrared radiation is part of the electro-magnetic spectrum which includes gamma rays, X-rays, micro-waves, ultra-violet, visible light, and radio waves. Infrared falls between the visible light of the spectrum and radio waves. Infrared wavelengths are normally expressed in micrometers with the infrared spectrum extending from 0.65 micrometers to 1,000 micrometers.
In practice, the 0.65 micrometers to 14 micrometers band is used for jnfrared temperature measurement over a range from -50 deg C to 3,000 deg C.
Infrasound – It is sometimes referred to as low frequency sound. It describes sound waves with a frequency below the lower limit of human audibility (normally 20 hertz). Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure is to be sufficiently high. Although the ear is the primary organ for sensing low sound, at higher intensities it is possible to feel infrasound vibrations in various parts of the body.
Infrastructure – It is the physical components of interrelated systems providing commodities and services necessary to enable, sustain, or improve societal living conditions and maintain the surrounding environment. It is composed of public and private physical structures such as roads, railways, bridges, airports, public transit systems, tunnels, water supply, sewers, electrical grids, and tele-communications (including Internet connectivity and broadband access).
Infusorial earth – It is normally known as diatomaceous earth (DE), diatomite, or kieselguhr. It is a naturally occurring, soft, siliceous sedimentary rock which is easily crumbled into a fine white-to-off-white powder. From an engineering perspective, it is defined by its high porosity, low density, and high surface area, consisting of the fossilized, skeletal remains of single-celled aquatic algae called diatoms.
Ingate – It is the portion of the runner in a mould through which molten metal enters the mould cavity. The generic term is sometimes applied to the entire network of connecting channels which conduct
metal into the mould cavity.
Ingot – It is a casting of simple shape, suitable for hot working or remelting. It is a casting intended for subsequent rolling, forging, or extrusion.
Ingot break-down – It is the primary hot-working process which converts a large, as-cast ingot into a smaller, semi-finished form (such as a bloom, slab, or billet). This initial step is critical to transform the weak, coarse-grained, cast structure into a refined, uniform, and workable wrought structure.
Ingot conversion – It refers to the primary fabrication process of taking solid, cast metal ingots (produced by pouring molten metal into moulds) and reducing or shaping them into intermediate, semi-finished products. This process typically involves transforming large, cast ingots into more manageable forms such as blooms, billets, or slabs through mechanical working, mainly hot rolling or forging.
Ingot, extrusion – It is a cast form which is solid or hollow, normally cylindrical, suitable for extruding.
Ingot, fabricating – It is a cast form suitable for subsequent working by such methods as rolling, forging, extruding, and so on (rolling ingot, forging ingot, extrusion ingot).
Ingot, forging – It is a cast form intended and suitable for subsequent working by the forging process.
Ingot homogenization – It is a high-temperature heat treatment process applied to cast metal ingots to reduce chemical segregation and create a uniform microstructure, making the alloy more stable and workable for subsequent processing like rolling or extrusion. This treatment redistributes alloying elements, eliminating localized concentration differences (micro-segregation) which form during solidification, improving mechanical properties like strength and ductility.
Ingot iron – It is iron of comparatively high purity produced in open-hearth furnace under conditions which keep down the carbon, manganese, and silicon content.
Ingotism – It refers to the characteristic, as-cast dendritic crystal structure of a metal ingot which possesses substantial, non-uniform, and undesirable variations in grain structure from the surface to the centre.
Ingot metallurgy – It consists of the metallurgical aspects which are involved during the casting of molten metal in ingot moulds.
Ingot production -It is the process of casting molten metal into large, solid blocks (ingots) in moulds, serving as an essential intermediate form for subsequent processing like rolling, forging, or extrusion into final products. This controlled solidification forms specific micro-structures and textures, important for the material’s final properties, while also allowing easier handling and transport.
Ingot reduction – It refers to the thermo-mechanical process of reducing the cross-sectional area of a cast metal ingot (through forging, rolling, or extrusion) to transform it into a smaller, more refined, and usable form such as a bloom, billet, or slab. This process is important for converting raw cast metal, which frequently has a coarse grain structure, into a final material with improved mechanical properties, better homogeneity, and, for forging, the closing of internal cavities.
Ingot, remelt – It is a cast form intended and suitable for remelting, normally for producing castings.
Ingot, rolling – It is a cast form suitable for rolling.
Ingot slag skin – It is a thin, solid, or semi-solid layer of oxide-based, non-metallic slag which forms at the interface between the solidifying metal ingot and the water-cooled mould wall during casting processes, particularly in electro-slag remelting (ESR).
Ingot steel – It is a form of semi-finished steel. Liquid steel is teemed (poured) into ingot moulds, where it slowly solidifies. Once the steel is solid, the mould is stripped, and the ingot is then ready for subsequent rolling or forging.
Ingot structure – It refers to the characteristic internal grain arrangement formed as molten metal solidifies in a mould, typically showing distinct zones namely a surface chill zone (fine, random grains), an inner columnar zone (long, directional grains from mould wall inward), and a central equi-axed zone (larger, randomly oriented grains). This structure is important since it influences the metal’s final properties, frequently needing further working like forging or rolling to achieve uniform, desirable characteristics.
In-grain shear bands – These are defined as thin, localized zones of intense plastic deformation which form within individual grains during moderate to heavy deformation. Unlike macroscopic shear bands which cross multiple grain boundaries, In-grain shear bands are confined to single, normally large, grains, typically occurring in the middle-to-late stages of cold working, such as rolling.
Ingress– It means the act or means of entering, referring to the intrusion of external things (like dust, water, or signals) into a system or device, or the management of incoming network traffic. It is important in electrical enclosures for protection (ingress protection ratings) and in information technology (IT) for controlling external access to services, frequently through tools like Kubernetes Ingress for routing requests to internal applications.
Ingress protection (IP) ratings – It consist of are the ratings, which grade the resistance of an enclosure against the intrusion of dust or liquids. It is defined by IEC 60529, which is a standard that classifies and certifies the degree to which an electrical equipment’s enclosure protects against intrusion from solid objects (dust) and liquids (water), ensuring safety and reliable operation in diverse environments, indicated by ‘IP’ followed by two digits (e.g., IP67). The first digit denotes solid protection (0-6, 6 is dust-tight), and the second signifies liquid protection (0-9, higher numbers mean more resistance to water, with 9K for high-pressure jets).
Inherent controllability – It refers to the ability of a physical system (or plant) to be steered from any initial state to any desired final state within a finite time, using only its available, unconstrained control inputs (actuators), independent of the specific feedback control structure. It is an intrinsic property of the system’s dynamic design, evaluated before designing a controller, to determine if the process layout allows for effective regulation, disturbance rejection, and flexibility.
Inherent diaphragm pressure range – It is the high and low values of pressure applied to the diaphragm to produce rated valve plug travel with atmospheric pressure in the valve body. This range is frequently referred to as a bench set range since it is the range over which the valve strokes when it is set on the work bench.
Inherent discontinuities – Inherent discontinuities refer to the discontinuities which originate during the initial casting process of the liquid metal such as casting of ingots, continuous casting of semi-finished products, and casting of parts of any given shape in the foundries. Some of the initial casting discontinuities are removed by chopping or grinding but some of them remain and further change their shape and nature during the subsequent processing of the material.
Inherent durability – It is the natural, intrinsic ability of a material (such as concrete, or steel) to resist degradation, weathering, and chemical or physical attacks over time without needing additional, external protection. It is a measure of a material’s intrinsic resistance to decay, wear, or damage.
Inherent flow characteristic – It is the relationship between the flow rate and the closure member travel as it is moved from the closed position to rated travel with constant pressure drop across the valve.
Inherent frequency – It is the natural frequency. It is the rate at which a system oscillates or vibrates freely without external forces after an initial disturbance. It is a fundamental property determined by the system’s mass and stiffness, frequently leading to resonance when matched by external excitation frequencies.
Inherently fire resistant – It refers to materials, components, or structures which possess fire-resisting properties built into their chemical or physical structure, rather than relying on added coatings or treatments. In structural engineering, this is frequently described as ‘inherent fire capacity’, the ability of a structure to maintain integrity and functionality without additional active or passive fire protection.
Inherent mineral matter – It refers to inorganic constituents intimately bonded with or dispersed within the organic material, originating from original plants or entrapped during formation. This is specifically regarding fuels like coal and biomass. Unlike adventitious minerals, these are inseparable by physical cleaning, influencing thermal behaviour, liquefaction, and gasification.
Inherent randomness – It refers to the irreducible, natural variability within a system’s behaviour, input, or physical processes which cannot be eliminated by better modeling, measurement, or increased knowledge. Also known as aleatory uncertainty, this unpredictable, stochastic, or non-deterministic behaviour is fundamentally built into the system.
Inherent rate – It refers to the natural, intrinsic pace or frequency at which a system, component, or material operates or changes without external forcing. It represents the base behaviour determined by design or physical properties, such as the natural frequency of a structure or the intrinsic pacing rate of cardiac tissue.
Inherent safety – A process has inherent safety if it has a low level of danger even if things go wrong. Inherent safety contrasts with other processes where a high degree of hazard is controlled by protective systems. As perfect safety cannot be achieved, normal practice is to talk about inherently safer design.
An inherently safer design is one which avoids hazards instead of controlling them, particularly by reducing the quantity of hazardous material and the number of hazardous operations in the plant.
Inherent strain – It is the non-recoverable, permanent, and frequently incompatible strain within a material which remains when all external forces are removed, acting as the main source of residual stresses. It represents the accumulation of irreversible deformation processes, such as thermal contraction, plastic deformation, phase changes, and creep, normally analyzed in manufacturing, welding, and casting to predict residual deformation.
Inhibiting effect – It is the reduction, suppression, or slowing down of a physical, chemical, or biological process by an added agent or mechanism. It acts to control reaction rates, prevent unwanted side reactions, or protect materials, frequently by altering surface properties or blocking active sites (e.g., corrosion inhibition).
Inhibition zone – It refers to the systematic design and manipulation of materials, typically anti-microbial-loaded textiles, nano-composites, or polymers, to create a specific, functional, and measurable area surrounding the material where microbial growth is inhibited. This process combines micro-biology with materials science to engineer surfaces that prevent bio-fouling, infection, or bacterial growth.
Inhibitor – It is a substance which selectively retards some specific chemical reaction, e.g., corrosion. Pickling inhibitors retard the dissolution of metal without hindering the removal of scale from steel. Corrosion inhibitors are chemical substances which stop or retard corrosion of the metallic surface when added to the corrosive media in small quantities. An example in boiler work is the use of an inhibitor, when using acid to remove scale, to prevent the acid from attacking the boiler metal.
Inhibitor dosage – It refers to the amount of corrosion inhibitor applied to a system, which can influence the inhibitor concentration and, consequently, its effectiveness in reducing the corrosion rate.
Inhibitory connections – These are links in a neural network which have a negative weight value, which reduces the probability of the receiving nodes firing in response to input.
Inhomogeneous deformation – It describes how a material deforms unevenly across its volume, meaning strain is not uniform, unlike ideal homogeneous deformation where strain is constant everywhere. It occurs because of the microstructural variations (like grains, phases, defects) or external factors (stress, temperature), leading to localized plastic flow (e.g., Luders bands) or non-uniform strain distribution, impacting material properties and processing outcomes.
Inhomogeneous diffusion equation – It describes the transport of atoms (such as alloying elements or impurities) within a solid matrix where properties like the diffusion coefficient, mobility, or concentration profiles are not uniform, or where external driving forces are present. Unlike Fick’s second law (which assumes a homogeneous medium and often a constant diffusion coefficient), the inhomogeneous equation accounts for complex microstructures, such as grain boundaries, phases with different compositions, or temperature gradients.
Inhomogeneous equation – It is a linear ordinary differential equation (ODE) or partial differential equation (PDE) where the sum of terms involving the dependent variable and its derivatives equals a non-zero forcing function f(x). Formally, it is expressed as Lyp = f(x), where ‘L’ is a linear operator and f(x) is not zero represents an external input, source, or driving force.
Inhomogeneous grain coarsening – It refers to a, frequently undesirable, phenomenon during heat treatment or thermal processing where a small number of grains grow abnormally fast, resulting in a final micro-structure containing a few very large grains embedded within a matrix of smaller, uncoarsened grains. This is also known as abnormal grain growth (AGG) or discontinuous grain growth.
Inhomogeneous Helmholtz equation – It is an elliptic partial differential equation (V-square x u + k-square x u = -f) used to model time-harmonic wave propagation (acoustic, electromagnetic) driven by a source ‘f’. It describes steady-state oscillation, where ‘k’ is the wavenumber and ‘u’ is the field solution.
Inhomogeneous materials – These are substances with non-uniform physical, chemical, or mechanical properties, compositions, or micro-structures throughout their volume. These materials feature variations in phases, composition, or structural defects (such as grain boundaries, porosity, or inclusions) which differ based on location. Common examples include cast alloys, heat-treated parts with varying hardness, and composites.
Inhomogeneous micro-stresses – These refer to non-uniform, localized residual stresses which exist on the microscopic scale (e.g., between grains, phases, or within a single grain) and vary from point to point within the material. Unlike homogeneous micro-stresses, which are constant over larger regions, inhomogeneous micro-stresses are highly localized, causing broadening of X-ray diffraction lines. These stresses act on the scale of microstructural features (grains, particles, sub-grains, phases) and result from localized variations in material properties, such as grain orientation or elastic mismatch between phases. They are typically generated by inhomogeneous plastic deformation (such as in cutting, rolling, or welding), thermal mismatch during cooling, or phase transformations, which result in non-uniform local strain.
Inhomogeneous model – It refers to a mathematical framework where system properties (e.g., density, material, viscosity) or governing equations are not uniform, but rather vary spatially, temporally, or depend on local covariates. Unlike homogeneous models, these define parameters as functions of location or state, rather than constants, enabling precise modeling of complex, localized behaviours like non-uniform material stiffness or multi-phase flow, and are typically solved using advanced numerical methods or particular solutions in differential equations.
Inhomogeneous residual stress fields – These refer to non-uniform, self-equilibrating internal stresses trapped within a material’s volume, varying in magnitude and sign from point to point. Unlike homogeneous stress fields, which are uniform throughout, these fields develop because of the non-uniform plastic deformation, thermal gradients, or phase transformations during manufacturing processes like welding, casting, and machining.
Inhomogeneous wave equation – It is a partial differential equation which models wave propagation in a medium driven by external sources or forcing terms (f). Unlike the homogeneous form (which equals zero), this equation accounts for external inputs like electro-magnetic charges, currents, or physical driving forces.
Initial analysis -It is the foundational phase of a project or investigation where existing data, needs, and constraints are gathered and evaluated to define the scope, identify potential solutions, and assess feasibility. It acts as a ‘fact-finding mission’ to understand the problem before detailed design or, in data contexts, as a screening process to ensure data quality before formal statistical modeling.
Initial and boundary conditions – Initial conditions define the state of a system (e.g., velocity, temperature) at the starting time (t = 0), necessary for transient simulations. Boundary conditions define how the system behaves at its spatial limits (edges) for all times, determining interaction with the environment.
Initial capital cost – It refers to the total, one-time, upfront financial investment needed to design, procure, construct, and install all physical assets needed to bring a project to a fully operational state. It covers costs incurred before revenue generation, including land, equipment, infrastructure, and commissioning.
Initial classification – It is the foundational, systematic process of assigning data, components, or materials into specific categories based on defined, observable, or measurable criteria. It acts as a primary, frequently automated, step for identifying, grouping, and analyzing elements (e.g., in image, soil, or material classification) to inform subsequent design, security, or analysis.
Initial classifier – It is a foundational, frequently offline-trained algorithm designed to label data based on features, establishing an early, baseline model. It acts as the initial, sometimes imperfect, step which maps input data to predefined categories, which can later be refined by online, adaptive, or more advanced machine learning systems.
Initial concentration – It refers to the starting quantity of a substance in a spatially distributed system, such as a reactor, which is important for determining the product yield in a dynamic model. It is necessary to assign initial concentrations consistently to avoid artificially maximizing the product yield.
Initial configuration – It refers to the fundamental, defined starting position, orientation, or setting of a system, mechanism, or software, established before operational activity or simulation. It defines the baseline state (physical or logical) of components, which ensures consistency and sets the boundary conditions for subsequent performance.
Initial construction cost – It is the total upfront expenditure incurred to design, procure, and build a project before it becomes operational. It includes direct costs (labour, materials, equipment) and indirect costs (design fees, regulatory clearances, management). These costs, necessary for budgeting, are typically established through estimates early in the project lifecycle.
Initial contract – It is the foundational agreement established between the organization and the contractor, outlining the terms, conditions, and scope of work for the project, which serves as the basis for payment requests and change orders throughout the project’s duration.
Initial crack – It refers to the first, frequently microscopic, material failure, such as a surface scratch, manufacturing defect, or fatigue-induced fissure, which marks the beginning of structural degradation. It is the crack size (ai) at the start of propagation, typically ranging from 10 micro-meters to 30 micro-meters) in materials like aluminum alloys, which serves as the starting point for fracture mechanics calculations and service life prediction.
Initial crack length – It is defined as the size of a material flaw or defect at the beginning of a fatigue, fracture, or service life assessment. It represents the starting point for crack propagation, derived from manufactured defects, fatigue pre-cracks, or non-destructive inspection limits.
Initial crack size – It is the defined starting length or depth of a crack or flaw present in a component at the beginning of its service life or a fatigue test. It represents the boundary between crack initiation and propagation, frequently determined by the detection limit of non-destructive evaluation (NDE) techniques, such as X-ray or ultrasound, in damage-tolerant design.
Initial curvature – It refers to the slight, unintentional, or pre-existing bend in a structural member (like a beam or plate) before any external load is applied. It acts as a geometric imperfection which influences buckling behaviour and bending stress, normally considered a non-linear, small-deflection, or buckling-shape deviation.
Initial deflection – It refers to the pre-existing, unintentional curvature or displacement in a structural component (like a beam, plate, or column) present before any external live loads or operational forces are applied. It is frequently caused by manufacturing, welding, or assembly. It represents the initial geometric imperfection.
Initial deformation temperature – It is also known as the deformation temperature (DT). It, is the temperature at which a material, typically ash from coal or biomass, begins to show the first signs of softening or rounding because of melting. It is the point where the material starts to deform from its original shape under specific heating conditions. Initial deformation temperature is the temperature at which a material’s structure begins to change visibly under heat, indicating the onset of melting. In the context of ash fusion, it is the temperature where the edges of an ash sample start to round or soften.
Initial discontinuity – It refers to a pre-existing break, imperfection, or sharp, sudden change in the physical properties (such as velocity, pressure, or material structure) of a system or component. These are frequently introduced during initial manufacturing, forming, or welding processes (e.g., seams, cracks, laps) or established as conditions at the start of an analysis.
Initial elastic stiffness (Eo or Ko) – It is the measure of a material’s resistance to deformation during the initial, linear-elastic phase of loading, before any damage, yielding, or cyclic deterioration occurs. It is determined by the slope of the initial load-displacement curve, acting as a key baseline for calculating structural behaviour and stiffness reduction.
Initial energy – it is the total energy (kinetic, potential, thermal, or chemical) present within a system at the exact start of a process, analysis, or time interval, frequently used in conservation laws. It sets the reference state for determining how energy is transferred, converted, or dissipated.
Initial filter criteria – These are a core component of the IP (internet protocol) multi-media sub-system (IMS) service triggering mechanism, used by the ‘serving-call session control function’ (S-CSCF) to determine which ‘application servers’ (AS) are to be involved in a user’s session. They are downloaded from the ‘home subscriber server’ (HSS) during user registration and act as a set of rules, defined in XML (eXtensible markup language), which control the routing of ‘session initiation protocol’ (SIP) messages to specific application server.
Initial flaw size – It defines the assumed size of small, pre-existing manufacturing or material defects, such as cracks or inclusions, at the start of a structural component’s service life. It is a critical parameter in damage tolerance analysis, frequently defined using the ‘equivalent initial flaw size’ (EIFS) method to represent non-detectable, early-stage crack growth, typically ranging from 0.127 millimeters to 1.27 millimeters depending on structural criticality.
Initial flow stress – It is the minimum true stress needed to initiate plastic (permanent) deformation in a material, effectively marking the transition from elastic to plastic behaviour, frequently synonymous with the yield strength (Y) or (sigma-y) at near-zero strain. It acts as the starting point on a flow curve for subsequent deformation.
Initial fluid saturation – It defines the fraction or percentage of a reservoir rock’s total pore volume occupied by a specific fluid (water, oil, or gas) before any production begins. It quantifies the in-situ distribution of fluids, where So + Sw + Sa = 1. It is used to estimate initial hydrocarbons-in-place.
Initial flush – It refers to the preliminary stage of a cleaning or environmental process where highly concentrated contaminants or particles are removed. In lubricating systems, it is the initial, turbulent oil circulation designed to remove fabrication debris. In environmental engineering, it defines the initial stormwater runoff carrying high pollutant concentrations.
Initial gas in place – It refers to the total volume of natural gas trapped in a sub-surface reservoir before any production begins. It is an important calculation for estimating reserves and reservoir performance, calculated using rock volume, porosity, gas saturation, and pressure-based volume factors.
Initial gas in solution – It is also called solution gas-oil ratio. It is the quantity of natural gas dissolved in crude oil under initial reservoir pressure and temperature conditions, expressed in standard cubic feet per stock-tank barrel or cubic meter /cubic meter. It is a critical reservoir engineering parameter for calculating initial oil in place and predicting reservoir depletion, representing gas liberated from oil as pressure drops below the bubble point.
Initial geometric imperfections – These are unavoidable, as-built deviations (like bowing, twisting, or warping) of structural members from their intended, ideal geometry. They are introduced during manufacturing, fabrication, welding, or transport, and are critical for analyzing structural stability, reducing load-bearing capacity, and causing premature buckling.
Initial grain size – It refers to the average diameter of the microscopic, individual crystals (grains) within a poly-crystalline metal before processing, representing a fundamental characteristic which dictates mechanical properties like strength, hardness, and toughness, with smaller grains normally improving these properties because of more grain boundaries acting as barriers to dislocation movement. It is a key factor in material performance, determined from etched micro-structures and frequently standardized by methods, influencing everything from ductility to crack resistance.
Initial graphics exchange specification – It is a vendor-neutral file format that allows the digital exchange of information among computer-aided design (CAD) systems. Using initial graphics exchange specification, a computer aided design user can exchange product data models in the form of circuit diagrams, wireframe, freeform surface, boundary (B-rep) or solid modeling (constructive solid geometry, CSG) representations. Applications supported by initial graphics exchange specification include traditional engineering drawings, models for analysis, and other manufacturing functions.
Initial graphics exchange standard – It is a protocol for transferring graphics data between CAD (computer aided design) systems.
Initial hypothesis – It is the preliminary assumption made by a researcher before conducting an experiment, which is later evaluated based on the study’s results to determine its validity.
Initial imperfection – It refers to the unavoidable, pre-existing geometric deviations (such as out-of-straightness, sweep, or out-of-plumb) present in structural members or materials before loading. These imperfections, including local bows or global sways, trigger premature buckling, reduce structural capacity, and are typically modeled in non-linear analysis.
Initial incompatible strain – It refers to a pre-existing, prescribed, or inelastic strain field (ei) within a material which cannot be derived from a continuous, single-valued displacement field. It is a main driver of internal stress, as the material is to develop elastic strains to accommodate the incompatibility. It represents a mismatch in deformation between different microstructural components (e.g., grain-to-grain) or, in fabrication, between newly deposited material and an underlying substrate. Such strains arise from inelastic phenomena such as thermal expansion / contraction, plastic deformation, phase transformations, or nonuniform growth during processing.
Initial investment cost – It is the total, upfront capital expenditure (CAPEX) needed to design, acquire, construct, and commission a project before it begins operation. It includes direct costs (machinery, land, materials, labor) and indirect costs (engineering fees, permits, contingency).
Initial mass – It is defined as the total mass of a system, component, or material at the exact starting point of observation, analysis, or process simulation. It represents the reference quantity before any transformations, such as decay, consumption, or structural changes, occur over time.
Initial method – It refers to the preliminary stages of extracting pure metal from naturally occurring, unrefined mineral deposits (ores). This initial phase focuses on removing earthy, undesirable impurities (known as gangue or matrix) to increase the percentage of the desired metal.
Initial microstructure – It refers to the specific arrangement, orientation, size, and distribution of grains and phases within a material before undergoing manufacturing, processing (e.g., deformation), or thermal treatments. It acts as the starting state, defining necessary properties like grain shape and boundary, which dictate the material’s response to subsequent processes.
Initial modulus – It is the slope of the initial straight portion of a stress-strain or load-elongation curve.
Initial moisture content – It is the quantity of water present in a material (e.g., soil or manufactured goods) immediately before a drying, testing, or manufacturing process. It is a critical parameter for calculating drying time, ensuring material stability, and controlling quality, normally expressed as a percentage of either the wet or dry weight.
Initial permeability – It is the magnetic permeability of a ferro-magnetic material when it is in a demagnetized state and subjected to a very low magnetic field strength (H tends to 0). It represents the initial slope of the virgin magnetization curve (B -H curve). It is measured at the very beginning of the hysteresis loop, normally at low alternating current (AC) frequencies, where the magnetic domain walls do not undergo major jumps (Barkhausen jumps) but rather stay pinned and show slight bowing.
Initial phase difference – It is the angular difference between two sinusoidal signals or waves at time t = 0, measuring how much one signal leads or lags another in its oscillation cycle. It represents the relative positional offset, frequently in radians or degrees, crucial for analyzing interference, alternating current circuit behaviour, and wave synchronization.
Initial pitting – It is the surface fatigue which is occurring during the early stages of gear operation, associated with the removal of highly stressed local areas and running-in.
Initial point – It refers to the specific starting, reference, or datum point (t =0, or x0) for calculations, simulations, vectors, or surveys, establishing the foundation for analyzing system behaviour, motion, or spatial orientation. It defines the boundary conditions necessary to solve differential equations.
Initial recovery – It is the decrease in strain in a solid during the removal of force before any creep recovery takes place. It is normally determined at constant temperature. It is sometimes referred to as instantaneous recovery.
Initial relative density (Dr) – It is a dimensionless parameter measuring the packing density of cohesionless soil in its in-situ (initial) state relative to its loosest and densest states. It is defined by the ratio of void ratios, typically expressed as a percentage Dr = [[(emax – e0)/(emax – emin)] 100 %.
Initial reservoir pressure – it is the pressure within a reservoir at the beginning of production, which can be determined using methods such as the Horner plot from pressure buildup tests when boundary effects are negligible. It is the virgin, undisturbed pressure of a hydrocarbon reservoir before any production begins, typically measured at the discovery well. It represents the fundamental, equilibrium state of the system used for estimating reserves, calculating initial fluid properties, and determining if a reservoir is under-, normally, or over-pressured.
Initial setting time – It is the duration, measured from the moment water is added to cement, until the paste begins to lose its plasticity, stiffen, and starts to lose its workability. It signifies the maximum allowable time for mixing, placing, transporting, and initial compaction of concrete, typically needing a minimum of 30 minutes for ‘ordinary Portland cement’ (OPC).
Initial shock – It is a mechanical shock. It refers to an abrupt, transient, and high-amplitude excitation caused by sudden impact, drop, or explosion, resulting in rapid acceleration, velocity change and structural deformation or failure. It is characterized by a short-duration load pulse where peak acceleration occurs rapidly, typically lasting shorter than the natural period of the system.
Initial strain – It is the strain in a sample immediately upon achieving the given loading conditions in a creep test (before creep occurs). It is sometimes referred to as instantaneous strain.
Initial stress – It is the stress which is produced by strain in a sample immediately on achieving the given constant-strain conditions in a stress-relaxation test before stress-relaxation occurs. It is sometimes referred to as instantaneous stress.
Initial solution gas – It is natural gas dissolved within crude oil under high-pressure, high-temperature reservoir conditions. It is a critical reservoir parameter, measured as the volume of gas (in standard cubic feet) which liberates from a stock-tank barrel (STB) of oil as pressure drops to the bubble point.
Initial starting point – It is the specific, foundational value, coordinate, or state (e.g., position, velocity, temperature) chosen to begin numerical simulations, iterative calculations, or physical movement. It is critical for establishing simulation convergence, trajectory, and behavioural accuracy in system modeling.
Initial state – It is the defined starting condition of a system, process, or component at time t = 0, establishing the necessary baseline, such as temperature, pressure, configuration, or active software state, before operation, analysis, or simulation begins. It ensures compliance with mass, energy, or logical constraints and dictates subsequent behaviour.
Initial stiffness – It is the slope of the initial, linear-elastic portion of a load-deflection or stress-strain curve, representing a structure’s or material’s resistance to deformation before any yielding, damage, or degradation occurs. It serves as a baseline for determining stiffness degradation under cyclic loading.
Initial strain rate – It is the rate of deformation (strain) applied to a material at the very beginning of a loading process, defined as the time derivative of strain (e’ = de/dt). It represents how quickly a material is stretched or compressed initially, with units of inverse seconds (s to the power -1).
Initial tangent modulus – It is the slope of the stress-strain curve at the beginning of loading.
Initial temperature distribution – It refers to the spatial arrangement of temperatures within a system at the precise start of a transient heat transfer process (t = 0). It is a foundational boundary condition, frequently represented as a function T(x,y,z,0), determining how heat propagates through a material to reach equilibrium.
Initial transmission – It typically refers to the first, primary, or foundational transfer of power, motion, or data within a system. In mechanics, it is the initial stage of transferring engine power (frequently through clutch / flywheel) to the gearbox. In communication, it refers to the first attempt to send a data packet, frequently utilizing specific protocols (e.g., synchronous / asynchronous) or single-antenna modes in wireless systems.
Initial value – It is the defined state, value, or condition of a system at time t = 0 (or t =0+), important for solving differential equations and predicting transient behaviour. It represents the starting point, such as initial velocity, charge, or pressure, used to find unique solutions for dynamic systems.
Initial velocity – It is the vector quantity representing an object’s speed and direction at the exact moment motion begins or a specific time interval starts (t = 0). It is a critical kinematic parameter used to calculate future position, acceleration, and trajectories. If starting from rest, the initial velocity is 0 meters per second.
Initial water content – It is the quantity of moisture present within a material (soil, fuel cell, or building material) before processing, such as drying, loading, or testing. It is typically expressed as a percentage of the dry mass or total volume.
Initial water saturation – It is the fraction of reservoir pore volume occupied by water before any production begins, representing the irreducible water trapped by capillary forces. It is critical for calculating hydrocarbon reserves and determining reservoir wettability. It is determined using geophysical logging, sealed coring, or the J-function method.
Initial yield strength – It is the precise stress level at which a material transitions from elastic (reversible) to plastic (permanent) deformation. It defines the maximum stress a component can withstand without permanently changing shape, typically measured in pascals (Pa. It is important for engineering design, frequently determined using the 0.2 % offset method.
Initial yield stress – It is the critical stress level marking the transition from elastic (reversible) to plastic (permanent) deformation in a material. It is the minimum stress needed to initiate microstructural yielding (atomic slip or dislocation movement) and causes permanent, non-recoverable change in shape.
Initiated crack – It is the first stage of fatigue failure where localized, irreversible plastic deformation, frequently driven by cyclic loading, causes a microcrack to form at a stress concentrator like a surface defect, inclusion, or grain boundary. It represents the onset of structural degradation, frequently characterized by a small, non-visible crack before propagation occurs.
Initiate polymerization – It refers to the process of starting the chemical reaction which leads to polymer formation, which can be achieved using heat, radiation, or suitable initiators and catalysts.
Initiating event – It is the term used in safety engineering to refer to an initiating cause, when assessing consequences and outcomes. An initiating event can be defined as a challenge to plant operation. ‘Event tree analysis’ involves the analysis of initiating events and their consequences.
Initiation of crack – It is the initial phase of material failure where localized plastic deformation, stress concentration, or fatigue causes the formation of a microscopic crack, frequently starting at surface defects, inclusions, or grain boundaries. It represents the onset of structural degradation before substantial propagation occurs.
Initiation of stable crack growth – It is the initiation of slow stable crack advance from the blunted crack tip.
Initiation phase, project – Initiation phase of a project is the first phase when the design and engineering activities start. During this phase feasibility studies for the project are carried out for firming of the initial decision of setting up of the plant. This is the phase when various approvals are taken for the implementation of the project. One of the important approvals during this phase is the environmental clearance for the project. This clearance needs preparation of a study report for the environment impact assessment (EIA) and environment management plan (EMP). During this phase the project concepts are determined and a plot plan for the selected facilities is made. The technologies to be adopted are selected after assessing various available technologies, requirements of input materials, utilities, and power are estimated after carrying out preliminary balancing of capacities, materials, energies, and utilities etc. The suitability of the site location is also established in this phase after the study of the infrastructure development need for the project. This is the phase when the requirements of enabling facilities needed during the project implementation are determined. These enabling facilities include (i) site preparation including its leveling, (ii) road and / or rail approach for the selected site, (iii) building requirements for administration during construction, (iv) facilities for construction stores, (v) communication need during construction, (vi) requirements of water, power, and other utilities needed during project implementation, and (vii) housing facilities needed for the construction workers etc. Basic engineering for these enabling facilities starts during this phase.
Initiation time – It refers to the time elapsed from a specific, controlled, or observed start point until the first occurrence of a particular, frequently undesirable, event, such as a crack, corrosion, or chemical reaction. It is a critical parameter for predicting the service life of materials and components.
Initiator – It consists of the peroxides used as sources of free radicals. These peroxides are used in free-radical polymerizations, for curing thermosetting resins, as cross-linking agents for elastomers and polyethylene, and for polymer modification.
Initiator efficiency – In polymerization, it is the fraction of radicals generated from an initiator which successfully escape the solvent cage and initiate polymer chain growth, rather than undergoing termination or side reactions. It is represented as a factor between 0 and 1, it determines the actual rate of chain initiation.
Injected fluid – In petroleum and geological contexts, it refers to water, gas, or chemical agents introduced into underground reservoirs through injection wells to maintain pressure, increase, or facilitate the recovery of in situ fluids like oil and gas. These fluids are used in secondary / tertiary recovery processes such as waterflooding, gas injection, or steaming to optimize production.
Injected fuel – It refers to the pressurized, atomized spray of fuel introduced directly into an engine’s combustion chamber or intake manifold through an electronically controlled injector. This engineering process replaces carburetors, providing precise, metered fuel delivery based on demand, which improves efficiency, increases power, and reduces emissions.
Injected gas – It refers to the introduction of substances like natural gas, carbon di-oxide, or nitrogen into an underground reservoir to maintain pressure, increase oil viscosity reduction (miscible / immiscible displacement), and improve hydrocarbon recovery. It is an ‘enhanced oil recovery’ (EOR) technique, distinct from gas lift.
Injected gas volume – It the total quantity of gas (e.g., natural gas, carbon di-oxide) introduced into a reservoir or system over a specific period, typically measured in standard cubic feet per day, or cubic meters. It is important crucial for enhanced oil recovery (EOR) to boost reservoir pressure or for storing gas in underground fields.
Injected noise – It is the intentional addition of random signals (e.g., Gaussian, white noise) into a system, data set, or model to improve robustness, prevent overfitting in machine learning, or to study system dynamics. It acts as a regularization technique, reducing model sensitivity to small input changes.
Injected water – It refers to water introduced into an oil reservoir through man-made systems to maintain reservoir pressure and improve oil recovery. This process, frequently called water-flooding or injection, involves pumping water into the production zone to drive oil toward production wells.
Injecting cold water – It is the process of pumping water at a lower temperature into a hot, underground reservoir, well, or formation. This technique reduces heat in the rock matrix, causing thermal contraction and cracking, which improves permeability, increases injectivity, and stimulates production.
Injection current density – It is the quantity of electrical current injected per unit cross-sectional area into a semiconductor, device, or material. It defines the intensity of charge carrier injection, important for determining carrier density, stimulated emission in lasers, and preventing component overheating.
Injection – It is the process of forcing molten metal into the die casting die. It is also the process of injecting a powdered material in the molten metal filled in a ladle.
Injection blow moulding – It is a high-precision, three-stage engineering process used to manufacture small, hollow, neck-finished plastic containers (bottles / jars) without flash or waste. It involves injection moulding a molten thermoplastic ‘preform’ onto a core rod, rotating it to a blow mould for inflation with compressed air, and cooling the final part.
Injection compression moulding – It is a hybrid engineering process combining injection and compression techniques, where molten polymer is injected into a partially open mould, which is subsequently closed to compress and distribute the material. It reduces internal stress, minimizes warpage, and improves dimensional accuracy, especially for complex or thin-walled parts.
Injection efficiency – It defines the effectiveness of transporting, injecting, or injecting a substance / charge carrier into a system, typically measured as the ratio of useful output (particles, current, or material reaching the target) to total input. It represents the proportion of injected material which contributes to the desired process rather than being lost or wasted.
Injection fitting – It is a fitting through which lubricant or sealant is injected.
Injection lances – These lances are used for injecting either oxygen or auxiliary fuels into the blast furnace through tuyeres. These lances are normally inserted in blow-pipes.
Injection level – It refers to the ratio of excess charge carriers (electrons or holes) introduced into a semiconductor material to the equilibrium concentration of majority carriers. It is a critical parameter used to define the operating regime of a device, such as a solar cell or transistor, and dictates the dominant recombination mechanism.
Injection mechanism – It is a specialized system designed to force materials, such as molten polymers, fuel, or fluids, under high pressure into a cavity or chamber, typically to initiate manufacturing (moulding) or combustion. It comprises components like a screw / ram, nozzle, and heating unit to achieve precise, high-velocity delivery.
Injection metallurgy – It is used in conjunction with ladle furnaces. It is used to refine molten steel. In injection metallurgy, desulphurizing reagents are injected into the ladle through a lance using argon gas as a carrier, which helps remove sulphur. Ladle furnaces are used to reheat, stir, and refine steel in a ladle.
Injection mix – It consists of unshaped refractory which is specially designed to be injected by a pump using pressures of between 1megapascal and 2 megapascal. An injection mix can either be supplied ready for use, or can need mixing.
Injection model – It refers to a method used in power systems to model power flow from direct current to alternating current systems and vice versa, allowing for the control of real and reactive power injected into connection buses by varying control parameters. This model is particularly utilized for analyzing HVDC (high voltage direct current) systems within large power systems, enabling studies on slow dynamics, damping controller design, and optimal power dispatch.
Injection moulded part – It is a component produced by forcing molten material, typically thermoplastics, but also elastomers or metals, under high pressure into a precision-machined mould cavity. These parts are defined by their ability to achieve complex geometries, high consistency, and tight tolerances in mass production, cooling and solidifying into the final shape.
Injection moulding – It is a manufacturing process which creates precise, complex, and high-volume molten metal or other material plastic components by forcing melted material into a, normally, tool steel or aluminum mould cavity under high pressure. The process involves melting metal or other material, injecting the material under pressure into close moulds, cooling it, and ejecting the solidified part.
Injection moulding (ceramics) – It is a process for forming ceramic articles in which a granular ceramic-binder mix is heated until softened and then forced into a mold cavity, where it cools and resolidifies to produce a part of the desired shape.
Injection moulding (metals) – It is a process similar to plastic injection moulding using a plastic-coated metal powder of fine particle size (around 10 micrometer).
Injection moulding operation – It refers to a manufacturing process in which thermoplastic material is heated and forced into a mould under pressure, allowing for the production of items with precise dimensions and excellent surface finish. This process includes a cycle of operations that involves filling the mould, cooling, and ejecting the moulded product.
Injection moulding (plastics) – It is the method of forming a plastic to the desired shape by forcing the heat-softened plastic into a relatively cool cavity under pressure.
Injection moulding process – It is a manufacturing technique which produces large quantities of plastic or other material parts with high dimensional tolerance by compressing and melting the plastic pellets or other materials, injecting the molten material into a mould under high pressure, and allowing it to solidify before ejecting the finished product. This process is characterized by its speed, low costs, and minimal wastage.
Injection period – It is also called injection time / injection duration. It is the precise interval during which material (polymer / metal melt or fuel) is actively forced into a mould cavity or combustion chamber, starting from the initiation of plunger / screw advancement until the switchover to holding pressure. It is an important phase determining part quality, production rate, and injection pressure.
Injection pressure – It is the force per unit area applied by the injection screw or plunger to move molten material from the barrel into the mould cavity. Typically ranging from 70 mega-pascals to 140 mega-pascals, this pressure overcomes flow resistance to ensure complete cavity filling and, combined with packing, dictates part density, dimensional accuracy, and quality.
Injection process – It refers to a batch manufacturing technique where composite material is melted and injected into a mould at high pressure to create products with complex geometries. It is important to control the temperature during this process, particularly when using natural fibre reinforcements, to avoid damage to the fibres.
Injection rate – It is the volumetric or mass flow rate of a material (polymer, fuel, or fluid) introduced into a system per unit of time. It defines the speed of injection, important for controlling filling, pressure, and, in combustion, the rate of fuel mass exiting a nozzle.
Injection refining (IR) process – In this process, first lime and then calcium silicide are fed pneumatically through a vertical lance into the teeming ladle. A refractory-lined hood placed over the surface of the steel prevents ingress of atmospheric oxygen. As the relatively large lime particles rise through the melt, they cleanse it by collecting the essentially stationary smaller-diameter (around 1 micrometer to 10 micrometers) products of deoxidation.
Injection speed – It is the velocity at which the machine’s screw or plunger moves forward to push molten material into the mould cavity. It defines how quickly the material fills the mould, measured in millimeter per second, and directly impacts shear, viscosity, cooling, and surface finish.
Injection system – It is a specialized mechanism designed to precisely meter, pressurize, and deliver fluids (liquid or gas) into a combustion chamber, vessel, or process stream. It is mainly used in internal combustion engines (fuel injection) for atomization and efficiency, or in oil / gas operations to inject fluids into producing formations for reservoir pressure maintenance.
Injection time – It is the duration needed for the screw to move from the start of injection to the transfer (velocity-pressure) position, typically filling the mould cavity around 95 z% to 98 %. It is an important parameter influencing part quality, cycle time, and pressure.
Injection unit – It is the component of an injection moulding machine responsible for melting, mixing, and injecting plasticized material into a mould cavity. It consists of a hopper, heated barrel, and reciprocating screw, functioning to convert raw pellets into a homogeneous, pressurized melt, ensuring consistent quality and precise part formation.
Injection velocity – It is the rate, frequently measured in millimeter per second or meter per second, at which material (typically polymer melt or liquid metal) is forced into a mould cavity during injection moulding, directly influencing fill, pressure, and final part quality. It determines molecular orientation and is important for avoiding defects like incomplete filling or surface marks.
Injection well – It is a borehole which is used to place fluids underground into porous rock formations or shallow soil layers, frequently for purposes like waste disposal, enhanced oil recovery, or carbon storage.
Injectivity – It is a major determinant of the suitability of a site for carbon di-oxide storage. Injectivity is defined as the ratio of well volumetric flow rate to the corresponding pressure drop. It measures the possibility of inserting a fluid into a geological formation and is characterized by the rate at which carbon di-oxide can be injected and the ability of carbon di-oxide to migrate from the injection well, and is normally dependent on the permeability and porosity of the formation as well.
Injectivity index – It is defined as the ratio of the constant water injection flow rate to the difference between fluid pressures at the wellbore and the external reservoir, reflecting the instantaneous performance of a reservoir during fluid injection.
Injector – It is a device utilizing a steam jet to entrain and deliver feed water into a boiler.
Injector characteristics – These refer to the specific attributes of fuel injectors, such as spray shape, droplet size, penetration, and fuel flow rate, which are critical for optimizing fuel spray evaporation, fuel-air mixing, and fuel-wall impingement in combustion systems.
Injury – It consists of an abnormal condition or disorder, such as cuts, fractures, sprains, amputations, skin diseases, respiratory disorders, and several other types of bodily harm. The definition encompasses a wide range of situations, including accidents, injuries from repetitive motions, exposure to harmful substances, and illnesses caused by work activities.
Injury analysis – It is the process of systematically evaluating injury statistics to identify trends.
Injury environment – It refers to the surrounding physical, chemical, and operational conditions, including machinery, infrastructure, and ambient factors, which possess the potential to cause harm, injury, or death to humans. Engineering disciplines define this environment to identify risks, analyze mechanisms of injury (like impact or thermal stress), and implement protective designs (such as guarding, safety interlocks, or hazard containment) to mitigate these dangers.
Injury mechanism – It is defined as the physical process, vector, or method by which energy is transferred to the body, causing damage to tissues which exceeds their failure tolerance. It involves analyzing kinematics, forces (acceleration / deceleration, compression, shear), and load types to predict, evaluate, and prevent injury, frequently utilizing the Haddon matrix for analysis.
Injury severity score – It is an anatomical scoring system which quantifies the overall severity of multiple injuries by assigning scores to the most severely injured body regions, with the scores of the top three regions squared and summed to produce a total score ranging from 0 to 75. It is used to correlate with mortality, morbidity, and hospital stay.
Ink jet printing – It is a method of printing where tiny drops of ink are formed into a number, letter or image and are then sprayed onto the surface to be printed.
Inkjet printing technology – It is a process which involves the deposition of small droplets (1–100 pico-litre) of ink from a nozzle onto a collecting plate, resulting in coatings or 3D structures which solidify upon contact. This technology is characterized by its spatial resolution of around 10 micro-meters in the x–y axes and can be improved using multi-nozzle systems.
Inlet air – It refers to the air, gas, or ambient atmosphere entering a machine, system, or space (e.g., engines, compressors, turbines, heating, ventilation, and air conditioning systems) through a dedicated opening or duct, normally known as an intake or air inlet. It acts as the necessary intake point for combustion, cooling, or ventilation, where properties like velocity and temperature are important for system efficiency.
Inlet air temperature – It defines the temperature of air as it enters a machine, device, or system component (e.g., engines, compressors, turbines, or units). It is an important parameter for determining system efficiency, performance, and thermal management, as lower, denser air temperatures typically improve power output.
Inlet air velocity – It is the speed (V) at which air enters a system, component, or device, measured in distance per unit of time (typically or meters per second). It is important for determining volumetric flow rate (Q = A xn V), ensuring optimal performance in HVAC (heating, ventilation, and air conditioning) systems, combustion, and air handling.
Inlet area – It refers to the specific boundary, opening, or cross-sectional area through which fluids (liquids or gases) or materials enter a vessel, machine, or system. It acts as an important entry point designed to optimize flow, manage pressure, and frequently reduce turbulence before the fluid enters a process component.
Inlet boundary conditions – These are important CFD (computational fluid dynamics) parameters in engineering simulations, defining how fluid, mass, or energy enters a domain. Common types include velocity inlets (uniform/profile), mass flow rates, and pressure inlets. These conditions are crucial for modeling, with options such as pressure-inlet, velocity-inlet, and mass-flow-inlet.
Inlet composition – It defines the specific, measured mixture of chemical species, gases, or materials introduced into a process unit, reactor, or system. It encompasses the molar ratios, concentration of reactants, and presence of inert components, important for determining reaction conversion rates, product quality, and downstream system performance.
Inlet, cyclone – It is the entry point of a cyclone separator, which can be either circular or rectangular, and varies in size. It plays an important role in controlling particle cut size and improving classification performance in hydrocyclones.
Inlet flow – It refers to the conditions of fluid flow at the entrance of a pipe or vessel, where the velocity profile can change with distance from the entrance until it stabilizes beyond a certain distance known as the inlet length. This concept is particularly important in understanding how flow behaviour evolves in complex geometries. It defines the specific boundary conditions, velocity, pressure, temperature, and composition, of a fluid as it enters a pipe, vessel, or system. It is critical for calculating mass balances, designing pumps, and modeling fluid behaviour in ‘computational fluid dynamics’ (CFD). Key parameters include mass flow rate, velocity profile, and pressure.
Inlet flow rate – It defines the quantity of fluid (liquid or gas) entering a system, pipe, or vessel per unit of time. It is critical for mass balance, performance, and efficiency calculations, normally measured as volumetric flow rate (Q = A x V) or mass flow rate (m = d x A x V). It acts as a main input parameter for designing equipment like pumps, turbines, and chemical reactors.
Inlet flow stream – It involves specifying the physical properties, thermodynamic state, and mass flow rate of fluid entering an engineering system, such as a pipe, reactor, or vessel. It needs defining parameters like velocity, pressure, temperature, and composition to determine mass balances / energy balances and, in computational fluid dynamics (CFD), setting boundary conditions like velocity profiles and turbulence intensity.
Inlet fluid temperature – It is the temperature of a fluid (liquid or gas) as it enters a thermal system, component, or process, serving as an important boundary condition for calculating heat transfer, efficiency, and performance. It dictates the initial energy state of the fluid before it interacts with the system, such as a heat exchanger, turbine, or collector.
Inlet gas – It refers to the raw, untreated, or partially processed hydrocarbon gas (sweet or sour) along with unstabilized condensate received from upstream production units, pipelines, or wells, prior to being processed or treated in a facility. It represents the feed stream which enters a plant, reactor, or compressor system for purification, separation, or, liquefaction.
Inlet gas temperature – It defines the temperature of a gas stream immediately before it enters a specific component, such as a turbine, dryer, compressor, or storage tank. This parameter is important for determining thermal efficiency, heat load, material safety limits, and fluid properties (e.g., water content or density).
Inlet line – It is also called suction line. It refers to the pipe, conduit, or passage which delivers fluid (liquid or gas) into a machine, vessel, or process system. It is the upstream, supply-side piping designed to transport process material from a source to the entry nozzle of equipment such as pumps, compressors, or reactors.
Inlet loss – It is the non-recoverable drop in pressure or energy (head loss) which occurs as a fluid enters a pipe, duct, or device (like a valve or machine) due to turbulence, flow separation, and friction, frequently characterized by a coefficient Ke. It is an important ‘minor loss’ which reduces system capacity and performance, normally calculated using the formula Pl = Ke x 1/2p x v square.
Inlet Mach number (M) – It is the ratio of gas velocity (V) to the local speed of sound (A) at a component’s entrance, such as a turbomachine eye, diffuser, or nozzle. It defines flow compressibility and determines aerodynamic behaviour, with specific relevance to compressor blade performance, shock waves, and inlet choking.
Inlet manifold – It is also called intake manifold. It is a component comprising a series of pipes or tubes which delivers the air or fuel / air mixture to the intake ports of an engine’s cylinders. Its main purpose is to evenly distribute this mixture to each cylinder, optimizing volumetric efficiency and engine performance.
Inlet nozzle – It is a specially shaped component, pipe, or conduit designed to guide, control, and accelerate fluid (liquid or gas) into a machine, chamber, or vessel. It optimizes flow, frequently reducing pressure to increase velocity (kinetic energy) while ensuring smooth, efficient entry into systems like fans, pumps, or turbines.
Inlet pipe – It is a conduit, tube, or channel designed to allow fluids (liquids or gases) to enter a machine, device, vessel, or system. It frequently features specific diameters to match intake requirements, controls flow rate, prevents backflow using check valves, and sometimes includes features like baffles for mixing or ensuring structural efficiency.
Inlet port – It is the end of a valve which is connected to the upstream pressure zone of a fluid system.
Inlet pressure – It is the fluid (liquid or gas) pressure measured at the suction port, flange, or entry point of a pump, compressor, or system. It represents the energy level of the fluid entering the equipment, critical for determining performance, capacity, and preventing cavitation.
Inlet region – It defines the initial zone of a conduit, vessel, or system where fluid enters, frequently characterized by high velocity, turbulence, and developing flow profiles before becoming fully developed. It acts as the important interface for managing flow distribution, minimizing pressure losses, and transitioning fluid from outside to within.
Inlet stratifiers – These are devices used in storage tanks to minimize the mixing of hot and cold water, hence aiding thermal stratification by allowing for more efficient layering of temperatures within the tank. They can be designed to work with low-flow operation in the solar collector loop and are frequently made from flexible fabric piping to help equalize pressure.
Inlet stroke – It refers to the phase in an engine cycle during which the inlet valve opens, allowing the air-fuel mixture to flow into the cylinder before the valve closes at a specific timing, which can impact considerably engine performance and efficiency.
Inlet surface – It is normally physical, boundary at the entrance of a flow system, vessel, or channel where fluid (liquid or gas) enters. It is important for determining flow conditions, establishing velocity profiles, and minimizing turbulent disturbances to ensure optimal system performance.
Inlet swirl – It refers to the rotational or vortex motion of a fluid (air or gas) as it enters a machine component, such as a fan, compressor, or engine cylinder. It is characterized by tangential velocity components which can improve fuel-air mixing in combustion engines but frequently causes performance degradation, reduced efficiency, and instability (surging) in turbo-machinery.
Inlet temperature – It is the temperature of a working fluid (gas, liquid, or air) at the exact point it enters a system, component, or machine, serving as an important boundary condition for thermodynamic, heat transfer, and performance analysis. This parameter determines the initial energy state, directly influencing heat transfer efficiency, operating capacity, and thermal efficiency of systems like heat exchangers, compressors, and turbines.
Inlet valve – It is a mechanical gate controlling the entry of a working fluid (like air, fuel, or water) into a system, such as an internal combustion engine cylinder, air compressor, or hydro-electric turbine. It precisely opens and closes to manage flow, pressure, and timing for optimal performance, sealing the chamber when closed to prevent backflow or leakage.
Inlet vanes -These are frequently called inlet guide vanes (IGV) or inlet vane dampers. These are adjustable or fixed blades positioned at the entrance of fans, blowers, or compressors. They control capacity, pressure, and flow efficiency by pre-spinning air in the direction of impeller rotation. Key applications include optimizing energy efficiency in HVAC (heating, ventilation, and air conditioning) systems and controlling compressor surge.
Inlet velocity – It defines the speed and direction of fluid (liquid or gas) entering a system, machine, or computational domain. It is a critical boundary condition, often used in computational fluid dynamics (CFD), representing the velocity profile at an entrance, which influences downstream flow behaviour, turbulence, and mixing.
Inlet volume flow – It is the actual, instantaneous volumetric rate (cubic meter per second) of a fluid, liquid or gas, entering the intake of a machine or system, such as a compressor, pump, or reactor, based on local pressure and temperature conditions. It is calculated by multiplying the cross-sectional area of the inlet by the velocity of the fluid.
Inlet zone – It is the initial, critical area where fluid, air, or material enters a vessel, pipe, or structure, often characterized by high velocity, turbulence, and rapid changes in flow, such as contraction or expansion. It is designed to dissipate energy, distribute flow uniformly, and prevent excessive turbulence or erosion.
In-line coagulation – it is a water treatment process where chemical coagulants are injected directly into the raw water pipeline, bypassing traditional mixing basins and sedimentation tanks, followed immediately by filtration (normally membrane, e.g., ultra filtration, UF / micro-filtration, MF). It improves contaminant removal and reduces membrane fouling by promoting floc formation on the membrane surface rather than in a clarifier.
In-line flow forming process – It is a specialized, cold, chip-less, rotary metal-working process designed to produce high-precision, thin-walled, seamless hollow components by reducing the wall thickness of a preform (a cup or tube) through compressive, rotational, and axial forces. Unlike staggered-roll configurations, in-line flow forming positions all rollers (typically three or four) at the same axial and radial position to apply simultaneous pressure on the work-piece as it rotates on a mandrel.
In-line optical amplifier – It is an active fibre-optic device placed at intermediate points along a long-haul fibre link (typically every 80 kilometers to 100 kilometers) to directly amplify weakened optical signals without electrical conversion. It compensates for fibre attenuation, connector losses, and improves signal-to-noise ratio (SNR) in wavelength-division multiplexing (WDM)M networks using moderate gain and low noise.
In-line strip production process – This process produces hot-rolled coil down to finished gauges of 1 millimeter. One of the most striking characteristics of the in-line strip production process is the overall compactness of the plant. With a line length of only 180 meters from liquid steel to hot rolled coil, it is normally recognized as the shortest strip line. This characteristic is the result of three significant in-line strip production process features namely (i) continuous casting with liquid core reduction during slab solidification, (ii) direct linkage between steel casting and initial slab rolling, and (iii) the use of a compact induction heater combined with two coil box furnaces, rather than long tunnel furnaces at the entry side of the hot rolling mill. The liquid steel is cast in a multi-bending mould with servo-hydraulic oscillation and an exit thickness of 70 millimeters. The slab undergoes soft reduction as it travels down the 5.2 meters in-line strip production radius caster, to emerge at a speed of 5.5meters per minute and at a maximum thickness of 55 millimeters. The tundish nozzle is designed to ensure homogeneous shell growth and the casting of long sequences.
Inmetco process – It is a coal-based process similar to FASTMET which uses iron oxide fines and pulverized coal to produce a scrap substitute. Mill scale and flue dust, inexpensive by-products of steelmaking, can be mixed with the iron oxide fines. Inmetco, unlike other direct reduction products, is intended to be hot charged into an electric arc furnace, with attendant energy savings. The process includes three steps. First, iron oxide fines, pulverized coal and a binder are formed into pellets. Second, the pellets in two to three layers deep, are heated in a gas-fired rotary hearth furnace for 15 minutes to 20 minutes to produce sponge iron. Subsequently, the iron is to be desulphurized. The coal in the pellets provides much of the energy needed in the second phase.
In-mould labeling – It is a process where a pre-printed thermoplastic label is placed into a mould cavity before plastic injection, blow moulding, or thermoforming. The molten plastic fuses with the label during moulding, creating a single, decorated, durable, and waterproof product which needs no post-moulding labeling.
Inner frame forging machine – It is frequently recognized as a closed-type, single-point, or multi-point forged press. It is specialized metallurgical equipment designed for high-precision, high-strength metal shaping. It utilizes high-pressure, frequently hydraulic or mechanical, to force heated metal (such as steel or aluminum alloys) into a closed-die cavity to produce components with specific geometries, such as automotive chassis, or structural frames.
Inner seat ring – It is the inner part of a two-piece valve seat assembly.
Inner sheath (for multi-core cables) – The laid-up cores are surrounded by an inner sheath of any of the two types namely (i) extruded poly vinyl chloride (PVC) compound (for armoured cables), and (ii) wrapping of poly vinyl chloride / plastic tapes for unarmoured cables. Inner sheath is also known as bedding in case of armoured cables.
Inner volume, blast furnace – It is the total inner volume of the blast furnace between the hearth bottom and the level of the top ring.
Innovation -It is normally considered as new idea, creative thought, and new imagination in form of device or method. It is often viewed as the application of better solutions which meet new requirements, unarticulated needs, or existing needs of the market. It is also considered as the process of translating an idea or invention into a good or service which creates value or for which customers are going to pay. It often results when ideas are applied by the organization in order to further satisfy the needs and expectations of the customers. It is crucial to the continuing success of any organization. Hence the need of innovation is essential for the organization to be successful.
Innovative development – It consists of creative application and adoption of new technologies to generate new products, services, and processes which meet user needs while improving competitive advantage in a global market.
Inoculant – It is the material which, when added to the molten metal, modifies the structure and hence changes the physical and mechanical properties to a degree not explained on the basis of the change in composition resulting from their use. Ferro-silicon-base alloys are normally used to inoculate gray irons and ductile irons.
Inoculation – It is a process of adding some material to molten metal in the ladle for the purpose of controlling the structure to an extent not possible by control of chemical analysis and other normal variables. It is the addition of a material to molten metal to form nuclei for crystallization.
Inoperative equipment – It refers to any instrument, system, or component which does not function as intended, needing it to be treated as non-functional for operational, safety, or maintenance purposes. Such items are to be deactivated, removed, or placarded inoperative and, if allowed, managed through ‘minimum equipment list’ (MEL).
Inorganic – It is being or composed of matter other than hydrocarbons and their derivatives, or matter which is not of plant or animal origin.
Inorganic acid – It is a mineral acid which is derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Inorganic arsenic compounds -These are chemical substances containing arsenic (As) bonded to non-carbon elements (such as oxygen, sulphur, or chlorine), existing mainly as trivalent (AS 3+) arsenites or penta-valent (As 5+) arsenates. Engineered forms are typically crystalline, powder, or vitreous solids with specific gravity ranging from 1.9 to over 5, widely utilized in metallurgy, wood preservation, glass manufacturing, and semiconductors like gallium arsenide (GAAS).
Inorganic bond – It is the chemical bond which holds atoms together in an inorganic compound. Inorganic compounds are characterized by not containing carbon-hydrogen (C-H) bonds. They frequently involve ionic or metallic bonds and are normally found in minerals, salts, and other non-living materials.
Inorganic chemistry – It studies compounds without carbon-hydrogen bonds, including metals, minerals, and salts, while metallurgy is the science and technology of extracting metals from ores and refining them for use, making it a key application area for inorganic chemistry principles like redox reactions and electro-chemistry. Basically, inorganic chemistry provides the fundamental understanding of the metallic elements and their compounds, which metallurgy then applies to the large-scale production and processing of metals. Inorganic chemistry deals with synthesis and behaviour of inorganic and organo-metallic compounds. This field covers chemical compounds which are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disciplines is far from absolute, as there is much overlap in the subdiscipline of organometallic chemistry. It has applications in every aspect of the industry.
Inorganic coatings – Inorganic coatings are frequently used for providing a barrier between the atmosphere and the metal. Enamel, glass linings, and conversion coatings are all inorganic coatings. The treatment transforms the metal surface into a metallic oxide film or a compound which is more resistant to corrosion than the natural oxide film and provides an effective base or additional safety key, such as paints.
Inorganic compound – It is a substance in which two or more chemical elements (normally other than carbon) are combined, nearly always in definite proportions. The inorganic compound lacks carbon–hydrogen bonds.
Inorganic constituents – These are non-carbon-based materials (excluding simple oxides / carbides) like metals, minerals, and salts, frequently characterized by high melting points, electrical conductivity (metals), and ionic bonding. They are necessary components in materials science (fillers, alloys), environmental engineering (water quality), and chemical manufacturing.
Inorganic fillers – These are solid, non-carbon-based materials added to other substances (like plastics, rubber, or paints) to improve their properties or reduce costs. They are derived from minerals and other non-living sources. In case of lubricants, Inorganic fillers include solids such as white lead, talc, graphite, and molybdenum di-sulphide in a vehicle such as a neutral oil or paraffin oil.
Inorganic insulation – It refers to thermal or electrical insulating materials derived from non-organic sources like minerals and metals, as opposed to organic materials like wood or cellulose. These materials are typically used to resist heat or electrical flow and are frequently non-combustible and durable.
Inorganic matter – It refers to substances that are not derived from living organisms and typically lack carbon-hydrogen bonds, including rocks, minerals, water, and metals.
Inorganic ion exchange – It is a reversible chemical process using insoluble, naturally occurring or synthetic inorganic materials (e.g., zeolites, clays, metallic oxides) to exchange ions with a similar charge from an aqueous solution. It is used for water softening, purification, and selective removal of contaminants.
Inorganic lithium salts – These are ionic compounds containing lithium cations (Li+) combined with inorganic anions, e.g., (PF6)-, (ClO4)-, and BF-. Engineered for high ionic conductivity and stability, these salts serve as critical electrolytes in lithium-ion batteries and energy storage systems. Examples include LiPF6 (lithium hexa-fluoro-phosphate), LiClO4 (lithium per-chlorate), and LIBF4 (lithium tetra-fluoro-borate), chosen for their role in facilitating current conduction and ensuring safety.
Inorganic matter – It refers to non-living, non-carbon-based materials (or simple carbon compounds lacking C-H bonds) which are typically geological, mineral, or synthetic in origin. Key examples include metals, ceramics, glass, concrete, and minerals, frequently used for their durability, high melting points, and structural strength.
Inorganic nano-structures – These are non-carbon-based materials with at least one dimension between 1 nano-meter and 100 nano-meter, such as nano-particles, nano-wires, and nano-tubes. Engineered for unique electronic, optical, and magnetic properties, these materials are fabricated through controlled synthesis to improve reactivity, catalysis, or mechanical strength.
Inorganic particles – These are non-carbon-based materials (metals, oxides, salts, ceramics) engineered at the micro-scale or nano-scale (1 nano-meter and 100 nano-meter) to possess unique optical, magnetic, electronic, or catalytic properties. They are defined by high surface-to-volume ratios, allowing for improved reactivity and functionalization in applications like catalysis, and electronics.
Inorganic Perovskite solar cells – These are photo-voltaic devices featuring a crystal structure (ABX3) where organic cations are replaced by inorganic ions (e.g., Cesium, Cs+) in the A-site, typically using metal halides like CsPbI3 (cesium lead tri-iodide) or CsPBIxBr3-x. Engineered for superior thermal stability over organic-inorganic hybrids, they offer higher than 18 % efficiency. Key engineering challenges include preventing phase transition from the photo-active black phase (alpha-phase) to the non-perovskite yellow phase (delta-phase).
Inorganic phase change materials – These are non-flammable, high-density, salt-based substances (such as salt hydrates) which store / release substantial latent heat at constant temperatures during solid-liquid transitions. Engineered for latent heat storage (LHS), they offer superior thermal conductivity (0.5 W/m.K) and higher volumetric storage compared to organic counterparts, though they face challenges with corrosion and phase segregation.
Inorganic pigments – These are natural or synthetic metallic oxides, sulphides, and other salts which impart heat and light stability, weathering resistance, colour, and migration resistance to plastics.
Inorganic salt solutions – These are electrolyte solutions formed by dissolving inorganic, non-carbon-based ionic compounds, typically metal cations and non-metal anions, into a solvent, normally water. They are used to alter fluid properties, such as increasing density or conductivity for processes like flotation, heat transfer, or soil stabilization.
Inorganic trace elements – These are non-carbon-based elements present in minute quantities (typically less than 0.1 % 0r less than 100 parts per million) within materials, environmental samples, or industrial processes. They act as critical additives, contaminants, or catalysts, with specific compounds of antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, and selenium regulated as hazardous pollutants.
Inorganic zinc-rich paint – It is the coating containing a zinc powder pigment in an inorganic vehicle.
Inorganic wastewater – Inorganic wastewater is produced mainly in the coal and steel industry, in the non-metallic minerals industry, and in commercial organizations and industries for the surface processing of metals (iron picking works and electro-plating plants). These wastewaters contain a large proportion of suspended matter, which can be eliminated by sedimentation, frequently together with chemical flocculation through the addition of iron or aluminum salts, flocculation agents and some kinds of organic polymers. The purification of warm and dust-laden waste gases from blast furnaces, converters, cupola furnaces, refuse and sludge incineration plants, and aluminum works results in wastewater containing mineral and inorganic substances in dissolved and undissolved form.
In-plane compression – It refers to the application of a compressive load along the plane of a thin-walled, sheet, or cellular material, causing it to buckle, deform, or collapse in that same plane. It is a critical loading condition for evaluating the structural integrity of metallic honeycombs, sandwich panels, or sheets.
In-plane displacement – It refers to the movement or deformation of a component, structure, or material within its own 2D plane (parallel to its surface), rather than perpendicular to it (out-of-plane). It represents the change in position (u, v) of points in the x – y plane. It is important for measuring structural deformation, strain, or crack opening.
In-plane loading – It refers to forces acting parallel to the mid-surface or plane of a structural element, such as a wall, plate, or laminate. These forces lie within the structure’s 2D axis, producing direct tension, compression, and in-plane shear stresses rather than bending. Typical examples include structural loads, shear, or seismic forces.
In-plane shear – It refers to shear stress acting parallel to the material’s structural plane or within the cross-section of a component, causing internal layers to slide against each other. It occurs when parallel, opposing forces create deformation through changes in the angle between planes.
In-plane tension – It refers to a stress state where tensile forces are applied parallel to the surface of a thin material (such as sheet metal), while the stresses perpendicular to the plane (through the thickness) are negligible or zero. This condition is a form of plane stress, which reduces 3D stress analysis to a 2D problem, normally used in analyzing thin-walled structures and sheet metal forming.
In-process inspection – It is also known as in-process quality control. It is the process of inspecting products during different stages of manufacturing to ensure they meet quality standards. This proactive approach helps identify and address defects early in the production cycle, minimizing waste and rework. It involves checking for conformance to specifications, dimensions, and other quality parameters at various points in the production process.
Input – It refers to the energy, data, signals, or materials fed into a system or process, defining what goes in to produce a desired output, from electrical current in circuits (like voltage from a sensor) to data for software or physical resources for manufacturing, important for system function, analysis, and design. It is about the interaction i.e., what the system receives and acts upon, whether it is physical (a button press) or abstract (a dataset).
Input amplitude – It refers to the maximum magnitude or intensity of an external signal, force, or displacement applied to a material or system during testing (such as fatigue, vibration, or acoustic emission analysis).
Input-based payment – This system of payment refers to a system where providers are paid based on the resources they use (inputs) rather than the services they deliver or the outcomes achieved. This type of payment is made where it is not possible / difficult to measure the output.
Input buffer – It is a temporary memory storage area (hardware or software) which holds incoming data from an input device (keyboard, network, sensors) before the CPU (central processing unit) or processing unit is ready to handle it. It decouples fast input sources from slower processors, ensuring data integrity and preventing loss, often implemented as a FIFO (first in first out) queue.
Input capacitance – It is the total equivalent capacitance, including intrinsic and parasitic, present at the input terminal of an electronic device relative to ground. It acts as a load on the signal source, storing charge (Q = C x V) and limiting high-frequency performance by introducing delay, filtering, or instability.
Input capacitor – It is a passive, two-terminal component placed at the input stage of a circuit, typically a voltage regulator or an amplifier, designed to stabilize the input voltage, filter noise, and handle high-frequency ripple currents. It acts as a local reservoir of energy, supplying sudden demand to prevent instability in the source.
Input combinations – These refer to the specific, varied sets of input parameters or signals analyzed to determine the most effective system configuration for optimizing output, performance, or accuracy. These combinations are used to evaluate system behaviour, such as in combinational logic circuits where inputs directly determine outputs without memory.
Input conditions – These are the defined, controlled, or measured sets of variables, parameters, and environmental factors provided to a system, model, or process to determine its response, behaviour, or performance. They represent the ‘what is put in’ and serve as the starting point for analysis, simulation, or operation.
Input constraints – These are the physical, operational, or mathematical limitations imposed on process inputs, variables, or system parameters. These constraints, which include range bounds (e.g., maximum / minimum valve positions, flow rates) and inequality or equality relations, define the feasible search space for optimizing systems while ensuring safe and realistic operation.
Input covariance matrix – It is a square, symmetric, positive semi-definite matrix which defines the relationships, variances and covariances, between multiple input random variables or signal elements. It generalizes variance to multiple dimensions, quantifying how inputs vary together.
Input energy – It is the total energy supplied to a system, machine, or process to perform specific work, frequently transformed from one form (e.g., electrical, fuel) into another (e.g., mechanical, thermal). It is a fundamental component in calculating system efficiency [Efficiency = (useful output energy / input energy) x 100 %] and represents the gross resource consumption, such as fuel in an engine or electricity in a motor.
Input facet – It is the surface of a ‘semiconductor optical amplifier’ (SOA) where light enters the device, facilitating the amplification process within the active region.
Input frequency – it defines the rate at which a periodic signal (voltage, current, or wave) enters a system, typically measured in hertz or cycles per second. It characterizes the speed of oscillating inputs—such as alternating current mains (50 hertz /60 hertz), audio (20 hertz to 20 kilo hertz), or radio signals, directly affecting system performance and responsiveness.
Input heat – It refers to the thermal energy added to a system or process to perform work, such as in thermodynamics (engines) or material joining (welding). It defines the total energy supplied to drive a process, with critical applications in calculating efficiency, cooling rates, and ensuring weld quality.
Input image – It is a 2D array of pixels, normally represented as an M x N x K matrix (height, width, channels), fed into systems like ‘convolutional Neural networks’ (CNNs) for processing. It is defined mathematically as a function F(x, y), where ‘x, y’ are spatial coordinates and ‘f’ represents pixel intensity.
Input impedance (Zin) – It is the measure of opposition (resistance and reactance) a circuit or device presents to a signal source at its input terminals, defined as the ratio of input voltage (Vi) to input current (Ii), Zi = Vi/Ii. It dictates how much current is drawn, crucial for minimizing loading effects and enabling maximum power transfer, typically measured in ohms.
Input inductor – It is a passive power electronics component (coil / choke) placed at the input stage of circuits, such as direct current-direct current converters or rectifiers, to smooth input current, minimize voltage ripples, and filter high-frequency electromagnetic interference (EMI). It resists rapid current changes by storing energy in a magnetic field.
Input loop – It normally refers to a control structure, either in software or hardware systems, which continuously receives data, processes it, and generates an output or action based on that input. In process control, this refers to a control loop (open or closed) which regulates a process based on input parameters. In computing, it refers to iterative code which accepts user input until a termination condition is met.
Input node – It is the foundational entry point in a network, model, or system where data, energy, or materials are introduced. It acts as the boundary interface which receives information from the external environment and passes it to subsequent processing units (hidden layers or components).
Input noise – It refers to the unwanted, spurious electrical fluctuations (voltage or current) present at the input terminal of a circuit, component, or system, which degrade the signal-to-noise ratio (SNR). It represents the total noise, including internal, modeled as a single source at the input.
Input noise power – It is the total undesired electrical power (Pn) present at the input of a device, calculated as Pn = k x T x B, where ‘k’ is Boltzmann’s constant, ‘T’ is absolute temperature in Kelvin, and ‘B’ is the effective noise bandwidth in hertz. It represents the maximum thermal noise power transferred to a matched load.
Input optical signal – It is a light wave, frequently carrying modulated data, which acts as the initial energy or information carrier introduced into a system (such as fibre optics or a photo-detector) for processing or measurement. It is defined by its intensity, frequency (ranging from 10 to the power 11 to 10 to the power 16 hertz), and modulated characteristics.
Input/output (I/O) – In computing, it is the communication between an information processing system, such as a computer, and the outside world, such as another computer system, peripherals, or a human operator. Inputs are the signals or data received by the system and outputs are the signals or data sent from it. The term can also be used as part of an action, to ‘perform I/O’ is to perform an input or output operation.
Input/output (I/O) devices – These are the pieces of hardware which are used by a human (or other system) to communicate with a computer.
Input/output (I/O) Interface – It is a hardware / software system mediating communication between a CPU (central processing unit) / memory and external peripheral devices, matching data rates, signal levels, and formats. It acts as a bridge, utilizing data, address, and control buses to enable synchronized input/output operations, such as peripheral control and data transfer.
Input path – It is the designated channel or signal flow pathway through which data, instructions, or physical energy are transmitted from a source into a system for processing. It acts as the initial interface that connects external inputs to internal functional units.
Input phasor – It is a representation of a single frequency wave characterized by its amplitude and phase, which can be treated as a complex number in system analysis.
Input port – It is a specialized interface or terminal on a device, module, or system designed to receive data, signals, or physical media from an external source. It facilitates communication by directing incoming information into a processor or component, typically acting as read-only for the destination system.
Input power – It is the total energy per unit time (rate) supplied to a system, machine, or device, typically measured in watts (W). It represents the total energy consumed to perform work, including energy lost to heat, and is always higher than the useful output power.
Input power factor – It is a dimensionless engineering metric, ranging from 0 to 1, defining the efficiency of alternating current electrical equipment by measuring the ratio of real power (P in watts) consumed to total apparent power (S in volt-ampere) supplied. It indicates how effectively input electrical power is converted into useful work.
Input prices – These are the costs organizations incur for resources, raw materials, labour, energy, and capital needed to produce goods or services. These costs directly impact production expenses, profitability, and supply chain, with increases normally causing a leftward shift in the supply curve.
Input price variables – These are numerical parameters representing the costs of production inputs, such as raw materials, labour, energy, or capital, which directly influence total production costs. These variables are critical for cost modeling, as increases generally drive-up expenses, forcing adjustments in supply, pricing, and operational strategy.
Input problem – It refers to a scenario in economics and trade analysis where data is structured around the quantity of resources (inputs), such as time, labour, or raw materials, needed to produce a single unit of a good or service. It is used to analyze comparative advantage by identifying which entity can produce a good with the lowest resource cost.
Input pulse – It is a transient, short-duration signal characterized by an abrupt rise and fall in voltage, current, or physical quantity, used to trigger, count, or control systems. It represents a sudden, temporary change from a baseline value, frequently used in digital systems for timing or in industrial applications for counting, such as flow or motor speed.
Input pump power – It is also known as shaft power or brake horsepower (BHP). It is the total mechanical power delivered to the pump shaft by the motor to operate the pump. It is measured in watts or kilo-watts and is always higher than the hydraulic output power because of the mechanical and hydraulic losses.
Input resistance (Rin) – It is the effective electrical resistance presented by a circuit’s input terminals to a source, defined as the ratio of input voltage (Vin) to input current (Iin), Rin = Vin/Iin. It measures the load an amplifier or device puts on a signal source, important for optimizing power transfer and signal integrity.
Input resistor’s power – It is also known as its power dissipation or wattage. It is defined as the quantity of electrical energy converted into heat by the component at the input of a circuit. It represents the rate at which the resistor absorbs energy to limit current or adjust voltage levels, measured in watts (W).
Input sample – It refers to a discrete, numerical value or data point captured from a continuous, analog signal at a specific moment in time for digital processing. These individual samples form an input sequence (data stream) used to analyze, model, or control systems based on defined rules, such as in signal processing, simulation, or manufacturing.
Input sensitivity – It is the minimum level of an input signal needed to drive an amplifier, sensor, or electronic system to its rated maximum output. It defines the input-output relationship, representing the ratio of a change in output magnitude to a change in input, frequently calculated as the slope of the calibration curve.
Input sensor – It is a device, module, or sub-system which detects changes in physical, or chemical properties (the stimulus) and converts them into a measurable, typically electrical, output signal. Acting as a transducer, it bridges the physical environment and electronic control systems (like microcontrollers or programmable logic controllers).
Input sequence – It refers to the systematic design, optimization, and preparation of ordered data sets to improve the performance, accuracy, and efficiency of computational models and physical systems. It spans several fields, including machine learning, and digital systems, focusing on defining optimal lengths, patterns, and distributions of data to achieve specific objectives.
Input signal optical power – It refers to the initial optical power of the signal entering an optical amplifier, which is used to assess the amplification effect as it passes through the gain medium.
Input spectrum – It is a graph plotting spectral intensity (acceleration, velocity, or displacement) against frequency, defining the excitation applied to a system. It is used in structural analysis, it represents the frequency content of external, time-dependent loads. It is distinct from a ‘response spectrum’, as it measures the source input rather than system output.
Input stage – It refers to the initial, critical interface of a system, normally in electronics, power supplies, or software, designed to receive, condition, and process input signals or data while minimizing noise, distortion, and impedance mismatch. It serves to set the operating point, manage input voltage ranges, and provide high differential gain or high impedance.
Input supply – It covers the procurement of raw materials and fuel for industrial projects, or the technical design of power delivery systems for devices, ensuring proper voltage, frequency, and regulation. It involves managing contracts, supply chain logistics, and ensuring electrical stability in processes such as power-to-gas.
Input surface – It refers to the detailed, mathematical, and geometric description of an object’s boundary which serves as the starting point for simulations, manufacturing, and design analysis. This typically includes nominal shape, tolerances, and surface texture, acting as the interface between the physical component and its surrounding environment.
Input symbol – It represents the entry of data or material into a system, process, or diagram. Commonly depicted as a parallelogram in flowcharts, it signifies the start of a process, such as reading data, receiving user input, or receiving raw materials. It acts as an important interface point for data flow.
Input transistor – It refers to the specific input stage, terminal (such as base or gate), or the initial transistor device within a circuit which receives an incoming electrical signal. It functions as a voltage-controlled or current-controlled switch / amplifier, governing the flow of current through the output terminals.
Input valve – It is frequently referred to as an inlet valve or intake valve. It is a mechanical device which regulates, directs, or controls the flow of a fluid (liquid, gas, or fluidized solid) into a chamber, machine, or piping system. It acts as the primary gatekeeper for the media entering a system.
Input waveform – It is the electrical signal that is fed into a circuit, which can be altered by components such as clipping circuits that modify its shape by cutting off parts of the waveform beyond specified voltage levels.
In-reactor creep – It is the time-dependent, permanent deformation of structural materials (like fuel cladding or core components) under constant stress, accelerated by high temperatures and intense neutron irradiation. Unlike thermal creep, this phenomenon involves atomic-level damage, specifically vacancy and dislocation movement, which considerably alters component dimensions over time.
Inrush current, input surge current – It is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers can draw several times their normal full-load current when first energized, for a few cycles of the input waveform. Power converters also frequently have inrush currents much higher than their steady-state currents, because of the charging current of the input capacitance. The selection of over-current-protection devices such as fuses and circuit breakers are made more complicated when high inrush currents are to be tolerated. The over-current protection is to react quickly to overload or short-circuit faults but is not to interrupt the circuit when the (normally harmless) inrush current flows.
Inscribed circle – It is the largest-area circle contained within a triangle, which touches all three sides of the triangle. In higher dimensions, the corresponding concept is referred to as the inscribed ball, which is the largest-volume ball contained within a simplex.
Insert – It is a part formed from a second material, normally a metal, which is placed in the moulds and appears as an integral structural part of the final casting. It is also a removable portion of a die or mould. In case of composites, it is an integral part of a plastic moulding consisting of metal or other material which can be moulded or pressed into position after the molding is completed.
Insert die – It is a relatively small die which contains part or all of the impression of a forging and which is fastened to a master die block.
Insert drilling – It is a high-performance machining process used to create holes in metal using a tool body equipped with replaceable, hardened cutting inserts, typically made of carbide. Unlike traditional solid drills, only the small cutting tips need to be replaced or rotated (indexed) when they wear out, while the hardened steel tool body remains in use.
Inserted-blade cutters – These are the cutters having replaceable blades which are either solid or tipped and are normally adjustable.
Insertion loss – It is the reduction in signal power (measured in decibels) resulting from the insertion of a component, device, or cable into a transmission system. Defined as the ratio of power received at the load before and after insertion, it represents energy lost to attenuation, reflection, or impedance mismatch.
insertion point – It refers to a specified, coordinate-based location used to anchor, place, or connect a component, object, or data element into a larger system. In structural software, the insertion point defines the relationship between a physical member (beam, column, shell) and its analytical, mathematical line (the ‘insertion line’). In computer-aided design (CAD) software, the insertion point is the specific reference point (or base point) on a block or component which attaches to the cursor when inserting it into a drawing. In systems and engineering, it is a part or component (insert) which is placed into a mould and becomes an integral part of the casting.
Insert materials – These are pre-formed, typically rigid components (frequently made of metal, plastic, or ceramic) which are placed into a mould cavity, cavity, or hole before or after a moulding / casting process. These materials are designed to be incorporated into a substrate material (normally plastic) to improve mechanical properties, provide specific functionalities, or allow for repetitive assembly / disassembly, such as adding a threaded hole to a plastic part.
In-service cracking – It refers to the development of fractures, discontinuities, or fissures in components, structures, or materials while they are operational. It is a form of damage caused by operational stressors, such as cyclic fatigue, environmental corrosion, creep, or excessive, unexpected loading, which can lead to catastrophic failure.
In-service monitoring – In-service monitoring of industrial manufacturing operations is the type of service corrosion testing which presents the highest challenge and for which there is a great need. In such operations, the expense of corrosion problems can be huge and the risks devastating. Corrosion monitoring has become an important aspect of the design and operation of modern industrial plants because it enables plant engineering and management personnel to be aware of the damage caused by corrosion and the rate of the deterioration. The term monitoring, as used in this context, includes any technique for evaluating the progress or rate of corrosion.
Inside diameter (ID) – Inside diameter of a hollow circular object, like a pipe, is a measurement of the distance of a straight line from one point on the inner wall of the object, through its center, to an opposite point also on the inside.
Inside draft – It is draft on surfaces which tightens on the die as the forging shrinks during cooling. Examples are cavities such as narrow grooves or pockets. It also refers to a cold air current entering an enclosed space, or a slight taper allowing easy removal from a mould.
Inside radius – It defines the radius of curvature of an internal, concave corner or bend, specifically the distance from the bend axis to the inner surface of the material. It is important for calculating material compression, bend allowance, and determining proper tooling in sheet metal, moulding, and casting.
Inside screw, rising stem – It is the common term for any valve design in which the stem threads are exposed to the fluid below the packing and the stem rises up through the packing when the valve is opened.
In-situ – is a Latin phrase meaning ‘in place’ or ‘on site’, derived from ‘in’ and ‘situ’ (place). The term refers to the examination or preservation of phenomena within their original place or context. This methodological approach, used across diverse disciplines, maintains contextual integrity essential for accurate analysis.
In situ composites – These are materials where the reinforcing phase (like ceramics, borides, or fibres) forms within the metal matrix during processing (e.g., solidification from a melt), rather than being added separately. This ‘in the same place’ synthesis creates strong interfacial bonding, fine particle / fibre distribution, and improved properties like wear resistance, frequently through controlled chemical reactions or eutectic solidification, offering advantages over traditional ex-situ composites.
In situ crystallization – It refers to the direct, real-time observation and analysis of crystal nucleation and growth, or phase transformations, as they occur within a material (normally from a liquid or melt). It allows for the measurement of microstructural evolution, such as the transition from liquid to dendrites, in real-time rather than relying solely on post-solidification analysis.
In situ natural gas hydrates – These are solid, ice-like clathrate compounds found naturally in arctic permafrost and deep-sea sediments, where methane and other gases are trapped inside water molecule cages under high-pressure, low-temperature conditions. Extraction involves destabilizing these deposits through depressurization or heating to convert solid hydrate back into gas and water.
In situ polymerization – It is a method where monomers are polymerized directly in the presence of fillers (like nano-particles) or within a specific medium, allowing the polymer matrix to form around the reinforcement. This technique ensures high filler loading, excellent dispersion, and strong interfacial bonding between the filler and the polymer matrix, producing advanced nanocomposites or conducting materials.
In situ processing – It refers to conducting chemical reactions, material synthesis, manufacturing, or measurements directly at the material’s original location or within its native environment. This approach eliminates the need to transport materials, reducing costs, contamination, and downtime. It is widely used in materials science, manufacturing, and maintenance.
In situ purification – It refers to the removal of impurities, contaminants, or unwanted substances directly within the operational environment, vessel, or process line, rather than removing the material for external treatment. This approach utilizes techniques like filtration, chemical reaction, or adsorption to isolate or convert impurities in place, reducing contamination risks and improving efficiency.
In situ stress – It refers to the natural, pre-existing stress state within rock or soil formations before any disturbance from engineering activities like drilling, mining, or excavation. It is characterized by three-dimensional, mutually orthogonal principal stresses, typically vertical, and two horizontal components, resulting from overlying weight (over-burden), tectonic forces, and geological history.
In-situ stress measurement – It determines the magnitude and direction of the natural, pre-existing stress state in rock masses or sub-surface formations before human disturbance, such as drilling or excavation. It is necessary for designing stable underground structures, predicting borehole failure, and hydraulic fracturing.
In situ testing – It refers to the direct, on-site measurement of material properties (normally soil, rock, or concrete) in their natural, undisturbed environment rather than through laboratory analysis of removed samples. It provides real-time, in-place data regarding strength, stiffness, and density under actual field stress conditions.
In situ transmission electron microscopy – It is an advanced analytical technique used to observe the dynamic, real-time structural, chemical, and physical transformations of materials at the nano-scale while they are subjected to external stimuli (such as heat, gas, liquid, electrical, or mechanical stress) inside the situ transmission electron microscope. Unlike traditional post-mortem analysis, which only shows the final state of a sample, in situ transmission electron microscopy allows researchers to visualize, record, and understand the intermediate stages and kinetic mechanisms of materials-related processes in their operating environment.
Insolubility – It is the inability of a substance (the solute) to form a solution by being dissolved in another substance (the solvent). It is the opposite of solubility.
Insoluble impurities – These are unwanted, solid particles or foreign materials present in liquids, melts, or chemical mixtures which do not dissolve in the surrounding medium. These materials, such as sludge, metals, or sand, remain suspended or settle out, necessitating separation techniques like filtration, sedimentation, or decantation.
Insoluble residue – It refers to the non-cementing, inert material remaining after a sample (normally Portland cement) is treated with specific acids (like hydrochloric acid, HCl) and filtered. It signifies impurities, such as siliceous or argillaceous materials, and is restricted by standards.
Inspectability – It is the measure of how effectively a structural component, system, or process can be examined for flaws, quality, and conformity to specifications throughout its lifecycle. It integrates design principles which ensure accessibility, detectability of defects, and reliability of inspection methods, such as non-destructive testing (NDT), in-process monitoring, and final validation.
Inspection – It is a systematic, formal evaluation or examination of materials, components, or processes, comparing them against specified standards, requirements, or designs to verify conformity, identify defects, ensure safety, and maintain quality throughout a product’s lifecycle, often using measurements, tests, and specialized equipment. It is important for quality control, preventing failures, ensuring fitness for service, and informing design improvements. It is an organized examination or formal evaluation exercise. In production, it involves the measurements, tests, measuring gauges and test equipments applied to certain characteristics in regard to a material or a product. It is normally non-destructive. It consists of the activity such as witnessing the measurement, examination, testing or gauging of one or more characteristics of an entity and comparing the results with specified requirements in order to establish whether the results are in order and to establish whether conformity is achieved for each characteristic. Inspection is an important tool to achieve quality concept. It is necessary to assure confidence to the producer and aims satisfaction to the customer. Inspection is an indispensable tool of the present-day production processes. It helps to control quality, reduces production costs, eliminate scrap losses, and assignable causes of defective work.
Inspection and analysis – It is the systematic process of measuring, testing, and examining components or systems to verify they meet functional requirements and safety standards. It combines physical assessment (inspection) with data interpretation (analysis) to validate design compliance, detect defects, and ensure operational reliability.
Inspection door – It is hinged or removable door in the conveyor or furnace structure, providing access for inspections, demanding routine checks for proper functioning and secure closure.
Inspection event – It is a planned, systematic examination, measurement, or test of components, equipment, or systems to verify compliance with specified requirements, safety standards, and functional, non-functional, or quality criteria. These events identify faults or defects to ensure asset integrity and often involve non-destructive testing, comparing findings against documented standards.
Inspection lot – For non-heat-treated tempers, it is an identifiable quantity of material of the same mill form, alloy, temper, section, and size submitted for inspection at one time. For heat treated tempers, it is an identifiable quantity of material of the same mill form, alloy, temper, section, and size traceable to a heat treat lot or lots and submitted for inspection at one time. (For sheet and plate, all material of the same thickness is considered to be of the same size).
Inspection method – It is a documented, systematic technique, such as laser scanning, ultrasonic, or visual examination, used to evaluate, measure, or test material / product characteristics against specifications to ensure quality and compliance. It validates that components meet design requirements through non-destructive or destructive testing.
Inspection plan – It is a structured, strategic document (frequently called an ‘inspection and test plan’) which outlines the precise methods, frequency, and criteria used to verify that metallic materials, components, or welded structures meet quality standards. It translates technical specifications into actionable steps during manufacturing, fabrication, or maintenance. A comprehensive inspection plan includes (i) what to inspect, (ii) how to inspect (method), (iii) where / when to inspect (stage), (iv) acceptance criteria, (v) responsibility, and (vi) documentation/records.
Inspection procedure – It is a documented, systematic process for measuring, examining, and testing materials or components to ensure they meet specified quality, safety, and design standards. It involves comparing results against predefined criteria, identifying defects, and verifying compliance to prevent non-conforming products.
Inspection, product – It refers to a systematic process of checking the quality of a product based on a specified set of standards. In this procedure, the inspector examines a product sample in terms of its appearance, construction, function, and other conditions to see if they meet the specified requirements.
Inspection programme – It is a systematic, documented strategy designed to ensure equipment, materials, and processes meet safety, quality, and performance standards. It outlines specific inspection tasks, methodologies, frequencies, and responsibilities (who, what, where, when, why) to identify, document, and correct defects.
Inspection, surface – It is the process of detecting, measuring, and analyzing surface imperfections, such as roughness, cracks, or contaminants, to ensure components meet quality standards. It involves comparing physical parts to design models (e.g., 3D-point clouds) using techniques like optical scanning, laser profiling, and machine vision, frequently to verify free-form shapes.
Inspection technology – It refers to the systematic application of tools, techniques, and automated systems, like AI (artificial intelligence), machine vision, and NDT (nondestructive testing), to measure, monitor, and evaluate components, materials, or products. Its main purpose is to verify conformance with design specifications, ensure safety, and detect defects.
Instability analysis – It is the systematic evaluation of a system, structure, or fluid flow to determine the conditions, thresholds, and mechanisms under which it transitions from a stable state to an unstable, erratic, or failed state. It involves analyzing how small-amplitude disturbances grow, leading to phenomena like buckling, vibrations, or thermal, structural, or hydraulic failure.
Instability mechanism – It is the specific physical process, such as buckling, yielding, or fluid-structure interaction, by which a system, structure, or material fails to maintain its original equilibrium configuration under external loading or stimulus. These mechanisms frequently lead to abrupt, rapid structural deformation or dynamic, unbounded growth of system responses, potentially causing catastrophic failure.
Instability mode – It refers to a specific, identifiable pattern of behaviour where a system’s output, structure, or flow, when disturbed, deviates and increases without bounds or shifts to a new state rather than returning to equilibrium. It defines the specific way a system fails, such as buckling in structures or flow, or dynamic oscillations, often triggered when parameters exceed critical thresholds.
Instability threshold – It is the critical point or boundary (e.g., specific load, speed, temperature, or flow rate) at which a system, structure, or component transitions from a stable state to an unstable state. Beyond this point, small disturbances cause unbounded, rapid, or destructive deformations, oscillations, or failures.
Instability wave – it is a small-amplitude, periodic disturbance which grows as it propagates through a flow field, leading to flow oscillations, transition to turbulence, or mechanical vibration. It acts as a bridge between laminar flow and turbulent breakdown.
Installation – It is the comprehensive process of assembling, placing, connecting, and testing equipment, systems, or components in their designated location to ensure they function correctly, reliably, and safely as per the specifications, involving detailed planning, adherence to codes, and skilled execution. It transforms components into a working unit, from large machinery in construction to software, encompassing rigging, wiring, calibration, and initial operational checks.
Installation and operation manual – It is a comprehensive document providing detailed instructions for the safe setup, configuration, and daily use of equipment or systems. It ensures personnel can properly install, operate, and troubleshoot machinery, reducing downtime, risks, and errors while ensuring compliance with technical standards.
Installation damage – It refers to the impairment, degradation, or structural flaws induced in materials, components, or systems during the assembly, placement, or construction phase, prior to operational use. It is a failure mode frequently caused by improper techniques, such as over-bending, excessive tension, or mechanical impact, resulting in reduced performance, functional failure, or premature, shortened lifespan.
Installation drawing – Installation drawing is the drawing which is based on the detailed design or coordination drawing with the primary purpose of defining that information needed for the installation of plant and equipment. This drawing is particularly important for complex installations. The drawing comprises plan, section and elevation. Installation drawing includes information about (i) precise positioning, (ii) supports and fixings, (iii) information from manufacturers shop drawings, (iv) space allowances for installation, (v) installation work in connection, such as cutting, and, sealing holes, chasing block and brickwork for conduits or pipes, lifting and replacing floors, constructing plinths and so on, (vi) plant and equipment requirement, (vii) requirements for service connections, (viii) requirement to leave access space for operation and maintenance, and (ix) other maintenance access requirements such as access panels, decking, platforms, ladders and handrails. It is important that the information presented is carefully coordinated so that clashes are avoided.
Installation engineering – It involves designing, planning, and executing the safe, precise placement and assembly of equipment or structures. Operation Engineering defines the procedures, monitoring, and maintenance required to ensure the system functions reliably and efficiently throughout its lifecycle. Together, they bridge construction and long-term functional performance.
Installation equipment – It refers to the specialized tools, machinery, and apparatus needed to transport, position, assemble, and secure permanent machinery or structures onto foundations. This includes lifting devices, rigging, and fastening tools necessary for commissioning and making equipment operational.
Installation guidelines – These are documented, approved, and structured procedures detailing the safe, efficient, and compliant assembly, positioning, and connection of equipment, systems, or software. They define technical requirements (dimensions, materials) and safety standards (codes, regulations) to ensure proper functionality and performance.
installation method – It is a documented, technical procedure for securely placing, assembling, and integrating components or systems into their final, functional position. It involves detailed planning, such as reviewing schematics and calculating loads to ensure safety, efficiency, and adherence to codes, particularly for complex machinery or marine, structural, and electrical projects.
Installation procedure – It is a detailed, approved, and structured document which defines the specific steps for securely, accurately, and efficiently setting up, assembling, aligning, and connecting components or equipment. It serves as a, ‘how-to’ guide for site personnel to achieve mechanical completion, preventing damage from improper handling (e.g., over-bending or excessive tension) and ensuring the system operates as designed.
Installation process – It is the documented, systematic, and approved sequence of activities, such as rigging, alignment, and assembly. It is used to safely position and integrate equipment or systems into a structure. It transforms design specifications into a functional, on-site, or installed asset. It involves strict adherence to engineering drawings, schematics, and safety codes.
Installation sequence – It defines the precise, logical, and chronological order for assembling components, machinery, or structures to ensure safety, efficiency, and structural integrity. It involves optimizing the steps to prevent interference, manage stress (like fastener ‘bubble effects’), and adhere to structural curing constraints.
Installation technology – It refers to the systematic planning, design, and execution of processes needed to place machinery, equipment, or systems into a fixed or operational position. It bridges the gap between design theory and practical application, ensuring that components are correctly assembled, tested, and integrated to operate reliably.
Installation vessel – It focuses on designing and optimizing specialized ships, such as ‘wind turbine installation vessels (WTIVs) and heavy-lift barges, for the safe transport and installation of offshore structures. It involves naval architecture for stability, structural engineering for crane loads, and dynamic positioning systems, ensuring efficient, high-capacity, and stable operations in challenging marine environments.
Installed capacity – It bis also nameplate capacity. It is the maximum, theoretical output power a generation station or engineering system can produce under ideal, manufacturer-specified conditions. It represents the sum total of all installed equipment (units) and is typically measured in mega-watts or kilo-watts, focusing on potential rather than actual average production.
Installed diaphragm pressure range – It is the high and low values of pressure applied to the diaphragm to produce rated travel with stated conditions in the valve body. It is because of the forces acting on the closure member which the inherent diaphragm pressure range can differ from the installed diaphragm pressure range.
Installed flow characteristic – It is the relationship between the flow rate and the closure member travel as it is moved from the closed position to rated travel as the pressure drop across the valve is influenced by the varying process conditions.
Installed solar capacity – It is frequently measured in mega-watts (MW) or kilo-watts (kW), represents the maximum potential power output a photovoltaic (PV) system can generate under ‘standard test conditions’ (STC). It is the cumulative rated capacity of all operational solar panels, representing the peak direct current output, not the actual daily energy yield.
Installers – Installers are skilled professionals, technicians, or contractors responsible for assembling, positioning, configuring, and commissioning equipment, machinery, or complex systems in industrial, commercial, or residential settings. They ensure systems are installed safely and operate correctly, frequently managing technical connections and adhering to strict technical procedures.
Instantaneous active and reactive power – It refers to the real-time values of power in an electrical system, which can be decomposed into average and oscillatory components. These powers are calculated using transformed voltage and current quantities in the alpha- beta frame, as described by instantaneous reactive power (IRP) theory.
Instantaneous active power – It is the product of instantaneous voltage and instantaneous current at a specific moment, measured in watts (W). It represents the exact power consumed or produced at any instant, fluctuating with time in alternating circuits at twice the supply frequency.
Instantaneous approximation – It refers to a modeling technique where a process which actually takes a finite quantity of time is assumed to occur instantly, or where a system’s response is assumed to follow its input immediately without delay. This simplification reduces complex, time-dependent, or differential equations into simpler algebraic or static equations.
Instantaneous availability – It is the probability that a system or component is functional (operable) at a specific random instant in time. Unlike long-term average availability, this metric is time-dependent, incorporating both failure rates and maintainability to predict if a system is ‘up’ at a precise, future moment.
Instantaneous energy release – It refers to the rapid, almost immediate liberation of stored energy (chemical, nuclear, or mechanical) within a localized area, typically causing intense pressure waves or heat, frequently modeled as a sudden, nearly zero-duration event. This concept is crucial for modeling combustion, explosions, and fracture mechanics.
Instantaneous erosion rate – It is the slope of a tangent to the cumulative erosion-time curve at a specified point on that curve.
Instantaneous field of view (IFOV) – It is the angular cone of visibility of a single detector element (pixel) in an imaging sensor at any given instant. It defines the minimum spatial resolution, representing the smallest ground area or object size that one pixel can detect. It is typically calculated as the ratio of detector pixel size to the lens focal length (IFOV = Pixel size / focal length), normally expressed in milli-radians.
Instantaneous frequency – It is defined as the time derivative of the instantaneous phase of a signal, normally represented by its analytic signal. It describes the frequency of a signal at a specific moment in time, which is necessary for analyzing non-stationary, time-varying signals, frequency modulation (FM), and chirped pulses.
Instantaneous gas – It refers to a continuous flow, tankless, or on-demand system which heats water or fluids immediately as they flow through a heat exchanger when a tap is turned on, without storing heated fluid. Unlike storage systems, it consumes gas only when needed, improving energy efficiency, and is common in compact, wall-mounted residential water heaters.
Instantaneous imaginary power – It is a concept in three-phase power theory (p-q theory) defining the rate of energy exchange between phases, rather than between source and load, at a specific moment. It represents energy oscillating between phases without doing real work.
Instantaneous injection – It refers to the theoretical idealization or practical approximation of introducing a material, energy, or substance into a system over a time interval which is negligible compared to the system’s characteristic response time. It is modeled as a pulse of zero or near-zero duration, effectively introducing a finite quantity at a specific moment in time (a Dirac delta function in the temporal domain).
Instantaneous phase – It is the time-varying, unique angle of a signal at any precise instant, typically measured in radians. It is calculated through the Hilbert transform from the analytic representation of a signal and is used to analyze modulation, signal timing, and wave propagation, independent of amplitude.
Instantaneous power, p(t) – It is the electrical power, or rate of energy transfer, at a specific, precise moment in time, defined as the product of instantaneous voltage, v(t) and current, i(t), represented by ‘p(t) = v(t) x i(t). It is measured in watts, and in alternating current circuits, it varies with time, frequently at double the source frequency, indicating both energy transfer to the load (positive) and back to the source (negative).
Instantaneous pulse – It is a transient signal, electrical impulse, or energy discharge which occurs over an infinitesimally small or very short duration at a specific moment in time. It represents a sudden change in amplitude or a rapid transfer of energy, such as a sharp rise, peak, or spike, which can be measured using tools like Hilbert transform.
Instantaneous rate – It is the precise rate of change of a process variable (such as velocity, concentration, or temperature) at a specific, infinitesimal moment in time, rather than over an average duration. It is calculated as the derivative of the quantity with respect to time, representing the tangent slope on a graph.
Instantaneous reactive power theory – it is a framework used to analyze power transfer in three-phase systems, incorporating both instantaneous real power and instantaneous reactive power to understand energy transfer between a source and a load under various conditions of asymmetry and distortion.
Instantaneous real power, p(t) – It is the exact electrical power at any specific moment, defined as the product of instantaneous voltage, v(t) and current, i(t), p(𝑡) = v(t) x i(t). Measured in watts (W), it represents the actual energy transfer rate at a precise instant. It is critical for analyzing power fluctuations in alternating current circuits.
Instantaneous recovery – It is the decrease in strain in a solid during the removal of force before any creep recovery takes place. It is normally determined at constant temperature. It is sometimes referred to as instantaneous recovery.
Instantaneous strain – It is the strain in a sample immediately upon achieving the given loading conditions in a creep test (before creep occurs). It is sometimes referred to as instantaneous strain.
Instantaneous stress – It is the stress which is produced by strain in a sample immediately on achieving the given constant-strain conditions in a stress-relaxation test before stress-relaxation occurs. It is sometimes referred to as instantaneous stress.
Instantaneous value – It is the specific magnitude of a time-varying quantity (such as alternating current voltage v(t) or current i(t) at a precise moment, rather than an average or peak value. It represents the value of a sinusoidal wave at a particular angle theta = omega t.
Instantaneous velocity -it is the precise rate of change of an object’s position with respect to time at a specific, infinitesimal instant. It is defined as the derivative of displacement (x) with respect to time (t), calculated as the limit of average velocity as the time interval approaches zero.
Instantaneous voltage – It is the value of voltage at a specific moment in time within a sinusoidal waveform, calculated as the peak voltage multiplied by the sine of the angle theta. It is specific electrical potential difference between two points at a precise moment in time, rather than an average or root-mean-square (RMS) value. Represented by lowercase letters, it is defined in alternating current circuits by the instantaneous value of a sinusoidal wave
Institutional appraisal – It is a systematic process of evaluating an institution’s performance, effectiveness, and impact to identify strengths, weaknesses, and areas for improvement, ultimately aiming to enhance its mission and goals. The main objective of this appraisal system is to recognize, encourage, and facilitate the professional and personal development of the employees. By systematically evaluating their performance, it provides a structured mechanism for feedback, personal improvement, and career progression. The appraisal system is crucial as it (i) identifies strengths and areas which need improvement for employees, (ii) encourages a culture of continuous learning, innovation, and professional growth, (iii) recognizes and rewards exceptional contributions and achievements, and (iv) fosters a sense of accountability and motivation among the employees to excel in their roles. This appraisal system not only serves as a tool for assessing individual performance but also contributes to overall institutional growth and quality enhancement.
Institutional controls – These controls are non-engineered instruments such as administrative and regulatory controls which help minimize the potential for human exposure to contamination and / or protect the integrity of the remedy.
Instructional materials – These refer to resources used to facilitate learning, which can range from instructor-led lesson plans to complex simulations. Their selection is influenced by factors such as availability, constraints, and the need for alignment with performance objectives, learners, instructional strategies, and context. These materials are strategically selected to improve engagement, support diverse learning styles, and align with performance standards in technical fields.
Instruction book – It is frequently termed an instruction manual, user guide, or technical manual. It is a structured document, booklet, or electronic file that provides detailed, authoritative, and step-by-step guidance on how to install, operate, maintain, and trouble-shoot a specific piece of machinery, device, software, or system. It serves as the main communication link between the manufacturer and the end-user, intended to ensure the safe, efficient, and proper utilization of technical equipment.
Instruction manual – It is meant to be a comprehensive resource for knowing about a given equipment, product, or system. The main purpose of the document is to make clear to user how to assemble / use / operate the equipment, product, or system it to its maximum potential. Instruction manuals provide detailed guidance. They are frequently provided by manufacturers and are essential tools for users to understand the use of equipment, product, or system effectively and safely.
Instructions – These are precise, documented directives for a sequence of actions, ranging from binary commands for a central processing unit (instruction sets) to detailed guides for manufacturing processes (process instructions) or project execution (installation instructions), ensuring quality, safety, and compliance by specifying what to do, how, and in what order.
Instrument – It can be defined as a device for determining the value or magnitude of a quantity or variable. It is is a device which turns some physical property into a measurement. Measuring instruments, and formal test methods which define the instrument’s use, are the means by which the variables and the relations between variables are found.
Instrumental broadening – It is the artificial widening of spectral lines, peaks, or diffraction profiles caused by the physical limitations and optical imperfections of measuring instruments (e.g., X-ray diffraction, spectrometers) rather than the sample’s inherent properties. It is a key factor needing correction to determine true sample characteristics like crystallite size or strain.
Instrumental measurement – It is the process of using physical devices (sensors, transducers, instruments) to quantify, monitor, or control physical variables, such as pressure, temperature, flow, or voltage, by comparing them to a known standard. It involves signal conditioning to convert sensor responses into readable, often automated, data.
Instrument analysis – It consists of the methods of chemical analysis with the help of different types of instruments. These methods are widely used for the qualitative and quantitative elemental analysis of raw materials, iron (hot metal), steel, slag, refractories, and sludges samples. Compared to the wet analysis, the advantage of instrument analysis is that it is cost effective and multi elemental besides being very fast. The worries caused by interfering elements in the wet chemical analysis are eliminated. Instrument analysis avoids the need of waiting several hours for certain elements, which is a necessity when the wet chemical methods are employed. Furthermore, instrument analysis provides a fairly uniform detection limit across a large list of elements or compounds and is applicable to a wide range of concentrations, ranging from 100 % to few parts per million (ppm). The instrumental methods are reproducible with lesser scope of human error because of lesser human intervention. They are rugged, reliable and accurate with the accuracy depends upon the calibration and the standards used for the calibration.
Instrumentation – It is a collective term for measuring instruments which are used for indicating, measuring, and recording physical quantities. Instrumentation is the basis for the control of a process. It provides the different indications to the operator for controlling the process. In some cases, operator records these indications for evaluating the current condition of the process and to take actions if the conditions are not as expected. Because of the continuous interactive nature of the most of the processes, manual control is not feasible and is unreliable. With instrumentation, automatic control of such processes can be achieved. Instrumentation is used in almost every industrial process and generating system, where consistent and reliable operations are required. Instrumentation provides the means of monitoring, recording and controlling a process to maintain it at a desired state.
Instrumentation amplifier – It is as a precision differential amplifier which is typically pre-packaged in a monolithic device, with its gain determined by a resistor. It operates by ensuring that the inputs of the buffer op-amps draw no current, allowing for accurate voltage measurement and amplification.
Instrumentation and control engineering – It is a branch of engineering which studies the measurement and control of process variables, and the design and implementation of systems which incorporate them. Process variables include pressure, temperature, humidity, flow, pH, force and speed. Instrumentation and control engineering combines two branches of engineering. Instrumentation engineering is the science of the measurement and control of process variables within a production or manufacturing area. Control engineering is also called control systems engineering. It is the engineering discipline which applies control theory to design systems with desired behaviours. Control engineers are responsible for the research, design, and development of control devices and systems, typically in manufacturing facilities and process plants. Control methods use sensors to measure the output variable of the device and provide feedback to the controller so that it can make corrections toward desired performance. Automatic control manages a device without the need of human inputs for correction. Control systems engineering activities are multi-disciplinary in nature. They focus on the implementation of control systems, mainly derived by mathematical modeling. Since instrumentation and control play an important role in gathering information from a system and changing its parameters, they are a key part of control loops.
Instrumentation diagrams – These are the descriptive diagrams made following standardized methods and rules. However, the scope of instrumentation is so wide that a single form of diagram is not sufficient to capture all what is required to be represented. The different types of instrumentation diagrams which are commonly used are (i) process flow diagram (PFD), (ii) loop diagrams (loop sheets), (iii) process and instrument diagrams (P&ID), and (iv) functional diagrams.
Instrumentation engineering – It is the discipline dealing with development of measuring systems.
Instrumentation requirement – It involves determining the necessary specifications for monitoring and controlling plant processes, ensuring safety and performance during operation, startup, and shutdown. It translates, or ‘instruments’, high-level, frequently non-technical, requirements into detailed technical, measurable, and verifiable specifications for sensors, transmitters, and control devices.
Instrumentation system – It is a structured collection of devices, sensors, transmitters, and controllers, designed to measure, monitor, and control physical quantities (like pressure, temperature, flow, or level) for automation and process stability. It acts as the ‘nervous system’ of industrial processes, converting raw physical data into usable signals for display, recording, or control actions.
Instrument calibration – It is the process of comparing a measuring device’s output against a known, traceable standard to verify its accuracy and, if necessary, adjusting it to match that standard within specified tolerance limits. It ensures reliability, safety, and compliance with quality standards, accounting for errors from environmental factors or device drift.
Instrument data sheet – It is a table summarizing data such as service, valve size, and supply pressure etc., necessary for actuator sizing.
Instrumented Charpy impact test – The use of additional instrumentation (typically an instrumented tup) allows a standard Charpy impact testing equipment to monitor the analog load-time response of Charpy V-notch sample deformation and fracturing. The primary advantage of instrumenting the Charpy test is the additional information obtained while maintaining low cost, small samples, and simple operation. The normal used approach is the application of strain gauges to the striker to sense the load-time behaviour of the test sample. In some cases, gauges are placed on the sample as well. Instrumentation of the tup provides valuable data in terms of the load-time and the history during impact.
Instrumented impact test – It is an impact test in which the load on the sample is continually recorded as a function of time and / or sample deflection prior to the fracture.
Instrument identification tags – Instrumentation diagrams, reference is made to different instruments by lettered identifiers such as TT (temperature transmitter), PDT (pressure differential transmitter), or FV (flow valve) etc., without formally defining all the letters. Each instrument within an instrumented facility normally has its own unique identifying tag consisting of a series of letters describing the instrument’s function, as well as a number identifying the particular loop it belongs to. An optional numerical prefix typically designates the larger area of the facility in which the loop resides, and an optional alphabetical suffix designates multiple instances of instruments within one loop. As an example, if an instrument bearing the tag FC-135 means that it is a flow controller (FC) for loop number 135. In a large manufacturing facility with multiple processing ‘unit’ areas, a tag such as this can be preceded by another number designating the unit area. As an example, the hypothetical flow controller might be labeled 12-FC-135 means flow controller for loop number 135, located in unit number 12. If this loop happened to contain multiple controllers, then there is a need to distinguish them from each other by the use of suffix letters appended to the loop number (e.g. 12-FC-135A, 12-FC-135B, and 12-FC-135C etc.).
Instrument loop diagram – It is a detailed, graphical schematic showing the inter-connection of field devices, cabling, junction boxes, and control system input/output (distributed control system (DCS) / programmable logic controller (PLC) for a specific process measurement or control loop. It acts as a main document for engineering design, installation, commissioning, and trouble-shooting, tracing signals from sensors to final control elements.
Instrument output – It refers to the signal, data, or physical representation produced by a measuring device which corresponds to the measured process variable. It is the actionable result of an instrument’s sensing and processing, typically taking the form of analog signals (4-20 milli-ampere to 0-10 volts), digital protocols (Modbus), or direct display readings.
Instrument response time – It is the time needed for an indicating or detecting device to attain a defined percentage of its steady-state value following an abrupt change in the quantity being measured.
Instruments and controls – Instruments are devices which are used to measure or to manipulate process variables like flow, pressure, or temperature. Controls, on the other hand, refer to the systems or mechanisms which use these measurements to regulate or adjust process parameters, ensuring desired outcomes. Essentially, instruments provide the data, and controls act on that data to maintain or change a system’s behaviour.
Instrument testing – It is the systematic, pre-installation, or in-situ verification of sensors, transmitters, and controllers to ensure they accurately measure, record, and control physical variables (pressure, temperature, flow) within specified tolerances. It involves calibration, functional checks, and, for electronics, 24-hour warm-up periods.
Insulated cable – It is an electrical conductor, typically copper or aluminum, surrounded by a non-conductive, dielectric material, such as Polyvinyl chloride (PVC), cross-linked polyethylene (XLPE,) or rubber, designed to prevent leakage current, short circuits, and electrical hazards. Engineered for safety, these cables protect against thermal, chemical, and physical stress, ensuring reliable energy or signal transmission.
Insulated gate bipolar transistor (IGBT) – It is a power semi-conductor device which combines some of the advantages of field-effect and bipolar transistors. It is a three-terminal power semiconductor device primarily forming an electronic switch. It has been developed to combine high efficiency with fast switching. It consists of four alternating layers (NPNP) which are controlled by a metal-oxide semi-conductor (MOS) gate structure. Although the structure of the insulated gate bipolar transistor is topologically similar to a thyristor with a ‘metal-oxide semi-conductor gate’ (MOS-gate thyristor), the thyristor action is completely suppressed, and only the transistor action is permitted in the entire device operation range. It is used in switching power supplies in high-power applications.
Insulated roof – It is an engineered building envelope system designed to minimize heat transfer (conduction, convection, and radiation) between a building’s interior and the exterior environment. It incorporates materials with high thermal resistance (such as poly-urethane, polyisocyanurate, or poly-styrene foam) to regulate indoor temperatures, reduce energy consumption for heating / cooling, and prevent moisture accumulation.
Insulated vessel – It is a container designed to maintain the temperature of its contents, solid, liquid, or gas, by reducing heat transfer with the surrounding environment. These vessels, frequently used for temperature-sensitive materials, cryogenics, or process stabilization, utilize materials like stainless steel, advanced insulation, and specialized cladding, with key features including vacuum layers, pressure relief valves, and structural support for insulation systems.
Insulating concrete – It is a type of lightweight concrete which improves thermal efficiency in buildings, serving as an alternative construction material to improve energy performance and reduce heat losses in cold weather.
Insulating concrete formwork – It is a modern, energy-efficient construction system using interlocking, hollow foam panels (typically expanded polystyrene) as permanent formwork for reinforced, poured concrete walls. It combines the high structural load-bearing strength of concrete with the continuous thermal insulation of foam to create airtight, durable, and fire-resistant building envelopes.
Insulating layer – It is a material application designed to restrict the flow of heat, electricity, or sound between components or environments. It improves thermal efficiency in systems, prevents electrical conduction / short circuits in electronics, and protects against environmental factors like moisture. In electrical devices, it is a film which isolates electrical conduction between components in devices such as thin-film transistors (TFTs), while also serving as a dielectric layer that affects device performance and prevents defect formation and current leakage.
Insulating materials, thermal – These are the materials or material complexes apparently resistant to thermal currents. These materials are used for thermal preservation and heat insulation.
Insulating matrix – It is the continuous phase of a composite material, typically a polymer, ceramic, or glass, which electrically isolates conductive fillers or fibres, preventing charge flow and improving dielectric properties. It acts as a protective, structural, or insulating, dielectric barrier to reduce electrical leakage or thermal transmission.
Insulating pads and sleeves – Insulating material, such as gypsum, diatomaceous earth, and so forth, used to lower the rate of solidification. As sleeves on open risers, they are used to keep the metal liquid, hence increasing the feeding efficiency.
Insulating refractories – The function of insulating refractories is to reduce the rate of heat flow (heat loss) through the walls of furnaces. The desirable feature of insulating refractories is the low thermal conductivity, which usually results from a high degree of porosity. Structure of air insulating material consists of minute pores filled with air which have in them very low thermal conductivity. The air spaces inside the brick prevent the heat from being conducted but the solid particles of which the brick is made conduct the heat. So, in order to have required insulation property in a brick a balance has to be struck between the proportion of its solid particles and air spaces. The thermal conductivity is lower if the volume of air space is larger. Importantly, the thermal conductivity of a brick does not so much depend on the size of pores as on the uniformity of size and even distribution of these pores. Hence, uniformly small sized pores distributed evenly in the whole body of the insulating brick are preferred.
Insulating refractory brick (IRB) – It is the term used for heat insulating bricks and it covers those heat insulating materials which are applied up to 1,000 deg C. Insulating refractory bricks are frequently mistakenly referred to as rear insulation materials. These bricks are assigned to the group of light-weight refractory bricks and are manufactured on the basis of naturally occurring light-weight raw materials. Insulating refractory brick is a class of brick, which consists of highly porous fireclay or kaolin. Insulating refractory bricks are light-weight, low in thermal conductivity, and yet sufficiently resistant to temperature to be used successfully on the hot side of the furnace wall, hence permitting thin walls of low thermal conductivity and low heat content. The low heat content is particularly important in saving fuel and time on heating up, allows rapid changes in temperature to be made, and permits rapid cooling. Insulating refractory brick is characterized by the presence of large quantity of porosity in it. The pores are mostly closed pores. The presence of porosity decreases the thermal conductivity of the insulating bricks.
Insulating refractory materials – These materials can be classified into four types with respect to application temperature. These four types are (i) heat resistant insulating materials for application temperatures up to 1,100 deg C (examples are calcium silicate materials, products from siliceous earth, perlite or vermiculite, silica based micro porous heat insulators, and alumino-silicate fibres), (ii) refractory insulating materials for application temperatures up to 1,400 deg C (examples are lightweight chamotte and kaolin bricks, lightweight castables, and mixed and aluminum oxide fibres), (iii) high refractory insulating materials for application temperatures up to 1,700 deg C (examples are lightweight mullite and alumina bricks, lightweight hollow sphere corundum castables and bricks, and special high refractory fibres) and (iv) ultra-high refractory insulating materials for application temperatures up to 2,000 deg C (examples are zirconia lightweight bricks and fibres, and non-oxide compounds). Several other types of insulating refractory materials include castables, granular insulation, and ceramic fibre insulation, which is light weight. Extremely lightweight materials have a porosity of 75 % to 85 % and ultra-lightweight, high-temperature insulating materials have a total porosity higher than 85 %.
Insulating sleeves – These are hollow cylinders or sleeves formed of gypsum, diatomaceous earth, pearlite, and vermiculite etc. These are placed in the mould at sprue and riser locations to decrease heat loss and rate of solidification of the metal contained in them.
Insulating washer – It is a specialized, non-conductive, and non-corrosive ring (or flange) designed to be used with fasteners (bolts, screws, nuts) to provide electrical isolation between a fastener and a substrate, or to separate two different metallic surfaces to prevent galvanic corrosion. They also serve to distribute load, dampen vibration, and seal against liquids or gases.
Insulation – It is a material of low thermal conductivity used to reduce heat losses.
Insulation board – It is a rigid, flat, manufactured panel designed to minimize heat transfer, sound transmission, or electrical conduction within structures or equipment. Mainly used in building envelopes (roofs, walls, foundations) for thermal efficiency, they feature high R-values and are made from materials like polystyrene, polyisocyanurate, or fibre.
Insulation coatings – These are specialized liquid-applied materials engineered to create a protective, seamless barrier on substrates which reduces heat transfer (thermal conductivity), prevents condensation, and protects against corrosion. Frequently utilizing fillers like ceramic micro-spheres or aerogel, they improve energy efficiency in buildings and industrial equipment, typically limited to 3 millimeters to 5 millimeters thickness for personnel protection or anti-sweat applications. It is a specialized, typically liquid-applied, or spray-applied substance which creates a durable, low-conductivity barrier on surfaces to minimize heat transfer, reduce energy loss, and prevent condensation or corrosion. Frequently incorporating ceramic beads or aerogels, these coatings improve thermal efficiency, provide personnel protection, and are used across industrial, and building applications.
Insulation core – It is the central, primary, or functional material within a composite, panel, or device designed specifically to minimize the transfer of heat, electricity, or sound. It acts as a high-resistance barrier surrounded by structural or protective layers (skin / shell).
Insulation failure – It is the degradation or breakdown of dielectric materials, causing them to lose their ability to prevent unintended electrical current flow between conductors or to the ground. This failure results in short circuits, electrical arcing, or equipment damage, frequently caused by thermal stress, aging, contamination, or mechanical damage.
Insulation layer – It is a material application designed to impede the transfer of energy, either heat (thermal) or electricity, between components, environments, or systems. It acts as a barrier to improve thermal efficiency, manage temperature, prevent corrosion, or provide electrical isolation, typically characterized by low conductivity, high resistance, and low moisture absorption.
Insulation level – It defines the rated dielectric strength of equipment, indicating the maximum voltage, including power-frequency and impulse voltages, which insulation can safely withstand without breakdown. It ensures safety against operational over-voltages and lightning strikes by setting standardized withstand levels, mainly determined by the ‘basic insulation level’ (BIL).
Insulation material, electrical – Insulation material means a material having good dielectric properties, which is used to separate or isolate the conducting electrical parts. Insulation to be used for cables is required to have several properties namely (i) it is to have a high specific resistance and dielectric strength; (ii) it is to be tough and flexible, (iii) it is not to be hygroscopic i.e. it does not absorb moisture from air or surroundings, (iv) it is to be capable of standing high temperatures without much deterioration, (v) it is to be non-inflammable and fire retardant, (vi) it does not be attacked by acids or alkalis, and (vi) it is to be capable of withstanding high rupturing voltages. Electrical insulation materials are utilized to provide electrical isolation over the metallic conductors of underground cables. The insulating materials physically protect the conductor and provide a margin of safety. The common insulating material is poly vinyl chloride (PVC) compound which is applied to the conductors by the extrusion process. It is so applied that it can be removed without damaging the conductor.
Insulation measures – It refer to the techniques, materials, and processes implemented to obstruct the transfer of heat, electricity, or sound between two points. These measures are designed to increase safety, energy efficiency, and operational reliability in systems ranging from building construction to electrical circuits and industrial processes.
Insulation monitoring device – It is a supervisory device to detect failure of electrical insulation.
Insulation properties – These properties define a material’s capacity to resist the transfer of heat, electricity, or sound, hence improving safety, efficiency, and stability. These properties include high electrical resistivity, low thermal conductivity (frequently measured by R-value), sound absorption, and structural, non-porous characteristics necessary for durability, such as high mechanical strength and dielectric strength.
Insulation resistance – It is the electrical resistance between two conductors or systems of conductors separated only by insulating material. It is also the ratio of the applied voltage to the total current between two electrodes in contact with a specified insulator. It is also the electrical resistance of an insulating material to a direct voltage.
Insulation screening – Cables rated for 6.35 kilovolts / 11 kilovolts are provided with insulation screening. It consists of two parts, namely non-metallic (semi-conducting) and metallic.
Insulation system – It is a designed, multi-component assembly used to restrict the flow of energy—thermal, electrical, or acoustic, between environments. It includes the insulation material itself, fasteners, vapour retarders, and protective finishes, specifically engineered to improve energy efficiency, ensure safety, or control process temperatures.
Insulation, thermal – It is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
Insulation thickness – It is the depth of material applied to surfaces (pipes, walls, equipment) to restrict heat transfer, directly affecting thermal resistance and energy efficiency. It is important for reducing heat loss / heat gain, with key definitions including ‘optimal thickness’ (minimizing cost + energy) and ‘critical radius’ (the point where adding insulation stops increasing heat loss on cylinders / spheres).
Insulator – It is a substance which does not permit easy flow of electric current. It is a fitting intended to support a conductor. It is a material of such low electrical conductivity that the flow of current through it can normally be neglected. Similarly, it is a material of low thermal conductivity, such as which is used to insulate structural shells.
Insulator contamination – It refers to the accumulation of foreign materials, such as dust, salt, industrial waste, or organic matter, on the surface of high-voltage insulators. This accumulation, when combined with moisture (rain, fog, dew), creates a conductive layer which lowers surface resistance, increases leakage current, and can lead to flashover (short circuits).
Insulators, transmission line – These insulators are devices used to contain, separate, or support electrical conductors on high voltage electricity supply networks. Transmission insulators come in various shapes and types, including individual or strings of disks, line posts or long rods. They are made of polymers, glass and porcelain, each with different densities, tensile strengths and performing properties in adverse conditions. Types of insulators include (i) pin type, (ii) suspension type, (iii) strain insulator, and (iv) shackle insulator.
Insurance – It is a means of protection from financial loss in which, in exchange for a fee, a party agrees to compensate another party in the event of a certain loss, damage, or injury. It is a form of risk management, mainly used to protect against the risk of a contingent or uncertain loss.
Insurance spare – An insurance spare is a spare part whose impact of not holding the spare part in stores can be massive. Downtime costs of the equipment for such spares frequently far outweigh all the other costs. Hence, by definition, it is an insurance against such failures for which the down time costs are very high. They do not become obsolete until the parent equipment remains under use. These spare parts may lie in the stores for many years. These spares need conservation activities at regular intervals. These spares block the working capital.
Intactness – It refers to the structural integrity, completeness, or unimpaired state of a component, system, or material, ensuring it remains unbroken, functional, and capable of withstanding operational stresses. It indicates that a structure has not been altered or compromised by degradation, fatigue, or damage.
Intact condition – It refers to the state of a structure, system, or material which is complete, undamaged, and unaltered by external forces or deterioration. It serves as the baseline for assessing structural integrity, stability, or mechanical properties.
Intact rock – It refers to the solid, unbroken material between fractures in a rock mass, containing no joints, faults, or substantial planes of weakness. It acts as the fundamental building block for evaluating rock mechanics, representing the material strength before discontinuities (like joints or bedding planes) dominate the rock mass behaviour.
Intact rock material – It refers to solid rock sections devoid of substantial fractures, joints, or weathering, acting as the fundamental, unbroken building block for analyzing rock mass behaviour. Engineering assessment focuses on quantifying physical (porosity, density) and mechanical (strength, deformation) properties to determine competence for foundations, tunnels, or construction materials.
Intake – It is a structure on the upstream face of a dam or within a reservoir created for directing water into a confined conduit, tunnel, canal, or pipeline.
Intake facility – It is a hydraulic structure designed to collect water from surface sources (rivers, lakes, reservoirs) and discharge it into a conveyance system leading to a treatment plant, industrial site, or pump station. These structures protect conduits from debris, ice, and sediment, typically using submerged inlets, towers, or screens to ensure a consistent, clean raw water supply.
Intake filter – It is an air intake filter which is a component within an air intake system designed to remove particulate matter and contaminants from the air before it enters an engine or other system. Its primary function is to protect the system from damage and ensure optimal performance by preventing dust, debris, and other pollutants from being drawn in. In the context of water, it refers to a device which removes solid particles and debris from water as it enters a system, such as a pump or pipeline. This prevents damage to downstream equipment and ensures cleaner water for several applications. It is basically a strainer which prevents larger contaminants from passing through.
Intake process – It refers to two distinct concepts namely (i) a structured workflow for capturing and prioritizing project requests (project management), and (ii) the mechanical method of drawing fluids / gas into a machine (mechanical / civil engineering). It normally defines the initial, controlled entry point for resources or materials.
Intake pump house – It is an engineered structure, frequently a building or secured housing, which shelters pumping equipment, valves, and screening devices used to withdraw raw water from sources like rivers, lakes, or reservoirs and transfer it to treatment plants or industrial facilities. It acts as a secure, functional interface between the water source and the distribution system, ensuring a steady, debris-free flow.
Intake stroke – It is also called induction stroke. It is the first stage in a four-stroke engine cycle where the piston moves from ‘top dead centre’ (TDC) to ‘bottom dead centre’ (BDC). The intake valve opens, and the downward piston motion creates a vacuum, drawing air or an air-fuel mixture into the cylinder.
Intake structure – It is an engineering construction, typically made of concrete or masonry, designed to withdraw water from sources like rivers, lakes, or reservoirs and convey it to treatment plants, pumping stations, or power turbines. It acts as a main barrier against debris, sand, and pollution.
Intake system – It is a critical component or assembly designed to manage, clean, and transport a working fluid, typically air, into an engine’s combustion chamber or a mechanical system, maximizing efficiency and performance. It optimizes airflow through filtration, acoustic tuning, and pressure regulation.
Intake temperature – It is also called the intake air temperature. It is the measured temperature of air as it enters an engine’s combustion chamber, typically monitored between the air filter and intake manifold. It is a critical parameter used by the ECU (electronic control unit) to determine air density for optimizing fuel delivery, ignition timing, and emission control.
Intake valve – It is a mechanical component located in an internal combustion engine’s cylinder head which regulates the flow of air or fuel-air mixture into the combustion chamber. Operating through a camshaft-driven mechanism, it opens during the intake stroke to allow charge entry and seals the chamber during compression and combustion.
Intake valve closing – It is the specific moment, measured in crankshaft angle degrees (typically after bottom dead centre, ABDC), when the intake valve seals the combustion chamber, ending the induction phase and beginning the compression stroke. It is important for maximizing volumetric efficiency, managing effective compression ratio, and reducing pumping losses.
Intake valve deposits – These are solid, carbonaceous, or varnish-like residues which accumulate on the intake valves of internal combustion engines, particularly in ‘gasoline direct injection’ (GDI) systems. Formed through the oxidation and polymerization of engine oil and fuel residues at high temperatures (230 deg C to 350 deg C), these deposits restrict airflow and impair fuel atomization.
Intake water – It refers to the raw water withdrawn from a natural or artificial surface source (river, lake, reservoir) or groundwater, collected through a dedicated intake structure (concrete / masonry tower or conduit) for supply to a water treatment plant. These structures are designed to safely admit water, exclude debris using screens, and ensure a consistent supply.
Intangible asset – It is a non-physical, non-monetary asset which provides future economic benefits to the organization. These assets lack physical substance but are valuable because of their ability to generate revenue, reduce costs, or improve the organizational overall value. Examples include patents, trademarks, copyrights, brand recognition, and goodwill.
Intangible costs – These are non-physical, subjective, and difficult-to-quantify expenses arising from projects or operational decisions, such as damage to brand reputation, decreased employee morale, lower productivity, or reduced customer satisfaction. Unlike tangible costs, they lack a precise monetary value but significantly affect long-term profitability.
Intangible incentives – These also known as intangible rewards. These are non-monetary benefits given to employees to recognize their contributions and motivate them. These incentives focus on emotional and psychological rewards rather than financial ones, and frequently include things like praise, recognition, and opportunities for growth.
Integer number – It is a whole number which can be positive, negative, or zero, and it cannot include decimal fractions. Examples of integers include 0, 2, 5, −82, and 3546.
Integer vector – It is defined as an ordered sequence of whole numbers (integers), stored contiguously in memory for efficient processing. Unlike real-valued vectors, integer vectors are specifically restricted to integer types (e.g., 32-bit or 64-bit), making them ideal for exact, compact, and high-performance data manipulation.
Integrability – It is the ability to include new systems and components within an existing production system, enabling the integration of new technologies and the addition or removal of resources. It encompasses the capacity to integrate components and processes through interfaces while considering the effort needed for such integration.
Integral approach – It refers to a holistic, systems-thinking methodology which integrates different disciplines, technologies, and project phases, such as design, construction, and control, to optimize overall system performance. It emphasizes collaboration, sustainability, and life-cycle efficiency, frequently reducing costs and timelines through early, coordinated efforts.
Integral approximate method – It is defined as a technique for solving heat conduction problems, particularly useful in cases of melting and solidification, which simplifies the analysis through integral approximations of governing equations. This method is recognized for its clarity and applicability to both linear and non-linear transient conduction scenarios.
Integral blower – It is a blower built as an integral part of a device to supply air thereto.
Integral blower burner – It is a burner of which the blower is an integral part.
Integral colour anodizing – It consists of developing coloured surfaces either by anodizing certain aluminum alloys and / or by using special organic electrolytes which produce colours during anodizing.
Integral composite structure – It is the composite structure in which several structural elements, which are conventionally assembled together by bonding or mechanical fasteners after separate fabrication, are instead laid up and cured as a single, complex, continuous structure, e.g., spars, ribs, and one stiffened cover of a wing box fabricated as a single integral part. The term is sometimes applied more loosely to any composite structure not assembled by mechanical fasteners. All or some parts of the assembly can be co-cured.
Integral constant (Ki) – It is the parameter (gain) which determines the strength of the control action by integrating the error signal over time. It is part of the ‘proportional-integral-derivative (PID) algorithm. It brings the controlled variable back to the set point, eliminating the ‘offset’ (residual error) inherent in purely proportional controllers.
Integral control – It is a feedback mechanism which eliminates steady-state error by adjusting the system’s output based on the cumulative sum of past errors over time. Frequently part of PID (proportional-integral-derivative) controllers, it ensures the process variable reaches the setpoint, acting proportionally to the integral of the error signal.
Integral controller – It is a feedback mechanism which eliminates steady-state error by adjusting the output based on the accumulation (integral) of past errors over time. It acts to drive the error to zero, making it important for precision in temperature, pressure, and speed control, although it can reduce system stability.
Integral dose – It is the total quantity of energy (in Joules, or Gray-kilogram) deposited by ionizing radiation within a specific volume, such as an organ, or the entire body. It represents the comprehensive radiation burden, accounting for both the dose magnitude and the volume of tissue irradiated.
Integral equation – It is used to model physical processes (e.g., heat transfer, diffusion, scattering) where the state at one point depends on the state of the entire system.
Integral gain – It is a control parameter in PID (proportional-integral-derivative) systems which reduces steady-state error by multiplying the accumulated sum of past error over time to generate the control output. It acts to ‘reset’ the system by pushing the process variable toward the setpoint, eliminating offset, though high values can cause oscillation and overshoot.
Integral heat – It is the integral heat of solution / mixing. It is the total, cumulative quantity of heat released or absorbed when a solute is dissolved into a solvent to reach a specific final concentration, starting from the pure components. It represents the net enthalpy change, which can be exothermic or endothermic.
Integral length scale – It measures the correlation distance of a process in terms of space or time. In short, it looks at the overall memory of the process and how it is influenced by previous positions and parameters. An intuitive example would be the case in which you have very low Reynolds number flows (e.g., a Stokes flow), where the flow is fully reversible and hence fully correlated with previous particle positions. This concept can be extended to turbulence, where it can be thought of as the time during which a particle is influenced by its previous position.
Integral linearity – It defines how well the actual transfer function of a device (like an analog-to-digital converter, ADC) matches an ideal straight line. It measures the maximum deviation of a device’s actual output from this ideal line across its entire operating range, representing the accumulated error.
Integrally heated – It is a term referring to tooling which is self-heating, through use of electrical heaters such as cal rods. Majority of the hydroclave tooling is integrally heated. Some autoclave tooling is integrally heated to compensate for thick sections, to provide high heat-up rates, or to permit processing at a higher temperature than is otherwise possible with the autoclave.
Integral method – It is an approximate analytical technique used to solve complex partial differential equations (PDEs), particularly in heat transfer and fluid mechanics, by integrating governing equations across a domain (e.g., boundary layer) to reduce them to ordinary differential equations (ODEs). It assumes velocity or temperature profiles to simplify analysis, frequently applied to Stefan (melting / solidification) or boundary layer problems.
Integral process – It is frequently referred to as process integration. It is a holistic approach to designing or optimizing industrial systems by combining multiple unit operations under unified control to improve efficiency, reduce costs, and minimize energy consumption. It focuses on system-level interactions rather than individual component optimization.
Integral scale – In fluid mechanics and turbulence, it is a statistical measure representing the average size (length scale) or duration (time scale) of the largest, most energetic eddies in a turbulent flow. It characterizes the distance or time over which turbulent velocity fluctuations remain correlated. It measures the size of the largest energy-containing eddies, frequently related to the overall geometry of the flow, such as boundary layer thickness.
Integral skin foam – It is urethane foam with a cellular core structure and a relatively non-porous skin.
Integral term – It is a control component which eliminates steady-state error by accumulating (integrating) the error between a process variable and the setpoint over time. It forces the controller output to change until the error is reduced to zero. It eliminates steady-state offset in control systems. It continuously sums up the past error (error time). It increases system stability but can introduce overshoot and slower response times if too high.
Integral time scale – In fluid mechanics and turbulence, it is a measure of the average time duration over which a turbulent flow field, or a fluctuating data series. It remains correlated with itself. It represents the memory or ‘lifetime’ of large-scale eddies in a turbulent flow. It is formally calculated by integrating the normalized autocorrelation function of a fluctuating quantity (like velocity) over time.
Integral transform – It is a type of transform which maps a function from its original function space into another function space through integration, where some of the properties of the original function can be more easily characterized and manipulated than in the original function space. The transformed function can normally be mapped back to the original function space using the inverse transform.
Integral transformation – It is a mathematical technique which applies a linear integral transformation to simplify or eliminate differential forms in governing equations, facilitating the solution of partial differential equations.
Integrated assessment – It is a method of analysis which combines results and models from the physical, biological, economic, and social sciences, and the interactions between these components, in a consistent framework, to evaluate the status and the consequences of environmental change and the policy responses to it is known as integrated assessment.
Integrated automation system – It combines several automated processes and technologies into a single, cohesive framework to optimize work-flows, improve efficiency, and facilitate real-time decision-making. It involves integrating different automation systems, like control systems, software, and machinery, to work together seamlessly. This allows for the coordination and synchronization of different manufacturing or operational processes, leading to improved efficiency, increased productivity, and reduced downtime. Integrated automation is not just about automating individual tasks. It is about connecting these automated tasks and processes to create a unified system. This can involve integrating hardware, software, and even third-party applications.
Integrated beam – It refers to a beam which combines radar and communication functionalities, allowing both tasks to be performed simultaneously with minimal interference by utilizing the same spatial resources and waveforms for both detection and communication. This approach improves spectral efficiency and optimizes resource usage in integrated radar-communication systems.
Integrated beams – These are specialized, normally steel, floor beams designed to support concrete floor slabs within their own structural depth. This integration enables the slab to rest on the bottom flange, reducing overall building height by 25 centimeters to 30 centimeters per floor. They offer high structural efficiency for supporting hollow-core or precast planks.
Integrated blade inspection system – It is the quantitative assessment of process performance capabilities and process characterization is absolutely necessary in implementing automated non-destructive examination systems. At a gas turbine overhaul facility, e.g., quantitative assessment methods have been applied to the implementation of an integrated blade inspection system with an automated fluorescent penetrant inspection module. The processed blades are introduced into a robotic handling system which manipulates the blade in a high-gain optical-laser scan readout system to produce a digitized image of the fluorescent penetrant indications. A computerized data processing and image analysis system provides the readout and decision processing to accept or reject the blades.
Integrated circuit – It is also known as a micro-chip, computer chip, or simply chip. It is a small electronic device made up of multiple interconnected electronic components such as transistors, resistors, and capacitors. These components are etched onto a small piece of semiconductor material, normally silicon. Integrated circuits are used in a wide range of electronic devices to perform different functions such as processing and storing information. They have greatly impacted the field of electronics by enabling device miniaturization and improved functionality.
Integrated circuit board – It refers to the physical substrate (like silicon) where tiny, interconnected electronic components (transistors, resistors, capacitors) are fabricated into a single, miniature unit (the chip / microchip), forming complex circuits for functions like processing or memory, revolutionizing electronics by enabling miniaturization and higher performance compared to discrete components.
Integrated circuit design – It is a specialized engineering process, frequently called VLSI (very-large-scale integration) design, which involves creating, modeling, and arranging millions to billions of miniaturized components, such as transistors, resistors, and capacitors, onto a single silicon substrate. It transforms logical descriptions into precise physical layouts, using CMOS (complementary metal-oxide-semi-conductor) technology for digital, analog, or mixed-signal devices.
Integrated circuit interconnects – These are the microscopic, high-conductivity metal lines (typically copper or aluminum) which electrically connect transistors, resistors, and capacitors within a chip to form functional circuits. They are important in the ‘back end of line’ (BEOL) fabrication, facilitating signal, power, and clock distribution, separated from the substrate by dielectric layers.
Integrated circuit layout – It is also called IC (integrated circuit) mask design. It is the 3D physical representation of an electronic circuit’s schematic, defining the geometric shapes (polygons) of transistors, resistors, and interconnections on a semiconductor substrate. It acts as a blueprint, normally generated through computer-aided design (CAD) software, used to produce masks for photo-lithography, enabling mass manufacturing.
Integrated circuit manufacture – It is the engineering process of fabricating miniature electronic circuits, containing millions to billions of transistors, resistors, and capacitors, onto a single semi-conductor substrate, normally silicon. It involves multi-layered micro-fabrication techniques, including lithography, doping, thin-film deposition, and etching, to build complex 3D structures. The process involves creating layers of conductive, semiconductive, and insulating materials on a wafer.
Integrated coal gasification combined cycle power plant – It is an advanced, high-efficiency electricity generation system which converts coal into synthesis gas (syngas) through gasification, removes pollutants, and burns the clean gas in a combined-cycle turbine setup. It offers higher efficiency (higher than 45 %) and lower emissions (up to 36 % less carbon di-oxide) than conventional coal plants.
Integrated collector storage solar water heater – It a system designed to collect solar energy for heating water, typically featuring a tank which combines both the collector and storage functionalities. It is a passive solar device which combines the functions of solar radiation absorption and hot water storage into a single, compact unit. The system consists of black-painted tanks or tubes placed inside an insulated, glazed box, acting as both the collector and the storage tank.
Integrated collector storage system— It is a passive solar technology which combines water heating and storage in one unit, where the storage tank acts as the absorber surface. These systems are designed to directly heat water through solar radiation, relying on natural convection for heat transfer, making them ideal for simple, low-maintenance, and cost-effective residential hot water applications.
Integrated computational materials engineering – It is a methodology which integrates computational materials science tools, data, and models with engineering product performance analysis and manufacturing process simulation. It links material structures, properties, processing, and performance across multiple length scales (from atomic to macroscale) to accelerate development, reduce costs, and improve design efficiency.
Integrated computer-aided system – It is a unified framework combining multiple software toolboxes (such as computer-aided design, computer-aided engineering, computer-aided manufacturing) to manage complex design, simulation, and manufacturing tasks. It bridges disparate engineering processes, from modeling to production, by utilizing shared, standardized data models, ensuring seamless information flow and increased efficiency across the product lifecycle.
Integrated control and safety system – It combines process control (distributed control system), safety instrumented systems (SIS), fire and gas system (FGS), and electrical control system (ECS) into a single, unified platform for complex industrial operations, improving efficiency and safety by sharing data, tools, and resources while maintaining separation for critical safety functions, using common hardware / software for cost savings but needing careful design for reliability.
Integrated control system – It is a centralized, unified architecture that combines hardware (programmable logic controller, supervisory control and data acquisition, human-machine interface, sensors) and software to manage, monitor, and automate multiple, often disparate, industrial subsystems or machinery through a single interface. It enables seamless data exchange, real-time visibility, and coordinated control, improving operational efficiency and reliability.
Integrated demand response – It is the extension of traditional demand response to encompass the flexible adjustment of different energy demands, including thermal energy, in an optimal manner. This approach facilitates the management of multi-energy systems by allowing consumers to adjust their energy consumption patterns in response to real-time energy price signals.
Integrated desalination – It refers to combining multiple desalination technologies (e.g., reverse osmosis + membrane distillation) or coupling desalination with renewable energy sources (e.g., solar-powered systems) to improve efficiency, reduce energy consumption, and manage brine. This approach aims to maximize water recovery while minimizing environmental impacts, such as by integrating brine management with mineral extraction.
Integrated design – It refers to a collaborative approach where different design disciplines work together from the outset of a project to create a cohesive and functional outcome. It emphasizes synergy and shared decision-making among all stakeholders to achieve optimal results. This holistic approach considers all aspects of a project, including environmental, social, and economic factors, to produce a more sustainable and efficient design.
Integrated energy storage systems – These systems refer to the combination of multiple energy storage technologies (e.g., chemical, physical, thermal) within a single, optimized system to improve grid efficiency, reliability, and renewable energy integration. These systems bridge the gap between energy production and demand, balancing intermittent sources like solar or wind.
Integrated energy system – It is a coordinated, multi-carrier infrastructure combining electricity, heating / cooling, and chemical networks (such as gas or hydrogen) to maximize efficiency and sustainability. It physically and digitally links diverse energy sources, including renewables and fossil fuels, through advanced conversion technologies to improve flexibility, reliability, and cost-effectiveness for consumers.
Integrated floor beams – These are typically I-shaped sections, frequently cut in half and welded with a plate, allowing the slab to sit within the beam’s profile, saving substantial construction height.
Integrated gasification combined cycle – It is an advanced power generation technology which converts solid fuels, such as coal or biomass, into synthetic gas (syngas) through high-temperature gasification. This cleaned syngas fuels a gas turbine, while waste heat drives a steam turbine to achieve high efficiency (over 45 %) and lower emissions compared to conventional coal plants.
Integrated gasification combined cycle plant – It is an advanced, high-efficiency power generation technology which converts solid fuels (like coal) or biomass into pressurized synthesis gas (syngas) through gasification. This cleaned syngas fuels a gas turbine, while waste heat produces steam for a steam turbine, creating a highly efficient combined cycle which reduces emissions and enables carbon capture.
Integrated gasification combined cycle power plant – It is an advanced, high-efficiency electricity generation system which converts carbon-based feedstocks (coal, biomass) into pressurized synthesis gas (syngas) through a gasifier. This cleaned syngas fuels a gas turbine, while waste heat generates steam for a steam turbine, combining both cycles for superior thermal efficiency (up to 45 % plus) and lower emissions compared to conventional coal plants.
Integrated gate-commutated thyristor – It is a power semi-conductor electronic device which is used for switching electric current in industrial equipment. It is related to the gate turn-off (GTO) thyristor. Like the gate turn-off thyristor, the integrated gate-commutated thyristor is a fully controllable power switch, meaning that it can be turned both on and off by its control terminal (the gate). Gate drive electronics are integrated with the thyristor device. An integrated gate-commutated thyristor is a special type of thyristor. It is made of the integration of the gate unit with the gate-commutated thyristor wafer device. The close integration of the gate unit with the wafer device ensures fast commutation of the conduction current from the cathode to the gate.
Integrated heat pump – It is a system which combines space heating, cooling, and water heating into a single, highly efficient unit, frequently using waste heat recovery. These systems, frequently utilizing vapour-compression cycles, are designed to optimize energy efficiency by sourcing heat from ambient air or industrial processes.
Integrated intensity – It is the total, background-corrected area under a spectral band, scattering peak, or within a specific image region, representing the cumulative signal or energy. It measures total absorption, scattering, or concentration, providing a robust, resolution-insensitive metric compared to peak height.
Integrated intensity ratio – It is the normalized scalar value got by dividing the total area under one spectral band (integrated intensity) by that of another. It is used to normalize data, reducing errors from instrumental fluctuations or sample variability, frequently representing structural defects, relative concentration, or phase changes, such as the Id/Ig ratio in Raman spectroscopy or Iuv/Ivis in photo-luminescence.
Integrated knowledge – It refers to the systematic synthesis of diverse data, models, and expert heuristics across different, frequently siloed, domains (e.g., design, simulation, and manufacturing) into a common, cohesive framework, typically using ontologies or knowledge bases to solve complex, interdisciplinary problems.
Integrated life – It refers to the comprehensive approach in the life-cycle design process of structures, encompassing stages from initiation and design to construction, operation, and end of life, with an emphasis on reducing resource consumption and pollution while promoting recycling and reuse of materials.
Integrated management – It is the management of a system of functions under a single general control in a way which seeks a compromise to simultaneously maximize the combined benefits from the individual functions.
Integrated market – It involves strategically aligning market boundaries. geographical and product-related, to create a unified economic space where prices, demand, and supply are harmonized. It merges distinct markets by removing barriers, allowing for free movement of goods, services, and capital. This approach ensures that market dynamics are, in effect, a single, integrated ecosystem.
Integrated membrane system – It is a strategic, combined process which utilizes multiple membrane technologies (e.g., micro-filtration, ultra-filtration, nano-filtration, reverse osmosis) in series or parallel, often with conventional treatment methods, to improve efficiency, selectivity, and overall performance. It leverages the unique, complementary strengths of different membranes to achieve superior purification, reduced fouling, and increased product yield.
Integrated mills, integrated plants – These facilities make steel by processing iron ore and other raw materials in blast furnaces. Technically, only the hot end differentiates integrated mills from mini-mills. However, the differing technological approaches to molten steel imply different scale efficiencies and, hence, separate management styles, labour relations, and product markets.
Integrated opto-electronics – It is the incorporation of both optical and electronic components into a single, highly functional chip, aimed at providing low-cost, reliable devices for applications in communications, consumer electronics, and high-speed broadband networks.
Integrated passive devices – These are electronic components where passive elements like resistors, capacitors, inductors, and sometimes even more complex structures like baluns, are fabricated on a single substrate or within a single package. They are designed to replace discrete passive components, leading to smaller, lighter, and more cost-effective electronic systems. Integrated passive devices combine multiple passive components (resistors, capacitors, inductors) into a single unit, frequently using integrated circuit manufacturing techniques.
Integrated product and process design – It is also known as integrated product development or integrated product and process development. It is a management technique which involves all relevant stakeholders and disciplines throughout the product lifecycle to optimize design, manufacturing, and support processes. It emphasizes collaboration and concurrent engineering to reduce time-to-market, development costs, and risks while improving product quality and sustainability.
Integrated product development team – It is a flexible, collaborative, multi-disciplinary team assigned with the responsibility of developing a product and the process to manufacture it. In addition to design and manufacturing engineers with the appropriate technical backgrounds, the team is to include members with operational, quality control, financial, marketing, field service, and purchasing experience.
Integrated reliability – It refers to the evaluation of process, equipment, task, and human reliability in industrial processes, aimed at improving safety, performance, and availability of operations. It involves assessing different factors such as automation, complexity, and human factors to ensure effective and safe operation within critical processes.
Integrated renewable energy systems – It is a combination of renewable energy sources, such as solar, wind, biomass, and micro-hydro power, designed to meet the energy demands of isolated areas while maximizing energy efficiency and reliability. These systems frequently include storage devices to manage the variability of renewable energy generation and need strategic planning to align local energy needs with available resources.
Integrated resource planning – It is a structured, long-term framework used by utilities to meet electricity demand by combining supply-side options (power plants) and demand-side options (energy efficiency) at the lowest cost. It optimizes resource allocation while considering environmental regulations, reliability, risks, and stakeholder input.
Integrated risk assessment – It is a comprehensive approach which evaluates and manages risks by considering all potential events and their potential impact, encompassing ecological, economic, and social aspects, to provide a realistic picture of potential damage. It allows a single monitoring and management system to handle one or more risks, providing greater clarity to assess risks at the organizational level, manage risks and understand interactions between different types of risks.
Integrated rolling, annealing, and pickling line – It is a continuous line used for stainless-steel production. It integrates rolling, annealing and pickling operation. This integration is done for high-efficiency production of stainless steels for general applications. This kind of integration is sub-divided into two types namely (i) integration of up-stream processes from HAP (hot annealing and pickling) to cold rolling, and (ii) that of down-stream processes from cold rolling through annealing, pickling, skin pass rolling to tension leveling. In a typical integrated rolling, annealing, and pickling (RAP) line, cold rolling on a 3-stand tandem mill, annealing, pickling, skin pass rolling, and leveling are integrated into one continuous line.
Integrated service – It involves creating a unified framework for delivering, managing, and optimizing multiple, frequently disparate, services or systems, such as information technology, communications, or building utilities, through a single, cohesive, and efficient interface. It leverages standardized, modular, or automated approaches to improve quality, reduce costs, and ensure consistent, high-performance, and reliable outcomes in technical or organizational settings.
Integrated solar combined cycle – It is a hybrid power generation system which combines a ‘concentrating solar power’ (CSP) field with a ‘natural gas combined cycle’ (NGCC) plant. It utilizes solar thermal energy to supplement or replace fossil fuel in the steam generation process (typically within the ‘heat recovery steam generator’), boosting efficiency and reducing carbon di-oxide emissions.
Integrated solar combined cycle system – It is a hybrid power plant that merges concentrating solar thermal technology (normally parabolic troughs or towers) with a natural gas-fired combined cycle (NGCC) plant. It involves integrating solar-generated steam or hot air into the power block, typically feedwater heating or steam generation, to boost output, increase efficiency, and reduce fuel consumption.
Integrated steel plant – It is one in which all the processes involved in steel making are done in one place. It is normally huge in size and employ a large workforce to carry out the complete steel manufacturing process from iron ore to the finished product (e.g., TMT rebar, angle, steel channels, coils, and plates etc.).
Integrated system – It is a single system which combines multiple subsystems or components to function as a unified whole, enabling communication and coordinated action between them. It involves linking different systems and software applications to streamline operations and improve efficiency, frequently replacing separate, isolated solutions for various business functions.
Integrated transport system – It refers to the integration of information and communication technologies within the transportation system, aimed at improving safety, efficiency, and sustainability. It encompasses several applications including traffic management, fleet and freight management, and driver assistance, leveraging technologies such as ‘global positioning system’ (GPS) and dedicated short-range communication.
Integrated waste strategy – It describes how a plant site optimizes its approach to waste management. It includes the waste streams and discharges expected from present and future operations at the site, and the actions needed to improve the site’s approach to waste management.
Integrating energy storage system – It refers to the incorporation of energy storage systems within a smart grid to improve the grid’s reliability and operational efficiency, enabling effective management of distributed generation and load demands.
Integrating instruments – These instruments totalise measurements over a specified period of time. The summation, which these instruments give, is the product of time and an electrical quantity. Examples are ampere hour and watt hour (energy) meters. The integration (summation value) is normally given by a register consisting of a set of pointers and dials.
Integration – A layout is required to have a close integration of men, materials and equipment and support services in order to get the optimum output of the resources.
Integration approach – It is a structured, frequently iterative, methodology used to combine separate subsystems or technical components into a unified, functional system. It focuses on managing interfaces, verifying performance, and minimizing risks through strategic assembly rather than testing all components simultaneously.
Integration method – It refers to a numerical technique used to solve differential equations of motion by integrating the equations in terms of changes in velocity or other variables, hence improving error propagation characteristics and the ability to handle rapidly varying loads and stiffnesses in engineering applications.
Integration platform – It is a structure which allows for the combination of different components, such as lasers, detectors, modulators, and passive devices, in a single system. It enables the optimization of devices and functions by providing a platform for interaction and integration of various materials and technologies.
Integration principle – This principle states that all other things being equal, a good layout is one which integrates 4Ms i.e., men, materials, machines, and methods in the best possible manner.
Integrity management – It is a systematic, risk-based process which manages the entire lifecycle of physical assets, from design to decommissioning, to ensure safety, reliability, environmental compliance, and operational efficiency. It integrates maintenance, inspection, and operational strategies to prevent failures and maintain an asset’s ‘fitness-for-service’.
Integrity management strategy – It is a systematic, risk-based approach ensuring assets (pipelines, structures, equipment) remain safe, reliable, and compliant throughout their lifecycle. It involves identifying, assessing, and mitigating risks, such as corrosion or fatigue, through inspection, maintenance, and monitoring to prevent failures, optimize costs, and protect personnel, the environment, and organizational interests.
Integrity monitoring – It is the continuous process of assessing the health, reliability, and state of a system, structure, or component to detect damage, faults, or degradation, allowing for proactive maintenance and safety assurance. It is a critical component of ‘asset integrity management’ (AIM), which ensures systems remain within authorized operational limits.
Integrity protection – It refers to technical mechanisms, protocols, and design strategies designed to ensure systems, data, or physical structures remain accurate, authorized, and functional. It prevents unauthorized alteration, tampering, or failure by maintaining structural or digital consistency throughout the lifecycle.
Intellectual property – It is the knowledge-based property, normally represented by patents, copyrights, trademarks, or trade secrets.
Intellectual property core – It is a reusable, pre-verified unit of logic, cell, or integrated circuit layout design used as a building block for ‘application-specific integrated circuit’ (ASIC) or ‘field-programmable gate array’ (FPGA) chips. Licensed from third parties or owned internally, these cores, ranging from processors to memory controllers’ considerably speed up ‘system-on chip’ (SoC) development.
Intellectual property protection – It refers to the legal mechanisms, such as patents, copyrights, trademarks, and trade secrets, which safeguard original works and inventions from unauthorized use or reproduction, particularly in the context of challenges posed by digital information transfer and varying international laws.
Intelligent building – It is a structure which integrates advanced technology systems to improve operational efficiencies, management functions, and occupant experience, while also supporting energy control and cost savings, hence aligning with the principles of green building. It utilizes advanced communication and control technologies to create a comfortable, convenient, energy-efficient, and environmentally friendly environment for occupants, while also effectively organizing information resources and ensuring a reasonable return on investment.
Intelligent communication system – It is an advanced system which combines artificial intelligence and communication technology to improve information exchange and interaction, facilitating more human-friendly access to services and resources in different fields.
Intelligent compaction – It is a technology using specialized vibratory rollers equipped with accelerometers, ‘global positioning system’ (GPS), and onboard computers to monitor and optimize the compaction of soils, aggregate bases, or asphalt in real-time. It provides, 100 % coverage, recording stiffness, pass counts, and temperature to improve uniformity and material quality.
Intelligent control – It is the application of artificial intelligence techniques to process control.
Intelligent device – It is a term for equipment, instruments, or machines which incorporate micro-processors, sensors, and connectivity to perform data acquisition, processing, and autonomous or semi-autonomous decision-making. Unlike traditional ‘dumb’ devices, intelligent devices analyze data locally (frequently at the edge) or through the cloud to adapt to their environment, improve efficiency, and perform self-diagnosis.
Intelligent instruments – These are advanced, micro-processor-based measurement devices which incorporate digital signal processing, memory, and software to improve performance beyond traditional sensors. They enable automatic error correction, environmental compensation, self-diagnostics, and digital communication, functioning independently or within complex automation networks.
Intelligent instrumentation – It refers to advanced measuring devices incorporating micro-processors, memory, and software to provide self-calibration, diagnostic, and data processing capabilities beyond simple sensing. These systems, which frequently include smart sensors, translate raw data into useful information, improving accuracy by compensating for environmental factors and enabling automated, flexible, or adaptive control.
Intelligent metering – It is a system utilizing digital meters to continuously measure and record, in near real-time, resource consumption (electricity, gas, water). It facilitates bi-directional, secure communication between consumers and utility providers through smart meter gateways to enable remote monitoring, automated billing, and load management.
Intelligent network – It is a standardized, service-independent telecommunications network architecture which separates service control functions from the switching hardware (the transport layer). By moving service logic to specialized, centralized nodes, intelligent network enables network operators to rapidly create, deploy, and manage value-added services without modifying the underlying switching equipment.
Intelligent pigs (smart pigs) – These are inspection vehicles which move inside a pipeline pushed along by the flowing fluid. These are mainly used for the detection of wall thinning caused by ordinary corrosion.
Intelligent prediction – It means generation of predictive models based on historical records stored within the system. It accelerates issue resolution by providing contextual suggestions and actions based on what is learnt from previous interactions. In data analysis, it also known as predictive analytics. It uses historical data and statistical models to forecast future outcomes. It involves techniques like machine learning and artificial intelligence to identify patterns and trends, allowing organizations to anticipate future events and make more informed decisions.
Intelligent pump – It is a pump which has the ability to regulate and control flow or pressure. Typical advantages are energy savings, lifetime improvements, and system cost reductions.
Intelligent reflecting surface – It is a planar meta-surface composed of several low-cost, passive, software-controlled metamaterial elements which manipulate electro-magnetic waves to reconfigure wireless environments. By independently adjusting the phase, amplitude, or polarization of reflected signals, it achieves 3D passive beamforming to improve signal quality, network capacity, and energy efficiency without radio frequency (RF) chains.
Intelligent sensors – These sensors are also called smart sensors, These are devices which integrate a measurement unit, information processing unit, and data transfer unit, enabling them to directly convert analog signals to digital signals while performing pre-processing tasks such as correction and digital filtering. They improve system performance by reducing the load on central control systems and allowing for efficient monitoring and control of multiple process variables.
Intelligent structures – These are advanced, frequently multi-functional, material systems which integrate sensors, actuators, and control units (processors) to actively monitor their environment, diagnose their own health, and respond adaptively to changing conditions. Unlike conventional, passive structures, intelligent structures act as interactive, autonomous systems which improve performance, improve safety, and extend service life.
Intelligent transport systems – These systems refer to information and communications technologies which improve the operation of transport systems, providing benefits such as real-time information on public transport and traffic advisories for drivers.
Intended operation – It refers to a system, product, or component functioning according to its design specifications, purpose, and planned operational parameters. It encompasses the intended usage, environmental conditions, and performance goals for which the system has been engineered, ensuring it operates safely and effectively.
Intended path – It is the calculated, optimal, or prescribed trajectory, route, or sequence of actions designed for a system, vehicle, or process to move from an initial state to a target destination while adhering to constraints like safety, obstacles, and efficiency. It involves mapping, planning, and validating the specific path to minimize risk or maximize performance.
Intended speed – It refers to the premeditated, targeted rate of motion, operation, or production set for a system, machine, or process to achieve specific performance goals. It differs from instantaneous or average speed, acting instead as the operational benchmark.
Intense quenching – It is the quenching in which the quenching medium is cooling the part at a rate at least two and a half times faster than still water.
Intensified controlled rolling – It is an advanced form of thermo-mechanical processing (TMP), designed to produce ultra-fine-grained microstructures in steels to achieve superior strength and toughness. It involves using higher rolling reductions at lower temperatures, frequently in the non-recrystallization zone or the austenite-ferrite region, to introduce heavy deformation.
Intensified plant – It is a manufacturing facility designed using process Intensification (PI) principles to be considerably smaller, safer, cleaner, and more energy-efficient than traditional plants. It achieves this through radical, frequently order-of-magnitude, reductions in equipment size, optimization of energy use, and the consolidation of multiple unit operations into fewer, highly efficient, multi-functional units.
Intensified reactor – It is an advanced chemical processing unit designed to improve considerably transport phenomena (heat transfer / mass transfer) and reaction kinetics, resulting in a much smaller, safer, and more energy-efficient system. These reactors maximize productivity by overcoming mixing limitations, reducing equipment volume, and combining multiple unit operations, like reaction and separation, into a single, compact device.
Intensified unit operation – It is a process which drastically improves efficiency, reduces equipment size, and lowers energy consumption compared to conventional methods. It improves heat transfer / mass transfer, frequently using micro-systems /nano-systems or external energy, to produce smaller, cleaner, and safer manufacturing processes.
Intensifier – It is a very simple device which uses a large swept volume from a low-pressure source to generate a small swept volume at high pressure to be supplied to an instrument. The commercial intensifiers are normally cyclic so that after a volume is delivered to the instrument.
Intensiostatic – It is an experimental technique whereby an electrode is maintained at a constant current in an electrolyte.
Intensity – It normally refers to the quantitative magnitude or rate of energy, force, or processing power applied to a material per unit area, volume, or time. It is a critical parameter for determining material changes, such as in heat treatment, deformation, or energy consumption during production.
Intensity analysis – It is a quantitative, mathematical framework used to evaluate the magnitude, rate, and nature of changes within a system over time, or to assess structural integrity through signal processing. It compares observed changes against a uniform rate to identify, for example, rapid land-use transitions or structural degradation using acoustic emission data (historic index / severity).
Intensity category – It defines a classification system which categorizes the magnitude, severity, or concentration of a physical phenomenon, load, or environmental impact on a structure or system. These categories are used for risk assessment, design optimization, and safety monitoring.
Intensity of scattering – It is the energy per unit time per unit area of the general radiation diffracted by matter. Its value depends on the scattering power of the individual atoms of the material, the scattering angle, and the wave-length of the radiation.
Intensity, X-rays – It is the energy per unit of time of a beam per unit area perpendicular to the direction of propagation.
Intensive cooling – With intensive cooling, an increase in cooling capacity of around 200 % can be achieved compared with conventional cooling. This water-pillow cooling offers a high cooling power density (up to 5 mega-watts per square meter), high cooling rate (e.g., 750 deg C per second for a strip thickness of 2 millimeters and a large control range (cooling power density control range 1:10). For high strength low alloy (HSLA) steels and ultra-thin strip, the intensive cooling header is installed between the finishing mill and the laminar cooling section. In case of advanced high strength steel (AHSS) grades e.g., DP (dual phase), TRIP (Transformation Induced Plasticity) and multi-phase steels, a two-step cooling is preferred and a second intensive cooling header is placed between the laminar cooling section and the down coiler.
Intensive jet cooling – It is a high-efficiency thermal management technique which involves spraying a cooling medium (typically high-pressure water or specialized air) directly onto a hot metal surface (such as in hot rolling, forging, or die casting) to achieve extremely high heat transfer rates. It is designed to rapidly remove heat from localized hotspots, improve microstructural properties (e.g., increasing martensite or acicular ferrite), and improve surface hardness.
Intensive quenching – It is a high-velocity, water-based, or low-concentration salt solution heat treatment process which rapidly cools steel parts to create high surface compressive stresses. It replaces conventional oil quenching to reduce distortion, prevent cracking, improve surface hardness, and improve fatigue strength.
Intensity ratio – It is the ratio of two (relative) intensities.
Intensive risk – In the context of disaster risk, it refers to the risk associated with low-probability, high-impact events, often involving major hazards which can lead to catastrophic impacts with high mortality and asset loss.
Interacting jets – These refer to a fluid mechanics phenomenon where multiple closely spaced, parallel air or fluid jets influence each other’s flow, velocity, and temperature, eventually merging into a single, combined jet downstream. This interaction impacts considerably mixing performance, jet spread, and velocity decay compared to isolated jets.
Interaction – In statistics, an interaction can arise when considering the relationship among three or more variables, and describes a situation in which the effect of one causal variable on an outcome depends on the state of a second causal variable.
Interaction devices – These are hardware components, such as keyboards, touchscreens, or sensors, which act as intermediaries between humans and computers, translating user actions into machine commands. They facilitate human-computer interaction (HCI) by enabling data input, control, and feedback. These devices are necessary developing user-friendly interfaces, ranging from traditional input tools to advanced haptic or gesture-based systems.
Interaction effect – It refers to the fact that the behaviour of the response to one factor with respect to the factor’s levels depends on the level of another factor. interaction effect occurs when the combined influence of two or more independent input factors on a response variable is considerably different (higher or less) than the sum of their individual, independent effects. It signifies that the effect of one variable depends on the specific level of another variable.
Interaction energy – It refers to the non-additive component of total energy resulting from interactions (attractive or repulsive) between atoms, solute atoms, or defects within a crystalline structure or alloy. It is calculated as the difference between the total energy of the combined system and the sum of the energies of isolated, non-interacting components. It is the non-additive, potential energy component (delta E) arising from forces (electrostatic, gravitational, or atomic) between objects or particles, calculated as the difference between the total system energy (E) and the sum of isolated subsystem energies (sigma Ei). It represents the energy change because of the relative positions and intermolecular forces, typically expressed as ‘delta E = E – sigma Ei’. Interaction energy is the energy component which makes the total energy of a system non-additive, meaning the whole is not simply the sum of its isolated parts because of the interaction.
Interaction equation – It is a mathematical formula used to predict the failure or capacity of a component subjected to combined loading conditions (e.g., bending + compression). It ensures safety by setting the sum of ratios of applied loads to allowable loads less than or equal to 1.
Interaction graph – It is a formal, graphical representation (G = V, E) used to model, analyze, and visualize complex relationships, dependencies, or communication pathways between components, systems, or variables. Nodes (V) represent system elements (e.g., devices, variables) and edges (E) represent interactions, which can be weighted, directed, or undirected to denote strength or direction of influence.
Interaction matrix – It is a structured, table-based tool used to identify, analyze, and visualize the relationships, dependencies, and inter-dependencies among different components, sub-systems, or factors of a system. It maps how changes in one element affect others, acting as a critical tool for system design, risk assessment, and functional analysis.
Interaction order – It defines the sequence, timing, and complexity of relationships between system components or entities (such as objects in software, agents in systems, or physical parts in structures). Higher-order interactions indicate intricate, emergent effects, while in software, it dictates the ordered, step-by-step exchange of messages.
Interaction plot – It is a graphical tool used in design of experiments (DOE) to visualize how two factors jointly affect a process response. It displays mean response values at combinations of factor settings, where non-parallel lines indicate a substantial interaction, meaning the effect of one factor depends on the level of another.
Interaction potential – It is a mathematical function describing how a system’s potential energy changes based on the coordinates of its particles, accounting for both bonded (covalent) and non-bonded (van der Waals, electro-static) interactions. It determines atomic forces, allowing simulation of material properties like elasticity, defect energy, and bonding.
Interaction probability – It defines the likelihood (0 to 1) of a specific physical, chemical, or system event occurring between entities (e.g., particles, components, software agents). It quantifies uncertainty in system design, such as particle collisions in reactors, component failure risks, or structural interactions.
Interaction properties – These properties define the behaviour and characteristics at the interface between two or more contacting bodies or particles. They characterize mechanical, thermal, or electrical interactions, including friction, normal behaviour / tangential behaviour, adhesion, and damping.
Interaction region – It involves specifying the spatial, physical, and functional boundaries where two or more components, materials, or physical phenomena meet and interact. This is a critical step in simulation, design, and analysis, particularly in fields like structural engineering, and material science, where it ensures accurate representation of contact, load transfer, or chemical reactions.
Interaction strength – It quantifies the magnitude of influence or coupling between two or more components, materials, or forces, such as the shear resistance at a soil-geotextile interface, or the non-linear coupling in fibre optics. It is used to determine how different factors, like bending and shear forces, combine to cause system failure or to characterize molecular interactions in material simulation.
Inter-actions between knives and strip during slitting – While dish knives are mainly used for slitting plastic film, paper, and metal foil, rotary slitter knives are mostly used in steel strip slitting. The inter-actions between slitter knives and steel strip during slitting with proper slitter tooling and set-up normally can be divided into four steps described below. The first step is at the beginning of slitting, when the steel strip moves forward to the slitter knives before a shearing point, plastic deformation occurs on the material by compressive force at knife contact surface. This can result in edge distortion or ‘roll over’ along the slit strip edge, especially in soft materials. In the second step, as the steel strip moves further to the knife shearing point, the knives penetrate into the strip and create the flat, shiny or so-called shear or ‘burnished’ surface on the portion of the slit edge. The depth of the burnished shear surface portion depends on the material strength, ductility, and thickness of the strip as well as the slitter knife clearance. In the third step as the knife penetrates further into the strip, the maximum shear strength of the material is exceeded, and fracture takes place, which results in a total separation of the material. The fracture surface on the edge appears dull, in contrast with the shiny, burnished shear area in the second slitting stage. The angle of fracture normally falls between 6-degree and 12-degree depending on the type and mechanical properties of the material. In the fourth step, a burr is formed on the strip edge on the opposite side of the roll-over. Burr is attributed mainly to a compressive plastic deformation displacement around the edge corner of the knife.
Interaction term – In statistics, it is a model component, normally the product of two or more independent variables (x1 x x2), used to capture combined effects which differ from the sum of their individual contributions. It defines how the relationship between an outcome and one variable changes, depending on the value of another, allowing for non-linear, conditional analysis.
Interaction time – It refers to the total duration of active, direct engagement between a user (or agent) and a system, tool, or environment, encompassing both cognitive processing and physical actions. It measures the accumulated time spent in active, continuous, uninterrupted usage sessions.
Interactive boundary – It refers to a collaborative or iterative process used to define the limits, interfaces, or constraints of a system. This approach is applied across several fields, mainly in fluid dynamics (interactive boundary layer), computer-aided design (boundary representation), and system analysis / design thinking.
Interactive failure – It refers to mutually dependent failures where the deterioration or failure of one component accelerates or causes the failure of others, and vice versa. Common in complex systems, these failures arise from inadequate design or unexpected component behaviours. They are frequently analyzed through methods like ‘common cause analysis’ (CCA) or ‘systems theoretic process analysis (STPA) to identify cascading failures.
Interactive forces – These are mutual actions between objects (contact or action-at-a-distance) which alter their motion or shape, always occurring in equal and opposite pairs. They define how systems, structures, and materials affect one another, forming the basis for analyzing collisions, stability, and inter-molecular behaviour like electrostatic forces in materials.
Interarrival time – It is the time duration between two consecutive arrivals or events in a system. It is a critical, frequently stochastic, variable (Xn = Tn- Tn-1) representing the time between customer requests, tasks, or machine failures.
Interatomic bonds – These are the fundamental electro-magnetic forces holding atoms together to form solid metals and alloys, determining properties like strength, ductility, and conductivity. Mainly consisting of metallic bonds (where metal cations are surrounded by a ‘sea’ of delocalized electrons) these bonds also include ionic or covalent interactions in ceramics / compounds. Key aspects of interatomic bonding include (i) metallic bonding, (ii) primary bonds, (iii) impact on properties, (iv) bond energy, and (v) secondary bonds. These bonds dictate the structural integrity of materials, allowing them to withstand different stresses and environmental conditions.
Interatomic potentials – These are mathematical functions to approximate the potential energy of a system based on atomic positions, dictating forces in molecular dynamics (MD) simulations. They model interatomic forces (attractive and repulsive) to predict material properties like structural stability, defect formation, and radiation damage.
Intercalation pseudo-capacitance – It is a high-rate energy storage mechanism where ions (e.g., Li+, Na+, H+) reversibly insert into the crystalline structure of redox-active materials, such as T-Nb2O5 (ortho-rhombic phase of niobium pentoxide), TiO2-B (bronze-type titanium di-oxide, a metastable monoclinic crystal phase of TiO2), or MXenes, without undergoing phase changes. This bulk process combines the rapid kinetics of surface-based supercapacitors with the high capacity of batteries, offering superior power density and long-term cycling stability.
Inter-carrier interference – It is a performance-degrading impairment, especially in OFDM (orthogonal frequency-division multiplexing) systems, where energy from one sub-carrier ‘leaks’ or interferes with adjacent sub-carriers because of a breakdown of their orthogonality, typically caused by ‘carrier frequency offsets’ (CFOs), Doppler spread from motion, or sampling errors, leading to poor signal quality and higher bit-error rates (BER). Essentially, it is noise between carriers, disrupting the clean separation which makes orthogonal frequency-division multiplexing efficient.
Intercast process – It is a patented procedure for die casting ‘cast-assemble’ units with moving parts.
Interception – In this method, particles which do not cross the fluid streamlines come in contact with fabrics because of the fibre size.
Intercept factor – It is the ratio of energy (or radiation) actually received by the absorber/receiver to the total energy reflected by the concentrator (mirror / reflector). It is a critical metric for evaluating the optical efficiency of solar concentrators, representing the fraction of focused sun rays that land on the target.
Intercept method – It is a quantitative metallographic technique in which the desired quantity, such as grain size or inclusion content, is expressed as the number of times per unit length a straight line on a metallographic image crosses particles of the feature being measured.
Intercepts – They refer to the points where a line or curve intersects the x-axis (x-intercept) or y-axis (y-intercept) on a graph. The x-intercept is the point where the line crosses the horizontal x-axis, and the y-coordinate is zero. Conversely, the y-intercept is the point where the line crosses the vertical y-axis, and the x-coordinate is zero. These intercepts are crucial for understanding and analyzing the behaviour of functions and equations in various engineering applications. In crystallography, intercepts refer to the distances at which a crystal face intersects the crystallographic axes. These intercepts are used to define the orientation of the face within the crystal structure. Essentially, they are the points where a plane (representing a crystal face) cuts the ‘x’, ‘y’, and ‘z’ axes of the crystal’s coordinate system.
Interchangeability – Interchangeability is the suitability for a process, product or service to be used in place of another to fulfill a relevant requirement. Interchangeability can be introduced through an intentional standardization process. Process of standardization assists in the interchangeability even if the processes, products or services are created in different countries.
Interchangeable parts – These are components manufactured to such precise, standardized specifications (drawings and tolerances) that any one part can be selected at random and fitted into an assembly without needing custom fitting, adjustment, or alteration. Interchangeability allows for mass production and facilitates easy repair or replacement of parts in the field.
Inter-channel interference – It is the degradation of signal quality caused by unwanted interference between separate, adjacent, or overlapping frequency bands. It occurs when signals from neighbouring channels bleed into each other, leading to data collisions, throughput loss, and reduced reliability, particularly in crowded wireless networks.
Interconnected composites – These are also known as ‘interpenetrating phase composites, (IPCs) or co-continuous composites. These are a class of materials where two or more distinct constituents (e.g., metal-ceramic or metal-metal) are topologically continuous, forming mutually intertwined 3D networks. Unlike traditional particulate or fibre-reinforced composites, where the reinforcement is dispersed within a matrix, in an interconnected composite, both phases form continuous skeletons throughout the entire volume.
Interconnected pore space – It refers to a continuous network of linked voids within a material which allows for the flow, transport, and storage of fluids (gas, oil, or water) through the material’s bulk matrix. It is an important component of engineering design, since it determines a material’s effective porosity and permeability.
Interconnected pore volume – It is the volume fraction of pores which are interconnected within the entire pore system of a compact or sintered product.
Interconnected porosity – It is a network of connecting pores in a sintered object which permits a fluid or gas to pass through the object. It is also referred to as interlocking or open porosity.
Interconnecting pores – These are networks of linked voids within a material which create continuous pathways, enabling the transport of fluids, or gases from one boundary to another. Unlike isolated or dead-end pores, these open-cell structures facilitate high permeability, and improved mass transfer in catalysts.
Interconnection – It refers to the physical and logical linking of systems, components, or networks to enable the exchange of data, energy, or materials. It is the structural or technical interface which allows disparate units to work together securely. Key applications include power grids, telecommunications, and integrated circuits.
Interconnection diagram – It depicts only external connections between assemblies, units, or higher-level items. It is prepared to show the interconnections between units, sets, groups, and systems. It is prepared either as a wiring type diagram which shows each wire, or as a cabling type diagram which primarily shows cables but can also include wires. It does not necessarily show physical relationship.
Interconnection standards – These are mandatory technical, safety, and operational requirements which govern how distributed generation (like solar / wind), energy storage, or loads connect to, and interact with, the utility electrical grid. They ensure stability, safety, and power quality through standardized equipment performance, grid codes, and compliance testing.
Interconnectivity – It refers to the physical and logical linking of systems, devices, or networks to enable seamless, real-time data exchange, communication, and mutual interdependence. It goes beyond simple connectivity to create a meshed, collaborative, and frequently, decentralized infrastructure, important for modern technological, industrial, and information technology (IT) environments.
Interconnectors – These are components which transport electric current between cells, ensure gas distribution, and act as separators between the anode and cathode of contiguous cells. They are required to possess excellent electrical conductivity, corrosion resistance, and suitable mechanical properties to maintain structural integrity during operation.
Intercooled absorber – It is a gas absorption column which withdraws a portion of the liquid solvent, cools it externally, and returns it to the column to manage heat generated by exothermic reactions. This process improves carbon di-oxide (CO2) capture efficiency by reducing the temperature, increasing the solvent’s absorption capacity, and lowering reboiler energy consumption.
Inter-critical annealing – It is an annealing treatment which involves heating to, and holding at, a temperature between the upper and lower critical temperatures to get partial austenitization, followed by either slow cooling or holding at a temperature below the lower critical temperature.
Inter-critical heat-affected zone – It is a specific region within the heat-affected zone (HAZ) of a welded material. It is characterized by a peak temperature range during welding which falls between the lower critical temperature (Ac1) and the upper critical temperature (Ac3). This temperature range results in a unique microstructure with properties distinct from the base metal and other parts of the heat affected zone. It has a mixed structure of fine re-austenitized grains and tempered martensite retained from the base metal.
Inter-critically reheated coarse-grained heat-affected zone (ICR CGHAZ) – It is the location with the poorest fracture toughness in the multi-pass welding heat-affected zone. The mechanical properties of steel’s inter-critically reheated coarse-grained heat-affected zone directly affects the service life of machinery equipment. The hardness and toughness of inter-critically reheated coarse-grained heat-affected zone can be optimized simultaneously through tailoring microstructure where cooling rate plays a key role.
Intercritical rolling – It refers to a process where steel is plastically deformed within the temperature range between the lower critical temperature (Ac1) and the upper critical temperature (Ac3). This temperature range is also known as the inter-critical region. During inter-critical rolling, the steel contains a mixture of austenite and ferrite phases, and the deformation influences the distribution and stability of these phases. This process is used to enhance the mechanical properties of steels, particularly dual-phase (DP) and TRIP-aided steels.
Inter-crystalline – It means between the crystals, or grains, of a poly-crystalline material.
Inter-crystalline (inter-granular) corrosion – Inter-crystalline corrosion is a special form of localized corrosion, where the corrosive attack takes place in a quite narrow path preferentially along the grain boundaries in the metal structure. The most common effect of this form of corrosion is a rapid mechanical disintegration (loss of ductility) of the material. Normally, it can be prevented by using the right material and production process. A well-known example relevant to the construction industry is the so-called sensitization of stainless steel. When certain grades of stainless steel are kept at a temperature within the range of 500 deg C to 800 deg C for a considerable time, e.g., during a welding process, chromium-rich carbides are formed, resulting in chromium depletion at the grain boundaries. Consequently, the grain boundaries possess a lower degree of corrosion resistance than the residual material, leading to localized corrosion.
Inter-crystalline cracking – It is the cracking or fracturing which occurs between the grains or crystals in a poly-crystalline aggregate. It is also called inter-granular cracking.
Inter-crystalline cracks – These are the cracks or fractures which occur between the grains or crystals in a poly-crystalline aggregate.
Inter-crystalline failure – It consists of cracks or fractures which follow along the grain boundaries in the micro-structure of metals and alloys.
Inter-dendritic attack – It is a -type of electrochemical corrosion which sometimes occurs in as-cast alloys or alloys that have had very little working.
Inter-dendritic corrosion – It is the corrosive attack that progresses preferentially along inter-dendritic paths. This type of attack results from local differences in composition, such as coring normally encountered in alloy castings.
Inter-dendritic -It means located within the branches of a dendrite or between the boundaries of two or more dendrites.
Inter-dendritic porosity – It is the voids occurring between the dendrites in cast metal.
Interdependence – It refers to the bi-directional, mutual reliance between systems, components, or tasks, where the state, action, or failure of one directly impacts the others. It shows that the performance of a system is reliant on the inputs or outputs from another system, creating, for example, complex infrastructure connections (physical, cyber, geographical) or interconnected tasks in project management.
Interdependency – It refers to the bi-directional, mutual, or reciprocal relationships between systems, components, or infrastructures, where the functional state of one directly influences, or is correlated to, the state of others. It shows that the operation of one system relies on inputs or services provided by another.
Interdiffusion – It is the process of atomic or molecular exchange across the interface of two different materials in contact, driven by gradients in chemical potential (frequently concentration). It normally occurs in solid alloys, thin films, and polymers at high temperatures to create a more homogeneous, uniform mixture.
Interdiffusion coefficient – It is a material-specific, frequently concentration-dependent, parameter which quantifies the rate of atomic or molecular mixing between two different materials or phases. It governs homogenization processes and is necessary for calculating the speed of mass transport across interfaces in alloys, polymers, and coatings.
Interdiffusion zone – it is also called interdiffusion layer. It is the region formed at the interface of two different materials (such as two metals, an alloy and a coating, or a composite component) where atomic migration has occurred, creating a transition layer with a changing chemical composition. It forms at high temperatures, where thermal energy enables atoms to move from regions of high concentration to low concentration (chemical diffusion) across the boundary. The zone is characterized by a gradual or sigmoidal concentration profile of the constituent elements, rather than a sharp boundary.
Interdigital transducer – It is a device consisting of two interlocked, comb-shaped arrays of metallic electrodes on a piezoelectric substrate. It acts as a transducer, converting electrical energy into mechanical wave energy (specifically, surface acoustic waves or Lamb waves) and vice versa through the piezoelectric effect. In essence, interdigital transducers are used to generate and detect acoustic waves in several applications.
Interdigitated design – It refers to a configuration featuring alternating, interlocking ‘finger-like’ structures or components, normally used to maximize surface area or improve material transport within a compact, planar, or 3D space. This design is widely applied in micro-electronics (electrodes, capacitors), sensors, and fuel cells to improve sensitivity, improve conductivity, or optimize flow paths.
Interdigitation – It refers to the interlinking of components, materials, or features, resembling interlocking fingers. It is a design technique used to improve structural strength, improve adhesion between materials, maximize contact surface areas, or create efficient electronic, chemical, or mechanical junctions.
Interdisciplinary engineering – It integrates multiple, traditionally distinct engineering domains (e.g., mechanical, electrical, chemical) and, frequently, natural or social sciences to solve complex, systemic, and modern technical challenges. This approach breaks down silos to create optimized, innovative solutions, such as AI (artificial intelligence)-driven renewable energy systems, which cannot be achieved through a single, domain-specific method.
Interelectrode gap – It is the precise distance, typically measured in micro-meters or millimeters, between the anode and cathode in electro-chemical machining, electric discharge machining, or battery cells. It is a critical parameter influencing electrical resistance, voltage potential, material removal rate, and machining precision, normally kept under 3 millimeters to optimize performance.
Interest during construction – A large amount of funds is needed during the implementation of a project. A major portion of these funds are borrowed from the funding institutions. Interest is needed to be paid on these funds to the funding agencies during the project stage of the steel project. The amount of interest paid till the project is handed over to operating set up and capitalization of the project cost is done is part of the project cost. Longer project period means higher expenditure on interest during construction. Further, during the commissioning phase of the project, raw materials, operating parts, fuel and utilities, operating consumables, organizational operational set up is needed for which expenditure to be made. The funds needed for this expenditure is mostly borrowed from the funding agencies and is known as working capital. Interest paid on working capital till the project is handed over to operating set up and capitalization of the project cost is part of the Interest during construction.
Interface – It is a surface which forms the boundary between any two phases. Among the three phases (gas, liquid, and solid), there are five types of interfaces namely gas-liquid, gas-solid, liquid-liquid, liquid-solid, and solid-solid. It is the boundary or surface between two different, physically distinguishable media. On fibres, it is the contact area between fibres and sizing or finish. In a laminate, it is the contact area between the reinforcement and the laminating resin.
Interface activity – It is a measure of the chemical potential between the contacting surfaces of two particles in a compact or two grains in a sintered body.
Interface circuit – It is a mediating, signal-conditioning hardware component which connects two systems with different operating characteristics (e.g., speed, voltage, data format) to enable seamless, synchronized, and compatible communication. It typically handles data conversion, buffering, and impedance matching between components, such as a fast processor and a slow I/O (input / output) device.
Interface condition – It defines the mathematical, physical, or logical constraints at the boundary where two systems, components, or material phases interact. These specifications, covering geometry, forces, and material properties, ensure compatibility, continuity, and proper energy transfer/ mass transfer, frequently documented through ‘interface control documents’ (ICDs).
Interface control drawing – It depicts physical and functional interfaces of related or co-functioning items. It does not establish item identification. This drawing controls one or more of the interfaces such as mechanical, electrical, interconnections, configuration, installation, operational sequence requirements, and system switching etc. The drawing includes (i) configuration and interface dimensional data applicable to the envelope, mounting, and interconnection of the related items, (ii) complete interface engineering requirements (mechanical, electrical, electronic, hydraulic, and pneumatic etc.) which affect the physical or functional characteristics of the co-functioning items, and (iii) any other characteristics which cannot be changed without affecting system interfaces.
Interface crack – It is a fracture located at the boundary between two dissimilar materials, normally causing delamination in composites or coating failures. It is characterized by complex, combined mode I (opening) and mode II (shear) stresses because of the elastic mismatch. These cracks are critical failure points because of the lower interface toughness.
Interface decohesion – It is the failure process where the bond between two materials (e.g., particle and matrix, coating and substrate) breaks, causing cracks to nucleate and propagate along their interface. Driven by stress, strain, or chemical embrittlement, it involves both the separation strength and the energy needed to detach the surfaces.
Interface electronics – It refers to circuits, components, or systems which facilitate communication, signal conditioning, and power regulation between two or more disparate devices, modules, or systems. These interfaces bridge, for example, high-speed processors with slower peripherals, ensuring compatibility, data integrity, and synchronized operation.
Interface element – It involves specifying the precise points of interaction, physical, functional, or numerical, between system components to ensure seamless communication, structural integrity, and performance. It defines boundaries for exchanging data, energy, or material, frequently documented in ‘interface control documents’ (ICDs) to prevent failures.
Interface forces -These are actions occurring at the boundary between two materials or phases, encompassing interfacial tension, friction, and pressure. These are defined by vectors (magnitude and direction), representing loads, stresses, or energy (e.g., surface energy). These forces are critical for modeling friction and structural connections.
Interface friction – It is the tangential resisting force which occurs at the boundary where two distinct materials or surfaces meet and interact, opposing relative motion or the tendency of motion between them. It is a critical, complex phenomenon in tribology and mechanics, frequently involving high, non-uniform contact pressures, thermal effects, and material deformation.
Interface friction factor (m) – It is a dimensionless parameter used to quantify the frictional resistance at the interface between the work-piece and the die. It defines the frictional shear stress (t) as a fraction of the shear yield strength (k) of the material being deformed. The interface friction factor (m) is defined by the shear friction model (frequently associated with the Tresca yield criterion) as ‘t =m x k’ Where ’t’ is interface shear stress. ‘m’ is interface friction factor (ranging from 0 to 1), and ‘k’ is the shear yield stress of the work-piece material.
Interface functionality – It formally specifies the interactions, data exchanges, and operational protocols between system components, modules, or users. It defines the ‘contract’ (inputs, outputs, behaviours) without dictating implementation, ensuring modularity, interoperability, and independence between, say, software and hardware sub-systems.
Interface ground – It is a specialized, isolated reference plane or conductor used to manage electro-magnetic compatibility (EMC), shielding, and signal integrity at the boundary between subsystems or equipment. It typically connects to the main circuit ground at a single point to prevent noise contamination while shunting incoming transient or RF (radio frequency) interference away from sensitive circuitry.
Interface heat transfer – It defines the rate of heat exchange (thermal energy) occurring across the boundary between two materials, such as a solid-liquid interface (e.g., casting) or two touching solids, driven by a temperature difference. This process is quantified by the interfacial heat transfer coefficient (h), frequently influenced by interface materials, pressure, and surface roughness.
Interface heat transfer coefficient (h) – It is a parameter quantifying the rate of heat transfer across a boundary between two phases or materials, defined as the heat flux (q) divided by the temperature difference (delta T) across that interface (h = 1/delta T). It measures heat transfer efficiency, expressed in W/square-meter.K).
Interface layer – It acts as a specialized boundary or intermediary component managing interaction, data exchange, or material compatibility between two distinct systems, layers, or materials. In computing, it decouples components (e.g., user interface, application programming interfaces), while in materials science, it mitigates stress or chemical reactions between substances, such as in 3D-printed concrete or battery electrolytes.
Interface microcontroller – It is a specialized, compact computing device (micro-controller unit, MCU) integrating a processor, memory, and programmable I/O (input / output) peripherals on a single chip to control, monitor, and exchange data with external components like sensors, actuators, and displays. It acts as a bridge for communication through protocols such as UART (universal asynchronous receiver-transmitter).
Interface pressure – It is the mechanical force per unit area acting at the boundary between two contacting materials, components, or systems. It measures how load is distributed across a contact surface, frequently analyzed to understand structural, or thermodynamic interactions.
Interface reaction – It is the chemical, physical, or electro-chemical process occurring at the boundary between two distinct phases (e.g., solid-liquid, solid-gas). It governs mass transfer, energy exchange, and product formation, with interfacial engineering optimizing these boundary properties to improve material performance.
Interface recombination – It is the annihilation of charge carriers (electrons and holes) at the junction or boundary between two different materials (e.g., semi-conductor-metal or hetero-junctions). It is caused by surface defects, dangling bonds, or impurity atoms which introduce states within the bandgap, this process acts as a, substantial loss mechanism for photo-generated carriers, reducing efficiency in devices like solar cells.
Interface shape – It involves defining the precise geometric boundaries, contours, and physical characteristics where two distinct materials, phases (e.g., solid-liquid), or components meet. It ensures structural integrity, optimizes performance, and manages interactions like load transfer or heat flow through tailored geometries, surface treatments, or specialized elements.
Interfacial shear strength – It is the maximum tangential stress which an interface can withstand before sliding or debonding occurs between two distinct materials or phases. It is a critical parameter for evaluating the mechanical performance and integrity of composite materials, coatings, and welded joints.
Interface slip – It refers to the relative movement or displacement between two contacting surfaces, materials, or structural components, frequently occurring when shear stress exceeds frictional resistance. This phenomenon is critical in tribology, where it causes wear, and in structural mechanics, where it represents imperfect bonding.
Interface state – It defines and controls the electronic or structural properties at the boundary between two materials, frequently a semi-conductor and an insulator, to optimize device performance, such as reducing charge trapping or improving carrier mobility. Key techniques include surface passivation, chemical treatment, and atomic layer deposition to minimize unwanted interface states.
Interface strength – It defines the maximum adhesion, bonding, or shear resistance between two distinct materials before failure. It quantifies the capacity of an interface to withstand applied tensile or shear loads, important for the durability of composites, coatings, and soil-structure systems.
Interface temperature – It is the temperature at the boundary or contact surface between two different materials, phases (e.g., solid-liquid), or components. It is a critical parameter for determining heat transfer rates, thermal resistance, and material degradation due to friction or chemical reactions.
Interface traps (Nit) – These are localized electronic states at the interface between a semi-conductor and an insulator (e.g., silicon /silicon oxide, Si/SiO2) resulting from structural defects or unsatisfied dangling bonds. These defects act as charged traps, capturing and releasing charge carriers (electrons or holes), causing threshold voltage shifts, decreased carrier mobility, and degraded semi-conductor device performance and reliability.
Interface value – It involves precisely defining the structural, behavioural, or functional constraints at the boundary between two systems, components, or materials to ensure seamless interaction and performance. It covers technical specifications, such as structural loads, material behaviour, or software API (application programming interface) contracts, ensuring interoperability and preventing failures.
Interface velocity – It refers to the speed and direction at which a boundary (interface) separating two distinct phases or materials (e.g., solid-liquid, liquid-gas) moves. In modeling, it is frequently defined by the velocity vector which drives the motion of the interface normal to itself.
Interfacial adhesion – It defines the strength of the bond, or the attractive forces holding two distinct, contiguous material surfaces together, such as coatings on a substrate or adhesives between parts. It is governed by physical interactions / chemical interactions (van der Waals, chemical bonds, diffusion, mechanical interlocking) important for durability, performance, and failure prevention in materials.
Interfacial area – It is the total surface area of contact between two distinct, immiscible phases (e.g., gas-liquid, liquid-liquid) within a specific volume or system. Frequently expressed as interfacial area concentration (square meter /cubic meter), it is a critical parameter quantifying the available surface for heat, mass, and momentum transfer in chemical reactors, distillation columns, and multi-phase flows.
Interfacial bond – It is the physical, chemical, or mechanical connection formed at the boundary between two distinct materials (e.g., reinforcement and matrix in composites). It acts as the critical link for load transfer, dictating the composite’s overall strength, durability, and thermal properties. It is influenced by surface chemistry, wetting, and pressure.
Interfacial bonding – It refers to the physical, chemical, or mechanical adhesion at the boundary between two distinct materials (e.g., fibre and matrix in composites, or coating and substrate). This boundary strength dictates load transfer efficiency, structural integrity, and overall mechanical performance. Improved through surface treatments, coupling agents, or wetting, a strong interface prevents premature failure and improves durability.
Interfacial crack – It is a fracture located precisely at the boundary between two dissimilar materials, such as in composite materials, coatings, or adhesive joints. These cracks are characterized by complex shear and tensile stress states (mixed-mode) caused by differences in elastic properties, even under pure tension.
Interfacial damage – It refers to the progressive degradation and failure of the bond between two distinct materials or phases (e.g., fibre / matrix, coating / substrate, steel / concrete) within a composite structure. It represents a reduction in the load-transfer efficiency, mechanical strength, and structural integrity at the interface.
Interfacial debonding – It is the separation or failure of the bond between two distinct materials (e.g., fibre-matrix, adhesive-adherend, steel-concrete), creating a crack or gap. It reduces the effective stiffness and load-bearing capacity of components, frequently caused by localized stresses exceeding the interface’s strength, particularly under cyclic loading.
Interfacial defects – These are two-dimensional (2D) planar imperfections which separate regions of different crystal structure, orientation, or phase within a material. These boundaries, such as grain boundaries, twin boundaries, or external surfaces, are high-energy, atomic-scale disruptions which considerably impact mechanical strength, corrosion resistance, and chemical reactivity, acting as barriers to dislocation motion.
Interfacial diffusion – It refers to the transport of atoms, molecules, or polymer chains along or across the boundary (interface) between two distinct phases (solid-solid, liquid-liquid, or solid-liquid). Driven by concentration gradients or stress, this mechanism controls phenomena like adhesion, sintering, and interfacial sliding, frequently acting as a main mass transport pathway at high temperatures or in material processing.
Interfacial dislocations – These are linear crystallographic defects located at the boundary between two different crystalline materials or phases, serving as a mechanism to accommodate strain and facilitate sliding. They form because of the lattice mismatches at the interface and, when active, can act as either barriers or transmitters for dislocation movement, considerably influencing the mechanical strength and deformation behaviour of materials.
Interfacial energy – It is the excess Gibbs free energy per unit area (joules per square meter) located at the boundary between two immiscible phases (solid-liquid, liquid-liquid, or solid-gas) because of the unsatisfied molecular bonds. It represents the work needed to create or increase a surface area and acts as a driving force for surface phenomena like wetting, adhesion, and grain boundary movement.
Interfacial engineering – It is the deliberate manipulation, modification, and control of the boundary regions (interfaces) between distinct phases or materials to improve their mechanical, electrical, thermal, or chemical properties. It involves tailoring interactions at atomic or molecular levels to improve performance, such as adhesion, charge transfer, or stability.
Interfacial fracture energy (Gc) – It is the critical energy per unit area needed to propagate a crack along the interface between two bonded materials. It represents the material’s resistance to delamination, typically measured in joules per square meter or newton per meter, and is an important parameter for analyzing composite adhesion, coating integrity, and structural bonding failure.
Interfacial friction factor (fi) – It is a dimensionless parameter in fluid mechanics that quantifies the shear resistance at the boundary interface between two different phases (e.g., gas-liquid in stratified or annular flow). It acts as a closure relation for predicting pressure drops. It is a parameter which quantifies the frictional resistance at the interface between different phases in a two-phase flow, which varies based on flow patterns, interface geometry, and can be influenced by factors such as liquid Reynolds number and shear at the interface.
Interfacial heat transfer coefficient (hi) – It is a parameter which quantifies the rate of heat transfer per unit area across the boundary between two contacting bodies (e.g., solid-solid or liquid-solid) for a given temperature difference (q” = hi x delta T)). It represents the thermal resistance at the contact interface, frequently influenced by pressure, surface roughness, and intermediate fluids. It is a parameter which quantifies the rate of heat transfer across the phase boundary between continuous and disperse phases.
Interfacial imperfections – These are two-dimensional defects or irregularities occurring at the boundary between different phases, grains, or materials, resulting in disrupted atomic symmetry, high energy, and lowered structural integrity. Common examples include grain boundaries, twin boundaries, phase boundaries, and surface cracks.
Interfacial interaction – It refers to the physical and chemical forces acting at the boundary between two distinct materials or phases (e.g., solid-liquid, polymer-filler), determining how they bond, adhere, or transfer energy / load. It includes van der Waals forces, electrostatic interactions, and chemical bonding, which are crucial for optimizing material strength, adhesion, and performance.
Interfacial layer – It is a distinct, thin region between two phases (e.g., solid-liquid, polymer-filler) where physical and chemical properties differ considerably from the bulk material, frequently featuring unique, ordered structures. Engineering this layer involves manipulating these properties to improve thermal conductivity, adhesion, or dispersion in composite materials.
Interfacial polarization – It is also called space charge polarization. It is the accumulation of free charge carriers at the interfaces between materials with differing dielectric constants or conductivities under an applied electric field. It occurs in heterogeneous materials (e.g., ceramics, composites) where charge mobility is impeded by boundaries.
Interfacial polymerization – It is a rapid, frequently room-temperature, step-growth polymerization technique where two reactive monomers, dissolved in immiscible solvents (typically oil and water), meet at their boundary to form an insoluble polymer film. This method allows for the creation of ultra-thin films, coatings, and nano-fibres, frequently without needing precise stoichiometry.
Interfacial pressure – It refers to the force per unit area acting at the boundary between two distinct phases (e.g., solid-solid, liquid-gas, or fluid-fluid). It measures the perpendicular pressure exerted at the interface of contact, influenced by interfacial tension, surface curvature, or applied mechanical loads.
Interfacial region – It is the boundary zone between two distinct, contacting phases (e.g., solid-liquid, liquid-gas, or solid-solid) where physical and chemical properties differ from the bulk materials. This transition zone dictates mass, energy, and momentum transfer, affecting stability, adhesion, and reaction efficiency in composite materials, nano-technology, and chemical processes.
Interfacial resistance – It is the opposition to the flow of energy (heat), charge (electricity), or mass (species) across the boundary between two distinct, contacting materials or phases. It represents a kinetic barrier, frequently caused by imperfect contact, surface contaminants, or structural differences between the materials, and is important for determining the efficiency of electro-chemical, thermal, and mechanical systems.
Interfacial shear – It to the shear stress or strength occurring at the contact boundary between two distinct materials or fluid phases. It represents the resistance to sliding or deformation parallel to this interface, caused by friction, adhesion, or cohesion. Key applications include composite material strength (fibre-matrix), layer adhesion (concrete or pavement), and multi-phase fluid flows.
Interfacial shear strength – It is the maximum shear stress which a bond between two materials, typically a fibre reinforcement and a surrounding matrix, can withstand before failure (debonding) occurs. It is a critical, measurable parameter determining load transfer efficiency, adhesive performance, and failure mechanisms in composite materials.
Interfacial shear stress – It is the tangential force per unit area acting along the boundary between two adjacent materials, layers, or phases. It signifies the internal resistance to sliding or delamination at the interface, normally arising from thermal mismatch, mechanical loading, or fluid flow interactions.
Interfacial stiffness – It is also called contact stiffness. It is a measure of how resistant the interface between two contacting solid surfaces is to deformation (relative displacement) when subjected to a load. It is formally defined as the rate of change of contact pressure (p) with respect to the relative displacement (h) of the contacting surfaces’ mean lines: K = delta p/delta h.
Interfacial temperature – It refers to the specific, frequently unique, temperature at the boundary separating two distinct phases (e.g., solid-liquid, liquid-vapor, or two immiscible liquids). It differs from bulk temperatures because of the heat transfer resistance, evaporation / condensation, or chemical changes, impacting phase stability and heat flux.
Interfacial tension – It is the contractile force of an interface between two phases.
Interfacial thermal resistance – It is also known as thermal boundary resistance or Kapitza resistance. It is a measure of the resistance to heat flow at the boundary between two dissimilar materials. It represents a temperature discontinuity (delta T) which occurs at the interface when heat flows across it.
Interfacial traction – It is the force per unit area acting at the interface (boundary) between two adhering materials or layers. It encompasses both normal and shear components of stress which act on this interface, and is important for analyzing adhesion, friction, and structural integrity, especially in composite materials, adhesives, and coatings.
Interfacial transition zone – It is a 10 micro-meter to 50 micro-meter thick, heterogeneous layer in concrete surrounding aggregate particles, acting as the weakest link between the cement paste and aggregate. It has higher porosity, larger calcium hydro-oxide crystals, and lower mechanical strength compared to the bulk paste, frequently causing premature crack initiation.
Interfacial wetting – It refers to the ability of a liquid to spread and adhere to a solid surface at the interface between the two phases. It is essentially the process where adhesive forces between the liquid and solid overcome cohesive forces within the liquid, causing the liquid to spread and potentially minimize the overall interfacial energy.
Interference – It is the effect of a combination of wave trains of different phases and amplitudes.
Interference alignment – It is a wireless communication technique which mitigates signal interference by intelligently coordinating transmission, ensuring that multiple undesired, interfering signals align within the same, restricted subspace (or shadow) at receivers. This approach allows desired signals to occupy separate dimensions, maximizing channel capacity and achieving optimal degrees of freedom (DoF) at high signal-to-noise ratios (SNR).
Interference cancellation – It is a signal processing technique which is used to detect and subtract unwanted interfering signals from a desired received signal, improving signal quality and capacity. It is normally used in wireless communications, such as 5G and mobile networks, to manage multi-user or self-interference by estimating the noise and removing it, frequently using iterative or adaptive filtering methods.
Interference cancellation method – It refers to a technique which aims to eliminate intrinsic interference effects by selecting pilot FBMC (filter bank multi-carrier) symbols in a way which nullifies interference at specific points, hence allowing for accurate channel state estimation.
Interference channel – It is a multi-user communication system where multiple sender-receiver pairs share the same spectrum, causing mutual interference. Each receiver gets a desired signal along with unintended, interfering signals from other transmitters, degrading signal quality, reducing data rates, and limiting the overall capacity region.
Interference constraint – It defines the maximum allowable disruption, power, or physical overlap between systems to ensure functionality. In telecommunications, it restricts secondary users’ interference on primary, licensed users. In mechanical design, it refers to the intentional, designed overlap between parts (interference fit) to secure them together.
Interference detection and mitigation – It refers to the systematic process of identifying unwanted, degrading signals (interference) and using techniques to minimize their impact on a desired signal, hence ensuring system performance, reliability, and data integrity.
Interference filter – It is a combination of several thin optical films to form a layered coating for transmitting or reflecting a narrow band of wave-lengths by interference effects.
Interference fits – It is a joint or mating of two parts in which the male part has an external dimension larger than the internal dimension of the mating female part. Distension of the female by the male creates a stress, which supplies the bonding force for the joint.
Interference fringes – These are a pattern of alternating bright and dark bands (or lines) produced when light waves, reflected from two closely spaced surfaces (such as a polished metal sample and an optical flat) overlap and interact (super-impose). These fringes are basically contour maps of the surface topography, with each fringe representing a specific, constant optical path difference, typically corresponding to a change in height equal to half the wavelength of the light used.
Interference function – It is also called interference phenomenon. It describes the superposition of two or more waves, signals, or physical components that interact to create a resultant effect (amplitude, signal strength, or physical fit). This includes constructive interference / destructive interference in wave physics, electromagnetic interference (EMI) in electronics, or a mechanical fit where parts intersect.
Interference level – It defines the intensity of unwanted energy, signals, or physical overlap which degrades system performance. It measures the ratio of disturbance power to desired signal power (S/I) or the magnitude of physical intersection between components, needing mitigation to prevent malfunctions or failures.
Interference management – It involves techniques, strategies, and processes designed to minimize or mitigate unwanted electro-magnetic signals, noise, or signal degradation in communication systems. It ensures reliable, high-quality data transmission and improves capacity by managing interference through coordination, avoidance, and suppression, particularly in dense wireless networks.
Interference of waves – It is the process whereby two or more waves of the same frequency or wave-length combine to form a wave whose amplitude is the sum of the amplitudes of the interfering waves.
Interference pattern – It is a stationary, periodic arrangement of light and dark fringes (or high / low intensity regions) produced by the superposition of two or more coherent waves. It results from constructive interference (waves in phase, reinforcing) and destructive interference (waves out of phase, canceling), used to measure wavelength, analyze thin film thickness, and create microstructures.
Interference protection – It refers to methods, technologies, and regulations designed to prevent unwanted electro-magnetic radiation or signals (interference) from disrupting the, functionality, signal integrity, or performance of electronic devices, circuits, and communication systems. It ensures electro-magnetic compatibility (EMC) through shielding, grounding.
Interference ratio – It refers to the measure of interference power relative to the total signal power in a communication system, affecting the quality of signal reception and transmission. It is a critical factor in evaluating the performance of systems, particularly in the context of signal-to-interference and noise ratio (SINDR) analysis.
Interference region – It is the specific space or condition where waves (optical, mechanical, acoustic) interact to produce a pattern of constructive and destructive superposition. It refers to areas of maximum / minimum amplitude, or, in mechanical design, the spatial overlap between components (interference fit) or stress-strength distributions.
Interference signal – It is any unwanted electro-magnetic radiation, voltage, or current which disrupts the intended operation, degrades the signal-to-noise ratio (SNR), or causes data loss in a communication system. It manifests as distortion caused by external, adjacent-channel, or internal emissions, frequently referred to as electro-magnetic Interference (EMI) or radio frequency interference (RFI).
Interference temperature – It is a regulatory metric to quantify and manage radio interference by measuring the aggregate radio frequency (RF) power level at a receiver. It represents the total interference power, expressed as an equivalent temperature (Ti =I/Wk), which a main receiver can tolerate from secondary users without violating quality of service.
Interference term – It is the mathematical or physical component representing the interaction between two or more waves, signals, or components which results in a combined effect, such as amplification (constructive), cancellation (destructive), or noise (interference). It normally refers to signal distortion, mechanical overlap, or unwanted energy.
Interference theory – It refers to the analysis of how overlapping waves (light, sound, radio) interact, producing constructive or destructive patterns. It also refers to a reliability model analyzing the intersection of stress (load) and strength distributions to determine component failure probabilities.
Interference well test – It is a multi-well procedure used to assess reservoir connectivity, permeability, and storativity by monitoring pressure changes in one or more observation wells caused by production or injection rate changes in an active (pulsing) well. This test is necessary for evaluating inter-well communication, reservoir heterogeneity, and anisotropy, as the pressure response at the observation well depends on the rock properties between them.
Interferential-optical methods – These are high-precision, non-contact optical techniques which utilize the interference of light waves to analyze the surface topography, microstructure, and deformation of metallic materials. These methods, including interferometric microscopy and holography, are capable of detecting, with nano-meter-level sensitivity, surface roughness, grain boundary grooving, crystal growth, and micro-scale deformations in metallurgical samples.
Interferents – These refer to any materials or conditions which t can distort the measurement of a target gas concentration, resulting in either a higher (positive interferents) or lower (negative interferents) reading than the actual concentration. Positive interferents can cause false alarms, while negative interferents can mask dangerous gas levels, posing significant risks.
Interfering beams – These are two or more coherent light waves which superpose in space to produce a stable, spatial pattern of varying intensity, known as an interference pattern. These beams, frequently derived from a single source to maintain phase coherence, create bright (constructive) and dark (destructive) fringes based on their relative phase differences.
Interfering signal – It refers to a light wave or beam which interacts with another beam (or multiple beams) through superposition to alter the total irradiance, resulting in patterns of constructive (bright) and destructive (dark /r educed intensity) interference. It needs coherent, overlapping light fields.
Interfering transmitter – It refers to an unintended or extraneous light source, such as neighbouring ‘access points’ (APs) in a LiFi (light fidelity) system, ambient lighting, or signal leakage, which disrupts the transmission between a desired transmitter and receiver by contributing unwanted optical power or noise.
Interferogram – It is a photographic or digital record of the interference pattern produced by an interferometer, created by superimposing two or more coherent light beams. These patterns, frequently seen as light and dark fringes, represent optical path differences (OPD), measuring surface topography, refractive index changes, or wavefront errors with high precision.
Interferometer – It is an instrument in which the light from a source is split into two or more beams, which are subsequently reunited and interfere after traveling over different paths.
Interferometer arms – These refer to the distinct pathways within an interferometer through which light or atoms travel, allowing for the observation of interference patterns which provide insights into different physical phenomena, including coherence properties and interactions at the atomic level.
Interferometric fibre optic sensor – It is a high-precision optical device which measures physical parameters, such as strain, temperature, pressure, or rotation, by detecting minute shifts in the interference pattern (fringe pattern) of light, which are caused by phase changes in coherent beams propagating through optical fibres.
Interferometric method – It is a high-precision, non-contact measurement technique which utilizes the superposition (interference) of coherent waves (typically light, such as from a laser) to measure minute displacements, surface irregularities, or refractive index changes. It works by splitting a wave, traveling different paths, and recombining them to create an interference pattern (fringes) which indicates phase differences.
Interferometry – It is a measurement technique which utilizes the phenomenon of wave interference to extract information about the properties of waves or the objects they interact with. It works by combining two or more waves, causing them to interfere, and then analyzing the resulting interference pattern to make precise measurements. Interferometry is based on the principle of wave superposition, where waves combine to create a new wave.
Inter-fibre failure – It refers to the failure of the matrix or the matrix-fibre interface (matrix cracking, debonding) rather than the rupture of the reinforcement fibres themselves in composite materials. It reduces transverse stiffness (E2) and shear stiffness (G12) while leaving the longitudinal fibre-driven modulus (E1) relatively unaffected.
Interfuel substitution – It refers to the ability to replace one type of fuel with another to meet fixed demands for end-use energy forms, considering competition among alternative fuels to satisfy these energy needs.
Intergovernmental Panel on Climate Change – The Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body tasked with reviewing and assessing the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It provides the world with a clear scientific view on the current state of climate change and its potential environmental and socio-economic consequences, notably the risk of climate change caused by human activity. The panel was first established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), two organizations of the United Nations, an action confirmed on 6 December 1988 by the United Nations General Assembly through Resolution 43/53.
Intergranular – It means between the grains or crystals. It is also called intercrystalline.
Intergranular attack – it is also known as intergranular corrosion. It is a form of corrosion where the boundaries of crystallites of the material are more susceptible to corrosion than their insides.
Intergranular beta – It is the beta phase situated between alpha grains. It can be at grain corners, as in the case of equiaxed alpha-type micro-structures in alloys having low beta-stabilizers contents.
Intergranular brittle fracture – It is a type of fracture in a material where cracks propagate along the grain boundaries, rather than through the grains themselves, and the fracture occurs with little to no plastic deformation. This frequently occurs when the grain boundaries are weakened, making them more susceptible to crack propagation. In contrast to transgranular fracture, which occurs through the grains, intergranular fracture occurs between the grains, along their boundaries. Intergranular brittle fracture is frequently associated with weakened grain boundaries. This weakening can be caused by several factors, including (i) segregation of impurities, (ii) precipitates, and (iii) residual stresses.
Intergranular corrosion – It is the corrosion occurring preferentially at grain boundaries, normally with slight or negligible attack on the adjacent grains.
Intergranular cracking – It is the cracking or fracturing which occurs between the grains or crystals in a polycrystalline aggregate. It is also called intercrystalline cracking.
Intergranular effects – These refer to localized phenomena, degradation, or structural changes which occur specifically along or adjacent to the grain boundaries (the interfaces where crystals of different orientations meet) within a metal or alloy, rather than through the bulk of the grains themselves. These effects typically stem from the high energy, disorder, or unique chemical composition of the grain boundaries, which make them more reactive or weaker than the grain interiors. Key types of intergranular effects are (i) intergranular corrosion / intergranular attack, (ii) intergranular fracture / embrittlement, (iii) sensitization, and (iv) exfoliation corrosion.
Intergranular fatigue crack initiation – It is the localized nucleation of micro-cracks along grain boundaries because of the cyclic stress, frequently driven by plastic strain incompatibility, accumulation of persistent slip band (PSB) extrusions / intrusions at boundary junctions, or boundary embrittlement. It occurs when localized stress causes separation of grain boundaries before or instead of transgranular cracking.
Intergranular films – These are nanometer-thick (around 1 nano-meter to 2 nan-meter thick), amorphous or ordered layers which form at grain boundaries in polycrystalline materials, particularly ceramics like Si3N4 (silicon nitride), SiC (silicon carbide), and Al2O3 (aluminum oxide). These films maintain a stable, equilibrium thickness, affecting sintering and material properties like creep, fracture toughness, and electrical behaviour.
Intergranular fracture – It is the brittle fracture of a polycrystalline material in which the fracture is between the grains, or crystals, which form the material. It is also called intercrystalline fracture.
Intergranular penetration – In welding, it is the penetration of a filler metal along the grain boundaries of a base metal.
Intergranular precipitation – It is the localized formation of second-phase particles (e.g., carbides) at the grain boundaries of metals, frequently occurring during high-temperature service or welding (sensitization). This metallurgical process depletes nearby regions of alloying elements (like chromium), creating anodic paths which cause localized corrosion, embrittlement, and material failure.
Intergranular stress-corrosion cracking – It is a form of environmentally induced cracking that occurs along the grain boundaries of a material. It is a synergistic process where tensile stress, a corrosive environment, and material susceptibility combine to cause crack initiation and propagation along the grain boundaries. This type of cracking is particularly concerning because it can lead to unexpected and catastrophic failure, even in materials that are typically corrosion-resistant. Intergranular stress-corrosion cracking refers to the location of the crack, which specifically follows the grain boundaries (the interfaces between individual crystals) of the material. It is the stress-corrosion cracking in which the cracking occurs along grain boundaries.
Interim approval to operate – It is a temporary authorization letting a system, device, or service to function for a limited time under specific conditions, despite not yet meeting all final requirements, frequently while awaiting full ‘authorization to operate’ or official rulemaking, allowing necessary operations or testing to continue safely, with clear limits on scope, duration, or risk accepted.
Interim authorization to test – It is a temporary approval granted by an authorizing official or principal accrediting authority for a system to operate in a specified, limited, or operational environment for a set period. This authorization is normally provided based on preliminary security evaluation results to allow testing, evaluation, or trials of systems before they receive full authorization to operate.
Interim remedial actions – These are short-term, discrete actions taken at a contaminated site to protect public health or the environment, often before a full remedial investigation and feasibility study is completed.
Interim spent fuel store – It is a store where spent fuel cools until it is suitable for disposal or where such fuel is stored pending disposal.
Interior angle – It is the angle formed inside a closed polygon by two adjacent sides at a vertex. These angles are critical for designing structural elements, where the sum of interior angles in an n-sided polygon is calculated using the formula (n-2) x 180-degree. For finite element analysis (FEA), ideal interior angles are 90-degree for quadrilaterals and 60-degree for triangles.
Interior application – It involves the technical planning, design, and implementation of functional, safe, and aesthetic elements within a built environment. It integrates materials, structural requirements, and building systems to optimize spaces for user health, comfort, and efficiency, bridging the gap between artistic design and construction execution.
Interior core – It refers to the innermost, central, or structural component of a system, machine, or building, frequently composed of dense materials designed to withstand high pressure or provide structural integrity. Examples include the solid, iron-nickel centre of the earth or a central core structure in construction.
Interior design – It is the art and science of improving building interiors to achieve healthier, more functional, and aesthetically pleasing environments. It bridges creative design with technical engineering principles, focusing on space planning, structural integrity, material safety, and user experience. This profession involves technical, functional, and aesthetic considerations for living and working spaces.
Interior designer – Interior designer is a qualified professional who blends art and science to create safe, functional, and sustainable indoor environments. They specialize in space planning, technical building systems (lighting, acoustics, heating, ventilation, and air conditioning), material specifications, and regulatory compliance (building codes, fire safety).
Interior neighbour-exchange mechanism – It is also known as the direct interchange mechanism. It is a form of atomic diffusion in a solid lattice where two or more adjacent atoms jump directly past each other to exchange positions without needing a vacancy to move.
Interior noise – It refers to the acoustic environment inside an enclosed space (vehicles, buildings) produced by airborne and structure-borne vibrations. It is mainly analyzed through ‘noise, vibration, and harshness (NVH) metrics to evaluate passenger comfort, typically dominated by low-frequency, engine, road, and wind sources.
Inter-laboratory standard – It is a device which travels between the laboratories for the sole purpose of relating the magnitude of the physical unit represented by the standards maintained in the respective laboratories.
Interlaminar– It is the descriptive term pertaining to an object (e.g., voids), event (e.g., fracture), or potential field (e.g., shear stress) referenced as existing or occurring between two or more adjacent laminae.
Interlaminar failure – It is frequently called delamination. It is a failure mode in fibre-reinforced composite materials where the layers (laminae) separate, typically occurring at the interface between adjacent plies. It is characterized by the degradation of interfacial strength because of out-of-plane normal (peel) or shear stresses.
Interlaminar fracture toughness – It is a measure of the ability of a material to resist delamination.
Interlaminar shear – It is the shearing force tending to produce a relative displacement between two laminae in a laminate along the plane of their interface.
Interlaminar shear strength – It is the maximum shear stress a layered composite material can withstand between its plies before failing through delamination. As an important, matrix-dominated property, it measures the interfacial bond strength resisting parallel, relative movement of adjacent layers, very frequently determined using short-beam shear test.
Interlaminar strength – For fibre-reinforced composites, it is the resistance of a laminated material to failures which occur between its layers, frequently known as delamination. It represents the strength of the matrix-fibre bond resisting out-of-plane shear or tensile stresses which tend to separate adjacent plies.
Interlayer bond – It refers to the adhesive strength, cohesion, and interfacial integrity between two adjacent, stacked, or layered materials. It is important for structural integrity, frequently determining the anisotropic, tensile, and shear strength of additive manufactured parts, asphalt pavements, and laminated materials. Weak bonding results in delamination, slippage, or premature failure.
Interlayer crack – It is a failure or discontinuity occurring at the interface between two bonded material layers, frequently caused by high stress concentrations, poor adhesion, or differential movement. Common in composite materials (delamination) and asphalt pavements (slippage cracking), these cracks result from stress, thermal cycles, or traffic loads, propagating within the thin boundary layer.
Interlayer distance – It is the spacing between layers in layered materials. It is the spacing between adjacent, typically parallel, atomic or molecular layers in a material, important for determining mechanical strength, ionic intercalation, and electronic properties. It is measured along the crystallographic c-axis or z-axis. It is frequently adjusted through techniques like material intercalation of ions, polymers, or carbon monolayers, hence improving properties such as ionic diffusion rates and electro-chemical performance. It is also frequently adjusted through technique of exfoliation-reassembly to optimize diffusion paths and structural performance.
Interlayer heterogeneity – it refers to the substantial differences in physical, geological, or material properties (such as permeability, strength, density, or grain size) between distinct vertical layers or strata in a system. It is an important factor in both geological reservoir engineering (subsurface fluids) and material science / advanced manufacturing (layered structures), frequently leading to uneven performance, such as preferential fluid flow in reservoirs or uneven stress distribution in composites.
Interlayer interaction – It refers to the physical, chemical, or electro-magnetic coupling between adjacent, distinct layers in materials (e.g., 2D materials, composites, or thin films) which determines the overall structural, mechanical, and electronic properties. Engineered control of these interactions, frequently through interlayer spacing, intercalation, or stress, tunes material performance for applications like energy storage, sensors, and electronic devices.
Interlayer method – It is also called interlayer engineering. It is a strategic approach involving the deliberate insertion, modification, or design of a thin, distinct, intermediate layer between two major functional components, materials, or structural layers. The objective is to improve overall system performance, improve bonding, manage thermal stress, or modify interfacial electronic properties. It is a technique which involves the insertion of an interlayer between ceramic and metal with a coefficient of thermal expansion and elastic modulus which are intermediate to the two materials. The interlayer can be introduced in either liquid or solid form and forms a composite brazed joint structure, which can reduce residual stress and improve joint performance to a certain extent. Based on the physical properties of the materials, the interlayer can be classified into soft interlayers, hard interlayers, composite interlayers, and some porous interlayers.
Interlayer slip – It refers to the relative longitudinal displacement, or sliding, which occurs between adjacent layers of a multi-layered component (e.g., composite steel-concrete beams, laminated wood) under bending loads. It represents partial interaction, where bonding is imperfect, reducing overall structural stiffness and increasing deflection.
Interlayer space – It involves manipulating the distance between atomic or molecular layers in 2D materials (e.g., graphene, MXenes, layered double hydro-oxides) to optimize properties like electro-chemical storage, ionic conductivity, and structural stability. This is achieved through intercalation (inserting guest ions / molecules), pillaring, or expanding the d-spacing to improve ion mobility and reduce restacking.
Interleaver – It is a device which permutes sequences of symbols to improve error correction capabilities in coding schemes, particularly over bursty channels.
Interleaving – It is the insertion of paper or application of suitable strippable coatings between layers of metal to protect from damage.
Interline power flow controller – It is a device consisting of multiple direct current / alternating current converters which provide series compensation and can transfer active and reactive power between lines, improving the effectiveness of the compensating system and reducing line overloads.
Inter-lock – It is a device provided to ensure that an event does not occur inadvertently or that a specific sequence of events is followed where the sequence is important or necessary and a wrong sequence of events can cause a mishap. It is a device to prove the physical state of a needed condition, and to furnish that proof to the primary safety control circuit.
Interlocking – It is a safety mechanism or design feature which forces components, systems, or processes to operate in a specific, mandatory sequence. By using mechanical, electrical, or software-based controls, it prevents dangerous, unintended actions (e.g., closing a door or starting a motor) unless specific prerequisites are met.
Interlocking signal – It involves creating a fail-safe system which coordinates railway signals, points, and other appliances to ensure safe, non-conflicting train movements, primarily through a sequence of locking, setting, and holding routes. The process is highly standardized, moving from manual, mechanical, and electrical (relay-based) methods to modern, software-driven electronic interlocking (EI) or computer-based interlocking (CBI).
Interlocking signal system – It is a safety-critical railway engineering arrangement where points, signals, and other appliances are interconnected through mechanical or electrical locking, ensuring they operate only in a specific, safe sequence. It prevents conflicting movements (like collisions) by ensuring signals cannot show ‘proceed’ unless the route is properly set, locked, and unoccupied.
Intermediary level – It refers to a stage in a distribution channel involving intermediaries such as brokers, wholesalers, and retailers, which facilitate the flow of products from producers to consumers. As the number of intermediary levels increases, the complexity of the channel also increases, leading to decreased control for the producer over product flows.
Intermediate annealing – Intermediate annealing treatment is carried out after case-hardening in order to carry out further machining such as turning, drilling, and milling, etc. It consists of holding components below the Ac1 temperature, i.e., around 630 deg C to 680 deg C, for 4 hours to 6 hours, followed by slow cooling. The object of this treatment is the same as that of spheroidizing, i.e., improved machinability through the formation of globular cementite.
Intermediate band solar cells – These are defined as novel photovoltaic devices which incorporate a third electronic band within the semiconductor bandgap, allowing for increased photogenerated current without reducing output voltage, with a theoretical efficiency limit of 63.2 %. These cells need materials which enable split quasi-Fermi levels at room temperature and low non-radiative recombination rates.
Intermediate bed – It is a central section of the conveyor which does not house the drive or tail assemblies. Periodic assessments of the intermediate bed contribute to overall conveyor system maintenance.
Intermediate blocking – Within filtration, It is a membrane fouling mechanism where particles deposit on top of previously deposited particles or directly obstruct pore areas. It serves as a transitional mechanism between complete pore blocking and cake filtration, reducing the effective membrane surface area over time.
Intermediate casing – It is a structural steel pipe string set in a wellbore after the surface casing and before the production casing to isolate unstable formations, lost circulation zones, and abnormal pressure sections. It protects up-hole formations from higher mud weights needed for deeper drilling and ensures well integrity.
Intermediate coating – It is a protective layer applied between the primer and topcoat in a multi-layer coating system. It acts as a tie-coat to improve adhesion, builds total film thickness for increased durability, and provides a barrier against oxygen / moisture penetration.
Intermediate component – It refers to a material, sub-assembly, or product generated during a multi-stage production process which is not the final consumer good but is necessary for creating it. These components frequently need further processing, assembly, or refining before reaching their final form.
Intermediate configuration – It is a transient, temporary state of a system, component, or material reached during a process (e.g., deformation, assembly, or protocol) which lies between its initial and final states. It represents an important, frequently reversible, milestone used to define, analyze, or control the progression towards a final, stable configuration.
Intermediate cooler – Intermediate cooler functions as a tuyere cooler. It is situated between the breast cooler and the tuyere. It is the water-cooled copper device in which the tuyeres become fixed in the furnace housing. It helps to make the heat exchange of the tuyere, taking away heat and preventing its passage into the surroundings of the blast furnace.
Intermediate crack debonding – It is a failure mechanism in fibre-reinforced polymer (FRP) strengthened concrete structures where high interfacial stresses, caused by tensile stresses from major flexural or shear cracks, lead to the delamination of the fibre-reinforced polymer plate from the concrete substrate. It initiates at flexural cracks and propagates towards plate ends.
Intermediate drive – It consists of additional drive units positioned along the length of a conveyor to provide added power, demanding periodic inspections for alignment and efficiency.
Intermediate duty refractories – These are a class of refractory materials, typically characterized by a pyrometric cone equivalent (PCE) value between 28 and 30. This pyrometric cone equivalent value indicates their refractoriness, or ability to withstand high temperatures without softening or deforming under load. These values fall between low and high duty refractories in terms of refractoriness.
Intermediate electrode – It is an electrode in an electrolytic which is not mechanically connected to the power supply, but is so placed in the electrolyte, between the anode and cathode, that the part nearer the anode becomes cathodic and the part nearer the cathode becomes anodic.
Intermediate file format – It refers to a neutral, standardized digital file format used to exchange 3D model data between CAD (computer aided design) software and manufacturing systems (like computer numerical control machines or 3D printers) without losing critical geometric information. These formats bridge the gap between design and production, allowing for the translation of complex geometries into instructions that machines can interpret for fabrication, or simulations, in computer-aided engineering (CAE).
Intermediate frequency – In communications and electronic engineering, an intermediate frequency is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception.
Intermediate fuel oil – It is a blended marine fuel combining heavy fuel oil (HFO) with lighter gasoil to achieve specific kinematic viscosities, primarily 180 centi-stokes or 380 centi-stokes at 50 deg C. It is used in medium-to-low speed marine diesel engines, frequently containing up to 3.5.% sulphur.
Intermediate heat treatment – It is frequently called process annealing, in-process annealing, or subcritical annealing. It is a thermal treatment applied to a metal or alloy between stages of cold-working or manufacturing operations. Its main purpose is to restore ductility and reduce hardness in a component which has become hardened and brittle because of previous manufacturing steps (like cold rolling, drawing, or bending). This allows the material to be subjected to further cold-working without breaking or cracking.
Intermediate image – It is an image formed by a refracting surface within an optical system which acts as an object for subsequent surfaces, leading to the formation of a final image. These intermediate images can be either real or virtual and are produced in succession as rays of light pass-through multiple refracting surfaces.
Intermediate layer – It is a distinct, frequently engineered, material layer situated between two primary materials (bulk phases, coatings, or layers) to manage compatibility, improve bonding, improve performance, or prevent degradation.
Intermediate level waste – It is the waste with radioactivity levels exceeding the upper boundaries for ‘low level waste’ (LLW), but which do not need temperature to be taken into account in the design of storage or disposal facilities. Intermediate level waste arises mainly from the reprocessing of spent fuel, and from general operations and maintenance of radioactive plant. The main components of the intermediate level waste are metals, sludges, and organic materials, with smaller quantities of cement, graphite, glass, and ceramics.
Intermediate maintenance strategy – This strategy can be implemented once the basic strategy has been established. There are 5 disciplines in ‘intermediate maintenance strategy’ which are (i) RCFA (root cause failure analysis), (ii) lubrication strategy, (iii) reliability Initiatives, (iv) life cycle management, and (v) spare parts inventory management.
Intermediate metal – it is more formally known as an intermediate phase or intermetallic compound. It refers to a solid phase formed by two or more metallic elements (sometimes with non-metals) whose crystal structure is distinct from that of the parent metals. These phases are important since their properties, such as high hardness, strength, and stability at high temperatures, frequently differ considerably from the constituent metals.
Intermediate mill – It consists of a set of rolling stands which processes metal after it has undergone initial hot rolling in roughing mill but before the final rolling stages in the finishing mill. It is a bridge between roughing and finishing, allowing for further reduction in thickness while potentially improving dimensional control and surface finish.
Intermediate mode – It refers to a transitional operating state, structural phase, or functional stage located between two distinct, extreme, or boundary conditions. Examples include the intermediate stage of sintering where pores form tubes, the region between choke and capacitor filter inputs, or hybrid software development modes.
Intermediate node – It is a connection point within a network, system, or graph which lies between the source (start) and destination (end) points. These nodes act as intermediaries to process, route, or switch data, signals, or physical materials, rather than simply initiating or terminating the flow. Examples include routers in networks, middle layers in data structures, or intermediate steps in production.
Intermediate orientation – It normally refers to a transient, intermediate, or transitional state of an object, molecule, or material during a transformation process, rather than a fixed initial or final state. It represents a position or angle lying between two extremes (e.g., parallel against perpendicular, or initial against final position).
Intermediate phase – In an alloy or a chemical system, it is a distinguishable homogeneous phase whose composition range does not extend to any of the pure components of the system.
Intermediate pressure steam turbines – These turbines operate at pressures from 3 mega-pascals to 8 mega-pascals and inlet temperatures exceeding 600 deg C. Since the pressure level is relatively low compared to a typical high-pressure turbine, horizontally split cylinder and flanges are used in a two-shell casing design.
Intermediate principal stress (s2) – It is the intermediate value of the three mutually perpendicular normal stresses (eigenvalues of the stress tensor) acting at a point in a 3D structural body, where shear stresses are zero. It lies between the maximum (s1) and minimum (s3) principal stresses, frequently satisfying ‘s1’ is higher than or equal to ‘s2’ higher than or equal to ‘s3’.
Intermediate resistance – It normally describes a condition of partial conductivity or resistance, falling between the extremes of a direct short circuit (0 ohm) and an open circuit (infinity ohm). It represents a state where current flow is restricted but not entirely blocked.
Intermediate rock – It is an igneous rock which contains 52 % to 66 % quartz.
Intermediate solid solution – It is a solid solution or phase having a composition range which does not extend to either of the pure components of the system. A terminal solid solution is a solid solution which exists over a composition range extending to either composition extremity of a binary phase diagram.
Intermediate stage – It refers to a transition in pore structure characterized by the formation of tubular pores at particle junctions, where the pore channels shrink in diameter, leading to potential instability because of the surface fluctuations. This stage is influenced by lattice or grain boundary diffusion mechanisms for shrinkage control.
Intermediate temperature – It typically refers to a thermal range between roughly 150 deg C and 400 deg C to 500 deg C, bridging the gap between water-based cooling / processes and high-temperature metal applications. It is a critical, frequently challenging regime used in solar thermal power, advanced heat pipes, fuel cells, and industrial processes needing moderate heat, where conventional materials can lose strength and special alloys or fluids are needed.
Intermediate temperature setting adhesive – It is an adhesive which sets in the temperature range from 30 deg C to 100 deg C.
Intermediate tie – It is a transverse reinforcement bar (typically 8 millimeters to 12 millimeters diameter) used in concrete columns to confine concrete, prevent buckling of longitudinal bars, and resist shear / spacing stresses. It serves as a connecting element to improve structural integrity and stability.
Intermediate wettability – It is a state where a solid surface shows no strong preference for either of two immiscible fluids (such as oil and water), resulting in similar adhesion tendencies for both. It frequently occurs in porous media where surface wettability is heterogeneous, allowing some pores to be oil-wet while others are water-wet.
Intermediate zone – It is a transitional region between two distinct functional, physical, or environmental states. Examples include the combustion area in gas turbines, the zone between deep and shallow water, a layer within geological strata, or a middle area in a solar pond, designed to stabilize, connect, or control gradient properties.
Intermetallic – It is a type of alloy which forms an ordered solid-state compound between two or more metallic elements, frequently including metalloids, which show a distinct crystal structure and ordered atomic arrangement differing from their parent metals. Intermetallics are normally hard and brittle, and have useful mechanical properties at high temperatures. They are characterized by strong bonding (a mixture of metallic and covalent/ionic) and fixed, or narrow-range, stoichiometry (e.g., A3B, AB, A2B7).
Intermetallic alloys – These are ordered metallic solids formed from two or more elements, possessing distinct crystal structures and frequently fixed chemical compositions (stoichiometry) different from their parent metals, resulting in unique properties like high strength, hardness, and high-temperature resistance, unlike disordered solid-solution alloys. They bridge the gap between metals and ceramics, offering metallic properties (conductivity, lustre) with ceramic-like characteristics (ordered structure, brittleness).
Intermetallic compound – It is an intermediate phase in an alloy system, having a narrow range of homogeneity and relatively simple stoichiometric proportions. The nature of the atomic binding can be of different types, ranging from metallic to ionic. Intermetallic compounds are ordered metallic phases formed from two or more elements, possessing distinct crystal structures and properties (like hardness, high melting points, and brittleness) which differ considerably from the parent metals, unlike simple solid solutions. They have fixed composition ratios, can show metallic, covalent, or ionic bonding, and are crucial in advanced materials for high-temperature strength and corrosion resistance, such as NiAl (nickel aluminide).
Intermetallic materials – These materials are compounds formed by two or more metallic elements in a specific, fixed ratio, unlike solid solutions where elements mix randomly. They possess a unique crystal structure distinct from their constituent elements, and their properties can be quite different from those of the individual metals. Intermetallics often exhibit high melting points and high resistance to deformation, making them suitable for high-temperature applications.
intermetallic NiAl – It is an ordered, stoichiometric intermetallic compound formed from nickel and aluminum (typically 50 / 50 atomic ratio), possessing a B2 (cesium chloride type) crystal structure. It is a high-temperature structural material characterized by a high melting point (approx. 1638 deg C–1640 deg C), low density (5.86 grams per cubic centimeter to–5.9 grams per cubic centimeter), and excellent oxidation / corrosion resistance, frequently compared to ceramics.
Intermetallic phases – These are compounds, or intermediate solid solutions, containing two or more metals, which normally have compositions, characteristic properties, and crystal structures different from those of the pure components of the system.
Intermetallics – These are solid-state compounds formed from two or more metallic elements (sometimes with metalloids) which show a distinct, ordered crystal structure, stoichiometry (fixed ratios like AB, A2B, A3B), and properties differing from their constituent metals. They are characterized by strong bonding, high melting points, and high brittleness at room temperature. The interior layers of the galvanized coating are intermetallics since they have distinct proportions of the alloying metals iron and zinc, examples are delta, gamma and zeta layers.
Intermittent blow-down – It is the blowing down of boiler water at intervals.
Intermittent energy source – It is an energy source whose availability is not under human control. It can be sporadically available or available on some natural schedule not coincident with human demands. These are the energy sources which are not dispatchable.
Intermittent flow – It describes a non-continuous, fluctuating, or periodic movement of materials, fluids, or products through a system, characterized by alternating periods of motion and rest, or alternating phases (e.g., gas-liquid). It differs from steady-state flow by creating transient, cyclic behaviour.
Intermittent flow regime – It is a two-phase gas-liquid flow pattern characterized by alternating, transient, and periodic surges of liquid slugs and high-velocity gas bubbles, frequently leading to flow instability. It typically occurs in pipes during transition from stratified to dispersed flow, featuring a ‘unit cell’ of a liquid slug, a gas bubble, and a liquid film.
Intermittent power – It refers to electricity generation which is not continuously available, with output fluctuating considerably because of the uncontrollable environmental factors like weather, time of day, or seasons. Predominantly associated with renewables like solar and wind, these sources are non-dispatchable, meaning their generation cannot be turned on or off to match demand.
Intermittent regime -It refers to a process, system, or flow pattern which does not operate continuously, instead showing alternating phases of activity and rest (or low activity), or alternating phases of different flow structures. It is characterized by high instability and variability.
Intermittent renewables – These are power generation sources, mainly solar and wind, which are not continuously available or dispatchable because of the natural, fluctuating environmental conditions. Engineered systems are to manage this non-programmable, variable output, which causes grid imbalances, by utilizing energy storage, demand-response, and geographical diversification to ensure stability.
Intermittent renewable energy resources – These are non-dispatchable power sources, mainly solar and wind, which are not continuously available because of the environmental, weather-dependent, and daily cycles. Engineered systems face challenges with these resources, including unpredictable volatility, lack of constant power flow, and inability to control output.
Intermittent weld – It is a weld in which the continuity is broken by recurring unwelded spaces.
Intermodal transport – It is a logistics strategy moving freight from origin to destination using two or more modes (e.g., ship, rail, truck) within the same standardized container, such as ISO (International Organization for Standardization) container, trailer, or swap body. It streamlines supply chains by eliminating cargo handling during mode transfers, improving security, reducing damage, and optimizing speed / cost.
Intermodulation – It is the unwanted amplitude modulation of signals occurring when two or more frequencies pass through a non-linear component, producing spurious output frequencies at sums and differences (mf1 +/- nf2) of the original signals. These new, frequently uncontrollable, frequencies can cause severe interference within communication systems.
Intermodulation product – It involves mitigating spurious, unwanted frequencies created when multiple signals pass through nonlinear components like amplifiers, mixers, or corroded connectors. By analyzing mf1 +/- nf2 rules, engineers manage 2nd-order / 3rd-order products, especially 3rd-order (2f1 – f2, 2f2 – f1) which frequently fall in-band. Key mitigation techniques include frequency planning, filtering, power control, and optimizing component linearity.
Intermolecular attractive forces – These refer to the electro-magnetic and dipole interactions between atoms and molecules, typically categorized into Keesom forces, Debye forces, and London or dispersion forces. These forces are important in understanding the behaviour of real gases and material properties.
Intermolecular bonds – These are weak electrostatic attractions between distinct molecules, ions, or atoms, distinct from strong internal covalent bonds. These bonds dictate material physical properties like viscosity, melting points / boiling points, and cohesive strength. Key types include hydrogen bonds, dipole-dipole forces, and van der Waals forces.
Intermolecular collision – It is a brief interaction between molecules resulting in a change in their path, speed, or energy state, frequently without direct physical contact because of the repulsive forces. These interactions are fundamental to calculating energy / momentum transfer, gas behaviour, and reaction rates in transport phenomena.
Intermolecular force – It is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles, e.g., atoms or ions. Intermolecular forces are weak relative to intramolecular forces, the forces which hold a molecule together. For example, the covalent bond, involving sharing electron pairs between atoms, is much stronger than the forces present between neighboring molecules. Both sets of forces are essential parts of force fields frequently used in molecular mechanics.
Intermolecular hydrogen bonds – These are relatively strong, directional attractive forces occurring between distinct molecules, where a hydrogen atom covalently bonded to a highly electro-negative atom (nitrogen, oxygen, fluorine) interacts with a lone pair on another electro-negative atom. These non-covalent interactions (around 4 kilo-joules per mol to 167 kilo-joules per mol) drive molecular association, raise boiling points, and enable physical crosslinking in polymers and hydrogels.
Internal absorption – It refers to the process where a substance (absorbate) penetrates and is taken up into the interior bulk phase of another material (absorbent), rather than merely adhering to its surface. It is a volumetric, physical or chemical mechanism used for mass transfer, energy absorption, or material moisture regain.
Internal actions – These are the internal stresses, shear forces, bending moments, and torque generated within a structure or material to resist externally applied loads, ensuring equilibrium. These actions, such as tension, compression, or twisting, change the body’s internal state.
Internal air temperature – It refers to the temperature of the air within a defined, enclosed space or system, frequently acting as a main controlled variable for thermal comfort in HVAC (heating, ventilation, and air conditioning) systems or for thermal management of components. It measures the heat intensity of the air immediately surrounding occupants or equipment, distinct from mean radiant temperature.
Internal architecture – It defines the structural, functional, and logical arrangement of a system’s internal components, including their relationships, interfaces, and behaviour. It focuses on how sub-systems are organized to meet needs, frequently visualized through block diagrams to show technical components, data flows, and spatial distribution, bridging high-level design with physical implementation.
Internal assessment – It is a comprehensive, self-conducted evaluation of organizational own resources, capabilities, processes, and performance (like management, marketing, finance, operations) to identify strengths, weaknesses, and areas for improvement, frequently to inform strategy, improve efficiency, or ensure alignment with goals, using methods like internal audits, SWOT (strengths, weaknesses, opportunities, and threats) analysis, and VRIO (value, rarity, imitability, and organization) framework. It helps gauge internal fitness, skill gaps, and overall readiness for strategic decisions, providing a deeper understanding than external reviews might allow.
Internal audit – It is a systematic, independent assessment of technical processes, project management, and quality management systems (QMS) to ensure compliance with standards, safety, and efficiency. It involves evaluating design, procurement, and construction practices to mitigate risk, improve performance, and ensure adherence to specifications.
Internal auditing – It is a systematic, independent, and documented process for evaluating an organization’s quality management system (QMS), project management, technical processes, and internal controls. It ensures that practical engineering activities conform to established standards (such as ISO 9001), regulatory requirements, and organizational policies, while identifying inefficiencies and risks to improve performance.
Internal axial force – It is a longitudinal, internal force acting parallel to the long axis of a structural member, either creating tension (pulling apart) or compression (pushing together). It acts throughout the material’s cross-section to resist external, collinear loads, crucial for determining structural stability in columns, beams, and trusses.
Internal bonding – It defines the internal tensile strength measured perpendicular to the material’s surface. It indicates the cohesion between internal fibres or particles, representing the maximum force needed to split the material internally. It is particularly important for materials like particle-board, fibre-board, and paper.
Internal branch – It refers to a segment of a system, network, or process which exists within a defined, enclosed, or boundary-restricted environment. It is distinct from external or ‘public’ components, as it is designed for, controlled by, and connects elements within that specific system.
Internal bulkhead – It is an upright, load-bearing, or water-tight partition wall constructed inside a structure. It increases structural rigidity, separates internal compartments for safety (fire containment / flood containment), and reinforces the main structure against bending or torsional stresses.
Internal bus – It is a high-speed, onboard communication system which transfers data, addresses, and control signals between core computer components, such as the central processing unit (CPU), random-access memory (RAM), and chip-set. Typically located on the mother-board, it acts as the main data path and is normally faster than external peripheral buses.
Internal chills – These are solid pieces of metal or alloy, similar in composition to the casting, placed in the mould prior to filling it with molten metal. These increase the rate of solidification in their areas and are used only where feeding is difficult or impossible.
Internal clock – It is an on-chip, integrated electronic circuit (typically an oscillator) which produces a continuous, periodic signal, frequently a square wave, used to synchronize, time-stamp, and drive the operations of components like microcontrollers (MCUs) and central processing units (CPUs). It provides a fundamental ‘heart-beat,’, allowing digital systems to manage data flow and function properly without relying on external timing sources.
Internal coil – It refers to a, normally copper, conductive component designed to be inserted inside a work-piece or vessel for localized, high-efficiency heat transfer, induction heating (hardening / tempering), or to generate, measure, and filter magnetic fields. Internal coils are engineered in configurations like solenoid or hairpin shapes to maximize, for example, induction heating of interior surfaces.
Internal combustion – It refers to the process in which fuel is combusted within an internal combustion chamber of an engine, such as the Otto engine or diesel engine, to produce mechanical energy. This technology is widely utilized in transportation vehicles and electricity generation because of its durability, affordability, and good performance.
Internal combustion engine – It is a heat engine which converts chemical energy from fuel into thermal energy through combustion within a chamber, subsequently transforming it into mechanical work (rotational motion) using pistons, rotors, or turbines. It operates by burning fuel with an oxidizer (air) internally, typically in four-stroke (intake, compression, power, exhaust) or two-stroke cycles.
Internal combustion engine combustion – It is the high-temperature, exothermic chemical reaction of a fuel-oxidizer (normally air) mixture inside a confined cylinder. This rapid oxidation releases thermal energy, increasing the pressure of the gases to push a piston or turbine, hence converting chemical energy directly into mechanical work.
Internal components – These are structural or functional parts housed within a main system’s casing or shell, necessary for operation, structural integrity, or specific functionality. These elements, ranging from mechanical fasteners in pressure vessels to processors in computers, are frequently ‘part-of’ relationships which cannot function independently of the assembly.
Internal concentration polarization – It is the accumulation or dilution of solutes within the porous support layer of an asymmetric membrane (typically in forward osmosis), creating a concentration gradient distinct from the bulk solutions. This phenomenon reduces the effective osmotic pressure difference across the active layer, considerably decreasing water flux.
Internal consumption – It refers to the use of resources (materials, energy, or products) within an organization’s own operations, rather than selling them externally. It frequently involves tracking materials used during a production cycle or using raw materials internally, such as a supplier using their own extracted silicon. It is frequently associated with cost tracking and inventory management in production environments.
Internal convection – It refers to heat transfer between a solid surface and a fluid (liquid or gas) flowing within a confined, enclosed space, such as pipes, tubes, or ducts. It is characterized by fully developed laminar or turbulent boundary layers, where fluid temperature and velocity profiles are constrained by the walls.
Internal conversion – It is a radioactive decay process where an excited nucleus transfers energy directly to an orbital electron, ejecting it (the conversion electron) instead of emitting a gamma ray. This mechanism competes with gamma decay, particularly in heavy nuclei, allowing for non-radiative de-excitation, often utilized in spectroscopy to measure nuclear transitions.
Internal controls – These are the policies, procedures, and systems management implements to ensure project goals (operations, quality, cost, safety) are met, risks are managed, resources are protected, and operations are efficient, reliable, and compliant with standards, preventing errors and fraud through systematic checks and process definitions. While frequently associated with accounting, in engineering, they apply to design, production, and maintenance, ensuring predictable outcomes and adherence to specifications.
Internal corrosion – It refers to the electro-chemical degradation of a component’s inner surface, very frequently in pipelines, tanks, and vessels, caused by contact with transported substances like liquids, gases, or contaminants. It causes material thinning, pitting, or cracking because of the substances like water, carbon di-oxide, or hydrogen sulphide (H2S), frequently worsening with time.
Internal crack – It is a sub-surface, hidden material separation or discontinuity which forms inside a component, rather than on its surface, because of the material inconsistencies, manufacturing processes (e.g., cooling, forging), or stress concentrations. These defects frequently form at solidification fronts or grain boundaries, reducing material ductility and leading to potential structural failure.
Internal cracking – It refers to fractures that form within the bulk of a solid material, not on the surface, frequently developing during processing like metal forming or solidification due to internal stresses, thermal gradients, or material weaknesses, leading to partial or full separation inside the metal. These defects, such as centerline cracks, reduce structural integrity and can propagate under service loads.
Internal curing – It is the process of supplying internal water throughout a freshly placed cementitious mixture using pre-wetted reservoirs, typically lightweight aggregates or super-absorbent polymers (SAPs), to promote ongoing cement hydration from the inside out. This method mitigates autogenous shrinkage, reduces cracking, and increases internal relative humidity, particularly in low water-to-cement ratio mixes, without increasing the overall water-to-cement ratio.
Internal customers – They are the stakeholders / departments within the organization (e.g., employees) who need assistance from another individual or department to get their job done. This is in contrast to external customers who pay for the products / services and are not directly connected to the organization.
Internal damage variable – In ‘continuum damage mechanics’ (CDM), t is a state variable representing the isotropic or anisotropic degradation of material stiffness and strength because of the micro-structural defects like voids and cracks. It typically ranges from 0 (undamaged) to 1 (fully fractured), acting as a measure of structural integrity loss under stress.
Internal damping – It is the inherent, material-level property which dissipates vibrational energy as heat during cyclic loading, caused by intermolecular friction, microstructural inhomogeneities, or elastic hysteresis. It reduces vibration amplitude and prevents resonance in structures by converting kinetic energy into thermal energy.
Internal data structures – These are specialized, frequently hidden formats for organizing, managing, and storing data within a software component to ensure efficient access, manipulation, and memory management. They encapsulate data, such as nodes or arrays, allowing for optimized operations like searching, insertion, and traversal, frequently abstracting implementation details from client code.
Internal defect – It is a flaw or imperfection which exists within a material, product, or system that is not visible from the outside and can need specialized methods to detect. These defects can include issues like cracks, voids, inclusions, or other imperfections which can compromise the integrity, performance, or quality of the item.
Internal deflection method of shot peening – It is a specialized metallurgical process designed to treat the inner surfaces of holes, bores, or tubes which are difficult to reach with conventional, direct-line-of-sight peening equipment. It is a technique involving specialized equipment (an internal lance or deflector) to introduce beneficial compressive residual stresses on the internal surfaces of cylindrical components, typically used when the depth of a bore exceeds its diameter. Instead of firing shot directly, a nozzle directs a high-velocity stream of spherical shot (steel, ceramic, or glass) onto a deflecting tip (often made of tungsten carbide) placed inside the bore. The shot strikes the target surface at an angle, creating the necessary plastic deformation and, consequently, a layer of compressive residual stress to increase fatigue life and prevent stress corrosion cracking.
Internal degrees of freedom – These refer to the independent, microscopic ways a molecule or system can store energy beyond its overall motion, including translational, rotational, and vibrational modes. They define the internal state and are important for calculating internal energy, specific heat, and thermodynamic properties based on the ‘equipartition theorem’.
Internal dimension grinding – It is a precision machining process used to finish the inner surfaces of cylindrical or tapered holes, bores, and tubes. It utilizes a small, high-speed rotating abrasive wheel to remove material from the inside diameter of a work-piece, achieving high dimensional accuracy, tight tolerances (frequently +/- 0.013 millimeters to +/- 0.025 millimeters), and superior surface finishes.
Internal distortion – It refers to unintended changes in the shape or dimensions of a component, resulting from differential contraction, residual stresses, or microstructural changes (such as phase transformations) which occur during manufacturing processes like casting, welding, or heat treatment. These internal, frequently unseen, forces create permanent, undesired geometric deviations, potentially causing functional failure.
Internal effectiveness factor – It is the ratio of the actual overall rate of reaction within a catalyst particle to the rate if the entire interior were exposed to the surface concentration and temperature. It quantifies how internal pore diffusion limitations reduce reaction efficiency, ranging from 0 to 1. It is the ratio of the reaction rate influenced by internal diffusion to the reaction rate without diffusion influence, reflecting the impact of internal mass transfer resistance in a reaction process.
Internal electric field – It is the total, microscopic, or local field (Eloc) acting on an atom or molecule within a material, resulting from the sum of an applied external field and the fields produced by neighboring polarized dipoles. It is important in di-electric engineering, determining polarization, and, in semi-conductors, represents the built-in field (Ei) which affects charge carrier transport.
Internal energy – It is the sum of the kinetic energy (energy of motion) and potential energy (stored energy) of a system. Internal energy is characterized solely by the state of the system.
Internal energy density (u) – It is defined as the total internal energy (U) of a system per unit volume (V), or ‘u = U/V’. It represents the sum of microscopic kinetic and potential energies of molecules (vibration, rotation, translation) within a material, excluding macroscopic motion or potential energy.
Internal energy gain – It refers to the increase in a system’s total microscopic energy, molecular kinetic and potential energies, resulting from heat transfer (Q) or work done on it (W), calculated as ‘delta U = Q + W’. It represents the accumulation of thermal energy due to temperature changes or phase changes.
Internal entropy production – It is the irreversible, positive-valued generation of disorder within a system because of the internal processes like friction, chemical reactions, heat transfer across finite temperature differences, and mixing. It represents energy degradation and directly dictates system efficiency.
Internal environment – It refers to controllable, inside-the-organization factors which directly affect project, product, or system development, including resources, technical capabilities, organizational culture, and management policies. It encompasses the immediate operational surroundings, such as machinery, workforce, and technical processes, allowing teams to influence performance and achieve objectives.
Internal exergy loss – It is also called internal exergy destruction. It is the irreversible, non-recoverable consumption of useful work potential within a system, driven by entropy generation. It represents inefficiencies from internal processes like friction, chemical reactions, mixing, and heat transfer across finite temperature differences, rather than energy leaving the boundary.
Internal failure costs – These are expenses incurred when products or services fail to meet quality standards before delivery to the customer. These costs arise from defects identified during internal inspections, including scrapped materials, rework, and process failures, directly impacting profitability.
Internal fault – It refers to a failure, short circuit, or insulation breakdown occurring within the protective boundary (shell / casing) of an electrical device or system, such as a transformer, motor, or generator. Unlike external faults, internal faults need immediate isolation of the specific equipment to prevent catastrophic damage, frequently detected using differential protection.
Internal feedback – It refers to a regulatory mechanism within a system where a portion of the output signal is returned to the input to control, stabilize, or adjust performance automatically. It acts as a self-regulating process, important for optimizing system behaviour, such as in electrical amplifiers, or mechanical controls, based on internal, rather than external signals.
Internal flow – It refers to the movement of fluid materials (such as molten metal, slag, or shielding gas) completely confined within boundaries, such as in casting moulds, ladle nozzles, pipes, or furnaces. Unlike external flow, internal flow is entirely constrained by surrounding solid surfaces, forcing viscous effects to dominate the entire flow field rather than just a boundary layer.
Internal flow field – It refers to the study of fluid motion completely bounded by solid surfaces, such as pipes, ducts, channels, or machinery components. It is defined by velocity, pressure, and temperature profiles which are heavily influenced by viscous shear effects along the boundary walls.
Internal fluid flow – It refers to the movement of a liquid or gas completely confined within a solid boundary or structure, such as pipes, ducts, or conduits. It is characterized by the fluid being enclosed on all sides, forcing viscous effects to dominate the entire flow field as the boundary layer develops.
Internal flux – It refers to the magnetic flux (lines of force) which exists inside a current-carrying conductor. It contributes to the conductor’s self-inductance and decreases towards the centre, as the magnetic field intensity (hx) is proportional to the enclosed current (ix) at a given radius (x).
Internal forces – These are defined as forces which act within the material of a structure. These forces help maintain equilibrium and determine the structure’s reaction when under external loadings. This is crucial because it essentially forms the backbone for understanding mechanics in engineering, particularly in the field of civil and mechanical engineering. Examples of different types of internal forces at work based on the reaction of the structure are tensile and compressive forces, shear forces, and bending moments etc.
Internal force system – It refers to the collective forces and moments developed within a structural member or body to balance externally applied loads. These forces, including axial (tension / compression), shear, and bending moments, are necessary to maintain structural integrity and equilibrium. They arise from interactions between particles of the system, normally acting in opposite pairs to prevent net motion.
Internal force vector – It is a, normally, 3D representation of forces and moments (Fx, Fy, Fz, Mx, My, Mz) acting within a material to maintain equilibrium against external loads. It represents the collective stress distribution across a cross-section, calculated by integrating stress over the element’s area.
Internal friction – It is the conversion of energy into heat by a material subjected to fluctuating stress. It is the ability of a metal to transform vibratory energy into heat. It normally refers to low stress levels of vibration. Damping has a broader connotation since it can refer to stresses approaching or exceeding yield strength.
Internal friction angle – It is a shear strength parameter in geo-technical engineering representing the friction between soil or rock particles, indicating their resistance to deformation under loading. It defines the maximum angle of shear resistance, frequently equal to the angle of repose for dry, granular materials. It represents the slope of a linear representation of shear strength, determining how well materials like sand, gravel, or soil can withstand shear stress. It represents the angle between the normal force and the resultant force at the point of failure. It is the inclination at which particles start sliding. It is important for calculating slope stability, earth pressure against retaining walls, and bearing capacity of foundations.
Internal grinding – It consists of grinding an inside of a rotating work-piece by use of a wheel spindle which rotates and reciprocates through the length or depth of the hole being ground.
Internal heat exchanger – It frequently used in refrigeration and heat pump systems. It is a component designed to improve energy efficiency by transferring heat from the high-temperature liquid line to the low-temperature compressor suction line. This process sub-cools the refrigerant before the expansion valve, securing sufficient superheat, increasing ‘coefficient of performance’ (COP), and protecting the compressor.
Internal heat gain – It refers to the thermal energy generated by sources inside a building’s envelope—specifically occupants, lighting, electrical equipment, and appliances. In HVAC (heating, ventilation, and air conditioning engineering), this is an important component of the total cooling load, representing sensible and latent heat which is to be removed to maintain comfort.
Internal heat generation – It refers to the conversion of other energy forms (electrical, chemical, nuclear, or mechanical) into thermal energy within a material or component, rather than heat transferred from an external source. It is characterized as a volumetric source term (normally W/cubic meter) in heat transfer, important for modeling systems like nuclear fuels, electrical resistances (I-square x R), and exothermic chemical reactors.
Internal impedance – It is the total opposition (resistance and reactance) a source or device presents to alternating current (AC) flow, measured in ohms. It combines internal resistance and reactance (Z = R + jX), causing voltage drops and energy losses during operation. It determines a source’s maximum current output, efficiency, and voltage regulation.
Internal instability – It refers to a material or structure’s inability to maintain its internal configuration, integrity, or state under load, frequently leading to localized failure like buckling, particle migration, or kinematic mechanism formation. It is driven by inherent material, structural, or, in soils, seepage-induced, characteristics rather than external constraints.
Internal irreversibility – It refers to dissipative effects occurring within a system’s boundaries, causing entropy production, energy degradation, and loss of potential work. Examples include internal friction, turbulence, viscosity, and unrestricted expansion. It reduces efficiency regardless of external conditions, contrasting with external losses.
Internal latent heat, true – It is the internal energy of steam. It is the energy needed to change the phase. Hence, it is the actual heat energy stored in the steam above 0 deg C. It can be calculated by subtracting the external work of evaporation from the enthalpy. Its unit is kilojoule per kilogram.
Internal length parameter – It is a characteristic length scale (frequently denoted as ‘l’ or ‘Lc’) used in advanced continuum models (e.g., Cosserat, gradient, or couple stress theories) to account for material microstructure, size effects, or to regularize strain localization zones. It introduces a ‘hidden’ physical dimension which influences mechanical behaviour, such as in buckling analysis of nano-materials.
Internally-fired boiler – Internally-fired boiler has the combustion chamber located within the shell of the boiler, or the furnace is surrounded by water-tubes.
Internal mandrel – It is a metal tool (core, rod, or shaft) inserted into a hollow work-piece to provide internal support, maintain precise dimensions, or shape the internal diameter during processes such as bending, forging, drawing, or welding. They are typically made of hardened tool steel, tungsten carbide, or other durable materials to withstand high pressure and friction.
Internal market – It is a structured framework which simulates external market dynamics, competition, supply, and demand, within a single entity, enabling internal units to act as buyers and sellers of services. It transforms overhead centres into performance centres, replacing top-down, rigid budgeting with a supplier-customer model which influences service quality, cost, and efficiency.
Internal mass transfer – It is the diffusion of chemical species within a solid matrix or catalyst pore structure, frequently occurring simultaneously with chemical reactions. It is driven by concentration gradients and considerably affects reaction rates when internal resistance is high, characterized by the Thiele modulus. It constitutes the transport step inside a solid particle, as opposed to external transfer, which is transport through the surrounding boundary layer. It is mainly driven by molecular diffusion within the pore network, such as in catalytic reactors or adsorption beds.
Internal mixer – It is an enclosed device designed for high-intensity, batch-wise mixing, plasticizing, or compounding of materials like rubber and polymers. Utilizing intermeshing or tangential rotors within a sealed, heated chamber, it provides rapid mixing with controlled temperature and shear to ensure homogeneous dispersion.
Internal model control (- It is a control strategy which embeds a mathematical model of the process in parallel with the actual plant to predict behaviour and improve robustness. By calculating the difference between real-time output and model output, internal model control compensates for disturbances and model inaccuracies, offering a transparent framework for designing, tuning, and stabilizing systems.
Internal network – It is a private, secure computer network owned and controlled by an organization, using private IP (internet protocol) addresses and restricted access for employees, distinguishing it from the public internet, and frequently featuring components like ‘local area networks’ (LANS), intranets, firewalls, routers, and servers to share resources and data securely. Its design focuses on protecting sensitive systems (like directory / file servers) through strong security controls, segmentation, and encryption, managing traffic within its boundaries for internal operations.
Internal node – It is a node within a data structure (like a tree or graph) or a computational domain which has at least one child node or neighbour, distinguishing it from a leaf or boundary node. They act as branch points, storing data or representing, for example, internal mesh points in finite element analysis.
Internal oscillator – It is a clock signal generator integrated directly into an integrated circuit (e.g., micro-controller), eliminating the need for external components like crystals or capacitors. It utilizes on-chip resistance-capacitance (RC) circuits to generate timing pulses for instruction execution, typically offering lower cost and reduced space at the expense of higher frequency drift and lower precision compared to external, quartz-based oscillators.
Internal overpressure – It is the condition where the pressure inside a vessel, piping system, or component exceeds its maximum allowable working pressure (MAWP) or normal operating pressure. It results from process upsets, thermal expansion, or chemical reactions, needing safety measures like relief valves to prevent structural failure.
Internal oxidation – It is the formation of isolated particles of corrosion products beneath the metal surface. This occurs as the result of preferential oxidation of certain alloy constituents by inward diffusion of oxygen, nitrogen, sulphur, and so forth. Though internal oxidation which is formation of relatively fine sub-surface oxide inclusions, is mainly talked about in steel.
Similar phenomena have also been reported in silver-aluminum, copper-aluminum and silver- indium alloys. Such mechanism has also been attributed to the formation of nitrogen, sulphur, selenium and tellurium bearing internal inclusions. The mechanism and kinetics of internal oxidation is fairly well studied. The stability of internally oxidized zone can best be described in terms of relative fluxes of oxygen and metal and the number of oxygen atoms per metal atom of the oxide compound. Normally the internal oxidation is harmful and can be classified as a surface / subsurface defect strongly affecting the property.
Internal phase – It is also called dispersed phase. It refers to the discontinuous liquid droplets suspended within a second, immiscible continuous (external) phase. It is characterized by small droplets, frequently 0.1 micro-meter to 100 micro-meters, which are separated from each other by the continuous medium, forming important mixtures in drilling fluids.
Internal polymer sheath – It is a primary, fluid-tight thermoplastic layer, particularly within flexible pipe design / riser design, which acts as a barrier to maintain bore fluid integrity. It protects outer armour layers from corrosion, typically made from high-density poly-ethylene (HDPE), or poly-vinylidene fluoride (PVDF), with thickness tailored to pressure, temperature, and fluid composition.
Internal porosity – It refers to the presence of unintended, microscopic, or macroscopic voids, cavities, or holes trapped inside a solid metal component, particularly within castings, welded joints, or powder metallurgy parts. Unlike surface porosity, these voids are not visible to the naked eye on the surface, needing methods like X-ray CT (computed tomography) scanning or cross-sectioning to detect.
Internal pressure – It is the force per unit area exerted by a contained fluid or gas against the internal surfaces of a vessel, pipe, or container. It acts uniformly in all directions, causing tensile stresses like hoop and longitudinal stress.
Internal pressure containment – It refers to designing leak-tight structures, such as vessels, pipes, or containment buildings, capable of withstanding high internal forces from gases or fluids without rupture, typically ensuring safety under both operational and accident conditions. It utilizes robust materials (e.g., steel, concrete) to manage hoop stress.
Internal pressure, gasket – It is the forces which are continually trying to unseal a gasketed joint by exerting pressure against the gasket (blow-out pressure) and against the flanges holding the gasket in place (hydrostatic end force).
Internal pressure relief – It is a self-relieving feature in non-independent seating valves which automatically relieves excessive internal body pressure caused by sudden changes in line pressures. By means of the piston effect principle, the excessive body pressure moves the seat away from its seating surface and relieve it to the lower pressure side.
Internal quantum efficiency – It defines the ratio of photons generated internally to the number of electrons injected into an LED’s (light emitting diode) active region. It measures the effectiveness of radiative carrier recombination against non-radiative losses. Internal quantum efficiency represents the internal conversion efficiency, independent of extraction, and is always higher than ‘external quantum efficiency’ (EQE).
Internal gears – They are also called ring gears. Internal gears produce an output rotation that is in the same direction as the input, As the name implies, teeth are cut on the inside surface of a cylindrical ring, inside of which are mounted either a single external tooth spur gear or a set of external tooth spur gears, typically consisting of three or four larger spur gears (planets) usually surrounding a smaller central pinion (sun). Normally, the ring gear is stationary, causing the planets to orbit the sun in the same rotational direction as that of the sun. For this reason, this class of gear is often referred to as a planetary system. The orbiting motion of the planets is transmitted to the output shaft by a planet carrier. In an alternative planetary arrangement, the planets may be restrained from orbiting the sun and the ring left free to move. This causes the ring gear to rotate in a direction opposite that of the sun. By allowing both the planet carrier and the ring gear to rotate, a differential gear drive is produced, the output speed of one shaft being dependent on the other.
Interionic interactions – These are the electrostatic forces of attraction or repulsion which occur between charged particles (ions) in a solid lattice or in solution. These forces include strong, direct ion-ion attractions and weaker ion-dipole interactions, which considerably influence properties like solubility, stability, melting points, and electrical conductivity.
Internal rate of return – It is a rate of return which is used in capital budgeting to measure and compare the profitability of investments. In the context of savings and loans, the internal rate of return is also called the effective interest rate. The term ‘internal’ refers to the fact that its calculation does not incorporate external or environmental factors (e.g., the interest rate or inflation). The internal rate of return on an investment is the annualized effective compounded return rate which makes the net present value (NPV) of all cash flows (both positive and negative) from a particular investment equal to zero. It can also be defined as the discount rate at which the present value of all future cash flow is equal to the initial investment or in other words the rate at which an investment breaks even. In more specific terms, the internal rate of return of an investment is the discount rate at which the net present value of costs (negative cash flows) of the investment equals the net present value of the benefits (positive cash flows) of the investment. Calculations of internal rate of return are normally used to evaluate the desirability of investments or projects. The higher a project’s internal rate of return, the more desirable it is to undertake the project. Since the internal rate of return is a rate quantity, it is an indicator of the efficiency, quality, or yield of an investment.
Internal rate of return method – It is a, discounted cash flow technique which calculates the specific interest rate at which a project’s net present value (NPV) equals zero. It represents the expected annual rate of return, used to evaluate and compare project profitability by determining if the ‘internal rate of return’ (IRR) exceeds the organization’s minimum needed return.
Internal redundancy – It refers to the design of a single structural member with multiple, independent load-carrying elements, allowing it to sustain loads even if one component fails. Common in steel construction, it prevents catastrophic failure by ensuring that if a crack forms in one part of a member, it does not propagate through the entire section.
Internal reflection – It is an optical phenomenon occurring when light travels from a higher refractive index medium to a lower one, striking the boundary at an angle higher than the critical angle. The light is completely reflected back into the denser medium, enabling efficient light transmission in fibre optics.
Internal relay – It is also known as an auxiliary relay, marker, internal bit, or bit storage. It is a software-simulated component which mimics the behaviour of a physical relay. Unlike physical electro-mechanical relays which use electro-magnetic coils and mechanical contacts to open / close circuits, internal relays are virtual components residing in the PLC’s (programmable logic controller) memory.
Internal representation – It refers to the structured, encoded format (e.g., feature vectors, latent variables, neural activations) which a model uses to store, process, and interpret input data. It acts as a compressed, abstract mental model of the external world, facilitating reasoning, classification, and decision-making by capturing essential features and relationships.
Internal resistance (r) – It is the inherent opposition to current (I) flow within an electrical source (battery, generator) or component, causing voltage drops (V = I x r) and heat generation. Modeled in series with an ideal source (Thevenin’s theorem), it reduces terminal voltage under load. It is measured in ohms
Internal resistors – These refer to resistive components integrated within a differential amplifier, which improve stability and reduce susceptibility to parasitic capacitances on the PCB (printed circuit board) layout by containing sensitive feed-back loop nodes within the chip.
Internal resonance – It is a mechanism in structural mechanics which facilitates energy transfer between different vibrational modes, needing an integer ratio between the modes involved. It is normally studied in different structures, including MEMS (micro-electro-mechanical systems) resonators, and is important for applications like energy harvesting and frequency stabilization. It is a non-linear structural mechanism where energy transfers between different vibration modes of a system, occurring when natural frequencies exist in an integer ratio. It causes increased, complex, or unstable vibrations because of the modal coupling, unlike external resonance.
Internal rotary inspection system (IRIS) – It an ultrasonic NDT (non-destructive testing) method using a water-driven turbine and rotating mirror to measure pipe / tube wall thickness.
Internal screw – It is normally known as an internal thread or female thread’ It refers to helical grooves cut into the inside surface of a cylindrical hole, nut, or machine component. It is designed to engage with an external (male) screw thread to create a threaded, removable fastening connection.
Internal shapes – It refers to the specific, often complex, voids, cavities, or geometric configurations located within a metal part, typically achieved through casting or powder metallurgy techniques. These are frequently formed by cores in a mould and are important for the functionality of components like engine blocks or housings.
Internal shear -It refers to the internal force acting within a beam which resists the sliding of one segment of the beam relative to another, which can be quantified by analyzing the equilibrium of forces acting on a section of the beam.
Internal shear force – It is the internal, transverse force acting parallel to a structural member’s cross-section (e.g., in beams) which resists sliding between adjacent parts because of the external loads. It is defined as the algebraic sum of all transverse loads acting on either side of a specific section.
Internal shrinkage – It is a void or network of voids within a casting caused by inadequate feeding of that section during solidification.
Internal spur gear – It is a cylindrical, ring-shaped gear with straight teeth cut on its inner diameter rather than its exterior. It meshes with an external, smaller pinion gear (annular gear) to create compact, high-torque, and quiet transmissions, where both gears rotate in the same direction.
Internal standard – In spectroscopy, it is a material present in or added to samples which serves as an intensity reference for measurements. It is used to compensate for variations in sample excitation and photographic processing in emission spectroscopy.
Internal state variables – These are internal, typically unmeasurable, microstructural parameters (e.g., dislocation density, grain size, damage parameters) which track the history-dependent evolution of a material’s state during inelastic deformation. They are used in constitutive models alongside observable variables (stress, temperature, strain) to predict non-linear material behaviour.
Internal standard line – In spectroscopy, it is a spectral line of an internal standard, with which the radiant energy of an analytical line is compared.
Internal strain – It refers to deformation or strain energy stored within a material’s lattice structure, frequently caused by crystal defects, manufacturing processes (like thermal gradients), or phase changes, rather than direct, active external loading. It represents microscopic lattice deformation, normally measured through XRD (X-ray diffraction) peak shifts.
Internal stress – It is the stress present in a body which is free of external forces or thermal gradients. It is the stress which is not depending on external forces resulting from such factors as cold working, phase changes, or temperature gradients. It is also known as residual stress. It is the stress present in a steel member or fabrication which is free of external forces or thermal gradients.
Internal strength – It refers to the inherent ability of a metal or alloy to withstand applied external loads, forces, or stresses without undergoing permanent (plastic) deformation, cracking, or fracturing. It is a measure of the material’s structural integrity and its capacity to maintain its shape under service conditions. Key aspects of internal strength include (i) resistance to deformation, (ii) yield strength, (iii) ultimate tensile strength, (iv) microstructural dependence, and (v) strengthening mechanisms.
Internal sub-division – It refers to the strategic arrangement, partitioning, and division of interior space within a building, involving the creation of smaller, functional areas or rooms from a larger, open, or existing unit. It focuses on maximizing efficiency, frequently involving structural adjustments like reconfiguring partitions, plumbing, or lighting to adapt to specific uses or increased occupancy.
Internal thread rolling – It is frequently termed thread forming or cold-form tapping. It is a chipless, cold-plastic deformation process used to produce internal threads by displacing, rather than cutting, material within a pre-drilled hole. Instead of using a cutting tap, this method utilizes a forming tap (or rolling tap) with a lobular (a shape, structure, or component characterized by rounded projections or division), thread-shaped profile to press the material into the shape of the thread.
Internal threads – These are helical grooves, ridges, or profiles, such as those found on nuts or within tapped holes, designed to mate with external (male) threads for fastening or motion transfer. They are typically produced through tapping, drilling, or machining processes (e.g., lathe) on the inner diameter of a component.
Internal threshold – It is a specific, pre-defined value or limit within a system which triggers a change in state, action, or behaviour when reached or exceeded. It is used to define operational boundaries, such as in control systems, neural networks, or material stress analysis, where a node fires or a material fails only after exceeding this specific internal limit.
Internal transistor – It is also called the internal structure of a transistor. It refers to the microscopic arrangement of semi-conductor material (silicon or germanium) within a device which controls, switches, or amplifies electrical signals. It consists of three doped regions (emitter, base, collector) creating p-n junctions, modulating current flow through voltage / current.
Internal transport – It refers to the systematic movement of materials, products, components, and goods within a single industrial site, facility, or warehouse. It encompasses all logistical flows between production areas, storage, and processing points to optimize production efficiency, speed, and safety.
Internal treatment – The internal treatment for softening of water is also known as conditioning of water. In the internal treatment, the softening of water is carried out in the water-cooling circuit. In this method, some types of chemicals are added to hard water to remove the negative effect of calcium and magnesium. Chemical treatment for softening results into low levels of hardness of water. For purifying hard water from a single source, it is economically feasible method. Selection of the proper chemical is determined by the raw water composition and the desired quality after softening. In case several chemicals are applicable, aspects of operational management also become important. During the internal treatment for softening of water, the hardness causing salts are removed (i) by complexing the hardness causing salts to soluble salts by adding suitable reagents, (ii) by precipitating the scale forming impurities in the form of sludge which can be removed by blow down operation, and (iii) by converting the scale forming salts into other compounds which stay in ‘dissolved form’ and do not cause any trouble to the cooling elements, pipelines, and fittings of the cooling system. The important internal conditioning methods are (i) colloidal conditioning, (ii) phosphate conditioning, (iii) carbonate conditioning, (iv) Calgon conditioning, and (v) conditioning with sodium aluminate.
Internal upset – It refers to a hot-forging process used on tubular products (such as drill pipe or casing) to increase the wall thickness at the ends by forcing material to flow inward, decreasing the inside diameter (ID) while keeping the outside diameter (OD) constant.
Internal validity – It is the extent to which treatment-group differences on a study endpoint represent the causal effect of the treatment on the study endpoint.
Internal venting – These are holes on the inside of enclosed fabrications which allow cleaning solutions, zinc, and any gases to freely flow throughout the structure.
Internal virtual work – It is the energy absorbed by a deformable body’s internal forces (such as bending moments, axial forces, or shear) as they act through an infinitesimal virtual deformation or strain, consistent with structural constraints. It is defined mathematically as the integral of internal stress over a virtual strain and, by the principle of virtual work, equals external virtual work for systems in equilibrium.
Internal waves – These are gravity-driven, sub-surface oscillations occurring within stratified fluids (such as oceans or lakes) which travel along density interfaces, like the thermocline or pycnocline. Unlike surface waves, they possess large amplitudes and, as they propagate, transfer substantial energy and momentum across the water column.
Internal wear liner – It is a protective layer applied to the internal surfaces of conveyor / equipment components to mitigate wear, needing regular inspections and replacement as needed.
International alloy designation system – It is a universally accepted, standardized method for identifying and classifying aluminium alloys based on their chemical composition. It is used to classify wrought (formed) and cast (poured) aluminium alloys to ensure consistent material identification across global industries.
International annealed copper standard – It is a 100 % reference benchmark for electrical conductivity, defined as a copper wire with a density of 8.89 grams per cubic centimeter, 1 meter long, weighing 1 gram, with a resistance of 0.15328 ohms at 20 deg C. . It represents annealed, high-purity (99.9 % plus) copper, used to measure conductivity in other metals.
International Atomic Energy Agency – It is an inter-governmental organization which seeks to promote the peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons.
International atomic time – It is a high-precision atomic coordinate time standard based on the notional passage of proper time on earth’s geoid. It is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories worldwide. It is a continuous scale of time, without leap seconds, and it is the principal realization of Terrestrial time (with a fixed offset of epoch). It is the basis for ‘coordinated universal time’ (UTC), which is used for civil timekeeping all over the earth’s surface and which has leap seconds.
International Electrotechnical Commission – It is an international standards organization devoted to electrical standards. Majority of the countries are its members.
International Energy Agency – It is an international energy forum comprised of 29 industrialized countries under the Organization for Economic Development and Cooperation (OECD). International Energy Agency has been established it to help its members respond to major oil supply disruptions, a role it continues to fulfill today. International Energy Agency has expanded over time to include tracking and analyzing global key energy trends, promoting sound energy policy, and fostering multinational energy technology cooperation. As the global energy picture has changed, the International Energy Agency has sought to engage key non-members in its activities, including Brazil, China, India, Indonesia, South Africa, Thailand, Singapore, Morocco and accession countries Mexico and Chile. The International Energy Agency energy analyses, international data collection, and coordinated collective emergency response capabilities are unique and highly regarded.
International Labour Organization – It is devoted to promoting social justice and internationally recognized human and labour rights, pursuing its founding mission that social justice is essential to universal and lasting peace. It is a United Nations agency dedicated to promoting social justice and internationally recognized human and labour rights, with a mission to advance decent work for all.
International Maritime Organization – It is a specialized agency of the United Nations regulating maritime transport. Its purpose is to develop and maintain a comprehensive regulatory framework for shipping and its remit includes maritime safety, environmental concerns, and legal matters.
International measurement standard – It is a standard recognized by an international agreement to serve internationally as the basis for assigning values to other standards of the quantity concerned.
International nuclear events scale – It is a scale from 1 to 7 introduced by the International Atomic Energy Agency (IAEA) in 1990 to assess and classify the impact(s) of nuclear accidents, where 1 is an anomaly and 7 is a major accident.
International Organization for Standardization – It is an international organization coordinating the efforts of national technical standards organizations. It develops and publishes international standards in technical and nontechnical fields, including everything from manufactured products and technology to food safety, transport, information technology (IT), agriculture, and healthcare.
International practical temperature scale – It is based on six reproducible temperatures (defining fixed points), to which numerical values are assigned, and on formulas establishing the relation between temperature and the indications of instruments calibrated by means of values assigned to the six defining fixed points. These fixed points are defined by specified equilibrium states, each of which, except for the triple point of water, is under a pressure of 101,325 newtons per square meters (1 standard atmosphere).
International standard – It is a globally recognized document, developed through consensus, which provides rules, guidelines, or specifications for products, services, or processes. These standards are established by international standards organizations and are available for worldwide use, aiming to harmonize practices, ensure quality, and facilitate international trade by overcoming technical barriers. International standards are created through a collaborative process involving experts from different countries and organizations, ensuring a broad agreement on the best practices.
International standard atmosphere – It is an engineering model defining average atmospheric conditions (temperature, pressure, density, viscosity) against altitude, providing a universal reference for aviation and aerospace by standardizing calculations for aircraft design, performance, and instrument calibration, assuming a dry, ideal gas at mid-latitudes with specific sea-level values (15 deg C, 1013.25 hecto-pascal) and temperature lapse rates.
International system of units – It is internationally known by the abbreviation ‘SI’, is the modern form of the metric system. It is widely used system of measurement and is the only system of measurement used in science, technology, industry, and everyday commerce. The ‘SI’ comprises a coherent system of units of measurement starting with seven base units, which are the second (symbol ‘s’, the unit of time), metre (‘m’, length), kilogram (‘kg’, mass), ampere (‘A’, electric current), kelvin (‘K’, thermodynamic temperature), mole (‘mol’, quantity of substance), and candela (‘cd’, luminous intensity). The system can accommodate coherent units for an unlimited number of additional quantities. These are called coherent derived units, which can always be represented as products of powers of the base units. Twenty-two coherent derived units have been provided with special names and symbols.
International temperature scale of 1990 (ITS-90) – It is an equipment calibration standard specified by the International Committee of Weights and Measures (CIPM) for making measurements on the Kelvin and Celsius temperature scales. It is an approximation of thermodynamic temperature that facilitates the comparability and compatibility of temperature measurements internationally. It defines fourteen calibration points ranging from 0.65 Kelvin to 1,357.77 Kelvin (−272.50 deg C to 1,084.62 deg C) and is subdivided into multiple temperature ranges which overlap in some instances.
International Telecommunication Union (ITU) – It is the United Nations specialized agency for information and communication technologies (ICTs). It has been founded as the International Telegraph Union to facilitate international connectivity in communication networks. Today, International Telecommunication Union is a global organization that coordinates the use of radio spectrum and satellite orbits, develops technical standards, and works to improve access to I information and communication technologies for underserved communities.
International Union of Pure and Applied Chemistry (IUPAC) – It is an international federation of chemists which is recognized as the world authority in developing standards for chemical nomenclature and other methodologies in chemistry.
Internet – It is a massive, global network of networks using the TCP (transmission control protocol) /IP (internet protocol) protocol suite to link private, public, academic, and government networks through different technologies (fibre, wireless) for global information exchange, with engineers designing, building, and maintaining this complex infrastructure for communication, services (‘world wide web’, WWW, email, streaming), and data flow.
Internet access – It is the technical ability to connect computing devices to the global system of interconnected networks, enabling data transfer, retrieval, and sharing. It is facilitated through infrastructure provided by ‘internet facility providers’ (ISPs), using different technologies such as broadband such as fibre, digital subscriber line (DSL), wireless such as cellular, wireless fidelity (Wi-Fi), and satellite to establish communication channels.
Internet connection – It is a physical or logical link between a local device or network and the global, decentralized network of networks (internet), enabling data exchange through the TCP / IP (transmission control protocol/ internet protocol) protocol suite. It utilizes different media—such as fibre optics, coaxial cables, copper wire (digital subscriber line), or wireless radio waves (5G/satellite), to facilitate packet-switched communication, allowing nodes to exchange information regardless of their physical location.
Internet of things (IoT) – It is a network of physical objects (things) embedded with sensors, software, and other technologies which connect and exchange data with other devices and systems over the internet. These objects range from ordinary household items to sophisticated industrial tools. From an engineering perspective, internet of things integrates operational technology (OT) with information technology (IT) to enable remote monitoring, control, and automation of physical systems, oft Internet of things en without needing human-to-human or human-to-computer interaction.
Internet protocol (IP) – It is the fundamental set of rules (protocol) for addressing and routing data packets across networks, enabling the internet by assigning unique internet protocol (IP) addresses to devices and directing information from source to destination, defining packet structures with headers for addressing, length, and time-to-live (TTL) for efficient, connectionless data transfer. It functions at the network layer of the TCP (transmission control protocol) /IP (internet protocol) stack, working with other protocols like TCP (transmission control protocol) for reliable delivery and UDP (user datagram protocol) for speed.
Internet protocol (IP) address – It is a unique numerical label identifying a device on a network (like the internet) for communication, acting as a digital ‘return address’ for data packets, enabling source / destination identification, with versions like IPv4 (32-bit) and IPv6 (128-bit) to support growing device numbers, defining how devices find and talk to each other using established rules (the protocol).
Internet telephony – It is also called VoIP (voice over internet protocol). It is the systems which deliver real-time voice, fax, and multimedia data over IP (internet protocol) networks instead of traditional circuit-switched PSTN (public switched telephone network) lines. It uses packet-switched networking, signaling protocols like SIP (session initiation protocol) for call control, and RTP (real-time transport protocol) for media transport.
Internet traffic – It is the flow of data packets (voice, video, and information) transmitted across internet network links, measured by volume (bytes) or throughput over specific timeframes. It represents the combined uplink / downlink activities, analyzed for performance optimization. Traffic engineering involves measuring, modeling, and controlling this data flow to optimize network resource usage, improve performance, and ensure reliability, frequently addressing packet delay and loss.
Internet website – It is a collection of publicly accessible, interrelated web pages, images, videos, and digital assets sharing a common domain name. Hosted on web servers and accessed through browsers using HTTP (hypertext transfer protocol) / HTTPS (hypertext transfer protocol secure), websites serve several purposes and are typically organized around a home page.
Internuclear distance – It is the measurement between the nuclei of two adjacent, bonded atoms in a molecule or crystal lattice, representing the equilibrium bond length. It defines molecular structure and varies inversely with bond order (higher bond order, shorter distance). This parameter is critical for understanding molecular stability, atomic interactions, and solid-state materials.
Interoperability – It refers to the degree to which a software system, devices, applications or other entity can connect and communicate with other entities in a coordinated manner without effort from the end user. Examples are nuts and bolts, screw threads, railway gauges, electrical plugs and outlets etc.
Interparticle contact – It refers to the mechanical interaction, force transmission, or physical touching between neighbouring discrete particles within a granular material, powder, or suspension. It is a fundamental concept in modeling material behaviour, specifically in discrete element methods (DEM), where contact is identified when the separation distance between particles is less than a specific threshold (e.g., sum of radii).
Interoperability test – It verifies that two or more different systems, software, or components can seamlessly communicate, exchange data, and function together as intended, following specific standards and protocols, ensuring end-to-end functionality without errors or data loss, crucial for integrated applications like banking or IoT (internet of things). It is a non-functional testing type checking communication through ‘application programming interfaces’ (APIs), data formats, and protocols, confirming they work cohesively in a shared environment.
Interparticle oxides – These are thin oxide layers or films which form on the surfaces of individual metal powder particles during production, storage, or handling. When these powders are compacted, these oxide layers remain at the boundaries where particles touch, acting as a barrier to atomic diffusion and hindering the formation of metallic bonds during the subsequent sintering process.
Interpenetrating continuum – It is a modeling framework where multiple distinct phases (solid, liquid, or gas) are assumed to coexist and occupy the same space simultaneously. Each phase is treated as a continuous medium using Eulerian-Eulerian approaches, defined by individual volume fractions and interacting through averaged conservation equations, crucial for simulating multi-phase flows and complex composites.
Interpass precipitation – In the context of hot rolling and micro-alloyed steels, it refers to the precipitation of alloying elements (such as titanium, niobium, and vanadium) which occurs during the holding time between rolling passes. This process is important in high strength low alloy (HSLA) steels to control the micro-structure and mechanical properties.
Interpass static recrystallization – It is the process by which deformed, high-dislocation-density grains are replaced by a new set of defect-free, nucleated grains during the holding time (rest period) between consecutive hot deformation passes (e.g., in multi-pass hot rolling or forging). It is an important restoration mechanism which softens the material, reduces dislocation density, and alleviates accumulated strain, hence preventing crack formation and reducing the force needed for subsequent deformation passes.
Interpass temperature – In a multiple-pass weld, it is the temperature (minimum or maximum as specified) of the deposited weld metal before the next pass is started.
Interpenetrating phase composites – These are unique materials where two or more phases are mutually continuous, forming intertwined, 3D interconnected networks, unlike traditional composites with discrete particles in a matrix. This co-continuous structure allows each phase to maintain its distinct properties while synergistically providing superior combined properties, frequently with high strength, energy absorption, and damage resistance, making them useful in energy, and impact-resistant applications.
Interpenetrating polymer network – It consists of a combination of two polymers in a network in which at least one (or both) is crosslinked around the other. Interpenetrating polymer networks are frequently used to toughen epoxy matrices, where the epoxy is continuous and a thermoplastic polymer is discontinuous.
Interphase – It is the boundary region between a bulk resin or polymer and an adherend in which the polymer has a high degree of orientation to the adherend on a molecular basis. It plays a major role in the load transfer process between the bulk of the adhesive and the adherend or the fibre and the laminate matrix resin.
Interphase forces – These are interfacial interactions between two different phases (e.g., gas-liquid or gas-solid) caused by their relative motion, crucial for momentum, heat, and mass transfer. Primarily acting at the boundary, these forces, including drag, lift, virtual mass, and turbulent dispersion, drive flow patterns, especially in multi-phase pumps and chemical reactors.
Interphase interface – It is the shared boundary between the fibre and polymer matrix in fibre-reinforced polymers, which facilitates load transfer and is characterized by a finite volume region where mechanical or chemical bonds are formed. This interface is important for maintaining strain compatibility and optimizing the performance of composite materials.
Interphase mass transfer – It is the movement of chemical species between two distinct, contacting phases (e.g., gas-liquid, liquid-liquid, or solid-liquid) across an interface, driven by concentration gradients or differences in chemical potential. This process occurs in stages namely from the bulk of one phase to the interface, across it, and into the bulk of the second phase until equilibrium is reached.
Interphase precipitation – It is a metallurgical phenomenon in which precipitates (normally alloy carbides, nitrides, or carbo-nitrides) form at the moving boundary between two phases (specifically, the austenite (gamma) / ferrite (alpha) interface) during phase transformation in steel. As the ferrite grows into the austenite, the interface moves in a ‘ledge’ or step-wise manner. Precipitates nucleate on these interface ledges, creating a characteristic sheeted or rows-of-particles distribution within the ferrite grains.
Interplanar distance – It is the perpendicular distance between adjacent parallel lattice planes.
Interplanar spacing – It is frequently denoted as ‘d’ or ‘dhkl’. It is the perpendicular distance between adjacent, parallel planes of atoms within a crystal lattice. It is a fundamental crystallographic parameter used to identify material phases, analyze crystal structures, and determine internal stresses using X-ray diffraction (XRD). It represents the repeating distance between layers of atoms in a specific orientation defined by Miller indices (hkl). These planes repeat throughout the crystal lattice, and ‘d’ determines how X-rays diffract from the material.
Interply cracks – These are through-cracking of individual layers within a composite lay-up, perpendicular to the ply interfaces.
Interply delamination – It is a critical failure mode in laminated composite materials characterized by the separation of adjacent plies (laminae) because of the high interlaminar stresses. It acts as an interfacial crack or disbond between layers, frequently caused by elastic mismatch, impact, or manufacturing defects, considerably reducing compressive strength and structural integrity.
Interply hybrid – It is a composite in which adjacent laminae are composed of different materials.
Interpolate – It is the action of calculating intermediate measurements within a given range. This process is essential for maintaining accuracy and consistency in conveyor system operations.
Interpolated function – It is a mathematical model which constructs a continuous curve passing exactly through a set of discrete data points, allowing estimation of unknown intermediate values within that range. It acts as an approximation function, normally using polynomial or spline techniques to simplify complex analysis in simulations, graphics, and numerical methods.
Interpolation – In the field of numerical analysis, interpolation is a type of estimation, a method of constructing new data points based on the range of a discrete set of known data points.
Interpolation coefficients – These are numerical weights used in numerical analysis to determine the contribution of surrounding known data points to an estimated intermediate value. They define the shape of the interpolation function (linear, cubic, etc.) between known points.
Interpolation constraint – It is a kinematic or structural constraint applied to a set of points (nodes) within a numerical model, very frequently in ‘finite element method’ (FEM) or ‘multi-body dynamics’ (MBD), where the displacement, velocity, or rotation of a dependent node is calculated as a weighted interpolation of the displacements of two or more independent nodes. Unlike rigid constraints that force nodes to move exactly together, interpolation constraints allow for flexible, smooth, and physically realistic deformation (such as in shell or solid elements) while preventing unwanted numerical singularities.
Interpolation filter – It is a digital low-pass filter used in signal processing to increase a signal’s sampling rate by inserting zero-valued samples between existing ones and smoothing them. It acts to remove imaging artifacts (high-frequency aliases) created during up-sampling. The process reconstructs a higher-resolution signal by filling in gaps between data points.
Interpolation function – It is a mathematical model used to estimate unknown, intermediate values within a range of discrete, known data points. It constructs a continuous function, frequently a polynomial or spline, which passes exactly through these known points, enabling the approximation of data between measurements.
Interpolation model – It is a mathematical, numerical, or computational framework used to estimate unknown intermediate values within a range of discrete, known data points. It acts as an approximation tool for data resampling, signal reconstruction, or finding values between points on a curve. Key methods include linear, polynomial, and spline interpolation.
Interpolation operator – It is a mathematical operator which constructs new data points within the range of a discrete set of known data points. It functions as tool mapping coarse grid / data points to a finer grid in simulations (e.g., finite element analysis), frequently represented in matrix form.
Interpolation point – It is an unknown value estimated within the range of a discrete set of known data points. It involves using techniques like linear, polynomial, or spline interpolation to construct new data points, enabling the prediction of intermediate values between measured, known data points [2,3, 10].
interpolation property – It defines a method for constructing new data points within the range of a discrete set of known, sampled data points. The key constraint is that the approximating function, ‘I(x)’, is required to pass exactly through the known data points, yi = f(xi), typically satisfying the Kronecker delta condition, phi(n) =delta n,0 [i.e., phi(0) = 1 and phi(n) = 0 for ‘n’ is not 0]. This ensures that at the sampled locations, the interpolated value matches the observed value.
Interpolation scheme – It is a numerical method used to estimate unknown, intermediate values within the range of a discrete set of known data points. It constructs a function, frequently a polynomial or spline, which passes through existing data points to predict values, normally used in simulation, modeling, and image processing /signal processing.
Interpole – It is also called commutating pole. It is a small, auxiliary magnetic pole placed between the main poles of a direct current motor or generator, connected in series with the armature to improve commutation and reduce sparking. By producing a counter-flux, they cancel armature reaction effects in the neutral zone, allowing higher load capabilities without shifting brushes.
Interposer – It is a substrate used in the packaging industry to interconnect different components, such as an integrated circuit (IC) to a package or an integrated circuit to a passive device. Originally made of silicon, interposers can also be constructed from glass and organic materials, providing efficient connectivity and benefits like power routing with minimum latency and impedance.
Inter-process communication – It involves designing and implementing mechanisms for separate processes (programmes / threads) to talk, share data, and synchronize activities, important for building modular, parallel, and high-performance software. Key inter-process communication methods include ‘shared memory’ (fastest for same-machine data exchange), ‘message passing’ (safer for isolated data), pipes, sockets, and ‘remote procedure calls’ (RPC), enabling complex systems like web servers or distributed applications to function efficiently by coordinating tasks.
Interquartile mean – It is frequently referred to in engineering and statistics as a type of trimmed mean or mid-mean. It is a measure of central tendency calculated by taking the arithmetic mean of the middle 50 % of a dataset. It is used to calculate a central value that is robust against extreme outliers, as it excludes the lowest 25 % and highest 25 % of the data.
Inter-quartile range – The interquartile range is the difference between the upper and lower quartiles. If the lower and upper quartiles are denoted by Q1 and Q3, respectively, the interquartile range is (Q3 – Q1). The phrase ‘inter-quartile range’ was first used by Galton in 1882.
Interrelationships – These refer to the complex connections between multiple events or factors, where each element influences and is influenced by others, frequently visualized through an interrelationship diagram to analyze cause-and-effect relationships systematically.
Interrogator – It is a device which consists of a radio frequency (RF) module, a signal processing and control unit, a coupling element for communication with tags through radio frequency signals, and an interface to communicate with a host system, enabling it to send and receive information.
Interrupt controller – It is a specialized hardware component or IP (internet protocol) block which manages, prioritizes, and routes multiple peripheral interrupt signals to a CPU (central processing unit), preventing the need for constant polling. It enables efficient real-time event handling by allowing the processor to respond immediately to critical tasks.
Interrupted aging – It is the aging at two or more temperatures, by steps, and cooling to room temperature after each step.
Interrupted-current plating – It is the plating in which the flow of current is discontinued for periodic short intervals to decrease anode polarization and elevate the critical current density. It is very frequently used in cyanide copper plating.
Interrupted quenching – It is a quenching procedure in which the work-piece is removed from the first quench at a temperature substantially higher than that of the quenchant and is then subjected to a second quenching system having a different cooling rate than the first.
Interrupter – It is any of a series of automatically operated electro-mechanical switches which periodically opened and closed a circuit.
Interrupt handling – It is the engineering process where a CPU (central processing unit) suspends its current execution flow to address a high-priority, asynchronous event (from hardware) or synchronous event (from software). It involves saving the current context, running a dedicated ‘interrupt service routine’ (ISR) to process the event, and resuming the original programme.
Interruptible load – It refers to industrial, commercial, or residential electrical loads which can be voluntarily reduced or shed by consumers, frequently at short notice, in response to utility signals, high demand periods, or system contingencies. It acts as a flexible, fast-acting, and cost-effective operating reserve in power systems, used for grid stability.
Interruptible tariff – It is a demand-side management rate structure where customers receive lower electricity rates in exchange for allowing utilities to curtail or interrupt power supply during grid peak demand or emergencies. It acts as an operational reserve, allowing for scheduled load shedding with advance notice, predominantly used for large industrial or commercial loads.
Interrupt service routine – It is also called interrupt handler. It is a specialized software function invoked by hardware or software to manage asynchronous events, such as timer overflows, button presses, or data arrival. It temporarily suspends the main programme, handles the request, and returns control to the previous task.
Interrupt vector – It is a specific memory address pointing to the start of an ‘interrupt service routine’ (ISR), enabling a CPU (central processing unit) to instantly locate the code needed to handle a hardware or software interrupt. It is a critical component in vectored interrupt systems, where each of the 0 to 255 possible interrupt numbers is mapped to a 4-byte address within an ‘interrupt vector table’ (IVT), typically located at the start of system memory.
Interrupt vector table – It is a dedicated data structure, often in low-memory ROM (read-only memory) or RAM (random access memory), storing pointers (vectors) to the memory addresses of specific ‘interrupt vector routines’ (ISRs). It enables the CPU (central processing unit) to instantly map hardware or software interrupts to corresponding handlers.
Intersecting curve – It is the specific, frequently complex line formed at the junction where two or more solid surfaces penetrate or intersect each other. It represents the boundary common to both objects and is important for creating precise, high-contact, or leak-proof joints in design and manufacturing.
Interstage cooler – It is a heat exchanger situated between stages of a multi-stage compressor or chemical process to reduce the temperature of compressed gas or fluid. By removing heat generated during compression, it increases gas density, reduces the work required for the next compression stage, improves efficiency, and lowers operating temperatures.
Interstage pressure – It is the pressure existing between consecutive stages of a multi-stage compressor, pump, or refrigeration system. It represents the discharge pressure of a preceding stage and the suction pressure of the following stage, frequently chosen to minimize total power consumption and balance compression ratios across stages.
Inter-stand tension – In continuous rolling in a tandem mill, it refers to the tensile or compressive force exerted on the rolled material between adjacent rolling mill stands. It arises from differences in the speeds and material flow between these stands, influencing the tension within the strip or bar as it moves through the mill.
Interstate pipelines – These are high-pressure, large-diameter (500 millimeters to 1200 millimeters) steel transmission systems which transport natural gas, crude oil, or refined products across state lines. They function as critical, long-distance infrastructure, utilizing booster compressor stations to maintain flow, and are subject to stringent national, safety, and environmental regulations.
Interstitial atoms – These are small-sized elements (such as carbon, hydrogen, nitrogen, or oxygen) which occupy the, normally empty, interstitial sites or voids between larger host metal atoms within a crystal lattice. They cause lattice distortion, significantly increasing the metal’s strength and hardness (e.g., steel). These atoms do not replace metal atoms (unlike substitutional atoms) but fit into the spaces in face-centered cubic or body-centered cubic structures
Interstitial cations – These are positively charged metal ions (cations) which occupy the small, normally unoccupied spaces (interstitial sites or voids) between the regular lattice positions of a crystal structure. These ions are typically smaller than the atoms forming the host lattice (anions) and, by fitting into these gaps, they act as a type of point defect, frequently affecting the material’s structural, electrical, and optical properties.
Interstitial compound – It is a compound composed of a transition metal bonded to either hydrogen, boron, carbon, or nitrogen, whose crystal structure consists of closely packed metal ions with the non-metal atoms located in the interstices.
Interstitial element – It is a small atom (such as carbon, hydrogen, nitrogen, oxygen, or boron) which occupies the small voids (interstices) between larger host metal atoms within a crystal lattice, rather than replacing them. These elements considerably increase material strength and hardness, normally used in alloys like steel.
Interstitial free (IF) steel – The term ‘Interstitial Free steel or IF steel’ refers to the fact, that there are no interstitial solute atoms to strain the solid iron lattice, resulting in very soft steel. IF steels have interstitial free body centered cubic (bcc) ferrite matrix. These steels normally have low yield strength, high plastic strain ratio (r-value), high strain rate sensitivity and good formability. Conventional interstitial free steels have been developed commercially following the introduction of vacuum degassing technology. These steels contain carbon in the range of 40 parts per million to 70 parts per million and nitrogen in the range of 30 parts per million to 50 parts per million. Later, niobium and / or titanium have been added to these steels to stabilize the interstitial carbon and nitrogen atoms. Interstitial free steel is a sheet steel product with very low carbon levels. Interstitial free steel is used mainly in automotive deep drawing applications. The improved ductility (drawing ability) of interstitial free steels is made possible by vacuum degassing.
Interstitial loop – It is a disk-shaped, two-dimensional defect formed by the agglomeration of excess interstitial atoms (atoms forced into non-lattice positions) within a crystal lattice. These loops act as planar, edge-type dislocation loops which grow by absorbing more interstitials, serving as a main mechanism for material swelling and radiation-induced hardening.
Interstitial oxygen – It refers to oxygen atoms occupying non-lattice positions (interstices) within a crystal structure, acting as critical point defects or impurities which considerably affect mechanical properties like strength, ductility, and diffusivity in metals (e.g., titanium) and oxides. These atoms squeeze into open spaces between larger lattice atoms, causing localized lattice distortion, increased covalent character, and increased lattice parameter c/a.
Interstitial phase – It is a solid solution or compound formed when small atoms (e.g., hydrogen, carbon, nitrogen, boron) occupy the vacant spaces (interstices) within the crystal lattice of larger host metal atoms (frequently transition metals). They are normally rigid, hard materials, such as metallic carbides, nitrides, and hydrides, which considerably improve the strength and magnetic properties of alloys.
Interstitial position – It is also called interstitial site. It is a small, typically unoccupied space located between the atoms of a packed crystal lattice. These voids, usually tetrahedral or octahedral, exist since atoms do not fill 100 % of the volume. Smaller impurity or host atoms can occupy these spaces, creating interstitial defects which considerably affect mechanical properties like strength, hardness, and ductility, as in carbon-strengthened steel.
Interstitial site – It is a small, typically unoccupied void or gap located between atoms within a crystal lattice structure. These sites, classified by geometry (e.g., tetrahedral, octahedral, cubic), allow smaller impurity atoms (like carbon in steel) to reside within the larger host lattice, considerably altering properties such as strength, ductility, and magnetic behaviour.
Interstitial solid solution – It is a type of solid solution which sometimes forms in alloy systems having two elements of widely different atomic sizes. Elements of small atomic size, such as carbon, hydrogen, and nitrogen, frequently dissolve in solid metals to form this solid solution. The space lattice is similar to that of the pure metal, and the atoms of carbon, hydrogen, and nitrogen occupy the spaces or interstices between the metal atoms.
Interstitial solution – It is a type of solid solution where small solute atoms (such as carbon, hydrogen, or nitrogen) occupy the small voids or ‘interstices’ between the larger atoms in a host metal’s crystal lattice, rather than replacing them. This alloy structure, such as steel, strengthens materials by increasing lattice distortion.
Interstitial void – It refers to the empty, unoccupied space located between atoms, ions, or packed particles within a crystal lattice or granular material. These 3D voids account for roughly 26 % of total space in close-packed structures, mainly taking the form of tetrahedral or octahedral shapes.
Interstitial volume – It normally refers to the space, void, or capacity between structural components, particles, or within a lattice structure, frequently filled with fluid, gas, or smaller atoms. It represents a quantifiable, unoccupied, or functional volume (e.g., pore space in soil, or interstitial sites in metal alloys).
Inter-story drift – It is the relative horizontal displacement (sway) between two consecutive floors in a building, typically induced by seismic or wind loads. It is normally expressed as a ratio (Inter-story drift ratio, IDR) of the relative deflection to the story height, used to assess potential damage to non-structural elements and structural integrity.
Inter-symbol interference – It is a digital communication distortion where a transmitted symbol’s energy ‘smears’ into adjacent symbols, causing them to overlap and making them hard to distinguish at the receiver, leading to data errors. It is caused by channel effects like bandwidth limitations, multipath propagation (echoes), and filtering, which distort pulses, making them spread out in time. Inter-symbol interference degrades signal quality, requiring techniques like equalization or pulse shaping to minimize errors.
Inter-system crossing – It is a transition between electronic states which differ in total spin quantum number.
Intertrack porosity – It refers to manufacturing defects in additive manufacturing (3D printing) and welding, characterized by elongated voids located at the interface between adjacent material tracks. These defects, caused by insufficient melting or improper bonding between tracks, typically result from excessive feed rates, low heat input, or poor overlap.
Interval erosion rate – It is the slope of a line connecting two specified points on the cumulative erosion-time curve.
Interval estimate – It is the estimate of a parameter given by two statistics, defining the end points of an interval.
Interval estimation – It is the use of sample data to estimate an interval of possible values of a parameter of interest. This is in contrast to point estimation, which gives a single value.
Interval method – It is a numerical analysis technique using interval arithmetic to compute with ranges of values rather than precise numbers, ensuring solutions incorporate all possible uncertain inputs. It provides guaranteed, rigorous upper and lower bounds for global optimization, structural simulations, and differential equations.
Interval scale – It measures data where differences between values are meaningful and equal (e.g., 10 deg against 20 deg C is same as 20 deg C against 30 deg C), but the zero point is arbitrary (0 deg C is not no temperature). Key examples include temperature (Celsius) and time, allowing addition / subtraction (differences) but not meaningful ratios (20 deg C is not ‘twice as hot’ as 10 deg C). It is the third level of measurement, stronger than ordinal but weaker than ratio scales.
Interval test – It is the method used to test heat extraction rates of various quenchants. This test measures the increase in temperature of a quenchant when a standard bar of metal is quenched for five seconds. Faster quenchants show greater temperature increases.
Interval weights – These refer to a range of values assigned to criteria in multi-criteria decision-making, representing uncertainty, vagueness, or subjective judgment instead of a precise point estimate. They are normally used in the ‘analytic hierarchy process’ (AHP) to model inconsistency in human judgments.
Intervenor – For getting environmental clearance, an intervenor is an individual, group, or organization which formally joins an ongoing, third-party proceeding, such as a facility licensing, regulatory hearing, or legal action, to influence decisions in their favour. They hold a stake in the outcome and seek to protect their rights or interests.
Interview – It is a formal assessment to evaluate a candidate’s technical skills, problem-solving ability, and cultural fit for an engineering role, often involving in-depth technical questions, coding challenges, and discussions about past projects to gauge practical expertise and thought processes beyond just knowledge. It combines general questions about motivation and personality with specific technical scenarios to see how a candidate applies engineering principles to real-world challenges.
Inter-well communication – It refers to the fluid pressure or physical interaction between adjacent wells in a reservoir, frequently caused by natural fractures or hydraulic fracturing. This phenomenon causes interference, where producing from or injecting into one well directly impacts the pressure and production rates of nearby wells.
Interzonal flow – It refers to the movement of mass, energy, or fluids (air, water, steam) between distinct, designated, and interconnected areas or volumes, known as zones. This term is mainly used in building ventilation analysis, HVAC (heating, ventilation, and air conditioning) system modeling, and sub-surface energy engineering (geothermal or oil / gas) to describe how fluid moves through gaps, openings, or porous media from one controlled environment to another.
Intimate blending – It is the process of mixing two or more different types of staple fibres together in the early stages of production (to create a highly uniform, homogeneous mixture. It ensures the final yarn or product combines the specific properties of each fibre, resulting in consistent colour, strength, and particularly within laser physics.
Intracavity dispersion – It refers to the frequency-dependent phase shift or velocity change experienced by light as it propagates through the components inside a laser resonator (cavity), such as gain media, mirrors, or tuning elements. It is the cumulative, round-trip result of material dispersion (refractive index changes with wave-length) and wave-guide / geometrical dispersion (because of the component structure).
Intracavity etalon – It is a device which can control both the mode location and the spacing between modes in a laser cavity, contributing to the stabilization of frequency comb parameters.
Intracoating spallation – It refers to the failure and detachment (flaking or peeling off) of a coating material that occurs within the coating layers themselves rather than at the interface between the coating and the substrate. It is a specific type of failure, commonly studied in thermal barrier coatings (TBCs) and industrial spray coatings, where cracks propagate through the internal micro-structure, causing fragments to break away.
Intracrystalline – It means within or across the crystals or grains of a metal. It is same as transcrystalline and transgranular.
Intracrystalline cracking – It is the cracking or fracturing which occurs through or across a crystal or grain. It is also called transcrystalline cracking.
Intragranular cracking / fracture – It consists of cracks which propagate through the body of a grain (trans-granular) rather than along the boundaries. This is common in brittle fracture and in battery cathode materials (nickel-rich layered oxides) during cycling, where stresses cause cracking within the primary crystal particle
Intragranular crystalline effects – These refer to phenomena, structural changes, or deformation mechanisms which occur inside (intra-) the individual crystal grains of a poly-crystalline material, as opposed to at the grain boundaries (inter-granular). These effects are important in determining the internal strength, deformation behaviour, and failure mechanisms of metals. Key aspects of intragranular crystalline effects include (i) intragranular deformation and strain, (ii) intragranular heterogeneity, (iii) intragranular cracking / fracture, (iv) intragranular precipitation, (v) lattice misorientation. These effects are often studied in contrast to inter-granular effects, which are related to corrosion or fracture along grain boundaries.
Intragranular deformation and strain – It is plastic deformation of metals mainly occurs through the motion of dislocations within the crystal lattice inside the grains, known as slip.
Intragranular heterogeneity – This occurs even within a single grain, and because of it the localized response to stress can vary because of the interaction with neighbouring grains, resulting in non-uniform dislocation distribution and internal strain gradients.
Intragranular precipitation – It the formation of alloying element compounds (precipitates) within the grain bulk, rather than at the grain boundaries, which can considerably harden the material.
Intralaminar – It is descriptive term pertaining to an object (e.g., voids), event (e.g., fracture), or potential field (e.g., temperature gradient) existing entirely within a single lamina without reference to any adjacent laminae.
Intralaminar crack – It is a fracture which initiates and propagates within a single ply or layer (intra-), rather than between layers (interlaminar / delamination). These cracks normally run parallel to the fibres, frequently causing matrix cracking or fibre-matrix debonding, which leads to stiffness degradation and acts as a precursor to delamination.
Intralaminar damage – It is a type of degradation occurring within a unidirectional ply, resulting from fibre / matrix debonding and small cracks within the matrix, which leads to a substantial decrease in stiffness without visible transverse cracking.
Intra-molecular force – It is a force which binds together the atoms making up a molecule. Intra-molecular forces are stronger than the inter-molecular forces which govern the interactions between molecules.
Intranet – It is a private, secure internal network for an organization, using internet technologies to share information, tools, and foster collaboration among employees, distinct from the public internet but frequently featuring modern platforms for digital work-places, project management, training, and internal communication. It acts as a central hub for the organizational resources like human resource (HR) forms, project files, organizational news, and employee directories, accessible only to authorized personnel through secure logins.
Intraply hybrid – It is a composite in which different materials are used within a specific layer or band.
Intricate shape – It refers to a component characterized by complex, high-detail, non-prismatic, or organic geometry, frequently featuring, intricate curves, thin walls, or, non-uniform, sections. These shapes are designed using, computer aided design (CAD) environments, and, typically, need advanced manufacturing techniques like, 3D printing or, precision casting because of their, high, shape complexity index.
Intrinsic adhesion – It refers to the inherent, thermo-dynamic molecular forces of attraction (such as van der Waals forces, hydrogen bonds, and acid-base interactions) acting at the interface between an adhesive and a substrate. It defines the fundamental, theoretical bond strength determined by surface energy, distinguishing it from practical, measured, or mechanical interlocking adhesion.
Intrinsic curvature – it is also called Gaussian curvature It is a fundamental geometric property of a surface measurable from within, without requiring an external reference frame. It defines how the surface deviates from being locally flat, affecting internal measurements like the sum of angles in a triangle (not equal to 180-degree or the circumference of a circle.
Intrinsic dimensionality – It is the minimum number of free parameters or independent variables needed to accurately describe a dataset or represent a system’s behaviour, frequently while minimizing information loss. While data can be recorded in a high-dimensional space (ambient dimension D), it frequently lies on a lower-dimensional structure or surface (manifold) with dimension –‘d’ where ‘d’ is less than ‘D’.
Intrinsic fault – It is a type of planar structural defect in crystalline materials (frequently face centred cubic, FCC metals) caused by the removal of a close-packed atomic plane, disrupting the normal stacking sequence. Unlike extrinsic defects (impurities), these are native to the material’s structure, increasing energy and affecting mechanical behaviour.
Intrinsic healing – It is a process by which certain materials can recover from damage through specific properties like reversible covalent bonds, thermo-reversible physical interactions, or supra-molecular chemistry, with or without external stimuli. This healing mechanism involves the dissociation and reassociation of bonds, enabling materials to restore their original structure and properties after sustaining damage.
Intrinsic kinetics – It refers to the fundamental, true rate of a chemical reaction or molecular process, measured specifically in the absence of external transport limitations like mass or heat transfer. It describes the chemical reaction rate at the molecular level, defining reaction orders, rate constants, and mechanisms, which are necessary for reactor design.
Intrinsic layer – It is an undoped or very lightly doped, high-purity semiconductor region sandwiched between p-type (positive) and n-type (negative) layers, creating a P-I-N structure. It plays a critical role in engineering electronic and opto-electronic devices by acting as a wide depletion region, which allows for improved voltage handling, fast switching, and efficient light absorption.
Intrinsic loss – It refers to the unavoidable, fundamental energy dissipation inherent to a material or device’s physical properties, rather than manufacturing defects or external factors. Examples include Rayleigh scattering in fibre optics, thermodynamic limits in magnetic heating, or switching losses in semi-conductors.
Intrinsic mode function – It is a fundamental, oscillating component derived from ‘empirical mode decomposition (EMD) of non-stationary, nonlinear signals. An intrinsic mode function is required to satisfy two conditions: the number of extrema and zero-crossings are to be equal or differ by at most one, and the mean value of its upper / lower envelopes are to be zero.
Intrinsic nature – It refers to the essential, inherent, and inseparable properties of a material or system which exist independently of external, environmental factors. These innate characteristics, such as density, chemical composition, or crystal structure, do not change based on how the object is measured or its surroundings.
Intrinsic parameters – These are the internal, inherent characteristics of a camera sensor and lens system which determine how a 3D point in the physical world is projected onto a 2D image plane. Unlike extrinsic parameters, which define a camera’s location and orientation (pose) in the world, intrinsic parameters are fixed to the camera itself, regardless of where it is pointing. In computer vision, these parameters are necessary for tasks like 3D reconstruction, robot navigation, and augmented reality, as they allow for the translation of pixel coordinates into spatial measurements.
Intrinsic permeability – It is a fundamental engineering property of a porous medium (soil, rock, or material) which quantifies its ability to transmit fluids, independent of the fluid’s properties (like viscosity or density). It depends solely on the internal geometry, structure, and connectivity of the pores.
Intrinsic phase – It refers to the inherent, bulk material structure or state, such as a specific crystal lattice, atomic arrangement, or material property (density, melting point), which exists independently of size, shape, or external boundaries. It defines the fundamental, characteristic state of a material in its pure form or its default structural state (e.g., crystalline, amorphous) before any external processing, impurities (doping), or boundary conditions are applied.
Intrinsic point defects – These are zero-dimensional, thermodynamic, or stoichiometric flaws within a pure crystal lattice which occur naturally because of the configurational entropy, needing no impurities. These imperfections involve missing atoms (vacancies), extra atoms in non-lattice sites (interstitials), or shifted atoms (anti-sites), which affect material electrical, optical, and mechanical properties.
Intrinsic property – It is a property of a specified subject which exists itself or within the subject. For example, mass is an intrinsic property.
Intrinsic sensor – It is a sensing device where the transducer element is integrated directly into the transmission medium or structure being monitored, rather than being attached externally. Normal in fibre optics, these sensors use the fibre itself to detect environmental changes (pressure, temperature, strain) by modulating light characteristics, such as phase, intensity, or polarization, directly within the fibre core.
Intrinsic stacking fault – It is a planar crystallographic defect where a single atomic layer is missing from the normal stacking sequence of a crystal, such as ABCBCA instead of ABCABC in FCC (face centred cubic) metals. It represents a local interruption in the atomic plane sequence frequently caused by vacancy agglomeration, thermal fluctuations, or partial dislocation movement, acting as an important defect influencing deformation mechanisms.
Intrinsic stress – It refers to internal, non-thermal stresses which develop within a material, typically thin films or coatings, during its deposition or growth process. Unlike thermal stress, it results from structural changes, such as microstructural evolution, grain boundary formation, or atomic bombardment, which cause volume changes which are constrained by the substrate.
Intrinsic test – This test refers to a subjective assessment used to determine if two works are substantially similar in their overall concept and feel, focusing on the perspective of an ordinary, reasonable observer. If the extrinsic test (analyzing specific, objective elements) is met, the intrinsic test is then used to decide if the similarity is substantial enough to constitute infringement.
Intrinsic thermal resistance (Rcf) – It measures a material’s inherent ability to impede heat flow per unit area, defined as the ratio of the temperature difference across the material to the heat flux (Rcf = delta T//Q). It represents the bulk, material-specific resistance excluding interfacial contact or boundary layer effects.
Intrinsic viscosity [η]- It is a measure of a solute’s contribution to the viscosity of a solution. It a dimensionless number.
Intrusion – It refers to the unauthorized, unintentional, or forced penetration of a system, space, or material, frequently compromising its integrity or safety. The definition varies considerably based on the engineering discipline, mainly covering cyber-security and physical domains / mechanical domains. It also consists of body of igneous rock which invades older rocks.
Intrusive – It is a body of igneous rock formed by the consolidation of magma intruded into other rocks, in contrast to lavas, which are extruded upon the surface.
Intumescence – It means the swelling or bubbling of a coating normally because of heating (term currently used in space and fire protection applications).
Intumescent flame retardants – These are eco-friendly, halogen-free additives or coatings which swell up upon exposure to heat or fire, forming a thick, porous, carbonaceous char layer. This insulating barrier protects underlying structural materials (polymers, steel, wood) by reducing heat transfer, preventing oxygen access, and inhibiting ignition.
Invalidate – It refers to the process of declaring that a previously accepted result, model, calculation, or component is no longer accurate, valid, or functional. It signifies that data has become obsolete, or that a design assumption has proven false, needing a re-evaluation or update.
Invar – It is a nickel–iron alloy notable for its uniquely low coefficient of thermal expansion. Invar is a solid solution, i.e., it is a single-phase alloy.
Invariant case – It focuses on the systematic identification, definition, and enforcement of logical constraints (invariants) which are to hold true throughout the entire execution or lifetime of a system. Invariants are ‘sanity clauses’ that, when properly engineered, allow engineers to prove programme correctness, improve debuggability, and ensure system reliability by identifying exactly which component is at fault when a constraint fails.
Invariant equilibrium – As per the phase rule, three phases can exist in stable equilibrium only at a single point on a urinary diagram. In a hypothetical urinary pressure-temperature diagram, the three states (or phases) i.e., solid liquid and gas are represented by three correspondingly fields. Stable equilibrium between two phases occurs along their mutual boundary, and invariant equilibrium among all three phases occurs at the so-called triple point where three boundaries intersect. This point is also called an invariant point because, at that location of the diagram, all externally controllable factors are fixed (no degree of freedom). At this point, all the three phases are in equilibrium, but any changes in pressure / temperature causes one or two of the states (phases) to disappear.
Invariant-plane strain – It is a type of displacive phase transformation (such as martensite or bainite formation) where the interface between the parent (austenite) and product (martensite) phases (known as the habit plane) remains undistorted and unrotated during the transformation. It is a shape deformation which can be described as a combination of a shear component (frequently 0.22 to 0.26 magnitude) and a dilatational (volume change) component (frequently 0.02 to 0.03 magnitude).
Invariant point – It is a specific point which remains unchanged or unmoved after a coordinate transformation, such as reflection, rotation, or scaling (e.g., the centre of rotation). In thermodynamics, it refers to a specific, fixed pressure condition / temperature condition where multiple phases coexist with zero degrees of freedom. Invariant points in phase diagram represent invariant reactions.
Invariant property – It is a characteristic, quantity, or condition of a system, material, or model which remains unchanged (constant) despite specific transformations, operations, or coordinate system changes. These properties are important for simplifying analysis, ensuring system stability, and verifying algorithm correctness.
Invariant reaction – In a binary alloy, it is one which occurs when three phases are in equilibrium. Application of the Gibbs phase rule to this system under constant pressure conditions indicates that it has no degrees of freedom and, hence, the composition of the phases and the temperature of the reaction are all fixed. Hence, invariant reactions occur only at particular conditions of concentration, temperature, and pressure etc. In binary systems, there are several invariant reactions. Eutectic, peritectic, monotectic, peritectoid and eutectoid reactions are all invariant reactions which take place at an invariant temperature for the system.
Invariant relationship – It is a condition, predicate, or logical assertion which remains true throughout the execution of a process, algorithm, or over the lifetime of a system component, regardless of how the system transforms.
Invariant set – It is a sub-set of the state space where any trajectory starting within the set remains inside it for all future time. If the system is initialized inside an invariant set ‘S’, its behaviour is confined to ‘S’ indefinitely.
Invariant subspace – It is a subset ‘W’ of a vector space ‘V’ which remains unchanged (maps into itself) under a linear operator T: V -> V, meaning T-invariant subspace ‘w’ for every vector ’W’ is an element of set ‘W’. This simplifies system analysis (e.g., control systems, vibration) by decomposing complex operators into block-diagonal or block-triangular forms, isolating specific dynamic behaviours.
Invariant system – It is a system where a shift or delay in the input signal produces a corresponding, identical shift in the output signal, with the system’s internal characteristics remaining constant over time. If input ‘x(t)’ produces output ‘y(t)’, then ‘x(t – a)’ produces ‘y(t -a)’.
Invariant theory – It studies algebraic expressions, properties, or system characteristics which remain constant (invariant) despite undergoing specific transformations, such as rotations, translations, or coordinate changes. It identifies essential, stable features, like distance, volume, or system behaviour, which are independent of the viewpoint or operating conditions.
Inventory – In an organization there are stock of finished products, semi-finished products, in process materials raw materials, spare parts, operating parts, fuels, and consumables. The collective name of these entire items is inventory. The organization holds the inventory for the ultimate goal of sale, production, or utilization. Inventory management is a discipline primarily about specifying the shape and placement of stocked goods.
Inventory analysis – It is the systematic, data-driven evaluation of stock levels, material flows, and production demand to optimize inventory, minimize waste, and streamline supply chain efficienc=y. It involves analyzing inventory composition, turnover, and holding costs, often utilizing techniques like ABC (A, B, and C categories), HML (high, medium, low), or SDE (scarce, difficult, easy) analysis.
Inventory control – It is the systematic process of regulating raw materials, work-in-progress, and finished goods to maintain optimal stock levels. It ensures high operational efficiency by balancing customer demand against storage costs, using techniques like ‘economic order quantity’ (EOQ) to avoid stockouts or overstocking.
Inventory cost – It represents the total expenses associated with ordering, holding, and managing stock, including capital tied up in materials, storage, insurance, and risk of obsolescence. These costs are critical for determining economic order quantities (EOQ) to minimize total expenditure while ensuring production continuity.
Inventory holding costs – These are the total expenses incurred for storing unsold goods over a specific period, typically 15 % to 30 % of total inventory value. This includes capital, storage space, services (taxes / insurance), and inventory risk (obsolescence / damage). These costs are important critical for calculating economic order quantities (EOQ) and optimizing inventory levels to prevent excessive capital from being tied up in stock.
Inventory levels – These levels define the precise quantity of raw materials, work-in-process (WIP), and finished goods stored at any given time within a production or supply chain network. It acts as an important buffer between supply and demand, with optimal levels minimizing storage costs and preventing stockouts.
Inventory management – It involves systematically tracking, organizing, and optimizing the stock of spare parts which are used in an operating plant for ensuring efficient maintenance, minimizing downtime, and improving overall operational reliability.
Inventory planning – It is the strategic, data-driven process of determining the optimal quantity, location, and timing of stock to meet demand while minimizing total costs and maximizing operational efficiency. It acts as a bridge between demand forecasting and daily operations, using mathematical models to determine how much inventory to hold (raw materials, work-in-progress, or finished goods) to avoid both stockouts and over-stocking.
Inventory reduction – It is a strategic process of minimizing on-hand stock levels, including raw materials, work-in-progress, and finished goods, to improve operational efficiency, reduce holding costs, and improve cash flow. It involves optimizing inventory levels to match actual demand, hence reducing waste and preventing obsolescence.
Inverse analysis for flow stress and friction determination – It is a computational method which uses experimental data (like loads, displacements, or geometry changes) from metal forming tests, compares them to ‘finite element method’ (FEM) predictions, and iteratively adjusts material / friction parameters (flow stress, friction coefficient) until the model accurately matches reality, efficiently finding material behaviour (flow stress) and interface conditions (friction) simultaneously, especially in complex processes.
Inverse analysis method – It is an iterative computational technique used to determine unknown system parameters (material properties, boundary conditions, loads) by minimizing the difference between experimental measurements and numerical model outputs. It reverses the standard modeling approach to infer causes from observed effects.
Inverse boundary problem – It is the process of determining unknown boundary conditions (such as heat flux, traction, or geometry) by using known, measured data from the interior or another part of the system’s boundary. Unlike forward problems, these are normally ill-posed, requiring specialized optimization techniques to ensure stability and uniqueness.
Inverse calculation – It is the process of determining unknown input parameters, causes, or physical properties of a system by analyzing its measured output data. It reverses the ‘forward problem’ (calculating effect from cause) to infer hidden, difficult-to-measure parameters, such as identifying material defects from surface scans or reconstructing internal structures in imaging.
Inverse chill – It is the condition in a casting section in which the interior is mottled or white, while the other sections are gray iron. It is also known as reverse chill, internal chill, and inverted chill.
Inverse control – It is a control technique which uses the mathematical inverse of a system’s dynamic model as a controller to achieve desired performance. It works by cancelling out non-linearities in the plant’s dynamics to achieve decoupling, improving control accuracy and managing actuator behaviour.
Inverse design – It is a methodology which starts with desired performance requirements (outputs) and uses optimization algorithms or machine learning to determine the necessary physical parameters (inputs), such as geometry or material composition, to meet those goals. Unlike traditional forward design, which iterates by testing structures, inverse design automates finding the optimal solution, frequently using gradient-based methods or generative AI (artificial intelligence) to solve complex, nonlinear design problems.
Inverse design process – it is a method which involves two main processes namely (i) an analysis process for flow simulation, and (ii) a design process which solves inverse problems to modify geometry. It aims to achieve a target pressure distribution by iteratively correcting the geometry until design requirements are met.
Inverse discrete Fourier transform – It is a fundamental digital signal processing technique which converts a signal from its frequency-domain representation ‘X( k)’ back into the time-domain or spatial-domain sequence ‘x(n)’. It is the inverse operation of the ‘discrete Fourier transform’ (DFT), important for reconstructing processed signals, such as in digital filtering or communication systems.
Inverse dynamic problem – It determines the necessary forces, torques, and joint moments needed to produce a specific motion (trajectories, velocities, accelerations) of a rigid body or multi-body system, given its kinematics and inertial properties. It acts as a bridge between known kinematic motion and the necessary driving forces, used in robotics for control.
Inverse fast Fourier transform – It is an efficient algorithm that reverses the Fourier transform, converting a signal from the frequency domain (showing frequency components) back to the time domain (the original signal), reconstructing the actual wave-form by summing its constituent sinusoids. It is important for tasks like signal reconstruction, digital communications, and audio processing.
Inverse filter – It is a signal processing technique used to reverse the effects of a known degrading process (such as blurring, distortion, or channel noise) and reconstruct the original signal or image. It operates by applying the inverse of the distortion function, frequently in the frequency domain, to cancel out the degradation.
Inverse form – It refers to a systematic approach where desired performance outputs or observed effects are used to determine the necessary input parameters, system properties, or geometry. It is the reverse of ‘forward’ modeling, which predicts effects from causes.
Inverse Fourier transform – It is a mathematical operation that converts a signal from the frequency domain F(w) or F(f) back into the time domain f(t). It reverses the Fourier transform.
Inverse function – It reverses the action of a given function ‘f(x) = y’, mapping the output ‘y’ back to the original input ‘x’. This ‘undoes’ a process (e.g., finding time from speed / distance), mapping unique outputs back to unique inputs, necessary for solving for unknown initial conditions.
Inverse gas chromatography – It is a versatile, sensitive, and non-destructive thermo-dynamic technique used to characterize surface and bulk properties of solids (powders, fibres, films). Unlike conventional gas chromatography (GC), the solid sample is packed into a column (stationary phase), while known vapour probes pass through to measure surface energy, adsorption isotherms, and phase transitions.
Inverse heat conduction problem solution – It is a technique for calculating unknown surface heat flux or temperature histories by using measured internal temperature data from a solidifying or quenching component. It resolves ‘ill-posed’ mathematical problems where boundary conditions are unknown, relying on methods like Beck’s sequential algorithm to stabilize results against noisy sensor data.
Inverse image – Inverse image of a sub-set ‘A’ under a function f:X -> Y is the set of all elements in the domain ‘X’ which map into ‘A’. It represents the inputs needed to produce specific output behaviours and exists for any function, not just invertible ones.
Inverse iteration – It is a numerical linear algebra algorithm used to compute an approximation to an eigenvector (v of a matrix (A), specifically the eigenvector corresponding to the eigenvalue (lambda) closest to a given shift value (sigma). It is particularly valuable for finding the lowest eigenvalue / eigenvector (natural frequencies and mode shapes) of large, sparse matrices, as it converges to the eigenvalue closest to the shift ‘sigma’.
Inverse kinematics – It is a technique used in robotics to calculate the necessary joint angles and parameters needed to position a robot’s end-effector (tool or hand) at a specific Cartesian coordinate (‘x’, ‘y’ ‘z’) and orientation. Unlike forward kinematics, which calculates end position from joint angles, inverse kinematics (IK) reverses this to determine motion from a desired target.
Inverse Laplace transform – It is a mathematical operation that converts a function of a complex variable ‘F(s)’ (frequency domain) back into a function of time ‘f(t)’. It is the reverse of the Laplace transform used to solve linear differential equations, analyze control systems, and reconstruct signals.
Inverse matrix – It is a matrix which, when multiplied by the original matrix, yields the identity matrix. For square matrices, this inverse is unique and is called the two-sided inverse, while for rectangular matrices, it can have generalized left or right inverses which produce the identity matrix when multiplied from the left or right, respectively.
Inverse method – It is a computational technique used to determine unknown causes, system parameters, or input data by analyzing observed consequences, effects, or output data. It is the reverse of direct modeling (predicting effects from known causes) and is necessary for calibrating models, identifying material properties, and optimizing designs based on experimental data.
Inverse mode – It is the process of calculating unknown causes, such as system parameters, material properties, or initial conditions, from observed system outputs or effects. Unlike forward problems which predict outputs from known inputs, this approach estimates parameters like structural stiffness, shape, or density from measurements.
Inverse modeling – It is a process which infers the causes of a system’s behaviour by using observations and a mathematical or mechanistic model. It is used when certain parameters are difficult to measure directly, and it aims to estimate these parameters from known outputs or responses. Essentially, it is the process of working backward from observed effects to determine the underlying causes or parameters that produced them.
Inverse residual stress problem – It is a mathematical and numerical approach used to determine the unknown, complex, and ‘locked-in’ stress state within a material by using measurable surface deformations or strains as input data. Unlike the ‘forward problem’, which predicts residual stresses based on known manufacturing histories (welding, quenching, the inverse approach acts as a reconstruction technique, frequently necessary since direct measurement of internal stress is difficult or impossible.
Inverse scattering problem – It is the process of determining the physical properties (shape, size, material composition, or location) of an unknown, hidden object by analyzing the scattered waves (sound, light, electro-magnetic) it produces when hit by a known incident wave. It reverses the direct scattering problem, which calculates waves from a known object.
Inverse segregation – It is a concentration of low-melting constituents in those regions of an alloy in which solidification first occurs. It is a concentration of certain alloy constituents which have lower melting points in the region corresponding to that first solidifying. It is caused by interdendritic flow of enriched liquid through channels where the pressure drops with contraction of dendrites. The internal evolution of hydrogen can also give a positive pressure, aiding this flow and causing a liquidated surface as tin sweat.
Inverse sensitivity analysis – It determines how much system inputs (parameters, design variables) need to change to achieve a desired output (response, performance), basically reversing the standard sensitivity analysis which shows output changes from input variations. It helps in model calibration, parameter estimation, and identifying critical measurements for accurate predictions. It quantifies the Cause-and-Effect in reverse, finding the parameters that are most sensitive to output errors, guiding engineers to adjust inputs or improve sensor precision.
Inverse solution – It is also called inverse method / problem. It is a mathematical technique used to determine unknown, hard-to-measure input parameters, boundary conditions, or material properties by analyzing known, directly observable outputs or experimental data. It is the opposite of a forward problem (or direct problem), which starts with known causes (parameters) to calculate the final effects (outputs).
Inverse square – It refers to a principle in dosimetry which describes how the dose of radiation decreases with the square of the distance from the radiation source to the detector, which is validated through measurements involving a farmer-type ion chamber and different source-to-detector distances.
Inverse square law – It dictates that the intensity of a physical quantity (such as radiation, light, or signal strength) from a point source decreases proportionally to the inverse square of the distance from that source (I) is proportional to 1/ r square). It signifies that doubling the distance reduces the intensity to one-quarter.
Inverse square root singularity – It refers to the characteristic behaviour of stress and strain fields near a crack tip in linear elastic fracture mechanics, where these fields are defined by an inverse square-root mathematical relationship.
Inverse system – It is a controller or mapping which reverses the operation of a main plant, outputting the original input when fed the plant’s output. It enables exact tracking, decoupling of complex systems, and is necessary for designing high-performance controllers, frequently implemented as an alpha-order integral inverse system.
Inverse tangent – It is the function which computes the angle whose tangent is a given number. The returned value is in radians and ranges between −pi/2 and pi/2.
Inverse transform – it is a mathematical operation which reverses a forward transformation (such as Laplace, Fourier, or Z-transform) to convert a function from a transformed domain (frequency s-domain) back to its original domain, typically the time domain ‘t’. It is necessary for analyzing systems, interpreting data, and solving differential equations by returning frequency-domain results to time-dependent behaviour.
Inverse transformation -It reverses a mathematical process, converting a function or signal from a transformed domain (like frequency or ‘s’-domain) back to its original form (like time-domain), enabling analysis and recovery of original data, commonly seen in Fourier (frequency to time) and Laplace (s-domain to time) transforms for solving systems. It basically undoes an operation to find the original input from the modified output.
Inversion – It means a reversal of position, order, or relationship. It is the act or process of inverting. It refers to inversion casting, a casting process where a mould is inverted after the outer surfaces have hardened, allowing molten metal to drain off. It also means inversion of a phase which refers to a change in the stability of a material’s phase, such as a solid-liquid phase transition. This can occur due to changes in temperature, pressure, or the presence of other substances. In meteorology, an inversion is a phenomenon in which a layer of warmer air overlies cooler air. Normally, air temperature gradually decreases as altitude increases, but this relationship is reversed in an inversion.
Inversion analysis – It is a method of back-analysis where internal parameters (like stress or load) are determined from external observations (like displacement or strain).
Inversion casting – It involves creating a mould, normally ceramic around a wax pattern, then inverting it to drain molten wax out, leaving a cavity, and subsequently pouring molten metal into this inverted mould before it solidifies, offering precise, complex shapes with smooth finishes. Key features include bottom feeding, preventing oxidation by enclosing metal in furnace during pouring, and eliminating heavy risers, ideal for high-strength alloys like steel.
Inversion, kinematic mechanism – It is the process of fixing different links in a kinematic chain to create new mechanisms from the same set of links. For example, fixing a different link on a four-bar mechanism produces distinct, functional linkages.
Inversion, mechanism – It is a method of getting different mechanisms by fixing different links in a kinematic chain.
Inversion method – It is a technique which determines unknown input parameters or physical causes by analyzing observed output data, consequences, or system behavior. Unlike direct methods which predict outputs from inputs, this approach works backward to solve ill-posed problems, —where solutions may not exist, be unique, or are highly sensitive to change.
Inversion, phase – Inversion of phase occurs in liquid-liquid emulsions (like oil and water) when the continuous phase and dispersed phase switch roles.
Inversion point – It normally refers to the critical condition at which a system, phase, or process reverses its behaviour, switches characteristics, or changes its continuous phase.
Inversion pressure – It is the pressure at which a gas undergoing Joule–Thomson throttling (isenthalpic expansion) experiences zero temperature change, marking the transition between heating and cooling regimes. It defines the point where the Joule-Thomson coefficient changes sign.
Inverse problem – It is a computational or experimental technique used to infer the parameters of a model from observed data (e.g., determining soil resistivity from surface measurements).
Inversion technique – It normally refers to reversing a process, mechanism, or data flow to achieve a new configuration, solve inverse problems, or optimize systems. Key applications include kinematic linkage re-fixing, membrane fabrication through phase separation, and using output data to determine input parameters.
Inversion temperature – It is the critical point at which a gas’s Joule-Thomson coefficient changes sign, meaning it switches from cooling to heating upon expansion. Below this temperature, a real gas cools during adiabatic expansion; above it, the gas heats up.
Inversion thinking – It is also called inversion design. It is a problem-solving strategy, frequently known as a ‘pre-mortem’, where engineers focus on how a design can fail to uncover blind spots and prevent errors.
Inverted dies – These dies refer to a die setup where the punch is mounted on the press bed (lower die) and the die block is mounted on the slide (upper die). This configuration is opposite to the more common ‘drop through’ die setup where the blank falls through the die. Inverted dies frequently need knockout devices to remove the blank from the die.
Inverted microscope – It is a microscope which is so arranged that the line of sight is directed upward through the objective to the object.
Inverted pendulum – It is a non-linear, inherently unstable mechanical system with its centre of mass located above its pivot point, needing active, continuous control to maintain an upright position. It is a under-actuated mechanical system which needs continuous control to maintain its upright position. It serves as a benchmark for training and validating new control strategies in robotics and control theory. It is frequently mounted on a movable cart.
Inverted swaging – It is also called internal swaging. It is a metal-working process used to expand or form metal by applying pressure from the inside out, frequently to create a secure, leak-proof, or strengthened connection in tubes or hoses.
Inverter – It is a power electronic device or circuitry which changes direct current (DC) to alternating current (AC). The resulting alternating current frequency achieved depends on the particular device used. Inverters do the opposite of rectifiers. The input voltage, output voltage and frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the direct current source. A power inverter can be entirely electronic or can be a combination of mechanical effects (such as a rotary apparatus) and electronic circuitry. Static inverters do not use moving parts in the conversion process. In a conveyor system, an inverter is a device used to control the speed of a conveyor motor, necessitating periodic checks for proper calibration and functionality.
Inverter-based resources -These are power generation or storage systems, such as solar PV (photo-voltaic), wind, and battery storage, which connect to the grid via power electronic converters (inverters) rather than synchronous generators. These systems lack physical inertia and are defined by fast, software-controlled responses, enabling rapid grid support but introducing stability challenges. Engineering inverter-based resources involves managing their non-synchronous, fast-acting nature, with a focus on grid-following or grid-forming capabilities and adherence to standards.
Inverter drive – It is a drive system which utilizes an inverter to control the speed of the conveyor motor, demanding regular inspections for calibration and efficiency.
Inverter efficiency – It is the ratio of alternating current (AC) output power to direct current (DC) input power, measuring how effectively an inverter converts direct current energy (e.g., from solar panels or batteries) into usable alternating current power. Typical high-quality inverters operate at 90 % 95 % plus efficiency, with losses normally emitted as heat, directly impacting system energy yield, return on investment (ROI), and component life-span.
Inverter motor – It is a motor designed to work with an inverter for variable speed control, requiring periodic checks for proper functionality and alignment.
Invertibility – It defines a system where the unique input signal can be fully recovered from its output, implying a one-to-one mapping. It needs the existence of an inverse system (cascade) which compensates for distortion, such as an equalizer in communications. It is necessary for reversing transformations in signal processing and control.
Invertible matrix – It is a square ‘n x n’ matrix ‘A’ for which there exists a unique matrix ‘B’ (denoted by ‘A to the power -1’) such that ‘AB = BA = I’, where ‘I’ is the ‘n x n’ identity matrix. It represents a reversible transformation where the determinant ‘det (A) is not zero’ and all columns are linearly independent. It is important for solving engineering systems.
Invertible tensor (A) – It is a second-order tensor for which a unique inverse tensor ‘B’ (A to the power -1) exists, satisfying the relationship ‘AB = BA =I’, where ‘I’ is the identity tensor. Invertibility needs the tensor’s determinant to be non-zero, allowing the recovery of input, frequently used in stress-strain constitutive equations.
Inverting amplifier – It is an electronic circuit which produces an output voltage with a polarity opposite to that of the input voltage, characterized by an amplification factor which can be controlled by varying feedback and input resistances.
Inverting operational amplifier – It is a closed-loop circuit configuration where the input signal is applied to the negative (inverting) terminal, producing an amplified output 180-degree out of phase with the input. It utilizes negative feedback, typically through a resistor from output to the inverting input, creating a virtual ground at the terminal.
Inverting terminal – It denoted by a negative sign (-). It is one of the two differential input terminals on an operational amplifier (operational amplifier, op-amp). It receives the input signal in an inverting amplifier configuration, producing an output 180-degree out of phase with the input. It is typically associated with a ‘virtual ground’.
Invert level – It is the base interior level of a pipe, trench or tunnel. It can be considered the ‘floor’ level. The invert is an important datum for determining the functioning or flowline of a piping system. Conversely, the obvert level is the highest interior level, and can be considered the ‘ceiling’ level, being the highest level.
Investigation process – It is a systematic, evidence-based approach to analyzing failures, incidents, or system performance to identify root causes and establish preventive measures. It involves gathering data, conducting tests / simulations, and applying engineering principles to determine why a component or system failed to function as intended.
Investing – In investment casting, it is the process of pouring the investment slurry into a flask surrounding the pattern to form the mould.
Investment – It is a flowable mixture, or slurry, of a graded refractory filler, a binder, and a liquid vehicle which, when poured around the patterns, conforms to their shape and subsequently sets hard to form the investment mould. It also means committing capital (money, resources) to projects or assets (equipment, infrastructure, research and development) expecting future returns, growth, or cost savings, analyzed using engineering economics for viability (net present value, internal rate of return). It involves systematic evaluation of costs (fixed capital, operational) versus benefits, applying engineering principles to manage risk and optimize outcomes, differentiating from simple saving by aiming for wealth growth over time, not just preservation.
Investment casting – It is the casting metal into a mould produced by surrounding, or investing, an expendable pattern with a refractory slurry coating which sets at room temperature, after which the wax or plastic pattern is removed through the use of heat prior to filling the mould with liquid metal. It is also called precision casting or lost wax process. It is a part made by the investment casting process. In investment casting, a ceramic slurry is applied around a disposable pattern, normally wax, and allowed to harden to form a disposable casting mould. The term disposable means that the pattern is destroyed during its removal from the mould and that the mould is destroyed to recover the casting. There are two distinct processes for making investment casting moulds namely the solid investment (solid mould) process, and the ceramic shell process. The ceramic shell process has become the predominant technique for engineering applications, displacing the solid investment process. Today the solid investment process is primarily used to produce dental and jewelry castings and has only a small role in engineering applications, mostly for non-ferrous alloys. Investment casting can produce parts of similar geometric shapes and size. Since the disposable pattern is made by injecting wax into a mould, features which are difficult or costly to injection mould or die cast (e.g., undercuts) are also costly to investment casting. Investment casting is typically used when low production volumes are expected (e.g., less than 10,000 pieces).
Investment casting process – It is a pattern casting process in which a wax or thermo-plastic pattern is used. The pattern is invested (surrounded) by a refractory slurry. After the mould is dry, the pattern is melted or burned out of the mould cavity, and molten metal is poured into the resulting cavity.
Investment compound – It is a mixture of a graded refractory filler, a binder, and a liquid vehicle, which is used to make moulds for investment casting.
Investment moulding – It is the process which is also known as the lost wax process. Moulds are produced by dipping wax or thermoplastic patterns in a fine slurry to produce as smooth a surface as possible. The slurry is air dried and redipped several times using cheaper and coarser, more permeable refractory until the shell is of sufficient thickness for the strength needed to contain molten metal. Investment moulds also are produced as solid moulds by putting the pattern assembly in a flask, which is then filled with a refractory slurry and air dried. The moulds then are put into a furnace where the wax or plastic is melted and burned out of the mould cavity. Molten metal is poured into the moulds while the moulds are still superheated, hence making it possible to pour very thin wall sections. A metal pattern die is used to produce the wax or plastic expendable patterns. Investment moulding produces casting of superior surface finish, dimensional accuracy, and without parting fins or seams. This process is expensive and is used to produce parts which are very difficult or impossible to machine, such as turbine engine parts, particularly high-temperature, heat-resistant alloy applications such as turbine blades.
Investment pre-coat – It is an extremely fine investment coating applied as a thin slurry directly to the surface of the pattern to reproduce maximum surface smoothness. The coating is surrounded by coarser, cheaper, and more permeable investment to form the mould.
Investment review board – In project management context, it is a governing body responsible for overseeing the entire lifecycle of capital investments. It ensures that projects align with strategic goals, adhere to budgets, manage risks, and meet performance milestones.
Investment shell – It is the ceramic mould got by alternately dipping a pattern set up in dip coat slurry and stuccoing with coarse ceramic particles until the shell of desired thickness is achieved.
Inviscid core – It refers to a region within a fluid flow, usually located away from solid boundaries, where viscous (frictional) and turbulent effects are negligible compared to inertial forces. While no real fluid has zero viscosity, the inviscid core acts as an idealization where the Navier-Stokes equations can be simplified to the Euler equations or potential flow equations because viscous shear stresses are practically zero.
Inviscid flow – It is an idealized fluid flow model where viscosity (internal friction) is assumed to be zero or negligible, frequently applied to high-Reynolds-number, external flows far from solid boundaries. It simplifies complex Navier-Stokes equations into Euler equations, normally used for aerodynamics.
Inviscid fluid – It is a theoretical, ideal fluid with zero viscosity (mu = 0), meaning it experiences no internal friction, shear stress, or resistance to deformation. Used in engineering to simplify complex fluid dynamics, this concept assumes energy loss is negligible and is governed by the Euler equations rather than Navier-Stokes equations.
Invisible costs – These costs are also known as hidden costs. These are the costs which are not visible to the management. These costs are expenses which are not apparent or accounted for in a budget. They frequently arise from inefficiencies, oversight, or unexpected events, making them harder to spot.
Invitation to bid – It is a formal procurement document issued by a buyer to receive bids from potential vendors for a specific product or service, focusing on price and adherence to specified requirements.
Invoice – It is a formal, itemized, and time-stamped document sent by a supplier, consultant, or contractor to a customer to request payment for professional services rendered or technical goods provided. It acts as a legal document establishing a record of transaction, outlining the scope of work completed, the total quantity due, and specific payment terms.
Involute curve – It is the locus of a point on a taut string as it is unwrapped from (or wrapped around) a stationary curve, normally a base circle. It represents the path traced by the tip of a string as it is unwound. Involutes are primarily used in gear tooth profiles to ensure constant velocity ratio and efficient energy transmission.
Involute gear – It is a type of gear where the teeth profiles are designed using an involute curve, which is generated by tracing the path of a taut string as it unwinds from a base circle. This design ensures constant rotational speed, smooth power transmission, and efficient operation.
In-wall batter – It is the negative slope of in-wall expressed numerically as the base of a right triangle whose altitude is 300 millimeters and whose hypotenuse is the slope of the in-wall.
Inwall brick – It is the refractory lining of the inwall section of blast furnace or cupola.
Inward-flow radial turbine – It is a turbomachine where working fluid (gas or liquid) flows radially inward from the circumference towards the centre of the rotor, reversing direction to exit axially. It acts similarly to a reversed centrifugal compressor, commonly used for high-pressure, low-mass flow, and smaller load applications like turbo-chargers and small gas turbines.
Iodide – It consists of compounds with iodine in formal oxidation state -1. Iodide is one of the largest monatomic anions. Majority of the iodide salts are soluble in water, but frequently less so than the related chlorides and bromides. Iodide, being large, is less hydrophilic compared to the smaller anions.
Iodine – It is a chemical element. It has symbol ‘I’ and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid. It melts to form a deep violet liquid at 114 deg C, and boils to a violet gas at 184 deg C.
Iodine molecule (I2) – It is a non-polar, diatomic halogen composed of two iodine atoms covalently bonded, forming violet-black, lustrous crystals with a molecular weight of 253.81 grams per mol. It is defined by weak intermolecular London dispersion forces, low solubility in water, and substantial reactivity as a weak Lewis acid.
Iodine number – Iodine number is the measure of the degree of the unsaturation of the lubricating oil. It is the amount of iodine, in grams, which is taken up by 100 grams of the oil. It determines the extent of contamination of oil. Each type of the lubricating oil has its specific iodine number. Low iodine number is desirable in oils.
Iodine process – It is a process used for ultrapure titanium (Ti) production and involves the decomposition reaction of titanium iodides. In this process, for example, titanium sub-iodide is produced by reacting raw titanium with titanium tetra-iodide (TiI4). Ultrapure titanium is produced by disproportionation reaction of the titanium sub-iodides on the heated filament. The disproportionation reaction of TiI2 can be written as 2TiI2(s,g) = Ti4 (g) + Ti (s). The iodine process can be applied to other metals, including zirconium, iron, and chromium. Although the process has advantages for the production of high-purity metals, it also has the drawback of low productivity. This is since the reaction is pyrolysis on a solid / gas interface, which limits the production rate.
Iodine production process – It involves the extraction and purification of elemental iodine (I2) from natural sources, mainly underground brines and caliche ore, using reduction-oxidation chemistry. The two main commercial processes are the blowing-out method (used for brines) and the ion exchange resin method (used for smaller-scale or lower-concentration sources).
Iodine transfer polymerization – It is a controlled radical polymerization (CRP) method utilizing degenerative iodine transfer to create polymers with narrow molecular weight distribution, frequently in bulk, solution, or emulsion. It uses an alkyl iodide (R-I) transfer agent with a radical initiator to generate living, end-functionalized chains, offering a metal-free alternative to techniques like atom transfer radical polymerization (ATRP).
Iodine value – it is a metric quantifying the degree of unsaturation in fats, oils, or waxes, defined as the grams of iodine absorbed per 100 grams of sample. It measures carbon-carbon double bonds, indicating chemical stability, susceptibility to oxidation / rancidity, and is used to classify oils into drying, semi-drying, or non-drying types for applications in fuels and coatings.
Iodonium salts – These are hypervalent iodine(III) compounds acting as highly efficient cationic photo-initiators, photoacid generators (PAGs), and polymerization initiators in engineering applications, particularly for ultra-violet (UV) curable coatings, adhesives, and electronics. They are valued for providing strong Bronsted acids upon ultra-violet exposure, enabling fast, precise curing of epoxides, vinyl ethers, and in surface modification.
Ion – It is an atom, or group of atoms, which by loss or gain of one or more electrons has acquired an electric charge. If the ion is formed from an atom of hydrogen or an atom of a metal, it is normally positively charged. If the ion is formed from an atom of a non-metal or from a group of atoms, it is normally negatively charged. The number of electronic charges carried by an ion is termed its electro-valence. The charges are denoted by superscripts which give their sign and number, e.g., a sodium ion, which carries one positive charge, is denoted by Na+; a sulphate ion, which carries two negative charges, by (SO4)2-.
Ion battery – It -is an electro-chemical energy storage device which uses ions (e.g., lithium, sodium, aluminum) as charge carriers, shuttling between electrodes through an electrolyte to store and release energy. Engineered for high energy density and efficiency, these batteries operate through reversible intercalation, where ions insert into and extract from electrode structures.
Ion beam analysis – It refers to a family of non-destructive techniques using energetic ion beams to probe the near-surface elemental composition, depth profiles, and structural properties of materials, crucial for characterizing thin films, semi-conductors, and coatings by detecting emitted particles (X-rays, gamma rays, scattered ions) or analyzing scattering patterns. Key methods like Rutherford backscattering spectrometry (RBS) and particle-Induced X-ray emission (PIXE) map elements and their distribution, offering high sensitivity for quality control and research in materials science, and micro-electronics.
Ion beam assisted deposition – It is a materials engineering surface modification technique which combines physical vapour deposition (PVD) with simultaneous, independent ion beam bombardment (normally 100 electron volts to 2000 electron volts). It improves coating adhesion, density, and morphology control by modifying the micro-structure and atomic structure of the growing film in a high-vacuum environment.
Ion beam mixing – It is an ion implantation technique in which deposited layers (electroplating, sputtering) tens or hundreds of nano-meters thick are mixed and bonded to the substrate by an argon or xenon ion beam. It is a surface modification technique where energetic ion bombardment causes atomic-level interdiffusion and alloying at the interface of layered materials. It improves coating adhesion, creates metastable alloys, and produces a tailored interfacial layer (frequently several micro-meters thick) by using ion radiation to mix components.
Ion beam sputtering – It is an ion implantation technique in which an ion beam of argon or xenon directed at a target sputters material from the target to a substrate, the sputtered material arrives at the substrate with enough energy to promote good adhesion of the coating to substrate.
Ion carburizing – It is a method of surface hardening in which carbon ions are diffused into a work-piece in a vacuum through the use of high-voltage electrical energy. It is synonymous with plasma carburizing or glow discharge carburizing.
Ion chromatography – It is an area of high-performance liquid chromatography which uses ion exchange resins to separate various species of ions in solution and elute them to a suitable detector for analysis.
Ion collector – It is a device or component designed to attract, capture, and measure or store ionized particles, typically using electrostatic fields, electrodes, or chemical mechanisms. Common applications include ion detection in spectrometers, electrostatic precipitation, particle monitoring, and energy harvesting.
Ion concentration – It defines the quantity of charged species (ions) present within a specific volume or mass of a solution, typically measured in moles per litre or molarity (M). It is critical for controlling electro-kinetic phenomena like ion concentration polarization (ICP) in membranes, scale formation, corrosion, and electrical conductivity in systems like desalination and electro-chemistry.
Ion concentration polarization – It is an electro-kinetic phenomenon where, under an applied electric field, ion-selective membranes or nano-channels create non-uniform ion distributions, resulting in an ion-depleted zone (low concentration) and an ion-enriched zone (high concentration). It occurs because of different transport rates of ions between the solution and the membrane.
Ion current density – (n) – It is normally the number of ions (N) within a specific volume (V), expressed by the formula ‘n = N/’. It is the quantity of electric charge carried by ions flowing per unit time through a unit cross-sectional area. Expressed in amperes per square meter, it measures ion flux intensity, important for applications like plasma processing, semi-conductor manufacturing, and ion beam implantation.
Ion density – It refers to the concentration of charged particles, specifically ions, in a plasma, and is a component of the overall plasma density, which is the sum of electron density and the densities of different ions.
Ion diffusion – It is the net, passive movement of charged particles (ions) from regions of higher concentration to lower concentration, driven by concentration gradients or electric potential differences. It is a critical mass transport process, governed by the Nernst-Planck equation to account for electrostatic interactions, influencing technologies like fuel cells, ion-exchange membranes, and semi-conductor doping.
Ion energy – It refers to the kinetic energy, typically measured in electron-volts (eV) or kilo-joules per mole, possessed by charged atoms or molecules, frequently accelerated in fields for material processing, surface modification, or propulsion. It is important for determining how ions interact with surfaces.
Ion engines – These are highly efficient electric propulsion systems which generate thrust by ionizing a propellant (typically xenon) and accelerating the resulting positive ions to high speeds using electric fields. These systems produce low, constant thrust but achieve high specific impulse (Isp), allowing for reduced propellant consumption and long-duration, high-velocity missions.
Ion etching – It is the surface removal by bombarding with accelerated ions in vacuum (1 kilovolt to 10 kilovolt).
Ion exchange – It is the reversible interchange of ions between a liquid and solid, with no substantial structural changes in the solid. It is also an exchange of ions in a crystal with irons in a solution. It is used as a method for recovering valuable metals, such as uranium, from solution.
Ion-exchange capacity – It is a measure defining the total number of exchangeable ionic groups (milli-equivalents) available per unit weight (milli-equivalents per gram, dry) or volume (milli-equivalents per litre, wet) of an ion-exchange resin or membrane. It quantifies the material’s maximum capacity to exchange ions, important for determining performance, regeneration frequency, and efficiency in separation systems.
Ion-exchange chromatography – It is liquid chromatography with a stationary phase which possesses charged functional groups. This technique is applicable to the separation of ionic (charged) compounds.
Ion exchange demineralization – It is an application of ion exchange. Two main types of water treatment are exercised with the use of the ion exchange technology namely (i) water softening, and (ii) demineralization. Water softening is when minerals which give hardness to the water like calcium and magnesium are exchanged for sodium (which is a lighter molecule). Soft water is needed for several processes. Demineralization is when the ions in the solution are almost completely removed. This process is the basis on which the demineralization plant operates and produces demineralized water.
Ion exchange equilibrium – It is the state in a reversible, stoichiometric process where the rate of ions leaving an ion-exchange material (resin) equals the rate of ions entering it from a surrounding solution, resulting in constant, non-zero concentrations in both phases. This phase equilibrium, frequently analyzed using isotherms, maintains electro-neutrality and determines the resin’s selectivity for specific ions, key for designing separation processes.
Ion exchange materials – These are insoluble solid matrices, typically synthetic polymeric resins, zeolites, or clays, containing exchangeable cations or anions which reversibly swap with ions in a surrounding electrolyte solution. Engineered for high surface area and selectivity, they are used in industrial water softening, demineralization, and purification.
Ion exchange process – It uses resin beads with sodium (sometimes potassium) attached to them. An ion exchange occurs when hard water containing ions of calcium and / or magnesium flows through the resin beads. The resin beads release sodium ions to the water while capturing the calcium and / or magnesium ions. Once the resin is depleted, it is to be regenerated to flush out the captured hard water ions and replace them with a new source of sodium ions. This is done by using a salt solution (sodium chloride) from a brine tank. Once the regeneration process is complete, the system is rinsed to remove residual hard water ions and chloride ions from the salt, and the rinse water is sent to the drain. After being put back on-line, the newly soft water contains all the original substances which are in the incoming supply water minus the hard water ions which have been replaced with sodium ions. The process continues until the resin is again depleted of sodium, and regeneration of the resin beads is to be done. process occurs.
Ion exchange resin – It is a synthetic resin containing active groups (normally sulfonic, carboxylic, phenol, or substituted amino groups) which give the resin the property of combining with or exchanging ions between the resin and a solution. Ion exchange resins are insoluble, cross-linked, long chain organic polymers with a micro porous structure, and the ‘functional groups’ attached to the chains are responsible for the ion exchange properties. Resins containing acidic functional groups (-COOH, -SO3H) are capable of exchanging their H+ ions with other cations, which comes in their contact. Resins containing basic functional groups (amino groups) are capable of exchanging their anions with other anions, which comes in their contact. Ion-exchange resins can be classified as (i) cation exchange resins (R.H+), and anion exchange resins (R.OH-). Ion exchange resins are synthetic polymers which are insoluble in all solvents. They are capable of reacting like acids, bases, or salts. The resins, however, differ from acids, bases, and salts in one way. Only the cations (in cation exchange resins) or anions (in anion exchange resins) are free to take part in chemical reactions. Those exchange units in which the anionic portions are able to react are called anion exchange units whereas, the ones in which the cationic portions are able to react are called cation exchange units. In aqueous media and sometimes in non-aqueous media, cation exchange resins are able to exchange their cations with other cations and similarly anion exchange resins are able to exchange their anions with other anions.
Ionic bond – It is a type of chemical bonding in which one of more electrons are transferred completely from one atom to another, hence converting the neutral atoms into electrically charged ions. These ions are around spherical and attract each other because of their opposite charges. It is also a primary bond arising from the electrostatic attraction between two oppositely charged ions.
Ionic bonding – It is a type of chemical bonding which involves the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electro–negativities, and is the primary interaction occurring in ionic compounds. It is one of the main types of bonding, along with covalent bonding and metallic bonding. Ions are atoms (or groups of atoms) with an electrostatic charge. Atoms which gain electrons make negatively charged ions (called anions). Atoms which lose electrons make positively charged ions (called cations).
Ionic charge – It is the positive or negative charge of an ion.
Ionic clusters – These are nano-meter-sized, charged or neutral aggregates of atoms, molecules, or ionizable groups (typically ranging from 3 atoms to 20,000 plus atoms) which serve as a bridge between molecular and bulk material properties. They are utilized in surface modification, high-sensitivity analysis, and ionomer performance studies because of their ability to deposit high energy density or modify polymer mobility.
Ionic concentration – It defines the quantity of charged species (ions) present within a specific volume or mass of a solution, often expressed as molarity (mol per litre) or parts per million (ppm). It dictates electrical conductivity, chemical reactivity, and electro-chemical behaviour in systems like electro-kinetic processes, desalination, and material corrosion.
Ionic crosslinking – It is a physical crosslinking technique where oppositely charged polymer chains are linked by multivalent ions (e.g., Ca2+) to form a 3D network. It is a reversible process used to create bio-degradable hydrogels, nanoparticles, and coatings by creating ionic bridges between polymer chains, increasing material strength, stability, and water resistance.
Ionic crystals – These are solid materials composed of alternating positively charged cations and negatively charged anions arranged in a rigid, highly ordered 3D lattice structure. Held together by strong electrostatic forces of attraction, these crystals are characterized by high melting points, electrical insulation in solid state, high brittleness, and typical formation from metallic and non-metallic elements.
Ionic current flow – It is the transport of electrical charge through the movement of positive or negative ions (atoms / molecules) rather than electrons, occurring in electrolytes, and plasma systems. Measured in amperes, it occurs because of the electric fields or concentration gradients, frequently enabling energy storage, and corrosion.
Ionic dissolution – It is the process where solid materials (frequently minerals, or metals) release constituent ions into a liquid solvent, breaking down their crystalline structure. This phenomenon is important for surface interaction, corrosion studies, and material performance in environments like metal corrosion in coolant.
Ionic distribution – It defines the spatial arrangement and concentration of ions within a fluid, material, or near a surface, typically governed by Boltzmann statistics, diffusion, and interionic interactions. It is critical for analyzing electrochemical systems, such as electric double layers (EDL) in capacitors, ion penetration in concrete, and plasma processing.
Ionic liquid-based electrolytes – These are innovative, non-flammable, and low-volatility ionic salts which remain liquid below 100 deg C, consisting of bulky organic cations and inorganic / organic anions. Engineered for high-performance energy storage (batteries, super-capacitors), they provide high thermal stability and wide electro-chemical windows (up to 6 volts), replacing conventional, flammable organic electrolytes.
Ionic polymerization – It is a chain-growth polymerization process where the active propagating species is an ion, either a cation (+) or an anion (-). Engineered for high-speed synthesis and precise control over polymer architecture and molecular weight, it frequently results in ‘living’ polymerization with no inherent termination, enabling the production of block copolymers, particularly at low temperatures.
Ionic polymer metal composites -These are smart electroactive materials consisting of an ion-exchange polymer membrane (sandwiched between noble metal electrodes (e.g., platinum, gold). They are engineered to bend significantly at low voltages (1 volt to 5 volts) because of the ion migration, serving as soft actuators, and sensors.
Ionic radius – It is the effective distance from the centre of an ion’s nucleus to its outermost electron shell within an ionic crystal lattice, typically treated as a hard sphere, measuring roughly 31 pico-meter to over 200 picometer (0.3 Angstrom to 2 Angstroms). It is used in engineering to predict crystal structure, coordination numbers, and bond lengths in materials, with values varying based on charge and electron shielding.
Ionic strength – It is a measure of the concentration of ions in a solution. It is normally expressed in terms of molarity (mol per litre of solution) or molality (mol per kilogram of solvent).
Ionic surfactants – These are amphiphilic, surface-active agents containing ionizable hydrophilic heads” (carboxylates, sulphates, or ammonium) which dissociate into charged ions (anions / cations) and counterions in water. They reduce surface tension, enabling emulsification, wetting, and foaming, primarily used for cleaning, detergent formulation, and improved oil recovery.
Ion implantation – It is the process of modifying the physical or chemical properties of the near surface of a solid (target) by embedding appropriate atoms into it from a beam of ionized particles. The properties to be modified can be electrical, optical, or mechanical, and they can relate to the semi-conducting behaviour of the material or its corrosion behaviour. The solid can be crystalline, poly-crystalline, or amorphous and need not be homogeneous. Related techniques are also used in conjunction with ion implantation to increase the ratio of material introduced into the substrate per unit area, to provide appropriate mixtures of materials, or to overcome other difficulties involved in surface modification by ion implantation alone.
Ion implantation enhanced vapour phase deposition – it is frequently referred to in metallurgy as ‘plasma immersion ion implantation and deposition’ or ‘ion beam assisted deposition’. It is a hybrid surface engineering technique which combines the simultaneous application of high-energy ion bombardment and vapour deposition to create high-performance coatings. This method modifies the near-surface region of a substrate, typically a metal or alloy, to considerably improve wear, friction, and corrosion resistance.
Ionizable surface – It refers to materials containing surface functional groups (e.g., carboxyl, amine, sulphate) capable of dissociating into charged ions when in contact with a medium, typically water, characterized by their dissociation constants (pKa). These surfaces are engineered to manipulate electrostatic interactions, improve interfacial conductivity, or facilitate selective adsorption.
Ionization – It is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, frequently in conjunction with other chemical changes. The resulting electrically charged atom or molecule is called an ion. Ionization can occur because of high temperatures, electrical discharges, or nuclear radiations, It can also result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules, electron, positron, protons, antiprotons and ions, or through the interaction with electro-magnetic radiation.
Ionization chamber – It is a gas-filled detector which measures ionizing radiation (like X-rays, gamma rays, beta particles) by collecting the electric charge produced when radiation ionizes gas atoms, creating a current proportional to radiation intensity, used extensively in dosimetry, and nuclear power for reliable, high-level radiation measurement without gas multiplication.
Ionization constant (Ka) – It is the equilibrium constant quantifying the strength and partial dissociation of a weak acid or base into ions in a solution [Ka = (A- x H+) / HA. It serves as an important metric for predicting chemical equilibrium, buffering capacity, and pH in chemical processes, and environmental systems. It is a quantitative measure of acid / base strength in water, with higher values indicating stronger dissociation. It is used to determine the extent of ionization, necessary for designing reaction systems, controlling wastewater treatment pH, and understanding pharmaceutical solubility.
Ionization efficiency – It refers to the ability of a mass spectrometry technique to effectively convert analyte molecules into gaseous ions that can be detected and analyzed. It is a critical parameter in the performance of mass spectrometry instruments, particularly in the context of magnetic-sector instruments used for the analysis of small molecules. It is a measure of how efficiently a sample is converted into gas-phase ions, impacting the sensitivity of mass spectrometry instruments. It depends strongly on the analyte’s chemical structure (polarity, functional groups) and the ionization technique used, such as electron Ionization (EI) or electrospray Ionization (ESI). It is frequently determined by comparing the number of ions generated against the total number of species. In mass spectrometry studies, this can be measured as the ratio of detected analyte ion current to the theoretically expected maximum current. It is crucial for optimizing analytical methods for maximum sensitivity, especially in detecting compounds with low proton affinity or in atmospheric pressure chemical ionization (APCI).
Ionization gauge – It is an instrument used to measure extremely low pressures (13.33 milli-pascals to 0.0133 micro-pascals or lower) by ionizing gas molecules and measuring the resulting ion current. It operates by colliding electrons (emitted from a hot cathode or generated by cold cathode discharge) with gas molecules, creating positive ions, where the collected ion current is directly proportional to the gas pressure.
Ionization gauge head – It is a sensor component used to measure high to ultra-high vacuum pressures (typically 13.33 milli-pascals to 0.0133 micro-pascals or lower) by ionizing residual gas molecules. It works by emitting electrons, through a hot cathode (filament) or cold cathode. to ionize gas, then collecting the resulting positive ion current (Ic) on an electrode, which is proportional to pressure.
Ionization potential – It is the minimum energy needed to remove the most loosely bound electron from an isolated gaseous atom, molecule, or ion, converting it into a positive ion (cation). It determines electrical conductivity, electron binding energy, and reactivity, typically measured in electron volts (eV) or kilo joule per mol.
Ionization rate – It is the frequency or probability of electron-ion pair production per unit time, frequently defined as the number of ionization events occurring per unit volume per second. It represents the efficiency of turning neutral atoms / molecules into ions and is important in determining plasma density in processes like magnetron sputtering.
Ionization volume – It refers to the specific, enclosed, or defined spatial region within a device (such as an ionization smoke detector or gauge) where air or gas is ionized by a radiation source, allowing for the detection of particles or measurement of pressure by monitoring changes in electrical conductance. It is the active sensing area.
Ionized species – These are charged atoms, molecules, or fragments (ions) produced by removing or adding electrons, normally through high-energy impact, UV (ultra-violet) radiation, or electric fields. They are critical to plasma processes (e.g., sputtering, semiconductor etching), mass spectrometry, and radiation detection, characterized by increased chemical reactivity compared to neutral counterparts.
Ionizing agent – It is a charged particle (e.g., electrons, alpha particles / beta particles) or high-energy radiation source which induces ionization by colliding with molecules, forming ion pairs. It is used in sensors. These particles, such as radioactive sources or hot filaments, convert gaseous, liquid, or solid materials into ionized states.
Ionizing irradiation – It is the process of exposing materials to high-energy beams (electrons, ions, X-rays, or gamma-rays) which possess sufficient energy to detach electrons from atoms, creating ions and inducing structural, electrical, or chemical changes. It is used to modulate, modify, or analyze material properties through defect creation, polymerization, or surface treatment.
Ionizing particles – These are high-energy sub-atomic particles (e.g., electrons, protons, alpha particles) or ions capable of causing ionization, removing electrons from atoms or molecules, upon collision with matter. These particles are classified by their ability to directly or indirectly disrupt atomic structures, primarily used in radiation detection, materials processing, and sterilization.
Ionizing radiation – It is a radiation capable of displacing electrons from atoms or molecules, thereby producing ions. High doses of ionizing radiation can produce severe skin or tissue damage. Some examples are alpha, beta, gamma, X-rays, neutrons, and ultra-violet light.
Ion neutralization – It is the generic term for a class of charge-exchange processes in which an ion is neutralized by passage through a gas or by interaction with a material surface.
Ion nitriding – It is a method of surface hardening in which nitrogen ions are diffused into a work-piece in a vacuum through the use of high-voltage electrical energy. It is synonymous with plasma nitriding or glow discharge nitriding.
Ionomer performance studies – These studies focus on analyzing how these ionic interactions, which act as physical, thermo-reversible crosslink, affect material behaviour under different environmental and mechanical stresses.
Ionomers -These are a class of polymers containing both neutral and ionized repeating units (typically less than 15 mol percent) which form ion clusters within the matrix, providing unique physical, mechanical, and transport properties.
Ionosphere – It is the ionized part of earth’s upper atmosphere, extending from roughly 48 kilometers to 965 kilometers above sea level, where solar radiation ionizes atmospheric gases, affecting radio wave propagation.
Ion number density (ni) – It is the concentration of ions (charged particles) within a given volume, calculated as the total number of ions (N) divided by the volume (V). It represents the spatial distribution and abundance of positively or negatively charged particles, typically expressed in units of ions per cubic centimeter or per cubic meter.
Ion pair – It is a discrete chemical entity comprising a cation and an anion held together by electrostatic coulomb forces without forming a true covalent bond. These transient or stable pairs form in electrolyte solutions or ionic liquids to influence conductivity, solubility, and molecular structure.
Ion-pair chromatography – It is the liquid chromatography with a mobile phase containing an ion which combines with sample ions, creating neutral ion pairs. The ion pairs are typically separated using bonded-phase chromatography.
Ion penetration – It refers to the movement and embedding of ions into a material’s surface, utilized either as a precision surface modification technique (ion implantation) or analyzed as a degradation mechanism (ion diffusion). It involves ion energy, collision with the target, and resultant structural, chemical, or physical changes.
Ion plating – It is a generic term applied to atomistic film deposition processes in which the substrate surface and / or the depositing film is subjected to a flux of high-energy particles (normally gas ions) sufficient to cause changes in the interfacial region or film properties.
Ion properties – These properties refer to the characteristics of ions which influence the behaviour of salts, including their melting point, which is affected by factors such as charge density and steric hindrance. These properties determine the strength of electrostatic interactions among ions and hence govern the physical state of salts at different temperatures.
Ion release – It is the process where materials (metals, ceramics, polymers) discharge charged atoms (ions) into a surrounding medium (water, electrolyte) through corrosion, dissolution, or chemical exchange. It is critical for evaluating material degradation, and designing functional, responsive surfaces.
Ion-scattering spectrometry – It is a technique to elucidate composition and structure of the outermost atomic layers of a solid material, in which principally mono-energetic, singly charged, low-energy (less than 10 kilo-electronvolt, keV) probe ions are scattered from the surface and are subsequently detected and recorded as a function of the energy.
Ion-scattering spectrum – It is a graph of scattered ion intensity as a function of the ratio of the scattered ion energy to the incident ion energy.
Ion-selective exchange membranes – These are dense polymeric membranes which contain fixed charges in the polymer matrix, allowing the selective passage of oppositely charged ions (counter-ions) while blocking similarly charged ions (co-ions). Their ion permselectivity is important for different industrial applications.
Ion sensitive field effect transistor – It is a specialized MOSFET (metal-oxide-semiconductor field-effect transistor) which measures ion concentrations (e.g., pH, H+) in a solution by substituting the conventional metal gate with an electrolyte solution and a reference electrode. It acts as a potentiometric transducer, where ion-sensitive membrane potential changes modulate the semi-conductor channel current.
Ion separation – It is the process of isolating specific charged atoms or molecules (ions) from a solution or mixture based on their charge, size, or mobility. It is a critical, often reversible, operation using methods like ion exchange resins, membranes, or electrodialysis to purify water, remove contaminants, or recover valuable metals in industrial, and environmental applications.
Ion source – It is a device which produces, accelerates, and directs a beam of charged particles (ions) from gases, liquids, or solids. Necessary in mass spectrometry, particle accelerators, and ion implantation, these sources use electric / magnetic fields or plasma to ionize atoms, enabling precise mass-to-charge analysis or material modification.
Ion species – It is a type and charge of an ion. If an isotope is used, it is to be specified.
Ion transport membranes – These membranes are frequently referred to as ion-exchange or mixed-conducting membranes. They semi-permeable barriers which selectively allow specific cations or anions to pass through while blocking others, driven by electro-chemical potential. Used extensively in energy and separation engineering, these membranes facilitate ionic movement, such as oxygen ions through ceramic vacancies or protons / hydro-oxides in fuel cells, for applications like gas separation, desalination, and electrolysis.
Ion transport membrane (ITM) air separation process – It is a method for separating oxygen from air using a ceramic membrane which conducts oxygen ions at high temperatures. This technology offers potential advantages over traditional cryogenic air separation, particularly when integrated with power generation cycles or syngas production. Ion transport membranes are typically made of dense, mixed ion and electron-conducting ceramic materials. The core of the process is the ion transport membrane, normally a ceramic material composed of mixed ion and electron-conducting oxides. Ion transport membranes operate at elevated temperatures (typically above 973 K or 700 deg C).
IoT sensor – It is a component which detects physical environmental parameters (temperature, motion, light, humidity, pressure) and converts them into digital data for transmission over a network. Acting as the data-acquisition foundation of the Internet of Things (IoT), these devices integrate sensing elements, micro-controllers, and connectivity to enable real-time monitoring and automation.
IP (internet protocol) address – It is a unique, logical, 32-bit (IPv4) or 128-bit (IPv6) numerical identifier assigned to every device on a network, enabling location, identification, and routing of data packets. It acts as a digital address for communication, allowing devices to locate each other across local or global networks.
IPsec tunnel – It is a secure, encrypted, and authenticated logical connection established at the ‘network layer’ (layer 3) of the OSI (open systems interconnection) model, mainly used to protect data traffic between two endpoints (typically gateways or hosts) across an untrusted, public network like the Internet. By implementing tunnel mode, the entire original IP (internet protocol) packet, including the payload and the original IP header, is encrypted and encapsulated within a new IP packet, which prevents intermediate routers from viewing the ultimate destination or content.
IPv4 address – It is a 32-bit numerical label used to identify devices on a network, represented in four decimal values known as octets (e.g., 192.168.1.1). It consists of a portion which indicates the network ID (identifier) and another that specifies the host ID.
IPv6 address – It is a 128-bit alpha-numeric identifier, structured as eight 16-bit hexa-decimal groups force) to replace IPv4. It provides a massive, 340-undecillion (3.4 x 10 to the power 38) unique address space, addressing IPv4 exhaustion while supporting efficient hierarchical routing, auto-configuration, and improved security.
Irgarol – It is a potent, high-performance booster biocide used in marine antifouling paints to prevent algal growth and slime accumulation. It belongs to the s-triazine class of chemicals and works as a photosynthesis inhibitor.
IRG transition diagram – It is also called ‘lubrication mode diagram’ (LMD). It is a graphical representation used in tribology to visualize the different lubrication regimes like ‘elasto-hydrodynamic lubrication’ (EHL), ‘mixed lubrication’ (ML), and ‘boundary lubrication’ (BL) in concentrated contacts as a function of operating variables and material properties. It helps in understanding and predicting the transition between these lubrication regimes, particularly the transition from mild wear to severe wear. The primary goal of an IRG (International Research Group) transition diagram is to map out the lubrication behavior of a contact under varying conditions. This allows for the identification of the lubrication regime (EHL, ML, or BL) present at a given set of parameters.
Iridium (Ir) – It is a chemical element having atomic number 77. It is a dense, very hard, brittle, silvery-white transition metal and a member of the platinum group metals (PGMs). It is characterized as the most corrosion-resistant metal known, able to withstand extreme environments and high temperatures. It is highly valued for its extreme density (22.56 grams per cubic meter), high melting point (2446 deg C), and exceptional hardness.
Iridium oxide (IrO2) – It is a highly stable, blue-black noble metal ceramic material characterized by metallic-type electrical conductivity and superior corrosion resistance. Engineered mainly for harsh anodic environments, it is considered the state-of-the-art catalyst for the oxygen evolution reaction (OER) in water electrolysis, fuel cells, and sensors.
Iron – Iron is a chemical element with symbol Fe (from Latin word Ferrum). Its atomic number is 26 and atomic mass is 55.845. It has a melting point of 1,538 deg C and boiling point of 2,862 deg C. The density of iron is 7.87 grams per cubic meter. It is a metal in the first transition series. Like the elements of other group 8 elements (ruthenium and osmium), iron exists in a wide range of oxidation states, +2 to +6, although +2 and +3 are the most common. Iron as a common metal is mostly confused with other metals such as different types of steels. Iron is by mass the most common element on the earth, forming much of earth’s outer and inner core. It is the fourth most common element and the second most common metal in the earth crust. Steels contain over 95 % Fe. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen and water.
Iron alloy – It refers to a type of engineering material which is produced by combining iron with different alloying elements, such as carbon. These alloys have a wide range of micro-structures and properties, allowing them to be used in different applications.
Iron alloys and steels – These are ferrous metals mainly composed of iron, combined with carbon (less than 2.1 %) and other elements to improve properties like strength, hardness, and corrosion resistance. Steels are distinguished from cast irons by lower carbon content (typically 0.2 % to 2.1 %) and higher ductility, allowing for shaping, while alloying elements (manganese, nickel, chromium) tailor the material for specific industrial uses.
Iron-aluminide alloys – These are a class of intermetallic compounds, mainly composed of iron (Fe) and aluminum (Al), typically containing 20 to 50 atomic percent aluminum. These alloys are notable for their low cost, low density, ease of fabrication, and good oxidation and corrosion resistance. They are of interest for several applications, including heating elements, furnace fixtures, and heat-exchanger piping.
Iron aluminides – These are intermetallic compounds of iron and aluminum (typically higher than or equal to 18 % aluminum, normally Fe3Al phases) engineered for high-temperature structural applications, featuring excellent oxidation / sulphidation resistance, low density, and high strength-to-weight ratios. They serve as low-cost alternatives to stainless steel and nickel-based superalloys, though their use is limited by low ambient ductility.
Iron-aluminum-carbon (Fe-Al-C) alloy – It is a specialized, light-weight, non-magnetic, or low-density steel system which incorporates substantial quantities of aluminum (frequently 3 % to 10 % or higher) and carbon (normally 0.5 % to 2 % or more) into an iron base. Unlike conventional steels, this alloy system focuses on utilizing aluminum and carbon to form unique, high-strength phases, such as B2 intermetallics or kappa-carbides, which provide excellent heat resistance, corrosion resistance, and a considerably lower density than conventional steel.
Iron and steel scrap – It is also known as ‘ferrous metal scrap’ is a recyclable material which is left- over during the production of iron and steel products and fabrication of ferrous materials or generated at end of life of the ferrous products. Ferrous scrap is normally recycled during steelmaking. Amongst all kinds of ferrous scraps, steel scrap constitutes the maximum percentage. Ferrous metal scrap is the primary raw material for the production of liquid steel in the electric arc furnace and the induction furnace.
Iron atom – It is the fundamental unit of the element iron, symbolized as Fe, which has an atomic weight of 56 and can arrange themselves in crystalline structures such as body centered cubic (bcc) and face centered cubic (fcc) depending on temperature.
Iron bacteria – It is a group of aerobic bacteria which oxidize ferrous and manganous ions, leading to the formation of coloured deposits from ferric and manganese salts. They can cause localized corrosion of passive metals by producing aggressive ferric chlorides, which create low pH conditions.
Iron-base alloys – These are materials composed mainly of iron (Fe) with other elements added to modify its properties. These alloying elements, such as carbon, chromium, nickel, and manganese, are incorporated to improve strength, hardness, corrosion resistance, and other desirable characteristics. They are widely used in various applications because of their versatility and relatively low cost.
Iron-based superalloys – These are a type of alloy, mainly composed of iron, which are designed to maintain strength and resistance to creep, oxidation, and corrosion at high temperatures. These alloys typically contain other elements like nickel, chromium, and different strengthening additives, and are frequently used in applications where high-temperature performance is crucial, such as in gas turbine engines.
Iron bath – It refers to a molten, liquid pool of iron (normally hot metal) operated at high temperatures (1,300 deg C to 1,600 deg C) inside a vessel or furnace, used mainly for smelting, reducing iron ore, or gasifying coal. It acts as a reaction medium for converting iron oxide, carbon, and other materials into liquid iron and slag, frequently utilizing top and bottom blowing with oxygen.
Iron block – It refers to a solid, heavy-duty component, normally made of cast iron, which acts as the main, high-strength structural foundation for machinery, such as an internal combustion engine cylinder block. It is designed to withstand extreme thermal loads, high pressure, and substantial vibrations.
Iron brake block – It is a traditional frictional component in railway engineering, manufactured from cast iron (frequently containing phosphorus) and attached melting to a steel support, designed to rub against wheel treads to stop rolling stock. Known for low cost and durability, these blocks generate high friction but are prone to producing substantial noise, dust, and wheel corrugation.
Iron carbide – It is a high point, non-pyrophoric, strongly magnetic synthetic compound got in granular or powder form. It is composed of three atoms of iron and one atom carbon and its chemical formula is Fe3C. The commercial iron carbide consists of around 90 % total iron and around 6 % to 6.5 % of total carbon. The primary use of the product is as a metallic charge during steelmaking for the substitution of hot metal, direct reduced iron, or steel scrap. Iron carbide is an inter-metallic compound of iron and carbon. It is, more precisely, intermediate transition metal carbide. Its stoichiometric composition consists of 6.67 % carbon and 93.3 % iron. It has an orthorhombic crystal structure). It is a hard, brittle material and normally classified as a ceramic in its pure form. It is a frequently found and important constituent in ferrous metallurgy. While iron carbide is present in majority of the steels and cast irons, it is produced as a raw material by the iron carbide process, which belongs to the family of alternative ironmaking technologies.
Iron carbonate (FeCO3) – It is a chemical compound composed of iron (II) cations (Fe2+) and carbonate anions (CO2)3-, frequently occurring naturally as mineral siderite. It is a green-brown, water-insoluble ionic solid acting as a key corrosion product in engineered systems. It precipitates on mild steel surfaces in carbon di-oxide saturated aqueous environments (e.g., pipelines), This iron carbonate protective layer on steel acts as a diffusion barrier, reducing the rate of further corrosion, while industrially, it is used as a precursor for iron / steel production.
Iron-carbon-chromium-manganese (Fe-C-Cr-Mn) steels – These are a broad category of alloy steels where chromium and manganese are added to the foundational iron-carbon system to improve specific mechanical properties, such as hardenability, strength, and wear resistance. These steels range from low-alloy, high-strength structural steels to specialized, high-alloy abrasion-resistant steels (e.g., Hadfield steel).
Iron-carbon-chromium-manganese-silicon steels – These are advanced, highly engineered alloy steels with a base of iron and carbon (less than 2 % carbon), improved with chromium (for corrosion resistance and hardness), manganese (for toughness and wear resistance), and silicon (for deoxidation and strength). These steels frequently fall into the category of stainless or high-performance alloy steels used in demanding industrial applications, offering superior corrosion resistance and high strength.
Iron-carbon-chromium-nickel-manganese steel – It frequently referred to as austenitic stainless steel (specifically within the 200 and 300 series) or complex alloy steel, is a ferrous alloy composed of iron (Fe), carbon (C), chromium (Cr), nickel (Ni), and manganese (Mn). These elements are added to tailor the steel’s metallurgical properties for high corrosion resistance, high-temperature strength, and improved ductility.
Iron-carbon-chromium-nickel-molybdenum steel – It is frequently known as high-performance alloy or stainless steel. It is an iron-based alloy containing carbon (less than 2 %), chromium (for corrosion resistance), nickel (for toughness), and molybdenum (for strength and hardenability). This combination is designed to optimize strength, corrosion resistance, and heat resistance, normally used in demanding structural, industrial, and marine environments.
Iron-carbon-chromium-silicon (Fe-C-Cr-Si) steel – It is a type of alloy steel which incorporates specific quantities of chromium (Cr) and silicon (Si) alongside carbon (C) to improve properties like hardenability, corrosion resistance, and strength. While mainly based on the iron-carbon (Fe-C) system, the addition of chromium improves resistance to corrosion and wear, while silicon increases strength without substantial loss of ductility.
Iron-carbon-manganese-nickel-molybdenum steel – It is a high-performance alloy steel (frequently low-alloy, less than 5 % alloying elements) designed to surpass the strength, toughness, and hardenability of plain carbon steels. It combines iron with manganese for hardenability, nickel for toughness, and molybdenum for strength at elevated temperatures.
Iron-carbon-manganese-silicon-nickel steel – It is a type of alloy steel, specifically frequently a low-alloy steel, designed to improve mechanical properties, particularly toughness, strength, and hardenability, by adding nickel, manganese, and silicon to a base carbon steel. This combination is engineered to balance strength (from carbon and manganese) with toughness and resistance to brittleness, particularly at low temperatures (from nickel).
Iron-carbon-manganese-silicon-nickel-vanadium steel – It is a type of low-alloy steel engineered to possess superior mechanical properties, specifically high strength, toughness, and wear resistance, beyond those of plain carbon steel. It is composed of a ferritic or martensitic iron matrix, with alloying elements added in specific, low percentages (normally less than 5 % total) to control micro-structure and performance.
Iron-carbon-manganese-silicon (Fe-C-Mn-Si) steel – It is the foundational definition of plain carbon steel, representing the most common type of steel produced globally. It is a metal alloy consisting of iron (base), carbon (strengthening agent), and residual / added manganese and silicon.
Iron-carbon-manganese-silicon-vanadium steel – It is a type of low-alloy structural steel engineered for high strength, toughness, and wear resistance. It consists of iron (Fe) and carbon (C), with manganese (Mn) and silicon (Si) added for deoxidation and strength, plus vanadium (V) to form fine carbides, improving hardenability and toughness.
Iron-carbon-nickel-chromium-manganese-silicon steel – It is a type of high-alloy steel where iron (Fe) is alloyed with a substantial quantity of chromium (typically 10 % to 20 %) and nickel (6 % to 26 %), frequently with manganese (Mn) and silicon (Si) to improve specific mechanical and chemical properties. This combination is normally known as stainless steel, specifically austenitic grades, which are characterized by high corrosion resistance, toughness, and non-magnetic properties.
Iron-carbon-nickel-chromium-molybdenum steel (Ni-Cr-Mo steel) – It is a high-performance low-alloy steel (typically less than 5 % alloy content) designed for superior strength, hardness, and toughness. It combines iron, carbon (0.25 % to 0.55 %), nickel (1 % to 3.5 %), chromium (0.5 % to 1.5 %), and molybdenum (0.2 % to 0.5 %), to provide deep hardenability, wear resistance, and high-temperature performance.
Iron-carbon-nickel-chromium-molybdenum-silicon steel – It is a highly alloyed low-alloy or medium-alloy engineering steel designed to balance high strength, toughness, hardenability, and corrosion resistance. It is frequently used for critical, high-load, and high-fatigue components, such as shafts, fasteners, and heavy machinery parts.
Iron-carbon-nickel-chromium-molybdenum-vanadium steel – It is a highly alloyed, heat-treatable engineered material, frequently referred to as a nickel-chromium-molybdenum (Ni-Cr-Mo) steel or within the broader family of high-performance alloy steels. This steel is specifically formulated to balance extreme hardness, toughness, tensile strength, and fatigue resistance by combining iron and carbon with multiple alloying elements.
Iron-carbon phase diagram – It is a graphical representation of different phases of iron which exists within a given temperature, pressure, or weight percentage, it is an equilibrium diagram of iron and carbon. With its help, the relationship between the carbon content and the temperature is derived. On this basis, the phase composition can be determined. Carbon is the most important alloying element in iron. The iron-carbon phase diagram is widely used to understand the different phases of steel and cast iron.
Iron casting – It is a part made of cast iron.
Iron-chromium (Fe-Cr) alloys – These are metallurgical materials composed mainly of iron and chromium, with chromium acting as the key alloying element to provide superior corrosion resistance and strength. These alloys are characterized by chromium content, normally ranging from 10.5 % in stainless steels up to 70 % in ferro-chrome, and are used extensively for high-temperature resistance, wear resistance, and passivation.
Iron-chromium-aluminum-yttrium (FeCrAlY) coating – It is a high-temperature, oxidation-resistant alloy coating frequently referred to as a type of MCrAlY overlay coating (where M = iron, nickel, cobalt, or a mixture). It is designed to protect structural components, particularly steel or superalloys, from oxidation, corrosion, and erosion at temperatures exceeding 1000 deg C by forming a stable, self-healing aluminum oxide (Al2O3) layer on the surface.
Iron-chromium-nickel-molybdenum-aluminum-titanium (Fe-Cr-Ni-Mo-Al-Ti) alloy – It represents a highly complex, advanced high-alloy steel or superalloy, typically designed for extreme environments needing a combination of high corrosion resistance, oxidation resistance, and superior mechanical strength at high temperatures. This combination of elements constitutes a precipitation-hardened, corrosion-resistant alloy used in demanding industries.
Iron coagulants – These are compounds, specifically inorganic metal salts like ferric sulphate, ferric chloride, and ferrous sulphate, used in water treatment to destabilize suspended, negatively charged colloidal particles. They function by neutralizing charge and forming dense, insoluble ferric hydro-oxide flocs (precipitates) which settle faster than aluminum-based alternatives.
Iron composition – It refers to the specific, controlled mixture of iron (Fe), carbon (C), silicon (Si), and other alloying elements which determine the micro-structure, mechanical, and physical properties of cast irons and steel. Mainly, cast irons consist of 2.5 % to 4 % carbon and 1 % to 3 % silicon, while wrought iron has less than 0.1 % carbon.
Iron-constantan thermocouple (type J) – It is a widely used thermocouple type for temperature measurement, consisting of a positive iron wire and a negative constantan (roughly 55 % copper, 45 % nickel) wire. It provides a strong, consistent output of around 51 micro-volts per deg C, making it ideal for industrial, heat-treating, and heating element applications.
Iron content – It is the Fe content. It refers to the mass percentage or proportion of elemental iron present within a material, such as iron ore, pig iron, slag, or alloys. It is a fundamental measurement for determining the quality, purity, and commercial value of raw materials, as well as the mechanical properties of finished iron and steel products.
Iron-copper-carbon (Fe-Cu-C) alloys – These are a specialized category of ferrous metallurgy, particularly within powder metallurgy, where copper (typically 2 % to 10 %) and graphite (carbon) are admixed to an iron base to improve mechanical properties. These materials are designed to create a strong, durable, and frequently self-lubricating structural part through sintering, combining the high strength of steel with the ductility and thermal conductivity of copper.
Iron-copper (Fe-Cu) steels – These are a class of alloyed materials, normally produced via powder metallurgy (PM), consisting of an iron matrix with copper added (typically 2 % to 10 % by weight) to improve mechanical properties like strength, hardness, and wear resistance. These materials are frequently used in structural applications, such as gears, bushings, and automotive components, because of their ability to be sintered to precise dimensions and, in lower-density forms, impregnated with oil for self-lubrication.
Iron-copper (Fe-Cu) system – It refers to binary alloys and powder metallurgy mixtures consisting of iron and copper, characterized by limited solubility in the solid state and the formation of separate phases (typically an iron-rich phase and a copper-rich phase). Because of their distinct crystal structures and atomic sizes, they do not form a continuous solid solution.
Iron core – It is a ferromagnetic component, typically made of laminated silicon steel, used in transformers, inductors, and motors to concentrate and guide magnetic flux. It improves magnetic coupling between coils, considerably increasing inductance and improving energy transfer efficiency compared to air-cores.
Iron deposits – These are naturally occurring, concentrated accumulations of iron-bearing minerals, mainly hematite (Fe2O3) and magnetite (Fe3O4), from which metallic iron can be economically extracted for industrial use, particularly steel production. These deposits are typically found within geological formations, such as ‘banded iron formations’ (BIFs), and are evaluated based on their grade, tonnage, and viability for extraction methods like surface or underground mining.
Iron Dynamics ironmaking (IDI) process – It is based upon a rotary hearth furnace which reduces a carbonaceous iron oxide charge to metallic iron solids which are charged to a sub-merged arc furnace to complete the reduction and to melt and desulphurize the reduced iron. Melting the direct reduced iron also allows for a phase separation of the resulting liquid slag and iron. The Iron Dynamics ironmaking process is composed of five process areas namely (i) raw material receiving, (ii) ore and reductant (coal) grinding and preparation, (iii) pelletizing, (iv) rotary hearth reduction, and (v) sub-merged arc furnace smelting.
Iron grain – It is a microscopic, individual crystal region within a solid piece of iron or steel, where the iron atoms are arranged in a continuous, specific lattice orientation (normally body-centered cubic or face-centered cubic). As molten iron cools, these crystal structures nucleate and grow until they impinge upon neighboring grains.
Iron-hydrogen-oxygen system -It is the equilibrium diagram for iron (Fe) and iron oxides with a mixture of the gases hydrogen and steam (H2O).
Ironing – It is an operation which is used to increase the length of a tube or cup through reduction of wall thickness and outside diameter, the inner diameter remaining unchanged.
Ironing process – It is a bulk metal forming process which reduces the wall thickness of a cylindrical part, such as a can, increasing its height while ensuring uniform wall thickness. It involves forcing a pre-drawn cup through a die with a clearance smaller than the original wall thickness.
Iron-intermetallic alloys – These are a specialized class of metallic materials. These are solid-state compounds formed between iron (Fe) and one or more alloying elements (typically aluminum, silicon, or nickel) which show a distinct, ordered crystal structure and stoichiometry. Unlike standard alloys which are solid solutions with random atom arrangements, iron-intermetallics have a highly ordered, unique lattice where atoms sit on specific sites, resulting in properties which differ considerably from their constituent metals.
Iron-iron carbide (Fe-Fe3C) diagram – It is a fundamental engineering tool mapping phases (ferrite, austenite, cementite, pearlite) in iron-carbon alloys (steels, cast irons) against temperature and carbon content, important for predicting micro-structures and designing heat treatments to tailor properties like hardness and strength, with cementite (Fe3C) being the hard, brittle iron carbide phase.
Iron loss – It is that portion of the wasted power of a machine or transformer which is attributed to hysteresis and eddy currents in the iron core.
Iron-making – It is the process of reduction of iron ore using the relevant reducing agent (reductant).
Ironmaking process – It is the industrial process of reducing iron oxides (ore) into liquid metallic iron (hot metal / pig iron) or solid direct-reduced iron (DRI), mainly using blast furnaces or direct reduction technologies. This core metallurgical process involves chemical reduction, heat exchange, and slag formation to separate impurities.
Iron-manganese (Fe-Mn) alloys – These are metallic materials composed mainly of iron and manganese, frequently including carbon, silicon, and other elements, used extensively to increase steel strength, hardness, and wear resistance. They act as important deoxidizers, desulphurizers, and austenite stabilizers.
Iron matrix – It refers to the continuous, main phase of an iron-based alloy or metal matrix composite (MMC) which surrounds and binds other microstructural constituents, such as graphite nodules in cast iron or reinforcing particles, e.g., titanium carbide (TiC), aluminum oxide (Al2O3) in composites. This matrix determines the overall bulk properties, such as strength, hardness, toughness, and ductility.
Iron melt – It defines the physical phase transition of solid iron or its alloys (steel, cast iron) into a liquid state through intense heating, typically occurring at 1,538 deg C for pure iron. It represents the transformation from solid-phase stability to a molten state, enabling casting and moulding.
Iron metallurgy – It is the engineering branch focused on extracting iron from ores (e.g., hematite), refining it, and converting it into iron and steel alloys using techniques like smelting and forging. It covers the entire production chain, from raw material processing to forming finished, durable components for construction and engineering.
Iron micro-powders -These are fine, particulate metallic iron (Fe) with particle sizes typically ranging from a few micro-meters to tens of micro-meters (frequently defined as less than 100 micro-meters, with ultrafine grades below 37 micro-meters). They are characterized by high purity ( higher than 98 % to –99 %), high surface area-to-volume ratios, and high reactivity, making them necessary raw materials for specialized powder metallurgy, particularly micro-powder injection moulding and metal additive manufacturing (3D printing). ‘
Iron mine – It is an industrial site designed for the large-scale extraction of iron-bearing minerals, principally hematite and magnetite, from the earth’s crust using open-pit (surface) or underground mining methods. It involves a sequence of technical operations including geological exploration, drilling, blasting, loading, and transportation to produce ore for metallurgical processing.
Iron-nickel-chromium (Fe-Ni-Cr) alloys – These alloys are a versatile family of materials composed primarily of iron, nickel, and chromium, engineered for exceptional resistance to high-temperature oxidation, corrosion, and superior creep strength. They are often classified as stainless steels or nickel-based superalloys designed for severe chemical and petrochemical environments.
Iron-nickel-cobalt (Fe-Ni-Co) alloys – These are specialized metallurgical materials, frequently known by trade names like Kovar, designed for superior low thermal expansion and high structural strength. They typically contain 25 % to 35 % nickel and roughly 15 % to 25 % cobalt (with examples containing around 33 % nickel, around 4 % cobalt), tailored for sealing to glass and ceramics in electronics. These alloys are characterized by low Curie temperatures, high magnetic permeability, and excellent corrosion resistance, making them ideal for precision electronics.
Iron-nickel-cobalt-molybdenum-titanium steel – It is a class of ultra-high-strength, low-carbon alloy steels normally known as maraging steels. They are characterized by their ability to achieve exceptional strength and toughness through heat treatment (specifically, martensitic aging or ‘maraging’) without relying on carbon for hardening.
Iron-nickel-molybdenum-tungsten-titanium (Fe-Ni-Mo-W-Ti) steel – It is a highly alloyed, specialized material which combines the strength of iron-based metallurgy with the extreme heat resistance and toughness provided by heavy alloying elements. This combination is characteristic of high-speed tool steels or advanced maraging / precipitation-hardening alloys designed for demanding, high-temperature, or high-wear applications.
Iron-nickel (Fe-Ni) powder – It is a blend or pre-alloyed powder (frequently 1 % to 4 % nickel for steel, or 50 % nickel for soft magnets) used for producing high-strength, wear-resistant, or magnetic components through powder metallurgy (pressing and sintering). It offers superior strength, dimensional stability, and corrosion resistance.
Iron-nickel steels – These are engineering alloys mainly composed of iron (Fe) and nickel (Ni), known for exceptional toughness, corrosion resistance, and low thermal expansion (e.g., Invar 36 % Ni). Ranging from 5 % to 9 % nickel for cryogenic structural use to high-percentage alloys for magnetic applications, they feature improved strength and a fine-grained structure.
Iron-nickel superalloys – These are high-performance materials based on iron and nickel, engineered for excellent mechanical strength, creep resistance, and stability at extremely high temperatures, frequently used in jet engine components like blades, discs, and casings for their superior performance and lower cost compared to pure nickel or cobalt superalloys, achieving this through solid solution and precipitation hardening with elements like aluminum, niobium, and carbon.
Iron-nickel-tungsten-molybdenum-titanium steel – It is a highly alloyed, ultra-high-strength steel, very frequently identified in metallurgy as a maraging steel (specifically the 18Ni maraging steel family). These steels are designed to achieve exceptional tensile strength and toughness, often exceeding 2,000 mega-pascals, through a unique combination of low carbon content and precipitation hardening mechanisms.
Iron nitrides – These are interstitial compounds of iron and nitrogen (FexN, such as Fe4N, Fe3N, Fe16N2), formed by introducing nitrogen into the iron lattice, primarily used in metallurgy to harden steel surfaces, improve wear resistance, and provide high-performance magnetic properties. These hard, brittle materials are created through nitriding, typically at 500 deg C to 520 deg C. These are metallic, crystalline interstitial compounds where nitrogen atoms occupy space within the iron lattice, resulting in face-centered cubic (FCC), body-centered cubic (BCC), or hexagonal close-packed (HCP) structures.
Iron notch – It is also known as tap hole. It is the opening in the furnace hearth for draining the hot metal as well as slag from the furnace. The iron notch is opened by drilling for tapping and after tapping closed with taphole mass by the mud gun.
Iron nuggets – These are pebble shaped with elliptical structure solid, high-density, highly metalized iron produces from dry green balls using a direct reduction process. The reduction process is carried out in a rotary hearth furnace, using coal as the reductant and energy source. Iron nuggets are a premium grade iron product with superior shipping and handling characteristics. They can be stored outside with no special precautions. They can be handled as a bulk commodity using conventional magnets, conveyors, bucket loaders, clams, and shovels. They are having size in the range of 5 millimeters to 25 millimeters and a density in the range of 6.5 grams per cubic meters to 7 grams per cubic meters. The chemical composition of iron nuggets is metallic iron – 96 % to 97 %, carbon – 2 % to 3 %, and sulphur – 0.05 % to 0.07 %.
Iron ore – Iron ore is a type of mineral rock from which metallic iron is extracted economically. This ore is normally rich in iron oxides and vary in colour from dark grey, bright yellow and deep purple to rusty red. The mineral in the iron ore can vary depending on the deposit. Iron ore is capable of smelting iron under modern technological conditions and is economically cost-effective. Iron ore is composed of one or more iron containing minerals and gangues, which are also entrained with some impurities. The gangue is also composed of one or several minerals (compounds). Iron-bearing minerals and gangues are called minerals and are compounds with a certain chemical composition and crystal structure. The mineral in the iron ore can vary depending on the deposit. The minerals normally found in the iron ore are magnetite (Fe3O4), hematite (Fe2O3), goethite [FeO(OH)], limonite [FeO(OH).n(H2O)], or siderite (FeCO3).
Iron ore agglomeration technologies – These are the technologies for the agglomerating of iron ore fines. Five iron ore agglomeration technologies can be defined which are briquetting, nodulization, extrusion, pelletization, and sintering. Sintering and pelletization are the most important agglomeration technologies.
Iron ore mining – It is the process of extracting, beneficiating, and processing iron-bearing minerals, mainly hematite (Fe2O3) and magnetite (Fe3O4), from the earth’s crust for industrial steel production. It involves geological exploration, drilling, blasting, loading, and transportation through open-pit or, rarely, underground methods, followed by crushing, screening, and, frequently, sintering to prepare raw material for furnaces.
Iron ore pellet – It is a type of agglomerated iron ore fines which has better tumbler index when compared with that of the parent iron ore. Iron ore pellets are widely used as a substitute of lump ore for the production of direct reduced iron and in the blast furnace for the production of hot metal. The term iron ore pellet refers to the thermally agglomerated material formed by heating a variable mixture of iron ore, limestone, olivine, bentonite, dolomite, and miscellaneous iron bearing materials in the range of 1,250 deg C to 1,350 deg C. Iron ore pellets are normally produced in two types of grades namely direct reduced iron grade and blast furnace grade. The requirements of direct reduced iron grade pellets are (i) low quantity of silica and alumina (less than 0.9 %), (ii) high basicity, (iii) low reduction disintegration, (iv) low sticking tendency, and (v) high reducibility. The requirements of blast furnace grade pellets are (i) high and consistent quality, (ii) high productivity, (iii) low energy demand, (iii) additives to optimize blast furnace process performance and (iv) pellets to match high basicity sinter. Direct reduced iron grade pellets are also known as acid pellets while the blast furnace grade pellets are basic pellets. These pellets are fluxed pellets and have higher basicity than the direct reduced iron grade. Direct reduced iron grade pellets do not contain calcium oxide (CaO), while the blast furnace grade pellets are fluxing pellets containing calcium oxide. For the blast furnace grade pellets, reducibility and swelling index are important properties while for direct reduced iron grade disintegration is an important property.
Iron ore reduction – It is a metallurgical process which removes oxygen from iron oxides (Fe2O3, Fe3O) ) to produce metallic iron (Fe). It involves high-temperature chemical reactions (solid-state or smelting) using reducing agents like hydrogen (H2) carbon mono-oxide (CO), or coal / coke to convert ore into hot metal or solid direct reduced iron (DRI).
Iron ore sinter – It is normally the major component of a blast furnace iron bearing burden material. Sinter normally consists of different mineral phases produced by sintering of iron ore fines with fluxes, metallurgical wastes and a solid fuel. Coke breeze is normally used as fuel in the sinter mix since it supplies necessary heat energy for sintering of sinter mix. A sinter is regarded as consisting of essentially three types of materials namely (i) original unaltered (primary) material, (ii) original secondary material which is the result of alteration of the structure and shape through recrystallization in the solid state, and (iii) secondary constituents which result from material that has fused or dissolved during sintering. These constituents can either mutually dissolved or can precipitate from the solution. Two types of bonding are theoretically possible depending on the mineralogical changes. These bonding are slag or fusion bond and diffusion bond.
Iron oxide – It is a versatile chemical compound of iron and oxygen, occurring in different forms like hematite (Fe2O3), magnetite (Fe3O4), and rust (hydrated Fe2O3.nH2O), important as pigments, magnetic materials, catalysts, and in construction for colouring concrete because of its durability and stability, with applications from paints and electronics to environmental remediation. This material as prepared for foundry use normally contains around 85 % ferric oxide and is produced by pulverizing a high grade of pure iron ore. It can be added to core sand mixes to assist in keeping the core from cracking before the metal solidifies during the casting operation and also helps to resist metal penetration during this period. Added to moulding sand mixtures for control of finning and veining. It also can reduce carbon pick up.
Iron oxide pellets – These are thermally hardened, spherical agglomerates (typically 8 millimeters to 16 millimeters) produced from fine iron ore concentrate, binders (like bentonite), and additives. They act as a high-grade feed substitute for lump ore in blast furnaces and direct reduced iron (DRI) processes, for superior strength, uniform size, and high reducibility.
Iron pipes – These are cylindrical, ferrous components made mainly from cast iron or ductile iron, designed for high-strength, durable transport of water, sewage, and gas. Characterized by high compressive strength and corrosion resistance, these pipes are used for durable infrastructure, though ductile iron has largely replaced traditional, brittle gray cast iron for modern piping.
Iron plate – It is a flat, rectangular, structural component manufactured from iron or steel, typically used for its high strength, durability, and load-bearing capacity in construction, machine fabrication, and industrial applications. These plates serve as foundational base plates, structural reinforcements, or durable surface components, and are available in different thicknesses to suit different structural loads.
Iron powder – It is finely divided metallic iron particles, typically ranging from a few micrometers to several hundred micrometers in diameter. It is a versatile material with several industrial applications because of its unique properties like high purity, controlled particle size, and magnetic characteristics.
Iron research – It is the scientific investigation of iron and its alloys (ferrous materials) to improve their properties, production techniques, and applications, particularly within metallurgical, mechanical, and civil engineering. It focuses on improving strength, corrosion resistance, and, in modern contexts, sustainable, low-carbon manufacturing processes for iron and steel.
Iron rot – It is the deterioration of wood in contact with iron-base alloys.
Iron-silicon (Fe-Si) alloys – These are a class of ferrous materials mainly composed of iron (Fe) and silicon (Si), frequently containing 15 % to 90 % silicon, or lower levels (around 3 % to 4 %) for electrical, magnetic, and casting applications. These alloys are necessary in the production of high-performance materials, serving as vital deoxidizers, alloying agents, and structural components in steelmaking and foundry operations.
Iron soldering – It is a soldering process in which the heat needed is got from a soldering iron.
Iron sponge process – It is a fixed-bed absorption method used to selectively remove hydrogen sulphide (H2S) and mercaptans from gas streams, such as natural gas or biogas, by passing them over wood chips impregnated with hydrated iron oxide (Fe2OP3). It operates at low temperatures, typically below 43 deg C, in a slightly alkaline environment (pH 8 to pH 10).
Irradiance – It is the instantaneous radiant power (P) incident on a surface per unit area (A), typically measured in watts per square meter. It represents the rate of electro-magnetic energy (E), such as solar radiation or laser light, received per unit surface area (E = dP/dA).
Irradiance of a receiver – It is the radiant power per unit area incident on a receiver.
Irradiance values – These refer to the quantity of light incident on a unit area, measured in watts per square meter, which is important for uniformity in accelerated weathering tests and affects degradation rates in materials exposed to different light sources.
Irradiated field – It refers to a defined, targeted area or volume exposed to a specific, controlled intensity of radiation (e.g., thermal, electro-magnetic, or particle). It is frequently used in material processing, such as powder bed fusion to delineate, through or, and, a target area with a specific dosage.
Irradiated material – It is a substance (metal, polymer, or compound) which has been exposed to ionizing radiation (such as neutrons, gamma rays, or ion beams), causing permanent physical, chemical, or structural changes. This exposure frequently creates internal atomic defects, such as void formation, helium bubbles, and lattice displacement, leading to degraded mechanical properties like hardening and embrittlement.
Irradiated region – It is the specific area or volume of a material, component, or surface directly exposed to an energy source, such as lasers, electron beams, or nuclear radiation, causing localized structural, physical, or chemical modifications. This region typically experiences nonuniform intensity, high stress, and defect formation.
Irradiated spot – It is a precise, localized area on a material’s surface or within its volume that is intentionally exposed to a concentrated beam of radiation (such as laser, electron, ion, or X-ray) to induce specific physical, chemical, or structural changes. It is the fundamental unit of action in spot-scanning irradiation techniques.
Irradiated surface – It refers to a material surface exposed to incident electro-magnetic or particle radiation (e.g., laser, ultra-violet, X-ray, electron beams), resulting in altered physical, thermal, or chemical properties. It defines the target area receiving radiation, frequently causing surface heating, ablation, micro-structure modification, or structural degradation.
Irradiated zone – It refers to the specific area on a substrate or material surface directly exposed to high-energy radiation (such as laser beams, electron beams, or ultra-violet light). This region experiences altered physical or chemical properties, such as increased hardness, phase transformation (e.g., martensite formation), or surface energy changes, because of rapid heating, cooling, or chemical crosslinking.
Irradiation – It is the exposure of a material or object to X-rays, gamma rays, ultra-violet rays, or other ionizing radiation. This is the process by which an item is exposed to radiation.
Irradiation creep – It is the time-dependent deformation of a material under stress when exposed to radiation, particularly in nuclear environments. It is a significant factor in the dimensional stability of materials used in nuclear reactors, where it can cause components to change shape and potentially fail. Unlike thermal creep, which is mainly driven by temperature, irradiation creep is specifically induced by the effects of radiation.
Irradiation data – It refers to the quantitative measurement of solar energy (or other radiation) incident on a surface over a specific time period, typically expressed in kilo watt hour per square meter or joule per square meter. It is distinct from instantaneous irradiance (power, watt per square meter) and is crucial for analyzing energy potential, material degradation, and solar system performance.
Irradiation growth – It refers to the dimensional changes which occur in a material because of irradiation (exposure to radiation, typically in a nuclear reactor), even in the absence of any applied stress. This phenomenon is mainly observed in zirconium alloys and other materials used in nuclear reactors. The dimensional changes are anisotropic, meaning they differ in different directions within the material, and occur at a constant volume.
Irrational number – It is a real number which cannot be expressed as a simple fraction (p/q, where p, q are integers, and q is not zero) and has a non-terminating, non-repeating decimal expansion. They represent precise, continuous, and frequently physical constants, such as pi, or root 2, which need approximation for calculations.
Irreducible form – It refers to a representation of a system, equation, or data set which has been reduced to its simplest, most fundamental components and cannot be further decomposed, simplified, or block-diagonalized without losing essential information. It is the minimum possible representation, frequently used to improve computational efficiency, analyze system symmetry, or define governing equations in finite element methods.
Irreducible formulation – It is also called displacement formulation. It is a method of modeling physical problems where all unknown variables are expressed in terms of a single primary field variable, normally displacement (u), and cannot be reduced further without solving the entire system of equations.
Irreducible water saturation (Sw, or Swirr) – It is the minimum water saturation achievable in a porous rock medium through displacement by oil or gas, representing immobile water held by capillary forces. It is a critical petrophysical parameter for calculating initial oil / gas in place, defining net pay, and is typically measured through centrifuge or porous plate experiments.
Irreducible mesh – It is a closed loop or path in a circuit which contains no other smaller loops within it. It is the fundamental, indivisible loop used for ‘mesh current analysis (or mesh analysis) and Kirchhoff’s voltage law (KVL) to determine currents in planar networks.
Irregular mesh – It is frequently being called an unstructured mesh. It is a, non-uniform grid consisting of varied element shapes (tetrahedra, triangles, pyramids, or prisms) and sizes, used to discretize complex 3D geometries for simulation. It provides high flexibility to conform to intricate boundaries, allowing for dense, accurate, and localized refinement in critical areas, frequently at the cost of higher memory usage compared to structured meshes.
Irregular particle shape – It refers to the complex, non-uniform geometry of particles used in concrete, which cannot be easily defined or simulated because of their varied configurations. It cannot be defined by a single, simple dimension. These particles are frequently characterized by high surface-area-to-volume ratios, varying angularity, and lack of unique axis symmetry, needing advanced imaging, sphericity, or circularity measurements to quantify their behaviour.
Irregular parting line – It is also called non-planar parting surface. It is a parting which does not lie on a single flat plane where the two halves of a mould (cope and drag) meet. Instead, it follows a 3D contour, featuring curves, steps, or offsets to accommodate complex geometries, ensuring the casting can be removed from the mould.
Irregular path – It refers to a non-linear, unpredictable, or non-uniform route taken by physical phenomena, signals, or design elements, often characterized by lack of symmetry, complexity, and variation in, e.g., structural loads, fluid motion, or network connections. It necessitates specialized analysis because of the potential inefficiencies, stresses, or unpredictable behaviour.
Irregular sampling – It refers to a, signal acquisition process where data points are captured at non-uniform, non-equidistant intervals rather than at fixed, periodic time steps. It is used to reconstruct band-limited signals or manage data with varying sampling rates, frequently necessitated by random, natural, or non-deterministic measurement points, such as in laser Doppler velocimetry.
Irregular powder – It is a powder having particles which lack symmetry.
Irregular shape – It refers to particles, powders, or structural grains which lack symmetry and possess non-uniform, non-spherical geometries. These shapes are typically characterized by angular, rough, jagged, or complex morphologies, frequently resulting from specific manufacturing processes like mechanical grinding, chemical reduction, or crushing, rather than atomization.
Irregular shaped inclusion – It is a foreign substance, particle, or phase embedded within a host material (matrix) which lacks a uniform, symmetric, or spherical geometry. These inclusions typically have non-uniform, complex, or angular configurations (e.g., jagged, elongated, stringers) and are frequently formed because of manufacturing, solidification, or casting processes.
irregular structure – It is a building or system lacking symmetry in its configuration, mass, stiffness, or strength, frequently leading to complex load paths and poor seismic performance. These structures feature discontinuities, such as abrupt geometry changes, soft stories, or substantial eccentricities between the centre of mass and resistance, needing advanced analysis (e.g., 3D modeling).
Irreversibility – It is the inability of a system and its surroundings to return to their exact initial states after a process has occurred, signifying a loss of energy quality, frequently because of the friction, heat transfer across finite temperature differences, or unrestrained expansion. It represents the difference between maximum (ideal) work and actual work, fundamentally linked to the unavoidable, unidirectional increase of entropy in real-world, spontaneous processes.
Irreversibility rate – It refers to the analysis and optimization of energy systems to minimize the rate of exergy destruction, the rate at which useful energy is lost due to inefficiencies such as friction, heat transfer across finite temperature differences, and mixing. It is a critical, second-law-of-thermodynamics approach to design, focusing on reducing the ‘one-sidedness’ of physical processes to increase overall efficiency.
Irreversible – It means not capable of redissolving or remelting. Chemical reactions which proceed in a single direction and are not capable of reversal (as applied to thermosetting resins).
Irreversible attachment – It describes the adhesion of particles, bacteria, or materials to a surface which cannot be removed by simple physical, hydraulic, or shear forces, needing substantial chemical or physical disruption. This permanent immobilization frequently marks the transition from temporary surface interaction to fixed, long-term adhesion.
Irreversible cycle – It is a real-world thermodynamic cycle which cannot return both the system and its surroundings to their initial states without leaving net changes, such as increased entropy, energy dissipation, and lost work. Driven by factors like friction, rapid expansion, and heat transfer across finite temperatures, these processes occur at finite rates and always increase the total entropy of the universe.
Irreversible deformation – It is also called plastic deformation. It is the permanent alteration in the shape or size of a material which persists after applied stress is removed and the material’s elastic limit is exceeded. It is caused by atomic-level mechanisms like dislocation motion, twinning, or grain boundary diffusion, preventing the material from returning to its original state.
Irreversible effect – It is also called irreversible process. It is a physical or chemical change which cannot be reversed to return both the system and its surroundings to their original state. Unlike ideal, reversible processes, real-world irreversible effects are spontaneous, unidirectional, and accompanied by energy dissipation, which causes a net increase in entropy.
Irreversible injury – It is the damage which exceeds the capacity for adaptation or repair, resulting in a ‘point of no return’.
Irreversible loss – It refers to the permanent dissipation of energy or reduction in system performance (e.g., pressure, voltage, or capacity) which cannot be recovered or reversed to the initial state without causing changes to the surroundings. It represents lost work (exergy) because of the factors like friction, heat transfer, and mixing.
Irreversible process – It is a real-world, spontaneous, and typically fast process which cannot return both the system and its surroundings to their initial states simultaneously, resulting in a net increase in total entropy. These processes are characterized by energy degradation because of the friction, heat transfer across finite temperature differences, or unrestrained expansion, making them less efficient than theoretical reversible processes.
Irreversible reactions – These chemical reactions are unidirectional reactions. The irreversizble reactions are those reactions in which, the reactants convert to products and where the products cannot convert back to the reactants. An example of an irreversible reaction is combustion.
Irritant – It is a substance which, in sufficient quantities, can inflame or irritate the eyes, other mucosa, skin or respiratory system (lungs, etc.). Symptoms include pain and reddening.
Irrotational flow – It is a fluid motion type where fluid particles move along paths without rotating about their own axes. It is characterized by zero vorticity and no swirling or vortex motion. Mainly used in aerodynamic design (e.g., airfoils) and ideal fluid modeling, this flow assumes negligible viscosity.
Irrotational motion – It is a type of fluid flow where, although fluid particles may travel along curved paths, they do not rotate about their own axes (zero angular velocity). It is characterized by a velocity field with a curl of zero, implying zero vorticity and no viscous torque effects.
IR-UT (Injection refining-up temperature) process – It is a secondary steelmaking process. This process has two capabilities namely injection refining and temperature raising. In the process, chemical heating is carried out through the exothermic reaction of aluminum with the oxygen gas (4Al + 3O2 = 2Al2O3). The process needs a snorkel and two types of top lances. One type is the deeply immersed bubbling lance for stirring the liquid steel and the second lance is for blowing of oxygen. The treatment of liquid steel is carried out in three stages. In the first stage, argon gas bubbling is done in the liquid steel to homogenize the chemical composition. At the end of this stage aluminum is added. In the second stage, the temperature of the liquid steel is increased by chemical heating. Oxygen gas is blown through the top lance to the surface of the liquid steel in the snorkel. In this stage gas, oxygen gas bubbling homogenizes the liquid steel temperature. In the third and final stage, argon gas bubbling is carried out for improving the steel cleanliness. All the three stages are carried out without interruption between the stages to shorten the treatment time in the process.
I-section – It is also called I-beam. It is a structural steel member with a cross-section resembling the letter ‘I’, consisting of two flanges (horizontal elements) and a web (vertical element). It is known for its high strength and efficiency in resisting bending and shear loads.
I-section beam – It is a structural member featuring an ‘I’ or ‘H’ shaped cross-section, normally made of structural steel to provide high, efficient bending and shear resistance. It consists of a vertical web for resisting shear forces and horizontal flanges for resisting bending moments.
I-sections with narrow and medium flanges – These are ‘I’ sections in which the flange width is equal to or less than 0.66 × the nominal height of the section and less than 300 mm.
Isenthalpic expansion – It is a thermodynamic process where a fluid expands (drops in pressure) while its enthalpy remains constant (delta h = 0), typically occurring adiabatically without work extraction, such as in throttling valves or capillary tubes. It is characterized by a substantial pressure drop and frequently a temperature change (Joule-Thomson effect), normally used in refrigeration cycles.
Isentropic – It refers to a process which occurs at constant entropy, typically describing a reversible and adiabatic cycle where no heat transfer takes place.
Isentropic bulk modulus – It is a measure of a fluid’s resistance to compression under rapid, adiabatic conditions (no heat transfer). Defined as the ratio of an infinitesimal pressure increase to the resulting relative decrease in volume, it represents the fluid’s stiffness during fast processes, such as hydraulic pump pulses or pressure wave propagation.
Isentropic compression – It is an idealized thermodynamic process where a gas is compressed with zero heat transfer (adiabatic) and no internal friction or irreversibilities (reversible), resulting in constant entropy (dS = 0) It serves as a, 100 % efficient, theoretical benchmark for real-world compressors, turbines, and engine cycles to maximize pressure and temperature increase.
Isentropic efficiency – It is a performance parameter that compares the actual performance of a device (like a turbine or compressor) to its ideal, reversible, and adiabatic performance, expressed as the ratio of actual work to isentropic work.
Isentropic expansion – It is an idealized, theoretical process where a fluid expands reversibly (no friction / turbulence) and adiabatically (no heat transfer), keeping its entropy constant, converting internal thermal energy into useful work or kinetic energy, crucial for analyzing turbines, nozzles, and compressors. It is a benchmark for ideal efficiency, with real-world expansions (like in engines) never achieving perfect isentropic conditions because of irreversibilities like friction.
Isentropic exponent – It is a dimensionless thermodynamic property defining the relationship between pressure and density / volume during an ideal (constant entropy, reversible, adiabatic) process in fluids. It is defined as the ratio of specific heats for ideal gases, but for real gases / fluids, it is derived from local derivatives.
Isentropic flow – It is an idealized fluid flow which is both adiabatic (no heat transfer) and reversible (no friction or dissipative losses), resulting in constant entropy throughout the process. It acts as a model for analyzing ideal performance in devices like nozzles, diffusers, and turbines, where friction is negligible.
Isentropic process – It is an idealized thermodynamic process where a fluid’s entropy remains constant, meaning it is both reversible (no friction / losses) and adiabatic (no heat transfer). It serves as a benchmark for evaluating real-world devices like turbines, compressors, and nozzles, using isentropic efficiency to compare actual performance to this ideal, frictionless state, frequently described by ‘PV to the power gamma = constant’ for ideal gases.
Iserine – It is also known as iron sand. It refers specifically to a type of black sand which mainly consists of magnetic iron ore mixed with a substantial quantity of titanium. It is classified as a raw material, typically in the context of foundry, metallurgy, or mineral processing.
Ising model -It is a statistical model of magnetism on a lattice which incorporates ferro-magnetic interactions between nearest-neighbour spins, where each site can be in one of two states, represented as up-spin (+1) or down-spin (−1). It serves as a foundational framework for studying phase transitions and the associated properties of magnetic systems.
Islanded microgrid – It is a localized power system comprising distributed generation (DG), energy storage, and loads, capable of operating independently from the main utility grid, frequently after a planned or unplanned disconnection at the point of common coupling (PCC). Engineering this mode needs self-sufficient voltage / frequency regulation using grid-forming sources, ensuring stability without main grid inertia.
Islanded mode – It refers to a microgrid or portion of the utility grid operating independently after disconnecting from the main power grid, with local distributed energy resources (DERs), such as solar, batteries, or generators, supplying power to local loads. It is characterized by self-sustaining voltage and frequency control.
Islanded operation – It refers to a microgrid or portion of an electrical utility network continuing to operate independently after being disconnected from the main grid. Powered by local distributed generators (DGs) or energy storage, this autonomous mode maintains power to critical loads. It can be intentional (planned for maintenance) or unintentional (caused by faults), needing specialized, self-sufficient controls for voltage and frequency management.
Island silicates – These are technically known as nesosilicates. These are a class of silicate minerals defined by having isolated silicon-oxygen [(SIO4)4-] tetrahedra which do not share any oxygen atoms with neighboring tetrahedra. They are the simplest, least polymerized type of silicate, frequently found in igneous and metamorphic rocks, with high density and hardness.
Isobar – In atomic physics, one of two or more atoms which have a common mass number ‘A’, but differ in atomic number ‘Z’. Hence, although isobars possess around equal masses, they differ in chemical properties, they are atoms of different elements.
Isobaric heat capacity (Cp) – It is a fundamental thermodynamic property defined as the quantity of heat energy needed to raise the temperature of a unit quantity of a substance by one degree while pressure remains constant. It represents the change in enthalpy (H) with respect to temperature (T) at constant pressure (P), specifically Cp = (dH/dT)p.
Isobaric process – It is a thermodynamic process where a system’s pressure (P) remains constant (delta P = 0) as its volume (V) and / or temperature (T) changes, with heat transfer used for both internal energy change and work done, frequently seen in phase changes like boiling water or engine cycles, represented by a horizontal line on a P-V diagram.
Isobutane (C4H10, 2-methylpropane) – It is a colourless, flammable, branched-chain isomer of butane normally used as an eco-friendly refrigerant, petro-chemical feedstock, and aerosol propellant. It is a saturated hydrocarbon gas which acts as a low-global-warming-potential alternative to fluoro-carbons.
isochronal lines – These are also called isochrones’ These refer to curves on a graph which represent data points collected or calculated at the same amount of time. These lines are mainly used in (i) isochronal annealing, (ii) property mapping, and (iii) microstructural evolution.
Isochoric cooling – It is a thermodynamic process where a substance is cooled within a rigid, closed container, keeping the volume (V) constant (delta V = 0). As temperature (T) decreases, the pressure (p) of the system also decreases, while no boundary work is performed (W = 0).
Isochoric deformation – It is a type of material deformation where the volume remains constant, meaning the material is incompressible. Characterized by a Jacobian determinant ‘J = det (F) = 1’, it occurs when shear strains dominate, frequently analyzed in materials like rubbers and metals where total volume is conserved during shape changes.
Isochoric heating – It is a thermodynamic process where a substance is heated within a rigid, closed container, keeping its volume constant (delta V = 0). Since the volume does not change, no boundary work is performed (W = 0), causing all added heat (Q) to directly increase the system’s internal energy (delta U) and pressure.
Isochronous curve – It is a curve where the time taken for a particle to descend to the lowest point is the same regardless of its starting point on the curve. This property is often associated with the cycloid curve, where objects sliding without friction under uniform gravity reach the bottom in the same quantity of time, regardless of where they start. Another related concept is the isochronous stress-strain curve, which is used to describe the relationship between stress and strain in materials undergoing creep at different time intervals.
Isochronous stress-strain curve – It is a specialized engineering graph plotting stress against total strain (elastic + plastic + creep) at a fixed temperature and specific, constant time intervals. Derived from creep tests, these curves allow designers to analyze time-dependent material deformation under constant load as a simplified time-independent elastic-plastic problem.
Isocline – It is a curve or line in a coordinate plane (x, y) along which the slope (dy/dx) of the solutions to a differential equation is constant [f(x, y) = c]. They are used to visualize slope fields and sketch solution curves, helping analyze dynamic systems, stability, and control, where they indicate where solutions have the same gradient.
Isocon – In geology and geochemistry, particularly relating to ore deposits, an isocon is a straight line passing through the origin on a plot comparing the chemical concentrations of an altered rock to its original precursor. It represents a ‘constant concentration’ line (iso = equal, con = concentration) for components which remained immobile during chemical alteration, serving as a reference to calculate the mass, volume, and concentration changes of other, mobile elements.
Isocorrosion diagram – It is a graph or chart which shows constant corrosion behaviour with changing solution (environment) composition and temperature.
Isocratic elution – In liquid chromatography, it is the use of a mobile phase whose composition is unchanged throughout the course of the separation process.
Isocure – It is trade name of a binder system developed for use in the cold box process of core construction.
Isocyanate – It is the functional group with the formula R−N=C=O. Organic compounds which contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a di-isocyanate. Di-isocyanates are manufactured for the production of polyurethanes, a class of polymers.
Isocyanate group (−N=C=O) – It is a highly reactive, unsaturated functional group consisting of a nitrogen atom double-bonded to a carbon atom, which is in turn double-bonded to an oxygen atom. Engineered as the foundational building block for polyurethanes, they react with alcohols, water, and amines to create versatile foams, coatings, and elastomers. -N
Isocyanate plastics – These are the plastics based on resins made by the condensation of organic isocyanates with other compounds. These are normally reacted with polyols on a polyester or polyether backbone molecule, with the reactants being joined through the formation of the urethane linkage. See also polyurethane and urethane plastics.
Isocyanic acid (HNCO) – It is the most stable, predominant isomer of cyanic acid (HOCN), characterized as a colourless, volatile, and toxic liquid which acts as a vital industrial intermediate in the production of polyurethanes, and specialized chemicals. It is a highly reactive compound which readily polymerizes into cyanuric acid and cyamelide at temperatures above -20 deg C.
Isoelectric focusing – It is an electrophoretic technique used for the separation of amphoteric species based on their isoelectric points (pI) within a pH gradient. The separation occurs as analytes migrate according to their net charge until they reach a position where the pH equals their pI, resulting in cessation of movement.
Isoelectric point – It is the specific pH at which a molecule, particle, or surface carries no net electrical charge, resulting in zero net migration in an electric field. It is critical for optimizing stability, as particles (e.g., ceramics, colloids) frequently flocculate or precipitate at this neutral point due to reduced electrostatic repulsion.
Isoelectronic impurity – It is a substitutional dopant in a semiconductor which possesses the same number of valence electrons as the host atom it replaces, thus contributing no net charge (neither donor nor acceptor) to the crystal. These impurities create local strain and short-range potential perturbations, acting as charge traps for electrons or holes to improve optical properties, normally used in light emitting diode (LED).
Isolated chain – It mainly refers to a single polymer chain in a solution or on a surface which is separated from other chains, allowing for the study of its intrinsic properties (such as conformation, elasticity, or dynamics) without interference from neighbouring molecular chains.
Isolated nitrogen atom – It is a single nitrogen atom (N), atomic number 7, existing without chemical bonding to other atoms, typically achieved in specialized, high-energy applications rather than natural states. These atoms can be implanted into silicon lattice sites, frequently creating stable, isolated, and highly reactive, non-molecular defects.
Isolated-phase bus – It is a bus where each phase is in its own grounded metal enclosure to prevent faults from spreading from phase to phase. It is frequently used in large power plant generators.
Isolated point – It is a pixel which differs considerably in intensity from its neighbours and does not belong to a larger object or structure, appearing as a single, set pixel (e.g., 1) surrounded by unset pixels (e.g., 0). These points are detected using masks or filters that highlight intensity variations.
Isolating device – It is a mechanical device which physically prevents the transmission or release of energy. This includes valves, breakers, switches, blank flanges for piping systems, and restraining devices to prevent movement of parts etc.
Isolation – It is the deliberate separation of systems, components, or circuits to prevent interference, improve safety, or improve performance, achieved through physical barriers, electrical gaps (like transformers), or software techniques, stopping unwanted energy / data transfer while allowing controlled signals. It can involve electrical isolation (blocking direct current / transients), mechanical isolation (like valves for maintenance), seismic isolation (base isolation for buildings), or software isolation (separating applications).
Isolation method – It refers to techniques for deliberately separating systems, components, or circuits to improve safety, improve signal integrity, or prevent unwanted energy transfer. It involves creating a physical, electrical, or functional barrier to isolate hazardous energy (lockout / tagout), disruptive ground loops (galvanic isolation), or components for maintenance.
Isolation monitoring – It is a safety function which continuously measures the electrical resistance between an ungrounded system (e.g., high-voltage battery) and the ground / chassis to detect insulation failures. It ensures that hazardous currents do not flow through the chassis, protecting personnel and components by preventing electrical faults, typically maintaining levels above 500 ohms per volt.
Isolation procedure – It is a systematic, documented, and pre-determined series of steps (frequently LOTO – lockout / tagout) designed to safely disconnect machinery, electrical systems, or process equipment from all energy sources. It ensures that equipment is rendered de-energized, safe, and incapable of accidental operation during maintenance or inspection.
Isolation transformer – It is a transformer especially intended to prevent leakage current from passing from its primary circuit to the secondary circuit.
Isolation valve – It is a valve in a fluid handling system which stops the flow of process media to a given location, normally for maintenance or safety purposes.
Isolator – It is a mechanical, off-load switching device designed to completely disconnect a section of an electrical system or machine from the power source. It ensures safety by creating a visible, physical break, allowing for maintenance, repair, or isolation of faulty sections.
Isolines for temperature – These are normally known as isotherms. These are lines on a phase diagram or temperature distribution plot which connect points of equal temperature. They are critical for visualizing thermal gradients, solidification, and phase transformations.
Isomerization – It is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure.
Isomers – These are Ions or molecules with identical chemical formulas but distinct structures or spatial arrangements. Isomers do not necessarily share similar properties. The two main types of isomers are structural isomers and stereo-isomers.
Isometric – It is a crystal form in which the unit dimension on all three axes is the same.
Isometric drawing – This drawing is used for piping. Isometric drawing is 3-D representation of piping on two dimensions of the drawing sheet. Isometric drawing covers a complete line as per the line list connecting one piece of equipment to another. It shows all information necessary for the fabrication and erection. It is not drawn to scale but is to be proportional for easy understanding. Dimensions are given relative to centre-line of piping. Isometric drawing also includes (i) plant North with the direction so selected as to facilitate easy checking of general arrangement drawing with isometric drawing, (ii) dimensions and angles, (iii) reference number of piping and instrument diagrams (P&IDs), general drawings, line numbers, direction of flow, insulation and tracing, (iv) equipment location and equipment identification, (v) nozzle identification on the connected equipment, (vi) details of flange on the equipment if the specification is different from the connecting piping, (vii) size and type of every valve and direction of operation, (viii) size and number of control valve, (ix) location, orientation and number of each equipment, (x) field weld, preferred in all directions to take care of site variations (it can also be covered with a general note), (xi) location of high point vents and low point drains, which is preferably covered with a standard arrangement note, (xii) any special requirement such as line to be tested prior to installation etc., (xiii) bill of materials, and (xiv) requirements of stress relieving, seal welding, pickling, and coating etc.
Isometric pipeline drawings – These are detailed 2D technical illustrations which represent a 3D view of piping systems. They provide a comprehensive representation of the arrangement, dimensions, and connections of pipes within a system, using isometric projection to show all three spatial dimensions on a single plane. These drawings are crucial for material take-off, fabrication, and construction of piping systems. Isometric drawings use a specific projection where all three axes (length, width, and height) are shown at 30-degree angles, creating the illusion of depth on a flat surface. They include single-line representations of pipes, along with symbols for fittings, valves, flanges, and other components, all accurately dimensioned.
Isometry – It is a distance-preserving transformation (mapping) between two metric spaces. It transforms an object, such as a rigid body, without altering its size or shape, meaning the distance between any two points in the original figure remains equal to the distance between corresponding points in the image.
Isomorphism – It means two different systems, structures, or objects are fundamentally the same in structure and function, differing only in labels or appearance, allowing properties and analyses from one to directly apply to the other. It is a one-to-one mapping that preserves crucial relationships (like connections in networks or operations in math), necessary for comparing complex models in areas like graph theory (networks), chemical informatics (molecules), and control systems, simplifying analysis by treating structurally identical things as equivalent.
Isomorphous – It is having the same crystal structure. This normally refers to intermediate phases which form a continuous series of solid solutions.
Isomorphous system – It is a complete series of mixtures in all proportions of two or more components in which unlimited mutual solubility exists in the liquid and solid states.
Isooctane (C8H18, specifically 2,2,4-tri-methyl-pentane) – It is a highly branched alkane and a critical, colourless liquid hydrocarbon used as the 100-point reference standard for the antiknock octane rating scale. It represents high-performance fuel quality, maximizing compression ratios without engine knock.
Iso-parametric coordinates – In finite element method (FEM), It define a technique using identical interpolation functions (shape functions) to map both an element’s geometric shape and its internal displacement field from a local, normalized, natural’ coordinate system (Xi, Eta, Zeta) to the physical, global Cartesian coordinate system (x, y, z). This method facilitates modeling complex, curved boundaries using simple, regular shapes, typically with local coordinates ranging from -1 to +1.
Iso-parametric elements – These are a foundational, high-performance formulation used in finite element analysis (FEA), including metallurgical simulations of casting, forging, and welding, to model complex, irregular, or curved geometries. They are defined by using the same shape functions to interpolate both the geometric coordinates (x, y, z) and the field variables (such as displacements or temperature) within the element.
Isophorone diisocyanate – It is a cycloaliphatic diisocyanate, C12H18N2O2, mainly engineered for producing high-performance, ultra-violet (UV) resistant, and non-yellowing poly-urethanes, coatings, and adhesives. As a monomeric, low-viscosity liquid with high curing efficiency, it provides exceptional weather resistance and mechanical properties, making it superior to aromatic isocyanates for specialty applications.
Isoquant – It is a curve on a graph representing all combinations of two inputs, typically capital (K) and labour (L), which yield the same, constant level of output. Also known as an iso-product curve or producer’s indifference curve, it is a key tool in economics for determining the cost-minimizing combination of inputs, as any point on the curve produces the same quantity.
Isosceles triangular duct – It is a conduit featuring a cross-section with two equal-length sides and an apex angle, normally used in heat exchangers for efficient fluid flow and thermal management. These ducts allow for specialized flow, where turbulence frequently initiates near the wide base before spreading toward the narrow apex.
Isostatic mould – It is a sealed container of glass or sheet of carbon steel, stainless steel or a nickel-based alloy.
Isostatic moulding – It is a powder-compaction process which applies uniform, hydrostatic pressure to a flexible mould from all directions simultaneously, frequently using a liquid medium. This technique achieves near-net-shape components with uniform density, homogeneous micro-structure, and no residual stresses.
Isostatic pressing – It is a process for forming a powder metallurgy compact by applying pressure equally from all directions to metal powder contained in a sealed flexible mould.
Isosteric enthalpy of adsorption – It is the heat released per mole of gas adsorbed onto a solid surface at constant surface coverage and temperature. It measures the energy released during adsorption and determines the regeneration energy needed for the adsorbent. It is a critical parameter derived from adsorption isotherms.
Isosurface – It is a 3D representation of a constant scalar value (isovalue) within a volumetric data field, acting as a 3D equivalent of a 2D contour line or isoline. It is used to visualize and analyze surfaces of equal, temperature, pressure, or velocity in simulation and scan data.
Isosurface extraction – It is the process of generating a 3D surface representing a constant value (isovalue) within a volumetric scalar field, such as pressure, temperature, or density. It translates 3D data into 2D triangular meshes for visualization and analysis, normally using the marching cubes algorithm to identify and interpolate the surface within grid cells.
ISO system management standards – These are standards are for management systems. A management system is the way in which an organization manages the interrelated parts of its operations in order to achieve its objectives. These objectives can relate to a number of different topics, including product or service quality, operational efficiency, environmental performance, health and safety in the workplace and many more. The level of complexity of the system will depend on each organization’s specific context. These standards include ISO 9000 for quality management, ISO 14000 for environment management, ISO 50001 for energy management, ISO 45001 for occupational health and safety, and ISO 27000 for Information security management etc. These standards have a set of individual but related international standards.
Isotachophoresis – It is a technique which involves the injection of a sample between a leading and a terminating electrolyte, where applied voltage causes analytes to form zones in order of decreasing mobility, with zone length proportional to analyte concentration. It is particularly effective for trace analysis, improving the concentration of low abundant components to a steady-state plateau defined by the leading electrolyte’s composition.
Isotherm – It is a line which is drawn on a geographic map joining all the places which have the same temperature. It is a line on a map connecting points having the same temperature at a given time or on average over a given period.
Isothermal – It is pertaining to changes or other phenomena occurring at a constant temperature. It refers to a condition in which the temperature of a system is maintained constant while other parameters, such as humidity, can vary.
Isothermal annealing – It is the austenitizing of a ferrous alloy, then cooling it to and holding at a temperature at which austenite transforms to a relatively soft ferrite-carbide aggregate.
Isothermal compressibility – It is a property measuring a substance’s volume change in response to pressure changes while holding temperature constant. It represents the fractional volume reduction per unit pressure increase. It is the reciprocal of the bulk modulus.
Isothermal compression – It is a thermodynamic process where a gas is compressed while its temperature is kept constant by continuously removing the heat generated during compression, following the relationship ‘PV =C’ (Boyle’s Law), which maximizes efficiency but needs cooling, unlike adiabatic processes.
Isothermal compressive tests – These are experimental procedures used to determine the flow stress and microstructural evolution of materials (such as metals and alloys) by compressing a sample at a constant temperature and specific, controlled strain rates. These tests are necessary for simulating industrial metalworking processes, like hot forging, rolling, or extrusion, to understand how material behaviour changes under high-temperature, slow-strain-rate conditions.
Isothermal condition – It is a thermodynamic process where a system’s temperature remains constant (dT = 0) throughout operation, despite energy transfer, such as work being performed or heat being exchanged. It needs, for an ideal gas, that PV = constant (Boyle’s Law) and that heat added equals work done.
Isothermal constitutive model – It describes how a material deforms under mechanical loading at a constant temperature. It relates stress, strain, and temperature, but in this case, the temperature is held constant throughout the deformation process. These models are crucial for predicting material behavior in various engineering applications where temperature variations are minimal or controlled, such as in many metal forming processes or in specific temperature-controlled environments.
Isothermal cooling – It refers to a heat treatment process where a metal component (typically steel) is rapidly cooled from an elevated, high-temperature phase (normally austenite) to a specific lower temperature, and then held at that constant temperature until a desired phase transformation (such as to pearlite or bainite) is completed. It differs from continuous cooling (like quenching or normalizing) since the transformation occurs entirely while the temperature is held steady, allowing for more uniform, finer microstructures throughout the material.
Isothermal expansion – It is a thermodynamic process where a gas expands (volume increases, pressure decreases) while its temperature remains constant, achieved by continuously supplying heat from the surroundings to match the work done by the gas, following the ideal gas law (PV = C) and important for designing efficient heat engines and compressors.
Isothermal flow – It is a type of fluid motion where the fluid’s temperature remains constant, despite changes in pressure, density, or velocity, frequently assumed for long-distance gas pipelines where heat transfer with the surroundings keeps the fluid in thermal equilibrium. This model assumes friction-induced heating is perfectly balanced by heat transfer through walls.
Isothermal forging – It is a hot-forging process in which a constant and uniform temperature is maintained in the work-piece during forging by heating the dies to the same temperature as the work-piece. In the isothermal forging process, the dies are maintained at the same temperature as the forging stock. This eliminates the die chill completely and maintains the stock at a constant temperature throughout the forging cycle. The process permits the use of extremely slow strain rates, thus taking advantage of the strain rate sensitivity of flow stress for certain alloys. The process is capable of producing net shape forgings that are ready to use without machining or near-net shape forgings which need minimal secondary machining.
Isothermal-isobaric ensemble – It is a statistical mechanical ensemble which models a system at constant particle number (N), pressure (P), and temperature (T), allowing volume (V) and energy (E) to fluctuate. It represents systems in thermal / mechanical contact with a bath, normally used for simulating chemical reactions and phase transitions
Isothermal nitriding – It is a thermo-chemical case-hardening process in which a steel or metal component is held at a constant, elevated temperature (typically in the ferritic range between 400 deg C and 600 deg C, frequently around 500 deg C to 550 deg C), while nitrogen is diffused into the surface. Since this process occurs below the transformation temperature (Ac1), the crystal structure remains ferritic, which prevents the need for quenching and results in minimal distortion of the parts.
Isothermal process – It is a thermodynamic change where a system’s temperature remains constant, even as other properties like pressure (P) or volume (V) change, needing slow heat transfer to maintain thermal equilibrium, meaning any heat added does work, and any work done removes heat (or vice versa) to keep temperature steady. This is key in cycles like steam power where phase changes absorb heat without temperature rise, and for calculating work in engines, frequently governed by Boyle’s Law (PV = constant) for ideal gases.
Isothermal quenching – It is a procedure in which the work-piece is quenched, and held for some time, in a fluid which is held at a constant temperature between the solution treatment temperature and room temperature. This permits precipitation hardening.
Isothermal recovery – It is a process of treating a cold-worked metal or alloy at a constant, high temperature (below the recrystallization temperature) to relieve internal stresses, rearrange dislocations, and improve ductility without causing substantial changes in the grain structure. It is the initial stage of annealing, allowing the material to reduce its stored energy of deformation.
Isothermal roll forming – It is an advanced metallurgical manufacturing process that combines continuous rolling with constant-temperature conditions to deform materials (particularly difficult-to-form alloys) without the rapid surface cooling (die chilling) associated with conventional hot working.
Isothermal roll forging – It is a specialized metallurgical metal-forming process which combines the continuous reduction in thickness of roll forging with isothermal conditions, where both the work-piece and the rolls (dies) are maintained at the same high temperature throughout the operation. This technique eliminates ‘die chilling’ (the rapid cooling of the work-piece upon contact with cooler tools), which allows for improved metal flow, higher dimensional accuracy, and the ability to form complex shapes with minimal waste.
Isothermal rolling – It is a specialized metallurgical metal-working process in which the work-piece is maintained at a constant, uniform temperature throughout the entire deformation process, normally at a high temperature (hot rolling conditions). Unlike conventional hot rolling, where the metal cools upon contact with colder rolls (causing thermal gradients and potential defects), isothermal rolling keeps the material and the rolls at the same, regulated temperature.
Isothermal section – It is a 2D map representing the stable phases and phase boundaries of a material system (normally ternary or higher) at a single, constant temperature, parallel to the composition base. It shows which phases coexist at equilibrium for different compositions after quenching.
Isothermal superplastic roll forming – It is an advanced, high-temperature manufacturing process used to shape materials (typically titanium or nickel alloys) by leveraging their superplastic (high-elongation) properties while maintaining a constant temperature (isothermal) throughout the work-piece and tools.
Developed specifically for producing complex, high-precision axisymmetric parts, it utilizes small, computer-controlled rollers to deform a rotating heated work-piece, allowing for near-net shape manufacturing with high material utilization.
Isothermal system – It is a thermodynamic system which operates at a constant temperature (dT = 0) throughout a process. It implies that any heat added to or removed from the system is perfectly balanced by energy transfers (like work), maintaining constant internal energy.
Isothermal transformation – It is a change in phase which takes place at a constant temperature. The time needed for transformation to be completed, and in some cases the time delay before transformation begins, depends on the quantity of super-cooling below (or super-heating above) the equilibrium temperature for the same transformation.
Isothermal transformation (IT) diagram – It is a diagram which shows the isothermal time needed for transformation of austenite to begin and to finish as a function of temperature. It is also called as time-temperature-transformation (TTT) diagram or S-curve. Isothermal transformation diagram illustrates the isothermal process of austenite precipitation. In this diagram, the transformation time is in the x-axis shown on the logarithmic scale and the temperature is plotted on the y-axis. From this diagram, the incubation period (left hand curve) can be determined and also the time needed for completion of the process (right hand curve). The instant, steel passes the points A3 temperature and A1 temperature during quenching, is normally taken as the zero-time reference. The time required to achieve the temperature of the quenching medium is frequently neglected. The start and finish of the transformation are difficult to determine from the transformation curve behaviour at the initial and final sections of the curve. Hence, the lines of the isothermal transformation diagram normally correspond to a certain final volume which has undergone transformation, e.g., 2 % and 98 % for the transformation start and finish, respectively. The volume value is normally not shown in the isothermal transformation diagram.
Isotherm fields – These are also called isothermal regions, sections, or lines. These refer to areas within a material, or on a metallurgical phase diagram, where the temperature remains constant during a transformation, heat treatment, or processing operation. These are used to define equilibrium phases, control microstructure, and manage heat transfer during solidification or heat treatment.
Isotherms – These refer to diagrams, curves, or plots which represent the behaviour or properties of a material at a constant, uniform temperature (delta T = 0). These are used to visualize, analyze, or predict phase changes, transformations, or interactions without the confounding effects of changing temperature.
Isotone – It consists of one of two or more atoms which display a constant difference A-Z between their mass number A and their atomic number Z. Hence, despite differences in the total number of nuclear constituents, the numbers of neutrons in the nuclei of isotones are the same.
Isotope – It consists of the atoms of the same element which have the same number of protons but different numbers of neutrons. Hydrogen has three isotopes – all with one proton but with zero (normal hydrogen), one (deuterium) or two (tritium) neutrons in the nucleus. Similarly, the two common isotopes of Uranium, U-235 and U-238 both have 92 protons in their nuclei but 143 (235-92), or 146 (238-92) neutrons respectively.
Isotope separation – It is the process of concentrating specific isotopes of a chemical element by exploiting minor differences in their physical or chemical properties, mainly mass. It involves separating isotopes, which have identical chemical behaviours but different atomic weights, using advanced, frequently multi-stage, techniques like centrifuges, gaseous diffusion, or lasers.
Isotropic – It means having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.
Isotopic exchange – It is a process where atoms of a specific element, in one compound or phase, swap positions with isotopes of the same element in a different compound or phase without causing a net chemical change. This technique is used for isotope separation (e.g., producing heavy water for reactors) and investigating surface reaction kinetics.
Isotopic ratio – It is the measurement of the relative abundance of two different isotopes of the same element (e.g., 13C/12C or 18O/16O) within a sample. Used for material tracing, and quality control, these ratios act as intrinsic fingerprints, frequently measured through mass spectrometry (isotope-ratio mass spectrometry, IRMS) to determine origin, age, or processing history.
Isotropic antenna – It is a theoretical, lossless, point-source antenna which radiates or receives electro-magnetic energy uniformly in all directions, creating a spherical radiation pattern. It has a directivity of 1 and serves as the fundamental, ideal reference for measuring the gain of actual, directional antennas.
Isotropic case – It defines a material which shows identical physical and mechanical properties (e.g., Young’s modulus, strength, thermal conductivity) in all directions. It ensures consistent stress-strain responses regardless of loading orientation, simplifying FEA (finite element analysis) modeling. Common examples include metals, plastics, and glass.
Isotropic damage – It is a material degradation model where stiffness reduction occurs uniformly in all directions, regardless of loading orientation. It uses a scalar variable, omega (frequently ranging from 0 to 1), to represent a random, spatial distribution of micro-cracks and cavities, simplifying constitutive modeling for isotropic materials.
Isotropic diffusion – It refers to a transport process where the movement of particles, energy, or information occurs at the same rate in all directions. It is a physical phenomenon where the spreading of a substance (such as gas, heat, or dye) lacks any preferred direction, resulting in uniform, spherical, or Gaussian spreading.
Isotropic direction – It refers to the uniformity in wave propagation characteristics in all directions within a medium, where the polarization vector behaves identically regardless of the orientation, in contrast to anisotropic media where the polarization can vary based on direction.
Isotropic dissipation – It refers to the uniform, direction-independent rate at which turbulent kinetic energy (k) is converted into internal energy (heat) by viscous stresses in fluid flow, typically modeled as ‘e’ in ‘k-e’ turbulence models. It represents the final stage of energy cascade where small-scale eddies dissipate, assuming rotational symmetry and homogeneity.
Isotropic expansion – It refers to a material or substance expanding uniformly in all directions at the same rate, typically because of the temperature changes. In isotropic materials, properties are identical regardless of the direction of measurement, resulting in an equal increase in length, width, and height.
Isotropic function theory – It refers to the mathematical description of material behaviour (such as stress, strain, yield, or failure) which is independent of the direction of measurement. An isotropic material possesses identical physical properties (such as elasticity, conductivity, or strength) in all directions.
Isotropic hardening – It is a material plasticity model where the yield surface expands uniformly in all directions in stress space because of the plastic deformation, without shifting its centre. It indicates that as a material is deformed, its yield strength increases equally in tension and compression. This model represents straight-forward strain hardening, normally used for monotonic loading.
Isotropic-hardening hypothesis – It is frequently simply called isotropic hardening. It is a principle stating that when a material is plastically deformed, its yield surface expands uniformly in all directions in the stress space, without changing its centre or shape. This means the material becomes stronger, its yield strength increases equally, regardless of the direction of subsequent loading.
Isotropic layer – It is a layer of material with identical physical properties, such as strength, stiffness (Young’s modulus), thermal conductivity, and electrical conductivity, in all directions and orientations. These layers show uniform behaviour regardless of the loading direction, simplifying structural analysis. Common examples include metals (steel, aluminum) and glass.
Isotropic linear elastic material – It is a material which shows identical mechanical properties (Young’s modulus, Poisson’s ratio) in all directions, with deformation directly proportional to applied stress (obeying Hooke’s law). It fully recovers its original shape upon unloading and is fully defined by just two independent elastic constants.
Isotropic materials – These are those materials whose properties remain the same when tested in different directions. Isotropic materials differ from anisotropic materials, which display varying properties when tested in different directions. Common isotropic materials include glass, plastics, and metals.
Isotropic matrix – It is a material whose physical properties, such as elasticity, stiffness, thermal expansion, and conductivity, are uniform in all directions. In structural analysis, the stress-strain relationship for these materials is represented by a symmetric stiffness matrix characterized by only two independent elastic constants (e.g., Young’s modulus and Poisson’s ratio).
Isotropic medium – It is a material whose physical properties, such as elastic modulus, thermal conductivity, electrical conductivity, and refractive index, are identical in all directions. Unlike anisotropic materials, isotropic materials maintain consistent behaviour regardless of the orientation of measurement or stress application, normally found in metals, glasses, and plastics.
Isotropic plate – It is a structural, flat, two-dimensional component having a small thickness compared to its width, characterized by uniform mechanical properties (such as elasticity, stiffness, and strength) in all directions. These plates show consistent deformation behavior regardless of the loading direction and are frequently modeled using classical plate theory (CPT) for analysis, particularly in civil and mechanical engineering.
Isotropic radiator – It is a theoretical, lossless point source in antenna engineering which radiates electro-magnetic or sound energy with equal intensity in all directions. As an ideal, non-physical, omni-directional reference, it features a gain of unity and is used to define antenna gain, dBi (decibels relative to isotropic), and effective isotropic radiated power (EIRP).
Isotropic shell – It is a structural element with uniform mechanical properties (such as Young’s modulus, Poisson’s ratio, and strength) in all directions at any given point. Unlike composite or orthotropic materials, these shells behave consistently regardless of the orientation of applied loads, simplifying analysis.
Isotropic source – It is an ideal, theoretical point source which radiates energy (light, sound, or electro-magnetic waves) uniformly in all directions with equal intensity. It serves as a fundamental, non-physical reference standard, with 0 dBi (decibels relative to isotropic) gain, for measuring the directive gain of real antennas, as no real, physical antenna can radiate equally in all directions.
Isotropic sample – It is a material which shows identical physical and mechanical properties, such as stiffness, strength, and elasticity, in all directions. Since properties are independent of orientation, stress-strain relationships remain consistent regardless of how the material is loaded or tested.
Isotropic steel – It refers to steel with uniform mechanical and physical properties (like strength, stiffness, and hardness) in all directions, meaning it behaves the same regardless of how force is applied. This consistency, frequently achieved through processing like hot rolling, makes its performance predictable for applications in construction, vehicles, and other structural uses where uniform response to stress is important.
Isotropic strain – It refers to a condition where a material deforms equally in all directions (‘x’, ‘y’, and ‘z’ axes) when subjected to a specific stress, such as uniform pressure or thermal expansion. This behaviour implies that the material’s strain response is independent of the direction of the applied force.
Isotropic surface – It is a surface, typically produced by advanced finishing processes, which shows identical physical, mechanical, or topographical properties in all directions. It lacks directional, lay-oriented machining marks (peaks / valleys) and has consistent surface roughness, reducing friction and fatigue while improving wear resistance in any direction.
Isotropic tensor – It is a tensor whose components remain invariant (unchanged) under any rotation of the coordinate system, representing physical properties that are identical in all directions. Common examples include the Kronecker delta for rank-2 and the Levi-Civita symbol for rank-3, which are used to describe orientation-independent material behaviour.
Isotropic turbulence – It is a theoretical state in fluid mechanics where statistical properties of velocity fluctuations are uniform in all directions and invariant under rotation. It lacks preferred orientation, meaning directional velocity correlations are zero. Though rarely found in nature, it simplifies modeling by assuming no mean flow gradient.
Isotropy – It is the condition of having the same values of properties in all directions.
Issue a certificate – It is the formal, authorized act of generating, signing, and delivering an official document confirming that a structure, system, or process meets predefined technical standards, safety codes, or contractual obligations, frequently allowing for operation, occupancy, or project handover. It acts as a verification of compliance by a qualified professional.
Itabirite – It also known as banded-quartz hematite and hematite schist, is a laminated, metamorphosed oxide-facies iron formation in which the original chert or jasper bands have been recrystallized into megascopically distinguishable grains of quartz and the iron is present as thin layers of hematite, magnetite, or martite (pseudomorphs of hematite after magnetite).
Item – It is an object or quantity of material on which a set of observations can be made. It is also an observed value or test result got from an object or quantity of material.
Iteration – It is a concept from iterative software development which specifies a fixed time cycle for development work, typically a few weeks long. The development life cycle consists of a number of iterations, sometimes with a functional version of the software produced at the end of each one. Iterative development prioritizes time over scope, so there are rarely concrete requirements to be achieved in an iteration.
Iteration count – It defines the number of times a specific process, calculation, simulation, or design cycle is repeated to approach a desired result, optimize performance, or satisfy, predefined criteria. It measures progress in algorithms, numerical simulations, or product development, where each cycle improves the solution or design.
Iteration method – It is also called iterative method. It is a computational technique used to find approximate, increasingly accurate solutions to complex engineering, chemical, or thermal problems by repeatedly applying a specific algorithm. It is widely used when direct analytical methods are inefficient or impossible, particularly in simulating processes that require refining an initial guess to match physical, chemical, or thermal constraints.
Iteration number – It refers to the specific count of times a design, model, algorithm, or process has been executed, tested, or refined. Each iteration represents a single cycle of improvement, where the output of the previous step becomes the input for the next, aiming to reduce errors or converge toward an optimal solution.
Iteration period – It is a defined, time-boxed, and recurring cycle during which a specific set of development, design, or testing tasks are completed to create a stable, incremental version of a product or system. It is the core unit of work in iterative, agile, and DevOps [software development (Dev) and IT operations (Ops)] methodologies.
Iteration process – It is a cycle of repeating steps, designing, prototyping, testing, and analyzing, to progressively refine a solution. It involves small, incremental improvements based on feedback and performance data, rather than a single linear, waterfall-style path. This method enables continuous improvement and flexibility to meet specifications.
Iteration step – It is a single, complete cycle within an iterative design or development process (frequently adhering to Plan-Do-Check-Adjust cycles), where a prototype, model, or algorithm is refined based on feedback from previous iterations. Each iteration step aims to improve the product’s quality, functionality, or performance, bringing it closer to the final desired specification.
Iteration variable – It is a control variable in engineering programming and modeling which takes on successive values (e.g., i = 1, 2, 3 ……) from a specified range to manage loop execution, track progress, and facilitate repeated calculations or process data. It 9s necessary for automating repetitive tasks, such as in numerical simulations (e.g., I = I + h) to avoid manual repetition and manage loop termination.
Iterative algorithm – It a mathematical or computational procedure which solves a problem by employing successive approximations. It begins with an initial guess or estimate and repeatedly refines it through a sequence of calculations, using the result of each step as the starting point for the next, until a specified termination condition (e.g., sufficient accuracy or a maximum number of repetitions) is met.
Iterative and incremental development – Iterative and incremental development is any combination of the iterative and incremental development approaches. It is an alternative to the waterfall development method. Instead of focusing on sequential development with a single end product, it passes through a number of development cycles, with an improved version of the product, called an increment, produced at the end of each iteration.
Iterative closest point algorithm – It is a widely used method in engineering and computer vision for precisely aligning (registering) two 2D or 3D datasets, typically point clouds or surfaces, by iteratively minimizing the spatial differences between them.
Iterative convergence – It is the process where numerical methods (e.g., finite element method, computational fluid dynamics) approach a stable, accurate solution over successive, repeating calculations. It signifies that residuals (imbalances) have minimized, or results have stabilized within a set tolerance, ensuring reliable results.
Iterative development – Iterative development focuses on developing products in a series of repeated fixed-time iterations, instead of working towards a single deliverable. At the end of an iteration, the team assesses progress and sets targets for the next iteration.
Iterative learning control – It is a specialized, memory-based control technique designed for dynamical systems which perform the same task repeatedly over a fixed, finite time interval (a ‘trial’ or ‘batch’). The core engineering objective of iterative learning control is to achieve high-precision tracking performance, reducing tracking errors to near zero, by learning from the error of previous trials and adjusting the input signal for the next trial. It is widely used in industrial robotics (e.g., assembly line welding), chemical batch processing, and precision motion control systems (e.g., wafer stages), where the reference trajectory and disturbances repeat exactly or almost exactly.
Iteratively decodable codes -These are a class of powerful, capacity-approaching forward error correction (FEC) schemes where the decoder iteratively improves its estimate of the transmitted data by exchanging information between component decoders. They are designed to break down a complex, high-dimensional decoding problem into a series of smaller, manageable stages (iterations), allowing performance to approach the Shannon limit with reasonable computational complexity.
Iterative process – It is a cyclical method of designing, prototyping, testing, and refining a product or system to progressively improve it based on feedback. Unlike linear models, it allows for flexibility, enabling engineers to catch risks early, incorporate changes, and reach optimal performance through repeated, small, incremental steps.
Iterative technique – It is a repetitive process which uses successive approximations, simulations, or prototypes to refine a design or solve complex mathematical problems. By applying a function or process repeatedly, using the output of one cycle as the input for the next, it progressively converges toward a stable, optimal, or desired solution.
ITmk3 process – It is also known as Ironmaking technologies (IT) mark 3 and is one of the coal reduction technologies. It is a rapid ironmaking process which includes reducing of ore, carburizing and melting iron and separating slag, all at relatively low temperatures. The four-step process consists of (i) agglomerating iron-ore and coal, (ii) reducing and melting of the agglomerates, (iii) separating of metallic iron from slag, and (iv) treating of exhaust gases and recovering of the heat. In this process, iron ore concentrate and non-coking coal (reducing agent), limestone (flux), and bentonite (binder) are mixed together and agglomerated into green self-reducing pellets. These pellets are fed into a rotary hearth furnace (RHF) where self-reducing, fluxing dried green balls are reduced, carburized and smelted. The product is granular iron called iron nuggets.
ITS-90 – ITS stands for international temperature scale. ITS-90 is defined for temperatures above 0.65 K and up to the highest temperature measurable according to Planck’s law for monochromatic radiation. The temperature measured with this scale (T90) is the closest to the thermodynamic temperature. This means it is universal. ITS-90 covers several temperature ranges. For each temperature range, it therefore defines fixed temperature points and a specific instrument for measurement and interpolation between these fixed points. The fixed temperature points correspond to phase transitions in pure substances. For example, the freezing points of zinc, tin, or silver, the melting point of gallium, or the triple points of oxygen, mercury or water.
Izod – normally refers to a notched specimen impact. It is a test which measures the energy needed to break a notched sample by striking it with a pendulum, acting as a stress concentrator to evaluate notch sensitivity rather than true impact resistance.
Izod impact – It measures energy ne3ded to break a sample a specific size bar with a pendulum. Izod normally refers to a notched sample impact.
Izod impact test – It is a type of impact test in which a V-notched sample, mounted vertically, is subjected to a sudden blow delivered by the weight at the end of a pendulum arm. The energy needed to break off the free end is a measure of the impact strength or toughness of the material. Izod impact testing is similar to the Charpy V-notch sample. The principal difference is that the sample is gripped at one end only, allowing the cantilevered end to be struck by the pendulum. An advantage of this method is that several notches can be made in a single sample and the ends broken off one at a time. The disadvantage which has caused it to lose the popularity is that the required time needed for clamping and method of clamping the sample in an anvil precludes low-temperature testing. Izod samples can also be round. All dimensional tolerances are +/- 0.05 millimeters unless otherwise specified. The clamping surfaces of the sample are flat and parallel within 0.025 millimeters. Finish on unmarked parts is 2 micrometers. Striker width is to be greater than that of the sample being tested. Several testing equipments can be used for both Charpy and Izod testing.
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