Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘O’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘O’
Object – It refers to a physical entity which can be seen or touched. It is something which receives action.
Object attribute – It is a named property or characteristic which describes a specific feature or piece of data of an object. Attributes have a name and a corresponding value, such as ‘colour’ with the value ‘green’ and provide the important information which defines an object’s state, features, or behaviour.
Object boundaries – These are defined as the distinct edges which delineate the perimeter of objects within an image, which can be tracked systematically using methods such as intensity thresholding or edge detection. Tracking these boundaries involves ensuring continuous movement without reversal and recording encountered boundaries until returning to the starting point.
Objective – It is an optical element that gathers light from an object being observed and focuses the light rays from it to produce a real image of the object. Objectives can be a single lens or mirror, or combinations of several optical elements. They are used in microscopes, binoculars, telescopes, cameras, slide projectors, compact disk players and countless other optical instruments. Objectives are also called object lenses, object glasses, or objective glasses.
Objective aperture – In optical microscopy, it is the working diameter of a lens or a mirror. It is used for accepting a transmitted wave or one of diffracted waves to get a bright-field image or a dark-field image. The objective aperture is inserted into the back focal plane of the objective lens.
Objective evaluation – It is the impartial assessment of a system, process, or product based on measurable, standardized criteria and verifiable data, rather than personal opinion or bias. This approach ensures consistency, accuracy, and reproducibility, allowing engineers to gather reliable data for decision-making, identify areas for improvement, and meet quality and performance standards in a trustworthy and transparent manner.
Objective function – In design optimization, it is the grouping of design parameters which is attempted to be maximized or minimized, subject to the problem constraints. It is also known as criterion function.
Objective function contour – It is a line on a graph which connects points where the objective function has a constant value. These contour lines, also known as isolines, are a graphical tool for visualizing and analyzing optimization problems, helping engineers to identify the optimal or best possible solutions by showing how the objective function’s value changes across the input variables.
Objective lens – Objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought very close to the specimen being examined so that the light from the sample comes to a focus inside the microscope tube. The objective itself is normally a cylinder containing one or more lenses which are typically made of glass. Its function is to collect light from the sample.
Objective optimization – It is the process of finding the best possible outcome for a system or design by minimizing or maximizing a defined objective function, which quantifies a specific goal like cost, performance, or efficiency. This can be a single-objective optimization, focusing on one goal, or a multi-objective optimization, where multiple, frequently competing, objectives are simultaneously optimized, leading to a set of ‘Pareto-optimal solutions’ which represent different trade-offs.
Objective optimization problem – It is a situation where a desired outcome is quantified and optimized, either by minimizing or maximizing a function of decision variables. It can be categorized as single-objective, focusing on one goal, or multi-objective, involving trade-offs between competing objectives such as performance and cost.
Objective stress rate – It is a time derivative of the stress tensor which is frame-indifferent, meaning its value is independent of the observer’s frame of reference. This concept is crucial in continuum mechanics and finite element analysis, especially for large strains, to ensure that material constitutive laws (which relate stress and strain) are physically realistic and do not depend on how the observer is moving.
Objective turret – Majority of microscopes have several objective lenses mounted on a rotating turret to facilitate changing lenses. The objectives are mounted in ascending order of magnification so the user can easily change to progressively higher power lenses.
Object-oriented analysis and design – Object-oriented analysis and design is a technical approach for analyzing and designing an application, system, or business by applying object-oriented programming, as well as using visual modeling throughout the software development process to guide stakeholder communication and product quality. Object-oriented analysis and design in modern software engineering is typically conducted in an iterative and incremental way. The outputs of object-oriented analysis and design activities are analysis models (for object-oriented analysis) and design models (for object-oriented design) respectively. The intention is for these to be continuously refined and evolved, driven by key factors like risks and business value.
Object-oriented data-base management system – It is a database management system which supports the modelling and creation of data as objects.
Object-oriented management – It is a model for management and for project management. The objective of object-oriented management is to provide a clear set of principles set into a framework which enables all participants while minimizing management overhead.
Object-oriented programming – It is a computer programming model that organizes software design around data, or objects, rather than functions and logic.
Object recognition – It is the process of identifying and labeling objects within an image, which encompasses both instance recognition, handling single reference images, and category recognition. It extends beyond simple pattern recognition to include complex tasks such as action and activity recognition in both still images and videos.
Oblateness – It is the deviation of an object’s shape from a perfect sphere, resulting in an oblate spheroid form, where the moment of inertia about the spin axis is higher than that about any diameter. This shape affects gravitational interactions, causing forces which are not always directed towards the geometric centre.
Oblate rhombohedron – It is a rhombohedron (a six-faced parallelepiped with all faces being congruent rhombi) which is ‘flattened’ or ‘squashed’ in shape. It has two opposite apices where the common angle is obtuse (higher than 90-degree), in contrast to a prolate (stretched) rhombohedron, which has an acute angle at these vertices.
Oblique beam – Oblique beam (also called a pencil) of rays from an extra-axial (or off-axis or non-axial) object point contains meridional rays which can be traced by the ordinary computing procedures, and also a large number of skew rays which do not lie in the meridional plane. Each skew ray intersects the meridional plane at the object point and again at a ‘diapoint’ in the image space, and nowhere else. Skew rays need special ray-tracing procedures. These are much more complex than for a meridional ray, and it is observed that skew rays have been seldom used before the advent of electronic computers. Now they are routinely traced by all lens designers since the available computing.
Oblique evaporation shadowing – It consists of the condensation of evaporated material onto a substrate that is inclined to the direct line of the vapour stream to produce shadows.
Oblique illumination – It is the illumination from light inclined at an oblique angle to the optical axis.
Oblique image – It is an aerial image captured with the camera’s optical axis deliberately tilted away from the vertical, showing a perspective of the ground that includes a combination of horizontal and vertical views. Unlike a nadir (straight-down) view, oblique images reveal building facades, roof slopes, and other structural details, making them ideal for creating 3D models, assessing urban environments, and performing detailed visual inspections.
Oblique impact – It is a collision between two objects where the line of impact is not aligned with the line of motion of either object, or where the impulse line of action does not pass through their centres of gravity. Unlike direct impacts, which are essentially one-dimensional, oblique impacts are inherently two-dimensional, needing the breakdown of velocities into components parallel and perpendicular to the line of impact. This type of collision alters both the direction and speed of the colliding bodies and is analyzed using the conservation of momentum along the line of impact and perpendicular to it, along with the coefficient of restitution.
Oblique incidence – It refers to a wave (such as ultrasonic or electromagnetic) striking a surface or interface at an angle other than perpendicular or parallel to the surface’s normal. This occurs when the wave’s propagation vector is at a non-zero angle to the surface normal, leading to complex reflection and transmission behaviours governed by principles like Snell’s law, which differ from those observed in normal incidence (striking at 0-degree).
Oblique shock – It is a type of shock wave which forms at an acute angle relative to the upstream supersonic flow, occurring when the flow is compressed to maintain parallelism with a wall. The strength of the oblique shock is influenced by the normal component of the upstream Mach number.
Oblique projection – It is a simple type of technical drawing of graphical projection used for producing two-dimensional (2D) images of three-dimensional (3D) objects. The objects are not in perspective and so do not correspond to any view of an object which can be obtained in practice, but the technique yields somewhat convincing and useful results. Oblique projection is normally used in technical drawing.
Oblique section – It is a simple type of technical drawing of graphical projection used for producing two-dimensional (2D) images of three-dimensional (3D) objects. It is an orthographic projection of a section made by cutting with a plane which is neither parallel nor perpendicular to the long axis of an object.
Oblique sketch – It is a 3D pictorial representation where the front face of an object is shown to its true size and shape, while the receding depth lines are drawn parallel to each other, typically at a 45-degree angle to the plane, to create a sense of depth. This method provides a quick, non-realistic, 3D-view of an object, with circles and parallel features appearing as their actual size and shape on the front plane, making it useful for depicting mechanical objects and their curves.
Oblong weaves – These weaves are a development of square weaves for increasing the open screen area. With oblong weaves the number of weft wires is reduced, hence enlarging the mesh opening in the warp direction. The typical weave ratio of this asymmetrical mesh is 3:1. Customized weave ratios for specific requirements are also possible.
Obreimoff – It refers to a concept in which energy in a bent elastic beam can drive a crack, disregarding both crack-tip stresses and stress intensity factors. This principle is applied in cantilever beam tests to evaluate the energy dynamics associated with crack propagation in materials.
Observable – It refers to a property of a system which can be detected and estimated from its outputs, or to the system itself when its internal states are knowable through its external behaviour. The term is also used for a feature or phenomenon which can be measured or experienced, or more abstractly, as a value predicted by a mathematical model. The concept of observability is the degree to which a system’s state can be understood by examining its outputs, which is crucial for monitoring and debugging complex distributed systems in fields like software engineering.
Observable phenomenon – It is a real-world event, occurrence, or effect which can be directly measured, experienced, or perceived through sensors and empirical research. These phenomena serve as the practical basis for applying and validating engineering theories, influencing the design of systems and components, and guiding the development of solutions to engineering problems.
Observability – In control theory, it is the measure of how well the internal state of a system corresponds to its measurable outputs.
Observational data – Observational data are non-experimental data, and there is no control of potential confounding variables in the study. Because of the weak inferential grounds of statistical results based on observational data, the support for conclusions based on observational data is to be strongly supported by logic, underlying material explanations, identification of potential omitted variables and their expected biases, and caveats identifying the limitations of the study.
Observational study – It is the study in which the study treatments (or levels of the explanatory variables) are not randomly assigned to cases.
Observation model – It defines the mathematical relationship between the true, hidden state of a system and the measurements or observations which a system’s sensors provide. It frequently involves a function representing the system’s behaviour and a term for noise or random perturbations which corrupt the true signal, allowing engineers to estimate the actual system state from noisy sensor data, especially within frameworks like state estimation and Bayesian filters.
Observation noise – It refers to undesirable fluctuations or inaccuracies introduced into measurement data by external factors or internal system limitations, frequently obscuring the true signal. It can manifest as random variations or systematic errors in measurements from devices, or as unwanted signal components in data transmission, which can degrade signal quality and impact system performance.
Observation post – It is a strategic location, structure, or even a designated period used to gather data, monitor events, and collect information about a system or environment, frequently for purposes of safety, or research. While the term is rooted in military contexts for observing enemy movements, it extends to engineering fields like weather monitoring, system analysis, and even urban planning, using technologies from sensors to simple visual observation.
Observation process – It is the systematic collection of data under controlled conditions, where measurements are taken consistently over a defined period to ensure that variables remain steady, applicable in batch, cyclic, and continuous processes.
Observation range – It consists of the known span of values for a variable where direct measurements or data are available, distinguishing it from the extrapolated values used for estimations beyond that known data. It represents the domain of collected and confirmed data points for analysis, frequently applied when analyzing failures, predicting performance, or establishing performance limits.
Observation window – It is a physical transparent opening, like a glass window on a machine, allowing for direct visual inspection of internal components or external phenomena. It also refers to a defined time period used in system analysis to monitor equipment performance, evaluate data quality, or identify variables influencing system behaviour.
Observed corrosion – It refers to the visible, surface-level degradation of a material, particularly metals, which is directly seen or measured after it has been affected by environmental factors like moisture and oxygen. It is the physical evidence of the underlying chemical and electrochemical processes which cause a material to transform into more stable compounds, leading to material loss and potential equipment failure.
Observed disturbance – It is a signal representing the estimated effects of an external or internal disturbance within a system, as measured by sensors or inferred by a disturbance observer. A disturbance observer is a control method which estimates these unknown disturbances and uncertainty to achieve disturbance rejection, aiming to improve a system’s performance, accuracy, and robustness against unwanted influences. The observed disturbance signal’s accuracy and speed depend on the quality of the system’s plant and sensor models used by the observer.
Observed image – It refers to the actual, real-world image or data captured by a sensor or imaging system at a specific time, frequently contrasted with a reconstructed or modeled version of that image. It represents the raw, unprocessed data containing visual information, such as discrepancies between the ‘observed’ data and a theoretical ‘reconstruction’ or prediction, which can highlight anomalies or new content within the observed image.
Observed interference – It is the measurable phenomenon where two or more coherent waves (like light or sound) interact in a medium, creating a stable pattern of amplified and reduced wave intensity because of constructive and destructive superposition. This interaction is not limited to light. It can involve any type of wave and forms the basis for technologies such as noise-cancelling headphones, advanced optics, and precise testing of polished surfaces like lenses.
Observed property – It refers to a characteristic of a material or system which can be directly perceived or measured without altering the material’s fundamental identity. These are frequently physical properties, which encompass qualities like colour, density, hardness, and melting point, and are necessary for selecting materials for specific applications. Engineers use these observed properties to understand how a material performs and to make informed decisions about its use in designs and structures.
Observed rate – It is the rate of reaction per unit volume of catalyst, which can be measured by analyzing the rate at which substrate is converted in a batch reaction system or through continuous in situ monitoring when substrate consumption is rapid.
Observed reaction rate – It is the rate at which substrate is converted per unit volume of catalyst, determined through batch measurements or continuous monitoring of substrate concentration or oxygen uptake during a catalytic reaction.
Observed value – It is the particular value of a characteristic determined as a result of a test or measurement.
Observer bandwidth– It is the frequency range within which an observer can effectively respond to input signals, with its performance frequently limited by the sample rate and influenced by sensor noise. It can be intentionally set lower than the maximum achievable bandwidth to mitigate the effects of noise in the system.
Observer feedback – It refers to a control strategy which utilizes an observer to estimate unmeasured states in a system, allowing for the design of state-feedback control even when only partial state information is available. This approach is crucial for ensuring stability and performance in both linear and nonlinear systems, where the dynamics of the closed-loop system depend on the integration of the observer’s estimates and the feedback control design.
Obsolete scrap – It is also called old or post-consumer scrap. It results when industrial and consumer steel products (such as automobiles, appliances, buildings, bridges, ships, cans, and railroad coaches and wagons etc.) have served their useful life. Obsolete scrap is collected after a consumer cycle, either separately or mixed, and it is frequently contaminated to a certain degree, depending highly on its origin and the collection systems. Since the life time of several products can be more than ten years and sometimes even more than 50 years (for example products of building and construction), there is an accumulation of steel products in use since the production of the steel has started on a large scale. Obsolete steel scrap accounts for around 48 % of total steel scrap.
Obstruction devices – These are specialized instruments, such as venturi tubes, Dall flow tubes, and flow nozzles, designed to minimize pressure loss in fluid measurements while offering varying degrees of accuracy and cost-effectiveness.
Obtuse angle – It is simply an angle measuring higher than 90-degrees but less than 180-degree. It appears wider than a right angle (90-degree) and can be found in architectural designs and the shapes of several structures and components, impacting load distribution and overall design dynamics.
Obvert level – It is the highest interior level of the sewer pipe, and which can be considered the ‘ceiling’ level, being the highest level of that sewer pipe.
Occluded gas – It consists of any of several gases which enter rocks or a mine atmosphere from pores, as feeders and blowers, and also from blasting operations. These gases pollute the mine air mainly by the absorption of oxygen by the coal, and in addition by chemical combination of oxygen with carbonaceous matter, for example, from decaying timbers, rusting of iron rails, burning of lights, and breathing of humans and animals. These gases include oxygen, nitrogen, argon, carbon dioxide, and methane.
Occlusion – It is the trapping of undissolved gas in a solid during solidification.
Occupational environment – It refers to the sum of external conditions and factors at a workplace that influence worker health, safety, and performance, encompassing physical (like temperature and noise), chemical, biological, machine, and psychosocial (like organizational culture and stress) aspects. Engineering disciplines, particularly safety, environmental, and industrial engineering, apply principles to understand and control these factors through industrial hygiene, environmental ergonomics, and the design of safer and more productive systems and processes.
Occupational exposure limit (OEL) – It is the maximum concentration of a chemical or physical agent which a worker can be exposed to, typically over an 8-hour workday and 40-hour workweek, without experiencing adverse health effects. Occupational exposure limits serve as a scientific basis for evaluating existing exposure controls, informing workers of potential risks, and ensuring work-place safety through engineering controls like ventilation systems, safe work practices, and personal protective equipment (PPE). These limits are established by regulatory bodies and professional organizations using toxicological and epidemiological data, and they can differ between different organizations.
Occupational hazard – It is a term which signifies both long-term and short-term risks associated with the work-place environment. It is a hazard experienced in the work-place. This encompasses several types of hazards, including chemical hazards, biological hazards (bio-hazards), psychosocial hazards, and physical hazards.
Occupational health – It is normally defined as the science of the anticipation, recognition, evaluation, and control of hazards arising in or from the workplace which can impair the health and well-being of the employees, taking into account the possible impact on the surrounding communities and the general environment. This field is necessarily vast, encompassing a large number of disciplines and numerous workplace and environmental hazards. A wide range of structures, skills, knowledge, and analytical capacities are needed to coordinate and implement all of the ‘building block’ which make up the occupational health system so that protection is extended to both the employees and the environment. The scope of occupational health has evolved gradually and continuously in response to social, political, technological, and economic changes. In recent years, globalization of the world’s economies and its repercussions have been perceived as the greatest force for change in the world of work, and consequently in the scope of occupational health, in both positive and negative ways.
Occupational health and safety management system – Occupational health and safety constitutes a system which deals with the prevention of injuries and illnesses related to work, as well as the protection and improvement of the health of the employees. It aims to improve the working conditions and the surrounding environment. Occupational health includes promoting and maintaining the highest degree of physical and mental health and social well-being of the employees of all professions in the organization. In this context, the basic principles of the process of assessing and managing occupational hazards is based on the expectation, recognition, evaluation, and control of the risks arising in or from the workplace and which are harmful to the health and well-being of the employees. Occupational health and safety management systems have been defined as ‘a combination of the planning and review, the management organizational arrangements, the consultative arrangements, and the specific programme elements which work together in an integrated way to improve occupational health and safety performance’. These systems differ from earlier methods. They make those in the workplace more responsible for occupational health and safety, but this responsibility is discharged through an integrated management system rather than the earlier method consisting of ad-hoc structures and prescriptions.
Occupational safety – It refers to the measures taken to protect emploeew from dangers and risks arising from their working conditions, including hazards such as fire, machinery injuries, and health risks. It encompasses both direct and indirect safety measures aimed at ensuring a safe workplace environment.
Occupational safety and health administration (OSHA) – It is a regulatory agency of the United States of America whose mission is to ‘assure safe and healthy working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education, and assistance’. The agency is also charged with enforcing a variety of whistle-blower statutes and regulations. Its work-place safety inspections have been shown to reduce injury rates and injury costs without adverse effects on employment, sales, credit ratings, or organizational survival.
Occurrence probability – It is the quantifiable likelihood that a specific failure, event, or condition is going to happen, frequently for a product or system over its design life or a specified period. It is a key component of risk management and is determined using historical data, statistical analysis, or expert judgment, and is used in formulas like the ‘risk priority number’ (RPN) to help prioritize tasks and allocate resources effectively.
Ocean energy – It is the different types of renewable energy which can be derived from oceans or other marine sites, mainly manifesting as thermal, mechanical, and chemical energy.
Ocean sequestration – It is a technique for carbon di-oxide storage where carbon di-oxide is injected into water bodies at depths of 1 kilometer, allowing it to dissolve and spread because of the density difference. It has the potential to store around 40,000 Giga tons of carbon di-oxide and can accommodate around 90 % of present carbon di-oxide emissions.
Ocean ton – It is also known as a shipping ton or measurement ton. It is a unit of volume (not weight) used in marine shipping to measure cargo for rate calculation, equivalent to 40 cubic feet (1.1 cubic meter) in the United States of America and 42 cubic feet (1.2 cubic meter) in the United Kingdom. This system is used for light, bulky goods which can take up more space than their weight suggests, affecting freight costs based on the higher volume or weight of the shipment.
OCP slag granulation process – OCP is acronym for open cycle process. In this process, granulated slag after granulation is dewatered in open gravel layered filtering bed.
Octadecene – It is a long-chain hydrocarbon and an alkene used as a non-coordinating solvent for high-temperature nano-material synthesis, and as a capping agent to protect nano-particles. It forms a stable, hydrophobic barrier on surfaces, improving their electrical passivation and chemical protection, which extends fatigue life and prevents oxidation. Its high boiling point and non-coordinating nature make it ideal for growing nano-particles and quantum dots.
Octadecyl-trichlorosilane (OTS) – It is an organosilicon compound used to create self-assembled monolayers (SAMs) on different substrates, making surfaces hydrophobic and providing specific functions for applications like chromatography, surface functionalization, and coatings. As a silanization agent, its long alkyl tails form tightly packed molecular layers, creating low-energy, water-repellent surfaces with applications in advanced materials and sensing.
Octagonal shape – It is characterized by having eight straight sides and eight angles. It is the adjective form of the word ‘octagon’, which refers to a polygon with these specific characteristics.
Octahedral – It describes a shape or structure with eight faces. It is a three-dimensional shape, specifically a polyhedron, composed of eight equilateral triangles, with four triangles meeting at each vertex. It can also be thought of as two square pyramids joined base-to-base. In chemistry, the term ‘octahedral’ is frequently used to describe the molecular geometry of molecules where a central atom is surrounded by six other atoms or groups of atoms arranged at the vertices of an octahedron.
Octahedral plane – It is a plane whose normal vector is equally inclined to all three principal stress axes, creating eight such planes which intersect at a single point within a material’s stress state. These planes are important since they show octahedral stresses (a specific combination of normal and shear stresses) which are crucial for analyzing material behaviour, particularly plastic yielding and failure in solid mechanics, materials science, and geotechnical engineering.
Octahedral shearing stress theory – This theory states that the failure of a member by yielding occurs when the octahedral shearing stress in the member reaches the octahedral shearing stress at yielding in the simple tension or compression test.
Octahedron – It is a three-dimensional shape, specifically a polyhedron, with eight faces, twelve edges, and six vertices. It is one of the five Platonic solids, and a regular octahedron has eight equilateral triangles as its faces. It can be visualized as two square pyramids joined at their bases.
Octane – It is a hydrocarbon and alkane with the chemical formula of C8H18. The octane rating of a fuel is a measure of the fuel’s resistance to knock. The octane number is a parameter to measure the capability of fuel to prevent the detonation and knocking during combustion. Hence, octane refers to the chemical compound C8H18 and its ability to resist knocking during combustion in an engine.
Octane fuel – It is not a specific fuel type but rather a reference to a fuel’s octane rating, which measures its resistance to engine knock (premature ignition) under compression. Fuels are rated on a scale where isooctane has a rating of 100 (excellent anti-knock quality) and n-heptane has a rating of 0 (poor anti-knock quality). A higher-octane number indicates higher resistance to knocking, allowing for higher compression ratios, improved engine efficiency, and smoother operation.
Octane number – It is a quantitative measure of the maximum compression ratio at which a particular fuel can be utilized in an engine without some of the fuel / air mixture ‘knocking’. Octane number in gasoline indicates the ability of the fuel to resist the auto-ignition, which can make engine knockings. Octane number is the percentage by volume of iso-octane in a mixture with n-heptane which produces a specific knocking intensity during testing.
Octave – It is a logarithmic unit in electronics for ratios between frequencies, with one octave corresponding to a doubling of frequency. For example, the frequency one octave above 40 hertz is 80 hertz.
Octave band – It refers to a frequency range in which the upper frequency is twice that of the lower frequency. It is used to categorize noise into specific bands for measuring sound power and pressure levels. Common mid-frequencies for octave bands include 63 hertz, 125 hertz, 250 hertz, 500 hertz, 1,000 hertz, 2,000 hertz, 4,000 hertz and 8,000 hertz.
Octave band spectrum – It analyzes sound or vibration by dividing the overall frequency range into segments (octave bands) where the upper frequency is twice the lower frequency, such as the band from 1,000 hertz to 2,000 hertz. This logarithmic representation allows for the assessment of energy within these bands and is frequently used in noise and vibration analysis to better reflect human perception of sound, providing a compressed and stable representation of the signal’s frequency content.
Octet – It is a unit of digital information in computing and telecommunications which consists of eight bits. The term is frequently used when the term byte can be ambiguous, as the byte has historically been used for storage units of a variety of sizes. Octet is used to provide a precise and unambiguous term for an eight-bit data unit, whereas a ‘byte’ historically has been varied bit sizes depending on the system, though today it frequently also refers to eight bits.
Octet rule – It is a chemical rule of thumb which reflects the theory that main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas. The rule is especially applicable to carbon, nitrogen, oxygen, and the halogens, although more generally the rule is applicable for the s-block and p-block of the periodic table.
Ocular – It is also known as eyepiece. It is a lens or system of lenses for increasing magnification in a microscope by magnifying the image formed by the objective.
Ocvirk number – It is a dimensionless number used to evaluate the performance of journal bearings, and defined by the equation ‘Ocvirk number = (P/eta x U) x (c/r)square x (d/b)square’ where ‘P’ is the load per unit width, ‘eta’ is the dynamic viscosity, ‘U’ is the surface velocity, ‘c’ is the radial clearance, ‘r’ is the bearing radius, ‘b’ is the bearing length, and ‘d’ is the bearing diameter. This number can be used in its inverted form and is related to the Sommerfeld number.
Odds – It is the ratio of probabilities for two different events for one group.
Odds ratio – It is the ratio of the odds of an event for two different groups.
Odour – It is the sensation of smell perceived from airborne volatile organic or inorganic compounds. Odour pollution occurs when these unpleasant-smelling substances are present in the air at levels that cause discomfort, distress, or a substantial impact on people’s quality of life. These odors can stem from different anthropogenic sources, including industrial activities, and waste management, and are perceived differently by individuals.
Odour control – It is the deliberate process of managing and eliminating unpleasant odours from sources like industrial processes, and waste treatment, using technologies such as air scrubbers, bio-filters, activated carbon systems, chemical treatments, and vapour neutralization to improve air quality and meet regulatory standards. The goal is to convert odorous compounds into odourless or less offensive substances, frequently volatile organic compounds (VOCs), and release clean air into the environment.
Oedometer tests – These are experiments used in geotechnical studies to determine the compressibility characteristics of sediments, based on the assumption of no lateral strain and the homogeneity of the sediment.
OEM – It stands for original equipment manufacturer. OEM is an organization which manufactures and sells products or parts of a product that their buyer, another organization, sells to its own customers while putting the products under its own branding.
OEM procurement – It refers to an organization purchasing components or parts from another organization (the (original equipment manufacturer, OEM) to be incorporated into the purchasing organization’s own finished product. Essentially, it is when a manufacturer buys parts from the original maker to use in their product. This sourcing strategy is common when an organization needs specific, high-quality components designed and produced by an expert in that field.
OEM vendors – They are suppliers of components to original equipment manufacturers (OEM), i.e., those who manufacture and sell the completely assembled product. For example, a typical OEM vendor can provide small electrical motors to the producer of home appliances.
Oersted (Oe) – It is the coherent derived unit of the auxiliary magnetic field ‘H’ in the centimeter–gram–second system of units (CGS). It is equivalent to1 dyne per maxwell.
Oersted’s law – It is also known as Oersted’s principle. It states that an electric current creates a magnetic field around it. Essentially, moving electric charges (current) produce a magnetic field. This discovery established a fundamental link between electricity and magnetism, forming the basis of electro-magnetism.
Offal – It is the metal cut away from the part after the press has completed its cycle. It is normally in the form of a ring. This material is to be disposed of in one way or another. If allowed to remain in ring form, it needs manual or mechanical removal from the die. To avoid this, scrap cutters are designed and built as integral units of the lower trimming steels. These are knife-like blades mounted perpendicular to the trim line. Mating steels are also mounted on the punch. These scrap cutters are normally designed to part the material at distances from 300 millimeters to 450 millimeters.
Off-axis laminate – It is a laminate whose principal axis is oriented at an angle (theta) other than 0-degree or 90-degree with respect to a reference direction, normally related to principal load or stress direction.
Off-dimension – It is a casting defect caused by any incorrect dimension resulting from improper setting of cores, using wrong core, shifts, and swells etc.
Off-gas – It is a gas which is produced as a by-product of an industrial process or which is given off by a manufactured object or material.
Off gauge – It is the deviation of thickness or diameter of a solid product, or wall thickness of a tubular product, from the standard or specified dimensional tolerances.
Off-grade metal – It is the metal whose composition does not correspond to the designated or applicable specification.
Off-hand grinding – It is the grinding where the operator manually forces the wheel against the work, or vice versa. It frequently implies casual manipulation of either grinder or work to achieve the desired result. Dimensions and tolerances frequently are not specified, or are only loosely specified. The operator relies mainly on visual inspection to determine how much grinding should be done.
Office automation – It refers to the application of information technology (IT) and software systems to automate or streamline repetitive, rule-based tasks in an office or administrative environment. This involves using electronic equipment, computer software, and networks to digitize and manage data collection, storage, processing, and communication, ultimately improving efficiency, accuracy, and productivity while freeing employees for more strategic activities.
Office ergonomics – It consists of designing and arranging office components, equipment, and environments to create a comfortable, safe, and efficient work-space which fits the employee, not the other way around. It uses engineering principles and interdisciplinary knowledge from fields like anatomy and psychology to optimize the interaction between people and their workstations, hence reducing injuries and improving employee’s well-being and overall system performance.
Off Iron – It is the pig iron which is not of the desired composition.
Off-peak electricity – It refers to electrical power consumed during periods of unusually low demand on the power grid, typically during late nights or early mornings, when electricity rates are frequently lower to encourage usage during these times. This strategy helps stabilize the grid, reducing strain during peak demand hours, lowering costs for consumers, and supporting the integration of renewable energy sources.
Offset – It is the distance along the strain coordinate between the initial portion of a stress-strain curve and a parallel line which intersects the stress-strain curve at a value of stress (normally 0.2 %) that is used as a measure of the yield strength. The term is used for materials which have no obvious yield point. In statistical analysis, offset is the log of the length of the time period over which an event count is taken, entered into a regression model with its coefficient constrained to equal 1. This converts the study end point into the rate of event occurrence.
Offset, carbon – A carbon offset is a reduction in emissions of carbon or green-house gases made in order to compensate for or to offset an emission made elsewhere. Carbon offsets are measured in metric tons of carbon di-oxide-equivalent (CO2e) and may represent six primary categories of green-house gases. One carbon offset represents the reduction of one metric ton of carbon dioxide or its equivalent in other green-house gases.
Offset dies – These are specialized press brake tooling used to create Z-bends or joggles in sheet metal in a single stroke. They allow for two bends to be formed at the same time, improving efficiency in applications where materials need to be joined or when a second bend is required without interfering with the first.
Offset link chains – These chains have all links alike. These include integral link chains, such as bar-link, flat-top, and welded steel chains, where internal rollers cannot be installed.
Offset modulus – It is the ratio of the off-set yield stress to the extension at the off-set point (plastics).
Offset printing – It is a common printing technique in which the inked image is transferred (or ‘off-set’) from a plate to a rubber blanket and then to the printing surface. Offset printing is a widely used printing technique. It involves transferring an image from a plate to a rubber blanket, and then onto the desired printing surface. It is a cost-effective and high-quality method used to produce large quantities of printed materials. Offset printing involves several essential components which work together to produce high print quality. These components include the plate, blanket, ink, and printing press. The plate is typically made of aluminum and carries the image to be printed. The blanket acts as an intermediary, transferring the inked image from the plate to the printing surface. High-quality inks are used to ensure vibrant and accurate colour reproduction. The printing press is the machine which brings all these components together to produce the final printed material.
Offset side frame – It is a deliberately misaligned side frame within a conveyor system, uniquely tailored to meet specific production demands. Routine checks are essential for preserving the stability and precise alignment of offset side frames.
Offset tool – Offset tooling allows two ‘V’ bends to be formed closer together than regular press brake dies allow. This creates a ‘Z’ shaped profile in the sheet metal. This type of bend is also normally referred to as a jog. The two basic forms of offset tooling are ‘Spring Up’ and ‘Horizontal’. Beyond these two forms there are three types of tooling, balanced, unbalanced and versatile types. The spring up type causes the material to move from a horizontal plane up to the bend angle, similar to a regular ‘V’ bend operation except the rear of the work piece will move down instead of up. The horizontal type allows the work-piece to stay level while the offset is formed. Spring up offset tooling is the more common version since it reduces thrust forces.
Offset upsetting – In most of the forgings produced in upsetters, the upset portions are symmetrical and concentric with the axis of the initial forging stock. However, upsetters are not limited to the production
of this type of forging. With proper die design and techniques, parts having eccentric, or offset, upsets can be produced. Such upsets are normally, but not necessarily, symmetrical to the plane through the axis of the stock in the direction of the offset. Dies for offset upsetting are to be designed so that the metal for the upset is directed eccentrically, but is sufficiently restricted in movement to prevent folding or buckling which cause cold shuts in the finished forging.
Offset valve – It is a valve construction having inlet and outlet line connections on different planes, but 180-degree opposite each other.
Offset voltage – It is the small input voltage difference needed to force an amplifier’s output to zero, because of the manufacturing imperfections. It is a direct current error caused by slight mismatches in the amplifier’s internal components, such as the transistors in an op-amp’s input stage. This voltage is present regardless of the input signal and causes uncertainty in readings or can lead to undesirable direct current levels at the output.
Offset yield strength – It is the stress at which the strain exceeds by a specific quantity (the off-set) an extension of the initial, approximately linear, proportional portion of the stress-strain curve. It is expressed in force per unit area.
Offshore cable – It is a specialized cable designed to transmit electrical power or signals in a marine environment, connecting offshore structures like oil rigs or wind turbines to shore or other offshore facilities. These cables are engineered for extreme durability and reliability, featuring robust, corrosion-resistant, and waterproof materials to withstand harsh conditions such as saltwater, high pressure, extreme temperatures, and exposure to mud and hydrocarbons. Key design considerations include high tensile strength, flame retardancy, and compliance with stringent international standards. Offshore construction – It is the installation of structures and facilities in a marine environment, normally for the production and transmission of electricity, oil, gas and other resources. It is also called maritime engineering.
Offshore pipeline – It is also called a subsea or marine pipeline. It is a pipe system laid on or under the seabed to transport fluids like oil, gas, and water from subsea wells and production platforms to onshore facilities or vice versa. These complex systems need specialized engineering to address challenges such as harsh marine environments, high pressures, corrosion, and seabed conditions, involving the design, installation, and maintenance of large-diameter pipes made from materials like carbon steel or composites.
Offshore pipeline engineering – It designs, installs, and manages subsea systems for transporting fluids like oil and gas from subsea wells to production facilities and onshore. This specialized engineering discipline requires a deep understanding of harsh marine environments, including high salinity, strong currents, extreme temperatures, and complex seabed conditions, necessitating robust materials and sophisticated risk-based design to ensure system integrity and safety throughout the pipeline’s operational lifespan.
Offshore structure – It is a facility or platform built in the marine environment, such as the ocean, to support activities like oil and gas extraction, wind energy generation, and other resource exploitation. These structures are required to withstand harsh environmental conditions, including high waves, currents, wind, and saltwater, needing specialized designs, materials, and construction methods to ensure stability and durability far from shore. Key examples include fixed platforms, floating platforms, and wind turbines, all designed to provide stable bases for different offshore operations.
Offshore wind farm – It is an installation of wind turbines located in a body of water, such as the ocean or a large lake, to generate electricity from strong, consistent winds. It is a complex system of wind turbines, substructures (fixed or floating foundations), substations, and submarine cables designed to withstand harsh marine environments and efficiently transfer generated power to the onshore grid. The engineering challenges include the structural stability of turbines and foundations in dynamic ocean conditions, the transmission of power through submarine cables, and the integration of large-scale energy production with existing infrastructure.
Offshore wind turbine – It is a large, typically three-bladed, horizontal-axis wind turbine designed to harness wind energy in marine environments, such as oceans and lakes. Engineered to withstand harsh marine conditions like strong winds and corrosive saltwater, offshore wind turbines feature robust construction, specialized foundations (e.g., monopiles, jackets, or floating platforms), and unique maintenance strategies. These turbines convert wind’s kinetic energy into electricity, which is then transmitted through array cables to an offshore substation for collection and onward transmission to the electrical grid.
Off-site release – It means the release of a pollutant or radioactivity which leaves the plant site boundary.
Off-stream use – It consists of water withdrawn from a surface water source for uses such as industrial water supply, and steam electric power generation etc.
Off the bars – It means a situation when a nuclear power station is not generating electricity.
Ogive – It is also known as a cumulative frequency polygon, can refer to one of two things namely (i) any hand-drawn graphic of a cumulative distribution function, and (ii) any empirical cumulative distribution function. The points plotted as part of an ogive are the upper-class limit and the corresponding cumulative absolute frequency or cumulative relative frequency. The ogive for the normal distribution (on one side of the mean) resembles (one side of) an Arabesque or orgival arch, which is likely the origin of its name. Along the horizontal axis, the limits of the class intervals for an ogive are marked. Based on the limit values, points above each are placed with heights equal to either the absolute or relative cumulative frequency. The shape of an ogive is obtained by connecting each of the points to its neighbours with line segments.
OG system – It is an oxygen converter gas recovery system. It is suppressed type basic oxygen furnace (LD) gas recovery system for the converters of steelmaking shops. This system basically has no space between the throat and the hood skirt, and controls pressure at the closed throat. The OG system is frequently used because of its operational stability. The OG type cooling system makes it possible not only to recover the sensible heat of exhaust gas as steam, but also to increase the IDF (induced draft fan) efficiency by lowering the temperature of the exhaust gas by use of a cooling device. The system is normally designed to recover a high percentage of the latent heat and sensible heat of the top converter gas.
Ohm – It is the unit of electrical resistance in the International System of Units (SI). The ohm is defined as an electrical resistance between two points of a conductor when a constant potential difference of one volt (V), applied to these points, produces in the conductor a current of one ampere (A), the conductor not being the seat of any electromotive force.
Ohmic conduction – It describes a linear, proportional relationship between current and voltage, meaning a material’s resistance remains constant regardless of the applied voltage or current. This predictable behaviour, known as Ohm’s law, is characteristic of ohmic conductors, such as most metals like copper and aluminum. This constant resistance is crucial for the predictable design and analysis of electrical circuits, where it allows for straightforward calculations and ensures components operate within specified voltage and current limits.
Ohmic drop – It is also known as an IR drop. It is the voltage loss which occurs because of the Ohmic resistance of a material when an electric current flows through it, as described by Ohm’s law.. It is a critical factor in electrochemical systems, representing the potential lost as current travels through the electrolyte, connectors, or other components, and can considerably impact measurement accuracy and system efficiency.
Ohmic loss – It is also known as Joule heating or resistive heating. It is the dissipation of electrical energy into heat as it flows through a conductor with resistance. This loss is quantified by the formula P = I square R, where ‘P’ is the power lost as heat, ‘I’ is the current, and ‘R’ is the resistance of the conductor. Ohmic losses are a fundamental consequence of electron collisions with the atoms of a conductor’s material, converting electrical energy into thermal energy.
Ohmic resistance – It is the constant opposition to electric current flow in a material or device which adheres to Ohm’s law (V=IR), meaning the resistance value (R) remains the same regardless of the applied voltage (V) or current (I). Materials showing ohmic resistance, such as copper or aluminum, show a linear relationship on a voltage-current graph and allow for predictable circuit analysis and design.
Ohm-meter – It is an instrument for the measurement of electrical resistance.
Ohm’s law – It states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, one arrives at the three mathematical equations used to describe this relationship. These three equations are (i) V = IR, (ii) I = V/R, and (iii) R = V/I, where ‘I’ is the current through the conductor, ‘V’ is the voltage measured across the conductor, and ‘R’ is the resistance of the conductor. More specifically, Ohm’s law states that the ‘R’ in this relation is constant, independent of the current. If the resistance is not constant, the previous equation cannot be called Ohm’s law, but it can still be used as a definition of static / direct current resistance. Ohm’s law is an empirical relation which accurately describes the conductivity of the vast majority of electrically conductive materials over several orders of magnitude of current. However, some materials do not obey Ohm’s law. These materials are called non-ohmic.
Oil – It is a liquid of vegetable, animal, mineral, or synthetic origin which feels slippery to the touch.
Oil analysis – It is the laboratory testing of a lubricating oil sample to assess its physical and chemical properties, and to detect contaminants like wear debris and water. It serves as a crucial tool for predictive maintenance, providing actionable insights into the health of both the lubricant and the machinery it serves. By monitoring trends in oil condition over time, engineers can identify potential problems, prevent costly failures, reduce downtime, and extend equipment life.
Oil and whiting test – It is a method of detecting fine cracks by applying a penetrating oil and painting the tested metal surface with a mixture of whiting and a thinner. Oil in the cracks emerges to stain the whiting.
Oil ash corrosion – It is a type of accelerated, high-temperature corrosion which occurs when vanadium-containing ash deposits from fuel oil combustion melt on boiler tube surfaces. These molten deposits dissolve protective oxide layers on the metal, leading to rapid metal wastage and potential tube failure.
Oil-based paints – These are the paints with films which form solids by the air-induced cross-linking of certain unsaturated plant oils known as drying oils. Oxygen is consumed in the process.
Oil burner – It is a burner for firing oil. The purpose of the oil burner is to mix the fuel oil with enough air to cause heat release from the fuel. This act needs the combustion of the fuel, but the combustion takes place outside the burner, that is at the tip. The performance of the burner is achieved by proper air-fuel mixing. The good burner mixes well and liberates a maximum amount of heat from the fuel. A poor burner does not accomplish this task well at all. Oil burners for industrial use are normally classified according to the method used for atomizing the oil.
Oil canning – It is a dished distortion in a flat or nearly flat sheet metal surface.
Oil composition – It refers to the complex mixture of chemical components which make up crude oil or formulated oils, which are characterized by the types and quantities of hydrocarbons, heterocyclic compounds (containing sulphur, nitrogen, oxygen), metallic compounds, and other constituents. This composition dictates an oil’s properties and performance, with engineers analyzing fractions like saturates, aromatics, resins, and asphaltenes (the SARA analysis) or the balance of base oils and additives in lubricants to understand stability, flow characteristics, and suitability for different applications like fuel, lubricants, or industrial processes.
Oil content – It refers to the quantity of oil in a mixture, material, or environment. It is talsohe quantity of oil which an impregnated part, such as a self-lubricating bearing, retains.
Oil cooler – It is a device which that regulates the temperature of engine oil, preventing it from overheating and maintaining optimal operating conditions. It works by circulating the oil through a heat exchanger, typically a radiator-like structure, to dissipate heat. This helps to prolong the life of the engine oil, improve engine performance, and prevent potential damage from overheating.
Oil cooling – It is the use of engine oil as a coolant, typically to remove surplus heat from an internal combustion engine. The hot engine transfers heat to the oil which then normally passes through a heat-exchanger, typically a type of radiator known as an oil cooler. The cooled oil flows back into the hot object to cool it continuously. This process helps maintain optimal engine temperatures, protects internal components from friction and wear, and extends the lifespan of the lubricating oil.
Oil core – It Is a core bonded with oil.
Oil country tubular goods (OCTG) – Oil country tubular goods is a collective term applied in the oil and gas industries to three kinds of pipes used in oil wells namely (i) drill pipe, (ii) casing, and (iii) tubing. These products conform to respective standard specifications. The chemical composition requirements and the strength requirements are given in the respective standards. Drill pipe is used to transmit power by rotary motion from ground level to a rotary drilling tool below the surface and to convey flushing media to the cutting face of the tool. Drill pipe is produced in sizes ranging from 60 millimeters to 170 millimeters in outside diameter. Size designations refer to actual outside diameter and weight per meter. Drill pipe is usually upset, either internally or externally, or both, and is prepared to accommodate welded-on types of joints. Casing is used as a structural retainer for the walls of oil or gas wells, to exclude undesirable fluids and to confine and conduct oil or gas from productive sub-surface strata to ground level. Casing is produced in sizes from 110 millimeters to 500 millimeters outside diameter. Size designations refer to actual outside diameter and weight per meter. Ends are normally threaded and furnished with couplings, but can be prepared to accommodate other types of joints. Tube is used within the casing of oil wells to conduct oil and gas to ground level. It is produced in sizes from 25 millimeters to 115 millimeters in outside diameter, in several weights per meter. Ends are threaded for special integral type joints or fitted with couplings and may or may not be upset externally.
Oil crisis – It is a severe market disruption marked by a rapid increase in oil prices and a reduction in supply, frequently leading to a global recession or substantial economic downturn. These crises challenge the design and efficiency of systems which rely on oil by forcing engineers to find solutions for energy conservation, demand reduction, and the development of alternative energy sources and technologies.
Oil cup – It is a device connected to a bearing which uses a wick, valve, or other means to provide a regulated flow of lubricant.
Oil, crude – It means a mixture of hydro-carbons which exists in liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface separating facilities.
Oil, diesel – It is a liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a result of compression of the inlet air and then injection of fuel. Hence, diesel fuel needs good compression ignition characteristics. The most common type of diesel fuel is a specific fractional distillate of petroleum fuel oil.
Oil drilling – It is a complex process which involves the drilling and pumping of oil from underground wells.
Oil droplet – It is a distinct, discrete volume of oil, typically spherical, which forms when oil is dispersed into a continuous medium, such as water or air, because of the forces like impact, emulsification, or airflow. These droplets are characterized by their size, shape, and concentration, which are influenced by factors such as oil viscosity, interfacial tension, fluid flow, and temperature. They are studied and engineered for different applications, including lubrication, oil spill recovery, and the development of artificial cells.
Oil equivalent – It is a standard unit of energy which allows for the comparison of energy from different sources by normalizing it to the energy content of a specific quantity of crude oil, typically a tonne. The most common unit is the tonne of oil equivalent (toe), which represents the energy released by burning one tonne of crude oil. It is a standardized, conventional value used to express and compare large quantities of energy in a consistent way.
Oil exchanger – It is a type of a heat exchanger. It is a device designed to transfer thermal energy between two different fluids, typically including oil, without allowing them to mix directly. It is used to either cool down hot oil, such as in engines, or to heat cold oil using a heating fluid like water or air, thereby optimizing system temperatures, increasing efficiency, and extending the lifespan of machinery.
Oil-filled, inert-gas system, transformer – A positive seal of the transformer oil can be provided by an inert-gas system. Here, the tank is slightly pressurized by an inert gas such as nitrogen. The main tank gas space above the oil is provided with a pressure gauge. Since the entire system is designed to exclude air, it is required to operate with a positive pressure in the gas space above the oil, otherwise, air is admitted in the event of a leak. Smaller station service units do not have nitrogen tanks attached to automatically add gas, and it is common practice to add nitrogen yearly early winter as the tank starts to draw partial vacuum, because of the cooler weather. The excess gas is expelled each summer as loads and temperatures increase. Some systems are designed to add nitrogen automatically from the pressurized tanks when the pressure drops below a set level. A positive pressure of around 3.5 kilopascal (kPa) to 35 kilopascal is maintained in the gas space above the oil for preventing the ingress of air. This system includes a nitrogen gas cylinder, three-stage pressure-reducing valve, high-pressure and low-pressure gauges, high-pressure and low-pressure alarm switch, an oil / condensate sump drain-valve, an automatic pressure-relief valve, and necessary piping.
Oil-filled – self-cooled transformers – In small-sized and medium-sized transformers, cooling takes place by direct radiation from the tank to surrounding air. In oil-filled, self-cooled types, tank surfaces can be corrugated to provide a larger radiating surface. Oil in contact with the core and windings rises as it absorbs heat and flows outward and downward along tank walls, where it is cooled by radiating heat to the surrounding air. These transformers can also have external radiators attached to the tank to provide larger surface area for cooling.
Oil film bearings – These are machine elements which designed to produce smooth (low friction) motion between solid surfaces in relative motion and to generate a load support for mechanical components. The lubricant between the surfaces is a liquid is a lubricating oil. Oil film bearings are hydrodynamic bearings. These bearings are flood lubricated, precision journal bearings which operate on a hydro-dynamically generated film of oil. These bearings completely enclose the roll neck. The bearing surfaces are separated by a liquid film. These bearings have a low co-efficient of friction at high speeds. They have a long life and low space requirement. These are used in flat rolling in slabbing mills, hot strip mills and cold rolling mills. Oil film bearing being of hydrodynamic design distributes the bearing load over a large area with no concentration points. The film of oil on which the bearing operates has enormous load carrying capacity. Because of its continuous, unbroken nature, the film eliminates wear caused by metal-to-metal contact. This oil film is constantly maintained by the hydrodynamic action of the rotating sleeve to which a surplus of oil is presented at controlled temperatures.
Oil film thickness – It is the measurement of the lubricating film between surfaces in motion, which can deviate from the nominal value because of the machining and assembly errors, and is important for maintaining stable operational ability in mechanisms such as hydrostatic guideways.
Oil flow rate – it is the rate at which a specified oil passes through a porous sintered compact under specific test conditions.
Oil fog lubrication – It is the lubrication by an oil mist produced by injecting oil into a gas stream.
Oil, fuel – It consists of any of the different fractions got from the distillation of crude oil. Such oils include distillates (the lighter fractions) and residues (the heavier fractions). Fuel oils include heavy fuel oil (bunker fuel), marine fuel oil (MFO), furnace oil (FO), gas oil (gasoil), heating oils, diesel fuel, and others. The term fuel oil normally includes any liquid fuel which is burned in a furnace or boiler to generate heat, or used in an engine to generate power. However, it does not normally include other liquid oils, such as those with a flash point of around 42 deg C, or oils burned in cotton-wick or wool-wick burners. In a stricter sense, fuel oil refers only to the heaviest commercial fuels which crude oil can yield, i.e., those fuels heavier than gasoline (petrol) and naphtha. Fuel oil consists of long-chain hydro-carbons, particularly alkanes, cyclo-alkanes, and aromatics. Small molecules, such as those in propane, naphtha, gasoline, and kerosene, have relatively low boiling points, and are removed at the start of the fractional distillation process. Heavier petroleum-derived oils like diesel fuel and lubricating oil are much less volatile and distill out more slowly.
Oil, furnace – It is a dark viscous residual fuel got by blending mainly heavier components from crude distillation. Furnace oil is classified into four grades namely low viscosity, medium viscosity 1, medium viscosity 2, and high viscosity. Furnace oil falls under the category of Class C, under PESO (Petroleum and Explosives Safety Organization) classification.
Oil furnace – It is a furnace in which oil is used as fuel for heating
Oil groove – It consists of a channel or channels cut in a bearing to improve oil flow through the bearing. A similar groove can be used for grease-filled bearings.
Oil gun – It is a tool designed to deliver oil accurately and efficiently, mainly in industrial settings for fuel combustion or in specific mechanical applications. In industrial combustion, it atomizes and sprays fuel into a furnace, mixing it with air for ignition and stable combustion. It is also used to deliver precise quantities of fuel for several mechanical processes.
Oil hardening – It is quench-hardening treatment involving cooling in oil.
Oil heating and pumping set – It is a group of apparatus consisting of a heater for raising the temperature of the oil to produce the desired viscosity, and a pump for delivering the oil at the desired pressure.
Oil-impregnated paper – It is a composite insulating material used in high-voltage electrical equipment, particularly power transformers and bushings, where carefully layered paper (kraft paper) is saturated with transformer-grade mineral oil. This combination leverages the excellent dielectric properties of both the solid cellulose paper and the liquid oil to create a high-performance insulation system which prevents electrical breakdown and ensures the safe, reliable operation of the equipment.
Oil impregnation – It consists of filling of a sintered skeleton body with oil by capillary attraction or under the influence of an external pressure or a vacuum.
Oiliness – It is the ability of a lubricant to reduce wear and friction, other than by its purely viscous properties.
Oil-in-water emulsion – It is a type of emulsion where small droplets of oil are dispersed within a continuous phase of water. In this heterogeneous mixture, oil is the dispersed phase and water is the continuous phase, stabilized by an emulsifier.
Oil jacking pumps – It is a high-pressure pump which supplies oil at around 160 kilograms per square centimeter to 200 kilograms per square centimeter to create a thin oil film, allowing the rotor shaft to float and reduce friction before starting a turbine from a standstill condition. This prevents damage to the rotor and bearing during startup.
Oil-less bearing – It is the non-standard term for self-lubricating bearing which is a sintered product whose accessible pore volume is filled with a liquid lubricant which produces a lubricating film on the bearing surface during running of a shaft. This is because of a pumping action of the shaft and the frictional heat which lowers the viscosity of the oil. After completion of the running cycle, the oil is reabsorbed into the pore system of the bearing by capillary action.
Oil-lift drop hammer – It is also known as hydraulic gravity power drop hammer. In this hammer, the ram is lifted with oil pressure against an air cushion. The compressed air slows down the upstroke of the ram and contributes to its acceleration during the down stroke.
Oil, light diesel – it is a blend of distillates feed and residual oil. It is primarily recommended for stationary or slow speed diesel engines and as industrial fuel. Light diesel oil is a Class C product, under Petroleum and Explosives Safety Organization classification.
Oil mould – It is a mould in which the sand is bonded by an oil binder.
Oil-oxygen binder – it is cold-setting, air-setting binder. It is a synthetic auto-oxidizing liquid, oil-based binder which partially hardens at room temperature, using an oxygen releasing agent. Baking is needed to complete the hardening.
Oil-permeability – It is a measure of the capacity of the sintered bearing to allow the flow of an oil through its open pore system.
Oil pipeline – It is an interconnected network of steel or polyethylene tubes designed for the efficient, long-distance transport of crude oil and refined products between production sites, refineries, and markets. These engineered systems are built with different protective coatings and techniques, such as external coatings and cathodic protection, to prevent corrosion. Engineering considerations for oil pipelines include route selection, hydraulics, materials selection, mechanical design, corrosion prevention, and maintenance through practices like pigging.
Oil pocket – It consists of a depression which is designed to retain oil in a sliding surface.
Oil pump – It is a mechanical device which circulates a lubricating fluid, typically oil, under pressure to different parts of an engine or other machinery. Its primary function is to create a lubrication film between moving components, hence reducing friction, preventing wear, and assisting in heat dissipation. Oil pumps are essential for the proper and long-lasting performance of internal combustion engines and other complex mechanical systems.
Oil quenching – It means hardening of carbon steel in an oil bath. Oils are categorized as conventional, fast, martempering, or hot quenching. Oil quenching facilitates hardening of steel by controlling heat transfer during quenching, and it improves wetting of steel during quenching to minimize the formation of undesirable thermal and transformational gradients which can lead to increased distortion and cracking.
Oil resistant conveyor belt – It is an ingeniously crafted conveyor belt, purpose-built to endure the corrosive effects of oil exposure. Ordinary grade belts are damaged quickly by imbibition of oil into cover rubber, peeling of cover rubber, and reverse troughing of the belt if oily materials are transported. Hence, oil resistant belts are to be used to transport oily materials. Regular inspections are imperative to affirm the enduring resilience and structural integrity of oil-resistant belts.
Oil-resistant rollers – These rollers which are thoughtfully designed for a conveyor system to effectively withstand the adverse impacts of oil exposure. Periodic checks become imperative for assessing the roller’s condition, alignment, and overall structural integrity in the face of oil-related challenges.
Oil ring lubrication – It consists of a system of lubrication for horizontal shafts. It is a ring of larger diameter which rotates with the shaft and collects oils from a container beneath.
Oil sand core – It is the core in which sand mass is bound by an oil-based binder.
Oils and greases – Oils and greases are complex mixtures of hydrocarbons and degradable under bacterial action. The bio-degradation rate is different for different oils and greases with the bio-degradation rate for the tars being one of the slowest. Oil enters in to water through oil spills, leak from oil pipes, and waste water from the by-product plant of the coal carbonization plant. Being lighter than water, oils and greases spread over the surface of water, separating the contact of water with air, hence resulting in reduction of the dissolved oxygen. A surface film of oil on water restricts reoxygenation and together with bacterial degradation of the oil hydrocarbons causes the dissolved oxygen content to fall quickly. Oils and greases are also responsible for endangering water birds and coastal plants due to coating of oily materials and adversely affecting their normal activities. It also results in reduction of light transmission through surface waters, thereby reducing the photosynthetic activity of the aquatic plants. Oils include polycyclic aromatic hydrocarbons (PAH), some of which are known to be carcinogenic.
Oil sands – It is the sand bonded with such oils as linseed and the synthetics.
Oil shale – It is a fine-grained, sedimentary rock containing kerogen, a solid, combustible organic matter which can be converted into liquid hydrocarbons, like shale oil, and combustible gases through destructive distillation. Unlike shale gas, oil is not mobile in oil shale and needs heating to release from the kerogen. The extraction process involves thermal decomposition of kerogen through heating, followed by purification to produce fuels, or direct combustion for steam and electricity.
Oil shale processing – It is an engineering process for extracting liquid petroleum-like fuel (shale oil) from oil shale, a sedimentary rock containing kerogen. This involves mining the oil shale (either on or underground), crushing it, and then heating it through a thermal process called retorting or pyrolysis to convert the solid kerogen into liquid and gaseous products. The resulting shale oil is then upgraded through refining processes to meet fuel or petrochemical feedstock specifications.
Oil shot – In die casting, it is a sponge like whirl on the surface of casting resulting from an excess of oil applied to the sprue hole before the shot has been made.
Oil sludge – It is a thick, gel like, and frequently dark substance which forms inside an engine or other machinery when engine oil breaks down and mixes with contaminants like dirt, debris, moisture, and combustion byproducts. This build-up can considerably hinder engine performance and potentially lead to severe damage if not addressed.
Oil spill – It is the release of a liquid petroleum hydrocarbon into the environment because of human activity, and it is a form of pollution. The term is normally given to marine oil spills, where oil is released into the ocean, but spills can also occur on land. Oil spills can involve spills of refined petroleum products as well as their by-products. Additionally, spills of any oily refuse or waste oil contribute to such incidents. These spills can have severe environmental and economic consequences.
Oil staining – It is the surface staining which is caused by the partial decomposition during thermal treatment of residual lubricant.
Oil starvation – It is a condition in which a bearing, or other tribo-component, which receives an inadequate supply of lubricant.
Oil-water emulsion – It is a heterogeneous mixture where one liquid, either oil or water. It is dispersed as fine droplets within the other immiscible liquid phase, which forms the continuous phase. These unstable systems, like water-in-oil (W/O) or oil-in-water (O/W), need mechanical agitation and chemical emulsifiers to form and remain stable, preventing spontaneous separation over time.
Oil well – It is a drillhole boring in earth which is designed to bring petroleum oil hydro–carbons to the surface. Normally some natural gas is released as associated petroleum gas along with the oil. A well which is designed to produce only gas can be termed a ‘gas well’. Wells are created by drilling down into an oil or gas reserve and if necessary equipped with extraction devices such as pump-jacks.
Oil whirl – It is the instability of a rotating shaft which is associated with instability in the lubricant film. Oil whirl is to be distinguished from shaft whirl, which depends only on the stiffness of the shaft.
O-ing – In the UOE (U-O-Expanding) process for manufacturing large-diameter steel pipes, the O-ing refers to the O-forming stage. This stage involves pressing a pre-formed U-shaped steel plate into a circular shape using specialized hydraulic presses and dies. The O-ing process is a crucial step in achieving the desired pipe geometry and dimensional accuracy.
Oldhamite – It is a calcium magnesium sulphide mineral with the chemical formula (Ca,Mg)S. Ferrous iron can also be present in the mineral resulting in the chemical formula (Ca,Mg,Fe)S. It is a pale to dark brown accessory mineral in meteorites. It crystallizes in the cubic crystal system, but typically occurs as anhedral grains between other minerals.
Old or post-consumer scrap – It results when industrial and consumer steel products (such as automobiles, appliances, buildings, bridges, ships, cans, railroad coaches and wagons, etc.) have served their useful life. Old scrap is collected after a consumer cycle, either separately or mixed, and it is frequently contaminated to a certain degree, depending highly on its origin and the collection systems.
Olefin – It is also known as alkene. It is a hydro-carbon containing a carbon-carbon double bond. The double bond can be internal or in the terminal position. Terminal alkenes are also known as alpha-olefins.
Olefin polymerization – It is the industrial process of chemically linking small olefin (alkene) molecules with a carbon-carbon double bond into long chains called polymers, mainly using catalysts like Ziegler-Natta to produce different plastics, such as polyethylene and polypropylene. This process is necessary for creating a vast range of materials used in packaging, textiles, and engineering applications by controlling the polymer’s structure and properties through specific catalysts and reaction conditions.
Oleic acid – It is a fatty acid that occurs naturally in different animal and vegetable fats and oils. It is an odorless, colorless oil, although commercial samples can be yellowish because of the presence of impurities.
oleic oil – It is a plant-based oil characterized by a high content of oleic acid (a monounsaturated fatty acid), which provides excellent thermal and oxidative stability. These oils are engineered for specific industrial applications such as lubricants, hydraulic fluids, and transformer oils, as well as for producing chemicals like surfactants and plasticizers. Their improved stability and more uniform molecular structure compared to oils with higher levels of polyunsaturated fatty acids make them valuable industrial feedstocks.
Oleum – It is a term referring to solutions of different compositions of sulphur trioxide in sulphuric acid, or sometimes more specifically to di-sulphuric acid (also known as pyro-sulphuric acid). It is a strong oxidant. It reacts with combustible and reducing materials and organic materials. This generates fire and explosion hazard. Oleums can be described by the formula ySO3·H2O where ‘y’ is the total molar mass of sulphur tri-oxide content. The value of ‘y’ can be varied, to include different oleums. They can also be described by the formula H2SO4.xSO3 where ‘x’ is now defined as the molar free sulphur tri-oxide content. Oleum is normally assessed according to the free SO3 content by mass. It can also be expressed as a percentage of sulphuric acid strength, for oleum concentrations, that would be over 100 %.
Olsen ductility test, Olsen cup test – It is a cupping test in which a piece of sheet metal, restrained except at the centre, is deformed by a standard steel ball until fracture occurs. The height of the cup at the time of fracture is a measure of the ductility.
Oligotrophic – It is also known as eutrophic, hypereutrophic, and mesotrophic. It pertains to a lake or other body of water characterized by extremely low nutrient concentrations such as nitrogen and phosphorous and resulting very moderate productivity.
Olive – It is a naturally occurring mineral composed of fosterite and fayalite, crushed and used as a moulding sand. It is normally the sand of choice in manganese steel casting because of its basicity.
Oliver-Pharr method – it is a widely used technique in instrumented indentation testing to determine the elastic modulus and hardness of a material by analyzing the load-displacement data from an indentation test, mainly using the unloading portion of the curve to calculate the contact stiffness and projected contact area. This method is crucial for characterizing materials at the micro-scale and nano-scale, especially in industries like semiconductor manufacturing, but it relies on specific assumptions such as perfectly flat surfaces and purely elastic contact.
Olivine – It is a naturally occurring mineral of the composition (Mg,Fe)2SiO4 which is crushed and used as a moulding sand. It is magnesium-iron-orthosilicate composed of forsterite and fayalite. It does not contain free silica. It can be used as possible moulding material.
Olivine phosphate – It is a class of inorganic compounds, such as lithium iron phosphate (LiFePO4), which adopt a specific olivine crystal structure and are used as cathode materials in high-performance lithium-ion batteries. These materials offer advantages like high energy density, safety, long cycle life, and low cost, making them a popular alternative to traditional cobalt-based cathodes. Their ability to facilitate lithium-ion insertion and extraction within their structure enables them to store and release electrical energy.
Omega phase – It is a non-equilibrium, sub-microscopic phase which forms as a nucleation growth product. It is frequently thought to be a transition phase during the formation of alpha from beta. It occurs in metastable beta alloys and can lead to severe embrittlement. It typically occurs during aging at low temperature, but can also be induced by high hydrostatic pressures.
Omitted variable bias – Variables which affect the dependent variable that are omitted from a statistical model are problematic. Irrelevant omitted variables cause no bias in parameter estimates. Important variables which are uncorrelated with included variables also cause no bias in parameter estimates, but the estimate of ‘sigma’ square biased high. Omitted variables which are correlated with an included variable X1 produce biased parameter estimates. The sign of the bias depends on the product of the covariance of the omitted variable and X1 and b1, the biased parameter. For example, if the covariance is negative and b1 is negative, then the parameter is biased positive. In addition, ‘sigma’ square is also biased.
Omnidirectional camera – It is a type of imaging device which captures a 360-degree view of an area, using different configurations such as multiple cameras, special lenses, or catadioptric systems which combine mirrors and lenses. These cameras are particularly notable for their ability to provide a wide field of view and can be designed to have a single center of projection for easier image analysis.
Omnidirectional image – It is a spherical image which captures visual information from all directions, represented on a unitary sphere centered at a point, allowing for a 360-degree field of view. It enables immersive experiences by providing three degrees of freedom for users to observe a scene as if they are inside it.
Once-through boiler – This type of boiler does not have a drum. Simply put, a once-through boiler is merely a length of tube through which water is pumped, heat is applied, and the water is converted into steam. In actual practice, the single tube is replaced by numerous small tubes arranged to provide effective heat transfer, similar to the arrangement in a drum type boiler. The fundamental difference lies in the heat-absorbing circuit. Feedwater in this type of boiler enters the bottom of each tube and discharges as steam from the top of the tube. The working fluid passes through each tube only once and water is continuously converted to steam. As a result, there is no distinct boundary between the economizing, evaporating, and superheating zones. The circulation ratio of this type boiler is unity. These boilers can be operated either at sub-critical or at super-critical pressures.
One-coat ware – It consists of work-pieces finished in a single coat of porcelain enamel. It is also known as one-coat work. It is also sometimes a contraction of one-cover-coat ware in which the finish consists of a single cover coat applied over the ground coat.
One-dimensional flow – It is a type of fluid flow which can be analyzed using mean velocity and simplified to a single dimension, frequently applied in scenarios such as flow in a tube where the continuity, Bernoulli’s, and momentum equations are utilized.
One-dimensional Fourier transform – It is a mathematical operation which transforms a one-dimensional density curve into its frequency representation, allowing the analysis of frequency components in the data. It is got by dividing the curve into segments or peaks and summing their corresponding phasor-waves.
One-line diagram – It is popularly known as single-line diagram (SLD). It is a simplest symbolic representation of an electric power system. The one-line diagram typically corresponds to more than one physical conductor. In a direct current system, the line includes the supply and return paths, in a three-phase system, the line represents all three phases (the conductors are both supply and return because of the nature of the alternating current circuits). The one-line diagram has its largest application in power flow studies. Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors are shown by standardized schematic symbols. Instead of representing each of three phases with a separate line or terminal, only one conductor is represented.
One-phase convection heat transfer – It refers to the process where heat is transferred between a surface and a fluid (either liquid or gas) where the fluid remains in a single phase (either liquid or gas, but not both) throughout the process. It involves the movement of the fluid, carrying thermal energy with it, and is driven by either forced or natural (free) means.
One-piece pattern – It is a solid pattern, not necessarily made from one piece of material. The pattern can have one or more loose pieces.
One-screen – It is a distribution of a clean sand or a sand with two maximum screens separated by a minimum screen. These high-expansion problem sands are also referred to as camel back distributions.
One-step laser deposition – It refers to a single, continuous process of laser-based material deposition, frequently implying a single pass of the laser over the target, resulting in deposition.
One-tail test – It is a test of hypothesis for which the study hypothesis is directional, i.e., if the null hypothesis is false, the true parameter value is hypothesized to be either strictly above the null-hypothesized value or strictly below it. One-tail test is also known as a one-sided test, a test of a statistical hypothesis in which the region of rejection consists of either the right-hand tail or the left-hand tail of the sampling distribution of the test statistic. Philosophically, a one-sided test represents the analyst’s a priori belief that a certain population parameter is either negative or positive.
One-to-one mapping – It is a relationship where each distinct input element is uniquely paired with a distinct output element, ensuring that no two inputs share the same output. This concept is applied in several engineering domains.
One-way analysis of variance (ANOVA) – It is an extension of the independent group t-test where one has more than two groups. It computes the difference in means both between and within groups and compares variability between groups and variables. Its parametric test statistic is the F-test.
One-way valve – It is also known as a check valve or non-return valve. It is a mechanical device which allows fluid (liquid or gas) to flow in only one direction while preventing backflow. It is designed to ensure unidirectional flow within a system, preventing undesirable reverse flow.
Online catalogue – It is a list of items or services available to the customers presented over the internet. Online catalogues simplify the purchasing process. Online catalogues are also referred to as B2B e-commerce catalogues or digital catalog. B2B suppliers frequently have searchable databases of their goods and new features which considerably improve their browsing experience and buying on the platform. These catalogues can be e-designs of magazines, newspapers, brochures, flyers, books, etc. There is no limit to what can be included in online catalogues.
Online learning – It is an educational process which uses the internet and digital tools to deliver instruction to learners, frequently through virtual laboratories and simulations to overcome hands-on limitations.
On-line monitoring system (OLMS) – It is a system which uses permanently installed sensors to continuously collect, transmit, and analyze real-time data from a machine, structure, or process to assess its operational status, detect abnormal conditions, and predict potential failures, ultimately aiming to reduce downtime, increase efficiency, and improve safety.
On-load tap changer (OLTC) – It is a device in a power transformer which regulates the output voltage by changing the number of active turns on the transformer’s winding while the transformer is still energized and carrying load, ensuring continuous power supply and stable voltage levels without needing a shutdown. It works by using selector and diverter switches, frequently with a resistor or reactor to limit current during switching, to adjust the turns ratio of the transformer winding.
On/off permanent magnets – These have the safety of an ‘always on’ permanent magnet and the controlled ‘on/off’ of an electro-magnet. These magnets frequently use rare earth magnetic material in two separate fields. When both fields are lined up, ‘north to north’ and ‘south to south’, the magnetic field goes down into the steel. When one field is reversed, caused by rotating the ‘on/off’ handle, the field stays within the magnet, no longer holding the steel. The ‘on/off’ magnets normally have two parallel poles which give this magnet a deep penetrating magnetic field for rougher, and flat surfaces and work well on round pipe or shaft material. When this type of permanent magnet is ‘off’ all collected fuzz iron falls away. In most sizes, the ‘on/off’ magnet is needed to be on steel to rotate the handle to the ‘on’ position. This is a safety feature which prevents pre-energizing of the magnet prior to being placed on steel, reducing the chance of injury or equipment damage.
Onset temperature – It is the lowest temperature at which a chemical reaction or thermal event, like decomposition, begins to occur at a measurable rate. This temperature is highly dependent on the sensitivity of the instrumentation used, the reaction kinetics, and experimental conditions, rather than being a strict ‘switch’ which starts the reaction.
Onset voltage – It is the specific voltage level at which a particular electrical phenomenon, such as a corona discharge or electrospray, begins to occur in a given system. It represents the threshold where the electric field is strong enough to cause a transition from a non-ionized to an ionized state or to overcome a physical barrier like surface tension, leading to the ejection of charged particles or electrical breakdown.
On-site construction time – It refers to the total duration from the beginning of work at the project site until all on-site construction and related activities are complete, including site preparation and cleanup. This time frame measures the period when a contractor is actively working on the project’s physical location, differing from off-site prefabrication.
Opacifier – It is a material which imparts or increases the diffuse reflectance of porcelain enamel.
Opacity – It is the measure of impenetrability to electro-magnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc. In porcelain enamel, it is the property of reflecting light diffusely and non-selectively.
Opaque object – It is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general, some can be reflected, some absorbed, some scattered, and the rest transmitted. Reflection can be diffuse, for example light reflecting off a white wall, or specular, e.g., light reflecting off a mirror. An opaque substance transmits no light, and hence reflects, scatters, or absorbs all of it.
Open access – It means free access to information and unrestricted use of electronic resources for everyone. Any kind of digital content can be open access, from texts and data to software, audio, video, and multi-media. While most of these are related to text only, a growing number are integrating text with images, data, and executable code.
Open-back inclinable (OBI) press – It consists of a vertical crank press which can be inclined so that the bed has an inclination normally varying from 0-degree to 30-degree. The formed parts slide off through an opening in the back. It is frequently called an OBI press.
Open burning – It consists of burning of any matter if the resultant combustion products are emitted directly to the atmosphere without passing through a stack, duct or chimney.
Open-cell foam – It is the foamed or cellular material with cells which are normally inter-connected. Closed cell refers to cells which are not inter-connected.
Open channel – It is a conduit or passage through which a liquid, typically water, flows with a free surface which is exposed to the atmosphere and atmospheric pressure. Unlike pipe flow, open channels are not completely enclosed, allowing for a free surface where the water interacts with the air. Flow in open channels is mainly driven by gravity and occurs in both natural formations like rivers and artificial structures such as canals, ditches, and sewers.
Open circuit – It is an electrical circuit which is incomplete or ‘broken’, preventing the flow of electric current since the continuous path for electrons is interrupted at some point. This interruption can be intentional, like turning off a switch, or unintentional, caused by component failure, broken wires, or other disruptions. An open circuit effectively has infinite resistance, resulting in zero current flow.
Open-circuit mill – It is a type of grinding or size reduction equipment where material is passed through the mill only once without any recirculation of coarser particles back to the mill for further grinding. Unlike a closed-circuit system which uses classifiers to return oversized particles, an open circuit simply discharges the ground material directly. This process is simpler, needs less equipment, and is frequently used for applications like;,., initial grinding stages, or when a uniform product size is not critical.
Open-circuit potential – It is the potential of an electrode measured with respect to a reference electrode or another electrode when no current flows to or from it.
Open-circuit time constant method – It is a method for approximately evaluating the transfer function of an electrical network.
Open-circuit voltage – It is the difference in electrical potential between the terminals of a device, such as a battery or solar cell, when it is disconnected from any circuit or load, resulting in zero current flow. It represents the maximum possible voltage a device can provide under no-load conditions and serves as a key performance indicator for devices like fuel cells and solar panels, reflecting their internal health and maximum potential output.
Open collaboration – It is a goal-oriented, decentralized innovation and production system where participants, regardless of background or status, voluntarily work together with loose coordination to create products, services, or knowledge of economic value. Key principles include egalitarian participation (no barriers to entry), meritocracy (decisions based on merit, not status), and self-organization (collaborators choose their own processes). This model fosters collective intelligence by allowing diverse perspectives to build on shared ideas, leading to more creative solutions and faster innovation, as seen in open-source software and other creative works.
Open contract – It is a type of agreement where the specific terms, like price or quantity, are not fixed and can be adjusted during the contract’s duration, often without mutual consent. This contrasts with traditional contracts where terms are pre-defined and frequently need mutual agreement for changes. Open contracts offer flexibility to adapt to changing market conditions or needs.
Open crack – It is a crack or tear in the surface of a brick or block whose length is more than 10 millimeters and whose width is more than 0.2 millimeters.
Open cross-section – It is a structural component’s shape which is not fully enclosed, such as I-beams, channel sections, or angles. These beams are characterized by open, non-continuous sides and are analyzed for their response to bending, shear, and torsional loads. Open sections are not as strong in torsion as closed sections and can be susceptible to lateral buckling, needing additional design considerations.
Open cycle gas turbine (OCGT) – It is a type of internal combustion engine which draws in fresh atmospheric air, compresses it, combusts fuel in the compressed air to create hot, high-pressure gases, and then uses these gases to drive a turbine and generate power. Unlike a closed-cycle system, the exhaust gases are released directly into the atmosphere rather than being recirculated. The main components are a compressor, a combustor, and a power turbine.
Open cycle vapour recompression – The open cycle vapour recompression uses compression to increase the pressure (and consequently the temperature) of the waste vapour. Mechanical vapour recompression uses a mechanical compressor, while thermal vapour recompression uses a steam ejector, and hence is heat driven rather than mechanically driven.
Open-die contour forging – It is a metal-shaping process where a hot or cold metal work-piece is deformed between two flat or contoured dies which do not completely enclose the material. Unlike closed-die forging, the metal is allowed to flow more freely, making it suitable for producing large, custom, and complex shapes such as shafts, discs, and hollow components with improved internal grain structure and high mechanical properties.
Open-die forging – It consists of the hot mechanical forming of metals between flat or shaped dies in which metal flow is not completely restricted. It is also known as hand or smith forging. Open-die forging can be distinguished from most other types of deformation processes in that it provides discontinuous material flow as opposed to continuous flow. Forgings are made by this process when (i) the forging is too large to be produced in closed dies, (ii) the needed mechanical properties of the worked metal which can be developed by open-die forging cannot be obtained by other deformation processes, (iii) the quantity needed is very small to justify the cost of closed dies, and (iv) the delivery date is too close to permit the fabrication of dies for closed-die forging. All forgeable metals can be forged in open dies.
Open-die forging press – It is hydraulic or mechanical equipment which uses simple, unrestrained dies to shape a heated metal work-piece by applying repeated compression or impact. Unlike closed-die forging, the work-piece is never fully enclosed by the dies, allowing the metal to freely deform and flow laterally. This process is used to create large, simple shapes like bars, shafts, rings, and discs in heavy engineering, frequently needing subsequent machining for complex final parts.
Open dies – These are dies with flat surfaces which are used for preforming stock or producing hand forgings.
Open drip proof (ODP) motors – These motors allow air to circulate through the windings for cooling, but prevent drops of liquid from falling into motor within a 15-degree angle from vertical. Typically, these motors are used for indoor applications in relatively clean, and dry locations. These motors allow for direct airflow over their windings, providing natural cooling for higher power output in relatively clean and dry, non-hazardous indoor industrial environments, such as in pumps, fans, and air handlers.
Open dump – It is a land disposal site at which solid wastes are disposed of in a manner which does not protect the environment, are susceptible to open burning, and are exposed to the elements, vectors, and scavengers. Open dumping can include solid waste disposal facilities or practices which pose a reasonable probability of adverse effects on health or the environment.
Open-end pipe pile – It is a pile in which the pipe can be driven with the lower end open. It is installed by driving the pipe to the needed depth, removing the material from inside, by burst of compressed air, a mixture of water and compressed air, and filling the space with concrete. Since the open-end pipe piles offer lesser driving resistances than closed-end piles, a smaller pile hammer can be used. The use of light hammers is desirable when piles are driven near a structure whose foundation can be damaged by impact of the blows from a large hammer. Open-end pipe piles can be driven to depths which can never be reached with the closed-end pipe piles.
Open face mould – It is a mould which has no cope or other covering.
Open flame burners – These are those burners where the flame is not confined as is the case in radiant tubes, nor are the flames mainly attached to a surface as in porous refractory burners. Open flame burners are normally visible to the naked eye where the radiant heat from the flame, rather than from a surface heated by the flame, can directly heat the load.
Open flame furnace – It is a furnace, in which the metal charge is confined in the refractory lining, with the flame and products of combustion coming in direct contact with the metal.
Open forward extrusion – It is also known as direct extrusion. It is a metal forming process where a heated metal billet is placed in a container and then forced to flow through a die opening at the opposite end by a ram or plunger. This process creates a product with a constant cross-section which matches the die’s shape. Friction between the billet and the container walls is a key consideration in this method.
Open frame structure – It is a skeletal framework which intentionally exposes its supporting components, such as beams and columns, for functional support and aesthetic purposes, frequently seen in industrial facilities and modern architecture. Unlike concealed structures, these frames are designed for transparency, ease of assembly, and flexibility, allowing for clear inspection and modification at a construction site.
Open grain structure – It is a defect wherein a casting, when machined or fractured, appears to be coarse grained and porous. It is normally because of a shrink area.
Open hearth furnace – It is a reverberatory melting furnace with a shallow hearth and a low roof. The flame for heating of the bath passes over the charge on the hearth, causing the charge to be heated both by direct flame and by radiation from the roof and sidewalls of the furnace. The furnace fuel can be producer gas, coke-oven gas, powdered coal, or oil.
Open hearth steel – It is the steel made in open-heart furnace.
Open hole compression (OHC) test – This test is used to determine the influence of a hole on the compressive strength of a laminate. The ratio of the open hole compression strength to compressive strength of the same unnotched laminate provides the open hole compression strength knockdown factor.
Open hole section – It is the part of a wellbore which has not been fitted with casing or liner pipe, leaving the producing formation exposed to the wellbore itself. This ‘barefoot’ completion allows direct access to the entire pay zone, reducing costs associated with cementing and perforating, but it increases risks like wellbore collapse, sand production, and challenges in controlling fluids and selective simulation treatments.
Open impeller – It is a pump component consisting of vanes attached to a central hub, but without any enclosing sidewalls or shrouds. This exposed design offers easier maintenance and better handling of fluids with large solids or debris, though it typically results in slightly lower efficiency and structural strength compared to closed impellers.
Open industrial control panels – An open industrial control panel is comprised of a mounting sub-panel and all components mounted to the sub-panel. It is intended for installation into an enclosure in the field. This category also covers industrial control panel enclosures. The enclosures can contain ventilation openings, observation windows, conduit fittings, environmental control devices, or maintenance luminaires. These control panels include wiring, terminals, and several other types of components, as well as mounting devices attached to a sub-panel which do not include a complete enclosure. The enclosure which is included with this type of industrial control panel is only intended to be a part of the overall installation. An open industrial control panel includes internal wiring, field wiring terminals, and components mounted on a sub-panel without a complete enclosure.
Open ion source (OIS) – It is a hot-cathode ion source. The filament wire (cathode) is to be heated to high temperatures (higher than 1,300 deg C) in order to establish an electron emission current. In the high vacuum, most of the energy needed to heat the filament is dissipated to the surroundings through radiative processes.
Open-loop controller – It is a control system where the control action does not depend on the system’s output or performance, instead operating based on pre-set instructions or inputs without any feedback mechanism. These systems lack the ability to monitor the actual output and adjust the control input accordingly, leading to a simpler, cost-effective design but with lower accuracy and reliability compared to closed-loop systems.
Open-loop control system – It is a non-feedback system where the control action depends solely on the input signal and is not influenced by the system’s actual output. It operates based on preset instructions or a timed sequence, lacking any feedback mechanism to monitor or correct errors or variations in the output. This simplicity makes these systems cost-effective, low-maintenance, and fast, but it also results in lower accuracy and less reliability compared to closed-loop systems.
Open-loop supply chain – In it, the used products are recovered by other organization and reused instead of being returned to the original producers. This stands in contrast to a closed-loop supply chain, where such materials are returned to the original manufacturer, who redistributes them to recover value.
Open moulding – It is also known as contact moulding, open laminating, and wet lay-up. It is the method used longest in the polymer-matrix composites industry to make thermoset composite products, and it is still the selected production process for a wide range of composite products. It is a basic process which provides several of the advantages of composites processing, using relatively basic materials technology and processing methods. The moulding method involves placing reinforcements and liquid resin onto the surface of an open mould (which may or may not be precoated with gel coat), or onto other substrates, as, for example, when making a one-off sandwich construction, when making on-site repairs by applying a reinforcing vacuum-formed acrylic, corrosion-resistant lining on steel, or when making on-site repairs of tanks and pipes. The hand lay-up version involves applying the reinforcements and the resin by hand, while the spray-up version uses tailored spray equipment to deposit both reinforcements and resin on the mould or an alternative substrate.
Open pile storage – It refers to the storage of bulk materials in a way that is not fully enclosed, covered, or chemically stabilized, and that attains a certain height and surface area. It is the opposite of storing materials within a building or a fully covered structure. Bulk ores and coals are frequently stored in open storage piles. A number of different methods and types of equipments are used for handling these plied materials. The main types of equipments used in the open pile storage are (i) stacking equipment, (ii) reclaiming equipment, and (iii) belt conveyors. Materials which are not weathered easily and need to be stored and reclaimed at substantial high hourly rate are kept in the open pile storage. The piles can contain materials from 5,000 tons to some million tons, while handling rate can vary from 100 tons per hour to 2,000 tons per hour. The capacity of the open pile storage normally ranges from 7 days to 45 days requirement of the consuming unit of the plant. Such wide variation of pile size and handling rate has influence on the selection of type and size of materials handling plant and equipments needed.
Open pit mine – It is a mine which is entirely on surface. It is also referred to as open-cut or open-cast mine. A typical open pit mine can produce up to 150,000 tons of ore every day.
Open pit mining methods – These are also known as surface mining methods. These are designed for extracting ore from surface deposits. Heavy machinery and blasting procedures are used to remove large quantities of surface rock, which considerably disturbs the land. Sometimes whole mountains (or tops of mountains) are removed through open pit mining processes. The most predominant open pit mining methods used to extract ore are open-pit and open-cut methods. These two methods are considered to be the least expensive extraction techniques. The recovery of material is normally done from an open pit in the ground. After the soil and overlying rock are cleared, the ore is drilled and the holes are loaded with explosive mixtures for blasting. The wide holes in the ground created by drilling, blasting, and ore removal are referred to as open pits. Areas for open pit mining are selected using the mining plan. Identified areas are then tagged. The ore is mined from large open pits by progressive extraction along steps or benches. The benches provide access to progressively deeper ore, as upper level is removed. Drilling in the benches of open pit mining is done for production of iron ore with mechanized drills specific for each mining method. When the ore lies close to the surface, it frequently can be uncovered by stripping away a layer of dirt, sometimes only a metre or two thick. The ore is mined from large open pits by progressive extraction along steps or benches. The benches provide access to progressively deeper ore, as upper-level ore is removed.
Open pore – It is a pore which is open to the surface of a compact. Open pore is connected with a network of connecting pores.
Open pores – These are pores in a refractory which are penetrated by the immersion liquid in the test specified in ISO 5017. These pores are, in principle, all those which are connected with the atmosphere, either directly or through one another.
Open porosity – It consists of a network of connecting pores in a sintered object which permits a fluid or gas to pass through the object.
Open riser – It is the riser whose top is open to the atmosphere through the top of the mould.
Open rod press – It is a hydraulic press in which the slide is guided by vertical, cylindrical rods (normally four) which also serve to hold the crown and bed in position.
Open-sand casting – It is the casting made in a mould which has no cope or other covering.
Open seam pipe – It is also known as a seamed or welded pipe. It is a pipe manufactured by bending and welding a steel plate or strip. This contrasts with seamless pipes, which are made from a single piece of metal without any welding or seams.
Open storage – It is also called outdoor storage. It refers to the placement of materials, equipment, or goods in an open, uncovered area or within structures which lack a full roof and four walls, specifically on an industrial property. It is a practical approach for items which do not need protection from the elements or are too large for indoor spaces, such as heavy machinery, raw materials, and even inventory or bulk goods. Engineering considerations for outdoor storage involve designing for land use efficiency and ensuring the storage methods meet safety and regulatory requirements, like proper containment to prevent environmental runoff.
Open systems inter-connection (OSI) model – It is a conceptual model created by the International Organization for Standardization (ISO) which enables diverse communication systems to communicate using standard protocols. In plain English, the open systems inter-connection provides a standard for different computer systems to be able to communicate with each other. The open systems inter-connection model can be seen as a universal language for computer networking. It is based on the concept of splitting up a communication system into seven abstract layers, each one stacked upon the last. Each layer of the open systems inter-connection model handles a specific job and communicates with the layers above and below itself.
Open tendering process – It is a procurement method where a public invitation is issued inviting suppliers to submit proposals for a specific project or service. This process is characterized by its transparency and competitiveness, allowing all interested suppliers to participate and submit bids. It aims to ensure value for money and fair treatment by encouraging maximum competition and minimizing the risk of favoritism or bias. Key benefits of the process include (i) equal opportunity for suppliers, (ii) improved accountability and compliance, (iii) access to a broader pool of suppliers, and (iv) optimized value for money.
Open thermodynamic system – It is a system which can exchange both energy and mass with its surroundings, such as boiling water where heat and steam are transferred out of the system.
Open tolerance – It refers to a specification where only one limit (either the maximum or minimum) of a dimension is defined, while the other limit is unrestricted or open. This contrasts with ‘closed tolerance’ where both upper and lower limits are specified. Open tolerance allows for more flexibility in manufacturing, potentially reducing costs and simplifying production, but it needs careful consideration of functional requirements to ensure the part still performs as intended.
Open top hot metal ladles – These ladles are with dished bottom. Important parameters while specifying the open top hot metal ladle are (i) capacity of ladles in tons, (ii) weight of the hot metal to be handled, (iii) maximum allowable weight of ladle, (v) limiting height of ladle, (v) limiting diameter of ladle, (vi) centre line of trunnion to top of lining flange, (vii) centre line of trunnion to underside of bottom, (viii) maximum inside diameter of ladle at top, (ix) thickness of ladle hooks, (x) diameter of trunnions, and (xi) distance between centerlines of trunnions and ladle hooks. The normal capacities of these ladles are of 50 cubic meters, 100 cubic meters, and 140 cubic meters. These ladles are tilted with a tilting winch or an overhead crane for its emptying. These ladles are mounted on hot metal ladle cars which are normally designed for rail transportation of hot metal from blast furnace to pig casting machines and steel melting shop.
Open type roll stand housings – They have a removable top connected to the housing by screws for easier rolls changing. Open type housings facilitate easy removal of rolls. When the housings have to withstand large horizontal forces, the pillars are made with an I-section. The integrally cast construction presents many difficulties in manufacturing. In such case the housing can be made up of two forged pillars bolted to two cast cross beams.
Open valve – It allows a fluid (liquid or gas) to pass through its passageway, from higher to lower pressure, by having its internal components (such as a disc or ball) moved away from the sealing surface. This contrasts with a closed valve, which blocks the fluid’s path.
Operating control – In a boiler, it is a control to start and stop the burner. It is in addition to the high limit control.
Operating cost – It is the ongoing expense associated with the routine operation and maintenance of a system, equipment, or facility, including costs for materials, labour, utilities, fuel, and regular upkeep to ensure continuous functionality. These costs are frequently distinguished from capital costs (which are for purchasing or building), and include both fixed costs (like rent) and variable costs (like fuel or raw materials) which fluctuate with operational levels.
Operating environment – It is the collection of conditions, requirements, and interactions under which a system is designed to operate. It encompasses physical factors like weather and terrain, the broader social and regulatory landscape, and the specific technical conditions of hardware, software, and other systems the product must interact with, all of which influence the system’s design, functionality, and performance.
Operating expenses (OPEX) – These are the ongoing costs needed to run and maintain a manufacturing plant. These costs include recurring expenses like salaries, utilities, maintenance, and materials used in daily operations, contrasting with capital expenditures (CAPEX) for acquiring large assets. Effectively managing operating expenses is important for maintaining profitability and the operational success of the organization.
Operating floor level – It refers to the height of the main functional area within a structure, such as the floor where machinery or equipment is located, facilitating easy access and maintenance. This level is distinct from other architectural elements like the ground floor or basement, and it is a crucial consideration in planning, design, and construction to ensure efficient operations and structural integrity.
Operating force – It is the force needed to be applied to the actuator to move from the free position to the operating position.
Operating frequency – It is the specific rate at which a device, system, or process functions, and is frequently the preferred or most effective frequency for optimal output or performance. It is a critical factor which influences performance, efficiency, and function, with examples including the clock rate of a CPU (central processing unit), the transmission rate of an RFID (radio-frequency identification) tag, or the operational rhythm of a ball mill.
Operating hazard analysis (OHA) – It is a hazard analysis which focuses on operating the product, including testing, maintaining, repairing, transporting, and handling. In this analysis, emphasis is on people performing tasks.
Operating hours – These are the defined periods during which a facility, machine, or process is actively functioning or being utilized for its intended purpose. This concept is used to schedule processes, manage resources, track machine usage, and analyze performance, sometimes using terms like equivalent operating hours (EOH) to account for stresses beyond simple duration.
Operating load – It is a realistic measure of the energy consumed by electrical devices and systems which are operating simultaneously, as opposed to the maximum possible load if all devices are running at once. It is a key figure for determining the appropriate size of power system components like transformers and for calculating a user’s contractual electricity demand, as it provides a more accurate reflection of typical daily energy use.
Operating margin – It is a profitability metric which shows the financial performance pf the organization from its core operations. It is calculated as operating income divided by total revenue, expressed as a percentage. This metric reveals how efficiently the organization converts sales into profit after deducting operating costs like salaries, rent, and depreciation, but before accounting for interest and taxes. A higher operating margin indicates better operational efficiency and management control over costs.
Operating personnel – These are the individuals responsible for the direct, hands-on execution of the organization’s core functions or processes, carrying out the daily tasks, services, and maintenance which ensure the smooth and safe operation of its equipment, systems, and activities. Their role is necessary for achieving the organization’s primary purpose, interacting with customers, producing goods, or delivering services in a way which aligns with established procedures.
Operating pressure – It is the actual, normal, and steady pressure at which a system, such as a pipeline, or pressure vessel, functions continuously under normal conditions. It is determined by process engineers based on process requirements, reflects the actual internal force exerted during normal operation, and is to be less than the design pressure and maximum allowable working pressure (MAWP) to ensure safety and proper performance.
Operating principle – It is the fundamental scientific concept or the basic mechanism which describes how a system, device, or component functions and achieves its intended purpose. It explains the underlying rules and processes, such as mutual induction in a transformer or conservation of angular momentum in a gyroscope, which allow the engineering work or task to be performed.
Operating stress map – It is one way to assess potential fracture for an alloy of given toughness and operating stress. Operating stress maps are based on the same principle as a residual strength diagram. Construction of an operating stress map is based on calculations of net section yield and fracture mechanics.
Operating system – It is the system software which manages computer hardware and software resources, and provides common services for computer programmes. Time-sharing operating systems schedule tasks for efficient use of the system and can also include accounting software for cost allocation of processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programmes and the computer hardware, although the application code is normally executed directly by the hardware and frequently makes system calls to an operating systems function or is interrupted by it. Operating systems are found on several devices which contain a computer.
Operating temperature – Itis the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device operates effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature (or peak operating temperature). Outside this range of safe operating temperatures, the device can fail.
Operating tension – It is the tension of longitudinal sections of a belt system when moving material.
Operation – It refers to the everyday running of the plant. This involves several activities such as (i) proper starting and stopping of the plant, (ii) the correct handling of the plant to ensure long component life, (iii) ensure such setting of the plant so that the products produced are as per the specification needed by the customer, (iv) running of the plant efficiently for meeting of the targets and the capacities, (v) running of the plant without the violation of the technological discipline, and (vi) running of the plant with meeting of all the requirements for the safety of both the personnel and the plant. The proper operation results into (i) high plant productivity, (ii) motivated plant operators, (iii) optimum use of the plant, and (v) a reduction in breakdowns and maintenance needs.
Operation and maintenance (O&M) – It refer to the day-to-day activities which ensure a facility, system, or equipment functions effectively, safely, and efficiently throughout its lifecycle. It includes both operations, which focuses on ongoing tasks and procedures for daily use, and maintenance, which involves inspections, repairs, and preventive actions to keep assets in good working order and extend their lifespan. The primary goal of operation and maintenance is to maximize asset availability and prevent failures, which reduces costs and downtime.
Operation and maintenance cost – It refers to the ongoing expenses necessary to keep a system, asset, facility, or device running, monitored, and functional. It includes costs for day-to-day activities, routine and non-routine repairs, spare parts, consumables, administrative overhead, and insurance, all aimed at ensuring the continuous, efficient, and safe operation of the entire system.
Operational amplifier – It is a type of amplifier with differential inputs. It is widely used in circuits where feed-back determines the circuit properties.
Operational considerations – It is important in the selection of crusher and includes power demand, equipment availability (hours / annum), availability and cost of replaceable parts, reduction ratio, maintenance requirements, needed manpower, approachability of parts for maintenance, availability of spares, safety and environment.
Operational control – It is defined as the activities needed to manage and oversee a production process, including operating procedures, monitoring, and follow-up actions, aimed at ensuring that the final product meets quality, safety, and legality standards. In the context of organizational management, it refers to the processes and procedures used to manage and monitor the day-to-day activities of an organization, ensuring they align with established plans and objectives. It focuses on the efficient and effective execution of tasks, rather than on the overall strategic direction of the organization. In essence, it is about making sure things get done correctly and efficiently on a routine basis.
Operational control system – It is a cost management system designed to provide accurate and timely feedback concerning the performance of the processes and others relative activities to the managers for their planning and control of activities. Operational control system is concerned with what activities are to be performed and assessing how well they are performed. It focuses on identifying opportunities for improvement and helping to find ways to improve. A good operational control system provides information which helps managers engage in a programme of continuous improvement of all aspects of the operations. Product cost information plays a role in this process, but by itself, is not sufficient. The information needed for planning and control is broader and encompasses the entire value chain. Cost information concerning quality, different product designs, and post-purchase customer needs is important for managerial planning and control.
Operational discipline – It means complying with a set of ‘well thought out’ and ‘well defined’ processes, and consistently executing them correctly. It is defined as ‘the deeply rooted dedication and commitment by every member of an organization to carry out each task the right way every time’. In short, operational discipline can be stated as ‘everyone in the organization doing it right every time’. It means complying with a set of well thought out and well-defined processes, and consistently executing them correctly. It is an essential ingredient when trying to achieve operational excellence. Operational discipline provides an organized and systematic way to complete tasks and implement operational changes through a fundamental set of procedures which are specific to the steel organization’s unique product. Regardless of the final products of the steel plant, operational discipline increases reliability and decreases the risk of the occurrence of a high magnitude incident.
Operational environment – It defines the complete set of conditions, requirements, and interactions a system is to function within to achieve its intended purpose, encompassing physical, human, and informational aspects. It includes physical surroundings, other interacting systems, human operators, and the information processing and data requirements necessary for the system’s optimal performance and functional processing.
Operationalization – It is the process of translating a theoretical concept, requirement, or goal into a concrete, measurable, and executable set of procedures, specifications, or variables which can be used for design, analysis, manufacturing, or testing. It involves defining abstract ideas into tangible actions or indicators, specifying exactly how something is to be measured or performed, and establishing the instruments and methods for data collection and validation.
Operational personnel – Operational personnel are the individuals responsible for carrying out the core tasks of operating, maintaining, and managing the plant and its processes to ensure safe and efficient production. Their duties include executing operating procedures, overseeing equipment, managing emergencies, and ensuring that the plant’s activities run smoothly to meet organizational objectives.
Operational optimization – It is a systematic approach to improve processes, systems, and resource utilization to achieve the best possible outcome (such as maximizing efficiency, minimizing costs, or increasing productivity) within defined constraints. This process involves applying scientific and mathematical methods, frequently utilizing computational tools and algorithms, to analyze current operations, identify inefficiencies, and implement changes to reach the highest level of performance.
Operational parameters – These are measurable variables or key metrics which define, influence, and are used to monitor the performance of a system, process, or organization. These parameters provide important data points for controlling, optimizing, and evaluating how effectively an operation is running to achieve its goals, such as efficiency, quality, and safety.
Operational phase – It is the period after a product, system, or building is completed and delivered to the customer for use, where it is actively used for its intended purpose, monitored, maintained, and potentially enhanced over its lifespan. This phase involves managing operations, performing maintenance and repairs, ensuring functionality and safety, and sometimes upgrading or decommissioning the asset.
Operational plan – It describes the specific steps in any given strategic planning model and explains how and what portion of resources are going to be put into operation during a given operational period. The operational plan is the basis for, and justification of, an annual operating budget needed to achieve an overall strategic plan. It draws from an organization’s strategic plans to describe organizational missions and goals, organizational objectives, and organizational activities. While an operational plan can differ depending on the industry sector, the core components of an operational plan include bench-marking and determining how progress is measured.
Operational planning (OP) – It is the process of implementing strategic plans and objectives to reach specific goals. Operational planning is one of the four basic types of planning involved in organizational management.
Operational procedure – It is a documented, step-by-step set of instructions which an organization creates to ensure routine tasks are performed consistently, safely, and efficiently, thereby promoting uniformity, quality, and compliance with standards. These standard operating procedures (SOPs) serve as training materials, reduce errors and miscommunication, and provide a framework for continuous improvement by making processes repeatable and measurable across the organization.
Operational process – It is a sequence of core activities within an organization which directly delivers value to customers and the organization. It is crucial for generating revenue and profit, and ensures the organization remains competitive. These processes focus on single, key functions and are frequently called main or core processes, including tasks like resource acquisition, manufacturing, storage, distribution, and customer service.
Operational requirement – It defines the conditions, capabilities, performance, and processes an organization or system is required to meet to function effectively in its intended environment. For organizations, this definition helps create a structured framework to articulate specific needs, allocate resources, and implement actions based on risk assessments and mission goals. Key aspects include performance standards, system interactions, environmental factors, user needs, logistics, and maintenance etc.
Operational resilience – It is an organization’s ability to anticipate, prevent, adapt to, and recover from disruptions to continue delivering critical products and services. It encompasses proactive engineering efforts to identify potential operational risks (like system failures, or supply chain issues etc.) and build systems which can resist, absorb, and quickly recover from adverse events, ensuring operational continuity and stability through planned responses and ongoing testing.
Operational risk – It refers to the potential for losses or failures arising from inadequacies or failures in internal processes, people, and systems, or from external events, all of which can disrupt the day-to-day operations of a project or an organization. This includes a wide range of threats like human error, system malfunctions, software failures, supply chain disruptions, and natural disasters. For engineers, managing operational risk means identifying, assessing, and mitigating these risks to ensure projects are completed safely, on time, and within budget, maintaining the integrity and efficiency of organizational operations.
Operational risk management (ORM) – It is the continuous process of identifying, assessing, and mitigating risks associated with the design, construction, and operation of engineering projects, organizational operations and systems. It encompasses internal factors like failed processes, human errors, or system malfunctions and external factors such as natural disasters or regulatory changes. The objective of operational risk management is to ensure project safety, prevent system failures, maintain efficient operations, and minimize financial losses and reputational damage.
Operational specifications – These are official, detailed documents, approved by a regulatory body, which define the authorized operating conditions, limits, and procedures for an organization, to ensure safety, compliance, and defined outcomes. They serve as contractual definitions of needed performance, outlining specifics such as approved equipment, locations, flight rules, maintenance protocols, and special authorizations, ensuring that an organization’s operations align with regulatory and internal standards.
Operational standard – It defines the criteria for how a product, system, or process performs, behaves, and be managed during its entire lifecycle, ensuring consistent quality, safety, and efficiency. These standards provide clear guidelines, frequently in the form of procedures, specifications, or quality parameters, which are established to be repeatable and effective in achieving desired operational outcomes and managing risks.
Operational status indicator – It is an insightful indicator integrated into a conveyor system, offering real-time information about its present operational state. Consistent monitoring is indispensable for ensuring the precision and continued functionality of these operational status indicators.
Operational stores – This store refers to the storage of raw material, consumables, operating parts, maintenance spares, and energy which is for active use of current organizational operations and processes. The key characteristic is its role in supporting ongoing, active processes.
Operational structure – It is an organizational framework which defines how an engineering project or organization operates, including how tasks are delegated, resources are managed, and information flows to achieve goals efficiently. It specifies roles, responsibilities, and reporting lines, determining the overall structure for operations, from functional units like design and production to the management of complex processes like startup and shutdown in chemical plants.
Operational system – It supports an organization’s daily operations, handling routine transactions and data for core functions.
Operational technology – It refers to the hardware and software systems which directly monitor and control physical devices, processes, and events within an organization, focusing on ensuring the safe, efficient, and reliable operation of industrial equipments, processes, and infrastructure. Unlike information technology (IT), which handles data and information, operational technology is concerned with the physical world of manufacturing, energy, transportation, and other industries, utilizing systems like industrial control systems (ICS) and supervisory control and data acquisition (SCADA)system to manage physical operations.
Operational testing – It is the testing of equipments, processes, and facilities to ensure that these perform seamlessly in real-world environments and diverse conditions.
Operational testing, magnets – New and reinstalled lifting magnets are to be tested by a qualified person, or a designated person under the direction of a qualified person, prior to initial use to verify compliance with applicable provisions, including, but not limited to (i) moving parts, (ii) latches, (iii) stops, (iv) switches, (v) control devices, and (vi) alarms. Altered, repaired, or modified lifting magnets are to be tested by, or under the direction of, a qualified person. The test can be limited to the provisions affected by the alteration, repair or modification as determined by a qualified person with guidance from the manufacturer. All indicator lights, gauges, horns, bells, alarms, pointers and other warning devices are to be tested. Reports with date of all operational tests are to be made available.
Operation and maintenance (O&M) – It consist of a set of activities that keep a facility, equipment, or system functioning properly. It includes the day-to-day running of a facility and the maintenance which prevents deterioration.
Operation and maintenance costs – It is the operational costs of running a plant excluding fuel and any capital costs.
Operation and maintenance manual – Operation and maintenance (O&M) manual for an equipment / facility (frequently referred as ‘plant’) is necessary for the smooth operation of the plant. The operation and maintenance manual serves as an important tool for existing and new employees to safely and successfully operate and maintain the plant. When put together properly, employees at the workplace are able to utilize the operation and maintenance manual as a quick reference guide for anything from trouble-shooting to facing of an emergency during the plant operation. It provides necessary details about the upkeep of the plant. The manual also summarizes the actions necessary and identify those steps needed for cost effective, efficient, safe, and reliable plant operation.
Operation guidance system (OGS) – It has been developed by the KSC (Kawasaki Steel Corporation) with the objective of achieving a stable permeability of the sinter bed for achieving an optimal sinter quality. After inputting production data of sintering process, main system evaluates permeability, sinter quality, and productivity. It has two sub-systems. One of the sub-systems is used to assess permeability, while the other is used for auto-adjusting the standard value for assessment.
Operations design – It refers to the process of designing and organizing the systems, processes, and resources which an organization uses to produce goods or services. It involves identifying the most efficient and effective ways to produce and deliver a product or service to meet customer demand.
Operation set up – It refers to the process of preparing and organizing resources, systems, or procedures to enable a specific operation or task to be performed. This can involve a wide range of activities depending on the context, from physically arranging equipment to establishing protocols and procedures.
Operations management (OM) – It consists of the administration of organizational practices to create the highest level of efficiency possible within an organization. It is concerned with converting materials and labour into goods and services as efficiently as possible to maximize the profit of the organization. Operations management teams attempt to balance costs with revenue to achieve the highest possible net operating profit.
Operation switch – It is a device which, through manual or automatic action, makes or breaks an electrical circuit, allowing for control and safety by turning devices on or off, rerouting signals, or triggering safety protocols. The operation method can be momentary, where the switch is active only while pressed, or alternate, where it stays in an activated state until pressed again. Switches are used in a wide range of applications in industrial machinery field.
Operation team – It is a group responsible for the efficient management and execution of the day-to-day processes of the organization, ensuring smooth production of goods or delivery of services to meet organizational goals and customer needs. Their key functions include overseeing the production or service process, improving efficiency, coordinating internal departments, managing logistics, and sometimes handling customer service and IT (information technology) systems.
Operator – An operator is a person whose job is to use and control a machine or vehicle. In mathematics, an operator is normally a mapping or function which acts on elements of a space to produce elements of another space (possibly and sometimes needed to be the same space). There is no general definition of an operator, but the term is frequently used in place of function when the domain is a set of functions or other structured objects. An operator is also a function over a space of physical states onto another space of states.
Operator console – It is an electronic device which is used to control various field equipment in a production unit. Operator consoles are designed for ergonomic mounting of all types of operator interface devices: pushbuttons, display screens, human machine interfaces (HMIs), gauges, and meters etc. Larger free-standing consoles include ample enclosure space for other control devices to be mounted on interior sub-panels.
Operator work-stations – These are used for monitoring all system operations and for effecting control actions and parameter adjustments. These operator workstations are normally referred to as ‘clients’ since they get their current and historical data from the ‘server’ computer. There are normally multiple operator workstations for a production unit, each of which contains all of the process graphic displays and historical trend displays for the system.
OPEX – It means operating expenses. An operating expense is an expenditure which an organization incurs as a result of performing its normal operations.
Opinion – It is a belief or conviction, based on what seems probable or true but not demonstrable fact. The collective views of a large number of people, especially on some particular topic. Several studies have shown that individuals do not possess the skills to adequately assess risk or estimate probabilities, or predict the natural process of randomness. Hence, opinions can frequently be contrary to statistical evidence.
Opportunity costs – These costs are also known as alternative costs. These costs are the potential benefits which are foregone if a decision is made in favour of a particular option and other alternatives are hence excluded. These costs represent the value of the next best alternative which is not chosen. Opportunity costs are a central concept in economics, since these costs help to understand and weigh up the true costs of decisions. Opportunity costs play an important role in decision making since these costs help to evaluate the relative advantages and disadvantages of different courses of action and make an informed choice. Opportunity costs always arise when a decision is made and an alternative option is foregone. They occur in different contexts and situations, both in the personal and in the professional and organizational environment. By being aware of opportunity costs, one can make more informed and efficient decisions.
Opportunity maintenance – It is a set of maintenance activities which are performed on an equipment or a facility when an unplanned opportunity exists during the period of performing planned maintenance activities to other equipments or facilities. This maintenance is used in multi component systems. When an equipment or system is taken down for maintenance of one or few worn out component, the opportunity is utilized for maintaining or changing other wear out components, even though they are not failed. It is actually not a specific maintenance system, but it is a system of utilizing an opportunity which can come up any time.
Optical axis – It is the line formed by the coinciding principal axes of a series of optical elements comprising an optical system. It is the line passing through the centers of curvature of the optical surfaces.
Optical bandwidth – It consists of a range of optical frequencies available for signal modulation, data transmission, or the operational range of an optical device, frequently characterized by the frequency at which the optical power drops to half its maximum value (-3 dB). It can also refer to the width of an optical spectrum from a light source or the maximum data rate a fibre optic cable can support.
Optical control – It refers to the manipulation and management of light, including its direction, intensity, and distribution, frequently through the use of devices like lenses, reflectors, and diffusers, or through more advanced techniques like optical switching in communication networks. It can also involve the use of light to control biological processes or the behaviour of molecules.
Optical density – It is also called absorbance. It quantifies a material’s ability to absorb or block light, measured as the logarithmic ratio of incident light intensity to transmitted light intensity. A higher optical density indicates less light transmission and higher absorption by the material, with applications in fields like spectroscopy, and determining the effectiveness of protective lenses.
Optical emission spectrometry – It involves applying electrical energy in the form of spark generated between an electrode and a metal sample, whereby the vapourized atoms are brought to a high energy state within a so-called ‘discharge plasma’. These excited atoms and ions in the discharge plasma create a unique emission spectrum specific to each element. Hence, a single element generates several characteristic emission spectral lines.
Optical emission spectroscopy – It is pertaining to emission spectroscopy in the near-ultraviolet, visible, or near-infrared wave-length regions of the electro-magnetic spectrum. Optical emission spectroscopy is a well trusted and widely used analytical technique used for determining the elemental composition of a broad range of metals. The type of samples which can be tested using optical emission spectroscopy include samples from the melt in primary and secondary metal production, and in the metals processing industries, tubes, bolts, rods, wires, plates and many more. The part of the electromagnetic spectrum which is used by optical emission spectroscopy includes the visible spectrum and part of the ultraviolet spectrum. In terms of wave-length, it ranges from 130 nanometers up to around 800 nanometers.
Optical emission spectrometry (OES) with pulse discrimination analysis (PDA) – The optical emission spectrometry method is conventionally used for analysis of dissolved elements in steel. This technique has been further improved to analyze the total oxygen content, micro-inclusion size distribution and composition within 10 minutes of collecting the sample. To discriminate solid inclusions (optical emission spectrometry-pulse discrimination analysis), light logging is made at the frequency of the emission spark. Electrical characteristics are defined to optimize the light ratio between the background signal of the dissolved elements and the disturbance signal because of the heterogeneities such as inclusions. The number of high intensity Al peaks spark is the pulse discrimination analysis index.
Optical engineering – It is the field of applying the science of optics to design, develop, manufacture, and test systems and devices which generate, control, and utilize light. Optical engineers solve problems by creating functional tools such as cameras, lasers, telescopes, microscopes, and fibre-optic communication systems. They work across diverse industries, from healthcare and telecommunications to aerospace and manufacturing, using physics principles and specialized software to bring optical technologies to life.
Optical etching – It consists of development of micro-structure under application of special illumination techniques, such as dark-field illumination, phase contrast illumination, differential interference contrast illumination, and polarized light illumination.
Optical fibre – It is a flexible glass or plastic fibre which can transmit light from one end to the other. Such fibres find wide usage in fibre-optic communications, where they permit transmission over longer distances and at higher band–widths (data transfer rates) than electrical cables. Fibres are used instead of metal wires since signals travel along them with less loss and are immune to electro-magnetic interference. Fibres are also used for illumination and imaging, and are frequently wrapped in bundles so they can be used to carry light into, or images out of confined spaces, as in the case of a fibre-scope. Specially designed fibres are also used for a variety of other applications, such as fibre optic sensors and fibre lasers. Glass optical fibres are typically made by drawing, while plastic fibres can be made either by drawing or by extrusion. Optical fibres typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fibre to act as a wave–guide. Fibres which support several propagation paths or transverse modes are called multi-mode fibres, while those which support a single mode are called single-mode fibres (SMF). Multi-mode fibres normally have a wider core diameter and are used for short-distance communication links and for applications where high power are to be transmitted. Single-mode fibres are used for majority of the communication links longer than 1,050 meters.
Optical fibre technology – It is the study and application of light propagation in waveguides, focusing on the properties and fabrication of optical fibres, as well as the components and devices used in optical fibre systems, including sensing applications.
Optical fibre transmission – It is the process of transporting light signals through a dielectric waveguide, known as an optical fibre, which consists of a core surrounded by cladding. This method enables high bandwidth communication with low transmission losses and immunity to electromagnetic interference.
Optical fiber types – These are classifications based on their structural properties and light transmission characteristics, including the material (glass or plastic), the refractive index profile (step-index or graded-index), and the number of light propagation modes (single-mode or multi-mode).
Optical gas imaging camera – It can be considered a highly specialized version of an infrared or thermal imaging camera. There is a lens, a detector, some electronics to process the signal from the detector, and a viewfinder or screen for the user to see the image produced by the camera. The detectors used for optical gas imaging cameras are quantum detectors which need cooling to cryogenic temperatures (around 70 K or -203 deg C). Mid-wave cameras which detect gases such as methane commonly operate in the 3 micrometers to 5 micrometers range and use an indium antimonide (InSb) detector. Long-wave cameras which detect gases such as sulphur hexa-fluoride tend to operate in the 8 micrometers to 12 micrometers range and use a quantum well infrared photo-detector (QWIP).
Optical gas sensors – Optical sensors’ operation mainly includes controlling, then detection of the beam propagating through the target area where the photons which got detected generate the electrical signals. Frequently utilized optical sensors are, namely fibre-optic gas sensors and photonic-crystal gas sensors. These sensors are based on the principle of the detection of the beam propagation through utilization of devices. Fibre-optic-based sensor measures the modification in optical property (namely, wave-length) and detects the analytes introduced on the sensing polymeric layer by employing optical fibre. These sensors are enriched with excellent sensitivity, stability with respect to the environmental factor as well as longer lifetime. Implementation of optical fibre in the structure causes complications in the miniaturization. Structure of the photonic crystal sensor utilizes the periodic arrangements of dielectric materials with several refractive indexes.
Optical gauges – These are instruments which measure physical quantities by analyzing changes in light, frequently using optical fibres. They are non-contact measurement devices, meaning they don’t require direct physical contact with the object being measured. These gauges are particularly useful for measuring strain, displacement, and other parameters where traditional electrical gauges can be unsuitable because of the factors like electro-magnetic interference or harsh environmental conditions. Optical gauges measure by analyzing light patterns or properties, avoiding direct contact with the object, minimizing the risk of introducing errors or damaging the object.
Optical-geometrical methods – These are also known as geometrical optics. It is a branch of optics which simplifies the study of light by treating it as rays traveling in straight lines, ignoring its wave nature. This approach is useful for analyzing how light interacts with optical systems and for understanding phenomena like reflection, refraction, and image formation in lenses and mirrors.
Optical holography – It is a technique which enables an optical wavefront to be recorded and later re-constructed. Holography is best known as a method of generating three-dimensional images but it also has a wide range of other applications. A hologram is made by superimposing a second wavefront (normally called the reference beam) on the wavefront of interest, thereby generating an interference pattern which is recorded on a physical medium. When only the second wavefront illuminates the interference pattern, it is diffracted to recreate the original wavefront. Holograms can also be computer-generated by modelling the two wavefronts and adding them together digitally. The resulting digital image is then printed it onto a suitable mask or film and illuminated by a suitable source to reconstruct the wavefront of interest.
Optical inspection – It is a non-destructive evaluation method which uses light and optical components to examine the surface and features of an object. It is used to detect defects, verify dimensions, and assess the quality of different products and materials. This can be done manually with the naked eye or using specialized equipment like cameras, microscopes, or automated systems.
Optical interferometry – It is a measurement technique which utilizes the interference of light waves to precisely measure distances and surface profiles, or to analyze refractive index variations. It works by splitting a beam of light into two or more paths, then recombining them to create interference patterns. By analyzing these patterns, subtle changes in the light’s path length can be detected with high accuracy.
Optical lithography – It is a photon-based technique which involves projecting an image onto a photo-sensitive emulsion (photo-resist) on a substrate, normally used in the high-volume manufacturing of nano-electronics in the semi-conductor industry. This method is characterized by its highly parallel nature, enabling rapid information transfer and high-resolution patterning.
Optically detected magnetic resonance (ODMR) – It is a double resonance technique by which the electron spin state of a crystal defect may be optically pumped for spin initialization and readout. Like electron paramagnetic resonance (EPR), optically detected magnetic resonance makes use of the Zeeman effect in unpaired electrons.
Optically isotropic material – It has the same optical properties in all directions, meaning light behaves the same regardless of its direction of travel through the material. Examples include liquids, glasses without structural order, and crystalline solids with cubic symmetry.
Optical metallography – It is one of three general categories of metallography, entails examination of materials using visible light to provide a magnified image of the micro-structure and macro-structure microscopy (micro-structural examination) involves magnifications of around 50× or higher. Macroscopy (macro-structural examination) involves magnifications of around 50× or lower. Optical microscopy and, is used to characterize structure by revealing grain boundaries, phase boundaries, inclusion distribution, and evidence of mechanical deformation.
Optical metrology – It is a measurement technique which uses light to gather data about the physical properties of objects. This can include measurements of distance, shape, size, surface roughness, and more. Optical metrology has a wide range of applications across different fields e.g., manufacturing and engineering.
Optical microscope – It is frequently referred to as the light microscope. It is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest and simplest of the microscopes. It is a very important instrument for the study of microstructure, despite the evolution of sophisticated electron metallographic instruments.
Optical microscopy – It is the microscopic examination of materials through the optical microscope. The visible part of electromagnetic spectrum is the type of radiation used by optical microscopy.
Optical modulation – It is the controlled process of altering a light wave’s amplitude, phase, or polarization to encode information from an electrical signal onto the light. This enables the transmission of digital or analog data through optical fibres and other media by varying the light’s intensity, timing, or orientation to represent information, similar to how a radio wave carries information.
Optical modulation index – It measures how much a modulation signal changes an optical transmitter’s light output, typically a laser. Expressed as a percentage, optical modulation index indicates the extent of signal variation relative to the average output power. A properly set optical modulation index is critical for balancing signal quality against noise and distortion, ensuring optimal performance and stability in optical communication systems.
Optical parameter – It defines a measurable characteristic of light or an optical component, specifying its interaction with matter or its physical properties. Key optical parameters include transmittance, reflectance, absorption, dispersion, and refractive index, which describe how light passes through, reflects off, or is absorbed by materials. For optical systems, parameters like focal length, numerical aperture, and wave-front aberration define the performance of lenses, fibres, and other optical elements.
Optical parametric amplifier (OPA) – It is a laser light source which emits light of variable wave-lengths by an optical parametric amplification process. It is essentially the same as an optical parametric oscillator, but without the optical cavity (i.e., the light beams pass through the apparatus just once or twice, rather than many-many times).
Optical probe – It is a device with optical components which uses light to measure, analyze, or communicate with a target, frequently by converting light signals into electrical data or vice versa. It typically contains both a light source (emitter) and a light detector (receiver) and can transmit and receive signals non-invasively, making it useful in applications like smart meter reading, and material inspection.
Optical properties of nanomaterials – These refer to the characteristics associated with the interaction of electromagnetic radiation with nanosized materials, which can show size-dependent behaviour and unique phenomena such as localized surface plasmon resonance. These properties are influenced by factors such as shape, size, aggregation state, and surface chemistry, leading to distinct absorption and scattering behavior compared to bulk materials.
Optical properties of semi-conductors – These refer to the behaviour of light interactions within semiconductor materials, including phenomena such as inter-band absorption, excitonic effects, and stimulated emission. These properties are important for applications in opto-electronics and photonics.
Optical pyrometers – These pyrometers are non-contact temperature measuring devices used for such purposes as flame temperature measurement and for specialized research purposes such as the measurement of piston-ring surface temperatures by sighting through a hole in the cylinder wall. These instruments provide a no-touch means of estimating the surface temperatures of hot objects in the range of 700 deg C to 4,200 deg C, such as metals being hot-worked, liquid metals, gas plasmas, and furnace interiors. Optical pyrometers make use of the fact that all objects at temperatures above 0 K radiate heat in the form of broad-band, electro-magnetic energy. Optical pyrometers operate within the visible spectrum to measure temperatures by comparing the photometric brightness of the heated object against the brightness of a standard source, such as an incandescent tungsten filament. A mono-chromatic filter for the red wave-length radiation (630 nano-meter) is used to support the operation. The comparison of the brightnesses is dependent on the sensitivity of the human eye (on manual versions) to distinguish the brightness difference between two surfaces of the same colour. The brightness comparison is made adjusting the current through the filament of the standard brightness source until its brightness becomes equal to that of the measured object. It is possible to get measurements with accuracy better than 1%. There are also commercial automatized versions of optical pyrometers.
Optical quality – It refers to the ability of an optical component or system to accurately transmit, focus, and resolve light by minimizing distortions and defects, such as surface flaws (scratches and digs) and variations in material refractive index. It is a relative measure of performance determined by the presence of imperfections and is frequently quantified using standards like the scratch-dig rating (e.g., 80-50), which assesses the severity of surface imperfections on a given component.
Optical receiver – It is a device which converts an incoming optical signal (light) into an electrical signal, enabling the recovery of information from optical communication systems. It typically comprises a photodetector (like a photodiode) to convert light to a weak current, followed by amplifiers to boost the signal, filters to reduce noise, and decision circuits to interpret the signal as digital data. The performance of an optical receiver is characterized by factors such as its band-width, noise figure, responsivity, and frequency response flatness.
Optical reflectivity – It quantifies the fraction of incident light which a material or surface reflects, representing an intrinsic property of the material itself. It is calculated as the ratio of reflected light intensity to incident light intensity and varies based on the material’s refractive index, surface properties like roughness, and the wavelength of the light. This property is important for applications such as designing mirrors, coatings, and optical instruments, as well as in areas like remote sensing and material analysis.
Optical rotation – It is also known as polarization rotation or circular birefringence. It is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror interactions symmetry.
Optical sensor – It is a device which detects and converts light into an electrical signal. It essentially measures the intensity of light and translates that measurement into a usable form, often an electronic signal that can be interpreted by a machine or system. Optical sensors are mainly a non-contact sensing technology that detect variations in light energy and produce a resultant electrical signal or change in conductivity based on the photo-electric or photo-conductive effect respectively. The output response by photoconductive sensors makes them effective for infrared based detection. These sensors are crucial for various applications where contactless detection or measurement of light is needed.
Optical signal – It is a modulated light signal carrying information by altering optical properties like frequency, phase, wavelength, or intensity. It is created from an electrical signal by a transmitter, such as a laser, and travels through a medium, often optical fibre, before being converted back to an electrical signal by a receiver. Optical signals enable transparent data transmission in networks, allowing them to carry data without needing intermediate optical-to-electrical conversions.
Optical spectrometry – It refers to the analysis of a light spectrum separated by wave-lengths. It can be of two types – absorption or emission. An atomic optical / emission spectrometer (AES / OES) is one which analyses an optical (light) spectrum emitted by an excited sample. The excitation can be by a number of means, such as application of a spark, plasma, and flame etc. The term ‘optical emission spectrometry’ is now almost ubiquitously used to refer to the arc-spark optical emission spectrometry technique.
Optical spectrum – It refers to the range of electro-magnetic radiation which includes ultraviolet (UV), visible, and infrared (IR) light, with wavelengths normally from about 10 nanometers to 1 millimeter. It is the distribution of light power or energy across different wave-lengths or frequencies, frequently shown in a diagram plotting a spectral quantity against wave-length or frequency. This spectrum is fundamental to several engineering fields, including opto-electronics, imaging, and optical communications.
Optical spectrum analyzer (OSA) – It is an instrument which measures and displays the power distribution of an optical light source across a range of wave-lengths, showing power on the vertical axis and wave=length on the horizontal axis. Optical spectrum analyzers are critical for analyzing light signals in telecommunications to identify wave-lengths, measure power levels, determine optical signal-to-noise ratio (OSNR), and assess optical bandwidth. They are also used in laser characterization, and other areas needing precise spectral analysis of light.
Optical system – It consists of components which work together to manipulate light for a specific purpose. Engineers use these systems in several applications, including telecommunications, scientific research, imaging, and sensing. The components that make up an optical system can include lenses, mirrors, prisms, filters, and other specialized elements. All these are designed to influence the properties of light, such as direction, polarization, wave-length, and intensity. Optical systems are critical features in several modern technologies.
Optical transparency – It means a material allows light to pass through it with minimal scattering, enabling a person to see clearly through it, as opposed to translucent materials which scatter light diffusely, or opaque materials which block light entirely. Examples include clean water, clear glass, and some plastics and ceramics
Optical wave – It is a high-frequency electromagnetic wave which consists of oscillating electric and magnetic fields and propagates through space. It encompasses the infrared to ultraviolet light spectrum and is described by Maxwell’s equations. The wave nature of light explains phenomena like interference, diffraction, and polarization.
Optics – It is the branch which studies the behaviour and properties of light, including its with matter and the construction of instruments that use or detect it. Optics normally describes the behaviour of visible, ultra-violet, and infra–red light. Light is a type of electro-magnetic radiation, and other forms of electro-magnetic radiation such as X-rays, micro-waves, and radio waves show similar properties. Majority of the optical phenomena can be accounted for by using the classical electro-magnetic description of light, however complete electro-magnetic descriptions of light are frequently difficult to apply in practice. Practical optics is normally done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference which cannot be accounted for in geometric optics.
Optimal band – It is a specifically selected range of values, parameters, or wavelengths which provides the best possible performance or outcome for a given application, determined through optimization processes like particle swarm optimization.
Optimal control – It is the branch of control theory studying optimization of a control system to fit some optimization criterion.
Optimal design – It is normally considered as the design process which seeks the ‘best’ possible solution(s) for a mechanical structure, device, or system, satisfying the requirements and leading to the ‘best’ performance, through optimization techniques. It also refers to the design points that best satisfy objective(s) which are in contrast to non-optimal design. A formal definition of design is ‘design establishes and defines solutions to pertinent structures for problems not solved before, or new solutions to problems which have previously been solved in a different way’. Optimal indicates a searching and decision-making process which is needed to determine the best possible design alternatives. Optimization techniques are used to evaluate the trade-off among design alternatives and determine the best one(s).
Optimal flow rate – It is the specific flow rate of a fluid or gas which maximizes a desired outcome, such as separation efficiency in chromatography, material morphology in electrospinning, or pump efficiency, while minimizing losses or damage. The ideal flow rate varies depending on the application, material properties, and operating conditions.
Optimal frequency – It is the ideal operating frequency which yields the best performance for a specific application, such as a communication system or a mechanical structure, by maximizing desired characteristics like signal quality or system stiffness and minimizing unwanted behaviours like interference or excessive vibration. This frequency is determined by the system’s design and operating conditions, balancing factors like signal propagation, structural integrity, and available technology.
Optimal insulation thickness – It is the insulation depth which minimizes the combined costs of the insulation material and the fuel / energy consumed for heating or cooling, providing the most cost-effective balance between installation and operating expenses over the system’s life. It represents the ‘sweet spot’ where adding more insulation offers diminishing returns in terms of energy savings compared to the escalating cost of the material itself, resulting in the lowest total cost.
Optimal load scheduling – It is an optimization process which coordinates and schedules the operation of electricity supply and demand to meet load requirements at the lowest possible cost, while ensuring system stability, reliability, and minimizing environmental impact. This is achieved by balancing power generation (supply) and consumption (demand) over a specific time horizon, frequently using mathematical models and algorithms to determine the most efficient use of resources, control demand-side devices, and manage energy storage systems.
Optimal performance – It means achieving a system’s highest possible efficiency, effectiveness, and desired qualities under specific operational conditions and constraints. This involves identifying and meeting performance objectives for criteria like speed, resource use, and reliability, which are defined by non-functional requirements. It frequently needs a complex balancing of trade-offs, as a system can need to compromise between high-speed and low-load operation to perform best across a wide range of conditions.
Optimal pore size – It refers to the pore dimension that maximizes efficiency, function, or a desired outcome for a specific application, such as hydrogen adsorption. It is not a universal value but varies based on the material, the substance interacting with the pores, and the intended function. For example, a 0.6 nanometer to 1 nanometers range is optimal for hydrogen adsorption on carbon materials.
Optimal process control – It is the application of optimal control theory to find the control actions which make a dynamic system achieve a desired goal by minimizing a cost functional (like time or energy) or maximizing a performance metric, subject to constraints. This involves defining the system’s dynamics, identifying constraints, setting an optimality criterion, and then using mathematical models to determine the best control inputs.
Optimal solution – It is the single best possible outcome which satisfies all the constraints of a problem while maximizing or minimizing an objective function. This solution provides the highest quality or most desired result, such as minimum cost, maximum profit, or highest efficiency, within the defined limitations of the system or problem.
Optimal topology – It refers to the best material layout and shape within a design space to maximize performance (like stiffness or strength) while minimizing material usage or weight. It is a computational process where software algorithms add or remove material from a design to find an efficient, lightweight structure which effectively carries loads, frequently resulting in organic-looking, strong, yet minimal designs.
Optimization – It is the action of making the best or most effective use of a situation or resource. It is the process of searching for the best combination of design parameters.
Optimization constraint – It is a boundary or condition which are to be satisfied by the solution of an optimization problem, defining the ‘feasible region’ of possible solutions. Constraints can be simple bounds (maximum or minimum values), or complex equalities and inequalities involving decision variables, and they determine whether a particular solution is acceptable for the design or system being optimized. The goal of optimization is then to find the best solution within these defined constraints.
Optimization, engineering – It is the process of finding the most effective or favourable value or condition. The purpose of optimization is to achieve the ‘best’ design relative to a set of prioritized criteria or constraints. Design optimization suggests that for a given set of possible designs and design criteria there exists a single design which is best or optimal.
Optimization method – It is a systematic process using mathematical models and algorithms to find the best solution (maximum or minimum value) for a design or system, given a set of objectives, variables, and constraints. The goal is to improve performance, efficiency, or cost-effectiveness by selecting the optimal design from feasible alternatives. These methods are applied to different problems, including structural design, resource allocation, and process improvement, to achieve the most desirable outcome.
Optimization procedure – It is a systematic, iterative process which uses mathematical models and algorithms to find the best possible solution (maximum or minimum) for a system, design, or process by adjusting its variables within defined constraints to meet specific objectives like cost minimization, performance maximization, or efficiency improvement. These procedures are used across different engineering fields to improve designs, allocate resources, optimize schedules, and improve processes, ultimately leading to more effective and efficient outcomes.
Optimization strategy – It is a methodical approach to finding the best possible solution for a problem by minimizing or maximizing a specific objective function (like cost or efficiency) while satisfying a set of predefined constraints. This involves using mathematical models, algorithms, and techniques to systematically evaluate design alternatives and identify the one which yields the most favourable outcome.
Optimized design – It is the best possible solution to a design problem, achieved by systematically identifying design variables, setting performance goals (objectives), and applying constraints to select a solution which maximizes performance or minimizes cost. This involves a mathematical formulation of the problem and the use of algorithms to find the most efficient and effective design that meets all needed specifications.
Optimized process – It is a systematically improved workflow that is more efficient, effective, and productive, achieving defined goals by minimizing waste, reducing costs, and enhancing quality within specific constraints. This involves analyzing existing processes to identify bottlenecks, streamlining steps, and often implementing strategies like automation to ensure the best possible use of resources and achieve superior outcomes.
Optimum angle – It refers to the ideal tilt angle of a solar collector or panel which maximizes solar insolation gain, which varies with latitude and is critical for the effective design of solar-based conversion technologies. This angle is determined through calculations of maximum annual absorbed energy for different tracking orientations and configurations.
Optimum diameter – It is the ideal size of a component, such as a pipe or propeller, which achieves a specific performance goal, normally minimizing total cost by balancing material expenses against operational costs. For pipes, it balances the higher fixed costs of larger pipes against the increased energy costs of higher fluid velocities in smaller pipes. For propellers, it maximizes efficiency given a specific power, speed, and rotational speed.
Optimum moisture – It is that moisture content which results in developing the maximum of any property of a sand mixture.
Optimum pressure ratio – It is the specific pressure ratio at which a system, like a gas turbine or compressor, achieves maximum efficiency or net power output, determined by balancing competing factors such as temperature, operating costs, and isentropic efficiency. This ratio is found at a point where the slope of the network or efficiency curve with respect to the pressure ratio is zero, indicating a maximum.
Optimum processing parameters – These are the ideal, specific conditions and settings (like temperature, pressure, or speed) in a process which achieve the most desirable outcome, such as maximizing yield, quality, efficiency, or productivity, while minimizing waste or defects. Finding these parameters frequently involves optimization methods to avoid trial-and-error and ensure the process fully exploits its capabilities for economic and effective production.
Optimum recovery – It is the process of achieving the ideal balance between maximizing product recovery and minimizing associated costs. It is the recovery which maximizes overall profitability by considering all aspects of a process, including raw material costs, operating expenses, and the value of the final product.
Optimum temperature – It is the specific temperature at which a process or reaction operates most efficiently, yielding the highest desired output or rate of activity. This ideal temperature is a balance, where reaction rates are maximized.
Optimum water content – It is the specific moisture level at which a soil or granular material achieves its maximum dry density when subjected to a given compactive effort. This is determined by plotting water content against dry density in a compaction curve, where the peak of the curve indicates the optimum water content and the maximum dry density.
Opto-electronics – It is a field which deals with the study, design, and manufacture of devices which interact with light and electrical signals, mainly by converting electrical energy into light and vice versa using semiconductor materials. Opto-electronic engineering involves creating hardware for applications like communication (lasers, fibre optics), displays (light emitting diodes, LEDs), sensors (photo-diodes), and energy generation (solar cells).
Orange peel – It is a pebble-grained surface which develops in the mechanical forming of sheet metals with coarse grains. It is a surface roughening in the form of a pebble-grained pattern which occurs when a metal of unusually coarse grain size is stressed beyond its elastic limit. It has the appearance of an orange skin. It is also called pebbles and alligator skin. In painting, it is a pebbled film surface caused by too rapid drying after spraying, by failure of the coating material to show the desired leveling effects, or by uneven flow (application) in roller coating techniques. In porcelain enamel, it is a surface condition characterized by an irregular waviness that resembles an orange skin in texture, which is sometimes considered a defect.
Orange peel bucket – It is a bottom-drop bucket used for charging cupola or electric arc furnace. The drop-bottom of the bucket is divided into a number of sections which appear to peel back as the bucket opens.
Orbit – It is the fixed path on which electron moves or revolves around the atom’s nucleus. Furthermore, an orbit is a simple planar representation of a particular electron. Moreover, it is the path whose establishment takes place because of a circular motion as the electron revolves around the nucleus.
Orbital – It is a region of an atom or molecule in which one or more electrons can be found. The term can refer to either an atomic orbital or a molecular orbital.
Orbital angular momentum – It is a vector quantity describing the rotational motion of a particle, such as an electron, around a fixed point or centre. In the quantum realm, it is a quantized property related to an electron’s orbital motion within an atom, characterized by the azimuthal quantum number. The concept of orbital angular momentum is also applied to electromagnetic waves, where it represents a property of light beams with helical wavefronts, enabling information transmission in new ways.
Orbital angular velocity – It describes how quickly an object rotates or revolves around a fixed point, typically the origin, over time. It is the rate of change of an object’s angular position relative to that origin. Essentially, it measures how fast an object sweeps out an angle around a central point.
Orbital forging – It is a process in which the work-piece is pressed between a flat anvil and a swiveling (rocking) die with a conical working face. The platens move toward each other during forging.
Orbital grinder – It is a hand-held power tool used for grinding with abrasives sheets and discs. Grinding is also known also as de-burring, fettling, polishing, sanding and buffing.
Orbital maneuvering system (OMS) – It is a key component of spacecraft propulsion, responsible for making orbital adjustments and maneuvers during spaceflight.
Orbital motion – It is the motion of an object in orbit around another object and an orbit is the curved path of an object around another object in space. An orbital motion is a motion over a repeating path taken by an object around another object. In general, orbits are elliptical.
Orbital scanning – It is an angle probe technique which is used to get information about the form of discontinuity previously located. The scanning is made around the discontinuity.
Order (in X-ray reflection) – It is the factor ‘n’ in the Bragg equation. In X-ray reflection from a crystal, the order is an integral number that is the path difference measured in wave-lengths between reflections from adjacent planes.
Order-disorder transformation – It is a phase change among two solid solutions having the same crystal structure, but in which the atoms of one phase (disordered) are randomly distributed. In the other, the different kinds of atoms occur in a regular sequence upon the crystal lattice, i.e., in an ordered arrangement.
Ordered crystal structure – It is a structure held together by atoms, ions, or molecules arranged in a highly ordered 3-dimensional arrangement is a crystal structure. Crystal structure can be thought of as the highest level of ordering which can exist in a solid material. This arrangement can be referred to as the crystal lattice structure.
Ordered structure – Ordered structures, frequently called ‘superlattices’, result from the ability of the atoms within several alloy phases to arrange themselves into specific configurations. It is the crystal structure of a solid solution in which the atoms of different elements seek preferred lattice positions.
Order hardening – It is a low-temperature annealing treatment which permits short-range ordering of solute atoms within a matrix, which greatly impedes dislocation motion.
Ordinal logistic regression – It is a logistic regression model for a study end point with more than two values where the values also represent rank order on the characteristic of interest.
Ordinal data – It is the ordered groups or categories where the intervals between measurements are not meaningful, indicating relative ranking without implying equal distances between ranks.
Ordinal scale – The ordinal scale of measurement occurs when a random variable can take on ordered values, but there is not an even interval between levels of the variable. Examples of ordinal variables include the choice between three automobile brands, where the response is highly desirable, desirable, and least desirable. Ordinal variables provide the second lowest quantity of information compared to other scales of measurement.
Ordinal variable – An ordinal variable is a categorical variable in which the categories have an obvious order, e.g. (strongly disagree, disagree, neutral, agree, strongly agree), or (dry, trace, light rain, heavy rain).
Ordinary differencing – It consists of creating a transformed series by subtracting the immediately adjacent observations.
Ordinary differential equation – It is a differential equation dependent on only a single indipendent variable. As with any other differential equation, its unknown(s) consists of one (or more) function(s) and involves the derivatives of those functions. The term ‘ordinary is used in contrast with partial differential equations which can be with respect to more than one independent variable, and, less commonly, in contrast with stochastic differential equations where the progression is random.
Ordinary least squares (OLS) – It is a means of estimating coefficients in linear regression and ANOVA models which depends on finding the estimates which minimize the sum of squared prediction errors.
Ordinary or one-sided Laplace transform – It is also known as the unilateral Laplace transform. It is a specific application of the Laplace transform which focuses on functions defined for non-negative time (‘t’ is greater than or equal to 0). It is mainly used in the analysis of causal systems and signals. The ‘ordinary’ Laplace transform, often referred to as the bilateral or two-sided Laplace transform, considers functions defined for all real numbers (-infinity less than ‘t’ less than infinity).
Ordinary portland cement (OPC) – It is available in several grades, namely 33-grade, 43-grade, and 53-grade etc. If 28-day strength is not less than 33 mega pascals (MPa) then it is called cement of 33-grade. If 28-day strength is not less than 43 MPa then it is called cement of 43-grade. Use of higher-grade cement offers several advantages and makes stronger concrete. Although higher grade cement is little costlier than the low-grade cement, it offers 10 % to 20 % saving in the cement consumption and it also offers several other hidden advantages. One of the most important advantages is the faster rate of development of the strength. Ordinary portland cement is used for the ordinary works. This type of cement is used in constructions where there is no exposure to sulphates in the soil or ground-water. The lime saturation factor (LSF) for this cement [(CaO-0.7 SO3)/(2.8 SiO2 + 1.2 Al2O3 + 0.65 Fe2O3)] is limited between 0.66-1.02. Here each oxide denotes the percentage of the oxide in cement composition.
Ordovician age – It refers to a geological time period characterized by specific rock formations, such as the Utica Shale, which dates to this era and is noted for its significant reserves of natural gas and high total organic carbon content.
Ordovician rock – It refers to geological formations from the Ordovician period, characterized by specific compositions, such as potassium, uranium, and thorium, which influence their heat production rates due to radioactive decay processes.
Ore – It is a natural mineral which can be mined and treated for the extraction of any of its components, metallic or otherwise, at a profit. Ore is a mixture of ore minerals and gangue from which at least one of the metals can be extracted at a profit.
Ore-body – It is a natural concentration of valuable material which can be extracted and sold at a profit.
Ore carriers – These are specialized bulk vessels designed to transport mineral ores and are included in the category of oil / bulk /ore (OBO) carriers, which can handle a variety of cargoes.
Ore characteristics – It includes material specification, feed (input) size, material friability, and material abrasiveness of the ore.
Ore deposits – These are rock volumes containing selected elements in sufficient concentration and quantity that they can be extracted economically. The formation of ore deposits, like all other geologic processes, is the consequence of multiple events spread through geologic time. Two groups of ore deposits can be established syngenetic and epigenetic depending on their formation time relationship to the rocks associated with them. Syngenetic ore deposits are formed at the same time as the associated rocks as in magmatic segregation during the orthomagmatic stage of consolidation of magma or during precipitation of sedimentary rocks. Formation of ore deposits in gossans and laterites because of in situ residual gossans are also considered as syngenetic because as the new rock (laterite, bauxite, kaolinite, or duricrust) is formed it is at that same time the ore deposit is formed. The epigenetic mineral deposits are formed later after the enclosing or host rocks have been formed in filled or opened fissures in the country rocks and such ore bodies are called lodes or veins. These vein and lode deposits occur as in interstices of the country where the rock forms first and then ores form as impregnations or replacements of the country rock. In contact metamorphism mineral deposits form irregular ore bodies on the margins of metamorphosed rocks. In sedimentary rocks epigenetic processes, ore deposits are formed because of weathering and deposition of detrital sedimentary rocks in basins where placer deposits are emplaced.
Ore dressing – It consists of physical and chemical concentration of raw ore into a product from which a metal can be recovered at a profit.
Ore particle – It is an individual unit or constituent part of an ore, a naturally occurring rock or mineral deposit from which a valuable metal or mineral can be economically extracted. These particles vary in size, shape, and composition and are characterized by the mineralogy (like sulphides or quartz) and grade (concentration) of the valuable substance they contain.
Ore pass – It is the vertical or inclined passage for the downward transfer of ore connecting a level with the hoisting shaft or a lower level.
Ore processing – It is the process of separating commercially valuable minerals from their ores in the field of extractive metallurgy. Depending on the processes used in each case, it is frequently referred to as ore dressing or ore milling.
Ore reserve – An Ore reserve is the economically mineable part of a Measured and / or Indicated Mineral resource. It includes diluting materials and allowances for losses, which can occur when the material is mined or extracted and is defined by studies at Pre- Feasibility or Feasibility level as appropriate that include application of the Modifying factors. Such studies demonstrate that, at the time of reporting, extraction can reasonably be justified.
Ore reserves – It is the calculated tonnage and grade of mineralization which can be extracted profitably. Ore reserves are classified as possible, probable, and proven as per the level of confidence which can be placed in the data.
Ore roasting – It is a metallurgical process where a sulphide ore is heated in the presence of excess air or oxygen to convert it into a metal oxide, releasing sulphur di-oxide gas. This conversion to a more chemically reactive form, such as a metal oxide, is a key step in extracting metals from ores, allowing them to be further processed by reduction to obtain the free metal.
Ore-shoot – It is the portion, or length, of a vein or other structure which carries sufficient valuable minerals to be extracted profitably.
Ore sintering – It is a process which heats and agglomerates fine iron ore, along with fluxes (like limestone) and fuel (like coke fines), into larger, porous, and stronger lumps called sinter. This thermal treatment transforms the powder-like raw materials into a semi-molten mass that solidifies, creating a material with improved size and strength suitable for charging into a blast furnace for iron production.
Ore treatment – It is also known as mineral processing. It is the process of physically or chemically separating valuable minerals from waste rock (gangue) to create a concentrated ore ready for extractive metallurgy. This initial separation, a crucial step after mining, involves crushing, grinding, and applying techniques like flotation or magnetic separation to increase the concentration of the desired minerals before further processing.
Ore type – It refers to a classification of naturally occurring minerals from which a metal can be extracted profitably and conveniently. Ore types are categorized based on the chemical form of the metal, such as native (free metal), oxide, sulphide, or carbonate. These categories distinguish ore deposits which are rich enough in a valuable mineral to be economically mined for their constituent metal.
Organic – It means being or composed of hydrocarbons or their derivatives. It is the matter originating in plant or animal life, or composed of chemicals of hydrocarbon origin, either natural or synthetic.
Organic acid – It is a chemical compound with one or more carboxyl radicals (COOH) in its structure; examples are butyric acid, CH3(CH2)2COOH; maleic acid, HOOCCH-CHCOOH; and benzoic acid, C6H5COOH. It is an organic compound with acidic properties.
Organic aerosols (OA) – These are aerosol particles consisting predominantly of organic compounds, mainly C, H and O, and lesser quantities of other elements. These aerosols refer to fine particulate matter in the atmosphere which is composed of organic compounds emitted from both natural (biogenic) and human activities (anthropogenic), as well as those formed through chemical reactions in the atmosphere.
Organic air pollutants – These are sometimes divided according to particulate organic compounds (POCs) and volatile organic, although there are some species which are actually distributed between the particulate and gaseous phases. The emission of unburned or partially burned fuel from combustion processes and escape of organic vapours from industrial operations are the major anthropogenic sources of organic air pollutants. There are a large number of volatile organic compounds. They include hydro-carbons (CxHy) and also other organic chemicals which are emitted from a very wide range of sources, including fossil fuel combustion, industrial activities, and natural emissions from vegetation and fires. Volatile organic compounds are an important outdoor air pollutant. In this field they are frequently divided into the separate categories of methane (CH4) and non-methane volatile organic compounds (NMVOCs). Major anthropogenic sources of methane include natural gas production and use, coal mining, livestock, and rice paddies. Methane, the simplest and most long-lived volatile organic compounds is an extremely efficient greenhouse gas which contributes towards increased global warming. Other hydrocarbon volatile organic compounds are also significant greenhouse gases through their role in creating ozone (O3) and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the non-methane volatile organic compounds, the aromatic compounds benzene (C6H6), toluene (C7H8), and xylene (C8H10) are suspected carcinogens. The compound 1, 3-butadiene (C4H6) is another dangerous compound which is frequently associated with industrial uses.
Organic base – It is an organic compound which acts as a base. Organic bases are normally, but not always, proton acceptors. They normally contain nitrogen atoms, which can easily be protonated. For example, amines or nitrogen-containing heterocyclic compounds have a lone pair of electrons on the nitrogen atom and can thus act as proton acceptors.
Organic bond – It consists of bond of organic nature with bonding or hardening at ambient temperature or at a higher temperature.
Organic carbonate – It is a class of organic compounds where the hydrogen atoms of carbonic acid (H2CO3) have been replaced by carbon-containing groups, making them esters. These compounds, such as dimethyl carbonate (DMC), are known for their low toxicity, high biodegradability, and use as green solvents and intermediates in the production of polymers.
Organic chemistry – It is the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds.
Organic coated steel – It is the steel which has been coated with a non-metallic material, typically paint or a similar coating, to improve its properties and appearance. This process frequently involves cleaning the steel surface, applying the coating, and then baking it at high temperatures. It is also known as pre-painted galvanized steel (PPGI).
Organic coating – It is a type of coating formed by carbon-based polymeric chains derived from natural (vegetable, animal) or synthetic matter. Solid, adhesive, and cohesive organic coatings can be found in the form of paints, varnishes, and lacquers.
Organic compound – It is defined as a chemical compound which contains a carbon–hydrogen or carbon-carbon bond, others consider an organic compound to be any chemical compound which contains carbon. For example, carbon-containing compounds such as alkanes (e.g., methane CH4) and its derivatives are universally considered organic, but several others are sometimes considered inorganic, such as halides of carbon without carbon-hydrogen and carbon-carbon bonds (e.g., carbon tetra-chloride, CCl4), and certain compounds of carbon with nitrogen and oxygen (e.g., cyanide ion CN-, hydrogen cyanide HCN, chloro–formic acid ClCO2H, carbon di-oxide CO2, and carbonate ion (CO3)2−.
Organic contaminants – It consists of carbon-based chemicals, such as solvents and pesticides, which can get into water through run-off from discharge from factories. Organic contaminants include herbicides, pesticides, and plant and animal tissues, and are normally expected to cause adverse impacts on the environment. Trace levels of organic contaminant residues present in the soil, water, air, and sometimes food can result in harmful effects for human and environmental health.
Organic emissions – Organic emissions from primary steel operations can include benzene, toluene, xylene, solvents, PAHs, dioxins and phenols. The scrap steel used as raw material can include a variety of these substances, depending on its source and the way it had been used (e.g., paint and other coatings, other metals, and lubricants). Not all of these organic pollutants are captured by the conventional gas cleaning systems.
Organic fibres – These are defined as high-performance materials used in textile applications and advanced composites, characterized by high stiffness and strength, with common examples including aramid and polyethylene fibers. They possess unique properties such as low density, high specific strength, and varying resistance to moisture and temperature.
Organic field effect transistors (OFET) – These are three-terminal devices which use a gate voltage to control the conductance between the source and drain terminals, forming a channel of mobile charges at the semiconductor / dielectric interface. They are utilized as electrically controlled switches and current drivers in various electronic applications, including logic integrated circuits and active-matrix displays.
Organic film – It is an extremely thin layer of an organic (carbon-based) material, frequently a polymer, which is deposited onto a substrate to impart specific properties, such as electrical conductivity, mechanical strength, or corrosion resistance. These films are engineered for applications like flexible electronics, including organic thin-film transistors (OTFT), sensors, and protective coatings, because of their mechanical flexibility, chemical tunability, and low-cost processing potential.
Organic fluids – These are heavy compounds characterized by large molecular weights and low boiling temperatures and pressures, frequently used in applications like ‘organic Rankine cycles (ORC) for efficient thermal performance.
Organic insulation materials – These materials are derived from a petro-chemical or renewable feedstock (bio-based). Almost all of the petro-chemical insulation materials are in the form of polymers and are cellular. A material is cellular when the material’s structure consists of pores or cells. On the other hand, several plants contain fibres for their strength. Hence, almost all the bio-based insulation materials are fibrous (except expanded cork, which is cellular). Examples of petro-chemical materials (oil / coal-derived) are expanded poly-styrene (EPS), extruded poly-styrene (XPS), poly-urethane (PUR), phenolic foam, and poly-iso-cyanurate foam (PIR). Examples of renewable materials (plant / animal-derived) are cellulose, cork, wood-fibre, hemp fibre, flax wool, sheep wool, and cotton insulation.
Organic ion exchange resin – It is a porous, high-molecular-weight polymer network containing fixed, charged functional groups which can exchange mobile ions of the same charge with ions from a surrounding solution. These cross-linked poly-electrolytes act as insoluble ion exchangers, normally in the form of small microbeads, and are used in applications like water treatment and chemical purification by removing unwanted dissolved ions and selectively trapping others.
Organic linings – These linings are made of organic substances (i.e., chemically speaking these are complex carbon molecules) such as cellulose and phenolic resin. Organic linings are a separate category of lining distinct from other types of linings made out of different materials such as semi-metallic, metallic and carbon.
Organic liquids – These are used in a wide variety of industrial applications. They can be characterized as liquids which consist of one or more carbon atoms joined to other atoms through covalent bonds. Common atoms included in organic molecules are hydrogen, oxygen, nitrogen, sulphur, and halogens. Both the rate and yield of certain reactions have been found to greatly increase when performed in organic liquids. Hence, they are widely used in the chemical process industry for synthesis. With the increase in the use of organic liquids, increases in observed corrosion problems associated with the exposure of materials to them have also occurred. In some cases, failures involve an unacceptably large loss of metal or degradation of material properties.
Organic materials – These are substances derived from living organisms, or materials containing carbon-based compounds. This frequently refers to carbon-containing compounds, including those synthesized in laboratories, not just those from natural sources. These materials play a crucial role in several natural processes and can be found in various environments like soil and water.
Organic matrix composite (OMC) – It is a composite material composed of a variety of short or continuous fibres bound together by a matrix of organic polymers. Organic matrix composites are designed to transfer loads between fibres of a matrix. Some of the advantages with organic matrix composites include their light weight, high resistance to abrasion and corrosion, and high stiffness and strength along the direction of their reinforcements.
Organic matter – It is the compounds containing carbon frequently derived from living organisms.
Organic maturation – It is the process of turning peat into coal.
Organic molecule – It is a compound containing carbon atoms covalently bonded to other atoms, normally hydrogen, oxygen, and nitrogen. While the presence of carbon is key, the definition also includes exceptions, specifically excluding simple inorganic compounds such as carbonates, cyanides, and simple oxides like carbon dioxide. These molecules form the basis of all life and include important substances like carbohydrates. It is a complex carbon-containing compound, where the carbon atoms form chains and rings, enabling the creation of unique physico-chemical properties necessary for applications in areas like opto-electronics and material science.
Organic petrology – It consists of the studies of the organic matter within sedimentary rocks and coal using microscopic and geochemical methods to determine its composition, origin, and thermal maturity. It analyzes microscopic organic components called macerals, categorizes their proportions, and assesses their maturity to understand burial history and predict fossil fuel potential.
Organic pollution – It is the presence of organic matter in water which contributes considerably to the wastewater pollution, mainly measured by biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Biochemical oxygen demand indicates the biodegradable fraction of organic pollution, while chemical oxygen demand encompasses all oxidizable substances, including both biodegradable and non-biodegradable organic compounds.
Organic pollutants – Organic pollutants include proteins, carbo-hydrates, fats and oils, dyestuffs, organic acids, phenols, detergents and organo-pesticides. Organic pollutants are organic compounds which are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this property of the organic pollutants, these pollutants have potential adverse impacts on the human health and the environment. Organic pollutants can be further divided into three categories namely (i) oxygen demanding wastes, (ii) synthetic organic compounds, and (iii) oils and grease.
Organic Rankine cycle (ORC) – The organic Rankine cycle operates similar to the steam Rankine cycle, but uses an organic working fluid instead of steam. Alternatives include silicon oil, propane, halo-alkanes (e.g. freons), iso-pentane, iso-butane, p-xylene, and toluene, which have a lower boiling point and higher vapour pressure than water. This allows organic Rankine cycle to operate with significantly lower waste heat temperatures. The most appropriate temperature range depends on the fluid used, as fluids’ thermo-dynamic properties influence the efficiency of the cycle at various temperatures. In comparison with water vapour, the fluids have a higher molecular mass, enabling compact designs, higher mass flow, and higher turbine efficiencies. However, since organic Rankine cycle functions at lower temperatures, the overall efficiency is low and depends on the temperature of the condenser and evaporator. While the efficiency is lower than a high temperature steam power plant, it is important to remember that low temperature cycles are inherently less efficient than high temperature cycles. Limits on efficiency can be expressed according to Carnot efficiency which is the maximum possible efficiency for a heat engine operating between two temperatures. A Carnot engine operating with a heat source at 150 deg C and rejecting it at 25 deg C is only about 30 % efficient. In this light, a low efficiency in the range of 10 % to 20 % in case of organic Rankine cycle is a substantial percentage of theoretical efficiency, especially in comparison to other low temperature alternatives, such as piezoelectric generation, which are only 1 % efficient. Although the economics of organic Rankine cycle, heat recovery need to be carefully analyzed for any given application, it is a useful alternative in those industries which do not have in-house use for additional process heat or no neighbouring plants which can make economic use of the heat.
Organic resin – It is a natural or synthetic substance which is typically solid or semi-solid, water-insoluble, and viscous, with a tendency to flow when heated. Natural organic resins are secretions from plants, like terpenes, used in varnishes. Synthetic organic resins are manufactured to have similar properties to natural resins and are used to make plastics, coatings, and composites.
Organic solvents – It is a common designation for a large group of more than 200 chemical compounds capable of dissolving non-water-soluble materials such as fats, oils, waxes, resins, rubber, asphalt, cellulose filaments, and plastic materials. Compounds from several different chemical groups can serve as solvents. Organic refers to compounds which contain carbon bonds and in which at least one carbon atom is covalently linked to an atom of another type (normally hydrogen, oxygen, or nitrogen). Organic solvents contain at least one carbon and one hydrogen molecule. Aliphatic compounds form a chain, whereas aromatic compounds form a six-carbon ring. The hydrogen group can be substituted by some other element such as a hydroxyl group in alcohols or a carbonyl group in ketones and esters. Halogenated hydro-carbons contain a substituted halogen element, often a chloride. As a group, they share few physical features and even fewer chemical properties.
Organic thin film field-effect transistors (OTFTs) – These are particularly interesting as their fabrication processes are much less complex compared with conventional silicon technology, which involves high-temperature and high-vacuum deposition processes and sophisticated photolithographic patterning methods. In general, low-temperature deposition and solution processing can replace the more complicated processes involved in conventional silicon technology. In addition, the mechanical flexibility foldable products.
Organic thin-film transistors – These are electronic devices which use organic, carbon-based semi-conductors to control current flow, functioning like conventional transistors but with the advantages of low-cost, solution-based fabrication on flexible substrates. The engineering of Organic thin-film transistors involves designing the organic semi-conductor materials and device structures to achieve desired electrical properties, such as charge carrier mobility and on / off current ratios, for applications ranging from flexible displays and wearable sensors to logic and memory circuits.
Organic waste – It is biodegradable material generated from some industrial processes. It differs from inorganic waste like plastic or metal since it can decompose naturally into simpler organic molecules through the action of micro-organisms, forming nutrients that can benefit the soil.
Organic zinc-rich paint – It consists of coating containing zinc powder pigment and an organic resin.
Organization – It is a body built for a collection of individuals who join together to achieve some common of organic materials makes them naturally compatible with plastic substrates for lightweight and goals and objectives bounded by legal entities. Organizations are frequently referred to as a company, institution, association, and government body etc. They follow certain legal procedures like organization registration, tax identification, and maintaining corporate book records.
Organizational activity – It refers to any task or process, whether operational, managerial, or supportive, carried out within an organization to achieve its specific goals and ensure its smooth, efficient functioning. These activities include the planning, organizing, and execution of daily operations, the management of resources and people, and the implementation of strategies and policies designed to support the organization’s overall objectives.
Organizational agility – It is the ability of the organization to manage continuous, rapid and sustainable change. It is the capacity and flexibility of the organization to be consistently adaptable to market and environmental changes with rapidness and speed. It is the efficiency with which the organization can respond to nonstop change. It is the organizational ability to exploit both revenue enhancing and cost cutting opportunities within its core business more quickly, effectively, and consistently than its competitors. It makes the organization to operate at the speed with which the opportunities are getting created. In the fast-changing complex environment of the present-day organizational agility is the key differentiator between organizations.
Organizational barriers – These barriers include faulty organization structure such as lack of clarity of responsibilities and authority delegated, too wide spans of control and too long chains of command. Organization barriers can cause communication breakdown.
Organizational behaviour – It deals with employee attitudes and feelings, including job satisfaction, organizational commitment, job involvement, and emotional labour.
Organizational competencies – These are the competencies needed in the organization so that it can excel and remain competitive in the market. The competencies provide an inventory of expected behaviours, skills and attitudes which lead to the successful performance of the organization. They depend heavily on the competencies of the employees of the organization. Organizational competencies, in the most general terms, are those ‘things’ which the employees of the organization are to demonstrate to be effective in their job, role, function, task, or duty. These ‘things’ include (i) job-relevant behaviour (what the employees say or do which result in good or poor performance), (ii) motivation (how the employees feel about a job, organization, or geographic location), and (iii) technical knowledge / skills (what the employees know / demonstrate regarding facts, technologies, their professions, procedures, jobs, and the organization, etc.).
Organizational communication – It is frequently defined as an evolutionary, culturally dependent process of sharing information and creating relationships in environments designed for manageable, cooperative, goal-oriented behaviour. It is the flow and impact of messages within a network of interactional relationship to cope with environmental uncertainty. It is a system of networks linking the three hierarchical levels (top management, middle management, and employees) together in order to enhance productivity. The two major types of communication channel within the organization are: (i) formal communication, and (ii) informal communication. Formal communication consists of the official paths recognized by the management. This communication follows the established chain of command or line of authority. Formal communication can be transmitted internally or externally. The purpose of communication in the organization includes (i) achieve coordinated action, (ii) express feelings and emotion, (iii) share information regarding organizational goals, task directions, results of efforts, and decision making, (iv) achieve effective control, (v) encourage employees’ participation in decision making, and (vi) create a good public image and reputation for the organization.
Organizational culture – It means work related activities and meanings attached to such activities in the framework of norms and values of the organization. These activities, norms, and values are normally contextualized in the organization. The organizational culture normally focuses on employee centricity, teamwork and continuous process improvement. It is also expressed in terms of values, ideologies of the organization. It further makes the foundation of integrity, thoughts and actions of the employees working there. The culture of the organization is to be developed to support continuous improvement, improve employees’ style of performing their job and thus develop quality awareness. Organizational culture has influence on employee work behaviour as a result on the acceptable behaviours and attitudes to different jobs in the organization. Organizational culture is a major determinant of the employees’ efficiency and effectiveness in carrying out their jobs. Hence, organizational culture determines of how employees perform or behaves in their job.
Organizational discipline – It is the force which prompts individuals or groups to observe rules, regulations, standards, and procedures deemed necessary for the organization. It means orderly and systematically conducting the different operations of the organization by the employees who strictly adhere to the necessary procedures. The employees work together as a team and cooperate harmoniously with each other so as to achieve organizational goal and objectives as well as mission and vision and they truly understand that the individual and group aims and desires are to match so as to achieve organizational success. Organizational discipline is the force or fear of a force which deters the employee or a group of employees from doing things which are detrimental to the accomplishment of the goal and objectives of the organization. In other words, organizational discipline is the orderly conduct by the employees of the organization who adhere to its rules and regulations since they desire to cooperate harmoniously in forwarding the end which the organization has in view.
Organizational environment – It is defined as a set of characteristics which describe the organization and distinguish it from other organizations within a given time period affecting behaviour of the employees therein. These characteristics affect the functional behaviour of the employees, their trends and motives. These characteristics basically interconnect the internal work environment in the organization and make it a distinct feature of the organization. Organizational environment also differentiates the organization with other organizations. It also provides relative stability to the organization.
Organizational ethics – It is a broad and dynamic concept comprising ethical environment, levels of trust, moral awareness, and ways of acting which ensure that a shared set of values which promotes the common good becomes the prevailing culture of the organization. It includes both the corporate values and the financial practices of the organization. They relate to all aspects of the organization including mission, vision, governance, and leadership. It includes not only culture and trust, but also processes, outcomes, and character and denotes a way of acting, and not a code of principles. It is at heart, pumping blood which perfuses the entire organization with a common sense of purpose and a shared set of values. It refers to the attempt of the organization to define its values, recognize values which can cause tension, seek best solutions to these tensions, and manage the operations to maintain the values. It constitutes the principles and standards which determine acceptable conduct in the organization. It relates to actions, which are characterized by honesty, integrity, morality, and good management practices.
Organizational learning – It is the ability of an organization to gain insight and understanding from experience through experimentation, observation, analysis, and a willingness to examine both successes and failures. It denotes a change in organizational knowledge. It typically adds to, transforms, or reduces organizational knowledge. It changes in the state of knowledge. It involves knowledge acquisition, dissemination, refinement, creation and implementation. It is the ability to acquire diverse information and to share common understanding so that this knowledge can be exploited for the ability to develop insights, knowledge, and to associate among past and future activities.
Organizational manual – It is a comprehensive, frequently loose-leaf document which describes an organizational structure, policies, procedures, and roles and responsibilities to promote consistent, efficient, and standardized operations and management. It provides a framework for employees to understand management processes, decision-making, strategic planning, and how their work aligns with the organizational goals.
Organizational mission – It is related to goals, and refers to the domineering purpose of the organization. Mission is frequently stated in terms of the seemingly simple but challenging statement which defines purpose of the organization. Hence, mission statement enables management to emphasize on the essential area of the organizational strategy.
Organizational objectives – These are described in a clear-cut and quantifiable statement of the organizational goals over the selected time period. This can refer to different targets which the organization desires to achieve in the selected time period. Objectives introduce discipline to strategy. They state what the organization is going to accomplish in the selected time period.
Organizational performance – It is defined as the outcome which indicate or reflect the organization efficiencies or inefficiencies in term of corporate image, competencies and financial outcomes. It is concerned with the effectiveness, productivity, efficiency, excellence, or quality of the organization. It means the transformation of inputs into outputs for achieving certain outcomes. With regards to its content, organizational performance informs about the relation between minimal and effective cost (economy), between effective cost and realized output (efficiency), and between output and achieved outcome (effectiveness). Organizational performance is the process to enhance both the effectiveness of the organization and the well-being of its employees through planned interventions. It refers to the actual output or results of the organization as measured against its intended outputs, goals and objective. There are four types of organizational performance measures namely (i) human resource outcomes, (ii) organizational outcomes, (iii) financial accounting outcome, and (iv) capital market outcomes
Organizational policies and procedures– These reflect their vision, values, and culture as well as the needs of their employees. Organizational policy is a statement of principles, rules, and guidelines which the organization follows in order to achieve a desired outcome. The policy is a set of general guidelines which outline the organization’s plan for tackling an issue. It exists to communicate the organizational point of view to its employees and to ensure that actions carried out at the organization take place within the defined boundaries of the policies and procedure. Policies and procedures communicate the connection between the organization’s vision and values and its day-to-day operations. A procedure explains a specific action plan for carrying out a policy. It is a set of actions which an employee takes to complete an activity within the confines of an organizational policy. It exists as a reference for employees to understand their roles and responsibilities. Procedures tell employees how to deal with a situation and when. Using policies and procedures together gives employees a well-rounded view of the organization.
Organizational procedures – These are documented, step-by-step set of instructions which define how a specific task or process is to be performed consistently to achieve a desired outcome. These procedures act as the operational backbone for the organizational activities, ensuring safety, quality, and efficiency by standardizing workflows, assigning responsibilities, and ensuring alignment with organizational goals and technical standards.
Organizational profile – It is a framework for understanding the internal and external factors which shape the operating environment of a business and affect the organizational decisions made.
Organizational restructuring – It is a strategic process of making fundamental changes to the organizational structure, systems, and processes to improve efficiency, achieve new organizational goals, or adapt to external market changes. Common forms include reorganizing departments, changing reporting structures, merging with other organizations, or downsizing the workforce to achieve better financial performance or competitiveness.
Organizational strategy – It consists of the direction and scope of the organization over the long-term which helps it to attain benefit through its configuration of resources within a challenging environment aimed at meeting market needs and fulfilling stake-holder expectations. It constitutes large scale action plans for relating with the environment in order to accomplish long-term goals. It is a form of actions and resource apportionments designed to accomplish the goals of the organization. It consists of the determination of long-term goals and objectives, the adoption of courses of action and associated allocation of resources needed to achieve goals. Organizational strategy is an indispensable tool for the success of an organization, since as it helps the organization to be more proactive than reactive in moulding its own future. It makes the organization to initiate and affect activities so that it can exert control over its own purpose.
Organizational structure – It refers to the relations between the components of an organization as a whole. The organization structure can be considered mostly of two types namely (i) physical, and (ii) social. Physical structure refers to the relations between physical elements of organizations as buildings and geographical places in which the works are carried out. Social structure refers to the relations between social elements as people, positions and organizational units (e.g. departments and sectors). It is the social structure which is normally referred to as ‘organizational structure’. Organizational structure refers to the model of internal relations in the organization. Through it are clarified the (i) power, relations and reporting, (ii) formal communication channels, and (iii) responsibility and decision-making delegation. Organizational structure is the framework of the relations on jobs, systems, operating process, people and groups making efforts to achieve the goals. It is a set of methods dividing the task to determine the duties and coordinates them. Through the organizational structure, the organizational activities are divided, organized and coordinated. The organization creates the structure to coordinate the activities of work factors and control the employees’ actions. The organizational structure determines the way the job tasks are formally divided, grouped, and coordinated within the organization. When the organizational management develops or changes the structure, it is engaged in organizational design, a process which involves decisions about six key elements namely (i) work specialization, (ii) departmentalization, (iii) chain of command, (iv) span of control, (v) centralization and decentralization, and (vi) formalization.
Organizational vision – It is connected to organizational goals, and refers to the anticipated future state of the organization. Vision is an aspiration which can help mobilize the energy and passion of the employees. It states what the organization want to achieve.
Organizing – It is the function of management which follows planning. It is the process of establishing orderly uses for all resources within the management system of the organization. It is a function in which the synchronization and combination of human, physical, financial, and information resources takes place for the achievement of the results. Organizing function is necessary since it facilitates administration as well as the functioning of the organization.
Organoclay – It is a naturally occurring clay mineral, such as bentonite, which has been chemically modified by replacing its original inorganic cations with organic cations, typically from quaternary ammonium surfactants. This modification makes the clay surface hydrophobic and ‘organophilic’, allowing it to interact with organic materials and solvents instead of water. Organoclays are used as rheological additives in paints, adsorbents for pollutants, and emulsifiers in lubricants and other formulations.
Organogel – It is a non-crystalline, non-glassy thermo-reversible (thermo-plastic) solid material composed of a liquid organic phase entrapped in a three-dimensionally cross-linked network. The liquid can be, e.g., an organic solvent, mineral oil, or vegetable oil. The solubility and particle dimensions of the structurant are important characteristics for the elastic properties and firmness of the organogel. Frequently, these systems are based on self-assembly of the structurant molecules. An example of formation of an undesired thermo-reversible network is the occurrence of wax crystallization in petroleum.
Organo-metallic chemical vapour deposition (CVD) – It is an advanced technique in materials science used for the precise deposition of organo-metallic materials on substrates. This method has wide applications in the production of thin films, coatings and nano-structures. In organo-metallic chemical vapour deposition, an organo-metallic compound is used as the starting material. This compound normally contains metal atoms that carry organic ligands. During the chemical vapour deposition process, the organo-metallic compound is transported in a gas stream and passed over the substrate to be coated. By heating the substrate, the organo-metallic molecules are dissociated and the metal atoms are deposited on the substrate surface, creating a thin layer. Organo-metallic chemical vapour deposition offers precise control over the thickness and composition of the deposited layers. By selecting specific organo-metallic compounds, different metals and compound types can be deposited, enabling a wide range of applications. This technique is used in particular in the semi-conductor industry, micro-electronics and the production of thin films for solar cells.
Organo-silane – It is a silicon-based chemical compound containing at least one direct carbon-silicon (Si-C) bond. It features a central silicon atom bonded to a variety of organic and inorganic functional groups. Organo-silanes are widely used as silane coupling agents to improve adhesion between organic materials, such as polymers and resins, and inorganic surfaces like glass and metal by forming a stable chemical interface.
Orientation – It is the alignment of the crystalline structure in polymeric materials in order to produce a highly aligned structure. Orientation can be accomplished by cold drawing or stretching in fabrication. In crystals, orientation is the arrangements in space of the axes of the lattice of a crystal with respect to a chosen reference or coordinate system.
Orientation distribution function (ODF) – It is sometimes also called orientation density function. It is a function on the orientation space which associates to each orientation ‘g’ the volume percentage (V) of crystals in a poly-crystalline sample which are in this specific orientation. Formally, this is frequently expressed by the formula ODF(g) = (1/V) x [(dV(g)/dg].
Orientation imaging microscopy (OIM) – It is a scanning electron microscope (SEM) technique which rapidly measures the crystallographic orientation of individual grains in a polycrystalline material on a grid. It uses electron backscatter diffraction (EBSD) to analyze Kikuchi patterns from electron beams, automatically indexing these patterns to determine the orientation of each point. The resulting data creates grain maps which show the micro-structure and are used for studying structure-property relationships in materials science.
Orientation pinning (OP) – It is a phenomenon which relates to the experimental observation that small-angle boundaries and coherent twin boundaries have low mobility and can be regarded as essentially sessile.
Oriented materials – These are the materials, particularly amorphous polymers and composites, whose molecules and / or macro-constituents are aligned in a specific way. Oriented materials are anisotropic. Orientation can normally be divided into two classes, uniaxial and biaxial.
Oriented nucleation – It refers to the phenomenon where crystal nuclei preferentially form with a specific crystallographic orientation relative to a substrate or another existing structure. This means the newly formed crystals are not randomly oriented but rather aligned in a particular way, frequently dictated by the underlying material or surface. This preferential alignment can considerably influence the texture and properties of the resulting material.
Oriented poly-ethylene terephthalate (OPET) – It refers to a polymer film made by stretching PET in two directions, resulting in aligned molecular chains which improve its mechanical strength, chemical stability, clarity, and barrier properties. This orientation process gives oriented poly-ethylene terephthalate films properties like high tensile strength, dimensional stability, and excellent clarity, making them suitable for several applications, including barrier laminates, and thermal insulation.
Orifice – It is the opening from the whirling chamber of a mechanical atomizer or the mixing chamber of a steam atomizer through which the liquid fuel is discharged. It is also a calibrated opening in a plate, inserted in a gas stream for measure velocity of flow.
Orifice flange – It is a special type of flange, typically used in pairs, which houses an orifice plate between pipe joints to measure the flow rate of liquids or gases. The flanges include integral pressure taps with jack screws, which allow a differential pressure gauge to be connected to measure the pressure drop across the orifice plate, hence calculating the fluid’s flow rate. Orifice flanges are normally made to standards and are available in different types, such as weld-neck and slip-on, and pressure classes from 300 to 2,500.
Orifice gas (plasma arc welding and cutting) – it is the gas which is directed into the torch to surround the electrode. It becomes ionized in the arc to form the plasma and issues from the orifice in the torch nozzle as the plasma jet.
Orifice meter – It is a differential pressure flow meter used in engineering to measure the flow rate of a fluid in a pipe by creating a constriction with a sharp-edged, circular hole (the orifice) in a plate. This restriction increases fluid velocity and causes a measurable drop in pressure across the plate, which is then correlated to the flow rate using Bernoulli’s principle.
Orifice plate – It is a device which used for measuring flow rate, for reducing pressure, or for restricting flow. In the latter two cases, it is frequently called a restriction plate. An orifice plate is a thin plate with a hole in it, which is normally placed in a pipe. When a fluid (whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice, but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases. A little downstream of the orifice the flow reaches its point of maximum convergence, the ‘vena contracta’ where the velocity reaches its maximum and the pressure reaches its minimum. Beyond that, the flow expands, the velocity falls and the pressure increases. By measuring the difference in fluid pressure across tappings upstream and downstream of the plate, the flow rate can be obtained from Bernoulli’s equation using coefficients established from extensive research.
Original crack length – It is also initial crack length. It is the precise length of a crack in a material at the beginning of a test or examination, before any substantial crack growth has occurred because of the loading or testing conditions. This initial measurement is crucial in fracture mechanics for determining fracture toughness (material resistance to fracture) and predicting the remaining fatigue life of a component.
Original crack size – It is the physical crack size at the start of testing.
Original equipment manufacturer (OEM) – It is an organization which supplies components that are used in the production of goods by other manufacturers. Original equipment manufacturer procurement for manufacturers comes with a range of benefits such as cost savings as well as freeing up resources to look into areas which need deep involvement.
Original investment – It is the initial total cost incurred to start a project, including all associated expenses like equipment, materials, labour, and land. It serves as the starting capital for a project and is used to calculate financial metrics like the ‘return on investment’ (ROI), ensuring the project’s viability and potential to generate future profit.
Original resource – It is the amount of a resource before production.
O-ring – It is also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, forming a seal at the interface. The O-ring can be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. Static applications of O-rings include fluid or gas sealing applications in which (i) the O-ring is compressed resulting in zero clearance, (ii) the O-ring material is vulcanized solid such that it is impermeable to the fluid or gas, and (iii) the O-ring material is resistant to degradation by the fluid or gas. The wide range of potential liquids and gases which need to be sealed has necessitated the development of a wide range of O-materials. O-rings consist of circular bands which are strategically utilized to facilitate the transmission of drive power between spools and rollers on a conveyor. Their seamless operation needs periodic assessments for wear, alignment, and overall integrity.
O-ring drive – It is a drive system within a conveyor which harnesses the power of O-ring belts for seamless power transmission. Regular inspections are vital for evaluating the condition, tension, and alignment of O-ring belts, safeguarding the efficiency of the entire operation.
O-ring seal – It is a torus-shaped (doughnut-shaped) mechanical seal, typically made of rubber or other flexible materials, which is installed in a groove between two parts to prevent the leakage of fluids or gases. When the two parts are assembled, the O-ring is compressed, filling gaps and creating a tight, leak-proof seal. O-rings are versatile and widely used in various applications, including hydraulic, pneumatic, and automotive systems, and they can function in both static (stationary) and dynamic (moving) conditions.
Orogeny – It is a period of mountain-building characterized by the folding of a portion of the earth’s crust.
Orowan mechanism – It is a strengthening mechanism in metallic materials where moving dislocations bend around large, non-shearable obstacles like precipitates, leaving behind a dislocation ring and hence impeding further dislocation movement. This process needs considerably higher applied stress to overcome the bowing of the dislocation, leading to increased strength and hardness in the material. It i’s a key strategy for improving the mechanical properties of materials, particularly superalloys, and is based on tailoring precipitate size and distribution to control the strengthening effect.
Orowan stress – It is the additional shear stress needed for a dislocation to bend around and bypass a non-shearable precipitate or obstacle in a material, such as a metallic alloy. This bypass process is known as the Orowan mechanism, where the dislocation leaves a ring of itself around the bypassed particle, and the Orowan stress represents the critical threshold needed to complete this process. This concept is important for understanding and predicting the strengthening of materials through precipitation hardening.
Orphan source – It is a radioactive source which is not under the control of a licensee.
Orsat – It is a gas-analysis apparatus in which certain gaseous constituents are measured by absorption in separate chemical solution.
Orsat analyzer – It is an atmosphere analysis device in which gases are absorbed selectively (volumetric basis) by passing them through a series of preselected solvents.
Ortho-chlorobenzyl chloride – It is also known as 2-chlorobenzyl chloride or 1-chloro-2-(chloromethyl) benzene. It is an organic compound with the chemical formula C7H6Cl2. It is a colourless to pale yellow liquid with a pungent, irritating odour. This compound is mainly used as a building block in the synthesis of several organic compounds.
Orthochromatic filter It consists of a colour filter which modifies the illumination quality reaching the film so that the brightness of coloured objects is relatively the same in the resultant black-and-white positive.
Orthogonal – The term is used to describe lines which meet at a right angle, it also describes events which are statistically independent, or do not affect one another in terms of outcome.
Orthogonal array – A balanced fractional factorial type of design of experiments. It is used as a key part of robust design to determine the effect each factor has on the mean and the variability in an experiment where several factors are involved. It consists of a ‘table’ (array) whose entries come from a fixed finite set of symbols (for example, {1,2,…,v}, arranged in such a way that there is an integer ‘t’ so that for every selection of ‘t’ columns of the table, all ordered t-tuples of the symbols, formed by taking the entries in each row restricted to these columns, appear the same number of times. The number ‘t’ is called the strength of the orthogonal array.
Orthogonal coordinate system – It is a frame of reference where the coordinate axes (or the families of surfaces which define the coordinates) are mutually perpendicular, meaning they intersect at right angles. This perpendicularity ensures that the coordinate directions are independent, simplifying the mathematical analysis of a system by making calculations like vector component analysis and transformations more straightforward compared to non-orthogonal systems. Common examples include Cartesian, circular cylindrical, and spherical coordinate systems.
Orthogonal distance – It is the shortest, perpendicular distance from a given point to a geometric feature, such as a curve, surface, or subspace, or a non-geometric entity like a set of eigenvectors. This concept is crucial in fields like data analysis (e.g., principal component analysis) and geometric fitting, where it provides a more accurate measure of ‘fit’ than simply measuring vertical or horizontal distances, ensuring that the distance measured is the true minimum distance.
Orthogonal frequency-division multiplexing (OFDM) modulator – It is a component within the orthogonal frequency-division multiplexing transceiver which encodes digital data by splitting it into several parallel, low-rate streams, modulating each stream onto a unique, orthogonal subcarrier frequency, and then combining these modulated subcarriers into a single, high-rate signal for transmission. It uses an ‘inverse fast Fourier transform’ (IFFT) to generate the modulated signal efficiently, enabling high data rates and robust communication by dividing a broadband channel into multiple narrowband, interference-resistant subchannels.
Orthogonal frequency-division multiplexing (OFDM) transceiver – It is a combined transmitter and receiver system which uses orthogonal frequency-division multiplexing (OFDM) to transmit and receive high-speed data by dividing a wide communication channel into several closely spaced, parallel narrow-band subchannels, each carrying a portion of the data. The transceiver’s transmitter converts the digital data into complex symbols, uses an ‘inverse fast Fourier transform’ to create the orthogonal subcarriers, and then converts the signal to an analog carrier for transmission. The receiver performs the reverse process, using a ‘fast Fourier transform’ (FFT) to separate the signals and recover the original data bits.
Orthogonality – It signifies independence and a lack of interaction between two or more distinct elements, whether they are vectors, functions, or components of a system. Mathematically, this is frequently expressed by their dot product being zero, meaning they are perpendicular and do not influence each other. In system design, true orthogonality ensures that changing one component does not cause unexpected side effects in others, simplifying complex systems and facilitating easier development and testing.
Orthogonality condition – It is the assumption that the experimental- error term in a statistical model is uncorrelated with the explanatory variables in the model.
Orthogonal polarization state – It refers to a pair of light polarization states which can propagate independently of each other, meaning one can exist without affecting the other. These states, such as vertical and horizontal linear polarization or right-handed and left-handed circular polarization, are mathematically perpendicular, allowing them to carry separate information simultaneously. This property is exploited in applications like imaging and optical communication to increase data capacity or achieve unique signal manipulation.
Orthogonal projection – It refers to the technique of creating 2D representations of 3D objects by projecting them onto a plane using lines that are perpendicular to the plane. This creates a parallel and precise view, such as the top, front, or side views of an object, and is frequently called orthographic projection. It is also used in vector mathematics to decompose vectors into orthogonal components, finding the closest vector to a given vector in a specific subspace, which is important for applications like computer-aided design (CAD) / computer-aided manufacturing (CAM).
Orthogonal projector – It is a square matrix which projects a vector onto a subspace, ensuring the projection is perpendicular to any other component of the vector within that space. Orthogonal projectors are crucial for techniques like least squares approximations and are used in multi-view engineering drawings, where they depict objects from multiple perpendicular perspectives.
Orthogonal space – It refers to a mathematical framework where vectors are mutually perpendicular, allowing for the representation of distinct patterns or components in data analysis, such as in empirical orthogonal function (EOF) analyses which concentrate data variance across spatial patterns.
Orthogonal subcarrier frequencies – These are a set of closely spaced carrier waves used in orthogonal frequency-division multiplexing (OFDM), where the frequency spacing is precisely set so that the subcarriers are mathematically independent and do not interfere with each other. This orthogonality is achieved when the frequency difference between any two subcarriers is an integer multiple of the symbol rate (1/T, where T is the symbol period), allowing for maximum spectral efficiency by eliminating guard bands and preventing ‘inter-carrier interference’ (ICI).
Orthographic drawing – It is a drawing in which a three-dimensional object is represented in two dimensions. This is done making multiple two-dimensional drawings of the object, viewed from different angles.
Orthographic projection – It is a means of representing three-dimensional objects in two dimensions. Orthographic projection is a form of parallel projection in which all the projection lines are orthogonal to the projection plane, resulting in every plane of the scene appearing in affine transformation on the viewing surface. The obverse of an orthographic projection is an oblique projection, which is a parallel projection in which the projection lines are not orthogonal to the projection plane.
Orthographic views – These are two-dimensional views used to define a three-dimensional model. More than one orthographic view is needed to define a model unless the model is of uniform thickness. Standard practice calls for three orthographic views, a front, top, and side view, although more or fewer views can be used as needed. The International Organization for Standardization (ISO) standard ISO 5456-2 specifies the orthographic projection methods.
Orthonormal coordinate system – it is a special type of coordinate system whose basis vectors are mutually perpendicular (orthogonal) and each have a magnitude of one (normalized). The Cartesian coordinate system (x, y, z) is the most common example of a global orthonormal system, but engineers also use local orthonormal systems in complex geometries, such as for the analysis of stress on a curved shell.
Orthorhombic – It consists of having three mutually perpendicular axes of unequal lengths.
Orthorhombic crystal system – It is one of the seven crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (‘a’ by ‘b’) and height (‘c’), such that ‘a’, ‘b’, and ‘c’ are distinct. All three bases intersect at 90-degree angles, so the three lattice vectors remain mutually orthogonal.
Orthorhombic phase – It refers to a crystal structure characterized by three unequal axes (a, b, and c) which are all perpendicular to each other (intersect at 90-degree angles). This means that the unit cell, the smallest repeating unit in the crystal, is a rectangular prism with a rectangular base and height, where the lengths of the sides (a, b, and c) are different.
Orthosilicate – It is a compound or mineral containing the silicon tetroxide anion, (SiO4)4-, where a single silicon atom is bonded to four oxygen atoms with no shared oxygen atoms between other (SiO4)4-, units. It is also known as a nesosilicate. The orthosilicate structure is the simplest form of silicate and is typically found in minerals where metal cations neutralize the 4-minus charge of the (SiO4)4- anion.
Orthotropic – It means having three mutually perpendicular planes of elastic symmetry.
Orthotropic linear elastic material – It shows different elastic properties along three mutually perpendicular axes, frequently called principal directions, and its behaviour under stress follows a linear relationship (Hooke’s law) within its elastic limit. These materials possess three orthogonal planes of symmetry, and examples include wood, composite laminates, and fibre-reinforced materials. Key characteristics include distinct Young’s moduli, shear moduli, and Poisson’s ratios for each principal direction.
Orthotropic plate – It is a plate with different mechanical properties (like Young’s modulus and stiffness) along three mutually perpendicular directions. These differing properties arise from the plate’s material, geometry (e.g., internal ribbing), or a combination of both. A common example is an orthotropic bridge deck, which consists of a steel plate stiffened by welded ribs and beams, creating a monolithic unit with distinct stiffness in different directions.
Ortho-xylene – It is an aromatic hydrocarbon with the formula C6H4(CH3)2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene, the mixture being called xylene or xylenes. Ortho-xylene is a colourless slightly oily flammable liquid.
Oscillating behaviour – It describes a system’s tendency to fluctuate repeatedly around an equilibrium point, driven by a restoring force after displacement. It involves periodic motion characterized by repetition, amplitude, and frequency. This phenomenon can be observed in both mechanical and electrical systems, from pendulums and tuning forks to automatic transmission systems and power grids, and is important for understanding and designing systems which show such repetitive patterns, such as oscillators which generate signals.
Oscillating body – It refers to a system or structure which undergoes repetitive, back-and-forth motion about a fixed equilibrium position. This oscillatory motion involves a repeated variation, frequently periodic, where the body moves to and fro, gaining and losing kinetic energy as it moves under the influence of a restoring force. Examples include a pendulum or a mass on a spring, and in broader applications, a physical structure designed to move with ocean waves to capture their kinetic energy for conversion into electricity.
Oscillating fluid flow – It refers to the periodic variation in fluid velocity and direction, where the flow periodically reverses or oscillates, frequently creating eddies and vortices. This type of flow is seen in applications like ‘oscillating heat pipes’ (OHPs), where it improves heat transfer, and in active flow control, where the oscillations are used to improve system efficiency. It can also lead to flow-induced vibrations in pipes, which engineers are to manage for system stability.
Oscillating die press – It is a small high-speed metal forming press in which the die and punch move horizontally with the strip during the working stroke. Through a reciprocating motion, the die and punch return to their original positions to begin the next stroke.
Oscillating piston totalizers – In this type of totalizer, the oscillating piston in a cylindrical housing a hollow cylinder, oscillates eccentrically. In this manner it transports defined volumes. The stationary outer cylinder is also the housing, in which a dividing wall and a guide ring are mounted. The dividing wall on the bottom of the housing provides the boundary between the inlet and outlet openings. The bearing for the oscillating piston is mounted in the sleeve and is guided along the dividing wall. Openings for filling and draining are located in its base. The movement of the piston bearing is transmitted to an indicator using a magnet and follower arrangement. In a direct piston totalizer, the magnetic coupling is not utilized and the rotary motion of the piston is transmitted directly from the piston to the totalizer. Since the oscillating piston wears rapidly, proper material selection is very important. Various materials are available such as gray cast iron, bronze, hard rubber, carbon and plastics. For high temperature operation an intermediate spacer is used to provide additional separation from the totalizer. Oscillating piston totalizers are especially used for water and oil measurement.
Oscillating screens – They are suitable for wet and dry materials, particles and chips. They provide for a precise classification of material into different fractions, which are then sent to further processing. The principle of operation is based on the oscillation of a sifting case equipped with several sifting decks located inside. The vibration intensity is adjustable by means of counter-weights. The quantity of the screening fractions depends upon the number of the sifting decks, while the obtainable particle size depends upon the type and mesh size of the single screens. The relative motion between the sieve and the particle mass can be gyratory, with a vertical rocking oscillation super-imposed on the circular motion or oscillating in a straight-line, simple harmonic motion.
Oscillating trough cooler – It is a steel trough conveyor within a plenum where reclaimed sand is cooled prior to reuse.
Oscillating water column (OWC) – It is a wave energy converter which harnesses wave motion to compress and decompress air, driving an air turbine to generate electricity. It consists of a hollow, partially submerged chamber open to the sea, which forces the water column inside to oscillate with the waves. This rising and falling water column acts as a piston, pushing air through a specially designed turbine which produces a unidirectional airflow to spin a generator above the water surface.
Oscillation – It is the repetitive or periodic variation, typically in time, of some measure about a central value (frequently a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum and alternating current. Oscillations can be used in physics to approximate complex interactions, such as those between atoms. Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science.
Oscillation characteristic – It refers to the quantifiable properties which define the periodic back-and-forth motion of a system, including its amplitude, frequency, and period. These characteristics, such as the duration of a mould’s strip times in a casting process or the signal frequency from an electronic oscillator, dictate how a system behaves and are fundamental for designing, analyzing, and controlling mechanical, electrical, and other engineering systems.
Oscillation cycle – It refers to one complete back-and-forth or up-and-down movement of a system around a central equilibrium point, returning to its initial state of displacement and velocity. This repeating sequence of states, frequently characterized by periodic changes in quantity or position, is a fundamental concept in understanding dynamic systems, from mechanical vibrations in a spring-mass system to electrical fluctuations in alternating current (AC) circuits.
Oscillation marks – These marks appear as grooves perpendicular to the casting direction. They are typically 0.1 millimeter to 1 millimeter deep. The oscillation marks can work as initiation point for cracks and beneath them there is a zone with higher risk for inclusions, pores, and segregation.
Oscillation time – It normally to the time period, which is the duration it takes for an oscillating system to complete one full cycle of motion, returning to its initial position and state. However, the term can also describe the duration of damped oscillations, referring to the time over which the amplitude and energy of a vibrating system decrease due to damping.
Oscillator – It is an electronic circuit which generates a continuous, repetitive alternating current signal (like a sine wave, square wave, or triangle wave) from a direct current power source without any external input signal. It functions as a self-sustained amplifier with positive feedback, converting direct current energy into alternating current energy at a specific frequency determined by its components. Oscillators are fundamental building blocks in electronics, used in applications from clock generation and signal generators to radios and computers.
Oscillatory baffled reactor (OBR) – It is a continuous tubular reactor which uses strategically placed baffles and an oscillatory flow to achieve superior mixing and heat / mass transfer, mimicking a series of ‘continuous stirred-tank reactors’ (CSTR) to produce a plug-flow profile. This reactor design creates eddies and vortices on either side of the baffles during the oscillatory movement, leading to very effective mixing, even under laminar flow conditions. Oscillatory baffled reactors are used in process engineering for process intensification, offering advantages like improved yields, higher control, and higher efficiency in continuous processes needing long residence times.
Oscillatory pattern – It describes the periodic, back-and-forth variation in a system’s state or properties, such as a signal’s magnitude, frequency, or spatial distribution, over time. This dynamic behaviour is a fundamental concept in wave phenomena, mechanical systems like pendulums and springs, and electrical circuits, characterized by parameters like frequency, amplitude, and period. Understanding these patterns is important for designing, analyzing, and controlling different engineered systems, from communication devices to complex networks.
Oscilloscope – It is an instrument for graphically displaying a wave-form as a function of time.
Osmium (Os) – It is a chemical element having an atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group which is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element. When experimentally measured using X-ray crystallography, it has a density of 22.59 grams per cubic meter. Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness.
Osmondite – It is an obsolete term once used to designate a ferrous microstructure. It is not so well defined as ‘troosite’.
Osmosis – It is the spontaneous net movement or diffusion of molecules of a solvent (e.g., water) through a selectively permeable membrane separating two solutions with different concentrations of dissolved solutes, in the direction that tends to equalize the solute concentrations on the two sides, i.e., from the more dilute solution to the more concentrated solution, or, equivalently, from a region of high-water potential to a region of low water potential. Since the solute is unable to cross the membrane, the tendency towards equilibration compels the solvent to cross the membrane instead. This continues until an equilibrium is reached, where neither side of the membrane is more or less concentrated than the other.
Osmotic pressure – It is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semi-permeable membrane. It is also defined as the measure of the tendency of a solution to take in its pure solvent by osmosis. Potential osmotic pressure is the maximum osmotic pressure which can develop in a solution if it is separated from its pure solvent by a semi-permeable membrane.
Osprey process – It converts a stream of molten metal into a particulate spray by gas atomization, which then produces a preform shape by impingement directly on to a collector. Molten metal poured into a tundish is atomized by a mixture of argon and nitrogen gas. The particulate droplets are sprayed onto a preform die. The established preform then undergoes hot working processes to result in its final shape.
O-temper – In aluminum alloy designations, the letter ‘O’ indicates an annealed temper. This means the aluminum has been heat-treated to achieve the lowest strength and highest ductility, making it more workable and less likely to fracture during forming operations.
Otto cycle – It is an idealized thermodynamic cycle which models the operation of spark-ignition internal combustion engines. It consists of four distinct processes namely isentropic compression, constant-volume heat addition (combustion), isentropic expansion (power stroke), and constant-volume heat rejection (exhaust). This cycle provides a theoretical framework for understanding how fuel-air mixtures are converted into mechanical work through a series of piston movements and ignitions at constant volume.
Otto cycle engine – It is a type of four-stroke, spark ignition internal combustion engine which uses the Otto cycle, an ideal thermodynamic cycle, to convert fuel into power. It operates on four piston strokes namely intake, compression, ignition, and exhaust. The key feature is that the fuel-air mixture is compressed, then ignited by a spark, causing a sudden heat release at basically constant volume, which is the basis of the ‘constant volume’ nature of the cycle.
Oudin coil – It is an early form of high-voltage induction coil which is identical in principle to a Tesla coil except for being constructed essentially as an auto-transformer. Oudin coil is a type of resonant transformer circuit which produces high-voltage, high-frequency alternating current (AC) electricity at low current levels. The primary and secondary windings of an Oudin coil are connected in series, acting like an autotransformer, with the output taken across both. Like a Tesla coil, an Oudin coil uses resonance to step up voltage. This involves a primary coil and a secondary coil, with the secondary coil having many more turns than the primary. The Oudin coil differs slightly from a Tesla coil in that its primary and secondary windings are connected in series, essentially acting as an auto-transformer.
Outage – It is a period when a service or an application is not available or when equipment is not operational. It can be planned or unplanned.
Outage event – It is an incident where a service or system experiences a temporary loss of functionality or availability, such as a power cut, network failure, or an internet service becoming unavailable. These events can be triggered by different causes, including equipment failure, natural disasters, security breaches, or even scheduled maintenance. While some outages are noticeable and inconvenient to users, others might be internal to a system and not immediately apparent to customers.
Outage, power– A power outage (also called a power cut, a power out, a power failure, a power blackout, a power loss, or a blackout) is the loss of the electrical power network supply to an end user.
Outage time – It refers to the period during which a plant or part of it is not operational, including planned maintenance and forced outages, impacting overall availability.
Out-crop – It is an exposure of rock or mineral deposit which can be seen on surface, that is, not covered by soil or water.
Outcome – It is the result of either planned or unplanned actions. For planning purposes, ‘outcomes’ are the desired end-point and are to guide the development and implementation of related programmes. Outcomes can be broad and long-term in nature or focused. They are used in both direction setting and performance measurement.
Outdoor equipment – It refers to any machinery, instruments, or systems designed and built to operate reliably and safely in outdoor environments. The design considerations for these equipments need to withstand external factors like weather, temperature fluctuations, and environmental hazards.
Outdoor storage – It is also called open storage. It refers to the placement of materials, equipment, or goods in an open, uncovered area or within structures which lack a full roof and four walls, specifically on an industrial property. It is a practical approach for items which do not need protection from the elements or are too large for indoor space, such as heavy machinery, raw materials, and even inventory or bulk goods. Engineering considerations for outdoor storage involve designing for land use efficiency and ensuring the storage methods meet safety and regulatory requirements, like proper containment to prevent environmental runoff.
Outer diameter (OD) – It is the measurement across the widest part of an object, from one outer edge to the opposite outer edge, passing through its centre. This dimension is critical for a variety of applications, such as determining the clearance for fitting or installation, calculating material usage, and guiding trenchless construction processes like horizontal directional drilling.
Outer noise – It consists of external sources or factors which are operating in the environment in which the product is functioning and whose variation is transmitted through the design to the output performance of the product. Examples of outer noise factors are temperature, humidity, contaminants, voltage fluctuations, vibrations from nearby equipment, and variations in human performance.
Outer ply – It refers to the external layer or layers of a multi-layered component or joint, such as in a composite material or a reinforced component like a hose. These outer layers are designed to provide structural integrity, pressure resistance, and protect internal components, allowing for continued safe operation even if inner layers are damaged. The thickness and material properties of these outer plies are critical for a component’s overall performance and durability.
Outer raceway – It is the grooved outer ring of a rolling-element bearing, which provides the track or channel for the balls or rollers to move within, facilitating the transfer of load and reducing friction between the inner and outer components. This grooved surface can be shaped to influence the load distribution and strain characteristics of the bearing.
Outer radius – It is the distance from the central axis or point to the farthest edge of a curved or circular object or region. It is a critical measurement for determining volumes and areas, specifying dimensions in technical drawings, and ensuring proper material flow and strength in manufactured parts
Outer sheath, electrical cable – Outer sheaths are made of black poly-vinyl chloride compound, which protect the armour material from corrosion. This PVC compound is applied by extrusion method. Outer sheath is applied over the non-magnetic metallic tape covering the insulation or over the non-magnetic metallic part of insulation screening in case of unarmoured single core cables and over the armouring in case of armoured cables.
Outer shell – It refers to a protective outer layer that defines a system’s boundary, provides protection from environmental factors, and can contribute to structural integrity, aesthetic appeal, or thermal regulation. The specific definition depends on the engineering discipline, such as an outer shell of an atom being the outermost energy level containing electrons, a building’s outer shell being its exterior envelope, or a structural shell being a self-supporting curved element.
Outer tube – It refers to the external, frequently structural, component of a tubular assembly or a device which encloses an inner element or fluid. It is characterized by its position as the outermost layer in a multi-layered system, like the glass casing of a solar tube, providing a protective function, structural support, or acting as a component in a flow measurement device.
Outfall – It is the point at which a pipe or channel discharges to a water body.
Outflow – It can refer to capital outflow which means the leaving of the capital. In hydrology, outflow, is the discharge of a lake or other reservoir system. In meteorology, outflow is the air which flows outwards from a thunderstorm.
Out-gassing – It is the release of solvents and moisture from composite parts under vacuum. It also occurs during the normal curing process under vacuum. It is sometimes called off-gassing, particularly when in reference to indoor air quality. It is the release of a gas which has been dissolved, trapped, frozen, or absorbed in some material. Out-gassing can include sublimation and evaporation (which are phase transitions of a substance into a gas), as well as desportion, seepage from cracks or internal volumes, and gaseous products of slow chemical reactions. Boiling is generally thought of as a separate phenomenon from out-gassing since it consists of a phase transition of a liquid into a vapour of the same substance.
Outlet – It is a discharge opening which is lower than the spillway crest designed to release reservoir water through or around a dam.
Outlet gate – It is a gate which is designed to control the flow of water through a reservoir outlet in or around a dam.
Outlet nozzle – It is a specific type of nozzle (a conduit of varying cross-sectional area) which directs the flow of a fluid (liquid or gas) out of a system, increasing its velocity and dropping its pressure in the process. It is designed to manage the fluid exiting a chamber or pipe, controlling its speed, direction, and the shape of the exiting stream, and may include features like flaring to handle high inlet velocities or prevent flow restrictions.
Outlet pipe – It is a pipe designed to discharge or channel a fluid (liquid or gas) away from a system, component, or vessel to another location or point of use. It serves as the exit point for fluids, allowing them to escape from a distributing channel, tank, or process into a watercourse or another part of a system.
Outlet port – It is a designated opening or connection point for fluid or electrical flow to exit a system, device, or component. It serves as the termination point for an intake and the start of an exit for gases, liquids, or electrical currents, facilitating the controlled release or transfer of these substances or energy.
Outlet static pressure – It is the static pressure at the outlet of a fan or system, calculated as the total outlet pressure minus the outlet velocity pressure. It represents the force pushing outwards on the duct or system walls, which is used to overcome the resistance to airflow caused by friction and components like filters or bends. This pressure is a measure of the system’s potential energy and is crucial for designing and selecting fans for heating HVAC (heating, ventilation, and air conditioning) and other ducting systems.
Outlet valve – It is a mechanical device, often placed at the end of a pipeline or vessel, that controls the flow of fluids or gases out of a system by opening and closing to regulate discharge. These valves are essential for regulating flow rates and preventing issues like overflows or leaks, serving crucial roles in industries from chemical processing to hydropower for tasks such as draining tanks, or controlling the release of sediment.
Outlier – In a set of data, a value so far removed from other values in the distribution that it is probably not a bona fide measurement. There are statistical methods for classifying a data point as an outlier and removing it from a data set.
Outlier ratio – It is a measure of prediction consistency, indicating how well a metric predicts subjective scores relative to content and impairments. It is calculated as the ratio of the number of outlier data points—those exceeding a threshold distance from the mean opinion score (MOS)—to the total number of data points.
Outliers – An outlier is an observation which is very different to other observations in a set of data. Since the most common cause is recording error, it is sensible to search for outliers (by means of summary statistics and plots of the data) before conducting any detailed statistical modelling. Outliers are identified as such since they ‘appear’ to be outlying with respect to a large number of apparently similar observations or experimental units according to a specified model. In several cases, outliers can be traced to errors in data collecting, recording, or calculation, and can be corrected or appropriately discarded. However, outliers can be so without a plausible explanation. In these cases, it is normally the analyst’s omission of an important variable which differentiates the outlier from the remaining otherwise similar observations, or a mis-specification of the statistical model which fails to capture the correct underlying relationships. Outliers of this latter kind are not to be discarded from the ‘other’ data unless they can be modelled separately, and their exclusion justified. Several indicators are normally used to identify outliers. One is that an observation has a value which is more than 2.5 standard deviations from the mean. Another indicator is an observation with a value more than 1.5 times the interquartile range beyond the upper or the lower quartile. It is sometimes tempting to discard outliers, but this is imprudent unless the cause of the outlier can be identified, and the outlier is determined to be spurious. Otherwise, discarding outliers can cause one to under-estimate the true variability of the data.
Out of phase – It is the condition when the alternating current (AC) generation sources are not synchronized with the grid.
Out-of-plane loads – These are the loads which are applied to the composite structures that are perpendicular to the surface of the composite structure. These loads, uniform and non-uniform, are a combination of the applied forces due to wind, roofing materials, equipment, machinery, live loads, and other factors.
Out-of-register – It is an embossed pattern distortion because of the misalignment of the male and female embossing rolls.
Out-of-roundness – It is deviation of the circumference from a circle. This can be an ovalization, i.e. an elliptic cross-section, or a local out-of-roundness, e.g., flattening. The numerical definition of out-of-roundness and ovalization is the same.
Output – It is the result of an activity which is carried out by an organization, while the outcome is the added value that is derived from the output. Output can include results, products, or outcomes produced by the processes. In case of a computer system, output is the visual, auditory, or tactile perceptions provided by the computer after processing the provided information. Examples are text, images, sound, or video displayed on a monitor or through speaker.
Output-based payment system – It consists of a compensation structure where the earnings of individuals are directly tied to the quantity or quality of their produced output, meaning that they are paid based on the results they achieve rather than the time they spent on working. Essentially, it means that people get paid for what they produce.
Output circuit – It is an electronic circuit designed to control or activate external devices and perform real-world functions, such as lighting light-emitting diodes (LED), moving motors, or switching power to loads. It takes signals from a main electronic system, like a microprocessor, and translates them into actions that affect the physical world, using components such as relays, triacs, or thyristors. Output circuits can provide digital signals (On/off) or analogue signals (variable levels) to control a wide range of devices.
Output torque – It is the quantity of twisting or rotational force produced by a rotating machine, such as an engine or motor, which is used to perform mechanical work. It is measured in units like Newton-meters (Nm) and represents the capacity of the system to cause rotation or to rotate a load.
Output transformer – It is an equipment which performs impedance matching between a high-impedance amplifier stage, such as those in tube amplifiers, and a low-impedance loudspeaker, converting a high-voltage, low-current signal into a low-voltage, high-current signal for efficient power transfer. It uses electro-magnetic induction with an iron core to transfer the signal between its primary and secondary coils, which are wound to create the desired impedance ratio. Output transformers also provide isolation between the amplifier’s high-voltage circuitry and the speaker, preventing electrical hazards.
Output valve – It is a component in several systems that controls the release or flow of a fluid or gas out of the system, frequently functioning as a release point in a piping system or tank. In electronics, an output valve can also refer to the output signal of a valve, which can be analog (like a 4-20mA current or 0-10 V voltage) or digital, indicating the valve’s status or the pressure / flow it is controlling. The term is not a single type of valve but describes the valve’s function relative to the system’s fluid discharge.
Outside diameter (OD) – Outside diameter of a hollow circular pipe is the measurement of the outside edges of the pipe passing through its centre. In case of gears, the outside diameter (or the tip diameter) is the diameter of the circle produced by connecting the tooth tips.
Outside draft – It is the draft on surfaces such as ribs or bosses that shrink away from the die during cooling. It is the draft applied to the outer side (or sides) of vertical elements of a forging. Hence, it pertains to the draft applied to the outer side of a peripheral rib or to the sides of a projecting boss. The metal at those vertical surfaces to which outside draft is applied shrinks away from the die impressions when the forging cools from forging temperature.
Outside screw and yoke valve – It is a valve in which the fluid does not come in contact with the stem threads. The stem sealing element is between the valve body and the stem threads.
Outsourcing – Outsourcing is when any operation or process that could be (or would usually be) performed in-house by the organizational employees is sub-contracted to another organization for a substantial period. The outsourced tasks can be performed on-site or off-site. By outsourcing, the organization uses third parties to perform noncore activities of the organization. Contracting third parties enables the organization to focus its efforts on its core competencies. Third parties that specialize in an activity are likely to be lower cost and more effective, given their focus and scale. Through outsourcing, the organization can access the state of the art in all of its operational activities without having to master each one internally.
Out time – It is the time a prepreg is exposed to ambient temperature, namely, the total quantity of time the prepreg is out of the freezer. The primary effects of out-time are to decrease the drape and tack of the prepreg while also allowing it to absorb moisture from the air.
Oval gear totalizers – The measuring element of an oval gear totalizer consists of two oval gears. The driving liquid produces the required torque, which varies as a function of the gear position, to rotate the gears. For example, the torques on the lower gear cancel each other while the torque on the upper gear is one sided and actually causes the rotation. Around the upper gear a bounded crescent like volume exists which is pushed towards the outlet of the meter. Each rotation of the pair of oval gears transports a defined liquid volume. The number of rotations is hence an exact measure of the quantity of liquid which has flowed through the meter. The precision teeth assure a good seal between the two gears. The clearance between the oval gears and the walls of the measuring chambers is so small that the leakage flow (gap loss) is negligible.
Ovality – It consists of the variation from a true circle of the cross section of a round tube, bar, or wire.
Oval offset bore throttle plate – In the conventional system, gate throttling results in a highly skewed and biased flow in the tundish-to-mould flow channel both upstream and downstream of the gate. These effects have considerably diminished the offset bore system. The offset gate design extracts the fluid more centrally from the tundish well nozzle. Hence, the system is less sensitive to any build-up on the walls of the well nozzle, which extends the useful life of the tundish well nozzle and hence, allowing longer tundish sequences. In practice, it has also been found that clogging within the plates of the offset bore gate is considerably reduced as compared to the conventional gate.
Ovaloid – It is a surface of revolution symmetrical about the polar axis which forms the end closure for a filament wound cylinder.
Oven – It is a heating furnace which is used to expose materials to a hot environment. Ovens contain a hollow chamber and provide a means of heating the chamber in a controlled way. Ovens are used to accomplish a wide variety of tasks needing controlled heating. Since they are used for a variety of purposes, there are many different types of ovens. These types differ depending on their intended purpose and based upon how they generate heat.
Oven, drying – It is a furnace or oven for drying moulds or cores.
Oven machines, coke oven battery – These machines are an integral part of any coke oven battery. These machines charge the coke ovens with the coal feedstock, push the coke from the ovens after coking, and feed it to the coke quenching process. In recent times, coke oven machines are acquiring a more prominent role in the coke making process. The increasing dimensions of coke oven chambers and the demand for the high performance have spurred the development of complex coke oven machines. Apart from the traditional handling of the coal and coke flow, coke oven machines are to meet the requirements for automation, productivity, safety, and user friendliness. Nowadays, where there can be up to 150 pushing cycles per day, so called ‘single spot operation’ of these machines, which involves no additional travelling, has become standard norm for each cycle.
Oven pressure – In a coke oven battery, oven pressure, specifically coking pressure, refers to the internal gas pressure generated within the plastic coal layer during the coke-making process. This pressure pushes outward against the oven walls, and its management is crucial for preventing damage and maintaining efficient operation.
Oven pressure regulation system – At any given point of time, pressure inside individual coke ovens is different since they are at different stages of coking periods. It is a known fact that coke ovens which are freshly charged witness highest pressure while coke ovens which are nearing their coking time witness lowest pressures. This has two effects namely (i) coke ovens at a higher pressure in comparison to gas collecting main are more prone to have fugitive emissions, and (ii) adjacent coke ovens operating at different pressures have different levels of stress on the oven chamber walls hence, reducing the refractory life considerably. In order to overcome these serious issues, it is important to regulate pressures in individual ovens so as to maintain a slightly negative pressure throughout the coking period. This can be easily achieved by installing oven pressure regulation system.
Oven regulation – In a coke oven battery, oven regulation refers to the control and optimization of the heating process within individual ovens and across the entire battery to ensure consistent and efficient coke production while minimizing emissions and maximizing byproduct recovery. This involves managing different parameters like temperature, fuel flow, and combustion air to achieve the desired coke quality and operational efficiency. Each oven in a battery is a separate unit where coal is heated to high temperatures to produce coke. Oven regulation involves controlling the heating process within each oven to ensure uniform heating and optimal coking conditions.
Oven soldering – It is a non-standard term for furnace soldering.
Oven wall temperature – In a coke oven battery, the oven wall temperature refers to the temperature of the silica brick walls that separate the individual ovens. These walls are heated by combustion gases (coke oven gas and mixed gas) within the heating flues located between the ovens, and they, in turn, heat the coal inside the ovens to high temperatures, facilitating the coking process.
Over-aging – It consists of aging under conditions of time and temperature higher than those needed to get maximum change in a certain property, so that the property is altered in the direction of the initial value. Over-ageing is artificial ageing treatment at too high a temperature, or for too long a time, after the maximum hardening effect has been achieved. It causes some loss of properties. In some cases, it can be a deliberate act, e.g., to improve resistance to stress corrosion or to minimize any further loss of properties in alloys operating at higher temperatures.
Overall equipment effectiveness (OEE) – It is a key performance indicator (KPI) which measures the percentage of planned production time that is truly productive. It provides a comprehensive view of manufacturing productivity by analyzing availability, performance, and quality. Essentially, overall equipment effectiveness helps identify areas where equipment is not running at its full potential, allowing manufacturers to pinpoint losses and improve efficiency.
Overall length (OAL) – It is a term characterizing the span of a conveyor from one exterior pulley to the other. The overall length encompasses the dimension from outside pulley to outside pulley, inclusive of belting or lagging, defining the conveyor’s lengthwise configuration.
Over ball diameter – In gear measurement, it refers to the measurement of the distance across a gear’s tooth thickness, taken by placing precision balls or pins into the tooth spaces. This technique is particularly useful for assessing the accuracy of involute gear teeth, where the tooth thickness is a critical parameter. The number and placement of the balls / pins depend on whether the gear has an even or odd number of teeth. Over ball measurement is a method used to determine the tooth thickness of a gear, especially involute gears.
Overbasing – It is a technique for increasing the basicity of lubricants. Overbased lubricants are used to assist in neutralizing acidic oxidation products.
Over-bending – It consists of bending metal through a higher arc than that needed in the finished part to compensate for spring-back.
Overburden – It consisting of surface vegetation, soil, and rock material, is removed (stripped) to reach buried ore deposits. Overburden is continually removed during the life of the mine as the high wall is cut back to permit deepening of the pit. Overburden and stripping ratios are important in determining whether a deposit is to be mined. The stripping ratio describes the unit of overburden which is to be removed for each unit of crude ore mined.
Overcurrent – It refers to an electrical current with a magnitude higher than a safe or limiting value, occurring because of a short circuit, overload, or ground fault. This excess current can generate excessive heat, potentially leading to equipment damage, insulation failure, fires, or even explosions. Devices such as fuses, circuit breakers, and overcurrent protection devices (OCPDs) are used to detect and interrupt these excessive currents to protect electrical systems.
Over-dispersion parameter – It is a parameter in the negative binomial regression model which allows for the possibility that the variance of the study end point can be larger than the mean of the study end point.
Over-draft – An overdraft occurs when something is withdrawn in excess of what is in a current account. For financial systems, this can be funds in a bank account. During rolling, It is a condition wherein a metal curves upward on leaving the rolls because of the higher speed of the lower roll. It is also a condition which occurs in a groundwater basin when pumping exceeds recharge over an extended period of time.
Overend discharge – It is the discharge over the head of the conveyor.
Over-fill – it is the fill of a die cavity with a quantity of powder which is in excess of the specification.
Overfiring – In porcelain enamel, it is a condition sometimes occurring during firing when the temperature of the furnace is too high or the ware is left in the furnace for a greater length of time than necessary.
Overflow – It refers to the excess quantity of liquid or material which exceeds the capacity of a container, pipe, or system. In the construction industry, overflow occurs when water, sewage, or other fluids exceed the capacity of drainage systems such as gutters, downspouts, and stormwater drains.
Overflow wells – These are separated cavities cut into the face of die casting dies adjacent to the main cavity and connected to it by a channel, ensuring filling of cavity.
Overhand – It is the extension of the end surface of the cope half of a core print beyond that of the drag to provide clearance for closing of the mould.
Overhang – It is the extension on the vertical surface of a core print, providing clearance for closing the mould over the core. It is also known as ‘shingle’.
Overhaul spares – These spares are those spare parts which are to be replaced every time the equipment is dissembled and re-assembled.
Overhead chargers – Chargers consist of an integral part of any conversion process is the ability to efficiently transfer material to and from the conversion equipment. Overhead chargers are similar to floor chargers, except that they are suspended from a rail system, similar to that of an overhead crane. This design is also capable of transferring material very quickly. This type of charger can also reach areas of the shop floor which are inaccessible to floor chargers due to obstacles on the shop floor, although one is to consider the ramifications of the potential that the work-piece can be dropped during transfer when taking advantage of this capability.
Over-head conveyor – It is a distinctive conveyor system strategically positioned above the working area, serving the purpose of material transport in an overhead arrangement. Consistent periodic inspections become imperative to uphold safety standards, ensure precise alignment and maintain the overall functionality of the system.
Over-head costs – It is the cost which is not directly associated with the production of identifiable goods or services. In production costs there are usually two types of overhead namely works overheads and administrative overheads. Works overheads are for the fixed expenditure directly related to production departments while the administrative overheads are because of those fixed expenditure which are outside the production departments. Over-head costs is sometimes called burden or indirect costs.
Overhead drive – It is a specialized unit positioned above a conveyor, providing crucial clearance and space for products in motion. The overhead drive is a drive assembly mounted over the conveyor, offering necessary clearance for the products in transit.
Over-head drive press – It is a mechanical press with the driving mechanism mounted in or on the crown or upper parts of the uprights.
Over-head guard – It is a robust protective structure installed above a conveyor system, effectively mitigating potential overhead hazards. Regular checks are mandated to guarantee the ongoing stability and effectiveness of overhead guards.
Over-head line – It consists of the power transmission or telecommunication wires which run on poles or other structures outside plant.
Over-head position – It is the position in which welding is performed from the underside of the joint.
Overhead tank – It is a container for storing water which is elevated above ground level, frequently on a rooftop or a specially constructed platform, to provide pressure for water distribution through gravity. Water is pumped into the tank from the ground and then flows down to different outlets in buildings, maintaining constant pressure and flow without needing complex pumping systems at the point of use.
Over-head travelling crane – An overhead travelling crane is also known as a bridge crane. It is a type of crane where the hook and the line mechanism run along a horizontal beam which itself runs along two widely separated rails normally in a long factory building and runs along rails along the two long walls of the building. The crane includes a hoist to lift the items, the bridge, which spans the area covered by the crane, and a trolley to move along the bridge. The bridge girders of the overhead travelling crane can be built using typical steel beams or a more complex box girder type. The advantage of the box girder type configuration results in a system which has a lower deadweight yet a stronger overall system integrity. The configuration of overhead travelling crane can be either under running or top running.
Over-head trolley conveyor – It is a conveyor system employing overhead trolleys or carriers for the efficient transport of materials. Regular inspections are imperative to validate proper alignment, assess the functionality of trolleys, and uphold the overall reliability of the system.
Over-head valve engine – It is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with flat-head (or side-valve) engines, where the valves are located below the combustion chamber in the engine block.
Overheated – It is a term applied when, after exposure to an excessively high temperature, a metal develops an undesirable coarse grain structure, but is not necessarily damaged permanently. Unlike burned structure, the structure produced by overheating can be corrected by suitable heat treatment, by mechanical work, or by a combination of the two.
Over-heating – It consists of heating a metal or alloy to such a high temperature that its properties are reduced. When the original properties cannot be restored by further heat treating, by mechanical working, or by a combination of working and heat treating, the overheating is known as burning. In ferrous alloys, heating to an excessively high temperature so that the properties/ structure undergo modification. The resulting structure is very coarse grained. Unlike burning, it can be possible to restore the original properties / structure by further heat treatment, mechanical working, or both. In aluminum alloys, over-heating produces structures that shows areas of resolidified eutectic or other evidence indicating the metal has been heated within the melting range.
Overheat ratio – It is a dimensionless parameter which quantifies the rise in a thermal sensor’s temperature above its reference temperature, typically expressed as the ratio of the sensor’s operating resistance to its cold resistance or as the percentage increase in temperature. It is an important metric in hot-wire anemometry, where it indicates how much hotter the hot wire becomes than the surrounding fluid, which affects its heat transfer and hence the accuracy of flow velocity measurements.
Over-lap – it is an imperfection at the toe or root of a weld caused by an overflow of weld metal onto the surface of the parent metal, without fusing with the latter. It is caused when the welding rod has been used at an incorrect angle, the electrode has travelled too slowly, or the current has been low. In resistance seam welding, it is the area in a given weld which is remelted by the succeeding weld. It is the protrusion of the weld metal over the weld toe or weld root (because of lack of fusion). This can be caused by insufficient amperage or travel speed. It is the portion of the preceding weld nugget remelted by the succeeding weld.
Overlay – It is a process which combines multiple map layers into one. It is an essential operation used to merge geographic and attribute data from two or more geographic layers to create a new map layer.
Over-laying – It is a nonstandard term for surfacing.
Overlay sheet – It is a non-woven fibrous mat (of glass, synthetic fibre, and so on) which is used as the top layer in a cloth or mat lay-up to provide a smoother finish, minimize the appearance of the fibrous pattern, or permit machining or grinding to a precise dimension. It is also called surfacing mat.
Overload factor – It is defined as a measure that accounts for all externally applied loads exceeding the nominal tangential load in a specific application.
Over-loading – An electrical system is said to be overloaded when the current drawn by the devices connected to the circuit exceeds the pre-fixed capacity of electricity. Overload relays protect the motor, motor branch circuit, and motor branch circuit components from excessive heat from the overload condition.
Over-load protection It consists of intricate safety mechanisms intricately designed to avert potential damage to the conveyor system caused by excessive loads. Consistent checks are indispensable to validate the precise functioning and calibration of overload protection systems, ensuring the sustained reliability of the entire system.
Overload ratio – It generally refers to the relationship between a system’s maximum load capacity and its actual operating load, frequently expressed as a ratio or percentage. It indicates how close a system is to operating at its limit and can be used to assess the potential for failure or inefficiency.
Over-mix – It is the mixing of a powder longer than necessary to produce adequate distribution of the powder particles. Over mixing can cause particle size segregation.
Over-peening effects – Over-peening is excessive peening because of which the shot peening effect on the peened surface is decreased because of the reduction in the cold work generated by the shot impacts.
Over-pickling – It consists of using pickling solutions of greater strength or at higher temperature than recommended, or allowing the work-piece to remain in the pickling tanks for a greater length of time than necessary. Over-pickling can lead to blistering of subsequently applied porcelain enamel finishes.
Over-pressure – It is the minimum operating pressure of a hot water boiler sufficient to prevent the water from steaming.
Over-pumping – It refers to the extraction of groundwater in excess of supply to a basin or aquifer, resulting in depletion of water resources. Over-pumping of a well can lead to the intrusion of saline water if the well is near the sea coast.
Over-sampling – It consists of sampling a signal at a rate which is higher than needed by the Nyquist criterion.
Over-shoot – It is the occurrence of a signal or function exceeding its target. It arises especially in the step response of band-limited systems such as low-pass filters. It is frequently followed by ringing, and at times conflated with the latter. In control theory, overshoot refers to an output exceeding its final, steady-state value.
Over-sinter – It is sintering of a compact at higher temperature or for longer time periods than necessary to get the desired micro-structure or physical properties. It frequently leads to swelling because of the excessive pore formation.
Oversize – It means being of more than standard or ordinary size.
Oversize material – It refers to material particles which are larger than the intended mesh size and hence cannot pass through the screen. This material is retained on the screen and discharged separately. Oversize particles can be considered a type of contamination if they are not to be present in the final product.
Oversize powder – It consists of powder particles which are larger than the maximum permitted by a particle size specification.
Oversteer – It is what occurs when a vehicle steers by more than the amount commanded or expected by the driver. It is very subjective and depends on the driver’s specific intentions.
Over-stressing – In fatigue testing, cycling at a stress level higher than that used at the end of the test. It is also permanently deforming a metal by subjecting it to stresses which exceed the elastic limit.
Over-temperature sensor – It is a sensor in a conveyor system which is designed to detect and respond to elevated temperatures. Regular inspections and calibrations are necessary to maintain the accuracy and functionality of over-temperature sensors.
Over-tensioning – It is the condition wherein a conveyor belt is excessively tensioned, leading to increased wear and reduced system efficiency. Regular assessments are required to prevent over-tensioning and ensure optimal belt tension.
Over-tightening – It is the condition wherein components in a conveyor system, such as bolts or fasteners, are excessively tightened. Regular checks are necessary to prevent over-tightening, which can lead to mechanical issues and system damage.
Overtopping discharge – It is the volume of water per unit time which flows over the crest of a barrier, such as a breakwater, dike, or seawall, when waves are higher than the structure. This discharge is normally measured as the average over a specific period, expressed in litres per second per meter of structure width. Overtopping is a critical consideration in the design of coastal structures, as excessive discharge can lead to flooding and damage to the structure or the area it protects.
Overturned – It is the case, where the oldest sedimentary rock beds are lying on top of a younger bed.
Overturning moment – It is the force which is of causing a conveyor system to tip or overturn. Periodic assessments are essential to identify and address factors contributing to overturning moments for system stability and safety.
Over-voltage – It is the application of more than rated voltage to a device.
Over-voltage protection – It prevents equipment damage from voltage levels exceeding the normal operating range, caused by lightning or switching operations. Protection methods include surge diverters and surge arresters, which divert excess voltage to the ground, and the use of an overhead earth wire, which intercepts direct lightning strikes.
Owen jet dust counter – An instrument similar to the Konimeter but differing in that the air to be sampled undergoes humidification prior to being blown through the jet. The velocity of impingement is about 200 meters per second to 300 meters per second and the jet is rectangular instead of circular. The prior humidification of the air causes condensation of moisture upon the dust particles by super saturation because of the pressure drop at the jet, and so assists in the deposition and retention of the particles on the slide.
Oxalic acid – It is an organic acid with the chemical formula (COOH)2 or (CO2H)2 or H2C2O4. It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colourless solution in water. It is a reducing agent and its conjugate bases hydrogen oxalate (HC2O−4) and oxalate (C2O2−4) are chelating agents for metal cations. It is used as a cleaning agent, especially for the removal of rust, since it forms a water-soluble ferric iron complex, the ferrioxalate ion. Oxalic acid typically occurs as the dihydrate with the formula H2C24·2H2O.
Oxalate coating – It is a chemical coating which is suitable to act as a lubricant carrier. It is produced on stainless steels and most types of nickel / chrome alloys with a process based on oxalates and oxalic acid. Oxalate coatings are formed on alloy steel substrates to facilitate cold working because of the lower coefficient of friction of the coating.
Oxalate film – It is the film of calcium oxalate which is a salt of the organic oxalic acid. This film can be present as mono-hydrate (whewellite, CaC2O4·H2O) and / or di-hydrate (weddellite, CaC2O4·2H2O) form.
Oxidant concentration – It is the quantity of an oxidizing substance within a specific volume of a medium, such as a gas, liquid, or solution. It is a critical measure, and is typically expressed using units like moles per cubic meter or moles per cubic decimeter, representing the moles of oxidant per unit volume.
Oxidation – It is the chemical combination with oxygen. It is a reaction in which there is an increase in valence resulting from a loss of electrons. It is also a corrosion reaction in which the corroded metal forms an oxide which is normally applied to reaction with a gas containing elemental oxygen, such as air. High temperatures increase the rate of oxidation. Oxidation is also a chemical reaction in which one substance is changed to another by oxygen combining with the substance. Much of the dross from holding and melting furnaces is the result of oxidation of the alloy held in the furnace. In case of minerals, oxidation is a chemical reaction caused by exposure to oxygen which results in a change in the chemical composition of the mineral. In carbon / graphite fibre processing, it is the step of reacting the precursor polymer (rayon, poly-acrylo-nitrile abbreviated as PAN, or pitch) with oxygen, resulting in stabilization of the structure for the hot stretching operation.
Oxidation effect – It refers to the several chemical and physical changes which occur when a substance undergoes oxidation, defined as the loss of electrons, gain of oxygen, or removal of hydrogen, frequently leading to degradation and altering material properties, as seen in processes like rusting.
Oxidation grain size – It means determination of grain size by holding a sample at a suitably high temperature in a mildly oxidizing atmosphere. The sample is polished before oxidation and etched afterwards. It refers to the method involving heating a polished steel sample to a specified temperature, followed by quenching and repolishing. The grain boundaries are sharply defined by the presence of iron oxide.
Oxidation-induced stacking fault (OISF) – It is a crystallographic defect in silicon crystals which forms during high-temperature oxidation processes, such as those used in manufacturing semiconductor devices. It arises from the injection and condensation of silicon self-interstitials into the crystal lattice, a process frequently triggered by mechanical damage or grown-in precipitates and which can lead to reduced performance in integrated circuits.
Oxidation kinetics – It is the study of the rates and mechanisms by which oxidation reactions occur. It involves understanding how factors like temperature, concentration, and the properties of materials influence the speed of oxidation, and how chemical species are transported during the process to form new oxide layers. By examining these rates, engineers can predict and control oxidation in different fields.
Oxidation losses – It is the reduction in the quantity of metal or alloy through oxidation.
Oxidation pond – It is also known as a stabilization pond or lagoon, is a man-made water treatment system designed to purify waste-water through biological processes naturally. The main purpose of an oxidation pond is to treat and eliminate contaminants in waste-water, rendering it safe for discharge into the environment. This treatment mechanism relies on the principles of microbial degradation and oxidation to break down organic matter and remove pollutants, offering an environmentally friendly and cost-effective solution for waste-water treatment.
Oxidation rate – It is the speed or velocity at which a substance undergoes oxidation, a chemical reaction involving the loss of electrons and an increase in oxidation state. This rate is frequently measured by the rate at which an oxide layer forms on a metal, increasing its weight or changing its composition over time. Factors like temperature and the presence of oxygen sconsiderably influence the oxidation rate.
Oxidation reaction – In electro-chemistry, it is a chemical reaction which occurs at an anodic site by the liberation of electrons.
Oxidation reduction – It is also known as a redox reaction. It is defined as a chemical process where there is a transfer of electrons between reactants, leading to an increase in the oxidation number of one atom and a decrease in another. It means to change the valence state of oxide scale and rust to soluble forms for removal from metal surfaces. Rust is chemically changed in this way to a more soluble form, easily dissolved by acids.
Oxidation resistance – It is the ability of a material to resist degradation by reacting with air or another gas to form a surface oxide.
Oxidation zone – It is a geologically or biologically active surface layer where materials are transformed through chemical reactions involving oxygen and water, resulting in the formation of new minerals and the leaching of existing ones. Common examples include ore deposits exposed by erosion, where minerals are altered, dissolved, and redeposited, sometimes forming profitable concentrations. In biological contexts, oxidation zones can be areas of coal or other organic matter which are weathered and altered by temperature, gas, water, and microbial activity.
Oxidative coupling of methane (OCM) – It is a catalytic process which directly converts methane (CH4) into higher-value C2 hydrocarbons like ethane and ethylene, along with by-products such as water, carbon mono-oxide (CO), and carbon di-oxide (CO2). This heterogeneous catalytic reaction occurs at high temperatures (650 deg C to 950 deg C) and involves the initial activation of methane into methyl radicals, which then couple to form ethane, followed by the dehydrogenation of ethane to ethylene.
Oxidative degradation – It is a chemical reaction which occurs in polymers when exposed to oxygen, leading to surface attacks and chemical changes, which can be initiated by either physiological or external environmental conditions. An example of this process is stress cracking, commonly observed in polyether urethane elastomers.
Oxidative desulphurization – It is a two-stage process for removing sulphur from fuels by first oxidizing sulphur compounds (like thiophenes) into more polar sulphones or sulphoxides, and then separating these oxidized, polar compounds from the fuel using solvent extraction or adsorption. This method is a promising alternative to traditional desulphurization (like hydrodesulphurization) as it operates under milder conditions (lower temperature and pressure) and can effectively remove refractory sulphur compounds which are difficult to process with other methods.
Oxidative pyrolysis – It refers to a pyrolysis process conducted in the presence of an oxidizing agent, where the peak mass loss rate occurs at lower temperatures compared to traditional pyrolysis because of the influence of oxygen, resulting in improved reaction rates and the subsequent combustion of char.
Oxidative wear – It is a corrosive wear process in which chemical reaction with oxygen or oxidizing environment predominates. It is a type of wear resulting from the sliding action between two metallic components which generate oxide films on the metal surfaces. These oxide films prevent the formation of a metallic bond between the sliding surfaces, resulting in fine wear debris and low wear rates.
Oxide – It is a binary chemical compound formed when another element chemically bonds with one or more oxygen atoms, such as silicon di-oxide (SiO2) or magnesium oxide (MgO). These compounds are important since their diverse properties, like electrical insulation (MgO) or semi-conducting characteristics (oxide semiconductors), enable their use in critical applications such as catalysts, fuel cells, sensors, and insulating materials in industrial and electronic components.
Oxide discolouration – It is a discolouration because of non-uniform oxidation of the metal surface during solution heat treatment.
Oxide dispersion strengthened (ODS) alloys – These alloys consist of a class of materials in which fine oxide particles are incorporated in metal powders, compacted, and then fabricated into finished forms by deformation processing. The resulting material has improved thermal softening resistance with excellent thermal and electrical conductivity. Oxide dispersion strengthened alloys are alloys which consist of a metal matrix with small oxide particles dispersed within it. They have high heat resistance, strength, and ductility. Alloys of nickel are the most common but includes iron aluminum alloys. Applications include high temperature turbine blades and heat exchanger tubing, while steels are used in nuclear applications. Oxide dispersion strengthened materials are used on spacecraft to protect the vehicle, especially during re-entry.
Oxide dispersion strengthened (ODS) ferritic steel – It is an advanced alloy which features an ultra-fine, uniformly distributed dispersion of nano-oxide particles within a ferritic (iron-based body-centered cubic) steel matrix, such as Fe-Cr-W-Ti-Y2O3 (iron-chromium- tungsten-titanium-yttrium oxide). These nano-oxides, typically Y-Ti-O (yttrium-titanium-oxygen) complex oxides, improve considerably the steel’s high-temperature strength, creep resistance, and thermal stability. Because of its excellent high-temperature performance and superior radiation resistance compared to austenitic steels, oxide dispersion strengthened ferritic steel is considered a prospective structural material for advanced nuclear reactor components and other high-temperature applications.
Oxide-dispersion-strengthened (ODS) superalloy powders – These are metallic powders containing a high-volume fraction of nanoscale oxide particles, typically rare earth oxides like Y2O3, dispersed within a metallic matrix. These alloys are known for their exceptional high-temperature strength and creep resistance, making them suitable for demanding applications like gas turbines and nuclear reactors. The oxide particles inhibit the movement of dislocations, which are responsible for plastic deformation, thus enhancing the alloy’s strength, especially at elevated temperatures.
Oxide film – It is a typical ultra-thin oxide film consists of a single monolayer of an oxide material on a crystalline metal support. In case of iron and steel, an oxide film refers to a layer of compounds formed on the surface of iron, consisting of inner magnetite and outer hematite or maghemite layers. These films can impact the performance of iron in reactions by hindering mass and electron transport. In case of aluminum, whenever a freshly created surface is exposed to air or water at room temperature, an oxide film is formed immediately and grows to a thickness of around 5 nanometers in air and to a somewhat higher thickness in water. The film thickness increases at high temperature. Majority of the aluminum alloys have good corrosion reistance resulting from a thin, compact, adherent oxide film that forms on the surface. Without this protective film, aluminum is a reactive metal with poor corrosion resistance.
Oxide film replica – It is a thin film of an oxide of the sample to be examined. The replica is prepared by air, oxygen, chemical, or electro-chemical oxidation of the parent metal and is subsequently freed mechanically or chemically for examination.
Oxide fuels – In nuclear power plant, it is the enriched or natural uranium in the form of oxide UO2, or mixed oxide (MOX) which is used in several types of reactors. Pure metal fuels can also be used in other reactor designs (e.g., Magnox).
Oxide glasses – These are a type of amorphous solid material which mainly consists of oxygen anions and one or more metallic or non-metallic cations. They are formed by melting a mixture of oxides or compounds which convert to oxides upon heating, and then rapidly cooling the molten mixture to prevent crystallization.
Oxide glazes – In ceramics, oxide glazes are essentially a type of glaze where the colour and other properties are derived from metallic oxides. These oxides, when heated, react with other glaze ingredients to create a glassy surface that can be decorative or protective. They are a key component in achieving a wide range of colors and effects in fired ceramic pieces.
Oxides inclusions – These are ferrous oxide (FeO), manganese oxide (MnO), chromium oxide (Cr2O3), silica (SiO2), alumina (Al2O3), titanium oxide (TiO2) and others. By mineralogical content, oxide inclusions divide into two main groups namely (i) free oxides such as FeO, MnO, Cr2O3, SiO2 (quartz), Al2O3 (corundum) and others, and (ii) spinels which are compound oxides formed by bivalent and trivalent elements. Ferrites, chromites and aluminates are in this group. The fundamental tool for the description of the chemical composition of the oxide inclusions is the ternary phase diagram (CaO-SiO2-Al2O3), since this is the main system ruling the formation of these non-metallic compounds. This class of non-metallic compounds are formed by the deoxidizing elements added to the liquid steel for removing the oxygen content. Composition, size, and distribution of precipitated oxides are greatly influenced by the deoxidants, conditions of the liquid metal, and the solidification process. Aluminum is widely accepted as deoxidant in steelmaking process. Its addition is very convenient and it effectively reduces oxygen content in liquid steel to low levels. However, the most of the steel problems can be traced to alumina or aluminum rich oxides. Solid alumina inclusions in the liquid steel tend to rapid clustering because of their dendritic morphology. The alumina clusters hardly float to the top of the liquid steel because of their high apparent density in view of oxide clusters plus engulfed liquid steel. They are detrimental to the castability and quality of continuously cast steel.
Oxide layer – It js a surface layer formed on a work-piece during the electro-chemical micro-machining (EMM) process because of the evolution of oxygen gas from anodic reactions, which can be classified as either passive, acting as insulation against current flow, or nonpassive.
Oxide layer glaze – It describes the frequently shiny, wear-protective layer of oxide formed when two metals (or a metal and ceramic) are slid against each other at high temperature in an oxygen-containing atmosphere. The layer forms on either or both of the surfaces in contact and can protect against wear.
Oxide matrix – it is a structural material mainly composed of metal oxides, such as alumina (Al2O3) or titania (TiO2), which provides the main structure and binding for other components, like fibres, in a composite material. These matrices are known for properties like high-temperature stability, thermal insulation, and resistance to corrosion and oxidation, making them suitable for demanding environments found in industrial applications.
Oxide scale – It is almost always associated with the hot working. Except for highly reactive and expensive metallic systems, where jacketing (e.g., zirconium alloys) or protective coating (e.g., glass coating) is used, the oxide scale is typically a part of any thermo mechanical process practice of warm / hot working. The oxide scale is frequently complex. For example, in hot steel, the scale consists of three layers namely (i) inner wustite (FeO), (ii) intermediate magnetite (Fe3O4), and (iii) outer hematite (Fe2O3), with interesting surface characteristics. The scale has strong implications to die-tool and metal interactions and to heat transfer. But the more important technologically is the control and removal of oxide scale. High-pressure water jets are an integral part of a modern hot rolling mill where water jets are used to control the severity of oxide scale. Even then an entire pickling process and the technology of pickling are usually associated with the thermo mechanical process technology. Improper pickling leads to surface defects (such as pickling blisters etc.) and even to embrittlement.
Oxide semiconductor – It is a material, normally a metal oxide, which shows semiconductor properties, meaning its conductivity falls between that of a conductor and an insulator. These materials are used in different advanced applications, such as transparent electronics, solar cells, gas sensors, and fuel cells, since they can be engineered to combine properties like transparency with controlled conductivity.
Oxides of nitrogen – Nitrogen oxides (NOx) are a group of gases made up of varying quantities of oxygen and nitrogen molecules. Two most important oxides of nitrogen, which are air pollutants, are nitric oxide (NO) and nitrogen di-oxide (NO2). These two oxides are frequently lumped together under the designation NOx, although analytical techniques can distinguish clearly between them. Of the two, nitrogen di-oxide is the more toxic and irritating compound. Nitric oxide is a principal by-product of combustion process, arising from the high temperature reaction between nitrogen and oxygen in the combustion air and from the oxidation of organically bound nitrogen in certain fuels such as coal and oil. While nitric oxide is the dominant NOx compound emitted by most sources, nitrogen di-oxide fraction from a source varies somewhat with the type of source. Once emitted, nitric oxide can be oxidized quite effectively to nitrogen di-oxide in the atmosphere through atmospheric reactions. Nitric oxide is colourless, odourless gas. It is nonflammable and is soluble in water. It is a toxic gas. Nitrogen di-oxide is a reddish-orange-brown gas with sharp and pungent odour. It is toxic and highly corrosive. It absorbs light over much of the visible spectrum.
Oxide stringers – Any oxides which form during welding are to be removed by abrasive blasting or grinding. If such films are not removed as they accumulate on multiple-pass welds, then they can become thick enough to inhibit weld fusion and produce unacceptable laminar-type oxide stringers along the weld axis.
Oxide-type inclusions – These are oxide compounds occurring as non-metallic inclusions in metals, normally as a result of deoxidizing additions. In wrought steel products, they can occur as a stinger formation composed of distinct granular or crystalline-appearing particles.
Oxidized mineral – It is normally known as an oxide mineral. It is a naturally occurring inorganic compound formed by the combination of oxygen with one or more other elements, typically metals. These minerals feature a structure where positively charged metal ions occupy the spaces between tightly packed oxygen atoms. A well-known example is iron oxide, which gives rust its red colour and is the result of iron reacting with oxygen.
Oxidized surface – It is the result of a chemical reaction where a substance, typically a metal, interacts with oxygen (or other oxidizing agents) and forms a layer of oxide on its surface. This process, known as oxidation, involves the transfer of electrons from the substance to the oxygen, leading to the formation of metal oxides. In case of steel, oxidized surface is a surface having a thin, tightly adhering oxidized skin (from straw to blue in colour), extending in from the edge of a coil or sheet.
Oxidizer – It is also known as an oxidizing agent or oxidant. It is a substance which accepts electrons from another substance during a chemical reaction, causing the other substance to be oxidized (lose electrons). Essentially, it is a chemical which causes another substance to lose electrons. Common examples include oxygen, hydrogen peroxide, and the halogens.
Oxidizing agent – It is a compound which causes oxidation, hence itself being reduced. It is a substance in a redox chemical reaction which gains or ‘accepts’ / ‘receives’ an electron from a reducing agent. In other words, an oxidizer is a substance which oxidizes another substance.
Oxidizing atmosphere – It is an atmosphere resulting from the combustion of fuels in an atmosphere where excess oxygen is present, and with no unburned fuel lost in the products of combustion. Oxidizing atmosphere tends to promote the oxidation of immersed materials. It is a furnace atmosphere with an oversupply of oxygen which tends to oxidize materials placed in it.
Oxidizing element – It is a chemical species which accepts electrons in a redox reaction, causing another substance to lose electrons (be oxidized). This acceptance of electrons causes the oxidizing element itself to be reduced (its oxidation state decreases), making it a potent electron acceptor like oxygen, halogens (fluorine, chlorine), and hydrogen peroxide.
Oxidizing flame – It is a gas flame produced with excess oxygen in the inner flame which has an oxidizing effect.
Oxy-acetylene cutting – It is an oxy-fuel gas cutting process in which the fuel gas is acetylene.
Oxy-acetylene torch – It is a device which combines acetylene and oxygen gases to produce an extremely high-temperature flame, used for welding and cutting metals. The operator can control the flame’s shape and intensity by adjusting the flow of each gas through valves on the torch handle.
Oxy-acetylene welding – It is an oxy-fuel gas welding process in which the fuel gas is acetylene.
Oxy-ethylene – It is a specific repeating chemical unit, -OCH2CH2-, which forms the basic structure of polyethylene glycol (PEG), also known as polyethylene oxide (PEO) or poly(oxyethylene) (POE). These compounds are synthetic, water-soluble polymers with numerous applications in industrial manufacturing because of their biocompatibility, low toxicity, and versatile properties like binding, thickening, and film formation.
Oxy fuel burners – Oxy-fuel burners are installed in electric arc furnaces to reduce electricity consumption by substituting electricity with oxygen and hydrocarbon fuels. This technology has been introduced for improving melting rates and to provide more even heat distribution throughout the furnace. It reduces total energy consumption because of reduced heat times, increases heat transfer during the refining period, and facilitates slag foaming, which increases efficiency of oxygen usage and injected carbon.
Oxy-fuel combustion – It is the process of burning a fuel using pure oxygen, or a mixture of oxygen and recirculated flue gas, instead of air. Since the nitrogen component of air is not heated, fuel consumption is reduced, and higher flame temperatures are possible. Historically, the primary use of oxy-fuel combustion has been in welding and cutting of metals, especially steel, since oxy-fuel allows for higher flame temperatures than can be achieved with an air-fuel flame. Oxy-fuel combustion represents an emerging novel approach to near zero-emission and cleaner fossil fuel combustion. It is accomplished by burning the fuel in pure oxygen instead of air. By eliminating nitrogen in the combustion process, the exhaust of the flue gas stream is mainly composed of water and carbon di-oxide, without any nitrogen. High purity carbon di-oxide can be recovered by condensation of water. However, when fuel is burnt in pure oxygen, the flame temperature is much higher than that in a normal air-blown burner and the conventional material of construction for the burner is not able to withstand this high temperature. Hence, either the material of construction is to be improved or the flame temperature is to be lowered. The development of high temperature resistant materials has been slow because it is a major research and development undertaking. There are a number of methods, which can be used to moderate the flame temperature, the most common being carbon di-oxide recycling. In carbon di-oxide recycling, a portion of the carbon di-oxide rich flue gas stream is recycled back to the burner to lower the flame temperature similar to that in a normal air-blown burner. Another method is to use water injection rather than carbon di-oxide recycling to control the flame temperature. This is frequently referred to as ‘hydroxy-fuel’ combustion. Effectively, these two options allow the continual use of conventional refractory material until new high temperature resistant material can be developed. A primary benefit of oxy-fuel combustion is the very high-purity carbon di-oxide stream which is produced during combustion. After trace contaminants are removed, this carbon di-oxide stream is more easily purified and removed than post-combustion capture. Because of this, oxy-fuel combustion has also received a lot of attention in recent decades as a potential carbon capture and storage technology.
Oxy-fuel combustion capture – It is a carbon capture technology which combusts fossil fuels in pure oxygen instead of air, producing a flue gas mainly consisting of carbon di-oxide (CO2) and water vapour. After condensing the water, the remaining carbon di-oxide at a high concentration, which facilitates its efficient separation and storage. This method avoids the high nitrogen content found in typical air combustion, which dilutes the carbon di-oxide stream and makes capture more difficult.
Oxy-fuel conditions – These refer to combustion environments where fuel is burned in an atmosphere of oxygen and carbon di-oxide, leading to different emissions characteristics compared to traditional air-based combustion. These conditions can influence the conversion of fuel nitrogen to nitrogen oxides (NOx) and affect overall emissions dynamics.
Oxy-fuel detonation process – It is the other name of oxy-fuel powder spray process.
Oxy-fuel gas – It is the gas used for oxy-fuel processes. Oxy-fuel processes can use a variety of fuel gases (or combustible liquids), the most common being acetylene. Other gases which can be used are propylene, liquified petroleum gas (LPG), propane, natural gas, hydrogen, and MAPP gas which is a stabilized mixture of methyl-acetylene (propyne), propadiene and propane.
Oxy-fuel gas cutting – It is any of a group of processes which is used to sever metals by means of chemical reaction between hot base metal and a fine stream of oxygen. The necessary metal temperature is maintained by gas flames resulting from combustion of a specific fuel gas such as acetylene, hydrogen, natural gas, propane, propylene, or Mapp gas (stabilized methylacetylene-propadiene).
Oxy-fuel gas spraying – it is a non-standard term for flame spraying.
Oxy-fuel gas welding (OFW) – It is any of a group of processes which is used to fuse metals together by heating them with gas flames resulting from combustion of a specific fuel gas such as acetylene, hydrogen, natural gas, or propane. The process can be used with or without the application of pressure to the joint, and with or without adding any filler metal.
Oxy-fuel powder (OFP) spray process – It is a thermal spray process. This process extends the range of available coatings and subsequent applications to include ceramics, cermets, carbides, and fusible hard-facing coatings. Using either gravity flow or pressurized feed, powder is fed into the gun and carried to the gun nozzle, where it is melted and projected by the gas stream onto a prepared surface. For general-purpose spraying, the gravity-flow system is used. When exacting coating consistency and / or high spray rates are desired, the pressurized feed system is used. Oxy-fuel powder guns are the lowest cost thermal spray equipment and are easiest to set up and change coating materials. The oxy-fuel powder spray process finds widest use in short-run machinery maintenance work and in the production spraying of abradable clearance-control seals for gas turbine engines.
Oxy-fuel wire spray process – It is also called wire flame spraying or the combustion wire process. It is the oldest of the thermal spray coating methods and among the lowest in capital investment. The process utilizes an oxygen-fuel gas flame as a heating source and coating material in wire form. Solid rod feed stock has also been used. During operation, the wire is drawn into the flame by drive rolls which are powered by an adjustable air turbine or electric motor. The tip of the wire is melted as it enters the flame and is atomized into particles by a surrounding jet of compressed air and propelled to the work-piece.
Oxy-gas cutting – The preferred term is oxygen cutting which consists of a group of cutting processes that is used to sever or remove metals by means of the chemical reaction between oxygen and the base metal at high temperatures. In the case of oxidation-resistant metals, the reaction is facilitated by the use of a chemical flux or metal powder.
Oxygen – It is a chemical element with the symbol ‘O’ and atomic number 8. It is a highly reactive non-metal, and a potent oxidizing agent which readily forms oxides with majority of the elements as well as with other compounds. At standard temperature and pressure, two oxygen atoms bind covalently to form di-oxygen, a colourless and odourless di-atomic gas with the chemical formula O2. Di-atomic gas presently constitutes 20.95 % molar fraction of the earth’s atmosphere. Oxygen is an active component of the atmosphere making up 20.94 % by volume or 23 % by weight of the air. It is a colourless, odourless, and tasteless gas. It is highly oxidizing. Oxygen reacts vigorously with combustible materials, especially in its pure state, releasing heat in the reaction process. Several reactions need the presence of water or are accelerated by a catalyst. Oxygen has a low boiling / condensing point which is -183 deg C. The gas is around 1.11 times heavier than air and is slightly soluble in water and alcohol. Below its boiling point, oxygen is a pale blue liquid slightly heavier than water. Oxygen is produced in large quantities and at high purity as a gas or liquid by cryogenic distillation process and in smaller quantities as a lower purity gas (typically around 93 %) by adsorption technologies such as pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA) or vacuum swing adsorption (VSA).
Oxygen activity – It is the measure of the availability of oxygen in a medium, which can be determined using different types of oxygen electrodes, such as a Clark-type oxygen probe.
Oxygen arc cutting – It consists of an oxygen cutting process which is used to sever metals by means of the chemical reaction of oxygen with the base metal at elevated temperatures. The necessary temperature is maintained by an arc between a consumable tubular electrode and the base metal.
Oxygenated additives – These additives refer to chemical compounds containing oxygen which are added to fuels to improve combustion and ignition quality by improving the Cetane number and reducing ignition temperature of particulates. Examples of these additives include methanol, ethanol, and butanol, among others.
Oxygenated fuels – These are defined as fuels which contain oxygen in their chemical structures, differentiating them from fossil diesel fuel. These fuels, which include biodiesel, alcohols, and ethers, are characterized by their miscibility with diesel and their ability to improve combustion efficiency while potentially increasing NOx (nitrogen oxides) emissions.
Oxygen attack – It is the corrosion or pitting in a boiler caused by oxygen.
Oxygen barrier – It is a material, such as a plastic film or coating, designed to block or considerably reduce the passage of oxygen molecules through a barrier. These barriers are crucial in packaging prevent oxidation, which can degrade product quality, and shelf life. The effectiveness of an oxygen barrier is measured by its Oxygen transmission rate (OTR), indicating how much oxygen passes through a unit area of the material over a given time.
Oxygen binder – It is also known as oxygen scavenger. Oxygen binders are chemical substances which chemically bind and remove dissolved oxygen in water-bearing systems. They are used to protect metallic system components from oxygen corrosion which occur in cooling circuits, boiler systems, and other industrial water treatment systems. Oxygen which comes into contact with metal surfaces leads to electro-chemical reactions that can cause material damage and considerably shorten the service life of the system.
Oxygen blowing – It is a steelmaking process where high-velocity, supersonic jets of pure oxygen are injected into a bath of molten metal (liquid iron and scrap) to rapidly remove impurities like carbon, silicon, and phosphorus. This oxidation process forms slag that traps the impurities and generates substantial heat and gas, which agitates the melt, promoting efficient conversion of the liquid iron into steel.
Oxygen blowing lance, basic oxygen furnace – In the basic oxygen furnace (BOF) steelmaking a water-cooled lance is used for injecting a high velocity (super-sonic) stream of oxygen onto the liquid bath for its refining. The velocity or momentum of the oxygen jet results in the penetration of the liquid slag and metal to promote oxidation reactions over a relatively small area. The velocity of the oxygen jet and the penetration characteristics are functions of the nozzle (lance tip) design. The top-blowing lance oxygen jet of the basic oxygen furnace converter works as the source of feeding oxygen and energy for stirring of the liquid metal in the bath.
Oxygen bomb calorimeter – It is a constant-volume device to measure the heat of combustion of a sample, like fuels, by burning it under high pressure in excess oxygen and measuring the subsequent temperature rise of a surrounding water bath. The ‘bomb’ is a robust, corrosion-resistant steel vessel which is to withstand the high-pressure, high-temperature combustion reaction. Engineering aspects include the design of this high-pressure vessel, the selection of corrosion-resistant materials, the precision measurement of temperature, and the development of safety protocols to handle miniature, controlled explosions.
Oxygen concentration cell – It is also known as differential aeration cell. It is an electrolytic cell , the electromotive force of which is because of a difference in air (oxygen) concentration at one electrode as compared with that at another electrode of the same material.
Oxygen corrosion – It is the degradation of metals and the reaction of dissolved ions in the presence of oxygen to form insoluble deposits due to the rapid rate of oxidation.
Oxygen cutter – It is the person who performs a manual oxygen cutting operation.
Oxygen cutting – It consists of a group of cutting processes which are used to sever or remove metals by means of the chemical reaction between oxygen and the base metal at high temperatures. In the case of oxidation-resistant metals, the reaction is facilitated by the use of a chemical flux or metal powder.
Oxygen cutting operator – It is the person who operates machine or automatic oxygen cutting equipment.
Oxygen deficiency – It is a form of crevice corrosion in which galvanic corrosion proceeds since oxygen is prevented from diffusing into the crevice.
Oxygen demanding wastes – These are the waste waters such as, domestic and municipal sewage and waste water from certain industries have considerable concentration of bio-degradable organic compounds either in suspended, colloidal or dissolved form. These wastes undergo degradation and decomposition by bacterial activity. The dissolved oxygen available in the water body gets consumed for aerobic oxidation of organic matter present in the waste water. Hence, depletion of the dissolved oxygen takes place. This adversely affects the aquatic life if the dissolved oxygen falls below critical level. The decrease of dissolved oxygen is an index of pollution.
Oxygen diffusion coefficient (ODC) – It quantifies the rate at which oxygen molecules move through a specific medium. It is a physical property of the oxygen and the medium it is diffusing through, with a higher coefficient indicating a faster rate of diffusion. This coefficient is necessary for understanding how oxygen penetrates materials, influencing factors like the kinetics of chemical reactions, material properties such as ductility, and the efficiency of energy devices.
Oxygen electrode – It is a device which measures oxygen concentration in a liquid or gaseous medium by generating an electric current proportional to the quantity of oxygen present. It works by using a membrane to allow oxygen to diffuse to a special cathode, typically made of platinum, where it undergoes a reduction reaction (e.g., O2 + 4H+ + 4e- = 2H2O). This reaction produces a current which is measured and calibrated to determine the oxygen concentration, which is important for applications like monitoring dissolved oxygen in water.
Oxygen enrichment – It refers to the process of increasing the oxygen concentration in combustion systems to improve furnace capacity, reduce fuel consumption, and improve combustion efficiency. It mainly influences the burning process by lowering nitrogen levels in combustion gases, resulting in higher flame temperatures and faster flame propagation.
Oxygen enrichment of air – It is a crucial process to get oxygen-rich streams for several industrial applications. In recent years, oxygen-enriched air (OEA) is seen as a promising technology to facilitate energy-efficient carbon capture. High purity oxygen-enriched air (90 % to 95 % oxygen) can be used for oxy-combustion to directly sequester or valorize the carbon di-oxide rich flue gas. Also, coupling of oxygen enrichment (50 % to 80 % oxygen) with the post-combustion capture can be an attractive hybrid capture strategy for the reduction of energy penalty. oxygen-enriched air can also be highly advantageous for economic fuel combustion as the quantity of fuel needed in combustion processes for a fixed power production can be significantly reduced with low-purity oxygen-enriched air with oxygen concentration of 25 % to 30 %. Normally, replacing air with low-purity oxygen-enriched air can reduce the volume of process gas and can increase process efficiency. For example, the use of oxygen-enriched air in the Claus process for sulphur recovery has been predicted to yield cost savings up to 40 % attributing to the increase in the combustion temperature and the sulphur processing capacity of the furnace. Hydrocarbon oxidation processes can also benefit from oxygen-enriched air, e.g., the yield of terephthalic acid from p-xylene can be increased and corresponding production cost can be decreased. oxygen-enriched air has also been proposed for increasing the capacity of catalyst regeneration in fluidized catalytic cracking.
Oxygen-free – It is referred to the absence of oxygen in an environment or in a material.
Oxygen-free copper – It is the electrolytic copper free from cuprous oxide, produced without the use of residual metallic or metalloidal deoxidizers. It is a grade of copper which is preferred for electrical applications for its low electrical resistance.
Oxygen gouging – It consists of an application of oxygen cutting in which a bevel or groove is formed.
Oxygen grooving – It is a non-standard term for oxygen gouging.
Oxygen impingement process – It refers to the technique of blowing pure oxygen onto a molten metal bath, most notably in steelmaking, to oxidize and remove impurities, refine the metal, and control slag formation. This process, also known as oxygen blowing, uses high-velocity oxygen jets to improve chemical reactions, improve mixing, and increase the efficiency of the refining process.
Oxygen injection lance – It is a specialized tool which is used in industrial processes to introduce controlled quantities of oxygen into high-temperature environments. It typically consists of a long tube or lance made of heat-resistant materials, with an opening or nozzle at the end for oxygen release. The lance is designed to withstand extreme temperatures and harsh conditions. The purpose of an oxygen injection lance is to improve combustion and improve the efficiency of various industrial processes. By injecting oxygen directly into the combustion zone, it increases the availability of oxygen for chemical reactions, resulting in more complete and intense combustion. This, in turn, leads to increased heat generation, improved energy efficiency, and enhanced productivity in industries such as steel production, waste incineration, and other applications where high temperatures and controlled combustion are crucial.
Oxygen interface – It refers to the boundary where oxygen interacts with another material, affecting its properties and processes like dissolution or adsorption.
Oxygen ion – It is an atom of oxygen which has gained or lost one or more electrons, resulting in a net electrical charge. Normally, oxygen atoms gain two electrons to form a negatively charged oxide ion (O2-), which has 8 protons and 10 electrons. However, oxygen can also form positively charged ions, such as O+, by losing electrons, although these are less common.
Oxygen lance – It is a length of pipe which is used to convey oxygen to the point of cutting in oxygen lance cutting.
Oxygen lance cutting – It is an oxygen cutting process which is used to sever metals with oxygen supplied through a consumable lance. The preheat to start the cutting is done by other means.
Oxygen lancing – It is a non-standard term for oxygen lance cutting.
Oxygen limitation – It refers to a condition in which the rate of oxygen consumption by aerobic micro-organisms exceeds the rate of oxygen supply, leading to a situation where the dissolved oxygen concentration falls below a critical level necessary for optimal growth rates. Under this limitation, the specific growth rate of the micro-organisms becomes dependent on the dissolved oxygen concentration.
Oxygen molecule – It is chemically known as di-oxygen and represented by the formula O2. It is a molecule consisting of two oxygen atoms joined by a strong double covalent bond. It is a di-atomic molecule, which means two atoms are bonded together, and this O2 form is the stable and normal state of oxygen at standard conditions.
Oxygen partial pressure (pO2) – It is the pressure exerted by oxygen molecules within a mixture of gases. It represents the proportional contribution of oxygen to the total pressure and is a crucial concept for understanding gas transport and exchange, as it drives the diffusion of oxygen from areas of high oxygen partial pressure to low oxygen partial pressure.
Oxygen permeability – It is the material’s inherent capacity to allow oxygen to pass through it, a property quantified by a coefficient (Dk) derived from the product of oxygen’s diffusion rate and solubility within the material. High oxygen permeability allows oxygen to move easily through a material.
Oxygen probe – It is an atmosphere-monitoring device which electronically measures the difference between the partial pressure of oxygen in a furnace or furnace supply atmosphere and the external air.
Oxygen reduction – It is an electrochemical process, in which oxygen gains electrons, typically to form water or hydrogen peroxide. This fundamental process is crucial in many electrochemical devices, including fuel cells and metal-air batteries, where it acts as a cathodic reaction to generate electrical potential.
Oxygen reduction electrode – It is an electrode where oxygen molecules gain electrons in an electrochemical reaction to form water (H2O) or hydroxyl (OH-) ions, or oxide (O2-) ions. These electrodes are important for the function of several electrochemical devices like fuel cells, batteries, and electrochemical synthesis systems. The electrode facilitates both the diffusion of oxygen gas and the movement of ions, frequently using specific catalyst materials to promote the oxygen reduction reaction.
Oxygen reduction reaction (ORR) – It is an important electrochemical process where oxygen molecules gain electrons, typically being reduced to water or hydrogen per-oxide, and is important in technologies like fuel cells and batteries. This reduction is a cathodic process which converts oxygen into a usable form, a key step in generating electrical potential and enabling energy storage and conversion.
Oxygen solubility – It is the maximum concentration of dissolved oxygen which can exist in a solvent, like water, at a given temperature and pressure. This concentration is influenced by factors such as temperature (higher temperature decreases oxygen solubility), pressure (higher pressure increases solubility), and the presence of other dissolved substances, such as salts.
Oxygen steelmaking process – It is a generic name given to those processes in which gaseous oxygen is used as the primary agent for autothermic generation of heat as a result of the oxidation of dissolved impurities like carbon, silicon, manganese, and phosphorus, and to a limited extent the oxidation of iron itself. Several types of oxygen steelmaking processes are practiced, including top blowing, bottom blowing and combined blowing. The essential features of conventional steelmaking are the partial oxidation of the carbon, silicon, phosphorus and manganese present in the hot metal and the accompanying reduction in sulphur levels.
Oxygen storage – It refers to the methods of storing oxygen either as gas in compressed cylinders or as liquid in storage units, with liquid storage being preferred for large quantities because of its cost-effectiveness and efficiency in gas delivery.
Oxygen top blown converter process – This process involves the charging of hot metal and steel scrap into a vessel or ‘converter’. A ‘lance’ is inserted into the top of the converter, and oxygen is blown into the liquid. The oxygen reacts with the iron to form an iron oxide, which reacts with carbon, as per the reaction FeO + C = Fe + CO.
Oxygen transfer efficiency – It is the percentage of oxygen which is actually dissolved in a liquid relative to the total flow of oxygen gas applied, and it is influenced by factors such as contact area, oxygen saturation, and turbulence.
Oxygen transport membrane (OTM) – It is a dense, ceramic-based membrane which facilitates the separation and transport of pure oxygen from air or other gas mixtures at high temperatures (typically above 500 deg C). It functions as a mixed ionic and electronic conductor (MIEC), allowing oxygen ions and electrons to move simultaneously through the membrane under a partial pressure gradient, which is the driving force for oxygen separation. Oxygen transport membranes offer substantial energy efficiency advantages over traditional separation methods like cryogenic distillation and pressure swing adsorption (PSA).
Oxygen vacancy – It is a defect in the crystal lattice of a metal oxide or other oxygen-containing compound where an oxygen atom or ion is missing, leaving behind a vacant site. This absence of an oxygen atom creates an empty spot in the structure and can lead to changes in the material’s electronic properties, such as increased conductivity, and influence its chemical reactivity.
Oxy-hydrogen welding – It is an oxy-fuel gas welding process which produces coalescence of materials by heating them with a gas flame or flames obtained from the combustion of hydrogen with oxygen, without the application of pressure and with or without the use of filler metal.
Oxy-tetra-methylene – It has been a formally called Poly(oxy-tetra-methylene) (POTM) or poly-tetra-hydro-furan. it is a type of polyether characterized by a chain of four-carbon (butylene) units linked by oxygen atoms, frequently terminated with alcohol groups. It’s produced by the polymerization of tetra-hydro-furan or 1,4-butanediol and serves as a soft segment in materials like poly-urethanes and polyesters, contributing flexibility and specific thermal properties.
Oyane damage criterion – It is based on stress triaxiality, which implicates the initiation of fracture.
Ozonation – It is a chemical treatment process that uses ozone (O3), a powerful oxidizing agent, to eliminate contaminants and impurities from different substances, including water, and wastewater. By either directly interacting with contaminants or generating highly reactive free radicals, ozone effectively breaks down pollutants, disinfects, decolorizes, and removes odours, making the treated substance safer and improving its quality.
Ozone – It is an inorganic molecule with the chemical formula ‘O3’ It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the di-atomic allotrope oxygen (O2), breaking down in the lower atmosphere to O2 (di-oxygen). Ozone is formed from di-oxygen by the action of ultra-violet (UV) light and electrical discharges within the earth’s atmosphere. It is present in very low concentrations throughout the atmosphere, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun’s ultraviolet (UV) radiation. Ozone’s odour is reminiscent of chlorine, and detectable by several people at concentrations of as little as 0.1 parts per million (ppm) in air.
Ozone attack – It is the deterioration and cracking of materials, mainly rubber products, caused by exposure to atmospheric ozone (O3). Ozone chemically breaks down the double bonds in polymer chains, leading to the formation of cracks which are frequently perpendicular to the direction of stress. This process, also called ozonolysis in organic chemistry, degrades the material’s integrity, potentially causing product failure, and is particularly dangerous for seals and pipes under tension.
Ozone cracking – It is a phenomenon where rubber products degrade and crack because of their exposure to ozone, a reactive gas. This occurs when rubber with unsaturated chemical bonds is subjected to tensile stress in the presence of ozone, leading to cracks which are typically perpendicular to the stress direction. The cracks can weaken the material and potentially lead to failure, especially in critical applications like fuel lines, and conveyor belts.
Ozone depletion potential (ODP) – It is a measure of a chemical’s relative ability to destroy ozone in the stratosphere compared to tri-chloro-fluoro-methane (CFC-11), which is assigned an ozone depletion potential of 1. Gases with a higher ozone depletion potential are more damaging to the ozone layer, while those with a lower ozone depletion potential are less harmful. This metric helps the international community regulate ozone-depleting substances, such as those addressed in the Montreal protocol.
Ozone layer – It is the term which is used for the high concentration of ozone (O3) that is found in the stratosphere around 15 kilometers to 35 kilometers above the earth’s surface. It covers the entire planet and protects life on earth by absorbing harmful ultraviolet-B (UV-B) radiation from the sun. It contains a high concentration of ozone in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer peaks at 8 parts per million to 15 parts per million of ozone while the average ozone concentration in earth’s atmosphere as a whole is about 0.3 parts per million. The ozone layer thickness varies seasonally and geographically.
Ozone layer depletion – Ozone depletion describes two distinct but related observations namely (i) a slow, steady decline of around 4 % per decade in the total volume of ozone in earth’s stratosphere (the ozone layer) since the late 1970s and (ii) a much larger but seasonal decrease in stratospheric ozone over earth’s polar regions during the same period. The latter phenomenon is normally referred to as the ozone hole. In addition to this well-known stratospheric ozone depletion there are also tropospheric ozone depletion events which occur near the surface in polar regions during spring.
Ozone pollution – It is a form of pollution which is characterized by high concentrations of ozone at ground level. Exposure to ozone can cause serious health problems in plants and people, and ozone pollution is a major problem in some regions of the world.
Ozonolysis – It is an organic chemical reaction where an ozone (O3) molecule cleaves (breaks) the unsaturated bonds of alkenes, alkynes, or azo compounds. This process converts the double or triple bond into carbonyl groups (aldehydes, ketones, or carboxylic acids) and is used to split larger molecules into smaller fragments, helping to determine the position of double bonds within a molecule.
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