Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘L’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘L
L1 loss – It is also known as ‘mean absolute error’ (MAE). It is a loss function used in regression tasks which calculates the average absolute differences between predicted values from a machine learning model and the actual target values. L1 Loss does not square the differences, treating all errors with equal weight regardless of their magnitude.
L2 loss – It is also known as ‘mean squared error’ (MSE). L2 loss is a loss function which quantifies the magnitude of the error between a machine learning algorithm prediction and an actual output by taking the average of the squared difference between the predictions and the target values. Squaring the difference between the predictions and actual target values results in a higher penalty assigned to more significant deviations from the target value. A mean of the errors normalizes the total errors against the number of samples in a dataset or observation.
Label – It is an informative small document attached to an object. It is a piece of paper, plastic film, cloth, metal, or other material affixed to a product, on which is written or printed information or symbols about the product or item.
Label design – It is the process of creating the aesthetic and layout for a product’s label, including images, text, and other graphics, to inform customers and make the product stand out. A good label design is important for attracting attention, increasing brand recognition, and influencing purchasing decisions. It combines brand identity with important information like the logo, ingredients, and usage instructions to communicate value to the customer.
Laboratory – It is a facility which provides controlled conditions in which scientific or technological research, experiments, and measurement can be performed. In industries, laboratory carries out the function of process control, product development, testing, and inspection.
Laboratory balance – It is a highly precise instrument used to accurately measure the mass or weight of samples in a laboratory setting. These balances are essential for several scientific and analytical tasks, including research, quality control, and production. They come in different types with each designed for specific levels of precision and capacity.
Laboratory glassware – It refers to a variety of specialized glass items used in scientific experiments and research, particularly in chemistry and biology. These items, including beakers, flasks, pipettes, and test tubes, are designed for specific functions like measuring, mixing, heating, and storing liquids.
Laboratory information management system (LIMS) – It performs in-process analysis as well as quality assurance inspections.
Laboratory of mechanical systems engineering – It is a facility for designing, testing, and researching mechanical systems, which are assemblies of components that work together to perform a function. These laboratories conduct research and development, test material properties like strength and thermal conductivity, and provide a hands-on environment to develop and test designs for systems like engines.
Laboratory report – It is a formal document which details the methods, results, and conclusions of a test or experiment. It serves as a record of the process, ensuring that the experiment can be understood, replicated, and evaluated. These reports are common in several fields and frequently follow a structured format which includes an introduction, methods, results, and discussion / conclusion.
Laboratory safety – It is a set of practices, procedures, and guidelines designed to prevent accidents and injuries by managing risks associated with a laboratory environment. This includes the proper use of personal protective equipment (PPE), correct handling of chemicals and equipment, emergency preparedness, and following established safety protocols to protect individuals and prevent the release of harmful substances.
Laboratory sample – It is a sample, intended for testing or analysis, prepared from a gross sample or otherwise got, the laboratory sample is required to retain the composition of the gross sample. Reduction in particle size is frequently necessary in the course of reducing the quantity.
Laboratory technicians – They are the person who work in a laboratory performing analytical or experimental procedures, maintaining laboratory equipment. They are skilled professionals who support scientific research and testing in a laboratory setting. They perform a variety of tasks, including preparing samples, operating equipment, analyzing data, and maintaining the laboratory’s organization and cleanliness.
Labour rate – It is the hourly cost of a worker, encompassing wages, taxes, and benefits. It is used for budgeting, pricing, and quoting projects by calculating the total expense of an employee’s time, not just their base pay. This rate helps organizations determine the true cost of labour to ensure profitability.
Labyrinth packing – It is a type of sealing mechanism, frequently used in turbines and compressors, which uses a tortuous, maze-like path to restrict the flow of fluids like gas or steam without physical contact. It consists of a series of teeth or ribs on a stationary and a rotating part which create a labyrinthine path, causing the fluid to lose energy through multiple turns and turbulence, hence minimizing leaks and preventing damage from friction.
Lacing – It is the method of attaching both ends of a belt segment using specialized fastening materials, demanding careful installation and periodic checks for tightness and integrity.
Lack of fusion (LOF) – It is a condition in a welded joint in which fusion is less than complete. Lack of fusion is the failure of the filler metal to fuse with the adjacent base metal (or weld metal from previous pass) because the surface of base metal has not reached to the melting temperature during welding. This typically occurs when welding large components which can dissipate heat quickly especially when it is at a relatively low temperature before welding. Lack of fusion is frequently seen at the beginning of the first pass and in such case, it is normally called a cold start. Also, lack of fusion can occur when the surface of the previous pass is not properly cleaned from slag where slag reduces the heating of the under-laying surface.
Lack of penetration (LOP) – It is a condition in a welded joint in which joint penetration is less than that specified. Lack of penetration is insufficient (less than specified) penetration of the weld metal into the root of the joint. This is mostly caused by improper welding parameters such as low amperage, oversized electrode, improper angle, high travel speed, or inadequate surface pre-cleaning. Also, lack of penetration can happen when the root face is too large, the root opening is too narrow, or the bevel angle is too small.
Lacquer – It is a coating formulation based on thermoplastic film-forming material dissolved in organic solvent. The coating dries primarily by evaporation of the solvent. Typical lacquers include those based on lac, nitro-cellulose, other cellulose derivatives, vinyl resins, acrylic resins, and so forth. In lubrication, it is a deposit resulting from the oxidation and / or polymerization of fuels and lubricants when exposed to high temperatures. Softer deposits are described as varnishes or gums.
Lactic acid – It is an organic acid. It has the molecular formula C3H6O3. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colourless solution. Production includes both artificial synthesis as well as natural sources.
Ladder diagram – It is a graphical programming language for industrial control systems which resembles the electrical relay logic diagrams formerly used to wire control panels. It uses two vertical ‘rails’ and horizontal ‘rungs’ to show the logical relationship between inputs (contacts) and outputs (coils). This method is normally used for programming PLCs (programmable logic controllers) and represents virtual circuits with a series of series and parallel connections.
Ladder frame – It is a structural design used in automobiles and trucks, consisting of two major frame rails connected by cross members, which provides a simple and inexpensive platform for mounting components like suspension and engines. It serves as the basis for several light-duty vehicles and can be adapted into high-performance structures.
Ladder logic – It is a conventional form of programming for programmable logic controllers (PLCs) which has been developed to replace electrical relays in control circuits. It is best suited for discrete control and interlocking applications.
Ladder network – It is a string of many, frequently equally dimensioned, impedances connected between two reference voltages.
Ladle – It is the metal receptacle frequently lined with refractories used for transporting and pouring molten metal. It is a ‘bucket’ lined with refractory (heat resistant) bricks, used to transport molten steel from process to process in a steel plant.
Ladle brick – It is the refractory brick suitable for lining ladles used to hold molten metal.
Ladle coating – It is the material which is used to coat metal ladles to prevent iron pickup in aluminum alloys. The material can only consist of sodium silicate, iron oxide, and water, applied to the ladle when it is heated.
Ladle, bottom-pour – It is the ladle from which metal flows through a nozzle in the bottom.
Ladle, bull – It is a large ladle for transporting and pouring of molten metal.
Ladle free open performance – Upon arrival of the ladle at the tundish of the continuous casting machine, it has to be opened to allow the steel to flow into the tundish. When the ladle slide gate is stroked open and steel starts to flow without operator assistance, the procedure is classified as ‘free open’. If poking or oxygen lancing is required to open the ladle, the process is classified as ‘assisted open’. When all attempts to open the ladle are unsuccessful, it is classified as ‘non-free open’. Several factors determine the opening performance of a ladle. The most dominant factor is the residence time of the steel in the ladle, followed by the ladle pre-heat practice, the elapsed time between the end of stirring and the opening of the ladle at the CCM, the cycle time for an empty ladle, and the argon stirring practice.
Ladle furnace – A ladle furnace is used to relieve the primary process of steelmaking of several of the secondary refining operations. It is one of the key components of ladle metallurgy processes. The main functions of a ladle furnace are (i) reheating of liquid steel by electric power which is conducted by graphite electrodes, (ii) homogenization of steel temperature and chemistry through argon gas rinsing, (iii) formation of slag layer which protects refractory from arc damage, concentrates and transfer heat to the liquid steel, trap inclusions and metal oxides, and provides means for desulphurization, (iv) additions of ferro-alloys to provide for bulk or trim chemical control, (v) cored wire addition for trimming and morphology control, (vi) provide a means for deep desulphurization, (vii) provide a mean for dephosphorization, and (viii) act as a buffer for downstream equipment and process.
Ladle hook – It is also known as a ‘J-hook’. It is a specialized, heavy-duty lifting device used mainly in the metals industry to safely lift, transport, and pour molten metal. These hooks are engineered to withstand high temperatures and are typically made of laminated steel plates, frequently with features like hardened steel pins and reinforced chase blocks for secure and reliable operation in steel plants and foundries. They are also used in other industrial applications, such as handling large rolls of material.
Ladle injection – Liquid steel can be reheated by oxidizing aluminum and / or silicon by means of oxygen injection through a lance. Reheating of steel in the ladle with submerged oxygen injection is being practiced in some steel plants. Injection techniques have the advantages of dispersing the reactants in the steel bath and at the same time provide a large reaction surface area. The type of powders used is governed by the purpose of injection.
Ladle, lip-pour – It is a ladle in which the metal is poured over a lip.
Ladle metallurgy – Ladle metallurgy plays a crucial role in ensuring the quality of steel products. Ladle metallurgy is sometimes also called ladle refining or secondary steelmaking. Ladle metallurgy processes are normally performed in ladles. The precise role of the ladle metallurgy varies depending on the configuration and the product range of the steel plant but there are three parameters which are required to be controlled in the processes of ladle metallurgy for ensuring high quality of steel products. These three parameters are (i) homogeneity and final value of temperature, (ii) homogenization of chemistry controlling the final levels of carbon, sulphur, phosphorus, oxygen, nitrogen, calcium, silicon, manganese, aluminum, and other alloying elements, and (iii) control of inclusions characteristics consisting of number, size, morphology, and chemistry. During the ladle metallurgy, control of these key parameters is achieved through the manipulation of three main variables namely (i) addition of chemical reagents and fluxes, (ii) heating through electrodes mounted in the roof of the ladle metallurgy station or through chemical methods, and (iii) stirring of the liquid steel in the ladle by the injection of an inert gas mainly argon gas. For achieving these controls, the operator at the ladle metallurgy station is normally provided with (i) the incoming steel chemistry, (ii) the incoming steel temperature, and (iii) the quantity of carry-over slag and its chemistry. The objectives of ladle metallurgy are (i) homogenization of chemical composition and temperature of liquid steel in the ladle, (ii) deoxidization or killing of steel for the removal of dissolved oxygen, (iii) adjustment of superheat, i.e., heating of the liquid steel to a temperature suitable for its continuous casting, (iv) additions of ferro-alloys and carburizer for making adjustments in the chemistry of liquid steel, (v) vacuum degassing for the removal of dissolved hydrogen and nitrogen gases, (vi) decarburization for the removal of carbon for meeting the requirement of certain grades of steel, (vii) desulphurization for the reduction of sulphur concentrations to levels as low as 0.002 %, (viii) micro-cleanliness i.e., removal of undesirable non-metallic inclusions, (ix) inclusion morphology i.e., changing the composition of remaining non-metallic inclusions for improving the micro-structure of the steel, and (x) improvement in the mechanical properties such as toughness, ductility, and transverse properties etc.
Ladle metallurgy furnace (LMF) – It is an intermediate steel processing unit which further refines the chemistry and temperature of molten steel while it is still in the ladle. The ladle metallurgy step comes after the steel is melted and refined in the electric arc or basic oxygen furnace, but before the steel is sent to the continuous casting machine.
Ladle opening – Ladle self-open is a heat in which the ladle nozzle does not have to be lanced open, but opens on its own. When the nozzle is to be lanced open, then the shroud is to be removed. The cast is unshrouded from ladle to tundish during the first 600 millimeters to 1,200 millimeters of the cast, and hence the reoxidation by air occurs. Hence, the total oxygen level for the self-open ladle is lower than the lanced-opened ladle. Careful packing ladle opening sand is helpful to realize ladle self-open.
Ladle preheating – It is the process of heating a ladle prior to the pouring of molten metal in it. This procedure reduces metal heat loss and eliminates moisture-steam safety hazards.
Ladle refining – The refining of steel in the ladle is broadly defined here as comprising of the operations such as deoxidation, desulphurization, dephosphorization, controlled additions of alloying elements and inclusion modification. There are a number of benefits which are available with the use of ladle refining furnace (LRF) are (i) homogenizing the composition and temperature of the liquid steel, (ii) making the steel cleaner, by the removal of oxygen inclusions, (iii) improving grain refinement in the micro-structure, (iv) degassing of the steel, through inert gas purging, (v) saving on ferro-alloys consumption, and (vi) increasing productivity, as the melting furnace gets emptied earlier. A ladle refining furnace looks similar to a ladle furnace but without the electric heating facility. The refining steel in the ladle is normally done by deoxidation of steel with ferro-manganese, ferro-silicon, silico-manganese, and aluminum.
Ladle refractories – These are the refractories which are used for the lining of ladles. These can be shaped refractories or monolithic refractories.
Ladle shroud – It is a refractory tube located between the ladle and the tundish whose main function is to protect the steel flow from secondary oxidation. Ladle shrouds do not need preheating before initial use but do if they are to be re-used after cooling down.
Ladle slag – It is a byproduct which arises from refining processes in a ladle furnace, which involves processes such as deoxidation, alloying, and desulphurization during steelmaking. It has distinct composition and properties due to the incorporation of fluxes. It is a dusty, frequently considered industrial waste material which is mainly composed of calcium, silicon, magnesium, and aluminum oxides, along with other hydraulic compounds like calcium silicates. Because of its properties, it has potential applications as a binder in construction materials.
Ladle slag reduction treatment – It has been found that minimizing slag carryover, together with adding a basic ladle slag and basic lining to lower the ladle slag to less than 1 % to 2 % of FeO + MnO, can reduce total oxygen content to 10 parts per million for low carbon aluminum killed steel. Another way to lower the FeO + MnO content of the ladle slag is to add a slag conditioner (i.e. slag reduction or deoxidation treatment), which is a mixture of aluminum and burnt lime or limestone. There is a drop in FeO + MnO content after ladle slag reduction treatment. On an average, this treatment lowers the FeO + MnO level to below 5 %. This results in sharp improvement of coil cleanliness.
Ladle, teapot – It is a ladle in which, by means of an external spout, metal is removed from the bottom rather than the top of the ladle.
Ladle to ingot mould degassing – Preheated ingot mould with hot top is placed in vacuum chamber. Above the chamber a tundish is placed. Liquid steel tapped in the ladle is at superheat equivalent of 30 deg C. The ladle is placed above the tundish. Bottom pouring of liquid steel is into the tundish is desirable.
Ladle to ladle degassing – In ladle-to-ladle degassing, a ladle with the stopper rod is placed in a vacuum chamber. Ladle containing liquid steel from primary steelmaking furnace is placed on top of the vacuum chamber and the gap is vacuum sealed. Alloy additions are made under vacuum. Stream is allowed to fall in the ladle where liquid steel is degassed. Alloy additions are made under vacuum.
Ladle turret – It is a mechanical device used in continuous casting machines to hold and rotate ladles filled with molten metal, typically steel, between the charging and casting positions. It allows for the efficient and precise transfer of molten metal from a ladle to the tundish, which then feeds the casting mould.
Lag – It is retardation or delay in the response which the instrument has to the changes in the measurement.
Lagged pulley – t is a pulley featuring a surface crowned with material, typically rubber, to improve friction with the conveyor belt. Regular checks are necessary for maintaining the effectiveness of the lagged pulley.
Lagging – It is the protective covering, often made of rubber, is applied to pulley surfaces to enhance grip and reduce slippage between the pulley and the conveyor belt. Periodic inspections are necessary to ensure proper alignment and condition. In mining, it consists of planks or small timbers placed between steel ribs along the roof of a stope or drift to prevent rocks from falling, rather than to support the main weight of the overlying rocks. In boiler, it is a light gauge steel covering used over a boiler, normally combined with insulation, to provide a low temperature outer surface.
Lag, lag time – It is a necessary break or delay between activities.
Lagoons – These are shallow, frequently elongated bodies of water separated from a larger body of water by a shallow or exposed shoal, coral reef, or similar feature. Some authorities include fresh water bodies in the definition of lagoon, while others explicitly restrict lagoon to bodies of water with some degree of salinity.
Lagrange equations – These refer to a formalism used to derive the equations of motion in mechanical systems, particularly when the geometry of movement is complex or constrained. They are based on generalized coordinates and incorporate generalized forces, allowing for the analysis of both mechanical and electro-mechanical systems.
Lagrange multipliers method – It is a local optimization technique which optimizes a function with respect to equality constraints, allowing for the analysis of complex engineering problems without needing a parametric study of system variables.
Lagrangian approach – It refers to a method which tracks the motion of individual fluid particles over time, allowing for the determination of Lagrangian coherent structures in turbulent flows. This method utilizes the initial positions of particles and the local fluid velocity to trace their paths.
Lagrangian description – It is an approach to analyze fluid motion and heat transfer by tracking the trajectories of ‘fluid parcels’ and ‘heat parcels’, which describe their positions and velocities over time. This method allows for the examination of flow and thermal behaviour in both two-dimensional and three-dimensional transient situations.
Lagrangian-based finite element method – It is a numerical simulation approach in which the computational mesh is fixed to the material and deforms with it. This contrasts with the Eulerian method where the mesh is fixed in space and material flows through it.
Lagrangian mechanics – It is a formulation of classical mechanics that uses energy rather than force to describe the motion of a system. It provides an alternative approach to Newtonian mechanics, particularly useful when dealing with complex systems or constraints. The core idea is to define a Lagrangian function, typically the difference between kinetic and potential energy, and then use the Euler-Lagrange equations to derive the equations of motion. The Lagrangian is a scalar function which depends on the generalized coordinates and velocities of a system. It is normally defined as the difference between the kinetic energy and potential energy.
Lagrangian motion – It is the analysis of a system’s movement by tracking the trajectories of individual particles over time, as opposed to observing the system from a fixed point. This approach, rooted in Lagrangian mechanics, uses the Lagrangian (L), a function defined as the system’s kinetic energy (T) minus its potential energy (V) i.e., L = T – V. By following these particles, their paths can be determined, providing a detailed understanding of the system’s dynamics.
Lagrangian representation – It refers to a method in mechanics which describes the motion of a system by focusing on individual particles and their trajectories, allowing for the application of conservation laws such as mass, linear momentum, and energy in a comprehensive manner.
Lake – It is frequently a naturally occurring, relatively large and fixed body of water on or near the earth’s surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although they can be connected with the ocean by rivers. Lakes, as with other bodies of water, are part of the water cycle, the processes by which water moves around the earth. Majority of the lakes are fresh water and account for almost all the world’s surface freshwater, but some are salt lakes with salinities even higher than that of seawater. Lakes vary significantly in surface area and volume of water.
Lake water – It is a body of standing water, either freshwater or saltwater, contained within a land-based basin. It is distinct from flowing rivers and is a part of the earth’s water cycle, frequently fed by rivers, streams, or precipitation. While most are freshwater, some can be saltwater if they have high evaporation rates and no outlet.
Lambert’s law – It states that the intensity of light decreases exponentially with the thickness of the medium it passes through. This is frequently combined with Beer’s law to form the Beer-Lambert law, which relates absorbance to both path length and concentration.
Lamb wave propagation – It refers to the elastic disturbance in thin plate-like structures characterized by unique propagation properties, which are utilized for damage identification due to their low attenuation ratio, strong penetration capability, and sensitivity to small structural damage.
Lamb waves – Lamb waves refer to a type of wave recognized for its potential in structural health monitoring systems, despite challenges such as sensitivity to environmental and operational conditions. They propagate in solid plates or spheres. They are elastic waves whose particle motion lies in the plane that contains the direction of wave.
Lamel model – It is a statistical model used for predicting deformation textures, especially during processes like rolling. It improves upon earlier models like the Taylor model by incorporating grain interactions and stress equilibrium at grain boundaries.
Lamella clarifier – It is a compact, inclined-plate type of sedimentation device used to efficiently remove suspended solids from liquids, such as waste-water. It utilizes a series of inclined plates to provide a large settling surface area in a small footprint, increasing the rate at which particles settle and collect at the bottom. This makes them ideal for space-constrained locations like waste-water treatment plants.
Lamellar corrosion – It is the corrosion which proceeds laterally from the sites of initiation along planes parallel to the surface, normally at grain boundaries, forming corrosion products which force metal away from the body of the material, giving rise to a layered appearance.
Lamellar cracking – It is a type of weld-related defect that occurs in the base metal of steel plates, particularly those with poor through-thickness ductility. It appears as cracks which run parallel to the surface of the plate, frequently in a stepped or layered pattern. This cracking is caused by tensile stresses acting perpendicular to the plate surface, especially in areas of high restraint where the weld fusion boundary is parallel to the plate’s rolling direction.
Lamellar interface – It refers to the non-bonded areas between lamellae in a thermally sprayed deposit, characterized by gaps which indicate limited contact between the layers formed during the spray coating process. These interfaces contribute to the overall microstructure and can be quantitatively characterized by parameters such as mean bonding ratio and gap width.
Lamellar morphology – It is a structure where materials are arranged in thin, alternating layers, like sheets of material stacked on top of each other. This layered arrangement is found in different fields, such as polymers, where it forms from chain folding. The specific arrangement can be influenced by factors like material composition, growth conditions, and the type of material.
Lamellar structure – It is a layered arrangement of materials, organized into flat, sheet-like layers called lamellae. This structure is found in different fields, such as materials science where it is formed from alternating layers of different materials.
Lamellar tear – It is a terrace-like fracture in the base metal with a basic orientation parallel to the wrought surface. It is caused by the high stress in the thickness direction that results from welding.
Lamellar tearing – It occurs in the base metal adjacent to weldments because of the high through-thickness strains introduced by weld metal shrinkage in highly restrained joints. Tearing occurs by decohesion and linking along the working direction of the base metal. Cracks normally run roughly parallel to the fusion line and are steplike in appearance. Lamellar tearing can be minimized by designing joints to minimize weld shrinkage stresses and joint restraint.
Lamella suspension system – This system relies on suspending the basic oxygen furnace vessel from the lower surface of the trunnion ring by means of a series of two flexible plates oriented in an inclined tangential plane to the shell. These plates, called lamellae, are separated from each other by means of a spacer, and enable radial movement of the lower vessel shell against flexural deflection of the two plates about their weak axes. In the direction of their own plane, they possess large strength and stiffness. Hence, with the aid of a stabilizer bracket between the top shell at the trunnion ring, the system can sustain loads resulting from a tilted or inverted furnace, in addition to an upright vessel. This system also provides a clean smooth inside shell surface for easy dependable bricking of the basic oxygen furnace. One of the positive features of this design is that the lamella load carrying bracket attached to the lower shell is provided in the shell region of lowest temperature. The stability of the shell, hence, is expected to be favourable. A breakout because of a burn-through does not cause difficulties in repairing or replacing the lower brackets of the lamellae.
Lamel model – Along with its successor, the advanced Lamel or ALAMEL model is a poly-crystal plasticity model used to predict the evolution of crystallographic texture (grain orientation) during plastic deformation processes like cold rolling.
Lame’s theory for thick compound cylinders – It is a method used to analyze the stresses in cylinders with thick walls which are made of multiple layers. It uses a set of equations based on assumptions like a homogeneous and isotropic material to calculate the radial and hoop stresses at any point within the cylinder wall. This theory is applicable to both a single thick cylinder and a compound one, where different layers are shrunk or shrunk-fit together to handle high internal pressures.
Lamina – It is a single ply or layer in a laminate, which is made up of a series of layers.
Laminar boundary layer – It is a thin layer of fluid along a surface where viscous forces are substantial, and the flow is smooth, orderly, and consists of parallel layers. In this layer, the fluid moves in parallel streamlines with no mixing between layers, and the fluid velocity increases from zero at the surface to around 99 % of the free stream velocity at the outer edge. This orderly flow is characterized by a low Reynolds number, typically below 500,000.
Laminar cooling process (LCP) – It is an important process in hot steel strip rolling. It is carried out for cooling of hot strip on the run-out cooling table after the last finishing stand. It is used to cool the steel strip from an initial temperature of around 800 deg C to 950 deg C down to a coiling temperature of around 550 deg C to700 deg C.
Laminar flow – It is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another smoothly. There are no cross-currents perpendicular to the direction of flow, nor eddies or swirls of fluids. In laminar flow, the motion of the particles of the fluid is very orderly with particles close to a solid surface moving in straight lines parallel to that surface. Laminar flow is a flow regime characterized by high momentum diffusion and low momentum convection.
Laminar flow separation – It is the phenomenon where the smooth, orderly flow of a fluid detaches from a surface, causing the flow to break away from the object it is moving past. This occurs when the fluid’s boundary layer, moving parallel to the surface, can no longer stay attached because of the factors like adverse pressure gradients. When this happens, a region of chaotic, recirculating flow can form downstream of the point of separation.
Laminar sub-layer – It is a thin layer of fluid adjacent to a pipe wall where turbulence effects are negligible, characterized by a no-slip boundary condition and a constant shear stress, resulting in a linear velocity variation within this layer.
Laminate – It consists of a composite metal, normally in the form of flat sheets, composed of two or more metal layers so bonded that the composite metal forms a structural member. It also means forming a metallic product of two or more bonded layers. It also means to unite laminae with a bonding material, normally with pressure and heat (normally used with reference to flat sheets, but also rods and tubes). Laminate is a product made by such bonding.
Laminate coordinates – It consists of a reference coordinate system (used to describe the properties of a laminate), normally in the direction of principal axes, when they exist.
Laminated beam – It is a structural element made by bonding multiple layers of material, very frequently wood, together to create a single, stronger, and more stable component. This lamination process, also known as a glued laminated timber (glulam) process, uses durable adhesives to join layers of wood, allowing for the creation of beams with larger size and higher strength than those achievable from a single piece of lumber.
Laminated composite materials – These are made from multiple layers of different materials, or the same material with different fibre orientations, bonded together to create a single, stronger material with improved properties. These layers, called plies, are stacked and then consolidated using adhesives or other bonding agents. The orientation of the fibres in each layer can be varied, and the resulting material frequently has superior strength, stiffness, and impact resistance compared to its individual components.
Laminated composite plate – It is a multi-layered structural component made by bonding layers (laminae) of different materials, typically fibre-reinforced materials, together to create a single, cohesive unit. These plates are engineered to achieve superior properties like high strength-to-weight ratio, stiffness, and durability which are superior to the individual materials alone. They are custom-designed by adjusting the number, orientation, and thickness of the layers, making them crucial in applications needing high performance.
Laminated composite structure – It is a material made by stacking and bonding multiple layers (laminae) together with different orientations and properties to create a single, strong component. These structures have a high strength-to-weight ratio and are used in applications which need high performance, since the layered design allows for properties to be tailored for specific needs.
Laminated glass – It is a type of safety glass made by bonding two or more glass panes together with a plastic interlayer, very frequently poly-vinyl butyral (PVB). This interlayer holds the glass fragments together if the glass breaks, preventing it from shattering into dangerous pieces. It is used in applications like car windshields, high-rise windows, skylights, and floors to increase safety, security, and noise insulation.
Laminated metal composites (LMCs) – These are a unique form of composite material in which alternating metal or metal containing layers are bonded together with discrete interfaces. The mechanical properties of these materials are reviewed.
Laminated object manufacturing – It is a rapid prototyping system. In it, layers of adhesive-coated paper, plastic, or metal laminates are successively glued together and cut to shape with a knife or laser cutter.
Laminated structure – It is a composite material made of multiple layers, or ‘laminae’, of different materials which are permanently bonded together with an adhesive. This stacked structure is designed to achieve desired properties, such as high strength and stiffness, by orienting the layers in specific ways, allowing them to act as a single unit.
Laminate layup – It is the process of stacking multiple layers (plies) of material in a specific sequence and orientation to create a composite material. This arrangement is designed to achieve desired mechanical properties, such as strength and stiffness, by combining the properties of individual layers in different directions. The ‘layup’ specifies the material, thickness, and orientation angle for each ply in the stack.
Laminate level – It is a term used to describe the structural level where multiple plies or layers are bonded together in a specific orientation. This layered structure is designed to give the material desired strength and stiffness properties, and the orientation of each layer is critical to its overall performance. In the context of laminate flooring, a laminate level refers to the individual layer within the floor’s multi-layered construction, such as the wear layer, decorative layer, core layer, or backing layer.
Laminate orientation – It is the configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.
Laminate ply – It consists of one fabric-resin or fiber-resin layer of a product which is bonded to adjacent layers in the curing process.
Laminate’s shear modulus – It is the ratio of shear stress to shear strain, measuring its resistance to shear deformation, or ‘sliding’ between layers. It is a mechanical property of a multi-layered material which can be expressed in relation to the moduli of its constituent layers. This value quantifies how much stress is needed to produce a certain quantity of shear strain within the composite material.
Laminate stiffness – It is a composite material’s resistance to deflection under an applied force, such as bending or stretching. It is determined by the combined properties of its individual plies, including their material, thickness, and how they are stacked. Higher stiffness means the laminate is more resistant to deformation.
Laminate thickness – It is the measurement of a laminate material’s depth, which determines its durability, stiffness, and suitability for different applications. It is typically measured in millimeters for sheets and flooring, or in micrometers for films and pouches. For example, laminate sheets range from 0.6 millimeters to 1.5 millimeters, while flooring can be from 6 millimeters to 15 millimeters or more.
Lamination – It is a type of discontinuity with separation or weakness normally aligned parallel to the worked surface of a metal. It can be the result of pipe, blisters, seams, inclusions, or segregation elongated and made directional by working. In forged products, laminations are large porosity, pipe and non-metallic inclusions in slabs, blooms, or billets which are flattened and spread out during forging process. Laminations can also occur in powder metallurgy compacts. In electrical products such as motors, it is a blanked piece of electrical sheet which is stacked up with several other identical pieces to make a stator or rotor.
Lamination process – It is the method of assembling individual sheets of materials into a multi-layered component, typically involving the pressing of sheets together with or without adhesives, and can include the application of heat.
Lamination technology – It is the process of bonding two or more layers of material, such as plastic, paper, or glass, together using heat, pressure, or adhesive to create a single, stronger, or more durable composite product. This layered structure can improve properties like strength, durability, scratch resistance, and water resistance. Common applications range from protective paper documents and durable flooring to reinforced materials like safety glass and advanced packaging.
Lamp – It is a device for giving light, either one consisting of an electric bulb or tube together with its holder and shade or cover, or one burning gas or oil and consisting of a wick or mantle and a glass shade.
Lampblack – It is the fine soot which is used in the reduction and carburization of tungsten tri-oxide and titanium di-oxide to produce tungsten carbide, and titanium carbide powders respectively.
Lamprophyre – It is an igneous rock, composed of dark minerals, which occurs in dykes. It sometimes contains diamonds.
LAN – It is local area network, which is an interconnection of computers over a building or small campus.
Lance – In a blast furnace, it is a small diameter pipe fitted at an angle in the blow pipe through which auxiliary fuel / oxygen is injected in the blast furnace. In the basic oxygen furnace steelmaking, it is a long metallic tube through which oxygen is blown into the converter under high pressure. The 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 works as the source of feeding oxygen and energy for stirring of the liquid metal in the bath. Major in-furnace phenomena of a basic oxygen converter that involve the top-blowing lance oxygen jet are formation of a cavity as a result of physical interaction between the oxygen jet and liquid metal, stirring of liquid metal, generation of spitting and dust, and post combustion of carbon mono-oxide gas generated by decarburization and reaction with oxygen.
Lance bubbling equilibrium (LBE) process – It is a combined blowing process which is much more closely related to the basic oxygen furnace process in that all the oxygen is supplied from the top lance. The combined blowing aspect is achieved by a set of porous elements installed in the bottom of the converter through which argon or nitrogen is blown. In this process, nitrogen gas is typically used almost exclusively for the majority of the blow in the range of 3 normal cubic meter per minute to 11 normal cubic meter per minute. However, in the later part of the blow, when nitrogen absorption can create a problem, argon gas is used for stirring. The inert gases are introduced at the bottom of the furnace by means of permeable elements.
Lancing – It is a press operation in which a single-line cut is made in strip stock without producing a detached slug. It is mainly used to free metal for forming, or to cut partial contours for blanked parts, particularly in progressive dies. It is also a piercing (cutting) process carried out by metal powder cutting or oxy-fuel gas cutting. Lancing with oxygen is a cutting process. In this process, oxygen is supplied through a consumable steel pipe to pierce holes in metallic and mineral work-pieces. The lance is lighted and steadily consumed. It involves a number of steel wires packed into the steel tube.
Lance, oxygen – It is a device which used to deliver pure oxygen into a high-temperature industrial process, such as steelmaking. It consists of a long, heat-resistant tube with a nozzle at the end which directs a controlled, frequently supersonic, jet of oxygen onto molten metal or other materials to remove impurities or improve combustion. The term can also be used more generally for a long steel tube which conveys oxygen for thermal cutting or other piercing operations.
Lance tip – It is the specialized, frequently multi-nozzled end of a lance used to direct a high-velocity stream of gas, typically oxygen, onto a molten metal bath. Its main function is to control and accelerate chemical reactions in metallurgical processes like steelmaking, which involves high-temperature environments that can cause rapid erosion of the tip itself.
Land – For profile-sharpened milling cutters, it is the relieved portion immediately behind the cutting edge. For reamers, drills, and taps, it is the solid section between the flutes. On punches, it is the portion adjacent to the nose which is parallel to the axis and of maximum diameter. In die design, land is the straight, parallel inner wall section of a die opening, located just below the cutting edge. In case of cutting tool geometry, land is a small, flat area on a cutting tool which connects the tip of the cutting edge to the rake angle. In welding, it is a non-standard term for root face.
Land degradation – It refers to the persistent reduction of land’s productive capacity, often manifested through processes like soil erosion, nutrient depletion, loss of biodiversity, deforestation, or declining vegetative health.
Landfill – It is a location on land where wastes are placed for permanent disposal.
Landfill gas – It refers to the carbon di-oxide, methane, and other compounds which are produced during the decomposition of organic waste.
Land lease – It is a contract where a landowner (lessor) grants another party (lessee) the right to use and occupy the land for a specified period, typically with the option for the lessee to build on the land, with the land and any improvements reverting to the landowner at the lease’s end.
Land pollution – It is the degradation of land surfaces frequently caused by human activities and the misuse of land resources. It occurs when waste is not disposed properly.
Land preparation – It is the process of transforming a site into a suitable state for its intended purpose, which can be for construction. This involves a range of activities like clearing, grading, tilling, and installing infrastructure to ensure the land is physically capable of supporting the project and meets operational, safety, and environmental standards.
Land reclamation – It is the process of creating new land or improving existing land, frequently by dredging, filling, or raising the elevation of waterbeds or low-lying areas, to make it suitable for various uses like agriculture, building, or industry.
Landscape drawing – The landscape drawing is the aerial view of the whole area in which the building is built. It includes the areas designated for trees, street lights, parks, pools, and everything else. Landscape plan is more frequently used to depict the external aesthetics of the building. One can also include in them the paths, roads, pavements, parking areas, and several other things.
Landslide – It is a mass of material which has moved downhill by gravity. It is frequently assisted by water when the material is saturated. The movement of soil, rock, or debris down a slope can occur rapidly, or may involve slow, gradual failure.
Land surface air temperature – It is the air temperature as measured in well-ventilated screens over land at 1.5 meters to 2 meters above the ground.
Land surveying – It refers to the determination of the three-dimensional position of points and the distances and angles between them, frequently on the earth’s surface. This involves measuring and mapping land features to create maps, establish property boundaries, and guide construction projects. Essentially, it provides the spatial data necessary for different engineering and construction activities.
Land thickness – It is the length measurement of the straight, parallel inner wall section of a die opening.
Land use – It is the term used to describe the human use of land. It represents the economic and cultural activities (e.g., agricultural, residential, industrial, mining, and recreational uses) which are practiced at a given place. Public and private lands frequently represent very different uses.
Land use change – It refers to the alteration or conversion of land’s use by humans from one purpose to another, such as transforming forests into agricultural land or industrial areas.
Land use Intensity – It is the measure of the extent and impact of human activity on a given land area, considering factors like resource application, development, and ecological modification. It quantifies how heavily a piece of land is utilized, with higher intensity indicating more significant human effort, resource use, and development.
Langelier saturation index – It is an index calculated from total dissolved solids, calcium concentration, total alkalinity, pH, and solution temperature which shows the tendency of a water solution to precipitate or dissolve calcium carbonate.
Lang lay – In lang lay, the wires form an angle with the axis of the rope. The wire lay and strand lay around the core in the same direction. The wires and strands appear to run at a diagonal to the centre line of the rope. Lang lay wire ropes are distinguished between left hand lang lay (LHLL) and right hand lang lay (RHLL). Because of the longer length of the exposed outer wires, lang lay ropes have higher flexibility. These ropes are more likely to twist, kink, and crush. Lang lay ropes have a higher fatigue-resistance and are more resistant to abrasion. The advantages of lang lay ropes are (i) better contact in the groove of the sheaves, (ii) superior resistance to wear, (iii) longer lifetime in case of high dead loads, and (iv) considerably better spooling behaviour on a multi-layer drum.
Langmuir adsorption – It is a model for monolayer adsorption which describes how molecules from a fluid phase (gas or liquid) adhere to a homogeneous solid surface at equilibrium. It is based on the assumptions that each adsorption site on the surface can only hold one molecule, there are no interactions between adsorbed molecules, and the surface is uniform. This model is used to quantify adsorption capacity and has applications in areas like catalysis, separation processes, and surface area measurement.
Langmuir affinity constant – It quantifies the affinity of a species for a surface in an adsorption process, indicating the strength of interaction between an adsorbate and an adsorbent. A higher value of this constant indicates a stronger interaction and a higher tendency for the substance to adsorb onto the surface. This is a key parameter in the Langmuir adsorption model, which assumes a homogeneous surface and monolayer adsorption.
Langmuir-Blodgett (LB) method – It is a technique for creating ultrathin, ordered films by transferring monolayers from a liquid (air-water) interface onto a solid substrate. In this process, molecules are spread on the water’s surface to form a mono-layer, which is then compressed to the desired density using a barrier. A solid substrate is then dipped vertically through the mono-layer, with the film transferring to the surface in a controlled manner. This process can be repeated to build multi-layers with controlled thickness and molecular arrangement.
Langmuir–Freundlich isotherm – It is a model which explains the distribution of adsorption energy on the surface of heterogeneous sorbents, showing Langmuir behaviour at high adsorbate concentrations and Freundlich behaviour at low concentrations.
Langmuir isotherm – It is a model describing the relationship between a gas or solute and a solid surface at equilibrium, assuming a monolayer adsorption onto a homogeneous surface with no interaction between adsorbed molecules. It is used to predict the quantity of a substance adsorbed as a function of pressure (for gases) or concentration (for solutes) at a constant temperature. The model assumes adsorption and desorption are reversible and that all adsorption sites are equivalent and have the same energy.
Langmuir kinetics – It describes the rates of reactions which occur on a surface, particularly when reactants first adsorb onto active sites before reacting. It is used to model processes like heterogeneous catalysis, where a reaction is limited by the surface steps of adsorption, reaction, and desorption. The Langmuir-Hinshelwood mechanism is a common model which mathematically represents these steps using Langmuir adsorption isotherms to define reactant coverage on the surface.
Langmuir volume – It refers to the gas volume at infinite pressure, representing the maximum storage capacity for gas in a solid surface as described by the Langmuir isotherm.
Lankford coefficient – It is also known as the plastic strain ratio or R-value. It measures a metal sheet’s plastic anisotropy by defining the ratio of true strain in width to true strain in thickness during a tensile test. A higher R-value indicates a higher resistance to thinning, which improves the material’s formability, especially in processes like deep drawing where thickness uniformity is critical. It is an important parameter in sheet metal forming, particularly in processes like deep drawing, where maintaining uniform thickness is essential.
Lantern ring – It is a perforated hollow ring located near the centre of the stuffing box of a pump. In spite of its simplistic appearance, it plays a crucial role in successfully operating a pump system.
Lanthanide series – It is also known as the lanthanoids or rare earth elements. It refers to a group of 15 chemically similar metallic elements with atomic numbers 57 through 71, starting with lanthanum and ending with lutetium. These elements are characterized by the filling of the 4f electron shell and are typically found in the f-block of the periodic table. he series includes lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).
Lanthanoids – It is also known as lanthanides. These are a series of 15 metallic chemical elements with atomic numbers 57 to 71, from lanthanum (La) to lutetium (Lu). They are part of the f-block of the periodic table and are often referred to as rare earth elements.
Lanthanum (La) – It is a chemical element having atomic number 57. It is a soft, ductile, silvery-white metal which tarnishes slowly when exposed to air. It is traditionally counted among the rare earth elements. Like most other rare earth elements, its normal oxidation state is +3, although some compounds are known with an oxidation state of +2.
Lanthanum manganite – It is an inorganic compound with the formula LaMnO3. It belongs to the perovskite family of materials. It has a perovskite crystal structure and is known for its electronic and magnetic properties, which can be altered by doping it with other elements like strontium or calcium to create materials used as cathode materials in high-temperature applications such as solid oxide fuel cells.
Lanthanum strontium manganite – It is an oxide ceramic material with the general formula La1-xSrxMnO3, where x describes the doping level. It has a perovskite-based crystal structure, which has the general form ABO3. In the crystal, the ‘A’ sites are occupied by lanthanum and strontium atoms, and the ‘B’ sites are occupied by the smaller manganese atoms. In other words, the material consists of lanthanum manganite with some of the lanthanum atoms substitutionally doped with strontium atoms. The strontium (valence 2+) doping on lanthanum (valence 3+) introduces extra holes in the valence band and hence increases electronic conductivity. This compound is normally used as a cathode material in high-temperature solid oxide fuel cells (SOFCs), known for its high electrical conductivity, electro-chemical activity for oxygen reduction, thermal stability, and excellent micro-structural and long-term performance stability.
Lap – It is a surface imperfection, with the appearance of a seam, caused by hot metal, fins, or sharp corners being folded over and then being rolled or forged into the surface but without being welded. In case of forging, lap is a surface imperfection in worked metal caused by folding over a fin overfill or similar surface condition, then impressing this into the surface by subsequent working without welding it. In filament winding, it is the quantity of overlay between successive windings, normally intended to minimize gapping. In bonding, it is the distance one adherend covers another adherend.
Lap gate – It is also known as a kiss gate or touch gate. It is a specific type of ingate where the connection point between the runner and the casting intentionally overlaps onto the cope (top) surface of the mould. The main characteristic is that the molten metal enters the mould cavity in a way that the connection point is spread across or overlaps the parting line area, specifically favouring the upper mould half (cope) surface. This design helps manage the flow of metal and can assist in the removal of the gating system after the metal has solidified. This differs from other gate types (like bottom or top gates) by its specific placement relative to the mould’s parting line and is used to achieve specific flow characteristics or aid in manufacturing ease, for example, making it easier to ‘flog’ or knock off the gate from the finished casting.
Laplace distribution – It is also known as the double exponential distribution. It is a continuous probability distribution which is symmetric with a sharp peak and heavier tails than a normal distribution. It is defined by two parameters namely a location parameter and a scale parameter. It can be thought of as the combination of two exponential distributions with different signs, and it is frequently used to model phenomena with heavy-tailed noise or high concentrations of values near the mean.
Laplace transform – It converts a function of a time variable, into a function of a complex frequency variable. This transformation is a mathematical tool which simplifies differential equations by converting them into algebraic equations, which are easier to solve. It is widely used in engineering and applied mathematics, especially for analyzing systems like circuits and mechanical systems.
Laplace transform method – It is a technique for deriving the response of a system to different stimuli by transforming time-varying functions into a complex frequency domain, hence simplifying the integration process and allowing for easier solution of differential equations.
Lap joint – A lap joint is formed when the surfaces of the two pieces overlap one another. The weld is deposited in the joint where the two intersect. A lap joint shows good mechanical properties, especially when a person weld both sides of the overlapped pieces, which provides extra reinforcement. The quantity of overlap needed in the joint id determined by the thickness of the two work-pieces. The thicker is the material, the more overlap is needed. Lap joints are very common for joining plates or sheet metal. With lap joints, it is important to make sure there are no gaps between the two workpieces. One wants them to be as flush as possible. In composites, lap joint is a joint made by placing one adherend partly over another and bonding the overlapped portions.
Lap joint flange – Lap joint flange is used with a lap joint stub end fitting and comprised of a hub or ‘stub end’ welded to the pipe and a backing flange or capped flange which is used to bolt the joint together. This means the stub end always makes the face. It is similar to a slip-on flange, but with two differences. The radius and the flat face, both allow the flange to secure against the stub end fitting. This is useful where alignment of bolt holes is difficult, such as with spools to be attached to flanged nozzles of the vessels. This type of flanged joint is typically found on high alloy pipework.
Lapping – It is a surface finishing process involving motion against an abrasive embedded in a soft metal. It is a finishing operation which uses fine abrasive grits loaded into a lapping material such as cast iron. It is also rubbing of two surfaces together, with or without abrasives. It is a precision finishing process which uses abrasive particles suspended in a liquid (a slurry) to smooth and refine surfaces, frequently after grinding or other machining operations. It achieves high levels of flatness, surface finish, and dimensional accuracy. Lapping is also a construction method involving the overlapping of materials like reinforcement bars or concrete to ensure structural integrity.
Lapping machine – It is a precision tool which creates extremely smooth and flat surfaces on a work-piece by using an abrasive slurry on a rotating plate. It works by holding a part against a lapping plate, which is frequently a rotating disc, while a liquid abrasive mixture is applied to the surface. This process is used in different industries to achieve high levels of flatness, parallelism, and surface finish with very tight tolerances.
Lapping plate – It is a flat, precision tool used to achieve ultra-smooth and accurate surfaces through a process called lapping. It serves as the surface on which a work-piece is rubbed with an abrasive slurry to remove imperfections like scratches and burrs, resulting in a highly flat and polished finish. These plates are made from different materials like cast iron, glass, or ceramic, depending on the application.
Lapping process – It is a precision machining technique which is used for achieving high levels of flatness, surface finish, and dimensional accuracy. It is an abrasive machining method which involves use of a highly abrasive slurry or paste, along with a rotating lap or work-piece, to remove material from the surface of a work-piece. This process produces flat and smooth surfaces.
Lap-seam welding – It is a type of resistance welding where two or more work-pieces are placed with their edges slightly overlapping and then continuously joined together by a seam weld. The process uses rotating, wheel-shaped electrodes which apply pressure and pass an electric current to melt, mash, and fuse the overlapping metal into a single, continuous seam, creating an airtight and watertight joint. This technique is frequently used for applications like fuel tanks, pressure vessels, and watertight appliances.
Lap seam weld joint – It is formed when two pieces of material are overlapped and then continuously welded along the seam of the overlap. This creates a strong, frequently fluid-tight joint, especially useful when welding sheet metal. The overlapping metal is welded along the seam, and the joint is characterized by the continuous weld bead along the overlap.
Lap shear joint – It is a joint where two materials overlap each other, and it is subjected to a force which attempts to pull them apart in shear. This type of joint is normally studied to measure the strength of the bond, using a lap shear test to determine the force required to break the adhesive or weld. Despite being called a ‘lap shear’ test, it frequently fails because of the peel forces concentrated at the ends of the overlap, not pure shear.
Lap shear strength – It is the measure of a bonded joint’s ability to withstand shear stress, which is force applied parallel to the bonded surfaces. It is determined by testing the force needed to pull two overlapped materials apart until the adhesive bond fails. This value is expressed as a force per unit area and indicates an adhesive’s long-term durability in applications.
Lap shear test – It is a destructive test which measures the strength of an adhesive joint by pulling two bonded surfaces in opposite directions until they fail. This test is used to determine how much shear stress the bond can withstand, making it a key method for evaluating the effectiveness of adhesives and bonded materials like metals, composites, and plastics in different industries.
Lap splice – It is a method used in construction to join two reinforcement steel bars (rebar) by overlapping them for a specific length, called the lap length. This process is necessary when a single bar is not long enough to span a needed distance, and it ensures that the load is transferred from one bar to the next through bond stress with the surrounding concrete.
Large amplitude vibration – It refers to oscillations which are substantial in size, frequently meaning they deviate substantially from the equilibrium position. This term is used to describe loud sounds and mechanical systems, and to describe phenomena like flow-induced vibrations.
Large complex systems – These refer to systems characterized by a large number of interacting components which show complex behaviours and dynamics, frequently needing advanced modelling and control techniques to analyze and design effectively. These systems are prevalent across different engineering fields, including power systems, and manufacturing.
Large deformation – It describes a substantial change in an object’s shape or size because of the stress, where traditional assumptions of small, infinitesimal changes are no longer valid. This type of deformation introduces geometric non-linearities, meaning the object’s stiffness and response change continuously as it deforms. It is important for analyzing complex behaviours in applications like metal forming, and rubber elasticity.
Large-end bearing – It is a bearing at the larger (crankshaft) end of a connecting rod in an engine.
Large flow rate – It is a high volume of a fluid passing through a point per unit of time, with the exact definition depending on the context and specific application. For example, it can mean a high rate of fluid delivery in processes like nano-fibre production, a high volume of gas from a well, or the maximum capacity of a pump.
Large industrial customer – It is an entity with a substantial and complex process load which demands a high volume of industrial goods and services, frequently exceeding that of medium industrial customers. They are typically distinguished by substantial energy consumption, complex operations, and long-term relationships with suppliers. Specific definitions can vary based on industry, but they are frequently defined by a high level of consumption (e.g., exceeding a certain megawatt threshold) or through specific classifications within a rate tariff.
Large molecular mass – It refers to materials with a molecular weight above a certain threshold, typically considered higher than 500 atomic mass units (amu) or Daltons (Da). This is common in large molecules like polymers and macromolecules, and it often requires specialized techniques such as size exclusion chromatography or specific mass spectrometry methods for characterization.
Large production volume – It refers to the manufacturing of a high quantity of standardized products to meet market demand, characterized by the use of automation, assembly lines, and specialized equipment to achieve efficiency and lower per-unit costs through economies of scale. This is also known as mass production and is crucial for several industries.
Large Reynolds number (Re) – It indicates a fluid flow where inertial forces dominate viscous forces, resulting in highly turbulent flow. It is a dimensionless quantity representing the ratio of inertia to viscosity, and a high value means the flow is chaotic, with vigorous mixing rather than smooth, streamlined motion. The formula for Reynolds number is Re = UL/v, where ‘U’ is velocity, ‘L’ is a characteristic length, and ‘v’ is kinematic viscosity.
Larger heat exchanger surface – It refers to an expanded physical area within a heat exchanger, designed to increase the efficiency of heat transfer between two fluids. This is achieved by increasing the total surface area of the walls which separate the fluids, frequently using features like fins or corrugations to maximize contact and improve performance. A higher surface area allows for a higher rate of heat exchange, making the device more effective at transferring thermal energy.
Large-scale fire – It is a fire which is extensive in area or intensity, such as a wildfire burning over 120 hectare or a fire whose behaviour is determined by its interaction with weather conditions. It can also refer to fires which are large enough to generate substantial toxic gases, heat, and radiant energy, or fires used in large-scale testing to evaluate the safety of different systems.
Large-scale hydrogen storage – It is the practice of storing substantial quantities of hydrogen, frequently to balance the intermittency of renewable energy sources like solar and wind. This can involve storing hydrogen in large, geologically stable underground caverns (especially salt caverns), using compressed gas or liquid hydrogen, or using chemical methods like liquid organic hydrogen carriers (LOHCs). The main goal is to ensure a reliable, consistent supply for industrial use and to stabilize the electrical grid over long periods, such as weeks or months.
Large scale integrated circuit – It is an electronic circuit with thousands of components, such as transistors, etched onto a single chip. Large scale integrated circuits have been a significant step in semi-conductor technology, bridging the gap between medium and very large-scale integration. They enabled the creation of more powerful and compact electronics by consolidating several discrete components into one chip, making systems cheaper, more efficient, and faster.
Large-scale integration – It is the process of creating an integrated circuit by combining millions or billions of metal-oxide-semiconductor (MOS) transistors onto a single chip.
Large-scale processing environment – It is a computing infrastructure and associated methodologies designed to handle vast volumes of data, high computational complexity, or a substantial number of simultaneous users, which exceed the capacity of conventional or local resources.
Large-scale renewable energy integration – It is the process of connecting substantial quantities of renewable energy sources, such as solar and wind, into the existing electrical grid. This involves overcoming technical challenges like the intermittent nature of these sources and ensuring grid stability, reliability, and power quality. The goal is to achieve a clean energy future by increasing the proportion of renewable energy without compromising the security of the electricity supply.
Large-scale solar thermal plant – It is a facility which uses concentrated sunlight to generate heat, which then produces electricity. These plants work like traditional power plants, but instead of burning fuel, they use a system of mirrors, such as heliostats or parabolic troughs, to focus solar radiation onto a receiver. This focused heat generates steam to spin a turbine connected to an electric generator.
Large-scale systems – These are complex, high-order systems with several interconnected parts which are difficult to model and control using conventional methods. They are defined by a large number of variables, components, or users, and frequently need special approaches like partitioning into smaller subsystems, distributed control, or specialized software to manage their complexity. Examples include the internet, large-scale distributed computer networks, and complex industrial or transportation systems.
Large-scale wind integration – It is the process of connecting substantial wind farms to the electric power grid, needing new operational strategies to manage the variable nature of wind power. This process involves overcoming technical challenges like grid stability, power quality, and frequency control, frequently necessitating the use of technologies such as pumped storage, forecasting models, and updated grid codes to ensure reliable power delivery.
Large-scale yielding – It is a condition where a substantial portion of a material undergoes plastic deformation, extending beyond the localized area at a crack tip. This phenomenon is characterized by the plastic zone becoming large enough that its behaviour is dependent on the sample’s geometry rather than just the material’s intrinsic properties, as traditional elastic assumptions are no longer valid. It often occurs in situations with high applied loads, such as fatigue and thermal loadings.
Largest principal stress – It is the maximum stress value acting on a material, which, as per the maximum principal stress theory, leads to yielding when it equals the yield strength of the material. This stress is a critical factor in evaluating the failure of pressure vessels under biaxial states of stress.
Large volume pump – It is a term used for a pump designed to handle a high flow rate of fluid, rather than a high pressure. The definition of ‘large’ is relative to the specific application and industry, but in industrial contexts, it can refer to capacities of 115 cubic meters per hour or higher.
Larmor frequency – It is the classical frequency at which a charged body precesses in a uniform magnetic field. wL = -eB/2mc, where ‘e’ is the electron charge, ‘B’ is the magnetic field intensity, ‘m’ is mass, and ‘c’ is the velocity of light. Larmor precession is the precession of the magnetic moment of an object about an external magnetic field. The phenomenon is conceptually similar to precession of a tilted classical gyroscope in an external torque-exerting gravitational field.
Larmor period – It is the inverse of the Larmor frequency. It is the time it takes for a magnetic moment to complete one full cycle of precession around an external magnetic field. In simpler terms, it is the time it takes for a spinning charged particle to wobble once around the direction of the magnetic field.
Larson–Miller parameter (LMP) – It is also known as the Larson–Miller relation. It is a parametric relation used to extrapolate experimental data on creep and rupture life of engineering materials.
Laser – It is an acronym for light amplification by stimulated emission of radiation. Laser is a device which produces a concentrated coherent light beam by stimulating electronic or molecular transitions to lower energy levels.
Laser additive manufacturing – It is a digital manufacturing process which uses a laser to build 3D objects by adding material layer by layer, based on a computer design. Common methods include selective laser melting (SLM) and laser metal deposition (LMD), which create objects from materials like metal, polymer, or ceramic powders and are used for rapid prototyping and producing complex, high-performance parts.
Laser alloying – It is the use of lasers for surface (laser) alloying. In it the alloying elements are added to the melt pool to change the composition of the surface. The new structures produced by laser surface melting and alloying can show improved electro-chemical and tribological behaviour.
Laser application – It is the use of lasers in different fields, leveraging their unique properties like high directionality and coherence for purposes such as industrial cutting and welding, and tele-communications. These applications are categorized by the properties of the laser light, including its ability to precisely deliver energy for cutting, and its wave-like characteristics for data transmission and measurement.
Laser-arc hybrid welding – It is a welding technique which simultaneously combines a laser beam and an electric arc in the same joint area to join materials. This synergistic process merges the advantages of both methods, such as the deep penetration and high welding speed of laser welding with the excellent gap-bridging and cost-effectiveness of arc welding. It allows for faster production, deeper penetration, and improved weld quality compared to using either process alone.
Laser-based scanning system – It is a technology which uses a laser beam to measure and capture the physical characteristics of an object or environment, creating a digital representation, such as a 3D point cloud. These systems work by either projecting a laser onto a surface and analyzing the reflected light to calculate distances or by using the laser to scan across a sample to build up an image or model.
Laser beam axis – It is the straight line which represents the centre of the laser beam’s path, connecting the centroids of its cross-sectional power distribution at successive points along the direction of propagation. It is the central line along which the beam is directed, and it acts as a reference for measuring properties like divergence and position.
Laser beam butt welding – It is a process where two pieces of metal are placed end-to-end and joined by a highly focused, high-energy laser beam which melts and fuses the edges. This technique creates a high-strength weld with low thermal distortion, high precision, and fast speeds, making it ideal for automated and high-accuracy applications in several industries.
Laser beam cutting – It is a thermal cutting process which severs materials by melting or vapourizing them with the heat got from a laser beam, with or without the application of gas jets to augment the removal of material.
Laser beam energy – It is the total quantity of energy delivered by a laser beam, which is calculated by multiplying the laser’s power by the duration of its exposure. This energy can be measured in joules (J) and is a key factor in several applications, such as cutting materials, or transmitting signals. It is determined by the beam’s characteristics, including its output power, wavelength, and exposure time.
Laser beam machining – It consists of the use of a highly focused mono-frequency collimated beam of light to melt or sublime material at the point of impingement on a work-piece.
Laser beam power – It is the rate at which energy is delivered by a laser beam, measured in watts. It represents the total energy emitted per second, and it can be continuous or pulsed, with pulsed lasers also having a ‘peak power’ which is the maximum power of a single pulse.
Laser beam welding (LBW) – It is a welding process which produces coalescence of materials with the heat got from the application of a concentrated coherent light beam impinging upon the joint. In this process a high energy laser beam is targeted on the work-piece. The laser beam heats and melts the edges of the work-piece, forming a joint. Laser beam welding uses a moving high-density coherent optical energy source called a laser as the source of heat. The coherent nature of the laser beam allows it to be focused to a small spot, leading to high energy densities. The energy of a narrow laser beam is highly concentrated, so a weak weld pool is formed very rapidly. The solidification of the weld pool surrounded by cold metal occurs as rapidly as the melt. Since the time the molten metal is in contact with the atmosphere is low, there is no contamination and hence no gradient (neutral gas, flow) is needed. In laser beam welding the joint is made either as a sequence of overlapped spot welds or as a continuous weld.
Laser bending – It is a manufacturing process where a high-power laser beam heats a metal sheet to induce thermal stresses, which cause it to bend. This thermo-mechanical process uses a laser instead of traditional mechanical tools, deforming the material through mechanisms like temperature gradients and thermal expansion. It is a contactless method used for different applications for forming both simple and complex shapes.
Laser brazing – It is a joining process which uses a high-energy laser beam to melt a filler metal (like a wire or paste), which then flows into the gap between two base metal parts to join them, without melting the base metals themselves. This technique is valued for its high speed, precision, and the creation of high-quality, aesthetically pleasing joints with minimal distortion. It is widely used in the automotive industry to join different materials, such as steel and aluminum.
Laser brightness – It is the measure of optical power per unit area per unit solid angle, representing how concentrated the laser beam is. It is defined as the power emitted from a light source per unit area and per unit solid angle, and in laser technology, it is frequently used interchangeably with the term ‘radiance’. A high brightness laser has a concentrated beam, making it effective for applications like laser material processing and micro-machining.
Laser cavity – It is the optical resonator in a laser, a confined space with mirrors which reflects light back and forth to amplify it. The mirrors create positive feedback by bouncing the light, allowing it to pass through the gain medium multiple times to become more intense and coherent, eventually emerging as a laser beam.
Laser chemical vapour deposition (LCVD) – It is also known as laser induced chemical vapour deposition. It is a chemical process which is used to produce high purity, high performance films, fibres, and mechanical hardware. It is a form of chemical vapour deposition in which a laser beam is used to locally heat the semi-conductor substrate, causing the vapour deposition chemical reaction to proceed faster at that site. The process is used in the semi-conductor industry for spot coating, the MEMS (micro-electro-mechanical systems) industry for 3D printing of hardware such as springs and heating elements, and the composites industry for boron and ceramic fibres.
Laser chip – It is a semiconductor device which generates a laser beam, also known as a laser diode, which is a two-terminal electronic component which produces a highly concentrated and mono-chromatic beam of light through stimulated emission. It consists of a p-n junction in a semi-conductor material (like gallium arsenide) which emits photons when an electric current is passed through it, with reflective facets forming an optical cavity to improve the light output.
Laser cladding – It is a surface modification technique where a laser beam melts a material (typically a powder or wire) onto a substrate, creating a protective or functional layer with a strong metallurgical bond. It is a type of directed energy deposition (DED) process. It is frequently used for coating, repairing, and improving the properties of components.
Laser cladding process – It is a powder-based technique which involves melting a substrate with a laser while simultaneously feeding metallic or ceramic powder into the melted zone to create a strong metallurgical bond. This process allows for superior accuracy, minimal heat-affected zones, and the ability to work with diverse materials.
Laser cladding three-dimensional printing – It is a laser metal deposition (LMD) technique which uses a focused laser beam to melt and fuse powdered or wire-fed metal onto a substrate to build up a 3D object layer by layer. This method is a form of additive manufacturing used for creating complex metallic parts or for repairing and reconditioning existing components.
Laser cleaning – It is a non-contact surface treatment that uses a high-intensity laser beam to vapourize, sublimate, or ablate (remove) unwanted materials like rust, paint, or oil from a surface without damaging the underlying material. It is an environmentally friendly and precise method, as it uses the difference in the ‘ablation threshold’ between the contaminant and the substrate to selectively remove the target material.
Laser confocal scanning microscopy, laser scanning confocal microscopy – It is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation.
Laser cutting – It is a technology which uses a laser to vapourize materials, resulting in a cut edge. Laser cutting works by directing the output of a high-power laser most commonly through optics. The laser optics and CNC (computer numerical control) are used to direct the laser beam to the material. A commercial laser for cutting materials uses a motion control system to follow a CNC or G-code of the pattern to be cut onto the material. The focused laser beam is directed at the material, which then either melts, burns, vapourizes away, or is blown away by a jet of gas, leaving an edge with a high-quality surface finish.
Laser cutting process i- It is a method which creates a kerf through the relative motion between a laser beam and a work-piece surface, utilizing energy from the laser to remove material while balancing heat conduction, melting, vapourization, and environmental heat losses. It offers higher material removal rates and narrower kerf widths compared to mechanical cutting methods.
Laser diffraction particle size analyzer (LDPSA) – This laser technique can evaluate the size distribution of inclusions which have been extracted from a steel sample using another method such as slime.
Laser diode (LD) – It is a semi-conductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode’s junction.
Laser direct metal deposition (LDMD) – It is also known as laser metal deposition (LMD) or directed energy deposition (DED). It is an additive manufacturing process which uses a laser to melt and fuse powdered metal onto a substrate, building up a 3D object layer by layer. It is a versatile technique for creating or repairing metal parts with complex geometries.
Laser displacement sensor – It is a non-contact device which uses a laser beam to measure the distance, thickness, position, or displacement of an object. It works by emitting a laser, which reflects off a target and is then received by the sensor. The sensor analyzes the reflected light to calculate the distance to the object with high precision, often to a sub-millimeter level.
Laser Doppler anemometer – It is a non-intrusive optical instrument which measures fluid flow velocity by using the Doppler shift of laser light scattered by small particles moving with the fluid. It works by splitting a laser beam into two intersecting beams, which create an interference pattern. As particles pass through this pattern, they scatter light at a frequency which corresponds to their velocity, allowing the system to calculate the flow speed with high accuracy.
Laser Doppler anemometry – It is a non-intrusive technique which uses the Doppler shift of scattered laser light to measure fluid flow velocity at a specific point. It works by shining two intersecting laser beams into a fluid seeded with small particles, when particles pass through the intersection point, they scatter light with a frequency shift proportional to their velocity, which is then detected and used to calculate the flow speed.
Laser-drilled hole – It is an opening created in a material by using a focused laser beam to melt and vapourize the material. This non-contact process is highly precise, can produce very small holes (down to a few microns), and is used in a wide variety of industries for applications like creating microvias (tiny, plated holes) in printed circuit boards, making cooling channels, or drilling holes in hard-to-machine materials.
Laser drilling process – It is a non-contact process which uses a focused laser beam to create holes by repeatedly melting or vapourizing material from a work-piece. It is a versatile micro-manufacturing technique used across several industries for creating precise, small-diameter holes which can be difficult or impossible to achieve with conventional drilling methods. The process is adaptable, allowing the laser’s characteristics to be adjusted for different materials and applications.
Laser electronics – It refers to the field of laser technology that deals with the electronics controlling the laser’s components, or more specifically, the study of how laser radiation couples with electron clouds in atoms, molecules, or ions. It also refers to the use of lasers in the electronics manufacturing industry for processes like cutting, welding, and drilling circuits and components, which leverages the precision, speed, and non-contact nature of lasers.
Laser emission – It is the process of creating a coherent, mono-chromatic beam of light through the stimulated emission of photons from a gain medium. This happens when an external energy source excites atoms to a higher energy state, and when a photon of the right energy interacts with an excited atom, it stimulates that atom to release an identical photon. This triggers a chain reaction which results in an amplified, parallel, and in-phase beam of light.
Laser energy – It is a highly focused, coherent beam of electro-magnetic radiation produced by a process called ‘light amplification by stimulated emission of radiation’. This beam is mono-chromatic (one wave-length), which allows it to stay focused, deliver a high concentration of energy to a small area, and travel long distances.
Laser energy density – It is the quantity of energy delivered per unit area, and it is a critical parameter in applications like laser welding or material processing. For pulsed lasers, the term fluence is frequently used, which is the total energy per unit area, typically measured in joules per square centimeter. For continuous processes, the term power density is used, representing the power per unit area (watts per square centimeter).
Laser engineered net shaping (LENS) – It is a metal additive manufacturing technique that uses a high-powered laser to fuse metal powders layer by layer, building 3D objects. It is a process of melting and depositing metal powder using a laser, allowing for the creation of complex parts with improved properties. Laser engineered net shaping is a registered trademark of Sandia National Laboratories. It falls under the broader category of additive manufacturing, where objects are built by adding material layer upon layer, unlike traditional subtractive manufacturing that removes material from a block. This technique uses a high-power laser to melt metallic powder, which is fed through a deposition head coaxially to the focus of the laser beam.
Laser excitation – It is the process of providing energy to a material to elevate its electrons to a higher energy state, a crucial step for laser operation. This energy is often supplied by a ‘pump source’ like a flash lamp, electrical current, or another laser, which causes electrons in the material to jump from their ground state to an excited state. This excitation creates a temporary condition known as population inversion, where more electrons are in the higher energy state than the lower one, which is necessary for stimulated emission and the production of a laser beam.
Laser etching – It is an engraving process where lasers are used to engrave a design, pattern or text into a material.
Laser flash technique – It is also known as the laser flash method or laser flash analysis. It is a method for measuring the thermal diffusivity of materials, and subsequently, their thermal conductivity and specific heat capacity. It involves exposing one side of a sample to a short, intense pulse of radiant energy (normally from a laser) and measuring the temperature rise on the opposite side over time. The laser flash technique is based on the principle of measuring how quickly heat diffuses through a material.
Laser fluence – It is the measure of laser energy per unit area delivered to a target surface, typically expressed in joules per square centimeter. It is a critical metric for understanding how concentrated a laser’s energy is, which is important for applications like laser material processing. Calculating it involves dividing the laser pulse energy by the area of the beam.
Laser flux – It is a measure of laser energy intensity and typically refers to the power per unit area or, more commonly, laser fluence, which is the total energy delivered per unit area over a specific time. It is an important concept for understanding how lasers affect materials, particularly in applications like laser ablation, where it determines whether material evaporates or becomes a plasma.
Laser forming – It is a manufacturing process which uses a laser’s thermal energy to deform materials, such as metal sheets, into a desired shape without external mechanical forces or traditional tooling. This contactless method creates controlled plastic deformation by inducing thermal stresses through non-uniform heating and subsequent cooling. It is especially useful for rapid prototyping and forming challenging materials, such as titanium alloys.
Laser gauge – It is a non-contact measuring device which uses a laser to measure a variety of parameters with high accuracy, including distance, thickness, diameter, and gap and flush measurements. It works by emitting a laser beam and detecting the reflected light to calculate a measurement, offering benefits like speed, precision, and safety, especially for delicate or hard-to-reach objects. Laser gauges are used in several industries such as manufacturing, for quality control and process monitoring.
Laser hardening – It is a surface-hardening process which uses a laser to quickly heat a surface. Heat conduction into the interior of the part quickly cool the surface, leaving a shallow martensitic layer.
Laser heating – It is a process which uses a focused laser beam to rapidly and precisely heat a material by delivering a high-density energy source. The absorbed laser energy converts to heat, causing localized temperature increases which can lead to changes like melting, vapourization, or micro-structural modification, such as hardening through rapid cooling.
Laser heat treatment – It is a surface modification process which uses a high-energy laser beam to rapidly heat and then cool a material’s surface, increasing its hardness and wear resistance. The laser precisely targets a small area, and the surrounding cooler material acts as a heat sink, causing the surface to self-quench quickly, creating a hardened layer without causing substantial distortion or affecting the core of the material.
Laser hybrid welding – It is also known as hybrid laser-arc welding (HLAW). It is a welding process that combines a laser beam with an electric arc to join materials. This technique leverages the advantages of both laser welding (high speed, deep penetration) and arc welding (better fit-up tolerance, wider weld pool) to achieve high-quality welds with increased efficiency.
Laser illumination – It is the use of a laser beam to light up an object or scene for imaging, measurement, or other analysis. Unlike conventional light sources, lasers provide a highly focused, coherent, and intense beam which can be shaped to capture detailed information, such as three-dimensional contours, or to provide precise illumination in low-light or high-speed applications.
Laser-induced fluorescence imaging – It is a sensitive detection method which uses a laser to excite molecules in a sample, causing them to emit fluorescence, which is then captured to create an image. This technique is used to visualize and analyze the spatial distribution of specific components, providing detailed information about concentration, temperature, or velocity, and has applications in several fields such as combustion research and microfluidics.
Laser-induced graphene – It is a method for creating a porous, three-dimensional graphene material by using a laser to convert carbon-containing precursor materials, like polymers, into graphene at ambient conditions. This process uses the laser’s energy to convert carbon atoms from their original sp3 bonding state to sp2 bonding in the resulting graphene. The technique is fast, cost-effective, and can produce precise graphene patterns directly on various substrates, making it ideal for applications such as flexible electronics, energy storage (e.g., super-capacitors), and sensors.
Laser inspection – Lasers are used in inspection and measuring systems because laser light provides a bright, undirectional, and collimated beam of light with a high degree of temporal (frequency) and spatial coherence. These properties can be useful either singly or together. For example, when lasers are used in interferometry, the brightness, coherence, and collimation of laser light are all important. However, in the scanning, sorting, and triangulation applications, lasers are used because of the brightness, unidirectionality, and collimated qualities of their light, temporal coherence is not a factor. Lasers can be used in several different ways to measure the dimensions and the position of parts. Some of the techniques include (i) profile gauging of stationary and moving parts with laser scanning equipment, (ii) profile gauging of stationary parts by shadow projection on photo-diode arrays, (iii) profile gauging of small gaps, and small-diameter parts from diffraction patterns, (iv) gauging of surfaces that cannot be seen in profile (such as concave surfaces, gear teeth, or the inside diameters of bores) with laser triangulation sensors, (v) measuring length, alignments, and displacements with interferometers, (vi) sorting of parts, (vii) three-dimensional gauging of surfaces with holograms, and (viii) measuring length from the velocity of moving, continuous parts.
Laser intensity – It is the optical power per unit area, typically measured in watts per square centimeter. It is a measure of how concentrated the laser’s energy is, and is calculated by dividing the laser’s power by the beam’s area. Because of its coherence and directionality, a laser concentrates photons into a small region, resulting in much higher intensity than ordinary light.
Laser interaction – It is the process where a laser beam transfers energy to a material, causing a variety of effects depending on the laser’s properties and the material’s characteristics. This interaction can lead to absorption, heating, material ablation (material removal), or the creation of plasma, and is used in applications from material processing to scientific analysis.
Laser interference lithography – It is a maskless optical technique which uses the interference of two or more coherent laser beams to create high-resolution, periodic patterns on a substrate. By overlapping the beams, the resulting interference pattern is projected onto a photoresist or directly onto the material, allowing for the fabrication of structures like arrays of dots, holes, or stripes.
Laser interferometer – It is an instrument which uses the principles of light interference to perform high-precision, non-contact measurements of distance, displacement, and other quantities. It works by splitting a laser beam, sending the two resulting beams along different paths, and then recombining them to create an interference pattern. By analyzing changes in this pattern, the instrument can detect minute changes in length or displacement with nano-scale accuracy.
Laser ionization mass spectroscopy (LIMS) – It is based on a process similar to vapourization-dominated drilling. A laser beam is used to vapourize the surface of the sample and then the vapour or plasma cloud produced can be spectroscopically analyzed.
Laser irradiation – It is the process of using a focused laser beam to deliver energy to a specific area for purposes like industrial, or scientific applications. It is the exposure of an object or substance to a laser beam, which is characterized by its mono-chromatic (single wavelength), coherent, and collimated (narrowly focused) properties. This focused energy can induce changes in materials by processes such as heating, cutting, or triggering chemical reactions.
Laser line-width – It is the spectral width of a laser’s emission, measured as the full width at half maximum (FWHM) of its optical spectrum. It quantifies how mono-chromatic a laser is, indicating the range of frequencies or wave-lengths present in the output. A narrow line-width signifies a nearly pure, mono-chromatic light source, while a wider one means a larger range of wave-lengths are emitted.
Laser machining process – It is a thermal energy-based advanced machining technique which removes material by focusing a laser beam on the work surface to melt and vapourize unwanted material, utilizing high-intensity laser pulses for efficient energy transfer without generating cutting forces or tool wear.
Laser-material interaction – It is the process where laser energy is transferred to a material, causing physical and chemical changes. This phenomenon is governed by the laser’s properties, the material’s characteristics, and the surrounding environment, and can result in effects like heating, melting, vapourization, plasma formation, shock waves, or even void formation within transparent materials.
Laser materials processing – It is a manufacturing technique which uses a focused, high-intensity laser beam to heat, melt, cut, or vapourize materials with high precision. This non-contact process is used for applications like cutting, welding, drilling, engraving, and surface modification across different materials including metals, plastics, and ceramics. Key advantages include its precision, speed, flexibility, and the ability to work with delicate or complex components with minimal impact on the surrounding area.
Laser measuring device – It is also known as a laser distance meter or laser rangefinder. It is a handheld tool which uses a laser beam to determine the distance to an object. It works by emitting a laser pulse towards a target and measuring the time it takes for the light to reflect back, converting this time into a distance measurement. These devices are known for their accuracy, speed, and ability to measure in hard-to-reach or hazardous areas, offering an advantage over traditional measuring methods like tape measures.
Laser medium – It is also called the gain medium or lasing medium. It is the material within a laser which generates and amplifies light through stimulated emission. This substance can be a solid, liquid, or gas, and it becomes activated by a pump source which provides energy to raise its atoms to a higher energy state, from which they can then emit coherent light.
Laser melting – It is a type of additive manufacturing (3D printing) which uses a high-power laser to selectively melt and fuse layers of metallic powder to build a 3D object. The process involves a laser scanning a cross-section of a digital model, melting the powder in that area, and then repeating the process with new layers of powder until the final part is complete.
Laser metal deposition – It is a form of additive manufacturing where a high-power laser melts and fuses a metal powder or wire material onto a substrate to build a three-dimensional object layer by layer. This process is used for creating complex parts, adding functional layers, and repairing existing components with high precision and reduced waste.
Laser microprobe mass spectrometry (LAMMS) – Individual particles are irradiated by a pulsed laser beam, and the lowest laser intensity above a threshold value of ionization is selected for its characteristic spectrum patterns due to their chemical states. Peaks in laser microprobe mass spectrometry spectra are associated with elements, based on comparison with reference sample results.
Laser micro-welding – It is a precise joining process which uses a focused laser beam to fuse small components with minimal heat, creating a strong, permanent weld with little distortion. This technique is used for miniature parts across different industries because of its ability to join delicate and thermally sensitive materials with high accuracy.
Laser milling – It is a material removal process which uses a laser to vapourize or ablate material layer-by-layer from a solid surface, without physical contact with a cutting tool. It is a subtractive manufacturing technique used to create three-dimensional features like pockets and contours, especially in hard or delicate materials, with high precision and no tool wear.
Laser modification – It is the process of using a laser to alter a material’s surface properties, such as its texture, hardness, or composition, without changing the bulk material. This can be achieved through different techniques, including surface hardening, melting, texturing, and cladding, and is used to improve performance in applications like engineering.
Laser module – It is a self-contained device which combines a laser diode, optics, and control electronics to produce a focused, coherent beam of light. It includes a laser diode for light generation, a collimating lens to shape the beam, and a driver circuit to manage power and operation. These modules are designed for easier use than a bare laser diode and are found in applications ranging from laser pointers and distance measurement tools to industrial engraving and fibre optics.
Laser nitriding – It is a surface treatment process which uses a laser to form a hardened nitride layer on a metal’s surface, improving its hardness, wear resistance, and corrosion resistance. The process involves irradiating the metal’s surface with high-intensity laser pulses in a nitrogen-containing atmosphere, causing nitrogen to be absorbed and form nitrides. This method allows for precise control over the nitrided layer’s properties.
Laser output power – It is the total energy a laser emits per unit of time, typically measured in watts, kilowatts, or milliwatts. It quantifies the rate at which energy is delivered by the laser beam, and it is an important parameter which determines the laser’s capabilities, such as its cutting or engraving speed. The power can be either continuous or pulsed, with pulsed lasers also having a peak power which represents the instantaneous power during a single pulse.
Laser parameters – These are the characteristics which define a laser’s behaviour and performance, such as its wave-length, power, speed, and pulse duration. These parameters are important for controlling a laser’s effects and are adjusted based on the specific application, material, and desired outcome. Examples include wave-length, output power, pulse repetition rate, pulse duration, beam diameter, and focus (or Z-offset).
Laser patterning – It is a high-precision machining process which uses a laser to create a specific pattern on a material’s surface, frequently as a substitute for traditional methods like photo-lithography and etching. It can be used to ablate, modify, or deposit materials to create structures, such as electrodes, micro-channels, or textured surfaces. The term ‘digital’ patterning refers to the use of a computer-aided design (CAD) file to control the laser for precise, mask-free fabrication.
Laser peening – It is a surface engineering process which uses high-energy laser pulses to create shock-waves, which induce deep compressive residual stresses in a material. This process improves a material’s resistance to fatigue, stress corrosion cracking, and other surface-related failures by counter-acting tensile stresses which lead to cracks.
Laser percussion drilling – It is a process where a series of rapid, focused laser pulses are used to ‘punch’ a hole directly through a material, with no relative movement between the laser and the work-piece. Each pulse removes a small quantity of material, and with enough pulses, a through-hole is created. This method is used for creating small, deep, and accurate holes quickly.
Laser performance – It is a measure of how effectively a laser system operates and is defined by different metrics such as efficiency (e.g., converting energy into light), power (e.g., watts), pulse characteristics (e.g., repetition rate), and accuracy (e.g., for laser scanners). It is important for understanding a laser’s capabilities, diagnosing issues, and ensuring it functions correctly for its intended application.
Laser phase noise – It is the random fluctuation in the phase of a laser’s output light, causing its phase to deviate from an ideal, constant sinusoidal wave. These fluctuations are caused by factors like spontaneous emission and are a key measure of a laser’s short-term stability, directly affecting its spectral linewidth. Applications like coherent communications, LIDAR (light detection and ranging), and optical clocks require lasers with low phase noise to operate correctly.
Laser pointer – It is a pen-shaped pointing device that contains a small diode laser which emits an intense beam of light, used to direct attention during presentations.
Laser powder deposition – It is a 3D printing process which uses a focused laser beam to melt metal powder as it is fed into a melt pool on a substrate. By moving the laser and nozzle, overlapping tracks are created to form layers, which are built up sequentially to create a complete 3D object or coating. This method is used to manufacture and repair high-value, functional parts from different engineering materials.
Laser power – It is the rate at which a laser emits energy, measured in watts, and indicates the intensity of the light it produces. It can be measured as an average power for continuous-wave lasers or as a peak power for pulsed lasers, which is the highest power level achieved during a single pulse. This value is crucial for determining a laser’s ability to cut, weld, or otherwise interact with materials.
Laser power density – It is the quantity of laser power per unit area, frequently called irradiance, and it indicates how concentrated the laser’s energy is on a specific spot. It is calculated by dividing the laser’s power by the area of its beam, and its units are typically watts per square centimeter. Power density is an important factor in determining how a laser interacts with a material, influencing processing speed and quality.
Laser power transmission – It is a wireless technology which transmits energy as a directed laser beam from a transmitter to a receiver, which converts the light back into electricity. This method uses a laser diode to create an optical wave which is directed to a photo-voltaic array, which then converts the light into a direct current (DC) voltage. The system provides a line-of-sight, high-density, and focused power transfer for applications like remote charging or powering devices in harsh environments.
Laser printer – It is a type of computer printer which uses a laser beam and electrostatic charges to transfer toner (a dry powder) onto paper. This non-impact method produces high-quality, sharp text and graphics at fast speeds, making it ideal for high-volume office use. The process involves the laser drawing an image on a photo-sensitive drum, which attracts toner, and then the toner is transferred to the paper and fused with heat.
Laser probe – It is a device which uses a laser to perform a specific task, such as making precise, non-contact measurements, or analyzing material composition. In industrial settings, they are used for measurements like surface displacement, velocity, or scanning complex geometries.
Laser processing – It is a non-contact manufacturing technique which uses a focused beam of light to cut, weld, drill, engrave, or alter materials with high precision. It relies on the intense thermal energy from the laser to melt and vapourize material, enabling precise control over operations like cutting and surface engineering.
Laser processing parameters – These are the specific settings and conditions used in a laser system which can be adjusted to control the outcome of a laser application, such as cutting, engraving, or welding. Key parameters include the laser’s power, speed, wave-length, and spot size, along with material and machine-related factors like the material properties, the type of gas used, and the distance of the nozzle from the work-piece. Optimizing these parameters is crucial for achieving desired results, such as cut quality, accuracy, and efficiency.
Laser pulse – It is a burst of light from a laser, emitted in a series of short, non-continuous flashes rather than a steady beam. This operation is necessary for applications which need high peak power, such as precise material processing, and it involves controlling parameters like pulse duration, energy, and repetition rate.
Laser pulse duration – It is the length of time a laser emits a burst of light, very frequently defined as the full width at half-maximum (FWHM) of the laser’s optical power over time. This metric, also called pulse width or pulse length, is typically measured in units like nano-seconds, picoseconds, or femtoseconds. A shorter pulse duration means a more intense, shorter burst of energy, which has substantial effects on how the laser interacts with a material.
Laser pulse energy – It is the total energy delivered by a single laser pulse, typically measured in joules. It is calculated by multiplying the peak power of the pulse by its duration (E = Ppeak x t) and is a more reliable parameter than average power for applications which use pulsed lasers.
Laser pyrolysis – It is a process which uses an intense laser beam to decompose reactant gases in a vapour phase, producing nano-particles, thin films, or other materials. By precisely controlling the laser’s power and gas flow, the method allows for the synthesis of fine, uniform particles with narrow size distributions, frequently with minimal impurities since the reaction does not typically contact the reactor walls.
Laser radiation – It is coherent light emitted by a laser, characterized by a narrow emission spectrum and high stimulated-emission efficiency. It results from the process of stimulated emission within an amplifying medium, facilitated by mirrors that create a positive-feedback loop. It is highly mono-chromatic (single colour / wavelength), collimated (narrow and directional), and coherent (waves are in phase). This allows it to be focused into a very small spot and have high intensity.
Laser resonator – It is a component in a laser, typically made of two mirrors, which confines and amplifies light through multiple reflections. It provides feedback for stimulated emission by sending a portion of the light back into the gain medium, which sustains the laser process and helps define the characteristics of the output beam, such as its shape, frequency, and direction.
Laser safety – It is a set of practices and regulations for safely using lasers to minimize risks of injury to the eyes and skin. It involves understanding the potential hazards, which are categorized by laser classes based on power and wave-length, and implementing appropriate control measures like wearing safety goggles and following specific operating procedures.
Laser safety glasses – These are a type of personal protective equipment (PPE) with specialized lenses that filter or block hazardous laser radiation to safe levels. They are designed to protect the eyes from permanent damage by absorbing or reflecting specific laser wave-lengths, which regular safety glasses cannot do. The appropriate type of laser safety eyewear depends on the laser’s specific wave-length, power, and other specifications.
Laser safety goggles – These are specialty goggles to protect against intense concentrations of light produced by lasers. The laser safety goggles to be used depends upon the equipment and operating conditions in the work-place.
Laser scanning – It is a process which uses lasers to measure three-dimensional points on an object or environment, creating a detailed digital representation called a point cloud. It works by projecting laser light onto a surface and measuring the distance to that surface, then using this data to generate accurate 3D models or as-built drawings. The process is fast, non-contact, and highly accurate, making it useful for applications like mapping construction sites, creating CAD (computer aided design) models, and capturing the physical characteristics of objects.
Laser shock peening – It is a surface treatment process which uses high-energy laser pulses to create a shockwave, which generates beneficial compressive residual stresses in a material’s surface. This treatment improves mechanical properties like fatigue strength, wear resistance, and durability in metallic components. The process is frequently used to improve the performance of parts in high-stress applications.
Laser shock processing – It is a surface treatment technique which uses high-power laser pulses to create powerful shock waves on a material’s surface. These shock waves induce plastic deformation, leading to compressive residual stresses which improve the material’s fatigue life, wear resistance, and hardness. The process typically involves coating the surface with a sacrificial layer and covering it with a transparent confining layer, like water, to maximize the shock wave’s intensity and minimize thermal damage.
Laser-shot peening – It is a surface treatment, which uses laser-induced shocks to create deep compressive stresses beyond a 1-millimeter depth with magnitudes comparable to that produced by shot peening. Laser-shot peening has proven to considerably improve the damage tolerance of components and has generated sufficiently impressive results to move it from a laboratory-demonstration phase into a significant industrial process technology.
Laser sintering – It is a 3D printing process which uses a high-power laser to fuse powdered materials together, building a three-dimensional object layer by layer. It is a type of powder bed fusion technology, where a laser selectively melts and fuses powdered material based on a digital design.
Laser sintering system – It is an automated, additive manufacturing machine which uses a laser to selectively fuse powdered material into a three-dimensional object, layer by layer. It works by heating a powder bed to just below its melting point, then using a focused laser, guided by a CAD (computer aided design) model, to sinter (fuse) the powder particles together to form the desired shape.
Laser soldering – It is a technique where a precisely focused laser beam provides controlled heating of the solder alloy leading to a fast and non-destructive of an electrical joint. The process uses a controlled laser beam to transfer energy to a soldering location where the absorbed energy heats the solder until it reaches its melting temperature leading to the soldering of the contact and this completely eliminates any mechanical contact. Laser soldering uses solder, which in liquid state wet the materials to be joined and provide mechanically and electrically stable connections when solidified.
Laser spot diameter – It is the measure of the size of a laser beam, frequently defined as the distance across the beam’s centre where the power density (irradiance) has fallen to 1/e square (or about 13.5 %) of its maximum value. This is a crucial parameter in laser applications, as it determines the energy density delivered to a target, influencing precision and process outcomes like cutting, welding, or marking.
Laser spraying – It is also known as laser-assisted cold spray (LACS). It is a coating and manufacturing process which combines a supersonic powder stream with laser heating to deposit materials like metals and cermets onto a substrate. It is used for building, repairing, and coating parts, and the laser heating improves coating properties such as adhesion and density compared to conventional cold spray.
Laser structuring – It is a micro-machining process which uses a laser to create precise, regularly arranged geometries on a material’s surface to alter its physical properties. This is achieved by using the laser to either ablate (remove) or remelt the material, resulting in modified surface topography, improved adhesion and friction, and the ability to add new functionalities.
Laser surface – It refers to a material surface which has been intentionally modified using a laser to alter its properties, such as roughness, texture, or chemical composition. This is achieved through different techniques including laser surface texturing (creating micro-patterns), laser surface treatment (localized heating and cooling), or laser surface alloying (fusing new materials) to improve characteristics like wear resistance, adhesion, or wettability.
Laser surface engineering – It is a process of using a laser to modify the surface of a material to improve its properties, such as hardness, wear resistance, or corrosion resistance. This can be achieved by modifying the existing surface through rapid heating and cooling cycles (laser surface melting, hardening, or texturing) or by adding new material through processes like laser cladding or surface alloying.
Laser surface modification – It is a process which uses a laser to change the physical, chemical, or mechanical properties of a material’s surface without altering the bulk material. This is achieved through methods like surface hardening, texturing, melting, or cladding, and is used to improve properties such as wear resistance, hardness, corrosion resistance, and wettability for different applications.
Laser surface processing – It consists of the use of lasers with continuous outputs of 0.5 kilowatts to 10 kilowatts to modify the metallurgical structure of a surface and to tailor the surface properties without adversely affecting the bulk properties. The surface modification can take in three forms. The first is transformation hardening in which a surface is heated so that thermal diffusion and solid-state transformations can take place. The second is surface melting, which results in a refinement of the structure because of the rapid quenching from the melt. The third is surface (laser) alloying, in which alloying elements are added to the melt pool to change the composition of the surface. The new structures produced by laser surface melting and alloying can show improved electro-chemical and tribological behaviour.
Laser surface treatment – It is a process which uses a high-energy laser to selectively heat and modify the surface of a material, altering its micro-structure and improving its properties without affecting the bulk material. It involves heating the surface to cause changes in structure, composition, or other properties, followed by rapid cooling (self-quenching), which can lead to increased hardness and wear resistance. This technique can be used for applications like hardening, cladding, alloying, and surface texturing.
Laser transfer – It is a technology which uses a pulsed laser to move a material from a donor substrate to a receiving substrate with high precision. The laser creates vapour pressure, propelling a small quantity of material (like a droplet or micro-device) from the donor film to the target, a process known as ‘laser-induced forward transfer’ (LIFT). This versatile technique can be used for printing functional materials like electronics samples and is compatible with both solid and liquid materials.
Laser treatment parameters – These are the specific settings and conditions used during laser processing to achieve a desired outcome. Key parameters include wave-length, power, pulse width, pulse rate, and energy / power density, which are adjusted based on the specific application, target material, and desired effect. These settings influence factors like how the laser interacts with the target, its penetration depth, and the resulting thermal effects.
Laser wave-length – It is the distance between consecutive peaks of the light wave emitted by a laser, which determines its colour and properties. It is a measure of the light’s energy and is typically expressed in nano-meters. The specific wave-length is determined by the laser’s gain medium and structure, with different wave-lengths having different interactions with materials and applications.
Laser welding – It is a fusion welding process which uses a focused laser beam to join metals or thermoplastics. The intense, concentrated heat from the laser melts the materials at their seams, creating a strong, precise, and high-speed weld with minimal heat distortion. This process is used in different industries for high-precision applications.
Laser welding machine – It is a piece of equipment which uses a focused beam of laser light to melt and fuse materials together, creating strong, precise welds. This high-tech process is non-contact, highly automated, and ideal for applications needing high accuracy, speed, and minimal thermal distortion.
Laser welding parameters – These are the controllable variables which govern the outcome of a laser weld, including laser power, welding speed, focal position, and spot size. Adjusting these parameters, along with others like shielding gas and pulse duration, allows operators to control factors such as penetration depth, weld bead shape, and overall weld quality.
Latent demand – It is a desire for a product or service which a customer cannot satisfy because of the lack of awareness, availability, or financial ability. This demand is ‘latent’ since the customer is not be able to articulate the need or even realize that a suitable product exists, representing a potential market opportunity for the organizations.
Latent heat – It is the thermal energy absorbed or released when a substance undergoes a phase change.
Latent heat capacity – It is more accurately termed specific latent heat. It is the quantity of heat energy needed to change the state of a unit mass of a substance without a change in temperature. It is a measure of the energy absorbed or released during a phase transition, such as melting, freezing, boiling, or condensation. The SI (International System of Units) unit for specific latent heat is joules per kilogram.
Latent heat of fusion – It is also known as enthalpy of fusion. It is the quantity of energy which is to be supplied to a solid substance (typically in the form of heat) in order to trigger a change in its physical state and convert it into a liquid (when the pressure of the environment is kept constant).
Latent heat of melting – It is the heat which causes a phase / state change of a solid without raising its temperature. In case of ice, a total of 334 kilojoule of energy is needed to melt 1 kilogram of ice at 0 deg C into 1 kilogram of water at 0 deg C.
Latent heat of solidification – It is the quantity of heat energy an object releases as it changes from a liquid to a solid at a constant temperature. This is an exothermic process where energy is released as the molecules in the liquid come closer together to form a more ordered solid state. For example, when water freezes, it releases energy equal to its latent heat of solidification, which is why sprinkling plants with water can protect them from frost.
Latent heat of transformation – It is the energy absorbed or released during a phase change of a substance without a change in temperature. This energy is used to break or form the bonds between molecules, thus altering the state of matter (solid, liquid, or gas).
Latent heat of vapourization – It is the heat which causes a phase / state change of a liquid without raising its temperature. In case of water, 2,257 kilojoules of energy are needed to evaporate 1 kilogram of water at 100 deg C into 1 kilogram of steam at 100 deg C.
Latent heat storage – It is a thermal energy storage method which uses a phase-change material (PCM) to store large quantities of heat energy at a nearly constant temperature during its transition from solid to liquid. This process involves the ‘latent heat’ of fusion (melting) or solidification, which is the energy absorbed or released when a substance changes state without a change in temperature. When the material melts, it absorbs heat and when it solidifies, it releases the stored heat.
Latent heat thermal energy storage – It refers to a technology which stores thermal energy during the phase change of materials from solid to liquid at a constant temperature, providing a higher heat storage capacity compared to sensible heat thermal energy storage (SHTES). It is characterized by advantages such as minimal temperature fluctuation and high energy density.
Latent hydraulic property – It refers to the capacity of certain materials, like ground granulated blast-furnace slag or pozzolans, to react with water to form cementitious binders, but only after being activated by an alkaline solution. These materials are not hydraulic on their own and their hardening potential is ‘latent’, meaning it is hidden and is to be triggered by an external stimulus, such as the calcium hydro-oxide found in Portland cement, to begin the chemical reaction.
Latent solvent – It is a liquid which cannot itself dissolve a binder but increases the tolerance of the paint for a diluent.
Lateral acceleration – It is the sideways acceleration which occurs when a vehicle turns, pushing its occupants toward the outside of the curve. Technically known as centripetal acceleration, it is the force which keeps an object moving in a circular path by pulling it toward the centre of the circle. It is normally measured in units of ‘g’ (e.g., 0.81g) to indicate how hard a vehicle can turn before losing traction.
Lateral bearing capacity – It is the maximum horizontal force a soil or foundation can withstand before it fails through shear. It represents the horizontal load-carrying ability of the soil, which is critical for structures subjected to lateral forces like wind, earthquakes, or earth pressure against retaining walls.
Lateral boundary conditions – These conditions define the rules or values at the sides of a computational model’s domain, telling the model how to behave at its horizontal edges. These conditions are necessary since models frequently have to represent a limited area (limited-area models) and need to know how their edges interact with the outside environment. They influence model performance by specifying properties like wind speed, pressure, or other variables, and can be open, closed, or periodic.
Lateral bow – It is the deviation from straight of a longitudinal edge.
Lateral buckling – It is the sideways displacement and twisting of a structural member, like a beam, which is subjected to bending loads. It occurs when a compression flange, which is the top part of the beam, moves out of its plane under load, introducing a twist and causing the member to fail. This phenomenon is more likely in slender open-section members with an insufficiently large moment of inertia in the lateral direction and where the compression flange is not properly supported.
Lateral coupling – It is the interaction between different types of motion or systems, specifically referring to a connection or influence in a side-to-side or transverse direction. This term is used in several fields, such as in engineering to describe the interaction between torsional and lateral vibrations, in fluid dynamics for flow between a river and its floodplains, and in optics for the coupling of light between adjacent wave-guides.
Lateral crack – It is a type of fracture that propagates sideways, perpendicular to the main direction of stress. These cracks are frequently observed in materials under indentation or grinding, and they can form underneath the surface and emerge as surface cracks. They are a key factor in the fragmentation of brittle materials, as they can break off pieces and contribute to material removal.
Lateral creepage – It is the relative motion between a wheel and a rail in the lateral (sideways) direction, divided by the mean rolling velocity. It is a measure of the slip which occurs when a wheel and rail are in contact, and it is important for understanding forces like the lateral creep force, which is generated by this motion. A common cause of lateral creepage is the wheel flange pushing against the inside of the rail, which happens as a train navigates a curve.
Lateral curvature – It is also called edge curvature. It is the lateral departure, in arc form, of an edge from linear straightness.
Lateral deflection – It is the sideways movement or bending of a structural element perpendicular to its main axis. It occurs because of the forces like wind, earthquakes, or other lateral loads, and is a critical design consideration for structures, especially tall structures, to ensure stability and prevent damage.
Lateral deformation – It is a change in a material’s shape in a direction perpendicular to the applied force. It can involve both expansion and contraction and is frequently discussed in terms of engineering, e.g., when a material is stretched (longitudinal deformation) and simultaneously gets thinner (lateral deformation).
Lateral direction – It refers to side-to-side movement or orientation, as opposed to forward / backward movement. It describes motion, force, or position which is perpendicular to the main axis of a system or object, such as the pressure exerted on a pipe in a direction away from its centre.
Lateral displacement – It refer to the sideways movement of a structure because of the forces like wind or pressure, or the perpendicular distance between an incident ray’s original path and its emergent path after passing through a medium, as in optics. It can also describe the movement of a particle within a system, such as the horizontal shift in a pipeline.
Lateral disturbance – It is an undesirable force, motion, or other input that acts upon a system in a sideways or transverse direction relative to its main axis of motion or structural orientation. These disturbances can cause a system to deviate from its intended path or stable equilibrium.
Lateral earth pressure – It refers to the horizontal stress exerted by soil on a structure, which is influenced by factors such as vertical effective stress and the soil’s internal friction angle. It can be quantified using the lateral earth pressure coefficient at rest, which varies for normally consolidated and over consolidated soils.
Lateral expansion – It is a broad term which means horizontal growth, but its specific meaning depends on the context, such as an organization expanding into new markets, a quarry widening its boundaries, or a material expanding sideways during a test, for example, it is a measured property used in Charpy impact testing, where it refers to the increase width of the sample after fracture. It also refers to an organization growing by acquiring similar organizations or diversifying its operations within the same /+part of the supply chain.
Lateral extrusion – It is an operation in which the product is extruded sideways through an orifice in the container wall.
Lateral growth – It refers to the expansion of a structure or crystal in a direction parallel to a surface, as opposed to the perpendicular or ‘vertical’ growth. This process is important in semi-conductor manufacturing, where it allows for the growth of materials like GaN (gallium nitride) over masked surfaces to reduce crystal defects and form larger grains. It is also a concept in metallurgy and materials science, where it can occur in dendritic structures during solidification.
Lateral heat loss – It refers to the transfer of thermal energy away from a system in directions which are perpendicular to the main or intended direction of heat flow. This can be substantial in systems like pipes, which are designed to transport heat from one point to another, but also lose heat to the surrounding environment through their sides.
Lateral loads – These are horizontal forces which act on a structure, perpendicular to gravity, such as those from wind, earthquakes, or soil pressure. These forces are to be accounted to ensure structural stability, using elements like shear walls and bracing to resist them. These loads can cause a structure to sway, bend, or even collapse if not properly designed for.
Lateral load test – It is a field test for foundations, like piles, which determines their response to horizontal forces, such as wind or seismic activity. It involves applying increasing lateral loads to the pile head with hydraulic jacks and measuring the resulting horizontal deflection to evaluate the foundation’s load-carrying capacity, stability, and stiffness. This test verifies that a foundation can safely withstand horizontal forces, which is important for structures like bridges, towers, and industrial buildings.
Lateral movement – It refer to sideways or horizontal movement in a structure. In structural engineering, it frequently describes foundation or wall movement in the horizontal plane, like a basement wall bowing inward. In the context of mechanical engineering, it describes a component’s sideways motion.
Lateral offset – It is a measure of the sideways distance from a main line or reference point. Its specific meaning depends on the field e.g., in surveying, it is the perpendicular or oblique distance from a main chain line to an object.
Lateral plane – It is a vertical plane which runs from front to back, dividing a structure or object into right and left sides. It is used to describe orientation, especially in 3D modeling and engineering drawing, to visualize or analyze features from a side view.
Lateral pressure – It refers to the force exerted by soil against a vertical wall, which includes the pressure from the soil held by the wall, any water behind the wall, and the lateral pressure from any surcharge on the soil.
Lateral propagation – It normally refers to the spread of a wave or action in a direction which is perpendicular to its main axis of propagation, or parallel to a surface or interface. It is not a single concept but is applied across different engineering fields, such as in electrical engineering for electromagnetic waves traveling along a boundary between two media, or in mechanical engineering for vibrations propagating along a structure.
Lateral resistance – It is the ability of a structure or system to withstand forces acting parallel to the ground, such as wind and seismic activity. This resistance is achieved through the use of specific design elements and is important for preventing collapse and ensuring stability during adverse conditions. Examples include the lateral load-resisting systems in buildings, or the resistance of a pipe to breakout from soil.
Lateral resolution – It is the ability of an imaging system to distinguish between two objects which are side-by-side, perpendicular to the direction of the beam. It is fundamentally limited by the width of the system’s beam, meaning a narrower beam provides better lateral resolution by preventing adjacent echoes from overlapping. Key factors affecting it include beam focusing, transducer size and frequency, and the number of scan lines per frame.
Lateral slip – It typically refers to the angle between the direction a tyre is pointed and the direction it is actually traveling during a turn. This angle, also called the slip angle or tyre slip angle, is important for cornering and is generated by the sideways displacement of the tyre’s tread in the contact patch. In a different context, ‘lateral slip’ can also describe the horizontal movement of rock blocks along a fault line, such as the San Andreas Fault, in which case it is also known as strike-slip faulting.
Lateral spread – It refers to the increase in width of the rolled material as it is compressed in thickness. It is the dimensional change in the transverse direction (width) because of the material flowing outward to accommodate the reduction in height.
Lateral stability – It is the ability of a structure, vehicle, or component to resist sideways, horizontal forces and return to its original position after a disturbance. It is crucial for structural safety against loads like wind and earthquakes. This is achieved through specific design features, such as bracing in buildings. In conveyors, it is the capability of a conveyor system to maintain side-to-side stability during operation. Regular assessments are needed to prevent issues related to misalignment and potential material spillage.
Lateral stability system – It is a structural system designed to resist horizontal forces, such as those from wind or earthquakes, in order to prevent a structure from collapsing or deforming excessively. These systems can include elements like bracing, shear walls, and moment-resisting frames, and their design is crucial for ensuring the safety of buildings and other structures.
Lateral stiffness – It is the resistance of a structure or component to horizontal deflection when a lateral (sideways) force is applied, such as from wind or an earthquake. It is defined as the force needed to cause a unit of horizontal deformation, and it is a critical property for the stability of structures like buildings and bridges.
Lateral strain – It is the deformation in a material which occurs perpendicular (or ‘lateral’) to the direction of an applied axial load. It is calculated as the ratio of the change in a lateral dimension (like width or diameter) to the original lateral dimension. For example, when a rod is pulled, it gets longer (longitudinal strain) while its diameter gets smaller (lateral strain).
Lateral stress – It is the stress which acts in a direction perpendicular to the applied load. When a material is stressed axially (longitudinally), it experiences a secondary stress in the perpendicular, or lateral, direction. For example, if a rod is pulled, it thins in the lateral direction because of this stress, and if it is compressed, it bulges out laterally.
Lateral thinking – Lateral thinking involves using a roundabout method to inspire new ideas or solutions. It can be done in a variety of ways, from using a random word to choosing an object in a room as a basis for thought.
Lateral-torsional buckling – It is a structural instability where a beam subjected to bending loads deflects laterally (sideways) and twists simultaneously. This occurs in slender, unbraced members, particularly I-beams, since the compression flange buckles sideways, which then causes the entire cross-section to rotate and displace. It leads to a collapse of the beam before its bending stresses reach the material’s yield point.
Lateral vibration – It is the side-to-side, oscillatory motion of a component or structure in a direction perpendicular to its length or axis. This is common in rotating machinery, shafts, and beams, where it can cause issues like increased wear, noise, and potential failure if not managed.
Lateral wall – It is a wall designed to resist lateral loads, which are horizontal forces acting sideways on a structure, such as wind, earthquakes, or soil pressure. These walls are a key component of a building’s lateral stability system and can include structural elements like shear walls, bracing trusses, or a building’s core, and are made from materials like concrete, steel, or masonry.
Laterite – It is residual soil which is normally found in tropical countries, out of which the silica has been leached. It can form ore-bodies of iron, nickel, bauxite, and manganese.
Laterite deposits – These are residual formations rich in iron and aluminum oxides, created by intensive weathering of parent rock in hot, wet tropical climates. They are frequently reddish in colour and can harden when exposed to air, forming a rock-like material. Laterites can be a source of different minerals and are frequently associated with other deposits like bauxite.
Laterite ore – It refers to a naturally occurring, reddish-brown soil and rock, rich in iron and aluminum, which forms in hot, wet tropical regions through intensive weathering of underlying rock. It is an important ore for metals like nickel, aluminum, and iron, and is processed using different methods like hydrometallurgy (leaching) or pyrometallurgy (smelting) to extract these valuable components for use in steel, batteries, and other alloys.
Laterite soil – It is a highly weathered tropical or subtropical residual soil, rich in iron and aluminum oxides, which is soft when moist and hardens considerably when exposed to air. Its engineering significance lies in its use as a construction material for building bricks and aggregates, because of its unique characteristic of being easily cut when wet but becoming very hard and durable after it dries.
Latest start time of an activity – It is the latest time in a programme evolution review technique (PERT) network at which the activity can start without delaying the subsequent events. It is the latest moment at which an activity can start without delaying completion of the overall project.
Latest finish time of an activity – It is the latest time in a programme evolution review technique (PERT) network at which the activity can be completed without delaying the subsequent events. It is the latest time at which an activity can be completed without delaying the completion of the overall project. Latest finish time of an activity is equal to the smallest of the latest start times of its immediate successors.
Latest version – It refers to the most current iteration or update of a design, product, software, or document. This version typically incorporates new features, performance improvements, bug fixes, or design changes compared to its predecessors and is necessary for managing the product lifecycle.
Lathe – It is a machine tool which rotates a work-piece around an axis of rotation to perform different operations such as cutting, sanding, knurling, drilling, deformation, facing, threading and turning, with tools which are applied to the work-piece to create an object with symmetry around that axis. Lathes are used in metalworking, metal spinning, roll turning, thermal spraying, reclamation, and glass-working.
Latex blending – It is the process of mixing two or more different latex dispersions to create a new material with improved or combined properties. This is a technique used to improve characteristics like physical strength, chemical resistance, and processing, frequently by creating very fine, stable dispersions which allow for molecular-level incorporation of different components.
Latex emulsion – It is a stable dispersion of polymer particles in an aqueous (water) medium, created through emulsion polymerization. It is a type of oil-in-water emulsion used in applications such as coatings, adhesives, and materials for paper, textiles, and drilling fluids. Its key advantages include low viscosity, good heat dissipation, and the ability to create flexible, durable products.
Latex-modified concrete – It is a type of concrete which incorporates a liquid polymer latex admixture, very frequently styrene-butadiene rubber (SBR), to improve its bonding, durability, and water resistance. This polymer emulsion replaces some mixing water, forming a co-matrix with the hydrated cement which creates a more dense, less permeable, and stronger material. This makes latex-modified concrete ideal for high-performance applications like bridge deck overlays and repairs, since offers superior adhesion to existing concrete and is resistant to chloride and moisture penetration.
Lath boundary – It is the low-angle boundary which separates adjacent laths within a block, which is a substructure of lath martensite. These boundaries consist of a high density of dislocations and influence a material’s mechanical properties by controlling how dislocations propagate during deformation.
Lathe turning – It is a machining process where a rotating work-piece has material removed by a cutting tool to create cylindrical shapes. The cutting tool moves parallel to the axis of rotation, creating a helical path and shaping the work-piece. This process is used to produce several parts with specific diameters, lengths, and profiles.
Lath martensite – It is the martensite formed partly in steels containing less than around 1 % carbon and solely in steels containing less than around 0.5 % carbon as parallel arrays of packets of lath-shape units 0.1 micrometer to 0.3 micrometer thick.
Lath structure – It refers to a specific morphology of martensite or bainite crystals which are thin, flat, and elongated, forming parallel stacks or packets within a material’s micro-structure. It is also a building framework made of thin strips of wood, metal, or other material which serves as a base for plaster, stucco, or roofing materials. These strips are used to create a surface for walls, ceilings, and roofs to which plaster can be applied, and are also used to form latticework or trellises.
Lattice – A space lattice is a set of equal and adjoining parallellopipeds formed by dividing space by three sets of parallel planes, the planes in any one set being equally spaced. There are seven ways of so dividing space, corresponding to the seven crystal systems. The unit parallelopiped is normally chosen as the unit cell of the system. It is also a point lattice is a set of points in space located so that each point has identical surroundings. There are 14 ways of so arranging points in space, corresponding to the 14 Bravais lattices.
Lattice Boltzmann model – It is a mesoscopic method which tracks the evolution of the probability distribution function for particles in a discretized space and time domain, mainly used for simulating droplets, bubbles, and interfacial dynamics in fluid systems. It offers advantages over atomistic approaches and is particularly effective for modeling multiphase flows without needing explicit interface tracking.
Lattice constants – It consist of one of the physical dimensions and angles which determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. It is the length of any side of a unit cell of a given crystal structure. The term is also used for the fractional coordinates (‘x’, ‘y’, and ‘z) of lattice points when these are variable.
Lattice defects – These are also known as crystal defects. These are deviations from the perfect, repeating arrangement of atoms in a crystalline solid. These imperfections can significantly influence the properties of materials, such as their strength, electrical conductivity, and optical behaviour.
Lattice diffusion – It is one of the primary diffusion mechanisms during sintering. It is predominant for large particles and higher temperatures, and its diffusion coefficient for the same conditions is smaller than that of grain boundary diffusion, and much smaller than that for surface diffusion.
Lattice distortion – It is the local disruption of a crystal lattice structure caused by the presence of atoms with different sizes, leading to atomic displacements from ideal positions. This distortion creates internal strain and stress within a solid solution alloy, impacting properties like strength, ductility, and thermal and electrical conductivity. It is a key factor in materials like high-entropy alloys, where it influences their improved mechanical behaviour and can be manipulated to design materials with specific characteristics.
Lattice energy – It is the energy released upon the formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to exist initially in the gaseous state. Lattice energy can be viewed as a measure of the cohesive forces which bind ionic solids. It is hence directly related to several other physical properties of the solid, including solubility, hardness, and volatility.
Lattice girder – It is an iron or steel structure consisting of two horizontal beams connected by diagonal struts. It is a truss girder where the load is carried by a web of latticed metal.
Lattice imaging – It is a technique which utilizes multiple beams in a transmission electron microscope to resolve the periodicity of atomic structures in thin samples, allowing for the visualization of lattice planes and atomic positions under specific conditions.
Lattice parameter – It defines the size and shape of a unit cell, the smallest repeating unit of a crystal lattice, by specifying the lengths of the unit cell edges (a, b, c) and the angles between them (A, B, C). These six parameters are fundamental to describing the geometry of the crystal structure and its properties.
Lattice pattern – It is a pattern of filament winding with a fixed arrangement of open voids.
Lattice plane – It is a plane containing at least three non-collinear Bravais lattice points. Equivalently, a lattice plane is a plane whose intersections with the lattice (or any crystalline structure of that lattice) are periodic (i.e. are described by 2D Bravais lattices). A family of lattice planes is a collection of equally spaced parallel lattice planes that, taken together, intersect all lattice points. Every family of lattice planes can be described by a set of integer Miller indices which have no common divisors (i.e. are relative prime). Conversely, every set of Miller indices without common divisors defines a family of lattice planes. If, on the other hand, the Miller indices are not relative prime, the family of planes defined by them is not a family of lattice planes, because not every plane of the family then intersects lattice points. Conversely, planes which are not lattice planes have aperiodic intersections with the lattice called quasi-crystals. This is known as a ‘cut-and-project’ construction of a quasi-crystal (and is typically also generalized to higher dimensions).
Lattice rotation – It refers to the change in orientation of a crystal lattice during deformation. It is a fundamental mechanism in how materials respond to stress, particularly during plastic deformation, and plays a key role in the development of textures and microstructures.
Lattice sites – These are the specific points in a crystal lattice where atoms, ions, or molecules are located. These points are arranged in a periodic, three-dimensional pattern which represents the structure of a crystalline solid. Connecting these points with straight lines shows the overall structure, and the smallest repeating unit of this pattern is called a unit cell.
Lattice tower – It is a tall, open-framework structure, typically made of steel, which supports several types of equipment like antennas, power lines, or observation platforms. It is characterized by its crisscrossing framework, which provides strength and stability while keeping the structure relatively lightweight.
Laue equations – These three simultaneous equations which state the conditions to be met for diffraction from a three-dimensional network of diffraction centres.
Laue method (for crystal analysis) – It is a method of X-ray diffraction using a beam of white radiation, a fixed single crystal sample, and a flat photographic film normally normal to the incident beam. If the film is located on the same side of the sample as the X-ray source, the method is known as the back reflection Laue method, if on the other side, as the transmission Laue method.
Laue zone – It is a collection of reciprocal lattice planes which are all perpendicular to the direction of the incident X-ray or electron beam. In a diffraction pattern, the spots belonging to the same Laue zone appear as a circle or arc. The central zone is called the zero-order Laue zone (ZOLZ), and the subsequent outer zones are called higher-order Laue zones (HOLZ).
Launchers and receivers trap – It is also known as pig traps. Pig traps are specialized sections of pipe used to introduce and retrieve pipeline inspection gauges (pigs) for maintenance, cleaning, or inspection purposes. Launchers are located at the beginning of a pipeline segment, allowing pigs to be inserted, while receivers are at the end, enabling pig retrieval. In the launcher and receiver traps, consideration is given for mechanical handling facilities for pigs and line logging devices. The facilities include (i) overhead hoists or access for fork lift truck, (ii) winching points for logging device withdrawal, (iii) storage and inflation facilities for pigs and logging devices, and (iv) cradle for inserting the pig. Vertical launchers are to be placed on the outside area on the platform and are to be open to air. Provision is made within the closure for hydraulic connections to allow the operation of a hydraulic equipment, such as maintenance pigs and hydro-plugs.
Launder – It is a channel for transporting molten metal. It is also a box conduit conveying particles suspended in water. It is also a chute or trough for conveying pulp, water or powdered ore in a mill.
Lauth type three-high mills – These rolling mills are used for rolling of plates. This rolling mill differs from normal three-high rolling mills. In these rolling mills, the lower roll is fixed. The middle roll, which has smaller diameter than the upper and lower rolls is raised and lowered by a power-operated lever alternately as the rolling stock passed under or over it. The draft is achieved by adjusting the upper roll using a screw gear. The small middle roll is an idler roll, and it is set in rotation by the friction developed by the upper and lower rolls. It is not subject to bending stress, as it is always in contact with one or other of the large rolls. The advantage of smaller diameter of the intermediate roll consists in supporting the rolled stock elongation. The disadvantage is more rapid wear and tear of the intermediate roll.
Lava – It is a general name for the molten rock ejected by volcanoes.
Laval nozzle – It consists of a convergent inlet and a divergent outlet duct. Frequently, the term convergent-divergent (CD) nozzle is used.
Laves phase alloys – These are a class of intermetallic compounds with a specific AB2 stoichiometry and characteristic crystal structures. They are known for their ability to form in various systems and have been studied for their unique properties and potential applications in areas like superconductivity, magnetism, and structural materials.
Laves phases – These are a class of intermetallic compounds with the general formula AB2, characterized by their specific crystal structures and the way atoms are packed. They are frequently found in binary alloys and are known for their unique properties and potential applications in several fields.
Law of conservation of energy – It states that the total energy of an isolated system remains constant and it is said to be conserved over time. In the case of a closed system, the principle says that the total quantity of energy within the system can only be changed through energy entering or leaving the system.
Law of conservation of mass – It is the principle of mass conservation which states that for any system closed to all transfers of matter, the mass of the system remains constant over time. During a chemical reaction, the total mass of the products is to be equal to the total mass of the reactants. In other words, mass cannot be created or destroyed during a chemical reaction, but is always conserved.
Law of continuity – This law states that, for a system with impermeable walls and filled with an incompressible fluid, the rate of flow is same at all points in the system. This can be expressed as Q = A1v1 = A2v2, where ‘Q’ is the rate of flow, ‘A’ is the cross-sectional area of the stream, ‘v’ is the velocity of the stream, and the subscripts 1 and 2 designate two different locations in the system.
Law of definite proportions – It states that a given chemical compound always contains its component elements in a fixed ratio (by mass) and does not depend on its source or method of preparation. For example, oxygen makes up about 8/9 of the mass of any sample of pure water, while hydrogen makes up the remaining 1/9 of the mass, i.e., the mass of two elements in a compound are always in the same ratio. Along with the law of multiple proportions, the law of definite proportions forms the basis of stoichiometry.
Law of mass action – It states that the rate of a chemical reaction is directly proportional to the product of the active masses (concentrations) of the reactants, each raised to the power of its stoichiometric coefficient. This law helps predict the behaviour of solutions at equilibrium, stating that the ratio of the concentrations of products to reactants, raised to their respective powers, is a constant value.
Law of multiple proportions – It states that in compounds which contain two particular chemical elements, the quantity of element ‘A’ per measure of element ‘B’ differs across these compounds by ratios of small whole numbers. For example, the ratio of the hydrogen content in methane (CH4) and ethane (C2H6) per measure of carbon is 4:3. This law is also known as Dalton’s Law. Along with the law of definite proportions, the law of multiple proportions forms the basis of stoichiometry.
Laws of thermodynamics – These are a set of laws which define a group of physical quantities, such as temperature, energy, and entropy, which characterize thermodynamic systems in thermodynamic equilibrium. The laws also use different parameters for thermodynamic processes, such as thermodynamic work and heat, and establish relationships between them. They state empirical facts which form a basis of precluding the possibility of certain phenomena, such as perpetual motion. In addition to their use in thermodynamics, they are important fundamental laws.
Lay – It is the direction of predominant surface pattern remaining after cutting, grinding, lapping, or other processing. In the wire rope, lay is the helix or spiral of the wires and strands. The word ‘lay’ has got three meanings in the rope design. The first two meanings are descriptive of the wire and strand position in the rope. The first meaning describes the direction in which strands rotate around in the wire rope i.e. right lay or left lay. If the strands rotate around the wire rope in a clock wise direction, the rope is said to be right lay. When the strands rotate in the counter-clockwise direction, the wire rope is left lay. The second meaning shows the relationship between the direction strands lay in the wire rope and the direction wire lay in the strands. The third meaning is a length measurement used in manufacturing and inspection. In the third meaning it is the linear length along the rope that a strand makes one complete spiral around the rope core. Lay length is measured in straight line parallel to the centre line of the rope, not by following the path of the strand.
Layer bearing – It is a bearing constructed in layers such as bi-metal bearing and tri-metal bearing.
Layered graphite – It is a form of carbon where carbon atoms are arranged in multiple flat layers, with each layer consisting of atoms in a hexagonal pattern. Within each layer, the atoms are held by strong covalent bonds, but the layers themselves are weakly bonded by van der Waals forces, allowing them to slide past one another. This structure makes graphite soft, slippery, and an excellent lubricant, while the delocalized electrons within the layers enable electrical conductivity.
Layered silicates – These are a class of minerals with a crystal structure made of stacked, planar layers. These layers are formed from silicon-oxygen tetrahedra and metal-hydroxyl octahedra, creating a repeating structure with a characteristic thickness of about 1 nano-meter and varying lateral dimensions. The gaps between these layers are sometimes called interlayers or galleries.
Layered structure – It is a system design where components are organized into distinct, stacked layers, with each layer having a specific task and interacting only with the layers immediately above or below it. This modular approach improves manageability by allowing changes to be made to one layer without affecting others, and it is normally used in computer operating systems.
Layer-lattice material – It is a material having a layer like crystal structure, but particularly solid lubricants of this type.
Layer super-lattice – It is a structure with a periodic, nano-meter-thin alternating pattern of two or more different materials, frequently semi-conductors. These layers are so thin that the wave-functions of carriers (like electrons) can overlap, allowing them to tunnel between layers, which creates mini-bands and modifies the material’s electronic properties from those of conventional semi-conductors.
Layout -It refers to the arrangement of physical facilities such as machines, equipment, tools, utilities, furnaces, and control rooms etc. in such a manner so as to have quickest flow of material at the lowest cost and with the least quantity of handling in the production of the product from the receipt of the input materials to the dispatch of the finished products.
Layout design – It normally involves getting a suitable arrangement of equipments or units and their connections within a pre-defined area based on pre-specified criteria. These items can be process-equipment, furnaces, electric control rooms, instruments and control rooms, product inspection area, and quality control laboratory, stores, workshops, offices, canteen and change rooms, and fire station etc. with connections by pipes, conveyors, vehicular transport or any other suitable material handling equipment. Plant layout includes plant roads and rail tracks.
Layout diagram – It is a visual representation of the physical arrangement of components in a circuit, building, or software interface, showing their actual positions, sizes, and connections.
Layout drawing – A layout drawing depicts design development requirements. It is similar to a detail, assembly, or installation drawing, except that it presents pictorial, notational, or dimensional data to the extent necessary to convey the design solution used in preparing other engineering drawings. The layout drawing normally does not establish item identification. The layout drawing is prepared either as (i) a conceptual design layout to present one or more solutions for meeting the basic design parameters and to provide a basis for evaluation and selection of an optimum design approach, (ii) a design approval layout to present sufficient details of the design approach for cost estimating and design approval, (iii) a detailed design layout drawing depicting the final development of the design in sufficient detail to facilitate preparation of detail and assembly drawings, (iv) a geometric study to develop movement of mechanical linkages, clearances, or arrangements. The layout drawing includes (i) location of primary components, (ii) interface and envelope dimensions including a cross-reference to applicable interface control documentation, (iii) paths of motion, (iv) operating positions, (v) critical fits and alignments, (vi) selected materials, finishes, and processes, (vii) cellars, pipeline routing and sizes, (viii) adjustments, (ix) critical assembly details and sequence, and (x) identification of change parts and critical spare parts.
Layout sample – It is a prototype forging or a cast used to determine conformance to designed dimensions.
Layout strategy – It is a plan for arranging physical resources within a facility to optimize efficiency, productivity, and flow. This involves determining the placement and configuration of equipment, work-spaces, and people to minimize material handling costs, improve work-flows, and improve employee and customer satisfaction. Common types of strategies include product-oriented, process-oriented, cellular, and fixed-position layouts, with the best choice depending on factors like product volume, variety, and material flow.
Lay-up – It consists of the reinforcing material placed in position in the mould. It is the process of placing the reinforcing material in position in the mould. It is also the resin-impregnated reinforcement. Lay-up is also a description of the component materials, geometry, and so on, of a laminate. It is also a fabrication process involving the assembly of successive layers of resin-impregnated material.
Lay-up process -It is a moulding process for composite materials, in which the final product is got by overlapping a specific number of different layers, normally made of continuous polymeric or ceramic fibres and a thermoset polymeric liquid matrix. It can be divided into dry lay-up and wet lay-up, depending on whether the layers are pre-impregnated or not. Dry lay-up is mainly used in the areas which have higher performance requirements. In the dry lay-up, it is possible to get complex shapes with good mechanical properties. This is since a wet lay-up cannot be performed with uni-directional fabrics, which have better mechanical properties, so it is mainly used in the areas which have lower performance requirements. The main stages of the lay-up process are cutting, lamination and polymerization. Even though some of the production steps can be automated, this process is mainly manual (hence frequently referred to as the hand lay-up process), leading to laminates with high production costs and low production rates with respect to other techniques. Hence, nowadays, it is mainly suitable for small series production runs of 10 parts to 1000 parts
LC circuit – It is also called a resonant circuit, tank circuit, or tuned circuit; It is an electric circuit consisting of an inductor, represented by the letter ‘L’, and a capacitor, represented by the letter ‘C’, connected together.
LD converter – The LD converter, named after the Austrian towns Linz and Donawitz, is a refined version of the Bessemer converter, where blowing of air is replaced with blowing oxygen.
L-direction – It is the ribbon direction, that is, the direction of the continuous sheets of honeycomb.
L/D ratio – In bearing technology, it is the ratio of the axial length of a plain bearing to its diameter.
Leachability – It is the ability of a substance to be dissolved and washed out of a material by a liquid, such as water. It measures the potential for components, especially pollutants, to migrate from a solid material into the surrounding environment, like soil or groundwater.
Leachable – It means extractable by chemical solvents.
Leachant – It is the liquid solvent used to dissolve and separate a soluble material from an insoluble solid matrix in the process of leaching.
Leachate – It is a liquid which has been in contact with waste in a landfill or other porous substrate and can have undergone chemical or physical changes as a result, and has subsequently seeped out.
Leachate concentration – It refers to the specific quantities of dissolved substances (like organic matter, heavy metals, and inorganic chemicals) present in a liquid which has percolated through waste material. These concentrations are measured in units like parts per million (ppm) and are a key indicator of the liquid’s strength and potential for environmental contamination.
Leachate treatment – It is the process of purifying liquid which has passed through a landfill or other waste site to remove harmful contaminants before it is disposed of or discharged. This is necessary to prevent groundwater, soil, and air contamination, and involves several methods like biological, chemical, and physical-chemical processes.
Leached concentrations – These refer to the quantities of substances which are released from a material into water, which can be assessed through laboratory tests and field monitoring, and are calculated based on transport models which account for factors such as infiltration and mixing with groundwater.
Leached heavy metals – These are toxic metals which are released from a solid material (like waste or soil) and dissolved into a liquid medium, such as water, through the process of leaching. This occurs when a liquid, like rainwater or groundwater, percolates through contaminated material, drawing out the heavy metals like lead, cadmium, or chromium. The released metals can then contaminate groundwater and soil, posing an environmental and health risk.
Leaching – It is a chemical process for the extraction of valuable minerals from ore. It is also, a natural process by which ground waters dissolve minerals, hence leaving the rock with a smaller proportion of some of the minerals than it contained originally. It is also the movement of water carrying dissolved or suspended substances through soil.
Leaching behaviour – It refers to the process of extracting soluble materials from an insoluble solid through dissolution in a leachant, influenced by physical and chemical reactions, concentration gradients, and transport mechanisms such as advection and diffusion. It encompasses the dynamics of contaminant movement away from the solid matrix until equilibrium is reached.
Leaching properties – These refer to the characteristics which determine the transfer of chemical species from solid construction materials, such as cement and concrete, to the aqueous phase, influenced by environmental factors like rainfall and temperature. These properties are important for ensuring acceptable levels of leaching to soil and water, particularly in the development of new blended cements and concrete mix designs.
Leaching solution – It is a liquid solvent, such as an acidic solution or a chemical reagent, which is used to extract a soluble substance from a solid by dissolving it. This process is common in metallurgy, where the solution dissolves valuable metals from an ore, leaving the insoluble impurities behind. For example, sodium hydroxide can leach aluminum from bauxite ore, and sodium cyanide can be used to leach silver.
Leaching test – It is a laboratory procedure used to determine how much of a substance can be released from a solid material into a liquid, called a leachant. It involves agitating the solid with a liquid under controlled conditions, then analyzing the resulting liquid (leachate or eluate) for the dissolved substances. These tests are used to assess the potential for environmental contamination from materials like waste, soil, or construction byproducts when they interact with water.
Lead – It is the axial advance of a helix in one complete turn. It is also the slight bevel at the outer end of a face cutting edge of a face mill.
Lead (Pb) – It is a chemical element which has atomic number 82. It is a heavy metal and is denser than majority of the common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray colour when exposed to air. Lead is an undesirable element in steel. It increases the machinability of steel. It is virtually insoluble in liquid or solid steel. However, it is sometimes added to carbon and alloy steels by means of mechanical dispersion during pouring to improve the machinability. The addition of around 0.25 % lead improves machinability. It also causes a reduction in fatigue strength, ductility and toughness but this only becomes serious in the transverse direction and at high tensile levels. In creep resisting alloys, very small quantities of lead can be harmful. It has no effect upon the other properties of the steel.
Lead-acid battery – It is a rechargeable electro-chemical cell which uses lead plates and dilute sulphuric acid to store and supply electrical energy through reversible chemical reactions. It has a positive plate of lead di-oxide, a negative plate of spongy lead, and a sulphuric acid electrolyte, which are separated by a porous insulating material. Lead-acid batteries are normally used in vehicles and for backup power because they can deliver large amounts of power quickly, despite their low energy-to-weight ratio.
Lead alloys – These are metallic mixtures of lead with other elements, typically metals like antimony, tin, or calcium, to improve its mechanical properties such as hardness and strength. These alloys are used in applications ranging from lead-acid batteries to cable sheathing and roofing.
Lead angle – In cutting tools, it is the helix angle of the flutes.
Lead blast furnace – It is a vertical rectangular shaft furnace for the smelting of sintered lead oxide with coke and fluxes.
Lead burning – It is a misnomer for welding of lead.
Lead casting – It is a manufacturing process which involves pouring molten lead into a mould to create a solidified object with a specific shape, such as a battery part or a shielding component. The term can also refer to the specific job of a lead caster, who operates machinery and handles molten lead to produce these cast parts. This process utilizes lead’s properties, like its low melting point, for specific applications which benefit from radiation shielding, sound insulation, or electrical conductivity.
Lead compensation – It is a control system technique which uses a lead compensator to improve system stability and transient response by introducing a ‘phase lead’. It is particularly useful for systems with good steady-state accuracy but poor stability margins, as it increases the phase margin without considerably impacting steady-state error. This leads to a faster response time and less overshoot in the system’s output.
Lead compensator – It is a type of control system component which improves a system’s stability and transient response by providing a positive phase angle at high frequencies.
Lead-cooled fast reactor – It is a type of nuclear reactor which uses molten lead or lead-bismuth eutectic as its main coolant and operates with a fast neutron spectrum. These ‘generation IV reactor designs’ are characterized by a high degree of inherent safety, the ability to operate at high temperatures with low pressure, and the potential to efficiently burn or burning actinides from spent nuclear fuel to reduce waste. It is characterized by advantages such as high natural abundance, inertness, excellent thermodynamic properties, and the ability to operate at low pressures, while also addressing concerns related to coolant voiding and reducing the potential for disruptive problems.
Lead deposits – These are naturally occurring mineral deposits which contain lead, with the most common ore being the sulphide mineral galena (PbS). These deposits are frequently formed through hydrothermal processes, where hot, saline fluids transport lead from the earth’s crust to a specific site of deposition, where it precipitates out.
Leaded brass – It is a type of brass alloy which contains a small quantity of lead, typically between 1 % and 4 %. This lead addition improves the alloy’s machinability, making it easier to cut and shape during manufacturing. Leaded brass also shows good corrosion resistance and strength.
Leaded bronzes – These are copper-base alloys containing up to 10 % tin and up to 30 % lead.
Leaded copper-zinc alloys – These are brasses (copper and zinc alloys) which have lead added to improve their machinability and lubrication properties. The lead content allows the alloy to be machined at high speeds by creating small, easily cleared chips, making it ideal for applications needing extensive machining, such as electrical connectors and mechanical bearings.
Leaded petrol – It is gasoline which has been mixed with a lead compound called tetra-ethyl-lead (TEL) to boost its octane rating and prevent engine knocking. While it improves engine performance and efficiency, the lead is toxic, causing widespread environmental contamination and severe health problems. Leaded petrol has now been phased out globally, with unleaded gasoline being the standard for vehicles today
Leaded phosphor bronze, phosphor bronze – It is a hard and strong cast and wrought copper / tin alloys with small, deliberate, phosphorus additions. Wrought alloys contain 4 % to 8 % tin, whilst cast alloys contain 9 % to 12 % tin. Leaded phosphor bronzes, with lead contents up to 20 %, are normally available only as castings.
Leaded steels– These are steels to which lead, in quantities ranging from 0.15 % to 0.35 %, is normally added along with sulphur to improve the machinability of the steel product.
Lead, fastener – It is the linear distance which a point on a fastener thread advances axially in one revolution (equal to the pitch of the fastener).
Lead frame – It is a metal structure used in semi-conductor packages to connect a chip to the outside world. It consists of a central die pad for mounting the chip and a series of leads which are wire-bonded to the chip’s terminals. The lead frame supports and protects the chip, and its leads provide electrical connections for signals to travel between the chip and a circuit board.
Lead inductance – It is the parasitic inductance of the physical wires, or leads, connecting a component to a circuit board. Although it is not a closed loop like a coil, the leads have an equivalent inductance which can affect a circuit’s performance by opposing changes in current. This inductance is especially important in high-frequency applications, where it can increase a component’s overall inductance.
Leading dislocation – It is a type of crystal defect where a half-plane of atoms is missing or misplaced, causing a disruption in the crystal lattice. This imperfection allows the crystal to deform more easily under stress. Leading dislocations are a type of edge dislocation, where the defect is a line defect, not a point defect, and is associated with a missing or extra half-plane of atoms.
Leading indicator – It is a measurable metric which changes before the general economy or a specific outcome does, making it a tool for predicting future trends and turning points. These indicators are forward-looking, allowing organizational managements to anticipate what can happen rather than reacting to what already has.
Leading manufacturer – It is an organization which at the forefront of a particular industry, recognized for producing a high volume of goods, having substantial market share, and frequently setting industry standards for innovation and quality. These organizations are typically the dominant players in their specific field, known for their advanced position and substantial output of finished goods.
Leading power factor – It occurs in an alternating current circuit when the current leads the voltage, which is caused by a capacitive load. In a leading power factor, the current reaches its peak before the voltage does, unlike a lagging power factor where the current lags behind the voltage. This indicates that the circuit is absorbing reactive power from the grid.
Lead, lead time – it is the quantity of time an activity can be brought forward with respect to the activity it is dependent upon.
Lead mineral – It is a naturally occurring mineral compound which contains lead, with the most common being the ore galena (PBS). These minerals are the main source for extracting metallic lead, which is a dense, bluish-gray metal known for its corrosion resistance and malleability, but also its high toxicity. Other mineral forms include lead carbonate and sulphate.
Lead mine – It is a location where lead ore is extracted from the earth, mainly through mining, to be processed into lead metal. These are historic and modern sites where people dig for the mineral, which can then be used for several industrial purposes or recycled.
Lead paint – It is a type of paint which contains lead pigments, which is now largely replaced by less hazardous alternatives but remains a toxic hazard because of its potential to cause lead poisoning through inhalation of dust from deteriorating surfaces.
Lead plating – It is a process where a layer of lead is applied to the surface of another metal, typically to improve corrosion resistance, improve solderability, or provide radiation shielding. This process involves depositing lead ions onto a conductive material, normally through electroplating or other methods.
Lead refining – It is the process of purifying impure lead bullion by removing impurities like antimony, tin, arsenic, and copper to create high-purity lead suitable for industrial uses, such as batteries and radiation shielding. This is accomplished through methods such as electrolytic refining or fire refining, which chemically or physically separate the contaminants from the molten metal.
Leads – In pile foundations, it is a wooden or steel frame with one or two parallel members for guiding the hammer and piles in the correct alignment. There are three basic types of leads namely (i) fixed, which is fixed to the pile rig at the top and bottom, (ii) swinging, which is supported at the top by a cable attached to the crane, and (iii) semi-fixed or telescopic, which is allowed to translate vertically with relation to the boom tip.
Lead screw – It is a mechanical component which converts rotary motion into linear motion using a threaded rod and a matching nut. It is a type of power screw used in machinery for precise actuation and is common in applications like 3D printers and automated machinery. Unlike ball screws, lead screws have higher friction since the nut threads are in direct contact with the screw threads, but this also allows them to be self-locking, which is beneficial for vertical applications.
Lead sheath – It is a protective layer made of pure lead or lead alloy that encases electrical cables to shield them from moisture, chemicals, and mechanical damage. This metallic covering provides excellent corrosion resistance and mechanical strength, making lead-sheathed cables particularly useful for underground, underwater, and industrial applications where cables are exposed to harsh conditions.
Lead slag – It is a by-product formed during the production of lead, originating from lead ore smelting or the recovery of waste lead-acid batteries. It consists of a glassy matrix with embedded mineral phases and varies in composition based on factors such as ore type and impurities, typically containing iron oxides, silica, and lead in different forms.
Lead smelting – It is the process of extracting metallic lead from lead ore or recycled lead (like from batteries) by heating it with reducing agents to separate the metal from its ore. This process typically involves initial steps like crushing and concentration, followed by smelting in furnaces to reduce lead oxides, and finally, refining to remove impurities.
Lead solubility – It is the ability of lead compounds to dissolve in a solvent, with its solubility in water highly dependent on factors like pH and alkalinity. While elemental lead is not very soluble in water, different lead compounds are polar and readily dissolve, and their concentration in solutions like drinking water can be influenced by chemical factors such as pH and alkalinity, with lower pH normally increasing solubility.
Lead sulphate – Its chemical formula is PbSO4. It is an inorganic, white, crystalline solid which is sparingly soluble in water and known for its role in lead-acid batteries. It can be prepared in a laboratory or found naturally as the mineral anglesite. Because of the toxicity of lead, lead sulphate is to be handled with care, since it poses health risks if ingested or inhaled.
Lead time – It is the time from the initial contract / order to the time it takes the customer to receive their products. It is the delivery time for an item of inventory to be moved from a source location to a destination through a specific route. Detail is specific to the level of the location. It is also the time to produce a customer’s order from order placement to shipment.
Lead-tin alloy coated sheet and strip (terne plate) – This coated product is produced by coating with lead-tin alloy either by dipping in a bath of molten alloy or electrolytically. In general, the highest nominal mass specified for the coating corresponds to a minimum of 120 grams per square metre including both sides.
Lead titanium – It refers to a compound which can be synthesized as PbTiO3, normally prepared through techniques such as sputtering and chemical vapour deposition, where lead oxide (PbO) and titanium dioxide (TiO2) are co-deposited to form mixed films with substantial dielectric properties.
Lead zirconate titanate (PZT) – It is a piezoelectric ceramic material made from a solid solution of lead titanate and lead zirconate, with a chemical formula of Pb[ZrxTi(1-x)]O3. It is known for its strong piezoelectric properties, meaning it can change shape when an electric field is applied, making it widely used in applications like sensors, actuators, and transducers. Its specific properties are highly dependent on the ratio of zirconium to titanium.
Leaf chain – It is an assembly of alternating sets of pin links and articulating links on pins which are free to articulate in the holes of the articulating links. The pin link plates normally are press fitted onto the ends of the pins in the chain. The centre link plates are normally slip fitted on the pins. Leaf chains are intended to run over sheaves, so there is no provision for them to engage a sprocket. Leaf chains are used almost exclusively for lifting and counterbalancing. Tensions are very high, but speeds are slow. Normally the chains work intermittently. The main considerations in the design of the leaf chains are tensile loads, joint wear, and link plate and sheave wear.
Leafing – It is formation of a continuous film of metal through surface tension. The higher is the surface tension, the more rapid and complete is the leafing.
Leaf seal – It is a sealing structure composed of several thin plates arranged in a ring shape which, when in contact with a rotating rotor, form a thin fluid film whih lifts the plates slightly, allowing for non-contact sealing and reducing wear while effectively sealing high pressure differences.
Leaf spring – It is a simple form of spring normally used for suspension in wheeled vehicles. A leaf spring is one or more narrow, arc-shaped, thin plates which are attached to the axle and chassis in a way that allows the leaf spring to flex vertically in response to irregularities in the road surface. Lateral leaf springs are the most commonly used arrangement, running the length of the vehicle and mounted perpendicular to the wheel axle, but numerous examples of transverse leaf springs exist as well.
Leaf walls – These refer to walls constructed with multiple layers, typically made of barely-cut or pebble stone masonry, which can have an inner rubble core, and are categorized as double- or triple-leaf walls. These structures frequently show poor structural response during earthquakes, leading to the potential detachment and collapse of the external layers.
Leak – It is an undesirable flow of gas or liquid through the wall of a vessel through an imperfection such as a hole, crack or bad seal. Leaks need a pressure difference to generate the flow; They always flow from higher pressure to lower pressure. Typically, leaks are thought of as travelling from positive pressure (inside an object) to atmospheric pressure (outside an object). This is not always the case as a leak can be from atmosphere to inside an evacuated object.
Leakage – It is the uncontrolled quantity of fluid which enters or leaves through the enclosure of air or gas passages.
Leakage distance – It is also known as creepage distance. It is the shortest path between two conductive parts measured along the surface of an insulator. This distance is important for electrical insulation to prevent current from leaking across the surface from a high-voltage point to a lower-voltage or grounded point.
Leakage flow – It is the unwanted and unintended movement of a fluid (like liquid or gas) through a small gap or clearance between components, driven by a pressure difference. This flow bypasses the main system, reducing efficiency and causing losses. Examples include fluid escaping from a pump shaft seal, flow between compressor scroll stages, or current leaking through an electrical insulator.
Leakage inductance – It is an inherent characteristic of transformers and inductors resulting from imperfect magnetic coupling between windings. Instead of all magnetic flux linking the primary to the secondary, some flux ‘leaks’ and creates an unwanted series inductance in the main winding. This phenomenon reduces signal transfer efficiency and can be minimized by improving winding and core geometry or by designing for specific applications, like power supplies or resonant circuits, where it can be intentionally used.
Leakage loss – It refers to the unintended escape or flow of a substance (such as a fluid, gas, electric current, or even data or revenue) from its intended path or container, resulting in a reduction in efficiency, performance, or an actual quantifiable loss of the substance or value.
Leakage rate – It is the flow rate of a liquid or gas through a leak at a given temperature as a result of a specified pressure difference across the leak. Standard conditions for gases are 25 deg C and 100 KPa. Leakage rates are expressed in different units such as pascal cubic meters per second or pascal litres per second or standard cubic centimeter per second.
Leakage reactance – It is the opposition to the change in current in a coil because of a magnetic field which does not link with all the turns of the other winding. This happens in electrical devices like transformers and motors since some of the magnetic flux produced by one winding is not linked with the other, creating a self-reactance which can be modelled as a voltage drop and negatively impacts performance. Leakage reactance is a component of the total impedance in a transformer, along with winding resistance.
Leakage resistance – It is the resistance offered by an insulating material or an unintended path to the flow of electrical current. It is a measure of how much current ‘leaks’ through an insulator because of imperfections, contamination, or moisture, and is inversely related to leakance. A higher leakage resistance indicates better insulation and is desirable for proper circuit operation and safety.
Leakage stream – It is an unintended fluid flow which bypasses its intended path in a system, such as a heat exchanger or a turbo-machine, because of the pressure differences across clearance gaps. These streams reduce efficiency by lowering effective heat transfer area, decreasing work transfer, or causing other performance losses. Examples include fluid bypassing heat exchanger tubes or air leaking between different pressure zones in an HVAC (heating, ventilation, and air conditioning) system.
Leak-before-break (LBB) – It is a term which is used in reference to a methodology which means that a leak is going to be discovered prior to a fracture occurring in service. Leak-before-break has been applied to gas and oil pipelines, pressure vessels, and nuclear piping etc.
Leak detection system – It is a technology or an engineering system used to identify and locate unintended releases of liquids, gases, or other substances from pressurized or sealed environments, such as pipelines or storage tanks. These systems are designed to promptly alert operators to minimize damage, prevent incidents, and improve safety and reliability.
Leak detector – It is a device for detecting, locating or measuring or combination thereof, leakage.
Leaker – It is a foundry term for castings which leak under liquid or gaseous pressure.
Leak location – It is the process of identifying the precise point of escape for a fluid (liquid or gas) from a contained system. It is an important step after leak detection, which confirms a leak is present, and involves using different methods like acoustic sensors, pressure testing, or search gases to pinpoint the leak’s exact position in a pipeline, vessel, or sealed enclosure.
Leak position – It is the specific, physical location of a leak within a system, such as a pipe or vessel. It is frequently determined by analyzing how pressure waves, generated by the leak, travel through the system to pinpoint its exact spot.
Leak-proof – It describes a design or construction which is impermeable and does not allow the escape or entry of a substance (liquid or gas) under specified conditions of pressure and temperature. The term implies a higher standard of containment than ‘leak-resistant’, aiming for effectively zero leakage.
Leak proof doors – Leaking doors of a coke oven battery are always a major source of pollution. The design of oven doors has gone through a process of evolution, starting from luted doors to the present generation self-regulating zero leak doors. The imported features of the leak proof doors are (i) a thin stainless-steel diaphragm with a knife edge as a sealing frame built in between the door body and the brick retainer, (ii) spring loaded regulation on the knife edge for self-sealing, (iii) provision for air cooling of the door body, and (iv) large size gas canals for easier circulation of gas inside the oven. The advantage of leak proof doors is minimization of door leakages, regulation free operation, longer life because of less warping of the air-cooled door body and reduced maintenance.
Leak rate – It is the rate at which a fluid (liquid or gas) passes a seal or barrier. For vessels with vacuum, the leak rate of the vessel indicates the quantity of gas flow which escapes through the walls of the vessel. It is to be noted, however, that the leak rate for a leak depends on the type of gas.
Leak-resistant – It describes containers designed to minimize or prevent the escape of liquids. These containers frequently feature tightly fitting lids, sealed seams, or coatings which help contain liquids, though they are not entirely leakproof.
Leak testing – It is a non-destructive test for determining the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leak testing concerns the escape or entry of liquids or gases from pressurized or into evacuated components or systems intended to hold these liquids. Leaking fluids (liquid or gas) can penetrate from inside a component or assembly to the outside, or vice versa, as a result of a pressure differential between the two regions or as a result of permeation through a somewhat extended barrier. Leak testing encompasses procedures for one or a combination of the these (i) locating (detecting and pinpointing) leaks, (ii) determining the rate of leakage from one leak or from a system, and (iii) monitoring for leakage. Leak testing systems use a variety of gas detectors, are used for locating (detecting and pinpointing) leaks, determining the rate of leakage from one leak or from a system, or monitoring for leakage.
Lean amine – It is a regenerated amine solvent which has been stripped of its absorbed acid gases, such as carbon di-oxide (CO2) and hydrogen sulphide (H2S). It is a clean, ready-to-use solution which enters an absorber column to remove contaminants from a gas stream, becoming ‘rich amine’ after absorbing the acid gases. This rich amine is then sent to a regenerator where the acid gases are removed, and the amine is cleaned and converted back into lean amine for reuse.
Lean burn combustion – It is a process in which a fuel-air mixture with more air than is stoichiometrically needed is burned in an internal combustion engine. This excess air improves fuel economy and leads to more complete combustion, which reduces hydrocarbons (HC) and carbon mono-oxide (CO) emissions. However, the higher combustion temperatures can increase nitrogen oxides (NOx) emissions.
Lean concrete – It is a low-strength concrete mix with a high ratio of aggregate to cement, making it cost-effective for non-structural applications. It is mainly used as a base or sub-base layer in construction, such as under foundations, floors, and roads, to provide a level, stable surface and protect the main structural concrete from soil and moisture.
Lean execution system – It is a holistic approach which applies ‘lean principles’ to the organizational processes for planning, prioritizing, managing, and measuring work to maximize customer value. Unlike traditional systems which can have long feedback loops, a lean execution system enables employees to quickly identify and solve problems in real-time to reduce downtime, increase efficiency, and deliver results faster. It focuses on eliminating waste and non-value-adding activities through continuous improvement and a commitment to principles like value-stream mapping, flow, and pull systems.
Lean exothermic furnace atmosphere – It is a protective gas produced by the controlled combustion of hydrocarbons (like natural gas) with air in a ratio which is leaner than what is needed for complete combustion. This results in an atmosphere with very low levels of hydrogen and carbon mono-oxide, and a higher concentration of carbon di-oxide and nitrogen, used for processes like non-oxidizing annealing.
Lean manufacturing – It is a method of manufacturing goods aimed mainly at reducing times within the production system as well as response times from suppliers and customers. It is closely related to another concept called just-in-time manufacturing. It is a production methodology based on the idea of streamlining and doing more with less, such as by providing customers with the same product value while eliminating waste and thus reducing production costs.
Lean philosophy – It is a methodology which transforms work-place culture through principles aimed at eliminating waste, improving flow, and ensuring that all activities add value to the customer. Its ultimate goal is to create a perfect process that is valuable, capable, adequate, available, flexible, and linked to continuous flow.
Lean procurement – In supply chain management, it is defined as ‘achieving more with less’. This whole process is perceived differently by organizations and procurement professionals. For example, some organizations try to reduce their headcount. Others do it by reducing their inventory. Lean procurement is a systematic approach which defines what adds value within a manufacturing system. It reduces everything else which does not. Lean procurement is based upon lean production. The primary focus is on operational efficiency and customer satisfaction. It is a cycle of continuous improvement which has the target to streamline processes within the supply chain. It eliminates non-value-added activities and waste. Waste can be termed as inventory, time, or costs.
Lean six sigma – Lean six sigma combines the no-waste ideals of lean manufacturing with the no-defects target of six sigma. The goal of lean six sigma is to eliminate waste and defects so that products cost less and deliver more consistent quality.
Lean solution – It is a strategy or method which aims to deliver maximum value to customers by eliminating waste, such as unnecessary time, effort, or materials, and by continuously improving processes. It is based on the core principle of identifying and removing ‘Muda’, or waste, from the value stream and improving efficiency, quality, and productivity.
Lean start-up – It is an organized approach to starting a new business which focuses on validated learning and iterative product releases to shorten development cycles and test a business model’s viability. Instead of extensive upfront planning, it emphasizes creating a ‘minimum viable product’ (MVP) to quickly get customer feedback, allowing startups to efficiently adapt to market demands. The core loop is build-measure-learn, where hypotheses are tested through experiments to avoid wasting time, money, and resources on products customers do not want.
Lean stream – It refer to two main concepts namely a ‘lean fulfillment stream’ in supply chain management and a ‘lean value stream’ in manufacturing and process improvement. A lean fulfillment stream is a highly efficient, customer-focused supply chain which minimizes waste and operates on a ‘pull’ system to meet customer demand. A lean value stream is the set of all actions (both value-adding and non-value-adding) needed to take a product or service from a concept to the customer.
Lean supply chain – It is all about delivering a product to the end customer in the most efficient way and with the least amount of waste. It is not about cost advantages alone. It is the elimination of unnecessary elements and steps that ultimately lead to a substantial reduction in lead time, i.e., from manufacturing to delivering the end product. These builds supply chain resilience. With increasing complexity in global supply chains, the lean supply chain model has become a top priority for global organizations that do not want any lag in responding to changing market demands.
Lean thinking – It is a management philosophy which focuses on creating customer value by eliminating waste and continuously improving processes. It originated from the Toyota production system and involves a mindset of optimizing the entire value stream to increase efficiency, quality, and productivity.
Lean vapour compression – It is a process configuration which uses a vapour compressor to recycle vapour from the flashed lean solvent stream (solvent with low absorption) back into the bottom of a stripper column. This helps reduce the reboiler’s heat duty and energy consumption by using the compressed vapour to provide heat, leading to a lower solvent temperature and reduced condenser load. Lean vapour compression is a technique used to optimize energy in processes like carbon capture, although it needs an additional compressor and a two-phase separator.
Leap second – It is a one-second adjustment added to ‘coordinated universal time’ (UTC) to keep it synchronized with the earth’s rotation, which varies slightly. It is necessary since the earth’s rotation is slowing down, causing a small but growing discrepancy between atomic time (UTC) and astronomical time (UT1). Leap seconds are added around six months in advance, typically at the end of June or December.
Learning curve – It is a curve which shows the way that production time or manufacturing cost decreases with cumulative production because of higher worker experience.
Learning effects – It refer to the cost reduction resulting from technological experiences, where cumulative capacity, production, and skilled operators improve process performance through the learning process.
Learning management system – It is a software application which serves as a central platform for creating, delivering, and managing educational or training programmes. It streamlines the entire learning process by handling tasks like course creation, content delivery, user registration, and tracking learner progress through reports and analytics. Organizations use learning management systems for everything from corporate training to online university courses.
Learning mechanism – It is the process by which individuals or systems acquire knowledge, skills, and behaviours through experience. These mechanisms involve cognitive processes like perception, attention, and memory, and they allow for the adaptation of behaviour in response to new information and environments.
Learning scheme – It is a detailed, long-term structured plan (scheme of work) which outlines the process of learning is implemented in the organization over a specified period. It serves as a roadmap for the human resource development in the organization.
Learning technique – It is a specific method or strategy used to acquire, retain, and apply knowledge or skills more effectively. These techniques can be an action a learner takes, such as summarizing or practicing, to make learning more active and efficient than passive reading.
Leased land – It is a land under a contract where the owner (lessor) grants the right to use a parcel of land to another party (lessee) for a specific period in exchange for rent. The lessee does not own the land but can typically use it for a specific purpose, such as building a structure, while remaining responsible for its upkeep. These leases frequently involve long-term arrangements, sometimes for 99 years or more, particularly in commercial contexts like ground leases where the tenant constructs a building on the owner’s land.
Leased line – it is a dedicated, private communication circuit between two or more points, rented from a service provider for a fixed monthly fee. It provides a continuous, exclusive connection for data, internet, and telephone services, unlike shared broadband connections. This results in consistent, symmetrical (equal upload and download) speeds, high reliability, and greater security.
Least commitment policy of design – It is the concept that it is best to allow as much freedom as possible for downstream decisions in the design process so that engineers are free to develop the best possible solutions unconstrained by previous unnecessary commitments (decisions).
Least common multiple – It is the smallest positive integer which is a multiple of two or more numbers. For example, the least common multiple of 4 and 6 is 12 since 12 is the smallest number that both 4 and 6 divide into evenly. It is frequently used in mathematics, particularly when working with fractions, to find a common denominator.
Least count of a measuring instrument – It is the smallest value in the measured quantity which can be resolved on the instrument’s scale. It essentially indicates the precision of the instrument, e.g., a meter scale, with its smallest divisions in millimeters, has a least count of 1 millimeter.
Least mean squares (LMS) – It is an adaptive filtering algorithm used to minimize the mean square error between a desired and an actual output. It is a type of stochastic gradient descent method which iteratively adjusts filter weights to reduce the error signal (the difference between the desired signal and the filter’s output) using only the error from the current time step.
Least squares estimation – It is a technique of estimating statistical parameters from sample data whereby parameters are determined by minimizing the squared differences between model predictions and observed values of the response. The method can be regarded as possessing an empirical justification in that the process of minimization gives an optimum fit of observation to theoretical models, but for restricted cases such as normal theory linear models, estimated parameters have optimum statistical properties of unbiasedness and efficiency.
Least squares method – It is a statistical technique used to find the best-fit line or curve for a set of data points by minimizing the sum of the squares of the vertical distances (residuals) between the observed data points and the values on the curve. This method is widely used in regression analysis, data fitting, and predictive modeling.
Least squares techniques – These are a set of methods used to find the best-fitting curve or line for a set of data points by minimizing the sum of the squares of the differences between the observed values and the values predicted by the curve or line. This approach is widely used in various fields like statistics, data fitting, and regression analysis.
Leather gloves – These are sturdy and provide protection against cuts and burns. Leather gloves also protect against sustained heat. They protect against sparks, moderate heat, blows, chips and rough objects. These gloves can be used for tasks such as welding.
Leaving loss – It is the kinematic energy which cannot be utilized because of the absence of a following stage in the steam path of a turbine.
Le Chatelier’s principle – It states that if a dynamic equilibrium is disturbed by changing conditions, the position of equilibrium shifts to counteract the change and establish a new equilibrium. In simpler terms, if a people stress a system at equilibrium, it responds in a way which minimizes the stress. This principle applies to several factors like concentration, pressure, and temperature.
Ledeburite – It is the eutectic of the iron-carbon system, the constituents of which are austenite and cementite. The austenite decomposes into ferrite and cementite on cooling below Ar1 temperature, the temperature at which transformation of austenite to ferrite or ferrite plus cementite is completed during cooling.
Ledge – It a narrow, flat area like a shelf that sticks out from a building, cliff, or other vertical surface. In geology, a ledge is a narrow shelf or projection of rock, much longer than width, formed on a rock wall or cliff face.
Ledger – It is a book or system for recording financial transactions, such as income and expenses of the organization. It acts as a principal accounting book, organizing debits and credits for each specific account (like cash, customers, or vendors). Ledgers help create financial statements and can be physical books or digital documents.
LED lamp – It is a light-producing device which uses a light-emitting diode (LED) to emit light, a type of solid-state lighting. Instead of a filament or gas, it relies on an opto-electronic semi-conductor device which glows when an electric current passes through it, a process called electro-luminescence. This makes LED lamps more energy-efficient, durable, and longer-lasting than traditional incandescent or fluorescent bulbs.
LED voltage – It refers to the forward voltage (Vf), which is the minimum voltage needed across an LED’s anode and cathode to turn it on and make it conduct current. This voltage is specific to each LED (light-emitting diode), varying by colour, and is the voltage the LED ‘drops’ when it is lit.
Left-hand cutting tool – It is a cutter, whose all-flutes twist away in a counter-clockwise direction when viewed from either end.
Left-hand lay – It describes the direction of the strands in a wire rope, meaning they twist in a counter-clockwise direction as they spiral around the rope’s core. It is a term used in rope manufacturing and can also refer to a specific type of ‘hand lay-up’ manufacturing process in the composite materials industry, which involves manually applying resin to a mould.
Left hand rule – It is known as Fleming’s left-hand rule. It is a mnemonic device used to determine the direction of the force acting on a current-carrying conductor within a magnetic field; it is used for electric motors.
Left skewed – It is said of distributions where the majority of the cases have high values of the variable, and a few outliers have very low values.
Left-truncated cases – It is subjects in survival analysis who have already been at risk for event occurrence for some time when they come under observation.
Legal and regulatory framework – It is the overarching set of laws, rules, and guidelines which govern the activities of individuals, organizations, or industries within a specific jurisdiction. The legal framework consists of fundamental laws passed by legislatures, such as statutes and constitutions, which establish the foundation for legal rights and responsibilities. The regulatory framework provides more detailed, specific rules created by government agencies to oversee and enforce those laws, ensuring things like fair competition, consumer protection, and safety standards.
Legal Metrology – It is the application of measurement standards to the control of the daily transactions of trade and commerce. It is more commonly known as ‘Weights and Measures’. Internationally, coordination among nations on Legal Metrology matters is, by international agreement, handled by a quasi-official body ‘the International Organization for Legal Metrology (OIML)’.
Legal requirement – It can be anything which is demanded of a person or an organization by statute, regulation, common law, or by-law.
Legibility – It is the discernibility of text, focusing on whether the user can read the text rather than understanding its meaning. It is influenced by design factors such as font type, size, colour, and contrast.
Lehrer diagram – It is a specialized phase diagram used to control the gaseous nitriding process for steels. It plots the thermodynamic stability of different iron-nitrogen (Fe-N) phases (like alpha, gamma’ and eta iron nitrides) as a function of temperature and nitriding potential (the ratio of ammonia to hydrogen in the processing atmosphere).
Leidenfrost effect – It is a phenomenon in which a liquid, poured onto a glowing surface considerably hotter than the liquid’s boiling point, produces a layer of vapour which prevents the liquid from rapid evaporation. Rather than making physical contact, a drop of water floats above the surface.
Leidenfrost point – It is the temperature at which a liquid, when placed on a surface hotter than its boiling point, forms a vapour layer that suspends the liquid above the surface, preventing direct contact and rapid boiling. This vapour layer acts as an insulator, reducing heat transfer and causing the liquid to ‘dance’ or ‘skitter’ across the surface instead of immediately boiling away.
Leidenfrost phenomenon – It is slow cooling rates associated with a hot vapour blanket which surrounds a part being quenched in a liquid medium such as water. The gaseous vapour envelope acts as an insulator, hence slowing the cooling rate.
Leidenfrost temperature – It is the minimum surface temperature at which a liquid droplet, when placed on a hot surface, is insulated by a vapour layer which prevents direct contact. This phenomenon, known as the Leidenfrost effect, causes the droplet to ‘skate’ or hover on the vapour cushion, allowing it to evaporate more slowly than on a cooler surface. It marks a transition from nucleate boiling to film boiling.
Lemon bearing (elliptical bearing) – It is a two-lobed bearing.
Lendl procedure – It is an empirical procedure for roll pass design for simple square, diamond, round and oval grooves in which the pass cross section is subdivided into vertical strips. The spread of each of these strips is then calculated by the empirically derived spread formulae developed by Ekelund.
Lendl’s rule – It is a rule for the spread calculation. The spread calculation is computed using Wusatowski’s formula at each iteration, in conjunction with an iterative procedure, which is based on the method of maximum width. If the spread into the roll pass is within the admissible limit, roll pass design is completed.
Length – It is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In majority of the systems of measurement a base unit for length is chosen, from which all other units are derived. In the International System of Units (SI) system, the base unit for length is the metre.
Length, fastener – It is the axial distance between the bearing surface of the head and the extreme point.
Length, grip – It is the length of the unthreaded portion of the fastener (i.e. shank) measured axially from the underside of the bearing surface to the starting thread.
Length of a curved beam – It is the geometric length along a specific axis (like the centroidal or outer contour). It is also the length of the neutral axis, which is relevant for strain energy calculations. In engineering, the length is frequently defined based on the system line, which typically follows the beam’s centroidal axis, but can also be defined as the outer contour or another specified path depending on the context and software used.
Length of an arc – It is the distance along a curve between two points. This distance is measured along the curved path itself, not the straight-line distance between the two endpoints (the chord). It is a fundamental concept used in calculating the dimensions and behaviour of curved structures, and mechanical components.
Length scale – It is a particular length or distance determined with the precision of at most a few orders of magnitude. Length scale refers to the characteristic distance over which a phenomenon occurs or a physical feature exists, such as the size of an atom or the diameter of a pipe. It is a fundamental concept in physics and engineering that helps define the relevant physical laws or mechanisms governing a system, which can be analyzed independently for different scales.
Length, thread – It is the length of the threaded portion of the fastener. In all the commercial fasteners, threaded length is a function of fastener diameter.
Length-to-diameter ratio – It is a measurement which compares an object’s length to its diameter, calculated by dividing the length by the diameter. It is used in to describe shape, such as a long, thin object having a high length-to-diameter ratio or a flat, round object having a low length-to-diameter ratio. For example, in injection moulding, it describes the screw’s length compared to its diameter, which impacts how the plastic is processed.
Length-tolerance – It is the acceptable range of variation for a part’s length, ensuring it can still function correctly. It is defined by a nominal or target length and its upper and lower limits, which are the maximum and minimum dimensions allowed. For example, a drawing might specify a length of 60 mm with a tolerance of +0.045 mm and -0.000 mm, meaning the actual length can be anywhere from 60.000 mm to 60.045 mm.
Lennard-Jones parameter – It is the process of adjusting the parameters (sigma and eta) of the Lennard-Jones potential model to accurately describe the interactions between atoms or molecules. This is important for molecular dynamics simulations, where the parameters are optimized by comparing simulation results to experimental data, such as melting points or densities, to improve the accuracy of the model.
Lennard-Jones potential – It is a simplified model for describing the potential energy of interaction between two neutral, non-bonding particles like atoms or molecules, based on their distance of separation. It combines a short-range repulsive force (frequently modeled as proportional to ‘r’ to the power -12) which prevents the particles from occupying the same space and a long-range attractive force (frequently modeled as proportional to ‘r’ to the power-6) because of the factors like van der Waals forces. The potential energy reaches a minimum at an equilibrium distance, where the attraction and repulsion are balanced.
Leno weave – It is an open mesh fabric in which the warp yarns are held by the filling yarns, with the filling yarns twisted around alternating warp yarns in opposite direction. Sometimes used as impact breaker.
Lens – It is a transparent optical element, so constructed that it serves to change the degree of convergence or divergence of the transmitted rays.
Lens distortion – It is a type of optical distortion where straight lines in an object appear curved in the image, normally occurring with low-cost wide-angle lenses. This distortion can manifest as barrel distortion in lenses with short focal lengths and pincushion distortion in those with long focal lengths.
Lens, mining – It is normally used to describe a body of ore that is thick in the middle and tapers towards the ends.
Lenticular – It is a deposit having roughly the form of a double convex lens.
Lenz’s law – It states that the direction of the current induced in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes the change in magnetic flux that produced it. This opposing force is a direct result of the principle of conservation of energy and means that any induced current always acts to resist the change which is causing it.
Leptons – These are a class of elementary, sub-atomic particles which do not experience the strong nuclear force. There are six types of leptons, which are divided into two groups: charged leptons (electron, muon, and tau) and neutral leptons (three types of neutrinos). The best-known lepton is the electron, and all leptons are considered fundamental particles, meaning they are not made of smaller units.
Lesson learned – It is knowledge or understanding gained from an experience, whether positive or negative, which results in a change in behaviour or action. It is a summary of what happened, why it happened, and how to improve for the future by preventing mistakes or adapting to new situations.
Lester diagram – It is a project management tool which combines the speed of an arrow diagram with the logic of a precedence diagram, representing activities as flow lines rather than points. It is used for network planning and analysis, showing total and free float using vertical and horizontal differences, respectively, and is considered faster to draft and less space-intensive than traditional precedence diagrams.
Lethal dose (LD) – A lethal dose of radiation is the dose needed to cause death to 50 % of an exposed population within 30 days (LD 50/30). Typically, the LD 50/30 is in the range from 400 rem to 450 rem (4 Sievert to 5 Sieverts) received over a very short period. Duration of the exposure is important here as the dose received by patients in radiotherapy treatments can reach 20 Sieverts over time.
Letter of credit (LC) – It is also known as a documentary credit or bankers’ commercial credit, or letter of undertaking. It is a payment mechanism used in international trade to provide an economic guarantee from a credit-worthy bank to an exporter of goods.
Letter of interest – It is a proactive document sent to an organization to express one’s desire to work there, even if no specific job opening is advertised. It acts as one’s professional introduction, highlighting the skills, qualifications, and the value one can bring to the organization, with the goal of opening a conversation about potential future opportunities. It differs from a cover letter, which is a response to a specific job posting.
Level – In mining, it is the horizontal openings on a working horizon in a mine. It is customary to work mines from a shaft, establishing levels at regular intervals, normally around 50 metres or more apart.
Level control system – It is a mechanism, often automated, used to maintain a desired liquid or gas level within a container by adjusting the flow of fluid in or out of it. It operates by continuously measuring the current level and comparing it to a setpoint, then using a controller to send signals to an actuator (like a valve or pump) to correct any deviations, ensuring a constant and safe operational level.
Level control valve – It is an altitude control valve which automatically responds to changes in the height of a liquid in some storage system.
Level converter – It is an electronic device which translates a signal from one voltage level to another, enabling components with different operating voltages to communicate with each other. It acts as a translator, safely stepping signals up or down between logic levels, such as from a 5 volt system to a 3.3 volts system, preventing damage to components and ensuring accurate data transmission.
Levelized capital cost – It is the cost of a project’s initial investment, expressed as a per-unit cost over the asset’s lifetime. It is a key component of the ‘levelized cost of energy’ and helps compare different technologies by normalizing the initial investment to account for variations in project life, scale, and operational lifespan. This metric allows for the comparison of capital costs across different energy generation methods by representing the cost of capital on a per-unit-of-energy basis.
Levelized cost of electricity – It is a metric which calculates the average cost to build and operate a power plant over its lifetime, expressed in cost per unit of energy. It is used to compare the cost of different electricity generation technologies by factoring in the present value of all costs (construction, financing, operation, maintenance) divided by the present value of all electricity produced over the project’s lifespan. A key purpose of levelized cost of electricity is to provide a basis for economic comparison to determine the most viable energy source at a particular site.
Levelized cost of energy – It is a metric which calculates the average total cost to build and operate a power plant over its entire lifetime, divided by the total energy it produces. It represents the minimum price at which electricity must be sold to break even over the project’s lifespan. Levelized cost of energy is used for comparing different energy generation methods on a consistent basis for investment planning.
Levelized cost of heat – It is a metric which estimates the average cost per unit of heat produced by a system over its entire lifespan. It is calculated by dividing the total discounted costs (including initial investment, fuel, and operation and maintenance) by the total discounted heat produced. Levelized cost of heat allows for the comparison of different heating technologies by providing a single, consistent value which accounts for all life-cycle expenses and energy output.
Leveller – It is a machine in a rolling mill which utilizes a series of rollers to straighten and flatten metal sheets or plates which have been deformed during the rolling process. This process removes imperfections like coil set, cross bow, edge wave, and centre buckle, ensuring the material achieves the desired flatness.
Leveller chatter (roll or leveler) – It consists of several intermittent lines or grooves which are normally of full width and perpendicular to the rolling or extrusion direction.
Leveller lines – These are lines on sheet or strip running transverse to the direction of roller leveling. These lines can be seen upon stoning or light sanding after leveling (but before drawing) and can normally be removed by moderate stretching.
Leveller mark – It is the repeating depression caused by a particle adhering to a rotating roll over which the metal has passed.
Leveller streak – It is a streak on the sheet surface in the rolling direction caused by transfer from the leveller rolls.
Levelling – It is the mechanical flattening of rolled sheet, strip, plate or foil by reducing or eliminating distortions. In surveying, levelling is the process of determining the vertical position (elevation) of points relative to a reference datum (a fixed level). It is a crucial technique for establishing the height differences between points on the earth’s surface. Essentially, levelling helps surveyors understand how high or low different locations are in relation to each other, which is vital for several construction and engineering projects.
Levelling action -It is the ability of a plating solution to produce a plated surface smoother than that of the substrate.
Levelling effect – It is the effect of a solvent on the chemical properties of acids or bases which are dissolved in the solvent. The strength of a strong acid is limited or ‘levelled’ by the basicity of the solvent, and likewise the strength of a strong base is limited by the acidity of the solvent, such that the effective pH of the solution is higher or lower than is suggested by the acid’s or base’s dissociation constant.
Levelling factors – In work measurement, levelling factors are numerical adjustments applied to observed task times to account for variations in worker performance, skill, effort, and working conditions. These adjustments ensure that the final allowed time reflects a standard or desired performance level, rather than just the time taken by a specific individual. Essentially, they help to ‘level’ the playing field by standardizing the observed times.
Levelling feet – It is the adjustable supports or feet beneath the conveyor structure allowing precise levelling and stabilization. Regular adjustments can be needed for ensuring proper alignment and balance.
Levelling process – It is the process by which a levelling machine flattens metal strip, coil, or sheets by bending it up and down over the interrupting arcs of upper and lower sets of long, slender work rolls. Leveling machines normally use 17, 19, or 21 relatively small diameter rolls whose deflection under load is controlled by additional back-up rollers and a rigid frame.
Levelling, roller – It is levelling carried out by bending.
Levelling screws -These are essential components in precision engineering, used for fine-tuning and stabilizing machinery and equipment. They ensure that machines remain perfectly level, which is crucial for operational accuracy and longevity. These screws come in various types, including standard, heavy-duty, self-levelling, and precision variants, each designed to meet specific load and adjustment requirements.
Levelling, stretcher – It is levelling carried out by uniaxial tension.
Levelling, tension – It is levelling continuously carried out by uniaxial stretching, normally with the assistance of bending.
Levelling, thermal – It is levelling carried out at a high temperature under an applied load normal to the surface to be flattened.
Level of assurance – It is a measure of the confidence in a claimed identity, ensuring an electronic credential or transaction can be trusted to be from the correct individual. Higher levels of assurance mean higher certainty that the identity is legitimate, but also higher complexity and potential cost, while lower levels are less secure but more convenient. It is determined by factors such as the strength of the identity proofing process, the types of credentials used, and the authentication mechanisms in place.
Level of effort – It consists of work which is not directly associated with components of a work breakdown structure but which can instead be thought of as support work. Examples of level of effort include maintenance and accounting. It is one of three types of activities used to measure work performance as part of earned value management.
Level of measurement – It is also called scale of measure is a classification which describes the nature of information within the values assigned to variables. The best-known classification has with four levels, or scales, of measurement. These are nominal, ordinal, interval, and ratio. This framework of distinguishing levels of measurement originated in psychology and has since had a complex history, being adopted and extended in other disciplines. For example, ratio level of measurement is the highest level, characterized by data with a true zero point, allowing for meaningful ratios between values. This means one cannot only categorize and order data points but also perform calculations like multiplication and division to compare their magnitudes, e.g., if one object is twice as heavy as another (measured on a ratio scale), it truly represents a doubling in weight.
Level of safety – It is a discrete classification (from one to four) which specifies the safety integrity requirements for safety instrumented functions within safety instrumented systems, with level 4 representing the highest safety integrity and level 1 the lowest. It also means the degree of perceived safety.
Level of significance – The level of significance is the probability of rejecting a null hypothesis, when it is in fact true. It is also known as alpha, or the probability of committing a Type I error.
Level probe – The level probe, sometimes also referred to as a submersible transmitter, is a special type of pressure transmitter used for level measurements. For this purpose, the level probe measures the hydrostatic pressure at the bottom of the vessel. Particularly important is the choice of material for the case and cables, and also the seals at connection points, because of the complete and permanent submersion into the medium. Venting of the sensor system, needed for the gauge pressure measurement, is achieved through a ventilation tube passed through the cable.
Levels – The levels are the number of categories in a categorical (factor) variable. The categorical variable for gender (male, female) has two levels. There are five levels in the variable with the categories (very bad, bad, middling, good, and very good).
Level safety requirement – It is a safety criterion that is allocated to specific components of a system to meet overall safety standards, frequently defined by a classification system like the ‘safety integrity level’ (SIL) or ‘performance level’ (PL). It includes requirements for the system’s design, installation, performance, and maintenance, which are determined through risk assessment. These requirements ensure a specific level of safety integrity and reliability for safety-related functions within a system.
Level sensor – It is a device which detects or measures the quantity of a material, like a liquid or solid, inside a container. It works by converting this information into an electrical signal for monitoring or control, helping to manage storage levels and prevent overflows. There are two main types of level sensors namely point level sensors, which indicate a specific height, and continuous level sensors, which provide an ongoing measurement.
Levels of automation – There are five levels of automations which are normally used in the industry. These levels are level 0, level 1, level 2, level 3, and level 4. Under level 0, there is practically no automation and every control of the equipment and process consists of manual control. The level I automation is restricted to the production processes. It includes control of equipments and production processes. It includes dedicated digital controller (DDC). It does not include networking. The level 1 automation utilizes more and more modern field instruments, remote I/Os (input / output), field busses and graphical interfaces. Normally the level 1 control systems today are capable to handle more and more complex MIMO (multi-input and multi-output) systems and cascade systems with improved accuracy. Level 2 automation level includes supervisory control. Supervisory control combines the production scheduling and management information functions with the process control functions to form a hierarchical control system. It also includes process models, automatic material handling, tool setting, packing and other auxiliary systems. It utilizes physical process models to supplement the level 1 control giving calculated set-values to level 1 process control. The process monitoring and diagnostics play also important role in level 2 systems. The level 2 automation systems offer two main capabilities namely (i) tight optimized control of each operating unit of the plant based upon the production levels and constraints set by level 3 production planning and control (PPC) system by providing optimal operating set points to the manufacturing processes with this control reacting directly to any emergencies that occur in its own unit, and (ii) improved overall reliability and availability of the total control system through fault detection, fault tolerance, redundancy, and other applicable techniques built into the system’s specification and operation. Level 3 automation system contains scheduling and delivery status monitoring features. It includes production planning and control functions. Both production planning and production control functions are included in this level. It also includes maintenance planning and analysis of data. This system is a total integrated automation system. With this level of automation, the remote operation in-charge can view all the data. Enterprise resource planning (ERP) is a popular software-based technology related to level 3 automation. Level 4 control connects customer orders and material and makes capacity allocation to production. This complex enterprise resource planning system is used to manage the complete order-supply-chain follow-up and documentation.
Level sensors – These sensors detect the level of liquids and other fluids and fluidized solids, including slurries, granular materials, and powders that exhibit an upper free surface. Substances that flow become essentially horizontal in their containers (or other physical boundaries) because of gravity whereas most bulk solids pile at an angle of repose to a peak. The substance to be measured can be inside a container or can be in its natural form (e.g., a river or a lake). The level measurement can be either continuous or point values. Continuous level sensors measure level within a specified range and determine the exact amount of substance in a certain place, while point-level sensors only indicate whether the substance is above or below the sensing point. Normally, the latter detect levels which are excessively high or low.
Levels of total productive maintenance – There are five levels of total productive maintenance. At the first level, initial cleaning and inspection is performed. The aim of this level is to increase the efficiency of the equipments and to find problems, which have not been found before. Unnecessary items and equipment are also removed and general cleaning is performed to clear away the dirt and dust. At the second level, all the sources of contamination, dirt, and oil are eliminated. The places which are difficult to clean and inspect, are relocated or re-assembled to allow access. The third level introduces standards for cleaning, lubricating, and maintenance. The standards are to make sure that the cleaning is performed effectively. Problem areas are taken into closer look to pin-point the places where lubrication has been inefficient and insufficient. The process is also to be documented for auditing purposes, and what were the situations before the cleaning and after the cleaning are to be recorded. This is an easy way to realize the positive changes achieved by total productive maintenance. At the fourth level, the operators are to be trained and advised in the basic functions and controls of the equipments they use. This is to make sure that the operators are able to perform easy maintenance tasks on their own and they are aware of the functions of the equipment with which they are working. The fifth level sums up the standards and learning acquired by training at the third and fourth levels and it is time when the operator starts to perform the basic inspection and maintenance task autonomously. At this stage, the photographs of the final results are taken and the pictures are to be compared to with photographs taken at the earlier stages. Comparison of the pictures are very easy and straight forward method used to document the achievements of the total productive maintenance programme.
Level transmitters – These are instruments which provide continuous level measurement. They measure levels of media, such as water, viscous fluids, and fuels.
Level winding – In filament- wound reinforced plastics, It is a winding with the filaments essentially perpendicular to the axis (90 -degree or level winding).
Lever – It is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is divided into three types. A lever amplifies an input force to provide a higher output force, which is said to provide leverage, which is mechanical advantage gained in the system, equal to the ratio of the output force to the input force. As such, the lever is a mechanical advantage device, trading off force against movement.
Lever arm – It is the perpendicular distance from the axis of rotation to the line of action of a force. It is a crucial component for calculating torque, as torque is the product of the force and its lever arm. A longer lever arm means a higher torque can be applied with the same quantity of force.
Lever law – It refers to a method used in the analysis of binary alloy systems to determine the proportion of phases present at a given temperature and composition by utilizing a tie line on a phase diagram. It assists in calculating the compositions of solid and liquid phases during the solidification process.
Lever mechanism – It is a simple machine consisting of a rigid bar or rod which rotates around a fixed pivot point called a fulcrum. It uses the principles of torque to amplify force, allowing a smaller input force (effort) to move a larger load or to amplify movement over a distance. The three key components are the fulcrum, the effort, and the load.
Lever rule – It says that the fraction of one phase is computed by taking the length of tie-line from the overall alloy composition to the phase boundary for the other phase, and dividing by the total tie line length. In an alloy or a mixture with two phases, liquid and solid, which themselves contain two elements, A and B, the lever rule states that the mass fraction of the solid phase is given by equation phase percent = (opposite arm of the lever / total length of tie-line) x 100. Lever rule is used to determine the mole fraction or the mass fraction of each phase of a binary equilibrium phase diagram. It can be used to determine the fraction of liquid and solid phases for a given binary composition and temperature which is between the liquidus and solidus line. The lever rule is a mechanical analogy to the mass balance calculation.
Levigation – It is separation of fine powder from coarser material by forming a suspension of the fine material in a liquid. It is a means of classifying a material as to particle size by the rate of settling from a suspension.
Levitation melting – It is an induction melting process in which the metal being melted is suspended by the electro-magnetic field and is not in contact with a container.
Lewis-acid – It is a chemical species which accepts a pair of electrons from a Lewis base to form a coordinate covalent bond. This makes Lewis-acids electron-pair acceptors. Common examples include electron-deficient molecules like boron trifluoride (BF3) and aluminum chloride (AlCl3), as well as cations like ‘H+’ and ‘Fe2+’.
Lewis-base – It is a chemical species which can donate a pair of electrons, acting as an electron pair donor. These substances are typically electron-rich, meaning they have lone pairs of electrons available to form a new covalent bond with a Lewis-acid (an electron pair acceptor). Common examples of Lewis bases include ammonia (NH3), water (H2O), and hydroxide ions (OH-).
Lewis-acid-base bond – It is a coordinate covalent bond formed when a Lewis base (an electron donor) donates an electron pair to a Lewis acid (an electron acceptor). This theory is fundamental to understanding the formation of metal complexes and the reactions involved in metal processing, where metal cations (Lewis-acids) form bonds with ligands like water or ammonia (Lewis bases).
Lewis-acid catalyst – It is a substance which can accept an electron pair to speed up a chemical reaction. It works by activating a reactant, typically by coordinating with a Lewis base within that reactant to form a complex. This process makes the reactant more electrophilic, lowering the energy needed for the reaction to proceed and allowing it to complete more efficiently. Examples include metal salts like aluminum chloride (AlCl3) and zinc chloride (ZnCl2).
Lewis number – It is a dimensionless number which represents the ratio of thermal diffusivity to mass diffusivity, indicating how quickly heat diffuses through a material compared to how quickly mass diffuses. It is used in fluid dynamics and thermodynamics to analyze processes involving simultaneous heat and mass transfer, such as in combustion and HVAC (heating, ventilation, and air conditioning) systems. A Lewis number close to 1 means heat and mass diffuse at similar rates, while values above or below 1 indicate that one process is faster than the other.
Lewis-structure – It is a simplified visual representation of a molecule’s valence electrons, showing how they are arranged and shared in chemical bonds. It uses dots for valence electrons and lines to represent bonding pairs between atoms, and it also shows any lone pairs of electrons. Lewis structures help visualize electron distribution, predict molecular geometry, and understand chemical bonding, including single, double, or triple bonds.
Lexicographic method – It is a multi-objective optimization approach which minimizes objective functions in a prioritized order, ensuring that each function meets its specified constraints, resulting in a Pareto optimal solution.
Liability – It is a quantity of value which an organization owes. More technically, it is value which the organization is expected to deliver in the future to satisfy a present obligation arising from past events.
Library procedure – It is a set of documented, standardized steps and policies which a library follows to ensure consistency in its operations, maintain quality, and provide guidance to employees and users. These procedures cover everything from processing new materials and managing circulation to assisting patrons with research and enforcing rules.
License agreement – t is a legal contract which grants one party (the licensee) permission to use another party’s (the licensor) intellectual property, such as a brand, patent, or software, under specific terms and conditions. It allows the licensee to use, produce, or sell the property for a defined period and territory without the licensor transferring ownership. This agreement is common for software, franchising, and the use of copyrighted or patented materials.
Licensed product – It is a product for which an organization (the licensee) has legal permission from the owner (the licensor) to manufacture, market, and sell. This permission is granted through a legal agreement which outlines the terms, which frequently include royalty payments to the licensor. The products themselves are typically those which infringe on the licensor’s patents or intellectual property if produced without the license.
Licensed service – It is a service which is provided using another organization’s intellectual property, products, or methods, for which the provider has got permission (a license) from the owner. This permission allows the service provider to use the licensor’s technology, brands, or other proprietary assets to offer their service, frequently in exchange for fees or royalties. Examples include an organization providing contract research using another organization’s patented technology or an organization offering a service which incorporates licensed software.
Licensed user – It is an individual or device which has been granted permission to use a specific software or service by an organization, frequently in exchange for a license fee. This user is typically assigned a unique user account and is authorized to access the software, regardless of whether they are actively using it at any given moment. The specific software and permissions, a user has access to, are defined by the license agreement purchased by the organization.
License holder – License holder is an individual or entity which has been officially granted permission to perform a specific activity, use a product, or operate a business through a license. They are the person or organization to whom a license has been issued and are needed to comply with the terms and conditions of that license.
Lid – It is a removable or attached top for a ladle.
LIDAR survey – Laser Induced Differential Absorption Radar (LIDAR) is a high-resolution digital elevation maps generated by airborne Lidar have led to significant advances in the ability to detect subtle topographic features. Very precise topographical map data is created through Lidar surveys.
Lid lifters – These are a part of the coal charging car in coke oven batteries. The rotary magnetic lid lifters guided by the centering pins and installed on the charging lids, can follow the eventual misalignment occurring to the lids themselves. The lids are equipped with detection devices capable to verify the presence and correct engagement of the lids. For all the other functional units of the charging car, the hydraulic actuation is arranged above the top platform, in order to be completely protected from flames and heat. A second row of lid lifters called auxiliary lid lifter are arranged at coke oven N+2 in order to manipulate the lids opened for decarbonizing operations. The special electro-magnets are arranged on a cardanically suspended cross beam. Because of the cardanic suspension, the lids are concentrically replaced even when they have not concentrically been lifted.
Lid luting system – It is a part of the coal charging car in coke oven batteries. It consists of special designed horizontal tanks which have the scope to distribute the luting liquid along the four charging holes thus avoiding sticking problems. The mixture is prepared by a stationary device installed on coal tower and loaded onto the coal charging machines on shift basis.
life cycle – It refers to the entire sequence of stages a product, system, or project goes through, from conception to disposal. It is a concept that analyzes the evolution of an entity through distinct phases, such as initiation, development, operation, and termination.
Life cycle analysis – It is defined as a systematic approach to evaluating the environmental impact of a product, process, or activity from the acquisition of raw materials to final disposal. It helps in understanding the environmental consequences and enables strategic planning for future activities.
Life cycle approach – It is a holistic method which considers all stages of a product, service, or system, from raw material extraction through manufacturing, use, and final disposal, to understand its environmental, social, and economic impacts. This approach helps in making informed decisions by preventing problems from simply shifting from one life cycle stage to another, avoiding ‘trade-offs’ where an improvement in one phase creates a problem in another.
Life cycle assessment (LCA) – It is also known as life cycle analysis. It is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product, process, or service. For example, in the case of a manufactured product, environmental impacts are assessed from raw material extraction and processing (cradle), through the product’s manufacture, distribution and use, to the recycling or final disposal of the materials composing it (grave).
Life cycle assessment methodology – It is a systematic framework for evaluating the environmental impacts of a product, process, or service throughout its entire life cycle, i.e., from raw material extraction to production, distribution, use, and disposal. It is a science-based technique which quantifies environmental burdens, human health impacts, and resource consumption to help identify areas for improvement and make more sustainable choices.
Life cycle concept – It is the comprehensive evaluation of a product, system, or service through all of its stages, i.e., from conception, through design, manufacturing, use, and maintenance, to its final retirement and disposal. It is a holistic approach which includes environmental, economic, and social considerations throughout the entire lifespan to optimize performance and minimize negative impacts, a process frequently referred to as ‘life cycle engineering’.
Life cycle cost analysis – It is a method for evaluating the total cost of a project, product, or asset over its entire lifespan, from acquisition to disposal. It considers all costs, including initial purchase, operation, maintenance, and end-of-life costs like disposal or salvage, to help make informed long-term decisions. Life cycle cost analysis is used to compare different alternatives and select the option with the most favourable long-term economic value.
Life cycle costing – It is an accounting method of costing where expenses are allocated over the life of the product. Life cycle costs for a product are frequently lower than its alternatives despite a higher initial outlay since the product normally last longer and need little maintenance.
Life cycle engineering – It is the application of engineering principles to manage and optimize the entire life cycle of a product, system, or project, frequently with a focus on sustainability, economic viability, and minimizing environmental impact.
Life cycle footprint – It is a measure of the environmental impact of a product or system throughout its entire existence, from raw material extraction to final disposal. It is calculated using a ‘life cycle assessment’ (LCA) to quantify all inputs and outputs, including resource consumption, energy use, emissions, and waste generation. Engineers use this analysis to identify ‘hotspots’ and design more sustainable products and processes.
Life cycle interpretation – It is a systematic technique which identifies, quantifies, checks, and evaluates information from life cycle inventory and impact assessment results, leading to conclusions and recommendations for the study. Its key purpose is to determine the confidence level in the final results and communicate them accurately.
Life cycle inventory – It is the process of quantifying all inputs and outputs for a product or process throughout its entire life cycle, including energy and raw material requirements, along with all associated emissions and waste streams. It is a crucial phase of a larger ‘life cycle assessment’ (LCA) which collects and validates data from the creation of raw materials to final disposal.
Life cycle model – it is a framework that defines the distinct stages of a system, product, or project from its beginning to its end. It provides a structured process for managing evolution and development, frequently depicted visually, with each stage having entry and exit criteria which act as milestones. This concept is applied in different fields, such as software development, product management, and systems engineering, to ensure a disciplined and logical progression.
Life cycle of product – It is the journey a product takes from its introduction to the market until its eventual removal, typically broken down into four stages namely introduction, growth, maturity, and decline. Understanding this cycle helps organizations make strategic decisions about marketing, pricing, and management throughout a product’s existence.
Life cycle simulation with residual stress consideration – It is the use of computational models, frequently involving finite element analysis (FEA), to predict the long-term performance and durability (fatigue life, crack propagation, distortion, corrosion resistance) of an engineered component while explicitly accounting for the internal stresses locked within the material from its manufacturing history (e.g., welding, machining, and heat treatment).
Life cycle stages – These are the distinct phases of development a product, or project goes through from its beginning to its end. It refers to the phases of a project (initiation, planning, execution, closure) or the development of a product from manufacture to disposal.
LIFO – LIFO stands for ‘Last-In, First-Out’. It is an inventory valuation method where the most recently acquired items are sold or used first. This approach can impact financial statements and tax liabilities by reflecting current costs more accurately during periods of inflation.
Lift (force) – When a fluid flows around an object, the fluid exerts a force on the object. Lift is the component of this force which is perpendicular to the oncoming flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and hence can act in any direction. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force.
Lift and transfer – It is a device which is designed for lateral movement of products between conveyor lanes or systems, needing regular inspections for smooth operation and proper alignment.
Lift beam furnace – It is a continuously operating sintering furnace. It is also known as walking beam furnace.
Lift bridge – It is a type of moveable bridge which utilizes gantries and a hydraulic arrangement to elevate both the girder and floor system, allowing for the passage of ships beneath the span.
Lift check valve – It is a type of check valve which allows fluid to flow in one direction only, preventing backflow. It features a disc or ball that lifts off its seat when upstream pressure exceeds the cracking pressure, allowing flow. When flow decreases or reverses, the disc or ball returns to its seat, preventing backflow.
Lifted structure – It is a building or offshore platform which has been physically raised off its foundation, typically using hydraulic jacks or a crane, to allow for new construction below it or to address issues like flooding.
Lifter – It is a device designed to lift, move, and position heavy loads to reduce manual labour and the risk of injury. These can range from simple aids for manually lifting heavy items on a construction site to sophisticated systems like vacuum lifters for flat materials or vertical conveyors in a warehouse.
Lift height – The rated lift height means the distance between the upper and lower elevations of travel of the load block and arithmetically it is normally the distance between the beam and the floor, minus the height of the hoist. This dimension is critical in most applications as it determines the height of the runway from the floor and is dependent on the clear inside height of the building. It is to be remembered that any slings or below the hook devices which influence this value are to be included.
Lifting beams – They are made from solid or fabricated metal, or from wood and are suspended from a hoist/crane to provide multiple load lifting points for better security and control of the load’s movement. A spreader beam uses two or more hooks to spread the load over more than one lifting point.
Lifting bolt loop – It is a specialized bolt featuring a looped head designed for lifting or attaching components, needing meticulous inspections to verify correct installation and sustained structural integrity. Regular checks are necessary for preventing unintended disconnection and ensuring reliable lifting capabilities.
Lifting effect – It refers to the upward force exerted on a body immersed in a fluid, which is equal to the weight of the fluid which the body displaces. This effect influences the apparent mass of objects when weighed in air, as larger volumes displace more air and experience a higher lifting force.
Lifting eye fastener – It is a bolt characterized by a looped head, specifically designed for lifting or attaching components securely, demanding thorough inspections to validate proper installation and sustained integrity. Regular assessments are crucial to prevent issues related to lifting operations.
Lifting forks – These consist of two or more arms fixed to an upright with an upper arm, essentially to lift palletized or similar loads.
Lifting gear – It refers to equipment, such as slings and cranes, used for lifting and moving loads safely, with consideration for the weight and centre of gravity of the load. It is necessary that the lifting operations are planned and performed by suitably trained individuals to ensure safety.
Lifting lugs – These are projections or brackets attached to a component, designed to facilitate lifting, hoisting, and moving the component during installation or transportation. Lifting lug is essentially a temporary lifting point, frequently a plate with a hole, which allows for the attachment of rigging equipment like shackles and chains. These are the lugs which are provided on equipment for lifting and positioning. These are also termed as lifting eyes.
Lifting magnets – These are the lifting devices which are used for lifting and transporting of steel and ferrous metal stock or manufactured components. They are normally installed and used as single magnets or as arrangements of multiple magnets. In all of these cases, they are suspended from chains or wires or otherwise attached to the lifting equipment such as cranes. Electrically operated lifting magnets are widely used in the iron and steel plants. Lifting magnets can be provided with no power supply i.e. permanent magnets, or where power is supplied by cable from an external source or through an in-built battery. The magnet and any associated electrical equipment are to be designed for its intended purpose and constructed to withstand the environment in which it is required to operate. When used correctly lifting magnets handle magnetic materials and components safely, and without the need for slingers.
Lifting mechanism – It is a system or device which uses mechanical principles to raise or move heavy objects with less effort. These mechanisms are used across several fields, from construction and manufacturing to everyday applications, and can range from simple pulley systems to complex hydraulic cranes. These are necessary for safely and efficiently handling loads which are too heavy or difficult to move manually.
Lifting points – These are connectors (sometimes temporary) directly on the steel work-pieces article which help the galvanizer in handling the work-piece throughout the galvanizing process.
Lifting tackles – These are also known as lifting accessories. These are pieces of equipment which are used to attach the load to lifting equipment, providing a link between the two. Examples of lifting tackles are slings, hooks, shackles, eyebolts, lifting eyes, spreader beams, magnetic and vacuum devices, and lifting and plate clamps.
Liftout – It is the mechanism which is also known as knockout.
Lift-to-drag ratio – It is a measure of an object’s aerodynamic efficiency, calculated by dividing the lift force by the drag force. A higher lift-to-drag ratio means the object generates more lift for the same quantity of drag, making it more efficient.
Ligand – It is the molecule, ion, or group bound to the central atom in a chelate or a coordination compound.
Ligand density – it refers to the concentration of ligands on a surface or in a given volume. It is a critical parameter for controlling the interaction between molecules. For example, a high ligand density on a nano-particle can be used to increase its ability to bind with target molecules or receptors on a cell membrane, influencing processes like cell signaling and uptake.
Ligand-exchange chromatography – It is a technique used to separate compounds by forming temporary coordination complexes between analytes and transition metal ions immobilized on a stationary phase. Analytes which act as stronger ligands can displace weaker ligands attached to the metal ions, leading to their separation. This method is especially valuable for separating chiral compounds, such as amino acids and other molecules which can form complexes with metals.
Light – It is the radiant energy in a spectral range visible to the normal human eye (around 380 nano-meters to 780 nano-meters).
Light amplification by stimulated emission of radiation (LASER) – It is a device which emits light through a process of optical amplification based on the stimulated emission of electro-magnetic radiation. It produces radiant energy predominantly by stimulated emission, needing a material medium, population inversion of electron states, and a resonant structure to facilitate multiple passes through the excitation region. It describes a device which produces a powerful, narrow, and coherent beam of light through a process where photons trigger the emission of identical photons. This process is known as stimulated emission, and when amplified through an optical resonator, it creates a concentrated and powerful beam of light from a specific material.
Light brick – It is a building unit which is considerably lighter and less dense than traditional bricks, offering benefits like improved thermal insulation and reduced structural load. These bricks achieve their low weight through a porous internal structure created during manufacturing, and they are used in several applications such as industrial furnaces.
Light bulb – It is an electrical device which converts electrical energy into light energy, typically by heating a filament or using a gas-discharge or semi-conductor process. It is a common source of artificial lighting and consists of a base to connect to a socket, a glass or plastic bulb, and a filament or other light-producing mechanism inside.
Light coated electrodes – Light coated welding electrodes have a definite composition. A light coating has been applied on the surface by washing, dipping, brushing, spraying, tumbling, or wiping. The coatings improve the characteristics of the arc stream. The coating normally serves several functions namely (i) it dissolves or reduces impurities such as oxides, sulphur, and phosphorus, (ii) it changes the surface tension of the molten metal so that the globules of metal leaving the end of the electrode are smaller and more frequent and this helps make flow of molten metal more uniform, (iii) it increases the arc stability by introducing materials readily ionized (i.e., changed into small particles with an electric charge) into the arc stream, and (iv) some of the light coatings can produce a slag. However, the slag is quite thin and does not act in the same manner as the shielded arc electrode type slag.
Light crude oil – It is liquid petroleum that has a low density and flows freely at room temperature. It has a low viscosity, low specific gravity and high API gravity because of the presence of a high proportion of light hydrocarbon fractions. It normally has a low wax content.
Light diesel oil (LDO) – It is having flash point above 66 deg C. It is a blend of distillate components and a small quantity of residual components. It is used as a fuel in certain boilers and furnaces.
Light distillate – It is a petroleum product with a low boiling point, consisting of short hydro-carbon chains, produced from the fractional distillation of crude oil. It is collected at the top of a distillation tower and is highly volatile, with common examples including gasoline, LPG (liquefied petroleum gas), and naphtha. These are used as fuels and as feedstock for petro-chemical processes.
Light distribution – It refers to the manner in which light is spread over a task area, characterized by the uniformity of illuminance. Good light distribution minimizes visual stress by reducing the need for frequent eye adaptations between over-lit and under-lit areas.
Light drawn – It is an imprecise term, applied to drawn products such as wire and tubing, which indicates a lesser quantity of cold reduction than for hard drawn products.
Light duty – It refers to equipment, machinery, or systems designed to handle relatively moderate loads, stresses, or operational demands compared to their medium or heavy-duty counterparts. It indicates a lower capacity or less demanding application than what is considered standard or heavy-duty. Light duty also refers to work which is less physically or mentally demanding than an employee’s regular job duties. It is frequently implemented as a temporary or permanent adjustment to accommodate employees with injuries, illnesses, or disabilities who cannot perform their full range of tasks.
Light emission – It is the process where an atom’s electrons release energy in the form of photons (light) after being energized to a higher energy level. This happens when an electron, having absorbed energy from a source like heat or electricity, falls back to a lower, more stable energy level. The energy difference between the levels is released as a photon of light with a specific frequency and colour.
Light-emitting diode (LED) – It emits light when current flows through it. Electrons in the semi-conductor recombine with electron holes, releasing energy in the form of photons. The colour of the light is determined by the energy needed for electrons to cross the band gap of the semi-conductor. It is a semi-conductor device which produces light or infrared or ultraviolet radiation when properly energized.
Lightening holes – These are holes in structural components of machines and buildings to make structures lighter. The edges of the hole can be flanged to increase the rigidity and strength of the component. The holes can be circular, triangular, elliptical, or rectangular and need to have rounded edges, but they are not to have sharp corners, to avoid the risk of stress risers, and they are not to be very close to the edge of a structural component.
Light extraction – It is the process of efficiently getting light out of a light-emitting device, such as an LED (light-emitting diode) or OLED (organic light-emitting diode), into the surrounding air. A major challenge is that the light can get trapped inside the device because of the total internal reflection, where the difference in refractive index between the semi-conductor and the air causes most of the light to be reflected back. Techniques to improve this process involve structuring the surfaces or adding components like scattering media and high refractive index substrates to redirect the trapped photons so they can escape.
Light-field illumination – For reflected light, it is the form of illumination which causes specularly reflected surfaces normal to the axis of the microscope to appear bright. For transmission electron microscopy, it is the illumination of an object so that it appears on a bright background.
Light filter – It is a device which transmits principally a predetermined range of wave-lengths.
Light fraction – It is the first liquid produced during the distillation of a crude oil.
Light gas oil – It is a petroleum distillate with a low viscosity and a hydro-carbon chain length between C9 and C16, similar to diesel fuel. It is used for applications such as in diesel engines, heating oil, and as a carrier for pesticides. Unlike heavier oils, it is a ‘light’ fuel which can be burned without pre-heating.
Light gauge steel – This steel is in the form of very thin steel sheet which has been temper rolled or passed through a cold rolling mill. Light gauge steel normally is plated with tin or chromium for making cans to be used as food containers.
Light-house – It is a tower or structure built with a focused light system to serve as a navigational aid for maritime and aerial pilots, guiding them to safe harbours or warning them of hazards like reefs and rocks. The design is to account for factors like the earth’s curvature to maximize visibility, withstand harsh environmental forces like strong winds and waves, and use a sophisticated lens system to amplify the light.
Lighting product – It is a device designed to produce illumination, encompassing a wide range of solutions from simple bulbs to complex, integrated systems. These products serve different purposes, such as providing basic or ambient light, highlighting specific areas through accent lighting, or creating atmosphere with decorative fittings. Lighting products use technologies like LED (light-emitting diode), fluorescent, or halogen and can be permanently wired fixtures or portable lamps.
Lighting requirement – It consists of a set of specifications which define the necessary characteristics of light for a given space to ensure comfort, safety, and optimal performance of activities. These requirements include the illumination level (how much light is needed), uniformity (how evenly the light is distributed), colour rendering, and the absence of glare. Other factors include energy efficiency codes and the specific needs of the environment, such as the type of work being performed.
Lighting technology – It refers to the systems, tools, and techniques used to create artificial light for practical and aesthetic purposes. It includes a range of methods from traditional incandescent bulbs and fluorescent lamps to modern, energy-efficient solid-state lighting (SSL) like LEDs (light-emitting diodes), which are now prevalent because of their improved performance, functionality, and sustainability.
Light intensity – it is a measure of the power of light transferred per unit area in a specific direction. It essentially indicates how much light energy is concentrated in a given area. In simpler terms, it is how bright a light source appears to be, or how much light falls on a surface.
Light isotope – It is a variant of an element with a lower number of neutrons in its nucleus, resulting in a lower atomic mass compared to its heavier isotope counterparts. For example, carbon-12, with 6 protons and 6 neutrons, is a light isotope, while carbon-13 (6 protons and 7 neutrons) and carbon-14 (6 protons and 8 neutrons) are heavier. The distinction is very frequently applied to the lighter elements on the periodic table.
Lightly coated electrode – It is a filler-metal electrode used in arc welding, consisting of a metal wire with a light coating, normally of metal oxides and silicates, applied subsequent to the drawing operation mainly for stabilizing the arc.
Light metal – It is one of the low-density metals, such as aluminum, magnesium, titanium, beryllium, or their alloys.
Light microscope – It is a microscope which uses visible light to illuminate and image a sample, typically using techniques like brightfield, phase-contrast, darkfield, or differential interference contrast microscopy to improve the visibility of cellular structures.
Light microscopy – It is a technique which uses visible light and a system of lenses to create a magnified image of a sample, allowing for the scientific examination of objects too small to be seen with the naked eye. It involves a light source, a condenser, a sample on a stage, and an objective lens system to magnify the image, which can then be viewed directly or captured with a camera.
Light naphtha – It is a flammable, volatile hydrocarbon mixture distilled from crude oil, mainly containing alkanes with five carbons to six carbon atoms. It has a low boiling point range of around 30 deg C to 90 deg C and is a key feedstock for producing gasoline, petro-chemicals like ethylene and propylene, and several solvents.
Light oil – It very frequently refers to light crude oil, which is a type of crude oil that is less dense and flows more easily than heavy crude oil. However, the term can also be used more broadly to describe light mineral oil or light vegetable oil, which are oils that have a less viscous and lighter consistency than other oils.
Lightning arrester – It is a device, essentially an air gap between an electric wire and ground, used on electric power transmission and telecommunication systems to protect the insulation and conductors of the system from the damaging effects of lightning.
Lightning protection – It is a system designed to safely intercept lightning strikes and conduct their high electrical currents to the ground, preventing damage to a structure, equipment, or people. It works by providing a low-impedance path for the lightning to follow, consisting of external components like air terminals (lightning rods), down conductors, and an earthing system, and internal components like surge protection devices (SPDs).
Lightning protection system – It is a network of components designed to safely conduct a lightning strike from a structure into the ground to prevent damage, fire, and electrocution. It includes air terminals (like lightning rods) to intercept the strike, down conductors to carry the current, and a grounding system to dissipate the electrical charge safely into the earth. An internal system also uses surge protection devices to safeguard electronic equipment from power surges.
Lightning strike – It refers to the natural phenomenon where lightning, a powerful electrical discharge, hits a person or object on the ground. Figuratively, it can also describe a sudden and unexpected workers’ strike which occurs without warning.
Light propagation – It is the transmission of light as a wave, characterized by its wave properties, dispersion, and the relationship between its wave-length and frequency. Light propagates as an electro-magnetic wave traveling in a straight line (rectilinear propagation) in a uniform medium. When light encounters an obstacle or changes mediums, it can be reflected, refracted, diffracted, or absorbed. This straight-line path is fundamental to understanding phenomena like shadows, pinhole cameras, and eclipses.
Light ray – It is an idealized straight line with an arrow which represents the direction of light energy’s travel. It is a simplified model used in optics to explain phenomena like reflection and refraction, even though light is more accurately described as an electro-magnetic wave.
Light section mill – It is a specialized type of rolling mill used to produce a variety of steel profiles. The product range of the light section mill normally consists of those sectional products whose cross-section is smaller than the cross section of the products rolled in medium and heavy section rolling mills. The products of the mill are square, hexagon, flat, equal angle, unequal angle, T-section, and channel etc. The qualities of steel billet being rolled in these mills can range from low carbon, mild steel, medium carbon, high carbon, and micro-alloyed and low-alloyed steels. The design of the light section mill needs to provide right solutions for the required performance requirements which include high speed production, microstructure quality of the product, and shortest changeover time from one product to other product etc. The light section mills are normally sized for a medium range production up to 500,000 tons per year. In case higher capacity is needed, then the mill is normally designed and built as a multi-strand mill. These mills are normally installed at higher levels (around + 6 metres from the ground level). This is done so that all the facilities such as oil cellars etc. can be installed at ground level for ease of operation and maintenance.
Light source – It is an object which emits light, and it can be natural or artificial. Natural sources include the sun and stars, while artificial sources are human-made, such as light bulbs, lasers, and fire.
Light water reactor – Light water reactors use ordinary water as both a moderating material and a reactor coolant. It includes boiling water reactors (BWR) and pressurized water reactors (PWR), which are the most common types reactors used.
Light-weight aggregate – It is a granular material with a low bulk density, typically less than 1,200 kilograms per cubic meter, used to produce lighter and more insulating concrete. This reduced density comes from a cellular or porous internal structure, created through processes like heating clay or shale to expand them, using natural materials like pumice, or using industrial by-products such as sintered fly ash. Using light-weight aggregate reduces the self-weight of a structure, improves thermal insulation, and can be beneficial for applications like structural concrete, building blocks, and pavements.
Light-weight aggregate concrete – It is a concrete which uses light-weight aggregates instead of traditional ones like gravel and sand, resulting in a lower density. This material is made by incorporating porous aggregates like expanded clay, pumice, or recycled materials such as fly ash, which reduces the self-weight of structures. Light-weight aggregate concrete is used to improve thermal insulation, seismic performance, and reduce the load on high-rise buildings and bridges.
Light-weight design – It is the process of making a part, product, or structure as light as possible while maintaining or improving its needed strength, stiffness, and functionality. It involves optimizing the component structure, material choices, and manufacturing methods to achieve a high strength-to-weight ratio, which can lead to benefits like improved energy efficiency, reduced emissions, and lower costs.
Light-weight expanded clay aggregate – It is a porous, light-weight ceramic product made by firing clay to high temperatures, creating a honeycomb-like structure with thousands of small, air-filled bubbles. This process gives light-weight expanded clay aggregate properties such as low density, durability, and good thermal and acoustic insulation. It is used in several applications.
Light-weight fill – It is a construction material, like expanded polystyrene or light-weight expanded clay aggregate, used to replace heavier soils and reduce the load on the underlying ground. This is particularly useful for building on soft soils with low bearing capacity, as it minimizes settlement and stability issues. Common applications include bridge abutments, retaining walls, and embankments.
Light-weighting – It is the engineering process of reducing the weight of a component or assembly while maintaining or improving its performance. It is achieved through a combination of methods, including using advanced materials, optimizing designs with computational tools, integrating multiple functions into a single part, and employing advanced manufacturing processes. The main goals are to improve efficiency, reduce energy consumption, and lower costs.
Light-weight materials – These are substances engineered to have a high strength-to-weight ratio, meaning they provide substantial strength with minimal mass. Their definition centres on combining high performance with low density to improve efficiency, save energy, and reduce costs in applications like automotive, and construction.
Light-weight structures -These are normally made up of fibre-reinforced polymer matrix composites, light alloys, or a combination of both which can be assembled with high-performance structural epoxy adhesives.
Light-weight valve – It is a valve designed to have a reduced weight, frequently achieved through a hollow or drilled stem, or by using materials like titanium alloys. This reduction in mass makes the valve lighter, which improves performance by decreasing resistance to motion and allowing for higher operating speeds. They are used in applications like high-performance engines where reducing reciprocating mass is critical, and in mobile or sanitary equipment where weight is a concern.
Lignin – It is a complex, organic polymer found in the cell walls of plants, contributing to their rigidity and strength. It is a key structural component, particularly in wood and bark, acting as a binder between cellulose and other cell wall components. Lignin is a natural polymer made up of phenylpropane units and is the second most abundant renewable carbon source on earth, after cellulose.
Lignin powder – It is a fine powder made from lignin, a complex organic polymer found in the cell walls of plants which provides structural support. It is produced by grinding natural lignin, frequently a waste product from the paper-making process, and is used in a variety of industrial applications like building materials, carbon fibre, and chemical formulations.
Lignite coal – It is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It is considered to be the lowest rank of coal due to its relatively low heat content. It has lowest carbon content amongst all types of coals. It is mined all around the world and is mainly used as a fuel for steam and electric power generation. Since it is not economical to transport lignite coal, it is not traded extensively on the world market when compared with higher grades of coal.
Lignite mine – It is a site where lignite, a low-grade, brownish-black coal formed from partially decayed plant matter, is extracted from the earth for energy production. Because of the lignite’s low energy density and high moisture content, these mines are frequently located near power plants to reduce transportation costs. The mining process typically involves removing soil and rock to access the lignite seams, which are then broken up and hauled away.
Likelihood function – It is the probability or probability density of obtaining a given set of sample values, from a certain population, when this probability or probability density is regarded as a function of the parameter(s) of the population and not as a function of the sample data. It is the formula for the probability of observing the collection of study end points observed in the sample, written as a function of the statistical model in question. Once a sample is collected, this formula is only influenced by the values of the coefficients in one’s model.
Likelihood of occurrence – It is the probability or frequency with which an event is expected to happen. It is a measure used in risk assessment to estimate the chances of a specific outcome occurring, based on historical data and current conditions. This can be expressed qualitatively (e.g., high, medium, low) or quantitatively (e.g., a percentage or ratio).
Likelihood-ratio chi-squared test – It is the counterpart of linear regression’s F test for logistic regression. This is a test of overall model utility.
Likelihood ratio test – It is a statistical test aimed at distinguishing between two competing models which could have produced an observed event based on a comparison of the likelihoods of the observed event, given the two models.
LILO – It means ‘Last-In Last-Out’. It is the inventory management method by which the origin of the number of units of the materials or consumables last received into the inventory is considered as the origin in equal number of units of the materials or consumables removed last from the inventory. In computer technology, it means a method of storing data where the data stored last is accessed last.
Lime – It is calcium oxide (CaO) produced on heating (calcination) of limestone to a temperature of 900 deg C and above (normally 1,100 deg C). It is a versatile compound. It is a white crystalline solid with a melting point of 2,572 deg C. It is a basic oxide and is used to react with the acidic oxides (e.g. silica) in different smelting operations. With water, it makes milk of lime used for neutralizing acidic waste water. It is also being known as quick lime, lime flux, unslaked lime, and fluxing lime. Lime having some percentage of magnesium oxide (normally 2 % to 4 %) is also known as dolomitic lime. Lime is a hygroscopic material and absorbs moisture from the air. With the absorption of moisture, it loses its reactivity and gets hydrated. Different forms of lime are used in environmental, metallurgical, construction, and chemical / industrial applications etc. The largest single use of lime is in iron and steel production, where it serves as a flux for removing impurities (silica, phosphorus, and sulphur) during refining of steel. The fastest growing use of lime is in environmental applications, where lime is used for treatment of flue gases, waste-water, solid waste, and drinking water.
Lime coating – It is a surface finish or protective layer made mainly of lime (calcium hydro-oxide), frequently mixed with aggregates like sand, or sometimes pigments and other additives. These coatings are applied to several substrates, such as masonry, stone, and plaster, for aesthetic, sanitary, and functional purposes.
Lime content – It refers to the proportion of lime [CaO or Ca(OH)2] in a mixture, such as soil, cement, or other materials. In civil engineering, it determines how lime affects the material’s properties, like strength, durability, and stability, with an optimal range frequently cited for soil stabilization purposes.
Lime concrete – It is a composite mixture of hydraulic lime (or slaked lime) as binding material, sand as fine aggregate, and gravel as coarse aggregate in appropriate proportions.
Lime cycle – It is a series of chemical reactions which converts limestone (CaCO3) into quick-lime (CaO) by heating, then into slaked lime [Ca(OH)2] by adding water, and finally back into limestone through carbonation. This natural and industrial process is used in applications like cement and mortar, and demonstrates the transformation and reversion of calcium compounds.
Lime dust – It refers to the fine powder of lime, which can be either quicklime (calcium oxide, CaO) or hydrated lime [calcium hydro-oxide, Ca(OH)2]. It is produced by heating limestone (calcium carbonate) to high temperatures, a process which creates quick-lime. Quick-lime is then mixed with water to create hydrated lime, which is a very fine, white powder used in applications like construction, agriculture, and chemical processes.
Lime glass – It is more commonly known as soda-lime glass. It is the most common and inexpensive type of glass, composed mainly of silica (SiO2), soda (Na2O), and lime (CaO). It is used for everyday items like window-panes, bottles, and jars since it is inexpensive, workable, and can be recycled. Its composition includes around 70 % silica, 15 % soda, and 9 % lime, with a typical chemical formula of Na2O.CaO.6SiO2.
Lime, hydrated – Hydrated lime is also known as slaked lime. It is in the form of a dry white powder. Hydrated lime is an alkali and used for neutralizing acidic solutions.
Lime kiln – It is a type of oven used to produce quick-lime by heating limestone to a high temperature in a process called calcination. This reaction, represented by the chemical equation CaCO3 + heat = CaO + CO2, converts calcium carbonate (CaCO3) into calcium oxide (CaO), or quick-lime, and carbon di-oxide (CO2). Quick-lime is a white substance with several uses.
Lime mixture – It is a blend of lime with other materials like sand, water, and aggregates for construction, or with substances like pozzolana to improve strength and performance. Examples include lime mortar, which uses lime, sand, and water, and lime slurry, a mixture of hydrated lime and water used for soil stabilization.
Lime mortar – It is composed of lime (hydraulic, or non-hydraulic), water and an aggregate such as sand. The soft and porous properties of lime mortar provide certain advantages when working with softer building materials such as natural stone and terracotta.
Lime plaster – It is a construction material made from a mixture of slaked lime, sand, and water which hardens by absorbing carbon di-oxide from the air through a process called carbonation. It is a breathable and flexible material, valued for its durability, ability to regulate humidity, and use in both modern sustainable constructions.
Lime production process – It is the process of heating limestone (calcium carbonate) to high temperatures (900 deg C to 1,200 deg C) to decompose it into calcium oxide (CaO), also known as quick-lime, and carbon dioxide (CO2). This industrial process involves quarrying, crushing, and then heating the limestone in a kiln, with the resulting quick-lime being used for applications in construction, environmental remediation, and other industries.
Lime reactivity – Reactivity of lime is its activity for hydration and is the relative capacity of lime to reciprocate chemical change with water. Reactivity is a function of purity, particle size and other factors such as particle porosity. The slaking rate is a measurement of the time for the slaking process to reach completion. The reaction is considered complete when the temperature of a given sample reaches a maximum. As reactivity increases, the slaking rate, ultimate temperature rise, and surface area of hydrated lime increases also. The reactivity of lime is dependent on the homogeneity of lime, the degree of thermal decomposition of limestone, the specific surface area lime.
Lime refractory – It is the refractory which contains higher than or equal to 70 % by mass of calcium oxide and less than 30 % by mass of magnesium oxide.
Lime saturation factor – It is a ratio of calcium oxide to the other three main oxides (alumina, silica, and ferric oxide). Frequently, it is referred to as a percentage and hence multiplied by 100.
Lime slurry – It is a suspension of calcium hydro-oxide [Ca(OH)2] particles in water, normally known as ‘milk of lime’ or ‘slaked lime’. It is a versatile, free-flowing liquid used in several applications, such as water treatment, soil stabilization, and construction, because of its high alkalinity.
Lime-soda process – It is a water softening method which removes hardness-causing ions like calcium and magnesium by precipitating them out of the water. This is achieved by adding lime (calcium hydroxide) and soda ash (sodium carbonate) to the water. The process essentially converts soluble calcium and magnesium salts into insoluble compounds, which can then be removed through settling and filtration.
Lime solution – It is very frequently called lime water. It is an aqueous solution of calcium hydro-oxide [Ca(OH)2], made by mixing calcium hydro-oxide with water and filtering out the undissolved solid. This clear, colourless, and slightly alkaline liquid is frequently prepared for chemical testing (especially for carbon di-oxide), and used in applications like environmental remediation or concrete curing.
Limestone –It is an odourless white, grayish-white or tan material which ranges from sized stone to a granular powder. It consists mostly of calcium carbonate and used as a fluxing material. Limestone is a naturally occurring mineral. The term limestone is applied to any calcareous sedimentary rock consisting essentially of calcium carbonate (CaCO3) in the form of the mineral calcite. It forms predominantly on the sea floor where material rich in calcium carbonate (‘calcareous’ material) accumulates. This calcareous material can be organic, chemical or detrital in origin. Types of limestone include (i) bituminous limestone, (ii) carboniferous limestone, (iii) coquina which is a sedimentary rock composed mostly of fragments of shells, (iv) coral rag, (v) chalk which is a soft, white, porous sedimentary rock made of calcium carbonate, (vi) fossiliferous limestone, (vii) lithographic limestone, (viii) oolite which is a sedimentary rock formed from ooids, (viii) rag-stone which represents work done with stones that are quarried in thin pieces, (ix) shelly limestone, (x) travertine which is a form of limestone deposited by mineral springs, (xi) marl, and (xii) tufa which is a porous limestone rock formed when carbonate minerals precipitate out of ambient temperature water. Limestones altered by dynamic or contact metamorphism become coarsely crystalline and are referred to as ‘marbles’ and ‘crystalline limestones’. The limestone which is used by iron and steel industry in bulk quantity is a bedded type sedimentary limestone.
Limestone filler – It is finely ground calcium carbonate, a naturally occurring mineral, used as a raw material or additive in different applications. It is mainly used in the cement and concrete industry to improve workability, improve early strength, and reduce the clinker content, which lowers the carbon footprint of the cement. It also has uses in other sectors like paints, asphalt mixtures, and agriculture.
Limestone scrubbing – It is a process which is used to remove sulphur di-oxide (SO2) from flue gases, typically in power plants, by reacting the sulphur di-oxide with a limestone slurry, resulting in the formation of calcium sulphite or sulphate, which can then be removed from the gas stream.
Lime treatment – It is the process of using lime to modify or improve the properties of materials like soil or sludge. It works by changing the material’s chemical composition to improve characteristics like workability, strength, and stability, while also neutralizing acidity and deactivating pathogens. This process is widely used in construction to improve soil for roads and in environmental applications for stabilizing waste.
Limewater – It is also called milk of lime. It is the common name for a saturated aqueous solution of calcium hydroxide. Calcium hydroxide is sparsely soluble at room temperature in water (1.5 grams per litre at 25 deg C).
Liming – It is the application of calcium- (Ca) and magnesium- (Mg) rich materials in different forms, including chalk, limestone, burnt lime or hydrated lime to soil. In acid soils, these materials react as a base and neutralize soil acidity.
Limit – It is the value of a quantity used in certain specified activities or circumstances which is not to be exceeded.
Limit analysis – It is an engineering method used to determine the upper-bound or lower-bound estimate of the collapse load for a structure, without needing a full incremental, step-by-step elastic-plastic analysis. It is a technique within the theory of plasticity which provides bounds on the maximum load or safety factor a material can withstand, and is useful for predicting failure mechanisms in structures.
Limit analysis method – It is a technique in plasticity theory used to determine the maximum load or safety factor a structure can withstand before it fails. It works by finding upper and lower bounds for the collapse load without needing to perform a step-by-step elastic-plastic analysis. This is useful for finding the load-carrying capacity of structures like those in civil engineering (e.g., slope stability, retaining walls) and for problems in metal forming.
Limitation – It is a constraint or restriction which limits the capabilities, functionality, or performance of a system, component, or process. It can also refer to a shortcoming or incapability to achieve certain things. Limitations are frequently inherent to the design, materials, manufacturing processes, or operational environment.
Limit control – It is a switching device which completes or breaks an electrical circuit at pre-determined pressures or temperatures. It is also known as an interlock.
Limit design – It refers to a structural engineering method where a structure is designed to avoid reaching any ‘limit state,’ which is a condition that makes it unfit for its intended purpose. These limit states include ultimate limit states which relate to collapse and serviceability limit states that ensure the structure’s normal use, such as deflections or vibrations, are not compromised. This approach uses partial safety factors to ensure the structure remains reliable under different conditions, creating more efficient and economical designs compared to older methods.
Limit dimensioning – It defines a feature’s size with its maximum and minimum acceptable dimensions on a technical drawing. This method specifies the exact upper and lower limits, ensuring manufactured parts fall within this range so they can fit and function correctly, simplifying manufacturing and quality control.
Limited approach boundary – It is an approach limit at a distance from an exposed live part within which a shock hazard exists.
Limited ductility or workability – The limited ductility is inherent to the material or caused by some micro-structural feature. Examples are large prior transformation grain size, presence of embrittling phases or elements and inclusions etc.
Limited feedback – It refers to a situation where the quantity, detail, or frequency of information provided for evaluation or correction is constrained, making it challenging to efficiently assess a performance, train a model, or complete a task effectively.
Limited resolution – It refers to the smallest distance between two points which an instrument can distinguish as separate. It is the inverse of an instrument’s resolving power and is influenced by factors like the wave-length of light used and the instrument’s characteristics, such as the numerical aperture of a microscope or the pixel size of a digital camera. A smaller limit of resolution indicates a higher quality of detail and a higher ability to distinguish between two close objects.
Limited solid solution – It is a crystalline miscibility series whose composition range does not extend all the way between the components of the system, i.e., the system is not isomorphous.
Limiter – It is a device which prevents a signal from exceeding a specified value, which can involve electronic, electrical, or mechanical limitations. Common examples include electronic circuits which ‘clip’ wave-forms by flattening peaks, audio processors which prevent clipping, and safety devices which stop a process when a sensor reading becomes too high or too low.
Limiter function – It is a mechanism which restricts a variable or signal from exceeding a specific setpoint or threshold, used in fields like computational fluid dynamics, electronics, and process control to ensure stability, accuracy, or safety. Examples include flux limiters in numerical simulations to prevent oscillations, electronic limiters which prevent signal overload, and physical limit switches which shut down a process when a variable goes too high or low.
Limiting condition for operation – It is the lowest functional capability or performance level of safety-related structures, systems, and components and their support systems needed for normal, safe operation of a facility.
Limiting control setting – It is the settings on safety systems which control process variables to prevent exceeding a safety limit.
Limiting current density – It is the maximum current density which can be used to get a desired electrode reaction without undue interference such as from polarization.
Limiting dome height (LDH) test – It is a mechanical test which is normally performed unlubricated on sheet metal, which simulates the fracture conditions in a practical press-forming operation. The results are dependent on the sheet thickness.
Limiting drawing ratio (LDR) – It is a key indicator of a sheet metal’s formability in deep drawing processes. It is defined as the ratio of the maximum blank diameter which can be successfully drawn into a cup (without failure like tearing or wrinkling) to the punch diameter. A higher limiting drawing ratio means better deep drawability.
Limiting drawing ratio (LDR) test – It evaluates the deep drawability of sheet metals. It indicates the maximum ratio of circular blanks to the diameter of the die, by deep drawing the blank into a cup, without crack formation.
Limiting oxygen index – It is the minimum percentage of oxygen in a gas mixture which supports the combustion of a material. It is a measure of flammability and fire resistance, where a higher limiting oxygen index value indicates a more flame-retardant material that is more difficult to ignite. Limiting oxygen index is determined using standardized tests (such as ISO 4589) and is critical for safety-critical applications like electronics, and construction.
Limiting ratio – It refers to the specified width-to-thickness ratios which classify structural steel members as compact, non-compact, or slender-element sections, determining their susceptibility to local buckling and ability to achieve full yield strength.
Limiting reactant – It is the reactant which is completely consumed first in a chemical reaction, which dictates the maximum quantity of product that can be formed. This concept is critical for optimizing industrial processes by controlling reaction efficiency, minimizing waste, and determining theoretical yields. For example, in combustion, identifying the limiting reactant can help engineers adjust fuel-air ratios to ensure complete combustion and reduce emissions.
Limiting resistor – It is a component to restrict or control the quantity of electrical current flowing through a circuit, protecting other components from damage. It is typically placed in series with a device, such as an LED (light emitting diode) or a capacitor, to prevent excessive current which can cause overheating, burnout, or other damage.
Limiting static friction – It is the resistance to the force tangential to the interface which is just sufficient to initiate relative motion between two bodies under load. The term static friction, which properly describes a tangential resistance called into operation by a force less than this, is not to be substituted for limiting static friction.
Limit of design – It defines the boundary of a project along with the parameters and the quantities of the incoming and outgoing utilities. Limit of design also refers to the point where the initial concept or idea is translated into a detailed plan which can be practically implemented. This stage involves specifying the design requirements, constraints, and performance criteria which are to be met by the final product or system. It is a crucial phase where the abstract idea is transformed into a concrete blueprint, ready for manufacturing or construction.
Limit of detection (LOD) – It is the lowest concentration of a substance that can be reliably detected by an analytical method, but not necessarily quantified. It indicates the sensitivity of a method, with a lower limit of detection signifying higher sensitivity. Essentially, it is the point where a signal is distinguishable from background noise with a reasonable degree of confidence.
Limit of quantification – It is the lowest analyte concentration which can be quantitatively identified with a certain degree of accuracy and precision. It differs from the limit of detection, as the limit of quantification indicates a concentration which can be observed and measured consistently without bias or imprecision.
Limit, pressure – It is the maximum allowable pressure which a system, component, or material can safely withstand and operate under, without failure or damage. This limit is set by factors like the equipment’s design, the material’s properties, and safety regulations to prevent over-pressurization and ensure safe operation. The specific meaning can vary, such as the maximum operating pressure for a pressure vessel or the pressure at which a safety valve opens.
Limits – These refer to the maximum and minimum permissible sizes for a manufactured component, which define the acceptable range for its dimensions. These limits are important for ensuring that parts can be interchanged and function correctly when assembled, and they are determined by subtracting the tolerance from the basic size (to find the lower limit) and adding the tolerance to the basic size (to find the upper limit).
Limits and fits – These are a set of rules regarding the measurements and tolerances of mating machine parts to achieve the best working conditions.
Limits, specification – These are the established boundaries for acceptable quality, performance, or characteristics of a product, process, or service. They represent the ‘voice of the customer’ and define the range of values which a customer or regulatory body deems acceptable. A specification or standard is a detailed description which outlines these limits and other requirements.
Limit state design – It is also known as load and resistance factor design (LRFD). It refers to a design method used in structural engineering. A limit state is a condition of a structure beyond which it no longer fulfills the relevant design criteria. The condition can refer to a degree of loading or other actions on the structure, while the criteria refer to structural integrity, fitness for use, durability or other design requirements. A structure designed by limit state design is proportioned to sustain all actions likely to occur during its design life, and to remain fit for use, with an appropriate level of reliability for each limit state. Building codes based on limit state design implicitly define the appropriate levels of reliability by their prescriptions.
Limit state equation – It is a mathematical expression which compares a structure’s resistance to the loads it endures, with failure occurring when the load effect exceeds the resistance. It is frequently written as g (X) = R-S or g(X) = R/S, where ‘R’ is resistance and ‘S’ is the load, with failure defined as g(X) is less than or equal to 0. This equation is fundamental to the limit state design method, a probabilistic approach to structural engineering which ensures a structure can withstand loads and remain fit for its intended use.
Limit state function – It is a mathematical expression used in structural reliability analysis which defines the boundary between acceptable and unacceptable structural performance. It is typically written as g(X) = R-S, where ‘R’ is the structural resistance and ‘S’ is the applied load. A system is considered to be in a safe state when g(X) is greater than 0 and in an unacceptable or failed state when g(X) is less than or equal to 0.
Limit state surface – It is a boundary which represents the combination of different conditions where a structure or system is no longer fit for purpose, either through collapse or loss of serviceability. It is a visualization used in reliability engineering and can be described by a limit state function, where the ‘surface’ represents the set of all points at which the limit state is just reached. For a system with two or three variables, it can be visualized as a curve or a surface separating the ‘safe’ region from the ‘failure’ region.
Limit switch – It consists of switches which are actuated at preset values by the movement of the valve. These switches can be normally fully open or closed positions, but can be set at intermediate points of travel. Types of switches include mechanical, magnetic (reed) and proximity. In conveyors, limit switch is an electronic device strategically placed along the conveyor system to detect and identify the location of products within a fulfillment centre or storage are. Periodic checks are necessary to guarantee accurate functionality, ensuring timely responses to product positioning.
Limit volume fraction – It is the maximum proportion of a desired final volume which a structure can occupy within a total volume, calculated as the ratio of the desired final volume to the total volume of the maximum domain. This is a specific type of volume fraction frequently used in optimization and computational engineering, where it represents the maximum allowable volume for a component, for example, the maximum quantity of reinforcing material which can be used in a composite.
Limonite – It is a brown, hydrous iron oxide.
Limonite ore – Limonite is one of the principal iron ore which has been mined from the production of iron since at least 2500 BCE. It is a ferric oxide containing crystal water, and the chemical formula can be expressed by mFe2O3.nH2O. It is actually composed of a mixture of goethite (Fe2O3.H2O), water needle iron ore (2Fe2O3.H2O), iron hydroxide and mud. Most of the limonite in nature exists in the form of 2Fe2O3.3H2O. According to different crystal water content, limonite can be divided into water hematite, needle hematite, limonite, and the like. Limonite is weathered from other iron ore, so its structure is relatively soft, small specific gravity and large water content. The streak is yellowish brown. The crystal water of limonite is easily removed when it is dried. The limonite (the limonite after dehydration) has many pores and is easy to be reduced. However, because of the small hardness of the limonite structure and a large quantity of powder, it is normally necessary to pass the agglomeration before it is suitable for ironmaking. Limonite is relatively dense with a specific gravity varying from 2.7 to 4.3. It varies in colour from a bright lemony yellow to a drab greyish brown. The streak of limonite on an unglazed porcelain plate is always brownish, a character which distinguishes it from hematite with a red streak, or from magnetite with a black streak. The hardness is variable, but normally in the 4 – 5.5 range on the Mohs scale.
L-index – It is a voltage stability index which evaluates the steady-state voltage stability margin of each bus in a power system, with values ranging from 0 (no load) to 1 (voltage collapse). It identifies the most vulnerable bus and assists in determining areas needing reactive power support to improve voltage stability.
Line – It is a pipe, tube or hose for conducting fluids.
Lineage structure – It consists of deviations from perfect alignment of parallel arms of a columnar dendrite as a result of interdendritic shrinkage during solidification from a liquid. This type of deviation can vary in orientation from a few minutes to as much as two degrees of arc. It is also a type of sub-structure consisting of elongated sub-grains.
Linear absorption coefficient – It is a measure of how effectively a material absorbs or scatters radiation (like light or X-rays) as it passes through it. It quantifies the fraction of incident radiation which is attenuated (reduced in intensity) per unit length within the material. A higher linear absorption coefficient means the material absorbs radiation more strongly.
Linear acceleration method – It is a technique which assumes a linear variation of acceleration over a time interval, allowing for the calculation of displacement, velocity, and acceleration at discrete time points based on initial conditions and changes in acceleration.
Linear accelerometer – It is a device which detects rigid body motion by measuring linear acceleration, frequently utilized in applications such as motion detection and sensitivity enhancement in instruments.
Linear actuator – It is an actuator which creates linear motion (i.e., in a straight line), in contrast to the circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in several other places where linear motion is needed. Hydraulic or pneumatic cylinders inherently produce linear motion. Several other mechanisms are used to generate linear motion from a rotating motor.
Linear alternator – It is an electrical machine which generates electric power from the relative straight-line motion of its parts.
Linear amplitude sweep test – It is a procedure which assesses the fatigue behaviour of bituminous binders by applying systematically increasing load amplitudes under cyclic loading, utilizing oscillatory shear in a strain-controlled mode to evaluate damage parameters over multiple cycles.
Linear arch – It is an arch in which the internal forces are purely axial, meaning it is not subjected to internal shear forces and bending moments. The internal forces in a linear arch can be deduced by analyzing a cable of the same shape carrying identical loads, with the internal forces being compressive rather than tensile.
Linear chirp – It is a frequency modulation of a signal which increases or decreases linearly over time, which can occur through dispersion in fibre optics or using parallel gratings, resulting in an increase in pulse length when chirped.
Linear coefficient of expansion – It is the ratio of the change in length of a material to its original length, per degree rise in temperature. It quantifies how much a material expands in one dimension as its temperature increases, and is calculated with the formula ‘a = delta L / (Lo x delta T).
Linear control – It refers to a control system or theory which operates on systems described by linear equations, meaning the output is directly proportional to the input, and the principle of superposition holds. This allows for predictable behaviour and is governed by mathematical techniques like the Laplace transform. While real-world systems are frequently non-linear, they can sometimes be approximated as linear to simplify analysis and design.
Linear control design – It is a method for controlling a system using principles of linearity, meaning the output is directly proportional to the input and the sum of the inputs results in the sum of the outputs. It is based on linear system theory and uses techniques like negative feedback to maintain a desired state, often by designing a controller for a linearized version of a potentially nonlinear system. This approach simplifies the design process and is well-understood, but the design’s effectiveness depends on the accuracy of the linear approximation.
Linear controller – It is a control strategy that uses a linear mathematical model to manage a system’s behaviour. It works by applying linear control techniques, such as the ‘proportional-integral-derivative’ (PID) controller, to a system which has been simplified or linearized around a specific operating point. The main advantage is that it allows for well-understood and mathematically manageable control methods, though it omits nonlinear effects.
Linear dynamic range – It refers to the range of input values (e.g., light intensity, concentration) over which a sensor or detector provides a linearly proportional output. In simpler terms, it is the range within which the output of a device changes predictably and proportionally with the input, without saturation or significant deviation from a linear relationship.
Linear density – It is the mass per unit length of an object, frequently called linear mass density. It can also refer to the number of entities (like atoms or charges) per unit length. It is calculated by dividing the mass by the length, where the SI (International System of Units) unit is kilograms per meter.
Linear dispersion – It is a phenomenon where a substance separates light into its constituent wavelengths, or where the separation changes proportionally with position. In optics, it describes a wave-length-dependent refractive index which causes pulses to broaden. In spectroscopy, it is defined as the rate of change of linear distance with respect to wave-length, which is frequently measured in units like nano-meters per millimeter.
Linear displacement – It is the straight-line distance and direction from an object’s starting point to its final position. It is a vector quantity, meaning it has both magnitude (the distance) and direction, and is measured in units of length like meters. Unlike total distance travelled, linear displacement can be zero if an object returns to its original position.
Linear elastic finite element analysis (FEA) – It is a computational method for simulating a structure’s mechanical behaviour under load, assuming that the material’s response is linear and reversible, meaning it obeys Hooke’s law. This method is used for problems where deformations are small and the material returns to its original shape after the load is removed. The process involves breaking the object into smaller ‘finite elements’ to solve for stress, strain, and deformation numerically.
Linear elastic fracture – It is the failure of a material along a crack when the stress intensity factor (K) exceeds the material’s fracture toughness (Kic), and the material behaves as a linear elastic solid. This phenomenon is described by ‘linear elastic fracture mechanics’ (LEFM), which assumes that any plastic deformation at the crack tip is negligible and the material obeys the principles of linear elasticity.
Linear elastic fracture mechanics – It is a theoretical framework which analyzes crack propagation in elastic materials by focusing on the stress field at the crack tip and the energy needed to create new fracture surfaces. It is applicable when a material experiences only small plastic deformation, a condition quantified by the stress intensity factor (K). A crack grows when the stress intensity factor (K) exceeds the material’s fracture toughness (Kc).
Linear elasticity – It is a mathematical model used in engineering to describe how solid materials deform under stress. It is based on two key assumptions namely strains are small, and there is a linear, proportional relationship between stress and strain, meaning the material returns to its original shape once the load is removed. This model is widely used in structural analysis for materials which do not undergo permanent deformation, like metals and some polymers, under typical working conditions.
Linear elastic solid – It is a material which undergoes small deformations, returns to its original shape when external forces are removed, and shows a linear relationship between stress and strain, as described by Hooke’s law. This means the magnitude of its deformation is directly proportional to the applied load.
Linear energy density – It is the quantity of energy delivered per unit length during a laser processing operation, influencing the microstructure and growth morphology of materials, such as the formation of columnar dendrites.
Linear equation – It is an equation where the highest power of any variable is 1, and it represents a straight line when graphed. It can be in one or more variables and is often written in standard forms like aX + b = 0 (for one variable) or aX + bY + c = 0 (for two variables), where a, b, and c are constants.
Linear expansion – It is the increase in the length of a material as its temperature rises. This phenomenon occurs since an increase in temperature causes the particles within a material to move more vigorously, leading to an overall expansion in one dimension, or length. The extent of this expansion is quantified by the material’s coefficient of linear expansion, which is the fractional change in length per degree of temperature change.
Linear feedback controller – It is a type of control system which uses linear mathematical models to adjust a system’s output based on its current state and a desired setpoint. It operates by calculating a control signal as a linear combination of the system’s error (the difference between the desired and actual output) to drive the system toward the target behaviour. Classic examples include ‘proportional-integral-derivative’ (PID) controllers.
Linear Fresnel concentrator – It is a type of solar thermal system which uses multiple rows of long, flat, or slightly curved mirrors to reflect and concentrate sunlight onto a stationary receiver tube positioned above them. The concentrated solar energy heats a fluid flowing through the receiver, which is then used to generate electricity or provide process heat.
Linear Fresnel reflector – It is a solar concentrator which uses a field of long, linear mirror strips to focus sunlight onto a receiver tube mounted on a tower. These reflectors concentrate solar energy onto the receiver, where the heat is transferred to a working fluid. The linear Fresnel reflector is similar to a broken-up parabolic trough reflector but uses flat or slightly curved mirror segments instead of a single large curved one.
Linearity error – It is the maximum deviation of a sensor’s actual output curve from an ideal straight line, typically expressed as a percentage of the full-scale output. It measures how much a sensor’s response deviates from a perfectly linear relationship and affects measurement accuracy and calibration.
Linearly increasing frequency – It is a signal whose frequency rises at a constant rate over time, meaning the change in frequency per unit of time is constant. This is also known as a linear chirp. It is frequently used in applications like radar and sonar to improve range resolution and Doppler sensitivity.
Linear mixture rule – It is a principle which states that the property of a mixture can be calculated as a simple, weighted average of the properties of its components. It is based on the assumption that the components are linearly combined, meaning the overall property is a straight-line function of the component proportions. This rule is used in different fields to predict properties like reaction rates, spectral properties in remote sensing, and material strength.
Linear momentum – It is the product of an object’s mass and its velocity, calculated using the formula p=m x v. It is a vector quantity, meaning it has both magnitude and direction, and its direction is the same as the object’s velocity. Momentum is a measure of how much motion an object has and is a conserved quantity in a closed system.
Linear motor – It is an electric motor which converts electrical energy into linear motion, rather than the rotational motion of a conventional motor. It can be thought of as a rotary motor which has been ‘unrolled’, and it generates a straight driving force through the repulsion and attraction of magnetic fields. Linear motors are used in applications needing high speed and accuracy, such as in maglev trains, and automated industrial systems.
Linear polarization resistance – It is a non-destructive corrosion monitoring technique which measures a material’s resistance to corrosion in an electrolytic environment by applying a small voltage and measuring the resulting current. It involves applying a small, linear voltage scan around the material’s corrosion potential and observing the linear current response. The slope of the resulting potential versus current curve is the polarization resistance, which is inversely proportional to the corrosion rate.
Linear polarization resistance probe – It is an electro-chemical sensor used to measure the rate of corrosion in a conducting liquid by applying a small voltage to a metal electrode and measuring the resulting current. The probe measures the ratio of voltage to current, known as the polarization resistance, which is inversely proportional to the corrosion rate. This allows for real-time, in-situ monitoring of corrosion, normally used in systems like cooling water, oil and gas production, and chemical processing.
Linear shrinkage – It is the one-dimensional reduction in length of a material as it dries or cures, expressed as a percentage of its original length. It is used in soil mechanics to measure the decrease in a soil sample’s length as its water content is reduced from the liquid limit to the shrinkage limit, calculated by the formula ‘linear shrinkage = [(initial length – final length) / initial length] x 100 %’. In other fields like materials science, it can refer to the change in length of a thermoset material during its curing process.
Line-break system – It is a system which incorporates a pressure transmitter to sense the rate of pressure drop in a pipeline. When the rate of pressure drop, falls outside a preset value, the control system closes the valve. The system can be electrical or mechanical.
Linear correlation – It is a somewhat ambiguous expression used to denote either (a) Pearson’s Product Moment Correlation in cases where the corresponding variables are continuous, or (b) a Correlation Coefficient on ordinal data such as Kendall’s Rank Correlation Coefficient. There are other linear correlation coefficients besides the two listed here as well.
Line defect engineering – It involves manipulating dislocations, or line defects, in a crystal to control a material’s properties, such as its strength and ductility. This is achieved by managing dislocation movement, as their motion causes plastic deformation. Techniques like work hardening increase dislocation density to strengthen a material, while other methods focus on managing or eliminating them to improve properties.
Line defects – These are also called line dislocations. These are one-dimensional imperfections in a crystalline material where a line of atoms is misaligned, creating a discontinuity in the crystal lattice. These linear defects disrupt the perfect, repeating arrangement of atoms and are the main cause of plastic deformation in crystalline solids, as their movement under stress allows for the material to slip and change shape.
Linear dispersion – In spectroscopy, it is the derivative dx/dL, where ‘x’ is the distance along the spectrum and ‘L’ is the wave-length. Linear dispersion is normally expressed as millimeters per angstrom.
Linear elastic fracture mechanics – It is a method of fracture analysis that can determine the stress (or load) needed to induce fracture instability in a structure containing a crack-like flaw of known size and shape when the relationship between local stress and strain is assumed to be linear.
Linear elasticity – It is a mathematical model as to how solid objects deform and become internally stressed by prescribed loading conditions. It is a simplification of the more general nonlinear theory of elasticity and a branch of continuum mechanics.
Linear equation – It is an equation of the first degree where variables are only multiplied by constants, not by themselves or other variables, and it represents a relationship where a change in one variable corresponds to a proportional change in another. These equations are fundamental for modelling systems, solving problems with multiple variables, and are crucial in fields like structural engineering (e.g., using the finite element method) and control systems (e.g., state-space representation).
Linear expansion – It is the increase of a given dimension, which is measured by the expansion or contraction of a sample or component subject to a thermal gradient or changing temperature.
Linear flow characteristics – It is an inherent flow characteristic which can be represented ideally by a straight line on a rectangular plot of flow against per cent rated travel. Hence, equal increments of travel yield equal increments of flow at a constant pressure drop.
Linear function – It is a mathematical function which represents a straight line when graphed. It can be expressed in the form f(x) = mx + b, where ‘m’ represents the slope (or gradient) of the line, and ‘b’ represents the y-intercept (where the line crosses the y-axis). Essentially, it describes a relationship where the output (y) changes at a constant rate with respect to the input (x).
Linearity in the parameters – It is the condition in which the right-side of a statistical model is a weighted sum of coefficients times variables.
Linear low-density poly-ethylene (LLDPE) – It is a type of polyethylene polymer with a substantially linear molecular structure, but with substantial short side branches, making it more flexible and stronger than traditional low-density polyethylene (LDPE). It is produced by co-polymerizing ethylene with longer-chain alpha-olefins like 1-butene, 1-hexene, or 1-octene. Its properties include high impact and puncture resistance, flexibility, and good chemical resistance, which makes it ideal for applications like plastic films, stretch wrap, and containers.
Linear model – It is a mathematical model in which the equation relating the random variables and parameters are linear in parameters.
Linear mixture rule – It is also known as the rule of mixtures. It is a method used to estimate the properties of a composite material by combining the properties of its individual components, often based on their volume fractions. It is normally applied in materials science to predict properties like elastic modulus, tensile strength, thermal conductivity, and more.
Linear motion valve – It is a type of valve where the flow of fluid is controlled by a closure member (like a disc, gate, or diaphragm) which moves in a straight line to start, stop, or regulate the flow. Linear motion valves tend to be slower in operation, but they have a higher level of accuracy and stability in the position of the closure member. These valves are typically used in applications needing precise flow control and throttling, frequently in high-pressure systems.
Linear motor – It is an electrical machine which generates electric force in a straight line by the interaction of its moving parts and magnetic fields.
Linear particle accelerator – It is a type of particle accelerator which accelerates charged sub-atomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beamline.
Linear programming – It is a type of optimization algorithm which is very effective for problems where the objective and constraint functions are linear.
Linear regression – It is a type of analysis in which a quantitative study endpoint is posited to be determined by one or more explanatory variables in a linear equation, i.e., a formula involving a weighted sum of coefficients times variables plus an error term.
Linear scale – It is a method of representing data where equal intervals on the scale correspond to equal differences in the measured quantity. It is characterized by a constant ratio between the distance on the scale and the corresponding value it represents. In essence, it is a line divided into equal parts, used to show the relationship between a distance on a map (or other representation) and the actual distance on the ground. A key feature of a linear scale is that the ratio between any two points on the scale and the corresponding values is always the same.
Linear scheduling method – It is a graphical scheduling technique which used to assign resources when project work consists of repetitive tasks. It focuses on maximizing resource use and reducing time wastage due to interruptions.
Linear sequential model – It is a linear sequential model which moves through the phases of project life cycle systematically and sequentially. It is typically used for small projects with straightforward requirements, since sequential development makes it difficult to revise design based on testing or preliminary feedback.
Linear shrinkage – It is the shrinkage in one dimension of a compact during sintering.
Linear (tensile or compressive) strain – It is the change per unit length because of the force in an original linear dimension. An increase in length is considered positive.
Linear valve – It is a type of valve where the flow control element (like a disc or plug) moves in a straight line, either perpendicular or parallel to the flow direction, to regulate or stop the flow of a fluid. This linear movement contrasts with rotary valves, which use a rotating disc or ball to control flow. Linear valves are often preferred for applications requiring precise flow control, especially at low flow rates, and for reliable shut-off capabilities. Linear valves achieve flow control by moving a closure element (e.g., a plug, disc, or diaphragm) along a straight path. This movement is typically achieved through a sliding stem that is actuated by a manual, pneumatic, electric, or hydraulic actuator.
Linear variable differential transformer – It is a transducer which produces an electrical signal proportional to the movement between its parts. It converts the linear motion into an electrical signal using an inductive transducer. Because of to its superior sensitivity and accuracy over other inductive transducers, the linear variable differential transformer is extensively used in several different fields. For measuring linear distance, the linear variable differential transformer is a precise and trustworthy tool.
Linear vibration welding – It is a thermoplastic joining process which uses a high-frequency, linear, reciprocating motion to create friction heat, melting the surfaces of two parts which are held together under pressure. Once the material melts sufficiently, the vibration stops, and the parts are held under pressure to cool and solidify into a single, strong bond. This method is normally used for large parts with relatively flat or slightly curved seams and is prevalent in industries like automotive for creating components such as manifolds and lighting assemblies.
Line blinds – These are also known as line blanks. These are used to isolate a portion of pipe, normally for maintenance purposes. There are different types of line blinds used to isolate piping by normally inserting a solid disc with seals to eliminate the ability of upstream process liquids and gases to migrate downstream. Even if the seals failed, it is not possible for process fluids to migrate downstream. Location of line blinds are indicated on piping and instruments diagrams. The provision for blinding consists of a pair of flanges, one of which can be a flanged valve (except wafer type valves) or equipment nozzle. Spectacle blinds, blinds, and spacers are used as per the specification of the organization. Provision is made for using mechanical means of lifting either by davits or block and tackle lifting points, where the weight exceeds the standards. Wherever possible, blind / spacer are located in horizontal runs. Where pipeline blinds are installed, the piping is designed to allow enough flexibility to spring the pipeline by means of either jack screws or other jacking arrangements. On ring joint flanges, the flexibility allowance is to be sufficient to allow for the removal of the ring without overstressing the piping. If needed, a break out spool is provided for dismantling. For preventing galvanic corrosion, rubber or plastic lined insulation spools are used.
Line cutting – It consists of straight clearings through the bush to permit sightings for geophysical and other surveys.
Line focusing systems – These are set-ups which utilize individually tracked reflector rows to concentrate direct solar radiation onto a stationary linear receiver.
Line graph – It is a line graph is a scatter plot where individual points are connected by a line. The line represents a sequence in time, space, or some other quantity. Where the graph also includes a category variable, a separate line can be drawn for each level of this variable.
Line indices – These are the Miller indices of the set of planes producing a diffraction line.
Line, in X-ray diffraction patterns – It consists of an array of small diffraction spots arranged so that they appear to form a continuous line on the film.
Line leak – It is a failure in a pipeline which allows the unintended release of fluid, which can be detected through different monitoring systems designed to alert operators for necessary remedial actions.
Line, looper – It consists of closely spaced symmetrical lines on the surface of metal which has undergone non-uniform deformation, normally in a drawing operation.
Line, Lueders – It consists of elongated surface markings or depressions appearing in patterns caused by localized plastic deformation which results from nonuniform yielding.
Lineman – It is a specialist technician who installs outside plant wiring (overhead circuits, power transmission lines).
Line of balance – It is a graphical technique which is used to show relationships between repetitive tasks in process. Each set of repetitive tasks is shown as a single line on a chart. People are to look for places where dependent tasks intersect, indicating that the successor task is to be delayed.
Line of sight (LOS) – It is an imaginary line between an observer’s eye and an object.
Line pair – In spectroscopy, it is an analytical line and the internal standard line with which it is compared.
Line pipe – It is the pipe used in the surface transmission of oil, natural gas, water, or other fluids. Line pipe refers to large-diameter pipes specifically designed for transporting fluids over long distances, mainly in pipelines. These pipes are important for industries like oil and gas, ensuring the safe and efficient delivery of raw materials and finished products. These pipes are typically made of steel and engineered to withstand high pressure, corrosion, and extreme temperatures.
Line pipe steel – It is a specific type of steel used for constructing pipelines which transport large volumes of oil, gas, and water over long distances. It is engineered to be strong, durable, and corrosion-resistant, designed to withstand high pressure, temperature fluctuations, and harsh environmental conditions during transport and service. Key requirements include high toughness and excellent weldability for field conditions.
Line pressure – It is the applied force or pressure exerted by a conveyor to facilitate the movement of the conveyed product. Regular evaluations are essential to fine-tune line pressure, optimizing conveyor performance and efficiency based on material characteristics. It is also pressure of a fluid in a pipeline.
Line pressure drop – It refers to the reduction in pressure which occurs along a pipe or line in a refrigeration system, which can considerably affect the coefficient of performance (COP) of the system. It is particularly critical in the compressor suction line, where pressure drops can lead to substantial efficiency losses.
Liner – It is the slab of coating metal which is placed on the core alloy and is subsequently rolled down to clad sheet as a composite. In extrusion, it is a removable alloy steel cylindrical chamber which is having an outside longitudinal taper firmly positioned in the container or main body of the press, into which the billet is placed for extrusion. In a filament-wound pressure vessel, the continuous, normally flexible coating on the inside surface of the vessel, used to protect the laminate from chemical attack or to prevent leakage under stress.
Line reaming – It consists of simultaneous reaming of coaxial holes in different sections of a work-piece with a reamer having cutting faces or piloted surfaces with the desired alignment.
Liners – These are thin strips of metal inserted between the dies and the units into which the dies are fastened.
Line-source model – It simplifies a physical source (like a borehole or roadway) into a one-dimensional line to analyze heat transfer or pollutant dispersion, treating it as an infinitely long, continuous emitter within a homogeneous medium, fundamental in geothermal energy (ground heat exchangers) and environmental science (road emissions) for calculating temperature changes or air quality impacts over time and distance.
Line-to-line voltage – It is the electrical potential difference measured between any two phase conductors (lines) in a poly-phase system, like a three-phase power supply, representing the voltage available across two live wires, commonly used for heavy industrial loads. In a balanced three-phase system, its magnitude is ‘root 3’ (around 1.732) times the phase-to-neutral voltage and leads it by 30 degrees, with normal examples being 208 volts (from 120 volts phase) or 400 volts /415 volts (from 230 volts phase).
Line valve – It is a device installed directly in a pipeline to control, stop, or regulate the flow of fluids (liquids or gases), frequently featuring designs like ball valves or solenoid types for isolation, pressure management, and maintenance in systems ranging from gas networks to industrial processes. These valves provide important functions like sealing the line, preventing leaks, allowing for system isolation during repairs, and automating flow control, ensuring safety and operational efficiency.
Line voltage – It is the electrical potential difference measured between any two ‘hot’ phase conductors (lines) in a multi-phase AC (alternating current) power system, like the voltage between L1 and L2 in a three-phase setup, important for power transmission, differing from phase voltage (phase-to-neutral) and normally higher in star connections.
Line vortex – In fluid mechanics, it is an imaginary curve in a fluid flow which is everywhere tangent to the local vorticity vector, representing the axis or path of rotational fluid motion, like the invisible axis around which a whirlpool spins. It is a fundamental concept where vorticity (the curl of the velocity field) is concentrated, frequently forming part of a vortex tube, and outside the immediate core, the flow can be irrotational (potential flow).
Line, weld – It is the junction line of metal which has passed through a hollow die, separated and rejoined at the exit point. Seams are present in all extruded hollows produced from the direct extrusion process and in several cases are not visible.
Lining –It is the internal refractory layer of firebrick, clay, sand, or other material in a furnace or ladle. It is the material used on the furnace side of a furnace wall. It is normally of high-grade refractory tile, or brick, or plastic refractory material.
Lining, monolithic – It is a continuous, single layer of material, frequently a refractory material for high-temperature applications or a material like concrete for structures, applied to a surface without joints or seams. This technique creates a seamless and durable protective covering, derived from the Greek words ‘mono’ (single) and ‘lithos’ (stone). It is a lining made without the customary layers and joints of a brick wall. It is normally made by tamping or casting refractory material into place, drying, and then burning in place on the job.
Linishing – It is a method of finishing by grinding on a continuous abrasive belt.
Linkage, mechanical – It is an assembly of systems connected so as to manage forces and movement. The movement of a body, or link, is studied using geometry so the link is considered to be rigid. The connections between links are modeled as providing ideal movement, pure rotation or sliding for example, and are called joints. A linkage modeled as a network of rigid links and ideal joints is called a kinematic chain.
Linkage drive – It uses a four-bar linkage mechanism. In this mechanism, the load-stroke and velocity-stroke behaviour of the slide can be established, at the design stage, by adjusting the length of one of the four links or by varying the connection point of the slider link with the drag link.
Linked chains – These refer to polymer chains which are connected to each other at points other than their ends, a structure known as cross-linking. This arrangement considerably influences the properties of the polymer, differentiating thermosets from thermoplastics.
Linked hydrogel – It is a 3D network of hydrophilic polymer chains chemically or physically connected (cross-linked), allowing it to absorb and retain large quantities of water (over 10 %) while maintaining structural integrity. These cross-links prevent the polymer chains from dissolving, forming a stable, water-swollen gel.
Linked urethane – It refers to the urethane linkage (carbamate link), a specific chemical bond that joins repeating organic units together to form the versatile polymer material known as polyurethane. The urethane linkage has the chemical structure –NH–CO–O– (or R1-O-CO-NH-R2). This fundamental bond is formed by the reaction of two main types of chemical groups during the polymerization process namely (i) an isocyanate group (-NCO), and (ii) a hydroxyl group (-OH, typically from a polyol)
Linnaeite – It is a cobalt sulfide mineral with the chemical formula (Co,Ni)3S4. It is a member of the spinel group and is known for its metallic luster and steel-gray to violet-gray colour. Linnaeite is frequently found in hydrothermal vein deposits alongside other cobalt and nickel minerals. It is also notable as an ore of cobalt.
Linseed oil – It is also known as flaxseed oil. It is a colourless to yellowish oil obtained from the dried, ripened seeds of the flax plant. The oil is obtained by pressing, sometimes followed by solvent extraction. In a foundry, it is used as a core oil, which acts as a binder for foundry sands in the production of moulds and cores. It is valued for its ‘drying’ properties, meaning it undergoes oxidative polymerization to form a tough, rigid, and elastic film when exposed to air, which provides the necessary binding strength and water resistance for the sand core.
Lintel beam layout – Lintel beam is another form of support structure which is made above the doors and windows. It is reinforced structures which is made to provide strength to the part of the building that is made above the windows and doors. In this kind of drawings, one finds the correct positions, dimensions, and the number of lintel beams on every floor.
Lintels – These are the horizontal members placed over window, door and other openings to carry loads to the adjoining studs.
Lipids – These are a diverse group of organic compounds which are insoluble in water but soluble in nonpolar organic solvents like chloroform and ether. They are a broad class of molecules which includes fats, oils, waxes, phospholipids, steroids, and other related compounds.
Lipophilic – It means having an affinity for oil.
Lipped channel – It is also called lip channel, C-channel. It is a versatile, cold-formed steel structural profile with a C-shaped cross-section, featuring a vertical web, two horizontal flanges, and small lips or bends along the edges of the flanges which considerably improve its strength, rigidity, and resistance to buckling, making it ideal for lightweight yet robust construction, framing, and support systems.
Lip-pour ladle – It is the ladle in which the molten metal is poured over a lip, much as water is poured out of a bucket.
Lip seal – It is a circular seal ring of ‘U’. shaped cross section encompassing a spring element which provides resiliency and ensures a seal at the inner and outer lips of the ‘U’.
Liptinite – In coal geology, it is the finely-ground and macerated remains found in coal deposits. It replaced the term exinite as one of the four categories of kerogen. Liptinites have been originally formed by spores, pollen, dinoflagellate cysts, leaf cuticles, and plant resins and waxes.
Liptinite macerals -These are a group of hydrogen-rich organic components in coal, derived from the waxy, resinous parts of plants like spores, pollen, cuticles, resins, and algae, characterized by low reflectance in white light but bright fluorescence under UV (ultra-violet) light and high volatile matter yield, making them important for oil / gas generation. Key examples include sporinite (spores/pollen), cutinite (leaf cuticles), resinite (resins / waxes), and alginite (algae).
Liquation – It is the separation of a low-melting constituent of an alloy from the remaining constituents, normally apparent in alloys having a wide melting range. It is also the partial melting of an alloy, normally as a result of coring or other compositional heterogeneities. It is also the bleeding of the low-melting constituents through the solidified ingot surface.
Liquation temperature – It is the lowest temperature at which partial melting can occur in an alloy which shows the highest possible degree of segregation.
Liquefaction – It is a process which generates a liquid from a solid or a gas or which generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of the latter, a major commercial application of liquefaction is the liquefaction of air to allow separation of the constituents, such as oxygen, nitrogen, and the noble gases. Another is the conversion of solid coal into a liquid form usable as a substitute for liquid fuels.
Liquefaction point – It is also known as melting point. Liquefaction point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium.
Liquefaction process – This process converts a substance, normally a gas, into a liquid by controlling temperature and pressure, frequently involving cooling and compression to overcome molecular kinetic energy and allow inter-molecular forces to bond molecules, seen in natural gas or refrigerants, but also refers to soil losing strength in earthquakes.
Liquefaction temperature – It refers to the specific temperature, frequently very low (like -162 deg C for natural gas) or sometimes high (like 250 deg C to 400 deg C for biomass), and high pressure needed to change a substance from gas to liquid, with the critical temperature being the maximum point above which a gas cannot be liquefied by pressure alone, like Helium’s -269 deg C or carbon di- oxide’s 30.98 deg C. It also refers to the melting point for solids (like suppositories) or specific process temperatures in biomass conversion.
Liquefiable soil – It refers to saturated, loose soil (like sand or silt) which temporarily loses its strength and stiffness, behaving like a liquid when subjected to sudden stress, very frequently from earthquake shaking or rapid loading, causing it to lose its ability to support structures, leading to substantial ground failure and damage. This happens since increased water pressure (pore water pressure) pushes soil particles apart, reducing the effective stress holding them together.
Liquefied gas – It is sometimes referred to as liquid gas. It is a gas which has been turned into a liquid by cooling or compressing it. Examples of liquefied gases include liquid air, liquefied natural gas, and liquefied petroleum gas.
Liquefied natural gas (LNG) – It is natural gas which has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. It takes up around 1/600th the volume of natural gas in the gaseous state at standard conditions for temperature and pressure.
Liquefied natural gas process – It refers to the method of converting natural gas into liquefied natural gas by cooling it to temperatures between −159 deg C and −162 deg C, allowing it to condense into a liquid form for economical transport. This process includes two main sections namely pretreatment, which removes impurities, and liquefaction, which removes heat from the natural gas.
Liquefied petroleum gas (LPG) – It is a gas which is used is as a fuel gas for heating in various furnaces and in flame cutting machines. It is popularly known by its abbreviation or short form which is LPG. Liquefied petroleum gas is also used for oxy-LPG gas cutting and welding. Sometimes it is used for carburization of steel, flame heating, flame gouging, flame hardening, flame cleaning, and flame straightening. Like all fossil fuels, liquefied petroleum gas is a non-renewable source of energy. It is extracted from crude oil and natural gas. It is a safe, clean burning, reliable, high calorific value fuel. The main composition of Liquefied petroleum gas are hydrocarbons containing three or four carbon atoms. The normal components of Liquefied petroleum gas hence, are propane (C3H8) and butane (C4H10). Small concentrations of other hydrocarbons can also be present. Depending on the source of the Liquefied petroleum gas and how it has been produced, components other than hydrocarbons can also be present.
Liquefier – It is a device or machine which transforms a substance into a liquid state, frequently by cooling, or compression. It is normally used in industries to convert gases into liquids for easier storage and transportation, e.g., liquefied natural gas (LNG) is transported using specialized liquefaction plants and ships.
Liquefier head – In 3D printing (additive manufacturing), it is the heated component of an extruder which melts solid thermoplastic filament, transforming it into a liquid polymer which can be precisely deposited through a nozzle to build objects layer-by-layer, basically acting as the ‘hot end’ where the material is prepared for extrusion. It is a metal block with a channel and internal heaters, important for controlling the flow and consistency of the molten plastic.
Liquid – It is one of the four fundamental states of matter, characterized by nearly incompressible fluid particles which retain a definite volume but no fixed shape.
Liquid absorption – It is the process where a liquid is taken up and dispersed into the bulk (volume) of another solid or liquid material, rather than just sticking to the surface, like a sponge soaking up water. This involves the liquid’s molecules integrating and mixing throughout the absorbent’s structure, driven by the absorbent’s affinity for the liquid, frequently through capillary action in porous materials.
Liquid adhesive – It is a substance, like glue or cement, applied in liquid form to surfaces, which then hardens (by drying, evaporation, or chemical reaction) to bind two items together, resisting separation through mechanisms like mechanical interlocking in pores or chemical bonding. These adhesives offer advantages like joining diverse materials and efficient stress distribution but frequently need time to cure, which can slow production compared to tapes.
Liquid air – It is the air which that has been cooled to very low temperatures, so that it has condensed into a pale blue mobile liquid. It is stored in specialized containers, such as vacuum flasks, to insulate it from room temperature. Liquid air can absorb heat rapidly and revert to its gaseous state. It is normally richer in oxygen. It is frequently used for condensing other substances into liquid and / or solidifying them, and as an industrial source of nitrogen, oxygen, argon, and other inert gases through a process called air separation.
Liquid ammonia – It is pure ammonia (NH3) cooled or compressed into a colourless liquid, characterized by a strong, pungent odour, and used extensively as a refrigerant, industrial solvent, and in cleaning products, needing pressurized storage because of its low boiling point of around -33° deg C.
Liquid argon – It is a cryogenic colourless liquid. It has a boiling point of -186 deg C. Each volume of liquid argon gives 822 volumes of argon gas when it is converted to gas at room temperature and atmospheric pressure. Liquid argon is frequently used as a source of very pure argon gas for use in liquid steel rinsing, hot isostatic pressing and heat treatment atmospheres.
Liquidated damages – These are damages, whose amount the parties designate during the formation of a contract for the injured party to collect as compensation upon a specific breach. This is most applicable where the damages are intangible.
Liquidation cracks -These are also known as hot tearing which occur in the heat affected zone. When the temperature in that region reaches to the melting temperature of low melting point constituents causing them to liquidate and segregate at grain boundaries. As the weld cools down, shrinkage stresses cause the formation of small micro-scale cracks which later can link up due to the applied stresses to form a continuous surface or sub-surface crack.
Liquid barrier – It is a protective layer, frequently made from polyethylene, which prevents the penetration of liquids in packaging materials. This barrier can be applied to one or both sides of a packaging board, depending on the intended use and needed shelf-life.
Liquid biofuels – These are renewable, liquid fuels made from biomass (plants, algae, animal fats) used as alternatives to fossil fuels in transportation, mainly ethanol and biodiesel, produced through processes like fermentation or chemical conversion of sugars, starches, oils, or cellulosic materials. They offer lower sulphur / nitrogen content and can be blended with gasoline / diesel, aiding energy security and decarbonization.
Liquid bonding agent – It is a substance, frequently polymer-based (like latex, acrylics, epoxies), used to create strong adhesion between surfaces or materials, improving structural integrity, preventing separation (like new concrete to old), or ensuring micro-level attachment, functioning through mechanical interlocking, chemical bonding, or surface wetting to form a durable, single-unit connection. They are necessary in construction, and automotive, acting as advanced glues which improve compatibility and load-bearing capacity.
Liquid boundary layer – It is the thin zone of liquid right next to a solid surface where fluid velocity changes from zero (because of the no-slip condition) at the surface to the full ‘free-stream’ velocity further out, caused by viscous forces and friction, creating velocity gradients and influencing drag and heat transfer.
Liquid bridge – It is a small volume of liquid connecting two solid surfaces, held by surface tension, forming a curved connection which creates cohesive forces, like the water between sand grains making a sandcastle, or in aerosol particles to cause sticking, enabling applications from materials science to fluid dynamics. These bridges act as adhesives, their strength determined by liquid volume, surface properties, flow rate, and environmental factors, balancing gravity with capillary forces.
Liquid carbon di-oxide (LCO2) – It is the liquid state of carbon di-oxide (CO2), which cannot occur under atmospheric pressure. It can only exist at a pressure above 0.51 MPa, under 31.1 deg C (temperature of critical point) and above −56.6 deg C (temperature of triple point). Low-temperature carbon di-oxide is commercially used in its solid form, normally known as ‘dry ice’. The uses and applications of liquid carbon di-oxide is in fire extinguishers, and as a coolant.
Liquid carburizing – It is the surface hardening of steel by immersion into a molten bath consisting of cyanides and other salts. In this process the steel components are submerged in a liquefied carbon rich environment. The main component in such baths is cyanide. However, safety issues have led to baths which are non-toxic that accomplish similar results. The components are held in a molten salt which introduces carbon into the steel. Carbon is diffused inwards producing a hardened case by rapid quenching. The case produced by carbon diffusion is similar to that produced by gas carburizing. Cases formed by liquid carburizing have low nitrogen and high carbon content.
Liquid chromatography (LC) – It is an analytical technique in which the mobile phase is a liquid. It is carried out either in a column or a plane. The sample with the mobile phase is passed through a column or plane, accompanied by the stationary phase. Liquid chromatography is a separation method based on the distribution of sample compounds between a stationary phase and a liquid mobile phase.
Liquid chromatography-mass spectrometry – It is a powerful analytical technique combining liquid chromatography for separating complex mixtures with mass spectrometry for detecting, identifying, and quantifying components, offering high sensitivity, selectivity, and structural information for substances in environmental samples. Liquid chromatography separates compounds based on their chemical properties, while mass spectrometry then measures their mass-to-charge ratio, allowing precise identification of unknown molecules and quantification of known ones.
Liquid chromatography techniques – These refer to analytical methods which at utilize liquid mobile phase to separate and analyze components in a mixture, with high-pressure liquid chromatography (HPLC) being a specific type which uses a reusable column with a solid stationary phase and operates under high pressure.
Liquid circulation – It is the continuous movement or flow of liquid within a system, frequently creating closed loops, driven by pressure gradients, pumps, or density differences, and is a fundamental concept in engineering (like in pipes / reactors) to distribute substances, transfer heat, or mix components. In fluid dynamics, it is mathematically defined as the line integral of velocity around a closed curve, measuring the fluid’s rotation or swirl.
Liquid circulation velocity – It is the speed at which a liquid moves in a continuous flow or loop, crucial for mass transfer / heat transfer and mixing in systems like airlift reactors. It is determined by reactor geometry, fluid properties, and gas input, affecting holdup, mixing, and overall performance, measured by tracers or particle methods.
Liquid composite moulding – It consists of is a family of manufacturing processes where a dry, fibrous reinforcement (like carbon or glass fibres) is placed in a mould, then impregnated with a low-viscosity liquid polymer resin, which hardens (cures) to form a strong, lightweight composite part, offering excellent fibre control and environmental benefits over open-mould methods. Key liquid composite moulding types include ‘resin transfer moulding’ (closed mould, high pressure) and ‘vacuum-assisted resin transfer moulding’ (open mould sealed with a vacuum bag).
Liquid composite moulding processes – These processes are manufacturing methods for composite components where dry fibrous reinforcement is placed in a closed mould, compacted, and then impregnated with a liquid polymer matrix, followed by curing to form a rigid composite.
Liquid composition – It refers to the specific types and proportions (like mole or weight fractions) of different substances (solutes and solvents) which make up a liquid, determining its physical and chemical properties, such as density, viscosity, and how it behaves in mixtures or solutions (e.g., oil in water). It is important for understanding chemical behaviour and engineering applications, distinguishing the uniform bulk composition from surface composition.
Liquid contraction – It is the shrinkage or contraction in molten metal as it cools from one temperature to another while in the liquid state. It is the decrease in volume of a liquid when it is cooled, caused by the liquid’s particles slowing down and moving closer together. This phenomenon is the principle behind how liquid-in-glass thermometers work i.e., as the liquid cools, it contracts, and its level in the tube falls.
Liquid cooling – It refers to cooling by means of the convection or circulation of a liquid. It uses a liquid coolant (like water) circulated through tubes to absorb heat from hot components and move it to a radiator, which then dissipates the heat, offering superior cooling efficiency, quieter operation, and better performance for hot components compared to traditional air cooling. Examples of liquid cooling technologies include (i) cooling by convection or circulation of coolant, including water cooling, (ii) liquid metal cooled reactors, (iii) radiators (engine cooling), and (iv) cooling towers.
Liquid core reduction (LCR) – It refers to a process where a small quantity of reduction is applied to the surface of a cast product at the end of solidification to suppress solidification shrinkage and reduce internal defects.
Liquid crystal – It is a state of matter whose properties are between those of conventional liquids and those of solid crystals. As an example, a liquid crystal can flow like a liquid, but its molecules can be oriented in a common direction as in a solid.
Liquid-crystal display (LCD) – It is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information.
Liquid crystal elastomers – These are slightly crosslinked liquid crystalline polymer networks. These materials combine the entropy elasticity of an elastomer with the self-organization of the liquid crystalline phase.
Liquid crystalline structure – It is an intermediate state of matter (mesophase) between a solid crystal and an isotropic liquid, where molecules have fluidity but also show long-range orientational order, meaning they tend to align in a specific direction, unlike random liquids. These structures combine the fluidity of liquids (like flow) with the organized alignment of solids (anisotropy), forming ordered patterns like hexagonal or lamellar phases, and are important in ‘liquid crystal display’.
Liquid crystal polymers – These are polymers with the property of liquid crystal, normally containing aromatic rings as mesogens. Despite uncrosslinked liquid crystal polymers, polymeric materials like liquid crystal elastomers and liquid crystal networks can show liquid crystallinity as well.
Liquid density – It is its mass per unit volume, measured in units like grams per cubic centimeter, indicating how tightly its molecules are packed, with water at around 1 gram per cubic centimeter. It determines if a liquid floats (less dense) or sinks (more-dense) in another liquid, and changes with temperature and pressure.
Liquid desiccant – It is a hygroscopic (water-attracting) liquid, like a salt solution (e.g., lithium chloride) or glycol, which removes moisture from air or gas streams by absorbing or adsorbing water vapour, functioning as a drying agent in open-cycle systems for dehumidification, frequently needing heat for regeneration (drying out) to be reused.
Liquid desiccant system – It is an energy-efficient HVAC (heating, ventilation, and air conditioning technology) which uses a salt solution (like lithium or calcium chloride) to absorb moisture from the air, dehumidifying it, and then regenerates the solution using low-grade heat (solar or waste heat) to reuse it, offering independent control of temperature and humidity, reducing reliance on refrigerants, and improving indoor air quality.
Liquid disintegration – It is the process of producing powders by pouring molten metal on a rotating surface.
Liquid disturbance – It is the disruption to smooth fluid flow, caused by internal factors (like temperature changes, density shifts) or external forces (like impacts, pressure changes), leading to instabilities, waves, or chaotic motion, which can manifest as cavitation in pumps or splashes on surfaces, affecting system reliability and flow characteristics.
Liquid droplet – It is a small, discrete mass or sphere of liquid, frequently formed by surface tension pulling it into a rounded shape, appearing as tiny drops from condensation, spray, or accumulation on surfaces, acting as miniature fluid bodies with properties influenced by density, viscosity, and surrounding interfaces. They are fundamental in different fields, such as atmospheric science (rain) and engineering (fuel atomization).
Liquid effluent – It is waste-water or liquid waste discharged from a source like a sewage plant, or industrial facility, containing contaminants which need treatment before release into the environment to prevent pollution. It can be untreated or treated (e.g., secondary effluent) and includes sewage, industrial by-products, and run-off, frequently carrying chemicals, pollutants, and other harmful substances.
Liquid ejector – It is a device which uses the kinetic energy of a high-pressure liquid (motive fluid) to entrain, mix, and move other fluids (liquids, gases, slurries) by creating a low-pressure zone, functioning without moving parts based on Bernoulli’s principle and the venturi effect. It converts the liquid’s pressure energy into high velocity through a nozzle, creating suction to draw in the secondary fluid, which then mixes and is discharged at a higher pressure than the suction side.
Liquid entrainment – It is the unintentional carrying of liquid droplets by a faster-moving gas or vapour stream, basically pulling liquid from a film or pool into the flow, frequently seen in processes like steam generation or distillation, leading to reduced efficiency and potential equipment damage from carried-over solids or erosion. It is quantified as the ratio of entrained liquid mass to total liquid mass, driven by inertial forces overcoming surface tension, and is a key factor in two-phase flow dynamics.
Liquid entry pressure – It is the minimum pressure needed for a liquid to overcome the surface tension and hydrophobicity to penetrate the pores of a membrane, important in processes like membrane distillation (MD) to prevent wetting and maintain performance, dependent on pore size, liquid surface tension, and contact angle.
Liquid expansion – It is the thermal expansion of liquid. It is the tendency of liquids to increase in volume when heated because of the increased kinetic energy of molecules pushing apart, a phenomenon important in thermometers and hot water systems, though water shows anomalous contraction below 4 deg C. This expansion is normally higher than solids because of weaker inter-molecular forces, but unlike solids, liquids expand in volume, not fixed shapes.
Liquid film – It is a thin layer or coating of liquid, ranging from nano-meters to micro-meters thick, which behaves differently from bulk liquid because of the strong surface interactions, frequently found flowing on surfaces or separating other phases in applications like coatings, micro-fluidics, and lubrication. Key characteristics include inter-molecular forces, evaporation, and stability being important to its dynamics, leading to phenomena like rupture or wave formation.
Liquid film thickness – It is the measurement or average dimension of a thin layer of liquid adhering to a surface or flowing over it. It is important in heat transfer / mass transfer, lubrication, and fluid dynamics, varying from micro-meters in lubrication to thicker layers in falling films, and determined by forces like gravity, viscosity, speed, and shear stress.
Liquid filtration – It is a separation process which removes solid particles, impurities, and contaminants from a liquid by passing the mixture through a porous filter medium, allowing the clean liquid (filtrate) to pass through while trapping the solids, which frequently build up to form a filter cake. This important technique is used in industries like water treatment to ensure product purity, protect equipment, and meet environmental standards.
Liquid flow – It is the movement of liquids because of the unbalanced forces, like pressure differences or gravity, causing continuous deformation and motion, a core concept in fluid mechanics, important for understanding everything from weather to pipelines. It’s characterized by properties like viscosity, density, and compressibility, and categorized as laminar (smooth) or turbulent (irregular).
Liquid flow rate – It is the volume of liquid passing through a specific area over a given time, basically measuring how fast a liquid moves, and is calculated as volume per time, or the product of the liquid’s velocity and the pipe’s cross-sectional area (Q = A x v), typically measured in units like litres per second.
Liquid flow velocity – It is a vector quantity describing how quickly and in what direction a liquid is moving at a specific point in space and time. It is defined as the rate of change of a fluid particle’s position, frequently measured in meters per second. This velocity can be calculated by dividing the liquid’s volumetric flow rate (Q) by the cross-sectional area (A) it flows through, a relationship described by the formula v = Q/A.
Liquid free surface – It is the boundary where a liquid meets another medium (like air or vapour) or another liquid, characterized by the absence of external shear stress, allowing the surface to be shaped by gravity, pressure, and surface tension. It is the top layer of a liquid open to its surroundings, seen as the water level in a glass or the ocean surface, and is important for understanding fluid dynamics phenomena like waves and capillary action.
Liquid fuel combustion – It is the process where liquid fuels (like gasoline, diesel, kerosene) are broken down into fine droplets (atomization), vapourized into gas, mixed with air, and then ignited to release energy through a rapid chemical reaction, producing heat, light, and exhaust gases like carbon di-oxide and water vapour. This complex process mainly happens in the gas phase, involving sequential steps of spraying, evaporation, mixing, and burning, with efficiency depending heavily on droplet size, mixing, and temperature.
Liquid fuel droplet – It is a tiny, spherical volume of liquid fuel, frequently sprayed into a combustion chamber, which undergoes evaporation and combustion in an oxidizing atmosphere (like air) to release energy, forming a vapor which burns in a diffusion flame, with its behaviour studied as a model for complex spray combustion. These droplets, formed by atomization, are important in engines, where their size, heat transfer, and surrounding flow dictate efficiency, with processes like break-up and vapourization being key stages.
Liquid fuels – These are combustible or energy generating molecules which take the shape of their container. Majority of the liquid fuels are derived from fossil fuels mainly from crude oil. Main liquid fuels used in industry are (i) furnace oil, (ii) low sulphur heavy stock, (iii) light diesel oil, and (iv) high speed diesel oil. Coal tar fuel is a byproduct liquid fuel produced during the cleaning of the raw coke oven gas in the coke oven and byproduct plant. Liquid fuels are normally used in industry for the production of steam for power generation, for heating purpose in different furnaces, for injection in blast furnace, and for the operation of locomotives and the mobile equipment. Liquid fuels are chemically stable and incompatible with strong oxidizers. They do not react vigorously with common materials but can react with oxidizing agents. Liquid fuels are stored in a dry cool, well – ventilated area away from heat and flame. They are also kept away oxidizing agents.
Liquid honing – It consists of producing a finely polished finish by directing an air-ejected chemical emulsion containing fine abrasives against the surface to be finished.
Liquid hydrocarbon – It is a compound made of only hydrogen and carbon atoms which exists in a liquid state, typically derived from crude oil or natural gas, serving as essential fuels like gasoline and diesel, and characterized by varying viscosity, colour, and flammability based on the length of their carbon chains. They are the backbone of the energy sector, extracted from fossil fuels, and can also be produced from biomass, possessing high energy density for transportation and other uses.
Liquid hydrogen – It is abbreviated as LH2. It is the liquid state of the element hydrogen. It has a boiling point of -252.8 deg C. Hydrogen is normally transported and delivered as a liquid when high-volume transport is needed in the absence of pipelines. To liquefy hydrogen, it is to be cooled to cryogenic temperatures through a liquefaction process. The strong point about the liquid hydrogen is high hydrogen mass density as compared to pressurized hydrogen.
Liquid impact erosion – It is the loss of material from a solid surface because of the relative motion in contact with a fluid which contains solid particles. In it the erosion is because of the relative motion of particles is nearly parallel to the solid surface.
Liquid impingement erosion – It is the loss of material from a solid surface because of the relative motion in contact with a fluid which contains solid particles. In it the erosion is because of the relative motion of particles is nearly normal to the solid surface is called impingement erosion.
Liquid-in-glass thermometers – The major types have used mercury or alcohol as the liquid. The element mercury is liquid in the temperature range of around -38.9 deg C to 356.7 deg C. As a liquid, mercury expands as it gets warmer. Its expansion rate is linear and can be accurately calibrated. Because of toxicity of mercury and the strict governing laws, the use of the mercury-in-glass thermometer has declined. However, for high accuracy applications, laboratory grade and reference standard models are available with calibration certification to standards.
Liquid injection rate – It is the speed or volume at which a liquid is introduced into a system (like a well-bore, engine, or reactor) over time, critical for controlling fluid dynamics, mixing, pressure, and process efficiency, frequently measured in volume per unit time and influenced by factors like injection pressure and fluid properties. It is important in applications like oil drilling (gas lift), polymer flooding, and diesel engines (fuel spray) for optimizing performance and outcomes.
Liquid iron – It is the hot metal which is the output of the blast furnace.
Liquidity – It refers to the organizational ability to meet its short-term financial obligations, or debts, as they come due, using readily available cash or assets that can be quickly converted into cash. It essentially measures how easily the organization can turn its assets into cash to pay its bills.
Liquidity ratio – It measures the organizational ability to pay its short-term debts using its short-term assets, showing its financial health and capacity to cover immediate obligations without external help, with common types being the current ratio’ and ‘quick ratio’ (or ‘acid-test ratio’). These ratios compare readily convertible assets (like cash, marketable securities, receivables) against current liabilities, with higher ratios normally indicating higher financial stability.
Liquid jet – It is a high-speed, cohesive stream of liquid which shoots out from a nozzle or orifice, maintaining its shape because of the inertia and surface tension, and is used in everything from cooling systems to propulsion, behaving as a parabolic trajectory in free flight.
Liquid layer – It is a thin sheet or film of liquid, frequently one which behaves differently from a bulk liquid because of the confinement by solid surfaces, creating structured molecular arrangements (liquid layering), or showing distinct flow dynamics like boundary layers where velocity changes from zero at a surface to the bulk flow, impacting heat transfer/ mass transfer.
Liquid leakage – It is the unintentional escape or loss of liquid from a container, pipe, or sealed system through a fault like a crack, hole, or faulty seal, frequently driven by pressure or concentration differences. It can also occur through a solid material through permeation, where liquid molecules diffuse through the material itself, not just an opening, causing gradual loss. Leakage results in waste, potential damage, safety hazards, and environmental issues, needing detection and repair.
Liquid level – It refers to the height or depth of a liquid’s surface within a container or open body, measured from a specific reference point. It is important for monitoring, controlling, and managing processes in industries like water treatment, chemicals, and fuel storage. It is determined by measuring the vertical distance from the container’s base or another established zero point to the liquid’s top surface, frequently using instruments like float switches, pressure sensors, or ultrasonic devices, to prevent overflow, ensure inventory accuracy, and automate operations.
Liquid limit – It is the moisture content where a cohesive soil transitions from a plastic (moldable) state to a liquid (flowing) state, defined by a standard test as the water content causing a groove in the soil to close after 25 standard blows in a Casagrande cup, signifying minimal shear strength and tendency to flow.
Liquid-liquid chromatography (LLC) – Liquid chromatography with a stationary phase composed of a liquid dispersed onto an inert supporting material. It is also termed liquid-partition chromatography.
Liquid-liquid contraction – It occurs as a result of the liquid cooling from its pouring temperature, normally 110 deg C to 165 deg C above its melting point, down to the melting point or solidification temperature. This particular factor is of little consequence to designers and is fairly easily dealt with by the foundry engineer.
Liquid–liquid extraction – It also known as solvent extraction and partitioning. It is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an organic solvent (non-polar). There is a net transfer of one or more species from one liquid into another liquid phase, normally from aqueous to organic. The transfer is driven by chemical potential, i.e., once the transfer is complete, the overall system of chemical components that make up the solutes and the solvents are in a more stable configuration (lower free energy). The solvent that is enriched in solute(s) is called extract.
Liquid-liquid separation – It is a chemical process which separates components of a mixture by transferring a desired solute from one liquid phase (like water) into another immiscible liquid phase (an organic solvent), based on differences in their solubility and polarity. This process uses a separatory funnel or other equipment to physically separate the distinct layers which form, allowing for purification or recovery of compounds.
Liquid-liquid transition – It is a rare phase change where a single substance transforms between two distinct liquid states, each with different densities, structures, and properties (like high-density against low-density liquids), frequently occurring in super-cooled conditions and important for understanding liquid matter’s fundamental nature. It is a first-order thermodynamic transition, but proving its existence is tricky as it can be obscured by crystallization.
Liquid lithium -It is a highly reactive metallic state of lithium which can cause corrosion of different structural materials, including metals and ceramics, through dissolution and compound formation. Its reactivity can lead to substantial leaching of alloy constituents, particularly nickel, and is influenced by the presence of impurities such as nitrogen and carbon.
Liquid lubricants – Liquids are normally preferred as lubricants because they can be drawn between moving parts by hydraulic action. Apart from keeping the parts separated they also act as heat carriers. Liquid lubricants are classified based on the origin from which liquid has been extracted and can be (i) mineral oils, (ii) fixed oils, (iii) synthetic fluids, and (iv) soluble oils and compounds.
Liquid mass transfer – It is the movement of a chemical component from a region of higher concentration to lower concentration, occurring within a liquid or across a liquid-gas / liquid-liquid boundary, driven by concentration differences, and fundamental to processes like extraction, distillation, dissolution, and drying. It involves mechanisms like molecular diffusion (random motion) and convection (bulk fluid movement).
Liquid mercury – It is a metal which can form an ideally smooth surface and has minimal surface contamination because of the oxidation, making it capable of dissolving several metals to form amalgams. Its optical constants, including refractive index and extinction coefficient, show free-electron-like behaviour across a range of wave-lengths, with notable values in the visible region.
Liquid metal – It is a metal or a metal alloy which is liquid at or near room temperature. The only stable liquid elemental metal at room temperature is mercury, which is molten above −38.8 deg C.
Liquid metal battery – It is an advanced energy storage device using two liquid metal electrodes and a molten salt electrolyte, separated into distinct layers by density, ideal for grid-scale storage of renewable energy because of the low cost, high power, and long life, leveraging self-healing properties from the liquid states.
Liquid metal cleanliness analyzer – This is an on-line sensor which detects inclusions directly in the liquid. Particles which flow into this sensor through its tiny hole are detected because they change the electric conductivity across a gap. Liquid metal cleanliness analyzer measures total concentration and size distribution of inclusions suspended in the metal alloys. The heart of the measuring system consists of a closed glass tube (electrically insulating material) bearing a small orifice at its bottom. The tube is positioned in liquid metal.
Liquid metal cooled reactor – It is an advanced nuclear reactor using liquid metal (like sodium, lead, or lead-bismuth) as its main coolant instead of water, allowing it to operate at higher temperatures and pressures, leading to higher thermal efficiency and high-power density, frequently in a fast neutron spectrum for potential fuel breeding and inherent safety features like passive cooling. These reactors offer improved energy conversion, reduced waste, and robust safety through features like natural circulation for heat removal.
Liquid metal embrittlement – It is the catastrophic brittle failure of a normally ductile metal when in contact with a liquid metal and subsequently stressed in tension. Liquid metal embrittlement is a phenomenon of practical importance, where certain ductile metals experience drastic loss in tensile ductility or undergo brittle fracture when exposed to specific liquid metals.
Liquid metal fast breeder reactor – It is a nuclear reactor which uses liquid metal (typically sodium) as a coolant and is designed to generate more fissile fuel (like plutonium-239) than it consumes by converting fertile uranium-238 into plutonium, extending nuclear fuel supplies and efficiency. These reactors use ‘fast’ neutrons for fission and are called ‘breeders’ since they create more fuel than they use, improving fuel sustainability for power generation.
Liquid metal induced embrittlement – It is the decrease in ductility and toughness of a metal caused by contact with another metal in liquid form. It results in intergranular fracture.
Liquid metal infiltration – It is the process for immersion of metal fibres in a molten metal bath to achieve a metal-matrix composite, for example, graphite fibres in molten aluminum.
Liquid metal magneto-hydrodynamics – It is the study of electrically conductive liquid metals (like mercury or molten sodium) interacting with magnetic and electric fields, analyzing how induced currents and magnetic forces alter fluid motion, used in nuclear fusion blankets, electro-magnetic pumps, and materials processing. It combines fluid dynamics and electro-magnetism, describing complex flows in industrial settings, differing from plasma magneto-hydrodynamics because of simpler governing equations.
Liquid methanol – It has chemical formula CH3OH. It is the simplest alcohol, a clear, volatile, flammable, and highly toxic liquid known as ‘wood alcohol’ or ‘methyl alcohol’, used extensively as a solvent, fuel (like for camping stoves), and in producing different industrial chemicals and everyday products, distinguished by its polar nature and ability to form hydrogen bonds.
Liquid miscibility gap – It is a range on a phase diagram where two liquids, initially mixed, separate into two distinct liquid layers (phases) since they are only partially soluble at certain temperatures and compositions, forming a two-phase coexistence region bounded by liquidus lines. Inside this gap, the system is thermodynamically unstable and minimizes its Gibbs free energy by separating into two liquids with different compositions, rather than remaining as one homogeneous solution, like oil and water.
Liquid molecule – It refers to the atoms or molecules within a substance in the liquid state, characterized by having enough energy to move past each other but still being held together by moderate inter-molecular forces, giving it a definite volume but no fixed shape, allowing it to flow and take the shape of its container. These particles are closely packed but not rigidly fixed like solids, enabling fluidity.
Liquid monomer – It is a small, reactive molecule (a ‘single unit’) that serves as a building block, which, when combined with a catalyst or initiator (like acrylic powder in nails), polymerizes (links together) to form large, strong chains, creating solid materials like durable nail improvements or industrial plastics. Normally used in nail tech (e.g., ethyl methacrylate) and concrete repair (e.g., methyl methacrylate), these liquids range from low odour to strong-smelling and are necessary for creating custom, hard coatings.
Liquid nitriding – It is a method of surface hardening in which ferrous metal parts are exposed to molten nitrogen-bearing fused-salt baths containing cyanates, cyanides, or both at sub-critical temperatures. A typical commercial bath is a mixture of sodium and potassium salts. The anions are 30 % to 40 % cyanate, 1 % to 5 % cyanide, and the balance carbonate. The operating temperature for these salt baths is 510 deg C to 595 deg C.
Liquid nitro-carburizing – It is a nitro-carburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature. Liquid nitro-carburizing processes are used to improve wear resistance and fatigue properties of steels and cast irons.
Liquid nitrogen – It is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of -196 deg C. It is produced industrially by fractional distillation of liquid air. It is a colourless, mobile liquid whose viscosity is about one-tenth that of acetone. Liquid nitrogen is widely used as a coolant.
Liquid octane – It has chemical formula C8H18. It is a colourless, volatile, flammable hydro-carbon found in petroleum, known for its gasoline-like odour and used as a standard for fuel quality (octane rating), representing a fuel’s ability to resist engine knocking. It is a major component of gasoline, an alkane with eight carbon atoms and 18 hydrogen atoms, existing in several isomeric forms, with isooctane (2,2,4-trimethylpentane) being a key reference.
Liquid oxygen – Liquid oxygen is abbreviated as LOX. It is a clear cryogenic liquid form of di-oxygen (O2). It has a boiling point -183 deg C. It is produced industrially by fractional distillation of liquid air.
Liquid-partition chromatography (LPC) – It is the liquid chromatography with a stationary phase composed of a liquid dispersed onto an inert supporting material.
Liquid penetrant inspection – It is a type of non-destructive inspection which locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent which causes the penetrant to seep back out of the discontinuity and register as an indication. Liquid penetrant inspection is suitable for both ferrous and non-ferrous materials, but is limited to the detection of open surface discontinuities in non-porous solids.
Liquid penetrant testing – The basic principle of liquid penetrant testing is that when a very low viscosity (highly fluid) liquid (the penetrant) is applied to the surface of a part, it penetrates into fissures and voids open to the surface. Once the excess penetrant is removed, the penetrant trapped in those voids flow back out, creating an indication. Penetrant testing can be performed on magnetic and non-magnetic materials, but does not work well on porous materials. In order of decreasing sensitivity and decreasing cost, the liquid penetrant testing processes can be listed as (i) post emulsifiable fluorescent dye penetrant, (ii) solvent removable fluorescent dye penetrant, (iii) water washable fluorescent dye penetrant, (iv) post emulsifiable visible dye penetrant, (v) solvent removable visible dye penetrant, and (vi) water washable visible dye penetrant. The advantages of liquid penetrant testing are (i) relatively low cost, (ii) highly portable NDT technique, (iii) highly sensitive to fine, tight discontinuities, (iv) applicable to a variety of materials, and (v) large area inspection. The limitations of liquid penetrant technique are (i) test surface is to be free of all dirt, oil, grease, paint, and rust, etc., (ii) detects surface discontinuities only, (iii) cannot be used on porous and very rough surfaces, (iv) removal of all penetrant materials, following the test, is frequently needed, and (v) there is no easy method to produce permanent record.
Liquid phase – It is a state of matter with a definite volume but no fixed shape, meaning it flows and takes the shape of its container, unlike solids with fixed shapes or gases which expand to fill all space. Its molecules are close but can move past each other, allowing fluidity and making liquids nearly incompressible, though they can transition to solid (freezing) or gas (boiling / evaporation) states with temperature changes.
Liquid phase change – It is the transformation of matter between a liquid state and another state (solid or gas) because of the energy (heat) and pressure changes, involving specific processes like melting (solid to liquid), freezing (liquid to solid), vapourization (liquid to gas / boiling), and condensation (gas to liquid). During these transitions, the substance’s potential energy changes, but its temperature stays constant until the change is complete, absorbing or releasing latent heat.
Liquid phase epitaxy – It is a solution growth process whereby the driving force for crystallization is provided by the slow cooling of a saturated solution consisting of the material to be grown in a suitable solvent, while in contact with a single crystal substrate.
Liquid phase sintering – It is the sintering of a compact or loose powder aggregate under conditions where a liquid phase is present during part of the sintering cycle.
Liquid phase synthesis – It is a chemical method where reactions occur in a solution, allowing precise control over nano-particle formation by mixing precursors in a solvent, frequently using protecting groups and purification steps, offering cost-effectiveness, scalability, and good control over product properties like size and shape. It involves dissolving reactants, facilitating bond formation, and separating products, contrasting with solid-phase methods by keeping components in liquid form.
Liquid phase transformation – It is a change within a liquid substance, either to a different liquid state (liquid-liquid) with unique density / structure, or from liquid to another state like solid (freezing) or gas (boiling / evaporation), driven by changes in temperature or pressure, involving energy absorption / release and structural reorganization.
Liquid polymer – It is a long-chain molecule which remains in a liquid state, either as a solvent, plasticizer, or a precursor to solid materials, frequently with unique properties like being bio-degradable or possessing ordered structures (liquid-crystalline polymers), used in everything from paints and inks to advanced composites and water treatment. They bridge the gap between liquids and solids, offering flowability with polymeric characteristics, and can be transformed into solids through cross-linking or curing.
Liquid precursor – It refers to a substance in liquid form used in chemical vapour deposition (CVD) processes for synthesizing materials such as graphene, offering advantages in handling and cost-effectiveness compared to gaseous precursors. These precursors facilitate easier doping and can decompose at lower temperatures, impacting the morphology and quality of the synthesized material.
Liquid pressure – It is the force exerted by a liquid per unit area, arising from its weight and molecular motion, acting equally in all directions at a given depth, and increasing with depth due to the weight of the liquid column above. It is calculated by P = d x g x h, where ‘d’ is liquid density, ‘g’ is gravity, and ‘h’ is depth, acting perpendicularly to any surface it contacts.
Liquid pump – It is a mechanical device which transfers or circulates liquids by converting mechanical energy (from a motor) into hydraulic energy, basically moving fluid from one location to another by increasing its pressure, frequently from a lower to a higher elevation.
Liquid radioactive waste – It is defined as the residual liquids produced during the operation and decommissioning of nuclear power plants, which can have varying levels of radioactivity and chemical content, and are typically treated through methods such as evaporation and ion exchange to concentrate radio-nuclides.
Liquid ratio – It refers to the proportion of liquid to powder in a paste, considerably influencing the paste’s handling characteristics, setting reactions, viscosity, injectability, and the overall properties of the hardened cement.
Liquid refrigerant – It is a chemical fluid, which absorbs heat at low temperatures and pressures, then releases it at higher ones as it cycles between liquid and gas states in refrigeration / air-conditioning systems to provide cooling, frequently stored in a receiver tank after the condenser before use in the evaporator.
Liquid resin – It is a viscous, normally transparent or translucent, organic substance which can be either naturally derived from plants or synthetically produced. It is characterized by its ability to transform from a liquid into a solid or a rigid state, often through a chemical process called polymerization. Liquid resin is a class of resins frequently termed chemoset. Liquid resins are chemically activated to initiate a curing reaction which can be at either ambient (e.g., 15 deg C to 25 deg C) or higher temperatures. liquid resin functions as a wetting agent for the abrasive grains, powder resin and fillers.
Liquid Reynolds number – It is the ratio of inertial forces to viscous forces in the liquid phase, calculated by considering the mass flux of the liquid.
Liquid sampling and hot rolling (LSHR) method – It is a specialized technique which is used to determine the semi-macro and macro size distributions of non-metallic inclusions in liquid steel samples. This method provides a comprehensive assessment of steel cleanliness, which is critical for material quality.
Liquid seal – It is a barrier using liquid (like water or oil) to prevent gas or fluid leakage, frequently by forcing gases to bubble through it, acting as a flame arrestor and check valve in industrial systems like flare stacks, or as a sealant in pipes and tanks by curing into a solid, seamless barrier. Basically, it creates a reliable seal by leveraging the physical properties of liquids or liquid-based materials.
Liquid shim – It is the material used to position components in an assembly where dimensional alignment is critical. For example, epoxy adhesive is introduced into gaps after the assembly is placed in the desired configuration.
Liquid shrinkage – It is the reduction in volume of liquid metal as it cools to the liquidus.
Liquid slag – It is the molten, glassy by-product from smelting or refining metals, formed by impurities (like silica, sulphur, and phosphorus) reacting with added fluxes (like lime, limestone) at high temperatures, floating on the denser liquid metal for easy separation, and typically composed of several metal oxides and silicates, used after cooling in construction, road building, and fertilizer.
Liquid slug – It is a concentrated packet of liquid which accumulates in a pipeline, frequently blocking gas flow until enough pressure builds to force it through as a large, cohesive unit, creating intermittent two-phase (gas-liquid) flow, or it can refer to liquid refrigerant entering a compressor, causing severe mechanical issues like clattering and vibration. In energy systems, it is a substantial volume of liquids (like water or oil) separating from gas, needing special handling.
Liquid sodium – It is a shiny, soft, silvery-white metallic element which is liquid at relatively low temperatures (melting point around 98 deg C), prized for its exceptional heat transfer capabilities, high electrical conductivity, and use as a coolant in nuclear reactors and solar power systems, but it’s highly reactive with water and oxygen, needing careful handling in protective oil or inert gas.
Liquid-solid chromatography (LSC) – It is liquid chromatography with silica or alumina as the stationary phase.
Liquid-solid contraction – Majority of metals contract as they pass from the liquid to the solid state. Certain compositions of gray and ductile iron are the exceptions to this rule in the major alloys produced by foundries. The entire founding process is possible only since the volumetric contraction locates itself in solidifying castings in a systematic way.
Liquid spray quench – It is a quenching process using spray nozzles to spray water or other liquids on a part. The quench rate is controlled by the velocity and volume of liquid per unit area per unit of time of impingement.
Liquid structure – It describes the arrangement and interactions of molecules in a fluid state, characterized by short-range order (nearby molecules cluster predictably) but lacking the long-range order of solids, allowing molecules freedom to move and flow while staying relatively close, frequently with specific patterns like hydrogen bonding or layering around nano-particles. This intermediate order, revealed by techniques like radial distribution functions, results in properties such as surface tension, viscosity, and the ability to take container shapes.
Liquid temperature – It is the measure of thermal energy of a working liquid, which influences its physical properties such as viscosity, density, and surface tension, ultimately affecting the thickness and stability of liquid films. Liquid temperature is a measure of the average kinetic energy (thermal energy) of its molecules, indicating how hot or cold it is, affecting properties like viscosity and density, and determining its state (solid, liquid, or gas) at different pressures and temperatures.
Liquid-to-solid shrinkage – It is also known as solidification shrinkage. It is the reduction in volume which occurs when a material, such as molten metal, changes from a liquid state to a solid state. This volume loss happens during the solidification process and is an important consideration in casting, since it can cause voids or dimensional inaccuracies if not properly accounted for.
Liquid transport properties – These properties describe how mass, energy, and momentum move within a liquid, governed by inherent characteristics like viscosity (momentum transfer), thermal conductivity (heat transfer), and diffusivity (mass transfer). These properties quantify a liquid’s response to gradients (like temperature or velocity) and are important since they influence flow, mixing, and energy exchange.
Liquidus – It is the lowest temperature at which a metal or an alloy is completely liquid. In a phase diagram, it is the locus of points representing the temperatures at which the different compositions in the system begin to freeze on cooling or finish melting on heating.
Liquidus line – On a phase diagram, it is the curve marking the temperature above which a substance or alloy is entirely liquid, separating the single-liquid phase region from the two-phase (liquid + solid) region. As a material cools, it reaches the liquidus line and begins to solidify, forming solid crystals while coexisting with the remaining liquid until it hits the solidus line, below which it is fully solid.
Liquidus temperature – It is the temperature above which a material is completely liquid. It is the temperature at which a solid phase transitions entirely to a liquid phase. In other words, it is the highest temperature at which crystals can coexist with the liquid in thermodynamic equilibrium. For pure substances, the liquidus and solidus (the temperature below which a material is completely solid) are the same, and this is called the melting point. However, for alloys and mixtures, there is a range of temperatures between the solidus and liquidus where the material is a mixture of solid and liquid.
Liquid-vapour line – It is also called saturation curve on a phase diagram. It marks the boundary where a substance exists as both a liquid and its vapour in equilibrium, showing the conditions (temperature and pressure) where the first gas bubbles form in the liquid or the last liquid droplets disappear, separating the single-phase liquid region from the two-phase liquid-vapour region and the superheated vapour region.
Liquid velocity – It is the rate at which a liquid moves through a system, defined as a vector quantity describing its speed and direction at any point, measured in units like meters per second. It is an important concept in fluid dynamics, influencing flow rate, mixing, and pressure, and can vary considerably within a pipe because of the changes in pipe size or obstructions, even if the overall flow rate stays constant.
Liquid viscosity – It is a measure of a liquid’s resistance to flow, with dynamic viscosity and kinematic viscosity as its two common forms. A liquid’s viscosity determines its rheological behaviour, classifying it as either Newtonian or non-Newtonian based on whether viscosity is dependent on flow rate.
Liquid waste – It is a waste material in liquid form which is unwanted, discarded, or considered waste. This can include wastewater, used oils, acidic water, or other liquids from different industrial processes. It can range from non-hazardous to hazardous, depending on its composition and potential impact on human health and the environment.
Liquid water content – It is the measure of the mass of liquid water present in a specific volume or mass of air (or other medium like snow), typically expressed in grams per cubic meter or grams per kilogram. It is an important parameter in meteorology for understanding cloud formation, precipitation, and atmospheric dynamics, representing water droplets or suspended liquid water, excluding ice or vapour.
Liquid zone – Its definition varies by context. Normally it refers to the molten metal area in welding / casting (where it is the liquid state during processing) or a flexible period in production planning (where schedules can change, unlike frozen zones). In material science, it can describe the region in phase diagrams where a substance is liquid, or in fluid dynamics, the layers of moving fluid with varying velocities.
Lithic sandstone – It is also known as litharenite. It is a type of sandstone rich in sand-sized fragments (lithic clasts) of pre-existing igneous, metamorphic, or sedimentary rocks, rather than just individual mineral grains like quartz or feldspar, frequently appearing gray or ‘salt-and-pepper’ because of the dark rock fragments, and indicating rapid deposition near active tectonic settings.
Lithium (Li) – It is a chemical element having atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element.
Lithium-7 – It is a stable isotope of lithium, comprising around 92.58 % of naturally occurring lithium, and is used in reactor coolant systems because of its low neutron capture cross-section and non-radioactive nature when irradiated. It is utilized in the form of lithium hydro-oxide (LiOH) to control pH levels in reactor coolants, minimizing materials corrosion.
Lithium-air battery – It is an advanced energy storage device which uses lithium metal as the anode and oxygen from ambient air as the cathode reactant, offering potentially 5 times to 10 times higher energy density than current lithium-ion batteries by replacing heavy cathode materials with lightweight oxygen, making them ideal for electric vehicles and portable electronics, though still facing challenges in stability and efficiency.
Lithium battery – It is an energy storage device which uses lithium ions to transfer charge between positive (cathode) and negative (anode) electrodes during charging and discharging, enabling high energy density for portable electronics, electric vehicles, and long-life applications. lithium batteries are known for lightweight, high power, and long life.
Lithium battery performance – It refers to the capacity and efficiency of lithium batteries, which can be influenced by factors such as aging mechanisms, including the loss of active lithium ions, loss of active material, and increase of internal resistance. It encompasses the ability to maintain safety, reliability, and driving range as battery technology evolves.
Lithium battery systems – These refer to energy storage devices which utilize lithium as a key component, characterized by their strong reducing power and high energy density, making them widely used in portable devices.
Lithium bromide – It is an inorganic ionic salt, a white crystalline solid with the chemical formula LiBr, formed from lithium and bromine, known for being extremely hygroscopic (water-absorbing) and soluble in water, alcohol, and ether, making it important as a desiccant in absorption chillers and a reagent in chemical synthesis.
Lithium-bromide absorption cycle – It is a heat-driven refrigeration process using water as the refrigerant and a lithium bromide salt solution as the absorbent to provide cooling, normally for air conditioning, by leveraging the strong affinity between lithium-bromide and water vapour, making it an eco-friendly alternative to vapour-compression systems by using low-grade heat (like waste-heat or solar) instead of electricity to power the cycle.
Lithium-carbon di-oxide battery – It is a promising rechargeable battery technology which uses lithium metal as the anode and carbon di-oxide (CO2) as a cathode reactant, offering high energy density and the dual function of energy storage and direct carbon di-oxide capture, converting it into solid lithium carbonate and carbon during discharge, which helps mitigate green-house gas effects.
Lithium dendrites – These are tree-like, needle-shaped metallic lithium structures which grow on a battery’s anode during charging, forming because of uneven lithium deposition, frequently caused by fast charging, cold temperatures, or high current, and pose serious safety risks like short circuits and fires, reducing battery performance. They are a major challenge for next-generation lithium batteries, particularly lithium-metal batteries, needing solutions to ensure safer, more stable operation.
Lithium deposits – These are natural accumulations of lithium-bearing minerals or brines, found in diverse geological settings like hard-rock pegmatites (spodumene), claystones (hectorite), and under-ground salt-water aquifers (brines), forming economically viable sources of this critical metal for batteries. These deposits are formed through geological processes, with extraction methods tailored to each type, from mining solid rock to evaporating brine pools, all aiming to produce lithium carbonate or hydro-oxide.
Lithium di-silicate – Its chemical formula is Li2Si2O5. It is a strong, aesthetic, glass-ceramic material, known for its high strength (around 400 mega pascals), natural translucency, and durability, featuring interlocking, needle-shaped crystals within a glassy matrix that resist crack propagation.
Lithium-ion battery – It is a rechargeable energy storage device which works by moving lithium ions between a negative anode and a positive cathode through an electrolyte, allowing for the reversible conversion of electrical energy to chemical energy and vice versa, making them ideal for portable electronics and electric vehicles because of their high energy density and long life.
Lithium-ion cell – It is a rechargeable electro-chemical unit which stores energy by moving lithium ions between a negative electrode (anode) and a positive electrode (cathode) through an electrolyte, powering devices from smartphones to electric vehicles because of its high energy density, light weight, and long life.
Lithium iron phosphate – Its chemical formula is LiFePO4. It is a stable, low-cost cathode material for lithium-ion batteries, known for its safety, long cycle life, and resistance to overheating, making it ideal for electric vehicles, energy storage, and portable power, though it offers lower energy density than cobalt-based batteries. It is an inorganic compound appearing as a gray / black powder, characterized by abundant iron and phosphate, eliminating reliance on expensive and scarce cobalt and nickel.
Lithium manganese oxide – It has chemical formula LiMn2O4. It is a spinel-structured metal oxide used as a safe, abundant, and cost-effective cathode material in rechargeable lithium-ion batteries, known for its excellent ion flow, good power handling (high C-rates), and suitability for high-power devices like electric vehicles and power tools, despite challenges with high-temperature stability which researchers address with doping and surface coatings.
Lithium metal anode – It is a highly reactive, pure metallic lithium electrode used in advanced batteries (especially next-generation solid-state) for its extremely high energy density, offering superior capacity compared to graphite, but faces challenges with dendrite formation, high reactivity, and safety issues which researchers are working to overcome by controlling lithium deposition.
Lithium metal battery – It is an energy storage device using pure lithium metal for its anode, distinctive it from lithium-ion batteries which use graphite. This setup offers considerably higher energy density, making them ideal for high-performance, long-lasting applications, though rechargeable versions face challenges like dendrite formation.
Lithium nickel cobalt aluminum oxide – It is a high-energy mixed metal oxide used as a cathode material in lithium-ion batteries, known for its high energy density, fast charging, and long life, making it ideal for electric vehicles (EVs) and electronics, with aluminum improving thermal stability and nickel boosting capacity, though needing careful ‘battery management systems’ (BMS) for safety. Its general formula is LiNixCoyAlzO2, with common ratios around LiNi0.84Co0.12Al0.04O2, balancing performance and stability for demanding applications.
Lithium nitrate – It has chemical formula LiNO3. It is an inorganic, white crystalline salt of lithium and nitric acid, known for its strong oxidizing properties, high water solubility, and ability to absorb moisture (deliquescence); it is used in pyro-technics for red colour, thermal energy storage, and as a stabilizer in advanced lithium batteries.
Lithium polymer battery – It is a rechargeable battery, a type of lithium-ion battery, which uses a solid or gel-like polymer electrolyte instead of the liquid electrolyte found in traditional lithium-ion cells, allowing for flexible shapes, high energy density, and light-weight designs. They store energy by moving lithium ions between electrodes, offering excellent power-to-weight ratios but needing careful handling because of the fire risks if damaged.
Lithium-sulphur battery – It is a rechargeable battery using a lithium metal anode and a sulphur cathode, known for its high theoretical energy density, lightweight, and low cost because of sulphur’s abundance, but it faces challenges like cycle life and capacity fading, though research focuses on carbon encapsulation and electrolyte additives to improve performance for future applications like drones and electric vehicles.
Lithium thiolate – It is a chemical compound which consists of a lithium cation (Li+) ionically bonded to a thiolate anion (RS-), where ‘R’ is an organic group. It refers to a compound formed during the reversible redox cleavage of the sulphur-sulphur bond in lithium-organo-sulphur batteries, represented by the reaction R – S – S – R + 2 Li+ + 2 e− = 2 LiSR, where ‘R’ denotes a molecule fragment of the electrode material.
Lithium titanate – It has chemical formula (Li4Ti5O12), or LTO. It is a stable, spinel-structured ceramic material used as an anode in high-power lithium-ion batteries, known for its exceptional cycle life, safety (resists dendrites), and fast charging because of its zero-strain structure which allows rapid lithium-ion movement without substantial volume change, though it has lower energy density than traditional graphite anodes.
Lithography – It is a planographic method of printing originally based on the immiscibility of oil and water. The printing is from a stone (lithographic limestone) or a metal plate with a smooth surface. It has been used mostly for maps. Lithography can be used to print text or images onto paper or other suitable material. A lithograph is something printed by lithography.
Lithosphere – It is the solid, outer part of earth. The lithosphere includes the brittle upper portion of the mantle and the crust, the outermost layers of earth’s structure. It is bounded by the atmosphere above and the asthenosphere (another part of the upper mantle) below.
Lithostatic pressure – It is also called overburden / geostatic pressure. It is the immense, all-encompassing pressure on a rock layer deep within the earth, caused solely by the weight of the overlying solid rock and sediments. It is a fundamental concept in geology, increasing with depth because of the higher rock density, acting equally in all directions, and influencing rock volume changes and metamorphic processes, distinct from fluid pressure.
Lithotype – It refers to distinct, visible bands or layers in coal (like vitrain, clarain) or different rock types in geology, characterized by colour, lustre, and thickness, helping understand formation. It can also mean a printing plate made by a specific process (lithotypy) or the resulting print, involving etching stone or shellac-based plates.
Little-end bearing – It is a bearing at the smaller (piston) end of a connecting rod in an engine.
Litz wire – It is a kind of stranded wire used to minimize losses in coils.
Lived decay product, – It is the new, frequently radioactive, atom (nuclide) which forms when a parent radioactive isotope undergoes nuclear transformation (radioactive decay). These products can be stable or further decay, creating a chain of transformations until a stable atom is reached, like Uranium-238 decaying through many steps to stable Lead-206.
Lived radionuclides – These are normally known as long-lived radionuclides. These are radioactive isotopes with very long half-lives, typically thousands to billions of years, meaning they decay very slowly and persist in the environment for vast geological timescales, posing long-term health and environmental challenges, and are important for studying earth’s history, with examples including Uranium-238, Thorium-232, and Potassium-40.
Live loads—Live loads are produced by personnel, tools, and maintenance equipment and materials. The live loads used in design are to be the maximum loads expected during the service life of the equipment. For the majority of the designs, live loads are uniformly distributed over the floor areas of platforms of elevated support structures or to the access areas around at grade foundations. Typical live loads vary from 2.9 kilopascals (kPa) for personnel to as much as 7.2 kilopascals for maintenance equipment and materials.
Liveness – It is a property which states that something good is going to happen eventually in a system, contrasting with safety properties which ensure that something bad is not going to occur.
Live roller conveyor – It is a system comprising a series of powered rollers facilitating the movement of objects through the application of power to either all or some of the rollers. The power transmitting medium is typically in the form of a belting or chain. Regular inspections are vital to ensure the rollers’ functionality, preventing disruptions in material conveyance.
Living anionic polymerization – It is a controlled synthesis method where polymer chains grow from active, negatively charged (anionic) ends without spontaneous termination, allowing for precise control over molecular weight, narrow distribution, and complex architectures like block copolymers by adding monomer sequentially. The key is the absence of chain transfer / termination, meaning chains stay active indefinitely unless deliberately quenched, enabling predictable, uniform growth.
Living cationic polymerization – It is a controlled chain-growth method for making polymers with precise structures, characterized by an equilibrium between active, growing carbocations and dormant species, which prevents termination and chain transfer, enabling narrow molecular weight distributions and complex architectures like block copolymers. This precision is achieved by minimizing side reactions through a dynamic ‘dormant / active’ state, allowing for sequential monomer addition and post-polymerization modification, yielding well-defined materials for advanced applications.
Living free radical polymerization – It is a controlled chain-growth method which reversibly deactivates active radical chain ends, putting them in a dormant state, allowing for controlled growth without irreversible termination, leading to polymers with predetermined molecular weights, narrow distributions, and complex architectures like block copolymers. Key techniques like RAFT (reversible addition-fragmentation chain transfer) and ATRP (atom transfer radical polymerization) create a dynamic equilibrium between active radicals and dormant species, enabling precise control over polymer structure and functionality, unlike traditional free radical polymerization.
Lloyd’s Register – It is a leading global provider of classification, compliance, and certification services, mainly for the maritime industry, but also for energy and engineering, ensuring safety and performance standards for ships, offshore structures, and other complex projects through technical expertise, inspections, and adherence to international regulations. It provides important standards and certificates for marine insurance and operations, helping customers improve safety and sustainability.
Load – Load is a term frequently used in engineering. It means the force exerted on a surface or body. It is also the rate of output needed. It is also the weight carried. For testing machines, load is the force applied to a test piece which is measured in units such as pound-force, newton, or kilogram-force. In tribology, it is the force applied normal to the surface of one body by another contacting body or bodies. The term normal force is more precise and hence preferred. However, the term normal load is also in use. If applied vertically, the load can be expressed in mass units, but it is preferable to use force units such as newtons (N).
Load angle – It is also called power angle or torque angle. In electrical machines, it is the important angle between the rotor’s magnetic field and the stator’s rotating magnetic field, representing the phase difference which determines torque. For generators, it is the angle between the excitation voltage and terminal voltage and increases with load, causing the rotor to lag. For motors, the rotor leads the stator field (negative angle). This angle dictates power transfer, with a larger meaning more power, but exceeding of around 90-degree it causes a synchronous machine to lose synchronism and stall.
Load balancing – It is the process of efficiently distributing incoming network traffic and work-loads across multiple servers (a server farm) to maximize resource usage, improve performance, and ensure high availability and reliability for applications and websites. A load balancer acts as a ‘traffic cop’, sitting in front of servers and routing user requests to the least busy or most appropriate server, preventing any single server from becoming a bottleneck or overwhelmed, and providing fault tolerance if a server fails.
Load bearing – It describes a structural element which has been designed to support its own dead load in addition to the weight of other structural and non-structural elements. The weight of this load is carried down to the foundations of the building.
Load-bearing component – It is a structural part, like a wall, beam, or column, designed to support the weight (load) of a building and transfer it safely down to the foundation and ground, ensuring the structure’s stability and preventing collapse. These essential elements carry loads from floors, roofs, and other parts, distributing them downwards.
Load bearing piles – These piles are used to transfer the load of the structure to a suitable stratum by end bearing, by friction, or by both.
Load capacity – It is the maximum weight, force, or stress a structure, machine, or component can safely support or handle without failing, ensuring it performs its function reliably and safely over time. It applies to everything from buildings and vehicles to smaller parts like bearings, and factors in static weight, dynamic forces (like acceleration), and environmental stresses, with different types (e.g., normal, transverse, axial) depending on the load’s direction.
Load capacity, forklift – The load capacity of the forklift truck is a measure to indicate the maximum weight load which can be handled as a ‘load’ on the forks at a given ‘load centre’ with the mast held in a vertical position. The load capacity rating is expressed in kilograms and the load centre in millimeters.
Load-carrying capacity – It refers to the maximum weight or load which a structure, material, or system can safely support or bear without failing or experiencing damage. It essentially defines the limits of a system’s ability to withstand stress and maintain its intended function under load. This can apply to a wide range of contexts, from the load-bearing capacity of a building’s structure to the weight a vehicle can safely carry. In case of lubrications, it is the maximum load which a sliding or rolling system can support without failure. It is also the maximum load or pressure which can be sustained by a lubricant (when used in a given system under specific conditions) without failure of moving bearings or sliding contact surfaces as evidenced by seizure or welding.
Load cell – It converts a force such as tension, compression, pressure, or torque into a signal which can be measured and standardized. It is a force transducer. As the force applied to the load cell increases, the signal changes proportionally.
Load centering device – It is specialized mechanisms or devices meticulously crafted to maintain the material load precisely centred on the conveyor, ensuring a harmonized and efficient movement. Regular checks are imperative to validate the load-centering device’s proper functioning and prevent any deviations that may lead to imbalance.
Load-controlled test – It is an experimental procedure where the static load on a sample is increased slowly and steadily, with the resulting strain being the dependent variable. This type of test allows for the observation of material behaviour beyond its elastic limit, leading to plastic deformation and eventual failure.
Load controller – it is a device or system which manages electrical power consumption or physical weight distribution, either by limiting power to consumers to prevent overdraw, or controlling water flow in micro-hydro systems to maintain stable output. Its main function is to balance demand with supply or ensure operational limits are not exceeded.
Load cycle – It refers to the repeated application and removal of mechanical, thermal, or electro-magnetic forces (loads) on a component or structure over time, defining a full sequence from minimum to maximum load and back. These cycles are important for understanding material fatigue, wear, and designing for a component’s life-span, as continuous cycles can lead to failure even if individual loads are below the material’s ultimate strength.
Load-deflection curve – It is a curve in which the increasing tension, compression, or flexural loads are plotted on the ordinate axis and the deflections caused by those loads are plotted on the abscissa axis.
Load-displacement curve – It is a graphical representation of a material’s behaviour under load, plotting the applied force (load) against the resulting deformation (displacement). It shows how much force is needed to deform a material by a certain quantity, and the curve’s shape reveals insights into the material’s stiffness, elasticity, and other mechanical properties.
Load distribution factor – It is an engineering coefficient, especially in bridge design, which determines the proportion of a total load which is carried by a specific structural member (like a girder), accounting for the deck slab’s ability to spread the load across multiple supports, simplifying complex analysis. It helps engineers estimate forces (moments, shear) on individual beams, simplifying design by using simpler 2D models instead of complex 3D analyses, and depends on factors like girder spacing, span, and structural type.
Load-duration curve – It is a graphical representation which orders the actual demand for power over a year as per the decreasing intensity, illustrating the relationship between peak and average electricity demand in a specific consuming region. The area under the curve represents the total energy consumption for the year.
Loaded conditions – These conditions refer to the state of a cavity when a material load is added, resulting in modifications to the field configuration which depend on the size and material properties of the load. In this scenario, the original mode shapes can be altered, especially when the load has a high dielectric constant or losses.
Loaded relief valve – It is a conventional valve design where a disk is held against a seating surface by a spring, which can be adjusted to open at a specific set pressure, allowing fluid to flow when the pressure exceeds this threshold. The valve reseats when the pressure falls below the set point, typically at a lower pressure than when it opened.
Loaded state – It refers to the configuration of a body which has undergone deformation because of the application of external loads, contrasting with its initial undeformed or unloaded state.
Loaded surface – It refers to a physical or conceptual surface (like a floor, plate, or even a material’s boundary) which has a force, pressure, thermal load, or other stress applied to its area, frequently measured as force per unit area to analyze its behaviour. It is a distributed load over an area, distinct from loads on lines or points, defining how a structure or material responds to external pressures or heat.
Load electricity generation – It refers to the dynamic process of producing electrical power to match the real-time demand (the load) from all consumers, balancing the output of power plants (generation) with the consumption by different consumers, ensuring supply always meets demand, even as loads fluctuate from moment to moment. It is the constant effort to align power production with usage, accounting for losses and variations in demand for things like lights, motors, and appliances. It becomes increasingly complex with the integration of intermittent renewable energy sources like solar and wind. Balancing the supply and demand in this context is critical for maintaining stability in the national grid.
Load factor – It is the ratio of the average load in a given period to the maximum load carried during that period.
Load feeder – In electrical power distribution, it is a main conductor or cable which carries electrical power from a sub-station or main source to different distribution points, feeders, or end-use loads, while supplying power to downstream equipment, acting as the main link for delivering power to consumer areas. It is designed to distribute the total electrical load across the network efficiently and reliably, with protective devices to manage faults.
Load flow study – It is a mathematical prediction of the flow of electric power in a network, based on a model of the actual or proposed system. It is necessary for planning of electrical grids.
Load following power plant – It is a power plant which can economically be operated over a significant range of output, so as to meet varying electric power demand.
Load frequency control – It is the necessary process in power systems which balances electricity supply (generation) with demand in real-time, keeping the system frequency stable (around 50 hertz / 60 hertz) and managing power flow between inter-connected areas (like regions) through tie-lines, preventing blackouts and ensuring reliable operation. It achieves this by automatically adjusting generator outputs in response to frequency deviations and scheduled power transfers, acting as the secondary control layer after main governor responses.
Load impedance (Zload) – It is the total opposition (resistance + reactance) an electrical device or component presents to alternating current (AC) from a source, measured in ohms, dictating how much current flows and influencing system efficiency, crucial for matching source to load for maximum power transfer. It includes resistive (R) and reactive (X – from inductors and capacitors) parts, represented as Z = R + jX, and is important for optimizing performance in electronics, audio, and power systems.
Loading – In cutting, it is the building up of a cutting tool back of the cutting edge by undesired adherence of material removed from the work. In grinding, it is the filling the pores of a grinding wheel with material from the work, normally resulting in a decrease in production and quality of finish. In powder metallurgy, it is the filling of the die cavity with powder. In lubrication, it is the filling of an abrasive paper or other bound abrasive material by abraded material from a second body. It is also the concentration of abrasive bound in a matrix material or added to a lap wheel as a loose abrasive.
Loading conditions – These conditions describe the external forces (like tension, compression, shear, bending, torsion) and environmental factors (static against dynamic, constant against varying) which a physical object, structure, or system experiences, critically determining its performance, stress, strain, and potential failure, encompassing everything from how a bridge bears weight to how a material deforms under stress.
Loading cycle – It is the repeated application and removal (or variation) of a mechanical, thermal, or electro-magnetic load on a component, defining a full sequence from one load state back to a similar state. It is important for assessing fatigue life as these repeated stresses cause material weakening over time, unlike static (constant) or single-event dynamic / shock loads. It involves stress / strain cycles (e.g., tension / compression) which can be regular (like sinusoidal) or irregular, influencing material failure.
Loading device – It is a broad term for equipment which moves, transfers, or prepares items (like data, cargo, or equipment components) for transport or installation, ranging from a computer’s disk drive for loading software to forklifts for cargo, cranes, or specialized ‘unit load devices’ (ULDs). Basically, it is any tool designed to ‘load’ something else.
Loading effect – It is when a measurement instrument or connected load alters the behaviour (voltage, current, etc.) of the electrical circuit or system being measured, leading to inaccurate results, frequently since the instrument draws some power or creates an unintended path for current. For example, a voltmeter with finite resistance connected in parallel to a high-resistance circuit acts like a shunt, drawing current and lowering the voltage it is trying to measure. Minimizing this involves using instruments with much higher input impedance (for voltmeters) or lower internal resistance (for ammeters) to reduce their impact.
Loading effects – These refer to the influence of applied loads on the axial capacity and stiffness of structural elements, particularly piles, which can vary based on factors such as the nature of the loading (static against cyclic), material properties, and soil characteristics. These effects can result in either an increase or decrease in capacity and stiffness because of the repeated loading and the interactions between the pile and surrounding soil.
Loading frequency – It is the rate at which loads are applied in dynamic testing, which influences the time-dependent degradation behaviours of materials, such as magnesium alloys, under cyclic conditions. It typically ranges from 1 hertz to 20 hertz, with lower frequencies better simulating actual in vivo conditions.
Loading function – It is a mathematical representation of the load applied to a structural element, which can be expressed in terms of uniformly distributed loads or point loads, each characterized by specific functional forms.
Loading history – It refers to the sequence and magnitude of loads applied to a structural element during testing, which considerably impacts its observed performance, such as plastic rotation capacity. It is defined by the specific loading protocols used, which can vary in severity and affect the structural response.
Loading mean stress – It is the average of the maximum and minimum stresses in a cyclic load, calculated as ‘mean stress = [(stress)max – (stress)min]/2’. It represents the constant, unchanging component of a fluctuating stress and is an important factor in determining the fatigue life of a material. For example, a positive mean stress can reduce fatigue life, while a negative (compressive) mean stress can increase it.
Loading methods – These are the processes for transferring, adding, or applying something to a system, material, or structure. Loading methods refer to a variety of techniques such as adding chemicals to speed up sedimentation, placing goods onto a vehicle, or applying force to a structure.
Loading pattern – It is the specific spatial distribution of forces, displacements, or other effects which act on a structure or task, which can be applied to a model to simulate real-world conditions. In engineering, it involves assigning a design type (e.g., dead, wind, and quake) to a set of loads to define how they are applied. In project management, it defines how a task’s work effort is distributed over its duration, such as evenly (uniform) or concentrated at the beginning (front).
Loading pressure – It is the fluid, normally compressed air, applied to the diaphragm or piston in a pneumatic actuator.
Loading scheme – It refers to the systematic application of seismic excitations, including different strong earthquake records and artificial waves, to analyze the seismic response of structures under different loading conditions, such as those used in shake table tests. It is used to assess the effects of varying seismic severity on the structure’s performance before and after retrofitting.
Loading sheet – It is the part of a die assembly which is used as a container for a specific quantity of powder to be fed into the die cavity. Sometimes it is part of the feed shoe.
Loading slope – It refers to the incline or steepness of a ramp or surface used for moving items, calculated as the ratio of vertical rise to horizontal run (rise over run) or the angle it makes with the horizontal. It is important for determining effort needed (lifting / braking) and safety, frequently varying in steepness (e.g., constant, concave, convex) for different uses. It can also describe the slope (angle) of a beam’s elastic curve under load in structural engineering, representing the change in angle from the original axis. It is the stiffness of a sample, determined by fitting the apparent linear elastic section of the load-displacement curve with a least squares linear fit, reflecting the relative deformability of the sample under load.
Loading stress – It is the internal resistance force per unit area within a material which resists deformation caused by an external load. It is the effect of the load (the cause) and is calculated as the applied force divided by the cross-sectional area over which the force is distributed (S = F/A).
Loading transition – It refers to the change in the loading sequence applied to composite materials, such as transitioning from a low stress level to a higher stress level (L-H sequence) or vice versa (H-L sequence), which considerably affects the material’s fatigue behaviour and damage mechanisms.
Loading valve – It is a control device which manages fluid or pressure, with its specific function depending on the system. It can maintain stable back-pressure for dosing pumps (ensuring consistent delivery), hold heavy loads in hydraulic systems (like excavator arms), provide back pressure for boiler efficiency, or control flow during industrial loading / unloading of fluids like oil. Basically, it ‘loads’ the system by adding resistance or holding pressure to achieve precise, controlled operation.
Loading weight – It is the weight of a unit volume of powder, normally expressed as grams per cubic centimeter which is determined by a specified method.
Load introduction – It refers to the method by which load is applied to a structure, typically using load clamps or bonded pads, and is critical for assessing the structural integrity of components like wind turbine blades. It involves careful consideration of the clamp position to avoid critical areas where properties change considerably or where buckling is a concern.
Load lifting accessories – These are attachments to facilitate lifting of the load. These are end effectors or below the hook equipments. These consist of a variety of different, application-specific, attachments which can be added to the hoist to handle the lifting or positioning of different loads. Load lifting accessories are the components or equipment which are not part of the load lifting equipments but are either attached to the lifting equipment or load to be lifted and are placed either between the lifting device and the load or on the load in order to attach it. Examples are slings, spreader beams, lifting beam, magnet, lifting eyelet, clamps, shackle, C-hook, gripping lifters, lifting forks, and crane scales etc. Some of the load lifting accessories are described below.
Load lifting equipment – It refers to any equipment or machinery which is used to lift or move heavy loads or materials from one place to another. This can include cranes, hoists, lifts, forklifts, and other types of machinery which are specifically designed to lift and move heavy objects safely and efficiently.
Load lifting slings – These are accessories used for lifting and transferring of loads with the help of cranes, telphers, or hoists. Load lifting slings enable in the activities related to create anchors, attach to loads, lift loads, pull loads, and lower loads. The dominant characteristics of load lifting slings are determined by the components from which they are made. As an example, the strengths and weaknesses of a load lifting sling made of steel wire rope are essentially the same as the strengths and weaknesses of the wire rope from which it is made. Load lifting slings are normally one of six types namely (i) chain, (ii) wire rope, (iii) metal mesh, (iv) natural fibre rope, (v) synthetic fibre rope, or (vi) synthetic web. In general, use and inspection procedures tend to place these slings into three groups (i) chain, (ii) wire rope and mesh, and (iii) fibre rope web. Each type has its own particular advantages and disadvantages.
Load line – It is a graphical line showing current / voltage limits for a component (like a transistor) in a circuit. It represents a constraint, defining operating limits based on external conditions.
Load-loss factor – It is a factor for estimating energy lost in a distribution network due to load current.
Load management – It is the strategic control and adjustment of energy consumption (electricity, training stress, etc.) to balance supply and demand, prevent system overload, and optimize performance or efficiency, mainly by shifting usage from peak times to off-peak hours or reducing overall demand. In electricity, it smooths out peaks, reducing costs and strain. It is a strategy for altering the operation of customer loads so as to reduce peak demand on an electrical grid.
Load mismatch – It occurs when the electrical characteristics (like impedance) of a load do not properly align with the source, leading to inefficient power transfer, signal reflection, or a surplus / deficit of energy, normally seen in power systems (generation against demand) or RF (radio frequency) / audio circuits (source against load impedance). It means not all available energy is used or delivered efficiently, causing energy loss or requiring external supplementation.
Load pocket – It refers to a localized area in an electrical grid with high power demand but limited transmission capacity, creating a constraint which needs internal generation or storage for reliable supply. In mining, it is a chute area for loading materials into skips. Load pockets also refer to the areas in a bearing which are designed to hold oil and support the load, where the number of pockets can influence the static stiffness and load carrying capacity of the bearing. Increasing the number of load pockets normally improves performance but can also introduce complexity and variations in stiffness with angular position.
Load power – It refers to the electrical energy consumed by a device or system, measured in watts, which is the demand placed on a power source (like a generator or battery) and converted into other forms like heat, light, or motion. It is basically the work an electrical appliance does, from powering a small lamp to running a large factory motor, representing the power needed to operate it.
Load pre-heating – It refers to any efforts to use waste heat leaving a system to preheat the load entering the system. The most common example is boiler feed water preheating, where an economizer transfers heat from hot combustion exhaust gases to the water entering the boiler. Other applications utilize direct heat transfer between combustion exhaust gases and solid materials entering the furnace.
Load profile – It is the daily, weekly, or annual graph of electrical load against time. It is a graph of power consumption against real-time, illustrating how energy usage varies over a specified period.
Load regulation – It is a power supply’s ability to keep its output voltage constant despite changes in the load current (how much power the connected device draws). It measures how much the output voltage varies as the load changes, typically from no load (0 %) to full load, expressed as a percentage or in millivolts, with lower values indicating better regulation. An ideal regulator needs to have zero change, but real-world supplies have internal resistance which causes slight voltage shifts.
Load resistor -It is a component connected to a circuit’s output to simulate the electrical ‘load’ of a real device, drawing current and dissipating power to test, buffer, or stabilize the circuit, frequently preventing errors in systems which expect a certain resistance. It acts as a dummy load, mimicking the behaviour of things like speakers, lights, or motors, allowing engineers to analyze performance or trick sensors into functioning correctly.
Load sequence effects – These refer to the influence of the order in which stress levels are applied on the fatigue and residual strength of materials, where different loading sequences (such as low followed by high stress or high followed by low stress) can lead to varying levels of damage and premature failure.
Load-settlement curve – It is also called P-S curve. It is a graph in geo-technical engineering which plots the vertical load applied to a foundation or soil (y-axis) against the resulting downward movement / sinking (settlement) (x-axis), typically derived from field tests like plate load tests or pile load tests. It is used to determine a foundation’s bearing capacity and predicted settlement.
Load shortening curve – It is a graph in structural engineering showing the relationship between the axial load applied to a compression member (like a column or stiffened panel) and its resulting axial shortening (deformation), revealing its structural behaviour, buckling characteristics, ultimate strength, and post-buckling response. It is important for assessing stability and collapse in structures.
Load support – It is a point or connection which holds a structure or object and provides stability by resisting applied forces, like gravity and weight. It prevents movement or collapse by providing reaction forces against the applied loads. Key types of supports include fixed supports (which resist all movement and rotation), pinned supports (which resist translation but allow rotation), and roller supports (which allow translation but resist rotation). In conveyors, load support refers to the combination of the belt’s transverse rigidity and the supporting structures like idlers which prevent premature sagging and failure under a load. In essence, it defines the belt’s ability to bridge the gaps between supporting rollers without excessive sag, and the overall strength of the structure to carry the weight of the load. Load support is a critical design factor, influenced by belt stiffness, the distance between idlers, and the density of the conveyed material.
Load testing – It is a type of performance testing which evaluates how a system, application, or website behaves under expected or peak user loads. It simulates multiple users accessing a system simultaneously to identify performance bottlenecks, response delays, or stability issues. The goal is to determine how a system performs under normal and high-demand situations to ensure it can handle expected traffic and usage without issues.
Load torque – It is the rotational force (or resistance) which a mechanical system, like a motor, is to overcome to perform its intended work, consisting of the torque needed for useful work plus resistive forces like friction and windage. It is the demand placed on a motor by the attached machinery, varying from constant (like a conveyor) to speed-dependent (like a fan).
Load transfer platform – It is a reinforced soil structure, frequently using geo-synthetics, placed over soft ground or piles, designed to evenly distribute loads from an embankment or structure (like roads, railways) down to supporting elements, preventing excessive settlement and increasing stability by bridging gaps between piles or acting as a stiff mattress. It works through arching and membrane effects, acting as a stiff raft to transfer vertical loads to piles or firmer soil layers, crucial in civil engineering projects on weak soil.
Load transport – It refers to the movement of sediments, which occurs when bed shear stress exceeds a critical value, allowing particles to be transported as bed load or suspended load. The transport rate is influenced by factors such as sediment concentration, the thickness of the bed-load layer, and the average sediment velocity within that layer.
Load variation – It refers to the fluctuation or changes in demand for power, force, or stress on a system over time, common in electrical grids (peak hours), mechanical structures (vibrations, shifting weight), and software (user traffic). It is important for engineers to understand these variations to ensure system stability, efficiency, and reliability, as they can cause issues like voltage drops in power systems or material fatigue in structures.
Load vector – It is the assembly of individual forces into a vector which corresponds to the positions and directions of the freedom codes in a structure.
Load voltage – It is the actual voltage measured across an electrical device (the load) when it is connected to a power source, and it is typically slightly lower than the source’s ‘no-load’ voltage because of internal resistance and wire losses. It represents the voltage the load actually consumes, determined by the power source’s ability to deliver power under the specific demands (current draw) of that load.
Load zone – It is the designated section of the conveyor responsible for material loading onto the belt. Frequent inspections are essential to proactively address potential issues, such as spillage, misalignment, and excessive wear, safe-guarding the overall integrity of the conveyor system.
Loam – It is a moulding material consisting of sand, silt, and clay which is used over brickwork or other structural back-up material for making massive castings, normally of iron or steel.
Loam mould -It is a mould built up of brick, covered with a loam mud, and then baked before being poured.
Loam moulding – It is a system of moulding, especially for large castings, wherein the supporting structure is constructed of brick. Coatings of loam are applied to form the mould face.
Lobe – It normally refers to a rounded projection or division of a structure, frequently with a specific function or purpose. This term is used in several engineering fields, including antenna design, pump design, and engine valve timing.
Lobed bearing – It is a journal bearing with two or more lobes around its periphery produced by machining or by elastic distortion to increase stability or to provide adjustable clearance.
Lobed impeller gas totalizers – These consist of two rotating impellers, designed with a figure eight cross-section. The impellers rotate in opposite directions due to the forces exerted by the gas being measured. The shape of the impellers prevents contact while the gap between them remains constant. A gear drive external to the measuring chamber synchronizes the impellers. During each rotation four crescent shaped volumes are moved through the measuring chamber. The number of rotations is proportional to the gas flow. The rotation is coupled using an adjustable fine tooth gear train to the totalizer.
Lobe pump – It is also called rotary lobe pump. It is a type of positive displacement pump. It is similar to a gear pump except the lobes are designed to almost meet, rather than touch and turn each other. Lobe pumps are used in a variety of industries, It is very frequently used as an engine supercharger. Lobe pumps are popular since they offer superb sanitary qualities, high efficiency, reliability, corrosion resistance and good clean-in-place and sterilization-in-place (CIP/SIP) characteristics.
Local acceleration – It is also called temporal acceleration. It is the rate of change of velocity with respect to time at a fixed point in a fluid flow, occurring only in unsteady flows where velocity at that point changes over time (e.g., a water tap turning on / off). It is mathematically expressed as the partial derivative of velocity with respect to time, ‘delta V / delta t’. It contrasts with convective acceleration, which is because of a fluid particle moving to a different location with a different velocity.
Local action – It is the corrosion because of the action of local cells, i.e., galvanic cells resulting from inhomogeneities between adjacent areas on a metal surface exposed to an electrolyte.
Local anode – It is a specific, small spot on a metal surface where corrosion actively occurs (oxidation), acting as the site where electrons are lost, while the much larger surrounding area acts as the cathode, making corrosion highly localized and intense, frequently because of a breakdown of protective passive films.
Local area network – It is a network of computers and devices connected within a limited area like a home, office, or campus, allowing for the sharing of resources such as files and printers. These networks are managed locally and provide high-speed connections, typically using Ethernet or Wi-Fi.
Local authorities – The term is used for the representatives of government and statutory bodies who are stationed in the area of the industrial plant and have jurisdiction for monitoring the compliance of the statutory regulations by the industrial plant management and in case of non-compliance having decision making power to take actions.
Local brittle zones – These are small regions of hard, brittle phase which form in the heat affected zones (HAZ) of multi-pass welds. They normally contain untempered martensite which can lead to scatter in toughness data when the test sample shows a brittle zone. Local brittle zones are discrete microstructural regions in a weld heat affected zone which show lower resistance to fracture initiation than surrounding material. These zones can result in fracture initiation under near linear elastic conditions during fracture toughness testing. For example, in terms of crack tip opening displacement (CTOD), fracture toughness can be of the order of 0.01 millimeter in the local brittle zone when adjacent material can have a toughness of higher than 0.1 millimeter at the same temperature. During testing, Local brittle zones can result in sample fracture or an arrested brittle fracture. Hence, local brittle zone behaviour is a warning of potentially low resistance to brittle fracture initiation in the structural component being assessed. However, local brittle zones behaviour does not necessarily mean that the structural component is at high risk of failure by brittle fracture.
Local buckling – It is the instability and deformation of a specific, localized area or component of a structural member (such as the flange or web of an I-beam) under compressive stress, rather than the deformation of the entire structure. This phenomenon occurs when a structural element’s width-to-thickness ratio is too high.
Local cathode – It is a specific, small area on a metal surface where reduction (gain of electrons) occurs as part of a localized electro-chemical process, frequently seen in corrosion, forming a tiny cathodic site within a larger anodic region, contributing to the overall corrosion cell’s current. It is where oxygen or other species are reduced, contrasting with the adjacent anode (oxidation site) on the same surface or a connected one, leading to material degradation, like rust.
Local cell – It is a galvanic cell resulting from inhomogeneities between areas on a metal surface in an electrolyte. The inhomogeneities can be of physical or chemical nature in either the metal or its environment.
Local control panel – It is a physical interface, located near machinery, which allows operators to directly monitor, start, stop, and trouble-shoot specific equipment, providing necessary controls like push-buttons and switches for local operation, maintenance, and safety overrides, distinct from a centralized system. These customizable panels house components such as PLCs (programmable logic controller), protection devices, and indicators, reducing wiring to a main panel and enabling decentralized control for complex systems like manufacturing lines or utility equipment.
Local control unit – It is a self-contained processing device, frequently a micro-controller, which manages specific sub-systems or field devices in a larger system, providing real-time, independent control while communicating with central systems, acting as a smart, local brain for tasks like reading sensors, executing algorithms, and controlling actuators.
Local coordinate system – It is a temporary, object-specific reference frame (with X, Y, Z axes) used in 3D modeling, engineering, and computer graphics to simplify positioning, transformations, and analysis of parts relative to themselves, rather than the larger global system. It is like giving each component its own mini-grid, making it easier to define features and apply loads or movements independently, even when attached to a larger assembly.
Local criterion – It is a mathematical principle, common in algebraic geometry and ring theory, which simplifies proving a global property (like flatness) by checking if the property holds only in a small neighborhood or ‘local’ part of the structure, frequently at a specific point or ring, using conditions like flatness over a local ring or non-zero divisors. Basically, it is a shortcut i.e., if one can prove a condition holds locally, it implies the global property, or vice-versa, by examining relationships between a ring and its completions or quotients.
Local current density – It is the current density at a point or on a small area.
Localized corrosion – It is the corrosion at discrete sites, e.g., crevice corrosion, pitting, and stress-corrosion cracking.
Local defect – It is an imperfection which is confined to a specific, limited area of a product or system, as opposed to a global defect which affects the entire thing. Examples include a scratch on a single component, a pit in a metal bearing, or a partial blockage in a single pipe. Local defects are frequently addressed with targeted repairs or adjustments, while global defects can need more comprehensive redesign or process changes.
Local delamination – It refers to damage in composite structures characterized by inter-laminar cracks occurring between adjacent plies which are typically associated with other damage modes, such as micro-cracks. It can precede global delamination and can arise from severe damage induced during the fatigue process.
Local dimming – It is a technique which adjusts the brightness of LED (light-emitting diode) backlight segments based on image content to enhance visual contrast while minimizing power consumption and preventing clipping in image reproduction.
Local equilibrium – It is a concept in thermodynamics for systems not in overall equilibrium, where small, imaginary volumes within the system are assumed to be in equilibrium themselves, allowing properties like temperature and pressure to be defined locally as functions of space and time, even as the larger system changes. This approximation works when particles interact frequently enough (small mean free path) to maintain local balance faster than macroscopic changes occur, enabling the application of standard thermodynamic laws to these small regions.
Local exhaust ventilation – It is an engineering system which captures contaminants like dust, fumes, and vapours at their source, removing them from the work-place air before they spread to workers’ breathing zones, protecting health by using hoods, ductwork, fans, and filters to contain and exhaust hazardous substances efficiently. It is a more targeted and energy-efficient alternative to general ventilation, important for processes generating toxic or irritating airborne pollutants, such as welding, spray painting, or handling potent chemicals, with components like fume hoods, extraction arms, and enclosures.
Local fatigue strength – It refers to the strength of a material at a specific, localized point, considering factors like residual stresses and surface treatments, rather than just the bulk material properties. It involves analyzing the stress or strain in a specific region, such as a notch or surface-treated layer, to predict fatigue failure more accurately. This is crucial for components with surface treatments where material properties and residual stresses vary significantly with depth.
Local heat transfer – It refers to the variation in heat transfer rates at specific locations within a fluid flow, influenced by factors such as nozzle arrangement, fluid temperature, and Reynolds number. It is characterized by changes in the local Nusselt number, which reflects the effectiveness of heat transfer in response to flow conditions and nozzle configurations.
Local indentation – It refers to the localized deformation which occurs between two solids in contact, which can be analyzed through contact laws relating the relative displacement to the applied force, particularly during loading and unloading phases.
Local induction – It refers to a process used in tube bending which involves applying high temperatures to a short section of thick-walled pipes, enabling them to be bent with small radii while maintaining structural integrity. This method allows for continuous bending as the pipe moves through an induction coil, followed by cooling to stabilize the shape.
Local isotropy – Mainly in fluid dynamics (turbulence), it means that at very small scales (eddies), the statistical properties of fluid motion are uniform in all directions, independent of the large-scale flow’s overall orientation or direction, thanks to energy cascading from large to small scales. Basically, while the whole system can be anisotropic (direction-dependent), the tiny swirls at the end of the energy cascade behave isotropically, like uniform random motion, showing no preferred direction.
Localization accuracy -It refers to the precision with which a device or user’s location can be determined in an environment, as indicated by metrics such as median localization error, which can vary based on conditions like line-of-sight or non-line-of-sight scenarios.
Localization energy – It refers to the energy concentration in a specific region of a wave or a molecule, frequently because of the disorder or structural imperfections, causing energy to become spatially confined rather than distributed, a concept seen in engineering (vibrational energy). In simpler terms, it is the energy which gets ‘trapped’ in a particular spot, creating high-intensity zones.
Localization error – It is the discrepancy between an estimated or predicted location / position and its true, actual location, measured in different contexts like engineering (sensor networks), computer vision (object tracking), or software (translation). It quantifies the inaccuracy of systems designed to pinpoint something, such as a device’s coordinates.
Localization phenomena – It refer to the occurrence of localized vibrations in engineering structures, which can arise in disordered periodic systems because of the irregularities in their configuration. This concept encompasses both weak and strong localization, characterized by the exponential spatial decay rate of vibration amplitude along the structure, influenced by internal coupling and frequency range.
Localization problem – It is an issue in engineering which involves the analysis of material behaviour under conditions such as plasticity and damage, where the focus is on the evolution and response of materials to localized phenomena, including bifurcation and post-limit responses.
Localization zone – It is the region along a structural element where plastic curvature concentrates considerably after yielding, characterized by a rapid increase in curvature at a specific dividing point closer to the base. The length of this zone is influenced by loading conditions, with larger values observed under cyclic loading compared to monotonic loading.
Localized corrosion – It is the rapid, intense attack on specific, small areas of a metal surface, rather than uniform corrosion across the entire surface, often causing deep penetration and potentially catastrophic failure, with common types including pitting, crevice corrosion, stress corrosion cracking, and inter-granular corrosion. It happens when protective passive films (like oxide layers) break down locally because of the environmental factors or material defects, creating small anodic sites which corrode much faster, making it hard to detect and manage.
Localized deformation – It is a concentrated change in a material’s shape or structure within a specific region, rather than uniformly across the entire body, frequently occurring because of the stress concentrations, material instabilities, or application of loads, leading to phenomena like yielding, necking, buckling, or fracturing.
Localized effect – It refers to impacts, consequences, or phenomena which are confined to a specific, limited geographical area, or system, rather than affecting a broad region or the entire entity. It describes something concentrated in one place, distinguishing it from widespread or global occurrences.
Localized necking – It is a material’s localized thinning and reduction in cross-sectional area under tensile stress, where deformation concentrates in one spot after the material reaches its ultimate strength, causing further strain to occur only in that narrowed region before eventual fracture. It happens when the material’s strain hardening (strengthening from deformation) cannot keep up with the geometric softening (thinning), leading to instability and a sharp constriction, or ‘neck’.
Localized plastic flow – It is the phenomenon where permanent deformation concentrates into specific narrow bands or zones (shear bands) within a material, rather than being distributed evenly, frequently appearing as propagating ‘auto-waves’ of strain and indicating an instability leading to fracture, especially in ductile metals and alloys. It is the material’s way of self-organizing to reduce internal entropy during deformation, creating patterns of actively deforming and less-deforming regions. It is important for understanding failure processes in materials like metals, polymers, and even granular systems.
Localized precipitation – It is the precipitation from a super-saturated solid which is similar to continuous precipitation, except that the precipitate particles form at preferred locations, such as along slip planes, grain boundaries, or incoherent twin boundaries.
Localized surface plasmons – These are collective oscillations of free electrons in nano-structured metals or other conductive materials, confined to the dimensions of the nano-particle. When light interacts with these nano-particles, it can excite these oscillations, leading to improved electric fields near the particle’s surface and strong optical absorption at a specific resonant frequency.
Locally effective fatigue strength – It refers to the permissible cyclic stress a material can withstand at a specific critical point, such as a notch, defect, or weld, considering the non-uniform stress distribution and localized material properties at that exact location. Unlike traditional fatigue strength, which uses a nominal (average) stress value for an entire component, the ‘locally effective approach takes into account (i) stress concentrations, (ii) material Inhomogeneity, and (iii) averaging / critical distance’. This method frequently uses concepts like the ‘effective notch stress’ or ‘theory of critical distances’ to average the stress over a small material-specific length ahead of a potential crack location, providing a more realistic assessment of the local fatigue behaviour. This approach is especially important for components with complex geometries, surface treatments, or welds, where local conditions govern the fatigue life and overall structural integrity.
Local magnetic moment – It describes the magnetic strength and orientation of individual atoms or localized electrons within a material, arising from their spin and orbital motion, which acts like tiny bar magnets which interact with neighbours and external fields, influencing the material’s overall magnetism. It is a vector quantity (magnitude and direction) and is key in understanding complex magnetic behaviours like anti-ferro-magnetism or ferro-magnetism, frequently quantified using Bohr magnetons.
Local market power – It refers to the organization’s ability to influence prices, supply, or demand within a specific geographic or product market, frequently by controlling a substantial share of it, allowing them to set prices above competitive levels (above marginal cost) without losing customers, unlike organizations in perfect competition which are ‘price-takers’.
Local minimum point – Local minimum of a function is an element where, within a certain neighbour-hood, all values of the function are higher than or equal to the value at that element. In other words, it is a point where the function value is lower than or equal to values in its immediate vicinity.
Local necking – It is the development of a non-uniform strain gradient in tensile sheet samples with a large width-to-thickness ratio. The strain gradient results in the formation of a narrow trough across the face (width) of the sample. For uniaxial loading, the strain gradient is normally inclined at an angle to the load (typically around 55 degrees for isotropic materials). The local neck develops under plane-strain loading conditions, while diffuse necking develops under conditions of axisymmetric deformation, which is initially plane stress.
Local network – It is also called LAN (local area network). It connects devices (computers, phones, printers, smart devices) within a small, limited area like a home, office, or building, allowing them to share resources and communicate quickly without needing the broader internet.
Local Nusselt number (Nu) – It is a dimensionless quantity in heat transfer which measures the ratio of convective to conductive heat transfer at a specific point on a surface, defined by the formula Nu = (h x L)/k, where ‘h’ is the local convection coefficient, ‘L’ is a characteristic length, and ‘k’ is the fluid’s thermal conductivity, indicating the efficiency of convection versus pure conduction at that location.
Local oscillator – It is an electronic component in receivers (e.g., radios) which generates a stable, single-frequency signal, mixing it with the incoming radio frequency (RF) signal to convert it to a fixed, lower intermediate frequency (IF) for easier processing, improving performance, sensitivity, and design simplicity through heterodyning. It is ‘local’ since it creates its signal internally, and its quality dictates the overall signal quality.
Local positioning system – It is a navigation system which does not cover the whole earth, such as over a continent, or even within a building.
Local power generation – It is the production of electricity within a localized system, which can include small-scale renewable energy sources and micro-combined heat and power (micro-CHP) systems, to meet the energy needs of local consumers.
Local quenching – It refers to the sudden and localized deactivation or termination of a physical or chemical process in a specific area, frequently in contrast to a global or widespread effect. In turbulent combustion, local quenching is the phenomenon where a portion of a flame front extinguishes because of the factors such as intense flame strain (velocity gradients), high curvature, or heat loss to a cold wall. This results in a ‘hole’ in the flame front, where unburnt gas passes through. In metallurgy, it means the targeted rapid cooling of only a specific section of a work-piece. Localized cooling can be achieved through methods like precise water sprays or targeted gas jets, and can lead to localized hardness and potential stress issues if not controlled properly. In the study of quantum systems, a ‘local quench’ involves an instantaneous, localized perturbation or change to a system’s parameters in a specific spatial region.
Local thermal equilibrium – It is a concept in non-equilibrium thermodynamics where a system is not in overall equilibrium, but small, localized regions within it are considered to be in equilibrium, allowing intensive properties like temperature and pressure to be defined locally, even with gradients across the system. It is a necessary assumption for simplifying complex systems like stellar atmospheres or heat transfer in porous media, enabling the use of equilibrium laws locally, provided property variations are slow compared to the system’s relaxation time.
Local thermodynamic equilibrium – It refers to a state where intensive thermodynamic variables become functions of position and time, allowing for the determination of specific entropy and internal energy at every point, similar to substances in equilibrium.
Local turbulence – It refers to intense, random fluctuations in fluid flow (like air or water) occurring in a specific, limited area, frequently caused by obstacles or irregularities, leading to rapid mixing and unpredictable velocity changes, distinct from overall flow patterns. It is characterized by chaotic eddies and energy dissipation, seen in wind hitting a turbine or water flowing past a sharp bend, affecting things like wind energy generation.
Local variable – It is a temporary variable declared inside a specific function, method, or code block (like a loop), meaning it only exists and can be accessed within that limited scope. It is created when the block starts and destroyed when it ends, preventing conflicts with other variables and improving memory efficiency.
Local velocity – It is the velocity of a fluid or object at a specific point or location, measuring speed and direction relative to that spot, rather than an average across a whole system. It accounts for variations in flow, like faster speeds near walls or slower speeds around obstacles, and is important in fluid dynamics for understanding complex patterns like turbulence and flow reversals.
Local ventilation – It is frequently called ‘local exhaust ventilation’. It is an engineering control which captures air-borne contaminants (dust, fumes, and vapours) at their source, preventing them from spreading into the work-space and being inhaled, using components like hoods, ducts, fans, and filters to remove the pollution before it enters the breathing zone. It is more efficient than normal ventilation for hazardous substances as it needs less air-flow and provides better control, protecting workers, equipment, and products.
Local vorticity – It defines the local spinning motion or rotation of a fluid at a specific point, measured by the vorticity vector, which indicates the axis and rate of this spin, acting as the curl of the velocity field. It tells a person how much a fluid particle tends to rotate, unlike the linear motion of solid objects, and is key in understanding turbulence, weather systems, and aero-dynamics.
Locating bearing – It is a mechanical component which secures a rotating shaft in both its radial (side-to-side) and axial (along its length) directions, preventing movement relative to its housing while also supporting radial loads, unlike a non-locating (floating) bearing which only handles radial loads and allows for thermal expansion. It is necessary for precise positioning in machinery, frequently paired with a non-locating bearing to manage thermal growth. It is a fixed bearing.
Locating boss – It is a boss -shaped feature on a casting to help locate the casting in an assembly or to locate the casting during secondary tooling operations.
Locating leak – It is the process of identifying the precise point where liquid or gas escapes from a pipe, vessel, or system, using different detection methods like acoustic sensors, tracer gases, or infrared technology to pinpoint the defect for repair, frequently involving pre-locating suspect areas, correlating sound signals, and then pinpointing the exact spot. It is crucial for managing water loss, preventing damage, and ensuring system integrity, moving from general detection (a leak exists) to specific localization (exactly where it is).
Locating pad – It is a projection on a casting which helps to maintain alignment of the casting for machining operations. Locating pad (also known as a rest pad or support pad) is also a component used in jigs, fixtures, and machine tools to precisely position, support, and stabilize a work-piece or component during manufacturing, assembly, or inspection operations.
Locating pin – It is a cylindrical component used for precise and repeatable positioning of work-pieces or components within a fixture or assembly. Its main function is to ensure accurate alignment during manufacturing and assembly, eliminating errors and improving the quality and efficiency of the process. Locating pins can be simple cylindrical or diamond-shaped, and their placement is important for restricting a part’s movement and ensuring it is positioned correctly.
Locating surface – It is a specific surface on a part which is used to determine its precise position, frequently in a fixture, jig, or for measurement purposes. This surface is critical for accurately controlling the object’s position and orientation by restricting its degrees of freedom (movements) in a manufacturing or inspection process. For example, the main locating surface of a part is frequently a flat bottom surface which restricts three degrees of freedom. In case of castings, it is a casting surface which is to be used as a basis for measurement in making secondary machining operations.
Locational marginal pricing – It is the real-time price of electricity at specific points (nodes) on a power grid, reflecting the marginal cost to deliver the next megawatt (MW) of power there, considering energy costs, transmission congestion, and line losses, creating price signals to optimize generation and consumption for grid efficiency and reliability.
Location drawing – It is also referred to as general arrangement drawings. It is made to showcase the composition of the entire project. If the project has several parts and buildings to be constructed, then the location drawing is required to include details for all of them. Under it, one can consider adding elevations, projections, different plans, and sections.
Location estimation – It is the process of determining the physical or geographic position of an object, device, or person by analyzing data from sensors, signals, or known reference points, frequently using techniques like triangulation, trilateration, or machine learning to find coordinates or proximity within a system. It is important for location-aware services, asset tracking, and context-aware computing, providing real-time knowledge of where something is.
Location model – It is a mathematical or conceptual framework used to determine the optimal placement of facilities, resources, or services, considering factors like demand, cost, distance, and constraints, to maximize efficiency or meet specific goals, frequently seen in operations research, economics (e.g., Hotelling’s model), and GIS (geographic information system). These models help decide where to build a store, site an ambulance, or locate a ware-house, balancing competing objectives like minimizing travel time or costs for users.
Location parameter – It defines the central position or shift of a dataset or probability distribution, indicating where it lies on a number line without changing its shape or spread, frequently represented by the mean or median and shifting the entire curve left or right. It is a measure of central tendency, summarizing data by showing its typical value, and helps characterize distributions alongside scale (spread) and shape parameters.
Location plan – A location plan is a supporting document which is needed to be included as part of the detailed project report. The location plan provides an illustration of the proposed development in the surrounding area of the project. The location plan covers a wide area. This kind of drawing needs the engineer to check out the whole area where the project is to be constructed. The location plan represents the objects and more importantly, it shows the relationship between the different stages of project development.
Lock – In forging, it is a condition in which the flash line is not entirely in one plane. Where two or more plane changes occur, then it is called compound lock. Where a lock is placed in the die to compensate for die shift caused by a steep lock, it is called a counter-lock.
Locked dies – These are dies with mating faces which lie in more than one plane.
Locked up stress -It is a non-standard term for residual stress.
Lockhart-Martinelli correlation – It is a method for calculating the pressure drop in two-phase (e.g., liquid and gas) flow through a pipe. It assumes the phases flow separately and calculates the total pressure drop by multiplying the pressure drop of the single-phase liquid or gas by a specific multiplier, derived from the Martinelli parameter (X). This multiplier accounts for the interaction between the two phases and is a function of the single-phase pressure drops of each phase.
Lockhart-Martinelli parameter – It is denoted by X. It is a dimensionless quantity used in two-phase flow to calculate pressure drop. It is defined as the square root of the ratio of the pressure gradient of the liquid phase to the pressure gradient of the gas (or vapour) phase when flowing alone in the pipe. The square of the parameter X-square is equal to the ratio of the single-phase liquid pressure drop to the single-phase gas pressure drop.
Lock hopper – It is a mechanical device used in industrial processes to transfer bulk materials (like coal or biomass) between different pressure zones, acting as an ‘air-lock’ by sealing, pressurizing (or depressurizing) the material within, and then releasing it into a lower-pressure system, frequently using gas or water to manage flow and prevent back-flow, enabling continuous feeding. It typically involves a vessel with sealed gates, alternating between filling at atmospheric pressure and discharging under pressure, crucial for systems like gasifiers or pressurized boilers.
Lockin – It is a procedure in maintenance which maintains an event or prohibits an individual, an object, force, or other factor from leaving a safe zone.
Locking device – It is a device which can be fitted to either lever or gear operated valves to allow for the valve to be locked in either the fully open or closed position.
Locking mechanism – It is a device or system which secures an object, preventing unauthorized access or movement until released by a specific key, code, or action, functioning through mechanical parts (pins, tumblers), electronics (keycards), or a combination (mechatronics) to ensure stability and security in different applications.
Lock loop – It is a condition in a ‘phase-locked loop’ (PLL), where the output frequency matches the input reference frequency, resulting in a constant or zero phase difference between the two signals, hence achieving synchronization.
Lock nut – It is also known as a prevailing torque nut. It is a type of nut designed to resist loosening from vibrations or external forces, ensuring a secure connection. They are used in several applications where maintaining a tight connection is crucial, like in machinery, automotive parts, and aerospace components.
Lockout -It is a procedure in maintenance which prevents an individual, an object, force, or other factor from entering a dangerous zone.
Lock-seam – It is a joint created by folding the overlapping edges of two pieces of sheet metal, interlocking them, and then pressing them together to create a strong seal. This method is used to join and seal sheet metal, forming strong cylindrical structures like pipes, ducts, and metal roofing panels. The process creates a mechanically interlocked seam that is often stronger than the parent material itself.
Lock-seam die – It is a tooling component used in sheet metal fabrication to create a lock seam, which is a durable, mechanically interlocked joint formed by folding and pressing together the overlapping edges of two pieces of sheet metal.
Lock signal – It is a feedback mechanism which regulates the magnetic field in nuclear magnetic resonance (NMR) by monitoring the dispersion mode deuterium resonance, ensuring the resonance frequency remains constant and providing high sensitivity to changes in the magnetic field.
Locus of failure – It refers to the specific location, path, or set of conditions (like stress combinations) where failure initiates and propagates in a material, structure, or system, frequently categorized by where (e.g., adhesive against substrate) or how (e.g., cohesive against interfacial) it occurs, like a crack in a joint. It is important in engineering to predict and prevent failure by understanding the geometry and mechanism of the failure point, distinct from just the mode (like brittle fracture or fatigue).
Locomotive – It is a rail transport vehicle which provides the motive power for a train.
Lode – It consists of a mineral deposit in solid rock.
Lodestones – These are naturally magnetized pieces of the mineral magnetite. They are naturally occurring magnets, which can attract iron. Lodestone is one of only a very few minerals which is found naturally magnetized. Lodestone is a special type of the mineral magnetite. All varieties of magnetite display signs of magnetism, but of them, only lodestone possesses distinctly north-south polarity. Lodestone and other magnetic iron ores frequently occur in igneous and metamorphic rocks found around the world.
Loess soils – These are sediments formed by wind transport, characterized by a loose structure, large porosity, high compressibility, and strong wet subsidence, making them prone to geological disasters and engineering challenges. They are widely distributed.
Loft surface – In 3D modeling, it is a smooth, complex 3D shape created in CAD (computer-aided design) software by transitioning between two or more different sketch profiles (like circles, ellipses, or curves) along a path or spine, acting like a blend or sweep between cross-sections, used for organic shapes like product handles. It provides control through guide curves and constraints to ensure smooth, quality surfaces, defining complex geometry from simpler 2D inputs.
Log – It is the starting stock for extrusion billet. Extrusion log is normally produced in lengths from which shorter extrusion billets are cut.
Logarithmic amplifier (log amp) – It is an electronic circuit which produces an output signal proportional to the logarithm of its input, effectively compressing a wide dynamic range of input signals into a smaller, manageable output, using non-linear components like diodes or transistors in an operational amplifier (op-amp) feedback loop to achieve this compression. Logarithmic amplifiers provide high gain for small signals and lower gain for large signals, making them ideal for measuring signals which vary over several orders of magnitude.
Logarithmic creep – It is a type of time-dependent deformation (creep) where the strain rate is proportional to the inverse of time, or more specifically, strain increases proportionally to the logarithm of time. This behavior is often observed at the beginning of a creep test, particularly in the primary or transient creep stage.
Logarithmic rate – It describes how a process changes over time or magnitude using a logarithmic scale, showing proportional changes rather than absolute ones, useful for compressing large ranges (like sound intensity in decibels, or earthquake magnitude on the Richter scale, where growth slows as the base increases, contrasting with linear rates. It frequently models phenomena where change is proportional to the current value, like oxidation (frequently logarithmic at low temperatures).
Logarithmic scale – It is a non-linear scale where each step represents a multiplicative increase (like times 10) rather than an additive one (like plus 1), making it ideal for visualizing huge ranges of values (e.g., Richter scale for earthquakes, pH, decibels) by compressing vast differences into a manageable chart, showing proportional changes clearly.
Logarithmic scales – In a logarithmic scale, the values are not evenly spaced like they are on a linear scale. Instead, each unit represents a power of a base (normally base 10 or base ‘e’).
Log-Cosh loss – It is a loss function used in machine learning, particularly for regression tasks. It is defined as the logarithm of the hyperbolic cosine of the prediction error. This function provides a smooth, differentiable approximation to the absolute loss, making it less sensitive to outliers compared to ‘mean squared error’ (MSE).
Log frequency – It refers to the logarithmic scale of frequency used to plot spectral distributions, allowing for a compact representation of data which spans several orders of magnitude, typically represented as log(f) in relation to other spectral measures.
Logging – It is the process of recording geological observations of drill core either on paper or on computer disk.
Logging method – It refers to systematic ways of recording data, normally in geo-physics / geology (using tools in bore-holes to analyze rock layers for oil, gas, water), computing (recording system events / errors for debugging). The definition depends heavily on the field, but normally involves collecting and documenting information about a process or environment for analysis and decision-making, such as well logging methods for sub-surface analysis or logging functions in software for error tracking.
Logging tool – It is a device used to gather data from sub-surface formations or within IT (information technology) systems. In sub-surface formations, it is a downhole instrument measuring rock properties (porosity, fluid type) or well performance (pressure, flow), while in information technology, it is software collecting and analyzing system logs for monitoring, security, and trouble-shooting.
Log graph paper – It is a type of graph paper where both axes are scaled logarithmically, allowing raw data to be plotted directly in a way which produces straight lines for power law relationships, effectively transforming non-linear data into linear form.
Logical device – It is a software abstraction or functional representation of one or more physical hardware components, allowing applications to interact with resources without needing to know the specific hardware details, providing flexibility, abstraction, and simplified management, as seen with logical input devices (like a key-board) or logical network elements (like a virtual router). It acts as an interface, defining what a device does (its function) rather than how (its physical form).
Logical expression – It is also called Boolean expression. It is a statement in computer science and mathematics which evaluates to one of two possible truth values namely true or false (frequently represented as 1 or 0). These expressions are formed using comparison operators (like greater than, less than, or equal to) and logical operators (like AND, OR, NOT) to combine values, conditions, or variables, forming the basis for decision-making in programmes through conditional statements (if, while).
Logical function – It performs tests on data to return a Boolean (TRUE / FALSE) result, enabling decision-making by evaluating conditions like greater than, less than, or equal to, using operators like AND, OR, and NOT to handle multiple conditions, forming the basis for conditional actions in spread-sheets, data-bases, and programming. Key examples include the IF function (chooses between outcomes) and AND / OR (checks multiple criteria).
Logical operator – It is a symbol or key-word which connects conditions, performing operations on Boolean (true / false) values to control programme flow and create complex decisions, with common examples being AND (&&), OR (||), and NOT (!), which yield a single Boolean result. These are used in programming to combine expressions, like checking if both conditions are true (AND) or if at least one is true (OR), necessary for digital circuits and software logic.
Logical relationship – It is a dependency between project activities or between project activities and milestones.
Logic analyzer – It is a tool which captures and displays digital signals in different formats, enabling the analysis of digital behaviour in systems, such as digital counters, complex state machines, and system buses.
Logic circuit – It is an electronic system of connected logic gates (like AND, OR, NOT) which performs logical operations, making decisions or processing data based on binary inputs (0s and 1s) to produce a specific output, forming the fundamental building blocks for all digital devices, from simple calculators to complex computers.
Logic circuit diagram. It depicts the logic functions of a system at any level of assembly. It is prepared to (i) illustrate logic functions, and (ii) facilitate circuit analysis and diagnosis of equipment problems. It includes (i) logic functions depicted by logic symbols connected by lines which represent signal paths, and (ii) pin numbers, test points, assembly boundaries, and non-logic functions necessary to describe the physical and electrical aspects of the circuit.
Logic design – It is the process of developing a Boolean equation to solve a specific problem, which is then minimized and implemented using combinational circuits, frequently utilizing libraries of digital circuits for common functions. It involves splitting complex designs into sub-systems and inter-connecting available functions to meet design specifications.
Logic diagram – It is a graphical representation of a digital circuit or system, using standardized symbols (like AND, OR, NOT gates) to show how inputs are processed by logical operations to produce outputs, effectively illustrating the flow of true / false (1/0) signals. It is a crucial tool in electrical engineering and computer science for designing, understanding, and trouble-shooting digital systems, from simple functions to complex processors, by visualizing Boolean logic.
Logic die – In electronics, it refers to the actual, tiny piece of silicon (the ‘chip’) containing the core computational circuits (like central processing unit cores, arithmetic logic unis, control units, and inter-connects) which execute instructions and manage data, distinct from memory dies, and frequently integrated into a single package with other specialized dies (like memory or graphics processing unit) in advanced multi-die systems for high performance.
Logic equation – It is a mathematical statement using Boolean variables (True / False, 1/0) and logical operators (AND, OR, NOT, and XOR etc.) to express relationships between these variables, defining conditions where the equation holds true, frequently used in digital systems and computer science to represent circuits or logical propositions. It equates two logic functions (like A AND B = C OR NOT D) to find solutions where both sides yield the same truth value, forming the basis for analysis and design.
Logic formula – It is also called well-formed formula (WFF). It is a precisely structured expression in formal logic, built from basic statements (propositional variables like ‘p’ or ‘q’) and logical operators (like AND, OR, NOT, IMPLIES) with rules to define its syntax, determining its truth value (True / False) under specific interpretations. It is a fundamental building block for reasoning, allowing complex statements like (p AND NOT q) IMPLIES (p OR q) to be analyzed systematically.
Logic gate – It is a fundamental building block of digital circuits which performs a basic logical operation (like AND, OR, NOT) on one or more binary inputs (0s and 1s) to produce a single binary output, forming the foundation for all digital devices like computers, smart-phones, and memory. These gates operate based on Boolean algebra and are important for making decisions and performing calculations in electronic systems.
Logic input – It defines the voltage or signal conditions (High/1 or Low/0) a digital circuit recognizes, oft logic input defines the voltage or signal conditions (High/1 or Low/0) a digital circuit recognizes, frequently using voltage ranges, to process information, acting as the trigger for logic gates (AND, OR, NOT) which perform operations based on these binary inputs, ultimately producing a corresponding output (True / False, On / Off, 1/0). In computing, these are physical signals (voltage levels) representing abstract logical states (True / False). en using voltage ranges, to process information, acting as the trigger for logic gates (AND, OR, NOT) which perform operations based on these binary inputs, ultimately producing a corresponding output (True / False, On / Off, 1/0). In computing, these are physical signals (voltage levels) representing abstract logical states (True / False).
Logic network – It is a chronologically arranged diagram which shows relationships between project activities.
Logic synthesis – It is the automated process of converting a high-level, abstract digital design (like ‘register transfer level’ code in ‘very high-speed integrated circuit hardware description language’ or Verilog) into a low-level, optimized implementation of logic gates, forming a gate-level netlist ready for physical design. This important step in ‘electronic design automation’ involves translating behaviour into Boolean equations, optimizing for area / speed, and mapping to a specific technology library, ultimately creating an efficient digital circuit.
Logic variable – It is a symbol (like x or P) representing something which can be True / False (Boolean logic) or a place-holder for an unknown value (mathematical / programming logic) which becomes fixed during computation, necessary for formalizing arguments, defining rules, and expressing general principles in logic and computing. It is a fundamental concept for creating logical statements and performing operations like AND, OR, and NOT.
Logic vector – It is an array of standard-logic values which can represent different electrical levels in a design, with the ability to create sub-types and objects for specific applications.
Logistic function – It is a mathematical equation which produces a characteristic S-shaped curve (sigmoid), modeling growth that starts exponentially but slows as it approaches a maximum limit (carrying capacity). It is important in modeling limited growth in predicting probabilities in machine learning (logistic regression), and describing the diffusion of innovations, mapping any input to an output between 0 and 1.
Logistic regression – The logistic regression method contains multiple regressions with dichotomous outcome variables and categorical or metric predictor variables. Logistic regression derives its name from the sigmoid function, which is also known as the logistic function. The logistic function is an S-shaped curve which stretches from zero to one, while never being exactly zero and never being exactly one, either. There are three main types of logistic regression namely (i) binary, (ii) multinomial, and (iii) ordinal. They differ in execution and theory. Binary regression deals with two possible values, essentially ‘yes or no’. Multinomial logistic regression deals with three or more values. And ordinal logistic regression deals with three or more classes in a pre-determined order.
Logistics – It is the part of supply chain management which deals with the efficient forward and reverse flow of goods, services, and related information from the point of origin to the point of consumption as per the needs of customers. Logistics management is a component which holds the supply chain together.
Logistics activity – It is a core function within the supply chain, involving the planning, implementing, and managing of the efficient flow and storage of goods, services, and information from origin to consumption, encompassing tasks like transportation, ware-housing, inventory management, order fulfillment, packaging, material handling, and customer service, all to meet customer needs cost-effectively.
Logistics cost – It refers to all expenses incurred in moving and storing goods from origin to final customer, encompassing transportation, ware-housing, inventory management, packaging, labour, and administration. These costs cover the entire supply chain, from raw material acquisition to last-mile delivery, making them a substantial part of the organizational overall operating expenses.
Logistics industry – It refers to the sector involved in the planning, implementation, and management of the flow of goods and services, which is currently experiencing transformation because of the technological advancements like blockchain and drone delivery, aimed at improving transparency and efficiency. This industry faces challenges such as risk, variability, and disruption, necessitating better technology and integration with enterprise resource planning (ERP) systems.
Logistics decision – It involves planning, implementing, and controlling the efficient flow and storage of goods, services, and information from origin to consumption, aiming to meet customer needs at the right time, place, quantity, and quality while optimizing costs, using activities like transportation, ware-housing, inventory, and order fulfillment. These choices, ranging from selecting transport modes to ware-house strategies, are important for supply chain efficiency, impacting profitability, customer satisfaction, and resilience.
Logistics management – It refers to the acquisition, storage and transportation of inventory from its origin to its destination. It involves maintaining the inventory, resources and related information, and getting the goods to the right location at the right time and to the right customer. Advanced end-to-end logistics management solutions drive efficiency by optimizing inventory, cutting costs and overhead, and delivering improved customer service and profits.
Logistics management activity – It is the strategic process of planning, implementing, and controlling the efficient forward and reverse flow and storage of goods, services, and related information from the point of origin to the point of consumption to meet customer requirements, focusing on cost reduction, efficiency, and satisfaction. Key activities include transportation, ware-housing, inventory control, order fulfillment, demand forecasting, and customer service, integrating all parts of the supply chain for optimal results.
Logistics network – It is the inter-connected system of facilities (suppliers, factories, ware-houses, distribution centres) and processes (transport, inventory, and information technology) which efficiently moves goods from origin to customer, ensuring timely delivery, cost optimization, and customer satisfaction by coordinating all movement and storage points within the supply chain. It is the strategic road-map for product flow, managing everything from raw materials to the final product in a seamless operation.
Logistics operations – These mean the coordinated management of moving goods, from raw materials to finished products, ensuring they reach the right place, at the right time, in the right quantity, and condition, while minimizing costs. It encompasses key activities like transportation, ware- housing, inventory management, order fulfillment, packaging, and distribution, forming an important part of the broader supply chain.
Logistics strategy – It is a long-term, comprehensive plan for efficiently managing the flow of goods, information, and resources from origin to consumption, aligning with overall organizational goals like cost reduction, customer satisfaction, and competitive advantage, by coordinating transportation, ware-housing, inventory, and fulfillment. It is about making strategic decisions on how to move, store, and deliver products effectively, differentiating from short-term plans by providing overall direction for the supply chain.
Logistics system – It is the integrated network of people, technology, and processes managing the flow of resources (raw materials, goods, information) from origin (supplier) to consumption (customer), ensuring the right product, in the right quantity, at the right time, in the right condition, to the right place, for the right customer, and at the right cost. It involves procurement, ware-housing, inventory, transportation, and distribution, aiming for efficiency, cost reduction, and customer satisfaction within the broader supply chain.
Log-log graph – It is a two-dimensional graph where both the horizontal (x) and vertical (y) axes use logarithmic scales. This means that instead of plotting data points directly, people plot the logarithm of the data values. Log-log plots are particularly useful for visualizing data which spans a wide range of values or when people suspect a power-law relationship between the variables.
Log mean temperature difference – It is a logarithmic average of the temperature difference between the hot and cold flows at each end of a heat exchanger, used to evaluate heat transfer in the design of such systems. It assumes constant thermo-physical properties and does not account for energy stored during phase changes.
Log-normal – It refers to a type of probability distribution of a random variable which is defined such that the logarithm of the variable is normally distributed. This means that the variable only takes positive real values, making it particularly useful for modeling variables in engineering, such as material strengths and dimensions.
Logo – It is the sign, mark, or distinguishing letter designating the organization. It is a graphic mark, symbol, or emblem used to represent an organization, its values, and its expertise, serving as a unique visual identifier for a brand. It can be a combination of images and text, like the name of the organization and a symbol, designed to be easily recognizable and to communicate the identity of the organization, such as a focus on stability, precision, or innovation.
Log plot – It is also called logarithmic plot. It is a graph where one or both axes use a logarithmic scale, meaning the distance between grid lines represents multiplication (e.g., 1, 10, 100) rather than uniform addition (1, 2, 3). It is used to visualize data spanning several orders of magnitude, reveal power-law relationships (as straight lines on a log-log plot), and show exponential growth (as straight lines on a semi-log plot).
Log scale – Iti s defined as a plotting method which allows points spread over several orders of magnitude to be equally spaced along an axis, normally used in graphs where data varies widely, such as log-log or log-lin formats. This approach facilitates easier interpretation of data trends and relationships.
Longest path – It is the longest sequence of dependent tasks in a project which determines the minimum time needed to complete the project, where delays in any task can impact the overall schedule.
Longest relaxation time – It refers to the slowest characteristic time for a complex system (like polymers or glass-forming liquids) to return to its equilibrium state after a disturbance, frequently representing the relaxation of the entire chain or large-scale structural changes, distinguishing itself from shorter, local relaxation processes like electron scattering or molecular vibrations, and is important for understanding material properties like viscosity and elasticity.
Long-fibre-reinforced thermoplastic – It is a type of easily mouldable thermoplastic used to create a variety of components. Long-fibre-reinforced thermoplastics are one of the fastest growing categories in thermoplastic technologies.
Long flame burners – These are the burners which produce a long flame. A large variety of long flame burners of various characteristics and different capacities are available. These burners are available in various capacities and to suit use of different fuels such as oil, gas or multiple fuels. Long flame burners produce high velocity gases which entrain and recirculate the combustion gases to achieve temperature uniformity in the furnace with minimum of excess air.
Longitudinal – It refers to an orientation or property which is along the length of an object, as opposed to its width or cross-section. It can describe a direction of force, a wave, a section view, or a component’s alignment. Examples include a longitudinal engine, which is aligned with the vehicle’s length, or longitudinal waves, which travel parallel to the direction of particle vibration.
Longitudinal acceleration – It is the change in speed (acceleration or deceleration) along the direction of travel, typically the forward / backward movement of a vehicle, measured in meters per second squared.
Longitudinal arrangement – It describes components or data organized along the length or longest axis of an object, body, or system, extending from front to back (head to tail) or end to end, contrasting with transverse (across) arrangements, and frequently involving sequential, length-wise patterns.
Longitudinal axis – It is the axis of sample which is parallel to the major direction of grain flow.
Longitudinal bow – It is the curvature in the plane of sheet or plate in the rolling direction.
Longitudinal bowing – It is a type of distortion where a long, flat or curved product bends along its length (longitudinally) into a curved shape, frequently seen in welded or roll-formed metal parts, caused by uneven internal stresses from welding shrinkage or plastic deformation during forming. It is a shape defect measured as the maximum deviation from a straight line, where the curvature can be either concave or convex, affecting structural integrity and appearance in fabrication.
Longitudinal centre – It refers to a key point along an object’s length, frequently its centre of gravity, defining where weight balances or around which it trims, measured from a fixed reference point along the length. It is basically the balance point in the fore-and-aft (length-wise) direction.
Longitudinal component – It refers to a part or effect acting along the length or main axis of an object or wave, contrasting with transverse (perpendicular) components, and can describe physical parts (like rods in engineering), forces, or wave motions (like compressions in sound waves). It is frequently the part of a field or wave parallel to the direction of propagation. In materials science, it is a lengthwise structural element.
Longitudinal compression – It refers to a region in a longitudinal wave (like sound) or a mechanical structure where particles or material are squeezed closer together, resulting in increased density and pressure along the direction of wave propagation or applied force, contrasting with rarefaction where particles spread out. In engineering, it can mean shortening a structure (like a stent) along its length because of the axial forces.
Longitudinal compressive stress – It is the squeezing force, or stress, applied along the length of an object, causing it to shorten. It is a type of longitudinal stress (stress along the length) and is defined as the internal restoring force per unit of cross-sectional area which arises from equal and opposite forces pushing inward on the ends of a body.
Longitudinal corrugation – It refers to a structural configuration where a series of alternating rid’’ges and grooves (corrugations) run parallel to the length (longitudinal direction) of the object. This design is frequently used in engineering applications to increase stiffness and buckling resistance in specific directions. For example, in a corrugated cylindrical shell, the longitudinal corrugations define its name and considerably improve its mechanical performance by increasing material utilization and improving stability.
Longitudinal coupling – It describes interactions or connections along the length or main direction of a system, varying considerably by field. In quantum physics, it is a spin-interaction enabling qubit control (like entanglement without energy exchange). In electrical engineering (railways), it is connecting overhead lines for power supply. In particle accelerators, it is a beam’s interaction with its surroundings, influencing particle dynamics. Basically, it is a directional linkage or influence parallel to the main axis, contrasting with transverse (perpendicular) couplings.
Longitudinal cracking – It is a type of fracture which runs parallel to the length or principal axis of a material or structure, such as a road, weld, or concrete beam, frequently occurring because of the stress, fatigue, thermal effects, or construction issues like poor joints, leading to potential structural failure and moisture infiltration. In pavements, it runs along the centre-line, while in welds, it is parallel to the weld’s axis, affecting appearance and integrity in various materials from asphalt to composite fibres.
Longitudinal cracks – These cracks normally found in continuous cast products, are formed in the direction of extraction of the steel. The presence of these defects results into the rejection of the steel. Longitudinal cracks occur mainly because of the (i) uneven primary cooling in the mould, (ii) turbulent flow of liquid steel and a meniscus level variation in the mould, (iii) non uniform or very intensive secondary cooling, (iv) variance in thermal conductivity coefficient along the mould length causing unequal, advanced wear of the mould, (v) casting of liquid steel with high superheat, (vi) high speed of casting, and (vii) use of the casting powder with improper characteristics.
Longitudinal corrugations – These corrugations make the cylindrical shell to have a non-zero curvature in the direction of the central axis, and the trough can take part of the buckling deformation. In short, the corrugations improve the material utilization rate of cylindrical shells, so the mechanical performance is improved.
Longitudinal direction – It is the direction of major metal flow in a working operation. It is that direction which is parallel to the direction of maximum elongation in a worked material. Two labeling conventions are common for designating the orientations of rolled sheet and plate material. The first is ‘L’, ‘T’, and ‘S’ designations in which ‘L’ means longitudinal, ‘T’ means long transverse, and ‘S’ means short transverse. The second is ‘RD’, ‘ND’, and ‘TD’ designations, in which ‘RD’ means rolling direction, ‘ND’ means normal direction, and ‘TD’ means transverse direction.
Longitudinal elasticity modulus – It is also known as Young’s modulus or the modulus of elasticity. It is a measure of a material’s stiffness. It is defined as the ratio of longitudinal stress to longitudinal strain when a force is applied to a material, causing it to deform either by stretching or compression.
Longitudinal expansion – It is also called linear expansion. It is the increase in an object’s length (its dimension along its longest axis) because of a change in temperature or applied force, representing one-dimensional expansion, where materials get longer when heated and shorter when cooled, calculated by the formula ‘delta L = alpha Lo delta T’. It is important in engineering (bridges, rails) to prevent buckling or breakage from temperature swings.
Longitudinal feed radial forging – It is a metal-forming process where a work-piece is shaped by multiple radially moving dies (hammers) while being simultaneously advanced along its axis (longitudinally fed).
Longitudinal field – It is a magnetic field which extends within a magnetized part from one or more poles to one or more other poles and which is completed through a path external to the part.
Longitudinal fin – It is a heat transfer improvement feature, typically a metal strip or channel, attached to the outside (or sometimes inside) of a tube, running parallel to its length (axis) to increase substantially the surface area for better heat exchange with a fluid flowing alongside it. These fins are important in heat exchangers, boilers, and HVAC (heating, ventilation, and air conditioning systems), especially when dealing with low heat transfer coefficients or viscous fluids, as they maximize heat dissipation or absorption.
Longitudinal force – It is a force acting parallel to an object’s length or direction of motion, causing it to speed up (traction / thrust) or slow down (braking / resistance). In structures like bridges, it is the force along their length, resisting movement or bending.
Longitudinal girder – It is a large, heavy structural beam running length-wise (fore-and-aft) in a structure like a bridge, providing main support, resisting bending, and transferring loads along its length, frequently acting as a main load-bearing member in bridge decks. These girders improve the overall structural integrity, preventing buckling and deflection from stresses like bending moments, and are important for longer spans.
Longitudinal groove – It is a channel, slot, or furrow which runs length-wise (along the longest axis) of an object, serving different functions from structural reinforcement (like keyways in shafts), drainage (in pavements). It is a length-wise indentation which creates a line or channel, frequently affecting stress distribution or facilitating movement / separation, depending on the context (e.g. engineering).
Longitudinal load – It is a force or stress applied along the length (longitudinal axis) of an object, causing it to stretch (tension) or compress (compression) in that direction, like pulling on a rope or pushing a spring. It is important in engineering for designing structures like pressure vessels, rails, and vehicles, differing from transverse loads (across the width) by acting purely length-wise.
Longitudinal magnetization – It refers to the component of a material’s net magnetic vector which aligns parallel to the main applied magnetic field (the z-axis). In non-destructive testing (NDT), it is the magnetization where magnetic flux runs along the length of a part, frequently induced by coils, creating external poles at the ends.
Longitudinal mode – It describes a specific standing wave pattern along the axis of a resonant cavity (like a laser), where the wave’s peaks and troughs align perfectly to reinforce itself after reflecting, creating distinct, closely-spaced wave-lengths (or frequencies) which the cavity can sustain, determined by the cavity’s length. Longitudinal modes refer to the specific wave-lengths at which laser oscillation can occur, determined by the need which the cavity length is to be an integral multiple of half the wave-length within the gain medium’s bandwidth.
Longitudinal (parallel) fillet weld – It is the weld in which the applied force is parallel to the length of the weld.
Longitudinal ply – In composite materials, it refers to a layer (ply) of fibres oriented parallel to the main length or load direction of the composite structure, providing substantial strength and stiffness along that axis, much like unidirectional composites. These plies are important for handling tensile and compressive loads along the length of a component, with their properties (like longitudinal modulus) defined by the strong fibres running in that direction.
Longitudinal residual stress – It refers to the residual stress which acts along the length or longitudinal direction of a component or structure, frequently introduced during manufacturing processes like welding or forming. It is one of the three main types of stresses in welded joints, alongside transverse and through-thickness stresses.
Longitudinal resistance seam welding – It is the making of a resistance seam weld in a direction essentially parallel to the throat depth of a resistance welding machine.
Longitudinal rib – It is a structural element that runs along the length or the long axis of an object, typically a bar or a plate. In the context of TMT (thermo-mechanically treated) steel bars, longitudinal ribs are the raised patterns or ridges that run parallel to the vertical axis of the bar. They are a key feature of thermo-mechanically treated bars, improving their bonding with concrete and improving overall structural strength.
Longitudinal rolling – In longitudinal rolling, rolls are driven and they draw the material in-between and press it through the height. Because of it, the rolled material is considerably extended (elongated) and spread to a lesser extent. The longitudinal rolling is most popular method of rolling. Longitudinal rolling with plain rolls is used to roll flat rolled products (sheets, plates, strips), while longitudinal rolling in grooved rolls is used for shaped rolled products (rails, sheet piles, bars, sections, and wire rod).
Longitudinal rolling mill – It is a type of rolling mill where the metal being processed moves in a straight line parallel to the axis of the rotating rolls. In this process, the rolls rotate in opposite directions, and the material is drawn between them, resulting in a reduction in thickness and an increase in length.
Longitudinal sections – These are those which are cut lengthwise along the line of the long axis of the object or one of its constituent parts. They can be cut in any plane and are independent of the position of the object, unlike vertical sections.
Longitudinal spacing – It is the distance between items or components measured along their length or main axis, differing from transverse spacing (across the width) and is important in fields like engineering (battery cooling, structural design, aero-dynamics) for managing airflow, heat, and structural integrity, frequently defining clear paths for fire suppression or fluid dynamics.
Longitudinal stiffener – It is a structural element, frequently a plate or angle, attached along the length (longitudinal direction) of a thin-walled structure, like a bridge girder, to prevent its slender panels from buckling under compression or shear, hence increasing the overall stiffness and load-bearing capacity of the plate element. They work by sub-dividing large panels into smaller, more rigid ones, effectively boosting resistance to local instability, especially in deep webs or box sections.
Longitudinal strain – It is the measure of deformation along the length of an object when a force is applied, calculated as the ratio of the change in length (delta L) to the original length (L), making it a dimensionless quantity (e = delta L/L). It quantifies how much a material stretches (tensile) or compresses (compressive) parallel to the force, indicating its response to stress, and is important for understanding material behaviour.
Longitudinal strength – It refers to a material’s or structure’s ability to resist forces (pushing or pulling) acting along its length, or its long axis, without failing or deforming excessively. It is important for measuring resistance to compression or elongation, and is calculated as force per unit of cross-sectional area (longitudinal stress) or the relative change in length (longitudinal strain).
Longitudinal stress – It is the stress acting along the length (or axis) of an object, parallel to the direction of applied force, causing stretching (tensile) or squeezing (compressive). It is important especially for pressure vessels like pipes where internal pressure creates both longitudinal and hoop stresses, acting along the length and circumference, respectively. Think of it as the force pulling or pushing a stretched rubber band or a pressurized pipe length-wise. It is also the applied stress which is parallel to the major direction of grain flow, in the plane of the component.
Longitudinal stress distribution – It describes how stress varies along the length (axis) of a material, typically in pipes, pressure vessels, or beams, caused by axial forces (pulling / pushing) or internal pressure. It is the force per unit area acting parallel to the object’s length, causing stretching (tensile) or compression, and is important for designing structures to prevent failure, especially when compared to hoop stress.
Longitudinal stringers – These are because of non-metallic inclusions or pearlite banding. They are related to melting and solidification practices. In severe cases, these defects can lead to lamination which drastically reduces the strength in the thickness direction.
Longitudinal submerged arc welded (LSAW) pipe – It is a type of steel pipe made by forming a steel plate into a pipe shape and welding the seam along its length (longitudinally) using the submerged arc welding process. This welding method utilizes a submerged arc to join the edges of the plate, creating a strong and durable longitudinal weld. Longitudinal submerged arc welded pipes are produced by first forming a steel plate into a cylindrical shape. The edges of the plate are then joined together using the submerged arc welding (SAW) process, which involves an electric arc submerged under a layer of flux.
Longitudinal surface crack – It is a surface defect which runs parallel to the length of a material or structure. These cracks can occur in several materials like asphalt pavements, steel billets, and welds, and are typically caused by stress from factors like temperature changes, shrinkage, or high stress points.
Longitudinal tensile strength – It is the maximum pulling force (stress) a material, like a pipe, can withstand along its length (long axis) before breaking or failing, basically measuring its resistance to being pulled apart length-wise. It is important for evaluating components in fluid systems, determining how much a device can stretch or be pushed / pulled during use without losing structural integrity, measured as force per unit area.
Longitudinal tension – It is the pulling force (stress) acting along the length (axis) of a material, causing it to stretch or elongate, defined as force per unit area parallel to the material’s length, important for understanding how structures like pipes or cables hold up under axial loads. Itis basically tensile stress acting in the length-wise direction, distinct from forces acting side-ways, and is important for material strength.
Longitudinal velocity – It is the speed of movement or wave propagation along the length or forward direction of an object or medium, differing from transverse (side-ways) motion; it is the speed of compression / rarefaction in waves (like sound) or the forward speed of a vehicle, crucial for safety systems. It is calculated for waves by material properties (Young’s modulus / bulk modulus and density) and for vehicles by sensors, often measured parallel to the main axis.
Longitudinal vibration – It is a type of wave where particles in the medium oscillate parallel to the direction the wave travels, causing alternating regions of compression (particles bunched together) and rarefaction (particles spread apart). Think of sound waves in the air or a Slinky being pushed and pulled along its length, while the energy moves forward, but the coils just move back and forth in place, creating pressure changes.
Longitudinal wave – It is a type of wave in which the displacement of particles occurs in the same direction as the wave motion, characterized by alternating regions of compression and rarefaction.
Longitudinal weld – It is a type of weld which runs along the length or longitudinal direction of a pipe or plate. It is essentially a seam which joins two edges together in a parallel fashion to the overall length of the material being welded. This is in contrast to a circumferential weld, which joins the material around its circumference.
Long length natural fibre composites – These are composite materials which utilize long natural fibres as reinforcement, offering high tensile and flexural properties suitable for construction applications. These composites benefit from advancements in fibre extraction, treatments, and processing technologies, enabling their potential commercialization.
Long-line current – It is the current which flows through the earth from an anodic to a cathodic area of a continuous metallic structure. It is normally used only where the areas are separated by considerable distance and where the current results from concentration-cell action.
Longos – It is low-angle helical or longitudinal windings.
Long product rolling mills – These are the rolling mills which roll long products. Based on the product being rolled, these mills are called, merchant bar mill, bar and rod mill, light section mill, rebar mill, light merchant mill, special bar quality (SBQ) mill, and wire rod mill etc.
Long product steel – This steel is used for rolling long products. As per the classification of steel products bar, rod and structural products are the long products.
Long-range ordering – It means atoms or molecules in a material are arranged in a perfectly regular, repeating pattern which extends across very large distances, like a crystal lattice, allowing prediction of atomic positions far away from a known point. It contrasts with short-range order (local order only) and is important for defining crystalline solids, affecting material properties like electronic structure and phase transitions, frequently quantified by an order parameter which measures deviation from perfect order.
Long range transport – It refers to the process of movement of substances over large distances in the environment, involving either advective or dispersive transport through air and water mediums.
Long-range transport of air pollutants – It refers to the atmospheric movement of pollutants over distances higher than 100 kilometers, potentially impacting areas far from their source.
Long rectangular plate – It refers to a flat structural element where the length is considerably higher than its width (high aspect ratio), used in analyses for structures like civil engineering elements, focusing on buckling, bending, and stress under different loads. It is a basic building block in mechanical and civil fields, frequently studied in contexts of vibration and structural behaviour, where its high aspect ratio allows for specific analytical simplifications or complex behaviours.
Long rotary kilns – The long rotary kiln consists of a rotating cylinder up to 150 metres long and inclined at an angle of 1-degree to 4- degree to the horizontal with a diameter of around 2 metres to 4.5 metres. Limestone is fed into the upper end and fuel plus combustion air is fired from the lower end. Lime is discharged from the kiln into a lime cooler, where it is used to preheat the combustion air. Different designs of lime coolers are used including planetary units mounted around the kiln shell, travelling grates, and various types of counter-flow shaft coolers. In long rotary kiln, there is no pre-heater and the fuel burners are at the lime discharge end. Type of fuel can be gas, liquid, pulverized solid fossil fuels, waste fuels, or biomass. The structure of the kiln is inclined rotating cylinder with refractory lining and ‘mixers’ to improve the heat exchange. Types of coolers can be (i) planetary around kiln shell, (ii) travelling grate, (iii) rotating cylinder, or (iv) static shaft cooler. The combustion air injection is through cooling air at the extremity of the cooler and primary air with the fuel. Flue gas extraction is by an induced draft (ID) fan at the end of the rotating cylinder at the limestone feeding side through a duct. The gas is cooled and dedusted before discharge. Drawing of lime is at the extremity of the cooler. Important points are the quality of the refractory and fine grinding of coal to ensure good combustion and reduction of the build-up (ring formation) in the kiln.
Long shapes – These are products which are considerably longer than their cross-sectional dimensions, mainly used in the construction and infrastructure industries. They are normally made from semi-finished products such as billets and blooms through hot rolling or drawing processes.
Long steel products – These are the steel products which include wire, rod, rail, and bars as well as types of steel structural sections and girders. The term long steel products can include hot rolled bar, cold rolled or drawn bar, reinforcement bar, railway rails, wire, rope (stranded wire), woven cloth of steel wire, shapes (sections) such as ‘U’, ‘I’, or ‘H’ sections, and can also include continuous cast blooms and billets. Fabricated structural units, such bridge sections are also classed as long products. The definition excludes flat products such as slab, plate, strip and coil, tinplate, and electrical steel; and also excludes certain tubular products including seamless and welded tube.
Long taper die – It is a specialized cutting tool which features a prolonged conical shape to gradually cut external threads on cylindrical work-pieces, such as rods or pipes. The extended taper facilitates a smoother, and more gradual cutting action compared to a standard die. The main function of the long taper is to ensure gradual material removal, which offers several benefits.
Long-term competitiveness – It is the organization’s sustained ability to create value, adapt to change, and maintain success in a market by leveraging resources, innovation, and strategic advantages, ensuring enduring prosperity, and stakeholder benefits over extended periods, not just short-term gains. It involves a forward-looking capacity to evolve, innovate, and improve productivity while managing internal capabilities (like skills, technology) and external factors (like infrastructure, policies).
Long-term durability – It is the ability of a product, material, or system to maintain its important properties, performance, and structural integrity over an extended period, resisting wear, damage, and environmental stresses without substantial degradation, ensuring prolonged functionality and reducing the need for repair or replacement. It is about lasting power, not just initial strength, frequently measured against challenging conditions like temperature, humidity, and usage.
Long-term etching – It is the etching in which the etching times range from a few minutes to hours.
Long term evolution – It is the fourth-generation (4G) cellular radio network standard, designed by the 3GPP (3rd generation partnership project) to provide high-speed, high-capacity wireless communication with low latency. Its architecture is based on an all-IP (internet protocol) network and includes key technologies like OFDMA (orthogonal frequency division multiple access) in the downlink, a simplified radio access network with only an eNodeB (evolved NodeB) base station, and the use of MIMO (multiple-input multiple-output) radios to handle high data rates. The goal of long-term evolution has been continuous improvement in speed and capacity to meet the growing demands of mobile broadband and other services.
Long-term forecasting – It is predicting future events, trends, or conditions over extended periods (months to years or decades) for strategic planning, resource allocation, and major investment decisions, focusing on broad factors like economic shifts, technology, and demographics, unlike short-term forecasts which use immediate data for operational needs. It helps organizations plan for expansion, manage risks, set policies, and allocate capital for future projects by analyzing historical data and using methods like trend analysis, scenario planning, and expert consensus (Delphi method).
Long-term monitoring system – It is a framework for the continuous, systematic collection and analysis of data over extended periods to track changes, identify trends, and assess the status of complex systems like ecosystems, engineered structures, or environmental contaminants. It goes beyond simple data collection to provide insights for adaptive management, early warning signals, and informed decision-making regarding long-term sustainability, safety, and health, using technologies like sensors, and integrated data analysis.
Long terne steel sheet – It is carbon steel sheet continuously coated by the hot dip process with terne metal (lead with 3 % to 15 % tin). This coated sheet is duller in appearance than tin coated sheet, hence the name (terne) from the French, which means dull or tarnished. The smooth, dull coating gives the sheet corrosion resistance, formability, excellent solderability, and paintability. The term long terne is used to describe terne-coated sheet, while short terne is used for terne-coated plate.
Long ton – It is defined as exactly 2,240 pounds. One long ton is 1.01605 metric ton which is 1,000 kilograms. The long ton arises from the traditional British measurement system.
Long transverse – It is a direction or plane which is perpendicular to the direction of working. In rolled plate or sheet, it the direction across the width which is the direction through the thickness, short transverse. Long transverse for thin components is the axis of sample perpendicular to the axis of major grain flow, in the plane of the component.
Long transverse direction. For plate, sheet, and forgings, It is the direction which is perpendicular to the longitudinal direction which is also at right angles to the thickness of the product.
Long transverse stress – It is the applied stress perpendicular to the axis of major grain flow, in the plane of the component.
Long-wall mining – It is a highly productive, mechanized method of underground coal mining which extracts coal from a long, continuous ‘wall’ or ‘face’ using a shearer machine, armoured face conveyors, and hydraulic roof supports, allowing high recovery rates by letting the roof collapse into the mined-out area (gob) in a controlled manner. It is known for high output and efficiency but needs stable geology, and the resulting subsidence affects the surface. Gob refers to the worked-out area in a mine where coal or ore has been removed, and the roof rock has caved in, forming a zone of broken rock and waste material.
Long wave-length – It refers to waves with a large distance between consecutive crests (or troughs) and, consequently, lower frequency and less energy, allowing them to travel farther and penetrate obstacles more easily, like radio waves. Conversely, short wavelengths have high frequency, high energy, and less penetration, like X-rays, with the specific ‘long’ range depending on the type of wave, such as over 580 nano-meters for certain light.
Long welded rail – It is a length of railway track, typically exceeding 250 meters on broad gauge and 500 meters on meter gauge, where the central portion experiences minimal longitudinal movement because of temperature variations. These rails are welded together to form a continuous unit, and are designed to minimize the expansion and contraction effects of temperature changes. Long welded rails are created by welding together individual rail sections, eliminating traditional rail joints. The key characteristic is their substantial length, which is considerably longer than standard jointed rails. This longer length helps to distribute thermal stresses more effectively. While long welded rails are designed to minimize the effects of temperature changes on the central portion, they do experience expansion and contraction at the ends, known as breathing lengths.
Look-back – It normally means to reflect on or remember past events, experiences, or periods of time, but it also has specific technical meanings in finance (like look-back options) and computer science (optimization techniques) for reviewing historical data. In finance, a look-back period defines how far back data (like asset prices or interest rates) is reviewed for calculations, while in computer simulations, a look-back is a strategy to improve performance by referencing past states.
Loop amplifier – It typically refers to an electronic circuit using feedback (a closed loop) to control the gain of a basic, high-gain amplifier, making it stable and predictable, unlike its extreme open-loop state where it amplifies signals without feedback. Common examples include inverting/non-inverting amplifiers using op-amps, where a portion of the output is fed back to the input, creating a stable, lower, and controllable ‘closed-loop gain’.
Loop classifier – It is a cyclone-type classifier, sometimes connected with a conical ball mill in an airtight system.
Loop compensation – It is the design of a network (frequently resistors-capacitors components) within a feedback control system (like a power supply) to stabilize it, improve its dynamic response (speed / transient handling), and ensure stability by manipulating the loop’s poles and zeros to achieve adequate gain and phase margins, preventing oscillations and ensuring it meets performance goals. Basically, it tunes the system’s frequency response to make it fast and stable.
Loop control – It refers to a system which continuously monitors a process variable (like temperature, pressure, flow), compares it to a desired value (set-point), and automatically makes adjustments to keep the output stable and accurate, using feedback to correct errors, crucial for automation in industrial settings. It involves sensors, controllers, and final elements (like valves or motors) working together iteratively to maintain desired conditions without constant human input, differing from open-loop systems by its self-correction mechanism.
Loop controller – It is a device or algorithm which automatically regulates a system by continuously comparing its actual output to a desired set-point, calculating the error, and then adjusting the input to minimize that error, creating a self-correcting feed-back system for stable, precise process automation (e.g., temperature, speed, flow).
Loop control system – It automatically regulates a process by continuously monitoring its output, comparing it to a desired target (set-point), and making real-time adjustments to correct any deviations, ensuring precision and stability without constant human intervention.
Looped connection junction – It is an innovative approach to joining the ends of a conveyor belt using a looped connection, necessitating the expertise of skilled installers and periodic checks for wear and security. The intricacies of this method demand ongoing attention to ensure sustained effectiveness and secure connectivity.
Looped connection splice – It is a specialized technique used for joining the ends of a conveyor belt through a looped connection, needing the proficiency of expert installers and regular checks for wear and security. The intricacies of this splicing method demand continuous monitoring to uphold secure and reliable belt connectivity.
Looper control by torque (LCT) – The looper control by torque achieves the regulation of the inter-stand tension by acting on the torque reference used by the hydraulic torque controller. Normally, the looper control by torque is fed by the tension error generated by a load cell mounted on the looper or, alternatively, by the estimation of the inter-stand tension derived by the looper hydraulic force.
Looper control by speed (LCS) – It aims at regulating the looper angular position by acting on the speed reference of the upstream stand (i.e., by acting on the reference for the speed controller acting on the upstream stand). This regulator is also referred to as the mass flow regulator.
Looper line – It consists of closely spaced symmetrical lines on the surface of metal which has undergone non-uniform deformation, normally in a drawing operation.
Loopers – Loopers are placed between the mill stands. They manage the material in steel rolling mills by regulating the movement and processing of hot steel bars. These loopers comprise a set sequence of rollers which assist in moving hot steel bars across the rolling mill. They not only control the mass flow of the two stands but also to generate a constant specific strip tension during rolling.
Loop gain – It is the total gain around a feedback loop in an electronic or control system, calculated as the product of all gains (amplifier gain x feedback factor) within that loop, critically determining system stability, linearity, and regulation. A loop gain higher than 1 can cause oscillation, while less than 1 indicates stability, but frequently too low for good performance.
Loop gain function – It is frequently denoted as G(s)H(s). It represents the total gain or transfer function around an entire feedback path in a system, calculated by multiplying gains of all components in the loop (amplifier, sensor, and controller etc.) when the loop is ‘opened’. It is important for determining a system’s stability (preventing oscillation) and performance (gain, bandwidth, linearity) in control systems and operational amplifier circuits, showing how input changes circulate and get amplified before being fed back.
Loop growth – It refers to the process in which prismatic loops, formed by the coalescence of thermal vacancies or interstitial atoms, increase in size, frequently characterized by their polygonal shape in bulk materials. This growth is influenced by factors such as the nucleation of jog-pairs and the driving force related to stress and stacking fault energy.
Looping – It is a type of error in a network diagram. Looping error is also known as cycling error
Looping mill – It is an arrangement of hot rolling stands such that a hot bar, while being discharged from one stand, is fed into a second stand in the opposite direction.
Looping pit – It is a pit or recessed area designed to hold a loop of material, typically metal strip or sheet, during processing. This loop allows for the continuous operation of equipment while another part of the line stops and starts, like a slitter or recoiler.
Loop laying head – In a wire rod mill, the laying of different wire rod sizes in uniform loops with the loop laying head even at high rolling speed is an important criterion. The loop laying head is to have the very good characteristics in terms of reliability, noise level, and coil formation. Further due to thermo-mechanical rolling for several grades, the laying temperatures for certain grades are greatly reduced because of the metallurgical reasons. This has put higher demands on the laying head particularly on the laying tubes and they are to be made of special material. The loop laying head is composed by several parts. The input shaft transmits rotation from motor. A guide pipe is located at entrance of laying head device to guide the wire rod into the laying pipe. A pair of bevel gears is assembled on the input shaft and output shaft. The output shaft is connected with laying pipe holder. There are two bearings supporting the output shaft. There is cantilever part of the laying pipe holder. Laying pipe is the most important part for this laying head device.
Loop mechanism – It is a cyclical process where the output of a system feeds back as input, creating repetitive cycles for control, repetition, or amplification, common in engineering (control systems, mechanisms), and programming (iteration), functioning to either stabilize (negative loop) or improve (positive loop) a system’s state.
Loop method – It is a technique to solve complex circuits by applying Kirchhoff’s voltage law (KVL) to independent closed paths (loops) to form a system of linear equations, which are then solved for the unknown loop currents, simplifying analysis by reducing variables compared to branch analysis, especially useful for non-planar circuits or those with shared current sources.
Loop phase – It refers to the phase shift in a control system’s feedback loop, which can vary depending on the load and is critical for stability. A a phase shift approaching 180-degree indicates potential instability.
Loop plot – It is defined as a graphical representation of the frequency response characteristics of a control loop, such as the velocity loop, used to analyze system stability and performance, typically involving gain and phase margins.
Loop power control – It refers to the external power control mechanism which regulates the frequency and inverter output voltage based on the droop characteristics for real and reactive power, utilizing instantaneous power components calculated from measured output voltage and current.
Loop reactor – It is a continuous chemical reactor design featuring a pipe or vessel loop where fluids are rapidly circulated by a pump or gas lift, creating intense mixing and high mass / heat transfer, ideal for gas-liquid reactions, polymerization, and bio-reactions, offering benefits like smaller size, better yield, and efficient operation compared to traditional batch reactors by quickly exposing reactants to catalysts or reacting conditions.
Loop resistance – It is the total electrical resistance in a complete, closed electrical path (a loop), including all wires, connectors, and components like busbars or switches, important for assessing circuit health, especially in power systems where it indicates connection quality and can affect safety and performance by causing voltage drops or overheating. It is measured by sending current through the path and measuring the voltage drop to determine resistance (using Ohm’s Law) and ensures connections, like those in switchgear or communication lines, are not too high.
Loop response – It describes how a control system reacts to inputs or disturbances, particularly in closed-loop (feedback) systems, revealing performance like speed, stability, and accuracy, frequently analyzed via Bode / Nyquist plots for frequency characteristics (gain / phase) or step changes to find time constants and dead time. It shows the system’s output changes as it continuously corrects errors, distinguishing from simpler open-loop systems which lack this feedback correction.
Loop tenacity – It is the tenacity or strength value got by pulling two loops, as two links in a chain, against each other in order to demonstrate the susceptibility which a fibrous material has for cutting or crushing itself. It is the loop strength.
Loop test – It is a diagnostic check used in different fields, mainly to verify the integrity and functionality of a closed path or sequence, normally in software (to check programme loops) or electrical systems (checking fault protection), ensuring they work correctly, safely, and efficiently. In software, it is a white-box testing method for code loops, while in electrical systems, it measures fault loop impedance to ensure circuit breakers trip during a fault.
Loose metal – It refers to an area in a formed panel which is not stiff enough to hold its shape. It can be confused with oil canning.
Loose moulding – It is the moulding process utilizing unmounted patterns. Gates and runners are normally cut by hand.
Looseness – It refers to the condition of a joint or connection, typically in mechanical systems, where components, such as bolts, are not adequately tightened, potentially leading to failure. It can be detected through different methods, including sensor-based, vision-based, and percussion-based techniques.
Loose piece – It is a part of a pattern which is temporarily attached to the main pattern but is removed separately from the mould after the main pattern is withdrawn. They are used to create complex casting features like undercuts which otherwise prevent the main pattern from being pulled out of the sand mould. The loose piece is pulled out after the main pattern has been removed.
Loose-piece pattern – It is a casting pattern with extra parts which are temporarily attached to the main body to create complex shapes that cannot be removed from the mould in a single piece. After the mould is formed, the main pattern is removed first, leaving the loose pieces behind in the sand. The loose pieces are then individually removed to leave a complete mould cavity, preventing damage to intricate or overhanging features. It is used in sand casting when the shape of the part has complex features or undercuts which prevents the pattern from being withdrawn from the mould in one piece.
Loose powder – It is uncompacted powder.
Loose powder sintering – It is the sintering of uncompacted powder using no external pressure.
Loose tolerance – It allows for a larger range of variation in a component’s dimensions, meaning small deviations from the ideal size are acceptable without affecting its function. This is normal in applications where high precision is not critical, as it can lead to lower manufacturing costs and faster production speeds. In contrast, tight tolerances require high precision with very little allowable deviation.
Loose wrap – It is a condition in a coil because of insufficient tension which creates a small void between adjacent wraps.
Lorenz coefficient – It is defined as a parameter which quantifies the degree of heterogeneity within a pay zone section, varying between 0 for a completely homogeneous system and 1 for a completely heterogeneous system. It is calculated by analyzing the normalized cumulative permeability and volume capacities, with its value indicating the severity of deviation from a straight line in a plotted graph of these capacities.
Lorentz distribution – It is also called Cauchy distribution. It is a continuous probability distribution frequently used in statistics. It is characterized by its heavy tails, meaning it has a higher probability of extreme values compared to a normal distribution. It is also known for having undefined mean and variance.
Lorentz equation – It normally refers to the Lorentz force law, defining the total electro-magnetic force on a charged particle as F = q x (E + v x B) force from electric field (qE) plus magnetic force q x (v x B). It describes how charges move in fields, important for motors and particle accelerators. It also refers to a relationship which connects the refractive index of a medium to its polarizability, specifically in the context of high-frequency alternating current (AC) fields where orientational polarization is negligible, and electronic and atomic polarizations dominate.
Lorentz force – It is the total force on a charged particle from both electric and magnetic fields, defined as the vector sum of the electric force (FE = qE) and the magnetic force [FB = q(v x B)]. It explains how charged particles move through electro-magnetic environments, resulting in straight-line acceleration from the electric field and curved motion (circular or helical) from the magnetic field, which acts perpendicularly to both velocity (v) and the magnetic field (B).
Lorentz force law – It is the mathematical relation between currents in conductors and the resulting magnetic forces between them.
Lorenz model – It is a mathematical representation of fluid convection which describes how complex, sustainable patterns of fluid motion emerge from a uniformly heated, homogeneous fluid through the interactions of its microscopic elements. It consists of three interrelated differential equations and shows shifts between different dynamic regimes, indicated by changes in system behaviour and structure.
Lorenz number (L) – It is a fundamental constant, representing the ratio of a metal’s electronic thermal conductivity to its electrical conductivity scaled by temperature. It is a measure of how efficiently free electrons transport both heat and charge, ideally following the Wiedemann-Franz Law, with the theoretical free-electron value (Sommerfeld value). While Lorenz number normally stays close to L0 for several metals, deviations occur at low temperatures or in complex materials because of the factors like electron-phonon scattering or other thermal carriers (phonons, magnons).
Los Angeles abrasion test = This test is for testing of toughness (resistance to abrasion and degradation) of construction aggregate or gravel and its suitability for road construction. Test methodology and equipment are is defined in the standards. Los Angeles machine is a simple ball mill of specified size and shape. The standard charge of rock is set at 2.5kilograms to 5 kilograms depending on the size of the particles. The drum of the mill has a single shelf plate that scoops test samples and steel balls from the bottom, lifts them up and then drops them, creating a crushing impact. The interaction of the drum, steel balls and the samples at the bottom of the drum causes further abrading and grinding. The complete test requires 500 drum revolutions at a speed of 30 to 33 revolutions per minute. Crushed sample is then separated from fine dust on a sieve, washed, dried and weighed. The test reports loss of mass to abrasion and impact, expressed as a percentage of initial sample mass. Maximum acceptable loss for the base course of the road is 45 %, and for the more demanding surface course is to be 35 % or less.
Loss – Loss is the financial result when the organizational expenses exceed its revenues over a specific period. It is essentially the opposite of profit, where revenue surpasses expenses. A loss is also referred to as a net loss, negative net income, or negative operating income, depending on the context.
Loss behaviour – It refers to the total magnetic energy loss in metallic materials, which can be decomposed into three distinct contributions namely hysteresis, classical, and excess loss, each influenced by magnetization frequency, peak induction, and micro-structure. This behaviour is determined by the complex interactions of eddy currents and magnetic domain structures.
Loss budget – It is the quantity of loss which a cable plant is required to have if it is installed properly. It is calculated by adding the estimated average losses of all the components used in the cable plant to get the estimated total end-to-end loss. The loss budget has two uses namely (i) during the design stage it is used to ensure the cabling being designed is going to work with the links intended to be used over it, and (ii) after installation, the loss budget for the cabling is compared to the actual test results to ensure the cable plant is installed properly.
Loss coefficient (K-factor) – It is a dimensionless number in fluid mechanics which quantifies energy loss (head loss or pressure drop) in pipes and fittings because of the flow disturbances like bends, valves, or expansions, relating head loss (hL) to velocity head (v-square/2g) through hL = K(v-square/2g). It measures how much energy is lost compared to a straight pipe, with higher K-values indicating higher energy dissipation, affecting system efficiency. Loss coefficient is also defined as a measure of the energy dissipated during vibration of micro-mechanical resonators and oscillators, typically expressed as the inverse of the mechanical quality factor. It quantifies intrinsic losses associated with different material properties and operational conditions.
Loss compensation – It is the financial payment made to an individual or entity to offset an economic loss, damage, or injury, aiming to restore them to their prior financial state, common in insurance, legal settlements (for lost wages / earning capacity), or corporate payouts (for job loss). It covers actual harm, lost profits, or future earning potential, ensuring the harmed party is not left worse off due to events like accidents, natural disasters, or contract breaches.
Loss component – It refers to a specific source or part of energy / signal dissipation (like copper loss, dielectric loss, eddy current loss) which reduces efficiency, or in AI (artificial intelligence), a part of a loss function measuring prediction error (like ‘mean squared error’), aiming to quantify and minimize energy waste or model inaccuracy in systems from power grids to machine learning.
Losses in a steam turbine – These are reductions in efficiency from the ideal conversion of steam’s thermal energy to mechanical work, caused by factors like steam leakage, friction (blades, bearings, discs), aerodynamic effects (turbulence, incomplete expansion), and residual kinetic energy in the exhaust, categorized into internal (steam flow related) and external (mechanical / radiation) losses, all lowering overall power output.
Loss exponent – It is an important parameter showing how fast signal power drops with distance in a specific environment, calculated in path loss models. It quantifies path loss, with values typically 2 (free space) to 6+ (indoors / urban), indicating environment effects like fading, shadowing, reflection, and diffraction, helping predict signal strength for localization or network design.
Loss factor – It is the product of the dissipation factor and the dielectric constant of a dielectric material.
Loss function – It is a mathematical function which quantifies the difference between the predicted output of a model and the actual, true output (ground truth) for a given input. It essentially measures how ‘wrong’ a model’s prediction is, with lower loss values indicating better model performance. Loss functions provide a numerical value that represents the error or discrepancy between the model’s prediction and the actual value. In statistics, a loss function is used for parameter estimation, and the event in question is some function of the difference between estimated and true values for an instance of data.
Loss in pipe – It refers to the reduction of head due to friction, sudden changes in flow area, or fittings such as bends and valves, which can be quantified using different equations and factors which depend on flow velocity, pipe dimensions, and specific characteristics of the fittings.
Lossless compression – It refers to techniques which allow data to be compressed without any loss of information, enabling the exact recovery of the original data from the compressed version. This type of compression is necessary for applications where maintaining the integrity of the data is critical, such as text compression and certain types of numerical data.
Lossless data compression – It is a data compression method where the source can be reconstructed exactly, where approximations are tolerable, lossy data compression can be used.
Lossless image compression – It is a reversible process which reduces an image’s file size by removing statistical redundancy using algorithms without discarding any data, allowing for perfect reconstruction of the original image, important for archival, or technical drawings where data integrity is paramount. It achieves smaller files by rewriting data more efficiently, unlike lossy compression which permanently removes some details.
Lossless line – It is a transmission line which does not dissipate any power, has a real characteristic impedance, and is non-dispersive, meaning the phase constant varies linearly with frequency.
Lossless transmission line – It is a transmission line which does not show any resistive losses, characterized by the absence of energy dissipation in the form of heat, and is analyzed using telegrapher equations under sinusoidal steady-state conditions.
Loss modulus – It is a damping term describing the dissipation of energy into heat when a material is deformed. It quantifies a material’s energy dissipation, measuring the mechanical energy converted to heat during deformation, reflecting its viscous, liquid-like behaviour and damping ability, contrasting with the storage modulus which measures elastic energy storage. It is important for viscoel3astic materials like polymers, revealing how much energy is lost as internal friction (chain flow / molecular movement) during cyclic loading, helping predict performance and design for shock absorption or damping.
Loss of circulation – It is the partial or total escape of drilling fluid (mud) into the surrounding underground rock formations instead of returning up the wellbore, normally because of the fractures or porous zones (thief zones) encountered, causing major non-productive time (NPT) and increased costs. It happens when wellbore pressure exceeds formation strength, creating fractures, or when drilling through highly permeable, fractured, or cavernous rock.
Loss-of-coolant accident – It is the is a mode of failure for a nuclear reactor. If not managed effectively, the results of a loss-of-coolant accident can result in reactor core damage. Nuclear plants have emergency core cooling system (ECCS) specifically to deal with a loss-of-coolant accident.
Loss on ignition – It is a test used in inorganic analytical chemistry and soil science, particularly in the analysis of minerals and the chemical makeup of soil. It consists of strongly heating a sample of the material at a specified temperature, allowing volatile substances to escape, until its mass ceases to change. In composites, it is the weight loss, normally expressed as percent of total, after burning off an organic sizing from glass fibres, or an organic resin from a glass fiber laminate.
Loss of load probability – It is a key reliability metric measuring the probability that a power system’s available generation capacity is going to be insufficient to meet the electrical demand over a specified period, essentially the likelihood of a shortage or blackout, calculated probabilistically by considering generation outages and load fluctuations to help planners ensure adequate supply. It is expressed as a percentage or a ratio, indicating how frequently the system cannot serve its load, helping utilities plan for resource adequacy.
Loss penalty – It refers to a cost or penalty factor applied to account for inefficiencies, especially transmission losses in power systems (making power more expensive to deliver) or penalties for violating constraints in optimization (adding cost for infeasible solutions), effectively increasing the cost of generating / transmitting power or making undesirable solutions less favourable to achieve system efficiency and accuracy.
Loss prevention – It is the systematic application of safety principles to prevent catastrophic failures, accidents, and damage to people, assets, and the environment, moving beyond simple process safety to cover fire, explosion, toxic release, and security threats, using techniques like hazard analysis, safety layers (like relief valves), and robust design to stop incidents before they happen, minimizing operational losses and protecting profits.
Loss probability – It is the statistical likelihood of a system failing, exceeding a performance limit, or incurring a negative consequence (like data loss or power outage) within a given time, calculated as the ratio of failure / undesirable events to total events, crucial for risk assessment and system design, with specific terms like ‘packet loss probability’ (networks) or ‘loss of load probability’ (power systems) quantifying these risks.
Loss reduction – It means implementing strategies and technologies to minimize energy, resource, or financial waste within systems (like power grids, manufacturing, or data), focusing on improving efficiency, lowering costs, and boosting performance, contrasting with ‘loss prevention’ (stopping losses entirely) by managing the severity of unavoidable losses through optimization, better design, and control measures like capacitor placement or thermal insulation.
Loss separation – It means breaking down total energy losses (like heat or pressure) in a system (motors, transformers, fluid flows) into specific, quantifiable components, such as hysteresis loss, eddy current loss, or flow separation in turbo-machinery, to better understand, model, and reduce inefficiencies, revealing the root causes for better design and optimization.
Loss spectrum – It describes how much energy (or signal) is lost in a system or material across different frequencies or energy levels, frequently visualized as a graph showing ‘counts against energy loss’ (electron energy loss spectroscopy) or ‘power loss against frequency’ (micro-wave systems), revealing material properties, defects, or performance issues like absorption, scattering, or poor impedance matching. Key examples include ‘electron energy loss spectroscopy’ (EELS) for nano-scale material analysis and frequency-dependent loss in transmission lines or filters
Loss tangent – It is the ratio of the power loss in a dielectric material to the total power transmitted through it, hence, the imperfection of the dielectric. It is equal to the tangent of the loss angle.
Loss time injury – It is an industrial injury causing loss of time from the job on which the injured person in normally employed beyond the day or shift on which the injury occurred. In addition, cases where loss of time does not immediately follow the injury, but where there is a direct relation between absence and injury, are regarded as lost time injuries.
Lossy data compression – It is a data compression method which allows only a close approximation of the source to be reconstructed. It is useful for images, where the human perceptual system compensates for the errors.
Lossy transmission line – It is a transmission medium where voltage and current waveforms show exponential attenuation in amplitude because of the resistive losses in conductors and dielectric losses, characterized by a propagation constant which combines attenuation and phase constants.
Loss zone – It is also called lost circulation zone or thief zone. It is a specific section in the sub-surface rock formation where drilling fluid (mud) unexpectedly escapes from the well-bore into natural fractures, highly permeable layers, or voids, instead of returning to the surface, creating substantial operational and cost challenges. These zones, frequently fractured or cavernous, need special materials (lost circulation materials – LCMs) to plug the pathways and regain control, preventing serious issues like well-bore instability, dry drilling, or even blowouts.
Lost foam casting – It is a type of evaporative-pattern casting process which is similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of foam to simplify the investment casting process by removing the need to melt the wax out of the mould. It is an expendable pattern process in which an expandable polystyrene pattern surrounded by the unbonded sand, is vapourized during pouring of the molten metal. Lost foam casting is also known as full-mould, poly-cast, cavity’s molding, evaporative-pattern, or expendable-pattern casting.
Lost foam mould – It is a type of mould used in a casting process where a polystyrene foam pattern is used to create the mould cavity. The foam pattern is embedded in sand, and when molten metal is poured in, it vapourizes the foam, leaving behind a metal casting which replicates the shape of the original foam pattern. This method is also known as evaporative pattern casting.
Lost foam process – It is a casting technique where a polystyrene foam pattern of the desired part is coated in a refractory material, buried in unbonded sand, and then filled with molten metal. The heat from the molten metal vapourizes the foam, and the liquid metal takes its place, creating an exact replica after the sand is removed and the metal solidifies. This process allows for the creation of complex metal castings with high precision and minimal machining.
Lost production – It is the quantifiable quantity of output (goods, or energy etc.) which a system or facility failed to produce compared to its potential, caused by downtime, inefficiencies, or equipment issues like failures, maintenance, or operational constraints, representing lost income and potential value. It is the difference between what could have been made and what was actually made, measured in units or financial terms.
Lost time injuries (LTI) – It is any work-related injury, resulting in the organization, contractor or third-party contractor employee not being able to return to work for their next scheduled work period. Returning to work with work restrictions does not constitute a lost time injury status, no matter how minimal or severe the restrictions, provided it is the employee’s next scheduled shift
Lost time injury frequency rate (LTIFR) – It is calculated as number of lost time injuries per million man-hours.
Lost wax process – It is also known as investment casting or cire-perdue. It is a foundry technique for creating detailed metal objects. It involves creating a wax model, encasing it in a ceramic shell to form a mould, and then heating the mould to melt and drain the wax away. Molten metal is then poured into the hollow ceramic mould to create a metal duplicate of the original wax model.
Lot – It is a specific quantity of material which is produced at one time using one process and constant conditions of production, and offered for sale as a unit quantity. It is also a quantity of material which is thought to be uniform in one or more stated properties such as isotopic, chemical, or physical characteristics. It is also a quantity of bulk material of similar composition whose properties are under
study. In powder metallurgy, it is the total output of on mixing. It is also a tray or basket of compacts placed in a sintering furnace. In statistical analysis, lot is a group of units produced under similar conditions.
Lot, heat treat – It is the material of the same mill form, alloy, temper, section, and size traceable to one heat treat furnace load (or extrusion charge or billet in the case of press heat treated extrusions) or, if heat treated in a continuous furnace, charged consecutively during an 8 hours period.
Lot, inspection – For non-heat-treated products, it an identifiable quantity of material of the same mill form, alloy, temper, section, and size submitted for inspection at one time. For heat treated products, it is an identifiable quantity of material of the same mill form, alloy, temper, section, and size traceable to a heat treat lot or lots and submitted for inspection at one time. (For sheet and plate, all material of the same thickness is considered to be of the same size).
Lot sample – It consists of one or more increments of material taken from a larger quantity (lot) of material for assay or record purposes. It is also termed bulk sample or lot sample.
Lot size (N) – It refers to the total quantity of items or units which are considered a single, identifiable batch for quality control purposes. Sampling is the process of selecting a subset of items (the sample, size ‘n’) from this lot to inspect and make inferences about the overall quality of the entire lot.
Loudspeaker – It is a transducer which converts electrical current into sound, perceptible to more than one listener.
Low alloy ferritic steel – It is a type of steel with a body-centered cubic (BCC) structure, low carbon content, and small additions of alloying elements (like chromium, molybdenum, nickel, and vanadium) totaling under around 12 %, giving it good high-temperature strength, low thermal expansion, magnetizability, and decent corrosion resistance, making it ideal for heat exchangers, automotive exhausts, and industrial equipment where cost and performance balance is key factor.
Low-alloy pipe steel – It is a type of steel which contains a small quantity of alloying elements, typically less than 3 % to 5 %, such as chromium, molybdenum, nickel, and manganese. These additions provide superior strength, toughness, and corrosion resistance compared to ordinary carbon steel, making it suitable for demanding applications like high-pressure pipelines.
Low-alloy high-strength steels – These are a group of alloy steels with improved mechanical properties like higher strength and toughness compared to conventional carbon steels, achieved by adding small amounts of alloying elements like niobium, vanadium, and chromium. Their low carbon content (typically 0.05 % to 0.25 %) is maintained to ensure good formability and weldability, and they are widely used in applications needing a good strength-to-weight ratio, such as in automotive parts, bridges, and pipelines.
Low-alloy plasma-nitrided steels – These are steels with a low concentration of alloying elements which have undergone a plasma nitriding surface treatment. This process uses a plasma glow discharge to introduce nitrogen into the steel’s surface, creating a hard, wear-resistant layer which considerably improves durability and performance. The resulting steel is strengthened in its surface layers while retaining the properties of the core.
Low-alloy steels – It is a category of ferrous materials which show mechanical properties superior to plain carbon steels as the result of additions of such alloying elements as nickel, chromium, and molybdenum. Several attempts have been made to differentiate low alloy steels from high alloy steels but the definition of low alloy steel vary from country to country and between the standard setting organizations. As a general indication, low alloy steels can be regarded as alloy steels (by the International Organization for Standardization, ISO definition) containing more than 1 % and less than 5 % of alloying elements deliberately added for the purpose of modifying properties.
Low-alloy structural steel – It is a type of steel which has a small quantity of alloying elements, typically between 1 % and 5 %, added to iron and carbon to improve its properties. These additions, such as chromium, nickel, and molybdenum, considerably improve the steel’s strength, toughness, and corrosion resistance, making it suitable for demanding applications.
Low alloy tool steel – It is a type of steel which includes alloying elements like chromium, molybdenum, nickel, and vanadium to improve properties such as strength, toughness, and wear resistance, making it suitable for demanding applications like dies, punches, and cutting tools. These elements are typically added in small amounts (between 1 % and 5 %) compared to plain carbon steels to create a higher-performing material.
Low alumina fireclay refractory – It is the refractory which is composed of alumino-silicate and silica, containing less than 85 % by mass of silica and a minimum of 10 % and less than 30 % by mass of aluminum oxide.
Low and cryogenic temperatures – These temperatures are extremely cold ranges, normally considered below -150 deg C (123 K), leading to altered material properties, with the cryogenic range extending down towards absolute zero (0 K or -273.15 deg C) where molecular motion nearly ceases, crucial for applications like liquefying gases (nitrogen, or helium) and enabling super-conductivity in MRI (magnetic resonance imaging) machines and research.
Low-angle boundaries – These are boundaries with small angles of crystallographic misorientation between neighboring grains. They can be represented by arrays of dislocations in the boundary and have energies approximately proportional to the misorientation.
Low-angle diffraction methods – These are techniques which use radiation, such as X-rays or electrons, to study the structure of a material at a very low angle of scattering. These methods are used to analyze features with sizes ranging from nanometers to microns, such as thin films, or layered structures. Since they are sensitive to small-scale and surface features, low-angle methods are useful for characterizing the thickness and periodicity of layers and can provide insights into the nano-scale structure of materials.
Low-angle grain boundaries – These are boundaries with a misorientation less than about 15 degrees. Normally they are composed of an array of dislocations and their properties and structure are a function of the misorientation.
Low-carbon building – It is a structure designed, built, and operated to minimize carbon emissions throughout its entire life cycle, using energy-efficient systems, sustainable materials (like mass timber, bamboo, cork), renewable energy, smart technology, and circular economy principles to reduce considerably its environmental footprint and move towards net-zero goals.
Low-carbon concrete – It is a sustainable concrete mix designed to considerably reduce greenhouse gas emissions, mainly by replacing a portion of traditional Portland cement (a major carbon di-oxide source) with supplementary cementitious materials (SCMs) like fly ash, slag, or calcined clay, while optimizing other components and processes for a lower overall carbon footprint, frequently meeting specific environmental performance targets. It aims to maintain or improve performance (strength, durability) compared to conventional concrete.
Low-carbon ferritic steels – These are a class of steel alloys with a low carbon content (typically below 0.2 %) and a ferritic (body-centered cubic) crystal structure. This combination results in a non-hardenable material which cannot be strengthened by heat treatment but can be moderately hardened by cold work. These steels are known for being magnetic, relatively inexpensive, ductile, and resistant to stress corrosion cracking.
Low carbon ferro-chrome – It is an alloy of iron and chromium with a very low carbon content, typically below 0.1 %. It is a key component in the production of high-grade stainless steel and other corrosion-resistant alloys, where its low carbon content is necessary for improving mechanical properties and resistance to corrosion.
Low carbon ferro-manganese – It is an alloy of iron and manganese with a very low carbon content, typically below 0.1 %. It is a crucial additive in steelmaking for producing high-quality steel with controlled carbon levels, as it acts as an alloying agent, deoxidizer, and desulphurizer. Its addition improves the mechanical properties of steel, such as strength, toughness, and wear resistance.
Low-carbon fuels – These are energy sources which produce considerably fewer green-house gas (GHG) emissions than traditional fossil fuels over their lifecycle, including biofuels (ethanol, biodiesel), renewable natural gas (RNG), hydrogen, and synthetic fuels (e-fuels), frequently derived from biomass, waste, or renewable electricity, helping decarbonize transport, industry, and power grids by using existing infrastructure while bridging to fully electric future.
Low carbon fuel standard – It is a market-based policy which sets progressively stricter limits on the life-cycle green-house gas intensity of transportation fuels, incentivizing cleaner energy by creating tradable credits for fuels with lower emissions (e.g., electricity, biofuels) and deficits for higher-emission fuels (like gasoline / diesel), compelling suppliers to buy credits or reduce their overall carbon footprint. It focuses on the entire fuel life-cycle, from production to consumption, and encourages innovation by not picking specific technologies, but rewarding fuels which perform best against the standard.
Low-carbon gas – It is a fuel, like hydrogen or bio-methane, which produces considerably fewer green-house gas (GHG) emissions over its lifecycle (production, transport, use) compared to fossil natural gas, helping decarbonize energy, frequently meeting thresholds like 70 % to 80 % reduction, and can come from renewables or fossil sources with carbon capture, but strict standards focus on actual green-house gas reduction for true climate benefit.
Low carbon green growth – It is a national development strategy balancing economic growth with environmental sustainability, focusing on reducing green-house gas (GHG) emissions and pollution by shifting to clean energy, improving resource efficiency, and investing in green technologies to create new jobs and industries, essentially making growth ‘greener’ and less carbon-intensive. It is a vision for a sustainable future where economic progress does not come at the cost of climate stability, promoting a ‘development-first’ approach with lower emission pathways.
Low-carbon steel – It is the steel with less than 0.005 % carbon. It is more ductile (malleable) and is capable of being drawn out or rolled thin for use in automotive body applications. Carbon is removed from the steel bath through vacuum degassing.
Low cement castable – It consists of deflocculated castable which contains higher than 1 % and a maximum of 2.5 % calcium oxide on a calcined basis.
Low-cost automation – It is a strategy to make automation accessible, especially for ‘small and medium enterprises0 (SME), by using simple, standard, off-the-shelf components (pneumatic, electric, mechanical) to automate existing processes, relieving humans from repetitive tasks without huge investments in complex robots. It focuses on smart, affordable solutions, frequently using principles like Karakuri (gravity / levers) or basic pneumatics, to boost productivity, improve quality, and reduce unit costs with a fast payback, bridging the gap between manual labour and advanced robotics.
Low current density – It refers to a low flow of electric current (amperes) spread over a specific cross-sectional area (like square centi-meter, square meter), meaning a large area for a given current, leading to less heating and different electro-chemical behaviours, frequently seen as negligible mass transfer issues in electro-chemical systems below a certain threshold (e.g., less than 0.4 amperes per square centi-meter). It is the opposite of high current density, where current is concentrated over a small area.
Low-cycle fatigue – It is the fatigue which occurs at relatively small numbers of cycles (less than 10,000 cycles). Low-cycle fatigue can be accompanied by some plastic, or permanent, deformation.
Low-density ceramic – It is a light-weight ceramic material, frequently porous, made from fibres or powders, characterized by a high void fraction (lots of empty space) to reduce weight and improve thermal shock resistance, making them ideal for high-temperature insulation, or filtration, differing from dense technical ceramics which prioritize hardness and strength.
Low-density polyethylene – It is a type of thermoplastic in the polyethylene family. It’s formed of long chains of ethylene molecules called monomers. Its chemical formula is (C2H4)n, the same as high-density polyethylene. Their differences lie in density, as their names suggest. Once LDPE is created, it is typically flexible and transparent in colour. It is a common choice for manufacturing plastic goods. It is corrosion-resistant, flexible, durable, and low-cost.
Low dielectric loss – It means a material minimally converts electrical energy into heat when under an alternating electric field, indicating high efficiency for high-frequency signals by reducing energy dissipation (signal attenuation) and improving signal integrity in electronics like printed circuit boards (PCBs), quantified by a small loss tangent (tan delta). These materials, frequently more expensive, can achieve dissipation factors as low as 0.003, allowing for longer routing lengths with minimized signal loss.
Low discharge rate – It means a battery releases its stored energy slowly, delivering lower power over a longer time, which can increase total usable energy (capacity) and improve longevity for certain types (like lead-acid) or long-term storage, contrasted with high rates which provide bursts of power but drain faster. It is measured in C-rates (e.g., C/10), indicating how many hours it takes to fully discharge, with lower numbers (like C/20) being slower than higher ones (like 1C).
Low-duty refractories – These are a class of refractory materials which are characterized by their refractoriness, which is the ability to withstand high temperatures without softening or deformation. Specifically, low-duty refractories have a refractoriness ranging from 1,520 deg C to 1,630 deg C. These refractories have PCE (pyrometric cone equivalent) value ranging from 19 to 28. They are frequently used in applications where the operating temperature is lower compared to higher-duty refractories.
Low emission technology – It refers to innovations reducing green-house gases (GHGs) and pollutants from energy use, encompassing cleaner power sources (renewables, and nuclear), higher efficiency (buildings, and transport), carbon capture, and low-carbon fuels (hydrogen, biofuels) to help transition to a sustainable, low-carbon economy and combat climate change.
Low emissivity – It describes a surface’s ability to emit low levels of radiant thermal (heat) energy, meaning it is highly reflective and less effective at emitting its own electromagnetic waves.
Low-energy building – It is a structure designed to reduce considerably the energy consumption through efficient design, materials, and technologies, needing less energy for heating, cooling, and lighting than conventional buildings, frequently by minimizing reliance on active systems and maximizing passive strategies, moving towards nearly / net-zero energy. Key features include high insulation, air-tightness, energy-efficient windows, smart orientation, and integration of renewable energy, providing high comfort with minimal energy input.
Low energy cost – It means minimizing expenses from power usage, either by reducing consumption (efficiency) or lowering the price per unit, frequently measured by the ‘levelized cost of energy’ (LCOE) i.e., the total lifetime cost to generate one unit of energy (like a kilo-watt hour), factoring in construction, fuel, operation and maintenance, and decommissioning. Basically, it is about getting more work done with less energy or paying less for the energy used, benefiting consumers with savings and industries with better competitiveness.
Low energy density – It refers to the relatively low bulk density and heating value of bio-mass, which is only 10 % to 40 % of that of most fossil fuels, resulting in challenges for bio-mass conversion and necessitating close proximity to processing facilities.
Low-energy electron diffraction – It is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons and observation of diffracted electrons as spots on a fluorescent screen.
Low energy input – It means using minimal energy for a process, system, or product, focusing on efficiency, sustainability, and reduced resource consumption, which can be achieved by optimizing components, reducing heat, or using less power for tasks like manufacturing (e.g., lower laser power in 3D printing) or computing, leading to lower operational costs and environmental impact.
Low-energy ion scattering spectroscopy – It is sometimes referred to simply as ion scattering spectroscopy. It is a surface-sensitive analytical technique which is used to characterize the chemical and structural makeup of materials.
Low enriched uranium – it is the enriched uranium which contains less than 20 % of Uranium-235 U-235).
Low environmental impact – It means designing and doing things (activities, products, lifestyles) to minimize negative effects on earth, by using fewer resources, cutting waste, reducing pollution (air, water, land), lowering carbon footprints, and preserving eco-systems, basically living and operating as lightly as possible on the planet. It is about balancing human needs with ecological health, focusing on sustainability through efficiency and responsible choices.
Lower bainite – Lower bainite has a micro-structure and crystallographic features which are very similar to those of upper bainite. The major distinction is that cementite particles also precipitate inside the plates of ferrite. There are, hence, two kinds of cementite precipitates namely (i) those which grow from the carbon-enriched austenite which separates the platelets of bainitic ferrite, and others which appear to precipitate from supersaturated ferrite. These latter particles show the ‘tempering’ orientation relationship which is found when carbides precipitate during the heat treatment of martensite, frequently described as the Bagaryatski orientation relationship.
Lower calorific value – It is also called net calorific value. It is the net heat released from burning a unit of fuel when the water vapour produced during combustion is allowed to escape (not condensed), meaning its latent heat of vapourization is not recovered, making it the practical measure of usable energy for engines and turbines. It is calculated by subtracting the latent heat of the water vapour from the higher calorific value (HCV).
Lower control limit – It is the minimum acceptable variation from the mean for a process which is in a state of control. It is the control limit on the lower side of the central line of a control chart. A value below this line indicates presence of an assignable cause and need for corrective action.
Lower critical temperature – It is the temperature below which ferrite is the stable phase. It is also called the A1 temperature.
Lower cut-off frequency – It is the frequency where a system (like a filter or amplifier) starts significantly reducing the strength (power / amplitude) of signals, marking the boundary between the passband and stopband, typically defined as the point where output power drops to half its maximum (or -3 decibels). For high-pass filters, it is the lowest frequency passed. For low-pass, it is the frequency above which signals are blocked, but it is also used in bandpass systems to define the lower edge of the desired frequency range.
Lower explosive limit – It is defined as the lowest concentration (by percentage) of a gas or vapour in air which is capable of producing a flash of fire in presence of an ignition source (arc, flame, heat, etc.). Concentrations lower than the lower explosive limit are ‘too lean’ to burn. The explosive range is delineated by the upper and lower explosive limits.
Lower flammability limit – It is normally expressed in volume per cent. It is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is delineated by the upper and lower flammability limits.
Lower heating value (LHV) – It also known as the net calorific value (NCV). It is defined as the quantity of heat released by fully combusting a specified quantity less the heat of vapourization of the water in the combustion product. Lower heating value of a fuel is one in which the H2O in the products has not condensed. The lower heating value is equal to the higher heating value minus the latent heat of the condensed water vapour.
Lower limit – It defines the minimum acceptable size, value, or concentration for a component, process, or substance, ensuring it stays within the permissible range (tolerance zone) to function correctly, with common uses in dimensional tolerance (e.g., smallest shaft size), statistical process control (lower control limit), and material safety (lower flammability limit).
Lower oxidation state – It means an atom has gained electrons (been reduced), has a more negative or less positive charge, indicating a higher electron density, making it a good reducing agent (electron donor) in redox reactions, important for understanding corrosion, batteries, catalysis, and processes like metal treatment or organic fuel oxidation. It represents the minimum electron loss potential an element has, like carbon in methane (-4) or nitrogen in ammonia (-3).
Lower punch – It is the lower member of a die assembly which form the bottom of the die cavity. It may or may not move with respect to the die body.
Lower ram – It is the part of a pneumatic or hydraulic press which is moving in a lower cylinder and transmits pressure to the lower punch.
Lower range value – In data analysis or measurement systems, the lower range value (LRV) represents the minimum value within a specified range of acceptable or measurable data points. It is the lowest point on a scale or within a defined set of numbers that the system or instrument can reliably measure or process.
Low-rank coal -It refers to lignite and sub-bituminous coal, characterized by high moisture, high volatile matter, lower carbon content, and lower energy density than higher-rank coals (like bituminous or anthracite). These coals have undergone less coalification, retaining more oxygen-containing functional groups and water, making them softer, frequently brown, and challenging for traditional combustion / processing because of their unique physical and chemical properties, yet they are significant energy sources globally.
Lower specification limit – It is the minimum value as per the specification.
Lower triangular matrix – It is a square matrix where all entries above the main diagonal are zero, meaning aij = 0 for all row index ‘I’ and column index ‘j’. This structure simplifies solving systems of linear equations (using forward substitution) and is crucial in numerical methods like LU decomposition, found in areas from structural analysis to signal processing.
Lower transition temperature – It refers to a critical point where materials, especially polymers or complex mixtures (like bitumen), shift from a rigid, glassy state to a softer, more-rubbery, or fluid-like (visco-elastic) state, crucial for performance in temperature-sensitive applications like roads, food packaging, or electronics. For metals, a related concept, the ductile-to-brittle transition temperature (DBTT), marks where they lose ductility and become prone to sudden brittle failure, with a lower ductile-to-brittle transition temperature being highly desirable for safety in cold environments.
Lower yield point – It is the minimum stress needed to sustain plastic (permanent) deformation in materials like low-carbon steel, occurring just after the initial stress peak (upper yield point) where the material’s resistance temporarily drops as dislocations move freely. It represents the stable, practical limit for elastic behaviour, used in design for safety.
Lowest natural frequency – It is also known as the fundamental frequency. It is the slowest rate at which a system (like a bridge, or molecule) vibrates naturally when disturbed. It is determined by its inherent physical properties such as mass and stiffness, and is frequently associated with the simplest mode of vibration. It is important since the external forces matching this frequency cause resonance, potentially leading to large, destructive oscillations.
Lowest permissible water level – The lowest permissible water level is the lowest water level at which the boiler can be safely operated without damaging or overheating any part of the boiler.
Lowest unoccupied molecular orbital – It is the lowest energy orbital in a molecule which is empty (unoccupied by electrons), serving as the main target for incoming electrons, is important for defining reactivity, electron acceptance (reduction), and electronic transitions in chemical reactions. It is the next available energy level after the ‘highest occupied molecular orbital’ and dictates how easily a molecule gains electrons, frequently being a pi-star or sigma-star anti-bonding orbital.
Low-expansion alloys – These are materials with dimensions which do not change appreciably with temperature. These alloys include different binary iron-nickel alloys and several ternary alloys of iron combined with nickel-chromium, nickel-cobalt, or cobalt-chromium alloying.
Low feed rate – It means the cutting tool moves very slowly or advances a small distance per revolution / pass into the material, creating thin chips, which frequently results in a smoother surface finish but can cause rubbing, dulling, or overheating if too slow. In extrusion, it is a slow material supply rate frequently because of the issues like worn parts. In short, it is a slower rate of material removal or tool advancement compared to a high feed rate.
Low-flow operation – It normally means running a system (like a pump, or faucet) with considerably reduced fluid, frequently below typical rates, to save resources or achieve specific effects, but it needs careful management to avoid negative consequences like system inefficiency, as seen in decreased separation in hydrocyclones. The specific definition varies by field. In engineering, it can mean low fluid volume through a pump, impacting performance. For plumbing, it is less than 0.4 cubic meter per hour faucets for water saving.
Low flow rate – It is the slow movement of fluid (liquid or gas) through a system, varying by application but normally under 1 litre per minute to 4 litres per minute, meaning reduced volume or speed, crucial in water conservation or industrial processes (chemical reactors) where less fluid volume slows processes, impacts separation efficiency (hydrocyclones), or indicates drought (streams).
Low-frequency band – It refers to a segment of the electro-magnetic spectrum, typically 30 kilo-hertz to 300 kilo-hertz) for radio, characterized by long wavelengths (10 kilo-meters to 1 kilo-meter) and good propagation, allowing signals to travel far, penetrate obstacles like walls, and support applications like rural broadband and marine navigation. It is also used in acoustics (below 300 hertz) for deep, long-traveling sounds, and normally for low-pitch sounds.
Low-frequency stability – It refers to a system’s ability to resist oscillations (swings) in its operating frequency, typically between 0.1 hertz to 3 hertz for power grids or around 1 hertz to 2 hertz for amplifiers, preventing shutdowns or damage from power imbalances (generation vs. load) or poor controller design, ensuring reliable operation by damping these slow frequency variations.
Low-frequency vibration – It refers to oscillations in a slow, rhythmic pattern, typically below 100 hertz (or even lower, like below 10 hertz for ultra-low) and frequently felt as a deep rumble or pressure rather than heard, characterized by long wave-lengths and substantial energy, impacting structural integrity, industrial processes (like machining), and human health (causing fatigue or relaxation, depending on context). It is defined more by its effects and frequency range (e.g., less than 1,000 hertz for melt treatment, less than 10 Hz for some research) than a single number, needing specialized sensors to measure.
Low gas pressure control – It is a control to stop the burner if gas pressure is too low.
Low-grade heat source – It is the thermal energy available at relatively low temperatures (frequently below 100 deg CF to 150 deg C), typically wasted from industrial processes, geothermal, or solar sources, possessing low exergy (limited ability to do work) and needing specialized systems (like heat pumps or ‘organic Rankine cycles’) for efficient utilization in heating or power generation.
Low growth rate – It refers to a condition in material growth processes, particularly in MOVPE (metal-organic vapour phase epitaxy) and MBE (molecular beam epitaxy) techniques, where the rate of layer formation is intentionally reduced, resulting in improved photo-luminescence properties and improved incorporation of nitrogen in certain alloys.
Low heat cement – Hydration of the cement is exothermic process which liberates high quantity of the heat. This causes the formation of the cracks. A low heat evolution is brought by reducing the C3A (tri-calcium aluminate) and C3S (tri-calcium silicate) which are the compounds evolving the greater heat of hydration and increasing C2S (di-calcium silicate). Rate of evolution of heat of hydration is therefore less and evolution of heat extends over a large period. The limits for the heat of hydration of this cement are 259 joules per gram at 7 days age and 300 joules per gram at 28 days age. It has lower early strength (half the strength at 7 days age and two third the strength at 28 days age) compared with ordinary portland cement (OPC). Its fineness is not less than 3200 square centimeter per gram. Hence in case of low heat cements, the rate of the development of the strength is very low. It is used for the mass construction works. The rise of temperature in mass concrete due to progression in heat of hydration can cause serious cracks. Hence, it is important to limit the rate of heat evolution in this type of construction, by using the low heat cement.
Low hydrogen carbon steel electrodes – These high-quality welding electrodes are coated with low hydrogen iron powders and are used primarily for welding carbon and low alloy steels. The normal tensile strength which welding can have using these electrodes is under 480 mega pascals (MPa). These electrodes are for versatile applications and can be used for welding through all directions. It results in advanced, long-lasting, and non-cracking weld deposits on steel materials. Relatively high-stress welding can also be done using these electrodes.
Low-hydrogen electrode – It is a covered arc welding electrode which provides an atmosphere around the arc and molten weld metal that is low in hydrogen.
Low hydrogen-sodium coatings (EXXX5) – These are the coatings on electrode which contain a high proportion of calcium carbonate or calcium fluoride are called low hydrogen, lime ferritic, or basic type electrodes. In this class of coating, cellulose, clays, asbestos, and other minerals which contain combined water are not used. This is to ensure the lowest possible hydrogen content in the arc atmosphere. These electrode coatings are baked at a higher temperature. The low hydrogen electrode family has superior weld metal properties. They provide the highest ductility of any of the deposits. These electrodes have a medium arc with medium or moderate penetration. They have a medium speed of deposition, but require special welding techniques for best results. Low hydrogen electrodes are to be stored under controlled conditions. This type is normally used with DC power with electrode positive (reverse polarity).
Low hydrogen-potassium coating (EXXX6) – This type of coating is similar to the low hydrogen-sodium coating, except for the substitution of potassium for sodium to provide arc ionization. This electrode is used with alternating current (AC) power and can be used with direct current (DC) power, electrode positive (reverse polarity). The arc action is smoother but the penetration of the two electrodes is similar.
Low hydrogen-potassium coatings (EXXX8) – The coatings in this class of electrodes are similar to the low-hydrogen type EXXX6. However, iron powder is added to the electrode, and if the content is higher than 35 % to 40 %, the electrode is classified as an EXX18.
Low hydrogen-iron powder (EXX28) – This electrode is similar to the EXX18, but has 50 % or more iron powder in the coating. It is usable only when welding in the flat position or for making horizontal fillet welds. The deposition rate is higher than EXX18. Low hydrogen coatings are used for all of the higher-alloy electrodes. By additions of specific metals in the coatings, these electrodes become the alloy types where suffix letters are used to indicate weld metal compositions. Electrodes for welding stainless steel are also the low-hydrogen type.
Low intensity magnetic separators (LIMS) – These separators are designed to recover magnetic material from non-magnetic matter. The separators have modular design with several frames and process tank designs using a common magnetic drum for ease of selection of the best machine for each individual application. Strong magnetic minerals (ferromagnetic) can be processed by these separators. Only very few naturally occurring materials are sufficiently magnetic (i.e., high magnetic susceptibility) to be captured by the relatively low magnetic field of these separators. Examples are, maghemite, magnetite, and pyrrhotite etc. The only mineral with economic importance in the mining industry for separation by the low intensity magnetic separators, is the magnetite ore.
Low-level waste – It consists of nuclear waste which includes metals, soil, building rubble and organic materials, arising principally as lightly contaminated miscellaneous scrap. These are wastes other than those suitable for disposal to landfill, but not normally not exceeding 4 giga-becquerels per ton (GBq/t) of alpha or 12 giga-becquerels per ton of beta / gamma activity. Metals are mostly in the form of redundant equipment or from decommissioning of radioactive / nuclear facilities. Organic materials are mainly in the form of paper towels, clothing and laboratory equipment which have been used in areas where radioactive materials are used, such as research laboratories, and general industry etc. as well as the nuclear industry.
Low level waste repository – It is a central place for long-term storage of the low-level radioactive waste arising from nuclear power stations, research laboratories, and general industry etc.
Low load condition – It means a machine or system operates at a considerably reduced power output, frequently below 30 % to 50 % of its rated capacity, where it is producing much less than it is designed for, leading to issues like poor efficiency, increased wear, and carbon buildup, especially in engines and generators. It is basically the opposite of full load, and while ‘no load’ means zero output, low load involves minimal but still present operation.
Low-loss optical fibre – It is a highly pure glass strand designed to transmit light signals over long distances with minimal signal degradation (attenuation), achieving losses as low as 0.14 decibel per kilo-meter, crucial for high-bandwidth telecom, cloud, and 5G / 6G (fifth generation / sixth generation) networks by reducing need for costly signal repeaters.
Low Mach number flow – It is a fluid dynamics condition where flow speeds are much slower than the speed of sound, typically Mach number less than 0.3, meaning density changes are small but still matter, unlike incompressible flow (Mach number less than less than 0.1) where they are ignored. It is a special limit where fast acoustic waves are decoupled from slower flow dynamics, needing specific numerical methods (like pressure-based solvers) for accurate simulation, especially in applications like combustion or internal flows where density variations are crucial but acoustics are not the focus.
Low mass flux – It is a condition where a small quantity of mass moves through a unit area per unit time, frequently occurring in large pipes or systems with low driving forces (like low pressure / concentration gradients) in engineering, leading to different physical behaviours, such as increased boiling instability in nuclear reactors or different heat transfer characteristics, compared to high mass flux systems. It is basically a low mass flow rate per area, frequently seen in natural circulation systems with big pipes, contrasting with faster, more confined flows.
low-medium viscosity – It describes fluids (liquids, polymers) with moderate resistance to flow, allowing relatively easy, fast flow (low internal friction) for applications like 3D printing resins or efficient lubrication, balancing quick filling / movement with enough body for structural integrity or coating. It is not too sluggish (high viscosity), not too watery (very low), enabling processes like quick mould filling or rapid polymer curing.
Low melting alloys – These are also known as fusible alloys. These are metallic materials which melt at relatively low temperatures, typically below 300 deg C, compared to most common metals. These alloys are frequently composed of combinations of metals like bismuth, tin, lead, indium, and cadmium. Their low melting points make them useful in several applications where lower temperatures are needed, such as soldering, brazing, and creating specific devices and components.
Low-noise block downconverter – It is a device which amplifies and converts signals to a lower frequency band which has lower losses in interconnecting cables.
Low melting point materials – These are substances (metals, alloys, polymers) which liquefy at relatively low temperatures (frequently less than 300 deg C for metals, less than 100 deg C for organics). These materials are important for thermal management, casting, soldering, and energy storage, possessing properties like good thermal conductivity, low volume change upon phase transition, and suitability for low-temp processing.
Low melting point metals – These are metals or alloys which solidify / melt below around 300 deg C, considerably lower than typical metals, enabling processing at lower temperatures for applications like soldering, thermal management, and rapid casting, with examples including gallium, tin, lead, and their alloys (e.g., solder). Their key properties include good thermal conductivity, controllable melting points, and low volume change during phase transition, making them ideal for electronics, heat sinks, and specialized moulds.
Low modulation frequency – It refers to varying a carrier wave’s properties (amplitude, frequency, phase) using an information signal that itself changes slowly, frequently in the low hertz range, to encode data or reduce noise, enabling systems to detect subtle signal changes or capture rhythm in audio, contrasting with high-frequency modulations which shift signals to higher bands for long-distance transmission. It is used in techniques like ‘wavelength modulation spectroscopy’ for precise measurements or to extract rhythm from sound.
Low natural abundance – It means an isotope of an element exists in very small percentages (e.g., deuterium at around 0.01 % of hydrogen, or carbon-13 at around 1 %) in a typical, unenriched natural sample, posing challenges but also offering opportunities for tracing in fields like NMR (nuclear magnetic resonance) spectroscopy where their signals need correction or leverage unique properties. It refers to the condition of an isotope being present in a small percentage within a natural sample, exemplified by 61Ni, which has a natural abundance of 1.14 %.
Low oil temperature control (cold oil switch) – It is a control to prevent burner operation if the temperature of the oil is too low.
Low output capacitance – It refers to the minimal capacitance at the output of a transistor, which is critical for ensuring high-frequency performance and reducing signal distortion, particularly in configurations such as a cascode constant current source (CCS).
Low output resistance (or impedance) – It means a circuit or device which can deliver voltage and current efficiently to a connected load with minimal signal loss, acting more like an ideal voltage source (zero resistance), ensuring stable output voltage, good current driving capability, and reduced signal distortion. It is important for voltage amplifiers and driving speakers. It is the inverse of high resistance, allowing for better power and signal integrity across varying load conditions.
Low oxygen activity – It normally refers to conditions where the concentration or availability of oxygen is below a critical level needed for a specific process, safety standard, or desired material property.
Low-pass filter – It is an electric filter network which passes lower frequencies and blocks higher ones.
low Peclet number – It means Peclet number is less than 1. It indicates that diffusion (or dispersion) dominates over convection in heat / mass transport, meaning fluid movement is very slow or stagnant, and random particle motion spreads things out more than bulk flow does. It indicates that heat / mass transfer is mainly driven by conduction / diffusion rather than advection (bulk fluid movement).
Low-permeability gas reservoir – It is a geological formation holding natural gas, but with extremely small pore spaces and narrow connections (pore throats), severely restricting gas flow, typically having matrix permeabilities below 1milli-darcy to 10 milli-darcies and frequently in the micro-darcy range, making gas extraction challenging and needing advanced stimulation like hydraulic fracturing.
Low permeability reservoirs – These are geological formations, frequently rich in oil or gas, with very low inter-connected pore spaces (pore throats) that restrict fluid flow, typically having rock permeability below 10 milli-darcies to 50 milli-darcies, needing advanced stimulation like hydraulic fracturing to extract resources efficiently. They are characterized by small pores, high capillary pressure, and resistance to fluid movement, making them ‘tight’ formations like shale or certain sand-stones, contrasting with conventional reservoirs.
Low power consumption – It refers to the reduced energy usage of hardware components, achieved through techniques such as power gating and clock gating, which deactivate power supply to inactive elements, fostering energy efficiency in systems like CPUs (central processing unit), and memory technologies.
Low-power electronics – These are devices and circuits engineered to use minimal electrical energy, achieved through techniques like voltage reduction, sleep modes, and optimized circuitry, making them ideal for battery-operated gadgets, wearables, and IoT (Internet of Things) devices by extending battery life and improving energy efficiency without substantial performance loss.
Low power factor – It refers to a condition where the ratio of active power to apparent power is less than unity, indicating the presence of reactive power in the system. This results in a higher requirement for power to perform work than necessary, leading to increased energy costs and potential operational issues in electrical systems.
Low power operation – It refers to the efficient use of minimal electrical current in devices, particularly in portable applications reliant on battery power, with some micro-controllers operating at less than 2 milli-amperes at 5 volts and around 15 micro-amperes at 3 volts.
Low pressure casting – It is a process where molten metal is introduced to the mould by the application of pressure to a hermetically-sealed metal bath forcing the molten metal up through a narrow diameter fill stalk tube from a furnace normally residing below the casting machine, although, there is a version using electromagnetic forces to lift metal into the mould. The process is considered for low to high volumes of castings from 5 grams to 100 grams and normally incorporates the use of iron or steel permanent moulds. Recent developments in sand-moulding technology have made precision sand moulds a viable choice for high-volume, low-pressure casting as well. A wide range of casting core options such as expendable sand and shell cores and mechanical single or multipiece permanent cores are successfully used in the low-pressure process.
Low pressure chemical vapour deposition (LPCVD) – It is a chemical vapour deposition technology which uses heat to initiate a reaction of a precursor gas on the solid substrate. This reaction at the surface is what forms the solid phase material. The process takes place at pressures between 13.33 pascals and 1,333 pascals and temperatures between 200 deg C and 800 deg C. A dedicated shower head which is part of a precursor delivery system is used to introduce the reactants into the chamber. To encourage heterogeneous surface reactions, the shower head and the chamber walls are made colder, while the substrate is made warmer. After the reaction is finished, the by-products are extracted using vacuum pumps as soon as possible. The manufacture of resistors, capacitor dielectrics, MEMS (micro-electro-mechanical system), and anti-reflective coatings are the primary applications for low-pressure chemical vapour deposition.
Low-pressure evaporator – It is a heat transfer device which operates under vacuum or reduced pressure, allowing liquids (like water or refrigerants) to boil and vapourize at much lower temperatures than at atmospheric pressure. It is important in refrigeration (cooling) or desalination (freshwater production) systems to absorb heat efficiently or create fresh water from saltwater. It is typically on the low-pressure side of a system, taking in liquid refrigerant / water and releasing low-pressure vapour, frequently using waste heat for energy.
Low-pressure generator – It refers to systems creating low pressure for processes like plasma etching (using vacuum chambers) or generating specific gases like low-pressure acetylene for welding, frequently involving calcium carbide. It can also describe components in power systems, like a ‘low pressure turbine extracting energy from already used steam, or a component in chillers, all characterized by operating at reduced or below-normal pressures compared to standard systems.
Low-pressure injection moulding – It is a manufacturing process which uses relatively low pressures to inject molten thermoplastic material into a mould, typically ranging from 0.15 megapascals (MPa) to 4 megapascals. It is a specialized technique within traditional injection moulding, designed for delicate parts which cannot tolerate high pressures or temperatures. This method is particularly useful for encapsulating and protecting sensitive electronic components like circuit boards, sensors, and connectors. Instead of the high pressures used in traditional injection moulding, low-pressure injection moulding operates at considerably reduced pressures. This lower pressure helps prevent damage to sensitive components during the moulding process.
Low-pressure laminates – In general, these are laminates moulded and cured in the range of pressures from 2,760 kilo-pascal down to and including pressure got by the mere contact of the plies.
Low-pressure last-stage blade – It is the largest, longest blade in a steam turbine’s final section, designed to extract maximum energy from the low-pressure, high-volume steam before it exits to the condenser, critically determining turbine efficiency, size, and cost, but facing extreme challenges from vibration, centrifugal forces, and wet steam corrosion.
Low-pressure membrane – It is a semi-permeable barrier (like micro-filtration or ultra-filtration used in water treatment which operates at lower pressures (e.g., less than 100 kilo-pascals for RO, reverse osmosis, or even lower for micro-filtration / ultra-filtration) to effectively remove suspended solids, bacteria, and larger particles, focusing on physical separation rather than dissolving contaminants, making them energy-efficient for producing clean water, pre-treating feed for high-pressure systems, or reclaiming waste-water.
Low-pressure permanent mould casting – It uses a gas at low pressure, usually between 20 kilo-pascal to 100 kilo-pascal to push the liquid metal into the mould cavity. The pressure is applied to the top of the pool of liquid, which forces the liquid metal up a refractory pouring tube and finally into the bottom of the mould. The pouring tube extends to the bottom of the ladle so that the liquid metal being pushed into the mould is very clean. No risers are required because the applied pressure forces liquid metal in to compensate for shrinkage. Yields are normally more than 85 % because there is no riser and any metal in the pouring tube just falls back into the ladle for reuse. The vast majority of low-pressure permanent mould castings are from aluminum and magnesium, but some are copper alloys. Advantages include very little turbulence when filling the mould because of the constant pressure, which minimizes gas porosity and dross formation. Mechanical properties are around 5 % better than gravity permanent mould castings. The disadvantage is that cycles times are longer than gravity permanent mould castings.
Low pressure plasma spraying – It is a thermal spray process variation in which the process is carried out under controlled atmosphere conditions. The process is carried out in a vacuum chamber and the thermal spray gun is normally operating in a low-pressure environment of an inert gas, normally argon.
Low-pressure pump – It is a device designed to move fluids (like water or fuel) at lower forces, focusing on high flow rates rather than extreme pressure, typically handling pressures up to around 1,000 kilo-pascals, and used in such application as HVAC (heating, ventilation, and air conditioning), frequently employing centrifugal or diaphragm designs.
Low-pressure separator – It is a three-phase separator designed to separate free water from oil and emulsion, as well as gas from liquid. It is normally referred to as a ‘free-water knock-out’.
Low-pressure steam boiler – Low-pressure steam boiler is a boiler which operates at a pressure not above 100 kilo pascals.
Low-pressure storage tank – It stores substances at a slight internal pressure, typically above atmospheric but not exceeding 100 kilo-pascals, holding liquids with vapour pressures higher than 17 ilo-pascals but below 100 kilo-pascals, like fuels or solvents, and preventing excessive vapour loss or air ingress, unlike atmospheric tanks. They are normally made of steel, frequently cylindrical, and are necessary for volatile materials needing controlled environments.
Low production run – It consists of manufacturing small batches of products, often 10s to 1000s of units (sometimes up to 100,000), focusing on flexibility, customization, and reduced inventory, ideal for prototypes, niche items, or testing new products, characterized by lower tooling costs and faster setup times compared to mass production.
Low-recovery valve – It is a valve design which dissipates a considerable quantity of flow stream-energy because of turbulence created by the contours of the flow path. Hence, pressure downstream of the valve vena contracta recovers to a lesser percentage of its inlet value than is the case with a valve having a more streamlined flow path. Although individual designs vary, conventional globe-style valves normally have low pressure recovery capability.
Low relaxation pre-stressed concrete – It is a high-strength steel strand which has been specially heat-treated to retain its tension over time, with minimal stress loss. This low relaxation property makes it ideal for pre-stressed concrete structures like bridges, buildings, and infrastructure projects where long-term strength and reliability are critical. The treatment, called stabilizing or strain tempering, involves heating the steel while under tension, which increases its resistance to creep and ensures the concrete maintains its compressive force.
Low residual, black foundry busheling – It constitutes 1000 series black carbon steel scrap, with 3 millimeters and above in thickness, size not more than 300 millimeters x 600 millimeters, manganese content is 0.5 % maximum. Other parameters are subject to agreement between the user and the supplier.
Low residual, ductile quality shredded clips – It constitutes shredded black 1000 series carbon steel scrap, with 3 millimeters and above in thickness, minimum average density of 1.2 tons per cubic meter, and manganese content 0.5 % maximum. Other parameters are subject to agreement between the user and the supplier.
Low-residual-phosphorus copper – It is the deoxidized copper with residual phosphorus present in quantities (normally 0.004 % to 0.012 %) normally too small to decrease appreciably the electrical conductivity of the copper.
Low resistive state – It refers to a condition in memristors where the resistance is low, allowing for efficient electrical conduction, and is determined by changes in the width of the insulator layer and the concentration of dopant.
Low-resolution image – It is an image which shows poor-quality and lower detail, frequently resulting from the intrinsic characteristics of certain imaging modalities, such as ultrasound. Low-resolution image has fewer pixels, resulting in less detail, blurriness, and blockiness (pixelation), sacrificing image clarity for smaller file sizes, making them ideal for web / social media but poor for large prints where details get lost. It is characterized by lower DPI / PPI (dots per inch / pixels per inch) and appears indistinct when zoomed in or enlarged. These limitations in resolution make subsequent image processing tasks, like super-resolution, more challenging.
Low rolling resistance – It means a conveyor belt needs less force to move since there is less friction when the belt rolls over idlers. This is achieved through specialized rubber compounds in the belt’s bottom cover which reduce indentation rolling resistance (IRR) which is the resistance created when the belt material is squeezed at the contact points with the idler rolls. Low rolling resistance considerably lower power consumption, saving operating costs. In a vehicle, low rolling resistance refers to a tyre design which minimizes the energy lost as the tyre deforms and reforms while rolling, which needs less effort to move the vehicle and improves fuel efficiency. This is achieved through innovations in tyre construction, shape, tread pattern, and the optimization of rubber compounds and weight.
Low shear strength – It means a material poorly resists forces trying to slide its layers past each other, leading to easy failure, deformation, or breakage under parallel stress, common in brittle things like weak adhesives or loose soil, unlike strong materials which can handle substantial sliding forces before failing. It is defined by a low capacity to withstand shear stress (force per area), frequently because of the weak internal bonds or particle friction.
Low silicon content – It means having a reduced level of silicon (Si) in materials like steel or ferro-alloys, frequently below specific thresholds like less than 3 % for ferro-chromium, less than 0.1 % in some steels, or tailored quantities for special grades, as silicon can affect properties like ductility, magnetism, and inclusion formation, with ‘low’ defined contextually for specific applications like stainless steel (undesirable) against electrical steel (desired up to around 3.5 % for magnetic properties).
Low sliding speed – It refers to the conditions where surfaces in contact move relative to each other at relatively slow velocities, which can still generate considerable heat because of the friction, particularly in applications like fretting with high frequencies and small contact dimensions.
Low-stacking fault energy materials – These are crystalline materials where the energy needed to create a stacking fault is relatively low. This means that the material is more prone to deformation through the movement of partial dislocations and twinning, rather than full dislocations.
Low strain hardening – It describes a material’s reduced ability to get stronger when plastically deformed, frequently since it already has several internal defects (dislocations) or specific micro-structures (like fine particles) which hinder further dislocation movement, leading to faster strengthening but often less ductility or localized failure compared to materials with strong strain hardening. It means the material’s strength increases slowly or saturates quickly with strain, making it less able to stretch before cracking, as seen in heavily processed materials.
Low-strength steel – It is a type of steel with a low carbon content and limited alloy elements, making it more malleable and less strong than high-carbon or high-alloy steels. It includes common materials like mild steel, which has low strength but high ductility and is cost-effective and easy to work with for a wide range of applications like construction and machinery.
Low-stress abrasion – It is a form of abrasion in which relatively low contact pressures on the abrading particles or protuberances cause only fine scratches and microscopic cutting chips to be produced.
Low stress grinding (LSG) – It is a process in which materials are ground in a non-abusive manner. Special refined grinding equipment is utilized. The process takes place with equipment using highly accurate temperature controlled hydrostatic bearings. Low stress grinding would be an effective method for producing aerospace bearing surfaces as well as precision gauging and fixtures. Low stress grinding uses wheel speeds of about 20 metres per second and can normally be done on conventional grinding machines in any of the grinding modes. Majority of the surface grinding operations use wheel speeds of 30 metres per second to 35 metres per second.
Low-stress scratching abrasion – It is a type of wear where a hard surface scratches a softer one with low contact pressure, causing material to be removed through micro-cutting and micro-plowing without crushing the abrasive particles. This process results in surface scratches with minimal sub-surface deformation. It differs from high-stress abrasion, where the abrasive particles are crushed by high contact pressure, leading to more severe damage.
Low styrene emission (LSE) resins – These resins are produced by adding vapour suppressant additives to the resin formulation. These additives form a film over the resin surface once the moulding is left to stand.
Low surface tension – It refers to a property of liquids which allows them to atomize into smaller droplets more efficiently and improves their wetting ability on substrates with low surface energy, such as plastics or fluorinated coatings.
Low-sulphur diesel – It is frequently called ‘ultra-low sulphur diesel’. It is a cleaner diesel fuel with drastically reduced sulphur content, typically 15 parts per million (ppm) or less, compared to older fuels (up to 3,000 parts per million), enabling advanced emission controls, cleaner engine operation, reduced soot, and less air pollution like acid rain. This cleaner fuel is necessary for modern diesel engines and is mandated in several regions for highway and off-road use to lower harmful emissions.
Low sulphur heavy stock (LSHS) – It is a residual fuel processed from indigenous crude oil. This fuel is normally used in lieu of furnace oil in the same applications where the furnace oil is suitable. The main difference with low sulphur heavy stock and furnace oil is the higher pour point, higher calorific value and lower sulphur content in low sulphur heavy stock as compared to furnace oil. Since low sulphur heavy stock is having pour point higher than the ambient temperature, it needs specially designed oil handling systems such as steam traced or electrically traced storage tanks, pipelines, pumps and filters. Low sulphur heavy stock is handled hot at all stages and is maintained at 75 deg C. Special care is also taken so that no ‘boil over’ of low sulphur heavy stock takes place in the storage tank. The main advantage in the use of low sulphur heavy stock lies is its low sulphur content.
Low temperature – The term ‘low temperature’ is typically defined in terms of boundaries, where metallurgical processes change. One general definition of ‘low-temperature’” is ‘T’ is less than 0.5 ‘Tm’ where ‘T’ is the exposure temperature, and ‘Tm’ is the melting point of a material (both given on the absolute temperature scale, K). For several structural metals, another definition of low temperature Is ‘T’ is less than 0.3 ‘Tm’, where recovery processes are not possible in metals and where the number of slip systems is restricted. For these definitions, room temperature (293 K) is almost always considered a low temperature for a metal with a few exceptions, such as metals which have melting temperatures below 200 deg C (indium and mercury). In a structural engineering sense, low temperature can be one caused by extreme cold weather. For several applications, low temperature refers to the cryogenic temperatures associated with liquid gases. Gas liquefaction, aerospace applications, and super-conducting machinery are examples of areas in engineering which need the use of materials at very low temperatures. The term cryogenic typically refers to temperatures below 150 K. Service conditions in superconducting magnets that use liquid helium for cooling are in the 1.8 K to 10 K range.
Low temperature application – It refers to using reduced temperatures for thermal management, process efficiency, or material behaviour, spanning from standard refrigeration (around 0 deg C) to cryogenics (below -150 deg C) in fields like electronics cooling, gas liquefaction, and energy-efficient heating / cooling systems, all focusing on optimizing performance or creating new states of matter at cooler conditions.
Low-temperature catalyst – It is a substance which accelerates chemical reactions efficiently at considerably reduced temperatures (frequently below 150 deg C or 300 deg C), enabling processes with lower energy consumption, reduced by-product formation, and higher sustainability, by facilitating reactions which are kinetically slow at ambient conditions, like specialized catalysts for emissions control or gas shift reactions.
Low-temperature collector – It is a type of solar thermal device designed to heat fluids (like water or air) to relatively low temperatures, typically under 45 deg C, mainly for non-intensive uses such as ventilation air, or for specific industrial processes like drying and preheating of materials, frequently featuring simpler, sometimes unglazed, designs which maximize heat absorption without needing high concentrations of sunlight.
Low-temperature deformation – It refers to the plastic deformation of materials at relatively low temperatures. It frequently involves mechanisms like grain-scale crystal plasticity, rotation, fracture, and pressure solution. It is characterized by the material retaining its primary texture while undergoing deformation through several crystal-plastic features like twin lamellae and deformation bands. This type of deformation is influenced by factors such as temperature, strain rate, and the material’s inherent properties. Low-temperature deformation often results in uneven strain distribution within the material, with some areas deforming more than others.
Low-temperature drying – It is a technique which removes moisture from materials (like sludge) using minimal heat, frequently below 45 deg C, or even sub-zero, to preserve their quality contrasting with high-temperature methods which dry faster but degrade sensitive products, with techniques including heat pumps, desiccants, or vacuum to control humidity and temperature.
Low-temperature ductility – It is a material’s capacity to deform considerably (stretch, bend) without fracturing when tested at reduced temperatures, contrasting with its tendency to become brittle (low ductility) as it cools, a shift frequently marked by the ‘ductile-to-brittle transition temperature’ (DBTT), crucial for applications in cold environments like shipbuilding or pipelines.
Low-temperature Fischer-Tropsch – It is a catalytic process converting synthesis gas (carbon mono-oxide + hydrogen) into high-quality liquid hydro-carbons, mainly diesel and waxes, operating at milder temperatures (around 200 deg C to 250 deg C) using cobalt or iron catalysts, which favours longer-chain molecules and transport fuels over lighter products like methane, differing from ‘high-temperature Fischer-Tropsch which yields more gasoline and olefins.
Low-temperature forged material – It is a metal product which is shaped by forging below its recrystallization temperature, resulting in increased strength and hardness but also making it more resistant to brittle fracture in sub-zero environments. It is a type of metal product created by applying compressive force at temperatures below hot forging (typically room temperature or slightly above) to increase strength and toughness, making it ideal for applications exposed to low temperatures, such as pipelines for liquefied gas.
Low-temperature growth – It is a technique used in epitaxial processes which occurs at temperatures typically around 600 deg C to 850 deg C, aimed at minimizing dopant diffusion and the formation of dislocations, particularly in the fabrication of hetero-junction devices and advanced structures. This method is technically challenging because of the difficulty in achieving clean surfaces and the complex kinetics of dopant incorporation at these lower temperatures.
Low-temperature heat – It is the thermal energy available at modest temperatures, normally below 100 deg C to 150 deg C, frequently waste heat from industries or renewables like geothermal / solar, used for efficient heating, cooling, or power through systems like heat pumps, district heating, or radiant floor heating, improving energy efficiency.
Low-temperature heat demand – It refers to the requirement for thermal energy at relatively moderate temperatures, typically below 100 deg C (or sometimes up to 200 deg C), used for applications like space heating, drying, pre-heating water, and some industrial processes, frequently sourced sustainably from waste heat or renewables, reducing reliance on high-grade energy for less demanding tasks. This demand focuses on utilizing energy efficiently, frequently in systems like underfloor heating (around 45 deg C) or by capturing ubiquitous, lower-grade heat sources.
Low-temperature heat source – It provides thermal energy below 200 deg C (frequently less than 60 deg C or even less than 45 deg C), typically from wasted industrial – It heat, geothermal, or solar, which is too cool for direct use in conventional systems but valuable for sustainable heating, cooling (like heat pumps), and power generation through ‘organic Rankine cycles’ (ORC) or absorption chillers. These sources are important for improving energy efficiency by utilizing ‘low-grade’ energy which is otherwise lost, often powering district heating or specialized systems.
Low-temperature nitriding – It is a thermo-chemical surface treatment, normally at 350 deg C to 450 deg C, which diffuses nitrogen into steel surfaces to create a hard layer (S-Phase) for wear resistance, but crucially does so below temperatures where detrimental chromium nitrides form, hence preserving or improving corrosion resistance, especially in stainless steels. This process super-saturates the metal’s surface with nitrogen, causing lattice expansion for increased hardness without the brittle compounds of traditional nitriding, frequently using plasma or gas methods.
Low-temperature processing – It is a set of industrial methods which use low temperatures to preserve, manufacture, or alter materials. This process involves removing thermal energy, frequently through refrigeration or freezing, to slow down or prevent physical deterioration, extend shelf life, and sometimes achieve specific properties. It can also refer to manufacturing processes which use lower production temperatures to save energy and improve material stability.
Low-temperature production – It refers to industrial processes using considerably reduced heat, frequently 200 deg C less than traditional methods, to save energy, enable new materials (like certain polymers or ceramics), improve stability, to advanced material synthesis, with specific definitions varying by industry but normally focusing on energy efficiency and novel product properties.
Low temperature sensitization – It normally refers to a heat treatment below 500 deg C. However, a low temperature sensitization heat treatment of 500 deg C per 24 hours has become common, and frequently, low temperature sensitization (if not otherwise defined) means 500 deg C/24 hours.
Low-temperature shift reactor – It is a catalytic reactor, normally the second stage in a water-gas shift (WGS) process, which uses a copper-based catalyst (CuO / ZnO / Al2O3) at lower temperatures (around 200 deg C to 260 deg C) to convert remaining carbon mono-oxide (CO) and steam into more hydrogen and carbon di-oxide, considerably boosting hydrogen yield and purity for applications like ammonia or fuel production.
Low temperature steels – These are steels which are especially suited for extremely cold climates and for the handling of liquefied gases such as oxygen, nitrogen, propane, anhydrous ammonia, carbon di-oxide, and ethane.
Low-temperature testing – It is an engineering process which evaluates how materials, components, or systems perform, function, and maintain integrity in cold or freezing environments, checking for issues like brittleness, contraction, or operational failure to ensure reliability in cold climates or extreme conditions, frequently using standards like IEC 60068-2-1.
Low-temperature toughness – It is a material’s ability to resist fracture and absorb energy under stress at cold temperatures, describing how well it maintains ductility (toughness) rather than becoming brittle as temperature drops, a critical property for steels in cold environments, influenced by micro-structure, grain size, and alloying elements like nickel. Several materials, especially body-centered cubic (BCC) metals like steel, undergo a ductile-to-brittle transition, meaning they shift from tough, sliding failure to brittle cleavage failure as they cool.
Low-temperature waste heat – It is excess heat from industrial processes, typically below 230 deg C, frequently too low for traditional recovery but valuable for new tech like ‘organic Rankine cycles’ (ORC) or absorption chillers to produce power, heating, or cooling, improving energy efficiency and reducing emissions.
Low tensile strength – It means a material cannot withstand much stress when being pulled or stretched before it breaks. It describes materials which are weak under tension, making them prone to breaking when subjected to pulling forces, unlike high-tensile strength materials like steel. For example, concrete has low tensile strength and needs steel reinforcement to handle tension in structures like bridges and beams, which is why it needs reinforcement to handle tension in structures like bridges and beams.
Low thermal conductivity – It refers to the property of a material which minimizes heat transfer, which is necessary for maintaining a large thermal gradient and improving trans-membrane water vapour transport. It is influenced by factors such as the material type, thickness, and porosity of the membrane, with polymeric membranes normally showing lower thermal conductivity than ceramic membranes.
Low thermal diffusivity – It means a material heats up and cools down slowly, indicating it transfers heat inefficiently since heat energy spreads slowly through it, making it a good insulator or thermal buffer. It signifies a material which absorbs heat (because of high heat capacity) rather than rapidly conducting it away, creating larger temperature gradients within itself.
Low velocity impact damage – Low velocity impact occurs at velocities below 10 metres per seconds and is likely to cause some dents and visible damage on the surface due to matrix cracking and fibre breaking, as well as delamination of the material.
Low viscosity lubricant – It is a thin, fluid oil which flows easily, offering reduced friction, better heat transfer, and lower energy loss in applications like modern engines, but provides less load-bearing protection than thicker oils. Its low resistance to flow makes it ideal for fast-moving parts and cold starts, but its thin film needs careful application to prevent metal-to-metal contact under heavy loads, frequently seen in hydraulic systems.
Low volatile coal – It is a higher-rank coal with a low percentage of volatile matter (VM), meaning it releases fewer gases and smokes less when heated, making it more energy-dense, harder to ignite, and frequently used in specific industrial processes like coking or for its high heat content in power generation, distinguishing it from high-volatile coals which ignite easily but produce more smoke.
Low-volume production – It is manufacturing products in small quantities, typically from a few dozen to a few thousand units, bridging the gap between rapid prototyping and mass production. It is frequently used for specialized items, market testing, or custom parts where flexibility, speed, and precision outweigh mass-scale cost savings, relying on methods like CNC (computer numerical control) machining or additive manufacturing for quick setup and customization.
Low water cut-off – It is a safety device which shuts off the boiler / burner in the event of low water, preventing pressure vessel failure.
Low wear rate – It means minimal material loss from surfaces in relative motion, characterized by low coefficient of friction and fine, stable debris, indicating good wear resistance under specific operating conditions like lubrication or specific pressures, contrasting with high wear rates where surfaces become rough, leading to component failure. It’s quantified by specific wear rate [volume loss / (load x distance), where smaller K values (like below 10 to the power – 10) signify excellent resistance, frequently achieved through mild wear mechanisms like plastic flow or oxidation rather than brittle fracture.
Low wind speed – It consists of periods when the mean wind speed at 10 meters above ground level is less than 2 meters per second, which is important for air pollution dispersion because of weak dispersion conditions. Low wind speed is frequently associated with stable atmospheric conditions, such as high atmospheric pressure, and can lead to higher pollution severity.
L-radiation – It is the characteristic X-rays produced by an atom or ion when a vacancy in the ‘L’ shell is filled by an electron from another shell.
L-section – It is a structural shape with a cross-section which resembles the capital letter ‘L’. This profile, also called an L-angle, has two legs joined at a right angle and is normally used in construction for beams, columns, and bracing members.
L-series – It is the set of characteristic X-ray wave-lengths making up L-radiation for the various elements.
L shell – It is the second shell of electrons surrounding the nucleus of an atom, having electrons with principal quantum number 2.
LSI (large-scale integration) circuits – These are integrated circuits (ICs) from the early 1970s which packed thousands of transistors (around 1,000 to 10,000) onto a single chip, enabling complex functions like early micro-processors (e.g., Intel 4004) and offering better speed and cost than earlier MSI (medium-scale integration) chips, representing a major step towards modern highly dense integrated circuits like VLSI (very large-scale integration).
Lube – It is short for lubricant.
Lube, high – It means that the lubricant limit exceeds the maximum agreed-upon limit measured in weight per unit area.
Lube, low – It is the failure of the lubricant to meet the agreed-upon minimum limit measured in weight per unit area.
Lube oil – It is a specialized oil used to reduce friction, heat, and wear between moving mechanical parts. It is also known as lubricating oil or simply ‘lube’, and it serves to cool, clean, and protect machinery, which extends its lifespan and ensures smooth operation. Lube oil can be derived from mineral (crude oil), synthetic, or vegetable sources, and frequently contains additives to improve its performance.
lube oil system – It is a machine’s circulatory network which delivers oil to critical moving parts, creating a protective film to reduce friction, prevent wear, cool components, clean debris, and protect against corrosion, typically using pumps, filters, coolers, and a reservoir to manage oil flow and cleanliness for equipment like turbines, engines, and compressors.
Lube seats – These are seats which are equipped with a lubricant injecting system.
Lubricant – It is a substance interposed between two surfaces in relative motion for the purpose of reducing the friction or wear between them. This definition implies intentional addition of a substance to an interface. However, species such as oxides and tarnishes on certain metals can also act as lubricants even though they are not added to the system intentionally. Lubricant is also a material applied to dies, moulds, plungers, or work-pieces which promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part. It is also a substance mixed with a powder to facilitate compacting and subsequent mould ejection of the compact, frequently a stearate or a proprietary wax. It can also be applied as a film to the surfaces of the punches or the die cavity wall such as spray coating. In composites, it is a material added to most sizings to improve the handling and processing properties of textile strands, especially during weaving.
Lubricant additive – It is a chemical compound (organic or inorganic) blended into base oils to boost performance, adding new functions or improving existing properties like wear resistance, oxidation stability, and detergency, allowing lubricants to protect modern machinery in demanding conditions, with concentrations varying from trace quantities to 30 %. These necessary components create specialized lubricants (like engine oils, hydraulic fluids) which resist breakdown, reduce friction, prevent corrosion, and handle extreme temperatures, extending equipment life.
Lubricant application – It is the process of introducing a substance, such as oil or grease, between two moving surfaces to reduce friction, wear, and heat. This process ensures smoother operation, increases efficiency, and prolongs the life of machinery by keeping surfaces from direct contact and preventing damage from heat and foreign particles.
Lubricant breakdown – It is the degradation of a lubricant’s properties, leading to a loss of its ability to function effectively. This can occur through various mechanisms, such as (i) oxidation, which chemically degrades the oil, (ii) film breakdown, where the protective layer between surfaces fails, or (iii) physical breakdown caused by contamination, extreme temperatures, or shear forces that change its viscosity.
Lubricant bulk property – It describes its general physical characteristics, like compressibility, density, viscosity (flow resistance), flash points / fire points (flammability), and pour points / cloud points (low-temperature flow), which define its performance, stability, and suitability for specific applications under varying conditions, ensuring it forms protective films and functions effectively. These are not just about reducing friction but encompass its overall behaviour in a system, from how easily it pours to how it handles heat and pressure, ensuring proper lubrication.
Lubricant compatibility – In tribology, it is a measure of the degree to which lubricants or lubricant components can be mixed without harmful effects such as formation of deposits.
Lubricant dilution – It is the reduction of lubricant viscosity and performance because of the mixing of fuel or other contaminants. It is the thinning of engine oil by unburned fuel (gasoline or diesel) mixing in the crankcase, which lowers the oil’s viscosity, reduces its film strength, increases friction, and leads to accelerated engine wear and potential damage. It is a common contamination issue in internal combustion engines, frequently caused by incomplete combustion during cold starts, injector problems, or excessive idling, and is a critical concern in oil analysis.
Lubricant film – It is a thin layer of lubricant which separates solid surfaces in motion, preventing direct contact and reducing friction. Its thickness is influenced by factors such as viscosity, applied load, and sliding velocity, and it exists in different lubrication regimes, including hydrodynamic, mixed, and boundary lubrication.
Lubricant flow rate – It is the volume or mass of lubricant moving through a system per unit of time, measured in units like litres per minute or kilograms per hour. It is important for proper lubrication, with formulas relating it to velocity (Q = A x v) and influenced by pressure, pipe area, and fluid properties, ensuring adequate lubrication film and heat dissipation.
Lubricant residue – It is the carbonaceous residue resulting from lubricant which is burned onto the surface of a hot forged part.
Lubricant viscosity – It is a lubricant’s resistance to flow or internal friction, basically its ‘thickness’ or ‘thinness’, crucial for creating a protective film between moving parts to reduce wear. High viscosity means thick, slow-flowing lubricating oil for heavy loads, while low viscosity means thin, fast-flowing lubricating oil for lighter, faster applications, with viscosity normally decreasing as temperature rises.
Lubricate – It is the application of lubricant for lubrication.
Lubricated concentrated contacts – These refer to the conditions at the interface between two solid surfaces where they meet over a very small, concentrated area, and a lubricant is present. These contacts typically occur in machine elements such as (i) rolling element bearings, (ii) gears, (iii) cams, and (iv) wheels on a rail. In a lubricated concentrated contact, the high pressure generated in the contact zone causes the materials to deform elastically and considerably increases the lubricant’s viscosity, a phenomenon known as elasto-hydrodynamic lubrication (EHL). The behaviour of lubricated concentrated contacts is studied to understand different lubrication regimes (elasto-hydrodynamic lubrication, mixed lubrication, boundary lubrication) and to predict friction and wear, which are critical for the design and durability of machinery.
Lubricated friction – It is characterized by the presence of a thin film of the pressurized lubricant (squeeze film) between the two moving surfaces. The ratio of the squeeze film (oil film) thickness to the surface roughness determines the type of the lubrication regime.
Lubricated wear – It is the gradual loss of material from surfaces in relative motion which are separated by a lubricant, occurring under conditions where the lubricant film is not perfect (mixed or boundary lubrication), involving complex interactions between the fluid, additives, and surfaces, leading to phenomena like surface fatigue, material transfer, and chemical reactions, even with lubrication present. While lubrication reduces overall wear considerably by separating surfaces, it introduces unique failure modes and complicates wear prediction compared to dry contacts.
Lubricating – It is the mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity. It is also applying a lubricant to die walls and / or punch surfaces.
Lubricating oils – They are made from the more viscous portion of the crude oil which remains after removal by distillation of the gas oil and lighter fraction. The chemical structure of lubricating oils contains (i) hydrocarbons of the crude oils which consist of namely paraffinic components, (ii) naphthenic components, (iii) aromatic components, and (iv) non hydrocarbon components. The classifying of hydrocarbon as paraffinic, naphthenic and aromatic groups which are normally used for characterizing the base oil is not to be taken as absolute but as an expression of the predominating chemical tendencies of the base stocks.
Lubrication – The principle of supporting a sliding load on a friction reducing film is known as lubrication. The main purpose of lubrication is to reduce wear and heat between the contacting surfaces in relative motion. While wear and heat cannot be completely eliminated, they can be reduced to negligible or acceptable levels. Other purposes of the lubrication include (i) reduce friction, (ii) reduce oxidation and prevent corrosion, (iii) disperse contaminants, (iv) act as a sealant against dust, dirt, and water, (v) transmit mechanical power in hydraulic fluid power applications, and (vi) provide insulation in the transformer applications. In powder metallurgy, it is mixing or incorporating a lubricant with a powder to facilitate compacting and ejecting of the compact from the die cavity. It is also, applying a lubricant to die walls and / or punch surfaces.
Lubrication fluid – It is a substance, typically a liquid like oil, introduced between moving surfaces to reduce friction, wear, and heat, preventing direct metal-to-metal contact, thereby ensuring smooth, efficient operation and extending machinery life by forming a protective barrier which also carries away contaminants and prevents corrosion. These fluids work by creating a film, but can also include semi-solids (greases) or even solids, with their performance depending heavily on viscosity and additives.
Lubrication force – It is a hydrodynamic force arising from the pressure built up in a thin fluid film squeezed between two approaching or moving solid surfaces, preventing direct contact and controlling friction and wear, basically acting as a repulsive force which resists rapid closure of the gap, critical in fluid-solid systems like particle collisions or bearings. It is described by fluid viscosity and relative surface motion, frequently leading to the ‘Stokes Paradox’ where infinite force seems to prevent contact, though surface roughness and other factors modify this in reality.
Lubrication mode diagram (LMD) – It is a graphical representation used in tribology to show the different regimes of lubrication which occur between two moving surfaces, typically as a function of operating conditions like speed, load, and lubricant viscosity.
Lubrication modes – These modes are also known as lubrication regimes. These modes describe the different ways in which a lubricant film separates or fails to separate moving surfaces, influencing friction and wear. The three main lubrication modes are boundary lubrication, mixed lubrication, and full-film (or fluid-film) lubrication. Each mode is characterized by the degree of separation between the surfaces and the dominant mechanisms of friction and wear.
Lubrication parameters – These parameters define the conditions of contact between moving surfaces, mainly focusing on the lubricant’s ability to separate them, with key parameters including viscosity, film thickness, and surface roughness, which combine to determine the lubrication regime (hydrodynamic, mixed, boundary) and influence friction and wear, alongside applied load and speed. The lubrication parameter, a ratio of film thickness to roughness, helps classify these regimes, while material properties like elastic modulus (E) also play a role.
Lubrication regimes – These are the ranges of operating conditions for lubricated tribo-systems which can be distinguished by their frictional characteristics and / or by the manner and quantity of separation of the bearing surfaces.
Lubrication system – It is a systematically designed system tailored to apply lubricants to crucial equipment components, such as bearings and chains, mitigating friction and preventing premature wear. Rigorous maintenance practices are critical to uphold the optimal performance of the lubrication system, ensuring prolonged conveyor efficiency.
Lubrication technique – It is the specific method of introducing a friction-reducing substance (lubricant like oil, grease, or solid film) between moving surfaces to minimize wear, lower friction, dissipate heat, and prevent corrosion, ensuring smooth, efficient operation of machinery and components. These techniques vary from simple oiling to complex systems like hydrodynamic or grease lubrication, focusing on maintaining a protective film between surfaces.
Lubrication type – It refers to the method or classification of materials used to reduce friction, wear, and heat between moving surfaces, categorized by the lubricant’s physical state (liquid oil, semi-solid grease, solid powders / coatings, or gas) and the specific mechanism of surface separation, such as full-film (hydrodynamic, elasto-hydrodynamic), mixed, or boundary lubrication. These types dictate how effectively surfaces are separated and protected, crucial for machinery’s lifespan and efficiency.
Lubricator – it is a device which adds controlled quantities of lubricant to a fluid power system.
Lubricious (lubricous) – It is relating to a substance or surface condition which tends to produce relatively low friction.
Lubricity – It is the ability of a lubricant to reduce wear and friction, other than by its purely viscous properties.
Lubricity improver – It is a fuel additive, typically fatty acids or esters, which restores lubrication in low-sulphur fuels (like diesel) by forming a protective film on metal parts (pumps, injectors) to reduce friction, prevent wear, and extend component life, addressing the loss of natural lubrication from sulphur removal.
Luder bands – They are also known as Luder lines or stretcher strain marks. They become visible after press forming of a sheet and have a typical ‘flame-like’ pattern. This surface pattern in most applications is unacceptable for visible parts. The phenomenon is well known in most steels and in certain aluminum alloys. Luder bands can easily be detected with a simple tensile test. Materials which are prone to form Luder bands during press forming always show a ‘yield point elongation’ or ‘Luder strain’ in the stress–strain curves obtained in a tensile test. The reason for these Luder strains is the pinning of dislocations by carbon atoms in steel or by substitutional atoms in aluminum. In steel, the effect can be eliminated by giving the skin pass rolling or by roll leveling (bending/unbending). This liberates the dislocations from their pinning points. In aluminum, the effect can be avoided by grain size control (a grain size of above 10 micrometers to 15 micrometers is needed).
Luders front – It is the boundary between the still-elastic and the plastically deforming regions of a material undergoing discontinuous yielding during a tensile test. This phenomenon typically occurs in certain metals, such as low-carbon steel, after they are strained beyond their elastic limit.
Luders lines – These are elongated surface markings or depressions in sheet metal, frequently visible with the unaided eye. Luders lines are formed along the length of sheet metal or a tension sample at an angle of around 45-degree to the loading axis. These are caused by localized plastic deformation. These result from discontinuous (inhomogeneous) yielding. These are also known as Luders bands, Hartmann lines, Piobert lines, or stretcher strains.
Ludwik equation – It is a mathematical model which describes a material’s work hardening (or strain hardening), expressed as S = Sy + K x (‘e’ to the power ‘n’). It is a modification of the Hollomon equation which includes the material’s yield stress (Sy) as a separate term, in addition to the strength coefficient (K), true plastic strain (e), and the strain hardening exponent (n). This makes the Ludwik equation more accurate for some materials, especially at low strains, since it accounts for the initial stress needed to start plastic deformation.
Luffing and slewing stacker – It is a type of material handling machine used to pile bulk materials, like coal or ore, into stockpiles. It utilizes two main movements namely (i) luffing, which is the vertical raising and lowering of the boom, and (ii) slewing, which is the horizontal rotation of the boom. These movements allow the stacker to distribute material across a wide area and build stockpiles with specific shapes and sizes. Luffing movement is typically achieved by hydraulic cylinders or a winch system. It allows the stacker to adjust the height of the boom, which in turn controls the height of the material pile. Slewing movement involves rotating the entire boom structure around a central axis. This allows the stacker to discharge material in different directions, enabling the formation of different stockpile shapes and the ability to switch between different stockpile locations. In essence, a luffing and slewing stacker combines vertical and horizontal movement capabilities to efficiently and precisely distribute material in a designated area.
Luffing conveyor – It is an adaptable conveyor system featuring an adjustable conveyor belt angle, accommodating changes in elevation. Periodic inspections are indispensable to uphold the precise luffing adjustments and preemptively address any issues related to material flow, safeguarding the conveyor’s overall functionality.
Luffing pulley – It is a specialized pulley crafted to regulate the conveyor belt angle in a luffing conveyor system. Regular checks are imperative to preserve proper functionality, preventing misalignments that could disrupt the conveyor’s seamless operation.
Luffing stacker – It is a type of bulk material handling machine which utilizes a luffing mechanism (vertical movement) to raise and lower its boom, enabling it to stack materials in a specific pattern on one side of a conveyor. This contrasts with a slewing stacker, which can rotate its boom to stack on both sides of the conveyor. Luffing stackers are known for their simple structure and cost-effectiveness, particularly when stockpiling on only one side of the conveyor.
Lug – It consists of any projection, like an ear, used for supporting or grasping.
Luggin probe – It is a small tube or capillary filled with electrolyte, terminating close to the metal surface under study, and used to provide an ionically conducting path without diffusion between an electrode under study and a reference electrode.
Lug seal – It refers to a sealing mechanism, frequently used in electrical connectors, where a metal or plastic lug (a projecting piece) engages with a corresponding groove or thread to create a secure and reliable seal.
Lumen – It is the SI (International System of Units) unit of luminous flux, the energy of visible light.
luminance – It is the photometric measure of the perceived brightness of a surface from a specific viewing angle, representing the amount of light emitted, transmitted, or reflected from a unit area of that surface into a given solid angle. It is defined as the ratio of luminous intensity to the projected area perpendicular to the viewing direction, with the standard unit of candela per square meter, also known as nits. This makes it a key metric for fields like display technology, lighting design, and illumination engineering.
Luminescence property – It is a material’s ability to emit light (photons) after absorbing energy from an external source, not from heat, involving electrons moving to higher energy states and then releasing that energy as light as they return to their ground state, seen in things like glow sticks (chemi-luminescence) or UV (ultra-violet)-lit signs (photo-luminescence).
Luminosity – It is an absolute measure of radiated electro-magnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In SI (International System of Units) units, luminosity is measured in joules per second, or watts.
Luminous efficacy – It measures how well a light source converts power into visible light, measured in lumens per watt. A higher luminous efficacy means a light is more efficient, producing more light for less energy consumption. This is a key factor for evaluating energy-saving lighting devices like LEDs (light emitting diode), which have high luminous efficacies.
Luminous efficiency – It is a measure of how well a light source produces visible light, expressed as a ratio of luminous flux (in lumens) to power consumption (in watts). A higher luminous efficiency, measured in lumens per watt, means a light source uses less energy to produce the same quantity of light, leading to higher electricity savings. It is calculated by dividing the total luminous flux (output) by the total power input.
Luminous flux – It is the measure of power emitted by a light source, frequently quantified in lumens, which indicates the perceived brightness of the light. It differentiates between the energy consumed by a light bulb (wattage) and the actual brightness emitted (lumens).
Luminous intensity – It is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI (International System of Units) unit of luminous intensity is the candela, which is a SI base unit.
Lump – It is a piece of something hard or solid, usually without a particular shape.
Lumped approach – It is also known as ‘lumped parameter analysis’. It is a simplification method in engineering where a complex body or system is treated as a single, uniform ‘lump’ or element, ignoring internal variations (like temperature gradients) to simplify analysis, especially for unsteady processes. It works when internal resistance to heat / energy flow (conduction) is much smaller than external resistance (convection), meaning the entire body’s temperature changes uniformly over time, not space. The core idea is assuming the object’s temperature is uniform at any instant, making it a function of time only, not position.
Lumped-parameter model – It is a mathematical model in which the distributed properties of physical quantities are replaced with their lumped equivalents. When a problem can be analyzed in terms of a finite number of discrete elements, it can be expressed by ordinary differential equations. To describe the more realistic case of distributed parameters having several values spread over a field in space needs the use of partial differential equations.
Lumped parameters – It describes an electrical network where the circuit elements are small compared to the wave-lengths of the signals passing through it.
Lumps – These are the defects in porcelain enamel caused by coarse enamel particles, spitting of guns, or falloff of accumulation on guns.
Lump size – It is the maximum dimensions of material particles which a conveyor can efficiently handle. Regular assessments are necessary for ensuring the conveyor’s compatibility with the specific lump size of materials, preventing potential challenges and optimizing material handling efficiency.
Lump sum contract – It is also known as a fixed-price contract. It is an agreement where a contractor agrees to complete a project for a predetermined, fixed price. This means the client knows the total cost upfront, and the contractor bears the risk of any cost overruns.
Lumpy zone – It is a zone in the blast furnace. It is also known as stack zone. In this zone, coke and ore particles make a stratified descent down the furnace and indirect reduction takes place.
Lurgi dry ash gasifier – It is a pressurized, fixed-bed reactor which converts crushed, non-caking coal into syngas (synthesis gas) using steam and oxygen / air at high pressure, operating at temperatures below the ash melting point to remove ash as a dry solid, unlike its slagging counterparts. This counter-current process heats coal from the top, gasifies it with rising steam / oxygen, and removes dry ash from the bottom, producing a gas rich in methane.
Lurgi process – It is a large-scale, pressurized, dry-ash coal gasification method that converts non-caking coal into synthetic natural gas (SNG) by reacting it with steam and oxygen in a moving bed, producing a high-methane gas suitable for pipelines, though it creates complex byproducts needing extensive cleaning. It operates in zones of pyrolysis, gasification, and combustion within a vertical kiln, removing ash as dry solid.
Lusec – It is a unit of flow rate which is equal to 0.133 pascal cubic meter per second.
Lustre – Lustre is gentle shining light which is reflected from a surface, e.g., from polished metal. It is also a physical property which is used to help identify minerals. Lustre describes how a mineral’s surface reflects light and how the interior of the mineral can refract or bend light. Some minerals have a metallic lustre while some other have a non-metallic lustre.
Lustre finish – It is a bright, as-rolled finish, produced on ground metal rolls. It is suitable for decorative painting or plating, but normally is to undergo additional surface preparation after forming.
Lutetium (Lu) – It is a chemical element having atomic number 71. It is a silvery white metal, which resists corrosion in dry air, but not in moist air. Lutetium is the last element in the lanthanide series, and it is traditionally counted among the rare earth elements; it can also be classified as the first element of the 6th-period transition metals. Lutetium metal is slightly unstable in air at standard conditions, but it burns readily at 150 deg C to form lutetium oxide. The resulting compound is known to absorb water and carbon di-oxide, and it can be used to remove vapours of these compounds from closed atmospheres.
Luting – It is the use of a specialized compound (luting cement or sealing compound) to seal joints, fill voids, or mask areas in high-temperature industrial processes. These materials are designed to withstand extreme heat and prevent the ingress of molten metal into unwanted spaces during casting or relining, such as in white metal bearings.
Lyapunov function – It is a scalar function which determines the stability of a dynamical system by acting like an ‘energy’ function for the system. It is to be strictly positive for all states except the equilibrium point, where it is zero, and its time derivative is to be non-positive, meaning the function’s value does not increase over time. If these conditions are met, it proves that the system is stable and any initial perturbations will decay over time, causing the system to return to its stable state.
Lyapunov stability -It is a criterion for stability of a dynamical system. If disturbances from a stable point reduce and the system returns to that stable point, it can be said to be Lyapunov stable.
Lyotropic liquid crystals – These are phases of matter which form when amphiphilic molecules (molecules with both hydrophilic and hydrophobic parts) are mixed with a solvent, very frequently water. These are a type of liquid crystal whose structure depends on the concentration of the amphiphile in the solvent. Depending on the concentration, these can arrange into different ordered phases like micelles, lamellar sheets, or hexagonal arrays.
Lytag – It is artificial gravel manufactured by cindering spherical fly ash pellets, which can serve as a replacement material for conventional mineral aggregates such as gravel or crushed rock.
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