Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘N’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘N’
Nabarro–Herring creep (NH creep) – It is a mechanism of deformation of crystalline materials (and amorphous materials) which occurs at low stresses and held at high temperatures in fine-grained materials. In Nabarro–Herring creep, atoms diffuse through the crystals, and the rate of creep varies inversely with the square of the grain size so fine-grained materials creep faster than coarser-grained ones. Nabarro–Herring creep is solely controlled by diffusional mass transport. This type of creep results from the diffusion of vacancies from regions of high chemical potential at grain boundaries subjected to normal tensile stresses to regions of lower chemical potential where the average tensile stresses across the grain boundaries are zero.
NACE International – It is a professional organization for the corrosion control industry which publishes papers articles and standards on all aspects of corrosion and has written the definitive standard for valve materials for sour gas service. It has been formerly known as the National Association of Corrosion Engineers.
Nails – These are fasteners consisting of a smooth cylindrical-shaped piece of metal. They have a sharp point on one end and a flat head on the opposite end.
Name-plate capacity – It is also known as the rated capacity, nominal capacity, installed capacity, maximum effect or gross capacity. It is the designed output of a facility. Nameplate capacity is the intended full-load sustained output of a facility such as a power station, electric generator, a chemical plant, fuel plant, mine, metal refinery, and several others.
Nano-crystalline (NC) material – It is a polycrystalline material with a crystallite size of only a few nano-meters. These materials fill the gap between amorphous materials without any long-range order and conventional coarse-grained materials. Definitions vary, but nano-crystalline material is normally defined as a crystallite (grain) size below 100. Grain sizes from 100 nano-meters to 500 nano-meters are typically considered ‘ultra-fine’ grains. The grain size of a nano-crystalline sample can be estimated using X-ray diffraction.
Nano-engineering – It is the practice of engineering on the nano-scale. It derives its name from the nano-meter, a unit of measurement equaling one billionth of a meter. Nano-engineering is largely a synonym for nano-technology, but emphasizes the engineering rather than the pure science aspects of the field.
Nano-filtration – It is a membrane filtration process which uses nano–meter sized pores through which particles smaller than around 1 nano-meter to 10 nano-meters pass through the membrane. Nano-filtration membranes have pore sizes of around 1 nano-meter to 10 nano-meters, smaller than those used in micro- filtration and ultra-filtration, but a slightly bigger than those in reverse osmosis. Membranes used are predominantly polymer thin films. It is used to soften, disinfect, and remove impurities from water.
Nano-hardness test – It is an indentation hardness testing procedure, normally relying on indentation force against tip displacement data, to make assessments of the resistance of surfaces to penetrations of the order of 10 nano-meters to 1,000 nano-meters deep. The prefix ‘nano-’ normally implies hardnesses one thousand times smaller than ‘micro-hardness’, however, use of this prefix has been primarily designed as a means to distinguish this technique from the more traditional micro-indentation hardness procedures. Majority of the nano-hardness testing procedures use three-sided pyramidal diamond indenters first described by Berkovich.
Nano-inverter – It is the grid tied inverters rated less than 100 watts. It is useful for connection of single solar photo-voltaic (PV) panels to a building alternating current power system.
Nano-meter (nm) – It a unit of length in the International System of Units (SI), equal to one billionth part of a meter (0.000,000,001 meter) and to 1,000 picometres. One nano-meter can be expressed in scientific notation as 1/1,000,000,000 meter.
Nano-scale – It is defined as the range of dimensions from 1 nano-meter (nm) to 1,000 nano-meters where materials show unique physico-chemical and biological properties because of their small size.
Nano-second (ns) – It is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, 1/1,000,000,000 of a second,
Nano-technology – It is the manipulation of matter with at least one dimension sized from 1 nano-meter (nm) to 100 nano-meters. At this scale, surface area and quantum mechanical effects become important in describing properties of matter. This definition of nano-technology includes all types of research and technologies which deal with these special properties.
Nano-tesla (nT) – A nano-tesla is an extremely small unit of magnetic flux density, or magnetic field strength. in the International System of Units (SI). A nano-tesla is a SI-multiple (see prefix nano) of the magnetic flux density unit tesla and equal to one billionth of a tesla (0.000,000,001 T). It is used to measure very weak magnetic fields.
Naphtha – It is a flammable liquid hydro-carbon mixture. It is normally a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat.
Naphthalene – It is an organic compound with formula C10H8. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 parts per million (ppm) by mass. As an aromatic hydro-carbon, naphthalene’s structure consists of a fused pair of benzene rings. It is the main ingredient of traditional mothballs.
Naphthalene oil – It is a liquid with a brown to dark brown colour. It is complex combination of hydro-carbons and consists primarily of aromatic and other hydro-carbons, naphthalene, phenolic compounds, benzo-thiophene, and aromatic nitrogen compounds. It has boiling range of 210 deg C to 220 deg C and solidifying point of 65 deg C to 75 deg C. It is a flammable liquid. It has a moth ball odour. Its flash point is 56 deg C to 81 deg C. The specific gravity is in the range of 0.987 to 0.993.
Napped cloth – It is a woven cloth in which some fibres are aligned approximately normal to one of its surfaces.
Narrow-gap welding – It is used to describe processes that have been designed to reduce weld metal volume in butt welds, particularly in carbon and low-alloy steels. These processes are all mechanized. The cost benefits of narrow-gap welding result from its low energy and filler material costs, together with the shorter time needed to fill the considerably smaller weld volume. Other factors include less complicated joint preparation, reduced time at high working temperatures and less distortion of the work-piece because of the smaller volume of weld metal. Narrow-gap welding is suitable for joining sheet and plate in the 25 millimeters to 300 millimeters range. Joints to be welded are prepared with parallel sides or slightly U-shaped. Joints with parallel sides are cheap to prepare, although difficulties can arise as a result of contraction during welding, which has the effect of narrowing the remaining (unwelded) gap.
Nascent surface – It is a completely uncontaminated surface, produced for example by cleavage fracture under ideal vacuum conditions.
National Lubricating Grease Institute (NLGI) – This institute describes the different grease grades mainly based on viscosity and, specifically, working penetration testing.
National measurement standard – It is a standard recognized by a national decision to serve, in a country, as the basis for assigning values to other standards of the quantity concerned.
National reference standard – It is a standard maintained by national laboratories, and which are the legal standards of their respective countries.
Native metal – It is a deposit in the earth’s crust consisting of a metal which is occurring in nature in pure form, uncombined with other elements.
Natural aging – It is spontaneous aging of a super-saturated solid solution at room temperature. It is the process which can alter the hardness and strength in some alloys after a period of time at ambient (room) temperature. It is caused by the spontaneous precipitation of constituents from a super-saturated solid solution. Normally, it increases mechanical properties but can also, in some circumstances, cause loss of properties by over-ageing.
Natural circulation boiler – This is the boiler in which motion of the working fluid in the evaporator is caused by thermo-siphon effect on heating the tubes. In the natural circulation boilers, circulation of water depends on the difference between the density of a descending body of relatively cool and steam-free water and an ascending mixture of hot water and steam. The difference in density occurs since the water expands as it is heated, and hence, becomes less dense. All natural circulation boilers are drum-type boilers.
Natural draft – It takes place when air or flue gases flow due to the difference in density of the hot flue gases and cooler ambient gases. The difference in density creates a pressure differential which moves the hotter flue gases into the cooler surroundings.
Natural draft burner – It is a burner which depends mainly on the natural draft created in the chimney or the venting system to induce air needed for combustion into the burner. In this type of burner, the pressure drop and combustor stack height are critical in producing enough suction to induce enough combustion air into the burners. The main significance of the natural draft type on heat transfer is that the natural-draft flames are usually longer than the forced-draft flames so that the heat flux from the flame is distributed over a longer distance and the peak temperature in the flame is frequently lower.
Natural fibres – These fibres are obtained from organic material (such as materials produced by plants). Natural fibres suffer from several problems including susceptibility to rotting, degradation, mildew, and wear out very quickly. These fibres can be used as a component of composite materials, where the orientation of fibers impacts the properties. Natural fibres can also be matted into sheets to make paper or felt. Natural fibres are good water absorbents and can be found in different textures. Cotton fibres made from the cotton plant, for example, produce fabrics which are light in weight, soft in texture, and which can be made in different sizes and colours.
Natural fibre rope – It is a rope which is made from natural fibres. Cotton, sisal, manila, coir, and papyrus are materials which can be used to create a natural rope. Natural ropes have a susceptibility to rot, degrade, and mildew. They also wear out very quickly and lose much of their strength when placed in water.
Natural gas – It is an environmentally friendly non-renewable gaseous fossil fuel which is extracted from deposits in the earth. It is a clean fuel with a high efficiency. It is transported to long distances (up to 5,000 kilometers) through a pipeline network. It is normally supplied to the consumers as (i) piped natural gas (PNG), (ii) compressed natural gas (CNG), and (iii) liquefied natural gas (LNG). Piped natural gas which is supplied to the consumer with the pipeline pressure at the consumer end normally less than 1.6 mega-pascal (MPa). Compressed natural gas is a form of natural gas which undergoes compression (200 MPa to 250 MPa) is supplied in containers. Liquid natural gas is made by cooling natural gas to a temperature of minus 162 deg C. At this temperature, natural gas becomes a liquid and its volume is reduced by 600 times. Natural gas is a mixture of hydro-carbons consisting primarily of methane (CH4), normally in a percentage of over 85 % by volume. Other hydro-carbons in natural gas include varying amounts of various higher alkanes such as ethane, propane, and butane etc. It also contains water vapour (H2O) at varying degrees of saturation, or condensed water. It can also contain percentages of nitrogen (N2), carbon di-oxide (CO2), hydrogen sulphide (H2S), and helium (He) etc. Natural gas is an odourless, colourless, tasteless and non-toxic gas. It is lighter than air and burns with a clean blue flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning it produces primarily heat, carbon di-oxide, and water. Quantities of NG are measured in normal cubic meters (corresponding to 0 deg C and 0.1 MPa pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 pounds per square inch absolute pressure). The higher heat value of one cubic meter (cum) of natural gas varies from around 39.75 mega-joules to 41.85 mega-joules. Its density is around 0.85 kilograms per cubic meters.
Naturally bonded moulding sand – It is a sand containing sufficient bonding material as mined to be suitable for moulding purposes.
Naturally-occurring radio-active materials (NORM) – These are materials found naturally and are frequently found in the wastes arising from the oil, gas, and mining industries.
Natural phenomena hazard (NPH) – It is an act of nature (for example, earthquake, wind, hurricane, tornado, flood, precipitation [rain or snow], and volcanic eruption etc.), lightning strike, or extreme cold or heat) which poses a threat or danger to workers, the public, or to the environment by potential damage to structures, systems, and components.
Natural phenomena hazard (NPH) mitigation – It is an action taken to reduce the impacts of natural phenomena hazard. This includes natural phenomena hazard resistant design, evaluation, construction requirements, and operational procedures.
Natural rubber – It is a good material for belt cover rubbers since it has a very good tensile strength and elongation, high heat resistance and elasticity, high shear and tearing strength, and good abrasion resistance characteristics. It is stable within the temperature range of -30 deg C to + 80 deg C. With special rubber compounding a widening of this range can be achieved from -40 deg C to + 100 deg C. Natural rubber is resistant to water, alcohol, acetone, dilute acids, and alkalis. It has limited resistance to concentrated acids and alkalis where compounding and service temperatures are major consideration. With special compounding, natural rubber-based mixes can be made antistatic and flame resistant. By adding anti-ozonants a substantial protection against harsh temperature effects, sunlight, and ambient weather conditions can be achieved.
Natural strain – It is the ratio of the change in dimension, resulting from a given load increment, to the magnitude of the dimension immediately prior to applying the load increment. In a body subjected to
axial force, the natural logarithm of the ratio of the gauge length at the moment of observation to the original gauge length. It is also known as true strain.
Natural uranium– This refers to the properties of naturally-occurring uranium (U) as found in natural sources. It contains 0.7 % Uranium-235, 99.3 % Uranium-238, and a trace of Uranium-234. In terms of the quantity of radioactivity, it contains around 2.2 % Uranium-235, 48.6 % Uranium-238, and 49.2 % Uranium-234.
Naval brass – It is a nominal 62 % copper / 37 % zinc brass which has a 1 % tin addition to improve its corrosion resistance in marine environments.
Navier–Stokes equations – These are partial differential equations which describe the motion of viscous fluid substances. These equations mathematically express momentum balance for Newtonian fluids and make use of conservation of mass. They are sometimes accompanied by an equation of state relating pressure, temperature, and density.
Near-infrared radiation – It is the infrared radiation in the wavelength range of 0.78 micrometers to 3 micrometers (7,800 angstrom to 30,000 angstroms).
Near-net shape – It is a manufacturing technique, in which the initial production of the item is very close to the final, or net shape. This reduces the need for finishing operations (e.g., surface finishing). By minimizing the use of finishing methods like machining or grinding, near-net-shape production substantially reduces the production time and costs.
Near-net-shape processes – These are shape replication processes which produce parts needing little or no subsequent processing to get the finished part.
Near miss – it is an incident, which did not show a visible result, but had the potential to do so.
Near miss incident – It is an incident which physically occurred but there was no personal injury to the employee, contractor or visitor bur which could have resulted in a serious injury and needs to be followed up in the same way as a lost time injury but recorded as a near miss.
Neat oil – It is a hydro-carbon oil with or without additive. It is used undiluted. This term is used particularly in metal cutting to distinguish these fluids from soluble oils (emulsions).
Neat resin – It is the resin to which nothing (additives, reinforcements, and so on) has been added.
Nebulizer – It is a device for converting a sample solution into a gas-liquid aerosol for atomic absorption, emission, and fluorescence analysis. This can be combined with a burner to form a nebulizer burner.
Necessary costs – It is a component of cost of quality. Necessary costs are required to achieve and sustain a defined objective or standard of work. These are those costs which are needed to carry out an activity efficiently and to achieve and sustain a defined standard of work. These costs are required to be incurred. Any action to cut or reduce these costs has an adverse effect on the organizational performance. Necessary costs include prevention and inspection costs.
Neck – It is the contact area between abutting particles in compact undergoing sintering.
Neck formation – It is the growth of inter-particle contacts through diffusion processes during sintering.
Necking – It is the process by which a material in tension reduces locally its cross-sectional area. It is -important in creating imperfections and voids in metal deformation processes. A high strain-rate sensitivity in the material means which an incipient neck becomes stronger and spreads the deformation to neighbouring material, thereby resisting neck formation. It is also the reduction of the cross-sectional area of a material in a localized area by uniaxial tension or by stretching. It is also the reduction of the diameter of a portion of the length of a cylindrical shell or tube.
Necking down – It is the localized reduction in area of a sample during tensile deformation.
Needle bearing – It is a bearing in which the relatively moving parts are separated by long, thin rollers which have a length-to-diameter ratio exceeding 5 (five).
Needled mat – It is a mat formed of strands cut to a short length, then felted together in a needle loom with or without a carrier.
Needles – These are elongated or rodlike particles with a high aspect ratio.
Needle valve – It is a type of small valve which is used for flow metering having a tapered needle-point plug or closure element and a seat having a small orifice. Needle valves are used to make relatively fine adjustments in the amount of fluid flow. The distinguishing characteristic of a needle valve is the long, tapered, needle like point on the end of the valve stem. This ‘needle’ acts as a disk. The longer part of the needle is smaller than the orifice in the valve seat and passes through the orifice before the needle seats. This arrangement permits a very gradual increase or decrease in the size of the opening. Needle valves are frequently used as component parts of other, more complicated valves. For example, they are used in some types of reducing valves.
Neel temperature, Neel point – It is the temperature below which spins in an anti-ferro-magnetic material are ordered anti-parallel so that there is zero net magnetic moment.
Negative distortion – It is the distortion in the image which occurs when the magnification in the centre of the field exceeds that in the edge of the field. It is also termed barrel distortion.
Negative eye-piece – It is an eye-piece in which the real image of the object forms between the lens elements of the eye-piece.
Negative feedback It is the feedback from a control system output which tends to oppose the input.
Negative replica – It is a method of reproducing a surface got by the direct contact of the replicating material with the sample. Using this technique, the contour of the replica surface is reversed with respect to that of the original.
Negative resistance – It is a voltage / current characteristic where increasing current leads to decreased voltage drop across the device.
Negative temperature coefficient (NTC) of resistance – A negative temperature coefficient refers to materials which experience a decrease in electrical resistance when their temperature is raised. Materials which have useful engineering applications normally show a relatively rapid decrease with temperature, i.e., a lower coefficient. The lower the coefficient, the higher a decrease in electrical resistance for a given temperature increase. Negative temperature coefficient materials are used to create inrush current limiters (since they present higher initial resistance until the current limiter reaches quiescent temperature), temperature sensors, and thermistors.
Negative temperature coefficient (NTC) of resistance of a semi-conductor – An increase in the temperature of a semiconducting material results in an increase in charge-carrier concentration. This results in a higher number of charge carriers available for recombination, increasing the conductivity of the semi-conductor. The increasing conductivity causes the resistivity of the semi-conductor material to decrease with the rise in temperature, resulting in a negative temperature coefficient of resistance.
Negligence – It is the omission to do something, which a reasonable person, guided upon those considerations which ordinarily regulate the conduct of human affairs would do, or something, which a prudent and reasonable person would not do.
Negotiation – It is normally done so as to reach agreement without causing future barriers to communications. Negotiation takes place when two or more people / parties, with differing views, come together to attempt to reach agreement on an issue. It is persuasive communication or bargaining. It is a cooperative process whereby participants try to find a solution which meets the legitimate interests of the negotiating parties. It is the process between two or more parties to settle differences. In the process of negotiation parties try to reach compromise or agreement while avoiding argument and dispute. In case of any disagreement, parties understandably aim to achieve the best possible outcome for their position (or perhaps an organization they represent). However, the principles of fairness, seeking mutual benefit and maintaining a relationship are the keys to a successful outcome. It is the process of communicating back and forth, for the purpose of reaching a joint agreement about differing needs or ideas. It is a collection of behaviours that involves negotiation skills, communication, sales, marketing, psychology, sociology, assertiveness and conflict resolution. A method of negotiation is normally judged by three criteria namely (i) it is to produce wise agreement if agreement is possible, (ii) it is to be efficient, and (iii) it is to improve or at least not damage the relationship between the parties. Negotiations are viewed hard where the participants are adversaries, the goal is victory, there is application of pressure, there is distrust between participants, and there is demand of concessions as a condition of the relationship. Negotiation is considered soft when the participants are friends, goal is agreement, concessions are made to cultivate the relationship, there is trust in each other, and there is no imposement of the viewpoint of one of the parties.
NEMA standards – These standards are voluntary standards of the National Electric Manufacturers Association (NEMA) and represent general practice in the industry. They define a product, process, or procedure with reference to nomenclature composition, construction, dimensions, tolerances, operating characteristics, performance, quality, rating, and testing. National Electric Manufacturers Association has standardized frame-size motor dimensions, including bolt-hole sizes, mounting-base dimensions, shaft height, shaft diameter, and shaft length.
Neodymium (Nd) – It is a chemical element, having atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes in air and moisture.
Neodymium-doped yttrium aluminum garnet (Nd:YAG, Nd:Y3Al5O12) – It is a crystal which is used as a lasing medium for solid-state lasers. The dopant, neodymium in the +3 oxidation state, Nd(III), typically replaces a small fraction (1 %) of the yttrium ions in the host crystal structure of the yttrium aluminum garnet (YAG), since the two ions are of similar size. It is the neodymium ion which provides the lasing activity in the crystal, in the same fashion as red chromium ion in ruby lasers.
Neon sign – Strictly, it is a sign which glows orange because of a discharge through neon gas. Less pedantically, it is gas discharge tube formed into a sign.
Neon-sign transformer – It is a high-voltage transformer with features intended to support operation of a neon sign.
Neo-pentyl glycol – It is an organic chemical compound. It is used in the synthesis of polyesters, paints, lubricants, and plasticizers. When used in the manufacture of polyesters, it improves the stability of the product towards heat, light, and water. By esterification reaction with fatty or carbolytic acids, synthetic lubricating esters with reduced potential for oxidation or hydrolysis, compared natural easters, can be produced.
Neoprene – It is also known as poly-chloroprene. It is a family of synthetic rubbers which are produced by polymerization of chloroprene. Neoprene shows good chemical stability and maintains flexibility over a wide temperature range. Neoprene is used either as solid rubber or in latex form and is used in a wide variety of commercial applications, such as laptop sleeves, electrical insulation, gloves, liquid and sheet-applied elastomeric membranes or flashings, and automotive fan belts.
Nernst equation – It is an equation which expresses the exact electro-motive force of a cell in terms of the activities of products and reactants of the cell.
Nernst diffusion layer, Nernst thickness – It is the diffusion layer or the hypothetical thickness of this layer as given by the theory of Nernst. It is a fictitious layer which shows the concentration profile along the direction perpendicular to an electrode surface. The thickness ‘d’ of this layer is called the effective (or equivalent) thickness of the diffusion layer. It is the thickness which the diffusion layer has if the concentration profile is a straight line coinciding with the tangent to the true concentration profile at the interface, and that straight line is extended up to the point where the bulk concentration is reached. ‘d’ has a formal significance only. It is simply another way of writing the mass transfer coefficient ‘kd’ defined in terms of a resistivity instead of a conductivity.
Nesting – It is a condition found when surface finishing or machine assembling small parts where they cluster together, making them difficult to treat as individual parts. It is also orientation of sheet metal parts so as to minimize waste when cut from a large sheet. In reinforced plastics, it consists of the placing of plies of fabric so that the yarns of one ply lie in the valleys between the yarns of the adjacent ply (nested cloth).
Net income – It is obtained after deducting from the net sales (i) the cost of goods sold, (ii) operating expenses, (iii) expenses on interest and depreciation, and (iv) taxes to be paid. It is also called net profit.
Net metering – It is a metering plan which allows grid customers with their own generation to be billed only for their net import of energy from the grid.
Net positive suction head (NPSH) – It is a consideration in selecting different types of the pumps In positive displacement pumps, net positive suction head varies as a function of flow determined by the speed. Net positive suction head gets reduced in the positive displacement pump with the reduction of the speed. In a centrifugal pump, net positive suction head varies as function of flow determined by the pressure.
Net resin content prepreg – It is a prepreg product form which contains the final desired resin content and does not need resin bleeding (removal) during the cure process.
Net sales – It is a final value of sales which the organization has made after the deduction of allowances (such as damaged goods), returns and discounts.
Net shape – It is the shape of a powder metallurgy part, casting, or forging which conforms closely to the specified dimensions. Such a part needs no secondary machining or finishing. A near-net shape part can
be either one in which some but not all of the surfaces are net or one in which the surfaces require only minimal machining or finishing.
Net surface – It is a surface in a manufactured part which needs no finishing in a subsequent operation.
Netting analysis – It is the analysis of filament- wound structures which assumes the stresses induced in the structure are carried entirely by the filaments, and the strength of the resin is neglected, and assumes also that the filaments possess no bending or shearing stiffness and carry only the axial tensile loads.
Network analyzer – It is an analog computer system for modelling power grids. It is now displaced by digital computers.
Network cable – It is the cables intended for use in data inter-connections, with defined performance parameters.
Network etching – It is the formation of networks, especially in mild steels, after etching in nitric acid. These networks relate to sub-grain boundaries.
Network protector – It is a type of circuit breaker used to isolate a fault from a multi-transformer supply network.
Network structure – It is a structure in which one constituent occurs mainly at the grain boundaries, hence enveloping the grains of the other constituent(s). It is a desirable feature in cemented carbide, since in the system cobalt / tungsten carbide, where the cobalt phase forms a ductile network surrounding the brittle carbide grains.
Net worth – It is the difference between total assets and total liabilities.
Neumann band – It is as mechanical twin (deformation twin) in ferrite.
Neural network – It is an artificial neural network, or one of the biological neural networks which the artificial networks are inspired by.
Neural network method – It is a method in artificial intelligence (AI) which teaches computers to process data in a way that is inspired by the human brain. It is a type of machine learning (ML) process, called deep learning, which uses inter-connected nodes or neurons in a layered structure that resembles the human brain.
Neutral axis – It is an axis in the cross section of a beam (a member resisting bending) or shaft along which there are no longitudinal stresses or strains.
Neutral conductor – It receives and returns alternating current to the supply during normal operation of the circuit; to limit the effects of leakage current from higher-voltage systems, the neutral conductor is frequently connected to earth ground at the point of supply. By contrast, a ground conductor is not intended to carry current for normal operation, but instead connects exposed metallic components (such as equipment enclosures or conduits enclosing wiring) to earth ground. A ground conductor only carries significant current if there is a circuit fault that would otherwise energize exposed conductive parts and present a shock hazard. In that case, circuit protection devices can detect a fault to a grounded metal enclosure and automatically de-energize the circuit, or can provide a warning of a ground fault.
Neutral filter – It is a colour filter which reduces the intensity of the transmitted illumination without affecting its hue. It is also a colour filter having identical transmission at all wavelengths throughout the spectrum. Such an ideal filter does not exist in practice.
Neutral flame – It is a gas flame in which there is no excess of either fuel or oxygen in the inner flame. Oxygen from ambient air is used to complete the combustion of carbon di-oxide and hydrogen produced in the inner flame. It is also an oxy-fuel gas flame in which the portion used is neither oxidizing nor reducing.
Neutralization – It consists of the balancing of acidity and alkalinity by interaction. In the context of cleaning, the removal of acid soils by alkalines and alkaline soils by acids.
Neutralization number – It is an ASTM (American Society for Testing and Materials) number given to quenching oils which reflects the oil’s tendency towards oxidation and sludging. It is also known as saponification number.
Neutralization point – It determines acidity or alkalinity of oil. Acidity / acid value / acid number is milligrams of KOH (potassium hydroxide) needed to neutralize acid in 1 gram of oil. Alkalinity / base value/ base number is the milligrams of acid needed to neutralize all bases in 1 gram of oil. As the neutralization point of the oil increases, age of the oil decreases.
Neutral oil – It is a lubricating oil obtained by distillation, which is not treated with acid or with alkali.
Neutral plane – It is a conceptual plane within a beam or cantilever. When loaded by a bending force, the beam bends so that the inner surface is in compression and the outer surface is in tension. The neutral plane is the surface within the beam between these zones, where the material of the beam is not under stress, either compression or tension. As there is no lengthwise stress force on the neutral plane, there is no strain or extension either. When the beam bends, the length of the neutral plane remains constant. Any line within the neutral plane parallel to the axis of the beam is called the deflection curve of the beam. The neutral plane is shown by the dotted line.
Neutral point – The neutral point is defined as the point on the rolled strip which has no slipping or sliding motion. It lies at the centre of the arc of contact between the strip and the rolls.
Neutral refractories – These are the refractories which are resistant to chemical attack by both acid and basic slags, refractories, or fluxes at high temperatures. Neutral refractories are chemically stable to both acids and bases and used in the areas where slag and environment are either acidic or basic. Examples are carbon graphite, chromites and alumina. Graphite is the least reactive and is extensively used in the furnaces where the process of oxidation can be controlled.
Neutron – It is an uncharged atomic particle found in the nuclei of atoms, which can cause fission in some atoms. Neutron is an elementary particle which has around the same mass as the proton, but no electric charge. Rest mass is 1.67495 × 10 to the power -27 kilograms. An unbound (extra-nuclear) neutron is unstable and beta-particles decays with a half-life of 10.6 min.
Neutron absorber – It is a material in which a significant number of neutrons entering combine with nuclei and are not re-emitted.
Neutron absorption – It is a process in which the collision of a neutron with a nucleus result in the absorption of the neutron into the nucleus with the emission of one or more prompt -rays. In certain cases, emission of alpha-particles, protons, or other neutrons or fission of the nucleus results. It is also known as neutron capture.
Neutron activation analysis (NAA) – It is a nuclear process used for determining the concentrations of elements in several materials. Neutron activation analysis allows discrete sampling of elements as it disregards the chemical form of a sample, and focuses solely on atomic nuclei. The method is based on neutron activation and hence needs a neutron source. The sample is bombarded with neutrons, causing its constituent elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element have long been studied and determined. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the various elements within it. A particular advantage of this technique is that it does not destroy the sample, and hence has been used for the analysis of works of art and historical artifacts. Neutron activation analysis can also be used to determine the activity of a radioactive sample. If neutron activation analysis is conducted directly on irradiated samples it is termed instrumental neutron activation analysis (INAA). In some cases, irradiated samples are subjected to chemical separation to remove interfering species or to concentrate the radioisotope of interest. This technique is known as radiochemical neutron activation analysis (RNAA). Neutron activation analysis can perform non-destructive analyses on solids, liquids, suspensions, slurries, and gases with no or minimal preparation.
Neutron capture – It is a process in which the collision of a neutron with a nucleus result in the absorption of the neutron into the nucleus with the emission of one or more prompt -rays. In certain cases, emission of alpha-particles, protons, or other neutrons or fission of the nucleus results. It is also known as neutron absorption.
Neutron cross-section – It is a measure of the probability which an interaction of a given kind takes place between a nucleus and an incident neutron. It is an area such that the number of interactions which occur in a sample exposed to a beam of neutrons is equal to the product of the cross-section, the number of nuclei per unit volume in the sample, the thickness of the sample, and the number of neutrons in the beam which enters the sample if their velocities are perpendicular to it. The normal unit is the barn (10 to the power of -24 square centimeter).
Neutron detector – It is a device which detects passing neutrons, for example, by observing the charged particles or gamma-rays released in nuclear reactions induced by the neutrons or by observing the recoil of charged particles caused by collisions with neutrons.
Neutron diffraction – It is the application of neutron scattering to the determination of the atomic and / or magnetic structure of a material. A sample to be examined is placed in a beam of thermal or cold neutrons to get a diffraction pattern which provides information of the structure of the material. The technique is similar to X-ray diffraction but because of their different scattering properties, neutrons and X-rays provide complementary information: X-Rays are suited for superficial analysis, strong X-rays from synchrotron radiation are suited for shallow depths or thin samples, while neutrons having high penetration depth are suited for bulk samples.
Neutron embrittlement – It is the embrittlement resulting from bombardment with neutrons. It is normally encountered in metals which have been exposed to a neutron flux in the core of the reactor. In steels, neutron embrittlement is evidenced by a rise in the ductile-to-brittle transition temperature.
Neutron flux – This term refers to the number of neutrons passing through an area over a span of time. It is a measure of the intensity of neutron radiation, which is measured in neutrons per square centimeter-second.
Neutron radiation – It is a form of ionizing radiation which presents as free neutrons. Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides—which, in turn, can trigger further neutron radiation.
Neutron radiography – It is a form of non-destructive inspection which uses a specific type of particulate radiation, called neutrons, to form a radiographic image of a test-piece. The geometric principles of shadow formation, the variation of attenuation with test-piece thickness, and several other factors which govern the exposure and processing of a neutron radiograph are similar to those for radiography using X-rays or gamma-rays.
Neutron scattering – It involves creating a beam of neutrons, passing that beam through a sample, and noting where (and possibly when) neutrons scattered from the sample hit a detector. At SNS (spallation neutron source), a particle accelerator sends protons to collide with a heavy metal target to produce the neutrons in a process known as spallation.
Neutron source – This is a general term referring to the variety of materials which emit neutrons. An example of which is a mixture of radium and beryllium, which can be inserted into a reactor to ensure a neutron flux large enough to be distinguished from background radiation on neutron detection equipment.
Neutron spectrometer – Neutron spectrometer is a scientific instrument designed to detect neutrons in different energy bands. It is used to search for and determine the abundance of hydrogen, particularly in the form of buried water ice, by measuring the neutron flux and its energy dependence. The instrument uses a neutron-absorbing detector and different scintillator types to differentiate between thermal, epithermal, and fast neutrons. The data output of the instrument is typically represented as histograms of the measured amplitudes integrated over time.
Neutron spectroscopy – It consists of determination of the energy distribution of neutrons. Scintillation detectors, proportional counters, activation foils, and proton recoil are used.
Neutron spectrum – It is the distribution by energy of neutrons impinging on a surface, which can be measured by neutron spectroscopy techniques or sometimes from knowledge of the neutron source.
New scrap – It is also called prompt or industrial scrap is generated from manufacturing units which are involved in the fabricating and producing various products from steel material. Scrap is generated when steel is cut, stamped, drawn, extruded, or machined. This type of scrap is generally transported quickly back to steel plants for re-melting. The supply of new scrap is a function of industrial activity. When activity is high, more quantity of new scrap is generated. The chemical composition and physical characteristics of new scrap is well known and in principle new scrap does not need any pre-treatment process before it is re-melted, although cutting to size might be necessary. This scrap is typically clean, meaning that it is not mixed with other materials.
Newt – It is the former English unit of kinematic viscosity.
Newton (unit) – The SI (International System of Units) unit of force, which uses the symbol ‘N’. It is defined as 1 kilogram metre per square second, the force which gives a mass of 1 kilogram an acceleration of 1 metre per second per second.
Newtonian fluid – It is a fluid showing Newtonian viscosity wherein the shear stress is proportional to the rate of shear. It is a fluid in which the viscous stresses arising from its flow are at every point linearly correlated to the local strain rate, i.e., the rate of change of its deformation over time. Stresses are proportional to the rate of change of the fluid’s velocity vector.
Newton’s law of heat transfer – It states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings while under the effects of a breeze.
Newton’s laws of motion – These consist of are three laws of classical mechanics which describe the relationship between the motion of an object and the forces acting on it. The fist law states that a body continues in its state of rest, or in uniform motion in a straight line, unless acted upon by a force. The second law states that a body acted upon by a force moves in such a manner that the time rate of change of momentum equals the force. The third law states that if two bodies exert forces on each other, these forces are equal in magnitude and opposite in direction.
Newton’s law of universal gravitation – The law states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
Nib – It is a pressed pre-heated, shaped, sintered, hot pressed, rough drilled, or finished compact. It is a generic term for a piece of cemented carbide intended for use as a wire drawing die.
Nibbling – It is the contour cutting of sheet metal by use of a rapidly reciprocating punch which makes numerous small cuts.
Nick – For rolled products, it is a mark / an area of broken surface which is introduced after processing. The mark normally has no relationship to the rolling direction.
Nickel (Ni) – Nickel is a metallic element with a silvery-white, shiny appearance. It is the fifth-most common element on earth and occurs extensively in the earth’s crust and core. Nickel, along with iron, is also a common element in meteorites. Nickel occurs naturally in soil and water. It is also an essential nutrient for plants. It increases strength, and improves toughness. It is ineffective in increasing the hardness. It is a ferrite former. It is normally added in quantities ranging from 1 % to 4 % in alloy steels. In some stainless steels it is sometimes as high as 20 %. It is used for strength, corrosion resistance, and toughness. It increases the strength of ferrite, and hence increasing the strength of the steel. It is used in low alloy steels to increase toughness and hardenability. Nickel also tends to help reduce distortion and cracking during the quenching phase of heat treatment.
Nickel alloy electro-plating – It is done for engineering applications and includes nickel-iron, nickel-cobalt, nickel-manganese, and zinc-nickel. Iron is a cheap metal, and solutions for plating nickel-iron alloys have been developed mainly in order to reduce the cost of the metal used to form a layer of given thickness, but they have also been developed for special magnetic purposes. Cobalt and manganese are
used to increase the hardness and strength of nickel plating. Additionally, nickel-manganese alloys have improved resistance to sulphur embrittlement when heated. Alloy layers 20 micrometers to 30 micro-meters thick of nickel with around 15 % molybdenum show higher hardness and resistance to corrosion than pure nickel but at the expense of a reduction in ductility to around 1 %. Coatings of nickel-tungsten show very high resistance to corrosion, but they are believed not to be true alloys and have not been used in practice. Alloys nickel-iron, nickel-cobalt, and nickel-manganese are of practical interest.
Nickel aluminide – It refers to either of two widely used inter-metallic compounds, Ni3Al or NiAl, but the term is sometimes used to refer to any nickel–aluminium alloy. These alloys are widely used because of their high strength even at high temperature, low density, corrosion resistance, and ease of production. Ni3Al is of specific interest as a precipitate in nickel-based super-alloys, where it is called the gamma prime phase. It gives these alloys high strength and creep resistance up to 0.7 to 0.8 of its melting temperature. Meanwhile, NiAl displays excellent properties such as lower density and higher melting temperature than those of Ni3Al, and good thermal conductivity and oxidation resistance. These properties make it attractive for special high-temperature applications like coatings on blades in gas turbines and jet engines. However, both these alloys have the disadvantage of being quite brittle at room temperature, with Ni3Al remaining brittle at high temperatures as well. To address this problem, has been shown that Ni3Al can be made ductile when manufactured in single-crystal form rather than in polycrystalline form.
Nickel electro-plating – It is a process of depositing nickel onto a metal part. It is a technique of electro–plating a thin layer of nickel onto a metal object. The nickel layer can be decorative, provide corrosion resistance, wear resistance, or used to build up worn or undersized parts for salvage purposes.
Nickel-hard iron – Nickel hard is a generic name for white cast iron, alloyed with nickel, chromium, and molybdenum. It is having extremely high strength, abrasion, corrosion resistance, fracture resistance, and toughness. The alloy is best suited to applications in mining, minerals and the iron processing industries. It is ideal for metal-working rolls, grinding mill liners, pulverizer rings, slurry pump parts, grinding media, impact blow bars etc.
Nickel silver – It consists of copper, nickel and zinc alloys. Their copper content is similar to that of brasses but up to 20 % of the zinc is replaced by nickel. Silvery white in colour they have good corrosion resistance and remain ‘springy’ at moderate temperatures.
Nickel steels – These are the steels which contain nickel as an alloying element. Different quantities of nickel are added to increase the strength in the normalized condition to enable hardening to be performed in oil or air instead of water.
Nicol prism – It is a prism which is used for polarizing or analyzing light made by cementing together two pieces of calcite using Canada balsam so that the extraordinary ray from the first piece passes through the second piece while the ordinary ray is reflected to the side into an absorbing layer of black paint. No light pssses through when two Nicol prisms are crossed. In such a prism the ordinary ray is totally reflected at the calcite / cement interface while the orthogonally polarized extraordinary ray is transmitted. The prism can hence be used to polarize light or analyze the polarization of light.
Nil-ductility temperature (NDT) – It is defined as the on-heating temperature where ductility is reduced to zero. Essentially, this can be viewed as the temperature of liquation onset, where grain boundary surfaces are coated by a thin continuous liquid film.
Nil-ductility transition temperature (NDTT) – The selection of test temperatures is based on finding, with as few samples as possible, a lower temperature where the sample breaks and an upper temperature where it does not break, and then testing at intervals between these temperatures until the temperature limits for break and no-break performance are determined within 5 deg C. The nil ductility transition temperature is the highest temperature where a sample breaks when the test is conducted by this procedure. Test at least two samples that show no-break performance at a temperature 5 deg C above the temperature judged to be the nil ductility transition temperature.
Niobium (Nb) – It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has similar ductility to iron. It increases the yield strength and to a lesser degree the tensile strength of carbon steel. The addition of small quantities of niobium can significantly increase the yield strength of steels. Niobium can also have a moderate precipitation strengthening effect. Its main contributions are to form precipitates above the transformation temperature, and to retard the recrystallization of austenite, thus promoting a fine-grain microstructure having improved strength and toughness. Niobium occurs in association with tantalum (Ta), to which it is closely related. Niobium is a strong carbide-forming element and as such is added to certain austenitic corrosion-resistant steels of the 18/8 chromium-nickel type for the prevention of inter-crystalline corrosion.
Nip – In a bearing, It is the quantity by which the outer circumference of a pair of bearing shells exceeds the inner circumference of the housing. It is also known as crush.
Nip angle – In the rolling of metals, it is the location where all of the force is transmitted through the rolls. It is the maximum attainable angle between the roll radius at the first contact and the line of roll centres. Operating angles less than the angle of bite are termed as contact angles or rolling angles. In roll, jaw, or gyratory crushing, nip angle is the entrance angle formed by the tangents at the two points of contact between the working surfaces and the (assumed) spherical particles to be crushed.
Nipple – It is a short stub of pipe normally of threaded steel, brass, chlorinated poly-vinyl-chloride or copper; occasionally just bare copper. A nipple is defined as being a short stub of pipe which has external male pipe threads at each end, for connecting two other fittings. Nipples are commonly used for hoses.
Nitric acid – It is an inorganic compound with the formula HNO3. It is a highly corrosive mineral acid. The compound is colourless, but samples tend to acquire a yellow cast over time because of the decomposition into oxides of nitrogen. Majority of the commercially available nitric acid has a concentration of 68 % in water. When the solution contains more than 86 % HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen di-oxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86 %, or white fuming nitric acid at concentrations above 95 %. Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock-sensitive and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as synthetic dyes and medicines. Nitric acid is also normally used as a strong oxidizing agent.
Nitride -It is a chemical compound of nitrogen. Nitrides can be inorganic or organic, ionic or covalent. The nitride anion, N3- ion, is very elusive but compounds of nitride are many, although rarely naturally occurring. Some nitrides have a found applications, such as wear-resistant coatings (e.g., titanium nitride, TiN), hard ceramic materials (e.g., silicon nitride, Si3N4), and semiconductors (e.g., gallium nitride, GaN). Metal nitrido complexes are also common.
Nitride-carbide inclusion types – It is a compound with the general formula Mx(C,N)y observed normally as coloured idiomorphic cubic crystals, where M includes titanium, niobium, tantalum, and zirconium.
Nitriding – The nitriding process consists in subjecting machined and heat-treated steel, free from surface decarburization, to the action of a nitrogenous medium, generally ammonia gas, at a temperature of around 500 deg C to 540 deg C. A very hard surface is obtained by this process. The surface-hardening effect is due to the absorption of nitrogen and subsequent heat treatment of the steel becomes not necessary. The time needed is relatively long, normally being 1 day to 2 days. The case, even after 2 days of nitriding, is normally less than 0.5 mm. And the highest hardness exists in the surface layers to a depth of only a few hundredth of a millimeter. Special low-alloy steels have been developed for nitriding. These steels contain elements which combine readily with nitrogen to form nitrides. The most favourable of these elements are aluminum, chromium, and vanadium. Molybdenum and nickel are used in these steels to add strength and toughness. The carbon content normally is around 0.20 % to 0.50 %, although in some steels, where high core hardness is necessary, it can be as high as 1.3 %. Stainless steels can also be subjected to nitriding. Since nitriding is carried out at a relatively low temperature, it is advantageous to use quenched and tempered steel as the base material. This gives a strong, tough core with an intensely hard-wear resistant case which is much harder, indeed, than can be obtained by quench hardening either carbonized or cyanided steel. Although warpage is not a problem during the nitriding, steels increase slightly in size during this treatment. Allowance can be made for this growth in the finished article. Protection against nitriding can be achieved by tin, copper, or bronze plating, or by the application of certain paints.
Nitriding steels – These steels are normally suited for the nitriding process. These steels form a very hard and adherent surface upon proper nitriding process (heating in a partially dissociated atmosphere of ammonia gas). These steels have a composition normally containing of carbon in the range of 0.20 % to 0.40 %, chromium in the range of 0.90 % to 1.5 %, molybdenum in the range of 0.15 % to 1 %, and aluminum in the range of 0.85 % to 1.2 %.
Nitrile – It is an organic compound which has a −C≡N functional group. The name of the compound is composed of a base, which includes the carbon of the −C≡N, suffixed with ‘nitrile’, so for example CH3CH2C≡N is called ‘propionitrile’ (or propane-nitrile). The prefix cyano- is used inter-changeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyano-carbons.
Nitrile rubber – It is a copolymer of butadiene and acrylo-nitrile. It is not resistant to ketones, esters, aromatics, and hydrocarbons. The physical properties are slightly lower than those of natural rubber. The temperature operating range can be controlled between -40 deg C to +120 deg C. It is normally abrasion resistant, resistant to ageing and used for oil and grease resistant belt covers.
Nitrile chloroprene rubber – The use of nitrile in chloroprene rubber enhances the dynamic properties. It is used for cover rubber which needs high oil and fat resistance whether it be animal, vegetable or mineral and also requiring superior mechanical properties. Nitrile chloroprene rubber is better than chloroprene rubber.
Nitro-carburizing – It includes several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitro-carburizing is performed mainly to provide an anti-scuffing surface layer and to improve fatigue resistance.
Nitrogen (N) – It is a chemical element. It is a non-metal. At standard temperature and pressure, two atoms of the element bond to form N2 which is a colourless and odourless diatomic gas. Nitrogen forms around 78 % of earth’s atmosphere, making it the most abundant chemical species in air. Nitrogen is produced in large quantities and at high purity as a gas or liquid through the liquefaction and distillation of ambient air at the cryogenic air separation plants. It is also produced on commercial scales as a lower purity gas by adsorption technologies (pressure swing adsorption, PSA), or diffusion separation processes (permeation through specially designed hollow fibers). Gaseous nitrogen is called in short as GAN while the liquid nitrogen is called in short as LIN. Liquid nitrogen is a cryogenic liquid. Cryogenic liquids are liquefied gases that have a normal boiling point below – 150 deg C. Liquid nitrogen has a boiling point of -195.8 deg C. Because the temperature difference between the product and the surrounding environment is substantial, it is necessary to keep the liquid nitrogen insulated from the surrounding heat. Nitrogen is frequently stored as a liquid, although it is used primarily as a gas. Liquid storage is less bulky and less costly than the equivalent capacity of high-pressure gaseous storage.
Nitrogen oxides (NOx) – These are a group of gases made up of varying amounts of oxygen (O2) and nitrogen (N2) molecules. Two most important oxides of N2, which are air pollutants, are nitrogen mono-oxide (NO) and nitrogen di-oxide (NO2). These two oxides are frequently lumped together under the designation NOx, although analytical techniques can distinguish clearly between them. Of the two, NO2 is the more toxic and irritating compound.
Nitrous oxide (N2O) – It is a greenhouse gas. It is emitted during agricultural, land use, industrial activities, combustion of fossil fuels and solid waste, as well as during treatment of waste-water. It absorbs 265 times more heat per molecule than carbon di-oxide. Nitrous oxide accounts for around 7 % of the radiative forcing by the long-lived greenhouse gases. It is the third most important individual contributor to the combined forcing. It is emitted into the atmosphere from both natural sources (around 60 %) and anthropogenic sources (around 40 %), including oceans, soils, biomass burning, fertilizer use and various industrial processes.
NLGI number – It is the abbreviation for the National Lubricating Grease Institute number, which is the numerical classification of the consistency of greases, based on the American Society for Testing and Materials standard ASTM D 217 test.
N-Methyl-pyrrolidone (NMP) – It is a solvent used in a variety of industries and applications, such as paint and coating removal, petrochemical processing, engineering plastics coatings, agricultural chemicals, electronic cleaning and industrial / domestic cleaning.
No-bake binder – It is a synthetic liquid resin sand binder which hardens completely at room temperature, normally not needing baking. It is used in a cold-setting process.
Noble – It is the positive direction of electrode potential, hence resembling noble metals such as gold and platinum. Noble is a term used to indicate the corrosion resistance, or the lack of it, of a material. If metals are listed in order of their general corrosion resistance, most resistant at the top and going down to the least at the bottom, the higher a metal is in the list the more ‘noble’ it is said to be. When two different metals are connected in a corrosive environment then the least ‘noble’ is attacked preferentially. This effect can be used to protect structures from corrosion buy using a ‘sacrificial anode’ of a less noble metal.
Noble ferro-alloys – These are of high value ferro-alloys which are consumed in low proportions. These ferro-alloys are one of the vital inputs needed for the production of special types of steels and are used as additive inputs especially in the production of alloy and special steels. Noble ferro-alloys are ferro-nickel (Fe-Ni), ferro-molybdenum (Fe-Mo), ferro-vanadium (Fe-V), ferro-tungsten (Fe-W), ferro-niobium (Fe-Nb), ferro-titanium (Fe-Ti), ferro-aluminum (Fe-Al), and ferro-boron (Fe-B). There are some noble ferro-alloys which are having more than one non-ferrous metal as alloying elements. Examples are ferro-silico-magnesium (Fe-Si-Mg), ferro-silico-zirconium (Fe-Si-Zr), and ferro-nickel-magnesium (Fe-Ni-Mg) etc.
Noble gases – These are also called the inert gases. Noble gases are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some cases, oganesson (Og). Under standard conditions, the first six of these elements are odourless, colourless, monatomic gases with very low chemical reactivity and cryogenic boiling points. The properties of the seventh, unstable, element, Og, are uncertain.
Noble metal – It is a metal whose potential is highly positive relative to the hydrogen electrode. It is a metal with marked resistance to chemical reaction, particularly to oxidation and to solution by inorganic acids. The term as frequently used is synonymous with precious metal.
Noble potential – It is a potential more cathodic (positive) than the standard hydrogen potential.
Nodal analysis – It is a technique for analysis of currents in an electrical network.
Nodal point – It is either of two points on the axis of a lens or other optical system, determined by extending an incident oblique ray and the corresponding refracted ray to the axis for the pair of rays which are parallel outside the optical system. Some examples of nodal points are (i) the nodal points of a curved interface between two optical media are located at the centre of curvature of the surface, possibly far away from the surface, (ii) for a thin lens, the two nodal points coincide in the center of the length. Therefore, a ray directed to that center will go through the lens without any deflection or parallel offset.
Node – It is a defined point in an electrical network, with some potential relative to a reference node and where currents can be summed. In case of composites, node is the connected portion of adjacent ribbons of honeycomb.
No-draft (draft-less) forging – It is a forging with extremely close tolerances and little or no draft which needs minimal machining to produce the final part. Mechanical properties can be improved by closer control of grain flow and by retention of surface material in the final component.
Nodular fireclay – It is a rock containing aluminous or ferruginous nodules, or both, bonded by fireclay.
Nodular graphite – It consists of rounded clusters of tempered carbon, such as that obtained in malleable cast iron as a result of the thermal decomposition of cementite. Nodular graphite is characteristic of malleable iron. The graphite of nodular or ductile iron is spherulitic in form, but called nodular.
Nodular graphite iron – The preferred term is ductile iron. It is a cast iron which has been treated while molten with an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherulites, which imparts a measurable degree of ductility to the cast metal.
Nodular pearlite – It consists of the pearlite which has grown as a colony with an approximately spherical morphology.
Nodular powder – It is irregular powder having knotted, rounded or similar shape.
No harm threshold – It is the risk of death of 1 in 1 million per annum which is normally considered in the radiation protection community as equating to a dose of 10 micro-Sieverts.
Noise – It is the sounds which can lead to so called noise-induced hearing loss, tinnitus or stress, or interfere with the ability to hear other sounds, to concentrate, to relax or to communicate. Noise is also an undesired signal that tends to interfere with the normal reception or processing of a desired signal.
Noise cancelling – It is a type of microphone which preferentially picks up a nearby sound source and rejects ambient noise.
Noise factors – These are factors which are either inherently uncontrollable or impractical to control because of technological / economic reasons. These factors can be further classified into outer noises and inner noises. Outer noise consists of external sources or factors which are operating in the environment in which the product is functioning and whose variation is transmitted through the design to the output performance of the product. Examples of outer noise factors are temperature, humidity, contaminants, voltage fluctuations, vibrations from nearby equipment, and variations in human performance. Inner noise consists of internal change in product characteristics such as drift from the nominal over because of the deterioration. Inner noise can be precipitated by such factors as mechanical wear and aging.
Noise level – It is the sound pressure level, normally expressed as dB(A) (audible decibels), emitted by a control valve when operating under specified process conditions.
Noise reduction – It is the techniques used to reduce the perception of noise in a communications path. In case off fans, and blowers, noise reduction can be accomplished by several methods like (i) insulating the duct, (ii) mounting the fan on a soft material, such as rubber or suitable spring isolator as needed to limit the quantity of transmitted vibration energy, or (iii) installing sound damping material or baffles to absorb noise energy.
Noisy-channel coding theorem – It is a theorem which establishes the limits of the error-free data transmission in a noisy communication channel.
NOL ring – It is a parallel filament-wound or tape-wound hoop test sample for measuring different mechanical strength properties of the material, such as tension and compression, by testing the entire ring or segments of it. It is also known as a parallel fibre reinforced ring.
Nomex – It is a trade name for an aramid fibre or paper used for honeycomb construction.
Nominal area (of contact) – It is the area bounded by the periphery of the region in which macroscopic contact between two solid bodies is occurring. This is frequently taken to mean the area enclosed by the boundaries of a wear scar, even though the real area of contact, in which the solids are touching instantaneously. It is normally much smaller.
Nominal bore (NB) – This term is frequently used inter-changeably with NPS (North American set of standard sizes for pipes).
Nominal diameter, Diametre Nominal (DN) – It is the European designation equivalent to NPS (North American set of standard sizes for pipes), in which sizes are measured in millimeters.
Nominal dimension – It is the size of the dimension to which the tolerance is applied. For example, if a dimension is 50 millimeters +/- 0.5 millimeters, the 50 millimeters is the nominal dimension, and the +/- 0.5 millimeter is the tolerance.
Nominal pipe size (NPS) – NPS is a North American set of standard sizes for pipes used for high or low pressures and temperatures. In this standard ‘NPT’ is used for tapered and ‘NPS’ is used for straight threads to join pipes and fittings. Pipe size is specified with two non-dimensional numbers namely (i) a nominal pipe size based on inches, and (ii) a schedule (Sch.) which specifies the wall thickness.
Nominal strain – It is a macroscopic global strain. It is defined with respect to the gauge length over the representative volume element (RVE) (or a whole sample in a material test), while a macroscopic local strain is equivalent to the mesoscopic global strain defined as a measure of the average deformation experienced by each cell (or a row of cells if one-dimensional simplification is adopted).
Nominal strength – It is calculated for a cross-sectional area, taking into account the stress raising effects of the macro-geometrical shape of the component of which the section forms a part, but disregarding the local stress raising effects from the section shape and any weldment or other fixing detail.
Nominal stress – It consists of the stress at a point calculated on the net cross section without taking into consideration the effect on stress of geometric discontinuities, such as holes, grooves, fillets, and so forth. The calculation is made using simple elastic theory.
Nominal value – It is the value of input and output which has been stated by the manufacturer of the measuring instruments in the user manual.
Nomogram – It is also called a nomograph, alignment chart, or abac. It is a graphical calculating device, a two-dimensional diagram designed to allow the approximate graphical computation of a mathematical function. Nomograms use a parallel coordinate system rather than standard Cartesian coordinates. A nomogram consists of a set of ‘n’ scales, one for each variable in an equation. Knowing the values of ‘n-1’ variables, the value of the unknown variable can be found, or by fixing the values of some variables, the relationship between the unfixed ones can be studied. The result is got by laying a straight-edge across the known values on the scales and reading the unknown value from where it crosses the scale for that variable. The virtual or drawn line created by the straightedge is called an index line or isopleth.
Non-circular gears – Though frequently overlooked, non-circular gears can provide several types of unusual motion or speed characteristics. Cams and linkages can provide these special motion requirements as well, but non-circular gears often represent a simpler, more compact, or more accurate solution. Common requirements handled by non-circular gears include converting a constant input speed into a variable output speed, and providing several different constant-speed segments during an operating cycle. Other applications need combined translation and rotation, or stop-and-dwell motion. Several types of non-circular gears, particularly elliptical gears, generate variable output speeds. Other, less commonly used types are triangular and square gears.
Non-coking coal – It is defined as a type of hard coal which do not have coking properties. This coal is also known as thermal coal, steam coal, or boiler coal. Non-coking coal is that coal which when heated in the absence of air leaves a coherent residue. This residue does not possess the physical and chemical properties of the coke and is not suitable for the manufacture of coke. Non coking coal like any other coal is an organic rock (as opposed to most other rocks in the earth’s crust, such as clays and sandstone, which are inorganic). It contains mostly carbon (C), but it also has hydrogen (H2), oxygen (O2), sulphur (S) and nitrogen (N2), as well as some inorganic constituents which are known as ash (minerals) and water (H2O).
Non-conformal surfaces – These are the surfaces whose centres of curvature are on the opposite sides of the interface, as in rolling element bearings or gear teeth. In wear testing, non-conformal surface is a geometric configuration in which a ‘point’ or ‘line’ of contact is initially established between samples before the test is started. Examples of non-conformal contacts are ball-on-ring and flat block-on-ring geometries (tangent to the circumferential surface). When wear occurs, the nominal area of contact tends to increase.
Non-contact bearings – These are the bearings in which no solid contact occurs between relatively moving surfaces. These include fluid bearings and magnetic bearings. The lack of mechanical contact means that static friction can be eliminated, although viscous drag occurs when fluids are present. However, life can be virtually infinite if the external power units needed to operate them do not fail. Strictly speaking, a bearing in which full-film lubrication is occurring would be considered a non-contact bearing. However, this term is more typically applied to gas bearings and magnetic bearings.
Non-cryogenic air separation processes – These processes are near ambient temperature separation processes and are used for the production of either nitrogen or oxygen as gases. These processes are cost effective choices when demand of gases is relatively small and when very high purity of the gases is not needed. Non cryogenic air separation plants are compact and produce gaseous nitrogen which is typically 95.5 % to 99.5 % oxygen free or gaseous oxygen which is 90 % to 95.5 % pure. Non-cryogenic plants are less energy efficient than cryogenic plants (for comparable product purity) but at the same time cost less to build. The physical size of the plant can be reduced as required purity is reduced, and the power needed to operate the unit is reduced as well. Non-cryogenic plants are relatively quick and easy to start up and can be brought on line in less than half an hour. This is useful when product is not needed full time. Like cryogenic plants, non-cryogenic air separation processes also start with compression of air. Unlike cryogenic plants which use the difference between the boiling points of nitrogen and oxygen to separate and purify these products, non-cryogenic air separation plants use physical property differences such as molecular structure, size, and mass to produce nitrogen and oxygen. Non-cryogenic processes are based on either selective adsorption or permutation through membranes. The most common technologies used for non-cryogenic air separation plants are adsorption process technology, (ii) chemical process technologies, (iii) membrane separation technology, and (iv) ion transport membrane technology.
Non-destructive evaluation (NDE) – It is broadly considered synonymous with non-destructive inspection (NDI). More specifically, it is the quantitative analysis of non-destructive inspection findings to determine whether the material is acceptable for its function, despite the presence of discontinuities. With non-destructive evaluation, a discontinuity can be classified by its size, shape, type, and location, allowing the investigator to determine whether or not the flaw(s) is acceptable. Damage tolerant design approaches are based on the philosophy of ensuring safe operation in the presence of flaws.
Non-destructive examination (NDE) – It consists of a wide group of analysis techniques which are used in industry to evaluate the properties of a material, component or system without causing damage. Since non-destructive examination does not permanently alter the article being examined, it is a highly valuable technique which can save both money and time in product evaluation, trouble-shooting, and research. The six most frequently used non-destructive examination methods are eddy-current, magnetic-particle, liquid penetrant, radiographic, ultrasonic, and visual testing.
Non-destructive inspection (NDI) – It is a process or procedure, such as ultrasonic or radiographic inspection, for the determination of the quality or characteristics of a material, part, or assembly, without permanently altering the subject or its properties. It is used to find internal anomalies in a structure without degrading its properties or impairing its serviceability.
Non-destructive testing (NDT) – It consists of a wide group of analysis techniques which are used the industry to evaluate the properties of a material, component or system without causing damage to the material being tested. It is broadly considered synonymous with non-destructive inspection (NDI).
Non-expendable mould casting processes – The non-expendable mould casting is a casting process in which the mould need not be reformed after each production cycle. Non-expendable mould casting is a casting technique which has at least 4 distinct casting processes. These are (i) continuous casting, (ii) centrifugal casting, (iii) die casting, and (iv) permanent mould casting. This form of casting also results in improved repeatability in parts produced and delivers near net shape casting.
Non-ferrous metals – These are metals or alloys which do not contain iron (allotropes of iron, ferrite, and so on) in appreciable quantities. Normally more costly than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g., aluminum), higher conductivity (e.g., copper), non-magnetic properties or resistance to corrosion (e.g. zinc). Some non-ferrous materials are also used in the iron and steel industries. For example, bauxite is used as flux for blast furnaces, while others such as wolframite, pyrolusite, and chromite are used in making ferrous alloys. Important non-ferrous metals include aluminum, copper, lead, tin, titanium, and zinc, and alloys such as brass. Precious metals such as gold, silver, and platinum and exotic or rare metals such as mercury, tungsten, beryllium, bismuth, cerium, cadmium, niobium, indium, gallium, germanium, lithium, selenium, tantalum, tellurium, vanadium, and zirconium are also non-ferrous. They are normally obtained through minerals such as sulphides, carbonates, and silicates. Non-ferrous metals are normally refined through electrolysis.
Non-ferruginous wastes – are lime and dolomite dust and fines, coal and coke dust, sludge (lime sludge, tar sludge, biological treatment sludge, oil sludge, and sewage sludge etc.), non-ferrous scrap, refractory wastes, ironmaking and steelmaking slag, ash (fly ash and bottom ash), and muck, and debris etc.
Non-fill (under-fill) – It is a forging condition which occurs when the die impression is not completely filled with metal.
Non-fired refractory bricks – These are refractory materials which can be used directly without firing. They have the advantages of energy saving, good thermal shock stability, and simple process, and can replace fired refractory products in a wide range of fields.
Non-fluoborate – It is tin-lead electro-plating solution. Non-fluoborate solution are stannous methane sulphonate with lead methane sulphonate, methane sulphonic acid, grain refiners (wetting agents), anti-oxidants, and fungicides. These components, as well as various addition agents, are available in commercial quantities. The solution operates at 100 % cathode and anode efficiency.
Non-fusion welding – It is a method in which similar or dissimilar metals are joined together without melting the edges of the base metal by using a low melting point filler rod but without the application of pressure.
Non-hazardous waste – It is a waste which causes no harm to human or environmental health. Although non-hazardous waste does not sound like it poses a threat, this type of waste can cause significant environmental damage. This type of waste can be subject to certain management requirements.
Non-heat treatable alloy – It is an alloy which is incapable of being strengthened by thermal treatment. Non-heat treatable alloys gain their strength from cold-working.
Non-homogeneous material – It is a material which has non-uniform physical properties. For example, its density at one location can be different from another. Non-homogeneous materials are also known as heterogeneous materials.
Non-hydraulic cement – It is a less common form of cement for example slaked lime (calcium oxide mixed with water), which hardens by carbonation in contact with carbon di-oxide, which is present in the air (around 0.04 %).
Non-hygroscopic – It means of lacking the property of absorbing and retaining an appreciable quantity of moisture (water vapour) from the air.
Non-ionic detergent – It is a detergent which produces aggregates of electrically neutral molecules with colloidal properties.
Non-linear control – It is the class of control problems relating to the control of systems which are non-linear.
Non-magnetic materials – Such materials have little reaction to magnetic fields. They can be composed of molecules where electrons spinning one way are always balanced by electrons spinning the other, or their spins can simply interact only weakly.
Non-magnetic steels – These are steels which have a stable fully austenitic micro-structure.
Non-martensitic transformation product (NMTP) – It comprises all micro-structural features other than martensite which transform from austenite upon cooling when a fully martensitic micro-structure is intended.
Non-metal – It is a chemical element which mostly lacks distinctive metallic properties. Non-metals range from colour-less gases like hydrogen to shiny crystals like iodine. Physically, they are normally lighter (less dense) than elements which form metals and are frequently poor conductors of heat and electricity. Chemically, non-metals have relatively high electro–negativity or normally attract electrons in a chemical bond with another element, and their oxides tend to be acidic.
Non-metallic bush bearings – These are slider bearings which use fabric base moulded section. These bearings are normally preferred over the gun metal bearings. The most popular non-metallic bush bearing which is normally used in low-capacity rolling mills is the fibre bearing. The non-metallic bush bearings provide good bearing for rolls having considerable speed variation or where reversal of rotation can take place. The co-efficient of friction is lower in these bearings when compared with the co-efficient of friction of slider bearing with metal bush. Due to the inherent properties, fabric base moulded bush bearings have a low co-efficient of friction, low wear and tear, low maintenance costs, good impact strength, and longer life resulting in higher rate of production. These bearings can with-stand operational temperatures which are in the range of 80 deg C to 120 deg C. Beyond these temperatures fibre bearings generally get charred. Water is used as a general source for lubrication on fibre bearing. These bearings are cheaper than metallic slider bearings and have higher load carrying capacities. Fibre bearings offer better abrasion resistance and does not need machining. These bearings are of light weight and hence easy to handle. They have peculiar frictional behaviour. They are easy to slide when wet and hard to slide when dry.
Non-metallic gaskets – For these gaskets, sheet materials are used in low to medium pressure services. With careful selection, these gaskets are not only suitable for general service but also for extreme chemical services and temperatures. Examples of these gaskets are elastomers, cork, compressed fibre sheets, poly tetra fluoro ethylene (PTFE), bi-axially orientated reinforced PTFE, graphite, thermiculite, and insulating gaskets etc.
Non-metallic inclusions – These are also called simply inclusions. These consist of a physical and mechanical discontinuity occurring within a material or part, normally consisting of solid, encapsulated foreign material. Inclusions are frequently capable of transmitting some structural stresses and energy fields, but to a noticeably different degree than from the parent material. Non-metallic inclusions are also particles of foreign material in a metallic matrix. The particles are normally compounds, such as oxides, sulphides, or silicates, but can be of any substance which is foreign to (and essentially insoluble in) the matrix. Non-metallic inclusions can be exogenous inclusion, indigenous inclusion, or stringer.
Non-Newtonian viscosity – It is the apparent viscosity of a material in which the shear stress is not proportional to the rate of shear.
No-node – It is an electron device (although practically, only vacuum tubes) with nine internal active electrodes controlling electron flow.
Non-oriented electrical steel (NOES) – Non-oriented electrical steel can be fully processed or semi processed. Non-oriented, fully processed electrical steel has varying silicon levels which range from 0.5 % silicon to 3.25 % silicon. It has uniform magnetic properties in all directions. This type of electrical steel does not need recrystallization processes to develop its properties. The low silicon alloy grades provide better magnetic permeability and thermal conductivity. For high alloy grades, better performance is expected in high frequencies, with very low losses. This type of steel is good for the magnetic circuits in motors, transformers, and electrical system housing. This fully processed type provides difficulty in punchability because of a completed annealing process. Organic coatings are added to improve lubrication in the punching process. Non-oriented semi-processed electrical steels are largely non-silicon alloyed steel and are annealed at low temperatures after the final cold rolling. The end-user, however, has to provide the final stress-relief annealing as per the intended application of the steel. The punchability of this type of the electrical steel is better than the non-oriented fully processed type, so organic coatings are not needed. Non-oriented semi-processed grades are good core materials for small rotors, stators, and small power transformers. Non-oriented electrical steel is the mostly used material among all soft magnetic materials. It is functional material for the generation of energy as well as for the use of electrical energy in electrical machines and components. The relevant magnetic properties (magnetization behaviour and magnetic losses) of the non-oriented electrical steel are determined by the intensities of the texture components and the inhomogeneity of the micro-structure of the finally processed material (grain size distribution, precipitations, and internal stresses). The number of the processing steps and the process parameters differ remarkably for the non-oriented electrical steel compared to the grain-oriented electrical steel. The processing steps after casting comprises of hot rolling, cold rolling and final annealing. Product and process development in the field of non-oriented electrical steel is characterized, like for the grain-oriented electrical steel, by optimization of the magnetic properties and other physical properties for special application areas as well as by the developments.
Non-oxide ceramics – These are obtained by reacting a metal, or a semi-metal in some cases, with oxygen-free elements such as, sulphur, nitrogen, carbon, boron, phosphorus, arsenic, antimony, selenium, and tellurium. Unlike oxides, barring diamond and graphitic as well as many of the amorphous carbons, these compounds of non-oxide ceramic systems constitute some of the largest manmade substances.
Non-oxide refractories – These are refractories which do not have oxygen in their chemical composition. Example of non-oxide refractories are carbon-based refractory materials, and carbides, nitrides, borides, and silicides. This group also includes sialons which are the silicon nitride sinterable derivatives.
Non-point sources – These sources of water pollution are those which arrive from different sources of origin and are usually scattered or spread over large areas. These types of sources deliver pollutants indirectly through environmental changes and account for majority of the contaminants in streams and lakes. For example, the contaminated water which runs off from agriculture farms, construction sites, abandoned mines, and acid rains enters streams and lakes. It is quite difficult to control non-point sources.
Non-polar compound – It is a compound consisting of covalent molecules with no permanent dipole moment.
Non-positive displacement pumps – These pumps are also known as hydro-dynamic pumps. In these pumps the fluid is pressurized by the rotation of the propeller and the fluid pressure is proportional to the rotor speed. These pumps cannot withstand high pressures and generally used for low-pressure and high-volume flow applications. The fluid pressure and flow generated is due to inertia effect of the fluid. The fluid motion is generated due to rotating propeller. These pumps provide a smooth and continuous flow but the flow output decreases with increase in system resistance (load). The flow output decreases because some of the fluid slip back at higher resistance. The fluid flow is completely stopped at very large system resistance and thus the volumetric efficiency becomes zero. Therefore, the flow rate not only depends on the rotational speed but also on the resistance provided by the system. The important advantages of non-positive displacement pumps are lower initial cost, less operational maintenance because of lesser moving parts, simplicity of operation, higher reliability, and suitability with wide range of fluid etc. These pumps are primarily used for transporting fluids and find little use in the hydraulic or fluid power industries. Centrifugal pump is the common example of non-positive displacement pumps.
Non-process waste – These are the waste materials which are generated from sources other than the process lines (during the production process).
Non-processible waste – It means solid waste which cannot be processed at a processing facility because of the physical characteristics of the solid waste or potential harmful effects to the processing facility.
Non-recovery coke ovens – In the non-recovery coke ovens, volatiles evolved during coal carbonization are not recovered as by-products but are combusted in the oven itself in the presence of controlled quantity of air and the heat of the volatiles of evolving gases is utilized for coking of the coal mass into coke and hence no external heating is needed. The heat is generated by the combustion of volatile matter which is then penetrated into the coal mass through radiation from the oven top and also by conduction. The higher level of heat importantly is used to break up the potentially polluting hydro-carbons into the constituent combustible compounds and to burn them hence avoiding the potentially hazardous pollution. The heat consequent to combustion is only partially utilized during the process and the balance heat in the waste flue gas is recovered for energy generation. The key elements of the non-recovery coke oven technology are (i) coke is produced by heating coal, in a controlled atmosphere, thus liberating volatile matter (gas and moisture), (ii) the gas is combusted in an environmentally ‘smart’ way so as to produce the heat to make the coke, (iii) excess heat which is produced in the process is used to generate electricity, (iv) the process does not rely on the combustion of coal, only the gas liberated from the coal, (v) the greenhouse gas emissions of the process are typical of a simple gas fired power generator, that is, one which raises steam that passes through a turbine. Non-recovery coke ovens produce a quality coke for blast furnaces, cupolas, and ferroalloy furnaces etc. These ovens are useful to get high quality coke for blast furnace operation with high pulverized coal injection, where better properties of coke are needed, or to obtain standard quality based on blends with some proportion of non-coking coals.
Non-return valve – A non-return valve is a single-way valve which allows the fluid to flow only in one direction. The main importance of non-return valves is their working of allowing flow in the downstream direction and preventing the flow in the upstream direction.
Non-rising stem valve – It is a gate valve having its stem threaded into the gate. As the stem turns, the gate moves but the stem does not rise. In this valve, stem threads are exposed to line fluids.
Non-soap grease – It is a grease made with a thickener other than soap, such as clay or asbestos.
Non-stoichiometric compounds – These are chemical compounds, almost always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers (i.e. an empirical formula). Very frequently, in such materials, some small percentages of atoms are missing or too many atoms are packed into an otherwise perfect lattice work. Contrary to earlier definitions, modern understanding of non-stoichiometric compounds, view them as homogeneous, and not mixtures of stoichiometric chemical compounds.
Non-transferred arc (plasma arc welding and cutting, and plasma spraying) – It is an arc established between the electrode and the constricting nozzle. The work-piece is not in the electrical circuit.
Non-uniform reduction in cross-section – In this case, the reduction in the thickness direction is not uniform. The material (i) is elongated in the rolling direction, (ii) is spread in the width direction, and (iii) is reduced non-uniformly in the thickness direction. Along the width, material flow occurs only toward the edges of the section. The rolling of an oval section in rod rolling or of an airfoil section is considered to be in this category. In case of highly non-uniform reduction in cross-section, the reduction in the thickness direction is highly non-uniform. A portion of the rolled section is reduced in thickness, while other portions can be extruded or increased in thickness. As a result, in the width (lateral) direction material flow can be toward the centre. Of course, in addition, the material flow takes place in the thickness direction as well as in the rolling (longitudinal) direction.
Non-wetting liquids – These are the liquids in which the cohesive forces are dominant rather than adhesive forces. These liquids have very high contact angle.
Non-woven fabric – It is a planar textile structure produced by loosely compressing together fibres, yarns, rovings, and so on, with or without a scrim cloth carrier. It is accomplished by mechanical, chemical, thermal, or solvent means, and combinations thereof.
No objection certificate (NOC) – It is a type of legal certificate issued by any agency, organization, institute or, in certain cases, an individual.
Norm – It can be defined as sets of relations that define forms of communicating, feeling, acting, and thinking. Norms define what is allowed and what is not allowed to be said, felt, done, or thought. They are situational and relationally negotiated. Normally described in terms of their functions (descriptive, constitutive, prescriptive), the term commonly designates prescriptive guides. Norms can be more or less explicit, more or less prescriptive, and be more or less opposed and resisted. Although sometimes viewed as limiting possibilities rather than creating them, they can be seen as producing a certain set of possibilities and transformed through people’s engagement with them in their relations to others.
Normal – It is an imaginary line forming right angles with a surface or other lines sometimes called the perpendicular. It is used as a basis for determining angles of incidence, reflection, and refraction.
Normal continuous load – It means that the given load current is going to flow continuously through cable. Standards are to be referred for current ratings for poly vinyl chloride (PVC) cables which are based on the normal conditions of installation. If the actual conditions are not the same as the normal conditions, the values for the normal current ratings are to be multiplied by the relevant rating factors as given in the standards.
Normal direction – It is that direction which is perpendicular to the plane of working in a worked material.
Normal distribution – It is the probability density function which is used to describe the mechanical properties of materials and the distribution of most random variables encountered in engineering design.
Normal force – In tribology, it is the force This applied normal to the surface of one body by another contacting body or bodies. term 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).
Normality – It is a measure of the number of gram-equivalent weights of a compound per litre of solution. It is defined as the number of gram or mole equivalents of solute present in one litre of solution. The SI (International System of Units) unit of normality is equivalents per litre (Eq/L). Normality is given by the equation N = Msol / (EWsol + Vsol), where ‘N’ is normality, ‘Msol’ is the mass of solute in grams, ‘EWsol’ is the equivalent weight of solute, and ‘Vsol’ is the volume of the entire solution in litres.
Normalized erosion resistance – It is the volume loss rate of a specified reference material divided by the volume loss rate of a test material got under similar testing and analysis conditions. ‘Similar testing and analysis conditions’ means that the volume loss rates of the two materials are determined at the corresponding portions of the erosion rate-time pattern, for example, the maximum erosion rate or the terminal erosion rate. A desired complete wording has the form, ‘the normalized erosion resistance of (test material) relative to the (reference material) based on (criterion of data analysis) is (numerical value)’.
Normalizing – Normalizing treatment is frequently applied to the steel in order for the achievement of any one or more of these objectives, namely (i) to refine the grain structure, (ii) to obtain uniform structure, (iii) to decrease residual stresses, and (iv) to improve the machinability of the steel. Normalizing is a process in which steel is heated, to a temperature above the A3 temperature or the Acm temperatures and then cooled in atmospheric air. The purpose of the normalizing treatment is to remove the effects of any previous heat treatment (including the coarse-grained structure sometimes resulting from high forging temperatures) or cold-working. The normalizing process is done to ensure a homogeneous austenite on reheating for hardening or full annealing. The resultant structures are pearlite or pearlite with excess ferrite or cementite, depending upon the composition of the steel. The structures after normalizing are different from the structures resulting after annealing and the steels of the same carbon content in the hypo-eutectoid or hyper-eutectoid ranges, there is less excess ferrite or cementite and the pearlite is finer. These are the results of the more rapid cooling. Since the type of structure, and, hence, the mechanical properties, are affected by the rate of cooling, substantial variations can take place in normalized steels because of differences in section thickness of the shapes being normalized.
Normal load – In tribology, it is the force applied normal to the surface of one body by another contacting body or bodies. However, the term normal force is more precise and hence preferred. If applied vertically, the load can be expressed in mass units, but it is preferable to use force units such as newtons (N).
Normally-closed valve – It is a condition wherein the valve closure member moves to a closed position when the actuating energy source fails.
Normally closed solenoid valve – It is an electrically operated valve whose inlet orifice is closed when the solenoid coil is not energized. It is to be energized to open.
Normally-open valve – It is a condition wherein the valve closure member moves to an open position when the actuating energy source fails.
Normally open solenoid valve – It is an electrically operated valve whose inlet orifice is open when the solenoid coil is not energized. The valve is to be energized to close.
Normal-phase chromatography (NPC) – It refers to liquid-solid chromatography or to bonded-phase chromatography with a polar stationary phase and a non-polar mobile phase.
Normal segregation – It consists of concentration of alloying constituents which have low melting points in those portions of a casting which solidify last.
Normal solution – It is an aqueous solution containing one gram equivalent of the active reagent in 1 litre of the solution.
Normal strain – It occurs when the elongation of an object is in response to a normal stress (i.e., perpendicular to a surface), and is denoted by the Greek letter epsilon. A positive value corresponds to a tensile strain, while negative is compressive.
Normal strength – It is the strength of a material which is its ability to withstand an applied load without failure or plastic deformation.
Normal stress – It is the stress component which is perpendicular to the plane on which the forces act. Normal stress can be either tensile or compressive.
Normal temperature and pressure (NTP) -NTP means a temperature of 20 deg C (293.15 K) and an absolute pressure of 1 atmosphere (101.325 kilo-pascal, kPa).
Normal wear – It is the loss of material within the design limits expected for the specific intended application. The concept of normal wear depends on economic factors, such as the expendability of a worn part.
Norton’s theorem – it is a theorem which states that any network of current sources, voltage sources, and resistors can be simplified to an equivalent network with only a current source and shunt admittance. It is the dual of Thevenin’s theorem.
Nose radius – It is the radius of the rounded portion of the cutting edge of a tool.
Notch – It refers to a V-shaped, U-shaped, or semi-circular defect deliberately introduced into a planar material. In structural components, a notch causes a stress concentration which can result in the initiation and growth of fatigue cracks. Notches are used in materials characterization to determine fracture mechanics related properties such as fracture toughness and rates of fatigue crack growth.
Notch acuity – It relates to the severity of the stress concentration produced by a given notch in a particular structure. If the depth of the notch is very small compared with the width (or diameter) of the narrowest cross section, acuity can be expressed as the ratio of the notch depth to the notch root radius. Otherwise, acuity is defined as the ratio of one-half the width (or diameter) of the narrowest cross-section to the notch root radius.
Notch brittleness – It is the susceptibility of a material to brittle fracture at points of stress concentration. For example, in a notch tensile test, the material is said to be notch brittle if the notch strength is less than the tensile strength of an unnotched sample. Otherwise, it is said to be notch ductile.
Notch depth – It is the distance from the surface of a test sample to the bottom of the notch. In a cylindrical test sample, it is the percentage of the original cross-sectional area removed by machining an annular groove.
Notch, double shear – It is an abrupt deviation from straight on a sheared edge. This offset can occur if the flat sheet or plate product is longer than the blade for the final shearing operation.
Notch ductility – It is the percentage reduction in area after complete separation of the metal in a tensile test of a notched sample.
Notched bar impact test– It this test, a one-time force with a large load is applied to the metal sample, resulting in multiaxial stresses. Tests are performed at high or low temperatures. The objective of the test is to accurately predict the probability of a brittle fracture.
Notched impact testing – Ferritic steels, with their body-centered cubic (bcc) structure, have the disadvantage of breaking in a brittle fashion at low temperatures. This means, in terms of the ideas of the tensile test that the % elongation at failure is close to zero. As the temperature is lowered, there is a small temperature range over which the steels with bcc structure suddenly begin to fail in the brittle mode. An average temperature of the small range, called the ‘ductile brittle transition temperature’ (DBTT), is often chosen to characterize the temperature where the transition occurs. The simple tensile test detects this transition, but unfortunately, it detects DBTT values well below those that occur in complex steel parts. The tensile test applies stress in only one direction while in complex steel parts, the applied stress acts in all three possible directions, a situation called a tri-axial stress state. The DBTT is raised by a tri-axial stress state. A tri-axial stress state develops at the base of a notch when a notched sample is broken in a tensile machine, and such tests are called notched tensile tests. However, it is more useful to break the sample with an impact test, where the load is applied much more rapidly than in a tensile machine, because the combination of the notch geometry and the high load rate produces values of DBTT close to the temperature where brittle failure begins to occur in complex steel parts.
Notched sample – It is a test sample which has been deliberately cut or notched, normally in a V-shape, to induce and locate point of failure.
Notch factor – It is the ratio of the resilience determined on a plain sample to the resilience determined on a notched sample.
Notch filter – It is a filter with a narrow reject band which is used to block, for example, a pilot tone out of a communications network.
Notching – It consists of cutting out different shapes from the edge of a strip, blank, or part. Notching is also a vibration testing control technique engineers can use to limit vibration at an input response channel to prevent over-testing or potential damage.
Notching press – It is a mechanical press which is used for notching internal and external circumferences and also for notching along a straight line. These presses are equipped with automatic feeds since only one notch is made per stroke.
Notch rupture strength – It is the ratio of applied load to original area of the minimum cross section in a stress-rupture test of a notched sample.
Notch sensitivity – It is the extent to which the sensitivity of a material to fracture is increased by the presence of a stress concentration, such as a notch, a sudden change in cross section, a crack, or a scratch. Low notch sensitivity is normally associated with ductile materials, and high notch sensitivity is normally associated with brittle materials.
Notch strength – It is the maximum load on a notched tensile-test sample divided by the minimum cross-sectional area (the area at the root of the notch). It is also known as notch tensile strength.
Notch tensile strength (NTS) – Notch tensile strength of a material is the value given by performing a standard tensile strength test on a notched sample of the material. The ratio between the notch tensile strength and the tensile strength is called the notch strength ratio (NSR).
Notch tensile test – It uses a notched sample. This test aims to measure the resistance of planar sample with uniform thickness and sharp notch(es) to a slow crack growth, under boundary conditions of constant or accelerated loading rates.
Notch toughness – It is measured normally in terms of the absorbed impact energy needed to cause fracturing of the sample. The change in potential energy of the impacting head (from before impact to after fracture) is determined with a calibrated dial that measures the total energy absorbed in breaking the sample. Other quantitative parameters, such as fracture appearance (percent fibrous fracture) and degree of ductility / deformation (lateral expansion or notch root contraction), are also frequently measured in addition to the fracture energy. Impact tests can also be instrumented to obtain load data as a function of time during the fracture event. In its simplest form, instrumented impact testing involves the placement of a strain gauge on the tup (the striker).
Notice inviting tender (NIT) – It is published by the organizations to get biddings from the contractors for the proposed works. It means this document and its annexures, any corrigendum, addendum, and any other documents provided along with this notice inviting tender or issued during the selection of the bidder, seeking a set of solution(s), services(s), materials and / or any combination of them.
Novolac – It is a linear, thermoplastic, B-staged phenolic resin, which, in the presence of methylene or other cross-linking groups, reacts to form a thermoset phenolic.
Nozzle – It is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe. A nozzle is frequently a pipe or tube of varying cross-sectional area, and it can be used to direct or modify the flow of a fluid (liquid or gas). Nozzles are frequently used to control the rate of flow, speed, direction, mass, shape, and / or the pressure of the stream that emerges from them. In a nozzle, the velocity of fluid increases at the expense of its pressure energy. In case of welding, nozzle is a device which directs shielding media.
Nozzle, air mist – The essential features of the air mist nozzles are the mixing chamber, extension pipe, water and air inlet adapters and their internal geometries, and geometry of nozzle tip. These components are to be precision designed to ensure a very high heat transfer coefficient, stable spray angles and uniform water distribution. The air mist nozzles have non clogging characteristics and there are no wear parts in the mixing chamber of air and water. The spray width of these nozzles is stable within a wide range of water pressure. Hence, these nozzles have constant and uniform spray characteristics. Air mist nozzle is to meet the requirements of (i) atomization of cooling water into a fine mist for uniform cooling of the steel, (ii) wide angle discharge of the mist stream in order to reduce the installation of number of nozzles, (iii) increase in the size of the nozzle outlet to have reduction in the nozzle clogging and increase in the discharged water volume range, and (iv) the nozzle size is to facilitate its installation between the rolls.
Nozzle clogging – Clogging in continuous casting nozzles is the build-up of material in the flow passage between the tundish and mould. The nozzle clogging phenomenon has been one of the most disruptive problems for the continuous casting process as long as the casting machines have been operating. This phenomenon produces an inconsistent flow and temperature variations, steel level fluctuations in the mould, impairment of steel quality, and the abrupt interruption of the steel casting. Clogging starts when solid compounds, mainly steel skull, and non-metallic inclusions, are non-uniformly deposited at the inner wall of the submerged entry nozzle (SEN) at some typical preferential zones characterized for neighbouring dead flow conditions. The primary sources of these inclusions are (i) the reaction between the dissolved oxygen with the deoxidizers, (ii) re-oxidation in the tundish or the nozzle, and (iii) the entrainment of slag or refractory particles. The consequences of nozzle clogging include (i) decreased productivity, (ii) increased cost, and (iii) decreased quality. Nozzle clogging is a serious productivity and quality problem in continuous casting.
Nozzle refractory – It is a refractory shape containing an orifice for the purpose of transmitting molten metal from a refractory-lined container.
N shell – It is the fourth layer of electrons surrounding the nucleus of an atom, having electrons with the principal quantum number 4.
‘n’th root – ‘n’th root of a number ‘x’ is a number ’r’ (the root) which, when raised to the power of the positive integer ‘n’ yields ‘x’.
Nuclear – It relates to, or constituting a nucleus. It also relates to, producing, or using energy which is created when the nuclei of atoms are split apart or joined together.
Nuclear accident – Other terms used are nuclear disaster, and radiation accident. It is defined by the International Atomic Energy Agency (IAEA) as ‘an event that has led to significant consequences to people, the environment or the facility’. Examples for nuclear accident are lethal effects to individuals, large radio-activity release to the environment, or a reactor core melt.
Nuclear cermet fuel – Cermet fuels consist of ceramic fuel particles such as uranium di-oxide (UO2) embedded in a metal matrix, which is typically tungsten (W) because of a high melting point and excellent compatibility with hot hydrogen. It is in the form of a sintered fuel rod composed of a fissile carbide or oxide constituent and a metallic matrix.
Nuclear charge – It refers to the total positive charge found in the nucleus of an atom. In the context of transition elements like copper, it plays a significant role in determining the energy levels of orbitals and the hybridization between them.
Nuclear concrete – It is the concrete which is used for the construction of the nuclear island in a nuclear power plant. It is normally the radiation shielding ultra-high-performance concrete (RS-UHPC) which is an advanced type of concrete engineered for optimal packing density to improve mechanical properties and durability while effectively attenuating radiation.
Nuclear cross-section (sigma) – It is the probability that a nuclear reaction is going to occur between a nucleus and a particle, expressed in units of area (normally barns).
Nuclear decay – It is called radio-active decay. It is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radio-active. Three of the most common types of decay are alpha, beta, and gamma decay.
Nuclear energy – It is the energy released by a nuclear reaction (either fission or fusion) or by radio-active decay.
Nuclear engineering – It is the engineering discipline concerned with designing and applying systems which utilize the energy released by nuclear processes. The most prominent application of nuclear engineering is the generation of electricity.
Nuclear fission -It is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process frequently produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio-active decay.
Nuclear fuel – It refers to a substance, typically a fissile material, which is used by nuclear power stations or other nuclear devices to generate energy. It is uranium or plutonium which has been fabricated into pins, assemblies, plates, or other such similar form for the purposes of fuelling a nuclear reactor. Other High-Z elements are capable of being used as nuclear fuel (e.g., thorium) normally used for fusion reactors.
Nuclear fuel cycle – It is the sequence of steps involved in supplying, using, and disposing of the fuel used in nuclear reactors. The fuel cycle is ‘closed’ if it includes the reprocessing of spent fuel and recycling of fissile materials resulting from reprocessing. The term ‘open’ or ‘once-through’ cycle means that the fuel is disposed of in a permanent storage site after use in the reactor.
Nuclear fusion – It is a reaction in which two or more atomic nuclei, combine to form one or more atomic nuclei and neutrons. The difference in mass between the reactants and products is manifested as either the release or absorption of energy.
Nuclear gamma resonance (NGR) – Nuclear gamma resonance on the resonant emission and absorption of gamma-ray photons by atomic nuclei in a solid. In spite of the large energies of the gamma-rays involved, these processes occur without an energy loss because of the nuclear recoil, i.e., they are recoilless. This is known as the Mossbauer effect.
Nuclear grade – It is a material of a quality adequate for use in nuclear application.
Nuclear island – It is that part of a nuclear power plant which incorporates all equipment, systems, installation and control and other relevant hardware installed within the reactor and reactor auxiliary buildings. The boundaries of the nuclear island are normally defined as being one metre outside the external boundaries of the above-mentioned buildings in the case of piping and two metres for cable.
Nuclear liability – It is the strict legal liability of the operator of the nuclear facility. Majority of the national nuclear liability laws worldwide are (i) the exclusive liability of the operator of the nuclear installation where the nuclear incident occurred, (ii) the strict (absolute) liability of such operator, (iii) the establishment of a maximum liability amount to be borne by the operator with the nuclear liability conventions providing for a minimum threshold (only a few countries have provided for unlimited liability under their nuclear liability legislation), (iv) the obligation for the operator to have and maintain financial security to cover its nuclear liability and ensure availability of funds, and (v) the obligation of the victims to file claims within a certain period (prescription period).
Nuclear life-cycle – It is a whole life-cycle approach to a nuclear power project consisting of several phases namely research and development, conceptual design, detailed design, construction, commissioning, operations and maintenance, refurbishment or life extension (if applicable), and decommissioning.
Nuclear magnetic resonance (NMR) – It is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electro-magnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved. In practical applications with static magnetic fields up to around 20-tesla, the frequency is similar to VHF (very high frequency) and UHF (ultra-high frequency) television broadcasts (60 mega-hertz to 1,000 mega-hertz).
Nuclear magnetic resonance (NMR) spectroscopy – It is a technique which exploits the magnetic properties of certain atomic nuclei. This technique is useful for identifying unknown compounds. Nuclear magnetic resonance is a radio frequency (RF) spectroscopy involving the interaction of the nuclear magnetic dipole or electric quadrupole moments with external or internal magnetic fields or electric-field gradients. These interactions provide detailed information on the atomic (chemical) environment. Majority of the nuclear magnetic resonance spectra are got using radio transmitters, pulse generators, sensitive radio receivers, and a large laboratory electro-magnet. The frequency or the magnetic field is swept to get a resonance. The information in such a resonant spectrum includes line position, frequently related to the chemical shift or the metallic (Knight) shift, quadrupole splitting, and linewidths. This information can then be interpreted to give insight into the local atomic environment of those atoms responsible for the resonance.
Nuclear materials – It refers to the metals uranium, plutonium, and thorium, in any form, as per the International Atomic Energy Agency (IAEA). This is differentiated further into ‘source material’, consisting of natural and depleted uranium, and ‘special fissionable material’, consisting of enriched uranium (U-235), uranium-233, and plutonium-239. Uranium ore concentrates are considered to be a ‘source material’, although these are not subject to safeguards under the Nuclear Non-Proliferation Treaty.
Nuclear metallurgy – It is the branch of the metallurgy which deals with the science and technology of the nuclear materials.
Nuclear non-proliferation – It is a process by which the spread of nuclear weapons technology is prevented.
Nuclear power – It is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium in nuclear power plants. Nuclear decay processes are used in niche applications such as radioisotope thermoelectric generators in some space probes. Reactors producing controlled fusion power have been operated since 1958 but have yet to generate net power and are not expected to be commercially available in the near future.
Nuclear power plant (NPP) – It is also known as a nuclear power station (NPS), nuclear generating station (NGS) or atomic power station (APS). It is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam which drives a steam turbine connected to a generator that produces electricity. A nuclear power plant is divided into two main parts namely the nuclear island and the conventional island. The nuclear island is further sub-divided into the nuclear steam supply system and the balance of nuclear island i.e., everything else which needs to be designed, constructed and tested to complete the nuclear island.
Nuclear pressure equipment (NPE) – A nuclear pressure equipment is the reactor pressure vessel (RPV) in a nuclear power plant which is the pressure vessel containing the nuclear reactor coolant, core shroud, and the reactor core.
Nuclear quadrupole resonance (NQR) – It is a chemical analysis technique related to nuclear magnetic resonance (NMR). Unlike nuclear magnetic resonance, nuclear quadrupole resonance transitions of nuclei can be detected in the absence of a magnetic field, and for this reason nuclear quadrupole resonance spectroscopy is referred to as ‘zero field nuclear magnetic resonance’. The nuclear quadrupole resonance is mediated by the interaction of the electric field gradient (EFG) with the quadrupole moment of the nuclear charge distribution. Unlike nuclear magnetic resonance, nuclear quadrupole resonance is applicable only to solids and not liquids, since in liquids the electric field gradient at the nucleus averages to zero (the electric field gradient tensor has trace zero).
Nuclear reaction – It is a process in which two nuclei, or a nucleus and an external sub-atomic particle, collide to produce one or more new nuclides. Hence, a nuclear reaction causes a transformation of at least one nuclide to another.
Nuclear reactor – It is a device in which nuclear fission can be sustained and controlled in a self-supporting nuclear reaction. The varieties are several, but all incorporate certain features, including fissionable material or fuel, a moderating material (unless the reactor is operated on fast neutrons), a reflector to conserve escaping neutrons, provisions of removal of heat, measuring and controlling instruments, and protective devices. It is also a device in which a fusion chain reaction can be initiated, maintained, and controlled. Its essential components are fuel, shielding, and coolant. There are different approaches to fusion. Nuclear reactors are used at nuclear power plants for electricity generation. Nuclear reactor is the heart of a nuclear power plant.
Nuclear safety – It consists of the protection of people and the environment from the harmful effects of ionizing radiation.
Nuclear safety culture – IAEA safety series No. 75-INSAG-4 defines nuclear safety culture as ‘that assembly of characteristics and attitudes in organizations and individuals which establishes that, as an overriding priority, nuclear plant safety issues receive the attention warranted by their significance’.
Nuclear steam supply system (NSSS) – It is that part of a nuclear power plant which incorporates the nuclear heat source, the heat transport system, and other systems directly connected to the nuclear steam supply system. It is normally referred to as ‘N-triple S’.
Nuclear structure – It is the atomic nucleus at the centre of the atom, containing more than 99.975 % of the total mass of the atom. Its average density is around 3 × 1,011 kilogram per cubic centimeter. Its diameter is around 10 to the power -12 centimeter and hence is much smaller than the diameter of the atom, which is around 10 to the power -8 centimeter. The nucleus is composed of protons and neutrons. The number of protons is denoted by ‘Z’, the number of neutrons by ‘N’. The total number of protons and neutrons in a nucleus is termed the mass number and is denoted by ‘A’ which is equal to ‘N + Z’.
Nuclear supply chain – It is the system of organizations, people, technology, activities, information and resources involved in moving nuclear energy from generator / supplier to customer.
Nuclear transmutation – It is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed. A transmutation can be achieved either by nuclear reactions (in which an outside particle reacts with a nucleus) or by radioactive decay, where no outside cause is needed.
Nuclear waste – It is a particular type of radio-active waste which is produced as part of the nuclear fuel cycle. Radio-active waste is a broader term which includes all waste that contains radio-activity. Nuclear waste is produced as a result of the activities needed to produce nuclear fission. These include extraction of uranium from ore, concentration of uranium, processing into nuclear fuel, and disposal of by-products.
Nucleation – It is the initiation of a phase transformation at discrete sites, with the new phase growing on the nuclei. In case of the formation of non-metallic inclusion, nucleation is the stage in which nuclei of new phase are formed as a result of super saturation of the solution (liquid or solid steel) with the solutes (e.g. Al and O) due to dissolution of the additives (deoxidation or desulfurization agents) or cooling down of the steel. The nucleation process is determined by surface tension on the boundary inclusion-liquid steel. The less the surface tension, the lower super saturation is needed for formation of the new phase nuclei. The nucleation process is much easier in the presence of other phase (other inclusions) in the liquid steel. In this case the new phase formation is determined by the wetting angle between a nucleus and the substrate inclusion. Wetting condition (low wetting angle) are favorable for the new phase nucleation.
Nucleation kinetics – It is the rate of formation of stable nuclei.
Nucleation processes – These processes play a key role in the solidification of castings by controlling to a large extent the initial structure type, size scale, and spatial distribution of the product phases. During several solidification processes, the size scale of critical nucleation events is too small and the rate of their occurrence too rapid for accurate observation by direct methods. Nonetheless, nucleation effects in the solidification micro-structure exert a strong influence on the grain size and morphology as well as the compositional homogeneity. The final micro-structure is also modified by the crystal growth, fluid flow, and structural coarsening processes which are important in the later stages of ingot freezing.
Nucleon – It is either a proton or a neutron, which is considered in its role as a component of an atomic nucleus.
Nucleophile – It is an atom or molecule which can donate an electron pair to another atom or molecule. All molecules or ions with a free pair of electrons or at least one pi bond can act as nucleophiles, by which they are attracted to electron-deficient regions of other species; a chemical reaction involving a nucleophile donating an electron pair to an electrophile can be referred to as nucleophilic attack. Because they donate electrons, nucleophiles are Lewis bases by definition.
Nucleus – It is the heavy central core of an atom, in which majority of the mass and the total positive electric charge are concentrated. It is the first structurally stable particle capable of initiating recrystallization of a phase or the growth of a new phase and possessing an interface with the parent metallic matrix. The term is also applied to a foreign particle which initiates such action.
Nuclide – It is a species of atom distinguished by the constitution of its nucleus. Nuclear constitution is characterized by its mass number, atomic number, and nuclear energy state, provided that the mean life in that state is long enough to be observable.
Nugget – It is a small mass of metal, such as gold or silver, found free in nature. It is the weld metal joining the work-pieces in a spot, seam, or projection welds.
Nugget size (resistance welding) – It is the diameter of a spot or projection weld or width of a seam weld measured in the plane of the faying surfaces.
Number density – It is a measure of the concentration of countable objects (atoms, and molecules etc.) in space, expressed as the number per unit volume.
Numerical analysis – It is the study of algorithms which use numerical approximation (as opposed to the symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics). It is the study of numerical methods which attempt to find approximate solutions of problems rather than the exact ones. Numerical analysis finds application in all fields of engineering. Current growth in computing power has enabled the use of more complex numerical analysis, providing detailed and realistic mathematical models in science and engineering.
Numerical aperture (NA) – It is the product of the lowest index of refraction in the object space multiplied by the sine of half the angular aperture of the objective.
Numerical code – It is the numerical designation of each class or sub-class of resource quantity as defined by the United Nations Framework Classification for Mineral Resources (UNFC). Numerical codes are always quoted in the same sequence (i.e., E, F, G).
Numerical control (NC) – It is also called computer numerical control (CNC). It is the automated control of tools by means of a computer. It is used to operate tools such as lathes, drills, mills, grinders, routers, and 3D-printers. Computer numerical control transforms a piece of material (metal, plastic, wood, ceramic, stone, or composite) into a specified shape by following coded programmed instructions and without a manual operator directly controlling the machining operation.
Numerical control programming – It is the process of developing a set of instructions which controls a machine tool or other manufacturing device to produce a part.
Nut – It is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten multiple parts together. The two partners are kept together by a combination of their threads’ friction (with slight elastic deformation), a slight stretching of the bolt, and compression of the parts to be held together.
Nut coke – It is fraction of the coke in the size range of +10 millimeters to -30 millimeters. It is charged with the ore burden in the blast furnace.
Neutralization – There is a wide range of pH of the untreated wastewater and it is not so easy to treat the wastewater with such type of varying range of the pH value. To optimize the treatment efficiency the neutralization process is used to adjust the pH value. To reduce the pH value sulphuric or hydrochloric acids can be added and to raise the pH value, dehydrated lime or sodium hydroxide alkalis can be added. Normally the process of neutralization is carried in a rapid mix holding tank or in a tank used for equalization. To control the pH of the discharge in order to meet the standards, the process of neutralization can be carried out at the end of the treatment.
Nutrients – Both nitrogen and phosphorus, along with carbon, are essential nutrients for growth. When discharged to the aquatic environment, these nutrients can lead to the growth of undesirable aquatic life. When discharged in excessive amounts on land, they can also lead to the pollution of groundwater.
Nutrient requirements (C:N:P ratio) – Maintaining the correct ratio between carbon, nitrogen, and phosphorus. (C:N:P ratio ) is very important for plant nutrition but also for maintaining the correct chemical and biological balance of aquatic ecosystems. Besides carbon, hydrogen, and oxygen, bio-mass needs nitrogen, phosphorous, and micro-nutrients such as iron, calcium, magnesium, copper, zinc and so on. Most industrial wastewaters lack nitrogen and phosphorus which is to be added (in the form of urea, super-phosphate or ammonium phosphate) to maintain optimal microbial growth conditions. The minimum C:N:P ratio needed for optimal microbial growth in the in aerobic processes is 100:5:1, and anaerobic processes is 330:5:1.
n-value – It is also called the strain-hardening exponent. It is equal to the slope of the true stress / true strain curve up to maximum load, when plotted on log-log coordinates. The n-value relates to the ability of as sheet metal to be stretched in metal-working operations. The higher is the n-value, the better is the formability (stretchability).
Nylon – It is the generic name for all synthetic polyamides. It is polyamide which has high strength, high elongation, and good resistance to abrasion, fatigue and impact. While moisture absorption not as high as cotton, it absorbs up to 10 % of its own weight in moisture, and hence, it has poor dimensional stability.
Nylon plastics – These are the plastics based on a resin composed principally of a long-chain synthetic polymeric amide which has recurring amide groups as an integral part of the main polymer chain. Numerical designations (nylon 6, nylon 6/6, and so on) refer to the monomeric amides of which they are made. These plastics are characterized by high toughness and elasticity.
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