Copy of `DiracDelta - Science & Engineering encyclopedia`

The wordlist doesn't exist anymore, or, the website doesn't exist anymore. On this page you can find a copy of the original information. The information may have been taken offline because it is outdated.

DiracDelta - Science & Engineering encyclopedia Category: Sciences > Science & Engineering Date & country: 01/12/2007, UK Words: 4470

Myopia
Nearsightedness. Images of distant objects are formed in front of the retina.

Myriagram
A unit of weight equal to ten thousand grams or 10kg. See also: gram.

Myrialitre
A unit of volume of ten thousand litres. See also: Litre.

Nadir
The point on the celestial sphere directly below an observer, diametrically opposite the zenith. See also: Zenith.

Nand Gate
Gate whose output is 0 whenboth input are 1 and 1 in all other cases.NAND gates can be used to form other gates.AND gateInverterOR gateNOR gateEXCLUSIVE-OR gate

Nanometre
Abbreviated as nm, unit of length equal to 10^-9 metres, and equal to 10 Š(Angstroms).nanometreObject1,000,000 = 1 mmDiameter of pin head100,000Width of a human hair10,000Size of red blood cell MEMS1,000 = 1µmWidth of circuit lines on a chip100Size of a Virus10The distance between the head on a hard disk drive and the media.1 = 1nmdiamet…

Naphtha
Volatile solvent distilled from petroleum used for cleanup and to thin solvent-based coatings.

National Physical Laboratory
National measurement standards laboratory for the UK.

Nato Alphabet
Used when communicating over the radio to ensure there is no miscommunication of important information.AAlphaBBravoCCharlieDDeltaEEchoFFoxtrotGGolfHHotelIIndiaJJulietKKiloLLimoMMikeNNovemberOOscarPPapaQQuebecRRomeoSSierraTTangoUUniformVVictorWWhiskyXX-RayYYankeeZZulu

Natural Frequency
The frequency of free vibration of a system. The frequency at which an undamped system with a single degree of freedom will oscillate upon momentary displacement from its rest position. Also known as Normal Mode. See also: Damped Natural Frequency, Modal Analysis, Ringing.

Natural Gas
The cleanest fossil fuel, and hence a potential short-term aid to slowing climate change.

Natural Number
Any one of the numbers 1, 2, 3, 4, 5, .. See also: Composite Number, Integer, Whole Numbers.

Naturally Aspirated
An engine that draws air in without the assistance of a supercharger or turbocharger. See also: Internal Combustion Engine, Turbocharger.

Nautical Chain
A unit of length equal to 15 feet.Conversions1 nautical chain=15 feet1 nautical chain=4.572mttle='Length';xiunt='m';yiunt='nautical chain';mconv=4.572;cconv=0.0; See also: Chain, Foot.

Nautical Mile
The average distance on the earth's surface subtended by one minute of latitude. The International nautical mile (used by the Admiralty and most other nations) is 1852m (~6076ft 1inch).Maps were drawn to follow this standard and world aviation standards still use the nautical mile.ttle='Length';xiunt='m';yiunt='nautical mile';mconv=1852;cconv=0.0; …

Naval Brass
A brass made with 60% copper 40% zinc with 1% tin added for extra corrosion resistance.

Navier Stokes Equation
The primary equation of computational fluid dynamics, relating pressure and external forces acting on a fluid to the response of the fluid flow. Forms of this equation are used in computations for aircraft and ship design, weather prediction, and climate modelling.

Near Field
Locations close to the sound source between the source and the far field. The near field is typically characterized by large sound pressure level variations with small changes in measurement position from the source.The sound pressure does not obey the inverse-square law and the particle velocity is not in phase with the sound pressure. See also: F…

Nebula
Orion NebulaA cloud of dust and gas in space which is visible to observers on the Earth because it either emits, reflects or absorbs starlight.

Necking
Reduction of the cross-sectional area of a material in a localized area caused by uniaxial tension or a machined groove or undercut in a shaft to permit mating parts to be screwed tightly against a shoulder or to provide clearance for the edge of a grinding wheel.

Needle Roller Bearing
A special bearing which has a small OD when compared to its ID. The rolling elements take the form of needle rollers that allow high radial loads to be taken. Not capable of taking axial loads.

Negative
Symbol : -A quantity or value that is less than zero.

Negative Feedback
Feedback from the output of an analogue circuit that tends to oppose the input. This has the effect of stabilizing the circuit. See also: Feedback.

Negative Ground
A system where the negative terminal of the source is connected to the system's metal chassis.

Negative Numbers
Numbers that are less than zero are negative numbers. Usefulness suggested by Raffael Bombelli in 1572.Addition of a negative is equivalent to subtracting a positive.For example;Subtraction of a negative is equivalent to adding a positive.For example;A positive multiplied by a negative creates a negative.For example;A negative multiplied by a negat…

Negative Resistance
A device having negative voltage-current characteristics. For a certain value of voltage, a point is reached where a voltage increase causes a current decrease (equivalent to a resistance decrease).

Negative Temperature Coefficient
A term used to describe a component whose resistance or capacitance decreases when temperature increases.

Neodymium
Neodymium is one of the more reactive members of the lanthanide group. It oxidises rapidly in air to form an oxide which rapidly spalls away to reveal fresh metal. The metal reacts slowly with cold water and rapidly with hot water. The metal is found in monazite (CePO₄, a principal source of the rare earths and thorium) and orthite. The …

Neon
Light gaseous inert element. Symbol NeDiscoveredDiscovered from its bright red spectral lines by the Scottish chemist William Ramsay and the English chemist Morris William Travers in 1898 from a liquified air sample.

Neon Bulb
Glass envelope filled with neon gas which when ionized by an applied voltage will glow red. See also: Neon.

Neper
A unit expressing the ratio of two numbers as a natural logarithm. See also: Logarithm.

Neptune
The methane in Neptune's atmosphere causes it to be blue. The outermost gas giant in our solar system. For the years 1979 to 1999, it is actually the outer most planet in the solar system since Pluto has such an eccentric orbit that it crosses over to be inside Neptune's orbit during those years. Neptune is a dynamic world with cloud features and c…

Neptunium
Produced artificially by nuclear reaction between uranium and neutrons. Symbol Np

Network Polymer
A polymer composed of trifunctional mer units that form three-dimensional molecules. See also: Polymer.

Neutral Density
An optical coating that appears grey to the eye and has a flat absorption curve throughout the visible spectrum.Neutral density filters decrease the intensity of light without changing the relative spectral distribution of energy.

Neutral Flame
A gas flame in which the oxygen and acetylene volumes are balanced and both gases are completely burned.

Neutral Plane
Plane through a beam where compression and tension stresses are zero. See also: Compressive Stress, Stress, Tensile Stress.

Neutral Solution
An aqueous solution in which the concentrations of aqueous hydrogen ions and hydroxide ions are equal. At 25 °C their concentrations are each 1.0x10^-7mol litre^-1. See also: pH.

Neutrino
A neutral lepton; one exists for each of the charged leptons (electron, muon, and tau) all of which are very light and could possibly have zero mass. Neutrinos participate only in weak and gravitational interactions and are therefore very difficult to detect. Neutrinos are created in energetic collisions between nuclear particles. The universe is f…

Neutron
A sub-atomic particle, within the nucleus of an atom,which has unit mass and zero charge. A member of thebaryon and hadron familiesof elementary particles. It was discovered by Chadwick in 1932.Protons and neutrons comprise atomic nuclei and they are both classed as nucleons.Click on an item to paste into clipboard or use clipboard symbol at end to…

Neutron Star
A star (approximately sun-sized or larger), a remnant of a supernova explosion, in which gravity has caused all matter to collapse to a giant nucleus, composed only of neutrons. The collapse is also expected to greatly amplify any magnetic field present in the pre-collapse star, as well as speed up enormously any rate of rotation. It is believed th…

New Car Assessment Program
The U.S. government “crash testing� program.

New General Catalogue
A catalogue of non-stellar celestial objects that was compiled by JLE Dreyer of Armagh Observatory and published in 1888. The original listed 7,840 objects and was followed by a supplement which now includes 5,386 not on the original. Objects on the original list are identified by the letter NGC followed by the catalogue number. Those objects on th…

newton
The SI unit of force. 1 newton is defined as the force required to accelerate a mass of 1 kilogram by 1 metre per second per second.ttle='Force';xiunt='N';yiunt='poundal (pdl)';mconv=0.138255;cconv=0.0; See also: Force, Newton Metre.

Newton Metre
The SI unit of torque. Abbreviated as Nm. The torque or turning moment acting on a body is defined as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis about which the body is being rotated.ttle='Torque';xiunt='Nm';yiunt='ftlb';mconv=1.35582;cconv=0.0; See also: Metre, Newton, …

Newton, Sir Isaac (1642-1727)
Newton was a mathematician and natural philosopher (physicist). Newton's principle achievement was that he went beyond the theoretical; he did experimental work. Though he built on the work of Copernicus, Kepler, and Galileo; it is to Newton to whom we point as the person primarily responsible for the mechanistic theory which accounts for the perce…

Newton's Laws of Motion
Sir Isaac Newton published Philosophiae Naturalis Principia Mathematica in 1687. This text contains the three basic laws on which mechanics is basedNewton's First LawEvery body continues in its state of rest or of uniform motion in a straight line unless acted on by some external force.No force = no acceleration

Newtonian Fluid
A fluid whose viscosity doesn't depend on gradients in flow speed. Gases and low-molecular weight liquids are usually Newtonian fluids. See also: Non-Newtonian Fluid, Viscosity.

Newtons Alloy
A low melting point alloy.

Nibble
A group of four bits or half a byte (8-bits). See also: Binary Notation, Bit, Byte, Least Significant Bit (LSB), Most Significant Bit (MSB).

Nickel
Nickel is a silver-white metal which occurs mainly in the sulphide and arsenic ores. It is extracted by roasting to NiO and then reducing using carbon. Pure nickel is manufactured by the Mond process, in which impure nickel is reacted with carbon monoxide (CO) to produce Ni(CO)₄, which is then decomposed at 200°C to yield 99.99% Ni. Pure…

Nickel Brass
A copper alloy containing zinc and a small quantity of nickel.

Nickel Cadmium Battery
The battery has a nickel-hydroxide cathode, a cadmium anode, and aqueous potassium hydroxide electrolyte.

Nickel Metal Hydride Battery
The battery has a nickel-hydroxide cathode, a metal hydride (a variety of metal alloys are used) anode, and aqueous potassium hydroxide electrolyte.

Nickel Silver
Copper nickel zinc alloy.

Nicotine
Colourless, very poisonous oily liquid. Symbol C

Nimonic
An alloy consisting of roughly 80% nickel and 20% chromium with additives such as titanium and aluminium. The main use is in gas turbine blades.

Niobium
Niobium is a silver coloured metal which is generally found in conjunction with tantalum, the two elements being separated by fractional crystallisation of their respective fluoro-complexes. As a pure metal, is very reactive and forms an extremely stable oxide when exposed to air which enhances its corrosion resistance. Niobium will react with a va…

Nitrating
A case hardening process in which ammonia or some other form of nitrogen is introduced to the surface of certain alloys. See also: Ammonia, Case Hardening, Nitrogen.

Nitric Acid
Colourless, corrosive, acid liquid that attacks most metals and other substances releasing nitrogen dioxide. Symbol HNO₃ Also known as Aqua Fortis - literally meaning 'strong water'.

Nitric Oxide
A colourless gas that forms nitrogen dioxide in contact with air. Symbol NO

Nitrile
An organic compound which has a -C=N functional group. See also: Carbon, Nitrogen.

Nitrobenzene
A yellow liquid obtained from the action of concentrated nitric and sulphuric acid on benzene. Symbol C₆H₅NO₂ Also known as Oil of Mirbane

Nitrogen
A gaseous colourless and odourless element that makes up about 80% of the atmosphere. Symbol NDiscovered1772 by Daniel Rutherford.

Nitrogen Oxides
Several air-polluting gases composed of nitrogen and oxygen which play an important role in the formation of photochemical smog. Nitrogen oxides are collectively referred to as NO_x, where x represents a changing proportion of oxygen to nitrogen.Internal combustion engines are significant contributors to the worldwide nitrogen oxide emiss…

Nitrous Oxide
An anaesthetic. Symbol N₂O Also known as Laughing gas

Nobel Prize
Awarded annually as per Alfred Nobel's last will and testament.1901Chemistry - Jacobus Henricus Van't Hoff in recognition of the extraordinary services to the discovery of the laws of chemical dynamics and osmotic pressure in solutions.1921Chemistry - Frederick Soddy for his contribution to the chemistry of radioactive substances and his investigat…

Nobelium
A man-made element with an atomic number of 102. Symbol No

Noble Gases
The gaseous chemical elements helium, neon, argon, krypton, xenon and radon, which are all placed in Group 0 of the Periodic Table. They are so named because of their marked reluctance to 'lower' themselves by combining with other chemical elements to form compounds.HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAg…

Noble Metals
Metals, such as gold, silver and platinum, that show a marked reluctance to combine with other elements to form compounds.HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcLanthanidesCePrNdPmSmEuGdTbDyHoErTmYbLuActinidesThPaUNpPuAmCmBkCfEsFmMdNoLr See also: Noble…

Node
ElectronicsJunction or branch point in a circuit.Noise and VibrationA point or line on a vibrating structure that remains stationary.PhysicsThe probability of finding an electron at an orbital node is zero.

Noise
Noise is any undesired signal.AcousticsBy extension, noise is any unwanted disturbance within a useful frequency band, such as undesirable sound waves in a car passenger cabin. The word 'noise' is derived from the same Latin root as the word 'nausea'.In the Roman times of Julius Caesar, chariots were prohibited from the streets of Rome after nightf…

Noise & Vibration Books
Vibrations and Waves By A.P. French, Published By: Nelson Thornes.Sound Intensity By Frank J Fahy, Published By: Spon Press.Psychoacoustics By Eberhard Zwicker, H. Fastl, Published By: Springer-Verlag Berlin and Heidelberg GmbH & Co. KG.Fundamentals of Acoustics By Lawrence E. Kinsler, Austin R. Frey, Alan B. Coppens, James V. Sanders, Published By…

Noise & Vibration Calculations
Acoustic BarriersAn acoustic barrier between two rooms.Acoustic CavityThe acoustics of enclosed volumes are important when considering sound propagation within the volume.Angular FrequencyThe frequency of a steady recurring phenomenum in radians per second.Articulation IndexA quantitative measure of the intelligibility of speech; the percentage of …

Noise & Vibration Conversions
BAn abbreviation of bel, the logarithm of the ratio of two powers. The decibel is one tenth of a bel.belThe bel is the logarithm of the ratio of two powers, and the decibel is one tenth of a bel.DecibelThe human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.PascalThe SI derived unit of pressure.Pres…

Noise Control
The technology of obtaining an acceptable noise environment.The basic system is:Source - Path - ReceiverBased on this system there are three areas in which to control the noise:Control at source - this is the most effective and cost effective solution.Control at path to reduce noise propagation - this is can be applied to just the routes that are m…

Noise Criteria
Standard spectrum curves by which a given measured background noise may be described by a single NC number. Some early problems with the levels set for NC curves lead to the introduction of Preferred Noise Criteria (PNC).Each NC curve is defined by its sound pressure level at eight octave-band centre frequencies: 63, 125, 250, 500 1000, 2000, 4000 …

Noise Exposure Limits
The amount of hearing loss is dependent on the noise level and duration. Based on this a number of limits were set out in 1970 by the Ocupational Safety and Health Act for companies working for the US government.Limiting Daily Exposure Time [hours]Sound Pressure Level [dB(A)]89069249539721001.510211050.5110

Noise Floor
Normally the lowest threshold of useful signal level.

Noise Isolation Class
A single-number rating calculated in accordance with Classification E 413 using measured values of noise reduction. It provides an estimate of the sound isolation between two enclosed spaces that are acoustically connected by one or more paths.

Noise Pollution
Unwanted noise, including traffic noise, machinery noise or music. See also: A Weighting, Community Noise Criteria, Decibel, Noise, Sound Pressure Level.

Noise Reduction Coefficient
Arithmetic mean of sound absorption coefficients at 250, 500, 1000, and 2000 Hz, rounded to the nearest 0.05 metric sabin per square metre. See also: Absorption Coefficient.

Noise Reduction Rating
Indicates a hearing protectors noise reduction capability. It is a single number rating that is required by law to be shown on the label of each hearing protector sold in the United States. See also: Hearing, Hearing Protector.

Noise Reduction
The difference in sound pressure level between any two points along the path of sound propagation. As an example, noise reduction is the term used to describe the difference in sound pressure levels between the inside and outside of an enclosure.There are a number of methods that may be employed to reduce noise. These will vary depending on the sys…

Non-Metal
A term usually reserved for those chemical elements that are very poor electrical conductors in the solid state and liquid states. A number of them are gases at room temperature. When solid or liquid, they tend to have a matt rather than a lustrous appearance. Non-metals gain electrons easily to form anions. About 20% of the known chemical elements…

Non-Newtonian Fluid
A fluid whose viscosity changes when the gradient in flow speed changes. Colloidal suspensions and polymer solutions like ketchup and starch/water paste are non-Newtonian fluids. See also: Newtonian Fluid, Viscosity.

Nonagon
A nine sided polygon. Each internal angle is 140° and the sum of the internal angles is 1260°. See also: Polygon.

Nonary
Associated with 9.

Noncrystalline
The solid state wherein there is no long-range atomic order. Sometimes used synonymously with the terms amorphous, glassy and vitreous. See also: Crystal.

Nonferrous
Metals which contain no iron. Aluminum, brass, bronze, copper, lead, nickel, and titanium are nonferrous. See also: Aluminium, Brass, Bronze, Copper, Iron, Lead, Nickel, Titanium.

Nonillion
A number equal to 10³⁰. See also: Decillion, Octillion.

Noninertial Reference System
Any reference system in which the law of inertia (Newton's first law of motion) is not valid. An accelerating reference system is noninertial. See also: Inertial Reference System, Newtons Laws of Motion, Reference System.

Nonmaskable Interrupt
A hardware interrupt that software cannot disable. See also: Interrupts.

Nonpolar Molecule.
A molecule in which the center of positive charge and the center of negative charge coincide.Examples of nonpolar molecules:CCl₄ and CO₂Examples of polar molecules:CHCl₃ and H₂O.

Nonvolatile Memory
A type of memory that retains information without electrical power. Most ROM memories are also nonvolatile memories.

Nor Gate
Gate whose output is 0 ifany of its inputs is a 1.The truth table for the NOR Gate is:The NOR Gate can be made from NAND Gate:

Nordic Gold
A 89% copper, 5% aluminium, 5% zinc and 1% tin alloy.

Normal
A line perpendicular to a surface or curve.

Normal Stress
Stress acting perpendicular to an imaginary plane cutting through an object. Normal stress has two senses: compression and tension. Normal stress is often simply called stress. See also: Stress.

Normalized Noise Isolation Class
A single-number rating calculated in accordance with Classification E413 using measured values of normalized noise reduction.