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


Chadwick, Sir James (1891-1974)
English physicist who discovered the neutron.1935 Received the Nobel Prize for physics for the discovery of the neutron.

Chain
The chain is a unit of length.Conversions1 chain (engineers or Ramden)=100 feet1 chain (US or Gunter)=66 feet1 chain (engineers or Ramden)=30.48m1 chain (US or Gunter)=20.1168m1 chain (engineers or Ramden)=33.33 yards1 chain (US or Gunter)=22 yardsttle='Length';xiunt='m';yiunt='chain';mconv=30.48;cconv=0.0; See also: Furlong, Mile, Nautical Chain, …

Chain Drive
Power transmission by means of an endless chain running around chain wheels or sprocket wheels.Examples of uses:Transmit power between pedals and rear wheel on a bicycle - probably the most common use.Transmit power from engine to rear wheel on a motorbike.Provide speed ratio change, transmit power and phase lock between crankshaft and camshafts on…

Chain Reaction
A process in which the fissioning of one nucleus initiates the fissioning of others. See also: Critical Chain Reaction, Critical Mass.

Chamfer
Beveled corner.

Chandrasekhar Limit
A limit which mandates that no white dwarf (a collapsed, degenerate star) can be more massive than about 1.4 solar masses. Exclusion principle repulsion among the electrons in a star more massive than this can`t support the star against its own gravity.Any degenerate object more massive must inevitably collapse into a neutron star. See also: Neutro…

Change of State
The change in a substance between solid and liquid or between liquid and gas.

Channel
ElectronicsA frequency interval or frequency band assigned for communications.A single path for the transmission of electric signals, where the term 'path' may refer to separate frequencies or time slots.The conducting layer in an FET between the source and drain.

Characteristic Impedance
The ratio of voltage and current at every point along a transmission line on which there are no standing waves. See also: Impedance, Standing Wave.

Characteristic X-ray
An X-ray having a unique energy that is emitted by an atom during its de-energization after ionization of one of its electrons.

Charcoal
Used to describe different forms of carbon. Formed by heating vegetable or animal matter in the absence of air.

Charge
The excess or deficiency of electrons resulting in the body having negative or positive charge. The unit of charge is the Coulomb (C).ttle='Ampere-Hour';xiunt='C';yiunt='Ah';mconv=3600;cconv=0.0; See also: Charged, Conservation of Charge, Coulomb, Faraday.

Charge Coupled Device
A self-scanning semiconductor imaging device which uses metal-oxide-semiconductor, surface storage and information transfer technologies.

Charged
Possessing a net negative or positive charge. See also: Charge.

Charged Particles
Particles with positive or negative charge, for example electrons, protons or ions.

Charles' Gas Law
For a fixed mass of gas at constant pressure the volume is directly proportional to the temperature [Kelvin]. Therefore, if the pressure remains constant, the volume of a gas will increase with the increase of temperature. It was developed by Jacques Charles and is Also known as the Charles-Guy-Lussac Law. Therefore, if pressure and amount of gas…

Charm
The flavor of the fourth quark. See also: Bottom, Down Quark, Quark, Top.

Charpy Test
An impact test in which a V-notched, keyhole-notched, or U-notched specimen, supported at both ends horizontally, is struck behind the notch by a striker mounted at the lower end of a pendulum; the energy that is absorbed in fracture is calculated from the height to which the striker would have risen had there been no specimen and the height to whi…

Chasing Threads
The process of cutting threads in a lathe or screw machine. See also: Thread.

Chatter
The vibrations caused between the work and the cutting tool which leave distinctive tool marks on the finished surface that are objectionable.

Check Valve
A valve that permits the passage of a liquid or gas in one direction only. It stops, or checks, reverse flow.

Checksum
A number formed by an algorithm, possibly addition, applied to a data record. A communications system will transmit the record and the checksum for error detection by the receiver.

Chelate
A stable complex of a metal with one or more polydentate ligands. For example, calcium complexes with EDTA to form a chelate.

Chemical
1. of or pertaining to chemistry. 2. a substance.

Chemical Bond
A chemical bond is a strong attraction between two or more atoms. Bonds hold atoms in molecules and crystals together. There are many types of chemical bonds, but all involve electrons which are either shared or transferred between the bonded atoms.

Chemical Equation
A compact notation for describing a chemical change. The formulas of the reactants are added together on the left hand side of the equation; the formulas of the products are added together on the right side. Coefficients are inserted before the formulas to ensure that the equation is balanced. The phase in which each substance is found is usually i…

Chemical Formula
A representation of a chemical substance that uses chemical symbols to denote the constituent atoms, and subscripts to indicate the relative numbers of atoms of each type.Example:water is represented by the formula H2O

Chemical Set Cement
A cement that sets through reaction or precipitation. Often subjected to a high temperature during manufacture or use. See also: Cement.

Chemical Stability
The tendency of a substance or mixture to resist chemical change. See also: Mixture.

Chemistry Books
Periodic Table of the Chemical Elements By John David Edlin, Published By: J D Edlin.Laminated Poster: Periodic Table of the Elements By David Dorwood, Published By: Schofield & Sims Ltd.Introduction to the Thermodynamics of Materials By David R. Gaskell, Published By: Taylor & Francis Inc.

Chemistry Conversions
AmagatThe unit of density of a gas at stp equal to 44.614774 molm-3.atmAn abbreviation of atmosphere.haAn abbreviation of hectare, a derived SI unit of area that is mainly used in agriculture to describe the area of fields.kJAn abbreviation of kilojoule, one thousand joules. The SI unit of energy is the joule.Rankine Temperature ScaleAn …

Cherenkov Radiation
Radiation emitted by a massive particle which is moving faster than light in the medium through which it is travelling. No particle can travel faster than light in vacuum, but the speed of light in other media, such as water, glass, etc., are considerably lower. Cherenkov radiation is the electromagnetic analogue of the sonic boom, though Cherenkov…

Chestnut
Very durable and much like oak. Comparitavely easy to work and does not shrink much when drying.

Cheval Vapeur
Metric horsepower.A unit of power representing that required to raise a 75kg mass 1 metre in 1 second.Conversions1 cheval vapeur (ch)=1 PS1 ch=735.5 W1 ch=0.986 hp1 ch=75 kgf m s-1ttle='Power';xiunt='W';yiunt='PS';mconv=735.5;cconv=0.0; See also: Horsepower, Power.

Chip
A piece of semiconductor substrate on which active and/or passive circuit elements have been fabricated. See also: Integrated Circuit.

Chipping
The process of cutting metal with a cold chisel and hammer. See also: Hammer.

Chirality
Handedness, the quality of having non-superimposable mirror images. For example, a shoe or a glove is chiral. See also: Dextrorotatory, Levorotatory, Racemic Mixture.

Chirp
A chirp is a sound that has a rapid increase in frequency. See also: Tone Burst.

Chlorine
A greenish yellow gas and second in the halogen group. It has an irritating smell and a destructive effect on the respiratory system. It is a powerful oxidising agent. It was first used to purify water by William Cruikshank in 1800. Symbol Cl

Chloroethane
A colorless, flammable gas or refrigerated liquid with a faintly sweet odour. Symbol C2H5Cl Also known as Ethyl Chloride, Monochloroethane

Chloroform
Volatile colourless heavy liquid used as an anaesthetic and solvent. It is produced by reaction of chlorine with ethanol and by the reduction of carbon tetrachloride with moist iron. It was once used as a general anesthetic in surgery but has been replaced by less toxic, safer anesthetics, such as ether. Chemically, it is employed as a solvent for …

Chloromethane
A colourless extremely flammable gas with a slightly sweet odor. Once commonly used as a refrigerant. Symbol CH3Cl Also known as Methyl Chloride

Choke
An inductor designed to present a high impedance to alternating current. See also: Inductance, Radio Frequency Choke.

Chord
AcousticsThree or more notes sounded simultaneously.AerodynamicsThe distance measured from the leading-to trailing-edge of an airfoil.MathematicsA line segment that connects two points of a curve or circle.

Chromatic Aberration
A defect in lenses that causes different colors (wavelengths) of light to have different focal lengths. See also: Aberration.

Chromatography
A method for separating mixtures based on differences in the speed at which they migrate over or through a stationary phase. See also: Column Chromatography, Mixture.

Chromel
An alloy of nickel with about 10% chromium, used with Alumel in K-type thermocouples.

Chromium
Chromium is a bright, blue/white metal with excellent corrosion resistance. It is obtained by the aluminium reduction of Cr2O3, the source of which is chromite, a double oxide of chromium and iron which generally also contains magnesium. Chromium is soluble in HCl and H2SO4, but not in H3PO
Chromium Dioxide
A black crystalline solid. Symbol CrO2

Chromium Oxide
The only stable oxide of chromium. It is a bright to dark green crystalline powder insoluble in alkalis and acids. Used as a pigment. Symbol Cr2O3

Chromium VI Oxide
Highly poisonous. Symbol CrO3

Chromophore
A group or substructure on a molecule that is responsible for the absorption of light.

Chromosphere
The layer of the solar atmosphere above the photosphere and beneath the transition region and the corona. It is seen during eclipses as a bright red ring around the Sun, and the term burning prairie has been used to describe it. See also: Sun.

Chronology Protection Conjecture
The concept that the formation of any closed timelike curve will automatically be destroyed by quantum fluctuations as soon as it is formed. In other words, quantum fluctuations prevent time machines from being created.S.W. Hawking

Chuck
Photograph courtesy of Draper.co.ukA device on a machine tool to hold the workpiece or a cutting tool, attached to a rotating spindle.Independent ChuckA chuck in which each jaw may be moved independently of the others. See also: Collet, Drill Bits, Drill Press.

Circle
The set of points equidistant from a given point (the centre).function init(){}Circle of radius rmulticalc_form(0)

Circle Fitting
This is a common method of extracting mode shape vectors from a set of frequency response functions. It is based upon the principle that a plot of the out of phase, or imaginary component versus the in-phase, or real component will trace a circular arc for each resonance. The method uses single degree of freedom technology and has been extended to …

Circlip
Photograph courtesy of Draper.co.ukA clip that fits in a groove on a shaft and locates the shaft axially in one direction.Circlip PliersPhotograph courtesy of Draper.co.ukPliers with a round bar at the end of each jaw that fit in the holes of a circlip so that it may be sprung open to fit or remove from the workpiece.

Circuit
Interconnection of components to provide an electrical path between two or more components.

Circuit Breaker
A protective device used to open a circuit when current exceeds a maximum value. In effect a reusable fuse.

Circular Cone
A cone whose base is a circle. See also: Circle.

Civil Engineering Calculations
Cantilever BeamA beam that is held in an encastre at one end whilst the other end is unsupported.

Clamp
A fastening device which secures something within its jaws without constant human pressure.Band ClampFor clamping round, oval and odd-shaped pieces. Consists of nylon band and ratchet mechanism. When used in conjunction with corner blocks it can be used to clamp objects such as picture frames.Bar ClampA tool with a stationary head and a sliding foo…

Clamping Force
The compressive force which a fastener exerts on the joint. See also: Force, Joint.

Clapboard
Thin, narrow boards of tapering cross-section applied horizontally as siding on wood-frame houses.

Clarity
In concert hall acoustics, the ratio, expressed in decibels, of the energy in the first 80 milliseconds of an impulse sound arriving at a listener's position divided by the energy in the sound after 80 milliseconds. The divisor is approximately the total energy of the reverberant sound.More generally, clarity refers to the degree to which the separ…

Clearance
The distance or angle by which one object or surface clears another.

Cleavage
Transcrystalline fracture along specific crystallographic planes; usually associated with low-energy fracture; may exhibit river patterns and/or tongues. See also: Brittle Fracture, Crystal.

Clerk-Maxwell, James (1831-79)
Clerk-Maxwell's greatest work was his initial contribution to electromagnetic radiation.As a boy of fifteen he devised a method of drawing certain oval curves, a method which was written up by the Royal Society of Edinburgh. He attended Cambridge and graduated there as second wrangler. He went into teaching physics; first at Aberdeen then at London…

Click
When the duration of a sound is less than a time threshold required for pitch recognition, the sound is heard as a click rather than a tone.The time threshold is roughly 20 milliseconds.

Climate Change
The average global temperature is rising sharply. Humans are contributing to the greenhouse effect by emitting greenhouse gases that trap energy and warm the atmosphere. See also: Greenhouse Effect.

Clipper Circuit
A circuit that blocks or removes the portion of a voltage waveform above some threshold voltage. See also: Clipping.

Clipping
Refers to a type of distortion that occurs when an amplifier is driven into an overload condition. Usually the 'clipped' waveform contains an excess of high-frequency energy.The sound becomes hard and edgy.On an oscilloscope clipping appears to flatten the tops and/or bottoms of the wave forms as if someone took a pair of scissors and 'clipped or c…

Closed Interval
An interval that includes it's endpoints.

Closed Loop
A system in which the output is used to control the input.Any deviation from the standard is fed back into the control system in such a sense that it will reduce the deviation of the controlled quantity from the standard. See also: Control Loop, Open Loop.

Closed System
A system which can exchange only energy with its surroundings.

Clouds
A visible collection of minute particle matter, such as water droplets and/or ice crystals, in the free air. A cloud forms in the atmosphere as a result of condensation of water vapour. Condensation nuclei, such as in smoke or dust particles, form a surface upon which water vapour can condense.AltocumulusComposed of flattened, thick, gray, globular…

CMYK
Cyan, magenta, yellow, and black are the base colours used in printing processes. CMY are the primary colourants of the subtractive colour model. See also: Additive Colour System, Additive Primaries.

Coal
A fossil fuel which is made mostly of carbon. It is formed from plants that grew around 150 million years ago.

Coal Tar
A dark brown to black cementitious material produced by the destructive distillation of bituminous coal.

Coanda Effect
The effect that indicates that a fluid tends to flow along a surface, rather than flow through free space.

Coaxial Cable
A round cable with a central conductor and screening around with a insulating medium between. The characteristic impedance is given by:whereZc = characteristic impedance [O]µ = µ0µr = permeabilitye = e0er = permittivitya = radius of inner conductorb = radius of outer conductor

Cobalt
Cobalt is a hard, grey metal which is ferromagnetic. It is usually found in association with nickel in arsenical ores. Cobalt is relatively unreactive, being stable in airand only slowly attacked by dilute acids. It does not combine with hydrogen and nitrogen but it does react with carbon, oxygen and steam at elevated temperatures, producing CoO in…

Code
When used as a verb, code means to write a program. As a noun, code refers to thebinary instructions of a program. See also: Bug, Computer, Programming Languages, Pure Procedure Code.

Codec
Acronym for compressor/decompressor.

Codons
Organic bases in sets of three that form the genetic code.

Coercive Force
Magnetizing force needed to reduce residual magnetism in a material to zero.

Cog
A tooth in the rim of a wheel or a gear tooth in a gear wheel. See also: Gear Design.

Cognition
The processes of human or animal thought. The acquisition, understanding, representation and manipulation of knowledge. See also: Cognitive Science.

Cognitive Science
The study of thought processes in animals and machines. See also: Cognition.

Coherence
This gives a measure of the linear dependence between signal A and B.whereGAB(f) = cross-spectrum between signal A and B obtained by averagingGAA(f) and GBB(f) = power spectra of signal A and B obtained by averagingA two channel function which is used when an output (e.g. displacement) is caused by more than one inp…

Coherent
A property of two or more sources of waves that have the same wavelength and maintain constant phase differences.

Cohesive Force
The attractive force exerted on a liquid molecule by the neighbouring liquid molecules.

Coincidence
The sound radiation efficiency of a plate is dependant upon the coupling of sound waves in the air and flexural waves (vibration) in the plate. Optimum efficiency (maximum energy transfer from vibration to sound or visa versa) is achieved when the plate is vibrated such that the wavelength of flexural waves in the plate is equal to the wavelength o…

Coke
A hard, dry substance containing carbon that is produced by heating bituminous coal to a very high temperature in the absence of air.

Cold Drawing
This is a process for finishing a hot rolled rod or bar at room temperature by pulling it through the hole of a die of the same shape but smaller in size. The bars or rods are cleaned of scale by pickling or other methods prior to cold drawing and then coated with lime which aids as a lubricant in the drawing operation. See also: Cold Rolling, Cold…

Cold Rolling
The cold working of hot rolled material by passing it between power driven rolls. The process is generally used for flat bars of such a size that they cannot be pulled through a die and for the production of cold rolled sheets by cold reducing hot rolled and pickled sheets. See also: Cold Drawing, Cold Working.

Cold Treatment
A heat treat process which converts unstable retained Austenite into stable untempered Martensite. Deep Freeze is usually performed at -73°C to -100°C indry ice mixed with alcohol or mechanical refrigeration. Deep freezing is actually an extension of quenching. Insome instances, the Mf (Martensite finish) temperature may be well below room temperat…

Cold Working
The plastic deformation of a metal at a temperature below that at which it re-crystallizes. Increasing the amount of cold work causes the dislocation density to rise in the material, making it more difficult to plastically deform the material and eventually cause brittle fracture. There are five methods:Cold rollingCold drawingCold drawing and grin…

Collagen
The most abundant protein in mammals. A major component of tendons, bones, skin, teeth and cartilage.