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

Canonical Form
In a mathematical context this term is taken to mean a generic or basic representation.

Cantilever Beam
A beam that is held in an encastre at one end whilst the other end is unsupported.

Capacitance
The capacitance is defined as the total electric charge on a body divided by its potential.whereC = capacitance [farad]Q = charge [coulomb]V = potential difference across the capacitor [volt]

Capacitor
An electrical component that passes alternating currents but blocks direct currents.Also called a condenser, it is capable of storing electrical energy or to buffer power supply lines to provide extra charge when needed. Can also be used in other places to filter out sudden changes in voltage. The amount of charge a capacitor can store is measured …

Capacitor Microphone
Microphone whose operation depends on variations in capacitance caused by varying air pressure on the movable plate of a capacitor. See also: Carbon Microphone, Microphone, Pressure, Sound Pressure Level.

Capillary Action
A phenomenon whereby the narrower the tube the higher the liquid will climb above it's normal bulk level in the container.Liquid rises in a capillary to an equilibrium position determined by the balance of the surface tension force and the gravity force acting on the column of elevated fluid. Note that the rise height will increase as the radius of…

Carat Gold
Measure of parts of gold per 24 parts of an alloy and equal to 41.667 milligrams of gold per gram of alloy.CaratPercentage of fine gold241002291.7518751458.51250.251042937.8833.75

Carat Precious Stones
A standard measure of weight for precious stones.The term riginated in ancient times when gemstones were weighted against the carob bean, each bean weighing roughly one carat.The system was standardised in 1913 so that one carat equals 0.2 grams (200 milligrams).ttle='Carat';xiunt='kg';yiunt='carat';mconv=0.2e-3;cconv=0.0; See also: Mass, SI Units.

Carbohydrate
A class of organic compounds including sugars and starches. The name comes from the fact that many, but not all, carbohydrates have empirical formula CH₂O. See also: Sugars.

Carbon
Carbon occurs naturally in two allotropic forms, namely graphite and diamond; the discovery in 1985 of fullerenes has increased the number of allotropic forms of this element. The study of carbon and its organic compounds is the basis of organic chemistry. The applications for carbon are many and include its use as an alloying element with iron in …

Carbon Dioxide
A heavy, colourless gas. Carbon dioxide is given out by animals during respiration and is used by plants during photosynthesis. It is also produced when fuels burn. Carbon dioxide is used in fire extinguishers. Carbon dioxide is a greenhouse gas that contributes to the potential for global warming. The world's oceans contain the bulk of the world's…

Carbon Disulphide
Used as a solvent in the vulcanization of rubber. Symbol CS₂ Also known as Carbon Bisulphide

Carbon Microphone
Microphone whose operation depends on pressure variation in carbon granules causing a change in resistance. See also: Capacitor Microphone, Microphone, Pressure, Sound Pressure Level.

Carbon Monoxide
A colourless gas that is very poisonous as it combines with the haemoglobin in blood forming a stable compound so reducing the ability to carry oxygen. Present in car exhaust fumes and cigarette smoke. Compression ignition (diesel) engines generate significantly lower CO emissions than spark ignited engines. Symbol CO

Carbon Tetrachloride
Colourless liquid with a sweet smell used as a solvent. Symbol CCl₄ Also known as Tetrachloromethane, Freon 10

Carbon-Nitrogen-Oxygen Cycle
In stars more massive than the sun (>1.1 Solar masses), this cycle is the primary process which converts hydrogen into helium. ¹²C serves as a catalyst, an ingredient which is necessary for the reaction but is not consumed. See also: Carbon, Helium, Hydrogen, Nitrogen, Oxygen, Star.

Carbonado
Carbon that has metamorphosed into its diamond phase but remains black. See also: Carbon, Diamond.

Carbonic Acid
A weak acid formed by carbon dioxide dissolved in water. Symbol H₂CO₃

Carbonitriding
Introducing carbon and nitrogen into a solid ferrous alloy by holding above the temperature at which austenite begins to form during heating, in an atmosphere that contains suitable gases such as hydrocarbons, carbon monoxide and ammonia The carbonitrided alloy is usually quench hardened. See also: Carbon, Nitrogen.

Carboxamide
The main nitrogenous excretion of most animals. It has the distinction of being the first organic compound to have been made in a laboratory (1828). Urea is used in the manufacture of ammonia and carbon dioxide. Symbol NH₂CONH₂ Also known as Urea

Carboxylic Acid
A compound with molecules containing a carboxylic acid group -COOH. Carboxylic acids have the general formula R - COOH.

Carboy
A very large bottle. Glass carboys are usually encased in a wire mesh or wooden box for protection.

Carburizing
Introducing carbon into a solid ferrous alloy by holding above Ac, in contact with a suitablecarbonaceous material, which may be a solid, liquid or gas. The carburized alloy is usually quench hardened. See also: Direct Quenching.

Carcinogens
Substances known to cause cancer.

Cardboard
A stiff form of paper most commonly used to manufacture packaging.

Carnivore
An animal that eats only meat.

Carotene
Carotene is an unsaturated hydrocarbon pigment found in many plants. Carotene is the basic building block of vitamin A.

Carrier Particle
A fundamental boson associated with quantum excitations of the force field corresponding to some interaction. Gluons are carrier particles for strong interactions (colour force fields), photons are carrier particles of electromagnetic interactions, and the W and Z bosons are carrier particles for weak interactions. See also: Bosons, Gluon.

Carrier Suppression
The degree to which the carrier signal is reduced in amplitude in a modulator or mixer. Carrier suppression is usually expressed in dB. See also: Decibel.

Carrington Longitude
A system of fixed longitudes rotating with the sun.

Cartesian Coordinates
Coordinates where the position of a point is described by the distance it is from 2 lines in 2 dimensional space or from 3 planes in 3 dimensional space.The transformation from polar to rectangular coordinates is:The transformation from rectangular to polar coordinates is:The transformation from spherical to rectangular coordinates is:The transform…

Cartridge Brass
A brass made with 75.5% copper and 24.5% zinc.

Cascamite
Trade name for a urea-formaldehyde glue. This is a waterproof resin based glue that comes as a white powder and is mixed two parts water to one part powder in a glass container. Note that it must be stirred thoroughly until it has a consistency of cream.

Case
In a ferrous alloy, the outer portion that has been made harder than the inner portion, or core, by casehardening.

Case Hardening
Hardening a ferrous alloy so that the outer portion, or case, is made substantially harder than theinner portion, or core. Typical processes used for case hardening are carburizing, cyaniding, carbonitriding,nitriding, induction hardening and flame hardening. See also: Nitrating.

Casimir Effect
A quantum mechanical effect, where two very large plates placed close to each other will experience an attractive force, in the absence of other forces. The cause is virtual particle-antiparticle pair creation in the vicinity of the plates. Also, the speed of light will be increased in the region between the two plates, in the direction perpendicul…

Cassegrain Telescope
Two-mirror reflecting telescope in which the primary mirror has a concave parabolic shape and the secondary mirror has a convex hyperbolic shape. A hole in the primary allows the image plane to be located behind the large mirror.

Cast Iron
A ferrous alloy; the carbon content is greater than the maximum solubility in austenite at the eutectic temperature.

Castigated Nut
A nut with grooves cut entirely across the top face.

Casting
A generic term referring to a process where a fluid material(usually a molten alloy) is made to flow into a shaped mold cavity where it solidifies;this method is used to produce complex component shapes and propertiesdifficult to achieve otherwise.A guide as to the surface finish that is achievable using different casting techniques is shown below …

Cataclysmic Variable
A binary star system containing a white dwarf that exhibits sudden outbursts of energy. See also: White Dwarf.

Catadioptric
An optical system containing both reflective and refractive elements.

Catalan's Constant
G = 0.915965594177219015 .......ttle='Catalans Constant';consttxt='Catalans constant';constval=0.915965594177219015;constunt='';given by:

Catalyst
Substance that speeds up a chemical process without actually changing the products of reaction. It lowers the activation energies of both, the forward and the reverse reaction. A catalyst provides a different pathway for a reaction. It may appear in a rate law. A catalyst does not change thermodynamic data, such as the equilibrium constant or the f…

Catalytic Cracking
The use of a catalyst to break down the molecules of the high boiling temperature fractions of crude oil (long-chain alkanes) to alkenes and alkanes of lower relative molecular mass.

Catenary
A chain suspended from two points forms this curve.A curve whose equation is:

Cathode
ChemistryElectrode where electrons are gained (reduction) in redox reactions.ElectronicsIn a semiconductor diode, the terminal to which positive charge carriers flow internally and into which negative charge carriers enter from the external circuit. In electron tubes, the electrode from which electrons are emitted into the inter-electrode space.

Cathode Ray
An electron emitted from the negative electrode in an evacuated tube. See also: Cathode Ray Tube, Electron.

Cathode Ray Tube
An evacuated tube containing an anode and a cathode that generates cathode rays (electrons) when operated at a high voltage. The cathode rays produce an image on a screen when they strike phosphors on the screen, causing them to glow. See also: Cathode Ray, Crookes, William, Electron.

Cathodic Protection
A means of corrosion prevention whereby electrons are supplied to the structure to be protected from an external source such as another more reactive metal or a dc power supply. See also: Anodic Protection, Corrosion.

Cations
Ion with a positive charge. Metals typically form cations. See also: Anion.

Cauchy Window
A weighting that is applied in the time domain to reduce leakage within a Fourier Transform analysis.There are a family of cauchy windows defined by awhereTypical values of a are 3.0, 4.0, 5.0

Cauchy-Schwarz Inequality
The dot product of two vectors cannot be greater in magnitude than the product of the magnitudes of the vectors.

Causality Principle
The principle that cause must always preceed effect. More formally, if an event A ('the cause') somehow influences an event B ('the effect') which occurs later in time, then event B cannot in turn have an influence on event A. That is, event B must occur at a later time t than event A, and further, all frames must agree upon this ordering. See also…

Cavendish, Henry (1731-1810)
English physicist and chemist; discovered hydrogen (1766); discovered nitric acid. The eccentric scientist, after whom the Cavendish Laboratory at Cambridge, England, is named. See also: Hydrogen.

Cavitation
A condition which can occur in liquid handling machinery (e.g. centrifugal pumps) where a system pressure decrease in the suction line and pump inlet lowers fluid pressure and vaporization occurs. The result is mixed flow which may produce vibration and damage to components.Cavitation can occur in a hydraulic system as a result of low fluid levels …

Cavity Acoustics
The acoustics of enclosed volumes are important when considering sound propagation within the volume. The acoustic modes will 'colour' the sound, ie enhance certain frequencies and dull others. The acoustic modes will be dependent on the enclosure dimensions and for a simple rectangular cavity the frequency of a mode is given by:

Cedar
A durable wood used in ancient buildings. Easy to work and strongly scented.

Ceiling
The overhead upper surface.

Ceiling Attenuation Class
This is a rating value for the efficiency of the ceiling as a barrier to airbornesound transmission between adjacent rooms when the dividing wall doesn'tconnect with the structural ceiling.35 is a typical CAC for offices.A ceiling system with a CAC < 25 is consider low performance, whereas one with CAC > 35 is high performance.

Ceiling Function
The ceiling function of x is the smallest integer greater than or equal to x.

Celcius Temperature Scale
The centigrade scale of temperature was defined as 0°C at the ice point of water andas 100°C at the boiling point of water (at 1 standard atmosphere). The SI Unit of thermodynamic temperatureis the kelvin.ttle='Kelvin';xiunt='K';yiunt='°C';mconv=0.0;cconv=273.16;Historical Notes1742 Anders Celcius invented the Celcius temperature scale. In its orig…

Celestial Sphere
An imaginary sphere of infinite radius centered on the Earth and poles aligned with the poles of the Earth.A point on the celestial sphere is really only a direction in space. Parallel lines meet the celestial sphere at the same point.

Cellophane
Cellophane is a thin, transparent, waterproof, protective film that is used in many types of packaging.DiscoveredIt was invented in 1908 by Jacques Edwin Brandenberger, a Swiss chemist. He had originally intended cellophane to be bonded onto fabric to make a waterproof textile, but the new cloth was brittle and not useful.

Cellulose
A polysaccharide made of linked glucose molecules that strengthens the cell walls of most plants.

Celsius Temperature Scale
The centigrade scale of temperature was defined as 0°C at the ice point of water andas 100°C at the boiling point of water (at 1 standard atmosphere). The SI Unit of thermodynamic temperatureis the kelvin.ttle='Kelvin';xiunt='K';yiunt='°C';mconv=0.0;cconv=273.16;Historical Notes1742 Anders Celsius invented the Celsius temperature scale. In its orig…

Cement
A substance that can be used to build together aggregates of sand or stone into a cohesive structure. May be a single compound or a mixture. May be hydraulic set, air set or chemical set. See also: Chemical Set Cement, Hydraulic Set Cement.

Cementite
A compound of iron and carbon, known chemically as iron carbide and having the approximatechemical formula Fe₃C. It is characterized by an orthorhombic crystal structure. When it occurs as a phase insteel, the chemical composition will be altered by the presence of manganese and other carbide-forming elements.

Cent
In musical research, a unit of pitch change equal to 0.01 semitones.

Centigrade Heat Unit
The amount of heat necessary to raise one pound weight of water through 1° C.Conversions1 centigrade heat unit=1 Chu1 Chu=1.8 Btu1 Chu=1899 Jttle='Energy';xiunt='J';yiunt='Chu';mconv=1899;cconv=0.0; See also: Energy.

Centillion
A number equal to 10³⁰³. See also: Googol.

Centimetre
The centimetre or cm is a unit of length and is one hundredth of a metre by definition.ttle='Length';xiunt='cm';yiunt='inch';mconv=2.54;cconv=0.0; See also: Decimal Prefixes, Length, Metre.

Central Angle
Angle whose vertex is placed at the center of a circle.

Central Limit Theorem
An important mathematical result which states that for a random sample of observations from any distribution with a finite mean and a finite variance, the average will tend to follow a normal distribution for large samples. This theorem is the main justification for the widespread use of confidence intervals based on the normal distribution and for…

Central Processing Unit
The computer chip primarily responsible for executing instructions. Normally abbreviated as CPU. See also: Computer, Microprocessor, Moore's Law, Semiconductor.

Centre
A point or axis around which anything revolves or rotates.

Centre Drill
A combined countersink and drill used to prepare work for mounting centres. See also: Drill Bits.

Centre Frequency
Frequency to which an amplifier is tuned.The frequency half way between the cut-off frequencies of a tuned circuit.The midpoint of a bandpass filter such as for an octave filter.

Centre of Mass
The balance point of an object. The location in an object that has the same translational motion as the object if it were shrunk to a point.Laminar Triangle of height hDistance d is perpendicular from the base.

Centre of Pressure
The point at which the aerodynamic forces on a body appear to act, and at which there is no aerodynamic movement. It is similar to the centre of gravity in mechanical terms.

Centre Punch
Photograph courtesy of Draper.co.ukA pointed hand tool made of hardened steel and shaped somewhat like a pencil.

Centre Tap
Midway connection between the two ends of a winding.

Centres
Headstock and tailstock centres come in a number of different forms:Dead centreA centre that does not rotate; commonly found on the tailstock of a lathe. Also, an expression for the exact centre of an object.Half male centreA dead center that has a portion of the 60 degree cone cut away.Live centreA centre that revolves with the work, for example t…

Centrifugal Force
A fictitious force arising in a rotating reference system. It points awayfrom the centre, in the direction opposite to the centripetal acceleration.whereF = centrifugal force [N]m = mass [kg]? = angular velocity [rads^-1]r = distance from centre of rotation [m]

Centripetal
An adjective meaning 'centre-fleeing.'

Centroid
The centre of mass of a figure. The centroid of a triangle is the intersection of the medians. The centroid of a curve or irregular surface area are located with calculus.

Century
One hundred of something.

Cepheid Variable
A type of variable star which exhibits a regular pattern of changing brightness as a function of time. The period of the pulsation pattern is directly related to the star's intrinsic brightness. Thus, Cepheid variables are a powerful tool for determining distances in modern astronomy.

Cepstrum
A cepstrum is a time history defined as the power spectrum of the logarithmof the Power spectrum. This, you can interpret as the spectrum of a spectrum.It extracts periodicities in the spectrum, such as harmonic families andsidebands. The imaginary part is the Hilbert transform.If a spectrum contains several sets of sidebands or harmonic series, th…

Ceramic
Inorganic, nonmetalllic products for which the interatomic bonding is predominantly ionic. See also: Cermet, Defect Structure, Engineering Ceramics, Glass Ceramic, Refractory, Vitrifying Tendency.

Ceramic Capacitor
Generally a single layer capacitor that is flat and has a brown coating, Also have the name monoblock or monolithic in which the capacitor is made even smaller by creating multy-layers and coated in orange or blue paint. See also: Capacitance, Capacitor, Electrolytic Capacitor, Greencap Capacitor.

Cerenkov Radiation
A charged particle emits Cerenkov radiation (light) in a cone around its direction of travel when it travels through any medium faster than the speed of light through that medium.Cerenkov - is the name of the scientist who first recognized the nature of this effect and its possible use for distinguishing particle types.Although the speed of light i…

Cerium
Cerium is a reactive grey metal and is one of the most abundant of the lanthanide group of metals. It oxidises in air, ignites when heated and reacts rapidly in water. It must be stored in an air free enviroment. Cerium can be used as an alloying element with iron and other constituents to produce a flint material used in automatic ignition devices…

Cerium Oxide
The oxide of the rare earth element cerium. Cerium oxide usually appears as a yellow powder. It is insoluble in water and moderately soluble in strong mineral acids. Used alone or together with other substances as a polishing agent for glass. Symbol CeO₂

Cermet
A composite material consisting of a combination of ceramic and metallic materials.The most common cermets are the cemented carbides, composed of an extremely hard ceramic (e.g. WC, TiC), bonded together by a ductile metal such as cobalt or nickel.

Cetane Index
A calculated value, derived from fuel density and volatility, giving a reasonably close approximation to cetane number. See also: Cetane Number.

Cetane Number
A percentage indicating the ignition quality of diesel fuels. It is actually a measure of a fuel's ignition delay. This is the time period between the start of injection and start of combustion (ignition) of the fuel. In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels. Cetane number i…

Cetene
An oily hydrocarbon of the ethylene series, obtained from spermaceti. Symbol C₁₆H₃₂

Cevian
A line segment extending from a vertex of a triangle to the opposite side. See also: Triangle.

CGS Units
Abbreviation for centimetre-gramme-second. In this system of units the fundamental units are:centimetregrammesecond