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

Constantan
An alloy of 40% nickel and 60% copper, with a high volume resistivity and almost negligible temperature coefficient. Used with copper in T-type thermocouples.

Constellation
A named grouping of fixed stars, e.g. Orion or the Big Dipper.

Contact Potential
The voltage generated by the contact of two dissimilar metals or materials, or the same metal at different temperatures. See also: Electromotive Force.

Contaminant
Any foreign or unwanted substance that can have a negative effect on system operation, life or reliability.

Continuous Spectrum
A plot of the relative absorbance or intensity of emitted light vs. wavelength or frequency that shows a smooth variation, rather than a series of sharp peaks or bands. See also: Line Spectra.

Continuous System
A continuous system is one that is considered to have an infinite number of possible independent displacements. Its configuration is specified by a function of a continuous spatial variable or variables in contrast to a discrete or lumped parameter system which requires only a finite number of co-ordinates to specify its configuration.

Continuously Variable Transmission
A drive system where a belt running on pairs of cones allows the ratio between the input and output shafts to be varied continuously between the maximum and minimum ratios. See also: Automatic Gearbox.

Contour
The outline of an object.

Control Chart
A chart used to determine whether the distribution of data values generated by a process is stable over time. A control chart plots a statistic versus time. See also: Warning Limits.

Control Group
The subjects in a controlled experiment who do not receive the treatment.

Control Loop
Feedback circuit used to control an output signal. See also: Closed Loop.

Control Variable
The inputs and outputs which a control system manipulates and measures to keep proper control.

Converging Lens
Lens that causes light rays to converge; usually a convex lens. See also: Convex Lens, Lens.

Conversions
AerodynamicsFlow RateVolume per unit of time.Kinematic ViscosityThe dynamic viscosity of a fluid divided by the fluid density.Mass Flow RateDefines the volumetric rate with which fluids flow, maintaining the equation of continuity.PressureDefined as the force exerted per unit area.ReynBritish unit of dynamic viscosity.ViscosityA measure of the inte…

Convex
The curved surface of a cylinder, as a sphere when viewed from without. See also: Concave.

Convex Lens
Lens that is thicker in center than at edges.The diagram shows the cross-section through a convex lens (shown as grey) and the light rays traced in red. See also: Converging Lens, Lens.

Convolution
Convolution meaning ..intertwined, coiled… See also: Correlation, Filter.

Coolant
A fluid used to remove heat. See also: Cooling Fan.

Cooling Fan
The size, specification and location of a cooling fan will depend upon the amount of heat that has to be dissipated from the object that has to be cooled. Therefore, in selecting a fan the first task is to estimate the heat to be dissipated, because the overall system air temperature differential above the inlet ambient is directly proportional to …

Coordinated Universal Time
By international agreement, the local time at the prime meridian, which passes through Greenwich, England. Therefore, it is Also known as Greenwich Mean Time, or sometimes simply Universal Time. See also: Time.

Coordinates
Numbers that specify the position of a point or the position or orientation of a geometric object.Cartesian CoordinatesCoordinates 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.Polar CoordinatesThe position of a point is defined as the distance from the o…

Coordination Number
The number of atomic or ionic nearest neighbours.

Cope
The top half of a horizontally parted mould.

Copernican Principle
The idea, suggested by Copernicus, that the Sun, not the Earth, is at the centre of the Universe. We now know that neither idea is correct, but it set into effect a long chain of demotions of Earth's and our place in the Universe, to where it is now.N. Copernicus

Copernican System
A theory of planetary motions, proposed by Copernicus, according to which all planets move in circular orbits around the Sun, the ones closer to the Sun moving faster, with the Earth itself a planet orbiting between Venus and Mars.

Copernicus, Nicolaus (1473-1543)
Polish astronomer who advanced the theory that the Earth and other planets revolve around the Sun, the 'heliocentric' theory. This was highly controversial at the time, since the prevailing Ptolemaic model held that the Earth was the centre of the universe, and all objects, including the sun, circle it. The Ptolemaic model had been widely accepted …

Coplanar
A set of points or lines that are all on a common plane. See also: Collinear.

Copolymer
A polymer that consists of two or more dissimilar mer units in combination along its molecular chains. The different monomers can be linked randomly, or in repeating sequences, or in blocks, or as side chains off the main chain. See also: Block Copolymer, Mer, Polymer.

Copper
Photograph courtesy of MineraliteCopper is a orange/reddish coloured metal which is malleable and ductile. It has excellent thermal and electrical conductivities and good corrosion resistance. It is found in sulphide ores and as carbonate, arsenide and chloride. Extraction of the metal involves roasting the ore to produce the oxide, followed by red…

Copper I Bromide
Yellowish green or white crystalline solid. Symbol CuBr

Copper I Chloride
White crystalline solid. Turns green in moist air. Symbol CuCl

Copper I Iodide
White crystalline solid. Symbol CuI

Copper I Oxide
A red powder. Symbol Cu₂O

Copper I Sulphide
Yellow, red, or brown crystalline solid. Symbol Cu₂S

Copper II Bromide
Black crystalline solid. Reacts violently with potassium. Symbol CuBr₂

Copper II Carbonate
Green or blue powder forming most of the patina one sees on weathered brass, bronze, and copper. Used as a pigment. Symbol CuCO₃

Copper II Hydroxide
Used as a fungicide. Symbol Cu(OH)₂

Copper II Oxide
A black-brown crystalline solid used as a catalyst in many reactions. Symbol CuO

Copper II Sulphide
Blue-black or black crystalline solid. Symbol CuS

Copper Sulphate
A water soluble salt used in copper plating. Used as a layout solution which turns a copper colour when applied to a clean polished metal surface. Symbol CuSO₄ Also known as Blue Vitriol

Coprime
Integers m and n are coprime if the greatest common divisor of m and n is 1.

Corbel
A projecting wall member used as a support for some element of the superstructure. Also, courses of stone or brick in which each course projects beyond the one beneath it. Two such structures, meeting at the topmost course, creates an arch. See also: Arch.

Cord
An imperial unit of volume used mainly in the timber industry.Conversions1 cord=3.625 m³1 cord=8 ft x 4 ft x 4 ft1 cord=128 ft³ttle='cord';xiunt='m³';yiunt='cord';mconv=3.625;cconv=0.0; See also: Volume.

Core Electron
Electrons occupying completely filled shells under the valence shell. See also: Valence Electrons.

Coriolis Force
A fictitious force that occurs in rotating reference frames. It is responsible for the direction of the winds in hurricanes. It is dependent on the latitude and the speed of the moving object. In the Northern Hemisphere, air is deflected to the right of its path, while in the Southern Hemisphere, air is deflected to the left of its path. It is grea…

Cork
Outer waterproof layer covering most trees and shrubs. The cork material used in flooring and for it's properties is from the tree Quercus Suber.

Corner Frequency
The frequency at which linear extrapolations of two contiguous sections of a device's or component's transfer function drop by 3 decibels. See also: Decibel, Frequency.

Cornice
A cornice is an ornamental molding, or composition of two or more moldings, located at the exterior wall-roof junction of a building, beneath the eaves, or beneath the sloping ends of a gable roof.

Corona
The outermost layer of the Sun´s atmosphere, visible to the eye during a total solar eclipse; it can also be observed through special filters and best of all, by X-ray cameras aboard satellites. The corona is very hot, up to 1-1.5 million degrees centigrade, and is the source of the solar wind. The shape of the corona is different at solar maximum …

Coronal Mass Ejection
A huge cloud of hot plasma, occasionally expelled from the Sun. It may accelerate ions and electrons and may travel through interplanetary space as far as the Earth´s orbit and beyond it, often preceded by a shock front. When the shock reaches Earth, a magnetic storm may result. See also: Sun.

Correlation
Generally speaking, a similarity between data; the extent to which data are related. Usually, a relationship between two data sequences. If two variables tend to move up or down together, they are said to be positively correlated. If they tend to move in opposite directions, they are said to be negatively correlated.Correlation CoefficientA measure…

Correspondence Principle
The principle that when a new, more general theory is put forth, it must reduce to the more specialized (and usually simpler) theory under normal circumstances. There are correspondence principles for general relativity to special relativity and special relativity to Newtonian mechanics, but the most widely known correspondence principle (and gener…

Corrosion
Deteriorative loss of a metal as a result of dissolution environmental reactions. It is a transformation process in which the metal passes from its elemental form to a combined (or compound) form. See also: Cathodic Protection.

Corrosive
Having the power to dissolve. Can burn and destroy living tissue.

Cosecant
Note: In this series A is in radians and See also: Cosine, Cotangent, Secant, Series Expansions, Sine, Tangent.

Cosine
function init(){}Note: In this series A is in radians.Note: Valid for 0 = A = p/2Note: Valid for 0 = A = p/2The following expression is Also known as the half angle formula:

Cosmic Background Radiation
The background of radiation mostly in the frequency range 3x10⁸ to 3x10¹¹Hz discovered in space in 1965. It is believed to be the cosmologically redshifted radiation released by the Big Bang itself. Also known as the primal glow.Presently it has an energy density in empty space of about 4x10^-14Jm^-3.

Cosmic Ray
An extremely energetic (relativistic) charged particle.

Cosmological Redshift
An effect where light emitted from a distant source appears redshifted because of the expansion of spacetime itself. See also: Redshift.

Cosmology
The study of the history of the universe.

Cosmos
The universe regarded as an orderly, harmonious whole.

Cotangent
Note: In this series A is in radians and See also: Cosecant, Cosine, Secant, Series Expansions, Sine, Tangent.

Coulomb
Defined as the quantity of charge which passes any section of a conductor in one second when a current of one ampere is flowing.1 Coulomb = the charge of 6.24x10¹⁸ protons. See also: Abcoulomb, Ampere-Hour, Elementary Charge, Faraday, Statcoulomb.

Coulomb Damping
Coulomb damping is the dissipation of energy that occurs when a particle in a vibrating system is resisted by a force whose magnitude is constant independent of displacement and velocity, and whose direction is opposite to the direction of the velocity of the particle. See also: Critical Damping.

Coulombic Force
A force between charged particles, such as ions, that grows stronger as the charges become closer to each other. See also: Ion.

Counter Weight
A weight added to a body so as to reduce a calculated unbalance at a desired place. See also: Balancing.

Countersink
To counter bore a hole such that the head of a screw may sit flush with the surface.

Couple
Two equal forces acting on a body in opposite directions and located at a specific distance apart produce a turning effect on the body. See also: Torque.

Coupled Modes
Coupled modes are modes of vibration that are not independent but which influence one another because of energy transfer from one mode to the other. Coupling occurs for example when the centre of mass of a beam does not coincide with the centre of shear. The beam cannot then have a mode of vibration in which it bends without twisting. The bending a…

Coupling
Mechanical fixture for joining two shafts.

Course
Level layer of stones or bricks. See also: Brick.

Covalent Bond
A covalent bond is a very strong attraction between two or more atoms that are sharing their electrons. In structural formulas, covalent bonds are represented by a line drawn between the symbols of the bonded atoms.Localized Covalent BondA localized covalent bond describes the mutual electrostatic attraction of two adjacent nuclei for a shared pair…

Covariance
A measure of the joint variability of a pair of numeric variables. It is based upon the sum of crossproducts of the values other variables.AutocovarianceThe degree to which a time signal is correlated with itself.Cross CovarianceThe degree to which two time signals are correlated.

Cover Glass
A clear glass used in goggles, hand shields, and helmets to protect the filter glass from spattering material. See also: Goggles.

Crack
A fracture type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement. See also: Fracture Toughness.

Cracking
The thermal decomposition of the molecules of high molecular mass organic compounds to produce molecules of compounds of lower molecular mass.

Crank
That part of the crankshaft, which is in the form of a crank and crank pin. See also: Crankshaft, Internal Combustion Engine.

Crank Rumble
This is an amplitude modulation of engine noise perceived inside a car with a modulation frequency of 0.5 order. Some of the factors affecting crank rumble are:Bearing clearancesPowertrain mount bracket stiffnessAncillary bracket stiffnessCrankshaft counter balance weightFlywheel-end bearing housing stiffnessBed-plate stiffnessCrankshaft pin diamet…

Crankcase
The middle part of the engine structure surrounding the working parts. See also: Crankshaft, Internal Combustion Engine.

Crankcase Emissions
Pollutants allowed to escape into the atmosphere from the crankcase of an internal combustion engine. See also: Internal Combustion Engine.

Crankshaft
That part of the engine which transmits the reciprocating motion of the pistons to the driven unit in the form of rotary motion. That part to which the connecting rods are attached.In the case of many of the older stationary engines the crankcase was open.Open crank stationary engine.

Crash
Slang used to describe a program with errors that cause it to stop functioning correctly. See also: Bug, Computer.

Creep
The time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures. See also: Stress.

Crenelated
Notched or indented, usually with respect to tops of walls, as in battlements.

Crest
The peak of a wave disturbance. See also: Trough, Wave.

Crest Factor
Peak value divided by the R.M.S. value, used as a measure of the severity of a segment of data. For example, a long time history can be divided into a number of small segments and the crest factor of each segment calculated. An inspection of the crest factors highlights the time segments of high activity. The crest factor provides a measure of the …

Critical Angle
The minimum angle of incidence for which total internal reflection occurs.

Critical Band
The ear behaves as if it contains a bank of filters, each filter passing frequencies within the critical band. Two tones seperated by more than a critical bandwidth are recieved by the cochlea more-or-less independently. In human hearing, only those frequency components within a narrow band,called the critical band, will mask a given tone. Critical…

Critical Chain Reaction
A chain reaction in which an average of one neutron from each fission reaction initiates another reaction. See also: Chain Reaction, Fission.

Critical Cooling Rate
The minimum rate of continuous cooling just sufficient to prevent undesired transformations.For steel, the slowest rate at which it can be cooled from above the upper critical temperature to prevent thedecomposition of austenite at any temperature above the Ms.

Critical Damping
The smallest value of damping required for a displaced system to return to its equilibrium position without overshooting or oscillating about that position. Devices fitted above doors to prevent slamming are usually critically damped. See also: Coulomb Damping, Friction, Hysteresis Damping.

Critical Distance
The distance from a sound source at which direct sound and reverberant sound are at the same level.

Critical Frequency
A particular resonant frequency at which damage or degradation in performance is likely. See also: Critical Speeds, Resonant Frequency.

Critical Mass
The minimum mass of a substance that will allow a chain reaction to continue without dying out. See also: Chain Reaction.

Critical Point
The temperature or pressure at which a change in crystal structure, phase or physical propertiesoccurs. Same as transformation temperature.In the equilibrium diagram, that specific value of composition,temperature and pressure, or combinations thereof, at which the phases of a heterogeneous system are inequilibrium.ExampleAt pressures higher than 2…

Critical Resolved Shear Stress
The shear stress, resolved within a slip plane and direction, which is required to initiate slip. See also: Stress.

Critical Speeds
Any rotating shaft will have lateral (or flexural) and torsional natural frequencies. If the shaft is subjected to a force at any of these frequencies, the amplitude of vibration will be particularly large. The dynamic forces in a rotating machine will generally occur at multiples of rotational frequency and at certain speeds one of the forcing fre…

Critical Temperature
The temperature at the critical point. A gas above the critical temperature will never condense into a liquid, no matter how much pressure is applied. Most substances have a critical temperature that is about 1.5 to 1.7 times the standard boiling point, in kelvin.The transition temperature of a substance from one crystalline form to another. See al…

Crocket
A projecting, foliate ornament of a capital, pinnacle, gable or buttress.

Crookes, William (1832-1919)
English chemist and physicist who discovered thallium. He also developed tubes designed to study cathode rays.