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


Collet
A precision work holding chuck which centres finished round stock automatically when tightened. See also: Chuck.

Collider
An accelerator in which two beams traveling in opposite directions are steered together to provide high-energy collisions between the particles in one beam and those in the other. See also: Accelerator, Synchrotron.

Colligative Properties
Properties of a solution that depend only on the number of particles dissolved in it, not the properties of the particles themselves. The main colligative properties are boiling point elevation and freezing point depression.

Collimation
The alignment of the direction of the photons, so the beam of radiation can be directed at a well-defined part of a target material. See also: Collimator.

Collimator
A mechanical device, sometimes called a 'slit', installed along the trajectory of a beam to reduce the size of the beam. Collimators are also useful for removing stray radiation. See also: Collimation.

Collinear
Points are said to be collinear if they all lie on the same line. See also: Coplanar.

Collision
An encounter between two ojects that changes their existing momentum and energy conditions. See also: Elastic Collisions.

Colloid
A heterogeneous mixture composed of tiny particles suspended in another material. The particles are larger than molecules but less than 1 µm in diameter. Particles this small do not settle out and pass right through filter paper. Milk is an example of a colloid. The particles can be solid, tiny droplets of liquid, or tiny bubbles of gas; the suspen…

Colour
A quality of light, depending on its wavelength. Spectral colour of an emission of light is its place in the rainbow spectrum. Perceived colour (or visual colour) is the quality of light emission as conveyed by the human eye, combining the impressions of 3 types of light-sensitive cells which the eye contains. Perceived colour can be the response t…

Colouration
A listening term. A visual analog. A 'coloured' sound characteristic adds something not in the original sound. The colouration may be euphonically pleasant, but it is not as accurate as the original signal.

Colourmap
This is a method of plotting noise or vibration versus engine speed and frequency simultaneously. Normally frequency is plotted along the x-axis, engine speed along the y-axis and the level is shown by the colour (the rpm and frequency axes can be plotted the other way).

Column
A pillar, usually of round cross-section but sometimes square or octagonal, used to support the roof of a building, porch, or portico.

Column Chromatography
A method for separating mixtures. A solution containing the mixture is passed through a narrow tube packed with a stationary phase. Different substances in the mixture have different affinities for the stationary phase, and so move through the tube at different rates. This allows the substances in the mixture to be detected or collected separately …

Columnar Structure
Coarse structure of parallel columns of grains caused by highly directional solidification of molten metal resulting from sharp thermal gradients.

Coma
A spherical cloud of material surrounding the head of a comet. This material is mostly gas that the Sun has caused to boil off the comet's icy nucleus. This gas shines both by reflected sunlight and light emitted by excited molecules. A cometary coma can extend up to a million miles from the nucleus.

Combination Square
A drafting and layout tool combining a square, level, protractor, and centre head. See also: Micrometer.

Combined-Cycle Engine
Engine concepts using some combination of air-breathing and rocket components which are integrated into a single propulsion system.

Combustible
Substance that can easily be set on fire and that will burn readily or quickly. Flammable.

Combustion Chamber
The space above the piston in which the fuel-air mixture starts to burn in an internal combustion engine. See also: Combustion Reaction.

Combustion Reaction
The vigorous and exothermic reaction that takes place between certain substances, particularly organic compounds, and oxygen. See also: Exothermic, Oxygen.

Comet
A chunk of frozen gasses, ice, and rocky debris that orbits the Sun. A comet nucleus is about the size of a mountain on earth. When a comet nears the Sun, heat vaporizes the icy material producing a cloud of gaseous material surrounding the nucleus, called a coma. As the nucleus begins to disintegrate, it also produces a trail of dust or dust tail …

Common Return
return conductor common to two or more circuits.

Common-Mode Rejection Ratio
The ability of the differential amplifier to obtain the difference between the + and - inputs whilst rejecting the signal common to both. See also: Differential Amplifier.

Common-Mode Signal
A signal applied simultaneously to both inputs of a differential amplifier. See also: Differential Amplifier.

Community Noise Criteria
There are a number of different noise criteria measurements, some of which are described below:CNEL = Community Noise Equivalent LevelThis is used to characterize average sound levels over a 24-hour period, with weighting factors included for evening and nighttime sound levels. Leq values for the evening period (7:00 p.m. to 10:00 p.m.) …

Commutative
Describes an operator that gives the same result irrespective of the order of arguments.For example;

Compact Disc
An optical disc designed to store digitally 74 minutes of stereo audio data. See also: Digital Versatile Disc.

Compass
The earliest-known compass dates from China, during the Han Dynasty (2nd century BC - 2nd century AD). This early compass was made from lodestone, a naturally-magnetic variety of magnetite ore. A spoon-shaped piece of lodestone was placed upon a bronze disk, and the lodestone always pointed north. This early compass was not used for navigation at f…

Compiler
A computer program that translates high-level language statements to machinelanguage. Making a complete program may require other software besides the compiler.

Complement
The complement of a subset of a given set is the collection of all elements of the set that are not elements of the subset.

Complementarity Principle
The principle that a given system cannot exhibit both wave-like behavior and particle-like behavior at the same time. That is, certain experiments will reveal the wave-like nature of a system, and certain experiments will reveal the particle-like nature of a system, but no experiment will reveal both simultaneously.N. Bohr

Complementary Angles
Two angles whose sum is 90°. See also: Plane Angle.

Complementary Colour
For lights, two colours that combine to form white.

Complementary Rules
Rules in Boolean Algebra derived from the combination of a single variable with the inverse of itself.

Complex Conjugate
A complex number whose imaginary part is the negative of that of a given complex number, their real parts being equal.For example, if;then the complex conjugate is;Also,

Complex Numbers (Exponential Form)
The polar form of a complex number is;The cosine and sine functions can be expressed as series;also;e can be expressed as;If x in the above equation is changed to i? then;then;therefore;

Complex Numbers (Logarithms Of)
A complex number can be expressed as;therefore;

Complex Numbers (Polar Form)
If;then;This is the polar form of the complex number, where;and;where r is the modulus of z, written mod z or z and ? is the argument of z, written arg z.

Complex Numbers
The theory of complex numbers was developed by Jean le Rond d'Alembert in 1746. The vector representation of complex numbers was introduced by Casper Wessel in 1798.A complex number consists of a real and imaginary part.For example, if;where a and b are real numbers and i is imaginary. The real part of z, denoted Re z or re z, is a. The imaginary p…

Complex Tone
Sound wave containing simple harmonic components of different frequencies. See also: Sound.

Compliance
The displacement caused by a unit force applied to a spring or structural component. It is the reciprocal of stiffness (Units m/N). AcousticsThe springiness of the system. A higher value means softer. whereC = compliance [m6kg-1]V = volume [m3]? = ratio of specific heats?0 = density of the gas [kgm-3…

Compliance Voltage
The output dc voltage of a constant current supply. See also: Voltage.

Component
An element or chemical compound that helps make up a material system; the composition of a phase or system can be described by giving the relative amounts of each component. See also: Compound, Mixture.

Composite
A material brought about by combining materials differing in composition or form on a macroscale for the purpose of obtaining specific characteristics and properties. The constituents retain their identity such that they can be physically identified and they exhibit an interface between one another.

Composite Number
A natural number that is not prime. See also: Natural Number, Prime Numbers.

Compound
A pure substance which contains two or more different elements chemically bonded together in stoichiometric proportions. See also: Component, Dissociation, Mixture.

Compressed Natural Gas
Natural gas compressed to a volume and density that is practical as a portable fuel supply. See also: Gas, Liquefied Natural Gas.

Compressibility
The change in volume of a unit volume of a fluid when subjected to a unit change of pressure. See also: Bulk Modulus.

Compressible Fluids
Compressible flow requires the integration of the equations of conservation of mass and momentum with that of energy conservation. These three conservation requirements are closely coupled to each other in a way that increases the complexity of the problem. Also, the energy conservation equation explicitly incorporates thermodynamic properties of t…

Compression Ignition
Ignition of a fuel charge by the heat of the air in a cylinder, generated by compression of the air, as in the diesel engine. See also: Diesel Engine.

Compression Ratio
In an engine, the ratio of the cylinder volume at BDC (Bottom Dead Centre) to cylinder volume at TDC (Top Dead Centre).

Compressional Wave
Wave in an elastic medium which causes an element of the medium to change its volume without undergoing rotation. A compressional wave is a longitudinal wave.Sound waves propagating through air are a good example.

Compressive Strength
For metals, the compressive strength is the same as the tensile yield strength. Polymers are approximately 20% stronger in compression than in tension. In Ceramics, compressive strength is governed by crushing and is much larger than the tensile strength. Composites which contain fibres (including natural composites like wood) are a little weaker (…

Compressive Stress
Stress on the cross-sectional area of a body normal to the compression force acting on the body See also: Bending Stress, Neutral Plane, Shear Stress, Stress, Tensile Stress.

Compton Effect
An effect that demonstrates that photons (the quantum of electromagnetic radiation) have momentum. A photon fired at a stationary particle, such as an electron, will impart momentum to the electron and, since its energy has been decreased, will experience a corresponding decrease in frequency. See also: Compton Wavelength, Linear Momentum.

Compton Wavelength
The Compton Wavelength is the wavelength associated with the mass of any particle,given by ? = h / mc, where h is Plancks constant, m is the mass of the particle and cis the speed of light.ParticleCompton Wavelength (m)electron2.426310215×10-12mmuon11.73444197×10-15mneutron1.319590898×10-15mproton1.321409847×10…

Computational Chemistry
A branch of chemistry concerned with the prediction or simulation of chemical properties, structures, or processes using numerical techniques.

Computer
Charles Babbage began construction of the first mechanical computer for calculating logarithms and trigonometric functions in 1822.Central Processing UnitThe computer chip primarily responsible for executing instructions. Normally abbreviated as CPU.InterfaceA boundary across which two systems communicate.MemoryIn a computer system memory is used t…

Computer Aided Design
Usually applied to that part of CAE which has to do with the drawing or physical layout steps of engineering design. See also: Computer Aided Engineering.

Computer Aided Engineering
A technique for using computers to help with all phases of engineering design work. See also: Computer Aided Design.

Computing Conversions
HexadecimalCounting system based on 16.Unsigned Binary NumberA binary number in which all the bits are used to represent positive quantities.

Concatenate
To link together or place end to end. Two 8-bit binary numbers can be concatenatedto make a 16-bit number.

Concave
Curved from the inside, a curved depression in the surface of an object. See also: Convex.

Concave Lens
Lens thinner in centre than edges; a diverging lens. See also: Lens.

Concentrated Force
A force considered to act along a single line in space. Concentrated forces are useful mathematical idealizations, but cannot be found in the real world, where all forces are either body forces acting over a volume or surface forces acting over an area. See also: Body Force, Distributed Load, Force, Surface Force.

Concentration
The amount of substance in a specified space. See also: Titration, Unsaturated Solution.

Concentration Cell
A voltaic cell in which both compartments contain the same components, but at different concentrations. See also: Battery.

Concentric
Having a common centre.

Concert Pitch
Established by the International Organisation for Standardisation in 1955, the agreed reference frequency of 440 Hz. for the note called middle A.

Concrete
Building material made from cement, sand, stone and water.DiscoveredRomans first use concrete around 200BC.

Condensation
The process by which vapour molecules reform a liquid; phase change from gas to liquid state.When a moisture laden gas comes in contact with a cooler surface a change of state from gaseous to liquid occurs e.g. when you breath onto a cold pane of glass the water vapour in your breath condenses onto the glass.Condensation is the opposite process of …

Condensation Polymerization
The formation of polymers by an intermolecular reaction involving at least two monomer species, usually with the production of a low molecular weight by-product such as water. See also: Polymer.

Condition Monitoring
The measurement, recording and analysis of machinery parameters (such as acceleration) to determine machinery health. Today's condition is compared with earlier condition, as when a machine was new.

Conductance
The electrical conductance of a conductor is the reciprocal of the resistance of the conductor. See also: Mho, Siemens, Statmho.

Conduction Band
Lowest empty or partially filled band in a semiconductor.

Conductive Hearing Loss
Hearing loss due to the impairment of sound transmission before it reaches the inner ear. See also: Ear, Hearing Damage.

Conductor
A material that allows the passage of electric charge or the easy transfer of thermal energy. Metals are good conductors. See also: Heat Flow Rate, Metal, Skin Effect, Thermal Conduction.

Cone Pulley
A one-piece stepped pulley having two or more diameters. See also: Belt Drive.

Congruent
Equilateral, equal, exactly the same size and shape. See also: Congruent Figures.

Congruent Figures
Two geometric figures that are identical in size and shape. See also: Congruent.

Congruent Transformation
A transformation of one phase to another that does not involve any change in composition.

Conic Section
The cross section of a right circular cone cut by a plane. An ellipse, parabola, and hyperbola are conic sections.

Conjecture
A statement that may seem to be true, but has yet to be proven. This may be an educated guess or opinion. See also: Deduction.

Conjugate Acid
A substance which can lose a H+ ion to form a base. See also: Acid, Base, Conjugate Base.

Conjugate Base
A substance which can gain a H+ ion to form an acid. See also: Acid, Base, Conjugate Acid.

Connecting Rod
The part in an internal combustion engine that connects the piston to the crankshaft. It changes reciprocating motion of the piston into rotary motion of the crankshaft or vice versa.The conrod mass is mcThe effective mass at the gudgeon pin end isThe effective mass at the crankpin or big end is

Connection
Connection is similar to the concept of support, except that connection refers to a relationship between members in a structural model. A connection restrains degrees of freedom of one member with respect to another. For each restrained degree of freedom, there is a corresponding force transferred from one member to the other; forces associated wit…

Consecutive Sides
Sides of a polygon that share an endpoint. See also: Consecutive Vertices, Polygon.

Consecutive Vertices
Endpoints of a single side of a polygon. See also: Consecutive Sides, Polygon.

Conservation of Angular Momentum
The total angular momentum of a system is constant unless an external torque acts on it.This is observed in ice skating when the skater spins on the spot, bringing their arms in close reduces their moment of inertia and hence their angular momentum increases so that the resultant angular momentum is constant. See also: Angular Momentum, Angular Vel…

Conservation of Charge
In an isolated system the total charge is conserved. See also: Charge.

Conservation of Energy
The total energy of an isolated system does not change.This means that energy (or its equivalent in mass) cannot be created or destroyed. See also: Energy.

Conservation of Mass
The total mass in a closed system does not change even when physical and chemical changes occur. See also: Mass.

Conservation of Momentum
If the net external force on a system is zero, the total linear momentum of the system does not change. See also: Impact, Linear Momentum.

Conservatory
A greenhouse attached to a house.

Conserved
This term is used in physics to mean that a number associated with a physical property does not change; it is invariant.

Console
An array of controls and indicators for controlling a complex system or sequence of events.

Consonance
Two or more sounds that, when heard together, sound pleasant.

Constancy Principle
One of the postulates of Einstein's special theory of relativity, which puts forth that the speed of light in vacuum is measured as the same speed to all observers, regardless of their relative motion. That is, if I'm travelling at 0.9 c away from you, and fire a beam of light in that direction, both you and I will independently measure the speed o…

Constant
A quantity that does not change. This quantity may be a number or a variable. See also: Physical Constants, Variable.