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


Waterfall Plot
A series of spectral maps taken at regular intervals of time or at regularly spaced shaft speeds, similar to the flow of a waterfall. See also: Campbell Diagram, Colourmap.

Waterline
The line of the water's edge when the ship is afloat.

Waterwheel
A wheel with paddles designed to extract power from flowing water.Undershot waterwheelThe water runs left to right and is controlled by the sluice gate. The wheel turns counter-clockwise.Breast waterwheelThe water arrives at the wheel at roughly axle height and turns the wheel counter-clockwise.Overshot waterwheelThe water arrives over the top of t…

Watt
The watt is the SI unit of power and is equal to 1 joule per second.Conversions1 watt=1 J s-11 watt=3.414 Btu h-11 watt=1.0194x10-4 hp (boiler)1 watt=0.001359 hp (metric)1 watt=0.10197 kgf m s-11 watt=1.0x107 erg s-11 watt=2655.22 ft lb h-11 watt=0.239006 cal s-1
Wave
The movement of energy from one place to another without any accompanying matter.Sound waves, ocean waves and electromagnetic waves are some of the examples; other, more complicated types of waves can spread in plasmas.All waves have 4 basic properties which they exhibit; Reflection, Refraction, Diffraction and Interference.Famous Quotes:'An ocean …

Wave Equation
The wave equation describes the propagation of waves.wherec = wave velocity

Wave Particle Duality
The observation that electrons; photons; and other very small entities behave like particles in some experiments and like waves in others. See also: Davisson-Germer Experiment, Electron, Photons.

Waveband
A series of wavelengths forming a group. See also: Wavelength.

Waveform
The shape of a time domain signal as seen on an oscilloscope screen. It is a visual representation or graph of the instantaneous value of the signal plotted against time. Inspection of the waveform can sometimes reveal information about the signal that the spectrum of the signal does not show.For instance a sharp spike or impulse and a randomly var…

Wavefront
A set of points at which the phase of vibration of the physical quantity associated with a wave is the same.The surfaces joining all points of equal phase are known as wavefronts.

Wavefunction
A mathematical function that gives the amplitude of a wave as a function of position and sometimes, as a function of time and/or electron spin. Wavefunctions are used in chemistry to represent the behaviour of electrons bound in atoms or molecules.It is analogous to the amplitude of electromagnetic radiation which is a measurement of the disturbanc…

Wavelength
The shortest repetition length for a periodic wave. For example, it is the distance from crest to crest or from trough to trough. In compressional waves, such as sound waves, it is the measurement of the distance from rarefaction to rarefaction, or compression to compression.The wavelength of visible light lies in the range 400nm to 700nm.The wavel…

Wavelet
The wavelet allows a rapidly changing time history (e.g. door slam noise) to be investigated in the frequency domain. The Fourier transform decomposes a signal using a set of sine waves as the basis functions. The Wavelet transform decomposes a signal using a set of wavelets, these are concentrated in time resulting in a higher time localization of…

Wavenumber
Wavenumber describes the spatial variation of waves, phase change per unit distance.

Wax
Esters of monohydric alcohols. An ester formed from long-chain fatty acids and alcohols that is usually solid at room temperature.

Weak Acid
Substances capable of donating hydrogen but do not completely ionize in solution. See also: Acid, Weak Bases.

Weak Bases
Substances capable of accepting hydrogen but do not completely ionize in solution. See also: Base, Weak Acid.

Weak Force
The force responsible for beta decay. This force occurs through the exchange of the W and Z0 particles. All leptons and hadrons interact via this force. The weak force controls many of the reactions that produce energy in the sun and the stars. The weak force is some hundred thousand times weaker than the strong force. See also: Beta Par…

Wear Pattern
A pattern of wear visible at the point where two parts touch.

Weathering
The action of wind, temperature changes, chemicals and water that breaks the surface of rocks into smaller particles. See also: Acid Rain, Erosion.

weber
The weber is the SI unit of magnetic flux. The surface integral of the product of the permeability of the medium and the magnetic field intensity normal to the surface. An electromotive force of 1 volt is induced in a circuit through which the magnetic flux is changing at a rate of 1 weber per second.Conversions1 weber=1.0x105 kilolines1…

Weber-Fechner Law
An approximate psychophysical law relating the degree of response or sensation of a sense organ and the intensity of the stimulus. The law asserts that equal increments of sensation are associated with equal increments of the logarithm of the stimulus, or that the just noticeable difference in any sensation results from a change in the stimulus whi…

Weft
The yarns running perpendicular to the warp in a woven fabric. See also: Warp.

Weibull Distribution
A distribution used for random variables which are constrained to be greater or equal to 0. It is characterized by two parameters: shape and scale. The Weibull distribution is one of the few distributions which can be used to model data which is negatively skewed.

Weight
The support force needed to maintain an object at rest relative to a reference system. For inertial systems, the weight is sometimes taken to be the force of attraction of the Earth for an object. See also: Mass.

Weightlessness
Sometimes termed 'zero g' or 'agravic', it is the condition when no force (such as weight) is sensed. Occurs in orbit or free fall, when gravity already produces its full acceleration and can produce no further effect. See also: Standard Acceleration due to Gravity.

Weiss Constant
A characteristic constant dependent on the material, used in calculating the susceptibility of paramagnetic materials. See also: Curie Constant.

Welding
Welding is the process of joining two pieces of metal together by hammering, pressure or fusion. Filler metal may or may not be used.The thickness of the filler material is much greater than the capillary dimensions encountered in brazing. The filler material has a melting point approximately the same or below that of the base metals, but always ab…

Wentworth-Udden Particle Scale
A common system of grading the size of grains in a rock or sediment. If the grains can be seen the grade is at least silt, if it is not gritty between the teeth it is clay.>256mmboulder64 to 256mmcobble4 to 64mmpebble2 to 4mmgravel1/16 to 2mmsand1/256 to 1/16mmsilt<1/256mmclay

Wet
To come in contact with, and flow across (a surface, body, or area) - said of air or other fluid.

Wet Bulb Temperature
The temperature at which water, by evaporating into air, can bring the air to saturation at the same temperature. Traditionally this was the temperature indicated by a thermometer whose bulb is wrapped in a wet sheath. The wet bulb temperature and the dry bulb temperature (i.e air temperature) would then be used to calculate relative humidity or de…

Wet Bulb Thermometer
When a wet wick is placed over a standard thermometer and air is blown across the surface, the water evaporates and cools the thermometer below the dry-bulb temperature. This cooler temperature (called the wet-bulb temperature) depends on how much moisture is in the air.

Wetting
Covering with a surface with thin film of liquid. Liquid beads up on a surface if it cannot wet it. See also: Surface Tension.

Wheatstone Bridge
Four arm bridge circuit used to measure resistance, inductance or capacitance. See also: Capacitance, Inductance, Resistance.

Wheel
The Mesopotamians are credited with the invention of the wheel. The wheel was a revolution as it allowed larger loads to be moved a greater distance.

Wheel Dresser
A tool or device for dressing or truing a grinding wheel.

Wheelbase
The distance between the centres of the front and rear wheel axles as viewed from the side of the car. See also: Wheel.

Whirl
Rotating shafts tend to bow out at certain speeds and whirl in a complicated manner. Whirling is defined as the rotation of the plane made by the bent shaft and the line of centres of the bearing. The phenomenon results from various causes such as:mass unbalancehysteretic damping on the shaftgyroscopic forcesfluid friction in the bearingsThe whirli…

White Body
A hypothetical body whose surface absorbs no electromagnetic radiation of any wavelength, i.e., one which exhibits zero absorptivity for all wavelengths; an idealization exactly opposite to that of the black body. In nature, no true white bodies are known. Most white pigments possessing high reflectivity for visible radiation are fairly good absorb…

White Dwarf
A star that is the remnant core of a star that has completed fusion in its core. The sun will become a white dwarf. White dwarfs are typically composed primarily of carbon, have about the radius of the earth, and do not significantly evolve further. Often found in planetary nebulae.It can be within a wide range of temperatures between 100,000 and 4…

White Light
Light that can be resolved into a continuous spectrum.

White Noise
The power spectral density of white noise is independent of frequency. Since there is essentially the same energy between any two identical frequency intervals (for example 84-86Hz and 543-545Hz), white noise narrow band FFT analysis will show as flat. However octave band analysis will show the level to rise by 3dB per octave because each band has …

White Room
A clean and dust-free room used for assembly and repair of precision equipment.

White Spirit
A petroleum distillate that is often used as a cheap substitute for turpentine.

Whittle, Frank (1907-1996)
Inventor of the turbojet and turbofans.

Whole Body Vibration
The vibration experienced by a person whilst operating equipment or vehicles. The human body is most sensitive to vibration in 4 to 8Hz range, although vibration in the 0.5Hz to 80Hz range may cause discomfort or even permanent damage. The effect of whole body vibration may vary from a minor irritation to a major health risk depending on the exposu…

Whole Numbers
The whole numbers is the set of natural number plus zero, that is 0, 1, 2, 3, 4, 5, . . . See also: Natural Number.

Wide Open Throttle
The throttle of an internal combustion engine is fully open and so demanding maximum power at any given engine speed. See also: Internal Combustion Engine.

Wiedemann Effect
The mechanical torsion that occurs when anelectric current is passed along or through a long thin ferromagnetic material while it is subjected to an axial magnetic field.

Wiedemann-Franz Law
The ratio of the thermal conductivity of any pure metal to its electrical conductivity is approximately constant for any given temperature. This law holds fairly well except at low temperatures. See also: Thermal Conduction.

Wien Displacement Law
For a blackbody, the product of the wavelength corresponding to the maximum radiancy and the thermodynamic temperature is a constant, the Wien displacement law constant. As a result, as the temperature rises, the maximum of the radiant energy shifts toward the shorter wavelength (higher frequency and energy) end of the spectrum.Wien displacement la…

Winch
A winch is a machine, the essential part of which consists of a drum driven by hand or powered through gearing, and used to receive a rope which is wound upon it.

Wind Noise
Aerodynamic noise - often referred to as Wind noise, is a major component of passengercompartment noise, which becomes dominant especially at high speed cruising.Because of its broad band and often tonal frequency characteristics, this typeof noise tends to have a high hygiene factor and as such has a major influence onthe overall refinement of a v…

Wind Power
Windmills are used in a number of different applications for generating electrical power to pumping water.The power output of a windmill may be estimated using the following equation:whereP = power [kW]A = swept area of sails [m2]v = velocity of wind [ms-1]

Winding Number
The number of times a closed curve in the plane passes around a given point in the counter clockwise direction.

Window
A piece of glass with plane parallel sides which admits light into or through an optical system and excludes dirt and moisture. See also: Balconet, Balcony, Bay Window, Door, Dormer Window, Double Hung Window, Skylight.

Windowing
An amplitude weighting of the time signal used with gated continuous signals to give them a slow onset and cut-off in order to reduce the generation of side lobes in their frequency spectrum.Transient analysisUniform window - for general purposes.Force window - for short impulses and transients, to improve the signal to noise ratio.Exponential wind…

Wing
A surface that has an airfoil cross-section and is used to generate lift. See also: Aerofoil, Aircraft, Fuselage, Wing Warping.

Wing Warping
The earliest form of roll control was produced by warping the whole wing.Raising the trailing edge of the right hand wing and lowering the trailing edge of the left hand wing will result in the aircraft rolling to the right.The problem is if the wing is too stiff it is difficult to warp, if the wing is not very stiff it is easy to warp but is prone…

Wire
A metal strand, normally pliable. See also: Pliers, Side Cutters.

Wire Brush
Photograph courtesy of Draper.co.ukA brush with metal bristles used to remove loose material from metal surfaces.Photograph courtesy of Draper.co.ukA rotary wire brush may be used in an electric drill. See also: Emery Cloth, Sandpaper.

Witness Mark
A punch mark or scratch used to position or locate some part in its proper spot. The mark is made on each half of the assembly so that upon reassembly the marks can be lined up.

Wolf Number
An historic term for sunspot number. In 1849, R. Wolf of Zurich originated the general procedure for computing the sunspot number. See also: Sun.

Wood
A hard substance which forms the branches and trunks of trees and which can be used as a building material, for making things, or as a fuel. Wood properties depend on moisture content. Wood is a composite fibrous material (cellulose and lignin fibres) that starts to decompose at 550 K.Acacia A durable wood used for palings and posts. A lot of the g…

Wood Screws
The diameter and pilot drill size versus wood screw gauge.

Woods Metal
A fusible bismuth based low melting point alloy. 50 percent bismuth, 25 percent lead, 12.5 percent tin, and 12.5 percent cadmium

Woodward-Hoffmann Rules
Rules governing the formation of products during certain types of organic reactions.

Woofer
Large loudspeaker designed primarily to reproduce low frequency audio signals. See also: Loudspeaker.

Wool
Specifically sheep covering. The hairs vary in length and diameter according to breed. Diameters are in the range 0.015mm to 0.04mm and length from 25mm to 350mm.

Word
AudioIn audio engineering the term word describes one sample of audio data.ComputingAn ordered set of bits that is the normal unit in which information may be stored, transmitted, or operated upon within a given computer - commonly a word or shortword is 16 and a double word is 32 bits.

Work
The product of the force along the direction of motion and the distance moved.Measured in energy units, joules.whereW = work done [J]F = applied force [N]s = distance moved in the direction of the force [m]

Work Function
This is the energy required to remove an electron from the highest filled level in the Fermi distribution of a solid to a point a long way away, at absolute zero.whereI = thermionic current [A]T = temperature [K]f = work function [eV]A = constant with a theoretical value of 120 Acm-2K-2k = Boltzmann`s constant = 1.38062x10
Working Drawing
A drawing. blueprint, or sketch of a part, structure, or machine.

Working Fluid
A fluid (gas or liquid) used as the medium for the transfer of energy from one part of a system to another part.

Working Stress
The allowable stress considered to be safe in the design of part. It is the ultimate stress of the material divided by a safety factor. See also: Stress, Ultimate Strength.

World Wide Web Consortium
Organisation that produces standards for the world wide web.

Worm
The threaded cylinder or shaft designed to mesh with a worm gear. See also: Gear Design, Worm Gear.

Worm Gear
A gear with helical teeth made to conform with the thread of the mating worm. See also: Gear Design, Worm.

Woulfe Bottle
A bottle with two or more necked orifices that was used in distillation. See also: Distillation.

Wrought Alloy
An alloy that is suitable for mechanical forming below melting-point temperatures. The hot or cold deformation of a cast product removes the original cast crystal structure. See also: Alloy.

Wrought Iron
The purest commercial form of iron, nearly free of carbon. Contains less than 0.3% carbon and 1.0 or 2.0% slag, giving it ductility and toughness. Other properties are more rust resistant than steel and more easily welded.

Wyde
The name for 2 bytes or 16 bits. The name wyde for the 'double byte' was proposed by the American computer scientist Donald Knuth.

Xanthophyll
Xanthophylls are a class of oxygen-containing carotenoid pigments, which provide the characteristic yellow and brown colours of autumn leaves.

Xenobiotic
A substance which is not normally found in a living thing.

Xenon
Xenon is one of the rare gases formed as a result of radioactive decay of uranium fission fragments. It is colourless and inert, used to fill cathode ray tubes. Symbol Xe

XLR Connector
A three pin connector widely used in the audio industry.

Xylol
A commercial preparation of xylenes. Symbol C6H4(CH3)2 Also known as Dimethylbenzenes

Yagi Antenna
A directional antenna consisting of a rod pointed in the direction of the transmission/reception and several cross bars oriented at a 90° angle to the main rod and whose length and spacing is optimized to transmit and receive transmission in the desired frequency band.

Yard
The Imperial Standard yard was defined in the British system of units as a standard unitof length. The foot was defined as one third of a yardThe abbreviation of yard is yd.Conversions1 yard=3 feet1 yard=36 inches1 yard=0.9144 m1 fathom=2 yardsThe U.S. yard before 1 July 1959 was 0.91440183 metre.ttle='Length';xiunt='m';yiunt='yd';mconv=0.9144;ccon…

Yawing Moment
A moment that tends to rotate an aircraft, an airfoil, a rocket, etc., about a vertical axis.The moment is considered positive when it rotates clockwise.

Yeast
Any of a number of species of single-celled fungus. Most important are the Saccharomyces, which are used in bread making and beer brewing.

Yellow Dwarf
Any star with a spectral classification of G which is on the main sequence, for example, the Sun.The Hertzsprung-Russell diagram relates the brightness of a star to its temperature.

Yellow Supergiant
A supergiant star with a spectral type of G. See also: Star, Supergiant.

Yield
The amount of product actually obtained in a chemical reaction.

Yield Point
The point at which there is a large increase in extension when the elastic limit is increased beyond the stressMetals, particularly mild steel, generally have a very well defined yield stress compared to other materials.

Yield Strain
A material deformed beyond its yield strain, no longer exhibits linear elastic behaviour. See also: Strain, Yield Point.

Young Stellar Object
The generic name for a star prior to its main sequence phase. See also: Star.

Young's Double-Slit Experiment
A famous experiment which shows the wave nature of light (and indeed of other particles). Light is passed from a small source onto an opaque screen with two thin slits. The light is diffracted through these slits and develops an interference pattern on the other side of the screen. See also: Light Ray.

Young's Modulus
The modulus of elasticity is the slope of the initial, linear-elastic part of the stress-strain diagram.whereE = Young's modulus [Nm-2]F = applied load [N]A = cross-sectional area [m2]x = extension [m]L = original length [m]

Ytterbium
Ytterbium is a soft, silvery-white metal of the lanthanide group. The metal is soft and malleable, oxidises slowly in air and reacts with water. Applications of the metal are limited, research being the principal area of its use as well as in special alloys for X-ray sources. Symbol YbDiscovered1878 by J.C.G. de Marignac in Geneva, Switzerland.Abun…