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


Flux
Mechanical EngineeringChemically or physically active formulation capable of cleaning oxides and enabling wetting of metals with solder. PhysicsThe rate of flow of a physical quantitiy through a reference surface.

Fly Cutter
A single-point cutter mounted on a bar in a fly cutter holder or a fly cutter arbour used for special applications for which a milling cutter is not available. See also: Mill.

Flywheel
The wheel on the end of the crankshaft that gives the crankshaft momentum to carry the pistons through the compression stroke.A flywheel has two main functions:Moderating speed fluctuations in an engine through its inertia. Any sudden increase due to fuelling changes or load on the system will be evened out.Energy storage medium, as an alternative …

Flywheel Effect
The continuous interchange of electric energy between the capacitor and inductor of a parallel resonant circuit wherein the energy level is diminished only by circuit resistance and radiated energy.

Foam
A colloid in which bubbles of gas are suspended in a solid or liquid. Aerogel and Styrafoam are examples of solid foams; whipped cream is an example of a liquid foam. See also: Colloid.

Focal Length
The distance from a mirror or the centre of a lens to its focal point.

Focal Plane
A surface upon which the image of all points in the field of view of an optical instrument is created. See also: Focus, Optic Axis.

Focal Point
The location at which a mirror or a lens focuses rays parallel to the opticaxis or from which such rays appear to diverge.

Focus
Point at which converging rays meet and at which a clearly defined image can be obtained. See also: Focal Length, Focal Plane, Focal Point.

Food Chain
A list of organisms showing how each depends on another for food.

Foot
One foot was defined as one third of the Imperial Standard yard. The abbreviation of footis ft or sometimes 'The plural of foot is feet.Conversions1 inch=25.4 mm1 foot=12 inches1 yard=36 inches6 feet=1 fathomttle='Length';xiunt='m';yiunt='ft';mconv=0.3048;cconv=0.0; See also: Inches, Mile, Nautical Chain, Yard.

Foot Pound
Imperial unit of mechanical energy.The foot pound is also a unit of torque as is the metric unit Newton metre (also a unit of energy equal to a joule).Conversions1 ft lb=1 foot pound1 ft lb=1.3558179 J1 ft lb=0.001285067 Btu1 ft lb=8.4623462085x1018 electronvolt1 ft lb=13.558179x106 erg1 ft lb=1.3558179 Nmttle='Energy';xiunt='…

Footprint
The area occupied by a device or machine.

Force
A force is that which when acting on a body that is free to move accelerates the motion of the body. The SI unit of force is the newton. 1 newton is defined as the force required to accelerate a mass of 1 kilogram by 1 metre per second per second.Conversions1 dyne=1x10-5 N1 poundal (pdl)=0.138255 N1 pound-force (lbf)=4.44822 N1 ton-force…

Force Fit
A fitting which one part is forced of pressed into another to form a single unit. There are different classes of force fits depending on standard limits between mating parts.

Forced Vibration
The oscillation of a system under the action of a forcing function. If the excitation is periodic and continuous, the response motion eventually becomes steady-state. See also: Forcing Frequency, Free Vibration, Vibration.

Forcing Frequency
In sinusoidal vibration testing or resonance searching, the frequency at which a shaker vibrates. See also: Forced Vibration, Frequency.

Forge Welding
A group of welding processes in which fusion is produced by heating in a forge or furnace and applying pressure or blows. See also: Welding.

Forging
Mechanical forming of a metal or alloy by heating and hammering. See also: Blacksmithing.

Formaldehyde
Used widely by industry to manufacture building materials and numerous household products. It is also a by-product of the incomplete combustion of carbo containing materials. Symbol H2CODiscovered1867 by the German chemist August Wilhem von Hofman.

Fortran
From Formula Translation this is a computer programming language that is best known amongst scientists and engineers. Within the engineering community it is being replaced by packages such as Matlab. See also: Computer, Programming Languages.

Fossil Fuel
A fuel such as coal, oil or natural gas that was formed through the decomposition of ancient plant and animal life. Fossil fuels are generally burnt to release the energy stored in the chemical bonds of the hydrocarbons. A side effect of this combustion is the release of gases such as carbon dioxide, which has been linked to global warming through …

Foundation Stiffness
A term used to refer to the stiffness of a machine support or the region of contact between a structure and its surroundings (e.g. the piles and surrounding soil for an offshore platform). Usually one of the areas of uncertainty in static or dynamic calculations. See also: Vibration, Vibration Isolation.

Four Colour Theorem
It is desired to colour a political map on a plane so that countries sharing a common boundary are coloured differently. Experience of map-makers has shown that four colours suffice. This assertion in its precise formulation was an unsolved problem in mathematics for over a hundred years. It has now been 'proved' with the assistance of a computer.

Four-Stroke Engine
An engine operating on a cycle which is completed in four strokes, or two revolutions of the crankshaft.The four strokes are:Induction Stroke - The stroke where the fuel-air mixture is drawn into the cylinder.Compression Stroke - The stroke of the internal Combustion Engine where the piston moves into the cylinder, compressing this fuel-air mixture…

Fourier Analysis
A mathematical analysis of waves, discovered by the French mathematician Fourier (1768-1830). Fourier proved that any periodic sound, or any non-periodic sound of limited duration, could be represented (Fourier analysis) or created out of (Fourier synthesis) the sum of a set of pure tones with different frequencies, amplitudes and phases.For the fu…

Fourier Transform
The mathematically rigorous operation which transforms from the time domain to the frequency domain and vice versa.The fourier transform of f(t) isthe inverse fourier transform of F(?) is

Fovea
The central portion of the retina where visual acuity, or the ability to distinguish small objects and details, is greatest. Only about half a millimetre in diameter, the fovea is the retina's 'rod-free zone' and is densely packed with cones.

Fractals
Discovered by Benoit Mandelbrot in 1964. See also: Mandelbrot Set.

Fraction
A ratio of two integers, or any number that can be expressed as such a ratio.Fractions can be added together once the fractions being added have a common denominator.For example;Subtraction of fractions is performed in a similar way to addition.For example;To multiply fractions, the numerators are multiplied together and the same is done with the d…

Fracture Testing
Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, or presence of defects. See also: Fracture Toughness.

Fracture Toughness
Critical value of the stress intensity factor for which crack extensions occurs. The fracture toughness Kc, is a measure of the resistance of a material to the propagation of a crack. It can be measured by loading a sample containing a deliberately-introduced crack of length 2c and then recording the tensile stress s at which the crack p…

Francium
The heaviest alkali metal with no stable isotopes. Symbol Fr

Free Bend Test
A method of testing weld specimens without the use of a guide.

Free Cut
An additional cut with a machine tool with no advancement of depth. See also: Mill.

Free Electron
Electron which is not attached to a nucleus. See also: Electron.

Free Energy
A thermodynamic quantity that is a function of both the internal energy and entropy of a system, at equilibrium the free energy is at a minimum.

Free Ferrite
Ferrite that is structurally separate and distinct, as may be formed without the simultaneous formationof carbide when cooling hypoeutectoid austenite into the critical temperature range. Also proeutectoid ferrite.

Free Fit
A class of fit intended for use where accuracy is not essential or where large temperature variations are likely to be encountered, or both conditions. See also: Drive Fit, Fit.

Free Progressive Wave
Wave in a medium free from boundary effects. See also: Wavefront.

Free Vibration
Free vibration occurs without forcing, the vibration of a string after it has been plucked. See also: Forced Vibration.

Freeze
To change from a liquid to a solid by cooling. See also: Liquid, Phase Change, Solid.

Frenkel Defect
In an ionic solid, a cation-vacancy and cation-interstitial pair.

Frequency
The rate of repetition of periodic motion measured in hertz (cycles per second).Rate of repetition of changes.wheref = frequency [Hz]T = period [s]v = wave speed [ms-1]? = wavelength [m]? = angular frequency [rad s-1]Enter values into 2 of the 5 fields. The others will be calculated.function init(){}For low frequency events (e…

Frequency Counter
Counts digital pulses over a defined gate time. A typical gate time is between 0.1 and 10 seconds. See also: Frequency.

Frequency Modulation
The information signal is used to vary the carrier signal frequency. Signal-to-noise ratio may be increased over amplitude modulation without increasing power (though bandwidth will suffer). See also: Amplitude Modulation.

Frequency Response
An important parameter in specifying the performance of measuring or recording devices (e.g. accelerometers or tape recorders). Ideally, the frequency response of a transducer or recorder should be linear over the range of frequencies likely to be present in the physical quantity being investigated (e.g. bearing acceleration or waveheight). In othe…

Fricative
A speech sound produced by frication, that is, by forcing air through a constriction in the vocal tract. Examples are 's' and 'f'.

Friction
The resistance to motion which is called into play when it is attempted to slide one surface over another, with which it is in contact. The frictional force opposing the motion is equal to the moving force up to a value known as the limiting friction. Any increase in the moving force will then cause slipping. Static friction is the value of the lim…

Friction Clutch
A shaft coupling used where it is necessary to provide a connection that can be readily engaged or disengaged while one of the shafts is in motion. See also: Friction.

Frisch, Otto (1904-1979)
Austrian-English physicist; advanced the theory that uranium, when bombarded by neutrons, breaks into smaller atoms. He coined the term 'fission' for this process. See also: Fission.

Froude Number
A dimensionless number used in the study of fluid flow problems relating the ratio of inertial to buoyancy forces applicable to homogeneous shallow water flow, or two layer flow. Explicitly, in the shallow water approximation the Froude number is:whereF = Froude NumberU = characteristic velocity, ms-1L = characteristic length scale (flui…

Fuel Cell
A device that converts the chemical energy obtained from a redox reaction directly into electrical energy.The most commonly cited example is the hydrogen fuel cell, in which hydrogen and oxygen are combined, producing electric current and water.Historical Notes1839 Fuel Cell invented by William Grove.1932 First successful fuel cell produced by Fran…

Fuel Consumption
There are three components used to fully determine the fuel consumption of an internal combustion engine powered vehicle; urban driving, constant 90 kmph and 120 kmph.The urban simulation is carried out on a chassis dynamometer whereas the constant speed tests can be carried out on the road if necessary.The distance over which these tests are condu…

Fulcrum
The support on which a lever turns. See also: Lever.

Full Duplex
Operational mode of a communication circuit in which each end can simultaneously transmit and receive data. See also: Half Duplex, Synchronous.

Full Scale Deflection
The maximum value on the scale of an instrument.

Fullering
The process of hammering grooves in hot iron to spread it out thinner. See also: Anvil, Blacksmithing, Drawing, Hammer.

Fulmination
Any very rapid reaction which produces heat, light, and noise - explosions.

Fundamental
In periodic forced vibration, the term fundamental refers to the lowest frequency component present in a harmonic train. For example, most rotating machines have frequency components at multiples of shaft rotational frequency and the fundamental component is usually at rotational frequency (e.g. at 30 Hz in a machine rotating at 1800 rpm). In struc…

Fundamental Interaction
In the Standard Model the fundamental interactions are the strong, electromagnetic, weak, and gravitational interactions. There is at least one more fundamental interaction in the theory that is responsible for fundamental particle masses. Five interaction types are all that are needed to explain all observed physical phenomena.Strong forceA short-…

Funicular
A funicular shape is one similar to that taken by a suspended chain or string subjected to a particular loading.

Furanose Ring
A five-membered cyclic hemiacetal or hemiketal of a carbohydrate.

Furlong
A distance of one-eight of a mile. The name is derived from the Old English word fuhrlang that means 'the length of a furrow'. It represents the distance a team of oxen could plow without needing a rest.Conversions1 furlong=0.125 mile1 furlong=220 yards1 furlong=201.168 metres1 furlong=660 feet1 furlong=10 chains (Gunter)1 furlong=40 rods1 furlong=…

Fuse
Photograph courtesy of Draper.co.ukA short length of wire that will easily burn out when excessive current flows. The fuse wire may be held in a plastic or glass holder.

Fused Silica
The glassy isotropic form of quartz. Crystal quartz is melted at high temperature to make an amorphous, non-birefringent glass of low refractive index. Symbol SiO2

Fuselage
The main body of the aircraft. See also: Aircraft, Wing.

Fusion
Mechanical EngineeringA thorough and complete mixing between the two edges of the base metal to be joined or between the base metal and the filler metal added during welding.PhysicsNuclear Fusion, the combining of light nuclei to form a heavier nucleus.

Fuzzy Logic
Invented by Lofti Zadeh in 1962.

Gadolinium
Gadolinium is a member of the lanthanide group of elements, and is obtained from the same sources as europium. It is a silvery white metal which is ductile and malleable. It is stable in a dry atmosphere but forms an oxide coating when exposed to moist air. It reacts slowly with water and is soluble in acids. Gadolinium has limited uses as a pure m…

Gain
The ratio of the output level of a circuit to the input. This will be positive for an amplifier and negative for an attenuator.

Galactic Corona
A huge spherical region, with a theorised radius of about 250,000 light years, that exists around our own and other spiral galaxies. The corona is thought to consist of dark matter. See also: Galactic Disc, Galaxy.

Galactic Disc
The plane in which the spiral arms of spiral galaxies or barred spiral galaxies exist. Lenticular galaxies also possess disks but no spiral arms. See also: Galactic Corona, Galaxy.

Galaxy
Spiral Galaxy NGC 4414 9925A system of about 100 billion stars. Our Sun is a member of the Milky Way Galaxy, which is sometimes just designated by capitalization: Galaxy. There are billions of galaxies in the observable universe. Exactly when and how galaxies formed in the Universe is a topic of current astronomical research.

Galaxy Clusters
Groups of galaxies that may contain up to a few thousand galaxies. See also: Galaxy.

Galilean Principle of Relativity
The laws of motion are the same in all inertial reference systems. See also: Inertial Reference System.

Galileo, Galilei (1564-1642)
Astronomer, mathematician and physicist he dwelt, not on the useless question, why do things happen? but, how do things happen?1581 Galileo uses his pulse to time the swinging of the lamps in the cathedral at Pisa. He concludes that the time for a lamp to swing does not depend on the angle through which it swings. This observation eventually leads …

Galling
A severe form of adhesive wear which occurs during sliding contact of one surface relative to another. Clumps of one part stick to the mating part and break away from the surface. See also: Friction.

Gallium
One of four metals which can be liquid at room temperature, gallium has the longest liquid range of any metal (2175 °C). Below its melting point, it is a soft, silvery white metal which is stable in both air and water. Extraction of the element is achieved by electrolytic reduction in aqueous solution. Gallium is used in the semiconductor industry …

Gallon
This unit of volume is defined in the British and American system of units. The US gallon is also know as the Winchester gallon.Note: 1 UK gallon = 1.2 US gallons.Old DefinitionThe Imperial (UK) gallon contains 277.274 in3 of distilled water at the temperature of 62°F, with a barometer standing at 30 inches, and weighs 10lbs of distilled…

Galvanic Cell
A cell in which chemical change is the source of electrical energy; it usually consists of two dissimilar conductors in contact with each other and with an electrolyte, or of two similar conductors in contact with each other and with dissimilar electrolytes.A cell or system in which a spontaneous oxidation-reduction reaction occurs, the resulting f…

Galvanic Corrosion
Corrosion associated with the current of a galvanic cell consisting of two dissimilar conductors in an electrolyte or two similar conductors in dissimilar electrolytes; where the two dissimilar metals are in contact, the resulting reaction is referred to as couple action.

Galvanic Couple
A pair of dissimilar conductors, commonly metals, in electrical contact. See also: Galvanic Current.

Galvanic Current
The electric current that flows between metals or conductive nonmetals in a galvanic couple. See also: Galvanic Couple.

Galvanize
To coat a metal surface with zinc using various processes. See also: Zinc.

Galvanometer
An instrument for detecting and measuring a small electric current by movements of a magnetic needle or of a coil in a magnetic field. See also: Current.

Game Theory
A branch of mathematics that seeks to model decision making in conflict situations.

Gamma Iron
The face-centered cubic form of pure iron, stable from 910 to 1400°C. See also: Alpha Iron, Face Centred Cubic, Iron.

Gamma Rays
Gamma rays are electromagnetic waves or photons emitted from the nucleus of an atom, typically with wavelengths of less than 3 pm. A highly penetrating type of nuclear radiation. Gamma ray emission is a decay mode by which the excited state of a nucleus de-excite to lower (more stable) state in the same nucleus.Wavelengths from about 10-14
Gas
Matter with no definite shape or volume. See also: Boyles Gas Law, Charles Gas Law, Ideal Gas, Ideal Gas Law, Liquid, Noble Gases, Ratio of Specific Heats, Solid, Specific Gas Constant.

Gas Mark
Gas cooker temperature scale.Gas MarkCelcius °CFahrenheit °F1/41102251/2120250114027521503003160-170325418035051903756200400722042582304509240-260475 See also: Celsius Temperature Scale, Fahrenheit, Temperature.

Gas Metal Arc Welding
An arc welding process that produces coalescence of metals by heating them with an arc between a continuous filler metal electrode and the work pieces; shielding is obtained entirely from an externally supplied gas. See also: Welding.

Gas Turbine
A turbine driven by the expansion of burning fuel. See also: Afterburner, Brayton Thermodynamic Cycle, Engine, Jet Engine, Ramjet.

Gas Welding
A process in which the welding heat is obtained from a gas flame. See also: Cutting Torch, Welding.

Gauge Blocks
Steel blocks machined to extremely accurate dimensions.

Gauss
The unit of magnetic induction in the cgs system, 10-4 tesla. Also known as the abtesla.ttle='Gauss';xiunt='gauss';yiunt='tesla';mconv=1e4;cconv=0.0;The earth`s average magnetic field strength is approximately 0.3 - 0.5 G. Named for Karl Friedrich Gauss, the great German mathematician and astronomer. A long straight wire carrying 100 A…

Gaussian Optics
Optical characteristics limited to infinitesimally small pencils of light. Also known as paraxial or first-order optics.

Gear Design
AbutThe action of two gear teeth making contact. AddendumThat portion of a gear tooth that extendsfrom the pitch circle to the outside diameter.Conjugate Tooth PairsTwo gear teeth are conjugate if they produce uniform motion as they roll together. This is equivalent to saying that one tooth form generates the other as they move. For gears with para…

Gear Mesh Frequency
A potential vibration frequency on any machine that contains gears; equal to the number of teeth multiplied by the rotational frequency of the gear. See also: Automatic Gearbox, Gear Design, Gear Noise.

Gear Noise
Gear whine - Generated by meshing gears due to the vibration causedby failure of the rolling action between the mating teeth due toMinute imperfections in manufacture ofTooth pitch circle (radius and centre)Tooth involute formGear shaftGear shaft bearing positionGear tooth finishTooth helix angles (relative)Radii at tooth tip and rootSmall design e…