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


Factorial
The product of all whole numbers less than or equal to a number.For example, factorial 5, written 5!, is equal to .Factorial zero is defined as 1.

Failure
The event, or inoperable state, in which any item or part of an item does not, or would not, perform as previously specified.Hard FailureA product under test ceases to work correctly. It does not resume correct operation, even when the stressing environment is eased.Soft FailureA product under test ceases to operate correctly, but resumes correct o…

Failure Mode and Effects Analysis
A procedure by which each potential failure mode of a system is analyzed to determine the effects on the system and classify each potential failure mode according to its severity. See also: Failure.

Famous Scientists & Engineers Books
The Works of Archimedes By edited by T. L. Heath, Published By: Dover Publications Inc.Subtle Is the Lord: The Science and the Life of Albert Einstein By Abraham Pais, Published By: Oxford University Press.

Fan Noise
For small fans such as those used on electric motors the noise generated by their centrifugal cooling fans can be controlled by:Reducing the fan rotational speed; noise has been shown to increase at a rate of 53 to 64 dB/decade increase of speed. A larger, slower fan will be quieter than a smaller, faster fan delivering the same airflow.Reducing th…

Fans
There are several simple relationships between fan capacity, pressure, speed, and power, which are referred to as the fan laws. The first three fan laws are the most useful and are stated as follows:The capacity is directly proportional to the fan speed.The pressure (static, total, or velocity) is proportional to the square of the fan speed.The pow…

Far Field
AcousticsThe distribution of sound energy at a very much greater distance from a sources than the linear dimensions of the source and in which the sound waves can be considered to be plane waves. That part of the sound field in which sound pressure decreases inversely with distance from the source. This corresponds to a reduction of approximately 6…

Farad
The SI unit of capacitance. A capacitance of 1 farad is defined as a capacitor that carries a charge of 1 coulomb when a potential difference of 1 volt is applied across it. See also: Abfarad, Capacitance, Statfarad.

Faraday
Quantity of electrical charge associated with one mole of chemical charge equal to 96485.3Cttle='Electrical Charge';xiunt='coulomb';yiunt='faraday';mconv=96485.3;cconv=0.0; See also: Charge, Coulomb.

Faraday Constant
The electric charge carried by one mole of electrons (or singly-ionized ions). It is equal to the product of the Avogadro constant and the (absolute value of the) charge on an electron.F = 9.648456x104 Cmol-1ttle='Faraday Constant';consttxt='F';constval=9.648456e4;constunt='Cmol-1';

Faraday Effect
The generation of a voltage by a coil when the coil is subjected to a changing magnetic field.

Farenheit
On the Fahrenheit scale 0°C = 32°F and 100°C = 212°Ftemperature °F = 1.8 x temperature in °C + 32

Fast Fourier Transform
An algorithm, or digital calculation routine, that efficiently calculates the discrete Fourier transform from the sampled time waveform. In other words it converts, or 'transforms' a signal from the time domain into the frequency domain.ApplicationsSpectral Estimation (Periodograms)Fast Convolutions (Fast Frequency Domain FIR Filters)Transform Codi…

Fata Morgana
A complex mirage display that involves multiple images, alternately expanded and compressed vertically, often giving the impression of buildings, cliffs, etc. where no such objects exist. The name is traditionally used in Italy for the vivid mirages seen across the Strait of Messina. See also: Inferior Mirage, Mirage.

Fathom
The fathom is an obsolete unit of length, mainly used to measure the depth of water. 1 fathom= 1.8288m= 72in= 6ftttle='Length';xiunt='fathom';yiunt='m';mconv=0.546807;cconv=0.0; See also: Cable Length, Length, Nautical Mile.

Fatigue
An important mode of failure of engineering components subjected to dynamic stresses. Failure can occur at stresses well below the yield point and tends to initiate at sharp changes in cross sectional area or other stress raisers. See also: Fatigue Resistance, Strain, Stress.

Fatigue Resistance
The ability of a material to withstand repeated and varying loads. See also: Fatigue.

Faying Surface
That surface of a member that is in contact with another member to which it is joined.

Feedback
Occurs when some or all of the output of the device (such as an amplifier) is taken back to the input. This may be accidental (such as the acoustic feedback from a speaker to microphone) or intentional, to reduce distortion, as used in a closed-loop control process. See also: Negative Feedback.

Feeler Gauges
A set of steel 'fingers' of different thicknesses that can be used to set the gap between two objects. They are used in isolation or a combination to give the required thickness.

Feet per Minute
Old imperial units of velocity, abbreviated as fpm or ft min-1.ttle='Velocity';xiunt='ms-1';yiunt='ft min-1';mconv=0.00508;cconv=0.0; See also: Velocity.

Feet per Second Squared
Old imperial unit of acceleration.written as:ft s-2orft/sec/sec

Female Part
A concave piece of equipment which receives a mating male, convex, part.

Femtometre
Abbreviated as fm, unit of distance equal to 10-15m. See also: Decimal Prefixes, Metre.

femtosecond
Abbreviated as fs, unit of time equal to 10-15s. See also: Decimal Prefixes, Second.

Fermat Number
The integers Fn=22n+1 are Fermat numbers. Every prime divisor of the Fermat number Fn=22n+1 is of the form 2n+2k+1.

Fermat's Last Theorem
States thathas no whole number solutions for n greater than 2

Fermat's Principle
The principle, put forth by P. de Fermat, that states the path taken by a ray of light between any two points in a system is always the path that takes the least time. See also: Light Ray.

Fermi
A derived SI Unit of length. Through common usage 10-15m has been named the fermi.1 fermi (fm) = 10-15m

Fermi Constant
The Fermi constant shows the coupling between a nucleon and a lepton field.F = 1.4x10-50Jm-3ttle='Fermi Constant';consttxt='F';constval=1.4e-50 ;constunt='m-1';

Fermi Energy
The average energy per particle when adding particles to a distribution but without changing the entropy or the volume. Chemists refer to this quantity as being the electro-chemical potential.

Fermi, Enrico (1901-1954)
American physicist born in Rome; researched the transmutation of elements through neutron bombardment; his team produced the first controlled nuclear chain reaction at the University of Chicago. He received the Nobel Prize for physics for the development of neutron-induced nuclear reactions in 1938.Famous Quotes:'Experimental confirmation of a pred…

Fermions
Fermions are particles that satisfy the Pauli exclusion principle and obey the Fermi-Dirac statistics of statistical mechanics. When a collection of identical fermions are described in terms of single particle wave functions no two fermions can have the same wave function.

Fermium
A man-made element with an atomic number of 100. Symbol Fm

Ferrite
A solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated (forinstance, as chromium ferrite), the solute is generally assumed to be carbon. On some equilibrium diagrams thereare two ferrite regions separated by an austenite area. The lower area is alpha ferrite; the upper, delta ferrite. Ifthere is no designa…

Ferrite Rod Aerial
A coil of wire wound on a ferrite material to increase the inductance of the coil. It's signal capturing capability.

Ferroelectric
A dielectric material that may exhibit polarization in the absence of an electric field. See also: Dielectric.

Ferromagnetism
Permanent and large magnetizations found in some metals (e.g., Fe, Ni, and Co), which result from the parallel alignments of neighboring magnetic moments. See also: Cobalt.

Fibonacci (1180-1228)
Also known as Leonardo of Pisa. He was a merchant and traveled throughout the Mideast and this is where he cam into contact with Arabic mathematics. His book “Liber Abaci� he introduced Arabic notation for numerals and their algorithms for arithmetic. See also: Fibonacci Number.

Fibonacci Number
A member of the sequence 0, 1, 1, 2, 3, 5,... where each number is the sum ofthe previous two numbers. Invented by Leonardo of Pisa in 1220.The first 45 of the Fibonacci numbers are:061083204019871346269115972178309225843524578341815702887567659227465810946149303521317711241578172128657390881693446368632459865575025102334155891213931655801411441964…

Fibre
Any material that has been drawn into a cylinder with a length-to-diameter ratio greater than about ten.

Fibre Optics
The transmission of radiant energy through transparent fibres of glass, plastic or fused silica.ModeA term used to describe an independent light path through a fibre, as in multimode or single-mode:Single Mode Fibre An optical fiber that supports only one mode of light propagation above the cutoff wavelength. Multimode Fibre An optical waveguide in…

Fick's Laws
Fick's first lawThe diffusion flux is proportional to the concentration gradient; this relationship is employed for steady-state diffusion situations.Fick's second lawThe time rate of change of concentration is proportional to the second derivative of concentration; this relationship is employed in nonsteady-state diffusion situations.

Fidelity
As applied to sound quality, the faithfulness to the original.

Field Effect Transistor
A three-terminal transistor device where the output current flowing between the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide semiconductor FET).Each type has two polarities:P - JFET positive, or p-chan…

Field of View
The maximum visible space seen through an optical instrument or lens.

Field Sound Transmission Class
The same as STC rating except as measured in the field in accordance with standard methods. The FSTC is used to quantify actual as-built partition transmission loss across the frequency range of speech sounds. The FSTC incorporates corrections for receiving room sound absorption and requirements to assess and eliminate sound flanking paths. See als…

Field Transmission Loss
Sound transmission loss measured in accordance with Annex A1 of Test Method E 336. See also: Sound Transmission Class.

Fields Metal
A low melting point alloy. 51% Indium, 32.5% Bismuth, and 16.5% Tin. A non-toxic replacement for Wood's Metal.

FIFO Buffer
A first in, first out, store. The first value placed in the buffer (queue) is the first value subsequently read. See also: Memory.

File
A hand tool used to shape material by abrasion. See also: Sandpaper.

File Hardness
Hardness as determined by the use of a file of standardized hardness on the assumption that amaterial which cannot be cut with the file is as hard as, or harder than, the file. Files covering a range of harnessesmay be employed. See also: Knoop Hardness Test.

Filler
An inert foreign substance added to a matrix to improve or modify its properties.

Fillet
A curved surface connecting two surfaces that form an angle.

Filter
Audio, Electronics, Signal ProcessingAny of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others. Think sieve: pass what you want, reject all else. For audio use the most common electronic filter is a bandpass filter, characterized by three parameters…

Finite Element Method
A numerical method which is used to calculate displacements or stresses in structures or components subjected to external and internal loads. It can also be used to evaluate natural frequencies and mode shapes of complex structures. The structure has to be idealised in terms of simple elements such as beams, plates or shells. The equations which re…

Finite Impulse Response Filter
A commonly used type of digital filter. Digitized samples of the audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number of previous inputs. An FIR filter can be designed to have linear phase (i.e., constant time delay, regardless of frequency). FIR filters designed for frequencies much lower that t…

Fir
A light coloured and soft wood. Needs to be dried very well before use.

Fire Damp
The gases found naturally in coal are a mixture of methane and other hydrocarbons. Given the name as they are highly combustible when mixed with air.

Firing
A high-temperature heat treatment that increases the density and strength of a ceramic piece. See also: Ceramic, Heat Treatment.

Firing Order
The order in which combustion is initiated in an internal combustion engine. Normally starting from number 1 cylinder.

Firmament
The celestial sphere and the collection of stars whose position is fixed on it.

First Law of Thermodynamics
This simply states that energy cannot be created nor destroyed but can only be converted from one form to another.?U = ?W + ?Qwhere?U = change in total internal energy?W = work done?Q = total heat supplied

First Order Reaction
The sum of concentration exponents in the rate law for a first order reaction is one. Many radioactive decays are first order reactions. See also: Reactants, Second Order Reaction, Zero Order Reaction.

Fission
The splitting of a heavy nucleus into two or more lighter nuclei, releasing a large amount of energy. See also: Critical Chain Reaction, Frisch, Otto, Fusion, Nuclear Reaction.

Fit
The desired positive or negative clearance between the surfaces of two machined parts. See also: Drive Fit, Free Fit, Running Fit.

Fixed Connection
In two dimensions, a fixed connection between two members restrains all three degrees of freedom of the connected member with respect to one another. A fixed connection is sometimes called a rigid connection or moment-resisting connection. See also: Degrees of Freedom.

Fizeau Method
One of the first truly relativistic experiments, intended to measure the speed of light. Light is passed through a spinning cogwheel driven by running water, is reflected off a distant mirror, and then passed back through the spinning cogwheel. When the rate of running water (and thus the spinning of the cogwheel) is synchronized so that the return…

Flag
A variable which can take one of only two values.

Flame Annealing
Annealing in which the heat is applied directly by a flame. See also: Annealing.

Flame Hardening
Quench hardening in which the heat is applied directly by a flame. See also: Annealing, Flame Annealing.

Flame Test
A test to identify some metals, e.g. with sodium the flame turns orange.MetalColourArsenicBlueAntimonyPale greenBariumYellowish greenBoronBright Green CaesiumPale violetCalciumRed-orange CopperGreen/Blue-green IndiumBlue LeadPale greenLithiumCrimson MolybdenumYellowish green PhosphorusPale bluish green PotassiumLilac SodiumIntense yellow RubidiumPa…

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

Flange
A relatively thin rim around a part.

Flanking Sound Transmission
In sound transmission measurement, the transmission of sound from the sound source room to the receiving room by paths other than through the partition under test. Flanking transmission may include structure-borne sound transmission.In this simplified example the isolated double barrier is let down by the flanking paths through the roof and floor s…

Flash Memory
Non-volatile computer memory that can be electrically erased and reprogrammed.USB Memory Stick Flash memory with a USB interface built in. A portable storage device that is plug and play.SD Flash Memory Card Flash memory storage used for digital cameras and other portable devices.Smartmedia Flash Memory Card Flash memory storage used in digital cam…

Flash Point
The temperature when vapour pressure of a substance becomes high enough to allow the air/vapour layer over the substance to be ignited. Ether and acetone have flash points below room temperature, which makes them very dangerous.Click on an item to paste into clipboard or use clipboard symbol at end to clipboard all values Acetic Acid 315.38 KClip A…

Flashing
A thin edge of material formed at the parting line of a casting or forging where it is forced out between the edges of the form or die. See also: Casting.

Flat Wood Drill
A wood drill that has a centre point to locate the drill and flats that bore the hole.These drill bits have a tendency to splinter the wood as they break through, the best way of reducing this problem is to use a sacrificial piece of wood on the back of the piece of wood you are drilling. See also: Drill Bits.

Flattop Window
The Flattop window has negligible ripple (

Fleming's Left Hand Rule
Also known as the Motor Rule this is a way of determining the direction of a force on a current carrying conductor in a magnetic field.The thumb, the first and the second fingers on the left hand are held so that they are at right angles to each other.If the first finger points in the direction of the magnetic field and the second finger the dire…

Fleming's Right Hand Rule
Also known as the Generator Rule this is a way of determining the direction of the induced emf of a conductor moving in a magnetic field.The thumb, the first and the second fingers on the right hand are held so that they are at right angles to each other.If the first finger points in the direction of the magnetic field and the thumb in the direct…

Fletcher-Munson Curve
Our sensitivity to sound depends on its frequency and volume. Human ears are most sensitive to sounds in the midrange. At lower volume levels humans are less sensitive to sounds away from the midrange, bass and treble sounds 'seem' reduced in intensity at lower listening levels.Curves originally obtained by two Bell Lab scientists. See also: Hearin…

Flexible Fuel Vehicle
A vehicle that can be run on any blend of unleaded gasoline with up to 85 percent ethanol. See also: Ethanol, Ethanol E85.

Flexural Strength
A property of a solid that indicates its ability to withstand bending. See also: Young's Modulus.

Flexure Mode
Flexure modes are associated with thin slender beams.

Flicker
Impression of fluctuating luminance or colour.

Flint Glass
An optical glass with higher dispersion and higher refractive index than crown glass; a heavy, brilliant glass, softer than crown glass.

Flip Flop
An astable multivibrator. A square wave oscillator that has no stable states. Also half a shift register. Flip Flops can be unclocked and triggered by the input pulses or CLOCKED by a clock pulse to a special clock input. See also: Astable, Bistable.

Floating Point Number
A number represented in the computer in mantissa and exponent form.

Flock
An old British unit of quantity equal to 2 score or 40.

Flow Noise
A term generally used to describe aerodynamic noise produced when a gas flows within a duct or when the gas exits the duct. This is a typical problem observed in the exhaust systems of internal combustion engines and high engine rotational speeds and hence high gas flow rates.There is a balance between the attenuation provided by a reactive silence…

Flow Rate
Volume per unit of time.Conversions1 ft3s-1=0.028316847m3s-11 ft3s-1=1 cusec1 ft3s-1=28.316847 litre s-11 cubic foot per minute=1 cufm1 cufm=1.699m3h-11 cufm=28.32 litre min-11 gallon per minute=0.7577 litre s-1
Fluid Film Bearing
A bearing which supports the shaft on a thin film of oil. The fluid-film layer may be generated by journal rotation (hydrodynamic bearing), or by externally applied pressure (hydrostatic bearing). See also: Bearing, Hydrodynamic Bearing, Hydrostatic Bearing.

Fluid Ounce
Unit of volume most commonly used in cooking.Conversions1 fluid ounce (UK)=28.41308x10-6m31 fluid ounce (US)=29.57353x10-6m320 fluid ounces=1 ttle='Volume';xiunt='fluid ounce (UK)';yiunt='m3';mconv=35195.05805072875;cconv=0.0; See also: Tablespoon, Teaspoon, Volume.

Fluids
Substances in which the binding forces are weaker than in solids, so that the atoms or molecules do not occupy fixed positions and move at random. Liquids and gases are fluids. See also: Compressible Fluids, Liquid.

Fluorescence
The property of a material whereby it emits visible light when it is illuminated by ultraviolet light. See also: Ultraviolet Light.

Fluorine
Fluorine is a pale greenish yellow gas that is the first in the halogen group. Symbol F

Flute
The groove in a cutting tool which provides a cutting edge and a space for the chips to escape and permits the cutting fluids to reach the cutting edges. See also: Drill Bits.

Flutter Echo
A repetitive echo set up by parallel reflecting surfaces. This can result in a perception of a pitch or timbrecolouration of music and a reduction in the speech intelligibility within the room.Sound absorption material on the walls or ceiling can be used to absorb some of the sound energy at each reflection. Alternatively, sound diffusers can be us…