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


Inclusion
Foreign particle present as an undesirable impurity in a material.

Inconel
A nickel based alloy with good corrosion resistance.

Index Register
A microprocessor register that holds part of or all the effective address used by an instruction. See also: Effective Address, Register.

Indicated Mean Effective Pressure
During the cycle of an engine useful work is only done on the power stroke. By measuring the cylinder pressure through a cycle it is possible to calculate the average pressure that is useful. This is the Indicated Mean Effective Pressure. See also: Brake Horse Power, Brake Mean Effective Pressure, Net Indicated Mean Effective Pressure.

Indicator
A substance that undergoes a sharp, easily observable change when conditions in its solutions change. See, for example, acid-base indicator and redox indicator. See also: pH.

Indicator Diagram
A plot of pressure vs. volume. Also, known as a PV diagram. Lines or curves on the indicator diagram represent processes. The areas under curves on the indicator diagram are equal to the work released by the process. See also: Pressure, Volume, Work.

Indium
Indium derives its name from the characteristic indigo line in its spectrum. It is a soft, malleable and ductile metal which is generally unaffected by air or water but is soluble in acids. It is found only in the form of minor components of various minerals (as are gallium and thallium, other members of the boron group of elements in the periodic …

Induced Current
Current that flows as a result of an Induced EMF. See also: Current, Induced Electromotive Force.

Induced Electromotive Force
Voltage induced in a conductor in a varying magnetic field. See also: Electromotive Force, Induced Current.

Inductance
The inductance is the property of an electric circuit to store magnetic energy when carrying a current. The SI unit of inductance is the henry. An electromotive force of 1 volt is induced in a circuit with an inductance of 1 henry when the current variation is 1 ampere per second. See also: Distributed Inductance, henry, Wheatstone Bridge.

Inductor
A magnetic device that stores energy in a magnetic field produced by flowing current. See also: Capacitor.

Inelastic
A collision or interaction in which kinetic energy is not conserved. See also: Elastic Collisions, Kinetic Energy.

Inequality
A relationship between two expressions that are not equal, often written in the form of an equation but using the symbols > or < meaning is greater than and is less than. If the end values are included then the symbols (greater than or equal to) or (less than or equal to) are used. If there is a great difference the expressions then the symbols >> …

Inert Gas
A gas which does not normally combine chemically with other elements. See also: Halogen.

Inertance
Inertance is the ratio of an acceleration-like quantity to a force-like quantity when the arguments of the real (or imaginary) parts of quantities increase linearly with time.AcousticsDescribes the inertial properties of a gas in a duct.whereL = inertance [kgm-4]?0 = density of the gas [kgm-3]?x = incremental distan…

Inertia
An object's resistance to a change in its velocity. The tendency of an object at rest to remain at rest, and of an object in motion to remain in motion, in the absence of applied forces. Newton`s first law of motion stated this tendency, while his second law effectively states that momentum (the quantification of inertia) is proportional to both th…

Inertial Confinement
Methods of producing nuclear fusion by compressing a pellet of fuel using a laser, particle beam, or other external driver. If the compression produces a high enough density rapidly enough while heating the fuel to a sufficiently high temperature, economically attractive amounts of fusion energy can be produced. The resulting confinement is called …

Inertial Force
A fictitious force that arises in accelerating (noninertial) reference systems. For an accelerating body, the inertial force is considered as a body force whose resultant acts at the object's centre of gravity in a direction opposite to the acceleration. The magnitude of the force is the mass of the object times the magnitude of the acceleration. S…

Inertial Mass
An object's resistance to a change in its velocity. Measured in kilograms.The force required to change the velocity of a body is give by Newton's Second Law:The rate of change of momentum of a body is directly proportional to the external force acting on the body and takes place in the direction of the force.whereF = force acting on the body [N]m =…

Inertial Reference System
Any reference system in which the law of inertia (Newton's first law of motion) is valid. Thus, inertial reference frames move at constant velocities. See also: Galilean Principle of Relativity, Newtons Laws of Motion, Noninertial Reference System, Reference System.

Inferior Mirage
Inferior means 'lower'; this is the mirage in which the inverted image is below the normal one. The common example is the hot-road mirage seen on sunny days. See also: Fata Morgana, Mirage.

Infinite
Becoming large beyond bound. Uncountable.Denoted by the symbol:8

Infinitesimal
A variable that approaches zero as a limit. See also: Limit.

Inflection
A point of inflection of a plane curve is a point where the curve has a stationary tangent, at which the tangent is changing from rotating in one direction to rotating in the oppostie direction. See also: Curve Sketching.

Infra-Red Radiation
The region of the electromagnetic spectrum adjacent to that of visible light,but with longer wavelengths. Infra-red radiation is emitted by hot objects and by excited molecules. It is produced by the movement of charges on the molecular scale, by vibrational or rotational motion of molecules.Covering wavelengths from 0.75x10-6m to 1000x1…

Infrasound
Acoustic waves below 20Hz are normally inaudible, but may be experienced as being in a region of high pressure.2-5Hz range played at 100-125dB may produce difficulty in swallowing and slight post-exposure headache.2-5Hz range played at 125-137dB may produce chest wall vibration; difficulty in speaking and voice modulation; swaying sensations; letha…

Ingot
A steel casting that is cast into a mould which when solidified will be rolled in a blooming mill to plates and slabs for sheets. See also: Bloom, Steel.

Inhale
To take into the lungs by breathing.

Initial Time-Delay Gap
The time gap between the arrival of the direct sound and the first sound reflected form the surfaces of the room. It corresponds with the subjective impression of 'intimacy'.

Initiator
A compound required to start a chain reaction. Unlike a catalyst, it is consumed in the reaction, but only a small quantity is normally required.

Inscribed Angle
The angle formed by two chords of a curve that meet at the same point on the curve. See also: Plane Angle.

Insertion Loss
AcousticsThis may be applied to a silencer or other sound-reducing element, in a specified frequency band, the decrease in sound power level, measured at the location of the receiver, when a sound insulator or a sound attenuator is inserted in the transmission path between the source and the receiver.ElectronicsThe loss in power caused by the inser…

Instantaneous Speed
The limiting value of the average speed as the time interval becomes infinitesimally small. The magnitude of the velocity. See also: Averaging, Velocity.

Institution of Electrical Engineers
The IEE is an innovative international organisation for electronics, electrical, manufacturing and IT professionals, with specifically tailored products, services and qualifications to meet the needs of today's technology industry.

Instruction
A binary code number that directs the control unit of a computer to perform a certain operation. Each operation has a unique instruction code.

Instruction Set
The collection of the instruction codes recognized by the control unit of acomputer. See also: Computer, Instruction.

Instrumentation Books
Sound Intensity By Frank J Fahy, Published By: Spon Press.Handbook of Modern Sensors By Jacob Fraden, Published By: Springer-Verlag Berlin and Heidelberg GmbH & Co. KG.Fast Fourier Transform and Its Applications By E.Oran Brigham, Published By: Prentice-Hall.

Insulator
A material that does not allow the passage of electric charge or is a poor conductor of thermal energy. Ceramics are good insulators. A nonmetallic material that has filled valence band at 0 K and a relatively wide energy band gap.

Integer
A whole number.The positive integers are 1,2,3,,...The negative integers are -1,-2,-3...Then there is 0 ,the zero integer. Numbers with no fractional part.

Integrated Circuit
First proposed by G. W. A. Dunner in 1952.Ultra Large Scale Integration (ULSI)a chip with over 1,000,000 components. Very Large Scale Integration (VLSI)An integrated crcuit with 100,000 to 1,000,000 components.

Integration
The inverse of differentiation. Mathematical process used in calculus. See also: Differential Equations, Standard Integrals.

Intensity of Magnetism
This is the magnetic moment per unit volume of a magnet. The SI unit of magnetic moment is Am-1.

Intensity Stereo
A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes based on retaining at high frequencies only the energy envelope of the right and left channels. See also: M/S Stereo, Stereo Irrelevance.

Intensive Properties
Properties which are independent of the amount of the substance.e.g. temperature, pressure, entropy, density, specific volume.

Interaural Fluctuation Strength
Phase differences between ears lead to an inferred source location. If this location changes as a function of time this may be inferred as a signal instability. See also: Interaural Cross-Correlation Coefficient, Interaural Level Difference.

Interaural Level Difference
In binaural hearing the interaural level difference has an impact on lateralization throughout the frequency spectrum. Experimental results show that Interaural Level Differences of 15-20 dB will completely move an image to one side. Interaural Level Differences above 8-10 dB increased the width of the image. In general, Interaural Level Difference…

Interaural Phase Difference
Coincident with the interaural time delay, varies systematically with source azimuth and wavelength due to distance from source and refraction around the head. This is the dominant cue for horizontal localization for frequencies up to 1500 Hz.Rayleigh noted that human listeners are sensitive to differences in the phase of low frequency tones at the…

Interface
A boundary across which two systems communicate. An interface might be a hardware connector used to link to other devices, or it might be a convention used to allow communication between two software systems.IEEE 1394 (Firewire)A very fast external bus standard that supports data transfer rates of up to 400 Mbps. A single 1394 port can be used to c…

Interference
The combining of two or more signals (superposition of waves) results in an interaction called interference. This may be constructive or destructive. Another use of the term is to refer to undesired signals, such as noise on a radio transmission.Constructive InterferenceWhen the peaks and troughs of two interfering waves match, the amplitudes add t…

Intermetallic
A compound of two metals that has a distinct chemical formula. The bonds in intermetallic compounds are often partly ionic. See also: Metal.

Intermolecular Forces
Forces between molecules. See also: Force, Intramolecular Forces, Ion Dipole Forces, Molecule.

Internal Combustion Engine
Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the engine rather than outside of the engine.Induction StrokeThe stroke where the fuel-air mixture is drawn into the cylinder.Compression StrokeThe stroke of the internal Combustion Engine where the piston moves into the cylinder, compressing this fuel-air …

Internal Energy
A property of a system that can be changed by a flow of work, heat or both; it is represented by the symbol E (E represents the change in internal energy of a system) and is given in units of energy (Joules). See also: Gibbs Free Energy.

Internal Force
Forces which hold an object together when external forces or other loads are applied. Internal forces are sometimes called resisting forces since they resist the effects of external forces. See also: External Force, Force.

International Phonetic Alphabet
A system of words identifying the letters of the alphabet and numbers. The system was reached through international agreement, and uses words chosen for their ease of pronunciation by people of all language backgrounds.

Interrupts
An efficient method to quickly request a computer's attention to a particular external event. See also: Nonmaskable Interrupt.

Intersecting Planes
Planes that share a line.

Interstitial Site
Octahedral and tetrahedral open spaces within a close-packed arrangement of atoms or ions in which a cation can fit.

Intramolecular Forces
Forces within molecules. Forces caused by the attraction and repulsion of charged particles. See also: Force, Intermolecular Forces, Molecule.

Intrinsic Carrier Density
The density of electrons and holes in an intrinsic semiconductor. See also: Intrinsic Semiconductor.

Intrinsic Semiconductor
A semiconductor free of defects or impurities. See also: Intrinsic Carrier Density.

Invar
Low thermal expansion alloy of iron and nickel. Typically 36% Nickel and 64% Iron.

Invariant Point
A point on a binary phase diagram at which three phases are in equilibrium.

Inventor
A person who thinks up new ideas or processes. See also: Patent.

Inverse Proportionality
A relationship in which a quantity is related to the reciprocal of a second quantity. See also: Inverse Square, Proportionality.

Inverse Square
A relationship in which a quantity is related to the reciprocal of the square of a second quantity.AcousticsUnder far field/free field conditions, sound intensity varies inversely with the square of the distance from the source. In pure spherical divergence of sound from a point source in free space, the sound pressure level decreases 6 dB for each…

Inversion
Referring to something being upside down.

Inverter
A circuit in both analogue and digital systems that provides an output that is inverse to the input. Also a circuit that converts DC to AC.

Investment Casting
Also known as lost wax and precision casting, is based on surrounding an expendablepattern, typically pattern wax, in a ceramic mould and then removing (by melting orvaporizing) the pattern prior to pouring molten alloy into the mould.A guide as to the surface finish that is achievable using different casting techniques is shown below (the solid …

Iodine
In the halogen group of elements. Symbol I

Iodine Number
The number of grams of iodine required to saturate 100 grams of fat. See also: Iodine.

Ion
An atom (or group of atoms) which has either gained or lostelectrons; e.g., a chloride anion, 17Cl1-, contains 18 electrons (i.e.,one more than neutral atom, 17Cl0), and a copper(II) cation, 29Cu2+,contains 27 electrons (i.e., two less than the neutral atom, 29Cu0
Ion Dipole Forces
Intermolecular force that exist between charged particles and partially charged molecules. See also: Intermolecular Forces, Molecule.

Ionic Bond
This describes the electrostatic attraction of two oppositelycharged ions in a crystalline lattice. When two oppositely charged atoms share at leastone pair of electrons but the electrons spend more time near one of the atoms thanthe other.The potential energy due to the attraction between sodium chloride (Na+-Cl -) ions is gi…

Ionization Energy
Energy required to remove an electron from a specific atom. See also: Atom, Electron, Ionizing Radiation.

Ionizing Radiation
A particle or a photon with enough energy to knock off an electron from an atom. See also: Ionization Energy.

Ionosphere
The region of the Earth's upper atmosphere containing a small percentageof free electrons and ions produced by photo ionization of the constituentsof the atmosphere by solar ultraviolet radiation at very short wavelengths(less than 1000 angstroms). The ionosphere significantly influences radio wavepropagation of frequencies less than about 30 MHz. …

Iridium
Iridium is a rare, precious metal which is hard, brittle and has a low ductility, which makes it a difficult material to work. In appearance, it is a lustrous, silvery metal. It has an abundance in the earth`s crust of approximately 3x10-6 ppm. As might be expected from its position in the periodic table, iridium is stable to air and wat…

Iron
Probably one of the most important, being used on the largest scale of any metal. Its production in the blast furnace is well documented. When pure, iron is a lustrous white metal which is soft and very workable. However, it is reactive and easily forms a coating of hydrated oxide on its surface in the presence of moist air. This is non-coherent an…

Iron Foundry
A place where iron castings are made. See also: Cast Iron, Iron.

Iron Hydroxide
Found as the minerals Siderogel and Feroxyhyte. Symbol FeO(OH) Also known as Lepidocrocite

Iron II Chloride
Pale yellow to white crystalline solid. Symbol FeCl2

Iron II Hydroxide
Green colour. Symbol Fe(OH)2

Iron II Oxide
Black colour powder. The powder in particular can cause explosions as it readily ignites. Symbol FeO

Iron II Sulphate
Green Vitriol is hydrated Iron II Sulphate. Symbol FeSO4 Also known as Melanterite, Copperas

Iron II Sulphide
Photograph of iron pyrites courtesy of MineraliteA brassy yellow colour. Brass Lump was the name miner's gave to a large lump of fools' gold. Symbol FeS2

Iron III Chloride
Brown black or green crystalline solid. Symbol FeCl3

Iron III Oxide
Photograph of Haematite courtesy of MineraliteKnown in its natural state as Haematite, but also purified for use as a coating in magnetic audio and computer media, where it is known as Ferric oxide. Symbol Fe2O3

Iron Sulphide
White crystalline solid. Symbol FeS

Irrational Number
Any number that cannot be expressed as the ratio of two integers. A decimal number that never ends and never repeats.For example, p, e, or .First discovered by Hipparcos of Metapontum around 450BC.

ISO Metric Threads
Coarse ThreadMajor Diameter mmPitch mmTensile Stress Area mm2Tapping Drill mm1.60.351.271.351.80.351.701.5520.402.11.702.20.452.51.902.50.453.42.2030.505.02.653.50.606.83.1040.708.83.504.50.7511.54.050.8014.24.5061.0020.15.371.0081.2536.67.191.25101.5058.08.8111.50121.7584.310.7142.00162.00157.014.5182.50202.50222.50243.00Fine ThreadMajo…

ISO Paper Sizes
A series is mainly used for standard book print and stationery.A Seriesmm4A1682 x 23782A1189 x 1682A0841 x 1189A1594 x 841A2420 x 594A3297 x 420A4210 x 297A5148 x 210A6105 x 148A774 x 105A852 x 74A937 x 52A1026 x 37B series is mainly used for posters and wall-charts.B SeriesmmB01000 x 1414B1707 x 1000B2500 x 707B3353 x 500B4250 x 353B5176 x 250B612…

Isobaric
Constant pressure. See also: Isothermal, Pressure.

Isochrony
A sequence of events is called isochronous if the time separating each pair of successive events is strictly equal. The absence of isochrony is called anisochrony. See also: Anisochrony.

Isometry
a transformation that keeps the same size and shape of a figure but moves it to a new location.e.g. reflection, rotation, translation, glide reflection

Isosceles Tetrahedron
A tetrahedron in which each pair of opposite sides have the same length.

Isosceles Triangle
A triangle with two equal sides. See also: Triangle.

Isotactic
A type of polymer chain configuration wherein all side groups are positioned on the same side of the chain molecule. See also: Polymer.

Isothermal
Constant temperature. See also: Celsius Temperature Scale, Isobaric, Isothermal Transformation, Kelvin.

Isothermal Expansion
The expansion or compression of a gas at constant temperature.ieThe work done on a perfect gas during isothermal expansion is given bywhereW = work done [J]n = number of moles of gasR = molar gas constant = 8.31441 JK-1mol-1T = gas temperature [K]P1 = pressure before expansion [Nm-2]P2 = pressu…