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DiracDelta - Science & Engineering encyclopedia
Category: Sciences > Science & Engineering
Date & country: 01/12/2007, UK
Words: 4470
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Magnesium FluorideUsed as antireflection coating for lenses because of its low refractive index.
Magnesium OxideFormed by igniting Magnesium in air.
MagnetA magnet is a device that produces a magnetic field. Wires carrying electrical current produce magnetic fields which are circular around the wire. When wires are wound into a coil these are called electro-magnets. Another type of magnet is a permanent magnet in which an atoms in the material produce a magnetic field without the need for current. Ma…
Magnetic BearingA bearing that separates comparative rotating surfaces through the use of a magnetic field. See also: Bearing.
Magnetic ConfinementMethod of containing a plasma or charged particles in a finite region using magnetic fields. Charged particles travel in helical paths around the magnetic field lines and this confines their motion to the local vicinity of the magnetic field. A properly shaped magnetic field prevents particles from escaping the confining field. One example of a mag…
Magnetic DeclinationThe angle between magnetic north and true north at a given point on the Earth's surface.
Magnetic Field IntensityThe force that drives the generation of rnagnetic flux in a material. it is also called magnetizing force and can be produced by the application of an electric current.
Magnetic Field StrengthThe intensity of an externally applied magnetic field.
Magnetic FluxThe surface integral of the product of the permeability of the medium and the magnetic field intensity normal to the surface. The SI Unit of magnetic flux is the weber. 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. See also: maxwell, Permeance, Reluctance, Weber…
Magnetic Flux DensityThe magnetic flux density is the product of field intensity and the permeability of the medium. The SI unit of magnetic flux density is the tesla or weber per square metre. See also: Biot-Savart Law, Tesla.
Magnetic HysteresisWhen a ferromagnetic material is placed in an alternating magnetic field, the flux density (B) lags behind the magnetizing force (H) that causes it. The area under the hysteresis loop is the hysteresis loss per cycle, and is high for permanent magnets and low for high-permeability, low-loss magnetic materials.
Magnetic MomentThis is the couple exerted on a magnet placed at right angles to a uniform field with unit magnetic flux density. The SI unit of magnetic moment is Am
2. See also: Magnetic Flux Density, Torque.
Magnetic MonopoleA hypothesized, isolated magnetic pole. See also: Magnetic Pole.
Magnetic Particle InspectionA nondestructive method of inspection for determining the existence and extent ofpossible defects in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, areattracted to and outline the pattern of any magnetic-leakage fields created by discontinuities.
Magnetic PermeabilityThis indicates the ability of a material to support magnetic lines of flux. The magnetic permeability of a material is the product of the relative permeability of that material and the permeability of free space. The relative permeability of most nonferrous materials is near unity.
Magnetic PoleOne end of a magnet; analogous to an electric charge. See also: Magnetic Monopole.
Magnetic SaturationThe upper limit of the abilIty of a ferromagnetic material to carry flux.
Magnetic SusceptibilityThe proportionality constant between the magnetization and the magnetic field strength.
MagnetizationThe total magnetic moment per unit volume of material.A measure of the contribution to the magnetic flux by some material within an H field.
MagnetosphereThe outermost environment of Earth, dominated by the Earth's magnetic field. The magnetosphere is the site of the radiation belt and many intricate phenomena.
MagnetostrictionThe change of size and/or shape of aferromagnetic material due to the application of a magnetic field. See also: Piezoelectric.
MagnificationThe enlargement of an object by an optical instrument. Ratio between the size of the image and the actual size of the object.
MagnitudeThe size of a vector quantity. For example, speed is the magnitude of a velocity.Given the vector A:The magnitude of A is expressed as:
MahoganyA very hard wood that is very durable and can be polished to a fine finish with a rich colour. Less liable to crack or twist in seasoning than almost any other wood.
Mains NoiseUnwanted noise in electrical signals related to mains signals. See also: Noise.
Major AxisThe major axis of an ellipse is it's longest chord. See also: Minor Axis.
MalleableCapable of being extended or shaped by hammering or rolling.
Malus' LawNamed after Etienne Louis Malus (17
th Century).Malus' law defines the transmitted intensity through 2 polarisers with an angle ? between the transmission directions of said polarisers.The maximum transmission occurs when ? = 0 and is a minimised when ? = 90 degrees.
Mandelbrot SetThe most famous fractal, named after Benoit Mandelbrot. It is created by iterating an equation many times.'If the entire Mandelbrot set were placed on an ordinary sheet of paper, the tiny sections of boundary we examine would not fill the width of a hydrogen atom. Physicists think about such tiny objects; only mathematicians have microscopes fine e…
MandrelA precision-made tapered shaft to support work for machining between centres. See also: Morse Taper.
ManganeseObtained by reduction with aluminium or in a blast furnace. Pure manganese is a hard, brittle, silvery coloured, metallic element which exists in three polymorphic forms (alpha, beta and gamma) and has a complicated crystal structure. It resembles iron in being moderately reactive and dissolving in cold, dilute non-oxidising acids. When exposed to …
Manganese IV OxideThis blackish or brown solid occurs naturally as the mineral pyrolusite. Symbol MnO
2 Also known as Manganese dioxide, Pyrolusite, Black Wad.
ManganinAlloy with 84% copper, 12% manganese and 4% nickel used in wire form for making heating elements.
ManometerA U-shaped glass tube, partly filled with a liquid, water or mercury, employed to measure pressure.p
1 = p
2p
1 < p
2p
1 > p
2 See also: Mercury Hg, Pressure.
MarbleA granular metamorphosed limestone that is often polished and used for decoration. Sometimes used more loosely to describe any hard polished stone that is used for decorative purposes.
MarsThe fourth planet from the sun in our solar system.Click on an item to paste into clipboard or use clipboard symbol at end to clipboard all values Equatorial diameter 6786000 mClip Average Density 3940 kgm
-3Clip Axial tilt 24 degreesClip Rotational period 24.62 hoursClip Average surface temperature -40 °CClip Maximum apparent magnitude -…
MartemperingQuenching an austenitized ferrous alloy in a medium at a temperature in the upper part of themartensite range, or slightly above that range, and holding it in the medium until the temperature throughout thealloy is substantially uniform. The alloy is then allowed to cool in air through the martensite range. See also: Martensite.
MartensiteMartensite is a microconstituent or structure in quenched steel characterized by an acicular orneedle-lie pattern on the surface of polish. It has the maximum hardness of any of the structures resulting from thedecomposition products of austenite. See also: Martempering.
MaskingA property of the human auditory system by which an audio signal cannot be perceived in the presence of another audio signal.More intense sounds mask less intense ones. The amount of masking depends on the proximity of the frequency components of the two sounds, as well as on the global intensity of the masker. The greater the level, the greater th…
Masking SoundElectronically generated background sound of a specified level and frequency content, that is introduced into occupied environments to provide masking of intrusive noises and to enhance speech privacy.
MassThe SI unit of MassThe SI unit of mass is the kilogram and is equal to the mass of the International Prototype kilogram kept at Sevres, Paris and is a cylinder of platinum and iridium.Conversions1 gram (g)=1x10
-3 kg1 pound (lb)=0.453592 kg1 Tonne (t)=1x10
3 kg1 ton=1016.047 kg1 ounce (oz)=28.34952 g15.4324 grain (gr)=1 g1 troy …
Mass Action LawThe law which describes the relation between the densities of species involved in a chemical reaction.
Mass Flow RateSimply put, this defines the volumetric rate with which fluids flow (kgs
-1).In a system where there is a fluid flow and no sources or sinks the the mass flow rate must be equal at all points within that systemThis yields the Equation of Continuity:where:? = density [kgm
-3]A = cross sectional area [m
2]v = velocity [m…
Mass NumberThe mass number (A) of an atom is the number of protons and neutrons it has in its nucleus; e.g., A = 35 for a chlorine atom which contains 18 neutrons (35Cl), and A = 37 for one which contains 20 neutrons (
37Cl).Click on an item to paste into clipboard or use clipboard symbol at end to clipboard all values Beryllium 9 Clip Carbon 12 Cli…
Mass SpectrometerAn instrument for producing ions in a gas and determining their mass and hence composition. See also: Spectrometer.
MaterialA physical substance used as an input to production or manufacturing.
Material Safety Data SheetSafety information sheet for a particular substance that lists physical properties, hazards, cleanup and disposal procedures, fire and explosion data, and protective equipment required.
Mathematical Symbol sCommon symbols used in mathematics.+plus >greater than-minus
Mathematical Model
A mathematical representation of a process or physical object. See also: Model.
Mathematics Books
Fourier Transform and Its Applications By Ronald Bracewell, Published By: McGraw-Hill Book Company Ltd.Fermat's Last Theorem By Simon Singh, Published By: Fourth Estate Ltd.Fast Fourier Transform and Its Applications By E.Oran Brigham, Published By: Prentice-Hall.Engineering Mathematics By K.A. Stroud, Dexter Booth, Published By: Palgrave Macmillan…
Mathematics Calculations
Angular FrequencyThe frequency of a steady recurring phenomenum in radians per second.Antilogarithmx=by is called the antilogarithm of y to the base b.AveragingIn any process it is often necessary to average a number of measurements to gain any confidence in the measured value.Briggsian LogarithmAnother name for the Common Logarithm.Circ…
Mathematics Conversions
HexadecimalCounting system based on 16.Plane AngleThe plane angle between two radii of a circle which cut off on the circumference an arc equal in length to the radius is 1 radian.PointA zero-dimensional figure.QuartA unit of volume.RadianThe radian is the plane angle between two radii of a circle which cut off on the circumference an arc equal in …
Matlab
High-performance numeric computation language from Mathworks. See also: Programming Languages.
Matrix
MaterialsThe body constituent of a composite or two-phase alloy that completely surrounds the dispersed phase and gives the body its bulk form.MathematicsA rectangular array of elements. The dimensions of a matrix are often written as m x n. Where m is the number of rows and n the number of columns.Examples2 x 2 matrix, Also known as a square mat…
Maxima
The maxima are points where the value of a function is greater than other surrounding points. See also: Maximum, Minima.
Maximum
In a sample of data, the largest observation. See also: Maxima, Minima, Minimum.
maxwell
The CGS unit of magnetic flux, equal to 1x10-8weber.ttle='Maxwell';xiunt='weber';yiunt='maxwell';mconv=1e-8;cconv=0.0; See also: CGS Units, Magnetic Flux, Weber.
Maxwell Equations
Describe the relationship between electric and magnetic fields at any point in space as a function of charge density and electric current at such a point.The wave equation for the propagation of light is derivable from Maxwell's equations, and these are the basic equations of classical electrodynamics. They are used throughout the science of plasma…
Mayer Method
A method of evaluating the propagation delay of a transmission line. See also: Transmission Line.
Mean
The average, between the extremes. The sum of all values in the data, divided by the number of values. This is the sample mean, a value we can actually measure and compute, which approximates the population mean which we generally cannot measure. But we do expect the population mean to be within 'a few multiples' of the standard error of the comput…
Mean Free Path
For sound waves in an enclosure, it is the average distance travelled between successive reflections.
Mean Time Between Failure
The average time between failures for a continuously operating system. See also: Mean Time to Failure.
Mean Time to Failure
The measured operating time of a system or component divided by the number of failures that occurred during that time. See also: Mean Time Between Failure.
Mechanical Engineering Books
Introduction to the Thermodynamics of Materials By David R. Gaskell, Published By: Taylor & Francis Inc.Engineering Mathematics By K.A. Stroud, Dexter Booth, Published By: Palgrave Macmillan.Copper in the Automotive Industry By Hansjorg Lipowsky, Emin Arpaci, Published By: John Wiley and Sons.Art of Coppersmithing By John Fuller, Published By: Astr…
Mechanical Engineering Calculations
Cantilever BeamA beam that is held in an encastre at one end whilst the other end is unsupported.DecibelThe human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.Drag CoefficientA dimensionless value that allows the comparison of drag incurred by different sized and different shaped bodies.Dynamic vis…
Mechanical Engineering Conversions
atmAn abbreviation of atmosphere.BarrelA unit of capacity in the oil industry.BaryeThe CGS unit of pressure, equal to 1 dyne per square centimetre.bblAbbreviation of barrel. A unit of capacity in the oil industry.BHPAbbreviation of Brake Horse Power, the useful power available at the flywheel of an engine.Brake Horse PowerThis is the useful power a…
Mechanical Impedance
The mechanical properties of a machine system (mass, stiffness, damping) that determine the response to periodic forcing functions. See also: Impedance.
Mechanical Properties
The properties of a material that reveal its elastic and inelastic behaviour where force is applied, thereby indicating its suitability for mechanical applications; for example, modulus of elasticity, tensile strength, elongation, hardness and fatigue limit.
Medial Triangle
The triangle whose vertices are the midpoints of the sides of a given triangle.
Median
A statistic which measures the centre of a set of data by finding that value which divides the data in half. A technical definition is that the median is the value which is greater than or equal to half of the values in the data set and less than or equal to half the values. To compute the median yourself, you would sort the data from smallest to l…
Medical Conversions
Apothecaries OunceOnce used as a measurement of weight for drugs and other medical substances.GrainAn individual crystal in a poly-crystalline metal or alloy.
Meissner Effect
The decrease of the magnetic flux within a superconducting metal when it is cooled below the transition temperature. That is, superconducting materials reflect magnetic fields. See also: Superconductivity.
Mel
A proportional scale, in which equal intervals (measured in mel) correspond to equal perceived interval sizes. The mel scale is roughly proportional to the logarithm of frequency but becomes linear at low frequencies. See also: Acoustics, Decibel, Psychoacoustics.
Melting Point
The temperature at which a solid substance changes to a liquid state. The melting temperature of an alloy is usually less than the melting temperature of the parent metals.Click on an item to paste into clipboard or use clipboard symbol at end to clipboard all values Acetaldehyde 150.15 KClip Acetamide 355.15 KClip Acetanilide 387.15 KClip Acetic A…
Melting Range
The temperature range between solid and liquid. See also: Liquid, Melting Point, Solid.
Memory
In a computer system memory is used to store data temporarily or permanently. The capacity of the memory is normally measured in bytes. There are a number of different types of memory:CacheStatic random access memory containing recently used information. Used to buffer the central processing unit from any slower memory devices.DDR SDRAMDouble data …
Mendelevium
Man-made element with an atomic number of 101. Symbol Md
Meniscus
The curved surface of a liquid in a container produced by the cohesive forces between the liquid molecules and the adhesive forces between the liquid and the container. See also: Capillary Action, Surface Tension.
Mensuration
The measurement of lengths, areas and volumes. See also: Area, Length, Volume.
Mer
The group of atoms that constitutes a polymer chain repeat unit. See also: Alternating Copolymer, Copolymer, Monomer, Polymer.
Mercalli Scale
A measure of the intensity of an earthquake. This is a subjective value that varies depending on where the earthquake is observed. The ratings vary from I (felt only under especially favourable circumstances) to XII (total destruction).IGenerally not felt.IIFelt by a few people, suspended objects may swing.IIIFelt by a few people, similar vibration…
Mercuric Sulphide
The ore of mercury. Occuring as red crystals. Symbol HgS
Mercury
The planet nearest to the sun in our solar system.Click on an item to paste into clipboard or use clipboard symbol at end to clipboard all values Equatorial diameter 4878000 mClip Average Density 5420 kgm-3Clip Axial tilt 2 degreesClip Rotational period 58.65 hoursClip Average surface temperature -170 to 430 °CClip Maximum apparent magni…
Mercury Hg
The chemical symbol, Hg, comes from the Latin word 'hydragyrum' which means liquid silver, it being the most common liquid metal at room temperature. As a liquid, the metal is extremely mobile and dense and as a solid, it is ductile and malleable. It is a readily accessible element as it occurs in concentrated ores, mercury (II) oxide being decompo…
Mersenne Number
A number of the form 2p-1 where p is a prime. See also: Mersenne Prime, Prime Numbers.
Mersenne Prime
A Mersenne number that is prime. See also: Mersenne Number, Prime Numbers.
Mesh
To engage as the teeth between two gears. See also: Gear Design.
Meson
A type of hadron with whole-number units of spin. This family includes the pion, kaon, and eta. It is made up of a quark and its antimatter counterpart, bonded together. Mesons have a short mean life (less than 10-8 second) because (in the case of pi-zero meson) the quark and antiquark can soon annihilate one another. See also: Blackett,…
Metal
An opaque lustrous elemental chemical substance that is a good conductor of heat and electricity and, when polished, a good reflector of light. Most elemental metals are malleable, ductile, and are generally denser than the other elemental substances.Metals are structurally distinguished from nonmetals by their atomic bonding and electron availabil…
Metallurgy
The science and technology of metals and alloys.
Metastable
Nonequilibrium state that may persist for a very long time, a longer life time than that of regular excited states.
Meteor
A meteoroid that has entered Earth's atmosphere. See also: Meteorite, Meteoroid.
Meteorite
The remnants of a meteor after it has actually impacted the Earth. See also: Meteor, Meteoroid.
Meteoroid
An object in space similar to but smaller than an asteroid. See also: Meteor, Meteorite.
Meteorology Conversions
Celsius Temperature ScaleThe centigrade scale of temperature was defined as 0°C at the ice point of water and as 100°C at the boiling point of water (at 1 standard atmosphere).TemperatureA measure as to whether two bodies are hot or cold relative to one another.
Methane
The first alkane. Occurs naturally as marsh gas and in oil wells. Symbol CH4
Methyl Acetate
A clear, flammable liquid with a characteristic, not unpleasant smell like certain glues or nail polish removers. Symbol C3H6O2 Also known as Methyl Ethanoate
Methyl Alcohol
Also known as methanol. Symbol CH4O
Metonic Calendar
Named for the Athenian astronomer Meton, it is based on the moon, counting each cycle of the phases of the Moon as one month. Days are kept approximately in step with the seasons by including 7 leap years of 13 months in each cycle of 19 years. Used by the Chinese and the Jews. See also: Julian Day, Moon.
Metre
The metre is the SI unit of length and is equal to 1650763.73 wavelengths in vacuum of the radiation corresponding to the transition 2p10-5ds of a krypton 86 atom.
