As

As
A brittle, crystalline solid which tarnishes readily in air and burns in oxygen.
As Welded
The condition of weld metal, welded joints, and weldments after welding and prior to any subsequent thermal, mechanical, or chemical treatments.
as
Abbreviation of attosecond a time of 10-18seconds.
As2O3
Chemical formula for Arsenic III Oxide.
As2O5
Chemical formula for Arsenic V Oxide.
ASA Number
A measure of the speed of the photographic emulsion.
Asbestos
This description covers a number of fibrous silicate minerals such as calcium magnesium silicate.
Asbestosis
Fibrosis of the lungs caused by inhalation of asbestos fibres.
As-Cast Condition
Casting without subsequent heat treatment.
Ascendent
A vector with magnitude equal to the maximum spatial rate of change of that function at a given point at a given time and directed toward increasing values of the function along the line of maximum change.
ASCII
Coding for text files.
Ash
A very tough and elastic timber used for oars, blocks and pulleys, spokes of wheels and milk-pails.
Ash Flow
A turbulent mixture of gas and rock fragments, most of which are ash-sized particles, ejected violently from a crater or fissure.
Ash Frame
On some old cars the bodywork was built with a wooden frame, normally made from Ash, with panels attached to the wooden frame.
Ash
The mineral content of a product remaining after complete combustion.
AsH3
Chemical formula for Hydrogen Arsenide.
Ashes of Tin
Old name for Tin IV Oxide.
Ashlar Masonry
Uniform, rectangular blocks of stone with parallel faces, as used in the construction of classical Greek and Roman buildings.
Ashpan
A container beneath the furnace, catching ash and clinker that falls through the firebars.
ASIC
An abbreviation of Application Specific Integrated Circuit.
ASME
Abbreviation of American Society of Mechanical Engineers.
Asn
The inverse of sine. Note that asn(A)=sin-1(x).
Asparagine
A natural amino acid that is the amide of aspartic acid.

Aspartic Acid
A nonessential amino acid that is abundant in molasses.
Aspect Ratio
For a graphics device it is the ratio of the screen dimensions, normally defined as vertical screen dimension divided by horizontal screen dimension.
Asphalt
A black sticky semi-solid material mainly bitumen with minerals, occurs naturally, but made artificially and used in the construction of roads and buildings.
Aspherical
Not spherical. To reduce spherical aberration, a lens may be altered slightly so that one or more surfaces are aspherical.
Aspin Engine
A rotary valve engine developed by Frank Aspin.
Aspirin
Common name for Acetyl-Salicyclic Acid.
Assay
A quantitative determination of the metal in an ore or alloy.
Assemble
The action of putting something together from a number of component parts.
Assembler
A computer program that converts symbolic assembly language programs into equivalent binary machine language programs.
Assembly
A unit made from many parts. May refer to a molecule, machine tool, or any grouping of objects to form a larger entity.
Assembly Line
The production line where an assembly is put together from its component parts.
Asserted High
The asserted, true, one, or active case of a binary signal is the high or most positive voltage level.
Asserted Low
The asserted, true, one, or active case of a binary signal is the low or less positive voltage level.
Associative Property
When adding or multiplying three numbers, it doesn′t matter if the first two or the last two numbers are added or multiplied first.
Astable
A circuit that has no stable state and thus oscillates at a frequency dependent on component values.
Astable Multivibrator
A multivibrator that has no stable state.
Astatine
The heaviest halogen and radioactive.
Asterism
A group of stars which are traditionally imagined to represent a pattern.
Asteroids
These are rocky bodies, the vast majority of which orbit the Sun between Mars and Jupiter.
Asthenosphere
The shell within the earth, some tens of kilometres below the surface and of undefined thickness.
Astigmatism
An aberration, or defect, in a mirror or lens that causes the image of a point to spread out into a line.
ASTM
Abbreviation of American Society For Testing Material.
Astragal
A moulding, attached to one of a pair of swinging double doors, against which the other door strikes.
Astrolabe
An instrument that was used to determine the altitude of objects in the sky.
Astrometric Position
The position of a heavenly body on the celestial sphere corrected for aberration but not for planetary aberration.
Astrometry
The branch of astronomy concerned with measuring the positions of celestial bodies, such as stars and galaxies, and their real and apparent motions.
Astronaut
A person who rides in a space vehicle.
Astronomic Theory of Glaciation
Theory based on the changing position of the Earth in its orbit around the Sun.
Astronomical Constants
The elements of the orbits of the bodies of the solar system, their masses relative to the sun, their size, shape, orientation, rotation, and inner constitution, and the velocity of light.
Astronomical Unit
Defined as the mean distance of the Earth from the Sun.
Astronomy
The generic name for the study of the universe around us.
Astronomy Weblinks
Lists all Astronomy Weblinks in the Encyclopaedia
Astrophysics
The physics of astronomical objects such as stars and galaxies.
Asymmetric
A pattern in which one side does not correspond to the other side.
Asymmetric Capacitor
A capacitor where the two plates differ in surface area.
Asymmetric Carbon Atom
A carbon atom that is covalently bonded to four different groups and thus may exist in two different stereospecific configurations.
Asymmetric Digital Subscriber Line
A method of connecting a computer to the internet over an ordinary phone line using ethernet office networking technology instead of an ordinary modem.
Asymmetric Waveform
A waveform that has unequal excursions above and below the horizontal axis.
Asymmetrical Multivibrator
A multivibrator that generates rectangular waves.
Asymmetrical Support
A rotor support system that does not provide uniform restraint in all radial directions.
Asynchronous
The transmission of data between a transmitting and a receiving device that occurs as a series of zeros and ones.
Asynchronous Orbit
One where the satellite does not rotate or move at the same speed as the earth.