Ar
- Ar
- An inert gas that makes up about 1% of the atmosphere.
- Arabesque
- Ornament consisting of garlands of foliage with figures, fancifully interlaced to form graceful curves and painted, inlaid, or carved in low relief.
- Arago Spot
- A bright spot that appears in the shadow of a uniform disc being backlit by monochromatic light emanating from a point source.
- Aramid
- An artificially-made organic material that forms very long and stiff fibres.
- Arbitrary Unit
- A unit that is not part of the standardized metric or other system.
- Arbor
- A shaft or spindle for holding cutting tools; most usually on a milling machine.
- Arbor Press
- A hand-operated machine tool designed for applying high pressure for the purpose of pressing together or removing parts.
- Arc
- Part of a circle.
- Arc Brazing
- A brazing process wherein the heat is obtained from an electric arc formed between the base metal and an electrode.
- Arc Cutting
- A group of cutting processes in which the cutting of metals is accomplished by melting with the heat of an arc between the electrode and the base metal.
- Arc Flash
- An electrical explosion that results from a low-impedance connection to ground or another voltage phase in an electrical system.
- Arc Length
- The distance between the endpoints of an arc along the path of the circle.
- Arc Oxygen Cutting
- An oxygen-cutting process used to sever metals by a chemical reaction of oxygen with a base metal at elevated temperatures.
- Arc Welding
- A group of welding processes in which fusion is obtained by heating with an electric arc or arcs, with or without the use of filler metal.
- Arcade
- A series of arches supported by columns or piers, or a passageway formed by these arches.
- Arccos
- The inverse of cosine. Note that arccos(A)=cos-1(x).
- Arccot
- The inverse of cotangent. Note that arccot(A)=cot-1(x).
- Arccsc
- The inverse of cosecant. Note that arccsc(A)=csc-1(x).
- Arch
- A curved structural member that spans an opening and is generally composed of wedge-shaped blocks that transmit the downward pressure out laterally.
- Arch Bridge
- A curved structure that converts the downward force of its own weight, and of any weight pressing down on top of it, into an outward force along its sides and base.
- Arch Dam
- A dam with an arched shape that resists the force of water pressure; requires less material than a gravity dam for the same distance.
- Archaean
- The geological eon covering about 3.9 billion years ago to 2.6 billion years ago.
- Archaeozic
- The geological period from 4.6 billion to 1.0 billion years ago.
- Archimedes
- Forever to be known for the Archimedean principle: "a body plunged in a fluid loses as much weight as... "
- Archimedes Constant
- More commonly known as Pi.
- Archimedes′ Principle
- The buoyant force is equal to the weight of the displaced fluid.
- Architect
- A person who designs all kinds of structures.
- Architectural Acoustics
- Lists all Architectural Acoustics topics in the Encyclopaedia.
- Architectural Acoustics Calculations
- Lists all Architectural Acoustics Calculations in the Encyclopaedia
- Architectural Acoustics Conversions
- Lists all Architectural Acoustics Conversions in the Encyclopaedia
- Architectural Acoustics Weblinks
- Lists all Architectural Acoustics Weblinks in the Encyclopaedia
- Architectural Coatings
- Coverings such as paint and roof tar that are used on exteriors of buildings.
- Architecture
- Lists all Architecture topics in the Encyclopaedia
- Architecture Books
- Lists all Architecture Books in the Encyclopaedia
- Architecture Calculations
- Lists all Architecture Calculations in the Encyclopaedia
- Architecture Conversions
- Lists all Architecture Conversions in the Encyclopaedia
- Architecture Weblinks
- Lists all Architecture Weblinks in the Encyclopaedia
- Architrave
- The lowest part of an entablature resting on the capital of a column. Also, the holdings around a doorway.
- Arcminute
- Defined as 1/60 of a degree.
- Arc-Resistance Switchgear
- Switchgear designed to withstand the effects of an internal arcing fault, without causing harm to personnel.
- Arcsec
- The inverse of secant. Note that arcsec(A)=sec-1(x).
- Arcsecond
- Defined as 1/360 of a degree.
- arcsin
- The inverse of sine. Note that arcsin(A)=sin-1(x).
- Arctan
- The inverse of tangent. Note that arctan(A)=tan-1(x).
- Are
- A derived SI Unit of area. 1 Are = 100m2
- Area
- The derived SI unit of area is the m2.
- Areal Weight
- The weight of fibre per unit area, width times length, of tape or fabric.
- Arene
- A hydrocarbon that contains at least one aromatic ring.
- Argentite
- Naturally occuring Silver Sulphide. An important ore of silver.
- Argentum
- Latin for silver, hence the symbol Ag.
- Arginine
C6H14N4O2
A semiessential or conditionally essential amino acid in mammals.
- Argon
- An inert gas that makes up about 1% of the atmosphere.
- Aristotle
- A Greek philosopher who stressed the importance of direct observations in securing facts and data.
- Arithmetic
- The type of mathematics that studies how to solve problems involving numbers, but not variables.
- Arithmetic Coding
- Arithmetic coding removes this restriction by representing messages as intervals of the real numbers between 0 and 1.
- Arithmetic Error
- As error that occurs when discarding least significant bits of a fixed-point arithmetic operation.
- Arithmetic Mean
- The arithmetic mean of n numbers is the sum of the numbers divided by n.
- Arithmetic Operators
- Symbols and signs used in mathematics.
- Arjuna Asteroids
- Asteroids that orbit the Sun in a near circular path and are no more than 100m in diameter.
- Arko Metal
- A brass made with 80% copper and 20% zinc.
- Armature
- In a relay, the movable portion of the relay. The windings in which the output voltage is generated in a generator or in which input current creates a magnetic field that interacts with the main field in a motor.
- Armature Losses
- Copper losses, eddy current losses, and hysteresis losses that act to decrease the efficiency of armatures.
- Armature Reaction
- The effect in a dc generator of current in the armature creating a magnetic field that distorts the main field and causes a shift in the neutral plane.
- Armstrong, Edwin Howard
- American electrical engineer and inventor of the modern frequency modulation radio.
- Aromatic
- Aromatic compounds have strong, characteristic odors.
- Aromatic Compound
- A compound containing an aromatic ring.
- Aromatic Ring
- An exceptionally stable planar ring of atoms with resonance structures that consist of alternating double and single bonds, e. g. benzene.
- ARPANET
- Abbreviation of Advanced Research Projects Agency Network.
- Arrhenius Equation
- Variation of rate constant with temperature for several elementary reactions.
- Arrhenius, Svante August
- Swedish physicist and chemist who originated the modern theory of ionization of electrolytes. Received the Nobel Prize for chemistry in 1903.
- Arrhythmia
- Absence of rhythm,eg in heart beat.
- Arrol, Sir William
- Scottish engineer who most notably built the Tay Rail Bridge in 1887, Forth Rail Bridge in 1890 and Tower Bridge in 1894.
- Arsenic
- A brittle, crystalline solid which tarnishes readily in air and burns in oxygen.
- Arsenic III Oxide
As2O3
White crystalline solid, used as an opacifier in glazes.
- Arsenic V Oxide
As2O5
White solid.
- Arsenical Bronze
- An alloy of copper and arsenic in addition to other metals.
- Arsenical Copper
- An alloy of copper and arsenic in addition to other metals.
- Arsine
- Old name for Hydrogen Arsenide.
- Artery
- A blood vessel that carries blood away from the heart. All arteries, except for the pulmonary artery, contain oxygen.
- Artesian Well
- A well in which the water in the aquifer is under pressure that raises the water above the point that the well first encounters it.
- Articulated Piston
- Two-piece pistons incorporating an entirely separate piston crown or dome with a separate skirt.
- Articulation Class
- A measure for rating the speech privacy performance of a ceiling in an open plan environment.
- Articulation Index
- A quantitative measure of the intelligibility of speech; the percentage of speech items correctly perceived and recorded.
- Articulation Loss of Consonants
- The measured percentage of Articulation Loss of Consonants by a listener.
- Artificial Gravity
- Gravity established within a space vehicle by rotation or acceleration.
- Artificial Intelligence
- Field of computer science concerned with the concepts and methods of symbolic inference by computer, and the symbolic representation of the knowledge to be used in making inferences.
- Artificial Reverberation
- Reverberation generated by electrical or acoustical means to simulate that of concert halls, etc.
- Artificial Satellite
- A man made satellite.
- Artificial Transmission Line
- An LC network that is designed to simulate characteristics of a transmission line.
- Aryl
- A molecular fragment or group attached to a molecule by an atom that is on an aromatic ring.