Page 58 - Electrical Engineering Dictionary

arbiter a unit that decides when multi- arcing ground a ground fault on a power
ple requestors may have access to a shared line which alternately clears and restrikes,
resource. causing high, repetitive voltage surges.

arbitrary reference frame atwo-
dimensional space that rotates at an unspec-
ified angular velocity ω. In electric ma-
chines/power system analysis, an orthog-
onal coordinate axis is established in this
space upon which fictitious windings are areal density a measure for the improve-
placed. A linear transformation is estab- ment in the capacity of a disk. It is the prod-
lished in which the physical variables of the uct of the number of tracks per inch and the
system (voltage, current, flux linkage) are number of bits per inch, i.e., it is the number
referred to variables of the fictitious wind- of bits per square inch.
ings. See also
rotor reference frame, stationary reference argon ion laser See Ar+ laser.
frame, synchronous reference frame.
argument (1) an address or value that is
arbitration See bus arbitration. passed to a procedure or function call, as a
way of communicating cleanly across proce-
ARC See antireflective coating. dure/function boundaries.
(2) a piece of data given to a hardware
arc detector a device placed within a operator block.
microwave power tube or within one or more
of the external cavities of a microwave power arithmetic and logic unit (ALU) a com-
tube whose purpose is to sense the presence binational logic circuit that can perform basic
of an overvoltage arc. arithmetic and logical operations on n-bit bi-
nary operands.
arc fault interrupter the mechanism that
breaks the fault current arc in a power circuit arithmeticcoding amethod(duetoElias,
breaker. Pasco, Rissanen and others) for lossless data
compression. This incremental coding algo-
arc lamp lamp made by driving a high rithm works efficiently for long block lengths
current across a gap between two electrodes. and achieves an average length within one
Sometypesoperateinairconsumingtheelec- bit of the entropy for the block. The name
trode, for example, a carbon arc in which comes from the fact that the method utilizes
the electrode material is made as a rod and the structures of binary expansions of the real
fed into the discharge to replace what is con- numbers in the unit interval.
sumed. Others operate in a vacuum envelop
that reduces the electrode consumption. arithmetic instruction a machine in-
struction that performs computation, such as
arc resistance period of time that the sur- addition or multiplication.
face of an insulating material can be submit-
ted to the action of an electrical arc without arithmetic operation any of the follow-
becoming conductive. ing operations and combination thereof: ad-
dition, subtraction, multiplication, division.
architecture See computer architecture.
arithmetic radian center frequency the
arcing fault See arcing ground. linear radian center frequency, it is the mid-

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