Page 46 - Electrical Engineering Dictionary

allocation of authority process by which in the stored charge. Such an accumulation
the authority (scope of competence) is allo- of errors in a digital system has the effect of
cated to various decision units; this allocation creating a noise signal.
may result form the natural reasons or be a
product of system partitioning. alpha-cut the set of all crisp, or nonfuzzy,
elements whose membership function in A is
almost sure convergence for a stochas- greater than or equal to a given value, α.
tic process, the property of the sample values
converging to a random variable with proba-
alphanumeric mode relates to alpha-
bility one (for almost all sample paths).
betic characters, digits, and other characters
such as punctuation marks. Alphanumeric
alnico a permanent magnet material con-
is a mode of operation of a graphic terminal
sisting mainly of aluminum, nickel, cobalt,
or other input/output device. The graphics
and iron, which has a relatively low-energy
terminal should toggle between graphic and
product and high residual flux density. An
alphanumeric data.
alnico is most suitable for high-temperature
applications.
alternate channel power a measure of
the linearity of a digitally modulated system.
ALOHA a random access, multiple ac-
The amount of energy from a digitally trans-
cess protocol, originally developed by Nor-
mitted RF signal that is transferred from the
man Abramson at the University of Hawaii in
intended channel to one which is two chan-
1970. Agivenusertransmitsamessagewhen
nels away. It is the ratio (in decibels) of the
the message is generated without regard for
power measured in the alternate channel to
coordination with the other users sharing the
the total transmitted power.
channel. Messages involved in collisions are
retransmitted according to some retransmis-
alternating current (AC) a periodic cur-
sion algorithm. Literally, “aloha” is a greet-
rent the average value of which over a period
ing in the Hawaiian native language.
is zero.
alpha channel a grayscale image associ-
ated with the color channels of an image that alternating current machine an electro-
dictates the opacity/transparency of the cor- mechanical system that either converts alter-
responding color channel pixels. If the color nating current electrical power into mechan-
channels are multiplied by the alpha chan- ical power (AC motor), or converts mechan-
nel when stored, the image is referred to as ical power into alternating current electrical
premultiplied; otherwise, it is known as un- power (AC generator, or alternator). Some
premultiplied. AC machines are designed to perform either
of these functions, depending on the energy
alpha particle a subatomic particle source to the dynamo.
emitted by ceramic packaging materials that
causes soft errors in memory integrated cir- alternator-rectifier exciter a source of
cuits. field current of a synchronous machine de-
rived from the rectified output voltage of an
alpha particle noise this type of noise alternator. The components of the exciter
occurs exclusively in small semiconductor consist of the alternator and the power rec-
capacitors, when an energetic alpha particle, tifier (including possible gate circuitry), ex-
either from cosmic rays or from the packag- clusive of all input control elements. The
ing or substrate itself, traverses the capaci- rectifier circuits may be stationary, or rotate
tor, discharging it, thereby creating an error with the alternator, which may be driven by

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2000 by CRC Press LLC