Page 43 - Electrical Engineering Dictionary

continuous-time and discrete-time state ag- cross over another strip. Air bridges are also
gregation is obtained by linear transforma- used to suspend metalization in spiral induc-
tion of the original state represented by an tors off of the semi-conducting substrate in a
aggregation matrix G endowed with the fol- way that can lead to improved performance
lowing properties: in some cases.

∗ ∗ 0 ∗
GA = A G; GB = B ; CG = C ; air capacitor a fixed or variable capacitor
in which air is the dielectric material between
where A, B, C are original system matrices the capacitor’s plates.
(respectively state, input, and output ones)
∗
and A ,B ,C are aggregated system ma- air circuit breaker a power circuit
∗
∗
trices. The aggregation is an eigenvalues- breaker where the power contacts operate in
preservation approach and it provides order air. Some versions employ an air blast to
reduction by neglecting some of the system extend and clear the arc on contact opening,
modes. while others employ arc chutes with mag-
For uncertainties, the aggregation defines netic or thermal assists.
some deterministic measures for a set of un-
certain variables. For stochastic model of air core transformer two or more coils
uncertainty the aggregation may be given by placed so that they are linked by the same flux
meanvalue, higherstochasticmodelsorother with an air core. With an air core the flux is
statistical characteristics, while set member- not confined.
ship uncertainties could be aggregated by
their maximal or minimal values, mass center air gap See magnetic recording air gap.
of the set or higher inertial moments.
air ionization chamber a device used to
AGI See address generation interlock. monitor neutron flux.

Aiken, Howard Hathaway (1900–1973) air line a coaxial transmission line in
Born: Hoboken, New Jersey, U.S.A. which the volume between the inner and
Aiken is best known as the inventor of outer conductors are air-filled.
the Mark I and Mark II computers. While
not commercially successful, these machines air terminal a lightning rod; any device
were significant in the development of the which extends upward into the air from a
modern computer. The Mark I was essen- structureforpurposesoflightningprotection.
tially a mechanical computer. The Mark II
was an electronic computer. Unlike UNI- air-blast circuit breaker a circuit breaker
VAC ( See Eckert, John Presper) these ma- in which the arc which forms between the
chines had a stored memory. Aiken was a contacts on opening is extinguished with a
professor of mathematics at Harvard. He was blast of high-pressure air.
given the assignment to develop these com-
puters by the Navy department. Among his air-gap line the line that is obtained by
colleagues in this project were three IBM sci- continuing the linear portion of the saturation
entists and Grace Hopper. It was while work- curve of a synchronous machine or a DC ma-
ing on the Mark I that Grace Hopper pulled chine. The figure shows a plot of generated
the first “bug” from a computer. voltage vs. field current at constant machine
speed. Initially, an increase in field current
air bridge a bridge made of metal strip yields a linear increase in the generated volt-
suspendedinairthatcanconnectcomponents age, but as the iron becomes saturated, the
on an integrated circuit in such a way as to voltage rolls off. The air-gap line gives the

c
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