Page 146 - Electrical Engineering Dictionary

with the use of only a single frequency state because it uses a dissipative process to create,
variable. rather than destroy, a quantum coherence.

coherent integration where magnitude
coil a conductor shaped to form a closed
and phase of received signals are preserved
geometric path. Note that the coil will
in summation.
not be a closed conducting path unless the
two ends of the coil are shorted together.
coherent acousto-optical processor
Coils may have multiple turns, and may have
acousto-optical (AO) signal processor where
various constructions including spool, pre-
the light is amplitude-modulated by the
formed, and mush-wound. The coil may be
acoustic wave in the AO device as opposed
wrapped around an iron core or an insulating
to intensity or power modulated.
form, or it may be self-supporting. A coil
offers considerable opposition to AC current
coherent detection detection technique
but very little to DC current.
in which the signal beam is mixed with a
locally generated laser beam at the receiver.
coil pitch See coil span.
This results in improved receiver sensitivity
and in improved receiver discrimination be-
tween closely spaced carriers. coil side that portion of a motor or gen-
erator winding that cuts (or is cut by) lines
coherent illumination a type of illumi- of magnetic flux and, thus, contributes to the
nation resulting from a point source of light production of torque and Faraday EMF in the
that illuminates the mask with light from only winding.
one direction. This is more correctly called
“spatially coherent illumination.”
coil span the distance, measured either
in number of coil slots or in spatial (me-
coherent light light having a relatively
chanical) degrees, between opposite sides of
long coherence length; laser light.
a winding of an electric machine. A full-
span (full-pitch) winding is one in which the
coherent optical communication opti-
winding span equals the span between adja-
cal communication approaches where infor- centmagneticpoles. Windingswithspanless
mation is conveyed in the phase of the optical
than the distance between adjacent magnetic
signal, therefore requiring that the phase of
poles are called short-pitch, fractional-pitch,
the optical sources be well controlled. See
or chorded windings. Also called coil pitch.
also optical communications.
coherent population trapping a tech- cold plasma a simplified model of the
plasma state where the effects that depend on
nique for creating a quantum mechanical co-
electron temperature are neglected. The par-
herence in a lambda system by a dissipative
ticles are assumed to have no kinetic thermal
process. Ideally, the intermediate excited
motion of their own. The particles are at rest
state in the lambda system decays rapidly
except for their induced velocities through
compared to the other two states. The coher-
the action of the self consistent electromag-
ence arises because a particular linear com-
netic fields.
bination of ground states is not coupled to
the excited state. Atoms accumulate into this
uncoupled superposition state by a process cold reserve the state of an idle thermal
analogous to optical pumping, thereby creat- generating plant whose boilers and turbine
ing a quantum mechanical coherence. This are cold and must be brought up to operating
system often has counterintuitive properties, temperature before power can be generated.

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2000 by CRC Press LLC