Page 145 - Electrical Engineering Dictionary

and distribution of the luminaire, its mount- eration designs are generally adopted to in-
ing height, the room proportions, and the re- crease the overall efficiency of a power gen-
flectances of the walls, ceiling, and floor. eration process.
(2) typically, the production of heat en-
coefficient sensitivity let a transfer func- ergy, e.g. to heat buildings, as an adjunct to
tion be a ratio of polynomials the production of electric power.
N(s) a 0 + a 1 s + ... + a m s m
F(s) = = cognitive map the cognitive map, intro-
D(s) d 0 + d 1 s + ... + d n s n
duced by R. Axelrod to study decision mak-
in which the coefficients a i and d i are real ing processes, consists of points, or nodes,
and can be functions of an arbitrary circuit and directed links between the nodes. The
element x. For such an element x one may nodes correspond to concepts. See also fuzzy
define the relative coefficient sensitivities as cognitive map.
follows:
coherence (1) measure of the extent to
∂a i x ∂d i x
a i d i
S = S = which knowledge of a field at one point in
x x
∂x a i ∂x d i
space permits prediction of the field at an-
The relationship between the function sensi- other point.
tivity and coefficient sensitivities can be es- (2) in an optical fiber.
tablished as well. (3) the coherence between two wide-sense
stationary random processes is equal to the
coercive field the electric field value at
cross power spectrum divided by the square
which the polarization is zero when a ferro-
root of the product of the two auto-power
electric material is cycled through the hys-
spectra. The magnitude of the coherence so
teresis loop. A material has a negative and a
defined is thus between 0 and 1.
positive coercive field and these are usually,
but not always, equal in magnitude to each
coherence bandwidth the bandwidth
other.
over which the effect of communication
channel can be assumed constant. Signals of
coercive force the demagnetizing field
bandwidth less than this can be transmitted
applied to a permanent magnet that reduces
without significant distortion.
its magnetic induction to zero; the x-intercept
of the normal demagnetization curve. A
coherence distance See coherence
commonly listed material property that in-
length.
dicates magnet performance in static condi-
tions.
coherence length distance over which
coercivity See coercive force. See also the amplitude and phase of a wave can be
intrinsic coercive force. predicted.
COGEN See cogeneration. coherence time the time over which the
effect of communication channel can be as-
cogeneration (1) any of a number of sumed constant. Signals of duration less than
energy generation systems in which two (or this can be transmitted without significant
more) forms of energy are produced in forms distortion.
practical for use or purchase by an end user.
Typical systems produce electrical energy for coherency a property of a control area
sale to a utility and process steam for local that has stiff interconnections between gen-
space heating or other process uses. Cogen- erators. Such an area thus may be described

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2000 by CRC Press LLC