Page 227 - Electrical Engineering Dictionary

dispatch the determination of the power dispersion of control See dispersion of
output of each plant in an electric power sys- authority.
tem.
dispersion shifted fiber single mode opti-
dispersed generation problem in eco- cal fibers with zero dispersion in the 1550 nm
nomic dispatch calculations, the task of ac- telecommunications window. Prior to 1985,
counting for the production capacity of co- single mode optical fibers were designed to
generation or dispersed sources such as pho- have zero dispersion in the 1310 nm telecom-
tovoltaic or wind generation plants. munications window.

dispersive medium (1) a medium for
dispersion (1) a characteristic of a
which the permittivity or the permeability (or
medium in which the propagation velocity
both) are frequency dependent.
of a wave varies as a function of signal fre-
quency. (2) in optics, medium in which the in-
dex of refraction varies significantly with fre-
As a pulse propagates through an optical
quency.
fiber, its chromatic components will spread
out or “disperse” in time. This phenomenon
displaced frame difference (DFD) the
limits the distance between optical regenera-
difference between a given digital image
tors in fiber communication systems. There
frame and its estimate obtained by using the
are four sources of dispersion: modal disper-
motion compensation technique. It is useful
sion, material dispersion, waveguide disper-
in image (sequence) data compression and
sion, and nonlinear dispersion.
motion estimation.
(2) the variation of the index of refraction
of a material as a function of wavelength.
displacementcurrent afieldquantitythat
describes the completion of a circuit when a
dispersion compensator a device that conducting path is not present.
compensates for the accumulated chromatic
dispersion in a fiber optic transmission sys- displacement parameter complex pa-
tem. Three main schemes exist: fiber grating rameter representing the displacement of the
dispersion compensators, dispersion com- amplitude and phase centers of a Gaussian
pensating fiber, and phase conjugation or beam from the axis of an optical system.
mid-span spectral inversion.
display a device that provides a visual
dispersion diagram a plot of propagation non-permanent display of system input and
constant versus frequency. or output. Common display technology in-
cludes CRT (cathode ray tube), LED (light
dispersion of authority a situation in emitting diode), PDP (plasma display panel),
which the decisions, for example, decisions EL (electroluminescense) and LCD (liquid
concerned with the manipulated inputs to the crystal display).
controlled process, are distributed between
several (control) decision units; dispersion dissipated power the power dissipated as
of authority may result either from natural, a heat, which is defined by subtracting an RF
legislative, or other reasons, or may appear output power from a DC input power.
due to design of the controller; decentralized
control, in particular, is based on the disper- dissipation the phenomenon associated
sion of authority between the local decision with the attenuation of a propagating wave in
units. Also known as dispersion of control. a medium with material losses.

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2000 by CRC Press LLC