relative element address designate scheme.
The position of each changing element on
the present line is coded with respect to the
changing element on the reference line or the
preceding changing element on the present
line.

The reference line lies immediately

above the present line.

CCR

See

cochannel reuse ratio

CCS

See

common channel signaling

CCVT

See

coupling capacitor voltage

See

See

See

CD-I

See

compact disk-interactive

CD-ROM

a read-only compact disk. See

also

compact disk

CDF

See

cumulative distribution function

CDMA

See

code division multiple

access

CdS

abbreviation for cadmium sulfide,

a photoconductor with good visible light re-
sponse.

CEL

See

contrast enhancement layer

CELL

See

surface-emitting laser logic

cell

(1) in mobile radio communica-

tions, the area serviced by one base sta-
tion. One way of categorizing the cells is
according to their size. Cell sizes may range
from a few meters to many hundred kilome-
ters. See also

(2) in ATM systems a small packet of fixed

length. The CCITT chose a cell size of 53-
bytes comprising a 5-byte header and 48-byte
payload for their ATM network.

cell library

a collection of simple logic

elements that have been designed in accor-
dance with a specific set of design rules and
fabrication processes.

Interconnections of

such logic elements are often used in semi-
custom design of more complex IC chips.

cell switching

means of switching data

among the ports (inputs and outputs) of a

2000 by CRC Press LLC

switch such that the data is transferred in units
of a fixed size.

cell-cycle-specific control

a type of con-

trol arising in scheduling optimal treatment
protocols in the case when treated popula-
tion is sensitive to the therapy only in cho-
sen phases of its cell cycle. A mathematical
model of population dynamics used to solve
the problem of such control should be com-
posed of subsystems sensitive and insensitive
to the drug. It may be achieved by the use
of compartmental models. Typical types of
perturbations of the cell cycle considered as
cel-cycle-specific control are as follows: cell
arrest, cell killing, and alteration of the transit
time. They could be applied for representa-
tion of cell synchronization, cell destruction,
and cell recruitment from the specific phase.

cellular automaton

system designed

from many discrete cells, usually assem-
bled in one- or two-dimensional regular ar-
rays, each of which is a standard finite
state machine.

Each cell may change its

state only at fixed, regular intervals, and
only in accordance with fixed rules that de-
pend on cells’ own values and the values of
neighbors within a certain proximity (usually
two- for one-dimensional, and four- for two-
dimensional cellular automata). Cellular au-
tomata are a base of cellular computers; fine
grain systems that are usually data-driven and
used to implement neural networks, systolic
arrays, and SIMD architectures.

cellular communications

traditionally,

an outside-of-building radio telephone sys-
tem that allows users to communicate from
their car or from their portable telephone.

cellular manufacturing

grouping of

parts by design and/or processing similarities
such that the group (family) is manufactured
on a subset of machines which constitute a
cell necessary for the group’s production.

cellular spectral efficiency

the cellular

spectral efficiency of a system is defined as

the sum of the maximum data rates that can be
delivered to subscribers affiliated to all base
stations in a re-use cluster of cells, occupying
as small a physical area as possible. Mathe-
matically, the cellular spectral efficiency,

η,

is defined as

η =

j=1

i=1

cluster

bit

/s/Hz/km

where

r denotes the number of cells in a re-

use cluster,

denotes the data rate mea-

sured in bits/s at some predefined BER avail-
able to subscriber

I in cell j of the re-use

cluster,

B denotes the total bandwidth mea-

sured in hertz allocated to all cells in the re-
use cluster, and

cluster

denotes the physical

area, measured in square kilometers occupied
by the re-use cluster.

CELP

See

code excited linear prediction

center frequency

(1) the frequency of

maximum or minimum response for a band-
pass or a bandstop filter, respectively; often
taken as the geometric mean of the lower and
upper cutoff frequencies.

(2) the frequency at the center of a spec-

trum display.

(3) the average frequency of the emitted

wave after modulation by a sinusoidal signal.

(4) the frequency of a non-modulated

wave. See also

channel

center of average

an approach of defuzzi-

fication that takes the weighted average of the
centers of fuzzy sets with the weights equal
to the firing strengths of the corresponding
fuzzy sets.

center of gravity method

See

centroid

method

center of projection

the point within a

projector from which all the light rays ap-
pear to diverge; the point in a camera toward
which all the light rays appear to converge

2000 by CRC Press LLC

before they cross the imaging plane or pho-
tographic plate.

central absolute moment

for random

variable

x, the pth central absolute moment

is given by

E[|x − E[x]|

. See also

central limit theorem (CLT)

in proba-

bility, the theorem that the density function of
some function of

n independent random vari-

ables tends towards a normal curve as

n tends

to infinity, as long as the variances of the vari-
ables are bounded: 0

< σ ≤ v

≤ γ < ∞.

Here

σ and γ are positive constants, and v

the variance of the

ith random variable. See

also

Gaussian distribution

central moment

for random variable

the

nth central moment is given by

E[(X − m)

] =

∞

−∞

(x − m)

(x)dx

where

(x) is the probability density func-

tion of

X. See also

central absolute moment

absolute moment

. See also

expectation

central processing unit (CPU)

a part

of a computer that performs the actual data
processing operations and controls the whole
computing system. It is subdivided into two
major parts:

1. The arithmetic and logic unit (ALU),

which performs all arithmetic, logic, and
other processing operations,

2. The control unit (CU), which sequences

the order of execution of instructions, fetches
the instructions from memory, decodes the
instructions, and issues control signals to all
other parts of the computing system. These
control signals activate the operations per-
formed by the system.

centralized arbitration

a bus arbitration

scheme in which a central bus arbiter (typ-
ically housed in the CPU) accepts requests
for and gives grants to any connected device,
wishing to transmit data on the bus. The con-
nected devices typically have different prior-

ities for bus access, so if more than one de-
vice wants bus access simultaneously, the one
with the highest priority will get it first. This
prioritization is handled by the bus arbiter.

centrifugal switch

a speed-sensitive

switch operated by centrifugal force, mounted
on the shaft of a motor, used to perform a cir-
cuit switching function. Used in single-phase
induction motors to disconnect the starting
winding when the motor approaches operat-
ing speed.

centripetal force

force that is present

during the robot motion. The force depends
upon the square of the joint velocities of the
robot and tend to reduce the power available
from the actuators.

centroid

(1) a region in the pattern space

to which a remarkable number of patterns be-
long.

(2) the center of a mass.
(3) description of the center of a particle

beam profile.

centroid defuzzification

a defuzzifica-

tion scheme that builds the weighted sum of
the peak values of fuzzy subsets with respect
to the firing degree of each fuzzy subset. Also
called height defuzzification.

centroid method

a widely used method

of defuzzification whereby the centroid of the
membership function of the fuzzy set is used
as the defuzzified or crisp value. It is also
known as the center of gravity method or the
composite moments method.

centroidal profile

a method for charac-

terizing and analyzing the shape of an object
having a well defined boundary. The cen-
troid of the shape is first determined. Then
a polar

(r, θ) plot of the boundary is com-

puted relative to this origin: this plot is the
centroidal profile, and has the advantage of
permitting template matching for a 2-D shape
to be performed relatively efficiently as a 1-D
process.

2000 by CRC Press LLC

centrosymmetric medium

a material

that possesses a center of inversion symme-
try. Of importance because, for example,
second-order nonlinear optical processes are
forbidden in such a material.

cepstrum

inverse Fourier transform of the

logarithm of the Fourier power spectrum of a
signal. The complex cepstrum is the inverse
Fourier transform of the complex logarithm
of the Fourier transform of the signal.

ceramic ferrite

a relatively inexpensive

permanent magnet material with decent co-
ercivity and low energy product that is com-
posed of strontium or barium oxide and iron
oxide. Also called hard ferrite.

cerebellar model articulation (CMAC)
network

a feedforward network devel-

oped originally as a model of the mam-
malian cerebellum.

Several variants now

exist, but basic operation involves the first
layer of the network mapping the input into a
higher-dimensional vector and a second layer
forming the network output by means of a
weighted sum of the first layer outputs. The
weights can be trained using the LMS rule.
Developed mainly for application in robotics,
it has also been used in pattern recognition
and signal processing. Often called a CMAC
network.

Cerenkov counter

a detector for charged

particles. It consists essentially of a trans-
parent medium such as a gas, which emits
Cerenkov radiation when a charged particle
passes through at a velocity greater than the
velocity of light in the medium. The mass of
a particle in a beam of known momentum can
be determined with such a counter by mea-
suring the characteristic angle at which the
Cerenkov radiation is emitted.

Cerenkov radiation

light emitted when

a charged particle traverses a medium with a
velocity greater than the velocity of light in
the medium. The Cerenkov light is emitted
in a cone centered on the particle trajectory.

The opening angle of this cone depends on
the velocity of the particle and on the veloc-
ity of light in the medium. The phenomenon
involved is that of an electromagnetic shock
wave and is the optical analogue of sonic
boom. Cerenkov radiation provides an im-
portant tool for particle detection.

certainty equivalence principle

a design

method in which the uncertainties of process
parameters are not considered. Found in self-
tuning regulators where the controller param-
eters or the process parameters are estimated
in real-time and are then used to design the
controller as if they were equal to the true pa-
rameters. Although many estimation meth-
ods could provide estimates of parameter un-
certainties, these are typically not used in the
control design.

CFD

See

crossed field devices

CFIE

See

combined field integral

equation

CGA

See

color graphics adapter

chain code

a method for coding thin con-

tours or lines, for example, in a bilevel pic-
ture, which encodes the direction of move-
ment from one point to the next.

For 8-

connected contours, a three-bit code may be
used at each point to indicate which of its
eight neighbors is the succeeding point.

chain matrix

See

ABCD matrix

chain parameters

See

ABCD parameters

chain reaction

a process in which high-

energy neutrons emitted from fissile radioac-
tive material are directed into more fissile
material such that more neutrons are emit-
ted. The process creates heat which is used
to power thermal power plants.

chaining

when the output stream of one

arithmetic pipeline is fed directly into another

2000 by CRC Press LLC

Content .. 27 28 29 30 ..