Page 182 - Electrical Engineering Dictionary

Seealsoautocovariance, correlation, variance. theCramer-Raoboundwithequalityforall x,
it is efficient; if an efficient estimator exists,
it is the maximum likelihood estimator. See
covert channel a mechanism by means of also bias, maximum likelihood estimation.
which information can be communicated in-
directly despite design features that prevent crash an incorrect operation of computer
direct communication. Many covert chan- software or hardware leading to temporary or
nels utilize side effects of operations, such permanent loss of part of the data.
as effects on timing or scheduling that can
be seen from programs or processes that are CRC See cyclic redundancy check.
not supposed to be direct destinations of any
communications from a sender that in fact CRC character a type of error detection
performs operations that emit signals by af- codecommonlyusedondiskandtapestorage
fecting timing or scheduling within the sys- devices. Data stored on a device using CRC
tem. has an additional character added to the end
of the data that makes it possible to detect
COVQ See channel optimized vector and correct some types of errors that occur
quantization. when reading the data back.

cow magnet a long, pill-shaped alnico CRC-code code that employs cyclic re-
magnet that is placed in the second stomach dundancy checking. See cyclic redundancy
of a cow to capture ferrous debris and prevent check.
it from passing through the digestive system.
CRCW See concurrent read and concur-
CPA acronym for compensated pulsed al- rent write.
ternator. See compulsator.
credit assignment problem during neu-
CPI See color preference index or cycles ral network learning, the problem of deter-
per instruction. mining how to apportion credit (blame) to
individual components for network behavior
CPMlaser Seecolliding-pulse-modelocked that is appropriate (inappropriate) to the task
laser. being learned.

CPU See central processing unit. crest factor the ratio of the peak value of
a signal to its RMS value.
CPU time the time that is required to com-
plete a sequence of instructions. It equals to CREW See concurrent read and exclusive
the (cycle time) × (number of instructions) write.
× (cycles per instruction).
CRF See contrast rendition factor.
CR See cavity ratio.
crisp set in fuzzy logic and approximate
Cramer-Rao bound a lower bound on reasoning, this term applies to classical (non-
the estimation error covariance for unbiased fuzzy Boolean) sets that have distinct and
estimators. In particular, the estimation error sharply defined membership boundaries. See
covariance 3 e (x), which is a function of the also fuzzy set.
unknown quantity x to be estimated, must
satisfy 3 e (x) ≥ I(x), where I is the Fisher critical refers to the state of a chain reac-
information matrix. If an estimator achieves tion which is self-sustaining but which pro-

c
2000 by CRC Press LLC