arithmetic pipeline; used in vector computers
to improve their performance.
chaining of fuzzy rules
a reasoning strat-
egy which searches the knowledge base and
chain from rule to rule to form inferences and
draw conclusions. In forward chaining, a
chain of data-driven rules are evaluated for
which the conditional parts are satisfied to
arrive at the conclusion. Backward chain-
ing is goal-driven in which subgoals are es-
tablished, where necessary, through which a
chain of rules are selected, eventually satis-
fying the goal.
chamfer distance
a digital distance based
on a chamfer mask, which gives the distance
between a pixel and those in its neighbor-
hood; then the chamfer distance between two
non-neighboring pixels (resp., voxels) is the
smallest weighted length of a digital path
joining them. The word “chamfer” comes
from the fact that with such a distance a circle
is in fact a polygon. The
n-dimensional Man-
hattan and chessboard distances are chamfer
distances; the Euclidean distance is not. In
the 2-D plane, the best chamfer distances are
given by the
(3, 4) and (5, 7, 11) Chamfer
masks: in the
(3, 4) mask, a pixel is at dis-
tance 3 from its horizontal/vertical neighbors
and at distance 4 from its diagonal neigh-
bors, while in the
(5, 7, 11) mask, it is at
distance 5 from its horizontal/vertical neigh-
bors, at distance 7 from its diagonal neigh-
bors, and at distance 11 from its neighbors
distant by 1 and 2 respectively along the two
axes.
See
chessboard distance
,
Euclidean
distance
,
Manhattan distance
.
channel
(1) the medium along which data
travel between the transmitter and receiver in
a communication system. This could be a
wire, coaxial cable, free space, etc. See also
I/O channel
.
(2) the conductivity path between the
source and the drain of a field effect tran-
sistor.
(3) a single path for transmitting electri-
cal signals. Example 1: The band of fre-
quencies from 50 Hz to 15 KHz (Channel A)
and 15 KHz to 75 KHz (Channel B) which
frequency modulate the main carrier of an
FM stereo transmitter. Example 2: A portion
of the electromagnetic spectrum assigned for
operation of a specific carrier from the FM
broadcast band (88 to 108 MHz) of frequen-
cies 200 KHz wide designated by the center
frequency beginning at 88.1 MHz and con-
tinuing in successive steps to 107.9 MHz.
channel allocation
the act of allocating
radio channels to cells, base stations, or cell
sectors, in a radio network, also referred to
as frequency allocation, or frequency plan-
ning. The allocation typically follows an al-
gorithm that attempts to maximize the num-
ber of channels used per cell and minimize
the interference in the network.
channel architecture
a computer sys-
tem architecture in which I/O operations are
handled by one or more separate processors
known as channel subsystems. Each chan-
nel subsystem is itself made up of subchan-
nels, in which control unit modules control
individual I/O devices. Developed by IBM,
and used primarily in mainframe systems, the
channel architecture is capable of a very high
volume of I/O operations.
channel capacity
a fundamental limit on
the rate at which information can be reliably
communicated through the channel. Also re-
ferred to as “Shannon capacity,” after Claude
Shannon, who first formulated the concept of
channel capacity as part of the noisy channel
coding theorem.
For an ideal bandlimited channel with ad-
ditive white Gaussian noise, and an input av-
erage power constraint, the channel capacity
is
C = 0.5 log(1 + S/N) bit/Hz, where S/N
is the received signal-to-noise ratio.
channel code
a set of codewords used to
represent messages, introducing redundancy
in order to provide protection against errors
introduced by transmission over a channel.
See also
source code
.
c
2000 by CRC Press LLC