Page 95 - Electrical Engineering Dictionary

connectingsignalsaregivenasLaplacetrans- a two-level quantizer is designed for each
formations. Although the system blocks and block. Encoding is essentially a local bina-
signals have the same mathematical form, the rization process consisting of a n×n bit map
blocks represent operators that act on the in- indicating the reconstruction level associated
coming signals while the signals represent with each pixel. Decoding is a simple pro-
functions of time. cess of associating the reconstructed value at
each pixel as per the bit map.
block matching the process of finding the
closest match between a block of samples in block carry lookahead adder (BCLA)
a signal and a block of equal size in another an adder that uses two levels of carry looka-
signal (or a different part of the same sig- head logic.
nal) over a certain search range. Closeness
is measured by correlation or an error metric block-diagram simulator a simulator
such as mean square error. Used in data com- that allows the user to simulate systems as
pression, motion estimation, vector quantiza- a combination of block diagrams, each of
tion, and template matching schemes. which performs a specific function. Each
function is described using a mathematical
block multiplexer channel an I/O chan- equation or a transfer function.
nel can be assigned to more than one data
transfer at a time. It always transfers infor- blocked state See blocking.
mation in blocks, with the channel released
for competing transfers at the end of a block. blocked-rotor current See locked-rotor
See also byte multiplexer channel, selector current.
channel.
blocked-rotor test an induction motor
block transfer the transmission of a sig- test conducted with the shaft held so it cannot
nificantlylargerquantityofdatathanthemin- rotate. Typically about 25% of rated voltage
imum size an interconnect is capable of trans- is applied, often at reduced frequency and the
mitting, without sending the data as a number current is measured. The results are used to
of small independent transmissions (the goal determine the winding impedances referred
being to reduce arbitration and address over- to the stator.
head).
blocking state entered if a new user finds
block transform a transform that divides all channels or access mechanisms busy and
the image into several blocks and treats each hence is denied service. Generally accom-
block as an independent image. The trans- panied by a busy signal. The call blocking
form is then applied to each block indepen- probability may be given by the Erlang B or
dently. This occurs in the JPEG standard im- Erlang C formula. See also adequate service,
age compression algorithm, where an image multiple access interference (MAI).
is divided into 8 × 8 blocks and the DCT
is applied independently to each block. Usu- blocking artifact the visibility in an im-
ally the blocks do not overlap each other, that age of rectangular subimages or blocks af-
is, they have no signal samples in common. ter certain types of image processing. Also
See also transform coding, called blocking effect distortion.
lapped orthogonal transform.
blocks world a visual domain, typical
block truncation coding (BTC) tech- of early studies on machine vision, in which
nique whereby an image is segmented into objects are light, plane-faced solids over a
n × n nonoverlaping blocks of pixels, and dark background.

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2000 by CRC Press LLC