Page 84 - Electrical Engineering Dictionary

bell insulator a type of strain insulator, Berry, Clifford Edward Berry is best
shaped like saucer with ribs on its lower side known as the co-developer, along with John
and frequently used in insulator strings. Vincent Atanasoff, of the first functioning
electronic digital computer. Berry was rec-
Bello functions a group of alternative ommended to Atanasoff by the Dean of En-
methods of characterizing a wideband com- gineering at Iowa State College as a most
munication channel, named after their pro- promising student who understood the elec-
poser, P. Bello. The four functions charac- tronics well enough to help Atanasoff imple-
terizing deterministic channels are the Input ment his ideas for a computing machine. Un-
Delay-spread Function, the Output Doppler- fortunately, Berry’s contributions as a com-
spread function, the Time-variant Transfer puting pioneer were not honored until after
Function and the Delay Doppler-spread func- his death.
tion.
beryllium oxide a compound commonly
BEM See boundary-element method. used in the production of ceramics for elec-
trical applications and whose dust or fumes
benchmark standard tests that are used are toxic.
to compare the performance of computers,
processors, circuits, or algorithms. Bessel beam transverse wave ampli-
tude distribution in which the radial varia-
bending loss in a fiber depends exponen- tion is approximately describable in terms of
tially on the bend radius R. It is proportional truncated Bessel functions; collimation for
to exp(−R/R c ) where the critical radius Bessel beams is sometimes considered bet-
a ter than for more usual polynomial-Gaussian
R c = , beams.
2n (n co − n cl )
a is the fiber radius, n co is the refractive index Bessel functions a collection of func-
of the core, and n cl is the refractive index of tions, denoted as J ν (x) and Y ν (x), that satisfy
the cladding. Bessel’s equation
2
BER See bit error rate. 2 d f df 2 2
x + x + x − ν f = 0 ,
dx 2 dx
Bernoulli distribution a random variable
where f is equal to either J ν or Y ν ; ν is the
X with alphabet {0, 1} and parameter α such
order of the function and x is its argument.
that its probability mass function is
Typically, Bessel functions arise in boundary
x 1−x
p(x) = (1 − α) α . value problems that are based upon a cylin-
drical coordinate system.
Bernoulli process a binary valued, best-fit memory allocation a mem-
discrete-time random process defined on an ory allocator for variable-size segments must
index set corresponding to fixed increments search a table of available free spaces to find
in time. A typical example is a sequence of memory space for a segment. In “best-fit” al-
coin tosses where the values of the process location, the free spaces are linked in increas-
are denoted as “Heads” or “Tails” depending ing size and the search stops at the smallest
on the outcome of the tosses. The output val- space of sufficient size. Compare with buddy
uesoftheprocessisasequenceofstatistically memory allocation.
independent random variables with the same
probability distribution. The two outcomes beta function a measure of beam width.
may or may not have equal probabilities. The beta function details how the beam

c
2000 by CRC Press LLC