Page 298 - Electrical Engineering Dictionary

resigning in protest. His contributions to the fractional arithmetic mean radian band-
field of electrical engineering are well recog- width dimensionless ratio of the band-
nized. width (bw = ω H − ω L ) to the arithmetic ra-
dian center frequency (ω oa ). The band edges
Fowler–Nordheim oscillation oscilla- are usually defined as the highest (ω H ) and
tions in internal field emission tunneling cur- lowest (ω L ) frequencies within a contigu-
rent due to quantum interference. ous band of interest at which the loss equals
L Amax , the maximum attenuation loss across
the band.
Fox and Li method iterative diffraction
integral method for calculating the electro- ω H − ω L 2 (ω H − ω L )
bw a = =
magnetic modes of a laser resonator. ω oa ω H + ω L

FPC coefficients the parameters of the fractional Brownian motion a nonsta-
linear system that performs the linear predic- tionary generalization of Brownian motion;
tion of a given stochastic process. it is a zero-mean Gaussian process having
the following covariance:
FPGA See field-programmable gate
E [B H (t)B H (s)] =
array.
σ 2 2H 2H 2H
|t| +|s| −|t − s| .
2
FQO See four-quadrant operation.
This process has interesting self-similarity
and spectral properties; it is a fractal with
fractal from the Latin fractus, meaning
dimension D = 2 − H. See also Brownian
broken or irregular, a fractal is a rough ge-
motion.
ometric shape that is self-similar over mul-
tiple scales, i.e., its parts are approximate
fractional discrimination coding a pre-
copies of larger parts, or ultimately of the
processing scheme where the images are pro-
whole. Magnifying a fractal produces more
cessed with fractional discrimination func-
detail. Fractals are good models of many nat-
tions and then coded. This method of coding
ural phenomena such as coast lines, clouds,
enables efficient local feature based encoding
plant growth, and lightning as well as arti-
of pictures while preserving global features.
ficial items such as commodity prices and
This is a type of contextual coding scheme.
local-area network traffic. See also fractal
coding.
fractional geometric mean radian band-
width dimensionless ratio of the band-
fractal coding the use of fractals to width (bw = ω H − ω L ) to the geometric ra-
compress images. Regions of the image dian center frequency (ω oa ). The band edges
are represented by fractals, which can then are usually defined as the highest (ω H ) and
be encoded very compactly. Fractal cod- lowest (ω L ) frequencies within a contigu-
ing provides lossy compression that is in- ous band of interest at which the loss equals
dependent of resolution and can have ex- L Amax , the maximum attenuation loss across
tremely high compression ratios, but it is the band.
not yet practical for general images. Some
ω H − ω L (ω H − ω L )
of the methods are covered by patents. See bw a = = √
also compression, compression ratio, fractal, ω oa ω H + ω L
image compression, image resolution, lossy
compression, model based image coding, fractional horsepower National Elec-
spatial resolution, vector image. trical Manufacturers Association (NEMA)

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2000 by CRC Press LLC