Page 53 - Electrical Engineering Dictionary

that point (e.g., gray-level gradient, curva- (2) dependence of the response of a
ture, etc.) in order to smooth image noise medium on the direction of the fields, for ex-
while preserving crisp edges. The progres- ample, the x component of the electric dis-
sively smoothed image I(x, y, t) (where x, y placement might dependin part on they com-
are spatial coordinates and t is time) satisfies ponent of the fields.
the differential equation
annealing a process often used in semi-
∂I/∂t = div(c∇I), conductor processing to cause a change in
materials or device properties to improve the
where the diffusion factor c is a decreasing circuit performance and/or reliability. See
function of the spatial gradient ∇I. When c also simulated annealing.
is constant, this reduces to the heat diffusion
equation annealing schedule specifies the se-
∂I/∂t = c1I. quence of temperature values that are to be
used in an application of simulated anneal-
Other mathematical formulations have been
ing and also specifies the number of param-
given, where edge-preserving smoothing is
eter changes that are to be attempted at each
realized by a selective diffusion in the di-
temperature.
rection perpendicular to the gradient. See
also multiresolution analysis, mathematical
annihilation a process in which a particle
morphology.
and its anti-particle meet and convert sponta-
anisotropic etch an etch with an etch neously into photons.
rate that is direction-dependent. In wet etch-
ing, the direction dependence has to do with annul bit a bit that is used to reduce the
crystallographic axis – some planes etch at effect of pipeline breaks by executing the in-
different rates than others. struction after a branch instruction. The an-
nul bit in a branch allows one to ignore the
anisotropic medium (1) a medium in delay-slot instruction if the branch goes the
which the index of refraction varies with wrong way. With the annul bit not set, the
the light propagation direction within the delayed instruction is executed. If it is set,
medium. In such a medium, the constitutive the delayed instruction is annulled.
relation involves a tensor.
(2) a medium that exhibits anisotropy. Ex- annular cathode a cathode of a vacuum
amples are anisotropic crystals, ferrites in tube with the shape of the emitting surface of
the presence of a static magnetic field, and the cathode is annular. The annular cathode
plasma in the presence of a static magnetic can produce a hollow electron beam.
field.
annular illumination a type of off-axis
anisotropic scatterer inhomogeneous illumination where a doughnut-shaped (an-
medium, usually consisting of suspension of nular) ring of light is used as the source.
anisotropic molecules, capable of producing
effects like birefringence or dichroism. As anode the positive electrode of a device.
such, its dielectric permittivity is a tensor act- Contrast with cathode.
ing differently upon each component of the
electromagnetic field. anomalous dispersion decrease of the in-
dex of refraction with increasing frequency;
anisotropy (1) the degree of variation in tends to occur near the center of absorbing
a property such as index of refraction with transitions or in the wings of amplifying tran-
light propagation direction. sitions.

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2000 by CRC Press LLC