operation of the discarded bits, indicating
whether at least one of the discarded bits was
equal to 1.
stiction
in variable-speed drives, the ini-
tial static friction that must be overcome
when the load is at rest.
stiff system
when an electrical circuit has
widely separated time constants, the circuit
is said to be stiff. The system of equations
associated with the circuit is known as a stiff
system, and special numerical methods must
be used to maintain stability and accuracy
when simulating a stiff system.
stiffness
as applied to a tie-line be-
tween generators, a low-impedance connec-
tion which forces the two generators to run in
synchronization regardless of load variations
on one or the other.
stiffness control
in stiffness control a gen-
eralized joint force and/or torque is generated
in response to small position error as to a con-
stant task space stiffness matrix. See also
stiffness matrix
.
stiffness matrix
the stiffness matrix of the
arm endpoint is the inverse of the compliance
matrix. See also
compliance matrix
.
stiffness of a manipulator arm
an at-
tribute of a robot arm.
Assume that a force is applied to the end-
effector of a manipulator arm.
The end-
effector will deflect by an amount that de-
pends on the stiffness of the arm and the force
applied. In other words, the stiffness of the
arm’s end-effector determines the strength of
the manipulator arm. Usually, actuator it-
self has a limited stiffness determined by its
feedback control system, which generates the
drive torque based on the discrepancy be-
tween the reference position and the actual
measured position. We model the stiffness by
a spring contact that relates the small defor-
mation at the joint to the force or torque trans-
mitted through the joint itself. It is called the
joint stiffness. See also
stiffness matrix
.
still image
stationary image or single
frame as opposed to moving image or video.
Includes photographic images, natural im-
ages, medical images, remote sensing im-
ages. Usually implies multilevel (grayscale
or color) rather than bilevel.
still image coding
compression of a still
image. A coder consists of the four steps:
data representation (typically by transform,
decomposition into subbands or prediction),
quantization (in which data is approximated
or discarded according to some measure of
its importance), clustering of nulls (in which
runs or blocks of zero values are coded com-
pactly), entropy coding (in which the statis-
tical properties of the data are exploited in
lossless compression).
stimulated emission
enhanced emission
of electromagnetic radiation due to the pres-
ence of radiation at the same frequency; also
called induced emission.
stimulated light scattering
scattering of
light from refractive index variations that
are produced or amplified by the interac-
tion of laser light with the material system,
e.g., stimulated Brillouin scattering and stim-
ulated Raman scattering.
stirrup
See
saddle
.
stochastic ARMA (ARMAX) model
a
generalized ARMA model in which the un-
certain environmental effects are included as
an independent noise input.
stochastic independence
independence
of two random variables or two random pro-
cesses.
stochastic neuron
an artificial neuron
whose activation determines the probability
with which its output will enter one of its
two possible states.
The most commonly
c
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