ciency corresponds to the ratio of power ra-
diated from the junction to electrical power
supplied.
internal stability
defines the stability of
a system to signals that enter the loop at all
possible points. The difference between the
traditional concept of stability and the mod-
ern concept of internal stability is illustrated
by the open loop control configuration, which
is internally unstable yet might easily have
been classified as stable under the traditional
definition. The relevant equations are
y = g(s)k(s) × e + g(s) × v
=
1
s + 1
× e +
1
s − 1
× v
where blocks
g(s) and k(s) are transfer func-
tions, signals
e and v are inputs, signal u is an
internal variable, and signal
y is the output.
Clearly the relationship between
y and e is
stable, while that between
y and v remains
unstable. The traditional definition of stabil-
ity would have missed the latter phenomena.
Exactly the same effect is observed when the
above system is put into closed loop. The
concept of internal stability relates closely to
those of controllability and observability in
state space theory of dynamic systems. See
also
internal performance
.
Illustration of internal stability.
International Electro-technical Commis-
sion (IEC)
the international standards and
conformity assessment body for all fields of
electrotechnology.
International Radio Consultative Com-
mittee (CCIR)
one of two international
committees that exist for the purpose of car-
rying out studies of technical and other prob-
lems related to the interworkings of their
respective national telecommunication sys-
tems to provide a worldwide telecommuni-
cations network. It operates under the aus-
pices of the International Telecommunica-
tion Union (ITU). After each plenary assem-
bly, the ITU publishes recommendations that
deal with point-to-point radio relay systems.
A purpose of those recommendations is to
make the performance of such systems com-
patible with metallic line systems that follow
the CCITT (The International Telegraph and
Telephone Consultative Committee) recom-
mendations.
internet
a network formed by the inter-
connection of networks.
interpixel redundancy
the tendency of
pixels that are near each other in time or space
redundancy to have highly correlated gray
levels or color values. Reducing interpixel
redundancy is one way of compressing im-
ages. See also
image compression
.
interpolation
(1) the process of finding a
value between two known values on a chart
or graph.
(2) the reconstruction of missing signal
samples based on observed samples. Fre-
quently, the conversion of a discrete signal to
a discrete signal on a finer time step or (in the
limit) to a continuous signal.
interpolative coding
coding schemes that
involve interpolation.
interpolative vector quantization (IRVQ)
technique in which a subsample of the in-
terpolated original image is used to form the
predicted image, and then a residual image
is formed based upon this prediction. This
approach reduces blocking artifacts by using
a smooth prediction image.
interpole
a set of small poles located mid-
way between the main poles of a DC ma-
chine, containing a winding connected in se-
ries with the armature circuit. The interpole
improves commutation by neutralizing the
c
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