Electrical Engineering Dictionary - part 170

supercomputer

at any given time, the

most powerful class of computer available.

superconducting magnetic bearing

magnetic bearing utilizing levitation between
a magnet and a superconductor.

superconductivity

a state of matter

whereby the correlation of conduction elec-
trons allows a static current to pass without
resistance and a static magnetic flux to be ex-
cluded from the bulk of the materials.

superconductor

a material that loses all

electrical resistance below a certain tempera-
ture. Superconductors prevent externally ap-
plied magnetic fields from penetrating their
interior. They are considered perfect diamag-
netic materials. Once the externally applied
field exceeds a critical value, the materials
revert back to a nonsuperconducting status.

superdirectivity

a condition of a phased

array in which the excitation of the array
elements is adjusted to obtain a directivity
greater than that achievable with uniform ex-
citation. Such antennas are often impracti-
cal, because high excitation currents are usu-
ally required, leading to ohmic losses that
more than offset the additional directivity.
Superdirective antennas also typically have
high reactive fields and thus exhibit very nar-
row bandwidth.

superfluorescence

usually refers to the

enhanced spontaneous emission that occurs
due to self-organization into a coherent state
by a system of atoms or molecules.

superheater

a heat exchanger that in-

creases the steam temperature to about
1000 degrees F. It is heated by the flue gases.

superheterodyne

an architecture used in

virtually all modern-day receivers. In the
early days of radio, tuned stages of ampli-
fication were cascaded in order to secure a
sufficiently high level of signal for detection
(demodulation).

superheterodyne receiver

most receivers

employ the superheterodyne receiving tech-
nique, which consists of either down-
converting or up-converting the input signal
to some convenient frequency band, called
the intermediate frequency band, and then ex-
tracting the information (or modulation) by
using an appropriate detector. This basic re-
ceiver structure is used for the reception of all
types of bandpass signals, such as television,
FM

< AM< satellite, and radar signals.

superinterleaving

See

interleaved memory

superlattice

a stack of ultrathin layers

of material.

Layer thicknesses are suffi-

ciently thin to produce quantum-confined ef-
fects, typically 100–1000 angstroms; gener-
ally, there are two different layer composi-
tions, and the superlattice is built with layer
composition in an alternating scheme.

supernode

a cluster of nodes, intercon-

nected with voltage sources, such that the
voltage between any two nodes in the group
is known.

superparamagnetism

a form of mag-

netism in which the spins in small particles
are exchange coupled by may be collectively
switched by thermal energy.

superpipelined processor

a processor

where more than one instruction is fetched
during a cycle in a staggered manner. That
is, in an n-issue superpipelined processor, an
instruction is fetched every 1

/n of a cycle.

For example, in the MIPS R4000, which is
two-issue superpipeline, a new instruction is
fetched every half cycle. Thus, in effect, the
instruction pipeline runs at a frequency dou-
ble than the system (in the R4000 the pipeline
frequency is 100 MHz, while the external fre-
quency is 50 MHz). Superpipeline proces-
sors usually have a relatively deep pipeline,
of about 7 stages or more (8 stages on the
R4000).

2000 by CRC Press LLC

superpipelining

a pipeline design tech-

nique in which the pipeline units are also
pipelined internally so that multiple instruc-
tions are in various stages of processing
within the units. The clock rate is increased
accordingly.

superpolish

methods for producing a

surface of low RMS roughness, typically
10 angstroms RMS or less; methods include
special mechanical, chemical, and ion pol-
ishing techniques.

superposition

for a system

T [], the prop-

erty that

T [a

(t) + a

(t)] =

t[x

(t)] + a

t[x

(t)].

superposition coding

multiple-access

channel coding technique in which each user
encodes independently, such that at the re-
ceiver, the transmitted signals may be es-
timated using successive cancellation. See
also

successive cancellation

superposition integral

for a linear shift-

invariant system characterized by an impulse
response,

h(t), the output, y(t), for a given

input,

x(t), is calculated as

y(t) =

∞

−∞

x(s)h(t − s)ds.

Also called the convolution integral.

superradiance

usually refers to the

strongly enhanced spontaneous emission that
is emitted by a coherently prepared system of
atoms or molecules.

superscalar processor

a processor where

more than one instruction is fetched, de-
coded, and executed simultaneously. If

instructions are fetched and processed simul-
taneously, it is called an

n-issue superscalar

processor. For example, the Pentium is a two-
issue, and the DEC 61164 is a four-issue su-
perscalar processor. This feature was imple-

mented both on CISC (Pentium) and RISC
(61164) processors.

supervised learning

(1) a procedure in

which a network is trained by comparing its
output, in response to each training data item,
with a target value (label) for that item. Net-
work weights are adjusted so as to reduce the
differences between outputs and targets until
these differences reach acceptable values.

(2) a training technique in statistical pat-

tern recognition or artificial neural networks
in which the training set includes a predefined
desired output.

supervised learning for self-generating
neural network

there are two ways for

supervised learning in SGNN. The first is the
same as that of supervised learning for a self-
organizing system. The second is to make
use of information gains of the attributes
to the classification. That is, use the inner
product of the training vector and the infor-
mation gain vector corresponding to its at-
tributes to train the network. Experiments
show that this way of supervised learning
for SGNN can significantly improve both the
performance of the network and the train-
ing speed. See also

self-generating neural

supervised learning for self-organizing
system

See

learning vector quantization

supervised neural network

neural net-

work that requires input–output pairs to form
the interconnection weight matrix of a net-
work. The Hopfield model, perceptron, and
backpropagation algorithm are supervised
neural networks.

supervisor call instruction (SVC)

See

software interrupt

supervisor instructions

processor in-

structions that can be executed when the pro-
cessor is running in supervisor mode. The
separation of supervisor instructions is re-

2000 by CRC Press LLC

quired to isolate the system’s control infor-
mation from tampering by user programs.

supervisor mode

one of two CPU modes,

the other being user mode. Sometimes called
privileged mode, this mode allows access to
privileged system resources such as special
instructions, data, and registers.

supervisor state

one of two CPU states,

the other being user state. When the CPU is
in supervisor state, it can execute privileged
instructions.

support of a fuzzy set

the crisp set of

all points

x in X with membership positive

(

(x) > 0), where A is a fuzzy set in the

universe of discourse

X. See also

fuzzy set

membership function

supporting plane

a planar structure that is

an external support for a packaging and inter-
connecting structure, used to alter the struc-
ture’s coefficient of thermal expansion.

supremal decision unit

control agent or

a part of the controller of the partitioned sys-
tem, which perceives the objectives and the
operation of this system as a whole and is
concerned with following these overall ob-
jectives; in case of a large-scale system with
hierarchical multilevel (two-level) controller,
the coordinator unit is often regarded as the
supremal decision unit.

supremum operator

an operation that

gives the least upper bound function. For
example, if

S is the supremum of a set A,

then

S is the upper bound of A, and no value

less than

S is an upper bound of A.

surface acoustic wave (SAW)

a surface

acoustic wave (also known as a Rayleigh
wave) is composed of a coupled compres-
sional and shear wave. On a piezoelectric
substrate, there is also an electrostatic wave
that allows electroacoustic coupling.

The

wave is confined at or near the surface and
decays away rapidly from the surface.

surface acoustic wave (SAW) device

this device, electrical signals are converted
to acoustic signals, processed, and then con-
verted back to electrical energy. Due to their
small propagation velocity, acoustic waves
have small wavelengths; thereby, one can
construct miniature high performance com-
ponents such as filters using SAW devices.

surface impedance

the impedance exhib-

ited by the surface of a conductor/dielectric
due to the variation in its conductivity with
frequency.

surface mount technology (SMT)

the

electrical connection of components to the
surface of a conductive pattern without com-
ponent lead holes.

surface mounting

See

surface mount

technology

surface plasmon

a surface polariton in a

plasma medium.

surface polariton

a polariton that propa-

gates as a wave along the interface between
two media.

surface rendering

See

rendering

surface roughness

the RMS value of the

peaks and valleys in the profile of a solid sur-
face. High frequency currents flow near the
skin of conductors due to a skin effect phe-
nomenon. Therefore, high frequency cur-
rents follow the contours on the surface of
conductors. For this reason, surface rough-
ness should be minimized so the patch of cur-
rent flow is as short as possible.

surface scattering

scattering at the rough

boundary between two media of different re-
fractive index.

surface texture

See

texture

analysis

texture modeling

2000 by CRC Press LLC

surface wave

a wave that propagates with

dissipation in one direction and exponentially
decays (without propagating) in the other di-
rections. Most of the field is contained within
or near the interface.

Surface waves are supported, for example,

by a dielectrically coated conductor or by a
corrugated conductor.

surface-emitting laser logic (SELL)
a device that integrates a phototransistor
with a low-threshold vertical-cavity surface-
emitting laser.

surface-mounted package

in both elec-

trical and mechanical devices, a mounting
technique between chip and substrate using
solder joints between pads on the two sur-
faces. The advantage is that higher circuit
densities can be achieved on the board.

surge

a short-duration (microsecond to

millisecond) increase in power line voltage.
Also called a spike or an impulse.

surge arrestor

a device that limits over-

voltages by conducting large currents in re-
sponse to an overvoltage. Surge arrestors are
typically connected line to ground in trans-
mission and primary distribution systems.
They can be employed in a variety of connec-
tions in secondary distribution, and can be
necessary in communications, sensing, and
control circuits.

surge impedance

the ratio of voltage to

current on that line for a high speed wave
propagating down the line. The surge impe-
dance of a line is a constant which depends
on the line geometry and conductor charac-
teristics. On power transmission lines, these
waves are typically generated by lightning
strokes, circuit breaker switching, etc. Also
called characteristic impedance.

surge impedance loading (SIL)

of a

transmission line, the characteristic impe-
dance with resistance set to zero (resistance is
assumed small compared to reactance). The

power that flows in a lossless transmission
line terminated in a resistive load equal to
the line’s surge impedance is denoted as the
surge impedance loading of the line.

surge response voltage

the voltage that

appears at the output terminals of surge pro-
tection equipment and is seen by loads con-
nected to that device both during and after a
surge condition.

surge tank

an empty vessel located at the

top of the penstock. It is used to store wa-
ter surge when the turbine valve is suddenly
closed.

susceptibility

the part of the permittiv-

ity or permeability that is attributable to the
electromagnetic behavior of the medium. In
a linear, isotropic medium, the electric sus-
ceptibility is numerically equal to the rela-
tive permittivity minus one, and the mag-
netic susceptibility is equal to the relative
permeability minus one. See also

electric

susceptibility

sustained interruption

all interruptions

that are not momentary.

Generally used

when referring to long duration voltage in-
terruptions of greater than 1 minute.

SV system

single variable system. See

also

single-input–single-output system

SVC