Page 202 - Electrical Engineering Dictionary

definite time DC motor acceleration was noted for controversial, and often poor,
whenDCmotorsaccelerateduringtheirstart- business decisions.
ing sequence, starting resistors are removed
from the armature circuit in steps. In definite deformable mirror device a type of de-
time DC motor acceleration (also referred vice for light modulation, especially spatial
to as open loop DC motor acceleration), the light modulation, employing micromechan-
starting resistors are removed in definite time ical structures, such as cantilevered mirrors
increments, whether the motor is actually ac- or mirrors with torsional motions, to deflect
celerating or not. incident light rays.

definite-purpose motor any motor de- defuzzification the process of transform-
sign, listed and offered in standard ratings ing a fuzzy set into a crisp set or a real-valued
with standard operating characteristics, with number.
special mechanical features for use under ser-
vice conditions other than usual or for use on defuzzifier a fuzzy system that produces
a particular type of application. a crisp (non fuzzy) output from the results of
the fuzzy inference engine. The most used
defuzzifiers are
definition phase or statement in which a
new type, or a class, or a frame for variables 1. maximum defuzzifier that selects as its
is defined. The definition of typed constant output the value of y for which the mem-
is also typically allowed. bership of the output membership function
µ B (y) is maximum;
2. centroid defuzzifier determines the cen-
deflector any of a number of optical de-
ter of gravity (centroid), y of B, and uses this
vices that change the direction of an optical
value as the output of the fuzzy inference sys-
beam, using mechanisms such as diffraction,
tem.
mechanical mirror motion, and refraction.
See also fuzzy inference engine, fuzzy
inference system.
defocus the distance, measured along the
optical axis (i.e., perpendicular to the plane
degenerate common emitter a combi-
of the best focus) between the position of
nation of the common-emitter and emitter-
a resist-coated wafer and the position if the
follower stages with a very well-defined gain.
wafer were at best focus.
degenerate four-wave mixing a four-
defocusingquadrupolemagnet aquadru-
wave mixing process in which all of the in-
pole magnet that focuses beam in the vertical
teracting waves have the same frequency. In
plane and defocuses in the horizontal plane.
certain geometrical arrangements, this pro-
cess leads to optical phase conjugation and
DeForest, Lee (1873–1961) Born: Coun- in addition can be for certain types of optical
cil Bluffs, Iowa, U.S.A. information processing.
DeForest is best known for his contribu-
tions to the development of radio communi- degenerate modes two modes with dif-
cations. DeForest’s greatest invention was ferent field structures having the same cutoff
called the audion triode. This vacuum tube frequency in a waveguide or the same reso-
was based on an earlier patented tube devel- nant frequency in a cavity.
oped by John A. Fleming. This tube, which
was both an amplifier and a rectifier, allowed degenerate two-wave mixing a special
the development of radios, radar, television, case of two wave mixing in which the two
and some early computers. DeForest’s life beams are of exactly the same frequency. In

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