Page 317 - Electrical Engineering Dictionary

gallium arsenide (GaAs) a composite cameras implement gamma correction di-
widely used in the fabrication of active el- rectly on the signal that they generate. Some
ements. computer monitors allow modification of the
factor γ or gamma correction through soft-
gallium phosphide (GaP) (1) a semicon- ware.
ductor for high-speed electronics and that is
part of the family of III-V compounds for gamma rays electromagnetic radiation of
semiconductor lasers. very high energy (greater than 30 keV) emit-
(2) an acousto-optic material with good ted after nuclear reactions or by a radioactive
acousto-optic figure of merit and with atom when its nucleus is left in an excited
low acoustic attenuation for high-bandwidth state after emission of alpha or beta particles.
acousto-optic cells.
gamma-ray laser laser producing its out-
galloping a low-frequency vibration of put in the gamma-ray region of the spectrum,
electric power lines caused by wind. often considered to be any wavelength below
about 0.1 angstrom; graser, not yet demon-
Galois field a finite field with q elements strated.
denoted as GF(q), important in the study of
cyclic codes. See also finite field. ganged operation of a multiple phase de-
vice with all phases operated simultaneously.
Galvani, Luigi (1737–1798)
Born: Bologna, Italy GaP See gallium phosphide.
Galvani is best known for the use of
his name in the description of zinc plating, gap filler a low-power transmitter that
or “galvanizing” metals. Galvani was an boosts the strength of transmitted DAB RF
anatomist who studied the flow of electric- signals in areas that normally would be shad-
ity in frog’s legs when metal contacts were owed due to terrain obstruction. Gap fillers
applied. Many of Galvani’s ideas were later can operate on the same frequency as DAB
proved incorrect by Alessandro Volta. How- transmissions or on alternate channels that
ever, his pioneering work was honored by can be located by DAB receivers using auto-
the reference to Galvanic current as an early matic switching.
name for electric current. Andre Ampere
also honored him by naming his current mea- gapless arrester a lightning arrester
surement apparatus a galvanometer. which is distinguished from a gapped arrester
by having a continuous conductive path be-
gamma camera a device that uses a scin- tween the conductor and ground.
tillation crystal to detect gamma photons for
radionuclide imaging. Also known as a scin- gapped arrester a lightning arrester
tillation camera. whose conducting path contains a gas- or air-
filled spark gap which must be broken down
gamma correction inside a CRT, the lu- by the lightning impulse voltage.
minance of a pixel is represented by a volt-
age V ; however, the luminance of the ray garbage an object or a set of objects that
produced by that voltage is not proportional can no longer be accessed, typically because
γ
to V , but rather to V , where γ is a device- all pointers that direct accesses to the object
dependent constant between 2 and 2.5. It is or set have been eliminated.
thus necessary to compensate for this effect
by transforming the luminance L into L 1/γ ; garbage collection the process by which
this is called gamma correction. Some CCD the memory, a program no longer uses, is

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2000 by CRC Press LLC