Page 176 - Electrical Engineering Dictionary

operation to the cache that is not accompa- molecules as the dipoles in a structure change
nied with a write operation to main memory. direction of alignment in response to an ap-
In copy-back, the data is written only to the plied alternating voltage, while eddy current
2
block in the cache. This block is written to losses are resistive losses (I R), due to cir-
main memory only when it is replaced by an- culating currents in the core.
other block.
core memory See magnetic core
CORDIC Seecoordinatedrotationdigital memory.
computer.
core-type transformer a transformer in
core (1) the operating image of a pro- which the magnetic circuit upon which the
cess (sometimes used to refer to the part re- windings are wound takes the form of a single
siding in physical memory), often written to ring. When the coils are placed on the core,
disk if the program crashes (dumping core). they encircle the core. See also core.
Since magnetized ferrite rings (cores) were
once used in main memory to store a single coriolis forces forces/torques that depend
bit each. The name remained and now core upon the product of joint velocities.
memory means the same as main memory,
although currently, main memory is chip- corner cube antenna a traveling wave
based. See also magnetic core memory. antenna typically four wavelengths long and
(2) the ferromagnetic portion of a trans- placed 1.2 wavelengths from the apex of a
former or electric machine on which the coils 90-degree corner reflector other used in the
are mounted. Typically made of laminated submillimeter wave and terahertz frequency
magnetic material, encircled by the wind- range for mixers and detectors.
ings, that provides a low reluctance path for
magnetic flux. corner detection the detection of corners,
(3) the central region of an optical fiber. often with a view to locating objects from
The refractive index of the core must be their corners, by a process of inference, in
higher than that of the cladding so that the digital images.
optical power is guided through the fiber by
total internal reflection at the core-cladding corona a visible glow discharge which
boundary. The core refractive index may be emanatesfromhigh-voltageconductorsinre-
constant or may decrease with distance from gions of extremely high electric field inten-
the axis to the cladding. See also graded sity.
index and step index optical fiber.
(4) the section of a nuclear reactor in corona effect flow of electrical energy
which the chain reaction is contained, com- from a high-voltage conductor to the sur-
prising fuel rods, control rods, moderator, rounding ionized air. This effect only be-
and coolant. comes significant for potentials higher than
1000 V. This effect is characterized by a faint
core lamination See lamination. glow, a crackling noise and conversion of at-
mospheric oxygen to ozone.
core loss loss in the ferromagnetic ma-
terial comprising the core of an electric ma- corona loss the electric power lost in high
chine or transformer, composed of the sum voltage lines due to the radiation of energy
of hysteresis losses and eddy current losses. by corona discharge. See corona.
These magnetic losses are caused by time
varying fluxes in a ferromagnetic structure. corona resistance capacity of a mate-
Hysteresis losses are caused by friction in rial to bear the action of the corona effect.

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2000 by CRC Press LLC