Page 337 - Electrical Engineering Dictionary

electronic mail, handwriting recognition for Hanning window a raised cosine window
taking notes, and holding addresses and ap- function whose impulse response is
pointments. Also called a “palm-top.”

0.5 + 0.5 cos(nπ/N) |n| <N
hand-off in a cellular system, the pro- w n = 0 |n|≥ N.
cess by which the mobile terminal switches
from communicating with one base station
to a communication with neighboring base
hard bake the process of heating the
station as the mobile travels through the dif-
wafer after development of the resist in order
ferent radio cells. to harden the resist patterns in preparation
for subsequent pattern transfer. Also called
handline a rope used to pull tools and postbake.
equipment from an assistant on the ground to
a worker atop a utility pole.
hard bug a name for a crimped copper
wire connector.
handover See hand-off.
hard contaminant a contaminant or for-
handshaking I/O protocol in which a de-
eign object which is at least partly opaque to
vice wishing to initiate a transfer first tests the
X-radiation: typical hard contaminants are
readiness of the other device, which then re-
pieces of metal, glass or stone.
sponds accordingly. The transfer takes place
only when both devices are ready.
hard decision demodulation that outputs
a q-ary value for each demodulated symbol
handwritten character recognition the
in a sequence of q-ary symbols. See also soft
process of recognizing handwritten charac-
decision.
ters that are clearly separated.
hard disk a rigid magnetic disk used for
Hankel transform the 2-D Fourier trans-
storing data. A typically nonremovable col-
form of a function with circular symmetry
lection of one or more metallic disks cov-
and arises in the analysis of optical systems.
ered by a magnetic material that allows the
The (zero-order) Hankel transform F(ρ) of
recording of computer data. The hard disk
a function f(r) for r ≥ 0is
spins about its spindle while an electromag-
netic head on a movable arm stays close to
Z
∞
F(ρ) = 2π rf (r)J 0 (2πρr)dr the disk’s surface to read from or write to the
0 disk. Each disk is read and written on both
above and below. N disks are read/written by
and the (zero-order) inverse Hankel trans-
using 2N heads. The information is stored by
form is
cylinders, circular segments of the collection
Z of the disks. Cylinders are divided in sectors
∞
f(r) = 2π ρF(ρ)J 0 (2πρr)dρ, as a pie. The mean time to access data is
0
typically close to 10 msec.
where J 0 (r) is the zero-order Bessel function Generally, hard disks are the backing
of the first kind, i.e., memory in a hierarchical memory. See also
floppy disk.
Z π
1
J 0 (r) = cos(r sin θ)dθ.
π 0 hard fault See permanent fault.
See also Fourier transform. hard ferrite See ceramic ferrite.

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2000 by CRC Press LLC