Page 193 - Intro Predictive Maintenance

184 An Introduction to Predictive Maintenance

Atmospheric attenuation The process whereby some or all of the
energy of the soundwaves or electromag-
netic radiation is absorbed and/or scattered
when traversing the atmosphere.
Atmospheric emission Electromagnetic radiation emitted by the
atmosphere.
Atmospheric radiance The radiant flux per unit solid angle per
unit of projected area of the source in the
atmosphere.
Atmospheric reflectance Ratio of reflected radiation from the atmos-
phere to incident radiation.
Band A specification of a spectral range (say,
from 0.4 to 0.5 microns) that is used for
radiate measurements. The term channel is
also in common use, with the same meaning
as band. In the electromagnetic spectrum,
the term band refers to a specific frequency
range, designated as L-Band, S-Band, X-
Band, and so on.
Bandwidth A certain range of frequencies within a
band.
Conduction The transfer of heat through or between
solids.
Convection The transfer of heat through or between
fluids.
Corona The glow or brush discharge around con-
ductors when air is stressed beyond its ion-
ization point without developing flashover.

Electromagnetic spectrum Electromagnetic radiation is energy propa-
gated through space between electrical and
magnetic fields. The electromagnetic spec-
trum is the extent of that energy ranging
from cosmic rays, gamma rays, and X-rays
to ultraviolet, visible, and infrared radiation,
including microwave energy.
Emissivity Consideration of the characteristics of ma-
terials, particularly with respect to the
ability to absorb, transmit, or reflect infrared
energy.