Page 247 - Electrical Engineering Dictionary

eigenvalue the multiplicative scalar as- elastomer a polymer material that can un-
sociated with an eigenfunction or an eigen- dergo reversible shape changes, expanding
vector. For example, if Ax = λx, then λ or contracting under influence of an applied
is the eigenvalue associated with eigenvec- electric field; often used for mechanical light
tor x.If A is a covariance matrix, then λ modulation devices.
represents the variance of one of the princi-
pal components of A. See also eigensystem, elbow in URD work, the termination of a
eigenvector, principal component. buried cable where it attaches to the distribu-
tion transformer.
eigenvalue assignment a technique that,
electret a material similar to ferro-
given a set of desired eigenvalues, has the
electrics, but charges are macroscopically
objective to compute a constant state feed-
separated and thus are not structural. In some
back gain K such that the closed-loop state
cases the net charge in the electrets is not
equation has precisely these eigenvalues.
zero, for instance when an implantation pro-
cess was used to embed the charge.
eigenvector for a linear system A,any
vector x whose direction is unchanged when
electric charge a basic physical quantity
operated upon by A. See also eigensystem,
that is a source of electromagnetic fields. The
eigenvalue.
units of electric charge are coulombs.
eight connected See pixel adjacency. electric charge density the fundamental,
macroscopic source of the electromagnetic
eighteenconnected Seevoxeladjacency. field that quantifies the average number of
discrete electric charges per unit volume. SI
Einstein coefficients coefficients intro- units are coulombs per cubic meter.
duced by Einstein to represent the sponta-
electric current density a source vec-
neous decay rate, A, and the stimulated emis-
tor in electromagnetics that quantifies the
sion or absorption coefficient, B, in the pres-
amount of electric charge crossing some
ence of an electromagnetic energy density or
cross–sectional area per unit time. The di-
intensity.
rection of the electric current density is in
the direction of electric charge motion. SI
EIRP See effective isotropically radiated
units are amperes per square meter.
power.
electric field in a region of space, if a test
EISA See extended industry standard charge q experiences a force F then the re-
architecture. gion is said to be characterized by an electric
field of intensity E given by
elastic scattering (1) a scattering process
F
in which energy is conserved.
E =
q
(2) the state in which there is no en-
ergy transfer between the light wave and the
scattering medium, and hence no frequency electric field integral equation (EFIE)
change. the integral equation based on the boundary
condition of the total electric field. It is often
elasto-opticeffect thechangeinrefractive used in moment method description of mi-
index of a medium due to mechanical forces. crostrip circuits and metallic antennas. See
Also known as the photoelastic effect. also moment method.

c
2000 by CRC Press LLC