Page 286 - Electrical Engineering Dictionary

filter calculations. Also called quantization first order system the system that can
effects. be described by a linear first-order difference
equation. Theoutputofthefirst-ordersystem
finite-extent sequence the discrete-time y(n) is equal to a linear combination of the
signals with finite duration. The finite-extent past output value y(n−1) and the input value
sequence {x(n)} is zero for all values of n x(n), i.e.,
outside a finite interval.
y(n) = αx(n) + βy(n − 1).
FIR See far-infrared, finite impulse
response filter.
first-fit memory allocation a memory
firing angle time in electrical degrees allocation algorithm used for variable-size
from the instant the valve voltage is positive units (e.g., segments). The “hole” selected is
to the application of firing pulse to the valve the first one that will fit the unit to be loaded.
(start of conduction). Also called delay an- This hole is then broken up into two pieces:
gle. one for the process and one for the unused
memory, except in the unlikely case of an
firm power an amount of electric power exact fit, there is no unused memory.
intended to be available at all times to a com-
mercial customer, regardless of system con- first-in-first-out (FIFO) a queuing dis-
ditions. cipline whereby the entries in a queue are
removed in the same order as that in which
firmreal-time Seefirmreal-timesystem. they joined the queue.

firm real-time system a real-time system
first-in-last-out (FILO) a queuing rule
that can fail to meet one or more deadlines
whereby the first entries are removed in the
without system failure. Compare with soft
opposite order as that in which they joined
real-time, hard real-time.
the queue. This is typical of Stack structures
and equivalent to last-in-first-out (LIFO).
firmware software that cannot be modi-
fied by the end user.
first-swing stability criterion to deter-
mine transient stability by use of the swing
first difference for a sequence {x(n)} the
equation. The rotor angle immediately
sequence obtained by simply subtracting its
following a severe disturbance usually in-
(n − 1)th element from its nth element, i.e.,
creases. The criterion states that if the ro-
tor angle swings back and decreases a short
y(n) = x(n) − x(n − 1)
time after the disturbance, then the system is
first-swing stable.
first order hold (FOH) for a signal f(k),
Fisher information a quantitative mea-
the sequence of straight lines connecting the
surement of the ability to estimate a specific
sample points of f(k). It interpolates the
set of parameters. The Fisher information
values between two adjacent samples f(k)
J(θ) is defined by
and f(k + 1) using a linear approximation
given by 2
∂ ln f θ (y)
J(θ) = E θ
t − kT s ∂θ
x(t) = x(kT s ) +
2
T s ∂ ln f θ (y)
(x((k + 1)T s ) − x(kT s )). =− E θ ∂ θ
2
c
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