Often called the quality factor of a circuit, Q is defined in various ways, depending upon the particular application. In the simple RL and RC series circuits, Q is the ratio of reactance to resistance, as in Eqs. (1),
where XL is the inductive reactance, XC is the capacitive reactance, and R is the resistance. An important application lies in the dissipation factor or loss angle when the constants of a coil or capacitor are measured by means of the alternating-current bridge.
Q has greater practical significance with respect to the resonant circuit, and a basic definition is given by Eq. (2),
where Q0 means evaluation at resonance. For certain circuits, such as cavity resonators, this is the only meaning Q can have.
For the RLC series resonant circuit with resonant frequency f0, Eq. (3)
holds, where R is the total circuit resistance, L is the inductance, and C is the capacitance. Q0 is the Q of the coil if it contains practically the total resistance R. The greater the value of Q0, the sharper will be the resonance peak.
The practical case of a coil of high Q0 in parallel with a capacitor also leads to Q0 = 2&pgr;f0L/R. R is the total series resistance of the loop, although the capacitor branch usually has negligible resistance.
In terms of the resonance curve, Eq. (4) holds,
where f0 is the frequency at resonance, and f1 and f2 are the frequencies at the half-power points.
Q (pop culture)
The being known only as “Q” was first encountered by the crew of the U.S.S. Enterprise-D in the year 2364 near the outer space station called Farpoint. Although he appeared as a human male in a 1987 TV episode of Star Trek: The Next Generation (played by actor John DeLancie, who also voiced the character in the computer game, Star Trek: Borg), Q claimed to be a member of a race called the “Q,” immortal beings possessing nearly omnipotent powers, residing in the Q Continuum. Other members of the Q also appear humanoid, with varying features of either gender, though they are actually noncorporeal beings. The Q feel immensely superior to human beings; Q considers humankind “grievously savage,” and takes great delight in testing the nerve and will of these inferior beings. Q also made the mechanized, hive-like collective called the “Borg” aware of the existence of humanity, initiating a series of attempts by the Borg to subjugate and assimilate humankind. Despite this, the Q seem to have an unending curiosity about humankind, and, at times, even a concern for the welfare of the species, though this is never couched in such amiable terms. Q once suggested that eventually the humankind might advance beyond the level of the Q. The episode “Death Wish” of Star Trek: Voyager (1995–2001) features the first recorded visit by outsiders to the Q Continuum, and in “The Q and the Grey,” Q proclaims his desire to have a child with U.S.S. Voyager Captain Katherine Janeway. Q also appeared in a handful of episodes of Star Trek: Deep Space Nine (1993–1999), including “Q-Less,” in which Commander Benjamin Sisko punches Q in the face, an experience both Picard and Janeway must have envied. Q has also appeared in a number of novels including Encounter at Farpoint (by David Gerrold, 1987), a novelization of the first episode of Star Trek: The Next Generation; and original titles such as Q-in- Law (1991) and Q-Squared (1993), both by Peter David, I,Q by John DeLancie and Peter David (2000), and the Q Continuum trilogy: Q-Space, Q-Zone and QStrike, all by Greg Cox in 1998. Q is the narrator of Q's Guide to the Continuum, by Michael Jan Friedman and Robert Greenberger (1998). In 1999, Alien Voices, a producer of audio books, released Spock vs. Q, in which actors Leonard Nimoy and John DeLancie, respectively, played their famous Star Trek characters in their first meeting. This project was followed up in 2000 with the release of Spock vs. Q: The Sequel, with the same cast.
A very high level language by Per Bothner based
on lazy generalised sequences. Q has lexical scope
some support for logic programming
programming. The language includes small subsets of Common Lisp
Q was a test-bed for programming language ideas. Where APL
uses arrays for looping, Q uses generalised sequences which
may be infinite and may be stored or calculated on demand. It
has macros, primitives to run programs, and an
Q is implemented in C++
, and comes with an interpreter
framework, libraries, and documentation. It runs
and SUN-4 and should work on any 32-bit Unix
Latest version: 1, as of 1993-06-07. Development stopped in
E-mail: Per Bothner <email@example.com>.