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electronic oscillator
electronic oscillator , electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifier having part of its output returned to the input by means of a feedback loop; the necessary and sufficient condition for oscillation is that the sign...
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El Niño-Southern Oscillation
El Niño-Southern Oscillation (ENSO) , large-scale climatic fluctuation of the tropical Pacific Ocean. The El Niño [Span.,=the child] itself is a warm surface current that usually appears around Christmas in the Pacific off Ecuador and Peru and disappears by the end of March, but ev...
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Aleksandr Mikhailovich Prokhorov
Aleksandr Mikhailovich Prokhorov , 1916-2002, Russian physicist, b. Atherton, Queensland, Australia. In 1923 he was taken to the Soviet Union by his parents, who had emigrated to Australia to escape the czarist regime. In 1947 he began his research into the coherent radiation of electrons, followed ...
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atomic clock
atomic clock electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a uniform rate to control the rate of movement of its hands or the rate of change of its digits. Mech...
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watch
watch small, portable timepiece usually designed to be worn on the person. Other kinds of timepieces are generally referred to as clocks . At one time it was generally believed that the first watches were made in Nuremburg, Germany, c.1500. However, there is now evidence that watches may have appe...
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Barnard's star
Barnard's star star with the largest observed proper motion (rate of motion across the sky with respect to other stars); located in the constellation Ophiuchus. The star's large proper motion, 10.28′′ per year (or half the moon's apparent diameter in a century), is due in part to the ...
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magnetron
magnetron , vacuum tube oscillator (see electron tube ) that generates high-power electromagnetic signals in the microwave frequency range. Its operation is based on the combined action of a magnetic field applied externally and the electric field between its electrodes. The tube is a diode hav...
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maser
maser , device for creation, amplification, and transmission of an intense, highly focused beam of high-frequency radio waves. The name maser is an acronym for m icrowave a mplification by s timulated e mission of r adiation, microwaves being radio waves of short wavelength, or high frequency...
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neutrino
neutrino [Ital.,=little neutral (particle)], elementary particle with no electric charge and a very small mass emitted during the decay of certain other particles. The neutrino was first postulated in 1930 by Wolfgang Pauli in order to maintain the law of conservation of energy during beta deca...
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antenna
antenna , in electronics, system of wires or other conductors used to transmit or receive radio or other electromagnetic waves (see radio ); sometimes called an aerial. The idea of using an antenna was developed by Guglielmo Marconi (c.1897). In a transmitting antenna, the signal from an electronic...
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