时间：2011-03-11 23:11来源：蓝天飞行翻译 作者：admin 点击：次
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audio-frequency oscillator (electronic component). An electronic circuit that produces an alternating current whose frequency is in the audio-frequency range. audio-frequency vibrations. Vibrations at a frequency which produce sound that can be heard by the normal human ear. Audio frequencies range from about 16 hertz to 16,000 hertz. audiovisual system (communications system). A system of communications that produces signals that can be both seen and heard. Television is a form of audiovisual communications system. augend (mathematics). The number in an addition problem to which another number, the addend, is added. augmentor. Another name for afterburner. See afterburner. augmentor tube. A long, specially shaped, stainless steel tube mounted around the exhaust tail pipe of an aircraft reciprocating engine. As the exhaust gases flow through the augmentor tube, they produce a low pressure in the engine compartment which draws cooling air into the compartment through the fins on the cylinders. Heat may be taken from the augmentor tubes and directed through the leading edges of the wings for thermal anti-icing. aural radio range (aerial navigation system). A navigation system that directs the pilot with an audible signal. The four-course, low-frequency radio range is an aural radio range. The pilot flies down the center of the course line by positioning the aircraft so that a solid tone is heard. If the aircraft drifts to one side of the course line, the letter N (– .) in Morse code) is heard. If it drifts to the other side, the letter A (. –) is heard. aural warning device. A warning device that signals the presence of a problem by emitting a signal that can be heard. aurora (meteorology). A luminous, radiant emission over middle and high latitudes confined to the thin air of high altitudes and centered over the earth’s magnetic poles. These interesting sights are called “aurora borealis” (northern lights) in the northern hemisphere and “aurora australis” (southern lights) in the southern hemisphere. austenite. A form of iron in which a supersaturated solution of carbon is dissolved in the iron. Austenite exists in the iron only when the iron is at a high temperature. austenite steel. Gamma iron into which carbon can dissolve. Below its critical temperature, iron carbides are scattered throughout the iron matrix in a physical mixture. At its critical temperature, the carbon dissolves into the matrix and becomes a solid solution rather than a physical mixture. authorized. Having a legal right to act in a certain way or to perform certain duties. autoclave. A pressure vessel in which the air inside can be heated to a high temperature and the pressure raised to a high value. Autoclaves are used in the composite manufacturing industry to apply heat and pressure to plastic resins. Heat and pressure decrease the amount of time needed to cure plastic resins and improve the quality of the curing process. |
