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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There are two absolute temperature scales, Kelvin and Rankine. The Kelvin scale uses the same size increments as the Celsius scale, and the Rankine scale uses the same size increments as the Fahrenheit scale. See temperature. absolute value. The numerical value of a number without considering whether its sign is plus or minus. For example, positive eight (+8) has the same absolute value as negative eight (–8). absolute vorticity (meteorology). The swirling motion, or vorticity, imparted to the atmosphere by the combination of the rotation of the earth and the circulation of the air relative to the earth. absolute zero. The temperature at which all molecular movement inside a material stops. Absolute zero is 0° Kelvin, 0° Rankine , –273° Celsius, and –460° Fahrenheit. absorptance (electromagnetic radiation). The ratio of the total unabsorbed radiation to the total amount of radiation falling on the object whose absorptance is being measured. abvolt. A basic unit of electromotive force in the electromagnetic-centimeter-gram-second system. One abvolt is equal to 10-8 volts in the absolute meter-kilogram-second-ampere system. The abbreviation for abvolt is aV. AC (Advisory Circular). Information published by the FAA explaining the Federal Aviation Regulations and describing methods of performing certain maintenance and inspection procedures. Compliance with ACs is not mandatory, and the information in the ACs is not necessarily approved data. AC (alternating current). Electrical current in which the electrons continually change their rate of flow and periodically reverse their direction. ACARS (aircraft communication addressing and reporting system). A two-way communication link between an airliner in flight and the airline’s main ground facilities. Data is collected in the aircraft by digital sensors and transmitted to the ground facilities. Replies from the ground may be printed out so the appropriate flight crewmember can have a hard copy of the response. ACC (active clearance control). A system for controlling the clearance between tips of the compressor or turbine blades and the case of high-performance turbofan engines. When the engine is operating at maximum power, the blade tip clearance should be minimum, and the ACC system sprays cool fan-discharge air over the outside of the engine case. This cool air causes the case to shrink enough to decrease the tip clearance. For flight conditions not requiring such close clearance, the cooling air is turned off, and the case expands to its normal dimensions. Control of the ACC system is done by the FADEC, or Full-Authority Digital Electronic Control. accelerate. To increase the speed of an object, or make it move faster. accelerated-life test. A form of operational test of a system or component in which unusual conditions are used to cause a premature failure. An accelerated-life test is used to locate weak points and predict the service life the system or component will likely have under normal operating conditions. The test conditions used in an accelerated-life test are much more severe than will ever be encountered in normal operation. |
