时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
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hidden line (aircraft drawing). A medium-weight line made up of short dashes that shows a surface of a part that is not visible in the view shown. hidden surface (aircraft drawing). Any surface on an object that cannot be seen in the view depicted by a drawing. A hidden surface is represented in outline form by a hidden line, a series of medium-weight dashes. high (meteorology). An area of high barometric pressure with its attendant system of anticyclonic winds, winds that circulate in a clockwise direction in the northern hemisphere and counterclockwise in the southern hemisphere. high blower (aircraft engine supercharger condition). The condition of supercharging of a reciprocating engine in which a two-speed, single-stage internal supercharger is operating at its high-speed ratio. This ratio is normally about ten times the speed of the crankshaft. high-bypass turbofan engine. A turbofan engine in which the fan moves more than four times as much air as is moved by the core engine compressor. This type of engine is said to have a bypass ratio of more than 4:1. high-carbon steel. Steel that contains at least 0.50% carbon. High-carbon steel can be hardened to increase its strength, but this causes it to become brittle. high-frequency communications. Radio communications using frequencies between three and 30 megahertz. HF communication is used between aircraft and ground facilities in over water operations. high-impedance voltmeter. A voltmeter whose meter movement requires very little current for full-scale deflection. Most high-impedance voltmeters have a sensitivity of at least 20,000 ohms per volt, and when a very-high-impedance voltmeter is needed, vacuum-tube or FET voltmeters are used. The sensitivity of these meters is measured in megohms per volt. High-impedance voltmeters do not load the circuit, which would give erroneous reading when voltage is measured across a high resistance. high-level language (computer language). A computer language whose instructions are terms similar to those used in normal communications. Statements in the high-level language entered into the computer produce a series of machine-language instructions the computer can understand. BASIC, FORTRAN, COBOL, and PASCAL are examples of high-level languages. high-lift device (aircraft component). Any component used to increase the lift produced by an aircraft wing. High-lift devices include leading edge flaps, slots, slats, trailing edge flaps, and boundary layer control systems. High-lift devices allow the wing to reach a higher angle of attack and thus produce more lift, before the airflow over its surface separates and the wing stalls. high metal ion concentration cell corrosion. Corrosion that results from a concentration of metallic ions in the electrolyte. The area of high concentration of metallic ions is the cathode of the cell. high-pass filter (electronic circuit). A type of electronic filter that passes, with little opposition, alternating current above a certain frequency. A high-pass filter blocks direct current, and blocks or reduces the amplitude of all alternating current having a frequency lower than that for which it is designed. |
