時間：2011-03-11 23:18來源：藍(lán)天飛行翻譯 作者：航空 點擊：次
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tetrode (electron tube). An electron tube with four active electrodes. A tetrode has a cathode, a control grid, a screen grid, and an anode, or plate. thallium. A soft, bluish-white, malleable, highly toxic, metallic chemical element. Thallium’s symbol is Tl, its atomic number is 81, and its atomic weight is 204.37. Thallium is used in the manufacture of photocells and infrared detection devices and in poison for rodents. theodolite. An optical instrument used for surveying and weather observation. A theodolite contains a telescope fitted with cross hairs, and mounted on a platform. The platform is fitted with two bubble levels and an accurate magnetic compass. The platform is leveled and pointed toward true north by applying the correction for declination, or variation, to compensate for the difference between magnetic north and true north. An azimuth scale (a scale that measures the horizontal direction the telescope moves) measures the bearing from the theodolite to any object visible through the telescope. A vertical scale measures the angle the telescope is inclined upward from its level position. In weather observation, the theodolite is used to track the movement of a weather balloon to find the direction and velocity of the wind at various altitudes. A theodolite is also used with a ceiling light to measure the height of the base of clouds at night. therapeutic mask adapter (oxygen system component). A type of adapter used in a constant-flow oxygen system to increase the flow of oxygen to a mask being used by a passenger known to have a heart or respiratory problem. thermal (meteorology). A column of rising air. Buildings and automobile traffic heat the air above cities and this heated air rises in a column, called a thermal. Sailplanes gain altitude by circling in a thermal and being carried upward by it. Thermals are easily found, because clouds normally form at their top. Air containing water vapor is carried upward until it reaches a level at which the vapor condenses and becomes visible droplets of liquid water. These droplets form the cloud. thermal anti-icing system (TAI). An aircraft anti-icing system that uses hot air to prevent ice forming on the leading edges of the wings and tail surfaces. Hot air from the turbine-engine compressor or from a shroud around the exhaust system of a reciprocating engine flows through ducts in the leading edges of the wings and tail surfaces to heat them so ice cannot form on them. thermal barrier (high-speed aerodynamics). A term used to describe one of the limits to the speed at which an aircraft can fly. The thermal barrier is the speed limit caused by heat produced by friction of the air passing over the aircraft surfaces. At this speed, the heat is severe enough to damage the aircraft structure. thermal circuit breaker. A type of circuit breaker that opens an electrical circuit when excessive current flows through it. Movable contacts are mounted on a bimetallic strip which is bent in such a way that they are forced tightly against fixed contacts in the circuit breaker housing. When more current than the circuit breaker is designed to carry flows through the bimetallic strip, the strip heats up and warps. When it warps, it snaps the contacts apart and opens the circuit. |
