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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negative moment. A moment, or rotational force, that causes a body to rotate in a counterclockwise direction. negative number. A number less than zero. It is a number preceded by a minus sign. negative pressure. Gage pressure less than the atmospheric pressure from which it is measured. Negative pressure is sometimes called suction, or vacuum. negative pressure relief valve (aircraft pressurization system component). A valve in an aircraft cabin pressurization system that prevents the pressure inside the cabin ever becoming lower than the pressure of the air outside of the cabin. negative resistance. A condition in which an increase in voltage across a device causes a decrease in current through it. Under certain operating conditions, a tunnel diode shows negative resistance (the more voltage across it, the less current through it). negative stagger (aircraft structure). The vertical alignment of the wings of a biplane in which the lower wing is ahead of the upper wing. Most biplanes have positive stagger, in which the upper wing is ahead of the lower wing. But the distinctive appearance of the classic Beech Model 17, called the Staggerwing Beechcraft, is due to its negative stagger. negative static stability (aircraft stability). The type of static stability which causes an aircraft, once disturbed from a condition of rest, to move further from its condition of rest. Negative static stability is also called static instability. negative temperature coefficient. A decrease in a value, such as resistance or capacitance, with an increase in the temperature. A thermistor is a semiconductor material with a large negative temperature coefficient of resistance. Its resistance decreases greatly as its temperature increases. This makes thermistors valuable in fire detection systems. negative terminal (batteries). The terminal of a battery from which electrons leave. negative torque sensing system (propeller feathering system). The portion of a propeller feathering system that senses the torque being produced by the engine. If an engine fails in flight, its torque drops off drastically. The NTSS senses this loss of torque and sends a signal to the propeller feathering system. The propeller then automatically feathers. The blade pitch increases until the blades are parallel with the air passing over them. Feathering the propeller stops the engine rotation and reduces the drag. negative vorticity (meteorology). Vorticity caused by anticyclonic turning. Negative vorticity is associated with downward motion of the air. neodymium. A bright, silvery, rare-earth chemical element. Neodymium’s symbol is Nd, its atomic number is 60, and its atomic weight is 144.24. Neodymium is used for coloring glass and in laser technology. neon. An inert gaseous chemical element. Neon’s symbol is Ne, its atomic number is 10, and its atomic weight is 20.183. Neon is widely used in electric signs in which neon gas in glass tubes is ionized. The ionized gas glows with a reddish-orange light. |
