时间：2011-03-11 23:18来源：蓝天飞行翻译 作者：航空 点击：次
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Dynamic storage is used for RAM (random-access-memory). Data can be both written into RAM and read from it, and this data can be changed as needed. The data stored in a dynamic RAM (D-RAM) is volatile. This means that all data is lost when computer power is shut off. The data in a D-RAM must be continually refreshed (the charge renewed) as the charge (the data) leaks off. semiconductor transducer. A piezoelectric crystal that converts input energy of one form, such as pressure, into output energy of another, such as an electrical signal. semimonocoque structure (aircraft structure). A form of stressed skin structure used in the construction of aircraft. Most of the strength of a semimonocoque structure is in the skin, but the skin is supported on a substructure of formers and stringers that gives the skin its shape and increases its rigidity. semirigid rotor (helicopter rotor). A type of helicopter rotor that allows the pitch of the blades to be changed by rotating the blades about their feather axis (the axis that extends along the length of the blade). The blades cannot flap up and down individually, but the entire rotor can flap as a unit. It is free to teeter (rock back and forth) about the mast. sender (fuel quantity measuring system). The part of a fuel quantity measuring system located at the tank to measure the level of the fuel in the tank. In most simple systems, the sender is a variable resistor mounted outside the tank with a wire arm protruding into the tank. A float mounted on the arm rides on the top of the fuel, and the arm is connected to the wiper of the variable resistor. As the level of fuel in the tank changes, the position of the arm on the variable resistor changes. The fuel quantity gage on the instrument panel measures the current flowing through the variable resistor and translates this current into the amount of fuel in the tank. sense antenna (automatic direction finder antenna). A type of nondirectional radio antenna used with an automatic direction finder. The sense antenna picks up signals with equal strength from all directions. An ADF system uses two antennas — a loop antenna and a sense antenna. The loop antenna is highly directional; the strength of the signal it picks up changes with the direction between the antenna and the station. But the signal strength is the same if the station is in front of the antenna or behind it. The signals picked up by both the loop antenna and the sense antenna are fed into the same equipment, and as the two signals mix, they form a pattern that allows the ADF system to measure the exact direction between the loop antenna and the station being received. Using the sense antenna eliminates the problem of 180° ambiguity. It allows the system to distinguish whether the station is in front of the antenna or behind it. sensible heat. Heat energy added to a material that causes it to change its temperature, but not its physical state. The other kind of heat is latent heat, which causes a material to change its physical state but not its temperature. |
