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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The light beam from a laser is highly concentrated, very narrow, and has an extremely high intensity. High-power lasers produce a great deal of heat in an extremely small area, and laser technology is opening new doors in all aspects of science. laser memory (computer memory). A method of storing a large amount of digital information permanently and inexpensively on a disk similar to but smaller than a phonograph record. A high-power laser (see laser) burns extremely small pits into the reflective surface of a disk to write, or record, digital data on the disk. The information stored on the disk is read by the reflection or the lack of reflection of a low-power laser shone on the surface. A reflection is read as a logic one, and a space where there is no reflection, an area caused by a pit, is read as a logic zero. The fact that billions of bits can be stored on a relatively small disk makes laser memory an inexpensive method of storing video programs. laser printer. A type of printer used to produce a hard copy of the information being processed by a computer. A laser (see laser) shines a series of dots of light in a matrix pattern onto the surface of the paper as it moves in front of the print head, and each dot of light leaves the paper with an electrostatic charge. A dust of metallic powder, called toner, is blown across the paper, and some of it sticks to the charged areas. None, however, sticks to the uncharged portion of the paper. The paper with the powder sticking to the charged areas passes over a heater, which fuses, or melts, the powder into the paper to form a permanent image. laser tachometer. A highly accurate tachometer that shines a laser beam on the rotating element and senses the reflection from a reflective tape or contrasting mark. The reflected laser beam is converted into electrical pulses which are counted and displayed on a monitoring instrument. laser welding. A method of welding by the heat produced by a laser beam. The high-intensity, concentrated heat allows the welding of exotic alloys that cannot be welded by other methods. last-chance filter (gas turbine engine component). An oil filter installed in the lubricating system of a gas turbine engine just ahead of the jets that spray oil onto the bearings. These filters trap any contaminants that get past the main system filters and prevent the oil jets becoming clogged. Last-chance filters cannot be serviced during normal engine maintenance. They are cleaned only when the engine is disassembled for overhaul. latching relay (locking relay). A relay that, once energized, remains in its energized condition after the current stops flowing in its coil. When the relay is energized, the contacts are locked in the energized position by a mechanical latch. A mechanical release must be actuated to allow the relay to return to its de-energized condition. Latching relays are being replaced to a great extent by solid-state flip-flop circuits. latent heat. Heat added to a material which changes its physical state, but does not change its temperature. When a pan of water is put on a hot stove and heat is added to it, its temperature rises — but in standard conditions, only until it reaches 100°C. Heat which changes the temperature of water is called sensible heat. |
