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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straight-run gasoline (petroleum product). Gasoline refined from crude oil without the addition of any of the additives used in some of the other methods of refining. straight-through combustor (turbine engine component). A combustor in a gas turbine engine through which the air from the compressor to the turbine flows in an essentially straight line. strain. A deformation, or physical change, in a material caused by a stress. According to Hooke’s law, the strain in a material, the amount it stretches or compresses, is directly proportional to the stress, until the elastic limit of the material is reached. Spring scales and certain types of torque wrenches work on the principle that strain is proportional to stress. strain gage. A device attached to the surface of a piece of equipment to measure the amount of strain acting on the surface. A strain gage is a piece of extremely fine wire bonded (glued) to the surface, with the length of the wire parallel to direction of the strain to be measured. When the surface is stressed, it is also strained (deformed), and it either stretches or compresses. Since the strain gage is bonded to the surface, it also stretches or compresses. The resistance of the strain gage is measured with a precision bridge-type instrument, and the resistance change caused by the wire stretching or compressing is measured. Strain gages are calibrated so the change in resistance indicates the amount of strain acting on the surface. strain hardening (metallurgy). A method of hardening metals that cannot be hardened by heat treatment. Copper, some aluminum alloys, and low-carbon steel cannot be hardened by heat treatment, but they can be hammered, rolled, pulled, or bent to change their grain structure enough that they become hard. stranded wire (electrical conductor). An electrical conductor made up of a number of small wires. These wires are either twisted together or braided and are usually enclosed in an insulating material. A stranded wire is often called a cable. stratiform clouds (meteorology). Clouds that form in stable air and appear to be in layers. Stratus clouds, stratocumulus, and nimbostratus clouds are all stratiform clouds. stratocumulus (meteorology). Low clouds that are predominantly stratiform in nature. Stratocumulus clouds are gray with some dark parts and often with white patches. stratosphere. The upper part of earth’s atmosphere. The stratosphere extends upward from the tropopause, which is about seven miles (11 kilometers) above the surface of the earth, to an altitude of about 22 miles (35 kilometers). The temperature of the air in the stratosphere remains constant at –56.5°C (–69.7°F), and since there is no water vapor in the stratosphere, there are no clouds, nor any of the weather conditions that exist at the lower altitudes. stratus (meteorology). A low, gray cloud layer or sheet with a fairly uniform base. Stratus clouds sometimes appear in ragged patches. They seldom produce precipitation but may produce drizzle or snow grains. |
