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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sodium-vapor lamp. A type of lamp used for outdoor lighting, especially along highways. Metallic sodium is vaporized inside a glass tube that contains a low-pressure gas. A voltage is placed across electrodes inside the glass tube, and the gas between the electrodes becomes ionized and glows enough to produce an orange light. soft-faced hammer. A hammer whose head has one or more soft faces made of plastic, rubber, rawhide, or a soft metal such as lead or aluminum. Soft-faced hammers are used to pound on surfaces that could be damaged by hard hammers. soft magnetic material. Ferromagnetic material that is easy to magnetize and demagnetize. Only a small coercive (demagnetizing) force is needed to remove any magnetism from the material. Low-carbon steel is a soft magnetic material. soft solder. An alloy of tin and lead that melts at a temperature of less than 800°F (427°C). This temperature is much lower than the melting temperature of the metal on which the solder is used. Soft solder is normally available in the form of a hollow wire filled with a resin flux. Soft solder is melted with a hot soldering copper, called a soldering iron, and the liquid solder wets the surface on which it is melted. When the soldering iron is removed, the solder solidifies and forms a bond between the pieces of metal that have been wetted. Soft solder does not form a physically strong bond, but is used on sheet metal, over a locked seam to make the joint liquid-proof, or on wires after they have been twisted together to make a connection having a low electrical resistance. soft vacuum tube. A vacuum tube that is faulty because air has leaked into the tube envelope. software (computer operation). The package of instructions or programs used to control a computer. Software consists of written instructions that can be easily changed by a computer programmer. The electronic components, switches, and wiring used in computer operation are called hardware. soft X-rays. Low-powered X-rays that have comparatively long wavelengths. Soft X-rays do not penetrate a material nearly as deeply as the high-powered, hard X-rays. soil cement. A material used as a base for roads and airport runways. Soil cement is made by mixing portland cement with soil and water and then compacting the mixture. solar cell. A silicon semiconductor device that converts light energy directly into electrical energy. These devices are called solar cells because they are designed to convert energy from the sun directly into electricity. solar radiation. Electromagnetic radiation emitted by the sun. |
