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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nitriding. A method of case hardening steel. The steel to be case hardened is placed in a retort (a sealed, high-temperature furnace) and heated to a specified high temperature while it is surrounded by ammonia gas (NH3). The ammonia breaks down into nitrogen and hydrogen, and the nitrogen unites with some of the alloying agents in the steel to form an extremely hard surface. Nitriding, which is used to harden crankshaft bearing surfaces and cylinder walls, is done at a lower temperature than other forms of case hardening, and it does not warp the parts being hardened. nitrogen. A colorless, odorless, tasteless, inert, gaseous chemical element. Nitrogen’s symbol is N, its atomic number is 7, and its atomic weight is 14.0067. Nitrogen makes up about 78% of the volume of the earth’s atmosphere and is used as an ingredient in fertilizers and explosives. nobelium. A radioactive, synthetic chemical element in the actinide series. Nobelium’s symbol is No, its atomic number is 102, and its atomic weight is 254. noble. Inactive or inert. In the electrochemical series of metals, the metal in a combination that does not corrode is the more noble. noble gas. Another name for inert gas. The noble (inert) gases are helium, neon, argon, krypton, xenon, and radon. noctilucent clouds (meteorology). Clouds of unknown composition which occur at great heights, probably around 75 to 90 kilometers. They resemble thin cirrus, but usually have a bluish or silvery color, although sometimes orange to red. nodal suspension system (helicopter rotor suspension system). A method of vibration dampening, used in certain Bell helicopters to reduce the vibration of the main rotor system. no-gyro approach (air traffic control). A radar approach or vector provided by ATC to an aircraft in case of a malfunctioning gyro compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions such as “turn right/left” or “stop turn,” as appropriate. noise (electronic equipment). Any unwanted electrical interference. Noise may come from static electricity or from signals fed into the circuit by inductive or capacitive coupling from other circuits. no-load current (electrical transformer current). Current flowing in the primary winding of a transformer connected to a source of AC voltage when no current is flowing in the secondary winding. No-load current is also called excitation current, or idling current. Nomex. A patented nylon material that is used to make the honeycomb core for certain types of aircraft structural sandwich-type materials. Nomex is also used to make fire-resistant fabrics. nominal value. A stated value that may be different from an actual value. For example, an electrical resistor may have a nominal resistance of 1,000 ohms, with a tolerance of plus or minus ten percent. Its nominal value is 1,000 ohms, but its actual value may be anywhere between 900 and 1,100 ohms. |
