航空術(shù)語詞典Dictionary of Aeronautical Terms 下

時(shí)間：2011-03-11 23:18來源：藍(lán)天飛行翻譯 作者：航空 點(diǎn)擊：次

sonic cleaning. A method of cleaning delicate mechanical parts. The parts are placed in a sonic cleaning machine and covered with a cleaning fluid. High-intensity sound waves are produced in the cleaning fluid, and the vibrations caused by these waves shake loose any contaminants on the parts being cleaned.
sonic frequencies. Frequencies of mechanical vibrations that can be heard by the human ear. Sonic frequencies are normally considered to be those between 20 hertz and 20,000 hertz (20 kHz).
sonic soldering. A method of soldering metals, such as aluminum, that are normally difficult to solder because of the speed with which surface oxides build up. The surface to be soldered is covered with a flux to prevent oxygen reaching it, and the tip of the soldering iron used to heat the surface is vibrated at a sonic rate. The vibrations loosen the surface oxides, and they float to the top of the flux. Since no new oxides can form under the molten flux, the solder can reach the hot, clean metal and adhere to it.
sonic speed. The speed of sound.
sonic venturi. A venturi in a line between a turbine engine compressor or turbocharger and the pressurization system of an aircraft. When the air flowing through the venturi reaches the speed of sound, a shock wave forms across the throat of the venturi and restricts the flow. A sonic venturi is also called a flow limiter.
soot. A black residue left when a hydrocarbon material is burned in an atmosphere in which there is not enough oxygen for complete combustion. Soot is composed mostly of carbon.
sound suppressor. The airframe component that replaces the turbine engine tail pipe. It decreases the distance sounds made by the exhaust gases can propagate by converting low-frequency vibrations into high-frequency vibrations.
sound waves. Longitudinal pressure waves within an elastic medium, such as air, water, or a solid material, that has been disturbed. Sound waves cannot travel through a vacuum.
source region (meteorology). An extensive area of the earth’s surface characterized by relatively uniform surface conditions. Large masses of air remain long enough over these surfaces to take on characteristic temperature and moisture properties from the surface.
south geographic pole. The location of the southern spin axes of the earth. The south geographic pole is located at 90° south latitude.
south magnetic pole. The location near, but not at, the south geographic pole, at which the magnetic lines of flux of the earth’s magnetic field enter. These lines of flux are considered to leave from the north magnetic pole and enter at the south magnetic pole.
south pole of a magnet. The pole of a magnet at which lines of magnetic flux are considered to enter after leaving the magnet at its north pole.
space charge (electron tube). The negative charge in an electron tube between the cathode and the plate. This space charge is caused by the cloud of electrons that collect around the cathode of the tube when the cathode emits more electrons than the plate can accept.

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