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in the air is absorbed and held by the silica gel.
silicon. A dark brown, tetravalent (having four valence electrons), nonmetallic crystalline chemical element.
Silicon’s symbol is Si, its atomic number is 14, and its atomic weight is 28.086. Silicon is the second most
abundant chemical element in nature (oxygen is the most abundant). Because of the ease with which silicon
unites with oxygen to form silicon dioxide (sand and quartz), it is never found in nature in its pure state.
Silicon is used to make semiconductor diodes, transistors, and all forms of integrated circuit
devices.
silicon carbide. An abrasive that is often ground into small particles and bonded to sheets of paper or cloth
or formed into grinding wheels for use on power grinders.
silicone. A group of semi-inorganic polymers that have good thermal stability, are chemically inert, water
repellent, and are good lubricants. Silicone products are available as liquids, solids, and semisolids. They
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are used in the manufacture of adhesives, lubricants, sealants, and electrical insulators.
silicone rubber. An elastomeric material made from silicone elastomers. Silicone rubber is compatible
with fluids which attack other natural or synthetic rubbers.
silicon glaze (spark plug contaminant). A form of contamination on aircraft spark plugs that can lead to
engine failure. Silica is found in sand and dust, and if a carburetor air filter leaks and allows sand or dust to
get into the engine, the silica can form a hard, glass-like deposit on the nose core insulators of the spark
plugs. Silicon glaze is an insulator at low temperatures, and will not cause a spark plug to show up as bad
on a tester. But when the spark plug gets hot, the silicon glaze becomes conductive, and short-circuits the
high voltage to ground before it builds up high enough to jump the gap between the electrodes.
silicon solar cell. A special type of semiconductor device made of P-type silicon doped with boron and
N-type silicon doped with arsenic. When light strikes the PN junction, electrons flow through the load
circuit from the N-silicon to the P-silicon.
silicon steel. An alloy steel that contains between 0.5% and 4.5% silicon. Silicon steel in sheet form is used
for laminations to make up the core of electrical transformers.
silver. A lustrous white, ductile, malleable, metallic chemical element. Silver’s symbol is Ag, its atomic
number is 47, and its atomic weight is 107.870. Silver has the highest thermal and electrical conductivity of
any metal, and it is used in electrical contacts and printed circuits. One of the primary industrial uses of
silver is in photography.
silver brazing. A form of brazing in which the filler metal is a silver-base alloy. See brazing.
silvered-mica capacitor. A high-voltage capacitor that uses thin sheets of mica as the dielectric. Both sides
of the mica are electrolytically coated with silver. This silver forms the plates of the capacitor.
silver solder. An alloy of copper, silver, and zinc. The melting point of silver solder is lower than that of
silver, but higher than that of lead-tin solder (soft solder).
simple flap (airplane flap). A type of wing flap installed on some of the smaller airplanes. A portion of the
trailing edge of the wing inboard of the ailerons can be folded downward in flight to increase the camber of
the wing. This increases both the lift and the drag the wing produces. See plain flap.
simple fraction (mathematics). A mathematical fraction with whole numbers for both its numerator and
its denominator. An example of a simple fraction is 3/4. Fractions that are not simple fractions are called
complex fractions. An example of a complex fraction is: 1/2 / 3/4.
simple machine. Any of the basic, or elementary, mechanical devices from which all machines are built.
Simple machines include the wheel and axle, the lever, and the inclined plane.
simple motion. Motion along a straight line, a circular path, or a helix.
simplex communications. A method of communications in which one station transmits while the other
receives, then the second station transmits and the first receives. Simplex communications differs from
duplex communications, such as telephone, in which both stations can transmit and receive at the same
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time.
simplex fuel nozzle (gas turbine engine component). A type of fuel nozzle in a gas turbine engine in
which all of the fuel is fed to the nozzle through a single fuel manifold.
simulate. To copy something or to make something that represents or acts like something. When a person
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航空术语词典Dictionary of Aeronautical Terms 下(50)
