曝光台 注意防骗
网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
diameter is attached to a small reservoir completely filled with mercury. The volume of mercury in the
reservoir is determined by its temperature. As the mercury absorbs heat, it expands and rises inside the tube.
A temperature scale is marked alongside the tube, and, since the height of the mercury in the tube relates to
the temperature of the mercury in the reservoir, the level of the top of the column of mercury can be
marked to indicate the temperature.
mercury vapor lamp. A form of electric-arc lamp. An arc is formed inside a transparent tube between two
electrodes in an atmosphere of mercury vapor. Mercury-vapor lamps produce a bluish-green light
containing a large amount of ultraviolet radiation.
mercury vapor rectifier (electrical component). A type of electrical component, used to change
alternating current into direct current. Drops of liquid mercury inside an evacuated glass tube are changed
into mercury vapor by heat from a built-in filament. Mercury vapor can be ionized by a low voltage of one
polarity, but it must have an extremely high voltage of the opposite polarity to ionize it. This makes it a
good rectifier. Mercury rectifiers have a small voltage drop across them when they are conducting, and they
are efficient conductors of large amounts of current in high-voltage circuits.
meridian (navigation). An imaginary great circle on the surface of the earth that passes through the North
and South geographic poles. The reference, or prime, meridian passes through the Royal Observatory in
Greenwich, England, and the meridians are numbered in degrees east and west to the 180° meridian, which
is the international date line.
mesosphere. The portion of the earth’s atmosphere extending from about 45 to 55 kilometers (28 to 34
miles) up to about 80 to 95 kilometers (50 to 59 miles). The mesosphere begins at the top of the
stratosphere, and in the mesosphere, the temperature generally decreases with altitude.
metal. A fusible, ductile, lustrous material. Fusible means it can be melted, ductile means its shape can be
changed by drawing or stretching, and lustrous means it reflects light evenly without sparkling. Nearly all
metals are good conductors of electricity and heat, and all metals readily lose electrons to form positive
ions.
metal-film resistor (electrical component). A type of electrical resistor made by depositing an extremely
thin film of metal on a ceramic form. The thickness and type of metal film determines the resistance and
the power-dissipating ability of the resistor.
metal foil (electrical capacitor component). A very thin sheet of metal used as an electrode in electrolytic
capacitors. The use of foil allows a large-area electrode to be contained in a small physical space.
metal-ion concentration-cell corrosion. A type of concentration-cell corrosion that forms in the metal
skin of an aircraft along the edges of a lap joint where moisture can be trapped. When trapped water
absorbs oxygen from the air, it attracts electrons from the metal and forms negative hydroxide ions.
When electrons are taken from the metal, positive metallic ions are left, and these positive ions
collect in the stagnant moisture trapped between the skins in the lap joint. The positive ions attract electrons
from the metal along the edges of the lap joint and cause the metal to unite with the hydroxide ions in the
moisture to form a salt. This salt is corrosion.
metallic pigment. Thin flakes of aluminum or copper that are mixed with a liquid vehicle to serve as the
pigment for paint. When the paint is applied to a surface, these tiny flakes spread out to form a solid,
opaque covering.
metallic ring test (test for bonded-structure delamination). A very simple test for delamination in a
bonded structural component. The material is tapped with a coin, and the sound is noted. If the sound is a
clear metallic ringing, the material is good, and there is no delamination. But if the tapping produces a dull
thudding noise, there is a good possibility that the laminations of which the material is made have begun to
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 381
separate.
metal oxide rectifier. A form of electrical rectifier that operates on the principle that electrons can flow
from a base metal through a film of oxide, but cannot flow through the oxide into the base metal. Copper
oxide and selenium oxide rectifiers have both been used in the past, but they have been replaced, to a great
extent, by silicon or germanium semiconductor diode rectifiers.
metal oxide semiconductor capacitor. See MOS capacitor.
metal oxide semiconductor field effect transistor. See MOSFET.
metal spinning. A method of forming sheet metal. A disk of metal is clamped in a lathe in front of a male
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：
航空术语词典Dictionary of Aeronautical Terms 中(129)
