时间：2011-03-11 23:13来源：蓝天飞行翻译 作者：admin 点击：次
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launching pad (rocket operation). A smooth, debris-free, nonflammable area from which rockets are fired to launch them. law of conservation of energy. One of the basic laws of physics stating that energy can be neither created nor destroyed, but it can be changed from one form into other forms. Regardless of the form or forms into which the energy is changed, the total amount of energy always remains the same. lawrencium. A synthetic, radioactive chemical element. Lawrencium’s symbol is Lr, and its atomic number is 103. One of the isotopes of lawrencium has a mass number of 257 and a half-life of eight seconds. layer (meteorology). With regard to sky cover, layers refer to clouds or other obscuring phenomena whose bases are at approximately the same level. The layer may be continuous or composed of detached elements. The term layer does not imply that a clear space exists between the layers or that the clouds or obscuring phenomena composing them are of the same type. lay line (flexible hose). A colored line that runs the length of a piece of flexible hose. A lay line is used to indicate whether or not the hose was twisted during installation. If the lay line spirals around the hose, the hose is twisted. lay-up (composite structure). The placement of the various layers of resin-impregnated fabric in a mold in the process of manufacturing a piece of laminated composite material. L-band radar. Airborne radar which operates in the frequency range of 0.39 to 1.55 gigahertz. The wavelength of L-band radar is between 77 and 19 centimeters. LC circuit (electrical circuit). An alternating current circuit containing both inductance (L) and capacitance (C). An LC circuit is considered to have no resistance. In a purely capacitive circuit, changes in current lead changes in voltage by 90°. In a purely inductive circuit, current changes lag 90° behind voltage changes. Because the effects of capacitance and inductance are 180° apart, the total opposition to the flow of current in an LC circuit is the difference between the capacitive and the inductive reactances. LCD (liquid crystal display). A type of visual display used in digital watches, computers, calculators, and some of the newer aircraft instruments. An extremely thin layer of a normally transparent liquid crystal material is sealed between two sheets of glass. The outsides of the two pieces of glass are coated with an electrically conductive oxide. The oxide coating on one side of the glass is etched to form the segments of letters and numbers, and each segment is connected by a printed circuit lead to a connector at the edge of the display. |
