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air navigation
air navigation science and technology of determining the position of an aircraft with respect to the surface of the earth and accurately maintaining a desired course (see navigation ).
Visual and Instrument Flight
The simplest and least sophisticated way to keep track of position, course...
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Shanhaiguan
Shanhaiguan or Shanhaikwan [Chin.,=mountain sea door], city, NE Hebei prov., China, on the Bohai. Strategically situated where the Great Wall meets the sea and on the narrow coastal route to Manchuria, it has been the site of many battles and the route of many invasions. It now lies on a doub...
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cube
cube in geometry, regular solid bounded by six equal squares. All adjacent faces of a cube are perpendicular to each other; any one face of a cube may be its base. The dimensions of a cube are the lengths of the three edges which meet at any vertex. The volume of a cube is equal to the product of i...
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artificial satellite
artificial satellite object constructed by humans and placed in orbit around the earth or other celestial body (see also space probe ). The satellite is lifted from the earth's surface by a rocket and, once placed in orbit, maintains its motion without further rocket propulsion. The first artifi...
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beacon
beacon. 1. Normally a stake surmounted by a distinctive topmark erected over a shoal or sandbank. In many coastal estuaries without important shipping the low water level is marked by local beacons, often withies. 2. A prominent erection on shore that indicates a safe line of approach to a harbour ...
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volume
volume measure of solid content or capacity, usually expressed in units that are the cubes of linear units, such as cubic inches and cubic centimeters, or in units of dry and liquid measure, such as bushels, gallons, and liters. Volumes of complicated geometric forms are often calculated using inte...
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magnetic levitation
magnetic levitation or maglev , support and propulsion of objects or vehicles by the use of magnets. The magnets provide support without contact or friction, allowing for fast, quiet operation. In a typical system, the vehicle, which resembles a railroad car, travels above a guideway. Arrays of ...
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liter
liter abbr. l, unit of volume in the metric system , defined since 1964 as equal to 0.001 cubic meters, or 1 cubic decimeter. A cube that has each of its edges equal to 10 centimeters has a volume of 1 liter. The liter is equal to 1.057 liquid quarts, 0.908 dry quarts, and 61.024 cubic inches.
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railroad
railroad or railway, form of transportation most commonly consisting of steel rails, called tracks, on which freight cars, passenger cars, and other rolling stock are drawn by one locomotive or more. However, there are other types of railways, including those whose units consist of single sel...
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polyhedron
polyhedron , closed solid bounded by plane faces; each face of a polyhedron is a polygon . A cube is a polyhedron bounded by six polygons (in this case squares) meeting at right angles. Although regular polygons are possible for any number of sides, there are only five possible regular polyhedrons,...
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