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polar front

(Encyclopedia)polar front, zone of transition between polar and tropical air masses. Its average position during the winter is at about 30° lat. and during the summer at about 60° lat. In the N Atlantic Ocean, fo...

evaporation

(Encyclopedia)evaporation, change of a liquid into vapor at any temperature below its boiling point. For example, water, when placed in a shallow open container exposed to air, gradually disappears, evaporating at ...

Douhet, Giulio

(Encyclopedia)Douhet, Giulio jo͞oˈlyō do͞oāˈ [key], 1869–1930, Italian military officer and early advocate of airpower. He was an early supporter of strategic bombing and the military superiority of air for...

compressor

(Encyclopedia)compressor, machine that decreases the volume of air or other gas by the application of pressure. Compressor types range from the simple hand pump and the piston-equipped compressor used to inflate ti...

shad

(Encyclopedia)shad, fish of the genus Alosa, family Clupeidae (herring family), found in North America, Europe, and the Mediterranean. The American shad, A. sapidissima, is one of the largest (6 lb/2.7 kg average) ...

Chennault, Claire Lee

(Encyclopedia)Chennault, Claire Lee shĕnˈôltˌ [key], 1890–1958, American general, b. Commerce, Tex. In World War I he was a pioneer in air pursuit tactics. Retired (1937) from the army, he went to China and o...

fuel injection

(Encyclopedia)fuel injection, system in an internal-combustion engine that delivers fuel or a fuel-air mixture to the cylinders by means of pressure from a pump. It was originally used in diesel engines because of ...

balloon

(Encyclopedia)balloon, lighter-than-air craft without a propulsion system, lifted by inflation of one or more containers with a gas lighter than air or with heated air. During flight, altitude may be gained by disc...

aerodynamics

(Encyclopedia)aerodynamics, study of gases in motion. As the principal application of aerodynamics is the design of aircraft, air is the gas with which the science is most concerned. Although aerodynamics is primar...

White, Robert Michael

(Encyclopedia)White, Robert Michael, 1924–2010, American aviator, b. New York City. A fighter pilot during World War II, he was shot down over Germany and held in a prisoner-of-war camp (Feb.–Apr, 1945); he was...