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An amphibious vehicle (or simply amphibian), is a vehicle that is a means of transport, viable on land as well as on (or under) water. Amphibious vehicles include amphibious bicycles, ATVs, cars, buses, trucks, military vehicles, and hovercraft. Classic landing craft are not amphibious vehicles as they do not offer any real land transportation at all, although they ''are'' part of amphibious assault. Ground effect vehicles, such as Ekranoplans, will likely crash on any but the flattest of landmasses so are also not considered to be amphibious vehicles. == General technical notes == Apart from the distinction in sizes mentioned above, two main categories of amphibious vehicle are immediately apparent: those that travel on an air-cushion (Hovercraft) and those that do not. Amongst the latter, many designs were prompted by the desire to expand the off-road capabilities of land-vehicles to an "all-terrain" ability, in some cases not only focused on creating a transport that will work on land and water, but also on intermediates like ice, snow, mud, marsh, swamp etc. This explains why many designs use tracks in addition to or instead of wheels, and in some cases even resort to articulated body configurations or other unconventional designs such as screw-propelled vehicles which use auger-like barrels which propel a vehicle through muddy terrain with a twisting motion.〔(development of this concept is so-called "TESH-drive or transformable worm" from russian inventor Alexey Burdin.verb=getRecord&metadataPrefix=html&identifier=AD0456539 Marsh Screw Amphibian )〕〔(Getty Images - Unsupported browser detected )〕 Most land vehicles – even lightly armoured ones – can be made amphibious simply by providing them with a waterproof hull and perhaps a propeller. This is possible as a vehicle's displacement is usually greater than its weight, and thus it will float. Heavily armoured vehicles however sometimes have a density greater than water (their weight in kilograms exceeds their volume in litres), and will need additional buoyancy measures. These can take the form of inflatable floatation devices, much like the sides of a rubber dinghy, or a waterproof fabric skirt raised from the top perimeter of the vehicle, to increase its displacement. For propulsion in or on the water some vehicles simply make do by spinning their wheels or tracks,〔(Fast Track Amphibian FastTrack 1 )〕〔(Howe and Howe Tech Personal Assault Lander )〕 while others can power their way forward more effectively using (additional) screw propeller(s) or water jet(s). Most amphibians will work only as a displacement hull when in the water – only a small number of designs have the capability to raise out of the water when speed is gained, to achieve high velocity hydroplaning, skimming over the water surface like speedboats. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「amphibious vehicle」の詳細全文を読む スポンサード リンク
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