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Unpowered Flight
Unpowered flight is the ability to stay airborne for a period of time without using any power source. There are several types of unpowered flight. Some have been exploited by nature, others by humankind, and some by both. Unpowered aircraft are aerial vehicles that can fly without any propulsion mechanism. The ability to fly short or long distances without power has evolved many times in nature. Many creatures capable of sustained wing-powered flight also soar unpowered for much of the time they are airborne. Flight without power Classification of flight methods Pennycuick divides animal flight into three types: parachuting, gliding and powered. He observes however that these have no sharp boundaries. For example, at one point he sees parachutes as unpowered and as a primitive form of soaring, while soaring itself he sees as being powered by air movement (wind). Other methods, such as lighter-than-air flight, are used only by man. This article makes the following distinctions b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unpowered Aircraft
Unpowered aircraft can remain airborne for a significant period of time without onboard propulsion. They can be classified as gliders, lighter-than-air balloons and tethered kites. In the case of kites, lift is obtained by tethering to a fixed or moving object, perhaps another kite, to obtain a flow of wind over the lifting surfaces. In the case of balloons, lift is obtained through inherent buoyancy and the balloon may or may not be tethered. Free balloon flight has little directional control. Gliding aircraft include sailplanes, hang gliders, and paragliders that have full directional control in free flight. History The first manned aircraft were kites, balloons and gliders. Man-lifting kites were used in ancient China and Japan, often as a punishment for prisoners. Unmanned hot-air balloons and toy "bamboo-copters" are also recorded in Chinese history. The first manned free flight was in a hot-air balloon built by the brothers Joseph-Michel and Jacques-Etienne Montgolf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helium
Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the Chemical element, elements, and it does not have a melting point at standard pressures. It is the second-lightest and second-most Abundance of the chemical elements, abundant element in the observable universe, after hydrogen. It is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this in both the Sun and Jupiter, because of the very high nuclear binding energy (per nucleon) of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay. The most common isotope of helium in the universe is helium-4, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flying Frog
A flying frog (also called a gliding frog) is a frog that has the ability to achieve gliding flight. This means it can descend at an angle less than 45° relative to the horizontal. Other nonflying arboreal frogs can also descend, but only at angles greater than 45°, which is referred to as parachuting.Emerson, S.B., Travis, J., & Koehl, M.A.R. (1990). "Functional complexes and additivity in performance: A test case with 'flying' frogs." ''Evolution'', 44(8), 2153-2157. Evolution Gliding flight has evolved independently several times among frogs from both New World ( Hylidae) and Old World ( Rhacophoridae) families.Emerson, S.B., & Koehl, M.A.R. (1990). "The interaction of behavioral and morphological change in the evolution of a novel locomotor type: 'Flying' frogs." ''Evolution'', 44(8), 1931-1946. This parallel evolution is seen as an adaptation to their life in trees, high above the ground. Characteristics of the Old-World species include "enlarged hands and feet, full ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sycamore
Sycamore is a name which has been applied to several types of trees, but with somewhat similar leaf forms. The name derives from the Ancient Greek () meaning . Species of otherwise unrelated trees known as sycamore: * ''Acer pseudoplatanus'', a species of maple native to central Europe and southwestern Asia * ''Ficus sycomorus'', the sycamore (or sycomore) of the Bible; a species of fig, also called the sycamore fig or fig-mulberry, native to the Middle East and eastern Africa * '' Platanus orientalis'', chinar tree (Old World sycamore) * Some North American members of the genus ''Platanus ''Platanus'' ( ) is a genus consisting of a small number of tree species native to the Northern Hemisphere. They are the sole living members of the family Platanaceae. All mature members of ''Platanus'' are tall, reaching in height. The type ...'', including ** '' Platanus occidentalis'', the American sycamore ** '' Platanus racemosa'', the California sycamore or western sycamore ** '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pine
A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as current, with additional synonyms, and ''Plants of the World Online'' 126 species-rank taxa (113 species and 13 nothospecies), making it the largest genus among the conifers. The highest species diversity of pines is found in Mexico. Pines are widely species distribution, distributed in the Northern Hemisphere; they occupy large areas of boreal forest, but are found in many habitats, including the Mediterranean Basin, and dry tropical forests in southeast Asia and Central America. Wood from pine trees is one of the most extensively used types of timber, and some pines are widely used as Christmas trees. Description Pine trees are evergreen, coniferous resinous trees (or, rarely, shrubs) growing tall, with the majority of species reachin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
