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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 be ... [...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 fixed-wing gliders, lighter-than-air balloons and tethered kites. This requires a trajectory that is not merely a vertical descent such as a parachute. 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 fligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling and melting point are the lowest among all the elements. It is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant). 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 in Jupiter, due to 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, the vast majority of which was formed during t ... [...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 webbing ... [...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 ' (''sūkomoros'') meaning "fig-mulberry". Species of 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'', including ** ''Platanus occidentalis'', the American sycamore ** ''Platanus racemosa'', the California sycamore or western sycamore ** ''Platanus wrightii'', the Arizona sycamore ** ''Platanus mexicana''. the Mexican sycamore * In Australia, there are numerous trees which have the common name "sycamore": ** ''Litsea reticulata'' or ''Cryptocarya glaucescens'' (silver sycamore) ** ''P ... [...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. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts 187 species names of pines as current, together with more synonyms. The American Conifer Society (ACS) and the Royal Horticultural Society accept 121 species. Pines are commonly found in the Northern Hemisphere. ''Pine'' may also refer to the lumber derived from pine trees; it is one of the more extensively used types of lumber. The pine family is the largest conifer family and there are currently 818 named cultivars (or trinomials) recognized by the ACS. Description Pine trees are evergreen, coniferous resinous trees (or, rarely, shrubs) growing tall, with the majority of species reaching tall. The smallest are Siberian dwarf pine and Potosi pinyon, and the tallest is an tall ponderosa pine located in southern Oregon's Rogue Riv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maple
''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http://www.mobot.org/MOBOT/research/APweb/. There are approximately 132 species, most of which are native to Asia, with a number also appearing in Europe, northern Africa, and North America. Only one species, ''Acer laurinum'', extends to the Southern Hemisphere.Gibbs, D. & Chen, Y. (2009The Red List of Maples Botanic Gardens Conservation International (BGCI) The type species of the genus is the sycamore maple, '' Acer pseudoplatanus'', the most common maple species in Europe.van Gelderen, C. J. & van Gelderen, D. M. (1999). ''Maples for Gardens: A Color Encyclopedia'' Maples usually have easily recognizable palmate leaves ('' Acer negundo'' is an exception) and distinctive winged fruits. The closest relatives of the maples are the horse c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Populus
''Populus'' is a genus of 25–30 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar (), aspen, and cottonwood. The western balsam poplar ('' P. trichocarpa'') was the first tree to have its full DNA code determined by DNA sequencing, in 2006. Description The genus has a large genetic diversity, and can grow from tall, with trunks up to in diameter. The bark on young trees is smooth, white to greenish or dark gray, and often has conspicuous lenticels; on old trees, it remains smooth in some species, but becomes rough and deeply fissured in others. The shoots are stout, with (unlike in the related willows) the terminal bud present. The leaves are spirally arranged, and vary in shape from triangular to circular or (rarely) lobed, and with a long petiole; in species in the sections ''Populus'' and ''Aigeiros'', the petioles are laterally flattened, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milkweed
''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans and many other species, primarily due to the presence of cardenolides, although, as with many such plants, there are species that feed upon them (e.g. their leaves) and from them (e.g. their nectar). Most notable are monarch butterflies, who use and require certain milkweeds as host plants for their larvae. The genus contains over 200 species distributed broadly across Africa, North America, and South America. It previously belonged to the family Asclepiadaceae, which is now classified as the subfamily Asclepiadoideae of the dogbane family, Apocynaceae. The genus was formally described by Carl Linnaeus in 1753, who named it after Asclepius, the Greek god of healing. Flowers Members of the genus produce some of the most complex flowe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dandelion
''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and North America, but the two most commonplace species worldwide, ''Taraxacum officinale, T. officinale'' (the common dandelion) and ''Taraxacum erythrospermum, T. erythrospermum'' (the red-seeded dandelion), were introduced from Europe into North America, where they now propagate as wildflowers. Both species are List of leaf vegetables, edible in their entirety. The common name ''dandelion'' ( , from French language, French , meaning 'lion's tooth') is also given to specific members of the genus. Like other members of the family Asteraceae, they have very small flowers collected together into a composite Head (botany), flower head. Each single flower in a head is called a ''floret''. In part due to their abundance, along with being a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who can exit from an aircraft at height and descend safely to earth. A parachute is usually made of a light, strong fabric. Early parachutes were made of silk. The most common fabric today is nylon. A parachute's canopy is typically dome-shaped, but some are rectangles, inverted domes, and other shapes. A variety of loads are attached to parachutes, including people, food, equipment, space capsules, and bombs. History Middle Ages In 852, in Córdoba, Spain, the Moorish man Armen Firman attempted unsuccessfully to fly by jumping from a tower while wearing a large cloak. It was recorded that "there was enough air in the folds of his cloak to prevent great injury when he reached the ground." Early Renaissance The earliest evidence f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paratrooper At Spanish Drop Zone During Exercise Iberian Eagle
A paratrooper is a military parachutist—someone trained to parachuting, parachute into a military operation, and usually functioning as part of an airborne forces, airborne force. Military parachutists (troops) and parachutes were first used on a large scale during World War II for troop distribution and transportation. Paratroopers are often used in surprise attacks, to seize strategic objectives such as airfields or bridges. Overview Paratroopers jump out of airplanes and use parachutes to land safely on the ground. This is one of the three types of "forced entry" strategic techniques for entering a theater (warfare), theater of war; the other two being by land and by water. Their tactical advantage of entering the battlefield from the air is that they can attack areas not directly accessible by other transport. The ability of air assault to enter the battlefield from any location allows paratroopers to evade emplaced fortifications that guard from attack from a speci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orchid
Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering plants. The Orchidaceae have about 28,000 currently accepted species, distributed in about 763 genera. (See ''External links'' below). The determination of which family is larger is still under debate, because verified data on the members of such enormous families are continually in flux. Regardless, the number of orchid species is nearly equal to the number of bony fishes, more than twice the number of bird species, and about four times the number of mammal species. The family encompasses about 6–11% of all species of seed plants. The largest genera are ''Bulbophyllum'' (2,000 species), ''Epidendrum'' (1,500 species), ''Dendrobium'' (1,400 species) and ''Pleurothallis'' (1,000 species). It also includes ''Vanilla'' (the genus of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
