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Ski Wax
Ski wax is a material applied to the bottom of snow runners, including skis, snowboards, and toboggans, to improve their coefficient of friction performance under varying snow conditions. The two main types of wax used on skis are glide waxes and grip waxes. They address kinetic friction—to be minimized with a glide wax—and static friction—to be achieved with a grip wax. Both types of wax are designed to be matched with the varying properties of snow, including crystal type and size, and moisture content of the snow surface, which vary with temperature and the temperature history of the snow. Glide wax is selected to minimize sliding friction for both alpine and cross-country skiing. Grip wax (also called "kick wax") provides on-snow traction for cross-country skiers, as they stride forward using classic technique. Modern plastic materials (e.g. high-modulus polyethylene and Teflon), used on ski bases, have excellent gliding properties on snow, which in many circumstances ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ski Warfare
Ski warfare is the use of skiing, ski-equipped troops in war. History Early Ski warfare is first recorded by the Denmark, Danish historian Saxo Grammaticus in the 13th century. During the Battle of Oslo (1161), Battle of Oslo in 1161, Norwegian troops used skis for reconnoitering. They were also used in 1452 in Sweden, and in the 15th to 17th centuries by various other Scandinavia, Scandinavian countries. Norwegian Captain Jens Emahusen wrote a military ski manual ''Skiloperegglement'' in 1733. In 1767, military ski competitions began. They evolved into the biathlon. Napoleonic Wars Denmark–Norway (though only Norwegian) ski troops were used against Sweden during the Gunboat War in the Napoleonic Wars. File:Johannes Senn og Johan F. L. Dreier - En norsk Skielöber - Norske Nationale Klædedragter - NMK.2020.0101 - National Museum of Art, Architecture and Design.jpg, A Norwegian soldier on skis, 1801 World War I Just prior and during World War I many combatants deployed ski ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sámi People
The Sámi ( ; also spelled Sami or Saami) are the traditionally Sámi languages, Sámi-speaking indigenous people inhabiting the region of Sápmi, which today encompasses large northern parts of Norway, Sweden, Finland, and of the Kola Peninsula in Russia. The region of Sápmi was formerly known as Lapland, and the Sámi have historically been known in English as Lapps or Laplanders, but these terms are regarded as offensive by the Sámi, who prefer their own endonym, e.g. Northern Sámi . Their traditional languages are the Sámi languages, which are classified as a branch of the Uralic language family. Traditionally, the Sámi have pursued a variety of livelihoods, including coastal fishing, fur trapping, and Shepherd, sheep herding. Their best-known means of livelihood is semi-nomadic reindeer herding. about 10% of the Sámi were connected to reindeer herding, which provides them with meat, fur, and transportation; around 2,800 Sámi people were actively involved in reindeer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrograph
A micrograph is an image, captured photographically or digitally, taken through a microscope or similar device to show a magnify, magnified image of an object. This is opposed to a macrograph or photomacrograph, an image which is also taken on a microscope but is only slightly magnified, usually less than 10 times. Micrography is the practice or art of using microscopes to make photographs. A photographic micrograph is a photomicrograph, and one taken with an electron microscope is an electron micrograph. A micrograph contains extensive details of microstructure. A wealth of information can be obtained from a simple micrograph like behavior of the material under different conditions, the phases found in the system, failure analysis, grain size estimation, elemental analysis and so on. Micrographs are widely used in all fields of microscopy. Types Photomicrograph A light micrograph or photomicrograph is a micrograph prepared using an optical microscope, a process referred to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sublimation (phase Transition)
Sublimation is the Phase transition, transition of a substance directly from the solid to the gas state, without passing through the liquid state. The verb form of sublimation is ''sublime'', or less preferably, ''sublimate''. ''Sublimate'' also refers to the product obtained by sublimation. The point at which sublimation occurs rapidly (for further details, see #False correspondence with vaporization, below) is called critical sublimation point, or simply sublimation point. Notable examples include sublimation of dry ice at room temperature and atmospheric pressure, and that of solid iodine with heating. The reverse process of sublimation is deposition (phase transition), ''deposition'' (also called ''desublimation''), in which a substance passes directly from a gas to a solid phase, without passing through the liquid state. Technically, all solids may sublime, though most sublime at extremely low rates that are hardly detectable under usual conditions. At standard condi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrite (crystal)
A crystal dendrite is a crystal that develops with a typical multi-branching form, resembling a fractal. The name comes from the Ancient Greek word (), which means "tree", since the crystal's structure resembles that of a tree. These crystals can be synthesised by using a supercooled pure liquid, however they are also quite common in nature. The most common crystals in nature exhibit dendritic growth are snowflakes and frost on windows, but many minerals and metals can also be found in dendritic structures. History Maximum velocity principle The first dendritic patterns were discovered in palaeontology and are often mistaken for fossils because of their appearance. The first theory for the creation of these patterns was published by Nash and Glicksman in 1974, they used a very mathematical method and derived a non-linear integro-differential equation for a classical needle growth. However they only found an inaccurate numerical solution close to the tip of the needle a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snow Friction Vs Water Film Thickness--Colbeck
Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout its life cycle, starting when, under suitable conditions, the ice crystals form in the atmosphere, increase to millimeter size, precipitate and accumulate on surfaces, then metamorphose in place, and ultimately melt, slide, or sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns, and rime. As snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow metamorphoses, by sintering, sublimation, and freeze-thaw. Where the climat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perfluorocarbon
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are commercial polymers, refrigerants, drugs, and anesthetics. Nomenclature Perfluorocarbons or PFCs, are organofluorine compounds with the formula CxFy, meaning they contain only carbon and fluorine. The terminology is not strictly followed and many fluorine-containing organic compounds are also called fluorocarbons. Compounds with the prefix perfluoro- are hydrocarbons, including those with heteroatoms, wherein all C-H bonds have been replaced by C-F bonds. Fluorocarbons includes perfluoroalkanes, fluoroalkenes, fluoroalkynes, and perfluoroaromatic compounds. Perfluoroalkanes Chemical properties Perfluoroalkanes are very stable because of the strength of the carbon–fluorine bond, one of the strongest in organic chemistry. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sintered Polyethylene
Sintered polyethylene is a polyethylene powder that is formed into a solid without melting it. It can be produced using heat, pressure, or selective laser sintering. It has applications as a coating on pipes and skis, and as a filter medium. Applications Pipes Sintered polyethylene is applied to steel pipes to resist corrosion. Pipes are heated and then polyethylene powder coated, either electrostatically or through immersion. Skis Sintered polyethylene was introduced as a coating on skis in 1962. It is more durable, and less dense than solid, extruded polyethylene. Its porous structure allows the ski to absorb wax. Filter medium Sinter plate filter elements were developed in Germany during the years of 1981 and 1982. These rigid filter elements are used in dust collectors and will produce clean gas values of 0.1 to 1.0 mg/m3 with emissions of 0.001 pounds per hour with a maximum of 0.0004 gr/ft3, even with dusts of D50 < 1 μm. The EP [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surfactant
Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word ''surfactant'' is a Blend word, blend of "surface-active agent", coined in 1950. As they consist of a water-repellent and a water-attracting part, they enable water and oil to mix; they can form foam and facilitate the detachment of dirt. Surfactants are among the most widespread and commercially important chemicals. Private households as well as many industries use them in large quantities as detergent, detergents and cleaning agents, but also for example as emulsion#Emulsifiers, emulsifiers, wetting agents, foaming agents, Antistatic agent, antistatic additives, or dispersants. Surfactants occur naturally in traditional plant-based detergents, e.g. Aesculus, horse chestnuts or Sapindus, soap nuts; they can also be found in the secretions of some caterpillars. Today one of the most commonly used anionic surfa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraffin Wax
Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and melting point, begins to melt above approximately , and its boiling point is above . Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons. Un-dyed, unscented paraffin candles are odorless and bluish-white. Paraffin wax was first created by Carl Reichenbach#Scientific contributions, Carl Reichenbach in Germany in 1830 and marked a major advancement in candlemaking technology, as it burned more cleanly and reliably than tallow candles and was cheaper to produce. In chemistry, ''paraffin'' is used synonymously with ''alkane'', indicating hydrocarbons with the general formula C''n''H2''n''+2. The name is derived from Latin ''parum'' ("very little") + ''affinis'', meaning ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astra AB
Astra AB was a former international pharmaceutical company headquartered in Södertälje, Sweden. Astra was formed in 1913 and merged with the British Zeneca Group in 1999 to form AstraZeneca. Product development was focused on therapeutics for gastrointestinal, cardiovascular and respiratory disorders and pain control. At the time of the merger, Astra was the largest Swedish pharmaceutical company. Astra also operated Astra Tech, a medical devices company, and marketed pharmaceuticals outside their primary development area, including anti-infective agents. History The issue of domestic industrial production of pharmaceuticals in Sweden, as opposed to manual preparations by pharmacists, had been discussed among Swedish pharmacists since mid-1890s. At this time, German and Swiss pharmaceutical companies dominated the Swedish market. For a long time, this never led to more than discussions, but in 1913 Astra was founded in Södertälje, and plans to produce some 40 pharmaceutical pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
