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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 d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ski Warfare
Ski warfare is the use of ski-equipped troops in war. History Early Ski warfare is first recorded by the Danish historian Saxo Grammaticus in the 13th century. During the 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 Scandinavian countries. 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 1807–1814 Napoleonic Wars. World War I During World War I the Italian Army raised 88 Alpini Battalions. Their purpose was to fight summer and winter in the highest regions of the Alpine Arch. Most of the battalions were dissolved after World War I. Only nine Alpini regiments remain in service today, and only four still train every soldier in ski warfare: the 4th Alpini Parachutist Regiment, 5th Alpini Regiment, 6th Alpini Regiment and 7th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sámi People
The Sámi ( ; also spelled Sami or Saami) are a Finno-Ugric languages#Speakers, Finno-Ugric-speaking people inhabiting the region of Sápmi (formerly known as Lapland), which today encompasses large northern parts of Norway, Sweden, Finland, and of the Murmansk Oblast, Russia, most of the Kola Peninsula in particular. The Sámi have historically been known in English as Lapps or Laplanders, but these terms are regarded as offensive by the Sámi, who prefer the area's name in their own languages, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Units (SI) equalling (SI standard prefix "micro-" = ); that is, one millionth of a metre (or one thousandth of a millimetre, , or about ). The nearest smaller common SI unit is the nanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (). The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria, and for grading wool by the diameter of the fibres. The width of a single human hair ranges from approximately 20 to . The longest human chromosome, chromosome 1, is approximately in length. Examples Between 1 μm and 10 μm: * 1–10 μm – length of a typical bacterium * 3–8 μm – width of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilson Bentley
Wilson Alwyn Bentley (February 9, 1865 – December 23, 1931), also known as Snowflake Bentley, was an American meteorologist and photographer, who was the first known person to take detailed photographs of snowflakes and record their features. He perfected a process of catching flakes on black velvet in such a way that their images could be captured before they either melted or sublimated. Kenneth G. Libbrecht notes that the techniques used by Bentley to photograph snowflakes are essentially the same as those used today, and that while the quality of his photographs reflects the technical limitations of the equipment of the era, "he did it so well that hardly anybody bothered to photograph snowflakes for almost 100 years". The broadest collection of Bentley's photographs is held by the Jericho Historical Society in his home town, Jericho, Vermont. Bentley donated his collection of original glass-plate photomicrographs of snow crystals to the Buffalo Museum of Science. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micrograph
A micrograph or photomicrograph is a photograph or digital image taken through a microscope or similar device to show a 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 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 as ''photomicroscopy''. At a basic level, photomicroscopy may be performed simply by connecting a camera to a microscope, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sublimation (phase Transition)
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. Sublimation is an endothermic process that occurs at temperatures and pressures below a substance's triple point in its phase diagram, which corresponds to the lowest pressure at which the substance can exist as a liquid. The reverse process of sublimation is deposition or desublimation, in which a substance passes directly from a gas to a solid phase. Sublimation has also been used as a generic term to describe a solid-to-gas transition (sublimation) followed by a gas-to-solid transition ( deposition). While vaporization from liquid to gas occurs as evaporation from the surface if it occurs below the boiling point of the liquid, and as boiling with formation of bubbles in the interior of the liquid if it occurs at the boiling point, there is no such distinction for the solid-to-gas transition which always occurs as sublimation from the surface. At ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrite (crystal)
A crystal dendrite is a crystal that develops with a typical multi-branching form. The name comes from the Greek word dendron (δενδρον) 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 and they f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snow Friction Vs Water Film Thickness--Colbeck
Snow comprises 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 climate is ... [...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 between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, or dispersants. The word "surfactant" is a blend of ''surface-active agent'', coined . Agents that increase surface tension are "surface active" in the literal sense but are not called surfactants as their effect is opposite to the common meaning. A common example of surface tension increase is salting out: by adding an inorganic salt to an aqueous solution of a weakly polar substance, the substance will precipitate. The substance may itself be a surfactant – this is one of the reasons why many surfactants are ineffective in sea water. Composition and structure Surfactants are usually organic compounds that are amphiphilic, meaning each molecule contains both a hydrophilic "water-seeking" group (the ''head''), and a hydro ... [...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 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. It is distinct from kerosene and other petroleum products that are sometimes called paraffin. Un-dyed, unscented paraffin candles are odorless and bluish-white. Paraffin wax was first created by 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'' (" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
