Regelation
Regelation is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced. This can be demonstrated by looping a fine wire around a block of ice, with a heavy weight attached to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire's track will refill as soon as pressure is relieved, so the ice block will remain intact even after wire passes completely through. This experiment is possible for ice at −10 °C or cooler, and while essentially valid, the details of the process by which the wire passes through the ice are complex. The phenomenon works best with high thermal conductivity materials such as copper, since latent heat of fusion from the top side needs to be transferred to the lower side to supply latent heat of melting. In short, the phenomenon in which ice converts to liquid due to applied pressure and then re-converts to ice once the pressure is removed is called reg ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ice Skating
Ice skating is the Human-powered transport, self-propulsion and gliding of a person across an ice surface, using metal-bladed ice skates. People skate for various reasons, including recreation (fun), exercise, competitive sports, and commuting. Ice skating may be performed on naturally frozen bodies of water, such as ponds, lakes, canals, and rivers, and on human-made ice surfaces both indoors and outdoors. Natural ice surfaces used by skaters can accommodate a variety of winter sports which generally require an enclosed area, but are also used by skaters who need Ice rink#Tracks and trails, ice tracks and trails for Tour skating, distance skating and speed skating. Man-made ice surfaces include ice rinks, ice hockey rinks, bandy fields, ice tracks required for the sport of ice cross downhill, and arenas. Various formal sports involving ice skating have emerged since the 19th century. Ice hockey, bandy, rinkball, and ringette are team sports played with, respectively, a flat sl ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Premelting
Premelting (also surface melting) refers to a quasi-liquid film that can occur on the surface of a solid even below melting point (T_m). The thickness of the film is temperature (T) dependent. This effect is common for all crystalline materials. Premelting shows its effects in frost heave, and, taking grain boundary interfaces into account, maybe even in the movement of glaciers. Considering a solid-vapour interface, complete and incomplete premelting can be distinguished. During a temperature rise from below to above T_m , in the case of complete premelting, the solid melts homogeneously from the outside to the inside; in the case of incomplete premelting, the liquid film stays very thin during the beginning of the melting process, but droplets start to form on the interface. In either case, the solid always melts from the outside inwards, never from the inside. History The first to mention premelting might have been Michael Faraday in 1842 for ice surfaces. He compared the ef ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Atmosphere (unit)
The standard atmosphere (symbol: atm) is a unit of pressure defined as Pa. It is sometimes used as a ''reference pressure'' or ''standard pressure''. It is approximately equal to Earth's average atmospheric pressure at sea level. History The standard atmosphere was originally defined as the pressure exerted by a 760 mm column of mercury at and standard gravity (''g''n = ). It was used as a reference condition for physical and chemical properties, and the definition of the centigrade temperature scale set 100 °C as the boiling point of water at this pressure. In 1954, the 10th General Conference on Weights and Measures (CGPM) adopted ''standard atmosphere'' for general use and affirmed its definition of being precisely equal to dynes per square centimetre (). This defined pressure in a way that is independent of the properties of any particular substance. In addition, the CGPM noted that there had been some misapprehension that the previous definition (from the 9th ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Glacier
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land“Glacier, N., Pronunciation.” Oxford English Dictionary, Oxford UP, June 2024, https://doi.org/10.1093/OED/7553486115. Accessed 25 Jan. 2025. and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions, but glaciers may be found in mountain ranges on ever ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Snow
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 Sublimation (phase transition), sublimate away. Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes Nucleation, nucleate around particles in the atmosphere by attracting supercooling, supercooled water droplets, which Freezing, freeze in hexagonal-shaped crystals. Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns, and Hard rime, rime. As snow accumulates into a snowpack, it may blow into drifts. Over time, accumulated snow m ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Cold Compaction
Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes are sometimes used to reduce or eliminate the need for subtractive processes in manufacturing, lowering material losses and reducing the cost of the final product. This occurs especially often with small metal parts, like gears for small machines. Some porous products, allowing liquid or gas to permeate them, are produced in this way. They are also used when melting a material is impractical, due to it having a high melting point, or an alloy of two mutually insoluble materials, such as a mixture of copper and graphite. In this way, powder metallurgy can be used to make unique materials impossible to get from melting or forming in other ways. A very important product of this type is tungsten carbide. Tungsten carbide is used to cut and form other metals and is made from tungsten carbide particles bonded with cobalt. Tungsten carbide is the lar ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ice Skate
Ice skates are metal blades attached underfoot and used to propel the bearer across a sheet of ice while ice skating. The first ice skates were made from leg bones of horse, ox or deer, and were attached to feet with leather straps. These skates required a pole with a sharp metal spike that was used for pushing the skater forward, unlike modern bladed skates. Modern skates come in many different varieties, each suited to specific conditions or activities. People across the globe wear skates recreationally in ice rinks or on frozen bodies of water, and skates are the standard footwear in many sports, including figure skating, bandy, ice hockey, ringette, rink bandy, rinkball, speed skating and tour skating. History According to a study done by Federico Formenti, University of Oxford, and Alberto Minetti, University of Milan, Finns were the first to develop ice skates some 5,000 years ago from animal bones. This was important for the Finnish populations to save energy in harsh ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Weight
In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weight as a scalar quantity, the magnitude of the gravitational force. Yet others define it as the magnitude of the reaction (physics), reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: so if one ignores Drag (physics), air resistance, one could say the legendary apple falling from the tree, on its way to meet the ground near Isaac Newton, was weightless. The unit of measurement fo ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and even by industry. Further, both spellings are often used ''within'' a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling. is the pressure relative to the ambient pressure. Various #Units, units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the International System of Units, SI unit of pressure, the Pascal (unit), pascal (Pa), for example, is one newton (unit), newton per square metre (N/m2); similarly, the Pound (force), pound-force per square inch (Pound per square inch, psi, symbol lbf/in2) is the traditional unit of pressure in the imperial units, imperial and United States customary units, US customary systems. Pressure ma ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Michael Faraday
Michael Faraday (; 22 September 1791 – 25 August 1867) was an English chemist and physicist who contributed to the study of electrochemistry and electromagnetism. His main discoveries include the principles underlying electromagnetic induction, diamagnetism, and electrolysis. Although Faraday received little formal education, as a self-made man, he was one of the most influential scientists in history. It was by his research on the magnetic field around a Electrical conductor, conductor carrying a direct current that Faraday established the concept of the electromagnetic field in physics. Faraday also established that magnetism could Faraday effect, affect rays of light and that there was an underlying relationship between the two phenomena. the 1911 ''Encyclopædia Britannica''. He similarly discovered the principles of electromagnetic induction, diamagnetism, and the Faraday's laws of electrolysis, laws of electrolysis. His inventions of electric motor, electromagnetic rotar ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |