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Martin Knudsen
Martin Hans Christian Knudsen (February 15, 1871 in Hasmark on Funen – May 27, 1949 in Copenhagen) was a Danish physicist who taught and conducted research at the Technical University of Denmark. He is primarily known for his study of molecular gas flow and the development of the Knudsen cell, which is a primary component of molecular beam epitaxy systems. Knudsen received the University's gold medal in 1895 and earned his master's degree in physics the following year. He became lecturer in physics at the University in 1901 and professor in 1912, when Christian Christiansen (1843–1917) retired. He held this post until his own retirement in 1941. Knudsen was renowned for his work on kinetic-molecular theory and low-pressure phenomena in gases. His name is associated with the Knudsen flow, Knudsen diffusion, Knudsen number, Knudsen layer and Knudsen gases. Also there is the Knudsen equation; two instruments, the Knudsen absolute manometer and Knudsen gauge; and one g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knudsen Cell
In crystal growth, a Knudsen cell is an effusion evaporator source for relatively low partial pressure elementary sources (e.g. Ga, Al, Hg, As). Because it is easy to control the temperature of the evaporating material in Knudsen cells, they are commonly used in molecular-beam epitaxy. Development The Knudsen effusion cell was developed by Martin Knudsen (1871-1949). A typical Knudsen cell contains a crucible (made of pyrolytic boron nitride, quartz, tungsten or graphite), heating filaments (often made of metal tantalum), water cooling system, heat shields, and an orifice shutter. Vapor pressure measurement The Knudsen cell is used to measure the vapor pressures of a solid with very low vapor pressure. Such a solid forms a vapor at low pressure by sublimation. The vapor slowly effuses through the pinhole, and the loss of mass is proportional to the vapor pressure and can be used to determine this pressure.Peter Atkins and Julio de Paula, ''Physical Chemistry'' (8th ed., W.H.Freem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denmark
) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark , established_title = History of Denmark#Middle ages, Consolidation , established_date = 8th century , established_title2 = Christianization , established_date2 = 965 , established_title3 = , established_date3 = 5 June 1849 , established_title4 = Faroese home rule , established_date4 = 24 March 1948 , established_title5 = European Economic Community, EEC 1973 enlargement of the European Communities, accession , established_date5 = 1 January 1973 , established_title6 = Greenlandic home rule , established_date6 = 1 May 1979 , official_languages = Danish language, Danish , languages_type = Regional languages , languages_sub = yes , languages = German language, GermanGerman is recognised as a protected minority language in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States National Academy Of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the National Academy of Medicine (NAM). As a national academy, new members of the organization are elected annually by current members, based on their distinguished and continuing achievements in original research. Election to the National Academy is one of the highest honors in the scientific field. Members of the National Academy of Sciences serve '' pro bono'' as "advisers to the nation" on science, engineering, and medicine. The group holds a congressional charter under Title 36 of the United States Code. Founded in 1863 as a result of an Act of Congress that was approved by Abraham Lincoln, the NAS is charged with "providing independent, objective advice to the nation on matters related to science and technology. ... to provide scie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvay Conference
The Solvay Conferences (french: Conseils Solvay) have been devoted to outstanding preeminent open problems in both physics and chemistry. They began with the historic invitation-only 1911 Solvay Conference on Physics, considered a turning point in the world of physics, and continue to the present day. Following the initial success of 1911, they have since been organised by the International Solvay Institutes for Physics and Chemistry, founded by the Belgian industrialist Ernest Solvay in 1912 and 1913, and located in Brussels. The institutes coordinate conferences, workshops, seminars, and colloquia. Recent Solvay Conferences usually go through a three year cycle: the Solvay Conference on Physics, followed by a gap year, followed by the Solvay Conference on Chemistry. Notable Solvay conferences First conference Hendrik Lorentz was chairman of the first Solvay Conference on Physics, held in Brussels from 30 October to 3 November 1911. The subject was ''Radiation and the Quan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wyville Thompson Ridge
The Wyville Thomson Ridge is a bathymetric feature of the North Atlantic Ocean floor ca. 200 km in length, located between the Faroe Islands and Scotland. The ridge separates the Faroe–Shetland Channel to the north from the Rockall Trough to the south. Its significance lies in the fact that it forms part of the barrier between the colder bottom waters of the Arctic and the warmer waters of the North Atlantic. The Wyville Thomson Ridge is named after Charles Wyville Thomson who pioneered the first exploration of the area. Geology The Wyville Thomson Ridge, and the smaller but similar Ymir Ridge, form the northern boundary to the Rockall Basin, a mainly Mesozoic rift structure. The current form of the ridge is an anticline with up to 2 km of amplitude, formed by a period of shortening during the Eocene to Miocene period. This fold is interpreted to have formed by the reactivation of a pre-existing fault, and is, therefore, classified as an inversion Inversion or inver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe and Asia from the "New World" of the Americas in the European perception of the World. The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and North and South America to the west. As one component of the interconnected World Ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica). The Atlantic Ocean is divided in two parts, by the Equatorial Counter Current, with the North(ern) Atlantic Ocean and the South(ern) Atlantic Ocean split at about 8°N. Scientific explorations of the Atlantic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ingolf Expedition
HDMS ''Ingolf'' was a Danish schooner-rigged steam gunboat build in iron and launched in 1876. ''Ingolf'' marks a transition between the traditional gunships with muzzle-loading cannons placed along the sides of the ship and modern breechloading and turning guns placed in the centerline of the ship. The guns on ''Ingolf'' were breechloading guns from Krupp in Germany. The steam engine was British and could deliver 650 HP. The propeller could be hoisted up into a well on the underside of the ship, so as not to slow down the ship when she went for sails. ''Ingolf'' undertook a large number of voyages, often in the North Atlantic (Faroes, Iceland and Greenland) in summer and the Danish West Indies in winter. From 1897 ''Ingolf'' also served as training ship for non-commissioned officers and cadets. During World War I ''Ingolf'' was part of the Danish alerted fleet (not a true mobilization, as Denmark was neutral during the war). The last voyage as a training ship was in 1922 and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seawater
Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximately of dissolved salts (predominantly sodium () and chloride () ions). The average density at the surface is 1.025 kg/L. Seawater is denser than both fresh water and pure water (density 1.0 kg/L at ) because the dissolved salts increase the mass by a larger proportion than the volume. The freezing point of seawater decreases as salt concentration increases. At typical salinity, it freezes at about . The coldest seawater still in the liquid state ever recorded was found in 2010, in a stream under an Antarctic glacier: the measured temperature was . Seawater pH is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanography
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries. These diverse topics reflect multiple disciplines that oceanographers utilize to glean further knowledge of the world ocean, including astronomy, biology, chemistry, climatology, geography, geology, hydrology, meteorology and physics. Paleoceanography studies the history of the oceans in the geologic past. An oceanographer is a person who studies many matters concerned with oceans, including marine geology, physics, chemistry and biology. History Early history Humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knudsen Gauge
Knudsen may refer to: People Knudsen is a surname of Scandinavian origin, derived from the personal name Knud (Canute) and literally meaning "Knud's son." Notable people with the surname include: * Anthony Carl Knudsen (1874–1931), American businessman and politician * Gitte Moos Knudsen, Danish neurobiologist and neurologist *Gunnar Knudsen (1848–1928), Prime Minister of Norway 1908–1910 and 1913–1920 *Jens Martin Knudsen (1930–2005), Danish astrophysicist *Jens Martin Knudsen (born 1967), Faroese goalkeeper *Jesper Knudsen (badminton) (born 1960), Danish player * Karen Knudsen, American oncology researcher *Keith Knudsen (1948–2005), American musician, member of The Doobie Brothers *Knud Knudsen (linguist) (1812–1895), Norwegian linguist * Konrad Knudsen (1890–1959), Norwegian painter, journalist, and parliamentarian *Lars Knudsen (born 1962), Danish researcher in cryptography *Martin Knudsen (1871–1949), Danish physicist * Mort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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