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Electrical engineering is an engineering discipline concerned with the study, design and application of equipment, devices and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the latter half of the 19th century after commercialization of the electric telegraph, the telephone, and electrical power generation, distribution and use.
Superconductivity is the set of physical properties observed in certain materials, wherein electrical resistance vanishes and from which magnetic flux fields are expelled. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source.
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.
The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state when it is cooled below the critical temperature. The German physicists Walther Meissner and Robert Ochsenfeld discovered this phenomenon in 1933 by measuring the magnetic field distribution outside superconducting tin and lead samples. The samples, in the presence of an applied magnetic field, were cooled below their superconducting transition temperature, whereupon the samples cancelled nearly all interior magnetic fields. They detected this effect only indirectly because the magnetic flux is conserved by a superconductor: when the interior field decreases, the exterior field increases. The experiment demonstrated for the first time that superconductors were more than just perfect conductors and provided a uniquely defining property of the superconductor state. The ability for the expulsion effect is determined by the nature of equilibrium formed by the neutralization within the unit cell of a superconductor.
Electrical resistivity and its inverse, electrical conductivity, is a fundamental property of a material that quantifies how strongly it resists or conducts electric current. A low resistivity indicates a material that readily allows electric current. Resistivity is commonly represented by the Greek letter ρ (rho). The SI unit of electrical resistivity is the ohm-meter (Ω⋅m). For example, if a 1 m × 1 m × 1 m solid cube of material has sheet contacts on two opposite faces, and the resistance between these contacts is 1 Ω, then the resistivity of the material is 1 Ω⋅m.
The Royal Radar Establishment was a research center in Malvern, Worcestershire in the United Kingdom. It was formed in 1953 as the Radar Research Establishment by the merger of the Air Ministry's Telecommunications Research Establishment (TRE) and the British Army's Radar Research and Development Establishment (RRDE). It was given its new name after a visit by Queen Elizabeth II in 1957. Both names were abbreviated to RRE. In 1976 the Signals Research and Development Establishment (SRDE), involved in communications research, joined the RRE to form the Royal Signals and Radar Establishment (RSRE).
The Schön scandal concerns German physicist Jan Hendrik Schön who briefly rose to prominence after a series of apparent breakthroughs with semiconductors that were later discovered to be fraudulent. Before he was exposed, Schön had received the Otto-Klung-Weberbank Prize for Physics and the Braunschweig Prize in 2001, as well as the Outstanding Young Investigator Award of the Materials Research Society in 2002, both of which were later rescinded.
Philip Warren Anderson is an American theoretical physicist and Nobel laureate. Anderson has made contributions to the theories of localization, antiferromagnetism, symmetry breaking, and high-temperature superconductivity, and to the philosophy of science through his writings on emergent phenomena.
Paul Ching Wu Chu, JP is a Chinese-American physicist specializing in superconductivity, magnetism, and dielectrics. He is a Professor of physics and T.L.L. Temple Chair of Science in the Physics Department at the University of Houston College of Natural Sciences and Mathematics. He was the President of the Hong Kong University of Science and Technology from 2001 to 2009. In 1987, he was one of the first scientists to demonstrate high-temperature superconductivity.
Superconductivity is the phenomenon of certain materials exhibiting zero electrical resistance and the expulsion of magnetic fields below a characteristic temperature. The history of superconductivity began with Dutch physicist Heike Kamerlingh Onnes's discovery of superconductivity in mercury in 1911. Since then, many other superconducting materials have been discovered and the theory of superconductivity has been developed. These subjects remain active areas of study in the field of condensed matter physics.
Niobium–tin is an intermetallic compound of niobium (Nb) and tin (Sn), used industrially as a type II superconductor. This intermetallic compound has a simple structure: A3B. It is more expensive than niobium-titanium (NbTi), but remains superconducting up to a magnetic flux density of 30 teslas [T] (300,000 G), compared to a limit of roughly 15 T for NbTi.
Charles Eryl Wynn-Williams, was a Welsh physicist, noted for his research on electronic instrumentation for use in nuclear physics. His work on the scale-of-two counter contributed to the development of the modern computer.
In chemistry, oxypnictides are a class of materials composed of oxygen, a pnictogen and one or more other elements. Although this group of compounds has been recognized since 1995, interest in these compounds increased dramatically after the publication of the superconducting properties of LaOFeP and LaOFeAs which were discovered in 2006 and 2008. In these experiments the oxide was partly replaced by fluoride.
Superconducting wires are wires made of superconductors. When cooled below their transition temperatures, they have zero electrical resistance. Most commonly, conventional superconductors such as niobium-titanium are used, but high-temperature superconductors such as YBCO are entering the market. Superconducting wire's advantages over copper or aluminum include higher maximum current densities and zero power dissipation. Its disadvantages include the cost of refrigeration of the wires to superconducting temperatures, the danger of the wire quenching, the inferior mechanical properties of some superconductors, and the cost of wire materials and construction. Its main application is in superconducting magnets, which are used in scientific and medical equipment where high magnetic fields are necessary.
Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two isotopes of helium when they are liquefied by cooling to cryogenic temperatures. It is also a property of various other exotic states of matter theorized to exist in astrophysics, high-energy physics, and theories of quantum gravity. Superfluidity is often coincidental with Bose–Einstein condensation, but neither phenomenon is directly related to the other; not all Bose-Einstein condensates can be regarded as superfluids, and not all superfluids are Bose–Einstein condensates. The semiphenomenological theory of superfluidity was developed by Lev Landau.
Akhoury Purnendu Bhusan Sinha is an Indian sold state chemist and a former head of the Physical Chemistry Division of the National Chemical Laboratory, Pune. He is known for his theories on semiconductors and his studies on synthesis of manganites. He is an elected fellow of the Indian National Science Academy and the Indian Academy of Sciences. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 1972, for his contributions to chemical sciences.
Biswa Ranjan Nag was an Indian physicist and the Sisir Kumar Mitra chair professor at University of Calcutta. Known for his research in semiconductor physics, Nag was an elected fellow of Indian National Science Academy and Indian Academy of Sciences. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards for his contributions to Physical Sciences in 1974.
Mohit Randeria is a US-based Indian condensed matter physicist and a professor of physics at Ohio State University. Known for his research on condensed matter theory and superconductivity, Randeria is an elected fellow of the American Physics Society. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, for his contributions to physical sciences in 2002.
Niobium disulfide is the chemical compound with the formula NbS2. It is a black layered solid that can be exfoliated into ultrathin grayish sheets similar to other transition metal dichalcogenides. These layers exhibit superconductivity, where the transition temperature increases from ca. 2 to 6 K with the layer thickness increasing from 6 to 12 nm, and then saturates with thickness.
References
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- ↑ Hoddeson, L.; Kolb, A.W.; Westfall, C. (2009). Fermilab: Physics, the Frontier, and Megascience. University of Chicago Press. p. 203. ISBN 978-0-226-34625-0 . Retrieved September 5, 2017.
- Seidel, P. (2015). Applied Superconductivity: Handbook on Devices and Applications. Encyclopedia of Applied Physics. Wiley. p. 495. ISBN 978-3-527-41209-9 . Retrieved September 5, 2017.
- Schilders, W.H.; Maten, E.J.W.; Houben, S.H.M.J. (2013). Scientific Computing in Electrical Engineering: Proceedings of the SCEE-2002 Conference held in Eindhoven. Mathematics in Industry. Springer Berlin Heidelberg. p. 174. ISBN 978-3-642-55872-6 . Retrieved September 5, 2017.
- Koshizuka, N.; Tajima, S. (2013). Advances in Superconductivity XI: Proceedings of the 11th International Symposium on Superconductivity (ISS '98), November 16–19, 1998, Fukuoka. Springer Japan. p. 1380. ISBN 978-4-431-66874-9 . Retrieved September 5, 2017.
