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OFHC
Oxygen-free copper (OFC) or oxygen-free high thermal conductivity (OFHC) copper is a group of wrought high-conductivity copper alloys that have been electrolytically refined to reduce the level of oxygen to 0.001% or below. Specification Oxygen-free copper is typically specified according to the ASTM/ UNS database. The UNS database includes many different compositions of high conductivity electrical copper. Of these, three are widely used and two are considered oxygen-free: * C10100 – also known as ''oxygen-free electronic'' (OFE). This is a 99.99% pure copper with 0.0005% oxygen content. It achieves a minimum 101% IACS conductivity rating. This copper is finished to a final form in a carefully regulated, oxygen-free environment. Silver (Ag) is considered an impurity in the OFE chemical specification. This is also the most expensive of the three grades listed here. * C10200 – also known as ''oxygen-free'' (OF). While OF is considered oxygen-free, its conductivity rating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra-high Vacuum
Ultra-high vacuum (UHV) is the vacuum regime characterised by pressures lower than about . UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately 40 km, so the gas is in free molecular flow, and gas molecules will collide with the chamber walls many times before colliding with each other. Almost all molecular interactions therefore take place on various surfaces in the chamber. UHV conditions are integral to scientific research. Surface science experiments often require a chemically clean sample surface with the absence of any unwanted adsorbates. Surface analysis tools such as X-ray photoelectron spectroscopy and low energy ion scattering require UHV conditions for the transmission of electron or ion beams. For the same reason, beam pipes in particle accelerators such as the Large Hadron Collider are kept at UHV. Overview Maintaining UHV conditions requires the use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram (compare copper at about 0.06 grams). In minerals, phosphorus generally occurs as phosphate. Elemental phosphorus was first isolated as white phosphorus in 1669. White phosphorus emits a faint glow when exposed to oxygen – hence the name, taken from Greek mythology, meaning 'light-bearer' (Latin ), referring to the " Morning Star", the planet Venus. The term '' phosphorescence'', meaning glow after illumination, derives from this property of phosphorus, although the word has since been used for a different physical process that produces a glow. The glow of phosphorus is caused by oxidation of the white (but not red) phosphorus — a process now called chem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Home Cinema
Home cinema, also called home theaters or theater rooms, are home entertainment audio-visual systems that seek to reproduce a movie theater experience and mood using consumer electronics-grade video and audio equipment that is set up in a room or backyard of a private home. Some studies show films are rated better and generate more intense emotions when watched in a movie theater, however, convenience is a major appeal for home cinemas. In the 1980s, home cinemas typically consisted of a movie pre-recorded on a LaserDisc or VHS tape; a LaserDisc Player or VCR; and a heavy, bulky large-screen cathode ray tube TV set, although sometimes CRT projectors were used instead. In the 2000s, technological innovations in sound systems, video player equipment and TV screens and video projectors have changed the equipment used in home cinema set-ups and enabled home users to experience a higher-resolution screen image, improved sound quality and components that offer users more options (e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Signal
An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals, or a series of binary numbers for digital signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal back into sound. Digital audio systems represent audio signals in a variety of digital formats.Hodgson, Jay (2010). ''Understanding Records'', p.1. . An audio channel or audio track is an audio signal communications channel in a storage device or mixing console, used in operations such as multi-track recording and sound reinforcement. Signal flow Signal flow is the path an audio signal will take from source to the sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speaker Wire
Speaker wire is used to make the electrical connection between loudspeakers and audio amplifiers. Modern speaker wire consists of two or more electrical conductors individually insulated by plastic (such as PVC, PE or Teflon) or, less commonly, rubber. The two wires are electrically identical, but are marked to identify the correct audio signal polarity. Most commonly, speaker wire comes in the form of zip cord. The effect of speaker wire upon the signal it carries has been a much-debated topic in the audiophile and high fidelity worlds. The accuracy of many advertising claims on these points has been disputed by expert engineers who emphasize that simple electrical resistance is by far the most important characteristic of speaker wire. History Early speaker cable was typically stranded copper wire, insulated with cloth tape, waxed paper or rubber. For portable applications, common lampcord was used, twisted in pairs for mechanical reasons. Cables were often soldered in plac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Accelerators
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle physics. The largest accelerator currently active is the Large Hadron Collider (LHC) near Geneva, Switzerland, operated by the CERN. It is a collider accelerator, which can accelerate two beams of protons to an energy of 6.5 TeV and cause them to collide head-on, creating center-of-mass energies of 13 TeV. Other powerful accelerators are, RHIC at Brookhaven National Laboratory in New York and, formerly, the Tevatron at Fermilab, Batavia, Illinois. Accelerators are also used as synchrotron light sources for the study of condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including particle therapy for oncological purposes, radioisotope production for medical diagnostics, ion imp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconductivity
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. 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. The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the sup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Semiconductors
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glass. Its electrical resistivity and conductivity, resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping (semiconductor), doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second-most common s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sputtering
In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and can be an unwelcome source of wear in precision components. However, the fact that it can be made to act on extremely fine layers of material is utilised in science and industry—there, it is used to perform precise etching, carry out analytical techniques, and deposit thin film layers in the manufacture of optical coatings, semiconductor devices and nanotechnology products. It is a physical vapor deposition technique. Physics When energetic ions collide with atoms of a target material, an exchange of momentum takes place between them. These ions, known as "incident ions", set off collision cascades in the target. Such cascades can take many paths; some recoil back toward the surface of the target. If a collision cascade reaches the surfac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smelting
Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind. The reducing agent is commonly a fossil fuel source of carbon, such as coke—or, in earlier times, charcoal. The oxygen in the ore binds to carbon at high temperatures due to the lower potential energy of the bonds in carbon dioxide (). Smelting most prominently takes place in a blast furnace to produce pig iron, which is converted into steel. The carbon source acts as a chemical reactant to remove oxygen from the ore, yielding the purified metal element as a product. The carbon source is oxidized in two stages. First, the carbon (C) combusts with oxygen (O2) in the air to produce carbon monoxide (CO). Second, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
