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Degauss
Degaussing is the process of decreasing or eliminating a remnant magnetic field. It is named after the gauss, a unit of magnetism, which in turn was named after Carl Friedrich Gauss. Due to magnetic hysteresis, it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small "known" field referred to as bias. Degaussing was originally applied to reduce ships' magnetic signatures during World War II. Degaussing is also used to reduce magnetic fields in cathode ray tube monitors and to destroy data held on magnetic storage. Ships' hulls The term was first used by then-Commander Charles F. Goodeve, Royal Canadian Naval Volunteer Reserve, during World War II while trying to counter the German magnetic naval mines that were wreaking havoc on the British fleet. The mines detected the increase in the magnetic field when the steel in a ship concentrated the Earth's magnetic field over it. Admiralty scientists, including Goo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Cathode Ray Tube
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms (oscilloscope), pictures ( television set, computer monitor), radar targets, or other phenomena. A CRT on a television set is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term '' cathode ray'' was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons. In CRT television sets and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Naval Mine
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel or a particular vessel type, akin to anti-infantry vs. anti-vehicle mines. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake an expensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered. Although international law requires signatory nations to declare mined areas, precise locations remain secret; and non-complying individuals ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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USS Deperm (ADG-10)
USS ''Deperm'' (ADG-10) was a degaussing vessel of the United States Navy, named after the term '' deperm'', a procedure for erasing the permanent magnetism from ships and submarines to camouflage them against magnetic detection vessels and enemy marine mines. Originally planned as a patrol craft escort (PCE-883), she was laid down in 1943, launched in 1944, and commissioned in 1945. She was subsequently redesignated a degaussing vessel, YDG-10, and named ''Deperm''. Struck from the Naval Register A Navy Directory, formerly the Navy List or Naval Register is an official list of naval officers, their ranks and seniority, the ships which they command or to which they are appointed, etc., that is published by the government or naval autho ... 21 February 1975, ''Deperm'' was sunk as a target 22 September 1982 at . According to the available depth data in 2020, at this location the bottom is between 1250m and 1500m along the edge of a basin. References * Shipwrecks of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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List Of Auxiliaries Of The United States Navy
This is a list of auxiliaries of the United States Navy. It covers the various types of ships that support the frontline combat vessels of the United States Navy. Ship status is indicated as either currently active (including ready reserve), inactive or precommissioning Ships in the inactive category include only ships in the inactive reserve, ships which have been disposed from US service have no listed status. Ships in the precommissioning category include ships under construction or on order. Crane Ships (AB) * USS ''Kearsarge'' (AB-1), ex-BB-5 Colliers (AC) * USS ''Hannibal'' (1898) * USS ''Justin'' (1898) * USS ''Leonidas'' (1898) * USS ''Marcellus'' (1879) * USS ''Merrimac'' (1898) * USS ''Quincy'' (1918) * USS ''Saturn'' (1898) * USS ''Southery'' (1898) * USS ''Sterling'' (1898) * USS ''Vestal'' (AC-1), later AR-4 * USS ''Ontario'' (AC-2), later AR-3 * USS ''Jupiter'' (AC-3), later CV-1, AV-3 * USS ''Cyclops'' (AC-4), lost March 1918 * USS ''Vulcan' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Magnetic Hysteresis
Magnetic hysteresis occurs when an external magnetic field is applied to a ferromagnet such as iron and the atomic dipoles align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become ''magnetized''. Once magnetized, the magnet will stay magnetized indefinitely. To demagnetize it requires heat or a magnetic field in the opposite direction. This is the effect that provides the element of memory in a hard disk drive. The relationship between field strength and magnetization is not linear in such materials. If a magnet is demagnetized () and the relationship between and is plotted for increasing levels of field strength, follows the ''initial magnetization curve''. This curve increases rapidly at first and then approaches an asymptote called magnetic saturation. If the magnetic field is now reduced monotonically, follows a different curve. At zero field strength, the magnetization is offset from the origin by an am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Ampere
The ampere (, ; symbol: A), often Clipping (morphology), shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to electrons worth of charge moving past a point in a second. It is named after France, French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Denmark, Danish physicist Hans Christian Ørsted. As of the 2019 redefinition of the SI base units, the ampere is defined by fixing the elementary charge to be exactly C (coulomb), which means an ampere is an electrical current equivalent to elementary charges moving every seconds or elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current that would need to be passed through 2 parallel wires 1 metre apart to produce a magnetic force of Newton (unit), newtons per me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Dunkirk Evacuation
The Dunkirk evacuation, codenamed Operation Dynamo and also known as the Miracle of Dunkirk, or just Dunkirk, was the evacuation of more than 338,000 Allied soldiers during the Second World War from the beaches and harbour of Dunkirk, in the north of France, between 26 May and 4 June 1940. The operation commenced after large numbers of Belgian, British, and French troops were cut off and surrounded by German troops during the six-week Battle of France. In a speech to the House of Commons, British Prime Minister Winston Churchill called this "a colossal military disaster", saying "the whole root and core and brain of the British Army" had been stranded at Dunkirk and seemed about to perish or be captured. In his " We shall fight on the beaches" speech on 4 June, he hailed their rescue as a "miracle of deliverance". After Germany invaded Poland in September 1939, France and the British Empire declared war on Germany and imposed an economic blockade. The British Expediti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of its active battle fleet alone exceeding the next 13 navies combined, including 11 allies or partner nations of the United States as of 2015. It has the highest combined battle fleet tonnage (4,635,628 tonnes as of 2019) and the world's largest aircraft carrier fleet, with eleven in service, two new carriers under construction, and five other carriers planned. With 336,978 personnel on active duty and 101,583 in the Ready Reserve, the United States Navy is the third largest of the United States military service branches in terms of personnel. It has 290 deployable combat vessels and more than 2,623 operational aircraft . The United States Navy traces its origins to the Continental Navy, which was established during the American Re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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High-temperature Superconductivity
High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previously known superconductors, which function at even colder temperatures close to absolute zero. In absolute terms, these "high temperatures" are still far below ambient, and therefore require cooling. The first high-temperature superconductor was discovered in 1986, by IBM researchers Bednorz and Müller, who were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-c materials are type-II superconductors. The major advantage of high-temperature superconductors is that they can be cooled by using liquid nitrogen, as opposed to the previously known superconductors which require expensive and hard-to-handle coolants, primarily liquid helium. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Magnetic Proximity Fuze
A magnetic proximity fuse was patented by P.J. Eliomarkakis, (United States Patent US2434551 of January 13, 1948) although similar devices had been in service for nearly a decade. It is a type of proximity fuze that initiates a detonator in a piece of ordnance such as a land mine, naval mine, depth charge, or shell when the fuse's magnetic equilibrium is upset by a magnetic object such as a tank or a submarine. Magnetic field sensors and movement sensors inside the ordnance detect changes to the terrestrial magnetic field of the ordnance caused by another ferromagnetic object. A signal processor inside the ordnance receives the signals from the magnetic field sensors and movement sensors and activates the detonator which will then detonate the explosives within the ordnance. Examples Examples of pieces of ordnance that employ a magnetic fuze include: * the Chinese Chen-2 bottom mine * the Egyptian T-93 mine See also * Proximity sensor * Reed switch * Precision bombing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Cruiser
A cruiser is a type of warship. Modern cruisers are generally the largest ships in a fleet after aircraft carriers and amphibious assault ships, and can usually perform several roles. The term "cruiser", which has been in use for several hundred years, has changed its meaning over time. During the Age of Sail, the term ''cruising'' referred to certain kinds of missions—independent scouting, commerce protection, or raiding—fulfilled by frigates or sloops-of-war, which functioned as the ''cruising warships'' of a fleet. In the middle of the 19th century, ''cruiser'' came to be a classification of the ships intended for cruising distant waters, for commerce raiding, and for scouting for the battle fleet. Cruisers came in a wide variety of sizes, from the medium-sized protected cruiser to large armored cruisers that were nearly as big (although not as powerful or as well-armored) as a pre-dreadnought battleship. With the advent of the dreadnought battleship before Wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |