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Ultra-high vacuum (often spelled ultrahigh in American English, UHV) is the vacuum regime characterised by pressures lower than about 1 × 10 −6 pascals (1.0 × 10 −8 mbar; 7.5 × 10 −9 Torr). UHV conditions are created by pumping the gas out of a UHV chamber.
UHV may refer to: Ultra-high vacuum, the vacuum regime characterised by pressures lower than about 10 −7 pascal; Ultra-high voltage, a classification of overhead power line with an operating voltage of higher than 800 kV; University of Houston–Victoria, a university in Victoria, Texas, US
Ion pumps are commonly used in ultra-high vacuum (UHV) systems, as they can attain ultimate pressures less than 10 −11 mbar. [1] In contrast to other common UHV pumps, such as turbomolecular pumps and diffusion pumps, ion pumps have no moving parts and use no oil. They are therefore clean, need little maintenance, and produce no vibrations.
The langmuir (symbol: L) is a unit of exposure (or dosage) to a surface (e.g. of a crystal) and is used in ultra-high vacuum (UHV) surface physics to study the adsorption of gases. It is a practical unit, and is not dimensionally homogeneous, and so is used only in this field. It is named after American physicist Irving Langmuir.
Today the U.S. economy generates about a quarter of global output. U.S. stocks account for 65% of global equities, while Japan, China and the United Kingdom combined account for just over 10%.
UHV transmission and a number of UHVAC circuits have already been constructed in different parts of the world. For example, 2,362 km of 1,150 kV circuits were built in the former USSR, and 427 km of 1,000 kV AC circuits have been developed in Japan (Kita-Iwaki powerline). Experimental lines of various scales are also found in many countries. [7]
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