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A surface derived by geodetic means and taken as a surface of reference from which to reckon geodetic elevations. Also called VERTICAL DATUM, VERTICAL
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A surface derived by geodetic means and taken as a surface of reference from which to reckon geodetic elevations. Also called VERTICAL DATUM, VERTICAL
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Related Terms |
FLASH POINTThe lowest temperature at which a liquid gives off sufficient vapor to form a flammable mixture with air near the surface of the liquid. The flashpoint temperature is determined by laboratory testing in a prescribed apparatus. Establishes the danger point when transferring, pumping, and firing procedures are concerned. |
POLISHING
1. In petroleum refining, removal of final traces of impurities, as for a lubricant, by clay adsorption or mild hydrogen treating. Smoothing and brightening a surface such as a metal or a rock through the use of abrasive materials.
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POISON
A material which reduces the emission of electrons from the surface of a cathode.
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POINT CONTACT
A contact between a specially prepared semiconductor surface and a metal point, usually maintained by mechanical periphery.
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POINCARE SURFACE OF SECTION
A method of displaying the character of a particular trajectory without examining its complete time development, in which the trajectory is sampled periodically, and the rate of change of a quantity under study is plotted against the value of that quantity at the beginning of each period. Also known as surface of section.
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POINT-CONTACT DIODE
A semiconductor rectifier that uses the barrier formed between a specially prepared semiconductor surface and a metal point to produce the rectifying action.
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PLATEN
1.A flat plate against which something rests or is pressed. 2. The rubber-covered roller of a typewriter against which paper is pressed when struck by the typebars. 2. A flat surface for exchanging heat in a boiler or heat exchanger which may have extended heat transfer surfaces.
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PLANISHING
Smoothing the surface of a metal by a rapid series of overlapping, light hammerlike blows or by rolling in a planishing mill.
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PLASTER SHOOTING
A surface blasting method used when no rock drill is necessary or one is not available; consists of placing a charge of gelignite, primed with safety fuse and detonator, in close contact with the rock or boulder and covering it completely with stiff damp clay.
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PLASMA-SOURCE ION IMPLANTATION
A method of ion implantation in which the workpiece is placed in a plasma containing the appropriate ion species and is repetitively pulse-biased to a high negative potential so that positive plasma ions are accelerated to the surface and implant in the bulk material. Abbreviated PSII.
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