- 行业: Printing & publishing
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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A Hausdorff topological space with an <i>n</i>-dimensional atlas of charts for some integer <i>n</i>. The integer <i>n</i> is called the dimension of the manifold. If <i>M</i> is a Hausdorff space, an <i>n</i>-chart on <i>M</i> is a pair (<i>U</i>, ϕ) with <i>U</i> an open subset of <i>M</i> and ϕ a homeomorphism of <i>U</i> onto an open subset ϕ(<i>U</i>) of <i>n</i>-dimensional euclidean space <b>R</b><sup><i>n</i></sup>. An <i>n</i>-dimensional atlas for <i>M</i> is a system of <i>n</i>-charts (<i>U</i>, ϕ) such that the union of the sets <i>U</i> is all of <i>M</i>.
Industry:Science
A heart-shaped curve generated by a point of a circle that rolls (without slipping) on a fixed circle of the same diameter. In point-wise construction of the curve, let <i>O</i> be a fixed point of a circle <i>C</i> of diameter <i>a</i>, and <i>Q</i> a variable point of <i>C</i>. Lay off distance <i>a</i> along the secant <i>OQ</i>, in both directions from <i>Q</i>. The locus of the two points thus obtained is a cardioid (see <b>illus.</b>).If a rectangular coordinate system is chosen with <i>O</i> for origin initially and <i>y</i> axis tangent to <i>C</i> at <i>O</i>, the cardioid has the equation (<i>x</i><sup>2</sup> + <i>y</i><sup>2</sup> − <i>ax</i>)<sup>2</sup> = <i>a</i><sup>2</sup>(<i>x</i><sup>2</sup> + <i>y</i><sup>2</sup>). The equation expressed in polar coordinates is ρ = <i>a</i>(1 + cos θ). The cardioid's area is 3/2π<i>a</i><sup>2</sup>, or six times the area of <i>C</i>, and its length is 8<i>a</i>.
Industry:Science
A heating system for a building in which the heat-conveying medium is hot water. Heat transfer in British thermal units (Btu) equals pounds of water circulated times drop in temperature of water. For other liquids, the equation should be modified by specific heats. The system may be modified to provide cooling.
Industry:Science
A heating system that uses steam generated from a boiler. The steam heating system conveys steam through pipes to heat exchangers, such as radiators, convectors, baseboard units, radiant panels, or fan-driven heaters, and returns the resulting condensed water to the boiler. Such systems normally operate at pressure not exceeding 15 lb/in.<sup>2</sup> gage or 103 kilopascals gage, and in many designs the condensed steam returns to the boiler by gravity because of the static head of water in the return piping. With utilization of available operating and safety control devices, these systems can be designed to operate automatically with minimal maintenance and attention.
Industry:Science
A heat-transfer device that reduces a thermodynamic fluid from its vapor phase to its liquid phase. The vapor condenser extracts the latent heat of vaporization from the vapor, as a higher-temperature heat source, by absorption in a heat-receiving fluid of lower temperature. The vapor to be condensed may be wet, saturated, or superheated. The heat receiver is usually water but may be a fluid such as air, a process liquid, or a gas. When the condensing of vapor is primarily used to add heat to the heat-receiving fluid, the condensing device is called a heater and is not within the normal classification of a condenser.
Industry:Science
A heat-transfer device used for condensing steam to water by removal of the latent heat of steam and its subsequent absorption in a heat-receiving fluid, usually water, but on occasion air or a process fluid. Steam condensers may be classified as contact or surface condensers.
Industry:Science
A heat-transfer device used to condense a vapor, usually steam, by absorbing its latent heat in a cooling fluid, ordinarily water. Most surface condensers consist of a chamber containing a large number of 0.5–1-in.-diameter (1.25–2.5-cm) corrosion-resisting alloy tubes through which cooling water flows. The vapor contacts the outside surface of the tubes and is condensed on them. The tubes are arranged so that the cooling water passes through the vapor space one or more times. About 90% of the surface is used for condensing vapor and the remaining 10% for cooling noncondensable gases. Air coolers are normally an integral part of the condenser but may be separate and external to it. The condensate is removed by a condensate pump and the noncondensables by a vacuum pump.
Industry:Science
A heavier-than-air vehicle designed to use the pressures created by its motion through the air to lift and transport useful loads. Although airplanes exist in many forms adapted for diverse purposes, they all employ power to overcome the aerodynamic resistance, termed drag, thereby achieving forward motion through the air. The air flowing over specially designed wing surfaces produces pressure patterns which are dependent upon the shape of the surface, angle at which the air approaches the wing, physical properties of the air, and velocity. These pressure patterns acting over the wing surface produce the lift force necessary for flight.
Industry:Science
A heavily armored mammal in the family Dasypodidae, order Cingulata (previously Edentates or Xenarthra). Armadillos are characterized by bony dermal plates, which help to protect their bodies. Being mammals, they do have hair, but it is usually sparse and often quite inconspicuous. The anterior and posterior parts of the body are often heavily armored, whereas the midportion of the body is often encircled or partially encircled by rings. These rings are used taxonomically in describing and identifying many of the species of armadillos. The skin of the ventral part of the body is soft. The toes are clawed and used to burrow and dig for food. The hindlimbs always have five toes with claws; the forelimbs may have three, four, or five heavy claws used for digging. The snout is long, and the cylindrical viscous tongue is used in capturing food. The teeth are simple pegs with no roots and no enamel. Most species have about 14 to 18 teeth, but the giant armadillo, <i>Priodontes maximus</i>, has about 80 to 100 small teeth. It reaches a length of approximately 10 feet (3 m), whereas the smallest species, the fairy armadillo, <i>Chlamyphorus truncatus</i>, is about 5–6 in. (12–15 cm) long. When disturbed, many species roll into a ball or wedge themselves into a burrow opening, with the dermal plates helping to protect them.
Industry:Science
A heavy, dark-colored, phaneritic (visibly crystalline) igneous rock composed largely of pyroxene with smaller amounts of olivine or hornblende. Pyroxenite composed largely of orthopyroxene occurs with anorthosite and peridotite in large, banded gabbro bodies. These rocks are formed by crystallization of gabbroic magma (rock melt). Some of these pyroxenite masses are rich sources of chromium. Certain pyroxenites composed largely of clinopyroxene are also of magmatic origin, but many probably represent products of reaction between magma and limestone. Other pyroxene-rich rocks have formed through the processes of metamorphism and metasomatism.
Industry:Science
