- 行业: Printing & publishing
- Number of terms: 178089
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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 room whose boundaries absorb effectively all the waves incident on them, thereby providing free-field conditions. A free field is a field whose boundaries exert negligible effect on the incident waves. In practice, it is a field in which the effects of the boundaries are negligible over the frequency range of interest. Acoustic chambers and radio-frequency and microwave chambers will be discussed.
Industry:Science
A rotary tool used in drilling oil or gas wells in which the bit is rotated by a turbine motor inside the well. The principal difference between rotary and turbo drilling lies in the manner that power is applied to the rotating bit or cutting tool. In the rotary method, the bit is attached to a drill pipe, which is rotated through power supplied on the surface. In the turbodrill method, power is generated at the bottom of the hole by means of a mud-operated turbine.
Industry:Science
A rotating electric machine which delivers a unidirectional voltage and current. An armature winding mounted on the rotor supplies the electric power output. One or more field windings mounted on the stator establish the magnetic flux in the air gap. A voltage is induced in the armature coils as a result of the relative motion between the coils and the air gap flux. Faraday's law states that the voltage induced is determined by the time rate of change of flux linkages with the winding. Since these induced voltages are alternating, a means of rectification is necessary to deliver direct current at the generator terminals. Rectification is done by a commutator mounted on the rotor shaft.
Industry:Science
A rotating mass used to maintain the speed of a machine between given limits while the machine releases or receives energy at a varying rate. A flywheel is an energy storage device. It stores energy as its speed increases and gives up energy as the speed decreases. The specifications of the machine usually determine the allowable range of speed and the required energy interchange.
Industry:Science
A roughly spheroidal hollow body, lined on the inside with inward-projecting small crystals (see <b>illus.</b>). Geodes are found most frequently in limestone beds but may occur in some shales. Typically, a geode consists of a thin outer shell of dense chalcedonic silica and an inner shell of quartz crystals, sometimes beautifully terminated, pointing toward the hollow interior. Many geodes are filled with water; others, having been exposed for some time at the surface, are dry. Calcite or dolomite crystals line the interior of some geodes, and a host of other minerals are less commonly found. In some geodes there is an alternation of layers of silica and calcite, but almost all geodes show some banding suggestive of rhythmic precipitation.
Industry:Science
A rule for quantifying some characteristic or attribute of a computer software entity. For example, a simple one is the FileSize metric, which is the total number of characters in the source files of a program. The FileSize metric can be used to determine the measure of a particular program, such as 3K bytes. It provides a concrete measure of the abstract attribute of program size. Of course, there are better size metrics. The FileSize metric is used for source programs; other metrics can be used for software entities such as requirements documents, design object models, or database structure models. Metrics for requirements and design documents can be used to guide decisions about development and as a basis for predictions, such as for cost and effort. Metrics for programs can be used to support decisions about testing and maintenance and as a basis for comparing different versions of programs. Ideally, metrics for the development cost of software and for the quality of the resultant program are desirable; but, lacking those, metrics for size and complexity are commonly used.
Industry:Science
A ruminant, <i>Rangifer tarandus</i>, of the deer family, Cervidae. Caribou inhabit the Arctic region and have a circumpolar distribution. In Europe, caribou are called reindeer; in North America (Alaska and Canada), only the domestic forms are called reindeer. All caribou and reindeer throughout the world are considered to be the same species, although reindeer are slightly smaller. They have been domesticated for centuries and are economically important to the Laplanders, who use them as draft animals as well as for their skins, flesh, and milk. The Laplanders are nomadic people who migrate during the summer months with their herds from one feeding ground to another.
Industry:Science
A salt containing the negative ion S<sub>2</sub>O<sub>3</sub><sup>2−</sup>. This species is an important reducing agent and may be viewed as a structural analog of the sulfate ion (SO<sub>4</sub><sup>2−</sup>) where one of the oxygen (O) atoms has been replaced by a sulfur (S) atom. The sulfur atoms of the thiosulfate ion are not equivalent. Thiosulfate is tetrahedral, and the central sulfur is in the formal oxidation state 6+ and the terminal sulfur is in the formal oxidation state 2−.
Industry:Science
A scalar physical quantity indicating a one-dimensional extension in space. Length is one of the three fundamental physical quantities important in mechanics, the other two being mass and time. It can be measured by comparison with an arbitrary standard; the specific one in common usage is the international meter. The most recent definition of the meter was adopted in 1983 at the meeting of the General Conference on Weights and Measures (Conférence Général des Poids et Mesures, or CPGM), when the meter was redefined in terms of time and the speed of light: “The meter is the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.” The effect was to take the speed of light in a vacuum to be exactly 299,792,458 m/s and then to define the meter in terms of that speed and the most accurately known quantity, the second.
Industry:Science
A scenario for the transition of a natural process from regular motion to chaos. Various natural processes develop in time in a way that depends upon prevailing environmental details. A quantity that specifies the particular state of the environment of a process is called a parameter, and is taken as a fixed value over the course of development of the process. It is a frequent natural occurrence for a process to have a regular and easily describable motion for some range of parameters, but to have complex, irregular, and difficult-to-describe motions for other ranges of parameters. In the context of fluid flow, the latter circumstance is termed turbulence. In a more general context it is called chaos (which includes fluid turbulence but presages an underlying generality).
Industry:Science
