- 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.
The elementary antiparticle of an electron with mass equal to that of an electron but with positive rather than negative charge. Its existence was theoretically predicted by P. A. M. Dirac in 1928. It was first observed by C. D. Anderson in 1932. Positrons and electrons have the same spin and statistics. Positrons are naturally produced by radioactive decay of many heavier particles; this is referred to as beta-plus decay. Electron-positron pairs are also produced when high-energy photons or electrons interact with matter.
Industry:Science
The acronym for sound fixing and ranging. The concept is based on finding the geographic location of sound that is created by an explosive or other impulsive event, such as a missile impact, by using the time of arrival of the signal at three or more receiving stations. This is known as hyperbolic fixing. This concept was used to locate aircraft that crashed at sea. Although other techniques have replaced this application, the term sofar channel has remained in use, referring to what is also known as the deep sound channel.
Industry:Science
The infraclass, also called Dipneusti, consisting of the lungfishes. The Dipnoi plus the fossil infraclass Porolepimorpha make up the subclass Dipnotetrapodomorpha, one of five subclasses of the class Sarcopterygii. The extant lungfishes are in two orders as follows:
* Order Ceratodontiformes, Family Ceratodontidae
* Order Lepidosireniformes, Family Lepidosirenidae (South American lungfishes), Protopteridae (African lungfishes)
Industry:Science
Standard patterns of radiation distribution about their source. The term radiation applies primarily to the transport of energy by acoustic, elastic, electromagnetic, or gravitational waves, and extends to the transport of atomic or subatomic particles (as represented by quantum-mechanical wave functions). The time dependence of radiation waves is generally analyzed into sinusoidal components with constant frequency ν and wavelength λ (equal to the wave velocity divided by ν), radiation sources being generally smaller than λ.
Industry:Science
The evolution of flower morphology is beginning to be understood through research on the genetic mechanisms of reproductive development in angiosperms (flowering plants). The model organism <i>Arabidopsis thaliana</i> (thale cress) has figured prominently in these studies. Although <i>Arabidopsis</i> was the first plant completely sequenced (in 2000), earlier genetic studies of <i>Arabidopsis</i> (beginning in the late 1980s) paved the way for evolutionary interpretations of the molecular processes underlying floral diversity.
Industry:Science
The field of engineering involving computer-based hardware and software systems, and communication systems, to enable the acquisition, representation, storage, transmission, and use of information. Successful implementation of information technology (IT) is dependent upon being able to cope with the overall architecture of systems, their interfaces with humans and organizations, and their relationships with external environments. It is also critically dependent on the ability to successfully convert information into knowledge.
Industry:Science
Sustained human life and activities rely on a wide variety of minerals and rocks as fuel and raw material for production of goods. Mining and processing methods have evolved through millennia of human experience with terrestrial deposits. If a Moon base is established to learn more about the lunar environment and the Solar System, to prepare for Mars missions, to intercept the asteroids, and to launch deep-space missions, materials will need to be mined from the local environment, for example, to provide water and probably air.
Industry:Science
The general property of directional discrimination displayed by systems that receive or emit waves. Thus, loudspeakers, microphones, radio antennas, underwater sound projectors, hydrophones, and even telescopes all have the common property that their effectiveness depends upon the direction from which the wave is either emitted or received. The manner in which a sender or receiver is directional depends largely upon its geometrical shape and, in particular, upon its dimensions compared to those of the wavelength involved (λ).
Industry:Science
The Global Positioning System (GPS) is a space-based source for accurate and reliable positioning, navigation, and timing data available anywhere on Earth, 24 h a day, 7 days a week. The use of GPS timing has rapidly increased, and it is currently part of the critical infrastructure of the United States. In particular, GPS timing is increasingly used as the primary reference timing source for network synchronization in industries such as telecommunications and power distribution. This has been the trend internationally as well.
Industry:Science
The horizontal or vertical aerodynamic wing surfaces that provide aircraft stability and longitudinal balance in flight. Horizontal and vertical stabilizers (fins) are similar to the aircraft wing in structural design and function of providing lift at angle of attack to the wind. However, stabilizers are not required to supply lift to overcome aircraft weight during flight, and when the wing-fuselage center of pressure is behind the aircraft center of gravity, the aerodynamic load on the horizontal stabilizer may be downward.
Industry:Science
