- 行业: Printing & publishing
- Number of terms: 178089
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- Company Profile:
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 nuclear reaction that can take place when two nuclei collide at very high energy (typically 500 MeV per nucleon and up), in which the involved nuclei are either disintegrated into their constituents (protons and neutrons), light nuclei, and elementary particles, or a large number of nucleons are expelled from the colliding system resulting in a nucleus with a smaller atomic number. This mechanism is clearly different from fusion reactions induced by heavy or light ions with modest kinetic energy (typically 5 MeV per nucleon) where, after formation of a compound nucleus, only a few nucleons are evaporated. A spallation reaction can be compared to a glass that shatters in many pieces when it falls on the ground. The way that the kinetic energy is distributed over the different particles involved in a spallation reaction and the process whereby this results in residues and fluxes of outgoing particles are not well understood.
Industry:Science
A nucleotide composed of three subunits: ribose (5-carbon sugar), adenine (a nitrogenous base composed of two carbon-nitrogen rings), and a triphosphate group (a chain of three phosphate groups, designated α, β, and γ) (see <b>illus.</b>). ATP is a vital energy-rich chemical found in all living cells. The oxidation of carbohydrates, fats, and proteins provides chemical energy that is used to synthesize ATP, which then serves as the source of the chemical energy used for biosynthesis, ion transport, and muscle contraction. The idea that ATP serves as the common currency of energy exchange in all cells is a cornerstone of biology that was first described by Fritz Lipmann in 1941.
Industry:Science
A number of different processes, including alpha-, beta-, and gamma-ray emission, exist by which radioactive nuclei are transformed into stable nuclei. Because these processes are of importance in any situation involving radioactive nuclei, understanding them is important to subjects as disparate as the production of nuclei in stellar atmospheres and the operational characteristics of nuclear fission reactors.
Industry:Science
A number of diseases, such as St. Louis, Japanese B, and equine encephalitis, which are caused by arthropod-borne viruses (arboviruses). In their most severe human forms, the diseases invade the central nervous system and produce brain damage, with mental confusion, convulsions, and coma; death or serious aftereffects are frequent in severe cases. Inapparent infections are common (see <b>table</b>).
Industry:Science
A number of forces are bringing about fundamental changes in the way in which computing technology is applied in contemporary organizations. These include the transformation of society from one primarily dependent on the production of goods to one also much concerned with information and knowledge. Information technology has become a major support to humans and organizations in the development of new products and new services. One major change in organizations is that they have become more horizontal in structure. Reengineering, especially business process reengineering, is often used to accomplish this transformation. Other approaches, such as those based on total quality management (TQM), lead to organizational changes for improved quality and responsiveness. The technological enabler of each of these transformations is advanced information technology. It has enabled the construction of the information-system architecture of an organization to match the reengineered organizational structure and the desire for rapid communications throughout real and virtual organizations. In many cases, these are horizontal structures that require massively parallel communications capabilities between personnel in the organization. Client-server architectures and client-server systems are names generally given to these enablers of these transformations to new structural forms.
Industry:Science
A number of modern technologies, including computer, satellite navigation, and in some cases radar, are combined to create electronic charts. These charts display where a conveyance (marine, aerospace, or land vehicle) is located, as well as where it has been and where it is headed. Information is also provided to guide the conveyance to its destination while avoiding hazards that lie along the route. In these systems, a nautical chart or a land map is displayed on a computer's screen or on a hand-held device, showing appropriate detail. A symbol that marks the vehicle's present location and a track of its previous positions is drawn on the chart or map. In the case of marine vessels, radar images of objects in the water show the location of shore, lights, and buoys, as well as the presence and tracks of other ships in the area. Thus, the electronic chart shows a complete picture of the situation facing a pilot or driver.
Industry:Science
A number that characterizes the expansion rate of the universe and is required to determine its age. In the standard big bang model, the local universe expands uniformly according to the Hubble law, <i>v</i> = <i>H</i><sub>0</sub><i>d</i>, where <i>v</i> is the velocity of a galaxy at a distance <i>d</i>, and <i>H</i><sub>0</sub> is the Hubble constant. The wavelength of radiation is stretched due to the expansion of space so that the spectra of objects become progressively redder at greater distances. (For nearby objects, the observed redshift can be described as a Doppler effect.) The constant is named after Edwin P. Hubble, who discovered that the velocity of recession of a galaxy is proportional to its distance. A reliable and accurate measurement of the Hubble constant, an independent estimate of the ages of the oldest objects in the universe, and a further measurement of the average mass-energy density in the universe are all separately required in order to test and ultimately provide strong constraints on cosmological models. Measuring an accurate value of <i>H</i><sub>0</sub> was one of the motivating reasons for building the Hubble Space Telescope.
Industry:Science
A number, usually between 30 and 60, that indicates the ability of a diesel engine fuel to ignite quickly after being injected into the cylinder. The higher the cetane number, the more easily the fuel can be ignited. In high-speed diesel engines, a fuel with a long ignition delay tends to produce rough operation.
Industry:Science
A numbering system is a systematic method for representing numbers using a particular set of symbols. The most commonly used numbering system is the decimal system, based on the number 10, which is called the basis or radix of the system. The basis tells how many different individual symbols there are in the system to represent numbers. In the decimal system these symbols are the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. The range of these numbers varies from 0 to (10 − 1). This is a particular case of a more general rule: Given any positive basis or radix <i>N</i>, there are <i>N</i> different individual symbols that can be used to write numbers in that system. The range of these numbers varies from 0 to <i>N</i> − 1.
Industry:Science
A numerical analysis technique for obtaining approximate solutions to many types of engineering problems. The need for numerical methods arises from the fact that for most engineering problems analytical solutions do not exist. While the governing equations and boundary conditions can usually be written for these problems, difficulties introduced by either irregular geometry or other discontinuities render the problems intractable analytically. To obtain a solution, the engineer must make simplifying assumptions reducing the problem to one that can be solved, or a numerical procedure must be used. In an analytic solution, the unknown quantity is given by a mathematical function valid at an infinite number of locations in the region under study, while numerical methods provide approximate values of the unknown quantity only at discrete points in the region. In the finite element method, the region of interest is divided into numerous connected subregions or elements within which approximating functions (usually polynomials) are used to represent the unknown quantity.
Industry:Science
