- 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.
The design and operation of systems or processes to make them as good as possible in some defined sense. The approaches to optimizing systems are varied and depend on the type of system involved, but the goal of all optimization procedures is to obtain the best results possible (again, in some defined sense) subject to restrictions or constraints that are imposed. While a system may be optimized by treating the system itself, by adjusting various parameters of the process in an effort to obtain better results, it generally is more economical to develop a model of the process and to analyze performance changes that result from adjustments in the model. In many applications, the process to be optimized can be formulated as a mathematical model; with the advent of high-speed computers, very large and complex systems can be modeled, and optimization can yield substantially improved benefits.
Industry:Science
The branch of mechanics that describes bodies which are acted upon by balanced forces and torques so that they remain at rest or in uniform motion. This includes point particles, rigid bodies, fluids, and deformable solids in general. Static point particles, however, are not very interesting, and special branches of mechanics are devoted to fluids and deformable solids. For example, hydrostatics is the study of static fluids, and elasticity and plasticity are two branches devoted to deformable bodies. Therefore this article will be limited to the discussion of the statics of rigid bodies in two and three spatial dimensions.
Industry:Science
The continuing motion, repetitive and often periodic, of a solid or liquid body within certain spatial limits. Vibration occurs frequently in a variety of natural phenomena such as the tidal motion of the oceans, in rotating and stationary machinery, in structures as varied in nature as buildings and ships, in vehicles, and in combinations of these various elements in larger systems. The sources of vibration and the types of vibratory motion and their propagation are subjects that are complicated and depend a great deal on the particular characteristics of the systems being examined. Further, there is strong coupling between the notions of mechanical vibration and the propagation of vibration and acoustic signals through both the ground and the air so as to create possible sources of discomfort, annoyance, and even physical damage to people and structures adjacent to a source of vibration.
Industry:Science
The eastern Mediterranean region is one of the most actively excavated areas in archeology. Typically, sites there are in the form of tells (large, flat-topped artificial hills) comprising the accumulated layers of human habitation. Since this region also experiences earthquake activity, it is inescapable that earthquakes and archeology be intimately related. However, only recently have earth scientists and archeologists come together to formally address the evidence for earthquakes in archeological remains. As a result, there has been much disagreement through the years over the role that earthquakes played in ancient society.
Industry:Science
Specialized proteins in the nucleus that are involved in the regulation of gene activity in response to hormones and other signals. It has been estimated that approximately 30,000 genes are expressed in the human genome. The transcription of these genes into messenger ribonucleic acid (mRNA) and their subsequent translation into protein determines the identity and function of each cell in the human body. The balance between sickness and health requires that transcription of these genes be precisely regulated in response to both physiological and environmental changes. A variety of signaling strategies have evolved to coordinate the body's transcriptional response to such events. The nuclear hormone receptors represent one of the largest family of proteins that directly regulate transcription in response to hormones and other ligands (chemical entities that bind to and activate the receptor).
Industry:Science
The evolutionary chronicle of plant life on the Earth. Understanding of this history is largely based on knowledge of extant plants, but the fossil record is playing an increasingly important role in refining and illuminating this picture. Study of deoxyribonucleic acid (DNA) sequences has also been revolutionizing this process in recent years. In spite of a remarkably improved situation, controversy over interpretation of the available data can be expected to continue. The molecular data (largely in the form of DNA sequences from several genes) summarized below have been demonstrated to be highly correlated with other information.
Industry:Science
The insulated copper or aluminum wire used in the coils of all types of electromagnetic machines and devices. It is single-strand wire insulated with enamel, varnish, cotton, glass, asbestos, or combinations of these. To meet the immense variety of uses and to gain competitive advantage, a great number of kinds of enamel and of fiber insulations have been developed and are widely available. And to ensure that the many synthetic materials and combinations are properly applied, many elaborate test procedures have been devised to evaluate heat shock, solubility, blister and abrasion resistance, flexibility, and so on as covered in the National Electrical Manufacturers Association (NEMA) Standards. Most important, the thermal endurance is determined by repeated exposure to high temperature, moisture, and electrical stress, as specified in the American Society for Testing and Materials (ASTM).
Industry:Science
The <i>Solar and Heliospheric Observatory</i> (<i>SOHO</i>), a project of international cooperation between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), was launched on December 2, 1995, and began full scientific operation on February 14, 1996. It obtains a continuous, uninterrupted view of the Sun from its halo orbit around the point 1.5 million kilometers (930,000 mi) sunward from the Earth, where the gravitational forces of the Earth and the Sun balance each other. The spacecraft orbits this equilibrium point to keep Earth-based tracking telescopes from looking directly at the Sun.
Industry:Science
The generation of a capacitance which is some multiple of that of an actual capacitor. Capacitance multiplication circuits have an input impedance which is capacitive and which is proportional to that of an actual capacitor appearing somewhere in the circuit. In most applications, capacitance multiplication circuits are used to generate an equivalent input capacitance which is much larger than that of the actual capacitor. One scenario where capacitance multiplication might prove useful is where a physical capacitor of a required capacitance may be too large, too expensive, or unavailable. A second is where the capacitor must be reasonably large and capable of handling bidirectional signals, thus precluding the direct use of widely available electrolytic capacitors and hence making practical the utilization of a much smaller nonelectrolytic capacitor in a capacitance multiplication circuit.
Industry:Science
The application of technologies and agronomic principles to manage spatial and temporal variability associated with all aspects of agricultural production for the purpose of improving crop performance and environmental quality. The intent of precision agriculture is to match agricultural inputs and practices to localized conditions within a field (site-specific management) and to improve the accuracy of their application. The finer-scale management of precision agriculture is in contrast to whole-field or whole-farm management strategies, where management decisions and practices are uniformly applied throughout a field or farmstead.
Industry:Science
