- 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 technique for providing an inventory of the total amount of snow covering a drainage basin or a given region. Most of the usable water in western North America originates as mountain snowfall that accumulates during the winter and spring and appears several months later as streamflow. Snow surveys were established to provide an estimate of the snow water equivalent (that is, the depth of water produced from melting the snow) for use in predicting the volume of spring runoff. They are also extremely useful for flood forecasting, reservoir regulation, determining hydropower requirements, municipal and irrigation water supplies, agricultural productivity, wildlife survival, and building design, and for assessing transportation and recreation conditions.
Industry:Science
A technique for recording, and later reconstructing, the amplitude and phase distributions of a coherent wave disturbance. Invented by Dennis Gabor in 1948, the process was originally envisioned as a possible method for improving the resolution of electron microscopes. While this original application has not proved feasible, the technique is widely used as a method for optical image formation, and in addition has been successfully used with acoustical and radio waves. This article discusses holography with electromagnetic waves in the optical and microwave regions of the electromagnetic spectrum, and its potential use with x-rays. For holography with sound waves.
Industry:Science
A technique for the determination of the velocities of the parts of a machine or mechanism. Both graphical and analytical analyses of plane mechanisms will be discussed in this article, but of the several methods of each type available, only one of each type will be described. The graphical method will be discussed first, since the visualization which is an inherent part of the graphical analysis generally gives a better physical feel for the problem than most purely analytical methods. Analytical methods, however, are necessary for computer analyses.
Industry:Science
A technique in which a neutron, charged particle, or gamma photon is captured by a stable nuclide to produce a different, radioactive nuclide which is then measured. The technique is specific, highly sensitive, and applicable to almost every element in the periodic table. Because of these advantages, activation analysis has been applied to chemical identification problems in many fields of interest.
Industry:Science
A technique of analytical chemistry for determining the oxygen, hydrogen, and sometimes nitrogen content of metals. The method can be applied to a wide variety of metals, the alkali and alkaline earth metals being exceptions. The range of the method extends from 1% down to a few parts per million for oxygen and nitrogen and down to fractional parts per million for hydrogen.
Industry:Science
A technique of selective chemical etching to reveal tracks of heavy nuclear particles in a wide variety of solid substances. Developed in order to see fossil particle tracks in extraterrestrial materials, the technique finds application in many fields of science and technology.
Industry:Science
A technique that involves the study of dimensions of physical quantities. Dimensional analysis is used primarily as a tool for obtaining information about physical systems too complicated for full mathematical solutions to be feasible. It enables one to predict the behavior of large systems from a study of small-scale models. It affords a convenient means of checking mathematical equations. Finally, dimensional formulas provide a useful cataloging system for physical quantities.
Industry:Science
A technique that uses a fluorochrome to indicate the occurrence of a specific antigen-antibody reaction. The fluorochrome labels either an antigen or an antibody. The labeled reactant is then used to detect the presence of the unlabeled reactant, for example, a component of a section of body tissue seen under a microscope. The use of a labeled reactant (such as an antibody which both detects and indicates the antigen) to reveal the presence of an unlabeled one is termed direct immunofluorescence. The use of a labeled indicator antibody, which reacts with an unlabeled detector antibody that has previously reacted with an antigen, is termed indirect immunofluorescence. Both techniques can be used qualitatively to indicate the presence of a specific reactant in a preparation. They can also be used semiquantitatively, for example, to determine the highest dilution (lowest concentration) of a tested detector reactant that can detect a given substance. Substitution of a light meter for the human eye permits a quantitative measurement in immunofluorometry.
Industry:Science
A technique that uses field emission of electrons or positive ions from a needle-shaped emitter to produce a magnified image of the emitter surface on a fluorescent screen. In the field electron microscope, the image reveals the variation in work function of the emitter surface. Due to the large lateral velocity of the emitted electrons, a resolution of only about 2.5 nanometers can be achieved. The large lateral velocity arises from a diffraction effect of the de Broglie wave and the large kinetic energy of electrons inside the metal; these effects are intrinsic quantum properties of particles and cannot be eliminated.
The field electron microscope has been used to study adsorption and desorption of gases and vapor-deposited materials, surface migration of adsorption layers and absorbed atoms on single crystal faces, and surface reactions in catalysis. Medium-sized individual molecules such as phthalocyanin have been made visible also.
Industry:Science
A technique used by industrial engineers to improve productivity and quality and to reduce costs in both direct and indirect operations of manufacturing and service organizations. Methods engineering is applicable in any enterprise requiring human effort. It can be defined as the systematic procedure for subjecting all direct and indirect operations to close scrutiny in order to introduce improvements that will make work easier to perform while maintaining or improving quality, and will allow work to be done more smoothly, in less time, with less energy, effort, and fatigue, and with less investment per unit. The ultimate objective of methods engineering is increasing profits, but it is also important in improving worker health and safety.
Industry:Science
