- 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.
Systematic knowledge and action, usually of industrial processes but applicable to any recurrent activity. Technology is closely related to science and to engineering. Science deals with humans' understanding of the real world about them—the inherent properties of space, matter, energy, and their interactions. Engineering is the application of objective knowledge to the creation of plans, designs, and means for achieving desired objectives. Technology deals with the tools and techniques for carrying out the plans.
Industry:Science
The common name for four extinct classes of primitive echinoderms that have a flattened theca or body lacking radial symmetry. These enigmatic fossils were originally classified together in the class Carpoidea, but more recent echinoderm researchers have assigned them to four separate classes in the subphylum Homalozoa: the Stylophora (or Calcichordates), Homoiostelea, Homostelea, and Ctenocystoidea. These four classes include about 50 genera that range from the Early or Middle Cambrian to the Late Carboniferous.
Industry:Science
The accumulation of minerals and organic remains on the sea floor. Marine sediments vary widely in composition and physical characteristics as a function of water depth, distance from land, variations in sediment source, and the physical, chemical, and biological characteristics of their environments. The study of marine sediments is an important phase of oceanographic research and, together with the study of sediments and sedimentation processes on land, constitutes the subdivision of geology known as sedimentology.
Industry:Science
The helicopter is a flight vehicle using two or more rotor blades fixed to a common drive shaft rotated by an engine. In contrast to fixed-wing aircraft, the helicopter can take off vertically, land vertically, and hover. It can move forward, backward, and sideways. The helicopter is designed for effective operation in hover for long periods of time, for high-speed cruise, and for high range and payload. Helicopter aerodynamics usually refers to rotor-blade aerodynamics. Proper design of the rotor blades is essential.
Industry:Science
The component of a ship propulsion power plant that converts engine torque into propulsive force or thrust, thus overcoming the ship's resistance to forward motion by creating a sternward accelerated column of water. Early steamship propulsion forms, such as the jet propeller (1782) and the paddle wheel (1801), were gradually replaced by the screw propeller (1804), which since 1860 has been the only propeller type used in ocean transport, mainly because of the evolution of the marine engine toward higher rotative speed.
Industry:Science
The difference between the mass of an atom and the sum of the masses of its individual components in the free (unbound) state. The mass of an atom is always less than the total mass of its constituent particles; this means, according to Albert Einstein's well-known formula, that an energy of <i>E</i> = <i>mc</i><sup>2</sup> has been released in the process of combination, where <i>m</i> is the difference between the total mass of the constituent particles and the mass of the atom, and <i>c</i> is the velocity of light.
Industry:Science
The field of science and technology that is concerned with the diffraction of visible or infrared light (usually from a laser) by high-frequency sound in the frequency range of 50–2000 MHz. The term “acousto” is a historical misnomer; sound in this frequency range should properly be called ultrasonic. Such sound cannot be supported by air, but propagates as a mechanical wave disturbance in amorphous or crystalline solids, with a sound velocity ranging from 0.6 to 6 km/s (0.4 to 4 mi/s) and a wavelength from 3 to 100 μm.
Industry:Science
The largest order of fishes, comprising 20 suborders, 160 families, about 1540 genera, and over 10,000 species, which is about 36% of all fish species. Eighty percent of the perciforms are marine species; in contrast, the Ostariophysi, which comprise the next three largest orders (Cypriniformes, ~3300 species; Characiformes, ~1700 species; and Siluriformes, ~2900 species), are virtually all freshwater inhabitants. The ostariophysans are dominant in the freshwaters of the world; the perciforms are dominant in the oceans.
Industry:Science
The design of the airplane wing is fundamental to efficient flight. The choice of the wing shape for a particular airplane is dictated by the application, the plane's speed (subsonic or supersonic), and whether it is a transport or a fighter. Recent interest in drones (customarily termed unmanned aerial vehicles or UAVs) has led to unusual wing shapes. The next important requirement is the takeoff and landing distance. In the case of military aircraft, the maneuver and acceleration requirements also influence the design.
Industry:Science
The ejection of material from a solid or liquid surface following the impact of energetic ions, atoms, or molecules. Sputtering was first noted in 1853 by W. R. Grove and in 1854 by M. Faraday as the occurrence of a metallic coating on the glass walls of a discharge tube. E. Goldstein in 1902 showed that the sputtering effect was caused by positive ions of the discharge striking the cathode and ejecting cathode material. Sputtering now is the basis of a large variety of methods for the synthesis and analysis of materials.
Industry:Science
