- 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.
A form of elastic deformation of a dielectric induced by an electric field; specifically, the term applies to those components of strain which are independent of reversal of the field direction. Electrostriction is a property of all dielectrics and is thus distinguished from the converse piezoelectric effect, a field-induced strain which changes sign upon field reversal and which occurs only in piezoelectric materials.
Industry:Science
A form of electronic circuit that employs positive feedback to cross-couple two devices so that two distinct states are possible, for example, one device <small>ON</small> and the other device <small>OFF</small>, and in which the states of the two devices can be interchanged either by use of external pulses or by internal capacitance coupling. When the circuit is switched between states, transition times are normally very short compared to the <small>ON</small> and <small>OFF</small> periods. Hence, the output waveforms are essentially rectangular in form.
Industry:Science
A form of genetic variation, specifically, a discontinuous variation that occurs within plant and animal species in which distinct forms exist together in the same population, even the rarest of them being too common to be maintained solely by mutation. The human blood groups are examples of polymorphism. In contrast, geographic races are not an example of polymorphism; nor is the diversity of height among humans, because height varies along a continuum and does not fall into distinct tall, medium, and short types.
Industry:Science
A form of high-speed ship that supports its weight by means of wings (properly called hydrofoils, or simply foils) beneath the surface of the water. The hydrofoils generate lift by movement in the same manner as an airplane wing. The hydrofoil was conceived in order to produce faster ships. The most effective means of developing a faster ship is to find a way to lift the hull clear of the water. This greatly reduces the drag on the hull, in turn greatly reducing the power required to drive the ship. The hydrofoil ship is one means to this end.
Industry:Science
A form of human-computer interaction in which a real or imaginary environment is simulated and users interact with and manipulate that world. Users travel within the simulated world by moving toward where they want to be, and interact with things in the world by grasping and manipulating simulated objects. In the most successful virtual environments, users feel that they are truly present in the simulated world and that their experience in the virtual world matches what they would experience in the environment being simulated. This sensation is referred to as engagement, immersion, or presence, and it is this quality that distinguishes virtual reality from other forms of human-computer interaction.
Industry:Science
A form of motion found in the near-surface water of lakes and oceans under windy conditions. When the wind is stronger than 5–8 m/s (10–15 knots), streaks of bubbles, seaweed, or flotsam form lines running roughly parallel to the wind, called windrows. Windrows are seen at one time or another on all bodies of water, from ponds to oceans. In the 1920s, Irving Langmuir hypothesized that they are produced by convergences in the water rather than by a direct action of the wind. Langmuir proposed that as the surface water is blown downwind it moves in a spiral fashion, first angling toward the streaks along the surface, next sinking to some depth, then diverging out from under the streaks, and finally rising again in between the streaks (see <b>illus.</b>). In a series of observations and experiments conducted in the North Atlantic and on Lake George in New York, he was able to confirm this basic form of the circulation.
Industry:Science
A form of navigation that determines position of a craft by advancing a previous position to a new one on the basis of assumed distance and direction moved. The name probably stems from the early practice of determining speed by throwing overboard a buoyant object, called a Dutchman's log, and noting the time needed for a known length of the vessel to pass the floating object, or attaching a line to the object (when the whole device became known as a chip log) and noting the amount of line paid out in a given time. In either case, the floating object was assumed to remain dead in the water, thus providing an indication of speed through the water. The reckoning of future positions of the vessel by means of this speed was known as dead reckoning.
Industry:Science
A form of resistance welding that is used for mass production. The welding circuit consists of a low- voltage, high-current energy source (usually a welding transformer) and two clamping electrodes, one stationary and one movable.
Industry:Science
A form of spring used principally as a fastener. Piston rings are a form of snap ring used as seals. The ring is elastically deformed, put in place, and allowed to snap back toward its unstressed position into a groove or recess. The snap ring may be used externally to provide a shoulder that retains a wheel or a bearing race on a shaft, or it may be used internally to provide a construction that confines a bearing race in the bore of a machine frame (see <b>illus</b>.). The size of the ring and its recess determines its strength under load. Sufficient clearance and play is needed in the machine so that the ring can be inserted and seated.
Industry:Science
A form of tissue death, or necrosis, usually occurring in an extremity and due to insufficient blood supply.
Industry:Science
