- 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.
An aircraft landing instrument that provides the pilot with a set of vertical and horizontal cross pointers that indicate deviation from a radio-transmitted course to the threshold of the runway. A dual-frequency transmitter sends out one frequency to the right of the runway centerline and a second frequency to the left of the runway centerline. The reception of these signals in the aircraft biases the vertical needle to the left or right depending on the position of the aircraft relative to the transmitted 5° localizer path. Simultaneously, another dual-frequency transmitter causes a horizontal needle to indicate high or low as the aircraft descent path is compared to the transmitted 3° glide path. This indicator, when properly used with the other navigation instruments, allows approaches to be made to within 200 ft (60 m) of altitude and 0.5 mi (0.8 km) of the runway threshold, at which time the approach transfers to a visual type, or is aborted if no visual contact is made.
Industry:Science
An aircraft or helicopter that is flown without an on-board human pilot. These vehicles are now customarily termed “unmanned aerial vehicles” (UAVs). Until the late twentieth century, they were typically called drones or sometimes remotely piloted vehicles (RPVs) when a human operator controlled the vehicle remotely. Although guided missiles and cruise missiles have the same root heritage in the “aerial torpedoes” of the 1910s, missiles are not considered to be UAVs. Crewless versions of nonpowered aerial vehicles such as gliders and balloons can perform some of the same missions as UAVs, but are not considered to be UAV-class vehicles.
Industry:Science
An aliphatic or aromatic hydrocarbon in which one or more hydrogen atoms are substituted by halogen.
Industry:Science
An allergic inflammatory disease of the airways, involving mast cells, eosinophils, macrophages, fibroblasts, and neutrophils. Such inflammatory changes are associated with widespread airflow obstruction, which is variable and improves (reverses) spontaneously or with appropriate therapy. Inflammation progresses to increased airway irritability (hyperresponsiveness) and episodes of airflow obstruction induced by the inhalation of allergens, cold air, and occupational factors. Although a bronchospasm can be induced immediately after exposure to a specific allergen in an appropriately sensitized recipient, it is the late allergic response that most resembles the inflammatory reaction occurring in asthma. Central to this reaction is the release from mast cells, eosinophils, and lymphocytes of chemical mediators such as histamine, leukotrienes (potent bronchoconstricting agents), prostaglandins, and various cytokines that perpetuate the response. Potent neurohumoral agents derived from neural pathways contribute further to the bronchospasm.
Industry:Science
An alloy of copper and zinc. In manufacture, lump zinc is added to molten copper, and the mixture is poured either into castings ready for use or into billets for further working by rolling, extruding, forging, or a similar process. Brasses containing 75–85% copper are red-gold and malleable; those containing 60–70% are yellow and also malleable; and those containing 50% or less copper are white, brittle, and not malleable. Alpha brass contains up to 36% zinc; beta brass contains nearly equal proportions of copper and zinc. Specific brasses are designated as follows: gilding (95% copper: 5% zinc), red (85:15), low (80:20), and admiralty (70:29, with balance of tin). Naval brass is 59–62% copper with about 1% tin, less than that of lead and iron, and the remainder zinc. The nickel silvers contain 55–70% copper and the balance nickel. With small amounts of other metals, other names are used. Leaded brass is used for castings.
Industry:Science
An alloy of mercury. Practically all metals will form alloys or amalgams with mercury, with the notable exception of iron. Amalgams are used as dental materials, in the concentration of gold and silver from their ores, and as electrodes in various industrial and laboratory electrolytic processes.
Industry:Science
An all-weather aircraft landing-guidance system that operates at microwave frequencies and provides deviations from the landing runway centerline using a time-referenced scanning beam (TRSB) technique. The MLS was standardized in 1988 and approved for use in international civil aviation until at least the year 2020. MLS is used to support low-visibility instrument precision approach and landing operations in North America and Europe. In addition to the fixed-base MLS equipment design, a compact mobile microwave landing system (MMLS) equipment design exists. The instrument landing system (ILS) is also standardized internationally and approved for use indefinitely as countries implement their transition to new technologies. Standards for a third landing system, the Global Navigation Satellite System (GNSS), based primarily on Global Positioning System (GPS) technology, exist. Multimode receivers enable an aircraft to conduct an instrument approach using ILS, MLS, or GNSS.
Industry:Science
An alpine biological community in the central portion of the Andes Mountains of South America. Sparsely vegetated, treeless stretches cover high plateau country (altiplano) and slopes of central and southern Peru, Bolivia, northern Chile, and northwestern Argentina. The poor vegetative cover and the puna animals are limited by short seasonal precipitation as well as by the low temperatures of high altitudes. In spite of severe climate and limited use, some portions are inhabited by native Indians.
Industry:Science
An alternating-current (ac) commutator motor designed for single-phase operation. The chief distinction between the repulsion motor and the single-phase series motors is the way in which the armature receives its power. In the series motor the armature power is supplied by conduction from the line power supply. In the repulsion motor, however, armature power is supplied by induction (transformer action) from the field of the stator winding. For discussion of the ac series motor
Industry:Science
An alternating-current (ac) motor which operates at a fixed synchronous speed proportional to the frequency of the applied ac power supply. A synchronous machine can be operated as either a generator or a motor (and sometimes as a source of reactive power, fulfilling the function of a capacitor), depending only on its applied shaft torque (whether positive, negative, or zero) and its excitation. There is no fundamental difference in the theory, design, or construction of a machine intended for any of these roles, although certain design features are stressed for each of them. In use, the machine may change its role from instant to instant. As a result, it is preferable to set up a common general theory for synchronous generators, motors, and capacitors. The distinction between generator and motor is merely a difference in the direction of the currents and the sign of the torque angles.
Industry:Science
