- 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.
Air toxics computational fluid dynamics (CFD) is an emerging scientific method for calculating human exposure to toxic air pollutants. The U.S. Environmental Protection Agency (EPA) defines toxic air pollutants, also known as hazardous air pollutants, as those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects, birth defects, or adverse environmental effects. Most air toxics originate from human-made sources, including mobile sources (for example, cars, trucks, and buses) and stationary sources (for example, factories, refineries, and power plants), as well as indoor sources (for example, some building materials and cleaning solvents). Some air toxics are also released from natural sources, such as from volcanic eruptions and forest fires. People are exposed to toxic air pollutants in many ways that can pose health risks, including directly by breathing contaminated air or indirectly by consuming or contacting materials that have been exposed to contaminated air. Accurate estimates of exposures can be supported through a measurement of the contaminated air concentration being breathed or surrounding the material. However, measurements are expensive and very few in number. As a result, measurements are not possible everywhere that they are needed.
Industry:Science
Aircraft designed, or adapted from a general utility airframe, for use in agriculture and forestry and for control of insect vectors of human, animal, and plant diseases. Agricultural aircraft have become an indispensable tool for high-productivity agriculture and have contributed to the worldwide crop production revolution.
Industry:Science
Aircraft generally derive their propulsion from fuel-fed heat engines whose power is fed to a propulsor. The propulsor accelerates a stream of air through the engine (as in the case of turbojets, turbofans, and ramjets) or around the aircraft (as in the case of helicopter rotors and propeller rotors) in a direction rearward of the flight direction. The integrated pressure forces impacting on the surfaces of the propulsive machinery required to accelerate the propulsive stream ultimately react on the aircraft to propel it in the flight direction. This is an application of Newton's second and third laws: The force required to accelerate a mass flow is proportional to the quantity of the mass flow multiplied by the rate of its acceleration, and for every action (of accelerating the mass flow) there is an equal and opposite reaction (on the engine and ultimately on the aircraft).
Industry:Science
Aircraft icing encompasses a range of conditions during which frozen precipitation forms on an aircraft. It is usually separated into two broad classifications, ground icing and in-flight icing. Icing can compromise flight safety by affecting the performance, stability, and control of the aircraft, and as a result the ability of the pilot to maintain the desired flight path. The primary effect of icing is its adverse impact on the aerodynamics of the airplane. Ice accretion results in increased drag and reduced maximum lift which reduce the performance and safety of the flight. While ice does add weight to the aircraft, the amount is usually a very small percentage of the aircraft gross weight, and its effects are insignificant compared to the aerodynamic effects.
Industry:Science
Aircraft that are designed for highly specialized military applications. Fixed-wing aircraft, rotary-wing aircraft, free-flight balloons, and blimps have all been used in both crewed and crewless flight modes for military purposes.
Industry:Science
Air-inflated fabric structures are categorized as pretensioned structures. They are capable of many advantages not available with traditional structures, including lighter-weight design, rapid and self-erecting deployment, enhanced mobility, large deployed-to-packaged volume ratios, fail-safe collapse, and optional rigidification.
Industry:Science
Airplanes, helicopters, and high-speed road vehicles all produce annoying sounds or noise. Industrial processes and machinery produce noise, as do home appliances such as vacuum cleaners and fans. Some sounds such as music are pleasing to the ear, but most unwanted sounds cause annoyance to humans; the level of annoyance depends on the loudness, the duration, and the frequency content of the sound. Some sounds have dominant tones, such as the “singing” of high-voltage power lines in strong winds, and others are broadband, such as the noise of a jet-engine take-off.
Industry:Science
All aboveground organs of plants, including stems, leaves, branches, and flowers, are ultimately derived from a small pool of cells called the shoot apical meristem (SAM). Located at the tip of the growing stem, the SAM contains a pool of pluripotent stem cells that differ from animal stem cells owing to their intrinsic ability to sustain indeterminate growth throughout the life cycle of the plant. This unique property of the SAM to maintain embryolike growth during adult stages accounts for a major difference in developmental strategies between animals and plants. Whereas most animals cease organogenesis (organ formation) quite early in development, plants continue to grow via the addition of newly developed stems and leaves on top of stems and leaves formed earlier in development. As a result, the SAM must maintain a precise equilibrium whereby cells lost during organogenesis are replenished by stem cells that divide to maintain the SAM and furnish new cells toward the formation of additional organs. Thus, the SAM performs two essential functions, namely (1) organogenesis and (2) self-maintenance. Research on SAM biology is focused on understanding the genetic and biochemical parameters controlling these two fundamental components of SAM function.
Industry:Science
All aircraft activity not associated with major airlines or the military. Among all classifications of aviation in the United States, general aviation consists of the largest number of aircraft and pilots and accounts for the largest number of flying hours.
Industry:Science
All animals face the problem of producing, detecting, and correctly interpreting signals intended for communication. In any species, effective signals must be appropriately tuned to the sensory systems of receivers, but well-designed signals must also contend with the environment within which they are transmitted. This is particularly true for visual signals that are used underwater in marine or freshwater environments. Water is a particularly difficult medium within which to use visual signals. This is because particles in the water, and the water molecules themselves, tend to scatter light, degrading images (and signals) even at relatively short distances, making long-distance transmission impossible. Furthermore, water transmits light within a restricted spectral band, primarily at blue wavelengths in clear marine systems (but varying among water types; for example, in freshwater, green or even yellow may be best transmitted). This limited spectrum, which becomes ever narrower with increasing depth, makes color signals nearly useless in waters more than a few meters deep and favors patterns that stand out well under blue illumination.
Industry:Science
