- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- 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.
A device with two or more signal inputs and one common output. The two primary classes are linear (additive) and nonlinear (multiplicative) mixers. Linear mixers are used to add or blend together two or more signals, nonlinear mixers mainly to shift the spectrum (center frequency) of one signal by the frequency of a second signal.
Industry:Science
A device, more correctly described as a crystal detector, that detects ionizing radiations of all types and is adaptable to measuring neutrons. The sensitive element is a single crystal with a dc resistance normally higher than 10<sup>12</sup> ohms. The crystals are small and are cut or grown to volumes ranging from less than 1 mm<sup>3</sup> (6 × 10<sup>-5</sup> in.<sup>3</sup>) to approximately 200 mm<sup>3</sup> (1.2 × 10<sup>-2</sup> in.<sup>3</sup>).
Industry:Science
A diagnostic procedure that uses ultrasound at a frequency of 2.5–10 MHz to provide an image of the heart. It is based on the principle that the interface between tissues of different acoustical impedance causes the ultrasound to be reflected to the transducer, which spends a fraction of each second receiving these echoes. There are many interfaces between blood and the various structures in the heart that contact blood, such as the heart walls, valves, and great vessels. Also, the surface of the heart reflects ultrasound because it is surrounded by the lungs, which are filled with air.
Industry:Science
A diagram depicting those organisms that eat other organisms in the same ecosystem. In some cases, the organisms may already be dead. Thus, a food web is a network of energy flows in and out of the ecosystem of interest. Such flows can be very large, and some ecosystems depend almost entirely on energy that is imported. A food chain is one particular route through a food web.
Industry:Science
A diagram in which statistical information concerning the direction and speed of the wind at a particular location may be conveniently summarized. In the standard wind rose a line segment is drawn in each of perhaps eight compass directions from a common origin (see <b>illus.</b>). The length of a particular segment is proportional to the frequency with which winds blow from that direction. Parts of a given segment are given various thicknesses, indicating frequencies of occurrence of various classes of wind speed from the given direction.
Industry:Science
A digestive structure found within virtually all types of animal cells. Lysosome sizes, microscopic appearances, and other properties vary among different cell types and circumstances owing, in part, to differences in their functions and states. Typical lysosomes (<b>Figs. 1</b> and <b>2</b>) are roughly spherical or elongate bodies with largest dimensions of 0.1–1 micrometer or greater; tens to hundreds are present in a single cell.
Industry:Science
A digital computer whose central processing unit consists of a microprocessor, a single semiconductor integrated circuit chip. Once less powerful than larger computers, microcomputers are now as powerful as the mini- and super-minicomputers of just several years ago. This is due in part to the growing processing power of each successive generation of microprocessor, plus the addition of mainframe computer features to the chip, such as floating-point mathematics, computation hardware, memory management, and multiprocessing support.
Industry:Science
A dimensionless group is any combination of dimensional or dimensionless quantities possessing zero overall dimensions. Dimensionless groups are frequently encountered in engineering studies of complicated processes or as similarity criteria in model studies. A typical dimensionless group is the Reynolds number (a dynamic similarity criterion), Re = <i>vl</i>ρ/μ. Since the dimensions of the quantities involved are velocity <i>v</i>: (<i>L</i>/θ); characteristic length <i>l</i>: (<i>L</i>); density ρ: (<i>M</i>/<i>L</i><sup>3</sup>); and viscosity μ: (<i>M</i>/<i>L</i><i>T</i>) (with <i>M</i>, <i>L</i>, and <i>T</i> as the fundamental units of mass, length, and time), the Reynolds number reduces to a dimensionless group and can be represented by a pure number in any coherent system of units.
Industry:Science
A dioecious perennial monocot (<i>Asparagus officinalis</i>) of Mediterranean origin belonging to the plant order Liliales. Asparagus is grown for its young shoots or spears, which are canned, frozen, or cooked fresh as a vegetable. These aerial stems arise from rhizomes (underground stems). The rhizomes and the fleshy and fibrous roots constitute the massive underground part of the plant.
Industry:Science
A direct-fired heater used in processing petroleum. The basic feature of these heaters is that the fluid (liquid, vapor, or a mixture of both phases) is heated in carbon- or alloy-steel tubes, which in turn receive their heat from hot products of combustion. The fuel may be liquid, such as heavy fuel oil, or gas, such as natural gas or cracked refinery gas. Burners of the steam, gas, or mechanically atomizing type may be used for liquid fuels, and burners of the simpler ring-type, spider, or center-nozzle type for gas fuels. Combination burners designed to handle both fuels are in wide use.
Industry:Science
