- 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 material that blocks the flow of electric current across it. Insulators are to be distinguished from electrolytes, which are electronic insulators but ionic conductors.
Industry:Science
A material that conducts an electric current when it is fused or dissolved in a solvent, usually water. Electrolytes are composed of positively charged species, called cations, and negatively charged species, called anions. For example, sodium chloride (NaCl) is an electrolyte composed of sodium cations (Na<sup>+</sup>) and chlorine anions (Cl<sup>-</sup>). The ratio of cations to anions is always such that the substance is electrically neutral. If two wires connected to a light bulb and to a power source are placed in a beaker of water, the light bulb will not glow. If an electrolyte, such as sodium chloride, is dissolved in the water, the light bulb will glow because the solution can now conduct electricity. The amount of electric current that can be carried by an electrolyte solution is proportional to the number of ions dissolved. Thus, the bulb will glow more brightly if the amount of sodium chloride in the solution is increased.
Industry:Science
A material used for the first coat of paint or as the prime coat in a protective coating system. Primers are designed to promote adhesion of the coating system to the substrate, to furnish a good base for further coatings, and to prevent attack on the substrate by air, water, or other materials.
Industry:Science
A material used in paints and varnishes to adjust the consistency for application. Thinners are usually solvents for the vehicle used in the coating and are expected to evaporate after application. Because their only function is to make the application simple, it is important that their cost be low. Water is used as a thinner in emulsion paints and in certain water-soluble paints such as watercolors and calcimines.
Industry:Science
A material used to kill insects and related animals by disruption of vital processes through chemical action. Insecticides may be inorganic or organic chemicals. The principal source is from chemical manufacturing, although a few are derived from plants.
Industry:Science
A material useful for the mitigation, control, or elimination of plants or animals detrimental to human health or economy. Algicides, defoliants, desiccants, herbicides, plant growth regulators, and fungicides are used to regulate populations of undesirable plants which compete with or parasitize crop or ornamental plants. Attractants, insecticides, miticides, acaricides, molluscicides, nematocides, repellants, and rodenticides are used principally to reduce parasitism and disease transmission in domestic animals, the loss of crop plants, the destruction of processed food, textile, and wood products, and parasitism and disease transmission in humans. These ravages frequently stem from the feeding activities of the pests. Birds, mice, rabbits, rats, insects, mites, ticks, eel worms, slugs, and snails are recognized as pests.
Industry:Science
A material, usually finely divided, that when mixed with water forms a paste, and when molded sets into a solid mass. The term cement is sometimes used to refer to organic compounds used for adhering or for fastening materials, but these are more correctly known as adhesives.
Industry:Science
A materials-processing method that involves the repeated welding, fracturing, and rewelding of a mixture of powder particles, generally in a high-energy ball mill, to produce a controlled, extremely fine microstructure. The mechanical alloying technique allows alloying of elements that are difficult or impossible to combine by conventional melting methods. In general, the process can be viewed as a means of assembling metal constituents with a controlled microstructure. If two metals will form a solid solution, mechanical alloying can be used to achieve this state without the need for a high-temperature excursion. Conversely, if the two metals are insoluble in the liquid or solid state, an extremely fine dispersion of one of the metals in the other can be accomplished. The process of mechanical alloying was originally developed as a means of overcoming the disadvantages associated with using powder metallurgy to alloy elements that are difficult to combine. Using powder metallurgy, homogeneity is dictated by the size of the particle, but contamination and fire hazards become a concern when particle size is very small.
Industry:Science
A mathematical abstraction corresponding to an expression of the type <b>β</b>γb; + <b>δ</b><b>∊</b> + · · · , in which the elements (dyad symbols) consist of two vector symbols in juxtaposition without the intervention of either the dot (·) or cross (<b>×</b>). Essentially a dyad is an ordered pair of vectors subject to certain rules of operation. The first symbolic factor in a dyad (<b>β</b> in <b>β</b>γb;, for example) is called the antecedent and the second the consequent.
Industry:Science
A mathematical description or electrical equivalent circuit that represents the behavior of a device or system. Models for complex systems are often represented by networks of models for simpler electrical devices such as resistors, capacitors, transistors, and transformers. By using analogies between current or voltage and other physical parameters, equivalent circuits can also be used to analyze thermal, mechanical, magnetic, and acoustic systems. A recurring issue in development and in application of models is the use of simplifying assumptions to allow a compromise between accuracy and complexity. A hierarchy of models often exists, ranging from highly accurate but complex physics-based nonlinear time-domain computer models to linear equivalent-circuit models suitable for hand calculation. The best model for a particular application is the simplest one that predicts the relevant behavior with acceptable accuracy.
Industry:Science
