- 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 procedure of heating and cooling a material without melting. The heating and cooling sequence may involve temperatures above, below, and at the ambient. Controlled heating and cooling rates, and a variety of furnace atmospheres and heating media may be used. Plastic deformation may be included in the sequence of heating and cooling steps, thus defining a thermomechanical treatment. Typical objectives of heat treatments are hardening, strengthening, softening, improved formability, improved machinability, stress relief, and improved dimensional stability. Heat treatments are often categorized with special names, such as annealing, normalizing, stress relief anneals, process anneals, hardening, tempering, austempering, martempering, intercritical annealing, carburizing, nitriding, solution anneal, aging, precipitation hardening, and thermomechanical treatment.
Industry:Science
A procedure or arrangement in which one form of energy, such as heat at an elevated temperature from combustion of a fuel, is in part converted to another form, such as mechanical energy on a shaft, and the remainder is rejected to a lower-temperature sink as low-grade heat.
Industry:Science
A process for applying a coating to a metal surface by electrochemical means. Electroplating is extensively used to produce printed circuit boards. Its main advantage is that the circuit can be produced directly rather than having to be etched out of a piece of copper sheet. Electroplating is also widely used to impart corrosion resistance. Most parts of automobile bodies are zinc plated for corrosion resistance. Since zinc is more readily attacked by most corrosive agents that automobiles encounter than steel, it provides galvanic or sacrificial protection. An electrolytic cell is formed in which zinc, the less noble metal, is the anode and the steel, the more noble one, is the cathode. The anode corrodes and the cathode is protected. Zinc also provides a good base for paint. If a metal is more noble than the one on which it is electroplated, it provides protection against corrosion only if it is completely continuous. If a small area of the substrate is exposed such as under a pinhole, corrosion occurs there, rapidly forming a pit.
Industry:Science
A process for shaping superplastic materials, a unique class of crystalline materials that exhibit exceptionally high tensile ductility. Superplastic materials may be stretched in tension to elongations typically in excess of 200% and more commonly in the range of 400–2000%. There are rare reports of higher tensile elongations reaching as much as 8000%. The high ductility is obtained only for superplastic materials and requires both the temperature and rate of deformation (strain rate) to be within a limited range. The temperature and strain rate required depend on the specific material. A variety of forming processes can be used to shape these materials; most of the processes involve the use of gas pressure to induce the deformation under isothermal conditions at the suitable elevated temperature. The tools and dies used, as well as the superplastic material, are usually heated to the forming temperature. The forming capability and complexity of configurations producible by the processing methods of superplastic forming greatly exceed those possible with conventional sheet forming methods in which the materials typically exhibit 10–50% tensile elongation.
Industry:Science
A process in many plants resulting in the fusion of a female gamete and a male gamete to form a single cell, the zygote. Both vegetative (asexual) reproduction and sexual reproduction occur in plants. Reproduction by gamete fusion is very different from vegetative reproduction, which is a common mode of multiplication in many plants. Several steps can be distinguished in the fertilization process. First, the haploid male and female gametes have to be brought into proximity. The cell membranes of the two gametes then fuse (plasmogamy), resulting in a single cell, the zygote. The nuclear membranes next fuse (karyogamy), producing a cell with a single diploid nucleus. There is a wide variety of ways by which the male and female sex cells of the different groups of plants are produced and make contact with each other prior to fertilization. Among the more primitive plants, fertilization occurs between free-swimming male and female gametes. In somewhat more advanced plants, the female gamete is stationary and partly enclosed by other cells, but the male gametes are motile. In the most highly evolved plants, the flowering plants, fertilization takes place between nonmotile gametes in the female reproductive organ.
Industry:Science
A process in mathematics used to estimate an intermediate value of one (dependent) variable which is a function of a second (independent) variable when values of the dependent variable corresponding to several discrete values of the independent variable are known.
Industry:Science
A process in mathematics used to find the value of a function outside its tabulated values. This is done as in interpolation by assuming that over a small range of <i>x</i> the function may be closely approximated by a polynomial or some other readily computed function.
Industry:Science
A process in which a catalyst is in the same phase as the reactant. A homogeneous catalyst is molecularly dispersed (dissolved) in the reactants, which are most commonly in the liquid state. Catalysis of the transformation of organic molecules by acids or bases represents one of the most widespread types of homogeneous catalysis. In addition, the catalysis of organic reactions by metal complexes in solution has grown rapidly in both scientific and industrial importance.
Industry:Science
A process in which a hydrogen atom in an organic compound is replaced by an acyl group (R–CO where R = an organic group). The reaction involves substitution by a nucleophile (electron donor) at the electrophilic carbonyl group (C=O) of a carboxylic acid derivative. The substitution usually proceeds by an addition-elimination sequence (reaction). Two common reagents, with the general formula RCOX, that bring about acylation are acid halides (X = Cl,Br) and anhydrides (X = OCOR). There are also other acylating reagents. The carboxylic acid (X = OH) itself can function as an acylating agent when it is protonated by a strong acid catalyst as in the direct esterification of an alcohol. Typical nucleophiles in the acylation reaction are alcohols (ROH) or phenols (ArOH), both of which give rise to esters, and ammonia or amines (RNH<sub>2</sub>), which give amides.
Industry:Science
A process in which a liquid phase is converted into a vapor phase. The energy for phase change is generally supplied by the surface on which boiling occurs. Boiling differs from evaporation at predetermined vapor/gas–liquid interfaces because it also involves creation of these interfaces at discrete sites on the heated surface. Boiling is an extremely efficient process for heat removal and is utilized in various energy-conversion and heat-exchange systems and in the cooling of high-energy density components.
Industry:Science
