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991.
Journal of the Operational Research Society - 相似文献
992.
Alan K. Halder 《The Journal of the Operational Research Society》1970,21(2):267-278
The development of urban transportation planning models has accelerated in the past decade, until they are now widely accepted aids to the urban decision process. However, the models have had limited impact upon individual decisions, because of their complexity and size. In the absence of radical new approaches to planning, a methodology is suggested to complement the existing procedures.This methodology, which is referred to as "perturbation", is illustrated by reference to the choice of a future network. Some results are presented for the budgeting of capital for a set of investments. 相似文献
993.
994.
Alan W. Neebe Basheer M. Khumawala 《The Journal of the Operational Research Society》1981,32(2):143-149
Distribution systems designs commonly require the optimal location decisions of regional ware-houses or distribution centers which function as intermediate facilities between plants and customers. This paper deals with such a location problem in which the facilities can handle one of several commodities. We term this problem the multi-commodity facility location problem. A branch and bound algorithm is proposed for solving this problem. Improved bounds are developed for increasing the efficiency of the algorithm. Computational results are provided. 相似文献
995.
Alan F. Thomas 《Helvetica chimica acta》1970,53(3):605-608
The pyrolysis of fur-2-ylmethyl vinyl ether and its next highest homologue, the propenyl ether, is described. Products from two reaction mechanisms are observed namely a 3-substituted 2-methylfuran from an electrocyclic mechanism, and 1,2-di-(fur-2-yl)-ethane and furylpropanal from a biradical mechanism. 相似文献
996.
Alan Mercer 《The Journal of the Operational Research Society》1966,17(3):235-252
The pricing and selling of industrial products are considered in sections on decision theory, bidding and personal selling. It is suggested that the marketing of consumer durables and semi-durables can be studied by means of models which use aggregate data but that consumer panel data are needed for modelling consumer expendable markets. Finally, some problems which might be suboptimized are indicated. 相似文献
997.
998.
The Casimir energy of the gravitational field in Kaluza-Klein theories is investigated. The mathematical techniques needed to compute the contribution of a single graviton loop to the quantum effective potential on a background manifold of (Minkowski space) ? (N-sphere) are developed. In these computations the cosmological constant plays a dynamical role, acting like a mass for the graviton. The numerical work for the case N = 1 is done explicitly, and a solution to the one-loop corrected equations of motion is found, although it is not stable. The possibility of an imaginary part to the effective potential for N > 1 is noted, and its existence is attributed to tachyonic terms in the mode sum. 相似文献
999.
Alan L. Balch Rosalvina R. Guimerans Marilyn M. Olmstead 《Journal of organometallic chemistry》1984,268(2):c38-c42
The preparation and interconversion of the following clusters bridged by bis(diphenylphosphinomethyl)phenylphosphine (dpmp) are reported: [Rh3(μ-dpmp)2(CO)aXb][BPh4]; X = I, a = 2, 3, 4, b = 2; X = I, a = 3, 2, 1, b = 4; X = I, a = 1, b = 6. The structure of one of these, [Rh3(μ-dpmp)2(CO)I4][BPh4], has been determined by X-ray diffraction. 相似文献
1000.
Alan R. Fersht Jian-Ping Shi Anthony J. Wilkinson David M. Blow Paul Carter Mary M. Y. Waye Greg P. Winter 《Angewandte Chemie (International ed. in English)》1984,23(7):467-473
Structure-activity relationships of enzymes can now be analyzed for the first time by the systematic alteration of protein structure. Recent developments in the chemical synthesis of DNA fragments and recombinant DNA technology enable the facile modification of proteins by highly specific mutagenesis of their genes. Kinetic analysis of the mutant enzymes combined with high-resolution structural data from protein X-ray crystallography allow direct measurements on the relationships between structure and function. In particular, the strength and nature of enzyme-substrate interactions and their detailed roles in catalysis and specificity can now be studied. We have developed such analysis of enzyme structure-function by site-directed mutagenesis of the tyrosyl-tRNA synthetase from Bacillus stearothermophilus, concentrating so far on the subtle role of hydrogen bonding in both substrate specificity and catalysis. We find that the energetics of tyrosine and ATP binding must be analyzed in terms of an exchange reaction with solvent water. Based on this idea and structural data, we have engineered an enzyme of improved enzyme-substrate affinity, and there thus appear to be real prospects of engineering proteins of new specificities, activities, and structural properties. We are also using protein engineering to gather direct information on the nature of enzyme catalysis. For example, we find the catalysis of formation of Tyr-AMP from Tyr and ATP is due largely to electrostatic and hydrogen bonding interactions that are stronger in the transition state than in the ground state—a “strain” mechanism rather than acid-base or covalent catalysis. 相似文献