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821.
The electronic structure of substitutional non-magnetic impurities Cu, Ag, Cd, Mg, Zn, Ga, In, Ge, Si and Sn in Al is studied
using density functional theory. A simple physical model is proposed to calculate the effective charges on impurities in trivalent
metal Al. A linear relation is found between the effective charges on impurities and impurity vacancy capture radii. The spherical
solid model (SSM) is used to account for discrete nature of the host. The impurity-induced change in charge density, scattering
phase shifts, host-impurity potential, residual resistivity and impurity self-energy are calculated. Higher order scattering
phase shifts are found significant and the host-impurity potential is found proportional to effective charge on impurity in
its vicinity. The self-consistently calculated potential is used to calculate the electric field gradients (EFGs) at the first
and second nearest neighbours (1NNs, 2NNs) of impurity. The calculated values are in agreement with the experimental results. 相似文献
822.
B. Boffey Francisco Ramón Fernández García Gilbert Laporte Juan A. Mesa Blas Pelegrín Pelegrín 《TOP》1995,3(2):167-220
Summary Many network routing problems, particularly where the transportation of hazardous materials is involved, are multiobjective
in nature; that is, it is desired to optimise not only physical path length but other features as well. Several such problems
are defined here and a general framework for multiobjective routing problems is proposed. The notion of “efficient solution”
is defined and it is demonstrated, by means of an example, that a problem may have very many solutions which are efficient.
Next, potentially useful solution methods for multiobjective routing problems are discussed with emphasis being placed on
the use of shortest/k-shortest path techniques. Finally, some directions for possible further research are indicated.
Invited by B. Pelegrin 相似文献
823.
Excess molar Gibbs free energies of mixing for 1-propanol or 2-propanol + cyclohexane over the whole composition range at 298.15 and 308.15 K have been calculated from vapour pressure data measured by static method. The data have been analysed in terms of a Mecke-Kempter association model with a Flory contribution term. 相似文献
824.
A class of set covering problems is being introduced. This class is obtained from reformulation of a well-known combinatorial problem of Erdös on the hypercube. An algorithmic method of solution to the problem is proposed. Max-flow algorithms are the main ingredients of our method.The computational results which will be presented here, improves the best existing bound related to the combinatorial problem. This, at the same time, provides a good approximate solution to the corresponding set covering problem of more than a thousand variables and constraints.Moreover, we show that our special class of problems can be recognized from the class of all set covering problems, by a polynomial algorithm with O (MN) complexity, where M and N are numbers of constraints and variables of a given instant, respectively.This research is supported by EPSCOR-NSF of Puerto Rico and by FIPI, the institutional grant of University of Puerto Rico. 相似文献
825.
826.
O. P. Singh A. P. Singh Ajai Kumar L. S. Yadav J. S. Yadav 《Journal of Chemical Sciences》1988,100(5):441-446
Giambiagi’s definition of oxidation number of an atom in a molecule has been applied successfully in theab initio SCF theory to calculate oxidation numbers using STO-3G and 4–31G basis sets for some substituted benzenes involving -F, -OH,
-CH3 and -NH2 as substituents. The present study suggests that the oxidation numbers also seem to be indicative of their orientational
behaviour like the net atomic charges. 相似文献
827.
Kinetics of oxidation of ethylene glycol and glycerol by acidic solution of N-bromoacetamide (NBA) in the presence of ruthenium (III) chloride as a homogeneous catalyst and mercuric acetate as scavenger in the temperature range of 30–50°C have been reported. The reactions follow identical kinetics, being zero-order in substrate and first-order in Ru(III). First order dependence of the reaction on NBA at its low concentrations tends to zero order in the higher concentration range. Positive effect of [H?] and [Cl?] has been observed. A negative effect of acetamide and ionic strength of the medium is observed while D2O and mercuric acetate show zero effect on the reaction velocity. Various activation parameters have been computed. The main product of the oxidation is corresponding acid. (H2OBr)+ has been postulated as the oxidizing species. A suitable mechanism in conformity with the kinetic data has been proposed. 相似文献
828.
Sulphonated styrene-divinylbenzene resins with various cross-linking have been synthesized and the dehydration of 2-butanol
has been studied on these acid catalysts. The pore structure of the resin controls the rate of dehydration. Thecis totrans ratio of the 2-butene formed indicate that the resin catalysts behave like aqueous solution of acids, i.e.dissociated protons
are responsible for catalysis. 相似文献
829.
V. K. Gupta S. K. Badval I. K. Daftari G. L. Kaul L. K. Mangotra N. K. Rao S. K. Sharma Gian Singh Y. Prakash 《Zeitschrift fur Physik C Particles and Fields》1981,10(1):29-36
The shower particle multiplicity (〈n s 〉) in thep-nucleus interactions for different targets, in the incident energy range of ~6–500 GeV has been studied. The variation of multiplicity parameters with target mass (A) or with number of interactions that the incident hadron suffers inside the nucleus (v A ) and with the changed particle multiplicity inp-p interactions (〈n ch〉) has been examined in the light of the various models of multiparticle production. The present analysis favours the hydrodynamical model though some other models can not be conclusively ruled out. 相似文献
830.