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981.
982.
Let $M$ be a compact immersed submanifold of the Euclidean space, the hyperbolic space or the standard sphere. For any continuous
potential q on M, we give a sharp upper bound for the second eigenvalue of the operator −Δ+q in terms of the total mean curvature of M and the mean value of q. Moreover, we analyze the case where this bound is achieved. As a consequence of this result we obtain an alternative proof
for the Alikakos–Fusco conjecture concerning the stability of the interface in the Allen–Cahn reaction diffusion model.
Received: 18 June 1999 / Accepted: 6 July 1999 相似文献
983.
984.
Amir Azaron Reza Tavakkoli-Moghaddam 《European Journal of Operational Research》2007,180(3):1186-1200
We develop a multi-objective model for the time–cost trade-off problem in a dynamic PERT network using an interactive approach. The activity durations are exponentially distributed random variables and the new projects are generated according to a renewal process and share the same facilities. Thus, these projects cannot be analyzed independently. This dynamic PERT network is represented as a network of queues, where the service times represent the durations of the corresponding activities and the arrival stream to each node follows a renewal process. At the first stage, we transform the dynamic PERT network into a proper stochastic network and then compute the project completion time distribution by constructing a continuous-time Markov chain. At the second stage, the time–cost trade-off problem is formulated as a multi-objective optimal control problem that involves four conflicting objective functions. Then, the STEM method is used to solve a discrete-time approximation of the original problem. Finally, the proposed methodology is extended to the generalized Erlang activity durations. 相似文献
985.
In this paper, locating some warehouses as distribution centers (DCs) in a real-world military logistics system will be investigated. There are two objectives: finding the least number of DCs and locating them in the best possible locations. The first objective implies the minimum cost of locating the facilities and the latter expresses the quality of the DCs locations, which is evaluated by studying the value of appropriate attributes affecting the quality of a location. Quality of a location depends on a number of attributes; so the value of each location is determined by using Multi Attribute Decision Making models, by considering the feasible alternatives, the related attributes and their weights according to decision maker’s (DM) point of view. Then, regarding the obtained values and the minimum number of DCs, the two objective functions are formed. Constraints imposed on these two objectives cover all centers, which must be supported by the DCs. Using Multiple Objective Decision Making techniques, the locations of DCs are determined. In the final phase, we use a simple set partitioning model to assign each supported center to only one of the located DCs. 相似文献
986.
Reaction of substituted benzene rings with N‐bromophthalimide, under neutral conditions, gave the corresponding bromo derivatives with a preference for the formation of the para bromo isomer over the ortho isomer. The simple work‐up procedure minimizes loss of product and the yields are good. 相似文献
987.
Reza Zadmard Dr. Saeed Taghvaei‐Ganjali Dr. Banafsheh Gorji Dr. Thomas Schrader Prof. Dr. 《化学:亚洲杂志》2009,4(9):1458-1464
A dimeric calixarene, with an aliphatic C6‐bridge and six anilinium head groups at its upper rim, preferably complexes diphosphates and oligonucleotides with more than 10 bonds between both anionic moieties. Free binding energies correlate with the length of the aliphatic bridge in a roughly linear fashion. The binding event, which is monitored by fluorescence titrations and competition experiments, relies on Coulomb interactions, as opposed to a nonpolar variant with tert‐butyl instead of ammonium groups; here, hydrophobic forces prevail, rendering the calixarene dimer selective for less polar cofactors such as FAD. The best guest for the hexaanilinium dimer is found in ssDNA, which carries multiple copies of the optimal trinucleotide for maximum attraction towards the extended cationic host. The recognition event is also observed in the environment of a lipid monolayer, and provides a means to quantify dimer diphosphate interactions by measuring p/A shifts. 相似文献
988.
Saqib Ali Syed Usman Ahmad Sadiq‐ur‐Rehman Saira Shahzadi Masood Parvez Muhammad Mazhar 《应用有机金属化学》2005,19(1):200-200
A trigonal bipyramidal C2ClS2 coordination geometry for tin is found in Ph2Sn(S2CN(CH2)5)Cl. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
989.
P.J. Daly C.T. Zhang P. Bhattacharyya R. Broda Z.W. Grabowski D. Nisius I. Ahmad M.P. Carpenter L.R. Morss W.R. Phillips J.L. Durell M.J. Leddy A.G. Smith W. Urban B.J. Varley N. Schulz E. Lubkiewicz M. Bentaleb J. Blomqvist 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(2):203-204
Prompt γ-ray cascades in neutron-rich nuclei around doubly-magic 132Sn have been studied using a 248Cm fission source. Yrast states located in the N = 82 isotones 134Te and 135I are interpreted as valence proton and neutron particle-hole core excitations with the help of shell model calculations employing empirical nucleon-nucleon interactions from both 132Sn and 208Pb regions. 相似文献
990.
Steps, ledges and kinks on the surfaces of platinum nanoparticles of different shapes 总被引:1,自引:0,他引:1
Platinum nanoparticles with a high percentage of cubic-, tetrahedral- and octahedral-like shapes, respectively, have been synthesized by a shape-controlling technique that we developed recently [Ahmadi et al., Science 272 (June 1996) 1924]. High resolution transmission electron microscopy (HRTEM) is used here to directly image the atomic scale structures of the surfaces of these particles with different shapes. The truncated shapes of these particles are mainly defined by the {100}, {111}, and {110} facets, on which numerous atom-high surface steps, ledges and kinds have been observed. This atomic-scale fine structure of the surfaces of these particles is expected to play a critical role in their catalytic activity and selectivity. 相似文献