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51.
52.
We present vibrational dynamics and thermodynamics for the (1 0 0) surfaces of Cu, Ag, Pd, Pt and Au using a real space approach. The force field for these systems is described by density functional theory. The changes in the vibrational dynamics and thermodynamics from those in bulk are confined mostly to the first-layer. A substantial enhancement of the low-frequency end of the acoustic branch was found and is related to a loosening of the bond at the surface. The thermodynamics of the first-layer also show significant differences (higher heat capacity, lower free energy and higher mean vibrational square amplitudes) from what obtains in bulk. Comparing these results with those calculated using embedded-atom method potentials, we discovered that for Ag(1 0 0) and Cu(1 0 0), the two methods yield very similar results while for Pd(1 0 0), Pt(1 0 0) and Au(1 0 0) there are substantial differences.  相似文献   
53.
54.
The Knapsack Sharing Problem (KSP) is an NP-Hard combinatorial optimization problem, admitted in numerous real world applications. In the KSP, we have a knapsack of capacity c and a set of n objects, namely N, where each object j, j = 1,...,n, is associated with a profit p j and a weight w j. The set of objects N is composed of m different classes of objects J i, i = 1,...,m, and N = m i=1 J i. The aim is to determine a subset of objects to be included in the knapsack that realizes a max-min value over all classes.In this article, we solve the KSP using an approximate solution method based upon tabu search. First, we describe a simple local search in which a depthparameter and a tabu list are used. Next, we enhance the algorithm by introducing some intensifying and diversifying strategies. The two versions of the algorithm yield satisfactory results within reasonable computational time. Extensive computational testing on problem instances taken from the literature shows the effectiveness of the proposed approach.  相似文献   
55.
Ethyl α-cyano-4-(methacryloxy)cinnamate was synthesized to prepare new photosensitive polymers. Homopolymerization and copolymerizations were carried out in solution in chloroform at 65 °C using AIBN as an initiator. Methyl methacrylate was chosen as comonomer for the studies of copolymerzation. The structures formed were characterized by IR and 1H NMR spectroscopies. The values of reactivity ratios of the comonomers calculated according to the Finneman-Ross method indicated that the reactivity of the synthesized photosensitive monomer is lower than that of MMA. Thin films of the obtained polymers were prepared to study their ability to crosslink under UV irradiation. The photodimerization of the cinnamate moieties was characterized.  相似文献   
56.
We discuss conditions for the existence of at least one solution of semilinear evolution inclusions with a nonlocal condition and a nonconvex right-hand side. Our technique is based on fixed point theorems for multivalued maps.  相似文献   
57.
The goal of this paper is to analyse some spectral properties of time‐dependent monoenergetic linear transport equation with perfect reflecting boundary conditions.It is proved that the streaming operator generates a strongly continuous group and its explicit expression is derived. This enables us to investigate in details the compactness properties of the second‐order remainder term of the Dyson–Phillips expansion for a large class of collision operators. The validity of the obtained results for perfect periodic boundary conditions is also discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
58.
In this paper we study the stabilization of plate vibrations by means of piezoelectric actuators. In this situation the geometric control condition of Bardos, Lebeau and Rauch [6] is not satisfied. We prove that we have exponential stability for the low frequencies but not for the high frequencies. We give an explicit decay rate for regular initial data at high frequencies while clarifying the behavior of the constant which intervenes in this estimation there function of the frequency of cut n. The method used is based on some trace regularity which reduces stability to some observability inequalities for the corresponding undamped problem. Moreover, we show numerically at low frequencies, that the optimal location of the actuator is the center of the domain Ω. Research supported by the RIP program of Oberwolfach Institut and by the Tunisian Ministry for Scientific Research and Technology (MRST) under Grant 02/UR/15-01. Research supported by the RIP program of Oberwolfach Institut. (Received: September 17, 2003; revised: February 26, 2004)  相似文献   
59.
In the present work, we investigate nonlinear three-point boundary value problems (second-order differential equations with boundary conditions imposed at three consecutive points) in an effort to understand the conditions that must be imposed upon nonlinear perturbations of a linear problem in order to obtain a solution of a three-point problem. Both the noncritical case and the critical case are considered. In the first case, existence and uniqueness results are obtained, and in the second case we deal with local bifurcation problems when the nonlinearities are quadratic and cubic.  相似文献   
60.
We present a numerical study of large deformations of non-linearly elastic membranes. We consider the non-linear membrane model obtained by Le Dret and Raoult using Γ-convergence, in the case of a Saint Venant-Kirchhoff bulk material. We consider conforming P1 and Q1 finite element approximations of the membrane problem and use a non-linear conjugate gradient algorithm to minimize the discrete energy. We present numerical tests including membranes subjected to live pressure loads.  相似文献   
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