A new robust optimisation algorithm, which can be regarded as a modification of the recently developed cuckoo search, is presented. The modification involves the addition of information exchange between the top eggs, or the best solutions. Standard optimisation benchmarking functions are used to test the effects of these modifications and it is demonstrated that, in most cases, the modified cuckoo search performs as well as, or better than, the standard cuckoo search, a particle swarm optimiser, and a differential evolution strategy. In particular the modified cuckoo search shows a high convergence rate to the true global minimum even at high numbers of dimensions. 相似文献

This paper is concerned with a family of genetic algorithms for the pallet loading problem. Our algorithms differ from previous applications of genetic algorithms to two-dimensional packing problems in that our coding contains all the information needed to produce the packing it represents, rather than relying on a packing algorithm to decode each individual solution. We experiment with traditional one-dimensional string representations, and a two-dimensional matrix representation which preserves the notion of closeness between positions on the pallet. Two new crossover operators are introduced for the two-dimensional case. Our definition of solution space includes both feasible and infeasible solutions and we suggest a number of different fitness functions which penalise infeasibility in different ways and a repair operator which allows our populations to maintain feasibility. The results of experiments designed to test the effectiveness of these features are presented. 相似文献

This paper considers competitive Lotka-Volterra population dynamics with jumps. The contributions of this paper are as follows. (a) We show that a stochastic differential equation (SDE) with jumps associated with the model has a unique global positive solution; (b) we discuss the uniform boundedness of the pth moment with p>0 and reveal the sample Lyapunov exponents; (c) using a variation-of-constants formula for a class of SDEs with jumps, we provide an explicit solution for one-dimensional competitive Lotka-Volterra population dynamics with jumps, and investigate the sample Lyapunov exponent for each component and the extinction of our n-dimensional model. 相似文献

We present the necessary conditions for the existence of the Kolwankar-Gangal local fractional derivatives (KG-LFD) and introduce more general but weaker notions of LFDs by using limits of certain integral averages of the difference-quotient. By applying classical results due to Stein and Zygmund (1965) [16] we show that the KG-LFD is almost everywhere zero in any given intervals. We generalize some of our results to higher dimensional cases and use integral approximation formulas obtained to design numerical schemes for detecting fractional dimensional edges in signal processing. 相似文献

This paper presents a finite element visualization facility, FEView, which has been implemented based upon an object-oriented graphics library. The visualization tool works as an external module to an interactive program Geomview for viewing and manipulating geometric objects. The graphical user interface has been built on top of the Forms Library, a graphical user interface toolkit for Silicon Graphics workstations.

A finite element mesh can be considered as a collection of faces with edges, wire frame, or point cloud, and the corresponding numerical results gained through finite element analyses can be visualized via color shading and field icons (such as arrows) on the geometric shapes. Also, a scalar field can be represented as a weather map to highlight color shading domains with scalar values falling into the range of interest. Numerical results for two-dimensional cases can be shown with three-dimensional effects by using values of the scalar field. FEView provides animation control over single frame stepping and adjustable speed playing. It has been equipped with geometry operation functionality, in which a particular part of an object can be obtained by specifying material indices, element numbers, and cutting boxes. In local analysis mode, FEView is able to provide local information about finite element objects by picking up the position of interest via mouse manipulation. 相似文献

This paper is concerned with the use of simulated annealing in the solution of the multi-objective examination timetabling
problem. The solution method proposed optimizes groups of objectives in different phases. Some decisions from earlier phases
may be altered later as long as the solution quality with respect to earlier phases does not deteriorate. However, such limitations
may disconnect the solution space, thereby causing optimal or near-optimal solutions to be missed. Three variants of our basic
simulated annealing implementation which are designed to overcome this problem are proposed and compared using real university
data as well as artificial data sets. The underlying principles and conclusions stemming from the use of this method are generally
applicable to many other multi-objective type problems. 相似文献

We prove that the critical problem for the p-Laplacian operator admits a nontrivial solution in annular shaped domains with sufficiently small inner hole. This extends Coron's result [4] to a class of quasilinear problems. 相似文献

By using a coupling method, an explicit log-Harnack inequality with local geometry quantities is established for (sub-Markovian) diffusion semigroups on a Riemannian manifold (possibly with boundary). This inequality as well as the consequent L^{2}${L}^{2}$-gradient inequality, are proved to be equivalent to the pointwise curvature lower bound condition together with the convexity or absence of the boundary. Some applications of the log-Harnack inequality are also introduced. 相似文献

We study the existence and non-existence of positive singular solutions of second-order non-divergence type elliptic inequalities of the form $\sum\limits_{i,j = 1}^N {a_{ij} (x)\frac{{\partial ^2 u}} {{\partial x_i \partial x_j }}} + \sum\limits_{i = 1}^N {b_i (x)\frac{{\partial u}} {{\partial x_i }} \geqslant K(x)u^p ,} - \infty < p - \infty , $ with measurable coefficients in a punctured ball B_{ R } \{0} of ?^{ N }, N ≥ 1. We prove the existence of a critical value p* which separates the existence region from the non-existence region. We show that in the critical case p = p*, the existence of a singular solution depends on the rate at which the coefficients (a_{ i j }) and (b_{ i }) stabilize at zero, and we provide some optimal conditions in this setting. 相似文献