基于粗糙集和神经网络的联合模式识别系统

提出了一种划分属性离散区间的新方法．针对这种划分，提出一种约简和去噪的方法．随后，建立了粗糙集和LVQ神经网络的联合模式识别系统．最后，比较了用该系统和仅用神经网络进行识别的效果，证明了该方法的有效性．     

A numerical method for computing domains of attraction for dynamical systems

The backward mapping approach for computation of global domains of attraction of asymptotically stable non-critical equilibrium points of dynamical systems is presented. A basis for the proposed approach is an extension of Lyapunov's direct method due to LaSalle and Lefschetz. An iterative process that converges to the global domain of attraction of an asymptotically stable equilibrium point is formulated. The method applies to both continuous time and discrete time multidimensional systems. It is shown that the backward mapping approach proposed by C. S. Hsu for spiral equilibrium points of second order discrete time systems is a particular case of the algorithm presented here. The proposed method can be used for autonomous systems as well as for systems with periodic coefficients. When applied to discrete time formulation of dynamical systems, the method can be used to determine the regions of stability of periodic solutions. The paper concludes with a number of illustrative examples that demonstrate the usefulness of the proposed approach.     

On the construction and numerical solution of transmission-line and lumped network models of Maxwell's equations

It is sometimes convenient to express a numerical algorithm in terms of a network model. The physical picture given can often help the engineer to visualize the properties of the method. In field problems, a lumped network model corresponds to a space discrete field while a transmission-line model corresponds to a field which is discrete in space and time. In this paper, the relationship is given between the lumped network models and transmission-line network models used in the steady-state solution of Maxwell's equations in two and three space dimensions. The use of dual networks is also discussed. An analysis is given for the velocity of waves travelling in any direction across the networks and this is used to compare the accuracy of the models. The use of diakoptics or substructures for the solution of large networks is outlined and this is illustrated by a compound two-dimensional example.     

基于主成分分析与BP网络的锚杆支护方案优选

巷道特征与锚杆支护之间可以看作是一种非线性映射关系,用一般的数学方法难以表达巷道支护方案与其影响因素之间的非线性映射关系.神经网络已广泛应用于锚杆支护方案优选,并取得较好的效果.基于单一神经网络预测锚杆支护方案存在一些不足,构建了主成分分析与BP网络相结合的巷道锚杆支护方案优选模型.利用主成分分析对神经网络的输入数据进行预处理,使输入数据减少且不相关,加快网络的收敛速度,并且预测精度均在90%以上.研究结果表明:将主成分分析与BP神经网络结合优选巷道的锚杆支护方案,具有很高的预测精度;与单一BP神经网络相比,提高了预测精度．     

追究根基的结构拓扑优化方法

结合作者在结构拓扑优化方面的研究工作,围绕了ICM(独立、连续、映射)方法涉及的基本概念上的突破,叙述了将本质上为0-1离散变量的拓扑优化问题转化为连续变量优化问题的具体做法,其中介绍了若干要点:以阶跃函数把离散问题化为连续问题即完成关键的等价性转换是第一步;定义磨光函数逼近阶跃函数的可操作的近似是第二步;引入作为磨光函数反函数的过滤函数实现映射性建模是第三步;采用某些光滑算法求解连续变量模型则是第四步。通过连续体结构的典型数值算例说明了将结构拓扑优化的模型转化为独立层次的拓扑优化过程。该方法对于纯数学的0-1离散变量优化的求解也适用,方法与数值都表明了这一点。     

基于BP神经网络的非平稳激励机械系统响应预估

利用ＢＰ人工神经网络进行非平稳激励条件下机械系统动态响应评判指标值与系统设计参数之间函数的逼近，采用收敛效率较高的学习率自适应调整算法，利用少数几次的方程求解结果进行网络训练，便可得到高效的响应评估映射，较多地减少了动态优化中评判值的计算规模。     

Spatial-frequency Fourier polarimetry of human blood plasma in the diagnostics of pathological changes

A method of polarization mapping of the optical-anisotropic polycrystalline networks of the blood plasma albumin and globulin proteins with adjusted spatial-frequency filtering of the coordinate distributions of the azimuth and ellipticity of the polarization of laser radiation in the Fourier plane is proposed and substantiated. A set of criteria of diagnosing prostate cancer based on the statistical correlation and fractal analysis of the spatial-frequency filtered polarization distributions generated by dendritic networks of albumin and globulin spherulitic networks has been detected and substantiated.     

Socio-Bibliometric Mapping of Intra-Departmental Networks

The mapping of author networks at academic departments is the focus of this study. Papers from two departments at two different universities, but within the same field of research, were analyzed in terms of co-authorship, direct and indirect citations among the authors. Considerable overlap was found between the co-authorship and the citation based networks. The paper also introduces the idea of socio-bibliometric maps that can be used to make social interpretations of bibliometric networks. The nodes of the networks were labeled by sex and seniority and supervisor-student links were also indicated. When reading the maps and tabulating the links it could be concluded that the two departmental networks were structured differently by sex and seniority.     

Multiscale simulation of nanostructures based on spatial secant model: a discrete hyperelastic approach

The main objective of this paper is to present a coarse-grained material model for the simulation of three-dimensional nanostructures. The developed model is motivated by the recent progress in establishing continuum models for nanomaterials and nanostructures. As there are conceptual differences between the continuum field defined in the classical sense and the nanomaterials consisting of discrete, space-filling atoms, existing continuum measures cannot be directly applied for mapping the nanostructures due to the discreteness at small length scale. In view of the fundamental difficulties associated with the direct application of the continuum approach, we introduce a unique discrete deformation measure called spatial secant and have developed a new hyperelastic model based on this measure. We show that the spatial secant-based model is consistently linked to the underlying atomistic model and provides a geometric exact mapping in the discrete sense. In addition, we outline the corresponding computational framework using the finite element and/or meshfree method. The implementation is within the context of finite deformation. Finally we illustrate the application of the model in studying the mechanics of low-dimensional carbon nanostructures such as carbon nanotubes (CNT). By comparing with full-scale molecular mechanics simulations, we show that the proposed coarse-grained model is robust in that it accurately captures the non-linear mechanical responses of the CNT structures.     

An optimization technique using the characteristics of genetic algorithm

Optimization problems could happen often in discrete or discontinuous search space. Therefore, the traditional gradient‐based methods are not able to apply to this kind of problems. The discrete design variables are considered reasonably and the heuristic techniques are generally adopted to solve this problem, and the genetic algorithm based on stochastic search technique is one of these. The genetic algorithm method with discrete variables can be applied to structural optimization problems, such as composite laminated structures or trusses. However, the discrete optimization adopted in genetic algorithm gives rise to a troublesome task that is a mapping between each strings and discrete variables. And also, its solution quality could be restricted in some cases. In this study, a technique using the genetic algorithm characteristics is developed to utilize continuous design variables instead of discrete design variables in discontinuous solution spaces. Additionally, the proposed algorithm, which is manipulating a fitness function artificially, is applied to example problems and its results are compared with the general discrete genetic algorithm. The example problems are to optimize support positions of an unstable structure with discontinuous solution spaces.     

A comparative analysis of methods of measuring reactive power

A comparative analysis of methods of measuring reactive power for ac networks is carried out. Analytic relations for the systematic error as a function of the current and voltage parameters are obtained. For the method based on a Hilbert converter, the complexities of its practical realization are considered. It is shown that for ac networks, the method based on the discrete Fourier transform of the current and voltage is the most accurate.     

Optimal design of water distribution networks by a discrete state transition algorithm

In this study it is demonstrated that, with respect to model formulation, the number of linear and nonlinear equations involved in water distribution networks can be reduced to the number of closed simple loops. Regarding the optimization technique, a discrete state transition algorithm (STA) is introduced to solve several cases of water distribution networks. Firstly, the focus is on a parametric study of the ‘restoration probability and risk probability’ in the dynamic STA. To deal effectively with head pressure constraints, the influence is then investigated of the penalty coefficient and search enforcement on the performance of the algorithm. Based on the experience gained from training the Two-Loop network problem, a discrete STA has successfully achieved the best known solutions for the Hanoi, triple Hanoi and New York network problems.     

Evolution of cooperation on heterogeneous supply networks

Strategies can significantly influence the performances of individual players and groups in supply networks. However, these strategies evolve over time. Thus, it is essential to probe the evolution of strategies in this context. This paper investigates the evolution of cooperation on supply networks focusing on the impacts of network topologies. Due to the difficulty in mapping the topological structures of large-scale supply networks, we introduce a topological model for supply networks. Then repeated prisoner’s dilemma game is played on the resulting networks. The simulation results show that topological structures have close relevance to the cooperation level in the networks. Compared with homogeneous structures, heterogeneous structures are helpful to promote cooperation. In addition, strategy payoff and competition pressure are also involved with the evolution of cooperation. This work may offer a useful insight into understanding complex strategy behaviours in supply networks.     

河网水动力及综合水质模型的研究

采用Preissmann 4点隐式差分格式离散一维圣维南方程组,应用三级联解法求解河网水动力数学模型。基于河道-节点-河道算法的河网水质模型的求解特点,在WASP的水质模型理论基础上,建立了河网非稳态水动力综合生态水质数学模型,考虑了多个污染物变量的耦合计算、变量之间的相互转化和迁移。利用模型对4个河网算例进行验证。验证表明,水位和流量过程计算值与实测值吻合很好,各水质变量的计算值和实测值也符合较好,可见模型是合理可靠的,为河网的水质预测和管理提供了一个较为简便实用的工具。     

基于OLS算法的RBF神经网络在大坝安全监测中的应用

文章介绍了RBF网络的基本原理以及网络中心选取OLS算法（正交最小二乘法）,并将该方法应用于大坝渗流安全监测资料的分析预报上,应用结果表明：该神经网路可以很好地克服BP神经网络学习过程的收敛过分依赖于初值和可能出现局部收敛的缺陷,具有较快的运算速度、较强的非线性映射能力和较好的预报功能。     

Analysis of scenarios of the transition to chaos in a discrete two-mode model of a free-electron laser

A discrete two-parameter two-dimensional mapping, which describes the dynamics of two modes in a free-electron laser (FEL), is investigated by nonlinear dynamics methods. Pis’ma Zh. Tekh. Fiz. 25, 17–21 (June 26, 1999)     

On temperature‐dependence of RC networks

Abstract

Resistor‐Capacitor, abbreviated as RC, networks are widely used in discrete as well as integrated circuits. Both resistors and capacitors are functions of temperature, especially, the capacitors. For many applications, it is desired to temperature‐compensate the RC networks. In this paper, a technique is introduced to temperature‐compensate RC networks that are composed of mutually independent parts. An experiment is performed to check validity of the theory. And the experimental results agree well with the theory.     

On the robustness and efficiency of integration algorithms for a 3D finite strain phenomenological SMA constitutive model

Most devices based on shape memory alloys experience large rotations and moderate or finite strains. This motivates the development of finite‐strain constitutive models together with the appropriate computational counterparts. To this end, in the present paper a three‐dimensional finite‐strain phenomenological constitutive model is investigated and a robust and efficient integration algorithm is proposed. Properly defining the variables, extensively used regularization schemes are avoided and a nucleation–completion criterion is defined. Moreover, introducing a logarithmic mapping, a new form of time‐discrete equations is proposed. The solution algorithm as well as a suitable initial guess for the resultant nonlinear equations are also deeply discussed. Extensive numerical tests are performed to show robustness as well as efficiency of the proposed integration algorithm. Implementation of the integration algorithm within a user‐defined subroutine UMAT in the commercial nonlinear finite element software ABAQUS/Standard makes also possible the solution of a variety of boundary value problems. The obtained results show the efficiency and robustness of the proposed approach and confirm the improved efficiency (in terms of solution CPU time) when a nucleation–completion criterion is used instead of regularization schemes, as well as when a logarithmic mapping is used for the time‐discrete evolution equation instead of an exponential mapping. Copyright © 2010 John Wiley & Sons, Ltd.     

力学映射下板壳结构的截面离散优化设计

依据力学映射的方法把离散变量优化问题转换为连续变量优化问题,通过在连续优化最优解附近构造两节模型,采用无穷小单元的无穷组合方法和变量连接术对板壳结构进行优化。同时在MSC公司的Nastran软件平台上利用其PCL语言开发出优化模块,并进行了算例的优化设计。