基于Agent的建模技术研究

基于Agent的建模技术是对复杂系统进行问题求解的一种新方法.在面向Agent方法的基础上提出了"基于Agent的建模技术"方法,并针对这一技术方法从系统组织的角度进行了系统性的研究,详细分析了用这一方法建模的主要流程,还首次将这一建模技术运用于"网络坦克作战系统-协作故障诊断与技术维护系统"进行实例分析,根据系统的组织结构和组织目标,构建了3类Agent:系统接口Agent,故障分析Agent和故障区域分析Agent,系统通过3类Agent间的交互协作实现问题求解.最后讨论了应用该技术应注意的主要问题.     

基于Agent的智能决策支持系统

根据决策支持系统应用中存在的问题,提出了一种新的利用决策支持系统求解问题的思路,并将Agent思想和技术引入到这一思路的实现中,设计了一种基于Agent的智能决策支持系统的架构,该架构主要由模型选择Agent、模型构造Agent、模型求解Agent和人机交互Agent 4个部分组成。该结构的实现可有效地突破基于模型的决策支持系统在求解问题时难以适应动态环境变化的障碍,使决策支持系统真正成为面向问题系统,极大地提高了决策支持系统的智能型,能够根据问题的变化作出适应性的自主的调整,满足用户的求解问题的要求。     

基于可靠性分析的MAS构建优化算法

采用多Agent技术进行制造系统建模时,Agent间可靠有效的交互协作是系统成功处理离散制造任务的重要保障。以增强多Agent系统的可靠性为目的,提出了使用并联式结构来构建多Agent系统的思想。在此基础上,给出了并联式Agent系统的可靠性评价方法,建立约束条件下的多Agent系统可靠性极大化问题的数学模型,利用填充函数算法的思想构造该模型的求解算法,并通过实例说明并联式结构和求解算法的有效性。     

基于多Agent的动态数据并行计算方法研究

为实现动态数据的快速处理和计算,提出一种基于多Agent和分布式并行计算的动态数据处理方法。该方法以智能Agent作为计算和控制的最小单元,构建有向无环的动态网络拓扑结构,采用基于信任度的合同网模型,并与阈值相结合,实现动态数据处理和快速求解,体现系统的智能性和实时性。实验结果表明,该计算方式与传统计算方式相比,系统的计算速率显著提高,实现了动态数据的实时性处理。     

多Agent系统中实时消息传递机制

1 引言 Agent是具有信念、能力、决策和承诺等精神状态的实体,它的提出是以计算的社会学模型为背景,通过多个简单Agent协同工作,可以完成比较复杂的任务。分布式人工智能(DAI)的主要目标就是解决如何组织多Agent系统中的Agent,使它们能够协同工作以完成复杂问题求解。多Agent系统的关键问题是Agent间的协同,而根据计算社会学模型的观点,消息     

基于Agent的动态路网行车最短路径求解

针对动态路网中最短路径求解算法复杂度高、计算量大、响应不及时等问题,提出基于Agent的分布式求解方法。用kd-tree将整个路网分区,每个区域由一个RMA Agent进行管理,利用多个Agent协作求解最短路径。实验表明,在路网节点较多且变化频繁时,该方法具备优势。     

基于多Agent的复合模型求解自适应QoS机制

在基于网络的分布式系统应用基础上,分析了大型复杂问题复合模型协作求解的过程特征描述,提出基于多Agent 的领域问题协作求解的主动控制策略,探讨了用户交互Agent、系统主控Agent、协作Agent以及模型Agent和数据Agent等复合模型协作求解的4种Agent类型。应用多Agent层次结构,提出一种复合模型协作求解的自适应QoS体系结构,通过实现复合模型协作求解的主动调度规划算法对其进行了验证,支持分布式网络环境下实现模型资源和数据资源的共享,以提高协同计算环境分布式问题协作求解的运行效率和服务质量。     

一个基于Agent的电子商务系统框架

电子商务是信息技术、因特网技术在商务活动中的运用 ,而基于分布式人工智能的Agent技术为电子商务系统提供了一种新的计算和问题求解方法。以Agent以及多Agent技术为背景 ,对电子商务系统进行了探讨。在此基础上 ,提出了一个基于Agent的电子商务原型系统AODEEC ,并简介了系统中若干关键技术问题的解决办法。     

宏观经济智能预测决策支持系统(MEIFDSS)模型系统的Agent实现研究

将文中给出的数学模型用七元组表示,Agent用三元组表示后,给出了从模型到Agent的映射关系,由此构建MEIFDSS基于Agent的模型系统,并对系统中多模型Agent之间的合作进行研究,最后利用面向对象的继承机制实现具体求解模型Agent。为基于Agent的模型系统的实现提供了一种新的思路和方法。     

多Agent系统的安全性研究

移动Agent技术为建立电子商务、移动计算等分布式应用系统提供了灵活、强大的方法。在构建这些系统的过程中,安全性是一个十分关键的问题。我们必须建立一种足够安全的体系结构,防止恶意的Agent攻击主机和确保Agent自身的完整性。文章研究了多Agent系统中的安全问题和加强安全性的方法。     

3D IEM formulation with an IEM/FEM coupling scheme for solving elastostatic problems

In this paper, a detailed three-dimensional infinite element methodology (IEM) formulation with an infinite element (IE)–finite element (FE) coupling scheme for investigating elastostatic problems is presented. This method is equally well suited for a regular perfect domain and a domain with geometric singularity; for example, domains with cracks. In this method, the primary problem domain is subdivided into two sub-domains modeled separately using IEM and finite element method (FEM), respectively. All degrees of freedom related to the IE sub-domain, except for those associated with the coupling interface, are condensed and transformed to form a finite master IE with the master nodes on the sub-domain boundary. Finally, a symmetrical IE stiffness matrix containing only master node degrees of freedom is assembled into the system stiffness matrix for the FE sub-domain. A very fine mesh pattern can be established using these efficient numerical techniques without increasing the d.o.f.'s of the global FEM solution. Numerical examples are presented and compared with the corresponding analytical or numerical solutions to show the performance of the proposed methodology.     

并行计算在高超声速流场数值模拟中的应用

采用计算流体力学方法,对高超声速流场进行了多区并行计算研究。基于MPI消息传递库采用Fortran语言编制了CFD并行计算程序,对NS方程采用AUSMPW+格式和LU-SGS方法求解。针对流场采用多区剖分,将每一个子区分配给相应节点进行计算。每一迭代步,相邻子区域间交换边界数据。计算表明,本文所建立的程序和方法是可行的,能够进一步延伸到大规模并行计算和工程应用中。     

Direct Discretization Method for the Cahn–Hilliard Equation on an Evolving Surface

We propose a simple and efficient direct discretization scheme for solving the Cahn–Hilliard (CH) equation on an evolving surface. By using a conservation law and transport formulae, we derive the CH equation on evolving surfaces. An evolving surface is discretized using an unstructured triangular mesh. The discrete CH equation is defined on the surface mesh and its dual surface polygonal tessellation. The evolving triangular surfaces are then realized by moving the surface nodes according to a given velocity field. The proposed scheme is based on the Crank–Nicolson scheme and a linearly stabilized splitting scheme. The scheme is second-order accurate, with respect to both space and time. The resulting system of discrete equations is easy to implement, and is solved by using an efficient biconjugate gradient stabilized method. Several numerical experiments are presented to demonstrate the performance and effectiveness of the proposed numerical scheme.     

无结构网格上解油藏数值模拟方程的区域并行差分格式

1.导 论 我们知道,结构网格有很多优点,对简单几何区域网格生成是直接的,可利用其顶点间的连结特点发展解算法,算法易于向量化.对复杂的计算区域,特别是油藏数值模拟所要计算的区域,产生适当的(有)结构网格是困难的,因此对网格放弃内在的结构要求,采取了完全无结构网格.由于无结构网格结构复杂,如何在它们上离散油藏数值模拟方程(组)一直是     

Component-Based Derivation of a Parallel Stiff ODE Solver Implemented in a Cluster of Computers

A component-based methodological approach to derive distributed implementations of parallel ODE solvers is proposed. The proposal is based on the incorporation of explicit constructs for performance polymorphism into a methodology to derive group parallel programs of numerical methods from SPMD modules. These constructs enable the structuring of the derivation process into clearly defined steps, each one associated with a different type of optimization. The approach makes possible to obtain a flexible tuning of a parallel ODE solver for several execution contexts and applications. Following this methodological approach, a relevant parallel numerical scheme for solving stiff ODES has been optimized and implemented on a PC cluster. This numerical scheme is obtained from a Radau IIA Implicit Runge–Kutta method and exhibits a high degree of potential parallelism. Several numerical experiments have been performed by using several test problems with different structural characteristics. These experiments show satisfactory speedup results.     

A parallel finite element scheme for thermo-hydro-mechanical (THM) coupled problems in porous media

Many applied problems in geoscience require knowledge about complex interactions between multiple physical and chemical processes in the sub-surface. As a direct experimental investigation is often not possible, numerical simulation is a common approach. The numerical analysis of coupled thermo-hydro-mechanical (THM) problems is computationally very expensive, and therefore the applicability of existing codes is still limited to simplified problems. In this paper we present a novel implementation of a parallel finite element method (FEM) for the numerical analysis of coupled THM problems in porous media. The computational task of the FEM is partitioned into sub-tasks by a priori domain decomposition. The sub-tasks are assigned to the CPU nodes concurrently. Parallelization is achieved by simultaneously establishing the sub-domain mesh topology, synchronously assembling linear equation systems in sub-domains and obtaining the overall solution with a sub-domain linear solver (parallel BiCGStab method with Jacobi pre-conditioner). The present parallelization method is implemented in an object-oriented way using MPI for inter-processor communication. The parallel code was successfully tested with a 2-D example from the international DECOVALEX benchmarking project. The achieved speed-up for a 3-D extension of the test example on different computers demonstrates the advantage of the present parallel scheme.     

Error function scheme for Burgers' equation

The present paper is devoted to the development of a new scheme to solve the one-dimensional time-dependent Burgers' equation locally on sub-domains, using similarity reductions for partial differential equations. Each sub-domain is divided into three grid points. The ordinary differential equation deduced from the similarity reduction can be integrated and is then used to approximate the flux vector in the Burgers' equation. The arbitrary constants in the analytical solution of the similarity equation can be determined in terms of the dependent variables at the grid points in each sub-domain. This approach eliminates the difficulties associated with boundary conditions for the similarity reductions over the whole solution domain. Numerical results are obtained for two different test cases and are compared with other numerical results.     

A numerical scheme for mixed boundary value problems in elasticity

A numerical scheme, based upon the Kobayashi-Tranter method with certain modifications, is given for axisymmetric punch and crack problems in elasticity. The problems are reduced to solving a system of linear algebraic equations instead of a Fredholm integral equation of the second kind. A standard program thus allows the treatment of a range of different cases.The indentation of a rigid punch on an elastic layer overlying an elastic foundation is formulated in this fashion and numerical results for various cases are presented.     

Localized radial basis functions-based pseudo-spectral method (LRBF-PSM) for nonlocal diffusion problems

Spectral/pseudo-spectral methods based on high order polynomials have been successfully used for solving partial differential and integral equations. In this paper, we will present the use of a localized radial basis functions-based pseudo-spectral method (LRBF-PSM) for solving 2D nonlocal problems with radial nonlocal kernels. The basic idea of the LRBF-PSM is to construct a set of orthogonal functions by RBFs on each overlapping sub-domain from which the global solution can be obtained by extending the approximation on each sub-domain to the entire domain. Numerical implementation indicates that the proposed LRBF-PSM is simple to use, efficient and robust to solve various nonlocal problems.     

A modified predictor-corrector scheme for the Klein–Gordon equation

A numerical method based on a three-time level finite-difference scheme has been proposed for the solution of the two forms of the Klein–Gordon equation. The method, which is analysed for local truncation error and stability, leads to the solution of a nonlinear system. To avoid solving it, a predictor-corrector scheme using as predictor a second-order explicit scheme is proposed. The procedure of the corrector is modified by considering, as known, the already evaluated corrected values instead of the predictor ones. This modified scheme is applied to problems possessing periodic, kinks and soliton waves. The accuracy as well as the long-time behaviour of the proposed scheme is discussed and comparisons with the relevant known in the bibliography schemes are given.