A BOUNDARY ELEMENT METHOD FOR SOLVING DIRICHLET PROBLEM OF THE HELMHOLTZ EQUATION IN R~2

This paper presents a boundary element method for solving Dirichlet bou-ndary value problem of the Helmholtz equation in R~2.First,the existence andthe uniqueness of an extended solution for the problem are obtained.Then,thesolution is expressed in terms of simple layer potentials,and this expression,which is suitable to the interior as well as the exterior problem,leads to aboundary integral equation of the first kind.Finally,a finite element approachis applied to solve a variational form which is equivalent to the boundaryintegral equation.     

A Design of RBF Neural Networks Based on Genetic Algorithms

Genetic algorithms are proposed to automatically configure RBF neural networks.The network configuration is formed as a subset selection problem.Using new genetic operators,the genetic algorithms are improved in convergence and applicatility.The configuration and optimal principle of genetic algorithms are introduced.The method of generating the RBF networks is given.Finally,the simulated result on practical data is used to demonstrate the performance of the new algorithms.     

Elastic Buckling and Critical Load of an Pre- stressing Arch

According to the field theory of additional deformation on pre - stressed configuration , in the paper , the ordinary expression of the governing equation and variational equation of elastic buckling are brought forward . Under the theory system, through lowering dimensions, the governing equation and variational equation for the critical condition solution of elastic buckling of a plane arch are deduced, and the eigenvalues problem of the linear homogeneous differential equations corresponding to the equations are concluded While Abandoning the plane assumption and considering shearing deformation, the linear finite element method arithmetic of bending bar's cross section containing six degree of freedom is given. The process of derivation and calculational results show that, under this system info, the finite element equations of bending bar deduced are accurate and easy to be used to numeric calculations, and the conclusion achieved is more practical.     

Boundary Element Methods with Overlapping Domain Decomposition for Parabolic Problem

Boundary element method is a numerical method for solving partial differential equations. There are several formulations of boundary element method (BEM) applied to solve a parabolic differential equation.The approach,which employs time- dependent fundamental solution,allows longer time steps in time integration than other approaches,and this can cut down on time for computer implementation with high precision.Domain decomposition method,which decompose the domain that a given problem is to be solved into subdomains,has the advantages of reducing the large problem into smaller ones and reducing the complex problem into simpler ones,and allows parallel computing.An overlapping domain decomposition method is applied combining a boundary element formulation with time-dependent fundamental solution to solve a diffusion equation. Firstly, by domain decomposition, the problem divided into two problems on subdomains, and then the initial-Boundary problems are solved by boundry element method on each subdomain.Some numerical examples are presented to illustrate feasibility and efficiency of the method. The numerical experiments show that the convergence rate of the method is dependent with the overlapping degree of the subdomains.     

Investigations of Distribution System Planning of Loop Configurations Using a Genetic Algorithm

The distribution system planning is performed with a loop configuration constraint from scratch.With Evolutionary Algorithm,a sample distribution network is designed with a loop configuration,in which the system is operated as radial configuration.It firstly introduces the mathematical model for distribution network planning,then the application of Evolutionary Algorithm for the planning of distribution network.By using the theory mentioned above, Visual C++ is applied to develop the distribution network optimization software.Finally with the optimization process of 17 nodes system being showed,the presented algorithm's utility and validity is verified.     

SOME PROBLEMS BY USE OF BOUNDARY POINT ELEMENT IN BOUNDARY ELEMENT METHOD

Using boundary point element is one of the treatmentsof corner node problem.This paper further discusses some problems byuse of point element.They mainly include the calculation of stresses atpoint elements,the cause and treatment of singularity in boundary usingequations when point elements are used.An example is given.Correctlyboundary point element has certain practical significance for moreobjective simulation of the actual situation of quantities and improvesaccuracy of results.     

Non-linear finite element analysis based on the spatial catenary cables

According to the elastic catenary theory,this paper derives the spatial catenary cable element from the exact analytical expression,which is used for finite element analysis of the structure.It deduces the precise expression of two-node cable element tangent stiffness matrix and the tension of cable end.The equivalent node load of cable element is expressed by the total load algorithm,and the non-linear equation is solved by double Newdon-rapson method.The proposed non-linear semi-analytical finite element method based on spatial catenary cable element can take full account of the impact of non-linear geometry.The initial configuration and the internal forces on any directional spatial loads can be solved.The example shows that the calculation method is accurate and effective.     

AN IMPROVED MIXED FINITE ELEMENT METHOD OF ANALYZING THREE-DIMENSIONAL ELASTIC CONTACT PROBLEMS

This paper presents an improved mixed finite element method of analyzing elastic contact problems, in which a new numerical algorithm is developed to calculate the flexibility matrix of the contact region. With this method the contact problem of two teeth-engaging is initially solved as a three-dimensional elastic finite element analgsis, In comparison with mixed fimte element method, the improved mixed finite element method is much more efficiency in solving contact problems.     

Recognizing the reliability non-coherence components ofdistribution substation typical configuration

Reliability non-coherence components (RNC) may exist in a power system due to the effects of distribution substation connection modes, components reliability performance, load level, and other factors. Recognizing RNCs and removing them from a power system can improve system reliability. The reliability non-coherence phenomenon is analyzed and the reliability non-coherence probability, frequency and energy indices, which can describe the degree of the system reliability non-coherence feature, are proposed. Based on the reliability evaluation theory of substation configuration, recognizing technique of RNCs of distribution substation is proposed. The theoretical analysis and example show that the breaker connects high voltage buses may be the RNC when the rated capacity of one transformer can meet the load requirement, and the reliability parameters of breakers have some effects on the reliability non-coherence features of the typical substation configuration.     

Analytic Method for the Free Vibration of Plane Frame Structure

The analytic method for the free vibration of plane frame structure is presented. It is achieved by transforming the general eigenvalue problem of natural frequency and vibration mode of continuously distributed property system into typical boundary value problem of ordinary differential equation (ODE). A series of ODE, corresponding to the general eigenvalue problem, is formed, and then is solved by an general ordinary differential equation solver-COLSYS. Each component of a frame structure is regarded as an element in the analytic method. This makes it more efficient than that of finite element method which needs to increase elements to get the value of high-class natural frequency and vibration mode accurately. Some applications of the method show that it can solve the free bending vibration of plane-frame structure with various types of displacement constraint. The result indicates that this method is precise and efficient.     

A Three Dimensional Torso Model for the Numerical Simulation of ECG--Forward Problem of ECG(1)

In this paper,a numerical model of a three dimensional human torso has been presented.In this model,the torso part including anisotropic muscle layers has been discretized by means of the finite element method(FEM).The rest of torso have been divided into the surface elements by the boundary element method(BEM).This discretized model can be used in the field such as the forward problem and the inverse problem of the electrocardiogram(ECG).     

VBEM Analysis for Signorini Problem

the virtual boundary element method is applied for the numerical solution of a Signorini problem, which is conduced by an electro-paint process. The present method base on a switching algorithm, which can be applied to the problem defined in a non-regular domain, and it can reach good accuracy with less elements.     

Study on the Nonlinear Vibration System with Slow-changing Parameters

In this paper a posteriori error estimates for Galerkin approximation of general operator equations is firstly presented in the framework of Sobolev spaces. Then a practical posteriori error estimates formula for the adaptive boundary element method solving the acoustic scattering problem with a finite plane screen is obtained by triangulations. The mathematical model of this problem is the three dimensional Neumann boundary value problem of Helmholtz equation with finite plane boundary.     

A NEW BOUNDARY INTEGRAL EQUATION METHOD FOR SOLVING EXTERIOR BOUNDARY VALUE PROBLEMS OF THREE-DIMENSIONAL HELMHOLTZ EQUATION

This paper pressnts a new boundary integral equation method for solving exteri-or boundary value problems of three-dimensional Heimheltz equation by using the multiple reciproc-ity method.Firstly,integral representations of the solution in an exterior domain as well as on itsboundary,which have the peculiarity that integral kernels are infin ite seriesea developed from thenormal fundamental solution of Laplace equation and independent of the wavenumber,are given andproved under the Dirichlet condition.Then,based on the representation of the solution on the bound-ary,boundary integral equations for solving the Dirichlet and the Neumann boundary value prob-lems are obtained,and remarks for some problems concerned with solving these integral equationsnumerically are made.Finally, the advantages of the proposed method,as compared with the conven-tional boundary element methods,are summarized.     

Extension association analysis method for product family configuration

A product family extension configuration method based on evaluation model for customer demands, relational mapping and extension association rules is introduced to better realize rapid and effective product configuration. A demand-based evaluation model is confirmed by the information of customer demands and a mapping relationship between demand-based model and characters of product family cases is built. The similarity between evaluation model and product family cases is up to the association rules and a product family case with the highest similarity can be extracted according to association rules. According to the situation of the similarity, the extracted case is modified to meet the demands of configuration with case-based reasoning method. The method is validated by a speed reducer case.     

Three Dimensional Eddy-current Field computation by Edge Finite Element Method of Mixed Elements

The edge finite element interpolation function of 1-forms for prism is derived.The electrical field intensity is used as the unknown variable.If the tangential component of electrical field intensity is an enforcing condition on the interface of eddy-current region and non-eddycurrent region,the tangential component of magnetic field intensity is a natural continuous condition.At last,the mixed elements of prism and hexahedron are used to compute a three dimensional eddy-current problem.     

Nonlinear Analysis Method for Seismic Responses Considering Pounding between Girders of Curved Bridge with LRBs

A nonlinear constraint-surface impact element (CIE) was developed for simulating the pounding in axial direction between 3D shell-element-mesh bridge girders based on the engineering background of ChaoShan airport. Then, a method, different from the previous literatures, for calculating the stiffness of impact element was proposed based on the flexibility method. The methods proposed were adopted and used to analyze the elevated bridge of ChaoShan airport in GuangZhou for the purpose of investigating comprehensively the earthquake-resistance capability. The bridge girders were modeled by shell elements and CIEs were assigned to the positions of the corresponding expansion joints. Isolating elements were used to simulate LRBs, and typical bilinear LRB hysteresis stiffness model obtained from experiment were adopted to describe the dynamic hysteresis behavior. Pounding forces, dissipation capability of LRBs, lateral displacements of LRBs, pier base shear forces and moments as well as the pounding effect on these cases were investigated, respectively. The proposed methods and analysis results aim at improving the earthquake resistance of the elevated bridge, which provides reference for the similar project.     

Effects of Thorax Muscle Fiber on Body Surface Potentials

A numerical method calculating the forward problem of electrocardiogram (ECG) has been presented. By using this method, the torso part including anisotropic muscle layers has been discretized by means of the finite element method (FEM). The rest of torso have been divided into the surface elements by the boundary element method (BEM). The effects of the skelltel muscle layers over thorax wall, have been discussed in terms of a three-dimensional torso models.     

The edge element method in the forward problem of magnetic inductiontomography with homogeneous sinusoidal magnetic excitation

The edge finite element method and the imaging visualization have been studied in the forward problem of magnetic induction tomography MIT with homogeneous sinusoidal magnetic excitation. The definite equations of the forward problem were established using the electric field intensity as the vector variable. The edge FE method for solving the definite equations was introduced in detail and realized as the MATLAB program. In order to realize the visualization of MIT in imaging the intracranial hemorrhage, a real human brain finite element model was created with the human head MRI data. On the basis of this model, we realized the 3D visualization of MIT imaging in MATLAB. The research results demonstrated the validity of the definite equations and the edge FE method in calculating the forward problem. And the 3D visualization of MIT imaging with real human brain model established a foundation for the application study of MIT in imaging intracranial hemorrhage.     

AN EXTENDED TRANSFER MATRIX AND BOUNDARY ELEMENT METHOD

A combination of extended transfer matrix and boundary element method is proposed for solving two dimentional statics problems of complicated nonhomogeneous structure. It is explained with the theory and the example. The method can get greater numerical accuray and shorten computation time in small amount of computer storage without getting involved with large matrices.