Vibrations of grids by the finite element method

The finite element method is applied to the free vibration analysis of grids with arbitrary configuration. Grid bars are of solid or thin-walled doubly symmetric cross-section. Stiffness and consistent mass matrices for flexural behavior include the effects of shear deformation and rotary inertia in bending. The torsional behavior of solid sections is approximated by a linear displacement field, and of thin-walled sections, by a cubic. Rotary inertia in torsion is included in both cases and warping inertia, in the latter.

The computer program performs the free vibration analysis starting from the element stiffness and consistent mass matrices. A numerical solution of a thin-walled beam and a parametric solution of an orthogonal and a skew grid with solid and thin-walled bars are presented.     

Computerized ultimate strength analysis of reinforced concrete sections subjected to axial compression and biaxial bending

This article presents a method of evaluating the ultimate strength capacities of reinforced concrete sections of arbitrary shapes and with or without voids subjected to axial compression and biaxial bending. The concept of load fraction is introduced so as to provide a quantitative measure of structural adequacy. An iterative procedure to determine the load fractions is proposed. Necessary integration over arbitrary domains is dealt with by boundary integration method. This procedure can be computerized readily to high automation. A wide range of reinforced concrete sections are analysed, as examples, using a desk-top computer.     

Elastic torsion of thin walled bars of variable cross sections

An application of the finite element method to the theory of thin walled bars of variable cross sections has been presented in this paper. A solution of this problem is based on the linear membrane shell theory with the application of Vlasov's assumptions. A bar is divided into elements along its longitudinal axis and then, a shell mid-surface of the element is approximated by arbitrary triangular Subelements. Nodal displacements of the element are assumed to be polynomials of the third order and the equivalent stiffness matrix is obtained. Calculated nodal displacements enable an analysis of normal and shearing stresses.     

Dynamics of shells of revolution under axisymmetric load involving shear deformation

A general solution procedure, based on the linear theory, is presented for arbitrary shells of revolution subjected to arbitrary axisymmetric dynamic loads. The equations of motion admit shear deformation and rotational inertia. The numerical solution is obtained by Houbolt's method and by finite differences.     

A projection method for closed-loop identification

A new method for closed-loop identification that allows fitting the model to the data with arbitrary frequency weighting is described and analyzed. Just as the direct method, this new method is applicable to systems with arbitrary feedback mechanisms. This is in contrast to other methods, such as the indirect method and the two-stage method, that assume linear feedback. The finite sample behavior of the proposed method is illustrated in a simulation study.     

Approximating of conic sections by DP curves with endpoint interpolation

Conic sections have many applications in industrial design, however, they cannot be exactly represented in polynomial form. Hence approximating conic sections with polynomials is a challenging problem. In this paper, we use the monomial form of Delgado and Peña (DP) curves and present a matrix representation for them. Using the matrix form and the least squares method, we propose a simple and efficient algorithm for approximating conic sections by DP curves of arbitrary degree with endpoint interpolation. Finally, we test and compare the proposed algorithm on some numerical examples which validates and confirms efficiency of it.     

Surface Reconstruction From Non-parallel Curve Networks

Building surfaces from cross‐section curves has wide applications including bio‐medical modeling. Previous work in this area has mostly focused on connecting simple closed curves on parallel cross‐sections. Here we consider the more general problem where input data may lie on non‐parallel cross‐sections and consist of curve networks that represent the segmentation of the underlying object by different material or tissue types (e.g., skin, muscle, bone, etc.) on each cross‐section. The desired output is a surface network that models both the exterior surface and the internal partitioning of the object. We introduce an algorithm that is capable of handling curve networks of arbitrary shape and topology on cross‐section planes with arbitrary orientations. Our algorithm is simple to implement and is guaranteed to produce a closed surface network that interpolates the curve network on each cross‐section. Our method is demonstrated on both synthetic and bio‐medical examples.     

Forced vibration of a curved beam with viscous damping

A generalization of the dynamic solution for an arbitrary plane curved beam with viscous damping, under arbitrary load, is presented. The equation of motion, based on the linear theory, admits proportionality of the damping to the mass and stiffness matrices (Raleigh damping). The numerical solution is obtained by direct time-integration, using backward differences (Houbolt's method). A general computer program (CURBEAM) was written for this purpose and a numerical example is presented.     

基于支撑向量机的收敛问题研究

在文章中提出了一种基于支持向量机思想的对任意距离空间求解最大分类间隔的方法,其优化问题可以用输入空间的距离来表示。首先将输入空间等距嵌入到Hilbert空间,在线性的Hilbert空间对优化问题进行线性处理,但是这种方法只适用于特定的距离空间。在原方案的基础上扩展研究了对任意距离空间求解最大分类间隔的方法。     

Making Doo-Sabin surface interpolation always work over irregular meshes

This paper presents a reliable method for constructing a control mesh whose Doo-Sabin subdivision surface interpolates the vertices of a given mesh with arbitrary topology. The method improves on existing techniques in two respects: (1) it is guaranteed to always work for meshes of arbitrary topological type; (2) there is no need to solve a system of linear equations to obtain the control points. Extensions to include normal vector interpolation and/or shape adjustment are also discussed.     

The Use of Iteration Space Partitioning to Construct Representative Simple Sections

A method is presented of constructing a number of regions in a 2-dimensional array such that all accesses that can be induced by an arbitrary occurrence of this array in a program are limited to one of these regions. The index set of such regions will be described in terms of 2-dimensional simple sections. Furthermore, we show how simple loop transformations can be used to increase the number of resulting regions. In particular, this method is very useful for a restructuring compiler that performs data structure transformations.     

布尔函数与扩散码的组合安全性

本文对扩散码密码体制中多列扩散码组合对布尔函数次数的影响进行了探讨,引入了单项,、多项和函数的组合约化的概念,搪塞了组合约化的条件,给出了在扩散码列的任意线性组合下布尔函数ｒ次可约性的检验方法,并获得了一个布尔函数和扩散码的充分条件,在这个条件下对任意的线性组合布尔函数的次数不低于ｒ,文末给出了说明检验方法的实例。     

状态反馈极点配置问题

本文研究了线性时不变多变量系统引进状态反馈任意配置闭路极点问题,首先导出了系统的一种新的标准型,然后给出了计算状态反馈矩阵的一种新方法,其主要的运算是解一组含有n-p+1个未知数的线性代数方程,算法简单,然后举例说明了这种方法的应用。文中同时还证明了状态反馈闭路系统特征方程可以分解为二个多项式之积,其阶数分别为n-p+1和p-1,而其系数为反馈矩阵元素的线性函数。     

A novel algorithm for the design of selective FIR filters with arbitrary amplitude and phase characteristics

In this paper, a novel analytic technique is presented for the design of finite impulse response digital filters with simultaneous amplitude and phase requirements. The design process relies on the interpolation concept and is based on the generation of arbitrary amplitude and phase polynomials. The new class of FIR filters lays in between the exact linear phase filters at all frequencies and the minimum phase FIR filters based on the amplitude approximation only. It interpolates arbitrary (e.g., linear) phase response in the passband and arbitrary amplitude characteristics in pass- and stopbands. The introduced class of filters can be used on the amplitude and phase equalization of both FIR and IIR digital filters. Illustrative examples are included in order to investigate the main properties of these filters and to demonstrate that the proposed design method leads to a significant saving in the arithmetic computations.     

电涡流传感器特性曲线拟合的新方法

为了减小电涡流传感器的非线性误差,在最小二乘法的基础上,结合0.618优选法,使拟合方程式中的常数更合理。用这种方法可以求得最佳拟合直线方程和最小的非线性误差。此法适用于各种类型的线性传感器或可以通过适当的变量代换把变量之间的非线性关系化为线性关系的传感器或测量系统。     

A Linear Relaxation Technique for the Position Analysis of Multiloop Linkages

This paper presents a new method to isolate all configurations that a multiloop linkage can adopt. The problem is tackled by means of formulation and resolution techniques that fit particularly well together. The adopted formulation yields a system of simple equations (only containing linear, bilinear, and quadratic monomials, and trivial trigonometric terms for the helical pair only) whose structure is later exploited by a branch-and-prune method based on linear relaxations. The method is general, as it can be applied to linkages with single or multiple loops with arbitrary topology, involving lower pairs of any kind, and complete, as all possible solutions get accurately bounded, irrespective of whether the linkage is rigid or mobile.     

Eine Methode zur Nullstellenbestimmung von Funktionen

In the present paper we give a method for determining all the zeros of a function in an arbitrary given interval of the domain of definition of the function. Here the domain of definition and the rang values of the function are subsets of arbitrary ordered linear spaces. The method was tested on many numerical examples, some of which are given below.     

A Galerkin discretisation-based identification for parameters in nonlinear mechanical systems

In the paper, a new parameter identification method is proposed for mechanical systems. Based on the idea of Galerkin finite-element method, the displacement over time history is approximated by piecewise linear functions, and the second-order terms in model equation are eliminated by integrating by parts. In this way, the lost function of integration form is derived. Being different with the existing methods, the lost function actually is a quadratic sum of integration over the whole time history. Then for linear or nonlinear systems, the optimisation of the lost function can be applied with traditional least-squares algorithm or the iterative one, respectively. Such method could be used to effectively identify parameters in linear and arbitrary nonlinear mechanical systems. Simulation results show that even under the condition of sparse data or low sampling frequency, this method could still guarantee high accuracy in identifying linear and nonlinear parameters.     

Automatic piecewise linearization in ideal plasticity

A method is proposed for constructing a piecewise linear approximation to an arbitrary yield function. The approximation is constructed in the course of solving a given boundary value problem. Its use is illustrated with some simple examples.     

Windup prevention for unstable systems

Presented is a windup prevention method for linear, time-invariant, exponentially unstable systems with saturating input nonlinearity such that, given a linear nominal controller and disturbances of known maximum amplitudes, arbitrary reference input sequences do not cause closed loop instability.