Modeling of transverse shears of piecewise homogeneous composite bars using an iterative process with account of tangential loads

A nonclassical model for the stress-strain state of a piecewise homogeneous composite bar is proposed. The model is based on an iterative process and takes into account the deplanation of cross sections of the bar caused by transverse shears. Based on the shear strains of some particular approximation, higher approximation models are constructed. The model accounts for both the normal and tangential loads.Presented at the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 4, pp. 487–500, July–August, 2000.     

Theoretical and Experimental Deformation Parameters of Composite Beams with Account of Deplanation of Cross Sections in Bending

The results of calculating the stress-strain state of composite beams, based on a nonclassical iterative model, in relation to their physicomechanical, geometrical, and kinematic parameters are presented. The convergence of the iterative process and the influence of the initial conditions on deformations are analyzed and the theoretical and experimental components of the stress-strain state are compared.     

基于正交多项式的解不适定算子方程的隐式迭代法

该文研究了基于Chebyshev和Jacobi多项式的解不适定算子方程的隐式迭代法.建立了隐式迭代法和由Hanke提出的显式迭代法之间的关系. 给出了与Chebyshev第一和第二多项式相关的迭代格式的残差有理式的一个重要引理. 对精确和扰动的数据, 研究了方程的收敛性和收敛速率. 利用Morozov残差原则, 给出了一个可执行的强健的正则化算法.最后还给出了一些数值例子, 数值结果与理论分析基本一致.     

Banach空间中二阶积-微分方程初值问题的解

利用半序方法和新的比较结果,研究了Banach空间中二阶积-微分方程初值问题的最大解、最小解、解的存在与相应解的迭代逼近.本文结果仅使用了下解或上解以及某些较弱的条件,并推广和改进了某些已知结果(见文[1-10]).     

二阶椭圆问题的混合元方向交替法

本文研究了一般的二阶椭圆问题的混合元方向交替法，给出了两种迭代格式即Uzawa格式和Arrow－Hurwitz格式，并就系数是常数的情形给出了谱分析．本文的结果对油藏模拟有一定的理论和实际意义．     

The extrapolated first order method for solving systems with complex eigenvalues

An extrapolated form of the basic first order stationary iterative method for solving linear systems when the associated iteration matrix possesses complex eigenvalues, is investigated. Sufficient (and necessary) conditions are given such that convergence is assured. An analytic determination of good (and sometimes optimum) values of the involved real parameter is presented in terms of certain bounds on the eigenvalues of the iteration matrix. The usefulness of the developed theory is shown through a simple application to the conventional Jacobi method.     

Direct and inverse problems for prestressed functionally graded plates in the framework of the Timoshenko model

In this study, modelling and identification of prestress state in functionally graded plate within the framework of the Timoshenko theory are discussed. With the help of variational principles, statements of boundary problems for stationary vibration of inhomogeneous prestressed plates have been derived taking into account various factors of prestress state. The comparative analysis of classical and nonclassical models has been conducted. The effect of the prestress state factors on the solution characteristics has been estimated. New approaches to solving the inverse problems on a reconstruction of inhomogeneous prestress functions in a functionally graded plate have been proposed on the basis of derivation of reciprocity relations and iterative regularization. The results of numerical reconstruction experiments are presented; practical recommendations on a selection of frequency range for the purpose of getting the highest reconstruction accuracy are given.     

m-增生算子方程解的Mann和Ishikawa迭代逼近

研究了Ｂａｎａｃｈ 空间中具 ｍ＿ 增生算子的方程解的Ｍａｎｎ 和Ｉｓｈｉｋａｗａ 迭代逼近问题·　研究结果改进和发展了一些文献中的最新成果·     

Convergence analysis of an iterative aggregation/disaggregation method for computing stationary probability vectors of stochastic matrices

An aggregation/disaggregation iterative algorithm for computing stationary probability vectors of stochastic matrices is analysed. Two convergence results are presented. First, it is shown that fast, global convergence can be achieved provided that a sufficiently high number of relaxations is performed on the fine level. Second, local convergence is shown to take place with just one relaxation performed on the fine level. The convergence proofs are general and require no assumptions on the magnitude of off-diagonal elements (blocks). Furthermore, a relationship between the errors on the fine and on the coarse level is described. To illustrate the theory, the results of some numerical experiments are presented. © 1998 John Wiley & Sons, Ltd.     

线性定常广义系统的D型迭代学习控制收敛性

给出了线性定常广义系统在D型学习律作用下的迭代控制收敛性结果,这一结果是全新的,其对时变系统也成立,而且,本文结果和方法大部分可以移植到线性定常广义离散时间系统.     

关于一类一阶脉冲微分系统的初值问题

本文的目的是利用单调迭代方法研究一类一阶脉冲微分系统的初值问题的最小最大拟解的存在性及其迭代逼近程序。     

指标-2微分-代数系统的连续扩展Runge-Kutta迭代方法

1引言微分-代数系统包括具有约束条件的微分方程和奇异隐式微分方程,在实际应用中,如:约束力学系统、流体动力学、化学反应动力学、电子网络模拟、控制工程和机器人技术等领域就产生了诸多问题需要求解．近年来,微分-代数系统已极大地引起了许多工程师和数学工作者的关注,开展了众多相关问题的探讨,提出了许多新的算法理论[1-3]．在本文中我们对指标-2的微分-代数方程利用Runge-Kutta方法进行时间的离散和动力学迭代,研究离散迭代系统的收敛性．     

Galerkin approximation for inverse problems for nonautonomous nonlinear distributed systems

We develop an abstract framework and convergence theory for Galerkin approximation for inverse problems involving the identification of nonautonomous, in general nonlinear, distributed parameter systems. We provide a set of relatively easily verified conditions which are sufficient to guarantee the existence of optimal solutions and their approximation by a sequence of solutions to a sequence of approximating finite-dimensional identification problems. Our approach is based upon the theory of monotone operators in Banach spaces and is applicable to a reasonably broad class of nonlinear distributed systems. Operator theoretic and variational techniques are used to establish a fundamental convergence result. An example involving evolution systems with dynamics described by nonstationary quasi-linear elliptic operators along with some applications and numerical results are presented and discussed.Part of this research was carried out while the first and third authors were visiting scientists at the Institute for Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center. Hampton, VA, which is operated under NASA Contracts NAS1-17070 and NAS1-18107. Also, a portion of this research was carried out with computational resources made available through a grant to the second and third authors from the San Diego Supercomputer Center operated for the National Science Foundation by General Atomics, San Diego, CA. The research of the first author was supported in part under Grants NSF MCS-8504316, NASA NAG-1-517, AFOSR-84-0398, and AFOSR-F49620-86-C-0111. The second author's research was supported in part by the Fund for the Promotion of Research at the Technion and by the Technion VPR Fund. The research of the third author was supported in part under Grants AFOSR-84-0393 and AFOSR-87-0356.     

A skew-symmetric iterative method for solving a steady convection–diffusion–reaction equation with an indefinite reaction coefficient

An iterative product-type triangular skew-symmetric method (PTSM) is used to solve systems of linear algebraic equations (SLAEs) obtained by approximation with a central-difference scheme of a first-type boundary value problem for convection–diffusion–reaction and standard grid ordering. Sufficient conditions for non-negative definiteness of the SLAE matrix resulting from this approximation are obtained for the indefinite reaction coefficient. This property provides convergence of a wide class of iterative methods (in particular, the PTSM). In test problems, agreement of the theory with computational experiments is shown, and a comparison of the PTSM and SSOR is done.     

有限个平衡问题与非扩张映象不动点问题的复合迭代方法

在Hilbert空间中引进并研究一种新的复合粘性迭代算法,借以寻求有限个平衡问题的公共解集与非扩张映象不动点集的一个公共元素.所得结果改进并推广了最近一些人的最新结果.     

A numerical method for reflected diffusions: Control of the reflection directions and applications

We are concerned with a numerical method for the optimal control of the reflection directions of a reflected diffusion process, and with either a discounted or an ergodic cost criterion. The Markov chain approximation method is adapted to this nonclassical problem and convergence of the method is proved. The problem originally arose in the important application of rerouting in large trunk-line communications systems. A reasonable heavy-traffic approximation leads to the described model. The numerical method has been applied with success, but no proofs of convergence were given previously. Nonboundary controls can be easily added.This work was partially supported by Grants (AFOSR) F49620-92-J-008-1DEF, AFOSR-91-0375, and DAAH04-93-6-0070.     

Auto-associative models and generalized principal component analysis

In this paper, we propose auto-associative (AA) models to generalize Principal component analysis (PCA). AA models have been introduced in data analysis from a geometrical point of view. They are based on the approximation of the observations scatter-plot by a differentiable manifold. In this paper, they are interpreted as Projection pursuit models adapted to the auto-associative case. Their theoretical properties are established and are shown to extend the PCA ones. An iterative algorithm of construction is proposed and its principle is illustrated both on simulated and real data from image analysis.     

Real valued iterative methods for solving complex symmetric linear systems

Complex valued systems of equations with a matrix R + 1S where R and S are real valued arise in many applications. A preconditioned iterative solution method is presented when R and S are symmetric positive semi‐definite and at least one of R, S is positive definite. The condition number of the preconditioned matrix is bounded above by 2, so only very few iterations are required. Applications when solving matrix polynomial equation systems, linear systems of ordinary differential equations, and using time‐stepping integration schemes based on Padé approximation for parabolic and hyperbolic problems are also discussed. Numerical comparisons show that the proposed real valued method is much faster than the iterative complex symmetric QMR method. Copyright © 2000 John Wiley & Sons, Ltd.     

Preconditioning iterative algorithm for the electromagnetic scattering from a large cavity

A preconditioning iterative algorithm is proposed for solving electromagnetic scattering from an open cavity embedded in an infinite ground plane. In this iterative algorithm, a physical model with a vertically layered medium is employed as a preconditioner of the model of general media. A fast algorithm developed in (SIAM J. Sci. Comput. 2005; 27 :553–574) is applied for solving the model of layered media and classical Krylov subspace methods, restarted GMRES, COCG, and BiCGstab are employed for solving the preconditioned system. Our numerical experiments on cavity models with large numbers of mesh points and large wave numbers show that the algorithm is efficient and the number of iterations is independent of the number of mesh points and dependent upon the wave number. Copyright © 2008 John Wiley & Sons, Ltd.     

Iterative method for finding the eigenfunctions of a system of two Schrödinger equations with combined nonlinearity

An iterative method is proposed to determine the eigenfunctions of a system of two nonlinear Schrödinger equations governing the interaction of two femtosecond pulses in a medium with quadratic and cubic nonlinearity. The method produces soliton solutions of a new form for a wide range of nonlinearity coefficients corresponding to the first and second eigenvalues. A specially chosen initial approximation is required to determine the third and higher eigenfunctions.