渐近法在一类强非线性系统中的应用

本文采用文[1、2]的渐近解形式,将渐近法推广到如下较为广泛一类的强非线性振动系统式中g和f为x,的非线性解析函数,ε>0为小参数,并假设对应于ε=0的派生系统有周期解.本文推得系统(0.1)的渐近解递推方法,并应用于实例.     

Poincaré非线性振动理论在连续介质力学中的推广(Ⅱ)——若干应用

文本是文[1]的继续.文[1]中,提出和建议使用非线性偏微分方程直接摄动与加权积分方程法,计算连续介质系统的共振与非共振周期解.本文中,应用该方法计算了定跨度弹性梁在各种常见边界条件下强迫振动的共振与非共振周期解,方板在集中周期荷载作用下的共振周期解.指出了,非主振型对非线性振动周期解的影响及静荷载对幅频特性曲线的影响.     

一类非自治非线性微分方程周期解的存在性

本文讨论非自治非线性微分方程组■=ф(y)-f(x),■=-g(x)+e(t) (1)周期解的存在性.N.Levinson 曾给出■(y)≡y、g(x)≡x 时系统(1)存在周期解的条件,井竹君推广了文[1]的工作.本文给出方程组(1)存在周期解的一组充分条件,进一步推广了文[2]的结果.     

一类广义非线性Schr(o)dinger扰动方程的泛函渐近解法

研究了一类非线性Schr(o)dinger扰动耦合系统.利用近似解相关联的特殊方法,首先讨论了对应的线性系统,并得到了其精确解.再利用泛函迭代的方法得到了非线性Schr(o)dinger扰动耦合系统的泛函渐近解析解.这个渐近解是一个解析式,还可对它进行解析运算.这对使用简单的模拟方法得到的近似解是达不到的.     

具有缓变系数非线性周期系统周期解的存在唯一性

本文利用Liapunov函数的方法,讨论了一类具有缓变系数的非线性非自治周期系统的周期解的存在唯一性,得到了保证系统存在唯一稳定周期解的充分条件,并对系统的缓变范围作了精确的估计.     

带有临界指标的非线性Poisson-Schr(o)dinger系统解的不存在性

本文研究一个在强非线性项阻碍临界增长条件下Poisson-Schr(o)dinger(PS)系统的孤波解.分别利用变分不等式和Pohozaev型讨论,证明了径向对称解和非平凡解的不存在性.     

滑动轴承转子系统动力学稳定域的数值分析方法

根据Floquet理论定义了非线性非自治系统周期解的稳定度.从动力系统流的概念出发,给出利用非线性非自治系统稳态周期解受扰后的瞬态响应,计算周期解稳定度的数值计算方法.以稳定度等于零为临界判据,分析计算了滑动轴承平衡和不平衡刚性转子系统的稳定吸引域.研究发现,平衡转子随着转速的升高稳定域减小;不平衡转子随着不平衡量的增大稳定域减小;且工频周期解的稳定域比同样系统条件下平衡点的稳定域小.     

带有临界指标的非线性Poisson-Schrdinger系统解的不存在性(英文)

本文研究一个在强非线性项阻碍临界增长条件下Poisson-Schrdinger(PS)系统的孤波解.分别利用变分不等式和Pohozaev型讨论,证明了径向对称解和非平凡解的不存在性.     

二个自由度 Hamilton 系统的浑沌性质

近年来,关于浑沌现象的实验研究与数值计算的文献大量涌现,解析方法的研究也在开展,文[1—3]对这方面的工作做了很好的总结.Holmes 依照 Melnikov 方法提出的方法是目前处理浑沌现象的极少数解析方法之一.文[5]对单个自由度的 Hamilton 系统在弱周期扰动下的浑沌性质进行了讨论.在[6]中,Holmes 进一步提出处理二个自由度Hamilton 系统方法,并用此法讨论了一个人为的例子.本文处理在非线性振动领域中广     

非线性非齐次弹性材料模型的精确模态波解和动力学性质

本文研究一个非线性非齐次弹性材料模型的模态行波解,其行波系统是第一类奇行波方程.应用已经发展的奇系统理论和动力系统方法,本文得到行波系统的相图随参数而改变的分支行为;对应不同的水平曲线,得到周期行波解和有界紧解(compactons)的精确参数表示.     

Local Behavior of the Newton Method on Two Equivalent Systems from Linear Programming

Newton's method is a fundamental technique underlying many numerical methods for solving systems of nonlinear equations and optimization problems. However, it is often not fully appreciated that Newton's method can produce significantly different behavior when applied to equivalent systems, i.e., problems with the same solution but different mathematical formulations. In this paper, we investigate differences in the local behavior of Newton's method when applied to two different but equivalent systems from linear programming: the optimality conditions of the logarithmic barrier function formulation and the equations in the so-called perturbed optimality conditions. Through theoretical analysis and numerical results, we provide an explanation of why Newton's method performs more effectively on the latter system.     

The numerical solution of a periodic parabolic problem subject to a nonlinear boundary condition

The numerical solution by finite differences of a periodic parabolic problem subject to a nonlinear boundary condition is considered. It is shown that Newton's method can be used to solve the nonlinear equations provided a suitable initial approximation is known, and a method for constructing this first approximation is given.     

Convergence criterion of Newton's method for singular systems with constant rank derivatives

The present paper is concerned with the convergence problem of Newton's method to solve singular systems of equations with constant rank derivatives. Under the hypothesis that the derivatives satisfy a type of weak Lipschitz condition, a convergence criterion based on the information around the initial point is established for Newton's method for singular systems of equations with constant rank derivatives. Applications to two special and important cases: the classical Lipschitz condition and the Smale's assumption, are provided; the latter, in particular, extends and improves the corresponding result due to Dedieu and Kim in [J.P. Dedieu, M. Kim, Newton's method for analytic systems of equations with constant rank derivatives, J. Complexity 18 (2002) 187-209].     

Stein implicit Runge-Kutta methods with high stage order for large-scale ordinary differential equations

The Runge-Kutta method is one of the most popular implicit methods for the solution of stiff ordinary differential equations. For large problems, the main drawback of such methods is the cost required at each integration step for computing the solution of a nonlinear system of equations. In this paper, we propose to reduce the cost of the computation by transforming the linear systems arising in the application of Newton's method to Stein matrix equations. We propose an iterative projection method onto block Krylov subspaces for solving numerically such Stein matrix equations. Numerical examples are given to illustrate the performance of our proposed method.     

Existence of solutions and Gevrey class regularity for Leray-alpha equations

In this paper we consider some equations similar to Navier-Stokes equations, the three-dimensional Leray-alpha equations with space periodic boundary conditions. We establish the regularity of the equations by using the classical Faedo-Galerkin method. Our argument shows that there exist an unique weak solution and an unique strong solution for all the time for the Leray-alpha equations, furthermore, the strong solutions are analytic in time with values in the Gevrey class of functions (for the space variable). The relations between the Leray-alpha equations and the Navier-Stokes equations are also considered.     

Gauss-Newton法的收敛球与解的唯一性球

0　引　言本文研究非线性最小二乘问题min F( x)∶ =12 f( x) Tf ( x) ( EP)的 Gauss-Newton法的局部收敛性 ,其中 f:Rn→ Rm是 Frechet可微的 ,m≥ n.非线性最小二乘问题在数据拟合 ,参数估计和函数逼近等方面有广泛的应用 .在工程应用中也起到很大作用 ,例如在神经网络中 ,对小波问题 ,FP网络等方面的数据 (图形 )传输 ,数据 (图形 )压缩等方面有极其重要的理论和实际意义 .目前 ,求解最小二乘问题的最基本的方法之一是 Gauss-Newton法 [1 ]xn+1 =xn -[f′( xn) Tf′( x) ] - 1 f′( xn) Tf( xn) . ( GN)就我们所知 ,目前关于 Gau…     

混合互补问题牛顿型算法的二阶收敛性

在凸规划理论中,通过ＫＴ条件,往往将约束最优化问题归结为一个混合互补问题来求解。该文就正则解和一般解两种情形分别给出了求解混合互补问题牛顿型算法的二阶收敛性的充分性条件,并在一定条件下证明了非精确牛顿法和离散牛顿法所具有的二阶收敛性。     

Periodic solutions of second order non-autonomous singular dynamical systems

In this paper, we establish two different existence results of positive periodic solutions for second order non-autonomous singular dynamical systems. The first one is based on a nonlinear alternative principle of Leray-Schauder and the result is applicable to the case of a strong singularity as well as the case of a weak singularity. The second one is based on Schauder's fixed point theorem and the result sheds some new light on problems with weak singularities and proves that in some situations weak singularities may help create periodic solutions. Recent results in the literature are generalized and significantly improved.     

ON INTERACTION OF SHOCK AND SOUND WAVE （I）

This paper studies the interaction of shock and gradient wave (sound wave) of solutions to the system of inviscid isentropic gas dynamics as a model for the corresponding problems for nonlinear hyperbolic systems. The problem can be reduced to a boundary value problem in a wedged dormain, By using the method of constructing asymptotic solutions and Newton‘siteration process it is proved that if a weak shock hits a gradient wave, then the grandient wave will split into two gradient waves, while the shock continuses propagating. In this paper the author reduces the problem to a standard form and constructs asymptotic solution of the problem. The existence of the genuine solution will he given in the following paper.     

Local convergence theorems of Newton's method for nonlinear equations using outer or generalized inverses

We provide local convergence theorems for Newton's method in Banach space using outer or generalized inverses. In contrast to earlier results we use hypotheses on the second instead of the first Fréchet-derivative. This way our convergence balls differ from earlier ones. In fact we show that with a simple numerical example that our convergence ball contains earlier ones. This way we have a wider choice of initial guesses than before. Our results can be used to solve undetermined systems, nonlinear least squares problems and ill-posed nonlinear operator equations.