用加权残余法求解含大参数的Duffing方程

本应用加权残余法分析了含大参数的Duffing方程,并得到了整个区域的（0＜ε＜∞）一致有效的近似解,得到的近似周期的最大相对误差小于7．0％,当参数为小量时（ε≤1）,得到的近似解和摄动解完全一致。     

奇异扰动的p-Laplace方程非负非平凡解和正解的结构

精确地刻画了某些奇异扰动的p-Laplace方程非负非平凡解和正解的结构．利用上下解方法证明，方程存在很多非负非平凡的尖峰解和正的过渡尖峰解．当参数充分小时还对每个尖峰解支集的上下界进行了估计．     

Benjamin-Ono方程的广义解

讨论了Benjamin-Ono方程在Colombeau意义下的广义解的存在性，唯一性及在经典解存在的情况下与经典解的关系．     

一类非线性方程奇摄动问题的激波解

利用匹配条件，讨论了一类非线性奇摄动问题的激波解，得出了激波解与边界条件的对应关系。     

关于一类非线性微分方程组的边值问题的渐近解（Ⅰ）

应用新的方法 ,研究一类非线性微分方程组　　u″ =v,εv″ f(x ,u ,u′)v′ -g(x ,u ,u′)v =0　　 (0 <ε 1) ,的边值问题的解的渐近性质·　构造出解的渐近展开式 ,和估计了余项 ,改进并拓广了前人的工作·     

安道什猜想推广奇数解问题的几个新结论

安道什猜想的推广没有正奇数适合方程：ｘｘ１１·ｘｘ２２…ｘｘｋｋ＝ｚｚ（ｋ≥２）①当ｋ＝２时，即为安道什猜想：没有正奇数适合方程ｘｘ·ｙｙ＝ｚｚ．文［１］中笔者已给出了①的反例，此后笔者对此又作了进一步的研究，虽没能完全解决这一问题，但从不同的角度得...     

三元三次不定方程ax^(2)+by^(2)+cz^(2)=dxyz-1基础解的进一步研究

关于三元三次不定方程的研究,是不定方程研究中的重要课题,有许多尚未解决的问题.讨论了不定方程ax^(2)+by^(2)+cz^(2)=dxyz-1的基础解,其中(a,b,c)=1,a,b,c均为d的因子.利用文献中的方法,运用二元二次型理论和初等数论的结果,求出了该不定方程的所有基础解.     

具有时滞的细胞神经网络周期解与稳定性

本文研究了具有时滞的细胞神经网络周期解存在性和平凡解的稳定性问题。利用Ｌｙａｐｕｎｏｖ函数法并结合不等式分析技巧,我们首先证明了时滞细胞网络的解是有界的,然后建立了时滞细胞神经物周期解的存在准则,最后在时滞细胞神经网络有平衡点时,给出了神经网络系统的平衡点指数稳定的充分条件。其结果推广了文「７,８」的相应结果。     

关于运输问题最优解的进一步讨论

首先给出了运输问题最优解的相关概念,将最优解扩展到广义范畴,提出狭义多重最优解和广义多重最优解的概念及其区别.然后给出了惟一最优解、多重最优解、广义有限多重最优解、广义无限多重最优解的判定定理及其证明过程.最后推导出了狭义有限多重最优解个数下限和广义有限多重最优解个数上限的计算公式,并举例验证了结论的正确性.     

非线性耦合标量场方程显式解析解的研究

利用两种不同的变换,获得了一类非线性耦合标量场方程的若干类型的精确解析解,其中包括孤子解、奇性孤波解和三角函数解,从而丰富了方程解的内容。这些结论可以应用于其它的非线性方程。此外还纠正了一些文献的部分结论。     

解大系统稳定性的积分方程法

本文通过分解积分方程组，并建立积分方程法比较原理，化大系统为低维系统，进而讨论了带时滞的时变大系统的稳定性，给出了新的结果，这一方法也可以用来讨论其它类型大系统的稳定性问题．     

Parallel preconditioners for large scale partial difference equation systems

We propose a new preconditioner DASP (discrete approximate spectral preconditioner), based on the existing well-known preconditioners and our computational experience. Parallel preconditioning strategies for large scale partial difference equation systems arising from partial differential equations are investigated. Numerical results are given to show the efficiency and effectiveness of the new preconditioners for both model problems and real applications in petroleum reservoir simulation.     

Optique diffractive périodique à phases courbes

We give 3-scales WKB asymptotics for nonlinear hyperbolic systems with variable coefficients. Our profiles are transported, at the slower scale, along the rays of geometric optics, and are diffracted, at the intermediate scale, according to some (variable coefficients) Schrödinger equation.     

On methods for continuous systems with quadratic,cubic and quantic nonlinearities

Methods for study of weakly nonlinear continuous systems are discussed. The method of multiple scales is used to analyze the nonlinear response of a relief valve under combined static and dynamic loadings. We determine a second-order approximation to the response of the system for the case of primary resonance. Second, we derive a second-order nonlinear ordinary differential equation that describes the time evolution of a single-mode, the so-called single-mode discretization. Then, we use the multiple scales method to determine second-order approximate solutions of this equation, thereby obtaining the equations describe the modulations of the amplitude and phase of the response. We show that the results of the second approach are erroneous.     

The Validity of Generalized Ginzburg-Landau Equations

We consider parabolic systems defined on cylindrical domains close to the threshold of instability, in which the Fourier modes with positive growth rates are concentrated at a non-zero critical wave number. In particular, we consider systems for which a so-called Ginzburg–Landau equation can be derived. Due to the presence of continuous spectrum, classical bifurcation theory is not available to describe bifurcating solutions. Thus, we consider a modified system with artificial spectral gap, which possesses an infinite-dimensional centre manifold. The amplitude equation on this manifold is called a generalized Ginzburg–Landau equation. From previous work [18] it is known that the Fourier modes are exponentially concentrated at integer multiples of the critical wave number. Hence, the error made by this modification is exponentially small in powers of the bifurcation parameter. The approximations obtained via the generalized Ginzburg–Landau equation are valid on a much longer time scale than those obtained by using the classical Ginzburg–Landau equation as an amplitude equation.     

Deriving integral equations for radial distribution functions of multicomponent mixtures on the basis of scale transformations in the phase space

It is shown that scale transformations of the coordinate part of the phase space for one of the mixture components correspond to virtual variations in the local density for the same component in a thermodynamic system. The investigation results are used to construct different variants of a generating functional with the goal of deriving a system of integral equations for the radial distribution functions of mixtures. An equation of state, which is a modification of the Tate equation, is obtained. Systems of integral equations that imply, in the limit, the Perkus-Yevick equations and systems of equations for hypernetted chains are derived for radial distribution functions. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 111, No. 3, pp. 473–482, June, 1997.     

Modeling,simulation and validation of material flow on conveyor belts

In this paper a model comparison approach based on material flow systems is investigated that is divided into a microscopic and a macroscopic model scale. On the microscopic model scale particles are simulated using a model based on Newton dynamics borrowed from the engineering literature. Phenomenological observations lead to a hyperbolic partial differential equation on the macroscopic model scale. Suitable numerical algorithms are presented and both models are compared numerically and validated against real-data test settings.     

Averaging on slow and fast cycles of a three time scale system

Pontryagin–Rodygin?s Theorem for slow and fast systems describes the slow drift during the rolling up of the trajectories around the cycles of the fast dynamics. This drift is approximated by the averaging on the cycles. The calculation of this average is generally a difficult task since it requires the knowledge of the closed orbits and their periods. We present two paradigms of three time scale systems where we can overcome this limitation. It is the case of systems the fast dynamics of which have cycles with relaxation presenting or not a canard phenomenon. We can not apply Pontryagin–Rodygin?s Theorem to these systems because their fast equation is itself singularly perturbed. We also investigate the extension of the results to unbounded time intervals. The results are stated classically and proved within the framework of nonstandard analysis.     

MULTILEVEL AUGMENTATION METHODS FOR SOLVING OPERATOR EQUATIONS

We introduce multilevel augmentation methods for solving operator equations based on direct sum decompositions of the range space of the operator and the solution space of the operator equation and a matrix splitting scheme. We establish a general setting for the analysis of these methods, showing that the methods yield approximate solutions of the same convergence order as the best approximation from the subspace. These augmentation methods allow us to develop fast, accurate and stable nonconventional numerical algorithms for solving operator equations. In particular, for second kind equations, special splitting techniques are proposed to develop such algorithms. These algorithms are then applied to solve the linear systems resulting from matrix compression schemes using wavelet-like functions for solving Fredholm integral equations of the second kind. For this special case, a complete analysis for computational complexity and convergence order is presented. Numerical examples are included to demonstra     

Approximate inversion method for time‐fractional subdiffusion equations

The finite‐difference method applied to the time‐fractional subdiffusion equation usually leads to a large‐scale linear system with a block lower triangular Toeplitz coefficient matrix. The approximate inversion method is employed to solve this system. A sufficient condition is proved to guarantee the high accuracy of the approximate inversion method for solving the block lower triangular Toeplitz systems, which are easy to verify in practice and have a wide range of applications. The applications of this sufficient condition to several existing finite‐difference schemes are investigated. Numerical experiments are presented to verify the validity of theoretical results.