完整系统三阶Lagrange方程的一种推导与讨论

从牛顿运动方程出发,推导了完整系统关于广义加速度的Lagrange方程.讨论了该方程与传统分析力学中的Lagrange方程的相容性问题.结果显示,三阶Lagrange方程可以通过对Lagrange方程求一阶时间导数得到,表明它们是相容的.因此三阶Lagrange方程提供了一种不同于传统Lagrange方程方法的求解物体运动方程的途径.     

学会方程思想方法

<正>所谓方程思想方法,就是以方程的视角审视问题,通过建立相关的方程来解决问题的思想方法.由于方程思想方法贯穿了高中数学,因此加深对方程思想方法的理解掌握,提高运用方程思想方法解决问题能力,是学好高中数学的重要方面.本文拟从三个方面就如何学会方程思想方法,向同学们提出建议,供参考.一、增强方程意识所谓方程意识,即是运用方程角度看问题的意识.增强方程的意识,就是要养成一种当     

学会方程思想方法

所谓方程思想方法,就是以方程的视角审视问题,通过建立相关的方程来解决问题的思想方法.由于方程思想方法贯穿了高中数学,因此加深对方程思想方法的理解掌握,提高运用方程思想方法解决问题能力,是学好高中数学的重要方面.本文拟从三个方面就如何学会方程思想方法,向同学们提出建议,供参考.     

非等谱散焦非线性Schrdinger方程的规范变换和精确解

非线性Schrdinger方程及其相关方程在许多领域都得到广泛应用.为了研究谱参数随时间变化时散焦非线性Schrdinger方程的性质,研究了三个非等谱散焦非线性Schrdinger方程.对于前两个方程,给出了它们与等谱方程之间的规范变换,以及多孤子精确解.对于第三个方程给出了单孤子解.     

耦合Gerdjikov-Ivanov方程的多孤子解和无穷守恒律

借用Hirota方法找到耦合Gerdjikov-Ivanov方程的多孤子解.描述了单孤子解和双孤子解的动力特征.耦合Gerdjikov-Ivanov方程可约化至Gerdjikov-Ivanov方程,并且得出Gerdj ikov-Ivanov方程的解.还给出了耦合Gerdj ikov-Ivanov方程的无穷多守恒律.     

完整系统三阶Lagrange方程的一种推导与讨论

从牛顿运动方程出发，推导了完整系统关于广义加速度的Lagrange方程.讨论了该方程与传统分析力学中的Lagrange方程的相容性问题.结果显示，三阶Lagrange方程可以通过对Lagrange方程求一阶时间导数得到，表明它们是相容的.因此三阶Lagrange方程提供了一种不同于传统Lagrange方程方法的求解物体运动方程的途径.     

分式方程无解与增根之间的奥秘

分式方程的增根与无解是分式方程中常见的两个概念.同学们在学习分式方程后,常常会对这两个概念混淆不清,认为分式方程无解和分式方程有增根是同一回事,事实上并非如此. 分式方程有增根,指的是解分式方程时,在把分式方程转化为整式方程的变形过程中,方程的两边都乘了一个可能使分母为零的整式,从而扩大了未知数的取值范围而产生的未知数的值.因此增根具有两个特征:其一,它是分式方程化为整式方程后的整式方程的解;其二,它使最简公分母等于0.而分式方程无解则是指不论未知数取何值,都不能使方程两边的值相等.它包含两种情形:其一,原方程化去分母后的整式方程无解;其二,原方程化去分母后的整式方程有解,但这个解却使原方程的分母为0,它是原方程的增根,从而使原方程无解.现举例说明如下.     

几种广义非线性发展方程的新解

本文研究了构造了广义Kd V方程和广义KP-Burgers方程等几种广义非线性发展方程的新解的问题.利用三种辅助方程及其新解,获得了广义Kd V方程和广义KP-Burgers方程等几种广义非线性发展方程的新解.这些解由双曲余割函数、双曲正切函数、双曲正割函数、双曲余切函数和余割函数组成.     

FitzHugh-Nagumo方程的分歧北大核心

运用非线性分歧理论,研究FitzHugh-Nagumo方程的定态分歧和Hopf分歧.证明了FitzHugh-Nagumo方程在适当条件下有定态分歧发生,此时FitzHugh-Nagumo方程的定态方程有非平凡解存在.另外还证明了FitzHugh-Nagumo方程在适当的条件下有Hopf分歧发生,此时该方程从平凡解分歧出非平凡的周期解.最后分析得出影响FitzHugh-Nagumo方程分歧发生的主要因素是离子电压门控通道打开与关闭的延迟反应的快慢.理论分析所得结果与实验现象是相一致的.     

用Hirota双线性导数变换求MNLS方程的Rogue波解

修正的非线性薛定谔方程(MNLS方程)与导数非线性薛定谔方程(DNLS方程)是两个紧密相关且完全可积的非线性偏微分方程.该文通过Hirota双线性导数变换方法,首先求得MNLS方程在平面简谐波背景下的空间周期解,即Akhmediev型呼吸子解,再通过长波极限得其Rogue波解.根据简单的参数归零法使之自然地约化为DNLS方程的Rogue波解,并借助于一个积分变换将其变换为Chen-Lee-Liu方程的Rogue波解.文章还简要讨论了MNLS方程和DNLS方程在非局域情形整体解的存在性问题.     

常系数非齐次线性差分方程的特解

本文讨论了二阶常系数非齐次线性差分方程特解的求法,给出了用升阶法和常数变易法求特解的两种方法.     

由Lévy过程驱动的一类特殊的高维的BSRDE解的存在唯一性

讨论由Brownian运动和Lévy过程共同驱动的线性随机系统的随机LQ问题,其中代价泛函是关于Lévy过程生成的σ-代数取条件期望.得到由Lévy过程驱动的新的多维的倒向随机Riccati方程,利用Bellman拟线性原理和单调收敛方法证明了此随机Riccati方程的解的存在性.     

Numerical solution of the Burgers’ equation by local discontinuous Galerkin method

In this paper, the Burgers’ equation is transformed into the linear diffusion equation by using the Hopf–Cole transformation. The obtained linear diffusion equation is discretized in space by the local discontinuous Galerkin method. The temporal discretization is accomplished by the total variation diminishing Runge–Kutta method. Numerical solutions are compared with the exact solution and the numerical solutions obtained by Adomian’s decomposition method, finite difference method, B-spline finite element method and boundary element method. The results show that the local discontinuous Galerkin method is one of the most efficient methods for solving the Burgers’ equation. Even with small viscosity coefficient, it can get the satisfied solution.     

人机界面的模糊多层次综合评价

人机界面(HCI)是影响多媒体软件设计质量的重要因素之一。由于人机界面设计本身的复杂性,使得对它的评价具有一定的难度。本文提出了采用定性和定量相结合的模糊多层次综合评价方法对软件的人机界面进行评价,并讨论了基于模糊语言的单因素定量评价方法和利用层次分析法(AHP)确定各评价因素的权重。     

Finite Element Simulations with Adaptively Moving Mesh for the Reaction Diffusion System

A moving mesh method is proposed for solving reaction-diffusion equations. The finite element method is used to solving the partial different equation system, and an efficient scheme is applied to implement mesh moving. In the practical calculations, the moving mesh step and the problem equation solver are performed alternatively. Serveral numerical examples are presented, including the Gray-Scott, the Activator-Inhibitor and a case with a growing domain. It is illustrated numerically that the moving mesh method costs much lower, compared with the numerical schemes on a fixed mesh. Even in the case of complex pattern dynamics described by the reaction-diffusion systems, the adapted meshes can capture the details successfully.     

Strong Convergence of the Euler-Maruyama Method for Nonlinear Stochastic Volterra Integral Equations with Time-Dependent Delay

We consider a nonlinear stochastic Volterra integral equation with time-dependent delay and the corresponding Euler-Maruyama method in this paper. Strong convergence rate (at fixed point) of the corresponding Euler-Maruyama method is obtained when coefficients $f$ and $g$ both satisfy local Lipschitz and linear growth conditions. An example is provided to interpret our conclusions. Our result generalizes and improves the conclusion in [J. Gao, H. Liang, S. Ma, Strong convergence of the semi-implicit Euler method for nonlinear stochastic Volterra integral equations with constant delay, Appl. Math. Comput., 348 (2019) 385-398.]     

On the Matrix Equations of Higher Degrees

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一类特殊模糊矩阵方程的简便求解

给出了一类特殊模糊矩阵方程的简便且实用的求解方法.     

The postbuckling analysis of laminated circular plate with elliptic delamination

Based on the Von Karman plate theory, considering the effect of transverse shear deformation, and using the method of the dissociated three regions, the postbuckling governing equations for the axisymmetric laminated circular plates with elliptical delamination are derived. By using the orthogonal point collocation method, the governing equations, boundary conditions and continuity conditions are transformed into a group of nonlinear algebraically equation and the equations are solved with the alternative method. In the numerical examples, the effects of various elliptical in shape, delamination depth and different material properties on buckling and postbuckling of the laminated circular plates are discussed and the numerical results are compared with available data.     

On Weighted Estimates of Solutions for Nonlinear Higher Order Elliptic Problems

In the domain D = z m F it is considered a degenerate nonlinear higher order elliptic equation such that the corresponding energetic space is W 1, q (D, w q ) 7 W m , p ( D , w p ), mp < q < n , and w q , w p are weighted functions from some Muckenhoupt classes. A behavior of a solution u ( x ) is studied for the equation under consideration with the boundary value condition , where and f ( x ) = 1 for x ] F . The pointwise estimate for u ( x ) is proved in terms of the weighted higher order capacity of the set F and the distance from the point x to the set F .