"开关"问题的数值方法及在资料变分同化中的应用

提出了“开关”问题的一类微分方程模型，方程在临界值处是不连续的，用经典的数值方法求解此类问题时会出现很大的数值误差，数值精度降到了一阶，详细研究了这类问题，提出用Hermite插值方法确定开关时刻，分段求解连续的微分方程的间断装配方法，使原有的数值方法恢复其数值精度，将此方法应用到资料变分同化中，获得了高精度的数值解。     

大学学报

Darcy-Stokes方程的局部压力梯度投影的稳定化方法 摘要 对Darcy—Stokes方程,作者利用局部压力梯度投影的技巧．提出了稳定的P1—P1有限元格式．证明了方法的稳定性．导出了误差估计．数值实验验证了该方法对Darcy-Stokes方程有效．     

二维稳态线性对流扩散方程的Galerkin有限元方法

利用Galerkin有限元方法求解了二维稳态线性对流扩散方程边值问题,采用伴随算子理论进行了相应的误差分析,数值模拟表明该方法的可行性和有效性。     

Cauchy型奇异非线性方程的高精度数值解法研究

为获得Cauchy型奇异非线性方程的高精度数值解,提出利用数值逼近函数的方法来进行有效求解。首先,对Cauchy型含有复变量的非线性方程实现Cauchy奇异积分方程转换,利用方程式中具有特征算式的相关算子当作正则化算式,对奇异积分非线性方程实行正则化操作,从而消除Cauchy核奇异性;然后数值逼近非线性方程并利用Chebyshev多项式完成函数逼近,基于特定阶值奇异积分数值法定义Cauchy型奇异积分转换定理,最终通过定理的运用及固定阶值获得关于求解Cauchy奇异积分数值的公式,则完成非线性方程的高精度数值求解计算过程。仿真实验证明,文中提出的数值逼近函数法能够有效完成对Cauchy型奇异非线性方程的求解。     

基于改进Trefftz有限元法分析封闭多连通声腔响应

利用改进的Trefftz-有限元方法求解Helmholtz方程.将Trefftz-有限元方法应用到多连通封闭结构的声响应求解.使用满足控制方程的完备解系作为整个域内的场变量,利用变分原理推导出满足Helmholtz方程的Trefftz八结点四边形单元模型,推导出用Trefftz-有限元方法求解多连通封闭结构的声响应问题方程组的刚度矩阵.利用matlab工具进行数值仿真分析,分析结果表明改进的Trefftz-有限元方法可用于计算封闭多连通声腔的响应,且计算结果比传统的有限元方法简便.     

半空间的电势问题分析

分析了半空间Poisson方程边值问题用Poisson方程Direchlet问题Poisson公式求解的可能性,得出了该问题解的积分表达式。     

定常的Navier-Stokes方程非奇解支的最小二乘二重网格有限元法

文献[1]中给出了定常的Namer-Stokes方程的Petrov-Galerkin最小二乘二重网格有限元法。现在此基础之上对Namer-Stokes方程具有非奇解支的情况给出了有限元解的数学分析,并且证明了当h=O（min{H2l/21-1 ,H2k＋2/2k＋1}）时,此法和文献[2]、[3]提出的方法具有相同的收敛阶,且与文献[2]、[3]相比,可以节省很多计算量和计算时间。     

辐射传输方程的有限差分求解方法

辐射传输方程是渡尔兹曼方程的稳态形式，其光学成像领域有广泛的应用。本文给出了一种辐射传输方程的有限差分求解方法，应用该方法对空间变量和角度离散化，将该方程的求解问题转化为数组求解问题，实验模型采用组织光学参数模型，实验结果证明了该方法的正确性和有效性。     

一类非线性稳态对流扩散方程的有限体积元求解方法

用有限体积元法推导了非线性稳态对流扩散方程的Newton迭代形式,给出具体的求解步骤,并进行了误差分析,数值模拟表明该方法的可行性和有效性。     

基于有限差分法的泊松方程第一类边值问题求解

基于泊松方程第一类的边值问题求解,提出基于有限差分法的泊松方程第一类边值问题求解的方法。采用差分格式对边界条件下的泊松方程进行离散,在圆形的区域内进行网格的划分,利用有限差分法对泊松方程边值问题进行求解,经过算例的模拟试算,对有限差分法与四阶差分格式的近似解以及误差进行对比,结果表明,有限差分法的误差较小,求解的精确度较高,并且加速的性能较好。     

Robust stability criteria for uncertain systems with interval time-varying delay based on multi-integral functional approach

This paper is concerned with the robust stability analysis for uncertain systems with interval time-varying delay. In order to make full use of the delay information, a novel Lyapunov–Krasovskii functional (LKF) containing single, double, triple and quadruple integral terms is introduced, and a triple-integral state variable is also used. Then, by using the Wirtinger-based single and double integral inequality, introducing some positive scalars, the derivative of the constructed LKF is estimated more accurately. As a result, some stability criteria are derived, which have less conservatism and decision variables. Numerical examples are also given to show the effectiveness of the proposed method.     

An augmented Lagrangian algorithm for total bounded variation regularization based image deblurring

The augmented Lagrangian strategy has recently emerged as an important methodology for image processing problems. In this paper, based on this strategy, we propose a new projected gradient algorithm for image deblurring with total bounded variation regularization. The convergence property of our algorithm is discussed. Numerical experiments show that the proposed algorithm can yield better visual quality than the Rudin–Osher–Fatemi (ROF) method and the split Bregman iteration method.     

On stresses in a perforated strip

The convergence of the successive approximations in Howland's solution of an infinite perforated strip containing a symmetrically-located circular hole under longitudinal tension can be improved considerably by using the well known solution of an infinite perforated plate as the approximation of zero order. Further, by basing on a somewhat different physical concept, a corresponding direct solution of the problem can be formulated. Such a solution is presented in this paper. Numerical results are obtained from the solution over a wider range of values of the radius of hole, a feature hardly attainable in the previously known solutions of the problem. Further extension of the method of solution to the transverse bending problem as well as to the case of an unsymmetrically-located hole is also possible.     

一个求多项式零点的并行迭代及其收敛的初始条件

首先构造了一个求多项式零点的并行迭代,然后对它的收敛性进行了分析,得出其收敛的两种类型的初始条件     

Finite-time fuzzy game-based attitude control for on-orbit cooperative transporting

Substructure transporting is an important phase for on-orbit assembly. This paper investigates a problem of designing a control approach for multiple transporting agents attached to one substructure, so as to complete the task of attitude tracking and stabilization of the substructure in the transportation process. A finite-time fuzzy game control method is developed to solve this problem. Using the framework of differential game, a finite-time nonlinear game is formulated based on the individual performance index functions of agents and attitude dynamics of the combination consisting of transporting agents and the substructure, which can reflect the cooperation and coordination between agents. In order to realize finite-time convergence which is more suitable for engineering requirement, a speed function is introduced to transfer finite-time game into infinite-time game. Considering the limited computational ability of agents, Takagi-Sugeno (T-S) fuzzy is incorporated to divide the nonlinear game problem into weighted average of multiple linear games which are easy to get the Nash equilibrium. Numerical simulations validate the efficiency of the proposed method for attitude control and the advantage in less calculation and better performance in dynamics and steady state than the existing methods.     

Multiple graphs clustering by gradient flow method

The core issue of multiple graphs clustering is to find clusters of vertices from graphs such that these clusters are well-separated in each graph and clusters are consistent across different graphs. The problem can be formulated as a multiple orthogonality constrained optimization model which can be shown to be a relaxation of a multiple graphs cut problem. The resulting optimization problem can be solved by a gradient flow iterative method. The convergence of the proposed iterative scheme can be established. Numerical examples are presented to demonstrate the effectiveness of the proposed method for solving multiple graphs clustering problems in terms of clustering accuracy and computational efficiency.     

中国能源强度收敛性的理论与实证分析

首先结合内生增长模型,从理论上证明能源强度收敛性的存在;其次,采用我国2000—2012年相关数据,基于不同收敛模型的设定——σ收敛和β收敛模型,以及不同的估计方法——系统GMM和工具变量法,实证研究全国和高收入组、中收入组以及低收入组的能源强度收敛情况,研究得到如下结论:(1)从全国层面来看,我国能源强度存在σ收敛和β收敛;(2)从不同收入层面来看,高收入组、中收入组以及低收入组分别存在σ收敛和β收敛;(3)人均GDP、城市化水平、研发强度、能源价格是影响能源强度收敛的重要因素。     

Dissipative state observer design for nonlinear time-delay systems

This paper is concerned with the design of dissipative state observers for a family of time-delay nonlinear systems. The Dissipativity method, proposed by one of the authors for delay-free nonlinear systems, is extended here to a class of time-delay nonlinear systems. The design method consists in decomposing the time-delay estimation error dynamics into a time-delay linear subsystem and a time-varying memoryless nonlinearity, connected in a negative feedback loop. By using some storage functionals, both delay-independent and delay-dependent dissipativity criteria are derived in order to guarantee the exponential convergence property of the observer. The exponential stability of the estimation error is then ensured, assuming that the nonlinearity is dissipative with respect to a quadratic supply rate and the linear part is designed, through the observer gains, to be dissipative with respect to a complementary supply rate. The design conditions are formulated in terms of tractable bilinear (BMI’s) or linear matrix inequalities (LMI’s). An interesting advantage is that the proposed dissipative design extends and generalizes under a unified framework several methods available in the literature, since a wide diversity of nonlinearities can be considered. Numerical examples are provided to demonstrate the effectiveness of the theoretical results.     

Super finite-Time variable parameter ZNN models for time-Variant linear matrix inequality

Stuck in the speed and dimensionality of settling time-variant linear matrix inequality (LMI), this paper for the first time proposes two finite-time variable parameter zeroing neural network (FTVPZNN) models to settle the time-variant LMI. The first model is called the FTVPZNN-C model activated by the conventional sign-bi-power (S-B-P) function. The second model is called the FTVPZNN-T model activated by a tunable parameter S-B-P function. Different from the finite-time fixed-value zeroing neural network (FTFZNN) model, the proposed FTVPZNN models with variable parameters have better convergence performance and smaller upper bounds of finite-time convergence. Three theorems are presented to guarantee the stability and finite-time convergence of the FTVPZNN models. Especially, through detailed theoretical analysis and calculations, the finite-time convergence upper bounds of the proposed FTVPZNN models are obtained. Finally, a numerical simulative example is given to affirm the effectiveness and excellent convergent performance of the proposed models for settling the time-variant LMI.     

MIMO fuzzy sliding mode controlled dual arm robot in load transportation

The control problem of the cooperative motion of a two-link dual arm robot during handling and transportation of an object was studied in this paper. Since these types of robots are frequently preferred for hazardous applications such as transportation of radioactive materials and disposal of explosives, a robust non-chattering sliding mode controller (SMC) improved by a multiple-input multiple-output (MIMO) fuzzy logic unit was applied to the robot to track the desired trajectory with high accuracy and transport the load safely. In order to assess the performance of the proposed MIMO fuzzy sliding mode controller (MIMO-FSMC) in presence of parameter variations and external disturbances, a sudden load variation and noise were introduced to the robot system. If compared with classical SMC, tracking errors with smaller magnitudes and faster convergence to zero were obtained by using the proposed MIMO-FSMC. Numerical results suggest that this type of control method may safely be used for cooperative motion control of dual arm robots in load handling and transport applications in hazardous environments with high accuracy.