On the field method in non-holonomic mechanics

This paper deals with the generalization of the field method to non-holonomic systems whose motion is subject to either non-linear constraints or those of a higher order, while their motion is modeled by the generalized Lagrange equations of the second kind. Two examples are given to illustrate the theory.The project supported by the Ministry of Science, Technologies and Development, Republic of Serbia (1874)     

Numerical simulation of unsteady interaction of centrifugal impeller with its diffuser using Lagrangian discrete vortex method

In this study, an advanced Lagrangian vortex- boundary element method is applied to simulate the unsteady impeller-diffuser interactions in a diffuser pump not only for design but also for off-design considerations. In velocity calculations based on the Biot-Savart law we do not have to grid large portions of the flow field and the calculation points are concentrated in the regions where vorticity is present. Lagrangian representation of the evolving vorticity field is well suited to moving boundaries. An integral pressure equation shows that the pressure distribution can be estimated directly from the instantaneous velocity and vorticity field. The numerical results are compared with the experimental data and the comparisons show that the method used in this study can provide us insight into the complicated unsteady impeller-diffuser interaction phenomena in a diffuser pump.     

EXACT AUGMENTED LAGRANGIAN FUNCTION FOR NONLINEAR PROGRAMMING PROBLEMS WITH INEQUALITY CONSTRAINTS

An exact augmented Lagrangian function for the nonlinear nonconvex programming problems with inequality constraints was discussed. Under suitable hypotheses, the relationship was established between the local unconstrained minimizers of the augmented Lagrangian function on the space of problem variables and the local minimizers of the original constrained problem. Furthermore, under some assumptions, the relationship was also established between the global solutions of the augmented Lagrangian function on some compact subset of the space of problem variables and the global solutions of the constrained problem. Therefore, from the theoretical point of view, a solution of the inequality constrained problem and the corresponding values of the Lagrange multipliers can be found by the well-known method of multipliers which resort to the unconstrained minimization of the augmented Lagrangian function presented.     

基于拉格朗日乘子法和群论的具有任意位移边界条件的旋转周期对称结构有限元分析

对任意位移边界条件下的旋转周期对称结构，由拉格朗日乘子法建立有限元方程。在对称适应的坐标系下，由结构刚度矩阵的块循环性质，利用群变换给出一种新的求解方法。数值验证给出令人满意的结果。     

The Second Type Singularities of Symplectic and Lagrangian Mean Curvature Flows

This paper mainly deals with the type II singularities of the mean curvature flow from a symplectic surface or from an almost calibrated Lagrangian surface in a Kähler surface. The relation between the maximum of the Kähler angle and the maximum of |H|² on the limit flow is studied. The authors also show the nonexistence of type II blow-up flow of a symplectic mean curvature flow which is normal flat or of an almost calibrated Lagrangian mean curvature flow which is flat.     

含边界在内的一般极值的必要条件与拉格朗日乘数法

讨论包括定义域边界点在内的极值,称为一般极值.对可导的一元和多元函数给出了一般极值点的必要条件,这些必要条件与经典极值的必要条件是相容的.还利用一般极值的必要条件导出了条件极值的拉格朗日乘数法.     

3D Multiphase Piecewise Constant Level Set Method Based on Graph Cut Minimization

Segmentation of three-dimensional (3D) complicated structures is of great importance for many real applications. In this work we combine graph cut minimization method with a variant of the level set idea for 3D segmentation based on the Mumford-Shah model. Compared with the traditional approach for solving the Euler-Lagrange equation we do not need to solve any partial differential equations. Instead, the minimum cut on a special designed graph need to be computed. The method is tested on data with complicated structures. It is rather stable with respect to initial value and the algorithm is nearly parameter free. Experiments show that it can solve large problems much faster than traditional approaches.     

多元函数条件极值的几种求解方法

研究多元函数的条件极值问题．针对稳定点的各种不同情形．结合具体实例．给出判断条件极值中稳定点是否取得极值的几种方法．     

大气动力学方程组的半拉格朗日计算方案的数学研究

通过对大气动力学方程组的半拉格朗日方案的数学分析，得出主要结论如下：(1)说明了Robert的半拉格朗日方案并不是绝对稳定的，通过特征线理论和双曲拟线性方程组解的理论，进一步说明了Robert理论的不正确。(2)通过分析右端项沿轨道积分，给出了一个关于半拉格朗日方案成立的判据。该判据与CLF相仿。(3)根据浅水方程特征理论，发现半拉格朗日方案应包括沿轨道反向积分(大气中慢过程)和沿特征锥积分(大气中快过程)，而已有的方案仅含前一类。因此，今后有必要研究后一类的半拉格朗日方案并研究这两类过程之间的相互作用的计算问题。(4)即使研究沿轨道反向积分问题，其特征跟原方程组解直接有关，因此，不仅仅是一个常微分方程组的问题。而大气动力学方程组的经典解一般仅在小范围成立，并且一维、二维和三维间断均会出现。故大范围反向积分特征线一般是不可能的。     

泰劳公式的拉格朗日型余项中介值点的研究

当区间长度趋于0时,泰劳公式的拉格朗日型余项中介值点的变化规律.