On finite amplitude water waves

The modulation theory for finite amplitude water waves is developed using the variational technique. It is shown how Levi-Civita’s relation, Starr’s relation and the conservation equations all follow very simply and naturally from this approach. The present paper is limited to deep water waves, but the results can be extended to arbitrary depth. For deep water, the appropriate Lagrangian can be reduced to a single function, which can be taken from recent numerical calculations on periodic waves. This is used to discuss the stability of wavetrains to long modulations.     

VMD和随机森林在反应堆金属撞击信号识别中的应用研究

反应堆中脱落部件或金属遗留件的存在会与压力边界产生碰撞而严重影响反应堆的安全,为有效解决由于特征信息不足和模型构建不合理而导致的反应堆中金属撞击信号识别精度低的问题,提出了一种基于变分模态分解(variational mode decomposition,VMD)和随机森林算法(random forest,RF)的反应...     

基于变域变分原理的一种有限元方法

本文从变域变分原理出发,提出了一种新的有限元方法,并将所提算法用于求解形状最优化问题。我们给出了最优化问题解的存在性及其离散形式。讨论了数值解的收敛性,给出了数值解与精确解之间的误差估计。最后给出了算法的具体实施步骤和一个具有代表性的数值算例,数值结果表明该算法是正确、高效的。     

The principles of information processing based on the numerical solution of the nonlinear heat-conduction problem. Pt. 1. The three-dimensional discrete mathematical model

A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of the modeling is considered. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007.     

全变分自适应图像去噪模型

通过分析三种主要变分去噪模型(调和、全变分以及广义全变分模型)的优缺点,提出了一种基于全变分的自适应图像去噪模型。该模型根据噪声图像的信噪比,采用高斯滤波器对图像进行预处理,克服了全变分模型引入的阶梯效应;利用图像中每一像素点的梯度信息,自适应选取去噪模型中决定扩散强弱的参数p(x,y),使接近边缘处平滑较弱,远离边缘处平滑较强。数值实验表明,本方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪性能,其峰值信噪比(PSNR)在高噪声水平下,较其他变分方法至少提高1.0dB左右。     

A generalized variational model of magneto-thermo- elasticity for nonlinearly magnetized ferroelastic bodies

Based on a generalized variational principle of total energy functional, this paper presents a theoretical model to describe the magneto-thermo-elastic interaction of soft ferroelastic bodies with nonlinear magnetization under stationary thermal and magnetic fields. The energy functional of the magneto-thermo-elastic system is established by the summation of energy of sub-systems of nonlinearly magnetized magnetic field, thermal field, and mechanical deformation. By means of the manipulation of the mixed variational principle with independent variations of magnetic scalar potential, displacement vector, and temperature, all governing equations, which are nonlinear and coupling among magnetic, elastic and thermal fields, together with the expressions of magnetic forces are obtained from the variational approach. In order to valuate the obtained model, some existing models of the magneto-elasticity and the thermo-elasticity, which are validly demonstrated in literature, as special cases of the problem considered here are deduced out from the general case. Finally, an analytical analysis of magneto-thermo-elastic instability is conducted to a simply supported ferromagnetic rectangular thin plate under both a uniform distribution of temperature and a uniform transverse magnetic field by means of the linearized theory and the perturbation technique.     

尺寸驱动的变参设计系统研究

本研究在简介国际上先进的变参设计几种方法及优点后,叙述了一个国家863/CIMS项目:CAD/CAPP/NCP集成系统中二维尺寸驱动的变参设计子系统的构成与功能;然后着重阐述了本系统采用的尺寸驱动的变参设计思想和几何约束建立的原则,并提供了系统数据结构,最后以几个实例证明了此方法的正确性与工程实用性。     

基于时频分析和改进差分进化的多点泄漏定位方法

当管道同时发生多个泄漏点时,多个泄漏点的声波信号出现混叠,从而影响泄漏声信号的传播和衰减规律。在多点泄漏声波信号混叠的情况下,传统的泄漏定位方法无法对多个泄漏点进行有效定位。为此,提出了一种基于时频分析和改进差分进化的多点泄漏定位方法。由于变分模态分解(variational mode decomposing, VMD)的分解模态个数对特征提取有影响,因此采用能量函数估计分解模态个数,从而对VMD改进。然后采用改进VMD对多点泄漏声波信号进行处理。另外,通过时频分析(time-frequency analysis, TFA)估计多个泄漏点数量,从而得到多点泄漏的定位函数。差分进化(differential evolution, DE)算法易陷入局部最优,在进化后期收敛速度较慢,采用粒子群优化(particle swarm optimization, PSO)算法提高DE的全局收敛速度,并通过改进的差分进化算法估计多个泄漏点的位置。在管道现场进行多点泄漏的模拟试验,试验结果表明该方法能够准确地估计多点泄漏位置,泄漏定位的最小误差为18 m。     

Investigation of Free Vibrations of Multilayer Shallow Shells and Plates of Complex Shape in Plan

We propose an algorithm for the solution of the problem of free vibrations of multilayer shallow shells and plates based on the variational methods and the theory of R-functions. By using this algorithm, we solve the problems posed for shallow shells (spherical and cylindrical) and plates of complex shape in plan. We present the results of investigation of the dependences of the natural frequencies of vibrations of shallow shells and plates with different number of layers on the angle of rotation of the principal directions of each layer.     

一类Schrdinger方程组解的爆破

本文研究一类Schrodinger方程组解的爆破行为,在Y.Tsutsumi等(1998)文的基础上对非线性项作了修改,并用变分的方法得到了解在有限时间内爆破的一个充分条件。