模拟结构倒塌破坏的有限质点法

有限质点法是以向量式力学为基础的新兴结构分析方法,本文将其应用于冲击荷载作用下的网壳结构的倒塌破坏模拟中。以空间杆单元为例建立了有限质点法的基本方程,推导了求解几何和材料非线性问题的基本公式。为计算断裂问题,建立了空间杆单元的断裂准则和断裂模型,发展了有限质点法进行断裂分析的基本算法。通过对某双层网壳冲击荷载下破坏过程的模拟和分析,验证了该方法在结构倒塌破坏过程模拟中的有效性和适用性。     

对一道人船模型习题的剖析

【例1】如图1所示,质量为2m的木板停在光滑的水平面上,其左端有质量为m,可视为质点的遥控电动赛车,由静止出发,经过时间t后关闭电动机,此时赛车速度为v1,赛车在木板上滑行一段距离后,恰好停在木板的右端.若通电后赛车以恒定功率P行驶,赛车在运动过程中受到木板的摩擦阻力恒     

广义鞍点问题的松弛维数分解预条件子

本文将Benzi等提出的松弛维数分解(Relaxed dimensionalfactorization, RDF)预条件子进一步推广到广义鞍点问题上,并称为GRDF(Generalized RDF)预条件子.该预条件子可看做是用维数分裂迭代法求解广义鞍点问题而导出的改进维数分裂(Modified dimensional split, MDS)预条件子的松弛形式, 它相比MDS预条件子更接近于系数矩阵, 因而结合Krylov子空间方法(如GMRES)有更快的收敛速度.文中分析了GRDF预处理矩阵特征值的一些性质,并用数值算例验证了新预条件子的有效性.     

无旋性前进重力波传递在均匀流中的Lagrangen解析解与试验验证Ⅱ.试验验证

针对文献[1]中的无旋性自由表面周期性规则前进重力波传递在均匀流中,本文以与前进波波向同向与反向的均匀流两种特例情况,进行试验测量,所得的波形曲线、流速分布、流体质点的运动轨迹与运动周期及其质量传输速率与Lagrange平均高程等特性,均与文献[1]中全以Lagrange方式所得的三阶解结果符合得很好.这证实本研究取定的标注流体质点的参数,正好为其在原静止水中的位置坐标值.同时亦证实波流场中由流体质点所构成的波形曲线,其波长皆同于(纯)前进波,而其传播速度为(纯)前进波波速与均匀流流速之和是具Doppler效应的;而流体质点的运动周期与其运动周期平均高程、及其质量传输速率扣掉均匀流流速等,都与(纯)前进波的相符.另外,亦揭示出流体质点的运动轨迹,在前进波波向与均匀流同向中,当流体质点在波谷断面处时沿前进波波向的流速分量为反向、零与正向时,则其形状分别为朝波向前进的扁长辐状余摆线、在波谷断面处成尖点朝下的滚轮状线与短辐形余摆线;而在前进波波向与均匀流反向中,当流体质点的质量传输速率为沿前进波波向为正向与零时,则其形状分别为朝波向前进的缩短的扁长辐形余摆线与长轴在前进波波向上椭圆形封闭曲线;而当流体质点的质量传输速率为反前进波波向,但质点在波峰断面处时沿前进波波向的流速分量分别为正向、零与反向时,则其形状分别为反波向前进的倒扁长辐形余摆线、在波峰断面处成尖点朝上的倒滚轮状线与倒短辐形余摆线.     

4×4B-型KdV方程族

基于sl(4,(C))的loop代数的非平凡李代数分裂,构造了5类新的孤子方程族.这些代数分裂通过构造从正李子代数到负李子代数的线性箅子B统一得到.对所有可能的线性箅子B进行分类,证明存在5类4×4仿射B-型KdV方程族.利用Adler- Konstant- Symes理论获得了这些方程族的Hamilton结构,并利用loop群方法得到其B(a)cklund变换.     

由谱数据和主子矩阵构造Jacobi矩阵及其推广

研究由主子矩阵和谱数据构造Jacobi矩阵问题, 推广到弹簧质点系统谱约束下的双倍维扩展问题和对称三对角二次束逆特征值问题.给出了问题的数值解法.     

Influence of the Jahn—Teller distortion on magnetic ordering in TbMn1-xFexO3

The Jahn-Teller distortion plays an important role in determining the exchange interaction in rare-earth manganites.In this work we study the influence of the Jahn-Teller distortion on the magnetic structures of TbMn1-xFexO3（x = 0,0.02,0.05,0.10,and 0.20） single crystals in the basal MnO2 plane.The decrease in the quadruple splitting with the increasing Fe doping indicates the reduction of the Jahn-Teller distortion,which makes the nearest neighboring（NN） FM interaction dominant over the next nearest neighbor（NNN） AFM interaction.This alteration is favorable for the development of A-type AFM ordering instead of the spiral magnetic ordering,which collapses when x ≥ 0.05.The analysis of dielectric data indicates that the ferroelectricity is arising from the peculiar spiral magnetic ordering.     

Fracture mechanics analysis on Smart-Cut^R technology. Part 2： Effect of bonding flaws

In Part 2 of the paper on the Smart-Cut process, the effects of bonding flaws characterized by the size and internal pressure before and after splitting are studied by using fracture mechanics models. It is found that the bonding flaws with large size are prone to cause severe deviation of defect growth, leading to a non-transferred area of thin layer when splitting. In a practical Smart-Cut process where the internal pressure of bonding flaws is very small, large interfacial defects always promote defect growth in the splitting process. Meanwhile, increasing the internal pressure of the bonding flaws decreases the defect growth and its deviation before splitting. The mechanism of relaxation of stiffener constraint is proposed to clarify the effect of bonding flaws. Moreover, the progress of the splitting process is analyzed when bonding flaws are present. After splitting, those bonding flaws with large size and high internal pressure are vulnerable for the blistering of the thin film during high-temperature annealing.     

Quantum Information Splitting Based on Current Cavity QED Techniques

We propose two schemes for quantum information splitting via W-class state. The first scheme is based on the interaction of single atom with single-mode field, while the second scheme is based on the simultaneous interaction of two atoms with single-mode cavity. For the first scheme, the difIiculty of two atoms required to be simultaneously sent through one cavity is avoid. For the second scheme, it is immune to thermal field. Both schemes are experimentally feasible based on current cavity QED techniques.     

Branch Processes of Regular Magnetic Monopole

In this paper, by making use of Duan＇s topological current theory, the branch process of regular magnetic monopoles is discussed in detail. Regular magnetic monopoles are found generating or annihilating at the limit point and encountering, splitting, or merging at the bifurcation point and the degenerate point systematically of the vector order parameter field φ（x）. Furthermore, it is also shown that when regular magnetic monopoles split or merge at the degenerate point of field function φ, the total topological charges of the regular magnetic monopoles are stilI unchanged.