ITER磁体支撑结构有限元分析

磁体支撑结构是国际热核聚变实验反应堆(ITER)的重要部件,对其进行力学特性分析研究是确保整个反应堆正常运行的关键。通过对磁体支撑结构各工况下的强度、刚度的数值分析,给出了磁体支撑结构对应工况下各零部件的应力分布及变形量;分析结果表明磁体支撑结构各零部件的最大应力值均小于许用应力,满足强度要求,各零部件变形合理,不会出现脱开失稳现象。通过数值分析,为国际热核反应堆磁体支撑结构提供了理论设计数据,提升了磁体支撑结构的安全性和可靠性。     

应力梯度不均匀时平板表面裂纹的应力强度因子

本文采用考虑裂纹面上具有任意分布载荷的线弹簧模型,在Kirchhoff板弯曲理论的假设下,将含半椭圆型表面裂纹的平板问题化为一组耦合的积分方程组进行求解,对均匀拉伸和纯弯曲两种载荷作用下的应力强度因子数值解,同经典线弹簧模型和有限元解进行了比较,并给出了经典线弹簧模型不能得到的、裂纹面上承受幂次不均匀应力分布时应力强度因子的数值解.     

功能梯度压电带中裂纹对SH波的散射

研究功能梯度压电带中裂纹对SH波的散射问题,为了便于分析,材料性质假定为指数模型,并假设裂纹面上的边界条件为电渗透型的.根据压电理论得到压电体的状态方程,利用Fourier积分变换,问题转化为对偶积分方程的求解.用Copson方法求解积分方程.求得了裂纹尖端动应力强度因子、电位移强度因子的解析表达式,最后数值结果显示了标准动应力强度因子与入射波数、材料参数、带宽、波数以及入射角之间的关系.     

TENSILE STRENGTH FOR SPLITTING FAILURE OF BRITTLE PARTICLES WITH CONSIDERATION OF POISSON＇S RATIO

The core mechanism of comminution could be reduced to the breakage of individual particles that occurs through contact with other particles or with the grinding media, or with the solid walls of the mill. When brittle particles are loaded in compression or by impact, substantial tensile stresses are induced within the particles. These tensile stresses are responsible for splitting failure of brittle particles. Since many engineering materials have Poisson‘s ratios very close to 0.3, the influence of Poisson‘s ratio on the tensile strength is neglected in many studies. In this paper, the state of stress in a spherical particle due to two diametrically opposed forces is analyzed theoretically. A simple equation for the tensile stress at the centre of the particle is obtained. It is found reasonable to propose this tensile stress at the instant of failure as the tensile strength of the particle. Moreover, this tensile strength is a function of the Poisson‘s ratio of the material. As the state of stress along the z-axis in an irregular specimen tends to be similar to that in a spherical particle compressed diametrically with the same force, this tensile strength has some validity for irregular particles as well. Therefore, it could be used as the tensile strength for brittle particles in general. The effect of Poisson‘s ratio on the tensile strength is discussed.     

马氏调制强度的传染模型下CDS的CVA计算

本文考虑了具有马氏调制强度的传染模型下,信用违约互换(CDS)的双边信用估值调整(CVA).在我们考虑的模型中,利率、回收率以及CDS的买方、卖方和参照实体三方的违约强度均受宏观经济环境的影响,该经济状况由一连续时间状态的齐次马氏链所刻画.利用测度变换和累积强度的Laplace变换,我们给出了CDS合同的双边CVA的表达公式,该公式可以表示为线性常微分方程组的基本解的形式.利用所得到的公式,我们数值分析了马氏调制和违约相关性对双边CVA的影响.     

若干点不交的n阶路的并图的非正规强度

本文研究了若干点不交的n阶路的并图的非正规强度.利用构造矩阵的方法,获得了若干点不交的n阶路的并图(n=1(mod 4))的非正规强度,推广了文献[5]中的结论.     

压电薄板板边导电裂纹尖端的力电场分析

采用有限元方法，分析了压电薄板板边不同长度导电裂纹尖端的力电场分布规律，发现导电裂纹尖端的应力场和电场强度存在明显的集中和奇异现象，集中和奇异的程度与裂纹长度有关。而且，在裂纹延长线上分别存在两点，这里的应力和电场对裂纹长度不太敏感，总等于无裂纹时薄板的均匀应力和均匀电场强度；同时，还研究了导电裂纹尖端的应力强度因子和电场强度因子对裂纹长度的依赖关系，发现在线性本构的前提下，导电裂纹尖端的应力强度因子与电场强度因子之间具有近似的线性关系。     

养护条件对UHPC强度和毛细吸水性的影响

为优化超高性能混凝土(UHPC)预制构件养护工艺,研究了不同养护条件对UHPC强度和毛细吸水性的影响,并采用孔结构测试、热重分析和扫描电镜观察,对其机理进行了分析.结果表明:热养护显著提高了UHPC的7 d强度,这与加速火山灰反应有关,但高温和干热养护对其后期强度增大不利,甚至出现约3％的强度倒缩;不论何种养护,UHP...     

Spatial Dispersion Induced by Cross-Phase Modulation

We demonstrate our experiment of controlling spatial displacements of the probe beam induced by the cross-Kerr effect in a three-level V-type atomic system. By increasing the atomic density or the intensity of strong control laser beams, spatial displacements are enhanced. We further study the difference of effects from the atomic density and the laser intensity. In addition, the spatial displacement efficiencies of the probe beam in different energy level atomic systems are compared. Such studies of controlling spatial displacements can have potential applications in soliton deflection, spatial optical switch and generating spatially correlated （entangled） laser beams in multi-level EIT systems.     

取代基对N-H…O=C氢键二聚体中氢键强度的影响

使用MP2方法研究了N-H…O=C氢键二聚体的氢键强度,探讨了不同取代基对N-H…O=C氢键强度的影响.研究发现,可以通过改变取代基的供电性或吸电性来调控氢键强度:乙基等供电子基团对N-H…=C氢键强度的调节作用不大;-NO_2等强吸电子基团可极大地改变N-H…=C氢键强度;质子受体分子中的强吸电子基团如-NO_2可使N-H…O=C氢键强度减弱多达2.6 kcal/mol.自然键轨道(NBO)分析表明,N-H…O=C氢键强度越强,参与形成氢键的氢原子电荷越正,氧原子电荷越负,单体分子间电荷转移越多,N-H…O=C氢键中氧原子孤对电子n(O)对N-H反键轨道σ*(N-H)的二阶稳定化能越大.