浅析初三学生数学思维障碍的成因及突破

初三学生数学思维,是指学生在初一、初二数学感性认识基础上,运用比较、分析、综合、归纳、演绎等思维的基本方法,理解并掌握初中数学内容,并能对具体的数学问题进行推理与判断,从而认识初中数学的本质和规律的能力.     

Analysis of stress intensity factor in orthotropic bi-material mixed interface crack

Adopting the complex function approach, the paper studies the stress intensity factor in orthotropic bi-material interface cracks under mixed loads. With consideration of the boundary conditions, a new stress function is introduced to transform the problem of bi-material interface crack into a boundary value problem of partial differential equations. Two sets of non-homogeneous linear equations with 16 unknowns are constructed. By solving the equations, the expressions for the real bi-material elastic constant εt and the real stress singularity exponents λt are obtained with the bi-material engineering parameters satisfying certain conditions. By the uniqueness theorem of limit,undetermined coefficients are determined, and thus the bi-material stress intensity factor in mixed cracks is obtained. The bi-material stress intensity factor characterizes features of mixed cracks. When orthotropic bi-materials are of the same material, the degenerate solution to the stress intensity factor in mixed bi-material interface cracks is in complete agreement with the present classic conclusion. The relationship between the bi-material stress intensity factor and the ratio of bi-material shear modulus and the relationship between the bi-material stress intensity factor and the ratio of bi-material Young's modulus are given in the numerical analysis.     

纯扭各向异性复合材料板断裂分析的复变函数方法

对受纯扭载荷作用的线弹性各向异性纤维复合材料板裂纹尖端附近的应力场进行探讨.选取带复参数的挠度函数,利用复变函数方法和待定系数法,借助边界条件,确定复参数,从而推出了裂纹尖端附近的弯矩、扭矩、应力和位移计算公式.所得到的公式在有关的断裂分析中有一定的实用价值和参考作用,最后给出了数值算例.     

高场强下半导体沿面闪络现象的研究进展

 综述了国内外半导体沿面闪络的研究现状,阐述了电极结构的类型和影响闪络的主要因素;根据自定义的等值电导参数将闪络的发展划分为欧姆电导、局部闪络和贯通闪络3个阶段;通过对表面细丝电流的热过程进行实验和仿真研究,认为表面细丝电流通道的温度可以接近材料熔点,这一结果同时也支持了表面发热导致气体分子解吸附的假设;进一步通过气体解吸附的实验初步确定了存在外部的闪络通道。