A CFD-based high-order Discontinuous Galerkin solver for three dimensional electromagnetic scattering problems

In this paper, a CFD (Computational Fluid Dynamics) based DG (Discontinuous Galerkin) method is introduced to solve the three-dimensional Maxwell’s equations for complex geometries on unstructured grids. In order to reduce the computing expense, both the quadrature-free implementation method and the parallel computing based on domain decomposition are employed. On the far-field boundary, the non-reflecting boundary condition is implemented. Numerical integration rather than the quadrature-free implementation is used over the faces on the solid boundary to implement the electromagnetic solid boundary condition for perfectly conducting objectives. Both benchmark examples and complex geometry case are tested with the CFD-based DG solver. Numerical results indicate that highly accurate results can be obtained when using high order even on coarse grid and the present method is very suitable for complex geometries. Furthermore, the costs of CPU time and the speedup of the parallel computation are also evaluated.     

关于PCBA板使能控制引脚开路的失效分析

介绍了某通信设备中PCBA板使能控制引脚开路的失效分析结果。通过采用外观检查、X射线透视、切片分析、可焊性测试和镀层厚度测量,以及实验验证等一些列技术手段,确定了PCBA板上电源模块功能失效的根本原因,即在高温作用下PCB内层发生树脂收缩现象,产生的内应力使内层连接开路。     

不同加载方向下五边形截面钢管混凝土巨型柱抗震性能试验研究

为研究五边形钢管混凝土巨型柱不同加载方向的抗震性能,设计了6个1/7.5缩尺的巨型柱模型试件,试件截面构造包括单腔体腔内配置钢筋、4腔体腔内未配置钢筋和4腔体每腔体内配置钢筋。进行了两种不同加载方向的拟静力研究,一种沿截面对称轴方向加载,另一种沿垂直截面对称轴方向加载。分析了各试件的破坏特征、滞回特性、承载力、延性、刚度退化和耗能性能。结果表明：五边形截面钢管混凝土巨型柱三种截面构造中,4腔体每腔体内配置钢筋的试件抗震能力较强;不同加载方向五边形截面钢管混凝土巨型柱受力性能有明显差异,设计中应考虑两个方向抗震能力的均衡性;五边形截面钢管混凝土巨型柱,屈服位移角均值为1/75,最大弹塑性位移角均值达1/24,具有良好的延性。     

Optimum design of structures subjected to follower forces

In this paper, shape optimization is used to optimize the critical load of an Euler–Bernoulli cantilever beam with constant volume subjected to a tangential compressive tip load and/or a tangential compressive load arbitrarily distributed along the beam. This is achieved by varying appropriately the beam cross-section, thus its stiffness and mass properties, along its length, so that the critical load reaches its maximum or a prescribed value. The problem is reduced to a nonlinear optimization problem under equality and inequality constraints as well as specified lower and upper bounds, which, together with large slenderness ratios, ensure the validity of the Euler–Bernoulli theory and the serviceability of the beam. The evaluation of the objective function requires the solution of the dynamic stability problem of a cantilever beam with variable cross-section. This problem is solved using the analog equation method (AEM) of Katsikadelis for the fourth-order hyperbolic differential equation with variable coefficients, together with a simple and direct iterative method for the evaluation of the critical load based on the eigenvalue sensitivity. Besides its accuracy, this method overcomes the shortcoming of a possible FEM solution, which would require resizing of the elements and re-computation of their stiffness properties during the optimization process. Example problems of various types of follower forces are presented, which illustrate the method and demonstrate its applicability and efficiency.     

半刚性连接纲框架非线性分析的修正塑性区法

提出一种半刚性连接钢框架非线性分析的修正塑性区法。它考虑了轴力的Ｐ－Ｄｅｌｔａ效应、梁柱的半刚性连接、横截面的塑化和塑性区长度等几何和材料非线性因素的影响。该法既克服了塑性区法因单元划分过多而多占计算机内存和花费机时的缺陷，又弥补了塑性铰法不能考虑横截面塑化和塑性区长度影响的不足。计算分析表明，其结果令人满意。     

考虑动态增容效应的陆上风电场送出线路截面优化方法

现有风电场架空导线截面优化设计通常以典型环境参数为依据,未考虑风速等气象条件的动态变化,仍有进一步挖掘输电能力潜力的空间。为了进一步优化导线截面,文中基于Morgan公式,建立数学模型表征陆上风电场架空送出线路导线截面优化设计过程,提出一种适用于送出线路导线截面设计的优化方法。该方法综合考虑线路动态增容效应和风电场出力特性的匹配,根据地区历史气象数据等信息,选择送出线路导线截面,完成优化设计。通过算例分析验证了文中所提出的陆上风电场送出线路导线优化设计方法。结果表明,所提出的方法能够在满足风电送出需求的基础上有效降低导线截面积,节省导线材料,提高陆上风电场电气设计的经济性。     

变截面轧机液压系统的调试与维护

介绍了变截面板簧轧机的用途及工作原理，总结了现场调试时的经验，故障排除和分析的一般思路及应遵循的几条规则，并现场构建压力元件的测试台架。     

球形量子点量子阱中的电子拉曼散射研究

本文对HgS/CdS球形量子点量子阱中的电子拉曼散射进行了研究;推导了拉曼散射截面的表达式,给出了有关的选择定则,获得了丰富的拉曼散射谱线,给出了相邻能级差对于不同阱宽的色散图谱并对谱线特点进行了分析和讨论,讨论结果直接给出了电子的重要微观信息。     

浅谈混凝土桥梁裂缝的成因及控制

结合多年桥梁技术工作经验，分析了混凝土桥梁各部位裂缝产生的原因，介绍了在设计、施工阶段所采取的防治措施，论述了混凝土裂缝的处理方法，最终达到控制混凝土桥梁裂缝的目的。