New solar tracker

A new very simple solar tracker is described in detail in the paper as well as a tracking strategy which enables high-collectible energy surplus at medium tracking accuracy.     

熔融挤压成形大型原型精度控制研究

熔融挤压成形 (MEM )是快速成形 (RP)技术中的一种重要工艺 ,清华大学激光快速成形中心成功开发大型MEM设备MEM6 0 0 ,能够高速制造 5 0 0mm× 5 0 0mm× 6 0 0mm的大型原型。文章主要论述MEM工艺成形大型零件原型的精度控制。     

集成电路塑封模具错位、偏心问题探讨

就集成电路封装过程中塑封模具的错位和偏心问题做探讨,分析导致错位和偏心的各种原因,并就如何使塑封模具的错位、偏心问题对产品的质量影响降到最低提出了具体的改善措施.     

One-Sided Smoothness-Increasing Accuracy-Conserving Filtering for Enhanced Streamline Integration through Discontinuous Fields

The discontinuous Galerkin (DG) method continues to maintain heightened levels of interest within the simulation community because of the discretization flexibility it provides. One of the fundamental properties of the DG methodology and arguably its most powerful property is the ability to combine high-order discretizations on an inter-element level while allowing discontinuities between elements. This flexibility, however, generates a plethora of difficulties when one attempts to use DG fields for feature extraction and visualization, as most post-processing schemes are not designed for handling explicitly discontinuous fields. This work introduces a new method of applying smoothness-increasing, accuracy-conserving filtering on discontinuous Galerkin vector fields for the purpose of enhancing streamline integration. The filtering discussed in this paper enhances the smoothness of the field and eliminates the discontinuity between elements, thus resulting in more accurate streamlines. Furthermore, as a means of minimizing the computational cost of the method, the filtering is done in a one-dimensional manner along the streamline.     

滴水表的测试与应用探讨

通过滴水表加速磨损模拟试验和使用的某型号滴水表的实测试验,建立了运行时间-始动流量、实际用量-始动流量的函数关系,分析总结了不合格滴水表精度下降的原因.基于测试结果,提出水表选型、安装需考虑的问题、提高装表精度的策略等.     

0.1级高精度电容式电压互感器的开发

电力系统中新技术的应用促进了CVT向0.1级高精度方向的发展.如何保证准确级的准确性和稳定性是0.1级CVT设计中关键的问题.本文分析了附加误差对总误差的影响程度,并讨论了中间电压对输出容量及其他性能的影响关系,提出了关键问题的解决措施.     

大射电望远镜精调稳定平台结构设计及动力分析

设计了一种大型 Stewart型平台用于大射电望远镜 (L T)二级精调 ,通过坐标变换 ,推导出其运动控制的数学模型 ,并利用 Jacobian矩阵 ,进行了动力学分析 ,给出了其运动精度分析结果 ,证明其应用到 L T工程中是切实可行的     

切削加工尺寸精度模糊智能控制的研究

针对金属切削加工中影响工件尺寸精度非线性因素众多 ,精确数学模型难以建立的特点 ,提出尺寸加工精度控制的模糊智能化方法 ,设计了自寻优模糊控制器 ,实现了工件尺寸精度在线智能监控。仿真试验结果表明 ,这种控制器具有很好的鲁棒性 ,获得了满意的控制效果。