Revisiting Johnson and Jackson boundary conditions for granular flows

In this article, we revisit Johnson and Jackson boundary conditions for granular flows. The oblique collision between a particle and a flat wall is analyzed by adopting the classic rigid‐body theory and a more realistic semianalytical model. Based on the kinetic granular theory, the input parameter for the partial‐slip boundary conditions, specularity coefficient, which is not measurable in experiments, is then interpreted as a function of the particle‐wall restitution coefficient, the frictional coefficient, and the normalized slip velocity at the wall. An analytical expression for the specularity coefficient is suggested for a flat, frictional surface with a low frictional coefficient. The procedure for determining the specularity coefficient for a more general problem is outlined, and a working approximation is provided. Published 2011 American Institute of Chemical Engineers, 2012     

基于摄像头检测的防盗拍系统开发和算法研究

针对电影院中的非法盗拍现象,提出了对智能摄像头检测系统的改造和算法设计。硬件部分的人工光源模块提供定向光照,与之相配合的软件算法部分融合层级特征检测、直方图比较、主成分分析、K最近邻分析等多种方法,对摄像头镜头反射高光模式进行检测和识别。通过实验数据集的验证,系统对摄像头敏感度高,检测准确率高,具有理论研究价值和实际应用价值。系统硬件模块和算法模块可拓展且可移植于其他应用领域。     

基于图案完整性的高反射曲面缺陷检测新方法

高反射曲面零件的表面缺陷检测是一项具有挑战性的工作,以钢球为例,提出了一种通过识别反射图案的完整性进行表面缺陷检测的新方法.该方法基于钢球表面的反光率极高且达到镜面成像的特性,将钢球置于穹顶形光源内部,光源罩内壁修饰有规则、完整的图案.若钢球表面存在缺陷,则其反射形成的修饰图案的像将在缺陷部分发生扭曲变形或间断缺失.采集钢球表面图像,检测修饰图案所成像的完整性即可实现表面缺陷的检测.设计了内壁修饰同心圆图案的新型光源,利用上述方法,对钢球表面缺陷进行了有效提取与分析,取得了良好效果,验证了该方法对于高反射曲面零件表面缺陷检测的有效性.