Computing global visibility maps for regions on the boundaries of polyhedra using Minkowski sums

A global visibility map is a spherical image built to describe the complete set of global visible view directions for a surface. In this paper, we consider the computation of global visibility maps for regions on the boundary of a polyhedron. Both the self-occlusions introduced by a region and the global occlusions introduced by the rest of the surfaces on the boundary of the polyhedron are considered for computing a global visibility map. We show that the occluded view directions introduced between a pair of polyhedral surfaces can be computed from the spherical projection of the Minkowski sum of one surface and the reflection of the other. A suitable subset of the Minkowski sum, which shares the identical spherical projection with the complete Minkowski sum, is constructed to obtain the spherical images representing global occlusions. Our method has been successfully tested on many CAD models. It extends the previous methods for computing global visibility maps using convex decomposition, and it exhibits a better performance.     

Nd:YAG激光在泪道疾病中的应用

应用Nd:YAG泪道激光治疗机对80例(85只眼)各种泪道阻塞者进行治疗,取得较好的效果,治愈率达82.3％。手术反应轻、痛苦小、无并发症,可反复使用。     

一种基于视觉的交通检测方法

在实际交通图像检测中检测系统要面对照度变化、局部遮挡和道路阴影等问题，针对这些问题提出一种基于视觉的检测方法，实验表明新方法对解决上述问题的有效性，并在计算车辆数量和速度方面有较高的精确度和较快的执行速度。     

基于统计学习优化SIFT的面部遮挡人脸识别

针对传统的人脸识别算法受面部遮挡的影响导致很难兼顾鲁棒性和保持原始图像核心信息的问题,本文提出了一种基于统计学习优化尺度不变特征变换的面部遮挡人脸识别算法。首先,利用SIFT将所有给定训练图像用一组局部特征描述符表示出来;然后,通过执行统计学习获得正常脸部图像SIFT特征的概率分布函数,利用获得的概率分布函数在新观察到的测试图像中检测异常SIFT特征;最后,计算测试图像与训练图像之间的相似度,并利用K近邻分类器完成人脸识别。在AR人脸数据库上的实验验证了本文算法的有效性及可靠性,实验结果表明,相比其它几种较为先进的人脸识别算法,本文算法取得了更强的识别鲁棒性。     

玻璃体腔注射曲安奈德治疗视网膜分支静脉阻塞继发黄斑囊样水肿疗效观察

观察玻璃体腔注射曲安奈德(intravitreal triamcinolone acetonide,IVTA)治疗视网膜分支静脉阻塞(brach retinal vein occlusion,BRVO)继发黄斑囊样水肿(cystoid macular edema,CME)的临床效果.对33例(34眼)BRVO继发CME...     

Temporal Variations in Visual Completion: A Reflection of Spatial Limits?

The completion of partly occluded objects appears instantaneous and effortless, but empirically takes measurable time. The current study investigates how amount of occlusion affects the time course and mechanisms of visual completion. Experiment 1 used a primed-matching paradigm to determine completion times for objects occluded by various amounts. Experiments 2 and 3 used a dot-localization paradigm to probe completed contour representations for a qualitative shift above some spatial limit. The results demonstrate that time to completion rises with amount of occlusion. Nonetheless, the visual system can complete highly occluded objects, even when the occlusion renders visible contours nonrelatable. Furthermore, prolonged completion times for highly occluded objects do not result from a breakdown of low-level interpolation processes: The same contour completion mechanism operates on objects occluded by different spatial extents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

烟气污染物协同治理中的负协同效应串联作用现象

随着烟气污染物协同治理技术在燃煤电站的普遍应用,协同治理过程中各单元设备间的不良影响及其造成的设备治理能力下降或污染物增量排放现象日益显现,对此类负协同效应展开分析,并通过性能试验、检测化验、运行诊断等方法对某350 MW机组进行研究,结果表明：存在负协同效应串联作用现象,即上游设备的负协同效应不断蚕食本体或下游设备的污染物治理能力,最终导致设备治理能力不足。最后,提出控制及消纳负协同效应的建议。     

铝合金彩色瓷质阳极氧化新工艺

研究了在铝合金瓷质阳极氧化膜层表面进行染色、封闭一步处理的新工艺.通过对这种方法得到的瓷质阳极氧化膜层进行耐磨、耐腐蚀、耐候等性能试验,发现经过瓷质氧化后表面,进行染色封闭一步处理的膜层具有色泽正、染色牢固、表面装饰效果好的特点;同时这种瓷质彩色膜层还具有良好的耐磨、耐腐蚀和耐候性能.     

基于统计模型的三维场景重建补洞算法

提出了一种新的处理距离图像(即点云数据)算法。算法提取已经获得的表面数据的特性．计算各个被测的特征值,建立马尔可夫统计模型,描述整个表面的数学特征,进而利用最大似然概率预测丢失位置的数据值,得到被测物体表面的完整的数据描述。使用该算法恢复由于障碍物和表面小良反射特性产生的空洞,具有良好的视觉效果．与测量获得的表面数据具有统一的几何特征。     

一种改进型的粒子滤波器

针对复杂背景条件下图像序列中跟踪运动目标的问题,提出一种改进的粒子滤波图像跟踪算法,该算法利用遗传算法的研究成果,采用选择、交叉、变异等步骤实现对粒子的重采样,解决了粒子滤波器所面临的粒子退化和匮乏问题.由于该算法利用了遗传算法的全局寻优特性,因此该算法具有较强的稳健性.同时,粒子滤波可实现非线性非高斯状态空间模型的最优估计,将该粒子滤波用于目标跟踪,具有较好的过遮挡能力.实验结果表明,该算法状态估计性能好,能够很好地实现复杂图像序列中的目标跟踪.