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基于正向投影面积法的层析粒子图像测速权重系数计算方法
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作者 封明军 周骛 +3 位作者 黄浩钦 张大鹏 高丽敏 蔡小舒 《光学学报》 EI CAS CSCD 北大核心 2023年第11期17-30,共14页
三维重建是层析粒子图像测速(PIV)中重要的一步,重建过程中的权重系数计算通常较为繁琐。基于此,提出一种层析PIV快速权重计算方法——正向投影面积(FPA)法,即将离散体素投影在相应像元上的面积作为权重系数计算的方法。首先,基于针孔... 三维重建是层析粒子图像测速(PIV)中重要的一步,重建过程中的权重系数计算通常较为繁琐。基于此,提出一种层析PIV快速权重计算方法——正向投影面积(FPA)法,即将离散体素投影在相应像元上的面积作为权重系数计算的方法。首先,基于针孔相机模型构建三维空间内粒子多视角投影成像仿真程序,生成仿真图片用于方法分析与验证;其次,将FPA方法结合目前主流重建算法开展三维重建精度和耗时分析。结果表明,当用于本研究所述测量区域重建时,相比于传统后向方法与亚网格法权重系数计算方法,FPA法的权重矩阵元素个数分别降低了大约3个和1个数量级,计算时间分别减少了97%与85%,相应地降低了计算机的内存占用,且FPA法与传统后向方法所计算的权重矩阵的平均相似度高于0.9974。在常用实验粒子数分数(pppp=0.05)下,该方法结合目前主流重建算法的重建精度可达0.8以上。同时基于仿真图片分析了相机最佳采集角度以及实验相机噪声对重建结果的影响,结果表明,在实验噪声条件下重建结果仍然满足三维流场重建的要求。 展开更多
关键词 图像处理 层析粒子图像测速 三维重建 权重系数计算 正向投影面积法
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DETECTING COMMUNITY STRUCTURE: FROM PARSIMONY TO WEIGHTED PARSIMONY 被引量:4
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作者 Junhua ZHANG Yuqing QIU Xiang-Sun ZHANG 《Journal of Systems Science & Complexity》 SCIE EI CSCD 2010年第5期1024-1036,共13页
Community detection has attracted a great deal of attention in recent years. A parsimony criterion for detecting this structure means that as minimal as possible number of inserted and deleted edges is needed when we ... Community detection has attracted a great deal of attention in recent years. A parsimony criterion for detecting this structure means that as minimal as possible number of inserted and deleted edges is needed when we make the network considered become a disjoint union of cliques. However, many small groups of nodes are obtained by directly using this criterion to some networks especially for sparse ones. In this paper we propose a weighted parsimony model in which a weight coefficient is introduced to balance the inserted and deleted edges to ensure the obtained subgraphs to be reasonable communities. Some benchmark testing examples are used to validate the effectiveness of the proposed method. It is interesting that the weight here can be determined only by the topological features of the network. Meanwhile we make some comparison of our model with maximizing modularity Q and modularity density D on some of the benchmark networks, although sometimes too many or a little less numbers of communities are obtained with Q or D, a proper number of communities are detected with the weighted model. All the computational results confirm its capability for community detection for the small or middle size networks. 展开更多
关键词 CLIQUES community detection complex networks parsimony.
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