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心内膜散乱点云边界点检测算法研究 被引量:2
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作者 周学礼 万旺根 《计算机应用研究》 CSCD 北大核心 2012年第10期3942-3944,3996,共4页
针对心内膜散乱点云预处理中的边界点检测,利用截线云理论将散乱点云进行等间隔区域分层,将点云投影至点云切片,得到切片的散乱点集,同时建立链表结构分区存储点云数据;由平面上点的二维坐标定位,提出区域"十"字算法进行切片... 针对心内膜散乱点云预处理中的边界点检测,利用截线云理论将散乱点云进行等间隔区域分层,将点云投影至点云切片,得到切片的散乱点集,同时建立链表结构分区存储点云数据;由平面上点的二维坐标定位,提出区域"十"字算法进行切片数据边界点提取,获取切片数据的最外层点,将检测到的边界点存回原始三维数据源,完成预处理过程。实验结果证明,该算法对边界点具有较强的识别能力,能够在快速、有效地简化点云数据的同时保持原始特征的信息,可以提高后续三维建模的精度和速度。 展开更多
关键词 散乱点云 边界点 “十”字算法 点云切片
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Variance Reduction Technique for Estimating Value-at-Risk based on the Cross - Entropy
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作者 Mykhailo Pupashenko 《Journal of Mathematics and System Science》 2014年第1期37-48,共12页
Value-at-Risk (VaR) estimation via Monte Carlo (MC) simulation is studied here. The variance reduction technique is proposed in order to speed up MC algorithm. The algorithm for estimating the probability of high ... Value-at-Risk (VaR) estimation via Monte Carlo (MC) simulation is studied here. The variance reduction technique is proposed in order to speed up MC algorithm. The algorithm for estimating the probability of high portfolio losses (more general risk measure) based on the Cross - Entropy importance sampling is developed. This algorithm can easily be applied in any light- or heavy-tailed case without an extra adaptation. Besides, it does not loose in the performance in comparison to other known methods. A numerical study in both cases is performed and the variance reduction rate is compared with other known methods. The problem of VaR estimation using procedures for estimating the probability of high portfolio losses is also discussed. 展开更多
关键词 VALUE-AT-RISK Monte Carlo simulation Cross - Entropy method variance reduction importance sampling stratifiedsampling.
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