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基于E2LSH的轨迹KNN查询算法
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作者 邱磊 吴志兵 《计算机技术与发展》 2020年第3期13-18,共6页
目前海量时空轨迹数据近邻查询算法中存在计算时间复杂度较高的问题,因此提出了一种结合领域POI数据和E2LSH算法的轨迹KNN查询算法。首先利用GeoHash技术对地理空间进行编码,然后结合POI数据实现向量空间的初步降维,进而根据停留时间构... 目前海量时空轨迹数据近邻查询算法中存在计算时间复杂度较高的问题,因此提出了一种结合领域POI数据和E2LSH算法的轨迹KNN查询算法。首先利用GeoHash技术对地理空间进行编码,然后结合POI数据实现向量空间的初步降维,进而根据停留时间构建每条轨迹的向量,采用局部敏感哈希函数运算结果建立轨迹索引,最后对查询返回的相似轨迹集合分别进行距离计算,经过排序得到距离最近的K个查询结果。对于增量的轨迹数据,利用E2LSH算法计算哈希值,直接添加轨迹索引,从而避免了复杂的计算过程以及对现有轨迹索引的影响。基于合成数据及真实数据集的实验结果表明,该方法在海量时空轨迹数据的近邻查询中,虽然牺牲了一定的准确率,但有效提升了算法效率,并能够高效简便地处理增量的时空轨迹数据。 展开更多
关键词 海量轨迹大数据 近邻查询 地理空间编码 局部敏感哈希 轨迹索引
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Biosecurity Practices and Geospatial Map of Ontario Backyard Poultry Flocks
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作者 Jean Marie Buregeya Scott McEwen +2 位作者 John Neil Tom Baker Gwen Kerry Zellen 《Journal of Environmental Science and Engineering(B)》 2013年第12期694-701,共8页
The CFO (Chicken Farmers of Ontario) has taken important steps to increase biosecurity practices within backyard poultry flocks in order to thwart infectious diseases. The present study originally intended to descri... The CFO (Chicken Farmers of Ontario) has taken important steps to increase biosecurity practices within backyard poultry flocks in order to thwart infectious diseases. The present study originally intended to describe biosecurity practices within this milieu, so as to determine their nearest neighbor and density, as well as the average distance between backyard and commercial broiler flocks. To that effect, paper questionnaire and survey interviews were used (May-July, 2011), while backyard and commercial broiler chicken flocks were geocoded. The response rates collected from the study produced these findings regarding: growers' health practices toward flocks, hygienic precautions relative to the production area, regularity of bird inspection and cleaning after each folk, protocol used to dispose of dead birds, mixing (or lack thereof) of flocks with other livestock, as well as the average distance between small flocks and commercial farms. The study concludes that education material should focus on improving the growers' understanding of issues examined in the study, focusing on areas of weakness in respect to biosecurity practices. 展开更多
关键词 Backyard flocks BIOSECURITY infectious diseases Ontario poultry.
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