滤波是机载激光扫描的核心处理步骤之一,其主要任务是分离地面点和非地面点。经典渐进式不规则三角网致密化(Progressive TIN Densification)在众多滤波算法中效果较好、精度较高,但是PTD滤波算法阈值确定需要人工干预,无法满足自适应...滤波是机载激光扫描的核心处理步骤之一,其主要任务是分离地面点和非地面点。经典渐进式不规则三角网致密化(Progressive TIN Densification)在众多滤波算法中效果较好、精度较高,但是PTD滤波算法阈值确定需要人工干预,无法满足自适应滤波。本文针对关键格网参数阈值提出等值线确定方法,利用等值线的连续性、闭合性,根据建筑物同一边缘区域的明显高差来确定最大建筑面积与格网的参数阈值。实验证明通过等值线确定的面积与格网参数阈值对于具有建筑物的复杂地形有着更好的滤波效果。展开更多
In eukaryotes, crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes, ensuring accurate chromosome segregation during meiosis I and resulting in exchange of ge...In eukaryotes, crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes, ensuring accurate chromosome segregation during meiosis I and resulting in exchange of genetic information between homologues. The Arabidopsis PTD （Parting Dancers） gene affects the level of meiotic crossover formation, but its functional relationships with other core meiotic genes, such as AtSP011-1, AtRAD51, and AtMSH4, are unclear; whether PTD has other functions in meiosis is also unknown. To further analyze PTD function and to test for epistatic relationships, we compared the meiotic chromosome behaviors ofAtspoll-1 ptd and Atrad51 ptd double mutants with the relevant single mutants. The results suggest that PTD functions downstream of AtSP011-1 and AtRAD51 in the meiotic recombination pathway. Furthermore, we found that meiotic defects in rck pM and Atmsh4 ptd double mutants showed similar meiotic phenotypes to those of the relevant single mutants, providing genetic evidences for roles of PTD and RCK in the type I crossovers pathway. Moreover, we employed a pollen tetrad-based fluorescence method and found that the meiotic crossover frequencies in two genetic intervals were significantly reduced from 6.63% and 22.26% in wild-type to 1.14% and 6.36%, respectively, in the ptd^2 mutant. These results revealed new aspects of PTD function in meiotic crossover formation.展开更多
文摘针对山西地区Pb震相难以准确识别的现状,本文首先根据地壳速度模型计算了能够记录到Pb震相的震中距范围.然后针对Pb作为初至、后续震相分别提出了相应的识别方法:当Pb作为初至震相时周期大于Pg,振幅小于Pg,波性特征与Pn相似,可使用理论到时与波形特征相结合的方法识别;当Pb作为后续震相时,振幅和周期都不稳定、存在突变点,综合使用理论到时、波形特征和离散小波变换三种方法进行识别.最后,依照上述方法识别、标定了56个地震事件中的236个Pb震相,计算得出山西地区下地壳P波的速度为6.73 km/s,康拉德面的埋藏深度为21 km.
文摘滤波是机载激光扫描的核心处理步骤之一,其主要任务是分离地面点和非地面点。经典渐进式不规则三角网致密化(Progressive TIN Densification)在众多滤波算法中效果较好、精度较高,但是PTD滤波算法阈值确定需要人工干预,无法满足自适应滤波。本文针对关键格网参数阈值提出等值线确定方法,利用等值线的连续性、闭合性,根据建筑物同一边缘区域的明显高差来确定最大建筑面积与格网的参数阈值。实验证明通过等值线确定的面积与格网参数阈值对于具有建筑物的复杂地形有着更好的滤波效果。
基金supported by funds from Fudan Universityfunds from Rijk Zwaan,the Netherlands,and the Biology Department and the Huck Institutes of the Life Sciences at the Pennsylvania State University in USA
文摘In eukaryotes, crossovers together with sister chromatid cohesion maintain physical association between homologous chromosomes, ensuring accurate chromosome segregation during meiosis I and resulting in exchange of genetic information between homologues. The Arabidopsis PTD （Parting Dancers） gene affects the level of meiotic crossover formation, but its functional relationships with other core meiotic genes, such as AtSP011-1, AtRAD51, and AtMSH4, are unclear; whether PTD has other functions in meiosis is also unknown. To further analyze PTD function and to test for epistatic relationships, we compared the meiotic chromosome behaviors ofAtspoll-1 ptd and Atrad51 ptd double mutants with the relevant single mutants. The results suggest that PTD functions downstream of AtSP011-1 and AtRAD51 in the meiotic recombination pathway. Furthermore, we found that meiotic defects in rck pM and Atmsh4 ptd double mutants showed similar meiotic phenotypes to those of the relevant single mutants, providing genetic evidences for roles of PTD and RCK in the type I crossovers pathway. Moreover, we employed a pollen tetrad-based fluorescence method and found that the meiotic crossover frequencies in two genetic intervals were significantly reduced from 6.63% and 22.26% in wild-type to 1.14% and 6.36%, respectively, in the ptd^2 mutant. These results revealed new aspects of PTD function in meiotic crossover formation.
