同塔多回线路杆塔所处地形复杂,评定线路绕击耐雷水平较为困难。本文引进三维电气几何模型,与传统的EGM相比,避免了由各个截面绕击跳闸率的等效所带来的误差。将输电线路的裸露弧面进行了三维延伸扩展,计算了绕击跳闸率沿着档距内线路...同塔多回线路杆塔所处地形复杂,评定线路绕击耐雷水平较为困难。本文引进三维电气几何模型,与传统的EGM相比,避免了由各个截面绕击跳闸率的等效所带来的误差。将输电线路的裸露弧面进行了三维延伸扩展,计算了绕击跳闸率沿着档距内线路每一段与杆塔间长度的变化,通过沿着档距方向进行积分得出最终的绕击跳闸率,该方法也表明:线路不同位置绕击跳闸率差别很大,线路总绕击跳闸率根本不能反应实际情况。最后,通过计算分析220 kV输电线路和500/220 k V混合四回线路,证实了方法的正确性和实用性,在实际应用中具有借鉴意义。展开更多
Aims Plant height is a key functional trait related to aboveground bio-mass,leaf photosynthesis and plant fitness.However,large-scale geographical patterns in community-average plant height(cAPH)of woody species and d...Aims Plant height is a key functional trait related to aboveground bio-mass,leaf photosynthesis and plant fitness.However,large-scale geographical patterns in community-average plant height(cAPH)of woody species and drivers of these patterns across different life forms remain hotly debated.Moreover,whether cAPH could be used as a predictor of ecosystem primary productivity is unknown.Methods We compiled mature height and distributions of 11422 woody spe-cies in eastern Eurasia,and estimated geographic patterns in cAPH for different taxonomic groups and life forms.then we evaluated the effects of environmental(including current climate and historical climate change since the Last Glacial Maximum(LGM))and evolutionary factors on cAPH.Lastly,we compared the predictive power of cAPH on primary productivity with that of LiDAR-derived canopy-height data from a global survey.Important Findings Geographic patterns of cAPH and their drivers differed among taxonomic groups and life forms.the strongest predictor for cAPH of all woody species combined,angiosperms,all dicots and deciduous dicots was actual evapotranspiration,while temperature was the strongest pre-dictor for cAPH of monocots and tree,shrub and evergreen dicots,and water availability for gymnosperms.Historical climate change since the LGM had only weak effects on cAPH.No phylogenetic signal was detected in family-wise average height,which was also unrelated to the tested environmental factors.Finally,we found a strong correlation between cAPH and ecosystem primary productivity.Primary productivity showed a weaker relationship with cAPH of the tallest species within a grid cell and no relationship with LiDAR-derived canopy height reported in the global survey.Our findings suggest that current climate rather than historical climate change and evolutionary history determine the geographical patterns in cAPH.However,the relative effects of climatic factors representing environmental energy and water availability on spatial variations of cAPH vary among plant life 展开更多
In this paper, by using the wave data from a few oceanographic observation stations in the coastal zone of the Yellow Sea, the East China Sea and the South China Sea, the long-term joint distribution of the one-tenth ...In this paper, by using the wave data from a few oceanographic observation stations in the coastal zone of the Yellow Sea, the East China Sea and the South China Sea, the long-term joint distribution of the one-tenth large (or significant) wave height with average period is studied. The statistical data demonstrate that the long- term distribution of the one- tenth wave height or average period fits the log-normal distribution, thus the joint distribution also fits the two-dimensional log-normal distribution. Then the conditional probability distribution of the average period is derived, and the range as well as the mode of the average wave period corresponding to a certain return period of wave height can be calculated easily.展开更多
文摘同塔多回线路杆塔所处地形复杂,评定线路绕击耐雷水平较为困难。本文引进三维电气几何模型,与传统的EGM相比,避免了由各个截面绕击跳闸率的等效所带来的误差。将输电线路的裸露弧面进行了三维延伸扩展,计算了绕击跳闸率沿着档距内线路每一段与杆塔间长度的变化,通过沿着档距方向进行积分得出最终的绕击跳闸率,该方法也表明:线路不同位置绕击跳闸率差别很大,线路总绕击跳闸率根本不能反应实际情况。最后,通过计算分析220 kV输电线路和500/220 k V混合四回线路,证实了方法的正确性和实用性,在实际应用中具有借鉴意义。
基金This work was partly funded by the National Key Research Development Program of China(#2017YFA0605101)National Natural Science Foundation of China(#31522012,#31470564,#31621091)Chinese Academy of Sciences-Peking University Pioneer Collaboration Team.Y.L.thanks for the support from Chinese Scholarship Council(CSC).X.X.thanks for the Fundamental Research Funds for the central Universities(YJ201721).
文摘Aims Plant height is a key functional trait related to aboveground bio-mass,leaf photosynthesis and plant fitness.However,large-scale geographical patterns in community-average plant height(cAPH)of woody species and drivers of these patterns across different life forms remain hotly debated.Moreover,whether cAPH could be used as a predictor of ecosystem primary productivity is unknown.Methods We compiled mature height and distributions of 11422 woody spe-cies in eastern Eurasia,and estimated geographic patterns in cAPH for different taxonomic groups and life forms.then we evaluated the effects of environmental(including current climate and historical climate change since the Last Glacial Maximum(LGM))and evolutionary factors on cAPH.Lastly,we compared the predictive power of cAPH on primary productivity with that of LiDAR-derived canopy-height data from a global survey.Important Findings Geographic patterns of cAPH and their drivers differed among taxonomic groups and life forms.the strongest predictor for cAPH of all woody species combined,angiosperms,all dicots and deciduous dicots was actual evapotranspiration,while temperature was the strongest pre-dictor for cAPH of monocots and tree,shrub and evergreen dicots,and water availability for gymnosperms.Historical climate change since the LGM had only weak effects on cAPH.No phylogenetic signal was detected in family-wise average height,which was also unrelated to the tested environmental factors.Finally,we found a strong correlation between cAPH and ecosystem primary productivity.Primary productivity showed a weaker relationship with cAPH of the tallest species within a grid cell and no relationship with LiDAR-derived canopy height reported in the global survey.Our findings suggest that current climate rather than historical climate change and evolutionary history determine the geographical patterns in cAPH.However,the relative effects of climatic factors representing environmental energy and water availability on spatial variations of cAPH vary among plant life
文摘In this paper, by using the wave data from a few oceanographic observation stations in the coastal zone of the Yellow Sea, the East China Sea and the South China Sea, the long-term joint distribution of the one-tenth large (or significant) wave height with average period is studied. The statistical data demonstrate that the long- term distribution of the one- tenth wave height or average period fits the log-normal distribution, thus the joint distribution also fits the two-dimensional log-normal distribution. Then the conditional probability distribution of the average period is derived, and the range as well as the mode of the average wave period corresponding to a certain return period of wave height can be calculated easily.
