The tropical Asian and Australasian floras have a close relationship,and is a vital distribution pattern of seed plants worldwide.As estimated,more than 81 families and 225 genera of seed plants distributed between tr...The tropical Asian and Australasian floras have a close relationship,and is a vital distribution pattern of seed plants worldwide.As estimated,more than 81 families and 225 genera of seed plants distributed between tropical Asia and Australasia.However,the evolutionary dynamics of two floras were still vague.Here,a total of 29 plant lineages,represented the main clades of seed plants and different habits,were selected to investigate the biotic interchange between tropical Asia and Australasia by integrated dated phylogenies,biogeography,and ancestral state reconstructions.Our statistics indicated that 68 migrations have occurred between tropical Asia and Australasia since the middle Eocene except terminal migrations,and the migration events from tropical Asia to Australasia is more than 2 times of the reverse.Only 12 migrations occurred before 15 Ma,whereas the remaining56 migrations occurred after 15 Ma.Maximal number of potential dispersal events(MDE) analysis also shows obvious asymmetry,with southward migration as the main feature,and indicates the climax of bi-directional migrations occurred after 15 Ma.We speculate that the formation of island chains after the Australian-Sundaland collision and climate changes have driven seed plant migrations since the middle Miocene.Furthermore,biotic dispersal and stable habitat may be crucial for floristic interchange between tropical Asia and Australasia.展开更多
In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is rel...In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.展开更多
The changing climate threatens agricultural production and food security(Vincent et al.,2019).The limited genetic diversity of crops restricts the improvement potential,which acts as an inevitable barrier for breeding...The changing climate threatens agricultural production and food security(Vincent et al.,2019).The limited genetic diversity of crops restricts the improvement potential,which acts as an inevitable barrier for breeding new,climate-fluctuating tolerant cultivated varieties with higher yields.展开更多
基金supported by the National Natural Science Foundation of China (31670212,3206005631300181)+1 种基金the National Natural Science Foundation of China-Yunnan Joint Fund Project (U1802242)Guangxi Key Laboratory Construction Project (19-185-7)。
文摘The tropical Asian and Australasian floras have a close relationship,and is a vital distribution pattern of seed plants worldwide.As estimated,more than 81 families and 225 genera of seed plants distributed between tropical Asia and Australasia.However,the evolutionary dynamics of two floras were still vague.Here,a total of 29 plant lineages,represented the main clades of seed plants and different habits,were selected to investigate the biotic interchange between tropical Asia and Australasia by integrated dated phylogenies,biogeography,and ancestral state reconstructions.Our statistics indicated that 68 migrations have occurred between tropical Asia and Australasia since the middle Eocene except terminal migrations,and the migration events from tropical Asia to Australasia is more than 2 times of the reverse.Only 12 migrations occurred before 15 Ma,whereas the remaining56 migrations occurred after 15 Ma.Maximal number of potential dispersal events(MDE) analysis also shows obvious asymmetry,with southward migration as the main feature,and indicates the climax of bi-directional migrations occurred after 15 Ma.We speculate that the formation of island chains after the Australian-Sundaland collision and climate changes have driven seed plant migrations since the middle Miocene.Furthermore,biotic dispersal and stable habitat may be crucial for floristic interchange between tropical Asia and Australasia.
基金This work was supported by National Key Research and Development Program of China(2018YFB0904000).
文摘In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.
文摘The changing climate threatens agricultural production and food security(Vincent et al.,2019).The limited genetic diversity of crops restricts the improvement potential,which acts as an inevitable barrier for breeding new,climate-fluctuating tolerant cultivated varieties with higher yields.
