The fault current level analysis is important for bipolar direct current(DC)grids,which determines the operation and protection requirements.The DC grid topology significantly impacts the current path and then the fau...The fault current level analysis is important for bipolar direct current(DC)grids,which determines the operation and protection requirements.The DC grid topology significantly impacts the current path and then the fault current level of the grid,which makes it possible to limit the fault current by optimizing the grid topology.However,the corresponding discussion in the literature is indigent.Aiming at this point,the impact of grid topology,i.e.,the connecting scheme of converters,on the pole-to-ground fault current in bipolar DC grids,is investigated in this paper,and the ground-return-based and metallic-return-based grounding schemes are considered,respectively.Firstly,the decoupled equivalent model in frequency domain for fault current analysis is obtained.Then,the impacts of converters with different distances to the fault point on the fault current can be analyzed according to the high-frequency impedance characteristics.Based on the analysis results,a simplified fault current index(SFCI)is proposed to realize the fast evaluation of impact of grid topology on the fault current level.The SFCI is then applied to evaluate the relative fault current level.Finally,the simulation results validate the model,the analysis method,and the SFCI,which can effectively evaluate the relative fault current level in a direct and fast manner.展开更多
Diversity indexes of current forestry view, such as dominance degree, fragmentation degree and overcast degree, were evaluated by the software ARCVIEWGIS. And developing strategies to improve diversity were put forwar...Diversity indexes of current forestry view, such as dominance degree, fragmentation degree and overcast degree, were evaluated by the software ARCVIEWGIS. And developing strategies to improve diversity were put forward in this paper, that is, combining with the items of forestry tour and enhancing scientific management, and choosing typical trees to change forestry structure on the basis of general conditions of dominance degree, fragmentation degree and overcast degree.展开更多
Introduction:Smoking is the second leading risk factor for disease burden in China.This study aims to analyze smoking behaviors among urban and rural areas in China to evaluate the effectiveness of current tobacco con...Introduction:Smoking is the second leading risk factor for disease burden in China.This study aims to analyze smoking behaviors among urban and rural areas in China to evaluate the effectiveness of current tobacco control measures and formulate strategic adjustments for achieving the Healthy China 2030 tobacco control targets.Methods:This study analyzed smoking prevalence[with 95%confidence intervals(CIs)]using the 2024 China National Adult Tobacco Survey(NATS)data.Rao-Scottχ^(2)tests compared prevalence differences across subgroups.Linear,nonlinear,and logistic regression models tested age-related trends in smoking behaviors.Results:In 2024,the current and daily smoking prevalence among Chinese adults aged≥15 years were 23.2%and 20.3%,respectively,with males exceeding females,peaking in 30–59 years.Rural areas had higher rates(24.9%,22.1%)than urban areas(20.9%,17.9%),particularly among high-income rural households.Agricultural workers,government/public institution employees,and business/service workers showed higher rates than teaching staff and medical/health workers.Daily smokers initiated daily smoking at a mean age of 22.4 years,with younger smokers starting earlier.Current smokers consumed an average of 15.8 cigarettes/day,with higher consumption in rural than in urban areas.Slim cigarette use was reported by 32.9%of current smokers,with higher proportions in females,urban residents and adults aged<50 years.Conclusions:Targeted strategies are required to sustain tobacco use reduction:addressing inadequate enforcement of control policies,focusing on smoking initiation,and implementing enhanced regulation of industry-promoted misleading“harm reduction”products(e.g.,slim cigarettes).展开更多
基金supported by the Science and Technology Project of State Grid Corporation of China“Cloud energy storage framework-based AI dispatching strategy of renewable energy integration and contingency response” (No.5100-202199274A-0-0-00)。
文摘The fault current level analysis is important for bipolar direct current(DC)grids,which determines the operation and protection requirements.The DC grid topology significantly impacts the current path and then the fault current level of the grid,which makes it possible to limit the fault current by optimizing the grid topology.However,the corresponding discussion in the literature is indigent.Aiming at this point,the impact of grid topology,i.e.,the connecting scheme of converters,on the pole-to-ground fault current in bipolar DC grids,is investigated in this paper,and the ground-return-based and metallic-return-based grounding schemes are considered,respectively.Firstly,the decoupled equivalent model in frequency domain for fault current analysis is obtained.Then,the impacts of converters with different distances to the fault point on the fault current can be analyzed according to the high-frequency impedance characteristics.Based on the analysis results,a simplified fault current index(SFCI)is proposed to realize the fast evaluation of impact of grid topology on the fault current level.The SFCI is then applied to evaluate the relative fault current level.Finally,the simulation results validate the model,the analysis method,and the SFCI,which can effectively evaluate the relative fault current level in a direct and fast manner.
文摘Diversity indexes of current forestry view, such as dominance degree, fragmentation degree and overcast degree, were evaluated by the software ARCVIEWGIS. And developing strategies to improve diversity were put forward in this paper, that is, combining with the items of forestry tour and enhancing scientific management, and choosing typical trees to change forestry structure on the basis of general conditions of dominance degree, fragmentation degree and overcast degree.
基金Supported by National Major Scientific and Technological Special Project(2023ZD0506401)Global Health Capacity Building and Tobacco Control Project,Chinese Center for Disease Control and Prevention(2025).
文摘Introduction:Smoking is the second leading risk factor for disease burden in China.This study aims to analyze smoking behaviors among urban and rural areas in China to evaluate the effectiveness of current tobacco control measures and formulate strategic adjustments for achieving the Healthy China 2030 tobacco control targets.Methods:This study analyzed smoking prevalence[with 95%confidence intervals(CIs)]using the 2024 China National Adult Tobacco Survey(NATS)data.Rao-Scottχ^(2)tests compared prevalence differences across subgroups.Linear,nonlinear,and logistic regression models tested age-related trends in smoking behaviors.Results:In 2024,the current and daily smoking prevalence among Chinese adults aged≥15 years were 23.2%and 20.3%,respectively,with males exceeding females,peaking in 30–59 years.Rural areas had higher rates(24.9%,22.1%)than urban areas(20.9%,17.9%),particularly among high-income rural households.Agricultural workers,government/public institution employees,and business/service workers showed higher rates than teaching staff and medical/health workers.Daily smokers initiated daily smoking at a mean age of 22.4 years,with younger smokers starting earlier.Current smokers consumed an average of 15.8 cigarettes/day,with higher consumption in rural than in urban areas.Slim cigarette use was reported by 32.9%of current smokers,with higher proportions in females,urban residents and adults aged<50 years.Conclusions:Targeted strategies are required to sustain tobacco use reduction:addressing inadequate enforcement of control policies,focusing on smoking initiation,and implementing enhanced regulation of industry-promoted misleading“harm reduction”products(e.g.,slim cigarettes).
