针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动...针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动均压(disturbance voltage sharing,DVS)控制策略。通过建立EPS控制下的电流应力解析模型,求解最优电流应力对应下的内外移相比组合。进一步,设计逐级扰动方案,通过扰动模块的外移相比,对各模块内部参数失配时的输入电压进行补偿。DVS控制策略在实现串并联模块间功率平衡的前提下,降低变换器电流应力,从而提升变换器的工作效率。此外,由于无需在每个控制环路中增设输入电压传感器,系统结构更为简化,硬件成本更低。最后,通过仿真和实验验证了所提控制策略的正确性和有效性。展开更多
Metal–organic frameworks(MOFs)have attracted significant research interest in biomimetic catalysis.However,the modulation of the activity of MOFs by precisely tuning the coordination of metal nodes is still a signifi...Metal–organic frameworks(MOFs)have attracted significant research interest in biomimetic catalysis.However,the modulation of the activity of MOFs by precisely tuning the coordination of metal nodes is still a significant challenge.Inspired by metalloenzymes with well-defined coordination structures,a series of MOFs containing halogen-coordinated copper nodes(Cu-X MOFs,X=Cl,Br,I)are employed to elucidate their structure–activity relationship.Intriguingly,experimental and theoretical results strongly support that precisely tuning the coordination of halogen atoms directly regulates the enzyme-like activities of Cu-X MOFs by influencing the spatial configuration and electronic structure of the Cu active center.The optimal Cu–Cl MOF exhibits excellent superoxide dismutase-like activity with a specific activity one order of magnitude higher than the reported Cu-based nanozymes.More importantly,by performing enzyme-mimicking catalysis,the Cu–Cl MOF nanozyme can significantly scavenge reactive oxygen species and alleviate oxidative stress,thus effectively relieving ocular chemical burns.Mechanistically,the antioxidant and antiapoptotic properties of Cu–Cl MOF are achieved by regulating the NRF2 and JNK or P38 MAPK pathways.Our work provides a novel way to refine MOF nanozymes by directly engineering the coordination microenvironment and,more significantly,demonstrating their potential therapeutic effect in ophthalmic disease.展开更多
This study empirically examines whether child characteristics mitigate the negative impact of widowhood on the elderly’s mental health using follow-up survey data from the China Health and Retirement Longitudinal Stu...This study empirically examines whether child characteristics mitigate the negative impact of widowhood on the elderly’s mental health using follow-up survey data from the China Health and Retirement Longitudinal Study(CHARLS).A total of 5,326 older adults aged 60 years and older are selected from three waves of panel data(2013,2015,and 2018).Thefindings suggest that respondents who experienced widowhood exhibit an increase in depressive symptoms.However,the higher income of children and frequent face-to-face emotional interactions improve the mental health of the widowed elderly.Moreover,heterogeneity analyses show that the buffering effect of higher child income is more significant among men and the Midwestern widowed elderly,and frequent face-to-face emotional interactions are more effective in improving the psychological status of women and the Midwes-tern widowed elderly.In the special social and cultural background of China,family members remain the main support for the elderly,and the current social pension system is still imperfect.Therefore,children should strengthen emotional communication with their parents while increasing their economic income.In that way,widowhood can achieve both material and spiritual prosperity.The government should identify the vulnerable groups among the elderly widows and introduce policies aimed at improving their mental health and reducing the disparity in mental health status.展开更多
文摘针对输入串联输出并联双有源桥(dual active bridge,DAB)变换器子模块内部参数不匹配导致的功率不平衡,以及单移相(single phase shift,SPS)控制下变换器工作效率低的问题,该文基于拓展移相(extended phase shift,EPS)控制提出一种扰动均压(disturbance voltage sharing,DVS)控制策略。通过建立EPS控制下的电流应力解析模型,求解最优电流应力对应下的内外移相比组合。进一步,设计逐级扰动方案,通过扰动模块的外移相比,对各模块内部参数失配时的输入电压进行补偿。DVS控制策略在实现串并联模块间功率平衡的前提下,降低变换器电流应力,从而提升变换器的工作效率。此外,由于无需在每个控制环路中增设输入电压传感器,系统结构更为简化,硬件成本更低。最后,通过仿真和实验验证了所提控制策略的正确性和有效性。
基金the National Key R&D Program of China(Grant No.2020YFA0908100)the National Nature Science Foundation(Grant Nos.12274356,82070931,and 82271045)+1 种基金Fundamental Research Funds for the Central Universities(20720220022)the 111 Project(B16029)。
文摘Metal–organic frameworks(MOFs)have attracted significant research interest in biomimetic catalysis.However,the modulation of the activity of MOFs by precisely tuning the coordination of metal nodes is still a significant challenge.Inspired by metalloenzymes with well-defined coordination structures,a series of MOFs containing halogen-coordinated copper nodes(Cu-X MOFs,X=Cl,Br,I)are employed to elucidate their structure–activity relationship.Intriguingly,experimental and theoretical results strongly support that precisely tuning the coordination of halogen atoms directly regulates the enzyme-like activities of Cu-X MOFs by influencing the spatial configuration and electronic structure of the Cu active center.The optimal Cu–Cl MOF exhibits excellent superoxide dismutase-like activity with a specific activity one order of magnitude higher than the reported Cu-based nanozymes.More importantly,by performing enzyme-mimicking catalysis,the Cu–Cl MOF nanozyme can significantly scavenge reactive oxygen species and alleviate oxidative stress,thus effectively relieving ocular chemical burns.Mechanistically,the antioxidant and antiapoptotic properties of Cu–Cl MOF are achieved by regulating the NRF2 and JNK or P38 MAPK pathways.Our work provides a novel way to refine MOF nanozymes by directly engineering the coordination microenvironment and,more significantly,demonstrating their potential therapeutic effect in ophthalmic disease.
基金supported by the National Social Science Fund of China under Grant No.17BJL044。
文摘This study empirically examines whether child characteristics mitigate the negative impact of widowhood on the elderly’s mental health using follow-up survey data from the China Health and Retirement Longitudinal Study(CHARLS).A total of 5,326 older adults aged 60 years and older are selected from three waves of panel data(2013,2015,and 2018).Thefindings suggest that respondents who experienced widowhood exhibit an increase in depressive symptoms.However,the higher income of children and frequent face-to-face emotional interactions improve the mental health of the widowed elderly.Moreover,heterogeneity analyses show that the buffering effect of higher child income is more significant among men and the Midwestern widowed elderly,and frequent face-to-face emotional interactions are more effective in improving the psychological status of women and the Midwes-tern widowed elderly.In the special social and cultural background of China,family members remain the main support for the elderly,and the current social pension system is still imperfect.Therefore,children should strengthen emotional communication with their parents while increasing their economic income.In that way,widowhood can achieve both material and spiritual prosperity.The government should identify the vulnerable groups among the elderly widows and introduce policies aimed at improving their mental health and reducing the disparity in mental health status.
