Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will...Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will decrease.The insulator structure and equivalent salt deposition density(ESDD)are the main factors affecting the arc path and length.To investigate the forms of arc paths under different insulator structures and their influence on flashover characteristics,a platformfor recording arc paths is established.This study presents amethod to identify the pattern and distribution of insulator arc paths based on the effect of initial arc on electric field distribution.The results show that there are two main types of local arc paths between umbrellas—the cling-surface arc and the air-jump arc.Moreover,the air-jump arc includes two types—the bridging arc and the gap arc.With the increase in umbrella spacing and ESDD,the probability of arc propagation along the surface increases.The use of the creepage distance can be improved by changing the creepage coefficient to increase the distance between umbrellas.This method has over 90%accuracy.This study is of great significance for improving insulator structure and reducing pollution flashover accidents.展开更多
The commercialized binder carboxymethyl cellulose sodium(CMC-Na)is considered unsuitable for micro-sized SiO_(x) anode as it cannot endure the large volume change to retain the conductive network during repeated charg...The commercialized binder carboxymethyl cellulose sodium(CMC-Na)is considered unsuitable for micro-sized SiO_(x) anode as it cannot endure the large volume change to retain the conductive network during repeated charge/discharge cycles.Herein,a small amount of silicon nanoparticles(SiNPs)is added during slurry preparation process as“nano-combs”to unfold the convoluted CMC-Na polymer chains so that they undergo a coilto-stretch transition by interaction between polar groups(e.g.,-OH,-COONa)of polymer and SiNPs’large surface.Through maximizing the utilization of binders,a uniform conductive network is constructed with increased interfacial contact with micro-sized SiO_(x).As a result,the SiO_(x) electrode with optimized(10 wt%)SiNPs addition shows significantly improved initial capacity and cycling performance.Through revisiting CMCNa,a currently deemed unqualified binder in SiO_(x) anode,this work gives a brand-new perspective on the failing mechanism of Si-based anode materials and an improving strategy for electrode preparation.展开更多
Background:Vaccination has been shown effective in controlling the global coronavirus disease 2019(COVID-19)pandemic and reducing severe cases.This study was to assess the flare and change in disease activity after CO...Background:Vaccination has been shown effective in controlling the global coronavirus disease 2019(COVID-19)pandemic and reducing severe cases.This study was to assess the flare and change in disease activity after COVID-19 vaccination in patients with stable rheumatoid arthritis(RA).Methods:A prospective cohort of RA patients in remission or with low disease activity was divided into a vaccination group and a non-vaccination group based on their COVID-19 vaccination status.Each of them was examined every 3 to 6 months.In the vaccination group,disease activity was compared before and after vaccination.The rates of flare defined as disease activity scores based on 28-joint count(DAS28)>3.2 withΔDAS28≥0.6 were compared between vaccination and non-vaccination groups.Results:A total of 202 eligible RA patients were enrolled.Of these,98 patients received no vaccine shot(non-vaccination group),and 104 patients received two doses of vaccine(vaccination group).The median time interval from pre-vaccination visit to the first immunization and from the second dose of vaccine to post-vaccination visit was 67 days and 83 days,respectively.The disease activity scores at pre-vaccination and post-vaccination visits in the vaccination group patients were similar.At enrollment,gender,RA disease course,seropositivity,and disease activity were comparable across the two groups.Flare was observed in five(4.8%)of the vaccination group patients and nine(9.2%)of the non-vaccination group patients at post-vaccination assessment(P=0.221).In terms of safety,29(27.9%)patients experienced adverse events(AEs)after vaccination.No serious AEs occurred.Conclusions:COVID-19 vaccinations had no significant effect on disease activity or risk of flare in RA patients in remission or with low disease activity.Patients with stable RA should be encouraged to receive the COVID-19 vaccination.展开更多
Succinonitrile(SN)based solid-state electrolytes(SSEs)have potential applications in lithium(Li)batteries due to their ease of preparation and high ionic conductivity at room temperature.Here,a novel SSE consisting of...Succinonitrile(SN)based solid-state electrolytes(SSEs)have potential applications in lithium(Li)batteries due to their ease of preparation and high ionic conductivity at room temperature.Here,a novel SSE consisting of poly(vinylidene fluoride-hexafluoropropy-lene)(PVDF-HFP),poly(methyl methacrylate)(PMMA)and Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3) with SN is fabricated,where PMMA is added to serve as a polymer matrix for better wettability of SN.Due to the addition of PMMA,improved room-temperature ionic conductivity of the SSE is resulted.More importantly,better interfacial contact as well as more stable solid-state electrolyte(SEI)layer between SSE and Li anode can be also obtained.As a result,homogeneous and dendrite-free Li plating can be achieved for over 1000 h in Li symmetric cells.When coupled with LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2) cathode and Li anode,the proposed SSE delivers excellent cycling stability and rate capability in full-cells.By implementing SSEs with a polymeric wetting agent,this work provides fresh perspectives on stabilizing the interface between SSEs and Li metal anodes.展开更多
基金This work was supported by the National Natural Science Foundation of China(52007138)Chengdu Technology Innovation R&D Project(2022-YF05-00971-SN).
文摘Pollution flashover is one of themajor insulation accidents that can occur inmodern power systems.If the local arc is not sufficiently elongated by the creepage distance,the flashover performance of the insulator will decrease.The insulator structure and equivalent salt deposition density(ESDD)are the main factors affecting the arc path and length.To investigate the forms of arc paths under different insulator structures and their influence on flashover characteristics,a platformfor recording arc paths is established.This study presents amethod to identify the pattern and distribution of insulator arc paths based on the effect of initial arc on electric field distribution.The results show that there are two main types of local arc paths between umbrellas—the cling-surface arc and the air-jump arc.Moreover,the air-jump arc includes two types—the bridging arc and the gap arc.With the increase in umbrella spacing and ESDD,the probability of arc propagation along the surface increases.The use of the creepage distance can be improved by changing the creepage coefficient to increase the distance between umbrellas.This method has over 90%accuracy.This study is of great significance for improving insulator structure and reducing pollution flashover accidents.
基金support from the National Key R&D Program of China(2016YFB0700600,2020YFB0704500)China Postdoctoral Science Foundation(2019M660317)+1 种基金Engineering and Physical Sciences Research Council,UK(EP/S000933/1)Shenzhen Science and Technology Program(Grant No.RCBS20200714114820077).
文摘The commercialized binder carboxymethyl cellulose sodium(CMC-Na)is considered unsuitable for micro-sized SiO_(x) anode as it cannot endure the large volume change to retain the conductive network during repeated charge/discharge cycles.Herein,a small amount of silicon nanoparticles(SiNPs)is added during slurry preparation process as“nano-combs”to unfold the convoluted CMC-Na polymer chains so that they undergo a coilto-stretch transition by interaction between polar groups(e.g.,-OH,-COONa)of polymer and SiNPs’large surface.Through maximizing the utilization of binders,a uniform conductive network is constructed with increased interfacial contact with micro-sized SiO_(x).As a result,the SiO_(x) electrode with optimized(10 wt%)SiNPs addition shows significantly improved initial capacity and cycling performance.Through revisiting CMCNa,a currently deemed unqualified binder in SiO_(x) anode,this work gives a brand-new perspective on the failing mechanism of Si-based anode materials and an improving strategy for electrode preparation.
基金supported by grants from the National Natural Science Foundation of China(Nos.81771740,81901646)Interdisciplinary Clinical Research Project of Peking University First Hospital(No.2021CR30)Peking University Medicine Seed Fund for Interdisciplinary Research supported by the Fundamental Research Funds for the Central Universities(No.BMU2022MX003)
文摘Background:Vaccination has been shown effective in controlling the global coronavirus disease 2019(COVID-19)pandemic and reducing severe cases.This study was to assess the flare and change in disease activity after COVID-19 vaccination in patients with stable rheumatoid arthritis(RA).Methods:A prospective cohort of RA patients in remission or with low disease activity was divided into a vaccination group and a non-vaccination group based on their COVID-19 vaccination status.Each of them was examined every 3 to 6 months.In the vaccination group,disease activity was compared before and after vaccination.The rates of flare defined as disease activity scores based on 28-joint count(DAS28)>3.2 withΔDAS28≥0.6 were compared between vaccination and non-vaccination groups.Results:A total of 202 eligible RA patients were enrolled.Of these,98 patients received no vaccine shot(non-vaccination group),and 104 patients received two doses of vaccine(vaccination group).The median time interval from pre-vaccination visit to the first immunization and from the second dose of vaccine to post-vaccination visit was 67 days and 83 days,respectively.The disease activity scores at pre-vaccination and post-vaccination visits in the vaccination group patients were similar.At enrollment,gender,RA disease course,seropositivity,and disease activity were comparable across the two groups.Flare was observed in five(4.8%)of the vaccination group patients and nine(9.2%)of the non-vaccination group patients at post-vaccination assessment(P=0.221).In terms of safety,29(27.9%)patients experienced adverse events(AEs)after vaccination.No serious AEs occurred.Conclusions:COVID-19 vaccinations had no significant effect on disease activity or risk of flare in RA patients in remission or with low disease activity.Patients with stable RA should be encouraged to receive the COVID-19 vaccination.
基金financially supported by National Key R&D Program of China(No.2016YFB0700600)Soft Science Research Project of Guangdong Province(No.2017B030301013)。
文摘Succinonitrile(SN)based solid-state electrolytes(SSEs)have potential applications in lithium(Li)batteries due to their ease of preparation and high ionic conductivity at room temperature.Here,a novel SSE consisting of poly(vinylidene fluoride-hexafluoropropy-lene)(PVDF-HFP),poly(methyl methacrylate)(PMMA)and Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3) with SN is fabricated,where PMMA is added to serve as a polymer matrix for better wettability of SN.Due to the addition of PMMA,improved room-temperature ionic conductivity of the SSE is resulted.More importantly,better interfacial contact as well as more stable solid-state electrolyte(SEI)layer between SSE and Li anode can be also obtained.As a result,homogeneous and dendrite-free Li plating can be achieved for over 1000 h in Li symmetric cells.When coupled with LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2) cathode and Li anode,the proposed SSE delivers excellent cycling stability and rate capability in full-cells.By implementing SSEs with a polymeric wetting agent,this work provides fresh perspectives on stabilizing the interface between SSEs and Li metal anodes.
