Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentra...Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentration monthly and daily distribution characteristics,the weekend effect,and the variation characteristics on haze days and non-haze days,are analyzed.By using the Hybrid Single-Particle Lagrangian Integrated Trajectorymodel(backward trajectory model)and surface wind data,the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons.The results show that,in Taiyuan,the CO2 mole fraction in autumn and winter is higher than that in spring and summer,and on haze days is higher than that on non-haze days.The diurnal variation characteristic of CO2mole fraction in each season is‘single peak and single valley’with the peak value around 0700(hereafter refers to Beijing Time)and the valley value around 1600.The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak.Horizontal diffusion can reduce the CO2 mole fraction,while breezy weather is not beneficial to CO2 diffusion.The wind direction and speed in the upper levels are different from those near the surface,and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously.This indicates that the CO2 in Taiyuan is mainly contributed by local sources.展开更多
A molten salt reactor(MSR)has outstanding features considering the application of thorium fuel,inherent safety,sustainability,and resistance to proliferation.However,fissile material^(233)U is significantly rare at th...A molten salt reactor(MSR)has outstanding features considering the application of thorium fuel,inherent safety,sustainability,and resistance to proliferation.However,fissile material^(233)U is significantly rare at the current stage,thus it is difficult for MSR to achieve a pure thorium-uranium fuel cycle.Therefore,using plutonium or enriched uranium as the initial fuel for MSR is more practical.In this study,we aim to verify the feasibility of a small modular MSR that utilizes plutonium as the starting fuel(SM-MSR-Pu),and highlight its advantages and disadvantages.First,the structural design and fuel management scheme of the SM-MSR-Pu were presented.Second,the neutronic characteristics,such as the graphite-irradiation lifetime,burn-up performance,and coefficient of temperature reactivity were calculated to analyze the physical characteristics of the SM-MSR-Pu.The results indicate that plutonium is a feasible and advantageous starting fuel for a SM-MSR;however,there are certain shortcomings that need to be solved.In a 250 MWth SM-MSR-Pu,approximately 288.64 kg^(233)U of plutonium with a purity of greater than 90% is produced while 978.00 kg is burned every ten years.The temperature reactivity coefficient decreases from -4.0 to -6.5 pcm K^(-1) over the 50-year operating time,which ensures a long-term safe operation.However,the amount of plutonium and accumulation of minor actinides(MAs)would increase as the burn-up time increases,and the annual production and purity of^(233)U will decrease.To achieve an optimal burn-up performance,setting the entire operation time to 30 years is advisable.Regardless,more than 3600 kg of plutonium eventually accumulate in the core.Further research is required to effectively utilize this accumulated plutonium.展开更多
Simulation method is used to provide a guideline f or ultra thin body(UTB) MOSFET designs.Three important parameters of the UTB MOS FE T,i.e.the raised S/D height,Ge mole fraction of the Ge xSi 1-x gate,and the ...Simulation method is used to provide a guideline f or ultra thin body(UTB) MOSFET designs.Three important parameters of the UTB MOS FE T,i.e.the raised S/D height,Ge mole fraction of the Ge xSi 1-x gate,and the silic on body thickness,are comprehensively analyzed and optimized.The optimal region of feasible Ge mole fraction and the silicon body thickness for low operating po wer device are given.As the simulation results show that through changing Ge mole fraction coupl ed with the silicon body thickness tuning,UTB device with good performance can b e obtained.展开更多
基金This paper was supported by the Key Research and Development Project of Shanxi Province[grant number 201803D31220]the General Program of Shanxi Provincial Meteorological Bureau[grant numbers SXKMSDW20205214 and SXKQNDW20205241].
文摘Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentration monthly and daily distribution characteristics,the weekend effect,and the variation characteristics on haze days and non-haze days,are analyzed.By using the Hybrid Single-Particle Lagrangian Integrated Trajectorymodel(backward trajectory model)and surface wind data,the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons.The results show that,in Taiyuan,the CO2 mole fraction in autumn and winter is higher than that in spring and summer,and on haze days is higher than that on non-haze days.The diurnal variation characteristic of CO2mole fraction in each season is‘single peak and single valley’with the peak value around 0700(hereafter refers to Beijing Time)and the valley value around 1600.The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak.Horizontal diffusion can reduce the CO2 mole fraction,while breezy weather is not beneficial to CO2 diffusion.The wind direction and speed in the upper levels are different from those near the surface,and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously.This indicates that the CO2 in Taiyuan is mainly contributed by local sources.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)Chinese Academy of Sciences Talent Introduction Youth Program(No.SINAP-YCJH-202303)Chinese Academy of Sciences Special Research Assistant Funding Project and Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(JCYJ-SHFY-2021-003)。
文摘A molten salt reactor(MSR)has outstanding features considering the application of thorium fuel,inherent safety,sustainability,and resistance to proliferation.However,fissile material^(233)U is significantly rare at the current stage,thus it is difficult for MSR to achieve a pure thorium-uranium fuel cycle.Therefore,using plutonium or enriched uranium as the initial fuel for MSR is more practical.In this study,we aim to verify the feasibility of a small modular MSR that utilizes plutonium as the starting fuel(SM-MSR-Pu),and highlight its advantages and disadvantages.First,the structural design and fuel management scheme of the SM-MSR-Pu were presented.Second,the neutronic characteristics,such as the graphite-irradiation lifetime,burn-up performance,and coefficient of temperature reactivity were calculated to analyze the physical characteristics of the SM-MSR-Pu.The results indicate that plutonium is a feasible and advantageous starting fuel for a SM-MSR;however,there are certain shortcomings that need to be solved.In a 250 MWth SM-MSR-Pu,approximately 288.64 kg^(233)U of plutonium with a purity of greater than 90% is produced while 978.00 kg is burned every ten years.The temperature reactivity coefficient decreases from -4.0 to -6.5 pcm K^(-1) over the 50-year operating time,which ensures a long-term safe operation.However,the amount of plutonium and accumulation of minor actinides(MAs)would increase as the burn-up time increases,and the annual production and purity of^(233)U will decrease.To achieve an optimal burn-up performance,setting the entire operation time to 30 years is advisable.Regardless,more than 3600 kg of plutonium eventually accumulate in the core.Further research is required to effectively utilize this accumulated plutonium.
文摘Simulation method is used to provide a guideline f or ultra thin body(UTB) MOSFET designs.Three important parameters of the UTB MOS FE T,i.e.the raised S/D height,Ge mole fraction of the Ge xSi 1-x gate,and the silic on body thickness,are comprehensively analyzed and optimized.The optimal region of feasible Ge mole fraction and the silicon body thickness for low operating po wer device are given.As the simulation results show that through changing Ge mole fraction coupl ed with the silicon body thickness tuning,UTB device with good performance can b e obtained.
