Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3...Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3) formation and degradation under these two weather conditions remain unclear.Therefore,experiments were conducted in Beijing from 2019 to 2021 to observe O_(3),its precursors,and related meteorological elements.A total of 18 days with O_(3) exceedances were selected,including 10 sauna days and 8 roast days.The results of this study revealed that on roast days,the sensible heat flux was 143.5 W/m^(2) greater and the wind speed gradient was 0.018 s^(-1) greater than those on sauna days,indicating more intense thermal and dynamic turbulence.The strong turbulence enhanced the vertical cycle of nitrogen dioxide(NO_(2))and O_(3),resulting in a 58.2μg/(m^(2)·h)increase in NO_(2) upward transport rate and a 1034.4μg/(m^(2)·h)increase in O_(3) downward transport rate on roast days than sauna days.Subsequently,a box model analysis was used to examine O_(3) formation under the two types of weather conditions,revealing that the NO_(2)-O_(3) vertical cycling speed dominated the O_(3) sensitivity.The O_(3) sensitivity was synergistically controlled by nitrogen oxides(NO_(x))and volatile organic compounds on sauna days,while it tended to be NO_(x)-limited on roast days.The aim of this study was to provide a scientific theoretical basis for the control of O_(3) under different types of high temperature weather conditions.展开更多
The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity desig...The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity design methods,particularly when addressing high-dimensional complex engineering design problems.To address these challenges,we developed a surface sensitivity technique based on the multilevel fast multipole algorithm(MLFMA).An access and storage of sparse partial derivative tensor was improved to significantly enhanced the computation performance.The far-field interactions of the surface sensitivity equation were realized by differential the multipole expansion.In addition,we proposed a fast far-field multiplication method to accelerate the multiplication process.The surface mesh derivative with respect to the design variables was calculated by analytical and complex variable methods,substantially improving computational efficiency.These advancements enabled the MLFMAbased surface sensitivity method to millions meshes and large-scale gradients,extending gradientbased optimization for very large electrical size problems.Test cases have verified the effectiveness of this method in optimizing very large electrical objects in terms of both accuracy and efficiency.展开更多
Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 ...Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.展开更多
The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlM...The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlMoV,15CrMo)and hyper-peritectic steel(20CrMo)during solidification at growth velocities of 15,50,and 80 pm/s.At the dendritic boundaries,sulphide precipitates were found,promoting crack formation.Based on the statistical analysis of interdendritic cracks in peritectic steels,the area ratio(RA)of interdendritic cracks in a directional solidification structure was proposed to evaluate the crack sensitivity of peritectic steels.Furthermore,the crack sensitivities of peritectic steels(12CrlMoV,15CrMo,and 20CrMo)were tested,evaluated,and compared with the surface crack rates of three types of steels produced from a steel plant.The results demonstrated that RA was in good agreement with that of the steel plant,and the crack sensitivity of 12CrlMoV steel was the strongest,followed by that of 15CrMo and 20CrMo steels.Thus,RA can be used to evaluate the crack sensitivity of peritectic steel.展开更多
基金supported by the National Natural Science Foundation of China(No.42177081)the National Key R&D Program of China(No.2023YFC3706103)+1 种基金Beijing Municipal Natural Science Foundation(No.8222075)the Youth Cross Team Scientific Research Project of the Chinese Academy of Sciences(No.JCTD-2021–10).
文摘Temperature is a key meteorological factor that affects tropospheric ozone(O_(3)),with both humid-heat(sauna days)and dry-heat(roast days)conditions leading to O_(3) exceedances.However,the mechanisms influencing O_(3) formation and degradation under these two weather conditions remain unclear.Therefore,experiments were conducted in Beijing from 2019 to 2021 to observe O_(3),its precursors,and related meteorological elements.A total of 18 days with O_(3) exceedances were selected,including 10 sauna days and 8 roast days.The results of this study revealed that on roast days,the sensible heat flux was 143.5 W/m^(2) greater and the wind speed gradient was 0.018 s^(-1) greater than those on sauna days,indicating more intense thermal and dynamic turbulence.The strong turbulence enhanced the vertical cycle of nitrogen dioxide(NO_(2))and O_(3),resulting in a 58.2μg/(m^(2)·h)increase in NO_(2) upward transport rate and a 1034.4μg/(m^(2)·h)increase in O_(3) downward transport rate on roast days than sauna days.Subsequently,a box model analysis was used to examine O_(3) formation under the two types of weather conditions,revealing that the NO_(2)-O_(3) vertical cycling speed dominated the O_(3) sensitivity.The O_(3) sensitivity was synergistically controlled by nitrogen oxides(NO_(x))and volatile organic compounds on sauna days,while it tended to be NO_(x)-limited on roast days.The aim of this study was to provide a scientific theoretical basis for the control of O_(3) under different types of high temperature weather conditions.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3002800).
文摘The primary concern in stealth aircraft design is the very large electrical size objects.However,the computational and storage requirements of these objects present significant obstacles for current highfidelity design methods,particularly when addressing high-dimensional complex engineering design problems.To address these challenges,we developed a surface sensitivity technique based on the multilevel fast multipole algorithm(MLFMA).An access and storage of sparse partial derivative tensor was improved to significantly enhanced the computation performance.The far-field interactions of the surface sensitivity equation were realized by differential the multipole expansion.In addition,we proposed a fast far-field multiplication method to accelerate the multiplication process.The surface mesh derivative with respect to the design variables was calculated by analytical and complex variable methods,substantially improving computational efficiency.These advancements enabled the MLFMAbased surface sensitivity method to millions meshes and large-scale gradients,extending gradientbased optimization for very large electrical size problems.Test cases have verified the effectiveness of this method in optimizing very large electrical objects in terms of both accuracy and efficiency.
基金supported by the National Key R&D Program(No.2021YFE0117300)the National Natural Science Foundation of China(No.42375090)+6 种基金Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks(No.ZDSYS20220606100604008)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110713)Guangdong University Research Project Science Team(No.2021KCXTD004)the Major Talent Project of Guangdong Province(No.2021QN020924)Shandong Provincial Natural Science Foundation,China(No.ZR2020QD012)Shenzhen Science and Technology Program(Nos.KQTD20210811090048025,JCYJ20210324104604012 and JCYJ20220530115404009)supported by the Center for Computational Science and Engineering at Southern University of Science and Technology.
文摘Ozone production sensitivity is widely used to reveal the chemical dominant precursors of urban ozone rise.Here,we diagnose the impact of the decline in global human production activities level caused by the COVID-19 on ozone sensitivity through the ratio of formaldehyde(HCHO)and NO_(2)(FNR=HCHO/NO_(2))observations from the TROPOspheric Monitoring Instrument.We use a relative uncertainty threshold to clean the satellite FNR,and our satellite FNR present a good correlation(R=0.6248)with U.S.Environmental Protection Agency observations.We found that the outbreak of the COVID-19 did not change the pattern of global ozone sensitivity,while the global regimes was transforming or strengthening to VOC-limited regimes due to the significant decline of human production activities levels.During the COVID-19,ozone sensitivity in Eastern China and East Africa continued to shift to VOC-limited regimes,while India,Western Europe and North America first moved to NOx-limited regimes,and then changed to VOC-limited regimes with the resumption of production and the increase in travel.The clustering results tell that urban ozone sensitivity tends to shift towards NOx-limited regimes as economic growing.The ozone formation in cities with lower FNR and per capita gross domestic product(GDP)are more sensitive to changes in VOCs,while cities with higher FNR and per capita GDP are more sensitive to variations in NOx.Cities with intermediate FNR and GDP are good evidence of the existence of transitional regimes.Our study identifies the driving role of urban economics in orienting the evolution of ozone sensitivity regimes.
基金financially supported by the Science and Technology Plan Foundation of Xingtai,China (Grant No.2022zz099)the Jiangsu Key Laboratory of Oil-Gas Storage and Transportation Technology (Grant No.CDYQCY202204)Science and Technology Project of Hebei Education Department (Grant No.ZD2021338).
文摘The characteristics and sensitivity of solidification cracks in peritectic steels were investigated using directional solidifi-cation technology.Interdendritic cracks were observed in both hypoperitectic steels(12CrlMoV,15CrMo)and hyper-peritectic steel(20CrMo)during solidification at growth velocities of 15,50,and 80 pm/s.At the dendritic boundaries,sulphide precipitates were found,promoting crack formation.Based on the statistical analysis of interdendritic cracks in peritectic steels,the area ratio(RA)of interdendritic cracks in a directional solidification structure was proposed to evaluate the crack sensitivity of peritectic steels.Furthermore,the crack sensitivities of peritectic steels(12CrlMoV,15CrMo,and 20CrMo)were tested,evaluated,and compared with the surface crack rates of three types of steels produced from a steel plant.The results demonstrated that RA was in good agreement with that of the steel plant,and the crack sensitivity of 12CrlMoV steel was the strongest,followed by that of 15CrMo and 20CrMo steels.Thus,RA can be used to evaluate the crack sensitivity of peritectic steel.
