Since the beginning of the 21st century,advances in big data and artificial intelligence have driven a paradigm shift in the geosciences,moving the field from qualitative descriptions toward quantitative analysis,from...Since the beginning of the 21st century,advances in big data and artificial intelligence have driven a paradigm shift in the geosciences,moving the field from qualitative descriptions toward quantitative analysis,from observing phenomena to uncovering underlying mechanisms,from regional-scale investigations to global perspectives,and from experience-based inference toward data-and model-enabled intelligent prediction.AlphaEarth Foundations(AEF)is a next-generation geospatial intelligence platform that addresses these changes by introducing a unified 64-dimensional shared embedding space,enabling-for the first time-standardized representation and seamless integration of 12 distinct types of Earth observation data,including optical,radar,and lidar.This framework significantly improves data assimilation efficiency and resolves the persistent problem of“data silos”in geoscience research.AEF is helping redefine research methodologies and fostering breakthroughs,particularly in quantitative Earth system science.This paper systematically examines how AEF’s innovative architecture-featuring multi-source data fusion,high-dimensional feature representation learning,and a scalable computational framework-facilitates intelligent,precise,and realtime data-driven geoscientific research.Using case studies from resource and environmental applications,we demonstrate AEF’s broad potential and identify emerging innovation needs.Our findings show that AEF not only enhances the efficiency of solving traditional geoscientific problems but also stimulates novel research directions and methodological approaches.展开更多
Background Agroecological cropping systems are recognised as an alternative way to ensure the sustainability of cotton(Gossypium hirsutum L.) production in the context of climate change and degradation of soil fertili...Background Agroecological cropping systems are recognised as an alternative way to ensure the sustainability of cotton(Gossypium hirsutum L.) production in the context of climate change and degradation of soil fertility. A study was conducted in Benin from 2020 to 2023 to compare six different cotton cultivars in three agroecological cropping systems in two cotton-growing zones. Plough-based tillage plus incorporation of cover crop biomass(PTI), conservation agriculture with strip tillage(CA_ST), and conservation agriculture with no tillage(CA_NT) were compared with the reference plough-based tillage(PT). The objective was to identify morpho-physiological traits of cotton that increase yield in agroecological cropping systems. Our approach combined a field experiment and crop simulation model(CSM) of CROPGRO-Cotton to evaluate the effects of genotype(G) × environment(E) × management(M) interactions on seed cotton yield(SCY).Results Cultivars Tamcot_camde and Okp768 and simulated ideotypes performed best in CA systems. Increased seed mass, large and thick leaves, and later maturity were identified as beneficial for yield enhancement in CA systems. Cultivars and ideotypes that combine these traits also resulted in better nitrogen and water use efficiencies in CA systems. Under different climate scenarios up to 2050, ideotypes designed could increase SCY in Benin.Conclusion A set of morpho-physiological traits associated with vegetative vigour is required to ensure a good SCY in agroecological cropping systems. These results provide scientific evidence and useful knowledge for breeders and research programmes on cropping systems focused on the adaptation of cotton to climate change.展开更多
由于静态代码审计工具具有自动化、不容易出错的特点,开发人员经常使用它来检测代码漏洞,但是检测出的代码漏洞的结果会产生大量的警告信息,开发人员必须手动进行检查和纠正。此工具的缺点是浪费开发人员大量的时间。通过对用户的输入...由于静态代码审计工具具有自动化、不容易出错的特点,开发人员经常使用它来检测代码漏洞,但是检测出的代码漏洞的结果会产生大量的警告信息,开发人员必须手动进行检查和纠正。此工具的缺点是浪费开发人员大量的时间。通过对用户的输入以及敏感数据流的追踪来确定警告的缺陷是否真的被利用,从而减少静态检测工具产生的大量警告数量。同时提供给开发者更多真正能对软件产生威胁的警告信息。针对静态代码审计工具的缺点,研究三种不同的方法来提高静态代码审计工具的性能。第一,对于商业性的静态代码分析工具Coverity,重新分析它的结果,并且从安全的角度创建一组具体的相关警告。第二,对开放的源代码分析工具Findbugs进行修改,并只对被用户输入所污染的代码进行分析。第三,研发灰盒代码审计工具,此工具侧重于Java代码中的跨站脚本攻击XSS(Cross Site Scripting),使用数据流分析的方法来确定漏洞的切入点。实验结果证明工程B使警告数量降低了20%,工程E只产生了2%的警告,降低了工具产生警告的数量,为开发人员提供更多的信息来区分此警告是否是真正的安全威胁。展开更多
从协议测试的角度出发研究了基于时间自动机模型的无线传感器网络数据收集协议测试用例生成方法,提出利用UPPAAL工具对数据收集协议建立时间自动机模型,进而利用UPPAAL Co Ver工具生成满足特定覆盖标准的测试路径集合的方法。为了便于...从协议测试的角度出发研究了基于时间自动机模型的无线传感器网络数据收集协议测试用例生成方法,提出利用UPPAAL工具对数据收集协议建立时间自动机模型,进而利用UPPAAL Co Ver工具生成满足特定覆盖标准的测试路径集合的方法。为了便于生成实际测试用例,开发了辅助自动测试用例生成工具ATCGT。通过一个工业界的无线抄表数据收集协议的建模与测试用例生成实例,阐明了该方法的有效性。展开更多
城市用地空间扩张对生态环境的影响映射出人类社会活动和生态环境保护之间的交互作用,系统地研究城市空间无序蔓延所诱发的城市土地利用方式变化对城市生态环境的影响程度,对助推中国生态文明建设目标具有重要现实意义。为探究合肥市城...城市用地空间扩张对生态环境的影响映射出人类社会活动和生态环境保护之间的交互作用,系统地研究城市空间无序蔓延所诱发的城市土地利用方式变化对城市生态环境的影响程度,对助推中国生态文明建设目标具有重要现实意义。为探究合肥市城市扩张对生态安全格局的影响程度,综合运用生态遥感指数、最小累积阻力模型、电路理论和斑块生成土地利用模拟模型,构建合肥市生态安全格局,识别生态夹点和生态障碍点,再从模拟验证的基础上(总体精度为94.71%,Kappa系数为90.04%,Fom值为0.102),预测了2030—2040年的城市扩张,并根据预测结果探讨城市扩张对区域生态安全格局影响程度。研究发现:合肥市生态环境质量整体呈现南高中低的分布格局,识别出合肥市生态源地共计35处,源地间活跃生态廊道70条,非活跃廊道共17条,生态夹点290个,生态障碍点112个。2020—2040年合肥市城乡、工矿居民用地、林地、水域和未利用土地面积将不断增加,而耕地以及草地面积将持续减少。2020—2040年期间城镇建成区分别侵占了生态廊道、源地、夹点、障碍点面积为55.95、10.51、1.04、1.35 km 2。研究结果可为今后快速发展城市的生态环境治理和国土空间生态保护修复工作提供理论依据和技术参考。展开更多
To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different ma...To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.展开更多
This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal...This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal with the cosinusoidal phase to generate multi-false targets in range, and further rotates the jammer to generate multi-false targets in azimuth. The range multi-false targets and azimuth multi-false targets form the two-dimensional cover jamming or deception jamming, which can protect the important targets efficiently. The number of false targets, the interval of false targets, and the jamming square can be adjusted flexibly by setting different range jamming parameters and azimuth jamming parameters. The jamming performance and the choosing criteria of jamming parameters are also discussed. Finally, the simulated data verify the effectiveness of the jamming method.展开更多
Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspens...Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.展开更多
The Ice,Cloud and Land Elevation Satellite-2(ICESat-2),a new spaceborne light detection and ranging(LiDAR)system,was successfully launched on September 15,2018.The ICESat-2 data increase the types of spaceborne LiDAR ...The Ice,Cloud and Land Elevation Satellite-2(ICESat-2),a new spaceborne light detection and ranging(LiDAR)system,was successfully launched on September 15,2018.The ICESat-2 data increase the types of spaceborne LiDAR data archive and provide new control point data for large-scale topographic mapping and geodetic surveying.However,the accuracy of the ATL 08 terrain estimates has not been fully evaluated on a large scale and in complex terrain conditions.This article aims to quantitatively assess the accuracy of ICESat-2 ATL 08 terrain estimates.Firstly,the ICESat-2 ATL 08 terrain estimates were compared with the high-precision airborne LiDAR digital terrain model(DTM),and impacts of acquisition time,vegetation cover type,terrain slope,and season change on the terrain estimation accuracy were analyzed.We get the following conclusions from the analysis:1)the mean and RMSE of the terrain estimates of day acquisitions are 0.22 m and 0.59 m higher than that of night acquisitions;2)the accuracy of the ATL 08 terrain estimates acquired in vegetated areas is lower than those in non-vegetated areas;3)the accuracy of the ATL 08 terrain estimates is inversely proportional to the slope,and the elevation error increases significantly when the terrain slope is larger than 30°;4)in the non-vegetation covered area,the accuracy of the ATL 08 terrain estimates of summer and winter acquisitions has no obvious discrepancy,but in vegetated area,the accuracy of winter acquisitions is significantly better than that of summer acquisitions.This research provides references for the selection and application of ICESat-2 data.展开更多
Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-phar...Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-pharmaceutical approaches, including ventilation system and personal protection, are believed to have certain positive effects on the reduction of co-occupant＇s inhalation. This work then aims to numerically study the performances of mouth covering on co-occupant＇s exposure under mixing ventilation （MV）, under-floor air distribution （UFAD） and displacement ventilation （DV） system, using drift-flux model. Desk partition, as one generally employed arrangement in plan office, is also investigated under MV. The dispersion of 1, 5 and 10 grn droplet residuals are numerically calculated and CO2 is used to represent tracer gas. The results show that using mouth covering by the infected person can reduce the co-occupant＇s inhalation greatly by interrupting direct spread of the expelled droplets, and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person. The researches under MV show that the two interventions, mouth covering and desk partition, achieve almost the sarae inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.展开更多
In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effec...In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effects of key parameters such as size of specimens, tie configuration, transverse reinforcement ratio, and concrete cover were studied. The results show that for specimens with the same configuration and the same volumetric ratio of the transverse reinforcement, along with the increasing specimen size, the peak stress, peak strain and deformation of the post-peak show a down trend, however, the volumetric ratio of the transverse reinforcement is lowered, the decreasing of the peak stress is accelerated, but the decreasing of the deformation is slow down. For specimens with the same volumetric ratio but different configurations of transverse reinforcement, though the transverse reinforcement configuration becomes more complicated, the peak stress of the large size specimen does not improve more than that of the small size. However, the deformation occurs before the stress declines to 85% of peak stress, and the improvement with the grid pattern tie configuration is much greater due to size effect.展开更多
基金National Natural Science Foundation of China Key Project(No.42050103)Higher Education Disciplinary Innovation Program(No.B25052)+2 种基金the Guangdong Pearl River Talent Program Innovative and Entrepreneurial Team Project(No.2021ZT09H399)the Ministry of Education’s Frontiers Science Center for Deep-Time Digital Earth(DDE)(No.2652023001)Geological Survey Project of China Geological Survey(DD20240206201)。
文摘Since the beginning of the 21st century,advances in big data and artificial intelligence have driven a paradigm shift in the geosciences,moving the field from qualitative descriptions toward quantitative analysis,from observing phenomena to uncovering underlying mechanisms,from regional-scale investigations to global perspectives,and from experience-based inference toward data-and model-enabled intelligent prediction.AlphaEarth Foundations(AEF)is a next-generation geospatial intelligence platform that addresses these changes by introducing a unified 64-dimensional shared embedding space,enabling-for the first time-standardized representation and seamless integration of 12 distinct types of Earth observation data,including optical,radar,and lidar.This framework significantly improves data assimilation efficiency and resolves the persistent problem of“data silos”in geoscience research.AEF is helping redefine research methodologies and fostering breakthroughs,particularly in quantitative Earth system science.This paper systematically examines how AEF’s innovative architecture-featuring multi-source data fusion,high-dimensional feature representation learning,and a scalable computational framework-facilitates intelligent,precise,and realtime data-driven geoscientific research.Using case studies from resource and environmental applications,we demonstrate AEF’s broad potential and identify emerging innovation needs.Our findings show that AEF not only enhances the efficiency of solving traditional geoscientific problems but also stimulates novel research directions and methodological approaches.
基金supported by the Benin Cotton Research Institute (IRC)the Cotton Interprofessional Association (AIC)+1 种基金the French Agricultural Research Centre for International Development (CIRAD)the TAZCO_(2) project (Transition Agroécologique des Zones Cotonnières du Bénin),which is funded by the Republic of Benin and the French Development Agency (AFD)。
文摘Background Agroecological cropping systems are recognised as an alternative way to ensure the sustainability of cotton(Gossypium hirsutum L.) production in the context of climate change and degradation of soil fertility. A study was conducted in Benin from 2020 to 2023 to compare six different cotton cultivars in three agroecological cropping systems in two cotton-growing zones. Plough-based tillage plus incorporation of cover crop biomass(PTI), conservation agriculture with strip tillage(CA_ST), and conservation agriculture with no tillage(CA_NT) were compared with the reference plough-based tillage(PT). The objective was to identify morpho-physiological traits of cotton that increase yield in agroecological cropping systems. Our approach combined a field experiment and crop simulation model(CSM) of CROPGRO-Cotton to evaluate the effects of genotype(G) × environment(E) × management(M) interactions on seed cotton yield(SCY).Results Cultivars Tamcot_camde and Okp768 and simulated ideotypes performed best in CA systems. Increased seed mass, large and thick leaves, and later maturity were identified as beneficial for yield enhancement in CA systems. Cultivars and ideotypes that combine these traits also resulted in better nitrogen and water use efficiencies in CA systems. Under different climate scenarios up to 2050, ideotypes designed could increase SCY in Benin.Conclusion A set of morpho-physiological traits associated with vegetative vigour is required to ensure a good SCY in agroecological cropping systems. These results provide scientific evidence and useful knowledge for breeders and research programmes on cropping systems focused on the adaptation of cotton to climate change.
文摘由于静态代码审计工具具有自动化、不容易出错的特点,开发人员经常使用它来检测代码漏洞,但是检测出的代码漏洞的结果会产生大量的警告信息,开发人员必须手动进行检查和纠正。此工具的缺点是浪费开发人员大量的时间。通过对用户的输入以及敏感数据流的追踪来确定警告的缺陷是否真的被利用,从而减少静态检测工具产生的大量警告数量。同时提供给开发者更多真正能对软件产生威胁的警告信息。针对静态代码审计工具的缺点,研究三种不同的方法来提高静态代码审计工具的性能。第一,对于商业性的静态代码分析工具Coverity,重新分析它的结果,并且从安全的角度创建一组具体的相关警告。第二,对开放的源代码分析工具Findbugs进行修改,并只对被用户输入所污染的代码进行分析。第三,研发灰盒代码审计工具,此工具侧重于Java代码中的跨站脚本攻击XSS(Cross Site Scripting),使用数据流分析的方法来确定漏洞的切入点。实验结果证明工程B使警告数量降低了20%,工程E只产生了2%的警告,降低了工具产生警告的数量,为开发人员提供更多的信息来区分此警告是否是真正的安全威胁。
文摘从协议测试的角度出发研究了基于时间自动机模型的无线传感器网络数据收集协议测试用例生成方法,提出利用UPPAAL工具对数据收集协议建立时间自动机模型,进而利用UPPAAL Co Ver工具生成满足特定覆盖标准的测试路径集合的方法。为了便于生成实际测试用例,开发了辅助自动测试用例生成工具ATCGT。通过一个工业界的无线抄表数据收集协议的建模与测试用例生成实例,阐明了该方法的有效性。
文摘城市用地空间扩张对生态环境的影响映射出人类社会活动和生态环境保护之间的交互作用,系统地研究城市空间无序蔓延所诱发的城市土地利用方式变化对城市生态环境的影响程度,对助推中国生态文明建设目标具有重要现实意义。为探究合肥市城市扩张对生态安全格局的影响程度,综合运用生态遥感指数、最小累积阻力模型、电路理论和斑块生成土地利用模拟模型,构建合肥市生态安全格局,识别生态夹点和生态障碍点,再从模拟验证的基础上(总体精度为94.71%,Kappa系数为90.04%,Fom值为0.102),预测了2030—2040年的城市扩张,并根据预测结果探讨城市扩张对区域生态安全格局影响程度。研究发现:合肥市生态环境质量整体呈现南高中低的分布格局,识别出合肥市生态源地共计35处,源地间活跃生态廊道70条,非活跃廊道共17条,生态夹点290个,生态障碍点112个。2020—2040年合肥市城乡、工矿居民用地、林地、水域和未利用土地面积将不断增加,而耕地以及草地面积将持续减少。2020—2040年期间城镇建成区分别侵占了生态廊道、源地、夹点、障碍点面积为55.95、10.51、1.04、1.35 km 2。研究结果可为今后快速发展城市的生态环境治理和国土空间生态保护修复工作提供理论依据和技术参考。
基金Project(2017YFC0805307)supported by the National Key Research and Development Program of ChinaProjects(51838001,51878070,51878078,51911530215,51927814)supported by the National Natural Science Foundation of China+5 种基金Project(2018JJ1026)supported by the Excellent Youth Foundation of Natural Science Foundation of Hunan Province,ChinaProject(17A008)supported by the Key Project of Education Department of Hunan Province,ChinaProjects(kfj150103,kfj170106)supported by the Changsha University of Science&Technology via Key Project of Open Research Fund of National Engineering Laboratory of Highway Maintenance Technology,ChinaProject(kfj170404)supported by the Open Fund of Engineering Research Center of Catastrophic Prophylaxis and Treatment of Road and Traffic Safety of Ministry of Education(Changsha University of Science&Technology),ChinaProject(CX2018B527)supported by the Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(2018-025)supported by the Training Program for High-level Technical Personnel in Transportation Industry,China。
文摘To achieve durability of the embankment in southern China,a method to control the change of moisture content with the cushion and cover was proposed.A finite element model of cushion and cover considering different materials and thicknesses for a typical embankment was built,and 20 numerical analyses of transient seepage in the embankment were simulated.The results show that the sand cushion effectively blocks the effect of groundwater capillary rise and the minimum thickness of the sand cushion is 75 cm without considering the atmospheric environment.With the combination of sand cushion and clay cover,as the thickness of the clay cover increases,the duration time of the moisture content from the initial to relative equilibrium state increases,but the equilibrium moisture content is the same as that of the original embankment.Besides,with the combination of the sand cushion and sand cover,the moisture content inside the embankment remains the same,which is consistent with the optimum moisture content during construction.The combination of 75 cm sand cushion and 30 cm sand cover is a very effective method to block groundwater and atmospheric environment,and achieve the control of the humidity stability of the embankment in southern China.
基金supported by the National Defense Pre-research Program during the 13th Five-Year Plan(30603050303 301020302)
文摘This paper focuses on the jamming problem of bistatic synthetic aperture radar (BiSAR), and a jamming method against BiSAR based on modulation theory is proposed. The proposed jamming method modulates the BiSAR signal with the cosinusoidal phase to generate multi-false targets in range, and further rotates the jammer to generate multi-false targets in azimuth. The range multi-false targets and azimuth multi-false targets form the two-dimensional cover jamming or deception jamming, which can protect the important targets efficiently. The number of false targets, the interval of false targets, and the jamming square can be adjusted flexibly by setting different range jamming parameters and azimuth jamming parameters. The jamming performance and the choosing criteria of jamming parameters are also discussed. Finally, the simulated data verify the effectiveness of the jamming method.
文摘Flashover of ice-covered suspension insulator string is one of the major problems for the transmission lines in power grid.As leakage current is one of the important characteristics to predict the flashover of suspension insulator string,measuring method and analysis of the leakage current are developed for ice-covered XWP_2-160 porcelain suspension insulator string in this paper.The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover,in which the process can be divided into four periods according to the evolution of the leakage current.There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage,and the distortion on the leakage current waveform is detected because of the effect of arc discharge.A characteristic current(I_w)and a critical current(I_(FT))of flashover,two important parameters of the leakage current before ice-covered insulator string flashover,are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice.Statistical experimental results show that the average values of I_w and I_(FT) are within the major distribution zones,and both currents can be used for predicting the icing flashover.The values of two important leakage currents are approximately constant at different contamination degrees,while the direct relationships between the critical currents and the contamination degrees are not found in this paper.
基金Projects(41820104005,41904004,42030112)supported by the National Natural Science Foundation of China。
文摘The Ice,Cloud and Land Elevation Satellite-2(ICESat-2),a new spaceborne light detection and ranging(LiDAR)system,was successfully launched on September 15,2018.The ICESat-2 data increase the types of spaceborne LiDAR data archive and provide new control point data for large-scale topographic mapping and geodetic surveying.However,the accuracy of the ATL 08 terrain estimates has not been fully evaluated on a large scale and in complex terrain conditions.This article aims to quantitatively assess the accuracy of ICESat-2 ATL 08 terrain estimates.Firstly,the ICESat-2 ATL 08 terrain estimates were compared with the high-precision airborne LiDAR digital terrain model(DTM),and impacts of acquisition time,vegetation cover type,terrain slope,and season change on the terrain estimation accuracy were analyzed.We get the following conclusions from the analysis:1)the mean and RMSE of the terrain estimates of day acquisitions are 0.22 m and 0.59 m higher than that of night acquisitions;2)the accuracy of the ATL 08 terrain estimates acquired in vegetated areas is lower than those in non-vegetated areas;3)the accuracy of the ATL 08 terrain estimates is inversely proportional to the slope,and the elevation error increases significantly when the terrain slope is larger than 30°;4)in the non-vegetation covered area,the accuracy of the ATL 08 terrain estimates of summer and winter acquisitions has no obvious discrepancy,but in vegetated area,the accuracy of winter acquisitions is significantly better than that of summer acquisitions.This research provides references for the selection and application of ICESat-2 data.
基金funded by Research Grant Committee of the Hong Kong SAR government (RGC No. PolyU5265/08E)
文摘Existed evidences show that airborne transmission of human respiratory droplets may be related with the spread of some infectious disease, such as severe acute respiratory syndrome （SARS） and H1N1 pandemic. Non-pharmaceutical approaches, including ventilation system and personal protection, are believed to have certain positive effects on the reduction of co-occupant＇s inhalation. This work then aims to numerically study the performances of mouth covering on co-occupant＇s exposure under mixing ventilation （MV）, under-floor air distribution （UFAD） and displacement ventilation （DV） system, using drift-flux model. Desk partition, as one generally employed arrangement in plan office, is also investigated under MV. The dispersion of 1, 5 and 10 grn droplet residuals are numerically calculated and CO2 is used to represent tracer gas. The results show that using mouth covering by the infected person can reduce the co-occupant＇s inhalation greatly by interrupting direct spread of the expelled droplets, and best performance can be achieved under DV since the coughed air is mainly confined in the microenvironment of the infected person. The researches under MV show that the two interventions, mouth covering and desk partition, achieve almost the sarae inhalation for fine droplets while the inhalation of the co-occupant is lower when using mouth covering for large droplets.
基金Project(50838001) supported by the National Natural Science Foundation of China
文摘In order to investigate the size effect and other effects on the stress-strain relationship of confined concrete, 42 specimens with different sizes and section shapes were placed under axial compression loading. Effects of key parameters such as size of specimens, tie configuration, transverse reinforcement ratio, and concrete cover were studied. The results show that for specimens with the same configuration and the same volumetric ratio of the transverse reinforcement, along with the increasing specimen size, the peak stress, peak strain and deformation of the post-peak show a down trend, however, the volumetric ratio of the transverse reinforcement is lowered, the decreasing of the peak stress is accelerated, but the decreasing of the deformation is slow down. For specimens with the same volumetric ratio but different configurations of transverse reinforcement, though the transverse reinforcement configuration becomes more complicated, the peak stress of the large size specimen does not improve more than that of the small size. However, the deformation occurs before the stress declines to 85% of peak stress, and the improvement with the grid pattern tie configuration is much greater due to size effect.
