Monitoring of frozen soil hydrology in macro-scale was performed by Chinese and Japanese scientists from 1997 to 1998. Quality measured data were obtained. Measured data on soil moisture and temperature are preliminar...Monitoring of frozen soil hydrology in macro-scale was performed by Chinese and Japanese scientists from 1997 to 1998. Quality measured data were obtained. Measured data on soil moisture and temperature are preliminarily analyzed. Based on profiles of soil temperature and moisture in individual measured sites, intra-annual freezing and melting process of soil is discussed. Maximum frozen and thawed depths and frozen days in various depths are estimated. The work emphasized the spatial distribution on soil temperature and moisture in macro-scale and the effect of topography on conditions of soil water and heat.展开更多
Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runof...Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runoff estimates,but they are not fully intercompared and evaluated in China.This study assesses the routed-runoff from five offline LSM/GHM runs(VIC-CN05.1,CLM-CFSR,CLM-ERAI,CLM-MERRA,and CLM-NCEP)and three reanalysis datasets(ERAI/Land,JRA55,and MERRA-2)against the gauged streamflow(26 stations)in major Chinese river basins during 1980–2008.The Catchment-based Macro-scale Floodplain model(CaMa-Flood)is employed to route those runoff datasets to the hydrological stations.Four statistical quantities,including the correlation coefficient(R),standard deviation(STD),Nash–Sutcliffe efficiency coefficient(NSE),and relative error(RE),along with a ranking method,are used to quantify the quality of those products.The results show that the spatial patterns of both modeled and observed streamflow in summer are similar,but their magnitudes are different.Except for MERRA-2,the other products can reproduce well the interannual variability of streamflow in both the Yangtze and Yellow River basins.All products generally underestimate the magnitude and variance of monthly streamflow,while VIC-CN05.1 and JRA55 are closer to observations compared to other products.The correlation coefficients for all products are overall larger than 0.61,with the highest value(0.85)from VIC-CN05.1.In addition to CLM-MERRA,MERRA-2,and CLM-NCEP with relatively small precipitation,other products can simulate peak flow well with positive NSEs up to 0.41(ERAI/Land).Considerable uncertainties exist among the eight products at the Yellow River outlet,which might be because the LSMs ignore frequent human activities.Based on the above statistics,performances of the eight runoff products are ranked in descending order as follows:VIC-CN05.1,ERAI/Land,JRA55,CLM-CFSR,CLM-ERAI,MERRA-2,CLM-MERRA,and CLM-NCEP,which provides a reference for flood/hydro展开更多
A parallel algorithm suitable for simulating multi-sized particle systems and multi- phase fluid systems is proposed based on macro-scale pseudo-particle modeling (MaPPM). The algorithm employs space-decomposition of ...A parallel algorithm suitable for simulating multi-sized particle systems and multi- phase fluid systems is proposed based on macro-scale pseudo-particle modeling (MaPPM). The algorithm employs space-decomposition of the computational load among the processing ele- ments (PEs) and multi-level cell-subdivision technique for particle indexing. In this algorithm, a 2D gas-solid system is simulated with the temporal variations of drags on solids, inter-phase slip velocities and solids concentration elaborately monitored. Analysis of the results shows that the algorithm is of good parallel efficiency and scalability, demonstrating the unique advantage of MaPPM in simulating complex flows.展开更多
A metal additive manufacturing process results in a nearly net-shaped fabrication of parts directly from digital data.A local heat source melts the deposited material,and a part is built layer-by-layer.Residual stress...A metal additive manufacturing process results in a nearly net-shaped fabrication of parts directly from digital data.A local heat source melts the deposited material,and a part is built layer-by-layer.Residual stress and de-formation are critical issues experienced by additively manufactured parts.Modeling the additive manufacturing process provides important insights and can help determine an optimal build plan so as to minimize residual stress formation.Various approaches have been used for modeling of residual stresses,ranging from high-fidelity models to simplified models,for quicker results.This paper provides a state-of-the-art review of the approaches used to numerically model residual deformation and stresses in structures built using additive manufacturing.Fur-thermore,it describes the physical causes of residual-stress generation in an additively manufactured structure.展开更多
Aims We analyse here the variations in species composition and richness and the geographic ranges of the tree species occurring in south american subtropical atlantic and Pampean forests.our goals were to assess(i)the...Aims We analyse here the variations in species composition and richness and the geographic ranges of the tree species occurring in south american subtropical atlantic and Pampean forests.our goals were to assess(i)the floristic consistency of usual classifications based on vegetation physiognomy,climate and elevation;(ii)the leading role of temperature-related variables on the variations in species composition and richness;(iii)the predominance of species with tropical-subtropical ranges,possibly as a result of forest expansion over grasslands after the last glacial maximum(LGM);(iv)the restriction of most subtropical endemics to stressful habitats as a possible result of past forest refuges during the LGM.Methods The region was defined by the Tropic of Capricorn to the north,the rio de la Plata to the south,the atlantic shoreline to the east and the catchment areas of the upper Paranáand uruguay rivers to the west.multivariate analyses,multiple regression modelling and variance partition analyses were performed on a database containing 63994 occurrence records of 1555 tree species in 491 forest sites and 48 environmental variables.all species were also classified according to their known geographic range.Important Findingsa main differentiation in species composition and richness was observed between the eastern windward coastlands(rain and cloud forests)and western leeward hinterlands(Araucaria and semi-decid-uous forests).Pre-defined forest types on both sides were consistent with variations in tree species composition,which were significantly related to both environmental variables and spatial proximity,with extremes of low temperature playing a chief role.Tree species rich-ness declined substantially towards the south and also from rain to seasonal forests and towards the highland summits and sandy shores.species richness was significantly correlated with both minimum temperature and actual evapotranspiration.about 91%of the subtropical flora is shared with the much richer tropical flora,prob-ably extractin展开更多
文摘Monitoring of frozen soil hydrology in macro-scale was performed by Chinese and Japanese scientists from 1997 to 1998. Quality measured data were obtained. Measured data on soil moisture and temperature are preliminarily analyzed. Based on profiles of soil temperature and moisture in individual measured sites, intra-annual freezing and melting process of soil is discussed. Maximum frozen and thawed depths and frozen days in various depths are estimated. The work emphasized the spatial distribution on soil temperature and moisture in macro-scale and the effect of topography on conditions of soil water and heat.
基金Supported by the National Key Research and Development Program of China(2016YFA0602401)National Natural Science Foundation of China(41875106).
文摘Previous studies have demonstrated that offline land surface models(LSMs)and global hydrological models(GHMs)can reasonably reproduce streamflow in large river basins.Global reanalyses supply fine spatiotemporal runoff estimates,but they are not fully intercompared and evaluated in China.This study assesses the routed-runoff from five offline LSM/GHM runs(VIC-CN05.1,CLM-CFSR,CLM-ERAI,CLM-MERRA,and CLM-NCEP)and three reanalysis datasets(ERAI/Land,JRA55,and MERRA-2)against the gauged streamflow(26 stations)in major Chinese river basins during 1980–2008.The Catchment-based Macro-scale Floodplain model(CaMa-Flood)is employed to route those runoff datasets to the hydrological stations.Four statistical quantities,including the correlation coefficient(R),standard deviation(STD),Nash–Sutcliffe efficiency coefficient(NSE),and relative error(RE),along with a ranking method,are used to quantify the quality of those products.The results show that the spatial patterns of both modeled and observed streamflow in summer are similar,but their magnitudes are different.Except for MERRA-2,the other products can reproduce well the interannual variability of streamflow in both the Yangtze and Yellow River basins.All products generally underestimate the magnitude and variance of monthly streamflow,while VIC-CN05.1 and JRA55 are closer to observations compared to other products.The correlation coefficients for all products are overall larger than 0.61,with the highest value(0.85)from VIC-CN05.1.In addition to CLM-MERRA,MERRA-2,and CLM-NCEP with relatively small precipitation,other products can simulate peak flow well with positive NSEs up to 0.41(ERAI/Land).Considerable uncertainties exist among the eight products at the Yellow River outlet,which might be because the LSMs ignore frequent human activities.Based on the above statistics,performances of the eight runoff products are ranked in descending order as follows:VIC-CN05.1,ERAI/Land,JRA55,CLM-CFSR,CLM-ERAI,MERRA-2,CLM-MERRA,and CLM-NCEP,which provides a reference for flood/hydro
基金This work was supported by the National Key Program for Developing Basic Sciences(Grant No.G1999032801)the National Natural Science Foundation of China(Grant Nos.20336040and 20221603)the Chinese Academy of Sciences(Grant No.INF105-SCE-2-07).
文摘A parallel algorithm suitable for simulating multi-sized particle systems and multi- phase fluid systems is proposed based on macro-scale pseudo-particle modeling (MaPPM). The algorithm employs space-decomposition of the computational load among the processing ele- ments (PEs) and multi-level cell-subdivision technique for particle indexing. In this algorithm, a 2D gas-solid system is simulated with the temporal variations of drags on solids, inter-phase slip velocities and solids concentration elaborately monitored. Analysis of the results shows that the algorithm is of good parallel efficiency and scalability, demonstrating the unique advantage of MaPPM in simulating complex flows.
文摘A metal additive manufacturing process results in a nearly net-shaped fabrication of parts directly from digital data.A local heat source melts the deposited material,and a part is built layer-by-layer.Residual stress and de-formation are critical issues experienced by additively manufactured parts.Modeling the additive manufacturing process provides important insights and can help determine an optimal build plan so as to minimize residual stress formation.Various approaches have been used for modeling of residual stresses,ranging from high-fidelity models to simplified models,for quicker results.This paper provides a state-of-the-art review of the approaches used to numerically model residual deformation and stresses in structures built using additive manufacturing.Fur-thermore,it describes the physical causes of residual-stress generation in an additively manufactured structure.
基金Brazilian government research agencies Conselho Nacional de Desenvolvimento Científixo e Tecnológico(CNPq,grant number 301644/88-8)Royal Botanic Gardens Kew for the Kew Latin America Research FellowshipNew York Botanical Garden.
文摘Aims We analyse here the variations in species composition and richness and the geographic ranges of the tree species occurring in south american subtropical atlantic and Pampean forests.our goals were to assess(i)the floristic consistency of usual classifications based on vegetation physiognomy,climate and elevation;(ii)the leading role of temperature-related variables on the variations in species composition and richness;(iii)the predominance of species with tropical-subtropical ranges,possibly as a result of forest expansion over grasslands after the last glacial maximum(LGM);(iv)the restriction of most subtropical endemics to stressful habitats as a possible result of past forest refuges during the LGM.Methods The region was defined by the Tropic of Capricorn to the north,the rio de la Plata to the south,the atlantic shoreline to the east and the catchment areas of the upper Paranáand uruguay rivers to the west.multivariate analyses,multiple regression modelling and variance partition analyses were performed on a database containing 63994 occurrence records of 1555 tree species in 491 forest sites and 48 environmental variables.all species were also classified according to their known geographic range.Important Findingsa main differentiation in species composition and richness was observed between the eastern windward coastlands(rain and cloud forests)and western leeward hinterlands(Araucaria and semi-decid-uous forests).Pre-defined forest types on both sides were consistent with variations in tree species composition,which were significantly related to both environmental variables and spatial proximity,with extremes of low temperature playing a chief role.Tree species rich-ness declined substantially towards the south and also from rain to seasonal forests and towards the highland summits and sandy shores.species richness was significantly correlated with both minimum temperature and actual evapotranspiration.about 91%of the subtropical flora is shared with the much richer tropical flora,prob-ably extractin
