Research on spatial flow as it relates to the relationship between the supply and demand of ecosystem services supports a significant connection between the supply of ecosystem services and human well-being.Understand...Research on spatial flow as it relates to the relationship between the supply and demand of ecosystem services supports a significant connection between the supply of ecosystem services and human well-being.Understanding the entire process of the production and flow,as well as the use of ecosystem services,accurately assessing the balance of supply and demand of ecosystem services,and establishing a two-way feedback relationship between supply and demand are vital for the scientific management of the ecosystem and ensuring the sustainable development of regional resources.Based on a large number of relevant publications,this paper comprehensively summarizes the concepts and assessment methods of ecosystem service supply and demand from the perspective of ecosystem service supply and demand,and discusses the impacts of land use and climate change on the temporal and spatial changes of ecosystem services under the background of global change.Then,an analysis of the research progress in the ecosystem services spatial flow indicated that there are still deficiencies in the quantification of cultural services,the dynamics of ecosystem service flow and the driving mechanism of ecosystem services.We also propose that clarifying the driving mechanism and transfer process of ecosystem services,and realizing the mutual conversion between different spatial-temporal scales of ecosystem services,is an important approach for improving the application of ecosystem services research in practice in the future.展开更多
Through practical sampling survey for the overseas travelers in the 12 tourist hotspot cities of China, the analytical results of database of the spatial changes for overseas travelers have been established with the h...Through practical sampling survey for the overseas travelers in the 12 tourist hotspot cities of China, the analytical results of database of the spatial changes for overseas travelers have been established with the help of the software Visual FoxPro. The New concepts such as transferring state, which can be used to study the spatial flow intensity of travelers. is first put forward By analyzing the statistical results, the spatial flow intensity of 12 tourist hotspot cities in China for overseas travelers has been probed At last, a practical research of spatial flow intensity for overseas tourists is carried out in Beijing──the of tourist hotspots of China展开更多
A three-dimensional large eddy simulation （LES） of a spatially developing round jet is carried out in cylindrical coordinates using a dynamic subgrid model with strong inflow instability. Evolutions of large-scale v...A three-dimensional large eddy simulation （LES） of a spatially developing round jet is carried out in cylindrical coordinates using a dynamic subgrid model with strong inflow instability. Evolutions of large-scale vortex structures represented by tangential vortices are obtained and compared with flow visualization. Also presented are three-dimensional spatial evolutions of coherent structure, which are of quasi two-dimensional Kelvin-Helmholtz instability and vortex rings as well as breaking up of the vortex rings with fully three-dimensional characteristics. Predicted results of mean velocity and turbulent intensity agree well with experiments. They are also compared with the results predicted by LES using standard Smagorinsky model and show good self-similarity. Turbulence spectrum of the predicted velocity shows the -5/3 decay for higher wave number, as expected for turbulent round jet flows. In addition, fl-test and y-test are carded out for the instantaneous velocity, showing that the present LES method can successfully predict the hierarchical structure of round jet.展开更多
基金The National Natural Science Foundation of China(41971272)。
文摘Research on spatial flow as it relates to the relationship between the supply and demand of ecosystem services supports a significant connection between the supply of ecosystem services and human well-being.Understanding the entire process of the production and flow,as well as the use of ecosystem services,accurately assessing the balance of supply and demand of ecosystem services,and establishing a two-way feedback relationship between supply and demand are vital for the scientific management of the ecosystem and ensuring the sustainable development of regional resources.Based on a large number of relevant publications,this paper comprehensively summarizes the concepts and assessment methods of ecosystem service supply and demand from the perspective of ecosystem service supply and demand,and discusses the impacts of land use and climate change on the temporal and spatial changes of ecosystem services under the background of global change.Then,an analysis of the research progress in the ecosystem services spatial flow indicated that there are still deficiencies in the quantification of cultural services,the dynamics of ecosystem service flow and the driving mechanism of ecosystem services.We also propose that clarifying the driving mechanism and transfer process of ecosystem services,and realizing the mutual conversion between different spatial-temporal scales of ecosystem services,is an important approach for improving the application of ecosystem services research in practice in the future.
基金Under the auspices of the National Natural Science Foundation of China! 49571027
文摘Through practical sampling survey for the overseas travelers in the 12 tourist hotspot cities of China, the analytical results of database of the spatial changes for overseas travelers have been established with the help of the software Visual FoxPro. The New concepts such as transferring state, which can be used to study the spatial flow intensity of travelers. is first put forward By analyzing the statistical results, the spatial flow intensity of 12 tourist hotspot cities in China for overseas travelers has been probed At last, a practical research of spatial flow intensity for overseas tourists is carried out in Beijing──the of tourist hotspots of China
基金supported by the National Natural Science Foundation of China (Grant Nos. 50176027 and 50706021)a grant from the Research Committee of The Hong Kong Polytechnic University (Grant No.G-U294)
文摘A three-dimensional large eddy simulation （LES） of a spatially developing round jet is carried out in cylindrical coordinates using a dynamic subgrid model with strong inflow instability. Evolutions of large-scale vortex structures represented by tangential vortices are obtained and compared with flow visualization. Also presented are three-dimensional spatial evolutions of coherent structure, which are of quasi two-dimensional Kelvin-Helmholtz instability and vortex rings as well as breaking up of the vortex rings with fully three-dimensional characteristics. Predicted results of mean velocity and turbulent intensity agree well with experiments. They are also compared with the results predicted by LES using standard Smagorinsky model and show good self-similarity. Turbulence spectrum of the predicted velocity shows the -5/3 decay for higher wave number, as expected for turbulent round jet flows. In addition, fl-test and y-test are carded out for the instantaneous velocity, showing that the present LES method can successfully predict the hierarchical structure of round jet.
