In this study, we investigated the spatial characteristics of the rate of soil distribution and the mechanism of major element migration in a typical karst hillslope in Guangxi Province, Southwestern China. Soil redis...In this study, we investigated the spatial characteristics of the rate of soil distribution and the mechanism of major element migration in a typical karst hillslope in Guangxi Province, Southwestern China. Soil redistribution was examined using (137~)Cs technique under different hillslope components. With the combination of geochemical methods, the migration characteristics of major elements in soils of three hillslope components in both the horizontal and vertical directions were determined. Thirty-seven soil samples were collected and analyzed for 137 Cs and the major elements were determined. By using the profile distribution model the mean soil redistribution rates were found to be-17.01, 0.40 and-23.30t ha-1 yr-1 in the summit(BYSD), shoulder(BYSY) and toeslope(BYSJ) components of the studied hillslope, respectively. In comparison to BYSD, the sesquioxides of Fe_2O_3 and TiO_2 tend to be enriched, whereas the alkalis(CaO, MgO, Na_2O and K_2O) tend to be depleted, both in the shoulder and toeslope components. Due to human and animal activities, the contents of CaO, MgO, K_2O and Na_2O have somewhat increased within the topsoil. The results indicated that (137~)Cs activities are significantly correlated with clay particles and organic matter, and are affected by the pedogenic process and vegatation. Overall, it maybe necessary to use techniques such as (137~)Cs to investigate soil erosion with the combination of geochemical methods.展开更多
Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the sceni...Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the scenic spot and around its influencing area are focused on. It is found that the terrain, land use, nearby transport network and scenery point distribution have significant impact on the allocation of bicycle-sharing system. While the candidate bicycle-sharing stations installed at the inner scenic points, entrances/exits and metro stations are fixed, the ones installed at bus-stations and other passenger concentration buildings are adjustable. Aiming at minimizing the total cycling distance and overlapping rate, an optimization model is proposed and solved based on the idea of cluster concept and greedy heuristic. A revealed preference/stated preference （RP/SP） combined survey was conducted at Xuanwu Lake in Nanjing, China, to get an insight into the touring trip characteristics and bicycle-sharing tendency. The results reveal that 39.81% visitors accept a cycling distance of 1-3 km and 62.50% respondents think that the bicycle-sharing system should charge an appropriate fee. The sttrvey indicates that there is high possibility to carry out a bicycle-sharing system at Xuanwu Lake. Optimizing the allocation problem cluster by cluster rather than using an exhaustive search method significantly reduces the computing amount from O（2^43） to O（43 2）. The 500 m-radius-coverage rate for the alternative optimized by 500 m-radius-cluster and 800 m-radius-cluster is 89.2% and 68.5%, respectively. The final layout scheme will provide decision makers engineering guidelines and theoretical support.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)grants(Grant Nos.41473122,41073096)the National Key Basic Research Program of China(2013CB956702)the Hundred Talents Program of the Chinese Academy of Sciences
文摘In this study, we investigated the spatial characteristics of the rate of soil distribution and the mechanism of major element migration in a typical karst hillslope in Guangxi Province, Southwestern China. Soil redistribution was examined using (137~)Cs technique under different hillslope components. With the combination of geochemical methods, the migration characteristics of major elements in soils of three hillslope components in both the horizontal and vertical directions were determined. Thirty-seven soil samples were collected and analyzed for 137 Cs and the major elements were determined. By using the profile distribution model the mean soil redistribution rates were found to be-17.01, 0.40 and-23.30t ha-1 yr-1 in the summit(BYSD), shoulder(BYSY) and toeslope(BYSJ) components of the studied hillslope, respectively. In comparison to BYSD, the sesquioxides of Fe_2O_3 and TiO_2 tend to be enriched, whereas the alkalis(CaO, MgO, Na_2O and K_2O) tend to be depleted, both in the shoulder and toeslope components. Due to human and animal activities, the contents of CaO, MgO, K_2O and Na_2O have somewhat increased within the topsoil. The results indicated that (137~)Cs activities are significantly correlated with clay particles and organic matter, and are affected by the pedogenic process and vegatation. Overall, it maybe necessary to use techniques such as (137~)Cs to investigate soil erosion with the combination of geochemical methods.
基金Project(51208261)supported by the National Natural Science Foundation of ChinaProject(12YJCZH062)supported by the Ministry of Education of Humanities and Social Science of ChinaProject(30920140132033)supported by the Fundamental Research Funds for the Central Universities,China
文摘Bicycle-sharing system is considered as a green option to provide a better connection between scenic spots and nearby metro/bus stations. Allocating and optimizing the layout of bicycle-sharing system inside the scenic spot and around its influencing area are focused on. It is found that the terrain, land use, nearby transport network and scenery point distribution have significant impact on the allocation of bicycle-sharing system. While the candidate bicycle-sharing stations installed at the inner scenic points, entrances/exits and metro stations are fixed, the ones installed at bus-stations and other passenger concentration buildings are adjustable. Aiming at minimizing the total cycling distance and overlapping rate, an optimization model is proposed and solved based on the idea of cluster concept and greedy heuristic. A revealed preference/stated preference （RP/SP） combined survey was conducted at Xuanwu Lake in Nanjing, China, to get an insight into the touring trip characteristics and bicycle-sharing tendency. The results reveal that 39.81% visitors accept a cycling distance of 1-3 km and 62.50% respondents think that the bicycle-sharing system should charge an appropriate fee. The sttrvey indicates that there is high possibility to carry out a bicycle-sharing system at Xuanwu Lake. Optimizing the allocation problem cluster by cluster rather than using an exhaustive search method significantly reduces the computing amount from O（2^43） to O（43 2）. The 500 m-radius-coverage rate for the alternative optimized by 500 m-radius-cluster and 800 m-radius-cluster is 89.2% and 68.5%, respectively. The final layout scheme will provide decision makers engineering guidelines and theoretical support.
