Taking Ansai County located in loess hilly and gully area as a case, this study analyzes the land use changes driven by the SLCP （Slope Land Conversion Program） and the farmers＇ responses by household survey and pa...Taking Ansai County located in loess hilly and gully area as a case, this study analyzes the land use changes driven by the SLCP （Slope Land Conversion Program） and the farmers＇ responses by household survey and participatory rapid appraisal （PRA）. It is found that the SLCP aroused various changes in land use, agricultural production, rural incomes, etc. In the period of 1999-2005, the farmland and grasslands were reduced by 26,809 ha and 17,571 ha respectively, while forestland increased by 38,203 ha; greenhouse vegetable and orchard got a quick development, with the area enlarged by about 7 times and nearly doubled respectively. The SLCP reduced the area of crops particularly those that normally grown on slope lands, e.g. the sowing area of winter wheat ped from 19.39% of the total cropping area in 1999 to 0.98% in 2005. Draught animals, pigs and sheep have a decline in the number because the remained land and the ban on grazing on natural grasslands can not provide sufficient feed forage. Thanks to the financial subsidy, farmers increased land inputs and thus outputs. To achieve long-term sustainable development and improve rural income, the government should continuously support farmers to improve the land management, to adopt alternative land use systems, and to increase inputs on soil conservation. Vegetable and fruit production are two promise land use systems, and should be further developed.展开更多
P-median is one of the most important Location-Allocation problems. This problem determines the location of facilities and assigns demand points to them. The p-median problem can be established as a discrete problem i...P-median is one of the most important Location-Allocation problems. This problem determines the location of facilities and assigns demand points to them. The p-median problem can be established as a discrete problem in graph terms as： Let G = （V, E） be an undirected graph where V is the set of n vertices and E is the set of edges with an associated weight that can be the distance between the vertices dij= d（vi, Vj） for every i, j =1,...,n in accordance to the determined metric, with the distances a symmetric matrix is formed, finding Vp∈ V such that ｜ Vp｜∈ = p, where p can be either variable or fixed, and the sum of the shortest distances from the vertices in {V-Vp} to their closet vertex in Vp is reduced to the minimum. Under these conditions the P-median problem is a combinatory optimization problem that belongs to the NP-hard class and the approximation methods have been of great aid in recent years because of this. In this point, we have chosen data from OR-Library [1] and we have tested three algorithms that have given good results for geographical data （Simulated Annealing, Variable Neighborhood Search, Bioinspired Variable Neighborhood Search and a Tabu Search-VNS Hybrid （TS-VNS）. However, the partitioning method PAM （Partitioning Around Medoids）, that is modeled like the P-median, attained similar results along with TS-VNS but better results than the other metaheuristics for the OR-Library instances, in a favorable computing time, however for bigger instances that represent real states in Mexico, TS-VNS has surpassed PAM in time and quality in all instances. In this work we expose the behavior of these five different algorithms for the test matrices from OR-Library and real geographical data from Mexico. Furthermore, we made an analysis with the goal of explaining the quality of the results obtained to conclude that PAM behaves with efficiency for the OR-Library instances but is overcome by the hybrid when applied to real instances. On the other hand we have tested the 2 best algorithms （PAM and TS-VNS） with geographic data geographic from Jalisco, Queretaro and Nuevo Leon. In this point, as we said before, their performance was different than the OR-Library tests. The algorithm that attains the best results is TS-VNS.展开更多
The research process,main contents,methods and conclusions for some major engineering geological problems of the Three Gorges Project (TGP) are reviewed and introduced,including dam site selection,regional tectonic st...The research process,main contents,methods and conclusions for some major engineering geological problems of the Three Gorges Project (TGP) are reviewed and introduced,including dam site selection,regional tectonic stability and seismic activity,stability of reservoir bank and reservoir-induced earthquake.Meanwhile,the above mentioned engineering geological problems are evaluated according to the preliminary test results since TGP operation and impoundment in 2003.展开更多
基金supported by National Natural Science Foundation of China(Grant No.40671007)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-421)the National S&T Support Program(Grant No.2007BAC03A11-01)
文摘Taking Ansai County located in loess hilly and gully area as a case, this study analyzes the land use changes driven by the SLCP （Slope Land Conversion Program） and the farmers＇ responses by household survey and participatory rapid appraisal （PRA）. It is found that the SLCP aroused various changes in land use, agricultural production, rural incomes, etc. In the period of 1999-2005, the farmland and grasslands were reduced by 26,809 ha and 17,571 ha respectively, while forestland increased by 38,203 ha; greenhouse vegetable and orchard got a quick development, with the area enlarged by about 7 times and nearly doubled respectively. The SLCP reduced the area of crops particularly those that normally grown on slope lands, e.g. the sowing area of winter wheat ped from 19.39% of the total cropping area in 1999 to 0.98% in 2005. Draught animals, pigs and sheep have a decline in the number because the remained land and the ban on grazing on natural grasslands can not provide sufficient feed forage. Thanks to the financial subsidy, farmers increased land inputs and thus outputs. To achieve long-term sustainable development and improve rural income, the government should continuously support farmers to improve the land management, to adopt alternative land use systems, and to increase inputs on soil conservation. Vegetable and fruit production are two promise land use systems, and should be further developed.
文摘P-median is one of the most important Location-Allocation problems. This problem determines the location of facilities and assigns demand points to them. The p-median problem can be established as a discrete problem in graph terms as： Let G = （V, E） be an undirected graph where V is the set of n vertices and E is the set of edges with an associated weight that can be the distance between the vertices dij= d（vi, Vj） for every i, j =1,...,n in accordance to the determined metric, with the distances a symmetric matrix is formed, finding Vp∈ V such that ｜ Vp｜∈ = p, where p can be either variable or fixed, and the sum of the shortest distances from the vertices in {V-Vp} to their closet vertex in Vp is reduced to the minimum. Under these conditions the P-median problem is a combinatory optimization problem that belongs to the NP-hard class and the approximation methods have been of great aid in recent years because of this. In this point, we have chosen data from OR-Library [1] and we have tested three algorithms that have given good results for geographical data （Simulated Annealing, Variable Neighborhood Search, Bioinspired Variable Neighborhood Search and a Tabu Search-VNS Hybrid （TS-VNS）. However, the partitioning method PAM （Partitioning Around Medoids）, that is modeled like the P-median, attained similar results along with TS-VNS but better results than the other metaheuristics for the OR-Library instances, in a favorable computing time, however for bigger instances that represent real states in Mexico, TS-VNS has surpassed PAM in time and quality in all instances. In this work we expose the behavior of these five different algorithms for the test matrices from OR-Library and real geographical data from Mexico. Furthermore, we made an analysis with the goal of explaining the quality of the results obtained to conclude that PAM behaves with efficiency for the OR-Library instances but is overcome by the hybrid when applied to real instances. On the other hand we have tested the 2 best algorithms （PAM and TS-VNS） with geographic data geographic from Jalisco, Queretaro and Nuevo Leon. In this point, as we said before, their performance was different than the OR-Library tests. The algorithm that attains the best results is TS-VNS.
文摘The research process,main contents,methods and conclusions for some major engineering geological problems of the Three Gorges Project (TGP) are reviewed and introduced,including dam site selection,regional tectonic stability and seismic activity,stability of reservoir bank and reservoir-induced earthquake.Meanwhile,the above mentioned engineering geological problems are evaluated according to the preliminary test results since TGP operation and impoundment in 2003.
