1. Faculty of Geography, Yunnan Normal University, Kunming 650500, China
2. School of Geographical Sciences, China West Normal University, Nanchong 637009, China
3. Graduate School of Yunnan Normal University, Kunming 650500, China
4. School of Civil Engineering & Architecture, Zhejiang University of Science & Technology, Hangzhou 310023, China
5. School of Economics, Fudan University, Shanghai 200433, China