1. College of Tourism and Urban-Rural Planning, Chengdu University of Technology, Chengdu 610059, China
2. Department of Civil & Environmental Engineering, National University of Singapore, Singapore 119077, Singapore
3. Deptartment of Regional and City Planning, College of Architecture and Civil Engineering, Zhejiang University, Hangzhou 310058, China
4. Deptartment of Chemical Engineering, University College London, London WC1E 6BT, UK