1. School of Architecture and Planning, Hunan University, Changsha 410082, China
2. Hunan Key Laboratory of Sciences of Urban and Rural Human Settlements in Hilly Areas, Hunan University, Changsha 410082, China
3. Department of Engineering Science, University of Oxford, Oxford OX1 2JD, UK
4. Bartlett School of Planning, University College London, London WC1E 6BT, UK