1. Associate Professor, School of Geography, Geomatics and Planning, Jiangsu Normal Univ., No. 101, Shanghai Rd., Tongshan District, Xuzhou, Jiangsu 221116, China (corresponding author).
2. Professor, School of Architecture and Design, China Univ. of Mining and Technology, No. 1, Daxue Rd., Xuzhou, Jiangsu 221116, China.