1. Department of Mathematics and Information Technology, Jiangsu Second Normal University, Nanjing, Jiangsu, China
2. School of Management & Engineering, Nanjing University, Nanjing, Jiangsu, China
3. Energy Development and Environmental Protection Strategy Research Center, Jiangsu University, Zhenjiang, Jiangsu, China
4. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, Singapore