1. Decision Science Institute, School of Economics & Management, Fuzhou University, Fuzhou 350116, P. R. China
2. Key Laboratory of Spatial Data Mining & Information, Sharing of Ministry of Education, Fuzhou University, Fuzhou 350116, P. R. China
3. College of Computer and Information Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, P. R. China