1. College of Geography and Environment Shandong Normal University Jinan 250014 P. R. China Phone
2. Research Center for Engineering Ecology and Nonlinear Science North China Electric Power University Beijing 102206 P. R. China
3. School of Finance, Actuarial Studies and Applied Statistics The Australian National University Canberra, P.R. Australia
4. College of Chemistry and Chemical Engineering HEZE University Heze 250101 P. R. China
5. Dongying_institute Shandong Normal University Dongying 257000 P. R. China