1. Research Center of Wuling Mountain, Area Characteristic Resources Development and Utilization, College of Finance and Economics, Yangtze Normal University, Chongqing 408100, P. R. China
2. School of Economics and Management, Chongqing Metropolitan College of Science and Technology, Chongqing 402167, P. R. China
3. Graduate Admissions Office, Civil Aviation Flight University of China, Guanghan 618307, P. R. China
4. Department of Computer Science, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, Chennai, India