1. Professor, School of Sciences, Guangxi Univ. for Nationalities, Nanning, Guangxi 530006, P.R. China (corresponding author).
2. Teacher, Dongfeng High School, Langzhong, Sichuan 637400, P.R. China.
3. Professor, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan Univ., Chengdu, Sichuan 610065, P.R. China.
4. Secretary, Qushui Town Office, Qianjiang, Chongqing 409007, P.R. China.