College of Environmental Science & Engineering. Southwest Jiaotong University. Chengdu 610031;
P;
R. China;
College of Resources & Environmental Science;
Chongqing Uniiversity;
Chongqing 400044;
P. R. China;
School of Computer Sch & Eng;
University of Electronic Science & Technology of China. Chengdu 610054 P R;
China;