1. Researcher, Dept. of Civil and Environmental Engineering, Northeastern Univ., Boston, MA 02115; Lecturer, College of Hydraulic and Civil Engineering, Xinjiang Agricultural Univ., Urumqi 830052, P.R. China (corresponding author).
2. Professor, Dept. of Hydraulic Engineering, Tsinghua Univ., Beijing 100084, P.R. China.
3. Professor, College of Hydraulic and Civil Engineering, Xinjiang Agricultural Univ., Urumqi 830052, P.R. China.