1. School of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000, P. R. China, State Key Laboratory of ASIC and System, Fudan University, Shanghai 200433, P. R. China
2. School of Information Science and Engineering, Lanzhou University, Lanzhou 730000, P. R. China
3. Department of Hydraulics, Changjiang River Scientific Research Institute, Wuhan 430010, P. R. China
4. School of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000, P. R. China
5. CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, P. R. China