1. College of Information Science and Engineering, Guilin University of Technology, Guilin 541004, P. R. China
2. Guangxi New Future Information Industry Co. Ltd, Beihai 536005, P. R. China
3. State Key Laboratory Breeding Base of Nonferrous Metals and Specific Materials Processing, Guangxi Universities Key Laboratory of Nonferrous Metal Oxide, Electronic Functional Materials and Devices, College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, P. R. China