1. School of Mechatronics Engineering, Daqing Normal University, Daqing 163712, P. R. China
2. Key Laboratory of UV-Emitting Materials and Technology, Ministry of Education, Northeast Normal University, Changchun 130024, PR China
3. Mudanjiang Normal Univ, Sch Comp & Informat Technol, Mudanjiang 157011, P. R. China
4. School of Foreign Languages, Daqing Normal University, Daqing 163712, P. R. China