1. Faculty of Mathematics and Physics; Huaiyin Institute of Technology; Huai'an 223003 P. R. China
2. Faculty of Mechanical Engineering; Huaiyin Institute of Technology; Huai'an 223003 P. R. China
3. College of Physics Optoelectronics and Energy; Soochow University; Suzhou 215006 P. R. China
4. Department of Materials Science and Engineering; Monash University; Clayton Victoria 3800 Australia