| Affiliation: | 1. Department of Mathematics , China University of Mining and Technology , Xuzhou , 221116 , People's Republic of China sftian@cumt.edu.cn shoufu2006@126.com;3. School of Mathematical Sciences , Anhui University , Hefei , 230601 , People's Republic of China;4. School of Science , Xi'an University of Post &5. Telecommunications , Xi'an , 710121 , People's Republic of China;6. School of Mathematical Sciences , Dalian University of Technology , Dalian , 116024 , People's Republic of China;7. Department of Mathematics , China University of Mining and Technology , Xuzhou , 221116 , People's Republic of China |
