Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China
Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China
Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China
Dept. of Mathematics and Information Science,Tangshan Teachers’ College, Tangshan, China
Copyright © Guangfeng Zhao, Hongli Wang, Yufen Feng, Haiyan Fan et al. This is
an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.