Department of Mathematics, Dalian University of Technology, Liaoning 116024, P.R.China;
School of Science, University of Science and Technology Liaoning, Liaoning 114051, P.R.China;
Department of Mathematics, Dalian University of Technology, Liaoning 116024, P.R.China;
Department of Basic Sciences, Shenyang Institute of Engineering, Liaoning 110136, P.R.China;
School of Science, University of Science and Technology Liaoning, Liaoning 114051, P.R.China;