1. Department of Applied Mathematics, School of Sciences, Xi’an University of Technology, P.O.Box 1243, Yanxiang Road No. 58, Xi’an, Shaanxi 710054, People’s Republic of China
2. Department of Mathematics and Institute for Scientific Computing and Applied Mathematics, Indiana University Bloomington, 729 East Third Street, Bloomington, IN 47405, USA
3. School of Science and Engineering, The Chinese University of Hong Kong (Shenzhen), 2001 Longxiang Blvd., Longgang District, Shenzhen, Shenzhen 518172, People’s Republic of China