1. School of Mathematical Sciences, Queensland University of Technology, P.O. Box 2434, Brisbane, QLD 4001, Australia
2. Department of Mechanical Engineering and Energy Processes, Southern Illinois University, Carbondale, IL 62901, USA
3. Department of Mathematics, The University of Jordan, Amman 11942, Jordan
4. School of Mathematics, Cardiff University, Cardiff CF2 4YH, UK
5. Department of Engineering Mechanics, Hohai University, Xikang Road No. 1, Nanjing, Jiangsu 210098, China