1. Mathematical Sciences, Queensland University of Technology, GPO 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 CF24 4AG, UK
5. Department of Engineering Mechanics, Hohai University, Nanjing 210098, China