1. Department of Mathematics, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand
2. Department of Applied Mathematics and Statistics, Faculty of Science and Liberal Arts, Rajamangala University of Technology Isan, Nakhon Ratchasima 30000, Thailand
3. Rail System Institute of Rajamangala University of Technology Isan, Nakhon Ratchasima 30000, Thailand