1. Department of Mathematics, Faculty of Science; King Mongkut's University of Technology Thonburi (KMUTT); 126 Pracha-Uthit Road, Bang Mod, Thung Khru Bangkok 10140 Thailand
2. Theoretical and Computational Science Center (TaCS), Science Laboratory Building, Faculty of Science; King Mongkut's University of Technology Thonburi (KMUTT); 126 Pracha-Uthit Road, Bang Mod, Thung Khru Bangkok 10140 Thailand