1. College of Mathematics, Jilin Normal University, Siping, Jilin, PR China
2. School of Science, Shenyang Aerospace University, Shenyang, PR China
3. Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China
4. Department of Industrial Engineering, Management College of Engineering, Peking University, Beijing, PR China