1. Center for General Education, China Medical University, Taichung, Taiwan
2. Center for Fundamental Science, and Research Center for Nonlinear Analysis and Optimization, Kaohsiung Medical University, Kaohsiung, Taiwan
3. Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
4. Department of Mathematics, Kunming University, Kunming, People's Republic of China