1. Department of Computing Science, School of Mathematics and Statistics, Northwestern Polytechnical University, Xi’an City, Shaanxi Province 710072, P. R. China
2. Department of Mathematics and Sciences, College of Humanities and Sciences, Prince Sultan University, Riyadh 11586, Saudi Arabia
3. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 40402, Taiwan
4. Department of Mathematics, Faculty of Science, The Hashemite University, P. O. Box 330127, Zarqa 13133, Jordan