Affiliation: | 1. Department of Mathematics, Texas A & M University-Kingsville, 700 University Blvd., Kingsville, TX 78363-8202, USA;2. Department of Mathematics and Statistics, Missouri S&T, Rolla, MO 65409-0020, USA;3. Qingdao Technological University, Feixian, Shandong 273400, PR China;4. School of Control Science and Engineering, Shandong University, Jinan, Shandong 250061, PR China |