[1] Pusan Natl Univ, Sch Elect Elect & Comp Engn, Busan, South Korea
[2] Ulsan Natl Inst Sci & Technol, Dept Math Sci, Ulsan, South Korea
[3] Kyonggi Univ, Dept Comp Sci, Suwon, South Korea
[4] Kyungpook Natl Univ, Dept Math, KNU Ctr Nonlinear Dynam, Daegu, South Korea
[5] Catholic Univ Daegu, Dept Math Educ, Daegu, South Korea