[1] Suzhou Univ Sci & Technol, Sch Math Sci, Suzhou 215009, Jiangsu, Peoples R China
[2] Univ Ostrava, Inst Res & Applicat Fuzzy Modelling, Ostrava 70103, Czech Republic
[3] Slovak Univ Technol Bratislava, Fac Civil Engn, Dept Math & Descript Geometry, Bratislava, Slovakia