[1] Shandong Univ Technol, Sch Math & Stat, Zibo 255049, Shandong, Peoples R China
[2] Shandong Univ Technol, Business Sch, Zibo 255049, Shandong, Peoples R China
[3] Shandong Prov Inst Land Surveying & Mapping, Jinan 250102, Shandong, Peoples R China