[1] Univ Petr, Dept Appl Phys, Dongying 257062, Peoples R China
[2] Suzhou Inst Urban Construct & Environm Protect, Dept Basic Courses, Suzhou 215011, Peoples R China
[3] Shanxi Normal Univ, Dept Phys, Linfen 041004, Peoples R China
[4] Beijing Inst Technol, Dept Appl Mech, Beijing 100081, Peoples R China