XU Chun-long1,2, LIN Shu-yu1, WANG Cheng-hui1, YANG Qiu-fen3
(1 College of Physics and Information Technology, Shaanxi Normal University, Xi′an 710062, Shaanxi, China; 2 College of Science, Chang′an University, Xi′an 710064, Shaanxi, China3 Department of Physics, Xi′an University of Arts and Science, Xi′an 710065, Shaanxi China)