1. School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi’an 710072, China
2. Envision Group, SOHO Zhongshan Plaza, Shanghai 200051, China
3. Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, PO Box 3049, 67653 Kaiserslautern, Germany
4. School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710119, China