1. School of Science, Xi’an University of Architecture and Technology, Xi’an P. R. China
2. School of Mathematics and Information Science, Henan Polytechnic University, Jiaozuo, P. R. China
3. National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, 199 Ren-Ai Road, Suzhou, P. R. China