1. College of Mechanical Engineering Chengdu University Chengdu 610106 P. R. China
2. Antibiotics Research and Re-evaluation Key Laboratory of Sichuan Province Sichuan Industrial Institute of Antibiotics Chengdu University Huaguan Rd. 168 Chengdu 610052 P. R. China
3. Oil Production Plant 5 PetroChina Changqing Oilfield Company Shaanxi Xi'an 710200 P. R. China