国家自然科学基金项目21003163;中央高校基本科研业务费科研专项106112013025;重庆大学SRTP资金资助项目CQU-SRTP-2014378;the National Natural Science Foundation of China21003163;the Fundamental Research Funds for the Central Universities106112013025;SRTP by Chongqing UniversityCQU-SRTP-2014378