国家自然科学基金项目31172068,31471980;重庆市科委基金项目cstc 2010ca1010,cstc 2014jcyja80014;重庆市教委科技项目KJ1400502资助[Supported by the National Natural Science Foundation of China31172068,31471980;the Project of Chongqing Science& Technology CommissionCSTC,2010CA1010,cstc2014jcyjA80014;the Science Research Foundation of the Education Committee of Chongqing No.KJ1400502]