国家自然科学基金项目31370542、国家重点基础研究发展计划973计划2013CBA01807、四川省教育厅创新团队项目14TD0049和西南民族大学研究生创新型科研项目CX2014SZ113资助 Supported by the National Natural Science Foundation of China 31370542,the National Basic Research Program of China 2013CBA01807,the Innovation Team Project of Education Office of Sichuan Province 14TD0049,and the Graduate Innovative Research Project of Southwest University for Nationalities CX2014SZ113