教育部人文社会科学研究青年基金项目10YJCZH069;国家自然科学青年基金项目41201190;西北大学“仲英青年学者”支持计划联合资助.[Co-funded by Humanities and Social Science Research Program for Young Scholars from Ministry of Education of China10YJCZH069;National Natural Science Foundation of China41201190;Chung Ying Young Scholars Program of Northwest University]