Supported by the National Natural Science Foundation of China 31200605, by the Doctoral Fund of Ministry of Education of China 20121303120006, by the Natural Science Foundation of Hebei Province C2014205161 and by the Research Funding of Hebei Normal University L2011B14;国家自然科学基金项目31200605;教育部高等学校博士学科点基金项目20121303120006;河北省自然科学基金项目C2014205161;河北师范大学科研基金项目L2011B14