国家重点基础研究发展计划973计划2012CB720500;国家自然科学基金21006127;中国石油大学北京基础学科研究基金JCX K-2011-07资助Supported by National Basic Research Program of China 973 Program2012CB720500;National Natural Science Founda-tion of China21006127;Basic Subject Research Fund of China University of PetroleumJCXK-2011-07