国家自然科学基金51276033;东北电力大学博士科研启动基金BSJXM-201208;东北电力大学科研提升基金批准号:KYTSQN-201204资助的课题.*Project supported by the National Natural Science Foundation of ChinaGrant 51276033;the Doctoral Scientific Research Startup Foundation of Northeast Dianli University, ChinaGrant BSJXM-201208;the Scientific Research Ascension Foundation of Northeast Dianli University, ChinaGrant KYTSQN-201204