supported by the Doctoral Fund of Ludong University(LY2013001,LY201222);Science and Technology Development Projects of Shandong Province(2012YD01056);Shangdong Province Young and Middle-Aged Scientists Research Awards Fund(BS2013SF029);National Natural Science Foundation of China-Tianyuan Fund for Mathematics(11426126);Natural Science Foundation of Shandong Province(ZR2014AP007)