supported by the National Natural Science Foundation of China(21004024);the Natural Science Foundation of Fujian Province(2011J01046);the Program for New Century Excellent Talents in University of Fujian Province(2012FJ-NCET-ZR03);the Promotion Program for Young and Middle-Aged Teachers in Science and Technology Research of Huaqiao University(ZQN-YX103);the Special Foundation for Young Scientists of Fujian Province(2011J05131)~~