supported by the National Natural Science Foundation of China(Grant Nos.71471075,11501373,11701380);2015 Scientific Research Project of Shaoguan University(Grant No.S201501017)。
supported by the National Natural Science Foundation of China(11271081);2013 Young Teachers Scientific Research Project of University of International Business and Economics(12QD12)
Research partially supported by National Natural Science Foundation of China(19631040),Ph. D.Program Foundation of Ministry of Education of China and Special Foundation of Academia Sinica.