The authors greatly appreciate the financial support from Shandong Province Education Department (Grant No. J14LC11), National Natural Science Foundation of China (Grant No. 21406126 and 21576146), Department of Science and Technology of Shandong Pro-vince (Grant No. 2014GSF116001), 973 (Grant No. 2014CB460610), and Department of Science and Technology of Shandong Province (Grant No. 2015ZD-XX0403B03).
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