School of Mathematics and Statistics, Xian Jiaotong University, Xian, China.|Department of Mathematics, Hong Kong Baptist University, Hong Kong.|Department of Mathematics, Hong Kong Baptist University, Hong Kong.|Centre of Quantitative Medicine, Duke-NUS Medical School, Singapore.|Department of Mathematics, Hong Kong Baptist University, Hong Kong.|Department of Computer Science, Hong Kong Baptist University, Hong Kong.|School of Mathematics and Statistics, Xian Jiaotong University, Xian, China.