1. College of Computer Science and Electronic Engineering, Hunan University, 12569 Changsha, Hunan, China, 410082 (e-mail: weiliang99@hnu.edu.cn)
2. College of Computer Science and Electronic Engineering, Hunan University, 12569 Changsha, Hunan, China, (e-mail: 17yhli3@stu.edu.cn)
3. Computer Science Department, Colleage of Engineering, Shantou University, 12386 Shantou, Guangdong, China, (e-mail: xujianlong@stu.edu.cn)
4. Colledge of Computer Science and Electronic Engineering, Hunan University, Changsha, Hunan, China, (e-mail: zqin@hnu.edu.cn)
5. College of Computer Science and Electronic Engineering, Hunan University, Changsha, Hunan, China, (e-mail: dfzhang@hnu.edu.cn)
6. Dept. of Computer Science and Information Engineering (CSIE), Providence University, Shalu, Taichung, Taiwan, 43301 (e-mail: kuancli@pu.edu.tw)