1. Department of Electronic Science Xiamen University Xiamen Fujian People's Republic of China
2. Department of Physics, School of Science Jimei University Xiamen Fujian People's Republic of China
3. Russell H. Morgan Department of Radiology and Radiological Science Johns Hopkins University School of Medicine Baltimore Maryland USA
4. College of Information and Mechanical & Electrical Engineering Ningde Normal University Ningde Fujian People's Republic of China