Institution: | a Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea b Department of Information and Communication Engineering, Daejon University, Daejeon 300-716, Republic of Korea c Department of Physics, Pukyong National University, Pusan 608-737, Republic of Korea d Department of Environmental Atmospheric Science, Pukyong National University, Pusan 608-737, Republic of Korea |