1. Department of Physics, Universitas Jenderal Soedirman, Jl. Dr. Soeparno Utara, Grendeng, Purwokerto 53122, Indonesia
2. Department of Mechanical Engineering, Universitas Perwira Purbalingga, Jl. S. Parman No. 53, Purbalingga 53313, Indonesia
3. Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan