"H. Xu,H. Kamada,S. Nomura,H. Chikaraishi,H. Tsutsui,T. Isobe","A Simple Calculation Method for Center Magnetic Flux Density of a Magnetic Core Electromagnet With a Wide Air Gap",,"IEEE Transactions on Applied Superconductivity",,"vol. 32","no. 6","pp. 1-6",2022,Sept.