Development of MFL system for in-pipe robot for unpiggable natural gas pipelines. - Dae-Kwang Kim; Hui-Ryong Yoo; Jung-Soo Yoo; Dong-Kyu Kim; Sung Ho Cho; Sung-Ja Koo; Rho-Yong Woo; Hae-Kyo Jung (URAI, 2013)