Development of the untethered in-pipe inspection robot for natural gas pipelines. - Jaejun Park; Jeong Whan Moon; Hyoungkwon Kim; Seongcheol Jang; Dae Gyeong Kim; Kitak Ahn; SungMoo Ryew; Hyungpil Moon; Hyouk Ryeol Choi (URAI, 2013)