Complex sentence: She completed a postdoc at the Seoul National University in 1990 and was then made a principal research scientist at Korea Ocean Research Institute (KORDI) from 1991 to 2004.
Split into simpler sentences: She completed a postdoc at the Seoul National University in 1990. She was a senior later on a Principal research scientist at Korea Ocean Research Institute (KORDI) from 1991 to 2004.