A notice on the platform screen doors of the Seoul Metro warns commuters to make sure they don't get their bags trapped in the doors. The woman in the picture is shouting 'a-cha!' (아차!), which roughly translates as 'oops!'.
From Wikipedia (http://en.wikipedia.org/wiki/Seoul_Metropolitan_Subway):
The Seoul Metropolitan Subway, in Seoul, South Korea, is one of the most heavily used rapid transit systems in the world, with well over 8 million trips daily on the system's thirteen lines (total figures for Seoul Metro, Seoul Metropolitan Rapid Transit Corporation & Korail commuter lines). The system serves Seoul, Incheon, Gyeonggi-do and northern Chungcheongnam-do. There is a connection to the Incheon International Airport Railroad (A'REX) at Gimpo Airport Station on Line 5 and a free transfer with the single-line Incheon Subway system at Bupyeong on Seoul Subway Line 1. Over 70% of the total metro track length is underground. By 2008, all stations operated by Seoul Metro and SMRT are all installed with Platform Screen Doors, but only for Seoul area, excluding areas operated by Korail.
Curves adjustment to brighten in CNX2