Workers of the Guangzhou Railway Corporation check the high-voltage power module of a CRH high-speed train at a maintenance center in Changsha, capital of central China's Hunan Province, late Jan. 9, 2012. Dubbed "wingless aeroplanes" for their high speed, China's CRH trains require precise maintenance to ensure their smooth running: timing for the maintenance process of a 200-meter train is measured with minute-level accuracy. Each CRH train is sent to the maintenance center for a rudimentary inspection after running for 48 hours or covering a distance of 4,000 kilometers. Maintenance workers have to tighten up about 3,000 screws for the train's running gear alone. But prior to detailed inspection and maintenance, workers need to make a technical diagnosis using data retrieved from a "black box" installed on the train which keeps record of the train's operating status. "Normally we check six trains each day; nine during the Spring Festival travel rush in the previous year," said Liu Yonghua, director of the CRH train maintenance center in Changsha. "The maintenance time of each train is controlled within three and a half hours before the train is back in service without malfunctions." [Xinhua/Bai Yu]