China's deep-sea manned submersible Jiaolong started its test dives at the National Deep Sea Center in east China's coastal city of Qingdao on Thursday after going through its first major upgrades.Lasting for 15 months, the upgrades had seen 1,200 parts of the submersible thoroughly checked, while over 2,300 parts replaced.The submersible's main systems including the electric system, sample retrieving system,