The chairman of China's Tsinghua Unigroup traveled to the United States this week to meet with board members of Micron Technology and try to revive a politically fraught takeover bid of the U.S. chipmaker, people familiar with the matter said. Micron dismissed an informal $23 billion offer by state-backed investment firm Unigroup in July on the presumption that the U.S. regulatory committee that reviews foreign acquisitions of sensitive U.S. companies would block the deal on national security concerns, sources have said.