   "We're grateful, we're very, very grateful for everybody's
help and we're really happy to have him back home," she said of
herself and the couple's two children.   Hu was released just
ahead of a summit between President Barack Obama and Chinese
leader Xi Jinping, but Li said she didn't know if that played
any part in her husband's return.  She said the first she
learned that he was coming home in a call Monday from a relative
in China, who told her was on a plane to the United States.  "I
don't want to say too much at this point," she said. "I don't
really know too much."   He returned to China in 2004 after
years in the U.S., hoping to get in on the ground floor building
cleaner-running automobiles just as smog-choked China's economy
was booming.  Hu became chief scientist and president of a
company trying to build top-grade catalytic converters and was
honored by the province of Jiangsu as one of its leading
innovators. Li, meanwhile started her own business supplying
materials to the company that emplo