Three men were sentenced in federal court Thursday for attempting to send material that can be used to make spacecraft and weapons to China.

U.S. Chief Judge Michael Davis sentenced Jian Wei Ding, 51, of Singapore to 46 months in prison. He sentenced Kok Tong Lim, 37, of Singapore to a little more than a year behind bars. Ping Cheng, 46, of Manhasset, N.Y., was sentenced to a year's probation for his part in the operation.

Lim and Cheng received reduced sentences for helping officials in the investigation.

The three men had pleaded guilty this year to one count of conspiracy to violate national export regulations. They were indicted in October 2008.

Between March 2007 and April 2008, the men attempted to export high-modulus carbon-fiber material without an appropriate license. They were attempting to ship the material to the China Academy of Space Technology.

Ding controlled several Singaporean import and export companies, one of which was in the business of acquiring high technology for its customers. One of those customers, according to the indictment, was the China Academy of Space Technology. The academy oversees satellite systems research for the People's Republic of China.

The operation was uncovered after the men unknowingly worked with an undercover Minnesota company posing as a supplier of aerospace commodities.

JAMES WALSH