Jack H. Vollbrecht, president and chief executive officer of Aerojet-General Corp. until his retirement in 1981, has been elected to the UNC Resources board of directors. Vollbrecht has been chairman of the board of Frontier Airlines Inc.; vice president and group executive of International Telephone & Telegraph Corp., and vice president of Dresser Industries Inc. He also serves as a director of Geosource Inc., a petroleum industry supplier, and of For Better Living Inc., an industrial and publishing company based in California.

Ricardo R. Alvarado has been named vice president of government relations in the Washington office of the Signal Cos. Inc. He succeeds Frank Sanders, who has retired. Alvarado was formerly corporate director of government relations for Lockheed.

Brian Riley has been appointed Flow General's director general of international operations, a newly created position. Riley joined the company in 1972 as manager of the Flow Laboratories operation in Bonn, Germany. He was most recently responsible for the international sales and marketing of Flow General. In his new job, Riley will be in charge of all of the company's biomedical activities outside the United States, including product distribution for Worthington Diagnostic Systems, which Flow General acquired in March.

Sterling Solomon and Charlie Martin have joined the senior staff of Physical Dynamics Inc.

Dr. Richard Axel, a professor in the Columbia University departments of pathology and biochemistry and in its Institute of Cancer Research, has been elected to the board of directors of Bethesda Research Laboratories Inc.

Richard E. Duffy has been named executive vice president of the George Hyman Construction Co. He was previously vice president of operations for Turner Construction Co. in New York.

Kenneth E. Lanham has been appointed manager of unmanned tactical weapons systems at Fairchild Republic Co., a wholly-owned subsidiary of Fairchild Industries. Lanham formerly had his own consulting firm here.