Teradyne, a Boston supplier of automatic test equipment and interconnection systems, announced that its president, Michael Bradley, has been named chairman and CEO, effective May 27, and has been elected as a director. He succeeds George Chamillard, who will continue as the company's chairman.   . . .   Agilent Technologies announced it has established a system-on-a-chip (SOC) design center in Gurgaon, India, near New Delhi. The center, part of an existing facility that employs 1000 Agilent workers, provides ASIC (application-specific integrated circuit) and system design services to customers of Agilent's ASIC Products Division. Agilent said it expects the SOC design center to be staffed with approximately 50 engineers by the end of 2004. Agilent also has ASIC design centers in Fort Collins, Colo.; Corvallis, Ore.; Boise, Idaho; Santa Clara, Calif.; Penang, Malaysia; and Singapore.   . . .   Mozak Systems Inc., a Red Wing, Minn.-based semiconductor process cleaning equipment manufacturer, announced it has been appointed by Dyntest, of Grassau, Germany, to be its sales and service representative in North America and Asia. Dyntest is a manufacturer of Scriber breaker systems for compound semiconductor, optical, laser and thin-silicon applications.