· Software Engineer, A9/Amazon.com2008–
· Project researcher, National Institute of Informatics2006–
· Instructor, Baruch College2001–
· Instructor, Columbia University2001–
· Teaching Assistant, Columbia University2000–
· Summer intern, IBM Tokyo Research Lab1999–
· Funded Graduated Research Assistant, Columbia University1997–
· Summer internship, NTT Yokosuka Communications Research Lab1996–
· Junior network engineer, Southern Methodist University1995–
· Summer internship, Wang Inc.1992–
· Professor Emeritus of Public Health, Columbia University in the City of New York1980–2019
· Research Assistant, BROOKHAVEN MEMORIAL HOSPITAL1972–1980
· Senior Software Engineering Manager, Amazon