Dr. An Tzu Yang, known as Andy, who developed a geometric theory for broad use, died on Nov. 21 in Woodland, Calif. He was 80.
Dr. Yang was born in Shanghai, China, Oct 5, 1923. He fled the Japanese-occupied province in 1942 for the ancient city of Xian in northwest China. Living in a mud shack with no electricity, he earned his bachelor's degree from the Northwestern College of Engineering, a school for refugees in Xian. Dr. Yang immigrated to the United States in 1949 and earned a master's degree at Ohio State University and a doctorate at Columbia. His doctoral dissertation is often credited with modernizing the theory of screws that uses geometry to explain the forces acting on any solid object, like a car, as it moves through space. Today, it is one of the most heavily cited papers in its field. He retired in 1991. Throughout his career he won many awards and was a member of several scientific organizations, including the New York Academy of Sciences.
He is survived by his wife of 50 years and two sons, Eton Y., of Davis, Calif., and Yuelin T., of Singapore. (Source: Anahad O'Connor, The New York Times, Dec. 8, 2003; Bowker Biographical Dictionary).