Harry F. Tiersten – Renowned Theoretician on Piezoelectric Plate Vibrations 1930 – 2006 Prof. Harry Tiersten, a faculty member of the Renssaeler Polytechnic Institute (RPI) in the Department of Mechanical, Aerospace, and Nuclear Engineering passed away suddenly from a heart attack on June 12, 2006. Professor Tiersten was an unusual combination of an outstanding researcher, a gifted lecturer and teacher, and a strong source of guidance and inspiration for his graduate students. He is considered to be one of the founders of the macroscopic theories of continuum electrodynamics. He is the author of two technical books and of many research papers published in technical journals. Harry F. Tiersten was born in 1930 and grew up in the Far Rockaway section of Queens, New York City. He received a B.S. degree in civil engineering in 1952, and went on to earn M.S. and Ph. D. degrees in engineering mechanics in 1956 and 1961. All three degrees were awarded by Columbia University. At Columbia, his graduate study and doctoral dissertation were carried out under the guidance of Prof. Raymond Mindlin. His professional career was spent primarily at two illustrious institutions. From 1961 to 1967, he was a member of the Technical Staff at Bell Telephone Laboratories (now the Lucent Corp.) at two locations, first at Whippany NJ and later at Murray Hill NJ. From 1967 until his death, he served on the faculty of RPI. Dr. Tiersten had a distinguished and internationally recognized career. One of his early contributions after joining Bell Telephone Laboratories was to write the theoretical section of ANSI/IEEE Std 176-1978, “Standard on Piezoelectricity”. His first book “Linear Piezoelectric Plate Vibrations”, published in 1969 by Plenum Press, has been a major reference on the theory of piezoelectric vibrations ever since its publication. After his earlier contributions to the linear theory of piezoelectricity, Dr. Tiersten went on to develop the theory of nonlinear electroelasticity for large deformations and strong fields, the linear theory for infinitesimal fields superposed on large biasing fields, and the perturbation theory for frequency shifts in piezoelectric resonators. In the areas just mentioned, these theories continue to influence the work of present day researchers. His contributions also extend to theories for general nonlinear interactions of elastic deformations with electromagnetic fields in continuous media, including thermal effects and conduction or semiconduction. His distinctive point of view in this area of work is presented in his second book, completed late in his career, “A Development of the Equations of Electromagnetism in Material Continua”, published by Springer-Verlag in 1990. He was also highly regarded in the mechanics community internationally. He is considered to be one of the founders of the study of macroscopic theories of continuum electrodynamics. His style was exemplary of Mindlin’s school of applied mechanics researchers, ranging from fundamental theories to applications in technology. For example, Dr. Tiersten’s work on the sensitivity of resonator frequency to acceleration done in the 1980s is crucial to satellite systems in use today. During his career, Dr. Tiersten was the recipient of a number of honors and awards. He was a fellow of the Institute of Electrical and Electronic Engineers (IEEE), the Acoustical Society of America, and the American Society of Mechanical Engineers. He was a member of the American Physical Society and the Society of Engineering Science organizations. He was the recipient of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) Society C. B. Sawyer award in 1979, “for contributions to the theory of piezoelectric resonators”. He received the IEEE UFFC Society’s Achievement Award in 1993 “for developing several rational theories for analyzing the electroelastic behavior in anisotropic crystals, including piezoelectric, nonlinear and energy-trapping effects for bulk and surface acoustic waves”. He was awarded the Fellow membership grade of the IEEE in 1995 with the citation “for contributions to the analysis of thickness-shear quartz resonators and surface acoustic wave devices”. Dr. Tiersten is survived by his wife of 53 years, Helen, and by a daughter, Linda, and a son, Steven. Prof. Tiersten will be remembered as a man of great character and intellectual ability, with honesty and integrity as his core values. He will be missed by all who knew him; but his family, his former students, and his many friends can take some consolation in the fact that the work he has created will have an impact on the field of continuum mechanics far into the future.