KENNETH G. McCONNELL, PE, is Professor Emeritus, Aerospace Engineering and Engineering Mechanics, Iowa State University, and has over forty-three years' experience in vibrations and experimental mechanics. He is a Fellow of the Society of Experimental Mechanics, and recipient of SEM's M.M. Frocht Award for "outstanding achievement as an experimental mechanics educator"; SEM's highest award, the William M. Murray Lecturer, for his "outstanding contribution to SEM in the fields of dynamic instrumentation, vibration testing techniques, and fluid structure interaction"; the D.J. DeMichele Award for "promoting the scientific and educational aspects of modal analysis"; and the Brewer Award, "in recognition of his contributions as an outstanding practicing experimental stress analyst." He is the author of Instrumentation for Engineering Measurements, Second Edition (coauthored with James E. Dally and William F Riley and published by Wiley) and other books in the field. PAULO S. VAROTO is professor on Dynamics and Vibrations at the Mechanical Engineering Department, School of Engineering of São Carlos, University of São Paulo. Professor Varoto earned his BSc and MSc in mechanical engineering from the University of São Paulo and holds a PhD in engineering mechanics from the Department of Aerospace Engineering and Engineering Mechanics, Iowa State University, where he worked under the supervision of Ken McConnell.