时 间： 2018年6月26日上午9:00-12:00
地 点： 航空楼A310
邀请人： 王栋 教授
报告题目：Some Examples of Complexity-induced Coexistence of Traveling and Standing Waves in One-dimensional Linear Elastic Continua
报告人：Prof. Lawrence A. Bergman Department of Aerospace Engineering University of Illinois at Urbana-Champaign
摘 要：It has long been known, for non-dispersive one dimensional continua such as undamped linear elastic axial bars and taut strings of finite length subjected to harmonic base motion at one end, that a simple viscous damper at the opposite end can be designed to be a perfect absorbing boundary at a single operating frequency. However, development of the generalization, in which mode complexity due to a viscously damped local subsystem located nearly anywhere in the interior is employed to separate traveling and standing waves in the continuum, is a relatively new development. I will provide some background to the problem and discuss several examples including the taut string and the rigid circular acoustic wave guide. Some more recent results for a dispersive continuum, the Euler-Bernoulli beam, will also be briefly examined. The method provides the means to effectively transfer and localize vibrational energy within a continuum and may have application to isolation and energy harvesting.
报告人简介：Professor Lawrence A. Bergman received the B.S. in Mechanical Engineering from the Stevens Institute of Technology, and the M.S. in Civil Engineering and Ph.D. in Applied Mechanics from Case Western Reserve University. He works primarily in the areas of structural dynamics and control, nonlinear dynamics, applied stochastic processes, system identification, and computational methods. He is the author of more than 250 articles in archival journals and books, has co-authored one research monograph, edited or co-edited 6 volumes, and holds 5 United States patents. He was the co-recipient of the 1983 State of the Art in Civil Engineering Award and the 1999 Norman Medal from ASCE, and the recipient of the 2001 Senior Research Prize in Computational Stochastic Mechanics from the International Association for Structural Safety and Reliability. He was editor-in-chief of the ASME Journal of Vibration and Acoustics from 2000- 2004, and served as Chair of the Executive Committee of the Applied Mechanics Division of ASME in 2013-2014. Professor Bergman has been a faculty member at the University of Illinois at Urbana-Champaign since 1979, where he is currently research professor and professor emeritus in the Dep’t of Aerospace Engineering. He is a Fellow of ASME and an Associate Fellow of AIAA.
报告题目：Acoustic Wave Separation
摘要：An anechoic environment is normally required to conduct accurate measurement of sound quantities generated by a sound
source of interest in practice of nearfield acoustic holography. In many cases in reality, however, it is impossible to provide such a kind of ideal acoustical environment, for example, measuring sound radiation using microphone array from complex and over sized vibrating structures in spaces with reflective boundaries; assessing in-situ noise level and objective sound qualities of equipment and products in manufacturing or operating environments. This talk presents a study of acoustic wave separation, aiming for obtaining accurate sound quantities from a targeted source
in non-free sound field by eliminating the contribution from disturbing sources or reflecting boundary; directing acoustic energy to specified space to induce airborne acoustic impedance discontinuity for echoless sound space.