两个学术讲座通知

发布时间： 2012-05-02

日期：2012年5月8日

时间： 下午3-4:30

地点：交通大楼604

讲员： Vipperman副教授

题目：Structural Acoustics and Active Structural Acoustic Control（结构声学与结构声主动控制）

内容摘要：

Sound radiation from vibrating structures can often be found in launch vehicles, aircraft, automobiles, and ships. Severe radiation sound can worsen the environment for living things and instruments on board. Researchers have paid extensive effort to reduce sound radiation from structures. This talk will outline fundamental structural acoustic theory and then present some applications. The Kirchoff-Helmholtz integral equation and Rayleigh integral will be presented along with the theory governing sound radiation from infinite and finite structures. Of particular importance for finite structures, is the self- and mutual radiation efficiencies. The wavenumber transform will be presented as a popular tool for determining radiation conditions. The first application will be transmission loss through panels and cylinders. Next, an experimental implementation of a multivariable feedback active structural acoustic control system is demonstrated on a piezostructure plate with pinned boundary conditions. Here, four adaptive piezoelectric sensoriactuators provide an array of truly collocated actuator/sensor pairs to be used as control transducers. Radiation filters are developed based on the self- and mutual-radiation efficiencies of the structure and are included into the performance cost of an H₂ control law which minimizes total radiated sound power. In the cost function, control effort is balanced with reductions in radiated sound power. A similarity transform which produces generalized velocity states that are required as inputs to the radiation filters is presented. Up to 15 dB of attenuation in radiated sound power was observed at the resonant frequencies of the piezostructure.

日期：2012年5月9日

时间： 上午9-10:30

地点：交通大楼604

讲员： Vipperman副教授

题目：Thermoacoustic Refrigeration （热声制冷）

内容摘要：

Thermoacoustic effects, which convert heat energy to sound or use sound wave to pump heat, have been known for over a hundred years. They have generally been considered mere curiosities till the early 1980s. Since then, significant efforts on thermoacoustic multi-physics and experimental investigation have been made, and some environmentally friendly themoacoustics-based sound power devices, without moving parts, have been developed. One promise technology among them is the thermoacoustic refrigerators (TARs), which can use low-grade waste heat for refrigeration. As reported by the scientists in the Naval Postgraduate School in US, the thermoacoustic refrigeration system has the greatest potential to replace the second generation refrigeration system, currently used in Navy ships. Both standing wave and traveling wave versions of TARs exist. The former is simpler, but less efficient, while the latter is thermodynamically a Stirling engine. Work on standing wave TARs at the University of Pittsburgh looked at optimization and control methods. Additional work has also numerically and experimentally investigated traveling wave TARs. In particular, the influence of thermal conductivity and the effects of curvature (for miniaturization) on performance have been examined, along with multi-objective optimization methods used for design.

讲员简介

Jeffrey S. Vipperman

Associate Professor

Department of Mechanical Engineering and Materials Science

Department of BioEngineering

Director of Mechanical Engineering Graduate Studies

Director, Sound, Systems and Structures Laboratory

University of Pittsburgh

jsv@pitt.edu, 412-624-1643

Dr. Jeffrey S. Vipperman is an Associate Professor of Mechanical Engineering & Materials Science and Bioengineering at the University of Pittsburgh. He is also the founder and Director of the Sound, Systems and Structures Laboratory at Pitt. He earned BSME and MSME degrees from Va Tech and a PhD from Duke University. Over 75 publications have been authored or coauthored by Dr. Vipperman along with 116 presentations. He has also written two book chapters and has filed for his third patent. Dr. Vipperman has over 20 years of experience in the area of acoustics, vibrations, controls, and signal processing and has brought in over $7.1M ($2.8M as principal investigator) in current and past research funding from NSF, SERDP, NIOSH, US Air Force, Army, DARPA, US Dept. of Energy, and industry. He maintains close ties with industry through consulting and industrial research projects. During his tenure as a professor, he has mentored over 80 undergraduate and 20 graduate researchers and received the 2006 Beitle-Veltri Memorial Teaching Award, the 2011 Visiting Committee Outstanding Educator Award, a 2011 Pitt Innovator Award, and is a Fellow in the American Society of Mechanical Engineers (ASME). He currently serves as an Associate Editor for the ASME Journal of Vibration and Acoustics and is past chair of the Noise Control and Acoustics Division of ASME. He also co-chairs a panel to revise ANSI S1.1 Acoustical Terminology.