Keynote Speakers

Keynote Speakers

Prof. C.W. Lim
Department of Architecture and Civil Engineering, City University of Hong Kong, China

Short Bio: Currently a fellow of ASME, ASCE, EMI and HKIE, Ir Professor Lim received a B.Eng. from University of Technology of Malaysia, M.Eng. and PhD from National University of Singapore and Nanyang Technological University, respectively.  Prior to joining City University of Hong Kong, he was a post-doctoral research fellow at The University of Queensland and The University of Hong Kong.  He is also a visiting professor at various universities worldwide.  He has expertise in theory of plates and shells, dynamics of smart piezoelectric structures, nanomechanics, metamaterials and symplectic elasticity.  He is currently the subject editor for Journal of Sound and Vibration, joint-editor for Journal of Mechanics of Material and Structures, subject editor for Applied Mathematical Modelling, Managing Editor (Asia-Pacific Region) for Journal of Vibration Engineering & Technologies, Associate Editor for International Journal of Bifurcation and Chaos, etc. and also on the editorial board of some other top-ranked international journals.  He has published one very well-selling title entitled “Symplectic Elasticity”, co-authored with W.A. Yao and W.X. Zhong from Dalian University of Technology, as recorded by the publisher, World Scientific, in Engineering Mechanics and Mechanical Engineering.  He has published more than 370 international journal papers and have more than 14,500 citations.  His paper on the nonlocal strain gradient theory has attracted over 1,150 citations since first published in 2015.  Professor Lim was awarded the prestigious 2020 JN Reddy Medal as a recognition “for significant and original contributions to vibration of plates and shells, smart piezoelectric structures, nanomechanics, and symplectic elasticity”.  Recently he was elected by secret votes to deliver a Plenary Lecture at WCCM/APCOM 2022, the largest biennial meet for computational scientists worldwide.  He was also invited to chair another plenary lecture.  WCCM 2020 recorded over 400 mini-symposia and over 5,000 papers accepted.  He was also previously awarded Top Referees in 2009, Proceedings A, The Royal Society.  Professor Lim is a registered professional engineer in Hong Kong.

Speech Title: Voltage Controlled Topologically Protected Wave Propagation in Dielectric Membrane-type Acoustic Metamaterials

Abstract: Topological acoustic metamaterials have attracted enormous research attention in recent years.  A significant hallmark of these structures is that they can support interface modes that are robust to structural disturbance and protected by topology.  However, most of the studies are often limited to the passive structures that manifest wave propagation at fixed frequency ranges.  In view of the shortage of non-passive topological acoustic metamaterials, this work has a primary motive to study the active control of topologically protected wave propagation in soft dielectric membrane-type metamaterials (MAM) based on quantum spin Hall effect (QSHE).  The unit cell of the periodic structure is designed with symmetry. Then, the plane wave expansion method is adopted to analytically capture the system dispersion properties.  A finite element model is further developed and excellent convergence with the analytical result is presented.  By adjusting locations of spraying discs in the honeycomb unit cell, mode shape inversion is observed, separating the topologically trivial state from the nontrivial counterpart.  Consequently, the topologically protected interface modes (TPIMs) are observed.  Additionally, an electrical voltage that lies within the locking-up limit is applied to MAM to actively control the working frequency of the TPIM.  Further, several waveguide paths are designed to control the robust wave propagation in the structure.  Conclusively, a voltage-controlled topological metamaterial is designed to actively tune the working frequency range of the device.