Seminar Series: Dr. Kallivokas Shares Expertise on Wave Driven Inverse Problems

College Station, TX-

Dr. Loukas Kallivokas, PhD, PE, and Professor at the The University of Texas at Austin, visited Texas A&M University on October 6th to present his work on “Wave Driven Inverse Problems: From Full-Waveform Imaging to Wave-Shielding Metasurfaces,” to Civil Engineering Graduate Students. The graduate seminar, Structures, Geotechnical and Construction Division is instructed by Dr. Zenon Medina-Cetina, Associate Professor in the Zachry Department of Civil and Environmental Engineering at Texas A&M University.

Dr. Kallivokas, originally from Athens, Greece, has been working at the University of Texas since 1999 when he joined the Department of Civil, Architectural and Environmental Engineering as an assistant professor. He currently holds the position of Professor and the Brunswick-Abernathy Regents Professorship in Soil Dynamics and Geotechnical Engineering at UT-Austin. He has an MSc in Civil Engineering (1990) and a PhD in Computational Mechanics (1995) from Carnegie Mellon University. His research interests span computational engineering and sciences, with a focus on wave mechanics and their applications.

His presentation focused on recent progress in closely related inverse problems driven by elastic waves. First, he addressed the full-waveform-based imaging of probed solids. The driving problem is like geophysical probing, an inverse medium problem, albeit here the focus is on the characterization of the near-surface deposits.

Two key ingredients to the problem:

1. Modeling of the forward problem, which involves the numerical simulation of wave propagation in PML (perfectly-matched-layer)-truncated domains in the time-domain.

1. Inverse medium problem and the schemes we have implemented in an attempt to lend robustness to the inversion process. He reported successful imaging with synthetic and field data in 3D using elastic waves and involving hundreds of thousands of unknow subsurface properties.

Second, he discussed inverse metamaterial design for achieving user-defined band gaps in periodic structures with wave shielding applications in mind. A systematic procedure based on a Floquet-Bloch dispersion-constrained inversion approach is shown to be capable of producing metasurfaces exhibiting the prescribed band gaps, including omni-directional gaps for elastic waves. He reported numerical experiments that demonstrate feasibility for constructing omni-wave and omni-directional shields exhibiting sub-wavelength performance in 2D and 3D.*

*Abstract & Bio provided by Dr. Loukas Kallivokas