Conferences, Lectures, & Seminars
Events for February
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Astani Department of Civil and Environmental Engineering Seminar
Tue, Feb 02, 2021 @ 11:00 AM - 12:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Dr. Sanjay Govindjee, University of California, Berkeley
Talk Title: Soft and Semi-Soft Elasticity and for Liquid Crystal Elastomers
Abstract: Liquid crystal elastomers present a relatively new and interesting class of materials that display soft and semi-soft elastic behavior as well as viscoelastic behavior. These materials are comprised of liquid crystal molecules together with polymerizing agents to form a final solid that behaves as an elastomeric solid would, as well as like a liquid crystal would. The interaction of these two features provides for a wide and complex range of macroscopically observed phenomena, including for example optical actuation, extreme softness, pattern formation, and high damping to name a few. Because of the wide range of behaviors and the materials highly non-linear properties (material and geometric non-linearities), the modeling of these materials is somewhat challenging. A direct phenomenological approach is generally precluded or only applicable to a small range of loading states. On the other hand, developing models from an atoms-up approach has its own limitations in terms of feasibility. Past efforts mostly involve a compromise and blend of these two approaches, often opaquely, and as such the literature contains a number of different options and viewpoints as to what is important in the modeling of liquid crystal elastomers.
In this presentation, we revisit a number of proposed models for liquid crystal elastomers and try to clearly articulate their meaning. We do this by first examining the fundamental physics associated with the materials constituents. From there we build up, using statistical mechanics arguments, the appropriate structures for describing the materials free-energy functions. This will lead us to an understanding of the meaning of the so-call trace formula for soft elasticity, allowing us to give a precise statement as to what it accounts for and what it does not account for. In particular, we will see that the trace formula is not a strictly entropic result, but rather a hybrid relation. We will also see that the mathematical structure of this energy fails to be quasi-convex and we will discuss the implications of this defect for the solution of boundary value problems with regard to existence of solutions, quasi-convex approximations, and modeling of microstructure evolution. We will next examine microstructural feature of poly-dispersity and see that it gives rise to semi-soft elasticity, and compare and contrast the resulting model structure with a some phenomenological proposals found in the literature for semi-soft elasticity. Time permitting, we will also examine the unique nature of the governing balance laws for these materials which lead to non-symmetric Cauchy stresses.
Biography: Sanjay Govindjee is a Professor of Civil Engineering and the Horace, Dorothy, and Katherine Johnson Endowed Professor at the University of California, Berkeley (1993-2006, 2008-present). His main interests are in theoretical and computational mechanics with an emphasis on micro-mechanics, shape memory alloys, and elastomers. Prior to joining Berkeley he worked as an engineer at the Lawrence Livermore National Laboratory (1991-1993) in Livermore, California. He was also Professor of Mechanics at ETH Zürich (2006-2008) in Zürich, Switzerland.
Sanjay Govindjee obtained a Ph.D. in Mechanical Engineering with a minor in Physics from Stanford University in 1991 under the guidance of the late Prof. Juan C. Simo and a M.S. in Mechanical Engineering from Stanford University in 1987. His S.B. is in Mechanical Engineering from the Massachusetts Institute of Technology in 1986.
Noteworthy honors include a National Science Foundation Career Award, the inaugural 1998 Zienkiewicz Prize and Medal, an Alexander von Humboldt Foundation Fellowship 1999, a Berkeley Chancellor's Professorship 2006-2011, and a guest Professorship at ETH Zürich 2008-2013. In 2015 he was named a Fellow of the US Association for Computational Mechanics. In 2018 he received a Humboldt-Forschungspreis (Humboldt Research Award).
He currently serves as the Principal Investigator and co-Director of the National Science Foundation Natural Hazards Engineering Research Infrastructure SimCenter at Berkeley
Host: Dr. Roger Ghanem
Location: Zoom Meeting https://usc.zoom.us/j/97228056404 Meeting ID: 972 2805 6404 Passcode: 864779
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani Department of Civil and Environmental Engineering Seminar
Tue, Feb 09, 2021 @ 11:00 AM - 12:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Yu Hou, Civil Engineering Ph.D. Candidate, Astani Department of Civil and Environmental Engineering
Talk Title: An Innovative Approach to RGB Point Cloud and Thermal Information Data Fusion for Building Thermal Map Modeling Using Aerial Images: Fusion Performance Results under Different Experimental Conditions
Abstract: Three-dimensional thermal mapping provides many benefits for auditing building energy performance when compared with 2D thermal images that provide only limited representation. However, the current thermal mapping approaches have accuracy and efficiency tradeoffs when modeling large areas using aerial images. In particular, low-resolution thermal images make it harder to obtain a high-quality thermal mapping model. To avoid using low-definition thermal images to reconstruct building thermal models and improve the performance of large-area thermal mapping, we proposed a thermal and RGB data fusion framework for thermal mapping. This presentation aims to explain how different experimental conditions on the proposed fusion approach affected the results. The evaluated conditions included different camera altitudes (60 meters and 35 meters), distinct camera angles (45 degrees and 30 degrees), diverse flight path designs (mesh grid and Y path), and various building styles (university campus buildings and buildings in a central city area). The results demonstrated that different performances of conducting the proposed data fusion approach under different conditions were observed, and the study provides suggestions for using this approach in such conditions.
Biography: Yu Hou is a Ph.D. candidate working with Dr. Lucio Soibelman. He received his M.S. degree in construction management from China University of Mining and Technology. He joined USC in 2016 and earned a M.S. degree in computer science from USC in 2019. He is expected to graduate in May 2021. His research focuses on improving building energy efficiency by automatically detecting heat loss and moisture areas on building envelopes from 3D thermographic models reconstructed by drone-based thermal images.
Host: Dr. Burcin Becerik
Location: Zoom Meeting https://usc.zoom.us/j/97228056404 Meeting ID: 972 2805 6404 Passcode: 864779
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani Department of Civil and Environmental Engineering Seminar
Tue, Feb 16, 2021 @ 11:00 AM - 12:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Dr. Chung-Yuen (Herbert) Hui, Proessor, Cornell University
Talk Title: The role of surface stress on the mechanical behavior of soft solids
Abstract: Soft solids are ubiquitous: gels, foams, biomaterials, rubbers, and the stuff that makes up our very bodies. They are orders of magnitude more compliant than conventional engineering materials (e.g., stiff materials such as metals and ceramics). For this reason, the mechanical behavior of stiff solids is controlled by the resistance to bulk deformation: elasticity, plasticity, and the like; the mechanical role of the surface is utterly negligible, as noted by Gibbs. However, the surface of common soft solids carries considerable stress, just as liquids have a surface tension. Consequently, for soft solids, the pervasive influence of surface stress has required re-thinking a wide range of mechanical phenomena and properties. In this talk, I will show examples of phenomena where surface stress has radically changed mechanical behaviour. For example, how small particles interact with soft substrates can be governed more by surface stress than by the elasticity of the substrate. Surface stress can modify adhesion on rough surfaces by flattening them. The contact angle in partial wetting is no longer always governed by Young equation -“ it depends on the surface stress of the solid substrate as well as its elasticity.
Biography: Dr. Chung-Yuen(Herbert)Hui is the Joseph-Ford Professor of Mechanical and Aerospace Engineering(MAE)of Cornell University. He has a Bachelor of Science degree from the University of Wisconsin-Madison majoring in Physics and Mathematics. He received his Master degree in Applied Math and Ph.D.degree in Solid Mechanics from Harvard. He joined the Department of Theoretical and Applied Mechanics(TAM)at Cornell University in 1981 and stayed until 2010, when TAM became part of MAE. His primary research interest is Physics and Mechanics of materials. His recent research is primarily focused on adhesion science, fracture mechanics and mechanics of soft matter. He was the Chairman of Gordon Conference on Adhesion in 2010 and received the Adhesion Society Award for Excellence in Adhesion Science in 2011. He enjoys teaching and received several teaching awards including Tau-Beta-Pi Excellence in Teaching Award.
Host: Dr. Qiming Wang
Location: Zoom: https://usc.zoom.us/j/97228056404; Meeting ID: 972 2805 6404: Passcode: 864779
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani Department of Civil and Environmental Engineering Seminar
Tue, Feb 23, 2021 @ 11:00 AM - 12:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Jin Wen, Ph.D., Professor, Department of Civil, Architectural, and Environmental Engineering, Drexel University
Talk Title: Data Driven Smart Buildings
Abstract: Please see attachment.
Host: Dr. Burcin Becerik-Gerber
More Information: J. Wen_Abstract-Bio 2232021.pdf
Location: Zoom: https://usc.zoom.us/j/97228056404; Meeting ID: 972 2805 6404: Passcode: 864779
Audiences: Everyone Is Invited
Contact: Evangeline Reyes