Seminars

Seminars are held Wednesdays, at 3:30 pm, in Seaver Science Library, Room 150 (SSL 150), unless otherwise noted. Refreshments are served at 3:00 pm. Call (213) 740-8762 for further information.

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Keynote Lecture Series Archive

Spring, 2019

1/16/19 | Flow Control À la Mode, Maziar Hemati, U. Minn.

Flow Control À la Mode

Maziar Hemati

Assistant Professor
Department of Aerospace Engineering and Mechanics
Unversity of Minnesota, Twin Cities
Minneapolis, MN

Biological flyers and swimmers have a great capacity for interacting with their fluid environments. This ability is demonstrated through the agility, efficiency, and environmental awareness exhibited by numerous creatures, including birds, fish, and insects. While human-engineered systems have benefited from biological inspiration, the performance gains realized have often fallen short of their full potential. A primary limitation to attaining further improvement has been a scarcity of reliable low-dimensional fluid dynamics models, which are often needed (1) to determine the state of a complex flow from available on-board sensors (i.e., flow sensing), and (2) to exploit that knowledge to determine and execute a best course of action for achieving a desired objective (i.e., feedback control). In this talk, we will consider modal decomposition strategies aimed at obtaining low-dimensional dynamical systems models from empirical data. In particular, we will present recent advances in techniques tailored to extract descriptive insights and predictive models from large, streaming, and noisy datasets. The second half of the talk will present a dynamic mode shaping perspective for feedback flow control synthesis. The perspective will be used to highlight a fundamental performance limitation inherent to standard observer-based control structures, suggesting that flow reconstruction from sensor measurements may be inadvisable in some flow control applications.

Maziar Hemati is an Assistant Professor in the Department of Aerospace Engineering and Mechanics at the University of Minnesota, Twin Cities. Dr. Hemati’s research program is aimed at gaining an improved understanding of the various mechanisms required to achieve reliable fluid flow sensing and control in the context of human-engineered systems, including flight vehicles, robotic swimmers, and wind turbine arrays. He is a recipient of the 2019 AFOSR Young Investigator Award. Prior to joining the faculty at the University of Minnesota, he served as a Post-Doctoral Research Associate in the Department of Mechanical and Aerospace Engineering at Princeton University. He earned his Ph.D. and M.S. in Mechanical Engineering and his B.S. in Aerospace Engineering, all from UCLA.

Wednesday, January 16, 2019
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Spedding

1/16/19 | Active and Architectured Structures: From Nematic Elastomers Sheets to Rigidly-Foldable Origami, Paul Plucinsky, U. Minn.

Active and Architectured Structures: From Nematic Elastomers Sheets to
Rigidly-Foldable Origami.

Paul Plucinsky

Postdoctoral Researcher
Department of Aerospace Engineering and Mechanics
College of Science & Engineering
Unversity of Minnesota, Twin Cities
Minneapolis, MN

Thin and slender structures exhibit a broad range of mechanical responses as the competition between stretching and bending in these structures can result in buckling, localized deformations like folding, and tension wrinkling. Active and architectured materials also exhibit a broad range of mechanical responses as features that manifest at the micro and mesoscale in these materials result in mechanical couplings at the engineering scale (thermal/electrical/dissipative/…) and novel function (e.g., the shape memory effect, piezoelectricity in select metal alloys, the immense fracture toughness of Nacre and like materials, …). Given this richness in behaviors, my research broadly aims to address the following questions: What happens when active and architectured materials are incorporated into a thin and slender structures? Do phenomena inherent to these materials compete with or enhance those inherent to these structures? Does this interplay result in entirely new and unexpected phenomena? And can all this be exploited to design new functionality in engineering systems?

In this talk, I will explore these questions in the context of thin sheets of an active material in nematic elastomer as well as architectured sheets designed to fold continuously as origami. For the latter, I will completely characterize all rigidly and flat-foldable origami, and describe an effcient algorithm to compute their designs and deformations. For the former, I will show that a material instability inherent to nematic elastomers at the micron scale is capable of suppressing a structural instability (wrinkling) at the engineering scale. These results provide novel, yet concrete, design guidance for improving the effciency solar sails and the performance of other membrane structures (where wrinkling can be an impediment to their functionality), as well as tools to effciently investigate robust and elegant concepts for deployable space structures, reconfigurable antennas, and soft robotics using origami.

Maziar Hemati is a postdoctoral researcher studying the mechanics of Origami, helical structures and shape memory alloys at the University of Minnesota. He attended University of Michigan, receiving a Bachelors of Science in Civil Engineering (2010) and and Masters of Science in Structural Engineering (2011). He then moved to Caltech, where he received a Ph.D in Mechanical Engineering (2017) studying the deformations of thin nematic elastomer sheets. When not folding paper—and when his Achilles is functioning properly—you can often find him on the basketball court.

Wednesday, January 23, 2019
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

host: Oberai

2/6/19 | Ran Dai

2/13/19 |Quan Nguyen

4/3/19 | Balachandran, U. Maryland

4/10/19 | Owen McCarty, OHSU

4/17/19 | Krishna Garikipati, U. Michigan