MEAM Seminar Series Fall 2012

Seminars are held on Tuesday mornings, with coffee at 10:30 am in the Levine Hall Mezzanine and the seminar beginning at 10:45 am in Wu and Chen Auditorium (unless otherwise noted).

To be added to the MEAM Events mailing list (which sends notifications regarding all departmental seminars and events) please email us at meam-events@lists.seas.upenn.edu.

August 28

Lichao Pan, Ph.D. Candidate, University of Pennsylvania

Advisor: Paulo Arratia
"A subcritical elastic instability in channel flows at low Reynolds number"

Read the Abstract
Fluids containing polymers are of much interest spanning the petroleum, semiconductor, pharmaceutical, and chemical processing industries. They are also frequently encountered in everyday life in foods, paints, and cosmetics. Fluids containing polymer molecules do not flow like water. Even when flowing slowly, these fluids can exhibit hydrodynamic instabilities and a new type of turbulence - the so-called purely elastic turbulence even at low Reynolds numbers (Re) where linear viscous forces dominate non-linear inertial forces. These phenomena, driven by the extra elastic stresses in the flow due to the presence of polymer molecules in the fluid were experimentally observed in flows around objects (cylinders), Couette cells, and curved microchannels. A common feature of the above-mentioned geometries is the presence of curved streamlines, which are necessary for infinitesimal perturbations to be enhanced by the normal stress imbalances in viscoelastic flows. Thus, it is a common assumption that in the absence of curvature and inertia, the flow of viscoelastic fluids is linearly stable.

September 6 ** Special Seminar**

Towne Building, room 337, 2:00pm

Roger Howe, William E. Ayer Professor, Department of Electrical Engineering, Stanford University; Faculty Director, Stanford Nanofabrication Facility; Director of the National Nanotechnology Infrastructure Network (NNIN)
"Nano ElectroMechanical Systems (NEMS) Applications in Information Technology and Energy Conversion"

Read the Abstract and Bio

Abstract: Micro and nano-fabricated sensors (e.g., accelerometers, gyroscopes, and resonators) and actuators (e.g., light valves for projection and cell-phone displays) are commonplace. In this talk, I’ll briefly review decades of efforts to co-fabricate NEMS and CMOS, to provide the background for introducing a new logic device: the nanoelectromechanical (NEM) relay. At Stanford, we have developed a fabrication process for integrating a lateral (in-plane) electrostatic relay. Early in the project, a system application for NEM relays was identified – implementing the programmable routing for FPGAs. I will review the fabrication challenges, contact physics, and the potential post-CMOS integration of NEM relays.

Many NEMS require hermetically sealed, low-pressure ambients, a need that motivated the development of low-cost, wafer-scale vacuum encapsulation technologies. Over the past several years, my group and others at Stanford have been exploring applications that leverage wafer-level vacuum: thermionic energy conversion and vacuum cavity THz sources. Thermionic energy converters were conceived in 1915, demonstrated in 1939, and were the focus of astronomical investments during the space race by NASA and the Soviet Union. These devices, which achieved 15% efficiency, are suitable for wafer-scale processing, using high-temperature materials developed for harsh-environment sensors and other applications. I will review the current state of wafer-scale thermionic converters and potential applications to micro-cogeneration and concentrated solar power. Thermionic emitters are also useful for electron injection – an essential component a wafer-scale vacuum cavity oscillator. These devices have attractive characteristics for efficient generation of power in the THz frequency range.

Biography: Roger T. Howe is the William E. Ayer Professor in the Department of Electrical Engineering at Stanford University. He received a B.S. degree in physics from Harvey Mudd College and an M.S. and Ph.D. in electrical engineering from the University of California, Berkeley in 1981 and 1984. After faculty positions at Carnegie-Mellon University and MIT from 1984-1987, he returned to UC Berkeley where he was a Professor until 2005. His research interests include nano electromechanical system design, nanofabrication technologies, with applications in energy conversion and biomolecular sensing. A focus of his research has been processes to fabricate integrated microsystems, which incorporate both silicon integrated circuits and MEMS. Prof. Howe has made contributions to the design of MEMS accelerometers, gyroscopes, electrostatic actuators, and microresonators. He is an editor of the IEEE/ASME Journal of Micro-electromechanical Systems, was elected an IEEE Fellow in 1996 and was co-recipient of the IEEE Cledo Brunetti Award in 1998, and was elected to the U.S. National Academy of Engineering in 2005. He co-founded Silicon Clocks, Inc., a start-up company commercializing integrated MEMS resonator-based timing products, which was acquired in April 2010 by Silicon Laboratories, Inc. He is the Faculty Director of the Stanford Nanofabrication Facility and in September 2011, he became Director of the National Nanotechnology Infrastructure Network (NNIN).


September 11

Douglas Durian, Professor of Physics, University of Pennsylvania
"Mechanics of Granular Impact"

Read the Abstract and Bio

Abstract: Experiments on the low-speed impact of solid objects into granular media have been used both to mimic geophysical events and to probe the unusual nature of the granular state of matter. Observations have been interpreted in terms of conflicting stopping forces, reminiscent of high-speed ballistics impact in the 19th and 20th centuries when a plethora of empirical rules were proposed. To settle this controversy, we have measured the projectile dynamics during impact and have both reproduced prior observations and have found that the stopping force can be decomposed into the sum of velocity-dependent inertial drag plus depth-dependent friction. Furthermore, by changing the projectile shape and by imposing an upflow of air through the granular medium, we have established that friction acts normal to the projectile surface and that grain contacts are loaded by gravity rather than by the motion of the projectile. This work was done in collaboration with Hiroaki Katsuragi, Patrick Mayor, and Ted Brzinski.

Biography:  My general research interests are in soft condensed matter experiment, with emphasis on jamming and rheology in granular media, foams, emulsions, and colloids. Currently my group is supported by NSF, NASA, Penn’s MRSEC, and Rhodia. Both my undergraduate and graduate degrees are in physics, from The University of Chicago (1994) and Cornell University (1989) respectively. After a postdoctoral fellowship at Exxon Research and Engineering, I joined the physics faculty at the University of California Los Angeles in 1991. In 2004, I became Professor of Physics at the University of Pennsylvania. In addition I have enjoyed visiting positions at laboratories in Paris and in Strasbourg. I was appointed Sigma-Xi Distinguished Lecturer for 2003-2005, was named Fellow of the American Physical Society in 2005, and was elected Member at Large of the GSNP for the term 2005-2008. Currently, I am Associate Editor for “Research Letters in Physics” and am a member of the editorial board for “Journal of Statistical Physics: Theory and Experiment.”

September 18

Alexander Smits, Chairman and Eugene Higgins Professor of Mechanical and Aerospace Engineering,
Director, Gasdynamics Laboratory, Princeton University
"Hydrodynamics of Manta Ray Swimming"

Read the Abstract and Bio

Abstract: Aquatic animals propel themselves using a wide variety of mechanisms. In manta rays, propulsion is achieved by combining oscillating and undulatory motions of flexible surfaces. We are interested in studying the unsteady hydrodynamics of such motions to understand and model the wake structure. Experiments have been conducted on flapping flexible membranes, flapping rigid plates, and mechanical models of manta rays. Preliminary observations suggest a rich set of phenomena exist, depending on the non-dimensional frequency of flapping, the wavelength of the excitation, and the aspect ratio of the fin. Under certain conditions, simple wake structures are observed that bear a strong resemblance to the structure of co-flowing jets and wakes. In other cases, bifurcating wakes are seen, which appear to correspond to a decrease in efficiency. The performance of active and passive actuation methods is also explored.

Biography: Dr. Smits is the Eugene Higgins Professor of Mechanical and Aerospace Engineering at Princeton and Chair of his department. His research interests are centered on fundamental, experimental research in turbulence and fluid mechanics. In 2004, Dr. Smits received the Fluid Dynamics Award of the AIAA. In 2007, Dr. Smits received the Fluids Engineering Award from the American Society of Mechanical Engineers (ASME), the Pendray Aerospace Literature Award from the American Institute of Aeronautics and Astronautics (AIAA), and the President's Award for Distinguished Teaching from Princeton University. He is a Fellow of the American Physical Society, a Fellow of the American Institute of Aeronautics and Astronautics, a Fellow of the American Society of Mechanical Engineers, a Fellow of the American Academy for the Advancement of Science, and a Member of the National Academy of Engineering.

September 21

**Doctoral Defense** Towne Building, room 321, 11:00am
Qiwei Shi, Ph.D. Candidate

Advisor: John Bassani

"Diffusional Aggregation in Binary Solids "

Read the Abstract
A solid solution can spontaneously separate into phases, e.g. spinodal decomposition, that self assemble into patterns. This non-equilibrium thermodynamic process can be significantly affected by material anisotropy, including non-dilational transformation strains, anisotropic elastic properties, and orientation-dependent interfacial energy, along with elastic heterogeneity. A Cahn-Hilliard type phase field model is developed that incorporates chemical, interfacial, and elastic energies, and couples naturally with externally-imposed mechanical fields. Aggregation in the bulk under uniform loading and in thin films under patterned external tractions is investigated through simulations. The kinetics of aggregation and morphology of precipitates are shown to depend strongly upon material anisotropy and through coupling with external load. The major contributions of this dissertation are: i) development of phase field simulations coupled with mechanical fields that depend on heterogeneous elastic properties (in 2D and 3D), ii) demonstration of the effects of external loads, including patterned loads, on the evolution of microstructures, iii) investigation of the effects of material and loading anisotropy, and iv) demonstration that major features of the simulations can be predicted theoretically from interaction energies based upon the concept of Eshelby-type equivalent eigenstrains.

September 25

Shailendra Joshi, Assistant Professor, Department of Mechanical Engineering, National University of Singapore
"Fortifying Magnesium for Structural Applications"

Read the Abstract and Bio

Abstract: Magnesium (Mg) and its composites are potential candidates for structural applications ranging from fuel-intensive automotive sector to biomedical components, due to attractive properties such as low mass density (~35 % lighter than aluminum) and excellent biocompatibility. There has been a renewed emphasis toward developing novel Mg microstructures with impressive specific strengths (strength/ density) by introducing barriers to plastic deformation through a variety of techniques such as grain size refinement, nano-reinforcements, or combinations thereof. This talk presents our on-going experimental and computational efforts in understanding the mechanics of this low symmetry HCP material to enable designing Mg microstructures for strength and ductility. First, we present a novel hierarchical nano-composite where the Mg matrix hosts dilute fraction of reinforcement that is itself a composite at a finer scale. These hierarchical Mg configurations exhibit significant enhancement in the strength and ductility over its monolithic counterpart. We briefly discuss the length-scales involved in these highly heterogeneous microstructures and their influence on the macroscopic characteristics. Motivated by the need to understand the nexus between the microstructural heterogeneities and macroscopic strengthening in Mg, we then present a single crystal plasticity model that incorporates constitutive descriptions for the slip and twinning mechanisms and interactions thereof. In particular, the model emphasizes the differences between tension and compression twin evolution characteristics and their roles in the slip and twin hardening. The computational results are critically compared with the macroscopic and microscopic characteristics in experiments on single and polycrystalline specimens. Finally, we briefly discuss the possible extensions of this bottom-up modeling approach to include complicating features such as size-effects.


Biography: Shailendra Joshi is an Assistant Professor in Mechanical Engineering at National University of Singapore (NUS). Prior to joining NUS, he was a post doctoral fellow (2005-2008) in the Department of Mechanical Engineering at The John Hopkins University. He earned his PhD in Civil Engineering from Indian Institute of Technology-Bombay in 2002. Aster a short stint as a visiting scientist at University of Stuttgart (2002), he worked as a research engineer at GE-India Technology Center in Bangalore, India (2003-2005). His current research focuses on computational and experimental mechanics of strengthening and failure in advanced microstructures over a range of length and time-scales to enable designing light-weight materials with impressive mechanical behaviors. Shailendra enjoys playing amateur squash.

October 2

Robert Howe, Abbott and James Lawrence Professor of Engineering, Harvard School of Engineering and Applied Sciences
"Robot Hands for the Real World"

Read the Abstract and Bio

Abstract: Manipulating objects in unstructured environments like homes and workplaces is challenging because object properties are not known a priori and sensing is prone to error. Research in this area has largely focused on anthropomorphic hands that are complex, fragile, and difficult to control. We are pursuing an alternate approach that focuses on the passive mechanical behavior of the hand. By integrating carefully-selected joint compliance and adaptive transmissions, we have developed a simple and inexpensive hand that can grasp objects spanning a wide range of size, shape, weight, and position, while using only one motor. The hand is constructed using polymer-based Shape Deposition Manufacturing (SDM), resulting in a robust design that can withstand large impacts. Experimental testing demonstrates that the SDM Hand can autonomously grasp objects despite large positioning errors, while keeping contact forces low. A new hand, the HANDLE Manipulator, combines optimized passive mechanics with five motors to enable precision fingertip manipulation of a wide range of objects. We have also developed a sensor suite for these hands that includes low-cost distributed tactile sensors, flexture joint sensors, and piezoelectric contact sensors. By taking advantage of intrinsic finger compliance, these sensors can effectively measure the essential parameters of objects in the environment, enabling effective grasping and manipulation in unstructured environments.

Biography: Robert D. Howe is Abbott and James Lawrence Professor of Engineering and Area Dean for Bioengineering at the Harvard School of Engineering and Applied Sciences. Dr. Howe founded the Harvard BioRobotics Laboratory in 1990, which investigates the roles of sensing and mechanical design and motor control, in both humans and robots. His research interests focus on manipulation, the sense of touch, and human-machine interfaces. Biomedical applications of this work include of robotic and image-guided approaches to minimally invasive surgery. Dr. Howe earned a bachelors degree in physics from Reed College, then worked as a design engineer in the electronics industry in Silicon Valley. He received a doctoral degree in mechanical engineering from Stanford University in 1990, and then joined the faculty at Harvard. Dr. Howe is a Fellow of the IEEE and the AIMBE. He is a recipient of the National Science Foundation Young Investigator Award as well as Best Paper Awards at mechanical engineering, robotics, and surgery conferences.

Lab web site:
http://biorobotics.harvard.edu/

October 8 ** Special Seminar**

Towne Building, room 337, 11:00am

Sefi Givli, Senior Lecturer, Technion - Israel Institute of Technology
"A theorectical study of lamellipodia dynamics"

Read the Abstract and Bio
Abstract: The lamellipodia, a motility mechanism in motile cells, is a thin and wide region in the cell front. Inside this region lies a crowded network of polymers, mainly polarized actin filaments. These filaments depolymerize at their rear and polymerize at the other end which is directed towards the cell leading edge. This process affects the shape of the cell membrane and forces the lamellipodia edge to protrude in a crawl-like manner. In this work, we study the mechanical processes underlying the lamellipodia behavior by means of a coarse grained mechanical model. The model accounts for the membrane shape and its mechanical interaction with an active network of actin filaments. To this end we derive a non-linear integro-differential PDE to describe the shape dynamics, together with a non-linear conservation law for the actin concentration along the edge of the lamellipodia. The results of the model are compared with experimental observations. Special focus is put on comparison with quantitative measurements of steady state configurations and with qualitative observations of lamellipodia dynamics. The results are in very good agreement with these experiments, and suggest that the mechanical coupling between the membrane shape and the actin network is an important feature of the lamellipodia, which dominates its dynamic behavior. In addition, we show that the maximal crawling velocity is limited by dynamics stability rather than polymerization rate.

October 9

Marino Arroyo, Associate Professor, School of Civil Engineering of Barcelona, University of Catalunya, Barcelona

"Reverse engineering the euglenoid movement"

Read the Abstract and Bio

Abstract: Euglenids exhibit an unconventional motility strategy amongst unicellular eukaryotes, consisting of large amplitude highly concerted deformations of the entire body (euglenoid movement or metaboly). A plastic cell envelope called pellicle mediates these deformations. These protists have attracted the attention of scientists since the earliest days of microscopy, when van Leeuwenhoek referred to them in 1674 as microscopic motile “animalcules” that were green in the middle, which challenged the classification of organisms into animals and plants. Unlike ciliary or flagellar motility, the biophysics of this mode is not well understood, including its efficiency and molecular machinery. We examine quantitatively video recordings of four euglenids executing such motions with statistical learning methods. We then interpret the observations in the light of a theory for the pellicle kinematics, providing a precise understanding of the link between local actuation by pellicle shear and shape control. We systematically understand common observations, such as the helical conformations of the pellicle, and identify previously unnoticed features of metaboly. For instance, while two of our euglenids execute their stroke at constant body volume, the other two exhibit deviations of about 20% from their average volume, challenging current models of low Reynolds number locomotion. We find that metaboly accomplishes locomotion at hydrodynamic efficiencies comparable to those of ciliates and flagellates. Our results suggest new quantitative experiments, provide insight into the evolutionary history of euglenids, and suggest that the pellicle may serve as a model for engineered active surfaces with applications in micro-fluidics. This is joint work with L Heltai, D Millán and A DeSimone.

Biography: Marino Arroyo received his PhD in Mechanical Engineering at Northwestern University, was a postdoc at Caltech, and joined the Universitat Politècnica de Catalunya in Barcelona in 2004. His research interests are in small scale mechanics of materials and computational mechanics, and recently in molecular and cellular in biophysics. His work is supported by the European Research Council. He received the O.C. Zienkiewicz Award for Young Scientists in Computational Engineering Sciences (2010) and the ASME/Boeing 2003 Structures and Materials Award.

October 16

Dan Negrut, Associate Professor, Department of Mechanical Engineering, University of Wisconsin-Madison
"From the Dynamics of Sand to the Dynamics of Tanks: Using High Performance Computing to Advance the Pace of Innovation and Improve Designs in Mechanical Engineering"

Read the Abstract and Bio

Abstract: This presentation outlines a high performance computing-enabled software infrastructure aimed at supporting physics-based simulation in Computer Aided Engineering. The Computational Dynamics applications of interest include granular dynamics, rigid/flexible many-body dynamics, and fluid-solid interaction problems. The underlying theme of the solution proposed is that of partitioning the problem of interest into a number of sub-problems that are solved in parallel using Graphics Processing Unit
(GPU) cards, or multi-core CPUs. The five components at the cornerstone of the proposed Heterogeneous Computing Template (HCT) are: (a) modeling support for multi-physics phenomena; (b) scalable numerical methods for multi-GPU and multi-core hardware architectures; (c) methods for proximity
computation and collision detection; (d) support for domain decomposition and load balance; and (e) tools for carrying out visualization and post-processing in a distributed manner. Several engineering applications
will be used to demonstrate how these five components are implemented to leverage a heterogeneous CPU/GPU cluster operated by the Simulation-Based Engineering Lab at UW-Madison. The talk will conclude with a brief discussion of current trends in high performance computing and how they are poised to change the field of Computational Science in the near future.

Biography: Associate Professor Dan Negrut received his Mechanical Engineering Ph.D. in 1998 from the University of Iowa, working under the supervision of Professor Edward J. Haug. At the end of 2005 Dan joined the Mechanical Engineering faculty at the University of Wisconsin-Madison. His interests are in Computational Science and he leads the Simulation-Based Engineering Lab (http://sbel.wisc.edu) at the University of Wisconsin-Madison. Dan received in 2009 a National Science Foundation Career Award. Since 2010 he is an NVIDIA CUDA Fellow. Dan's research lab currently operates the one of the fastest supercomputers at the University of Wisconsin-Madison, which was assembled with US Army support. Dan received the 2012 UW-Madison College of Engineering Harvey Spangler Award for Technology-Enhanced Teaching and he is the co-founder and current Director of the Wisconsin Applied Computing Center.

October 25

Towne Building, room 337

Evan Galipeau, Ph.D. Candidate

Advisor: Pedro Ponte Castañeda
"Non-linear homogenization of magnetorheological elastomers at finite strain"

Read the Abstract
This presentation is concerned with the application of a finite-strain homogenization framework to develop constitutive models for magnetorheological elastomers (MREs) consisting of initially aligned, rigid magnetic particles distributed randomly in an elastomeric matrix. The effective magnetoelastic energy of the composite is written in terms of a purely mechanical component, together with a magnetostatic component evaluated in the deformed configuration of the composite, as estimated by means of the purely mechanical solution of the problem. It is argued that the resulting constitutive model for the material, which can account for the initial volume fraction, average shape, orientation and distribution of the generally anisotropic and non-spherical particles, should be accurate when the matrix is stiff compared to the magnetic forces and torques on the particles. The theory predicts the existence of certain "extra" stresses---arising in the composite beyond the purely mechanical and magnetic (Maxwell) stresses---which can be directly linked to changes in the effective magnetic permittivity of the composite with the deformation. For the special case of isotropic distributions of magnetically isotropic, spherical particles, the extra stresses are due to changes in the particle two-point distribution function with the deformation, and are of order volume fraction squared, arising from dipole interactions between the particles. On the other hand, for the case of aligned, ellipsoidal particles, the effect can be of order volume fraction, when changes are induced in the orientation of the particles, as a consequence of magnetic torques on individual particles. The theory is capable of handling the strongly nonlinear effects associated with finite strains and magnetic saturation of the particles at sufficiently high deformations and magnetic fields, respectively. It is then shown how to generate large magnetostriction, actuation stress, and changes in mechanical modulus by combining the previously described MRE in a laminated composite.

October 30

S. "Bala" Balachandar, Chairman and William F. Powers Professor of Mechanical and Aerospace Engineering, University of Florida
"On the Propagation, Instability and Turbulence of Advancing Material Fronts"

Read the Abstract and Bio
Abstract : Penetration of one material into another is a fundamental fluid mechanical process
that can be observed all around us in many industrial and environmental applications.
Filling/emptying pipelines, coating flows, falling films and sedimentation fronts
are some industrial applications. Tsunamis, volcanic plumes, lava and pyroclastic flows,
dust storms, powder snow avalanches, submarine turbidity currents and supernovae
offer fascinating examples of advancing material fronts. This talk will introduce
the concept of gravity currents, where the density difference between the propagating
and the ambient materials drives the flow. The examples mentioned above include both
scalar and particulate gravity currents, where in the former the density difference
is due to temperature or salinity, while in the later suspended particles contribute
to density difference. Particular attention will be paid to the front velocity and
simple theoretical models that attempts to predict it. The propagating fronts undergo
Rayleigh-Taylor, Lobe-and-cleft and Kelvin-Helmholtz instabilities, giving rise to
fascinating pathways to turbulence.

One particular example we will consider in greater detail is the sustained propagation
of submarine turbidity currents, whose propagation depends on an
interesting interplay between suspended particles and turbulence. The suspended
particles drive the flow and are the source of turbulence in a turbidity current,
while the flow turbulence enables resuspension of particles from the bed. If
resuspension dominates over deposition the intensity of the current can increase,
thereby further increasing resuspension and resulting in a runaway current. On
the other hand, stable stratification due to suspended sediment concentration
can damp and even kill turbulence. Then deposition dominates over resuspension
and the current could laminarize resulting in massive deposits.

In this talk we present results that indicate the existence of
conditions for the total damping of the near-bed turbulence. Under these conditions,
sediment in suspension rains out passively on the bed, even though the upper
layer may remain turbulent. The above scenario provides a reasonable (but not
unique) explanation for the formation of massive turbidities that have recently
been reported from field observations.

Biography: S. "Bala" Balachandar got his undergraduate degree in Mechanical Engineering
at the Indian Institute of Technology, Madras in 1983 and his MS and PhD in
Applied Mathematics and Engineering at Brown University in 1985 and 1988.
From 1990 to 2005 he was at the University of Illinois, Urbana-Champaign, in the
Department of Theoretical and Applied Mechanics. From 2005 to 2011 he
served as the Chairman of the Department of Mechanical and Aerospace Engineering
at the University of Florida. Currently he is the William F. Powers Professor and
the Director of College of Engineering Institute for Computational Engineering.

Bala received the Francois Naftali Frenkiel Award from American Physical
Society (APS) Division of Fluid Dynamics (DFD) in 1996 and the Arnold O.
Beckman Award and the University Scholar Award from University of
Illinois. In 2003, his student won the Andreas Acrivos Dissertation Award
from APS-DFD. He is Fellow of the American Physical Society and ASME. He is
currently an associate editor of the International Journal of Multiphase
Flow and Theoretical and Computational Fluid Dynamics.

November 6

Ronald Larson, George Granger Brown Professor of Chemical Engineering, and Professor of Mechanical Engineering and Macromolecular Science and Engineering, University of Michigan
"From Rheology to Biology: the Application of Polymer Hydrodynamics to Problems in Biology"

Read the Abstract and Bio

Abstract: Using Stokeslets, elastic elements, and Langevin dynamics, we develop meso-scale “bead-spring” methods to simulate the dynamics of polymer molecules in flow fields, and the self-propulsion of micron-sized bacterial swimmers. These methods allow us to predict the unraveling of long polymer molecules in shear and extensional flow, and in a droplet drying flow used for creating DNA micro arrays. In extensional flow, the unraveling is dominated by highly out-of-equilibrium “dumbbell” and “fold” configurations that produce a highly heterogeneous population of conformations. In shearing flow, the dynamics are dominated by tumbling of molecular configurations, due to vorticity. The results are successfully compared with experiments using single fluorescently stained DNA molecules, including DNA deposited during drying of a droplet. We apply these methods to study the hydrodynamics of swimming of multi-flagellated bacteria, such as Escherichia coli. These simulations reproduce the experimentally observed behaviors of E. coli, namely, a three-dimensional random-walk trajectory in run-and-tumble motion and steady clockwise swimming near a wall. We show using a modeled cell that the polymorphic transformation of flagellum in a tumble facilitates the reorientation of the cell, and that the time-averaged flow field near a cell in a run has double-layered helical streamlines. Finally, we use microfluidic methods to determine the kinetics of target search of proteins along DNA molecules and the rates of transcription of DNA into RNA.

Biography: Ronald Larson became a Professor of Chemical Engineering at the University of Michigan in 1996, after working for 17 years at Bell Laboratories in Murray Hill, New Jersey. He received a B.S in1975, an M.S. in 1977, and a Ph.D. in 1980, all in chemical engineering from the University of Minnesota.

Larson’s research interests include the structure and flow properties of viscous or elastic fluids, sometimes called “complex fluids”, which include polymers, colloids, surfactant-containing fluids, liquid crystals, and biological macromolecules such as DNA, proteins, and lipid membranes. He is also interested in fluid mechanics, including microfluidics, and transport modeling. He has written numerous scientific papers and two books on these subjects, including a 1998 textbook, “The Structure and Rheology of Complex Fluids.”

Larson was the President of the Society of Rheology (SOR) from 1997 to 1999, and served on the Executive Committee of that Society during the period 1991 to 2001. He is a Fellow of the American Physical Society (APS), and was Chairman of the Division of Polymers of the APS in 2010. He served as Chair of the Chemical Engineering Department of the University of Michigan from 2000 to 2008. He is also a member of the American Chemical Society (ACS), the American Association for the Advancement of Science (AAAS), and the American Institute for Chemical Engineers (AIChE). In 1996, he was named the Prudential Distinguished Visiting Fellow at the Isaac Newton Institute in Cambridge England; in 2000 he was awarded the Alpha Chi Sigma Award from the AICHE; and in 2002 he received the Bingham Medal from the Society of Rheology. He is a Fellow of the APS, a Fellow of the AICHE, and a member of the National Academy of Engineering. Since 2000, he has been the GG Brown Professorship of Chemical Engineering at the University of Michigan.

November 19

**Doctoral Defense** Towne Building, room 337, 10:00am

Evan Galipeau, Ph.D. Candidate

Advisor: Pedro Ponte

"Non-linear homogenization of magnetorheological elastomers at finite strain"

Read the Abstract
This presentation is concerned with the application of a finite-strain homogenization framework to develop constitutive models for magnetorheological elastomers (MREs) consisting of initially aligned, rigid magnetic particles distributed randomly in an elastomeric matrix. The effective magnetoelastic energy of the composite is written in terms of a purely mechanical component, together with a magnetostatic component evaluated in the deformed configuration of the composite, as estimated by means of the purely mechanical solution of the problem. It is argued that the resulting constitutive model for the material, which can account for the initial volume fraction, average shape, orientation and distribution of the generally anisotropic and non-spherical particles, should be accurate when the matrix is stiff compared to the magnetic forces and torques on the particles. The theory predicts the existence of certain "extra" stresses---arising in the composite beyond the purely mechanical and magnetic (Maxwell) stresses---which can be directly linked to changes in the effective magnetic permittivity of the composite with the deformation. For the special case of isotropic distributions of magnetically isotropic, spherical particles, the extra stresses are due to changes in the particle two-point distribution function with the deformation, and are of order volume fraction squared, arising from dipole interactions between the particles. On the other hand, for the case of aligned, ellipsoidal particles, the effect can be of order volume fraction, when changes are induced in the orientation of the particles, as a consequence of magnetic torques on individual particles. The theory is capable of handling the strongly nonlinear effects associated with finite strains and magnetic saturation of the particles at sufficiently high deformations and magnetic fields, respectively. It is then shown how to generate large magnetostriction, actuation stress, and changes in mechanical modulus by combining the previously described MRE in a laminated composite.

November 20

Sergio Pellegrino, Joyce and Kent Kresa Professor of Aeronautics and Professor of Civil Engineering, and Jet Propulsion Laboratory Senior Research Scientist, California Institute of Technology
"Ultra-thin composite deployable shell structures"

Read the Abstract and Bio

Abstract: Deployable structures made of only one or two plies of woven carbon-fiber composites, without any mechanical joints, can be folded elastically and are able to self-deploy through the release of elastic strain energy. However, the behavior of these structures is rather poor when they are “designed by intuition”: their deployment is unpredictable and the deployed stiffness disappointingly low considering the high performance materials from which they have been made. Because of uncertainty over the actual deformation that the structure will be subject to, intuitive designs tend to be over-conservative with respect to material failure, leaving the structural architecture compromised.

In this talk I will present numerical simulation techniques, with the finite element package ABAQUS/Explicit, that allow us to carry out complete simulations of the folding and deployment of a general elastic thin-shell structure. These simulations are remarkably realistic and capture closely the instabilities, dynamic snaps, and sliding contact events that are associated with folding and deployment. Coupled with an interactive failure criterion in stress-resultant space, these simulations provide a powerful tool to design better performing structures. I will apply this design approach to a particular type of deployable boom and will show experimental and simulation results for booms with different designs.

Biography: Sergio Pellegrino, Joyce and Kent Kresa Professor of Aeronautics and Professor of Civil Engineering at the California Institute of Technology and JPL Senior Research Scientist, received his Laurea in Civil Engineering from the University of Naples in 1982 and his PhD from the University of Cambridge in 1986. Between 1983 and 2007 he was on the faculty of the Department of Engineering, University of Cambridge. His main research focus is the mechanics of lightweight flexible structures and particularly problems related to packaging, deployment, shape control and stability. Currently his main interests are deployable space structures made of ultra-thin composite materials, active mirrors and stratospheric balloons. Dr Pellegrino received the ICE James Watt Medal 2000; a Pioneers’ Award in 2002 from the Space Structures Research Center, University of Surrey; AIAA Gossamer Spacecraft Forum Best Paper Awards in 2004, 2005, 2006 and 2011; IASS Tsuboi Awards in 2004, 2005, and 2007; the 2008 ASME/Boeing Best Paper Award; and the 2009 NASA Robert H. Goddard Exceptional Achievement Team Award. Dr Pellegrino is a Fellow of the Royal Academy of Engineering, a Fellow of AIAA and a Chartered Structural Engineer. He is the Chair of the AIAA Gossamer Systems Program Committee and Editor-in-Chief of the Journal of the IASS. Dr Pellegrino is the author of over 200 technical publications.


November 27

Darryll Pines, Dean and Nariman Farvardin Professor of Engineering, Clark School of Engineering, University of Maryland
"Evolving to a New Normal in Engineering Education"

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Abstract: The traditional model of higher education is changing, as demonstrated by the proliferation of colleges (particularly for-profit institutions), hybrid class schedules with night and weekend meetings, and, most significantly, synchronous and asynchronous online learning. The concept of four years away from home—spent living and learning will continue to evolve based on a need to prepare today’s students with 21st Century skills and experiences. Residential learning will still have a place in higher education, but it may be a smaller piece of the overall picture. This evolving new normal is driven by the rising cost of higher education, the emergence of online education, and the demand for experiential enhanced learning experiences. How will engineering education evolve to adapt to this new normal? This presentation will explore how engineering education is changing to not only adapt to this new normal, but to leverage and enhance opportunities and experiences for current and future students. Specifically, new curriculum models will be discussed including compressed degree programs, the growth in outside of the classroom experiences, and finally the potential impact of online educational initiatives such as Coursera, Udacity, and edX on enhanced learning opportunities and outcomes for students. This presentation will also discuss the challenges involved in online delivery as it relates to delivering a first rate engineering education.

Biography: Darryll Pines became Dean and Nariman Farvardin Professor of Engineering at the Clark School on January 5, 2009, having come to the school in 1995 as an assistant professor and served as chair of the school's Department of Aerospace Engineering from 2006 to 2009. As dean, Pines has led the development of the Clark School's current strategic plan and achieved notable successes in key areas such as improving teaching in fundamental undergraduate courses and raising student retention; achieving success in national and international student competitions; giving new emphasis to sustainability engineering and service learning; promoting STEM education among high school students; increasing the impact of research programs; and expanding philanthropic contributions to the school. Today, the school's one-year undergraduate retention rate is 90 percent, the university's Solar Decathlon team placed first worldwide in the most recent competition against other leading universities, our Engineers Without Borders chapter is considered one of the nation's best, and the Engineering Sustainability Workshop launched by Pines has become a key campus event. Pines has testified before Congress on STEM education and created the Top 25 Source Schools program for Maryland high schools. At $144 million, the school's research expenditures are at a record high, and the school is ranked 11th worldwide by the Academic Ranking of World Universities, which focuses on research citations.

November 28 ** Special Seminar** CANCELLED

Berger Auditorium, Skirkanich Hall room 13, 12:00 noon

Na Zhang, Research Professor, Institute of Engineering Thermophysics, Chinese Academy of Sciences
"High-efficiency low emissions hybrid power generation systems integrated with solar thermo- chemical conversion"

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Abstract: The presentation starts with a brief description of the research work in the Institute of Engineering Thermophysics, Chinese Academy of Sciences: aiming at clean and efficient conversion and utilization of energy, it is focused on power generation, renewable energy development, energy storage, fluid dynamics, heat and mass transfer, combustion, and related topics. A detailed presentation on solar thermal power generation system integrated with solar heat thermo-chemical conversion and upgrading follows. Following the principle of cascade utilization of multiple energy sources, several power systems integrated with solar thermo-chemical fuel conversion were proposed and analyzed. In some of the systems, CO2 capture is integrated with energy conversion and accomplished with low energy penalty.
The study mainly focuses on the application of low/mid temperature solar heat, with much attention being paid on the incorporation of solar heat into the advanced gas turbine and combined cycle power system, to take advantage of both the high-efficiency energy conversion in the advanced power system and he lower-cost solar concentration in low/mid temperature solar heat collectors. In these systems, the collected solar heat drives the endothermic fuel conversion reactions and is converted to the produced syngas chemical exergy, and then released as high-temperature thermal energy via combustion for power generation, achieving its high-efficiency heat-power conversion. The net solar-to-electric efficiency, based on the gross solar heat incident on the collector, is 30% and above, which is much higher than can be attained in the solar-alone thermal power system working at the same temperature level of 200~300C; and aproximately 30% of fossil fuel saving is feasible with a solar thermal share of about 20~25%, as compared with a non-solar assisted power cycle with the same power output; and the reduction of fossil fuel use results in a commensurate reduction of CO2 emissions. The system integrations provide a promising solution for saving of fossil fuel and high efficiency conversion of solar heat.

Biography: Dr. Na Zhang is a research professor at the Institute of Engineering Thermophysics of the Chinese Academy of Sciences (CAS), Beijing. She earned her bachelor’s degree in engineering from Tsinghua University, Beijing, in 1991 and the Ph.D. in the Chinese Academy of Sciences in 1999. From 2002 to 2003, she was a visiting scholar in the Department of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, Philadelphia. Her major research includes gas turbine and combined cycles, cogeneration systems, coal-fired power systems, CO2 capture from power plants, power generation with liquefied natural gas cold exergy, and solar thermal power generation. She has authored/co-authored more than 100 technical publications, and is an Associate Editor of Energy–the International Journal, and the Executive Editor of the Journal of Engineering Thermophysics (in Chinese). Her honors include CAS’ President Fellowship Award (1996), the National Electric Power Company Science and Technology Progress Award (1999), the National Electric Power Science and Technology of China Award (2002), the Zhonghua Wu Outstanding Young Scientist Award (2008) and the Chinese National Natural Science Award (2009). She, jointly with Dr. Noam Lior, received a Best Paper Award from the ASME Advanced Energy Systems Division in 2004, and an ASME Society Award-the Edward F. Obert Award in thermodynamics, in 2010.

December 4

Thomas Powers, Professor of Engineering and Professor of Physics, Brown University
"Swimming in Viscoelastic Fluids"

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Abstract: Many microorganisms commonly swim in viscoelastic fluids: mammalian sperm swim in cervical fluid, infectious bacteria penetrate the mucus lining our epithelial cells, and the ulcer-causing bacterium
Helicobacter pylori moves through gastic mucus. Although the basic theory for swimming in a Newtonian fluid is well-developed, many fundamental questions about swimming in a viscoelastic fluid remain
unanswered. In this talk I will present simple theoretical models for swimming in a polymeric liquid. I will also present the results of our precise scale-model table-top experiments for a swimming helix in a
polymeric liquid. We find that whether or not a helix swims faster in a polymeric liquid than in water depends on the Deborah number, the ratio of the polymer relaxation time to the rotation period.

Biography: Thomas Powers received his PhD in soft-condensed matter physics working with Phil Nelson at the University of Pennsylvania in 1995. He was a postdoctoral associate with Ray Goldstein at Princeton University and the University of Arizona, and also with Howard Stone at Harvard University. Powers was the inaugural holder of the James Rice Term Chair in Solid Mechanics at Brown University, and is currently a professor in the School of Engineering and Department of Physics at Brown.

December 11

Chelsey Simmons, Ph.D. Candidate, Stanford University

Towne Building, room 337, 10:30 am
"Dynamic Cell Culture Systems for Stimulation and Assessment of Cardiovascular Cells"

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Abstract: The heart and blood vessels are dynamic, active tissues subject to a variety of mechanical stimuli like tensile strain, positive pressure, and shear flow. Researchers are beginning to examine the
impact of these mechanical factors on cardiovascular physiology, and sophisticated tools can advance our understanding of these interactions to improve medicine and healthcare. I have developed a variety of tools to replicate aspects of the cardiovascular system /in vitro/, specifically, a silicone and acrylamide system to modulate strain and stiffness parameters independently. This presentation will also describe
complimentary systems I have created, including a MEMS device for probing microscale shear properties of soft materials and image processing tools to assess heart cell contractility.

Short Biography: Chelsey is currently finishing her PhD at Stanford University in Mechanical Engineering as a member of Beth Pruitt's Microsystems Lab. She has worked on a variety of MEMS-related topics,
and her current research focuses on dynamic cell culture systems to recreate /in vivo/-like environments. Chelsey graduated from Harvard University /cum laude/ with a B.S. in Mechanical and Materials
Engineering and has received a number of competitive awards, including an NSF Graduate Research Fellowship, that fund her graduate work at Stanford. In addition to her research, Chelsey has developed and led a recurring summer seminar series for high school math and science teachers. She is also a founding officer and former President of Stanford's American Society for Engineering Education.

December 12

Na Zhang, Research Professor, Institute of Engineering Thermophysics, Chinese Academy of Sciences

MEAM Conference room, Towne 227, 1:00pm

"High-efficiency low emissions hybrid power generation systems integrated with solar thermo- chemical conversion"

Read the Abstract and Bio

Abstract: The presentation starts with a brief description of the research work in the Institute of Engineering Thermophysics, Chinese Academy of Sciences: aiming at clean and efficient conversion and utilization of energy, it is focused on power generation, renewable energy development, energy storage, fluid dynamics, heat and mass transfer, combustion, and related topics. A detailed presentation on solar thermal power generation system integrated with solar heat thermo-chemical conversion and upgrading follows. Following the principle of cascade utilization of multiple energy sources, several power systems integrated with solar thermo-chemical fuel conversion were proposed and analyzed. In some of the systems, CO2 capture is integrated with energy conversion and accomplished with low energy penalty. The study mainly focuses on the application of low/mid temperature solar heat, with much attention being paid on the incorporation of solar heat into the advanced gas turbine and combined cycle power system, to take advantage of both the high-efficiency energy conversion in the advanced power system and he lower-cost solar concentration in low/mid temperature solar heat collectors. In these systems, the collected solar heat drives the endothermic fuel conversion reactions and is converted to the produced syngas chemical exergy, and then released as high-temperature thermal energy via combustion for power generation, achieving its high-efficiency heat-power conversion. The net solar-to-electric efficiency, based on the gross solar heat incident on the collector, is 30% and above, which is much higher than can be attained in the solar-alone thermal power system working at the same temperature level of 200~300?C; and aproximately 30% of fossil fuel saving is feasible with a solar thermal share of about 20~25%, as compared with a non-solar assisted power cycle with the same power output; and the reduction of fossil fuel use results in a commensurate reduction of CO2 emissions. The system integrations provide a promising solution for saving of fossil fuel and high efficiency conversion of solar heat.

Biography: Dr. Na Zhang is a research professor at the Institute of Engineering Thermophysics of the Chinese Academy of Sciences (CAS), Beijing. She earned her bachelor’s degree in engineering from Tsinghua University, Beijing, in 1991 and the Ph.D. in the Chinese Academy of Sciences in 1999. From 2002 to 2003, she was a visiting scholar in the Department of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, Philadelphia. Her major research includes gas turbine and combined cycles, cogeneration systems, coal-fired power systems, CO2 capture from power plants, power generation with liquefied natural gas cold exergy, and solar thermal power generation. She has authored/co-authored more than 100 technical publications, and is an Associate Editor of Energy–the International Journal, and the Executive Editor of the Journal of Engineering Thermophysics (in Chinese). Her honors include CAS’ President Fellowship Award (1996), the National Electric Power Company Science and Technology Progress Award (1999), the National Electric Power Science and Technology of China Award (2002), the Zhonghua Wu Outstanding Young Scientist Award (2008) and the Chinese National Natural Science Award (2009). She, jointly with Dr. Noam Lior, received a Best Paper Award from the ASME Advanced Energy Systems Division in 2004, and an ASME Society Award-the Edward F. Obert Award in thermodynamics, in 2010.