Penn Engineering Events

CBE Faculty Candidate Seminar: "Understanding and Controlling the Complexity of Catalytic Active Sites"
2020-02-05 15:00 - 16:00 (America/New_York) | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Heterogeneous catalysis is of central importance to the global economy today, facilitating the conversion of raw materials into valuable fuels and chemicals, and the abatement of chemical pollutants in an efficient way. As environmental concerns associated with the use of fossil fuels and increased viability of alternative technologies motivate a transition away from traditional chemical processes, continued development and understanding of catalytic reactions will be of vital importance. At the atomic level, catalytic reactions involve the making and breaking of chemical bonds between reacting molecules and active sites. As our understanding of catalytic reactions advances, it has become apparent that the environment in which active sites operate can significantly impact reactivity, both by influencing the structure of these active sites, and by directly affecting reaction energetics. Appreciation of the dynamic behavior of active sites and the influence of the reaction environment on catalysis is therefore required for a full description of a catalytic process, and once understood, can provide additional tools for designing catalysts. Control over both the binding site and the non-reactive components in its vicinity can lead to optimal activity, as elegantly demonstrated by nature’s catalysts, enzymes. In this talk, two illustrative examples are provided that demonstrate the consequences of the reaction environment surrounding an active site on catalyst structure and reactivity.

MSE Faculty Candidate Seminar: "Unsupervised Learning of Dislocation Motion"
2020-02-04 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
High-performance designs that utilize metallic alloys are driving a need to quantify deformation in-situ at the finest length scales in order to reduce weight, increase operating temperatures, and improve fatigue life. With improvements to data reconstruction algorithms, brighter X-ray sources, and more efficient detectors, these in-situ studies of microstructural and micromechanical evolution in 3-D (nm-µm length scales) and at rapid time scales (<ms) are now possible. As numerous projections are often required for inversion of 3-D physics-based scattering models, trade-offs typically must be made between microstructural detail and the time scale probed. Instead, utilization of unsupervised learning, specifically locally linear embedding (LLE), is proposed to analyze in-situ diffraction data and find lower-dimensional embeddings that characterize microstructural transients, thus by-passing the need for a scattering model chosen a priori and enabling material understanding to be recovered with sparser data sets. The approach is applied to diffraction data gathered during uniaxial deformation of additively manufactured Inconel 625. The evolution of the lower-dimensional representation of microstructure is directly connected to the evolution of the defect densities that dictate strength and plastic flow behavior using a well-established material model. The implications of the findings for future constitutive model development and wider applicability to the study of material evolution during processing, particularly additive manufacturing, will be discussed.

MEAM Seminar: "Microdevices Enabled by Rarefied Flows"
2020-02-04 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
In this talk we will review emerging applications of rarefied gas dynamics for microscale sensing, actuation and power generation. Performance of conventional fluidic devices such as pumps, combustors and heat engines decreases at the microscale due to greater viscous and heat transfer losses. Unconventional micro/nanodevices exploit the tight coupling between non-equilibrium gas, liquid and solid-state transport and electromagnetic phenomena to overcome these limitations. We consider three distinct MEMS based on i) very high thermal gradients; ii) increased capillary forces; iii) high electric fields. The first example is Microscale In-Plane Knudsen Radiometeric Actuator (MIKRA) that applies thermostress convection to achieve actuation and control of gas-phase transport by temperature gradients and offers novel methods for gas sensing, pumping, and species separation. In macroscale systems, the operating temperatures necessary to generate significant flow actuation by thermostress convection are prohibitively high. For microdevices, thermal gradients on the order of 107 Kelvin per meter could be achieved, allowing these effects to be exploited. Another examples is Film Evaporation MEMS Tunable Array (FEMTA), a micropropulsion technology that works on microscale effects of surface tension, hydrophobicity, and thin film boiling to create highly tunable thrust using ultra pure water as propellant for attitude control and maneuvering of small satellites and deployable space structures.

Thesis Defense: "Multiscale Predictions of Mechanical Response and Computational Circuit Dynamics After Traumatic Brain Injury”
2020-01-31 15:00 - 17:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
The Department of Bioengineering at the University of Pennsylvania and Dr. David Meaney are pleased to announce the Doctoral Dissertation Defense of David Gabrieli.
This event is open to the public.

PICS Seminar - Dr. Yoichiro Mori of the University of Pennsylvania & the University of Minnesota
2020-01-31 14:00 - 15:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: Mathematical Justification of Slender Body Theory
Systems in which thin filaments interact with the surrounding fluid abound in science and engineering. The computational and analytical difficulties associated with treating thin filaments as 3D objects has led to the development of slender body theory, in which filaments are approximated as 1D curves in a 3D fluid. In the 70-80s, Keller, Rubinow, Johnson and others derived an expression for the Stokesian flow field around a thin filament given a one-dimensional force density along the center-line curve. Through the work of Shelley, Tornberg and others, this slender body approximation has become firmly established as an important computational tool for the study of filament dynamics in Stokes flow. An issue with slender body approximation has been that it is unclear what it is an approximation to. As is well-known, it is not possible to specify some value along a 1D curve to solve the 3D exterior Stokes problem. What is the PDE problem that slender body approximation is approximating? Here, we answer this question by formulating a physically natural PDE problem with non-conventional boundary conditions on the filament surface, which incorporates the idea that the filament must maintain its integrity (velocity along filament cross sections must be constant). We prove that this PDE problem is well-posed, and show furthermore that the slender body approximation does indeed provide an approximation to this PDE problem by proving error estimates. This is joint work with Laurel Ohm, Will Mitchell and Dan Spirn.

MSE Faculty Candidate Seminar: "Structure-property relations in hybrid 2D halide perovskites"
2020-01-30 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
Two-dimensional (2D) hybrid organic-inorganic perovskites are under intense investigation due to their interesting physical properties and superior performance in thin-film based optoelectronic devices. The structural diversity embedded in the system provides a variety of parameters to target favorable properties for applications in photovoltaics (PV) and light emitting diodes (LEDs). In this talk, Dr. Mao will focus on the structure-property relationships in 2D hybrid perovskite materials, where large organic cations can be inserted in the structure to increase the stability and structural diversity. First, she will describe the development of the first completed series of 2D Dion-Jacobson (DJ) hybrid halide perovskites with a general formula A’An-1PbnI3n+1 (A’ = 3-(aminomethyl)piperidinium (3AMP) or 4-(aminomethyl)piperidinium (4AMP), A = methylammonium (MA)). The higher layer member (n = 4) has demonstrated good performance, with the initial power conversion efficiency (PCE) of 7.3% and increased PCE of 12.0% with formamidinium incorporation. Furthermore, she will introduce another set of hybrid perovskite materials for solid-state lighting applications. The lead bromide-based and mixed bromide/chloride systems have exhibited white-light broad emission and a direct correlation was found between the distortion of the inorganic framework and the emission. Last, a series of new hybrid double perovskite halide materials are developed as lead-free, environmentally friendly alternatives. The ability to structurally manipulate 2D hybrid halides catered to the needs opens new avenues for next-generation optoelectronics.

Britton Chance Distinguished Lecture: "Regenerative Immunology: The Role of Technology Translation in Guiding Discovery"
2020-01-29 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Biomaterial implants have a long history in the clinic, but regenerative biomaterials and regenerative medicine therapies, in general, have been slow to reach patients. Clinical translation provides a unique and critical opportunity to investigate the key therapeutic drivers of technology efficacy in people. Careful evaluation of clinical outcomes and reevaluation of design parameters is central to improving research and technology development. A key outcome of our clinical translation experiences in orthopedics and plastic surgery was the unexpected discovery of adaptive immune cells around synthetic implants. We are now working to understand the role of the immune system and cellular senescence in the biomaterial response and repair across different tissues. This new therapeutic target serves as the basis for the design of regenerative immunotherapies.

MEAM Doctoral Dissertation Defense: "Applications of a Double-stranded Elastic Rod Model to DNA"
2020-01-28 12:00 - 13:00 | 4E9, DRLB, 209 S. 33rd Street, Philadelphia, PA, 19104, United States
In the first part of the presentation, we discuss a double-stranded elastic rod (birod) model and apply it to study allosteric interactions between two ligands on DNA. Next, we combine the birod model with statistical mechanics and use it to study the temperature-induced strand separation in dsDNA.
Allosteric interaction between two ligands on DNA is quantified by measuring the change in free energy of the DNA complex (DNA + two ligands) as a function of the distance between the binding sites for two ligands. We show that trends in the interaction energy of two ligands binding to DNA can be explained using the birod model which accounts for the helical shape of DNA, elastic deformation of strands and base-pairs, and the stacking energy due to perturbations in position and orientation of the bases caused by the binding of ligands. The model predicts that the allosteric interaction energy between two ligands decays exponentially with the distance between them and oscillates with the periodicity of the double helix, which by appropriate parameter fitting is shown to quantitatively match with the experimental measurements. Our model predicts an identical trend (exponentially decaying sinusoid) in the perturbation of groove width produced by the binding of a single ligand—consistent with the published results from molecular simulations. Our analysis provides a new framework to understand allosteric interactions in DNA and can be extended to other rod-like macromolecules whose elasticity plays a key role in their biological functions.
In the next part of the presentation, we combine statistical mechanics with continuum mechanics to predict the mechanical response of DNA molecules. We observe that the external force and torque driven microstructure evolution in DNA leads to force-extension curves that exhibit strong signatures of first-order phase transitions. The effects of the electrostatic interactions on the mechanical-response predicted from the model resolve some important counter-intuitive experimental observations. Next, we focus on one such structural transition—temperature-driven disintegration of dsDNA into two single strands, known as DNA melting. We illustrate how the continuum mechanics of birod coupled with statistical mechanics can be used to study the micromechanics of DNA melting. We note that a nonlinear asymmetric interaction between the outer strands leads to a sudden and highly cooperative melting transition. The model enables us to couple the effect of tensile force on the melting temperature, which to the author’s knowledge is the first mechanics-based attempt to do so. The results from the models, after suitably choosing the parameter values, agree with multiple experiments reported in the literature and they generate new falsifiable predictions that can be experimentally tested.

MEAM Seminar: "Liquid Crystal Elastomers"
2020-01-28 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Liquid crystal elastomers are rubbery solids with liquid crystal mesogens incorporated into their main chains. They display an isotropic to nematic phase transformation accompanied by a large spontaneous deformation. This in turn leads to rich variety of phenomena including ultra-soft behavior, stripe domains, shape-morphing etc. Further, when made as slender structures, the structural instability of slender structures and the material instabilities of liquid crystal elastomers combine and compete in interesting ways. This talk will provide an introduction to these materials and provide examples from contemporary research about opportunities these materials present.

CBE Dissertation: "DNA Mediated Particle Adhesion"
2020-01-27 13:00 - 15:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Advisor: John Crocker, PhD; Committee Members: Talid Sinno, PhD; Scott Diamond, PhD; and Daniel Hammer, PhD

MSE Faculty Candidate Seminar: "Defect Structure Process Maps for Laser Powder Bed Fusion Additive Manufacturing"
2020-01-23 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
Additive manufacturing (AM) greatly expands the design freedom and near-net shape production of metallic components across multiple length scales. However, defects arising from starting materials, processing conditions, and post-processing may significantly affect the structural integrity and operational performance of metal AM parts. This paper seeks to elucidate common defects and defect formation mechanisms encountered in typical laser powder bed fusion (LPBF) AM processes. While the defect structures of conventional joining processes such as laser welding have been studied extensively, this talk primarily focuses on the nature of porosity transfer to the finished part exclusively for metal AM powder bed processing techniques. Multiple starting powders and analysis methods are summarized which demonstrate that the manifestation of defects within metal AM builds largely stems from the particular choice of process settings, with some influence of powder feedstock choice and post-processing heat treatments. Practical build strategies to limit the occurrence of defects by the use of process mapping and geometric modeling are also evaluated utilizing this fundamental understanding of defect formation. Such explorations may enable the validation and calibration of models to permit process qualification without the reliance on costly trial and error type experimentation currently employed.

CBE Seminar: "Collaboration and Competition Between Active Sheets for Self-Propelled Particles"
2020-01-22 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Biological species routinely collaborate for their mutual benefit or compete for available resources, thereby displaying dynamic behavior that is challenging to replicate in synthetic systems. Here, we use computational modeling to design microscopic, chemically active sheets and self-propelled particles encompassing the appropriate synergistic interactions to exhibit bio-inspired “feeding”, “fleeing” and “fighting”. This design couples two different mechanisms for chemically generating motion in fluid-filled microchambers: solutal buoyancy and diffusiophoresis. Catalyst-coated sheets, which resemble crabs with four distinct “claws”, convert reactants in solution into products, and thereby create local variations in the density and chemical composition of the fluid. Via the solutal buoyancy mechanism, the density variations generate fluid flows, which modify the shape and motility of the “crabs”. Concomitantly, the chemical variations propel the motion of the particles via diffusiophoresis and, thus, the crabs’ and particles’ motion becomes highly interconnected. For crabs with restricted lateral mobility, these two mechanisms can be modulated to either drive a crab to catch and appear to “feed” on all the particles or enable the particles to “flee” from this sheet. Moreover, by adjusting the sheet’s size and the catalytic coating, two crabs can compete and “fight” over the motile, diffusiophoretic particles. Alternatively, the crabs can temporally “share” resources by shuttling the particles back and forth between themselves. With completely mobile sheets, four crabs can collaborate to perform a function that one alone cannot accomplish. These findings provide design rules for creating chemically-driven soft robotic sheets that significantly expand the functionality of microfluidic devices.

CIS Seminar: "Networked Systems in the Era of Programmable Dataplanes"
2020-01-21 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
Emerging networking architectures are allowing for flexible and reconfigurable packet processing at line rate both on the switch and the NIC. Despite their promising new functionality, programmable switches and NICs are not all-powerful; they have limited state, support limited types of operations, and limit per-packet computation to operate at line rate. In this talk, I will describe how to mask resource limitations using approximation techniques and new scheduling algorithms and how to build a general framework for exposing in-network computing capability to distributed applications. In addition to presenting case studies of optimizing networked systems, I will reflect on the role of programmable dataplanes in datacenter computing.

MEAM Seminar: "Plate Mechanical Metamaterials and their Applications"
2020-01-21 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Recently, we introduced the concept of plate mechanical metamaterials—cellular plates with carefully controlled periodic geometry and unique mechanical properties—as well as its initial realization in the form of freestanding corrugated plates made out of an ultrathin film. We used atomic layer deposition (ALD) and microfabrication techniques to make robust plates out of a single continuous ALD layer with cm-scale lateral dimensions and thicknesses between 25 and 100 nm, creating the thinnest freestanding plates that can be picked up by hand. We also fabricated and characterized nanocardboard – plate metamaterials made from multiple layers of nanoscale thickness, whose geometry and properties are reminiscent of honeycomb sandwich plates or corrugated paper cardboard. Ultralow weight, mechanical robustness, thermal insulation, as well as chemical and thermal stability of alumina make plate metamaterials attractive for numerous applications, including structural elements in flying microrobots and interstellar light sails, high-temperature thermal insulation in energy converters, photophoretic levitation, as well as ultrathin sensors and resonators. I will briefly discuss our experimental progress on all these applications, including demonstrations of extremely robust thermal insulators that can sustain a temperature difference of ~1000 K across a micron-scale gap, hollow AFM cantilevers that offer greatly enhanced sensitivity and data acquisition rates, and macroscopic plates that levitate when illuminated by light.

MSE Grace Hopper Lecture: "Artificial Intelligence for Generating Materials Science Knowledge"
2020-01-16 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
The process of scientific inquiry involves observing a signal (data) and interpreting it to generate information (knowledge). For example, in electron microscopy the signal may be a diffraction pattern from which information on crystal orientation may be deduced by applying diffraction theory. Science advances both through improvements in gathering data and in techniques for extracting knowledge from it. Artificial intelligence (AI) – a broad term comprising data science, machine learning (ML), neural network computing, computer vision, and other technologies – opens new avenues for extracting information from high-dimensional materials data. In that sense, AI offers the possibility to advance materials science in the same way as a new imaging modality or a new theoretical model. The applications of AI in materials science cut a broad swath, from large, labelled data sets the fit naturally in the Big Data paradigm to small, sparse, multimodal data sets that test the limits of cutting-edge AI.
This presentation will focus on AI applications in the context of image-based data, including both visual features and composition, processing, or properties metadata. Computer vision (CV) representations are developed to numerically encode the visual information contained in images. ML tools are then selected based on the characteristics of the data set and the desired outcome. For example, a large, homogeneous data set of steel inclusions is best suited to a Deep Learning approach involving a purpose-built convolutional neural network. In contrast, a random-forest method can find significant trends in a small, multi-modal data set that includes microstructural, crystallographic, and micromechanical data. Complex image segmentation leverages a convolution neural network that has been trained using images very different from those it is applied to. These case studies will motivate a discussion of AI method selection based on data set characteristics and desired outcomes. The ultimate goal is to develop AI as a new tool for information extraction and knowledge generation in materials science.

MSE Materials in Practice Seminar: "So You're an Engineer...Now What?"
2020-01-15 15:00 - 16:00 | LRSM Reading Room, 3231 Walnut St., Philadelphia, PA, 19104, United States
Materials in Practice is a seminar series where technologists who are using materials science to shape the world we live in share their secret to doing this. We hope that anyone who wants to apply the research they are doing to solve real world problems will be able to attend this Seminar Series.

MEAM Seminar: "Confined Curved Shells and their Elaborate Conformations"
2020-01-14 10:30 - 12:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Curved shells, when confined, can deform to a broad assortment of large scale shapes and smaller scale wrinkling and folding patterns quite unlike what produced by their flat counterparts. The intrinsic, natural curvature of shells is the central element that allows for this rich and very interesting morphological landscape, but it is also the source of geometric nonlinearities that renders an analytic treatment of non‐Euclidean shells, even under small load, very difficult. In this talk we examine some snapshots of this morphological landscape. Inspired by the natural folding and unfolding of polled grains, we use theory, simulations and experiments to explore the large scale deformation of a confined thin spherical shell with an opening. We then proceed to investigate the surface topography of shallow doubly curved shells resting on a fluid substrate. The frustration due to the competing geometry of the flat substrate and the curved shell produces a wealth of highly reproducible and ordered, or random and disordered patterns. From these examples, we see Gaussian curvature emerging as a powerful tool that can generate complex patterns.

REACT@Penn 2020: Global Pathways to enable Innovative Materials Solutions for Urban Challenges
2020-01-13 10:00 - 16:00 | Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
How can science and technology help cities solve their problems? Are there common urban air, water and energy challenges for science to tackle?

10:00 am
Urban Challenges with (potential) Materials Solutions
Model cities of Grenoble, France, Philadelphia, USA and Seoul, Korea

1:30 pm
Adoption and Adaptation of New Technologies for Urban Challenges
Joshua Sperling, National Renewable Energy Laboratory

2:30 pm
Facilitating New Technology-based Solutions for Urban Challenges
Panel discussion that includes experts from the Water Center at Penn, City of Philadelphia’s Department of Planning and Development and Office of Transportation, Infrastructure & Sustainability

https://react.seas.upenn.edu/event/react-at-penn-2020/

Thesis Defense: "Transcriptional Control of Endothelial Cell Motility, Extracellular Matrix Sensing, and Vasculogenesis"
2020-01-10 14:00 - 15:00 | Class of 62 Auditorium, John Morgan Building, 3620 Hamilton Walk, Philadelphia, PA, 19104
The Department of Bioengineering at the University of Pennsylvania and Dr. Joel Boerckel are pleased to announce the Doctoral Dissertation Defense of Devon E. Mason.
This event is open to the public.

BE Seminar: "High-throughput T cell repertoire profiling enabled systems immunology and immune engineering"
2020-01-09 12:00 - 13:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
T cells are important to the initiation, prevention, and cure of many diseases. For example, various T cells based cancer immunotherapies have been quite effective in treating several types of cancers. However, a significant fraction of patients do not respond. A comprehensive understanding of the complexity of the T cells repertoire in health and diseases not only provide underlying mechanisms but also new therapeutic targets. In the past several years, we have developed several tools to profile the T cell repertoire from T cell receptor diversity to T cell receptor affinity to multi-dimensional profiling of single T cells in high-throughput. In this talk, I will first introduce these tools and then give examples on how we use them to answer some of the fundamental questions in systems immunology, which in turn help us design new approaches in immune engineering.

CBE Dissertation Defense: "Controllable, Synthetic Membrane-Less Organelles from Recombinant Proteins"
2019-12-17 13:00 - 15:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Committee: Dr. Daniel A. Hammer, Advisor; Drs. Kathleen J. Stebe, Daeyeon Lee and Elizabeth Rhoades

MEAM Doctoral Dissertation Defense: "Estimation, Mapping and Navigation with Micro Aerial Vehicles for Infrastructure Inspection"
2019-12-10 15:00 - 16:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Multi-rotor Micro Aerial Vehicles (MAV) have become popular robotic platforms in the last decade due to their manufacturability, agility and diverse payload options. Amongst the most promising applications areas of MAVs are inspection, air delivery, surveillance, search and rescue, real estate, entertainment and photography to name a few. While GPS offers an easy solution for outdoor autonomy, using onboard sensors is the only solution for autonomy in constrained indoor environments. In this work, we study onboard state estimation, mapping and navigation of a small MAV equipped with a minimal set of sensors inside GPS-denied axisymmetric tunnel-like environments such as penstocks. We primarily focus on state estimators formulated for different sensor suits which include 2D/3D lidars, cameras and Inertial Measurement Units (IMU). Penstocks are pitch dark environments and offer very weak visual texture even with onboard illumination, hence our estimators primarily rely on lidars and IMU. The point cloud data returned by the lidar consists of either elliptical contours or indiscriminate partial cylindrical patches making localization along the tunnel axis theoretically impossible. Cameras track features on the walls using the onboard illumination to estimate the velocity along the tunnel axis unobservable to range sensors. Information from all sensors are then fused in a central Kalman Filter for 6 Degrees-of-Freedom (DOF) state estimation. These approaches are validated through onsite experiments conducted in four different dams demonstrating state estimation, environment mapping, autonomous and shared control.

ESE PhD Thesis Defense: "Affordances and Control of a Spine Morphology for Robotic Quadrupedal Locomotion"
2019-12-06 15:00 - 16:30 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Abstract: How does a robot’s body affect what it can do? This talk explores this question with respect to a morphology common to biology but rare in robotics: the presence of a bendable back. Using the Canid and Inu quadrupedal robots, I describe and quantify several advantages afforded by this morphological design choice for legged machines that can be evaluated against the spine’s added weight and complexity. Additionally, I discuss control strategies related to quadrupedal running with a spine.

MSE Seminar: "In-Situ Resistance Degradation & Switching of Bulk Fe-doped SrTiO3 and Yttria-Stabilized Zirconia"
2019-12-05 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
Perovskite-type titanates are the standard dielectric used in multilayer ceramic capacitors (MLCCs), and yttria-stabilized (YSZ) is the prototypical fast oxygen conductor used in solid oxide fuel cells (SOFCs) and oxygen sensors. Under a DC electric field, the resistance of YSZ and Fe-doped strontium titanate (Fe-STO) degrades in an indistinguishable way. This is surprising because, unlike YSZ, Fe-STO is a p-type semiconductor, so they cannot possibly degrade by the same mechanism. For decades, it is known that the degradation of perovskite titanates is caused by the migration of oxygen vacancies towards the cathode, where they are blocked, and thus pile up, which changes the region to n-type. In contrast, through highly accelerated in situ lifetime tests, we determined, for the first time, that the DC voltage induces in YSZ a metal-insulator transition that propagates from the cathode to the anode, which lowers the resistance by orders of magnitude. In situ studies have further provided direct observations and mechanisms of resistance switching of both YSZ and Fe-STO. This is also of great importance as they relate to another technologically relevant device: resistance random access memory (ReRAM), which is currently explored for neuromorphic computing.

MEAM Special Seminar: "Differences in Material Properties of Trabecular Bone Tissue from Modeling- and Remodeling-Based Bone Formation in Rats"
2019-12-03 12:00 - 13:00 | CRB Auditorium, 415 Curie Boulevard, Philadelphia, PA, 19104, United States
Bone undergoes continuous changes during life through processes of bone modeling and remodeling. Modeling-based bone formation (MBF) i.e. bone formation without prior activation of osteoclastic resorption, only occurs during growth, healing, and in response to external mechanical loading. Remodeling-based bone formation (RBF), which is tightly coupled with bone resorption by osteoclasts, plays a predominant role maintaining skeletal health. Recent studies identified the activation of MBF as an important mechanism by which anabolic agents, such as intermittent parathyroid hormone (PTH), rapidly elicit new bone formation. Due to the challenge of differentiating between MBF and RBF on a thick bone specimen, the quality of the bone tissue generated through these two distinct cellular mechanisms is unknown. Therefore, the goal of this study is to (1) develop an imaging method that can be coupled with a mechanical testing platform for reliable identification and examination of material properties of MBF and RBF on thick bone sections, and (2) define the differences in material properties of trabecular bone tissue from MBF and RBF.

ESE Seminar: "Beyond Supervised Learning for Biomedical Imaging"
2019-12-03 11:00 - 12:00 | Smilow Center Auditorium, 3400 Civic Center Blvd, Philadelphia, PA, 19104, United States
Abstract: Today, many biomedical imaging tasks, such as 3D reconstruction, denoising, detection, registration, and segmentation, are solved with machine learning techniques. In this talk, I will present a flexible learning-based framework that has allowed us to derive efficient solutions for a variety of such problems, without relying on heavy supervision. I will primarily employ image registration as a concrete application and present the details of VoxelMorph, our unsupervised learning-based image registration tool. I will show empirical results obtained by co-registering thousands of brain MRI scans where VoxelMorph has yielded state-of-the-art accuracy with runtimes that are orders of magnitude faster than conventional tools. Finally, I will present some recent results where we used VoxelMorph to learn conditional deformable templates that can reveal population variation as a function of factors of interest, such as aging or genetics. Our code is freely available at https://github.com/voxelmorph/voxelmorph.

MEAM Seminar: "Physics-Informed Neural Networks (PINNs) for Physical Problems & Biological Problems"
2019-12-03 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
We will present a new approach to develop a data-driven, learning-based framework for predicting outcomes of physical and biological systems and for discovering hidden physics from noisy data. We will introduce a deep learning approach based on neural networks (NNs) and generative adversarial networks (GANs). We also introduce new NNs that learn functionals and nonlinear operators from functions and corresponding responses for system identification. Unlike other approaches that rely on big data, here we “learn” from small data by exploiting the information provided by the physical conservation laws, which are used to obtain informative priors or regularize the neural networks. We will also make connections between Gauss Process Regression and NNs and discuss the new powerful concept of meta-learning. We will demonstrate the power of PINNs for several inverse problems in fluid mechanics, solid mechanics and biomedicine including wake flows, shock tube problems, material characterization, brain aneurysms, etc, where traditional methods fail due to lack of boundary and initial conditions or material properties.

PSOC Seminar : 'Deconstructing tumor architecture'
2019-12-02 12:00 - 13:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States

ESE Seminar: "Management Strategies for Hyperscale Datacenters"
2019-11-26 11:00 - 12:00 | PICS Conference Room 534 – A Wing , 5th Floor, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: Hyperscale datacenters provide critical infrastructure for the information economy, refining data to extract value. Sharing datacenters improves energy efficiency but whether strategic users participate depends on management policies. I address these challenges by integrating practical insights from computer architecture with rigorous methods in algorithmic economics and machine learning. I illustrate this approach for power allocation and performance diagnosis. First, I allocate server power by anticipating strategic behavior and incentivizing participation. I design mechanisms in which users selfishly draw power to boost performance yet avoid oversubscribing the shared supply. Second, I diagnose performance anomalies by inferring interpretable causal relationships. I design statistical frameworks that learn performance models and extract recurring semantic structure from these models with natural language processing. Finally, I conclude by describing future directions for efficient and secure architectures in datacenters and beyond.

MEAM Seminar: "Micro/Nanomanufacturing of 3D Functional Coatings via Self-Limiting Electrospray Deposition"
2019-11-26 10:30 - 12:00 | Glandt Forum, Singh Center for Nanotechnology, 3205 Walnut Street, Philadelphia, PA, 19104, United States
Recent developments in nanostructured materials have demonstrated myriad desirable properties ranging from optical and mechanical metamaterials to biomanipulative surfaces. To bring these properties from the lab to the commercial space will require innovative nanomanufacturing strategies focused on scalable and cost-effective techniques. My lab, the Hybrid Micro/Nanomanufacturing Laboratory, applies the manipulation of fundamental driving forces to this challenge through combinations of top-down and bottom-up techniques for new hybrid lithographic strategies. In this seminar, I will highlight one such strategy: self-limiting electrospray deposition (SLED) of thin film microcoatings. Electrospray deposition is a well-established technique for the creation of thin films from the spray of highly charged droplets loaded with the materials to be deposited. In SLED, specific manipulation of the electrostatic repulsion, hydrodynamic forces, and evaporation kinetics can be employed to conformally cover 3D architectures with microcoatings. The generated coatings are hierarchical, possessing either nanoshell or nanowire microstructure. Having demonstrated the mechanism of the self-limiting effect, we have developed the ability to employ materials that would be otherwise incompatible with self-limiting. In this way we have incorporated a wide variety of functional systems, including: (1) biocompatible, (2) plasmonic, (3) elastomerically-toughened composite, (4) anti-corrosive epoxy or sol gel, and (5) electrically conductive coatings. We have also characterized the geometric limits of features that can be coated through this approach, showing that the 3D capabilities increase with decreasing feature size to the micron-scale. This property, combined with the hierarchical structure of the coatings, shifts the burden of micro/nanoscale resolution from a costly or slow technique to a more scalable method, thereby removing barriers for integration into advanced manufacturing techniques such as roll-to-roll or additive manufacturing.
