Penn Engineering Events

PICS Seminar: "Coupled Multiphysics Models of Cardiac Hemodynamics: From Fundamental Insights to Clinical Translation"
2019-03-15 14:00 - 15:00 (America/New_York) | Room 401B, 3401 Walnut, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Abstract: The mammalian heart has been sculpted by millions of years of evolution into a flow pump par excellence. During the typical lifetime of a human, the heart will beat over three billion times and pump enough blood to fill over 60 Olympic-sized swimming pools. Each of these billions of cardiac cycles is itself a manifestation of a complex and elegant interplay between several distinct physical domains including electrophysiology and mechanics of the cardiac muscles, hemodynamics, and flow-induced movement of the cardiac valves. Another multiphysics interaction that is key to hemostasis involves hemodynamics and blood biochemistry. The clotting cascade, which is a natural response to injury, is initiated by a sequence of biochemical reactions that are strongly modulated by the local flow conditions. In this regard, how the chambers and valves of a healthy heart manage to avoid thrombosis, remains an open question. The presence of heart conditions such as myocadial infarction (MI), cardiomyopathies, valve anomalies and atrial fibrillations, disturb the hemostatic balance and can lead to thrombosis with devastating sequalae such as stroke and MI. Computational models for thrombogenesis in the cardiac system have the potential to provide useful insights into this important phenomenon. In the current talk, I will describe high-fidelity chemo-fluidic modeling of thrombogenesis in the left heart and demonstrate how fundamental insights from these studies are translated into clinically relevant metrics. Application of these models to thrombogenesis in transcatheter aortic valves will also be described.

ESE Seminar: "Confluence of Electromagnetics, Circuits and Systems Enables The Third Wireless Revolution"
2019-03-15 11:00 - 12:00 | Berger Auditorium (Room 13), Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA, 19104, United States
Integrated circuits have fueled several revolutions that have deeply impacted modern society, including the computing revolution, the internet and the first two wireless revolutions. We are at the dawn of the third wireless revolution, which I call the Wireless Mobile Reality revolution. Over the next fifteen years, new wireless paradigms spanning from radio frequencies to millimeter-waves and terahertz will change the way in which we interact with the real world, through applications such as mobile virtual and augmented reality, vision quality imaging, gesture recognition and bio- and materials-sensing.
However, at the same time, integrated circuits are starting to run out of steam – technology scaling is no longer yielding better transistors that are faster and lower power. Therefore, circuit design needs to be refreshed with new tools and techniques that draw inspiration from the layers below (electromagnetics and device physics) and the layers above (communication systems and networking).
In this talk, I will describe research along these lines from the CoSMIC lab at Columbia University. I will start by describing a new approach to breaking Lorentz reciprocity to engineer high-performance non-reciprocal components, such as gyrators, isolators and circulators. I will then talk about how these integrated non-reciprocal circulators enable practical integrated full-duplex wireless radios. Finally, I will talk about the FlexICoN project at Columbia which is taking a holistic and cross-layer view of full-duplex networks from the physical layer to the networking layer. I will also briefly touch upon other work from CoSMIC lab in the same vein related to high-power, high-efficiency millimeter-wave radios, MIMO radios, opto-electronic LIDARs and city-scale wireless testbeds.

CIS Seminar: "Data Discovery: Unleashing the Value of Data"
2019-03-14 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Organizations use only a small portion of all data they own.
Consequently, most of the potential value is untapped. This happens
because their analysts suffer a data discovery problem: when solving a
task that requires data, analysts spend more time finding the relevant
data than solving the task at hand. The core problem is that there is
not adequate infrastructure to support the many different discovery
problems organizations face. Hence, finding data remains largely a
manual and time-consuming process.
In this talk I’ll present Aurum, a system that radically changes how
users interact with their organizations’s data. With Aurum users can
solve discovery problems in minutes instead of weeks. To achieve this,
Aurum has three novel features: 1) it makes data discovery programmable
so users can solve many different discovery problems by writing
different programs; 2) it solves data discovery queries fast, so users
can solve their problems in minutes instead of weeks; 3) it scales to
large amounts of data, so no relevant data is left behind. In addition,
I’ll explain how Aurum handles not only structured data such as tables
in databases, data lakes, and spreadsheets, but also unstructured data
such as PDF files, word documents, and even conversations from Slack
channels.
I’ll conclude with a vision for how to make data easier to work with and
to program, a key ingredient needed to exploit all data available in
organizations and enable new applications.

SEAS Special Seminar: "More than Pretty Pictures: Improving your Graphics and Figures"
2019-03-14 14:00 - 15:00 | College Hall

BE Seminar: "Microfluidics and Immuno-Materials for Organs-on-a-Chip"
2019-03-14 12:00 - 13:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
This presentation will describe microfluidic technologies to conveniently produce life-like pulsatile flows along with applications to study of lung injury, enhancement of in vitro fertilization, and analysis of frequency-dependent cellular responses. The microfluidic technologies range from adaptation of piezo-electric actuator arrays from Braille displays to design of microfluidic circuits that can be designed to switch fluid flow on and off periodically on their own. The presentation will also describe engineered materials to mimic an aspect of the innate immune system to combat bacterial infection. More specifically, reconstituted chromatin microwebs inspired by neutrophil extracellular traps. Using a defined composition reconstituted chromatin microweb, we reveal impact of microweb DNA-histone ratio on bacteria capture. Additionally, we found that E. coli, including clinical isolates and resistant strains, are killed more efficiently by the last-resort antibiotic, colistin, when bound to microwebs. Recent efforts towards incorporation of these materials into human cell systems will also be described. Time permitting, topics on organoids, fibrosis, liquid-liquid phase separation, and scaling may be incorporated.

ESE Seminar: "Software, Architecture, and VLSI Co-Design for Efficient Task-Based Parallel Runtimes"
2019-03-14 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Fast-paced changes across the computing stack are creating opportunities for innovation by bridging software, architecture, and VLSI. Cross-cutting research is challenging, but it can expose key insights that would otherwise be hidden by abstractions. In this talk, I will demonstrate a cross-stack approach to improve the efficiency of task-based parallel runtimes, which are important because they underpin the parallelization of state-of-the-art graph analytics and machine learning frameworks. Shifting the focus downward, I will discuss a cross-stack approach that addresses key circuit-level challenges in integrated voltage regulation. To finish the talk, I will discuss my future plans to apply a cross-stack research approach to expand beyond the perceived limits of intelligence on the edge and also to decrease the challenges of complex ASIC design with hardware design techniques based on Lego-like tiling.

MSE Seminar: "Nano-Emulsion design, synthesis and applications in medicine"
2019-03-14 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States

CBE Seminar: "Predicting and Controlling Stability and Protein-Protein Interactions for Therapeutic Antibodies"
2019-03-13 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States

CIS Seminar: "Language as a Scaffold for Grounded Intelligence:
2019-03-13 11:00 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:

Natural language can be used to construct rich, compositional descriptions of the world, highlighting for example entities (nouns), events (verbs), and the interactions between them (simple sentences). In this talk, I show how compositional structure around verbs and nouns can be repurposed to build computer vision systems that scale to recognize hundreds of thousands of visual concepts in images. I introduce the task of situation recognition, where the goal is to map an image to a language-inspired structured representation of the main activity it depicts. The problem is challenging because it requires recognition systems to identify not only what entities are present, but also how they are participating within an event (e.g. not only that there are scissors but they are they are being used to cut). I also describe new deep learning models that better capture compositionality in situation recognition and leverage the close connection to language ‘to know what we don’t know’ and cheaply mine new training data. Although these methods work well, I show that they have a tendency to amplify underlying societal biases in the training data (including over predicting stereotypical activities based on gender), and introduce a new dual decomposition method that significantly reduces this amplification without sacrificing classification accuracy. Finally, I propose new directions for expanding what visual recognition systems can see and ways to minimize the encoding of negative social biases in our learned models.

CIS Seminar: "Towards Embodied Visual Intelligence"
2019-03-12 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
What would it mean for a machine to see the world? Computer vision has recently made great progress on problems such as finding categories of objects and scenes, and poses of people in images. However, studying such tasks in isolated disembodied contexts, divorced from the physical source of their images, is insufficient to build intelligent visual agents. My research focuses on remarrying vision to action, by asking: how might vision benefit from the ability to act in the world, and vice versa? Could embodied visual agents teach themselves through interaction and experimentation? Are there actions they might perform to improve their visual perception? How might they construct visual plans to achieve long-term action goals? In my talk, I will set up the context for these questions, and cover some strands of my work addressing them, proposing approaches for self-supervised learning through proprioception, visual prediction for decomposing complex control tasks, and active perception. Finally, I will discuss my long-term vision and directions that I hope to work on in the next several years

ESE Seminar: "Ultra-Low-Power Neural Interfaces: from Monitoring to Diagnosis and Therapy"
2019-03-12 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Implantable and wearable medical devices are increasingly being developed as alternative therapies for intractable diseases. In particular, undertreated neurological disorders such as epilepsy, migraine, and Alzheimer’s disease are of major public health concern around the world, driving the need to explore such new approaches. Despite significant advances in neural interface systems, the small number of recording channels in existing technology remains a barrier to their therapeutic potential. This is mainly due to the fact that simultaneous recording from a large number of electrodes imposes stringent energy and area constraints on the integrated circuits that interface with these electrodes. In this talk, I will first discuss an efficient compressive sensing framework for multichannel cortical implants. Next, I will present the design of our sub-microwatt per channel closed-loop seizure control device and both its in-vivo and offline performance. I will then discuss our latest work on the integration of machine learning algorithms for on-chip classification of neural data. Finally, I will give examples of how these results may be used towards designing new devices, to enhance the lives of millions of people suffering from disabling neurological conditions in future.

ESE Seminar: "Towards Robotic Manipulation - Understanding the World Through Contact"
2019-03-08 11:00 - 12:00 | Berger Auditorium (Room 13), Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA, 19104, United States
Why is robotic manipulation so hard? As humans, we are unrivaled in our ability to dexterously manipulate objects and exhibit complex skills seemingly effortlessly. Recent research in cognitive science suggests that this ability is driven by our internal representations of the physical world, built over a life-time of experience. Our predictive ability is complemented by our senses of sight and touch, intuitive state-estimation, and tactile dexterity. Given the complexity of human reasoning, skill, and hardware, it is not surprising that we have yet to replicate our abilities in robots. In order to bridge this gap, we must take a holistic perspective on manipulation and build robotic systems that understand and interpret their physical world through contact.
In this talk, I will present two methodologies that strive to this end: First, a physics-based
methodology for the inference of contact forces and system parameters of rigid-bodies systems making and breaking contact. Second, how a robot can learn the physics of playing Jenga using a hierarchical-learning methodology purely from data. I will conclude the talk by touching upon data-augment contact models and providing perspectives on building robotic systems that embody intelligent manipulation.

ESE Seminar: "From Nanotech to Living Sensors: Unraveling the Spin Physics of Biosensing at the Nanoscale"
2019-03-07 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
I am a quantum engineer interested in how quantum physics informs biology at the nanoscale.
As a physicist, I have developed high-performance nanosensors that essentially worked due to room-temperature quantum effects in noisy environments. Currently, I am focusing on “living sensors” — organisms and cells that respond to minute stimuli, routinely outperforming technological probes in awe-inspiring ways. Unveiling and controlling the underlying physical mechanisms employed by “living sensors” impact: the engineering of ultrasensitive, bio-inspired electromagnetic probes; the elucidation of mesmerizing natural feats such as animal navigation; and the advancement of therapeutics for metabolic-related diseases.
Substantial in vitro and physiological experimental results are consistent with the fact that similar spin physics might underlie biosensing modalities as varied as organismal magnetic field detection and metabolic regulation of oxidative stress in cells.
Can spin physics be established — or refuted! — to account for physiologically relevant biosensing phenomena, and be manipulated to technological and therapeutical advantage? This is the broad, exciting question that I wish to address in my scientific career.

PSOC Spring 2019 Seminar Series: Theresa Whitehead, Ph.D.
2019-03-04 12:00 - 13:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States

ESE Seminar: "Quantum Nanophotonics: Engineering Atom-Photon Interactions on a Chip"
2019-03-01 11:00 - 12:00 | Berger Auditorium (Room 13), Skirkanich Hall, 210 South 33rd Street, Philadelphia, PA, 19104, United States
Abstract: The ability to engineer controllable atom-photon interactions is at the heart of quantum optics and quantum information processing. In this talk, I will introduce a nanophotonic platform for engineering strong atom-photon interactions on a semiconductor chip. I will first discuss an experimental demonstration of a spin-photon quantum transistor [1], a fundamental building block for quantum repeaters and quantum networks. The device allows a single spin trapped inside a semiconductor quantum dot to switch a single photon, and vice versa, a single photon to flip the spin. I will discuss how the spin-photon quantum transistor realizes optical nonlinearity at the fundamental single quantum level, where a single photon could switch the transmission of multiple subsequent photons [2]. I will next discuss the promise of realizing photon-mediated many-body interactions in an alternative solid-state platform based on a more homogeneous quantum emitter, silicon-vacancy (SiV) color centers in diamond. I will introduce our efforts in creating strong light-matter interactions through photonic crystal cavities fabricated in diamond [3], and the use of cavity-stimulated Raman emission to overcome the remaining frequency inhomogeneity of the emitters [4]. Finally, I will outline the exciting prospects of applying inverse designed nanophotonic structures into quantum optics, and their potential applications in engineering photon-mediated atom-atom interactions.
References
[1] S. Sun et al., Nature Nanotech. 11, 539–544 (2016).
[2] S. Sun et al., Science 361, 57-60 (2018).
[3] J. L. Zhang* and S. Sun* et al., Nano Lett. 18, 1360–1365 (2018).
[4] S. Sun et al., Phys. Rev. Lett. 121, 083601 (2018)

CIS Seminar: " Rethinking the hardware-software contract: Enabling practical and general cross-layer optimizations"
2019-02-28 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Layered abstractions in the computing stack are critical to building complex systems, but the existing *interfaces* between layers restrict what can be done at each level. Enhancing cross-layer interfaces–specifically, the hardware-software interface–is crucial towards addressing two important and hard-to-solve challenges in computer systems today: First, significant effort and expertise are required to write high-performance code that harnesses the full potential of today’s diverse and sophisticated hardware. Second, as a hardware or system designer, architecting faster and more efficient systems is challenging as the vast majority of the program’s semantic content and programmer intent gets lost in translation with today’s hardware-software interface. Moving towards the future, these challenges in programmability and efficiency will be even more intractable as we architect increasingly heterogeneous and sophisticated systems.
In this talk, I will highlight my work [ISCA‘15, MICRO‘16, ISCA‘18, ISCA‘18] on how to design rich cross-layer abstractions that provide layered interfaces to directly communicate higher-level program semantics and intent from the application to the lower levels of the stack. In doing so, we can effectively bridge the so-called “semantic gap” between applications and computer systems, and enable a wide range of cross-layer optimizations in future systems with a unifying interface. I will discuss how cross-layer approaches with these abstractions can significantly enhance (1) performance and efficiency by enabling the system to adapt to application characteristics and (2) programmability and portability by enabling application software to easily leverage diverse underlying hardware resources without specific knowledge of system details. For example, daunting aspects of programming GPUs can be made much simpler with a rich cross-layer programming abstraction. I will describe how such abstractions can be designed to be highly practical and low-overhead, requiring only small additions to existing abstractions.

ODI Seminar: Christopher Hart, Former NTSB Chairman, on the Future of Autonomous Vehicles
2019-02-28 12:00 - 14:00 | Raisler Lounge (Room 225), Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Join the Office of Diversity and Inclusion for an afternoon with Christopher Hart, who will discuss the state and future of autonomous vehicles. The talk will be followed by a reception.

ESE Seminar: "Towards Socially-Aware Autonomy for Mobility-Efficient Smart Cities"
2019-02-28 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
As cities grow everywhere, and urban roadways become overburdened, efficient strategies are required for improving mobility. With the prevalence of smart sensing and Internet of Things (IoT) devices, such as smartphones and smart intersections, the physical infrastructures of our cities are being connected to the cyber world. As a result, cities are becoming smart. Moreover, with the emergence of new and inevitable technologies, such as autonomous and connected vehicles, mobility on demand systems, and electric vehicles, smart cities are rapidly evolving. As we experience the arrival of such technologies, there is an opportunity to reclaim urban mobility. However, a blind utilization of these technologies may deflect us from reaching this goal. In my research, I leverage the connectivity that is inherent in smart cities as well as the opportunities that new technologies such as autonomous and connected vehicles provide, to study the efficient operation of smart cities via management strategies that can guarantee overall societal benefits.
In this talk, I will focus on the societal-scale mobility implications of the increased deployment of autonomous and connected vehicles in mixed-autonomy traffic networks, where both human-driven and autonomous vehicles will coexist on the roads. I will first talk about the mobility implications of selfish autonomy, in which autonomous cars are not aware of their overall impact and simply attempt to optimize their own travel benefits. In this context, I will introduce conditions under which an increase in the fraction of autonomous vehicles on a traffic network, even when operating selfishly, results in increased societal mobility benefits. Conversely, I will show that if these conditions do not hold, overall network mobility may degrade as the fraction of autonomous vehicles increases. Having shown the negative consequences that the increased deployment of autonomous and connected vehicles may have on the operation of traffic networks, I will further discuss the use of traffic management strategies, such as pricing, which can guarantee the overall societal-scale efficiency of traffic networks with mixed vehicle autonomy.

CBE Seminar: "Mechanisms of Cellulose Activation and Implications for Bioenergy"
2019-02-27 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States

CIS Seminar: "Perceiving Humans in the 3D World"
2019-02-26 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Since the dawn of civilization, we have functioned in a social environment where we spend our days interacting with other humans. As we approach a society where intelligent systems and humans coexist, these systems must also interpret and interact with humans that reside in the 3D world. While computer vision systems today work well for finding 2D patterns in images or reconstructing rigid objects in 3D, they still struggle to perceive non-rigid objects in 3D, like moving human bodies. My goal is to build a system that can perceive and understand embodied agents in the 3D world from visual input. Such systems can enable motion capture in-the-wild, robots that learn to act by visually observing people, and ultimately, socially intelligent machines that understand human behavior.

In this talk, I will discuss my work in reconstructing 3D non-rigid, deformable objects such as humans and animals from everyday photographs and video, and show how such systems can be used to train a simulated character to learn to act by watching YouTube videos. I will discuss the challenges related to the limited availability and quality of ground-truth 3D data and how we can overcome these challenges using weakly supervised approaches.

ESE Seminar: "New Designer Materials: Sculpting Electromagnetic Fields on the Atomic Scale"
2019-02-26 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
New optical nanomaterials hold the potential for breakthroughs in a wide range of areas from ultrafast optoelectronics such as modulators, light sources and hyperspectral detectors, to efficient upconversion for energy applications, bio-sensing and quantum information science. An exciting opportunity to realize such new nanomaterials lies in controlling the local electromagnetic environment on the atomic- and molecular-scale (~1-10 nm), which enables extreme local field enhancements. We use creative nanofabrication techniques at the interface between chemistry and physics to realize this new regime together with ultrafast optical techniques to probe the emerging phenomena. Here, I will provide an overview of our recent research including high-speed thermal photodetectors, ultrafast spontaneous emission and metasurface-enhanced biosensors.

MEAM Seminar: "Interfacial Soft Matter"
2019-02-26 10:30 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Surface tension plays a critical role in a wide range of biological, environmental, technological and geophysical settings. In this talk, I will present three different problems dealing with interfacial soft matter that find motivation in markedly diverse areas. First, I will discuss the evaporation kinetics and flow dynamics of non-spherical sessile drops undergoing phase change. While previous investigations have been restricted to axisymetric drops, I will illustrate a number of new geometry-induced effects emerging from consideration of a range of non-spherical drops. Second, I will describe the non-equilibrium dynamics and statistical behavior of a hydrodynamic pilot-wave system, a liquid drop self-propelling on the surface of a vibrating fluid bath through a resonant interaction with its own wave field. In particular, I will consider the wave-mediated interaction of this active system with variable bottom topography to illustrate the emergence of wavelike statistics around defects, and spontaneous collective order and phase transitions in spin lattices. The final part of this talk will deal with active colloids. Specifically, I will consider the realignment of a Janus drop, a double-emulsion drop formed by two immiscible fluids, in response to an externally-imposed temperature gradient. The development of dynamically reconfigurable microlenses based on this mechanism will also be discussed.

PRiML Seminar: "Optimizing probability distributions for learning: sampling meets optimization"
2019-02-22 15:00 - 16:00 | Room 401B, 3401 Walnut, 3401 Walnut Street, Philadelphia, PA, 19104, United States
Optimization and sampling are both of central importance in large-scale machine learning problems, but they are typically viewed as very different problems. This talk presents recent results that exploit the interplay between them. Viewing Markov chain Monte Carlo sampling algorithms as performing an optimization over the space of probability distributions, we demonstrate analogs of Nesterov’s acceleration approach in the sampling domain, in the form of a discretization of an underdamped Langevin diffusion. In the other direction, we view stochastic gradient optimization methods, such as those that are common in deep learning, as sampling algorithms, and study the finite-time convergence of their iterates to an invariant distribution.

CIS Seminar: "Towards Generalization and Efficiency in Reinforcement Learning"
2019-02-22 11:00 - 12:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:

In classic supervised machine learning, a learning agent behaves as a passive observer: it receives examples from some external environment which it has no control over and then makes predictions. Reinforcement Learning (RL), on the other hand, is fundamentally interactive : an autonomous agent must learn how to behave in an unknown and possibly hostile environment, by actively interacting with the environment to collect useful feedback. One central challenge in RL is how to explore an unknown environment and collect useful feedback efficiently. In recent practical RL success stories, we notice that most of them rely on random exploration which requires large a number of interactions with the environment before it can learn anything useful. The theoretical RL literature has developed more sophisticated algorithms for efficient learning, however, the sample complexity of these algorithms has to scale exponentially with respect to key parameters of underlying systems such as the dimensionality of state vector, which prohibits a direct application of these theoretically elegant RL algorithms to large-scale applications. Without any further assumptions, RL is hard, both in practice and in theory.

In this work, we improve generalization and efficiency on RL problems by introducing extra sources of help and additional assumptions. The first contribution of this work comes from improving RL sample efficiency via Imitation Learning (IL). Imitation Learning reduces policy improvement to classic supervised learning. We study in both theory and in practice how one can imitate experts to reduce sample complexity compared to RL approaches. The second contribution of this work comes from exploiting the underlying structures of the RL problems via model-based learning approaches. While there exist efficient model-based RL approaches specialized for specific RL problems (e.g., tabular MDPs, Linear Quadratic Systems), we develop a unified model-based algorithm that generalizes a large number of RL problems that were often studied independently in the literature. We also revisit the long standing debate on whether model-based RL is more efficient than model-free RL from a theoretical perspective, and demonstrate that model-based RL can be exponentially more sample efficient than model-free ones, which to the best of our knowledge, is the first that separates model-based and model-free general approaches.

CIS Seminar: "Cataloging the Visible Universe through Bayesian Inference at Petascale"
2019-02-21 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States
Abstract:
A key task in astronomy is to locate astronomical objects in images and to characterize them according to physical parameters such as brightness, color, and morphology. This task, known as cataloging, is challenging for several reasons: many astronomical objects are much dimmer than the sky background, labeled data is generally unavailable, overlapping astronomical objects must be resolved collectively, and the datasets are enormous — terabytes now, petabytes soon. Existing approaches to cataloging are largely based on algorithmic software pipelines. In this talk, I present a new approach to cataloging based on inference in a fully specified probabilistic model. I consider two inference procedures: one based on variational inference (VI) and another based on MCMC. A distributed implementation of VI, written in Julia and run on a supercomputer, achieves petascale performance — a first for any high-productivity programming language. The run is the largest-scale application of Bayesian inference reported to date. In an extension, using new ideas from variational autoencoders and deep learning, I avoid many of the traditional disadvantages of VI relative to MCMC, and improve model fit

ESE Seminar: "Physics-Driven Sensing and Processing: From Computational Periscopy to Particle Beam Microscopy"
2019-02-21 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
In many areas of science and engineering, novel signal acquisition methods allow unprecedented access to physical measurements. From digital cameras to microscopes and nano-scale biosensors, the data generated are shaped by both the underlying physics of the phenomena and characteristics of the acquisition device. Meanwhile, in many practical scenarios, the useful signals are remarkably weak, the measurements sparse, or even the acquisition process itself may damage the observed sample. These realities therefore necessitate the development of techniques that combine signal processing with physics-driven modelling to transcend current capabilities and enable, for instance: imaging of hidden scenes (or computational periscopy), the algebraic inversion of physical fields, and the reduction of sample damage in particle beam microscopy.
This concept of combining physics with signal processing will be the main theme of my talk. First, I will show that computational periscopy with ordinary digital cameras can be made possible by judiciously exploiting the physics of light transport to analyze subtle shadows, in a photograph of a visible surface. Second, I will briefly present an algebraic inversion method for fields constrained by partial differential equations and highlight its application to load-balancing in processors. Finally, by developing a detailed model and analysis for particle beam microscopy, I will show how introducing time-resolution into the acquisition process can significantly reduce beam dose, and sample damage, without compromising on imaging quality.

MSE Faculty Candidate Seminar: "Atom-Scale Engineering using 2D Materials"
2019-02-21 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States

CBE Seminar: "C4E – Computational Chemistry of Compounds for Catalysis and Energy"
2019-02-20 15:00 - 16:00 | Wu and Chen Auditorium (Room 101), Levine Hall, 3330 Walnut Street, Philadelphia, PA, 19104, United States

ESE Seminar: "Hybrid Quantum Networks: Interfacing Photons, Phonons, and Superconducting Qubits"
2019-02-19 11:00 - 12:00 | Room 337, Towne Building, 220 South 33rd Street, Philadelphia, PA, 19104, United States
Quantum information science strives to utilize the fundamental laws of physics to achieve revolutionary improvement in computation, communication, and sensing. Existing quantum protocols rely on a wide variety of physical platforms for storing, transferring, and processing of quantum information. Optical photons are the ideal carriers of information because of their low loss, large bandwidth of transmission, and resilience to thermal noise. However, the task of processing quantum information is exceedingly difficult to achieve in the optical domain because of the weakness of optical nonlinearities. Alternatively, superconducting quantum circuits provide a scalable means of storing and processing quantum information in the microwave regime but lack a mechanism for long-range information transfer.
Hybrid quantum networks promise to combine such essential functionalities in a system where superconducting processing nodes are joined via optical communication links. An integral element in this architecture is a quantum interconnect capable of interfacing the electrical and optical components across an immense frequency gap. I provide a summary of my past and current research on optical and microwave quantum systems and outline my future research directions, which aim to develop nano-engineered devices for entangling superconducting qubits with telecom-band optical photons and long-lived phonons.

MSE Faculty Candidate Seminar: “Tuning Nanoscale Materials Using the Local Environment”
2019-02-19 10:45 - 11:45 | Auditorium, LRSM Building, 3231 Walnut Street, Philadelphia, PA, 19104, United States
