SUNMONTUEWEDTHUFRISAT
Events for March 05, 2014
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Extracting Hidden Structure From Data: Provable Phase Retrieval by Non-Convex Optimization
Wed, Mar 05, 2014 @ 10:00 AM - 11:00 AM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Mahdi Soltanolkotabi, Stanford University
Talk Title: Extracting Hidden Structure From Data: Provable Phase Retrieval by Non-Convex Optimization
Abstract: A major challenge in modern data analysis is to reliably and automatically discover hidden structure in data with little or no human intervention. However, many mathematical abstractions of these problems are provably intractable in their most general form. Nevertheless, it may be possible to overcome these hardness barriers by focusing on realistic cases that rule out intractable instances.
In this talk we consider the question of recovering the seemingly hidden phase of an object from intensity-only measurements, a problem which naturally appears in X-ray crystallography, speech analysis and related disciplines. We study a physically realistic setup where one can modulate the signal of interest and then collect the intensity of its diffraction pattern. We show that a non-convex formulation of the problem recovers the phase information exactly from a number of near minimal random modulations. To solve this non-convex problem, we develop an iterative algorithm that combines a careful initialization together with a novel update that escapes all local minima and provably converges to the global optimum with a geometric rate. Our proposed scheme is near optimal in terms of usage of computational and data resources. We illustrate our methods with various real data experiments.
We will also briefly discuss other problems involving hidden structure in data (in particular subspace clustering and sparse recovery with coherent and redundant dictionaries) and conclude with a discussion of directions for future research.
Biography: Mahdi Soltanolkotabi is a Ph.D. candidate in Electrical Engineering at Stanford University, advised by Emmanuel Candes. Previously, he received a Master's degree in Electrical Engineering from Stanford University (2011) and a Bachelor's degree in Electrical Engineering from Sharif University of Technology (2009). His research interests include optimization, machine learning, signal processing, high-dimensional statistics, and geometry with emphasis on applications in the information and physical sciences. He was awarded the Benchmark Stanford Graduate Fellowship (2009-2012) as well as the Stanford teaching fellowship in electrical engineering (2011).
Host: Salman Avestimehr, avestimehr@ee.usc.edu, EEB 526, x07326
Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248
Audiences: Everyone Is Invited
Contact: Gerrielyn Ramos
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Wavefield Modeling and Signal Processing for Sensor Arrays of Arbitrary Geometry
Wed, Mar 05, 2014 @ 11:30 AM - 12:30 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Mário Costa, Aalto University
Talk Title: Wavefield Modeling and Signal Processing for Sensor Arrays of Arbitrary Geometry
Abstract: This talk considers wavefield modeling and its application to sensor array signal processing. In particular, we will see that wavefield modeling allows one to develop computationally-efficient and asymptotically-optimal array processing methods regardless of the array geometry. Wavefield modeling also facilitates incorporating array nonidealities, commonly present in real-world arrays, into array processing methods and performance bounds. Parameter estimation and beamforming in the azimuth-elevation-polarimetric domain will be addressed. Tools from harmonic analysis on the sphere, which are needed in wavefield modeling and manifold separation, will also be covered and novel results in the field will be provided. In addition to a review of well-known results in wavefield modeling, on-going research and open-problems in the area will be given.
Biography: Mário Costa was born in Portugal in 1984. He received the M.Sc.(Tech.) degree with distinction in Communications Engineering from Universidade do Minho, Portugal, in 2008, and the D.Sc.(Tech.) degree in Electrical Engineering from Aalto University (former Helsinki Univ. of Technology), Finland, in 2013. He has been with the Department of Signal Processing and Acoustics, Aalto University, Finland, since 2007. During 2007 as a Research Assistant, from 2008 to 2013 as a Researcher, and currently as a postdoctoral Researcher. From January to July 2011 he was an External Researcher at Connectivity Solutions Team, Nokia Research Center. His research interests include sensor array and statistical signal processing as well as wireless communications.
Host: Andreas Molisch, molisch@usc.edu, EEB 530, x04670
Location: Hughes Aircraft Electrical Engineering Center (EEB) - 349
Audiences: Everyone Is Invited
Contact: Gerrielyn Ramos
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EE-Electrophysics Seminar - Axel Scherer
Wed, Mar 05, 2014 @ 02:00 PM - 03:30 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Axel Scherer, California Institute of Technology
Talk Title: From Lab-on-a-Chip to Lab-in-the-Body: The Role of Nanotechnology in the Miniaturization of Medical Diagnostic Tools
Abstract: Miniaturization of devices has fueled the rapid evolution of microelectronic systems over the past decades. More recently, silicon has also emerged as an opto-electronic and electro-mechanical material. The manufacturability of high resolution silicon micro- and nanostructures is unparalleled, and the control over the precise geometry of silicon devices has followed the predictable path of Moore's law. In anticipation of the evolution of this trend, we will describe the opportunities of reducing the sizes of silicon devices to below 10nm to control mechanical, optical and electronic properties of silicon â with particular applications in medical instruments. We show some examples of nanostructures with dimensions below 10nm in all dimensions. This control enables many interesting devices with new optical, electrical and mechanical opportunities.
As the size of devices is reduced, it is possible to contemplate their integration within more complex and compact optical and electronic systems. During the second part of the presentation, the opportunities for integrated spectroscopy and data communications systems for implantable health monitors will be explored. The combination of power supply, data communications and biochemical detectors within small chips enables us to contemplate new microsystems for healthcare monitoring. Such systems could be implanted as glucometers, neural probes and other metabolic measurement tools and will enable a new class of continuous digital health monitors that hopefully leads to preventative healthcare at lower cost.
Biography: Axel Scherer is the Bernard A. Neches Professor of Electrical Engineering, Applied Physics, Medical Engineering and Physics at Caltech as well as a visiting professor at Dartmouth. He received his PhD in 1985, and after working in the Microstructures Research Group at Bellcore, joined the Electrical Engineering option at Caltech in 1993. Professor Scherer's group now works on micro- and nanofabrication of optical, magnetic and fluidic devices and their integration into microsystems. He has co-authored over 300 publications and holds over 100 patents in the fields of optoelectronics, microfluidics, and nanofabrication. Professor Scherer has co-founded three high-technology companies and built a state of the art cleanroom at Caltech. He has pioneered vertical cavity surface emitting lasers, microdisks, photonic crystals, silicon photonics and surface plasmon nanodevices, as well as microfluidic technologies. His group has perfected the fabrication and characterization of ultra-small structures with sizes down to 2nm, which are used in transistors and sensors. Presently, Professor Scherer works on the integration of microfluidic, electronic, photonic and magnetic devices for the purpose of building wireless implantable health monitors. The goal of this effort is to build inexpensive medical diagnostic tools that can provide feedback for the patients to control their health. Professor Scherer’s group also develops inexpensive and automated point-of-care instruments for clinical pathology.
Host: EE-Electrophysics
Location: EEB 132
Audiences: Everyone Is Invited
Contact: Marilyn Poplawski
