All Seminars
| Title: Isoperiodic Deformations and Stability for Finite-Gap Vortex Filaments |
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| Seminar: Analysis and Differential Geometry |
| Speaker: Professor Thomas A. Ivey of College of Charleston |
| Contact: Vladmir Oliker, oliker@mathcs.emory.edu |
| Date: 2011-03-30 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: The subject of this lecture concerns an integrable evolution equation for curves in R3, and the stability of some of its knotted solutions. |
| Title: EUMMA - Google PageRank |
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| Seminar: Mathematics |
| Speaker: Dr. Paul Horn of Emory University |
| Contact: Jodi-Ann Wray, jcwray@emory.edu |
| Date: 2011-03-30 at 6:00PM |
| Venue: MSC W301 |
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| Abstract: |
| Title: Zero cycles of degree one on principal homogeneous spaces |
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| Defense: Algebra |
| Speaker: Jodi Black of Emory University |
| Contact: R. Parimala, parimala@mathcs.emory.edu |
| Date: 2011-03-29 at 3:00PM |
| Venue: W306 |
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| Abstract: |
| Title: Numerical Methods for Optimal Experimental Design of Ill-posed Problems |
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| Defense: Dissertation |
| Speaker: Zhuojun Magnant of Emory Unviersity |
| Contact: Zhuojun Magnant, ztang4@emory.edu |
| Date: 2011-03-28 at 9:00AM |
| Venue: MSC E408 |
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| Abstract: The two goals of this thesis are to develop numerical methods for solving large-scale optimal experimental design problems efficiently and to apply optimal experimental design ideas to applications in regularization techniques and geophysics.\\ \\ The thesis can be divided into three parts. In the first part, we consider the problem of experimental design for linear ill-posed inverse problems. The minimization of the objective function in the classic A-optimal design is generalized to a Bayes risk minimization with a sparsity constraint. We present efficient algorithms for applications of such designs to large-scale problems. This is done by employing Krylov subspace methods for the solution of a subproblem required to obtain the experiment weights. The performance of the designs and algorithms is illustrated with a one-dimensional magnetotelluric example and an application to two-dimensional super-resolution reconstruction with MRI data.\\ \\ In the second part, we find the optimal regularization for linear ill-posed problems. We propose an optimal $L_2$ regularization approach enabling us to obtain inexpensive and good solutions to the inverse problem. In order to reduce the computational cost, several sparsity patterns are added to the regularization operator. Numerical experiments will show that our optimal $L_2$ regularization approach provides much better results than the traditional Tikhonov regularization.\\ \\ In the last part of the thesis, we design optimal placement of sources and receivers in a $CO_2$ injection monitoring. An optimal criteria is proposed based on a target zone and different treatments for placing sources and receivers are discussed. |
| Title: Coordinate Percolation |
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| Colloquium: Combinatorics |
| Speaker: Peter Winkler of Dartmouth College |
| Contact: Dwight Duffus, dwight@mathcs.emory.edu |
| Date: 2011-03-28 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: Percolation is the study of random subgraphs of a graph. In coordinate percolation, the big graph is a grid of some kind, and inclusion of a vertex depends on random values associated with the lines that cross there. Coordinate percolation arises in scheduling problems (in contrast to independent percolation, intended originally as a model for porous material).\\ \\ We'll consider several examples, including one that is notoriously difficult, and another that becomes miraculously easy when (with Lizz Moseman, NIST) combinatorial methods are applied. |
| Title: Limits of translates of divergent geodesics and Integral points on one-sheeted hyperboloids |
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| Seminar: Algebra and Number Theory |
| Speaker: Nimish Shah of Ohio State |
| Contact: Ken Ono, ono@mathcs.emory.edu |
| Date: 2011-03-22 at 3:00PM |
| Venue: MSC E406 |
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| Abstract: For any uniform lattice $\Gamma$ in $SL_2(R)$, we describe the limit distribution of the orthogonal translates of a {\it divergent} geodesic in $\Gamma/SL_2(R)$. We consider an important application to the theory of quadratic forms. This is joint work with Hee Oh. |
| Title: Fast Algorithms for Nonnegative Matrix Factorizations and Applications |
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| Seminar: Numerical Analysis and Scientific Computing |
| Speaker: Haesun Park of Georgia Institute of Technology |
| Contact: Veronica Bustamante, vmejia@emory.edu |
| Date: 2011-03-21 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: Nonnegative Matrix Factorization (NMF) has attracted much attention during the past decade as a dimension reduction method in machine learning and data mining. NMF is considered for high dimensional data where each element has a nonnegative value, and it provides a lower rank approximation formed by factors whose elements are also nonnegative. Numerous success stories were reported in application areas including text clustering, computer vision, and chemometrics. In this talk, we review several NMF algorithms available in literature and present our fast algorithms for NMF and their convergence properties. Our algorithms are based on alternating nonnegative least squares (ANLS) and active-set-type methods for non-negativity constrained least squares problem. They can naturally be extended to obtain highly efficient nonnegative tensor factorization (NTF) in the form of the PARAFAC (PARAllel FACtor) model, sparse NMF and NTF with L1 norm regularization. Extensive comparisons of algorithms using various data sets show that the proposed new algorithms outperform existing ones in computational speed. In addition, we introduce fast NMF algorithms with Bregman divergences, adaptive NMF algorithms for changing reduced ranks and data sets, symmetric NMF, and their performances in clustering and video analysis. |
| Title: Computing and Hedge Fund Management |
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| Seminar: Computer Science |
| Speaker: Dr. Tucker Balch of Georgia Institute of Technology |
| Contact: Valerie Summet, valerie@mathcs.emory.edu |
| Date: 2011-03-18 at 4:00PM |
| Venue: MSC W201 |
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| Abstract: Computing pervades today's equity markets. In addition to the electronic infrastructure in the markets to support orders from investors, many investors and traders use algorithmic methods for making trading decisions. I will provide an overview of some of the most popular quantitative tools for assessing portfolios and making trading decisions. I will also demonstrate the QuantSoftware ToolKit, an open source package for automating some of these processes.\\ \\ Bio: Tucker Balch is an associate professor in the School of Interactive Computing at Georgia Tech. He earned a BS and PhD in CS at Georgia Tech before joining the research faculty at CMU's Robotics Institute. He returned to Georgia Tech in 2001. Balch has published more than 140 peer reviewed conference and journal articles in Machine Learning and Robotics. He has a strong interest in finance and investing which led him to spend a sabbatical year as a quantitative analyst at a hedge fund. He is now shifting his teaching and research interests in that direction. |
| Title: Scattering for the cubic Klein Gordon equation in two space dimensions |
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| Seminar: Analysis and Differential Geometry |
| Speaker: Professor Betsy Stovall of University of California, Los Angeles |
| Contact: Shanshuang Yang, syang@mathcs.emory.edu |
| Date: 2011-03-15 at 4:00PM |
| Venue: MSC W301 |
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| Abstract: We will discuss a proof that finite energy solutions to the defocusing cubic Klein Gordon equation scatter, and will discuss a related result in the focusing case. (Don't worry, we will also explain what it means for a solution to a PDE to scatter.) This is joint work with Rowan Killip and Monica Visan. |
| Title: Numerical Solution of the k-Eigenvalue Problem |
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| Defense: Dissertation |
| Speaker: Steven Hamilton of Emory University |
| Contact: Steven Hamilton, sphamil@emory.edu |
| Date: 2011-03-15 at 4:00PM |
| Venue: MSC W303 |
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| Abstract: The k-eigenvalue problem is a generalized eigenvalue problem relevant to the design and analysis of nuclear reactors. The availability of robust and efficient solvers for this problem is an area of active interest in the nuclear engineering community and improved methods may lead to more efficient reactor designs. In this talk we present a survey of existing numerical strategies and offer a new framework based on the Davidson eigensolver which circumvents many standard difficulties. A multigrid-in-energy preconditioner is developed for use with the Davidson method as an alternative to the expensive matrix inversions that must typically be performed. Numerical results using the NEWT radiation transport code provide a comparison between several leading methods and demonstrate the effectiveness of this new approach. |