Seminars & Colloquia

Hamid Krim

ECE Department

"Convexity, Sparsity, Nullity and all that in Machine Learning "

Thursday September 14, 2017 04:00 PM
Location: 322, Daniels Hall NCSU Main Campus
(see for courtesy parking request)

This talk is part of the Data Science series


Abstract: High dimensional data exhibit distinct properties compared to its low dimensional counterpart; this causes a common performance decrease and a formidable computational cost increase of traditional approaches. Novel methodologies are therefore needed to characterize data in high dimensional spaces.

Considering the parsimonious degrees of freedom of high dimensional data compared to its dimensionality, we study the union-of-subspaces (UoS) model, as a generalization of the linear subspace model. The UoS model preserves the simplicity of the linear subspace model, and enjoys the additional ability to address nonlinear data. We show a sufficient condition to use l1 minimization to reveal the underlying UoS structure, and further propose a bi-sparsity model (RoSure) as an effective algorithm, to recover the given data characterized by the UoS model from errors/corruptions.


As an interesting twist on the related problem of Dictionary Learning Problem, we discuss the sparse null space problem (SNS). Based on linear equality constraint, it first appeared in 1986 and has since inspired results, such as sparse basis pursuit, we investigate its relation to the analysis dictionary learning problem, and

show that the SNS problem plays a central role, and may naturally be exploited to solve dictionary learning problems.


Substantiating examples are provided, and the application and performance of these approaches are demonstrated on a wide range of problems, such as face clustering and video segmentation.

Short Bio: As a Member of Technical Staff at AT&T Bell Labs, he has worked in the areas of telephony and digital communication systems/subsystems. Following an NSF postdoctoral fellowship at Foreign Centers of Excellence, LSS/University of Orsay, Paris, France, he became a Research Scientist at the Laboratory for Information and Decision Systems, Massachusetts Institute of Technology, Cambridge, performing and supervising research. He is presently on the faculty in the ECE Department, North Carolina State University, Raleigh, leading the Vision, Information and Statistical Signal Theories and Applications group, whose research interests are in statistical signal and image analysis and mathematical modeling with a keen emphasis on applied problems. Dr. Krim is also an Associate Editor of IEEE Transactions on Signal Processing.

Host: Joseph Hart, SIAM Student Chapter Data Science Lecture Series

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