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IMA Newsletter #412

February 2011

2010-2011 Program

See http://www.ima.umn.edu/2010-2011/ for a full description of the 2010-2011 program on Simulating Our Complex World: Modeling, Computation and Analysis.

News and Notes

Schedule

Tuesday, February 1

10:45am-11:15am Coffee breakLind Hall 400
11:15am-12:15pm On the coupling of surface/subsurface flow with transport Aycil Cesmelioglu (University of Minnesota)Lind Hall 305 PS

Wednesday, February 2

9:00am-10:00am Math 8994: Discontinuous Galerkin methods: An introduction - Linear, symmetric hyperbolic systems Bernardo Cockburn (University of Minnesota)Lind Hall 305
10:45am-11:15am Coffee breakLind Hall 400
1:30pm-2:30pm Tutorial Lectures: Modeling Hurricane Storm Surges - Lecture 2: The numerical approximation of the shallow water equations Clint Dawson (University of Texas at Austin)Lind Hall 305

Thursday, February 3

10:45am-11:15am Coffee breakLind Hall 400

Friday, February 4

10:45am-11:15am Coffee breakLind Hall 400
1:30pm-2:30pm Tutorial Lectures: Modeling Hurricane Storm Surges - Lecture 3: Applications of the shallow water equations, including hurricane storm surges Clint Dawson (University of Texas at Austin)Lind Hall 305

Monday, February 7

10:45am-11:15am Coffee breakLind Hall 400

Tuesday, February 8

10:45am-11:15am Coffee breakLind Hall 400

Wednesday, February 9

10:45am-11:15am Coffee breakLind Hall 400
2:30pm-3:30pm Math 8994: Discontinuous Galerkin methods: An introduction - Nonlinear scalar conservation lawsBernardo Cockburn (University of Minnesota)Lind Hall 305

Thursday, February 10

10:45am-11:15am Coffee breakLind Hall 400

Friday, February 11

10:45am-11:15am Coffee breakLind Hall 400
1:25pm-2:25pm Large scale information extraction from the webSathiya Keerthi (Yahoo! Inc.)Vincent Hall 570 IPS

Monday, February 14

10:45am-11:15am Coffee breakLind Hall 400

Tuesday, February 15

10:45am-11:15am Coffee breakLind Hall 400
11:15am-12:15pm FEMs and MG methods for axisymmetric problems Hengguang Li (University of Minnesota)Lind Hall 305 PS

Wednesday, February 16

10:45am-11:15am Coffee breakLind Hall 400
2:30pm-3:30pm Math 8994: Discontinuous Galerkin methods: An introduction - The RKDG method for scalar conservation lawsBernardo Cockburn (University of Minnesota)Lind Hall 305

Thursday, February 17

10:45am-11:15am Coffee breakLind Hall 400

Friday, February 18

10:45am-11:15am Coffee breakLind Hall 400
1:25pm-2:15pm CANCELLED! February 18, 2011, Darren Kaltved's Industrial Problem SeminarPhysics 210

Monday, February 21

10:45am-11:15am Coffee breakLind Hall 400

Tuesday, February 22

10:45am-11:15am Coffee breakLind Hall 400
11:15am-12:15pm An hp DPG method for linear elasticity with symmetric stressesWeifeng (Frederick) Qiu (University of Minnesota)Lind Hall 305 PS

Wednesday, February 23

10:45am-11:15am Coffee breakLind Hall 400
2:30pm-3:30pm Math 8994: Discontinuous Galerkin methods: An introduction - The RKDG method for gas dynamicsBernardo Cockburn (University of Minnesota)Lind Hall 305

Thursday, February 24

10:45am-11:15am Coffee breakLind Hall 400
5:00pm-6:00pm Screening of "Top Secret Rosies: The Female Computers of WWII"Murphy Hall 130

Friday, February 25

10:45am-11:15am Coffee breakLind Hall 400
1:25pm-2:25pm Role of signals and systems theory in solutions and services business Lalit K. Mestha (Xerox Research Center, Webster)Lind Hall 305 IPS

Monday, February 28

10:45am-11:15am Coffee breakLind Hall 400

Event Legend:

IPSIndustrial Problems Seminar
PSIMA Postdoc Seminar
Abstracts
Screening of "Top Secret Rosies: The Female Computers of WWII"
Abstract: This documentary tells the story of four women 'computers', presenting their exhilarating successes in aiding the war effort and the moral dilemmas they faced. WWII ushered in a new era for women in the workforce, including female mathematicians. In 1942, the United States military began recruiting college-educated female mathematicians to work as human 'computers'. Equipped with desktop calculators and a Differential Analyzer (a predecessor to the world's first electronic computer), these women computed firing tables which improved the accuracy and effectiveness of the Allies' weapons. Working 6 days a week, 24 hours a day from a lab at the University of Pennsylvania, the women were considered sub-professionals and paid only $2000 a year, but their efforts had profound effects on the war and on the dawn of computer programming.This event is sponsored by IMA and NSF and organized by Irina Mitrea, Alexandra Ortan, and Katharine Ott.
Aycil Cesmelioglu (University of Minnesota) On the coupling of surface/subsurface flow with transport
Abstract: The coupling of porous media flow with free flow arises in many applications an example of which is groundwater contamination through rivers. The free flow is characterized by the Navier-Stokes equations whereas the porous media flow is described by the Darcy equations. Beavers-Joseph-Saffman interface condition is prescribed at the interface separating two regions. A transport equation for the contaminant concentration is fully coupled to the flow problem via the velocity field and the viscosity. First, we discuss the existence result to the related weak formulation of the full coupling problem. Second, we analyze numerical schemes based on classical finite element methods and discontinuous Galerkin methods for the special case where the coupling is only one-way, that is, the velocity field from the Navier-Stokes/Darcy problem is an input for the transport equation. Numerical solutions for non homogeneous porous media are also presented.
Clint Dawson (University of Texas at Austin) Tutorial Lectures: Modeling Hurricane Storm Surges - Lecture 2: The numerical approximation of the shallow water equations
Abstract: I will discuss the predominant methods used to approximate solutions to the shallow water equations, including staggered finite difference methods, finite element and finite volume methods. Pros and cons of the different approaches will be discussed.
Clint Dawson (University of Texas at Austin) Tutorial Lectures: Modeling Hurricane Storm Surges - Lecture 3: Applications of the shallow water equations, including hurricane storm surges
Abstract: I will discuss various applications where large-scale shallow water simulators are used, and focus on modeling coastal inundation due to hurricane storm surges.
Sathiya Keerthi (Yahoo! Inc.) Large scale information extraction from the web
Abstract: The web has a vast wealth of information about various types of entities such as businesses (e.g., address, phone, category, hours of operation), products, books, doctors, etc. distributed over a very large number of web sites. Extracting this information from the websites can help us create extensive databases of the entities. These databases can then be used by search engines for better ranking and rendering of search results, e.g., a user can search for products with certain features. The websites usually contain the information in semi-structured formats which are varied and noisy. Extraction on a large scale is challenging because it is not feasible to provide supervision (say, via labeled examples) on a per site basis. In this talk I will give an overview of all the steps associated with a complete extraction pipeline and describe a few scalable machine learning approaches for large scale information extraction.Bio: Dr. Keerthi is a Principal Research Scientist in Yahoo! Research. Over the last twenty years his research has focused on the development of practical algorithms for a variety of areas, such as machine learning, robotics, computer graphics and optimal control. His works on support vector machines (fast algorithms), polytope distance computation (GJK algorithm) and model predictive control (stability theory) are highly cited. His current research focuses on machine learning algorithms for structured outputs as applied to information extraction. Prior to joining Yahoo!, he worked for 10 years at the Indian Institute of Science, Bangalore, and for 5 years at the National University of Singapore. Dr. Keerthi is a member of the editorial board of Journal of Machine Learning Research.
Hengguang Li (University of Minnesota) FEMs and MG methods for axisymmetric problems
Abstract: We shall discuss finite element and multigrid techniques solving the axisymmetric Poisson's equation and the azimuthal Stokes problem on polygonal domains with possible singular solutions. In particular, we construct stable interpolation operators and establish the well-posedness and regularity in some weighted Sobolev space, which in turn, leads to special finite element spaces to approximate the solutions in the optimal rate. With a careful formulation, we also obtain uniform convergence of the MG methods. These estimates can also be used to show the stability of the Taylor-Hood elements for the axisymmetric Stokes problem and to precondition the indefinite system from the axisymmetric Stokes equations.
Lalit K. Mestha (Xerox Research Center, Webster) Role of signals and systems theory in solutions and services business
Abstract: In this talk, we present how signals and system theory was used for creating novel color solutions for digital production printing. We describe the system, mathematical formulation of the process, use of specialized algorithms, methods and architectures briefly, and then present focused research topics we are working on for transportation and healthcare systems. Integration of modern theories (e.g, compressed sensing, control & optimization theory), specialized optics with various imaging devices in the visible and infrared red wavelength bands will be presented aimed at creating next generation solutions and services business.
Weifeng (Frederick) Qiu (University of Minnesota) An hp DPG method for linear elasticity with symmetric stresses
Abstract: Joint work with Jamie Bramwell 3, Leszek Demkowicz 2, and Jay Gopalakrishnan 1. In this research, we present two Discontinuous Petrov-Galerkin (DPG) finite element methods for linear elasticity. For the first method, we consider asymmetric test tensors for the constitutive equation and compute infinitessimal rotations, while in the second method we only use symmetric test tensors and therefore have fewer unknowns. We define optimal test functions which are shown to deliver the best approximation error if an optimal global test norm is used. To make the method practical, we show a localizable test norm is equivalent to the global optimal norm. The majority of this proof is the verification that the inf-sup condition holds for our DPG formulations using the localizable test space norm. From DPG theory, this proves our methods are quasi-optimal with constants independent of the mesh. We can then use results from approximation theory to show h and p convergence for both methods. Since the quasi-optimal test space norm is localizable, we have implemented practical finite element codes that show h and p convergence of both methods at optimal rates. Additionally, the DPG framework provides an a priori error estimator determined by a local auxilliary variational problems. We use this estimator as the basis for various 'greedy' adaptive schemes. We test our adaptive algorithm using a manufactured smooth solution as well as a singular solution L-shape domain problem and observe adaptive h and hp convergence. The principal contributions of this research are proving p convergence for the dual-mixed elasticity system, particularly without the need for a discrete exact sequence or commuting diagram, as well as a practical adaptive 2D elasticity code with a priori error estimation. We will present an overview of the theoretical DPG framework, the convergence proofs for both methods, and the numerical results for both a singular and smooth solution. References
  1. J. Bramwell, L. Demkowicz, and W. Qiu. Solution of Dual-Mixed Elasticity Equations using Arnold-Falk-Winther Element and Discontinuous Petrov-Galerkin Method, a Comparison. Technical Report 10-23, The Institute for Computational Engineering and Sciences, The University of Texas at Austin, June 2010.
  2. J. Bramwell, L. Demkowicz, J. Gopalakrishnan, and W. Qiu. An hp DPG Method for Linear Elasticity with Symmetric Stresses, in preparation.

1 Professor, Mathematics, University of Florida 2 Professor, Institute for Computational Engineering and Sciences, 3 Graduate Research Assistant, Institute for Computational Engineering and Sciences, University of Texas at Austin
Visitors in Residence
Douglas N. Arnold University of Minnesota 9/1/2010 - 6/30/2011
Gerard Michel Awanou Northern Illinois University 9/1/2010 - 6/10/2011
Nusret Balci University of Minnesota 9/1/2009 - 8/31/2011
Susanne C. Brenner Louisiana State University 9/1/2010 - 6/10/2011
Aycil Cesmelioglu University of Minnesota 9/30/2010 - 8/30/2011
Chi Hin Chan University of Minnesota 9/1/2009 - 8/31/2011
Bernardo Cockburn University of Minnesota 9/1/2010 - 6/30/2011
Jintao Cui University of Minnesota 8/31/2010 - 8/30/2011
Clint Dawson University of Texas at Austin 1/30/2011 - 2/5/2011
Laurie Derechin University of Minnesota 2/18/2011 - 2/18/2011
Selim Esedoglu University of Michigan 1/20/2011 - 6/10/2011
Randy H. Ewoldt University of Minnesota 9/1/2009 - 8/31/2011
Oscar E. Fernandez University of Minnesota 8/31/2010 - 8/30/2011
Jay Gopalakrishnan University of Florida 9/1/2010 - 6/30/2011
Shiyuan Gu Louisiana State University 9/1/2010 - 6/30/2011
Yulia Hristova University of Minnesota 9/1/2010 - 8/31/2011
Darren Kaltved University of Minnesota 2/18/2011 - 2/18/2011
Markus Keel University of Minnesota 7/21/2008 - 6/30/2011
Sathiya Keerthi Yahoo! Inc. 2/10/2011 - 2/12/2011
Pawel Konieczny University of Minnesota 9/1/2009 - 8/31/2011
Gilad Lerman University of Minnesota 9/1/2010 - 6/30/2011
Hengguang Li University of Minnesota 8/16/2010 - 8/15/2011
Zhi (George) Lin University of Minnesota 9/1/2009 - 8/31/2011
Mitchell Luskin University of Minnesota 9/1/2010 - 6/30/2011
Kara Lee Maki University of Minnesota 9/1/2009 - 8/31/2011
Yu (David) Mao University of Minnesota 8/31/2010 - 8/30/2011
Lalit K. Mestha Xerox Research Center, Webster 2/24/2011 - 2/27/2011
Irina Mitrea University of Minnesota 8/16/2010 - 6/14/2011
Dimitrios Mitsotakis University of Minnesota 10/27/2010 - 8/31/2011
Alexandra Ortan University of Minnesota 9/16/2010 - 6/15/2011
Cecilia Ortiz-Duenas University of Minnesota 9/1/2009 - 8/31/2011
Katharine Ott University of Kentucky 2/20/2011 - 4/7/2011
Weifeng (Frederick) Qiu University of Minnesota 8/31/2010 - 8/30/2011
Vincent Quenneville-Belair University of Minnesota 9/16/2010 - 6/15/2011
Fernando Reitich University of Minnesota 9/1/2010 - 6/30/2011
Fadil Santosa University of Minnesota 7/1/2008 - 6/30/2011
Shuanglin Shao University of Minnesota 9/1/2009 - 8/31/2011
Panagiotis Stinis University of Minnesota 9/1/2010 - 6/30/2011
Li-yeng Sung Louisiana State University 9/1/2010 - 6/15/2011
Nicolae Tarfulea Purdue University, Calumet 9/1/2010 - 6/15/2011
Dimitar Trenev University of Minnesota 9/1/2009 - 8/31/2011
Legend: Postdoc or Industrial Postdoc Long-term Visitor

IMA Affiliates:
Arizona State University, Boeing, Corning Incorporated, ExxonMobil, Ford, General Motors, Georgia Institute of Technology, Honeywell, IBM, Indiana University, Iowa State University, Korea Advanced Institute of Science and Technology (KAIST), Lawrence Livermore National Laboratory, Lockheed Martin, Los Alamos National Laboratory, Medtronic, Michigan State University, Michigan Technological University, Mississippi State University, Northern Illinois University, Ohio State University, Pennsylvania State University, Portland State University, Purdue University, Rice University, Rutgers University, Sandia National Laboratories, Schlumberger Cambridge Research, Schlumberger-Doll, Seoul National University, Siemens, Telcordia, Texas A & M University, University of Central Florida, University of Chicago, University of Delaware, University of Houston, University of Illinois at Urbana-Champaign, University of Iowa, University of Kentucky, University of Maryland, University of Michigan, University of Minnesota, University of Notre Dame, University of Pennsylvania, University of Pittsburgh, University of Tennessee, University of Wisconsin-Madison, University of Wyoming, US Air Force Research Laboratory, Wayne State University, Worcester Polytechnic Institute