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IMA Newsletter #396

October 2009

2009-2010 Program

See http://www.ima.umn.edu/2009-2010/ for a full description of the 2009-2010 program on Complex Fluids and Complex Flows.

2009-2010 IMA Participating Institutions Conferences

IMA Events

Board of Governor's Meeting

October 4-5, 2009

IMA Workshop

Research in Imaging Sciences

October 5-7, 2009

Organizers: Guillermo R. Sapiro (University of Minnesota Twin Cities)

IMA Tutorial

From Microscopic to Macroscopic Fluid Dynamics in Complex Fluids

October 11, 2009

Organizers: John F. Brady (California Institute of Technology), L. Pamela Cook (University of Delaware), Michael D. Graham (University of Wisconsin), Andrew M. Kraynik (Sandia National Laboratories), Gareth Huw Mckinley (Massachusetts Institute of Technology), Eric S. G. Shaqfeh (Stanford University)

IMA Annual Program Year Workshop

Flowing Complex Fluids: Fluid Mechanics-Interaction of Microstructure and Flow

October 12-16, 2009

Organizers: John F. Brady (California Institute of Technology), L. Pamela Cook (University of Delaware), Michael D. Graham (University of Wisconsin), Andrew M. Kraynik (Sandia National Laboratories), Gareth Huw Mckinley (Massachusetts Institute of Technology)

Math Institutes Modern Math Workshop

October 14-15, 2009

Organizers: Herbert Medina (Loyola Marymount University), Ivelisse Rubio Canabal (University of Puerto Rico), Chehrzad Shakiban (University of Minnesota Twin Cities), Mariel Vazquez (San Francisco State University)

Postdoc Seminar

October 20, 2009

Schedule

Thursday, October 1

All DayNSF site visit
10:45am-11:15amCoffee breakLind Hall 400

Friday, October 2

All DayNSF site visit
10:45am-11:15amCoffee breakLind Hall 400

Sunday, October 4

1:00pm-6:30pmBoard of Governor's MeetingLind Hall 409 BOG10.4-5.09

Monday, October 5

All DayMorning Chair: Matt Feiszli (Yale University)
Afternoon Chair: Mario Micheli (University of California, Los Angeles)
SW10.5-7.09
8:15am-8:45amRegistration and coffee Lind Hall 305 SW10.5-7.09
8:30am-2:30pmBoard of Governor's MeetingLind Hall 409 BOG10.4-5.09
8:45am-9:00amWelcome to the IMAFadil Santosa (University of Minnesota)Lind Hall 305 SW10.5-7.09
9:00am-9:45amLocal scales in oscillatory patterns and boundaries of objects Triet Minh Le (Yale University)Lind Hall 305 SW10.5-7.09
9:45am-10:30amTotal variation, relaxation & convex optimization for image segmentation & graph clusteringXavier Bresson (University of California, Los Angeles)Lind Hall 305 SW10.5-7.09
10:30am-11:00amBreakLind Hall 400 SW10.5-7.09
11:00am-11:30amMetric geometry in action: Non-rigid shape acquisition, processing and analysisRon Kimmel (Technion-Israel Institute of Technology)Lind Hall 305 SW10.5-7.09
11:30am-12:00pmDiffeomorphisms and active contoursLaurent Younes (Johns Hopkins University)Lind Hall 305 SW10.5-7.09
12:00pm-1:15pmLunch SW10.5-7.09
1:15pm-2:00pmSome recent developments in the use of Gromov-Hausdorff and Gromov-Wasserstein metricsFacundo Mémoli (Stanford University)Lind Hall 305 SW10.5-7.09
2:00pm-2:30pmLearning feature hierarchies with sparse codingYann LeCun (New York University)Lind Hall 305 SW10.5-7.09
2:30pm-3:00pmBreakLind Hall 305 SW10.5-7.09
3:00pm-3:30pmComputational conformal geometry and its applicationsXianfeng David Gu (SUNY)Lind Hall 305 SW10.5-7.09
3:30pm-4:00pm Selection of canonical subsets using nonlinear optimizationAli Shokoufandeh (Drexel University)Lind Hall 305 SW10.5-7.09
4:00pm-4:30pmGovernment/DoD/Navy talk:
Navy needs
Automated image understanding
Alan VanNevel (Naval Air Warfare Center)Lind Hall 305 SW10.5-7.09
4:30pm-4:40pmGroup Photo SW10.5-7.09

Tuesday, October 6

All DayMorning Chair: Triet Minh Le (Yale University)
Afternoon Chair: Facundo Memoli (Stanford University)
SW10.5-7.09
8:30am-9:00amCoffeeLind Hall 400 SW10.5-7.09
9:00am-9:45amMulti-scale metrics on plane curvesMatt Feiszli (Yale University)Lind Hall 305 SW10.5-7.09
9:45am-10:15amA fast view of real life video segmentation and a slower view of learning dictionaries for efficient representationsGuillermo R. Sapiro (University of Minnesota)Lind Hall 305 SW10.5-7.09
10:15am-10:45amBreakLind Hall 400 SW10.5-7.09
10:45am-11:15amStationary features and cat detectionDonald Geman (Johns Hopkins University)Lind Hall 305 SW10.5-7.09
11:15am-12:15pmModified immersed boundary modeling and simulation of concentrated suspensionsWeigang Zhong (University of Minnesota)Lind Hall 409 PS
11:15am-11:45amSparse subspace clustering René Vidal (Johns Hopkins University)Lind Hall 305 SW10.5-7.09
11:45am-1:15pmLunch SW10.5-7.09
1:15pm-2:00pmSectional curvature of the Riemannian manifold of landmarksMario Micheli (University of California, Los Angeles)Lind Hall 305 SW10.5-7.09
2:00pm-2:30pmRobust principal component analysis: Exact recovery of corrupted low-rank matrices via convex optimizationYi Ma (University of Illinois at Urbana-Champaign)Lind Hall 305 SW10.5-7.09
2:30pm-3:00pmBreakLind Hall 305 SW10.5-7.09
3:00pm-3:30pmGeometry based image processing - a survey of recent resultsAndrea L. Bertozzi (University of California, Los Angeles)Lind Hall 305 SW10.5-7.09
3:30pm-4:00pmNon-parametric Bayesian dictionary learning for sparse image representationsLawrence Carin (Duke University)Lind Hall 305 SW10.5-7.09
4:00pm-4:30pmGovernment/DoD/Navy TalkLind Hall 305 SW10.5-7.09
6:30pm-8:30pmWorkshop Dinner at Caspian BistroCaspian Bistro
2418 University Ave SE
Minneapolis, MN 55414
612-623-1133
SW10.5-7.09

Wednesday, October 7

All DayChair: Tristan Nguyen (Office of Naval Research) SW10.5-7.09
8:30am-9:00amCoffeeLind Hall 400 SW10.5-7.09
9:00am-9:45amToward real/interactive-time for l1 related problemJérôme Darbon (École Normale Supérieure de Cachan)Lind Hall 305 SW10.5-7.09
9:45am-10:15amClifford algebras and image processingMichel Berthier (Université de La Rochelle)Lind Hall 305 SW10.5-7.09
10:15am-10:45amBreakLind Hall 400 SW10.5-7.09
10:45am-11:15amOnline image processingJean-Michel Morel (École Normale Supérieure de Cachan)Lind Hall 305 SW10.5-7.09
11:15am-11:30amClosing RemarksLind Hall 305 SW10.5-7.09
11:15am-12:15pmThe generalized hydrodynamic theory - transient elasticity and other examplesHarald Pleiner (Max Planck Institute for Polymer Research)EE/CS 3-180 2009-2010Seminar
2:30pm-3:20pmTopics in the theory of the Navier-Stokes equationsVladimir Sverak (University of Minnesota)Lind Hall 305
3:35pm-4:35pmSchool of Mathematics, University of Minnesota PDE Seminar - Twist & shout: Maximal enstrophy production in the 3D Navier-Stokes equationsCharles Doering (University of Michigan)Vincent Hall 6

Thursday, October 8

10:45am-11:15amCoffee breakLind Hall 400
3:30pm-4:30pmColloquium: Wellposedness of the full water wave problem in two and three dimensions Sijue Wu (University of Michigan)Vincent Hall 16

Friday, October 9

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

Sunday, October 11

8:30am-9:00amRegistration and coffeeEE/CS 3-176 T10.11.09
9:00am-10:15amFluid dynamics and transport in particulate suspensions IJohn F. Brady (California Institute of Technology)EE/CS 3-180 T10.11.09
10:15am-10:30amBreak EE/CS 3-176 T10.11.09
10:30am-11:45amFluid dynamics and transport in particulate suspensions IIJohn F. Brady (California Institute of Technology)EE/CS 3-180 T10.11.09
11:45am-1:30pmLunch T10.11.09
1:30pm-2:45pmDynamics of flowing polymer solutions IEric S. G. Shaqfeh (Stanford University)EE/CS 3-180 T10.11.09
2:45pm-3:15pmBreakEE/CS 3-176 T10.11.09
3:15pm-4:30pmDynamics of flowing polymer solutions IIEric S. G. Shaqfeh (Stanford University)EE/CS 3-180 T10.11.09

Monday, October 12

All DayComplex flows of complex fluids I
Chair: Michael D. Graham (University of Wisconsin, Madison)
W10.12-16.09
8:15am-8:45amRegistration and coffeeEE/CS 3-176 W10.12-16.09
8:45am-9:00amWelcome to the IMAFadil Santosa (University of Minnesota)EE/CS 3-180 W10.12-16.09
9:00am-9:40amEffects of elasticity on high Reynolds number instabilities in Taylor-Couette flowSusan J. Muller (University of California, Berkeley)EE/CS 3-180 W10.12-16.09
9:40am-9:45amDiscussionEE/CS 3-180 W10.12-16.09
9:45am-10:25amNonlinear pattern formation and coherent structure dynamics in viscoelastic FlowsRadhakrishna Sureshkumar (Washington University)EE/CS 3-180 W10.12-16.09
10:25am-10:30amDiscussionEE/CS 3-180 W10.12-16.09
10:30am-11:00amCoffee breakEE/CS 3-180 W10.12-16.09
11:00am-11:40amData reduction in viscoelastic turbulent channel flowsAntony N. Beris (University of Delaware)EE/CS 3-180 W10.12-16.09
11:40am-11:45amDiscussionEE/CS 3-180 W10.12-16.09
11:45am-2:00pmLunch W10.12-16.09
2:00pm-2:40pmNon-modal amplification of disturbances in channel flows of viscoelastic fluids: A possible route to elastic turbulence?Satish Kumar (University of Minnesota)EE/CS 3-180 W10.12-16.09
2:40pm-2:45pmDiscussionEE/CS 3-180 W10.12-16.09
2:45pm-3:25pmComputing complex flows of complex fluidsMatteo Pasquali (Rice University)EE/CS 3-180 W10.12-16.09
3:25pm-3:30pmDiscussionEE/CS 3-180 W10.12-16.09
3:30pm-3:40pmGroup Photo W10.12-16.09
3:40pm-4:00pmCoffee breakEE/CS 3-176 W10.12-16.09
4:00pm-4:30pmSecond chancesEE/CS 3-180 W10.12-16.09
4:30pm-6:30pmReception and Poster Session
Poster submissions welcome from all participants
Instructions
Lind Hall 400 W10.12-16.09
Microscale shear flow of focal conic defects in layered liquids Shelley L. Anna (Carnegie Mellon University)
Simulation and experiments on selective withdrawal of polymer solutions James J. Feng (University of British Columbia)
Multiscale modeling and simulation of fluid flows in deformable porous mediaYuliya Gorb (University of Houston)
Effective viscosity and dynamics of dilute bacterial suspensions: A three-dimensional modelBrian Haines (Pennsylvania State University)
An O(N) iterative scheme for viscoelastic flow simulations with DEVSSOliver Harlen (University of Leeds)
Numerical prediction of the dynamics of nanoparticles embedded in a liquid crystalline solvent Juan Pablo Hernandez-Ortiz (National University of Colombia)
Simulation of particle migration in viscoelastic fluids using the extended finite element methodMartien A. Hulsen (Technische Universiteit Eindhoven)
A maximum entropy principle based closure method and hysteresis for macro-micro models of polymeric materialsYunkyong Hyon (University of Minnesota)
Teaching rheology using product designChristopher Macosko (University of Minnesota)
Human tear film dynamics on an eye-shaped domainKara Lee Maki (University of Minnesota)
Structural instability in sedimentation through viscoelastic fluidsRonald Phillips (University of California, Davis)
Spherical bubble collapse in viscoelastic fluidsTim Phillips (Cardiff University)
Purely-elastic instabilities in extensional flowsRob Poole (University of Liverpool)
The response of a hydrophobic superparamagnetic ferrofluid droplet suspended in a viscous fluid in a uniform magnetic field: the influence of microstructure on interfacial tensionYuriko Renardy (Virginia Polytechnic Institute and State University)
Efficient numerical computation of fluid interfaces with soluble surfactant: a viscous dropMichael S. Siegel (New Jersey Institute of Technology)
Planar extensional motion of an inertially-driven liquid sheet Linda B. Smolka (Bucknell University)
Hydrodynamic pattern formation in ultrathin metal films: Robust route to plasmonic nanomaterialsRadhakrishna Sureshkumar (Washington University)
A thermodynamically compatible rate type fluid to describe the response of asphaltKarel Tuma (Charles University in Prague)
Complex motions of vesicles and red blood cells in flowPetia M. Vlahovska (Dartmouth College)
Shape optimization of peristaltic pumpingShawn W. Walker (New York University)
Validity and limitations of the statistical scaling hypothesis for a nematic liquid crystal flowArghir Dani Zarnescu (University of Oxford)

Tuesday, October 13

All DayComplex flows of complex fluids II
Chair: Gareth Huw Mckinley (Massachusetts Institute of Technology)
W10.12-16.09
8:30am-9:00amCoffee EE/CS 3-176 W10.12-16.09
9:00am-9:40amThe effects of polymer molecular weight on filament thinning & drop breakup in microchannels Paulo E. Arratia (University of Pennsylvania)EE/CS 3-180 W10.12-16.09
9:40am-9:45amDiscussionEE/CS 3-180 W10.12-16.09
9:45am-10:25amMixing and instability in two complex fluid flowsMichael J. Shelley (New York University)EE/CS 3-180 W10.12-16.09
10:25am-10:30amDiscussionEE/CS 3-180 W10.12-16.09
10:30am-11:00amCoffee breakEE/CS 3-180 W10.12-16.09
11:00am-11:40amThe dynamics and stability of viscoelastic wormlike micelle solutions in strong extensional flowsJonathan P. Rothstein (University of Massachusetts)EE/CS 3-180 W10.12-16.09
11:40am-11:45amDiscussionEE/CS 3-180 W10.12-16.09
11:45am-1:30pmLunch W10.12-16.09
1:30pm-2:10pmInstabilities due to microstructure growth at fluid interfacesAndrew Belmonte (Pennsylvania State University)EE/CS 3-180 W10.12-16.09
2:10pm-2:15pmDiscussionEE/CS 3-180 W10.12-16.09
2:15pm-2:55pmModeling the inhomogeneous response in transient shearing and extensional flows of entangled/micellar solutionsL. Pamela Cook (University of Delaware)EE/CS 3-180 W10.12-16.09
2:55pm-3:00pmDiscussionEE/CS 3-180 W10.12-16.09
3:00pm-3:30pmCoffee breakEE/CS 3-176 W10.12-16.09
3:30pm-4:10pmShear alignment and mechanical properties of nanostructured hydrogels Lynn M. Walker (Carnegie Mellon University)EE/CS 3-180 W10.12-16.09
4:10pm-4:15pmDiscussionEE/CS 3-180 W10.12-16.09
4:15pm-4:45pmSecond chancesEE/CS 3-180 W10.12-16.09

Wednesday, October 14

All DayMathematical analysis and numerical methods for flowing complex fluids
Chair: L. Pamela Cook (University of Delaware)
W10.12-16.09
8:30am-9:00amCoffee EE/CS 3-176 W10.12-16.09
9:00am-9:40amMathematical issues in stability of viscoelastic flows Michael Renardy (Virginia Polytechnic Institute and State University)EE/CS 3-180 W10.12-16.09
9:40am-9:45amDiscussionEE/CS 3-180 W10.12-16.09
9:45am-10:25amLattice-Boltzmann methods for polymer solutions - A comparison with Brownian dynamics Tony Ladd (University of Florida)EE/CS 3-180 W10.12-16.09
10:25am-10:30amDiscussionEE/CS 3-180 W10.12-16.09
10:30am-11:00amCoffee breakEE/CS 3-180 W10.12-16.09
11:00am-11:40amNumerical investigation of drop deformation in shearYuriko Renardy (Virginia Polytechnic Institute and State University)EE/CS 3-180 W10.12-16.09
11:40am-11:45amDiscussionEE/CS 3-180 W10.12-16.09
11:45am-1:30pmLunch W10.12-16.09
1:30pm-2:10pmComplex Fluids: an abstract framework, some analysis, many open problems Peter Constantin (University of Chicago)EE/CS 3-180 W10.12-16.09
2:10pm-2:15pmDiscussionEE/CS 3-180 W10.12-16.09
2:15pm-2:55pmThe role of free energy in the mathematical and numerical analysis of complex fluids modelsClaude Le Bris (CERMICS)EE/CS 3-180 W10.12-16.09
2:55pm-3:00pmDiscussionEE/CS 3-180 W10.12-16.09
3:00pm-3:30pmCoffee breakEE/CS 3-176 W10.12-16.09
3:30pm-4:10pmContinuum-microscopic computational modeling of non-equilibrium viscoelastic flowSorin Mitran (University of North Carolina)EE/CS 3-180 W10.12-16.09
4:10pm-4:15pmDiscussionEE/CS 3-180 W10.12-16.09
4:15pm-4:45pmSecond chancesEE/CS 3-180 W10.12-16.09

Thursday, October 15

All DayComplex interfacial and multiphase flows
Chair: Andrew M. Kraynik (Sandia National Laboratories)
W10.12-16.09
8:30am-9:00amCoffee EE/CS 3-176 W10.12-16.09
9:00am-9:40amSingle particle motion in colloids: Microrheology and microdiffusivityJohn F. Brady (California Institute of Technology)EE/CS 3-180 W10.12-16.09
9:40am-9:45amDiscussionEE/CS 3-180 W10.12-16.09
9:45am-10:25amFoam structure and rheology: The shape and feel of random soap frothAndrew M. Kraynik (Sandia National Laboratories)EE/CS 3-180 W10.12-16.09
10:25am-10:30amDiscussionEE/CS 3-180 W10.12-16.09
10:30am-11:00amCoffee breakEE/CS 3-180 W10.12-16.09
11:00am-11:40amParticle pressure-induced phenomena in suspensions: from osmosis to granular dilation Jeffrey F. Morris (City College, CUNY)EE/CS 3-180 W10.12-16.09
11:40am-11:45amDiscussionEE/CS 3-180 W10.12-16.09
11:45am-1:30pmLunch W10.12-16.09
1:30pm-2:10pmJet break-up of polymer solutions in inkjet printingOliver Harlen (University of Leeds)EE/CS 3-180 W10.12-16.09
2:10pm-2:15pmDiscussionEE/CS 3-180 W10.12-16.09
2:15pm-2:55pmMoving contact lines and enhanced slip on textured substratesJames J. Feng (University of British Columbia)EE/CS 3-180 W10.12-16.09
2:55pm-3:00pmDiscussionEE/CS 3-180 W10.12-16.09
3:00pm-3:30pmCoffee breakEE/CS 3-176 W10.12-16.09
3:30pm-4:10pmPolymeric threads: formation and instabilityJens Eggers (University of Bristol)EE/CS 3-180 W10.12-16.09
4:10pm-4:15pmDiscussionEE/CS 3-180 W10.12-16.09
4:15pm-4:45pmSecond chancesEE/CS 3-180 W10.12-16.09
6:30pm-8:30pmWorkshop Dinner at Pagoda Pagoda Restaurant
1417 4th St. SE
Minneapolis, MN
612-378-4710
W10.12-16.09

Friday, October 16

All DayMesoscale and multiscale computational simulations of flowing complex fluids
Chair: John F. Brady (Caltech)
W10.12-16.09
8:15am-8:30amCoffeeEE/CS 3-176 W10.12-16.09
8:30am-9:10amMesoscopic simulation of the dynamics of confined complex fluids Michael D. Graham (University of Wisconsin)EE/CS 3-180 W10.12-16.09
9:10am-9:15amDiscussionEE/CS 3-180 W10.12-16.09
9:15am-9:55amModeling and simulation of complex fluids via field theory Hector D. Ceniceros (University of California, Santa Barbara)EE/CS 3-180 W10.12-16.09
9:55am-10:00amDiscussionEE/CS 3-180 W10.12-16.09
10:00am-10:15amCoffee breakEE/CS 3-176 W10.12-16.09
10:15am-10:55amStochastic Eulerian-Lagrangian methods for fluid-structure interactions with thermal fluctuations Paul J. Atzberger (University of California, Santa Barbara)EE/CS 3-180 W10.12-16.09
10:55am-11:00amDiscussionEE/CS 3-180 W10.12-16.09
11:00am-11:40amDissipative particle dynamics: Algorithms and recent applications Bruce Caswell (Brown University)EE/CS 3-180 W10.12-16.09
11:40am-11:45amDiscussionEE/CS 3-180 W10.12-16.09
11:45am-1:30pmLunch W10.12-16.09
1:30pm-2:10pmKinetic theories for complex fluids Qi Wang (University of South Carolina)EE/CS 3-180 W10.12-16.09
2:10pm-2:15pmDiscussionEE/CS 3-180 W10.12-16.09
2:15pm-2:55pmA seamless algorithm for multiscale simulationsWeiqing Ren (New York University)EE/CS 3-180 W10.12-16.09
2:55pm-3:00pmDiscussion EE/CS 3-180 W10.12-16.09
3:00pm-3:30pmSecond chances and closing remarksEE/CS 3-180 W10.12-16.09

Monday, October 19

10:45am-11:15amCoffee breakLind Hall 400
2:30pm-3:20pmTopics in the theory of the Navier-Stokes equationsVladimir Sverak (University of Minnesota)Lind Hall 305

Tuesday, October 20

10:45am-11:15amCoffee breakLind Hall 400
11:15am-12:15pmIdentifying, characterizing and modeling coherent structures of turbulent boundary layersCecilia Ortiz-Duenas (University of Minnesota)Lind Hall 305 PS

Wednesday, October 21

10:45am-11:15amCoffee breakLind Hall 400
11:15am-12:15pmTransition in inertialess flows of viscoelastic fluids: the role of uncertainty Mihailo Jovanovic (University of Minnesota)Lind Hall 305 2009-2010Seminar
2:30pm-3:20pmTopics in the theory of the Navier-Stokes equationsVladimir Sverak (University of Minnesota)Lind Hall 305

Thursday, October 22

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

Friday, October 23

10:45am-11:15amCoffee breakLind Hall 400
1:25pm-2:25pmOptimization algorithms for applications in industryTodd Plantenga (Sandia National Laboratories)Vincent Hall 570 IPS

Monday, October 26

10:45am-11:15amCoffee breakLind Hall 400
2:30pm-3:20pmTopics in the theory of the Navier-Stokes equationsVladimir Sverak (University of Minnesota)Lind Hall 305

Tuesday, October 27

10:45am-11:15amCoffee breakLind Hall 400
11:15am-12:15pm Thorough analysis of the Oseen system in 2D exterior domainsPawel Konieczny (University of Minnesota)Lind Hall 305 PS

Wednesday, October 28

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

Thursday, October 29

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

Friday, October 30

1:30pm-2:30pmPumpkin painting and treats
Contact Michelle Radtke, 6-9886 (radtke@ima.umn.edu) for further information on this event.
Lind Hall 400
Abstracts
Second chances
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Second chances
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Second chances
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Second chances
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Second chances and closing remarks
Abstract: No Abstract
Shelley L. Anna (Carnegie Mellon University) Microscale shear flow of focal conic defects in layered liquids
Abstract: Intermolecular interactions in liquid crystals and concentrated surfactant solutions lead to unique microstructures including lamellae, in which parallel layers are incompressible but bend easily. In such systems, planar layers are easily destabilized via external fields and nearby surfaces to produce topological defects of the order of tens of microns in size. These microscopic defects play a leading role in the flow behavior of such materials, and therefore impact numerous industrial applications including optoelectronic devices and displays and the processing of coatings, adhesives, and biomaterials to encapsulate drugs. To examine the interaction between such microscale defects and flow, we have developed a shear cell to impose a linear Couette flow in a microscale thin gap, while allowing for real time microscopic visualization. We use the shear cell to visualize the dynamics of defect formation in initially defect-free samples of a common small-molecule thermotropic liquid crystal, 8CB. We observe that the formation of focal conic defects, a specific topological defect typically found in thermotropic smectic liquid crystals, is triggered by edge effects and occurs in a series of phases, marked by distinct changes in the birefringence intensity. The defects are seen to annihilate partially or completely on reverse shear. The effect of shear rate and strain amplitude on defect formation and annihilation is studied.
Paulo E. Arratia (University of Pennsylvania) The effects of polymer molecular weight on filament thinning & drop breakup in microchannels
Abstract: In this talk, the effects of fluid elasticity on the dynamics of filament thinning and drop breakup processes are investigated in a cross-slot microchannel. Elasticity effects are examined using dilute aqueous polymeric solutions of molecular weight (MW) ranging from 1.5 x 10(^3) to 1.8 × 10(^7). Results for polymeric fluids are compared to those for a viscous Newtonian fluid. The shearing or continuous phase that induces breakup is mineral oil. All fluids possess similar shear-viscosity (~0.2 Pa s) so that the viscosity ratio between the oil and aqueous phases is close to unity. Measurements of filament thickness as a function of time show different thinning behavior for the different aqueous fluids. For Newtonian fluids, the thinning process shows a single exponential decay of the filament thickness. For low MW fluids (103, 104, and 105), the thinning process also shows a single exponential decay, but with a decay rate that is slower than for the Newtonian fluid. The decay time increases with polymer MW. For high MW (106 and 107) fluids, the initial exponential decay crosses over to a second exponential decay in which elastic stresses are important. We show that the decay rate of the filament thickness in this exponential decay regime can be used to measure the steady extensional viscosity of the fluids. At late times, all fluids cross over to an algebraic decay which is driven mainly by surface tension.
Paul J. Atzberger (University of California, Santa Barbara) Stochastic Eulerian-Lagrangian methods for fluid-structure interactions with thermal fluctuations
Abstract: Keywords: Statistical Mechanics, Soft Condensed Materials, Stochastic Eulerian Lagrangian Methods, Fluid Dynamics. Abstract: A modeling and simulation formalism is presented for the study of soft materials. The formalism takes into account microstructure elasticity, hydrodynamic interactions, and thermal fluctuations. As a specific motivation we consider lipid bilayer membranes and polymeric fluids. The approach couples a Lagrangian description of the microstructures (lipid molecules / polymers) with an Eulerian description of the hydrodynamics. Thermal fluctuations are incorporated in the formalism by an appropriate stochastic forcing of the resulting equations in accordance with the principles of statistical mechanics. The overall approach extends previous work on the Stochastic Immersed Boundary Method. Simulation studies are presenting showing applications of the methodology in the study of lipid flow in bilayer membranes, the shear viscosity of polymer fluids and lipid structures, and the diffusivity of particles in complex fluids.
Andrew Belmonte (Pennsylvania State University) Instabilities due to microstructure growth at fluid interfaces
Abstract: Keywords: wormlike micelles, hydrodynamic instability, micellar aggregation reactions Abstract: The viscoelasticity of a wormlike micellar fluid derives from the presence at the microscale of long tubelike surfactant aggregations (micelles), which occur at low concentrations due to the presence of an organic salt/cosurfactant. Without this salt the micelles are spherical, and the fluid is completely Newtonian. I will present recent experiments on hydrodynamic instabilities caused or modified by the formation of a viscoelastic micellar layer between two Newtonian liquids containing either the surfactant or the organic salt. The micellar "reaction" produces a fragile material which grows in competition with local stretching or advection at the interface, leading to new effects in Hele-Shaw fingering, in droplet sedimentation, and in microfluidic emulsions.
Antony N. Beris (University of Delaware) Data reduction in viscoelastic turbulent channel flows
Abstract: Direct Numerical Simulations (DNS) of turbulent viscoelastic channel flows typically generate a tremendous volume of information (terabytes per run. Data reduction is therefore essential in order to allow for an efficient processing of the data, let alone its preservation for future studies. However, previous attempts, using a projection of the velocity to the top Karhunen-Loeve (K-L) modes, failed to produce velocity fields that could generate the DNS conformation field adequately. In an effort to rectify this deficiency we investigate here three different approaches that attempt to introduce small scale information. First, we extended the K-L analysis that allowed us to use a hybrid measure, based on a weight of the pseudodissipation and the fluctuating kinetic energy, as a new objective function. Second, we used a K-L decomposition of the vorticity field using the enstrophy (average of the square of vorticity fluctuations) as our new objective function. As a third attempt, we used again the standard velocity K-L approach, but in the reconstruction stage of the conformation tensor we compensated by suitably rescaling the Weissenberg number. It is shown here that, whereas the first two methods fail to give any improvement over the classical K-L approach, we were able to reconstruct fairly accurately the conformation field using the third approach, even with a relatively small set of 1714 K-L modes. The rescaling factor in that method was calculated objectively, based on the ratio of DNS vs. K-L-reconstructed based estimates of the extensional deformation rate in the buffer layer. Given that fact, we hope that this approach can also provide the starting point for future investigations into low-dimensional modeling of viscoelastic turbulence as well as other multiscale applications.
Michel Berthier (Université de La Rochelle) Clifford algebras and image processing
Abstract: Keywords: Geometric and Clifford Algebras, Image and Signal Processing, Segmentation, Diffusion, Differential Geometry for Image Processing. Abstract: Since the seminal work of Hestenes, Clifford algebras (also called geometric algebras) appeared to be a powerful tool for geometric modeling in theoretical physics. During the last years, the so-called "geometric calculus" has found many applications in computer science, especially in vision and robotics (Lasenby, Bayro Corrochano, Dorst ...). Concerning image processing, Clifford algebras were already used implicitly by Sangwine through the coding of color with quaternions. The aim of this talk is first to give basic notions about these algebras and the related spinor groups. I will then detail two applications : a metric approach for edge detection in nD images and the construction of a Clifford Hodge operator that generalizes the Beltrami operator of Sochen et al. This latter can be used for diffusion in color images but also for diffusion of vector and orthonormal frame fields. The geometric framework of these applications is the one of fiber and Clifford bundles. Very roughly speaking, the basic idea is to take advantage of embedding an acquisition space in a higher dimensional algebra containing elements of different kinds and related to a specified metric. If time remains, I will also mention in few words applications for signal processing (Clifford Fourier transform and color monogenic signal). Two basic references : Math.:
Chevalley, C.: The Algebraic Theory of Spinors and Clifford Algebras, new edn. Springer (1995) Computer Science:
Sommer, G.: Geometric Computing with Clifford Algebras. Theoretical Fundations and Applications in Computer Vision and Robotics. Springer, Berlin (2001)
Andrea L. Bertozzi (University of California, Los Angeles) Geometry based image processing - a survey of recent results
Abstract: Keywords: geometry, image processing, diffuse interface, sparse representations, pan sharpening Abstract: I will present a survey of recent results on geometry-based image processing. The topics will include wavelet-based diffuse interface methods, pan sharpening and hyperspectral sharpening, and sparse image representation.
John F. Brady (California Institute of Technology) Fluid dynamics and transport in particulate suspensions I
Abstract: No Abstract
John F. Brady (California Institute of Technology) Fluid dynamics and transport in particulate suspensions II
Abstract: No Abstract
John F. Brady (California Institute of Technology) Single particle motion in colloids: Microrheology and microdiffusivity
Abstract: Keywords: Colloidal dispersions, Brownian motion, rheology Abstract: The motion of a single individual particle in a complex material is fundamental to understanding the dynamical properties of the material. Monitoring such motion has given rise to a suite of experimental techniques collectively known as ‘microrheology,’ with the ability to probe the viscoelastic properties of soft heterogeneous materials (e.g. polymer solutions, colloidal dispersions, biomaterials, etc.) at the micrometer (and smaller) scale. In microrheology, elastic and viscous moduli are obtained from measurements of the fluctuating thermal motion of embedded colloidal probes. In such experiments, the probe motion is passive and reflects the near-equilibrium (linear response) properties of the surrounding medium. By actively pulling the probe through the material one can gain information about the nonlinear response, analogous to large-amplitude measurements in macrorheology. But what exactly is measured in a microrheological experiment? And how does the micro-rheological response compare with conventional macrorheology? To answer these questions, we consider a simple model – a colloidal probe pulled through a suspension of neutrally buoyant bath colloids – for which both micro- and macro-results can be obtained exactly. The moving probe distorts the dispersion’s microstructure resulting in a reactive entropic or osmotic force that resists the probe’s motion, which can be calculated analytically and via Brownian Dynamics simulations and used to infer the dispersion's 'effective microviscosity.' By studying the fluctuations in the probe’s motion we can also determine the force-induced 'micro-diffusivity.' Connections between micro and macro behavior will be explored.
Xavier Bresson (University of California, Los Angeles) Total variation, relaxation & convex optimization for image segmentation & graph clustering
Abstract: Keywords: Image segmentation, Mumford-Shah model, graph clustering, relaxation method, total variation, operator splitting technique, normalized cut, Cheeger cut. Abstract: In this talk, I will introduce two algorithms for image segmentation and graph clustering. One of the most influential image segmentation models is the Mumford-Shah’s model. Several algorithms such as the level set method have been introduced to compute a minimizing solution to the MS’s problem, but none of them can compute a global solution. We introduce a convex formulation for the multiphase piecewise constant MS problem (which is equivalent to the NP-hard problem of Potts in the discrete literature) and compute exact global minimizing solutions. We believe our method is the first in the literature that can make this claim. The second model will focus on graph clustering, which aims at grouping similar high-dimensional data s.a. images. The main problem of graph clustering is to minimize a cut of a graph. Popular cuts are the normalized cut of Shi-Malik and the Cheeger’s cut, which are NP-hard problems. We introduce a continuous relaxation of the Cheeger’s cut problem and we show that the relaxation is actually equivalent to the original problem, which is not the case with the Shi-Malik’s relaxation. We also give an algorithm which is experimentally efficient on some clustering benchmarks since the algorithm can cluster 10,000 high-dimensional points in a few seconds. This is joint work with T.F. Chan, E. Brown (UCLA) and A. Szlam (NYU).
Lawrence Carin (Duke University) Non-parametric Bayesian dictionary learning for sparse image representations
Abstract: Non-parametric Bayesian techniques are considered for learning dictionaries for sparse image representations, with applications in denoising, inpainting and compressive sensing (CS). The beta process is employed as a prior for learning the dictionary, and this non-parametric method naturally infers an appropriate dictionary size. The Dirichlet process and a probit stick-breaking process are also considered to exploit structure within an image. The proposed method can learn a sparse dictionary in situ; training images may be exploited if available, but they are not required. Further, the noise variance need not be known, and can be nonstationary. Another virtue of the proposed method is that sequential inference can be readily employed, thereby allowing scaling to large images. Several example results are presented, using both Gibbs and variational Bayesian inference, with comparisons to other state-of-the-art approaches.
Bruce Caswell (Brown University) Dissipative particle dynamics: Algorithms and recent applications
Abstract: In its original version the governing equations of Dissipative Particle Dynamics (DPD) contain three forces which need to be specified in any application, namely: i. a conservative soft repulsion, ii. a random force, iii. a dissipative force. The required thermostat is enforced by balance of ii. and iii. through the Fluctuation-Dissipation theorem . With about 3 to 4 thousand particles (number densities of 3 to 4) these forces simulate a nearly incompressible fluid whose compressibility is close to water’s, and whose viscosity is constant. When the latter is combined with the self-diffusion coefficient a characteristic radius of the DPD particle can be calculated from the Stokes-Einstein relation. Drag force calculations on single DPD particles imersed in a streaming flow show consistency with Stokes law as the Schmidt numbe increases from one. Thus DPD particles are mesoscopic entities, and are hydrodynamically similar to the beads of Brownian Dynamics (BD). However, the hydrodynamic forces between DPD particles are implicit. Complex fluids such as polymers are modeled by connecting DPD particles with spring forces. Examples include dilute, concentrated and undiluted bead-spring chains in plane Couette and in Poiseulle flow which are simulated with periodic boundary conditions. Real boundaries require carefull treatment to avoid unphysical density fluctuations near a wall. Another application of DPD is in the ‘tripple decker’ which attemps to match regions described by continuum, DPD, and Molecular Dynamics (MD) respectively. In the original DPD all forces on a particle are central which obviates the need to deal with angular momentum. However, the calculated rotational drag on a single DPD particle was found to deveate subtantially from the Stokes value. The remedy adds a non-central term to the dissipative force, and includes angular momentum explicitly. The new formulation has been used to simulate a colloidal suspension of large hard DPD-particles in a solvent of soft DPD particles. The results show the model to be economical, and to exhibit the same features as those obtained by the Stokesian dynamics method. A more complex case is the red blood cell (RBC) model with a membrane constructed from DPD particles connected by nonlinear springs and with an extra dissipative force to describe the known viscolelastic properties of the RBC membrane. This model succeeds in describing quantitatively a number of static and dynamic experiments without adjustment of parameters. The models described above have been developed empirically by intuition. A more rigorous and difficult approach is to attempt to derive DPD from analysis at the molecular level. To this end MD simulations of Lennard-Jonesium (LJ) are interpreted statistically for clusters of O(10) LJ molecules to derive the soft potentials and also the dissipative forces which are found generally to be non-central.
Hector D. Ceniceros (University of California, Santa Barbara) Modeling and simulation of complex fluids via field theory
Abstract: Keywords: Field theoretic polymer models, flow-structure interaction, mesoscale models, phase field models. Abstract: We will present examples of field theoretic models of multi-component and complex fluids and discuss their main computational challenges and recent advances. We will start with simple phase field based models and progress to a class of field-theoretic models that incorporate exact thermodynamics. In particular, we will present a model for an inhomogeneous melt of elastic dumbbell polymers which incorporates thermodynamic forces acting on the polymers into the hydrodynamic equations. The resulting equations are composed of a system of fourth order PDEs coupled with a nonlinear optimization problem to determine the conjugate fields. We develop a semi-implicit numerical method for the resulting system of PDE's in addition to a parallel nonlinear optimization solver for the conjugate mean-fields. The semi-implicit method effectively removes the fourth order stability constraint associated with explicit methods and we observe a first order time-step restriction. The algorithm for solving the nonlinear optimization problem, which takes advantage of the form of the operators being optimized, reduces the overall computational cost of simulations by several orders of magnitude.
Peter Constantin (University of Chicago) Complex Fluids: an abstract framework, some analysis, many open problems
Abstract: Keywords: optimal transportation theory, nonlinear Fokker-Planck equations, gradient systems in metric space, Onsager equation Abstract: I will describe a framework for the study of the time evolution of probability distributions of complex systems based on ideas of optimal transportation theory and gradient systems in metric spaces.
L. Pamela Cook (University of Delaware) Modeling the inhomogeneous response in transient shearing and extensional flows of entangled/micellar solutions
Abstract: Surfactant molecules (micelles) can self-assemble in solution into long flexible structures known as wormlike micelles. These structures entangle, forming a dense network and thus exhibit viscoelastic effects, similar to entangled polymer melts. In contrast to 'inert' polymeric networks, wormlike micelles continuously break and reform leading to an additional relaxation mechanism and the name 'living polymers.' Experimental studies show that, in shearing flows, wormlike micellar solutions exhibit spatial inhomogeneities, or shear bands. The VCM model, a two-species elastic network model was formulated to capture, in a self-consistent manner, the micellar breakage and reforming. This model consists of a coupled set of partial differential equations describing the breakage and reforming of two micellar species (a long species 'A' and a shorter species ‘B’) - in addition to reptative and Rousian stress-relaxation mechanisms. Transient and steady-state calculations of the full inhomogeneous flow field show localized shear bands that grow linearly in spatial extent across the gap as the apparent shear rate is incremented. This model also captures the non-monotonic variation in the steady state elongational viscosity that has been reported experimentally and the marked differences between the response of micellar solutions in biaxial and uniaxial extensional flows. The non-monotonic variation in the extensional viscosity has important dynamical consequences in transient elongational flows; In filament stretching experiments designed to measure the extensional rheology of wormlike micelle solutions, it has been observed that the elongating filaments may suddenly rupture near the axial mid-plane at high strain rates [Rothstein]. This newly-observed failure mechanism is not related to the visco-capillary thinning observed in viscous Newtonian fluids. Results of time-dependent simulations with the model carried out in a slender filament formulation appropriate for elongational flows of complex fluids are presented. The simulations show that elongating filaments described by the VCM model exhibit a dramatic and sudden rupture event similar to that observed in experiments. This instability is purely elastic in nature (i.e. it is not driven by capillarity) but arises from coupling between the evolution in the tensile stress and the number density of the entangled species. The dynamics of this localized necking are contrasted with predictions of other nonlinear viscoelastic models.
Jérôme Darbon (École Normale Supérieure de Cachan) Toward real/interactive-time for l1 related problem
Abstract: Keywords: Parallel Programming, optimization, l1 Abstract: We consider the recovery of signal via compressive sensing where the signal itself or its gradient are assumed to be sparse. This amounts to solve a l1 or a Total Variation minimization problem. We propose minimization algorithms specifically designed to take advantage of shared memory, vectorized, parallel and manycore microprocessors such as the Cell processor, new generation Graphics Processing Units (GPUs) and standard vectorized multicore processors (e.g. standard quad core CPUs).
Charles Doering (University of Michigan) School of Mathematics, University of Minnesota PDE Seminar - Twist & shout: Maximal enstrophy production in the 3D Navier-Stokes equations
Abstract: It is still not known whether solutions to the 3D Navier-Stokes equations for incompressible flows in a finite periodic box can become singular in finite time. (This question is the subject of one of the $1M Clay Prize problems.) It is known that a solution remains smooth as long as the enstrophy, i.e., the mean-square vorticity, of the solution is finite. The generation rate of enstrophy is given by a functional that can be bounded using elementary functional estimates. Those estimates establish short-time regularity but do not rule out finite-time singularities in the solutions. In this work we formulate and solve the variational problem for the maximal growth rate of enstrophy and display flows that generate enstrophy at the greatest possible rate. Implications for questions of regularity or singularity in solutions of the 3D Navier-Stokes equations are discussed. This is joint work with Lu Lu, Indiana University Mathematics Journal Vol. 57, pp. 2693-2727 (2008).
Jens Eggers (University of Bristol) Polymeric threads: formation and instability
Abstract: We report on recent experimental and theoretical work on the pinch-off of dilute solutions of flexible polymers. Owing to the strong extensional hardening of such solutions, pinch-off of a liquid drop is delayed. Instead, long threads of uniform thickness form, whose radius decreases exponentially in time. We derive a relationship between the thread radius and the extensional viscosity. When the thread radius has decreased to about 10 microns, the thread becomes unstable to the rapid growth of small ``blisters''. Observations are in strong disagreement with conventional models for dilute suspensions. The ensuing dynamics are very rich, and include iterated instabilities and periodic ``breathing''. For sufficiently high polymer concentrations, the fluid never breaks, and a solid nanometer-sized thread is left behind.
Matt Feiszli (Yale University) Multi-scale metrics on plane curves
Abstract: Keywords: conformal, metric, shape, curves, harmonic, multiscale Abstract: We will present several families of metrics on plane curves, each of which is based on some multi-scale representation and is equivalent to a Sobolev-type norm. These metrics arise when trying to characterize local regularity of functions and curves. The underlying techniques are borrowed from harmonic and complex analysis. We will present theoretical and practical results; in particular we will show experimental results on the MPEG-7 Shape 1b test dataset.
James J. Feng (University of British Columbia) Moving contact lines and enhanced slip on textured substrates
Abstract: I will discuss the use of a diffuse-interface model for simulating moving contact lines. The Cahn-Hilliard diffusion is known to regularize the singularity and makes possible a continuum-level computation. But relating the results to physical reality is subtle. I will show numerical results that suggest a well-defined sharp-interface limit, with a finite contact line speed that can be related to measurements. Furthermore, I will discuss applications of this model to simulate enhanced slip on textured substrates due to contact line depinning, with viscous or viscoelastic liquids.
James J. Feng (University of British Columbia) Simulation and experiments on selective withdrawal of polymer solutions
Abstract: Selective withdrawal refers to the removal of stratified fluids by a suction tube placed near the interface. We view this as an interesting complex fluid flow problem since the interface is disturbed by the nearby sink flow, and the interfacial morphology depends on the bulk rheology of the fluids. The poster will show recent numerical and experimental results for the selective withdrawal of polymer solutions. The most notable result is a transition from a smooth continuous interface to one with a thin air jet emanating from the tip of the interface, reminiscent of the Taylor cone.
Donald Geman (Johns Hopkins University) Stationary features and cat detection
Abstract: Keywords: object detection, invariant features, hierarchical search Abstract: This talk is about research in scene interpretation. Most algorithms for detecting and describing instances from object categories consist of looping over a partition of a "pose space" with dedicated binary classifiers. This strategy is inefficient for a complex pose: fragmenting the training data severely reduces accuracy, and the computational cost is prohibitive due to visiting a massive pose partition. To overcome data-fragmentation I will discuss a novel framework centered on pose-indexed features, which allows for efficient, one-shot learning of pose-specific classifiers. Such features are designed so that the probability distribution of the response is invariant if an object is actually present. I will illustrate these ideas by detecting and localizing cats in highly cluttered greyscale scenes. This is joint work with Francois Fleuret.
Yuliya Gorb (University of Houston) Multiscale modeling and simulation of fluid flows in deformable porous media
Abstract: The main focus of the current poster presentation is on fluid flows in deformable elastic media and associated multiscale problems. Many upscaling methods are developed for flows in rigid porous media or deformable elastic media assuming infinitely small fluid-solid interface displacements relative to the pore size. Much research is needed for the most general and least studied problem of flow in deformable porous media when the fluid-solid interface deforms considerably at the pore level. We introduce a general framework for numerical upscaling of the deformable porous media in the context of a multiscale finite element method. This method allows for large interface displacements and significant changes in pore geometry and volume. For linear elastic solids we present some analysis of the proposed method.
Michael D. Graham (University of Wisconsin) Mesoscopic simulation of the dynamics of confined complex fluids
Abstract: Keywords: Microfluidics, polymer solutions, Brownian dynamics, blood flow Abstract: Many interesting and important phenomena in flowing complex fluids arise when the length scale of the microstructure becomes comparable with the length scale of the flow geometry. This is the case, for example, for solutions of genomic DNA in a microfluidic device or blood in the microcirculation. We describe here an efficient computational framework, based on a new real-space particle-particle/particle-mesh approach to solution of Stokes equations, for performing Brownian dynamics simulations of polymer solutions in micron-scale geometries and use them to illustrate and understand hydrodynamic migration phenomena of DNA in these geometries. The methodology will also be combined with a novel immersed boundary method for elastic capsules in Stokes flow. With this approach, we take some initial steps toward understanding the observed beneficial effects that addition of drag-reducing polymers have on blood flow.
Xianfeng David Gu (SUNY) Computational conformal geometry and its applications
Abstract: Keywords: Conformal, Ricci flow, Hodge, Teichmuller, Riemann surface Abstract: Conformal mappings are angle-preserving mappings. All closed surfaces can be conformally mapped to one of three canonical spaces: the sphere, the plane or the hyperbolic disk. All surfaces with boundaries can be mapped to the canonical spaces with circular holes. The computational algorithms for finding such mappings will be explained. Two surfaces are conformally equivalent if they can be mapped to each other by a conformal mapping. All conformal equivalence classes form a finite dimensional Riemannian manifold, the so-called Teichmuller space. Teichmuller space is a natural shape space model. The algorithm for computing Teichmuller coordinates for each surface will be introduced. The computational algorithms are based on Ricci flow, which refers to the process of deforming Riemannian metric proprotional to curvature, such that curvature evolves according to a heat diffusion. Discrete Ricci flow will be explained in details. The broad applications of conformal geometry in computer graphics, computer vision, medical imaging, and networking will be briefly introduced as well.
Brian Haines (Pennsylvania State University) Effective viscosity and dynamics of dilute bacterial suspensions: A three-dimensional model
Abstract: We present a PDE model for dilute suspensions of bacteria in a three-dimensional Stokesian fluid. This model is used to calculate the statistically-stationary bulk deviatoric stress and effective viscosity of the suspension from the microscopic details of the interaction of an elongated body with the background flow. A bacterium is modeled as a prolate spheroid with self-propulsion provided by a point force, which shows up in the model as an inhomogeneous delta function in the PDE. The bacterium is also subject to a stochastic torque in order to model tumbling (random reorientation). Due to a bacterium's asymmetric shape, interactions with a prescribed generic background flow, such as pure shear or planar shear, cause the bacterium to preferentially align in certain directions. Due to the stochastic torque, the steady-state distribution of orientations is unique for a given background flow. Under this distribution of orientations, self-propulsion produces a reduction in the effective viscosity. For sufficiently weak background flows, the effect of self-propulsion on the effective viscosity dominates all other contributions, leading to an effective viscosity of the suspension that is lower than the viscosity of the ambient fluid. This is in agreement with recent experiments on suspensions of Bacillus subtilis.
Oliver Harlen (University of Leeds) Jet break-up of polymer solutions in inkjet printing
Abstract: Keywords: dilute polymer solutions, FENE model, free surface flows, Finite Elements Abstract: The effects of polymer additives on the break-up of jets in continuous (CIJ) and drop on demand (DOD) inkjet printing are considered. In continuous inkjet printing the fluid jet is modulated at close to the Rayleigh frequency to produce a steady stream of uniform drops, while in drop on demand printing individual drops are generated by applying an impulse to the fluid. Even at very low concentrations the presence of high molecular weight polymers significantly affects how jets break-up into drops, due to the high extension-rates involved. By simulating these flows with the FENE dumbbell constitutive equation we are able to establish the parameter values controlling the break-up length and character of jet break-up, such as the production of small satellite droplets (which are detrimental to the inkjetting process). For the case of drop on demand printing, we compare our predictions to experimental measurements on dilute solutions of monodisperse polystyrene. By using Zimm theory to predict the parameter values in the FENE model, we are able to demonstrate quantitative agreement between simulations and experiments.
Oliver Harlen (University of Leeds) An O(N) iterative scheme for viscoelastic flow simulations with DEVSS
Abstract: In largescale finite element simulations of time-dependent viscoelastic flows the major computational difficulty is the solution of the linear system derived from the momentum and continuity equations. For Newtonian fluids highly efficient iterative solvers have been developed (Elman, Silvester & Wathen "Finite Elements and Fast Iterative Solvers") using block preconditioned Krylov space methods. These methods converge within a fixed number of outer iterations so that both the computational time and memory requirements are proportional to the number of unknowns. Based on these ideas we have developed an iterative scheme for viscoelastic computations discretised using the popular DEVSS (Discrete Elastic-Viscous Stress Splitting) algorithm. We show that this scheme also converges within a fixed number of outer iterations for both two and three dimensional calculations, allowing large three dimensional calculations to be performed efficiently.
Juan Pablo Hernandez-Ortiz (National University of Colombia) Numerical prediction of the dynamics of nanoparticles embedded in a liquid crystalline solvent
Abstract: A hierarchical modeling approach has been adopted to examine the structure and dynamics of nanoparticle suspensions in confined liquid crystals. A molecular model and a combination of Monte Carlo and molecular dynamics simulations are used to investigate the defects that arise around the nanoparticles, both at rest and other imposed flow fields, and to explore how such defects influence the aggregation behavior of the particles. The continuum molecular model is solved by resorting to a unsymmetric radial basis function based technique. The validity of the model and our numerical results are established by direct comparison to results of molecular simulations and to experimental mobility data in both the isotropic and nematic phases. The model is then used to examine the response of different types of confinement, surface treatment, and flow field on the aggregation pathways of nanoparticles in liquid crystals.
Martien A. Hulsen (Technische Universiteit Eindhoven) Simulation of particle migration in viscoelastic fluids using the extended finite element method
Abstract: We present an eXtended Finite Element Method (XFEM) combined with a DEVSS-G/SUPG formulation for the direct numerical simulation of the flow of viscoelastic fluids with suspended rigid particles. For the whole computational domain including both the fluid and particles, we use a regular mesh which is not boundary-fitted. Then, the fluid domain and the particle domain are fully decoupled by using XFEM enrichment procedures. For moving particle problems, we incorporate a temporary arbitrary Lagrangian-Eulerian (ALE) scheme without the need of any re-meshing. We show the motion of a freely moving particle suspended in a Giesekus fluid between two rotating cylinders. The particle migrates to a stabilized radial position near the outer cylinder regardless of its initial position. As the Deborah number increases, the stabilized radial position of the particle shifts toward the outer cylinder.
Yunkyong Hyon (University of Minnesota) A maximum entropy principle based closure method and hysteresis for macro-micro models of polymeric materials
Abstract: We consider the finite extensible nonlinear elasticity (FENE) dumbbell model in viscoelastic polymeric fluids. The maximum entropy principle for FENE model is employed to obtain the solution which maximizes the entropy of FENE model in stationary situations. Then the maximum entropy solution is approximated using the second order terms in microscopic configuration field to get an probability density function (PDF). The approximated PDF gives a solution to avoid the difficulties caused by the nonlinearity of FENE model. The moment-closure system satisfies the energy dissipation law. The moment-closure system can also show the hysteresis which is a nonlinear behavior of viscoelastic dilute polymeric fluids. The hysteresis of FENE model can be seen during a relaxation in simple extensional flow employing the normal stress/the elongational viscosity versus the mean-square extension. The hysteretic behaviors of viscoelastic dilute polymeric fluids with moment-closure approximation models, FENE-L, FENE-P, FENE-D, are presented in extensional/enlongational flows.
Mihailo Jovanovic (University of Minnesota) Transition in inertialess flows of viscoelastic fluids: the role of uncertainty
Abstract: In this talk a system theoretic approach is used to model and analyze the early stages of transition in inertialess channel flows of viscoelastic fluids. We argue that modeling of uncertainty, such as the approximate nature of polymer constitutive equations, is central to understanding the dynamics of viscoelastic fluids. Robustness with respect to uncertainty is quantified by induced norms from spatio-temporal body forces to components of velocity and polymer stress fluctuations. This input-output approach has strong connections to the analysis of pseudospectra of linear operators in Hilbert space, and it exhibits the importance of streamwise elongated flow patterns in viscoelastic fluids. For streamwise independent fluctuations, we establish an explicit unfavorable scaling of the L2-induced norms with the Weissenberg number. This suggests that small amount of modeling uncertainty can destabilize nominally stable dynamics and promote transition to elastic turbulence. We also demonstrate that small stability margins originate from the stretching of polymer stress fluctuations by a background shear and identify the spatial structure of the most amplified fluctuations. One of the main messages of this talk is that, at the level of velocity fluctuation dynamics, polymer stretching and the Weissenberg number in elasticity-dominated flows of viscoelastic fluids effectively play the role of vortex tilting and the Reynolds number in inertia-dominated flows of Newtonian fluids.
Ron Kimmel (Technion-Israel Institute of Technology) Metric geometry in action: Non-rigid shape acquisition, processing and analysis
Abstract: Gromov-Hausdorff distance (dGH) is a definition for the discrepancy between metric spaces. Until recently, it has been applied mainly in theoretical exploration of metric spaces in metric geometry, as well as in theoretical computer science, specifically, in the context of metric embedding of graphs. A couple of years ago it was introduced into the field of shape analysis by Memoli and Sapiro. In this talk we will explore the relation between the Gromov-Hausdorff distance and multi-dimensional scaling (MDS), a classical approach for embedding a given metric space into one in which distances can be analytically computed. The obvious example for such a target embedding space in MDS is Euclidean. Alternatively, we could use the Generalized MDS (GMDS) as a building block in numerically approximating dGH. This generalization deals with target spaces in which distances can be numerically approximated rather than evaluated analytically. The exposition of ideas in metric geometry and numerical optimization would be motivated through practical examples like 3D face recognition, texture mapping in computer graphics, defining and numerically exploring intrinsic symmetries and more. We will start from the actual acquisition process and also present a 3D color video camera we developed and demonstrate the potential of our computational tools on various applications.
Pawel Konieczny (University of Minnesota) Thorough analysis of the Oseen system in 2D exterior domains
Abstract: We construct Lp-estimates for the inhomogeneous stationary Oseen system studied in a two dimensional exterior domain with inhomogeneous slip boundary conditions. The main part of the talk is a presentation of results for the half space ℝ2+, which are substantial for the exterior problem. Main tools are given by the Fourier analysis in order to obtain maximal regularity estimates. In addition, these optimal estimates show us a difference between points on the boundary in front of the obstacle and behind the obstacle. The former are typical for elliptic problems while the latter show disturbance which is typical for parabolic problems.
Andrew M. Kraynik (Sandia National Laboratories) Foam structure and rheology: The shape and feel of random soap froth
Abstract: Soap froth—the quintessential foam—is composed of polyhedral gas bubbles separated by thin liquid films. Why do foams have a shear modulus and yield stress, which we usually associate with solids? How are the bubbles shaped and how are they packed? These and other questions have been explored through simulations with the Surface Evolver, a computer program developed by Brakke. The calculations are in excellent agreement with seminal experiments by Matzke (1946) on the foam structure and shear modulus measurements by Princen and Kiss (1986). The connection between elastic-plastic rheology and foam structure involves intermittent cascades of topological transitions; this cell-neighbor switching is a fundamental mechanism of foam flow. The structure and rheology of wet foams, which have finite liquid content, will also be discussed.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Satish Kumar (University of Minnesota) Non-modal amplification of disturbances in channel flows of viscoelastic fluids: A possible route to elastic turbulence?
Abstract: This talk will provide an overview of our recent work on amplification of disturbances in channel flows of viscoelastic fluids. Even if a standard linear stability (i.e., modal) analysis predicts that a particular flow is stable, the question of the sensitivity of the flow to various disturbances remains. If disturbances to the linearized governing equations are sufficiently amplified over a finite time interval, then nonlinearities may become important and cause transition to a more complex flow state. This can happen if the underlying linear operator is non-normal, and represents a non-modal mechanism of disturbance amplification. We address this issue by adopting an input-output point of view borrowed from the systems- and control-theory communities. The inputs to the linearized equations consist of spatially distributed and temporally varying body forces that are harmonic in the streamwise and spanwise directions and stochastic in the wall-normal direction and in time. Such inputs enable the use of powerful tools from linear systems theory that have recently been applied to analyze Newtonian fluid flows. We find that the most amplified disturbances are three-dimensional in nature, and that large amplification can occur under conditions of weak inertia and strong elasticity. The underlying physical mechanism involves polymer stretching that introduces an effective lift-up of flow fluctuations similar to vortex-tilting in inertia-dominated flows. The mechanism examined here provides a possible route for a bypass transition to elastic turbulence and might be exploited to enhance mixing in microfluidic devices. (Joint work with Mihailo Jovanovic, University of Minnesota.)
Tony Ladd (University of Florida) Lattice-Boltzmann methods for polymer solutions - A comparison with Brownian dynamics
Abstract: I will outline the application of the fluctuating lattice-Boltzmann equation to the simulation of polymer solutions. Then I will describe a numerical assessment of the accuracy of lattice-Boltzmann methods for polymers, by comparison with Brownian dynamics simulations on a similar model system. We will examine the relaxation spectrum of an isolated chain and the migration of individual chains in shear and pressure-driven flows.
Claude Le Bris (CERMICS) The role of free energy in the mathematical and numerical analysis of complex fluids models
Abstract: The talk will overview three recent works that make use of the notion of free energy to establish mathematical properties of some complex fluid models. The first work (in collaboration with B. Jourdain, T. Lelievre and F. Otto) studies the long-time behaviour of the solution to some multiscale models. The second work (by D. Hu and T. Lelievre) introduces a notion of free energy for purely macroscopic models. The third work (by S. Boyaval, T. Lelievre and C. Mangoubi) makes uses of the free energy to derive better numerical approaches.
Triet Minh Le (Yale University) Local scales in oscillatory patterns and boundaries of objects
Abstract: In this talk, we study the problem of extracting local scales of oscillatory patterns in images and on plane curves. In the first case, Given a multi-scale representation {u(t)} of an image f, we are interested in automatically picking out a few choices of t_i(x), which we call local scales, that better represent the multi-scale structure of f at x. We will characterize local scales coming from the Gaussian kernel. In the second case, we propose an approach to extracting local scales on curves to segment objects with irregular boundaries. Theory and experimental results will be presented with applications to image decomposition/denoising.
Yann LeCun (New York University) Learning feature hierarchies with sparse coding
Abstract: Keywords: unsupervised learning, object recognition, sparse coding, convolutional networks Abstract:Image processing and recognition has traditionally relied on hard-wired features and trainable classifiers. The next challenge of computer vision, machine learning, and image processing, is to devise methods that can automatically learn feature extractors and high-level image representations from labeled and unlabeled data. The set of methods collectively known as "Deep Learning" is an attempt to learn hierarchies of features with multiple levels of abstraction, and suitable invariances. I will describe several deep learning methods, some of which involve new forms of sparse coding. Specific model architectures for image recognition, based on stacks on non-linear filter banks, and trained with these methods will be described. A number of applications to object dectection, object recognition, and vision-based navigation for mobile robots will be shown.
Yi Ma (University of Illinois at Urbana-Champaign) Robust principal component analysis: Exact recovery of corrupted low-rank matrices via convex optimization
Abstract: Principal component analysis is a fundamental operation in computational data analysis, with myriad applications ranging from web search, to bioinformatics, to dynamical system identification, to computer vision and image analysis. However, its performance and applicability in real scenarios are limited by a lack of robustness to outlying or corrupted observations. In this work, we consider the idealized “robust principal component analysis” problem of recovering a low-rank matrix A from corrupted observations D = A + E. Here, the error entries E can be arbitrarily large (modeling grossly corrupted observations common in visual and bioinformatic data), but are assumed to be sparse. We prove that most matrices A can be efficiently and exactly recovered from most error sign-and-support patterns, by solving a simple convex program. Our result holds even when the rank of A grows nearly proportionally (up to a logarithmic factor) to the dimensionality of the observation space and the number of errors E grows in proportion to the total number of entries in the matrix. A by-product of our analysis is the first proportional growth results for the related but somewhat easier problem of completing a low-rank matrix from a small fraction of its entries. We propose a provably convergent algorithm based on proximal gradient and iterative thresholding that, for large matrices, is significantly faster and more scalable than general-purpose solvers. We provide simulations and real-data examples corroborating the theoretical results. The simulation results actually have revealed even more striking phenomena and remarkable pictures that merit future investigation. This is joint work with my students John Wright, Arvind Ganesh, and Shankar Rao. Brief Biography:
Yi Ma is an associate professor at the Electrical & Computer Engineering Department of the University of Illinois at Urbana-Champaign. He is currently on leave as research manager of the Visual Computing group at Microsoft Research Asia in Beijing. His research interests include computer vision, image processing, and systems theory. Yi Ma received two Bachelors’ degree in Automation and Applied Mathematics from Tsinghua University (Beijing, China) in 1995, a Master of Science degree in EECS in 1997, a Master of Arts degree in Mathematics in 2000, and a PhD degree in EECS in 2000, all from the University of California at Berkeley. Yi Ma received the David Marr Best Paper Prize at the International Conference on Computer Vision 1999 and the Longuet-Higgins Best Paper Prize at the European Conference on Computer Vision 2004. He also received the CAREER Award from the National Science Foundation in 2004 and the Young Investigator Award from the Office of Naval Research in 2005. He has given several Plenary Talks at international conferences. He is an associate editor of IEEE Transactions on Pattern Analysis and Machine Intelligence. He is a senior member of IEEE and a member of ACM, SIAM, and ASEE.
Christopher Macosko (University of Minnesota) Teaching rheology using product design
Abstract: The poster describes two courses on experimental rheology offered over the past several years to seniors and first year graduate students at our institutions (KU Leuven Belgium and U of Minnesota). These laboratory courses use complex materials available from the shelves of our local retailers. We have found that measuring the rheology of face cream, shampoo, paint, chewing gum or plastic bags provides great motivation for students to learn rheology fundamentals.
Kara Lee Maki (University of Minnesota) Human tear film dynamics on an eye-shaped domain
Abstract: We present recent progress in understanding the dynamics of human tear film on an eye-shaped domain. Using lubrication theory, we model the evolution of the tear film over a blink cycle. The highly nonlinear governing equation is solved on an overset grid by a method of lines coupled with finite difference in the Overture framework. Comparisons with experimental observations show qualitative agreement.
Mario Micheli (University of California, Los Angeles) Sectional curvature of the Riemannian manifold of landmarks
Abstract: Keywords: Shape spaces, landmark points, sectional curvature Abstract: In the past few years there has been a growing interest, in diverse scientific communities, in endowing "shape spaces" with Riemannian metrics, so to be able to measure similarities between shapes and perform statistical analysis on data sets (e.g. for object recognition, target detection and tracking, classification, and automated medical diagnostics). The geometry of such spaces has started to emerge only very recently; in this talk we will explore the sectional curvature for the Riemannian manifold of landmark points (which is one of the simplest, in that it is finite-dimensional) and discuss its effects on applications.
Sorin Mitran (University of North Carolina) Continuum-microscopic computational modeling of non-equilibrium viscoelastic flow
Abstract: The problem of coupling microscopic and continuum-level descriptions of complex fluids when the microscopic system exhibits slow relaxation times is considered. This type of problem arises whenever the fluid exhibits significant memory effects. The main difficulty in this type of multiscale computation is the initialization of microscopic configurations and establishing the duration of microscopic evolution that has to be computed before a continuum time step can be taken. Density estimation theory is applied to determine the distribution of random variables characterizing the microscopic system. Additional mesoscale equations for the probability density functions required to characterize microscopic states are determined from successive bursts of microscopic simulation. The time evolution of the mesoscale equations is computed using high-order Adams-Bashforth-Moulton predictor-corrector algorithms. The overall computational model is exemplified on a Rolie-Poly fluid. The main benefit of the approach considered here is that the complication of deriving an algorithm for complicated constitutive laws is sidestepped without the need for prohibitively expensive computation at the microscale.
Jean-Michel Morel (École Normale Supérieure de Cachan) Online image processing
Abstract: Keywords: Online image processing, unsupervised algorithms, fast algorithms, color balance, screened Poisson equation, denoising, image comparison, Retinex theory, affine invariant SIFT Abstract: This is a new concept of publication for image processing. Putting image processing and image analysis algorithms on line allows every researcher to test directly the algorithms on his (her) own images. Some sample images are also proposed on each algorithm site. This project is under construction, but several algorithms are already available at http://mw.cmla.ens-cachan.fr/megawave/algo/. Each on line algorithm is described in a web site, which gives the main bibliographic links, and which comments on many experimental results. Each algorithm is also thoroughly described, and a code can be downloaded. Image processing on line is only possible with algorithms which have been mathematically analyzed and rationalized to the point where they do not depend anymore on technical parameters. A publication on line is different from --but can be complementary to-- a journal publication. The online algorithms must be elaborated to the point where they are fully autonomous, or depend on at most one user's parameter (typically the scale). I'll describe briefly the online algorithms: Microtexture synthesis algorithm, a Cartoon + Texture decomposition, a fully autonomous line segment detector, a PDE implementation of the color perception Retinex theory or a fully affine invariant image comparison algorithm, ASIFT.
Jeffrey F. Morris (City College, CUNY) Particle pressure-induced phenomena in suspensions: from osmosis to granular dilation
Abstract: The coupling of microstructure to bulk flow behavior is a hallmark of non-Newtonian flows in general. When the non-Newtonian fluid is a two-phase material where the dispersed and continuous phases may readily segregate, this coupling is found to result in quite striking migration of particles and fluid, with significant impact on the flow structure as a consequence. In this talk, we first describe a general approach to understanding the migration phenomena based on particle pressure, the nonequilibrium continuation of osmotic pressure to sheared dispersions of solids (here in Newtonian liquids only), considering the microstructural origins of the behavior, its the macroscopic consequences, and how particle pressure may be measured. This will be followed by a consideration of the flow through a channel contraction of a very concentrated suspension – near and at the jamming limit of about up to 58% solids for the system studied experimentally, so that hydrodynamic and contact forces both play a role. In the contraction geometry, the effluent generally has a lower solid fraction than the upstream suspension, a phenomenon known as self-filtration, and we will show that self-filtration may be described by a mechanism where liquid flow is driven by variation of the particle pressure within the geometry.
Susan J. Muller (University of California, Berkeley) Effects of elasticity on high Reynolds number instabilities in Taylor-Couette flow
Abstract: Keywords: Elasticity, viscoelastic instability, nonlinear transitions, drag-reducing polymers Abstract: Taylor-Couette flow (i.e., flow between concentric, rotating cylinders) has long served as a paradigm for studies of hydrodynamic stability. For Newtonian fluids, the rich cascade of transitions from laminar, Couette flow to turbulent flow occurs through a set of well-characterized flow states that depend on the Reynolds numbers of both the inner and outer cylinders (Rei and Reo). While extensive work has been done on (a) the effects of weak viscoelasticity on the first few transitions for Reo = 0 and (b) the effects of strong viscoelasticity in the limit of vanishing inertia (Rei and Reo both vanishing), the viscoelastic Taylor-Couette problem presents an enormous parameter space, much of which remains completely unexplored. Here we describe our recent experimental efforts to examine the effects of drag reducing polymers on the complete range of flow states observed in the Taylor-Couette problem. Of particular importance in the present work is 1) the rheological characterization of the test solutions via both shear and extensional (CaBER) rheometry, 2) the wide range of parameters examined, including Rei, Reo, and Elasticity number El, and 3) the use of a consistent, conservative protocol for accessing flow states. We hope to gain insights into the roles of weak elasticity and of co- and counter-rotation on nonlinear transitions in this flow.
Facundo Mémoli (Stanford University) Some recent developments in the use of Gromov-Hausdorff and Gromov-Wasserstein metrics
Abstract: Keywords: Gromov-Hausdorff distance, Gromov-Wasserstein distance, shape analysis, metric geometry Abstract: The Gromov-Hausdorff distance provides a powerful tool for formalizing the problem of shape matching. Two problems with it are that (1) in practice it leads to combinatorial optimization problems which are NP hard and (2) despite its theoretical attractiveness and naturality, it has been difficult to use for studying and establishing links to the many other shape matching methods available in the literature. The Gromov-Wasserstein distance, a variant of the Gromov-Hausdorff distance that is based on mass transportation ideas, directly leads to continuous optimization problems with quadratic objective functions and linear constraints. Furthermore, it has been proved that the methods based on shape distributions, shape context/integral invariants, and eccentricity can all be related to this Gromov-Wasserstein distance via explicit lower bounds. In this talk we review the construction of the GW distance, its properties and lower bounds. In particular, we describe recent work done on (1) relating it to persistent topology based shape signatures, and (2) on defining a certain spectral notion of the GW distance. This spectral notion of the GW distance permits proving that several invariants constructed from the spectrum of the Laplace-Beltrami operator on manifolds are stable in a quantitative way.
Cecilia Ortiz-Duenas (University of Minnesota) Identifying, characterizing and modeling coherent structures of turbulent boundary layers
Abstract: Coherent structures, i.e. hairpin vortices, which align in groups or packets, were proposed as a fundamental structure of turbulent boundary layers more than 50 years ago in the literature. Although the existence of these structures and packets has been demonstrated, their generation, development, and interaction is not yet understood. Recently, planar and volumetric velocity measurements obtained by PIV provide direct information on spatial velocity variations as well as time-averaged statistics from which the characteristics of individual and of statistical ensembles of structures can be obtained. It is proposed here to integrate these experimental results into numerical models, such as the attached eddy model as described by Perry and Marusic (1995), to further the understanding of these structures under various conditions. The challenges in identifying, characterizing and modeling these coherent structures will be discussed.
Matteo Pasquali (Rice University) Computing complex flows of complex fluids
Abstract: Flows with free surfaces and free boundaries arise in many industrial and biological applications. Examples are coating, polymer processing, ink-jet printing, DNA arrays, spraying, deformation of blood cells, blood flow in arteries and capillaries, and flow in the deep pulmonary alveoli. Most of these flows have two distinguishing features: (1) the fluid is complex (microstructured ); thus, the stress includes a visco-elastic term which is important and sometimes dominant, and (2) the surface forces are comparable to the viscous and elastic ones. Inertia is usually immaterial in these flows, because the relevant length scales are well below a millimeter. The surface and viscoelastic forces give rise to large non-diagonal contributions in the momentum equation. Other non-diagonal terms come from the coupling of the shape of the free boundaries to the velocity field, and strong dependence of the microstructure evolution on the velocity gradient. Thus, fully-coupled algorithms for solving the steady as well as time-dependent equations of the flow are desirable. I will discuss developments in applying mesoscopic models of microstructured liquids to three-dimensional free surface flows. In such models, the liquid microstructure is captured by tensors obeying convection-diffusion-generation equations—e.g., the gyration tensor of ensembles of polymer molecules, or the shape tensor of droplets or blood cells. Mesoscopic non-equilibrium thermodynamics ties the elastic stress to velocity-gradient-dependent terms in the microstructure evolution. This dependence yields general theories accounting for disparate microstructural models that are compatible with macroscopic transport phenomena and thermodynamics. Such theories can be incorporated into general three-dimensional finite element codes based on fully coupled formulations. Combining Newton’s method with GMRES and a Sparse Approximate Inverse Preconditioner yields a robust and efficient method for computing three-dimensional flows on low-cost parallel clusters. I will show results on model flows of polymer solutions, and discuss developments and connections to fine-grain, microscopic models of complex fluids where microstructure is tracked by using stochastic differential equations.
Ronald Phillips (University of California, Davis) Structural instability in sedimentation through viscoelastic fluids
Abstract: A theory has been developed to describe a structural instability that is observed during the sedimentation of particulate suspensions through viscoelastic fluids. The theory is based on the assumption that the influence of hydrodynamic interactions in viscoelastic fluids, which tend to cause particles to aggregate, is in competition with hydrodynamic dispersion, which acts to maintain a homogeneous microstructure. In keeping with the experimental observations, it predicts that the suspension structure will stratify into vertical columns when a dimensionless stability parameter exceeds a critical value. The column-to-column separation, measured in particle radii, is predicted to be proportional to the square root of the ratio of the dimensionless dispersion coefficient to the product of the particle volume fraction and the Deborah number. The time for the formation of the columns is predicted to scale with the inverse of the average volume fraction. These predictions are in agreement with experimental data reported in the literature.
Tim Phillips (Cardiff University) Spherical bubble collapse in viscoelastic fluids
Abstract: The collapse of a spherical bubble in an infinite expanse of viscoelastic fluid is considered. For a range of viscoelastic models, the problem is formulated in terms of a generalized Bernoulli equation for a velocity potential, under the assumptions of incompressibility and irrotationality. The boundary element method is used to determine the velocity potential and viscoelastic effects are incorporated into the model through the normal stress balance across the surface of the bubble. In the case of the Maxwell constitutive equation, the model predicts phenomena such as the damped oscillation of the bubble radius in time, the almost elastic oscillations in the large Deborah number limit and the rebound limit at large values of the Deborah number. A rebound condition in terms of $ReDe$ is derived theoretically for the Maxwell model by solving the Rayleigh-Plesset equation. A range of other viscoelastic models such as the Jeffreys model, the Rouse model and the Doi-Edwards model are amenable to solution using the same technique. Increasing the solvent viscosity in the Jeffreys model is shown to lead to increasingly damped oscillations of the bubble radius.
Todd Plantenga (Sandia National Laboratories) Optimization algorithms for applications in industry
Abstract: The talk will describe the speaker's experience in designing and implementing optimization algorithms for applications in industry. Discussion will focus on a retail price optimization algorithm that uses stochastic methods to handle uncertainties. The project started with a textbook approach (stochastic optimization with recourse) and evolved into a special purpose solution suited to the business case. The speaker was directly involved in gathering requirements, prototyping a mathematical model and algorithmic approach, investigating issues with real world data, and writing production software for the final implementation. The completed project currently recommends optimal prices on over 10,000 items per day. Dr. Plantenga obtained a PhD from Northwestern University in 1994 studying large-scale nonlinear optimization methods. He has developed optimization software for PeopleSoft/Oracle, Gap Inc, Ziena Optimization, and his current employer, Sandia National Laboratories.
Harald Pleiner (Max Planck Institute for Polymer Research) The generalized hydrodynamic theory - transient elasticity and other examples
Abstract: For modeling complex fluids (and more generally soft matter) on the phenomenological level a generalization of the well-known hydrodynamic method is proposed. It preserves the basic thermodynamic rules and linear response structure of ordinary hydrodynamics, but allows the handling of additional mesoscopic degrees of freedom that make those materials 'complex'. This is exemplified by discussing transient elasticity and applying it explicitly to the non-Newtonian behavior of polymers (and colloidal systems). Transient elasticity seems to be the defining physics for those systems and also for yield stress soft matter. As a second example true 2-fluid systems and the problems of their generalized hydrodynamics are briefly described.
Rob Poole (University of Liverpool) Purely-elastic instabilities in extensional flows
Abstract: Using a finite-volume numerical technique we demonstrate that viscoelastic flow in a range of symmetric geometries - with symmetric inlet flow conditions - containing a region of strong extensional flow goes through a bifurcation to a steady asymmetric state. We show that this asymmetry is purely elastic in nature and that the effect of inertia is a stabilizing one. Our results in one such geometry - the so called “cross-slot” - are in excellent qualitative agreement with recent experimental visualizations of a similar flow in a micro-fluidic apparatus [Arratia et al. Phys. Rev. Lett., 2006 96(14)]. We investigate effects of constitutive equation (UCM, Oldroyd-B, PTT and FENE-CR models), model parameters and effects due to three dimensionality.
Weiqing Ren (New York University) A seamless algorithm for multiscale simulations
Abstract: I will present a seamless algorithm for the study of multiscale problems. The multiscale method aims at capturing the macroscale behavior of a given system which is modeled by an (incomplete) macroscale model. This is done by coupling the macro model with a micro model: The macro model provides the necessary constraint for the micro model and the micro model supplies the missing data (e.g. the constitutive relation or the boundary conditions) needed in the macro model. In the multiscale method, the macro and micro models evolve simultaneously using different time steps, and they exchange data at every step. The micro model uses its own appropriate (micro) time step. The macro model uses a macro time step but runs at a slower pace than required by accuracy and stability considerations in order for the micro dynamics to have sufficient time to adapt to the environment provided by the macro state. The method has the advantage that it does not require the reinitialization of the micro model at each macro time step or each macro iteration step. The data computed from the micro model is implicitly averaged over time.
Michael Renardy (Virginia Polytechnic Institute and State University) Mathematical issues in stability of viscoelastic flows
Abstract: "Traditional" hydrodynamic stability studies infer stability of a flow from a computation of eigenvalues of the linearized system. While this is well justified for the Navier-Stokes equations, no rigorous result along these lines is known for general systems of partial differential equations; indeed there are counterexamples for lower order perturbations of the wave equations. This lecture will discuss how recent results on "advective" equations can be applied to creeping flows of viscoelastic fluids of Maxwell or Oldroyd type. For spatially periodic flows, stability can be reduced to the study of a) the eigenvalues, and b) a system of non-autonomous ordinary differential equations that arises from a geometric optics approximation for short waves. A more complete result for the upper convected Maxwell model will also be discussed.
Yuriko Renardy (Virginia Polytechnic Institute and State University) The response of a hydrophobic superparamagnetic ferrofluid droplet suspended in a viscous fluid in a uniform magnetic field: the influence of microstructure on interfacial tension
Abstract: The microstructure of a ferrofluid influences its motion under applied magnetic fields. A ferrofluid typically consists of magnetite nanoparticles suspended in a solvent. Here, we consider a ferrofluid that has no solvent, with the advantage that the particles do not migrate under externally applied magnetic fields, and therefore the physical properties of the ferrofluid can be more easily characterized. The deformation of a biocompatible hydrophobic ferrofluid drop suspended in a viscous medium is investigated numerically and compared with experimental data. At high magnetic fields, experimental drop shapes deviate from numerical results when a constant surface tension value is used. One hypothesis for the difference is the dependence of interfacial tension on the magnetic field in the experimental data. This idea is investigated with direct numerical simulations.
Yuriko Renardy (Virginia Polytechnic Institute and State University) Numerical investigation of drop deformation in shear
Abstract: No Abstract
Jonathan P. Rothstein (University of Massachusetts) The dynamics and stability of viscoelastic wormlike micelle solutions in strong extensional flows
Abstract: Under the proper conditions, surfactant molecules can self-assemble into wormlike micelles, resembling slender rods, can entangle and impart viscoelasticity to the fluid. The behavior of wormlike micelles solutions is similar to that of polymer solutions. The primary difference being that, unlike covalently bound polymers, micelles are continuously breaking and reforming under Brownian fluctuations and the imposed shear or extensional flow field. In this talk, we will discuss the behavior of a series of viscoelastic wormlike micelle solutions in extensional flows and describe several newly observed instabilities and flow phenomena unique to these fluids. In the first part of the talk, we will describe the behavior of these fluids in the homogeneous uniaxial extensional flow produced by a filament stretching rheometer. Like polymer solutions, wormlike micelle solutions demonstrate significant strain hardening and a failure of the stress-optical. At a critical stress, the wormlike micelle solutions filaments were found to fail through a dramatic rupture near the axial midplane. This filament failure likely stems from the local scission of individual wormlike micelle chains. We will discuss the effect that pre-conditioning can have on the response of these materials and demonstrate that the presence of branching in wormlike micelle solutions can significant reduce the strain hardening of the extensional viscosity. In the second part of the talk, we will describe how the extensional rheology of these wormlike micelle solutions can affect more complex flows by presenting a series of interesting new flow phenomena unique to wormlike micelle solutions. The experiments will include the observation of a new instability in the flow past a falling sphere, through a periodic array of cylinders and past a single cylinder. The flows are investigated through a variety of experimental techniques including the use of high speed imaging, particle image velocimetry and flow induced birefringence measurements.
Guillermo R. Sapiro (University of Minnesota) A fast view of real life video segmentation and a slower view of learning dictionaries for efficient representations
Abstract: After spending about 5 minutes showing recent results on video segmentation (joint work with Adobe), I will describe some recent works in my group in the area of dictionary learning and sparse coding. In particular I will present new models derived from information theory, new models dedicated to go beyond standard sparse coding applications and into unsupervised clustering, and new models related to compressed sensing.
Eric S. G. Shaqfeh (Stanford University) Dynamics of flowing polymer solutions I
Abstract: No Abstract
Eric S. G. Shaqfeh (Stanford University) Dynamics of flowing polymer solutions II
Abstract: No Abstract
Michael J. Shelley (New York University) Mixing and instability in two complex fluid flows
Abstract: Keywords: Mixing, Instability, Complex Fluids Abstract: I will discuss two problems where flow instability drives a complex fluid -- or at least its mathematical model -- into intrinsic oscillations and unsteadiness. Both are in the Stokesian regiime where inertial effects are negligible. In the first, a visco-elastic fluid described by the Oldroyd-B model is driven by a background force that creates a local extensional flow. Beyond a critical Weissenberg number, stress accumulates rapidly there, and a symmetry breaking instability leads to coherent structures and multiple frequencies of oscillation. In the second, the complex fluid is a self-driven suspension of active swimmers. Analysis and simulation show the existence of long-wave instabilities that drive the system from isotropy to strongly mixing flows with system-size correlations.
Ali Shokoufandeh (Drexel University) Selection of canonical subsets using nonlinear optimization
Abstract: Keywords: Feature Selection, Canonical Elements, Object Recognition, and Reconstruction Abstract: The problem of representing a large dataset consisiting of complex patterns with a smaller more compact form has been tackled through synthesis of new data points to represent clusters of the original data points (feature transformation). In contrast, the focus of this research is on the development of a generic methods for selecting canonical subsets of data-sets that are highly representative of the original complex patterns. The development of the canonical subset method was motivated by the fact that in many cases feature transformation may not be practical, relevant, or even possible. Our objective is to expose the underlying structure of the data and have the global topology drive the subset-selection process. The contributions of the work are formulation of the subset selection problem as an optimization problem, an analysis of the complexity of the problem, the development of approximation algorithms to compute canonical subsets, and a demonstration of the utility of the algorithms in several problem domains.
Michael S. Siegel (New Jersey Institute of Technology) Efficient numerical computation of fluid interfaces with soluble surfactant: a viscous drop
Abstract: We address a significant difficulty in the numerical computation of fluid interfaces with soluble surfactant. At large values of bulk Peclet number for representative fluid-surfactant systems, a transition layer forms adjacent to the interface in which the surfactant concentration varies rapidly. Accurate calculation of the concentration gradient at the interface is essential to determine bulk-interface exchange of surfactant and the drop's dynamics. We present a fast and accurate `hybrid' numerical method that incorporates a separate singular perturbation reduction of the transition layer into a full numerical solution of the interfacial free boundary problem. Results are presented for a drop of arbitrary viscosity in the Stokes flow limit, where the underlying flow solver for insoluble surfactant uses a direct (primitive variable) boundary integral method.
Linda B. Smolka (Bucknell University) Planar extensional motion of an inertially-driven liquid sheet
Abstract: We derive a time-dependent exact solution of the free surface problem for the Navier-Stokes equations that describes the planar extensional motion of a viscous sheet driven by inertia. The linear stability of the exact solution to one- and two-dimensional symmetric perturbations is examined in the inviscid and viscous limits within the framework of the long-wave or slender body approximation. Both transient growth and long-time asymptotic stability are considered. For one-dimensional perturbations in the axial direction, viscous and inviscid sheets are asymptotically marginally stable, though depending on the Reynolds and Weber numbers transient growth can have an important effect. For one-dimensional perturbations in the transverse direction, inviscid sheets are asymptotically unstable to perturbations of all wavelengths. For two-dimensional perturbations, inviscid sheets are unstable to perturbations of all wavelengths with the transient dynamics controlled by axial perturbations and the long-time dynamics controlled by transverse perturbations. The asymptotic stability of viscous sheets to one-dimensional transverse perturbations and to two-dimensional perturbations depends on the capillary number (Ca); in both cases, the sheet is unstable to longwave transverse perturbations for any finite Ca. This work is in collaboration with Thomas P. Witelski.
Radhakrishna Sureshkumar (Washington University) Nonlinear pattern formation and coherent structure dynamics in viscoelastic Flows
Abstract: Ability to manipulate equilibrium self-assembly and dynamical self-organization in nonlinear systems is of central importance to the success of many emerging technologies. This seminar will focus on flow instability and pattern formation in complex fluids, i.e., fluids with internal microstructure such as solutions/melts of polymers, surfactant/colloidal gels and suspensions. Specific examples discussed will include coherence and chaos in turbulent flows of “viscoelastic” dilute polymer solutions (PRL, 100, 134504 (2008)), solitary vortex solutions that manifest as a result of elastic stress-mediated self organization in complex fluids (PRL, 97, 054501 (2006)) and purely flow-induced phase transitions in surfactant micelles (J. Rheol. . 52, 527-50 (2008)).
Radhakrishna Sureshkumar (Washington University) Hydrodynamic pattern formation in ultrathin metal films: Robust route to plasmonic nanomaterials
Abstract: Sustainable production, storage and transportation of renewable energy is one of the greatest challenges of the 21st century. Harnessing Sun's energy for powering our planet has long been a dream of scientists and engineers. Despite the universal appeal and growing usage of solar energy systems across the globe, notably in developing economies, the efficiency of energy conversion has remained well below desirable levels for commercial installations. This is especially a major concern for new generation photovoltaics, which utilize a thin film (~ 1 micron thick) of the photoactive material. In this case, traditional light trapping techniques such as optical gratings (~ several microns) employed for cells based on bulk photoconductors are not applicable. Metallic nanocomposites offer much promise in efficient and cost-effective solar energy harvesting especially for thin film photocells. The central idea is to exploit the plasmonic interaction between electromagnetic waves and the localized oscillations of the free electron gas density at the nanoparticle-dielectric interface. From a renewable energy perspective, plasmonics principles can be used to tailor the spectral response of a material to fit applications such as broadband solar absorption and photo-bioreactor design. This is accomplished by manipulating the particle size, aspect ratio and volume fraction as well as utilizing hybridization techniques (e.g. core-shell materials, multi-metal composites). In this talk, a robust manufacturing route for such materials, namely laser-induced melting, dewetting and self-organization of ultrathin (~ nm) metal films deposited on a suitable substrate, will be discussed [APL 91, 043105 (2007); Phys. Rev. B, 75, 235439 (2007); Nanotechnology, 17, 4229 (2006); Phys. Rev. Lett., 101, 017802 (2008)]. Specifically, it will be shown that the knowledge of thin film hydrodynamic instabilities can be utilized to predict nanoparticle size and spacing observed in such experiments. The mechanisms of pattern formation will be illustrated using experimental visualizations of the dewetting process.
Vladimir Sverak (University of Minnesota) Topics in the theory of the Navier-Stokes equations
Abstract: The course will cover certain selected topics in the theory of the Navier-Stokes equations. After a brief overview of the main issues of the general theory we will focus on problems in the theory of the steady-state solutions. There are many open problems concerning the steady-state solutions. These problems are presumably easier than the main open questions about the time-dependent equations. Nevertheless, some of them have remained unsolved since their first explicit formulation in the pioneering works of Jean Leray in the 1930s. There is a certain indirect similarity (or "duality") between the mathematical issues raised by these steady-state problems and the issues which come up in connection with the more well-known open problems about the time-dependent equations. In the lectures I hope to cover some of the important results about the steady-state solutions and discuss some of the open problems. The course will be accessible to postdocs and to graduate students with some knowledge of PDEs. For example, an introductory graduate PDE course should be a sufficient prerequisite.
Vladimir Sverak (University of Minnesota) Topics in the theory of the Navier-Stokes equations
Abstract: The course will cover certain selected topics in the theory of the Navier-Stokes equations. After a brief overview of the main issues of the general theory we will focus on problems in the theory of the steady-state solutions. There are many open problems concerning the steady-state solutions. These problems are presumably easier than the main open questions about the time-dependent equations. Nevertheless, some of them have remained unsolved since their first explicit formulation in the pioneering works of Jean Leray in the 1930s. There is a certain indirect similarity (or "duality") between the mathematical issues raised by these steady-state problems and the issues which come up in connection with the more well-known open problems about the time-dependent equations. In the lectures I hope to cover some of the important results about the steady-state solutions and discuss some of the open problems. The course will be accessible to postdocs and to graduate students with some knowledge of PDEs. For example, an introductory graduate PDE course should be a sufficient prerequisite.
Vladimir Sverak (University of Minnesota) Topics in the theory of the Navier-Stokes equations
Abstract: The course will cover certain selected topics in the theory of the Navier-Stokes equations. After a brief overview of the main issues of the general theory we will focus on problems in the theory of the steady-state solutions. There are many open problems concerning the steady-state solutions. These problems are presumably easier than the main open questions about the time-dependent equations. Nevertheless, some of them have remained unsolved since their first explicit formulation in the pioneering works of Jean Leray in the 1930s. There is a certain indirect similarity (or "duality") between the mathematical issues raised by these steady-state problems and the issues which come up in connection with the more well-known open problems about the time-dependent equations. In the lectures I hope to cover some of the important results about the steady-state solutions and discuss some of the open problems. The course will be accessible to postdocs and to graduate students with some knowledge of PDEs. For example, an introductory graduate PDE course should be a sufficient prerequisite.
Vladimir Sverak (University of Minnesota) Topics in the theory of the Navier-Stokes equations
Abstract: The course will cover certain selected topics in the theory of the Navier-Stokes equations. After a brief overview of the main issues of the general theory we will focus on problems in the theory of the steady-state solutions. There are many open problems concerning the steady-state solutions. These problems are presumably easier than the main open questions about the time-dependent equations. Nevertheless, some of them have remained unsolved since their first explicit formulation in the pioneering works of Jean Leray in the 1930s. There is a certain indirect similarity (or "duality") between the mathematical issues raised by these steady-state problems and the issues which come up in connection with the more well-known open problems about the time-dependent equations. In the lectures I hope to cover some of the important results about the steady-state solutions and discuss some of the open problems. The course will be accessible to postdocs and to graduate students with some knowledge of PDEs. For example, an introductory graduate PDE course should be a sufficient prerequisite.
Karel Tuma (Charles University in Prague) A thermodynamically compatible rate type fluid to describe the response of asphalt
Abstract: We consider a class of viscoelastic rate type models that in particular includes: (i) Oldroyd-B fluid model with three parameters, (ii) nonlinear fluid model derived Rajagopal and Srinivasa [2000] with three parameters, and (iii) nonlinear model with five parameters. We are interested in observing how well are these models capable to capture the experimental data for asphalt performed by J. Murali Krishnan, Indian Institute of Technology, Madras using dynamic shear rheometer. We find out that the model (i) is not able to capture the experimentally observed overshoot for the torque, while we obtain overshoots for the models (ii) and (iii).
Alan VanNevel (Naval Air Warfare Center) Government/DoD/Navy talk:
Navy needs
Automated image understanding
Abstract: No Abstract
René Vidal (Johns Hopkins University) Sparse subspace clustering
Abstract: We propose a method based on sparse representation to cluster data drawn from multiple low-dimensional linear or affine subspaces embedded in a high-dimensional space. Our method is based on the fact that each point in a union of subspaces has a sparse representation with respect to a dictionary formed by all other data points. In general, finding such a spare representation is NP hard. Our key contribution is to show that, under mild assumptions, the sparse representation can be obtained 'exactly' by using 1 optimization. The segmentation of the data is obtained by applying spectral clustering to a similarity matrix built from this sparse representation. Our method can be extended to handle noise, outliers as well as missing data by exploiting sparsity. Experiments on the Hopkins155 motion segmentation database and other motion sequences with outliers and missing data show that our approach significantly outperforms state-of-the-art methods.
Petia M. Vlahovska (Dartmouth College) Complex motions of vesicles and red blood cells in flow
Abstract: Blood flow in the microcirculation is an extensively studied problem, yet the behavior of red blood cells (RBCs) continues to surprise researchers. For example, recently it was discovered that in steady shear flow RBCs not only tank-tread or tumble, but can also "swing" (tank-treading accompanied by oscillations in the inclination angle) [Abkarian et al. PRL 2007]. I will present our analytical work that quantitatively explains this behavior and other features in the RBCs dynamics. In steady shear flows, the theory shows that a closed lipid membrane (vesicle or RBC) deforms into a prolate ellipsoid, which tumbles at low shear rates, and swings at higher shear rates. The amplitude of the oscillations decreases with shear rate. The viscosity of a dilute suspension of vesicles or RBCs exhibits a minimum at the tank-treading to tumbling transition. In quadratic flows, the theory predicts a peculiar coexistence of parachute- and bullet-like vesicle shapes at the flow centerline. Vesicles and RBCs always migrate towards the flow centerline unlike drops, whose direction of migration depends on the viscosity ratio. In time-dependent flows, vesicles can exhibit chaotic dynamics.
Lynn M. Walker (Carnegie Mellon University) Shear alignment and mechanical properties of nanostructured hydrogels
Abstract: Keywords: Block copolymer solutions, hydrogels, shear aligned, soft crystals Abstract: Self-assembled block copolymer templates can be used to control the nanoscale structure of materials that would not otherwise order in solution. In this work, we have developed a technique to use close-packed cubic and cylindrical mesophases of a thermoreversible block copolymer (PEO-PPO-PEO) to impart spatial order on dispersed nanoparticles. The thermoreversible nature of the template allows for the dispersion of particles synthesized outside the template. This feature extends the applicability of this templating method to many particle-polymer systems and also permits a systematic evaluation of the impact of design parameters on the structure and mechanical properties of the nanocomposites. The criteria for forming co-crystals has been fully characterized using contrast-matching small-angle neutron scatting (SANS) and the mechanical properties of these soft crystals determined. SANS experiments also demonstrate that shear can be used to align the nanocomposites into single-crystal macro-domains; the first demonstration of the formation of single-crystal nanoparticle superlattices. We are currently utilizing SANS to understand the flow mechanisms of both the neat block copolymer solutions and several types of these co-crystals.
Shawn W. Walker (New York University) Shape optimization of peristaltic pumping
Abstract: We present a variational method for optimizing peristaltic pumping in a two dimensional periodic channel with moving walls to pump fluid (peristalsis is common in biology). No a priori assumption is made on the wall motion, except that the shape is static in a moving wave frame. Thus, we pose an infinite dimensional optimization problem and solve it with finite elements. L2-type projections are used to compute quantities such as curvature and boundary stresses.
Qi Wang (University of South Carolina) Kinetic theories for complex fluids
Abstract: Keywords: kinetic theory, polymer-particulate nanocomposites, biaxial liquid crystal polymers. Abstract: In this talk, I will discuss some latest development in the modeling of polymer-particulate nanocomposites (PNC) and biaxial liquid crystal polymers (BLCP) using kinetic theories. Kinetic theory formulation allows one to integrate the microscopic dynamics to the background macroscopic flow field to yield a two-level or even multi-level model for various complex fluids. Equilibrium phases and dynamical states of the PNC and BLCP will be discussed and their rheological responses to shear investigated.
Sijue Wu (University of Michigan) Colloquium: Wellposedness of the full water wave problem in two and three dimensions
Abstract:
Laurent Younes (Johns Hopkins University) Diffeomorphisms and active contours
Abstract: Keywords: Shape evolution; Shape spaces; Active contours; Riemannian metrics on diffeomorphisms Abstract: We present a geometric flow approach to the segmentation of two- three- dimensional shapes by minimizing a cost function similar to the ones used with geometric active contours or to the Chan-Vese approach. Our goal, well-adapted to many shape segmentation problems, including those arising from medical images, is to ensure that the evolving contour or surface remains smooth and diffeomorphic to its initial position over time. This is formulated as a variational problem in a group of diffeomorphisms equipped with a right-invariant Riemannian metric. A resulting gradient descent algorithm is used, with an interesting variant that constrains the velocity in shape space to belong in a finite dimensional space determined by time-dependent control points. Experimental results with 2D and 3D shapes will be presented.
Arghir Dani Zarnescu (University of Oxford) Validity and limitations of the statistical scaling hypothesis for a nematic liquid crystal flow
Abstract: The transition from the isotropic into the nematic state occurs, in a thermotropic liquid crystals, through the creation of nematically ordered islands in the overall isotropic fluid. It was argued in the physics literature that the domain growth of the nematic state is a scaling phenomenon: the pattern of domains at a later time looks statistically similar to that at an earlier time, up to a time-dependent change of scale. The statistical scaling hypothesis states that at a large enough time the equal time scalar correlation function C(r,t) will assume a scaling form f(r/L(t)) where L(t) is the time-dependent length scale of nematic domains. The precise asymptotics of L(t) for large t have been the subject of a significant debate in the physics literature. We present a mathematically rigorous analysis of the equations that shows under what conditions the scaling hypothesis holds and what are the correct asymptotics of L(t) for large t. This is joint work with Eduard Kirr (University of Illinois at Urbana-Champaign).
Weigang Zhong (University of Minnesota) Modified immersed boundary modeling and simulation of concentrated suspensions
Abstract: One major example of dense multiphase flows in engineering is the extrusion process which is a crucial part in the industrial production of ceramic products. I study the extrusion batch flow through multi-scale modeling and a modified immersed boundary (IB) method with direct-forcing. A software package (IBAMR) with support for Cartesian grid adaptive mesh refinement developed by B. Griffith from New York University is utilized to implement the IB method. Preliminary numerical experiments for suspensions with mono-disperse and poly-disperse particles provide evidence for this new IB method's potential for solving the problems of extrusion flow.
Visitors in Residence
Iman Aganj University of Minnesota 10/5/2009 - 10/7/2009
Patrick Anderson Technische Universiteit Eindhoven 10/10/2009 - 10/16/2009
Shelley L. Anna Carnegie Mellon University 10/10/2009 - 10/16/2009
Arezoo Ardekani Massachusetts Institute of Technology 10/13/2009 - 10/16/2009
Paulo E. Arratia University of Pennsylvania 10/10/2009 - 10/15/2009
Paul J. Atzberger University of California, Santa Barbara 10/11/2009 - 10/17/2009
Nusret Balci University of Minnesota 9/1/2009 - 8/31/2010
Leah Bar University of Minnesota 10/5/2009 - 10/7/2009
Thomas Batard Université de La Rochelle 10/3/2009 - 10/8/2009
Peter W. Bates Michigan State University 10/2/2009 - 10/5/2009
Jennifer Beichman University of Michigan 9/1/2009 - 5/31/2010
Andrew Belmonte Pennsylvania State University 10/10/2009 - 10/14/2009
Antony N. Beris University of Delaware 10/11/2009 - 10/16/2009
Leonid Berlyand Pennsylvania State University 10/13/2009 - 10/16/2009
Michel Berthier Université de La Rochelle 10/3/2009 - 10/8/2009
Andrea L. Bertozzi University of California, Los Angeles 10/4/2009 - 10/7/2009
Meredith Betterton University of Colorado 9/29/2009 - 10/2/2009
Michael Booty New Jersey Institute of Technology 10/10/2009 - 10/16/2009
Olus N. Boratav Corning Incorporated 10/10/2009 - 10/17/2009
John F. Brady California Institute of Technology 10/10/2009 - 10/16/2009
Richard J. Braun University of Delaware 9/1/2009 - 12/20/2009
Michael P. Brenner Harvard University 10/4/2009 - 10/5/2009
Xavier Bresson University of California, Los Angeles 10/4/2009 - 10/7/2009
Maria-Carme T. Calderer University of Minnesota 9/1/2009 - 6/30/2010
Christine Cardinal University of Minnesota 10/12/2009 - 10/16/2009
Lawrence Carin Duke University 10/4/2009 - 10/7/2009
Gunnar Carlsson Stanford University 9/30/2009 - 10/2/2009
Alexey Castrodad University of Minnesota 10/5/2009 - 10/7/2009
Bruce Caswell Brown University 10/14/2009 - 10/17/2009
Hector D. Ceniceros University of California, Santa Barbara 10/11/2009 - 10/16/2009
Chi Hin Chan University of Minnesota 9/1/2009 - 8/31/2010
Bernard Chazelle Princeton University 10/3/2009 - 10/5/2009
Xianjin Chen University of Minnesota 9/1/2008 - 8/31/2010
Eric Choate University of North Carolina 10/10/2009 - 11/10/2009
David Chock Ford 10/4/2009 - 10/5/2009
Peter Constantin University of Chicago 10/13/2009 - 10/14/2009
L. Pamela Cook University of Delaware 9/6/2009 - 12/20/2009
Michael Earl Cromer Jr University of Delaware 9/1/2009 - 12/31/2009
Qing Cui University of Minnesota 10/1/2009 - 10/2/2010
Jérôme Darbon École Normale Supérieure de Cachan 10/3/2009 - 10/7/2009
Morton Denn City College, CUNY 10/12/2009 - 10/16/2009
Charles Doering University of Michigan 8/15/2009 - 6/15/2010
Julio Duarte Eastman Kodak Company 10/5/2009 - 10/7/2009
Jens Eggers University of Bristol 10/10/2009 - 10/17/2009
Bjorn Engquist University of Texas 10/11/2009 - 10/16/2009
Charles L. Epstein University of Pennsylvania 9/29/2009 - 10/2/2009
Katia Estabridis Naval Air Warfare Center 10/4/2009 - 10/7/2009
Dean M. Evasius National Science Foundation 9/29/2009 - 10/2/2009
Randy H. Ewoldt University of Minnesota 9/1/2009 - 8/31/2010
Angbo Fang Hong Kong University of Science and Technology 9/10/2009 - 10/18/2009
Matt Feiszli Yale University 10/4/2009 - 10/7/2009
James J. Feng University of British Columbia 10/11/2009 - 10/16/2009
Xiaobing Feng University of Tennessee 10/2/2009 - 10/31/2009
David Finn Rose-Hulman Institute of Technology 9/1/2009 - 11/23/2009
Arjuna Flenner Naval Air Warfare Center 10/4/2009 - 10/7/2009
Mark Gregory Forest University of North Carolina 9/11/2009 - 10/20/2009
Richard Garcia University of Puerto Rico 10/14/2009 - 10/15/2009
Donald Geman Johns Hopkins University 10/4/2009 - 10/6/2009
Sandip Ghosal Northwestern University 9/21/2009 - 12/12/2009
Robert Ghrist University of Pennsylvania 10/3/2009 - 10/5/2009
Anna Gilbert University of Michigan 10/2/2009 - 10/5/2009
Yuliya Gorb University of Houston 10/11/2009 - 10/17/2009
Michael D. Graham University of Wisconsin 9/1/2009 - 12/22/2009
Xianfeng David Gu SUNY 10/4/2009 - 10/7/2009
Thomas C. Hagen University of Memphis 9/1/2009 - 12/31/2009
Thomas Hagstrom University of New Mexico 9/29/2009 - 10/2/2009
Brian Haines Pennsylvania State University 10/11/2009 - 10/14/2009
Oliver Harlen University of Leeds 10/10/2009 - 10/16/2009
Ole Hassager Technical University of Denmark 10/11/2009 - 10/16/2009
Xuming He University of Illinois at Urbana-Champaign 9/29/2009 - 10/2/2009
Juan Pablo Hernandez-Ortiz National University of Colombia 10/11/2009 - 10/16/2009
Gary Arthur Hewer DR. Naval Air Warfare Center 10/4/2009 - 10/7/2009
Mary Ann Horn National Science Foundation 9/29/2009 - 10/6/2009
Anette (Peko) Hosoi Massachusetts Institute of Technology 10/13/2009 - 10/16/2009
Xianpeng Hu University of Pittsburgh 10/10/2009 - 10/15/2009
Martien A. Hulsen Technische Universiteit Eindhoven 10/10/2009 - 10/16/2009
Yunkyong Hyon University of Minnesota 9/1/2008 - 8/31/2010
Mark Iwen University of Minnesota 9/1/2008 - 8/31/2010
Srividhya Jeyaraman University of Minnesota 9/1/2008 - 8/31/2010
Lijian Jiang University of Minnesota 9/10/2008 - 8/31/2010
Mihailo Jovanovic University of Minnesota 9/11/2009 - 6/10/2010
Behzad Kamgar-Parsi Office of Naval Research 10/4/2009 - 10/7/2009
Joanna Kania-Bartoszynska National Science Foundation 9/29/2009 - 10/2/2009
Justin C.T. Kao Massachusetts Institute of Technology 10/10/2009 - 10/16/2009
Markus Keel University of Minnesota 10/4/2009 - 10/5/2009
Markus Keel University of Minnesota 7/21/2008 - 6/30/2010
Bamin Khomami University of Tennessee 10/11/2009 - 10/16/2009
Hyejin Kim University of Minnesota 9/1/2009 - 8/31/2010
Kwang-Yeon Kim Kangwon (Kangweon) National University 10/9/2009 - 10/17/2009
Ron Kimmel Technion-Israel Institute of Technology 10/4/2009 - 10/7/2009
Daniel J. Klingenberg University of Wisconsin 10/11/2009 - 10/16/2009
Pawel Konieczny University of Minnesota 9/1/2009 - 8/31/2010
Peter R. Kramer Rensselaer Polytechnic Institute 10/10/2009 - 10/17/2009
Andrew M. Kraynik Sandia National Laboratories 10/11/2009 - 10/16/2009
Satish Kumar University of Minnesota 10/12/2009 - 10/16/2009
Tony Ladd University of Florida 10/11/2009 - 10/15/2009
Diane Lambert Google Inc. 10/3/2009 - 10/5/2009
Ronald G. Larson University of Michigan 9/12/2009 - 12/22/2009
Triet Minh Le Yale University 10/4/2009 - 10/7/2009
Claude Le Bris CERMICS 10/11/2009 - 10/15/2009
Federico Lecumberry University of the Republic 10/4/2009 - 10/7/2009
Yann LeCun New York University 10/4/2009 - 10/7/2009
Chiun-Chang Lee National Taiwan University 10/22/2009 - 6/30/2010
Young-Ju Lee Rutgers University 9/11/2009 - 12/31/2009
Christophe Lenglet University of Minnesota 10/5/2009 - 10/7/2009
Marta Lewicka University of Minnesota 9/1/2009 - 6/30/2010
Yi Li University of Iowa 9/30/2009 - 10/1/2009
Yi Li Stevens Institute of Technology 9/16/2009 - 12/17/2009
Yongfeng Li University of Minnesota 9/1/2008 - 8/31/2010
Zhilin Li North Carolina State University 10/11/2009 - 10/16/2009
Zhi (George) Lin University of Minnesota 9/1/2009 - 8/31/2010
Chun Liu University of Minnesota 9/1/2008 - 8/31/2010
Deborah F. Lockhart National Science Foundation 9/29/2009 - 10/2/2009
Ellen K. Longmire University of Minnesota 9/1/2009 - 6/30/2010
John Lowengrub University of California, Irvine 10/11/2009 - 10/16/2009
Tie Luo National Science Foundation 9/29/2009 - 10/2/2009
Yi Ma University of Illinois at Urbana-Champaign 10/4/2009 - 10/7/2009
Christopher Macosko University of Minnesota 10/12/2009 - 10/16/2009
Yasunori Maekawa Kobe University 9/7/2009 - 3/1/2010
Krishnan Mahesh University of Minnesota 9/1/2009 - 6/30/2010
Kara Lee Maki University of Minnesota 9/1/2009 - 8/31/2010
Vasileios Maroulas University of Minnesota 9/1/2008 - 8/31/2010
Luca Martinetti University of Minnesota 10/12/2009 - 10/16/2009
Nader Masmoudi New York University 10/13/2009 - 10/16/2009
Gareth Huw Mckinley Massachusetts Institute of Technology 10/11/2009 - 10/16/2009
Facundo Mémoli Stanford University 10/4/2009 - 10/7/2009
Mario Micheli University of California, Los Angeles 10/4/2009 - 10/7/2009
Petar Minev Texas A & M University 10/11/2009 - 10/17/2009
Sorin Mitran University of North Carolina 10/11/2009 - 10/16/2009
Jean-Michel Morel École Normale Supérieure de Cachan 10/4/2009 - 10/7/2009
Yoichiro Mori University of Minnesota 9/1/2009 - 6/30/2010
Alexander Morozov University of Edinburgh 10/11/2009 - 10/17/2009
Jeffrey F. Morris City College, CUNY 10/12/2009 - 10/15/2009
Susan J. Muller University of California, Berkeley 10/10/2009 - 10/16/2009
Tristan Nguyen Office of Naval Research 10/4/2009 - 10/7/2009
Monika Nitsche University of New Mexico 9/1/2009 - 12/22/2009
David Olagunju University of Delaware 10/10/2009 - 10/16/2009
Cecilia Ortiz-Duenas University of Minnesota 9/1/2009 - 8/31/2010
Hans G. Othmer University of Minnesota 9/1/2009 - 6/30/2010
Matteo Pasquali Rice University 10/11/2009 - 10/16/2009
Arlie O. Petters Duke University 10/3/2009 - 10/5/2009
Ronald Phillips University of California, Davis 10/11/2009 - 10/16/2009
Tim Phillips Cardiff University 10/10/2009 - 10/16/2009
Todd Plantenga Sandia National Laboratories 10/22/2009 - 10/23/2009
Harald Pleiner Max Planck Institute for Polymer Research 9/12/2009 - 10/17/2009
Craig T. Poling Lockheed Martin 10/3/2009 - 10/5/2009
Rob Poole University of Liverpool 10/10/2009 - 10/17/2009
Keith Promislow Michigan State University 10/10/2009 - 10/16/2009
Ignacio Ramirez University of Minnesota 10/5/2009 - 10/7/2009
Gregory J. Randall University of the Republic 10/5/2009 - 10/7/2009
Weiqing Ren New York University 10/14/2009 - 10/16/2009
Michael Renardy Virginia Polytechnic Institute and State University 9/1/2009 - 12/20/2009
Yuriko Renardy Virginia Polytechnic Institute and State University 9/1/2009 - 12/20/2009
Rosemary Renaut Arizona State University 9/29/2009 - 10/2/2009
Juan Mario Restrepo University of Arizona 8/11/2009 - 6/15/2010
Donald Richards Pennsylvania State University 9/30/2009 - 10/5/2009
Fred Roberts Rutgers University 9/29/2009 - 10/2/2009
Scott Alan Roberts University of Minnesota 10/12/2009 - 10/16/2009
Peter Cornelis Roozemond Technische Universiteit Eindhoven 10/10/2009 - 10/18/2009
Jonathan P. Rothstein University of Massachusetts 10/11/2009 - 10/14/2009
Firooz Sadjadi Lockheed Martin 10/5/2009 - 10/7/2009
Gaurab Samanta University of Minnesota 10/12/2009 - 10/16/2009
Evelyn Sander George Mason University 9/29/2009 - 10/2/2009
Fadil Santosa University of Minnesota 7/1/2008 - 6/30/2010
Guillermo R. Sapiro University of Minnesota 10/5/2009 - 10/7/2009
Arnd Scheel University of Minnesota 9/1/2009 - 6/30/2010
George R Sell University of Minnesota 9/1/2009 - 6/30/2010
Tsvetanka Sendova University of Minnesota 9/1/2008 - 8/31/2010
Gregory Seregin University of Oxford 9/20/2009 - 10/18/2009
Shuanglin Shao University of Minnesota 9/1/2009 - 8/31/2010
Eric S. G. Shaqfeh Stanford University 10/10/2009 - 10/13/2009
David H. Sharp Los Alamos National Laboratory 10/3/2009 - 10/6/2009
Michael J. Shelley New York University 10/11/2009 - 10/13/2009
Steve Shkoller University of California, Davis 10/11/2009 - 10/16/2009
Ali Shokoufandeh Drexel University 10/4/2009 - 10/7/2009
Michael S. Siegel New Jersey Institute of Technology 10/11/2009 - 10/15/2009
Linda B. Smolka Bucknell University 10/11/2009 - 10/16/2009
Daniel Spirn University of Minnesota 9/8/2009 - 6/1/2010
Pablo Sprechmann University of Minnesota 10/5/2009 - 10/7/2009
Paul H. Steen Cornell University 10/15/2009 - 12/15/2009
Victor Steinberg Weizmann Institute of Science 10/12/2009 - 10/16/2009
Panagiotis Stinis University of Minnesota 9/1/2009 - 6/30/2010
Emily Stone Utah State University 9/29/2009 - 10/2/2009
Howard Stone Harvard University 10/11/2009 - 10/15/2009
Huan Sun Pennsylvania State University 8/16/2009 - 12/15/2009
Radhakrishna Sureshkumar Washington University 10/11/2009 - 10/16/2009
Vladimir Sverak University of Minnesota 9/1/2009 - 6/30/2010
Mark Taylor Sandia National Laboratories 9/1/2009 - 12/22/2009
Jean-Luc Thiffeault University of Wisconsin 9/1/2009 - 6/30/2010
Chad Michael Topaz Macalester College 9/1/2009 - 6/30/2010
Karel Tuma Charles University in Prague 10/9/2009 - 10/17/2009
Patrick Theodore Underhill Rensselaer Polytechnic Institute 10/11/2009 - 10/15/2009
Alan VanNevel Naval Air Warfare Center 10/4/2009 - 10/7/2009
Paula Andrea Vasquez University of Delaware 10/10/2009 - 10/16/2009
Miguel Velez-Reyes University of Puerto Rico 10/4/2009 - 10/6/2009
René Vidal Johns Hopkins University 10/4/2009 - 10/6/2009
Petia M. Vlahovska Dartmouth College 10/11/2009 - 10/16/2009
Jesenko Vukadinovic College of Staten Island, CUNY 10/11/2009 - 10/16/2009
Lynn M. Walker Carnegie Mellon University 10/10/2009 - 10/16/2009
Shawn W. Walker New York University 10/10/2009 - 10/16/2009
Changyou Wang University of Kentucky 9/1/2009 - 6/15/2010
Qi Wang University of South Carolina 10/12/2009 - 10/17/2009
Sijue Wu University of Michigan 9/1/2009 - 6/5/2010
Wei Xiong University of Minnesota 9/1/2008 - 8/31/2010
Tsuyoshi Yoneda University of Minnesota 9/4/2009 - 8/31/2010
Laurent Younes Johns Hopkins University 10/4/2009 - 10/7/2009
Haijun Yu Purdue University 10/11/2009 - 10/17/2009
Arghir Dani Zarnescu University of Oxford 10/10/2009 - 10/17/2009
Linbao Zhang University of Maryland 10/10/2009 - 10/16/2009
Likun Zheng University of Minnesota 10/12/2009 - 10/16/2009
Weigang Zhong University of Minnesota 9/8/2008 - 8/31/2010
Chunfeng Zhou University of Minnesota 10/12/2009 - 10/16/2009
Meijun Zhu University of Oklahoma 10/4/2009 - 10/7/2009
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, Kent 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, Microsoft Research, Mississippi State University, Motorola, Northern Illinois University, Ohio State University, Pennsylvania 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 Cincinnati, 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 Pittsburgh, University of Tennessee, University of Wisconsin, University of Wyoming, US Air Force Research Laboratory, Wayne State University, Worcester Polytechnic Institute