Tags: NanoBio Node

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  1. A Scalable Algorithm for Inverse Medium Problems with Multiple Sources

    04 Feb 2016 | Online Presentations | Contributor(s): Keith Kelly

    We consider the problem of acoustic scattering as described by the free-space, time-harmonic scalar wave equation given...


  2. Application of Multigrid Techniques to Magnetic and Electromagnetic Systems

    04 Feb 2016 | Online Presentations | Contributor(s): Benjamin Cowan

    We discuss the use of multigrid techniques for several novel systems related to electromagnetics. One of these is the magnetostatic problem, in which systems can involve highly anisotropic and...


  3. Compatible Relaxation Based Geometric-Algebraic Multigrid

    04 Feb 2016 | Online Presentations | Contributor(s): Fei Cao

    We develop compatible relaxation algorithms for smoothed aggregation-based multigrid coarsening. In the proposed method, we use the geometry of the given discrete problem on the finest level to...


  4. Discretization of Elliptic Differential Equations Using Sparse Grids and Prewavelets

    04 Feb 2016 | Online Presentations | Contributor(s): Christoph Pflaum

    Sparse grids can be used to discretize second order elliptic differential equations on a d-dimensional cube. Using Galerkin discretization, we obtain a linear equation system...


  5. Geometric Multigrid for MHD Simulations with Nedelec Finite Elements on Tetrahedral Grids

    04 Feb 2016 | Online Presentations | Contributor(s): Chris Hansen

    The Magneto-HydroDynamic (MHD) model is used extensively to simulate macroscopic plasma dynamics in Magnetic Confinement Fusion (MCF) devices. In these simulations, the span of time scales from...


  6. High Dimensional Uncertainty Quantification via Multilevel Monte Carlo

    04 Feb 2016 | Online Presentations | Contributor(s): Hillary Fairbanks

    Multilevel Monte Carlo (MLMC) has been shown to be a cost effective way to compute moments of desired quantities of interest in stochastic partial differential equations when the uncertainty in...


  7. HPGMG: Benchmarking Computers Using Multigrid

    04 Feb 2016 | Online Presentations | Contributor(s): Jed Brown

    HPGMG (https://hpgmg.org) is a geometric multigrid benchmark designed to measure the performance and versatility of computers. For a benchmark to be representative of applications, good...


  8. Hub Snub: Removing Vertices with High Degree from Coarse-grid Correction

    04 Feb 2016 | Online Presentations | Contributor(s): Geoffry Sanders

    Network scientists often employ numerical solutions to linear systems as subroutines of data mining algorithms. Due to the ill-conditioned nature of the systems, obtaining solutions with standard...


  9. Is the Ideal Approximation Operator Always "Ideal" for a Particular C/F Splitting?

    04 Feb 2016 | Online Presentations | Contributor(s): Erin Molloy

    Given a coarse grid, the ideal prolongation operator is defined by , where the weight matrix,  , interpolates a set of fine grid variable (-points) from a set of coarse grid...


  10. Least-Squares Finite Element Method and Nested Iteration for Electromagnetic Two-Fluid Plasma Models

    04 Feb 2016 | Online Presentations | Contributor(s): Christopher Leibs

    Efforts are currently being directed towards a fully implicit, electromagnetic, JFNK-based solver, motivating the necessity of developing a fluid-based, electromagnetic, preconditioning strategy...


  11. Monolithic Multigrid Methods for Coupled Multi-Physics Problems

    04 Feb 2016 | Online Presentations | Contributor(s): Scott Maclachlan

    While block-diagonal and approximate block-factorization preconditioners are often considered for coupled problems, monolithic approaches can offer improved performance, particularly when the...


  12. Multilevel Markov Chain Monte Carlo for Uncertainty Quantification in Subsurface Flow

    04 Feb 2016 | Online Presentations | Contributor(s): Christian Ketelsen

    The multilevel Monte Carlo method has been shown to be an effective variance reduction technique for quantifying uncertainty in subsurface flow simulations when the random conductivity field can...


  13. On the Design of a Finite Element Multigrid Solver for Mimetic Finite Difference Schemes

    04 Feb 2016 | Online Presentations | Contributor(s): Carmen Rodrigo

    The focus of this work is to study the relation between mimetic finite difference schemes on triangular grids and some finite element methods for two model problems based on curl-rot and grad-div...


  14. On the Preconditioning of a High-Order RDG-based All-Speed Navier-Stokes Solver

    04 Feb 2016 | Online Presentations | Contributor(s): Brian Weston

    We investigate the preconditioning of an all-speed Navier-Stokes solver, based on the orthogonal-basis Reconstructed Discontinuous Galerkin (RDG) space discretization, and integrated using a...


  15. Parallel Multigrid Preconditioner Based on Automatic 3D Tetradedric Meshes

    04 Feb 2016 | Online Presentations | Contributor(s): Frederic Vi

    Multigrid methods are efficient for solving large sparse linear systems. Geometric (GMG) and Algebraic Multigrid (AMG) have both their own benefits and limitations. Combining the simplicity of AMG...


  16. Reducing Communication Costs for Sparse Matrix Multiplication within Algebraic Multigrid

    04 Feb 2016 | Online Presentations | Contributor(s): Grey Ballard

    We consider the sequence of sparse matrix-matrix multiplications performed during the setup phase of algebraic multigrid. In particular, we show that the most commonly used parallel algorithm is...


  17. Seventeenth Copper Mountain Conference on Multigrid Methods

    04 Feb 2016 | Workshops

    HIGHLIGHTED TOPICS Uncertainty Quantification Optimization and Inverse Problems Data Mining, Large Graphs, and Markov Chains Nonsymmetric and Indefinite Problems Krylov...


  18. Space-time constrained FOSLS with AMGe upscaling

    04 Feb 2016 | Online Presentations | Contributor(s): Panayot Vassilevski

    We consider time-dependent PDEs discretized in combined space-time domains. We first reduce the PDE to a first order system. Very often in practice, one of the equations of the reduced system...


  19. Stable Discretizations and Robust Block Preconditioners for Fluid-Structure Interaction Systems

    04 Feb 2016 | Online Presentations | Contributor(s): Kai Yang

    In our work we develop a family of preconditioners for the linear algebraic systems arising from the arbitrary Lagrangian-Eulerian discretization of some fluid-structure interaction models. After...


  20. Support Graph Smoothing Techniques

    04 Feb 2016 | Online Presentations | Contributor(s): Alyson Fox

    Many tasks in large-scale network analysis and simulation require efficient approximation of the solution to the linear system $ Lx=b$, where $ L$ is a graph Laplacian. However, due to the large...