Now showing items 1-20 of 60

• A Branch Decomposition Algorithm for the p-Median Problem ﻿

(2017)
In this paper, we use a branch decomposition technique to improve approximations to the p-median problem. Starting from a support graph produced either by a combination of heuristics or by linear programming, we use dynamic ...
• A discrepancy-based penalty method for extended waveform inversion ﻿

(2017)
Extended waveform inversion globalizes the convergence of seismic waveform inversion by adding nonphysical degrees of freedom to the model, thus permitting it to fit the data well throughout the inversion process. These ...
• A Distributed-Memory Randomized Structured Multifrontal Method for Sparse Direct Solutions ﻿

(2017)
We design a distributed-memory randomized structured multifrontal solver for large sparse matrices. Two layers of hierarchical tree parallelism are used. A sequence of innovative parallel methods are developed for randomized ...
• A Topological Model of the Hippocampal Cell Assembly Network ﻿

(2016)
It is widely accepted that the hippocampal place cells' spiking activity produces a cognitive map of space. However, many details of this representation's physiological mechanism remain unknown. For example, it is believed ...
• An adaptive multiscale algorithm for efficient extended waveform inversion ﻿

(2017)
Subsurface-offset extended full-waveform inversion (FWI) may converge to kinematically accurate velocity models without the low-frequency data accuracy required for standard data-domain FWI. However, this robust alternative ...
• An Algebraic Exploration of Dominating Sets and Vizing's Conjecture ﻿

(2012)
Systems of polynomial equations are commonly used to model combinatorial problems such as independent set, graph coloring, Hamiltonian path, and others. We formulate the dominating set problem as a system of polynomial ...
• An accelerated Poisson solver based on multidomain spectral discretization ﻿

(2018)
This paper presents a numerical method for variable coefficient elliptic PDEs with mostly smooth solutions on two dimensional domains. The method works best for domains that can readily be mapped onto a rectangle, or a ...
• An alternating direction and projection algorithm for structure-enforced matrix factorization ﻿

(2017)
Structure-enforced matrix factorization (SeMF) represents a large class of mathematical models appearing in various forms of principal component analysis, sparse coding, dictionary learning and other machine learning ...
• An exact redatuming procedure for the inverse boundary value problem for the wave equation ﻿

(2018)
Redatuming is a data processing technique to transform measurements recorded in one acquisition geometry to an analogous data set corresponding to another acquisition geometry, for which there are no recorded measurements. ...
• Angola Cameia Development Casing-Settlement Calculations ﻿

(2017)
The amount of axial settlement of casings supported by regions of axial elastic foundations is computed. The differential equation of axial equilibrium, including the foundation stiffnesses, is solved by use of cubic axial ...
• An approximate inverse to the extended Born modeling operator ﻿

(2015)
Given a correct (data-consistent) velocity model, reverse time migration (RTM) correctly positions reflectors but generally with incorrect amplitudes and wavelets. Iterative least-squares migration (LSM) corrects the ...
• A Comparison of High Order Interpolation Nodes for the Pyramid ﻿

(2015)
The use of pyramid elements is crucial to the construction of efficient hex-dominant meshes [M. Bergot, G. Cohen, and M. Duruflé, J. Sci. Comput., 42 (2010), pp. 345--381]. For conforming nodal finite element methods with ...
• Compositional heterogeneity near the base of the mantle transition zone beneath Hawaii ﻿

(2018)
Global seismic discontinuities near 410 and 660 km depth in Earth’s mantle are expressions of solid-state phase transitions. These transitions modulate thermal and material fluxes across the mantle and variations in their ...
• Convergence of a high order method in time and space for the miscible displacement equations ﻿

(2015)
A numerical method is formulated and analyzed for solving the miscible displacement problem under low regularity assumptions. The scheme employs discontinuous Galerkin time stepping with mixed and interior penalty discontinuous ...
• Cytoplasmic sphingosine-1-phosphate pathway modulates neuronal autophagy ﻿

(2015)
Autophagy is an important homeostatic mechanism that eliminates long-lived proteins, protein aggregates and damaged organelles. Its dysregulation is involved in many neurodegenerative disorders. Autophagy is therefore a ...
• A DEIM Induced CUR Factorization ﻿

(2016)
We derive a CUR approximate matrix factorization based on the discrete empirical interpolation method (DEIM). For a given matrix ${\bf A}$, such a factorization provides a low-rank approximate decomposition of the form ...
• Edge Guided Reconstruction for Compressive Imaging ﻿

(2012-07-03)
We propose EdgeCS—an edge guided compressive sensing reconstruction approach—to recover images of higher quality from fewer measurements than the current methods. Edges are important image features that are used in various ...
• The Effects of Theta Precession on Spatial Learning and Simplicial Complex Dynamics in a Topological Model of the Hippocampal Spatial Map ﻿

(2014)
Learning arises through the activity of large ensembles of cells, yet most of the data neuroscientists accumulate is at the level of individual neurons; we need models that can bridge this gap. We have taken spatial learning ...
• An Efficient Gauss--Newton Algorithm for Symmetric Low-Rank Product Matrix Approximations ﻿

(2015)
We derive and study a Gauss--Newton method for computing a symmetric low-rank product $XX^{{T}}$, where $X \in{\mathbb{R}}^{n\times k}$ for $k<n$, that is the closest to a given symmetric matrix \$A \in{\mathbb{R}}^{n\times ...
• Efficient mesh management in Firedrake using PETSc-DMPlex ﻿

(2016)
The use of composable abstractions allows the application of new and established algorithms to a wide range of problems, while automatically inheriting the benefits of well-known performance optimizations. This work ...