Now showing items 1-20 of 60

• #### 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 ...
• #### Weight‐adjusted discontinuous Galerkin methods: Matrix‐valued weights and elastic wave propagation in heterogeneous media ﻿

(2018)
Weight‐adjusted inner products are easily invertible approximations to weighted L2 inner products. These approximations can be paired with a discontinuous Galerkin (DG) discretization to produce a time‐domain method for ...
• #### 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 ...
• #### Reduced order modeling for time-dependent optimization problems with initial value controls ﻿

(2018)
This paper presents a new reduced order model (ROM) Hessian approximation for linear-quadratic optimal control problems where the optimal control is the initial value. Such problems arise in parameter identification and ...
• #### 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. ...
• #### On discretely entropy conservative and entropy stable discontinuous Galerkin methods ﻿

(2018)
High order methods based on diagonal-norm summation by parts operators can be shown to satisfy a discrete conservation or dissipation of entropy for nonlinear systems of hyperbolic PDEsﾠ[1],ﾠ[2]. These methods can also be ...
• #### Multi-patch discontinuous Galerkin isogeometric analysis for wave propagation: Explicit time-stepping and efficient mass matrix inversion ﻿

(2018)
We present a class of spline finite element methods for time-domain wave propagation which are particularly amenable to explicit time-stepping. The proposed methods utilize a discontinuous Galerkin discretization to enforce ...
• #### Topological Schemas of Memory Spaces ﻿

(2018)
Hippocampal cognitive map-a neuronal representation of the spatial environment-is widely discussed in the computational neuroscience literature for decades. However, more recent studies point out that hippocampus plays a ...
• #### Shape Optimization of Shell Structure Acoustics ﻿

(2017)
This paper provides a rigorous framework for the numerical solution of shape optimization problems in shell structure acoustics using a reference-domain approach. The structure is modeled with Naghdi shell equations, fully ...
• #### 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 ...
• #### 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 ...
• #### Full-waveform inversion via source-receiver extension ﻿

(2017)
Full-waveform inversion produces highly resolved images of the subsurface and quantitative estimation of seismic wave velocity, provided that its initial model is kinematically accurate at the longest data wavelengths. If ...
• #### Landau Collision Integral Solver with Adaptive Mesh Refinement on Emerging Architectures ﻿

(2017)
The Landau collision integral is an accurate model for the small-angle dominated Coulomb collisions in fusion plasmas. We investigate a high order accurate, fully conservative, finite element discretization of the nonlinear ...
• #### 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 ...
• #### Reduced storage nodal discontinuous Galerkin methods on semi-structured prismatic meshes ﻿

(2017)
We present a high order time-domain nodal discontinuous Galerkin method for wave problems on hybrid meshes consisting of both wedge and tetrahedral elements. We allow for vertically mapped wedges which can be deformed along ...
• #### Reconstruction of Lamé Moduli and Density at the Boundary Enabling Directional Elastic Wavefield Decomposition ﻿

(2017)
We consider the inverse boundary value problem for the system of equations describing elastic waves in isotropic media on a bounded domain in $\mathbb{R}^3$ via a finite-time Laplace transform. The data are the dynamical ...
• #### Mapping Mantle Transition Zone Discontinuities Beneath the Central Pacific With Array Processing ofﾠSSﾠPrecursors ﻿

(2017)
We image mantle transition zone (MTZ) discontinuities beneath the Central Pacific using ~120,000 broadband SS waveforms. With a wave packet‐based array processing technique (curvelet transform), we improve the signal‐to‐noise ...
• #### Predicting solvation free energies and thermodynamics in polar solvents and mixtures using a solvation-layer interface condition ﻿

(2017)
We demonstrate that with two small modifications, the popular dielectric continuum model is capable of predicting, with high accuracy, ion solvation thermodynamics (Gibbs free energies, entropies, and heat capacities) in ...
• #### 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 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 ...