Now showing items 45-64 of 162

• #### Energy-norm-based and goal-oriented automatic hp adaptivity for electromagnetics: Application to waveguide Discontinuities ﻿

(IEEE Transactions on Microwave Theory and Techniques, 2008-12-31)
The finite-element method (FEM) enables the use of adapted meshes. The simultaneous combination of h (local variations in element size) and p (local variations in the polynomial order of approximation) refinements, i.e., ...
• #### Enhanced variational image dehazing ﻿

(SIAM Journal on Imaging Sciences, 2015-12-31)
Images obtained under adverse weather conditions, such as haze or fog, typically exhibit low contrast and faded colors, which may severely limit the visibility within the scene. Unveiling the image structure under the haze ...
• #### Existence of secondary bifurcations or isolas for PDEs ﻿

(Nonlinear Analysis, Theory, Methods and Applications, 2011-12-31)
In this paper, we introduce a method to conclude about the existence of secondary bifurcations or isolas of steady state solutions for parameter dependent nonlinear partial differential equations. The technique combines ...
• #### Explicit-in-Time Goal-Oriented Adaptivity ﻿

(Computer Methods in Applied Mechanics and Engineering, 2019-04-15)
Goal-oriented adaptivity is a powerful tool to accurately approximate physically relevant solution features for partial differential equations. In time dependent problems, we seek to represent the error in the quantity of ...
• #### Exponential decay of high-order spurious prolate spheroidal modes induced by a local approximate dtn exterior boundary condition ﻿

(Progress In Electromagnetics Research B, 2012-12-31)
We investigate analytically the asymptotic behavior of high-order spurious prolate spheroidal modes induced by a second-order local approximate DtN absorbing boundary condition (DtN2) when employed for solving high-frequency ...
• #### Fast 2.5D Finite Element Simulations of Borehole Resistivity Measurements ﻿

(Computational Geosciences, 2018-05-29)
We develop a rapid 2.5-dimensional (2.5D) finite element method for simulation of borehole resistivity measurements in transversely isotropic (TI) media. The method combines arbitrary high-order $H^1$ - and $H$ (curl)-conforming ...
• #### Fast One-dimensional Finite Element Approximation of Geophysical Measurements ﻿

(2018)
There exist a wide variety of geophysical prospection methods. In this work, we focus on resistivity methods. We categorize these resistivity prospection methods according to their acquisition location as (a) on the surface, ...
• #### Fast simulation of through-casing resistivity measurements using semi-analytical asymptotic models. Part 1: Accuracy study ﻿

(EAGE Workshop on High Performance Computing for Upstream 2014, 2014-12-31)
When trying to obtain a better characterization of the Earth's subsurface, it is common to use borehole through-casing resistivity measurements. It is also common for the wells to be surrounded by a metal casing to protect ...
• #### A FEniCS-HPC framework for multi-compartment Bloch-Torrey models ﻿

(Proceesings of ECCOMAS Congress 2016 VII European Congress on Computational Methods in Applied Sciences and Engineering, 2016-11-30)
In diffusion nuclear magnetic resonance (NMR) and diffusion magnetic resonance imaging (MRI), the multi-compartment Bloch-Torrey equation plays an important role in probing the diffusion characteristics from a nanometer ...
• #### FEniCS-HPC: Automated predictive high-performance finite element computing with applications in aerodynamics ﻿

(Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2016-01-01)
Developing multiphysics finite element methods (FEM) and scalable HPC implementations can be very challenging in terms of software complexity and performance, even more so with the addition of goal-oriented adaptive mesh ...
• #### Finite Element Simulations of Logging-While-Drilling and Extra-Deep Azimuthal Resistivity Measurements using Non-Fitting Grids ﻿

(Computational Geosciences, 2018-04-27)
We propose a discretization technique using non-fitting grids to simulate magnetic field-based resistivity logging measurements. Non-fitting grids are convenient because they are simpler to generate and handle than fitting ...
• #### Finite Element Simulations of Two-phase Flow and Floating Bodies Using FEniCS-HPC ﻿

(13th World Congress in Computational Mechanics WCCM, New York, USA, 2018-07)
We present a variational multiscale stabilized finite element method to solve the variable density incompressible Navier-Stokes equations for the simulation of two-phase flow. We introduce a level-set method based on the ...
• #### Fourier finite element modeling of light emission in waveguides: 2.5-dimensional FEM approach ﻿

(Optics Express, 2015-12-31)
We present a Fourier finite element modeling of light emission of dipolar emitters coupled to infinitely long waveguides. Due to the translational symmetry, the three-dimensional (3D) coupled waveguide-emitter system can ...
• #### Fractional Laguerre spectral methods and their applications to fractional differential equations on unbounded domain ﻿

(International Journal of Computer Mathematics, 2015-12-31)
In this article, we first introduce a singular fractional Sturm-Liouville problem (SFSLP) on unbounded domain. The associated fractional differential operator is both Weyl and Caputo type. The properties of spectral data ...
• #### Framework for adaptive fluid-structure interaction with industrial applications ﻿

(International Journal of Materials Engineering Innovation, 2013-12-31)
We present developments in the Unicorn-HPC framework for unified continuum mechanics, enabling adaptive finite element computation of fluid-structure interaction, and an overview of the larger FEniCS-HPC framework for ...
• #### Fusion-based variational image dehazing ﻿

(IEEE Signal Processing Letters, 2017-02-01)
We propose a novel image-dehazing technique based on the minimization of two energy functionals and a fusion scheme to combine the output of both optimizations. The proposed fusion-based variational image-dehazing (FVID) ...
• #### Gauss-Galerkin quadrature rules for quadratic and cubic spline spaces and their application to isogeometric analysis ﻿

(Computer-Aided Design, 2016-07-01)
We introduce Gaussian quadrature rules for spline spaces that are frequently used in Galerkin discretizations to build mass and stiffness matrices. By definition, these spaces are of even degrees. The optimal quadrature ...
• #### Gaussian quadrature for $C^1$ cubic Clough-Tocher macro-triangles ﻿

(Journal of Computational and Applied Mathematics, 2018-10-31)
A numerical integration rule for multivariate cubic polynomials over n-dimensional simplices was designed by Hammer and Stroud [14]. The quadrature rule requires n + 2 quadrature points: the barycentre of the simplex and ...
• #### Gaussian quadrature rules for $C^1$ quintic splines with uniform knot vectors ﻿

(Journal of Computational and Applied Mathematics, 2017-03-22)
We provide explicit quadrature rules for spaces of $C^1$ quintic splines with uniform knot sequences over finite domains. The quadrature nodes and weights are derived via an explicit recursion that avoids numerical solvers. ...
• #### Generalization of the Pythagorean Eigenvalue Error Theorem and its Application to Isogeometric Analysis ﻿

(Numerical Methods for PDEs, 2018-10-13)
This chapter studies the effect of the quadrature on the isogeometric analysis of the wave propagation and structural vibration problems. The dispersion error of the isogeometric elements is minimized by optimally blending ...