Now showing items 171-190 of 204

• #### A Secondary Field Based hp-Finite Element Method for the Simulation of Magnetotelluric Measurements ﻿

(2015-12-31)
In some geophysical problems, it is sometimes possible to divide the subsurface resistivity distribution as a one dimensional (1D) contribution plus some two dimensional (2D) inhomogeneities. Assuming this scenario, we ...
• #### Semi-analytical response of acoustic logging measurements in frequency domain ﻿

(2015-12-31)
This work proposes a semi-analytical method for simulation of the acoustic response of multipole eccentered sources in a fluid-filled borehole. Assuming a geometry that is invariant with respect to the azimuthal and vertical ...
• #### Sensitivity Analysis for the Appraisal of Hydrofractures in Horizontal Wells with Borehole Resistivity Measurements ﻿

(2013-06)
This paper numerically evaluates the possibility of using borehole electromagnetic (EM) measurements to diagnose and quantify hydraulic fractures that have been arti ficially generated in a horizontal well. Hydrofractures ...
• #### Sensitivity and Uncertainty Analysis by Discontinuous Galerkin of Lock-in Thermography for Crack Characterization ﻿

(2020-09)
This work focuses on the characterization of narrow vertical cracks of nite size using optically excited lock-in thermography (OLT). To characterize these cracks, we need to solve an ill-posed inverse problem. As a previous ...
• #### Sensitivity study of borehole-to-surface and crosswell electromagnetic measurements acquired with energized steel casing to water displacement in hydrocarbon-bearing layers ﻿

(2008-12-31)
We study the theoretical response of electromagnetically energized steel casing in the presence of subsurface variations of electrical resistivity. Casing is energized with a finite-size solenoid antenna located along the ...
• #### A Simulation Method for the Computation of the E ﻿

(2021-03)
We propose a set of numerical methods for the computation of the frequency-dependent eff ective primary wave velocity of heterogeneous rocks. We assume the rocks' internal microstructure is given by micro-computed tomography ...
• #### Simulation of DC dual-laterolog measurements in complex formations: A Fourier-series approach with nonorthogonal coordinates and self-adapting finite elements ﻿

(2009-12-31)
Dual laterolog (DLL) makes use of a galvanic conduction principle to focus electrical currents into rock formations, thereby minimizing shoulder and borehole effects in the measurement of formation resistivity. The tool ...
• #### Simulation of marine controlled source electromagnetic measurements using a parallel fourier hp-finite element method ﻿

(2011-12-31)
We introduce a new numerical method to simulate geophysical marine controlled source electromagnetic (CSEM) measurements for the case of 2D structures and finite 3D sources of electromagnetic (EM) excitation. The method ...
• #### Singular dynamics under a weak potential on a sphere ﻿

(2013-12-31)
We give a detailed analytical description of the global dynamics of a point mass moving on a sphere under the action of a logarithmic potential. We perform a McGehee-type blow-up in order to cope with the singularity of ...
• #### Snapshots location for Reduced Order Models: An approach based on Proper Orthogonal Decomposition and Mesh Adaptivity Techniques ﻿

(2019-06-28)
Solving Partial Differential Equations (PDE), is a key issue in science and engineering since they are widely used in many real problem modelling including fluid mechanics, acoustics, heat and mass transfer ...etc. Exact ...
• #### Some discrete maximum principles arising for nonlinear elliptic finite element problems ﻿

(2015-12-31)
The discrete maximum principle (DMP) is an important measure of the qualitative reliability of the applied numerical scheme for elliptic problems. This paper starts with formulating simple sufficient conditions for the ...
• #### Source time reversal (STR) method for linear elasticity ﻿

(2018)
We study the problem of source reconstruction for a linear elasticity problem applied to seismicity induced by mining. We assume the source is written as a variable separable function $\mathbf{f(x)}\>g(t)$ . We first present ...
• #### A source time reversal method for seismicity induced by mining ﻿

(2017-01-01)
In this work, we present a modified Time-Reversal Mirror (TRM) Method, called Source Time Reversal (STR), to find the spatial distribution of a seismic source induced by mining activity. This methodology is based on a known ...
• #### A space-time DPG method for the wave equation in multiple dimensions ﻿

(2019)
A space-time discontinuous Petrov–Galerkin (DPG) method for the linear wave equation is presented. This method is based on a weak formulation that uses a broken graph space. The well-posedness of this formulation is ...

(2020-07)
• #### Stabilization and a posteriori error analysis of a mixed FEM for convection–diffusion problems with mixed boundary conditions ﻿

(2020-06-02)
We introduce a new augmented dual-mixed finite element method for the linear convection-diffusion equation with mixed boundary conditions. The approach is based on adding suitable residual type terms to a dual-mixed ...
• #### Stabilized dual-mixed method for the problem of linear elasticity with mixed boundary conditions ﻿

(2014-12-31)
We extend the applicability of the augmented dual-mixed method introduced recently in Gatica (2007), Gatica et al. (2009) to the problem of linear elasticity with mixed boundary conditions. The method is based on the ...
• #### A stable discontinuous Galerkin-type method for solving efficiently Helmholtz problems ﻿

(2012-12-31)
We propose a stable discontinuous Galerkin-type method (SDGM) for solving efficiently Helmholtz problems. This mixed-hybrid formulation is a two-step procedure. Step 1 consists in solving well-posed problems at the element ...
• #### Studies on knot placement techniques for the geometry construction and the accurate simulation of isogeometric spatial curved beams ﻿

(2019-11)
The present paper investigates the use of different knot placement techniques for isogeometric analysis of spatial curved beams, to enhance analysis results in cases when geometries are given in terms of data points. ...
• #### A study of the apsidal angle and a proof of monotonicity in the logarithmic potential case ﻿

(2014-12-31)
This paper concerns the behaviour of the apsidal angle for orbits of central force system with homogeneous potential of degree $-2 \le \alpha \le 1$ and logarithmic potential. We derive a formula for the apsidal angle as ...