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Your search keyword '"Torsu, P."' showing total 9 results
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9 results on '"Torsu, P."'

1. An iterative method for solving elliptic BVP in one-dimension

Author

Zelaya, Christian O. Bernal and Torsu, Prosper

Subjects
Mathematics - Analysis of PDEs, Mathematics - Numerical Analysis
Abstract

This paper presents a decomposition method for solving elliptic boundary value problems in one-dimension. The method is an improvement to an existing technique for approximating elliptic systems. It is demonstrated to be computationally superior to the original formulation as less computations are required to obtain an approximation of the same accuracy. Convergence of the method is justified and supported by some theoretical results. We show that for a sufficiently smooth forcing data, the method always converge for a relatively small truncation order. The method is tested using some problems with exact solutions., Comment: 11 pages

Published
2024

3. On variational iterative methods for semilinear problems

Author

Torsu, Prosper

Subjects
Mathematics - Numerical Analysis
Abstract

This paper presents an iterative method suitable for inverting semilinear problems which are important kernels in many numerical applications. The primary idea is to employ a parametrization that is able to reduce semilinear problems into linear systems which are solvable using fast Poisson solvers. Theoretical justifications are provided and supported by several experiments. Numerical results show that the method is not only computationally less expensive, but also yields accurate approximations.

Published
2019

7. A locally conservative stabilized continuous Galerkin finite element method for two-phase flow in poroelastic subsurfaces

Author

Deng, Quanling, Ginting, V., McCaskill, B., Torsu, P., Deng, Quanling, Ginting, V., McCaskill, B., and Torsu, P.

Abstract

© 2017 Elsevier Inc. We study the application of a stabilized continuous Galerkin finite element method (CGFEM) in the simulation of multiphase flow in poroelastic subsurfaces. The system involves a nonlinear coupling between the fluid pressure, subsurface's deformation, and the fluid phase saturation, and as such, we represent this coupling through an iterative procedure. Spatial discretization of the poroelastic system employs the standard linear finite element in combination with a numerical diffusion term to maintain stability of the algebraic system. Furthermore, direct calculation of the normal velocities from pressure and deformation does not entail a locally conservative field. To alleviate this drawback, we propose an element based post-processing technique through which local conservation can be established. The performance of the method is validated through several examples illustrating the convergence of the method, the effectivity of the stabilization term, and the ability to achieve locally conservative normal velocities. Finally, the efficacy of the method is demonstrated through simulations of realistic multiphase flow in poroelastic subsurfaces.

Published
2017

8. Uncertainty Quantification of Parameters in SBVPs Using Stochastic Basis and Multi-Scale Domain Decomposition.

Author

Ginting, Victor, Torsu, Prosper, and McCaskill, Bradley

Subjects
STOCHASTIC processes, MONTE Carlo method, UNCERTAINTY, MATHEMATICAL decomposition, COEFFICIENTS (Statistics), NUMERICAL analysis
Abstract

Quantifying uncertainty effects of coefficients that exhibit heterogeneity at multiple scales is among many outstanding challenges in subsurface flow models. Typically, the coefficients are modeled as functions of random variables governed by certain statistics. To quantify their uncertainty in the form of statistics (e.g., average fluid pressure or concentration) Monte-Carlo methods have been used. In a separate direction, multiscale numerical methods have been developed to efficiently capture spatial heterogeneity that otherwise would be intractable with standard numerical techniques. Since heterogeneity of individual realizations can differ drastically, a direct use of multiscale methods in Monte-Carlo simulations is problematic. Furthermore, Monte-Carlo methods are known to be very expensive as a lot of samples are required to adequately characterize the random component of the solution. In this study, we utilize a stochastic representation method that exploits the solution structure of the random process in order to construct a problem dependent stochastic basis. Using this stochastic basis representation a set of coupled yet deterministic equations is constructed. To reduce the computational cost of solving the coupled system, we develop a multiscale domain decomposition method utilizing Robin transmission conditions. In the proposed method, enrichment of the solution space can be performed at multiple levels that offer a balance between computational cost, and accuracy of the approximate solution. [ABSTRACT FROM AUTHOR]

Published
2016
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9. Assessing the Surgical and Obstetrics-Gynecology Workload of Medical Officers: Findings From 10 District Hospitals in GhanaAssessing the Workload of Medical Officers

Author

Mehtsun, Winta T., Weatherspoon, Kimberly, McElrath, LaPortia, Chima, Adaora, Torsu, Victus E. K., Obeng, Ernestina N. B., Papandria, Dominic J., Mehes, Mira M., Ortega, Gezzer, Hesse, Afua A. J., Sory, Elias, Perry, Henry, Sampson, John, Anderson, Jean, and Abdullah, Fizan

Abstract

HYPOTHESIS Surgical and obstetrics-gynecology (Ob-Gyn) workload of medical officers (MOs) is substantial and may inform policies for training investment and surveillance to strengthen surgical care at district hospitals in Ghana. DESIGN Observational study. SETTING Academic research. PARTICIPANTS Using standardized criteria, 12 trained on-site observers assessed the surgical and Ob-Gyn workload of MOs at 10 district hospitals in each of 10 administrative regions in Ghana, West Africa. The number of patients seen by MOs and the time spent managing each patient were recorded. According to each patient's diagnosis, the encounters were categorized as medical/nonsurgical, Ob-Gyn, or surgical. MAIN OUTCOME MEASURES The proportions of patients having Ob-Gyn and surgical conditions and the time expended providing care to Ob-Gyn and surgical patients. RESULTS Of the observed patient encounters, 1600 (64.5%) were classified as medical or nonsurgical, 514 (20.7%) as Ob-Gyn, and 368 (14.8%) as surgical (9.0% nontrauma and 5.8% trauma). The most common diagnosis among Ob-Gyn patients was obstetric complication requiring cesarean section. The most common diagnosis among surgical patients was inguinal hernia. Medical officers devoted 24.8% of their time to managing Ob-Gyn patients and 18.9% to managing surgical patients (which included 5.4% for the management of traumatic injuries). CONCLUSIONS Surgical and Ob-Gyn patients represent a substantial proportion of the workload among MOs at district hospitals in Ghana. Strategies to increase surgical capacity at these facilities must include equipping MOs with the appropriate training and resources to address the significant surgical and Ob-Gyn workload they face.

Published
2012
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