Ahmed Elkhalfi - Academia.edu (original) (raw)

Papers by Ahmed Elkhalfi

Symmetry

In this paper, we present a numerical scheme for addressing the unsteady asymmetric flows governe... more In this paper, we present a numerical scheme for addressing the unsteady asymmetric flows governed by the incompressible Navier–Stokes equations under a general boundary condition. We utilized the Finite Element Method (FEM) for spatial discretization and the fully implicit Euler scheme for time discretization. In addition to the theoretical analysis of the error in our numerical scheme, we introduced two types of a posteriori error indicators: one for time discretization and another for spatial discretization, aimed at effectively controlling the error. We established the equivalence between these estimators and the actual error. Furthermore, we conducted numerical simulations in two dimensions to assess the accuracy and effectiveness of our scheme.

Industrial Engineering and Systems Management (IESM), Proceedings of 2013 International Conference on, Mar 13, 2014

Like any other industry sector in Morocco, the electric power industry is facing challenges invol... more Like any other industry sector in Morocco, the electric power industry is facing challenges involved with the increasing demand for interconnected system operations and control under the restructured electrical industry due to deregulation of the electrical market and the trend of the Smart Grid (The Ministry of Energy, Mines, Water and Environment for Morocco has launched in 2011 a consultation for developing a national regulation scheme for the electricity sector and the establishment of the authority of regulation to the end of 2013.). Morocco has embarked in the sustainable development revolution as the country is engaged in a tremendous economic and social development, the new Moroccan energy strategy adopted in March 2009, and which essential two objectives are to provide sufficient and reliable energy to the economy and the population as well as to prevent any harmful effect on the environment stemming from energy supply and uses. Smart Grid is a continuum from systems of today towards the visions of the next generation. In brief, a smart grid is the use of sensors, communications, computational ability and control in some form to enhance the overall functionality of the electric power delivery system. In this paper, smart grids and their important components in the distribution system are discussed. The basic aim of this paper is to study the Moroccan distribution system in the light of this new idea. In this paper, Morocco's national power utility initiatives to make existing power grids smart by considering SCADA (Supervisory Control and Data Acquisition System) and Distribution Management System (DMS) at distribution system are discussed.

Statistics, Optimization and Information Computing, Jan 23, 2023

In this investigation, we successfully employed the Non-Uniform Rational B-spline (NURBS) to stud... more In this investigation, we successfully employed the Non-Uniform Rational B-spline (NURBS) to study the fracture mechanics. the NURBS functions are very popular in the design field (CAD model) and it is used as an alternative to Lagrange interpolation polynomials. The extended isogeometric analysis based on this basis function is used to evaluate the stress intensity factors (SIFs) in order to control the crack propagation. For various crack lengths, SIFs were calculated to validate the accuracy of this technique. The results obtained are in good agreement with the available techniques as CFEM, X-FEM.

Monthly Weather Review, Jul 1, 1995

Annales Geophysicae, 1999

The hydrostatic model SALSA is used to simulate a particular event observed during the Greenland ... more The hydrostatic model SALSA is used to simulate a particular event observed during the Greenland Ice Margin EXperiment``GIMEX'' (on July 12th, 1991). The time evolution of the large-scale¯ow was incorporated in the model through time dependent boundary conditions which were updated using the closest upwind sounding. A turbulent scheme for the stable boundary layer and an appropriate parametrization of the surface¯uxes implemented in the same model, are used for this study. The simulation results are discussed and compared to the available observations. The computed turbulent¯uxes are correctly estimated. The model predicts a mixing zone of about 1500 m high which is in good agreement with tundra site observations. Over the ice cap, the katabatic layer is correctly simulated by the model. Its height of 80±300 m is well estimated. The comparison between the simulation and observations taken at ice cap sites is reasonably valid. The ablation computed along the ice cap corresponds well to the values reconstructed of observations at sites 4 and 9. Finally, a sensibility study to a speci®ed westward geostrophic wind (2 ms A1) shows that the consideration of this latter improves the simulated tundra wind evolution.

This paper is interested in a numerical method, we use the mini-element P1{P}_{1}P1-Bubble/P1 over ... more This paper is interested in a numerical method, we use the mini-element P1{P}_{1}P1-Bubble/P1 over triangles, as a solver to the steady Brinkman flow equation with the Dirichlet boundary condition in a heterogeneous porous media. We define the necessary hypotheses to prove the existence and uniqueness of the solution. An iterative solver for the global linear system (Uzawa conjugate gradient method) is applied to accelerate the approach solution. A series of numerical examples with Matlab software demonstrates the effectiveness of this method for these equations arising in modeling flow in anisotropic porous media.

Mathematics

In this paper, we approach two nonlinear differential equations applied in fluid mechanics by fin... more In this paper, we approach two nonlinear differential equations applied in fluid mechanics by finite element methods (FEM). Our objective is to approach the solution to these problems; the first one is the “p-Laplacian” problem and the second one is the “Quasi-Newtonian Stokes” problem with a general boundary condition. To study and analyze our solutions, we introduce the a posteriori error indicator; this technique allows us to control the error, and each is shown the equivalent between the true and the a posterior errors estimators. The performance of the finite element method by this type of general boundary condition is presented via different numerical simulations.

2022 2nd International Conference on Innovative Research in Applied Science, Engineering and Technology (IRASET), 2022

Pressure equipment containing a surface defect requires an important evaluation to ensure the saf... more Pressure equipment containing a surface defect requires an important evaluation to ensure the safety of these systems. The aim of this study is to analyse an external semi-elliptical crack in a thin wall cylinder. Due to the introduction of the Extended Finite Element Method (X-FEM) as an alternative to the conventional Finite Element Method (CFEM), in this paper we used X-FEM implemented in ABAQUS to compute the elastoplastic circumferential stress, it shows an accuracy result compared with the CFEM and CASTEM FE results. Based on these results we presented a new technique by coupling X-FEM and Volumetric Approach to evaluate the cracking stress in order to calculate the Stress Intensity Factors in the elastoplastic field.

International Journal on Interactive Design and Manufacturing (IJIDeM), 2018

Evaluation of structural integrity of a cracked structure has become an important matter in the i... more Evaluation of structural integrity of a cracked structure has become an important matter in the industrial field since couples of decades. However, damage process occurred in a structural component is not yet fixed. The objective of this research was to compute the stress intensity factor KI, in mode I, using in the linear elastic domain, by the finite element method and the extended finite element method. The defect studied in this survey has a form of a longitudinal semi-elliptic crack, located on the outer surface of the tube. A summary of the paper contains a numerical convergence for each method in terms of accuracy and limitations. The proposed methodology and outcomes released from this study act as novel design tool for the industrial engineers when is required to generate a robust solution for product development working in critical conditions.

Proceedings of 2013 International Conference on Industrial Engineering and Systems Management, Oct 1, 2013

Like any other industry sector in Morocco, the electric power industry is facing challenges invol... more Like any other industry sector in Morocco, the electric power industry is facing challenges involved with the increasing demand for interconnected system operations and control under the restructured electrical industry due to deregulation of the electrical market and the trend of the Smart Grid (The Ministry of Energy, Mines, Water and Environment for Morocco has launched in 2011 a consultation for developing a national regulation scheme for the electricity sector and the establishment of the authority of regulation to the end of 2013.). Morocco has embarked in the sustainable development revolution as the country is engaged in a tremendous economic and social development, the new Moroccan energy strategy adopted in March 2009, and which essential two objectives are to provide sufficient and reliable energy to the economy and the population as well as to prevent any harmful effect on the environment stemming from energy supply and uses. Smart Grid is a continuum from systems of today towards the visions of the next generation. In brief, a smart grid is the use of sensors, communications, computational ability and control in some form to enhance the overall functionality of the electric power delivery system. In this paper, smart grids and their important components in the distribution system are discussed. The basic aim of this paper is to study the Moroccan distribution system in the light of this new idea. In this paper, Morocco's national power utility initiatives to make existing power grids smart by considering SCADA (Supervisory Control and Data Acquisition System) and Distribution Management System (DMS) at distribution system are discussed.

Mathematics

This article highlights a study focused on resolving a nonlinear problem in fluid dynamics using ... more This article highlights a study focused on resolving a nonlinear problem in fluid dynamics using the Navier–Stokes equations as a mathematical model. The study focuses on comparing the isogeometric analysis (IGA) B-spline method with the traditional finite element method (FEM) in a two-dimensional context. The objective is to showcase the superior performance of the IGA method in terms of result quality and computational efficiency. The study employs GEOPDE’s MATLAB code for implementing and computing the NURBS method and COMSOL Software’s FEM code for comparison. The advantages of the IGA B-spline method are highlighted, including its ability to accurately capture complex flow behavior and its reduced computation time compared to FEM. The study aims to establish the superiority of the IGA method in solving nonlinear Navier–Stokes equations, providing valuable insights for fluid dynamics and practical implications for engineering simulations.

Mathematics

This study focuses on numerical solution to the Brinkman equation with mixed Dirichlet–Neumann bo... more This study focuses on numerical solution to the Brinkman equation with mixed Dirichlet–Neumann boundary conditions utilizing isogeometric analysis (IGA) based on non-uniform rational B-splines (NURBS) within the Galerkin method framework. The authors suggest using different choices of compatible NURBS spaces, which may be considered a generalization of traditional finite element spaces for velocity and pressure approximation. In order to investigate the numerical properties of the suggested elements, two numerical experiments based on a square and a quarter of an annulus are discussed. The preliminary results for the Stokes problem are presented in References.

The GIMEX experiment (Greenland Ice Margin EXperiment, 1991) was carried out in the Soendre Strom... more The GIMEX experiment (Greenland Ice Margin EXperiment, 1991) was carried out in the Soendre Stromfjord area (67{degree}05`N 50{degree}14W), in the southwestern part of Greenland during the summer of 1991. Van den Broeke et al. (1994) have described in detail the experimental set up. The topography of the area and the location of the stations along a west-east transect perpendicular to the edge of the Greenland ice sheet is presented. The micrometeorological measurements come from a series of masts, in particular masts 4, 5, 6, 7 and 9 and from the captive balloon (BC) site. From the 52 days of the experiment the authors have selected the 12 July 1991. This day was characterized by a calm and stationary large-scale meteorological situation with small inter-diurnal variations.

This paper describes a numerical solution for plane elasticity problem. It includes algorithms fo... more This paper describes a numerical solution for plane elasticity problem. It includes algorithms for discretization by mixed finite element methods. The discrete scheme allows the utilization of Brezzi-Douglas-Fortin-Marini (BDFM2) for the stress tensor and piecewise linear elements for the displacement. The numerical results are compared with some previously published works or with others coming from commercial code like ABAQUS.

Contributions to atmospheric physics, 1993

Mathematics, Sep 6, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Asociación Guyra Paraguay, Jun 1, 2017

El pecarí del Chaco conocido localmente en Paraguay como tagua (Catagonus wagneri) es una especie... more El pecarí del Chaco conocido localmente en Paraguay como tagua (Catagonus wagneri) es una especie en peligro de extinción endémica del Chaco Americano, cuya situación se mantiene en deterioro como consecuencia de la pérdida y transformación de su hábitat y de la caza excesiva en toda su área de distribución. Este trabajo presenta los resultados obtenidos y la información recopilada durante el taller “Estrategia Regional para la Conservación del Tagua” realizado en la ciudad de Asunción del Paraguay durante marzo del año 2016. En base a datos biológicos, parámetros poblacionales, puntos de presencia de la especie, datos de deforestación y cacería, describimos la situación de la especie en cada país, modelamos la distribución de la especie y aptitud del hábitat con el programa Maxent y los efectos de la cacería en la viabilidad poblacional con el programa Vortex. La ecoregión Chaqueña posee una de las mayores tasas de deforestación mundial, debido a la expansión de la ganadería y de la agricultura generando como consecuencia una pérdida de hábitat que representa la mayor amenaza para la supervivencia de la especie. En Paraguay, la deforestación en el centro del Chaco amenaza las poblaciones remanentes de tagua. En Argentina la rápida degradación de la vegetación nativa y las falencias en la implementación de normativas que manejan el bosque indican que la situación del tagua es precaria. La información disponible para la especie en Bolivia se restringe al Parque Nacional Kaa-Iya, sin embargo, la aptitud del hábitat dentro del parque y en el resto del Chaco boliviano es alta lo cual indicaría que el tagua podría estar en mejores condiciones de conservación que en los otros dos países. Los modelos de aptitud del hábitat muestran que la cobertura del suelo, la isotermalidad y la elevación son las variables mejor correlacionadas con la presencia de la especie. Aproximadamente 46% de la superficie del Gran Chaco sería apta para la especie, y únicamente el 12% del área con la mejor aptitud está incluido en un sistema oficial de protección. Según el modelo de viabilidad poblacional se requieren poblaciones mínimas de entre 1000 y 1300 individuos, en ausencia de amenazas de origen humano (ej.: caza), para que la especie sobreviva por lo menos 100 años sin perder variación genética. Con tasas anuales de cacería del 20% y del 10% la especie debería extinguirse en 20 y 100 años respectivamente. Sin embargo, una cacería que coseche el 5% de la población podría ser sustentable, si no hubiera pérdida de hábitat. La dramática conversión de superficies naturales sumada a la reducida superficie de áreas aptas protegidas y a la presión de caza determina que la conservación del tagua a largo plazo se vea amenazada. Es necesario continuar con trabajos de investigación que permitan obtener datos de calidad para posibilitar la gestión y manejo sostenible de la especie. Es indispensable que se revisen las políticas de uso del suelo y se implementen controles a la deforestación masiva que ponen en peligro el tagua y el resto de la biodiversidad del Chaco.The Chacoan peccary known locally in Paraguay as tagua (Catagonus wagneri) is an endangered species endemic to the Gran Chaco. Its situation continues to deteriorate as a consequence of habitat loss and transformation, as well as excessive hunting throughout its range. This study presents results and information obtained during the workshop “Regional strategy for the conservation of the tagua”, held in Asunción, Paraguay, in March 2016. Using population parameters as well as biological, species presence, hunting and deforestation data, we describe the conservation status in each country, model the species distribution and habitat suitability using Maxent software and the effects of hunting on population viability using Vortex software. The Chaco region has one of the highest deforestation rates in the world due to the expansion of agriculture and pastures, leading to habitat loss, which is currently the largest threat to the species survival. In Paraguay, high deforestation in the center of the Chaco threatens the remnant tagua populations. In Argentina, rapid degradation of the native vegetation and deficient implementation of land management legislation indicate a precarious situation for the species. The information about the species in Bolivia is restricted to the Kaa-Iya National Park, however, high habitat suitability in the park and outside indicate that the species may have a better conservation status than in the other countries. Habitat suitability models show that land cover, isothermality and elevation are the variables that best explain the species’ presence. Approximately 46% of the Gran Chaco is suitable for the species, but only 12% of the area with high suitability is under some type of protection. According to the population viability model done with the software Vortex, a minimum population of 1000 to 1300 individuals is required, with no human threats, to ensure…

Proceedings of the 15th International Conference on Software Technologies, 2020

Symmetry

In this paper, we present a numerical scheme for addressing the unsteady asymmetric flows governe... more In this paper, we present a numerical scheme for addressing the unsteady asymmetric flows governed by the incompressible Navier–Stokes equations under a general boundary condition. We utilized the Finite Element Method (FEM) for spatial discretization and the fully implicit Euler scheme for time discretization. In addition to the theoretical analysis of the error in our numerical scheme, we introduced two types of a posteriori error indicators: one for time discretization and another for spatial discretization, aimed at effectively controlling the error. We established the equivalence between these estimators and the actual error. Furthermore, we conducted numerical simulations in two dimensions to assess the accuracy and effectiveness of our scheme.

Industrial Engineering and Systems Management (IESM), Proceedings of 2013 International Conference on, Mar 13, 2014

Like any other industry sector in Morocco, the electric power industry is facing challenges invol... more Like any other industry sector in Morocco, the electric power industry is facing challenges involved with the increasing demand for interconnected system operations and control under the restructured electrical industry due to deregulation of the electrical market and the trend of the Smart Grid (The Ministry of Energy, Mines, Water and Environment for Morocco has launched in 2011 a consultation for developing a national regulation scheme for the electricity sector and the establishment of the authority of regulation to the end of 2013.). Morocco has embarked in the sustainable development revolution as the country is engaged in a tremendous economic and social development, the new Moroccan energy strategy adopted in March 2009, and which essential two objectives are to provide sufficient and reliable energy to the economy and the population as well as to prevent any harmful effect on the environment stemming from energy supply and uses. Smart Grid is a continuum from systems of today towards the visions of the next generation. In brief, a smart grid is the use of sensors, communications, computational ability and control in some form to enhance the overall functionality of the electric power delivery system. In this paper, smart grids and their important components in the distribution system are discussed. The basic aim of this paper is to study the Moroccan distribution system in the light of this new idea. In this paper, Morocco's national power utility initiatives to make existing power grids smart by considering SCADA (Supervisory Control and Data Acquisition System) and Distribution Management System (DMS) at distribution system are discussed.

Statistics, Optimization and Information Computing, Jan 23, 2023

In this investigation, we successfully employed the Non-Uniform Rational B-spline (NURBS) to stud... more In this investigation, we successfully employed the Non-Uniform Rational B-spline (NURBS) to study the fracture mechanics. the NURBS functions are very popular in the design field (CAD model) and it is used as an alternative to Lagrange interpolation polynomials. The extended isogeometric analysis based on this basis function is used to evaluate the stress intensity factors (SIFs) in order to control the crack propagation. For various crack lengths, SIFs were calculated to validate the accuracy of this technique. The results obtained are in good agreement with the available techniques as CFEM, X-FEM.

Monthly Weather Review, Jul 1, 1995

Annales Geophysicae, 1999

The hydrostatic model SALSA is used to simulate a particular event observed during the Greenland ... more The hydrostatic model SALSA is used to simulate a particular event observed during the Greenland Ice Margin EXperiment``GIMEX'' (on July 12th, 1991). The time evolution of the large-scale¯ow was incorporated in the model through time dependent boundary conditions which were updated using the closest upwind sounding. A turbulent scheme for the stable boundary layer and an appropriate parametrization of the surface¯uxes implemented in the same model, are used for this study. The simulation results are discussed and compared to the available observations. The computed turbulent¯uxes are correctly estimated. The model predicts a mixing zone of about 1500 m high which is in good agreement with tundra site observations. Over the ice cap, the katabatic layer is correctly simulated by the model. Its height of 80±300 m is well estimated. The comparison between the simulation and observations taken at ice cap sites is reasonably valid. The ablation computed along the ice cap corresponds well to the values reconstructed of observations at sites 4 and 9. Finally, a sensibility study to a speci®ed westward geostrophic wind (2 ms A1) shows that the consideration of this latter improves the simulated tundra wind evolution.

This paper is interested in a numerical method, we use the mini-element P1{P}_{1}P1-Bubble/P1 over ... more This paper is interested in a numerical method, we use the mini-element P1{P}_{1}P1-Bubble/P1 over triangles, as a solver to the steady Brinkman flow equation with the Dirichlet boundary condition in a heterogeneous porous media. We define the necessary hypotheses to prove the existence and uniqueness of the solution. An iterative solver for the global linear system (Uzawa conjugate gradient method) is applied to accelerate the approach solution. A series of numerical examples with Matlab software demonstrates the effectiveness of this method for these equations arising in modeling flow in anisotropic porous media.

Mathematics

In this paper, we approach two nonlinear differential equations applied in fluid mechanics by fin... more In this paper, we approach two nonlinear differential equations applied in fluid mechanics by finite element methods (FEM). Our objective is to approach the solution to these problems; the first one is the “p-Laplacian” problem and the second one is the “Quasi-Newtonian Stokes” problem with a general boundary condition. To study and analyze our solutions, we introduce the a posteriori error indicator; this technique allows us to control the error, and each is shown the equivalent between the true and the a posterior errors estimators. The performance of the finite element method by this type of general boundary condition is presented via different numerical simulations.

2022 2nd International Conference on Innovative Research in Applied Science, Engineering and Technology (IRASET), 2022

Pressure equipment containing a surface defect requires an important evaluation to ensure the saf... more Pressure equipment containing a surface defect requires an important evaluation to ensure the safety of these systems. The aim of this study is to analyse an external semi-elliptical crack in a thin wall cylinder. Due to the introduction of the Extended Finite Element Method (X-FEM) as an alternative to the conventional Finite Element Method (CFEM), in this paper we used X-FEM implemented in ABAQUS to compute the elastoplastic circumferential stress, it shows an accuracy result compared with the CFEM and CASTEM FE results. Based on these results we presented a new technique by coupling X-FEM and Volumetric Approach to evaluate the cracking stress in order to calculate the Stress Intensity Factors in the elastoplastic field.

International Journal on Interactive Design and Manufacturing (IJIDeM), 2018

Evaluation of structural integrity of a cracked structure has become an important matter in the i... more Evaluation of structural integrity of a cracked structure has become an important matter in the industrial field since couples of decades. However, damage process occurred in a structural component is not yet fixed. The objective of this research was to compute the stress intensity factor KI, in mode I, using in the linear elastic domain, by the finite element method and the extended finite element method. The defect studied in this survey has a form of a longitudinal semi-elliptic crack, located on the outer surface of the tube. A summary of the paper contains a numerical convergence for each method in terms of accuracy and limitations. The proposed methodology and outcomes released from this study act as novel design tool for the industrial engineers when is required to generate a robust solution for product development working in critical conditions.

Proceedings of 2013 International Conference on Industrial Engineering and Systems Management, Oct 1, 2013

Like any other industry sector in Morocco, the electric power industry is facing challenges invol... more Like any other industry sector in Morocco, the electric power industry is facing challenges involved with the increasing demand for interconnected system operations and control under the restructured electrical industry due to deregulation of the electrical market and the trend of the Smart Grid (The Ministry of Energy, Mines, Water and Environment for Morocco has launched in 2011 a consultation for developing a national regulation scheme for the electricity sector and the establishment of the authority of regulation to the end of 2013.). Morocco has embarked in the sustainable development revolution as the country is engaged in a tremendous economic and social development, the new Moroccan energy strategy adopted in March 2009, and which essential two objectives are to provide sufficient and reliable energy to the economy and the population as well as to prevent any harmful effect on the environment stemming from energy supply and uses. Smart Grid is a continuum from systems of today towards the visions of the next generation. In brief, a smart grid is the use of sensors, communications, computational ability and control in some form to enhance the overall functionality of the electric power delivery system. In this paper, smart grids and their important components in the distribution system are discussed. The basic aim of this paper is to study the Moroccan distribution system in the light of this new idea. In this paper, Morocco's national power utility initiatives to make existing power grids smart by considering SCADA (Supervisory Control and Data Acquisition System) and Distribution Management System (DMS) at distribution system are discussed.

Mathematics

This article highlights a study focused on resolving a nonlinear problem in fluid dynamics using ... more This article highlights a study focused on resolving a nonlinear problem in fluid dynamics using the Navier–Stokes equations as a mathematical model. The study focuses on comparing the isogeometric analysis (IGA) B-spline method with the traditional finite element method (FEM) in a two-dimensional context. The objective is to showcase the superior performance of the IGA method in terms of result quality and computational efficiency. The study employs GEOPDE’s MATLAB code for implementing and computing the NURBS method and COMSOL Software’s FEM code for comparison. The advantages of the IGA B-spline method are highlighted, including its ability to accurately capture complex flow behavior and its reduced computation time compared to FEM. The study aims to establish the superiority of the IGA method in solving nonlinear Navier–Stokes equations, providing valuable insights for fluid dynamics and practical implications for engineering simulations.

Mathematics

This study focuses on numerical solution to the Brinkman equation with mixed Dirichlet–Neumann bo... more This study focuses on numerical solution to the Brinkman equation with mixed Dirichlet–Neumann boundary conditions utilizing isogeometric analysis (IGA) based on non-uniform rational B-splines (NURBS) within the Galerkin method framework. The authors suggest using different choices of compatible NURBS spaces, which may be considered a generalization of traditional finite element spaces for velocity and pressure approximation. In order to investigate the numerical properties of the suggested elements, two numerical experiments based on a square and a quarter of an annulus are discussed. The preliminary results for the Stokes problem are presented in References.

The GIMEX experiment (Greenland Ice Margin EXperiment, 1991) was carried out in the Soendre Strom... more The GIMEX experiment (Greenland Ice Margin EXperiment, 1991) was carried out in the Soendre Stromfjord area (67{degree}05`N 50{degree}14W), in the southwestern part of Greenland during the summer of 1991. Van den Broeke et al. (1994) have described in detail the experimental set up. The topography of the area and the location of the stations along a west-east transect perpendicular to the edge of the Greenland ice sheet is presented. The micrometeorological measurements come from a series of masts, in particular masts 4, 5, 6, 7 and 9 and from the captive balloon (BC) site. From the 52 days of the experiment the authors have selected the 12 July 1991. This day was characterized by a calm and stationary large-scale meteorological situation with small inter-diurnal variations.

This paper describes a numerical solution for plane elasticity problem. It includes algorithms fo... more This paper describes a numerical solution for plane elasticity problem. It includes algorithms for discretization by mixed finite element methods. The discrete scheme allows the utilization of Brezzi-Douglas-Fortin-Marini (BDFM2) for the stress tensor and piecewise linear elements for the displacement. The numerical results are compared with some previously published works or with others coming from commercial code like ABAQUS.

Contributions to atmospheric physics, 1993

Mathematics, Sep 6, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Asociación Guyra Paraguay, Jun 1, 2017

El pecarí del Chaco conocido localmente en Paraguay como tagua (Catagonus wagneri) es una especie... more El pecarí del Chaco conocido localmente en Paraguay como tagua (Catagonus wagneri) es una especie en peligro de extinción endémica del Chaco Americano, cuya situación se mantiene en deterioro como consecuencia de la pérdida y transformación de su hábitat y de la caza excesiva en toda su área de distribución. Este trabajo presenta los resultados obtenidos y la información recopilada durante el taller “Estrategia Regional para la Conservación del Tagua” realizado en la ciudad de Asunción del Paraguay durante marzo del año 2016. En base a datos biológicos, parámetros poblacionales, puntos de presencia de la especie, datos de deforestación y cacería, describimos la situación de la especie en cada país, modelamos la distribución de la especie y aptitud del hábitat con el programa Maxent y los efectos de la cacería en la viabilidad poblacional con el programa Vortex. La ecoregión Chaqueña posee una de las mayores tasas de deforestación mundial, debido a la expansión de la ganadería y de la agricultura generando como consecuencia una pérdida de hábitat que representa la mayor amenaza para la supervivencia de la especie. En Paraguay, la deforestación en el centro del Chaco amenaza las poblaciones remanentes de tagua. En Argentina la rápida degradación de la vegetación nativa y las falencias en la implementación de normativas que manejan el bosque indican que la situación del tagua es precaria. La información disponible para la especie en Bolivia se restringe al Parque Nacional Kaa-Iya, sin embargo, la aptitud del hábitat dentro del parque y en el resto del Chaco boliviano es alta lo cual indicaría que el tagua podría estar en mejores condiciones de conservación que en los otros dos países. Los modelos de aptitud del hábitat muestran que la cobertura del suelo, la isotermalidad y la elevación son las variables mejor correlacionadas con la presencia de la especie. Aproximadamente 46% de la superficie del Gran Chaco sería apta para la especie, y únicamente el 12% del área con la mejor aptitud está incluido en un sistema oficial de protección. Según el modelo de viabilidad poblacional se requieren poblaciones mínimas de entre 1000 y 1300 individuos, en ausencia de amenazas de origen humano (ej.: caza), para que la especie sobreviva por lo menos 100 años sin perder variación genética. Con tasas anuales de cacería del 20% y del 10% la especie debería extinguirse en 20 y 100 años respectivamente. Sin embargo, una cacería que coseche el 5% de la población podría ser sustentable, si no hubiera pérdida de hábitat. La dramática conversión de superficies naturales sumada a la reducida superficie de áreas aptas protegidas y a la presión de caza determina que la conservación del tagua a largo plazo se vea amenazada. Es necesario continuar con trabajos de investigación que permitan obtener datos de calidad para posibilitar la gestión y manejo sostenible de la especie. Es indispensable que se revisen las políticas de uso del suelo y se implementen controles a la deforestación masiva que ponen en peligro el tagua y el resto de la biodiversidad del Chaco.The Chacoan peccary known locally in Paraguay as tagua (Catagonus wagneri) is an endangered species endemic to the Gran Chaco. Its situation continues to deteriorate as a consequence of habitat loss and transformation, as well as excessive hunting throughout its range. This study presents results and information obtained during the workshop “Regional strategy for the conservation of the tagua”, held in Asunción, Paraguay, in March 2016. Using population parameters as well as biological, species presence, hunting and deforestation data, we describe the conservation status in each country, model the species distribution and habitat suitability using Maxent software and the effects of hunting on population viability using Vortex software. The Chaco region has one of the highest deforestation rates in the world due to the expansion of agriculture and pastures, leading to habitat loss, which is currently the largest threat to the species survival. In Paraguay, high deforestation in the center of the Chaco threatens the remnant tagua populations. In Argentina, rapid degradation of the native vegetation and deficient implementation of land management legislation indicate a precarious situation for the species. The information about the species in Bolivia is restricted to the Kaa-Iya National Park, however, high habitat suitability in the park and outside indicate that the species may have a better conservation status than in the other countries. Habitat suitability models show that land cover, isothermality and elevation are the variables that best explain the species’ presence. Approximately 46% of the Gran Chaco is suitable for the species, but only 12% of the area with high suitability is under some type of protection. According to the population viability model done with the software Vortex, a minimum population of 1000 to 1300 individuals is required, with no human threats, to ensure…

Proceedings of the 15th International Conference on Software Technologies, 2020