Liz Añez | La Universidad del Zulia (original) (raw)

Papers by Liz Añez

Research paper thumbnail of Gas slippage in fractal porous material

Journal of Natural Gas Science and Engineering, 2018

Research paper thumbnail of Deficiencias en las ideas previas de los estudiantes de estática de la Facultad de Ingeniería de LUZ

Research paper thumbnail of Gas and liquid permeability in nano composites gels: Comparison of Knudsen and Klinkenberg correction factors

Microporous and Mesoporous Materials, 2014

ABSTRACT We measured gas and water permeability in sets of nano-composite silica gels, (silica ge... more ABSTRACT We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network with aerosil particles), which are highly porous but low permeability materials. Experimental results showed that gas and liquid permeability increased with aerosil content, allowing control of transport properties. Our results also showed that gas permeability was more than one order of magnitude higher than water permeability. This difference was analysed in view of the gas slippage effect. To this end, we tested and compared different correction factor models (Knudsen and Klinkenberg correction factors) proposed in the literature. We showed that the Klinkenberg factor increases with porosity, and discuss the effect of tortuosity. Models that account for porosity and tortuosity improve the accuracy of the prediction. The Knudsen correction increased the accuracy of the experimental data and made it possible to extrapolate the intrinsic permeability from the gas permeability with quite reasonable accuracy.

Research paper thumbnail of A Method for Elasticity Modulus Calculation in Porous Media with Known Geometry Using the Monte Carlo Technique

Key Engineering Materials, 2009

This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simu... more This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simulated porous media using the Monte Carlo technique. The porous media of known geometry is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum strain energy is calculated applying the Monte Carlo technique. The Elasticity Modulus is obtained from the theoretical relations between the elastic energy of a system and its deformation. The computational method is validated by applying it in systems of known analytic solution and over porous media generated through aggregation algorithm in two dimensions i.e. Random Sequential Aggregation and Diffusion Limited Cluster-Cluster Aggregation (RSA and DLCA respectively). The latter used to simulate the structure of silica aerogels. As for the range of concentrations studied for the DLCA and RSA systems, it was found that the elasticity modulus E decreases as the porosity of the system increases, be...

Research paper thumbnail of Monte Carlo method for computing the mechanical properties of porous media

This research reports the design of a method for computing the elasticity modulus (E) of a known ... more This research reports the design of a method for computing the elasticity modulus (E) of a known geometry porous medium. The porous medium is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum deformation energy is calculated applying the Monte Carlo Method. E is obtained from theoretical relations between the deformation energy of a system and its deformation. The method is validated by applying to a known analytical solution. The porous media model used in 2 dimensions is Random Sequential Aggregation (RSA). As for the range of concentrations studied for the RSA system, it was found that the elasticity modulus E decreases as the porosity of the system increases. Our method is able to differentiate the variations in the structures of different porous media. (In Spanish).

Research paper thumbnail of Permeability in nanocomposites gels : Knudsen and Klinkenberg approach

Research paper thumbnail of Diffraction operators in paraxial approach

12th Education and Training in Optics and Photonics Conference, 2013

Research paper thumbnail of Gas and liquid permeability in nano composites gels: Comparison of Knudsen and Klinkenberg correction factors

Microporous and Mesoporous Materials

We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network... more We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network with aerosil particles), which are highly porous but low permeability materials. Experimental results showed that gas and liquid permeability increased with aerosil content, allowing control of transport properties. Our results also showed that gas permeability was more than one order of magnitude higher than water permeability. This difference was analysed in view of the gas slippage effect. To this end, we tested and compared different correction factor models (Knudsen and Klinkenberg correction factors) proposed in the literature. We showed that the Klinkenberg factor increases with porosity, and discuss the effect of tortuosity. Models that account for porosity and tortuosity improve the accuracy of the prediction. The Knudsen correction increased the accuracy of the experimental data and made it possible to extrapolate the intrinsic permeability from the gas permeability with quite...

Research paper thumbnail of A Method for Elasticity Modulus Calculation in Porous Media with Known Geometry Using the Monte Carlo Technique

Key Engineering Materials

This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simu... more This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simulated porous media using the Monte Carlo technique. The porous media of known geometry is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum strain energy is calculated applying the Monte Carlo technique. The Elasticity Modulus is obtained from the theoretical relations between the elastic energy of a system and its deformation. The computational method is validated by applying it in systems of known analytic solution and over porous media generated through aggregation algorithm in two dimensions i.e. Random Sequential Aggregation and Diffusion Limited Cluster-Cluster Aggregation (RSA and DLCA respectively). The latter used to simulate the structure of silica aerogels. As for the range of concentrations studied for the DLCA and RSA systems, it was found that the elasticity modulus E decreases as the porosity of the system increases, be...

Research paper thumbnail of Diffraction operators in paraxial approach

12th Education and Training in Optics and Photonics Conference, 2013

Research paper thumbnail of Photoluminescent single wall carbon nanotube–silica composite gels

Carbon, 2008

Optically homogeneous single wall carbon nanotube-silica gel composites are prepared from aqueous... more Optically homogeneous single wall carbon nanotube-silica gel composites are prepared from aqueous supensions using a sol-gel process. The gels display a strong photoluminescent signal which indicates that no aggregation occurs during gelation, i.e. that the nanotubes are essentially dispersed as individuals in the composites.

Research paper thumbnail of Monte Carlo method for computing the mechanical properties of porous media

This research reports the design of a method for computing the elasticity modulus (E) of a known ... more This research reports the design of a method for computing the elasticity modulus (E) of a known geometry porous medium. The porous medium is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum deformation energy is calculated applying the Monte Carlo Method. E is obtained from theoretical relations between the deformation energy of a system and its deformation. The method is validated by applying to a known analytical solution. The porous media model used in 2 dimensions is Random Sequential Aggregation (RSA). As for the range of concentrations studied for the RSA system, it was found that the elasticity modulus E decreases as the porosity of the system increases. Our method is able to differentiate the variations in the structures of different porous media. (In Spanish).

Research paper thumbnail of Gas slippage in fractal porous material

Journal of Natural Gas Science and Engineering, 2018

Research paper thumbnail of Deficiencias en las ideas previas de los estudiantes de estática de la Facultad de Ingeniería de LUZ

Research paper thumbnail of Gas and liquid permeability in nano composites gels: Comparison of Knudsen and Klinkenberg correction factors

Microporous and Mesoporous Materials, 2014

ABSTRACT We measured gas and water permeability in sets of nano-composite silica gels, (silica ge... more ABSTRACT We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network with aerosil particles), which are highly porous but low permeability materials. Experimental results showed that gas and liquid permeability increased with aerosil content, allowing control of transport properties. Our results also showed that gas permeability was more than one order of magnitude higher than water permeability. This difference was analysed in view of the gas slippage effect. To this end, we tested and compared different correction factor models (Knudsen and Klinkenberg correction factors) proposed in the literature. We showed that the Klinkenberg factor increases with porosity, and discuss the effect of tortuosity. Models that account for porosity and tortuosity improve the accuracy of the prediction. The Knudsen correction increased the accuracy of the experimental data and made it possible to extrapolate the intrinsic permeability from the gas permeability with quite reasonable accuracy.

Research paper thumbnail of A Method for Elasticity Modulus Calculation in Porous Media with Known Geometry Using the Monte Carlo Technique

Key Engineering Materials, 2009

This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simu... more This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simulated porous media using the Monte Carlo technique. The porous media of known geometry is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum strain energy is calculated applying the Monte Carlo technique. The Elasticity Modulus is obtained from the theoretical relations between the elastic energy of a system and its deformation. The computational method is validated by applying it in systems of known analytic solution and over porous media generated through aggregation algorithm in two dimensions i.e. Random Sequential Aggregation and Diffusion Limited Cluster-Cluster Aggregation (RSA and DLCA respectively). The latter used to simulate the structure of silica aerogels. As for the range of concentrations studied for the DLCA and RSA systems, it was found that the elasticity modulus E decreases as the porosity of the system increases, be...

Research paper thumbnail of Monte Carlo method for computing the mechanical properties of porous media

This research reports the design of a method for computing the elasticity modulus (E) of a known ... more This research reports the design of a method for computing the elasticity modulus (E) of a known geometry porous medium. The porous medium is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum deformation energy is calculated applying the Monte Carlo Method. E is obtained from theoretical relations between the deformation energy of a system and its deformation. The method is validated by applying to a known analytical solution. The porous media model used in 2 dimensions is Random Sequential Aggregation (RSA). As for the range of concentrations studied for the RSA system, it was found that the elasticity modulus E decreases as the porosity of the system increases. Our method is able to differentiate the variations in the structures of different porous media. (In Spanish).

Research paper thumbnail of Permeability in nanocomposites gels : Knudsen and Klinkenberg approach

Research paper thumbnail of Diffraction operators in paraxial approach

12th Education and Training in Optics and Photonics Conference, 2013

Research paper thumbnail of Gas and liquid permeability in nano composites gels: Comparison of Knudsen and Klinkenberg correction factors

Microporous and Mesoporous Materials

We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network... more We measured gas and water permeability in sets of nano-composite silica gels, (silica gel network with aerosil particles), which are highly porous but low permeability materials. Experimental results showed that gas and liquid permeability increased with aerosil content, allowing control of transport properties. Our results also showed that gas permeability was more than one order of magnitude higher than water permeability. This difference was analysed in view of the gas slippage effect. To this end, we tested and compared different correction factor models (Knudsen and Klinkenberg correction factors) proposed in the literature. We showed that the Klinkenberg factor increases with porosity, and discuss the effect of tortuosity. Models that account for porosity and tortuosity improve the accuracy of the prediction. The Knudsen correction increased the accuracy of the experimental data and made it possible to extrapolate the intrinsic permeability from the gas permeability with quite...

Research paper thumbnail of A Method for Elasticity Modulus Calculation in Porous Media with Known Geometry Using the Monte Carlo Technique

Key Engineering Materials

This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simu... more This study introduces a method for a computational calculus of the Elasticity Modulus (E) of simulated porous media using the Monte Carlo technique. The porous media of known geometry is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum strain energy is calculated applying the Monte Carlo technique. The Elasticity Modulus is obtained from the theoretical relations between the elastic energy of a system and its deformation. The computational method is validated by applying it in systems of known analytic solution and over porous media generated through aggregation algorithm in two dimensions i.e. Random Sequential Aggregation and Diffusion Limited Cluster-Cluster Aggregation (RSA and DLCA respectively). The latter used to simulate the structure of silica aerogels. As for the range of concentrations studied for the DLCA and RSA systems, it was found that the elasticity modulus E decreases as the porosity of the system increases, be...

Research paper thumbnail of Diffraction operators in paraxial approach

12th Education and Training in Optics and Photonics Conference, 2013

Research paper thumbnail of Photoluminescent single wall carbon nanotube–silica composite gels

Carbon, 2008

Optically homogeneous single wall carbon nanotube-silica gel composites are prepared from aqueous... more Optically homogeneous single wall carbon nanotube-silica gel composites are prepared from aqueous supensions using a sol-gel process. The gels display a strong photoluminescent signal which indicates that no aggregation occurs during gelation, i.e. that the nanotubes are essentially dispersed as individuals in the composites.

Research paper thumbnail of Monte Carlo method for computing the mechanical properties of porous media

This research reports the design of a method for computing the elasticity modulus (E) of a known ... more This research reports the design of a method for computing the elasticity modulus (E) of a known geometry porous medium. The porous medium is simulated as an elastic network of central forces, to which a known deformation is applied. The minimum deformation energy is calculated applying the Monte Carlo Method. E is obtained from theoretical relations between the deformation energy of a system and its deformation. The method is validated by applying to a known analytical solution. The porous media model used in 2 dimensions is Random Sequential Aggregation (RSA). As for the range of concentrations studied for the RSA system, it was found that the elasticity modulus E decreases as the porosity of the system increases. Our method is able to differentiate the variations in the structures of different porous media. (In Spanish).