Documents disponibles écrits par cet auteur

High-Order Compact Difference Scheme for Convection-Diffusion Problems on Nonuniform Grids / X. Wang in Journal of engineering mechanics, Vol. 131, N°12 (Decembre 2005) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 131, N°12 (Decembre 2005) . - 1221-1228 p. Titre : High-Order Compact Difference Scheme for Convection-Diffusion Problems on Nonuniform Grids Titre original : Arrangement Compact de Différence d'Haut-Ordre pour des Problèmes de Convection-Diffusion sur des Grilles Non-Uniformes Type de document : texte imprimé Auteurs : X. Wang, Auteur ; Armero, Francisco, Editeur scientifique ; Huang, G. H. ; Yang, Z. F., Auteur Article en page(s) : 1221-1228 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Compaction  Grid  systems  Numerical  models  Diffusion  Fluid  flow  Contaminants  Tassement  Systèmes  de  grille  Modèles  numériques  Flux  de  fluide Index. décimale : 621.34 Résumé : In this study, a high-order compact (HOC) scheme for solving the convection-diffusion equation (CDE) under a nonuniform grid setting is developed. To eliminate the difficulty in dealing with convection terms through traditional numerical methods, an upwind function is provided to turn the steady CDE into its equivalent diffusion equation (DE). After obtaining the HOC scheme for this DE through an extension of the optimal difference method to a nonuniform grid, the corresponding HOC scheme for the steady CDE is derived through converse transformation. The Proposed scheme is of the upwind feature related to the convection diffusion phenomena, where the convective diffusion flux in the upstream has larger contributions than that in the downstream. Such a feature can help eliminate nonphysical oscillations that may often occur when dealing with convection terms through traditional numerical methods. Two examples have been presented to test performance of the proposed scheme. Under the same grid settings, the proposed scheme can produce more accurate results than the upwind difference, central difference, and perturbational schemes. The Proposed scheme is suitable for solving both convection and the diffusion dominated flow problems. In addition, it can be extended for solving unsteady CDE. It is also revealed that efforts in optimizing the grid configuration and allocation can help improve solution accuracy and efficiency. Consequently, with the proposed method, solution under nonuniform grid settings would be more accurate than those under uniform manipulations, given the same number of grid points. Dans cette étude, un arrangement (HOC) compact d'ordre élevé pour résoudre l'équation de convection-diffusion (CDE) sous un arrangement non-uniforme de grille est développé. Pour éliminer la difficulté en traitant des limites de convection par des méthodes numériques traditionnelles, une fonction à contre vent est fournie pour transformer le CDE régulier en son équation équivalente de diffusion (De). Après obtention de l'arrangement HOC pour ce De par une prolongation de la méthode optimale de différence à une grille non-uniforme, l'arrangement HOC correspondant pour le CDE régulier est dérivé par la transformation inverse. L'arrangement proposé est du dispositif à contre vent lié aux phénomènes de diffusion de convection, où le flux convecteur de diffusion dans l'ascendant a de plus grandes contributions que cela dans le descendant. Un tel dispositif peut aider à éliminer les oscillations nonphysical qui peuvent souvent se produire en traitant des limites de convection par des méthodes numériques traditionnelles. Deux exemples ont été présentés à l'exécution d'essai de l'arrangement proposé. Sous les mêmes arrangements de grille, l'arrangement proposé peut produire des résultats plus précis que la différence à contre vent, la différence centrale, et les arrangements de perturbational. L'arrangement proposé convient à résoudre la convection et les problèmes d'écoulement dominés par diffusion. En outre, il peut être prolongé pour CDE instable de solution. On l'indique également que les efforts en optimisant la configuration et l'attribution de grille peuvent aider à améliorer l'exactitude et l'efficacité de solution. En conséquence, avec la méthode proposée, la solution sous les arrangements non-uniformes de grille serait plus précise que ceux sous des manipulations uniformes, données le même nombre de points de grille. En ligne : wangtina@263.net, huangg@uregina.ca, zfyang@bnu.edu.cn [article] High-Order Compact Difference Scheme for Convection-Diffusion Problems on Nonuniform Grids = Arrangement Compact de Différence d'Haut-Ordre pour des Problèmes de Convection-Diffusion sur des Grilles Non-Uniformes [texte imprimé] / X. Wang, Auteur ; Armero, Francisco, Editeur scientifique ; Huang, G. H. ; Yang, Z. F., Auteur . - 1221-1228 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 131, N°12 (Decembre 2005) . - 1221-1228 p. Mots-clés : Compaction  Grid  systems  Numerical  models  Diffusion  Fluid  flow  Contaminants  Tassement  Systèmes  de  grille  Modèles  numériques  Flux  de  fluide Index. décimale : 621.34 Résumé : In this study, a high-order compact (HOC) scheme for solving the convection-diffusion equation (CDE) under a nonuniform grid setting is developed. To eliminate the difficulty in dealing with convection terms through traditional numerical methods, an upwind function is provided to turn the steady CDE into its equivalent diffusion equation (DE). After obtaining the HOC scheme for this DE through an extension of the optimal difference method to a nonuniform grid, the corresponding HOC scheme for the steady CDE is derived through converse transformation. The Proposed scheme is of the upwind feature related to the convection diffusion phenomena, where the convective diffusion flux in the upstream has larger contributions than that in the downstream. Such a feature can help eliminate nonphysical oscillations that may often occur when dealing with convection terms through traditional numerical methods. Two examples have been presented to test performance of the proposed scheme. Under the same grid settings, the proposed scheme can produce more accurate results than the upwind difference, central difference, and perturbational schemes. The Proposed scheme is suitable for solving both convection and the diffusion dominated flow problems. In addition, it can be extended for solving unsteady CDE. It is also revealed that efforts in optimizing the grid configuration and allocation can help improve solution accuracy and efficiency. Consequently, with the proposed method, solution under nonuniform grid settings would be more accurate than those under uniform manipulations, given the same number of grid points. Dans cette étude, un arrangement (HOC) compact d'ordre élevé pour résoudre l'équation de convection-diffusion (CDE) sous un arrangement non-uniforme de grille est développé. Pour éliminer la difficulté en traitant des limites de convection par des méthodes numériques traditionnelles, une fonction à contre vent est fournie pour transformer le CDE régulier en son équation équivalente de diffusion (De). Après obtention de l'arrangement HOC pour ce De par une prolongation de la méthode optimale de différence à une grille non-uniforme, l'arrangement HOC correspondant pour le CDE régulier est dérivé par la transformation inverse. L'arrangement proposé est du dispositif à contre vent lié aux phénomènes de diffusion de convection, où le flux convecteur de diffusion dans l'ascendant a de plus grandes contributions que cela dans le descendant. Un tel dispositif peut aider à éliminer les oscillations nonphysical qui peuvent souvent se produire en traitant des limites de convection par des méthodes numériques traditionnelles. Deux exemples ont été présentés à l'exécution d'essai de l'arrangement proposé. Sous les mêmes arrangements de grille, l'arrangement proposé peut produire des résultats plus précis que la différence à contre vent, la différence centrale, et les arrangements de perturbational. L'arrangement proposé convient à résoudre la convection et les problèmes d'écoulement dominés par diffusion. En outre, il peut être prolongé pour CDE instable de solution. On l'indique également que les efforts en optimisant la configuration et l'attribution de grille peuvent aider à améliorer l'exactitude et l'efficacité de solution. En conséquence, avec la méthode proposée, la solution sous les arrangements non-uniformes de grille serait plus précise que ceux sous des manipulations uniformes, données le même nombre de points de grille. En ligne : wangtina@263.net, huangg@uregina.ca, zfyang@bnu.edu.cn

Lab and field investigations on localized corrosion of casing / C. Q. Ren in Materials and corrosion, Vol. 63 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 2 (Fevrier 2012) . - pp. 168–172 Titre : Lab and field investigations on localized corrosion of casing Type de document : texte imprimé Auteurs : C. Q. Ren, Auteur ; X. Wang, Auteur ; L. Liu, Auteur Année de publication : 2012 Article en page(s) : pp. 168–172 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Localized  corrosion;  microstructure;  steel Résumé : The corrosion of casing was investigated in the laboratory and oilfield by series methods of EIS, SEM, EDS, well logging, and field coupon test. Data reveal the middle vertical profile along the casing is greatly threatened by localized form rather than generalized corrosion. The pit initiates in the micro-pore of the corrosion scale on the surface of the steel. The development of pitting depends on the water type classified by geochemist. The calcium chloride water shows highest acceleration to pitting due to the two orders of magnitude higher concentration of chloride ion by comparing sodium sulfate and sodium bicarbonate water types. The element analysis and microstructure observation were used to further describe the pit propagation. It is proposed to get a better understanding of the corrosion damage of casing in the petroleum industry. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005713/abstract [article] Lab and field investigations on localized corrosion of casing [texte imprimé] / C. Q. Ren, Auteur ; X. Wang, Auteur ; L. Liu, Auteur . - 2012 . - pp. 168–172. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 2 (Fevrier 2012) . - pp. 168–172 Mots-clés : Localized  corrosion;  microstructure;  steel Résumé : The corrosion of casing was investigated in the laboratory and oilfield by series methods of EIS, SEM, EDS, well logging, and field coupon test. Data reveal the middle vertical profile along the casing is greatly threatened by localized form rather than generalized corrosion. The pit initiates in the micro-pore of the corrosion scale on the surface of the steel. The development of pitting depends on the water type classified by geochemist. The calcium chloride water shows highest acceleration to pitting due to the two orders of magnitude higher concentration of chloride ion by comparing sodium sulfate and sodium bicarbonate water types. The element analysis and microstructure observation were used to further describe the pit propagation. It is proposed to get a better understanding of the corrosion damage of casing in the petroleum industry. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005713/abstract

Mesh dependence and nonlocal regularization of one-dimensional strain softening plasticity / S. Wu in Journal of engineering mechanics, Vol. 136 N° 11 (Novembre 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 11 (Novembre 2010) . - pp.1354-1365 Titre : Mesh dependence and nonlocal regularization of one-dimensional strain softening plasticity Type de document : texte imprimé Auteurs : S. Wu, Auteur ; X. Wang, Auteur Année de publication : 2011 Article en page(s) : pp.1354-1365 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Strain  softening  Localization  Plasticity  Finite  element  method. Résumé : Finite-element analysis of strain localization based on classical theory of continuum mechanics suffers from pathological mesh dependence when strain softening models are used. For quasistatic problems, the mesh dependence is demonstrated through an analysis of the tangent stiffness matrix of a one-dimensional problem. To regularize the mesh dependence, a nonlocal strain softening model is proposed, which is based on the nonlocal plasticity theory and the representative line element. Both analytical and numerical solutions of strain localization with the proposed model are developed and compared with each other. The model is also applied in the numerical simulation of a direct tensile test of a concrete specimen in the existing literature, and reasonable agreement is achieved between numerical solutions and the experimental response. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i11/p1354_s1?isAuthorized=no [article] Mesh dependence and nonlocal regularization of one-dimensional strain softening plasticity [texte imprimé] / S. Wu, Auteur ; X. Wang, Auteur . - 2011 . - pp.1354-1365. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 11 (Novembre 2010) . - pp.1354-1365 Mots-clés : Strain  softening  Localization  Plasticity  Finite  element  method. Résumé : Finite-element analysis of strain localization based on classical theory of continuum mechanics suffers from pathological mesh dependence when strain softening models are used. For quasistatic problems, the mesh dependence is demonstrated through an analysis of the tangent stiffness matrix of a one-dimensional problem. To regularize the mesh dependence, a nonlocal strain softening model is proposed, which is based on the nonlocal plasticity theory and the representative line element. Both analytical and numerical solutions of strain localization with the proposed model are developed and compared with each other. The model is also applied in the numerical simulation of a direct tensile test of a concrete specimen in the existing literature, and reasonable agreement is achieved between numerical solutions and the experimental response. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v136/i11/p1354_s1?isAuthorized=no

Microwave - assisted preparation of bamboo charcoal - based iron - containing adsorbents for Cr(VI) removal / X.J. Wang in Chemical engineering journal, Vol. 174 N° 1 (Octobre 2011) 

Public ISBD [article]  in Chemical engineering journal > Vol. 174 N° 1 (Octobre 2011) . - pp. 326–332 Titre : Microwave - assisted preparation of bamboo charcoal - based iron - containing adsorbents for Cr(VI) removal Type de document : texte imprimé Auteurs : X.J. Wang, Auteur ; Y. Wang, Auteur ; X. Wang, Auteur Année de publication : 2012 Article en page(s) : pp. 326–332 Note générale : Génie chimique Langues : Anglais (eng) Mots-clés : Bamboo  charcoal  Adsorption  Heavy  metal  Drinking  water Résumé : Bamboo charcoal-based, iron-containing adsorbent (Fe–BC) was developed by using bamboo charcoal (BC) as a supporting medium for ferric iron that was impregnated by Fe2(SO4)3 and H2SO4 simultaneous treatment, followed by microwave heating. The low-cost composite was characterized and used as an adsorbent for Cr(VI) removal from water. The results showed that the BET specific surface area, total pore volume, and average mesoporous diameter of Fe–BC all decreased with iron impregnation. As an adsorbent, Fe–BC showed an excellent adsorption capability for Cr(VI), the adsorption process followed the Langmuir model, and the adsorption kinetic followed pseudo-second-order model. The adsorption of Cr(VI) onto Fe–BC was spontaneous and exothermic under the studied conditions. Column adsorption experiment with Fe–BC showed that Cr(VI) could be removed to below 0.05 mg/L within 360 bed volumes at empty bed contact time 2 min when the groundwater containing approximately 0.12 mg/L of Cr(VI) was treated. The spent Fe–BC adsorbent could be readily regenerated for reuse by dilute NaOH solution. ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science/article/pii/S1385894711011028 [article] Microwave - assisted preparation of bamboo charcoal - based iron - containing adsorbents for Cr(VI) removal [texte imprimé] / X.J. Wang, Auteur ; Y. Wang, Auteur ; X. Wang, Auteur . - 2012 . - pp. 326–332. Génie chimique Langues : Anglais (eng) in Chemical engineering journal > Vol. 174 N° 1 (Octobre 2011) . - pp. 326–332 Mots-clés : Bamboo  charcoal  Adsorption  Heavy  metal  Drinking  water Résumé : Bamboo charcoal-based, iron-containing adsorbent (Fe–BC) was developed by using bamboo charcoal (BC) as a supporting medium for ferric iron that was impregnated by Fe2(SO4)3 and H2SO4 simultaneous treatment, followed by microwave heating. The low-cost composite was characterized and used as an adsorbent for Cr(VI) removal from water. The results showed that the BET specific surface area, total pore volume, and average mesoporous diameter of Fe–BC all decreased with iron impregnation. As an adsorbent, Fe–BC showed an excellent adsorption capability for Cr(VI), the adsorption process followed the Langmuir model, and the adsorption kinetic followed pseudo-second-order model. The adsorption of Cr(VI) onto Fe–BC was spontaneous and exothermic under the studied conditions. Column adsorption experiment with Fe–BC showed that Cr(VI) could be removed to below 0.05 mg/L within 360 bed volumes at empty bed contact time 2 min when the groundwater containing approximately 0.12 mg/L of Cr(VI) was treated. The spent Fe–BC adsorbent could be readily regenerated for reuse by dilute NaOH solution. ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science/article/pii/S1385894711011028

Modular high-force seismic magneto-rheological fluid damper / F. Gordaninejad in Journal of structural engineering, Vol. 136 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Journal of structural engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 135-143 Titre : Modular high-force seismic magneto-rheological fluid damper Type de document : texte imprimé Auteurs : F. Gordaninejad, Auteur ; X. Wang, Auteur ; G. Hitchcock, Auteur Année de publication : 2011 Article en page(s) : pp. 135-143 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Damping  Seismic  effects  Rheology  Vibration  Structural  control Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In this work, a large-scale magneto-rheological fluid (MRF) bypass valve damper for seismic mitigation applications is designed, constructed, and tested. The damper utilizes a simple design, with a modular bypass MRF valve, connected to a passive commercial seismic damper. The modular feature of the new MRF valve provides the flexibility of adding as much force as needed to the damper with minimal modification to an existing passive viscous damper. The performance of the MRF valve and the combined semiactive bypass MRF damper are examined through quasi-static and dynamic tests. It is demonstrated that the proposed modular MRF bypass damper can provide a maximum damping force over 200 kN which meets the high-force requirements of a semiactive seismic damper for large-scale structure vibration control. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i2/p135_s1?isAuthorized=no [article] Modular high-force seismic magneto-rheological fluid damper [texte imprimé] / F. Gordaninejad, Auteur ; X. Wang, Auteur ; G. Hitchcock, Auteur . - 2011 . - pp. 135-143. Génie Civil Langues : Anglais (eng) in Journal of structural engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 135-143 Mots-clés : Damping  Seismic  effects  Rheology  Vibration  Structural  control Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In this work, a large-scale magneto-rheological fluid (MRF) bypass valve damper for seismic mitigation applications is designed, constructed, and tested. The damper utilizes a simple design, with a modular bypass MRF valve, connected to a passive commercial seismic damper. The modular feature of the new MRF valve provides the flexibility of adding as much force as needed to the damper with minimal modification to an existing passive viscous damper. The performance of the MRF valve and the combined semiactive bypass MRF damper are examined through quasi-static and dynamic tests. It is demonstrated that the proposed modular MRF bypass damper can provide a maximum damping force over 200 kN which meets the high-force requirements of a semiactive seismic damper for large-scale structure vibration control. DEWEY : 624.17 ISSN : 0733-9445 En ligne : http://ascelibrary.org/sto/resource/1/jsendh/v136/i2/p135_s1?isAuthorized=no

Scheduling a single machine with multiple job processing ability to minimize makespan / X. Wang in Journal of the operational research society (JORS), Vol. 62 N° 8 (Août 2011) 

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