Documents disponibles écrits par cet auteur

Application of centered differentiation and steepest descent to maximum power point tracking / Zhang, Weidong in IEEE transactions on industrial electronics, Vol. 54 N°5 (Octobre 2007) 

Public ISBD [article]  in IEEE transactions on industrial electronics > Vol. 54 N°5 (Octobre 2007) . - 2539-2549 p. Titre : Application of centered differentiation and steepest descent to maximum power point tracking Type de document : texte imprimé Auteurs : Zhang, Weidong, Auteur ; Dunford, William G., Auteur ; Palmer, Patrick R., Auteur Article en page(s) : 2539-2549 p. Note générale : Electronique Langues : Anglais (eng) Mots-clés : Control  systems  Digital  control  Maximum  power  point  tracking  (MPPT)  Photovoltaic  power  systems  Systèmes  de  contrôle  Commande  numérique  Cheminement  maximum  de  point  de  puissance  Systèmes  d'alimentation  photovoltaïques Index. décimale : 621 Ingénierie mécanique en général. Technologie nucléaire. Ingénierie électrique. Machinerie Résumé : This paper concentrates on two critical aspects to improve the performance of maximum power point tracking (MPPT). One improvement is to accurately locate the position of the maximum power point (MPP) by using the centered differentiation. Another effort is to reduce the oscillation around the MPP in steady state by controlling active perturbations. This paper also adopts the method of steepest descent for MPPT, which shows faster dynamic response and smoother steady state than the method of hill climbing. Comprehensive experimental evaluations have successfully illustrated the effectiveness of the proposed algorithm. Ce document se concentre sur deux aspects critiques pour améliorer l'exécution du cheminement maximum de point de puissance (MPPT). Une amélioration est de localiser exactement la position du point de puissance maximum (MPP) près d'employer la différentiation centrée. Un autre effort est de réduire l'oscillation autour du MPP dans équilibré en commandant des perturbations actives. Ce document adopte également la méthode de la descente la plus raide pour MPPT, qui montre une réponse dynamique plus rapide et équilibré plus lisse que la méthode de s'élever de colline. Les évaluations expérimentales complètes ont avec succès illustré l'efficacité de l'algorithme proposé. DEWEY : 621 ISSN : 0278-0046 RAMEAU : Commande numérique-- Alimentations (électricité) En ligne : http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?isnumber=4282101&arnumber=4285715 [...] [article] Application of centered differentiation and steepest descent to maximum power point tracking [texte imprimé] / Zhang, Weidong, Auteur ; Dunford, William G., Auteur ; Palmer, Patrick R., Auteur . - 2539-2549 p. Electronique Langues : Anglais (eng) in IEEE transactions on industrial electronics > Vol. 54 N°5 (Octobre 2007) . - 2539-2549 p. Mots-clés : Control  systems  Digital  control  Maximum  power  point  tracking  (MPPT)  Photovoltaic  power  systems  Systèmes  de  contrôle  Commande  numérique  Cheminement  maximum  de  point  de  puissance  Systèmes  d'alimentation  photovoltaïques Index. décimale : 621 Ingénierie mécanique en général. Technologie nucléaire. Ingénierie électrique. Machinerie Résumé : This paper concentrates on two critical aspects to improve the performance of maximum power point tracking (MPPT). One improvement is to accurately locate the position of the maximum power point (MPP) by using the centered differentiation. Another effort is to reduce the oscillation around the MPP in steady state by controlling active perturbations. This paper also adopts the method of steepest descent for MPPT, which shows faster dynamic response and smoother steady state than the method of hill climbing. Comprehensive experimental evaluations have successfully illustrated the effectiveness of the proposed algorithm. Ce document se concentre sur deux aspects critiques pour améliorer l'exécution du cheminement maximum de point de puissance (MPPT). Une amélioration est de localiser exactement la position du point de puissance maximum (MPP) près d'employer la différentiation centrée. Un autre effort est de réduire l'oscillation autour du MPP dans équilibré en commandant des perturbations actives. Ce document adopte également la méthode de la descente la plus raide pour MPPT, qui montre une réponse dynamique plus rapide et équilibré plus lisse que la méthode de s'élever de colline. Les évaluations expérimentales complètes ont avec succès illustré l'efficacité de l'algorithme proposé. DEWEY : 621 ISSN : 0278-0046 RAMEAU : Commande numérique-- Alimentations (électricité) En ligne : http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?isnumber=4282101&arnumber=4285715 [...]

Atomistic SPH and a link between diffusion and interfacial tension / Nitsche, Ludwig C. in Aiche journal, Vol. 48 N°2 (Fevrier 2002) 

Public ISBD [article]  in Aiche journal > Vol. 48 N°2 (Fevrier 2002) . - 201-211 p. Titre : Atomistic SPH and a link between diffusion and interfacial tension Type de document : texte imprimé Auteurs : Nitsche, Ludwig C., Auteur ; Zhang, Weidong, Auteur Article en page(s) : 201-211 p. Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : Maille  d'hydrodynamique  Particules  Densité  Nœuds  Concentration  Corps  dissous  Molécules  Agrégats  Vitesse  de  diffusion  Méthode  atomistique  Transfert  de  masse Index. décimale : 660 Résumé : The mesh-free method of smoothed particle hydrodynamics (SPH) is interpreted atomistically to treat the local density of nodes as representing solute concentration, instead of interpolating a concentration field between function values at the nodes. We exploit the conceptual simplicity of tracking little packets (representing supermolecular aggregates) of solute, as in Brownian dynamics simulations, but replace the stochastic generation of diffusive spreading over statistically independent realizations with a purely deterministic summation for extracting the local diffusion velocity using only the instantaneous locations of nearby nodes. Four test problems demonstrate the versatility and accuracy of the atomistic SPH method (ASPH) for mass transfer. Finally, by comparing ASPH with a new Stokeslet-swarm technique for simulating drop flows (Nitsche and Schaflinger, 2001), a fundamental analogy between diffusion and interfacial tension is exposed. La méthode libre de maille d'hydrodynamique douce de particules (SPH) est interprétée atomistiquement pour traiter la densité locale des nœuds en tant que représentation de la concentration en corps dissous, au lieu d'interpoler un champ de concentration entre les valeurs de fonction aux nœuds. Nous exploitons la simplicité conceptuelle de dépister de petits paquets (représentant les agrégats moléculaires superbes) de corps dissous, comme dans des simulations browniennes de dynamique, mais remplaçons la génération stochastique de diffusif répartissant statistiquement des réalisations indépendantes avec une addition purement déterministe pour extraire la vitesse de diffusion locale en utilisant seulement les endroits instantanés des nœuds voisins. Quatre problèmes d'essai démontrent la polyvalence et l'exactitude de la méthode atomistique de SPH (ASPH) pour le transfert de masse. En conclusion, en comparant ASPH à une nouvelle technique d'essais de Stokeslet pour simuler la baisse coule (Nitsche et Schaflinger, 2001), une analogie fondamentale entre la diffusion et la tension dièdre est exposé. DEWEY : 660.627.3 ISSN : 0001-1541 RAMEAU : Diffusivité thermique En ligne : http://www3.interscience.wiley.com/journal/107061889/home?CRETRY=1&SRETRY=0 [article] Atomistic SPH and a link between diffusion and interfacial tension [texte imprimé] / Nitsche, Ludwig C., Auteur ; Zhang, Weidong, Auteur . - 201-211 p. Génie Chimique Langues : Anglais (eng) in Aiche journal > Vol. 48 N°2 (Fevrier 2002) . - 201-211 p. Mots-clés : Maille  d'hydrodynamique  Particules  Densité  Nœuds  Concentration  Corps  dissous  Molécules  Agrégats  Vitesse  de  diffusion  Méthode  atomistique  Transfert  de  masse Index. décimale : 660 Résumé : The mesh-free method of smoothed particle hydrodynamics (SPH) is interpreted atomistically to treat the local density of nodes as representing solute concentration, instead of interpolating a concentration field between function values at the nodes. We exploit the conceptual simplicity of tracking little packets (representing supermolecular aggregates) of solute, as in Brownian dynamics simulations, but replace the stochastic generation of diffusive spreading over statistically independent realizations with a purely deterministic summation for extracting the local diffusion velocity using only the instantaneous locations of nearby nodes. Four test problems demonstrate the versatility and accuracy of the atomistic SPH method (ASPH) for mass transfer. Finally, by comparing ASPH with a new Stokeslet-swarm technique for simulating drop flows (Nitsche and Schaflinger, 2001), a fundamental analogy between diffusion and interfacial tension is exposed. La méthode libre de maille d'hydrodynamique douce de particules (SPH) est interprétée atomistiquement pour traiter la densité locale des nœuds en tant que représentation de la concentration en corps dissous, au lieu d'interpoler un champ de concentration entre les valeurs de fonction aux nœuds. Nous exploitons la simplicité conceptuelle de dépister de petits paquets (représentant les agrégats moléculaires superbes) de corps dissous, comme dans des simulations browniennes de dynamique, mais remplaçons la génération stochastique de diffusif répartissant statistiquement des réalisations indépendantes avec une addition purement déterministe pour extraire la vitesse de diffusion locale en utilisant seulement les endroits instantanés des nœuds voisins. Quatre problèmes d'essai démontrent la polyvalence et l'exactitude de la méthode atomistique de SPH (ASPH) pour le transfert de masse. En conclusion, en comparant ASPH à une nouvelle technique d'essais de Stokeslet pour simuler la baisse coule (Nitsche et Schaflinger, 2001), une analogie fondamentale entre la diffusion et la tension dièdre est exposé. DEWEY : 660.627.3 ISSN : 0001-1541 RAMEAU : Diffusivité thermique En ligne : http://www3.interscience.wiley.com/journal/107061889/home?CRETRY=1&SRETRY=0

Experimental study of mass transfer in membrane absorption process using membranes with different porosities / Zhang, Weidong in Industrial & engineering chemistry research, Vol. 49 N° 14 (Juillet 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 14 (Juillet 2010) . - pp. 6641–6648 Titre : Experimental study of mass transfer in membrane absorption process using membranes with different porosities Type de document : texte imprimé Auteurs : Zhang, Weidong, Auteur ; Li Jiang, Auteur ; Geng Chen, Auteur Année de publication : 2010 Article en page(s) : pp. 6641–6648 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Mass  transfer  Membrane  absorption Résumé : Experimental study has been carried out to investigate the mass transfer behavior when carbon dioxide (CO2) is absorbed through microporous membranes with different porosities. Deionized water and sodium hydroxide (NaOH) aqueous solutions are chosen as absorbents. The effects of membrane porosity, absorbent pH value, and liquid velocity on mass transfer are studied. The effect of membrane porosity on mass transfer depends on both the absorbent pH value and liquid velocity. In the case of low pH values (7−11) in absorbent, membrane porosity almost has no effect on mass transfer at relatively lower liquid velocity, namely, the mass transfer coefficients based on the whole membrane area remain almost the same at different membrane porosities; the effect of membrane porosity on mass transfer becomes obvious with the increasing liquid velocity. Contrarily, as the absorbent pH value increases to 12 or 13, the influence of porosity on mass transfer coefficient becomes significant at varied liquid velocity. The modified mass transfer correlations are obtained with consideration of the effect of porosity over a varying membrane porosity range. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1001026 [article] Experimental study of mass transfer in membrane absorption process using membranes with different porosities [texte imprimé] / Zhang, Weidong, Auteur ; Li Jiang, Auteur ; Geng Chen, Auteur . - 2010 . - pp. 6641–6648. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 14 (Juillet 2010) . - pp. 6641–6648 Mots-clés : Mass  transfer  Membrane  absorption Résumé : Experimental study has been carried out to investigate the mass transfer behavior when carbon dioxide (CO2) is absorbed through microporous membranes with different porosities. Deionized water and sodium hydroxide (NaOH) aqueous solutions are chosen as absorbents. The effects of membrane porosity, absorbent pH value, and liquid velocity on mass transfer are studied. The effect of membrane porosity on mass transfer depends on both the absorbent pH value and liquid velocity. In the case of low pH values (7−11) in absorbent, membrane porosity almost has no effect on mass transfer at relatively lower liquid velocity, namely, the mass transfer coefficients based on the whole membrane area remain almost the same at different membrane porosities; the effect of membrane porosity on mass transfer becomes obvious with the increasing liquid velocity. Contrarily, as the absorbent pH value increases to 12 or 13, the influence of porosity on mass transfer coefficient becomes significant at varied liquid velocity. The modified mass transfer correlations are obtained with consideration of the effect of porosity over a varying membrane porosity range. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie1001026

Intensification of mass transfer in hollow fiber modules by adding solid particles / Zhang, Weidong in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8655–8662 Titre : Intensification of mass transfer in hollow fiber modules by adding solid particles Type de document : texte imprimé Auteurs : Zhang, Weidong, Auteur ; Geng Chen, Auteur ; Jiang Li, Auteur Année de publication : 2010 Article en page(s) : pp. 8655–8662 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hollow  fiber  contactor  Absorption  performance  Shell  side  absorbent  Ultrasound Résumé : A method of improving the absorption performance in hollow fiber contactor by adding a third solid phase into the shell side absorbent is proposed. Powdered kieselgur, graphite, and BaSO4 are chosen as the additives to intensify the absorption process of the CO2/NaOH(aq) system. Ultrasound is used in this work as an approach to make the solid particles suspend in the liquid absorbent. The mass-transfer rate is enhanced about 40% by adding solid particles into the absorbent liquid in the presence of ultrasound. As for different types of particles, the smaller the density difference between the absorbent and the solid, the higher enhancement factor obtained. The enhancement factor is a function of the solids loading as well as the liquid velocity in the shell side of the module. The mass-transfer coefficient and enhancement factor remain almost the same with increasing pH from 7 to 11; as pH further increases, both the mass-transfer coefficient and the enhancement factor are increasing dramatically. The results also indicate that the enhancement factors increase with an increase of the packing density. The residence time distribution (RTD) curves are measured to observe the flow status in the shell side; the results demonstrate that addition of solid particles can improve the flow conditions in the shell side. A mathematical model for the intensification process based on surface renewal theory is developed; the calculated results have a good agreement with the experimental results under the present experimental conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004964 [article] Intensification of mass transfer in hollow fiber modules by adding solid particles [texte imprimé] / Zhang, Weidong, Auteur ; Geng Chen, Auteur ; Jiang Li, Auteur . - 2010 . - pp. 8655–8662. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8655–8662 Mots-clés : Hollow  fiber  contactor  Absorption  performance  Shell  side  absorbent  Ultrasound Résumé : A method of improving the absorption performance in hollow fiber contactor by adding a third solid phase into the shell side absorbent is proposed. Powdered kieselgur, graphite, and BaSO4 are chosen as the additives to intensify the absorption process of the CO2/NaOH(aq) system. Ultrasound is used in this work as an approach to make the solid particles suspend in the liquid absorbent. The mass-transfer rate is enhanced about 40% by adding solid particles into the absorbent liquid in the presence of ultrasound. As for different types of particles, the smaller the density difference between the absorbent and the solid, the higher enhancement factor obtained. The enhancement factor is a function of the solids loading as well as the liquid velocity in the shell side of the module. The mass-transfer coefficient and enhancement factor remain almost the same with increasing pH from 7 to 11; as pH further increases, both the mass-transfer coefficient and the enhancement factor are increasing dramatically. The results also indicate that the enhancement factors increase with an increase of the packing density. The residence time distribution (RTD) curves are measured to observe the flow status in the shell side; the results demonstrate that addition of solid particles can improve the flow conditions in the shell side. A mathematical model for the intensification process based on surface renewal theory is developed; the calculated results have a good agreement with the experimental results under the present experimental conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004964

Intensification of mass transfer in hollow fiber modules by adding solid particles / Zhang, Weidong in Industrial & engineering chemistry research, Vol. 48 N° 18 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8655–8662 Titre : Intensification of mass transfer in hollow fiber modules by adding solid particles Type de document : texte imprimé Auteurs : Zhang, Weidong, Auteur ; Geng Chen, Auteur ; Jiang Li, Auteur Année de publication : 2010 Article en page(s) : pp. 8655–8662 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Hollow  fiber  contactor  Absorption  performance  Shell  side  absorbent  Ultrasound Résumé : A method of improving the absorption performance in hollow fiber contactor by adding a third solid phase into the shell side absorbent is proposed. Powdered kieselgur, graphite, and BaSO4 are chosen as the additives to intensify the absorption process of the CO2/NaOH(aq) system. Ultrasound is used in this work as an approach to make the solid particles suspend in the liquid absorbent. The mass-transfer rate is enhanced about 40% by adding solid particles into the absorbent liquid in the presence of ultrasound. As for different types of particles, the smaller the density difference between the absorbent and the solid, the higher enhancement factor obtained. The enhancement factor is a function of the solids loading as well as the liquid velocity in the shell side of the module. The mass-transfer coefficient and enhancement factor remain almost the same with increasing pH from 7 to 11; as pH further increases, both the mass-transfer coefficient and the enhancement factor are increasing dramatically. The results also indicate that the enhancement factors increase with an increase of the packing density. The residence time distribution (RTD) curves are measured to observe the flow status in the shell side; the results demonstrate that addition of solid particles can improve the flow conditions in the shell side. A mathematical model for the intensification process based on surface renewal theory is developed; the calculated results have a good agreement with the experimental results under the present experimental conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004964 [article] Intensification of mass transfer in hollow fiber modules by adding solid particles [texte imprimé] / Zhang, Weidong, Auteur ; Geng Chen, Auteur ; Jiang Li, Auteur . - 2010 . - pp. 8655–8662. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 18 (Septembre 2009) . - pp. 8655–8662 Mots-clés : Hollow  fiber  contactor  Absorption  performance  Shell  side  absorbent  Ultrasound Résumé : A method of improving the absorption performance in hollow fiber contactor by adding a third solid phase into the shell side absorbent is proposed. Powdered kieselgur, graphite, and BaSO4 are chosen as the additives to intensify the absorption process of the CO2/NaOH(aq) system. Ultrasound is used in this work as an approach to make the solid particles suspend in the liquid absorbent. The mass-transfer rate is enhanced about 40% by adding solid particles into the absorbent liquid in the presence of ultrasound. As for different types of particles, the smaller the density difference between the absorbent and the solid, the higher enhancement factor obtained. The enhancement factor is a function of the solids loading as well as the liquid velocity in the shell side of the module. The mass-transfer coefficient and enhancement factor remain almost the same with increasing pH from 7 to 11; as pH further increases, both the mass-transfer coefficient and the enhancement factor are increasing dramatically. The results also indicate that the enhancement factors increase with an increase of the packing density. The residence time distribution (RTD) curves are measured to observe the flow status in the shell side; the results demonstrate that addition of solid particles can improve the flow conditions in the shell side. A mathematical model for the intensification process based on surface renewal theory is developed; the calculated results have a good agreement with the experimental results under the present experimental conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9004964

Modeling of effect of pH on mass transfer of copper(II) extraction by hollow fiber renewal liquid membrane / Zhongqi Ren in Industrial & engineering chemistry research, Vol. 47 n°12 (Juin 2008) 

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The separation and concentration of Cr(VI) from acidic dilute solution using hollow fiber renewal liquid membrane / Junteng Liu in Industrial & engineering chemistry research, Vol. 48 N° 9 (Mai 2009) 

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