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An experimental and theoretical study of the influence of surfactant on the preparation and stability of ammonia-water nanofluids / Liu Yang in International journal of refrigeration, Vol. 34 N° 8 (Décembre 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1741–1748 Titre : An experimental and theoretical study of the influence of surfactant on the preparation and stability of ammonia-water nanofluids Titre original : Etude expérimentale et théorique sur l'influence d'agents tensio-actifs sur la préparation et la stabilité des nano-fluides à ammoniac / eau Type de document : texte imprimé Auteurs : Liu Yang, Auteur ; Kai Du, Auteur ; Xiaofeng Niu, Auteur Année de publication : 2012 Article en page(s) : pp. 1741–1748 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Absorption  Particle  Stability  Ammonia-water  Refrigerant Résumé : Two types of nanofluids are obtained by adding the mixture of carbon black nanoparticles with emulsifier OP-10, and Al2O3 nanoparticles with sodium dodecyl benzene sulfonate (SDBS) in the ammonia-water solution, respectively. The dispersion stability of the prepared nanofluids in different mass fractions of surfactants is investigated by the light absorbency ratio index methods. The results show that with the increase of mass fraction of surfactant, the stability of carbon black nanofluid is improved firstly and then is exacerbated, while the stability of Al2O3 nanofluid is exacerbated firstly, then is improved, and then is exacerbated again. The influences of surfactant on the stability of ammonia-water nanofluids abide by the monolayer adsorption theory or electric double layer adsorption theory. Finally, the theoretical surfactant mass fractions required in the preparation of ammonia-water nanofluids are calculated by simplifying the dispersion models and the results are in accordance with experimental results. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001526 [article] An experimental and theoretical study of the influence of surfactant on the preparation and stability of ammonia-water nanofluids = Etude expérimentale et théorique sur l'influence d'agents tensio-actifs sur la préparation et la stabilité des nano-fluides à ammoniac / eau [texte imprimé] / Liu Yang, Auteur ; Kai Du, Auteur ; Xiaofeng Niu, Auteur . - 2012 . - pp. 1741–1748. Génie mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 8 (Décembre 2011) . - pp. 1741–1748 Mots-clés : Absorption  Particle  Stability  Ammonia-water  Refrigerant Résumé : Two types of nanofluids are obtained by adding the mixture of carbon black nanoparticles with emulsifier OP-10, and Al2O3 nanoparticles with sodium dodecyl benzene sulfonate (SDBS) in the ammonia-water solution, respectively. The dispersion stability of the prepared nanofluids in different mass fractions of surfactants is investigated by the light absorbency ratio index methods. The results show that with the increase of mass fraction of surfactant, the stability of carbon black nanofluid is improved firstly and then is exacerbated, while the stability of Al2O3 nanofluid is exacerbated firstly, then is improved, and then is exacerbated again. The influences of surfactant on the stability of ammonia-water nanofluids abide by the monolayer adsorption theory or electric double layer adsorption theory. Finally, the theoretical surfactant mass fractions required in the preparation of ammonia-water nanofluids are calculated by simplifying the dispersion models and the results are in accordance with experimental results. ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700711001526

Experimental study on enhancement of ammonia–water falling film absorption by adding nano-particles / Liu Yang in International journal of refrigeration, Vol. 34 N° 3 (Mai 2011) 

Public ISBD [article]  in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 640-647 Titre : Experimental study on enhancement of ammonia–water falling film absorption by adding nano-particles Titre original : Etude expérimentale sur l'amélioration de l'absorption d'un film tombant utilisant une solution d'ammoniac/eau à l'aide de l'ajout de nanoparticules Type de document : texte imprimé Auteurs : Liu Yang, Auteur ; Kai Du, Auteur ; Xiao Feng Niu, Auteur Année de publication : 2011 Article en page(s) : pp. 640-647 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Ammonia–water  Falling  film  Absorption  Mass  transfer  Heat  transfer Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Based on the preparation of Al2O3, Fe2O3 and ZnFe2O4 nanofluid, the comparative experiments on the falling film absorption between ammonia–water and ammonia–water with various kinds of nano-particles are carried out. Experimental results show that the sorts and mass fraction of nano-particles, the viscosity and stability of nanofluid, as well as the mass fraction of ammonia in the basefluid are considered as the key parameters. The absorption of ammonia is weakened by only adding surfactants or adding poorly dispersed nano-particles. The increase of mass fraction of nano-particles with matched surfactants can improve the absorption rate of ammonia under the condition that the viscosity of nanofluid does not increase remarkably, and there is an optimal mass fraction for each kind of nano-particles and surfactant. With the increase in ammonia mass fraction of initial nanofluid, the absorption potential capacity decline, but the enhancing effect induced by the nanofluid is more obvious compared to that without nano-particles. The effective absorption ratio can be increased by 70% and 50% with Fe2O3 and ZnFe2O4 nanofluid respectively when the initial ammonia mass fraction is 15%. The absorption enhancement by the nanofluid is attributable to the heat transfer enhancement and the decrease in viscosity of nanofluid, which are strongly proved by the temperature differences in cooling water and nanofluids as well as the falling film flowing time. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002926 [article] Experimental study on enhancement of ammonia–water falling film absorption by adding nano-particles = Etude expérimentale sur l'amélioration de l'absorption d'un film tombant utilisant une solution d'ammoniac/eau à l'aide de l'ajout de nanoparticules [texte imprimé] / Liu Yang, Auteur ; Kai Du, Auteur ; Xiao Feng Niu, Auteur . - 2011 . - pp. 640-647. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 34 N° 3 (Mai 2011) . - pp. 640-647 Mots-clés : Ammonia–water  Falling  film  Absorption  Mass  transfer  Heat  transfer Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Based on the preparation of Al2O3, Fe2O3 and ZnFe2O4 nanofluid, the comparative experiments on the falling film absorption between ammonia–water and ammonia–water with various kinds of nano-particles are carried out. Experimental results show that the sorts and mass fraction of nano-particles, the viscosity and stability of nanofluid, as well as the mass fraction of ammonia in the basefluid are considered as the key parameters. The absorption of ammonia is weakened by only adding surfactants or adding poorly dispersed nano-particles. The increase of mass fraction of nano-particles with matched surfactants can improve the absorption rate of ammonia under the condition that the viscosity of nanofluid does not increase remarkably, and there is an optimal mass fraction for each kind of nano-particles and surfactant. With the increase in ammonia mass fraction of initial nanofluid, the absorption potential capacity decline, but the enhancing effect induced by the nanofluid is more obvious compared to that without nano-particles. The effective absorption ratio can be increased by 70% and 50% with Fe2O3 and ZnFe2O4 nanofluid respectively when the initial ammonia mass fraction is 15%. The absorption enhancement by the nanofluid is attributable to the heat transfer enhancement and the decrease in viscosity of nanofluid, which are strongly proved by the temperature differences in cooling water and nanofluids as well as the falling film flowing time. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S0140700710002926

Semiglobal stabilization for nonholonomic mobile robots based on dynamic feedback with inputs saturation / Hua Chen in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 134 N° 4 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 4 (Juillet 2012) . - 08 p. Titre : Semiglobal stabilization for nonholonomic mobile robots based on dynamic feedback with inputs saturation Type de document : texte imprimé Auteurs : Hua Chen, Auteur ; Chaoli Wang, Auteur ; Liu Yang, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Dynamic systems Langues : Anglais (eng) Mots-clés : Nanholonomic  mobile  robots  Dynamic  feedback  Semiglobal  stabilization  Inputs  saturation Index. décimale : 629.8 Résumé : This paper investigates the semiglobal stabilization problem for nonholonomic mobile robots based on dynamic feedback with inputs saturation. A bounded, continuous, time-varying controller is presented such that the closed-loop system is semiglobally asymptotically stable. The systematic strategy combines finite-time control technique with the virtual-controller-tracked method, which is similar to the back-stepping procedure. First, the bound-constrained smooth controller is presented for the kinematic model. Second, the dynamic feedback controller is designed to make the generalized velocity converge to the prespecified kinematic (virtual) controller in a finite time. Furthermore, the rigorous proof is given for the stability analysis of the closed-loop system. In the mean time, the position and torque inputs of robots are proved to be bounded at any time. Finally, the simulation results show the effectiveness of the proposed control approach. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000134000004 [...] [article] Semiglobal stabilization for nonholonomic mobile robots based on dynamic feedback with inputs saturation [texte imprimé] / Hua Chen, Auteur ; Chaoli Wang, Auteur ; Liu Yang, Auteur . - 2012 . - 08 p. Dynamic systems Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 134 N° 4 (Juillet 2012) . - 08 p. Mots-clés : Nanholonomic  mobile  robots  Dynamic  feedback  Semiglobal  stabilization  Inputs  saturation Index. décimale : 629.8 Résumé : This paper investigates the semiglobal stabilization problem for nonholonomic mobile robots based on dynamic feedback with inputs saturation. A bounded, continuous, time-varying controller is presented such that the closed-loop system is semiglobally asymptotically stable. The systematic strategy combines finite-time control technique with the virtual-controller-tracked method, which is similar to the back-stepping procedure. First, the bound-constrained smooth controller is presented for the kinematic model. Second, the dynamic feedback controller is designed to make the generalized velocity converge to the prespecified kinematic (virtual) controller in a finite time. Furthermore, the rigorous proof is given for the stability analysis of the closed-loop system. In the mean time, the position and torque inputs of robots are proved to be bounded at any time. Finally, the simulation results show the effectiveness of the proposed control approach. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JDSMAA000134000004 [...]