Documents disponibles écrits par cet auteur

Axisymmetric deformation of a pressurized thin elastic membrane with nonuniform thickness / Xi Chen in Journal of engineering mechanics, Vol. 133 N°10 (Octobre 2007) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 133 N°10 (Octobre 2007) . - pp. 1146-1150 Titre : Axisymmetric deformation of a pressurized thin elastic membrane with nonuniform thickness Type de document : texte imprimé Auteurs : Xi Chen, Auteur Année de publication : 2007 Article en page(s) : pp. 1146-1150 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Axisymmetry  DeformationElasticity  Membranes  Pressures  Thickness. Résumé : Many circular elastic membranes used in practice involve nonuniform thickness, which is a main source of error that affects the functionality of the membrane. An analytical framework is developed in this paper to solve the deflection profile of a pressurized circular membrane with nonuniform thickness. The nonlinear solution is established within the deformed configuration. The results are compared with finite-element simulation with good agreement. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?160821 [article] Axisymmetric deformation of a pressurized thin elastic membrane with nonuniform thickness [texte imprimé] / Xi Chen, Auteur . - 2007 . - pp. 1146-1150. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 133 N°10 (Octobre 2007) . - pp. 1146-1150 Mots-clés : Axisymmetry  DeformationElasticity  Membranes  Pressures  Thickness. Résumé : Many circular elastic membranes used in practice involve nonuniform thickness, which is a main source of error that affects the functionality of the membrane. An analytical framework is developed in this paper to solve the deflection profile of a pressurized circular membrane with nonuniform thickness. The nonlinear solution is established within the deformed configuration. The results are compared with finite-element simulation with good agreement. ISSN : 0733-9399 En ligne : http://cedb.asce.org/cgi/WWWdisplay.cgi?160821

Effects of Aquifer Anisotropy on the Migration of Infiltrated Stream Water to a Pumping Well / Chen, Xunhong in Journal of hydrologic engineering, Vol. 8, N° 5 (Septembre /Octobre 2003) 

Public ISBD [article]  in Journal of hydrologic engineering > Vol. 8, N° 5 (Septembre /Octobre 2003) . - 287-293 p. Titre : Effects of Aquifer Anisotropy on the Migration of Infiltrated Stream Water to a Pumping Well Titre original : Effets de l'Anisotropie de Couche Aquifère sur la Migration de l'Eau de Ruisseau Infiltrée à un Puits de Pompage Type de document : texte imprimé Auteurs : Chen, Xunhong, Auteur ; Xi Chen, Auteur Article en page(s) : 287-293 p. Note générale : Hydrologie Langues : Anglais (eng) Mots-clés : Aquifers  Wells  Pumps  Streams  Water  infiltration  Couches  aquifères  Puits  Pompes  Jets  Infiltration  de  l'eau Index. décimale : 551.4 Résumé : Pumping of groundwater near a stream can induce infiltration of stream water into the surrounding aquifers. Analysis of the migrationof the infiltrated stream water to the pumping well is important to better understand stream-aquifer interactions. The Paper analyzes the effects of aquifer anisotropy on the migration process of infiltrated stream water to a partially penetrating well. MODFLOW were plotted over a cross section to show the hydraulic connectivity between the well and the stream for various levels of aquifer anisotropy. Travel times, infiltration rates, and fractions of pumped river water were determined to characterize the migration process. Generally, the movement of the infiltrated stream water is slow; the water can take several months to arrive at a well located a short distance from a stream. Results suggest that the rate of produced stream water at the well is higher for the anisotropy Kh/Kz+10 and 20 (petit h et z)(ratio of horizontal to vertical hydraulic conductivity) than for Kh/Kz <10, or >20. On the other hand, when Kh/Kz is between 20 and 100, the first water particle that gets to the pumping well needs a shorter travel time than that for other Kh/Kz values. A gaining stream can significantly reduce the rate of stream infiltration and produced stream water. Areal recharge provides an additional source to the well, thus reducing the rate of stream infiltration as well as the rate of produced stream water. Le pompage des eaux souterraines près d'un jet peut induire l'infiltration de l'eau de ruisseau dans les couches aquifères environnantes. L'analyse du migrationof l'eau de ruisseau infiltrée au puits de pompage est importante pour comprendre mieux des interactions de jet-couche aquifère. Le papier analyse les effets de l'anisotropie de couche aquifère sur le procédé de migration de l'eau de ruisseau infiltrée à un puits partiellement pénétrant. MODFLOW ont été tracés au-dessus d'une coupe pour montrer la connectivité hydraulique entre le puits et le jet pour différents niveaux de l'anisotropie de couche aquifère. Des temps de voyage, les vitesses d'infiltration, et les fractions de l'eau de rivière pompée ont été déterminés pour caractériser le procédé de migration. Généralement, le mouvement de l'eau de ruisseau infiltrée est lent ; l'eau peut prendre plusieurs mois pour arriver à un puits a localisé une distance courte d'un jet. Les résultats suggèrent que le taux de l'eau de ruisseau produite au puits soit plus haut pour l'anisotropie Kh/Kz+10 et 20 (petit h et z)(ratio d'horizontal à la conductivité hydraulique verticale) que pour Kh/Kz 20. D'autre part, quand Kh/Kz est entre 20 et 100, la première particule de l'eau qui obtient au puits de pompage a besoin de plus peu de temps de voyage que cela pour d'autres valeurs de Kh/Kz. Un jet gagnant peut de manière significative réduire le taux d'infiltration de jet et d'eau de ruisseau produite. La recharge régionale fournit une source additionnelle au bien, de ce fait réduisant le taux d'infiltration de jet aussi bien que le taux de l'eau de ruisseau produite. En ligne : xchen2@unl.edu [article] Effects of Aquifer Anisotropy on the Migration of Infiltrated Stream Water to a Pumping Well = Effets de l'Anisotropie de Couche Aquifère sur la Migration de l'Eau de Ruisseau Infiltrée à un Puits de Pompage [texte imprimé] / Chen, Xunhong, Auteur ; Xi Chen, Auteur . - 287-293 p. Hydrologie Langues : Anglais (eng) in Journal of hydrologic engineering > Vol. 8, N° 5 (Septembre /Octobre 2003) . - 287-293 p. Mots-clés : Aquifers  Wells  Pumps  Streams  Water  infiltration  Couches  aquifères  Puits  Pompes  Jets  Infiltration  de  l'eau Index. décimale : 551.4 Résumé : Pumping of groundwater near a stream can induce infiltration of stream water into the surrounding aquifers. Analysis of the migrationof the infiltrated stream water to the pumping well is important to better understand stream-aquifer interactions. The Paper analyzes the effects of aquifer anisotropy on the migration process of infiltrated stream water to a partially penetrating well. MODFLOW were plotted over a cross section to show the hydraulic connectivity between the well and the stream for various levels of aquifer anisotropy. Travel times, infiltration rates, and fractions of pumped river water were determined to characterize the migration process. Generally, the movement of the infiltrated stream water is slow; the water can take several months to arrive at a well located a short distance from a stream. Results suggest that the rate of produced stream water at the well is higher for the anisotropy Kh/Kz+10 and 20 (petit h et z)(ratio of horizontal to vertical hydraulic conductivity) than for Kh/Kz <10, or >20. On the other hand, when Kh/Kz is between 20 and 100, the first water particle that gets to the pumping well needs a shorter travel time than that for other Kh/Kz values. A gaining stream can significantly reduce the rate of stream infiltration and produced stream water. Areal recharge provides an additional source to the well, thus reducing the rate of stream infiltration as well as the rate of produced stream water. Le pompage des eaux souterraines près d'un jet peut induire l'infiltration de l'eau de ruisseau dans les couches aquifères environnantes. L'analyse du migrationof l'eau de ruisseau infiltrée au puits de pompage est importante pour comprendre mieux des interactions de jet-couche aquifère. Le papier analyse les effets de l'anisotropie de couche aquifère sur le procédé de migration de l'eau de ruisseau infiltrée à un puits partiellement pénétrant. MODFLOW ont été tracés au-dessus d'une coupe pour montrer la connectivité hydraulique entre le puits et le jet pour différents niveaux de l'anisotropie de couche aquifère. Des temps de voyage, les vitesses d'infiltration, et les fractions de l'eau de rivière pompée ont été déterminés pour caractériser le procédé de migration. Généralement, le mouvement de l'eau de ruisseau infiltrée est lent ; l'eau peut prendre plusieurs mois pour arriver à un puits a localisé une distance courte d'un jet. Les résultats suggèrent que le taux de l'eau de ruisseau produite au puits soit plus haut pour l'anisotropie Kh/Kz+10 et 20 (petit h et z)(ratio d'horizontal à la conductivité hydraulique verticale) que pour Kh/Kz 20. D'autre part, quand Kh/Kz est entre 20 et 100, la première particule de l'eau qui obtient au puits de pompage a besoin de plus peu de temps de voyage que cela pour d'autres valeurs de Kh/Kz. Un jet gagnant peut de manière significative réduire le taux d'infiltration de jet et d'eau de ruisseau produite. La recharge régionale fournit une source additionnelle au bien, de ce fait réduisant le taux d'infiltration de jet aussi bien que le taux de l'eau de ruisseau produite. En ligne : xchen2@unl.edu

Nanomechanics modeling and simulation of carbon nanotubes / Xi Chen in Journal of engineering mechanics, Vol. 134 N°3 (Mars 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N°3 (Mars 2008) . - pp.211–216. Titre : Nanomechanics modeling and simulation of carbon nanotubes Type de document : texte imprimé Auteurs : Xi Chen, Auteur ; Yonggang Huang, Auteur Année de publication : 2008 Article en page(s) : pp.211–216. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Simulation  Models  Mechanical  properties Résumé : nanoelectronic and nanomechanical devices. Recent advances of modeling and simulation at the nanoscale have led to a better understanding of the mechanical behaviors of carbon nanotubes. The modeling efforts incorporate atomic features into the continuum or structural mechanics theories, and the numerical simulations feature quantum mechanical approach and classical molecular dynamics. Multiscale and multiphysics modeling and simulation tools have also been developed to effectively bridge the different lengths and time scales, and to link basic scientific research with engineering application. The general approaches of the theoretical and numerical nanomechanics of CNTs are briefly reviewed. This paper is not intended to be a comprehensive review, but to introduce readers (especially those with traditional civil engineering or engineering mechanics backgrounds) to the new, interdisciplinary, or emerging fields in engineering mechanics, in this case the rapidly growing frontier of nanomechanics through the example of carbon nanotubes. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=211&volume=134&issue=3&journalCo [...] [article] Nanomechanics modeling and simulation of carbon nanotubes [texte imprimé] / Xi Chen, Auteur ; Yonggang Huang, Auteur . - 2008 . - pp.211–216. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°3 (Mars 2008) . - pp.211–216. Mots-clés : Simulation  Models  Mechanical  properties Résumé : nanoelectronic and nanomechanical devices. Recent advances of modeling and simulation at the nanoscale have led to a better understanding of the mechanical behaviors of carbon nanotubes. The modeling efforts incorporate atomic features into the continuum or structural mechanics theories, and the numerical simulations feature quantum mechanical approach and classical molecular dynamics. Multiscale and multiphysics modeling and simulation tools have also been developed to effectively bridge the different lengths and time scales, and to link basic scientific research with engineering application. The general approaches of the theoretical and numerical nanomechanics of CNTs are briefly reviewed. This paper is not intended to be a comprehensive review, but to introduce readers (especially those with traditional civil engineering or engineering mechanics backgrounds) to the new, interdisciplinary, or emerging fields in engineering mechanics, in this case the rapidly growing frontier of nanomechanics through the example of carbon nanotubes. ISSN : 0733-9399 En ligne : http://ascelibrary.org/action/showAbstract?page=211&volume=134&issue=3&journalCo [...]

Object-oriented disjunctive programming with a nested heuristic and gradient-based solver for chemical process synthesis / Tian, Daqing in Industrial & engineering chemistry research, Vol. 49 N° 4 (Fevrier 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 4 (Fevrier 2010) . - pp 1779–1791 Titre : Object-oriented disjunctive programming with a nested heuristic and gradient-based solver for chemical process synthesis Type de document : texte imprimé Auteurs : Tian, Daqing, Auteur ; Zhu, Lingyu, Auteur ; Xi Chen, Auteur Année de publication : 2010 Article en page(s) : pp 1779–1791 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Disjunctive  programming  Chemical  process  synthesis. Résumé : The generalized disjunctive programming (GDP) model has been proposed and applied in the past decade as an alternative to the mixed integer nonlinear programming (MINLP) model because it has the advantages of being straightforward when used in conditional modeling and being able to reduce the complexity in the sub-NLP. In this paper, we introduced an improved variant of the traditional GDP model, otherwise known as the object-oriented disjunctive programming (ODP) model. Such a method helps generate well-posed sub-NLP, thereby improving the solving process. A nested method combining the heuristic algorithm and gradient-based optimizer is also proposed to solve the GDP and ODP. It is a two-layer method, wherein a heuristic algorithm performs master iterations in the outer-loop when dealing with the Boolean variables, and a gradient-based NLP solver is applied in the inner-loop when dealing with the sub-NLP. Excellent performance has been demonstrated by applying the modeling and solving methods into the process synthesis of heat exchanger networks (HENs) and water networks (WNs). DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901010a [article] Object-oriented disjunctive programming with a nested heuristic and gradient-based solver for chemical process synthesis [texte imprimé] / Tian, Daqing, Auteur ; Zhu, Lingyu, Auteur ; Xi Chen, Auteur . - 2010 . - pp 1779–1791. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 4 (Fevrier 2010) . - pp 1779–1791 Mots-clés : Disjunctive  programming  Chemical  process  synthesis. Résumé : The generalized disjunctive programming (GDP) model has been proposed and applied in the past decade as an alternative to the mixed integer nonlinear programming (MINLP) model because it has the advantages of being straightforward when used in conditional modeling and being able to reduce the complexity in the sub-NLP. In this paper, we introduced an improved variant of the traditional GDP model, otherwise known as the object-oriented disjunctive programming (ODP) model. Such a method helps generate well-posed sub-NLP, thereby improving the solving process. A nested method combining the heuristic algorithm and gradient-based optimizer is also proposed to solve the GDP and ODP. It is a two-layer method, wherein a heuristic algorithm performs master iterations in the outer-loop when dealing with the Boolean variables, and a gradient-based NLP solver is applied in the inner-loop when dealing with the sub-NLP. Excellent performance has been demonstrated by applying the modeling and solving methods into the process synthesis of heat exchanger networks (HENs) and water networks (WNs). DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901010a

Spherical indentation on an elastic coating/substrate system / Mills, James A. in Journal of engineering mechanics, Vol. 135 N° 10 (Octobre 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 10 (Octobre 2009) . - pp. 1189-1197 Titre : Spherical indentation on an elastic coating/substrate system : determining substrate modulus Type de document : texte imprimé Auteurs : Mills, James A., Auteur ; Xi Chen, Auteur Année de publication : 2009 Article en page(s) : pp. 1189-1197 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Elasticity  Substrates  Coating  Sensitivity  analysis  Errors. Résumé : A vast amount of indentation studies on coating/substrate systems focused on extracting the mechanical properties of the film, by either avoiding or subtracting off the substrate effect. However, in engineering and biomedical applications, very often the substrate properties, in particular the substrate modulus, need to be measured from an indentation test and the protective layer cannot be removed. For the model system of an elastic film deposited on an elastic substrate, we establish the general approach of spherical indentation focusing on the substrate property determination. Indentation data are taken from different indentation depths which reflect different degrees of film and substrate effects. An effective reverse analysis algorithm is established such that, from an indentation test if either the film modulus or film thickness is known, the other variable can be measured along with the substrate modulus. Error sensitivity of the proposed formulation is analyzed in a systematic way. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Spherical indentation on an elastic coating/substrate system : determining substrate modulus [texte imprimé] / Mills, James A., Auteur ; Xi Chen, Auteur . - 2009 . - pp. 1189-1197. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 10 (Octobre 2009) . - pp. 1189-1197 Mots-clés : Elasticity  Substrates  Coating  Sensitivity  analysis  Errors. Résumé : A vast amount of indentation studies on coating/substrate systems focused on extracting the mechanical properties of the film, by either avoiding or subtracting off the substrate effect. However, in engineering and biomedical applications, very often the substrate properties, in particular the substrate modulus, need to be measured from an indentation test and the protective layer cannot be removed. For the model system of an elastic film deposited on an elastic substrate, we establish the general approach of spherical indentation focusing on the substrate property determination. Indentation data are taken from different indentation depths which reflect different degrees of film and substrate effects. An effective reverse analysis algorithm is established such that, from an indentation test if either the film modulus or film thickness is known, the other variable can be measured along with the substrate modulus. Error sensitivity of the proposed formulation is analyzed in a systematic way. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

Toward polymer product design. I. dynamic optimization of average molecular weights and polydispersity index in batch free radical polymerization / Xi Chen in Industrial & engineering chemistry research, Vol. 48 N° 14 (Juillet 2009) 

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A two-stage method for identification of dual-rate systems with fast input and very slow output / Shengyong Mo in Industrial & engineering chemistry research, Vol. 48 N°4 (Février 2009) 

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