Documents disponibles écrits par cet auteur

Effects of drawing on the tensile fracture strength and its reliability of small-sized metallic glasses / Wu, Y. in Acta materialia, Vol. 58 N° 7 (Avril 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2564–2576 Titre : Effects of drawing on the tensile fracture strength and its reliability of small-sized metallic glasses Type de document : texte imprimé Auteurs : Wu, Y., Auteur ; H.H. Wu, Auteur ; X.D. Hui, Auteur Année de publication : 2011 Article en page(s) : pp. 2564–2576 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Metallic  glasses  Drawing  Tension  test  Strength  reliability Résumé : The effects of drawing on the structure and mechanical properties of a Co-based metallic glass under tension were thoroughly investigated. Surface changes induced by drawing, including removal of surface flaws, surface chemical homogenization and generation of compressive residual stress tend to increase the fracture strength, whilst open volumes created during drawing, particularly nano-voids, are likely to soften the wires. Initially, the surface changes are decisive factors, but as drawing proceeds, the open volumes gradually become dominant, yielding a maximum fracture strength in the wires with an area reduction ratio of 22%. Moreover, it was found that the fracture strength reliability was enhanced by the drawing, which is due not only to the surface perfection but also to the increase of plastic deformation capability, manifested by the decrease in the activation energy of individual shear transformation zones. Our results imply that the drawing technique could be a promising approach to continuously producing small-sized glassy wires with improved overall properties. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900901X [article] Effects of drawing on the tensile fracture strength and its reliability of small-sized metallic glasses [texte imprimé] / Wu, Y., Auteur ; H.H. Wu, Auteur ; X.D. Hui, Auteur . - 2011 . - pp. 2564–2576. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 7 (Avril 2010) . - pp. 2564–2576 Mots-clés : Metallic  glasses  Drawing  Tension  test  Strength  reliability Résumé : The effects of drawing on the structure and mechanical properties of a Co-based metallic glass under tension were thoroughly investigated. Surface changes induced by drawing, including removal of surface flaws, surface chemical homogenization and generation of compressive residual stress tend to increase the fracture strength, whilst open volumes created during drawing, particularly nano-voids, are likely to soften the wires. Initially, the surface changes are decisive factors, but as drawing proceeds, the open volumes gradually become dominant, yielding a maximum fracture strength in the wires with an area reduction ratio of 22%. Moreover, it was found that the fracture strength reliability was enhanced by the drawing, which is due not only to the surface perfection but also to the increase of plastic deformation capability, manifested by the decrease in the activation energy of individual shear transformation zones. Our results imply that the drawing technique could be a promising approach to continuously producing small-sized glassy wires with improved overall properties. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900901X

Modelling of containerized air cargo forwarding problems under uncertainty / Wu, Y. in Journal of the operational research society (JORS), Vol. 62 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of the operational research society (JORS) > Vol. 62 N° 7 (Juillet 2011) . - pp. 1211–1226 Titre : Modelling of containerized air cargo forwarding problems under uncertainty Type de document : texte imprimé Auteurs : Wu, Y., Auteur Année de publication : 2011 Article en page(s) : pp. 1211–1226 Note générale : Recherche opérationnelle Langues : Anglais (eng) Mots-clés : Air  container  Cargo  forwarding  Containerization  Globalization  Robust  optimization  Stochastic  programming Index. décimale : 001.424 Résumé : This paper examines air container renting and cargo loading problems experienced by freight forwarding companies. Containers have to be booked in advance, in order to obtain discounted rental rates from airlines; renting or returning containers on the day of shipping will incur a heavy penalty. We first propose a mixed-integer model for the certain problem, in which shipment information is known with certainty, when booking. We then present a two-stage recourse model to handle the uncertainty problem, in which accurate shipment information cannot be obtained when booking, and all cargoes have to be shipped without delay. The first-stage decision is made at the booking stage, to book specific numbers of different types of containers. The second-stage decision is made on the day of shipping, depending on the extent to which the uncertainty has been realized. The decisions include number of additional containers of different types that are required to be rented, or the number of containers to be returned, under the scenario that might occur on the day of shipping. We then extend the recourse model into a robust model for dealing with the situation in which cargoes are allowed to be shipped later. The robust model provides a quantitative method to measure the trade-off between risk and cost. A series of experiments demonstrate the effectiveness of the robust model in dealing with risk and uncertainty. DEWEY : 001.424 ISSN : 0160-5682 En ligne : http://www.palgrave-journals.com/jors/journal/v62/n7/abs/jors201084a.html [article] Modelling of containerized air cargo forwarding problems under uncertainty [texte imprimé] / Wu, Y., Auteur . - 2011 . - pp. 1211–1226. Recherche opérationnelle Langues : Anglais (eng) in Journal of the operational research society (JORS) > Vol. 62 N° 7 (Juillet 2011) . - pp. 1211–1226 Mots-clés : Air  container  Cargo  forwarding  Containerization  Globalization  Robust  optimization  Stochastic  programming Index. décimale : 001.424 Résumé : This paper examines air container renting and cargo loading problems experienced by freight forwarding companies. Containers have to be booked in advance, in order to obtain discounted rental rates from airlines; renting or returning containers on the day of shipping will incur a heavy penalty. We first propose a mixed-integer model for the certain problem, in which shipment information is known with certainty, when booking. We then present a two-stage recourse model to handle the uncertainty problem, in which accurate shipment information cannot be obtained when booking, and all cargoes have to be shipped without delay. The first-stage decision is made at the booking stage, to book specific numbers of different types of containers. The second-stage decision is made on the day of shipping, depending on the extent to which the uncertainty has been realized. The decisions include number of additional containers of different types that are required to be rented, or the number of containers to be returned, under the scenario that might occur on the day of shipping. We then extend the recourse model into a robust model for dealing with the situation in which cargoes are allowed to be shipped later. The robust model provides a quantitative method to measure the trade-off between risk and cost. A series of experiments demonstrate the effectiveness of the robust model in dealing with risk and uncertainty. DEWEY : 001.424 ISSN : 0160-5682 En ligne : http://www.palgrave-journals.com/jors/journal/v62/n7/abs/jors201084a.html