Documents disponibles écrits par cet auteur

Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete / C. Lee in Cement and concrete research, Vol. 40 N° 5 (Mai 2010) 

Public ISBD [article]  in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 810–819 Titre : Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete Type de document : texte imprimé Auteurs : C. Lee, Auteur ; H. Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 810–819 Note générale : Bibliogr. Langues : Anglais (eng) Mots-clés : Modeling  ;  Concrete  ;  Fiber  Reinforcement  ;  Orientation  Factor Résumé : Considering the probabilistic distributions of fibers in ring-type steel fiber reinforced concrete, the orientation factor and the number of ring-type steel fibers crossing the failure plane were theoretically derived as a function of fiber geometry, specimen dimensions, and fiber volume fraction. A total number of 24 specimens were tested incorporating different fiber types, specimen geometry, and fiber volume fractions of 0.2% and 0.4%: 5 beams and 5 panels containing straight steel fibers; and 6 beams and 8 panels containing ring-type steel fibers. Measurements were made to assess the number of fibers at fractured surfaces of steel fiber reinforced concrete. The developed theoretical expressions reasonably predicted the orientation factor and the number of ring-type steel fibers at failure plane: the average and the standard deviation for the ratios of the test to theory were 1.03 and 0.26, respectively. Theoretical investigations and comparisons were made for the values of orientation factor and the number of fibers at failure plane for straight steel fibers and ring-type steel fibers. En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900341X [article] Orientation factor and number of fibers at failure plane in ring-type steel fiber reinforced concrete [texte imprimé] / C. Lee, Auteur ; H. Kim, Auteur . - 2012 . - pp. 810–819. Bibliogr. Langues : Anglais (eng) in Cement and concrete research > Vol. 40 N° 5 (Mai 2010) . - pp. 810–819 Mots-clés : Modeling  ;  Concrete  ;  Fiber  Reinforcement  ;  Orientation  Factor Résumé : Considering the probabilistic distributions of fibers in ring-type steel fiber reinforced concrete, the orientation factor and the number of ring-type steel fibers crossing the failure plane were theoretically derived as a function of fiber geometry, specimen dimensions, and fiber volume fraction. A total number of 24 specimens were tested incorporating different fiber types, specimen geometry, and fiber volume fractions of 0.2% and 0.4%: 5 beams and 5 panels containing straight steel fibers; and 6 beams and 8 panels containing ring-type steel fibers. Measurements were made to assess the number of fibers at fractured surfaces of steel fiber reinforced concrete. The developed theoretical expressions reasonably predicted the orientation factor and the number of ring-type steel fibers at failure plane: the average and the standard deviation for the ratios of the test to theory were 1.03 and 0.26, respectively. Theoretical investigations and comparisons were made for the values of orientation factor and the number of fibers at failure plane for straight steel fibers and ring-type steel fibers. En ligne : http://www.sciencedirect.com/science/article/pii/S000888460900341X

Robust vehicle routing problem with deadlines and travel time/demand uncertainty / C. Lee in Journal of the operational research society (JORS), Vol. 63 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of the operational research society (JORS) > Vol. 63 N° 9 (Septembre 2012) . - pp. 1294–1306 Titre : Robust vehicle routing problem with deadlines and travel time/demand uncertainty Type de document : texte imprimé Auteurs : C. Lee, Auteur ; K. Lee, Auteur ; S. Park, Auteur Année de publication : 2012 Article en page(s) : pp. 1294–1306 Note générale : Operational research Langues : Anglais (eng) Mots-clés : Vehicle  routing  Robust  optimization  Column  generation Index. décimale : 001.424 Résumé : In this article, we investigate the vehicle routing problem with deadlines, whose goal is to satisfy the requirements of a given number of customers with minimum travel distances while respecting both of the deadlines of the customers and vehicle capacity. It is assumed that the travel time between any two customers and the demands of the customer are uncertain. Two types of uncertainty sets with adjustable parameters are considered for the possible realizations of travel time and demand. The robustness of a solution against the uncertain data can be achieved by making the solution feasible for any travel time and demand defined in the uncertainty sets. We propose a Dantzig-Wolfe decomposition approach, which enables the uncertainty of the data to be encapsulated in the column generation subproblem. A dynamic programming algorithm is proposed to solve the subproblem with data uncertainty. The results of computational experiments involving two well-known test problems show that the robustness of the solution can be greatly improved. Note de contenu : In an earlier version of this article S Park's affiliation was wrongly given as ETRI. The correct affiliation, KAIST, is shown in this final version of the article. DEWEY : 001.424 ISSN : 0160-5682 En ligne : http://www.palgrave-journals.com/jors/journal/v63/n9/abs/jors2011136a.html [article] Robust vehicle routing problem with deadlines and travel time/demand uncertainty [texte imprimé] / C. Lee, Auteur ; K. Lee, Auteur ; S. Park, Auteur . - 2012 . - pp. 1294–1306. Operational research Langues : Anglais (eng) in Journal of the operational research society (JORS) > Vol. 63 N° 9 (Septembre 2012) . - pp. 1294–1306 Mots-clés : Vehicle  routing  Robust  optimization  Column  generation Index. décimale : 001.424 Résumé : In this article, we investigate the vehicle routing problem with deadlines, whose goal is to satisfy the requirements of a given number of customers with minimum travel distances while respecting both of the deadlines of the customers and vehicle capacity. It is assumed that the travel time between any two customers and the demands of the customer are uncertain. Two types of uncertainty sets with adjustable parameters are considered for the possible realizations of travel time and demand. The robustness of a solution against the uncertain data can be achieved by making the solution feasible for any travel time and demand defined in the uncertainty sets. We propose a Dantzig-Wolfe decomposition approach, which enables the uncertainty of the data to be encapsulated in the column generation subproblem. A dynamic programming algorithm is proposed to solve the subproblem with data uncertainty. The results of computational experiments involving two well-known test problems show that the robustness of the solution can be greatly improved. Note de contenu : In an earlier version of this article S Park's affiliation was wrongly given as ETRI. The correct affiliation, KAIST, is shown in this final version of the article. DEWEY : 001.424 ISSN : 0160-5682 En ligne : http://www.palgrave-journals.com/jors/journal/v63/n9/abs/jors2011136a.html

Small strain stiffness of salt-cemented granular media under low confinement / Q. H. Truong in Géotechnique, Vol. 62 N° 10 (Octobre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 10 (Octobre 2012) . - pp. 949 –953 Titre : Small strain stiffness of salt-cemented granular media under low confinement Type de document : texte imprimé Auteurs : Q. H. Truong, Auteur ; C. Lee, Auteur ; Y. U. Kim, Auteur Année de publication : 2012 Article en page(s) : pp. 949 –953 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : FFabric/structure  of  soils  Laboratory  tests  Stiffness  Waves  and  wave  loading Résumé : The mechanical behaviour of granular soils is affected by particle bonding including natural cementation. This study addresses a simple model of small strain stiffness and salt concentration based on the wave measurements of salt-cemented particulate media. Glass beads with a median diameter of D 50 = 0·5 mm are prepared in rectangular cells using the water-pluviated method in salt water with different concentrations. Piezo disc elements and bender elements embedded in the cell are used for the measurements of the compressional and shear waves. The relationships between the elastic wave velocities and salt concentration show an exponential function. The measured small strain stiffness matches well the predicted small strain stiffness based on the micromechanics of simple cubic monosized spherical particles. This study demonstrates that the salt concentration in a salt-cemented specimen can be evaluated by using elastic wave velocities. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.T.004 [article] Small strain stiffness of salt-cemented granular media under low confinement [texte imprimé] / Q. H. Truong, Auteur ; C. Lee, Auteur ; Y. U. Kim, Auteur . - 2012 . - pp. 949 –953. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 10 (Octobre 2012) . - pp. 949 –953 Mots-clés : FFabric/structure  of  soils  Laboratory  tests  Stiffness  Waves  and  wave  loading Résumé : The mechanical behaviour of granular soils is affected by particle bonding including natural cementation. This study addresses a simple model of small strain stiffness and salt concentration based on the wave measurements of salt-cemented particulate media. Glass beads with a median diameter of D 50 = 0·5 mm are prepared in rectangular cells using the water-pluviated method in salt water with different concentrations. Piezo disc elements and bender elements embedded in the cell are used for the measurements of the compressional and shear waves. The relationships between the elastic wave velocities and salt concentration show an exponential function. The measured small strain stiffness matches well the predicted small strain stiffness based on the micromechanics of simple cubic monosized spherical particles. This study demonstrates that the salt concentration in a salt-cemented specimen can be evaluated by using elastic wave velocities. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.T.004