Documents disponibles écrits par cet auteur

Capillary force and water retention between two uneven-sized particles / Jeremy Lechman in Journal of engineering mechanics, Vol. 134 N°5 (Mai 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N°5 (Mai 2008) . - pp.374–384. Titre : Capillary force and water retention between two uneven-sized particles Type de document : texte imprimé Auteurs : Jeremy Lechman, Auteur ; Ning Lu, Auteur Année de publication : 2008 Article en page(s) : pp.374–384. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Absorption  Interfacial  tension  Unsaturated  soils  Granular  materials  Tensile  stress  Theory  Particles Résumé : Capillary force and water retention between two uneven-sized spherical particles are investigated. Previous studies have been limited to systems with even-sized particles. The appropriate definition of the boundary value problem for a water lens between two uneven-sized particles is presented under the consideration of thermodynamic free energy at the microscopic level. Capillary force and water retention under the consideration of toroidal approximation are also derived for a system with two uneven-sized particles. Comparison of normalized capillary force and water retention calculated by the free energy approach and toroidal approximation are conducted. The quantitative analysis shows that for a system with two identical particles, the behavior of water retention and normalized capillary force is very similar to some recent studies by others, confirming that the toroidal approximation provides reasonably good estimations for both capillary force and water retention. For a system with uneven-sized particles, it is shown that error in normalized capillary force could be significant as the matric suction approaches zero and the particle sizes become very different. The errors for the mean curvature of the meniscus for the toroidal approximation are significant where the matric suction is near zero. Thus for soils with varying particle sizes, it may be necessary to employ the exact solution to meniscus shape in order to accurately quantify normalized capillary force and water retention. The induced normalized capillary force increases inversely with the particle size, and is generally insensitive to the water content. For soil assembly with particle size of 0.01mm , the normalized capillary force could reach 10kPa , whereas for soil assembly with particle size of 1mm , the normalized capillary force is on the order of 100Pa . ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A5%2837 [...] [article] Capillary force and water retention between two uneven-sized particles [texte imprimé] / Jeremy Lechman, Auteur ; Ning Lu, Auteur . - 2008 . - pp.374–384. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°5 (Mai 2008) . - pp.374–384. Mots-clés : Absorption  Interfacial  tension  Unsaturated  soils  Granular  materials  Tensile  stress  Theory  Particles Résumé : Capillary force and water retention between two uneven-sized spherical particles are investigated. Previous studies have been limited to systems with even-sized particles. The appropriate definition of the boundary value problem for a water lens between two uneven-sized particles is presented under the consideration of thermodynamic free energy at the microscopic level. Capillary force and water retention under the consideration of toroidal approximation are also derived for a system with two uneven-sized particles. Comparison of normalized capillary force and water retention calculated by the free energy approach and toroidal approximation are conducted. The quantitative analysis shows that for a system with two identical particles, the behavior of water retention and normalized capillary force is very similar to some recent studies by others, confirming that the toroidal approximation provides reasonably good estimations for both capillary force and water retention. For a system with uneven-sized particles, it is shown that error in normalized capillary force could be significant as the matric suction approaches zero and the particle sizes become very different. The errors for the mean curvature of the meniscus for the toroidal approximation are significant where the matric suction is near zero. Thus for soils with varying particle sizes, it may be necessary to employ the exact solution to meniscus shape in order to accurately quantify normalized capillary force and water retention. The induced normalized capillary force increases inversely with the particle size, and is generally insensitive to the water content. For soil assembly with particle size of 0.01mm , the normalized capillary force could reach 10kPa , whereas for soil assembly with particle size of 1mm , the normalized capillary force is on the order of 100Pa . ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A5%2837 [...]

Comparison of soil thickness in a zero-order basin in the oregon coast range using a soil probe and electrical resistivity tomography / Michael S. Morse in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1470–1482 Titre : Comparison of soil thickness in a zero-order basin in the oregon coast range using a soil probe and electrical resistivity tomography Type de document : texte imprimé Auteurs : Michael S. Morse, Auteur ; Ning Lu, Auteur ; Jonathan W. Godt, Auteur Année de publication : 2013 Article en page(s) : pp. 1470–1482 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Direct  current  resistivity  Soil  thickness  Slope  stability  Unsaturated  soils  Site  characterization Résumé : Accurate estimation of the soil thickness distribution in steepland drainage basins is essential for understanding ecosystem and subsurface response to infiltration. One important aspect of this characterization is assessing the heavy and antecedent rainfall conditions that lead to shallow landsliding. In this paper, we investigate the direct current (DC) resistivity method as a tool for quickly estimating soil thickness over a steep (33–40°) zero-order basin in the Oregon Coast Range, a landslide prone region. Point measurements throughout the basin showed bedrock depths between 0.55 and 3.2 m. Resistivity of soil and bedrock samples collected from the site was measured for degrees of saturation between 40 and 92%. Resistivity of the soil was typically higher than that of the bedrock for degrees of saturation lower than 70%. Results from the laboratory measurements and point-depth measurements were used in a numerical model to evaluate the resistivity contrast at the soil-bedrock interface. A decreasing-with-depth resistivity contrast was apparent at the interface in the modeling results. At the field site, three transects were surveyed where coincident ground truth measurements of bedrock depth were available, to test the accuracy of the method. The same decreasing-with-depth resistivity trend that was apparent in the model was also present in the survey data. The resistivity contour of between 1,000 and 2,000 Ωm that marked the top of the contrast was our interpreted bedrock depth in the survey data. Kriged depth-to-bedrock maps were created from both the field-measured ground truth obtained with a soil probe and interpreted depths from the resistivity tomography, and these were compared for accuracy graphically. Depths were interpolated as far as 16.5 m laterally from the resistivity survey lines with root mean squared error (RMSE) = 27 cm between the measured and interpreted depth at those locations. Using several transects and analysis of the subsurface material properties, the direct current (DC) resistivity method is shown to be able to delineate bedrock depth trends within the drainage basin. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000717 [article] Comparison of soil thickness in a zero-order basin in the oregon coast range using a soil probe and electrical resistivity tomography [texte imprimé] / Michael S. Morse, Auteur ; Ning Lu, Auteur ; Jonathan W. Godt, Auteur . - 2013 . - pp. 1470–1482. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 12 (Décembre 2012) . - pp. 1470–1482 Mots-clés : Direct  current  resistivity  Soil  thickness  Slope  stability  Unsaturated  soils  Site  characterization Résumé : Accurate estimation of the soil thickness distribution in steepland drainage basins is essential for understanding ecosystem and subsurface response to infiltration. One important aspect of this characterization is assessing the heavy and antecedent rainfall conditions that lead to shallow landsliding. In this paper, we investigate the direct current (DC) resistivity method as a tool for quickly estimating soil thickness over a steep (33–40°) zero-order basin in the Oregon Coast Range, a landslide prone region. Point measurements throughout the basin showed bedrock depths between 0.55 and 3.2 m. Resistivity of soil and bedrock samples collected from the site was measured for degrees of saturation between 40 and 92%. Resistivity of the soil was typically higher than that of the bedrock for degrees of saturation lower than 70%. Results from the laboratory measurements and point-depth measurements were used in a numerical model to evaluate the resistivity contrast at the soil-bedrock interface. A decreasing-with-depth resistivity contrast was apparent at the interface in the modeling results. At the field site, three transects were surveyed where coincident ground truth measurements of bedrock depth were available, to test the accuracy of the method. The same decreasing-with-depth resistivity trend that was apparent in the model was also present in the survey data. The resistivity contour of between 1,000 and 2,000 Ωm that marked the top of the contrast was our interpreted bedrock depth in the survey data. Kriged depth-to-bedrock maps were created from both the field-measured ground truth obtained with a soil probe and interpreted depths from the resistivity tomography, and these were compared for accuracy graphically. Depths were interpolated as far as 16.5 m laterally from the resistivity survey lines with root mean squared error (RMSE) = 27 cm between the measured and interpreted depth at those locations. Using several transects and analysis of the subsurface material properties, the direct current (DC) resistivity method is shown to be able to delineate bedrock depth trends within the drainage basin. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000717

Experimental verification of capillary force and water retention between uneven-sized spheres / Ning Lu in Journal of engineering mechanics, Vol. 134 N°5 (Mai 2008) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 134 N°5 (Mai 2008) . - pp.385–395. Titre : Experimental verification of capillary force and water retention between uneven-sized spheres Type de document : texte imprimé Auteurs : Ning Lu, Auteur ; Jeremy Lechman, Auteur ; Kelly T. Miller, Auteur Année de publication : 2008 Article en page(s) : pp.385–395. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Absorption  Interfacial  tension  Unsaturated  soils  Granular  materials  Tensile  stress  Experimentation  Verification Résumé : The recently established theoretical results of the solid-water characteristic curve (SWCC) and capillary force characteristic curve (CFCC) are experimentally verified for mechanical and hydrologic interaction between uneven-sized spherical particles under partially saturated conditions. It is shown that the theoretical framework, based on the minimization of the free energy of the liquid meniscus between the two uneven-sized particles, can predict both water retention and capillary force accurately for spherical particles ranging in radius from 165to252μm . The experimental technique is novel and the results at such scale are valuable for the understanding of gas-solid-liquid interaction among granular media, since there is very limited experimental data available in the literature. The comparisons between the theoretical and experimental predictions of the SWCC and CFCC indicate that the agreements are generally very good, confirming the validity of the theory. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A5%2838 [...] [article] Experimental verification of capillary force and water retention between uneven-sized spheres [texte imprimé] / Ning Lu, Auteur ; Jeremy Lechman, Auteur ; Kelly T. Miller, Auteur . - 2008 . - pp.385–395. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 N°5 (Mai 2008) . - pp.385–395. Mots-clés : Absorption  Interfacial  tension  Unsaturated  soils  Granular  materials  Tensile  stress  Experimentation  Verification Résumé : The recently established theoretical results of the solid-water characteristic curve (SWCC) and capillary force characteristic curve (CFCC) are experimentally verified for mechanical and hydrologic interaction between uneven-sized spherical particles under partially saturated conditions. It is shown that the theoretical framework, based on the minimization of the free energy of the liquid meniscus between the two uneven-sized particles, can predict both water retention and capillary force accurately for spherical particles ranging in radius from 165to252μm . The experimental technique is novel and the results at such scale are valuable for the understanding of gas-solid-liquid interaction among granular media, since there is very limited experimental data available in the literature. The comparisons between the theoretical and experimental predictions of the SWCC and CFCC indicate that the agreements are generally very good, confirming the validity of the theory. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A5%2838 [...]

Fault diagnosis based on signed digraph combined with dynamic kernel PLS and SVR / Ning Lu in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9447–9456 Titre : Fault diagnosis based on signed digraph combined with dynamic kernel PLS and SVR Type de document : texte imprimé Auteurs : Ning Lu, Auteur ; Xiong Wang, Auteur Année de publication : 2009 Article en page(s) : p. 9447–9456 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Signed  digraph  Dynamic  kernel  PLS  and  SVR Résumé : The signed digraph (SDG) method for fault diagnosis, which is one of the model-based methods, has been widely applied in the chemical industry in recent years. However, how to elicit appropriate thresholds for SDG is a very difficult problem. This study presents a new hybrid method combining SDG with dynamic kernel partial least-squares (DKPLS) and support vector regression (SVR) for fault diagnosis. Using the relationships of each variable in SDG, a series of DKPLS-SVR models are built to estimate the values of the measured variables in process. The difference between the estimation and the measured value can determine the qualitative status of the variable, and then the fault can be diagnosed by SDG reasoning. Therefore, the threshold of each measured variable does not need to be decided in advance. The method can also overcome the limited availability of using the KPLS method alone in identifying the root cause. To verify the performance of the proposed method, its application is illustrated on the Tennessee Eastman (TE) challenge process. Through case studies, the proposed method demonstrates a good diagnosis capability compared with previous hybrid methods. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8009457 [article] Fault diagnosis based on signed digraph combined with dynamic kernel PLS and SVR [texte imprimé] / Ning Lu, Auteur ; Xiong Wang, Auteur . - 2009 . - p. 9447–9456. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9447–9456 Mots-clés : Signed  digraph  Dynamic  kernel  PLS  and  SVR Résumé : The signed digraph (SDG) method for fault diagnosis, which is one of the model-based methods, has been widely applied in the chemical industry in recent years. However, how to elicit appropriate thresholds for SDG is a very difficult problem. This study presents a new hybrid method combining SDG with dynamic kernel partial least-squares (DKPLS) and support vector regression (SVR) for fault diagnosis. Using the relationships of each variable in SDG, a series of DKPLS-SVR models are built to estimate the values of the measured variables in process. The difference between the estimation and the measured value can determine the qualitative status of the variable, and then the fault can be diagnosed by SDG reasoning. Therefore, the threshold of each measured variable does not need to be decided in advance. The method can also overcome the limited availability of using the KPLS method alone in identifying the root cause. To verify the performance of the proposed method, its application is illustrated on the Tennessee Eastman (TE) challenge process. Through case studies, the proposed method demonstrates a good diagnosis capability compared with previous hybrid methods. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8009457

Hysteresis of Capillary Stress in Unsaturated Granular Soil / Likos, William J. in Journal of engineering mechanics, Vol. 130 N°6 (Juin 2004) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 130 N°6 (Juin 2004) . - 646-655 p. Titre : Hysteresis of Capillary Stress in Unsaturated Granular Soil Titre original : Hystérésis de l'Effort Capillaire dans le Sol Granulaire Insaturé Type de document : texte imprimé Auteurs : Likos, William J., Auteur ; Ning Lu, Auteur ; Manzari, Madjid T., Editeur scientifique Article en page(s) : 646-655 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Unsaturated  soils  Granular  materials  Constitutive  relation  Dewatering  Hysteresis  Water  content  Sol  insaturé  Matériaux  granulaires  Relation  constitutive  Asséchage  Hystérésis  Teneur  en  eau Index. décimale : 621.34/624 Résumé : Constitutive relationships among water content, matric suction, and capillary stress in unsaturated granular soils are modeled using a theoretical approach based on the changing geometry of interparticle pore water menisci. A series of equations is developed to describe the net force among particles attributable to the combined effects of negative pore water pressure and surface tension for spherical grains arranged in simple-cubic or tetrahedral packing order. The contact angle at the liquid–solid interface is considered as a variable to evaluate hysteretic behavior in the soil–water characteristic curve, the effective stress parameter χ, and capillary stress. Varying the contact angle from 0 to 40° to simulate drying and wetting processes, respectively, is shown to have an appreciable impact on hysteresis in the constitutive behavior of the modeled soils. A boundary between regimes of positive and negative pore water pressure is identified as a function of water content and contact angle. Results from the analysis are of practical importance in understanding the behavior of unsaturated soils undergoing natural wetting and drying processes, such as infiltration, drainage, and evaporation. Des Rapports constitutifs parmi la teneur en eau, l'aspiration matricielle, et l'effort capillaire dans les sols granulaires insaturés sont modelés en utilisant une approche théorique basée sur la géométrie changeante du menisci d'eau interstitielle d'interparticle. Une série d'équations est développée pour décrire la force nette parmi des particules attribuables aux effets combinés de la pression négative d'eau interstitielle et de la tension superficielle pour les grains sphériques disposés dans l'ordre cubique ou tétraédrique simple d'emballage. L'angle de contact à l'interface pleine liquide est considéré comme comme variable évaluer le comportement par hystérésis dans la courbe caractéristique de l'eau de sol, le paramètre efficace d'effort ?, et effort capillaire. Changer l'angle de contact de 0 avec 40° pour simuler le séchage et processus de mouillage, respectivement, est montré pour avoir un impact appréciable sur l'hystérésis dans le comportement constitutif des sols modelés. Une frontière entre les régimes de la pression positive et négative d'eau interstitielle est identifiée en fonction de la teneur en eau et de l'angle de contact. Les résultats de l'analyse sont d'importance pratique dans l'arrangement le comportement des sols insaturés subissant le mouillage normal et les processus de séchage, tels que l'infiltration, le drainage, et l'évaporation. En ligne : likosw@missouri.edu [article] Hysteresis of Capillary Stress in Unsaturated Granular Soil = Hystérésis de l'Effort Capillaire dans le Sol Granulaire Insaturé [texte imprimé] / Likos, William J., Auteur ; Ning Lu, Auteur ; Manzari, Madjid T., Editeur scientifique . - 646-655 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 130 N°6 (Juin 2004) . - 646-655 p. Mots-clés : Unsaturated  soils  Granular  materials  Constitutive  relation  Dewatering  Hysteresis  Water  content  Sol  insaturé  Matériaux  granulaires  Relation  constitutive  Asséchage  Hystérésis  Teneur  en  eau Index. décimale : 621.34/624 Résumé : Constitutive relationships among water content, matric suction, and capillary stress in unsaturated granular soils are modeled using a theoretical approach based on the changing geometry of interparticle pore water menisci. A series of equations is developed to describe the net force among particles attributable to the combined effects of negative pore water pressure and surface tension for spherical grains arranged in simple-cubic or tetrahedral packing order. The contact angle at the liquid–solid interface is considered as a variable to evaluate hysteretic behavior in the soil–water characteristic curve, the effective stress parameter χ, and capillary stress. Varying the contact angle from 0 to 40° to simulate drying and wetting processes, respectively, is shown to have an appreciable impact on hysteresis in the constitutive behavior of the modeled soils. A boundary between regimes of positive and negative pore water pressure is identified as a function of water content and contact angle. Results from the analysis are of practical importance in understanding the behavior of unsaturated soils undergoing natural wetting and drying processes, such as infiltration, drainage, and evaporation. Des Rapports constitutifs parmi la teneur en eau, l'aspiration matricielle, et l'effort capillaire dans les sols granulaires insaturés sont modelés en utilisant une approche théorique basée sur la géométrie changeante du menisci d'eau interstitielle d'interparticle. Une série d'équations est développée pour décrire la force nette parmi des particules attribuables aux effets combinés de la pression négative d'eau interstitielle et de la tension superficielle pour les grains sphériques disposés dans l'ordre cubique ou tétraédrique simple d'emballage. L'angle de contact à l'interface pleine liquide est considéré comme comme variable évaluer le comportement par hystérésis dans la courbe caractéristique de l'eau de sol, le paramètre efficace d'effort ?, et effort capillaire. Changer l'angle de contact de 0 avec 40° pour simuler le séchage et processus de mouillage, respectivement, est montré pour avoir un impact appréciable sur l'hystérésis dans le comportement constitutif des sols modelés. Une frontière entre les régimes de la pression positive et négative d'eau interstitielle est identifiée en fonction de la teneur en eau et de l'angle de contact. Les résultats de l'analyse sont d'importance pratique dans l'arrangement le comportement des sols insaturés subissant le mouillage normal et les processus de séchage, tels que l'infiltration, le drainage, et l'évaporation. En ligne : likosw@missouri.edu

Hysteresis of Matric Suction and Capillary Stress in Monodisperse Disk-Shaped Particle / Jeremy Lechman in Journal of engineering mechanics, Vol. 132 N°5 (Mai 2006) 

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Hysteresis of unsaturated hydromechanical properties of a silty soil / Ning Lu in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 3 (Mars 2013) 

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Integrated framework of probabilistic signed digraph based fault diagnosis approach to a gas fractionation unit / Ning Lu in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

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Is matric suction a stress variable? / Ning Lu in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°7 (Juillet 2008) 

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Relationship between the soil-water characteristic curve and the suction stress characteristic curve / Seboong Oh in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 1 (Janvier 2012) 

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Tensile strength of unsaturated sand / Ning Lu in Journal of engineering mechanics, Vol. 135 N° 12 (Décembre 2009) 

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