Documents disponibles écrits par cet auteur

Bayesian framework for characterizing geotechnical model uncertainty / J. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 7 (Juillet 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 932–940 Titre : Bayesian framework for characterizing geotechnical model uncertainty Type de document : texte imprimé Auteurs : J. Zhang, Auteur ; Zhang, L. M., Auteur ; Wilson H. Tang, Auteur Année de publication : 2009 Article en page(s) : pp. 932–940 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Bayesian  analysis  Uncertainty  principles  Slope  stability  Centrifuge  model  Reliability Résumé : As any model is only an abstraction of the real world, model uncertainty always exists. The magnitude of model uncertainty is important for geotechnical decision making. If model uncertainty is not considered, the geotechnical predictions and hence the decisions based on the geotechnical predictions might be biased. In this study, a framework for characterizing geotechnical model uncertainty using observation data is proposed. The framework is based on the concept of multivariable Bayesian updating, in which the statistics of model uncertainty are updated using observed performance data. Uncertainties in both input parameters and observed data can be considered in the proposed framework. To bypass complex computational works involved in the proposed framework, a practical approximate solution is presented. The proposed framework is illustrated by characterizing the model uncertainty of four limit equilibrium methods for slope stability analysis using quality centrifuge test data. Parametric study in the illustrative example shows that both quality and quantity of the performance data could affect the determination of the model uncertainty, and that such effects can be systematically quantified with the proposed method. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000018 [article] Bayesian framework for characterizing geotechnical model uncertainty [texte imprimé] / J. Zhang, Auteur ; Zhang, L. M., Auteur ; Wilson H. Tang, Auteur . - 2009 . - pp. 932–940. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 932–940 Mots-clés : Bayesian  analysis  Uncertainty  principles  Slope  stability  Centrifuge  model  Reliability Résumé : As any model is only an abstraction of the real world, model uncertainty always exists. The magnitude of model uncertainty is important for geotechnical decision making. If model uncertainty is not considered, the geotechnical predictions and hence the decisions based on the geotechnical predictions might be biased. In this study, a framework for characterizing geotechnical model uncertainty using observation data is proposed. The framework is based on the concept of multivariable Bayesian updating, in which the statistics of model uncertainty are updated using observed performance data. Uncertainties in both input parameters and observed data can be considered in the proposed framework. To bypass complex computational works involved in the proposed framework, a practical approximate solution is presented. The proposed framework is illustrated by characterizing the model uncertainty of four limit equilibrium methods for slope stability analysis using quality centrifuge test data. Parametric study in the illustrative example shows that both quality and quantity of the performance data could affect the determination of the model uncertainty, and that such effects can be systematically quantified with the proposed method. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000018

Effect of sulphate reducing bacteria on corrosion of Al_Zn_In_Sn sacrificial anodes in marine sediment / F. Liu in Materials and corrosion, Vol. 63 N° 5 (Mai 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 5 (Mai 2012) . - pp. 431–437 Titre : Effect of sulphate reducing bacteria on corrosion of Al_Zn_In_Sn sacrificial anodes in marine sediment Type de document : texte imprimé Auteurs : F. Liu, Auteur ; J. Zhang, Auteur ; S. Zhang, Auteur Année de publication : 2012 Article en page(s) : pp. 431–437 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Metals  and  alloys;  corrosion;  electrochemical  impedance  spectroscopy  (EIS);  scanning  electron  microscopy  (SEM) Résumé : Microbiologically influenced corrosion (MIC) of Al_Zn_In_Sn sacrificial anodes in marine sediment was investigated by exposing samples to sulphate reducing bacteria (SRB). Samples exposed to the sterile marine sediment were used as control. The results show that pitting corrosion occurs in both the sterile marine sediment and the SRB-containing marine sediment. However, the corrosion can be increased sharply by the SRB metabolic activity due to the cathodic depolarization effect. In fact, the effect is based on the consumption of hydrogen which probably results in the acceleration of galvanic corrosion between corrosion products and metal substrate. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005955/abstract [article] Effect of sulphate reducing bacteria on corrosion of Al_Zn_In_Sn sacrificial anodes in marine sediment [texte imprimé] / F. Liu, Auteur ; J. Zhang, Auteur ; S. Zhang, Auteur . - 2012 . - pp. 431–437. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 5 (Mai 2012) . - pp. 431–437 Mots-clés : Metals  and  alloys;  corrosion;  electrochemical  impedance  spectroscopy  (EIS);  scanning  electron  microscopy  (SEM) Résumé : Microbiologically influenced corrosion (MIC) of Al_Zn_In_Sn sacrificial anodes in marine sediment was investigated by exposing samples to sulphate reducing bacteria (SRB). Samples exposed to the sterile marine sediment were used as control. The results show that pitting corrosion occurs in both the sterile marine sediment and the SRB-containing marine sediment. However, the corrosion can be increased sharply by the SRB metabolic activity due to the cathodic depolarization effect. In fact, the effect is based on the consumption of hydrogen which probably results in the acceleration of galvanic corrosion between corrosion products and metal substrate. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005955/abstract

Effect of water vapour on cyclic oxidation of Fe–Cr alloys / N. K. Othman in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Titre : Effect of water vapour on cyclic oxidation of Fe–Cr alloys Type de document : texte imprimé Auteurs : N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur Année de publication : 2011 Article en page(s) : pp. 496–503 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Alloy  depletion  Breakaway  Cyclic  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract [article] Effect of water vapour on cyclic oxidation of Fe–Cr alloys [texte imprimé] / N. K. Othman, Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur . - 2011 . - pp. 496–503. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 496–503 Mots-clés : Alloy  depletion  Breakaway  Cyclic  oxidation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Model Fe–Cr alloys containing 9, 17 or 25 wt% Cr were subjected to repeated 1 h cycles of exposure at 700 °C to flowing gas mixtures of Ar-20O2, Ar-20O2-5H2O and Ar-5O2-20H2O (all in volume %) for up to 400 cycles. The kinetics and morphological development of these reactions were compared with those found during isothermal exposure to the same gases. Under isothermal conditions, all alloys developed thin protective chromium-rich scales in dry oxygen. Addition of 5% H2O induced breakaway for Fe-9Cr within 48 h, but had little effect on higher chromium alloys. Isothermal chromia scale growth on Fe-17Cr and Fe-25Cr was accelerated by the addition of 20% H2O, but breakaway did not result. Under cyclic conditions in dry oxygen, Fe-9Cr quickly entered breakaway, oxidising according to fast, linear kinetics, but the higher chromium alloys exhibited protective behaviour. When 5% H2O was added to the oxygen, the 17% Cr alloy also underwent fast breakaway oxidation, but Fe-25Cr continued to be protected by a chromia scale. In the 20% H2O gas, all alloys failed under cyclic conditions, producing thick, iron-rich oxide scales. The synergistic effects of water vapour and temperature cycling are discussed in terms of alloy chromium depletion and the effects of H2O(g) on oxide transport properties. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005866/abstract

Efficient probabilistic back-analysis of slope stability model parameters / J. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 99-109 Titre : Efficient probabilistic back-analysis of slope stability model parameters Type de document : texte imprimé Auteurs : J. Zhang, Auteur ; Wilson H. Tang, Auteur ; Zhang, L. M., Auteur Article en page(s) : pp. 99-109 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Landslides  Slope  stability  Failure  investigation  Probability  methods  Reliability  Bayesian  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Back-analysis of slope failure is often performed to improve one's knowledge on parameters of a slope stability analysis model. In a failed slope, the slip surface may pass through several layers of soil. Therefore, several sets of model parameters need to be back-analyzed. To back-analyze multiple sets of slope stability parameters simultaneously under uncertainty, the back-analysis can be implemented in a probabilistic way, in which uncertain parameters are modeled as random variables, and their distributions are improved based on the observed slope failure information. In this paper, two methods are presented for probabilistic back-analysis of slope failure. For a general slope stability model, its uncertain parameters can be back-analyzed with an optimization procedure that can be implemented in a spreadsheet. When the slope stability model is approximately linear, its parameters can be back-analyzed with sensitivity analysis instead. A feature of these two methods is that they are easy to apply. Two case studies are used to illustrate the proposed methods. The case studies show that the degrees of improvement achieved by the back-analysis are different for different parameters, and that the parameter contributing most to the uncertainty in factor of safety is updated most. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Efficient probabilistic back-analysis of slope stability model parameters [texte imprimé] / J. Zhang, Auteur ; Wilson H. Tang, Auteur ; Zhang, L. M., Auteur . - pp. 99-109. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 99-109 Mots-clés : Landslides  Slope  stability  Failure  investigation  Probability  methods  Reliability  Bayesian  analysis Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Back-analysis of slope failure is often performed to improve one's knowledge on parameters of a slope stability analysis model. In a failed slope, the slip surface may pass through several layers of soil. Therefore, several sets of model parameters need to be back-analyzed. To back-analyze multiple sets of slope stability parameters simultaneously under uncertainty, the back-analysis can be implemented in a probabilistic way, in which uncertain parameters are modeled as random variables, and their distributions are improved based on the observed slope failure information. In this paper, two methods are presented for probabilistic back-analysis of slope failure. For a general slope stability model, its uncertain parameters can be back-analyzed with an optimization procedure that can be implemented in a spreadsheet. When the slope stability model is approximately linear, its parameters can be back-analyzed with sensitivity analysis instead. A feature of these two methods is that they are easy to apply. Two case studies are used to illustrate the proposed methods. The case studies show that the degrees of improvement achieved by the back-analysis are different for different parameters, and that the parameter contributing most to the uncertainty in factor of safety is updated most. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]

Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere / Wu, Q. in Materials and corrosion, Vol. 62 N° 6 (Juin 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 521–530 Titre : Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere Type de document : texte imprimé Auteurs : Wu, Q., Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur Année de publication : 2011 Article en page(s) : pp. 521–530 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Carburization  Cobalt  Graphite  Iron  Metal  dusting  Nickel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The metal dusting behaviour of total 11 nickel- and cobalt-base alloys at 680 °C in a gas of 68%CO[BOND]31%H2[BOND]1%H2O (aC = 19.0, equation image = 5.4 × 10−25  atm) was investigated. All samples were electropolished and reacted in a thermal cycling apparatus. On the basis of their reaction kinetics, these alloys can be classified into three groups: the first, with rapid carbon uptake and significant metal wastage, consists of alloys of relatively high iron content (AC 66, 800H and NS-163); the second, with intermediate rates, consists of some Co-base alloys (HAYNES 188, HAYNES 25 and ULTIMET) and the third, with very low reaction rates, consists of nickel-base alloys with high chromium levels (601, HAYNES HR 160, 230, G-35 and EN 105). An external chromia scale protected group 3 alloys from carburization and dusting. However, this protective scale was damaged and not rehealed for group 1 and group 2 alloys, allowing carbon attack. In all cases, coke deposited on the surface with two typical morphologies: filaments and graphite particle clusters. Subsurface spinel formation in high iron-content alloys led to rapid dusting due to the significant volume expansion. Alloy carbon permeability was calculated from a simple law of mixtures, and shown to correlate reasonably well with initial dusting rate except for one cobalt-base alloy in which iron spinel formation was significant. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005863/abstract [article] Metal dusting behaviour of several nickel- and cobalt-base alloys in CO-H2-H2O atmosphere [texte imprimé] / Wu, Q., Auteur ; J. Zhang, Auteur ; D. J. Young, Auteur . - 2011 . - pp. 521–530. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 6 (Juin 2011) . - pp. 521–530 Mots-clés : Carburization  Cobalt  Graphite  Iron  Metal  dusting  Nickel Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The metal dusting behaviour of total 11 nickel- and cobalt-base alloys at 680 °C in a gas of 68%CO[BOND]31%H2[BOND]1%H2O (aC = 19.0, equation image = 5.4 × 10−25  atm) was investigated. All samples were electropolished and reacted in a thermal cycling apparatus. On the basis of their reaction kinetics, these alloys can be classified into three groups: the first, with rapid carbon uptake and significant metal wastage, consists of alloys of relatively high iron content (AC 66, 800H and NS-163); the second, with intermediate rates, consists of some Co-base alloys (HAYNES 188, HAYNES 25 and ULTIMET) and the third, with very low reaction rates, consists of nickel-base alloys with high chromium levels (601, HAYNES HR 160, 230, G-35 and EN 105). An external chromia scale protected group 3 alloys from carburization and dusting. However, this protective scale was damaged and not rehealed for group 1 and group 2 alloys, allowing carbon attack. In all cases, coke deposited on the surface with two typical morphologies: filaments and graphite particle clusters. Subsurface spinel formation in high iron-content alloys led to rapid dusting due to the significant volume expansion. Alloy carbon permeability was calculated from a simple law of mixtures, and shown to correlate reasonably well with initial dusting rate except for one cobalt-base alloy in which iron spinel formation was significant. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005863/abstract

Recent advances in understanding metal dusting / D. J. Young in Materials and corrosion, Vol. 62 N° 1 (Janvier 2011) 

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Reliability-based optimization of geotechnical systems / J. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 12 (Décembre 2011) 

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Slope reliability analysis considering site-specific performance information / J. Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 3 (Mars 2011) 

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Stress–dilatancy relation for Mohr–Coulomb soils following a non-associated flow rule / J. Zhang in Géotechnique, Vol. 60 N° 3 (Mars 2010) 

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Synthesis of imidazoline-based dissymmetric bis-quaternary ammonium gemini surfactant and its inhibition mechanism on Q235 steel in hydrochloric acid medium / J. Zhang in Materials and corrosion, Vol. 63 N° 7 (Juillet 2012) 

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