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Bulk flotation of auriferous pyrite and arsenopyrite by using tertiary dodecyl mercaptan as collector in weak alkaline pulp / Jianhua Chen in Minerals engineering, Vol. 23 N° 11-13 (Octobre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 1070–1072 Titre : Bulk flotation of auriferous pyrite and arsenopyrite by using tertiary dodecyl mercaptan as collector in weak alkaline pulp Type de document : texte imprimé Auteurs : Jianhua Chen, Auteur ; Ye Chen, Auteur ; Zongwu Wei, Auteur Année de publication : 2011 Article en page(s) : pp. 1070–1072 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Gold  ores  Flotation  collectors  Froth  flotation  Sulphide  ores Résumé : Laboratory and industrial scale experiments were conducted to investigate the effect of tertiary dodecyl mercaptan (TDM) as a collector on the flotation of auriferous pyrite and arsenopyrite. The optimum recovery of gold associated with auriferous sulphides was obtained by adding a mixture of TDM and sodium butyl xanthate, together with only a little CuSO4 as an activator in a weak alkaline pulp adjusted by NaOH. A two-month industrial trial at the Liumei plant in Guangxi, China showed that an average gold recovery of 90.8% into a concentrate assaying 81.1 g/t Au from a feed assaying 2.9 g/t Au could be achieved at pH 8–8.5 using TDM as a collector. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001755 [article] Bulk flotation of auriferous pyrite and arsenopyrite by using tertiary dodecyl mercaptan as collector in weak alkaline pulp [texte imprimé] / Jianhua Chen, Auteur ; Ye Chen, Auteur ; Zongwu Wei, Auteur . - 2011 . - pp. 1070–1072. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 11-13 (Octobre 2010) . - pp. 1070–1072 Mots-clés : Gold  ores  Flotation  collectors  Froth  flotation  Sulphide  ores Résumé : Laboratory and industrial scale experiments were conducted to investigate the effect of tertiary dodecyl mercaptan (TDM) as a collector on the flotation of auriferous pyrite and arsenopyrite. The optimum recovery of gold associated with auriferous sulphides was obtained by adding a mixture of TDM and sodium butyl xanthate, together with only a little CuSO4 as an activator in a weak alkaline pulp adjusted by NaOH. A two-month industrial trial at the Liumei plant in Guangxi, China showed that an average gold recovery of 90.8% into a concentrate assaying 81.1 g/t Au from a feed assaying 2.9 g/t Au could be achieved at pH 8–8.5 using TDM as a collector. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001755

Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model / Jianhua Chen in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8172–8179 Titre : Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model Type de document : texte imprimé Auteurs : Jianhua Chen, Auteur ; Ning Yang, Auteur ; Wei Ge, Auteur Année de publication : 2009 Article en page(s) : pp. 8172–8179 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Regime  transition  Bubble  columns  Dual-bubble-size  model  Computational  fluid  dynamics  simulation Résumé : This article investigates the two regime transition points for bubble columns with the so-called dual-bubble-size (DBS) model featuring the utilization of a stability condition to analyze the compromise between dominant mechanisms. Our previous work indicated that the second point could be reasonably predicted and physically interpreted by the DBS model for various gas−liquid systems. This work further clarifies the relationship between the bifurcation of energy dissipation and of structural parameters and the regime transition. It is found that the bifurcation of energy dissipation exists for both the gas−liquid and gas−solid systems and can be used to predict and understand regime transition in multiphase flow. Then the DBS model is incorporated into the two-fluid model for calculating interphase coupling, and a computational fluid dynamics (CFD) calculation is performed to simulate a bubble column. The “shoulder” on the gas hold-up curve can be observed in the simulation with the new coupling method, and the second transition point predicted from the CFD simulation is consistent with experiments and the calculation of the DBS model. Sparger effects are investigated through the two simulation cases for uniform aeration and local aeration, and the radial distribution of local hydrodynamic parameters is comparable with experimental data in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801644d [article] Computational fluid dynamics simulation of regime transition in bubble columns incorporating the dual-bubble-size model [texte imprimé] / Jianhua Chen, Auteur ; Ning Yang, Auteur ; Wei Ge, Auteur . - 2009 . - pp. 8172–8179. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8172–8179 Mots-clés : Regime  transition  Bubble  columns  Dual-bubble-size  model  Computational  fluid  dynamics  simulation Résumé : This article investigates the two regime transition points for bubble columns with the so-called dual-bubble-size (DBS) model featuring the utilization of a stability condition to analyze the compromise between dominant mechanisms. Our previous work indicated that the second point could be reasonably predicted and physically interpreted by the DBS model for various gas−liquid systems. This work further clarifies the relationship between the bifurcation of energy dissipation and of structural parameters and the regime transition. It is found that the bifurcation of energy dissipation exists for both the gas−liquid and gas−solid systems and can be used to predict and understand regime transition in multiphase flow. Then the DBS model is incorporated into the two-fluid model for calculating interphase coupling, and a computational fluid dynamics (CFD) calculation is performed to simulate a bubble column. The “shoulder” on the gas hold-up curve can be observed in the simulation with the new coupling method, and the second transition point predicted from the CFD simulation is consistent with experiments and the calculation of the DBS model. Sparger effects are investigated through the two simulation cases for uniform aeration and local aeration, and the radial distribution of local hydrodynamic parameters is comparable with experimental data in the literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801644d

A DFT study on the effect of lattice impurities on the electronic structures and floatability of sphalerite / Ye Chen in Minerals engineering, Vol. 23 N° 14 (Novembre 2010) 

Public ISBD [article]  in Minerals engineering > Vol. 23 N° 14 (Novembre 2010) . - pp. 1120–1130 Titre : A DFT study on the effect of lattice impurities on the electronic structures and floatability of sphalerite Type de document : texte imprimé Auteurs : Ye Chen, Auteur ; Jianhua Chen, Auteur ; Jin Guo, Auteur Année de publication : 2011 Article en page(s) : pp. 1120–1130 Note générale : Génie Minier Langues : Anglais (eng) Mots-clés : Sulfide  ores  Froth  flotation  Simulation Résumé : The electronic structures of bulk sphalerite containing 14 typical kinds of impurities were studied by density-functional theory (DFT). The calculated results show that the presence of Cd, Hg, Ga, Ge, In, Ag, Sn, Pb and Sb could increase the lattice parameter of sphalerite. Ag, Sn, Pb, Sb, Cd and Hg impurities narrowed the band-gap and increased the conductivity of sphalerite. Moreover, Mn, Fe, Ga, In, Sn and Sb impurities changed the semiconductor type of sphalerite from p-type to n-type. All of the impurities except Cd and Hg made the Fermi level shift to higher energy and led to the occurrence of an impurity state in the forbidden band. Analysis of the frontier molecular orbital showed that the impurities Mn, Fe, Cu, Ge, Sn, Pb and Sb contributed greatly to the highest occupied molecular orbital (HOMO) and greatly influence the nucleophilicity of sphalerite. On the other hand, the impurities of Fe, Cu, Co, Ni, Cd and Ga greatly contributed to the lowest unoccupied molecular orbital (LUMO) and greatly affected the electrophilicity of sphalerite. The interactions of O2 and xanthate with sphalerite are discussed. Results suggest that Mn, Fe, Ni, Cu, Sn and Pb impurities favored the oxidization of sphalerite; however, the impurities of Cd, Hg, Ga and In had the opposite effect. Impurities of Mn, Fe, Co, Ni, Cu, Hg and Pb could enhance the reactivity of xanthate with sphalerite. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001743 [article] A DFT study on the effect of lattice impurities on the electronic structures and floatability of sphalerite [texte imprimé] / Ye Chen, Auteur ; Jianhua Chen, Auteur ; Jin Guo, Auteur . - 2011 . - pp. 1120–1130. Génie Minier Langues : Anglais (eng) in Minerals engineering > Vol. 23 N° 14 (Novembre 2010) . - pp. 1120–1130 Mots-clés : Sulfide  ores  Froth  flotation  Simulation Résumé : The electronic structures of bulk sphalerite containing 14 typical kinds of impurities were studied by density-functional theory (DFT). The calculated results show that the presence of Cd, Hg, Ga, Ge, In, Ag, Sn, Pb and Sb could increase the lattice parameter of sphalerite. Ag, Sn, Pb, Sb, Cd and Hg impurities narrowed the band-gap and increased the conductivity of sphalerite. Moreover, Mn, Fe, Ga, In, Sn and Sb impurities changed the semiconductor type of sphalerite from p-type to n-type. All of the impurities except Cd and Hg made the Fermi level shift to higher energy and led to the occurrence of an impurity state in the forbidden band. Analysis of the frontier molecular orbital showed that the impurities Mn, Fe, Cu, Ge, Sn, Pb and Sb contributed greatly to the highest occupied molecular orbital (HOMO) and greatly influence the nucleophilicity of sphalerite. On the other hand, the impurities of Fe, Cu, Co, Ni, Cd and Ga greatly contributed to the lowest unoccupied molecular orbital (LUMO) and greatly affected the electrophilicity of sphalerite. The interactions of O2 and xanthate with sphalerite are discussed. Results suggest that Mn, Fe, Ni, Cu, Sn and Pb impurities favored the oxidization of sphalerite; however, the impurities of Cd, Hg, Ga and In had the opposite effect. Impurities of Mn, Fe, Co, Ni, Cu, Hg and Pb could enhance the reactivity of xanthate with sphalerite. DEWEY : 622 ISSN : 0892-6875 En ligne : http://www.sciencedirect.com/science/article/pii/S0892687510001743

Modeling of regime transition in bubble columns with stability condition / Jianhua Chen in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 290-301 Titre : Modeling of regime transition in bubble columns with stability condition Type de document : texte imprimé Auteurs : Jianhua Chen, Editeur scientifique ; Ning Yang, Editeur scientifique ; Wei Ge, Editeur scientifique Année de publication : 2009 Article en page(s) : P. 290-301 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Regime  Transition  Hydrodynamique  Dual-bubble-size  (DBS) Résumé : Understanding the physical essence of regime transition is of crucial importance for the modeling and simulation of hydrodynamics and heat and mass transfer in bubble columns. The regime transition of the air−water system has been captured by the dual-bubble-size (DBS) model in our previous work [Yang et al. Chem. Eng. Sci. 2007, 62, 6978−6991] as a jump change from one minimum point of the stability criterion to the other. The DBS model features the incorporation of a stability condition with hydrodynamic conservation equations through the analysis of compromise between dominant mechanisms. This work reiterates our previous work and further explores some remaining issues and underlying physics related to the jump change by analyzing the trajectory of global minimum points in the three-dimensional space of structural parameters. The influence of drag coefficient correlations on the model prediction is investigated. The effect of liquid viscosity on regime transition is evaluated using the DBS model for saccharose and glycerin systems. The dual effects of liquid viscosity reported in literature, namely, suppressing the regime transition while slightly increasing viscosity and destabilizing the homogeneous regime at higher viscosity, can be reasonably predicted with this model. Finally, the concept of the compromise between dominant mechanisms is extended to understand the bubble behavior at different scales and its relationship with stability condition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003623 [article] Modeling of regime transition in bubble columns with stability condition [texte imprimé] / Jianhua Chen, Editeur scientifique ; Ning Yang, Editeur scientifique ; Wei Ge, Editeur scientifique . - 2009 . - P. 290-301. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - P. 290-301 Mots-clés : Regime  Transition  Hydrodynamique  Dual-bubble-size  (DBS) Résumé : Understanding the physical essence of regime transition is of crucial importance for the modeling and simulation of hydrodynamics and heat and mass transfer in bubble columns. The regime transition of the air−water system has been captured by the dual-bubble-size (DBS) model in our previous work [Yang et al. Chem. Eng. Sci. 2007, 62, 6978−6991] as a jump change from one minimum point of the stability criterion to the other. The DBS model features the incorporation of a stability condition with hydrodynamic conservation equations through the analysis of compromise between dominant mechanisms. This work reiterates our previous work and further explores some remaining issues and underlying physics related to the jump change by analyzing the trajectory of global minimum points in the three-dimensional space of structural parameters. The influence of drag coefficient correlations on the model prediction is investigated. The effect of liquid viscosity on regime transition is evaluated using the DBS model for saccharose and glycerin systems. The dual effects of liquid viscosity reported in literature, namely, suppressing the regime transition while slightly increasing viscosity and destabilizing the homogeneous regime at higher viscosity, can be reasonably predicted with this model. Finally, the concept of the compromise between dominant mechanisms is extended to understand the bubble behavior at different scales and its relationship with stability condition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003623

No-reference perceptual image quality metric using gradient profiles for JPEG2000 / Luhong Liang in Signal processing. Image communication, Vol. 25 N° 7 (Août 2010) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 25 N° 7 (Août 2010) . - pp. 502–516 Titre : No-reference perceptual image quality metric using gradient profiles for JPEG2000 Type de document : texte imprimé Auteurs : Luhong Liang, Auteur ; Shiqi Wang, Auteur ; Jianhua Chen, Auteur Année de publication : 2012 Article en page(s) : pp. 502–516 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Blur  Ringing  Perceptual  quality  Gradient  profile  Image  compression  JPEG2000 Résumé : No-reference measurement of perceptual image quality is a crucial and challenging issue in modern image processing applications. One of the major difficulties is that some inherent features of natural images and artifacts are possibly rather ambiguous. In this paper, we tackle this problem using statistical information on image gradient profiles and propose a novel quality metric for JPEG2000 images. The key part of the metric is a histogram representing the sharpness distribution of the gradient profiles, from which a blur metric that is insensitive to inherently blurred structures in the natural image is established. Then a ringing metric is built based on ringing visibilities of regions associated with the gradient profiles. Finally, a combination model optimized through plenty of experiments is developed to predict the perceived image quality. The proposed metric achieves performance competitive with the state-of-the-art no-reference metrics on public datasets and is robust to various image contents. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596510000160 [article] No-reference perceptual image quality metric using gradient profiles for JPEG2000 [texte imprimé] / Luhong Liang, Auteur ; Shiqi Wang, Auteur ; Jianhua Chen, Auteur . - 2012 . - pp. 502–516. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 25 N° 7 (Août 2010) . - pp. 502–516 Mots-clés : Blur  Ringing  Perceptual  quality  Gradient  profile  Image  compression  JPEG2000 Résumé : No-reference measurement of perceptual image quality is a crucial and challenging issue in modern image processing applications. One of the major difficulties is that some inherent features of natural images and artifacts are possibly rather ambiguous. In this paper, we tackle this problem using statistical information on image gradient profiles and propose a novel quality metric for JPEG2000 images. The key part of the metric is a histogram representing the sharpness distribution of the gradient profiles, from which a blur metric that is insensitive to inherently blurred structures in the natural image is established. Then a ringing metric is built based on ringing visibilities of regions associated with the gradient profiles. Finally, a combination model optimized through plenty of experiments is developed to predict the perceived image quality. The proposed metric achieves performance competitive with the state-of-the-art no-reference metrics on public datasets and is robust to various image contents. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596510000160

The first-principle study of the effect of lattice impurity on adsorption of CN on sphalerite surface / Ye Chen in Minerals engineering, Vol. 23 N° 9 (Août 2010) 

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