Documents disponibles écrits par cet auteur

Identification of Markov Matrices of Milling Models / Jayanta Chakraborty in Industrial & engineering chemistry research, Vol. 48 N° 21 (Novembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9763–9771 Titre : Identification of Markov Matrices of Milling Models Type de document : texte imprimé Auteurs : Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur Année de publication : 2010 Article en page(s) : pp. 9763–9771 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Grinding  mill  Markov  chain  models Résumé : Detailed modeling of a grinding mill can be achieved through Markov chain models without involving lengthy computations. However, estimation of the key parameters of the model, elements of the Markov transition matrix, using observable quantities is not trivial. This powerful modeling tool can find wide applicability in operation and control of industrial mills if this set of parameters can be estimated using suitably observed quantities. In this study we model a complex multiregion mill using Markov chain and propose a general technique for estimation of the Markov transition matrix for breakage problems. This technique estimates the transition matrix from observed evolution of particle size distributions in various regions of the mill, based on extracting spectral information of the transition matrix from the data. It has been shown in this study that a specific grouping of states can lead to lower triangular block structure of the Markov transition matrix for a breakage problem. Detailed analysis of such a block matrix reveals that simple semilogarithmic plots of a set of observed quantities can be used in order to extract the spectral information of the transition matrix which in turn can be used to reconstruct the Markov matrix. A numerical example has been presented to illustrate various ideas which demonstrate that the proposed technique can be used successfully to estimate the Markov transition matrix very accurately from observations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900456j#tfn1 [article] Identification of Markov Matrices of Milling Models [texte imprimé] / Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur . - 2010 . - pp. 9763–9771. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 21 (Novembre 2009) . - pp. 9763–9771 Mots-clés : Grinding  mill  Markov  chain  models Résumé : Detailed modeling of a grinding mill can be achieved through Markov chain models without involving lengthy computations. However, estimation of the key parameters of the model, elements of the Markov transition matrix, using observable quantities is not trivial. This powerful modeling tool can find wide applicability in operation and control of industrial mills if this set of parameters can be estimated using suitably observed quantities. In this study we model a complex multiregion mill using Markov chain and propose a general technique for estimation of the Markov transition matrix for breakage problems. This technique estimates the transition matrix from observed evolution of particle size distributions in various regions of the mill, based on extracting spectral information of the transition matrix from the data. It has been shown in this study that a specific grouping of states can lead to lower triangular block structure of the Markov transition matrix for a breakage problem. Detailed analysis of such a block matrix reveals that simple semilogarithmic plots of a set of observed quantities can be used in order to extract the spectral information of the transition matrix which in turn can be used to reconstruct the Markov matrix. A numerical example has been presented to illustrate various ideas which demonstrate that the proposed technique can be used successfully to estimate the Markov transition matrix very accurately from observations. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900456j#tfn1

Population balance modeling of environment dependent breakage / Jayanta Chakraborty in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13116–13128 Titre : Population balance modeling of environment dependent breakage : role of granular viscosity, density and compaction. model formulation and similarity analysis Type de document : texte imprimé Auteurs : Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur Année de publication : 2012 Article en page(s) : pp. 13116–13128 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Similarity  Compaction  Density  Viscosity  Modeling  Population  balance Résumé : In this work, we introduce mechanistic considerations in nonlinear milling of particulate material. We show that the mobility of the powder can have a significant effect on the breakage frequency. During grinding, the change in particle size leads to changes in the mobility of the powder which in turn alters the breakage rate. The mechanistic modeling, being able to accommodate different responses of powder mobility for wet and dry grinding, is able to distinguish naturally between dry and wet grinding, an attribute not possessed by other nonlinear models. It is shown that the rich variety of phenomena observed in grinding mills emanates from the interplay between opposing factors that influence the breakage environment in a mill. Such factors include viscosity, density, and compaction of the powder. For dry grinding, the change in powder porosity and viscosity leads to a variety of nonlinear effects. For wet grinding the viscosity and density of the slurry impart a nonmonotonic variation in the breakage rate with particle size. A population balance equation (PBE) for environment dependent breakage has been formulated by considering the foregoing effects. Similarity analysis of the model equation shows the existence of self-similar behavior even for the environment dependent breakage. Experimental investigation of such self-similarity provides an effective diagnostic process for validating model framework. Furthermore, when combined with the methodology of solving inverse problems (e.g., Sathyagal, A. N.; Ramkrishna, D. Chem. Eng. Sci. 1996, 51, 1377), an effective approach becomes available for model identification. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267469 [article] Population balance modeling of environment dependent breakage : role of granular viscosity, density and compaction. model formulation and similarity analysis [texte imprimé] / Jayanta Chakraborty, Auteur ; Doraiswami Ramkrishna, Auteur . - 2012 . - pp. 13116–13128. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 13116–13128 Mots-clés : Similarity  Compaction  Density  Viscosity  Modeling  Population  balance Résumé : In this work, we introduce mechanistic considerations in nonlinear milling of particulate material. We show that the mobility of the powder can have a significant effect on the breakage frequency. During grinding, the change in particle size leads to changes in the mobility of the powder which in turn alters the breakage rate. The mechanistic modeling, being able to accommodate different responses of powder mobility for wet and dry grinding, is able to distinguish naturally between dry and wet grinding, an attribute not possessed by other nonlinear models. It is shown that the rich variety of phenomena observed in grinding mills emanates from the interplay between opposing factors that influence the breakage environment in a mill. Such factors include viscosity, density, and compaction of the powder. For dry grinding, the change in powder porosity and viscosity leads to a variety of nonlinear effects. For wet grinding the viscosity and density of the slurry impart a nonmonotonic variation in the breakage rate with particle size. A population balance equation (PBE) for environment dependent breakage has been formulated by considering the foregoing effects. Similarity analysis of the model equation shows the existence of self-similar behavior even for the environment dependent breakage. Experimental investigation of such self-similarity provides an effective diagnostic process for validating model framework. Furthermore, when combined with the methodology of solving inverse problems (e.g., Sathyagal, A. N.; Ramkrishna, D. Chem. Eng. Sci. 1996, 51, 1377), an effective approach becomes available for model identification. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267469

A rationale for monod's biochemical growth kinetics / Doraiswami Ramkrishna 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. 9090–9098 Titre : A rationale for monod's biochemical growth kinetics Type de document : texte imprimé Auteurs : Doraiswami Ramkrishna, Auteur ; Hyun-Seob Song, Auteur Année de publication : 2009 Article en page(s) : p. 9090–9098 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Biochemical  Growth  Kinetics Résumé : A rationale is presented for Monod′s biochemical kinetics which has hitherto been viewed as purely empirical. It is shown here that this expression, which continues to be used by modelers of biochemical processes, has indeed an origin that relates to the detailed treatment of metabolism. This rationale originates from the resolution of the metabolic network into so-called elementary modes and assumes steady state for every metabolite in each elementary mode. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800905d [article] A rationale for monod's biochemical growth kinetics [texte imprimé] / Doraiswami Ramkrishna, Auteur ; Hyun-Seob Song, Auteur . - 2009 . - p. 9090–9098. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9090–9098 Mots-clés : Biochemical  Growth  Kinetics Résumé : A rationale is presented for Monod′s biochemical kinetics which has hitherto been viewed as purely empirical. It is shown here that this expression, which continues to be used by modelers of biochemical processes, has indeed an origin that relates to the detailed treatment of metabolism. This rationale originates from the resolution of the metabolic network into so-called elementary modes and assumes steady state for every metabolite in each elementary mode. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800905d

Stochastic analysis of multistate systems / Eric Sherer in Industrial & engineering chemistry research, Vol. 47 N°10 (Mai 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°10 (Mai 2008) . - p. 3430–3437 Titre : Stochastic analysis of multistate systems Type de document : texte imprimé Auteurs : Eric Sherer, Auteur ; Doraiswami Ramkrishna, Auteur Année de publication : 2008 Article en page(s) : p. 3430–3437 Note générale : Bibliogr. p. 3436-3437 Langues : Anglais (eng) Mots-clés : Multistate  systems;  Stochastic  framework;  Monte  Carlo  simulations Résumé : The treatment necessary to remove all cells for a periodic cell cycle specific regimen is analyzed using stochastic equations of a multistate model with state transition governed by residence time distributions. While the objective is to remove all cells, exactly when this occurs is uncertain due to the random timing of state transitions. Previous work has shown that removal of all cells requires great certainty that the number of cells is small; an expected population that is six standard deviations less than one cell is an indicator when cure is nearly likely. In developing the necessary stochastic framework, the expression for the standard deviation for multistate processes is derived and a simple two-state example is presented that illustrates the potential coupling between subpopulations. Finally, the methodology is applied to cell cycle specific chemotherapy and the number of cycles required to nearly be assured that zero cells remain is calculated. This method has computational advantages over Monte Carlo simulations when the initial number of cells is not small and only the variation in the total number of cells is of interest. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701723u [article] Stochastic analysis of multistate systems [texte imprimé] / Eric Sherer, Auteur ; Doraiswami Ramkrishna, Auteur . - 2008 . - p. 3430–3437. Bibliogr. p. 3436-3437 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°10 (Mai 2008) . - p. 3430–3437 Mots-clés : Multistate  systems;  Stochastic  framework;  Monte  Carlo  simulations Résumé : The treatment necessary to remove all cells for a periodic cell cycle specific regimen is analyzed using stochastic equations of a multistate model with state transition governed by residence time distributions. While the objective is to remove all cells, exactly when this occurs is uncertain due to the random timing of state transitions. Previous work has shown that removal of all cells requires great certainty that the number of cells is small; an expected population that is six standard deviations less than one cell is an indicator when cure is nearly likely. In developing the necessary stochastic framework, the expression for the standard deviation for multistate processes is derived and a simple two-state example is presented that illustrates the potential coupling between subpopulations. Finally, the methodology is applied to cell cycle specific chemotherapy and the number of cycles required to nearly be assured that zero cells remain is calculated. This method has computational advantages over Monte Carlo simulations when the initial number of cells is not small and only the variation in the total number of cells is of interest. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701723u

When is the quasi-steady-state approximation admissible in metabolic modeling? when admissible, what models are desirable? / Hyun-Seob Song 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. 7976–7985 Titre : When is the quasi-steady-state approximation admissible in metabolic modeling? when admissible, what models are desirable? Type de document : texte imprimé Auteurs : Hyun-Seob Song, Auteur ; Doraiswami Ramkrishna, Auteur Année de publication : 2009 Article en page(s) : pp. 7976–7985 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Quasi-steady-state  approximation  Metabolic  modeling Résumé : A strategy is presented for scrutiny of the quasi-steady-state (QSS) approximation in metabolic modeling that involves tracking dynamic data on extracellular products in so-called flux, as well as yield vector spaces when the substrate uptake flux is perturbed sinusoidally about some average value with specified frequency and amplitude. Criteria accrue for the diagnosis of any violation (and its extent) of the QSS approximation and are applied to data produced by simulations from models free from the QSS approximation. It is shown that, even when the assumption is admissible, the choice of the appropriate QSS model depends on the frequency and amplitude of the perturbation. Three different QSS models in the literature, viz., dynamic flux balance analysis, the macroscopic bioreaction model, and the hybrid cybernetic model, are evaluated, and circumstances are identified when one or more of the QSS models might be valid, as well as when none of them are. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900075f [article] When is the quasi-steady-state approximation admissible in metabolic modeling? when admissible, what models are desirable? [texte imprimé] / Hyun-Seob Song, Auteur ; Doraiswami Ramkrishna, Auteur . - 2009 . - pp. 7976–7985. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 7976–7985 Mots-clés : Quasi-steady-state  approximation  Metabolic  modeling Résumé : A strategy is presented for scrutiny of the quasi-steady-state (QSS) approximation in metabolic modeling that involves tracking dynamic data on extracellular products in so-called flux, as well as yield vector spaces when the substrate uptake flux is perturbed sinusoidally about some average value with specified frequency and amplitude. Criteria accrue for the diagnosis of any violation (and its extent) of the QSS approximation and are applied to data produced by simulations from models free from the QSS approximation. It is shown that, even when the assumption is admissible, the choice of the appropriate QSS model depends on the frequency and amplitude of the perturbation. Three different QSS models in the literature, viz., dynamic flux balance analysis, the macroscopic bioreaction model, and the hybrid cybernetic model, are evaluated, and circumstances are identified when one or more of the QSS models might be valid, as well as when none of them are. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900075f