Documents disponibles écrits par cet auteur

An efficient numerical method for solving a model describing crystallization of polymorphs / Shamsul Qamar in Industrial & engineering chemistry research, Vol. 49 N° 10 (Mai 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 10 (Mai 2010) . - pp. 4940–4947 Titre : An efficient numerical method for solving a model describing crystallization of polymorphs Type de document : texte imprimé Auteurs : Shamsul Qamar, Auteur ; Saima Noor, Auteur ; Andreas Seidel - Morgenstern, Auteur Année de publication : 2010 Article en page(s) : pp. 4940–4947 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Crystallization  Polymorphs Résumé : Polymorphism, in which a chemical compound exhibits different crystal forms or structures, has significant influence on the processing and storage of some crystalline powders in pharmaceutical industry. Different crystal structures, the so-called polymorphs, have different physical and chemical properties, such as crystal morphology, solubility, and color. These properties can have profound effect on the performance of products. This fact has motivated several researchers in this field to analyze, simulate, and control the crystallization of polymorphs. In this article, an efficient and accurate numerical method is introduced for solving a model describing crystallization of polymorphs. The proposed method has two parts. In the first part, a coupled system of ordinary differential equations of moments and the solute concentration is numerically solved in the time domain of interest. The resulting values are used to get the discrete growth and nucleation rates in the same time domain. In the second part, these discrete values along with the initial crystal size distribution (CSD) are used to construct the final CSD. The method is applied to a model describing crystallization of polymorphs of l-glutamic acid. For a validation, the results of the proposed technique are compared with those from the finite volume schemes. The numerical results demonstrate the potential of our scheme for the simulation of current model with high efficiency and accuracy. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9018353 [article] An efficient numerical method for solving a model describing crystallization of polymorphs [texte imprimé] / Shamsul Qamar, Auteur ; Saima Noor, Auteur ; Andreas Seidel - Morgenstern, Auteur . - 2010 . - pp. 4940–4947. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 10 (Mai 2010) . - pp. 4940–4947 Mots-clés : Crystallization  Polymorphs Résumé : Polymorphism, in which a chemical compound exhibits different crystal forms or structures, has significant influence on the processing and storage of some crystalline powders in pharmaceutical industry. Different crystal structures, the so-called polymorphs, have different physical and chemical properties, such as crystal morphology, solubility, and color. These properties can have profound effect on the performance of products. This fact has motivated several researchers in this field to analyze, simulate, and control the crystallization of polymorphs. In this article, an efficient and accurate numerical method is introduced for solving a model describing crystallization of polymorphs. The proposed method has two parts. In the first part, a coupled system of ordinary differential equations of moments and the solute concentration is numerically solved in the time domain of interest. The resulting values are used to get the discrete growth and nucleation rates in the same time domain. In the second part, these discrete values along with the initial crystal size distribution (CSD) are used to construct the final CSD. The method is applied to a model describing crystallization of polymorphs of l-glutamic acid. For a validation, the results of the proposed technique are compared with those from the finite volume schemes. The numerical results demonstrate the potential of our scheme for the simulation of current model with high efficiency and accuracy. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie9018353

Application of discontinuous galerkin scheme to batch crystallization models / Shamsul Qamar in Industrial & engineering chemistry research, Vol. 50 N° 7 (Avril 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 7 (Avril 2011) . - pp. 4113-4122 Titre : Application of discontinuous galerkin scheme to batch crystallization models Type de document : texte imprimé Auteurs : Shamsul Qamar, Auteur ; Iltaf Hussain, Auteur ; Andreas Seidel - Morgenstern, Auteur Année de publication : 2011 Article en page(s) : pp. 4113-4122 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Modeling  Crystallization  Batchwise Résumé : A discontinuous Galerkin finite element method is proposed for solving batch crystallization models. The suggested method has the capability of capturing sharp discontinuities and narrow peaks of the crystal size distribution (CSD). The accuracy of the method can be improved by introducing additional nodes in the same solution element and, hence, avoids the expansion of mesh stencils which is normally observed in the high order finite volume schemes. For that reason, the method can be easily applied up to boundary cells without losing accuracy. The method is robust and well suited for large-scale time-dependent computations in which a high degree of accuracy is demanded. Several test cases are carried out in this paper. The numerical results verify the efficiency and accuracy of the proposed method. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24027659 [article] Application of discontinuous galerkin scheme to batch crystallization models [texte imprimé] / Shamsul Qamar, Auteur ; Iltaf Hussain, Auteur ; Andreas Seidel - Morgenstern, Auteur . - 2011 . - pp. 4113-4122. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 7 (Avril 2011) . - pp. 4113-4122 Mots-clés : Modeling  Crystallization  Batchwise Résumé : A discontinuous Galerkin finite element method is proposed for solving batch crystallization models. The suggested method has the capability of capturing sharp discontinuities and narrow peaks of the crystal size distribution (CSD). The accuracy of the method can be improved by introducing additional nodes in the same solution element and, hence, avoids the expansion of mesh stencils which is normally observed in the high order finite volume schemes. For that reason, the method can be easily applied up to boundary cells without losing accuracy. The method is robust and well suited for large-scale time-dependent computations in which a high degree of accuracy is demanded. Several test cases are carried out in this paper. The numerical results verify the efficiency and accuracy of the proposed method. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24027659

Application of space – time CE/SE method for solving gas – solid reaction and chemotaxis models / Shamsul Qamar in Industrial & engineering chemistry research, Vol. 51 N° 26 (Juillet 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 26 (Juillet 2012) . - pp. 9173-9185 Titre : Application of space – time CE/SE method for solving gas – solid reaction and chemotaxis models Type de document : texte imprimé Auteurs : Shamsul Qamar, Auteur ; Waqas Ashraf, Auteur Année de publication : 2012 Article en page(s) : pp. 9173-9185 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Modeling  Gas  solid  reaction Résumé : This work is concerned with the simulation of two different convection―diffusion―reaction type partial differential equations. The first one is the one-dimensional heterogeneous gas―solid reaction model encountered in a variety of chemical engineering problems. The exothermic nature of such reactions enlarges the gradients of temperature and concentrations that generate steep reaction fronts. The second one is the two-dimensional Keller―Segel model of the chemotaxis that generates delta-type singularities in the solution during a finite time. In its simplest form, the model is a nonlinear-coupled system of the convection-diffusion equation for the cell density and the reaction―diffusion equation for the chemoattractant concentration. The space-time conservation element and solution element (CE/SE) method is proposed for approximating both systems. The method has capabilities to capture sharp discontinuities of the solutions without spurious oscillations. To validate the accuracy and efficiency of the method, several case studies are carried out. The results of the current method are compared with the staggered central schemes. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26107475 [article] Application of space – time CE/SE method for solving gas – solid reaction and chemotaxis models [texte imprimé] / Shamsul Qamar, Auteur ; Waqas Ashraf, Auteur . - 2012 . - pp. 9173-9185. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 26 (Juillet 2012) . - pp. 9173-9185 Mots-clés : Modeling  Gas  solid  reaction Résumé : This work is concerned with the simulation of two different convection―diffusion―reaction type partial differential equations. The first one is the one-dimensional heterogeneous gas―solid reaction model encountered in a variety of chemical engineering problems. The exothermic nature of such reactions enlarges the gradients of temperature and concentrations that generate steep reaction fronts. The second one is the two-dimensional Keller―Segel model of the chemotaxis that generates delta-type singularities in the solution during a finite time. In its simplest form, the model is a nonlinear-coupled system of the convection-diffusion equation for the cell density and the reaction―diffusion equation for the chemoattractant concentration. The space-time conservation element and solution element (CE/SE) method is proposed for approximating both systems. The method has capabilities to capture sharp discontinuities of the solutions without spurious oscillations. To validate the accuracy and efficiency of the method, several case studies are carried out. The results of the current method are compared with the staggered central schemes. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26107475

Bivariate extension of the quadrature method of moments for batch crystallization models / Shamsul Qamar in Industrial & engineering chemistry research, Vol. 49 N° 22 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 22 (Novembre 2010) . - pp. 11633-11644 Titre : Bivariate extension of the quadrature method of moments for batch crystallization models Type de document : texte imprimé Auteurs : Shamsul Qamar, Auteur ; Saima Noor, Auteur ; Qurrat ul Ain, Auteur Année de publication : 2011 Article en page(s) : pp. 11633-11644 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Modeling  Crystallization  Batchwise Résumé : This Article presents a bivariate extension of the quadrature method of moments for solving two-dimensional batch crystallization models involving crystals nucleation, size-dependent growths, aggregation, and dissolution of small nuclei below certain critical size in a dissolution unit. In this technique, orthogonal polynomials of lower order moments are used to find the quadrature abscissas (points) and weights. Several benchmark problems with different combinations of processes are considered in this Article. The accuracy and efficiency of the proposed method are validated against the analytical solutions and the high-resolution finite volume scheme. Excellent agreements were observed in all test problems. It was found that the current method is very efficient and accurate as compared to the high-resolution finite volume scheme. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23437862 [article] Bivariate extension of the quadrature method of moments for batch crystallization models [texte imprimé] / Shamsul Qamar, Auteur ; Saima Noor, Auteur ; Qurrat ul Ain, Auteur . - 2011 . - pp. 11633-11644. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 22 (Novembre 2010) . - pp. 11633-11644 Mots-clés : Modeling  Crystallization  Batchwise Résumé : This Article presents a bivariate extension of the quadrature method of moments for solving two-dimensional batch crystallization models involving crystals nucleation, size-dependent growths, aggregation, and dissolution of small nuclei below certain critical size in a dissolution unit. In this technique, orthogonal polynomials of lower order moments are used to find the quadrature abscissas (points) and weights. Several benchmark problems with different combinations of processes are considered in this Article. The accuracy and efficiency of the proposed method are validated against the analytical solutions and the high-resolution finite volume scheme. Excellent agreements were observed in all test problems. It was found that the current method is very efficient and accurate as compared to the high-resolution finite volume scheme. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23437862