Documents disponibles écrits par cet auteur

Capacity planning under clinical trials uncertainty in continuous pharmaceutical manufacturing, 2 / Arul Sundaramoorthy in Industrial & engineering chemistry research, Vol. 51 N° 42 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 42 (Octobre 2012) . - pp. 13703–13711 Titre : Capacity planning under clinical trials uncertainty in continuous pharmaceutical manufacturing, 2 : Solution method Type de document : texte imprimé Auteurs : Arul Sundaramoorthy, Auteur ; Xiang Li, Auteur ; James M. B. Evans, Auteur Année de publication : 2012 Article en page(s) : pp. 13703–13711 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Pharmaceutical  manufacturing Résumé : In Part 1 of this paper, we presented a scenario-based multiperiod mixed-integer linear programming (MILP) formulation for a capacity planning problem in continuous pharmaceutical manufacturing under clinical trials uncertainty. The number of scenarios and, thus, the formulation size grows exponentially with the number of products. The model size easily becomes intractable for conventional algorithms for more than 8 products. However, industrial-scale problems often involve 10 or more products, and thus a scalable solution algorithm is essential to solve such large-scale problems in reasonable times. In this part of the paper, we develop a rigorous decomposition strategy that exploits the underlying problem structure. We demonstrate the effectiveness of the proposed algorithm using several examples containing up to 16 potential products and over 65 000 scenarios. With the proposed decomposition algorithm, the solution time scales linearly with the number of scenarios, whereby a 16-product example with over 65 million binary variables, nearly 240 million continuous variables, and over 250 million constraints was solved in less than 6 h of solver time. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3003254 [article] Capacity planning under clinical trials uncertainty in continuous pharmaceutical manufacturing, 2 : Solution method [texte imprimé] / Arul Sundaramoorthy, Auteur ; Xiang Li, Auteur ; James M. B. Evans, Auteur . - 2012 . - pp. 13703–13711. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 42 (Octobre 2012) . - pp. 13703–13711 Mots-clés : Pharmaceutical  manufacturing Résumé : In Part 1 of this paper, we presented a scenario-based multiperiod mixed-integer linear programming (MILP) formulation for a capacity planning problem in continuous pharmaceutical manufacturing under clinical trials uncertainty. The number of scenarios and, thus, the formulation size grows exponentially with the number of products. The model size easily becomes intractable for conventional algorithms for more than 8 products. However, industrial-scale problems often involve 10 or more products, and thus a scalable solution algorithm is essential to solve such large-scale problems in reasonable times. In this part of the paper, we develop a rigorous decomposition strategy that exploits the underlying problem structure. We demonstrate the effectiveness of the proposed algorithm using several examples containing up to 16 potential products and over 65 000 scenarios. With the proposed decomposition algorithm, the solution time scales linearly with the number of scenarios, whereby a 16-product example with over 65 million binary variables, nearly 240 million continuous variables, and over 250 million constraints was solved in less than 6 h of solver time. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3003254

Factors that determine the performance of carbon fuels in the direct carbon fuel cell / Xiang Li 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. 9670–9677 Titre : Factors that determine the performance of carbon fuels in the direct carbon fuel cell Type de document : texte imprimé Auteurs : Xiang Li, Auteur ; Zhong Hua Zhu, Auteur ; Roland De Marco, Auteur Année de publication : 2009 Article en page(s) : p. 9670–9677 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Carbon  fuels Résumé : The direct carbon fuel cell (DCFC) is a promising power generation device, which has a much higher efficiency (80%) and a lower emission than conventional coal-fired power plants. In this study, different commercial carbon fuels including activated carbon (AC), carbon black (CB220 and CB660), and graphitic carbon (GC) were tested in DCFC at 600−800 °C. The relationship between the intrinsic properties of carbon fuels and their electrochemical performance in the DCFC was analyzed. It is found that a desirable carbon fuel for DCFC should have high mesoporous surface area and rich oxygen-containing surface groups. The anodic performance of the DCFC may also be improved by small carbon particle size, fast stirring rates, and high cell temperatures. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800891m [article] Factors that determine the performance of carbon fuels in the direct carbon fuel cell [texte imprimé] / Xiang Li, Auteur ; Zhong Hua Zhu, Auteur ; Roland De Marco, Auteur . - 2009 . - p. 9670–9677. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9670–9677 Mots-clés : Carbon  fuels Résumé : The direct carbon fuel cell (DCFC) is a promising power generation device, which has a much higher efficiency (80%) and a lower emission than conventional coal-fired power plants. In this study, different commercial carbon fuels including activated carbon (AC), carbon black (CB220 and CB660), and graphitic carbon (GC) were tested in DCFC at 600−800 °C. The relationship between the intrinsic properties of carbon fuels and their electrochemical performance in the DCFC was analyzed. It is found that a desirable carbon fuel for DCFC should have high mesoporous surface area and rich oxygen-containing surface groups. The anodic performance of the DCFC may also be improved by small carbon particle size, fast stirring rates, and high cell temperatures. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800891m

Influence of templates on the overgrowth of MCM-41 over HY and the hydrodesulfurization performances of the supported Ni-Mo catalysts / Xiang Li in Industrial & engineering chemistry research, Vol. 48 N° 6 (Mars 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 6 (Mars 2009) . - pp. 2870–2877 Titre : Influence of templates on the overgrowth of MCM-41 over HY and the hydrodesulfurization performances of the supported Ni-Mo catalysts Type de document : texte imprimé Auteurs : Xiang Li, Auteur ; Feng Zhou, Auteur ; Anjie Wang, Auteur Année de publication : 2009 Article en page(s) : pp. 2870–2877 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : MCM-41  HY  zeolite  Ni-Mo  sulfides  Hydrodesulfurization Résumé : Overgrowth of MCM-41 on HY zeolite was performed using different templates [cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl)]. The hydrodesulfurization (HDS) performances of Ni−Mo sulfides supported over these synthesized composites were evaluated with dibenzothiophene (DBT) as the model sulfur-containing molecule. TEM and STEM images revealed that zeolite HY overgrown with an MCM-41 layer (less than 20 nm) was obtained using CTABr as the template [MY(Br)], and the MCM-41 pore channels were assumed to be oriented outward from the inner HY core. Nevertheless, for the samples synthesized using CTACl [MY(Cl)], the HY crystals were buried independently in the MCM-41 phase. Both Ni−Mo/MY(Br) and Ni−Mo/MY(Cl) showed higher HDS activity and reducibility than Ni−Mo/MCM-41. The hydrogenation activity of Ni−Mo/MCM-41 was enhanced more than the direct desulfurization activity by the introduction of HY zeolite. Ni−Mo/MY(Br) and Ni−Mo/MY(Cl) exhibited hydrocracking activities equivalent to that of Ni−Mo/MCM-41, indicating that the HDS of DBT predominantly takes place in the mesopores of Ni−Mo/MY(Br) and Ni−Mo/MY(Cl). Because the active species located in the mesopores cannot have close contact with the strong acid sites of the HY zeolite, it is suggested that the spillover hydrogen might play an essential role in the HDS reaction over the supported Ni−Mo sulfides. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801389w [article] Influence of templates on the overgrowth of MCM-41 over HY and the hydrodesulfurization performances of the supported Ni-Mo catalysts [texte imprimé] / Xiang Li, Auteur ; Feng Zhou, Auteur ; Anjie Wang, Auteur . - 2009 . - pp. 2870–2877. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 6 (Mars 2009) . - pp. 2870–2877 Mots-clés : MCM-41  HY  zeolite  Ni-Mo  sulfides  Hydrodesulfurization Résumé : Overgrowth of MCM-41 on HY zeolite was performed using different templates [cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl)]. The hydrodesulfurization (HDS) performances of Ni−Mo sulfides supported over these synthesized composites were evaluated with dibenzothiophene (DBT) as the model sulfur-containing molecule. TEM and STEM images revealed that zeolite HY overgrown with an MCM-41 layer (less than 20 nm) was obtained using CTABr as the template [MY(Br)], and the MCM-41 pore channels were assumed to be oriented outward from the inner HY core. Nevertheless, for the samples synthesized using CTACl [MY(Cl)], the HY crystals were buried independently in the MCM-41 phase. Both Ni−Mo/MY(Br) and Ni−Mo/MY(Cl) showed higher HDS activity and reducibility than Ni−Mo/MCM-41. The hydrogenation activity of Ni−Mo/MCM-41 was enhanced more than the direct desulfurization activity by the introduction of HY zeolite. Ni−Mo/MY(Br) and Ni−Mo/MY(Cl) exhibited hydrocracking activities equivalent to that of Ni−Mo/MCM-41, indicating that the HDS of DBT predominantly takes place in the mesopores of Ni−Mo/MY(Br) and Ni−Mo/MY(Cl). Because the active species located in the mesopores cannot have close contact with the strong acid sites of the HY zeolite, it is suggested that the spillover hydrogen might play an essential role in the HDS reaction over the supported Ni−Mo sulfides. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801389w

Nonconvex generalized benders decomposition with piecewise convex relaxations for global optimization of integrated process design and operation problems / Xiang Li in Industrial & engineering chemistry research, Vol. 51 N° 21 (Mai 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 21 (Mai 2012) . - pp. 7287–7299 Titre : Nonconvex generalized benders decomposition with piecewise convex relaxations for global optimization of integrated process design and operation problems Type de document : texte imprimé Auteurs : Xiang Li, Auteur ; Yang Chen, Auteur ; Paul I. Barton, Auteur Année de publication : 2012 Article en page(s) : pp. 7287–7299 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Optimization  Nonconvex Résumé : This paper considers the global optimization of challenging stochastic or multiperiod mixed-integer nonconvex programs that arise from integrated process design and operation. The difficulties of the problems are large scale and the nonconvexity involved. Recently, a novel decomposition method, called nonconvex generalized Benders decomposition (NGBD), has been developed to solve this problem to global optimality finitely, and this method shows dramatic computational advantages over traditional branch-and-bound based global optimization methods because it can exploit well the decomposable structure of such problems. Since the convergence rate of NGBD is largely dependent on the tightness of the convex relaxations of the nonconvex functions, the efficiency of NGBD can be improved by generating tighter convex relaxations. Building on the success of piecewise linearization for bilinear programs in the process systems engineering literature, this paper develops a piecewise convex relaxation framework, which can yield tighter convex relaxations for factorable nonconvex programs, and integrates this framework into NGBD to expedite the solution. Case studies of a classical literature problem and an industry-level problem show that, while NGBD can solve problems that are intractable for a state-of-the-art global optimization solver, integrating the proposed piecewise convex relaxation into NGBD helps to reduce the solution time by up to an order of magnitude. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201262f [article] Nonconvex generalized benders decomposition with piecewise convex relaxations for global optimization of integrated process design and operation problems [texte imprimé] / Xiang Li, Auteur ; Yang Chen, Auteur ; Paul I. Barton, Auteur . - 2012 . - pp. 7287–7299. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 21 (Mai 2012) . - pp. 7287–7299 Mots-clés : Optimization  Nonconvex Résumé : This paper considers the global optimization of challenging stochastic or multiperiod mixed-integer nonconvex programs that arise from integrated process design and operation. The difficulties of the problems are large scale and the nonconvexity involved. Recently, a novel decomposition method, called nonconvex generalized Benders decomposition (NGBD), has been developed to solve this problem to global optimality finitely, and this method shows dramatic computational advantages over traditional branch-and-bound based global optimization methods because it can exploit well the decomposable structure of such problems. Since the convergence rate of NGBD is largely dependent on the tightness of the convex relaxations of the nonconvex functions, the efficiency of NGBD can be improved by generating tighter convex relaxations. Building on the success of piecewise linearization for bilinear programs in the process systems engineering literature, this paper develops a piecewise convex relaxation framework, which can yield tighter convex relaxations for factorable nonconvex programs, and integrates this framework into NGBD to expedite the solution. Case studies of a classical literature problem and an industry-level problem show that, while NGBD can solve problems that are intractable for a state-of-the-art global optimization solver, integrating the proposed piecewise convex relaxation into NGBD helps to reduce the solution time by up to an order of magnitude. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201262f