Browsing by Author "Ricardo Perez Correa, J."

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    Experimental determination and theoretical modeling of the vapor-liquid equilibrium and surface tensions of hexane plus tetrahydro-2H-pyran
    (ELSEVIER, 2012) Mejia, Andres; Segura, Hugo; Cartes, Marcela; Ricardo Perez Correa, J.
    Isobaric vapor-liquid equilibrium (VLE) data have been measured for the binary system hexane + tetrahydro-2H-pyran at 50, 75, and 94 kPa and over the temperature range 321-358 K using a vapor-liquid equilibrium still with circulation of both phases. Atmospheric surface tension data have been also determined at 303.15 K using a maximum bubble pressure tensiometer. Experimental results show that the mixture is zeotropic and exhibits slight positive deviation from ideal behavior over the experimental range. Surface tensions, in turn, exhibit negative deviation from the linear behavior.
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    Fast and reliable calibration of solid substrate fermentation kinetic models using advanced non-linear programming techniques
    (UNIV CATOLICA DE VALPARAISO, 2007) Macarena Araya, M.; Arrieta, Juan J.; Ricardo Perez Correa, J.; Biegler, Lorenz T.; Jorquera, Hector
    Calibration of mechanistic kinetic models describing microorganism growth and secondary metabolite production on solid substrates is difficult due to model complexity given the sheer number of parameters needing to be estimated and violation of standard conditions of numerical regularity. We show how advanced non-linear programming techniques can be applied to achieve fast and reliable calibration of a complex kinetic model describing growth of Gibberella fujikuroi and production of gibberellic acid on an inert solid support in glass columns. Experimental culture data was obtained under different temperature and water activity conditions. Model differential equations were discretized using orthogonal collocations on finite elements while model calibration was formulated as a simultaneous solution/optimization problem. A special purpose optimization code (IPOPT) was used to solve the resulting large-scale non-linear program. Convergence proved much faster and a better fitting model was achieved in comparison with the standard sequential solution/optimization approach. Furthermore, statistical analysis showed that most parameter estimates were reliable and accurate.
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    Hybrid simulation-optimization based approach for the optimal design of single-product biotechnological processes
    (PERGAMON-ELSEVIER SCIENCE LTD, 2012) Brunet, Robert; Guillen Gosalbez, Gonzalo; Ricardo Perez Correa, J.; Antonio Caballero, Jose; Jimenez, Laureano
    In this work, we present a systematic method for the optimal development of bioprocesses that relies on the combined use of simulation packages and optimization tools. One of the main advantages of our method is that it allows for the simultaneous optimization of all the individual components of a bioprocess, including the main upstream and downstream units. The design task is mathematically formulated as a mixed-integer dynamic optimization (MIDO) problem, which is solved by a decomposition method that iterates between primal and master sub-problems. The primal dynamic optimization problem optimizes the operating conditions, bioreactor kinetics and equipment sizes, whereas the master levels entails the solution of a tailored mixed-integer linear programming (MILP) model that decides on the values of the integer variables (i.e., number of equipments in parallel and topological decisions). The dynamic optimization primal sub-problems are solved via a sequential approach that integrates the process simulator SuperPro Designer (R) with an external NLP solver implemented in Matlab (R). The capabilities of the proposed methodology are illustrated through its application to a typical fermentation process and to the production of the amino acid L-lysine. (C) 2011 Elsevier Ltd. All rights reserved.
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    Parameter estimation in metabolic flux balance models for batch fermentation - formulation & solution using Differential Variational Inequalities (DVIs)
    (SPRINGER, 2006) Raghunathan, Arvind U.; Ricardo Perez Correa, J.; Agosin, Eduardo; Biegler, Lorenz T.
    Recent years have witnessed a surge in research in cellular biology. There has been particular interest in the interaction between cellular metabolism and its environment. In this work we present a framework for fitting fermentation models that include this interaction. Differential equations describe the evolution of extracellular metabolites, while a Linear Program (LP) models cell metabolism, and piecewise smooth functions model the links between cell metabolism and its environment. We show that the fermentation dynamics can be described using Differential Variational Inequalities (DVIs). Discretization of the system and reformulation of the VIs using optimality conditions converts the DVI to a Mathematical Program with Complementarity Constraints (MPCC). We briefly describe an interior point algorithm for solving MPCCs. Encouraging numerical results are presented in estimating model parameters to fit model prediction and data obtained from fermentation, using cultures of Saccharomyces cerevisiae reported in the literature.
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    Vapor-Liquid Equilibrium, Densities, and Interfacial Tensions of the System Ethanol plus Tetrahydro-2H-pyran
    (AMER CHEMICAL SOC, 2012) Mejia, Andres; Segura, Hugo; Cartes, Marcela; Ricardo Perez Correa, J.
    Isobaric vapor liquid equilibrium (VLE) data have been measured for the binary system ethanol + tetrahydro-2H-pyran at (50, 75, and 94) kPa and over the temperature range (331 to 358) K using a vapor-liquid equilibrium still with circulation of both phases. Mixing volumes were also determined at 298.15 K and atmospheric pressure with a vibrating tube densimeter, while a maximum differential bubble pressure tensiometer was used to measure atmospheric interfacial tensions at 303.15 K. According to experimental results, the mixture exhibits positive deviation from ideal, behavior, and minimum boiling point azeotropy is present at mid-range concentrations (0.55 < x(1)(Az) < 0.67). VLE measurements show also that the azeotropic mole fraction impoverishes in ethanol as pressure (or temperature) increases. The mixing volumes of the mixture evolve from positive to negative deviations as the concentration of ethanol increases. Finally, it is experimentally observed that the interfacial tensions exhibit positive deviations from the linear behavior. The VLE data of the binary mixture satisfy Fredenlund's consistency test and were well-correlated by the Wohl, nonrandom two-liquid (NRTL), Wilson, and universal quasichemical (UNIQUAC) equations for all of the measured isobars. The mixing volumes and interfacial tensions, in turn, were satisfactorily correlated using the Redlich-Kister equation.