Artículos en Revistas

Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/538

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Author: search.filters.author.Clementi, Luis A.

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    Alternativas para mejorar la eficiencia energética de un complejo industrial aprovechando calores residuales y energía fotovoltaica
    (Revista de la Asociación de Energías Renovables y Ambiente, 2021-06-10) Sangoi, Emmanuel; Vega, Jorge Rubén; Clementi, Luis A.
    En este trabajo se propone un modelo simplificado para el sistema energético de un complejo industrial petroquímico autoabastecido mediante cogeneración. El modelo se parametriza con datos disponibles en el complejo y se usa para evaluar el impacto de la incorporación de fuentes alternativas en su matriz energética. En este sentido, se analizan tres alternativas de configuración para el sistema energético actual del predio. Se propone aprovechar calores residuales con generadores eléctricos basados en ciclos Rankine orgánicos y energía solar con generadores fotovoltaicos. Luego se consideran distintas alternativas de penetración de estos recursos en base a factores ambientales de la zona y se comparan los resultados con el desempeño de la configuración actual. Se concluye que, al considerar otros recursos disponibles en el predio, es posible mejorar la eficiencia del sistema, diversificar su matriz energética y reducir el impacto ambiental.
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    Capillary hydrodynamic fractionation of hydrophobic colloids: errors in the estimated particle size distribution
    (2013) Vega, Jorge Rubén; Clementi, Luis A.; Arretxe, Zohartze; Aguirreurreta, Ziortza; Agirre, Amaia; Leiza, José R.; Gugliotta, Luis M.
    Capillary hydrodynamic fractionation (CHDF) with turbidity detection at a single wavelength is an analytical technique that is often used for sizing the submicrometric particles of hydrophobic colloids. This article investigates three sources of errors that affect the particle size distribution (PSD) estimated by CHDF: diameter calibration errors, uncertainties in the particle refractive index (PRI), and instrumental broadening (IB). The study is based on simulated and experimental examples that involve unimodal and bimodal PSDs. Small errors in the diameter calibration curve can produce important deviations in the number average diameter due to systematic shifts suffered by the PSD modes. Moderate uncertainties in the PRI are unimportant in the analysis of unimodal PSDs, but in the specific case of bimodal PSDs, errors in the PRI can strongly affect the estimated number concentration of each mode. The typical IB correction (based on the IB function estimated from narrow standards) produces slightly erroneous average diameters but can lead to PSDs with underestimated widths and distorted shapes. In practice, the three investigated sources of errors can be present simultaneously, and uncertainties in the average diameters, the shape and width of the PSD, and the number concentration of the PSD modes are unavoidable.
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    Estimation of the particle size distribution of colloids from multiangle dynamic light scattering measurements with particle swarm optimization
    (2015) Vega, Jorge Ruben; Clementi, Luis A.
    In this paper particle Swarm Optimization (PSO) algorithms are applied to estimate the particle size distribution (PSD) of a colloidal system from the average PSD diameters, which are measured by multi-angle dynamic light scattering. The system is considered a nonlinear inverse problem, and for this reason the estimation procedure requires a Tikhonov regularization method. The inverse problem is solved through several PSO strategies. The evaluated PSOs are tested through three simulated examples corresponding to polysty-rene (PS) latexes with different PSDs, and two experimental examples obtained by simply mixing 2 PS standards. In general, the evalu-ation results of the PSOs are excellent; and particularly, the PSO with the Trelea’s parameter set shows a better performance than other implemented PSOs.
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    Randomly-branched polymers by size exclusion chromatography with triple detection : computer simulation study for estimating errors in the distribution of molar mass and branching degree
    (2013) Vega, Jorge Rubén; Clementi, Luis A.; Meira, Gregorio
    This article theoretically evaluates the biases introduced into the distributions of molar masses (MMD) and the number of long chain branches per molecule (LCBD), when randomly-branched polymers are analyzed by size exclusion chromatography (SEC) with molar mass-sensitive detectors. The MMD of a polymer with tetrafunctional branch units has been calculated with the Stockmayer equation (1943); and an ideal SEC analysis has been simulated that assumes u-solvent, perfect measurements, and perfect fractionation by hydrodynamic volume except for a minor mixing in the detector cells. In ideal SEC, a negligible bias is introduced into the MMD, with the local dispersity exhibiting a maximum of 1.0035 at the high molar masses. This result is consistent with previous theoretical investigations, but differs qualitatively from experimental observationsofpolymerscontainingshort-andlong-chain branches. When including band broadening in the columns while still assuming perfect measurements, the MMDremainsessentiallyunbiased.Incontrast,poorMMD estimates are obtained when the chromatograms are contaminated with additive noise. Only qualitative estimates of the LCBD are possible, due to theoretical limitations combined with propagation of errors in a highly nonlinear calculation procedure.