Modified Soave-Redlich-Kwong Equations of State Applied to Mixtures Containing Supercritical Carbon Dioxide

Valderrama, Jose´ O.,Silva, Alexis 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

The well-known equation of state Soave-Redlich-Kwong and two of its modifications are applied to describe vapor-liquid equilibrium in binary asymmetric mixtures, which contain supercritical carbon dioxide and a heavy component. Several mixing rules including the classical van der Waals mixing rules with one and two interaction parameters, non-quadratic mixing rules, and the used of a Gibbs free energy model, are used with these equations. Seven mixtures containing supercritical carbon dioxide are considered in the study. The experimental data were obtained from literature sources and the adjustable parameters were found by minimizing the errors between predicted and experimental data of the concentration of the solute in the liquid phase. The work allows concluding on the advantages, disadvantages and expected accuracy of these equations of state and mixing rules for correlating vaporliquid equilibrium data in asymmetric systems as those studied.

Separation Technology, Thermodynamics : Modified Soave-Redlich-Kwong Equations of State Applied to Mixtures Containing Supercritical Carbon Dioxide

( Jose O. Valderrama ),( Alexis Silva ) 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.4

The well-known equation of state Soave-Redlich-Kwong and two of its modifications are applied to describe vapor-liquid equilibrium in binary asymmetric mixtures, which contain supercritical carbon dioxide and a heavy component. Several mixing rules including the classical van der Waals mixing rules with one and two interaction parameters, non-quadratic mixing rules, and the used of a Gibbs free energy model, are used with these equations. Seven mixtures containing supercritical carbon dioxide are considered in the study. The experimental data were obtained from literature sources and the adjustable parameters were found by minimizing the errors between predicted and experimental data of the concentration of the solute in the liquid phase. The work allows concluding on the advantages, disadvantages and expected accuracy of these equations of state and mixing rules for correlating vaporliquid equilibrium data in asymmetric systems as those studied.

Viscosity of ionic liquids using the concept of mass connectivity and artificial neural networks

José Omar Valderrama,Jéssica Makarena Muñoz,Roberto Erasmo Rojas 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.6

Artificial neural networks (ANN) and the concept of mass connectivity index are used to correlate and predict the viscosity of ionic liquids. Different topologies of a multilayer feed forward artificial neural network were studied and the optimum architecture was determined. Viscosity data at several temperatures taken from the literature for 58 ionic liquids with 327 data points were used for training the network. To discriminate among the different substances,the molecular mass of the anion and of the cation, the mass connectivity index and the density at 298 K were considered as the independent variables. The capabilities of the designed network were tested by predicting viscosities for situations not considered during the training process (31 viscosity data for 26 ionic liquids). The results demonstrate that the chosen network and the variables considered allow estimating the viscosity of ionic liquids with acceptable accuracy for engineering calculations. The program codes and the necessary input files to calculate the viscosity for other ionic liquids are provided.

Relationship between Body Mass Index and Complications during the First 45 Days after Primary Total Hip and Knee Replacement: A Single-Center Study from South America

Andrés Correa-Valderrama,Willy Stangl-Herrera,Andrés Echeverry-Vélez,Erika Cantor,Tamy Ron-Translateur,Julio Cesar Palacio-Villegas 대한정형외과학회 2019 Clinics in Orthopedic Surgery Vol.11 No.2

Background: The goal of this study was to evaluate the relationship between body mass index (BMI) and early complications of total hip replacement (THR) and total knee replacement (TKR). Methods: This is a retrospective study of patients who underwent primary THR and TKR between January 2011 and December 2015. We included patients between 18 and 90 years of age with BMI less than 40 kg/m2 with a minimal postoperative follow-up time of 45 days. The primary outcomes were the presence of infection, mechanical complications (dislocation, fractures, arthrofibrosis, or neuropraxia), and thromboembolic events. Overweight and obesity were defined as a BMI of 25–29.9 kg/m2 and ≥ 30 kg/m2, respectively. Results: In total 750 patients were included (THR, 268; TKR, 482) with a mean age of 65.0 ± 12.4 years. The percentage of patients with normal weight, overweight, and obesity was 24.9% (n = 187), 41.7% (n = 313), and 33.4% (n = 250), respectively. The early complication rate was 8.9% (95% confidence interval [CI], 7.1% to 11.2%). Infection and mechanical complications were most prevalent. There was no statistically significant relationship between the incidence of complications and BMI (obesity vs. normal weight: hazard ratio [HR], 1.49; 95% CI, 0.72 to 3.06; p = 0.282); however, there was a tendency toward a greater risk of infectious complications in the patients with obesity (HR, 6.08; 95% CI, 0.75 to 49.16; p = 0.090). Patients with diabetes mellitus (DM) had more risk of infectious complications than those without DM (HR, 2.60; 95% CI, 1.00 to 6.79). Conclusions: There was no statistical relationship between BMI and early complications of THR and TKR. Nonetheless, there was a tendency toward a higher risk of infection in patients with some degree of obesity.

Inhibition of cancer cell growth and migration by dihydroxynaphthyl aryl ketones

Julio Benites,Jaime A. Valderrama,David Ríos,Rosalba Lagos,Octavio Monasterio,Pedro Buc Calderon,Pedro Buc Calderon 대한독성 유전단백체 학회 2016 Molecular & cellular toxicology Vol.12 No.3

Dihydroxynaphthyl aryl ketones 1-5 exhibit activity as tubulin polymerization inhibitors by targeting the colchicine binding site of microtubules making them potential anticancer drugs. Therefore, analogues 1-5 have been evaluated for their cytotoxic activity against the cancer cell lines DU-145 (prostate), T24 (bladder) and MCF-7 (breast). Notable differences in biological activity were observed for compounds 1-5, most likely related to the nature of the aryl substituent bonded to the carbonyl group. Among the tested compounds, only compound 5 showed selectivity for cancer cells over healthy, non-transformed cells. T24 cancer cells treated with compound 5 presented a concentration-dependent decrease in cell proliferation and a loss of migration ability. The cytotoxicity of compounds 1-5 on the selected cell-based assays is discussed in terms of it lipophilicity and polarizability parameters.

수소발생기의 일차원 모델링

박재현,이효진,Edgar Willy Rimarachin Valderrama,임충식,양희성 한국추진공학회 2018 한국추진공학회지 Vol.22 No.2

This paper presents the one-dimensional model of a hydrogen generator, where the alkali solution was supplied from the top to the dry aluminum powders. Hydrogen was produced as the solution moved downward and reacted with aluminum. The species conservation equations were considered for the hydrogen gas and alkali solution, while the energy conservation equation was applied to the gas-liquid-solid mixture as a single medium. The gas rising velocity and liquid penetration velocity were also included in the theoretical approach. The developed code was validated with the experimental data of the hydrogen production amount and collector pressure. Additionally, the model successfully predicted the various reactor properties, such as the concentrations, volume fractions, and temperatures, and is expected to help significantly in the design of a novel hydrogen generator. 본 연구에서는 수소발생기에 대한 일차원 모델링을 수행하였다. 본 연구에서 고려하고 있는 수소발생기에서 알칼리용액은 위로부터 건조한 알루미늄 파우더로 공급되며, 알칼리용액이 아래방향으로 진행함에 따라 알루미늄과 반응하여 수소가 발생한다. 수소기체와 알칼리용액에 대한 화학종보존방정식과 기체-액체-고체 혼합물에 대한 에너지보존방정식을 고려하였으며, 기체의 상승속도와 액체의 하강속도는 이론적인 접근법을 이용하여 고려하였다. 개발된 프로그램은 수소발생량 및 수소포집기압력과 비교하여 검증한다. 또한, 개발된 프로그램은 농도, 부피분율, 온도 등 반응대의 내부 물성변화를 성공적으로 예측하였으며, 이는 혁신적인 수소발생기의 설계에 많은 도움을 줄 수 있을 것으로 사료된다.

Stock de Tecnología e Ingreso Per cápita en América Latina y Asia del Este y Sudeste

Cesaire Chiatchohua,Omar Neme Castillo,Ana Lilia Valderrama Santibane 한국라틴아메리카학회 2020 라틴아메리카연구 Vol.33 No.1

This paper discusses the relationship between technological stock and per capita income in 15 countries of Latin America and 12 of East Asia and Southeast Asia in the period of 1996-2017. A neoclassical endogenous growth model is developed that includes, in addition to physical and human capital, national and foreign technological stock. The econometric estimation employs a static and dynamic panel data methodology. It is estimated that the different versions of technology, classified as national, imported and exclusive of foreign companies, in addition to human capital, favor per capita income. There are also differences in per capita income between the two groups of economies.

Technological Determinants of Market Shares of Mexican Manufacturing Exports

Omar Neme Castillo,Ana Lilia Valderrama Santibane,Humberto Rios Bolivar 한국라틴아메리카학회 2011 라틴아메리카연구 Vol.24 No.1

The aim of this paper is to estimate the determinants of export market shares for Mexican manufacturing industries to United States, in order to do this; determinants related to technology are distinguished from those nonrelated to technology. Estimations are based on a theoretical model that allowed classifying industries in function of the competition process in each industry. Regarding technological aspects four categories were identified: industries with high technology, with high and low intra-industry trade, and low technology industries with high and low intra-industry. Distinction between these groups is represented by eight major elements, namely, process or product innovation, vertical or horizontal product differentiation, price or quality differences, domestic market structure, and labor costs.

A Molecular Model for Correlating Vapor-Liquid Equilibrium of Propane+Hydrocarbon Mixtures

( Claudio A. Faundez ),( Luis E. Tamblay ),( Jose O. Valderrama ) 한국화학공학회 2004 Korean Journal of Chemical Engineering Vol.21 No.6

Vapor-liquid equilibrium in low pressure water+congener mixtures

Claudio Alonso Faúndez,Felipe Andrés Urbina,José Omar Valderrama 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.5

Vapor-liquid equilibrium in binary water+congeners mixtures found in alcoholic distillation has been analyzed using the Peng-Robinson equation of state and one of the most popular modern mixing rules, the Wong-Sandler model. Accurate modeling of the concentration of congeners (substances different from ethanol and water) in the vapor phase is of special importance because these substances give some special characteristics of flavor and aroma to the final distilled spirit and also because their concentrations are regulated by law. In the Wong-Sandler mixing rules the van Laar model for the Gibbs excess energy has been used. The type of model used in this work is commonly used to correlate high pressure phase equilibrium and has not yet been used to treat complex low pressure water+congener mixtures as done in this work. Eight binary water+congeners mixtures have been considered for analysis. Comparison with available literature data is done and the accuracy of the model to correlate the pressure and the vapor phase concentration of the congeners is discussed. It is concluded that the model used is accurate enough for distillation analysis, modeling and simulation.