Scielo RSS http://bibliotecadigital.uns.edu.ar/rss.php?pid=0327-079320140011&lang=pt vol. 44 num. 1 lang. pt http://bibliotecadigital.uns.edu.ar/img/en/fbpelogp.gif http://bibliotecadigital.uns.edu.ar http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100001&lng=pt&nrm=iso&tlng=pt This paper deals with the study of the thermal radiation and chemical reaction effects on an unsteady MHD free convective mass transfer flow past an accelerated infinite vertical plate embedded in a porous medium. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The dimensionless governing equations of motion are solved by using Laplace transform technique in closed form. Expressions for the velocity, temperature and concentration are obtained. The resulting velocity and temperature profiles as well as the skin-friction, rate of heat and mass transfer are shown graphically for different values of the physical parameters viz., Grashof number, Prandtl number, Schmidt number, Chemical reaction parameter, Radiation parameter, Magnetic parameter and Porosity parameter. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100002&lng=pt&nrm=iso&tlng=pt An approximate solution to the problem of steady free convective MHD flow of an incompressible viscous electrically-conducting fluid over an infinite vertical isothermal porous plate with mass convection is presented here. A uniform magnetic field is assumed to be applied transversely to the direction of the flow, taking into account the induced magnetic field with viscous and magnetic dissipations of energy. The dimensionless governing equations are solved by using the series solution method. The induced magnetic field, current density, temperature gradient and flow velocity are studied for magnetohydrodynamic body force, magnetic Prandtl number, Schmidt number and Eckert number. It is observed that the induced magnetic field is found to increase with a rise in magnetic Prandtl number. Current density is strongly reduced with increasing magnetic Prandtl number, but enhanced with Schmidt number. The acquired knowledge in our study can be used by designers to control MHD flow as suitable for a certain applications such as laminar magneto-aerodynamics, and MHD propulsion thermo-fluid dynamics http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100003&lng=pt&nrm=iso&tlng=pt In this study, antioxidant activities of H. fursei were investigated. Different model were used for assay. IC50 for DPPH radical-scavenging activity was 7.5±1.2 μg ml-1. The IC50 value for BHA was 92.9±4.5 μg ml-1. The extract showed very good reducing power that was comparable with vitamin C (p> 0.05) but showed weak nitric oxide scavenging activity and Fe2+ chelating ability. Extract showed good activity in scavenging of H2O2. Inhibition was 99.1% at 800 μg ml-1. The IC50 values for extract and BHA were 333.1±14.7 and 52.0±4.5 μg ml-1, respectively. Total phenol compounds, by the Folin Ciocalteu method, was 274±9.6 mg gallic acid equivalent/g of extract and the total flavonoid content, by AlCl3 method was 23.9 ± 1.4 mg quercetin equivalent/g of extract. Antioxidant activity may be attributed to the presence of phenols and flavonoids in the extract http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100004&lng=pt&nrm=iso&tlng=pt There is evidence that oregano essential oil has a significant antioxidant effect on the process of lipid oxidation. In order to obtain fractions enriched in antioxidant properties, oregano essential oil samples were processed by molecular distillation. Molecular distillation experiments were done in two groups of tests, using an evaporating temperature between 22 and 30 °C. Pressure was varied between 0.7 and 53 mbar. Antioxidant activity, specifically radical scavenging capacity, was analyzed in the essential oil and the distillates and residues obtained by a free radical scavenging method, using DPPH* (2,2-diphenyl-1-picrylhydrazyl). The results obtained allowed to conclude that the free radical scavenging capacity was increased in the residue fractions obtained by molecular distillation. These fractions were concentrated in thymol. The IC50 values of the residues were similar to the synthetic antioxidant BHT, suggesting that fractions concentrated in oxygen derivatives obtained by molecular distillation could be used in the food industry to retard lipid degradation http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100005&lng=pt&nrm=iso&tlng=pt In the design of civil structures, it is necessary to consider the effect of the dynamic loads caused by changes in meteorological conditions such as wind speeds or ice deposits. In Argentina, the Standard of the Argentine Electrotechnical Association (AEA, 2006) is used to calculate structures of electrical transmission networks. This Standard specifies the value that must be assigned to the load by effect of the wind. This value is obtained from the meteorological records measured at conventional meteorological stations such as those of the National Meteorological Service. Nevertheless, to fit this parameter, it is also necessary to carry out local studies with updated information, considering the roughness and, in certain cases, the relief of the ground. Computational mechanics addresses this problem and is currently being used to estimate the values of maximum winds by simulations of severe meteorological events. However, it is also necessary to evaluate the results of this tool to know its accuracy in relation to the parameters of the numerical model. This work shows the use of the Large-eddy Simulation considering two options in the choice of element size used for a geographical grid domain in the thunderstorm occurred in Aranguren, Argentina, in 1998. In the first option, a processor is used to compute this event through a 406-meter grid-spacing in horizontal direction and in the second option a four-processor parallel method is used to obtain a more refined 200-meter grid-spacing. The last option allows simulating severe events such as down-burst or vortex occurrence with more details http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100006&lng=pt&nrm=iso&tlng=pt The effect of electrolytes in the temperature profile of saline extractive distillation columns is analyzed using a Newton-Raphson based program (acronym GKTM) with a new increase-by-step technique and applied to the system 1-propanol-water-LiNO3. In addition, the E-NRTL model is examined in order to validate its capability of making accurate predictions of phase equilibrium behavior and its suitability for simulation of extractive distillation columns. Special aspects of the phase equilibrium of mixed solvents electrolyte systems are analyzed. These particular features determine the special temperature profile in these cases http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100007&lng=pt&nrm=iso&tlng=pt Growing environmental concerns, along with the search for renewable energies that emit less CO2, put biodiesel in a favorable position. Biodiesel is commonly produced by the transesterification reaction between vegetable oils and methanol or ethanol, in the presence of a catalyst. With government incentives for biodiesel production in Brazil, there was an exaggerated increase in their production and hence the concern about the disposal of surplus glycerol. Therefore research is being developed with respect to the use of the surplus of glycerol. In this context, emerged as the alternative use of fuel additives, from glycerin to contribute to the development of new applications for innovative and environmentally-friendly processes. The bibliographic review presented here starts with describing the different glycerol production processes, characterization and analysis methods. Next, Glycerol-based processing methods are described, evaluating the main reaction parameters that interfere in process optimization http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100008&lng=pt&nrm=iso&tlng=pt The magnetohydrodynamics (MHD) boundary layer flow of nanofluids past a permeable moving flat plate with convective heating at the plate surface has been studied. The nanofluids considered contain water as the base fluid with copper (Cu) or Alumina (Al2O3) as the nanoparticles. The model equations are obtained and solved numerically by applying shooting iteration technique together with the fourth order Runge-Kutta-Fehlberg integration scheme. The influence of pertinent parameters on velocity, temperature, skin friction and Nusselt number are investigated. The obtained results are presented graphically and the physical aspects of the problem discussed quantitatively http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100009&lng=pt&nrm=iso&tlng=pt The objective of this contribution is to propose a reliable strategy to solver the problem of phase equilibrium calculations for non-ideal systems, using the Gibbs free energy minimization. This type of problem, using the Gibbs free energy minimization, is usually formulated as a Mixed Integer Non-Linear Programming (MINLP) Optimization. This optimization problem allows the compositions to be associated with continuous variables, and the presence of phases in the equilibrium to be associated with the integer variables. The solution strategy proposes a bi-level approach. The first level combines a stochastic (Simulated Annealing - SA) and a local deterministic algorithm (Sequential Quadratic Programming - SQP), and solves a Non Linear Programming Problem (NLP). The continuous variables are considered at this level. The second level considers the integer variables. The advantage of this bi-level strategy lies in its easy implementation and in its proven efficiency to locate global optima with acceptable computational load. This article includes the study of the Water-Ethanol-Cyclohexane and Water-Ethanol-Glycerin systems. A comparative analysis was conducted using experimental data reported in published works and theoretical calculations by means of the Gamma-Phi classic method. http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100110&lng=pt&nrm=iso&tlng=pt Theoretical investigation is presented here for the model of unsteady MHD thermal convection flow of a viscous incompressible absorbing-emitting optically thin gray gas along an impulsively-started semi-infinite vertical plate adjacent to the Darcian porous regime in the presence of a first order chemical reaction and significant thermal radiation effects. The conservation equations are nondimensionalized and are solved by an accurate and unconditionally stable implicit finite difference scheme of Crank-Nicholson type. The flow is found to be accelerated with increasing porosity parameter (K), whereas the temperature and concentration distributions are reduced in the Darcian regime. Flow velocity and Temperature are found to be depressed with progression of thermal radiation (Ra) contribution, but enhanced the concentration distribution. Applications of the model arise in solar energy collector analysis, magneto-fluid dynamics and industrial materials processing http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100111&lng=pt&nrm=iso&tlng=pt This paper presents an analysis of the Reed Solomon encoder model and GF (2m) multiplier component, with the aim of optimizing the power consumption for reconfigurable hardware. The methods used consisted of concatenation and reassignment circuit signals in the VHDL description. This treatment allowed achieving a reduction in the consumption of hardware resources and optimizing power consumption in the multiplier of 7.89%, which results in a reduction of the dynamic power of a 42.42% in the coder design optimized. With this development, it provides a design method with good performance, which can be applied to other circuits http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100112&lng=pt&nrm=iso&tlng=pt Acetone and dichloromethane were used as organic solvent to prepare ibuprofen-loaded PLGA microspheres by the emulsion-solvent evaporation method. Some microspheres properties, such as microencapsulation efficiency and particle size, were affected by the organic solvent used. Depending on the organic solvent used microparticles obtained exhibited different controlled release profiles. In all cases it was extended up to 15 days. The obtained formulations did not exhibit zero- or first-order release kinetics and non-agreement with the Higuchi or Korsmeyer-Peppas models was found. On the other hand, the model proposed by Gallagher and Corrigan for PLGA systems described fully the drug dissolution processes from the microspheres obtained. A relationship between the ibuprofen solubility in both organic solvents studied and some parameters estimated for the dissolution model of the microparticles prepared with these solvents was also found. Thus, it could be propose that the drug solubility in different organic solvents affects the physical characteristics of microparticles and their dissolution profiles http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100113&lng=pt&nrm=iso&tlng=pt Ultrasonic velocities and density of various concentrations (0.01 to 0.10M) of anti protozoal drog "Diloxanide Furoate" in methanol, dimethyl formamide and 1,4-dioxan have been measured at 308.15 K by using single crystal variable path ultrasonic interferometer operating at 2 MHz and pycnometer respectively. Using these experimental data, some acoustical parameters have been evaluated and they are interpreted in terms of solute-solute and solute-solvent interactions in these solutions http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100114&lng=pt&nrm=iso&tlng=pt We investigate a local similarity solution of an unsteady natural convection heat and mass transfer boundary layer incompressible fluid flow past a moving vertical porous plate in the presence of the heat absorption and generation. The effects of chemical reaction rate which is function of temperature and Arrhenius activation energy on the velocity, temperature and concentration are also studied in this paper. The governing partial differential equations are reduced to ordinary differential equations by introducing local similarity transformation (Maleque, 2010a). Numerical solutions to the reduced non-linear similarity equations are then obtained by adopting Runge-Kutta and shooting methods using the Nachtsheim- Swigert iteration technique. The results of the numerical solution are then presented graphically in the form of velocity, temperature and concentration profiles. The corresponding skin friction coefficient, the Nusselt number and the Sherwood number are also calculated and displayed in table showing the effects of various parameters on them http://bibliotecadigital.uns.edu.ar/scielo.php?script=sci_arttext&pid=S0327-07932014001100115&lng=pt&nrm=iso&tlng=pt In the operation process of centrifugal pumps, especially in multi-stage pumps, axial force is one of the main factors which affect the pump safety and reliability. This paper presents the axial force study in a deep-well centrifugal pump (DCP) with theoretical calculation, numerical simulation and experimental measure. Three different calculation formulas were respectively introduced and used in the model pump. The calculated results were compared and analyzed with the numerical simulation values and experimental results, and the detailed numerical simulation methods and experimental configuration were explained. Finally, the more accurate formula for calculating the axial force in oblique flow centrifugal impeller was selected out. At the rated flow point, the deviation of the axial force obtained by numerical simulation and the experimental value is approximately 3.8%, and the calculated result of selected formula only less than the experimental results of 2.6%. The results provide a theoretical basis for the axial force calculation in the centrifugal impeller design process