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Paper Title Page
Abstract: Flow in porous media occurs in many naturally-occurring and engineered systems. One of the key properties for understanding the fluid flow and pressure drop in porous media is permeability, which is varies widely among researchers. The current work presents systematic experimental data for packed spheres of uniform size (3 mm) having a porosity of 36.6% subjected to water flow. The experiments covered a sufficiently broad range of flow Reynolds number such that all flow regimes are encountered: pre-Darcy, Darcy, Forchheimer and Turbulent. The pre-Darcy regime is very scarce or non-present in the literature. As a necessary initial step, flow regimes were identified and different permeabilities exhibited by the porous medium in each flow regime were calculated. The length scales in defining the Reynolds number included the diameter of the sphere and the square root of the various permeabilities in order to study the transitional Reynolds numbers among the flow regimes. It is shown that the permeability in the Darcy regime is most appropriate and produces results consistent with accepted understanding in the literature of porous media.
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Abstract: A hybrid drying process based on the application of infrared (IR) radiation combined to non-heated air flow was proposed for bee-pollen drying. The IR source was located at a distance of 32 cm from the samples. Experiments in the hybrid dryer were conducted with pollen grains arranged in a single layer and exposed to three radiation intensity levels (150, 300 and 450 W/m2) and three air velocity levels (1.0, 2.0 and 3.0 m/s) at 25°C. The surface temperature of the material was measured during drying through an optical pyrometer. The effects of the process parameters on the drying kinetics and specific energy consumption were evaluated. Experimental results showed that for any particular air velocity increasing IR heat flux led to an intensification of mass transfer rate, decreasing drying time and thus reducing energy consumption. Minimum energy consumption in hybrid frying of pollen was associated with the application of the highest radiation intensity and lowest air velocity. It was also found that cooling effect increased with air velocity, which resulted in a decreased driving force for mass transfer and increased drying time and energy consumption.
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Abstract: Comparable analysis of the morphology of surface, IR-spectra and X-ray spectroscopy of source and mechanochemical dispersed samples of humic acid and humine of Kara-Keche coal has been made. Selective adsorption of ferricinium cation from water solutions of perchloric acid on the source and mechanochemical dispersed samples of humic acid and humine of Kara-Keche coal has been established.
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Abstract: Magnesium is one of the lightest metals and magnesium alloys have quite special properties, interest to which is continuously growing. In particular, their high strength-to-weight ratio makes magnesium alloys attractive for various applications, such as transportation, aerospace industry etc. However, magnesium alloys are still not as popular as aluminum alloys, and a major issue is their corrosion behavior.The present research investigated the influence of the PEO treatment on the corrosion behavior of MRI 230M magnesium alloy. Plasma electrolytic oxidation (PEO) of an MRI 230M alloy was accomplished in a silicate-base electrolyte with KF addition using an AC power source.The corrosion behavior of both treated and untreated samples was evaluated by open circuit potential (OCP) measurements, electrochemical impedance spectroscopy (EIS), linear polarization tests, linear sweep voltammetry (Tafel extrapolation) and chemical methods, such as mass loss and hydrogen evolution, in neutral 3.0 wt% NaCl solution.According to the tests results, PEO process can affect the corrosion resistance of MRI 230M magnesium alloy, though its action is not always unambiguous. An attempt to explain the influence of the PEO treatment on the corrosion behavior of the alloy is presented.
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Abstract: Ultra-low sulfur diesel (ULSD) is obtained by Light Gas Oil (LGO) and Light Cycle Oil (LCO) feedstocks (middle fractions from distillate petroleum). In addition to the environmental requirements related to the production of fuels with a lower content of nitrogen, technical specifications refineries also stimulate the need to remove such compounds. Nitrogenous compounds, for example, are strong inhibitors for hydrodesulfurization reactions. As Brazilian oil has a high amount of nitrogen compounds, an alternative process for nitrogen removal has been investigated, such as adsorption. In this paper, the nitrogen removal was investigated. The adsorption tests were carried out in a shaking water batchs, by performing kinetic and isotherm tests. Two commercial clays were used: Fuller's earth and bentonite.
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Abstract: In this paper a new methology for surface microgeometry modelling is presented, taking the surface of a polished magnesium alloy as an example . The proposed method essentially is based on the usage of the mathematical concept of the continuous non-differentiable manifold composed of cones. The cones’ aperture, eccentricity, height and angular orientation are model parameters, as well as the cones spread over the modelled surface. The spread of cones might be of very different nature ranging from simple deterministic patterns to purely random distribution accordingly to the theory of spatial point processes. The statistical parameters estimated in the model are: Rp, Rv, Rt, Ra, Rq, Rskew, Rkurt, the roughness distribution histogram and the bearing curve. The geometrical parameters are: surface area, surface development, surface capacity and volume. All of the computational methods have been carefully examined from the perspective of use on discrete grids. The simulated surfaces have been compared with experimental results obtained with the used AFM technique on samples of the polished AZ31 magnesium alloy. The very high level of conformity achieved between the results from the modeled surface and the experimentally obtained results gives us a promising prognosis for further use.
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Abstract: The aim of this study was to simulate the different loadings on NiTi Shape Memory Alloy in the form of wire that occurs in orthodontic praxis. Our main goals were to detect and determine the beginning of the stress-induced transformation from the austenite to martensite phases and to indicate the transformation plateau at different deformations during orthodontic treatment using in-vitro simulation. For this reason, we developed two prototype devices for in-situ simulation of orthodontic treatment by which we measured the electrical resistance and hardness. Accompanying these two properties and the microstructure observations of loaded wires by Transmission Electron Microscopy enabled us to detect successfully the stabilized stress-induced martensite due phase transformation. We found out that transformation depends strongly on the type of loading.
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Abstract: The marker method in studying the formation mechanism and defect structure of higher oxide during oxidation of lower oxide has been discussed. The approach to this problem needs specific treatment, both in experimental procedure and in the interpretation of results. It has been shown that the correct results of marker experiments in the case of highly defected substrates can be obtained, if these substrates before the marker deposition process are submitted to homogenization under highest oxidant activity, at which they remain stable at a given temperature. In addition, the nonstoichiometry must be considered in formulating appropriate chemical reactions, being the basis for foreseeing the location of markers in the interior of reaction product. The other very important problem consists in the possibility of the formation of reaction product not only on the surface of oxidized substrate but also inside of this substrate. In such a situation, the formulation of final conclusions concerning the crystalline lattice disorder from marker position should be combined with considerations of chemical reactions and transport processes occurring in a given substrate.
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Abstract: The porosity (void caused by technological reasons) in engineering materials always decrease their mechanical characteristics and usually affects the deterioration of the functional mechanical characteristics of the finished products. In the castings the porosity resulting from the specific casting processes phenomena occurs inevitably in the matrix structure. The paper shows this problem in relation to the High-Pressure-Die-Casting (HPDC) technology of Al-Si alloy. The analysis of the experimental results and the results from virtualization of HPDC process allowed to assess the effectiveness of this mixed scenario and improve the quality predictions probability for HPDC, with particular consideration of shrinkage and gas porosities. The problem of the tolerance (admissibility) of porosity occurrence in castings and the castings made of liquid Al-Si alloy to which the gas (hydrogen) was introduced intentionally are signalized.
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