Papers by Keyword: Mathematical Modeling

Abstract: The following work aims to present the numerical solution for a two-dimensional and transient model for heat transfer on storage bins during the period of one year, in which it was supposed that the structure is exposed to ambient temperature, which depends on time. From this hypothesis, it was executed curve fitting of a relation between those quantities, using meteorological data from the city of Pelotas/RS in the year 2021, and the influence that the outside temperature of a bin has over the process of heat transfer that occurs inside the structure was analyzed. Upon executing simulations of heat transfer inside fictitious bins located in this southern Brazilian city, results show that the boundary condition causes considerable variations in grain temperature, which are more intense in points near the bin's surface. Furthermore, it was concluded that containers of least storage show larger variations in inner temperature during the analyzed period when compared to the behavior of bins containing larger sizes.

Abstract: An evaporator-absorber geometry allows the absorption of incident solar radiation andconverts it into thermal energy useful for the evaporation of a working fluid. The evaporator-absorberworks with two fluids: a heat transfer fluid transmitting heat to a working fluid, which, circulatesalong the thermal circuit composed of an evaporator, a turbine, a condenser and a pump. The aim ofthis research work is to analyze the heat transfer through the evaporator-absorber and to extract themathematical equations model the heat exchange process between the component elements of theevaporator-absorber: a serpentine tube, a working fluid and a cylindrical tube. In this case, theworking fluid is water, and the heat transfer fluid is air, which is heated by the thermal energyconverted from solar energy. The mathematical equations describing the heat transfer are extractedby using the nodal method and discretized by the finite difference method. Afterwards, the presentwork estimates the outlet temperature of each element of the evaporator-absorber and studies thestorage capacity of the cylindrical tube. Then, the water temperature distribution on the geometry ofthe evaporator and the required quantity of water and the number of spires to have a high outlettemperature of the water vapor are determined. As a result, the mathematical modeling estimated thatthe outlet temperature of the serpentine tube is higher than the outlet temperature of the water.Additionally, the temperature of the storage tube maintains its increase throughout the day. Thequality of the heat transfer in the serpentine tube is improved by placing the tube in a vertical positionand by adopting a lower volume of water compared to the maximum volume, which is supported bythis tube.

Abstract: The aim of this study was to develop and characterize a delivery system for polyphenols from an extract of Carissa spinarum leaves, based on liposomes. Liposomes loaded with Carissa spinarum polyphenols (nanoliposomal CsP) were prepared by ethanol-solvent injection method and characterized in terms of zeta potential, size, and polydipersity index by using Zeta sizer and Fourier Transform Infrared spectrum analysis. Total Phenolic content was measured by using Folin-Ciocalteu method and entrapment efficiency was evaluated. The release behavior was conducted in Phosphate Buffer Saline (PBS) solution at pH, 7.4 and Kinetic model fitted to evaluate mechanism of release. Disc diffusion sensitivity test was used to evaluate antimicrobial activity of free extract and nanoliposomal CsP. The mean diameter of nanoliposomal CsP was 181 ± 1.02 nm and had 0.345 ± 0.014 polydipersity index. Zeta potential value for nanoliposomal CsP was-45.6 ± 8.84 mV. Entrapment efficiency under the optimum conditions was 66.11 ± 1.11%. and the nanoliposomal CsP was stable over 30 days. The antibacterial activity of nanoliposomal CsP exhibited inhibition zone diameter of 14.33 ± 1.53 mm and 12.00 ± 1.23 mm against S. aureus and E. coli respectively The results reveal the Carrisa spinarum liposome can be applied as potential carrier for delivery of polyphenols to improves therapeutic action against bacterial strain.

Abstract: At present the production paradigm undergoes a fundamental change when testing of actual units involving castings manufacturing gives way to digital simulation which allows to overcome constraints intrinsic to the traditional methods of trials and errors. This article presents the work on numerical study and prediction of shrinkage porosity in Nickel alloys castings made by precision casting method for further comparison of simulation results with the size of flaws produced during actual hardware testing.

Abstract: Modeling of the temperature distribution during electric arc surfacing with a strip electrode is carried out in relation to the design scheme of a semi-infinite body. Also, in the work, the temperature distribution was calculated when a flat layer was heated by a linear source, which made it possible to compare the temperature distribution data without and taking into account the heat release conditions at the product boundaries. The simulation results showed that the control of heat input into the base metal when using mechanical control actions makes it possible to reduce the overheating of the weld pool, reduce the area of the melting isotherm, and reduce the cooling rate of the heat-affected zone. By calculation, the previously determined optimal range of values of the frequency of control actions of 40÷60 Hz was confirmed, which makes it possible to ensure the minimum depth of penetration of the base metal and obtain a favorable structure in the heat-affected zone, prone to the formation of a coarse-grained structure.

Abstract: Mathematical modeling for 3D bioprinting allows us to avoid widespread errors and also time and financial losses. It is necessary for such critical processes as tissue spheroids fusion and diffusion of nutrients in them. The reason is that tissue spheroids fusion is the base of the 3D bioprinting technology. In this work, we propose an approach for tissue spheroids fusion modeling considering a need to compromise between fidelity of the geometric form and viability of the whole bioconstruct.

Abstract: The article focuses on the main mathematical modeling principles for engineering processes. The physical model of the red mud thickening process has been formed. The choice of mathematical model type has been described where the mathematical model represents the physicochemical character of the thickening process and allows estimating pulp water-yielding features at the stage of compression. Mathematical modeling of the engineering process, based on the studies of physicochemical patterns in its course and consideration of these patterns in the mathematical model, does not have certain disadvantages. Experimental data, used at the mathematical model formation where the mathematical model represents the physicochemical mechanism of the process, serve for their further analysis, physicochemical and mathematical interpretation. The mathematical model should be used as a method for detecting internal patterns in the process and for identification and quantitative assessment of its features.

Abstract: The environmental concern of many countries seeking to conserve natural resources is driving the development, production and consumption of biodegradable composites. However, in view of their high cost, adding various fillers to composites (such as, wood flour (WF)) is promising. The advantages of using composites with wood fillers are resistance to weathering, environmental friendliness, ease of mechanical processing, and the possibility of waste disposal. To improve the properties and expand the scope of such composites, it is possible to use thermal modification of the filler, which gives wood such properties as: high hardness, water resistance, chemical and biological resistance. Thermal modification consists in heating wood in the temperature range from 150 to 230 °C without oxygen. At the same time, color properties of the material are changed definitely: an increase in the processing temperature affects darkening of wood, which leads to a change in the color characteristics of the last composite. In this regard, a regression mathematical model is proposed for easy color control prediction of the product, which is obtained as a result of composites color analysis based on polylactide (PLA) and the RGB color code. The proposed mathematical model, setting the processing temperature of wood filler, lets predicting the intensities of red, green and blue components for the subsequent visual representation of the last composition color using standard computer programs.

Abstract: The paper considers the issue of theoretical prediction of characteristics at which separation of hydrogen isotopes occurs in the “gas-metal” system. Mathematical modeling of sorption is based on the use of the lattice gas model often used for metal hydrides. In contrast to the Leicher ideal solution model, it is taken into account that the dissolution of hydrogen in the metal increases the volume of the crystal lattice. This leads to additional contributions to potential energy. The model also takes into account the interaction between the atoms of the incorporated (absorbed) hydrogen isotopes. These phenomena are described by the methods of thermodynamic perturbation theory. The different composition of the gas (protium and deuterium) in contact with the metal leads to the fact that sorption, accompanied by the formation of hydride, proceeds for the same temperature at different equilibrium pressures. This phenomenon characterizes the isotope effect. The temperature dependences of the pressure on the "plateau" for palladium hydride and deuteride are obtained. The differences in these pressures can be used for the practical use of metal hydrides in the separation of hydrogen isotopes.

Abstract: Modeling the processes of forming contact regions (interface) of the multilayer niobium-cobalt nanosystem is carried out. The morphology and composition of a multilayer nanosystem interface is investigated. The layer boundaries morphology is shown to depend on the deposition substrate temperature and, largely, is determined by preparing the surface for deposition. The work considers the deposition surface modification by removing its defects. Simulation showed that surface preparation significantly affects the morphology and composition of a multilayer nanosystem interface, depending on the type of deposited atoms and atoms forming the deposition surface.