Latin American Applied Research - An international journal

Analysis of inherent irreversibility in a reacting variable viscosity MHD mixed convection of nanofluid in a space between two concentric pipes

2024-05-12T07:28:34-03:00

This study explores mixed convection of an electrically conducting and reacting variable viscosity nanofluid in a space between two concentric vertical pipes under the combined influence of an imposed magnetic field, variable viscosity, buoyancy forces, viscous dissipation, Joule heating, axial pressure gradient, velocity slip, thermophoresis and Brownian motion. Based on the Buongiorno two-phase nanofluid model assumption, the nonlinear differential equations governing the problem are obtained and numerically solved via the shooting technique with the Runge-Kutta- Fehlberg integration scheme.

The nanofluid velocity, temperature and concentration profiles are further utilized to compute the skin friction, Nusselt number, Sherwood number, entropy generation rate and the Bejan number. The impact of various emerging parameters is examined and presented graphically. It was found that the entropy generation rate escalates with an upsurge in buoyancy forces, reaction rate, thermal Biot number, thermophoresis and Brownian motion. In contrast, a rise in magnetic field intensity lessens it.

Determining dynamic load carrying capacity for bipedal robot using torque of actuators, stability and jerk limits constraints

2024-12-02T15:31:53-03:00

The paper refers to deriving dynamic equations of motion and applications to obtain dynamic load-carrying capacity (DLCC) for bipedal robots walking. The governing equations for determining the DLCC of a given end-effector trajectory are presented at the beginning. Then via an algorithm for finding the greatest load value, the DLCC for a specified trajectory is obtained for a biped robot for the curve path.10 degrees of freedom (DOF) biped is used, and a kinematic and dynamic model for this robot was obtained. Under these conditions of research, the main limiting factor to calculating the maximum allowable load for a prescribed dynamic trajectory is the constraint of the torque actuator. At the same time, the biped robot walking dictates the need for additional constraints, that is, the stability constraints of the robot. The actuator torque constraint of the joints was formulated in this study depending on typical (torque-speed) characteristics of DC motors. The study also considers the jerk limits, an important constraint in a robotic system's dynamic motion and trajectory planning. A strategy to calculate DLCC subjected to these limitations above-mentioned is formulated. Given an arbitrary path, a general computational technique for a 10 DOF biped robot case is laid out in detail. The results showed that the value of the maximum allowable load when the end-effector moved in a curve path was 0.702 kg. The path describes the strategy of dynamic motion by controlling dynamic forces on the robot's joints where the lower values of dynamic forces lead to decreasing energy consumption, which means an increased ability to lift larger loads. Lastly, the simulation results were validated by implementing an experimental biped robot.

Study of trans-2-hexen-1-ol oxidation over metal-modified mesoporous materials

2024-09-09T11:05:49-03:00

The liquid phase oxidation of trans-2-hexen-1-ol over V-MCM-41 using H₂O₂ (30 wt.% and 55 wt.%) as oxidant was studied. The V-MCM-41 was synthesized by direct incorporation according to the sol-gel method and characterized by XRD, N₂ adsorption-desorption, UV-Vis RD, ICP-OES and FTIR. The high water/oxidant molar ratio in the reaction medium with H₂O₂ 30 wt.% had an adverse effect on the catalytic activity due to the competition between water and oxidant for the active sites of the catalyst. Additionally, a proportional relationship between H₂O₂ concentration (55 wt.%) and alcohol conversion was observed. However, a decrease in the catalytic activities was found during the recycling tests, indicating the lack of stability of the catalyst under the conditions evaluated. Therefore, 0.1 wt.% of titanium was impregnated on V-MCM-41 and three catalytic cycles were achieved without significant loss of activity. In addition, a reaction mechanism was proposed to explain the oxidation products obtained.

Radical scavenging and antioxidant activities of the extracts of globe artichoke outer bracts

2024-06-11T15:53:49-03:00

This study investigates the antioxidant activities of extracts obtained from the outer bracts of globe artichoke using the Soxhlet extraction (SE) method. To investigate the polarity effect on antioxidant activity, the extracts were prepared in distilled water, ethanol, or ethyl acetate. Different antioxidant activity determination methods were applied. According to our results, the extracts prepared with ethanol (SE-Ethanol) showed the highest total phenolic compounds (182.19 µg pyrocatechol equivalent/mg extract), the greatest sum chlorophyll amount (10.81 µg/mL), the highest metal chelating activity (47.10 %), the highest reducing power, the highest ABTS^.+(85.47 %), and DPPH^.scavenging activity (89.42 %). However, the extracts prepared using distilled water in Soxhlet extraction (SE-Water) showed the highest proline amount (41.75 µg proline/mg extract) and the highest DMPD radical scavenging activity (93.32 %). The highest total flavonoid content (168.44 µg catechin equivalent/mg extract) was observed in the extracts prepared with ethyl acetate (SE-Ethylacetate).

Improvement of dissolution rate of ticagrelor gastro-retentive tablets using HPMC and PEO

2024-05-05T05:13:34-03:00

This study aimed to develop ticagrelor (TCG) gastro-retentive (GR) tablets with improved dissolution rates by exploiting the swelling property of the polymer. Seven formulations were identified by adjusting the ratio of hydroxypropyl methylcellulose (HPMC) to polyethylene oxide (PEO) and swelling and dissolution tests were performed. Formulation A1, comprising PEO alone, had a high swelling rate of 104.68 %; however, the dissolution rate (f2=36.39) was low because of the sustained-release function of PEO. Formulation A2, comprising HPMC alone, dissolved without maintaining the tablet form, with a very high dissolution rate (f2=25.92). Therefore, the two polymers were deemed suitable to be included at an appropriate ratio. Formulation B5, which dissolved while maintaining the tablet form and exhibited an appropriate swelling rate (119.43 %) and dissolution rate (f2=62.08), was deemed suitable as a TCG GR tablet. This study confirmed the swelling of TCG GR tablets and gastric residence time in vitro.

Evaluation of wheat bran from two different cultivars from grain to bread

2024-12-17T08:20:25-03:00

Wheat bran (WB) has gained significant importance since containing some valuable nutritional compounds, predominantly dietary fibers (DFs). The aim of this study was to compare the brans of two different bread wheat cultivars from grain to bread in order to evaluate the effects of their chemical, functional and bioactive properties on bread making quality. Therefore, two different wheat cultivars obtained from Thrace region of Turkiye, named Tekirdag and Rumeli. These wheat grains were similar in terms of thousand grain weight, hectoliter weight, protein, and gluten content while gluten index and Zeleny sedimentation value of Rumeli wheat cultivar were higher (p < 0.05). After milling wheat grains, the composition of WBs were determined and significant differences were observed except for moisture and protein content. Rumeli WB contained higher insoluble and total DF, leading to have higher total water retention capacity (T-WRC). Lower T-WRC of Tekirdag WB provided to have a better bread making quality than Rumeli WB since showing higher specific volume (p < 0.05). The breads produced from these WBs were similar in terms total phenolic content (TPC) and antioxidant properties although there were significant differences between WBs in terms of TPC and antioxidant activity (p < 0.05). The results of this study are suggestive in assessing the properties of WB from different cultivars for bread quality. It was indicated that some WB characteristics such as total DF content and T-WRC showed their effects on bread making while bioactive properties of WBs were not able to maintain in corresponding breads.

Influence of Soret, Dufour and heat source in a Darcy-Forchheimer magnetohydrodynamics (MHD) flow

2024-05-03T08:32:50-03:00

The consequence of Soret, Dufour and heat source in presence of radiation and chemical reaction is been examined in a steady 2-D (two dimensional) Darcy-Forchheimer (D-F) porous MHD flow over a stretching plate using boundary layer study. A constant transverse magnetic field is also taken into account on the stretching plate in occurrence of radiation and chemical reaction. The nonlinear controlling boundary layer PDEs (partial differential equations) of momentum, temperature and concentration are changed using the similarity transformation to a set of nonlinear ODEs (ordinary differential equations). The ODEs are then solved numerically using the MATLAB bvp4c approach. Graphs are used to address the flow, heat, and concentration profiles numerically for various parameters involved in the present problem, such as the inertial parameter, Hartmann number, heat source parameter, porosity parameter, radiation parameter, chemical parameter, Soret number, Eckert number, Dufour number, Schmidt number, and Prandtl number. Also impacts in skin friction (), nusselt number (Nu) and sherwood number (Sh) are shown using graphs for different parameters. While the inertial parameter has a negative impact on the velocity profile, it has a positive impact on the temperature and concentration profiles.

Thermal and mass diffusive studies of transient free convective radiative hybrid nanofluid along an infinite vertical plate

2024-11-17T13:41:23-03:00

Objectives: This research study scrutinizes the combined effect of heat and mass transfer on the unsteady free convective flow of a hybrid nanofluid past an infinite vertical plate, considering, mass diffusion and thermal radiation. Methods: The present study examines the influence of four nanoparticles, namely Al2O3, Cu, TiO2 and Ag - on flow behavior, heat, and mass transfer. Using the Laplace transform technique, the governing equation for concentration, temperature, and velocity profiles are solved and validated against existing literature. The research includes water, nanofluids, and hybrid nanofluids with nanoparticle volume fractions ranging from 0 to 0.04, and features a graphical representation of the Sherwood number, skin friction, and Nusselt number. Findings: Results show that the velocity profiles improve with increased radiation parameters and nanoparticle concentration, while temperature profiles vary among nanofluids, with TiO2-Al2O3/water achieving optimal velocity performance and TiO2-Ag/water provides the best temperature regulation. Novelty: This research is innovative in exploring the combined effects of TiO2-Al2O3, TiO2-Ag and TiO2-Cu nanoparticles in hybrid nanofluids for transient natural convection, which has not been previously investigated. This combined effect of nanoparticles enhances the efficiency of heat exchangers, cooling systems, renewable energy technologies, material processing, and nuclear reactor cooling systems.

The role of thermal conductivity variation in MHD Carreau fluid slip flow: An analysis of heat transport in porous material

2024-11-16T06:37:48-03:00

This analysis is novel as it examines the behaviour of a Carreau hydromagnetic fluidnovelty of this analysis is to examine the behaviour slip flow in Carreau fluid u hydromagnetic fluid over a porous medium with heat transport and viscous dissipation, while accounting for the impact of thermal radiation across an elongating surface with varying thermal conductivity and thickness. It is assumed that the fluid's thermal conductivity changes linearly with temperature. The non-linear governing equations have been transformed into ODEs by employing an appropriate similarity transformation. The impact of several parameters such as porosity parameter (D), magnetic parameter (M), wall thickness parameter (alpha), velocity parameter (lambda), Heat source (Q), power index parameter (m), Thermophoresis Diffusion (Nt), Brownian motion (Nb), Schmidt number (Sc) and chemical reaction parameter (Cr) are analyzed and studied graphically. It is observed that skin friction and Nusselt number having a reverse behaviour for velocity power index (m), both growing for m<1 but has reverse effect for m>1. Lower porosity in a porous medium reduces the amount of space available for fluid to flow through, which leads to an increase in fluid velocity to maintain the flow rate. Also, the concentration profile has a reverse effect on exothermic and endothermic reactions. These techniques can help future researchers develop advance technologies. The real-world applications of this research are that it can contribute to optimizing recovery strategies, and improving reservoir simulation models for cooling electronic devices or enhancing heat exchangers, and reducing environmental impact by understanding groundwater flow through porous layers.

Unsteady chemically reactive MHD Casson fluid over a plate under convective slip boundary conditions and activation energy

2024-12-17T07:26:03-03:00

Here, a chemically reactive unsteady magnetohydrodynamic Casson fluid flow in a plate with convective slip boundary conditions and activation energy is considered. Graphs were produced to examine the implications of the model's various parameters on the temperature, concentration, and velocity profiles. The model's foremost equations are solved using MATLAB - bvp4c. The Sherwood and Nusselt numbers and the skin friction are three relevant physical parameters of engineering. To get an understanding of these factors, numerical values have been estimated for a variety of scenarios. Velocity and concentration drop as the activation energy parameter improves. The tabulated statistics demonstrate that skin friction rises when the thermal and solutal Grashof numbers grow, but boosting the Biot number has the opposite effect. The current findings are compared to those found in the literature, and they are consistent.

On the activity of low-loaded CeOx-Pd/alpha-Al2O3 and Pd-CeOx/alpha-Al2O3 catalysts for CO2 hydrogenation

2024-10-16T08:17:38-03:00

In this study the catalytic properties of low-loaded CeOx-Pd/alpha-Al2O3 and Pd-CeOx/alpha-Al2O3 catalysts for CO2 hydrogenation with and without CH4 at 873 K is investigated. It was found that the presence of ceria significantly enhanced CO2 conversion and selectivity to CO, even with Pd content of about 0.1 wt%. The Ce and Pd impregnation order did not affect the catalytic performance. While CeOx-Pd/alpha-Al2O3 catalysts exclusively produced CO, Pd-CeOx/alpha-Al2O3 exhibited selectivity to CO over 99%. Both catalyst preparations were found suitable for syngas production, as needed for the CAMERE process. In a CH4-CO2-H2 gas mixture, only the RWGS reaction occurred, and the reaction rate increased by about 5 times compared to Pd/alpha-Al2O3, depending on Ce content. Pd-CeOx/alpha-Al2O3 showed rate independence with the Ce loading, while CeOx-Pd/alpha-Al2O3 exhibited a maximum rate for 3 wt% of Ce. FTIR spectroscopy and chemisorption measurements confirmed the surface characteristics of fresh and used catalysts. CeOx-Pd/alpha-Al2O3 catalysts exhibited a surface consistent with the absence of CH4 formation and promoted the formation of adsorbed bicarbonate species, potentially as intermediate reactions involving CO2 and surface hydroxyls.

Beef sausages containing mushroom (Agaricus bisporus) powder: Physicochemical, lipid oxidation, color and sensory properties during storage

2025-01-04T14:23:11-03:00

The aim of this study was to investigate the quality of beef sausages containing mushroom (Agaricus bisporus) powder (MP) with varying rates (0, 0.5, 1.0, and 1.5 %) under cold storage for 60 days. In particular, the study focused on changes to the jelly and fat separation (JFS) of sausage batter, as well as chemical, lipid oxidation, color, and sensory characteristics in the final product. The incorporation of MP resulted in a decline in the JFS, with the most notable reduction occurring at 1.5 % MP, from 10.92 to 7.67 % within the batter. The protein content of the sausage increased from 13.46 % to 15.76 % with the addition of 1.5 % MP. The pH level, which was elevated due to the existence of basic amino acids in MP, decreased during the storage period and reached a pH value comparable to that of the control. The considerable rise in thiobarbituric acid reactive substances (TBARS) observed in the control sausages showed a marked decrease throughout the storage period in the sausages to which MP had been incorporated. Additionally, these sausages exhibited a lower free fatty acid content than the control.

Subspace-based identification integrated to recursive PLS modeling: A preliminary result

2024-04-23T19:14:31-03:00

In this work a new multivariable dynamic recursive estimation approach is presented. The overall methodology is based on the classical subspace state-space identification (4SID) theory and integrated with the recursive partial least squares (RPLS) tools. The main theory and concepts are shown and some preliminary results are displayed for the classical Shell fractionator process.

Graph neural networks: A paradigm shift in static signature classification via Delaunay triangulation

2024-12-11T11:42:44-03:00

Handwritten static signatures are a fundamental biometric characteristic extensively utilized across various sectors such as finance, law, and business. Graph neural networks (GNNs) have emerged as a promising avenue, offering inherent advantages in processing graph-based data. Inspired by the success of neural networks, the present investigation centers on harnessing the potential of GNNs for graph classification, particularly in the domain of static signature verification. The present study introduces a novel end-to-end methodology named Static Signature Verification using Delaunay Triangulation-based Graph Neural Network (DTGNN). This innovative approach involves converting static signature images into graph-structured data while integrating position embeddings to effectively preserve spatial information. By leveraging the capabilities of GNNs, especially in aggregating graph information, the approach aims to enhance the performance of static signature verification systems. It introduced novel Delaunay Triangulation-based Features for efficient model training, facilitating enhanced accuracy and reliability. The experimental assessments carried out on the GPDSsynthetic_100 and MCYT_75 datasets reveal notable improvements in performance, characterized by increased accuracy (GPDSsynthetic_100 - 99.91%; MCYT_75 - 100 %) and minimal loss (GPDSsynthetic_100 & MCYT_75 - 0.0012) utilizing our proposed approach. These results underscore the potential of DTGNN in addressing real-world verification challenges, highlighting its efficacy in writer-independent and writer-dependent static signature verification scenarios.