Papers by Keyword: Magnetic Field

Abstract: In this study, natural convection of a hybrid nanofluid inside a cubic cavity under the influence of a constant external magnetic field is numerically investigated by using control volume method. The cavity is partially heated from the left wall with uniform temperature and cooled from the opposite wall while the other sides are kept adiabatic. Analysis is focused on the impact of some parameters, including Hartmann number (0≤Ha≤100), Rayleigh number (10³≤Ra≤10⁶), nanoparticle volume fraction (0≤Φ_s≤0.06) and heater band width (1/3≤ ɛ ≤1). The Analysis of the results related to the dynamic and thermal structures, as well as the average Nusselt number, revealed that the effect of the external magnetic field exerts a negative influence on heat transfer within the cavity. However, more favorable findings were observed when the volume fraction of nanoparticles was increased, as well as when the width of the heater band was increased.

Abstract: Electrochemical Machining (ECM) is a modern metal working process that make it possible to machine products that are challenging or even impossible to create using traditional machining methods. This study aims to explore how surface roughness and machining rate in ECM are influenced by magnetic field on the metal matrix composite with different machining process input. Neodymium magnets were employed to generate the magnetic field during experiments. The workpiece material used in this experiment is aluminum 6061 alloy, Al-B4C, Al-SiC and the tool material is copper. The input parameter used in this experiment was varying such as electrolyte concentration, voltage, gap, and type of material. Minitab software was used to analyze the results and orthogonal arrays are used in the Taguchi design of the experiment. The results showed that in all experiments, the magneto hydrodynamic effect both reduces surface roughness and increases the machining rate. Furthermore, the Al6061 alloy exhibited the smoothest surface finish and the highest machining rate.

Abstract: This study investigated the characteristics of a microtool used in electrochemical microdrilling under conditions with and without magnetic field assistance. The experimental results indicated that charged ions and the direction of bubble movement were affected by the Lorentz force under the condition with magnetic field assistance, forming a vortex to promote electrolyte renewal. Reaction products and heat generated by the machining process were effectively discharged. The zone affected by stray current corrosion and microhole expansion were also reduced.

Abstract: A mathematical model of diffraction of electromagnetic microwaves on explosive materials with different physical and electromagnetic parameters has been developed. The model was constructed by solving Maxwell's equation for two surfaces separating three dielectric materials, in particular air, explosive material, and the substrate on which the explosive material is located. Different types of soil and wood are considered as the substrate material, which meets the conditions for demining large areas of the locality. The results of the numerical calculation showed that 67 % to 92 % of the energy of electromagnetic radiation is concentrated in the explosive material. In this case, trinitrotoluene, which is placed on dry sand, has the highest absorption rates, while wet wood, due to its high coefficient of dielectric permittivity, successfully transmits electromagnetic microwaves through its surface. The obtained models and numerical results are considered as theoretical basis for predicting the effectiveness of remote methods of detection and disposal of explosive materials using electromagnetic microwaves. The obtained results showed that this method will be least effective for explosive materials placed on wet wood. In this case, the lowest reflection coefficient is observed that complicates the search for explosive material and the lowest absorption coefficient that complicates the artificial detonation of explosive material due to its heating under the influence of electromagnetic microwaves.

Abstract: Welding process is very important in numerous industries ranging from automotive and aviation to shipbuilding and pressure vessel production. Nowadays new methods to improve the productivity and quality of various welding techniques are searched. In many industrial applications even small process optimizations may lead to significant cost and energy savings and new applications. Large plate welding is particularly important in shipbuilding industry. It is common to weld multiple times to join thick plates, but this approach is not optimal from energy and time effectiveness and outcome quality is limited. Alternative is single high heat input welding, which causes various problems related to rapid local overheating and the formation of inhomogeneous post-weld microstructure. There are several heat affected zones near the weld pool, which has different properties and microstructure due to different cooling rates and heat flux orientation during solidification. Since welding is a complex multiphysical process there are various parameters such as electric current, oxygen presence, heat flow and weld pool flow which influence the quality of welding joint and efficiency of the process. In this paper we aim to experimentally and theoretically investigate how to modify heat and mass transfer in the weld pool and heat affected zone by static magnetic fields. Electromagnetic force is one of the ways how to affect the weld pool flow and to influence the heat and mass transfer from the weld pool to the base metal. Our research demonstrates that moderate DC magnetic field can cause various effects on the post-weld morphology, depending on the magnetic field direction. Analytical estimates and similarity analysis for high heat input welding on EH36 shipbuilding steel shows that electromagnetic methods, like application of DC magnetic field can be promising approach for improved welding outcome in some cases.

Abstract: In this paper, we report the effects of fractional relaxation time on the parameters of blood flow together with magnetic particles through straight circular cylindrical arterial segment. A mathematical model of blood flow subject to pulsatile pressure gradient in the axial direction with external magnetic field applied normal to the direction of flow is presented. Combining the momentum equation together with the Maxwell model parameter appropriately, leads to the governing fractional partial differential equation which permits to obtain the velocity profile of blood along with magnetic particles. By adopting the non-dimensionalized form of the new version of the governing fractional partial differential equation allowed us to obtain the dimensionless relaxation time parameter λ₁ which controls blood flow conditions. Solving the fractional partial differential equations using Laplace and finite Hankel transforms we found that the influence of the order of Caputo's fractional time-derivative and fractional relaxation time on the blood flow parameters with magnetic particles are enormous. The graphical results plotted of different influential parameters are presented and discussed in details. The velocities of blood flow and that of magnetic particles are reduced under the influence of the external magnetic field and the relaxation time parameter. The magnetic particles are assumed to be uniformly distributed within the blood, since they are flowing in the same axial direction designated by along a circular cylindrical coordinates of radius. This is a very good indication that blood velocity can be controlled by the application of external magnetic field as well as the relaxation time parameter during treatment to avoid tissues damage. The present study has important applications in magnetic field control of biotechnological processes, bio magnetic device technology, biomedical engineering and pathology. Keywords: Arterial segment, Blood flow, Relaxation time, Magnetic field, Magnetic particles

Abstract: The article presents the results of studying the magnetic materials obtained via fusing metallic powder with laser radiation in static magnetic field. The powder to be fused was prepared with milling the alloy containing rare-earth and transition metals. Austenitic stainless steel was used as a substrate material for obtaining samples. The structure of the magnets obtained was studied by means of SEM. EDS was used to estimate the distribution of elements in the samples. The study of magnetic properties showed the decrease of residual magnetization and coercivity in the magnets obtained with laser fusing as compared to raw material.

Abstract: Application of energy storage systems such as supercapacitors can not be separated from the magnetic fields effect. In the last decade, it’s rare to find research reports about various low magnetic field effects on supercapacitor performance. Asymmetric supercapacitors based on MnO₂-Carbon were made to analyze its electrochemical performance changes by magnetic field in 0-50 mT. Magnetic field was applied in flow direction from cathode (MnO₂-C) to anode (C) during electrochemical performance test using Galvanostatic Charge-Discharge (C-D) instrument. The electrochemical performance was increasing in charging (91%) and discharging (22%) time of asymmetric supercapacitors. Impressively, the 50 mT magnetic field showed a high specific capacitance of 61.9 F/g at 0.1 A/g. The supercapacitor system delivers specific energy (17.8 Wh/kg), specific power density (329.72 W/kg), and outstanding stability (79% in 50 cycles). The electrochemical improvement by magnetic field indicates a highly promising application of this method in future supercapacitor devices.

Abstract: In this study Fe₃O₄-polyethersulfone (PES) membranes were prepared in the present of a magnetic field or without a magnetic field by using the phase inversion process. A comparison of membrane properties was investigated. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) were used to determine the morphology and chemical composition of the prepared membranes. Furthermore, the fouling analysis of the non-magnetized and magnetized Fe₃O₄-PES membranes were also conducted through the filtration study. The pure water flux of membranes increased from 158.49±11.96 L/m^2·hr (neat PES) to 187.06±6.54 L/m^2·hr (magnetized Fe₃O₄-PES). These results showed that the magnetized Fe₃O₄-PES membrane not only had the high pure water flux but also had a high humic acid (HA) rejection and good antifouling ability. As such, magnetized Fe₃O₄-PES membrane had excellent comprehensive properties which could use for water remediation.

Abstract: One of the key challenges for the development of perovskite solar cells lies in the approach toward large-scale fabrication of the active materials that allows for good photovoltaic performance, as well as facile handling. The electrodeposition technique can potentially address such requirements. However, the technique has yet to be investigated in detail and still suffers from low efficiency of the device. In this study, we sought to significantly upgrade the electrodeposition approach by coupling the technique with an external magnetic field in the preparation of high-quality PbI₂ precursor layer and using Li-doped SnO₂ electron transport layer. Our results showed that the magnetic field-assisted electrodeposition yielded good crystallinity of PbI₂ and perovskite. Introducing the Li-doped mesoporous SnO₂ into the device structure resulted in a higher current density of 18.50–18.80 mA cm^-2, which can be attributed to, based on the linear sweep voltammetry, reduced resistance of the electron transport layer from 32.27 to 22.11 Ω cm^-2. Moreover, the carbon-based device prepared using this simple procedure also yielded 5.20% in photoconversion efficiency for 1-cm² active area and 0.45% for 25-cm² active area, all without any significant hysteresis.