Effect Of External Magnetic Field Research Articles

Experimental investigation of heat transfer characteristics of magnetic nanofluids (MNFs) under a specially designed revolving magnetic field effect

This study investigated the heat transfer characteristics of magnetic nanofluids (MNFs) under external magnetic field effects. Magnetic nanofluids used in the experiments were synthesised with Fe3O4 (iron oxide) nanoparticles (at mass ratios of 0.5, 1, and 2 %) in deionised water. Then, the thermal conductivity and viscosity values that directly affect the heat transfer results were measured after a comprehensive study on the stability of magnetic nanofluids. A unique set of experiments was designed to determine the effects of magnetic fields on different magnetic nanofluids. This system, which creates a rotating magnetic field effect, can be used stationary and with the effect of revolution at a certain speed. Heat transfer experiment results were evaluated considering average Nusselt numbers obtained from 3500 to 15,000 Reynolds numbers. The magnetic field acting on the magnetic nanofluids in heat transfer experiments was investigated for three circumstances. It was determined that the increasing rates of average Nu numbers in magnetic nanofluids with mass ratios of 0.5, 1 and 2% under the influence of constant magnetic field effects were 25, 38, and 60%, respectively, compared to deionised water. Moreover, when the magnetic field effects were constant, the increasing rates of average Nu numbers obtained 15, 20, and 33% in nanofluids with mass ratios of 0.5, 1, and 2%, respectively, compared to the case without magnetic field effects.

Experimentally determining the thermal properties of NiFe2O4 magnetic nanofluid under suitable stability conditions: Proposal the new correlation for thermophysical properties

Magnetic nanofluids are seen as new generation heat transfer fluids because they can act as smart fluids due to the fact that the applied external magnetic field effect can be easily controlled. In this study, NiFe2O4 magnetic nanofluids with 5 different mass ratios between 0.1 and 0.5% were produced with appropriate stability. Firstly, suitable stable nanofluids were prepared and their thermal conductivities, viscosities, specific heats, and densities were experimentally measured at different temperatures (20–60 °C) and concentrations. The obtained data were then used to develop artificial neural network models with MSE and R values of 9.3916E-04 and 0.99969, respectively, and a new concentration and temperature-dependent correlation was obtained for thermal properties. Furthermore, the thermal performance of the nanofluids was evaluated by comparing them with performance criteria such as the PER and Mo values, within the studied concentration and temperature range. The maximum PER value was calculated as 1.185, and the minimum Mo values for laminar flow conditions and turbulent flow conditions were calculated as 1.022 and 1.009, respectively, in the working temperature and concentration range.

Effects of external magnetic and electric field on multipactor and plasma breakdown of high-power microwave window

In this work, we investigated the effects of an external magnetic field, a DC electrostatic field, and a normal rf electric field on the multipactor and plasma ionization breakdown process near a microwave window by performing kinetic particle-in-cell/Monte Carlo collision simulations, and the underlying mechanism is also given. The magnetic field, parallel to the surface and perpendicular to the tangential rf field, can effectively suppress the electron multipactor process by delaying the electron incidence on the dielectric window and push the plasma breakdown bulk away from the dielectric window. However, when the magnetic field is too strong, the mitigation effect is not significant, and may even enhance the multipactor process at the beginning of the plasma breakdown. The external DC electrostatic field, perpendicular to the surface, can inhibit electron multipactor when it points toward the surface. On the other hand, when the DC electric field direction is reversed, then the electron multipactor process is found to be promoted, and the gas ionization bulk is closer to the dielectric window. The external normal rf electric fields perpendicular to the surface with small amplitudes are found to be capable of promoting the multipactor process. With increasing the amplitude of normal rf electric field, the multipactor process can be suppressed to some degree at the initial stage of the plasma breakdown and the gas ionization bulk region is kept away from the dielectric window surface.

Effect of external magnetic field on realistic bifurcated right coronary artery hemodynamics

Diagnostic technology based on magnetic fields is commonly used in medicine for diagnosis and therapy. However, the exposure to strong electromagnetic fields has adverse outcomes in patients. Thus, the objective of the current study is to investigate the effect of applying external uniform magnetic fields on the blood flow in both healthy and diseased cases of right coronary artery and determine the safe values of the applied magnetic field strengths. The diseased cases include a 40% stenosed artery along with two blood disorder cases with a hematocrit level of 20% and 60%. A comprehensive three-dimensional steady non-Newtonian flow model is developed using the Casson model to investigate the effect of the magnetic field on both shear rate and hematocrits. The model is numerically simulated at different values of magnetic field strengths and its orientation. The results indicated that the magnetic field in the Y-direction has a dominant effect compared to other directions. Moreover, the maximum increase in the main branch mass flow rate fraction is about 6.2%. Another interesting finding is that the wall shear stress is slightly affected by the magnetic field strength. For the stenosed case, it is found that the high magnetic field strengths can reduce the formulation of the vortices and hence reduce the risk of thrombosis, which agrees with published works. Additionally, the obtained results confirm that using a magnetic field up to 11.7 T, which is used in magnetic resonance imaging devices, is safe, and has a slight effect on blood flow parameters such as the wall shear stress.

Compensation temperatures and superparamagnetism phenomenon of a mixed spin square type Blume-Capel Ising nanowire

By using the molecular mean-field approach, a ferrimagnetic mixed spin square nanowire is dealt on the basis of Blume-Capel model. In this research paper, the core/shell structure is tested the effect of crystal fields and external magnetic fields on a ferrimagnetic mixed spin-1 and spin-7/2 square nanowire device, respectively. It is worth to note, spin-1 ions are located in the middle and in the corners of a rectangular plaquette there are four other spin-7/2 ions. One obtains a ferrimagnetic compensation behavior for the exchange interactions are modified with various crystal fields and different magnetic fields values. New features are found that the mixed spin square nanosystem has superparamagnetic behavior when DC/|J1|=0.5,−0.5, in the range −1.0≤DS/|J1|<−0.2, with KBT/|J1|=0.75, J2=−1.0, J3=−0.75, and J1=−1.0, respectively.

Investigation of external magnetic field effect on the performance of ferrofluid-based single-phase natural circulation loops

The goal of this study is to investigate the performance of a Single-Phase Natural Circulation mini Loop (SPNCmL) operating under the influence of an external magnetic field (EMF).For this purpose, a numerical SPNCmL model working with Fe3O4 ferrofluids (1–3 vol%.) under the influence of an EMF is developed to reflect the effect of a NdFeB permanent magnet with a remanence of 1.22 T located at the outlet of the cooler-end for the magnetic field generation. System characteristics such as temperature difference at heater-end (ΔTheater) and maximum temperature (Tmax) and performance in terms of effectiveness (ε) are investigated. In addition, the effect of EMF on boundary layer energy transport along the cooler-end is evaluated in terms of the change in the local Nusselt number. Applying an EMF dramatically affects the system performance in terms of an increase in ΔTheater and ε, respectively up to 34% and 25% compared to those with water. Tmax values are obtained by up to 9% higher for Fe3O4 ferrofluids compared to water, while applying EMF results in an increment in Tmax by up to 5%. Improved heat transfer performance by employing EMF at the cooler-end outlet of the SPNCmLs emphasizes their potential in cooling applications.

Effect of external magnetic field on mass transport of reactive species in the reaction between nano zero valent iron and selenate anions in a simulated flue gas desulfurization wastewater

The mechanism involved in the reaction of regulated ions with nano Zero-Valent Iron (ZVI) in the presence of an applied weak magnetic field (WMF) was investigated. The WMF effect on mass transport of reacting ions and morphology and composition of the oxide layer in nano ZVI was elucidated using Electron Energy Loss Spectroscopy (EELS). The magnetic gradient force produced by ferromagnetic ZVI particles had a greater influence on the rate of selenate diffusion in solution than the Lorentz force due to the externally applied weak magnetic field. Moreover, the magnetic gradient force was suggested to suppress ZVI corrosion reactions. Despite changes in the iron oxide layer under the WMF influence, the rate of selenate reduction has not been significantly affected over short term lasting several hours. Most crucially, WMF had a negligible effect on the rate of mass transport of selenate anions, as compared to the dominant effect of forced convection.

Catalytic LPG Conversion Over Fe-Ga Modified ZSM-5 Zeolite Catalysts with Different Particle Sizes: Effect of Confined-Space Zeolite and External Magnetic Field

Catalytic LPG Conversion Over Fe-Ga Modified ZSM-5 Zeolite Catalysts with Different Particle Sizes: Effect of Confined-Space Zeolite and External Magnetic Field

Free convection of nanofluids in a porous sensible heat storage unit: Combined effect of time periodic heating and external magnetic field

Nanofluids have gained much interest in recent years in heat transfer applications due to their improved thermal properties compared to conventional pure fluids. In many applications, the nanofluid may be subjected to unsteady heating and to the effect of external magnetic field, which can have a considerable effect on the behavior of the nanofluid, especially if the nanoparticles are metallic. In the present study, the flow and heat transfer characteristics of Cu/water nanofluid in a semi-circular cavity are analyzed. The fluid is heated by a heat source located at the bottom wall and having a time-periodic temperature profile. The other walls are adiabatic. Two magnetic sources are located on the top wall. The equations governing the flow and thermal behavior of the nanofluid are presented and converted into the dimensionless form. The equations are then solved by means of the finite volume method. The results are presented in the form of flow and thermal contours, as well as in the variation of the sensible heat, thermal stratification, and Nusselt numbers as functions of time. The impacts of various parameters, namely the temperature frequency, the magnetic number, the porosity, Darcy and Rayleigh numbers, on the results are discussed. In particular, it has been found that the porosity possessed the most important effect on the flow and thermal behaviors of the nanofluid. A 60% increase in Nusselt number is notably observed when the porosity is changed from 0.9 to 0.1.

Effect of External Magnetic Fields on the Amplitude‒Time Characteristics of Penning Ion Sources

The operation modes of pulsed Penning ion sources under the action of external magnetic fields corresponding to the operating conditions of geophysical well survey equipment are discussed. The obtained dependences of the amplitude‒time characteristics of the ion sources on the magnetic field value and configuration are reported. Based on the data obtained, options of neutron tube magnetic systems are proposed, which ensure an increase in the operation stability of neutron generators.

Effect of External Magnetic Fields on the Amplitude‒Time Characteristics of Penning Ion Sources

Effect of External Magnetic Fields on the Amplitude‒Time Characteristics of Penning Ion Sources

Modification of Landau Levels in a 2D Ring Due to Rotation Effects and Edge States

AbstractThe properties of a 2D quantum ring under rotating and external magnetic field effects are investigated. The Landau levels and their inertial effects on them are initially analyzed. Among the results obtained, it is emphasized that the rotation lifted the degeneracy of Landau levels. The second part deals with the electronic confinement in a 2D ring modeled by a hard wall potential. The eigenstates are described by Landau states as long as they are not too close to the ring edges. On the other hand, near the ring edges, the energies increase monotonically. These states are known as edge states. Edge states have a significant role in the physical properties of the ring. Thus, the Fermi energy and magnetization are analyzed. In the specific case of magnetization, two approaches are considered. In the first approach, an analytical result for magnetization is obtained but without considering rotation. Numerical results show the de Haas‐Van Alphen (dHvA) oscillations. In the second approach, rotating effects are considered. In addition to the dHvA oscillations, the Aharonov–Bohm‐type (AB) oscillations are verified, which are associated with the presence of edge states. The effects of rotation on the results are discussed and it is found that rotation is responsible for inducing AB oscillations.

Thermal stratification effect on gravity driven transport of hybrid CNTs down a stretched surface through porous medium

The purpose of the current article is to explore the impact of thermal stratification and medium porosity on gravity-coerced transport of hybrid carbon nanotubes down an upright extending sheet inspired by a constant applied magnetic field along with heat transfer investigation in existence of thermal radiation, viscous dispersal, and joule heating effect. Rectangular coordinates are chosen for the mathematical interpretation of the governing flow problem. Homothetic analysis is employed for the sake of simplification process. The reduced system of coupled nonlinear differential equations is dealt numerically by dint of computational software MATLAB inbuilt routine function Bvp4c. The numerical investigation is carried out for the distinct scenarios namely, (i) Presence of favorable buoyancy force, (ii) Case of purely forced convection and (iii) Presence of opposing buoyancy force. Significant Findings: The key findings include that the presence of hybrid carbon nanotubes and medium porosity contributes significantly to upsurging surface shear stress magnitude whereas, external magnetic field and velocity slip effects in an altered manner. The present study may be a benchmark in study of fueling process in space vehicles and space technology.

Plasmons in Z2 topological insulators

We study plasmonic excitations in the Kane-Mele model, a two-dimensional ${\mathbb{Z}}_{2}$ topological insulator on the honeycomb lattice, using the random phase approximation (RPA). In the topologically nontrivial phase, the model has conducting edge states that traverse the bulk energy gap and display spin-momentum locking. Such a state of matter is called the quantum spin hall (QSH) phase, which is robust against time-reversal (TR) invariant perturbations. We find that in the QSH phase, gapless spin-polarized plasmons can be excited on the edges of the system. The propagation of these plasmons is chiral for each individual spin component and shows spin-momentum locking for both spin components on the same edge. Moreover, we study the effect of external magnetic fields on the gapless edge plasmons. Specifically, out-of-plane magnetic fields delocalize edge plasmons propagating in one direction without affecting the other one, while an in-plane magnetic field can be applied to selectively excite a specific spin-plasmon branch with proper doping or gating to the system. Our findings may have potential applications in novel plasmonic and spintronic devices. We also investigate plasmons in the Kane-Mele model on a finite-sized diamond-shaped nanoflake and observe low-energy plasmons circulating the boundary of the material.

The effect of external force and magnetic field on atomic behavior and pool boiling heat transfer of Fe3O4 /ammonia nanofluid: A molecular dynamics simulation

BackgroundIn this study, the pool boiling heat transfer of Fe3O4 /ammonia nanofluid in a copper (Cu) nanochannel is done using the molecular dynamics (MD) simulation. MethodsTo increase and improve the performance of heat transfer, the effect of external force, and external magnetic field frequency on the atomic and thermal performance of the simulated nanostructure was checked. The results show that the density increased with a positive slope when the external force was imposed on the nanostructure with a growing trend. The amount of velocity and temperature similarly increased. So, by increasing the external force from 0.001 to 0.005 eV/Å, the maximum values ​​of density, velocity, and temperature converge to the values ​​of 0.1441 atom/Å3, 13.939 Å/fs, and 794.61 K. Moreover, increasing the applied external force caused an increase in the heat flux and thermal conductivity in the nanostructure. Finally, studying the effect of external magnetic field on the nanofluid's atomic behavior shows that with the change in the frequency of external magnetic field, Poiseuille behavior was remained. The results of the increase in the frequency of external magnetic field show the increasing trend of velocity and temperature. Numerically, the maximum values of velocity and temperature increase from 7.133 to 11.476 Å/fs, and from 210.23 to 410.07 K, respectively. Furthermore, HF increases by increasing the frequency of external magnetic field. Significant findingsAs particles' movement increased, the structure's thermal resistance decreased. So, by increasing external force, the thermal resistance in the structure decreased.

Noise and generation effects in parallel Josephson junction chains

We consider mutual effects of soliton dynamics and noise in a chain of Josephson junctions in the framework of the Frenkel-Kontorova model. The investigations are performed by the analysis of experimentally relevant quantities such as oscillation power and spectral linewidth, which both can be derived from the power spectral density of the system as, respectively, its integral and its width. Taking into account both ohmic and surface losses together with bias inhomogeneity, and considering dense soliton chain under the effect of external magnetic field, it is demonstrated that increase of the system discreteness (decrease of coupling between neighboring elements) leads to the oscillation power reduction and spectral linewidth increase, which signals about increase of the total noise in the system. Drastic increase of the linewidth is observed when the distance between elements becomes comparable with the soliton size, which is explained by an increase of stochasticity due to reflections of solitons from the system edges and noise.

Study of Magnetic and Magnetocaloric Properties of the Nano‐Graphene of Mixed Spins S = 3/2 and σ = 2: A Monte Carlo Simulation

The magnetic and magnetocaloric properties of the nano‐graphene monolayer structure consisting of mixed spins S = 3/2 and σ = 2 are studied by using Monte Carlo simulations. The ground‐state phase diagrams corresponding to several physical parameters are first discussed. The influence of the number of lattice sites on the total and partial magnetizations and the magnetic susceptibilities has been investigated. The critical temperature is deduced. The effect of exchange interaction, external magnetic, and crystal field on total magnetizations is studied. Magnetic hysteresis cycles are obtained. Specific heat change and magnetic entropy changes are inferred for several magnetic fields. Finally, the relative cooling power is determined.

Field coupling-induced synchronization of a functional neuron with magnetic field perception

It is difficult to explore the induced mechanism of neuronal firing activity and the cooperation between neurons experimentally, so some neuronal circuits are established to train mode transformation and selection. Furthermore, some functional device, for example, piezoelectric ceramic, thermistor, phototube are inset in neuronal circuits and the functional neurons are developed to perceive some specific physical signal. In this paper, a linear resistance and an ideal Josephson junction are parallelly connected to FitzHugh-Nagumo (FHN) neuronal circuit, and then a functional neuron is established to percept the induction currents induced by the external magnetic field. Some basic dynamics are analyzed in terms of two-parameter bifurcation, one-parameter bifurcation and interspike interval(ISI for short) bifurcation, it is indicated that the functional neuron is sensitive to the electromagnetic stimulation and has rich multimodal transformations. The period-adding bifurcations accompanied by multi-period and chaos between two period cascades occupy the entire bifurcation interval when the external magnetic field is given in steady state, while the irregular modal transformations between period and chaos can be observed when the functional neuron encounters a periodic external magnetic field. Furthermore, two functional neurons are bridged with a capacitor, so field coupling is induced, then the effects of coupling strengths on complete synchronization are investigated by calculating the synchronization error function and the bifurcation diagram. In addition, the local dynamics of the network node play an important role in collective behavior and synchronous transition, so two capacitor-coupled functional neurons is presented as the network nodes, and a chain neural network is constructed to explore the effects of external magnetic field and coupling strength on network synchronous behavior. Obviously, the orderliness of the neural network can enhance or destroy under different modulation of external magnetic stimulation and coupling strength. It can give insights to investigate synchronization on neural networks with field coupling and useful guidance for implementing artificial synapse for signal processing.

Effects of Fluorouracil-Carrying Nano Targeted Liposomes on Proliferation, Migration, and Invasion of Gastric Cancer Cells

Fluorouracil (FU) is a common chemotherapy drug. To overcome the shortcomings of the original drug, such as strong gastrointestinal reaction and short half-life, FU was placed in the Mahadevi layered complex (MLC) added with dextran (DEX) for surface modification to obtain the magnetic targeting nanoparticles (MLC-Dex-Fu) with sustained release. Next, the MLC-Dex-Fu was combined with liposome to obtain the FU-carrying nano targeted liposome (LMDF). MGC-803 gastric cancer (GC) cells were selected to establish the nude mouse model of GC solid tumor. The nude mice were rolled into different groups (a control group (Ctrl group), a FU group, a LMDF group without magnetic field, and a LMDF group with magnetic field). The diet and weight of nude mice were observed after interventions under the conditions of NMF and MF. The tumor tissues were removed, cleaned, cut into homogenate, transferred to the pre-cooled Eppendorf (EP) tube, and then performed with homogenation, suction by pipettes, and filtration to obtain the tumor cell suspensions of the corresponding groups. Partial tumor cell suspensions were based to analyze the cell proliferation by flow cytometry (FCT), and the other suspensions were based to investigate the migration and invasion by the Transwell method. The results suggested the cell viability in the LMDF groups was greatly decreased (P &lt; 0.05). In the nude mouse model test, LMDF exhibited a good magnetic targeted transport and sustained release chemotherapy, and could guide FU to move in vivo and enrich in the tumor site with a high concentration under the effects of external magnetic field, thus inhibiting the tumor proliferation. Such efficacy was more obvious in comparison with other groups (P &lt; 0.05).

External magnetic field effect on synthesis palladium nanoparticles via laser ablation deposited on porous silicon as a gas sensor application

External magnetic field effect on synthesis palladium nanoparticles via laser ablation deposited on porous silicon as a gas sensor application