Nonuniform Electromagnetic Field Research Articles

Effects of 60 Hz Non- Uniform Electromagnetic Fields on Tomato (cv L-05) Seed Germination, Photosynthesis and Seedling Growth Under Salt Stress Conditions.

Effects of 60 Hz non-uniform electromagnetic fields (EMFs) on the tomato (cv. L-05) seed germination, photosynthesis, and seedling growth under salt stress and laboratory conditions were investigated. A previous trial investigated the impact of salt stress levels (0, 40, 60, 80, and 100 mM NaCl) on tomato seeds, and the 100 mM NaCl level was selected to study the effects of EMFs in attenuating salinity stress on germination, physiology, and growth of tomato seedlings. In the second experiment, untreated seeds and seeds treated with nonuniform EMFs of 2, 4 and 6 mT for 9 min were exposed to a 100 mM NaCl saline solution (SS). The results of the first bioassay showed that the addition of SS drastically reduced the germination percentage (67%), mean germination time (54%), mean germination speed (69%), germination rate index (39%), and germination vigor (78%) of tomato seeds when compared to the control treatment. In the second experimental trial, the effect of pretreatment of tomato seeds with EMFs of 2 or 4 mT for 9 min exposed to SS stress revealed a significant increase in the germination percentage (224%-226%) and germination rate (128%-151%). Salinity stress drastically reduced the tomato seed germination while 60 Hz nonuniform EMFs induced a mitigating response of tomato seeds under salinity stress to improve the germination, photosynthesis, and seedling growth. The 60 Hz nonuniform EMFs of 4mT for 9 min showed the best biological responses under salinity stress. Applied EMFs to tomato seeds protect tomato plants under salinity stress. Bioelectromagnetics. 00:00-00, 2024. © 2024 Bioelectromagnetics Society.

Influence of cross baffle on heat transfer of nanofluid flow inside circular pipe in existence of electromagnetic field: Computational study

The usage of electromagnetic sources for the improvement of the heat transfer of ferrofluid is an efficient method in heat exchangers. In this article, the effects of the non-uniform electromagnetic field on the thermal characteristics of the nanofluid with 4 % nanoparticles of Fe3O4 streaming inside the pipe with a double cross barrier are extensively investigated. To simulate the nanofluid flow, Computational Fluid Dynamic is applied and a three-dimensional model is chosen to reveal the main effects of the electromagnetic field on the thermal efficiency of the nanofluid flow. The main novelty of this work is related to the application of the cross baffle and non-uniform magnetic field for the heat transfer improvements. The achieved results show that the existence of the electromagnetic field and cross barrier facilitates the production of the vortex inside the pipe. Therefore, the thermal layer diffusion into the stream more efficiently, and the thermal efficiency of nanofluid is improved. The influence of magnetic field intensity also shows that increasing the thermal efficiency is a direct function of magnetic source intensity.

Analytical determination of a quasi-stationary electromagnetic field created by magnetic moments and eddy currents in conducting half-space

Aim. Study of the distribution of a three-dimensional alternating quasi-stationary electromagnetic field at the surface of conducting half-space with strong skin-effect, the source of which is an arbitrarily oriented magnetic moment. Methodology. The expressions for non-uniform electromagnetic field with strong skin effect are used for the analysis, which is based on the found exact analytical solution of the general three-dimensional problem and the use of expansion into asymptotic series with respect to a small parameter that is proportional to the ratio of the field penetration depth to the distance between the sources of the external field and the surface of body. Specific expressions at the surface are completely determined by the known field of external sources. In this work, the external magnetic moment field is used. Results. For strong skin effect, expressions for the electric and magnetic field strength are obtained separately for the components of the magnetic moment oriented perpendicularly and parallel to the flat surface between the dielectric and conducting areas. The features of the electromagnetic field distribution are analyzed depending on the value of introduced small parameter. The results are presented for the module and phase shift of the field strength with respect to the phase of the external field source. Originality. The expressions found for the electromagnetic field appear to be more general than the use of closed contours with alternating current, since they extend types of external field sources and allow the use of the superposition method instead of integration over the entire contour. Practical value. The found specific analytical expressions of the electromagnetic field at the surface for the external field of magnetic moments significantly simplify the solution of the problems, since they do not require additional solution of the field equations. References 20, figures 8.

Dirac materials in parallel non-uniform electromagnetic fields generated by SUSY: a chiral Planar Hall Effect

Within a Supersymmetric Quantum Mechanics (SUSY-QM) framework, the (3+1) Dirac equation describing a Dirac material in the presence of external parallel electric and magnetic fields is solved. Considering static but non-uniform electric and magnetic profiles with translational symmetry along the y-direction, the Dirac equation is transformed into two decoupled pairs of Schrödinger equations, one for each chirality of the fermion fields. Taking trigonometric and hyperbolic profiles for the vector and scalar potentials, respectively, we arrive at SUSY partner Pöschl-Teller-like quantum potentials. Restricting to the conditions of the potentials that support an analytic zero-mode solution, we obtain a nontrivial current density perpendicular to the electric and magnetic fields, thus, defining a plane where these three vectors become coplanar, indicating the possibility of realizing the Planar Hall Effect. Furthermore, this non-vanishing current density is the sum of current densities for the left- and right-chiralities, suggesting that the net current is a consequence of chiral symmetry. Possible application in current steering of solitonic nature through a Type-I Weyl semimetal is discussed.

An Extended Asymptotic Model for Fast Evaluation of the Induced Current on Multiconductor Transmission Lines Excited by the High-Frequency Nonuniform Electromagnetic Field

An Extended Asymptotic Model for Fast Evaluation of the Induced Current on Multiconductor Transmission Lines Excited by the High-Frequency Nonuniform Electromagnetic Field

Dirac materials in parallel electromagnetic fields generated by supersymmetry

In a Supersymetric Quantum Mechanics framework, the Dirac equation describing a Dirac material in the presence of electromagnetic fields is solved. Considering parallel static non-uniform electromagnetic fields, the Dirac equation is transformed into a two-dimensional system of equations. By means of variable separation, we can define one-dimensional eigenfunctions, which are solutions for two pairs of supersymmetric partner Schrödinger-like Hamiltonians. For Pöschl-Teller-like quantum potentials, we look for conditions that guarantee the existence of bound states, and determine an analytic zero-mode solution for the Dirac equation.

Spin dynamics in nonuniform electromagnetic wave fields

Based on solution of Dirac equation, the dynamics of a quantum particle with a half-integer spin (fermion) in the field of an arbitrary inhomogeneous electromagnetic wave has been analysed revealing some features of bound motion defined by so-called optical lattice (channeling). It is shown that, in the first order of expansion in longitudinal energy, the effective interaction potential of a fermion coincides with that of a scalar particle, while the spin features of interaction in this field appear only in the next expansion term. Semiclassical approximation in a spin dynamics for an arbitrary particle in an inhomogeneous optical lattice field indicates that at channeling conditions the polarisation vector affirms a smooth precession, the rate of which is defined by the difference between the magnetic moment of the particle and its anomalous part.

Improved Coil Design for Magnetic Pulse Welding of Metallic Sheets

Magnetic pulse welding of overlapping dissimilar metallic sheets is an emerging technique and usually employs flat electromagnetic coils with rectangular-, H-, I-, and E-shaped cross-sections. The asymmetric cross-section of these coils results in a non-uniform electromagnetic field and in a non-uniform connection in the interface between the overlapping sheets. In this article, the use of a novel O-shaped flat coil is proposed to join an aluminium flyer sheet with a target steel sheet. A finite element-based numerical model is developed to calculate the electromagnetic field, flyer velocity, and its gradual impact onto the target, and the deformations of the sheet assembly. The calculated results with the O-shaped coil show a high-intensity electromagnetic field, the concentration of which decreases radially outwards in a uniform manner. The numerically computed and experimentally measured flyer velocity are found to be in fair agreement. The calculated results show a regularly decreasing impact behaviour between the flyer and target and their resulting deformation. The measured results show the formation of an annular ring-shaped joint profile that is generally found to be stronger compared to that obtained with flat coils with a rectangular cross-section.

An Efficient Model of the Transmission Lines Excited by the External Nonuniform Transient Electromagnetic Field Using the MPM

This letter proposes a modeling approach to handle nonuniform transient electromagnetic field coupling to transmission lines (TLs). In this approach, the matrix pencil method is applied to express the complex-valued external electric field at the horizontal direction along the TL by the first order of the exponential function in the frequency domain. The fitting procedure of the MPM only contains several matrix computation steps and does not need the initial value or any searching process, which leads to a significantly higher fitting efficiency. Moreover, the fitted results are formed with the first order of the exponential function, which ensures that the analytical solution of the TL equation can be formulated and thus has a high calculation efficiency. The proposed method was validated experimentally using a large scale of radiated wave simulator.

Study of Quench Behavior of No-Insulation REBCO Pancake Considering Complex Critical Current Density Distribution

This study analyzes the quench behavior of No-insulation (NI) REBCO pancake. An quench analysis simulation model considering the complex critical current density distribution was developed and validated experimentally. The developed model includes an equivalent circuit model, a thermal model, a magnetic model, and a magnet critical current estimation model. The simulation model is based on a co-simulation using MATLAB and COMSOL, considering the balance of accuracy and computation time. The lumped parameter of the NI magnet was used to solve the governing equations of the equivalent circuit module and thermal module in MATLAB. To accurately calculate the non-uniform electromagnetic field distribution over the coil, a magnetic finite element method was used in COMSOL. A neural network was used to predict the temperature-field-angle dependent magnet critical current. Considering the numerical convergence at different over-current phases, adaptive simulation was used to reduce the total simulation time. The quench behavior was analyzed using the proposed model, and the results were verified experimentally. The simulation results showed that when the azimuthal current is greater than the magnet critical current, it will gradually saturate and approach the magnet critical current, and then decrease at a similar speed. The rate of decrease is equal to the rate of decrease of the magnet critical current. Through the analyses, the corresponding sudden-discharging behavior was simulated and analyzed. The proposed model can be used to perform the post-quench and sudden discharging analyses of pancake coil and has promising applications in multi-pancake post-quench studies.

Novel strategy for enhanced visible light-responsive photoactivity of ZnFe2O4 with a single-mode microwave combustion process: Primary parameters

To date, the inferior physicochemical properties of nanomaterials synthesized with a household microwave (MW) oven have been attributed to a large extent to the non-uniform electromagnetic field. Herein, we developed a single-mode MW combustion process (MCP) considering criteria of green chemistry and further annealled the amorphous ZnFe2O4-based sol–gel precursors. The preferred single-mode MCP-based parameters mainly include 7 g : 2 g of the mass ratio (w/w) of SiC : sol–gel precursors, 1 : 1.5 of initial molar ratio of citric acid : metal ions (CA : M), 300 ℃ ∼ 600 ℃ range of the calcination temperature, N2 atmosphere of 3 L/min as well as the washing pretreatment of precursors. Moreover, based on Mössbauer spectroscopy, we infer that the reduction of structural ferric ions into ferrous ions in the lattice resulted in excellent magnetic separation of multiphase heterojunctions ZnO@ZnFe2O4 during a single-mode MCP. Furthermore, the ζ potentials of ZnO@ZnFe2O4 and ZnFe2O4 indicate that cationic dyes could be spontaneously adsorbed onto the negatively charged surface of ZnO@ZnFe2O4. Thus, the visible-light-driven catalytic mechanism of ZnO@ZnFe2O4 was also proposed. Additionally, the aforementioned single-mode MCP strategy could also endow P25-based TiO2 with excellent visible light-responsive photo-activities for effective degradation of estradiol. To our best knowledge, this is the first report associated with a novel single-mode MCP method to endow ZnO@ZnFe2O4 or P25-based TiO2 with an enhanced visible light-responsive (λ ≥ 420 nm) photoactivity.

A computational study for the effects of sample movement and cavity geometry in industrial scale continuous microwave systems during heating and thawing processes

Microwave (MW) applications in food processing are used to reduce process time and increase process efficiency. While 915 MHz frequency is dominant for industrial processes, 2450 MHz systems are also observed. Attained temperature uniformity is specific concern with significant effect of the non-uniform electromagnetic field distribution due to the cavity geometry and design. Therefore, the objective of this study was to determine the cavity geometry effect with applied frequency and to present industrial scale continuous process system with a computational approach. A computational model was developed for heating and thawing processes, and experimental validation was completed in a cylindrical MW cavity. Sample rotational movement and cavity geometry effects (conventional rectangular versus cylindrical, ellipsoidal and triangular) were determined, and industrial scale system designs were presented with frequency effect. Temperature change and electromagnetic field distribution were also introduced for improved design. The results demonstrated improved designs for industrial processes.

Approximate Transmission-Line Model for Field-to-Wire Coupling in Arbitrarily Routed Wiring Structures Above Ground

In this article, a comprehensive method for parametric representation of wire trajectories, allowing accurate geometric description of complex and arbitrarily oriented wire bundles, is introduced. This is the starting point to develop a computationally efficient numerical transmission-line (TL) model for predicting the radiated susceptibility of arbitrarily oriented bundles of wires, illuminated by (possibly) nonuniform electromagnetic fields. The proposed method foresees solution of the field-to-wire coupling problem through suitable discretization and sampling of the bundle geometry and the incident electromagnetic field. Differently from previous models, where bundles parallel to ground were assumed, the proposed model allows for arbitrary bundle orientation by exploiting, first, exact projection of the external field onto the bundle direction, and second, evaluation of the actual wire length (instead of the longitudinal one) of each TL section. Accuracy and computational efficiency of the proposed method are assessed versus full-wave simulation for two application examples, involving parabola-shaped and trefoil knot-shaped wiring structures above ground. Although the strong nonuniformity affecting these structures forces TL theory to work very close to its limits, the achieved agreement is satisfactory and the significant reduction of computational times makes the proposed method suitable for approximate yet efficient prediction of radiated susceptibility characteristics of complex wire bundles.

Heat generation in devices for magnetic-pulse processing of materials

The problem of analysis of non-stationary heat generation due to the flow of electric current in devices for magnetic-pulse processing of materials is considered. An analysis of the available information sources led to the conclusion that a large number of studies in this area are devoted to the study of heat transfer processes during technological operations of induction heating. In other technological operations of magnetic-pulse processing of materials, heat release is also significant. In this case, a non-stationary inhomogeneous temperature field can lead to significant temperature deformations. This, in turn, can cause a loss in the performance of the device due to destruction or irreversible deformation. Adequate modeling of non-stationary temperature propagation in this case is an obligatory step in carrying out computational analysis in the process of designing technological devices. A general strategy is proposed for determining the propagation of a non-stationary temperature field in the presence of a non-stationary non-uniform electromagnetic field. The proposed strategy presupposes a general solution of the problems of the propagation of the electromagnetic field and the temperature field within the framework of a unified design scheme. The use of the finite element method is proposed as a numerical method. The finite element method, when used in such problems, allows one to draw up iterative procedures that can be used to take into account the nonlinear effects associated with the influence of temperature on the electro-physical properties of materials. The problem of sequential determination of a non-stationary, non-uniform electromagnetic field and a non-stationary temperature field in composite matrices intended for electromagnetic pressing of powders of super-strong refractory materials is considered. The distribution of some quantitative characteristics of the electromagnetic field, as well as the dependence of temperature on time are presented.

Specific features of thermal deforming of composite inductors during magnetic-pulse processing of materials

The problem of taking into account a non-stationary inhomogeneous temperature field in the analysis of the stress-strain state of inductor systems for magnetic-pulse processing of materials is considered. It follows from the analysis of open information sources that the problem of analyzing a non-stationary temperature field arising from the presence of a non-uniform electromagnetic field and its effect on deformation has been sufficiently studied in relation to induction heating. At the same time, during other operations of magnetic-pulse processing of materials, heating of equipment can cause additional deformations of a significant magnitude, which, in turn, can lead to a loss of equipment performance due to destruction or irreversible deformation. A general approach to the analysis of such problems is proposed, which involves the determination of the spatial-temporal distributions of the quantitative characteristics of the electromagnetic field, temperature field and stress-strain state. The necessity of using numerical methods for carrying out such an analysis has been substantiated. The most effective numerical method is the finite element method, which makes it possible to analyze the unsteady electromagnetic field, temperature field, and stress-strain state within the same calculation scheme. In this case, within the framework of the finite element method, iterative schemes can be created that allow taking into account nonlinear effects. Here, nonlinear effects can be due to the dependence of the mechanical and electro-physical properties of the material on temperature, the plastic nature of deformation, and the need to take into account contact phenomena. The results of complex analysis for a composite single-turn inductor with a dielectric band are presented. The features of contact interaction were taken into account by introducing layers of contact finite elements. The stress-strain state of the inductor is estimated for two variants of the materials used: copper and non-magnetic steel.

Simulation and experiment investigaton of electromagnetic and thermal field during induction cladding

A fully electrical–magnetic–thermal coupled model is proposed to investigate the heating mechanism of induction cladding. The simulation results reveal that the coating and the thin layer close to the substrate surface were heated layer by layer. Furthermore, the non-uniform electromagnetic field generated an uneven temperature distribution, which had a larger impact in the longitudinal direction than in the cross section. The maximum relative errors between the simulated and measured temperatures indiacate that the numerical calculation fit the experimental results well. The impact of the non-uniform temperature distribution on the coating properties was experimentally studied. The specimen in the middle position had a more complicated phase composition, lower porosity, and higher microhardness than those at the two ends.

Penetration of non-uniform electromagnetic field into conducting body

The study is based on the exact analytical solution for the general conjugation problem of three-dimensional quasi-stationary field at a flat interface between dielectric and conducting media. It is determined that non-uniform electromagnetic field always decreases in depth faster than uniform field. The theoretical conclusion is confirmed by comparing the results of analytical and numerical calculations. The concept of strong skin effect is extended to the case when penetration depth is small not only compare to the characteristic body size, but also when the ratio of the penetration depth to the distance from the surface of body to the sources of the external field is small parameter. For strong skin effect in its extended interpretation, the influence of external field non-uniformity to electromagnetic field formation both at the interface between dielectric and conducting media and to the law of decrease field in conducting half-space is analyzed. It is shown, at the interface the expressions for the electric and magnetic intensities in the form of asymptotic series in addition to local field values of external sources contain their derivatives with respect to the coordinate perpendicular to the interface. The found expressions made it possible to generalize the approximate Leontovich impedance boundary condition for diffusion of non-uniform field into conducting half-space. The difference between the penetration law for the non-uniform field and the uniform one takes place in the terms of the asymptotic series proportional to the small parameter to the second power and to the second derivative with respect to the vertical coordinate from the external magnetic field intensity at the interface.

Analysis on components of characteristic X-ray yield of pure thick targets by positron impact near threshold energy

In the process of low-energy positron impact with pure thick target, the atomic inner-shell ionization is induced by not only the incident positrons whose energy is completely deposited in the target but also the other particles produced during positron-target collision, namely, the backscattered positrons that deposited part of their energy before escaping the target, the annihilation photons and the secondary electrons. In this paper, the W-M characteristic X-ray yields of two pure thick targets with different diameters impacted by a positron accelerated by the negative high voltage to 5–9 keV have been measured. The contributions from annihilation photons, secondary electrons, backscattered positrons, and the non-uniform electromagnetic field in the target chamber to the characteristic X-ray yields have been evaluated by the realistic Monte Carlo simulation. Besides, Nagashima et al. (Phys. Rev. Lett., 92 (2004) 223201) neglected the contribution from annihilation photons, secondary electrons and backscattered positrons to the yields when calculating the cross-section by the characteristic X-ray yields of thick target impacted by a positron. Here we also caculated the contribution share of the above particles to the Cu-K and the Ag-L characteristic X-ray yields of pure thick target impact by positrons below 30 keV. The results show that the contributions from the above components are non-negligible. Hence, it is necessary to modify the experimental yields for obtaining the accurate yields of pure thick targets by non-backscattered positron impact.

Wide-Band Electromagnetic Wave Propagation and Resonance in Long Cobalt Nanoprisms

Electromagnetic wave interaction with confined metallic magnetic structures is complex due to the excitation of nonuniform electromagnetic fields and magnetic precession and spin-wave modes over length scales that are dependent on the geometric, electromagnetic, and micromagnetic properties of the magnetic structures. Here, we solve the coupled system of Maxwell's equations and the Landau-Lifshitz-Gilbert equation using a stable algorithm based on the finite-difference time-domain method to study the transient wide-band electromagnetic propagation and resonance in infinitely long cobalt nanoprisms with a square cross section of side lengths 50--1000 nm. In particular, we identify the resonance mechanisms through studying the local transient and spectral distributions of magnetization in the prisms. The nanoprisms are excited by an axially polarized plane wave at normal incidence with a 70 GHz Gaussian pulse profile. For this incident wave condition, the simulations confirm that resonance in the cobalt prisms is excited mainly by the current-induced magnetic fields and indicate a magnetization curling resonance mode for prism side lengths less than 100 nm. The eigenfrequencies for the curling mode are confirmed theoretically using a model for an equivalent long circular cylinder with radial spin-wave modes. For prism side lengths longer than 100 nm (but less than the nonmagnetic skin depth), the magnetic response is confined to thin regions along the prism edges due to resonance-induced skin effects. The simulations indicate predominately uniform magnetization precession in the confined edge regions with increased pinning in the corners. The uniform resonance mode in the central part of the edge regions increases in intensity with prism size, with frequency described using Kittel's ferromagnetic resonance frequency of a thin planar structure. A higher-frequency size-independent uniform resonance mode is observed in the corner regions with frequency determined by the local demagnetizing factors. Local and integrated power absorption spectra are calculated using the simulated transient magnetization and fields, and confirm the resonance modes and frequencies in the cobalt prisms and their size dependence. The profile of the local power absorption spectra is also used to estimate the thickness of the confined edge regions or magnetic skin depth in the cobalt prisms at the fundamental resonance mode and is found to be approximately 50 nm. The outcomes of this work would benefit the design and engineering of lightweight and compact materials and devices incorporating metallic magnetic nanostructures. This work also provides a foundation for further modeling and understanding of electromagnetic transmission and propagation in more complex metallic ferromagnetic structures and composites excited by different electromagnetic wave conditions.

Spatially varying colloidal phase behavior on multi-dimensional energy landscapes.

A method is reported to determine equilibrium concentration profiles and local phase behavior of colloids on multi-dimensional energy landscapes. A general expression is derived based on local particle concentration and osmotic pressure differences that are balanced by forces on colloids due to energy landscape gradients. This analysis is applied to colloidal particles in high frequency AC electric fields within octupolar electrodes, where the energy landscape can be shaped in two dimensions. These results are also directly applicable to any particles having induced dipoles in spatially non-uniform electromagnetic fields. Predictions based on modeling colloids with an effective hard disk equation of state indicate inhomogeneous solid and fluid states coexisting on different shaped energy landscapes including multiple minima. Model predictions show excellent agreement with time-averaged Brownian dynamic simulations at equilibrium. Findings demonstrate a general approach to understand colloidal phase behavior on energy landscapes due to external fields, which could enable control of colloidal microstructures on morphing energy landscapes and the inverse design of fields to assemble hierarchically structured colloidal materials.