Electromagnetic Theory Research Articles

Analysis of the traction forces of two adjacent linear induction motors

Linear induction motors (LIMs) are positioned head-to-tail in medium and low-speed maglev (MLSM) trains, and the interaction due to small spacing between two LIMs is not yet clear. In this work, based on the 2D electromagnetic field theory, the vector magnetic potential (VMP) of each region was solved, and the traction forces of two adjacent LIMs were derived. Subsequently, the correctness of the theoretical model was verified by simulation. Finally, the effects of the spacing, wiring type, pole pitch, speed, etc., on the traction forces of two adjacent LIMs were analyzed. The results show that the traction force of LIM1 (arranged in front) is almost unaffected by LIM2 (arranged behind LIM1), while that of LIM2 fluctuates periodically with the spacing, and the smaller the spacing, the greater the fluctuation amplitude. Meanwhile, the larger the pole pitch, the more the pole number, the greater the slip frequency, and the lower the speed, the smaller the effect of LIM1 on LIM2. When the spacing takes 1.1 to 1.6 times the pole pitch, the traction force of LIM2 is larger than that of LIM1. The achievements can provide technical support for enhancing the traction performance of the LIMs in the MLSM trains.

Analytical prediction of electromagnetic performance for surface-embedded permanent magnet in-wheel machines considering iron’s nonlinearity

Accurate magnetic field calculation is the premise of electromagnetic performance prediction. Conventional subdomain (SD) techniques assume that the iron’s relative permeability is infinite, leading to falsely overestimated flux density. We propose an accurate magnetic field analytical model for permanent magnet (PM) in-wheel machines considering iron’s magnetization nonlinearity and saturation. Specifically, according to the excitation source and topology, the entire solution domain of the machine is divided into sub-regions such as stator slots/teeth, stator slot-openings/tooth-tips, air-gap, and rotor slots/teeth, etc. Poisson’s or Laplace’s magnetic vector potential (MVP) equations are solved using Maxwell’s electromagnetic theory and complex Fourier series methods in each sub-region. Specifically, in our approach, The Cauchy product theorem addresses the discontinuous magnetic permeability change at the slot and tooth interface. The machine’s magnetic saturation effect is considered by combining the actual magnetization characteristics of iron with an iterative algorithm. The general solution for the MVP is solved using the boundary conditions between adjacent subregions. Subsequently, electromagnetic properties such as air-gap flux density, back electromotive force (EMF), and electromagnetic torque are obtained. The accuracy of the analytical model is verified by finite element analysis (FEA) and prototype tests, which proved that the proposed analytical model can consider the iron’s nonlinearity and the magnetic saturation. In addition, the inaccurate overestimation of electromagnetic torque and air-gap magnetic flux density by the conventional SD techniques has also been proven.

Optimizing Aligned Steel Fiber Distribution in UHPC: Unraveling the Electromagnetic Influence of Steel Reinforcements

The performance of ultra-high performance concrete (UHPC) can be improved by the magnetic orientation of steel fibers. The reinforcement frame has strong interference with the magnetic field, and this interference may even make the production of oriented steel fibers fail. However, the study of the electromagnetic interference caused by fixed steel reinforcements has not been undertaken. In this paper, the steel fiber distributions under the interference of steel bars were tested, and the impact of different steel reinforcement diameters, lengths, and magnetic flux densities on the magnetic field was studied. The results reveal that stirrups minimally impact the magnetic field, whereas longitudinal reinforcement exerts a substantial influence. Therefore, it is feasible to manufacture an aligned steel fiber UHPC reinforced structure with a steel framework, and only the influence of longitudinal reinforcements needs to be considered. An analytical model based on electromagnetic theory was employed to elucidate the influence of longitudinal reinforcement and analyze the distribution of magnetic lines. Numerical analysis shows that the influenced range of the magnetic lines exhibited a logarithmic relationship with the flux density and a linear relationship with the length and diameter of the reinforcement. Therefore, when accompanied by a judiciously selected magnetic flux density, longer and thinner steel reinforcements are found to be conducive to achieving a comprehensive orientation of steel fibers.

Review of 3D electromagnetic modeling and inversion for mineral exploration

Many mineral deposits have low resistivity. This property makes the electromagnetic (EM) method a very useful tool for mineral exploration. In the past few decades, the application of EM exploration technologies has been reviewed by many researchers. However, most reviews focused on EM exploration methods, the development of equipment, or their applications. Three-dimensional forward modeling and inversions are high-accuracy EM interpretation techniques in which great progress has been made in recent years in mineral exploration. We review the development of EM technology for mineral exploration with a focus on 3D EM forward modeling, inversion technology, and its applications. We first briefly introduce the EM methods for mineral exploration. Next, we give a comprehensive review of 3D EM forward modeling, inversion, and data interpretation, with special attention paid to the development of EM theory and applications in mineral exploration. We hope this review can promote the application of 3D EM numerical simulation and inversion in mineral exploration.

A new variant of the electromagnetic field theory of consciousness: approaches to empirical confirmation.

There are various electromagnetic (EM) field theories of consciousness. They postulate an epineural EM field which, due to its binding properties, unifies the different neuronal information differences originating from various sensory and cognitive processes. Only through a real physical integration in space within this field could phenomenal consciousness arise. This would solve the binding problem mentioned in the philosophy of mind. On closer inspection, the electromagnetic interaction not only provides an explanation for the integrative property of the EM field, but also for the necessary differentiating contrasts of information. This article will take a closer look at the physical properties of a postulated EM field. It will also show how the problem of qualia in connection with emergentism could be solved by a new variant of EM field theory. If it can be clearly demonstrated that the postulated epineural EM field plays a decisive role in the origin of consciousness in addition to neuronal "wired" information processing, this also leaves less room for metaphysical assumptions that attempt to solve the binding problem. In experiments to prove the postulated epineural EM field by means of external electromagnetic manipulations, it can never be ruled out that these also have a direct effect on the "wired" neuronal signal processing. Therefore, on the way to proving the EM field theory of consciousness, an experimental method is needed that must ensure that external manipulations only affect the extensions of the EM field without directly influencing the neuronal network. A method will be discussed here that works with the shielding of EM fields instead of external electromagnetic stimuli.

Comparative Analysis Based on Near-Field Electromagnetic Theory Combined with Molecular Dynamics for Pulse Light-Induced Plasmonic Nanobubble in Gold and Silver Nanofluids

Comparative Analysis Based on Near-Field Electromagnetic Theory Combined with Molecular Dynamics for Pulse Light-Induced Plasmonic Nanobubble in Gold and Silver Nanofluids

Unconventional coil shape design of eddy current sensors and the effect of shape parameters on the micro/nano-scale metal film thickness measurement performance

Abstract The thickness of metal film is a critical parameter, especially in micro/nano-manufacturing, where high-precision measurement is essential. The eddy current method, a non-destructive testing technique, is well-suited for in-situ measurement of micro/nano-scale metal film thickness due to its superior performance. However, enhancing the measurement capabilities of eddy current sensors remains a significant challenge. In practical applications, thickness sensitivity and spatial resolution are two key performance indicators of eddy current sensors, and improving both simultaneously is difficult. While the sensitive element (coil) of an eddy current sensor has a substantial impact on thickness sensitivity, its effect on spatial resolution has received less attention.
This study establishes an eddy current coil model based on electromagnetic field theory, defining both thickness sensitivity and spatial resolution in the context of micro/nano-scale metal film thickness measurement. Two unconventional coil shapes are introduced, contrasting with the traditional cylindrical design, to investigate the influence of coil shape parameters, specifically the spatial distribution of the coil turns, on the key performance indicators. Simulation results are corroborated through experimental validation. Based on a series of calculations and analyses, an optimization method for coil shape parameters is proposed using a defined comparison factor that balances both thickness sensitivity and spatial resolution, which offers a promising approach for improving coil shape design.

Quantum mechanical effects in plasmonic sub-nanometer cavities formed by a tip and substrate structure

Enhancing local field intensity through light field compression is one of the core issues in surface plasmon-enhanced spectroscopy. The theoretical framework for the nanostructure composed of a tip and a substrate has predominantly relied on classical electromagnetic models, ignoring the electron tunneling effect. In this paper, we investigate the plasmonic near-field characteristics in the sub-nanometer cavity formed by the tip and the substrate using a quantum-corrected model. Additionally, we analyze the local electric field and Raman enhancement when hexagonal boron nitride (h-BN) monolayer is used as a decoupling layer for the nanocavity. The results indicate that classical electromagnetic theory fails to accurately describe the plasmonic electric field in smaller sub-nanometer gaps. When the gap is reduced to 0.32 nm, the quantum-corrected model shows that the local electric field in the sub-nanometer cavity is significantly reduced due to the tunneling current, aligning more closely with experimental results. Moreover, adding a high-barrier h-BN layer effectively prevents the occurrence of tunneling current, allowing for a strong local electric field even when the gap is less than 0.32 nm. The calculated maximum Raman enhancement reaches up to 15 orders of magnitude. Our research results provide a deep understanding of quantum mechanical effects in tip-enhanced spectroscopy systems, enabling the potential applications based on quantum plasmons in nanocavity.

State-restricted adaptive control of a multilevel rotating electromagnetic mechanical flexible device using electromagnetic actuators

This work presents the development of a multilevel electromagnetic actuation system that controls the shape of a flexible rotatory robotic structure. An array of electromagnets is used as the set of actuators that regulate the position of permanent magnets within the flexible device. The primary outcome of this study is the design and experimental validation of the multilevel rotating device. In addition, the theoretical description of the system motion under electromagnetic actuation is formulated using Euler–Lagrange and electromagnetic theories. Given the developed model, a theoretical study leads to designing an adaptive control that considers motion restrictions in the flexible device. The controller aims to modify the current applied to the electromagnets, which changes the interaction forces between the electromagnet and the permanent magnets in the robotic flexible structure. A set of numerical simulations confirms the proposed controller’s effectiveness compared to the traditional state feedback approach that does not consider the state restrictions, which is implemented in devices that also operate under an electromagnetic approach. Furthermore, an experimental version of the flexible device allows for testing of the developed controller. The experimental results show the suitability of the proposed control to generate non-oscillatory controlled motion during the regulation of the flexible mechanic device shape.

Multipath Characteristics of Orbital Angular Momentum Vortex Electromagnetic Radio Waves Over an Infinite Ground Plane

In this paper, the effect of an infinitely sized ground plane on the orbital angular momentum (OAM) vortex electromagnetic (EM) radio waves is investigated. Although the effect of an infinite ground on OAM wave propagation and communication has already been numerically examined in the literature using the method of moments (MoM), this situation needs to be examined analytically and theoretically derived final form expressions need to be obtained. The multipath characteristics of OAM waves in a superconducting ground plane are theoretically presented considering both horizontal and vertical polarization conditions. In addition to direct radiation to an observation point in the far-field from the array antenna, many reflected radiations from the ground plane are also transmitted. The most fundamental reflected radiation is analyzed over a uniform circular array (UCA), adopting electromagnetic image theory. Furthermore, the transmitted field expressions obtained by considering both the circular array parallel to the ground plane and the circular array upright to the ground plane are formulated in a general analytical form for an OAM wave on a superconducting ground plane. In addition, numerical simulations are applied to exemplify the properties of OAM waves in the superconducting ground plane, unlike the isolated medium.

THEORETICAL APPROACH FOR DETERMINING AN EMISSIVITY OF SOLID MATERIALS AND ITS COMPARISON WITH EXPERIMENTAL STUDIES ON THE EXAMPLE OF 316L POWDER STEEL

The work used Maxwell's electromagnetic theory to quantitatively describe the emissivity of solid materials through electrical resistivity and temperature. An equation is proposed for recalculating the emissivity of smooth surfaces into powdery or rough surfaces. The obtained theoretical characteristics of the change in the emissivity of 316L powder steel were compared with experimental ones. As a result of the comparison, it was established that the experimental results obtained correlate with theoretical calculations and do not go beyond the limits of the expanded uncertainty of measurement.

From higher-spin gauge interactions to Compton amplitudes for root-Kerr

We develop massive higher-spin theory as a framework for describing dynamics of rotating compact objects, such as Kerr black holes. In this paper, we explore gauge interactions up to quartic order and corresponding Compton amplitudes of higher-spin massive objects coupled to electromagnetism and Yang-Mills theory. Their classical counterparts are known as root-Kerr gauge-theory solutions, whose amplitudes are closely related to those of Kerr black holes. We use three distinct approaches: (i) massive higher-spin gauge symmetry to introduce cubic interactions for all spins and the quartic interactions up to spin 3, which is implemented both off shell and via Ward identities; (ii) a chiral higher-spin approach to construct quartic Lagrangians with correct degrees of freedom to all spins; (iii) on-shell functional patterns before and after taking the classical limit to constrain the Compton amplitudes. As final results, we arrive at simple local formulae for the candidate root-Kerr Compton amplitudes both in the quantum regime and classical limit, to all orders in spin. This is a precursor to the gravitational Kerr case, which is presented in a follow-up paper.

Analysis of broadband linear polarization-converting meta-materials and their sensing and detection functions

In this paper, we present a broadband perfect-reflective linear polarization-converting metamaterial, which achieves perfect-reflective linear polarization conversion over a broadband frequency range of 28.15 GHz–60.80 GHz, and the narrow-band perfect-polarization-converting peaks appearing at the high frequency of 67.121 GHz can be used for microwave solution concentration detection. The design consists of a surface metal resonator structure, a Roggers 5880 dielectric layer and a copper metal backing. The surface metal resonator is a combination of a circular open ring, a square open ring, and a centrally located cross-metal cross ring nested in a modified, highly anisotropic structure. The perfect polarization transition peak at the high frequency band can be used for the solution detection function, which can detect the concentration of salt solution, glucose solution, and alcohol solution. When the refractive index of the solution sample to be tested changes gradually from 1.0 to 1.4, the polarization conversion peak shows obvious frequency shift, and the peak polarization conversion rate is always kept above 99%. The polarization principle was analyzed using surface electromagnetic field distribution and related theories, and the sample structure was processed and tested. The designed super-surface polarization conversion structure has potential applications in the field of microwave detection and microwave communication.

Proportional-derivative control and motion stability analysis of a 16-pole legs rotor-active magnetic bearings system

This paper analyzes the motion stability of a 16-pole rotor-active magnetic bearings (rotor-AMB) system and investigates the complex vibrations under a proportional-derivative (PD) controller. First, electromagnetic theory and Newton’s second law are applied to derive the two-degree-of-freedom differential governing equations for the 16-pole rotor-AMB system, incorporating the PD control terms. The resulting differential equations include parametrically excited, quadratic nonlinear, and cubic nonlinear terms. Subsequently, the multiple time scales perturbation analysis method is performed on the obtained governing equations, yielding four-dimensional averaged equations in both Cartesian and polar coordinates. Finally, numerical simulations including the amplitude–frequency response characteristics, motion trajectories, energy–amplitude relationships, as well as bifurcation and chaotic motion of the system are studied. The results indicate that the PD controller affects the softening and hardening spring characteristics of the system and has significant control effects on the system’s amplitude, energy, and stability. Additionally, increasing the differential gain coefficient [Formula: see text] can change the system’s motion from chaotic to periodic.

Evaluating the Geo-Environmental Conditions within a Working Face Using a Hybrid Intelligent Optimization Model

Geological anomalies within the working face likely induce geological disasters, such as water, gas, and coal mine roof fall, directly impacting the rational planning and safe mining of underground resources. Constrained by the conditions of underground closed spaces, effective reconstruction under incomplete and highly sparse projection is the central challenge when evaluating geo-environmental conditions. This work proposes a new hybrid intelligent optimization model (MPGA-SIRT) that integrates a multiple-population genetic algorithm (MPGA) with the simultaneous iterative reconstruction technique (SIRT) to finely reconstruct the geo-environmental conditions within a working face based on electromagnetic wave tomography theory. MPGA-SIRT can provide a more precise initial inversion model for the conventional linear reconstruction technique of SIRT, incorporating a local search property by leveraging the robust global search capacity of MPGA. The advantages of MPGA-SIRT have been demonstrated through numerical modeling, theoretical testing, and engineering practices on the 8208 working face in the Datong mining area, Shanxi Province. In comparison to individual SIRT inversion models, MPGA-SIRT reconstruction yields more accurate and stable performance, as demonstrated by the evolution curve of the objective function and the corresponding convergence tomography results. Consequently, the geomagnetic wave absorption coefficient within the area of reconstruction can be precisely ascertained through the use of our proposed technique. This innovation represents a groundbreaking strategy for assessing geological anomaly zones within a working face. The introduced method stands as a valuable theoretical instrument for confronting the complexities associated with geo-environmental reconstruction in underground engineering.

A dual-band polarization independent dielectric metasurface-based absorber for sensing application in the visible light regime

We present a dual-band, polarization-independent dielectric terahertz absorber exhibiting near-perfect absorption and minimal reflection at frequencies of f 1 = 419 THz and f 2 = 528 THz. Using electromagnetic theory, we modeled the structure to derive the surface electric admittance and magnetic impedance of the metasurface, elucidating the conditions required for perfect absorption in terms of inverse electric and magnetic polarizabilities. The absorber features a tunable symmetrical design, facilitating precise frequency adjustment by modifying structural parameters and ensuring polarization independence for perpendicularly incident electromagnetic waves. This scalable and versatile absorber, constructed from readily available materials, is optimally suited for applications in resource detection, imaging, sensing, and medical diagnostics, attributed to its simplicity, cost-effectiveness, and high performance.

Implementation of Electromagnetic Theory: Improved Analysis and Design for Class F Power Amplifier

ABSTRACTThe general electromagnetic (EM) theory has not yet been applied to the analysis of Class F (CF) power amplifier (PA). In this paper, an alternative approach for CF PA is presented based on the EM theory. Theoretical analysis shows that the CF PA can be divided into two broad categories, forward voltage gain, and reflected voltage gain PA. The existing CF PA belongs to the reflected voltage gain PA. Even though both the CF PAs have the same voltage gain, the PA with forward voltage gain provides higher fundamental power Ps,1@F and drain efficiency PAE@F than that CF PA with reflected voltage gain and Class B PA. This important conclusion is obtained as a result of this analysis, which cannot be explained by available theory in the literature. The theoretical analysis is validated at 2.2 GHz by fabrication and measurements. According to the results, Ps,1@B = 31.8 dBm and PAE@B = 53.27% in Class B PA. In CF PA with reflected voltage gain, Ps,1@F = 30.20 dBm and PAE@F = 48.6%. Both cases have lower power and PAE as compared to new category of CF PA. This new CF PA with forward voltage gain has, Ps,1@F = 33.04 dBm and PAE@F = 63.7%.

Effect of chemical reaction on MHD Casson natural convection flow over an oscillating plate in porous media using Caputo fractional derivative

Fractional calculus is a branch of mathematics that extends the traditional definitions of calculus to include non-integer exponents. It has been successfully used to model a variety of physical processes, including the coiling of polymers, viscoelasticity, traffic flow, diffusive transport, fluid dynamics, electromagnetic theory, and electrical networks. However, fractional calculus has not yet been widely used to study the physical properties of non-Newtonian fluids flowing over accelerating porous plates. The present research examines the unsteady Casson flow over an infinitely horizontal porous plate, MHD and porosity impacts on fluid velocity are also discussed. The major goal here is to develop analytical outcomes for the tran-sient incompressible MHD Casson flow over an accelerating porous plate. This plate is oscillating in the x-direction and infinitely large in the y-direction and fluids flowing over it at y > 0 due to oscillation. Choosing the right choice of dimensionless variables allows the model's governing equations to become dimensionless. These dimensionless differential equations of the Casson fluid are calculated by applying the Laplace transform method. On velocity, the impacts of different factors are investigated. They are time, porosity parameter, oscillation frequency of plate, magnetic parameter, and Casson fluid parameter. As we rise the Casson flow parameter values, magnetic parameter, and Prandtl number we observe that the velocity drops. In contrast to other factors, the effects of Grashof number, oscillation frequency, fractional parameter, and porosity on the velocity profile are reversed. Using Mathcad software, graphs are sketched for various values of these parameters and are thoroughly described. The fluid properties discovered signif-icant findings and disclosed several characteristics for a range of flow parameters and fractional parameter values. Increasing the values of fractional parameters is shown to improve the characteristics of fluids, and this is beneficial in fitting experimental data related to heating and cooling processes, particularly in electronic equipment.

From waste to resource: Transforming Kraft black liquor into sustainable porous carbon fillers for radome applications

The study addresses environmental and commercial challenges posed by weak black liquor (WBL) generated through the Kraft process in the paper industry. WBL, a toxic waste, annually reaches a staggering 1.3 billion tonnes globally. Currently, it is either incinerated for energy production or subjected to costly and complex chemical treatments to extract valuable compounds. Despite efforts to develop a scalable value-added material, the existing methods are inefficient in fully reusing WBL. Here, we report a simple chemical synthesis process that reuses 100 % of WBL without generating any waste materials; even salts recovered during the process might be reintegrated into the industry as chemical byproducts. Furthermore, given the simplicity and efficiency of the proposed synthesis methodology to transform WBL into a novel and sustainable porous carbon material, the carbon Kraft (CK). The process can also be scaled by using the right synthesis proportions and within a circular economy. CK exhibited desirable characteristics with a renewable content of 65 wt%, including a turbostratic graphitic-like structure (48.8 % graphitized), carbon content of 85 wt%, large specific surface area of 234.0 m2∙g−1, nanoporosity of 0.13 cm3∙g−1, and density of 1.92 g∙(cm3)-1. Moreover, CK showed electrical and thermal insulating characteristics, essential for use as fillers for elastomeric composite in electromagnetic transparent radome structures used to protect antennas and radars of unmanned aerial vehicles (UAV) from harsh environmental effects. Radomes were designed through the electromagnetic impedance match theory of half-wavelength calculations over specific frequencies of 1.3, 10, 15, 20, and 30 GHz. Results showed excellent transmission loss between −0.41 and −1.48 dB, representing 90.8 % and 70.5 % of transmittance, respectively.

A terahertz chiral metamaterial with tunable dual-band to broadband circular dichroism based on Dirac semimetals

Chiral metamaterials play a crucial role in manipulating the electromagnetic waves. This paper intoduces a three-dimensional Dirac semimetal materials (3D DSM) metamaterial structure tailored for tunable and broadband circular dichroism (CD) effects at terahertz (THz) frequencies. Using the Jones matrix, electromagnetic multipole resonance theory, and the atomic orbital hybridization model, the resonant performance for the DSM based metamaterials in reflection and transmission design is systematically analyzed, in terms of the resonant peak and bandwidth. Simulation results show that the bilayer DSM metamaterial supports the chiral response with dual-band resonance in transmitted spectra, and its CD and working frequency could be tuned by adjusting the rotation angle between the upper and lower DSM metamaterial layers and Fermi level of DSM. Therefore, the tunable CD from 0 to 0.51 could be achieved across a wide THz frequency from 3.56 THz to 4.02 THz. Additionlly, the resonant frequency is highly sensitive to the surrounding refractive index (RI), yielding a RI sensing sensitivity up to 308.6 GHz/RIU. The proposed DSM based chiral metamaterial features a tunable and broadband design, offering a universal design method and potential applications for the modulation of light polarization, chiral sensing and imaging, and communications.