Electromagnetic Field Model Research Articles

Broadband Antireflective Hybrid Micro/Nanostructure on Zinc Sulfide Fabricated by Optimal Bessel Femtosecond Laser.

Enhancing the infrared window transmittance of zinc sulfide (ZnS) is important to improve the performance of infrared detector systems. In this work, a new hybrid micro/nanostructure was fabricated by an optimal Bessel femtosecond laser on ZnS substrate. The surface morphologies and profiles of ASS ablated by a 20× microscope objective Bessel beam are described, indicating that the nanoripples on the micropore were formed by the SPP interference and the SPP scattering in a particular direction. Further, the maximum average transmittance of ASS increased by 9.7% and 12.3% in the wavelength ranges of 5~12 μm and 8~12 μm, respectively. Finally, the antireflective mechanism of the hybrid micro/nanostructure is explored using the novel electromagnetic field model based on the FDTD method, and we attribute the stable antireflective performance of ASS in broadband to the interface effective dielectric effect and LLFE.

Special issue: The 12th International Symposium on Electric and Magnetic Fields (EMF 2021)

On behalf of the Editorial Board, we are pleased to present a selection of papers related to the 12th International Symposium on Electric and Magnetic Fields (EMF 2021), held online on July 6–8, 2021. The EMF symposium series, whose first edition was held in Liège, Belgium, in 1992, aims at building a bridge between recent research advances in mathematical and numerical modeling of electromagnetic fields and the growing number of industrial problems requiring such techniques. In the aftermath of the global COVID-19 pandemic, the 12th edition was organized online, and attracted 84 participants from 17 countries. Among the 62 presentations in the symposium program, 24 manuscripts were submitted for peer review. Fourteen papers were selected for publication in this special issue of the International Journal of Numerical Modelling: Electronic Networks, Devices and Fields. The high scientific and technical quality of the symposium is well reflected in the quality of the manuscripts contained in this special issue. Three broad topics were covered during the 12th edition of the symposium. The first major topic considers the mathematical modeling of electromagnetic problems in view of their eventual numerical solution on computers, with contributions on quasistatic time-domain formulations1-3 and high-frequency formulations.4 The second major topic treats general methodological advances in numerical methods.5, 6 The third major topic is the application of modeling to the study, design, and optimization of a wide range of technological devices, spanning low- to high-frequency electromagnetic regimes: from magnetostatics7, 8 to electro-9, 10 and magneto-quasistatics,11, 12 to full-wave.13, 14 This underlines the spirit of the conference, which encompasses both theory and practical applications. We express our gratitude to all the members of the EMF scientific committee—P. Alotto, J. P. A. Bastos, O. Biro, M. Clemens, S. Clenet, W. A. Cronje, A. Demenko, L. Dupré, J. Gyselinck, K. Hameyer, L. Kettunen, A. Kost, V. Mazauric, J. Melkebeek, G. Meunier, M. Petrun, A. Razek, M. Repetto, G. Rubinacci, R. Sabariego, S. Schöps, J. K. Sykulski, and M. Trlep—as well as to all the reviewers, who provided the necessary volunteer time and expertise to conduct a fair and detailed review, ensuring high publication standards for the selected manuscripts. We also thank the staff from the Association des Ingénieurs de Montefiore (AIM), and especially C. Dizier and L. Kara, for their help organizing the EMF symposium series. The next edition will be held in Marseille, France, on August 29–31, 2023. We hope that you will enjoy reading this selection of articles.

Simulation of a Multifractal Turbulent Electromagnetic Field in Cosmic Plasma

A two-dimensional model of a multifractal turbulent electromagnetic field is proposed that allows flexibly varying the width of the multifractal spectrum and the level of intermittency. The electromagnetic field is modeled using a superposition of wavelets that are distributed uniformly throughout the computational domain. By means of a special distribution of amplitudes, we ensure that the resulting field is multifractal and intermittent. This model was used to study the effect of multifractality and intermittency on the acceleration of charged particles in a turbulent field in the Earth’s magnetotail. It was shown that, in the case of a multifractal field, individual particles are able to achieve higher energy values in comparison with monofractal turbulence.

Investigation of signal integrity of fuzz button connectors under different compression states

AbstractFuzz button connectors are extensively used in vertical interconnection for high‐density integrated circuits. This work studied the impact of fuzz buttons under different compression states on high‐frequency signal transmission using theoretical analysis and experimental testing. The resistance values for fuzz buttons with different heights in compression states were measured. The physical dimensions were obtained for sample fuzz buttons subjected to various compression states. The effects of long‐term compression of fuzz button on the resistance values and S parameters of the device under test (DUT) were analyzed. In addition, the high‐frequency parameters were measured for the DUT with fuzz buttons in various compression states. Both a three‐dimensional (3D) electromagnetic field model and an equivalent circuit model for the fuzz buttons under compression states were developed and the results of these two models show good agreement with experimental results. In the circuit model, a fuzz button connector with a three‐wire transmission line structure was modeled as a π impedance network, composed of equivalent inductances and capacitances. It was found that the proposed 3D electromagnetic field model and an equivalent circuit model can accurately predict the effect of fuzz buttons under different compression states on the signal transmission in the affected frequency band. However, the models cannot evaluate the communication performance of the whole system.

Reduction in the Computational Complexity of Calculating Losses on Eddy Currents in a Hydrogen Fuel Cell Using the Finite Element Analysis

This paper considers the issues of the reduction in the computational complexity of the numerical problem and the requirements of the computer memory size when calculating the power of the eddy currents in a hydrogen fuel cell based on a proton exchange membrane. The study was performed on a model problem based on a geometric pattern of a hydrogen fuel cell of typical dimensions and characteristics operating at a nominal load in steady-state conditions. The power of the eddy currents was calculated using a numerical model based on a tetrahedral finite element mesh and a mathematical model of a quasi-stationary electromagnetic field in the classical formulation through the vector magnetic potential. The requirements for the minimum degree of the geometric model approximation by a finite element mesh to achieve mesh stability of the computational problem results were defined. The paper considers issues of finite element order selection, the method of ordering, and the solution of the systems of linear algebraic equations (SLAEs). It shows the techniques for determining the accuracy of the calculated SLAE solution obtained by the direct method, as well as the effectiveness of the low-rank approximation of the SLAE to reduce the computational complexity of the computational problem solution and reduce the requirements for the amount of computer memory needed, considering the reduced accuracy of the SLAE solutions.

The Impact of the Connection Failure of Ground Solder Balls on Digital Signal Waveform

Ball-grid array (BGA) packages are widely used in digital signal devices, whose reliability and signal integrity are critical. In this research, the impact of failed ground solder balls on digital signal waveforms was theoretically modeled and analyzed, and the results were experimentally verified. A 3-D electromagnetic field model of a digital signal transmission channel with failed ground solder balls was developed to analyze the signal transmission in the frequency domain. In addition, a time-domain waveform simulation system was developed to examine the changes in the digital signal waveforms before and after degradation. Based on the structural and signal transmission characteristics of the solder area with failed ground solder balls, an equivalent circuit model of the degraded solder area was developed, which accurately predicts the effect of the failed ground solder balls on the amplitude and rising edge of the digital signals. The results obtained from the simulation were validated using experimental tests. This study fully examines the effects of the location and number of failed ground solder ball on signal transmission in both the frequency and the time domain. It provides insight and guidance regarding the impact on signal integrity of such faults, which serves to assist in improved packaging reliability and the development of fault detection strategies for such electronic systems.

3-D Forward Modeling of Transient EM Field in Rough Media Using Implicit Time-Domain Finite-Element Method

In a heterogeneous medium (usually called a rough medium) with fractured formations, the propagation of an electromagnetic (EM) field is a type of subdiffusion. Current mainstream geophysical EM data processing methods cannot be applied to data acquired on heterogeneous Earth, as they are not governed by the classic diffusion theory. To evaluate the influence of roughness on the transient EM (TEM) signal for a complex model and contribute to data inversion, we proposed a novel three-dimensional (3-D) forward modeling scheme for TEM in rough media. First, we derived the governing equation with a fractional-order time derivative for the subdiffusion of EM waves in rough media. Then, we proposed a novel time discretization using an unequal step length for the Caputo operator, which significantly reduces the total number of time steps. Finally, an implicit time-domain finite-element method using unstructured tetrahedron discretization was adopted to solve the 3-D forward problem. Furthermore, an efficient time segmentation strategy combined with parallel RHS construction was proposed to accelerate modeling. The numerical results prove that the proposed method is accurate and efficient, and will be a powerful numerical method for analyzing TEM wave propagation and processing TEM data in areas with multiscale fractures or porosity.

Rotor Loss and Temperature Field of Synchronous Condenser Under Single-Phase Short-Circuit Fault Affected by Different Materials of Rotor Slot Wedge

A synchronous condenser (SC) can provide the dynamic reactive power for the ultra-high-voltage direct current converter station during the system voltage drop caused by the single-phase short-circuit fault, which is one of the prevalent faults. However, the single-phase short-circuit fault can also result in the increase of the rotor loss and temperature and thus restrict the transient operating ability of the SC. A key factor that affects the rotor loss and temperature rise is the material of the rotor slot wedges. For a 300-MVar SC with the rotor slot wedges made of the aluminum, beryllium bronze, and stainless steel, the rotor loss and temperature distribution under the single-phase short-circuit are calculated by coupling the electromagnetic and temperature field models of the SC with the models of the power grid. The variations of the rotor losses along with the rotor slot wedge conductivity are revealed. The rotor regions, where the highest temperature rise appears, are obtained. According to the maximum permissible temperature of the rotor material, the transient operating ability of the SC withstanding the single-phase short-circuit fault is obtained. This article can provide the theoretic basis for improving the transient operating ability of the SC.

Effect of steel rod embedded in electrode on continuous consumption of graphite by using numerical simulation

ABSTRACT Under the dual requirements of cost reduction and double carbon goal, it is more meaningful to reduce the continuous consumption of graphite electrode in ladle furnace. In this paper, the three-dimensional coupling model of electromagnetic field, heat transfer, flow field is established, and the influence of embedded steel rod on the current, temperature and continuous consumption of graphite in the electrode was studied. The current in graphite and steel rod is mainly distributed in the edge area near the left electrode, respectively. With the increase of the radius of the steel rod, the proportion of the current passing through the steel rod to the total current increases, the area of each temperature range above 500 K and the total continuous consumption rate of the electrode decrease.

Improving Online Adaptive Radiotherapy Quality Assurance with Streamlined Clinical Workflow through In-House Development

<h3>Purpose/Objective(s)</h3> Online adaptive radiotherapy has been clinically feasible through decades of research and development and is now available in the clinical routine with dedicated platforms using CBCT-LINAC or MR-LINAC. The quality assurance (QA) of online plans has become a bottleneck in the clinical workflow as it often requires manual data export/import through third party software, lengthy wait for the secondary dose calculation, and tedious work on report generation and checking, etc. The QA bottleneck not only impedes clinical workflow but also risks plan and treatment quality due to the time pressure with the patient waiting on the treatment table. We have developed and implemented in-house solutions to address such a bottleneck. <h3>Materials/Methods</h3> We developed dedicated in-house infrastructure to facilitate online adaptive plan QA and clinical workflow: 1) RT-PACK with SQLite database, which receives and organizes DICOM-RT data from any DICOM sender (e.g., clinical TPS); 2) a general purpose dose calculation server powered by the in-house GPU-based Monte Carlo particle transport engine with electromagnetic field modelling; 3) a report generator that automatically generates reports for secondary dose and plan quality check; 4) a web-portal that allows clinicians to review and sign the report anywhere with a network and VPN connection, even from a mobile phone. The reports and related documents will be automatically sent to the Record & Verify system after obtaining both physician and physicist signatures. An auto-commissioner was also developed to facilitate beam modeling based on water-tank measurements, which serves the purpose of fully independent verification. The dose calculation was performed on the whole patient volume with grid resolution of 2 mm x 2 mm x 2 mm. The 3D dose volume, treatment fields, point dose, Gamma Index with global 3%, 2mm criteria, three orthogonal dose profiles, dose volume histograms, and dosimetric constraints are metrics to compare the plan retrieved from TPS to the secondary dose verification and reported for clinicians' review. The whole in-house infrastructure went through extensive unit tests, dosimetric accuracy verifications, and alpha and beta tests before adopted for clinical use. <h3>Results</h3> The secondary dose and plan check infrastructure went live for CBCT-LINAC and MR-LINAC in our clinic and has since performed secondary check for every plan generated (846 plans and 622 plans, respectively, in less than 6 months.) The average processing time, from DICOM receiving to report generation, was 62 seconds for CBCT-LINAC and 130 seconds for MR-LINAC, which was 3-5 minutes shorter compared to using commercial software. More than 95% of CBCT-LINAC (MR-LINAC) plans had Gamma passing rates >99% (>95%). <h3>Conclusion</h3> The in-house developed software, through strict verification and validation, has been integrated into the clinical system. It has greatly improved online adaptive quality assurance with efficient and streamlined clinical workflow.

Calculation of the thermal field of a linear induction motor (LIM) considering a discontinuous secondary plate

PurposeThe purpose of this study is to analyze the linear induction motor (LIM) thermal field when the motor passes through the discontinuous area of the secondary plate in rail transit operation.Design/methodology/approachTo study the thermal field when the LIM passes through the discontinuous area of the secondary plate, the two-dimensional (2D) electromagnetic field model of the motor is first established to calculate and analyze the electromagnetic field of the LIM, and then the motor thermal field is calculated according to the calculation results of the motor electromagnetic field. Finally, the heat source (the motor loss) and the heat dissipation coefficient are added to the thermal field calculation model to calculate the motor thermal field.FindingsThis study found that the discontinuity of the secondary board would lead to changes in the electromagnetic field of the linear induction motor to change, which would reduce the motor efficiency and increase the loss, resulting in a sudden increase in the temperature field of the motor.Originality/valueThe LIM temperature field calculation when the LIM passes through the discontinuous area of the secondary board could provide an early warning for the potential risks of the LIM in rail transit applications.

Modeling of a 43 GHz microplasma within a photonic crystal

The electron density (ne) and argon metastable density (1s5) of a 43GHz microplasma are obtained using the zero-dimensional plasma kinetics solver (ZDPlasKin®) for an incident power of 160 and 1000mW and argon pressures of 10–600Torr (1.3×103 to 8.0×104Pa). These simulations are compared with previously published experimental data. To determine the self-consistent electric field in the modeled plasma, the three-dimensional millimeter wave fields are computed as a function of electron density using ANSYS EM19.2, HFSS®. This electromagnetic field model is coupled to ZDPlasKin such that any increase in the simulated plasma density correctly attenuates the simulated electric field within the microplasma. The electron density is found to be sensitive to argon gas temperature, so a two-zone temperature model was needed to obtain agreement with experimental measurements. The temperature in the central core of the microplasma was determined by a previous experimental study. That temperature was used as an input to the model for the simulation of volume recombination losses. The outer regions of the microplasma are assumed to be in equilibrium with the walls (300K). This second temperature was used in the model to determine diffusion losses. The modeled electron and metastable densities are of the order 1020 and 1018m−3, respectively. This is in good agreement with those measured experimentally as long as the two-zone temperature model is used. In the absence of a hot gas core, the modeled three-body recombination rates are excessive and the simulation severely under-predicts the electron density and over-estimates the metastable density. We conclude that the millimeter wave microplasma has a hot core (2500K at 600Torr) that rarifies the argon gas and effectively reduces three-body recombination. This allows one to achieve high electron density on the order of 1020m−3 with only 100mW of wave power.

Modeling and Characteristic Analysis of Magnetic Coupling Mechanism in Seawater Environment

The electrical conductivity and dielectric constant of seawater are quite different from those of air, so it is necessary to explore the differences between wireless power transmission characteristics in the air and seawater. The equivalent circuit model of the magnetic coupling mechanism is of great significance to the analysis of the transmission characteristics. In this article, a more accurate model analyzing the wireless power transmission in seawater environment is proposed, in which all parameters of the model can be obtained by specific expressions. First, by establishing the electromagnetic field analysis model in the seawater environment, the distribution laws of underwater electric field intensity and magnetic induction intensity are obtained. Then, the equivalent self- and mutual resistances of eddy current loss are introduced based on electromagnetic field model, and the analytical solutions of them are given. The lumped parameter equivalent circuit model of the underwater magnetic coupling mechanism is further derived, and the influencing factors of eddy current loss equivalent resistances are explored, which can provide theoretical guidance for multi-objective system optimization. Finally, an underwater platform was built to verify the accuracy of the equivalent circuit model.

Three‐dimensional electromagnetic parametric modelling and implementation of miniaturized lumped‐element power divider based on symmetrical configuration

Three-dimensional (3D) electromagnetic (EM) parametric modelling and implementation of miniaturized lumped-element power divider (PD) based on symmetrical configuration is investigated. The system design and schematic diagrams of PDs are first demonstrated; subsequently, the 3D EM field and field-circuit co-simulation models of PD utilizing computer simulation technology (CST) and advanced design system (ADS) tools are detailedly presented. Finally, one prototype is fabricated and measured. Simultaneously, the gain of the PD is −3.96 dB @ 100 MHz and the experimental curve is in excellent agreement with the simulation. As a conclusion, the novel design methodology applied in PD has important practical engineering value, which can be also applied in millimetre-wave (mmW) circuit

On Modelling of Maximum Electromagnetic Field in Electrically Large Enclosures

Abstract The maximum electromagnetic field formed in the electrically large enclosures for a given input power has always been the focus of electromagnetic compatibility issues such as radiation sensitivity and shielding effectiveness. To model the maximums in a simple manner, the electrically large enclosure can be regarded as a reverberation chamber (RC), thus the generalized extreme value (GEV) theory based framework is used for both undermoded and overmoded frequencies. Since the mechanical stirrer is not easy to be installed like that for RC, frequency stirring and mechanical stirring related configurations are discussed, and the corresponding results have confirmed the validity of frequency stirring with the estimate of the parameters in GEV distribution. As for the maximum field, a comparison has been made between GEV distribution and IEC 61000-4-21, and the corresponding results have also highlighted that the maximum field can be assessed by frequency stirring configuration, and by GEV distribution with a desired confidence.

Modeling of the Signal Transmission of a Coaxial Connector With a Degraded Dielectric Layer in a Humid Environment

Radio frequency coaxial connectors are key components in circuits for signal transmission and directly influence the stability of communication systems. It is well known that connectors operating in harsh environments for extended periods are subject to physical degradation, which may lead to deterioration of signal integrity and overall communication quality. However, little work has been done with regard to connector dielectric degradation in humid environments. In this current work, the specific effects of connector dielectric degradation in humid environments on signal transmission are studied by theoretical and experimental analysis. Both a 3-D electromagnetic field model and an equivalent circuit model for connectors before and after degradation are developed in order to evaluate signal reflection and transmission loss. The results of these two models are compared and show good agreement. In addition, based on the material properties of the connector dielectric, the equivalent dielectric layer of a degraded connector is considered to consist of a double-layer dielectric structure composed of polytetrafluoroethylene (PTFE) and a layer of water film. The equivalent dielectric constant and equivalent loss tangent of the double-layer dielectric structure are calculated and analyzed. A corresponding equivalent circuit is developed consisting of an impedance network with resistance and capacitance elements in parallel. Experiment tests are conducted to validate the electromagnetic field model and the circuit model results. The results of this research provide a better understanding of the electrical characteristics of degraded connectors in humid environments and theoretical support for engineering applications.

Задача Трикоми для одного класса многомерных смешанно гиперболо-параболических уравнений

It is known that in the mathematical modeling of electromagnetic fields in space, the nature of the electromagnetic process is determined by the properties of the medium. If the medium is non-conducting, we obtain degenerate multidimensional hyperbolic equations. If the medium has a high conductivity, then we come to degenerate multidimensional parabolic equations. Consequently, the analysis of electromagnetic fields in complex media (for example, if the conductivity of the medium changes) is reduced to degenerate multidimensional hyperbolic-parabolic equations. It is also known that the oscillations of elastic membranes in space can be modeled according to the Hamilton principle by degenerate multidimensional hyperbolic equations. The study of the process of heat propagation in a medium filled with mass leads to degenerate multidimensional parabolic equations. Therefore, by studying the mathematical modeling of the heat propagation process in oscillating elastic membranes, we also arrive at degenerate multidimensional hyperbolic-parabolic equations. When studying these applications, it becomes necessary to obtain an explicit representation of the solutions to the problems under study. Boundary value problems for hyperbolicparabolic equations on the plane are well studied, and their multidimensional analogues are little studied. The Tricomi problem for these equations was previously investigated. As far as we know, this problem has not been studied in space. In this paper, the Tricomi problem is shown to be ambiguously solvable for a class of multidimensional mixed hyperbolic-parabolic equations.

Application of Alternating Current Stress Measurement Method in the Stress Detection of Long-Distance Oil Pipelines

With the development of pipeline networks, many safety accidents were caused by pipeline stress concentration; it is of great significance to accurately monitor the pipeline stress state for maintaining pipeline safety. In this paper, based on alternating current stress measurement (ACSM) methods, a 3D simulation model of a pipeline electromagnetic field was established by ANSYS software. The distribution law of the pipeline magnetic field and eddy current field were analyzed, and the influence of size and structure parameters of the coil inside the probe were studied. The internal stress detection system of the pipeline was designed, and the static tensile stress measurement experiment was carried out. Simulation and test results showed that the excitation coil with a larger diameter-to-height ratio had a higher measurement sensitivity. The sensitivity of the probe decreased monotonically with the increase of the difference between inner diameter and outer diameter of the detection coil. It increased monotonically with the increase of the equivalent radius of the detection coil. The best measurement results were obtained when the detection coil was located at the center of the two legs of the U-magnetic core. The results showed that the system could identify the pipeline stress concentration area effectively after detection engineering.

Analysis of electromagnetic vibration and noise of permanent magnet synchronous motor based on field-circuit coupling

In order to study the influence of harmonics on the vibration and noise of permanent magnet synchronous motor, this paper introduces an analysis method based on field-circuit coupling, and establishes a complete analysis process from the control strategy to the vibration and noise response of the motor. Firstly, the coupling model including control strategy, main circuit model and electromagnetic field model is established. Secondly, the finite element model of the permanent magnet synchronous motor under the influence of coupling is established to analyze and compare the electromagnetic force wave characteristics of the coupling excitation and the sinusoidal excitation. Then, the coupled electromagnetic force is loaded into the structural field to simulate and calculate the vibration and noise. Finally, the effectiveness of the model is verified through experimental sound pressure level comparison under steady-state and speed-up conditions, and it provides a reference for vibration and noise prediction of the motor system.

Erbium-ytterbium co-doped photonic crystal fiber amplifier supporting amplification for orbital angular momentum

In order to reduce the loss in orbital angular momentum (OAM) long-distance communication systems, an OAM erbium-ytterbium co-doped fiber amplifier (OAM-EYDFA) based on photonic crystal fiber (PCF) is proposed and investigated for the first time in this work. We set up a three-dimensional electromagnetic field model of the PCF in Comsol and solved it by the finite element method. Then, we designed a three-dimensional model of the OAM-EYDFA based on the proposed PCF using Comsol and MATLAB. The results reveal that the proposed OAM-EYDFA has a flat-high gain of about 47 dB, a differential mode gain of lower than 0.3 dB and a noise figure of lower than 3.4 dB. Compared with existing studies, its gain is increased by at least 25 dB, and other properties are also improved. The proposed OAM-EYDFA can provide a reference for OAM-based long-distance communication systems.