Electromagnetic Applications Research Articles

An adaptive multigrid solver for DPG methods with applications in linear acoustics and electromagnetics

We propose an adaptive multigrid preconditioning technology for solving linear systems arising from Discontinuous Petrov–Galerkin (DPG) discretizations. Unlike standard multigrid techniques, this preconditioner involves only trace spaces defined on the mesh skeleton, and it is suitable for adaptive hp-meshes. The key point of the construction is the integration of the iterative solver with a fully automatic and reliable mesh refinement process provided by the DPG technology. The efficacy of the solution technique is showcased with numerous examples of linear acoustics and electromagnetic simulations, including simulations in the high-frequency regime, problems which otherwise would be intractable. Finally, we analyze the one-level preconditioner (smoother) for uniform meshes and we demonstrate that theoretical estimates of the condition number of the preconditioned linear system can be derived based on well established theory for self-adjoint positive definite operators.

Lightweight and flexible poly(ether-block-amide)/multiwalled carbon nanotube composites with porous structure and segregated conductive networks for electromagnetic shielding applications

An innovative method was firstly used to prepare lightweight, deformable, and stable conductive composites with segregated structure and microcellular morphology inside. The segregated structure enables the composites to achieve satisfactory conductivity and electromagnetic interference shielding effectiveness with low multiwalled carbon nanotube content. Additionally, the microcellular poly(ether-block-amide) beads promote the composites to display lightweight and outstanding deformability, while protecting the continuity of conductive network during deformation process. The elongation at break of composites has reached to be 70%, and the hysteresis during cyclic tension and compression is as low as 15%. After undergoing cyclic deformation behavior in tension and compression modes, the conductivity and electromagnetic interference shielding effectiveness of the composites remained almost the same as those original values, indicating well stable conductivity. Thus, this composite with light weight, outstanding deformability and stable conductivity obtained via an environmentally friendly and simple molding process has very advantageous application in flexible electronic field.

Dielectric Relaxation Spectroscopy and Synergy Effects in Epoxy/MWCNT/Ni@C Composites

The dielectric/electric properties of the Ni@C (carbon-coated Ni)/epoxy composites and Ni@C/MWCNTs (multi-walled carbon nanotubes)/epoxy composites loaded with fixed MWCNTs amount just below the percolation threshold (0.09 vol.%) and Ni@C at different concentrations up to 1 vol.% were investigated in broad frequency (20 Hz–40 GHz) and temperature (30 K–500 K) regions. In composites with the only Ni@C nanoparticles, the electrical percolation threshold was determined between 10 and 15 vol.%. Above the percolation threshold the dielectric permittivity (ε’) and the electrical conductivity (σ) of the composites loaded with Ni@C only are high enough, i.e., ε’ = 105 and σ = 0.6 S/m at 100 Hz for composites with 30 vol.% Ni@C, to be used for electromagnetic shielding applications. The annealing to 500 K was proved to be an effective and simple tool to decrease the percolation threshold in epoxy/Ni@C composites. For hybrid composites series an optimal concentration of Ni@C (0.2 vol.%) was determined, leading to the conductivity absolute values several orders of magnitude higher than that of a composite filled with MWCNTs only. The synergy effects of using both fillers have been discussed. Below room temperature the electrical transport is mainly governed by epoxy resin compression in all composites, while the electron tunnelling was observed only in hybrid composites below 200 K. At higher temperatures (above 400 K), in addition to the nanoparticles redistribution effects, the electrical conductivity of epoxy resin makes a significant contribution to the total composite conductivity. The dielectric relaxation spectroscopy allows estimating the nanoparticles distributions in polymer matrix and could be used as the non-destructive and fast alternate to microscopy techniques for general polymer composite fabrication control.

Ultra-wideband Transmissive Water-Based Metamaterial Absorber with Wide Angle Incidence and Polarization Insensitivity

A transmissive water-based metamaterial absorber(TWMA) is designed, simulated, and measured, which uses 3D-printing to manufacture. The TWMA uses a circular column and rectangular water layer structure and has no metal backplane. We have proved theoretically and experimentally that the TWMA has absorption rate exceeds 90% in the frequency ranging from 6.5 to 21.4 GHz. Furthermore, the TWMA is thermo-tunable when temperatures change from 10 to 60 °C and has the characteristics of wide angle incidence and polarization insensitivity. It can be applied to a variety of electromagnetic applications, such as reducing broadband scattering and collecting electromagnetic energy in a variable temperature environment.

Multi-Objective Optimization of a Line-Start Synchronous Machine Using a Self-Organizing Algorithm

This article introduces the design and optimization of line-start synchronous machines in fractional horsepower industry applications. The proposed optimized design will be considered as a replacement for the induction machine driven from an ac drive. The optimized design will be achieved using a 2-D finite-element transient analysis and multi-objective optimization algorithm. For the optimization, a multi-objective self-organizing migrating algorithm was chosen. The optimization results are compared with the more popular nondominated sorting genetic algorithm (NSGA-II) algorithm, to prove algorithm sufficiency with three objectives and five design parameters in the area of the electromagnetic design application.

An ultra-broadband and optically transparent metamaterial absorber based on multilayer indium-tin-oxide structure

In this work, an ultra-broadband and polarization-insensitive metamaterial absorber (MA) with high optical transparency is presented. Indium-tin-oxide (ITO) films are used as frequency selective surfaces in multiple conductive layers and also as the reflective backplane. Numerical simulation analysis demonstrates that the absorptivity of the proposed absorber exceeds 90% in the frequency range from 10 to 75.5 GHz, corresponding to a relative absorption bandwidth of 153%. The proposed structure has a total thickness of 2.9 mm, which is approximately 1/10 of the free space wavelength of its lowest operating frequency. The absorber also has good polarization insensitivity due to its symmetric geometry. Moreover, for TE-polarized waves, the proposed absorber can maintain an absorptivity greater than 70% for frequencies ranging from 10 to 80 GHz as the incident angle is increased to 45°. For TM-polarized waves, it provides absorptivity of more than 80% at incident angles up to 60°. Surface current distribution on each conductive ITO layer was simulated to analyze the absorption mechanism of the MA. A prototype composed of 16 × 16 unit cells was fabricated and the experimental results show a good agreement with the numerical simulations. Due to its ultra-wideband absorption and wide-incident-angle stability, the proposed MA has potential value in electromagnetic applications such as optically transparent EM shielding and microwave radiation protection.

Percolated cermets of nickel/yttrium iron garnet for double negative metacomposites

Dielectric and magnetic properties of percolative nickel/yttrium iron garnet cermets were investigated. With nickel content increasing, microstructure evolution of the cermets exhibited characteristics of percolation, resulting in electrical conductivity increased dramatically and conduction mechanism changed from hopping to metallic behaviors. Negative permittivity and negative permeability were observed. Negative permittivity was caused by the plasmonic state of delocalized electrons. Negative permeability was attributed to magnetic resonance of ferromagnetic constituents and diamagnetic responses of eddy currents induced in interconnected nickel networks. The obtained double negative metacomposites enriched metamaterials and have great potential in electromagnetic shielding, cloaking, and attenuation applications.

The dynamics of polarization and magnetization: Susceptibilities of magnetoelectric multiferroic heterostructure

The dynamic susceptibility is the crucial parameter of a material, especially when the material is needed to be applied in the electromagnetic applications. In this report, we discuss the magnetic and the electric susceptibilities of a magnetoelectric (ME) multiferroic heterostructure comprised of ferromagnetic (FM) and ferroelectric (FE) materials. Since the magnetoelectric couplings in multiferroic heterostructure have only existed at the interface between FM and FE, then the equation of motions in each lattice in every layer of FM and FE should be considered. The equations of motion in each lattice are solved simultaneously by employing entire-cell effective medium approximation. In numerical calculation, the parameters appropriate for Fe and BaTiO3 are used. We found that interfacial ME couplings shift down the resonance frequency for both FM and FE susceptibilities. We also noticed that the addition of the number of FE or FM layer, which raises the number of interface between FE and FM affects the susceptibility curves.

Virtual PTZE Symposium on Applied Electromagnetism in Contemporary Engineering and Medicine

13-16 September 2020On-lineThe beginnings of the Polish Society of Applied Electromagnetism (PTZE) date back to the end of the eighties of the last century, i.e. the time which was full of great historical events. Alongside those events, or perhaps along with them, other, smaller, but perhaps no less important, scientific, social and cultural initiatives germinated. One of them, initiated by a group of several people, was the idea of an association of specialists devoted to the applications of electromagnetic field.The goals of PTZE are generally concentrated on the following issues:• promotion of cooperation between scientists of various disciplines in the area of applied electromagnetism;• publishing books, monographs and training materials;• assistance in training young research staff through scholarship exchanges and organization of research internships;• organizing symposiums and conferences, both national and international;• collaboration with existing domestic and foreign companies,• coordination of research work in the area of various applications of electromagnetic field, with particular emphasis on research in response to social concern related to modern electromagnetic techniques.Fulfilling the above fields of activity the members of PTZE and collaborating scientists prepared contributions to the present issue of Journal of Physics Conference Series. The contributions were preceded and inspired by the conference presentations at the Virtual Symposium of Applied Electromagnetism in Modern Engineering and Medicine. Therefore, the papers are devoted to the subject of the conference and present wide spectrum of the electromagnetic field applications. However, the three areas of interests are to be highlighted: modern electrical engineering applications, biotechnological and agricultural applications and bioelectromagnetic and biomedical applications. They constitute the image of the contemporary situation in the world-wide research of applied electromagnetism.All the articles, submitted to the issue, have passed the peer review procedure. The Guest Editors hope that the articles will be helpful in grasping and adopting some ideas connected with the modern applications of electromagnetic field.All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.List of Editors of the conference proceedings, Scientifing Committee, Organizing Committee are available in this pdf.

Anapole Tolerance to Dissipation Losses in Thermally Tunable Water-Based Metasurfaces

We theoretically and experimentally demonstrate a thermally tunable anapole metasurface. By thermally changing the dielectric function, our studies unveil the tolerance of the nonradiating anapole source to the presence of dissipation losses in systems of all-dielectric meta-atoms. The so-called anapole state is an ac current distribution of electric and toroidal dipoles in such a relation that their exclusive destructive interference leads to the absence of far-field radiation. It has been shown to exist in variable dielectric configurations that involve assemblies of infinite dielectric rods, yet a systematic study of its tolerance to losses is still open. Here we examine two designs focusing on their tolerance to dissipation losses: one combining the toroidal mode of a peripheral four-cylinder system with the mixed toroidal mode of a single central cylinder of adjusted size, and another consisting of five rods in a regular pentagon arrangement. The first design exhibits a particularly enhanced toroidal dipole moment and high anapole precision. The second design exhibits anapole states with enhanced loss tolerance and, thus, it is the target of our experimental investigation. For the experiment, we use water-based rod metasurfaces designed for anapole operation in the microwave regime and we employ a characterization in a standard rectangular waveguide. The dielectric properties of water exhibit significant temperature dependence that allows for controlled permittivity and dissipation, leading to the dynamical modification of Mie resonances in meta-atoms. Thus, we experimentally prove the emergence of an anapole state and its tolerance to the losses in a well-controlled system; furthermore, we demonstrate and expose the potential of aqueous schemes for tunable electromagnetic applications.

ОБОБЩЕННАЯ МОДЕЛЬ ДВУХКАТУШЕЧНОЙ СИНХРОННОЙ ЭЛЕКТРОМАГНИТНОЙ МАШИНЫ ДЛЯ ТЕХНОЛОГИЧЕСКИХ СИСТЕМ ВИБРОУДАРНОГО ДЕЙСТВИЯ

Актуальность исследования обусловлена тем, что силовые электрические импульсные системы, созданные на основе линейных электромагнитных машин ударного и виброударного действия, являются перспективными для применения в технологиях по интенсификации процессов, связанных с поиском, добычей и переработкой георесурсов. В вопросах энергосбережения особый интерес вызывают линейные синхронные электромагнитные машины возвратно-поступательного движения ударного и виброударного действия. Частота ударов бойка в данных машинах синхронно связана с частотой источника промышленной сети переменного тока. К главным достоинствам оборудования, использующего линейные синхронные электромагнитные машины ударного и виброударного действия, относится снижение потребления электрической энергии при работе в резонансных режимах или близких к резонансным режимам. Исследование данных режимов связано с построением точных динамических моделей различных модификаций синхронных электромагнитных машин ударного и виброударного действия, работающих исключительно в переходных режимах. Цель: разработать обобщенную математическую модель двухкатушечной синхронной машины с электромагнитным приводом для технологических систем виброударного действия, упрощающей процесс математического описания известных вариантов схем машин при проведении динамических расчетов. Методы: дифференциальные уравнения электрического равновесия и механического взаимодействия, поступательно движущихся масс, уравнение Лагранжа второго рода, методы конечно-элементного моделирования двухмерного магнитного поля и структурного моделирования в программе Matlab Simulink, сопоставление расчетных и экспериментальных характеристик. Результаты. Предложена обобщенная расчетная схема построения многомассовой двухкатушечной синхронной электромагнитной машины, включающая известные модификации вариантов схем машин ударного действия. На основе расчетной схемы образована система дифференциальных уравнений обобщенной модели, позволяющая выполнять построение математических моделей, отражающих динамическое состояние известных вариантов схем синхронных ударных машин с электромагнитным приводом. Приведен пример реализации динамической модели четырехмассовой двухкатушечной синхронной электромагнитной машины с упругим реверсом бойка. Приведены результаты имитационного моделирования рабочего режима в виде диаграмм тока катушек, перемещения и скорости бойка, отражающие процессы включения и выхода на квазиустановившийся режим работы. На основе сопоставления значений интегральных характеристик показано, что расхождение результатов расчета и эксперимента составляет 4…6 %, что не превышает общепринятой погрешности для инженерных расчетов. Эффективность применения предложенной обобщенной модели заключается в упрощении математического описания вариантов схем синхронных машин с электромагнитным приводом и сокращении сроков реализации моделей.

Core/Shell Structured Ni/Fe3O4 Composites with Enhanced Electromagnetic Absorption Performances

Core/shell structured Ni/Fe3O4 composites with grain sizes of 200–800 nm were synthesized by using a hydrothermal method. The phase structure, morphology, magnetic and electromagnetic absorption properties of the as-prepared samples were characterized by various analysis techniques. Experimental results revealed that spinel Fe3O4 was in situ deposition on the surface of Ni spheres through electrostatic interactions. Moreover, the Ni/Fe3O4 mass ratios had a significant influence on the electromagnetic absorption performances. When the mass ratio of Ni/Fe3O4 was 1:1, the composites reached an outstanding reflection loss (RL) of [Formula: see text]48.06[Formula: see text]dB at 12.96[Formula: see text]GHz with a thin thickness of 1.8[Formula: see text]mm. Meanwhile, the effective absorption bandwidth was 5.36[Formula: see text]GHz (10.72–16.08[Formula: see text]GHz), covering the X and Ku bands. The enhanced electromagnetic absorption performance of core/shell structured Ni/Fe3O4 composites as compared to pure Ni, may be attributed to the multiple interfacial polarization, magnetic exchange coupling resonance and optimal impedance matching. Consequently, core/shell structured Ni/Fe3O4 composites would be promising candidates for a wider range of electromagnetic absorption applications.

Influence of High-Enthalpy Atmospheric Plasma Spraying Process Parameters on Microwave Dielectric Properties of Y2O3 Coatings

The low-dielectric inorganic adhesive is an important component of electromagnetic wave absorption coatings due to impedance matching with the atmospheric environment. Herein, high-enthalpy atmospheric plasma spraying (HE-APS) equipment is utilized to prepare Y2O3 ceramic coatings, and the influence of spraying power on dielectric and physical properties of Y2O3 ceramic coatings is systematically investigated. The surface and cross-sectional SEM images of Y2O3 coating show that the overall coating morphology is smooth and less porous at high spraying power. This result is consistent with the trend of coating density and porosity. The XRD pattern demonstrates that the Y2O3 coating possesses a stable cubic structure. The experimental results reveal that the dielectric properties of Y2O3 coating are mainly affected by the porosity. According to the dielectric mixing rule of composite materials, Y2O3 coating exhibits the minimum density of 4.86 g/cm3 and permittivity of 9.70 under the spraying power of 55 kW. The current work highlights the feasibility of Y2O3 as a low-dielectric inorganic adhesive in the field of electromagnetic wave applications.

A COMINRES‐QLP method for solving complex symmetric linear systems

AbstractSolving complex symmetric systems efficiently is a significantly important issue in the applications of electromagnetics since the discretization of the numerical model using the finite element method results in complex symmetric systems when computing the electromagnetic field. However, such complex symmetric systems are usually much more difficult to be solved because of the property of non‐Hermitian. Therefore, efficient numerical methods for the solution of complex symmetric systems are demanded. In this study, we proposed an iterative method called COMINRES‐QLP which is specially designed for complex symmetric linear systems. Moreover, we proposed a new stopping criterion which could be very useful in practical computations when the condition number of the coefficient matrix is unknown.

Dielectric passive left-handed symmetric metamaterial design for electromagnetic absorption reduction application

Electromagnetic exposure became an alarming issue in the 20th century, which has resulted in the creation of shielding metamaterial to reduce the radiation effects from any wireless devices. In this research work, a square-shaped metamaterial structure was designed and numerically simulated using a well-known computer simulation technology microwave studio software. The relationship between human head and cellular phone was explored for L- and S-bands, respectively. The proposed metamaterial design is utilized by placing inside a mobile phone to reduce the electromagnetic effect that is absorbed by the human head. The simulation frequency range is adopted from 1 to 6 GHz where the square-shaped metamaterial manifests resonance frequencies at 1.602 GHz (L-band), 2.712 and 3.888 GHz (S-band). Meanwhile, the specific absorption rate results reveal that the reduction happened approximately 1.591% at L-band, 36.646% and 17.864% at S-band over 1 g of tissue volume. Moreover, the second highest reduction value exhibited at 2.712 GHz for 10 g of tissue volume with 20.077% respectively. Briefly, the findings reveal a strong specific absorption rate reduction accomplishment and the proposed square-shaped metamaterial design believed to be a promising aspect in the telecommunication field.

The effects of vacancy and heteroatoms-doping on the stability, electronic and magnetic properties of blue phosphorene

In this work, we have systematically studied the stability, electronic structure and magnetic properties of the pristine, four defect states case of blue phosphorene and the six heteroatoms doping in blue phosphorene by first-principles calculations. In our findings, both defects and heteroatoms doping can regulate the band gap of blue phosphorene and the transition from indirect to direct band gap can be dramatically tuned by DV1BP, DV2BP and Al, Si atoms substitutional doping in blue phosphorene. The presence of defects and heteroatoms doping effectively modulates the electronic properties of blue phosphorene, rendering the defect-containing phosphorene semiconducting with a tunable band gap. Spin–orbit coupling can be induced by introducing SV-, DV- defects in blue phosphorene. The results provide theoretical guidance for future bandgap regulation and magnetism, defective and substitutional doping blue phosphorene may have potential electro-optical and electromagnetic applications.

A simulation and experiment coassisted learning platform for understanding electromagnetic interaction in a smart grid

AbstractAn innovative current measurement method in power systems has attracted more attention from both the industry and academia. Nevertheless, students can feel challenged when assigned to learn new concepts with the currently already difficult engineering courses. Therefore, in this paper, a training platform is designed based on finite element analysis simulation and laboratory experiments. With this training platform, simple and effective simulations and experiments can be performed. In addition, extended applications of this training platform are presented such as design of the magnetic shielding structure, magnetic flux density visualization and calculation of overhead power lines. This design can help engineering students to better understand the application of electromagnetics and the novel current measurement research field.

Structural, dielectric, and magnetic studies based on MWCNTs/NiFe2O4/ZnO nanoparticles dispersed in polymer PVA/PEO for electromagnetic applications

The hydrothermal and the co-precipitation methods were used for the formation of new multifunctional MWCNTs/NiFe2O4/ZnO (MNFZ) hybrid nanostructures. The MNFZ hybrid nanostructure formation was asserted by characterizing it via the X-ray diffraction (XRD) analysis and TEM. Then, the casting technique was used for preparing the MNFZ nanoparticle-doped Poly (vinyl alcohol) (PVA) and poly (ethylene oxide) (PEO) by various concentrations of MNFZ NPs as nanofiller. All polymer blend and nanocomposite films are shown by XRD studies to have a semicrystalline nature with a reduced degree of semi-crystallinity with the dopant. The infrared absorption band shift and the intensity change indicate the interaction or complexation between the blend and nanofiller is confirmed by FTIR studies. The volume percentage variation of the nanoparticles and the ferromagnetic response variation of the nanocomposite were in consistency. The dielectric characteristics and ac conductivity of the film polymer blend were higher upon adding the nanofiller because the charge carrier number was higher. Such features of MNFZ-doped PVA/PEO films prove their appropriateness as materials for electromagnetic applications.

Characterization of an electrically conductive proppant for fracture diagnostics

Fracture diagnosis with electromagnetic (EM) and electrical tools requires proppants with high electrical conductivity and mechanical strength. Lab measurements of the electrical and hydraulic conductivity of proppants are critical for selecting the best candidates. Such measurements greatly benefit simulations, field tests, and the ultimate application of such proppants in the field. To that end, a new lab protocol is developed for measuring the electrical and hydraulic conductivity of proppants. The lab setup, which mainly includes a resistivity core holder and a Hassler sleeve core holder, allows for simulation of realistic pressure and temperature conditions when making measurements. Petroleum coke (PC) is proposed as a candidate proppant because of its widespread availability and low cost. Lab measurements show that the effective electrical conductivity of pure PC in a model fracture is approximately 5000 S/m, under a closure stress greater than [Formula: see text] (4000 psi). When PC is mixed with sand, the effective electrical conductivity of the mixture decreases with an increasing weight percentage of sand. Although sand degrades the contact between PC particles, the electrical conductivity stays reasonably high (approximately 1700 S/m) when 50% sand is added. Hydraulic conductivity measurements show that when a fracture is propped with pure PC, the measured fracture conductivity is greater than [Formula: see text] ([Formula: see text]) (dimensionless fracture conductivity greater than 100 for a shale with [Formula: see text] or 100 nD permeability) under a confining pressure of [Formula: see text] (6000 psi). This means that a fracture propped with PC is infinitely conductive in a typical shale formation. When sand is added, the fracture’s hydraulic conductivity becomes even higher, which clearly shows PC’s ability of sustaining high stresses. The proposed protocol provides a robust and effective method that can be generalized for lab testing for other candidate proppants. The data presented clearly show that PC has the potential for field-scale applications in EM hydraulic fracture diagnostics.

Biodegradable nanocomposites based on PLA/PHBV blend reinforced with carbon nanotubes with potential for electrical and electromagnetic applications

Biodegradable nanocomposites based on PLA/PHBV blend reinforced with carbon nanotubes with potential for electrical and electromagnetic applications