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This contribution aims to analyze compliance with the rules relating to disturbances in the domain of health due to exposure to electromagnetic fields (EMF). This concerns safety standards for exposed living tissue and the integrity of exposed medical devices acting on the body. This investigation is carried out by reviewing and analyzing these exposure effects. In the paper, the EMF exposure, the nature of sources and the characters of their interactions with objects are first illustrated. Then, EMF exposure restrictions accounting for living tissues safety standards as well as medical devices constancy are discussed. Exposure biological effects comprising both thermal and non-thermal effects are then detailed. The verification and control of EMF effects are next illustrated including mathematical modeling of EMF effects, governing equations and body tissues representation in the solution of these equations. At the end of the paper, two examples representing the cases of tissues and devices are given to check the rules under exposure to EMF: biological effects on exposed human tissues and integrity of a magnetic resonance imager under external disturbance. [ABSTRACT FROM AUTHOR]

This paper proposes a way to represent the anisotropic nonlinear superconducting properties using a discrete model for magnetization with the corresponding critical parameters, equivalent to the Power Law model for currents. This simplified model makes it possible to analyze magnetic systems with superconducting elements in a stationary mode, which reduces the calculation time. Using of proposed model is demonstrated by the calculation of force interactions between high-temperature superconducting (HTS) samples and permanent magnet in zero-field-cooling (ZFC) and field-cooling (FC) modes. HTS bulks in the form of a prism and stack made of HTS tape are considered. The calculation of the electromagnetic field was carried out using the method of integral equations for field sources. The data of calculations are compared with the results of experimental studies. [ABSTRACT FROM AUTHOR]

Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a robust frequency-domain method to tune the d–q decoupled control system used in Modular Multilevel Converter-type Voltage Source Converter (MMC-VSC) systems. A linearized state-space model of the MMC-VSC system is developed and used to calculate the stability-related frequency-domain attributes. The controller design problem is formulated as an optimization problem. In this paper, the simulated annealing optimization technique is applied to find the proportional-integral (PI) controller parameters that give desired damping for the oscillatory modes and desired values for decaying exponential modes. The efficacy of this method is tested on the electromagnetic transient model of a two-terminal MMC-VSC system on the real-time digital simulators, and the results are provided in this paper. Finally, tuned controller parameters for different ac system strengths are discussed and it is shown that this mathematical model is suitable to tune the PI-controller parameters for MMC-VSC systems connected to strong as well as weak ac networks. [ABSTRACT FROM AUTHOR]

Numerical techniques for calculating electromagnetic fields within three-dimensional surfaces are computationally intensive. Therefore, this paper presents the application of a mode-matching technique developed for analyzing electromagnetic scattering from periodic comb surfaces illuminated by a plane wave. A set of linear equations has been developed to calculate mode coefficients of the field distribution for both E- and H-polarized incident waves. Analysis is performed for two cases where the comb thickness is either infinitely thin or of a finite thickness. The technique is shown to accurately predict both field intensities within the near-field of the periodic surface and far-field scattering patterns. Results are compared to those obtained using the finite integration techniques (FIT) implemented in CST Microwave Studio. Furthermore, numerical results are compared to measurements of an aluminum prototype. Additional far-field scattering measurements using a bi-static system provide additional confidence in CST simulations and the mode-matching methods presented here. [ABSTRACT FROM PUBLISHER]

The nonconformal domain decomposition methods (DDMs) of the hybrid finite element-boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA) are presented for computing large electromagnetic scattering/radiation problems. The numerical performance of different transmission conditions between finite element method (FEM) subdomains, and FEM and BI domains is studied in this paper. The Dirichlet transmission condition (DTC) employed at the interface between FEM and BI domains has faster convergence than the Robin-type transmission condition, and this finding is different from the conclusions for the FEM DDMs published in the literature. Furthermore, the cement-element (CE)-based dual-primal finite element tearing and interconnecting (FETI-DP) DDM has faster convergence than the Lagrange-multiplier-based FETI-DP method under the FE-BI system, and is also different from that under the system of the FEM with the absorbing boundary condition (FEM-ABC). It shows that the DDMs of FE-BI-MLFMA have some essential differences from those of FEM-ABC. The analysis of these numerical phenomena is presented in this paper. Further comparison between the DDMs of FE-BI-MLFMA and FEM-ABC demonstrates that the DDMs of FE-BI-MLMFA have essential advantages over those of FEM-ABC. Various numerical experiments confirm the accuracy, efficiency, and flexibility of the nonconformal DDM of FE-BI-MLFMA, which is the CE-based FETI-DP DDM with DTC connecting FEM and BI. [ABSTRACT FROM AUTHOR]

An analysis method for characteristics calculation of electric machines is proposed in order to take the effects of eddy currents and hysteresis phenomenon in laminated cores into account. In the proposed method, both the effects of eddy currents and hysteresis phenomenon are expressed as reaction magnetic fields against the exciting field. These fields are determined by coupling the main electromagnetic field analysis that neglects the detailed structures of laminated cores, and 1-D time-stepping analysis along the thickness of electrical steel sheets. The validity of this coupling is confirmed by comparing the measured and calculated results of the core-material characteristics. The effects of the reaction field on the torque characteristics of rotating machines are also clarified. [ABSTRACT FROM AUTHOR]

It is popular to use moving elements to improve heating uniformity during microwave heating under some situations. However, it is still a challenge to simulate moving elements during microwave heating due to the complexity of mathematical modeling. In this paper, a novel continuous algorithm based on implicit function and level set methods is developed to compute this heating process. By introducing the implicit function and level set methods, the moving region’s properties are set as a function of space coordinate and time, which means that the movement of the elements is represented by the variation of the parameters. In addition, with the coordinate transformation, the coupling process of electromagnetic field and heat transfer in microwave heating can be performed. A 2-D applicator model and a 3-D applicator model with a rotating turntable are used to illustrate the proposed method in detail. Experiments are also conducted to testify the validity of the proposed method. The results obtained by the proposed method are in accordance with those obtained by experiments. Moreover, compared with conventional methods, the proposed method is more accurate and efficient. [ABSTRACT FROM AUTHOR]

The article focuses on proposal and analysis of the physical models suitable to stress simulation and limit state prediction of components made of composite structure on Onyx basis. The observed parameters are physical properties of matrix and reinforcement. The additive manufacturing technologies also allow the production of complex shape constructions with cavities. The cavities are regions characteristic of damage initiations, but a realization of experimental measurements on inner surfaces of them to predict failure is problematic. Therefore, the exploitation of appropriate physical models and subsequently mathematical models is a method for observing of material behaviour using selected physical quantities beyond surface layers. The modelling of composite structures is viable using physical models, which working principle is based on homogenization of structure, for instance, representative volume elements (RVE). The primary disadvantage of RVE models is a complicated analysis of physical properties at inhomogeneity places of reinforcement. The physical model proposed in this paper describes each fibre separately regarding authentic physical properties and precise determination of fibre deposition in the matrix. Implementation of FEM programs with a primary objective to perform formation and analysis of the physical models, provides solution of various multiphysical problems, such as nonlinear behaviour of material induced by contact, temperature variation or interaction with other environments (temperature, fluid, electromagnetic fields), and so on. The main aspect of the presented concept is the generation of computational models with a precise definition of fibre deposition in the composite structure. The numerical analysis of loading and limit state prediction was executed on models of the composite structure. The structure includes onyx as a thermoplastic matrix and carbon fibres. The fundamental physical criterions for damage initiation assessment were stress state and strain at critical locations of matrix and reinforcement. [ABSTRACT FROM AUTHOR]

The air-cooled turbo-generator often works in the more frequent start-up and shut-down operation. Either the misoperation or the failure of synchronizing controllers can cause the out of phase synchronization fault. The fault can disturb the power angle and cause a strong impact electromagnetic force for the generator. With the traditional numerical calculation method, it is difficult to calculate the variations of key physical parameters and the electromagnetic field in the end region of the generator under complex working conditions, especially the out of phase synchronization fault. In order to solve the problem, a calculation method of the nonlinear transient electromagnetic field with multi-domain field-circuit-grid coupled is proposed. The correctness of the model and method is validated by comparing the calculated and test values of the magnetic density flux at the key points of the generator under the no-load condition. Based on this method, the power angle variation, the magnetic flux leakage distribution in the end region, and the electromagnetic force on the end winding in the transient process of the fault are calculated and analyzed. [ABSTRACT FROM AUTHOR]

The paper presents analysis of surface induction hardening of a cylindrical element made of steel 38Mn6. The mathematical model of the non-stationary process is elaborated. Calculations of coupled electromagnetic and temperature fields are provided by means of the Flux 2D software. Computations are compared with the measurements realized at the laboratory stand located in the Silesian University of Technology. The expected hardness distribution within the surface layer is noticed. [ABSTRACT FROM AUTHOR]

The aim of this paper is to highlight the capabilities of a new hybrid analytical modeling (HAM) approach for the analysis and design of various electromagnetic structures. After an introduction, where the aim of the development of this modeling approach is presented, the modeling approach is described. The new HAM is based on a strong coupling of the magnetic equivalent circuits method and analytical models (AMs). The AM, based on the formal solution of Maxwell’s equations, is established thanks to the separation of variables method. The HAM is applied to different permanent magnet electric machine structures, and the results are validated extensively by comparison with the finite-element analyses. [ABSTRACT FROM AUTHOR]

Solid dielectrics have been widely investigated as potential attractive candidates in compact portable pulsed-power systems. Slow-wave structure with good dispersion characteristics and broad transmission band can be used to increase the pulse duration while the size of pulse-forming line (PFL) decreases. In this paper, we present two different slow-wave structures, the tape helix for coaxial-line and the meander-line structure for the planar line, to increase the pulse duration of solid PFLs based on dispersion analysis. At first, the characteristic impedances, electric length, and dispersion curve of the PFL with the slow-wave structure are calculated by the electromagnetic dispersion theory. Based on the theoretical calculations, the PFLs are designed and simulated by the electromagnetic field tool. Finally, some test results on the PFLs are introduced. Currently, both the Al2O3 ( \varepsilon r= 9.3 ) helical PFL and the glass–ceramic ( \varepsilon r = 225 ) meander-line PFL can deliver a pulsewith 50-ns width, of which the dimension is \phi ~67~\mathrm mm \times 305 mm and 95~\mathrm mm \times 95~\mathrm mm\times 4 mm, respectively. [ABSTRACT FROM PUBLISHER]

A mathematical model is presented for the optimisation of an Electromagnetic Halbach Array (EHA) for wireless power transfer. The mathematical model is based on Biot‐Savart's law of magnetic field in a current‐carrying square loop. The model is validated through static electromagnetic simulations in ANSYS Maxwell and found to be accurate and effective when predicting the magnetic field within the EHA box. To verify the analytical and simulation results, an EHA was fabricated, and experimental verification was carried out. The results show that the mathematical model can be widely used in the analysis and design optimisation of EHAs of any size and with diverse parameters in the case of single‐layer square spiral planar coils. [ABSTRACT FROM AUTHOR]

Pneumothorax is the medical condition caused by the air concentration inside the pleural cavity, the space between the lung and the chest wall. Apart from traditional diagnostic methods, it can be detected by using microwave sensors that capture variations in reflected electromagnetic field (EMF). Sex and obesity, related to the internal composition of the biological tissues, can influence the reflected EMF and therefore the sensor diagnostic ability. This paper investigates the effect on the performance of a proposed on-body dual-patch antenna sensor for pneumothorax diagnosis, due to inter-subject variability in underlying tissue structure. The sensor operates at frequency range of 1-4GHz. The challenge of the paper is to propose frequency bands for robust and safe sensor operation. S12 parameter alternation versus frequency is assessed for healthy and pathological cases. Implemented thorax numerical models include modified (i) closed rectangular multilayered and (ii) MRI-based anatomical ones. In rectangular models, thickness and configuration of muscle, fat and bone tissues are varied, according to literature. Additionally, sex-related anatomical differences are taken into account in MRI-based models. All scenarios are solved using Finite Difference Time Domain method. Results revealed that the proposed frequency bands lie within 1-2.7 and 2.9-3.5GHz, for muscle, 1.4-3.5GHz for fat and 1-2.2 and 2.8-3.5GHz, for bone variations. Numerical evaluations for accurate anatomical models verify the findings. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the existence and multiplicity of solutions for perturbed Schrödinger equation with electromagnetic fields and critical nonlinearity in RN: -ε²ΔAu(x) + V(x)u(x) = |u|2*-2u + h(x, |u|²)u for all x ∈ RN, where ∇Au(x) := (∇ + iA(x))u, V(x) is a nonnegative potential. By using Lions' second concentration compactness principle and concentration compactness principle at infinity to prove that the (PS)c condition holds locally and by variational method, we show that this equation has at least one solution provided that ε < ε, for any m ∈ N, it has m pairs of solutions if ε < εm, where ε and εm are sufficiently small positive numbers. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor. [ABSTRACT FROM PUBLISHER]

Determination of the distribution of electromagnetic energy inside electrically large enclosed spaces is important in many electromagnetic compatibility applications, such as certification of aircraft and equipment shielding enclosures. The field inside such enclosed environments contains a dominant diffuse component due to multiple randomizing reflections from the enclosing surfaces. The power balance technique has been widely applied to the analysis of such problems; however, it is unable to account for the inhomogeneities in the field that arise when the absorption in the walls and contents of the enclosure is significant. In this paper, we show how a diffusion equation approach can be applied to modeling diffuse electromagnetic fields and evaluate its potential for use in electromagnetic compatibility applications. Two canonical examples were investigated: a loaded cavity and two cavities coupled by a large aperture. The predictions of the diffusion model were compared to measurement data and found to be in good agreement. The diffusion model has a very low computational cost compared to other applicable techniques, such as full-wave simulation and ray-tracing, offering the potential for a radical increase in the efficiency of the solution high frequency electromagnetic shielding problems with complex topologies. [ABSTRACT FROM PUBLISHER]

The aim of this paper was to estimate fermentation kinetic parameters to develop a mathematical model of the bioethanol production under magnetic field effect. Thus, a non-structured mathematical model was developed considering three non-lineal kinetic models typically known as Levenspiel, Aiba, Jerusalimsky, which take into account inhibitory effects of the high product concentration on yeasts. The non-lineal differential equations system solution was carried out by MatLab software using the Runge-Kutta fourth-order multivariable method. This method was improved through a replication scheme coupled with Newton-Raphson method modified with a damping Broyden parameter. Experimental data on substrate consumption, biomass formation and ethanol production were collected at magnetic field intensities (H) of 414, 796 and 1216 A/cm during 16 h of fermentation. Consequently, the adjusted model for biomass, consumed substrate and bioethanol produced allowed us to correlate fermentation kinetic parameters with the magnetic field. The best result was observed when Jerusalimsky model modified with a magnetic field parameter was considered, because the RMSD order and R-square correlation coefficient were around 10−3 and higher than 0.95, respectively. These results are important to understand the phenomenological behavior of this unconventional bioprocess and be helpful to further sensibility analysis and scale up of the bioethanol production assisted by electromagnetic field. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper deals with some aspects of formulation and implementation of a broadband algorithm with build-in analysis of some dispersive media. The construction of the finite element method (FEM) based on direct integration of Maxwell's equations and solution of some additional convolution integrals is presented. The broadband, fractional model of permittivity is approximated by a set of some relaxation sub-models. The properties of the 3D time-dependent formulation of the FEM algorithm are determined using a benchmark problem with the Cole-Cole and the Davidson-Cole models. Several issues associated with the implementation and some constraints of the broadband finite element algorithm are presented. [ABSTRACT FROM AUTHOR]

This paper describes iterative methods for the high frequency electromagnetic analysis using the finite element method of Maxwell equations including displacement current. The conjugate orthogonal conjugate gradient method has been widely used to solve a complex symmetric system. However, the conventional method suffers from oscillating convergence histories in large-scale analysis. In this paper, to solve large-scale complex symmetric systems arising from the formulation of the E method, an iterative substructuring method like the minimal residual method is presented, and the performance of the convergence of the method is evaluated by numerical results. As the result, the proposed method shows a stable convergence behavior and a fast convergence rate compared to other iterative methods. [ABSTRACT FROM AUTHOR]

A new wideband circular high-impedance surface (HIS) is proposed. Two models are developed to analyze the reflection characteristics of the proposed HIS. It is also shown through simulations that a circular HIS as a ground plane for loop antennas is superior to a rectangular HIS ground plane. The circular HIS was fabricated and a loop antenna was placed above it. Measurements were then performed and their results were compared with simulations. An excellent agreement was indicated. [ABSTRACT FROM PUBLISHER]

The interaction between an ensemble of cylinders and an inhomogeneous plane wave is introduced and is determined, in the present paper, through a rigorous theoretical approach. Scattered electromagnetic field generated by an indefinite number of infinite circular cylinders is analyzed by the application of the generalized vector cylinder harmonics (VCH) expansion. The exact mathematical model relied upon to represent this scenario considers the so-called complex-angle formalism reaching a superposition of vectorial cylindrical-harmonics and Foldy-Lax Multiple scattering equations (FLMSE) to account for the multi-scattering process between the cylinders. The method was validated by comparing the numerical results obtained with the use of the finite element method and a homemade Matlab code. [ABSTRACT FROM AUTHOR]

The article presents the author's views regarding the study on the design and analysis of hybrid coupler bandwidth 180°. The authors state the use of Klopfenstein taper and design proprietary techniques in developing broadband hybrid coupled structures. Also presented are graphs which depicts the performance of a hybrid coupler which includes the voltage standing wave ratio (VSWR) delta port input, insertion losses of two inputs and differential phase output.

The technological process of aluminium electrolysis is a complex scientific and technical task. This is due to a large number of internal, external and resultant factors. The aim of this work is to analyse these factors, assess them and their influence on the technological process of electrolysis and develop a comprehensive and mathematical model of aluminium production in the Soderberg electrolyser. The work analyses the technological process of primary aluminium production on the basis of the Bayer method and then on the basis of the Hall–Eru method. The existing methods and technologies for computer modelling of the technological process are analysed. The modern methods of analysis for thermal and electromagnetic fields in electrolysers are considered. On the basis of an in-depth analysis, a number of factors influencing the process of primary aluminium production are identified. Using the methods of system analysis to analyse the identified factors, a ranked list of factors according to the degree of influence is obtained. Using the Pareto diagram, we obtain a list of factors with maximum impact. A conceptual model of the technological process is derived. Based on the obtained conceptual model, the mathematical model of the technological process is derived. The conducted research may be useful to specialists in the field of metallurgy for the analysis of the technological processes of primary aluminium production. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of heating and the structural resultant changes of source rocks under the influence of the electromagnetic field in the microwave and radio-frequency ranges. The samples from the Bazhenov Formation (West Siberia, Russia) and the Domanic Formation (Ural, Russia) have been tested. It is shown that samples from these formations demonstrate very different heating rates at the same electromagnetic field parameters and the their heating rate depends on the type of the electromagnetic field (radio-frequency or microwave) applied. The temperature of the Bazhenov Formation samples reaches 300 °C within one hundred seconds of the microwave treatment but it slowly rises to 200 °C after twelve minutes of the radio-frequency influence. The samples of the carbonate Domanic Formation heat up more slowly in the microwave field (within two hundred seconds) and to lower temperatures in the radio-frequency (150 °C) than the Bazhenov Formation samples. The study of the structure of the samples before and after experiments on the electromagnetic treatment shows fracture formation during the heating process. Numerical simulations of heating dynamics of source rock samples have been based on a simple mathematical model of the electromagnetic influence and main features of heating for different types of source rock have been revealed. The opportunities for application of electromagnetic heating for oil source rock recovery are discussed. [ABSTRACT FROM AUTHOR]

This article proposes a calculation method for mechanical (electromagnetic) forces arising in an electromechanical energy converter acting on current circuits in a magnetic field, or on capacitor plates in an electric one. Transformations were performed on the basis of the principle of possible displacements involving the apparatus of partial derivatives. It was found that the power converted into mechanical power is partially spent on changing the energy of the electromagnetic field, and the remaining power, determined by the co-energy, is converted into mechanical power. Expressions for the mechanical (electromagnetic) forces were obtained based on the power balance. The reliability of the obtained results was compared with the known results. Of these, one can observe the well-known 50/50 principle, which states that only part of the power associated with the movement of the circuits is converted into mechanical power, while the rest is intended for changing the energy of the magnetic field. [ABSTRACT FROM AUTHOR]

Solid nano-structures exhibiting fast ion transport (cations moving in anionic crystal structures) are becoming increasingly relevant in industrial applications. However, it is challenging to model their mechanics due to the presence of electromagnetic couplings. In this paper, a mathematical, physical, and computational framework is introduced, for a cation particle moving through an anion sub-lattice structure in the presence of two electromagnetic fields: an external electromagnetic field; and a self-induced electromagnetic field coming from back-reaction phenomena caused by the relative movement of cations with respect to the mentioned structure. Our approach seeks to incorporate magnetic effects, such as magnetic induction and spin of cations, which are not incorporated in other models, mainly due to the intrinsic difficulty of 3D effects. We propose a quantum mechanical formalism based on a Schrödinger-type equation, where a wave function models the behavior of a cation in presence of an external electromagnetic potential, coupled with transient and self-induced electromagnetic effects. To solve the model, a space–time coupled numerical scheme is presented, which allows the possibility of time-evolving electromagnetic effects. The technique uses finite-elements in space and time-marching schemes in time. While a time-explicit marching scheme is used to update the magnetic and electric-potential fields, a time-implicit marching scheme is used to solve the coupled Schrödinger equation. This strategy allows us to update the electromagnetic contributions and wave functions at each time-step. Numerical examples in one and two spatial dimensions (and evolving in time) have been implemented for some meaningful models obtained from nanoionics literature. [ABSTRACT FROM AUTHOR]

Permittivity of biological tissue is a critical issue for studying the biological effects of electromagnetic fields. Many theories and experiments were performed to measure or explain the permittivity characteristics in biological tissue. In this paper, we investigate the permittivity parameter in biological tissues via theoretical and experimental analysis. Firstly, we analyze the permittivity characteristic in tissue by using theories on composite material. Secondly, typical biological tissues, such as blood, fat, liver, and brain, are measured by HP4275A Multi-Frequency LCR Meter within 10 kHz to 10 MHz. Thirdly, experimental results are compared with the Bottcher-Bordewijk model, the Skipetrov equation, and the Maxwell-Gannett theory. From the theoretical perspective, blood and fat are regarded as the composition of liver and brain because of the high permittivity in blood and the opposite in fat. Volume fraction of blood in liver and brain is analyzed theoretically, and the applicability and the limitation of the models are also discussed. These results benefit further study on local biological effects of electromagnetic fields. [ABSTRACT FROM AUTHOR]

A technique of accelerated movement of metallic element by means of a pulsed electromagnetic field is sufficiently known. Despite of that, a behavior of lightweight steel hollow spheres in pulsed electromagnetic fields is not fully explored. A particular emphasis of current study is a modeling of lightweight steel hollow spheres behavior in pulsed electromagnetic field. This phenomenon can be exploited for vibrations damping in granular dampers, where dissipation of mechanical energy via particle collisions occurs. In current paper some prospects of pulsed electromagnetic field usage for lightweight steel hollow spheres excitation and practical applications in vibration control are suggested. [ABSTRACT FROM AUTHOR]

The paper deals with the interaction between electromagnetic and hydrodynamic field of electromagnetic thruster. The mathematical model of the interaction defines the constant ruler of MHD interaction. [ABSTRACT FROM AUTHOR]

The electric and magnetic current volume integral equation formulation is developed for the electromagnetic scattering analysis of arbitrarily shaped 3-D bianisotropic objects. The eigenvalue spectrum of the operator is derived and analyzed in the case of bi-isotropic media. The effect of inhomogeneity and bianisotropy on the spectrum and convergence of iterative solutions is investigated numerically. [ABSTRACT FROM PUBLISHER]

A magnetic shield is widely used in the end region of a synchronous condenser (SC) to decrease the flux densities and losses of the end structural components. In order to investigate the influence of different magnetic shield thicknesses on the distributions of the flux density and loss in the end region, a 300-Mvar SC is selected as the investigation reference in this article. A three-dimensional (3-D) mathematical model used for the calculation of electromagnetic field and loss in the end region of the SC is established. The flux densities and losses of the end structural components are calculated and compared under the different thicknesses of the magnetic shield. From the detailed performance evaluations by the 3-D finite-element analysis, the variation of the flux densities and loss densities in the end region of the SC along with the thickness of the magnetic shield is revealed. The loss distributions of the main end structural components are studied and the end zones where the loss is most significantly affected by the magnetic shield thickness are obtained. The results provide the theoretical basis for the improvement of the loss distribution in the end region of the SC. [ABSTRACT FROM AUTHOR]

A new discontinuous Galerkin time-domain (DGTD) method based on generalized sheet transition conditions (GSTCs) for analyzing the transient response of electromagnetic metasurfaces is presented. The discontinuities in electromagnetic fields around the vicinity of the metasurface are modeled by placing virtual edges on both sides of the metasurface. The GSTCs are incorporated in the updating equations of the standard DGTD algorithm by integrating the time-domain GSTCs formula with Galerkin’ s-weighted residual method. The DGTD-GSTC formulation can also simulate a bf piecewise linear approximation of a curved metasurfaces due to the unstructured mesh. This is the first time that DGTD is applied to the simulation of GSTCs. The implementation of this new method is verified by numerical cases. [ABSTRACT FROM AUTHOR]

Radiated fields in the far-field zone of a small, thin-wire, square loop placed centrally above a finite image plane are analyzed by a set of 3-D electromagnetic simulations. The impact of a finite image plane on the maximum radiated fields and on the shape of the radiation pattern is addressed. The image theory is extended to include the modeling of finite image planes by modifying the contribution of the image loop to the total radiated fields as a function of two parameters: the size of the plane and the distance between the loop and the plane. The proposed analytic solution provides a fast and simple method to calculate radiated fields in the far-field zone of electrically small magnetically driven sources above a finite image plane. [ABSTRACT FROM AUTHOR]

The computation of electromagnetic (EM) fields for 1-Dlayered earth model requires evaluation of Hankel transform. In this paper we propose a stable algorithm for the first time that is quite accurate and fast for numerical evaluation of the Hankel transform using Sine-Cosine wavelets arising in seismology. We have projected an approach depending on separating the integrand rf ( r ) J ν ( pr ) into two components; the slowly varying components rf ( r ) and the rapidly oscillating component J ν ( pr ). Then either rf ( r ) is expanded into wavelet series using Sine-Cosine wavelets orthonormal basis and truncating the series at an optimal level or approximating rf ( r ) by a quadratic over the subinterval using the Filon quadrature philosophy. The solutions obtained by proposed Sine-Cosine wavelet method applied on 5 test functions indicate that the approach is easy to implement and computationally very attractive. We have supported a new efficient and stable technique based on compactly supported orthonormal wavelet bases. [ABSTRACT FROM AUTHOR]

This study presents an operation of custom power park (CPP) with wind turbine system (WTS). The classical power system stability, changes and challenges in the power system with installation of wind energy sources are given. The CPP is composed by static transfer switch (STS) for WTS. An electromagnetic transient model of a system is composed by WTS and STS in power system computer aided design/electromagnetic transient including DC (PSCAD/EMTDC) programme. The entire model of the proposed system is developed and simulating results are verified in PSCAD/EMTDC programme at different fault types. The system responses of the different fault types are given and obtained results are evaluated in detail for power quality problems. Moreover, of the different type faults are implemented to the WT feeder and the response of the proposed system is observed for all cases. Then, the simulating results are evaluated. The currents and voltages of all systems are investigated during normal, transfer and post-transfer periods and also these simulating results are evaluated. [ABSTRACT FROM AUTHOR]

When an external short circuit occurs, the axial electromagnetic force increases dozens of times. Under the effect of the axial short-circuit electromagnetic force, the transformer windings vibrate violently. The spatial distribution of the disks is constantly changing during vibration, which can change the temporal and spatial distributions of the leakage magnetic field and the axial electromagnetic force. This process is called the strong coupling phenomenon of the structural field and the leakage magnetic field. In this article, a strong coupled magnetic-structural model is proposed by using the analysis method. The strong coupling equations, where the independent variables are the axial position of the disks, are obtained. The vibration process with strong coupling phenomenon considered can be obtained. The accuracy of the strong coupling model is verified by the iterative method. By comparing the results calculated by the strong coupling model with those calculated by the weak coupling model, the influence of the strong coupling phenomenon on the vibration process is obtained. Due to the influence of the strong coupling phenomenon, the winding vibration intensity increases and the maximum displacement of the disks can be doubled, which implied that the strong coupling phenomenon cannot be ignored when investigating the short-circuit strength of power transformers. [ABSTRACT FROM AUTHOR]

In this article, a compact unconditionally stable two-dimensional (2-D) stochastic weighted Laguerre polynomial finite-difference time-domain (S-WLP-FDTD) method for geometric uncertainty in superconducting transmission lines is proposed. It calculates both the Maxwell equations and the London equations and uses a weighted Laguerre polynomial (WLP) scheme to eliminate the stability constraint. The mean and the standard deviation of electromagnetic fields, voltages, and currents are calculated. Compared with the Monte Carlo method and 2-D S-FDTD method, the proposed method has the same accuracy but much higher efficiency. The runtime of the proposed S-WLP-FDTD method is only 2.4% of that of the S-FDTD method. Thus, the proposed method is suitable for predicting the influence of geometric uncertainty on superconducting transmission lines. [ABSTRACT FROM AUTHOR]

Adverse effects of lightning strike are studied through the modeling of the lightning-induced overvoltage (LIOV) using the channel-base current (CBC) functions. A lightning current is characterized by the parameters like current peak value (Im), time-taken by the current to reach Im (tm), maximum rise-rate of the current (di/dt)max (steepness), and charge transferred at the contact point of the strike (Q). Using the CBC functions, the lightning electromagnetic fields are calculated to compute the LIOV using a coupling model. Since the choice of CBC function plays an important role in LIOV computation, this article studies its effect on the computed LIOV for matching and zero load impedance. As a case study, two functions: Heidler's and NCBC functions were examined. It was shown that a-sort-of delay characteristic from the NCBC function is reflected in the computed LIOV and also the tripolar nature of the LIOV for the case of imperfect ground. The difference between the LIOV computed using NCBC and Heidler's function shows space-time reflections of the order of 104 magnitude. [ABSTRACT FROM AUTHOR]

Electromagnetic method to measure water flow has been known for nearly 180 years. This paper presents how the method has undergone development and describes in detail the most common electromagnetic flowmeters used for open channels. It also presents specific methods of signal processing used in this type of flowmeters. The analysis is associated directly with the relevant types of induced magnetic field. Some of the analyzed types of magnetic fields considered are sine waves and bipolar rectangular fields. The concept of low-energy electromagnetic flow meter was introduced as part of deliberations concerning current development trends. [ABSTRACT FROM AUTHOR]

The distribution of the electron density along a plasma antenna can influence the antenna’s performance. But little has been done in this regard in former studies. In this paper, a model of a practical plasma antenna with an inhomogeneous distribution of electron density is founded according to the transmission-line equivalent theory of a metal monopole, from which the current distribution and the radiation pattern of a plasma antenna with appropriate parameters are calculated. The results show that the electrical current distribution, the maximum radiation direction, and the beamwidth of a plasma antenna vary with electron density distributions. To validate the model, the plasma antenna with the same parameters is also simulated based on electromagnetic software HFSS. It is found that the results from the two ways are almost consistent. [ABSTRACT FROM AUTHOR]

A stochastic finite-difference time-domain (S-FDTD) algorithm is presented for electromagnetic-wave propagation in anisotropic magnetized plasma. This new algorithm efficiently calculates in a single simulation not only the mean electromagnetic field values, but also their variance as caused by the variability or uncertainty of the electron and ion content of the ionosphere. The structure of the ionosphere is often too variable and uncertain for electromagnetic-wave propagation problems to be solved using a deterministic formulation, particularly during space weather events. For these cases, the S-FDTD ionospheric plasma algorithm will serve as an important tool. For example, it could be used to determine the confidence level at which a communications or remote sensing or radar system will operate as expected under abnormal ionospheric conditions. [ABSTRACT FROM PUBLISHER]

In this paper, we deal with the existence and multiplicity of solutions for perturbed Schrödinger equation with electromagnetic fields and critical nonlinearity in RN: -ε²ΔAu(x) + V(x)u(x) = |u|2*-2u + h(x, |u|²)u for all x ∈ RN, where ∇Au(x) := (∇ + iA(x))u, V(x) is a nonnegative potential. By using Lions' second concentration compactness principle and concentration compactness principle at infinity to prove that the (PS)c condition holds locally and by variational method, we show that this equation has at least one solution provided that ε < ε, for any m ∈ N, it has m pairs of solutions if ε < εm, where ε and εm are sufficiently small positive numbers. [ABSTRACT FROM AUTHOR]

Analytical modeling (AM) of the magnetic field for axial-flux switched reluctance motors (AFSRMs), considering 3-D features and nonlinear saturation effects, remains to be a knotty problem. This article proposes a quasi-3-D nonlinear AM method to predict magnetic field distributions and electromagnetic performances of an AFSRM. First, the harmonic modeling (HM) technique is applied to obtain the spatiotemporal distribution characteristics of the axial and tangential magnetic flux density at the mean radius. Second, the nonlinearity of the soft magnetic material in teeth is considered by an adaptive convergence rate algorithm. Finally, a radial dependence function is formulated to extend the solution of the annular Section to any point in the 3-D space of the AFSRM. To confirm the accuracy of the proposed method, the analytical solutions of magnetic flux density and electromagnetic torque have been compared with FEM simulation results. Meanwhile, an additional validation has been done for the stability of this nonlinear AM method under severe saturation conditions. Finally, the reasonable selection of the harmonic truncation order number has been discussed to reach a good balance between accuracy and time cost. The quasi-3-D nonlinear AM method can consider the curvature and edge effect, as well as the saturation effect effectively, which is suitable for performance predictions and parametric studies of AFSRMs. [ABSTRACT FROM AUTHOR]

This article presents a unified description of numerical methods for solving electromagnetic field problems. Traditionally, these methods are considered to be independent and alternative ways of solving Maxwell’s equations or equations derived therefrom. However, they all are projective approximations of the unknown solution by known expansion or basis functions with unknown amplitude coefficients that are determined using the so- called method of weighted residuals (MWR). This common feature forms the proposed unifying framework that may serve both as a systematic introduction to computational electromagnetics and as a way to provide insight into the nature, strengths, and limitations of the various algorithms used by present and future field solvers. For convenience, the fundamental equations and concepts of electromagnetics are summarized in order to facilitate the demonstration of the unified approach. Our aim is to provide students, designers, and researchers with a framework for developing new numerical algorithms, to guide users in the selection and application of electromagnetic design tools, and to foster informed engineering judgment. This article also serves as a review and summary of earlier theoretical works reported in different places and at different times. [ABSTRACT FROM AUTHOR]

In this article, the improved chaotic electromagnetic field optimization (ICEFO) algorithm is adopted to generate the optimal values of unknown parameters of fuel cells (FCs). The mathematical model of polymer electrolyte membrane FC (PEMFC) considers nonlinear and complex optimization problems with different control variables. The sum of squared error between the measured and computed stack voltages is considered as the main objective function. The performance of the ICEFO algorithm is tested on three PEMFC stacks. Moreover, sensitivity and statistical measures are presented to confirm the reliability and accuracy of ICEFO. In addition, the effect of changing the cell temperature and reactants pressures is studied for more validation of ICEFO. Furthermore, the results obtained by ICEFO are competitive compared with other optimization methods. These results confirm the effectiveness of ICEFO in solving the optimization problem of PEMFC parameter estimation. Finally, based on the optimization results a Simulink model for PEMFC is developed to examine the dynamic performance of the PEMFCs. [ABSTRACT FROM AUTHOR]

A transient three-dimensional coupled numerical model has been established to clarify the influence of the external transverse static magnetic field (TSMF) on droplet evolution behaviors during the electroslag remelting (ESR) process with an alternating current (50 Hz). The development of the electromagnetic field code and the calculation procedure showed that the periodic inverse Lorentz force (50 Hz) could be fully coupled with the volume of fluid model in each iteration when an external TSMF of 0.05 T is superimposed. The droplet evolution behaviors with and without the external TSMF were demonstrated and analyzed. The numerical results showed that the huge periodic inverse Lorentz force could smash the droplet neck into numerous smaller droplets during the ESR process with the external TSMF; simultaneously, the interfacial area and falling time could be increased, indicating that the purification efficiency could be expected to improve. [ABSTRACT FROM AUTHOR]

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We propose an approach to solving multisource induction logging problems in multidimensional media. According to the type of induction logging tools, the measurements are performed in the frequency range of 10 kHz to 14 MHz, transmitter-receiver offsets vary in the range of 0.5-8 m or more, and the trajectory length is up to 1 km. For calculating the total field, the primary-secondary field approach is used. The secondary field is calculated with the use of the finite-element method (FEM), irregular non-conforming meshes with local refinements and a direct solver. The approach to constructing basis functions with the continuous tangential components (from Hcurl(Ω) on the non-conforming meshes from the standard shape vector functions is developed. On the basis of this method, the algorithm of generating global matrices and a vector of the finite-element equation system is proposed. We also propose the method of grouping the logging tool positions, which makes it possible to significantly increase the computational effectiveness. This is achieved due to the compromise between the possibility of using the 1-D background medium, which is very similar to the investigated multidimensional medium for a small group, and the decrease in the number of the finite-element matrix factorizations with the increasing number of tool positions in one group. For calculating the primary field, we propose the method based on the use of FEM. This method is highly effective when the 1-D field is required to be calculated at a great number of points. The use of this method significantly increases the effectiveness of the primary-secondary field approach. The proposed approach makes it possible to perform modelling both in the 2.5-D case (i.e. without taking into account a borehole and/or invasion zone effect) and the 3-D case (i.e. for models with a borehole and invasion zone). The accuracy of numerical results obtained with the use of the proposed approach is compared with the one obtained by other codes for 1-D and 3-D anisotropic models. The results of this comparison lend support to the validity of our code. We also present the numerical results proving greater effectiveness of the finite-element approach proposed for calculating the 1-D field in comparison with the known codes implementing the semi-analytical methods for the case in which the field is calculated at a large number of points. Additionally, we present the numerical results which confirm the accuracy advantages of the automatic choice of a background medium for calculating the 1-D field as well as the results of 2.5-D modelling for a geoelectrical model with anisotropic layers, a fault and long tool-movement trajectory with the varying dip angle. [ABSTRACT FROM AUTHOR]