Complex Electromagnetic Field Research Articles

Design and research of grounding current monitoring device for converter transformer core and clamp

The effective monitoring of the grounding current of the core and clamp of the converter transformer can prevent partial overheating, gassing of oil, and other abnormal conditions caused by the grounding fault of the core and clamp, ensuring the safety and stability of the power system. At present, the main detection and diagnosis method is to use the clamp current meter to detect the effective value of the grounding current. However, due to the larger capacity, higher voltage level, more complex structure and electromagnetic field distribution of the converter transformer, there is no clear standard and detection diagnosis method. Firstly, this paper analyzes the causes of grounding current and related calculations. And the design of the monitoring system for the grounding current of the converter transformer core and clamp design of the hardware system for the grounding current of the converter transformer is studied and the design process of the main circuit is given. Secondly, aiming at the problem of amplitude measurement deviation and non-integer frequency of harmonic generated by the grounding current of the core and clamp, a harmonic current detection and analysis scheme based on four Blackman-harris algorithms and the specific design process are proposed. Third, a diagnostic method based on probabilistic neural network is proposed, and a software platform is built to display and diagnose the grounding current state according to it. Finally, a prototype was manufactured and experimental study was carried out to verify the correctness of the proposed scheme.

Near-Field Observation of the Photonic Spin Hall Effect.

The photonic spin Hall effect, referring to the spatial separation of photons with opposite spins due to spin-orbit interactions, has enabled potential for various spin-sensitive applications and devices. Here, using scattering-type near-field scanning optical microscopy, we observe spin-orbit interactions introduced by a subwavelength semiring antenna integrated in a plasmonic circuit. Clear evidence of unidirectional excitation of surface plasmon polaritons is obtained by direct comparison of the amplitude- and phase-resolved near-field maps of the plasmonic nanocircuit under excitation with photons of opposite spin states coupled to a plasmonic nanoantenna. We present details of the antenna design and experimental methods to investigate the spatial variation of complex electromagnetic fields in a spin-sensitive plasmonic circuit. The reported findings offer valuable insights into the generation, characterization, and application of the photonic spin Hall effect in photonic integrated circuits for future and emerging spin-selective nanophotonic systems.

Design and Optimization of Electromagnetic Induction Device based on Finite Element Analysis

Electromagnetic induction is the basis of most electrical and power equipment. In order to improve the overall performance of electromagnetic induction devices, it is necessary to analyze the distribution of electric and magnetic fields around and inside the devices, and guide the structural adjustment and material selection of devices. However, due to the integral and differential operations involved, complex electrical and magnetic field problems are often unable to be analyzed by analytical methods. With the improvement of numerical analysis theory and computer performance, the use of finite element analysis is expected to solve the complex electromagnetic field problems in practical applications. Using finite element analysis, the electromagnetic field distribution characteristics and influencing factors of electromagnetic induction devices of household induction cooker are studied, the corresponding mathematical model is established, the influence of electromagnetic parameters of each part of the induction heating system on heating energy efficiency is studied, and the optimization design is carried out according to different application requirements, so as to provide a basis for further improving the performance of devices.

Cylindrical first-order superintegrability with complex magnetic fields

This article is a contribution to the study of superintegrable Hamiltonian systems with magnetic fields on the three-dimensional Euclidean space E3 in quantum mechanics. In contrast to the growing interest in complex electromagnetic fields in the mathematical community following the experimental confirmation of its physical relevance [Peng et al., Phys. Rev. Lett. 114, 010601 (2015)], they were so far not addressed in the growing literature on superintegrability. Here, we venture into this field by searching for additional first-order integrals of motion to the integrable systems of cylindrical type. We find that already known systems can be extended into this realm by admitting complex coupling constants. In addition to them, we find one new system whose integrals of motion also feature complex constants. All these systems are multiseparable. Rigorous mathematical analysis of these systems is challenging due to the non-Hermitian setting and lost gauge invariance. We proceed formally and pose the resolution of these problems as an open challenge.

Attentional Ptycho-Tomography (APT) for three-dimensional nanoscale X-ray imaging with minimal data acquisition and computation time

Noninvasive X-ray imaging of nanoscale three-dimensional objects, such as integrated circuits (ICs), generally requires two types of scanning: ptychographic, which is translational and returns estimates of the complex electromagnetic field through the IC; combined with a tomographic scan, which collects these complex field projections from multiple angles. Here, we present Attentional Ptycho-Tomography (APT), an approach to drastically reduce the amount of angular scanning, and thus the total acquisition time. APT is machine learning-based, utilizing axial self-Attention for Ptycho-Tomographic reconstruction. APT is trained to obtain accurate reconstructions of the ICs, despite the incompleteness of the measurements. The training process includes regularizing priors in the form of typical patterns found in IC interiors, and the physics of X-ray propagation through the IC. We show that APT with ×12 reduced angles achieves fidelity comparable to the gold standard Simultaneous Algebraic Reconstruction Technique (SART) with the original set of angles. When using the same set of reduced angles, then APT also outperforms Filtered Back Projection (FBP), Simultaneous Iterative Reconstruction Technique (SIRT) and SART. The time needed to compute the reconstruction is also reduced, because the trained neural network is a forward operation, unlike the iterative nature of these alternatives. Our experiments show that, without loss in quality, for a 4.48 × 93.2 × 3.92 µm3 IC (≃6 × 108 voxels), APT reduces the total data acquisition and computation time from 67.96 h to 38 min. We expect our physics-assisted and attention-utilizing machine learning framework to be applicable to other branches of nanoscale imaging, including materials science and biological imaging.

Smart shape memory composite foam enabled rapid and conformal manipulation of electromagnetic wave absorption performance

With the development of communication and electronic technologies, smart electromagnetic wave (EMW) absorption materials with tunable performance are highly desirable for applications under complicated electromagnetic circumstances. However, the performance of the ordinary EMW absorption materials is dominated by their electromagnetic parameters which are constant unless their compositions are changed. This study presents a porous EMW absorption material with adjustable effective absorption bandwidth (EAB) and reflection loss (RL) to satisfy the requirements of tunability for complex electromagnetic applications. First, a composite foam is fabricated by assembling the reduced graphene oxide (rGO) to the melamine sponge (MS) framework. Next, the thermoplastic polyurethane (TPU) is introduced to endow the MS/rGO composites with the desired shape memory property after crosslinking. In specific, the obtained MS/rGO composites show high flexibility, elasticity, and low density of 10.7 mg cm−3, and present the minimum RL of −63.29 dB with EAB of 7.18 GHz. Additionally, the tunable EMW absorption performance of MS/rGO-TPU composites is achieved through their shape memory effect. Notably, the EAB can be adjusted to a wide range from 5.5 to 18 GHz under the compressive deformations of those composites as modulated by cooling/heating, and correspondingly the minimum RL changes from −15.4 dB down to −39.2 dB. In a word, the smart, lightweight MS/rGO and MS/rGO-TPU composite foams with adjustable EMW absorption performance are strong candidates for practical applications in complex electromagnetic fields.

A Massively Parallel Preconditioned FEM–BEM Method for Accurate Analysis of Complex Electromagnetic Field Problems

In this letter, a parallel preconditioned FEM-BEM method is presented for the solution of challenging electromagnetic (EM) field problems, especially for calculating the radiation characteristics of electrically large radome antenna systems. A preconditioner that combining the absorbing boundary condition (ABC) with the improved additive schwarz method is first proposed for the FEM-BEM system to improve the convergence. Then, an efficient parallel framework based on message passing interface (MPI) and open multi-processing (OpenMP) is designed to achieve massively distributed parallelization of the method. Numerical results demonstrate the benefits of the proposed preconditioner over traditional additive schwarz method, as well as the accuracy and parallel scalability of the implemented method. Finally, a complex EM system consisting of a waveguide slot antenna array and a dielectric radome with more than 127 medium wavelengths is simulated to verify the capability and effectiveness of the presented method.

Metasurface design with a complex residual neural network.

In recent years, researchers have made great progress in solving complex electromagnetic field computing problems by using deep learning methods. However, the approaches found in literature were devoted to solving the real-number problem of electromagnetic field calculations. For the complex number problem, there was no good solution. Here, we proposed an advanced computation method for metasurfaces based on a complex residual neural network (CRNN). We predicted the scattering (S)21 parameters of a cylindrical structure in the range of 1.2 to 1.7µm wavelengths. By providing a set of cylindrical structure parameters, we could quickly predict the S 21 parameters with CRNN and design a metalens, which proved the ability of the proposed method. In addition, our method can also be extended to the calculation of electromagnetic fields where the speed of the calculation of the complex number of metasurfaces should be accelerated.

Multistatic radar-based imaging in layered and dispersive media for biomedical applications

This paper presents a novel algorithm for near-field radar imaging in layered and dispersive media with application to biomedical imaging. The proposed algorithm compensates for variations in the dielectric properties and integrates each component’s frequency response to form an image. The algorithm uses both the amplitude and phase of the complex electromagnetic field. The proposed algorithm resolves dispersion issues using frequency-dependent velocity. The algorithm uses phase shift instead of time delay to overcome the disadvantage of time-shift radar-based methods, such as inaccurate signal transformation and wave flight time. Therefore, the proposed algorithm allows detecting small changes in dispersive media such as the human brain. The algorithm is validated using experimental data for different volumes of brain tissue affected by the accumulation of plaques and tangles due to Alzheimer’s disease. The accuracy and robustness of the proposed algorithm are evaluated using estimation factor and localisation error.A maximum estimation factor of 1.1 cm and localisation error of 5.3 mm in the actual and detected volume ensure that the proposed algorithm detects small changes in the brain more accurately. The paper also discusses comparisons with radar-based algorithms, demonstrating that the proposed algorithm is less compute-intensive and yields more accurate results.

Study of coil configuration and local optics effects for the GaToroid ion gantry design

GaToroid, a novel gantry configuration for hadron therapy, is based on superconducting coils that generate a toroidal magnetic field to deliver the beam to the tumour location. Designing the complex GaToroid coils requires careful consideration of the local beam optical effects. We present a Python-based tool for charged particle transport in complex electromagnetic fields. The code implements fast tracking in arbitrary three-dimensional field maps, and it does not require a definition of specific or regular reference trajectories, as is generally the case for accelerator physics codes. The tool was used to characterise the beam behaviour inside the GaToroid system: to automatically determine the reference trajectories in the symmetry plane and analyse three-dimensional beam dynamics around these trajectories. Beam optical parameters in the field region were compared for various magnetic configurations of GaToroid. This paper introduces the new tracker and shows the benchmarking results. Furthermore, first-order beam optics studies for different arrangements demonstrate the main code features and serve for the design optimisation.

Luminescence principle and characteristics of imaging plate

The imaging plate (IP) is a reusable detector for detecting radiation particles in a complex electromagnetic field environment, and it is widely used as a detection medium in laser-accelerated particle beam diagnostic equipment. Therefore, it is necessary to study the performance characteristics and physical mechanism of IP. An electron source with known activity is used to explore the performance characteristics of IP. A <sup>90</sup>Sr/<sup>90</sup>Y electron source is used to measure the time attenuation curve, calibrate the absolute sensitivity, and study the law of multiple scanning of BAS-SR and BAS-TR. In the case of a longer irradiation, the fading cannot be neglected, and the attenuation curves are modified. The time attenuation characteristics indicate that the IP should be cooled after irradiation, and the scanning should be carried out in the slow decay process to reduce the influence of the reading error in the decay process. The absolute sensitivity of BAS-SR and BAS-TR to <sup>90</sup>Sr/<sup>90</sup>Y source are (0.033±0.002) PSL/<i>e</i> and (0.018±0.0038) PSL/<i>e</i> (photostimulated light, PSL), respectively, which are consistent with the results of most absolute sensitivity. The absolute sensitivity is closely related to the type of IP, scanning equipment, and experimental environment. In addition, the energy spectrum integral effect of the broad spectrum <i>β</i> source has a significant influence on the absolute sensitivity. This method is only suitable for the rough evaluation of the sensitivity characteristic parameters of the IP. Multiple scanning approximately satisfies the double exponential function distribution, which is consistent with the physical model. The characteristics of IP are determined by its storage principle. The fluorescence layer of IP is composed of typical electron trapping materials <i>M</i>F<i>X</i> (<i>M</i> = Ca, Sr, Ba; <i>X</i> = C1, Br, I) alkaline earth metal fluorhalide BaFBr. When the IP is irradiated, a large number of free electron-hole pairs are excited by the deposited energy in the material, and the free electrons will be captured by the electron trap, so the fluorescence layer of the IP records the radiation particles’ information through the energy deposited. In this paper, we study three kinds of models. Based on the models, a photo-stimulated luminescence model is proposed to describe the electron transfer process. The photo-stimulated luminescence model describes the physical mechanism of energy deposition, information storage, and information scanning of radiation particles. The relationship between the physical mechanism and characteristics is explained effectively by combining the microscopic mathematical model with the macroscopic physical phenomenon. It provides a specific data basis for the subsequent application of IPs in laser plasma diagnostic experiments.

Emergence of coherent backscattering from sparse and finite disordered media

Coherent backscattering (CBS) arises from complex interactions of a coherent beam with randomly positioned particles, which has been typically studied in media with large numbers of scatterers and high opacity. We develop a first-principles scattering model for scalar waves to study the CBS cone formation in finite-sized and sparse random media with specific geometries. The current study provides insights into the effects of density, volume size, and other relevant parameters on the angular characteristics of the CBS cone emerging from sparse and bounded random media for various types of illumination, with results consistent with well-known CBS studies which are typically based on samples with much larger number of scatterers and higher opacity. The enhancements are observed in scattering medium with dimensions between 10× and 40× wavelength and the number of particles as few as 370. This work also highlights some of the potentials and limitations of employing the CBS phenomenon to characterize disordered configurations. The method developed here provides a foundation for studies of complex electromagnetic fields beyond simple incident classical beams in randomized geometries, including structured wavefronts in illumination and quantized fields for investigating the effects of the quantum nature of light in multiple scattering, with no further numerical complications.

Stochastic resonance behavior of FitzHugh–Nagumo neurons induced by electromagnetic field driven by phase noise

Noise widely exists in the nervous system, and plays an extremely important role in the information processing of the nervous system, which can enhance or weaken the ability of the nervous system to process information. Nerve cells exist in complex and changeable electromagnetic fields, and their potential changes are significantly regulated by electromagnetic induction. In response to this, first, a memristor is used to simulate the electromagnetic field environment where the nervous system is located, when using different weak periodic signals as the input of the neuron system, the rich stochastic resonance behavior of the FitzHugh–Nagumo neuron system is analyzed under the drive of phase noise. Second, taking the amplitude, period and intensity of phase noise as the main change parameters, and the changes of the parameters of the memristor and the period of the external signal as auxiliary conditions, the stochastic resonance dynamics analysis is carried out from three perspectives: the amplitude and period of phase noise, the amplitude and intensity of phase noise and the intensity and period of phase noise.

Research on Radiated Immunity Test Methods for ADAS Functions Considering Vehicle In-the-Loop

The radiated immunity of passenger cars and commercial vehicles is validated using electromagnetic interference from off-vehicle radiation sources in an anechoic chamber according to the procedure in ISO 11451-2. Common electrical or electronic vehicle systems, including dual flash, monitors, and entertainment systems, must be validated using a standardized immunity evaluation procedure. However, Automated Driver Assistance System (ADAS) functions often lack verification in complex electromagnetic fields, which might create potential risk due to electromagnetic compatibility problems. For example, radar and camera sensors based on autonomous emergency braking (AEB), adaptive cruise control (ACC), or lane departure warning (LDW) functions may be ineffective in the real world if subjected to electromagnetic interference. This paper presents a new methodology to evaluate vehicle immunity performance based on the main ADAS functions. A target simulator and a virtual driving environment are designed to trigger AEB, ACC, and LDW functions in an anechoic chamber. Moreover, the vehicle In-the-Loop (VHIL) conception is also applied by acquiring and analyzing key ADAS-related signals. The reliability of ADAS functions at the whole-vehicle level can be evaluated and improved using standardized external radiation sources.

A combination of failures of interfacial delamination and layer cracking in REBCO multilayered conductors

Rare-earth barium-copper-oxide (REBCO) coated conductors (CCs) are kinds of multiphase, multilayer, and composited superconducting tapes, which are becoming promising candidates for abundant high-energy and high-field applications owing to their outstanding superconducting properties. However, the mechanical failures of REBCO CCs composites, such as cracks in the brittle ceramic layers, and delamination on interfaces among weak multiple layers, have become the essential issues threatening the capability and stable operation of REBCO-based superconducting devices, especially under extreme low temperature and complex electromagnetic fields. In this study, a failure modeling in combination of the interfacial delamination and layer fracture in REBCO CCs composites was established and analyzed numerically by the finite element method. To effectively treat with the two mechanical failure modes, the interfacial delamination response and the fracture behavior were respectively captured using the cohesive zone model and the extended finite element method for the multilayered superconducting CCs. The failures initiation and evolution in REBCO multilayered structures were implemented based on the stress criteria. The characteristics of two failure modes of the multilayered superconducting CCs under uniaxial tension and bending were investigated, and those during cooling process from room temperature to 77 K were then simulated in consideration of residual thermal stresses accumulated. The results illustrated that the progressive mechanical failure behaviors were presented in combination of the interfacial delamination and fracture damages in the REBCO multilayered structure. The crack propagation in the superconducting layer can cause the delamination failure at the corresponding position on the interfaces between the superconducting layer and its adjacent layers, while the delamination damage on the interfaces releases the constraint between the layers further enhances the crack propagation. The residual thermal stress accumulated during cooling was found to significantly affect the mechanical behavior of the REBCO CCs, and the low-temperature makes a failure occurrence earlier compared to that at room temperature.

Equivalent magnetic circuit method of estimating iron losses in induction motor spindles

The iron losses in the motor of motorized spindles have a significant effect on their heat generation, thermal deformation, and machining accuracy. The equivalent magnetic circuit (EMC) method for estimating iron losses in the spindle motor is proposed, where the magnetic flux density distribution of any cross section inside the spindle motor is assumed as a uniform one. A mechanical loss separation method of no load running combined with a sudden loss of power supply is also proposed. The EMC method is verified by prototype experiment and a different analysis method comparison. The EMC does not need to solve complex electromagnetic fields, and to do 2D or 3D eddy current analysis and the corresponding post-processing. There is only need to perform a simple magnetic circuit calculation. Therefore, it can realize a fast analysis and prediction. The proposed mechanical loss separation method requires only one prototype during a whole testing process. There is no need for any other same prototype and a coupling device. It is simpler, and can eliminate the braking torque and electromagnetic losses of the spindle motor.

Ultra-Low Electromagnetic Fields Application on In Vitro Cartilage Regeneration: A Pilot Study to Improve Treatment of Osteoarticular Diseases

Extremely low-frequency and low-intensity electromagnetic fields show positive effects on the treatment of several osteoarticular diseases, such as osteoarthritis, and are currently applied in the clinical setting with promising results on tissue regeneration. However, the biological mechanisms underlying the beneficial effects triggered by this type of physical stimulation still need to be deciphered. We tested the hypothesis that ultra-low complex electromagnetic fields stimulation using an innovative medical device could enhance chondrogenesis in human adipose-derived stem cells (ADSCs), and analyzed its biological effects. Chondrogenic lineage markers, like ACAN, SOX9, RUNX2, COL2A1, and COL10A1, were evaluated after 21 days of treatment. Thus far, we have provided preliminary evidence that a dedicated pattern of ultra-weak complex electromagnetic sequences emitted by a cutting-edge technology can promote cartilage regeneration, inducing the chondrogenic differentiation and maturity of ADSCs.

The complex electromagnetic field

The complex electromagnetic field

Effect of cooling medium on the preparation and microwave absorption properties in low frequency for LiZn ferrites hollow microspheres

The lack of research on low-frequency absorbing materials working at frequencies lower than 8 GHz makes it difficult to meet the military needs of the large wavelength electromagnetic shielding. In this study, crystalline and amorphous lithium zinc ferrites hollow microspheres (LiZn FHMs) were prepared by self-reactive quenching technology, based on Fe+Zn+Fe2O3 +O2 +Li2CO3 reactive system, using distilled water and 15 wt% NaCl solution as cooling medium, respectively. Effect of cooling medium on the formation mechanism and microwave absorption properties in low frequency range for two kinds of LiZn FHMs was studied. The results show that LiZn FHMs surface with distilled water as cooling medium has polygonal crystal structure. While the surface of LiZn FHMs is smooth by using 15 wt% NaCl solution, and XRD patterns prove that LiZn FHMs are of amorphous structures. When the cooling medium is changed from distilled water to NaCl solution, the magnetic loss of amorphous LiZn FHMs changes from double loss mechanism (natural resonance and eddy current loss) to a single loss mechanism (natural resonance). Compared with crystalline materials, the emergence of "rheology unit" and the change of magnetic loss mechanism are the main reasons for the improvement of microwave absorption properties in low frequencies. When the thickness of the amorphous sample is equal to 2 mm, the minimum reflectivity is −29.8 dB, and the corresponding frequency is 7.1 GHz. The absorption frequency band below −10 dB is 5.3–10.3 GHz, and its bandwidth is 5 GHz. This effectively meets the low frequency new absorbent "thin, light, wide and strong" demand, and it could be promising in the application of invisible coatings on the weapon equipments. The survival performances of weapon equipments in the complex electromagnetic field are expected to be improved.

Simulation analysis and experimental research on the safety distance of UAV inspection on transmission lines

In recent years, unmanned aerial vehicle (UAV) inspection has become one of the main means of daily operation and maintenance of overhead transmission lines. Since the key components of the UAV inspection system are composed of electronic components, it relies on data communication to realize data link transmission. In the actual operation process, the complex electromagnetic field environment has an obvious impact on its control and communication performance, especially when inspecting near the DC line. In this paper, combined with the research on the safety assurance technology of UAV inspection operations, the electromagnetic field simulation model of the UAV inspection operation on DC transmission lines is established. The electromagnetic field distribution around the wire is analyzed when the UAV is at different inspection distances, and the influence range and degree of the DC electromagnetic field on UAV inspection system are obtained. A true test platform for the inspection safety distance of the ±500 kV line UAV inspection was built, and the inspection safety distance test and research of the small rotary-wing UAV with a typical size, structure, and material was carried out. Through the test, when the current of the transmission line is 3 kA, the minimum safety distance of the UAV inspection operation of the ±500 kV DC transmission line straight tower is 3 m, and the distance is corrected in combination with the current. The research results of this paper can provide technical support for the inspection operation of small multi-rotor UAVs on ±500 kV transmission lines.