Electromagnetic Waves Research Articles

Radio-electric Effect in Semi-parabolic Plus Semi-inverse Squared QuantumWells

Radioelectric field in semi-parabolicplus semi-inverse squared quantum wells has been studied in the presence of a linearly polarized electromagnetic wave. By using quantum kinetic equations for electrons in the case of electrons – optical phonons scattering, the analytical expression for the Radioelectricfield was obtained as a function of the frequency, the amplitude of the linearly polarized electromagnetic field and temperature. Numerical results of specific GaAs/GaAlAs semi-parabolicplus semi-inverse squared quantum wells were also achieved. The results showed that when temperature increases, the Radioelectric field increases nonlinearly.

Importance of the electron plasma parameter for excitation of chorus and formation of magnetic field irregularity in the region of their excitation

A threshold condition has been established for excitation of VLF electromagnetic radiation with a chorus structure of the dynamic spectrum in the daytime magnetosphere using the BPA (Beam Pulse Amplifier) mechanism for amplifying short noise electromagnetic pulses. The kappa distribution was used as a model function of the electron velocity distribution in the magnetosphere. Calculations performed for this distribution have shown that the threshold for excitation of chorus largely depends on the electron plasma parameter equal to the ratio of gas-kinetic pressure of electrons to magnetic pressure. This pattern is not contradicted by the dependence of the probability of excitation of chorus on the degree of magnetic field irregularity, which we derived from observations made by the Van Allen Probe spacecraft. It is sharp fluctuations in the magnetic field strength near its local minima outside the plasmasphere where the radiation under study can be excited. If there is an irregularity, the probability of detecting chorus is >70 %; and if there is no or very low irregularity, the probability of the absence of any emissions is ~80 %. The results indicate a common reason for the excitation of chorus and the magnetic field irregularity — a small but finite value of the plasma parameter.

Существенность величины плазменного параметра электронов для возбуждения хоров и формирования нерегулярности магнитного поля в области их возбуждения

A threshold condition has been established for excitation of VLF electromagnetic radiation with a chorus structure of the dynamic spectrum in the daytime magnetosphere using the BPA (Beam Pulse Amplifier) mechanism for amplifying short noise electromagnetic pulses. The kappa distribution was used as a model function of the electron velocity distribution in the magnetosphere. Calculations performed for this distribution have shown that the threshold for excitation of chorus largely depends on the electron plasma parameter equal to the ratio of gas-kinetic pressure of electrons to magnetic pressure. This pattern is not contradicted by the dependence of the probability of excitation of chorus on the degree of magnetic field irregularity, which we derived from observations made by the Van Allen Probe spacecraft. It is sharp fluctuations in the magnetic field strength near its local minima outside the plasmasphere where the radiation under study can be excited. If there is an irregularity, the probability of detecting chorus is >70 %; and if there is no or very low irregularity, the probability of the absence of any emissions is ~80 %. The results indicate a common reason for the excitation of chorus and the magnetic field irregularity — a small but finite value of the plasma parameter.

An incremental permeability detection method for yield strength of ferromagnetic materials based on permanent magnet excitation

ABSTRACT In this paper, in order to meet the engineering requirements of mechanical properties detection of materials with low power consumption, a novel incremental permeability detection system based on permanent magnet excitation is proposed to reduce system power consumption. Initially, a new incremental permeability sensor was designed to extract magnetic incremental permeability (MIP) signal. Through finite element simulation, experimental parameters were optimised, and a rational arrangement of double permanent magnets was devised to furnish an optimally strong AC bias field intensity. Subsequently, a practical detection platform was assembled to extract electromagnetic signal features. From the perspective of domain wall displacement, a characteristic value θ was proposed to predict the yield strength, with experimental results yielding a relative error of less than ±10%. These experiments have validated the capability of permanent magnet-type MIP to enable quantitative detection of the yield strength in ferromagnetic materials.

Microfiber Actuators With Hot-Pressing-Programmable Mechano-Photothermal Responses for Electromagnetic Perception.

Electromagnetic radiation (EMR) is a ubiquitous harm and hard to detect dynamically in multiple scenarios. A mechano-photothermal cooperative microfiber film (MFF) actuator is developed that can synchronously detect EMR with high reliability. The programmable actuation is deployed by a hot-pressing methodology, achieving the MFF with moderate modulus (378MPa) and superior toughness (87.26MJm-3) that ensure superior response (0.068cm-1s-1) and bending curvature (0.63cm-1). A secondary hot-pressing can further program the actuation behavior with black phosphorus local photothermal enhancement patterns to achieve 2D-3D transformable geometries. An amphibious robot with a land-water adaptive locomotion mechanism is designed by programming the MFFs. It can crawl on land and locomote on water with a velocity up to ≈1.8mms-1, and ≈2.39cms-1, respectively. Employing the conductive fabric layer of the actuator with electromagnetic induction effect, the amphibious robot can synchronously perceive environmental EMR with sensitivity up to 99.73%±0.15% during locomotion, with superior adaptability to EMR source intensity (0.1 to 3000W) and distance (≈9m) compared to a commercial EMR detector. This EMR detective microfiber actuator can inspire a new direction of environment-interactive smart materials, and soft robots with multi-scenario adaptivity and autonomous environment perceptivity.

Multi-Frequency Asymmetric Absorption-Transmission Metastructures-Photonic Crystals and Their Application as a Refractive Index Sensor.

In this paper, a kind of metastructure-photonic crystal (MPC) with multi-frequency asymmetric absorption-transmission properties is proposed. It is composed of various dielectric layers arranged in a periodically tilting pattern. When electromagnetic waves (EMWs) enter from the opposite direction, MPC shows an obvious asymmetry. EMWs are absorbed at 13.71 GHz, 14.37 GHz, and 17.10 GHz in forward incidence, with maximum absorptions of 0.919, 0.917, and 0.956, respectively. In the case of backward incidence, transmission above 0.877 is achieved. Additionally, the MPC is utilized for refractive index (RI) sensing, allowing for wide RI range detection. The refractive index unit is denoted as RIU. The RI detection range is 1.4~3.0, with the corresponding absorption peak variation range being 17.054~17.194 GHz, and a sensitivity of 86 MHz/RIU. By adjusting the number of MPC cycles and tilt angle, the sensing performance and operating frequency band can be tailored to meet various operational requirements. This MPC-based RI sensor is simple to fabricate and has the potential to be used in the development of high-performance and compact sensing devices.

РЕГИСТРАЦИЯ МАГНИТОМОДУЛЯЦИОННЫМ ДАТЧИКОМ НИЗКОЧАСТОТНОГО ЭЛЕКТРОМАГНИТНОГО ИЗЛУЧЕНИЯ В ЛАБОРАТОРНЫХ ЭКСПЕРИМЕНТАХ ПО РАЗРУШЕНИЮ ОБРАЗЦОВ ГОРНЫХ ПОРОД

The article presents the results of observations of variations in magnetic induction using magnetomodulation sensors, which made it possible to register the signals of electromagnetic (EM) emission in the range of 0.01–200 Hz generated by rock samples under fast and slow uniaxial loading in laboratory experiments. The description of the equipment and measurement techniques used in the experiments is given. At two modes of loading rock samples differences in EM emission signals reflecting the peculiarities of the development of their destruction processes are found. It is shown that during the destruction of rock samples, the amplitude-frequency spectrum of magnetic field components clearly reveals the contribution of low-frequency harmonics, which is mainly concentrated in the frequency range below 15 Hz. It is established that magnetomodulation sensors have sufficient sensitivity and resolution to observe and register EM emission signals in the frequency range of 0.01–200 Hz, manifested during the destruction of rock samples in the process of their loading.

The April 2023 SYM‐H = −233 nT Geomagnetic Storm: A Classical Event

AbstractThe 23–24 April 2023 double‐peak (SYM‐H intensities of −179 and −233 nT) intense geomagnetic storm was caused by interplanetary magnetic field southward component Bs associated with an interplanetary fast‐forward shock‐preceded sheath (Bs of 25 nT), followed by a magnetic cloud (MC) (Bs of 33 nT), respectively. These interplanetary structures were led by a coronal mass ejection erupted from the Sun in association with an M1.7 X‐ray flare. At the center of the MC, the plasma density exhibited an order of magnitude decrease, leading to a sub‐Alfvénic solar wind interval for ∼2.1 hr. Ionospheric Joule heating accounted for a significant part (∼81%) of the magnetospheric energy dissipation during the storm main phase. Equal amount of Joule heating in the dayside and nightside ionosphere is consistent with the observed intense and global‐scale DP2 (disturbance polar) currents during the storm main phase. The sub‐Alfvénic solar wind is associated with disappearance of substorms, a sharp decrease in Joule heating dissipation, and reduction in electromagnetic ion cyclotron wave amplitude. The shock/sheath compression of the magnetosphere led to relativistic electron flux losses in the outer radiation belt between L* = 3.5 and 5.5. Relativistic electron flux enhancements were detected in the lower L* ≤ 3.5 region during the storm main and recovery phases. Equatorial ionospheric plasma anomaly structures are found to be modulated by the prompt penetration electric fields. Around the anomaly crests, plasma density at ∼470 km altitude and altitude‐integrated ionospheric total electron content are found to increase by ∼60% and ∼80%, with ∼33% and ∼67% increases in their latitudinal extents compared to their quiet‐time values, respectively.

Fluid-Infiltrated Metalens-Driven Reconfigurable Intelligent Surfaces for Optical Wireless Communications.

A reconfigurable intelligent surface (RIS), a leading-edge technology, represents a new paradigm for adaptive control of electromagnetic waves between a source and a user. While RIS technology has proven effective in manipulating radio frequency waves using passive elements such as diodes and MEMS, its application in the optical domain is challenging. The main difficulty lies in meeting key performance indicators, with the most critical being accurate and self-adjusting positioning. This work presents an alternative RIS design methodology driven by an all-silicon structure and fluid infiltration, to achieve real-time control of focal length toward a designated user, thereby enabling secure data transmission. To validate the concept, both numerical simulations and experimental investigations of the RIS design methodology are conducted to demonstrate the performance of fluid-infiltrated metalens-driven RIS for this application. When combined with different fluids, the resulting ultra-compact RIS exhibits exceptional varifocal abilities, ranging from 0.4 to 0.5 mm, thereby confirming the adaptive tuning capabilities of the design. This may significantly enhance the modulation of optical waves and promote the development of RIS-based applications in wireless communications and secure data-transmission integrated photonic devices.

Comparative Approach to De-Noising TEMPEST Video Frames

Analysis of unintended compromising emissions from Video Display Units (VDUs) is an important topic in research communities. This paper examines the feasibility of recovering the information displayed on the monitor from reconstructed video frames. The study holds particular significance for our understanding of security vulnerabilities associated with the electromagnetic radiation of digital displays. Considering the amount of noise that reconstructed TEMPEST video frames have, the work in this paper focuses on two different approaches to de-noising images for efficient optical character recognition. First, an Adaptive Wiener Filter (AWF) with adaptive window size implemented in the spatial domain was tested, and then a Convolutional Neural Network (CNN) with an encoder–decoder structure that follows both classical auto-encoder model architecture and U-Net architecture (auto-encoder with skip connections). These two techniques resulted in an improvement of more than two times on the Structural Similarity Index Metric (SSIM) for AWF and up to four times for the SSIM for the Deep Learning (DL) approach. In addition, to validate the results, the possibility of text recovery from processed noisy frames was studied using a state-of-the-art Tesseract Optical Character Recognition (OCR) engine. The present work aims to bring to attention the security importance of this topic and the non-negligible character of VDU information leakages.

Cross-device Portability of Machine Learning Models in Electromagnetic Side-Channel Analysis for Forensics

The possession of smart devices has ingrained itself into daily life. Therefore, smart devices, such as IoT and smartphones, are crucial sources of evidence in instances where criminal activity occurs. Due to the challenges in traditional digital forensic techniques involving smart devices, it has been recently proposed in the literature to leverage electromagnetic side-channel analysis (EM-SCA) for the purpose. This paper identifies and discusses an important barrier that exists in the application of EM-SCA for digital forensics that hinders its successful use, namely, the issue of cross-device portability of machine learning (ML) models that are used for EM-SCA. Firstly, the paper empirically evaluates the possibility of using trained ML models to extract forensic insights from EM radiation data of IoT devices. During this empirical study, the inability to reuse a trained ML model across different devices is identified. Secondly, the paper surveys the literature in search of related work that has studied the use of EM-SCA to gather information from smart devices. The purpose of the survey is to identify whether any existing work has been able to introduce potential approaches to enable cross-device portability of ML models in EM-SCA. The findings of this survey point to the fact that the identified problem still exists and requires further studies opening the door to future research.

Electromagnetic field produced by radiation source submerged in non-homogeneous seawater

Electromagnetic (EM) waves are one of the important carriers for information exchange in seawater. The EM parameters of seawater are important factors that affect the performance of EM wave propagation. In the real marine environment, non-constant EM parameters make it impossible to consider seawater as a homogeneous media in the model. However, there are few targeted analyses in the existing studies. In this paper, an N-layered media model was established to investigate the influence of non-constant EM parameters on EM wave propagation in seawater. A direct global matrix method is proposed to solve the EM fields, whose result accuracy does not decrease with the increasing number of layers. The necessity and correctness of the model and methods are verified through numerical simulations and sea experiments. Combined with the existing marine environment database, the propagation characteristics of EM waves in different EM parameter profiles of seawater were analyzed through numerical experiments. The results indicated that the non-homogeneous seawater has a great impact on the intensity, phase, change rate, and spatial distribution of EM waves. Furthermore, the influence is not only reflected in the underwater EM field but also in the air and increases with frequency.

Multilayer porous poly (vinylidene fluoride)/MXene/cobalt ferrite composites with ternary gradients for electromagnetic wave absorption

A composite material with a high potential for absorbing electromagnetic waves (EMW) was obtained by selecting poly (vinylidene fluoride) (PVDF) as the matrix, MXene as the conductive filler, and cobalt ferrite (CoFe2O4) as the magnetic filler. A layer-by-layer assembly strategy involved hot pressing and sequential blade coating, followed by vapor-induced phase separation, was used to implement the preparation of PVDF/MXene/CoFe2O4 (PMC) composites. The process facilitates the formation of a well-organized multilayer porous framework, providing a gradient of positive conductivity, negative magnetism, and porosity within the composites. Incorporating distinct multilayer, porous, and gradient structures into a single composite led to exceptional impedance matching (Z), with an area percentage of up to 8.4 % in the optimal range of 0.8 to 1.2. Furthermore, the multiple interfaces formed by the various components, multilayer structure, and porous configuration significantly enhanced the EMW attenuation capability, with the attenuation constant reaching as high as 274. Consequently, the PMC composite demonstrated outstanding performance with a minimal reflection loss (RLmin) of −56.5 dB, a specific RLmin of 23.5 dB/mm, and the broadest effective absorption bandwidth of 3.2 GHz. The combination of the competitive EMW absorption capability, low density, flexibility, adequate tensile strength, and amphiphilic Janus surface may significantly broaden the application scenarios of PMC composites.

A Hybrid Perovskite-Based Electromagnetic Wave Absorber with Enhanced Conduction Loss and Interfacial Polarization through Carbon Sphere Embedding.

Electronic equipment brings great convenience to daily life but also causes a lot of electromagnetic radiation pollution. Therefore, there is an urgent demand for electromagnetic wave-absorbing materials with a low thickness, wide bandwidth, and strong absorption. This work obtained a high-performance electromagnetic wave absorption system by adding conductive carbon spheres (CSs) to the CH3NH3PbI3 (MAPbI3) absorber. In this system, MAPbI3, with strong dipole and relaxation polarization, acts dominant to the wave absorber. The carbon spheres provide a free electron transport channel between MAPbI3 lattices and constructs interfacial polarization loss in MAPbI3/CS. By regulating the content of CSs, we speculate that this increased effective absorption bandwidth and reflection loss intensity are attributed to the conductive channel of the carbon sphere and the interfacial polarization. As a result, when the mass ratio of the carbon sphere is 7.7%, the reflection loss intensity of MAPbI3/CS reaches -54 dB at 12 GHz, the corresponding effective absorption bandwidth is 4 GHz (10.24-14.24 GHz), and the absorber thickness is 2.96 mm. This work proves that enhancing conduction loss and interfacial polarization loss is an effective strategy for regulating the properties of dielectric loss-type absorbing materials. It also indicates that organic-inorganic hybrid perovskites have great potential in the field of electromagnetic wave absorption.

Multifunctional 3D pristine graphene with tunable electromagnetic properties via self-assembly strategy

Nowadays, there is an urgent demand for multifunctional materials with tunable properties to meet the requirements of intricate environments with alternating temperatures and electromagnetic conditions. Pristine graphene is a highly promising electromagnetic material owing to its intrinsic advantages. However, issues related to aggregation and weak gelation capability would hinder the fabrication and advancement of multifunctional pristine graphene. Herein, multifunction properties are first integrated into one 3D structured pristine graphene via a self-assembly method. By regulating the microstructures, 3D structured pristine graphene can exhibit a range of electromagnetic properties, including wave transmission (wave transmittance of 88 %-93 %), electromagnetic wave (EMW) absorption (reflection loss of −50.70 dB), and electromagnetic interference (EMI) shielding (shielding effectiveness (SE) of ∼37.90 dB), which are not available in existing graphene materials. Furthermore, the 3D structured pristine graphene exhibits mechanical stability and thermal performances to guarantee a stable and durable electromagnetic response for complex environmental applications. The outstanding multifunction can be attributed to the low defects and controllable microstructures of pristine graphene. This work supplies an inspiration for the development of multifunctional graphene materials as well as the microstructure design of 3D pristine graphene.

Multiple Tin Compounds Modified Carbon Fibers to Construct Heterogeneous Interfaces for Corrosion Prevention and Electromagnetic Wave Absorption

HighlightsExcellent impedance matching through component modulation engineering.Rich heterogeneous interfaces are constructed to realize excellent electromagnetic wave (EMW) absorption performance.Long-term corrosion protection and excellent EMW absorption properties.

Physical analysis of high refractive index metamaterial-based radiation aggregation engineering of planar dipole antenna for gain enhancement of mm-wave applications

A metamaterial-incorporated high-gain and broadband dipole antenna is proposed for 5G mm-wave applications. The designed high refractive index metamaterial (HRIM) properties are presented in detail with supporting results. The proposed dipole antenna achieved broadband features, and the antenna gain increased significantly by incorporating HRIM in the electromagnetic (EM) wave propagation path. Besides, the EM wave aggregation engineering of utilizing the HRIM on the dipole antenna is analyzed using the electric field, magnetic field, and power flow distributions. Both conventional and HRIM-based dipole antenna (HRIMDA) were fabricated on thin (0.254 mm) Rogers RT5880 substrate material with a low dielectric constant of 2.2, where the noticeable gain enhancement by HRIM is observed. The measured results show the operational bandwidth (BW) from 23 to 38 GHz frequency, and the highest gain of 9.5 dBi is accomplished at 35 GHz frequency. Finally, a four-element MIMO configuration is numerically and experimentally analyzed where the isolation of the two conjugated MIMO elements is < − 20 dB. The MIMO parameters like envelop correlation coefficient (ECC) < 1 × 10–3 and diversity gain (DG) value of > 9.9 were also achieved. Hence, the proposed HRIM base dipole antenna is a potential candidate for 5G mm-wave applications.

Does Radiofrequency Radiation From Mobile Phones Affect the Formation of Parotid Gland Malignancy? An Experimental Study.

Objectives: The use of mobile phone is increasing around the world. Although it is beneficial in terms of communication, the electromagnetic radiations emitted by mobile phones may cause undesirable biological effects on the human body. In practical use, the tissue with which mobile phones come into most and are closest is the parotid gland. This study investigated the effects of the 1800 MHz electromagnetic field created by a generator on the parotid gland in rats. Methods: A total of 21 Sprague-Dawley Albino rats were included in the study. The rats were randomly divided into three equal groups. To simulate a mobile phone in conversation mode, the first study group was exposed to an 1800-MHz electromagnetic field for 6 hours a day for 30 days, and the second study group was exposed to an 1800-MHz electromagnetic field for 12 hours a day for 30 days. After 30 days, rats were sacrificed, and histopathological and immunohistochemical methods were used to evaluate the effects on the parotid gland. The total antioxidant level and the total oxidant level were measured biochemically in homogenized parotid tissue. Results: Histopathological results showed an increase in degeneration in rats exposed to electromagnetic fields for 6 and 12 hours a day, and immunohistochemical analysis showed an increase in the apoptotic index in both study groups (P = .001, P < .001). Intranuclear inclusions was observed during histopathological examination performed by electron microscopy. Conclusions: This study observed that the 1800 MHz electromagnetic field caused undesirable adverse histopathological and biochemical effects on the parotid gland of rats. Histopathological and biochemical findings were detected with increasing contact and exposure time. This study will lead to other studies on this topic and contribute to the literature by completing other studies.

Enforcing interface field continuity to advance finite element approximations in heterogeneous materials

To investigate the discrete field continuity at the interface of inhomogeneous materials, this paper investigates the scattering of electromagnetic waves interacting with a perfect electrical conductor object coated with dielectric materials, employing the finite element method. In the derivation process of the variational formulation, the tangential continuity of electric fields eliminates any discrepancies occurring along the internal interfaces. However, while it is important to maintain tangential continuity of electric and magnetic fields at the interface between different dielectrics, this requirement is not met precisely within discrete space. As a result, approximations can exhibit inaccuracies and potentially fail to fully capture the underlying physical phenomena. To alleviate these issues, we propose an imposition of tangential continuity of the magnetic field within the minimizing functional, thereby ensuring adherence to interface conditions between two dielectric layers. This approach can be naturally applied to a variety of interface problems to enhance the approximation accuracy of interaction models in real-world environments.

Continuous evolution of Fermi arcs in a minimal ideal photonic Weyl medium

Propagation properties of electromagnetic waves in an optical medium are mainly determined by the contour of equal-frequency states in k\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\boldsymbol{k}}$$\\end{document}-space. In photonic Weyl media, the topological surface waves lead to a unique open arc of the equal-frequency contour, called the Fermi arc. However, for most realistic Weyl systems, the shape of Fermi arcs is fixed due to the constant impedance of the surrounding medium, making it difficult to manipulate the surface wave. Here we demonstrate that by adjusting the thickness of the air layer sandwiched between two photonic Weyl media, the shape of the Fermi arc can be continuously changed from convex to concave. Moreover, we show that the concave Fermi-arc waves can be used to achieve topologically protected electromagnetic pulling forces over a broad range of angles in the air layer. Our finding offers a generally applicable strategy to shape the Fermi arc in photonic Weyl media.