Electromagnetic Approach Research Articles

PC-SAFT Model on Molecular Interactions in Acetophenone with Chloroalkanes and Chloroalkenes Solutions at Different Temperatures: Volumetric, Acoustic, and Electromagnetic Approach

PC-SAFT Model on Molecular Interactions in Acetophenone with Chloroalkanes and Chloroalkenes Solutions at Different Temperatures: Volumetric, Acoustic, and Electromagnetic Approach

Decoding microwave modulation transfer: The impact of dissipation through stochastic processes

AbstractAn anomalous transfer of modulation from a modulated microwave beam () to an unmodulated one () has been experimentally demonstrated through accurate delay time measurements. These results are analyzed according to two possible interpretations: one based on an electromagnetic approach as reported elsewhere, and the other based on a purely stochastic model. This latter model, made up of random zig‐zag paths, is the focus of the current paper. It is demonstrated that it is possible to obtain a plausible description of the experimental data.

State-restricted adaptive control of a multilevel rotating electromagnetic mechanical flexible device using electromagnetic actuators

This work presents the development of a multilevel electromagnetic actuation system that controls the shape of a flexible rotatory robotic structure. An array of electromagnets is used as the set of actuators that regulate the position of permanent magnets within the flexible device. The primary outcome of this study is the design and experimental validation of the multilevel rotating device. In addition, the theoretical description of the system motion under electromagnetic actuation is formulated using Euler–Lagrange and electromagnetic theories. Given the developed model, a theoretical study leads to designing an adaptive control that considers motion restrictions in the flexible device. The controller aims to modify the current applied to the electromagnets, which changes the interaction forces between the electromagnet and the permanent magnets in the robotic flexible structure. A set of numerical simulations confirms the proposed controller’s effectiveness compared to the traditional state feedback approach that does not consider the state restrictions, which is implemented in devices that also operate under an electromagnetic approach. Furthermore, an experimental version of the flexible device allows for testing of the developed controller. The experimental results show the suitability of the proposed control to generate non-oscillatory controlled motion during the regulation of the flexible mechanic device shape.

Research on electromagnetic pulse signal detection method based on intelligent compressed sensing technology

Abstract Electromagnetic pulse signal measurement is crucial for national security, scientific research, technological advancement, and emergency preparedness, playing a vital role in various aspects of modern society. In this work, an electromagnetic pulse signal detection approach utilizing compressed sensing technology is suggested. By unitizing three parallel low-frequency analog-to-digital converters, the high-frequency acquisition waveform of the measured electromagnetic pulse signal can be recovered. The compressed sensing effect of the proposed system on electromagnetic pulse signal is tested by simulation, which verifies the feasibility of this method.

Возбуждение терагерцовых плазмонных мод в графеновом квадратном микрорезонаторе

We consider a graphene square located in the interface between two half-spaces with different dielectric constants. Using a self-consistent electromagnetic approach based on the integral equation method, we solve the problem of a linearly polarized terahertz electromagnetic wave scattering by the graphene square. The spectra of extinction, absorption, and scattering cross sections reveal the various plasmon modes excitation in graphene square. The properties of the plasmon modes different types are discussed.

Increased Thalamic Connectivity in Juvenile Myoclonic Epilepsy Based on Electroencephalography Source-Level Analysis.

Background: This study investigated alterations in the intrinsic thalamic network of patients with juvenile myoclonic epilepsy (JME) based on an electroencephalography (EEG) source-level analysis. Materials and Methods: We enrolled patients newly diagnosed with JME as well as healthy controls. The assessments were conducted in the resting state. We computed sources based on the scalp electrical potentials using a minimum-norm imaging method and a standardized, low-resolution, brain electromagnetic tomography approach. To create a functional connectivity matrix, we used the Talairach atlas to define thalamic nodes and applied the coherence method to measure brain synchronization as edges. We then calculated the intrinsic thalamic network using graph theory. We compared the intrinsic thalamic network of patients with JME with those of healthy controls. Results: This study included 67 patients with JME and 66 healthy controls. EEG source-level analysis revealed significant differences in the intrinsic thalamic networks between patients with JME and healthy controls. The measures of functional connectivity (radius, diameter, and characteristic path length) were significantly lower in patients with JME than in healthy controls (radius: 2.769 vs. 3.544, p = 0.015; diameter: 4.464 vs. 5.443, p = 0.024; and characteristic path length: 2.248 vs. 2.616, p = 0.046). Conclusions: We demonstrated alterations in the intrinsic thalamic network in patients with JME compared with those in healthy controls based on the EEG source-level analysis. These findings indicated increased thalamic connectivity in the JME group. These intrinsic thalamic network changes may be related to the pathophysiology of JME.

Modeling of electromagnetic propagation inside jet engine environment using statistical electromagnetic approach

In this paper, the distribution of the electromagnetic field inside a complex jet engine environment is analyzed using statistical electromagnetics. The jet engine environment is an extremely complex geometry and exhibits random behavior due to the presence of moving metallic parts. This renders traditional analytical and simulation modeling techniques highly inefficient. To address this issue, two different approaches are proposed to model the propagation characteristics of the jet engine environment. The first is an innovative dynamic system approach based on dynamic system simulation which is inspired by the analysis of mechanically stirred reverberation chambers. In the dynamic system simulation the dynamic system, which is characterized by the rotation of a distinct set of blades, is primarily studied through the simulation program. A dimension scaling method is also introduced along with the dynamic system simulation to solve the complex jet engine environment. In the second approach, a novel statistical excitation method is applied to develop an equivalent model for the dynamic jet engine system. The studied jet engine is considered as a static jet engine system without blade rotation (static blades), but with a random excitation.A small signal analysis method is used to integrate the static and dynamic system parameters to generate random excitation characteristics of the static system. The extracted electric field values from the dynamic jet engine simulation environment and the static system field values from the small signal analysis have been analyzed statistically to prove the statistical equality between the two systems. The numerical results of the static system model are presented and verified through comparison with finite element method simulation packages.

N atoms regulate heterogeneous crystal phase engineering of mesoporous magnetic FexN nanofibers to promote electromagnetic wave dissipation of magnetic composite aerogel absorbers

One dimensional (1D) soft magnetic nanomaterial and its lightweight porous composites are highly needed in promoting electromagnetic wave absorption for the high-frequency magnetic response and low density. In this study, lightweight magnetic composite aerogels were fabricated through the process of heterogeneous crystal phase, involving the modulation of 1D mesoporous magnetic FexN nanofibers with N atoms. The promotion of electromagnetic wave dissipation was achieved through meticulous composition design and interface optimization. The multi-mode magnetic resonance of 1D heterogeneous crystal FexN magnetic nanofibers, along with the N-doped reduced graphene/amorphous carbon three-dimensional conductive network, greatly enhances electromagnetic wave dissipation through the magnetic-dielectric synergistic effect. Consequently, the resulting composite absorber demonstrates remarkable microwave absorption capabilities, achieving a maximum effective absorption bandwidth (EABmax) of 6.63 GHz at a thickness of 2.13 mm, and a minimum reflection loss (RLmin) of −63.3 dB. In addition, the composite magnetic aerogel with the best microwave absorption performance shows a low density of 11.25 mg/cm3. This electromagnetic synergy approach is anticipated to serve as a guide for the development of highly efficient lightweight magnetoelectric composite for wideband microwave absorption in the future.

Decoupling and Cloaking of Rectangular and Circular Patch Antennas and Interleaved Antenna Arrays with Planar Coated Metasurfaces at C-Band Frequencies-Design and Simulation Study.

An electromagnetic cloaking approach is employed with the intention to curb the destructive effects of mutual interference for rectangular and circularly shaped patch antennas situated in a tight spacing. Primarily, we show that by coating the top surface of each patch with an appropriately designed metasurface, the mutual coupling is considerably reduced between the antennas. Furthermore, the cloak construct is extended to a tightly spaced, interleaved linear patch antenna array configuration and it is shown that the coated metasurfaces successfully enhance the performance of each array in terms of their matching characteristics, total efficiencies and far-field realized gain patterns for a broad range of beam-scan angles. For rectangular patches, the cloaked Array I and II achieve corresponding peak total efficiencies of 93% and 90%, in contrast to the total efficiencies of 57% and 21% for uncloaked Array I and II, respectively, at their operating frequencies. Moreover, cloaked rectangular Array I and II exhibit main lobe gains of 13.2 dB and 13.8 dB, whereas uncloaked Array I and II only accomplish main lobe gains of 10 dB and 5.5 dB, respectively. Likewise, for the cloaked circular patches, corresponding total efficiencies of 91% and 89% are recorded for Array I and II, at their operating frequencies (uncloaked Array I and II show peak efficiencies of 71% and 55%, respectively). The main lobe gain for each cloaked circular patch array is approximately 14.2 dB, whereas the uncloaked Array I and II only achieve maximum gains of 10.5 dB and 7.5 dB, respectively.

Deep Learning-based Computational Electromagnetics for Deep Exploration of Oil and Gas Reservoirs

Abstract The exploration potential of oil and gas is substantial, with considerable untapped resources available for future exploration and development. This paper investigates the application of time-frequency electromagnetic (EM) methods within the domain of computational electromagnetics, enhanced by deep learning techniques, for the profound exploration of oil and gas reservoirs. To identify zones favorable for hydrocarbon presence, it captures electric and magnetic field responses across time and frequency domains. From these responses, it extracts crucial parameters such as resistivity and excitation polarizability. The methodology initiates with a forward simulation to establish the most productive construction parameters for the time-frequency EM approach. Subsequently, data collected are processed and analyzed to qualitatively evaluate each physical parameter. This is followed by quantitative constraints on resistivity and polarizability, employing the adaptive differential evolution algorithm to execute a comprehensive parameter inversion using the horizontal E-field (Ex) data derived from the time-frequency EM method. This inversion facilitates the determination of resistivity and polarizability distributions at various depths, culminating in the generation of corresponding depth cross-sections. The inversion fitting and example analyses yielded that the apparent resistivity profiles of low-resistance backslope formations and backslope formations with high and low resistance interlayers form relative anomaly magnitudes of about 13% and 7.8%, respectively. In the real measurement from the depression to the uplift zone, the thickness of the giant inclined low-resistance conductive layer gradually decreases. The points of the extreme values and minima gradually move from the low-frequency band to the high-frequency band, which is identical to the simulation law. The anomaly amplitude is between [-0.4 Ω·m, 0.6 Ω·m], which can be accurately imaged. This study innovatively combines deep learning technology and electromagnetism, which provides a basis for the next decision on oil and gas exploration and target evaluation preference.

Study on the sweep control method of in-situ combustion reservoir in Xinjiang Hongqian oilfield based on asynchronous injection and production

Adjusting injection and production parameters is an essential tool for studying the effect of reservoir heterogeneity on in-situ combustion (ISC) sweep and associated control strategies, as well as for achieving stable ISC. An asynchronous injection and production in-situ combustion (AIPISC) method through the coupling of the gas injector and producer in order to accomplish the balanced sweep of ISC. Using the Hongqian (HQ) ISC in Xinjiang as an example, numerical simulation was utilized to define the reservoir and investigate the sweep characteristics under various sedimentary models. The AIPISC technology was applied to several heterogeneous reservoirs, and the design scheme of AIPISC was created. Under the same heterogeneous reservoir circumstances as the conventional ISC approach, the oil saturation of the AIPISC wall increases from 0.65 to 0.72. The roundness of the combustion chamber was better, and balanced displacement can be achieved. Then the parameters of AIPISC were optimized to determine that the vertical permeability difference of the reservoir should be less than 15, the asynchronous time difference was 6 ∼ 8 months, and the gas injection amplitude was 1.5 ∼ 2.0. The results show that the experiment in HQ Oilfield was successful, and the usefulness of AIPISC was investigated using the electromagnetic approach.

An SAR Imaging and Detection Model of Multiple Maritime Targets Based on the Electromagnetic Approach and the Modified CBAM-YOLOv7 Neural Network

This paper proposes an Synthetic Aperture Radar (SAR) imaging and detection model of multiple targets at the maritime scene. The sea surface sample is generated according to the composite rough surface theory. The SAR imaging model is constructed based on a hybrid EM calculation approach with the fast ray tracing strategy and the modified facet Small Slope Approximation (SSA) solution. Numerical simulations calculate the EM scattering and the SAR imaging of the multiple cone targets above the sea surface, with the scattering mechanisms analyzed and discussed. The SAR imaging datasets are then set up by the SAR image simulations. A modified YOLOv7 neural network with the Spatial Pyramid Pooling Fast Connected Spatial Pyramid Convolution (SPPFCSPC) module, Convolutional Block Attention Module (CBAM), modified Feature Pyramid Network (FPN) structure and extra detection head is developed. In the training process on our constructed SAR datasets, the precision rate, recall rate, mAP@0.5 and mAP@0.5:0.95 are 97.46%, 90.08%, 92.91% and 91.98%, respectively, after 300 rounds of training. The detection results show that the modified YOLOv7 has a good performance in selecting the targets out of the complex sea surface and multipath interference background.

Minimization of eddy power loss in the cryostat for a z-gradient array coil driven by an arbitrary pulse sequence: An electromagnetic approach.

This paper presents a novel computational approach to optimize gradient array performance for a given pulse sequence. Specifically, we propose an electromagnetic (EM) approach that minimizes eddy losses within the cryostat while maintaining key performance parameters such as field linearity, gradient strength, and imaging region's dimension and position. High-resolution EM simulations on the cryostat's surface are deployed to compute the net EM fields generated by each element of a gradient array coil at different frequencies. The computed fields are stored and combined for each frequency to form a quadratic vector-matrix-vector computation. The overall time-average eddy power loss within the cryostat assembly for arbitrary pulse sequences is computed using frequency domain superposition. The proposed approach estimates and regulates eddy power losses within the cryostat assembly. When compared to the stray field minimization approach, it can achieve over twice the reduction in eddy power loss. The proposed approach eliminates the need to sample the stray fields on the cryostat surface, which the number and position of the samples would be challenging when designing tunable array coils with capabilities that disrupt field symmetries. Additionally, the loss calculation considers the entire cryostat assembly rather than just the inner cylindrical surface of the warm shield. Our findings highlight the efficacy of an on-the-fly tuning method for the development of high-performance whole-body gradient array coils, effectively mitigating eddy losses within the cryostat and minimizing stray fields outside the coil assembly. This approach proves particularly advantageous for array coils with variable feeding currents.

Accurate Modeling of Intelligent Reflecting Surface for Communication Systems

In the conventional sense, a passive intelligent reflecting surface (IRS) is perceived as an ideal phase shifter to the incident signal. It is assumed that the phase of the incident signal can be altered to any desired value without affecting its magnitude. In this paper, we question the veracity of this assumption which forms the basis for the communication model that is widely used in the scientific community. Although there exist rigorous electromagnetic (EM) based models to analyze and design metasurfaces, the same cannot be said about its successor, intelligent reflecting surface. Therefore, we attempt to present an EM-based model that accurately describes intelligent scattering by any arbitrary-shaped IRS. Our objective in this paper is to bridge the gap between the fundamental EM formulation for an IRS and the communication model that accurately captures its functioning. We use Method-of-Moments (MoM), a computational electromagnetic approach to quantify the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">intelligent</i> scattering by an arbitrary-shaped IRS. The proposed theoretical model is then validated with computational EM simulation in Feko. We then adopt the general MoM-based model for a special case where each IRS element is a center-loaded wire. Closed-form expressions for pathloss and beamwidth are derived considering free space propagation. We show analytically and numerically, that the received power predicted by the conventional model vs. what is observed through computational EM simulations can differ by 6 dB. Furthermore, we demonstrate that the impact of optimizing an IRS using the conventional model, where each element is treated as an ideal passive phase shifter, can result in an additional 6 - 8 dB of power loss. As a final remark, we propose correction to the communication model that is currently used for IRS-aided networks when each IRS element is a center-loaded wire.

A Region-Folding Electromagnetic Transient Simulation Approach for Large-Scale Power Electronics System

This paper proposes a region-folding electromagnetic transient simulation approach for large-scale power electronics systems to boost simulation speed. In the region-folding approach, the loop tear method is proposed to decouple the connections among power electronics blocks, the grouping and pre-calculating method of identical structural blocks is proposed to avoid computing the inverse of matrices repeatedly, and the global simultaneous response procedure is proposed to handle the simultaneous and multiple switching events. The implementation of the proposed approach is combined with high-performance parallelization technology to shorten the simulation time. The Modular Multilevel Converter (MMC)-based High Voltage Direct Current (HVDC) model and DC photovoltaic power station model are simulated respectively to validate the accuracy and efficiency. Simulation results indicate that the proposed approach has the same accuracy as other Electromagnetic Transients (EMT) commercial software with better efficiency.

Library of rough hailstone backscattering coefficients at 2.8 GHz

The rough hailstone scattering library is created to fill the need for results of non-spheroidal hailstone backscattering characteristics. The listed backscattering coefficients at the S-band (2.8 GHZ) are specifically tailored for computing the polarimetric variables. The National Weather Service’s radar operates in this band; hence the library is pertinent to those studying hail in the USA. The library contains several axis ratios and a range of hail sizes from 5 mm to 100 mm. Moreover, hailstone surface roughness is expressed as a percentage of the equatorial diameter. Our computational electromagnetic approach to modeling hailstones is compared with typically employed simpler methods. The polarimetric variables calculated using our models can be compared to observations. Furthermore, we illustrate the potency of the CEM approach to hydrometeors with extreme axis ratios for which simpler methods (i.e., the T-matrix) fail.

Transient Analysis of Fluid Flow, Solidification, and Inclusion Behavior in Electromagnetically Stirred Bloom Caster Mold Using Bifurcated Submerged Entry Nozzle

Herein, the effect of bifurcated submerged entry nozzle (SEN) port angles on transient flow, solidification, and inclusion behavior in a bloom caster mold with electromagnetic stirring (EMS) is investigated. A 3D numerical model is developed to simulate the process, including time‐varying electromagnetic field and Lagrangian inclusion tracking approach, by varying inclusion density and size. The inclusion is modeled to be entrapped in the solidified shell when primary dendrite arm spacing (PDAS) is greater than inclusion size. As compared to the case without use of EMS, the percentage of shell thickness at the strand outlet is seen to increase by 22.18%, 9.45%, 8.03%, 9.31%, and 13.40% for different port angle values of 0°, 15°, 20°, 25°, and 30°, respectively, with EMS. The results show that EMS significantly influences the flow behavior by generating the swirl flow pattern that hinders the movement of inclusion downward in the domain. The bifurcated SEN with 30° port angle (without EMS) is seen to reduce inclusion entrapment and hence enhance inclusion removal. The outcome of present research may provide useful insights for optimizing the parameters of bloom caster mold to improve product quality, reduce production costs, and increase overall efficiency.

Additive manufacturing of metal matrix nanocomposites: Novel approach for nanoparticles dispersion by electromagnetic three-dimensional vibration

A novel electromagnetic three-dimensional vibration approach was employed for powder feedstock preparation oriented to additive manufacturing of metal matrix nano-composites (MMNCs). The efficiency of this promising mixing technique was validated by laser powder bed fusion (LPBF) of AlSi10Mg reinforced with 3 wt% of B4C nanopowder. Scanning electron microscopy (SEM) analysis revealed that a uniform dispersion of B4C was achieved on the AlSi10Mg powder surface, while retaining its original spherical morphology. The modified powder recycling had no influence on the adherence of nanoparticles to the powder surface. The LPBF-processed samples exhibited good homogeneity in the nano B4C distribution, resulting in an increase in hardness compared to unmodified AlSi10Mg. This high-productivity and cost-efficient approach provides a remedy for the process chain bottleneck in the additive manufacturing of MMNC.

Modeling and Design of Full Electromagnetic Integration of a Symmetrical EMI Filtering Circuit With Flexible Multi-Layer Foil Technique

In a high-frequency power electronic converter with wide-bandgap device, electromagnetic interference (EMI) filter is an essential module for mitigating the conducted EMI issues. However, traditional discrete EMI filter will significantly increase total size and weight of the system. In this article, an UU-core based fully integrated symmetrical EMI filter is proposed using flexible multilayer foil technique, all the common-mode (CM) and differential-mode (DM) filtering components are integrated in the same unit for a more compact design. Moreover, a function-decoupling state is realized between the CM and DM elements, which contributes to predigesting the lumped equivalent CM and DM circuits. Then the parameter design procedure can be simplified. Prototypes of the proposed and other typical types of EMI filters are built for a 100 kHz SiC- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> voltage source inverter, contrastive experiments have verified the feasibility and validity of the full electromagnetic integration approach.

Wave Propagation in Vegetation Field by Combining Fast Multiple Scattering Theory and Numerical Electromagnetics in a Hybrid Method

To calculate scattering of a vegetation field consisting of a large number of plants, an improved fast version of the hybrid method (FHM) combining fast multiple scattering theory (FMST) and a numerical electromagnetic approach has been developed. In the HM, we use a library of T-matrices and the Foldy–Lax (FL) equation to calculate the electromagnetic field interactions outside of the cylinders enclosing the individual plants. To improve CPU time and memory requirements, the FL equation is solved by a triplet of fast Fourier transforms (FFTs) consisting of two FFTs solving 2-D FFTs of spatial distribution of plants and one 1-D FFT for solving the transformation of the order of cylindrical waves in the translation addition theorem. The triple FFTs minimize the CPU time and the memory requirement for computing translation addition matrix, which has been the bottleneck of large-scale simulations in the HM. To account for nonperiodic distribution of scatterers in a corn field, the premultiplication and the postmultiplication processes were applied to the FHM. The proposed method is validated at L-band (1.4 GHz) for 100 corn plants of height 1.25 m occupying an area of 9.54 by 9.54 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{2}$ </tex-math></inline-formula> . On a standard laptop, the CPU time is less than 6 min and the memory consumption is less than 710 Mbytes. The CPU time and the memory requirements are orders of magnitude more efficient than those required for solving the problem with a commercial software or using the previous version of the HM.