Structure Of Electromagnetic Field Research Articles

Investigation of the limitations imposed on the possibilities of methods for forming "virtual" antenna arrays in conditions of significant distortion of the electromagnetic field structure near the receiving antenna array

Investigation of the limitations imposed on the possibilities of methods for forming "virtual" antenna arrays in conditions of significant distortion of the electromagnetic field structure near the receiving antenna array

Non-equilibrium dynamics of dipole-charged fields in the Proca theory

We discuss the dynamics of field configurations encoded in the certain class of electric (magnetic) dipole-charged states in the Proca theory of the real massive vector field. We construct such states so as to ensure that the long-distance structure of the mean electromagnetic field in them is initially set by the formula describing the electromagnetic field of the electric (magnetic) dipole. We analyze then how such a mean electromagnetic field evolves in time. We find that far away from the center of the initial field configuration, the long-range component of the mean electromagnetic field harmonically oscillates, which leads to the phenomenon of the periodic oscillations of the electric (magnetic) dipole moment. We also find that near the center of the initial field configuration, the mean electromagnetic field escapes from its initial arrangement and a spherical shock wave propagating with the speed of light appears in the studied system. A curious configuration of the axisymmetric mean electric field is found to accompany the mean magnetic field in magnetic dipole-charged states.

Black Hole Polarimetry I. A Signature of Electromagnetic Energy Extraction

In 1977, Blandford and Znajek showed that the electromagnetic field surrounding a rotating black hole can harvest its spin energy and use it to power a collimated astrophysical jet, such as the one launched from the center of the elliptical galaxy M87. Today, interferometric observations with the Event Horizon Telescope (EHT) are delivering high-resolution, event-horizon-scale, polarimetric images of the supermassive black hole M87* at the jet launching point. These polarimetric images offer an unprecedented window into the electromagnetic field structure around a black hole. In this paper, we show that a simple polarimetric observable—the phase ∠β 2 of the second azimuthal Fourier mode of the linear polarization in a near-horizon image—depends on the sign of the electromagnetic energy flux and therefore provides a direct probe of black hole energy extraction. In Boyer–Lindquist coordinates, the Poynting flux for axisymmetric electromagnetic fields is proportional to the product B ϕ B r . The phase ∠β 2 likewise depends on the ratio B ϕ /B r , thereby enabling an observer to determine the direction of electromagnetic energy flow in the near-horizon environment experimentally. Data from the 2017 EHT observations of M87* are consistent with electromagnetic energy outflow. Currently envisioned multifrequency observations of M87* will achieve higher dynamic range and angular resolution, and hence deliver measurements of ∠β 2 closer to the event horizon as well as better constraints on Faraday rotation. Such observations will enable a definitive test for energy extraction from the black hole M87*.

Design and optimization of superconducting CUSP electromagnetic field structure based on a COMSOL-GMDH-MOSO hybrid strategy

As the semiconductor industry gains momentum, there is a significant focus on producing high-quality silicon wafers with larger diameters. However, the preparation of major-diameter, high-quality silicon single-crystal has encountered challenges such as intense convection inside the melt and high oxygen impurity concentration at the interface between the fluid and solid phases. To tackle these problems, the external superconducting CUSP electromagnetic field structure was designed to optimize the crystal growth parameters. A hybrid strategy of the multiphysics field coupling method, Group Method of Data Handling (GMDH) type neural network identification, and the Multiple Objective Snake Optimizer (MOSO) algorithm was proposed to optimize the superconducting CUSP electromagnetic field structure. A two-dimensional axisymmetric model was established for 18-inch silicon single-crystal preparation using the Magnet system Applied Czochralski (MCZ) method. The amount of longitudinal plies of superconducting CUSP electromagnetic field coils, coil spacing, and the thickness of magnetic shields were selected as design variables, and the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume were used as dual objective functions. The required samples for GMDH training were provided by COMSOL Multiphysics (COMSOL) numerical calculations, and polynomial mathematical equations were established with the radial electromagnetic induction intensity at the graphite crucible inner wall and the superconducting magnet volume as the dual objective functions. Then the Pareto optimal solution for the electromagnetic field structure design variables was obtained using the dual objective function optimized by MOSO. With the hybrid strategy, numerical simulations and theoretical analysis of the crystal preparation process parameters under the effect of the superconducting electromagnetic field with the optimal structure were carried out. The results displayed that the added superconducting CUSP electromagnetic field reduced the crystal radial and axial thermal gradients and greatly suppressed the melt convection. As a result, the heat distribution inside the hot fused silicon was more even, the thermal gradient at the solid–liquid interface was reduced by 68.4%, and the oxygen impurity content was reduced by 82.1%, which effectively improved the crystal quality. The thermal field simulation results verified that the proposed hybrid strategy provided a new numerical calculation method for obtaining the optimal superconducting electromagnetic field structure.

Simulation of the dependence of the radiation pattern of a digital active phased array antenna on the main destabilizing factors

As for today digital active phased array antennas (DAPAA), based on the principle of functioning using digital diagram formation, are actively used as part of spacecraft and unmanned aerial vehicles in solving radio communication and radar problems. At the same time, for the purposes of radar, DAPAA allows you to perceive all the information contained in the structure of spatiotemporal electromagnetic fields in the opening of the array and transform it into data on the presence and parameters of objects, providing deep compensation for broadband interference signals, which, combined with the expansion of the dynamic range when accumulated during spatiotemporal processing, provides high noise immunity of radar stations. To solve communication problems, DAPAA allows you to form several beams simultaneously, which allows you to simultaneously serve several areas at once with the possibility of dynamically changing the bandwidth in the channels due to variations in partial power.

Investigation of methods for the formation of virtual antenna arrays under conditions of strong distortion of the electromagnetic field structure near the receiving antenna array

Investigation of methods for the formation of virtual antenna arrays under conditions of strong distortion of the electromagnetic field structure near the receiving antenna array

Particle motion around Schwarzschild-MOG black hole

In this paper, we present an analysis of the circular motion of test particles around a Schwarzschild-MOG black hole. Initially, our focus lies on studying the shadow cast by the spherically symmetric black hole within the framework of MOG gravity. Notably, we observe that the presence of MOG influences both the photon-sphere and the black hole’s shadow, causing them to increase in size. Furthermore, our research reveals that the characteristic radii of massive particles in circular orbits around the Schwarzschild-MOG black hole, specifically the innermost stable circular orbits (ISCO) and marginally bound orbits, are greater than those observed in the Schwarzschild metric alone. Additionally, we examine the electromagnetic field structure when a black hole is subjected to an external uniform magnetic field. Our findings demonstrate that in the vicinity of the Schwarzschild-MOG black hole, the magnetic field exhibits non-uniform behavior, with field lines becoming more densely distributed. Lastly, we delve into the motion of charged particles around the Schwarzschild-MOG black hole in the presence of an external magnetic field. Our investigation highlights that the ISCO position for charged particles is consistently less than that for neutral particles, indicating a significant distinction between the two scenarios.

Arbitrarily structured laser pulses

Spatiotemporal control refers to a class of optical techniques for structuring a laser pulse with coupled space-time dependent properties, including moving focal points, dynamic spot sizes, and evolving orbital angular momenta. Here we introduce the concept of arbitrarily structured laser (ASTRL) pulses which generalizes these techniques. The ASTRL formalism employs a superposition of prescribed pulses to create a desired electromagnetic field structure. Several examples illustrate the versatility of ASTRL pulses to address a range of laser-based applications.

RaDiO: An efficient spatiotemporal radiation diagnostic for particle-in-cell codes

This work describes a novel radiation algorithm designed to capture the three-dimensional, space-time resolved electromagnetic field structure emitted by large ensembles of charged particles. The algorithm retains the full set of degrees of freedom that characterize electromagnetic waves by employing the Liénard-Wiechert fields to retrieve radiation emission. Emitted electric and magnetic fields are deposited in a virtual detector using a temporal interpolation scheme. This feature is essential to accurately predict field amplitudes and preserve the continuous character of radiation emission, even though particle dynamics is known only in a discrete set of temporal steps. Our algorithm retains and accurately captures, by design, full spatial and temporal coherence effects. We demonstrate that our numerical approach recovers well known theoretical radiated spectra in standard scenarios of radiation emission. We show that the algorithm is computationally efficient by computing the full spatiotemporal radiation features of High Harmonic Generation through a plasma mirror in a Particle-In-Cell (PIC) simulation.

전자기 유도를 활용한 전자기 댐퍼의 구조 설계에 관한 연구

In this paper, we proposed and electro-magnetic (EM) damper that can have both the simple structure of the existing mechanical damper and the active damping ability of the Magnetic-Rheological fluid damper. The proposed EM damper has a structure similar to that of a mechanical damper, and the manufacturing cost is not high because the damping force can be generated only with the permanent magnet mounted on the plunger and the damping coil mounted on the inside of the cylinder. Damping force is generated according to the amount of change in flux linkage of the damping coil when the permanent magnet mounted on the plunger vibrates up and down. Therefore, the electromagnetic field structure of the EM damper, which is advantageous to generate a damping force that suppresses external vibration, is proposed. In order to verify the reliability of the damping capacity of the EM damper, it was analyzed by finite element analysis applying an axisymmetric analysis technique, and the damping ability to suppress external vibration was verified with the induced current waveform of the damping coil and the generated damping force waveform.

Azimuthally and Radially polarized pulsed Bessel-X vortices

Invariant wave packets get ever-increasing research attention due to their unique and useful properties such as diffraction resistance, non-dispersive propagation, self-healing, and others. These abilities become even more interesting when combined with optical vorticity, short pulse durations, high powers, and inhomogeneous polarization. In this work, we present an analytical model of pulsed, invariant to propagation, fields with both optical vorticity and radial/azimuthal polarization. We investigate the structure of electromagnetic fields, their propagation properties for different cone angles, and the duration of Bessel-X pulses. We also observed the influence of polarization inhomogeneity on the pulse duration.

Identifying the knowledge structure of electromagnetic fields and health research: Text network analysis and topic modeling.

BackgroundWith technological and scientific advancement, people are being increasingly exposed to electromagnetic fields, particularly from portable devices such as mobile phones. However, there is currently no consensus regarding the health effects of electromagnetic field exposure, despite the large amount of research conducted on this topic. This study aimed to understand the knowledge structure and trend of electromagnetic field and health research through text network analysis and topic modeling.MethodsPubMed, Embase, and Cochrane were searched, and 3,880 articles published before June 2021 were identified. We explored the main keywords and research topics regarding electromagnetic fields and human health by constructing a network of keywords. A social network analysis program was used to analyze the data, visualize the network, and perform topic modeling.ResultsFour keywords, “exposure,” “effect,” “cell,” and “cancer,” were highly correlated to other keywords and formed each colony in the knowledge structure of research on electromagnetic fields and health. Five topics were derived from topic modeling: cell research, research on the adaption of MRI, health effects of mobile phones, pain therapy, and exposure measurement. Cell research has been continuously performed, and many studies have been conducted on the health effects of mobile phones since 2000.ConclusionsThese findings will assist in gaining insights into and understanding changes in research on the health effects of electromagnetic fields, and suggest important areas and directions for future research.

Evolving electromagnetic chirality of a focused field from the Poincaré sphere perspective

Chirality, which describes not only the three-dimensional mirror-symmetry violation of objects but also the local handedness and spatial geometrical structure of electromagnetic fields, has gained enormous interest recently because of its fundamental features as well as practical and potential applications in chiral light–matter interactions. Analytical forms of the electric and magnetic field strength vectors as well as optical chirality density and flow of strongly focused full Poincaré sphere beams are presented. The evolution of nonparaxial electromagnetic chirality of input fields from the Poincaré sphere view is explored; in addition its roles in relation to ellipticity, handedness, and orientation are revealed based on the analytical model. Ellipticity affects the localization and magnitude of both chirality density and flow. In contrast, handedness mainly affects the magnitude of the optical chirality density and longitudinal component of flow, whereas both density and flow are independent of the input orientation. Moreover, the structure and appearance of the optical chirality density are dominated by the longitudinal component of its flow. These findings may be of help in chiral particle trapping, nanoscale chiral detection, and sensing.

Дисперсия поляритонных возбуждений в атомарных криокристаллах в окрестности частоты квадрупольно разрешенного экситонного резонанса

The paper is devoted to the propagation of exciton-polariton excitations in atomic cryocrystals in the frequency vicinity of a quadrupole resolved exciton resonance. The structure of the local electromagnetic field in a molecular crystal in the frequency vicinity of an isolated quadrupole transition in the spectrum of the molecule is investigated; the tensor of the quadrupole polarizability of the unit volume of a cubic crystal is obtained. The features of the exciton polaritons dispersion reflecting the presence of additional light waves in the investigated frequency neighborhood are studied.

Detailed characterization of a laboratory magnetized supercritical collisionless shock and of the associated proton energization

Collisionless shocks are ubiquitous in the Universe and are held responsible for the production of nonthermal particles and high-energy radiation. In the absence of particle collisions in the system, theory shows that the interaction of an expanding plasma with a pre-existing electromagnetic structure (as in our case) is able to induce energy dissipation and allow shock formation. Shock formation can alternatively take place when two plasmas interact, through microscopic instabilities inducing electromagnetic fields that are able in turn to mediate energy dissipation and shock formation. Using our platform in which we couple a rapidly expanding plasma induced by high-power lasers (JLF/Titan at LLNL and LULI2000) with high-strength magnetic fields, we have investigated the generation of a magnetized collisionless shock and the associated particle energization. We have characterized the shock as being collisionless and supercritical. We report here on measurements of the plasma density and temperature, the electromagnetic field structures, and the particle energization in the experiments, under various conditions of ambient plasma and magnetic field. We have also modeled the formation of the shocks using macroscopic hydrodynamic simulations and the associated particle acceleration using kinetic particle-in-cell simulations. As a companion paper to Yao et al. [Nat. Phys. 17, 1177–1182 (2021)], here we show additional results of the experiments and simulations, providing more information to allow their reproduction and to demonstrate the robustness of our interpretation of the proton energization mechanism as being shock surfing acceleration.

3D PIC Simulations for Relativistic Jets with a Toroidal Magnetic Field

AbstractParticle-in-Cell simulations can provide a possible answer to an important key issue for astrophysical plasma jets; namely on how a toroidal magnetic field affects the evolution of pair and electron-ion jets. We show that Weibel, mushroom, and kinetic Kelvin-Helmhotz instabilities excited at the linear stage, generate a quasi-steady x-component of the electric field which accelerates and decelerates electrons. We observe significant differences in the structure of the strong electromagnetic fields that are driven by the kinetic instabilities with the pair jet. We find that the two different jet compositions (e± and e– - i+) generate different instability modes respectively. Moreover, the magnetic field in the non-linear stage generated by different instabilities is dissipated and reorganized into new topologies. A 3D magnetic field topology depiction indicates possible reconnection sites in the non-linear stage where the particles are significantly accelerated by the dissipation of the magnetic field associated to a possible reconnection manifestation.

Optimisation of reverse salient rotor for interior permanent magnet synchronous motor and experimental validation

The prosperous development of electric vehicles has promoted the application of interior permanent magnet synchronous motors (IPMSMs). The flux-intensifying IPMSM has attracted more attention due to its high power-density and better flux-weakening performance. However, the optimisation efficiency and motor performance require further study in the actual optimisation design. To this end, this study is to optimise the electromagnetic field structure of motor rotors with the back propagation neural networks (BPNN) and multi-objective optimisation methods. Concretely, dimensional parameters of an initial motor are extracted as optimisation variables. Then, the BPNN are utilised to stimulate the motor performance obtained with finite element methods (FEM). With the trained BPNN, FEM tools are replaced in the subsequent optimisation process, which alleviates the computational burden. Besides, to address the problem of multi-objective optimisation with inequality constraints, the sequential unconstrained minimisation technique is incorporated into the non-dominated sorting genetic algorithm to obtain the Pareto frontier. Finally, the optimal design point is selected from the Pareto frontier. The simulation and experiment have been implemented to verify the superiority of the optimised rotor structure. Generally, this study has laid the foundation of the following motor optimisation with the higher executability and lower computational burden.

SPATIO-TEMPORAL STRUCTURE OF CHERENKOV RADIATION EXCITED BY A LASER PULSE IN AN IONIC DIELECTRIC WAVEGUIDE

The process of excitation of Cherenkov electromagnetic radiation by a laser pulse in an ionic dielectric waveguide, is investigated. The frequency spectrum and mode composition of the Cherenkov radiation are determined. The spatio-temporal structure of the Cherenkov electromagnetic field is obtained and investigated.

About copying a free-space electromagnetic field by an invisible object

The structure of a monochromatic electromagnetic field inside a spherical object that does not distort the wave field of external sources outside its surface has been studied using transformation optics methods. It is assumed that the object is made of isotropic materials with equal values of permittivity and permeability and consists of a spherical volume of material with a positive spatially uniform refractive index and an adjacent spherical layer of material with a negative inhomogeneous refractive index (i.e., it is a spherical superlens made of isotropic materials). It is shown that the field inside a sphere with a positive refractive index is the reduced-size copy of the field in which the object was located. This copy contains information about the radiation field of external sources in a spherical free-space volume whose radius depends on the object parameters and can be significantly larger than the radius of the object. It is shown that the copying properties of the object with given dimensions can be fully preserved if its outer layer is made of anisotropic materials.

Modifying light–matter interactions with perovskite nanocrystals inside antiresonant photonic crystal fiber

Structured environments are employed in a plethora of applications to tailor dynamics of light–matter interaction processes by modifying the structure of electromagnetic fields. The promising example of such a system is antiresonant photonic crystal fibers (AR-PCFs), which allow light–analyte interactions in a very long channel. Here we probe contribution of microstructuring and nontrivial mode hierarchy on light–matter interactions in AR-PCFs by investigating lifetime shortening of perovskite ( CsPbBr 3 ) nanocrystals grown to fiber capillaries. The crystals have been deposited using a wet chemistry approach and then excited by a supercontinuum source in the 450–500 nm range. Emission spectra have been measured and analyzed via the time-correlated single photon counting (TCSPC) technique, unravelling contributions of core and cladding modes. Fluorescence lifetime imaging inside an AR-PCF enables mapping input of various electromagnetic channels into light–matter interaction processes. Our results pave the way for tailoring the dynamics of high-order quantum processes, promoting the concept of AR-PCF as a light-driven reactor.