Electromagnetic Structure Research Articles

An overpressure monitoring system based on PVDF integrated Electronic sensor with enhanced noise attenuation capability

The measurement of shockwave overpressure is of great significance for the safe use of explosives. The traditional overpressure monitoring systems are based on Integrated Electronics Piezo-Electric (IEPE) ceramic sensors. However, the brittleness of piezoelectric ceramic limits the application of overpressure monitoring system in high impact overpressure testing. Herein, a novel overpressure monitoring system based on Integrated Electronic Poly (vinylidene fluoride) (PVDF) (PFIE) sensor with electromagnetic interference shielding capability and parasitic vibration noise elimination function was designed for intense overpressure acquiring. PVDF, as a polymer, can endure much higher impact pressures compared to piezoelectric ceramics. However, its larger internal resistance makes it more prone to electromagnetic interference. To address this, an electromagnetic shielding structure was designed, incorporating an impedance matching circuit that effectively reduces the sensor's output impedance. Additionally, to mitigate excessive vibration noise during overpressure testing, the differential noise reduction technique has been implemented. Both the laboratory testing and the real blast testing with 10 kg trinitrotoluene were performed to validate the PFIE overpressure monitoring system. The result shows that the electromagnetic noise suppression ability of the PFIE overpressure sensors developed for the monitoring system was improved by 45 dB, and the parasitic vibration noise could be attenuated from 30 % to 1 %, what’s more the RMS errors of the overpressure dynamic parameters obtained by the monitoring system were below 10 %. This work has successfully addressed the noise sensitivity issue inherent in PVDF when used as a pressure sensor, capitalizing on its robust impact resistance. This approach has provided a viable solution for measuring overpressure in scenarios involving intense shock pressures, leveraging the strengths of PVDF in such demanding applications.

Achieving focal invariance in different background refractive indices through a dual-environment metalens.

A conventional metalens is designed with a fixed working environment, and its focal length depends on the background refractive index. In this study, we propose a dual-environment metalens that can maintain the same focal length in both media of air and water. The metalens consists of 16 types of meta-atoms with different geometries, which can cover the 0-2π phase range in both air and water. We perform finite-difference time-domain simulations to investigate the metalens and demonstrate that its focal length remains unchanged, regardless of whether the background medium is air or water. Furthermore, we investigated the optical forces within the focal field of the metalens in both air and water, indicating its potential trapping capability in these media. Our method provides a new insight into dual-environment metasurfaces and advances the methodology of electromagnetic structures in extensive applications.

On the M87 jet structure near the central engine

ABSTRACT At present, there is no doubt that relativistic jets observed in active galactic nuclei pass from highly magnetized to weakly magnetized stage, which is observed as a break in the dependence on their width $d_{\rm jet}(z)$ on the distance z to the central engine. In this paper, we discuss the possibility of observing another break, which should be located at shorter distances. The position of this break can be associated with the region of formation of the dense central core near the jet axis which was predicted both analytically and numerically more than a decade ago, but has not yet received sufficient attention. In this case, the observed width should be determined by the dense core, and not by the total transverse size of the jet. The calculations carried out in this paper, which took into account both the transverse electromagnetic structure of the jet and the change in the spectrum of emitting particles along its axis, indeed showed such behaviour. We also found the evidence of the predicted break in the jet expansion profile using stacked 15 GHz Very Large Baseline Array (VLBA) image of M87 radio jet and constrain the light cylinder radius.

3D Lightweight Interconnected Melamine Foam Modified with Hollow CoFe2O4/MXene toward Efficient Microwave Absorption.

Considering the increasing severity of electromagnetic wave pollution, the development of high-performance low-filler-content microwave absorbers possessing wide frequency bands and strong absorption for practical applications is a demanding research hotspot. In this study, from the perspectives of the electromagnetic component coordination and structural design, a three-dimensional (3D) interconnected CoFe2O4/MXene-melamine foam (MF) was constructed via simple impregnation and a single freeze-drying step. By changing the absorber (CoFe2O4/MXene) concentration, the pore opening and electromagnetic properties of the 3D foams can be effectively adjusted. When the absorber concentration is sufficiently high to clog the internal pores, the microwave absorption is hindered. When the filler (CoFe2O4/MXene-MF) content is just ∼5.8 wt % (at a density of ∼33.3 mg cm-3), a minimum reflection loss (RLmin) of -72.1 dB is achieved at a matching thickness of 3.32 mm, and an effective absorption bandwidth (4.54 GHz) covering the whole X band is achieved at a thickness of 3 mm. CoFe2O4/MXene-MF, which possesses a 3D porous electromagnetic network structure, optimizes impedance matching and enhances multiple polarization relaxations and reflections/scattering, resulting in superior absorption capabilities. In particular, the continuous network structure ensures the uniform distribution of electromagnetic fields in the microstructure, achieving high absorption at low filler contents. This work provides a reference for subsequent 3D absorber concentration studies and a novel engineering strategy for preparing a low-filler-content, lightweight, and efficient electromagnetic wave absorber, which could be applied in the fields of radar security and information communications.

A Metamaterial Surface Avoiding Loss from the Radome for a Millimeter-Wave Signal-Sensing Array Antenna

Radar systems are a type of sensor that detects radio signals reflected from objects located a long distance from transmitters. For covering a longer range and a higher resolution in the operation of a radar, a high-frequency band and an array antenna are measures to take. Given a limited size to the antenna aperture in the front end of the radar, the choice of a millimeter-wave band leads to a denser layout for the array antenna and a higher antenna gain. Millimeter-wave signals tend to become attenuated faster by a larger loss of the covering material like the radome, implying this disadvantage offsets the advantage of high antenna directivity, compared to the C-band and X-band ones. As the radome is essential to the radar system to protect the array antenna from rain and dust, a metamaterial surface in the layer is suggested to meet multiple objectives. Firstly, the proposed electromagnetic structure is the protection layer for the source of radiation. Secondly, the metasurface does not disturb the millimeter-wave signal and makes its way through the cover layer to the air. This electromagnetically transparent surface transforms the phase distribution of the incident wave into the equal phase in the transmitted wave, resulting in an increased antenna gain. This is fabricated and assembled with the array antenna held in a 3D-printed jig with harnessing accessories. It is examined in view of S21 as the transfer coefficient between two ports of the VNA, having the antenna alone and with the metasurface. Additionally, the far-field test comes next to check the validity of the suggested structure and design. The bench test shows around a 7 dB increase in the transfer coefficient, and the anechoic chamber field test gives about a 5 dB improvement in antenna gain for a 24-band GHz array antenna.

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

A strong insulating, compressible Nd2O3@CNFs WPU foam for robust electromagnetic wave absorption

The portable fabrication of multifunctional, lightweight, and ultra-wide absorption bandwidth electromagnetic wave absorbing materials remains a significant challenge. In this study, both component modulation and architecture design were simultaneously employed to construct a layered porous electromagnetic wave absorbing foam (EMAF) with Nd2O3@CNFs as the backbone and waterborne polyurethane (WPU) and starch as the cross-linking agents. Due to the rich heterogeneous interfaces brought by multiple components and the electromagnetic coupling structure of Nd2O3@CNFs, EMAF-4 exhibits an ultra-wide effect absorption bandwidth (EAB) of 9GHz and a minimum Reflect Loss (RL) of -52.33dB. Furthermore, the layer structure of the foam enables the sample to rebound quickly when subjected to stress. The porous architecture effectively blocks heat conduction and radiation, resulting in an ultra-low thermal conductivity (0.036W/(m·K)), which enables the material to realize dual microwave-infrared stealth at the same time. This work provides new ideas and broaden the applications for multifunctional microwave absorbing materials.

A Generalized FDTD Scheme for Moving Electromagnetic Structures With Arbitrary Space–Time Configurations

A Generalized FDTD Scheme for Moving Electromagnetic Structures With Arbitrary Space–Time Configurations

Effect of a constant electric field on the electromagnetic spectrum structure of eucalyptus oil

Effect of a constant electric field on the electromagnetic spectrum structure of eucalyptus oil

Realizing multi-function absorptions through arbitrary octagonal meta-atoms.

Metasurface absorbers (MA) typically exhibit a single type of absorption function due to their regular structures. In this study, we propose an irregular MA structure with octagonal meta-atoms. The presence of eight vertices in each meta-atom allows for tunable coordinates and offers a multitude of degrees of freedom in terms of geometry. As a result, the proposed MA exhibits diverse functionalities, including perfect absorption, multi-peaks absorption, and high absorption with a filtering window. To predict the geometric parameters of the MA structure based on a given target absorption spectrum, as well as the inverse design of the structure using the absorption spectrum as input, we employ a deep neural network combined with the particle swarm optimization algorithm. Remarkably, the mean-square error for spectrum prediction and inverse design of the MA structure is found to be as low as 0.0008 and 0.0031, respectively. This study opens up new possibilities for designing irregular electromagnetic structures and holds great potential for applications in multifunctional metasurfaces and metamaterials.

Screen‐printed dual‐band wearable textile antenna incorporated with EBG structure for WBAN communications

SummaryA dual‐band, wearable coplanar microstrip patch antenna (CPW) integrated with electromagnetic bandgap structure (EBG) to operate dual wireless bands at 2.48 GHz industrial, scientific, and medical band (ISM) and 5.2 GHz WLAN. The proposed textile wearable antenna and EBG structure are screen‐printed using silver conductive ink on the cotton polyester substrate (εr = 1.6) for flexible wearable applications. A 3 × 3 EBG array is realized by a concentric square patch surrounded by the annular square ring to reduce back radiation and increase the forward gain and front‐back ratio. The proposed EBG‐backed antenna, compared with the conventional CPW‐fed antenna, improves forward gain from 2.18 to 6.59 dB at 2.48 GHz and 3.5 to 7.03 dB at 5.2 GHz. Moreover, the EBG array is used to isolate the human body from the antenna and reduces the specific absorption rate (SAR). The antenna is performed with a human phantom tissue model, which exhibits a specific absorption rate of 0.12 W/kg, and 0.260 W/kg for 1 g tissue at 2.48 GHz and 5.2 GHz, respectively.

Optimization Design of the Electromagnetic Flowmeter Excitation Structure Based on GA-BP-GWO Neural Network

Optimization Design of the Electromagnetic Flowmeter Excitation Structure Based on GA-BP-GWO Neural Network

An electromagnetic bandgap structure assisted MIMO antenna with an optimisation driven hybrid beam forming model

An electromagnetic bandgap structure assisted MIMO antenna with an optimisation driven hybrid beam forming model

Investigative Study of the Effect of Damping and Stiffness Nonlinearities on an Electromagnetic Energy Harvester at Low-Frequency Excitations

Ambient vibration energy is widely being harnessed as a source of electrical energy to drive low-power devices. The vibration energy harvester (VEH) of interest employs an electromagnetic transduction mechanism, whereby ambient mechanical vibration is converted to electrical energy. The limitations affecting the performance of VEHs, with an electromagnetic transduction structure, include its operational bandwidth as well as the enclosure-size constraint. In this study, an analysis and design of a nonlinear VEH system is conducted using the Output Frequency Response Function (OFRF) representations of the actual system model. However, the OFRF representations are determined from the Generalised Associated Linear Equation (GALE) decompositions of the system of interest. The effect of both nonlinear damping and stiffness characteristics, to, respectively, extend the average power and operational bandwidth of the VEH device, is demonstrated.

SIW Filter Based on a CPW Resonator and a Hybrid Electromagnetic Coupling Structure

SIW Filter Based on a CPW Resonator and a Hybrid Electromagnetic Coupling Structure

Toward the Unified Theory of SAID‐Linked Subauroral Arcs

AbstractWe present a unified approach to subauroral arcs within intense subauroral ion drifts (SAID), which explains the observed transition of a precursor Stable Auroral Red (SAR) arc into Strong Thermal Emission Velocity Enhancement (STEVE). This approach is based on the short‐circuiting concept of fasttime SAID as an integral part of a magnetospheric voltage generator between the innermost boundaries of the freshly injected plasma sheet electrons and ring current ions. Here, enhanced plasma turbulence rapidly heats the bulk plasma and accelerates suprathermal non‐Maxwellian “tails.” Heat and suprathermal electron transport rapidly elevate the ionospheric electron temperature—the source of a bright SAR arc. Through a substorm, the density altitude profile within the evolving ionospheric SAID channel transforms into a “fresh” F‐region trough with the E‐region valley. The ionospheric feedback instability within the depleted‐density SAID channel generates small‐scale, field‐aligned currents with parallel electric fields sufficient to produce the suprathermal electron population, exciting the STEVE and Picket Fence emissions. This approach also explains the inner electromagnetic structure of intense SAID, which is consistent with fine optical structures in STEVE and Picket Fence.

Studies of Time-like Electromagnetic Structure of Baryons with HADES

We present results of studies of Dalitz decays of baryon resonances (R→Ne+e−) in proton-proton (pp) and pion-proton (πp) collisions performed by the HADES collaboration. They provided the first measurement of electromag netic transition form factors of baryons in the time-like region and contribute to the understanding of the photon-baryon coupling and the role of Vector Dom inance Model in a baryonic sector. We discuss also implications of the results to the understanding of the emissivity of dense and hot QCD matter created in heavy-ion collisions and the role played by the in-medium modification of the ρ meson. Further prospects for future studies with pion beams at GSI with HADES are given in the outlook.

Flexible carbon fibres with magnetic ZIF-67 as core layer and in-situ grown NiMn-LDH nanosheets as shell layer for microwaves absorption

Fabrication of high-performance microwaves absorbers by assembling multi-dimensional nanocomponents into core-shell electromagnetic structures has been shown to be a new manufacturing strategy. In this work, a novel core-shell carbon-fibres@ZIF-67@NiMn-Layered double...

Superconducting rotor drive method with integrated driving and alignment

The high-speed rotating superconducting rotor can be used as a high-precision inertial device to measure the angular position or angular velocity of the carrier. The mass eccentricity and spherical error of the superconducting rotor are the main error sources that affect the measurement accuracy. The more complex the structure of the superconducting rotor, the greater the mass eccentricity and spherical error caused by its production and assembly process are, and the lower the accuracy of its measurement of angular velocity. Based on this, in this work, an electromagnetic drive structure with a simple rotor structure is designed. And the torque generated by the stator on the superconducting rotor is studied through finite element method (FEM). The effects of the stator on vertical alignment and acceleration of the superconducting rotor are analyzed. Based on the research results of the superconducting rotor torque, a superconducting rotor drive method with integrated driving and vertical alignment is proposed, which achieves the driving and vertical alignment functions simultaneously through the stator coil, and corresponding stator control timing is designed. Finally, the torque distribution in the driving process of the proposed driving method is analyzed, and the driving effect is quantitatively analyzed based on the response characteristics of the stator system. The time for the superconducting rotor to be accelerated to 50 Hz under different conditions is calculated. The results show that the designed driving electromagnetic structure and the proposed integrated driving method of vertical alignment and driving can be used for vertical aligning and driving the superconducting rotor. The research results provide a reference for further optimizing the superconducting rotor structure and driving methods of superconducting rotors.

Analysing Antennas with Artificial Electromagnetic Structures for Advanced Performance in Communication System Architectures

Analysing Antennas with Artificial Electromagnetic Structures for Advanced Performance in Communication System Architectures