Hasil untuk "Electricity and magnetism"

Kenichi Yamazaki, Hiroyuki Yasui, Tsuyoshi Noguchi et al.

Atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) enables low-temperature coating in open air, yet the interplay between precursor activation and ambient-derived species remains unclear. Here, thin films from an amine precursor are deposited using a helium plasma and characterized by gas chromatography–mass spectrometry (GC-MS), a quartz crystal microbalance (QCM), and X-ray photoelectron spectroscopy (XPS). GC-MS indicates partial precursor conversion and formation of oxygen- and nitrogen-containing products, consistent with participation of ambient air and moisture. QCM identifies a limited precursor-concentration window in which mass increases monotonically during plasma exposure and remains constant after shutdown; outside this window, post-discharge mass loss occurs, indicating desorption of weakly bound species. XPS confirms carbon-rich films incorporating oxygen- and nitrogen-containing functionalities and complete substrate coverage at higher precursor concentrations.

Tao Wang, Hongbo Zhang, Dawei Yin et al.

In this paper, a novel 3D-printed high-gain wideband antenna composed of split-ring resonators, a bowl-shaped reflector, and a circular-fractal, multilayered, stacked microstrip antenna is presented. The cambered internal surface of the bowl-shaped structure is coated with sliver conductive adhesive. The microstrip antenna and split-ring resonators are installed inside and on top of the bowl-shaped structure, respectively. High gain is achieved due to the split-ring resonators and the curved reflective surface formed inside the bowl-shaped structure. At the same time, a high bandwidth is realized owing to the split-ring resonators and the microstrip antenna’s multilayered, stacked, and fractal structure. The proposed antenna is fabricated and measured. Operating within the frequency range of 5.63–6.78 GHz (reflection coefficient ≤ −10 dB), the antenna achieved a gain between 10.9 dBi and 14.6 dBi, with a peak gain of 14.6 dBi at 5.7 GHz. In addition, the antenna offers other significant advantages–low cost, low cross-polarization, and easy fabrication.

Michael Ivliev, Konstantin Andryushin

In this paper, based on the developed statistical-thermodynamic model, which is based on data on the local structure of the compound and taking into account the striction interaction caused by the large sizes of the Ba and K cations, the formation of ferroelectric phases in BaTiO3 and KNbO3 perovskites has been studied. Based on the modified eight-minimum model, it has been possible to qualitatively identify the factors that determine the features of the thermodynamic behavior of these crystals and to reproduce the process of formation of the whole set of phase states observed in BaTiO3 and KNbO3.

Vladimir Lisy, Jan Busa, Jana Tothova

The Bohr-van Leeuwen (BvL) theorem, stating the absence of classical magnetization in equilibrium, a fundamental result in the field of magnetic phenomena, was originally proved for an electron gas. In the present work, we deal with the problem of whether this theorem applies to particles undergoing a non-Markovian Brownian motion in a static magnetic field. We consider a charged Brownian particle (BP) immersed in a bath of neutral particles. Generalizing the Zwanzig-Caldeira-Legget theory to the presence of a static external magnetic field, we come to the equation of motion for the BP in the form of a generalized Langevin equation that accounts for memory effects in the dynamics of the system. By using its solutions for the displacement and velocity of the BP, we calculate the angular momentum for the Ornstein-Uhlenbeck thermal noise. At long times, when the system should reach equilibrium, this momentum and, consequently, the classical magnetic moment of the BP are nonzero, in contrast to the BvL theorem. With the help of analytical and precise numerical calculations for different sets of system parameters, a simple formula for the angular momentum has been deduced.

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Contents: Preface Newton on electricity and the aether Force, electricity and the powers of living matter in Newtona (TM)s mature philosophy of nature Francis Hauksbeea (TM)s theory of electricity a "Newtonianisma (TM) and the theory of the magnet Out of the Newtonian straitjacket: alternative approaches to 18th-century physical science Leonhard Eulera (TM)s a /anti-Newtoniana theory of light The notion of experimental physics in early 18th-century France Nollet and Boerhaave: a note on 18th-century ideas about electricity and fire Franklina (TM)s electrical atmospheres Some manuscripts on electrical and other subjects attributed to Thomas Bayes, F.R.S. Electricity and the nervous fluid Electricity in France in the post-Franklin era On two supposed works by Leonhard Euler on electricity Aepinus, the tourmaline crystal, and the theory of electricity and magnetism Science as a career in 18th-century Russia: the case of F.U.T. Aepinus Aepinus and the British electricians: the dissemination of a scientific theory Scientific links between Great Britain and Russia in the second half of the 18th-century Physical principles and the possibility of a mathematical science of electricity and magnetism Poissona (TM)s memoirs on electricity: academic politics and a new style in physics Index.

Bincai Wu, Xingqi Xuan, Yuqi Chen et al.

Abstract Implementation of reconfigurable metasurfaces demands a complex structure. The design methodology for metasurface elements based on PIN diodes requires targeted optimisation tailored to the varying application environments and cannot be directly transplanted from one methodological approach to another. In addition, inclusion of varactors often imposes undesirable high‐power consumption with complex analog drive circuitry. Furthermore, the design method for the reconfigurable metasurface element has not been simplified and unified, hindering the rapid deployment of metasurface applications. The authors propose a general design model based on low‐power embedded circuitry for a multi‐function metasurface element and give the corresponding numerical analysis. The authors present a reconfigurable method based on the general design model and prove that the method achieves independent regulation of amplitude and phase for the reflected electromagnetic wave. Through analysis of the sensitive area at the bottom of the embedded circuit, a gradient descent algorithm is proposed to find the optimised phase points according to device sensitivity of the application scenario and suitable strategy. Finally, the authors demonstrate that the designed metasurface element possesses phase control capability and decent phase consistency obtained via far‐field scanning experiments. The proposed element design method will provide a theoretical reference for the integrated design of metasurface.

Le Li, Shuo Tan, Yunpeng Liu et al.

Abstract Syntactic foam materials, due to their advantages of low densities, low water absorption, and high dielectric strengths, have significant application potential in the cores of post insulators. However, because of a large number of microbubble structures within the syntactic foam, it might decrease the partial discharge inception voltage. It is necessary to investigate the partial discharge characteristics of the foam to assess the feasibility of its internal insulation application. In this study, the syntactic foam samples with four different microsphere contents (0%–2%) were prepared, and the physical structures of the materials were characterised by using Fourier transform infrared spectroscopy, scanning electron microscopy, and three‐dimensional computed tomography. Subsequently, finite element simulations of the electric field were performed to analyse the influence of the microsphere content and distribution on the internal electric field of the syntactic foam. The results suggested that both the microsphere content and distribution affected the partial discharge activity. When the microsphere content was low, the doping of microspheres essentially meant that more air gap defects were present, leading to a decrease in the partial discharge performance. However, when the microsphere content was high, the microspheres were distributed in a dense and orderly manner, improving the field concentration phenomenon and hence inhibiting the partial discharge to a certain extent. In conclusion, the findings of this study provide a data reference and theoretical support for the application of syntactic foam in the cores of composite post insulators.

Huiqin WANG, Fadong YANG, Yongqiang HE et al.

Ground Penetrating Radar (GPR) image detection currently faces challenges such as low accuracy, false detections, and missed detections. To overcome these challenges, we propose a novel model referred to as GDS-YOLOv8n for detecting common underground targets in GPR images. The model incorporates the DRRB (Dilated Residual Reparam Block) feature extraction module to achieve enhanced multiscale feature extraction, with certain C2f modules in the YOLOv8n architecture being effectively replaced. In addition, the space-to-depth Conv downsampling module is used to replace the Conv modules corresponding to feature maps with a resolution of 320×320 pixels and less. This replacement assists in mitigating information loss during the downsampling of GPR images, particularly for images with limited resolution and small targets. Furthermore, the detection performance is enhanced using an auxiliary training module, ensuring performance improvement without increasing inference complexity. The introduction of the Inner-SIoU loss function refines bounding box predictions by imposing new constraints tailored to GPR image characteristics. Experimental results on real-world GPR datasets demonstrate the effectiveness of the GDS-YOLOv8n model. For six classes of common underground targets, including metal pipes, PVC pipes, and cables, the model achieves a precision of 97.1%, recall of 96.2%, and mean average precision at 50% IoU (mAP50) of 96.9%. These results indicate improvements of 4.0%, 6.1%, and 4.1%, respectively, compared to corresponding values of the YOLOv8n model, with notable improvements observed when detecting PVC pipes and cables. Compared with those of models such as YOLOv5n, YOLOv7-tiny, and SSD (Single Shot multibox Detector), our model’s mAP50 is improved by 7.20%, 5.70%, and 14.48%, respectively. Finally, the application of our model on a NVIDIA Jetson Orin NX embedded system results in an increase in the detection speed from 22 to 40.6 FPS after optimization via TensorRT and FP16 quantization, meeting the demands for the real-time detection of underground targets in mobile scenarios.

Zhiwei SONG, Xinbo HUANG, Chao JI et al.

The transmission lines are complex in distribution and it is difficult to effectively detect their faults. Among them, the connecting fittings are susceptible to corrosion and other faults due to their long exposure to complex environments. Aiming at the problem that the transmission line connection fitting components are varied in scale and have poor accuracy in detecting their corrosion faults, a detection method is proposed for transmission line connection fittings and their corrosion faults based on dual attention embedding reconstruction and Swin Transformer, i.e., PCSA-YOLOv7 Former. The experimental results show that the proposed method is superior to 12 existing state-of-the-art object detection algorithms in comprehensive detection performance of the constructed TLCF dataset, with the mAP0.5 of the test set reaching 94.9 %. Compared with the baseline model YOLOv7, the proposed method improves the indexes F1 and mAP0.5 by 2.6 percentage points and 2.2 percentage points, respectively, indicating that the proposed method can more comprehensively understand the multi-scale semantic information in the images of transmission line connection fittings and learn their subtle details that are difficult to distinguish.

Zhongling HUANG, Chong WU, Xiwen YAO et al.

The current state of intelligent target recognition approaches for Synthetic Aperture Radar (SAR) continues to experience challenges owing to their limited robustness, generalizability, and interpretability. Currently, research focuses on comprehending the microwave properties of SAR targets and integrating them with advanced deep learning algorithms to achieve effective and resilient SAR target recognition. The computational complexity of SAR target characteristic-inversion approaches is often considerable, rendering their integration with deep neural networks for achieving real-time predictions in an end-to-end manner challenging. To facilitate the utilization of the physical properties of SAR targets in intelligent recognition tasks, advancing the development of microwave physical property sensing technologies that are efficient, intelligent, and interpretable is imperative. This paper focuses on the nonstationary nature of high-resolution SAR targets and proposes an improved intelligent approach for analyzing target characteristics using time-frequency analysis. This method enhances the processing flow and calculation efficiency, making it more suitable for SAR targets. It is integrated with a deep neural network for SAR target recognition to achieve consistent performance improvement. The proposed approach exhibits robust generalization capabilities and notable computing efficiency, enabling the acquisition of classification outcomes of the SAR target characteristics that are readily interpretable from a physical standpoint. The enhancement in the performance of the target recognition algorithm is comparable to that achieved by the attribute scattering center model.

Shima Amirinalloo, Zahra Atlasbaf

Abstract In this article, the authors propose a super wide band CPW‐fed fractal monopole antenna suitable for phased array antennas with a shaped beam radiation pattern, operating in the frequency ranges below and above 1 GHz at the same time. The antenna has an octagonal radiator with fractals of the same shape added to its edges and sides. Also, the symmetrical elliptical ground planes have reduced the antenna size and, consequently, the mutual coupling in the antenna array. Despite the super‐wide frequency range, the antenna's radiation pattern is relatively steady in the E‐plane, and the negligible ripple on the radiation pattern makes it suitable for shaped beam radiation patterns in phased array design. The single‐element antenna with an overall size of 0.24λ × 0.38λ at 500 MHz is printed on an FR‐4 substrate. The outcomes of the simulation and measurement are well agreed in the frequency band of [500 MHz to 5.5 GHz] with an impedance bandwidth (|S11|< −10dB) of 166.67% and VSWR< 2. Also, the fidelity factor of the antenna is studied to investigate the SWB performance.

Kwang-Ho Jang, Jong-Hyun Kim, Geun-Ju Kim et al.

This study showed the possibility of using a sub-terahertz (THz) traveling-wave tube (TWT) via measuring the transmission characteristics and TWT performance of the circuit by applying X-ray LIGA, a micro-fabrication process, to the interaction circuit. The applied circuit type, an E-bend folded waveguide, is a simple structure most suitable for lithography. A total of three applied frequencies were used the W-band, G-band, and 850 GHz. Among the manufactured circuits, the W-band circuit was applied to the TWT, one of the vacuum electronics devices (VEDs). This was done to prove the manufacturing accuracy of the circuit by comparing the nonlinear characteristics of the circuit with the prediction results. Through such testing, the small signal gain was measured as 13 ± 2 dB under the conditions of 13.96-kV and 24.2-mA electron beam energy. The frequency bandwidth was extremely wide, about 9 GHz, and showed similar characteristics to the simulation predictions. The maximum output of the device was obtained up to 1 W or more at 87.12 GHz by slightly increasing the beam current. These characteristic achievements showed the suitability of the TWT for very small circuits fabricated using the X-ray LIGA process, further suggesting the applicability of other sub-THz bands.

Hui WANG, Yi CAO, Ning LUO et al.

This paper proposes a three-terminals soft open point (SOP) operation control mode switching technology under the multi-feeder faults. Firstly, combined with the inner and outer loop structures of control mode of three-terminals SOP, a control mode switching strategy with improved control logic is proposed. Secondly, in order to realize the smooth transition between SOP working modes under multiple feeder faults, a control mode switching process suitable for three-terminals SOP under multiple feeder faults is proposed. Then, by adopting the phase angle pre-synchronization strategy, the smoothness of the phase angle when the power-loss feeder is connected to the grid is ensured. Thirdly, the phase angle pre-synchronization strategy is adopted to ensure the smoothness of the phase angle when the power-loss feeder is connected to the grid. Finally, A power distribution system model with three-terminals SOP is built for simulation. The simulation results show that the proposed operation control mode switching technology can reduce the maximum voltage fluctuation on the DC side, and the voltage and phase angle of each port can transition smoothly.

Haiping LIANG, Haoyan SHI, Yan WANG et al.

Extreme natural disasters and other events are likely to cause large-scale failures of the transmission networks. In order to minimize the economic losses and improve the post-disaster resilience of transmission networks, firstly, according to the connotation of transmission network resilience, the expected system load recovery efficiency is proposed as the resilience evaluation index; secondly, the post-disaster emergency maintenance process of transmission networks is analyzed, and a collaborative optimization model of time-uncertainty based post-disaster emergency maintenance strategy is established for transmission networks, which not only considers the resilience-improving economy of transmission networks, but also the constraints such as resources and path planning in the process of post-disaster maintenance. An improved particle swarm optimization (PSO) algorithm is proposed for the optimization model, which uses such methods as the multi-dimensional indefinite length coding, sub-group collaborative optimization, and Monte-Carlo-simulation-based fitness evaluation to improve the standard PSO algorithm. The simulation results of an IEEE RTS-79 case show that the improved particle swarm optimization algorithm can effectively solve the proposed optimization model, and the results of the collaborative optimization model can effectively improve the transmission network resilience index and the economy of post-disaster emergency maintenance.

Wei LI, Tingfang YANG, Lei ZHANG et al.

In order to reduce the workload of the operation and maintenance of distribution line arresters, this paper designs a frequency-dividing disconnector using double sphere gaps based on the inverse time principle, which can reliably shunt high and low frequency current. The disconnector can be separated automatically and reliably while the insulation of the arrester is damaged, and the fault section can be found. The disconnector realizes the mechanism of frequency division of leakage current by using inductance and large sphere gaps in parallel. Under the impulse or high frequency, the leakage currents flow through the big sphere gap and the disconnector would not act. While under the power or low frequency, the leakage currents flow through the inductor. When the current takes value from 40 mA to 0.5 A, resistance heating action would be utilized. When the current is larger than 0.5 A, the small sphere gap breakdown action would be adopted, which avoids the mal-operation of disconnector due to burned out resistance. In these two cases, the greater the leakage current, the faster the disconnector operates. Through the ATP model simulation, the parameters of the inductance and the operating characteristics of the large gap can be determined. The numerical simulation and experimental results show that the disconnector can operate reliably when the insulation of the arrester is damaged.

Xiaoxiao Zhang, Xiang Su, Zhensen Wu et al.

Abstract The target scattering characteristics in microwave band are necessary to be researched for Orbital‐Angular‐Momentum (OAM) wave‐based radar applications. A theoretical description of electromagnetic (EM) scattering from a typical target by OAM waves is proposed in this paper. First, OAM waves are decomposed into plane waves in the spectral domain with different elevation and azimuth angles. Then, the scattering form of each decomposed plane wave is determined through coordinate system transformation and physical optics approximation. Formulas and numerical results are presented for OAM‐based radar scattering cross section of a perfect electric conductor and dielectric plate and a cylinder. Unlike the conventional results of EM plane wave scattering, the scattering properties of OAM waves from plate and cylinder are analysed with particular emphasis on OAM mode influence. The results provide insights into OAM wave‐matter interactions and may find important applications in wave propagation and OAM wave‐based radar detection and imaging.

Teng Wen, Xiang Cui, Xuebao Li et al.

Abstract The working voltage of the high‐voltage high‐power electronic devices is the positive periodic square waveform (PPSW) voltage, which is much different from the conventional AC or DC voltage. For the composite insulation structure of devices, it is important to analyse the transient electric field under the PPSW voltage. However, the existing investigations are often conducted under the electrostatic field due to the high frequency of the PPSW voltage. Thus, the transient characteristics of the electric field are missed. To obtain some qualitative conclusions, this paper focusses on the theoretical analysis of the transient characteristics of electric field for the composite insulation structure under the PPSW voltage. First, the formula of the electric field intensity and the interfacial charge density are derived analytically. Second, the influence of the cycle and the duty cycle on the transient characteristics are investigated. Third, the maximum of the electric field intensity and the interfacial charge density in the positive square waveform steady‐state are discussed in detail. Besides, the engineering calculation methods for obtaining these maximum values are also suggested. Lastly, an actual model is employed to testify the validity of the analytical analysis. This work is significant for the numerical calculation of the transient electric field of composite insulation structure under the PPSW voltage in engineering.

Qiang Chen, Junshuai Li, Qiang Chen et al.

Abstract The aqueous phase hydrogen peroxide (H2O2aq) produced from the plasma–liquid interactions can directly or synergistically (with other substances) affect the liquid chemistry, and therefore it is important to unfold the H2O2aq formation mechanism. However, up to now, a consensus on the H2O2aq formation mechanism is not reached. This review aims to survey the recent advances on the understanding of the H2O2aq formation mechanism in the system of a direct current discharge plasma operated over a liquid electrode. Theoretical and experimental analyses indicate that the recombination of dissolved OH radicals (OHaq) is the dominant process for the H2O2aq formation, while the purported plasma‐induced photolysis of water and the dissolution of gaseous H2O2 are ruled out.

Nandana Bhattacharya, S. Middey

Anomalous Hall effect (AHE), which arises when a current is passed through a ferromagnetic material subjected to a perpendicular magnetic field, is proportional to the magnetization of the sample.Additional hump-like features in AHE are often attributed to the presence of non trivial spin textures leading to topological Hall effect (THE). However, several recent reports have emphasized in context of ferromagnetic SrRuO$_3$ based heterostructures that the sample inhomogeneity can also result in THE-like features. In order to investigate this issue in general for any ferromagnetic heterostructure, we have considered a phenomenological model to calculate the changes in the shape of hysteresis loop due to various interfacial effects. These changes in the magnetization have been accounted for by considering that the interdomain magnetic coupling parameter ($α$) varies exponentially with the distance from the interface along the growth direction of the heterostructure. In case of symmetric interfaces on both sides of a ferromagnet, we have considered the variation of $α$ as a Gaussian function. We have found that the additional AHE contribution due to the net change in magnetization in such cases are akin to experimentally observed THE, even though we have not considered any topological quantity explicitly in our model. Thus, we propose another situation with nonuniform magnetization profile that may be used to explain additional features in AHE, which might not necessarily be intrinsic THE.

Aurélien Bailly-Reyre, Hung T. Diep

We study in this article properties of a nanodot embedded in a support by Monte Carlo simulation. The nanodot is a piece of simple cubic lattice where each site is occupied by a mobile Heisenberg spin which can move from one lattice site to another under the effect of the temperature and its interaction with neighbors. We take into account a short-range exchange interaction between spins and a long-range dipolar interaction. We show that the ground-state configuration is a vortex around the dot central axis: the spins on the dot boundary lie in the $xy$ plane but go out of plane with a net perpendicular magnetization at the dot center. Possible applications are discussed. Finite-temperature properties are studied. We show the characteristics of the surface melting and determine the energy, the diffusion coefficient and the layer magnetizations as functions of temperature.