Hasil untuk "Electricity and magnetism"

Shaojing SONG, Xinjian LI, Feiyi FANG

As an important method of 3D (Three-Dimensional) data processing, point cloud fusion technology has shown great potential and promising applications in many fields. This paper systematically reviews the basic concepts, commonly used techniques, and applications of point cloud fusion and thoroughly analyzes the current status and future development trends of various fusion methods. Additionally, the paper explores the practical applications and challenges of point cloud fusion in fields such as autonomous driving, architecture, and robotics. Special attention is given to balancing algorithmic complexity with fusion accuracy, particularly in addressing issues like noise, data sparsity, and uneven point cloud density. This study serves as a strong reference for the future development of point cloud fusion technology by providing a comprehensive overview of the existing research progress and identifying possible research directions for further improving the accuracy, robustness, and efficiency of fusion algorithms.

Peng Zhang, Guoliang Zhang, Fei Zhou et al.

Abstract Predicting the future health state of a transformer can offer early warning of latent defects and faults within the transformer, thereby facilitating the formulation of power outage maintenance plans and power dispatch strategies. However, existing prediction methods based on the structure of ‘splicing prediction and diagnosis method’ suffer from limitations such as inability to achieve global optimality, error accumulation, and low prediction accuracy. To fill this gap, a novel direct prediction method of a transformer state based on knowledge and data fusion‐driven model (K&DFDM) is proposed in this paper. Firstly, a state quantity data space is constructed to comprehensively reflect the changes in the health state of the transformer over time, encompassing online monitoring, offline testing, evaluation results, and actual operation data. After that, correlation knowledge between state quantities, fault diagnosis mechanism knowledge, current diagnosis experience knowledge, and uncertain fuzzy knowledge are extracted separately. The actual fault mechanism, existing expert experience, and other knowledge in the diagnosis process are quantified. Then, the attention model is subsequently optimised, leveraging quantitative knowledge to effectively constrain and guide the data prediction process. Incorporating fault diagnosis mechanism knowledge into the data prediction model enables the achievement of global optimisation in both diagnosis and prediction. The integration of traditional expert experience knowledge and the correlation knowledge between state quantities serves as constraints during the process of attaining the global optimum. The verification results, comprising 327 cases, demonstrate that K&DFDM effectively addresses the issue of error superposition encountered by existing state prediction methods, leading to a direct state prediction accuracy of 96.33%.

Zhipeng Xia, Qing‐Yuan Lu, Shangjun Jiang et al.

ABSTRACT This paper presents a new design of circularly polarised (CP) antenna with wideband and high gain selectivity. To achieve good circular polarisation performance, a wideband quadrature phase feeding network is initially developed with two output signals characterised by equal magnitude and consistent 90‐degree phase difference. Then, to realise high gain selectivity, multi‐mode resonators are introduced into the feeding network. Therefore, a specific filtering quadrature phase feeding network (FQFN) that integrates the functions of power division, frequency selectivity and phase shifting is successfully produced. Afterwards, a three‐order FQFN operating at central frequency of 2.5 GHz is developed and measured for demonstration. As expected, the demonstrator has obtained wide impedance and phase bandwidths of 57.3% and 70.8%, respectively, together with two transmission zeros at about 1.25 and 3.75 GHz. Finally, a pair of crossed magneto‐electric dipole antennas are implemented by adopting the proposed FQFN to achieve wideband CP radiation with high selectivity. Experimental results exhibit that the proposed scheme has achieved both impedance bandwidth of 65.3% and 3‐dB axial ratio bandwidth of 62.4%, simultaneously. Moreover, attributing to the integration of the filtering function within the FQFN, performance of high gain selectivity is accomplished and ensured by three transmission zeros in gain response.

Italo L. Soares Andrade, Kleber Pirota, Amir O. Caldeira et al.

We report the observation of the Purcell effect in a cavity-metallic magnet hybrid system using electric-field-mediated coupling. In this configuration, microwave-induced axial currents in the microwire induce circular magnetic fields that drive the ferromagnetic resonance (FMR) of the magnetized microwire. Field-dependent transmission and reflection spectroscopies reveal a clear cavity perturbation consistent with the Purcell regime, in which the magnetic loss rate exceeds the light-matter coupling strength. Despite the small magnetic volume ($\sim 10^{-13}\,\text{m}^3$), measurements performed at both room temperature and $T = 7$ mK show coupling rates as high as $g/2pi = 56$ MHz, one order of magnitude stronger than the one expected from conventional coupling at the magnetic antinode. Time-domain ringdown measurements directly show the magnetic-field-dependent modification of the cavity photon lifetime, in agreement with theoretical predictions. These results establish a versatile approach for coupling microwave fields to metallic magnets via geometric and electric-field-mediated interactions, opening new opportunities for hybrid cavity-magnet systems.

Pufan Qi

This paper examines the impact of electric vehicles on total annual electricity consumption across 58 counties in California from 2010 to 2021. Employing a log linear model to analyze the relationship between electricity consumption and EV ownership, alongside a linear log model with an instrumental variable approach, the study finds that annual per capita electricity consumption increased by 0.23% for each additional electric vehicle per 10,000 residents over the 12 years period. The analysis identifies partisanship, measured as the annual percentage of voter registration for the Democratic Party by county, as a robust instrumental variable. Specifically, a 1% increase in Democratic voter registration corresponds to the adoption of approximately two additional EVs per 10,000 residents.

Guanlong Jia, Yuchen Yuan, Hongjiang Guo et al.

Abstract Multi‐terminal flexible high‐voltage direct current (HVDC) transmission and DC grid technology are developing rapidly. The hybrid DC circuit breaker (HCB) has broad application prospects in the field of HVDC transmission and DC power grid. Nevertheless, existing HCBs have one or more following blemishes: arc suppression scheme of mechanical switch, high cost and unreliable adaptive reclosure. In this paper, a modified thyristor‐based hybrid DC circuit breaker with short arcing capacity (SA‐HCB) is introduced, which consists of the main branch, the fault handling branch and the pre‐charging branch. Besides, the modified SA‐HCB has the inherent capability of adaptive reclosing. The advantages of thyristors are fully used in the SA‐HCB, such as low cost, low conduction voltage drop, and natural shutdown. The detailed structure diagram and mathematical model of the SA‐HCB are introduced, and the operation processes of the fault current transfer are also analysed. Later, a design method for parameters of the proposed SA‐HCB is provided. Then, a single‐ended equivalent system is built in PSCAD/EMTDC to verify the accuracy of the theoretical analysis and parameter design. Subsequently, based on four‐terminal simulation, the economy of the SA‐HCB is verified by comparing with the topology proposed by ABB. Finally, the small‐scale experiment of the proposed SA‐HCB is introduced.

Gurbax Singh Lakhina, Satyavir Singh

An analysis of the Magnetospheric Multiscale (MMS) spacecraft data shows the presence of slow electrostatic solitary waves (SESWs) in the Earth’s plasma sheet, which have been interpreted as slow electron holes (SEHs). An alternative mechanism based on slow ion-acoustic solitons is proposed for these SESWs. The SESWs are observed in the region where double humped ion distributions and hot electrons co-exist. Our theoretical model considers the plasma in the SESW region to consist of hot electrons with a vortex distribution, core Maxwellian protons drifting parallel to the magnetic field, <b>B</b> and beam protons drifting anti-parallel to <b>B</b>. Parallel propagating nonlinear ion-acoustic waves are studied using the Sagdeev pseudopotential technique. The analysis yields four types of modes, namely, two slow ion-acoustic (SIA1 and SIA2) solitons and two fast ion-acoustic (FIA1 and FIA2) solitons. All solitons have positive potentials. Except the FIA1 solitons which propagate parallel to <b>B</b>; the other three types propagate anti-parallel to <b>B</b>. Good agreement is found between the amplitudes of electrostatic potential, the electric field, the widths and speed of SIA1 and SIA2 solitons, and the observed properties of SESWs by the MMS spacecraft.

D. Sztenkiel, K. Gas, N. Gonzalez Szwacki et al.

We report magnetization changes generated by an electric field in ferromagnetic Ga$_{1-x}$Mn$_x$N grown by molecular beam epitaxy. Two classes of phenomena have been revealed. First, over a wide range of magnetic fields, the magnetoelectric signal is odd in the electric field and reversible. Employing a macroscopic spin model and atomistic Landau-Lifshitz-Gilbert theory with Langevin dynamics, we demonstrate that the magnetoelectric response results from the inverse piezoelectric effect that changes the trigonal single-ion magnetocrystalline anisotropy. Second, in the metastable regime of ferromagnetic hystereses, the magnetoelectric effect becomes non-linear and irreversible in response to a time-dependent electric field, which can reorient the magnetization direction. Interestingly, our observations are similar to those reported for another dilute ferromagnetic semiconductor Cr$_x$(Bi$_{1-y}$Sb$_y$)$_{1-x}$Te$_3$, in which magnetization was monitored as a function of the gate electric field. Those results constitute experimental support for theories describing the effects of time-dependent perturbation upon glasses far from thermal equilibrium in terms of an enhanced effective temperature.

Shuangchi Li, Fang Wang, Lanxin Tang et al.

Among the lead-free piezoceramics, ([Formula: see text])BiFeO[Formula: see text]BaTiO3 (BF-BT) is considered a promising candidate for high-temperature piezoelectric materials owing to its high Curie temperature ([Formula: see text]C) and good electromechanical properties. In this work, the hydrothermal synthesis method was used to prepare the precursor powders of BiFeO3 and BaTiO3, and then the mixed powder compacts with the chemical composition of 0.7BF–0.3BT were sintered under pressureless conditions. The influence of the hydrothermal reaction times (12–24[Formula: see text]h) of BiFeO3 on the structures and electric properties of the sintered ceramics was instigated. First, all the samples synthesized with the tetragonal BaTiO3 and BiFeO3 powders were identified with relatively stable dielectric properties. As the hydrothermal reaction time to synthesize BiFeO3 increased, the dielectric properties as well as the temperature stability of the 0.7BiFeO3–0.3BaTiO3 ceramics also improved. At the condition of a hydrothermal reaction time of 24[Formula: see text]h, the sample obtained possesses both the lowest temperature coefficient of dielectric constant ([Formula: see text]C between RT and [Formula: see text]C) and the highest Curie temperature ([Formula: see text]C at 100[Formula: see text]kHz). Moreover, at high temperatures, it exhibits a higher AC impedance than others. The calculating result based on the resistive constant-phase-element model (R-CPE) circuit model showed that the grain boundary of the 0.7BF–0.3BT ceramics contributes more resistance to the conductivity at high temperatures. In summary, the hydrothermal reaction proved to be a useful way that achieves the preparation of single-phase 0.7BF–0.3BT ceramics with improved electrical properties.

Tao LIANG, Xiaodong YIN, Yaxiang LIU

Reasonable optimization of integrated energy system (IES) capacity configuration is the basis for improving returns on investment and realizing efficient energy utilization. Aiming at the uncertainty influences of wind and photovoltaic power output and energy-using load on both cost and revenue, a robust optimal configuration method for return on investment is presented. Firstly, an IES optimal configuration model is built to maximize the internal rate of return, with consideration of the constraints of investment capacity, equipment operation, energy balance and internal and external network interaction. Then, by introducing the information gap decision theory (IGDT) to deal with the uncertainties of both source and load in IES, a robust optimization model for return on investment is constructed, and the complexity of the model is reduced through equivalent transformation and dual transform. A decomposition solution strategy is proposed to obtain the maximum fluctuation range of uncertain parameters and the corresponding optimal configuration scheme in the premise of meeting the expected return on investment. Finally, an actual IES is taken for case study, and the results show that the proposed method is more effective and practical than the traditional configuration methods in increasing the return on investment and improving the robustness of optimal configuration.

D.-W. Li, L. Bruschweiler-Li, A. L. Hansen et al.

<p>The quantitative deconvolution of 1D-NMR spectra into individual resonances or peaks is a key step in many modern NMR workflows as it critically affects downstream analysis and interpretation. Depending on the complexity of the NMR spectrum, spectral deconvolution can be a notable challenge. Based on the recent deep neural network DEEP Picker and Voigt Fitter for 2D NMR spectral deconvolution, we present here an accurate, fully automated solution for 1D-NMR spectral analysis, including peak picking, fitting, and reconstruction. The method is demonstrated for complex 1D solution NMR spectra showing excellent performance also for spectral regions with multiple strong overlaps and a large dynamic range whose analysis is challenging for current computational methods. The new tool will help streamline 1D-NMR spectral analysis for a wide range of applications and expand their reach toward ever more complex molecular systems and their mixtures.</p>

Benoît Reynier, Eric Charron, Obren Markovic et al.

Light-matter interactions are often considered governed by the electric optical field only, leaving aside the magnetic component of light. However, the magnetic part plays a determining role in many optical processes from light and chiral-matter interactions, photon-avalanching to forbidden photochemistry, making the manipulation of magnetic processes extremely relevant. Here, by creating a standing wave using a plasmonic nanomirror we manipulate the spatial distributions of the electric and magnetic fields and their associated local density of states, allowing the selective control of the excitation and emission of electric and magnetic dipolar transitions. This control allows us to image, in 3D, the electric and magnetic nodes and anti-nodes of the fields interference pattern. It also enables us to enhance specifically photoluminescence from quantum emitters excited only by the magnetic field, and to manipulate their quantum environment by acting on the excitation fields solely, demonstrating full control of magnetic and electric light-matter interactions.

Xi-Han Zhou, Tao Yu

We predict that ferromagnetic resonance in insulating magnetic film with inplane magnetization radiates electric fields polarized along the magnetization with opposite amplitudes at two sides of the magnetic insulator, which can be modulated strongly by adjacent superconductors. With a single superconductor adjacent to the magnetic insulator this radiated electric field is totally reflected with a $π$-phase shift, which thereby vanishes at the superconductor side and causes no influence on the ferromagnetic resonance. When the magnetic insulator is sandwiched by two superconductors, this reflection becomes back and forth, so the electric field exists at both superconductors that drives the Meissner supercurrent, which in turn shifts efficiently the ferromagnetic resonance. We predict an ultrastrong coupling between magnons in the yttrium iron garnet and Cooper pairs in NbN with the frequency shift achieving tens of percent of the bare ferromagnetic resonance.

Shahid Basir, Mubashar Sarfraz, Sajjad A. Ghauri et al.

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leaky-wave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (ɛr = 2.2 and h = 1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement.

Xianhai PANG, Boyan JIA, Zhijie CHEN et al.

To improve the electrical and hydrophobic properties of epoxy resins in switchgear equipment，the magnesium oxide nanoparticles (nMgO) are modified with silane coupling agent (KH560) and fluorinated silane coupling agent respectively, and characterized by FT-IR and XPS. And the epoxy composites of different concentrations (5%, 10%, 15% and 20%) are prepared with solution blending method, and characterized by testing dielectric constant, dielectric loss, conductivity and contact angle. The results show that the introduction of fluorine element can reduce the surface energy of the composites, and the hydrophobicity of the epoxy composites is significantly improved with the increase of the doping content, reaching 114° at 20 wt.%. The electrical properties of the epoxy composites all meet the requirements for the use of electrical equipment, with the dielectric loss being lower than the level of epoxy resin and the resistivity being higher than that of epoxy resin.

Yanhui Wei, Mingyue Liu, Xuejing Li et al.

Abstract A semi‐conductive shielding layer plays an important role in the uniform electric field for a high‐voltage cable. The electric‐thermal properties of the semi‐conductive layer and insulation layer directly affect the overall insulation performance of the cable. The physicochemical performances of semi‐conductive composites are firstly analysed herein. Furthermore, electric‐thermal properties of the semi‐conductive layer and insulation layer are discussed. The experimental results show that the thermal conductivity of the commercial semi‐conductive layer is about twice that of the insulation layer, owing to the effect of carbon black. The thermal expansion coefficient of the insulation layer rises from 1.86 × 10−4/K at 25°C to 3.20 × 10−4/K at 90°C. By contrast, the semi‐conductive layer begins to slowly decline at a certain temperature, and decreases significantly to 2.25 × 10−4/K at 80°C, owing to the effect of ethylene‐vinyl acetate copolymer (EVA). The electrical experiments show that the resistivity of semi‐conductive composite gradually rises with an increase in temperature, and gradually declines with an increase in the carbon black content. The dc breakdown strength of the composite structure of the semi‐conductive layer/insulation layer decreases significantly with an increase in temperature, decreasing from 307 kV/mm at 25°C to 203 kV/mm at 90°C. At four typical temperatures, the breakdown strength reaches the maximum value when the carbon black content is 25 phr. It is about 15% and 19% higher than carbon black contents of 20 and 30 phr. These findings have reference significance for high‐voltage cable breakdown fault analysis and material selection in cable design.

Haijing ZHANG, Yongqi YANG, Xin ZHAO et al.

Demand response aggregator aggregates users’ transferable loads and reducible loads through demand response to improve the flexibility and economy of regional integrated energy system. Considering the interactive game relationship between the integrated energy system operators and the demand response aggregators, a two-level optimal dispatching model of the regional integrated energy system is established with consideration of the demand response. By taking the maximum economic benefits of the regional integrated energy system operators and the demand response aggregators as objective respectively for the upper and lower layers, the KKT conditions and linearization method are used to convert the two-layer model into a single-layer mixed integer linear optimization model for solution. The results show that using the time-of-use electricity price and the demand response compensation price to guide users to adjust their energy use plans can increase the profits of integrated energy system operators and demand response aggregators while achieving peak load shaving and reducing the impact on the safe and stable operation of the power grid.

Roman Ya. Kezerashvili, Anastasia Spiridonova

We study direct and indirect magnetoexcitons in Rydberg states in monolayers and double-layer heterostructures of Xenes (silicene, germanene, and stanene) in external parallel electric and magnetic fields, applied perpendicular to the monolayer and heterostructure. We calculate binding energies of magnetoexcitons for the Rydberg states 1$s$, 2$s$, 3$s$, and 4$s$, by numerical integration of the Schrödinger equation using the Rytova-Keldysh potential for direct magnetoexciton and both the Rytova-Keldysh and Coulomb potentials for indirect excitons. Latter allows understanding a role of screening in Xenes. In the external perpendicular electric field, the buckled structure of the Xene monolayers leads to appearance of potential difference between sublattices allowing to tune electron and hole masses and, therefore, the binding energies and diamagnetic coefficients (DMCs) of magnetoexcitons. We report the energy contribution from electric and magnetic fields to the binding energies and DMCs. The tunability of the energy contribution of direct and indirect magnetoexcitons by electric and magnetic fields is demonstrated. It is also shown that DMCs of direct excitons can be tuned by the electric field, and the DMCs of indirect magnetoexcitons can be tuned by the electric field and manipulated by the number of h-BN layers. Therefore, these allowing the possibility of electronic devices design that can be controlled by external electric and magnetic fields and the number of h-BN layers. The calculations of the binding energies and DMCs of magnetoexcitons in Xenes monolayers and heterostructures are novel and can be compared with the experimental results when they will be available.

Yi LEI, Mingzhen LIU, Kaimin LIN

In the winter of China's northern area, the heating period of coal-fired units, the dry season of hydropower units and the period of large-scale wind power generation are superimposed, and there exist serious problems of wind curtailment and environmental pollution. The controllable heat storage electric boilers are used in this paper as peak regulation and dispatch resources, in order to reduce the forced output of CHP and get a lower load peak and a higher load valley when it's hard to regulate the peak load, and to increase the wind power accommodation capacity of power grid in winter, and to form a load-dispatching model featuring source-load coordination. The power-heat coupling characteristics of CHP units are firstly studied; and then a heat-power decoupling scheme is formulated for wind power-heat storage compensation, and a multi-objective load-dispatching model is built with the objective of minimizing both the operation cost and pollutant emission of the power system; finally, the corrected multi-objective particle swarm optimization algorithm is used to solve the model, and the diversity of the Pareto set is maintained by using niche method. Case study shows that the proposed dispatching scheme with electric boiler heat storage can effectively promote accommodation of wind power with optimum environmental and economic benefits, and has a very good application prospect.