Metal mesh with periodic knitting patterns is commonly attached to support structures in deployable reflector antennas as the reflecting surface. Mesh patterns change under different tension conditions, leading to variations in electrical properties. This paper presents a force-based elastic mesh modeling method for investigating these electrical property variations. The mechanical characteristics of the mesh are analyzed and then integrated with its geometric parameters to formulate representative equations for the proposed model. Furthermore, the establishment process of the mesh model is described using a commercial mesh as an example. Tensile tests are conducted to determine the engineering constants for the constitutive relation of the mesh material, which is crucial for deriving the force–displacement equation. An elastic mesh model is constructed for simulations. The simulated reflectance and transmittance match well with the measured results, thus verifying the feasibility and precision of the proposed model in analyzing and predicting variations in the electrical properties of metal meshes under varying forces.
Electrical engineering. Electronics. Nuclear engineering, Electricity and magnetism
Maksim Dybko, Sergey Brovanov, Aleksey Udovichenko
Energy storage systems (ESSs) and active power filters (APFs) are key power electronic technologies for FACTS (Flexible AC Transmission Lines). Battery energy storage has a structure similar to a shunt active power filter, i.e., a storage element and a voltage source inverter (VSI) connected to the grid using a PWM filter and/or transformer. This similarity allows for the design of an ESS with the ability to operate as a shunt APF. One of the key milestones in ESS or APF development is the DC-link design. The proper choice of the capacitance of the DC-link capacitors and their equivalent resistance ensures the proper operation of the whole power electronic system. In this article, it is proposed to estimate the required minimum DC-link capacitance using a spectral analysis of the DC-link current for different operating modes, battery charge mode and harmonic compensation mode, for a nonlinear load. It was found that the AC component of the DC-link current is shared between the DC-link capacitors and the rest of the DC stage, including the battery. This relation is described analytically. The main advantage of the proposed approach is its universality, as it only requires calculating the harmonic spectrum using the switching functions. This approach is demonstrated for DC-link capacitor estimation in two-level and three-level NPC inverter topologies. Moreover, an analysis of the AC current component distribution between the DC-link capacitors and the other elements of the DC-link stage was carried out. This part of the analysis is especially important for battery energy storage systems. The obtained results were verified using a simulation model.
Georgia Esselbach, Ka Wai Hui, Iliana Delcheva
et al.
The need for sustainable energy solutions is steering research towards green fuels. One promising approach involves electrocatalytic gas conversion, which requires efficient catalyst surfaces. This study focuses on developing and testing a hydrophobic octadiene (OD) coating for potential use in electrocatalytic gas conversion. The approach aims to combine a plasma-deposited hydrophobic coating with air-trapping micro- and nanotopographies to increase the yield of electrocatalytic reactions. Plasma polymerisation was used to deposit OD films, chosen for their fluorine-free non-polar properties, onto titanium substrates. We assessed the stability and charge permeability of these hydrophobic coatings under electrochemical conditions relevant to electrocatalysis. Our findings indicate that plasma-deposited OD films, combined with micro-texturing, could improve the availability of reactant gases at the catalyst surface while limiting water access. In the presence of nanotextures, however, the OD-coated catalyst did not retain its hydrophobicity. This approach holds promise to inform the future development of catalyst materials for the electrocatalytic conversion of dinitrogen (N<sub>2</sub>) and carbon dioxide (CO<sub>2</sub>) into green fuels.
Bi/multistatic Synthetic Aperture Radar (SAR) using spaceborne illuminator utilizes spaceborne platforms as transmitters and satellites, near-space vehicles, aircraft, and ground platforms as receivers, which allows high-resolution imaging of ground and marine scenes and targets. The system’s benefits include a broad imaging field of view, high concealment, and potent antijamming abilities. By using beam steering methods, a variety of imaging modes can be achieved, such as staring spotlight and sliding spotlight modes, which obtain abundant information about the imaging scene and offer broad application prospects both in civil and military fields. Thus far, the bi/multistatic SAR using spaceborne illuminator has been intensively investigated, and several research findings have been reported. This paper examines the technology from the aspects of system components, configuration design, echo model, imaging techniques, bistatic synchronization, and experimental verification and systematically reviews the state-of-the-art research progress. Finally, it is anticipated that spaceborne illuminator technology will be used to develop bi/multistatic SAR in the future.
In order to meet the requirements of power supply partition and grid planning, a comprehensive evaluation and mid-long term refined prediction method for load density based on big data under power supply scenarios is proposed, and similar units are clustered through the improved Agglomerative algorithm. The proposed method can effectively extract the typical features of various load densities, so as to reduce the requirement of the system for data sampling and provide support for the classified refined forecasting of various loads. Firstly, based on the data samples, the load density features of the plot samples in the grid are extracted with the kernel density estimation (KDE) method. Then, the entropy method is used to weight the eigenvalues to realize the evaluation of different types of load densities in each power supply unit, and further calculate the integrated load density level of the power supply units and power grids. Finally, the power supply units are clustered, and the parameters of the S-shaped growth curve are solved by the least square method, so as to realize the mid-long term prediction of various load densities. In case study, a detailed analysis is carried out, and the effectiveness of the method is verified by engineering examples.
Electricity, Production of electric energy or power. Powerplants. Central stations
Aiming at the problems of asymmetric voltage sag on the AC side of flexible DC transmission system, such as the power fluctuation and three-phase current imbalance during the operation of modular multilevel converter (MMC), a MMC coordinated control strategy for maximum power output under asymmetric voltage sag is proposed in this paper. Taking the coordinated control of suppressing the fluctuation of active power and outputting the three-phase balance current as objective, a linear weighted analytical formula is constructed to determine the regulation parameters according to the variation law of the operation characteristics of MMC system with the regulation parameters under asymmetric voltage sag, and then the maximum active power is outputted while ensuring that the outputted peak current of MMC system is within the maximum allowable working range; The proposed strategy not only expands the active power output capacity, but also improves the overall control and protection performance of the system. Finally, the effectiveness of the proposed method is verified through simulation and experiment.
Electricity, Production of electric energy or power. Powerplants. Central stations
Abstract As one of the major concerns of climate change, identifying a proper eco‐friendly insulation gas for replacing sulphur hexafluoride (SF6) becomes a prominent research topic in recent years. c‐C4F8, CF3I, C5F10O, C6F12O and C4F7N are some potential alternatives that are proved to have excellent characteristics, including high insulation strengths and low Global Warming Potentials (GWPs). Beyond these key factors, the decomposition products of these alternatives are closely related to the gases' insulation performance, as well as the safety of operators and the compatibility with other materials. In addition, the type and content of decomposition products can be used for fault diagnosis. Therefore, a number of studies were carried out to reveal the decomposition mechanism of these alternative gases, and then to explore the gases' application feasibility and strategy. The recent advances obtained in these studies, including theoretical calculation methods, detection of gas decomposition products, decomposition mechanism are reviewed, and some perspectives for future works are proposed. It is concluded that the phenomenon of solid matter precipitation in c‐C4F8 and CF3I gas decomposition cannot be ignored and that more research is needed to reveal the influence of buffer gases, micro‐aerobic, micro‐water and other impurities on the gas decomposition process.
Laser power-over-fiber (LPoF) technology is one of the crucial means to energize the monitoring sensor nodes for electrical equipment in high-voltage environment. The optimization of metal front contacts grid architecture for laser photovoltaic (PV) converters is crucial to the improvement and application of LPoF technology. Numerical simulation and optimization of metal grid architecture for PV converters is presented with application to devices of relatively small size. The model is constructed based on the open source Solcore library written in Python, and a three-step-process is developed to create a hybrid quasi-3D model for PV converters. In this paper, given different layer architectures of GaAs-based single-junction PV converters, numerical simulation is run to study how the photoelectric conversion efficiency is affected by the base thickness and the metal grid architecture under different illumination profiles. The results show that with the help of the model, the metal grid architecture can be optimized to yield the highest conversion efficiency under different layer architecture and illumination profiles. The model and optimization results can be used to guide the development of laser PV converters.
Electricity, Production of electric energy or power. Powerplants. Central stations
In an effort to examine students’ understanding about the structure of boundary conditions in upper-division courses, think-aloud interviews were conducted in the context of both quantum mechanics and electricity and magnetism. In the quantum mechanics task, students were presented with a standard potential step scenario. In the electricity and magnetism task, students were given a classical question about electromagnetic waves at the boundary of two media. The analysis of the interviews was guided by the use of a symbolic forms perspective. In this paper, we report the symbolic forms identified in students’ work and provide examples of students’ reasoning. Generally speaking, students were able to generate the correct symbolic templates while having difficulties with the underlying conceptual ideas. We also discuss instructional implications from this study.
To solve the problems of the low computing capacity and low integration degree of the data processing platform of the existing unmanned aerial vehicle (UAV) inspection systems for transmission lines, a new UAV inspection system is proposed based on cloud and fog-edge heterogeneous collaborative computing architecture, and a detail introduction is made to the system architecture, network architecture and operation process. Through integration of the advanced artificial intelligence technology and the specific functions of UAV patrol inspection, an overall UAV inspection solution scheme is given based on the artificial intelligence technology, with such three main functions as the independent path planning, multi-UAV multi-task synergy and intelligent recognition being displayed. The proposed system can comprehensively upgrade the intelligent level and independent running ability of UAVs, and improve the efficiency and quality, of power transmission line inspection and reduce the operational cost.
Electricity, Production of electric energy or power. Powerplants. Central stations
The random finite set-based extended target tracking methods generally partition measurements by spatial information. It is possible to place clutter measurements into target cells in a dense clutter environment resulting in degradation of tracking performance. To solve this issue, in this paper, the amplitude information of the target and clutter was introduced into the Gaussian Inverse Wishart Probability Hypothesis Density (GIW-PHD) filter, and thus, the optimal partition was found by calculating the amplitude likelihood of the measurement cells. Additionally, when calculating the centroid of a measurement cell, amplitude was used as a weighting factor to find the mass center instead of the widely used geometric center. This further reduced clutter interference. The tracking results of Swerling 1 fluctuating targets in a Rayleigh clutter when the signal-to-clutter ratios were 13 dB and 6 dB showed that the performance of the proposed algorithm in cardinality estimation and state estimation was better than that of the GIW-PHD filter.
In order to implement the new national energy security strategy and resolve three energy issues, the first thing is to study and explore an energy revolution path that breaks the pattern of inertial development. Focusing on the goal of promoting clean and low-carbon energy development and maintaining the improvement of energy self-sufficiency in China, the energy transition path characterized by a significant increase in non-fossil energy consumption proportion and terminal electrification rate is analyzed quantitatively, the trend of key energy development indicators is given, the connotation elements of this path are emphatically interpreted, the dominant position of electric power in energy transition is revealed and suggestions on policies and key measures for high-quality power development during the "14th Five-Year Plan" period are put forward.
Electricity, Production of electric energy or power. Powerplants. Central stations
Recently, microstrip antennas are preferred in all areas of wireless communication, due to their advantages such as low volume coverage, light weight, surface compatibility, high cost requirements and easy production etc. The main disadvantage of these antennas is their narrow band performance (~11%). In the literature, there are some wideband microstrip antenna designs. These broadband characteristics are obtained by changing the antenna geometry or by adding new parasitic patches to the antenna elements. In this study, a classical wideband microstrip dipole antenna (MDA) design which can be used in WLAN/WiMAX applications (covering the bands
2.4–2.5 GHz and 2.5–3.5 GHz) is introduced. The proposed antenna has a pair of twisted strip which are placed asymmetrically near the feed of the dipole element with a length of 52 mm (~λ/2). Also a pair of square loop elements is placed on a sublayer. The proposed MDA has a resonance between 2.06-3.72 GHz with a bandwidth of 57%. The antenna has a directive radiation pattern with a gain of 6.49-3.98 dBi.
Image registration is often used to transform images from different subjects into the same spatial space to ensure more accurate comparisons. With the traditional image registration methods, one image is usually specified as the reference image, while the other images are transformed into the space of the reference image. However, the image randomly selected as the reference image may have significant deviations from the group mean in datasets with large individual differences, causing registration biases and affecting the final results of groupwise comparisons. In this paper, a groupwise registration method based on the topology center of the image set was proposed. With the same open datasets, the performance of the proposed method was compared to that of two widely used traditional methods. The experimental results demonstrated that the proposed method had smaller groupwise registration bias and better registration results. The paper also proposed a simple measure for evaluating groupwise registration bias.
ZHANG Ming-guang, FENG Xiao-hu, YU Shui-tao
et al.
The ultraviolet spectra (UV), infrared spectra (IR), mass spectra (MS) and nuclear magnetic resonance (NMR) spectra (i.e., 1H NMR, 13C NMR, DEPT, HSQC, HMBC, COSY and NOESY) of besifloxacin hydrochloride were acquired and interpreted. All 1H and 13C NMR signals were assigned, and the structure of the compound was determined.
An ibuprofen-phillygenin ester was synthesized through the Schotten-Baumann reaction with ibuprofen and phillygenin as the starting materials. Ultraviolet absorption (UV) spectrum, infrared absorption (IR) spectrum, matrix-assisted laser desorption/ionization-mass spectra (MALDI-TOF-MS), and one-dimensional/two dimensional nuclear magnetic resonance (NMR) spectra (i.e., 1H-NMR, 13C-NMR, 13C-DEPT, 1H-1H COSY, 1H-1H NOESY, 1H-13C HSQC and 1H-13C HMBC) of the compound were collected. All 1H and 13C NMR signals were assigned.
G. M. Kaleva, A. V. Mosunov, N. V. Sadovskaya
et al.
Influence of BiFeO3 (BF) on phase formation, unit cell parameters, microstructure, dielectric and ferroelectric properties of solid solutions close to the morphotropic phase boundary in the (Na0.5Bi0.5)TiO3–(K0.5Na0.5)NbO3 system additionally modified by the low-melting KCl additives has been studied. The formation of pure perovskite structure samples decrease in the unit cell parameters and increase in the TC value stimulated by the BF addition have been revealed. It was proved that modification of compositions by small amounts of the BF and KCl additives leads to improvement of dielectric parameters.