Hasil untuk "Electricity and magnetism"

Zongwei Li, Huchen Han, Lingfeng Chao et al.

Recent years have seen increased interest in optoelectronic semiconductor materials, particularly those from groups II-VI, IV-VI, and perovskite, due to their outstanding electronic and optical properties. However, the toxicity and environmental concerns related to heavy metals like lead and cadmium have hindered their widespread commercial use, shifting the focus to AgBiS2, a nontoxic, cost-effective, and promising alternative. Despite significant progress, the efficiency of AgBiS2 remains lower than that of perovskite or cadmium-lead-based devices, primarily due to challenges in nanocrystals (NCs) synthesis and limitations in device structure and stability when using AgBiS2 thin films. This review evaluates these challenges by examining the synthesis process, addressing device-related limitations, and discussing recent advancements in AgBiS2 research and its potential applications. It includes an analysis of AgBiS2’s chemical and crystal structures, as well as its optoelectronic properties. Additionally, we review improvements in synthesizing high-quality AgBiS2 NCs and discuss applications such as photodetectors and X-ray/photoelectrochemical sensors. Finally, we highlight the challenges and future prospects for AgBiS2, offering insights into its potential for various applications.

Junjie KANG, Chunyang ZHAO, Guopeng ZHOU et al.

Source-network-load-storage integration and multi-energy complementary is of great significance for accelerating the construction of new power systems, achieving high-quality development of the power system, improving the coordination and mutual aid ability of multiple energy sources, and promoting China's green and low-carbon energy transformation and economic and social development. Firstly, based on an analysis of such factors as the national resource elements for integration and complementary, national development strategy, load development, electricity price level, new energy consumption conditions and regulatory capacity demand, a subjective and objective combination weighting evaluation system is established. And then, the entropy weight method is used to determine the objective weights of the influencing factors for each development route of integration, and the Delphi method is used to determine the objective weights. Through fusion calculation, the comprehensive weights of the influencing factors are obtained. Based on the scores and weights of the influencing factors, every development route is scored, and the development priority levels are divided. Finally, the construction priority order for integration projects in all provinces across the country is obtained, which can provide a technical support for the development of the integration projects in all provinces.

Yunxiao Zhang, Wenxin Lin, Yuanxiang Zhou et al.

Abstract Electrical tree degradation is one of the main causes of insulation failure in high‐frequency transformers. Electrical tree degradation is studied on pure epoxy resin (EP) and MgO/EP composites at frequencies ranging from 50 Hz to 130 kHz. The results show that the tree initiation voltage of EP decreases, while the growth rate and the expansion coefficient increase with frequency. Moreover, the bubble phenomenon at high frequencies in EP composites is discussed. Combined with trap distribution characteristics within the material, the intrinsic mechanism of epoxy composites to inhibit the growth of the electrical tree at different frequencies is discussed. It can be concluded that more deep traps and blocking effect are introduced by doping nano‐MgO into EP bulks, which can improve the electrical tree resistance performance of EP composites in a wide frequency range.

Guanjun FU, Fuqiang ZHANG, Peng XIA et al.

Natural gas power generation has the advantages of low emissions, high efficiency, and flexibility. It is an important component and effective power source for building a new power system under the dual carbon goals of reaching carbon emission peak and carbon neutrality. However, there are still problems in China's natural gas power generation development, such as the relatively low gas source guarantee, high fuel costs, and limited key core technologies. At present, disputes about the development of natural gas power generation in the dual carbon process still exist. It is urgent to have a unified understanding and clarify its development orientation and direction. This paper takes the integrated development of natural gas power generation and new energy generation into consideration in the overall planning of the power system. It uses self-developed carbon emission peak and carbon neutrality power planning software packages for optimization analysis and constructs a low-carbon transformation scenario for the power industry with zero carbon as the goal. It analyzes the future development scale and layout of natural gas power generation under the carbon neutrality goal and conducts sensitivity analysis on the uncertainty factors affecting the future scale of natural gas power generation. Based on the model calculation results, the paper establishes quantitative indicators to evaluate the functional role of gas-fired electricity in new power systems and analyzes its functional role in clean electricity supply, power balance, and peak shaving balance in the future. Natural gas power generation still needs moderate development in the future, with new layouts mainly concentrated in the southeast coastal areas and gradually increasing in the central and western regions. In the future, the focus must be on strengthening the coordination of natural gas production, transportation, storage, and sales, improving the pricing mechanism of natural gas and gas-fired electricity, and accelerating the development of core technologies, to give full play to the positive role of natural gas power generation in the construction of new power system.

Mingjia Jiang, Zhanhui Peng, Qiyuan Zhou et al.

Bi[Formula: see text]Na[Formula: see text]TiO3 (BNT)-based lead-free ceramics with superior ferroelectric properties are considered to be extremely advantageous in energy storage capacitors for future green technologies. Here, we demonstrate an approach to achieve both ultrahigh energy density [Formula: see text] and efficiency [Formula: see text] by regulating the multiscale electropolar structures and microstructure. A satisfactory energy storage performance of a high [Formula: see text] of [Formula: see text], and a decent [Formula: see text] of 80% under [Formula: see text] are attained in the 0.5(BNT-CS)-0.5SB[Formula: see text]T ceramic (abbreviated as BNT-0.2SBT). Moreover, BNT-0.2SBT exhibits superior power density ([Formula: see text]), ultrafast discharge time ([Formula: see text][Formula: see text]ns) at [Formula: see text], and good temperature stability. The findings in this work not only demonstrate that a valid candidate, but also provide a new idea of how to achieve both high-energy storage density and efficiency in lead-free ferroelectric materials.

Yongzhong Zhu, Fangxuan Zou, Wenxuan Xie et al.

Abstract In this paper, a new arc‐shaped meta‐atom like a fishbone controlled by Pancharatnam–Berry (PB) phase is designed for a microwave band, which can yield a high‐purity vortex electromagnetic (EM) waves ranged from 10.63 to 26.86 GHz (relative bandwidth of 86.6%) with an efficiency of more than 90%. A single‐beam metasurface with m = +1, −2 and +3 modes is designed, respectively. Finally, a prototype with m = −2 mode is manufactured in order to prove the feasibility of the designed metasurface. It shows that the experimental results are in good agreement with the ones of the simulation, which verified the excellent performance of the metasurface. The metasurface has a series of edges such as ultra‐broadband, high efficiency, high purity and low profile compared to the conventional metasurfaces, which have strong practical applied value and significance for wireless communication.

Quan Yuan, Lei Deng, Hao Guo et al.

Abstract Optical image method has been the earliest and most used direct method for observing gas discharge. Currently, research on gas discharge monitoring based on visible light mainly relies on high‐speed cameras, but the large size, significant data storage requirements, and susceptibility to interference from complex backgrounds and lighting conditions limit their further application. Dynamic vision sensing (DVS) technology is a neuromorphic sensing technology that asynchronously measures the luminance changes at each pixel. It offers advantages such as a large dynamic range (>120 dB), high temporal resolution (up to 1 µs), and small data volume (MB level). In this study, dynamic vision sensing technology was employed to monitor both 30 mm short‐gaps and 1080 mm long‐gaps discharge processes simultaneously. This study developed the CountImage encoding method for event data and conducted image reconstruction, time‐domain analysis, and frequency‐domain characteristic analysis based on the event data. The results show that the event‐reconstructed images are highly consistent with the high‐speed camera images, and the arc development process and its path can also be clearly observed. Additionally, this study discovered a correlation between the electrical characteristics and event information during the discharge process. In the time domain, the duration of the maximum DVS event count closely matches the duration during which the voltage drops to zero during flashover. In the frequency domain, the Pearson correlation coefficient between the event stream spectrum and the voltage signal spectrum is greater than 0.95. Both the maximum number of brightening events (ONmax) and the maximum number of darkening events (OFFmax) are positively correlated with the voltage applied between the electrodes. This study demonstrates that, compared to the GB/s data rate of high‐speed cameras, this approach can record the discharge process and accurately reconstruct the discharge process, arc morphology, and discharge path at MB/s data rates, while also adapting to changes in brightness without the need for exposure adjustment. Additionally, there is a positive correlation between the frequency‐domain characteristics of the event data and the voltage characteristics. These results indicate that dynamic vision sensing holds promise as a replacement for high‐speed cameras in laboratory discharge observations and could be even effectively applied to discharge monitoring in electrical equipment in real grid.

PEI Yun-shan1,2, ZHANG Cai1,2, LIU Xiao-li1, CHENG Kai1, ZHANG Ze-ting,1, LI Cong-gang1

Abnormally misfolded and aggregated α-synuclein (αsyn) is the hallmark of Parkinson's disease (PD). Molecular chaperone protein disulfide isomerase (PDI) has been shown to interact with αsyn and inhibit its aggregation in vitro, but the mechanism for the recognition of αsyn by PDI is not yet clear. Herein, we used nuclear magnetic resonance (NMR) spectroscopy to identify that human PDI b'xa' bound with the N-terminal domain of αsyn, and thioflavin T (ThT) fluorescence assay revealed that b'xa' domain of PDI significantly inhibited αsyn aggregation. Furthermore, by using NMR titration, we observed that PDI bound to αsyn mainly through its hydrophobic cavity of the b' domain. Based on these findings, a docking model of PDI binding with αsyn was established and a possible mechanism of how PDI inhibits αsyn aggregation was proposed. Our work provides experimental evidences for understanding the inhibitory role of PDI in αsyn aggregation.

Xing HUANG, Zi-li ZHANG, Xin-ning HU et al.

Highly stable magnetic field is essential to nuclear magnetic resonance (NMR) spectrometers. To maintain the magnetic field stability, high-quality superconducting joints are required. Along with the development of NMR superconductor magnet, researches on superconducting joints have also attracted lots of attention from all over the world in the past decades. This review paper introduces the research progress of superconducting joint technology. The first part briefly introduces the development of NMR superconducting magnet and superconducting joint. The second part summarizes the research progresses of superconducting joint between low temperature superconductor materials. The joint between high temperature superconductor materials is demonstrated in the third part. In the fourth part, the measurement technology regarding the resistance of superconducting joints is discussed. Finally, an outlook on superconducting joint research is presented for further discussion in the community.

Chenfei HUA, Lin ZHU, Jie YAO et al.

In this study, three resource-recycled titanium-based carriers and one fresh titanium-based carrier were selected and analyzed to study the differences between these two types of carriers by virtue of laser particle size analyzer, X-ray fluorescence (XRF) analyzer, inductive coupled plasma (ICP) emission spectrometer, BET testing method and mercury intrusion porosimeter, etc. Furthermore, the above four carriers were used as raw materials to prepare finished catalyst products through active component loading and extrusion molding. Then the main components and trace element contents, specific surface area, mechanical strength, denitration efficiency and activity were tested respectively in the finished catalysts. The results show that, compared with fresh titanium-based carriers, the resource-recycled titanium-based carriers have more uneven particle size distribution, smaller specific surface area, less specific pore volume, and higher contents of toxic elements, which will affect the qualities of the corresponding finished catalysts, and eventually result in low denitration efficiency and activity.

Yuzhen ZHAO, Longyong CHEN, Fubo ZHANG et al.

Waveform design of joint radar and communication has become a focus of intense research in recent years. Some scholars have proposed to use the odd and even carrier of Orthogonal Frequency Division Multiplexing (OFDM) signal to modulate the radar and communication functions, respectively, to realize the integration. However, OFDM systems generally use cyclic prefix to avoid Inter-Carrier Interference (ICI) and Inter-Symbol Interference (ISI) caused by multipath effects, reducing energy utilization and creating false targets, which affect radar performance. In addition, the traditional OFDM integrated signal is more sensitive to Doppler shift. A small Doppler frequency offset will also cause a considerable drop in orthogonal performance. On this basis, this paper proposes a new waveform design and processing method. This method uses blank guard intervals to replace cyclic prefixes, which can resist multipath effects while avoiding false targets introduced by cyclic prefixes, effectively preventing ICI and ISI. In terms of signal processing methods, this paper proposes a method for channel estimation and Doppler compensation using the priori information of the radar signal. Compared with the traditional method, this new method reduces the system’s resource overhead, such as pilot frequency and training sequence. It improves energy utilization and spectrum efficiency. The peak side lobe ratio, integration side lobe rate, and bit error ratio are also improved. Simulation experiments verify the effectiveness of this method.

Shangwen DAI, Li ZHANG, Ningning LIU et al.

As one of the major players in electricity trading, the electricity retailer should actively undertake the responsibility of consuming renewable energy. To analyze the influence of the renewable portfolio standard (RPS) on electricity retailers, this paper constructed a new portfolio investment model of energy purchasing. Scenario analysis is performed to describe the uncertainty about the spot price and renewable energy output in electricity markets. The optimal energy purchasing strategy is developed with the minimum transaction cost based on the conditional value-at-risk (CVaR) as the goal, and the punishment mechanism for consumption responsibility examination is introduced to evaluate different examination criteria. The YALMIP toolbox in MATLAB is adopted to solve linear programming in this model. In addition, the influence of risk preference, RPS quotas, renewable-energy forecast accuracy, and the degrees of penalties from regulatory authorities on the optimal energy purchasing strategy of electricity retailers is analyzed by simulation. The results show that the proposed model is effective.

BAO Qiu-lian, YANG Yun-han, WEI Ke-ke et al.

The host-guest complex of water-soluble phosphate salt pillar[5]arene (PP5A) and cationic fluorescent dye acridine orange (AO) was constructed, and studied with ultraviolet spectrum (UV), infrared absorption spectrum (IR), molecular fluorescence spectroscopy (MFS), and nuclear magnetic resonance (NMR) spectra (1H NMR and NOESY). And then, the effect of pH and two surfactants, including sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) on the fluorescence intensity of AO/PP5A complex system were investigated. Finally, the complexation mode and energy of PP5A with AO and CTAB were calculated by molecular docking. The results showed that AO and PP5A formed a 1:1 host-guest complex. PP5A reduced or quenched the fluorescence intensity of AO in the pH range of 3~11. The addition of SDS and CTAB did not affect the fluorescence intensity of AO/PP5A complex significantly. The fluorescence changes generated by AO and PP5A complexation can provide a theoretical basis for the design of fluorescence sensors.

S. Fantauzzi, L. Valletti, F. Di Paolo

This paper outlines an innovative approach to design a spatial power-combining structure based on waveguide polarizers. It presents the 3D CAD model of the new structure with the transversal probes and considerations in positioning and optimization of them. Exploiting the transformation of the dominant input mode TE10 into an elliptically polarized wave, provided by the polarizer, it has been possible to achieve a division of power by eight, completely carried out in space. With the insertion of the transversal probes made by microstrips, the RF signal can be sent to the MMIC solid state power amplifiers, and then recombined in the output section. Thanks to the large number of power divisions made in the waveguide section, the insertion loss of the power divider/combiner is less than 0.5 dB across the 32-34 GHz band, achieving a great power density as well. At the Author’s best knowledge, this is the first work where a waveguide polarizer is used in Spatial Power Combining technology.

XING Mengdao, LIN Hao, CHEN Jianlai et al.

The multi-platform-borne Synthetic Aperture Radar (SAR) has become one of the most explored research directions in the domain of SAR. This study discusses the imaging algorithms in multi-platform-borne SARs such as airborne SAR, missile-borne SAR, and spaceborne SAR. First, the establishment of the radar echo model is briefly introduced, including two main points: slant range-model and imaging mode. Subsequently, the imaging algorithms of the aforementioned multi-platform-borne SARs developed and used in recent years are summarized. In addition, the inherent characteristics and challenges are described. Finally, the future development trends of the research are discussed.

Hui Ye, Bai Xueru

Micromotion refers to the small and non-uniform motion of the target or several target components along the radar line of sight. Using the high-resolution three-Dimensional (3D) Inverse Synthetic Aperture Radar (ISAR) imaging, the structural information and motion status of micromotion targets can be obtained, providing essential features for the detection, tracking, identification, and classification, which play important roles in the space situation awareness and ballistic missile defense. Given the complex micromotion forms and the non-stationary radar echoes, the available parametric ISAR imaging methods are no longer applicable. To overcome this limitation, this study aims to propose a high-resolution 3D imaging method for micromotion targets based on the scattering center trajectory matrix decomposition. First, the Range Instantaneous Doppler (RID) image series is generated to extract the support region of scattering centers by the watershed method. Then, the scattering center association is achieved based on the minimum Euclidean distance criterion. Considering the insufficient accuracy in the instantaneous slant range estimation with limited range resolution, a method for refined estimation of the trajectory matrix based on the modern spectrum analysis is proposed. Finally, the high-resolution 3D imaging of the micromotion targets is obtained by the trajectory matrix decomposition with constraints. The simulation results have demonstrated that the proposed method could effectively obtain high-resolution 3D imaging of the targets in complex micromotions such as nutation.