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Scalable fabrication and active site identification of MOF shell-derived nitrogen-doped carbon hollow frameworks for oxygen reduction

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Journal of Materials Science & technology 2021年第7期66卷 186-192页

作者： Jiashen Meng Ziang Liu Xiong Liu Wei Yang Lianzhou Wang Yan Li Yuan-Cheng Cao Xingcai Zhang Liqiang Mai State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan430070China Nanomaterials Centre School of Chemical Engineering and Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandSt LuciaQLD4072Australia Shenzhen Power Supply Col.Ltd. Shenzhen CityChina State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan430074China John A.Paulson School of Engineering and Applied Sciences Harvard UniversityCambridgeMA02138United States

Nitrogen-doped carbon materials as promising oxygen reduction reaction(ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, high conductivity and low cost. To maximize their catalytic efficiency, rational design of efficient electrocatalysts with rich exposed active sites is highly desired. Besides, due to the complexity of nitrogen species, the identification of active nitrogen sites for ORR remains challenging. Herein, we develop a facile and scalable template method to construct high-concentration nitrogen-doped carbon hollow frameworks(NC), and reveal the effect of different nitrogen species on theirORRactivity on basis of experimental analysis and theoretical calculations. The formation mechanism is clearly revealed, including low-pressure vapor superassembly of thin zeolitic imidazolate framework(ZIF-8) shell on ZnO templates,in situ carbonization and template removal. The obtained NC-800 displays better ORR activity compared with other NC-700 and NC-900 samples. Our results indicate that the superior ORR activity of NC-800 is mainly attributed to its content balance of three nitrogen species. The graphitic N and pyrrolic N sites are responsible for lowering the working function, while the pyridinic N and pyrrolic N sites as possible active sites are beneficial for increasing the density of states.

关键词： MOF shell Nitrogen-doped carbon Hollow framework Oxygen reduction Active nitrogen sites

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Study on a 48-Slot Interior Permanent Magnet Synchronous Motor in the Aircraft Drive System 2

Study on a 48-Slot Interior Permanent Magnet Synchronous Mot...

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2nd Asia Power and Electrical technology Conference, APET 2023

作者： Xie, Yuhang Xiong, Fei Yan, Rui Xiang, Yu Yang, Kai Yan, Weican School of Reliability and Systems Engineering Beijing University of Aeronautics and Astronautics Beijing100191 China Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Technology Wuhan430074 China SG Micro Corp Marketing Department Beijing100089 China Wolong Electric Group Co. LTD Shangyu312300 China

ISBN: (纸本)9798350359428

The torque performance of the interior permanent magnet synchronous motor (IPMSM) has been widely concerned and studied for many years. This article focuses on the structure design and optimization of the IPMSM in the aircraft drive system, and aiming to improve the torque density and reduce the torque ripple. Firstly, the original structure of the IPMSM is given. And then, a fractional slot winding and Δ-type rotor magnetic pole topology are proposed as the optimized IPMSM structure in this article. In addition, the comparison of the original and optimized structure is studied by the simulation. Finally, the performance of an optimized prototype is analyzed by experimental test, and the validity of the design optimization method for proposed IPMSM structure is verified. © 2023 IEEE.

关键词： Topology

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An Improved Simplified Model of Capacitor Charging Power Supply with Homopolar Inductor Alternator Considering Field Flux Linkage and Speed Changes

An Improved Simplified Model of Capacitor Charging Power Sup...

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China International Electrical and Energy Conference (CIEEC)

作者： Songlin Guo Kexun Yu Zhengkang Yi Jiasong Wang Xianfei Xie Jiakang Yao State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China State Key Laboratory of Tribo logy Tsinghua University Beijing China

Homopolar inductor alternator (HIA) has shown its promising advantages in capacitor charging power supply (CCPS). For accelerating HIA-CCPS system design process, researchers have been making efforts to simplify the simulation analysis, but the models were not universal or effective enough. In this paper, a simplified look-up-table model considering the changes of speed and field flux linkage in HIA-CCPS is proposed. While realizing fast calculation, it can also reflect the dynamic process similar to the transient model, which is very exact and effective.

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Regulating the Space Charge at Interface by Negative Polar Biomolecule Enabling Ultrastable Zn Anode Chemistry

SSRN

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SSRN 2024年

作者： Jin, Qianzheng Jiang, Kai State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China School of Electrical Engineering Zhengzhou University Zhengzhou450001 China Zhengzhou University China

The irreversibility of Zn metal anode arising from uncontrollable dendrite growth and hydrogen evolution reaction, especially at high current densities, has challenged the commercialization application of aqueous Zn-ion batteries. Here we report biomolecule additive, named xanthan gum, to solve these issues through making use of dissociated -COO- groups to reduce space charge near the anode-electrolyte interface and form H2O-poor electrical double layer to regulate the Zn deposition behaviors. Meanwhile, the dissolved xanthan gum with multiple polar groups can break the association between H2O and Zn2+ to reconstruct solvated structures of Zn ions to suppress HER. Therefore, the Zn//Zn symmetric cells in ZnSO4 electrolyte with xanthan gum deliver an ultra-long cycle life (>4700 h), and also present excellent cycling performances in other electrolyte (Zn(OAc)2 and Zn(OTf)2). More importantly, a high coulombic efficiency of 99.7% is achieved using Zn//Cu half cells tested and excellent cycling life for KVO//Zn full cells. This work provides the guidance to design the electrolyte additive for highly reversible Zn metal batteries. © 2024, The Authors. All rights reserved.

关键词： Xanthan gum

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Numerical Investigation on Frequency Dependence of Hysteresis Characteristics of Conducting Ferromagnetic Materials

Numerical Investigation on Frequency Dependence of Hysteresi...

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International Conference on Wireless Power Transfer, ICWPT 2022

作者： Yubo, Zhang Tianyi, Liu Zhenyu, Liao Dong, Li Dezhi, Chen State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China State Grid Jiangsu Electric Power Company Suzhou Power Supply Bureau Suzhou215004 China State Grid Hunan Electric Power Company Electric Power Research Institute Changsha410007 China

ISBN: (纸本)9789819906307

The hysteresis characteristics of ferromagnetic materials have significant effects on the performance and loss of electrical devices and components. Studies have shown that the hysteresis loop changes significantly with the increase of frequency, which becomes an important factor in electrical designing and operating. In order to provide a reasonable explanation and analysis method for the variation of dynamic hysteresis loops in the wide frequency range, experimental measurements and theoretical simulations are carried out. In this paper, the change of the hysteresis loop shape caused by the increase of frequency is attributed to eddy currents in the sample, so only the static hysteresis loop is the real reflection of the material characteristics, at which frequency the eddy current effect can be ignored. In order to verify this conjecture, the static hysteresis loops and the dynamic hysteresis loops in the range of 20 Hz ~ 1000 Hz were measured for the annular sample made of 20# steel and B35A300 non-oriented silicon steel sheet. Then, based on the static hysteresis loops of their own, the finite-difference time-domain method was used to solve Maxwell equations at different frequencies to obtain the magnetic field distribution in the sample. The average magnetic induction intensity was used to get the hysteresis loops. The calculated curves are found in good agreement with the measured ones, which indicates that the loop swelling-up is due to the inaccuracy of the measurement principle, and frequency has no effect on the hysteresis characteristics of 20# steel and B35A300 non-oriented silicon steel sheet at least in the frequency range below 1 kHz. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Maxwell equations

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Dynamic Characteristics of Partial Discharge from Typical Defects of HV Cables 10

Dynamic Characteristics of Partial Discharge from Typical De...

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10th China International Conference on Electricity Distribution, CICED 2022

作者： Jia, Shiyuan Peng, Xiaosheng Wang, Hongyu Chu, Fanwu Xu, Qiyou State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan China China-EU Institute for Clean and Renewable Energy Huazhong University of Science and Technology Wuhan China China Electric Power Research Institute Wuhan China

ISBN: (数字)9781665452687

ISBN: (纸本)9781665452687

As the main equipment for power transmission in the distribution network, the insulation performance of the XLPE cable directly determines the stability and reliability of the testing of the power grid system. Based on the online partial discharge monitoring, cable defects can be effectively found, which is of great significance to ensure the safe operation of the distribution network. In this paper, by artificially producing different types of cable defect segments, and by means of long-term withstand voltage operation in the laboratory, partial discharge signals at different locations are collected, and the pulse amplitude and phase spectrum of cables with typical defects during long-term withstand voltage operation are analyzed. The study indicate that cables of the same defect type have time-invariant characteristics and change regularly with the propagation distance;the gap between cables of different defect types is huge. This paper has guiding significance for the identification of cable defect types, and provides corresponding consultation for the condition monitoring of industrial field cables. © 2022 IEEE.

关键词： Partial discharges

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Refractive Index Extraction from THz-TDS Measurement with the Neural Network Approach

Refractive Index Extraction from THz-TDS Measurement with th...

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International Conference on Infrared and Millimeter Waves

作者： Zesen Zhou Shanshan Jia Lei Cao State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (数字)9781728194271

ISBN: (纸本)9781728194288

The complex refractive index for optically thick low-loss materials is conventionally extracted via iterative algorithm based on the transmission-mode terahertz time domain spectroscopy (THz-TDS). Without assigning initial values, a new approach based on the neural network was investigated to obtain the optical parameters for three typical materials (TPX, quartz and SiC) in the THz frequency range. Comparisons with the iterative method were conducted. The neural network method is also expected to find applications in characterization of the two-dimensional material (like graphene) and the multilayer material system.

关键词： Spectroscopy Silicon carbide Neural networks Refractive index Optical computing Optical variables control Optical materials

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Design of Terahertz One-dimensional Photonic Crystal Cavity Based on Neural Network and Optimization Algorithm

Design of Terahertz One-dimensional Photonic Crystal Cavity ...

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International Conference on Infrared and Millimeter Waves

作者： Shanshan Jia Zesen Zhou Lei Cao State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (数字)9781728194271

ISBN: (纸本)9781728194288

Neural networks and optimization algorithms have great potential application in the physical analysis and design of optical components due to their high speed and high efficiency. Taking terahertz (THz) one-dimensional (1D) photonic crystal (PC) resonant cavity as an example, a neural network is proposed to predict the fundamental parameters of the PC cavity with high accuracy. However, the neural network alone suffers from low accuracy in the process of reverse prediction. In combination with a multi-objective optimization algorithm, the reverse prediction of the PC cavity is realized with high accuracy.

关键词： Neural networks Photonic crystals Prediction algorithms Optimization Optical devices

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An Improved Parameter Design Method of Active Clamping Circuit for Voltage Balancing of Series-Connected IGBTs

An Improved Parameter Design Method of Active Clamping Circu...

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Smart Power & Internet Energy Systems (SPIES), International Conference on

作者： Xiangyu Yang Hua Lin Tao Wang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuHan China

Connecting multiple insulated gate bipolar transistors (IGBTs) in series is the most direct and effective way to meet the voltage rating requirements of high power and high voltage converters, but there is severe voltage imbalance during the switching process of series-connected IGBTs. The active clamping circuit has been widely used for its simple structure and high reliability for voltage balancing of series-connected IGBTs. Based on the existing research, this paper presents an improved parameter design scheme for the active clamping circuit. Through theoretical analysis and experiments, it’s verified that the active clamping circuit using the proposed parameter design method can achieve static voltage balancing without additional power-side static voltage balancing resistance, and the influence of clamping circuit parameters on voltage balancing effect and IGBTs switching loss is also discussed. The work of this paper provides suggestions for the design and selection of appropriate active clamping circuit parameters in practical applications.

关键词： Insulated gate bipolar transistors Resistance Design methodology Switching loss Voltage Reliability theory Internet

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Optimization Decision Method based on Nonlinear Analytic Hierarchy Process for Active Distribution Network Planning

Optimization Decision Method based on Nonlinear Analytic Hie...

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2021 International Conference on Electrical, Electronics and Computing technology, EECT 2021

作者： Zheng, Xuejun Hu, Xin Li, Jingsong Li, Yan Luo, Xiaotong Wang, Shaorong State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science AndTechnology Hubei Province Wuhan430074 China

Aiming at the investment environment of the distribution network, this paper deeply analyses the investment conditions of the distribution network, introduces the analytic hierarchy process and modern investment theory, establishes the analytic hierarchy of the investment conditions in the distribution network project, and proposes an optimization decision-making method of investment plan in distribution network. This paper also establishes two new concepts: condition score and correlation score, uses the improving analytic hierarchy process to calculate the weights, proposes a priority ranking method for distribution network projects, and gives detailed process. to formulate distribution network investment plans. The application of the proposed method to optimize the distribution network planning scheme shows that the optimization investment scheme given has better investment benefits under the condition of the power supply reliability requirements of the distribution network and investment capital constraints. © Published under licence by IOP Publishing Ltd.

关键词： Analytic hierarchy process

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