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Dynamics of an impurity ion transport in oil-paper insulation under various electric fields

High Voltage 2024年第1期9卷 66-80页

作者： Yuanyang Ren Yang Wang Qiankai Zhang Jiayu Xiong Wen Cao Zepeng Lv Kai Wu State Key Laboratory of Electrical Insulation and power Equipment Xi'an Jiaotong UniversityXi'anChina School of electronics and Information Xi'an Polytechnic UniversityXi'anChina State Grid Sichuan Electric power Research Institute ChengduChina

The ionic transport process is an important counterpart to charge transport in oil-paper insulation,and it significantly impacts oil flow electrification at the oil-paper *** this,the dynamics of this phenomenon and the underlying mechanisms remain unclear,particularly at the molecular *** understand this fundamental aspect,we conduct Molecular Dynamics study on the transport behaviour of an impurity ion in different oil-paper insulation models under various external electric *** influence factors,such as external electric fields,temperatures,and local structural characteristics,are investigated in relation to the corresponding ionic mobility in different polymer *** to the simulations,ionic mobility and its response to electric fields are higher in weaker electrostatic *** a result,mineral oil exhibits the highest ionic mobility and the most substantial enhancement of ionic mobility by external electric fields,followed by vegetable oil,oil-paper blends,and insulating *** significant deviation in ionic mobility between oil and paper leads to the formation of an electric double layer near the oil-paper *** underlying physical mechanisms of different ionic mobility and its response to the electric field in different polymer models could be explained by the different polymer structural influences in terms of interaction energy and coordination numbers in a static manner,as well as by the interactions between the impurity ion and its surrounding atoms in terms of lifetime correlation functions and velocity autocorrelation functions in a dynamic *** addition,the influence of temperature on ionic mobility in mineral and vegetable oil is examined,and their activation energies are *** in the fundamental understanding of the dynamics of the ion transport process in oil-paper insulation is vital to improving their insulating properties for oil-impregnated power transformers.

关键词： insulation transport fields

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Experimental study on effects of gas flow rate on soot characteristics in diffusion flames coupled with plasma

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Science China(Technological Sciences) 2024年第2期67卷 475-485页

作者： QI DanDan CHEN MingXiao TU Xin LIU Dong MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China Advanced Combustion Laboratory School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China Department of Electrical Engineering and electronics University of LiverpoolLiverpool L693GJUK

This study examined the evolution of morphology and nanostructure of soot particles from the plasma-flame interaction for various gas flow *** current study used both optical diagnostic and sampling methods to explore the soot production and combustion *** particles were characterized at the same positions downstream from the flame zone by thermophoretic sampling and transmission electron ***,X-ray diffraction analysis,and thermogravimetric analysis were performed to study the nanostructure and oxidation reactivity of soot.A reduction in soot concentration was found with the plasma addition,which illustrated an inhibition effect of plasma on soot *** increased gas flow rate promoted soot concentration since a growing number of carbons participated in the combustion *** on the gas flow rate(carbon content)variation and plasma activation,either liquid-like soot material with irregularly shaped protrusions or chain-like structure,or a mixture of both,were generated from the diffusion *** soot produced by plasma-flame interaction also demonstrated a high correlation between nanostructure and *** soot from lower carbon content with plasma activation had a shorter fringe length and larger fringe tortuosity related to higher oxidation *** the contrary,soot from the highest carbon content without plasma-flame interaction exhibited prevalent fullerene-like nanostructures with evident large or small shells and also had a higher carbonization degree resulting in lower oxidation reactivity.

关键词： soot characteristics gas flow rate plasma diffusion flames

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Analytical Modeling of Disaster-induced Load Loss for Preventive Allocation of Mobile power Sources in Urban power Networks

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Journal of Modern power Systems and Clean Energy 2024年第4期12卷 1063-1073页

作者： Zhuorong Wang Qingxin Shi Ke Fan Haiteng Han Wenxia Liu Fangxing Li School of Electrical&electronics Engineering North China Electric Power UniversityBeijing 102206China College of Energy and Electrical Engineering Hohai UniversityNanjing 211100China The University of Tennessee Knoxville TN 37996USA

Continuous power supply of urban power networks(UPNs)is quite essential for the public security of a city be-cause the UPN acts as the basis for other infrastructure *** recent years,UPN is threatened by extreme weather *** accurate modeling of load loss risk under extreme weather is quite essential for the preventive action of ***-sidering the forecast intensity of a typhoon disaster,this paper proposes analytical modeling of disaster-induced load loss for preventive allocation of mobile power sources(MPSs)in ***,based on the topological structure and fragility model of overhead lines and substations,we establish an analytical load loss model of multi-voltage-level UPN to quantify the spatial dis-tribution of disaster-induced load loss at the substation ***,according to the projected load loss distribution,a pre-ventive allocation method of MPS is proposed,which makes the best use of MPS and dispatches the limited power supply to most vulnerable areas in the ***,the proposed meth-od is validated by the case study of a practical UPN in China.

关键词： Load loss fragility model pre-disaster allocation mobile power source urban power network

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Synchronization Stability Analysis of PLL-based Grid-connected VSC System by Voltage Space Vectors

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CSEE Journal of power and Energy Systems 2024年第5期10卷 2055-2064页

作者： Huadong Sun Shuyan Wang Shiyun Xu Jingtian Bi Yiming Wang State Key Laboratory of power Grid Safety and Energy Conservation China Electric Power Research InstituteBeijing 100192China

This paper focuses on synchronization stability analysis of the power system,in which power electronics are synchronized by the phase-locked loop(PLL).It provides new insight into the synchronization stability of power electronics from the voltage *** synchronization stability analysis based on space vector is carried out by establishing a simplified model of the grid-connected voltage source converter(VSC)*** complex mathematical calculation,the existence criterion of equilibrium points and the criterion of transient instability dominated by the unstable equilibrium point(UEP)are derived,*** the proposed method,synchronization stability can be determined by the voltage space vectors,which are more observable in potential engineering *** the end of this study,the steps of the synchronization stability determination by voltage space vectors are summarized,and the effectiveness and applicability of the proposed method are demonstrated by numerical simulations performed on the PSCAD/EMTDC platform.

关键词： Large disturbance phase locked loop(PLL) space vector synchronization stability voltage source converter(VSC)

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A Hybrid Feature Fusion Traffic Sign Detection Algorithm Based on YOLOv7

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Computers, Materials & Continua 2024年第7期80卷 1425-1440页

作者： Bingyi Ren Juwei Zhang Tong Wang School of Mechanical Engineering Henan University of Science and TechnologyLuoyang471000China School of Information Engineering Henan University of Science and TechnologyLuoyang471000China School of Electronic Information Zhengzhou Institute of Aeronautical Industry ManagementZhengzhou450046China Henan Province New Energy Vehicle power electronics and power Transmission Engineering Research Center Luoyang471000China

Autonomous driving technology has entered a period of rapid development,and traffic sign detection is one of the important *** target detection networks are difficult to adapt to scenarios where target sizes are seriously imbalanced,and traffic sign targets are small and have unclear features,which makes detection more ***,we propose aHybrid Feature Fusion Traffic Sign detection algorithmbased onYOLOv7(HFFTYOLO).First,a self-attention mechanism is incorporated at the end of the backbone network to calculate feature interactions within scales;Secondly,the cross-scale fusion part of the neck introduces a bottom-up multi-path fusion *** reuse paths at the end of the neck,paying particular attention to cross-scale fusion of highlevel *** addition,we found the appropriate channel width through a lot of experiments and reduced the superfluous *** terms of training,a newregression lossCMPDIoUis proposed,which not only considers the problem of loss degradation when the aspect ratio is the same but the width and height are different,but also enables the penalty term to dynamically change at different ***,our proposed improved method shows excellent results on the TT100K *** with the baseline model,without increasing the number of parameters and computational complexity,AP0.5 and AP increased by 2.2%and 2.7%,respectively,reaching 92.9%and 58.1%.

关键词： Small target detection YOLOv7 traffic sign detection regression loss

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An evolutionary multiobjective method based on dominance and decomposition for feature selection in classification

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Science China(Information Sciences) 2024年第2期67卷 5-19页

作者： Jing LIANG Yuyang ZHANG Ke CHEN Boyang QU Kunjie YU Caitong YUE Ponnuthurai Nagaratnam SUGANTHAN School of Electrical and Information Engineering Zhengzhou University State Key Laboratory of Intelligent Agricultural power Equipment School of Electrical Engineering and Automation Henan Institute of Technology School of electronics and Information Zhongyuan University of Technology KINDI Center for Computing Research College of EngineeringQatar University

Feature selection in classification can be considered a multiobjective problem with the objectives of increasing classification accuracy and decreasing the size of the selected feature subset. Dominance-based and decomposition-based multiobjective evolutionary algorithms(MOEAs) have been extensively used to address the feature selection problem due to their strong global search capability. However, most of them face the problem of not effectively balancing convergence and diversity during the evolutionary process. In addressing the aforementioned issue, this study proposes a unified evolutionary framework that combines two search forms of dominance and decomposition. The advantages of the two search methods assist one another in escaping the local optimum and inclining toward a balance of convergence and diversity. Specifically, an improved environmental selection strategy based on the distributions of individuals in the objective space is presented to avoid duplicate feature subsets. Furthermore, a novel knowledge transfer mechanism that considers evolutionary characteristics is developed, allowing for the effective implementation of positive knowledge transfer between dominance-based and decomposition-based feature selection methods. The experimental results demonstrate that the proposed algorithm can evolve feature subsets with good convergence and diversity in a shorter time compared with 9 state-of-the-art feature selection methods on 20 classification problems.

关键词： evolutionary algorithms feature selection multiobjective optimization knowledge transfer classification

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EMCO-based Optimal Layout Design of Hybrid Wind-wave Energy Converters Array

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Protection and Control of Modern power Systems 2024年第5期9卷 142-161页

作者： Bo Yang Jinhang Duan Yunfeng Yan Bingqiang Liu Jianxiang Huang Lin Jiang Rui Han Faculty of Electric power Engineering Kunming University of Science and TechnologyKunming 650500China College of Electrical Engineering Zhejiang UniversityHangzhou 310027China Company of Kunming Bureau of CSG EHV Transmission Company Kunming 650217China School of Electrical Engineering and electronics University of LiverpoolLiverpool L693GJUK Company of Electric power Science Research Institute State Grid Zhejiang Electric Power Company Ltd.Hangzhou 310014China

Marine renewable energy,combining wave energy converters(WECs)and floating wind turbines(FWTs)into hybrid wave-wind energy converters(HWWECs),garners significant global *** offer potential cost reductions,increased power generation,and enhanced system *** absorption power of high wind energy sites is primarily influenced by the complex hydrodynamic interactions among floating bodies,which are closely related to the location and wind-wave environment of high wind energy *** delve into the positive interactions among HWWECs,this paper proposes a HWWEC array optimization strategy based on the artificial ecosystem opti-mization-manta ray foraging optimization coordinated op-timizer(EMCO).In EMCO,the decomposition operator of artificial ecosystem optimization(AEO)and the flip-ping-dipper foraging operator of manta ray foraging opti-mization coordinated(MRFO)cooperate dynamically to effectively balance local exploitation and global *** validate the effectiveness of EMCO,experiments were conducted in scenarios with 3,5,8,and 20 HWWECs,and compared with five typical *** results demonstrate the existence of multiple optimal solutions for HWWEC *** achieves maximum total absorp-tion power and exhibits good ***,EMCO en-hances the q-factor values of HWWECs across four scales:1.0478,1.0586,1.0612,and 0.9965,*** Terms—Marine renewable energy,hybrid wind-wave energy converter,layout optimization,coordinating optimizer.

关键词： Marine renewable energy hybrid wind-wave energy converter layout optimization coordinating optimizer

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Exploring the Mechanism,Advancements,and Application of Thermogalvanic Effect in Hydrogels

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Chinese Journal of Chemistry 2024年第5期42卷 543-556页

作者： Xiaoyu Yang Peng Wang Xiaolong Wu Yongli Liao Senyun Liu Wei Duan Ying Yue School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBaodingHebei071000 China Hebei Key Laboratory of Electric Machinery Health Maintenance & Failure Prevention North China Electric Power UniversityBaodingHebei071003 China Electric power Research Institute China South Power GridGuangzhouGuangdong510000 China Key Laboratory of Icing and Anti/De-icing China Aerodynamics Research and Development CenterMianyangSichuan621000 China

The issue of energy consumption has garnered significant interest due to its excessive ***,thermoelectric devices have been getting increased attention,as they can harness waste heat from various sources,such as solar radiation,human body,and industrial ***,the recovery of low-grade heat has been a challenge,resulting in unsustainable energy use and significant *** considerable advances have been made in thermoelectric materials in recent decades,the majority of these devices still primarily employ ***,the emergence of quasi-solid-state thermoelectric materials represents a novel development with profound promise for the environment and *** materials offer several advantages,such as improved energy conversion capacities,cost-effectiveness,versatility,and scalability,to support increased ***,this review explores the application of thermoelectric materials in self-powered sensors,integrated modules,and heat harvesting ***,the potential of high-performance thermocouples based on thermogalvanic effects is assessed,along with the challenges that must be overcome to realize this goal.

关键词： Hydrogel Thermogalvanic effect Thermochemistry Electrolytes Flexible electronics

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On the size generalizibility of graph neural networks for learning resource allocation

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Science China(Information Sciences) 2024年第4期67卷 239-254页

作者： Jiajun WU Chengjian SUN Chenyang YANG Beihang University School of electronics and Information Engineering

Size generalization is important for learning resource allocation policies in wireless systems with time-varying scales. If a neural network for learning a wireless policy is not generalizable to the size of its input, it has to be re-trained whenever the system scale changes, which hinders its practical use due to the unaffordable training costs. Graph neural networks(GNNs) have been shown with size generalization ability empirically when optimizing resource allocation. Yet, are GNNs naturally size generalizable? In this paper,we argue that GNNs are not always size generalizable for resource allocation. We find that the aggregation and activation functions of the GNNs for learning a class of wireless policies play a key role in their size generalization ability. We take the GNN with the mean aggregator, called mean-GNN, as an example to reveal a size generalization condition. To demonstrate how to satisfy the condition, we learn power and bandwidth allocation policies for ultra-reliable low-latency communications and show that selecting or pretraining the activation function in the output layer of mean-GNN can make the GNN size *** results validate our analysis and evaluate the performance of the learned policies.

关键词： size generalization graph neural networks resource allocation permutation equivariance

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A comprehensive analysis of DAC-SDC FPGA low power object detection challenge

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Science China(Information Sciences) 2024年第8期67卷 300-320页

作者： Jingwei ZHANG Guoqing LI Meng ZHANG Xinye CAO Yu ZHANG Xiang LI Ziyang CHEN Jun YANG School of electronics Science and Engineering Southeast University

The lower power object detection challenge(LPODC) at the IEEE/ACM Design Automation Conference is a premier contest in low-power object detection and algorithm(software)-hardware co-design for edge artificial intelligence, which has been a success in the past five years. LPODC focused on designing and implementing novel algorithms on the edge platform for object detection in images taken from unmanned aerial vehicles(UAVs), which attracted hundreds of teams from dozens of countries to participate. Our team SEUer has been participating in this competition for three consecutive years from 2020 to 2022 and obtained sixth place respectively in 2020 and 2021. Recently, we achieved the championship in 2022. In this paper, we presented the LPODC for UAV object detection from 2018 to 2022, including the dataset, hardware platform,and evaluation method. In addition, we also introduced and discussed the details of methods proposed by each year's top three teams from 2018 to 2022 in terms of network, accuracy, quantization method, hardware performance, and total score. Additionally, we conducted an in-depth analysis of the selected entries and results, along with summarizing representative methodologies. This analysis serves as a valuable practical resource for researchers and engineers in deploying the UAV application on edge platforms and enhancing its feasibility and reliability. According to the analysis and discussion, it becomes evident that the adoption of a hardware-algorithm co-design approach is paramount in the context of tiny machine learning(TinyML).This approach surpasses the mere optimization of software and hardware as separate entities, proving to be essential for achieving optimal performance and efficiency in TinyML applications.

关键词： tiny machine learning object detection convolutional neural networks algorithm-hardware co-design low power field programmable gate array

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