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Simulation of Negative Streamer in Transformer Oil under Nanosecond Pulse Voltage

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Simulation of Negative Streamer in Transformer Oil under Nan...

Targets capture by distributed active swarms via bio-inspired reinforcement learning

中国物理学会第十八届全国静电学术会议

作者： Yuan Li Hai-bao Mu jun-bo deng Guan-jun Zhang Shu-hong Wang State Key Lab of Electrical Insulation and Power Equipment School of Electrical Engineering Xi’an Jiaotong University

As dielectric liquids such as transformer oil have been widely used in high-voltage power apparatus and pulse power system, their electrical behavior subjected to high electric fields and the possible breakdown phenomena are of great practical interest. In this paper, the propagation process of negative streamer discharge from initiation till breakdown in transformer oil under nanosecond pulse voltage is modeled by a two dimensional axis-symmetric fluid model with finite element method. In this fluid model, three kinds of charge carriers, such as electron, positive and negative ions are utilized to account for the charge generation, recombination, and transport mechanisms behind the discharging process. The streamer discharge profile and distribution of electric field and space charge density are obtained under different conditions such as the amplitude of applied voltage and rise time. Simulation results show that the discharging phenomena of negative streamers are fundamentally different from positive streamers, namely positive streamers tend to be filamentary while negative streamers form in a bushy shape, which implies that physical mechanisms of the these two different polarity streamers are different. It can be found that space charges play an important role in negative streamers initiation and propagation. The rise time of applied voltage have evident influences on the average speed of streamer propagation. The current of discharge is calculated as a clear evidence of breakdown. It can be observed that negative streamers require over twice amplitude of applied voltage to initiate, compared with the positive streamers. It is considered that field-dependent molecular ionization predominates charge generation mechanism of streamer discharge process in transformer oil. The study would dedicate to clarify the process of negative discharge from inception to breakdown in transformer oil, as well as ionization mechanism in liquid dielectric.

关键词： transformer oil fluid model negative streamer discharge

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 210-221页

作者： Kun Xu Yue Li jun Sun Shuyuan Du Xinpeng Di Yuguang Yang bo Li Institute of Biomechanics and Medical Engineering Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua University Institute of Nuclear and New Energy Technology Tsinghua University Shanghai Aerospace Control Technology Institute Shanghai Key Laboratory of Aerospace Intelligent Control Technology College of Automation Engineering Nanjing University of Aeronautics and Astronautics

Natural swarms arranged from cells to herds are usually decentralized but display intriguing collective intelligence in coordinating individuals across large scales to efficiently achieve their common goals. Learning from nature may provide new strategies for controlling collective dynamics of synthetic swarms to accomplish specific functions. Here, we present a bioinspired computational framework that steers distributed active swarms to collectively capture and merge targets via reinforcement learning. We exploit collective milling structures of natural herds to cage the targets, and adopt a switching control policy inspired by sperms' chiral dynamics to optimize the trajectories of individuals, through which the active swarms can selforganize to enclose single or multiple distant targets in a dynamical, adaptive and scalable manner. There exists a critical swarm size, beyond which the excessive competition between agents would generate large mechanical forces, leading to capture instability but enabling the transition from short-distance to long-distance merging capture of multiple targets. This work provides physical insights into distributed active swarms and could offer a multilevel, decentralized strategy toward controlling swarm robotics in wide applications such as bio-medical devices, machine immunity, and target clearance.

关键词： swarm intelligence robotics multi-tasks artificial intelligence bionics

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龙胆泻肝汤对PCOS模型大鼠的影响

中国实验方剂学杂志 2018年第7期24卷 121-126页

作者：李俊波邓芳李霄汉许丽绵广州中医药大学广州510405 广州中医药大学第一附属医院广州510405

目的：研究龙胆泻肝汤对多囊卵巢综合征（PCOS）模型大鼠药效观察及机制，为龙胆泻肝汤临床PCOS的应用提供初步实验依据。方法：将SD大鼠50只，随机分为2组，即正常组10只、模型制备组40只，采用胰岛素（INS）联合人绒毛膜促性腺激素（... 详细信息

目的：研究龙胆泻肝汤对多囊卵巢综合征（PCOS）模型大鼠药效观察及机制，为龙胆泻肝汤临床PCOS的应用提供初步实验依据。方法：将SD大鼠50只，随机分为2组，即正常组10只、模型制备组40只，采用胰岛素（INS）联合人绒毛膜促性腺激素（HCG）法复制大鼠PCOS模型，造模成功的大鼠分为模型组、达英-35（0．21g·kg^-1）及龙胆泻肝汤高、低剂量组（29．6，7．4g·kg^-1），除正常组外，其余各组连续灌胃给药15d；动物处理后测量卵巢质量及体积大小，检测各组大鼠血清中促黄体生成素（LH）／卵泡刺激素（FSH），睾酮（T），空腹血糖，空腹胰岛素（INS）激素水平及炎症因子白细胞介素-2（IL-2），IL-4，IL-6，IL-10水平；蛋白免疫印迹法（Westernblot）分析各组卵巢组织中JAK2，STAT3，p-STAT3和IL-6蛋白的表达量。结果：与正常组比较，模型组卵巢质量及体积明显升高，血清LH／FSH，T，空腹血糖及INS均明显升高，IL-2，IL-6，IL-10水平明显升高，JAK2，STAT3和IL-6蛋白的表达量明显升高（P〈0．05）；与模型组比较，龙胆泻肝汤高、低剂量组明显降低卵巢质量及体积，血清LH／FSH，T，空腹血糖及INS，IL-2，IL-6，IL-10水平，升高JAK2，STAT3蛋白的表达量，降低p-STAT3和IL-6蛋白的表达量（P〈0．05）。结论：龙胆泻肝汤对PCOS大鼠具有明显疗效，主要通过降低激素水平和抑制炎症反应；且其机制可能与JAK2／STAT3通路相关。

关键词：龙胆泻肝汤多囊卵巢综合征(PCOS) 激素水平炎症因子 JAK2/STAT3通路

A Modified Landweber Iteration for General Sideways Parabolic Equations

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Acta Mathematicae Applicatae Sinica 2011年第4期27卷 727-738页

作者： Jin-bo LIU You-jun deng Department of Mathematics Changsha University of Science and Technology Changsha 410076 China School of Mathematical Sciences and Computing Technology Central South University Changsha Hunan 410075China

Abstract In this paper, we introduce a modified Landweber iteration to solve the sideways parabolic equation, which is an inverse heat conduction problem （IHCP） in the quarter plane and is severely ill-posed. We shall show that our method is of optimal order under both a priori and a posteriori stopping rule. Furthermore, if we use the discrepancy principle we can avoid the selection of the a priori bound. Numerical examples show that the computation effect is satisfactory.

关键词： inverse heat conduction problem sideways parabolic equation Landweber iteration,discrepancy principle

Moment Redistribution Effect of the Continuous Glass Fiber Reinforced Polymer-Concrete Composite Slabs Based on Static Loading Experiment

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Structural Durability & Health Monitoring 2025年第1期19卷 105-123页

作者： Zhao-jun Zhang Wen-Wei Wang Jing-Shui Zhen bo-Cheng Li De-Cheng Cai Yang-Yang Du Hui Huang Offshore Oil Engineering Co.Ltd. Tianjin300461China Department of Bridge Engineering School of TransportationSoutheast UniversityNanjing211189China

This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment *** experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was *** composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab *** methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel *** experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal *** contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading *** the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan *** the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span *** GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span *** test specimens experienced compressive failure of concrete at the mid-span *** results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support *** proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.

关键词： Moment redistribution GFRP-concrete composite slabs bending moment experimental study analysis model

Travelling Solitary Wave Solutions for Generalized Time-delayed Burgers-Fisher Equation

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Communications in Theoretical Physics 2009年第8期52卷 284-286页

作者： deng Xi-jun HAN Li-bo LI Xi School of Information and Mathematics Yangtze University Jingzhou 434023 China College of Physical Science and Technology Yangtze University Jingzhou 434023 China Department of Mathematics University of Kansas Kansas 66045 USA

In this paper,travelling wave solutions for the generalized time-delayed Burgers-Fisher equation *** using the first-integral method,which is based on the ring theory of commutative algebra,we obtain aclass of travelling solitary wave solutions for the generalized time-delayed Burgers-Fisher equation.A minor error in theprevious article is clarified.

关键词： solitary wave first-integral method ring theory time-delayed Burgers-Fisher equation

Van der Waals force-induced intralayer ferroelectric-to-antiferroelectric transition via interlayer sliding in bilayer group-Ⅳmonochalcogenides

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npj Computational Materials 2022年第1期8卷 446-454页

作者： bo Xu junkai deng Xiangdong Ding jun Sun Jefferson Zhe Liu State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University710049Xi’anChina Department of Mechanical Engineering The University of MelbourneParkvilleVIC3010Australia

Two-dimensional materials with ferroelectric properties break the size effect of conventional ferroelectric materials and unlock unprecedented potentials of ferroelectric-related application at small length *** first-principles calculations,a sliding-induced ferroelectric-to-antiferroelectric behavior in bilayer group-IV monochalcogenides(MX,with M=Ge,Sn and X=S,Se)is *** this mechanism,the top layer exhibits a reversible intralayer ferroelectric switching,leading to a reversible transition between the ferroelectric and antiferroelectric states in the bilayer *** results show that the interlayer van der Waals interaction,which is usually considered to be weak,can actually generate an in-plane lattice distortion and thus cause the breaking/forming of intralayer covalent bonds in the top layer,leading to the observed anomalous *** unique property has advantages for energy harvesting over existing piezoelectric and triboelectric *** interlayer sliding-induced big polarization change(40μC cm^(−2))and ultrahigh polarization changing rate generate an open-circuit voltage two orders of magnitude higher than that of MoS_(2)-based *** theoretical prediction of power output for this bilayer MXs at a moderate sliding speed 1 m s^(−1)is four orders of magnitude higher than the MoS_(2)nanogenerator,indicating great potentials in energy harvesting applications.

关键词： ferroelectric interlayer layer

Effects of environmental factors on corrosion behaviors of metal-fiber porous components in a simulated direct methanol fuel cell environment

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International Journal of Minerals,Metallurgy and Materials 2014年第9期21卷 913-918页

作者： Wei Yuan bo Zhou Yong Tang Zhao-chun Zhang jun deng Key Laboratory of Surface Functional Structure Manufacturing of Guangdong Higher Education Institutes School of Mechanical and Automotive Engineering South China University of Technology

Abstract： To enable the use of metallic components in direct methanol fuel cells （DMFCs）, issues related to corrosion resistance must be considered because of an acid environment induced by the solid electrolyte. In this study, we report the electrochemical behaviors of metal-fiber-based porous sintered components in a simulated corrosive environment of DMFCs. Three materials were evaluated： pure copper, AISI304, and AISI316L. The environmental factors and related mechanisms affecting the corrosion behaviors were analyzed. The results demonstrated that AISI316L exhibits the best performance. A higher SO4^2- concentration increases the risk of material corrosion, whereas an increase in methanol concentration inhibits corrosion. The morphological features of the corroded samples were also characterized in this study.

关键词： corrosion metal fibers porous sintering direct methanol fuel cells environmental factors

Recent Research on the Deformation Behavior of Particle Reinforced Magnesium Matrix Composite: A Review

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Acta Metallurgica Sinica(English Letters) 2019年第4期32卷 413-425页

作者： Kun-Kun deng Cui-Ju Wang Kai-bo Nie Xiao-jun Wang Shanxi Key Laboratory of Advanced Magnesium-Based Materials College of Materials Science and Engineering Taiyuan University of Technology School of Materials Science and Engineering Harbin Institute of Technology

Particle reinforced magnesium matrix composite(PMMC) possesses the merits of high specific strength, high specific modulus, better dimensional stability, good wear resistance and lower production cost, which is thought as a promising material in the field of aerospace, automobile, electronic communication, etc. To eliminate the casting defect, the PMMC is usually experienced hot deformation process. The present paper mainly focuses on the deformation behavior of PMMCs. First, the development of PMMCs based on particle size is introduced. Then, the hot deformation technology and deformation mechanism of PMMCs at elevated temperature are given and analyzed, respectively. After reviewing the dynamic recrystallization and texture of PMMCs, its future development is suggested based on the current research progress.

关键词： Magnesium matrix composite Particle Hot deformation Deformation mechanism Recrystallization