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Tuning mechanical behaviors of highly entangled hydrogels with the random distribution of mobile entanglements

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Applied mathematics and Mechanics(English Edition) 2024年第2期45卷 277-294页

作者： Jinlong liu Di LU Bin chen Department of Engineering Mechanics Zhejiang UniversityHangzhou 310027China beijing system Design Institute of Electro-Mechanic Engineering Beijing 100854China Intelligent Robotic Research Center Zhejiang LaboratoryHangzhou 310027China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Hangzhou 311100China

Highly entangled hydrogels exhibit excellent mechanical properties,including high toughness,high stretchability,and low *** considering the evolution of randomly distributed entanglements within the polymer network upon mechanical stretches,we develop a constitutive theory to describe the large stretch behaviors of these *** the theory,we utilize a representative volume element(RVE)in the shape of a cube,within which there exists an averaged chain segment along each edge and a mobile entanglement at each *** employing an explicit method,we decouple the elasticity of the hydrogels from the sliding motion of their entanglements,and derive the stress-stretch relations for these *** present theoretical analysis is in agreement with experiment,and highlights the significant influence of the entanglement distribution within the hydrogels on their *** also implement the present developed constitutive theory into a commercial finite element software,and the subsequent simulations demonstrate that the exact distribution of entanglements strongly affects the mechanical behaviors of the structures of these ***,the present theory provides valuable insights into the deformation mechanism of highly entangled hydrogels,and can aid in the design of these hydrogels with enhanced performance.

关键词： highly entangled hydrogel constitutive theory entanglement gamma distribution

大型交流励磁变速抽水蓄能机组技术特征与研制框架

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电网技术 2024年第6期48卷 2366-2375,I0036页

作者：陈龙翔乐振春刘永奇国家电网有限公司北京市西城区100031

交流励磁变速抽水蓄能是国际上应用最广泛成熟的变速机组技术路线,是中国抽水蓄能发展需要重点攻克的关键技术。当前,国内大型交流励磁变速抽水蓄能技术自主化工程研制和应用仍处于起步阶段,从电机设计、变频系统设计到机网协调控制策... 详细信息

交流励磁变速抽水蓄能是国际上应用最广泛成熟的变速机组技术路线,是中国抽水蓄能发展需要重点攻克的关键技术。当前,国内大型交流励磁变速抽水蓄能技术自主化工程研制和应用仍处于起步阶段,从电机设计、变频系统设计到机网协调控制策略等方面关键技术都亟待突破。为进一步攻克交流励磁变速抽水蓄能关键技术、理清研发重点,该文首先从抽水蓄能技术基本原理出发,概括不同抽水蓄能技术路线的特点和适用条件。然后,重点分析了交流励磁变速抽水蓄能机组的技术特征,提出了交流励磁变速发电电动机、水泵水轮机、变频器等核心装备的研制框架和重点。最后,给出交流励磁变速机组研制的思考和总体方法。

关键词：抽水蓄能变速机组交流励磁技术特征装备研发重点

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振动对交流电压下针板电极局部放电起始特性的影响

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华北电力大学学报（自然科学版） 2024年第4期51卷 1-8页

作者：刘云鹏陈晓曼郭佳熠刘森赵涛河北省输变电设备安全防御重点实验室(华北电力大学) 河北保定071003 新能源电力系统国家重点实验室(华北电力大学) 北京102206

高压电气设备在实际运行过程中常伴随着持续的机械振动,为探究振动对极不均匀电场局部放电起始放电特性的影响,搭建了空气中振动条件下针板电极局部放电试验平台,采集了起始放电过程的局部放电信号,在工频电压下分别研究了电极间距、振... 详细信息

高压电气设备在实际运行过程中常伴随着持续的机械振动,为探究振动对极不均匀电场局部放电起始放电特性的影响,搭建了空气中振动条件下针板电极局部放电试验平台,采集了起始放电过程的局部放电信号,在工频电压下分别研究了电极间距、振幅、振动频率对局部放电起始过程的影响规律。研究结果表明:随着振幅增加,间隙最大电场强度增大,碰撞电离过程加剧,起始放电电压降低,负半周放电次数和放电量增加,正负半周放电相位扩大;随着电极间距增加,振动对电场不均匀程度影响减小,负半周起始放电过程受振动影响逐渐减弱;振动频率会影响起晕段内高场强区的作用时间,振动频率越高,带电粒子能够获得的最大动能越小,碰撞电离过程越微弱,放电的剧烈程度越低。

关键词：振动局部放电针板电极交流电压

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面向高比例新能源接入的电氢耦合系统设想及分析

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电力自动化设备 2024年第4期44卷 1-8页

作者：羡一鸣安之刘斯伟戚庆茹夏明超陈奇芳北京交通大学电气工程学院北京100044 国网经济技术研究院有限公司北京102209

高比例新能源接入电力系统,其高随机性与波动性将造成系统“源-荷”结构失衡,且高比例电力电子化将导致传统电力系统以同步发电机和机电动态特性为基础的技术特性发生深刻变化。为此,提出了一种采用“送端绿电离网外送-受端离网制氢-氢... 详细信息

高比例新能源接入电力系统,其高随机性与波动性将造成系统“源-荷”结构失衡,且高比例电力电子化将导致传统电力系统以同步发电机和机电动态特性为基础的技术特性发生深刻变化。为此,提出了一种采用“送端绿电离网外送-受端离网制氢-氢燃气并网发电”模式的电氢耦合系统,即在送端将新能源电力汇集接入至与交流电网无电气联系的直流输电网络中,在受端满足电解水制氢直流负荷并通过氢燃气发电方式支撑交流电网,从而将大量新能源消纳和新增“西电东送”需求与送端/受端交流电网解耦。所提电氢耦合系统不仅能改善系统电力电量平衡,促进高比例新能源消纳,还能够保障电力系统的安全可靠运行,可为我国高比例新能源电力系统的演进方向提供参考。

关键词：高比例新能源电氢耦合系统直流电网电解水制氢储氢

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热-力-电耦合下天线罩电性能仿真及分析

空军工程大学学报 2024年第3期25卷 2-11页

作者：吉建民王伟余慧龙刘涓陈博北京遥感设备研究所北京100854

在实际飞行工况下,热力载荷会改变高速飞行器天线罩原有的电磁特性,从而影响制导性能。提出了一种基于六面体网格划分的热-力-电耦合模型及仿真方法,可准确表征高速飞行工况下天线罩介电温漂和结构变形对电性能的影响。基于天线罩热-力... 详细信息

在实际飞行工况下,热力载荷会改变高速飞行器天线罩原有的电磁特性,从而影响制导性能。提出了一种基于六面体网格划分的热-力-电耦合模型及仿真方法,可准确表征高速飞行工况下天线罩介电温漂和结构变形对电性能的影响。基于天线罩热-力-电共享网格模型,首先通过瞬态热仿真得到天线罩响应温度场,通过静力分析得到天线罩结构变形场。然后,将天线罩介电温漂和结构变形准确传递到其电磁仿真模型中,并采用三维射线跟踪法计算其电性能。最后通过一个典型算例对高速飞行工况下天线罩电性能的变化进行仿真和分析,结果表明电性能变化非常明显,也进一步说明了所提方法的可行性和研究的必要性。

关键词：高速飞行器天线罩热-力-电耦合介电温漂结构变形电性能

Regional suitability for settling rural migrants in urban china

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Journal of Geographical sciences 2013年第6期23卷 1136-1152页

作者： chen Yangfen WANG Jieyong liu Yansui LI Xiande Institute of Agricultural Economics and Development CAAS Beijing 100081 China Institute of Geographic sciences and Natural Resouices Research.CAS Beijing 100101 China

Despite rapid urbanization, more than 200 million people living in urban areas are still registered as ＇agricultural＇ and are ineligible for most social benefits under china＇s Hukou （or household registration） system. This paper identifies the regional suitability for settling rural migrants in urban china based on three indicators （the degree of urgency, the skills and ability of the resettled community to adapt, and the ability of the government to support that resettlement）. It takes 2008 government socioeconomic data from a county level into con- sideration. Spatial, statistical, and decision tree analyses, supported by SPSS, Geodata, and ArcGIS software, show that there are five separate population types, each with different de- grees of suitability. These include highly suitable region, region suitable for settling migrants to outside regions, region suitable for settling migrants from outside regions, region with moderate potential, and unsuitable region. This paper suggests that regional policies for set- tling rural migrants are meaningful, since the five regions are distributed relatively separately. Due to the suitability for different bodies across regions, equal treatment should be applied to both the native migrants and that across counties and provinces. Furthermore, demolishment of the social welfare discrimination adhered to Hukou system and equalization of basic public services will be of more practical significance than the so-called settling rural migrants ac- tively and steadily.

关键词： urbanization Hukou rural migrants settle down regional suitability china

十二轴交流传动电力机车储能电源技术方案设计

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电力机车与城轨车辆 2024年第3期47卷 45-49页

作者：王蕾陈哲汪发现刘革中车株洲电力机车有限公司湖南株洲412001 重载快捷大功率电力机车全国重点实验室湖南株洲412001 北京北九方轨道交通科技有限公司北京100036

为解决铁路天窗点给乘务人员带来的不便,针对十二轴交流传动电力机车设计了储能电源供电方案;实现夏天提供制冷,冬天提供制热,同时具备机车库内移车功能。方案选用钛酸锂电池作为储能装置,同时配置ac/DC充电机用于储能系统充放电;另外,... 详细信息

为解决铁路天窗点给乘务人员带来的不便,针对十二轴交流传动电力机车设计了储能电源供电方案;实现夏天提供制冷,冬天提供制热,同时具备机车库内移车功能。方案选用钛酸锂电池作为储能装置,同时配置ac/DC充电机用于储能系统充放电;另外,为了确保电池系统与高压系统隔离,与机车主电路设置了互锁机制,保障机车安全。天窗点时,储能系统通过恒频恒压支路向空调和暖风机供电;库内动车时,储能系统通过辅助变压器、主变流柜驱动电机,实现动车功能。

关键词：电力机车天窗点储能装置充电机钛酸锂电池

FEW-NNN: A Fuzzy Entropy Weighted Natural Nearest Neighbor Method for Flow-Based Network Traffic Attack Detection

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china Communications 2020年第5期17卷 151-167页

作者： Liangchen chen Shu Gao Baoxu liu Zhigang Lu Zhengwei Jiang School of Computer Science and Technology Wuhan University of TechnologyWuhan 430063China Institute of Information Engineering Chinese Academy of SciencesBeijing 100093China School of Applied Technology China University of Labor RelationsBeijing 100048China School of Cyber Security University of Chinese Academy of SciencesBeijing 100049China

Attacks such as APT usually hide communication data in massive legitimate network traffic, and mining structurally complex and latent relationships among flow-based network traffic to detect attacks has become the focus of many initiatives. Effectively analyzing massive network security data with high dimensions for suspicious flow diagnosis is a huge challenge. In addition, the uneven distribution of network traffic does not fully reflect the differences of class sample features, resulting in the low accuracy of attack detection. To solve these problems, a novel approach called the fuzzy entropy weighted natural nearest neighbor(FEW-NNN) method is proposed to enhance the accuracy and efficiency of flowbased network traffic attack detection. First, the FEW-NNN method uses the Fisher score and deep graph feature learning algorithm to remove unimportant features and reduce the data dimension. Then, according to the proposed natural nearest neighbor searching algorithm(NNN_Searching), the density of data points, each class center and the smallest enclosing sphere radius are determined correspondingly. Finally, a fuzzy entropy weighted KNN classification method based on affinity is proposed, which mainly includes the following three steps: 1、 the feature weights of samples are calculated based on fuzzy entropy values, 2、 the fuzzy memberships of samples are determined based on affinity among samples, and 3、 K-neighbors are selected according to the class-conditional weighted Euclidean distance, the fuzzy membership value of the testing sample is calculated based on the membership of k-neighbors, and then all testing samples are classified according to the fuzzy membership value of the samples belonging to each class;that is, the attack type is determined. The method has been applied to the problem of attack detection and validated based on the famous KDD99 and CICIDS-2017 datasets. From the experimental results shown in this paper, it is observed that the FEW-NNN method

关键词： fuzzy entropy weighted KNN network attack detection fuzzy membership natural nearest neighbor network security intrusion detection system

Surface charge accumulation and preflashover characteristics induced by metal particles on the insulator surfaces of 1100 kV GILs under ac voltage

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High Voltage 2020年第2期5卷 134-142页

作者： Li Xing liu Weidong Xu Yuan chen Weijiang Bi Jiangang Department of Electrical Engineering Tsinghua UniversityNo.1Qinghuayuan RoadHaidian DistrictBeijingPeople's Republic of China china Electric Power Research Institute No.15Qinghe Xiaoying East RoadHaidian DistrictPeople's Republic of China State Grid Corporation of china No.86West Chang'an AvenueXicheng DistrictBeijingPeople's Republic of China

With the increase in the voltage and capacitance of gas-insulated transmission lines(GILs),the insulation failure of GIL has attracted more and more *** understanding of the partial discharge(PD)and flashover characteristics of metal particles on the insulator surface,as well as the flashover mechanism,is necessary to reduce the failure rate and improve the reliability of the *** this study,an ultra-high voltage(UHV)ac insulator PD test and measurement system based on the cross-reference pulse current(PC)and ultra-high frequency(UHF)methods were *** PD development and flashover characteristics of 5 mm-long metal particles at different positions on the surface of a UHV ac insulator,as well as the surface charge accumulation,were *** results show that the discharge of millimetre-scale metal particles on the insulator surface under PD test conditions is relatively low(generally lower than 2PC),and it is difficult to be detected by the conventional PC and UHF methods due to their insufficient ***,it is found that the weak PDs of the millimetrescale metal particles will result in a charge accumulation on the insulator surface under ac voltage,which eventually will lead to the insulator *** PDs of the UHV ac insulator before flashover are generally small,which will make it difficult for online monitoring systems to give an effective alarm before flashover.

关键词： flash insulator charge