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Research on the variation of dielectric properties of oil-paper insulation for power equipment over a wide temperature range

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High Voltage 2024年第3期9卷 648-658页

作者： Mingze Zhang Muhe Yu Wen Zhou Yilin Liang Shengjie Lei Yunbo Shi limin qu Key Laboratory of Engineering Dielectrics and Its Application Ministry of Education Harbin University of Science and TechnologyHarbinChina School of Measurement and Communication Engineering Harbin University of Science and TechnologyHarbinChina Electric Power Research Institute State Grid Heilongjiang Electric Power Company LimitedHarbinChina

The main part of oil-immersed power equipment is oil-paper *** lower ambient temperatures,transformer oil will become *** a result,compared to those at room temperature or operating temperature,the frequency domain dielectric properties of oil-paper insulation at low temperatures are drastically *** evaluating the insulation condition of electrical equipment,it is essential to accurately determine their dielectric *** paper described the FDS test,the DC conductivity test,and the transformer oil viscosity test,which was carried out in a laboratory environment for different ageing of oil-immersed pressboard and transformer oil at 233–373 *** ef-fects of temperature on the dielectric properties at the competing mechanisms of polarisation and conductivity loss were clarified based on variations of the FDS *** the viscosity change of ageing transformer oil at low temperatures,the Arrhenius and VFT viscosity equations were used to achieve a fitting calculation in the different temperature *** on the molecular/ion transition model in the force field and electric field,the characterisation relationships between the dynamic viscosity,DC conductivity,and test temperature of transformer oil were *** limita-tions of conventional transformer oil equivalent dielectric relaxation models over a wide temperature range were finally clarified by combining the test findings of the DC con-ductivity over a wide temperature range with observed and simulated *** paper provides an essential theoretical reference when using the FDS test to diagnose the insulation performance of oil-immersed power equipment in extremely cold regions.

关键词： insulation viscosity immersed

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基于PSO-ELM的变压器油纸绝缘状态无损评估方法

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电力工程技术 2024年第3期43卷 201-208页

作者：张德文张健曲利民吴迪星刘贺千张明泽国网黑龙江省电力有限公司电力科学研究院黑龙江哈尔滨150030 哈尔滨理工大学(工程电介质及其应用教育部重点实验室) 黑龙江哈尔滨150080

油浸式电力变压器作为电网的重要组成部分,其可靠运行至关重要。针对变压器长期运行后无法定量评估其绝缘状态的问题,文中开展了油纸绝缘模型的加速老化及受潮试验,探究了油纸绝缘老化及受潮程度对其回复电压曲线的影响规律,并提出采用... 详细信息

油浸式电力变压器作为电网的重要组成部分,其可靠运行至关重要。针对变压器长期运行后无法定量评估其绝缘状态的问题,文中开展了油纸绝缘模型的加速老化及受潮试验,探究了油纸绝缘老化及受潮程度对其回复电压曲线的影响规律,并提出采用粒子群优化-极限学习机(particle swarm optimization-extreme learning machine,PSO-ELM)算法的参数预测方法,实现了基于回复电压曲线特征参量的油纸绝缘老化与受潮状态量化评估。由油纸绝缘模型理化性能分析的对比结果可知,基于PSO-ELM方法的预测值精度远高于传统ELM方法,油纸绝缘内含水率及纸板聚合度预测的绝对误差范围分别小于±0.4%、±30。

关键词：油浸式变压器油纸绝缘回复电压粒子群优化-极限学习机(PSO-ELM)算法状态评估无损检测

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变压器油纸绝缘非线性介电弛豫模型构建方法研究

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绝缘材料 2024年第3期57卷 72-81页

作者：曲利民张健孟繁昊张亮张朋宫铭辰于沐禾国网黑龙江电力有限公司电力科学研究院黑龙江哈尔滨150030 哈尔滨理工大学工程电介质及其应用教育部重点实验室黑龙江哈尔滨150080

基于频域介电响应(FDS)对变压器油纸绝缘状态进行检测时,油纸绝缘频域介电响应的非线性变化会影响绝缘评估的准确性,因此亟须开展不同老化程度油纸绝缘材料FDS非线性变化规律的研究。在实验室环境下制备了多组不同老化程度的油纸绝缘模... 详细信息

基于频域介电响应(FDS)对变压器油纸绝缘状态进行检测时,油纸绝缘频域介电响应的非线性变化会影响绝缘评估的准确性,因此亟须开展不同老化程度油纸绝缘材料FDS非线性变化规律的研究。在实验室环境下制备了多组不同老化程度的油纸绝缘模型,并在不同温度下对油纸绝缘非线性FDS进行测试。结果表明:测试激励幅值越大,FDS曲线在低频段降低越明显,且随着测试温度的升高及老化程度的增加,介质损耗因数曲线出现非线变化的特征频段向高频方向移动;本文基于修正的Davidson-Cole模型,通过曲线拟合计算得到模型中的形状参数,并以此建立基于传递函数的等效电路模型,仿真计算得到了油纸绝缘阻抗模值非线性的变化规律。根据仿真结果可知,各阶阻抗模型的电路参数与油纸绝缘介电特性非线性的变化规律密切相关,而阻抗的改变使得曲线在相应频段发生变化。

关键词：油纸绝缘老化非线性介电特性扩展Davidson-Cole模型

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Effects of preventive acupuncture or moxibustion at the Guanyuan acupoint on expression of interleukin-2 and its receptors in hypothalamus, serum, and uterus of menopausal rats

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Neural Regeneration Research 2008年第1期3卷 49-52页

作者： Xiaohong Li Yuwei He Jieping Xie Lufen Zhang Dengfang Zhou Jinghui Zhai Rui Zhan Jun Zhou limin qu Yangchun Tian School of Acupuncture and Moxibustion Beijing University of Chinese Medicine Beijing 100029 China First Affiliated Hospital of Anhui College of Traditional Chinese Medicine Hefei 230038 Anhui Province China Basic Medical College Beijing University of Chinese Medicine Beijing 100029 China

BACKGROUND： Previous studies have indicated preventive acupuncture and moxibustion at the Guanyuan point have positive effects on the immune system of menopausal rats. OBJECTIVE： To observe the effects of preventive acupuncture or moxibustion at the Guanyuan point on interleukin-2 （IL-2） and its receptor （IL-2R mRNA） levels in hypothalamus, serum, and uterus of menopausal rats. DESIGN： Randomized control animal experiment. SETTING： School of Acupuncture and Moxibustion, Beijing University of Chinese Medicine. MATERIALS： This study was performed at the Laboratory of Beijing University of Chinese Medicine from November 2004 to July 2005. The vaginal smear method was used to determine the estrus cycle of 9.5-month-old Sprague Dawley （SD） female rats. Three continuous estrus cycles were measured, and 160 rats with estrus cycle disorder, weighing （300 _＋ 20） g, were included in this study. The rats were randomly divided into four groups： preventive acupuncture group （n =48）, preventive moxibustion group （n =48）, model groups （n =48）, and 10-month-old group （n =16）. Sixteen 3.5-month-old healthy SD female rats, weighing （240 ± 20） g, were also assigned to the young group. All rats were clean grade and were purchased from the Laboratory Animal Center, Beijing University of Chinese Medicine. The experiment was in accordance with animal ethics standards. METHODS： Acupuncture was applied to the preventive acupuncture group at 10 months of age. The needle was inserted upward and perpendicularly two fen to a point that was two fen below the Guanyuan point. The rats freely moved around during needle retention （20 minutes）. Acupuncture was administered twice a week and continued for eight weeks. A moxa cone （small） moxibustion was applied to the preventive moxibustion group at 10 months of age. The rats were caught gently and kept at the same position as the preventive acupuncture group. The moxa cone was ignited and held to the Guanyuan point directly. Only one moxa cone was use

关键词： preventive acupuncture preventive moxibustion Guanyuan IL-2 IL-2R mRNA menopausal rats

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Time-Periodic Solutions to quasilinear Hyperbolic Systems on General Networks

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Chinese Annals of Mathematics,Series B 2024年第1期45卷 41-72页

作者： Peng qu School of Mathematical Sciences Fudan UniversityShanghai 200433China

For quasilinear hyperbolic systems on general networks with time-periodic boundary-interface conditions with a dissipative structure,the existence and stability of the time-periodic classical solutions are discussed.

关键词： Time-periodic solution quasilinear hyperbolic system General net-work Classical solution Asymptotic stability

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Flat jet electrochemical milling of TC4 alloy with tailoring backward parallel flow

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Chinese Journal of Aeronautics 2024年第4期37卷 574-592页

作者： Huanghai KONG Ningsong qu College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In flat jet electrochemical milling, the electrolyte forms a backward parallel flow after impacting the workpiece, resulting in a weak current density distribution on the workpiece. Poor surface quality usually occurs on the machined titanium alloy surface because it inevitably suffers from the weak current density. In this study, a method of flat jet electrochemical milling with tailoring the backward parallel flow was proposed to eliminate the negative effects caused by the weak current density. Multiphysics simulations are carried out to comprehend the mechanism of flat jetEC milling with tailoring backward parallel flow and better construct the novel tool *** on flat jet electrochemical milling of TC4 alloy with and without tailoring backward parallel flow are conducted. The results reveal that, compared with flat jet electrochemical milling without tailoring backward parallel flow, the recommended tool reduces the surface roughness by86% to 93%, and improves the material removal rate by 93% to 163% with different feed ***, the recommended tool is more conducive to maintaining the inherent hardness of the material. Finally, a surface with low Sa of 0.37 μm is obtained.

关键词： Flat jet electrochemical milling TC4 alloy Surface roughness Micro-hardness Material removal rate

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Pathways toward a pollution-free planet and challenges

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Frontiers of Environmental Science & Engineering 2024年第6期18卷 3-8页

作者： Jiuhui qu Jiaping Chen School of Environment Tsinghua UniversityBeijing 100084China College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060China

The mission of“Establishment of Zero-Pollution Earth”defined by United Nations Environment Programme aims at creation of a clean,safe and prosperous home for all human *** is of rational choice from each individual to protect our environment and demonstrates our great ambition to achieve our *** key message given in this article is that,zero pollution does not mean no discharge of pollutants and instead it can be achievable through optimizing and controlling a sound balance between pollutants discharge and capacities of decontamination through treatment and natural environmental accumulation,which can be termed as“Principle of Equilibrium”between pollution and *** on this principle,we propose and illustrate several key factors and synergistic pathways toward a pollution-free planet:quantitative determination on purification and wastewater;source control through green measures;minimization of negative side-effects;precise management through digitalized systems;and keeping sound balance between pollutants and natural *** should be noted that we would face a series of difficulties and challenges in moving forward to“Zero-Pollution Earth”.We should further develop theories,principles and tools to achieve the balance between quantity of pollutants and decontamination *** should work together to break through the bottleneck limited by“Principle of equilibrium”to establish new environmental remediation systems leading to“Zero-Pollution Earth”.

关键词： Wastewater treatment Resources Recovery Greenhouse gases Energy Pollution-free

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Different Types of Bone Fractures Observed by Terahertz Time-Domain Spectroscopy

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Acta Mechanica Solida Sinica 2024年第3期37卷 468-477页

作者： Minghao Zhang Xianjia Meng Zhiyong Wang Chuanyong qu Chuan qu Donghui Fu Department of Mechanics Tianjin UniversityTianjin300072China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin300072China

Microcracks are common in compact bone,but their continued propagation can lead to macroscopic *** microcracks cannot be visualized radiographically,necessitating alternative noninvasive methods to identify excessive microcracking and prevent *** this study,terahertz time-domain spectroscopy(THz-TDS)was used to examine bone interiors near cracks resulting from loading in bovine tibia *** loading configurations,such as impact,quasi-static loading,and fatigue loading,known to induce different types of micro-scale damage,were *** values of refractive index and absorption coefficient of the bone samples were then determined from the THz-TDS spectra acquired before loading and after *** study revealed that different loading configurations led to varying terahertz optical coefficients associated with various types of bone ***,the refractive index notably increased under fatigue loading but remained relatively stable during quasi-static *** absorption coefficient of bone decreased only under fatigue ***,samples were subjected to axial and radial impacts without sustaining *** indicated that in the undamaged state,the change in refractive index was smaller compared to after impact failure,while the change in absorption coefficient remained consistent after *** radial impact loading,changes in refractive index and absorption coefficient were significantly more pronounced than under axial *** to loading,the measured value of refractive index was 2.72±0.11,and the absorption coefficient was 6.33±0.09 mm^(−1)at 0.5 THz.

关键词： Terahertz time-domain spectroscopy Bone Microdamage Noninvasive method

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Digital Twin Technology of Human-Machine Integration in Cross-Belt Sorting System

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Chinese Journal of Mechanical Engineering 2024年第2期37卷 195-212页

作者： Yanbo qu Ning Zhao Haojue Zhang School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China Institute of Microelectronics of the Chinese Academy of Sciences Beijing 100029China Wayzim Technology Co. LtdWuxi 214108China Business School Beijing Technology and Business UniversityBeijing 100048China

The Chinese express delivery industry processes nearly 110 billion items in 2022,averaging an annual growth rate of 200%.Among the various types of sorting systems used for handling express items,cross-belt sorting systems stand out as the most ***,despite their high degree of automation,the workload for operators has intensified owing to the surging volume of express *** the era of Industry 5.0,it is imperative to adopt new technologies that not only enhance worker welfare but also improve the efficiency of cross-belt *** a balance between efficiency in handling express items and operator well-being is *** twin technology offers a promising solution in this respect.A realization method of a human-machine integrated digital twin is proposed in this study,enabling the interaction of biological human bodies,virtual human bodies,virtual equipment,and logistics equipment in a closed loop,thus setting an operating *** technologies in the proposed framework include a collection of heterogeneous data from multiple sources,construction of the relationship between operator fatigue and operation efficiency based on physiological measurements,virtual model construction,and an online optimization module based on real-time *** feasibility of the proposed method was verified in an express distribution center.

关键词： Industry 5.0 Cross-belt sorting system Human-machine integrated Digital twin Online optimization

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Physiological and psychological responses to tended plant communities with varying color characteristics

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Journal of Forestry Research 2024年第1期35卷 183-201页

作者： Siyuan Zheng Yanzhen Zhou Haiyan qu School of Architecture and Urban Planning Shenyang Jianzhu UniversityShenyang 110168People’s Republic of China

Exposure to plants has been reported to promote health and reduce stress,and plant color has direct impacts on physical and mental *** used images of common types of tended plant communities in Shenyang,China,with combinations of yellow,green,and red foliage,as experimental stimuli.A total of 27 images were used as visual *** used electroencephalography to measureαwave activity(8-13 Hz)in 40 subjects while they viewed visual *** data were combined with subjective questionnaire data to analyze the relaxing effect of images of tended plant communities with different color types and proportions on *** results revealed that,although there were slight differences between the electroencephalography and psychological findings,women were significantly more relaxed than men after viewing the *** and psychological responses varied with the types and proportions of colors in the tended plant communities:those of foliage with combinations of two or three colors induced stronger responses than images with a single ***,(1)for one-color plant communities,green or yellow plant communities induced a stronger relaxation effect than red plant communities;(2)for two-color plant communities,the optimal color proportion was 55%+45%,and the green+yellow and green+red color combinations induced a stronger relaxation effect;(3)for three-color plant communities,the relaxation effect was strongest when the color proportion was 55%green+25%yellow+20%*** data would provide a plant color matching in future plant landscape design,which may be helpful for creating healthy and relaxing environments.

关键词： Plant community Color type Color ratio Electroencephalography Subjective questionnaire

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