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热老化下涂覆硅脂对110 kV电缆终端接头界面电-热-力场的影响

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绝缘材料 2024年第6期57卷 76-85页

作者：张巍韩圣斌李秀峰刘正第魏凯山东理工大学电气与电子工程学院山东淄博255000 山东七星电气科技发展有限公司山东淄博255000

为了研究热老化条件下高压电缆终端接头内涂覆硅脂对交联聚乙烯绝缘/硅橡胶绝缘复合界面多物理场分布的影响,采用COMSOL Multiphysics软件建立了110 kV电缆终端接头电-热-力多物理场模型,仿真分析了热老化下涂覆硅脂前后复合界面电场、... 详细信息

为了研究热老化条件下高压电缆终端接头内涂覆硅脂对交联聚乙烯绝缘/硅橡胶绝缘复合界面多物理场分布的影响,采用COMSOL Multiphysics软件建立了110 kV电缆终端接头电-热-力多物理场模型,仿真分析了热老化下涂覆硅脂前后复合界面电场、温度场以及应力场的分布。结果表明:界面涂覆硅脂后,增加了界面的密封性,使界面电场畸变程度减小,界面温升略微下降,但界面应力呈现不均匀分布。老化后,硅脂对硅橡胶的溶胀造成硅橡胶相对介电常数升高,界面电荷密度增大,电场强度进一步增大。温度升高加剧了硅脂对硅橡胶的渗透,使硅橡胶材料热导率降低,界面温度较老化前升高。老化后,涂覆硅脂的硅橡胶弹性模量大幅降低,界面应力进一步减小。

关键词：电缆终端接头电-热-力硅脂绝缘老化

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Study on the water-tree ageing characteristics of polyethylene/organic montmorillonite and crosslinked polyethylene/organic montmorillonite nanocomposites

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High Voltage 2023年第2期8卷 262-273页

作者： Xiufeng Li Yunmeng Yang Qiang Wang Yuan Gao Wei Zhang zhengdi liu College of Electrical and Electronic Engineering Shandong University of TechnologyZiboShandongChina State Grid Shandong Electric Power Company Weihai Wendeng Power Supply Company WendengShandongChina

The dispersion state of nanoparticles affects the properties of composites,and the crosslinking process of polymers affects the dispersion state of *** order to investigate the effects of crosslinking behaviour on the water-tree ageing characteristics of nanocomposite dielectrics at the molecular level,polyethylene/organic-montmorillonite(PE/organic montmorillonite(OMMT))and crosslinked polyethylene/organic-montmorillonite(XLPE/OMMT)nanocomposites were prepared by the melt blending method,after which the accelerated water-tree ageing experiments were conducted using a needle *** transform infrared spectroscopy,differential scanning calorimetry,successive self-nucleation annealing and scanning electron microscope(SEM)tests were conducted to characterise the properties of the samples before and after watertree *** results indicate that the initiation probability and the length of water trees in XLPE/OMMT are less than those in PE/*** carbonyl index in the watertree area of the two nanocomposites increases,indicating that the water-tree ageing is the result of electrochemical *** crystallisability of the water-tree area degrades,decreasing the crystallinity and the lamellar *** growth of water trees destroys molecular chains and crystal structures,which results in local *** are many holes for the water tree growth in the PE/OMMT ***,the crosslinked meshwork not only restricts the movement of macromolecular chains but also increases the stability of the lamellar barrier effect of *** combination of the two effects significantly improves the water-tree resistance of the XLPE/OMMT nanocomposite.

关键词： composites tree characteristics

交联度对XLPE/OMMT纳米复合材料水树枝老化特性的影响

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工程科学与技术 2023年第4期55卷 79-88页

作者：董芸滋高嫄李秀峰董瑞雪刘正第韩圣斌山东理工大学电气与电子工程学院山东淄博255000

电力系统日益提升的电压等级和复杂的运行环境,对电缆绝缘材料提出更多、更高的要求,工作在潮湿和强电场的极端环境下的绝缘材料应具有优越的电气、热和力学性能。而聚合物基纳米复合电介质以其独特的结构和优异的电气、力学及化学等性... 详细信息

电力系统日益提升的电压等级和复杂的运行环境,对电缆绝缘材料提出更多、更高的要求,工作在潮湿和强电场的极端环境下的绝缘材料应具有优越的电气、热和力学性能。而聚合物基纳米复合电介质以其独特的结构和优异的电气、力学及化学等性能获得了广泛关注。纳米复合材料的性能依赖于纳米粒子与交联所形成的微观结构形态的稳定性,为了从微观结构角度研究交联度对纳米复合材料水树枝老化特性的影响,通过调控交联时间,制备了两种不同交联度的交联聚乙烯/蒙脱土(XLPE/OMMT)纳米复合材料,并进行了加速水树枝老化实验。通过偏光显微镜观察水树枝形貌,统计水树枝长度和引发概率,并通过测试凝胶含量表征纳米复合试样的交联度;利用傅里叶红外光谱(FTIR)分析老化前后试样的化学组成变化,计算表征纳米复合试样老化程度的羰基指数和亚甲基指数;借助扫描电子显微镜(SEM)对比老化前后、水树区和非水树区结晶形态的变化,研究水树枝生长对晶体结构的破坏。结果表明:纳米复合材料的交联度影响了水树枝的引发概率,正交联状态下试样的水树枝形貌稀疏,分形维数和占空比小;试样老化过程中存在电化学降解现象,羰基基团增多;适当的交联度,可以使3维网状结构更加完善,试样的晶体尺寸差异性减小,晶体分布均匀,且老化后晶体破坏程度降低。有机化蒙脱土(OMMT)片层与基体之间形成牢固的界面作用力,增强了分子链韧性,且OMMT的屏障效应与完善的交联网络共同作用阻碍了水分子的扩散和聚集,抑制了微观水隙的产生,提高了纳米复合材料的耐水树枝能力。

关键词：交联度纳米复合材料交联聚乙烯有机蒙脱土水树枝老化

Frequency Regulation of VSC-MTDC System with Offshore Wind Farms

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Journal of Modern Power Systems and Clean Energy 2024年第1期12卷 275-286页

作者： Haoyu liu Chongru liu North China Electric Power University Beijing 102206China

Frequency regulation of voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC)system with offshore wind farms enhances the frequency stability by compensating the power for a disturbed AC ***,it is difficult to reasonably allocate frequency-regulation resources due to a lack of coordination mechanisms between wind farms and the MTDC ***,it is difficult for the frequency control of the wind farms to manage changes in wind speed;and the risk of wind-turbine stalls is ***,based on the kinetic energy of wind turbines and the power margin of the converters,the frequency-regulation capability of wind turbines is evaluated,and a dynamic frequency-support scheme considering the real-time frequency-support capability of the wind turbines and system frequency evolution is proposed to improve the frequency-support performance.A power adaptation technique at variable wind speeds is developed;the active power in the frequency-support stage and restoration stage is switched according to the wind speed.A hierarchical zoning frequency-regulation scheme is designed to use the frequency-regulation resources of different links in the MTDC system with wind *** simulation results show that the novel frequency-regulation strategy maintains frequency stability with wind-speed changes and avoids multiple frequency dips.

关键词： Wind generation voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC) frequency regulation cooperative control adaptive control variable wind speed

A Novel Design of a Pre-separation Panel Structure to Protect Against the Impact of an Explosion in an Aircraft Plenum Chamber

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Acta Mechanica Solida Sinica 2024年第1期37卷 166-180页

作者： Zongxing liu Xiang Yang Jun liu School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China COMAC Shanghai Aircraft Design and Research Institute Shanghai 201210China

To reduce the damage of the pressurizing panel structure of a fuselage caused by an explosion at the“least risk bomb location”in an aircraft structure,a new pre-separation panel structure was designed to resist blast ***,the dynamic strain response and morphology of impact damage of the new pre-separation panel were measured in an impact damage ***,the commercial software LS-DYNA was used to calculate the propagation of the blast shock wave,and the results were compared with empirical equations to verify the rationality of the numerical calculation ***,the fluid–structure coupling method was used to calculate the damage process of the pre-separation panel structure under the impact of an explosion wave and an impact *** calculated results were in good agreement with the test results,which showed the rationality of the calculation method and the *** residual strength of the damaged pre-separation panel was significantly higher than that of the original damaged *** results show that the new pre-separation panel structure is reasonable and has certain significance for guiding the design of plenum chambers with strong resistance to implosion for aircraft fuselages.

关键词： Pre-separation panel structure Explosive response Residual strength Aircraft plenum chamber Least risk bomb location

Effectiveness and safety of acupuncture in treatment of pregnancyrelated symptoms:a systematic review and Meta-analysis

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Journal of Traditional Chinese Medicine 2024年第1期44卷 16-26页

作者： liu Tingting liu Tongou liu Mingfu School of Traditional Chinese Medicine Clinical Medicine Hubei University of Traditional Chinese MedicineWuhan 430000China First Clinical College of Hubei University of Traditional Chinese Medicine Wuhan 430000China Department of Acupuncture and Tuina Affiliated Hospital of Hubei University of Traditional Chinese MedicineHubei Provincial Hospital of Traditional Chinese MedicineWuhan 430000China

OBJECTIVE:To systematically evaluate the efficacy and safety of acupuncture(AM)in the treatment of pregnancyrelated symptoms such as acute vomiting during ***:We comprehensively searched the available literature up to November 2021,including Pub Med,Embase,Cochrane Library,Chinese Biomedical Literature Database,and China National Knowledge Infrastructure Database,for randomized controlled trials(RCTs)on AM for the treatment of severe vomiting,insomnia,pharyngeal and pelvic pain,mood abnormalities,and dyspepsia during ***:Sixteen RCTs with a cumulative sample size of 1178 cases were *** these,964 patients were included in the *** Meta-analysis results showed that AM was more efficient than Western medicine in treating discomfort during pregnancy[odds ratio(OR)=1.19,95%confidence interval(CI)(1.11,1.28),P<0.01].AM was better than the control group in improving the visual analog scale scores[standard mean difference(SMD)=0.62,95%CI(0.53,0.71),P<0.01].AM was superior to the control group in improving Numerical Rating Scale(NRS)symptom scores[OR=7.31,95%CI(3.36,15.94),P<0.01].There was no significant difference in adverse effects between the AM and sham-AM groups and the analgesic drug group[OR=0.70,95%CI(0.39,1.28),P=0.25],but the treatment and control groups had mild adverse effects with a low ***:AM is more effective than other treatments or pharmacotherapy alone in the treatment of pregnancy-related symptoms,and is relatively ***,the quality of the included trials was rather poor,and high-quality studies are required to confirm our findings.

关键词： acupuncture pregnancy nausea vomiting sleep initiation and maintenance disorders low back pain pelvic pain mood abnormalities Meta-analysis systematic review

Stochastic Unit Commitment with High-Penetration Offshore Wind Power Generation in Typhoon Scenarios

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Journal of Modern Power Systems and Clean Energy 2024年第2期12卷 535-546页

作者： Yanqi liu Dundun liu Hongcai Zhang State Key Laboratory of Internet of Things for Smart City and Department of Electrical and Computer Engineering University of MacaoMacao 999078China University of Macao Zhuhai UM Science and Technology Research Institute ZhuhaiChina

To tackle the energy crisis and climate change,wind farms are being heavily invested in across the *** China's coastal areas,there are abundant wind resources and numerous offshore wind farms are being *** secure operation of these wind farms may suffer from typhoons,and researchers have studied power system operation and resilience enhancement in typhoon ***,the intricate movement of a typhoon makes it challenging to evaluate its spatial-temporal *** published papers only consider predefined typhoon trajectories neglecting *** address this challenge,this study proposes a stochastic unit commitment model that incorporates high-penetration offshore wind power generation in typhoon *** adopts a data-driven method to describe the uncertainties of typhoon trajectories and considers the realistic anti-typhoon mode in offshore wind farms.A two-stage stochastic unit commitment model is designed to enhance power system resilience in typhoon *** formulate the model into a mixed-integer linear programming problem and then solve it based on the computationally-efficient progressive hedging algorithm(PHA).Finally,numerical experiments validate the effectiveness of the proposed method.

关键词： Unit commitment two-stage stochastic programming offshore wind farm typhoon

Devolatilization of high viscous fluids with high gravity technology

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Chinese Journal of Chemical Engineering 2024年第7期71卷 249-257页

作者： Jibing Qi Youzhi liu Yandong liu Taiyuan University Taiyuan 030032China Shanxi Province Key Laboratory of Higee-Oriented Chemical Engineering North University of ChinaTaiyuan 030051China

Volatile organic compounds(VOCs)are generally toxic and harmful substances that can cause health and environmental *** removal of VOCs from polymers has become a key *** effective devolatilization to remove VOCs from high viscous fluids such as polymer is necessary and is of great *** this study,the devolatilization effect of a rotating packed bed(RPB)was studied by using polydimethylsiloxane as the viscous fluid and acetone as the *** devolatilization rate and liquid phase volume(KLa)have been *** results indicated that the optimum conditions were the high-gravity factor of 60,liquid flow rate of 10 L·h^(-1),and vacuum degree of 0.077 *** dimensionless correlation of KLa was established,and the deviations between predicted and experimental values were less than±28%.The high-gravity technology will result in lower mass transfer resistance in the devolatilization process,enhance the mass transfer process of acetone,and improve the removal effect of *** work provides a promising path for the removal of volatiles from polymers in combination with high-gravity *** can provide the basis for the application of RPB in viscous fluids.

关键词： High-gravity technology Devolatilization rate High viscous fluid Volatile organic compounds(VOCs)

Revealing the role of electrode potential micro-environments in single Mn atoms for carbon dioxide and oxygen electrolysis

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Nano Research 2024年第9期17卷 7957-7966页

作者： Pengcheng liu anyi liu Kaili Wang Shuai Shi Mengmeng Jin Jingxiu liu Tao Qin Qian liu Xijun liu Jia He Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion School of Chemistry and Chemical EngineeringInstitute of New-Energy Materials and Low-Carbon TechnologiesSchool of Materials Science and EngineeringTianjin University of TechnologyTianjin 300384China School of Chemistry and Chemical Engineering and Environmental Engineering Weifang UniversityWeifang 261061China Department of Electrical Engineering and Automation Luoyang Institute of Science and TechnologyLuoyang 471023China Institute for Advanced Study Chengdu UniversityChengdu 610106China State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured MaterialsSchool of ResourcesEnvironment and MaterialsGuangxi UniversityNanning 530004China

Elucidation the relationship between electrode potentials and heterogeneous electrocatalytic reactions has attracted widespread *** we construct the well-defined Mn single-atom(MnSA)catalyst with four N-coordination through a simple thermal pyrolysis preparation method to investigate the electrode potential micro-environments effect on carbon dioxide reduction reactions(CO_(2)RR)and oxygen reduction reactions(ORR).MnSA catalysts generate higher CO production Faradaic efficiency of exceeding 90%at-0.9 V for CO_(2)RR and higher H_(2)O_(2)yield from 0.1 to 0.6 V with excellent ORR *** functional theory(DFT)calculations based on constant potential models were performed to study the mechanism of MnSA on CO_(2)*** thermodynamic energy barrier of CO_(2)RR is lowest at-0.9 V *** hydrogen electrode(RHE).Similar DFT calculations on the H_(2)O_(2)yield of ORR showed that the H_(2)O_(2)yield at 0.2 V was *** study provides a reasonable explanation for the role of electrode potential micro-environments.

关键词： electrode potential micro-environments Mn single-atom catalyst carbon dioxide reduction reaction oxygen reduction reaction constant potential models