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Effect of Q-P-T Process on the Microstructure and Mechanical Properties of 300M Steel

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Effect of Q-P-T Process on the Microstructure and Mechanical...

基于虚拟阻抗的多落点混合级联直流系统故障电流抑制方法

中国材料大会2012

作者： Ruiwen Zhao tianqi liu Xinqing Zhao School of Materials Science and Engineering Beihang University Beijing Institute of Aeronautical Materials

ISBN: (纸本)9783037856093

The effect of Quenching-Partitioning-Tempering（Q-P-T） process on the microstructure and mechanical properties of 300M steel were investigated.X-ray diffraction,scanning electron microscopy and optical microscope were employed to characterize the evolution of microstructure as well as the volume fraction of retained *** results showed that the samples treated by Q-P-T possess more retained austenite compared with traditional Quenching-Tempering *** Q-P-T,the strength increased slightly,while the ductility and toughness improved *** analysis indicated the difference between Q-T and Q-P-T process lies in the amount of the retained austenite as well as the size and size distribution of the martensite *** Q-T resulted in a little of thin film-like retained austenite in addition to wide martensite strip,while the Q-P-T resulted in large amount of thick-like austenite accompanying narrow martensite ***,300M steel with better ductility and toughness could be obtained by Q-P-T heat treatment.

关键词： 300M steel Q-P-T Martensite Retained austenite Product of strength and elongation.

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电力自动化设备 2023年第2期43卷 191-196,202页

作者：吴海艳江琴李保宏刘天琪张敏王腾鑫四川大学电气工程学院四川成都610065 国网山西省电力有限公司电力科学研究院山西太原030012

多落点混合级联直流系统存在特有的模块化多电平换流器(MMC)功率盈余问题。当受端交流系统发生短路故障时,MMC过流、过压将引起MMC阀组闭锁,进一步可能导致系统功率中断。多落点混合级联直流系统整流侧采用电网换相型换流器(LCC)、逆变... 详细信息

多落点混合级联直流系统存在特有的模块化多电平换流器(MMC)功率盈余问题。当受端交流系统发生短路故障时,MMC过流、过压将引起MMC阀组闭锁,进一步可能导致系统功率中断。多落点混合级联直流系统整流侧采用电网换相型换流器(LCC)、逆变侧采用LCC与多台MMC级联。针对该系统提出一种适用于受端交流系统故障的故障电流限制方法,在逆变侧MMC控制中引入虚拟阻抗降低故障电流,无需额外添加设备。对虚拟阻抗的控制引入、计算以及投入实现过程进行了详细阐述,并在PSCAD/EMTDC中搭建模型进行仿真分析。结果表明,所设计的虚拟阻抗控制器可以实现故障电流的有效抑制,并防止功率倒送,从而实现混合级联直流系统的交流故障成功穿越和功率可靠传输。

关键词：多落点混合级联直流系统协调控制策略故障穿越限流措施虚拟阻抗

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

Research on the Voltage Interaction of Multi-Infeed HVDC System and Interaction Factor

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Journal of Power and Energy Engineering 2015年第4期3卷 41-48页

作者： Shengjun Zhou Guangyao Qiao Chuan He Wenhui Wang tianqi liu State Grid Corporation State Grid Smart Gird Research Institute Beijing 102200 China School of Electrical Engineering and Information Sichuan University Chengdu 610065 China

In multi-infeed HVDC system, the interactions and influences between DC systems AC systems are complex as the electrical distances among DC converter stations which are relatively short. Multi-infeed interaction factor (MIIF) can effectively reflect the interaction among DC systems. The paper theoretically analyzes the impact factors of MIIF like the electrical distances between two DC converter stations and the equivalent impedance of the receiving end AC system. By applying the Kirchhoff’s current law on the inverter AC bus, the paper deduces the analytical expressions for MIIF. From the expression, it is clear how the equivalent impedance of AC system and coupling impedance can affect MIIF. PSCAD simulations validate the effectiveness and the correctness of the proposed expression and some useful conclusions are drawn.

关键词： Multi-Infeed HVDC Inverter Bus Voltage Voltage Interaction Interaction Factor Equivalent Impedance Coupling Impedance

NON-YELLOWING2 （NYE2）, a Close Paralog of NYE1, Plays a Positive Role in Chlorophyll Degradation in Arabidopsis

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Molecular Plant 2016年第4期9卷 624-627页

作者： Wu, Shouxin Li, Zhongpeng Yang, Lifeng Xie, Zuokun Chen, Junyi Zhang, Wei liu, tianqi Gao, Shan Gao, Jiong Zhu, Yihua Xin, Jiwen Ren, Guodong Kuai, Benke Fudan Univ Sch Life Sci Fudan Inst Plant Biol State Key Lab Genet Engn Shanghai 200438 Peoples R China Huazhong Agr Univ Coll Plant Sci & Technol Natl Key Lab Crop Genet Improvement Wuhan 430070 Peoples R China

Dear Editor,Plant senescence is an integral part of plant development, with old organs senescing in association with the emergence and development of nascent ones. Rapid chlorophyll （Chl） degradation, the most prominent event during green organ senescence, is proposed to be a key detoxification process to facilitate massive nutrient remobilization （Lim et al., 2007）.

关键词： senescence integral development

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系统性金融风险如何认定

中国金融 2024年第10期 12-16页

作者：孙天琦刘通中国人民银行金融稳定局

系统重要性银行倒闭必然属于系统性金融风险,非系统重要性银行倒闭是否会引发系统性金融风险,需具体情况具体分析党中央高度重视防范系统性金融风险。习近平总书记在2023年中央金融工作会议上的讲话指出,“要提高紧急状态下风险研判的... 详细信息

系统重要性银行倒闭必然属于系统性金融风险,非系统重要性银行倒闭是否会引发系统性金融风险,需具体情况具体分析党中央高度重视防范系统性金融风险。习近平总书记在2023年中央金融工作会议上的讲话指出,“要提高紧急状态下风险研判的准确性,完善系统性风险认定机制”“牢牢守住不发生系统性金融风险的底线”;在2024年1月省部级主要领导干部推动金融高质量发展专题研讨班上的讲话指出,“防范化解系统性风险是防控风险的重中之重”“对系统性风险要有认定办法”。本文重点讨论如何完善符合我国实际的系统性金融风险认定框架。

关键词：系统性金融风险系统性风险防范化解系统重要性银行认定办法风险研判防控风险紧急状态

Experimental and numerical study on ignition and combustion characteristics of boron-magnesium composite powders

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Particuology 2024年第1期84卷 12-29页

作者： Shuyuan liu Luyang Han Hongmei liu Yingkai Song Linlin liu Songqi Hu Science and Technology on Combustion Internal Flow and Thermo-Structure LaboratoryNorthwestern Polytechnical UniversityXi'an710072China School of Mechanical Engineering and Rail Transit Changzhou UniversityChangzhou213164China Shanghai Institute of Space Propulsion Shanghai201112China Shanghai Engineering Research Center of Space Engine Shanghai201112China

A high-pressure laser ignition and combustion system with adjustable oxidizer gas atmosphere is established to investigate the ignition and combustion characteristics of boron-magnesium(BM)com-posite *** ignition and combustion model of BM powders is established and validated in the present *** results show that increasing water content,O_(2) content and Mg content all result in shorter ignition delay time of BM powders,among which the effect of water content is the most ***,ignition delay time increases as pressure *** combustion time decreases with increasing Mg content and ambient pressure but increases with water *** the increase of O_(2) content,combustion time of BM powders first increases and then decreases,which means a critical O_(2) content exists above which combustion time *** results show that there exists a trade-off between ignition and combustion performance of BM composite powders.

关键词： Boron magnesium powder Laser ignition Ignition and combustion model Reaction mechanism Numerical model

基于直流电流控制的特高压直流分层接入系统协调控制策略

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电力系统保护与控制 2022年第19期50卷 167-178页

作者：王顺亮谢洋马俊鹏刘天琪李小鹏曾雪洋四川大学电气工程学院四川成都610042 国网四川省电力公司电力科学研究院四川成都610095

为解决特高压直流分层接入系统中传统换相失败预防方法的失效问题,提出一种基于直流电流控制的协调控制策略。该策略在深入分析换相失败发生的主次要因素的基础上,通过检测交流系统故障,根据故障层换相失败预防控制的输出,提前触发非故... 详细信息

为解决特高压直流分层接入系统中传统换相失败预防方法的失效问题,提出一种基于直流电流控制的协调控制策略。该策略在深入分析换相失败发生的主次要因素的基础上,通过检测交流系统故障,根据故障层换相失败预防控制的输出,提前触发非故障层换相失败预防控制。同时根据交流母线电压的跌落程度自适应地降低故障初期的直流电流,增大非故障层的换相失败免疫能力,改善故障层的后续换相失败。在PSCAD/EMTDC中搭建特高压直流分层接入系统。仿真结果表明,该策略能够有效抑制非故障层的换相失败和缓解故障层的后续换相失败,大幅度提升故障时期直流功率的传输,有利于电力系统安全稳定运行。

关键词：特高压直流输电分层接入系统直流电流控制协调控制换相失败

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CFD-DEM simulation of high density particles fluidization behaviors in 3D conical spouted beds

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Particuology 2024年第5期88卷 266-281页

作者： Lin Jiang Mofan Qiu Rongzheng liu Bing liu Youlin Shao Malin liu Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing 100084China

The spouted bed has been used in the coating process of high-density nuclear fuel *** particle fluidization behaviors in pseudo-2D and 3D spouted beds were simulated and *** effects of four independent variables(cone angle,particle density,inlet gas velocity,and particle loading)on particle fluidization behaviors in the 3D spouted bed were investigated *** cone angle effect on fluidization mechanism was studied quantitatively first time.A new fluidization quality index was proposed based on the particle entrainment principle,and an extreme value was obtained when the cone angle was 60°,considered to be the optimum value for the 3D conical spouted *** was indicated the gas–solid contact efficiency can be kept up if the gas velocity was proportional to ρ_(p)^(0.65) and N_(p)^(0.78) when the particle density or loading was *** results will be useful for geometry and operation parameters design of the 3D conical spouted bed and helpful for developing the fluidization mechanism of high-density particles.

关键词： Spouted bed High-density particle CFD-DEM Fluidization quality index Particle loading