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Study on tungsten sintering temperature field based on electromagnetic simulation and computational fluid dynamics

Tungsten 2024年第2期6卷 355-366页

作者： Lu-Yan Wang Yue-Guang Yu Jian-Xin Dong Kai-Ping Du shan-Yu liu Cao-Bing Li University of Science and Technology Beijing Beijing 100083China BGRIMM Technology Group Beijing 100160China China Iron&Steel Research Institute Group Beijing 100081China

In order to study the influence of various sintering variables more intuitively and clearly,electromagnetic field analysis and computational fl uid dynamics are used to analyze the infl uence of gas flow,heating power and other process parameters on the temperature range of medium-frequency sintering in this paper.The results indicate that the uniformity of temperature fi eld is determined by the gas flow rate and heating power.When the heating power is 50 kW,the stable temperature drops about 10 K for every 1 m^(3)·h^(−1)increase of hydrogen flow.The peak value of the maximum temperature diff erence on the tungsten rods gradually increases with the increase of the hydrogen flow rate,and it appears slightly later.The temperature distribution of tungsten rods in furnace is similar with diff erent hydrogen flow rate.At the same time,the closer to the furnace wall,the higher the temperature of the tungsten rod.The temperature diff erence between tungsten rods mainly occurred within 1 h after the beginning of heating.Increasing the heating power can improve the stable temperature,but has little eff ect on the heating time.Increasing heating power can increase the peak value of the maximum temperature diff erence on the tungsten rods,but has little eff ect on the occurrence time of the peak value of the maximum temperature diff erence on the tungsten rods.Increasing the heating power will increase the temperature diff erence of a single tungsten rod,but the temperature diff erence of a single tungsten rod never exceeds 65 K.This study can be used to guide the process optimization design.Combined with numerical simulation calculation,the sintering parameters with low energy consumption and high temperature uniformity can be quickly and eff ectively found,thus improving the microstructure and properties of sintered tungsten products.

关键词： Tungsten products Sintering Hydrogen flow rate Heating power

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Acetylene/argon mixture plasma to build ultrathin carbon bridge of CFx/C/MnO2 for high-rate lithium primary battery

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Rare Metals 2024年第6期43卷 2574-2584页

作者： Da-Wei Zou Xing-Guang Fu Gao-Bang Chen Yi-Fan liu Bao-shan Wu Xian Jian School of Materials and Energy University of Electronic Science and Technology of China Yangtze Delta Region Institute (Huzhou) University of Electronic Science and Technology of China

Forming an ultrathin conducting layer on a fluorinated carbon（CFx） surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries（Li/CFx） remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFxwas modified by using acetylene/argon mixture plasma combined with MnO2particles.The CFx/C/MnO2composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CFx.The excellent rate performance of CFx/C/MnO2was due to the high electrochemical activity provided by the atomicscale conductive carbon layer and ultrafine MnO2particles.Compared with pristine CFx,the charge transfer resistance of the optimized CFx/C/MnO2decreased from 218.5 to 48.2 Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g-1,The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CFxdischarge,and the high electrochemical activity of the ultrafine MnO2particles provided a faster lithium-ion diffusion rate.

关键词： C 2 H 2 /Ar plasma Fluorinated carbon Lithium primary battery MnO 2

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Experimental and numerical simulation study on the erosion behavior of the elbow of gathering pipeline in shale gas field

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Petroleum Science 2024年第2期21卷 1257-1274页

作者： En-Bin liu Shen Huang Ding-Chao Tian Lai-Min Shi shan-Bi Peng He Zheng Petroleum Engineering School Southwest Petroleum UniversityChengdu 610500SichuanChina Chongqing Natural Gas Sales Center Natural Gas BranchSinopecChongqing400023China Zhejiang Zheneng Natural Gas Operation Co. Ltd.Hangzhou 310000ZhejiangChina School of Civil Engineering and Architecture Southwest Petroleum UniversityChengdu 610500SichuanChina Louisiana Tech Univ Trenchless Technol Ctr599 Dan Reneau DrRustonLA71270USA Southwest Oil and Gas Field Branch Natural Gas Research Institute Chengdu 610213SichuanChina

During the production period of shale gas, proppant particles and rock debris are produced together,which will seriously erode the elbows of gathering pipelines. In response to this problem, this paper takes the elbow of the gathering pipeline in the Changning Shale Gas Field as an example to test the erosion rate and material removal mechanism of the test piece at different angles of the elbow through experiments and compares the four erosion models with the experimental results. Through analysis, it is found that the best prediction model for quartz sand-carbon steel erosion is the Oka model. Based on the Oka model, FLUENT software was used to simulate and analyze the law of erosion of the elbow of the gas gathering pipeline under different gas flow velocities, gas gathering pressure, particle size, length of L1,and bending directions of the elbow. And a spiral pipeline structure is proposed to reduce the erosion rate of the elbow under the same working conditions. The results show that this structure can reduce erosion by 34%.

关键词： Shale gas Gas gathering pipeline Elbow Erosion CFD

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Iodine Nutrition, Thyroid-stimulating Hormone, and Related Factors of Postpartum Women from three Different Areas in China: A Cross-sectional Survey

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Biomedical and Environmental Sciences 2024年第3期37卷 254-265页

作者： shan Xiao Yun ZOU Yan HUANG Li Chun JIANG shan ZHOU Wei Wen QIN Qiu Lan liu Chang Qing LUO Xiao Yan LU Jia Xi MAO De Qian LI Min YANG Zhen Yu YANG Li Chen Key Laboratory of Trace Element Nutrition of National Health Committee National Institute for Nutrition and HealthChinese Center for Disease Control and PreventionBeijing 100050China Hunan Key Laboratory of Typical Environmental Pollution and Health Hazards School of Public HealthHengyang Medical SchoolUniversity of South ChinaHengyang 241001HunanChina Zhejiang Provincial Center for Disease Prevention and Control Hangzhou 310051ZhejiangChina Guangxi Zhuang Autonomous Region Center for Disease Control and Prevention Nanning 530028GuangxiChina Hebei Provincial Center for Disease Control and Prevention Shijiazhuang 050021HebeiChina

Objective Studies on the relationship between iodine,vitamin A(VA),and vitamin D(VD)and thyroid function are limited.This study aimed to analyze iodine and thyroid-stimulating hormone(TSH)status and their possible relationships with VA,VD,and other factors in postpartum women.Methods A total of 1,311 mothers(896 lactating and 415 non-lactating)from Hebei,Zhejiang,and Guangxi provinces were included in this study.The urinary iodine concentration(UIC),TSH,VA,and VD were measured.Results The median UIC of total and lactating participants were 142.00µg/L and 139.95µg/L,respectively.The median TSH,VA,and VD levels in all the participants were 1.89 mIU/L,0.44μg/mL,and 24.04 ng/mL,respectively.No differences in the UIC were found between lactating and non-lactating mothers.UIC and TSH levels were significantly different among the three provinces.The rural UIC was higher than the urban UIC.Obese mothers had a higher UIC and a higher prevalence of excessive TSH.Higher UICs and TSHs levels were observed in both the VD deficiency and insufficiency groups than in the VD-sufficient group.After adjustment,no linear correlation was observed between UIC and VA/VD.No interaction was found between vitamins A/D and UIC on TSH levels.Conclusion The mothers in the present study had no iodine deficiency.Region,area type,BMI,and VD may be related to the iodine status or TSH levels.

关键词： Median urinary iodine concentration Thyroid-stimulating hormone Vitamin A Vitamin D Postpartum women

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Impedance Analysis Considering Unstable Subsystem Poles for MMC-HVDC-based Wind Farm Integration System

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CSEE Journal of Power and Energy Systems 2022年第2期8卷 634-639页

作者： Ke Ji Hui Pang shan liu Guangfu Tang China Electric Power Research Institute Beijing100192China Global Energy Interconnection Research Institute Beijing 102211China

Employing the AC/DC impedance analysis method,extensive research has been conducted on issues pertaining to harmonic resonance observed in wind farm-connected MMCHVDC systems over the past 5 years.In general,this method divides the studied system into two subsystems at AC and DC sections.Subsequently,the impedance produced by these subsystems can be used to determine the system stability by implementing Nyquist criterion or generalized Nyquist stability criterion.However,the existing impedance analysis methods usually assume the subsystems to be stable and disregard certain special cases with potentially unstable subsystems,where the unstable poles of these subsystems must be evaluated before applying Nyquist criterion.In view of this consideration,a simplified method for identifying unstable subsystem poles is presented in this paper.Hence,the shortcoming of existing impedance analyses is rectified by considering the unstable subsystem poles.The proposed method and the stability analyses are validated by the electromagnetic transient simulation performed in PSCAD/EMTDC.

关键词： AC/DC side impedance method harmonic resonance MMC-HVDC small-signal stability wind farm

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Impedance Analysis of Grid Forming Control Based Modular Multilevel Converters

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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 967-979页

作者： Rongcai Pan Guangfu Tang shan liu Zhiyuan He China Electric Power Research Institute Beijing 100192China State Grid Smart Grid Research Institute Beijing 102209China

Grid-forming control(GFC)is promising for power electronics based power systems with high renewable energy penetration.Naturally,the impedance modeling for GFC is necessary and has gained significant attention recently.However,most of the impedance analyses for GFC are based on a twolevel converter(TLC)rather than a modular multilevel converter(MMC).MMC differs from TLC with respect to its dominant multi-frequency response.It is necessary to analyze the impedance of GFC-based MMC owing to its superiority in highvoltage direct current(HVDC)transmission to interlink two weak AC systems with high renewable energy penetration.As the main contribution,this paper presents the AC-and DC-side impedance analyses for the GFC-based MMC with both power and DC voltage control using the harmonic transfer function(HTF),and compares the impedances of GFC-based MMC and TLC.It is inferred that although the impedance is mainly influenced within 200 Hz,the instability still could occur owing to negative resistance triggered by relatively larger parameters.The difference in AC-side impedance with power and DC voltage control is not apparent with proper parameters,while the DC-side impedance differs significantly.The generalized Nyquist criterion is necessary for AC-side stability owing to the relatively large coupling terms under GFC.Moreover,the coupling between AC-and DC-side impedances is noneligible,especially considering the DC-side resonance around the system resonant peak.The effects of parameters,system strength,and virtual impedance on the impedance shaping are analyzed and verified through simulations.

关键词： Sequence impedance modular multilevel converter(MMC) grid-forming control(GFC) harmonic transfer function generalized Nyquist criterion

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Seismic response of a mid-story isolated structure considering SSI in mountainous areas under long-period earthquakes

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 151-161页

作者： Wan Feng Qin Shengwu liu Dewen Zhao Tiange Zheng Yanping shan Hang Li Zhiang Peng Fusong Xu Jingran Lei Min College of Construction Engineering Jilin UniversityChangchun 130015China College of Civil Engineering Southwest Forestry UniversityKunming 650024China College of civil engineering Southwest Jiaotong UniversityChengdu 610031China

At present,there is not much research on mid-story isolated structures in mountainous areas.In this study,a model of a mid-story isolated structure considering soil-structure interaction(SSI)in mountainous areas is established along with a model that does not consider SSI.Eight long-period earthquake waves and two ordinary earthquake waves are selected as inputs for the dynamic time history analysis of the structure.The results show that the seismic response of a mid-story isolated structure considering SSI in mountainous areas can be amplified when compared with a structure that does not consider SSI.The structure response under long-period earthquakes is larger than that of ordinary earthquakes.The structure response under far-field harmonic-like earthquakes is larger than that of near-fault pulse-type earthquakes.The structure response under near-fault pulse-type earthquakes is larger than that of far-field non-harmonic earthquakes.When subjected to long-period earthquakes,the displacement of the isolated bearings exceeded the limit value,which led to instability and overturning of the structure.The structure with dampers in the isolated story could adequately control the nonlinear response of the structure,effectively reduce the displacement of the isolated bearings,and provide a convenient,efficient and economic method not only for new construction but also to retrofit existing structures.

关键词： SSI in mountainous areas long-period earthquakes mid-story isolated structure structural dynamic analysis

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Information Heterogeneity: Implications for Liquidity and Price Efficiency

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Acta Mathematicae Applicatae Sinica 2024年

作者： Zhi-hua LI Hong liu Qing-shan YANG Northeast Normal University KLAS and School of Mathematics and Statistics

This paper discusses a model about information heterogeneity. The market size, information attention and information asymmetry affect market liquidity and price information. Larger market size can lead to an increase in market liquidity and the release of price information; however, traders who possess higher information attention can quickly affect price efficiency through their trading, leading to increased price fluctuations.In addition, the increase in asymmetry scale will lead to a decrease in liquidity and a reduction in the release of price information. Under information asymmetry, large trading groups attract followers, thereby increasing market liquidity and trading intensity.

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Tuning the exciton binding energy of covalent organic frameworks for efficient photocatalysis

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Chinese Chemical Letters 2024年第2期35卷 577-583页

作者： Zhangjie Gu Zhen shan Yulan Wang Jinjian Wang Tongtong liu Xiaoming Li Zhiyang Yu Jian Su Gen Zhang Key Laboratory for Soft Chemistry and Functional Materials of Ministry of Education School of Chemistry and Chemical EngineeringNanjing University of Science and TechnologyNanjing 210094China State Key Laboratory of Photocatalysis on Energy and Environment College of ChemistryFuzhou UniversityFuzhou 350002China MIIT Key Laboratory of Advanced Display Material and Devices School of Materials Science and EngineeringNanjing University of Science and TechnologyNanjing 210094China Key Laboratory of Preclinical Study for New Drugs of Gansu Province School of Basic Medical SciencesLanzhou UniversityLanzhou 730000China

Owing to the large exciton binding energy(>100 meV)of most organic materials,the process of exciton dissociation into free electrons and holes is seriously hindered,which plays a key role in the photocatalytic system.In this study,a series of chalcogen(S,Se)-substituted mesoporous covalent organic frameworks(COFs)have been synthesized for enhanced photocatalytic organic transformations.Photoelectrochemical measurements indicate that the introduction of semi-metallic Se atom and the enlargement of conjugation degree can not only reduce the exciton binding energy accelerating the charge separation,but also reduce the band gap of COFs.As a result,the COF-NUST-36 with the lowest exciton binding energy(39.5 meV)shows the highest photocatalytic performance for selective oxidation of amines(up to 98%Conv.and 97.5%Sel.).This work provides a feasible method for designing COFs with high photocatalytic activity by adjusting exciton binding energy.

关键词： Covalent organic frameworks Exciton binding energy Atom substitution Extended conjugation Photocatalysis

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Cationic engineered nanodiamonds for efficient antibacterial surface with strong wear resistance

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Nano Research 2024年第3期17卷 939-948页

作者： Fu-Kui Li Wen-Bo Zhao Yong Wang Wen-Tao Huang Ya-Lun Ku Hang liu Rui Guo Hui-Hui Yu Kai-Kai liu Chong-Xin shan Henan Key Laboratory of Diamond Optoelectronic Materials and Devices Key Laboratory of Materials PhysicsMinistry of Educationand School of Physics&MicroelectronicsZhengzhou UniversityZhengzhou 450052China

The spread of diseases caused by bacterial adhesion and immobilization in public places constitutes a serious threat to public health.Prevention of bacteria spread by the construction of an antibacterial surface takes precedence over post-infection treatment.Herein,we demonstrate an effective antibacterial surface with strong wear resistance by constructing cationic engineered nanodiamonds(C-NDs).The C-NDs with positive surface potentials interact effectively with bacteria through electrostatic interactions,where the C-NDs act on the phospholipid bilayer and lead to bacterial membrane collapse and rupture through hydrogen bonding and residual surface oxygen-containing reactive groups.In this case,bactericidal rate of 99.99%and bacterial biofilm inhibition rate of more than 80%can be achieved with the C-NDs concentration of 1 mg/mL.In addition,the C-NDs show outstanding antibacterial stability,retaining over 87%of the antibacterial effect after stimulation by adverse environments of heat,acid,and external abrasion.Therefore,an antibacterial surface with high wear resistance obtained by integrating C-NDs with commercial plastics has been demonstrated.The antibacterial surface with a mass fraction of 1 wt.%C-NDs improved abrasion resistance by 3981 times,with 99%killing of adherent bacteria.This work provides an effective strategy for highly efficient antibacterial wear-resistant surface,showing great practical applications in public health environments.

关键词： antibacterial surface cationic engineered nanodiamonds wear-resistant

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