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Effect of Ti/V ratio on thermodynamics and kinetics of MC in γ/α matrices of Ti-V microalloyed steels

Journal of Iron and Steel Research International 2021年第8期28卷 1019-1029页

作者： Ke Zhang Xin-jun Sun Zhao-dong Li Kun Xu Tao Jia Zheng-hai Zhu Xiao-yu Ye jun-yu kang Qi-long Yong State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization Panzhihua Group Co.Ltd.Panzhihua 617000SichuanChina School of Metallurgical Engineering Anhui University of TechnologyMaanshan 243032AnhuiChina Institute of Structural Steels Central Iron and Steel Research InstituteBeijing 100081China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina

Through the solubility product theory of the ternary secondary phase,classical nucleation theory,and Ostwald ripening theory,a model was established to describe the thermodynamics and kinetics of(Ti,V)C precipitates in austenite/ferrite(y/α)*** model was used to calculate the volume fraction,precipitation-temperature-time(PTT)curve,and nucleation rate-temperature(NrT)curve of MC(M=Ti,V)precipitates in γ/α matrices in Ti-V microalloyed steels with various Ti/V ratios,which is verified by hardness tester,transmission electron microscopy and energy-dispersive X-ray *** calculations indicate that,by decreasing Ti/V ratio from Ti4V0 steel to Ti0V4 steel,the complete-dissolution temperature decreases monotonically from 1226 to 830℃,and the equilibrium volume fraction of MC pre-cipitated from austenite decreases from 0.333%to 0.091%at 900℃.Moreover,the maximum nucleation temperature of MC precipitated from α matrix decreases from 748 to 605℃and the fastest precipitation temperature decreases from 844 to 675℃as Ti/V ratio *** and NrT diagrams of MC precipitated from α matrices in different Ti-V microalloyed steels all exhibit C-shaped and inverse C-shaped *** addition,both theoretical calculation and experimental results show that when tempered at 600℃for 100 h,Ti2V2 steel shows the largest hardness value of 312 HV among the three steels tested because it has a larger volume fraction(0.364%),a larger precipitate density(1689 μm-2),and the smallest average size(8.4 nm)of(Ti,V)C *** theoretical calculations are consistent with experimental results,which indicates that the thermodynamics and kinetics model for(Ti,V)C precipitates is reliable and accurate.

关键词： (Ti V)C precipitate Thermodynamics Kinetics Ti-V microalloyed steel Coarsening rate Hardness

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Microstructure and Mechanical Properties of Precipitation Strengthened Fire Resistant Steel Containing High Nb and Low Mo

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Journal of Iron and Steel Research International 2015年第4期22卷 337-343页

作者： Zheng-yan ZHANG Qi-long YONG Xin-jun SUN Zhao-dong LI jun-yu kang Guo-dong WANG Department of Structural Steels Central Iron and Steel Research Institute State Key Laboratory of Rolling and Automation Northeastern University

Through the thermo-mechanical control process （TMCP）, a high Nb low Mo fire resistant steel with the yield strength （YS） of 521 MPa at room temperature （RT） and 360 MPa at elevated temperature （ET） of 600 ℃ was developed based on MX （M=Nb, V, Mo; X=C,N） precipitation strengthening. A series of tensile and con- stant load tests were conducted to study the mechanical properties at ET. The dynamic continuous cooling transfor- mation （CCT） as well as precipitation behavior of microalloy carbonitride was investigated by means of thermal sim- ulator and electron microscopy approaches. Results showed that the failure temperature of tested steel was deter- mined as 653 ℃, and the granular bainite was obtained when the cooling rate was higher than 10 ℃/s. In the rolled state, a certain amount of M/A islands was observed. During heating from RT to ET, M/A islands disappeared, and cementites and high dense compound precipitates （Nb, Mo, V）C with size of less than 10 nm precipitated in ferrite at ET （600 ℃）, which resulted in precipitation strengthening at ET.

关键词： fire resistant steel elevated temperature property microalloying granular bainite precipitation strengthening

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Risk assessment of oil and gas investment environment in countries along the Belt and Road Initiative

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Petroleum Science 2024年第2期21卷 1429-1443页

作者： Bao-jun Tang Chang-Jing Ji yu-Xian Zheng kang-Ning Liu Yi-Fei Ma jun-yu Chen Center for Energy and Environmental Policy Research Beijing Institute of TechnologyBeijing100081China School of Management and Economics Beijing Institute of TechnologyBeijing100081China Collaborative Innovation Center of Electric Vehicles in Beijing BeijingChina Sustainable Development Research Institute for Economy and Society of Beijing BeijingChina Institute of Carbon Neutrality ShanghaiTech UniversityShanghai201210China

With the implementation of the Belt and Road Initiative, China is deepening its cooperation in oil and gas resources with countries along the Initiative. In order to better mitigate risks and enhance the safety of investments, it is of significant importance to research the oil and gas investment environment in these countries for China's overseas investment macro-layout. This paper proposes an indicator system including 27 indicators from 6 dimensions. On this basis, game theory models combined with global entropy method and analytic hierarchy process are applied to determine the combined weights, and the TOPSIS-GRA model is utilized to assess the risks of oil and gas investment in 76 countries along the Initiative from 2014 to 2021. Finally, the GM(1,1) model is employed to predict risk values for 2022-2025. In conclusion, oil and gas resources and political factors have the greatest impact on investment environment risk, and 12 countries with greater investment potential are selected through cluster analysis in conjunction with the predicted results. The research findings may provide scientific decisionmaking recommendations for the Chinese government and oil enterprises to strengthen oil and gas investment cooperation with countries along the Belt and Road Initiative.

关键词： Belt and Road Initiative Oil and Gas Investment Risk assessment

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Hydrogel-Assisted Electrokinetics for High-Resolution and Non-invasive Flow Monitoring in Microfluidic Chips

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Chinese Journal of Chemistry 2024年第6期42卷 571-577页

作者： Na Zhao Yanni Ma Zehua yu jun Huang Xiangqian Fu Tao Qiu kang Liu MOE Key Laboratory of Hydraulic Machinery Transients School of Power and Mechanical EngineeringWuhan UniversityWuhanHubei430072 China Department of Urology Renmin Hospital of Wuhan UniversityWuhanHubei430072 China Department of Organ Transplantation Renmin Hospital of Wuhan UniversityWuhanHubei430072 China

Convenient non-invasive flow monitoring would facilitate the operation and control in microfluidic chips,but is challenging due to the small space of microchannels and complex operation required in traditional optical *** this work,we propose a novel non-invasive strategy to probe microfluidic flows via streaming potential *** sealing one side of the microchannel with a piece of hydrogel film,streaming potential inside the channel can be clearly detected by electrodes at outer surface of the hydrogel due to ion diffusion in the *** is detected without sensors contacting with the internal ***,the electrodes shape like a tiny probe,which can move around mapping the flow distribution in a chip with the spatial resolution of 1 mm and flow rate detection limit of 3μL·min–*** inside the channels can also be detected,due to the fluctuation of streaming voltage when gas-liquid interface flows through the electrode,showing an easy and potential way for multi-functional flow monitoring in microfluidic chips.

关键词： Microfluidics Hydrogels Electrokinetics Flow monitoring Non-invasive Sensor Charge transport

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Topological Stability and Entropy for Certain Set-valued Maps

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Acta Mathematica Sinica,English Series 2024年第4期40卷 962-984页

作者： yu ZHANG yu jun ZHU School of Mathematical Sciences Xiamen UniversityXiamen 361005P.R.China

In this paper,the dynamics(including shadowing property,expansiveness,topological stability and entropy)of several types of upper semi-continuous set-valued maps are mainly considered from differentiable dynamical systems points of *** is shown that(1)if f is a hyperbolic endomorphism then for eachε>0 there exists a C^(1)-neighborhood U of f such that the induced set-valued map F_(f,U)has theε-shadowing property,and moreover,if f is an expanding endomorphism then there exists a C^(1)-neighborhood U of f such that the induced set-valued map F_(f,U)has the Lipschitz shadowing property;(2)when a set-valued map F is generated by finite expanding endomorphisms,it has the shadowing property,and moreover,if the collection of the generators has no coincidence point then F is expansive and hence is topologically stable;(3)if f is an expanding endomorphism then for eachε>0 there exists a C^(1)-neighborhood U of f such that h(F_(f,U,ε))=h(f);(4)when F is generated by finite expanding endomorphisms with no coincidence point,the entropy formula of F is ***,the dynamics of the set-valued maps based on discontinuous maps on the interval are also considered.

关键词： Set-valued map orbit space hyperbolic endomorphism perturbation shadowing expansiveness topological stability entropy

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Steel-refractory reactions in lanthanum-,cerium-,and ytrium-added steels

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Journal of Iron and Steel Research International 2024年第6期31卷 1473-1485页

作者： Jian kang Hong-po Wang yu Wang College of Materials Science and Engineering Chongqing UniversityChongqing 400044China The State Key Laboratory of Mechanical Transmissions Chongqing UniversityChongqing 400044China

A systematic experimental study was conducted on the similarities and differences in the reactions between commonly used rare earth elements(REEs)and frequently used refractories in the steelmaking *** results indicate that the reaction behaviors of La,Ce,and Y with MgO,Al_(2)O_(3),and MgO·Al_(2)O_(3) crucibles differed *** consumption rates of La,Ce,and Y in the molten steel were in descending order of La>Ce>Y for smelting with all three kinds of *** the REEs reacted with the crucible,the contents of Mg and Al showed a trend of first increasing and then *** laboratory-scale smelting conditions,the reactions related to REEs were dominated by steel-crucible reactions,and the contact area between the unit mass of molten steel and refractory materials mainly determined the consumption rates of ***-and Ce-crucible reactions generated loose and porous reaction interfaces;however,Y-crucible reactions generated a dense Y_(2)O_(3) layer,dramatically suppressing the consumption rate of *** calculation indicated that the reactions between rare earth and different refractory materials were first-order *** crucible materials significantly affected the product type and morphology of the steel-crucible reaction interfaces,thereby influencing the consumption rate of *** reactions between REEs and refractories must be seriously considered,especially for small-scale smelting.

关键词： Rare earth Inclusion Refractory Thermodynamics Dynamics

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Microstructure and texture evolution of Cu–Cr–Co–Ti alloys during the two-stage cryorolling

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Rare Metals 2024年第9期43卷 4535-4547页

作者： Jia-jun Zhang Long-Jian Li Zhi-Feng Liu Zong-Ning Chen En-yu Guo Hui-jun kang Ren-Geng Li Tong-Min Wang Key Laboratory of Solidification Control and Digital Preparation Technology (Liaoning Province) School of Materials Science and EngineeringDalian University of Technology Center of Hyper-Gravity Experimental and Interdisciplinary Research Zhejiang University Ningbo Institute of Dalian University of Technology！Ningbo315000 China Key Laboratory for Light-Weight Materials Nanjing Tech University

This study entailed an investigation of the mechanical properties, microstructural and texture orientation evolutions of CuDCrDCoDTi alloys prepared via twostage cryorolling and intermediate aging treatment. To this end, X-ray diffraction and electron backscatter diffraction were employed. The results indicate that the two-stage cryorolling and intermediate aging treatments led to the development of profuse twin bundles and significantly enhanced the mechanical properties. The initial cryorolling led to coplanar slip and developed a strong Y({111} ) orientation, accelerating the formation of Goss({011} ) orientation and a Brass-type *** intermediate aging treatment relieved the restriction on dislocation slip and reoriented the grains toward the Copper({112} ) and Z({111} ) *** Z orientation, with a relatively high volume fraction,dominated the macrotexture. Secondary cryorolling intensified twinning and shear banding, transforming the Copper-type shear bands into Brass-type shear bands with rhomboidal prism morphology. The areas inside the Brasstype shear bands exhibited a Y orientation, and the areas outside the shear bands exhibited a stable Brass-type texture. The evident decrease in the weighted Schmid factors demonstrated that the two-stage cryorolling and intermediate aging treatment can modify the texture evolution and aid the design of high-performance Cu alloys.

关键词： Copper alloys Electron backscatter diffraction Macrotexture evolution Schmid factor Two-stage cryorolling

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Experimental observations on the nonproportional multiaxial ratchetting of cast AZ91 magnesium alloy at room temperature

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International Journal of Minerals,Metallurgy and Materials 2024年第5期31卷 1115-1125页

作者： Binghui Hu yu Lei Hang Li Ziyi Wang Chao yu Guozheng kang Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 610031China

The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial-torsional cyclic tests controlled by stress with various loading paths at room temperature (RT).The evolutionary characteristics and path dependence of multiaxial ratchetting were *** illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths;multiaxial ratchetting presents strong path dependence,and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional45°linear loading paths;multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress ***,stress-strain curves show a convex and symmetrical shape in axial/torsional *** ratchetting exhibits quasi-shakedown after certain loading *** abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.

关键词： cast magnesium alloy ratchetting multiaxial loading loading path stress level

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Learning in games:a systematic review

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Science China(Information Sciences) 2024年第7期67卷 133-159页

作者： Rong-jun QIN Yang yu National Key Laboratory for Novel Software Technology Nanjing University Polixir Technologies

Game theory studies the mathematical models for self-interested individuals. Nash equilibrium is arguably the most central solution in game theory. While finding the Nash equilibrium in general is known as polynomial parity arguments on directed graphs(PPAD)-complete, learning in games provides an alternative to approximate Nash equilibrium, which iteratively updates the player's strategy through interactions with other players. Rules and models have been developed for learning in games, such as fictitious play and no-regret learning. Particularly, with recent advances in online learning and deep reinforcement learning,techniques from these fields greatly boost the breakthroughs in learning in games from theory to *** a result, we have witnessed many superhuman game AI systems. The techniques used in these systems evolve from conventional search and learning to purely reinforcement learning(RL)-style learning methods,gradually getting rid of the domain knowledge. In this article, we systematically review the above techniques,discuss the trend of basic learning rules towards a unified framework, and recap applications in large ***, we discuss some future directions and make the prospect of future game AI systems. We hope this article will give some insights into designing novel approaches.

关键词： non-cooperative games learning in games no-regret learning reinforcement learning superhuman AI

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Equivalence between the internal observability and equation

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 89-97页

作者： LIU Wen-jun TU Zhi-yu School of Mathematics and Statistics Nanjing University of Information Science and TechnologyNanjing 210044China

This paper is concerned with a third order in time linear Moore-Gibson-Thompson equation which describes the acoustic velocity potential in ultrasound wave *** by the work of Kaltenbacher,Lasiecka and Marchand(Control Cybernet.2011,40:971-988),we establish an observability inequality of the conservative problem,and then discuss the equivalence between the exponential stabilization of a dissipative system and the internal observational inequality of the corresponding conservative system.

关键词： Moore-Gibson-Thompson equation internal observability exponential stability

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