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Hydrogen trapping and diffusion in polycrystalline nickel:The spectrum of grain boundary segregation

Journal of Materials Science & Technology 2024年第6期173卷 225-236页

作者： yu Ding Haiyang yu Meichao Lin Michael Ortiz Senbo Xiao Jianying he Zhiliang Zhang Department of Structural Engineering Norwegian University of Science and Technology(NTNU)Trondheim 7491Norway Division of Applied Mechanics Department of Materials Science and EngineeringUppsala UniversityUppsala 75121Sweden Graduate Aerospace Laboratories California Institute of Technology1200 E.California Blvd.PasadenaCA 91125USA

Hydrogen as an interstitial solute at grain boundaries(GBs)can have a catastrophic impact on the mechanical properties of many *** the global research effort,the underlying hydrogen-GB interactions in polycrystals remain inadequately *** this study,using Voronoi tessellations and atomistic simulations,we elucidate the hydrogen segregation energy spectrum at the GBs of polycrystalline nickel by exploring all the topologically favorable segregation *** distinct peaks in the energy spectrum are identified,corresponding to different structural *** first peak(-0.205 eV)represents the most favorable segregation sites at GB core,while the second and third peaks account for the sites at GB *** incorporating a thermodynamic model,the spectrum enables the determination of the equilibrium hydrogen concentrations at GBs,unveiling a remarkable two to three orders of magnitude increase compared to the bulk hydrogen concentration reported in experimental *** identified structures from the GB spectrum exhibit vastly different behaviors in hydrogen segregation and diffusion,with the low-barrier channels inside GB core contributing to short-circuit diffusion,while the high energy gaps between GB and neighboring lattice serving as on-plane diffusion *** square displacement analysis further confirms the findings,and shows that the calculated GB diffusion coefficient is three orders of magnitude greater than that of *** present study has a significant implication for practical applications since it offers a tool to bridge the gap between atomic-scale interactions and macroscopic behaviors in engineering materials.

关键词： Hydrogen embrittlement Grain boundaries Impurity segregation Polycrystal Atomistic simulations

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Metal-to-insulator transitions in 3d-band correlated oxides containing Fe compositions

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 48-59页

作者： Yiping yu yuchen Cui Jiangang he Wei Mao Jikun Chen Key Laboratory of Advanced Materials and Devices for Post-Moore Chips Ministry of EducationUniversity of Science and Technology BeijingBeijing 100083China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Institute of Industrial Science The University of Tokyo4-6-1 KomabaMeguro-kuTokyo 153-8505Japan

Metal-to-insulator transitions (MITs),which are achieved in 3d-band correlated transitional metal oxides,trigger abrupt variations in electrical,optical,and/or magnetic properties beyond those of conventional *** such material families,iron(Fe:3d^(6)4s^(2))-containing oxides pique interest owing to their widely tunable MIT properties,which are associated with the various valence states of *** potential electronic applications also show promise,given the large abundance of Fe on *** MIT properties triggered by critical temperature (TMIT) were reported for ReFe_(2)O_(4)(Fe^(2.5+)),ReBaFe_(2)O_(5)(Fe^(2.5+)),Fe_(3)O_(4)(Fe^(2.67+)),Re_(1/3)Sr_(2/3)FeO_(3)(Fe^(3.67+)),Re Cu_(3)Fe_(4)O_(12)(Fe^(3.75+)),and Ca_(1-x)Sr_(x)FeO_(3)(Fe^(4+))(where Re represents rare-earth elements).The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of ***,we review the material family of Fe-containing MIT oxides,their MIT functionalities,and their respective *** the perspective of potentially correlated electronic applications,the tunability of the TMITand its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT *** particular,we highlight the abrupt MIT and wide tunability of TMITof Fe-containing quadruple perovskites,such as Re ***,their effective material synthesis still needs to be further explored to cater to potential applications.

关键词： metal-to-insulator transitions Fe-containing oxides charge ordering charge disproportionation

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Density-based ship detection in SAR images:Extension to a self-similarity perspective

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Chinese Journal of Aeronautics 2024年第3期37卷 168-180页

作者： Xueqian WANG Gang LI Zhizhuo JIANG yu LIU You he Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China

Nonlocal self-similarity is an important property of Synthetic Aperture Radar(SAR)images to characterize the repetitiveness of features embodied by SAR images within nonlocal areas and has been used for enhancement of SAR *** SAR ship detectors often independently handle small sub-images cropped from a large marine SAR image and do not exploit the nonlocal self-similarity *** this paper,we propose a new ship detector from the perspective of nonlocal self-similarity in SAR images to improve the ship detection performance,basically including three stages:prescreening,intra-cue calculation,and inter-cue *** the prescreening stage,we design a new Histogram-based Density(HD)feature to rapidly select candidate sub-images potentially containing ship targets from a large SAR *** the intra-cue calculation stage,target cues within a single candidate sub-image are *** the inter-cue calculation stage,thanks to the nonlocal self-similarity among different candidate sub-images in terms of density features,we innovatively extract a weighted superpixel-HD map to obtain accumulated intracues across all the candidate ***,for each candidate sub-image,we fuse its inter-cue and intra-cue to obtain final detection *** results based on real SAR images show that our newly proposed method provides a better target-to-clutter contrast and ship detection performance than those of other state-of-the-art detection approaches.

关键词： Ship detection Synthetic aperture radar(SAR) Density Self-similarity Histogram

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Numerical simulation of transient characteristics in a bulb turbine during the load rejection process

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Journal of Hydrodynamics 2024年第1期36卷 170-183页

作者： yue Lu yu-quan Zhang Zhong-wei he yuan Zheng College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China College of Energy and Electrical Engineering Hohai UniversityNanjing210098China Huadong Engineering Corporation Ltd. Hangzhou311122China

To evaluate the safety of the bulb tubular turbine,the dynamic hydraulic characteristics of a hydropower station system during the load rejection process are studied through numerical simulations and a prototype *** the developed model,a dynamic grid technology(DGT)controls the closure of the guide vane and the blade,whilst the moment balance equation and the user-defined function(UDF)provide the runner’s rotation *** 3-D transient simulation method can well predict the rotation speed and mass flow curves in the state of load *** simulation outcomes of the system performance are basically consistent with the measurement data of the *** observed,the runner is subjected to the reversely increased torque and axial force,the system is in a braking phase,and the maximum speed peaks at 144.6%of the rated ***,the internal flow of the runner is greatly affected by the closure of the guide vane,and the draft tube forms an eccentric spiral vortex *** breaks downstream,aggravating the instability of the draft ***,the transient characteristics span for the first five seconds,demonstrating the importance of establishing an efficient governing *** obtained results are useful for designing the turbine’s flow channel with a double regulating function and comprehending the turbine’s transient characteristics.

关键词： Bulb tubular turbine load rejection numerical simulation dynamic grid prototype test

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Segregation of binary particles in gas-solid fluidized bed

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Frontiers of Chemical Science and Engineering 2024年第6期18卷 113-121页

作者： Yaxiong yu Feng Lu Xuan he Fei Wei Chenxi Zhang Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China School of Chemical Engineering and Technology Xi’an Jiaotong UniversityXi’an 710049China Ordos Laboratory Ordos 017010China Institute for Carbon Neutrality Tsinghua UniversityBeijing 100084China

Particle segregation and mixing behavior play a crucial role in industrial *** study investigates the saturated jetsam fraction,which indicates the maximum capacity of flotsam to entrain jetsam,in an initially separated binary fluidized bed with particle size *** to the value of saturated jetsam fraction,three distinct regimes-segregation,mixing,and an intermediate regime-are ***,intriguing relationships between the saturated jetsam fraction and superficial gas velocity are observed,exhibiting monotonic trends in both the segregation and mixing regimes,while a unique volcano-shaped curve in the intermediate ***,a comprehensive entrainment model based on two-fluid model elucidates the observed phenomena,emphasizing the significance of mixing behavior in fluidized layer on the saturated jetsam *** work offers potential insights for evaluating segregation in industrial applications.

关键词： fluidized bed segregation binary bubbles entrainment

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Controlling underestimation bias in reinforcement learning via minmax operation

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Chinese Journal of Aeronautics 2024年第7期37卷 406-417页

作者： Fanghui HUANG Yixin he yu ZHANG Xinyang DENG Wen JIANG School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710129China College of Information Science and Engineering Jiaxing UniversityJiaxing 314001China

Obtaining the accurate value estimation and reducing the estimation bias are the key issues in reinforcement ***,current methods that address the overestimation problem tend to introduce underestimation,which face a challenge of precise decision-making in many *** address this issue,we conduct a theoretical analysis of the underestimation bias and propose the minmax operation,which allow for flexible control of the estimation ***,we select the maximum value of each action from multiple parallel state-action networks to create a new state-action value ***,a minimum value is selected to obtain more accurate value ***,based on the minmax operation,we propose two novel algorithms by combining Deep Q-Network(DQN)and Double DQN(DDQN),named minmax-DQN and ***,we conduct theoretical analyses of the estimation bias and variance caused by our proposed minmax operation,which show that this operation significantly improves both underestimation and overestimation biases and leads to the unbiased ***,the variance is also reduced,which is helpful to improve the network training ***,we conduct numerous comparative experiments in various environments,which empirically demonstrate the superiority of our method.

关键词： Reinforcement learning Minmax operation Estimation bias Underestimation bias Variance

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Floor heave mechanism for gob-side entry retaining with concrete blocks and control method:A case study

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Underground Space 2024年第2期15卷 244-259页

作者： Jiong Wang Peng Liu Manchao he Guangyuan yu Huanzhi Tian State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology(Beijing)Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China College of Mining Engineering North China University of Science and TechnologyTangshan 063210China

The issue of significant floor heave deformation in gob-side entry retaining has long been a challenging problem in the context of longwall *** paper studies the floor heave failure mechanism and control method for gob-side entry retaining with concrete blocks in Guizhou Faer Coal Mine in *** on Rankine’s earth pressure theory,the effective shear stress equation for the plastic slip of roadway floor is *** deformation mechanism of floor heave in a retaining roadway with a block wall is revealed in this *** new comprehensive control method is proposed,encompassing roof pre-splitting blasting for pressure relief,reinforcing cables for roof control,double directions control bolts for concrete block,and pliability cushion yielding ***3D numerical calculation model is established,which shows that the new method can effectively reduce the average vertical stress peak value of the entity coal floor by 34.6%and significantly reduce the pressure source causing the roadway floor ***,a multi-parameter real-time online monitoring system for mine pressure was designed,and field tests were carried *** results show that the maximum value of roadway floor heave under the new method is 163 mm,reduced by 66.9%,and the roadway floor heave is effectively *** research findings offer a fresh perspective and new ideas for controlling floor heave in mining operations.

关键词： Gob-side entry retaining Floor heave mechanism Plastic slip Control methods Mine pressure monitoring

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Theoretical insights into efficient oxygen evolution reaction using non-noble metal single-atom catalysts on W2CO2 MXene

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Rare Metals 2024年第10期43卷 5082-5094页

作者： Jing-yu Zhou Zhi-Cheng Han Shu Zhao Tao Yang da-Zhou Yan Hai-Jun yu Institute of Advanced Battery Materials and Devices College of Materials Science and EngineeringBeijing University of Technology Key Laboratory of Advanced Functional Materials Ministry of EducationBeijing University of Technology China ENFI Engineering Corporation National Engineering Research Center of Silicon-Based Materials Manufacturing Technology

The pursuit of highly active oxygen evolution reaction （OER） catalysts,especially those free of noble metals,is a focal point in fuel cell *** extensive density functional theory calculations,this study designed and evaluated the activity and stability of singleatom catalysts （SACs） composed of 3d,4d and 5d transition metals supported on tungsten-based MXene for OER *** highlighted the exceptional OER performance of Ni@W2CO2,Rh@W2CO2and Pt@W2CO2,displaying remarkably low overpotentials The catalytic activity of TM@W2CO2SACs exhibited a robust correlation with surface properties,particularly the d-band center index and surface work *** Ni@W2CO2,Rh@W2CO2and Pt@W2CO2emerged as promising candidates for OER and oxygen reduction reaction （ORR） bifunctional catalysis,while Pt@W2CO2and Rh@ W2CO2showed high potential for OER and hydrogen evolution reaction （heR） bifunctional catalysis The effectiveness of tungsten-based MXene as a substrate for non-noble-metal SACs marks a breakthrough in OER catalyst design,driving advancements towards sustainable energy solutions and addressing critical challenges in energy conversion and storage.

关键词： Density functional theory MXene Non-noble metal Oxygen evolution reaction Single-atom catalysts

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Phase Patterning of Poly(oxime-ester)for Information Encryption by Photo-induced Isomerization

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Chinese Journal of Polymer Science 2024年第10期42卷 1488-1494,I0010页

作者： yu-Fan Yang yun Bai Yi-Bao Li Chang-Fei he School of Chemistry and Chemical Engineering Gannan Normal UniversityGanzhou341000China

Crystal polymers or liquid crystal elastomers undergo a phase transition that results in a change in the corresponding optical properties,which has the potential to be applied in areas such as information encryption and *** utilization of these materials for patterning purposes requires different phase transition ***,once prepared,altering the phase transition temperature of them presents significant ***,a poly(oxime-ester)(POE)network is developed to achieve high-resolution and multilevel patterning by photo-induced *** as-prepared POE exhibits the ability to transition from an opaque state to a transparent state under temperature stimuli,with the transition temperature and kinetics dependent on UV light exposure ***,complex patterns and information can be encrypted through different selective regional exposure time and decrypted under specific temperature or cooling ***,we illustrate an example of temporal communication,where cooling time or temperature serves as the encoded *** research expands the application scope of advanced encryption materials,showcasing the potential of POE in dynamic information encryption and decryption processes.

关键词： Poly(oxime-ester) Isomerization Phase patterning Information encryption

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Microstructure and mechanical properties of a cast TRIP-assisted multiphase stainless steel

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China Foundry 2024年第3期21卷 221-228页

作者： Meng-xin Wang Zi-xiang Wu Jing-yu he Xiang Chen School of Materials Science and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory for Advanced Materials Processing Technology Ministry of EducationBeijing 100084China

Stainless steels are used in a wide range of complex environments due to their excellent corrosion *** stainless steels can offer an excellent combination of strength,toughness and corrosion resistance due to the coexistence of different *** microstructure and mechanical properties of a novel cast multiphase stainless steel,composed of martensite,ferrite,and austenite,were investigated following appropriate heat treatment processes:solution treatment at 1,050℃ for 0.5 h followed by water quenching to room temperature,and aging treatment at 500℃ for 4 h followed by water quenching to room *** show reversed austenite is formed by diffusion of Ni element during aging process,and the enrichment of Ni atoms directly determines the mechanical stability of *** austenite with a lower Ni content undergoes a martensitic transformation during plastic *** tensile strength of the specimen exceeds 1,100 MPa and the elongation exceeds 24%after solid solution,and further increases to 1,247 MPa and 25%after aging *** enhancement is due to the TRIP effect of austenite and the precipitation of the nanoscale G-phase pinning dislocations in ferrite and martensite.

关键词： multiphase stainless steel mechanical properties TRIP effect reversed austenite G-phase

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