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Modified constitutive models for Inconel 718 considering current density and temperature in electrically assisted forming process

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Chinese Journal of Aeronautics 2024年第2期37卷 524-540页

作者： Xuan CUI rui zhao Min WAN School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Jiangxi 330000China

Electrically Assisted Forming(EAF)technology has obvious advantages in material *** develop an effective constitutive model considering electrical effects,room temperature and electrically assisted quasi-static uniaxial tensile tests were conducted using ultrathin nickelbased superalloy plates with a thickness of 0.25 *** research focused on the two most widely recognized effects:the Joule thermal and the electric athermal *** mechanism of current action can be divided into two scenarios:one considering the Joule thermal effect only,and the other considering both effects *** basic constitutive models,namely the Modified-Hollomon model and the Johnson-Cook(J-C)model,were selected to be optimized through the classification of two different situations,and four optimized constitutive models were *** was found that the J-C model with simultaneous consideration of the Joule thermal effect and electric athermal effect had the best prediction effect by comparing the results of these four ***,the accuracy of the optimization model was verified by finite element simulation of the electrically assisted stretching optimization *** results show that the constitutive model can effectively predict the temperature effect caused by the Joule heat effect and the athermal effect of current on the material.

关键词： Joule heating Elastoplasticity Plastic deformation Superalloys Constitutive models

Cathodic corrosion as a facile and universal method for scalable preparation of powdery single atom electrocatalysts

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Nano Research 2024年第6期17卷 4943-4950页

作者： rui Li Xiayan Yan Meng Liu Qingkai zhao Jie Du Xinxin Tan Jingwen Ba Rongguang zeng Wenhua Luo Jingsong Xu Institute of Materials China Academy of Engineering PhysicsJiangyou 621907China Science and Technology on Surface Physics and Chemistry Laboratory Jiangyou 621908China

Top-down strategy has been widely applied for synthesis of metal single atom catalysts(SACs)via converting metal nanoparticles or bulk metals into atomically dispersed ***,we report a simple electrochemical atomic migration strategy for top-down synthesis of SACs via a facile cathodic corrosion process without involving high temperature or harsh *** of metal nanoparticles on cathode are firstly disbanded under high negative voltage,and emitted into the electrolyte in the form of atomic metal anions in Zintl *** escaped atomically dispersed metal species are then oxidized by water molecules and captured by the defects on the pre-added nitrogen doped carbon carriers in the *** cathodic corrosion strategy is confirmed to be suitable for scalable synthesis of kinds of metal SACs(e.g.,Pt,Pd,and Ir)on doped carbon ***,the as-prepared nitrogen doped carbon powder supported Pt SACs exhibit superior catalytic activity toward hydrogen evolution reaction(HER)with a low overpotential of 0.024 V at 10 mA·cm^(−2)and a low Tafel slope of 29.7 mV·dec^(−1)as well as a long-term durability.

关键词： cathodic corrosion top-down strategy powdery single atom catalysts hydrogen evolution reaction scalable synthesis

Plasma-exfoliated g-C_(3)N_(4) with oxygen doping: tailoring photocatalytic properties

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Frontiers of Chemical Science and Engineering 2024年第2期18卷 27-39页

作者： Yuxin Li Junxin Guo rui Han zhao Wang National Engineering Research Centre of Industry Crystallization Technology School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

Heteroatom doping and defect engineering have been proposed as effective ways to modulate the energy band structure and improve the photocatalytic activity of g-C_(3)N_(4). In this work, ultrathin defective g-C_(3)N_(4) was successfully prepared using cold plasma. Plasma exfoliation reduces the thickness of g-C_(3)N_(4) from 10 nm to 3 nm, while simultaneously introducing a large number of nitrogen defects and oxygen atoms into g-C_(3)N_(4). The amount of doped O was regulated by varying the time and power of the plasma treatment. Due to N vacancies, O atoms formed strong bonds with C atoms, resulting in O doping in g-C_(3)N_(4). The mechanism of plasma treatment involves oxygen etching and gas expansion. Photocatalytic experiments demonstrated that appropriate amount of O doping improved the photocatalytic degradation of rhodamine B compared with pure g-C_(3)N_(4). The introduction of O optimized the energy band structure and photoelectric properties of g-C_(3)N_(4). Active species trapping experiments revealed ·O_(2)^(–) as the main active species during the degradation.

关键词： graphitic carbon nitride cold plasma oxygen doping nitrogen defect visible-light photocatalysis

Microstructure evolution and mechanical properties of brazing joint for ultra-thin-walled Inconel 718 considering grain size effect and brazing temperature

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Chinese Journal of Aeronautics 2024年第2期37卷 541-556页

作者： rui zhao Yueshuai SONG Hui KANG Min WAN School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Jiangxi 330000China

The systematic investigation of the mechanical properties and microstructure evolution process of ultra-thin-walled Inconel 718 capillary brazing joints is of great significance because of the exceptionally high demands on its *** achieve this objective,this study investigates the impact of three distinct brazing temperatures and five typical grain sizes on the brazed joints’mechanical properties and microstructure evolution *** evolution analysis was conducted based on Electron Back Scatter Diffraction(EBSD),Scanning Electron Microscopy(SEM),X-Ray Diffraction(XRD),High-Resolution Transmission Electron Microscopy(HRTEM),and Focused Ion Beam(FIB).Besides,the mechanical properties and fracture behavior were studied based on the uniaxial tension tests and in-situ tension *** findings reveal that the brazing joint’s strength is higher for the fine-grain capillary than the coarse-grain one,primarily due to the formation of a dense branch structure composed of G-phase in the brazing *** effects of grain size,such as pinning and splitting,are amplified at higher brazing ***,micro-cracks initiate around brittle intermetallic compounds and propagate through the eutectic zone,leading to a cleavage fracture *** fracture stress of fine-grain specimens is higher than that of coarse-grain due to the complex micro-crack ***,this study contributes significantly to the literature by highlighting the crucial impact of grain size on the brazing properties of ultra-thin-walled Inconel 718 structures.

关键词： EYWORDS Ultra-thin-walled structure Brazing Inconel 718 Grain size effect Brazing temperature

Anomalous spin Josephson effect in spin superconductors

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Chinese Physics B 2024年第3期33卷 126-131页

作者：曾文沈瑞 School of Physics and Electronic Engineering Jiangsu UniversityZhenjiang 212013China Jiangsu Engineering Research Center on Quantum Perception and Intelligent Detection of Agricultural InformationZhenjiang 212013China National Laboratory of Solid State Microstructures and School of Physics Nanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor *** an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor *** we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin *** the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor *** the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane *** symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.

关键词： tunneling junction spin supercurrent 0-πtransition anomalous spin Josephson effect

Examination of two-phase behaviors in porous media during pool boiling

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Science China(Technological Sciences) 2024年第6期67卷 1695-1713页

作者： ZHANG ZhiHao GUAN ShuYa WU rui zhao ChangYing School of Mechanical Engineering Shanghai Jiao Tong University

The enhancement of pool boiling heat transfer using porous media has been extensively *** the two-phase distribution and evolution in porous media are crucial to the heat transfer performance,including the critical heat flux(CHF)and heat transfer coefficient(HTC),direct observation of the two-phase flow inside the media is limited owing to the blockage of the direct view from the porous *** this study,pool boiling visualization experiments were conducted on porous samples with different throat widths in deionized *** results showed that the HTC increased with the throat ***,the growth-contraction cycle of the vapor region and the formation and drying of the wall liquid film inside the porous media were *** vapor region,including the maximum and minimum areas in the boiling cycle,was quantitatively ***,the relationship between the minimum gas-phase area and HTC peak was identified.A one-dimensional transient model was developed considering solid skeleton heat conduction,liquid film evaporation,and vapor region growth to quantitatively study the influence of heat flux on the internal two-phase *** model successfully captured the maximum gas-phase area,duration of boiling cycles,and HTC trends at specific heat *** results of this quantitative study provide insights into the internal two-phase distribution and evolution induced by pool boiling.

关键词： porous media two-phase behaviors pool boiling

Self-initiated static-dynamic state transition behavior and triggering mechanism of strain rockburst using three-dimensional discrete element method

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Underground Space 2024年第3期16卷 143-163页

作者： Yuan Qian Cheng zhao rui Wei rui Zhang Lin Huang Huiguan Chen Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China School of Engineering Tibet UniversityLhasaTibet850000China

The accurate understanding of rockburst mechanism poses a global challenge in the field of rock *** for strain rockburst,achieving self-initiated static-dynamic state transition is a crucial step in the formation of catastrophic ***,the state transition behavior and its impact on rockburst have not received sufficient attention,and are still poorly ***,this study specifically focuses on the state transition behavior,aiming to investigate its abrupt transition process and formation mechanism,and triggering effects on *** facilitate the study,a novel burst rock-surrounding rock combined laboratory test model is proposed and its effectiveness is validated through experiment ***,corresponding numerical models are established using the three-dimensional(3D)discrete element method(DEM),enabling successful simulation of static brittle failure and rockbursts of varying intensities under quasi-static displacement loading ***,through secondary development,comprehensive recording of the mechanical and energy information pertaining to the combined specimen system and its subsystems is *** a result of numerical investigation studies,the elastic rebound dynamic behavior of the surrounding rock was discovered and identified as the key factor triggering rockburst and controlling its *** impact loading on the burst rock,induced by elastic rebound,directly initiates the dynamic processes of rockburst,serving as the direct ***,the transient work and energy convergence towards the burst rock resulting from elastic rebound are recognized as the inherent cause of ***,it has been observed that a larger extent of surrounding rock leads to a stronger elastic rebound,thereby directly contributing to a more intense *** findings can provide novel theoretical insights for the exploring of rockburst mechanism and the development of monitoring and

关键词： Strain rockburst Static-dynamic state transition Self-initiation Triggering mechanism Elastic rebound Discrete element method

Broadband intelligent programmable metasurface with polarization-modulated self-adaptive electromagnetic functionality switching

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Photonics Research 2024年第7期12卷 1395-1409页

作者： XIMING LI rui XU XIAOFENG SUN YUAN zhao zhao YANG GUOHONG DU College of Electronic Engineering Chengdu University of Information TechnologyChengdu 610225China

Programmable metasurfaces have received a great deal of attention due to their ability to dynamically manipulate electromagnetic(EM) waves. Despite the rapid growth, most of the existing metasurfaces require manual control to switch among different functionalities, which poses severe limitations on practical applications. Here, we put forth an intelligent metasurface that has self-adaptive EM functionality switching in broadband without human participation. It is equipped with polarization discrimination antennas(PDAs) and feedback components to automatically adjust functionalities for the different incident polarization information.

关键词： equipped adjust polarization

Tribological properties of low-temperature time-dependent pretreated graphite for mechanical seal pairs in high-speed turbopump

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Friction 2024年第2期12卷 305-318页

作者： Yangyang zhao Guoyuan ZHANG Junqian WANG He WANG Weigang zhao Qunfeng zeng School of Mechano-Electronic Engineering Xidian UniversityXi’an 710071China Xi’an Aerospace Propulsion Institute Xi’an 710071China Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi’an Jiaotong UniversityXi’an 710049China

The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester,and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear *** results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of *** range of the friction coefficients of pretreated graphite changes from 0.17 to *** the increase of liquid nitrogen pretreatment time,the wear mechanism of graphite would change from dominated three-body wear to adhesion *** experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm^(3)·N^(−1)·m^(−1),and the graphite shows a good low-temperature compatibility.

关键词： graphite low-temperature pretreatment mechanical seal friction and wear