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Effects of Cu addition on formability and surface delamination phenomenon in high-strength high-Mn steels

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journal of Materials Science & Technology 2020年第8期36卷 44-51页

作者： Min Chul jo jisung Yoo Min Cheol jo Alireza Zargaran Seok Su Sohn nack j.kim Sunghak Lee Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang 37673South Korea Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 37673South Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841South Korea

The formability of austenitic high-Mn steels is a critical issue in automotive applications under nonuniformly-deformed environments caused by dynamic strain *** austenite stabilizing alloying elements in those steels,Cu has been known as an effective element to enhance tensile properties via controlling the stacking fault energy and stability of *** effects of Cu addition on formability,however,have not been sufficiently reported *** this study,the Cu addition effects on formability and surface characteristics in the austenitic high-Mn TRIP steels were analyzed in consideration of inhomogeneous microstructures containing the segregation of Mn and *** reveal determining factors,various mechanical parameters such as total elongation,post elongation,strain hardening rate,normal anisotropy,and planar anisotropy were correlated to the hole-expansion and cup-drawing test *** respect to microstructural parameters,roles of(Mn,Cu)-segregation bands and resultant Cu-rich FCC precipitates on the formability and surface delamination were also discussed.

关键词： High-Mn steel Cu effects Cu-rich FCC phase Hole-expansion test Formability Stretch-flangeablity Surface delamination

Effect of 1Al addition on deformation behavior of Mg

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journal of Magnesium and Alloys 2021年第2期9卷 489-498页

作者： ji Hyun Hwang A.Zargaran Gyeongbae Park O.Lee B.-j.Lee nack j.kim Center for Advanced Aerospace Materials Pohang University of Science and Technology(POSTECH)PohangSouth Korea

Deformation behavior of 1 Al containing Mg alloy has been investigated in the present *** annealing,the Mg-1 Al alloy shows a typical basal *** compared to the pure Mg having a similar texture and grain size,the Mg-1 Al alloy shows much higher strength and larger *** trace analyses of the tensile strained specimens show that non-basal slips such as pyramidal I and II slips can be easily activated at an early stage of deformation in the Mg-1 Al alloy and the grains in the Mg-1 Al alloy are seen to accommodate a larger degree of deformation than those in the pure Mg at a given *** increasing tensile strain,however,there is a strain localization along the initially formed slip lines of non-basal slips,forming surface steps without activating multiple slip lines.

关键词： Deformation behavior Slip trace analysis Non-basal slip Strain localization Ductility

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自适应正则化滤波化极方法研究

地球物理学报 2024年第3期67卷 1255-1272页

作者：何涛王皓张义蜜王万银 Colin G.Farquharson j.kim Welford 长安大学地质工程与测绘学院西安710054 海洋油气勘探国家工程研究中心北京100028 中国科学院海洋地质与环境重点实验室山东青岛266071 Department of Earth Sciences Memorial University of NewfoundlandSt.John'sAlB 3X5Canada

化极是消除磁力异常斜磁化影响的关键步骤,可以在波数域(频率域)和空间域中实现.相比于空间域,在波数域(频率域)进行化极简单且高效,但在低纬度地区存在不稳定性问题,因此明确低纬度地区的范围,研究稳定、实用、精度高的低纬度地区化极... 详细信息

化极是消除磁力异常斜磁化影响的关键步骤,可以在波数域(频率域)和空间域中实现.相比于空间域,在波数域(频率域)进行化极简单且高效,但在低纬度地区存在不稳定性问题,因此明确低纬度地区的范围,研究稳定、实用、精度高的低纬度地区化极方法具有重要意义.本文通过理论研究得出化极因子振幅的最大值为2时,对应的磁化倾角的值为±45°,当磁化倾角在该范围内时,引起化极不稳定.因此采用正则化思想,提出了自适应正则化滤波化极方法(ARF-RTP),该方法利用化极因子振幅构建正则化滤波函数,并以振幅值等于2作为约束计算化极方法的参数值,从而实现自适应化极处理,提高了化极方法的稳定性及实用性.同时结合迭代算法提高了此方法的精度,有效地解决了低纬度地区化极的不稳定性问题.自适应正则化滤波这一思想不但可以解决化极的不稳定性问题,而且可以解决分量转换或者磁化方向转换的不稳定性问题以及类似数据处理中的不稳定性问题,具有广阔的推广应用前景.

关键词：化极低纬度地区振幅自适应正则化滤波迭代算法

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Polymer donors with hydrophilic side-chains enabling efficient and thermally-stable polymer solar cells by non-halogenated solvent processing

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Nano Research Energy 2024年第1期3卷 19-29页

作者： Soodeok Seo jun-Young Park jin Su Park Seungjin Lee Do-Yeong Choi Yun-Hi kim Bumjoon j.kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Department of Materials Engineering and Convergence Technology and ERI Gyeongsang National UniversityJinju 52828Republic of Korea Advanced Energy Materials Research Center Korea Research Institute of Chemical Technology(KRICT)Daejeon 34114Republic of Korea Department of Chemistry and ERI Gyeongsang National UniversityJinju 52828Republic of Korea

Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial *** the use of non-halogenated solvent processing is inevitable for the PSC fabrication,it significantly reduces the processability of polymer donors(PDS)and small-molecule acceptors(SMAs).This often results in unoptimized blend morphology and limits the device *** address this issue,hydrophilic oligoethylene glycol(OEG)side-chains are introduced into a PD(2EG)to enhance the molecular compatibility between the PD and L8-BO *** 2EG PD induces higher crystallinity and alleviates phase separation with the SMA compared to the reference PD(PM7)with hydrocarbon ***,the 2EG-based PSCs exhibit a higher PCE(15.8%)than the PM7-based PSCs(PCE=14.4%)in the ortho-xylene based ***,benefitted from the reduced phase separation and increased crystallinity of 2EG PDS,the 2EG-based PSCs show enhanced thermal stability(84%of initial PCE after 120 h heating)compared to that of the PM7-based PSCs(60%of initial PCE after 120 h heating).This study demonstrates the potential of OEG side-chain-incorporated materials in developing efficient,stable,and eco-friendly PSCs.

关键词： polymer solar cell polymer donor OEG side-chain non-halogenated solvent process side-chain engineering

Superplasticity of fine-grained Mg-10Li alloy prepared by severe plastic deformation and understanding its deformation mechanisms

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journal of Magnesium and Alloys 2024年第1期12卷 316-331页

作者： H.T.jeong S.W.Lee W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,were examined in a temperature range of 473 K to 623 *** microstructural refinement of this alloy was achieved by employing high-ratio differential speed *** best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were *** the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 ***,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and *** the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation *** was concluded that solute drag creep is unlikely to *** the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain *** mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.

关键词： Magnesium-lithium alloy Superplasticity Severe plastic deformation Grain size Grain growth

Liquid crystal-integrated metasurfaces for an active photonic platform

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Opto-Electronic Advances 2024年第6期7卷 5-29页

作者： Dohyun Kang Hyeonsu Heo Younghwan Yang junhwa Seong Hongyoon kim joohoon kim junsuk Rho Department of Mechanical Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Electrical Engineering Pohang University of Science and Technology(POSTECH)Pohang 36763Republic of Korea POSCOPOSTECH-RIST Convergence Research Center for Flat Optics and Metaphotonics Pohang 37673Republic of Korea National Institute of Nanomaterials Technology(NINT) Pohang 37673Republic of Korea

Metasurfaces have opened the door to next-generation optical devices due to their ability to dramatically modulate electromagnetic waves at will using periodically arranged ***,metasurfaces typically have static optical responses with fixed geometries of nanostructures,which poses challenges for implementing transition to technology by replacing conventional optical *** solve this problem,liquid crystals(LCs)have been actively employed for designing tunable metasurfaces using their adjustable birefringent in real ***,we review recent studies on LCpowered tunable metasurfaces,which are categorized as wavefront tuning and spectral *** to numerous reviews on tunable metasurfaces,this review intensively explores recent development of LC-integrated *** the end of this review,we briefly introduce the latest research trends on LC-powered metasurfaces and suggest further directions for improving *** hope that this review will accelerate the development of new and innovative LC-powered devices.

关键词： tunable metasurface liquid crystal active metasurface electrically tunable optical system

Driving inward growth of lithium metal in hollow microcapsule hosts by heteroatom‐controlled nucleation

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Carbon Energy 2024年第8期6卷 262-272页

作者： Siwon kim Hong Rim Shin Ki jae kim Min‐Sik Park jong‐Won Lee Division of Materials Science and Engineering Hanyang UniversitySeoulRepublic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)DaeguRepublic of Korea Department of Energy Science Sungkyunkwan UniversitySuwonRepublic of Korea Department of Advanced Materials Engineering for Information and Electronics Integrated Education for Frontier Science and Technology(BK21 Four)Kyung Hee UniversityYonginRepublic of Korea

The application of Li metal anodes in rechargeable batteries is impeded by safety issues arising from the severe volume changes and formation of dendritic Li ***‐dimensional hollow carbon is receiving increasing attention as a host material capable of accommodating Li metal inside its cavity;however,uncontrollable and nonuniform deposition of Li remains a *** this study,we synthesize metal–organic framework‐derived carbon microcapsules with heteroatom clusters(Zn and Ag)on the capsule walls and it is demonstrated that Ag‐assisted nucleation of Li metal alters the outward‐to‐inward growth in the microcapsule ***‐incorporated microcapsules are prepared via chemical etching of zeolitic imidazole framework‐8 polyhedra and are subsequently decorated with Ag by a galvanic displacement reaction between Ag^(+)and metallic *** introduced Ag significantly reduces the energy barrier and increases the reaction rate for Li nucleation in the microcapsule host upon Li *** combined electrochemical,microstructural,and computational studies,we verify the beneficial role of Ag‐assisted Li nucleation in facilitating inward growth inside the cavity of the microcapsule host and,in turn,enhancing electrochemical *** study provides new insights into the design of reversible host materials for practical Li metal batteries.

关键词： hollow carbon hosts lithium metal batteries lithium plating metal-organic frameworks nucleation

DESIGN AND IMPLEMENTATION OF REAL-TIME PHYSICS SIMULATION ENGINE FOR e-ENTERTAINMENT

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International journal of Modeling, Simulation, and Scientific Computing 2013年第S01期4卷 20-39页

作者： MYUNGSOO BAE YOUNG j.kim Computer Science and Engineering Ewha Womans University SeoulKorea

We present our recent research results regarding the designing and implementation of real-time physics simulation engines,which aim at developing physics-inspired e-entertainment such as computer games,mobile applications,interactive TV and other smart media in *** real-time physics engine consists of three functional components:rigid body dynamics simulation,deformable body simulation,and data-driven physics *** core simulation techniques to realize these simulation components include real-time collision detection and response,large-scale model simulation,and character model *** this paper,we highlight these features and demonstrate their *** also showcase some of the gaming applications that we have integrated our physics engine into.

关键词： Real-time physics simulation engine rigid body dynamics simulation deformable body simulation data-driven simulation.

Machine learning-guided accelerated discovery of structure-property correlations in lean magnesium alloys for biomedical applications

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journal of Magnesium and Alloys 2024年第6期12卷 2267-2283页

作者： Sreenivas Raguraman Maitreyee Sharma Priyadarshini Tram Nguyen Ryan McGovern Andrew kim Adam j.Griebel Paulette Clancy Timothy P.Weihs Department of Materials Science and Engineering Johns Hopkins University3400 N Charles StBaltimore21218MDU.S.A Hopkins Extreme Materials Institute Johns Hopkins University3400 N Charles StBaltimore21218MDU.S.A Department of Chemical and Biomolecular Engineering Johns Hopkins University3400 N Charles StBaltimore21218MDU.S.A Translational Tissue Engineering Center Johns Hopkins School of Medicine400 N BroadwayBaltimore21231MDU.S.A Department of Biomedical Engineering Johns Hopkins University3400 N Charles StBaltimore21218MDU.S.A Research and Development Fort Wayne Metals Research ProductsLLC9609 Ardmore AveFort Wayne46809INU.S.A Department of Mechanical Engineering Johns Hopkins University3400 N Charles StBaltimore21218MDU.S.A

Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability,biocompatibility,and impressive mechanical ***,their rapid in-vivo degradation presents challenges,notably in upholding mechanical integrity over *** study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy,*** rapid,cost-efficient characterization methods like X-ray diffraction and optical microscopy,we swiftly examine microstructural changes post-thermal *** Pearson correlation coefficient analysis,we unveil the relationship between microstructural properties and critical targets(properties):hardness and corrosion ***,leveraging the least absolute shrinkage and selection operator(LASSO),we pinpoint the dominant microstructural factors among closely correlated *** findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca_(2)Mg_(6)Zn_(3)phase in corrosion *** suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary *** thorough investigation furnishes valuable insights into the intricate interplay of processing,structure,and properties in magnesium alloys,thereby advancing the development of superior biodegradable implant materials.

关键词： Magnesium alloys Machine learning Corrosion Mechanical properties Rapid characterization