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Influence of Vanadium Content on Hot Deformation Behavior of Low-Carbon Boron Microalloyed Steel

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Acta Metallurgica Sinica(English Letters) 2020年第5期33卷 705-715页

作者： Kwang-Su Kim Lin-Xiu Du Hyo-sung Choe Tae-Hyong lee Gyong-Chol lee Department of Materials Science and Engineering Kim Chaek University of TechnologyPyongyang 999093Democratic People’s Republic of Korea State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Single-pass compression tests were performed to investigate the hot deformation behavior of low-carbon boron microalloyed steel containing three various vanadium contents at 900-1100℃and strain rate of 0.01-10 s-1 using the MMS-300 thermal mechanical *** flow stress curves of investigated steels were obtained under the different deformation conditions,and the effects of the deformation temperature and strain rate on the flow stress were *** characteristic points of flow stress were obtained from the stress dependence of strain hardening rate;the activation energy of investigated steels was determined by the regression analysis;the flow stress constitutive equations were developed;the effect of vanadium content on the flow stress and dynamic recrystallization(DRX)was *** result showed that the flow stress and activation energy(3-6.5 kJ mol-1)of the steel containing 0.18 wt%V were significantly higher than those of the steels with0.042 wt%and 0.086 wt%V,which was related to the increase in solute drag and precipitation effects for higher vanadium *** analysis showed that the addition of vanadium can delay the initiation and the rate of DRX.

关键词： Boron microalloyed steel Vanadium Flow stress Hot deformation Dynamic recrystallization

Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

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Journal of Magnesium and Alloys 2024年第2期12卷 779-793页

作者： Sumi Jo Gyo Myeong lee Jong Un lee Young Min Kim sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Magnesium Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al *** extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air *** extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during *** to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser *** AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,***,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and *** bending,a macrocrack initiates on the outer surface of bending specimen in both *** AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 *** bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the *** bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relation

关键词： Mg–Al alloy Extrusion Bending Precipitation Microstructure

Dynamic deformation behavior and microstructural evolution during high-speed rolling of Mg alloy having non-basal texture

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Journal of Materials Science & Technology 2019年第4期35卷 473-482页

作者： Sang-Hoon Kim Jeong Hun lee Chong Soo lee Jonghun Yoon sung Hyuk Park School of Materials Science and Engineering Kyungpook National University Ulsan Regional Division Korea Institute of Industrial Technology Graduate Institute of Ferrous Technology Pohang University of Science and Technology Department of Mechanical Engineering Hanyang University

The dynamic deformation behaviors and resultant microstructural variations during high-speed rolling(HSR) of a Mg alloy with a non-basal texture are investigated. To this end, AZ31 alloy samples in which the basal poles of most grains are predominantly aligned parallel to the transverse direction(TD) are subjected to hot rolling with different reductions at a rolling speed of 470 m/min. The initial grains with a TD texture are favorable for {10–12} twinning under compression along the normal direction(ND); as a result, {10–12} twins are extensively formed in the material during HSR, and this consequently results in a drastic evolution of texture from the TD texture to the ND texture and a reduction in the grain size. After the initial grains are completely twinned by the {10–12} twinning mechanism, {10–11} contraction twins and {10–11}-{10–12} double twins are formed in the {10–12} twinned grains by further *** the contraction twins and double twins have crystallographic orientations that are favorable for basal slip during HSR, dislocations easily accumulate in these twins and fine recrystallized grains nucleate in the twins to reduce the increased internal strain energy. Until a rolling reduction of 20%, {10–12}twinning is the main mechanism governing the microstructural change during HSR, and subsequently,the microstructural evolution is dominated by the formation of contraction twins and double twins and the dynamic recrystallization in these twins. With an increase in the rolling reduction, the average grain size and internal strain energy of the high-speed-rolled(HSRed) samples decrease and the basal texture evolves from the TD texture to the ND texture more effectively. As a result, the 80% HSRed sample, which is subjected to a large strain at a high strain rate in a single rolling pass, exhibits a fully recrystallized microstructure consisting of equiaxed fine grains and has an ND basal texture without a TD texture component.

关键词： Magnesium alloy High-speed rolling Texture Dynamic recrystallization Twinning

Self-motivated,thermally oxidized hematite nanoflake photoanodes:Effects of pre-polishing and ZrO_(2) passivation layer

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Journal of Energy Chemistry 2022年第2期31卷 415-423页

作者： Love Kumar Dhandole Hyun Hwi lee Weon-Sik Chae Jum Suk Jang Jae sung lee Department of Energy Engineering School of Energy and Chemical EngineeringUlsan National Institute of Science and Technology(UNIST)Ulsan 44919Republic of Korea Division of Biotechnology College of Environmental and Bioresource SciencesChonbuk National UniversityIksan 54596Republic of Korea Pohang Accelerator Laboratory Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Daegu Center Korea Basic Science InstituteDaegu 41566Republic of Korea

High-temperature thermal oxidation of an Fe foil produces a high-quality,crystalline hematite nanoflake suitable as a photoanode for the photoelectrochemical(PEC)water *** pre-polishing of the foil surface has a profound effect in the formation of a vertically-aligned nanoflakes of hematite phase with extended(110)planes by removing the loosely-bonded oxide *** the surface of the photoanode is modified with a ZrO_(2) passivation layer and a cobalt phosphate co-catalyst,the charge recombination at the photoanode-electrolyte interface is greatly suppressed to improve its overall PEC *** a result,the photocurrent density at 1.10 VRHE under 1 sun condition is enhanced from 0.22 mA cm^(-2) for an unmodified photoanode to 0.59 mA cm^(-2) for the fully modified photoanode,and the photocurrent onset potential is shifted cathodically by 400 ***,the photoanode demonstrates outstanding stability by showing steady production of H_(2) and O_(2) gases in the stoichiometric ratio of 2:1 in a continuous PEC operation for 10 h.

关键词： Fe foil Thermal oxidation Nanoflakes Photoelectrochemical water splitting Surface modifications

Enhanced prediction of anisotropic deformation behavior using machine learning with data augmentation

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Journal of Magnesium and Alloys 2024年第1期12卷 186-196页

作者： Sujeong Byun Jinyeong Yu Seho Cheon Seong Ho lee sung Hyuk Park Taekyung lee School of Mechanical Engineering Pusan National UniversityBusan 46241South Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566South Korea

Mg alloys possess an inherent plastic anisotropy owing to the selective activation of deformation mechanisms depending on the loading *** characteristic results in a diverse range of flow curves that vary with a deformation *** study proposes a novel approach for accurately predicting an anisotropic deformation behavior of wrought Mg alloys using machine learning(ML)with data *** developed model combines four key strategies from data science:learning the entire flow curves,generative adversarial networks(GAN),algorithm-driven hyperparameter tuning,and gated recurrent unit(GRU)*** proposed model,namely GAN-aided GRU,was extensively evaluated for various predictive scenarios,such as interpolation,extrapolation,and a limited dataset *** model exhibited significant predictability and improved generalizability for estimating the anisotropic compressive behavior of ZK60 Mg alloys under 11 annealing conditions and for three loading *** GAN-aided GRU results were superior to those of previous ML models and constitutive *** superior performance was attributed to hyperparameter optimization,GAN-based data augmentation,and the inherent predictivity of the GRU for *** a first attempt to employ ML techniques other than artificial neural networks,this study proposes a novel perspective on predicting the anisotropic deformation behaviors of wrought Mg alloys.

关键词： Plastic anisotropy Compression Annealing Machine learning Data augmentation

Comparison of commercial silicon-based anode materials for the design of a high-energy lithium-ion battery

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Nano Research 2024年第6期17卷 5270-5277页

作者： Minhong Choi Eunhan lee Jaekyung sung Namhyung Kim Minseong Ko Division of Convergence Materials Engineering Pukyong National UniversityBusan 48547Republic of Korea Department of Materials Engineering and Convergence Technology Gyeongsang National University501 Jinju-daeroJinju 52828Republic of Korea Department of Materials System Engineering Pukyong National UniversityBusan 48547Republic of Korea

Silicon(Si)is considered a potential alternative anode for next-generation Li-ion batteries owing to its high theoretical capacity and ***,the commercial use of Si anodes is hindered by their large volume expansion(~300%).Numerous efforts have been made to address this *** these efforts,Si-graphite co-utilization has attracted attention as a reasonable alternative for high-energy anodes.A comparative study of representative commercial Si-based materials,such as Si nanoparticles,Si suboxides,and Si−Graphite composites(SiGC),was conducted to characterize their overall performance in high-energy lithium-ion battery(LIB)design by incorporating conventional ***-Si was found to exhibit poor electrochemical performance,with severe volume expansion during *** suboxide provided excellent cycling stability in a full-cell evaluation with stable volume variation after 50 cycles,but had a large irreversible capacity and remarkable volume expansion during the first *** displayed a good initial Coulombic efficiency and the lowest volume change in the first cycle owing to the uniformly distributed nano-Si layer on graphite;however,its long-term cycling stability was relatively *** complement each disadvantage of Si suboxide and SiGC,a new combination of these Si-based anodes was suggested and a reasonable improvement in overall battery performance was successfully achieved.

关键词： silicon-based anode high-energy comparison lithium ion battery blended electrode

Improved thermal performance of a hydronic radiant panel heating system by the optimization of tube shapes

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第6期12卷 428-437页

作者： Young T.CHAE Kwang Ho lee Jae sung PARK School of Architecture University of Illinois at Urbana-Champaign Department of Architectural Engineering Hanbat National University Department of Mechanical Engineering University of Illinois at Urbana-Champaign

The thermal performance enhancement of the hydronic radiant floor heating system by tube shape refinements is investigated in this *** analytical and detailed numerical modelings are carried out to predict the performance of the radiant *** the simple analytical model briefly investigates the possibility of the effect of the tube shape improvement with the parametric analysis,the commercial computational fluid dynamics(CFD) code(Ansys/CFX) is used to perform the detailed 3D analysis under different tube shape *** fin thickness,the number of fins,and the tube thermal conductivity turn out to have significant effects on the radiant system *** potential energy saving impacts of the tube shape refinements are also *** tube shape improvement turns out to increase the floor surface temperature and to decrease the hot water temperature drop across the system,resulting in heating energy savings.

关键词： Radiant panel system Analytical modeling Computational fluid dynamics(CFD) Tube shape Energy saving

Estimation of marine winds in and around typhoons using multi-platform satellite observations: Application to Typhoon Soulik (2018)

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Frontiers of Earth Science 2022年第1期16卷 175-189页

作者： Seung-Woo lee sung Hyun NAM Duk-Jin KIM School of Earth and Environmental Sciences College of Natural SciencesSeoul National UniversitySeoul 08826Republic of Korea Research Institution of Oceanography College of Natural SciencesSeoul National UniversitySeoul 08826Republic of Korea

Estimating horizontal winds in and around typhoons is important for improved monitoring and prediction of typhoons and mitigating their ***,we present a new algorithm for estimating typhoon winds using multiple satellite observations and its application to Typhoon Soulik(2018).Four kinds of satellite remote sensing data,along with their relationship to typhoon intensity,derived statistically from hundreds of historical typhoon cases,were merged into the final product of typhoon wind(MT wind):(1)geostationarysatellite-based infrared images(IR wind),(2)passive microwave sounder(MW wind),(3)feature-tracked atmospheric motion vectors,and (4)scatterometer-based sea surface winds(SSWs).The algorithm was applied to two cases(A and B)of Typhoon Soulik and validated against SSWs independently retrieved from active microwave synthetic aperture radar(SAR)and microwave radiometer(AMSR2)images,and vertical profiles of wind speed derived from reanalyzed data and dropsonde *** Case A(open ocean),the algorithm estimated the realistic maximum wind,radius of maximum wind,and radius of 15 m/s,which could not be estimated using the reanalysis data,demonstrating reasonable and practical ***,for Case B(when the typhoon rapidly weakened just before making landfall in the Korean Peninsula),the algorithm significantly overestimated the parameters,primarily due to the overestimation of typhoon *** study highlights that realistic typhoon winds can be monitored continuously in real-time using multiple satellite observations,particularly when typhoon intensity is reasonably well predicted,providing timely analysis results and products of operational importance.

关键词： sea surface wind multi-platform satellites Typhoon Soulik(2018)

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Successful recanalization of chronic total occlusion of the superior mesenteric artery by transradial approach

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2010年第8期11卷 627-630页

作者： Woo Taek KIM sung Gyun AHN Jun-Won lee Joong Kyung sung Seung Hwan lee Junghan YOON Division of Cardiology Wonju College of MedicineYonsei University

It is a challenge to confirm chronic mesenteric ischemia(CMI) as a cause of gastrointestinal(GI) symptoms such as postprandial epigastric bloating,anorexia,and debilitating weight *** intervention for CMI has been gaining popularity because of the high morbidity associated with surgical ***,in EVI for superior mesenteric artery(SMA) occlusion,the transfemoral approach is limited by difficulty in coaxial alignment of the guiding catheter,which leads to insufficient back-up ***,we report on a 58-year-old male patient with chronic total occlusion of the SMA,which was successfully revascularized by endovascular intervention via the left radial *** endovascular therapy may be another treatment option for the treatment of CMI.

关键词： Transluminal angioplasty Radial artery Superior mesenteric artery Chronic mesenteric ischemia