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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

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Improved tensile properties of AZ31 Mg alloy subjected to various caliber-rolling strains

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Journal of Magnesium and Alloys 2019年第3期7卷 381-387页

作者： jeong hun lee Byung Je Kwak Taein Kong Sung Hyuk Park Taekyung lee Advanced Forming Process R&D Group Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation *** present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber *** improving trends in tensile properties were interpreted with various caliber-rolling *** oval/circular-shaped calibers imposed a high plastic strain at the center of crosssection,leading to effective grain refinement to submicron *** work also confirmed the texture randomizing effect of caliber *** microstructural evolutions gave rise to the fabrication of high-strength ***,the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled *** was discussed in terms of activation of non-basal slip systems and suppression of mechanical *** study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties.

关键词： Magnesium AZ31 alloy Caliber rolling Grain refinement Texture randomization Mechanical improvement

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Dynamic recrystallization behavior and microstructural evolution of Mg alloy AZ31 through high-speed rolling

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Journal of Materials Science & Technology 2018年第10期34卷 1747-1755页

作者： jeong hun lee Jong Un lee Sang-Hoon Kim Seok Weon Song Chong Soo lee Sung Hyuk Park Ulsan Regional Division Korea Institute of Industrial Technology School of Materials Science and Engineering Kyungpook National University Technical Research Laboratories POSCO Graduate Institute of Ferrous Technology Pohang University of Science and Technology

High-speed rolling （HSR） is known to improve the workability of Mg alloys significantly, which makes it possible to impose a large reduction in a single pass without fracture. In the present study, dynamic recrystallization （DRX） behavior and microstructural and textural variations of Mg alloy AZ31 dur-ing a HSR process were investigated by conducting rolling with different imposed reductions in the range of 20%-80% at a high rolling speed of 470 m/min and 400℃. High-strain-rate deformation during HSR suppresses dislocation slips but promotes twinning, which results in the formation of numer-ous twins of several types, i.e., {10-12} extension twins, {10-11} and {10-13} contraction twins, and {10-11}-{10-12} double twins. After twinning, high strain energy is accumulated in twin bands because their crystallographic orientations are favorable for basal slips, leading to subsequent DRX at the twin bands. Accordingly, twinning activation and twinning-induced DRX behavior play crucial roles in accommodating plastic deformation during HSR and in varying microstructure and texture of the high- speed-rolled （HSRed） sheets. Area fraction of fine DRXed grains formed at the twin bands increases with increasing rolling reduction, which is attributed to the combined effects of increased strain, strain rate, and deformation temperature and a decreased critical strain for DRX. Size, internal strain, and texture intensity of the DRXed grains are smaller than those of unDRXed grains. Therefore, as rolling reduction increases, average grain size, stored internal energy, microstructural inhomogeneity, and basal texture intensity of the HSRed sheets gradually decrease owing to an increase in the area fraction of the DRXed grains.

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

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Improvement in tensile strength of extruded Mg-5Bi alloy through addition of Sn and its underlying strengthening mechanisms

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Journal of Magnesium and Alloys 2022年第11期10卷 3100-3112页

作者： Sang-Cheol Jin Jae Won Cha jeong hun lee Taekyung lee Sang-Ho Han Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Ulsan Regional Division Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea Department of Materials Analysis Korea Institute of Materials ScienceChangwon 51508Republic of Korea

Through an investigation of the microstructure and mechanical properties of extruded Mg–5Bi–x Sn(BT5x, x = 0, 2, 4, and 6 wt%) alloys,this study demonstrates that the addition of Sn to an Mg–5Bi binary alloy significantly improves the tensile strength of the extruded *** the extruded alloys exhibit a typical basal fiber texture and a partially dynamically recrystallized(DRXed) microstructure consisting of fine DRXed grains and coarse un DRXed grains. As the Sn content increases from 0 wt% to 6 wt%, the average size of the DRXed grains decreases from 4.2 to 2.8 μm owing to the increase in the amount of precipitates via their grain-boundary pinning effect. The extruded B5 and BT52 alloys contain numerous Mg_(3)Bi_(2) precipitates, but their size and number density are smaller and higher, respectively, in the latter *** Mg_(2)Sn precipitates as well as Mg_(3)Bi_(2)precipitates are present in the extruded BT54 and BT56 alloys, and the number density of the Mg_(2)Sn precipitates is higher in the latter alloy because of its higher Sn content. The addition of 2 wt% Sn to the B5 alloy significantly improves the yield strength(YS) and ultimate tensile strength(UTS) of the extruded alloy—by 76 and 57 MPa, respectively. This drastic improvement is the combined outcome of enhanced grain-boundary hardening, precipitation hardening, and solid-solution hardening effects induced by the refined DRXed grains, numerous precipitates, and Sn solute atoms, respectively. The further addition of 2 wt% or 4 wt% Sn to the BT52 alloy leads to moderate increments in the YS and UTS of the extruded alloy. Specifically, each addition of 2 wt% Sn increases the YS and UTS by ~26 and ~20 MPa, respectively, which is attributed mainly to the additional precipitation hardening effect induced by the Mg_(2)Sn precipitates.

关键词： Mg-Bi-Sn alloy Extrusion Precipitation Microstructure Tensile property

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Colonic mucosa-associated lymphoid tissue lymphoma identified by chromoendoscopy

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World Journal of Gastroenterology 2014年第48期20卷 18487-18494页

作者： Sang-Wook Seo Seung-Hwa lee Duck-Joo lee Kwang-Min Kim Joon-Koo Kang Do-Wan Kim jeong-hun lee Center for Health Promotion Department of Family Practice and Community Health Ajou University School of Medicine Suwon 443-380 South Korea Department of Gastroenterology Ajou University School of Medicine Suwon 443-380 South Korea Department of Anesthesiology Ajou University School of Medicine Suwon 443-380 South Korea Department of Surgery Ajou University School of Medicine Suwon 443-380 South Korea

Colonic mucosa-associated lymphoid tissue (MALT) lymphomas are a rare occurrence and the definitive treatment has not been established. Solitary or multiple, elevated or polypoid lesions are the usual appearances of MALT lymphoma in the large intestine and sometimes the surface may reveal abnormal vascularity. Herein, we report a case of MALT lymphoma and review the relevant literature. Upon colonoscopy, a suspected pathologic lesion was observed in the proximal transverse colon. The lesion could be distinguished more prominently after using narrow-band imaging mode and indigo carmine-dye spraying chromoendoscopy. Histopathologic examination of this biopsy specimen revealed lymphoepithelial lesions with diffuse proliferation of atypical lymphoid cells effacing the glandular architecture and centrocyte-like cells infiltrating the lamina propria. Immunohistochemical analyses showed that tumor cells were positive for CD20 and Bcl-2e, and negative for CD10, CD23, and Bcl-6. According to Ann-Arbor staging system, the patient had stage IIE. A partial colectomy with dissection of the paracolic lymph nodes was performed. Until now, there is no recurrence of lymphoma at follow-up.

关键词： Chromoendoscopy Lymphoma Mucosa-associated lymphoid tissue Narrow-band imaging mode

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Tailoring strength-ductility balance of caliber-rolled AZ31 Mg alloy through subsequent annealing

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Journal of Magnesium and Alloys 2020年第1期8卷 163-171页

作者： Taein Kong Byung Je Kwak Jonghyun Kim jeong hun lee Sung Hyuk Park Ji Hoon Kim Young Hoon Moon Hyun Sik Yoon Taekyung lee School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea Advanced Forming Process R&D Group Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea College of Materials Science and Engineering Chongqing UniversityChongqing 400044China School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Naval Architecture and Ocean Engineering Pusan National UniversityBusan 46241Republic of Korea

Recently,multi-pass caliber rolling has been shown to be effective for Mg *** study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility *** annealing gave rise to different trends in mechanical properties depending on the temperature ***-temperature annealing(T≤473 K)exhibited a typical trade-off relationship,where an increase in annealing temperature resulted in increased ductility but decreased strength and *** a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy,suggesting that the mechanical properties could be tailored for different potential *** contrast,high-temperature annealing(T>473 K)caused a simultaneous deterioration in strength,hardness,and ductility with increasing annealing *** differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes.

关键词： AZ31 Mg alloy Caliber rolling Annealing Grain growth Mechanical improvement Twinning

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Texture tailoring and bendability improvement of rolled AZ31 alloy using {10-12} twinning: The effect of precompression levels

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Journal of Magnesium and Alloys 2019年第4期7卷 648-660页

作者： Jong Un lee Ye Jin Kim Sang-Hoon Kim jeong hun lee Min-Seong Kim Shi-Hoon Choi Byoung Gi Moon Young Min Kim Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Ulsan Regional Division Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea Department of Printed Electronics Engineering Sunchon National UniversitySuncheonJeonnam 57922Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

In this study,the texture of a rolled Mg alloy is effectively modified through the application of precompression and subsequent annealing treatment,leading to a remarkable improvement in the bending formability of the alloy at room *** induces lattice reorientation through{10-12}twinning,and annealing treatment reduces the stored strain energy of the precompressed material,which results in the formation of a stable grain structure with two dominant texture *** an increase in precompression,the tensile strain in the outer region of the bending samples is accommodated to a greater extent due to more pronounced{10-12}twinning and basal *** a result,the bending formability of the material at room temperature improves with greater *** variation in microstructure,texture,and bending behavior in relation to the degree of precompression is discussed in detail.

关键词： Magnesium Bending Formability Twinning Texture

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Ru/NiMnB spherical cluster pillar for highly proficient green hydrogen electrocatalyst at high current density

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Journal of Energy Chemistry 2025年第1期100卷 397-408页

作者： Md Ahasan Habib Shusen Lin Mehedi Hasan Joni Sumiya Akter Dristy Rutuja Mandavkar Jae-hun jeong Jihoon lee Department of Electronic Engineering College of Electronics and Information Kwangwoon University

Advanced OER/HER electrocatalytic alternatives are crucial for the wide adaptation of green hydrogen ***,Ru/NiMnB spherical cluster pillar （SCP）,denoted as Ru/NiMnB,is synthesized using a combination of electro-deposition and hydrothermal *** investigation of Ru doping in the NiMnB matrix revealed significant improvements in electrocatalytic *** Ru/NiMnB SCPs demonstrate superior OER/HER activity with low overpotentials of 150 and 103 mV at 50mA/cm2in 1 M KOH,making them highly competitive with state-of-the-art ***,the Ru/NiMnB SCPs exhibit a low 2-E cell voltage of 2.80 V at ultra-high current density of 2,000 m A/cm2in 1 M KOH,outperforming the standard benchmark electrodes of RuO2||Pt/C,thereby positioning Ru/NiMnB as one of the best bifunctional *** SCPs exhibit exceptional high-current characteristics,stability and corrosion resistance,as evidenced by continuous operation at 1,000 mA/cm2high-current density for over 150 h in 6 M KOH at elevated temperatures under harsh industrial *** a small amount of Ru incorporation significantly enhances the electrocatalytic performances of NiMnB,attributed to increased active sites and improved intrinsic properties such as conductivity,adsorption/desorption capability and reaction ***,Ru/NiMnB SCPs present a promising bi-functional electrode concept for efficient green H2production.

关键词： Advanced electrocatalyst High current Corrosion resistance Industrial requirement

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Single-cell and spatial omics:exploring hypothalamic heterogeneity

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Neural Regeneration Research 2025年第6期20卷 1525-1540页

作者： Muhammad Junaid Eun jeong lee Su Bin Lim Department of Biochemistry&Molecular Biology Ajou University School of MedicineSuwonSouth Korea Department of Biomedical Sciences Graduate School of Ajou UniversitySuwonSouth Korea Department of Brain Science Ajou University School of MedicineSuwonSouth Korea

Elucidating the complex dynamic cellular organization in the hypothalamus is critical for understanding its role in coordinating fundamental body functions. Over the past decade, single-cell and spatial omics technologies have significantly evolved, overcoming initial technical challenges in capturing and analyzing individual cells. These high-throughput omics technologies now offer a remarkable opportunity to comprehend the complex spatiotemporal patterns of transcriptional diversity and cell-type characteristics across the entire hypothalamus. Current single-cell and single-nucleus RNA sequencing methods comprehensively quantify gene expression by exploring distinct phenotypes across various subregions of the hypothalamus. However, single-cell/single-nucleus RNA sequencing requires isolating the cell/nuclei from the tissue, potentially resulting in the loss of spatial information concerning neuronal networks. Spatial transcriptomics methods, by bypassing the cell dissociation, can elucidate the intricate spatial organization of neural networks through their imaging and sequencing technologies. In this review, we highlight the applicative value of single-cell and spatial transcriptomics in exploring the complex molecular-genetic diversity of hypothalamic cell types, driven by recent high-throughput achievements.

关键词： cellular diversity hypothalamus multi-omics single-cell transcriptomics spatial transcriptomics

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Enhancement of motor functional recovery in thoracic spinal cord injury: voluntary wheel running versus forced treadmill exercise

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Neural Regeneration Research 2025年第3期20卷 836-844页

作者： Do-hun lee Dan Cao Younghye Moon Chen Chen Nai-Kui Liu Xiao-Ming Xu Wei Wu Spinal Cord and Brain Injury Research Group Stark Neurosciences Research InstituteIndiana University School of MedicineIndianapolisINUSA Department of Neurological Surgery Indiana University School of MedicineIndianapolisINUSA Department of Neuroscience Baylor College of MedicineHoustonTXUSA

Spinal cord injury necessitates effective rehabilitation strategies, with exercise therapies showing promise in promoting recovery. This study investigated the impact of rehabilitation exercise on functional recovery and morphological changes following thoracic contusive spinal cord injury. After a 7-day recovery period after spinal cord injury, mice were assigned to either a trained group(10 weeks of voluntary running wheel or forced treadmill exercise) or an untrained group. Bi-weekly assessments revealed that the exercise-trained group, particularly the voluntary wheel exercise subgroup, displayed significantly improved locomotor recovery, more plasticity of dopaminergic and serotonin modulation compared with the untrained group. Additionally, exercise interventions led to gait pattern restoration and enhanced transcranial magnetic motor-evoked potentials. Despite consistent injury areas across groups, exercise training promoted terminal innervation of descending axons. In summary, voluntary wheel exercise shows promise for enhancing outcomes after thoracic contusive spinal cord injury, emphasizing the role of exercise modality in promoting recovery and morphological changes in spinal cord injuries. Our findings will influence future strategies for rehabilitation exercises, restoring functional movement after spinal cord injury.

关键词： behavioral assessment motor function neural plasticity running wheel exercise spinal cord injury treadmill exercise voluntary exercise

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