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

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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Effective parameters on diameter of carbon nanotubes by plasma enhanced chemical vapor deposition

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中国有色金属学会会刊：英文版 2012年第S3期22卷 712-716页

作者： Kang Young JEONG Hyun kyung JUNG Hyung Woo lee National Core Research Center for Hybrid Materials Solution Hybrid Graduate SchoolPusan National University Department of Diagnostic Radiology Inje University College of MedicineHaeundae Paik Hospital

The effective parameters on the diameter of carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) were *** lots of influential parameters,the effects of the catalytic film thickness and the pretreatment plasma power on the growth of CNTs were *** results show that the size of catalytic islands increases by increasing the thickness of catalytic layer,but the density of CNTs *** pretreatment duration time of 30 s is the optimal condition for growing CNTs with about 50 nm in *** increasing the pretreatment plasma power,the diameter of CNTs decreases ***,the diameter of CNTs does not change drastically from 80 to 120 *** uniformly grown CNTs with the diameter of 50 nm are obtained at the pretreatment plasma power of 100 W.

关键词： carbon nanotubes catalytic film thickness pretreatment plasma power plasma enhanced chemical vapor deposition

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Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?

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Neural Regeneration Research 2015年第3期10卷 463-466页

作者： Yong Hyun Kwon kyung Woo Kang Sung Min Son Na kyung lee Department of Physical Therapy Yeungnam University College Department of Physical Therapy College of Rehabilitation ScienceDaegu University Department of Physical Therapy College of Health Science Cheongju University

Transcranial direct current stimulation （tDCS）, an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimu- lator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels （levels 1, 2, 3） of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of mod- erate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.

关键词： neural regeneration transcranial direct current stimulation visuomotor coordination task difficulty primary motor area motor learning neural regeneration

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Water hammer in the pump-rising pipeline system with an air chamber

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Journal of Hydrodynamics 2014年第6期26卷 960-964页

作者： KIM Sang-Gyun lee Kye-Bock KIM kyung-Yup Korea Water Resources Corporation School of Mechanical Engineering Chungbuk National University School of Mechanical Engineering Korea Polytechnic University

Water hammer following the tripping of pumps can lead to overpressure and negative pressure. Reduction in overpressure and negative pressure may be necessary to avoid failure, to improve the efficiency of operation and to avoid fatigue of system components. The field tests on the water hammer have been conducted on the pump rising pipeline system with an air chamber. The hydraulic transient was simulated using the method of characteristics. Minimizing the least squares problem representing the difference between the measured and predicted transient response in the system performs the calibration of the simulation program. Among the input variables used in the water hammer analysis, the polytropic exponent, the discharge coefficient and the wave speed were calibrated. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system. The correct selection of air chamber size and the effect of the inner diameter of the orifice to minimize water hammer have been investigated by both field measurements and numerical modeling.

关键词： air chamber design parameter field test pump pipeline system water hammer

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Site-selective oral delivery of therapeutic antibodies to the inflamed colon via a folic acid-grafted organic/inorganic hy brid nanocomposite system

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Acta Pharmaceutica Sinica B 2022年第11期12卷 4249-4261页

作者： Sang Hoon lee Jae Geun Song Hyo-kyung Han College of Pharmacy Dongguk University-SeoulGoyang 10326South Korea

This study aimed to develop a pH-responsive folic acid-grafted organic/inorganic hybrid nanocomposite system for site-selective oral delivery of therapeutic antibodies. A folic acid-grafted aminoclay(FA-AC) was prepared via an in situ sol-gel method. Then, a drug-loaded nanocomplex was prepared via the electrostatic interaction of FA-AC with infliximab(IFX), a model antibody, and coated with Eudragit? S100(EFA-AC-IFX). FA-AC exhibited favorable profiles as a drug carrier including low cytotoxicity, good target selectivity, and capability to form a nanocomplex with negatively charged macromolecules. A pH-responsive FA-AC-based nanocomplex containing IFX(EFA-AC-IFX) was also obtained in a narrow size distribution with high entrapment efficiency(>87%). The conformational stability of IFX entrapped in EFA-AC-IFX was well maintained in the presence of proteolytic enzymes. EFA-ACIFX exhibited pH-dependent drug release, minimizing premature drug release in gastric conditions and the upper intestine. Accordingly, oral administration of EFA-AC-IFX to colitis-induced mice was effective in alleviating the progression of ulcerative colitis, while oral IFX solution had no efficacy. These results suggest that a pH-responsive FA-AC-based nanocomposite system can be a new platform for the site-selective oral delivery of therapeutic antibodies.

关键词： Infliximab Aminoclay Colonic delivery:TNF-x Infammation Folate rceptor Anibody Nanocomposite

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Production of high-purity Mg metal from dolomite through novel molten salt electrolysis and vacuum distillation

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Journal of Magnesium and Alloys 2023年第4期11卷 1308-1320页

作者： Hyeong-Jun Jeoung Tae-Hyuk lee Jin-Young lee kyung-Woo Yi Jungshin Kang Korea Institute of Geoscience and Mineral Resources 124 Gwahak-ro Yuseong-guDaejeon 34132Republic of Korea Department of Materials Science and Engineering Seoul National University1 Gwanak-roGwanak-guSeoul 08826Republic of Korea Department of Resources Engineering University of Science and Technology217 Gajeong-ro Yuseong-guDaejeon 34113Republic of Korea School of Materials Science and Engineering Pusan National University2 Busandaehak-roGeumjeong-guBusan 46241Republic of Korea

In this study,a novel Mg production process for producing high-purity Mg metal from dolomite was *** the electrolysis of calcined dolomite was conducted using Cu cathode and C anode in MgF_(2)–LiF molten salt at 1083–1173 K by applying an average current of 1.42–1.46 A for 9.50–21.0 h,the current efficiency of 66.4–88.6%was *** produced Mg alloys consisted of MgCu_(2)and Cu(Mg)or MgCu_(2)and CuMg_(2)phases,depending on the Mg concentration in the Mg *** the electrolysis of calcined dolomite was conducted in MgF_(2)–LiF–CaF_(2)molten salt at 1083 K,the current efficiency was 40.9–71.4%,owing to undesired reactions such as electroreduction of Ca^(2+)or/and CO_(3)^(2−)***,the current efficiency increased from 40.9%to 63.2%by utilizing a Pt anode,because the occurrence of CO_(3)^(2−)ions in the molten salt was *** vacuum distillation of the obtained Mg alloys at 1300 K for 10 h,Mg metal with a purity of 99.9996–99.9998%was ***,the feasibility of this novel process for the production of high-purity Mg metal from dolomite was demonstrated.

关键词： High-purity magnesium Dolomite Magnesium oxide Electrolytic process Copper metal cathode Vacuum distillation

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Synthesis and Characterization of SiO_2 Coated γ-Fe_2O_3 Nanocomposite Powder for Hyperthermic Application

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Journal of Materials Science & Technology 2010年第4期26卷 333-336页

作者： Ji-hun Yu Jai-Sung lee Yong-Ho Choa Heinrich Hofmann Korea Institute of Materials Science Changwon 641-831 Korea Division of Materials and Chemical Engineering Hanyang University Ansan 426-791 Korea Swiss Federal Institute of Technology at Lausanne Lausanne CH-1015 Switzerland

SiO2 coated γ-Fe2O3 nanocomposite powder has been successfully synthesized by chemical vapor condensation process and its feasibility on hyperthermic application was investigated in this study. The power loss of SiO2 coated γ-Fe2O3 nanocomposite powder which means the magnetic heating effect under alternative magnetic field was much higher than the single phase γ-Fe2O3 nano powder due to the very fine size under 20 nm and well dispersion in biologically compatible SiO2 matrix. The superparamagnetism and hyperthermic property of SiO2 coated γ-Fe2O3 nanocomposite powder were discussed in terms of microstructural development in this study.

关键词： Hyperthermia Nano-Bio Chemical vapor condensation Silica coated iron oxide nanoparticle Superparamagnetism

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Focal incidental colorectal fluorodeoxyglucose uptake:Should it be spotlighted?

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World Journal of Clinical Cases 2024年第15期12卷 2466-2474页

作者： Haejun lee kyung-Hoon Hwang Department of Nuclear Medicine Gachon University College of MedicineGil Medical CenterIncheon 21565South Korea

Fluorine-18 fluorodeoxyglucose(F-18 FDG)positron emission tomography/computed tomography(PET/CT)has emerged as a cornerstone in cancer evaluation imaging,with a well-established history spanning several *** imaging modality,encompassing the examination of the body from the base of the skull to the upper thighs,comprehensively covers the chest and abdominopelvic regions in a singular scan,allowing for a holistic assessment of nearly the entire body,including areas of marginal *** inherent advantage of this expansive scan range lies in its potential to unveil unexpected incidental abnormal hypermetabolic *** identification of incidental focal FDG uptake within colorectal regions during PET/CT scans is not an uncommon occurrence,albeit fraught with challenges associated with non-specific FDG *** presence of benign colorectal lesions or physiological uptake poses a particular obstacle,as these may manifest with FDG uptake levels that mimic ***,physicians are confronted with a diagnostic dilemma when encountering abnormal FDG uptake in unexpected colorectal *** studies have presented divergent results concerning these *** uptake value and its derivatives have served as pivotal metrics in quantifying FDG uptake in PET *** this article,we aim to succinctly explore the distinctive characteristics of FDG,delve into imaging findings,and elucidate the clinical significance of incidental focal colorectal *** discussion aims to contribute valuable insights into the nuanced interpretation of such findings,fostering a comprehensive understanding.

关键词： Focal Incidental Colorectal Fluorodeoxyglucose Positron emission tomography Hypermetabolism

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Unexpected focal fluorodeoxyglucose uptake in main organs;pass through or pass by?

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World Journal of Clinical Cases 2024年第11期12卷 1885-1899页

作者： Haejun lee kyung-Hoon Hwang Department of Nuclear Medicine Gachon University College of MedicineGil Medical CenterIncheon 21565South Korea

Since the inception of fluorine-18 fluorodeoxyglucose(F-18 FDG),positron emission tomography/computed tomography(PET/CT)utilizing F-18 FDG has become widely accepted as a valuable imaging modality in the field of oncology,with global prevalence in clinical *** that a single Torso PET/CT scan encompasses the anatomical region from the skull base to the upper thigh,the detection of incidental abnormal focal hypermetabolism in areas of limited clinical interest is both feasible and not *** investigations have been undertaken to delineate the distinctive features of these findings,yet the outcomes have proven *** incongruent results of these studies present a challenge for physicians,leaving them uncertain about the appropriate course of *** article provides a succinct overview of the characteristics of fluorodeoxyglucose,followed by a comprehensive discussion of the imaging findings and clinical significance associated with incidental focal abnormal F-18 FDG activity in several representative *** conclusion,while the prevalence of unrecognized malignancy varies across organs,malignancies account for a substantial proportion,ranging from approximately one-third to over half,of incidental focal *** light of these rates,physicians are urged to exercise vigilance in not disregarding unexpected uptake,facilitating more assured clinical decisions,and advocating for further active evaluation.

关键词： Incidental Focal Incidentaloma Fluorodeoxyglucose Positron emission tomography Hypermetabolism

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Ecotoxicity evaluation of Cu-and Fe-CNT complexes based on the activity of bacterial bioluminescence and seed germination

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Journal of Environmental Sciences 2018年第5期30卷 198-205页

作者： In Chul Kong kyung Seok Ko Mun Hui lee Ji Hwoan lee Young-Hwan Han Department of Environmental Engineering Yeungnam UniversityGyungsan 38541Republic of Korea Geologic Environment Division Korea Institute of Geoscience and Mineral Resources(KIGAM)Daejeon 34132Republic of Korea School of Materials Science and Engineering Yeungnam University Gyungsan 38541Republic of Korea International School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430079China

The toxic effects of the composites of Fe^0 and Cu^0 with different percentages of CNTs were examined based on the activity of bacterial bioluminescence and seed germination. In terms of the EC50 values, the toxic effects of Cu^0 on bacterial bioluminescence and seed germination were approximately 2 and 180 times greater than that of Fe^0, respectively. The toxicity increased with increasing CNT content in the Cu-CNT mixtures for both organisms,whereas opposite results were observed with Fe-CNT mixtures. The mean toxic effects of Cu-CNT（6%） were approximately 1.3–1.4 times greater than that of Cu-CNT（0%）, whereas the toxic effects of Fe-CNT（6%） were approximately 2.1–2.5 times lower than that of Fe-CNT（0%） for both the bioluminescence activity and seed germination. The causes of this phenomenon are unclear at this point. More research will be needed to elucidate the mechanism of the toxicity of nano-mixture materials and the causes of the different patterns of toxicity with Cu-and Fe-CNT mixtures.

关键词： Metal-CNT complex Bioluminescence Seed germination Toxic effect

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