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Effect of pre-deformation on precipitation behavior of AZ80 alloy:Comparison of slip-and twinning-dominant deformation

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Journal of Magnesium and Alloys 2024年第9期12卷 3616-3630页

作者： hyun Ji Kim Sang Cheol Jin Sumi Jo Sung Hyuk park Department of Materials Science and Metallurgical Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Graduate School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigates the effect of the deformation mode on the precipitation behavior of an extruded Mg-8.0Al-0.5Zn-0.2Mn(AZ80)*** alloy samples are compared after the application of 3.5%tension and 3.5%compression along the extrusion direction to induce slip-dominant and twinning-dominant deformation modes,*** pre-compressed(PC)sample,which contained numerous{10-12}tension twins,has a reduced grain size and a higher internal strain than the pre-tensioned(PT)sample,which is attributed to the inherent internal strain that occurs during the formation and growth of the *** a result,the precipitation behavior of the PC sample is accelerated,leading to its short peak aging time of 32 h,which is lower than those of the PT and as-extruded samples(48 and 100 h,respectively).Furthermore,fine continuous precipitates(CPs)rapidly form within the{10-12}twins,contributing to the enhanced *** precipitates(DPs),which have a hardness comparable to the CP-containing twinned regions,in the PC sample experience less coarsening during aging than those in the PT sample due to growth inhibition by the{10-12}***,the{10-12}twins generated under the twinning-dominant deformation condition lead to enhanced precipitation behaviors,including the preferential formation and refinement of CPs and the suppressed coarsening of ***,pre-deformation that occurs{10-12}twinning exhibits more pronounced effects on precipitation acceleration and microstructural modification than slip-inducing pre-deformation.

关键词： AZ80 alloy Slip Twinning Precipitation Hardness

Complications and management of forgotten long-term biliary stents

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World Journal of Gastroenterology 2017年第4期23卷 622-628页

作者： Se Hoon Sohn Jae hyun park Kook hyun Kim Tae Nyeun Kim Division of Gastroenterology and Hepatology Department of Internal MedicineYeungnam University College of MedicineDaegu 42415South Korea

AIMTo evaluate complications and management outcomes of retained long-term plastic biliary *** plastic biliary stent placement was performed in 802 patients at Yeungnam University Hospital between January 2000 and December 2014. Follow-up loss with a subsequently forgotten stent for more than 12 mo occurred in 38 patients. We retrospectively examined the cause of biliary stent insertion, status of stents, complications associated with biliary stents and management outcomes of long-term plastic biliary stents. Continuous variables were analyzed using the t test. Observed frequencies in subsets of the study population were compared using Fisher’s exact test and χ2 tests. Statistical significance was defined as P < 0.05 (two-tailed).RESULTSMean age of patients was 73.7 ± 12 years and male-to-female ratio was 2.2:1. Indications of plastic biliary stent insertion were bile duct stones (63.2%, 24/38) and benign bile duct stricture (52.6%, 20/38). Mean duration of retained plastic stent was 22.6 ± 12.2 mo, and in 10 cases (26.3%), stents were retained for more than 24 mo. Common bile duct (CBD) stones or sludge were found in most cases (92.1%, 35/38). The most common complication was acute cholangitis (94.7%, 36/38). Stent removal by endoscopic approach was successfully performed in 92.1% (35/38) of the cases. In 3 cases, an additional plastic stent was inserted alongside the previous stent due to failure of the stent removal. Endoscopic removal of bile duct stones was successful in 73.7% (28/38) of the cases. When patients were divided into two groups by duration of stent placement (12 to 24 mo vs over 24 mo), there were no differences in the development of cholangitis, presence of biliary stones, and success rate of endoscopic removal of stones and biliary *** most common complication of retained long-term plastic biliary stents was acute cholangitis associated with CBD stones. Endos

关键词： Biliary stent Long-term complications Forgotten stents Acute cholangitis Biliary stone

Influence of undissolved second-phase particles on dynamic recrystallization behavior of Mg–7Sn–1Al–1Zn alloy during low-and high-temperature extrusions

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Journal of Materials Science & Technology 2021年第12期71卷 87-97页

作者： hyun Ji Kim Sang-Cheol Jin Jae-Gil Jung Sung Hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508Republic of Korea

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg–7 Sn–1 Al–1 Zn(TAZ711)alloy on the dynamic recrystallization(DRX)behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the *** this end,partially homogenized(PH)and fully homogenized(FH)billets are extruded at temperatures of250 and 450°*** PH billet contains fine and coarse undissolved Mg_(2) Sn particles in the interdendritic region and along the grain boundaries,*** fine particles(<1μm in size)retard DRX during extrusion at 250°C via the Zener pinning effect,and this retardation causes a decrease in the area fraction of dynamically recrystallized(DRXed)grains of the extruded *** addition,the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce *** contrast,in the FH billet,numerous nanosized Mg_(2) Sn precipitates are formed throughout the material during extrusion at 250°C,which,in turn,leads to the formation of small,uniform DRXed grains by the grain-boundary pinning effect of the *** the PH billet is extruded at the high temperature of 450°C,the retardation effect of the fine particles on DRX is weakened by their dissolution in theα-Mg matrix and the increased extent of thermally activated grain-boundary *** contrast,the coarse Mg_(2) Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon,which results in an increase in the area fraction of DRXed *** both low and high extrusion temperatures,the extruded material fabricated using the PH billet,which contains both fine and coarse undissolved particles,has a lower tensile strength than that fabricated using the FH billet,which is virtually devoid of second-phase *** lower strength of the former is attributed mai

关键词： Mg–Sn alloy Second-phase particle Extrusion Homogenization Dynamic recrystallization

Characterization of flexible copper laminates fabricated by Cu electro-plating process

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中国有色金属学会会刊：英文版 2009年第4期19卷 965-969页

作者： Chang-Min LEE Jun-hyung LIM Soo-Min HWANG Eui-Cheol park Jong-hyun SHIM Jin-hyun park Jinho JOO Seung-Boo JUNG School of Advanced Materials Science and Engineering Sungkyunkwan University

Flexible copper clad laminates(FCCLs) were fabricated using the electro-plating process and the combined effect of the current density and plating time on their surface morphology,texture,hardness,electrical resistivity and folding behavior was *** achieve Cu layers with similar thicknesses,the current density was varied in the range of 0.2-3 A/dm2 and the plating time was controlled in the range of 0.5-7.5 h to compensate for the variation of the current *** surface morphology,hardness,and folding behavior were characterized by atomic force microscopy,nanoindentation technique and Massachusett Institute of Technology folding endurance test,*** X-ray diffraction patterns indicated that the Cu phase was formed without any secondary phases;however,the preferred orientation changed from(220) to(111) as the current density increased over 1 A/*** addition,it was observed that the root-mean-square and hardness values decreased when the current density increased and the plating time decreased *** electrical resistivity was as low as approximately 21 nΩ·m and the number of cycles without failure in the folding test was over 15 000,which were comparable to those of commercial FCCLs.

关键词：电镀工艺层压板铜层制备表征电流密度原子力显微镜纳米压痕技术

Improved photocatalytic activity of surface charge functionalized ZnO nanoparticles using aniline

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Journal of Materials Science & Technology 2021年第17期76卷 1-10页

作者： Chatchai Rodwihok Korakot Charoensri Duangmanee Wongratanaphisan Won Mook Choi Seung hyun Hur hyun Jin park Jin Suk Chung School of Chemical Engineering University of Ulsan680-749.South ICorea Department of Biotechnology College of Life Sciences andBiotechnologyKorea University145 Anam-roSeongbuk-guSeoul02841South Korea Research Center in Physics andAstronomy Faculty of ScienceChiang Mai UniversityChiang Mai50200Thailand

Functionalization of aniline molecules on zinc oxide(ZnO)nanoparticles is reported using a simple impregnation *** ZnO samples were systematically characterized based on morphology,surface and optical properties,and photocatalytic performance towards methyl orange(MO).Aniline functionalization increased the surface charge of the modified *** to pristine ZnO,the aniline-functionalized ZnO yielded faster photodegradation of MO,degrading 98.29%of MO in 60 min and superoxide radicals were the major species during the MO photodegradation *** results indicate that the improvement of photocatalytic degradation could be attributed to opposite charge-induced surface ***,protonated amine as a positively charged molecule was expected to increase the surface adsorption of MO(as an anionic dye)on ZnO nanoparticles surfaces,thereby increasing their photocatalytic degradation performance.

关键词： Photocatalysts Surface charge ZnO Aniline Methyl orange

Free radical scavenger effect of rebamipide in sperm processing and cryopreservation

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Asian Journal of Andrology 2003年第3期5卷 195-201页

作者： Nam Cheol park hyun Jun park Kyeong Mi Lee Dong Gil Shin Department of Urology College of Medicine Pusan National University Busan 602 739 KoreaDepartment of Urology College of Medicine Pusan National University Busan 602 739 KoreaDepartment of Urology College of Medicine Pusan National University Busan 602 739 KoreaDepartment of Urology College of Medicine Pusan National University Busan 602 739 Korea

Aim: To study the effect of rebamipide added to semen samples and cryoprotectant on reactive oxygen species (ROS) production. Methods: Semen samples from 30 fertile and healthy volunteers were collected by masturbation after 2 days - 3 days of abstinence. After liquefaction, the specimens were diluted with sperm wash media to a uniform density of 20×106/mL. Rebamipide was added to semen samples and cryoprotectant to a final concentration of 10 μmol/L, 30 μmol/L, 100 μmol/L or 300 μmol/L. Specimens were incubated at 37 ℃ in a 0.5 % CO2 incubator for 1 h or cryopreserved at -196 ℃ LN2 for 3 days. The sperm motility and viability and the levels of ROS and lipid peroxidation of sperm membrance were assessed before and after incubation and cryopreservation by means of computer assisted semen analyzer, eosin-nigrosin stain, chemiluminescence and thiobarbituric acid assay, respectively. Results: The sperm motility was significantly increased after incubation with 100 μmol/L and 300 μmol/L rebamipide (P0.05). The levels of ROS and lipid peroxidation in semen were significantly decreased in proportion to the concentrations of rebamipide both after incubation and cryopreservation (P<0.05). Conclusion: Rebamipide is an effective free radical scavenger in semen in vitro.

关键词： male infertility reactive oxygen species rebamipide

Intraoperative neurophysiological monitoring in spinal surgery

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World Journal of Clinical Cases 2015年第9期3卷 765-773页

作者： Jong-Hwa park Seung-Jae hyun Department of Neurosurgery Spine CenterSeoul National University Bundang Hospital Seoul National University College of Medicine

Recently, many surgeons have been using intraoperative neurophysiological monitoring(IOM) in spinal surgery to reduce the incidence of postoperative neurological complications, including level of the spinal cord, cauda equina and nerve root. Several established technologies are available and combined motor and somatosensory evoked potentials are considered mandatory for practical and successful IOM. Spinal cord evoked potentials are elicited compound potentials recorded over the spinal cord. Electrical stimulation is provoked on the dorsal spinal cord from an epidural electrode. Somatosensory evoked potentials assess the functional integrity of sensory pathways from the peripheral nerve through the dorsal column and to the sensory cortex. For identification of the physiological midline, the dorsal column mapping technique can be used. It is helpful for reducing the postoperative morbidity associated with dorsal column dysfunction when distortion of the normal spinal cord anatomy caused by an intramedullary cord lesion results in confusion in localizing the midline for the myelotomy. Motor evoked potentials(MEPs) consist of spinal, neurogenic and muscle MEPs. MEPs allow selective and specific assessment of the functional integrity of descending motor pathways, from the motor cortex to peripheral muscles. Spinal surgeons should understand the concept of the monitoring techniques and interpret monitoring records adequately to use IOM for the decision making during the surgery for safe surgery and a favorable surgical outcome.

关键词： Motor-evoked potentials Somatosensoryevoked potentials Intraoperative neurophysiological monitoring Direct wave Spinal surgery

Efficient Gauss-Seidel Precoding with Parallel Calculation in Massive MIMO Systems

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Computers, Materials & Continua 2022年第1期70卷 491-504页

作者： hyun-Sun Hwang Jae-hyun Ro Chan-Yeob park Young-Hwan You Hyoung-Kyu Song Department of Information and Communication Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea Department of Convergence Engineering for Intelligent Drone Sejong UniversitySeoul05006Korea Department of Computer Engineering Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea

A number of requirements for 5G mobile communication are satisfied by adopting multiple input multiple output(MIMO)*** inter user interference(IUI)which is an inevitable problem in MIMO systems becomes controllable when the precoding scheme is *** this paper,the horizontal Gauss-Seidel(HGS)method is proposed as precoding scheme in massive MIMO *** massive MIMO systems,the exact inversion of channel matrix is impractical due to the severe computational ***,the conventionalGauss-Seidel(GS)method is used to approximate the inversion of channel *** GS has good performance by using previous calculation results as ***,the required time for obtaining the precoding symbols is too long due to the sequential process of ***,the HGS with parallel calculation is proposed in this paper to reduce the required *** rows of channel matrix are eliminated for parallel calculation *** addition,HGSuses the ordered channelmatrix to prevent performance degradation which is occurred by parallel *** HGS with proper number of parallelly computed symbols has better performance and reduced required time compared to the traditional GS.

关键词： Massive MIMO GS matrix inversion linear precoding

Expression of prothymosin α predicts early recurrence and poor prognosis of hepatocellular carcinoma

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Hepatobiliary & Pancreatic Diseases International 2015年第2期14卷 171-177页

作者： Sang Yun Ha Dae hyun Song Soo hyun Hwang Soo Youn Cho Cheol-Keun park Department of Pathology Samsung Medical CenterSungkyunkwan University School of Medicine

BACKGROUND：Prothymosinα（PTMA）is a nuclear oncoprotein-transcription factor essential for cell cycle progression and *** was overexpressed in several human malignancies including hepatocellular carcinoma（HCC）.However,the prognostic significance of PTMA protein expression in HCC remains *** the present study,we evaluated PTMA protein expression by immunohistochemistry in order to elucidate the prognostic roles of PTMA in HCC ***： By immunohistochemistry, we investigated the expression of PTMA protein in tumor tissue from 226 HCC patients who underwent curative hepatectomy. Univariate and multivariate analyses were performed to evaluate its predic- tive value for tumor recurrence and survival of patients. The median follow-up period was 120 months. RESULTS： PTMA expression was observed in 162 （71.7%） of the 226 HCC patients and was significantly associated with higher Edmondson grade, microvascular invasion, intrahe- patic metastasis, higher American Joint Committee on Cancer （AJCC） T-stage, and lower albumin level. PTMA expression was an independent predictor of early recurrence （P=0.001）. PTMA expression showed an unfavorable influence on recurrence- free survival （RFS）（P〈0.001）. Subgroup analysis showed that among patients with tumor size _〈5.0 cm （140 patients）, patients at AJCC T-stage I （95 patients） and patients with a-fetoprotein ≤20 ng/mL （83 patients）, the differences in RFS between PTMA- positive and PTMA-negative groups were also statistically sig- nificant （P=0.017, P=0.002 and P=0.002, respectively）. In addi- tion, PTMA expression was an independent predictor of shorter RFS （P=0.011）. PTMA expression showed an unfavorable influ- ence on overall survival （P=0.014）, but was not an independent predictor of shorter overall survival （P=0.161）. CONCLUSIONS： PTMA protein expression might be a novel predictor of early recurrence and RFS in HCC patients, even those at early stage or with a-fetoprotein-negative after curative hep

关键词： prothymosin a hepatocellular carcinoma recurrence