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Effects of homogenization temperature on microstructure and mechanical properties of high-speed-extruded Mg–5Bi–3Al alloy

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Journal of Magnesium and Alloys 2022年第10期10卷 2833-2846页

作者： jae Won Cha Sang-Cheol Jin jae-gil jung Sung Hyuk Park School of Materials Science and Engineering Kyungpook National University80 DaehakroDaegu 41566Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effects of billet homogenization temperature on the dynamic recrystallization behavior during high-speed extrusion and resultant microstructure and tensile properties of the Mg–5Bi–3Al(BA53,wt%)*** billets homogenized at 350 and450℃(350H and 450H billets)are extruded at a high speed of 69 m/*** 350H billet has a relatively smaller grain size and a higher abundance of fine Mg3Bi2particles compared to the 450H *** extrusion of the 350H billet,enhanced dynamic recrystallization occurs as a result of its finer grains and abundance of particles,while the growth of recrystallized grains is suppressed by the grain-boundary pinning effect of ***,the extruded 350H material is characterized by smaller grains,relatively greater number of Mg3Bi2particles,and a higher internal strain energy than the extruded 450H *** tensile strength of the extruded 350H material is higher than that of the extruded 450H material owing to stronger grain-boundary hardening,particle hardening,and strain hardening *** extruded 350H material also exhibits a higher tensile elongation as its smaller grains inhibit the formation of crack-inducing undesirable twins during *** results from this study demonstrate that a decrease in the homogenization temperature from 450 to 350℃leads to improved strength and ductility in the high-speed-extruded BA53 material.

关键词： Mg–Bi–Al alloy High-speed extrusion Homogenization Dynamic recrystallization Tensile properties

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

Prediction of grain structure in direct-chill cast Al–Zn–Mg–Cu billets using cellular automaton-finite element method

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Progress in Natural Science:Materials International 2021年第3期31卷 434-441页

作者： Min-Seok Kim Sang-Hwa Lee jae-gil jung Kwangjun Eah Department of Materials Science and Engineering Gachon University Metallic Materials Division Korea Institute of Materials Science Department of Materials Science and Engineering Yonsei University

A cellular automaton-finite element(CA-FE) model was used to predict the solidification grain structure of permanent mold cast A7086 alloy. In this model, a Gaussian distribution of nucleation sites was adopted, and the Kurz-Giovanola-Trivedi model was extended to a multicomponent Al–Zn–Mg–Cu alloy system to determine the growth kinetics of the dendrite tip. For describing the Gaussian distribution of nucleation sites on the mold surface, an empirical relationship between the initial cooling rate of the melt and the nucleation density was proposed. Under various casting conditions, the calculated grain structures agreed well with the experimental results. Subsequently, the model was applied to the direct-chill(DC) cast billets, and the simulated grain structures reproduced well the experimental results. This confirmed that the current CA-FE model can be used practically and effectively in DC casting processes.

关键词： Cellular automaton-finite element (CA-FE) model Direct-chill casting Al–Zn–Mg–Cu alloy A7068 alloy Grain structure

EXPERIMENTAL ESTIMATION OF A SCALING EXPONENT FOR TIP VORTEX CAVITATION VIA ITS INCEPTION TEST IN FULL-AND MODEL-SHIP

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Journal of Hydrodynamics 2012年第5期24卷 658-667页

作者： LEE Jeung-Hoon jung jae-Kwon LEE Kyung-Jun HAN jae-Moon PARK Hyung-gil SEO Jong-Soo Samsung Ship Model Basin(SSMB) Marine Research InstituteSamsung Heavy IndustriesScience TownDaejeon 305-380Korea

Tip vortex cavitation noise of marine propeller became primary concems to reduce hazardous environmental impacts from commercial ship or to keep the underwater surveillance of naval ships. The investigations of the tip vortex and its induced noise are normally conducted through the model test in a water cavitation tunnel. However the Reynolds number of model-test is much smaller than that of the full-scale, which subsequently results in the difference of tip vortex cavitation inception. Hence, the scaling law between model- and full-scales needs to be identified prior to the prediction and assessment of propeller noise in full scale. From previous researches, it is generally known that the incipient caivtation number of tip vortex can be represented as a power of the Reynolds number. However, the power exponent for scaling, which is the main focus of this research, has not been clearly studied yet. This paper deals with the estimation of scaling exponent based on tip vortex cavitation inception test in both full- and model-scale ships. Acoustical measurements as well as several kind of signal processing technique for an inception criterion suggest the scaling exponent as 0.30. The scaling value proposed in this study shows slight difference to the one of most recent research. Besides, extrapolation of model-ship noise measurement using the proposed one predicts the full-scale noise measurement with an acceptable discrepancy.

关键词： tip vortex cavitation underwater radiated noise scaling exponent

Ecological evaluation of marine macroalgal communities on five islands of Korea in the Yellow Sea

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Acta Oceanologica Sinica 2023年第6期42卷 49-56页

作者： Su Jin Han jae-gil Jang Hyun-jung Kim Tae-Ho Seo Joo Myun Park Marine Eco-Technology Institute Co. Ltd.Busan 48520R.O.Korea Coastal Production Institute Yeosu 59699R.O.Korea Dokdo Research Center Korea Institute of Ocean Science&TechnologyUljin 36315R.O.Korea

Macroalgae have long been used as biological indicators of marine ecosystem health worldwide due to their ecological importance and sensitivity to environmental stress.A number of previous studies have utilized macroalgal communities in monitoring surveys of environmental *** study examined the characteristics and patterns of marine macroalgal communities in the Yellow Sea off the western coast of *** were analyzed for the number of species,biomass,and coverage ratio by macroalgal *** the study period,82 macroalgal species(10 green algae,17 brown algae,and 55 red algae)were identified at the five study sites,with the highest number of species found at Gwanrido and Uido(both containing 41 species)and the lowest at Daeijakdo(27 species).The average biomass(via dry weight)was 98.63 g/m^(2),consisting of green algae(8.39 g/m^(2)),brown algae(35.08 g/m^(2)),and red algae(55.16 g/m^(2)).The dominant macroalgae species in terms of biomass were Corallina pilulifera,Sargassum thunbergii,and Ulva australis in the intertidal zones,and Botryocladia wrightii and Gelidium elegans in the subtidal ***,evenness,and diversity indices based on the biomass of abundant species were 5.08,0.65,and 2.30,respectively,over the entire study *** on the evaluation of the environmental states by the community indices,overall,the Ecological Evaluation Index of macroalgae communities in the study area was marked as“Good-Moderate”,but was determined as“ModerateLow”at several sites during *** results can be a direct approach in the assessment of coastal habitats in which anthropogenic as well as climate change influences persist.

关键词： macroalgae Yellow Sea ecological state groups ecological index Ecological Evaluation Index(EEI) community variable

Reduced interface energy loss in non-fullerene organic solar cells using room temperature-synthesized SnO2 quantum dots

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Journal of Materials Science & Technology 2020年第17期52卷 12-19页

作者： In Su Jin Minwoo Park jae Woong jung Department of Advanced Materials Engineering for Information&Electronics Kyung Hee University1732 Deogyeong-daeroGiheung-guYongin-siGyeonggi-do 446-701Republic of Korea Department of Chemical and Biological Engineering Sookmyung Women's UniversitySeoul 04310Republic of Korea

We herein report the room temperature synthesis of colloidal SnO2 quantum dots and their application in non-fullerene organic solar cells as an excellent electron transport *** thiourea-assisted hydrolysis at room temperature affords the nanocrystalline SnO2 quantum dots with a diameter of 3-4 *** utilization of the SnO2 quantum dots as an electron transporting layer effectively reduces the interfacial trap density and charge recombination in the solar cell devices,leading to not only the reduced energy loss but also excellent photocurrent *** optimized organic solar cells employing SnO2 quantum dots with polyethylenimine ethoxylated achieves power conversion efficiencies up to 12.023%with a VOC,a JSC,and a FF of 0.89 V,18.89 mA cm^–2,and *** work suggest that the SnO2 quantum dot is a promising electron transporting material to construct efficient organic solar cells for practical *** work also demonstrates the key strategy for thiourea-assisted hydrolysis to synthesize fine and nanocrystalline SnO2 quantum dots.

关键词： Energy loss Organic solar cells Interface SnO2 Quantum dots

Simultaneously enhanced efficiency and ambient stability of inorganic perovskite solar cells by employing tetramethylammonium chloride additive in CsPbI2Br

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Journal of Materials Science & Technology 2022年第7期102卷 224-231页

作者： In Su Jin Bhaskar Parida jae Woong jung Department of Advanced Materials Engineering for Information and Electronics Kyung Hee University1732 Deogyeong-daeroGiheung-guYongin-siGyeonggi-do 446-701Republic of Korea Integrated Education Institute for Frontier Materials(BK21 Four) Kyung Hee University1732 Deogyeong-daeroGiheung-guYongin-siGyeonggi-do 446-701Republic of Korea

Although all-inorganic perovskites possess suitable bandgap and thermal stability for photovoltaic ap-plications,the unstable film morphologies,and poor moisture stabilities lag behind the organic-inorganic hybrid ***,we demonstrate that high qualityα-CsPbI_(2 ) Br films with improved phase sta-bility,high crystallinity,and pinhole-free film morphology was achieved by employing tetramethylammo-nium chloride(TMACl)as an *** a result,the TMACl-added CsPbI_(2) Br films exhibited high power conversion efficiency of 14.12%with an open-circuit voltage of 1.19 V,a short-circuit current density of 15.08 mA/cm^(2),and a fill factor of *** importantly,the TMACl addition imparts hydrophobicity to the film surface of CsPbI_(2) Br,which delivered excellent stability up to 30 days in the ambient condition and thermal stability at 85℃ for 156 h,***,the TMACl-added device also exhibited excellent PCE of 27.16%under indoor light source(1000 lux),which presents a promising approach for designing stable but high performance all-inorganic perovskite solar cells.

关键词： Inorganic perovskite solar cells CsPbI2Br Additive Tetramethylammonium chloride Efficiency

Porous Microspheres Comprising CoSe2 Nanorods Coated with N-Doped Graphitic C and Polydopamine-Derived C as Anodes for Long-Lived Na-Ion Batteries

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Nano-Micro Letters 2022年第7期14卷 118-139页

作者： jae Seob Lee Rakesh Saroha jung Sang Cho Department of Engineering Chemistry Chungbuk National UniversityCheongjuChungbuk 361-763Republic of Korea

Metal–organic framework-templated nitrogen-doped graphitic carbon(NGC)and polydopaminederived carbon(PDA-derived C)-double coated one-dimensional CoSe_(2) nanorods supported highly porous threedimensional microspheres are introduced as anodes for excellent Na-ion batteries,particularly with long-lived cycle under carbonate-based electrolyte *** microspheres uniformly composed of ZIF-67 polyhedrons and polystyrene nanobeads(φ=40 nm)are synthesized using the facile spray pyrolysis technique,followed by the selenization process(P-CoSe_(2)@NGC NR).Further,the PDA-derived C-coated microspheres are obtained using a solution-based coating approach and the subsequent carbonization process(P-CoSe_(2)@PDA-C NR).The rational synthesis approach benefited from the synergistic effects of dual carbon coating,resulting in a highly conductive and porous nanostructure that could facilitate rapid diffusion of charge species along with efficient electrolyte infiltration and effectively channelize the volume ***,the prepared nanostructure exhibits extraordinary electrochemical performance,particularly the ultra-long cycle life *** instance,the advanced anode has a discharge capacity of 291(1000th cycle,average capacity decay of 0.017%)and 142 mAh g^(-1)(5000th cycle,average capacity decay of 0.011%)at a current density of 0.5 and 2.0 A g^(-1),respectively.

关键词： Spray pyrolysis Sodium-ion batteries Cobalt selenide nanorods Porous microspheres Dual carbon coating

Survival improvement and prognostic factors in recent management of extrahepatic cholangiocarcinoma:A single-center study

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Hepatobiliary & Pancreatic Diseases International 2020年第2期19卷 153-156页

作者： jung Wan Choe Hyo jung Kim jae Seon Kim Division of Gastroenterology Department of Internal MedicineKorea University Ansan HospitalKorea University College of Medicine516 Gojan-dongDanwon-guAnsan-siGyeonggi-do15355Korea Division of Gastroenterology Department of Internal MedicineKorea University Guro HospitalKorea University College of Medicine148 Gurodong-roGuro-guSeoul 08308Korea

Background:Cholangiocarcinoma was considered as a dismal disease with very poor prognosis until *** is increasingly found due to increased life *** surgical and medical management were advanced recently,data on the prognosis,especially extrahepatic cholangio-carcinoma(ECC),were *** study aimed to identify clinicopathologic features and prognosis of patients with ***:Patients followed up and diagnosed with ECC between January 2014 and December 2016 at a tertiary hospital were included,whereas those with intrahepatic cholangiocarcinoma,gallbladder cancer,and ampullary cancer were ***:A total of 83 patients were followed after the treatment(49 men and 34 women;median age 73.3 years).Cancer location was classified as distal common bile duct(25 patients),proximal com-mon bile duct(24 patients),common hepatic duct(20 patients),and hilar(14 patients).About 14.5%of patients had history of another malignant neoplasm,and 24.1%patients had chronic ***-cal resection was performed in 54 patients(65%)and dysplasia was combined in 63%(34/54).Adjuvant chemotherapy was performed in 54%(29/54),but only 7 underwent palliative chemotherapy in 29 non-surgical *** median overall survival in all patients was 30.9 *** analyzing the treatment modality,median survival of adjuvant chemotherapy,surgery only,palliative chemotherapy,and support-ive care groups were 42.9,30.9,12.0,and 8.9 months,respectively(P<0.05).In the Cox regression analy-sis of survival,age,surgical resection,chemotherapy,and comorbidity were significant prognostic factors,and the comorbidity was the only significant prognostic factor in the multivariable analysis(hazard ratio[HR]=2.80;95%CI:1.32–5.95;P=0.007).In a subgroup analysis of surgical patients,the presence of dysplasia was a favorable prognostic factor in the multivariable analysis(HR=0.29;95%CI:0.09–0.91;P=0.033).Conclusions:The overall survival of patients with ECC wa

关键词： Cholangiocarcinoma Survival Prognosis