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Chemical and mechanical properties of stainless, environment-friendly, and nonflammable Mg alloys (SEN alloys): A review

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Journal of Magnesium and Alloys 2024年第3期12卷 841-872页

作者： Jong Un Lee Hyun Ji kim Sang-cheol jin Ye jin kim Young Min kim Bong Sun You Jun Ho Bae Sung Hyuk park Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea Department of Materials Science and Metallurgical Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Missile Research Institute Agency for Defense DevelopmentDaejeon 34060Republic of Korea

This review article provides overall understanding of stainless,environment-friendly,and nonflammable Mg alloys(SEN alloys)recently developed at the Korea Institute of Materials *** alloys are produced by adding small amounts of Ca and Y(each<1 wt%)into commercial Mg–Al based alloys,resulting in exceptional ignition and corrosion resistances and impressive mechanical *** main advantages of SEN alloys are as follows.(1)A dense multi-oxide layer of SEN alloys comprising MgO,CaO,and Y_(2)O_(3) impedes the outward dispersion of Mg vapor and the inward penetration of O_(2) during oxidation,thereby enhancing the oxidation and ignition resistances.(2)The presence of Ca-and Y-based second-phase particles in SEN alloys can enhance their corrosion resistance because Ca-containing particles prevent the spread of corrosion,and the replacement of Al-containing particles with less noble ones containing Y(e.g.,Al–Mn–Y or Al–Y particles)retards corrosion.(3)The addition of minor amounts of Ca and Y renders excellent mechanical properties due to improved strengthening *** enhanced properties are attributed to more pronounced dynamic recrystallization and grain refining behaviors caused by the second-phase particles during extrusion.(4)Despite the presence of various types of second-phase particles,the fatigue properties of SEN9 alloys are similar to those of commercial AZ91 alloys.(5)Simultaneous introduction of Ca and Y suppresses the formation of Mg17Al12 discontinuous precipitates during aging,leading to the enhanced elongation of aged SEN alloys.(6)Adding mischmetal into the SEN9 alloy leads to a six-fold enhancement in ***,the studies conducted on SEN alloys demonstrate their excellent ignition and corrosion resistances and mechanical properties,which broaden the industrial applications of Mg alloys by addressing their inherent weaknesses.

关键词： SEN magnesium alloy Corrosion resistance Ignition resistance Mechanical properties Extrudability.

Validity of fatty liver prediction scores for diagnosis of fatty liver by Fibroscan

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Hepatobiliary & Pancreatic Diseases International 2024年第4期23卷 353-360页

作者： Seogsong Jeong Sun Jae park Seong kyun Na Sang Min park Byung-cheol song Yun Hwan Oh Department of Biomedical Sciences Seoul National University Graduate SchoolSeoul 03080Korea Department of Biomedical Informatics CHA University School of MedicineCHA UniversitySeongnam 13488Korea Department of Internal Medicine Inje University College of MedicineSeoul 50834Korea Department of Family Medicine Seoul National University HospitalSeoul National University College of MedicineSeoul 03080Korea Department of Internal Medicine Jeju National University HospitalJeju National University College of MedicineJeju 63241Korea Department of Family Medicine Jeju National University HospitalJeju National University College of MedicineJeju 63241Korea Department of Family Medicine Chung-Ang University Gwangmyeong HospitalChung-Ang University College of MedicineGwangmyeong 14353Korea

Background:The Korea National Health and Nutrition Examination Survey nonalcoholic fatty liver disease(K-NAFLD)score was recently developed with the intent to operationally define nonalcoholic fatty liver disease(NAFLD).However,there remained an external validation that confirmed its diagnostic performance,especially in patients with alcohol consumption or hepatitis virus ***:Diagnostic accuracy of the K-NAFLD score was evaluated in a hospital-based cohort consisting of 1388 participants who received Fibroscan®.Multivariate-adjusted logistic regression models and the contrast estimation of receiver operating characteristic curves were used for validation of the K-NAFLD score,fatty liver index(FLI),and hepatic steatosis index(HSI).Results:K-NAFLD-moderate[adjusted odds ratio(aOR)=2.53,95%confidence interval(CI):1.13-5.65]and K-NAFLD-high(aOR=4.14,95%CI:1.69-10.13)groups showed higher risks of fatty liver compared to the K-NAFLD-low group after adjustments for demographic and clinical characteristics,and FLI-moderate and FLI-high groups revealed aORs of 2.05(95%CI:1.22-3.43)and 1.51(95%CI:0.78-2.90),*** addition,the HSI was less predictive for Fibroscan®-defined fatty *** K-NAFLD and FLI also demonstrated high accuracy in the prediction of fatty liver in patients with alcohol consumption and chronic hepatitis virus infection,and the adjusted area under curve values were comparable between K-NAFLD and ***:Externally validation of the K-NAFLD and FLI showed that these scores may be a useful,noninvasive,and non-imaging modality for the identification of fatty *** addition,these scores also predicted fatty liver in patients with alcohol consumption and chronic hepatitis virus infection.

关键词： Nonalcoholic fatty liver disease Fatty liver index Hepatic steatosis index

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(Science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa Lee joong Wook Lee Jae Hee Sung Seong Ku Lee Ki-Yong kim Advanced Photonics Research Institute GISTGwangju61005Korea Department of Physics and Optoelectronics Convergence Research Center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangju61005Korea Institute for Research in Electronics and Applied Physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched

Ultra-flexible graphene/nylon/PDMS coaxial fiber-shaped multifunctional sensor

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Nano Research 2023年第4期16卷 5541-5547页

作者： Peddathimula Puneetha Siva Pratap Reddy Mallem Sung cheol park Seoha kim dong Hun Heo cheol Min kim Jaesool Shim Sung jin An dong-Yeon Lee Kwi-Il park Department of Robotics and Intelligent Machine Engineering/College of Mechanical and IT Engineering Yeungnam UniversityGyeongsan 38541Republic of Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Advanced Material Research Center Kumoh National Institute of TechnologyGumi 39177Republic of Korea School of Mechanical Engineering Yeungnam UniversityGyeongsan 38541Republic of Korea Department of Materials Science and Engineering Kumoh National Institute of TechnologyGumi 39177Republic of Korea

The development of flexible and wearable devices is mainly required for tactile sensing;as such devices can adapt to complicated nonuniform surfaces,they can be applied to the human ***,it remains necessary to simultaneously achieve small-scale,portable,and stable developments in such ***,this work aims at fabricating a novel,lightweight,ultra-flexible,and fiber-shaped coaxial structure with a diameter of 0.51 mm using polydimethylsiloxane/graphene/nylon material,based on piezoresistive and triboelectric *** piezoresistive-based robotic-hand-controlled sensor thus realized exhibits a response time of 120 ms and a fast recovery time of 55 ***,the piezoresistive-based sensors effectively feature whisker/joystick-guided behaviors and also sense the human finger *** to the triboelectric-based selfpowered nanogenerator behavior,the resulting sensor can convert mechanical motion into electrical energy,without adversely affecting human ***,this triboelectric-based human finger sensor can be operated under different bending modes at specific ***,this multifunctional sensor is cost-effective and suitable for various applications,including robotichand-controlled operations in medical surgery,whisker/joystick motions in lightweight drone technology,and navigation with highsensitivity components.

关键词： extremely lightweight ultra-flexible piezoresistive/triboelectric sensor human-machine whisker

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

High-performance non-enzymatic glucose sensor based on Co_(3)O_(4)/rGO nanohybrid

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Rare Metals 2023年第9期42卷 3046-3053页

作者： Ling-Yun Xiong You-joong kim won-cheol Seo Han-kyu Lee Woo-Chul Yang Wan-Feng Xie Department of Physics Dongguk UniversitySeoul04620South Korea School of Electronics and Information Industry Joint Center for Ocean Observation and Broadband CommunicationQingdao UniversityQingdao266071China

There has been substantial interest in designing and fabricating electrochemical non-enzyme sensors for glucose detection with a focus on the nanocomposites used between metal oxide and the two-dimensional *** this work,Co_(3)O_(4)/reduced graphene oxide(rGO)nanocomposite was obtained and used as a modified electrochemical electrode for the detection of trace *** to the results,the electrocatalytic performances of Co_(3)O_(4)nanoparticles for the oxidation of glucose were substantially enhanced with the addition of a small amount of r ***,the Co_(3)O_(4)/r GO modified electrode exhibited a sensitivity of 82μA·mmol^(-1)·cm^(-2),a detection limit of 50μmol·L^(-1)(signal noise ratio(S/N)=3),and a fast response time of about 1 s under optimal *** enhanced performances of the Co_(3)O_(4)/r GO modified electrode are attributable to the high absorption oxygen(O_(Ads))and synergistic effect between Co_(3)O_(4)and r *** results indicate that Co_(3)O_(4)/r GO nanocomposite is a promising candidate for being used as the active material in real-world electrochemical biosensors.

关键词： Co_(3)O_(4) Reduced graphene oxide(rGO) Glucose Electrocatalytic

Vapor-Liquid Equilibrium of Toluene-Polycyclic Aromatic Hydrocarbon System in Sub- and Supercritical State

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Chinese Journal of Chemical Engineering 2002年第6期10卷 657-660页

作者： cheol-joong kim dong-bok won 等 R&Dcenter SKcorporationTaejon305-370Korea DeptartmentofChemicalEngineering ChungnamNationalUniversityTaejon305-765Korea

关键词：亚临界状态超临界流体萃取选择性甲苯多环芳香烃气液平衡

A Regional Economy's Resistance to the COVID-19 Shock: Sales Revenues of Micro-, Small-, and Medium-Sized Enterprises in south Korea

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International Journal of Disaster Risk Science 2022年第2期13卷 190-198页

作者： Seong-jin Lee joong-Hoo park Seung-Min Cha donghyun kim Department of Public Policy and Management.Pusan National University Busan 46241South Korea Department of Urban Planning and Engineering Pusan National UniversityBusan 46241South Korea

The coronavirus disease 2019(COVID-19) is a global pandemic that has heavily impacted not only the health sector, but also the economic sector in *** countries have projected a negative economic impact, and the effect on micro-, small-, and medium-sized enterprises(MSMEs) is predicted to be significantly *** study estimated the regional resistance of MSME sales revenues and identified the regional economic factors that affect resistance by analyzing south Korea, a country with one of the lowest economic impact projections from COVID-19. Resistance was estimated by comparing sales revenues and changes in resistance observed during the early COVID-19 period to those recorded in the same weeks(weeks 6 to 9) of 2019. The factors that affect regional resistance were determined by conducting robust regression and spatial regression analyses. The results show that the number of confirmed COVID-19 cases, a direct risk factor, is negatively related to regional resilience, while diversity is positively related to regional resistance. To improve the regional resistance against uncertain events, this study recommends increased diversity among regional industrial structures to reduce the duration of the early shock of an unexpected adverse event.

关键词： COVID-19 Economic resistance MSMEs south Korea

Comparative study of extrudability, microstructure, and mechanical properties of AZ80 and BA53 alloys

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Journal of Magnesium and Alloys 2023年第1期11卷 249-258页

作者： Sang-cheol jin Jae won Cha Jongbin Go Jun Ho Bae Sung Hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering Kyoto UniversityKyoto 606-8501Japan Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

The extrudability,microstructural characteristics,and tensile properties of the Mg–5Bi–3Al(BA53)alloy are investigated herein by comparing them with those of a commercial Mg–8Al–0.5 Zn(AZ80)*** AZ80 is extruded at 400℃,severe hot cracking occurs at exit speeds of 4.5 m/min or *** contrast,BA53 is successfully extruded without any surface cracking at 400℃ and at high exit speeds of 21–40 m/*** extruded at 3 m/min(AZ80–3)and 40 m/min(BA53–40),both AZ80 and BA53 exhibited completely recrystallized microstructures with abasal ***,BA53–40 has a coarser grain structure owing to grain growth promoted by the high temperature in the deformation ***80–3 contains a continuous network of Mg_(17)Al_(12) particles along the grain boundaries,which form via static precipitation during natural air-cooling after the material exits the extrusion ***53–40 contains coarse Mg_(3)Bi_(2) particles aligned parallel to the extrusion direction along with numerous uniformly distributed fine Mg_(3)Bi_(2) ***80–3 has higher tensile strength than BA53–40 because the relatively finer grains and larger number of solute atoms in AZ80–3 result in stronger grain-boundary and solid-solution hardening effects,*** BA53 is extruded at a high temperature and extrusion speed of 400℃ and 40 m/min,respectively,the extruded material has a high tensile yield strength of 188 *** can be primarily attributed to the large particle hardening effect resulting from the numerous fine Mg_(3)Bi_(2) particles.

关键词： Mg-Bi-Al alloy Extrusion Hot cracking Second phase Tensile properties