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Effect of refinement of grains and icosahedral phase on hot compressive deformation and processing maps of Mg-Zn-Y magnesium alloys with different volume fractions of icosahedral phase

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Journal of Materials Science & Technology 2019年第1期35卷 181-191页

作者： T.Y.kwak W.J.Kim Department of Materials Science and Engineering Hongik University

The effect of the volume fraction of I-phase on the hot compressive behavior and processing maps of the extruded Mg-Zn-Y alloys was examined, and the obtained results were compared with those of the cast alloys in a previous work. The average grain sizes, fractions of dynamically recrystallized(DRXed) grains,and sizes of DRXed grains of the extruded alloys after compressive deformation were significantly smaller,higher and smaller, respectively, than those of the cast alloys after compressive deformation under the same experimental conditions. This was because the microstructures of the extruded alloys, having much more grain boundaries and more refined I-phase particles than the cast alloys, provided a larger number of nucleation sites for dynamic recrystallization than those of the cast alloys. The constitutive equations for high-temperature deformation of the extruded and cast alloys could be derived using the same activation energy for plastic flow, which was close to the activation energy for lattice diffusion in *** with the cast alloys, the onset of the power law breakdown(PLB) occurred at larger ZenerHolloman(Z) parameter values in the extruded alloys. This was because the extruded alloys had finer initial grain sizes and higher fractions of finer DRXed grains compared to the cast alloys, such that the onset of PLB caused by creation of excessive concentrations of deformation-induced vacancies was delayed to a higher strain rate and a lower temperature. The flow-stress difference between the extruded alloys and the cast alloys could be attributed to the difference in the fraction of DRXed grains. According to the processing maps, the extruded alloys exhibited higher power dissipation efficiency and flow stability than the cast alloys. This agreed with the microstructural observations.

关键词： Hot compression Magnesium alloy Processing map Grain refinement Dynamic recrystallization

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Integrated Design of D.D.I., Filament Winding and Curing Processes for Manufacturing the High Pressure Vessel(Type Ⅱ)

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Chinese Journal of Mechanical Engineering 2019年第5期32卷 170-181页

作者： Hyoseo kwak Gunyoung Park Hansaem Seong Chul Kim Research Institute of Mechanical Technology Pusan National UniversityPusan 609-735Korea Department of Mechanical Convergence Technology Pusan National UniversityPusan 609-735Korea School of Mechanical Engineering Pusan National UniversityPusan 609-735Korea

As energy crisis and environment pollution all around the world threaten the widespread use of fossil fuels,compressed natural gas(CNG)vehicles are explored as an alternative to the conventional gasoline powered *** of the limited space available for the car,the composite pressure vessel(TypeⅡ)has been applied to the CNG vehicles to reach large capacity and weight lightening *** pressure vessel(TypeⅡ)is composed of a composite layer and a metal *** metal liner is formed by the deep drawing and ironing(D.D.I.)process,which is a complex process of deep drawing and *** cylinder part is reinforced by composite layer wrapped through the filament winding process and is bonded to the liner by the curing *** this study,an integrated design method was presented by establishing the techniques for FE analysis of entire processes(D.D.I.,filament winding and curing processes)to manufacture the CNG composite pressure vessel(TypeⅡ).Dimensions of the dies and the punches of the 1 st(cup drawing),2 nd(redrawing-ironing 1-ironing 2)and 3 rd(redrawing-ironing)stages were calculated theoretically,and shape of tractrix die to be satisfied with the minimum forming load was suggested for life improvement and manufacturing costs in the *** of the composite material was determined in the filament winding process,finally,conditions of the curing process(number of heating stage,curing temperature,heating rate and time)were proposed to reinforce adhesive strength between the composite layers.

关键词： Pressure vessel(Type Ⅱ) D.D.I. Filament winding Curing process FEM

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Superplastic behavior of an ultrafine-grained Mg-13Zn-1.55Y alloy with a high volume fraction of icosahedral phases prepared by high-ratio differential speed rolling

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Journal of Materials Science & Technology 2017年第9期33卷 919-925页

作者： T.Y.kwak W.J.Kim Rare Metal R&BD Group Korea Institute of Industrial Technology Department of Materials Science and Engineering Hongik University

An ultrafine-grained（UFG） Mg-13Zn-1.55 Y alloy（ZW132） with a high volume fraction（7.4%） of icosahedral phase（I-phase, Mg;Zn;Y） particles was prepared by applying high-ratio differential speed rolling（HRDSR） on the cast microstructure following homogenization. The alloy exhibited excellent superplasticity at low temperatures(tensile elongations of 455% and 1021% 473 K-10;s;and 523 K-10;s;,respectively). Compared with UFG Mg-9.25Zn-1.66 Y alloy（ZW92） with a lower volume fraction of I-phase particles（4.1%）, which was prepared using the same processing routes, the UFG ZW132 alloy exhibited a higher thermal stability of grain size. Rapid grain coarsening, however, occurred at temperatures beyond523 K, leading to a loss of superplasticity. The high-temperature deformation behavior of the HRDSRprocessed ZW132 alloy could be well described assuming that the mechanisms of grain boundary sliding and dislocation climb creep competed with each other and considering that the grain-size was largely increased by accelerated grain growth at the temperatures beyond 523 K.

关键词： Magnesium alloy Superplastic deformation Ultrafine grain Icosahedral quasicrystal Grain growth

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Novel Architecture of Security Orchestration, Automation and Response in Internet of Blended Environment

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Computers, Materials & Continua 2022年第10期73卷 199-223页

作者： minkyung Lee Julian Jang-Jaccard Jin kwak ISAA Lab Department of Cyber SecurityAjou UniversitySuwon16499Korea Department of Computer Science and Information Technology Massey UniversityAuckland0745New Zealand Department of Cyber Security Ajou UniversitySuwon16499Korea

New technologies that take advantage of the emergence of massive Internet of Things(IoT)and a hyper-connected network environment have rapidly increased in recent *** technologies are used in diverse environments,such as smart factories,digital healthcare,and smart grids,with increased security *** intend to operate Security Orchestration,Automation and Response(SOAR)in various environments through new concept definitions as the need to detect and respond automatically to rapidly increasing security incidents without the intervention of security personnel has *** facilitate the understanding of the security concern involved in this newly emerging area,we offer the definition of Internet of Blended Environment(IoBE)where various convergence environments are interconnected and the data analyzed in *** define Blended Threat(BT)as a security threat that exploits security vulnerabilities through various attack surfaces in the *** propose a novel SOAR-CUBE architecture to respond to security incidents with minimal human intervention by automating the BT response *** Security Orchestration,Automation,and Response(SOAR)part of our architecture is used to link heterogeneous security technologies and the threat intelligence function that collects threat data and performs a correlation analysis of the *** is operated under Collaborative Units of Blended Environment(CUBE)which facilitates dynamic exchanges of data according to the environment applied to the IoBE by distributing and deploying security technologies for each BT type and dynamically combining them according to the cyber kill chain stage to minimize the damage and respond efficiently to BT.

关键词： Blended threat(BT) collaborative units for blended environment(CUBE) internet of blended environment(IoBE) security orchestration,automation and response(SOAR)

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Influence of external loading and halocline on phosphorus release from sediment in an artificial tidal lake

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International Journal of Sediment Research 2020年第2期35卷 146-156页

作者： Yong-Hoon Jeong Dong-Heui kwak Industry-Academia Collaboration Foundation Chonbuk National University Center for Jeongeup Industry-Academy Cooperation Chonbuk National University

Many of the dams built in estuaries in the last century have difficulty with water quality *** factors have affected the estuary lake water,most importantly external loadings,tidal currents,and increases in the phosphorus(P) release from sediment,so that most water quality characteristics in the estuary are highly interactive and *** the current study,water quality measurements were made in the laboratory and field,and a series of phosphorus release experiments was done to understand the behavior of P in an estuary *** concentrations of chemical oxygen demand(COD),chlorophyll-a(Chl-a),and total P(TP) showed an increasing trend when the pollutant loading of the influent stream water was *** measurements showed increasing trends,which indicates the constituents are produced in the internal environment of the *** a large amount of freshwater flowed in from the upper watershed,density stratification was observed,which forms strongly because of the salinity of *** the period of stratification,a hypoxic layer formed,which can accelerate P *** the open and dosed conditions of the release experiments,the P release rate was much higher under the closed condition than under the open *** maximum P release rates from the sediment collected from the five main sites of the lake were more than 2.5 times the P loading from the inflowing streams in ***,the release rate was higher mid-reservoir than down-reservoir where a halocline was evident The pollutant load discharged from the tributary watershed was deposited on the bottom mid-reservoir,whereas it was washed out downreservoir because of the density stratification and strong tide in that *** sustainably manage water quality and decrease lake eutrophication in brackish environments formed by freshwater from streams mixing with seawater entering through sluice dikes,different measures than those applied in strictly freshwater environments ar

关键词： Estuary Halocline Phosphorus release Reservoir Sediment Stratification

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Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy

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中国有色金属学会会刊：英文版 2008年第A01期18卷 369-373页

作者： S.O.KIM J.S.kwak Graduate School of Mechanical Engineering Pukyong National UniversitySouth Korea School of Mechanical Engineering Pukyong National UniversitySouth Korea

The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing *** in a case of polishing nonferrous materials,the strength of magnetic force is very low and it leads lower polishing *** magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength is one of the most famous nonferrous *** improving strategy of the magnetic force for the AZ31 magnesium alloy installed with a permanent magnet was proposed and experimental verification was carried *** the proposed strategy,the effect of process parameters on the surface roughness of the AZ31 magnesium alloy was evaluated by a design of experimental method.

关键词：镁合金物理性能磁力最优化设计磁性

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Elucidating Ion Transport Phenomena in Sulfide/Polymer Composite Electrolytes for Practical Solid-State Batteries

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Nano-Micro Letters 2023年第10期15卷 416-432页

作者： Kyeong‑Seok Oh Ji Eun Lee Yong‑Hyeok Lee Yi‑Su Jeong Imanuel Kristanto Hong‑Seok min Sang‑Mo Kim Young Jun Hong Sang Kyu kwak Sang‑Young Lee Department of Chemical and Biomolecular Engineering Yonsei University50 Yonsei‑roSeodaemun‑guSeoul 03722Republic of Korea Department of Chemical and Biological Engineering Korea University145 Anam‑roSeongbuk‑guSeoul 02841Republic of Korea School of Energy and Chemical Engineering Ulsan National Institute of Science and Technology(UNIST)50 UNIST‑gilEonyang‑eupUlju‑gunUlsan 44919Republic of Korea Hyundai Motor Company 150Hyundaiyeonguso‑roNamyang‑eupHwaseong‑siGyeonggi‑do 18280Republic of Korea

Despite the enormous interest in inorganic/polymer composite solid-state electrolytes(CSEs)for solid-state batteries(SSBs),the underlying ion transport phenomena in CSEs have not yet been ***,we address this issue by formulating a mechanistic understanding of bi-percolating ion channels formation and ion conduction across inorganic-polymer electrolyte interfaces in CSEs.A model CSE is composed of argyrodite-type Li_6PS_5Cl(LPSCl)and gel polymer electrolyte(GPE,including Li~+-glyme complex as an ion-conducting medium).The percolation threshold of the LPSCl phase in the CSE strongly depends on the elasticity of the GPE ***,manipulating the solvation/desolvation behavior of the Li~+-glyme complex in the GPE facilitates ion conduction across the LPSCl-GPE *** resulting scalable CSE(area=8×6(cm×cm),thickness~40μm)can be assembled with a high-mass-loading LiNi_(0.7)Co_(0.15)Mn_(0.15)O_(2)cathode(areal-mass-loading=39 mg cm~(-2))and a graphite anode(negative(N)/positive(P)capacity ratio=1.1)in order to fabricate an SSB full cell with bi-cell *** this constrained cell condition,the SSB full cell exhibits high volumetric energy density(480 Wh L_(cell)~(-1))and stable cyclability at 25℃,far exceeding the values reported by previous CSE-based SSBs.

关键词： Solid-state batteries Composite solid-state electrolytes Ion transport phenomena Bi-percolating ion channels Interfacial resistance

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Duo Property Applied to Powers and Regular Elements

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Algebra Colloquium 2023年第1期30卷 15-30页

作者： TaiKeun kwak Yang Lee Zhelin Piao Yeonsook Seo Department of Mathematics Daejin UniversityPocheon 11159Korea Department of Mathematics Yanbian UniversityYanjiJilin 133002China Institute of Basic ScienceDaejin UniversityPocheon 11159Korea Department of Mathematics Yanbian UniversityYanjiJilin 133002China Department of Mathematics Pusan National UniversityBusan 46241Korea

The object of this article is to initiate the study of a class of rings in which the right duo property is applied in relation to powers of elements and the monoid of all regular *** rings shall be called right *** investigate the structures of group rings,right quotient rings,matrix rings and(skew)polynomial rings,through the study of right exp-DR *** addition,we provide a method of constructing finite non-abelian p-groups for any prime p.

关键词： right(exp-)DR ring regular element (weakly)right duo ring right quotient ring group ring

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ATA指南、kwak TI-RADS、ACR TI-RADS及C TI-RADS对儿童甲状腺结节的诊断效能比较

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肿瘤影像学 2024年第3期33卷 276-281页

作者：高文会孙颖华复旦大学附属儿科医院超声科上海201102

目的:对比2011年kwak版甲状腺影像报告和数据系统(Thyroid Imaging Reporting and Data System,TIRADS),2015年美国甲状腺协会(American Thyroid Association,ATA)《成人甲状腺结节与分化型甲状腺癌指南》(ATA指南),2017年美国放射学会(American College of Radiology,ACR)TI-RADS及2020年中华医学会超声医学分会发布的《2020甲状腺结节恶性危险分层的中国指南:C TI-RADS》这4种甲状腺结节分级系统对儿童甲状腺良恶性结节的诊断效能。方法:收集2008年1月1日—2021年12月31日在复旦大学附属儿科医院超声科行超声检查并经甲状腺穿刺活检或术后病理学检查确诊的80例甲状腺结节患儿,根据kwak TI-RADS、ATA指南、ACR TI-RADS以及C TI-RADS对甲状腺结节超声图像进行回顾性分级,以最终病理学检查结果为金标准,计算不同风险分层的恶性百分比,并绘制受试者工作特征(receiver operating characteristic,ROC)曲线,比较这4种分级系统ROC曲线的曲线下面积(area under curve,AUC)、诊断灵敏度及特异度。结果:ATA指南、kwak TI-RADS、ACR TI-RADS及C TI-RADS的灵敏度分别为85.7%、74.3%、71.4%及77.1%,特异度分别为64.4%、66.7%、80.0%及69.3%,AUC分别为0.764、0.772、0.809及0.770。这4种检测方法对儿童甲状腺结节均具有较高的诊断效能,其中ACR TI-RADS诊断效能稍高于其他3种指南(Pkwak TI-RADS 4c,ATA指南中的高度可疑恶性以及C TI-RADS中的4C(高度可疑恶性)。结论:将4种成人甲状腺超声风险评级标准应用于儿童,均有较好的诊断效能,其中ACR TI-RADS诊断效能高于其他3种。

关键词：甲状腺结节超声甲状腺影像报告和数据系统

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Matrix Rings over Reflexive Rings

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Algebra Colloquium 2018年第3期25卷 459-474页

作者： Jeoung Soo Cheon Tai Keun kwak Yang Lee Department of Mathematics Pusan National University Busan 46241 Korea Department of Mathematics Daejin University Pocheon 11159 Korea Institute of Basic Science Daejin University Pocheon 11159 Korea

The concept of reflexive property is introduced by Mason. This note concerns a ring-theoretic property of matrix rings over reflexive rings. We introduce the concept of weakly reflexive rings as a generalization of reflexive rings. From any ring, we can construct weakly reflexive rings but not reflexive, using its lower nilradical. We study various useful properties of such rings in relation with ideals in matrix rings, showing that this new property is Morita invariant. We also investigate the weakly reflexive property of several sorts of ring extensions which have roles in ring theory.

关键词： weakly reflexive ring reflexive ring power of ideal matrix ring ring of minimal order

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