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Grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic Fe(41)Mn(25)Ni(24)Co8Cr2high entropy alloy

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journal of Materials Science & Technology 2020年第7期42卷 190-202页

作者： H.T.jeong W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic Fe(41)Mn(25)Ni(24)Co8 Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5μm),8.1μm and 590.2μ*** the temperature between 298 and773 K,the material with the large grain size of 590.2μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain *** material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%)due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement *** tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5μ*** deformation behavior of the Fe(41)Mn(25)Ni(24)Co8 Cr2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic *** activation energies for plastic flow for the materials with different grain sizes were similar as^199 kj/*** predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation *** sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85%due to it

关键词： High entropy alloys Grain size High temperature deformation mechanism Tensile behavior Grain boundary sliding

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Microstructure tailoring of Al_(0.5)CoCrFeMnNi to achieve high strength and high uniform strain using severe plastic deformation and an annealing treatment

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journal of Materials Science & Technology 2021年第12期71卷 228-240页

作者： H.T.jeong W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

Ultrafine-grained alloys fabricated by severe plastic deformation(SPD)have high strength but often poor uniform *** via high-ratio differential speed rolling(HRDSR)followed by an annealing treatment was applied to Al_(0.5)CoCrFeMnNi to design the microstructure from which both high strength and high uniform strain can be *** optimized microstructure was composed of an ultrafine-grained FCC matrix(1.7-2μm)with a high fraction of high-angle grain boundaries(61%-66%)and ultrafine BCC particles(with a size of 0.6-1μm and a volume fraction of8%-9.3%)distributed uniformly at the grain boundaries of the FCC *** the severely plastically deformed microstructure,the nucleation kinetics of the BCC phase was *** static recrystallization(CSRX)took place during the annealing process at 1273 *** of the BCC phase particles occurring concurrently with CSRX effectively retarded the grain growth of the FCC *** precipitation of the hard and brittleσphase was,however,*** annealed sample processed by HRDSR with the optimized microstructure exhibited a high tensile strength of over 1 GPa with a good uniform elongation of 14%-20%.These tensile properties are comparable to those of transformation-induced plasticity *** mechanisms of the severely plastically deformed alloy before and after annealing were identified,and each strengthening mechanism contribution was *** calculated results matched well with the experimental results.

关键词： High entropy alloys Severe plastic deformation Uniform ductility High strength Dual phase Annealing

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Effects of grain size and Al addition on the activation volume and strain-rate sensitivity of CoCrFeMnNi high-entropy alloy

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journal of Materials Science & Technology 2023年第12期143卷 242-252页

作者： H.T.jeong W.j.kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

The activation volume(V∗)and strain-rate sensitivity exponent(m)of CoCrFeMnNi and Al_(0.5)CoCrFeMnNi high entropy alloys(HEAs)with various grain sizes(ranging between 2.4 and 356μm)were measured at different strain rates and strain levels at room *** the strain rate decreased,the plastic strain decreased,and the grain size increased,V∗*** enhanced solid-solution strengthening by addition of aluminum decreased V∗.The Hassen plot was modified to capture the grain-size depen-dence of V∗by considering the grain-size dependence of the dislocation *** the plastic strain increased,the strain rate decreased,and the grain size decreased,m *** behavior of m could be quantitatively predicted by using equations derived for the grain-size-dependent V∗and flow *** difference in the grain-size dependence of m between conventional face centered cubic(FCC)metals and FCC HEAs over the nanograin size range could not be explained in terms of a relatively large Hall-Petch slope of the FCC HEAs compared with that of the FCC conventional metals,but was explainable in terms of a substantially higher probability of activation of grain-boundary diffusion-controlled grain-boundary-sliding mechanism at nanograin sizes in the FCC conventional metals than in the FCC HEAs.

关键词： Grain size High entropy alloys Activation volume Strain-rate sensitivity Solid solution

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Strain-induced the dark current characteristics in InAs/GaSb type-Ⅱ superlattice for mid-wave detector

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journal of Semiconductors 2020年第6期41卷 35-38页

作者： H.j.Lee S.y.Ko y.H.kim j.Nah i3system Inc.26-32Gajeongbuk-roDaejeon34113Yuseong-guKorea Department of Electrical Engineering Chungnam National UniversityDaejeon34134Yuseong-guKorea

Type-Ⅱsuperlattice(T2SL)materials are the key element for infrared(IR)***,it is well known that the characteristics of the detectors with the T2SL layer are greatly affected by the strain developed during the growth process,which determines the performance of IR ***,great efforts have been made to properly control the strain effect and develop relevant analysis methods to evaluate the strain-induced dark current *** this work,we report the strain-induced dark current characteristics in InAs/GaSb T2SL MWIR *** overall strain of InAs/GaSb T2SL layer was analyzed by both high-resolution X-ray diffraction(HRXRD)and the dark current measured from the absorber layer at the elevated temperatures(≥110 K),where the major leakage current component is originated from the reduced minority carrier lifetime in the absorber *** findings indicate that minority carrier lifetime increases as the tensile strain on the InAs/GaSb T2SL is more compensated by the compressive strain through‘InSb-like’interface,which reduces the dark current density of the ***,tensile strain compensated devices exhibited the dark current density of less than 2×10^-5 A/cm^2 at 120 K,which is more than one order of magnitude lower value compared to that of the device without tensile strain relaxation.

关键词： mid-wave detector InAs/GaSb typeⅡsuper lattice dark current

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Serum Levels of Antioxidant Vitamins in Relation to Coronary Artery Disease: A Case Control Study of Koreans

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Biomedical and Environmental Sciences 1996年第2期9卷 229-235页

作者： kim S. y. LEE-kim y. C. kim M. K. SUH j. y. CHUNG E. j. CHO. S. y. CHO. B. K. AND SUHI(Department of Food and Nutrition Cardiovascular Center Department of Preventive Medicine yonsei University, Seoul, Korea) Department of Food and Nutrition Yonsei University Seoul Korea.

With the changes in trends of disease pattern from infectious to chronic degenerative disease, cardiovascular disease has been considered as the major cause of death in *** studies have been done on the antioxidant effects of some vitamins in the prevention of chronic illness, but not many in relation to the cardiovascular ***, the relation between antioxidant vitamins, mainly α-tocopherol (α-T) and B-carotene (B-C), and coronary artery disease (CAD) such as angina pectoris and myocardial infarction has been investigated in this *** blood samples were obtained from the CAD patients who were angiographically diagnosed within a month (100 case group). Patients who had an experience of PTCA or CABG were excluded from the study. Control subjects were healthy adults who had normal EKG values, no chest pain and no past history of cardiac disease (100 control group). All subjects were free of serum lipid lowering drugs. Serum α-T and B-C were analysed using HPLC. In addition to antioxidant vitamins, serum lipids (total cholesterol, HDL, TG) were also measured. Each case and control was matched in terms of age and sex. And all the CAD risk factors such as blood pressure, smoking, alcohol, serum lipid profile and BMI were adjusted to determine pure effect(s) of α-T and B-C on the *** concentrations of both α-T and B-C were significantly lower in the CAD group than those in control group (Py. As for the levels of B-C, it shows inverse relation with age, but not for the α-T Ievels. Serum levels of both vitamins did not show any significant differences in terms of sex, but men have a tendency o higher levels of B-C,but lower levels of α-T

关键词： Case Serum Levels of Antioxidant Vitamins in Relation to Coronary Artery Disease A Case Control Study of Koreans GSH

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Present Status of the KSTAR Superconducting Magnet System Development

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Plasma Science and Technology 2004年第5期6卷 2445-2450页

作者： Keeman kim H.K.Park K.R.Park B.S.Lim S.I.Lee M.K.kim y.Chu W.H.Chung S.H.Baek j.y.Cho H.yonekawa A.Chertovskikh y.B.Chang j.S.kim C.S.kim D.j.kim N.H.Song K.P.kim y.j.Song I.S.Woo W.S.Han D.K.Lee y.K.Oh K.W.Cho j.S.Park G.S.Lee H.j.Lee T.K.Ko S.j.Lee National NationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalNationalKorea Atomic Energy Research InstituteDaejeonRepublic of KoreaYonsei UniversitySeoulRepublic of KoreaYonsei UniversitySeoulRepublic of Korea Fusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science InstituteDaejeonRepublic of KoreaFusion R&D CenterKorea Basic Science

The mission of Korea Superconducting Tokamak Advanced Research (KSTAR)project is to develop an advanced steady-state superconducting tokamak for establishing a scientificand technological basis for an attractive fusion reactor. Because one of the KSTAR mission is toachieve a steady-state operation, the use of superconducting coils is an obvious choice for themagnet system. The KSTAR superconducting magnet system consists of 16 Toroidal Field (TF) coils and14 Poloidal Field (PF) coils. Internally-cooled Cable-In-Conduit Conductors (CICC) are put into usein both the TF and PF coil systems. The TF coil system provides a field of 3.5 T at the plasmacenter and the PF coil system is able to provide a flux swing of 17 V-sec. The major achievement inKSTAR magnet-system development includes the development of CICC, the development of a full-size TFmodel coil, the development of a coil system for background magnetic-field generation , theconstruction of a large-scale superconducting magnet and CICC test facility. TF and PF coils are inthe stage of fabrication to pave the way for the scheduled completion of KSTAR by the end of 2006.

关键词： superconducting magnet KSTAR CICC

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Physical properties of sprayed antimony doped tin oxide thin films:The role of thickness

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journal of Semiconductors 2011年第5期32卷 10-17页

作者： A.R.Babar S.S.Shinde A.V.Moholkar C.H.Bhosale j.H.kim K.y.Rajpure Electrochemical Materials Laboratory Department of PhysicsShivaji UniversityKolhapur-416 004India Department of Materials Science and Engineering Chonnam National University300 Yongbong-DongBuk-GuGwangju500-757South Korea

Transparent conducting antimony doped tin oxide （Sb：SnO2） thin films have been deposited onto pre- heated glass substrates using a spray pyrolysis technique by varying the quantity of spraying solution. The structural, morphological, X-ray photoelectron spectroscopy, optical, photoluminescence and electrical properties of these films have been studied. It is found that the films are polycrystalline in nature with a tetragonal crystal structure having orientation along the （211） and （112） planes. Polyhedrons like grains appear in the FE-SEM images. The average grain size increases with increasing spraying quantity. The compositional analysis and electronic behaviour of Sb：SnO2 thin films were studied using X-ray photoelectron spectroscopy. The binding energy of Sn3ds/2 for all samples shows the Sn^4＋ bonding state from SnO2. An intensive violet luminescence peak near 395 nm is observed at room temperature due to oxygen vacancies or donor levels formed by Sb^5＋ ions. The film deposited with 20 cc solution shows 70 % transmittance at 550 nm leading to the highest figure of merit （2.11 × 10^-3 Ω^-1）. The resistivity and carrier concentration vary over 1.22 × 10^-3 to 0.89 × 10^-3Ω cm and 5.19 ×10^20 to 8.52 × 10^20 cm^-3, respectively.

关键词： semiconductors microstructure optical properties electrical properties

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The Stanley Neuropathology Consortium Integrative Database (SNCID) for Psychiatric Disorders

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Neuroscience Bulletin 2019年第2期35卷 277-282页

作者： Sanghyeon kim Maree j.Webster Stanley Brain Research Laboratory Stanley Medical Research Institute

The Stanley Medical Research Institute(SMRI)is a nonprofit organization with a primary mission to fund research on the cause and treatment of severe mental *** SMRI also supports a brain bank as part of the mission to facilitate research into mental *** SMRI brain bank distributes postmortem samples from individuals with serious mental illness,free of charge,to scientists around the *** SMRI brain bank is recognized for the unique way it is set up,organized,and *** of demographically-matched groups of patients with schizophrenia,bipolar disorder(BP),or major depression(DEP)and unaffected controls are organized such that all researchers applying for tissue received samples from the same cohort.

关键词： SNCID for Psychiatric Disorders DRD RNA

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Aqueous-processable,naphthalene diimide-based polymers for eco-friendly fabrication of high-performance,n-type organic electrolyte-gated transistors

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Science China Chemistry 2022年第5期65卷 973-978页

作者： Dahyun jeong Min je kim Seungjin Lee jin-Woo Lee youngwoong kim Hyeong jun kim jeong Ho Cho Bumjoon j.kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical and Biomolecular Engineering Sogang UniversitySeoul 04107Republic of Korea

Organic electrolyte-gated transistors(OEGTs) have the benefits of low power consumption and large current ***,the electrical performance of n-type OEGTs lags far behind that of p-type *** this study,we design a series of polymers,P(NDITEG-T) and P(NDIMTEG-T),comprising a naphthalene diimide backbone for n-type charge transport and oligo(ethylene glycol)(OEG) side chains for high ionic conductivity and eco-friendly solution *** incorporation of the OEG chain facilitates the electrochemical doping of the semiconductor by ions to realize high-performance,n-type ***,in OEGTs,P(NDITEG-T) achieves a high electron mobility of 1.0 × 10^(-1) cm^(2) V^(-1) s^(-1),which represents the highest value reported for solution-processed,n-type *** is noted that the fabrication of the OEGTs is achieved by solution processing with eco-friendly ethanol/water mixtures in virtue of the hydrophilic OEG *** work demonstrates the molecular design of the P(NDITEG-T) polymer and its significant ability to produce aqueous-processable,high-performance,and n-type OEGTs.

关键词： organic electrolyte-gated transistors n-type transistors oligo(ethylene glycol)polymers eco-friendly solution process high electron mobility

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Portable System for CWA Detection Using Micro Array Gas Sensor

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稀有金属材料与工程 2006年第A3期35卷 124-128页

作者： j.H.Kwak y.T.Lim G.H.kim N.j.Choi H.D.Park G.H.Rue j.S.Huh j.C.kim D.D.Lee School of Electrical Engineering and Computer Science Kyungpook National UniversityDaegu 1370Korea Electronics and Telecommunications Research Institute Future Technology Research Division New Functional Information Devices TeamGajeongYuseong-GuDaejeon 161 Korea Korea Electronics Technology Institute Yatap-DongBundang-GuSeongnam-SiGyeonggi-Do #68Korea Department of Materials Science and Metallurgy Kyungpook National UniversityDaegu 1370Korea Department of Chemical Engineering Kyungpook National UniversityDaegu 1370Korea

Biochemistry weapon is raising new tools of war and *** research is an experiment about portable system for CWAs (chemical warfare agents) detection using micro array gas *** were divided into four types such as blood, nerve,vesicant,and choking *** detect various CWAs,semiconductor thick film sensor array based on tin oxide was fabricated and their gas responses were *** temperature was range of 250℃to 350℃and gas concentration was range of 0.1μg/g to 10μg/*** array was measured as operating temperatures,concentrations for four simulant agents of *** parameters from results were carried out classification among CWAs through the principal component analysis (PCA).Also,classification of gases is studied using adaptive resonance theory (ART) that is one of neural network *** displayed using PDA system.

关键词： SnO2 chemical warfare agents(CWAs) portable system ART array PCA

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