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CO_2 laser-micro plasma arc hybrid welding for galvanized steel sheets

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 47-53页

作者： C.H.kim Y.N.AHN j.H.kim Advance welding & joining Research Group Korea Institute of Industrial Technology Incheon 406-840 South Korea

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-beat the weldment according to the arrangement of the laser beam and the arc. CO2 laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.

关键词： galvanized steel CO2 laser micro plasma hybrid welding

The Effect of Non-equilibrium Condensation on the Drag Coefficient in a Transonic Airfoil Flow

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journal of Thermal Science 2012年第6期21卷 518-524页

作者： I.w.kim M.M.A.Alam S.j.Lee Y.D.Kwon S.B.Kwon School of Mechanical Engineering Kyungpook Nat.Uni.1370Sankyuk-dongDaegu 702-701Korea Dept.of Advanced & Control Eng.Saga Uni.japan

In this study, a transonic flow past NACA0012 profile at angle of attack α=0^0 whose aspect ratio AR is 1.0 with non-equilibrium condensation is analyzed by numerical analysis using a TVD scheme and is investigated using an intermittent indraft type supersonic wind tunnel. Transonic flows of 0.78-0.90 in free stream Mach number with the variations of the stagnation relative humidity（φ0） are tested. For the same free stream Mach number, the increase in φ0 causes decrease in the drag coefficient of profile which is composed of the drag components of form, viscous and wave. In the case of the same Moo and To, for more than φ0=30%, despite the irreversibility of process in non-equilibrium condensation, the drag by shock wave decreases considerably with the increase of φ0. On the other hand, it shows that the effect of condensation on the drag coefficients of form and viscous is negligible. As an example, the decreasing rate in the drag coefficient of profile caused by the influence of non-equilibrium condensation for the case of M∞=0.9 and φ0 =50% amounts to 34%. Also, it were turned out that the size of supersonic bubble （that is, the maximum height of supersonic zone） and the deviation of pressure coefficient from the value for M=1 decrease with the increase of φ0 for the same M∞.

关键词： Non-equilibrium condensation Transonic Moist air Drag coefficient Pressure coefficient

Optical and luminescence characteristics of Eu^(3+)-doped B_2O_3:SiO_2:Y_2O_3:CaO glasses for visible red laser and scintillation material applications

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journal of Rare Earths 2018年第5期36卷 482-491页

作者： Pabitra Aryal C.R.Kesavulu H.j.kim S.w.Lee Sang jun Kang j.Kaewkhao N.Chanthima B.Damdee Department of Physics Kyungpook National University Daegu 41566 Republic of Korea College of Liberal Arts Semyung University Jechon 27136 Republic of Korea Center of Excellence in Glass Technology and Materials Science （CEGM） Nakhon Pathom Rajabhat University Nakhon Pathom 73000 Thailand Physics Program Faculty of Science and Technology Nakhon Pathom Rajabhat University Nakhon Pathom 73000 Thailand

Europium（Eu^3＋） doped glasses of chemical compositions（55-x）B2O3：10 SiO2：25 Y2O3：10CaO：xEu2O3,where x denotes mol% and ranges 0≤ x ≤ 2.5, were synthesized by adopting conventional melt quenching technique, Physical properties like density, molar volume, polaron radius, inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu2O3. Optical and luminescence properties of the glasses were characterized with optical absorption, photoluminescence,X-ray induced emission spectra, temperature dependence emission spectra and decay times. judd-Ofelt（jO） intensity parameters（Ωλ） of the glasses were evaluated based on the absorption spectrum of 0.5 mol%. jO parameters, calculated from absorption spectra with thermal corrections on oscillator strength, were used to evaluate radiative properties such as radiative transition probability（AR）,branching ratio（βR）, stimulated cross section emission（σ） and radiative lifetime（τR） for 5D0→7 Fj（j = 0,1,2,3 and 4） transitions. The decay rate of 5D0 fluorescent level for all the glass samples was single exponential. Lifetimes of the 5D0 level were decreased with increasing concentrations of Eu^3＋ions from 0.05 mol% to 2.5 mol% which might be due to energy transfer through cross-relaxation in the glasses. The chromaticity coordinates（x, y） were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram. Hence, these results confirm that the Eu^3＋ doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.

关键词： BSYCaEu glasses judd-Ofeltintensity parameters Luminescence properties CIE color co-ordinates Glass scintillation Rare earths

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

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

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys for Advanced Die-Materials Applications

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journal of Materials Science & Technology 2008年第3期24卷 305-308页

作者： w.Y.kim H.S.kim Y.G.Yoo I.D.Yeo Advanced Materials R&D Division Korea Institute of Industrial Technology7-47Songdo-dongYeonsu-gu

In this study, we report on advanced Ni3Al based high temperature structural alloys with Zr and B addition in order to apply in the fields of die-casting and high temperature press forming as die materials. Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting were investigated in terms of phase analysis by using a scanning electron microscope （SEM） equipped with an X-ray energy dispersive spectrometer （EDS）, an X-ray diffractometer （XRD） and tensile test. The duplex microstructural feature consisting of γ＇ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure. The ultimate tensile strength of the present alloy was superior to commercial iron-based and Ni-based die-materials especially in the high temperature region.

关键词： Intermetallic Die material Alloying effect Mechanical property

Effects of Mo and Zr on Microstructure,Mechanical Properties and wear Resistance of Fe-Al Based Alloys

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journal of Materials Science & Technology 2008年第3期24卷 309-312页

作者： I.D.Yeo H.S.kim Y.G.Yoo w.Y.kim Advanced Materials R&D Division Korea Institute of Industrial Technology7-47Songdo-dongYeonsu-gu

In this work the microstructure, mechanical properties and wear resistance of Fe-Al based alloys with various alloying elements were studied. The microstructures were examined by optical and scanning electron microscopy （SEM） equipped with an energy dispersive X-ray spectroscope （EDS）. Two types of alloys were prepared by vacuum arc melting. One is Fe-28Al based alloys （D03 structured） with and without alloying elements such as Mo and Zr. The other one is Fe-35Al based alloys （B2 structured） produced with the same manner. For both types of alloys, Mo addition had found to exhibit an equiaxed microstructure, while dendritic structure was observed to show the effect of Zr addition. These microstructural features were more evinced with increasing content of alloying element. Concerning the mechanical properties and wear resistance, Fe-35Al based alloys were superior to Fe-28Al based alloys over the whole temperature range investigated.

关键词： Fe-Al alloy Intermetallic Mechanical properties wear resistance

New para-magnetic(CoFeNi)(50)(CrMo)(50-x)(CB)x(x=20,25,30)non-equiatomic high entropy metallic glasses with wide supercooled liquid region and excellent mechanical properties

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journal of Materials Science & Technology 2020年第8期36卷 135-143页

作者： jeong Tae kim Sung Hwan Hong jin Man Park jürgen Eckert Ki Buem kim Erich Schmid Institute of Materials Science Austrian Academy of Sciences(ÖAW)Jahnstrae 128700LeobenAustria Hybrid Materials Center(HMC) Department of Nanotechnology and Advanced Materials EngineeringSejong University209Neungdong-roGwangjin-guSeoul143-747Republic of Korea Global Technology Center(GTC) Samsung Electronics Co.Ltd129 Samsung-roYeongtong-guSuwonsiGyeonggi-do443-742Republic of Korea Department of Materials Science Chair of Materials PhysicsMontanuniversität LeobenJahnstraße 128700LeobenAustria

In this study,high entropy metallic glasses(HEMGs)were developed through a combination of concepts for designing metallic glasses(main element+transition metal+metalloid element)and high-entropy alloys(more than five elements,each element having an atomic concentration between 5 at.%and 35 at.%).The developed metallic glass alloys are composed of Co-Fe-Ni main elements,transition metals(Cr,Mo)and metalloid elements(C,B).Moreover,the present work reports the thermal,mechanical and magnetic properties of(CoFeNi)(50)(CrMo)(50-x)(CB)x alloys with x=20,25,*** developed as-spun HEMGs exhibit typical paramagnetic properties even for a high amount of ferromagnetic elements(Co,Fe,and Ni)and have high elastic modulus(103–160 GPa)and hardness(14–27 GPa),thus possessing mechanical properties similar to well-known Co-based metallic glasses(Co-Cr-Mo-C-B system).In addition,some of the bulk samples prepared with a diameter of 2 mm form bulk metallic glasses with a high compressive strength around 3.5 *** mechanisms determining the stability of the supercooled liquid,as well as the paramagnetic and mechanical properties for the developed non-equiatomic HEMGs,are discussed.

关键词： Metallic glasses Paramagnetism High entropy alloys Phase stability

The Gas-to-Dust Relation in the Dark Cloud L1523-Observational Evidence for CO Gas Depletion

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Chinese journal of Astronomy and Astrophysics 2008年第6期8卷 686-692页

作者： H.G.kim B.G.kim j.H.jung Korea Astronomy and Space Science Institute 61-1 Hwaam Yuseong Daejeon 305-348 Korea

Correlation between gas and dust column density has been studied for the dark globule L1523. The 13CO（j=1→0） emission is used for tracing the gas, and the IR emissions, for tracing the dust constituent. In order to match the beam resolution between the images, a beam de-convolution algorithm based on the Maximum Correlation Method （MCM） was applied on the Infrared Astronomical Satellite （IRAS） data. The morphology of 13CO column density map shows a close correlation to that of 100μm dust optical depth. The distribution of the optical depth at 100 μm follows that of gas column density more closely than does the flux map at either 60 or 100μm. The ratio of the 13CO column density to the 100μm optical depth shows a decreasing trend with increasing dust optical depth in the central part, indicating possible molecular gas condensation onto dust particles. The excessive decrease in the CO column density in the envelope may most probably be due to the photo-dissociation of CO molecules.

关键词： ISM: clouds ISM: dust ISM: molecules