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A new strengthening mechanism driven by disruptive shear and solute segregation during warm rolling in 1.4 GPa class 12.5 wt% Al added-FeMnC ultra-lightweight steel

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Journal of Materials Science & Technology 2023年第26期157卷 174-188页

作者： Chiwon Kim Hyun-Uk hong Joonoh Moon bong ho lee Seong-Jun Park Chang-hoon lee Department of Materials Convergence and System Engineering Changwon National University 20 Changwondaehak-roChangwonGyeongnam 51140Republic of Korea Advanced Analysis Team Daegu Gyeongbuk Institute of Science and Technology 333 Technojungang-daeroDaegu42988Republic of Korea Ferrous Alloy Department Korea Institute of Materials Science 797 ChangwondaeroChangwonGyeongnam 51508Republic of Korea

Novel strengthening of Fe-29.1Mn-12.5Al-1.35C-4.95Cr steel achieved by warm rolling was *** solution-treated steel consisted of aγ-matrix containing nano-sizedκ-carbide((Fe,Mn)_(3) AlC)and elongated prior ferrite,which was transformed into FeAl-type B2 and Fe_(3) Al-type D0_(3) *** solution-treated steel exhibited poor strain hardening owing to glide softening associated withκ-carbide shearing by ***,after warm rolling with a reduction ratio of 30%at 300℃,the yield and tensile strengths significantly increased from 917 to 1300 MPa and 1025 to 1419 MPa,*** tensile test conducted at 300℃to simulate warm rolling exhibited serrated flows,indicating dy-namic strain aging(DSA).Atom probe tomography exhibited that the C atoms inκ-carbide were swept away along the slip direction by disruptive shear during rolling at 300℃.The swept C atoms along the slip direction interacted strongly with dislocations at 300℃,with repeated pinning and breakaway of dislocations from the C *** contributed to significant strengthening owing to the formation of a solute-rich atmosphere after warm *** results of the tensile tests at 300℃indicated that the de-gree of strengthening was proportional to the pre-strain *** strength of 1.4 GPa can be achieved with good ductility(17%elongation)by warm *** novel warm-rolling strengthening method ex-pedites the potential application of Fe-29.1Mn-12.5Al-1.35C-4.95Cr as a 1.4 GPa class ultra-lightweight steel.

关键词： FeMnAlC Cr addition κ-carbide Dynamic strain aging Strengthening

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New strategy for reversal tolerant anode for automotive polymer electrolyte fuel cell

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Chinese Chemical Letters 2019年第6期30卷 1186-1189页

作者： Chanho Pak Seung Woo lee Chaekyung Baik bong ho lee Dae Jong You Eunyoung You Graduate Program of Energy Technology School of Integrated Technology Institute of Integrated Technology Gwangju Institute of Science and Technology Gwangju 61005 Republic of Korea Fuel Cell Engineering Core Technology Team Division of Electric Powertrain Hyundai Mobis Co. Ltd. Yongin Gyeonggi-do 16891 Republic of Korea

Since the commercialization of the fuel cell electric vehicles (FCEVs), the polymer electrolyte membrane fuel cell system has been actively improved as a powertrain for ultimate environment-friendly vehicle. During the FCEV operation, various transient conditions such as start-up/shut-down and fuel starvation occur irregularly, which deteriorates the durability of the membrane electrode assembly. In particular, when fuel starvation occurs, the carbon support in the anode is oxidized within few minutes, thus the mitigation of this phenomenon is essential for securing the durability. This short review introduces the concept of reversal tolerant anode (RTA), which is a mitigation method using an oxygen evolution catalyst and reviews some previous reports. In addition, new approach for RTA suggested by authors recently, which is the replacement of Pt anode catalyst by multifunctional IrRu alloy catalyst that simultaneously exhibits the activities for the hydrogen oxidation reaction and the oxygen evolution reaction is introduced.

关键词： Multifunctional IrRu alloy catalyst Reversal tolerant anode Hydrogen oxidation reaction catalyst Oxygen evolution reaction catalyst Cell reversal durability Polymer electrolyte membrane fuel cell

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Synthesis and Gas Sensing of TiO_2 Ultrafine Powders by Precipitating

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稀有金属材料与工程 2006年第A3期35卷 163-164页

作者： Min-Hyun Seo bong-ho lee Jong-Won Kim Gi-hong Rue Duk-Dong lee Jeung-Soo Huh Department of Sensor and Display Engineering Kyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea Department of Materials Science and Metallurgy Kyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea Department of Nano-science and Technology Kyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea School of Electronic Engineering Kyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea Department of Sensor and Display Engineering Kyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea.Department of Nano-science and TechnologyKyungpook National UniversitySangyuk-DongBukguDaegu 1370Korea

We investigated the gas sensing characteristics of rutile and anatase TiO_2 nano-particle sensors for chemical warfare ***_2 nano-powders with rutile and anatase structure were fabricated by controlling pH value without heat treatment *** mean particle size of TiO_2 powders were below 10 ***-prepared TiO_2 powders have several advantages of nano particle size and high surface area and could be a prominent candidate for ***_2 sensors were examined with DMMP for chemical warfare agents detection.

关键词： TiO2 chemical warfare agents sensor nano-sensor pH

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Effect of molybdenum on interfacial properties of titanium carbide reinforced Fe composite

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Journal of Materials Science & Technology 2022年第12期107卷 252-258页

作者： Seungchan Cho Junghwan Kim Ilguk Jo Jae Hyun Park Jaekwang lee Hyun-Uk hong bong ho lee Wook Ryol Hwang Dong-Woo Suh Sang-Kwan lee Sang-Bok lee Composites Research Division Korea Institute of Materials Science(KIMS)Changwon 51508South Korea Advanced Materials Engineering Dong-Eui UniversityBusan 47340South Korea Department of Aerospace and Software Engineering Gyeongsang National UniversityJinju 52828South Korea Department of Physics Pusan National UniversityBusan 46241South Korea Department of Materials Convergence and System Engineering Changwon National UniversityChangwon 51140South Korea Center for Core Research Facilities Daegu Gyeongbuk Institute of Science and TechnologyDaegu 42988South Korea School of Mechanical Engineering Gyeongsang National UniversityJinju 52828South Korea Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyGyeongbuk 37673South Korea

This study shows that the mechanical strength of the composite of Fe matrix and titanium carbide(Ti C)ceramic particles is significantly enhanced with addition of molybdenum(Mo) atoms. Ti C reinforced Fe(Fe-0.2C-7Mn) composites with and without Mo were fabricated by a liquid pressing infiltration(LPI)process and the effect of Mo on interfacial properties of TiC–Fe composite was investigated using atomic probe tomography(APT) analysis, molecular dynamics(MD) simulations, first-principle density functional theory(DFT), and thermodynamic calculations. First, DFT calculations showed that total energies of the Mo-doped Ti C–Fe superlattices strongly depend on the position of Mo defects, and are minimized when the Mo atom is located at the TiC/Fe interface, supporting the probable formation of MoC-like interphase at the TiC/Fe interface region. Then, APT analysis confirmed the DFT predictions by finding that about6.5 wt.% Mo is incorporated in the Ti C–Fe(Mo) composite and that sub-micrometer thick(Ti,Mo)C interphase is indeed formed near the interface. The MD simulations show that Mo atoms migrate to the Mo-free TiC–Fe interface at elevated temperatures and the mechanical strength of the interface is considerably enhanced, which is in good agreement with experimental observations.

关键词： Metal matrix composites(MMCs) Titanium carbide Fe matrix composite Infiltration Molybdenum Interfacial property

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Identification and Biological Activities of the Phenolic Compounds in <i>Eisenia arborea</i>

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American Journal of Plant Sciences 2021年第2期12卷 259-265页

作者： Hyeon Cheol Shin Ignacio Beamonte Wayas Byoung Wook Choi bong ho lee CEWIT Center for Systems Biology The State University of New York 119 Songdo Moonhwaro Yeonsu-gu Incheon Korea Baja Kelp Talasoterapia Ensenada Mexico Department of Chemical and Biological Engineering Hanbat National University 125 Dongseodaero Yuseong-gu Daejeon Korea

Four polyphenols were isolated and purified from a brown alga Eisenia arborea. These phlorotannin compounds showed strong radical scavenging and some enzyme inhibitory activities. All of the compounds showed strong antioxidative, acetylcholinesterase and butyrylcholinesterase inhibitory, and tyrosinase inhbibitory activities at 100 μg/mL. Dieckol and PFF inhibited butyrylcholinesterase, a new target for the treatment of Alzheimer’s disease, very strongly even at 10 μg/mL, more strongly than AChE. These two compounds also effectively inhibited tyrosinase. These results support the potential of developing natural antioxidants and antidementia agents from the brown alga.

关键词： Eisenia arborea Phenolic Compounds DPPH Radical Scavenger Enzyme Inhibition Isolation

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Advanced operation of heated fluidic resonators via mechanical and thermal loss reduction in vacuum

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Microsystems & Nanoengineering 2023年第5期9卷 255-262页

作者： Juhee Ko bong Jae lee Jungchul lee Department of Mechanical Engineering Center for Extreme Thermal Physics and ManufacturingKorea Advanced Institute of Science and Technology(KAIST)34141 DaejeonKorea

For simultaneous and quantitative thermophysical measurements of ultrasmall liquid volumes,we have recently developed and reported heated fluidic resonators(HFRs).In this paper,we improve the precision of HFRs in a vacuum by significantly reducing the thermal loss around the sensing element.A vacuum chamber with optical,electrical,and microfluidic access is custom-built to decrease the convection loss by two orders of magnitude under 10-4 mbar *** a result,the measurement sensitivities for thermal conductivity and specific heat capacity are increased by 4.1 and 1.6 times,*** differentiating between deionized water(H2O)and heavy water(D2O)with similar thermophysical properties and~10%different mass densities,the signal-to-noise ratio(property differences over standard error)for H2O and D2O is increased by 9 and 5 times for thermal conductivity and specific heat capacity,respectively.

关键词： fluid operation vacuum

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Effect of light scattering on the performance of a direct absorption solar collector

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Frontiers in Energy 2018年第1期12卷 169-177页

作者： Kwang Hyun WON bong Jae lee Department of Mechanical Engineering Korea Advanced Institute ofScience and Technology Daejeon 34141 South Korea

Recently, a solar thermal collector often employs nanoparticle suspension to absorb the solar radiation directly by a working fluid as well as to enhance its thermal performance. The collector efficiency of a direct absorption solar collector （DASC） is very sensitive to optical properties of the working fluid, such as absorption and scattering coefficients. Most of the existing studies have neglected particle scattering by assuming that the size of nanoparticle suspension is much smaller than the wavelength of solar radiation （i.e., Rayleigh scattering is applicable）. If the nanoparticle suspension is made of metal, however, the scattering cross-section of metallic nanoparticles could be comparable to their absorption cross-section depending on the particle size, especially when the localized surface plasmon （LSP） is excited. Therefore, for the DASC utilizing a plasmonic nanofluid supporting the LSP, light scattering from metallic particle suspension must be taken into account in the thermal analysis. The present study investigates the scattering effect on the thermal performance of the DASC employing plasmonic nanofluid as a working fluid. In the analysis, the Monte Carlo method is employed to numerically solve the radiative transfer equation considering the volume scatter- ing inside the nanofluid. It is found that the light scattering can improve the collector performance if the scattering coefficient of nanofluid is carefully engineered depending on its value of the absorption coefficient.

关键词： direct absorption solar collector plasmonicnanofluid light scattering

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Reduction of gastrointestinal motility by unilateral thyroparathyroidectomy plus subdiaphragmatic vagotomy in rats

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World Journal of Gastroenterology 2012年第33期18卷 4570-4577页

作者： Jun ho lee Oh Deog Kwon Seon ho Ahn Keun Han Choi Ji Hye Park Seoul lee bong Kyu Choi Kyu Yong Jung Department of Pharmacology Wonkwang University School of Medicine Jeonbuk 570-749 South Korea Department of Clinical Pathology College of Veterinary Medicine Kyungpook National University Daegu 702-701 South Korea Department of Internal Medicine Wonkwang University School of Medicine Jeonbuk 570-749 South Korea

AIM: To investigate whether the combined methods of unilateral thyroparathyroidectomy (TPX) and subdiaphragmatic vagotomy (VAX) can be adapted for rats and used as a reliable method to produce a rat model of long-term reduction of gastrointestinal (GI) motor function. METhoDS: Male Sprague-Dawley rats were randomly divided into 3 groups, normal, sham-operated and unilateral TPX plus VAX. The TPX plus VAX rats received VAX 7 d after application of TPX, and dietary intake and fecal output were then measured daily for 1 *** completion of the experiments, gastric emptying and small bowel transit were measured in vivo, and the contractile responses of colonic strips to excitatory and inhibitory neurotransmitters were estimated using isometric force transducers in vitro. RESULTS: In comparison with normal and sham-operated rats, rats which received unilateral TPX plus VAX showed a significant decrease in body weight and in fecal pellet number and weight throughout the entire week. Application of TPX plus VAX to rats markedly delayed gastric emptying and small bowel transit. In TPX plus VAX rats, the longitudinal muscles of the proximal colon showed a significant reduction in contractile responses to acetylcholine (5 × 10-6 mol/L), and a dramatic attenuation of contractile responses was also observed in both the longitudinal and circular muscles of the distal colon. however, the spontaneous contractility of the colonic strips from TPX plus VAX rats was not significantly affected by treatment with N-nitro-Larginine-methyl ester (0.1 mol/L). CONCLUSION: The results indicate that unilateral TPX plus VAX reduced the motor function of the GI tract in rats, and the reduced gut motility is likely mediated, at least in part, by inhibition of the excitatory neurotransmitter system.

关键词： Unilateral thyroparathyroidectomy Subdiaphragmatic vagotomy Gastric emptying Small bowel transit Rat

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Accelerated precipitation behavior of cast Mg-Al-Zn alloy by grain refinement

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Journal of Materials Science & Technology 2018年第2期34卷 265-276页

作者： Sang-hoon Kim Jong Un lee Ye Jin Kim Jun ho Bae bong Sun You Sung Hyuk Park School of Materials Science and Engineering Kyungpook National University Implementation Research Division Korea Institute of Materials Science

This study demonstrates that the precipitation behavior of 13-Mg17Al12 phase during aging and the resultant variation in hardness and mechanical properties of cast Mg-Al-Zn alloy are strongly dependent on initial grain size. Grain size reduction accelerates discontinuous precipitation at the early stage of aging treatment by increasing the area fraction of grain boundaries that can act as nucleation sites for discontinuous precipitates （DP）, but it does not influence DP growth rate. Grain refinement also prematurely terminates continuous precipitation because the formation of a large number of DP reduces the amount of AI dissolved in the matrix, which is required for the formation of continuous precipitates （CP）. This promotion of DP formation and early termination of CP formation significantly decrease the peak-aging time to one-third. The enhanced precipitation behavior also leads to an additional hardness improvement in the aged alloy, along with an increase in hardness owing to grain boundary strengthening by grain refinement. The amount of increase in hardness changes with aging time, which is determined by the variation of three variables with aging time： DP fraction difference between refined and nonrefined alloys, hardness difference between DP and matrix, and matrix hardness difference between the two alloys. Grain refinement improves both tensile strength and ductility of the homogenized alloy owing to grain boundary strengthening and suppression of twinning activation, respectively. however, the loss of ductility after peak-aging treatment is greater in the refined alloy because of the larger amount of DP acting as a crack source in this alloy.

关键词： Magnesium Grain refinement Aging Precipitation Tensile properties

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Study on wear behavior of plasma electrolytic oxidation coatings on aluminum alloy

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Rare Metals 2006年第Z2期25卷 141-145页

作者： KANG Suk-bong lee Jung-Moo Department of Materials Engineering Korean Institute of Machinery & Materials Gyeongnam 641831 Korea

Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation(PEO) technique. The microstructure and phase composition of the PEO coatings were examined by using SEM and XRD method. It is found that the PEO coatings are mainly composed of crystalline α-Al2O3 and mullite. The dry sliding wear test of PEO coatings were carried out on a ring-on-ring wear machine. Results shows that there is hardly no wear loss of polished PEO coatings while the wear rate of uncoated aluminum alloy is 4.3×10-5 mm3·(N·m)-1 at a speed of 0.52 m·s-1 and a load of 40 N.

关键词： aluminum alloy plasma electrolytic oxidation ceramic coating wear

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