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Fatigue-Induced Micro-damage Characterization of Austenitic Stainless Steel 316 Using Innovative Nonlinear Acoustics

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Chinese Physics Letters 2012年第6期29卷 82-85页

作者： Chung-Seok kim kyung-Young JHANG Automotive Engineering Hanyang UniversityHangdang-dongSeongdong-guSeoul133-791South Korea Mechanical Engineering Hanyang UniversityHangdang-dongSeongdong-guSeoul133-791South Korea

We present innovative nonlinear acoustics for characterizing fatigue-induced micro-damage of austenitic stainless steel 316 subjected to high-cycle *** fatigue-driven deformations are accumulated at several positions near the middle of hourglass-shaped specimens.A bell-shaped curve of acoustic nonlinearity as a function of position is observed,and the variation in acoustic nonlinearity is attributed to the evolution of a lattice defect (dislocation) and stress-induced martensite based on transmission electron microscopy (TEM) *** oblique incidence technique using a longitudinal waveform is a potentially viable method for characterizing the high-cycle fatigue deformation of austenitic stainless steel 316 alloys.

关键词： fatigue steel martensite

A review on technologies with electricity generation potentials using liquified natural gas regasification cold energy

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Frontiers in Energy 2023年第3期17卷 332-379页

作者： Muhammad Tauseef NASIR Mirae kim Jaehwa LEE Seungho kim kyung Chun kim School of Mechanical Engineering Eco-friendly Smart Ship Parts Technology Innovation CenterPusan National UniversityBusan 46241South Korea School of Mechanical Engineering Pusan National UniversityBusan 46241South Korea Korea Gas Corporation Daegu 41062South Korea

In modern times,worldwide requirements to curb greenhouse gas emissions,and increment in energy demand due to the progress of humanity,have become a serious *** such scenarios,the effective and efficient utilization of the liquified natural gas(LNG)regasification cold energy(RCE),in the economically and environmentally viable methods,could present a great opportunity in tackling the core issues related to global warming across the *** this paper,the technologies that are widely used to harness the LNG RCE for electrical power have been *** systems incorporating,the Rankine cycles,Stirling engines,Kalina cycles,Brayton cycles,Allam cycles,and fuel cells have been ***,the economic and environmental studies apart from the thermal studies have also been ***,the discussion regarding the systems with respect to the regassification pressure of the LNG has also been *** aim of this paper is to provide guidelines for the prospective researchers and policy makers in their decision making.

关键词： liquified natural gas cold energy power generation

Surface treatment to improve corrosion resistance of Al plate heat exchangers

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中国有色金属学会会刊：英文版 2009年第B9期19卷 28-31页

作者： Jong-Soon kim tae-Ho KANG In-Kwan kim Department of Mechanical Engineering Pu kyong National University

The correlations between thermal and physical properties were studied through thermal conductivity measurements, hardness tests, salt spray tests (AASS) among the surface treatment samples named K20, K40 with thickness of 20, 40 μm respectively and raw sample named K00. In thermal conductivity measurements, there are little differences among the samples as K00, K20 and K40, they exhibit 153.39, 150.69 and 149.76 W/(m·K), respectively. According to hardness tests, K00, K20 and K40 exhibit 87.9, 259.7 and 344.8 in Vickers values. In the result of salt spray tests to examine the effects on corrosion resistance, K00, K20 and K40 exhibit the grade of 3?5, 2.0?9.8 and 10, respectively. The mutual relation of the above results was analyzed. It is found that the surface treatments do not affect the thermal conductivity of aluminum and result in the improvement of physical properties. As a result of the technology, the surface improvement of aluminum alloy specimen is achieved without thermal degradation. It validates the ability of the aluminum plate heat exchangers with surface treatment to enhance the corrosion resistance. Present work is performed as the first fundamental threshold in the process of aluminum plate heat exchangers development to check out its possibility, therefore the next step-experimental and numerical study of practical aluminum plate heat exchangers will be made.

关键词：板式换热器表面处理耐铝性物理性能导热系数硬度测试盐雾试验耐腐蚀性

Acoustic Nonlinearity of a Laser-Generated Surface Wave in a Plastically Deformed Aluminum Alloy

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Chinese Physics Letters 2012年第12期29卷 39-43页

作者： kim Chung-Seok JHANG kyung-Young Metallurgy and Materials Engineering Chosun UniversitySeosuk-dongGwangju501-759South Korea Mechanical Engineering Hanyang UniversityHangdang-dongSeongdong-guSeoul133-791South Korea

The acoustic nonlinearity of surface waves is studied to evaluate plastic deformation in aluminum alloys.A narrow-band surface wave is successfully generated by a pulsed Nd-YAG laser system consisting of a beam expander and a slit *** degrees of tensile deformation are induced by interrupting the tensile tests so as to obtain aluminum specimens with different degrees of plastic *** normalized acoustic nonlinearity increases as a function of tensile *** experimental results show that the acoustic nonlinearity of a laser-generated surface wave has a good correlation with the level of tensile deformation and has a potential to evaluate microdamage induced by dislocation microplasticity.

关键词： deformation nonlinearity Deform

Mechanical properties of high-strength concrete subjected to high temperature by stressed test

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中国有色金属学会会刊：英文版 2009年第B9期19卷 128-133页

作者： Gyu-Yong kim Young-Sun kim tae-Gyu LEE Division of Architecture Engineering Chun gnam National University

Recently, the effects of high temperature on compressive strength and elastic modulus of high strength concrete were experimentally investigated. The present study is aimed to study the effect of elevated temperatures ranging from 20 ℃ to 700 ℃ on the material mechanical properties of high-strength concrete of 40, 60 and 80 MPa grade. During the strength test, the specimens are subjected to a 25% of ultimate compressive strength at room temperature and sustained during heating, and when the target temperature is reached, the specimens are loaded to failure. The tests were conducted at various temperatures (20-700 ℃) for concretes made with W/B ratios of 46%, 32% and 25%, respectively. The results show that the relative values of compressive strength and elastic modulus decrease with increasing compressive strength grade of specimen.

关键词：高强混凝土高温作用力学性能测试抗压强度温度升高弹性模量强度试验

Generation of mesenchymal stem-like cells for producing extracellular vesicles

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World Journal of Stem Cells 2019年第5期11卷 270-280页

作者： Soo kim tae Min kim Brexogen Research Center Brexogen Inc. Seoul Songpa-gu 05718 South Korea Graduate School of International Agricultural Technology and Institute of Green- Bio Science and Technology Seoul National University Gangwon-do Pyeongchang 25354 South Korea

Mesenchymal stem cells (MSCs) are multipotent progenitor cells with therapeutic potential against autoimmune diseases, inflammation, ischemia, and metabolic disorders. Contrary to the previous conceptions, recent studies have revealed that the tissue repair and immunomodulatory functions of MSCs are largely attributed to their secretome, rather than their potential to differentiate into desired cell types. The composition of MSC secretome encompasses cytokines and growth factors, in addition to the cell-derived structures known as extracellular vesicles (EVs). EVs are membrane-enclosed nanoparticles that are capable of delivering biomolecules, and it is now believed that MSC-derived EVs are the major players that induce biological changes in the target tissues. Based on these EVs’ characteristics, the potential of EVs derived from MSC (MSC-EV) in terms of tissue regeneration and immune modulation has grown during the last decade. However, the use of MSCs for producing sufficient amount of EVs has not been satisfactory due to limitations in the cell growth and large variations among the donor cell types. In this regard, pluripotent stem cells (PSCs)-derived MSC-like cells, which can be robustly induced and expanded in vitro, have emerged as more accessible cell source that can overcome current limitations of using MSCs for EV production. In this review, we have highlighted the methods of generating MSC-like cells from PSCs and their therapeutic outcome in preclinical studies. Finally, we have also discussed future requirements for making this cell-free therapy clinically feasible.

关键词： Mesenchymal stem cells Extracellular vesicles Preclinical studies Exosomes

Influence of tool deflection on micro channel pattern of 6:4 brass with rectangular tool

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中国有色金属学会会刊：英文版 2009年第B9期19卷 164-170页

作者： tae-Jin JE Kang-Won LEE Sang-Cheon PARK Jae-Gu kim Doo-Sun CHOI Kyoung-Taik PARK kyung-Hyun WHANG Nano Mechanical Systems Research Division Korea Institute of Machinery & Materials (KIMM)

Machining experiment of micro channel structure with 6:4 brass was carried out by shaping process using a single crystal diamond tool. FEM simulation using solid cantilever beam model was analyzed. In result of experiment, tool deflection is observed as machining characteristics through result of experiments such as surface roughness, cutting force and burr formations. And the influence of tool deflection is experimentally proved.

关键词：金刚石工具挠度通道模式黄铜矩形实验证明加工特性有限元模拟

Electrochemical determination of the degree of atomic surface roughness in Pt-Ni alloy nanocatalysts for oxygen reduction reaction

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Carbon Energy 2021年第2期3卷 375-383页

作者： tae-Yeol Jeon Seung-Ho Yu Sung J.Yoo Hee-Young Park Sang-kyung kim Beamline Department Pohang Accelerator Laboratory(PAL)PohangRepublic of Korea Department of Chemical and Biological Engineering Korea UniversitySeoulRepublic of Korea Fuel Cell Center Korea Institute of Science and Technology(KIST)SeoulRepublic of Korea Fuel Cell Research Center Korea Institute of Energy Research(KIER)DaejeonRepublic of Korea

Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and *** changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area,the potential of zero total charge(PZTC),and relative surface roughness,which were determined from CO-and CO_(2)-displacement experiments before and after 3000 potential cycles under oxygen reduction reaction *** the highest activity and durability were achieved in hydroquinone-treated Pt–Ni,sulfuric acidtreated one showed the lower activity and durability despite its higher surface Pt concentration and alloying *** PZTC and QCO_(2)/QCO ratio(desorption charge of reductively adsorbed CO_(2) normalized by COad-stripping charge)depend on surface *** particular,QCO_(2)/QCO ratio change better reflects the roughness on an atomic scale,and PZTC is also affected by the electronic modification of Pt atoms in surface *** this study,a comparative study is presented to find a relationship between surface structure and electrochemical properties,which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt-Ni alloy catalysts with Pt-rich surfaces.

关键词： electrocatalyst fuel cell oxygen reduction reaction Pt-Ni surface roughness

Surgical outcome of pancreatic cancer using radical antegrade modular pancreatosplenectomy procedure

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World Journal of Gastroenterology 2012年第39期18卷 5595-5600页

作者： Ye Rim Chang Sung-Sik Han Sang-Jae Park Seung Duk Lee tae Suk Yoo Young-Kyu kim tae Hyun kim Sang Myung Woo Woo Jin Lee Eun kyung Hong Department of Surgery Seoul National University HospitalSeoul 110-744South Korea Center for Liver Cancer National Cancer CenterGyeonggido 411-764South Korea

AIM:To evaluate the surgical outcomes following radical antegrade modular pancreatosplenectomy (RAMPS) for pancreatic cancer. METHODS:Twenty-four patients underwent RAMPS with curative intent between January 2005 and June 2009 at the National Cancer Center, South Korea. Clinicopathologic data, including age, sex, operative findings, pathologic results, adjuvant therapy, postop-erative clinical course and follow-up data were retro-spectively collected and analyzed for this study. RESULTS:Twenty-one patients (87.5%) underwent distal pancreatectomy and 3 patients (12.5%) underwent total pancreatectomy using RAMPS. Nine patients (37.5%) underwent combined vessel resection, including 8 superior mesenteric-portal vein resections and 1 celiac axis resection. Two patients (8.3%) underwent combined resection of other organs, including the colon, stomach or duodenum. Negative tangential margins were achieved in 22 patients (91.7%). The mean tumor diameter for all patients was 4.09 ± 2.15 cm. The 2 patients with positive margins had a mean diameter of 7.25 cm. The mean number of retrieved lymph nodes was 20.92 ± 11.24 and the node positivity rate was 70.8%. The median survival of the 24 patients was 18.23 ± 6.02 mo. Patients with negative margins had a median survival of 21.80 ± 5.30 mo and those with positive margins had a median survival of 6.47 mo (P = 0.021). Nine patients (37.5%) had postoperative complications, but there were no postoperative mortalities. Pancreatic fistula occurred in 4 patients (16.7%):2 patients had a grade A fistula and 2 had a grade B fistula. On univariate analysis, histologic grade, positive tangential margin, pancreatic fistula and adjuvant therapy were significant prognostic factors for survival. CONCLUSION:RAMPS is a feasible procedure for achieving negative tangential margins in patients with carcinoma of the body and tail of the pancreas.

关键词： Carcinoma Pancreas Surgical resection Sur-vival Radical antegrade modular pancreatosplenectomy