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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

Effects of aqueous extract from red Liriope platyphylla on phthalic-anhydride-induced atopic dermatitis in Interleukin-4/Luciferase/Consensus non-coding sequence-1 transgenic mice evaluated in terms of luciferase signal and general phenotype biomarkers

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Journal of Traditional Chinese Medicine 2017年第4期37卷 475-485页

作者： Moon hwa Kwak Ji Eun kim Jun Go Hong Joo Son Hee Seob Lee Jin tae Hong Dae Youn hwang College of Natural Resources and Life Science/Life and Industry Convergence Research Institute Pusan National UniversityMiryang 627-706South of Korea College of Human Ecology Pusan National UniversityBusan 609-735south of Korea College of Pharmacy and Medical Research Center Chungbuk National UniversityChungju 361-763south of Korea College of Pharmacology Chungbuk National UniversityChungju 361-763south of Korea

OBJECTIVE: To quantitatively evaluate the therapeutic effects of Red Liriope platyphylla(RLP) on atopic dermatitis(AD), alterations in the luciferase(Luc) signal and general phenotype biomarkers were compared in phthalic anhydride(PA) treated Interleukin-4(IL-4)/Luc/Consensus non-coding sequence-1(CNS-1) transgenic(Tg) mice following treatment with aqueous extract of RLP(AEt RLP) for4 ***: Alterations in AD phenotypes were measured in IL-4/Luc/CNS-1 Tg mice following treatment with AEt RLP using inflammation parameter analysis, bioluminescence imaging analysis, histological analysis, reverse transcription-polymerase chain reaction, enzyme linked immunosorbent assay and Western blot ***: RLP contained high concentrations of total phenolic compounds, total flavonoid compounds and 5-HNE related to AD therapy. The Luc signal was only detected in the abdominal region and the submandibular lymph node(SL), mesenteric lymph node(ML), thymus and pancreas of the PA treated group. This signal was significantly decreased by 28%-73% throughout the body and in the four organs in PA + AEt RLP treated group. Furthermore, the lymph node weight, immunoglobulin E concentration and dermal thickness were decreased by 37%-67% in the PA + AEt RLP treated ***: Our findings suggest that the therapeutic effect of AEt RLP on PA induced AD could be successfully quantified by comparison of Luc signals and AD phenotype markers in IL-4/Luc/CNS-1Tg mice, and that the Luc signal was as sensitive as the general AD phenotypes, enabling detection of effects without euthanasia.

关键词： Dermatitis, Atopic Liriope plant Interleukin-4 Luciferases Mice, transgenic Phthalic anhydrides Immunoglobulin E

Electrodeposition behavior and characteristics of Ni-carbon nanotube composite coatings

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 68-72页

作者： Sung-Kyu kim tae-Sung OH Department of Materials Science and Engineering Hongik University

Ni-CNT (carbon nanotube) composite coatings were processed by electrodeposition and their hardness and corrosion characteristics were investigated with variations of CNT concentration in an electrolyte solution and electrodeposition current density. With increasing the CNT concentration in the electrodeposition bath and the current density, more CNTs are incorporated into Ni matrix. Hardness values of the Ni-CNT coatings are irrelevant to the CNT concentration in the solution, the current density, and current mode, implying poor adhesion of CNTs to Ni matrix. With increasing the CNT content in the coating, the corrosion resistance of the Ni-CNT composite coating becomes inferior due to the porous microstructure.

关键词： composite coating carbon nanotube electrodeposition

Solid-state phase transformations toward a metal-organic framework of 7-connected Zn_(4)0 secondary building units

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Nano Research 2021年第2期14卷 411-416页

作者： Jaehui kim Junsu Ha Jae hwa Lee Hoi Ri Moon Department of Chemistry Ulsan National Institute of Science and Technology(UNIST) Ulsan 44919Republic of Korea

In the development of metal-organic frameworks(MOFs),secondary building units(SBUs)have been utilized as molecular modules for the construction of nanoporous materials with robust *** solvothermal synthetic conditions,dynamic changes in the metal coordination environments and ligand coordination modes of SBUs determine the resultant product ***,MOF phases with new topologies can also be achieved by post-synthetic treatment of as-synthesized MOFs via the introduction of acidic or basic moieties that cause the simultaneous cleavage/reformation of coordination bonds in the solid *** this sense,we studied the solid-state transformation of two ndc-based Zn-MOFs(ndc=1,4-naphthalene dicarboxylate)with different SBUs but the same pcu topology to another MOF with sev *** of the chosen MOFs with pcu nets is[Zn_(2)(ndc)_(2)(bpy)]_(n)(bpy=4,4,-bipyridine),(6C_(bpy)-MOF)consisting of a 6-connected pillared-paddlewheel SBU,and the other is IRMOF-7 composed of 6-connected Zn40(C 00)6 SBUs and *** post-structural modification,these pcu MOFs were converted into the same MOF with sev topology constructed from the uncommon 7-connected Zri_(4)O(COO)_(7)SBU(7C-MOF).The appropriate post-synthetic conditions for the transformation of each SBUs were systematically *** addition,the effect of the pillar molecules in the pillared-paddlewheel MOFs on the topology conversion was studied in terms of the linker basicity,which determines the inertness during the solid-state phase *** post-synthetic modification approach is expected to expand the available methods for designing and synthesizing MOFs with controlled topologies.

关键词： metal-organic framework secondary building units solid-state transform ation linker basicity ligand addition reaction

Study of Spiral Flow Generated through an Annular Slit

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Journal of Thermal Science 2005年第2期14卷 97-102页

作者： tae Hun kim Shigeru MATSUO Toshiaki SETOGUCHI Heuy-Dong kim Graduate school of Science and Technology Saga University 1Honjo-machiSaga shiSaga 840-8502JapanDepartment of Mechanical Engineering Saga University1Honjo-machiSaga shiSaga 840-8502JapanDepartment of Mechanical Engineering Saga University1Honjo-machiSaga shiSaga 840-8502JapanSchool of Mechanical Engineering College of Natural ScienceAndong National University388Song Cheon DongAndongKyung PookKorea

The effect of pressurized air inlets in the reservoir upstream of the annular slit on characteristics of the axial and tangential velocity components is investigated numerically, and the mechanism of occurrence of spiral nozzle flow is clarified. In simulations, Unified Platform for Aerospace Computational Simulation (UPACS) is used. The governing equations under consideration are the unsteady compressible Navier - Stokes. A second-order finite volume scheme with MUSCL (Roe scheme) is used to discretize the spatial derivatives, and a second order-central difference scheme for the viscous terms, and a MFGS (Matrix Free Gauss Seidel) is employed for time integration. Spalart-Allmaras model was used as a turbulence model. The results obtained are compared with velocity distributions in the experiment measured by the two-component fiber optic laser Doppler velocimeter system. The existence of discrete pressurized air inlets that leads to the occurrence of asymmetrical characteristics is a very important factor for the formation of spiral flow.

关键词： spiral nozzle flow Coanda effect convergent nozzle annular slit simulation.

Modified analogue forecasting in the hidden Markov frameworkfor meteorological droughts

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Science China(Technological Sciences) 2019年第1期62卷 151-162页

作者： CHEN Si CHUNG GunHui kim Byung Sik kim tae-Woong Department of Civil and Environmental Engineering Hanyang University Department of Civil Engineering Hoseo University Department of Urban Environmental Disaster Prevention Engineering Kangwon National University

An analogue method(AM) is a nonparametric approach that has been applied to predict the future states of a dynamic system by following the evolution of the analogues in the historical archive. In this study, we proposed a hidden Markov model(HMM)framework for a modified analogue forecasting(MAF) approach for meteorological droughts in Korea. The unobservable(hidden) state process in the framework aims to model the underlying drought state, while the observation process was formed from the time series of the standardized precipitation index(SPI) as a drought index. Within the framework, the likelihood estimator was used as the measure of similarity between past SPI analogues and current data. The MAF approach was conducted on the selected analogues to make forecasts at lead times of one and three months. The proposed model was applied to five selected stations in Korea using the SPI data from 1973 to 2016. The forecasting performance of the proposed model was tested during the validation period(2003–2016) using several statistical criteria and it was compared to a persistence-based benchmark model. The results showed significant improvement in the forecasting capacity, and satisfactory performance for numerical SPI forecasting and categorical drought forecasting. The results also suggested that the proposed model was able to provide useful information for determining future drought categories for early drought warning with a lead time of up to three months.

关键词： modified analogue forecasting hidden Markov model meteorological drought standardized precipitation index

Comparative toxicity of silver nanoparticles and silver ions to Escherichia coli

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Journal of Environmental Sciences 2018年第4期30卷 50-60页

作者： Yoojin Choi Hyun-A kim Kyoung-Woong kim Byung-tae Lee Department of Chemical and Biomolecular Engineering (BK21 Plus Program) Korea Advanced Institute of Science and Technology (KAIST) School of Earth Sciences and Environmental Engineering Gwangju Institute of Science and Technology (GIST)

With the increase in silver（Ag）-based products in our lives, it is essential to test the potential toxicity of silver nanoparticles（Ag NPs） and silver ions（Ag ions） on living organisms under various conditions. Here, we investigated the toxicity of Ag NPs with Ag ions to Escherichia coli K-12 strain under various conditions. We observed that both Ag NPs and Ag ions display antibacterial activities, and that Ag ions had higher toxicity to E. coli K-12 strain than Ag NPs under the same concentrations. To understand the toxicity of Ag NPs at a cellular level, reactive oxygen species（ROS） enzymes were detected for use as antioxidant enzymatic biomarkers. We have also studied the toxicity of Ag NPs and Ag ions under various coexistence conditions including： fixed total concentration, with a varied the ratio of Ag NPs to Ag ions; fixed the Ag NPs concentration and then increased the Ag ions concentration; fixed Ag ions concentration and then increasing the Ag NPs *** to Ag NPs and Ag ions clearly had synergistic toxicity; however, decreased toxicity（for a fixed Ag NPs concentration of 5 mg/L, after increasing the Ag ions concentration） to E. coli K-12 strain. Ag NPs and Ag ions in the presence of L-cysteine accelerated the bacterial cell growth rate, thereby reducing the bioavailability of Ag ions released from Ag NPs under the single and coexistence conditions. Further works are needed to consider this potential for Ag NPs and Ag ions toxicity across a range of environmental *** Significance Statement： As silver nanoparticles（Ag NPs）-based products are being broadly used in commercial industries, an ecotoxicological understanding of the Ag NPs being released into the environment should be further considered. Here, we investigate the comparative toxicity of Ag NPs and silver ions（Ag ions） to Escherichia coli K-12 strain, a representative ecotoxicological bioreporter. This study showed that toxicities of Ag NPs and Ag ions to E. coli

关键词： Nanotoxicity Silver nanoparticles Silver ions Coexist condition Escherichia coli

Injection molding of micro patterned PMMA plate

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 148-152页

作者： Yeong-Eun YOO tae-Hoon kim tae-Jin JE Doo-Sun CHOI Chang-Wan kim Sun-Kyung kim Department of Nanomanufacturing Technology KIMM 171 Jang-dong Yusung-gu Daejeon 305-343 Korea Department of Product Design and Manufacturing Seoul National University of Technology

A plastic plate with surface micro features was injection molded to investigate the effect of pressure rise of melt on the replication of the micro structures. Prism pattern, which is used in many optical applications, was selected as a model pattern. The prism pattern is 50 μm in pitch and 108° in the vertical angle. The overall size of the plate was 335 minx213 mm and the thickness of the plate varied linearly from 2.6 mm to 0.7 ram. The prism pattern was firstly machined on the nickel plated core block using micro diamond tool and this machined pattern core was installed in a mold for injection molding of prism patterned plate. Polymethyl methacrylate （PMMA） was used as a molding material. The pressure and temperature of the melt in the cavity were measured at different positions in the cavity and the replication of the pattern was also measured at the same positions. The results show that the pressure or temperature profile through the process depends on the shape and the size of the plate. The replication is affected by the temperature and pressure profiles at the early stage of filling, which is right after the melt reaches the position to be measured.

关键词： micro prism pattern injection molding replication pressure profile temperature profile