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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B09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

Aging Behavior of Mg-Y-Zr and Mg-Nd-Zr Cast Alloys

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Journal of Materials Science & Technology 2008年第1期24卷 80-84页

作者： Yang-Do kim Nam-hyun Kang Il-Guk Jo Kyung-hyun kim In-Bae kim School of Materials Science and Engineering Pusan National University 30 Jangjun-dongGeumjeong-guBusan 609-735Korea Deptartment of Materials Engineering Korea Institute of Machinery & Materials 66 Sangnam-dongChangwonGyeongsangnam-do 641-010Korea

Aging behavior of Mg-3.6Y-0.5Zr and ***-0.5Zr alloys was investigated by microhardness measurement and transmission electron *** the case of Mg-Y-Zr alloy,the presence ofβ″phase,a major strength- ener,having base centered orthorhombic structure with its lattice constants of a-（β″）=0.64 nm,b-（β″）=2.22 nm, and c-（β″）=0.52 nm was *** the case of Mg-Nd-Zr alloy aged at 250℃,the presence ofβ″andβ′phases was *** crystal structure ofβ″phase was found to be DO-（19） and its orientation relationships with Mg matrix were [0001]-（β″）//[0001]-（Mg） and [01（？）0]-（β″）//[01（？）0]-（Mg）.Theβ′phase had face centered cubic structure and its orientation relationships with Mg matrix were [011]-（β′）//[0001]-（Mg） and [（？）1（？）]β′//[（？）110]）-（Mg）. The ***-0.5Zr alloy showed higher hardness compared with Mg-3.6Y-0.5Zr alloy.

关键词： Mg-Y-Zr alloy Mg-Nd-Zr alloy Precipitation sequence

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

Efficacy of 0.5-L vs 1-L polyethylene glycol containing ascorbic acid as additional colon cleansing methods for inadequate bowel preparation as expected by last stool examination before colonoscopy

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World Journal of Clinical Cases 2019年第1期7卷 39-48页

作者： Joon hyun Cho Eun Joo Goo Kyeong Ok kim Si hyung Lee Byung Ik Jang tae Nyeun kim Division of Gastroenterology and Hepatology Department of Internal Medicine Yeungnam University College of Medicine

BACKGROUND No consensus has been reached in patients suspected of having inadequate bowel preparation regarding optimal salvage methods, which negatively affects the efficacy and quality of colonoscopy. The most ideal and reasonable rescue option involves early suspicion and identification of patients with inadequate preparation before sedation, additional oral ingestion of a suitable preparation formulation, and same-day *** To compare 0.5-L and 1-L polyethylene glycol containing ascorbic acid(PEG +Asc) as additional bowel cleansing methods after a 2-L split-dose PEG + Asc regimen in patients with expected inadequate bowel preparation before *** Individuals with expected inadequate bowel preparation based on last stool form, such as turbid liquid, particulate liquid, or liquid with small amounts of feces, were randomized to either a 0.5-L PEG + Asc group or a 1-L PEG + Asc group. The primary endpoint was bowel preparation as assessed using the Aronchick bowel preparation scale(ABPS) and Boston bowel preparation scale(BBPS) scores. The secondary endpoints were cecal intubation time, withdrawal time, polyp detection rate(PDR), adenoma detection rate(ADR), individual compliance with additional PEG + Asc, and patient *** Initially, 98 patients were included, but 8 were later excluded due to withdrawal of consent to participate in the study. Adequate bowel preparation(as assessed by ABPS) was observed in 80.9%(38/47) of subjects in the 0.5-L group and in88.4%(38/43) of subjects in the 1-L group(P = 0.617). Mean total BBPS was 6.7 points in the 0.5-L group and 7.0 points in the 1-L group(P = 0.458). ADRs and PDRs were similar in the two groups, and cecal intubation and withdrawal times were not significantly different. However, mean patient satisfaction score was significantly higher in the 0.5-L group(P = 0.041).CONCLUSION The bowel cleaning efficacy of additional 0.5-L PEG + Asc was not inferior to that of 1-L PEG + Asc. Add

关键词： Inadequate bowel preparation Additional colon cleansing Colonoscopy Polyethylene glycol

Counter-balancing effects of Si on C partitioning and stacking fault energy of austenite in 10Mn quenching and partitioning steel

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Journal of Materials Science & Technology 2022年第3期98卷 248-257页

作者： Dong Hwi kim Jee-hyun Kang Hojun Gwon Joo hyun Ryu Sung-Joon kim Graduate Institute for Ferrous Technology Pohang University of Science and TechnologyPohang 37673Republic of Korea School of Materials Science and Engineering Institute of Materials TechnologyYeungnam UniversityGyeongsan 38541Republic of Korea POSCO Technical Research Laboratories POSCOGwangyang 57807Republic of Korea

Silicon is an essential alloying element in quenching and partitioning(Q&P)steels,because it is known to suppress carbide precipitation during partitioning step and promote carbon partitioning to stabilize *** 2 wt%Si was added to 10Mn-2Al-0.2C steel,the size and fraction of the carbides formed during partitioning became smaller than in the Si-free ***,the suppression of carbide formation promoted C partitioning into austenite as ***,austenite stability was always lower with Si under the equivalent partitioning condition because Si effectively decreased the stacking fault energy of *** partitioning progressed,the both yield and tensile strengths of the Si-added steel exceeded that of the Si-free steel with the similar ductility *** was because Si was an effective solid solution strengthener,and the austenite in the Si-added steel exhibited the appropriate stability to gradually transform into martensite throughout the *** resulting strengthening effect compensated for the softening caused by martensite ***,strain hardening rate decreased continuously throughout deformation,which resulted in high tensile strength and ductility.

关键词： Steels Q&P steel Silicon Austenite stability Tensile deformation Stacking fault energy Medium Mn steel

Polymer-based membranes for solvent-resistant nanofiltration:A review

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Chinese Journal of Chemical Engineering 2017年第11期25卷 1653-1675页

作者： Slow Kee Lira Kunli Goh tae-hyun Bae Rong Wang Singapore Membrane Technology Center Nanyang Environment and WaterResearch InstituteNanyang Technological UniversityI Cleantech Loop637141 SingaporeSingapore Nanyang Environment and Water Research Institute Interdisciplinary Graduate SchoolNanyang Technological University637141 SingaporeSingapore School of Chemical and Biomedical Engineenng Nanyang Technological University62 Nanyang Drive637459 SingaporeSingapore School of Civil and Environmental Engineering Nanyang Technological University50 NanyangAvenue639798 SingaporeSingapore

Separation of organic mixture is an inevitable process in most modern industrial processes. In the quest for a more sustainable and efficient separation, solvent-resistant nanofiltration(SRNF) has emerged as a promising answer. This is because SRNF is a membrane-based process which offers the key advantages of high efficacy and low energy intensity separation. In particular, polymer-based membranes can offer compelling opportunities for SRNF with unprecedented cost-effectiveness. As a result, intensive research efforts have been devoted into developing novel polymer-based membranes with solvent-resistant capacities as well as exploring potential applications in different types of industries. In this review, we aim to give an overview of the recent progress in the development of the state-of-the-art polymer-based membranes for SRNF in the first section. Emerging nanomaterials for mixed matrix and thin film nanocomposite membranes are also covered in this section. This is followed by a discussion on the current status of membrane engineering and SRNF membrane commercialization. In the third section, we highlight recent efforts in adopting SRNF for relevant industrial applications such as food, bio-refinery, petrochemical, fine chemical and pharmaceutical industries followed by separations of enantiomers in stereochemistry, homogeneous catalysis and ionic liquids. Finally, we offer a perspective and provide deeper insights to help shape future research direction in this very important field of SRNF.

关键词： Nanofiltration Solvent-resistant Polymeric membranes Nanomaterials Crosslinking Industrial applications

Feasibility of wear reduction for soft nanostructured thin film through enhanced elastic recoverability and contact stress relief

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Friction 2023年第7期11卷 1292-1306页

作者： Kuk-Jin SEO hyun-Joon kim Dae-Eun kim Department of Mechanical Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Precision Mechanical Engineering Kyungpook National UniversitySangju 37224Republic of Korea Department of Advanced Science and Technology Convergence Kyungpook National UniversitySangju 37224Republic of Korea

This work shows that a soft,thin film comprising randomly aligned carbon nanotubes(CNTs)can reduce surface wear more effectively than a homogeneous thin film because of enhanced elastic recoverability and contact stress relief originating from its mesh *** investigate the wear characteristics of the mesh structure compared to those of the homogeneous thin film,multi-walled CNTs(MWCNTs)and diamond-like carbon(DLC)thin films were prepared to conduct nanoscale tribological experiments using the atomic force microscopy(AFM).The MWCNT thin film showed unmeasurably low wear compared with the DLC thin film under a certain range of normal *** demonstrate the wear reduction mechanism of the MWCNT thin film,its indentation and frictional behaviors were *** indentation behavior of the MWCNT thin film revealed repetitive elastic deformation with a wide strain range and a significantly lower elastic modulus than that of the DLC thin *** permanent deformation of the MWCNT thin film was observed through frictional experiments under relatively high normal load *** results are expected to provide insights into the design of highly wear-resistant surfaces using nanostructures.

关键词： carbon nanotube(CNT) thin film wear friction elastic recovery

Clinical advantages of single port laparoscopic hepatectomy

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World Journal of Gastroenterology 2018年第3期24卷 379-386页

作者： Jae hyun Han Young Kyoung You Ho Joong Choi tae Ho Hong Dong Goo kim Division of Hepatobiliary-Pancreas Surgery and Liver Transplantation Department of SurgerySeoul St.Mary’s HospitalCollege of MedicineThe Catholic University of Korea

AIM To evaluate the clinical advantages of single-port laparoscopic hepatectomy(SPLH) compare to multiport laparoscopic hepatectomy(MPLH).METHODS We retrospectively reviewed the medical records of 246 patients who underwent laparoscopic liver resection between January 2008 and December 2015 at our hospital. We divided the surgical technique into two groups; SPLH and MPLH. We performed laparoscopic liver resection for both benign and malignant disease. Major hepatectomy such as right and left hepatectomy was also done with sufficient disease-free margin. The operative time, the volume of blood loss, transfusion rate, and the conversion rate to MPLH or open surgery was evaluated. The post-operative parameters included the meal start date after operation, the number of postoperative days spent in the hospital, and surgical complications was also *** Of the 246 patients, 155 patients underwent SPLH and 91 patients underwent MPLH. Conversion rate was 22.6% in SPLH and 19.8% in MPLH(P = 0.358). We performed major hepatectomy, which was defined as resection of more than 2 sections, in 13.5% of patients in the SPLH group and in 13.3% of patients in the MPLH group(P = 0.962). Mean operative timewas 136.9 ± 89.2 min in the SPLH group and 231.2 ± 149.7 min in the MPLH group(P < 0.001). The amount of blood loss was 385.1 ± 409.3 m L in the SPLH group and 559.9 ± 624.9 m L in the MPLH group(P = 0.016). The safety resection margin did not show a significant difference(0.84 ± 0.84 cm in SPLH vs 1.04 ± 1.22 cm in MPLH, P = 0.704). Enteral feeding was started earlier in the SPLH group(1.06 ± 0.27 d after operation) than in the MPLH group(1.63 ± 1.27 d)(P < 0.001). The mean hospital stay after operation was non-significantly shorter in the SPLH group than in the MPLH group(7.82 ± 2.79 d vs 7.97 ± 3.69 d, P = 0.744). The complication rate was not significantly different(P = 0.397) and there was no major perioperative complication or mortality case in both groups. CONCLUS

关键词： Hepatectomy Laparoscopy Minimally invasive surgery Treatment outcome Feasibility study

Programmed death ligand-1 expression and its prognostic role in esophageal squamous cell carcinoma

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World Journal of Gastroenterology 2016年第37期22卷 8389-8397页

作者： Ryul kim Bhumsuk Keam Dohee Kwon Chan-Young Ock Miso kim tae Min kim Hak Jae kim Yoon Kyung Jeon In Kyu Park Chang hyun Kang Dong-Wan kim Young tae kim Dae Seog Heo Department of Internal Medicine Seoul National University HospitalSeoul 03080South Korea Cancer Research Institute Seoul National University College of MedicineSeoul 03080South Korea Department of Pathology Seoul National University HospitalSeoul 03080South Korea Department of Radiation Oncology Seoul National University HospitalSeoul 03080South Korea Department of Thoracic and Cardiovascular Surgery Seoul National University HospitalSeoul 03080South Korea

AIM To investigate the expression and prognostic role of programmed death ligand-1(PD-L1) in locally advanced esophageal squamous cell carcinoma(ESCC).METHODS A total of 200 patients with ESCC who underwent radical esophagectomy with standard lymphadenectomy as the initial definitive treatment in Seoul National University Hospital from December 2000 to April 2013 were eligible for this analysis. Tissue microarrays were constructed by collecting tissue cores from surgical specimens, and immunostained with antibodies directed against PD-L1, p16, and c-Met. Medical records were reviewed retrospectively to assess clinical outcomes. Patients were divided into two groups by PD-L1 status, and significant differences in clinicopathologic characteristics between the two groups were assessed. RESULTS Tumor tissues from 67 ESCC patients(33.5%) were PDL1-positive. Positive p16 expression was observed in 21 specimens(10.5%). The H-score for c-Met expression was ≥ 50 in 42 specimens(21.0%). Although PDL1-positivity was not significantly correlated with any clinical characteristics including age, sex, smoking/alcoholic history, stage, or differentiation, H-scores for c-Met expression were significantly associated with PDL1-positivity(OR = 2.34, 95%CI: 1.16-4.72, P = 0.017). PD-L1 expression was not significantly associated with a change in overall survival(P = 0.656). In contrast, the locoregional relapse rate tended to increase(P = 0.134), and the distant metastasis rate was significantly increased(HR = 1.72, 95%CI: 1.01-2.79, P = 0.028) in patients with PD-L1-positive ESCC compared to those with PD-L1-negative *** PD-L1 expression is positively correlated with c-Met expression in ESCC. PD-L1 may play a critical role in distant failure and progression of ESCC.

关键词： Esophageal neoplasm Programmed death ligand-1 protein c-Met protein Prognosis p16INK4A protein