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Sang‑Wook Kim,Hyeon‑Woo Son,Taek‑Kyun Jung,Young‑Bum Chun,Yi‑Hyun Park,Ji‑Woon Lee,Soong‑Keun Hyun 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The hot deformation behavior of advanced reduced-activation alloy (ARAA) was investigated using hot torsion tests. Thefl ow stress decreased as deformation temperature increased and as strain rate decreased. The fl ow behavior demonstratedthe typical dynamic recrystallization (DRX). Based on the constitutive analysis of peak stress, the activation energy for hotdeformation was found to be 330.3 kJ mol −1 . Peak stress was analyzed as a function of the Zener–Hollomon parameter, andcalculated and experimental values were in good agreement. A DRX kinetic model for ARAA was derived with deformationconditions based on the Avrami-type model. It was confi rmed that the volume fraction of dynamically recrystallized grainsincreased as deformation temperature increased and as strain rate decreased. The necklace structure and grain boundarybulging were observed in the deformed microstructure of ARAA. The suggested DRX mechanism for ARAA during hotworking is discontinuous DRX.
산업단지 및 일반생활 지역의 공기 중 톨루엔에 대한 개인노출 및 생체시료의 상관성 분석
이병준(Byoungjun Lee),허 정(Jung Heo),정다영(Dayoung Jung),김순신(Sunshin Kim),류현수(Hyeon-Su Ryu),최민지(Min-Ji Choi),솨이지엔페이(Jian-Fei Shuai),임성국(Sung-Guk Im),양원호(Wonho Yang) 한국환경보건학회 2017 한국환경보건학회지 Vol.43 No.4
Objectives: The purpose of this study was to assess the correlation relationship between personal exposure and urinary hippuric acid in biological monitoring for airborne toluene in an industrial complex and in general environments. Methods: Personal exposure to toluene and its metabolite, hippuric acid, in urine were simultaneously measured in occupational environments area near an industrial complex and in general environments. The study subjects were divided into three types: 137 workers who use organic solvents in the workplace, 210 residents living near a dyeing industrial complex, and 379 residents living in general environments. The toluene exposures of workers and residents were measured by a passive sampler for four days. The urine of participants was sampled when the passive samplers of personal exposure were collected. Results: The toluene and hippuric acid concentrations of workers were the highest, followed by the concentrations of residents living near a dyeing industrial complex and residents living in general environments. The coefficient of correlation between the concentrations of toluene and hippuric acid among workers was 0.749 (p<0.01) in the workplace. On the contrary, correlations between the concentrations of toluene and hippuric acid among residents living near a dyeing industrial complex and residents living in general environments were all not significant. The relationship between the concentrations of hippuric acid and toluene in three types could be described by the exponential growth model. Conclusions: This study analyzed the relationships between toluene exposure and the concentrations of hippuric acid in urine in high, middle, and low exposure environments, and could be described by the exponential growth model.
Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 ADVANCED MATERIALS Vol.22 No.19
<B>Graphic Abstract</B> <P>The cover shows an image of fully rollable transparent nanogenerators synthesized using chemical vapor deposition grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO nanorod arrays. Sang-Woo Kim, Jae-Young Choi, and co-workers report on p. 2187 the electrical and structural stability of the nanogenerators, with excellent charge scavenging performance under external mechanical loads such as bending and rolling. This study shows that graphene-based nanogenerators are very promising for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content'> </P>
Performance of patient-reported index in outcome assessment of rheumatoid arthritis
( Hyeon Su Kim ),( Sung-hoon Park ),( Jung-yoon Choe ),( Seong-kyu Kim ),( Hwajeong Lee ) 대한내과학회 2015 대한내과학회 추계학술대회 Vol.2015 No.1
Background/Objective: The objective of this study is, the first, to evaluate a feasibility in assessing the rheumatoid arthritis (RA) disease activity with these four RA disease activity indices and to assess the correlation with routine assessment of patient index data 3 (RAPID3), and the second, to evaluate an interrater agreement with Boolean-criteria proposed by American college of rheumatology (ACR) and European league against rheumatology (EULAR) in categorizing remission group. Methods: A total of 503 RA patients who visited usual rheumatology outpatient clinic were investigated cross-sectionally. Medical records of patients were reviewed and data regarding demographics, disease duration, and laboratory parameters were collected. Shapiro-Wilk W test was used to identify normality of distribution in the study population. Wilcoxon rank sum test was used to compare the age, RAPID3 in RA patients group. Stratification of the patients group by disease activity with different measure was done and Cohen’s kappa (κ) was analyzed to evaluate interrater agreement. In general, kappa value >0.8 corresponds to almost perfect, 0.61-0.8 to substantial, 0.41-0.6 to moderate and 0.2-0.4 to fair agreement. Results: The proportion of remisson patients was highest in RAPID3≤3 category as 20.1% and the lowest in clinical disease activity index (CDAI) category. Comparably, high disease activity group was highest in RAPID3 category as 38.5%. Categorization of study population by Boolean-definition remission criteria was done and 8.3% of patients were shown to satisfied with remission criteria (patients with tender joint count≤ 1, swollen joint count≤1, C-reactive protein ≤ 1 mg/dl and patient’s global≤1). Inter-criteriaagreement in disease activity categorization was compared between composite measures. A substantial level of agreement was shown by RAPID3 and Boolean definition with 0.67 of kappa value and a modest agreement with DAS28, simplified disease activity indexand CDAI. Conclusions: On the basis of these results, Korean version of RAPID3 has an substantial efficacy and validity in assessment of disease activity in RA patents on the setting of usual clinical practice.
Advantages of a buried-gate structure for graphene field-effect transistor
Lee, Sang Kyung,Kim, Yun Ji,Heo, Sunwoo,Park, Woojin,Yoo, Tae Jin,Cho, Chunhum,Hwang, Hyeon Jun,Lee, Byoung Hun Institute of Physics 2019 Semiconductor science and technology Vol.34 No.5
<P>Graphene field effect transistors (GFETs) with top-gate and back-gate structures have been extensively used without much consideration for compatibility with graphene. A comparative study of the electrical characteristics of buried-gate GFETs and top-gate GFETs revealed that the performance of buried-gate GFETs is drastically enhanced by having a better gate controllability, achieving three times higher field effect mobility (∼3000 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>) than top-gate GFETs with on/off ratio ∼10. Carrier scattering was also substantially improved by minimizing the fringing field effect, which is found to be the origin of high series resistance in top-gate GFETs. Moreover, we showed by electromagnetic (EM) simulation that the electric field distribution inside the transistors is more uniform at the buried-gate GFETs than the top-gate GFETs.</P>
Lee, Sang-Hyeon,Seong, Minho,Kwak, Moon Kyu,Ko, Hyunwook,Kang, Minsu,Park, Hyung Wook,Kang, Seong Min,Jeong, Hoon Eui American Chemical Society 2018 ACS NANO Vol.12 No.11
<P>Anti-icing materials that can efficiently limit ice formation have a strong potential to replace existing anti-icing techniques, such as Joule heating, chemical release, or mechanical removal, which are usually inefficient, expensive, and environmentally harmful. In this study, an anti-icing material based on a magnetically responsive hierarchical hair array that can actively modulate drop bouncing dynamics is presented. The magnetically responsive hair array exhibits an immediate and reversible structural bending motion in response to an external magnetic field. The array also exhibits superhydrophobicity, regardless of its tilt angle, due to the tapered geometry of the hairs and the multiscale surface roughness of the array. Due to its dynamic structure and water-repellent characteristics, the array can induce distinct multiple modes of drop bouncing behavior by adjusting its structural bending state in a reversible fashion. Three different types of bouncing behavior, namely, quasi-pancake bouncing, directional bouncing, and macrotexture-induced droplet fragmentation, can be obtained with the vertical, tilted, and fully bent hair arrays, respectively. We demonstrate that the dynamically controllable drop bouncing behavior of the magnetically responsive hierarchical array enables the efficient and robust prevention of ice formation and accumulation.</P> [FIG OMISSION]</BR>
Characteristics of Pediatric Inflammatory Bowel Disease in Korea: Comparison with EUROKIDS Data
( Hyeon Ah Lee ),( Jung Yoon Suk ),( Sung Youn Choi ),( Eun Ran Kim ),( Young-ho Kim ),( Chang Kyun Lee ),( Kyu Chan Huh ),( Kang Moon Lee ),( Dong Il Park ) 대한소화기학회 2015 Gut and Liver Vol.9 No.6
Background/Aims: Pediatric inflammatory bowel disease (IBD) has been increasing worldwide. The characteristics of pediatric-onset IBD have mainly been reported in Western countries. We investigated the clinical characteristics of pediatric IBD in Korea and compared these with the data from the 5-year European multicenter study of children with new-onset IBD (EUROKIDS registry). Methods: Children who were diagnosed with IBD between July 1987 and January 2012 were investigated at five Korean university hospitals. Their clinical characteristics were retrospectively evaluated by medical record review. The results were compared with the EUROKIDS data. Results: A total of 30 children with Crohn’s disease (CD) and 33 children with ulcerative colitis (UC) were enrolled. In comparison with the EUROKIDS group, Korean pediatric IBD patients showed a male predominance (86.7% vs 59.2%, p=0.002 in CD, 75.8% vs 50%, p=0.003 in UC). Korean pediatric CD patients had a higher prevalence of terminal ileal disease (36.7% vs 16.3%, p=0.004) and perianal disease (33.3% vs 8.2%, p<0.001) than patients in the EUROKIDS group. Korean pediatric UC patients had a higher prevalence of proctitis than patients in the EUROKIDS group. Conclusions: Our results suggest that the characteristics of Korean pediatric IBD patients and European pediatric IBD patients may be different. (Gut Liver 2015,9:756-760)