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조현만(Hyun-Man Cho),김서현(Seo-Hyun Kim),류연선(Yeon-Sun Ryu),김정태(Jung-Tae Kim) 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.5
This study presents the results of collision analyses of burial cable protector under anchor collision. For the analyses, burial environment such as collision distance, the type cf soils and burial depth was estimated. Dynamic finite element program, ANSYS WB Explicit STR was used to collision analyses of burial cable protector. This study focuses on two parameters that are considered two of the fundamental items for the design: the type of soils and burial depth. The purpose of this work is to present fundamental design criteria of burial cable protector.
조현만(HYUN-MAN CHO),류연선(YEON-SUN RYU) 한국해양공학회 2004 韓國海洋工學會誌 Vol.18 No.6
In order to increase the load carrying capacity of tubular structures, the joints of tubular members are usually reinforced with various reinforcement system. A stiffening method with internal ring stiffeners is effectively used for the steel tubular joint with a large diameter. In this study, the behavior of internally ring-stiffened tubular T-joints subjected to axial loading is assessed. For the parametric study, nonlinear finite element analyses are used to compute the static strength on non-stiffened and ring-stiffened T-joints. Based on the numerical results, an internal ring stiffener is found to be efficient in improving the static strength. The influence of geometric parameters has been determined, and the reinforcement effect are evaluated. Based on the FE results, regression analises are performed considering the practical size of ring stiffener. Finally strength estimation formulas for ring-stiffened tubular T-joints are proposed.
조현만(Hyun-Man Cho),김서현(Seo-Hyun Kim),류연선(Yeon-Sun Ryu),김정태(Jung-Tae Kim) 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
This study presents the results of collision analyses of burial cable protector under anchor collision. For the analyses, burial environment such as collision distance, the type of soils and burial depth was estimated. Dynamic finite element program, ANSYS WB Explicit STR was used to collision analyses of burial cable protector. This study focuses on two parameters that are considered two of the fundamental items for the design: the type of soils and burial depth. The purpose of this work is to present fundamental design criteria of burial cable protector.
조현만(Hyun Man Cho),류연선(Yeon Sun Ryu),김정태(Jeong Tae Kim) 한국강구조학회 1997 韓國鋼構造學會誌 Vol.9 No.3
Fatigue cracking and stress concentration due to repeated loading has been asignificant problem occurred in tubular joints. Analytical methods to calculate stress in welding joints are in general not available. Thus semi-analytical formulae for the stress computation have been used. The stress concentration factor(SCF) of tubular joints may be obtained through model experiment, use of approximate formulas, and finited element analysis. Among them, FEM is known to be very efficient. In this study, the conceptual mechanism and stress analysis of tubular joints are to be discussed, and the analysis results using FEM will be compared with custormary appoximate formulas. Also, the variations of maximum principal stresses and SCFs of tubular T-joints according to the change of size and boundary conditions will be presented, which would be very helpful and given an insight in the design of structures with tubular members.
Interleukin-1의 기관지 투여 후 나타나는 폐세척액 내 대식세포의 수적변화에 따른 Xanthine Oxidase의 활성변화
조현국,윤종국,최정목,박원학,이영만,Cho, Hyun-Gug,Yoon, Chong-Guk,Choi, Jeung-Mok,Park, Won-Hark,Lee, Young-Man 한국현미경학회 2001 Applied microscopy Vol.31 No.3
The pulmonary alveolar macrophage is thought to play an important role in the mediation of acute inflammatory lung injury by secretory products including degraded enzymes, cytokines, and reactive oxygen metabolites . This study was conceived to understand the role of alveolar macrophage in oxidative stress induced acute lung injury. To examine the alveolar macrophages and xanthine oxidase (XO) activity in bronchoalveolar lavage fluid (BALF), time-dependent changes of numbers of alveolar macrophages, monocytes and neutrophils in alveolar cavity were counted in association with ultrastructural and cytochemical observations of lung tissue and alveolar cells. The number of monocytes was increased (p<0.001) at 1h after IL-1 treatment compared with that of sham. At 2h after instillation of IL-1, the number of alveolar macrophages was the highest, XO activity in BALF was elevated at 2h after IL-1 instillation and the activity was markedly elevated(p<0.05) at 3h after IL-1 treatment. On the basis of these experimental results, it is suggested that, during early phase of acute lung injury induced by IL-1, alveolar macrophage-derived XO contributes to lung injury earlier than the neutrophilic respiratory burst. 폐포강 대식세포는 사이토카인, 유해산소 대사물을 포함한 그들이 분비하는 물질들로 인해 급성 폐손상에 있어서 직접, 간접적으로 폐손상의 초기반응에 중요한 역할을 담당하는 것으로 알려져 있다. 본 연구에서는 $interleukin-1\alpha$(IL-1)로 유도된 급성 폐손상에서 폐포강 대식세포의 역할을 알아보고자 하였다. 실험군은 대조군과 IL-1투여 후 1시간, 2시간, 3시간, 4시간 그리고 5시간군으로 나누었으며, 폐포강 대식세포와 XO와의 관계를 분석하기 위해 폐세척액 내 XO의 활성도와 폐포강 대식세포, 단핵구, 그리고 호중구의 수적 변화를 측정하였다. 그리고 각 군의 미세구조 변화를 관찰하였다. 실험 결과, 폐포강 내 단핵구의 수는 IL-1투여 후 1시간군에서 대조군과 비교하여 현저히 증가되었으며 (p<0.001), 폐포강 대식세포의 수는 IL-1 투여 2시간 후에 가장 높았고, 폐세척액 내 XO의 활성도는 IL-1 투여 후 점차적으로 증가되다가 3시간 후에 현저히 증가되었다(p<0.05). 폐포강 내 호중구의 수는 IL-1투여 3시간 후부터 뚜렷이 증가되기 시작하였다. 이러한 결과로 보아 IL-1을 기관지 내로 투여한 후 유도된 급성 폐손상에서 폐포강 대식세포에서 유리된 XO는 호중구의 축적에 의한 손상보다 더 초기단계에서 폐손상을 유도하는 인자인 것으로 추정된다.
Glass 첨가량에 따른 ZnO 바리스터의 전기적 특성
조현무,이종덕,박상만,이성갑,Cho, Hyun-Moo,Lee, Jong-Deok,Park, Sang-Man,Lee, Sung-Gap 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.9
ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was $1100^{\circ}C$. The average grain sizes were showed increased from $8.6{\mu}m\;to\;10{\mu}m$, and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient $\alpha$, of all were with increasing the amount of glass-frit more than 70, in case of added on $0.03wt\%$ glass-frit was 83. And leakage current were less than $1{\mu}A$ with applied at $82\%$ of varistor voltage. The clamping voltage ratio of the specimens added $0.03wt\%$ glass-frit was 1.41 at applied 25A $[8/20\;{\mu}s]$. In the specimen added $0.03wt\%$ glass-frit, endurance of surge current and deviation of varistor voltage were $6200A/cm^2,\;\Delta-1.67\%$, respectively and clamping voltage ratio was 2.33. In the Specimen added $0.03wt\%$ glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at $85^{\circ}C$, and deviation of the varistor voltage were $\Delta-1.29\%$.
지부재에 축하중을 받는 K형 관이음부의 내부 환보강재의 설치 및 배치효과 평가
조현만,류연선,임동주,Cho, Hyun-Man,Ryu, Yeon-Sun,Lim, Dong-Joo 한국전산구조공학회 2011 한국전산구조공학회논문집 Vol.24 No.3
본 연구에서는 K형 관이음부의 내부에 단일 및 이중 환보강재를 설치할 경우에 발생하는 보강효과를 수치적으로 평가하였다. 지부재에 축하중을 받는 비보강 이음부와 환보강 이음부의 국부적 최대응력을 평가하기 위해 유한요소해석을 수행하였다. 작용하중과 내부 환보강재의 기하학적 형상이 이음부 거동에 미치는 영향을 평가하고 보강효과를 산정하였다. 또한 단일 환보강재와 이중 환보강재를 비교 평가하여 배치에 따른 응력분포 변화 및 응력의 분산효과를 산정하였다. 수치해석 결과로부터 이음부의 보강설계 자료에 활용 가능한 환보강재의 경제적 규격을 제시하였다. The effect of internal ring stiffeners is numerically evaluated for reinforcement of tubular K-joints. Finite element analyses are performed to compute stress of un-stiffened and ring-stiffened K-joints subjected to axial loading. The influence of loading condition and geometrical parameters of ring stiffener on joint behavior is assessed to determine the installation effect of single and double ring stiffeners. The arrangement effect of ring stiffener are evaluated using quantitative analysis compared single ring with double ring stiffeners. Based on the numerical results, practical size of ring stiffener is proposed for design of tubular K-joints.