• The KSFM Journal of Fluid Machinery
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• v.10 no.4
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• pp.9-14
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• 2007

The purpose of present work is to analyze the convective heat transfer downstream of mixing vane in subchannel of nuclear reactor with three-dimensional Navier-Stokes equations. SST model is selected as a turbulence closure by comparing the performances of two different turbulent closures. Three different shapes of mixing vane are tested. And, thermal-hydraulic performances of these vanes are discussed. The results show that twist of the vane improves the heat transfer performance far downstream of the vane.

• The KSFM Journal of Fluid Machinery
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• v.12 no.4
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• pp.7-13
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of inverse of heat transfer rate and friction loss. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.1-8
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• 2009

The purposes of present work are to analyze the convective heat transfer with three-dimensional Reynolds-averaged Navier-Stokes analysis, and to optimize shape of the mixing vane taken tolerance into consideration by using the analysis results. Response surface method is employed as an optimization technique. The objective function is defined as a combination of heat transfer rate and inverse of pressure drop. Two bend angles of mixing vane are selected as design variables. Thermal-hydraulic performances have been discussed and optimum shape has been obtained as a function of weighting factor in the objective function. The results show that the optimized geometry improves the heat transfer performance far downstream of the mixing vane.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.500-505
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• 1996

고온의 정상상태에서 조사된 후 재조직(restructuring)과 균열(cracking)이 일어난 핵연료 내에서 결정립 외부 공극의 을 결정할 수 있는 퍼콜레이션(Percolation) 모델을 개발하였다. 핵연료 펠렛은 다수의 작은 정육각형 결정립들로 구성된 큰 정육각형으로 모의한다. 핵연료봉은 형상과 열적 특성이 다른 네 개의 영역으로 구분하고 각 경계 위치를 임계온도로부터 계산한다. 공극의 상호연결분율은, 몬테카를로 방법으로써 싸이트(Site)의 채워짐 여부를 점검하고 Hoshen-Kopelman 방법으로써 자유 공간에 연결된 클러스터(Cluster)에 포함된 싸이트들의 수를 계산하여 채워진 싸이트의 총 개수에 대한 연결 싸이트들의 개수의 비로써 구한다. AECL-2230, CBX 핵연료봉 실험의 기체 방출분율 자료에 대하여, FASTGRASS 코드의 상호연결분율 함수를 영역별로 계산한 상호연결분율로 대치하여 계산한 결과와 비교하였다. 균열과 재조직은 핵분열 기체 방출에 상당히 영향을 미치는 것으로 나타났다. 이 모델의 주요 장점은 결정립계에서의 상호연결현상을 단순 상호연결분율보다 좀더 사실적으로 모의하며 결정립의 성장과 균열을 고려할 수 있다는 점이다.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.118-124
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• 2017

To investigate and analyze the cause of the failure of the connecting rod bolt and the crank pin bearing bolt of the diesel engine of this study, the following results were obtained through site surveying, the investigation of literature referring to similar failures, testing and inspection of the fracture surface, and the experience of the researchers. The fractured crank pin bearing bolt of the diesel engine is estimated to be damaged later than the connecting rod bolt. From the shape of fracture surface, it is evident that the failed connecting rod bolt is fractured by fatigue failure due to abnormally repeated loads (e.g. loosening of the connecting bolt, etc.), and is not failed by brittle fractures due to the impact load. The surface of the U-nut on the fractured connecting rod bolt has been worsening due to the improper use of lubricant (agent for prevention of thread fixing) and no usage of separating the each connecting rod on each cylinder. Moreover, there is the possibility that those poor surface conditions of the fractured connecting rod bolt have affected the failure of the connecting rod bolt of the main engine. And it could be assumed that the mechanical characteristic and manufacturing process of the failed connecting rod bolt and crank pin bearing bolt, which were made by a domestic company, conform to the design requirements for those bolts.

• Korean Journal of Environment and Ecology
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• v.11 no.4
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• pp.486-492
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• 1998

The forests of Osaek-Taech'ongbong-Shinhungsa district in Soraksan National Park was studied to investigate forest structure of tree strata in relation to aspect and altitude of the slope. Excepting the main ridge area which has tyoical environmental condition, tree siwe in canopy of the wouthern slope was smaller, density in canopy of the southern slope was higher and species diversity in tree stratum of the southern slope was lower as compared those of the northern slope of same elevation belts. Elevation trend was found for forest structure of the southern slope where geographical features were similar among elevation belts. With incleasing elevation of the southern slope, basal area of canopy and understory increased. With increasing elevation of the southern slope, importance values of Quercus mongolica, Styrax obassia, and Lindera obtusiloba decreased while those of Pinus koraiensis, Betula ercani, Acer tschonoskii var. rubripes and Rhododendron schlippenbachii increased. According to cluster and ordination analysis, the studied forests was classifide into Quercus mongolica community at the low, middle and high elevation belts of the southern slope and the low and middle elevation belts of the northern slope, Betula ermani community at the elevation belt of the northern slope, and Abies koreana community at the top area.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.67-67
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• 1993

GM-CSF의 중추 신경계에 미치는 영향을 추구하기 위하여 실험동물에 대한 일반 약리 작용실험을 실시하였다. 실험항목과 방법은 hexobarbital-Na(70mg/kg, ip)에 의한 마우스의 수면시간 측정, Dunham 등의 rotarod시험 (12rpm)에서 마우스가 회전봉에 지탱하는 시간의 측정, locomotor activity cage에서의 마우스의 운동 활동성측정, 흰쥐의 정상체온에 미치는 작용, 0.7% HAc(0.1ml/10g, b.w.) 복강투여에 대한 마우스의 writhing의 억제율의 측정 실험, strychnine(1.5mg/kg)을 피하주사시 마우스의 경련성 치사에 미치는 효과, pentetrazole(85mg/kg)의 피하주사에 의한 마우스 경련의 억제실험을 실시하였다.

• Journal of Energy Engineering
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• v.9 no.3
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• pp.184-191
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• 2000

본 연구에서는 국내 10MW급 기력발전소의 소형 터빈 로터에 대한 응력 해석을 실시하였다. 터빈 로터의 기하학적 형상, 증기의 온도 및 압력 등의 기동조건 변화, 로터 재료의 온도에 따른 물성값 등을 고려하여 대류 열 전달계수를 계산하는 사용자 부프로그램을 구성하였으며, 이를 바탕으로 열해석을 실시하여 로터의 온도 분포를 결정하였다. 이 온도분포 조건에서 시간 경과에 따른 열응력 해석을 실시하여 로터의 응력 분포를 결정하였으며 그 결과 취약부위에서의 응력변동 범위 및 가동중 정상상태 응력수준을 결정하였다. 이 취약부위의 응력값과 운전이력을 이용하여 크리프 수명과 피로수명을 계산하고 로터의 잔여수명을 결정하는 방법을 논의하였다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.145-148
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• 2009

본 논문에서는 2007년도 유네스코 지정 세계자연유산으로 등재되어 많은 내외국인 관광객이 찾는 유명 관광지로 각광받고 있는 성산 일출봉 조명설비의 해석 및 모델링에 대하여 연구하였다. 정상으로 오르는 보행자도로 중에서 경사도가 완만한 잔디광장부분에서의 조명 기구 실태 파악하고 조도분포에 대하여 실측하였다. 적합한 관광지 조명 모델링을 위한 시뮬레이션을 통하여 쾌적하고 안전을 도모할 수 있는 설계안을 제시하였다.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.837-840
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• 1998

In this paper, we designed the computer input device for rehabilitation of people with hand disabilities. This input device is made up of two Gyrostar sensors attached in the orthnormal directions of x, y axes. Gyrostar is a sensor for angular Acceleration. This device is attached by the user's head side. Head movement is detected by analysing and processing the output wave signals from the sensors therefore enabling the user to move the mouse pointer that helps to operate the computer. This method does not necessitate a complex hardware or a long installation process, which was formerly the case, and uses real time algorithms which enables simple emulation of a computer mouse. The interface of this device and the mouse are the same.