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유승환,윤성한,홍석영,최진용,Yu, Seung-Hwan,Yun, Seong-Han,Hong, Seok-Yeong,Choe, Jin-Yong 한국관개배수위원회 2007 한국관개배수논문집 Vol.14 No.2
Agricultural water demand in North Korea must be considered for the near-future investment in agricultural consolidation projects and to prepare for the future unification. Thus, the objective of this study is to estimate the agricultural water demand of paddy fieldss in North Korea. GIS data including land cover classification map, Thiessen network and administration maps of North Korea, and meteorological data were synthesized. In order to estimate paddy water demand for a 10-year return period, the FAO Blaney-Criddle method and the fixed effective rainfall ratio method were used. The results showed that 4.77 billion $\beta$(c)/year paddy water demand is required for the 512,400 ha of paddy fieldss. Paddy water demand in the three major regions - Hwanghaedo, Pyeongando, Hamgyeongnamdo - was estimated chargong 81.7 percent of total paddy water demand in North Korea.
농업용수 수요량 분석을 위한 잠재증발산량 공간 분포 추정
유승환,최진용,Yu, Seung-Hwan,Choe, Jin-Yong 한국관개배수위원회 2006 한국관개배수논문집 Vol.13 No.1
Weather station based PET(Potential Evapotrarspiration) analysis has often been inadequate to meet the needs of regional-scale irrigation planning. A map of continuous PET surface would be better a solution for the spatial interpolation considering spatial variations. Using a normal PET data collected at the 54 meteorological stations in Korea, 10-days spatial distribution PET map was created using universal Kriging(UK). These estimation methods were evaluated by both visual assessments of the output maps and the quantitative comparison of error measures that were obtained from the cross validation. The universal Kriging method showed appropriate results in spatial interpolation from weather station based PET to spatial PET with low statistical errors.
잉크에 부분적으로 잠겨 회전하는 롤 주위의 액막 유동 해석
유승환(Seung-hwan Yu),강수진(Soojin Kang),이관수(Kwan-soo Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This study is intended to analyze the effect of thin ink-film thickness around rotating printing roll on the printing quality in the gravure printing process which is used for making electronics circuit like a RFID tag with a conductive ink. The present work numerically estimates the film thickness around rotating roller partially immersed in ink, for which the volume of fluid (VOF) method was adopted to figure out the film formation process around rotating roller. Parameter studies were performed to compare the effect of ink viscosity, surface tension, roller rotating speed, immersed angle on the film thickness. The result indicates that the film thickness has a strong dependency on the fluid viscosity, while the surface tension has negligible effect.
잉크에 부분적으로 잠긴 회전하는 롤 주위의 액막 유동 해석
유승환(Seung-hwan Yu),이관수(Kwan-Soo Lee),엄석기(Sukkee Um) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.12
This study is intended to analyze the effect of thin ink-film thickness around rotating printing roll on the printing quality in the gravure printing process which is used for making electronics circuit like a RFID tag with a conductive ink. The present work numerically estimates the film thickness around rotating roller partially immersed in ink, for which the volume of fluid (VOF) method was adopted to figure out the film formation process around rotating roller. Parameter studies were performed to compare the effect of ink properties (viscosity, surface tension), operating condition (roller rotating speed, initial immersed angle) on the film thickness. The result indicates that the film thickness has a strong dependency on the rotating speed, while the surface tension has negligible effect.
유승환(Seung-hwan Yu),이관수(Kwan-soo Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The present work numerically estimated the film thickness around a rotating roller partially immersed in ink, of which properties satisfies the non-Newtonian fluid condition, using the volume of fluid (VOF) method to figure out the film formation process around the rotating roller. The characteristics of the non-Newtonian film flow were compared with those of the Newtonian film flow. Parametric studies were performed to compare the effects of the operation conditions, i.e. the rotating speed and initial immersed angle of the roller, on the film thickness.
유승환(Seung Hwan Yu),이관수(Kwan Soo Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.5
본 연구는 LED 조명기구와 같은 원형 모양에 적합한 원형 히트싱크의 주위의 열유동을 실험 및 해석적으로 분석하였다. 기존 복사 열전달을 고려하지 않은 상관식을 이용하여, 추가적으로 복사열전달을 해석적으로 계산하였다. 본 해석 모델의 타당성을 실험적으로 확인하였다. 이 모델을 바탕으로 휜의 형상 및 열유속을 인자로 하여 히트싱크 평균 온도의 변화를 살펴보았다. 그 결과 열전달 성능을 최대로 할 수 있는 최적 휜의 길이가 존재하였고, 방사율이 클수록 형상 인자의 변화가 복사 열전달 변화에 미치는 영향이 상대적으로 감소하였다. The heat transfer over a radial heat sink, adapted for LED (light emitting diode) downlights, was experimentally and analytically investigated. We added radiation heat transfer into a previous calculation that neglected this factor. The numerical results agreed well with experimental results. Parametric studies were performed to compare the effects of the geometric parameters (fin length, fin height, ideal number of fins) and the operating parameter (heat flux) on the average heat-sink temperature from the heat-sink array. We found the fin length that maximizes the heattransfer performance. As the emissivity increased, the effect of geometric parameters on the radiation heat transfer decreased.
유승환(Seung-Hwan Yu),이관수(Kwan-Soo Lee) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
In the present study, natural convection over a heat sink with a horizontal circular base and rectangular fins was numerically analyzed. To calculate natural convection heat transfer, the assumptions of ideal gas and laminar flow were made for air. Flow patterns around the heat sink were chimney-like. The resultant temperature distribution on the circular base appeared almost uniform. Parametric studies were performed to compare the effects of fin length, fin height, the ideal number of fins, and heat flux on the average temperature of a heat sink and the average heat transfer coefficient from the heat sink array. Correlation to predict the average Nusselt number was presented.
유승환(Seung-hwan Yu),이관수(Kwan-soo Lee),엄석기(Sukkee Um) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
This study is intended to analyze the effect of thin ink-film thickness around rotating printing roll on the printing quality in the gravure printing process which is used for making electronics circuit like a RFID tag with a conductive ink. The present work numerically estimates the film thickness around rotating roller partially immersed in ink, for which the volume of fluid (VOF) method was adopted to figure out the film formation process around rotating roller. Parameter studies were performed to compare the effect of ink properties (viscosity, surface tension), operating condition (roller rotating speed, initial immersed angle) on the film thickness. The result indicates that the film thickness has a strong dependency on the rotating speed, while the surface tension has negligible effect.