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최지용,조안태,김광용,Choi Ji-Yong,Cho An-Tai,Kim Kwang-Yong 한국유체기계학회 2006 한국유체기계학회 논문집 Vol.9 No.4
In the present work, characteristics of the flow in the cage of a steam turbine bypass control valve for thermal power plant are investigated. Experimental measurement for wall static pressure has been carried out to validate numerical solutions. And, the flowfield is analyzed by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure. The effects of the flow area between stages of the cage on the pressure drop are also found.
최지용,박원규,이상일,Choi, Ji-Yong,Park, Won-Kqyu,Lee, Sang-Il 한국수자원학회 1996 물과 미래(한국수자원학회지) Vol.29 No.2
하천 및 호소수 수질의 온라인 계측을 위한 수질자동측정망의 설계에서 측정위치와 항목의 선정은 전체시스템의 성능을 결정짓는 중요한 인자이다. 본 논문에서는 상수원유역의 상시수질감시 및 사전경보 기능을 갖는 측정망의 구축이 측정위치와 항목을 결정하는 방법을 연구하였다. 측정위치를 결정하기 위한 선정기준은 상수취수량과 고정오염원의 위치를 바탕으로 대상지역에 대한 거시적 후보지점을 선정한 뒤, 구체적인 지점은 오염물질 유하거리를 기준으로 단계적으로 결정한다. 측정항목은 유역의 오염특성과 수질오염사고 이력을 참고하되, 경제적인 측면을 고려하여 필수측정항목과 선택항목으로 나누어 위치별로 달리하는 방안을 제시하였다. 제안방법을 낙동강유역에 적용함으로써 측정망 구성과정을 예시하였다. In designing automatic water quality monitoring networks for a river basin, determination of measurement locations and items is critical to the effectiveness of the total system. In this paper we studied how to decide these two design factors when a monitoring network is designed for the purposse of water quality surveillance and emergency alarm. For measurement locations, candidate sites are chosen based on the intake amount for water supply and the point sources of contamination. Then, detailed locations are decided according to the contaminant flow distance. As for measurement items, characteristics and the accident history of water pollution in the basin must be taken into account. Considering economic aspects, we proposed a two-stage measurement plan: basic components for all locations and selective ones variable for different locations. Proposed methodology is demonstrated through a case study for Nak-dong River Basin.
최지용,신은성 ( Ji Yong Choi,Eun Sung Shin ) 한국물환경학회 1997 한국물환경학회지 Vol.13 No.4
To assist in the dissemination of water quality information to expert as well as layman, Korea Water Quality Index(K-WQI) has been developed. The K-WQI is based on ten physico-chemical and biological determinants which were adopted by an intensive interview and questionnaire survey, and a review of water quality criteria. The sub-index is developed by use of both opinion research and mathematical techniques. The former involves the completion of a series of questionnaires by a panel of water experts thus facilitating the objective selection, transformation and weighting of determinants. The latter involves the use of regression for the construction of the sub-index functions. Aggregation for sub-index is used weighted product function. The weighted product, when applied to decreasing scale subindices, does not exhibit eclipsing. Application of the K-WQI to water quality data, drawn from a selection of Korean river reaches typifying a range of river qualities, has shown that the Index not only act as indicators of water quality change, but can also indicate the effects of these changes on potential water use.
관상동맥질환에서 운동부하 Tc - 99m Tetrofosmin 심근스캔의 진단적 유용성 : 운동부하심전도검사와의 비교
최지용(Ji Yong Choi),황진용(Jin Yong Hwang),황종현(Jong Hyeon Hwang),임현주(Hyeon Ju Lim),박헌식(Hun Sik Park),조용근(Yong Keun Cho),채성철(Shung Chull Chae),전재은(Jae Eun Jun),박의현(Wee Hyun Park),안병철(Byeong Cheol Ahn),이재태(J 대한내과학회 1997 대한내과학회지 Vol.53 No.6
Objectives: Tetrofosmin is a new Tc-99m labeled myocardial perfusion imaging agent that shows slow clearance from the myocardium and rapid clearance from background organs. The purpose of this study was to assess the ability of exercise Tc-99m tetrofosmin single photon emission computed tomography(SPECT) to identify and localize coronary artery disease. Methods : The study population consists of 49 patients with suspected coronary artery disease who underwent both exercise Tc-99m tetrofosmin SPECT and coronary angiography within 2 weeks. Using the one day imaging protocol, 7-10mCi of Tc-99m tetrofosmin was injected at rest and 4 hours later, 25 mCi of Tc-99m tetrofosmin was injected at peak exercise. Results: The sensitivity and specificity of exercise Tc-99m tetrofosmin SPECT was 94.9% and 60% for detection of coronary artery disease with luminal narrowing more than 50%, and 96.4% and 33.3% for detection of coronary artery disease with luminal narrowing more than 70%. The sensitivity of exercise Tc-99m tetrofosmin SPECT for detection of individual stenosed vessels(≥50% and ≥70% coronary stenosis) was 79.2%, 100% for LAD, 55.6%, 55.6% for LCx and 85.0%, 92.9% for RCA and the specificity was 88.0%, 75.0% for LAD, 100%, 87.5% for LCx, 86.2%, 77.1% for RCA respectively. Conclusion: Exercise Tc-99m tetrofosmin SPECT appears to be an feasible and useful noninvasive test for the diagnosis of coronary artery disease
최지용 ( Ji Yong Choi ),고은주 ( Eun Ju Koh ) 한국환경정책평가연구원 2008 환경정책연구 Vol.7 No.3
불투수면 비율은 유역의 건전성 정도를 나타내는 중요한 척도로 활용되고 있으며 특히 유역의 수환경특성을 파악하는 모델에서 이용되어 왔다. 불투수면은 총불투수면과 유효불투수면의 두 가지 있으며, 이들은 각 유역의 토지이용 특성에 따라 그 구성이 다양하다. 이중 총 불투수면은 기존의 토지이용도나 토지피복도를 사용하여 손쉽게 구할 수 있는 반면 유효불투수면은 물 흐름을 필지별로 파악하여야 하기 때문에 산정에 많은 노력과 비용이 소요된다. 본 연구에서는 우리나라 사례지역에 대해 총불투수면과 유효불투수면을 산정하여 그 특성을 상호 비교해 보고 유역관리에 있어 유효 및 총 불투수면 비율의 적용방안을 모색하고자 하였다. 사례지역 분석결과 유효불투수면 면적은 39.7%로 총 불투수면 면적 43%에 비해 약 3%적었다. 불투수면이 수환경에 미치는 영향을 분석하기 위한 기초 자료로 활용하기 위함임을 고려할 때 비용과 시간적 측면에서 볼 때 총불투수면을 유역의 대표적인 불투수면 비율로 사용할 수 있을 것으로 판단된다. The impervious cover ratio has been used as an important measure for tracing water environment characteristics in watershed. Impervious cover is divided into total impervious cover and effective impervious cover, and its size varies depending on the land use characteristics of a watershed. Total impervious cover can be easily measured using existing land use maps or land cover map, while it takes a considerable amount of time and labor to measure the effective impervious cover, as water flow should be identified at each site. This study is intended to calculate the total impervious cover and effective cover of a sample site, compare their characteristics, and find a method to apply effective and total impervious cover ratios toward watershed management. The analysis of the sample site showed that the effective impervious cover rate(39.7%) was less than the total impervious cover rate(43%). This suggests that it would be acceptable, in terms of time and cost, if total impervious cover is applied as the representative impervious cover ratio of a watershed considering that it was used as basic data to analyze the effect that impervious cover has on the water environment.