• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.361-361
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• 2009

KEPCO High Temperature Superconducting (HTS) cable system rated with $3\Phi$, 22.9kV, 1250A was laid in 2006, and the long term test is in progress. The HTS cable system with the cooling system has been operated below cryogenic temperature. That environment exposes the system to the thermo-mechanical stress due to the significant temperature difference, and the cooling system has moving parts for the forced circulation of the coolant. Therefore the HTS cable system experiences thermal fatigue and moving part such as liquid nitrogen pump need a regular replacement every 5000 hours Building the assessment criterion, the maintenance procedure was established and regular preventive maintenance was done; improvement of the termination structure and the replacement of the bearing of liquid nitrogen pump. Following the proper process, the reliability assessment test including He leakage detection and the stability of flow rate was performed. This paper describes the process and result of the first regular maintenance of KEPCO HTS cable system

• 한국항공우주학회지
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• 제38권6호
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• pp.605-611
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• 2010

정지궤도위성인 통신해양기상위성은 2010년 발사 예정인데, 관련된 일련의 성능 시험중에는 수백 기압의 헬륨 가스로 채워진 추진계 탱크의 고압 내구 시험도 포함되어 있다. 이 논문에서는 시험 시스템에 최악의 사고가 일어날 경우를 대비하여 그 위험도를 계산하여 보았다. 두 가지 시나리오가 있는데, 첫째는 310 기압의 헬륨 탱크가 현재의 시험챔버에서 일시에 파열하는 경우, 둘째는 116 기압의 감압된 헬륨 탱크가 방탄유리로 보호되고 있는 방에서 파열하는 경우를 가정해 보았다. 폭발파 전파 이론과 전산 수치 모사를 통하여, 제한된 공간에서 반사되는 파동의 역학을 매우 복잡한 비정상 유동 물리에 대하여 분석하였다.

• 한국물환경학회지
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• 제31권3호
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• pp.295-303
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• 2015

In Korea, Total Maximum Daily Loads(TMDLs) has been enforced to restore and manage water quality in the watersheds. However, some assesment of implementation plan of TMDLs showed that the achievement of the target water quality is not related to the proper allocation loads because difference of flow duration interval. In the United States, the discharge loads are determined by water quality modeling considering standard flow conditions according to purpose. Therefore, this study tried to develop the allocation method considering economical efficiency using water quality model. For this purpose, several allocation methods being used in the management of TMDLs is investigated and develope an allocation criteria considering regional equality and uniformity. Since WARMF(Watershed Analysis Risk Management Framework) model can simulate the time varying behavior of a system and the various water quality variables, it was selected for a decision support system in this study. This model showed fairly good performance by adequately simulating observed discharge and water quality in Miho watershed. Furthermore, the scenario simulation results showed that the effect of annual average water quality improvement to remove 1kg BOD is more than 25 times, even if point pollutants treatment facility is six times more expensive to operate than non-point pollutants treatment facility.

• 한국농공학회지
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• 제30권2호
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• pp.31-43
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• 1988

The Purpose of this study is to develop the rainfall-delayed response model (RDR Model) which influences the baseflow proportion of rivers as a result of the antecedent precipitation of the previous several months. The assesment of accurate baseflows in the rivers is one of the most important elements for the planning of seasonal water supply for agriculture, water resources development, hydrological studies for the availability of water and design criteria for various irrigation facilities. The Palukan river gauging site which is located in the Pulukan catchment on Bali Island, Indonesia was selected to develop this model. The basic data which has been used comprises the available historic flow records at 19 hydrologic gauging stations and 77 rainfall stations on Bali Island in the study. The methology adopted for the derivation of the RDR model was the water balance equation which is commonly used for any natural catcbment ie.P=R+(catchment losses) -R+(ET+DP+DSM+DGW). The catchment losses consist of evapotranspiration, deep percolation. change in soil moisture, and change in groundwater storage. The catchment areal rainfall has been generated by applying the combination method of Thiessen polygon and Isohyetal lines in the studies. The results obtained from the studies may be summarized as follows ; 1. The rainfall-runoff relationship derived from the water balance equation is as shown below, assuming a relationship of the form Y=AX+B. Finally these two equations for the annual runoff were derived ; ARO$_1$=0.855 ARF-821, ARF>=l,400mm ARO$_2$=0.290ARF- 33, ARF<1,400mm 2. It was found that the correction of observed precipitation by a combination of Thiessen polygons and Isohyetal lines gave good correlation. 3. Analysis of historic flow data and rainfall, shows that surface runoff and base flow are 52 % and 48% (equivalent to 59.4 mm) of the annual runoff, respectively. 4. Among the eight trial RDR models run, Model C provided the correlation with historic flow data. The number of months over which baseflow is distributed and the relative proportions of rainfall contributing in each month, were estimated by performing several trial runs using data for the Pulukan catchment These resulted in a value for N of 4 months with contributing proportions of 0.45, 0.50, 0.03 and 0.02. Thus the baseflow in any month is given by : P$_1$(n) =0.45 P(n) +0.50 P(n-I ) +0.03 P(n-$_2$) +0.02 P(n-$_3$) 5. The RDR model test gave estimated flows within +3.4 % and -1.0 % of the observed flows. 6. In the case of 3 consecutive no rain months, it was verified that 2.8 % of the dependable annual flow will be carried over the following year and 5.8 % of the potential annual baseflow will be transfered to the next year as a result of the rainfall-delayed response. The results of evaluating the pefformance of the RDR Model was generally satisfactory.

• 지적과 국토정보
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• 제44권2호
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• pp.209-230
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• 2014

2002년 최초 도입된 한국의 부동산투자회사(이하, 리츠)는 크게 3가지 형태가 있다. 한국거래소에 상장된 각각의 리츠는 그 특성이 다르지만 모두 부동산투자회사 종목으로 분류된다. 현행 "부동산투자회사법"은 그 개별 특성을 반영하지 못하고 일률적으로 적용되고 있다. 일부 리츠는 입법취지와는 달리 상장폐지되어 투자자의 투자손실을 야기하는 등 개별 리츠에 따라서는 법제도 운영이 적절하게 이뤄진다고 보기 어려운 일이 발생하였다. 본 연구는 부동산투자회사의 사업타당성 측면에서 동제도의 활발한 운용지원 방안 마련을 목적으로 한다. 부동산 개발 관련 부동산금융기법으로서 PF 평가분석시스템을 개선하여 리츠사업 타당성을 제고시킴으로써 리츠부문 활성화를 위한 정책방향을 제시한다. 리츠 관련 정책은 리츠회사 종류에 따른 차이를 고려하지 않은 일괄적인 제도 운영으로 부동산 시장을 주도하지 못하고 시장상황에 따라 대응하는 대증처리방식으로 운용되어 왔다고 할 수 있겠다. 리츠를 활용한 부동산금융의 고도화를 통하여 건설자금의 원활한 흐름과 상장된 리츠종목에 대한 일반투자자의 적정한 투자를 위한 정책이 실현되어야 할 것이다. 본 연구 결과는 시중부동자금의 투자흐름을 적절하게 유도하고 간접금융투자의 활성화를 위한 부동산 관련 정책에 반영하기 위한 정책 기초자료로 활용하고자 한다.

• 한국항만학회지
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• 제13권1호
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• pp.123-132
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• 1999

It is very important to quantitatively assess the movement of sea water and pollutant dispersion before or after constructing shore structures such as breakwater considering marine environment and long-term utilization of those structures. This assesment is possible through the use of simulation models designed to predict water movement and pollutant dispersion in a certain area. In this study the numerical computations were carried out to predict the sea water quality in the Ilgwang Harbor located at the east coast of Pusan. The flow patters were investigated before and after the development of Ilgwang Harbor. The computational models adopting ADI Method (Alternating Direction Implicit Method) were used here and were already verified from the previous studies. As a results of this study the tidal exchange in Ilgwang Harbor after development proved to be worse due to the increased semi-enclosed at the harbor limit. In order to improve the water quality of this area after development a new method was proposed to improve water quality in the semi-enclosed bay by creation and control of tidal residual currents. For this purpose the unsymmetric structures so called bottom roughness were introduced in this study. The simulation was carried out on the basis of the study by Komatsu et. al. and Gug and we made a conclusion that it is possible to generate a new tidal residual current and to increase the tidal exchange by application of bottom roughness arrangement.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.617-621
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• 2007

최근 관심을 받고 있는 지속가능한 하천관리는 과거에 이루어졌던 이수 및 치수중심의 하천관리와 90년대 고조된 자연형 하천관리에서 진일보된 하천관리로써, 전체적인 하천시스템을 고려하여 자연과 인간이 함께 하천을 공유할 수 있도록 하기 위한 것이다. 환경유량은 이를 위한 필수적인 요소이며 하천 시스템에 절대적인 영향을 미치게 된다. 따라서 환경유량 산정시에는 하천의 특정 분야만 고려했던 과거와는 달리, 이 치수, 어류, 식생, 저서생물 등 하천의 전체시스템을 고려하여야 한다. 이를 위해 대상 지역의 전체적인 개황을 조사하고 환경유량 산정시 우선적으로 고려되어야 하는 영향인자를 결정하게 되는데 이때 각 분야의 전문가적 견해가 요구되어진다. 하천에 대한 전체적인 시스템 분석은 매우 다양한 방법으로 수행 될 수 있는데 하천의 유황변화, 하도의 변화, 하천을 중심으로 하는 수생 동식물의 변화, 하천에 설치된 수공구조물의 변화 등 여러 분야에 걸쳐 다양한 자료의 수집과 연계분석이 이루어져야 한다. 하천 생태계를 구성하는 가장 기본적인 환경유량의 파악은 이러한 다양한 분야의 연계 분석을 통해 이루어지며, 하천특성에 맞는 적절한 환경유량은 손상된 하천 생태계를 회복하는 근간이 될 수 있다. 환경유량의 영향인자를 결정하기 위해 현장답사를 통한 조사 분석이 수행되는데, 지금까지는 특정분야의 특정 전문가가 현장답사를 실시하고 특정 전문가의 견해에서 결과분석이 이루어져 왔다. 그러나 최근 선진국에서는 다학제간 전문가 그룹(Multi-disciplinary Expert Team, MET)을 통해 하천의 전체 생태시스템을 고려하여 환경유량을 산정하고 이를 유지할 수 있는 방안을 마련하고 있다. 본 연구에서는 금강유역의 환경유량을 산정하기 위하여 다학제간 전문가그룹의 접근방법을 구축하고 하천, 수질, 식생, 어류, 저서생물 등 각 분야별로 국내외의 전문가가 참여하는 MET를 구성하였다. 환경유량 산정을 위한 금강유역의 현장답사에 있어 MET의 기능과 역할을 분석하였으며 현장답사를 통해 금강유역의 전반적인 하천환경을 조사 분석하고 상호간 의견 교환을 통해 도출한 답사결과를 환경유량 산정에 적용하는데 있어 구성된 MET의 기능 및 역할을 현장답사 내용을 중심으로 분석하였다.

• 대한전기학회논문지:전력기술부문A
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• 제49권4호
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• pp.195-198
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• 2000

This paper illustrates a new method for constructing composite power system effective load duration curve(CMELDC) at load points. The main concept of proposed method is that the CMELDC can be obtain from convolution integral processing of the outage probabilistic distribution function of not supplied power and the load duration curve given at each load point. The effective load duration curve (ELDC) at HLI plays an important part in probabilistic production simulation, reliability evaluation, outage cost assessment and power supply margins assesment for power system planning and operation. And also, the CMELDC at HLII will extend the application areas of outage cost assessment and reliability evaluation at each load point. The CMELDC at load points using the Monte Carlo method and a DC load flow constrained LP have already been developed by authors. The effective load concept at HLII, however, has not been introduced sufficiently in last paper although the concept is important. In this paper, the main concept of the effective load at HLII which is proposed in this study is defined in details as the summation of the original load and the probabilistic loads caused by the forced outage of generators and transmission lines at this load point. The outage capacity probabilistic distribution function at HLII can be obtained by combining the not supplied powers and the probabilities of the not supplied powers at this load point. It si also expected that the proposed CMELDC can be applied usefully to research areas such as reliability evaluation, probabilistic production cost simulation and analytical outage cost assessment, etc. at HLII in future. The characteristics and effectiveness of this methodology are illustrated by case study of IEEE-RTS.

• 한국환경생태학회지
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• 제21권5호
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• pp.442-448
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• 2007

본 연구는 샛강 기슭 훼손부의 물리적, 생태적 안정화를 도모하고자 돌망태틀놓기공법 및 버드나무울짱얽기공법을 시공한 구간에서 생태환경 개선 효과를 검증하기 위하여 수행되었다. 샛강의 생태적 건강도 평가를 위해 규조군집의 종풍부도, 종다양도지수, 수질오염도지수, 오염 민감종의 구성비, Achnanthes minutissima의 구성비, 우점도지수의 6개 메트릭을 활용하였다. 구간 상류의 유입부(ST. 1)와 구간 내 지점(ST. 2) 및 하류 유출부(ST. 3)를 대상으로 6개 메트릭의 변화값을 종합하면 평균 33.9%의 높은 생태환경 개선 효과를 확인할 수 있었다. 이 결과는 본 조사에서 적용된 샛강의 생태공학적 안정화기술이 하천의 생태학적 건강도를 보존하는 데 있어 효과적임을 시사해주는 것으로 평가할 수 있었다.

• 한국농림기상학회지
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• 제4권3호
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• pp.133-140
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• 2002

Site-specific minimum temperature forecasts are critical in a short-term decision making procedure for preventive measures as well as a long-term strategy such as site selection in fruits industry. Nocturnal cold air pools frequently termed in mountainous areas under anticyclonic systems are very dangerous to the flowering buds in spring over Korea, but the spatial resolution to detect them exceeds the current weather forecast scale. To supplement the insufficient spatial resolution of official forecasts, we developed a GIS - assisted frost risk assesment scheme for using in mountainous areas. Daily minimum temperature data were obtained from 6 sites located in a 2.1 by 2.1 km area with complex topography near the southern edge of Sobaek mountains during radiative cooling nights in spring 2001. A digital elevation model with a 10 m spatial resolution was prepared for the entire study area and the cold air inflow was simulated for each grid cell by counting the number of surrounding cells coming into the processing cell. Primitive temperature surfaces were prepared for the corresponding dates by interpolating the Korea Meteorological Administration's automated observational data with the lapse rate correction. The cell temperature values corresponding to the 6 observation sites were extracted from the primitive temperature surface, and subtracted from the observed values to obtain the estimation error. The errors were regressed to the flow accumulation at the corresponding cells, delineating a statistically significant relationship. When we applied this relationship to the primitive temperature surfaces of frost nights during April 2002, there was a good agreement with the observations, showing a feasibility of site-specific frost warning system development in mountainous areas.