• 한국지하수토양환경학회지:지하수토양환경
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• 제20권3호
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• pp.41-50
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• 2015

Hydrogeologic environment of the Mega City such as Seoul, suffers from rapid changes caused by urbanization, construction of underground subway or buildings, and contaminant loading by diverse anthropogenic activities. Understanding the present condition of groundwater environment and water budget is necessary to prevent natural and manmade disasters and to prepare for sustainable water resource management of urban environment. In this study, regional groundwater flow and water budget status of Seoul was analyzed using numerical simulation. Modeling result indicated that groundwater level distribution of Seoul generally followed the topography, but the significant decreases in groundwater level were observed around the subway network. Steady-state water balance analysis showed groundwater recharge by rainfall and leakage from the water supply network was about 550,495 m³/day. Surface water inflow and baseflow rate via Han River and major streams accounted for 799,689 m³/day and 1,103,906 m³/day, respectively. Groundwater usage was 60,945 m³/day, and the total groundwater leakage along the subway lines amounted to 114,746 m³/day. Modeling results revealed that the subway could decrease net groundwater baseflow by 40%. Our study result demonstrated that the subway system can have a significant influence on the groundwater environment of Seoul.

• 신재생에너지
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• 제19권4호
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• pp.27-34
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• 2023

In this study, microalgal oil was extracted from Nannochloropsis oceanica cultured in an open raceway pond and converted into biodiesel using a solid acid catalyst. Microalgal oil was extracted from two types of microalgae with and without nitrogen starvation using the KOH-solvent extraction method and the fatty acid content and oil extraction yield from each microalgae were compared. The fatty acid content of N. oceanica was 184.8 mg/g cell under basic conditions, and the oil content increased to 340.1 mg/g under nitrogen starvation conditions. Oil extraction yields were 90.8 and 95.4% in the first extraction, and increased to 97.5 and 98.8% after the second extraction. Microalgal oil extracted by KOH-solvent extraction was yellow in color and had reduced viscosity due to chlorophyll removal. In biodiesel conversion using the catalyst SO₄^2-/HZSM-5, solvent-extracted oil showed a FAME content of 4.8%, while KOH-solvent-extracted oil showed a FAME content of 90.4%. Solid acid catalyst application has been made easier by removal of chlorophyll from microalgal oil. The FAME content increased to 96.6% upon distillation, and the oxidation stability increased to 11.07 h with addition of rapeseed biodiesel and 1,000 ppm butylated hydroxyanisole.

• 한국환경과학회지
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• 제10권4호
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• pp.253-258
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• 2001

A macroeconomic minimodel was simulatedto suggest the public for sustainable us of Nakdong River Basin. The minimodel for the simulation shows the interrelationships between natural environment and economic activity. Topsoil, water, economic assets, and money stock are plotted for 300 years, beginning with 1996 in each simulation. The computer simulation runs suggest that the Nakdong River Basin system in the near future may strongly be influenced by the favorable availability of outside resources, while the economic assets and money stock may be declined by indigenous environmental stock depletion. The simulation run made under the constant decrease in systems purchased inputs with investment ratio of developed country and for sustainable use. The results of simulation shows the recover of natural environment and decrease of economic activity under these condition. Therefore, the economic structure of Nakdong River Basin should be transformed from the present industrial structure to the social-economic structure based on an ecological-recycling concept which depend on renewable resources rather than industrial structural which depend on outside resources.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.674-677
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• 2005

The characteristics of geothermal resources in Korea was roughly estimated using hot springs, 580 geothermal gradients and 338 heat flow data. In the aspect of hot springs with geologic structure, location of hot springs coincide with fault zone, especially younger age of Cretaceous to Tertiary. In the aspect of geothermal gradients, Pohang area shows the highest geothermal gradient anomaly, which is covered with unconsol idated rock of low thermal conductivity preserving the residual heat from igneous activity or radioactivity elements decay. In the aspect of heat flow density, high anomaly can be found along the zone connecting Uljin-Pohang-Busan on the southeastern part of Korean peninsula at which big fault zone as Yangsan fault is well developed.

• Journal of Advanced Marine Engineering and Technology
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• 제37권7호
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• pp.799-806
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• 2013

As a first step to develop the hybrid power generation system, on this study, the time-variable resources of wind and solar radiation of Yeongdo, Busan, Korea had been measured during June and July 2013. And the quantity of generated wind power and solar photovoltaic had also been measured during the same period. It is found out that the wind mainly flew from southwest at the average speed of 2 m/s during 2 months. And it is clear that, because of the low wind velocity, the wind quality to generate the power seems not enough at this area. Meanwhile solar radiation was measured every daytime (6:00~19:00) and the peak solar radiation occurred around 12:00~14:00. And it is clear that the time-based variations of quantity of generated power were proportional to the variations of these resources, respectively. As a proposal, these 2 natural energies can be combined as resources of a hybrid system, because these 2 patterns are not overlapped so much on time base.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.445-448
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• 2007

Three boreholes (BE-1, BE-2 and BE-3) were drilled for geothermal resources development in Haengbok (Sejong) city. Monitoring of temperature, electric conductivity (EC) and piezometric head were carried out at each borehole. Temperatures were measured at 10 m depth, it ranges from 13.22$^{\cdot}C$ to 14.4$^{\cdot}C$. EC of BE-1 and BE-3 declined with time because groundwater flowed in boreholes. Barometric efficiency was analysed by piezometric head of groundwater and atmospheric pressure, it ranges from 44.8% to 71.5%. These parameters can be used for a geothermal modeling.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.429-431
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• 2005

According to the second plan of the Korean Government about technology development, utilization and popularization of new renewable energy, the continuous growth of distributed resources are expected. Various studies about impact of distributed resource on distribution system have been already accomplished. Rut there is a few paper about recloser and sectionalizer coordination and protection scheme in distribution system interconnected a number of distributed resources. In this paper, it is dealt with that recloser and sectionalizer coordination at the cases concerned with fault position. The problems of these cases are investigated through simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.319-321
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• 2005

According to the second plan of the Korean Government about technology development, utilization and population of new renewable energy, the continuous growth of distributed resources are expected. But if those are interconnected with distribution system, there are many problem. In this paper, it is searched the biggest capacity of distributed resources under limit of actuating current o# protection devices and scheme.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.217-220
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• 2011

본 연구에서는 경상북도 북부지역의 5개의 소수력발전 후보지점을 설정하였으며, 5개 후보지점에 대하여 설치가능한 소수력 발전시설은 지형학적 측면을 비롯하여 다양한 타당성 검토를 통하여 댐식 소수력 발전시설이 타당한 것으로 분석되었다. 5개 후보지점에서 설정된 유량지속곡선을 이용하여 발전용량을 산정하고 수차를 선정하였다. 따라서 산정된 발전 용량을 편익비용 분석법과 내부수익률 분석법을 이용하여 경제성분석을 실시하였다. 본 연구에서는 3개의 소수력발전 후보지점(경상북도 봉화군 명호면, 경상북도 영주시 문수면 권선리, 경상북도 예천군 형호리)이 B/C 비율이 1이상으로 경제성이 있는 것으로 분석되었으나, 설비용량 500kW 이상인 최적 개발후보지는 경상북도 영양군 입암면 후보지점인 것으로 나타났다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.520-522
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• 2006

According to the second scheme of the Korean Government about technology development, utilization and popularization of new renewable energy, the continuous growth of distributed resources are expected. But there is a few paper about recloser and sectionalizer coordination and protection scheme in distribution system interconnected a number of distributed resources. In this paper, it is dealt with that recloser and sectionalizer coordination at the cases concerned with position among protection devices. Adding distributed resource, the problems of each case are investigated through simulation.