• 설비공학논문집
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• 제23권8호
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• pp.580-586
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• 2011

In this study, 3 cooling systems of apartment which are air-cooled air conditioner with indoor unit, water-cooled air conditioner with indoor unit and small capacity absorption chiller-heater with FCU have been evaluated by Multi-Criteria Decision Making Analysis. Weights of 7 selected factors which are economics, space, billing, constructability, human comfort, visibility and reliability are determined by expert group of 30 system designers and 30 construction engineers. Final weights were derived for 101 and 166 $m^2$ apartments. Analysis shows that small capacity absorption chiller-heater with FCU is the most favorable system for apartment cooling system.

• 전기학회논문지
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• 제64권12호
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• pp.1666-1672
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• 2015

Small islands are quite adequate places where microgrid system with renewable sources can replace diesel engines as operation costs of diesel engine in most small islands are very high. To get the large amount of renewable energy, the microgrid system has very large capacity of renewable sources. The system with large capacity of renewable sources can meet the case when supplied energy is greater than the load and the fluctuation of source output is very large. The battery energy storage system can be a solution to stabilize the system with large capacity of renewable sources. In this case, BESS can be utilized as a master source for the synchronous operation of all sources including diesel engine, wind turbine and PV. The diesel generators can be used as a backup in case the BESS SOC goes below a certain level. In this paper, we suggest a novel unit commitment of diesel generators and operation schedule of pump for water supply service with the information of wind forecast, PV forecast, and load forecast. The proposed methods has been implemented and tested at the test bed in Gasa-Island.

• 한국작물학회지
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• 제44권4호
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• pp.330-338
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• 1999

Extensive research has been conducted on effects of drought stress on growth and development of soybean but information is rather restricted on the limited-irrigation system by way of precaution against a long-term drought condition in the future. The experiment for limited-irrigation was conducted in transparent vinyl shelter at Asian Vegetable Research and Development Center (AVRDC), Taiwan in 1997. Two soybean varieties, Hwangkeum and AGS292, improved in Korea and AVRDC, respectively were used for this experiment. The relationships between normalized transpiration rate (NTR) and fraction of transpirable soil water (FTSW) in both varieties were similar that the NTR was unchanged until FTSW dropped to about 0.5 or 0.6. At FTSW less than those values, NTR declined rapidly. Days required to harvest in both varieties were significantly prolonged at IR6 treatment compared to any other treatments. Daily mean transpiration rate was significantly higher at IR5 treatment, as averaged over varieties. Similarly, water use efficiency was also high at 1R5 treatment. In both varieties, seed yield was the greatest at the IR5 treatment, as compared to any other limited-irrigation treatments, due to the increased seed number and high transpirational water use efficiency. The indices of input water and seed yield for the different limited-irrigation treatments against control indicated that Hwangkeum produced 59.6% or 60.7% of seed yield using 36.1% or 44.9% of input water, as compared to control, by irrigation at only R5 or R6 stages, respectively. The AGS292 produced 56.1% of seed yield with 35.4% of input water of control, when irrigated at R5 stage. The results of this study have elucidated that the limited irrigation at R5 stage in soybean can be minimized yield loss with such small quantity of water under the environment of long-term drought stress and the expected shortage of agricultural water in the future.

• 설비공학논문집
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• 제26권6호
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• pp.257-262
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• 2014

This paper describes an experimental study for heating performance that can be used in R-134a automobile heat pump systems. The heat pump system is widely studied for heating system in zero-emission vehicles to attain both the small power consumption and the effective heating of the cabin. This paper presents the experimental results of the influence on heating capacity and coefficient of performance of heat pump system. Tests were performed with different sizes of internal and external heat exchangers, and refrigerant flow rate was also considered in two-way flow devices. In addition, the heat, air, and water sources with the heat pump system were examined. The experimental results with the heat pump system were used to analyze the impact on performances. The best combination of performance was A-inside heat exchanger, B-outside heat exchanger, and B-flow device, respectively. In addition, a water heat-source was found to give roughly 40% of better performance than an air heat-source heat pump system.

• 한국태양에너지학회 논문집
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• 제39권6호
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• pp.41-54
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• 2019

The purpose of this study is to analyze the performance of solar thermal system according to regional weather conditions and feedwater temperature. The performance analysis of the system was carried out for the annual and winter periods in terms of solar fraction, collector efficiency and it's optimal degree. The system is simulated using TRNSYS program for 6 cities, Seoul, Incheon, Gangneung, Mokpo, Gwangju, and Ulsan. Simulation results prove that the solar fraction of the system varies greatly from region to region, depending on weather conditions and feedwater temperatures. Monthly average solar fraction for winter season from November to February, a time when heat energy is most required, indicated that the highest is 73.6% in Gangnueng and the lowest is 56.9% in Seoul. This is about 30% relative difference between the two cities. On the other hand, the collector efficiency of the system for all six cities was analyzed in the range between 40% and 42%, indicating small difference compare to the solar fraction. The annual average solar fraction is rated the highest at 40 collector degree, while monthly average solar fraction during winter season is rated at 60 degree.

• 대한환경공학회지
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• 제34권6호
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• pp.373-381
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• 2012

대전의 도시 소하천, 관평천 유역을 연구대상지역으로 강우시의 유량 및 수질 변화 특성을 파악하기 위한 원격 제어실시간 자동 모니터링 시스템을 설치하여 자료를 확보하고 이 시스템을 이용하여 확보된 강우시 연속측정 자료를 이용하여 도시유역 모델인 SWMM (Storm Water Management Model) 모델을 보정하는 데 사용하였다. 실시간 자동 모니터링 시스템은 강우량계, 초음파 수위계, 자동수질측정장치, 자동취수장치, 데이터 로거 및 전송장치 등으로 구성되었으며 원격으로 제어할 수 있도록 설계되었다. 강우시 유량은 초음파 수위계와 사각 위어 공식을 이용하여 지속적으로 측정이 가능하도록 설계되었으며 정확도는 수동측정을 병행하여 확인하였다. 수질센서로 측정할 수 없는 항목은 자동채수기에 의해 일정시간 간격으로 시료를 채취한 후 실험실로 이송하여 분석하여 자료를 확보하였다. 위에서 실측된 유량 및 수질 연속 자료를 이용하여 연구대상지역에 대해 SWMM 모델을 구축하였다. SWMM 모델의 보정과 검증 결과 유량은 매우 양호한 수준으로 예측하고 있으나 BOD, COD, SS, TN, TP 등의 예측은 강우 특성에 따라 차이가 있는 것으로 나타났다. 본 연구는 SWMM에 나타난 바와 같은 특정 유역에 고정된 형태의 오염물질 축적과 유출현상을 나타내는 경험식이 강우 및 선행강우 특성을 반영하여 수정될 필요가 있다는 것을 시사하고 있다. 본 연구에서 제안된 빗물 자동모니터링 및 모델링 시스템은 향후 강우에 따른 하천 수질관리를 위한 유역단위의 빗물 수량 수질 관리시설의 설계 및 운영에 중요한 자료로 활용될 수 있을 것으로 기대된다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권7호
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• pp.1044-1050
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• 2008

Most of developed countries, the consumption of fossil fuels has been serious problems that cause serious environment pollution like acid rain, global warming. Also, we have faced that limitation fossil fuels will be exhausted. Currently, small hydropower attracts attention because of its small, clean, renewable, and abundant energy resources to develop. By using a small hydropower generator of which main concept is based on using the different water pressure levels in pipe lines, energy which was initially wasted by use of a reducing valve at the end of the pipeline, is collected by turbine in the hydropower generator. A propeller shaped hydroturbine has been used in order to use this renewable pressure energy. In this study, in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the flow coefficient are examined in detail. Tubular-turbine among small hydraulic power generation can be used at low-head. The purpose of this study is to research turbine's efficiency due to runner vane angle using CFD analysis.

• 한국수소및신에너지학회논문집
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• 제13권4호
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• pp.330-338
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• 2002

A long-term energy system in the future is expected to be based on the ideal circulation system between water and hydrogen in the sense that the hydrogen prepared from water eventually returns to water again after its use. Currently, with respect to the hydrogen energy system, it is predicted that the turning-point at which the production cost of hydrogen will become to be lower than that of fossil fuels would be after 2010. However, fuel cell technology would be able to be practically used for the applications to the transportation vehicles and small-scale power sources from 2004, and therefore, an efficient construction of the infrastructure covering hydrogen production and supply systems would be required with short-/mid-term technologies for the $CO_2$ reduction associated with fossil fuel utilization. In this paper, the hydrogen quantity available in domestic market has been estimated focusing on the hydrogen by-produced from domestic industries, and also the infrastructure for hydrogen-driven vehicles like fuel cell cars has been reviewed.

• 한국물환경학회지
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• 제25권5호
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• pp.750-757
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• 2009

The ammonium ion exchange characteristics of natural zeolite were investigated to remove ${NH_4}^+-N$. The effect of water temperature, particle size and competitive cation on the exchange capacity was examined. Ammonium ion exchange capacity tended to decrease when the temperature increased from $25^{\circ}C$ to $40^{\circ}C$. Exchange capacity was increased according to the particle size of natural zeolite comes to be small. Batch isotherm experiments were conducted for measuring ammonium ion exchange capacity. The ion exchange capacity was well described either by the Langmuir isotherm model or by the Freundlich isotherm model. The ammonium ion exchange capacity ($q_m$) of zeolite carrier can be calculated $11.744mg-{NH_4}^+/g$-carrier. The ion exchange capacity of manufactured zeolite carrier was showed a similar tendency as ion exchange capacity of powder-sized natural zeolite. Therefore, zeolite carrier can be used for increasing of nitrogen removal efficiency in the wastewater treatment plants.

• 한국수자원학회논문집
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• 제52권7호
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• pp.505-514
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• 2019

우리나라는 효율적인 수자원 관리를 위해 노력하고 있으며, 향후 지역의 문제와 물이용 현황, 특성, 지형, 기후 등을 고려한 유역을 세분화한 후 계획을 수립하는 것이 필요하다. 이에 본 연구에서는 한강 권역을 대상으로 MODSIM 모형을 활용하여 중권역과 표준유역단위 물 수급 체계를 구축하고 분석 결과를 비교하였다. 분석 결과, 49개년(1967-2015)간 발생하는 평균 물 부족량은 중권역 단위 129.98 백만$m^3$, 표준유역단위 2,229.24 백만 $m^3$으로 약 21 억$m^3$ 가량의 차이가 나타났으나 물 부족이 발생하는 시기와 물 부족 발생 공간 분포에 대한 경향은 매우 유사하게 나타났다. 이러한 원인은 중권역 단위 분석의 경우, 모든 수량을 이용할 수 있다는 가정으로 대표 자연유량 값에 대한 생활, 공업, 농업용수 수요량에 대한 물 부족량이 산정된다. 그러나, 표준유역단위 분석에서는 분할된 공급량과 수요량의 차이로 인해 본류와 이격되어 있는 지류는 가용할 수 있는 수자원량이 상대적으로 작아져 물 부족이 크게 발생하는 것으로 나타났고, 본류는 오히려 회귀수량의 파급효과로 인해 물 부족이 나타나지 않는 것으로 분석되었다. 향후, 분석 단위의 세분화 뿐만 아니라 실제 물이용체계가 모형 내 고려된다면 지역적 특성이 반영된 물수급 평가가 가능할 것으로 판단된다.