• 대한기계학회논문집B
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• 제33권8호
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• pp.604-612
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• 2009

Water management has been recognized as a crucial factor for achieving better performance and stability in polymer electrolyte membrane fuel cells (PEMFCs). Proper water management should provide favorable water conditions, including the local humidity, membrane water content, and liquid water saturation in PEMFCs, thereby leading to more uniform electrochemical reaction and current generation. In this study, computational fluid dynamics (CFD) simulation was conducted to investigate the effects of the cathode relative humidity (RH) on the performance of a 3 by $3\;cm^2$ PEMFC with serpentine flow fields. The CFD results showed that the best performance of the PEMFC was obtained for the cathode RH of 80%, but the performance variation was small for the cathode RH range of $60{\sim}100%$. However, the loss of the PEMFC performance was significant when the cathode RH was reduced below 40%. The reason for such performance variation was investigated through the detailed inspection of ohmic loss, activation and concentration overpotential, and water and current distributions.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1586-1590
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• 2006

In order to calculate the actual erosion according to the universal soil loss equation (USLE) and to estimate the impact of land use on soil erosion in Saemangeum, it is important to know the C-factor. Based on the USLE crop-growth stages, the cover-management C-factors were calculated for the main crop and crop rotation systems by National Institute of Agricultural Science and Technology. Combining this result with statistical data about crop cultivation area and crop rotation systems, C-factors of each administrative district in Saemangeum watershed were calculated. The range of C-factors were between 0.28 and 0.35. High C-factor value was obtained with Gimje (C = 0.35) and small C-factor values were found in Wanju (C = 0.28) and Jeongeup (C = 0.29). With this result, calculated annual soil loss was 2,804,483 ton per year. Because of the lack of sufficient statistical data about crop rotation systems, further studies are required on collecting field survey data.

• 대한환경공학회지
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• 제30권12호
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• pp.1209-1217
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• 2008

본 연구에서는 고탁수 문제가 자주 발생하는 임하 안동 유역을 대상으로 효율적인 탁수 관리를 위한 유출현황 및 토사 유실평가를 목적으로 SWAT 모델을 구축하였다. 홍수기에 측정된 유량과 부유사 농도를 이용하여 모형의 검 보정을 실시하였다. 검 보정된 SWAT 모형을 이용하여 소유역별 연간 부유사 부하량에 대한 공간 분석결과, 전체 유역 대상으로 2005년에 최저 0.7$\sim$5.9 tons/ha에서 태풍 매미에 의해 심한 영향을 받은 2003년에 최고 3.0$\sim$34.0 tons/ha의 부하량을 보였다. 향후 유역전체의 효율적인 유사량 추정 및 저감대책마련을 위해서는 장기간에 걸쳐 보다 정확하고 광범위한 모니터링과 이를 활용한 모델의 정도 향상이 수반되어야 할 것이다.

• 대한공간정보학회지
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• 제16권1호
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• pp.75-81
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• 2008

본 연구의 목적은 공단지역의 환경개선과 폐수위탁관리체계의 투명성을 확보하기 위해 GIS를 활용한 공장폐수 위탁관리 시스템의 구축방안에 대하여 연구하는데 있다. 공장폐수 위탁 및 수탁처리 전산관리 시스템은 공장폐수 위탁 및 수탁관련 정보 입력과 위탁확인서 출력을 위한 위탁 및 수탁 관리 시스템, 관리자가 기간별, 업종별, 폐수종류별, 업체별 위탁량을 통계분석 할 수 있는 통계분석 시스템, 위탁 업체 및 수탁업체의 공간정보와 공장폐수 위탁량 및 수탁량 분포도를 시민들에게 제공하는 WebGIS 시스템으로 구성하였다. 구축된 공장폐수 위탁관리시스템은 폐수의 발생 시점에서부터 완전 처리까지의 전 과정에서의 정확하고 확실하게 파악할 수 있을 것으로 판단된다. 업무의 전산화로 업무처리 시 발생되는 시간적, 경제적 손실을 저감할 수 있을 것으로 판단된다. 또한 공장폐수에 대한 정확한 발생량을 관리함으로써 인천지역에서 발생되는 수질오염사고를 사전에 예방하고 오염사고 발생 시 신속한 대처방안을 도출 할 수 있을 것으로 판단된다. WebGIS를 이용`한 공장폐수의 위탁량 및 수탁량 분포를 관리함으로써 시민들의 환경오염에 대한 생각을 고취시키고 지속적인 관리가 가능 할 것으로 판단된다.

• 한국구조물진단유지관리공학회 논문집
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• 제23권3호
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• pp.51-55
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• 2019

저수지의 붕괴 발생 시 인명 및 재산피해의 예방 및 저감을 위하여 붕괴예보 시스템의 필요성은 대두되고 있는 상황이다. 붕괴 예보시스템의 효율적 활용을 위해서는 실시간 계측한 이상거동 및 붕괴징후에 따라 대응할 수 있는 관리기준은 가장 중요한 요소이다. 기 연구된 수위 관리기준의 검증을 위하여 저수량에 따라 10여개의 저수지를 선정하고 수위변화 자료를 분석하여 적정성을 검토하였다. 1년 동안의 수위계측 자료에서 가장 급격한 변화구간을 선정하여 가중치 및 추세선을 적용하여 분석한 결과 3분위로 수립된 관리기준값은 7%이내의 표준편차를 보여주었다. 이는 수립된 관리기준값은 적정하다고 판단된다.

• 한국농공학회논문집
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• 제58권6호
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• pp.23-30
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• 2016

Soil loss is an accompanying phenomenon of hydrologic cycle in watersheds. Both rainfall drops and runoff lead to soil particle detachment, the detached soil particles are transported into streams by runoff. Here, a sediment-laden water problem can be issued if soil particles are severely detached and transported into stream in the watershed. There is a need to estimate or simulate soil erosion in watersheds so that an adequate plan to manage soil erosion can be established. Universal Soil Loss Equation (USLE), therefore, was developed and modified by many researchers for their watersheds, moreover the simple model, USLE, has been employed in many hydrologic models for soil erosion simulations. While the USLE has been applied even in South-Korea, the model is often regarded as being limited in applications for the watersheds in South-Korea since monthly conditions against soil erosion on soil surface are not capable to represent. Thus, the monthly USLE factors against soil erosion, soil erodibility and crop management factors, were established for four major watersheds, which are Daecheong-dam, Soyang-dam, Juam-dam, and Imha-dam watersheds. The monthly factors were established by recent fifteen years from 2000 to 2015. Five crops were selected for the monthly crop management factor establishments. Soil loss estimations with the modified factors were compared to conventional approach that is average annual estimations. The differences ranged from 9.3 % (Juam-dam watershed) to 28.1 % (Daecheong-dam watershed), since the conventional approaches were not capable of seasonally and regionally different conditions.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.316-316
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• 2017

The objective of this study is to estimate quantitatively soil salinity and soil loss at upland soils in agriculture land region in Saemangeum reclaimed land on the south Korea coasts. Soil loss and soil salinity are the most critical problem at reclaimed tidal saline soil in Korea. The several thematic maps of research area such as land cover map, topographic and soil maps, together with tabular precipitation data used for soil erosion and soil salinity calculation. Meteorological data were measured directly as air temperature, wind speed, solar radiation, and precipitation. The experiment was conducted 2% sloped lysimeter ($5.0m{\times}20.0m$) with 14 treatments and it were separated by low salinity division (LSD) and high salinity division (HSD) install. The cation content in ground water increased during time course, but in the case of land surface water the content was variable, and $K^+$ was lower than that of $Na^+$ and $Mg^{2+}$. At the LSD under rainproof condition, the salinity was directly proportional to soil water content, but at the HSD the tendency was no reversed. In condition of rainproof, the amount of soil salinity was higher at the HSD than at the LSD. Positive correlation was obtained between the soil water content and available phosphorous content at the rainfall division, but there was no significance at the surface soil of the rainproof division. Sodium adsorption ratio and anion contents in soil were repressed in the order of vinyl-mulching > non-mulching > bare field. According to the result of analyzing soil loss, soil loss occurred in a vinyl-mulching, a non-mulching and a bare field in size order, and also approximately 11.2 ton/ha soil loss happened on the reclaimed land area. The average soil loss amount by the unit area takes place in a non-mulching and bare field a lot. Our results indicate that soluble salt control and soil erosion are critical at reclaimed tidal saline soil and the results can provide some useful information for deciding management plans to reduce soil loss and salt damage for stable crop production and diverse utilization or cultivation could be one of the management options to alleviate salt damage at reclaimed tidal saline soil in Korea.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.126-126
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• 2022

Climate change has continued to impact meteorological factors like rainfall in many countries including Nigeria. Thus, altering the rainfall patterns which subsequently affect the crop yield. Maize is an important cereal grown in northern Nigeria, along with sorghum, rice, and millet. Due to the challenge of water scarcity during the dry season, it has become critical to design appropriate strategies for planning, developing, and management of the limited available water resources to increase the maize yield. This study, therefore, determines the quantity of water required to produce maize from planting to harvesting and the impact of drought on maize during different growth stages in the region. Rainfall data from six rain gauge stations for a period of 36 years (1979-2014) was considered for the analysis. The standardized precipitation and evapotranspiration index (SPEI) is used to evaluate the severity of drought. Using the CROPWAT model, the evapotranspiration was calculated using the Penman-Monteith method, while the crop water requirements (CWRs) and irrigation scheduling for the maize crop was also determined. Irrigation was considered for 100% of critical soil moisture loss. At different phases of maize crop growth, the model predicted daily and monthly crop water requirements. The crop water requirement was found to be 319.0 mm and the irrigation requirement was 15.5 mm. The CROPWAT 8.0 model adequately estimated the yield reduction caused by water stress and climatic impacts, which makes this model appropriate for determining the crop water requirements, irrigation planning, and management.

• Nuclear Engineering and Technology
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• 제50권8호
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• pp.1412-1420
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• 2018

An experiment was performed using the large-scale test facility (LSTF), which simulated a 1% vessel upper head small-break loss-of-coolant accident with an accident management (AM) measure under an assumption of total-failure of high-pressure injection (HPI) system in a pressurized water reactor (PWR). In the LSTF test, liquid level in the upper head affected break flow rate. Coolant was manually injected from the HPI system into cold legs as the AM measure when the maximum core exit temperature reached 623 K. The cladding surface temperature largely increased due to late and slow response of the core exit thermocouples. The AM measure was confirmed to be effective for the core cooling. The RELAP5/MOD3.3 code indicated insufficient prediction of primary coolant distribution. The author conducted uncertainty analysis for the LSTF test employing created phenomena identification and ranking table for each component. The author clarified that peak cladding temperature was largely dependent on the combination of multiple uncertain parameters within the defined uncertain ranges.

• 상하수도학회지
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• 제24권5호
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• pp.495-508
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• 2010

The aim of this study is to develop a quantified water loss Index to evaluate and manage leakage scientifically for the reduction of non-revenue water in water distribution systems. For the purpose, unavoidable background leakage suggested from UK water industry and IWA, and allowable water leakage in accord with the concept of allowable water loss are proposed by analyzing the inflow into two study water districts and the short-term water use of each customer in the districts. The study distribution areas are selected among the metered districts with good maintenance of leakage after improvement activities in Nonsan, medium sized city in Korea. Estimation models of allowable leakage are developed by metering and analyzing the minimum night flow at residential and commercial areas in the city. In the results of the investigation, it is estimated that background night flow in residential area was larger than that of commercial area where the types of business shows small water use characteristics. Meanwhile, night flow and background water loss on internal plumbing systems show great differences for each district which is influenced much by the water use characteristics and facilities scale. Based on metering water use data in various districts, leakage management criteria can be established under the consideration of domestic conditions in Korea by analyzing separated real water use and background leakage and it is possible to apply into presentation of optimal leakage level and reasonable time for working activities for leakage reduction.