• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.567-571
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• 2008

PEM Fuel Cell operation mode can be classified into dead-end mode or open mode by whether the outlet port is blocked or not. Generally, dead-end type fuel cell has some merits on the pressure drop and system efficiency because it can generate more power than the open type fuel cell due to high operating pressure condition. However, the periodic purging process should be done for removing water which is formed as product of a reaction in the gas diffusion layer. In this study, cathode side dead-end type operation has been conducted. Moreover, pulsating flow generator at the outlet of cathode side has been suggested for increasing the period to purge the formed water because the pulsating flow can make formed water scattered uniformly over the whole channel. As a result, the purging period with pulsation increased by 1.5-2 times longer than that without pulsating.

• 한국수소및신에너지학회논문집
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• 제33권1호
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• pp.95-104
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• 2022

Micro hydropower is a readily available renewable energy source that can be harvested utilizing hydrokinetic turbines from shallow water canals, irrigation and industrial channel flows, and run-off river stream flows. These sources generally have low head (<1 m) and low velocity which makes it difficult to harvest energy using conventional turbines. A horizontal-axis screw turbine was designed and numerically tested to extract power from such low-head water sources. The 3-bladed screw-type turbine is placed horizontally perpendicular to the incoming flow, partially submerged in a narrow water channel at no-head condition. The turbine hydraulic performances were studied using Computational Fluid Dynamics models. Turbine design parameters such as the shroud diameter, the hub-to-shroud ratios, and the submerged depths were obtained through a steady-state parametric study. The resulting turbine configuration was then tested by solving the unsteady multiphase free-surface equations mimicking an actual open channel flow scenario. The turbine performance in the shallow channel were studied for various Tip Speed Ratios (TSR). The highest power coefficient was obtained at a TSR of 0.3. The turbine was then scaled-up to test its performance on a real site condition at a head of 0.3 m. The highest power coefficient obtained was 0.18. Several losses were observed in the 3-bladed turbine design and to minimize losses, the number of blades were increased to five. The power coefficient improved by 236% for a 5-bladed screw turbine. The fluid losses were minimized by increasing the blade surface area submerged in water. The turbine performance was increased by 74.4% after dipping the turbine to a bottom wall clearance of 30 cm from 60 cm. The final output of the novel horizontal-axis screw turbine showed a 2.83 kW power output at a power coefficient of 0.63. The turbine is expected to produce 18,744 kWh/year of electricity. The design feasibility test of the turbine showed promising results to harvest energy from small hydropower sources.

• 한국물환경학회지
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• 제27권4호
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• pp.445-460
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• 2011

The objective of this study was to construct and assess the applicability of the EFDC model for Saemangeum Reservoir as a 3D hydrodynamic and water quality modeling tool that is necessary for the effective management of water quality and establishment of conservation measures. The model grids for both reservoir system only and reservoir-ocean system were created using the most recent survey data to compare the effects of different downstream boundary conditions. The model was applied for the simulations of temperature, salinity, water quality variables including chemical oxygen demand (COD), chlorophyll-a (Chl-a), phosphorus and nitrogen species and algal biomass, and validated using the field data obtained in 2008. Although the model reasonably represented the temporal and spatial variations of the state variables in the reservoir with limited boundary forcing data, the salinity level was underestimated in the middle and upstream of the reservoir when the flow data were used at downstream boundaries; Sinsi and Garyuk Gates. In turn, the error caused to increase the bias of water quality simulations, and inaccurate simulation of density flow regime of river inflow during flood events. It is likely because of the loss of momentum of sea water intrusion at downstream boundaries. In contrast to flow boundary conditions, the mixing between sea water and freshwater was well reproduced when open water boundary condition was applied. Thus, it is required to improve the downstream boundary conditions that can accommodate the real operations of the sluice gates.

• 공업화학
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• 제28권1호
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• pp.118-124
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• 2017

공랭식 고분자전해질 연료전지는 개방된 cathode구조로 인하여 시스템의 단순화와 부품 수 저감의 장점이 있다. 공랭식 연료전지는 최근에 많이 연구되고 있지만, 성능이 외부 환경에 영향을 받으며, 공기의 상대습도가 낮은 경우 전해질막의 건조로 인한 성능 감소가 발생할 수 있다. 본 연구에서는 공랭식 연료전지의 성능에 영향을 주는 요인인 cathode 측 공기 유량과 anode 측 purge interval영향에 대해 분석하였으며, 스택을 운전하지 않는 상태로 장기간 보관하는 것이 성능에 미치는 영향에 대하여 실험을 수행하였다. 연료전지 외부에 설치한 fan의 전압을 조절하면 cathode 측 공기의 공급유량을 변화시킬 수 있고 스택의 온도도 제어할 수 있으므로, fan전압은 공랭식 연료전지의 성능에 영향을 주는 중요한 인자이다. 연료전지 시스템을 단순화하고 수소의 사용률을 높이기 위하여 anode 측은 dead ended anode (DEA) 기법을 사용하였다. 주기적인 purge를 실행하여 생성된 물과 가스를 배출하였으며, purge 주기를 변경하면서 스택의 성능에 미치는 영향에 대하여 실험을 수행하였다. 스택의 보관기간이 길어질수록 membrane dehydration으로 인해 성능이 감소하는 것을 실험을 통해 파악하였고, 단시간에 성능을 회복할 수 있는 기법을 제시하였다.

• 한국산학기술학회논문지
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• 제11권9호
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• pp.3610-3614
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• 2010

새만금 수역에서 2006년 5월부터 2007년 11월까지 8회의 조사를 통해 표영환경의 미소조류군집의 분류군 조성과 다양성지수 등을 연구하였다. 조사수역 미소조류군집의 출현종은 총 191종으로 규조류(Diatom) 94종, 녹조류(Chlorophyte) 31종, 와편모조류(Dinoflagellate) 24종, 남조류(Cyanophyte) 24종, 유글레나조류(Euglenophyte) 11종, 규질 편모류(Silicoflagellate) 3종, 크립토조류(Cryptophyte) 1종, 기타 미동정 미소편모조류 3종 등으로 구성되었다. 연구기간 동안 연구수역 미소조류군집의 다양성 지수는 시공간적으로 변화가 지속되어 일정한 변화의 규칙성을 찾기 어렵다. 이는 공사의 진행과 방조제 수문개폐에 따른 수질환경의 급변 등 인위적 요인이 부유성 미소조류에 스트레스로 작용한 것으로 보인다.

• 한국물환경학회지
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• 제31권1호
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• pp.1-11
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• 2015

In this study, the attraction efficiency of the by-pass fishway installed at Dalseong Weir in Nakdong River was assessed according to operation of the attraction waterway by using River2D which is a two-dimensional physical habitat simulation model. The model was calibrated and validated through the measured water elevation. The attraction efficiency of the fishway was evaluated at the low flow condition because the target fish, Zacco platypus (Z. platypus), have moved frequently up and downstream at the spawning season from April to June. From simulation results, it can be deduced that the attraction efficiency at situation of open attraction waterway is superior to that of close attraction waterway. Also it is shown that velocity field at inner region of the fishway is suitable for migration of the fish.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2009년도 춘계 학술논문 발표대회 산업계
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• pp.99-102
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• 2009

This paper is to present the performance data for pressure setting method using some tile bonds for application on the Ondol-Heating floor system. For this purpose, powder and liquid tile bonds(Organic.Inorganic mixed tile bonds) were compared with the conventional tile cement for pressure setting method in the sight of the adhesive stability of porcelain tile. It tested for tiles after 14, 28days under standard condition and severe conditions. The severe conditions were water immersion and heat ageing($70^{\circ}C$). Another experimental factors concerned tile bond properties such as mixing ratio(in case of using liquid admixture), open time, which are supposed to affect the tensile strength of tile, were studied and discussed through the experiments.

• Nuclear Engineering and Technology
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• 제31권1호
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• pp.68-79
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• 1999

The YGN Units 3&4 plant conditions during shutdown operation were reviewed to identify the possible event scenarios following the loss of shutdown cooling (SDC) event. For the five cases of typical reactor coolant system (RCS) configurations under the worst event sequence, such as unavailable secondary cooling and no RCS inventory makeup, the thermal hydraulic analyses were performed using the RELAP5/MOD3.2 code to investigate the plant behavior following the event. The thermal hydraulic analyses include the estimation of time to boil, time to core uncovery, and time to core heat up to determine the containment closure time to prevent the uncontrolled release of fission products to atmosphere. The result indicates that the containment closure is recommended to be achieved within 42 minutes after the loss of SDC for the steam generator (SG) inlet plenum manway open case or the large cold leg open case under the worst event sequence. The containment closure time is significantly dependent on the elevation and size of the opening and the SG secondary water level condition. It is also found that the containment closure needs to be initiated before the boiling time to ensure the survivability of the workers in the containment. These results will provide useful information to operators to cope with the loss of SDC event.

• 한국육종학회지
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• 제40권2호
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• pp.159-163
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• 2008

경남농업기술원 화훼육종연구소에서 스프레이국화 신품종육성을 위하여 '01년부터 국내외 종묘회사와 연구소 재배농가들로부터 우수한 유전자원들을 수집하여 '02년 10월에 흰색 홑꽃의 '안개소국'을 모본으로 하는 자연 방임수분으로부터 568개의 종자를 획득하였다. 채종 즉시 파종하였으며, 파종 10일 후 발아된 유 묘는 플러그 트레이(200공)에 옮겨 심고 1개월 정도 육묘하여 화훼육종연구소 비닐온실내의 선발포장에 정식하였다. 그 중 교잡 1세대를 육묘하여 특성검정후 초세가 좋고 화색이 선명하며 조기 개화하는 우수 5개체(AO02-109, 188, 362, 503, 545)를 1차로 선발하였다. 그 후 특성이 우수한 개체 AO02-188(경남CS-2호)을 삽목에 의해 개체증식 후 화훼육종연구소 비닐온실 내에 20 cm 포트에 모본을 정식하여 삽수를 생산하고 모종을 생산한 다음 특성검정 포장에 정식하여 2004년부터 2006년까지 3회에 걸쳐 안정성, 균일성에 대한 연차별 재현성 그리고 주년생산성(촉성, 억제재배), 생산자 및 소비자 기호성 평가를 받았다. 그 결과 기호성이 좋고, 화색 및 화형 등 품질이 우수하다고 판단되어 2006년 농작물 직무육성신품종선정위원회의 심의를 거쳐 'Water Fog'로 명명하였다. 'Water Fog' 품종은 선명한 백색 화색의 홑꽃으로서 개화소요기간이 7주로 짧은 편이며, 착화수도 34.4개로 다화성이다. 꽃 크기는 2.3 cm로 소륜이며, 초장이 89.7 cm인 산티니계 스프레이국화로서 평균 절화수명이 22.6일 로 긴 편이다.

• 해양환경안전학회지
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• 제17권4호
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• pp.339-343
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• 2011

본 연구에서는 EFDC모델과 입자추적모델을 이용하여 마산만의 담수유입에 의한 폐쇄성 내만의 물질체류시간을 산정하였다. 마산만의 해수유동을 재현하고 이를 바탕으로 평균체류시간을 계산하였다. 마산만의 조석에 의한 평균물질체류시간은 만 북측과 돝섬 부근까지가 약 110일이내, 모도 주변 해역이 약 40일, 부도에서 외해까지 약 20일 정도로 산정되었다. 담수유입에 따른 마산만의 4개 소해역별 평균물질체류시간은 I과 II영역에서 약 81일로 감소하였으나, 마산만의 외해측에 위치한 III과 IV영역은 각각 58일과 17일로 증가하였다.