• 방사성폐기물학회지
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• 제19권4호
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• pp.503-515
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• 2021

In this study, rainfall infiltration in vault of the second near-surface disposal facility was evaluated on the basis of various disposal scenarios. A total of four different disposal scenarios were examined based on the locations of the radioactive waste containers. A numerical model was developed using the FEFLOW software and finite element method to simulate the behavior of infiltrated water in each disposal scenario. The effects of the disposal scenarios on the infiltrated water were evaluated by estimating the flux of the infiltrated water at the vault interfaces. For 300 years, the flux of infiltrated water flowing into the vault was estimated to be 1 mm/year or less for all scenario. The overall results suggest that when the engineered barriers are intact, the flux of infiltrated water cannot generate a sufficient pressure head to penetrate the vault. In addition, it is confirmed that the disposal scenarios have insignificant effects on the infiltrated water flowing into the vault.

• 물과 미래
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• 제5권2호
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• pp.6-16
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• 1972

It has been well studied and known that the yields from the rice fields irrigated by the cold water such as the water directly flowing in from mountain valleies, underground water and subground water are largely influenced by the water temperature. However, the best method of raising water temperature has not yet been established. This is because there are some essentially difficult problems associated. When we examine the effects of $1^{\circ}C$ rise in the water temperature under natural condition on rice growing, the necessity of this line of study is verified. The results of Mihara's study show that rice bears its fruits at the water temperature above $19^{\circ}C$ and the difference of $1^{\circ}C$ in the range of $19^{\circ}C$ to $22^{\circ}C$ can produce the 20% of difference in yields. Because of these facts, most farmers have made use of water temperature raising ponds, zigzag waterways and shelter belts. But the most important factor in raising water temperature has been found to be the heat loss due to evaporation. Recently, a good deal of experiment on raising water temperature and soil temperature by reducing the evaporation are being carried out all over the world. The reduction of evaporation does not only reduce heat loss, from the surface but also reduce the loss of water. Present study is aimed to determine the efficiency of different chemicals by which monomolecular films are formed over different surfaces such as water surface, soil surface and the surface of plant leaves with a purpose of preventing the transpiration, and aimed to observe the effects of the temperature rise and its influence on growing state as well as the durability of the plants under drought condition.

• 대한기계학회논문집
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• 제16권6호
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• pp.1195-1204
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• 1992

본 연구에서는 등온 평면의 온도가 0.0.deg. C부터 8.0.deg. C까지, 그리고 주위물의 온 도가 1.0.deg. C부터 10.0.deg. C까지 일 대 상향 및 하향면 주위에서 일어나는 자연대류를 유한 차분법(FDM)으로 수치해석하여 등온면 주위에서 일어나는 유동형태, 속도분포, 평균 Nusselt수를 구하여 유동 및 열전달특성을 구명하였다.

• 한국지리정보학회지
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• 제24권1호
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• pp.1-11
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• 2021

위성영상을 활용한 하천, 습지, 호수 등 지표수 객체의 탐지는 해당 지역의 수자원 관리 및 조사 업무에 효율적으로 활용될 수 있다. 본 연구에서는 원격탐사 분야에서 물을 탐지하기 위해 제공하는 수분지수(Water Index)와 영상으로부터 객체를 인식하는 데 폭넓게 활용되는 기계학습(Machine learning) 기법을 대구광역시를 촬영한 Landsat-8 위성영상에 개별적으로 적용하여 하천, 호수 등 다양한 지표수 객체를 탐지하고 그 결과를 비교하였다. 우선 Landsat-8 위성영상의 다중분광 밴드로부터 NDWI(Normalized Difference Water Index), MNDWI(Modified Normalized Difference Water Index) 영상을 생성하였고, 임계치를 적용하여 개별 영상으로부터 물과 그 외 지역을 구분할 수 있는 이진 영상(Binary image)을 제작하였다. 그리고 기계학습 기법인 SVM(Support Vector Machine)을 동일 위성영상에 적용하여 토지 피복 영상을 제작하고 이로부터 이진 영상을 제작하였다. 최종적으로 100개의 검사점(Checkpoints)을 사용하여 세 이진 영상으로부터 지표수 탐지를 위한 정확도를 오차 행렬을 활용하여 계산하였다. 그 결과, MNDWI 영상으로부터 제작된 이진 영상의 정확도(84%)가 NDWI 영상으로부터 제작된 이진 영상의 정확도(94%)와 SVM에 의해 제작된 이진 영상의 정확도(96%)에 비해 낮았으며, 모든 이진 영상에서 그림자 등의 원인으로 인해 일부 육지 분류 결과가 지표수 객체로 오분류되었다.

• 신재생에너지
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• 제3권4호
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• pp.8-15
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• 2007

Liquid water in flow channel is an important factor that limits the steady and transient performance of PEM fuel cells. A computational fluid dynamics study based on the volume-of-fluid [VOF] multi-phase model was conducted to understand the two-phase flow behavior of liquid water in cathode gas channels. The liquid water transport in $180^{\circ}{\Delta}$ bends was investigated, where the effects of surface characteristics (hydrophilic and hydrophobic surfaces], channel geometries (rectangular and chamfered corners], and air velocity in channel were discussed. The two-phase flow behavior of liquid water with hydrophilic channel surface and that with hydrophobic surface was found very different; liquid water preferentially flows along the corners of flow channel in hydrophilic channels while it flows in rather spherical shape in hydrophobic channels. The results showed that liquid water transport was generally enhanced when hydrophobic channel with rounded corners was used. However, the surface characteristics and channel geometries became less important when air velocity was increased over 10m/s. This study is believed to provide a useful guideline for design optimization of flow patterns or channel configurations of PEM fuel cells.

• 한국수산과학회지
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• 제43권4호
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• pp.373-379
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• 2010

The artificial upwelling of deep seawater increases primary production. This study conducted a lab-scale experiment to investigate the growth of phytoplankton with the mixing ratio of deep and surface seawater. The chlorophyll content in the sample of pure deep seawater was highest, regardless of the phytoplankton groups. Nutrients contained in the deep seawater positively influenced the growth of phytoplankton. The optimum mixture to apply in an artificial upwelling system was a 1:1 ratio of deep and surface seawater. An experiment considering other environmental conditions, such as luminance and specific gravity, should be performed.

• Journal of Biosystems Engineering
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• 제34권4호
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• pp.234-242
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• 2009

This study was attempted to develop surface washing-system of ginseng. The effect of sterilization, washing and keeping freshness of ginseng through analyzing unit process were examined to establish optimal condition for washing system. Surface washing method of fresh ginseng used two way and full cone spray type. Sterilization was used at $2^{\circ}C$ water with electrolysis water of 50 and 80 ppm. Ginseng was sterilized with electrolysis water during 30 and 60 s, dehydrated during 1 min and dried during 1min at 30 and $50^{\circ}C$. Hardness of surface-washed ginseng showed good result on 1 min spraying time with 80 ppm electrolysis water at $10^{\circ}C$ storage. Ginseng with 80 ppm electrolysis water was sterilized better with $1.05{\times}103$. There are no changes with 0% on appearance quality at 80 ppm electrolysis.

• 한국농공학회지
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• 제34권1호
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• pp.87-99
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• 1992

A mathematical model, UNSATR which predicts the seepage flow through the body of dike especially under the tidal fluctuation has been developed. This model has been revised from UNSAT2 model which was developed on the basis of the saturated-unsaturated theory by Neuman. UNSATR has been verified and applied to the hydraulic model in order to estimated the seepage quantity, the formation of free water surface etc. The results lead to the following conclusions : 1. Seepage rates between the mathematical model and hydraulic model experiment are very similar to each other both in constant and transient water level conditions. 2. The lapsed time to be steady state of the free water surface becomes late as the tidal levels are relatively low mainly due to the seepage flow from the unsaturated zone of the body of dike. 3. Under the transient state of water levels, owing to the flow from the unsaturated domain, streamlines crossing to the free water surface are found and time lag during a falling tide may allow the free water surface inside the body of dike to stand at a high level than the outside water level. 4. The utility and validity of UNSATR model are convinced when the analyses on seepage problems through the porous embankment of the soil structures on the conditions of the steady and unsteady states are carried out.

• 한국표면공학회지
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• 제50권4호
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• pp.259-265
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• 2017

5000 series aluminium alloys and austenitic stainless steels have excellent corrosion resistance and sufficient strength, which are widely used as materials for marine equipment and their parts in the marine environment. The corrosion characteristics of materials are important factors for selecting the appropriate material due to fluid component changes in the estuarine and coastal areas where seawater and fresh water are mixed. Therefore, for 5083 Al alloy, STS304 and STS316L widely used in the marine environment, anodic polarization experiments were performed to compare the corrosion damage characteristics of each material by three kinds of solutions of 100 % tap water, 50 % tap water+50 % natural seawater and 100 % natural seawater. As a result of the anodic polarization experiments, aluminum alloy (5083) caused locally corrosion on the surface in the tap water, and corrosion damage occurred all over the surface when the seawater was included. Stainless steels (STS304 and STS316L) presented almost no corrosion damage in tap water, but they grew pitting corrosion damage with increasing seawater concentration. STS316L showed better corrosion resistance than STS304.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2193-2195
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• 2005

The hybrid discharge reactor was designed for the application of wastewater treatment and the removal of hazardous volatile organic substances in water. This discharge type was similar to the barrier discharge, and the surface discharge on the dielectric surface was propagated to the water surface. That caused the heterogeneous chemical reaction strongly at the interface between the working gases and the water surface. Changes of the conductivity, acidity, and the dissolved ozone with respect to the treatment time and water quantities were studied as the fundamental experiment. The concentration of hydrogen ions largely increased with increasing the treatment time and the conductivity increased with respect to the increase of water quantities under the constant other discharge parameters.