• 환경영향평가
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• 제21권5호
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• pp.715-724
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• 2012

In this study, we simulated water temperature in the downstream according to withdrawal types of dam using EFDC model. Three scenarios were assumed as water was released from the surface layer, the middle layer, and the bottom layer at intervals of 10m depth. In case of the surface layer withdrawal, the water temperature rose from March and lowered gradually after it reached a peak in August. The middle and the bottom layers effluence temperatures were lower than the surface layer temperature by maximum $15.9^{\circ}C$(in July), but after September, temperature inversion appeared. It was advantageous for the surface layer withdrawal to decrease cold damage and fog in downstream area and was possible to the middle and the bottom layers withdrawal from August to September. However, the reliability of model should be improved by accumulating the real-time information of water temperature.

• 환경위생공학
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• 제14권2호
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• pp.56-67
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• 1999

This study was performed to suggest the basic data and plans for the establishment of safe water supply plans in simple water supply piped system in the rural areas. In 4 different places, 24 points of water sources 36 points of taps from water sources were sampled. Of the whole 60 points, 55 points were ground water and 5 points were surface water. 14 items were measured for the analysis of water quality on each samples. The measured items were analyzed again by statistical method ; cluster analysis and principle components analysis. The results of this study are as followed. 1) In water quality analysis on water sources, 4 items, bacteria, E.coli, NH3-N and Fe exceed the standard. Of 24 points, 20 points(83%) on bacteria, 1 point(4%) on NH3-N and Fe exceed the standard. 2) In water quality analysis on near and remote taps, 4 items, bacteria, E.coli, NH3-N and Fe , exceed the standard. Of 36 points, 20 points (81%) on bactria, 1 pint(3%) on NH3-N and Fe exceed the standard. 3)Cluster analysis on water quality shows the differences by the kinds of water sources, geographical characteristics and distance from water sources. 4) Principle components analysis on ground water shows that Factor 1 and Factor 3 are natural fluctuation by the content of soil. Also, Factor 2 and Factor 4 are penetration of pollutants to underground. Therefore, it is needed to take deeper ground water in order to prevent from pollution in the areas which have ground water as water source . 5) Principle components analysis on surface water shows that Factor 1 is penetration of vacteria from surface to water source when rainfalls. Also, Factor 2 is fluctuation of water quality by the geographical characteristics. Therefore, the counterplans against non-point pollution source must be taken. Filtration and disinfection facilities are needed in the areas which have surface water as water source.

• Journal of applied mathematics & informatics
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• 제20권1_2호
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• pp.197-208
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• 2006

This paper deals with the exact solution of surface gravity waves in an ocean with irregular bed topography. In order to obtain water surface elevation and run-up of infra-gravity waves when the bed is either wavy or exponential, closed form solutions are obtained. Numerical computations indicate that when solitary wave or sinusoidal wave conditions are applied at the boundary, water surface elevation attains near Gaussian profile.

• 한국물환경학회지
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• 제25권5호
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• pp.785-791
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• 2009

Using artificial rainfall simulator, the soil loss, which is deemed as the most cause of muddy water problem among Non-point source (NPS) pollutant, was studied by the analysis of direct runoff, groundwater discharge, and soil water storage properties concerned with rainfall intensity, slope of area, and land cover. The direct runoff showed increasing tendency in both straw covered and bared soil as slope increases from 5% to 20%. The direct runoff volume from straw covered surface were much lower than bared surface. The infiltration capacity of straw covered surface increased, because the surface sealing by fine material of soil surface didn't occur due to the straw covering. Under the same rainfall intensity and slope condition, 2.4~8.2 times of sediment yield were occurred from bared surface more than straw covered surface. The volume of infiltration increased due to straw cover and the direct runoff flow decreased with decrease of tractive force in surface. To understand the relationship of the rate of direct runoff, groundwater discharge, and soil water storage by the rainfall intensity, slope, and land cover, the statistical test was performed. It shows good relationship between most of factors, except between the rate of groundwater storage and rainfall intensity.

• KIEAE Journal
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• 제16권3호
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• pp.83-88
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• 2016

Purpose : This study aimed to verify the surface hardness and water repellency of earth paint manufactured with earth, a natural material, and provide the results as basic data for paint made with natural materials. Method : After presenting the accurate manufacturing methods for basic materials for paint, the authors conducted and analyzed experiments to evaluate surface hardness and water repellency, fundamental performance indicators for paint, based on different mixture ratios. From the results of the experiment to assess the surface hardness of flour-based earth paint, we observed high surface hardness only after painting the specimen three times. Since potato starch-based earth paint has higher viscosity than its flour-based counterpart, the former did not paint well on the first occasion, resulting in low surface hardness. After painting two or more times, however, it was observed to have higher surface hardness than flour-based earth paint. Result : It was found that at least three iterations of painting was required to obtain high surface hardness of potato starch-based earth paint. Furthermore, the results of the water resistance experiment of earth paint suggest that the use of environment-friendly finishing materials coupled with boiled linseed oil will mitigate the drawbacks of earth paint. The experiment with one-year-old specimens also demonstrated similar water repellent characteristics, which indicates that the performance will improve once the paint has dried for a sufficient period of time.

• 대한전자공학회논문지TC
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• 제48권1호
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• pp.1-8
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• 2011

본 논문에서는 수조 실험을 통해 수중 다중경로 채널의 수면변동과 지연확산이 텍스트 전송성능에 미치는 영향 확인하였다. 수면변동과 지연확산은 채널의 코히어런스 대역폭을 제한하는 요인으로 수중음향 통신의 전송성능을 제한한다. 잔잔한 수면과 교란하는 수면에 따른 응답특성 실험결과에서 수면 반사파의 진폭변동과 지연확산 특성을 확인하였다. 각각의 지연확산 유효치는 각각 5ms, 4ms로 그에 대응하는 코히어런스 대역폭은 200Hz, 250Hz였다. BFSK (Binary Frequency Shift Keying) 방식을 이용한 수중 텍스트 전송성능에서 지연확산에 따른 채널의 코히어런스 대역폭 제한으로 인해 잔잔한 수면인 경우 200bps이하에서 $10^{-4}$, 교란하는 수면인 경우 250bps 이하에서 $10^{-4}$으로 오류율이 나타났다. 따라서 본 실험을 통해 수중 다중경로 채널에서 수면변동에 의한 코히어런스 대역폭 제한용 수중음향 통신의 전송성능을 결정하는 중요한 요인임을 확인하였다.

• 상하수도학회지
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• 제13권2호
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• pp.41-46
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• 1999

Backwashing is an important process for the efficient operation of granular filters, and the efficiency of the surface washing among the backwashing processes can affect the filtrations rate and filter run-time. In this study, the efficiency of surface washing is evaluated using real filters for three cases: with surface washing (with and without drainage of water to the surface of filter bed) and without surface washing. As a result, in the case of adopting both the drainage and surface washing, the filter of which condition is initially worse than those of the other filters shows improvement in head-loss development, filtration velocity, filter run-time, and total filtration volume. On the other hand, the conventional method of surface washing rarely has an effect on the filter washing.

• International Journal of Ocean System Engineering
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• 제1권1호
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• pp.28-31
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• 2011

An attempt was made to compute the free surface deformation due to the impact of a water droplet. The Cauchy Poisson, i.e. the initial value problem, was solved with the kinematic and dynamic free surface boundary conditions linearized. The zero order Hankel transformation and Laplace transform were applied to the related equations. The initial condition for the free surface profile was derived from a captured video image. The effect of the surface tension was not significant with the water mass used in this investigation. The computed and observed free surface deformations were compared.

• Journal of the Korean Wood Science and Technology
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• 제32권3호
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• pp.1-7
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• 2004

The application of abrasive-assisted high energy water-jet was investigated as a possible new method of cutting wood. In this study the maximum cutting speeds for species of various wood density were determined and water-jet machining characteristics were investigated for sixteen Korean domestic species. The maximum cutting speed ranged from 200 to 750 mm/min. The results indicate that wood density affects machining characteristics such as maximum cutting speed, surface roughness, and kerf width. Roughness of surface generated increased and kerf width decreased as penetration depth increased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2004년도 학술.기술논문발표회
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• pp.33-37
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• 2004

Recently, Growing tendency for structure surface to use water repellent agent has increased steadily. But investigation of it's protection and durability property is not sufficient. Therefore, this paper shows the investigation about repellent property and micro structure's change in surface layer of mortar that is applied by water repellent agent. Water repellent property, absorption coefficient, air permeability, porosity and observation of micro construct was investigated according to water repellent agent type. The test results indicated that mortar applied water repellent agent appears tiny absorption coefficient, but air permeability is maintained. The reason is because silane solution is coating at capillary surface of a wall and minute pore structure is changeless.