• Journal of Astronomy and Space Sciences
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• v.35 no.2
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• pp.105-109
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• 2018

El $Ni{\tilde{n}}o$ is the largest fluctuation in the climate system, and it can lead to effects influencing humans all over the world. An El $Ni{\tilde{n}}o$ occurs when sea surface temperatures in the central and eastern tropical Pacific Ocean become substantially higher than average. We investigated the change in sea surface temperature in the Pacific Ocean during the El $Ni{\tilde{n}}o$ period of 2015 and 2016 using the advanced very-high-resolution radiometer (AVHRR) of NOAA Satellites. We calculated anomalies of the Pacific equatorial sea surface temperature for the normal period of 1981-2010 to identify the variation of the 2015 El $Ni{\tilde{n}}o$ and warm water area. Generally, the warm water in the western tropical Pacific Ocean shifts eastward along the equator toward the coast of South America during an El $Ni{\tilde{n}}o$ period. However, we identified an additional warm water region in the $Ni{\tilde{n}}o$ 1+2 and Peru coastal area. This indicates that there are other factors that increase the sea surface temperature. In the future, we will study the heat coming from the bottom of the sea to understand the origin of the heat transport of the Pacific Ocean.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.679-688
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• 1997

In order to analyze the water quality variation of surface water around the Sudokwon landfill site, seasonal variations of water temperature, pH, DO. HOD, COD, SS, NH3-N, NO2-N, and NO3-N were examined at 10 sites from January to December, 1996. It was found that the estimates of COD, DO. SS, and $NH_3-N$ were Increased compared with the results of environmental Impact assessment carried out In 1988. Higher estimates of COD, DO, and SS were due to Industrial and agricultural wastewater, and the Increase of NH3-N at Jangdo reservoir strate was due to the leachate from the landfill. In particular, the estimate of 55 was found to be increased by the soil wash from the landfill during the heavy rainy days.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.441-444
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• 2007

Surge tank generally are used near the downstream end of tunnels of penstocks to reduce change in pressure caused by waterhammer resulting from load changes on the turbines. In this paper, the surge tank with chamber is selected to analyze water surface oscillation. the governing equation are derived using the law of conservation of mass and momentum. the water surface oscillation in the surge tank are computed using governing equation. In the case of upsurging, water surface oscillation is damped gradually and in the case of downsurging, it is damped rapidly.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.57-65
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• 2006

In this study, hydraulic model same as natural channel with junction area and curved reach is constructed, and after that the variation of difference of the water surface elevation at cross section in junction area is analyzed using constructed hydraulic model. In junction area, the variation of maximum water level based on downstream section is more affected in discharge ratio at upstream than downstream. The maximum water level increased as closed to junction and the peak level appeared at just downstream of junction. The slope of water elevation at cross section is affected in section shape and decreased as discharge ratio is reduce. The expressed formulas developed in the channel consist of constant curvature and section shape showed difference of 60% with measured value, but the suggested formula in this study to compute difference of water surface elevation showed difference of 10% with measured value.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.559-564
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• 2009

The variation in the shape of water droplet moving on atomistically smooth solid surface in the presence of a constant body force is simulated using molecular dynamics simulation. We investigated how the advancing and receding contact angle of the moving water droplet changes on a solid surface having various characteristic energies. From the MD simulation results, we obtained the density profile defined as the number of water molecules at a given position. Then, assuming the water droplet periphery to be a circle, we calculated the contact angles by using a nonlinear fitting of the half-density contour line. The present simulation clearly shows the different profile of the advancing and receding contact angle for these three different interaction potential between the water droplet and the solid surface.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.4
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• pp.90-95
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• 1989

The purpose of this study is to seek out the harrow water requirement applicable for the irrigation plan of paddy field and to find out the factors influenced on a variation in the requirement. The plots of experiment were arranged with randomized block design which was compo- sed of three kinds of soil texture (sandy loam, loam and silty loam) and ploughing depth (12cm, 17cm, and 22cm). The results obtained from this experimental study are summarized as follows. 1. Harrow water reguirement is not only changed by soil texture, but influenced by soil water content just before irrigating 2. Magnitude of total harrow water reguirement appli(able for the irrigation plan, when surface water depth and the water content just before irrigating is fixed on the basis of 30 mm and a shrinkage limit respectively, generally becomes to be 177.5mm, 116.3mm and 113. 8mm in the sandy loam, loam amd silty loam block, respectively. 3. The more a percolation of soil layer occurs, the more the harrow water requirement increases, but it is not much influenced by the increase in ploughing depth. 4. The larger a porosity of soil layer is, the more a net harrow requirement increases 5. The factors that influence on a variation in the harrow water requirement are appea- red to be percolation of soil layer, soil water content just before irrigating, porosity of soil layer, ploughing depth and designed surface water depth etc.

• Journal of Environmental Science International
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• v.7 no.1
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• pp.67-73
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• 1998

Surface heat budget of the Deukryang Bay from July 1, 1992 to September 12, 1993 is analyzed by us- ing the meteorological data (by Changhung Observatory and Mokpo Meteorological Station) and oceanogaphical data (by Research Center for Ocean Industrial Development. Pukyong National University). Each flux element at the sea surface which has annual variation Is derived with application of an aerodynamical bulk method and empirical formulae. The solar radiation Is the maximum In spring and sensible heat are the maximum in autumn and water. and minimum in summer The heat .storage rate is calclilated by using the rate of water temperature variation according to the depth. The oceanic transport heat is estimated as a residual. The net heat flux, the heat storage rate are positive In spring and summer, while they are negative in autumn and winter. The oceanic transport heat Is convergence In winter and divergence In the rest of seasons.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.44-48
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• 2004

A silent type ozone generator using water surface electrode was proposed. And it was investigated experimentally that a variation of water conductivity affected to water surface discharge. Important factors affecting to water surface discharge are ions in discharge space and ions and polarized molecules in water and so on. In this study, It was intended to change the characteristics of discharge by controlling the number of ions in water. The number of ions in water could be controlled by changing the water conductivity. Water conductivity was controlled by quantity of inserted NaCl to distilled water. At this time, current-voltage characteristics and characteristics of ozone generation quantity were investigated in each case. As a result, when NaCl was inserted in distilled water, more stable discharge was generated. As the quantity of NaCl was increased, discharge starting voltage could be lowered.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.59-65
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• 2007

Rapid variation of coastal ecosystem in the East Sea of Korea, such as fishery resource variation and subtropical chang of bentic flora, accordong to the global warming are actually noticed. In this study we try to identify the characterics of water mass existing in this coastal area and to consider the variation of their physical and chemical properties using data of temperature, salinity and dissolved oxygen obtained by National Fisheries Research & Development Institute from 1960 to 2005. The temperature of all water mass rise during last 45 years; the rise of North Korea Cold Water temperature (about $2.33^{\circ}C$) is 1.5 times higher than that of Tsushima warm water (about $1.6^{\circ}C$), and the temperature rise of Tsushima Surface Water, directly affected by climate chang is $2.57^{\circ}C$, higher than the atmospheric temperature rise during same period, indicating that subtropical change makes progress more rapidly in the coastal marine ecosystem than in the land ecosystem. Otherwise, the salinity in the surface water decrease $0.29\%_{\circ}$ during last 45 years due to the rising trend of rainfall with atmospheric temperature. The dissolved oxygen concentration in the all water mass make a decreasing trend. Specially for the North Korea Cold Water, the dissolved oxygen concentration diminish 0.021 mg/l per year and the decrease in the East Sea Proper Water indicate a change of inner water circulation system.

• Journal of the Korean Geophysical Society
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• v.6 no.2
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• pp.107-119
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• 2003

The behavior of pore pressure and effective stress in a highly saturated sand bed under variations in the water pressure in its surface were investigated to determine the mechanism of the collapse of hydraulic structures during flooding or when attacked by storm waves. The vertical, one-dimensional model was used as a basic model to clarify the effect of water pressure variation on only to the vertical direction. The theoretical results show that a sand bed under variations of water pressure is weakened by an increase in excess pore pressure and that under certain conditions the sand bed will liquefy. Although many factors related to water pressure variation and property of the material determine this phenomenon, the mist important factor seems to be the small amount of air present in the sand bed. The theoretical results reported are verified by experiments.