• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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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.

• The Journal of the Acoustical Society of Korea
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• v.6 no.2
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• pp.48-53
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• 1987

The depth dependent sound fields have been calculated for a single frequency source to reveal the fluctuating sound energy at both near the surface and the bottom of the water layer. Those fluctuation are mainly due to the mode function behavior along the depth where the sound-speed gradient acts like trapping lower mode sound energy in those medium.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.559-562
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• 2003

The results and discussions of surveyed case site at constructed steel pile in potential acid sulfate soil were as follows. Topography at surveyed site was local alluvial valley and that site soils was classified as BanGog and YuGye series as detailed soil surveyed results in RDA and soil texture was Clay/Clay Loam. Soils pH was neutral, which was average 7.5 but much decreased to average 4.2 after $H_2O_2$ treatment. Organic matter and sulfate ions contents were very rich. The corrosion was severe at ground water fluctuation depth. Deposits colored black were attached to steel pile surface, which because of violent reaction in treatment HCI solution, were guessed as corrosion products (FeS) reduced by sulfate reducing bacteria(SRB). Consequently, main cause was thought microbiologically induced corrosion at this site where there is ground water fluctuation occurring oxidation and reduction reactions in turn and the soil is potential acid sulfate soil.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.181-182
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• 2000

Due to the instability of the EKWC, the oceanic conditions in the East Sea are affected by the fluctuations of the moving paths of the TWC, polar fronts, and warm eddies. In particular, warm eddies play an important role in spreading the surface water of the East Sea from its southern coastal region to its interior region (Isoda, 1994). However, the fluctuation characteristics of the meandering TWC and the warm eddies in the East Sea are not yet known due to the instability of the TWC. Hideaki(1999) showed that the moving paths and features of the TWC in the coastal regions of Japan were not constant. (omitted)

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.227-233
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• 2009

Most of hydrological processes of groundwater recharge generally are occupied a rainfall, and recharged an aquifer along infiltrate into subsurface. These processes mainly have an influence by hydrological characteristics and topographic gradient of the aquifer. Development of water resources and its management is not good because of temporal and spatial disproportion in local rainfall. In order to deal with insufficiency of water resources from now on, development of groundwater dam requires a plan of a sustainable of new water resources. These are necessary that investigation of construction area of groundwater dam, effective groundwater development interconnected with surface water and groundwater, and assessment of an application of groundwater dam for utilization of water resources. Tn this study we were derived the input data by geological survey, hydraulic and hydrological analysis around Hoengchun-river, located in Hadong-gun, Gyeongsangnam Province where is a plan area for construction of groundwater dam. Based on input data we were carried out the interconnected analysis of surface water and groundwater using the SWAT-MODFLOW, and predicted groundwater fluctuation of its construction before and after.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.242-252
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• 2018

It is well known that an Oscillating Water Column Wave Energy Converter (OWC-WEC) is one of the most efficient wave absorber equipment. This device transforms the vertical motion of water column in the air chamber into the air flow velocity and produces electricity from the driving force of turbine as represented by the Wells turbine. Therefore, in order to obtain high electric energy, it is necessary to amplify the water surface vibration by inducing resonance of the piston mode in the water surface fluctuation in the air chamber. In this study, a new type of OWC-WEC with a seawater channel is used, and the wave deformation by the structure, water surface fluctuation in the air chamber, air outflow velocity from the nozzle and seawater flow velocity in the seawater channel are evaluated by numerical analysis in detail. The numerical analysis model uses open CFD code OLAFLOW model based on multi-phase analysis technique of Navier-Stokes solver. To validate model, numerical results and existing experimental results are compared and discussed. It is revealed within the scope of this study that the air flow velocity at nozzle increases as the Ursell number becomes larger, and the air velocity that flows out from the inside of the air chamber is larger than the velocity of incoming air into the air chamber.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.123-130
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• 1999

This paper presents a study of geotechnical treatment for artesian pressure after extensive investigation was performed on the distribution and characteristics of artesian condition which exists at Yangsan/Mulgeurn site. The result of analysis indicates that the artesian pressure seems to be up to 2.9M above the existing ground surface, originating from the higher ground water recharging sources in the surrounding hills and mountains. There is no harmful effect after the site development since the height of embankment is more than 4M above the existing ground surface.

• Spatial Information Research
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• v.12 no.3
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• pp.229-237
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• 2004

Debris flow in the mountainous river gives rise to serious environmental and flooding problems. According to flood white book of Kangwon-do in 2002, over 30% of total of flooding victims are attributable to debris flow. But it has been neglected to build countermeasure to minimize victims due to lack of collected data and knowledge in field of the sediment yield of mountainous river. The study calculated hydraulic and hydrological fluctuation for rainfall condition using GIS data, after all we estimated the water surface of flood caused by bed fluctuation. These efforts will of for effective information for planning of river management.

• 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 Korean Society of Coastal and Ocean Engineers
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• v.17 no.4
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• pp.269-279
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• 2005

Numerical simulations were done using depth integrated ADCIRC model in order to evaluate dynamic response on the inner Saemankeum reservoir due to flood flow and gate operation for the both situations of dike construction and inner development. According to 2-dimensional dynamic flood routing, temporal variation of hydrographs shows sensitive at upstream riverine region while it becomes stable from the center part of the reservoir due to sudden expansion of physical changes. Dynamic response of hydraulic changes such as water surface elevation and velocity on the inner region arises suddenly by gate operation and more rapidly after the inner development than dike construction. Temporal surface fluctuation arises during inflowging of outer sea water and propagates upstream up to 10km to 16km in accordance with inner development status.