• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.185-186
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• 2005

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.85-92
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• 1996

Numerical simulations are made for the three-dimensional flow around a wing in ground effect craft haying the complex geometry. A numerical tool is developed for the primary design of hull and wing shape of practical Wing-In-Ground effect(WIG) stop. The finite-difference method is utilized to descretize the governing equations and pressure field is obtained by using Marker-And-Cell(MAC) method. The air and water flows are simultaneously simulated in the time-marching solution procedure for the Navier-Stokes equation. The porosity technique and the density function are devised for the implementation of the three-dimensional body-boundary and the free-surface conditions, respectively. In this paper, a craft is modeled simply by three blocks containing a wing mounted on a main body horizontally, with the endplate. The numerical calculations of a WIG advancing in a calm water are performed and the WIG-generated wave profiles are also obtained. In the final paper, details of the numerical methods employed for the present study and calculated results are discussed.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.6
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• pp.871-879
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• 2009

The Korea has high population density, so the precipitation per capita is only one tenth to world average. The water resource in Korea is insufficient. But the leakage in the water distribution system is about 25%, and it is lower than other countries where water utilities are managed well. The pipelines' management also is getting worse because the leakage in the pipelines lower the ground density surrounding pipes. So, managing the leakage in the water distribution system is very important in the view of increasing the water resources and doing the efficient management of the pipeline system. Accordingly this study aimed to conduct a cause-analysis with scientific approaches considering key local factor related to water loss of distribution system and derive better performance indicators which are able to evaluate the real state of water loss management reasonably. Also this research aimed to develop a methodology capable of judging condition of infrastructure of water distribution system.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.2
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• pp.59-68
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• 2001

A water balance analysis was performed for a paddy field neighboring the Dongchang stream, downstream of the Unmun reservoir, which is constructed for the urban water supply. Daily rainfall data were collected and irrigation water flow rate, drainage flow rate, evaportranspiration, infiltration, and piezometeric head were measured in the field. The flow rates were continuously observed by water level logger during the growing season. The evaportranspiration and the infiltration were measured by N-type depletion meter and cylindrical infiltrometer, respectively. PVC pipes with 12mm diameter were used for piezometric head measurement. Total Irrigation and drainage flows were 3,608mm and 1,170mm in 1999, and 3,971mm and 1,548mm in 2000, respectively. The mean and range of the daily infiltration rate were 4.4mm/d and 3.4mm/d to 5.5mm/d in 1999 and 5.1mm/d and 4.1mm/d to 6.5mm/d in 2000, respectively. The net ground water flow including the change of soil water storage was 2,855mm in 1999 and 2,540mm in 2000. The evapotranspiration was 458.3mm in 1999 and 553.5mm in 2000. The range of daily evapotranspiration rate was from 1.6 to 8.7mm/d. The return flow ratio was about 32% in 1999 and 39% in 2000 and three year average was 35% including previous study in 1997. The amount of irrigation water was much higher than design standards or references in this study, This was caused by the inadequate water management practice in the area where water was oversupplied on farmers’ request rather than following sound water management principles.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1225-1231
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• 2014

This paper presents the performance characteristic of a Francis hydro turbine with an inline casing. This turbine is designed for city water supply system. Due to large changes in ground elevation with high points and low points, some systems may experience larger-than-normal required pressures in areas with low ground elevations. One way to dissipate these excess pressures is by the use of an inline-turbine instead of an inline-pressure reducing valve. For best applicability and minimal space consumption, the turbine is designed with an inline casing instead of the common spiral casing. As a characteristic of inline casing, the flow accesses to the runner in the radial direction, showing a low efficiency. The installation of vanes improves the internal flow and gives the positive encouragement to the output power. For the power transmission to the outside of the turbine casing from the runner axis, a belt passage is designed in the inline casing, as its influence, the region after the belt passage shows a relatively low output power. The clearance gap in the runner side space is considered, in which a small volume of flow is contracted into the clearance gap, forming the leakage flow. The leakage flow leads to a decrease in the efficiency.

• Journal of Korea Water Resources Association
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• v.53 no.12
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• pp.1049-1057
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• 2020

This study aimed to develop a flow measurement method using drone in flood season. Measuring flow in all branches is difficult to conduct annually due to budget and labor limitation, safety and river works. Especially when heavy rain like storm comes, changes in stage-discharge relationship should be reviewed; however, it is usually impeded by the aforementioned issues. To solve the problem, it developed a simple measuring method with a minimum of labor and time. A numeric map and numeric orthophoto coordinate of South Korea are mostly based on Transverse Mercator Projection (TM) in accordance with rectangular coordinate system and use World Geodetic Reference System 1980 (GRS80) oval figure for conversion. Applying a concept of aerial photogrammetry, it located four visible Ground Control Points (GCP) near the river at Uijeongbu-si (Singok Bridge) and Yeongdong-gun (Youngdong 2nd Bridge) station and measured the coordinates using VRS DGPS. Hovering at a same level, drones took orthophoto of water surface at an interval of 3 seconds. It defined the pictures with GRS80 TM coordinate system, a rectangular coordinate system and then conducted an orthometric correction using GCP coordinates. According to X and Y coordinate analysis, it estimated the distance between the floating positions at 3 seconds-intervals and calculated the flow through the flow area according to the flow path. This study attested applicability of the flow measurement method using drone in flood season by applying the rectangular coordinate system based on the concept of aerial photogrammetry.

• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.15-22
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• 2013

5 each permeable and impermeable debris dams were selected to analyze the characteristics of dredging and sedimentation according to facility type in Inje, Gangwon. Field tests for the ground water table and sedimentation characteristics of the selected dams were performed. Furthermore, data of the dredging amount, storage capacity, and drainage area were analyzed for the 51 more debris control facilities. From the results of field tests, it was found that the storage capacity of impermeable debris dam could be not enough when the large debris flow is produced since sediments are accumulated even if large debris flow was not occurred. Drainage can be a problem since the ground water table of impermeable debris dam was reached to the surface of ground. However, it was found that the ground saturation should not occur at heavy rain since ground water table of permeable debris dam was located in lower part of buttress. Furthermore, from the analysis results of relation among the dredging amount, basin area, and capacity of debris control facility, it was found that size of debris control facility was not reflected by the basin area. Effective planning and construction should be accomplished for the future since the real sedimentation amount was not significant even though large debris dams were constructed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1060-1067
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• 2009

Previous research on the slope failure has mainly reported that most of the slope failures occur due to surface rainfall infiltration in the rainy season. A slope of which surface is protected by shotcrete or plants, can also fail due to increase in pore water pressure from the ground water flow beneath the surface, rather than from the surface. In this study such case of slope behavior is investigated using the model test and numerical method including strength reduction method. Hydraulic boundary conditions of the slopes is considered using coupled numerical scheme. The failure mechanism of the slope is investigated and the effect of pore water pressure on slope safety is identified. Increase in pore water pressure due to lateral infiltration has significantly reduced the stability of slope.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.676-686
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• 2010

Damage Cases of variously type are reported that the ground subsidence is caused by the underground cavities at structure and construction works in lime stone or abandoned zone. A underground cavities by direct for zone having an effect on structure have been filled with cement agents. But this measure is urgently needed in materials and work methods, because ground water pollution at water down fillings and flow out, ground disturb at high participle, damage of farms and fishery. The research confirm application of filling method and filling materials of environmentally friendly and economical by Hi-FA new materials have both liquidity and viscosity from case reinforcement in APT site, Gunsan.

• Geomechanics and Engineering
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• v.4 no.2
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• pp.91-103
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• 2012

Focusing on the effect of excess pore pressure dissipation on liquefaction-induced ground deformation, a series of 1-g shaking table tests were conducted in a rigid soil container by use of saturated Toyoura sand, the relative density of which was 20-60%. These tests were subjected to the sinusoidal base shaking with step increased accelerations: 100, 200, 300 and 400 Gals for 2-4 seconds. Shaking table tests were done using either water or polymer fluid with more viscous than water, thus varying the sand permeability of model tests. Excess pore pressures, accelerations, settlements and lateral deformations were measured in each test. Test results are presented in this paper and the effect of sand permeability on liquefaction and liquefaction-induced ground deformation was discussed in detail.