• Journal of Urban Science
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• v.6 no.2
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• pp.17-27
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• 2017

Recently, civil complaints have increased due to water pollution and bad smell in rivers. Therefore, attention is focused on improving the river environment. The purpose of this study is to acquire RGB and thermal infrared images using UAV for sewage outlet and to monitor the status of stream pollution and the applicability UAV based images for river embankment maintenance plan was examined. The accuracy of the 3D model was examination by SfM(Structure from Motion) based images analysis on river embankment maintenance area. Especially, The wastewater discharged from the factory near the river was detected as an thermal infrared images and the flow of wastewater was monitored. As a result of the study, we could monitor the cause and flows of wastewater pollution by detecting temperature change caused by wastewater inflow using UAV images. In addition, UAV based a high precision 3D model (DTM, Digital Topographic Map, Orthophoto Mosaic) was produced to obtain precise DSM(Digital Surface Model) and vegetation cover information for river embankment maintenance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5956-5963
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• 2013

By the activation of environment-friendly river works, application of vegetation mats is increasing, however, evaluation techniques for hydraulic stability of vegetation mats are not presented. This study is conducted to develop the objective test method for vegetation mats. Two kind of vegetation mats are tested by the real scale experiments, and hydraulic quantities are measured and analyzed to evaluate acting shear stresses. To evaluate soil loss, Terrestrial 3D LiDAR measurement is conducted and soil loss index are calculated from changes of bed elevation. Quantified evaluation for permissible shear stresses is conducted by graphical method for acting shear stresses and soil loss index. By the results of precision survey, changes of sub soil are limited to local range in stable cases and relatively large changes of sub soil which is similar to natural river bed are detected in unstable cases. From the study, evaluation of permissible shear stresses by ASTM D 6040 is avaliable in the failure mechanism and failure criteria by soil loss index.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.21-35
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• 2017

The 3S Basin is described as an important contributor in terms of many aspects in the Mekong River Basin in Southeast Asia. However, the 3S Basin has been suffering adverse consequences of changing discharge and sediment, which are derived from farming, deforestation, hydropower dam construction, climate change, and soil erosion. Consequently, a large population and ecology system that live along the 3S Basin are seriously affected. Accordingly, the calculating and simulating discharge and sediment become ever more urgent. There are many methods to simulate discharge and sediment. However, most of them are designed only during a single rainfall event and they require many kinds of data. Therefore, this study applied a Catchment-scale Soil Erosion model (C-SEM) to simulate discharge and sediment in the 3S Basin. The simulated results were judged with others references's data and the observed discharge of Strung Treng station, which is located in the mainstream and near the outlet of the 3S Basin. The results revealed that the 3S Basin distributes 31% of the Mekong River Basin's total discharge. In addition, the simulated sediment results at the 3S Basin's outlet also substantiated the importance of the 3S Basin to the Mekong River Basin. Furthermore, the results are also useful for the sustainable management practices in the 3S Basin, where the sediment data is unavailable.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.41-49
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• 2010

Stepped weir of this study was suggested a type of natural type structures. Unique flow, such as Wave type flow, at downstream of mild slope stepped occurs. WTF(Wave type flow) is different with hydraulic jump occurred at Round crest weir. WTF is phenomenon to rise the water level by recirculation area occurred by step height at downstream of mild slope stepped. Wave height of WTF condition is higher than tailwater level and maximum velocity of WTF condition occurs in area of water surface. In this results, WTF presents to be important factor for design of join area of weir with levee. This study got and analyzed hydraulic condition occurred of WTF, scales of WTF and velocity profiles on flow patterns using experiments. WTF was not consider to stepped weir design and this results can be important data for design of stepped weir and structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1102-1108
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• 2014

This study was to compare the protection abilities of an SPF through ground or underwater casting. A mat of 1/10 scale was made and then mortar was placed on the ground and submerged conditions. A limit velocity of each mat was estimated with this experiment. As a result of the test, the mat failed because of the decrease of bearing power in the center of the waterway. On the one hand, the edge of the mat, where the velocity is slow, secures stability. The result of the limit velocity analysis suggests that a velocity of ground placement with 6.51m/s and underwater casting with 9.80m/s is the minimum to ensure stability. When SPF mat with a thickness of 0.50m is replaced with a concrete block, it is calculated to need a maximum thickness of 2.21m.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1291-1292
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• 2005

• Journal of Environmental Science International
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• v.23 no.1
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• pp.143-152
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• 2014

The results which are from naturalness assessment and visual assessment was examined to accomplish a classification, a conclusion, a comparison and an analysis. Also statistical test was examined to identify applicability of the survey to other rivers according to the result of visual assessment. As a result of naturalness assessment and visual assessment, evaluation rate of Geumho river is the highest rank of the grade as 2.5. Also t-test was examined to apply items of visual assessment at other rivers through differences in means of river naturalness rates from which visual assessment results. Most of differences in means of river naturalness rates are significant. Thus assessment criteria can be applied to other rivers to find out unique characteristics because each item has independent characteristics.

• Journal of Wetlands Research
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• v.9 no.3
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• pp.51-61
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• 2007

In natural river, river-bed change is greatly influenced by the various factors such as river improvement, change of watershed land use, construction of dam and reservoir, gravel mining, and so on. The knowledge about river-bed change in the river is essential in the river modification, wetlands plan, and maintaining stable alluvial rivers. In this study, river-bed change in the future was predicted by investigating river channel characteristics which play dominant role in the formation of channel and based on the numerical model through river survey and the grain size analysis. The Proposed investigation and model was applied to the Geum river and the Miho stream which have been experienced river degradation due to river aggregate dredging and now seams to be stable. The result of potential river-bed change which was estimated by investigating channel characteristic including slope of channel, friction velocity, and so on is similar to that which was estimated based on the numerical model. It was found that the Geum river and the Miho stream will be stable. In the future, if considering the characteristics of river channel which is estimated by the river-bed scour, sediment, and so on, it is possible that river improvement and wetland restoration plan are established stably and naturally.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2190-2199
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• 2009

Nihombashi is located in the central area of Tokyo, Japan. Tokyo has been the capital in Japan since the Edo period, which started approximately 400 years ago, and has accepted a variety of cultures, human resources, businesses for the last 400 years. This has resulted in building up the present prosperity. The Sumida River, one of the symbols of Tokyo and its tributaries including the Kanda River and the Nihombashi River, flows through the Nihombashi district. The river and tributaries used to benefit to the City of Edo. Due to the economic development and the industrial growth in Tokyo, however, they were polluted and lost their functions. In 1960s, approximately 40 years ago, the Sumida River became so dirty that local citizens kept away from it. The Nihombashi River was covered with an expressway, which was obscuring the river view. Since 1970s, local communities have proposed to rehabilitate rivers in Tokyo successively, and have proceeded with measures for river floods, improvement of sewage systems and construction of water purification facilities. Consequently, the quality of the river water was considerably improved in 1990. The stagnant rivers were turned into ones that local citizens were physically able to come close by. Today, restoring of the environment and the appearance of the city in the old days, Nihombashi district has been proposed as a model city of the future, which is alive with history and culture and harmonizing with rivers. The concept is "To Create, To Reserve, To Restore." This paper introduces a case study of the urban development, in which the local communities and public authorities collaborated with and proposed a brand-new style of the urban city harmonizing with the environment.

• Advances in concrete construction
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• v.10 no.5
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• pp.431-441
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• 2020

For the purpose of improving the properties of UHPC as well as the economic efficiency in production of the material, Availability of river sands as fine aggregate instead of micro silica sand were investigated. Four different sizes of river sands were considered. Using river sand instead of micro silica sand increased the flowability, and decreased the yield stress and plastic viscosity in rheological properties, and the effect was higher with larger particle size of river sand. It was demonstrated by analyses based on the packing density. In the results of compressive strength and elastic modulus, even though river sand was not as good as micro silica sand, it could provide high strength of over 170 MPa and elastic modulus greater than 40 GPa. The difference in compressive strength depending on the size of river sand was explained with the concept of maximum paste thickness based on the packing density of aggregate. The flexural performance with river sand also presented relatively lower resistance than micro silica sand, and the reduction was greater with larger particle size of river sand. The flexural performance was proven to be also influenced by the difference in the fiber orientation distribution due to the size of river sand.