• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.644-653
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• 2018

Landslides occur frequently due to the effects of heavy rainfall and typhoons caused by climate change. Erosion control measures are needed to effectively prevent landslide damage. In order to improve their efficiency, it is necessary to quantitatively measure the sediment discharge from the mountain stream. In this study, a load cell sensor was installed in a mountain stream and the measured values were compared according to the applicability and load test type in the mountain stream. The result of the load test showed that the effect of the loading type (load test 1, 2) was low at average (loadings) of 0.4kgf and 0.6kgf at sites 1 and 2, respectively. The load factor was also derived by regression analysis to increase the accuracy of the measured values. According to the results of the load factor (normalized) to the load-cell measurement value, the output value increased by 14.8% and 24.6% in sites 1 and 2, respectively, and was calculated to be similar to the reference value. The load cell sensor enabled us to quantitatively estimate the amount of sediment discharge in the mountain stream through time series analysis with the water level and rainfall information. If the monitoring is carried out for a long time, it can be used to find the sediment discharge mechanism for the mountain stream. In addition, applying sensors such as load-cells to a mountain stream is expected to contribute to the development of related industries, such as the manufacturing of measurement sensors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.2
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• pp.307-316
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• 2019

Development of vegetation in stream channel increases resistance to flow, resulting in increase in river stage upon flood and affecting change in stage-discharge relationship. Vegetation revealed in stream by water level reaching a peak and then declined upon flood is mostly found as prone. Taking an account of flow distribution with the number of vegetation, prone vegetation layer might be at height where discharge rate is zero (0) (Stephan and Guthnecht, 2002). However, there is a tendency that flow rate is overestimated when applying the height of river bed to flow area with no consideration of the height of vegetation layer in flow rate by float measurement. In this study, reliable flow measurement in stream with vegetation was calculated by measuring the height of vegetation layer after flood and excluding the vegetation layer-projected area from the flow area. The result showed the minimum 4.34 % to maximum 10.82 % of flow deviation depending on the scale of discharge. Accordingly, reliable velocity-area methods would be determined if vegetation layer-projected area in stream is considered in flow rate estimation using the flow area during the flood.

• Journal of Korea Water Resources Association
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• v.41 no.5
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• pp.503-515
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• 2008

In this study we calculate discharge by slope-area method using continuously observed water level data and analyse the results. This study is performed in the Dalcheon river reach of 960 m length including riffles and a pool, which is located downstream of the Goesan Dam. Three values of roughness coefficient are applied to discharge calculation, which are established using bed material size analysis. Another roughness coefficient value obtained from the river improvement plan is also used. Calculated discharges by slope-area method are compared with dam discharges. Relative difference from dam discharges appears to be largely affected by roughness values and a value of 0.042 or more seems most suitable for the entire study reach. Smaller roughness value is suitable to the reach which has gentler water surface slope than mean channel slope of the entire study reach, while a larger value to steeper reach. In case roughness value is set considering overall slope of the channel, it is desirable to select the entire calculation reach including both gentler and steeper sub-reaches. Since relative difference becomes nearly constant at over 500 cms, in case that verification of applied roughness is conducted with other directly measured discharge, accuracy of measurement by slope-area method for larger discharge may be improved.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.1
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• pp.73-80
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• 2008

An hydraulic experiment was carried out in an open channel flume in order to improve the technique of designing shape of the sluice used for tidal power generation, which greatly affects the economical efficiency of the construction of a tidal power plant. To predict the influence of change in the major design parameters relating to the sluice shape on the water discharge capability of the sluice, it was necessary to perform a precise experiment that is discriminated to previous feasibility studies or design projects. For this purpose, by installing various flow straighteners and rectifying structures inside the water supply system and the rectifying tank, the flow in the flume was stabilized as tranquil as possible. In addition, the measuring instruments and the location of installing them were carefully determined so as to minimize the errors intervened during the measurement of water discharge and water level. The method of estimating head difference between upstream and downstream of the sluice was also developed by taking account of the head loss due to the friction at the bottom and side walls in the flume.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.491-491
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• 2013

A novel plasma system has been developed for 3-dimensional modification of the carbon nano-powders. Improvement of dispersion of these nano materials are studied by plasma discharge, not using chemical modification. The plasma process is considered to great advantages over wet chemical process due to environmental, economic viewpoint, and uniformity over the treated volume. The uniform dispersion is a critical factor for these material's nano composite applications. Using this plasma system, graphene, carbon black, and CNT was treated and functionalized. Several key discharge conditions such as Ar/H2/O2 or Ar/H2/NH3 gas ratio, treatment time, power, feeder's vibration frequency are investigated. Hydrophobic of graphene has turned some more into hydrophilic by reaction test with water, electrophoresis, surface contact angle test, and turbidity analysis. The oxygen content ratio in the plasma treated CNT has increased about 3.7 times than the untreatedone. In the case of graphene and carbon black, the oxygen- and nitrogen- content has been enhanced average 10%. O-H (N-H) peak, C-O (C-N) peak, and C=O (C=N) peak data have been detected by FTIR measurement and intensified compared to before-plasma treatment due to O2 or NH3 content.

• Ecology and Resilient Infrastructure
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• v.8 no.2
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• pp.88-96
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• 2021

In surface image velocimetry, a wide area of a river is photographed at an angle to measure its velocity, inevitably causing image distortion. Although a distorted image can be corrected into an orthogonal image by using 2D projective coordinate transformation and considering reference points on the same plane as the water surface, this method is limited by the uncertainty of changes in the water level in the event of a flood. Therefore, in this study, we developed a tilt image correction technique that corrects distortions in oblique images without resetting the reference points while coping with changes in the water level using the geometric relationship between the coordinates of the reference points set at a high position the camera, and the vertical distance between the water surface and the camera. Furthermore, we developed a distortion correction method to verify the corrected image, wherein we conducted a full-scale river experiment to verify the reference point transformation equation and measure the surface velocity. Based on the verification results, the proposed tilt image correction method was found to be over 97% accurate, whereas the experiment result of the surface velocity differed by approximately 4% as compared to the results calculated using the proposed method, thereby indicating high accuracy. Application of the proposed method to an image-based fixed automatic discharge measurement system can improve the accuracy of discharge measurement in the event of a flood when the water level changes rapidly.

• Journal of the Korean Geographical Society
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• v.40 no.3 s.108
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• pp.274-284
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• 2005

On the subject of Yeoungsan River Yeoungbon c and Seumjin River Seumbon e site discussing as the measuring points of discharge and Quality by the Department of Environment, this study executes the tests of proprieties and examines the methods of flow measuring and assessment. The result of this study may summarize as belows. According to the hydrogeomorphological aspects and artificial effects, Yeoungbon c and Seumbon e site are not proper for the measuring points of the water levels. Also, the methods of river discharge measuring by the specific discharge method, first tried in this study, has an enough reliability which can be used to measure the site where is difficult to measure the flow directly or to select the representative site to measure on the up and downstream. In case of accumulating the specific discharge data throughout the flow observation by seasons and periods for a long time, these may be used to measure the flow as well.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.807-823
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• 2008

This paper presents a technique for estimating discharge rating curve parameters. In typical practical applications, the original non-linear rating curve is transformed into a simple linear regression model by log-transforming the measurement without examining the effect of log transformation. The model of pseudo-likelihood estimation is developed in this study to deal with heteroscedasticity of residuals in the original non-linear model. The parameters of rating curves and variance functions of errors are simultaneously estimated by the pseudo-likelihood estimation(P-LE) method. Simulated annealing, a global optimization technique, is adapted to minimize the log likelihood of the weighted residuals. The P-LE model was then applied to a hypothetical site where stage-discharge data were generated by incorporating various errors. Results of the P-LE model show reduced error values and narrower confidence intervals than those of the common log-transform linear least squares(LT-LR) model. Also, the limit of water levels for segmentation of discharge rating curve is estimated in the process of P-LE using the Heaviside function. Finally, model performance of the conventional log-transformed linear regression and the developed model, P-LE are computed and compared. After statistical simulation, the developed method is then applied to the real data sets from 5 gauge stations in the Geum River basin. It can be suggested that this developed strategy is applied to real sites to successfully determine weights taking into account error distributions from the observed discharge data.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2041-2043
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• 2000

Ozone is widely used to sterilize food and tap water because ozone is a strong oxidizer. To date, it has been difficult to dissolve a high concentration of ozone gas in water because the large size of the bubbles limits the contact area between the ozone gas and liquid water. The measurements of dissolved ozone can be used to control water quality and ozone dosage. Therefore the dissolved ozone measurement of most interest is that of residual ozone at the discharge point of a particular treatment chamber.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.434-439
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• 2007

Amended Water Quality Environment Preservation Law enacted that the areas where nonpoint pollution is serious can be designated as Nonpoint Source Management Region. According to Section 54 of Water Quality Environment Preservation Law, corresponding watersheds are areas where runoff from nonpoint pollution source may deteriorate river and lake water quality, residents' health and property, and ecosystem. The criteria are as followings; i) where nonpoint source contribution result in or will result in significant ecological destruction, iii) national or local industrial complexes and cities having population greater than one million where nonpoint source managements are necessary, iv) where specific measurement is necessary because of its geological and stratigraphic characteristics. In this research, detailed designation criteria was developed reflecting current nonpoint source management situation and its discharge characteristics. Depending on the result, target regions were also suggested. In additions, it will be desirable that the target regions are prioritized considering institutional execution availability, stakeholder's agreement, and connection with existing nonpoint source pollution management measures.