• Proceedings of the Korea Contents Association Conference
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• 2006.05a
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• pp.351-355
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• 2006

The purpose of this study is to develop an efficient and useful equation of discharge measurement which can calculate easily discharge using only the surface velocity in both channels and rivers. The research results show: (1) Natural river have a propensity to establish and maintain an equilibrium state the corresponds to a value of the entropy parameter M; (2) Velocity distribution estimated by the method using surface velocity was compared with that of actual survey. It shows fairly close agreements between the estimated and the observed; (3) Developed equations for calculating the discharge using the surface velocity at the spot of the maximum velocity in a river section were established and show that the method of using fairly acceptable. An entropy based method for determining the discharge using only surface velocity in the rivers has been developed. The method presented is also efficient and applicable in estimating the discharge in high flows during the flood season that are very difficult or impossible to measure before, due to technical or theoretical reasons.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.431-433
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• 2000

The hydroelectric Power plant of the KOWACO have been establishing and operating a full scale electric power facility, doing the largest generation during the flood period of the summer season. When the huge capacity generator is run like the Chung-Ju's hydroelectric Power plant, the generator current per generator flows a great current estimated at 5,900 A. The bus bar of a great current flows in cubicle, owing to the bus bar current Eddy current is created around magnetic substance and a local heating phenomenon occurs due to Joule heat finally. a local heating phenomenon still exists the danger of safety accident due to contact and accompanies losses enough to healing capacity inevitably. this study applies and examines related theory and numerical formula about the heating cause of a great current & enforces technical verification about the method of heating reduction previous managed at the site.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1708-1712
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• 2008

본 연구에서는 낙동강 수계 안동댐과 임하댐의 홍수시 연계운영시스템을 구축하여 안동댐과 임하댐의 하류부인 안동시에서의 피해를 최소화하기 위해서 HEC-5모형을 이용한 모의기법을 통해 해석을 실시하였다. 모의운영을 실시하여 얻어진 결과를 FLDWAV모형에 적용하여 댐하류부의 홍수추적을 실시하였다. 홍수시 안동댐과 임하댐의 연계운영을 위해 안동댐과 임하댐에 대해서 각각 100년 빈도조건, 200년 빈도조건, PMF 조건, 200년 빈도와 PMF가 조합된 조건을 적용하여 분석을 실시하였다. 저류지 모의기법을 적용한 모의운영을 위해서 안동댐의 경우 안동댐 치수능력 증대사업 기본 계획보고서에서 제시된 일정률-일정량 방식의 댐 운영률을 이용하였고, 임하댐의 경우는 임하댐 치수능력 보고서에 제시된 일정률-일정량 방식을 적용하였다. 하류부 하천 제방의 여유고를 확보하기 위해 안동댐 운영의 대안으로서는 기존의 일정률을 조정하여 100년 및 200년 빈도하에서 기존 3,800m3/s를 3,490m3/s으로 최대 방류량을 변경한 100년 빈도조건, 200년 빈도조건, PMF 조건, 200년 빈도와 PMF가 조합된 조건을 적용 분석하여 댐의 방류량을 결정하였다. 댐 하류부의 홍수추적을 위해서 안동댐 및 임하댐 하류부로부터 지보수위표 지점까지의 53.9 km 구간에 대해서 FLDWAV 모형을 적용한 부정류 해석을 실시하였다. 댐 하류부에서의 시나리오별 홍수위를 산정하여 기존의 제방고와 비교함으로써 안동시 구간에서의 제방 안전성을 평가하였다.

• Ocean and Polar Research
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• v.31 no.1
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• pp.77-95
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• 2009

Ciliate abundance and biomass were determined at three anchored stations in the Han River estuary trimonthly from May 2006 to February 2008. The total abundance of ciliates ranged from 0-13,853 cells $l^{-1}$ and biomass ranged from $0.00-73.98\;ugC\;l^{-1}$. Owing to the large seasonal temperature variation (range 0.20-$27.2^{\circ}C$), ciliate abundance displayed marked seasonal variation, being higher in summer than in other seasons. Tintinnids dominated the ciliate communities at station YC where suspended sediment was highest. Difference of ciliate biomass between ebb tide and flood tide were irregular. Seasonal variations of ciliate carbon biomass at each station were related to temperature, suspended sediment and chl.a, especially nano chl.a. Geographical variations of ciliate carbon biomass in each season were related to suspended sediment and salinity.

• Korean Journal of Ecology and Environment
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• v.45 no.2
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• pp.200-209
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• 2012

The current of the water body is very important information for the water quality management on reservoirs. It is applied to hydraulics and water quality model for simulation. In this regard, the current characteristic of water body is the basic information that can be used to predict various conditions. However, it is very slow flowing and is affected by the reservoir operations and external factors. As such, an accurate measurement of the current is a difficult problem. In order to measure the water current, we constructed a drifter. According to the result of flow survey at Yongdam reservoir, 5m and 10 m depth layer flow was investigated from the upstream to the downstream, during a flood period. Maximum flow rate of 5 m depth is 13.8 cm $sec^{-1}$ and 10 m depth shows 4 cm $sec^{-1}$, respectively. But 2m depth shows a backward flow and maximum flow rate is 4 cm $sec^{-1}$. Density currents flow plays the role of back flow in reservoirs. Flow velocity in the reservoir was measured in the range of 1~2 cm $sec^{-1}$, at normal flow season, and the flow direction were different for each survey. This phenomenon occurs because the reservoir volume is very large, compared to the inflow and outflow volume.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.4
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• pp.1-9
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• 2011

Forest area covers 64 % of the national land of Korea and the forest plays a pivotal role in the hydrological process such as flood, drought, runoff, infiltration, evapotranspiration, etc. In this study, soil moisture monitoring for conifer forest in experimental forest of Seoul National University has been conducted using FDR (Frequency Domain Reflection) for 6 different soil layers, 10, 20, 30, 60, 90 and 120 cm during 2009~2010, and precipitation data was collected from nearby AWS (Automatic Weather Station). Soil moisture monitoring data were used to estimate soil moisture recession constant (SMRC) for analyzing soil moisture recession characteristics. From the results, empirical soil moisture recession equations were estimated and validated to determine the feasibility of the result, and soil moisture contents of measured and calculated showed a similar tendency from April to November. Thus, the results can be applied for soil moisture estimation and provided the basic knowledge in forest soil moisture consumption. Nevertheless, this approach demonstrated applicability limitations during winter and early spring season due to freezing and melting of snow and ice causing peculiar change of soil moisture contents.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.47-57
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• 2018

This study implemented the rainfall-runoff analysis of the Mekong River basin using the SWAT (Soil and Water Assessment Tool). The runoff analysis was simulated for 2000~2007, and 11 parameters were calibrated using the SUFI-2 (Sequential Uncertainty Fitting-version 2) algorithm of SWAT-CUP (Calibration and Uncertainty Program). As a result of analyzing optimal parameters and sensitivity analysis for 6 cases, the parameter ALPHA_BF was found to be the most sensitive. The reproducibility of the rainfall-runoff results decreased with increasing number of stations used for parameter calibration. The rainfall-runoff simulation results of Case 6 showed that the RMSE of Nong Khai and Kratie stations were 0.97 and 0.9, respectively, and the runoff patterns were relatively accurately simulated. The runoff patterns of Mukdahan and Khong Chaim stations were underestimated during the flood season from 2004 to 2005 but it was acceptable in terms of the overall runoff pattern. These results suggest that the combination of SWAT and SWAT-CUP models is applicable to very large watersheds such as the Mekong for rainfall-runoff simulation, but further studies are needed to reduce the range of modeling uncertainty.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1965-1970
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• 2010

국내 하천은 하천의 관리, 이용, 개발, 치수경제 및 수질 보전을 위해 각 하천에 대해 하천기본계획이 작성되고 있다. 치수와 관련하여 조도계수는 각 하천의 계획홍수량 산정 및 하천제방 등 구조물 설계에 필수적인 인자로서 조도계수의 정확도에 따라 결과에 큰 오차범위를 가지게 된다. 국내 하천기본계획은 하천의 하상재료 및 하도조건에 따라 산정되어지는 조도계수를 각 하천의 일정빈도 홍수량에 맞추어 일정한 값으로 조도계수를 추정하고 있다. 본 연구에서는 국토해양부에서 2009년 한강유역 19개 지점에 대해 관측한 자료와 하천기본계획상에 제시된 조도계수를 적용하여 산정된 값을 비교 분석하였다. 국토해양부의 관측자료 분석에 있어서 유량 관측시 관측지점의 수면경사 및 하상경사의 관측 결함으로 하천기본계획상에 제시된 지형으로부터 하상경사를 추정하였으며 1차적으로 에너지경사는 하상경사와 동일하다고 가정하였다. 또한, 하천기본계획에 제시된 조도 계수의 값은 어느 일정 홍수빈도에 대하여 산정된 값으로 국토해양부 관측자료 중 갈수기 및 평수기의 자료는 제외하고 홍수기의 관측값에 대하여 분석을 실시하였다. 이러한 가정하에 하천기본계획상에 제시된 조도계수를 인용하여 Manning-Strickler 식으로 부터 산정된 유속과 국토해양부의 관측유속을 비교 분석하였다.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.161-166
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• 2015

The inappropriate hydraulic design criteria on the new revetment technique for the ecological river restoration project happens to lead to economic loss during the flood season. In this study, the hydraulic stability of the developed non-toxic revetment was evaluated at a maximum discharge of $3.0m^3/s$ and a maximum velocity of 3.0 m/s in a real scale experimental channel. The vertical movement of the non-toxic revetment block was in the range of ${\pm}3mm$ mm in the experimental conditions. The results show that the non-toxic revetment block was sufficiently hydraulically secured.

• Journal of environmental and Sanitary engineering
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• v.23 no.2
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• pp.55-63
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• 2008

All over the world, the existing process of water purification needs more flocculants and chlorine due to a gradual decline in the quality of source water. Therefore, the problem of the remaining aluminium and DBPs in purified water is on the rise. To solve this problem, the process of membrane filter has recently come into the spotight. This study reaches the following conclusions concerning TMP variation in order to solve the dropping of flux throgh a membrane filter when operating a membrane filter system in the process of water purification. 1. In case that a cohesion-precipitation process was introduced to pre-treatment of a membrane filter, initial TMP was very satisfactory(0.27kg/cm) in producing the constantly safe quality of water, $0.04{\sim}0.1$(mean 0.05) NTU by pouring 2mg/l of PACI(10% $Al_2O_3$) used for the existing process of water purification in high-density turbidity at a dry or flood season and at occurrence of high algae. 2. As flux increased at 0.5m/day.m, TMP increased 0.05 kgf/cm. 3. As filtering, operation mode of PVDF MF membrane filtering was 48 minutes and 1 cycle of back washing was 42 minutes, flux was increased 1.5m/day.m and TMP increased $0.25{\sim}0.27kgf/cm$. Without back washing, TMP increased 0.03 kgf/cm per a cycle.