• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.417-422
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• 2001

The purpose of this study is to investigate experimentally the workability, compressive and flexural strength properties of rapid-set concrete with various mixture. The kinds of fine aggregate(river sand, sea sand, crushed sand), water-cement ratio(40%, 45%, 50%), sand-aggrega to ratio(33%, 36%, 39%) were chosen as the experimental parameters. Test variables are temperature of concrete, slump, air contents, compressive and flexural strength. The compressive and flexural strength for 3 hours and 6 hours were tested. As result, it was shown that temperature of concrete involved 45$^{\circ}C$, some time later decreased. The workability were decreasing in steps as the sand-aggregate ratio increased and crushed sand was the highest value. Higher compressive and flexural strength was shown following the order of river sand, sea sand, crushed sand regardless of sand-aggregate ratio. But the values of gap was just a little.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.849-854
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• 2009

Pollutant unit load (unit-load) reported by Ministry of Environment (MOE) in 1995 has been a useful method for watershed management and environmental policy decision. The unit-load has been estimated using effective rainfall ratio method. However, reliability of unit-load determined by the method has been criticized especially for paddy field and upland conditions. In this paper the unit-load of paddy field estimated by effective rainfall ratio method was compared with continuous monitoring data. Annual loads was simulated by the method choosing 5~6 storm events randomly from whole events collected. Probability distribution of difference between results by the method and measured data was investigated. The results showed that unit-load derived by the method was generally lesser than measured unit-load and showed wide variations. Therefore, unit-load estimation of paddy fields by effective rainfall ratio method need caution.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.5
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• pp.15-26
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• 2020

There are fifteen non-point pollution management areas in Korea and three of them (Doam lake, Daegi district and Golji-cheon) are located in the upstream of the Namhan river watershed. Many efforts to reduce non-point sources (NPS) pollution have been conducted, however, water quality pollution in the watershed is still serious. To solve these problems, it is a priority to grasp water quality using statistical techniques. In this study, a trend analysis was conducted to evaluate the effect of NPS management in the watershed. The long-term trends from 1996 to 2018 of water quality properties were analyzed using data collected from the water environment information system. Seventeen monitoring stations were selected along the main stream in Namhan river basin. Monthly water quality properties (BOD, COD, TN, TP, TN/TP ratio, Conductivity, SS and Chlorophyll-a) were collected and analyzed by Mann-Kendall test and LOWESS. The results showed that the Conductivity tended to increase in all regions and was the highest level in Jijangcheon. Organic pollution such as BOD and COD tended to increase in the Jungseon area. SS did not show a large tendency, but it showed high concentration in the Doam watershed. In all regions, 40% of water quality properties showed a tendency to 'UP', 15% of water quality properties tended to 'DOWN', and 46% indicated no tendency. In order to determine the cause of this, additional research and measures for improvement are necessary. This study will be used for the establishment of water quality policy in the future.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.10
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• pp.558-565
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• 2016

Water quality data including flow rates and BOD/COD/T-N/T-P/SS/TOC concentrations in Nakdong river tributaries were analyzed to determine priority management areas using 699 data sets from 195 locations in 2015. It was pointed out that the coefficients of variation, the ratio of the standard deviation to the mean, for the concentrations and loading rates of BOD, T-P, and TOC in each monitoring location were so large that average values of water quality monitoring data might be not appropriate to determine the priority management areas among all 195 monitoring stations in Nakdoing river. Therefore we suggested two evaluation methods using each water quality data independently. In the first method the excess numbers of the BOD, T-P, and TOC concentrations comparing to the water quality standards in the medium-sized management areas in Nakdong river was evaluated for each monitoring station. In the second method the percentile ranks of the loading rates of the BOD, T-P, and TOC were obtained for each monitoring data. The two groups of the priority management areas determined by each method were compared and the water quality characteristics in Nakdoing river were investigated.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.2
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• pp.169-179
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• 1998

This paper was performed to estimate interrelations between humus level of sediments and nutrient release from sediments in Dae-cheong reservoir. For investigations, sediments were sampled in June and October, in 1997 at fish farms, embayment, and the main stream of Dae-cheong reservoir. Items for investigation are as follows; water content, weight loss on ignition(IG), porosities of sediments, contents of element such as hydrogen, nitrogen, carbon, and nutrient release rates. Water contents and porosities were measured to conjecture the physical trait and grain size trait. Weight loss on ignition was measured to determine the contents of organic substance. For determination of the humus level of sediments, carbon and nitrogen contents were measured by elemental analyzer. As a result of elemental analysis, C/N ratio was determined in the range of $3.0\~13.1$. From the elemental analysis, humus level of Dae-cheong reservoir sediment was estimated from mesohumic state to oligotrophic state. For the determination of nutrient release rate, $PO_4-P$ and $NH_4-N$ concentrations of interstitial water and overlying water were measured. By using the concentration difference between interstitial water and overlying water and using the Fick's diffusion law, the release rates of phosphorus and nitrogen from the sediment samples were calculated. Release rates of nutrients which directly influence to the water quality were $0.05\~8.63mgP/m^2day$ and $4.99\~36.56mgP/m^2day$. It was found that release rate was measured higher in the 1st sampling period than in the 2nd sampling period. For the determination of phosphorus content in sediment, TPs were measured in 807\~1542{\mu}g/g$ in the 1st samling period and $677\~5238{\mu}g/g$ in the End samling period. Phosphorus release rate and phosphorus content were not interrelated each other.

• Journal of Applied Biological Chemistry
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• v.59 no.1
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• pp.83-90
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• 2016

The aim of the present study was to evaluate the degree of metal contamination of the Turag River water and its suitability for irrigation. Twenty water samples were analyzed for physicochemical parameters and metals viz., calcium, magnesium, potassium (K), sodium, copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni). All water samples were slightly alkaline to alkaline. Regarding electrical conductivity (EC), all samples were suitable for crop in soils with moderate permeability and leaching. Water samples were medium salinity and low alkalinity hazard classes. In terms of total dissolved solids (TDS), all samples were classified as freshwater. As per sodium adsorption ratio (SAR) and soluble sodium percentage (SSP), all samples were classified as excellent. No residual sodium carbonate (RSC) was detected in any of the samples, indicating suitability for irrigation; and all samples were considered very hard. Cr and Mn contents in all samples were above FAO guideline values and, therefore, these metals were considered toxic. Zn, Cu, Pb, Cd, and Ni concentrations were below acceptable limit for irrigation and do not pose a threat to soil environment. Significant relationships were found between EC and TDS, SAR and SSP, SAR and RSC, and SSP and RSC. The combinations of ions such as K-Zn, K-Fe, K-Cu, K-Mn, K-Pb, Zn-Fe, Zn-Cu, Zn-Mn, Fe-Mn, Cu-Mn, Cu-Pb and Mn-Pb exhibited significant correlation. This study revealed that Turag River water samples are contaminated with Cr and Mn. This fact should not be ignored because water contamination by metals may pose a threat to human health through food chain.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.6
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• pp.17-25
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• 2003

The physical components of a river, such as water surface width/river width ratio, water level, and flow velocity vary according to different flowrates. Moreover, the riverside landscapes are greatly affected by the change of physical components of the stream or river. This paper provides an analysis of the influence of changing physical components of a river on the riverside landscape using a survey-based quantification method. The questionnaire was developed based on current literature, and was submitted to 326 people who each visited a representative station along the riverside.This survey was implemented three times at each representative station during periods of different flowrates. The results of this analysis and survey have Produced an understanding of the relationship between the variation of physical components and riverside landscapes. Survey results about the flow comparison are summarized as follows. Viewing riverside landscapes, most respondents are sensitive to the change of the flow velocity and prefer high water levels to low water levels. As a whole, respondents prefer abundant stream flows and moderate flow velocity in which they can perceive the flow of water. The minimum instream flows for riverside landscapes is estimated at each representative station by using a survey-based quantification method, and the estimated results of some representative stations were greater than the mean monthly flow at each station. The result of this analysis shows that establishing minimum instream flows for riverside landscapes is not only a technical problem, but also a legal problem. Therefore, in the to establish the instream flows in a river, the estimated results have to be considered as a relative standard. Regarding the survey results, respondents' satisfaction level didn't show any clear inclination according to the variation of various hydraulic properties. In determining the minimum instream flow using such an inquiry method, the structure of riverside scenery may vary according to the change of seasons or months. Therefore, to determine a consistent general inclination about the flow rate, it is necessary to have more detailed flow rates for each season or month combined with more inquiries.

• Journal of Environmental Science International
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• v.21 no.3
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• pp.277-287
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• 2012

The MFFn(Mass First Flush) was analyzed for various rainy events(monitoring data from 2008 to 2009) in Transportation area(Highway, National road, Trunk road). Estimated MFFn using SWMM was evaluated by comparison with observed MFFn. MFFn was estimated by varying n-value from 10% to 90% on the rainy events. The n-value increases, MFFn is closed to '1'. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good ($R^2$=0.89). Pollutants runoff loads by volume showed Highway 26.6%, National road 44.8%, Trunk road 35.0% at the MFF20(20% by total runoff). A case of MFF30, pollutants runoff loads by volume showed Highway 40.2%, National road 54.3%, Trunk road 46.8%. According to the results, Initial precipitation basis were Highway MFF30, National road MFF20, Trunk road MFF30 when the Non-Point source control facilities set up.

• Journal of environmental and Sanitary engineering
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• v.22 no.3
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• pp.13-26
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• 2007

Changes in the characteristics of dissolved organic matter was studied at selected stations in the Nakdong river basin using physical and chemical methods. Characteristics of dissolved organic matters were analysed and assessed. Production of disinfection byproducts were also investigated. 1. Result of relatedness study among each items of analyses showed that relatedness on BOD values were highest with cattle excrement treatment facilities where there is no synthetic organic materials and relatedness on $COD_{Mn}$ were highest at the mainstream Nakdong river. In case of $COD_{Cr}$ (which has more oxidative power than $COD_{Mn}$), the values were higher in the sidestreams indicating the higher content of recalcitrant compounds. The relatedness values for the $UV_{254}$ also showed higher values in the sidestreams and treatment facilities than mainstream indicating the presence of organic aromatic compounds. 2. Ratio of DOC on total organic carbon were higher in the mainstream which is attributable to the influent particulate organic materials produced by agricultural activities. The values were 10-15% higher in the mainstream compared with sidestreams. 3. Result of biodegradability test indicate that concentrations of recalcitrant DOC were higher in the sidestreams than in the mainstream. The values of recalcitrant DOC were higher with the forest stream indicating the effect of soil oriented humic substances. 4. Result of THM production test carried out at 10 stations in the Nakdong river show that $CHCl_3$ was detected with the highest value and the value was highest at Waekwan station.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.E
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• pp.55-62
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• 1995

The topographic influences for the hydraulic characteristics in the estuary were studied by the hydraulic model test. The upstream boundary is set up at the Kumkang estuary dike and the downstream boundary at the Kunsan outer port. The geometrical model scales in horizontal and vertical are 1/300 and 1/100 respectively so that the distorted ratio is 3. If there is no or little river flow through the gate, the highest water levels are varied with $\pm$ 5cm compared with those before the project. If there is a flood flow through the gate, the highest water levels in front of the estuary dike are reduced 5~2Ocm depending on the frequency of flood compared with those before the project. This means that there is no important risk of excessive water level rise after the dredging.