• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.345-354
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• 2006

Drought brings on long term damage in contrast to flood, on economic loss in the region, and on ecologic and environmental disruptions. Drought is one of major natural disasters and gives a painful hardship to human beings. So we have tried to quantify the droughts for reducing drought damage and developed the drought indices for drought monitoring and management. The Palmer's drought severity index (PDSI) is widely used for the drought monitoring but it has the disadvanges and limitations in that the PDSI is estimated by considering just climate conditions as pointed out by many researchers. Thus this study uses the SWAT model which can consider soil conditions like soil type and land use in addition to climate conditions. We estimate soil water (SW) and soil moisture index (SMI) by SWAT which is a long term runoff simulation model. We apply the SWAT model to Soyang dam watershed for SMI estimation and compare SMI with PDSI for drought analysis. Say, we calibrate and validate the SWAT model by daily inflows of Soyang dam site and we estimate long term daily soil water. The estimated soil water is used for the computation of SMI based on the soil moisture deficit and we compare SMI with PDSI. As the results, we obtained the determination coefficient of 0.651 which means the SWAT model is applicable for drought monitoring and we can monitor drought in more high resolution by using GIS. So, we suggest that SMI based on the soil moisture deficit can be used for the drought monitoring and management.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1505-1515
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• 2023

As extreme weather events caused by climate change are occurring around the world, blue carbon has recently been gaining attention as a carbon sink. Blue carbon has been officially recognized by the Intergovernmental Panel on Climate Change (IPCC) as a means of reducing greenhouse gases, and various studies are underway to discover new blue carbon sources both domestically and internationally. Domestic blue carbon research is centered on carbon absorption and storage in tidal flats, which account for most of the coastal wetlands, but there is a lack of research on spatial information. This study utilized the carbon storage of tidal flats from previous studies and converted it into location and spatial information for each basin of the Geumgang and Nakdong rivers. In addition, a proxy value of carbon storage per area by basin was calculated to compare and analyze the total carbon storage of various tidal flats in Korea and abroad. As a result of the analysis, both the Geumgang and Nakdong River basins showed different amounts of carbon storage depending on the tidal flats data, with the highest amount in the Geumgang basin coming from the National Ocean Survey (469,810.1 Mg C) and the highest amount in the Nakdong River basin coming from the Ministry of Environment (217,145.01 Mg C). The results of this study can be used as a basis for future research on the establishment of domestic blue carbon spatial information.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1059-1069
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• 2023

Dam-break flow occurs when an elevated dam suddenly collapses, resulting in the catastrophic release of rapid and uncontrolled impounded water. This study compares laminar and turbulent closure models for simulating three-dimensional dam-break flows using OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) model, specifically the k-ε model, is employed to capture turbulent dissipation. Two scenarios are evaluated based on a laboratory experiment and a modified multi-layered block obstacle scenario. Both models effectively represent dam-break flows, with the turbulent closure model reducing oscillations. However, excessive dissipation in turbulent models can underestimate water surface profiles. Improving numerical schemes and grid resolution enhances flow recreation, particularly near structures and during turbulence. Model stability is more significantly influenced by numerical schemes and grid refinement than the use of turbulence closure. The k-ε model's reliance on time-averaging processes poses challenges in representing dam-break profiles with pronounced discontinuities and unsteadiness. While simulating turbulence models requires extensive computational efforts, the performance improvement compared to laminar models is marginal. To achieve better representation, more advanced turbulence models like Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS) are recommended, necessitating small spatial and time scales. This research provides insights into the applicability of different modeling approaches for simulating dam-break flows, emphasizing the importance of accurate representation near structures and during turbulence.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.769-781
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• 2007

Factor analysis has been usually employed in reducing quantity of data and summarizing information on a system or phenomenon. In this analysis methodology, variables are grouped into several factors by consideration of statistic characteristics, and the results are used for dropping variables which have lower weight than others. In this study, factor analysis was applied for extracting primary factors influencing multi-dam system operation in the Han River basin, where there are two multi-purpose dams such as Soyanggang Dam and Chungju Dam, and water has been supplied by integrating two dams in water use season. In order to fulfill factor analysis, first the variables related to two dams operation were gathered and divided into five groups (Soyanggang Dam: inflow, hydropower product, storage management, storage, and operation results of the past; Chungju Dam: inflow, hydropower product, water demand, storage, and operation results of the past). And then, considering statistic properties, in the gathered variables, some variables were chosen and grouped into five factors; hydrological condition, dam operation of the past, dam operation at normal season, water demand, and downstream dam operation. In order to check the appropriateness and applicability of factors, a multiple regression equation was newly constructed using factors as description variables, and those factors were compared with terms of objective function used in operation water resources optimally in a river basin. Reviewing the results through two check processes, it was revealed that the suggested approach provided satisfactory results. And, it was expected for extracted primary factors to be useful for making dam operation schedule considering the future situation and previous results.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.4
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• pp.267-273
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• 1977

Rainbow trout were reared in a small indoor aquarium which was equipped with a simple recirculating biofilter combined with a small amount of inflowing water for 199 days from April 25 to November 10, 1977 in Busan where very hot summer air temperature is encountered, and results obtained were promissing as following; 1. The aquarium has dimensions of $1m\;\times\;1m\;\times\;67cm(depth)$, and a bottom center sedimentation chamber of conical type through which out-flowing water is pushing fecal matter and other detritus outward. The conical sedimentation chamber measures 20 cm depth and 20 cm diameter at its upper mouth and tapers to the bottom end which is connected to 4 cm diameter draining pipe. The draining pipe goes through under the tank and then is elevated on the side. The water depth was maintained at about 40 cm depth by adjusting the heigh of draining pipe. The filter bed contained 16 l of $3\~5\;mm$ zeolite gravels, and water circulation rate was about 1030 l/hr. 2. Continuous inflowing water resulted in a good elimination of waste materials through its outflowing water thus reducing waste loading in the filter. 3. Mean temperature of water in the rearing aquarium containing about 400 l water volume was maintained at around 20 to $22^{\circ}C$ by 0.59 l/min of the inflowing well water which usually maintained the temperature of $17^{\circ}C$ during the hot summer season from the first of July to the first of October when the 10-days-mean air temperature ranged from $20^{\circ}\;to\;27.3^{\circ}C$ $(total\;mean\;24.6^{\circ}C) $ and under this condition the fish continued normal growth. 4. The production per 1 l/min of inflowing water with this simple biofilteration reached 30 hg. 5. The total cost including all feed and power during this experimental rearing period fell well within the economic establishment and if the feed and filteration system are improved the benefit-cost ratio will be much increased.

• Food Science and Preservation
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• v.21 no.3
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• pp.404-411
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• 2014

This study was carries out to analyzed the antioxidant activities of extracts extrated from soybean and small black bean for the development of functional materials. Yields of hot-water and ethanol extracts were higher in the soybean than small black bea, and yields of hot-water extracts were higher than ethanol extracts. Total phenol contents were 26.22 mg/g in the ethanol extracts from small black bean, and were higher than those in the soybean extracts. Total flavonoid contents were 30.52 mg/g of hot-water extracts from small black bean. The EDA values were increased by the increase of extract concentrations and were high in the hot-water and ethanol extracts from bean and small black bean The EDA values was high in the extracts of small black bean from low concentrations. The SOD-like activity of hot-water and ethanol extracts from small black bean was higher than those of soybean extracts. The SOD-like activity was 73%, 62% of the hot-water and ethanol extracts from small black bean in 10 ml/mL extract concentration, respectably. The nitrite scavenging ability was high extracts from soybean was 47.60% in pH 1.2, Those of hot-water extracts were higher than in ethanol extracts in 10 ml/mL extract concentration. The xanthine oxidase inhibitory activities were increased by the increase of extract concentrations and were high in ethanol extracts from small black bean of low concentration. The xanthine oxidase inhibitory activities was hot-water extracts from soybean were higher than 5 ml/mL extract concentration than those of other extracts. The inhibitory activities of tyrosinase were increased by increase of extract concentrations and were high each other 42.05%, 45.67% of hot-water and ethanol extracts from small black bean in 10 ml/mL extract concentration. Reducing power was increased by increase of extract concentrations in extracts of small black bean, and were high more than double in hot-water and ethanol from small black bean than extracts of soybean.

• Preventive Nutrition and Food Science
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• v.6 no.3
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• pp.142-146
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• 2001

This study was performed to investigate chemical and functional properties of Glechoma hederacea leaves in respect to its potential use as food material or as a medicinal herb. The chemical compositions on a dry harris were 20.38% in protein, 3.96% in fat, 59.58% in carbohydrate, 15.78% in ash, 5.36% in reducing sugar, 14.11% in total sugar and 0.26% in polyphenol, respectively. The free sugars were mainly comprised of glucose, fructose and sucrose. In fatty acids compositiosn, linolenic acid showed the highest concentration at 45%, while the ratios of saturated to unsaturated fatty acids were 1 : 1.91. Seventeen kinds of total amino acids were determined, with the highest concentration (2,465.71 mg%) of glutamic acid. Among the free amino acids, praline showed the highest concentration (260.09 mg%), followed by glutamine, $\alpha$ -amino adipic acid, glutamic acid and valine. The contents of major minerals were 647.32 mg% in Na, 597.53 mg% in K and 239.75 mg% in Ca. The antioxidative activity of 10% water extract was similar to that of 50 ppm tocopherol. The nitrite scavenging ability reached the highest bevel at pH 1.2 and the lowest at pH 6.0.

• The KSFM Journal of Fluid Machinery
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• v.11 no.5
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• pp.44-49
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• 2008

As the alternative energy, renewable energy should have been developing by many techniques, in order to substitute the fossil fuel which will be disappeared in the near future. One of the small hydropower generator, main concept of tubular turbine is based on using the different water pressure levels in pipe lines, energy which was initially wasted by using a reducing valve at the end of the pipeline, is collected by turbine in the hydro power generator. A propeller shaped hydro turbine has been used in order to use this renewable pressure energy in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the guide vane opening angle are examined in detail. First, it ensures the reliance of CFD by that of compared with experiment data. After all, the results of performance characteristics of the CFD and experiment show to confirm the data that power, head and efficiency of less than 4%, 2% and 5% respectively. Moreover influences of pressure, tangential and axial velocity distributions on turbine performance are investigated.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3215-3220
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• 2007

Gas-liquid separator has been designed for the sake of reducing expenses associated with production operations. To date, a number of gas-liquid separators have been installed and put to use for various applications. Despite the advantages of simple and compact configuration of separator with no moving part, its efficient operation is limited in terms of total pressure losses, separation performance and flow-induced noise and vibration, which are closely associated with the very complicated flow phenomena involved. In the present study, a gas-liquid centrifugal separator with a swirl vane is investigated for the purpose of water separation from compressed moisture air. The 3D Navier-Stokes equations are numerically solved using a fully implicit finite volume scheme. Based upon the obtained solutions, tangential velocities, centrifugal forces, vortices and total pressure losses are analyzed to find out the best design parameters. From the present study, several attempts are made to improve the performance of conventional separators of centrifugal type.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2839-2844
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• 2007

Micro hydraulic power generation of which the output is less or equal to a 100kW is attracting considerable attention. This is because of its small, simple, renewable, and abundant energy resources. By using a small hydropower generator of which main concept is based on using the different water pressure levels in pipe lines, energy which was initially wasted by use of a reducing valve at the end of the pipeline, is collected by turbine in the hydropower generator. A propeller shaped hydroturbine has been used in order to use this renewable pressure energy. In this study, in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the flow coefficient are examined in detail. Moreover influences of pressure and velocity distributions with the variations of runner vane angle on turbine performance are investigated by using a commercial CFD code.