• Ocean Systems Engineering
• /
• v.3 no.4
• /
• pp.327-348
• /
• 2013

An Oscillating Water Column (OWC) is a relatively practical and convenient device that converts wave energy to a usable form, which is electricity. The OWC is kept inside a fixed truncated vertical cylinder, which is a hollow structure with one open end submerged in the water and with an air turbine at the top. This research adopts potential theory and Galerkin methods to solve the fluid motion inside the OWC. Using an air-water interaction model, OWC design for energy extraction from regular wave is also explored. The hydrodynamic coefficients of the scattering and radiation potentials are solved for using the Galerkin approximation. The numerical results for the free surface elevation have been verified by a series of experiments conducted in the University of New Orleans towing tank. The effect of varying geometric parameters on the response amplitude operator (RAO) of the OWC is studied and modification of the equation for evaluating the natural frequency of the OWC is made. Using the model of air-water interaction under certain wave parameters and OWC geometric parameters, a computer program is developed to calculate the energy output from the system.

• Journal of Korea Water Resources Association
• /
• v.45 no.2
• /
• pp.229-242
• /
• 2012

This study presents a physical habitat modeling of adult Zacco platypus in a reach of the Dalcheon Stream located downstream of the Goesaan Dam. CASiMiR model is used to estimate habitat suitability index based on the fuzzy logic. Results are compared with those from River2D model, which uses habitat preference curve for habitat suitability index. Hydraulic data simulated by River2D are used as input data for CASiMiR model after verification against field measurements. The result shows that the habitat suitability of the adult Zacco platypus is maximum around the riffle area located upstream of the bend. CASiMiR and River2D estimate the maximum weighted usable areas at the discharge rates of 7.23 $m^3/s$ and 9.0 $m^3/s$, respectively. Overall comparison of the two models employed in this study indicates that CASiMiR model overestimates the weighted usable area by 0.3~25.3% compared with River2D model in condition of drought flow (Q355), low flow (Q275), normal flow (Q185), and average-wet flow (Q95).

• Journal of Korea Water Resources Association
• /
• v.56 no.9
• /
• pp.553-562
• /
• 2023

The Gobiobotia naktongensis is a species endemic to Korea, and it has recently been designated as a class I endangered species of freshwater fish. Naeseong Stream, one of the tributaries of the Nakdong River, where the Gobiobotia naktongensis was first discovered, provided an optimal habitat for the Gobiobotia naktongensis in the past with fine sand beds and riffle. Currently, due to the construction of Yeongju Dam and the excessive dredging of river channels by the local government, the riverbed armoring in the downstream area of the dam is undergoing rapid changes, and as a result, the habitat environment of the Gobiobotia naktongensis is deteriorating. In this study, the variations of the habitat suitability of the Gobiobotia naktongensis due to the change in the riverbed grain size of the Naeseong Stream were analyzed based on the WUA (weight usable area) using the physical habitat model, River2D. The study domain is the reach from Seoktap Bridge to Hoeryong Bridge downstream of Yeongju Dam. The change in riverbed grain size was analyzed using D50 acquired in 2010 and 2020, respectively. The substrate grain size of Naeseong Stream in 2020 was thicker than that in 2010, and the riverbed coarsening phenomenon was evident overall. As a result of the River2D analysis, the area in which the Gobiobotia naktongensis could inhabit was only about 0.75% in 2010 compared to the entire area of the flow, and even this decreased to 0.55% in 2020 due to riverbed armoring.

• Journal of Ginseng Research
• /
• v.8 no.1
• /
• pp.65-74
• /
• 1984

This experiment was carried out to study the effects of light intensity and soil water regimes on the growth of ginseng seedling. The results were as follows: 1. The maximum light intensity and optimum temperature in 1,le photosynthesis of ginseng seedling were 10,000 lux and 23 $^{\circ}C$. Respiration rate was increased at high temperature. 2. Air and soil temperature under the shading were increased as the increase of light intensity but soil water contents were decreased as the increase of light intensity, whereas air and soil temperature were decreased as the increase of precipitation under the shade b5: soil water contents were increased as the increase of precipitation under the shade. 3. The higher the transmittance of the shade, the greater the specific leaf weight (S.L.W.) and stomatal density. In contrast, however, the contents of total chlorophyll, chlorophyll a and b, and stomatal length was decreased. There was no any significant difference light intensity of the a/b ratio of chlorophyll. 4. The highest photosynthesis was occurred in ginseng leaves grown under the shade 5% L.T.R. and net photosynthesis rates increased with increasing soil water contents. 5. Optimum condition for usable seedling yield were 5% L.T.R. and 3.3% precipitation under the shade. Useless seedling increased with increasing precipitation under the shade.

• The KSFM Journal of Fluid Machinery
• /
• v.20 no.2
• /
• pp.69-74
• /
• 2017

Sodium hypochlorite, used as water disinfectant, is generated by electrolysis of salt. Compared to chlorine gas disinfection, it is free from high-pressure gas regulation and does not generate toxic gas, so it is increasingly used as a safe disinfectant. Despite these advantages, the concentration of sodium hypochlorite decreases with temperature during long-term storage, and the amount of chlorate increases when a large amount is added, it has mainly been applied to small-scale waterworks. To solve this problem, high sodium hypochlorite generation was developed. In this study, the changes of concentration and chlorate of sodium hypochlorite with time has been studied. As a result of the test, it was found that the usable period of sodium hypochlorite produced at a certain temperature or less was increased from 1.5 days to 13 days. Overall, sodium hypochlorite can be applied even in large-scale waterworks, which makes operation more stable and also reduces the disinfection byproducts, thus it contributed greatly to securing water quality.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.334-337
• /
• 2003

The results of this numerical model is usable to analysis for the phenomena of precipitation during the periods of a rainy season in the Northeastern Asia. Case l(start of rainy season) dominates over precipitation by the processing of convection from the equator region through the East China region, and then the most of water vapor is transported by the processing of advection from the India-monsoon region to this study region. Case 2(heavy rainy season) faints precipitation by the processing of convection in the Korean peninsula, but dominates precipitation by the processing of microphysics. the water vapor originates from the India-monsoon region.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.39 no.3
• /
• pp.52-63
• /
• 1997

A CELTHYM(CEll-based Long-Term HYdrologic Model), a pre-processor and a post processor that can be integrated with geographic information system ( GIS) were developed to predict the stream flow of the small watershed. The CELTHYM was calibrated and verified with measured runoff data at the WS # 1 and WS # 3 that are testing water sheds of Seoul Nat' 1 Univ., dept. of agricultural engineering, in Ansan city, Kyunggi province, South Korea. The results of tests are in good agreement with measured data and usable for other application, but the component of direct runoff and water balance on paddy fields need more study.

• Journal of Korean Society of Water and Wastewater
• /
• v.31 no.5
• /
• pp.421-430
• /
• 2017

In this study, a model was developed to predict for Disinfection By-Products (DBPs) generated in water supply networks and consumer premises, before and after the introduction of advanced water purification facilities. Based on two-way ANOVA, which was carried out to statistically verify the water quality difference in the water supply network according to introduce the advanced water treatment process. The water quality before and after advanced water purification was shown to have a statistically significant difference. A multiple regression model was developed to predict the concentration of DBPs in consumer premises before and after the introduction of advanced water purification facilities. The prediction model developed for the concentration of DBPs accurately simulated the actual measurements, as its coefficients of correlation with the actual measurements were all 0.88 or higher. In addition, the prediction for the period not used in the model development to verify the developed model also showed coefficients of correlation with the actual measurements of 0.96 or higher. As the prediction model developed in this study has an advantage in that the variables that compose the model are relatively simple when compared with those of models developed in previous studies, it is considered highly usable for further study and field application. The methodology proposed in this study and the study findings can be used to meet the level of consumer requirement related to DBPs and to analyze and set the service level when establishing a master plan for development of water supply, and a water supply facility asset management plan.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.6 no.1
• /
• pp.41-50
• /
• 2003

The feasibility as floricultural crops and water garden plant materials of Korean native water plants was investigated. Propagation type, growing and flowering time were observed for development as water garden, interior aquarium plant and water purification materials. Flowering time of the water plant was 7 species in May, 28 species in June, 49 species in July, 55 species in August, 47 species in September, and 17 species in October. Beautiful flowering water plants were Nymphaeaceae, Nymphoides peltata, Nymphoides indica, Monochoria korsakowii, Iris pseudacorus, Iris laevigata, and etc. Ornamental leafy water plants were Ceratopteris thalictroides, Ludwigia ovalis, Myriophyllum verticillatim, Limnophila sessiliflora, Blyxa aubertii, Blyxa echinosperma, Vallisneria asiatica, Hydrilla verticillata and Eleocharis acicularis etc. Isoetes japonica, Isoetes coreana and Isoetes sinensis were propagated by spore. Blyxa aubertii, Blyxa echinosperma, Myriophyllum verticillatim, Nuphar japonicum, Nelumbo nucifera, Ottelia alismoides, Sagittaria aginashi, Trapa japonica, and Trapa natans were propagated by seed. Persicaria amphibia, Ceratophyllum demersum (hornwort), Myriophyllum verticillatim, Myriophyllum spicatum, Oenanthe javanica, Potamogeton crispus, Hydrilla verticillata and Acorus calamus were propagated by division. And Vallisneria asiatica, Hydrilla verticillata and Phragmites japonica were propagated by runner. Ceratophyllum demersum (hornwort), Myriophyllum verticillatim, Myriophyllum spicatum, Limnophila sessilifera were propagated by adventitious bud. Ceratopteris thalictroides was propagated by leaf cutting. The 35 genera, 68 species of water plants were available for horticultural use. The 45 species such as Iris laevigata, Eleocharis acicularis, Menyanthes trifoliata, Nymphaea minima, Nuphar pumilum, Nymphoides coreana, Nymphoides peltata, Nymphoides indica, Nymphaea tetragona (water lily), and Typha latifolia could be use for water garden plant. The 21 species such as Limnophila sessilifera, Vallisneria asiatica, Ceratophyllum demersum and Hydrilla verticillata available for indoor aquarium. The 19 species such as Ottelia alismoides, Oenanthe javanica, Limnophila sessilifera and Blyxa echinosperma could be culture in container. The 27 species such as Trapa japonica, Trapa incisa, Phramites commuris (reed), Phragmites japonica, and Zizania latifolia were usable for water purification plant materials.

• Journal of Korea Water Resources Association
• /
• v.52 no.spc2
• /
• pp.811-822
• /
• 2019

Environmental flows in the downstream sections of Yongdam Dam, Wonju Stream Dam, and Hongcheon River were estimated with selected target fish species such as Nigra for the site of Yongdam Dam, Splendidus for the site of Wonju Stream Dam, and Signifer for the site of Hongcheon River by considering endangered and domestic species. Physical habitat analysis was performed to estimate environmental flows for the study sites by applying the Physical Habitat Simulation (PHABSIM) and RIVER2D which combined hydraulic and habitat models. Based on the monitored data for ecological environment, the Habitat Suitability Index (HSI) for the target species was estimated by applying the Instream Flow and Aquatic Systems Group (IFASG). In particular, based on the result of fish monitoring, the HSI for each stage of the growth for target species was analyzed. As a result, the Weighted Usable Area (WUA) was maximized at $4.9m^3/s$ of flow discharge during spawning, $5.8m^3/s$ during the period of juvenile, and $8.9m^3/s$ during the adult fish season at the downstream section of Yongdam Dam. The result of the Wonju Stream Dam showed an optimal environmental flow of $0.4m^3/s$, $1.0m^3/s$, and $1.5m^3/s$ during the period of spawning, juvenile, and adult. The habitat analysis for the site of Hongcheon River, which is a non-regulated stream, produced an optimum environmental flow of $5m^3/s$ in the spawning period, $4m^3/s$ in the juvenile stage and $6m^3/s$ in the adult stage.