Ansan, South Korea
Ansan, South Korea

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Jeong H.J.,Seoul National University | Yoo Y.D.,Seoul National University | Kang N.S.,Seoul National University | Rho J.R.,Kunsan National University | And 4 more authors.
Aquatic Microbial Ecology | Year: 2010

A bloom-forming dinoflagellate was isolated from coastal waters in western Korea during a red tide event in March 2008 and clonal cultures were established. The dinoflagellate was identified as Gymnodinium aureolum based on morphological and genetic analyses (GenBank accession no. FN392226). We report here for the first time that the red-tide dinoflagellate G. aureolum, which has previously been thought to be exclusively autotrophic, is a mixotrophic species. G. aureolum fed on algal prey using a peduncle. Among the algal prey provided, G. aureolum ingested heterotrophic bacteria, the cyanobacterium Synechococcus sp., and small algal species that had equivalent spherical diameters (ESDs) of ≤11.5 μ. However, it did not feed on larger algal species (ESD ≤12 μ) or the small diatom Skeletonema costatum. The specific growth rates for G. aureolum on the cryptophyte Teleaulax sp. increased continuously with increasing mean prey concentration before saturating at prey concentrations of ca. 190 ng C ml-1 (11 050 cells ml-1). The maximum specific growth rate (mixotrophic growth) of G. aureolum on Teleaulax sp. was 0.169 d-1, at 20°C under a 14:10 h light:dark cycle of 20 μE m-2 s-1, while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.120 d-1. The maximum ingestion and clearance rates of G. aureolum on Teleaulax sp. were 0.058 ng C grazer-1 d-1 (3.4 cells grazer-1 d -1) and 0.003 μl grazer-1 h-1, respectively. The calculated in situ grazing coefficient for G. aureolum on co-occurring cryptophytes ranged up to 0.498 d-1. Bioassay results indicated that this strain of G. aureolum is not toxic. Results of the present study suggest that G. aureolum has a potentially considerable grazing impact on algal populations. © Inter-Research 2010.

Lee S.-H.,Texas A&M University | Yoo S.-H.,Chonnam National University | Choi J.-Y.,Seoul National University | Shin A.,Rural Research Institute
Irrigation and Drainage | Year: 2016

Trading in crops can be regarded as the primary source of water demand in terms of virtual water trade, and the main importers would have to consider the trading in crops from a water management perspective. The aim of this paper was to evaluate the dependency and intensity of the virtual water trade in Korea. The virtual water trade values of 41 crops were quantified from 2006 to 2010. About 9.5% of global blue water trade was captured by Korea through maize trade. In addition, we evaluated the water dependency and trade intensity of the virtual water trade. Water dependency was evaluated by examining the proportions of external to internal water footprints. Korea exhibited the highest water dependency of 99%, followed by maize and pulse crops. Virtual water trade intensity indicates the importance of trading partners. The results show that the USA and China have been the most important trading partners, and the trade intensity with Romania, Ukraine and Australia has increased from 2006 to 2010. These results, such as water dependency and trade intensity of virtual water trade, should be useful indices for sustainable crop trade and water management in Korea. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Lee S.,Louisiana State University | Lee G.,Rural Research Institute | Kam S.I.,Louisiana State University
Transport in Porous Media | Year: 2014

Among numerous foam applications in a wide range of disciplines, foam flow in porous media has been spotlighted for improved/enhanced oil recovery processes and shallow subsurface in situ NAPL (non-aqueous phase liquid) remediation, where foams can reduce the mobility of gas phase by increasing effective gas viscosity and improve sweep efficiency by mitigating subsurface heterogeneity. This study investigates how foams interact with and displace oleic contaminants in remediation treatments by using MoC (Method of Characteristics)-based three-phase fractional flow theory. Six different scenarios are considered such as different levels of foam strength (i.e., gas mobility reduction factors), different initial conditions (i.e., initially oil/water or oil/water/gas present), foam stability affected by water saturation (Sw) and oil saturation (So), and uniform versus non-uniform initial saturations. The process is analyzed by using ternary diagrams, fractional flow curves, effluent histories, saturation profiles, time-distance diagrams, and pressure and recovery histories. The results show that the three-phase fractional flow analysis presented in this study is robust enough to analyze foam-oil displacements in various conditions, as validated by an in-house numerical simulator built in this study. The use of numerical simulation seems crucial when the foam process becomes very complicated and faces multiple possible solutions. © 2013 Springer Science+Business Media Dordrecht.

Cho J.,Rural Research Institute | Bosch D.,U.S. Department of Agriculture | Vellidis G.,University of Georgia | Lowrance R.,U.S. Department of Agriculture | Strickland T.,U.S. Department of Agriculture
Hydrological Processes | Year: 2013

Simulation of watershed scale hydrologic and water quality processes is important for watershed assessments. Proper characterization of the accuracy of these simulations, particularly in cases with limited observed data, is critical. The Soil & Water Assessment Tool (SWAT) is frequently used for watershed scale simulation. The accuracy of the model was assessed by extrapolating calibration results from a well studied Coastal Plain watershed in Southwest Georgia, USA, to watersheds within the same geographic region without further calibration. SWAT was calibrated and validated on a 16.7-km2 subwatershed within the Little River Experimental Watershed by varying six model parameters. The optimized parameter set was then applied to a watershed of similar land use and soils, a smaller watershed with different land use and soils and three larger watersheds within the same drainage system without further calibration. Simulation results with percent bias (PB) ±15%≤PB<±25% and Nash-Sutcliffe efficiency (NSE) 0.50

Kim Y.-J.,Samsung | Kim H.-D.,Rural Research Institute | Jeon J.-H.,Andong National University
Water (Switzerland) | Year: 2014

The HSPF-Paddy model was applied to the Bochung watershed in Korea to compare water budget components by the land use types under the Asian monsoon climate. The calibration of HSPF-Paddy during 1992-2001 with PEST, a package program to optimize HSPF, and validation during 1985-1991 were carried out. The model efficiencies for monthly stream flow are 0.85 for calibration and 0.84 for validation. The simulation of annual mean runoff met the criteria of water budget analysis with the acceptable error level (less than 10 percent mean error). The simulation of the movement of water from paddy rice field to watershed was successful, and application of HSPF-Paddy coupled with PEST was able to improve accuracy of model simulation with reduced time and efforts for model calibration. The results of water budget analysis show that most of the outflow (86%) for the urban area occurred through surface runoff, showing the highest rate among the land use types compared. Significant amounts of water are irrigated to paddy rice fields, and the runoff depth as well as evapotranspiration from paddy rice field is higher than other land use types. Hydrological characteristic of paddy rice field is that most of water movement occurred at the surface area, resulting from the low infiltration rate and manning's coefficient, as well as ponded water throughout the growing season. Major impact on input and output of water were precipitation and runoff, respectively, influenced by an Asian monsoon climate. © 2014 by the authors.

Jung J.-S.,Rural Research Institute | Jung J.-S.,Hanyang University | Cho Y.-S.,Hanyang University
Journal of Coastal Research | Year: 2013

In this study, the variation of flood water level inside the Saemangeum Embankment is studied. In particular, the maximum flood level inside the Embankment is investigated for design of the land reclamation level. Water level inside the Embankment may be affected by flooding from connected rivers, tides and discharges through gates. The tidal range outside Embankment is about 6.0∼7.5m. The water level is numerically simulated by using a commercial hydrodynamic model: Delft3D-Flow. By analyzing measured tidal data measured over 31 years (1981-2011), the smallest tidal difference is selected for simulations. The maximum flood level inside Embankment generally increases as the tidal difference decreases because the sea level outside Embankment is relatively high during the ebb tide. © Coastal Education & Research Foundation 2013.

Choi J.-D.,Kangwon National University | Park W.-J.,Kangwon National University | Park K.-W.,Rural Research Institute | Lim K.-J.,Kangwon National University
Paddy and Water Environment | Year: 2013

An experimental study on the System of Rice Intensification (SRI) methods was conducted to investigate the feasibility of using them to conserve irrigation water and reduce non-point source (NPS) pollution in Korea. Eight experimental runoff plots were prepared at an existing paddy field. Runoff and water quality were measured during the 2010 growing season in which a Japonica rice variety was cultivated. The irrigation water requirements of SRI methods and conventional (CT) plots were 243. 2 and 547. 3 mm, respectively, meaning that SRI methods could save 55. 6% of irrigation water. Runoff from SRI methods plots decreased 5-15% compared with that from CT plots. Average NPS pollutant concentrations in runoff from SRI methods plots during rainfall-runoff events were SS 89. 4 mg/L, CODCr 26. 1 mg/L, CODMn 7. 5 mg/L, BOD 2. 0 mg/L, TN 4. 2 mg/L, and TP 0. 4 mg/L. Except for CODCr and TN, these concentrations were significantly lower than those from CT plots. Measured pollution loads from SRI methods plots were SS 874 kg/ha, CODCr 199. 5 kg/ha, CODMn 47 kg/ha, BOD 13 kg/ha, TN 36. 9 kg/ha, and TP 2. 92 kg/ha. These were 15. 8-44. 1% lower than those from CT plots. Rice plants grew better and healthier in SRI methods plots than in CT plots. However, rice production from SRI methods plots ranged between 76 and 92% of that of CT plots because the planting density in SRI methods plots was too low. It was concluded that SRI methods could be successfully adopted in Korea and could help save a significant amount of irrigation requirement in paddies and reduce NPS pollution discharge. © 2012 Springer-Verlag.

Kim J.-G.,Gangneung - Wonju National University | Ryoo Y.-S.,Rural Research Institute
Transactions of the Korean Institute of Electrical Engineers | Year: 2015

Recently, many advanced countries are devoted to the development of eco-friendly new-renewable energy to prepare for the depletion of resources. Korea belongs to the absolute lack of energy to import from abroad 97% of energy use. So, development and supply of eco-friendly energy such as small hydro power has been required even more. Our country has a large number of small-sized reservoirs and dams. So, hydro generator has been installed at the small reservoirs and dams with the economy. Since the discharge flow of agricultural reservoir is not constant, the guide vane of wicket gate is used for adjusting the output of the generator. In this study, we have confirmed that the guide vane control of water turbine under the conditions of flow variation will improve the output and efficiency of induction generator. Copyright © The Korean Institute of Electrical Engineers.

Ha T.,Kangwon National University | Park C.,Kangwon National University | Yoon J.,Rural Research Institute | Heo K.-Y.,Korea Advanced Institute of Science and Technology
Journal of Coastal Research | Year: 2016

In recent years, the eastern coast of Korea has been experiencing frequent large swell waves during winter. These waves, occasionally higher than 3 m, rarely occurred until recently and now cause severe casualties, damage to coastal structures, and extensive beach erosion along the eastern coast of the country. Therefore, the urgency for appropriately predicting large swell waves affecting these areas has increased. A convenient forecasting source is a numerical wave prediction system running in an operational mode. Since 2009, Korea Institute of Ocean Science and Technology (KIOST) has been developing and improving Korea Operational Oceanographic System (KOOS), funded by the Ministry of Oceans and Fisheries (MOF). The project aims at developing an integrated operational oceanographic system providing nowcasts and forecasts of ocean information around the Korean Peninsula. This study introduces an operational wave forecasting system using high-resolution multigrids, developed for its implementation in KOOS. A series of numerical experiments were conducted on previous cases of large swell waves along the eastern coast of Korea, using weather hindcasting products of KOOS. The new system was evaluated by comparing the obtained numerical results with data from the previous wave forecasting system and available observations. The wave forecasting system proposed yielded good qualitative and quantitative predictions for large swell waves in different locations. Furthermore, the obtained numerical results highly agree with available observational data. © Coastal Education and Research Foundation, Inc. 2016.

Heo N.,Rural Research Institute
Irrigation and Drainage | Year: 2014

Korea's massive agricultural projects have frequently exceeded the ecosystem's resilience, resulting in many environmental problems. Korea sought to remedy this situation via policy and adopted an environmental impact assessment (EIA) system. However, the EIA system needed to be modified for the agricultural sector. This is because agricultural development plans are somewhat different from urban or industrial development plans in terms of impact intensity and their multifunctional traits. Since adopting the system in 1977, Korea has gradually improved its EIA system in favour of wise use and strong implementation in the agricultural sector. Even though there is much that can still be improved upon in terms of compromise by stakeholders (including farmers), Korea has recently achieved some success by providing a unified channel for EIA work, an interactive platform for stakeholders, a specific EIA guideline suitable for the agricultural sector, and strong enforcement of EIA implementation. Korea's EIA development with respect to the agricultural sector can be a useful reference for all developing countries that are eager to realize systematic sustainable agricultural development. Copyright © 2014 John Wiley & Sons, Ltd.

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