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Ansan, South Korea

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. Source

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. Source

Seo I.-H.,Seoul National University | Lee I.-B.,Seoul National University | Shin M.-H.,Korea Rural Community and Agriculture Corporation | Lee G.-Y.,Rural Research Institute | And 7 more authors.
Transactions of the ASABE | Year: 2010

The Saemangeum reclaimed land located on the western coast of Korea is one of the world's largest reclamation projects, developing 40,100 ha of land area. After construction of sea dikes in 2006, the exposed land area has been increasing in relation to the water level height. Dust from the exposed land, containing high amounts of salt, disperses to nearby areas. The dust is harmful to human and animal health as well as to plant growth. Therefore, an estimation of fugitive dust dispersion is necessary for the development of plans to manage the problem. Field experiments are ideal for understanding aerodynamic phenomena. However, finding a correlation between weather conditions and dust dispersion is a difficult task due to limited measuring points. Moreover, weather conditions are unstable, unpredictable, and cannot be artificially controlled. Field experiments also involve high labor and time expenses. To overcome these limitations, a computational fluid dynamics (CFD) model has been developed to analyze dust dispersion phenomena, both quantitatively and qualitatively, according to the topography of the area, under various weather conditions. Effort was devoted to improving the accuracy of the CFD model by taking into account topographical design, mesh structure, turbulence models, particle generation, and other factors influencing the final solution. Computed results of the 3-D developed CFD model were compared against experimental data. Results showed an average error of-6.8%, which is within the acceptable range. CFD-computed vertical log-profiles of dust dispersion were similar to the vertical profiles presented by an earlier study. CFD results showed that dispersion of fugitive dust was mainly affected by particle size, wind speed, wind direction, and topography of the area. The estimated dispersion distance, measured at a height of 3 m for the 10 μm particles and a wind speed of 1.7 m s-1, was 3100 m. A dispersion distance of 6300 m was obtained when wind speed was 3.9 m s-1 for the 10 μm particles. This study showed that a CFD model can be effectively used to supplement field experiments when analyzing dispersion of fugitive dust. © 2010 American Society of Agricultural and Biological Engineers. Source

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. Source

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. Source

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