• Journal of Animal Science and Technology
• /
• v.46 no.3
• /
• pp.443-450
• /
• 2004

To examine the potentiality of grassland dominated with turf-type grasses, which are mainly used for the establishment of green spaces, forage production and its utilization as forage resources, dry matter yield and forage quality of three different turf-type mixtures were estimated throughout three consecutive experimental years. According to the experiment, the mean of dry matter(DM) yield, chemical composition, DM digestibility, crude protein dry matter(CPDM) and digestible dry matter(DDM) yield was not significantly different among species(p > 0.05) over three experimental years. Botanical composition of three dominant species(tall fescue, Kentucky bluegrass and perennial ryegrass) was 42, 35 and 28%, respectively, in three mixtures at the last cutting(6th) in 2001. The botanical composition of three dominated species such as tall fescue, Kentucky bluegrass and perennial ryegrass was maintained 84% of the total plants in all types of mixtures. Therefore, It is observed that the mixture types did not closely affect the botanical composition. But botanical composition of the other species such as redtop(8%) and creeping bentgrass(6${\sim}$7%) was low. Especially, that of red fescue was the least(1${\sim}$2%) of all mixed species. As mentioned above, any difference was not observed in DM yields, forage quality and botanical composition among mixture types. Therefore, any types of mixtures can be used as public green spaces like school ground areas or river-sides, and as forage resources additionally.

• Journal of Soil and Groundwater Environment
• /
• v.10 no.1
• /
• pp.65-74
• /
• 2005

National groundwater monitoring stations have been managed throughout the country by Korea Water Resources Corporation (KOWACO) in order to monitor variations in quantity and quality of groundwater resources. A multi-sensor installed in each monitoring station well measures groundwater level, water temperature and electrical conductivity every six hours and the logged data are automatically transmitted to a host computer in KOWACO. Meanwhile despite regular station inspection and replacement of deteriorate or broken devices, abnormal values or outliers often occur due to intrinsic limitations of automatic monitoring and transmission. Thus prompt recognition and measures to these values are essentially required to reduce disturbance and missing period of the data. In this study, time and frequency of outlier occurrence were analyzed for the water level data obtained from national groundwater monitoring stations within the Han river basin in 2000. The analysis results indicated that the most prominent patterns of the outliers were rapid decline for water level, no variation for temperature and steep decline for electrical conductivity. This study provided a sample criterion for determining the outlier for each parameter.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.5
• /
• pp.447-453
• /
• 2018

Since 1960, Korea the town center was developed intensively due to rapid industrial development. As a result of the development, the population was concentrated in urban areas and the green area was decreased. Due to the decrease of the green area, the circulation system of the rainwater was changed, hence the rainwater was not introduced into the groundwater., On the other hand, the water on the surface of the road was changed into the water for flowing to the river and evaporation. The changes in the water flow cause many problems, and the depletion of the groundwater does not create an environment in which microorganisms and plants can live. in Korea, permeable pavement construction is increased to solve these problems, but existing pavement blocks have many problems. The pores of the permeable block are clogged due to the accumulation of dust or whitening phenomenon, and the permeability is lost. In this study, the solution of the problems of existing permeable block were suggested by using polymer and artificial permeable pipe, and strength, permeability and service life are increased, The relationship between the substitution rate of the polymer and the mixing ratio of the artificial permeable pipe was analyzed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.38 no.1
• /
• pp.1-9
• /
• 2020

ABL (Airborne Bathymetric LiDAR) is an advanced survey technology that uses green lasers to simultaneously measure the water depths and oceanic topography in coastal and river areas. Seabed point cloud extraction is an essential prerequisite to further utilizing the ABL data for various geographic data processing and applications. Conventional seabed detection approaches often use return waveforms. However, their limited accessibility often limits the broad use of the bathymetric LiDAR (Light Detection And Ranging) data. Further, it is often questioned if the waveform-based seabed extraction is reliable enough to extract seabed. Therefore, there is a high demand to extract seabed from the point cloud using other sources of information, such as geometric information. This study aimed to assess the feasibility of a ground filtering method to seabed extraction from geo-referenced point cloud data by using CSF (Cloth Simulation Filtering) method. We conducted a preliminary experiment with the RIGEL VQ 880 bathymetric data, and the results show that the CSF algorithm can be effectively applied to the seabed point segmentation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.2
• /
• pp.412-424
• /
• 2019

In this study, the changes of the streamflow characteristics of the watershed were analysed depending on the infiltration methods of CAT. The study area, Boryeong-dam watershed located in Chungcheongnam-do area, has been suffered from severe drought in recent years and stabilized regarding on the storage rate through efforts such as constructing a channel connecting the upstream of Boryeong-dam from the downstream of the Geum river. In this study, the effects of soil infiltration parameters on the watershed streamflow characteristics were analyzed by the infiltration methods of CAT such as Rainfall Excess, Green&Ampt and Horton. And the parameter calibrations were conducted by SCEUA-P, a global optimization technique module of the PEST, the package for parameter optimization and uncertainty analysis, to compare the yearly variations of soil parameters for infiltration methods of CAT. In addition, the streamflow characteristics were analyzed for three infiltration methods by applying three different scenarios, such as applying calibrated parameters for every years to simulate the model for each years, applying calibrated parameters for the entire period to simulate the model for entire period, and applying the average value of yearly calibrated parameters to simulate the model for entire period.

• Journal of Korea Water Resources Association
• /
• v.55 no.10
• /
• pp.749-759
• /
• 2022

The paradigm of water cycle management in the watershed is changing due to the increase in abnormal climate phenomena caused by climate change and the increase in impervious area due to urbanization. Research is continuously underway based on Low Impact Development technology that can suppress water cycle distortion. In this study, factors that can reflect water cycle distortion were selected before applying LID, and the PSR index for each 148 watershed was calculated for the the Nakdonggang River basin. As of 1975, the PSR index is calculated by calculating the pressure index P, which represents the rate of change in impervious surface area to 2019, the phenomenon index S, which represents the rate of change in water cycle for each subwatershed, and the Low Impact Development area countermeasure index R. The lower PSR index value, the higher the priority management watershed, and the water cycle recovery priority management watershed was calculated in the order of 1, 2, 87, 90, 91, and 147. It is expected that the efficient application of low-impact development factors in accordance with the order of priority management of water cycle by subwatershed in the large area will contribute to the recovery of water cycle distortion.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.1
• /
• pp.95-104
• /
• 2022

Micro hydropower is a readily available renewable energy source that can be harvested utilizing hydrokinetic turbines from shallow water canals, irrigation and industrial channel flows, and run-off river stream flows. These sources generally have low head (<1 m) and low velocity which makes it difficult to harvest energy using conventional turbines. A horizontal-axis screw turbine was designed and numerically tested to extract power from such low-head water sources. The 3-bladed screw-type turbine is placed horizontally perpendicular to the incoming flow, partially submerged in a narrow water channel at no-head condition. The turbine hydraulic performances were studied using Computational Fluid Dynamics models. Turbine design parameters such as the shroud diameter, the hub-to-shroud ratios, and the submerged depths were obtained through a steady-state parametric study. The resulting turbine configuration was then tested by solving the unsteady multiphase free-surface equations mimicking an actual open channel flow scenario. The turbine performance in the shallow channel were studied for various Tip Speed Ratios (TSR). The highest power coefficient was obtained at a TSR of 0.3. The turbine was then scaled-up to test its performance on a real site condition at a head of 0.3 m. The highest power coefficient obtained was 0.18. Several losses were observed in the 3-bladed turbine design and to minimize losses, the number of blades were increased to five. The power coefficient improved by 236% for a 5-bladed screw turbine. The fluid losses were minimized by increasing the blade surface area submerged in water. The turbine performance was increased by 74.4% after dipping the turbine to a bottom wall clearance of 30 cm from 60 cm. The final output of the novel horizontal-axis screw turbine showed a 2.83 kW power output at a power coefficient of 0.63. The turbine is expected to produce 18,744 kWh/year of electricity. The design feasibility test of the turbine showed promising results to harvest energy from small hydropower sources.

• Journal of Korean Society of Environmental Engineers
• /
• v.38 no.2
• /
• pp.71-78
• /
• 2016

The study of water environment system in Changnyeong-Haman weir section using a statistical analysis has been conducted. Statistical analyses used in this study were the correlation analysis, the principal components, and the factor analysis. The purpose of the study is to establish better understanding of relationships between water quality factors in the Changnyeong-Haman weir section which can provide useful information to manage Nakdong river. According to correlation analyses on COD and TOC, it revealed that the value of correlation coefficient was 0.844. Furthermore, the results from the principal component analysis categorized the water quality factors into three factor groups, the first principal factor group included COD, TOC, BOD, pH, water temperature (WT). And, it was observed that the concentration of cyanobacteria in the water body decreased, while the concentrations of the diatoms and the green algae increased after the events of rainfall.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.58 no.3
• /
• pp.71-80
• /
• 2016

The component-based modeling framework for agricultural water-resources management (COMFARM) is a user-friendly, highly interoperable, lightweight modeling framework that supports the development of watershed-specific domain components. The objective of this study was to evaluate the suitability of the COMFARM for the design and creation of a component-based modeling system of agricultural reservoir watersheds. A case study that focused on a particular modeling system was conducted on a watershed that includes the Daehwa and Dangwol serial irrigation reservoirs. The hydrologic modeling system for the study area was constructed with linkable components, including the modified Tank, an agricultural water supply and drainage model, and a reservoir water balance model. The model parameters were each calibrated for two years, based on observed reservoir water levels. The simulated results were in good agreement with the observed data. In addition, the applicability of the COMFARM was evaluated for regions where reservoir outflows, including not only spillway release but also return flow by irrigation water supply, substantially affect the downstream river discharge. The COMFARM could help to develop effective water-management measures by allowing the construction of a modeling system and evaluation of multiple operational scenarios customized for a specific watershed.

• Journal of Marine Bioscience and Biotechnology
• /
• v.11 no.2
• /
• pp.81-88
• /
• 2019

In this study, effects of nitrogen (N) and phosphorus (P) starvation on the cell growth and fatty acid (FA) production of newly isolated freshwater microalgae were investigated. The microalgae were identified as Chlorella sp. and Parachlorella sp. through 18S rRNA sequencing. Optimal culture temperature and light intensity were investigated using a high-throughput photobioreator, and the result was validated in 0.5 L bubble column photobioreactors using BG-11 without NaNO₃ and/or K₂HPO₄. Under nutrient starvation conditions, total FA contents of the microalgae were significantly changed rather than FA composition. Starvation of both N and P was most effective for increasing FA contents in Parachlorella sp (24.4±0.1%) whereas highest FA contents (42.6±1.8%) was achieved when only P was starved in Chlorella sp. among tested conditions. These results suggest an effective strategy for increasing FA production from microalgae using appropriate nutrient starvation.