• Journal of Ocean Engineering and Technology
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• v.36 no.4
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• pp.280-294
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• 2022

This study reviews the recent development and research results of a fixed oscillating water column (OWC) wave energy converter (WEC). The OWC WEC can be divided into fixed and floating types based on the installation location and movement of the structure. In this article, the study on a stationary OWC WEC, which is close to commercialization through the accumulation of long-term research achievements, is divided into five research categories with a focus on primary energy conversion research. These research categories include potential-flow-based numerical analysis, wave tank experiments, computational fluid dynamics analyses toward investigation of fluid viscous effects, U-shaped OWC studies that can amplify water surface displacement in the OWC chamber, and studies on OWC prototypes that have been installed and operated in real sea environments. This review will provide an overview of recent research on the stationary OWC WEC and basic information for further detailed studies on the OWC.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.143-156
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• 2015

In order to understand the dynamic characteristics of water column environments in the Western Pacific seamount area (approximately $150.2^{\circ}E$, $20^{\circ}N$), we investigated the water mass and the behavior of water column parameters such as dissolved oxygen, inorganic nutrients (N, P), and chlorophyll-a. Physico-chemical properties of water column were obtained by CTD system at the nine stations which were selected along the east-west and south-north direction around the seamount (OSM14-2) in October 2014. From the temperature-salinity diagram, the main water masses were separated into North Pacific Tropical Water and Thermocline Water in the surface layer, North Pacific Intermediate Water in the intermediate layer, and North Pacific Deep Water in the bottom layer, respectively. Oxygen minimum zone (OMZ, mean $O_2$ $73.26{\mu}M$), known as dysoxic condition ($O_2<90{\mu}M$), was distributed in the depth range of 700~1,200 m throughout the study area. Inorganic nutrients typified by nitrite + nitrate and phosphate showed the lowest concentration in the surface mixed layer and then gradually increased downward with representing the maximum concentration in the OMZ, with lower N:P ratio (13.7), indicating that the nitrogen is regarded as limiting factor for primary production. Vertical distribution of water column parameters along the east-west and south-north station line around the seamount showed the effect of bottom water inflowing at around 500 m deep in the western and southern region, and concentrations of water column parameters in the bottom layer (below 2,500 m deep) of the western and southern region were differently distributed comparing to those of the other side regions (eastern and northern). The value of Excess N calculated from Redfield ratio (N:P=16:1) represented the negative value throughout the study area, which indicated the nitrogen sink dominant environments, and relative higher value of Excess N observed in the bottom layer of western and southern region. These observations suggest that the topographic features of a seamount influence the circulation of bottom current and its effects play a significant role in determining the behavior of water column environmental parameters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.4
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• pp.139-148
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• 2002

Pilot study was performed to examine the feasibility of the pond system for further polishing of treatment wetland effluent from December 2000 to June 2001. The wetland system used for the experiment was highly effective to treat the sewage during the growing season, but it was less effective and its effluent was still high to discharge to the receiving water body. Therefore, the wetland effluent may need further treatment to prevent water quality degradation. Pond system could be used to hold and further polish the wetland effluent during the winter season and ots feasibility was evaluated in this study. Additional water quality improvement was apparent in the pond system during winter season, and the pond effluent could be good enough to meet the effluent water quality standards if it is properly managed. Timing of the pond effluent discharge appears to be critical for pond system management because it is a closed system and whole water quality constituents are affected by physical, chemical, and biological pond environments. Once algae started to grow in mid-April, constituents in the pond water column interact each other actively and its control becomes more complicated. Therefore, upper layer of the pond water column which is clearer than the lower layer my need be discharged in March right after ice cover melted. In the experiment, water quality of the upper water column was markedly clear in March than ant other times probably because of freezing-thawing effect. The remaining lower water column could be further treated by natural purification as temperature goes up or diluted with better quality of wetland effluent for appropriate water uses. This study demonstrated the feasibility of pond system for subsequent management of wetland effluent during the winter season, however, more study is needed for field application.

• 한국해양학회지
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• v.26 no.3
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• pp.255-261
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• 1991

Bacterial abundance and production in the water column over two seamounts (Horizon Guyot and magellan rise) in the central North Pacific were studied in March 1987. Bacterial abundance (0.9-2.3${\times}$10/SUP 8/ l/SUP -1/) in surface waters during the study period were in the lower limit of the values reported for oligotrophic areas. further, bacterial abundance in mesopelagic zone (mostly<5${\times}$ 10/SUP 7/ l/SUP -1/) was much lower than that reported from other tropical areas. Bacterial production 920-466 ng C l/SUP -1/ d/SUP -1/) in surface waters was also low compared to other oligotrophic oceanic environments. However, comparison of bacterial production with the earlier reported values of primary production from these regions suggested a significant role of bacteria in the utilization of organic matter in further studies on spatial distribution of bacterial production on both small and large scales in very oligotrophic aquatic environments are suggested to be necessary.

• Ocean Science Journal
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• v.43 no.4
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• pp.223-232
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• 2008

In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.520-526
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• 2006

Wave Energy is a derivative of the solar energy input to the earth, which is accumulated on open water surfaces by the action of the winds Waves are disturbances in the water surface. This paper is interested primarily in progressive waves, which carry energy from one place to another Waves are irregular in size and frequency. Moreover the surface of the sea is one of the most hostile environments for engineering structures and materials. The idea of harnessing the tremendous power of the ocean's waves is not new. Hundreds of wave energy conversion techniques have been suggested over the last two centuries. Although many WECS (Wave Energy Conversion Systems) have been invented, only a few systems have been tested and evaluated. This paper describes the characteristic of WES (Wave Energy System) in terms of, devices, resource and potential, etc.. Finally, this paper provides a summary of general and specific conclusions and recommendations concerning WECS potential in Korea.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.43-51
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• 1992

The hydrodynamic performance of a floating-type OWC (Oscillating Water Column) chamber is studied numerically and experimentally in this study. The numerical approach based on two-dimensional linear theory of floating wave absorber was attempted to design an efficient wave energy absorber, while model test was performed in a wave basin to test a performance of designed model and validate the reliability of developed numerical code. The focus of study is placed mainly on the experimental study to evaluate the principal characteristics of the designed OWC chamber in regular waves. The effects of the variation of wave height on OWC device and of air pressure inside chamber are also presented. Finally, the measured results were compared with computed ones, and it was shown that the designed chamber works with high efficiency $(\eta_H>1$ over most of wave lengths covered by present study. It is therefore concluded that the developed code is capable of being successfully employed to design OWC chambers at various ocean environments, even though there exist some minor discrepancies between measured and computed results.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.23-26
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• 2004

Methyl Tertiary-Butyl Ether is one of several fuel oxygenates added to gasoline to improve fuel combustion and reduce tile resulting concentration of hydrocarbon. Thus, MTBE transfer readily to groundwater from gasoline leaking from Underground Storage Tank. Therefor, there are significant risks and costs associated with the water contamination. MTBE is far more water soluble than gasoline hydrocarbon. The purpose of the this study is to test the ability of ground tire with facultative bacteria. Bacillus brevis, to sorb MTBE. The process is consisted both batch and column experiment to determine the sorption capacity. And Biofilm is observed by SEM in the column. Finally, it is clear that ground tire represent an attractive and relatively inexpensive sorption medium for a MTBE. The authors can surmise that to determine the economic cost of ground tire utilization, tile cost to sorb a given mass of contaminant by ground tire will have to be compared to currently accepted sorption media. and Bacillus brevis strain was eliminated on MTBE, too. The biobarrier that ground tire with bacteria, has potential for use in the remediation of MTBE-contaminated environments.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.233-243
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• 2015

The bimodal flocculation of cohesive sediments in water environments describes the aggregation and breakage process developing a bimodal floc size distribution with dense flocculi and floppy flocs. A two class population balance equation (TCPBE) was tested for simulating the bimodal flocculation by a model-data fitting analysis with two sets of experimental data (low and high turbulent flows) from 1-D flocculation-settling column tests. In contrast to the Single-Class PBE (SCPBE), the TCPBE could simulate interactions between flocculi and flocs and the flocculation mechanism by differential settling in a low turbulent flow. Also, the TCPBE could perform the same quality of simulation as the elaborate Multi-Class PBE (MCPBE), with a small number of floc size classes and differential equations. Thus, the TCPBE was proven to be the simplest model that is capable of simulating the bimodal flocculation of cohesive sediments in water environments and water, wastewater treatment systems.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.2
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• pp.49-62
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• 2001

Hydrographic surveys were carried out seven times during May 31, 1998 and September 24, 1998 in order to study the physical environments of the coastal area between Narodo Is. and Sorido Is. in the southern sea of Korea (the South Sea) where the occurrence of Cochlodinium polykrikoides red tide is frequently observed in summer. Temperature and salinity of the water column from the surface to the depth of 30 m exhibit large seasonal variations. Mean temperature of the water column increased by 6 and mean salinity of the water column decreased by 2.71 psu during the observation period. Both the freshwater supplied from the adjacent land and the precipitation over the study area cannot account for the observed salinity variations. The influx of the low salinity water from the offshore area is considered to be the main cause for the observed salinity changes. Surface salinity in the study area shows different spatial distribution in the period of outbreaking, mid-stage and disappearance of the red tide. Especially, salinity was abruptly lowered at the stage of disappearance of red tide as compared to salinity of the previous observation period. Vertical structure of water properties also became vertically homogeneous at the disappearance stage, while it was highly stratified in the previous observation. Such changes can only be explained by the inflow of low salinity water from the offshore, which is considered as the most possible cause for the disappearance of the red tide in the study area. This study suggests that exchanges of water, and chemical and biological factors between coastal areas and of shore area in the South Sea need to be studied in association with the general circulation of the South Sea in order for the better understanding of the occurrence and disappearance of the red tide in the coastal area of the South Sea.