• Corrosion Science and Technology
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• 제17권6호
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• pp.272-278
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• 2018

Reinforced concrete (RC) has been used as a construction material in various environments, such as airports, bridges, and ocean concrete structures, etc. Over time, however, rebar in the concrete is prone to corrosion from environmental forces and structural defects of the concrete. Cathodic protection (CP) was invented to prevent problems with corrosion and is widely used for different applications. Cathodic protection is divided into two types: sacrificial anode cathodic protection (SACP) and impressed current cathodic protection (ICCP). There are several limitations to the use of sacrificial anode cathodic protection in complex reinforced concrete structures, including concrete resistivity, throwing power of the CP, and environmental conditions. These limitations can affect the protection performance of SACP. Therefore, we used impressed current cathodic protection in our study. We tested Ti-Mesh, Ti-Rod, and Ti-Ribbon anodes in slab type reinforced concrete specimens. Electrochemical tests were conducted to confirm the impressed current cathodic protection performance under different environmental conditions.

• 한국멀티미디어학회논문지
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• 제13권1호
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• pp.122-132
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• 2010

해양 환경 분석은 해양탐사에 필수적인 정보들을 제공한다. 그러나 해양 환경은 해류에 의한 노드의 이동과 염수에 의한 부식, 전파감쇠와 다중경로 발생, 그리고 센서 노드 설치의 어려움 등 다양한 환경변수가 존재한다. 따라서 해양 데이터 통신은 지상통신 환경과는 달리 이러한 환경적 제약 요소로 인해 해양 환경의 데이터들을 수집하는 과정이 복잡하고 힘들다. 이를 해결하기 위해 해양 환경과 유사한 경포호에서 실제 실험을 통해 수질 환경 모니터링을 위한 해양 데이터 통신망을 구축한다. 따라서 본 논문은 경포호 환경 모니터링 시스템의 구축을 통해 환경적 장애요소를 극복하고 해양 환경 모니터링을 위한 센서 노드들의 배치, 그리고 통신 환경의 효과적인 구조를 정의하는데 목적이 있다.

• 한국CDE학회논문집
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• 제17권5호
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• pp.353-363
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• 2012

As the distributed simulation system has been developed in the defense modeling and simulation, interoperability among heterogeneous simulators is essential to achieve the objectives of the distributed simulation system. However, the interoperability has been a problem to synchronize synthetic environment among many heterogeneous simulators that utilize different environmental data formats. SEDRIS (Synthetic Environmental Data Representation and Interchange Specification) was initiated to solve the problem of the interoperability. SEDRIS provides a standard mechanism to promote data interchange and reusability, and it represents all environmental things from ocean, land and atmosphere to the universe. Although SEDRIS provides various advantages as a standard environmental data format, applying of SEDRIS has been hindered by its broadness and complexity. The main objective of this paper is to explain application development process to improve SEDRIS usability for the atmosphere and ocean. The developed application of this paper provides auto-generation of SEDRIS data with minimum user's input, and the auto-generated SEDRIS data is also visualized and verified by the application.

• Advances in environmental research
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• 제4권1호
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• pp.17-24
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• 2015

In this study, we numerically investigated the effect of pressure (100-250 bar), temperature (274-288 K), and salinity (3.5% w/w electrolytes) on $CO_2$ hydrate dissolution rates in the ocean. Mass transfer equations and $CO_2$ solubility data were used to estimate the $CO_2$ hydrate dissolution rates. The higher pressure and lower temperature significantly reduced the $CO_2$ hydrate dissolution rates due to the increase of $CO_2$ particle density. In the high salinity condition, the rates of $CO_2$ hydrate dissolution were decreased compared to pure water control. This is due to decrease of $CO_2$ solubility in surrounding water, thus reducing the mass transfer of $CO_2$ from the hydrate particle to $CO_2$ under-saturated water. The results obtained from this study could provide fundamental knowledge to slow down or prevent the $CO_2$ hydrate dissolution for long-term stable $CO_2$ storage in the ocean as a form of $CO_2$ hydrate.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.245-250
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• 2022

As location-based services using the Global Navigation Satellite System (GNSS) are diversified, concerns about the vulnerability of GNSS to radio disturbance and deception are also growing. Accordingly, countries that own and operate GNSS, such as the United States, Russia, and Europe, are also developing additional navigation systems that can compensate for GNSS' weaknesses. Among them, an R-Mode system that transmits navigation signals using an infrastructure that transmits differential GNSS (DGNSS) information using signals from the medium frequency band currently in operation is being developed in Europe and Korea. Since 2020, Korea has improved four DGNSS transmission stations, including Chungju, Eocheongdo, Palmido, and Socheongdo, to transmit R-Mode signals and test navigation performance in some parts of the West Sea. In this paper, we intend to establish a testbed for measuring the distance of R-Mode signals currently being transmitted and analyze the results. It is confirmed that the distance measurement performance varies depending on the antenna type, diurnal variation, and propagation path of the signal.

• Journal of Positioning, Navigation, and Timing
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• 제11권1호
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• pp.23-28
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• 2022

The eLoran system is a high-power terrestrial navigation system that is recognized as the most appropriate alternative to complement the GNSS's vulnerability to radio frequency interference. Accordingly, Korea has conducted eLoran technology development projects since 2016. The eLoran system developed in Korea provides 20 m positioning accuracy to maritime user in Incheon and Pyeongtaek harbor. To accurately calculate the position with the eLoran signal, it is necessary to apply a compensation method that mitigates the propagation delay. In this paper, we develop the compensation method to mitigate the eLoran signal propagation delay and evaluate the positioning performance in Incheon harbor. The propagation delay due to the terrain characteristics is pre-surveyed and stored in the user receiver. Real-time fluctuations in propagation delay compared to the pre-stored data are mitigated by the temporal correction generated at a nearby differential Loran station. Finally, two performance evaluation tests were performed to verify the positioning accuracy of the Korean eLoran system. The first test took place in December 2020 and the second in April 2021. As a result, the Korean eLoran service has been confirmed to provide 20 m location accuracy without GPS.

• Ocean and Polar Research
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• 제32권1호
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• pp.15-22
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• 2010

Calcium carbonate ($CaCO_3$) content was measured from 3 box core (BC060301, BC060303, BC070301) sediments, in addition to pilot core (PC313) sediments, from deep waters within the Western Pacific Ocean. At the two collection sites (BC060301, PC313) located close to the equator, downcore variation exhibited low $CaCO_3$ content during the interglacial period and high $CaCO_3$ content during the glacial period. Variation of coarse fraction (>$63\;{\mu}m$) content also followed changes in $CaCO_3$ content, indicating that dissolution effect of bottom water decreased during the glacial period. Such variation pattern is typical of the Pacific Ocean. However, downcore variation at the two collection sites (BC060303, BC070301) in the Philippine Sea contrasted the trend of the previous two cores (i.e., high $CaCO_3$ content during the interglacial period and low during the glacial period). This pattern is typical of the Atlantic Ocean. Such results may be attributed to the increasing dilution effect, initiated possibly by the increased transportation of terrigenous materials from nearby continent and archipelago during the glacial period when sea level was low. Alternatively, it is possible that the non-carbonate biogenic particles may have been responsible for dilution. Because of these uncertainties, the record of $CaCO_3$ variation in the deep Western Pacific Ocean is not regionally consistent.

• 수산해양기술연구
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• 제56권4호
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• pp.407-418
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• 2020

Mass mortality of mariculture fish due to high summer temperatures is a major issue in the mariculture industry in many coastal waters of Korea, yet measures to mitigate the impact are generally limited. We injected a micro-bubble of liquefied oxygen into the bottom of rockfish cages (about 6-8 m deep) in order to maximize the dispersal of micro-bubbled seawater and reduce fish mortality. The injection of low-temperature oxygen in micro-bubbles lowered the water temperature at the injection area by as much as 1℃ and increased dissolved oxygen concentration by 0.5 ppm. In early August, following a week with persistent high water temperature (above 28.5℃), there was an increase in fish mortality despite the micro-bubble system, which resulted in approximately 7% death of the total introduced fish population. However, this mortality appeared to be much lower than mortality reported in a neighboring mariculture facility (approximately 50% mortality). We also estimated the volume that can be recirculated with pumped seawater using a micro-bubble system. We suggest that this approach of injecting liquefied oxygen through a micro-bubble system may reduce fish mortality during high temperature periods.

• 한국해양공학회지
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• 제28권3호
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• pp.245-253
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• 2014

This research analyzed the current situation and problems with an environmental impact assessment to provide a rational ocean physics assessment technique for power plant thermal effluent. This research also tried to create an improvement plan for heated effluent diffusion impact assessment by examining the reporting regulations for environmental impact assessment, national and international evaluation guidelines, etc. In the case of evaluating the oceanographic impact of heated effluent discharged from power plants, a pre-investigation is necessary before a full-scale presentence investigation, to accurately predict and minimize power plant construction effects on the surrounding environments. Before this presentence investigation, moreover, an integrated presentence plan, which agrees with the business plan, effect prediction, and post-investigation, needs to be established. A sufficient summit investigation must be made, which considers climate changes, and new and additional power plant construction. For accurate long-term oceanic environmental change prediction, the credibility of effect prediction must be elevated by presenting an evaluation method that is categorized by numerical organization models, verification methods, result presentation, and other things. Furthermore, unproductive conflicts between the people involved in heated effluent evaluation should be reduced by these improvement plans.

• 한국해안·해양공학회논문집
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• 제30권6호
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• pp.298-305
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• 2018

본 연구에서는 해양 항만 콘크리트 구조물의 보수작업을 위한 수중코팅제의 부착 특성을 조사하기 위하여 실험적 연구를 수행하였다. 고려된 실험변수는 코팅제의 종류, 코팅대상 모재의 표면 거칠기, 도포 작업환경(육상 혹은 수중)으로 부착 강도는 Pull-off 방식으로 측정하였다. 코팅제의 부착 강도는 각 수중코팅제의 도포 작업 완료 24시간 후에 ASTM C1583 규정에 따라 측정하였다. 또한, 콘크리트 모재와 코팅제 간의 부착파괴 거동(코팅제, 계면, 콘크리트 모재)을 육안으로 관찰하였으며 측정된 부착 강도 수치에 근거하여 각 실험요인의 비교분석을 수행하였다. 실험결과, 수중에서 도포한 코팅제의 부착 강도가 육상의 경우에 비해 감소하는 경향을 보였으며 수중환경에서는 부착 강도에 미치는 모재 표면 거칠기의 영향이 육상의 경우에 비하여 미비하였다. 마지막으로 수중코팅제의 선정, 사용 시에 유의할 점에 대하여 설명하였다.