• Ocean and Polar Research
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• v.38 no.4
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• pp.325-330
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• 2016

Partial high frequency bands were allocated to the operation of ocean surface radars that monitor the sea surface currents and waves in WRC-12. On that basis, government-related organizations revised the table of domestic frequency allocation. In order to study radio environments in the allocated bands for ocean radar, tests of the radio signal spectrum were carried at 7-sites using the receiver of the ocean surface radar system operated with a shutdown of the transmitter for 10-60 min. The results showed that no serious radio noises occur at 25 and 43 MHz bands, indicating a good radio environment for the ocean surface radar operation. However, at 13 MHz band, it was difficult to generate stable and confidential data from the ocean surface radar because serious radio noises occurred continuously.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.140-143
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• 2004

The west coast of the Korean Peninsula is famous for its large tidal range (up to 9 m) and vast tidal flats. With comparison the sedimentary environments of open and close tidal flat using remote sensing, we select Kanghwa tidal flat and Hwang-Do tidal flat in Cheonsu Bay. Prior to surface sediment discrimination using remote sensing, sedimentary environments including intertidal OEM, hydraulic condition, and relationship between grain size and various tidal condition are investigated. Remote sensing has the potential to provide synoptic information of intertidal environments. The objectives of this study are: (i) to generate an intertidal digital elevation model (OEM) using the waterline method of Lansat TM/ETM+, (ii) to investigate the tidal channel distribution using texture analysis, and (iii) to analyze the relationship between surface grain size by using in-situ data and intertidal OEM and tidal channel density by using high-resolution satellite data such as IKONOS and Kompsat EOC. The results demonstrate that satellite remote sensing is an efficient and effective tool for a surface sediment discrimination and long term morphologic change estimation in tidal flats.

• Journal of Microbiology and Biotechnology
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• v.31 no.2
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• pp.240-249
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• 2021

Phenotypic plasticity is a rapid response mechanism that enables organisms to acclimate and survive in changing environments. The Chinese mitten crab (Eriocheir sinensis) survives and thrives in different and even introduced habitats, thereby indicating its high phenotypic plasticity. However, the underpinnings of the high plasticity of E. sinensis have not been comprehensively investigated. In this study, we conducted an integrated gut microbiome and muscle metabolome analysis on E. sinensis collected from three different environments, namely, an artificial pond, Yangcheng Lake, and Yangtze River, to uncover the mechanism of its high phenotypic plasticity. Our study presents three divergent gut microbiotas and muscle metabolic profiles that corresponded to the three environments. The composition and diversity of the core gut microbiota (Proteobacteria, Bacteroidetes, Tenericutes, and Firmicutes) varied among the different environments while the metabolites associated with amino acids, fatty acids, and terpene compounds displayed significantly different concentration levels. The results revealed that the gut microbiome community and muscle metabolome were significantly affected by the habitat environments. Our findings indicate the high phenotypic plasticity in terms of gut microbiome and muscle metabolome of E. sinensis when it faces environmental changes, which would also facilitate its acclimation and adaptation to diverse and even introduced environments.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.705-712
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• 2009

The state changes of ocean covered over 70% of earth surface are one of the greatest factor of weather catastrophe. Recently weather extraordinary events are followed by steep increase of sea water temperature and scientists in various fields are studying and warning the weather changes. In this paper, floating buoy is developed to monitor ocean environments via Orbcomm satellite and a method is proposed to increase measurement accuracy of sea water temperature with common low price temperature sensor. Experimental results are presented to illustrate the usability and effectiveness of the developed system. A web-based real time monitoring system is built to monitor ocean environmental information such as sea and air temperature, salinity according to the position of buoy through the internet for user convenience.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1122-1140
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• 2024

The importance of indoor positioning has grown in numerous application areas such as emergency response, logistics, and industrial automation. In ships, indoor positioning is also needed to provide services to passengers on board. Due to the complex structure and dynamic nature of ship environments, conventional positioning techniques have limitations in providing accurate positions. Compared to other indoor positioning technologies, Bluetooth 5.1-based indoor positioning technology is highly suitable for ship environments. Bluetooth 5.1 attains centimeter-level positioning accuracy by collecting In-phase and Quadrature (IQ) samples from wireless signals. However, distorted IQ samples can lead to significant errors in the final estimated position. Therefore, we propose an indoor positioning method for ships that utilizes a Deep Neural Network (DNN) combined with IQ fingerprint maps to overcome the challenges associated with accurate location detection within the ship. The results indicate that the accuracy of our proposed method can reach up to 97.76%.

• Journal of the Korean institute of surface engineering
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• v.57 no.3
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• pp.192-200
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• 2024

Cu as a heat exchanger tube is an important component in thermal fluid transfer. However, Cu tubes are exposed to stress in certain environments, leading to stress corrosion cracking (SCC). In this study, the effect of Sn addition on microstructure and corrosion characteristics was examined. The microstructural examination revealed the presence of columnar crystal and a grain refinement due to the addition of Sn. Electrochemical measurements showed that the 5 wt.% NH₃ environment was the most vulnerable environment to Cu corrosion, and the corrosion current density increased as stress increased. The immersion test exhibited the formation of Cu2O and Cu(OH)₂ corrosion product in 3.5 wt.% NaCl and 5 wt.% NH₃ environments, respectively. Results indicated that Sn addition to Cu was an important factor in improving the mechanical strength.

• Ocean and Polar Research
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• v.34 no.4
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• pp.453-462
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• 2012

Ocean surface current data in Korea was collected using sets of High-Frequency Ocean Surface Radars (HFOSRs) with 25 radial sites in the frequency range of 5~43 MHz. Site selection and the correct installation of HFOSR are very important considerations in order to secure continuous and reliable results. The installation procedures of HFOSR are summarized as follows: 1. Survey area selection; 2. Investigation of ambient radio waves and installation environment; 3. Domestic license of radio station; 4. Installation of antenna and housing of electrical and communication devices. The current work describes the entire processes of HFOSR installation within Korea.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.89-90
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• 2008

We present an implementation and it's real-sea test of an underwater acoustic communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. For the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 20m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 9.6km.

• Ocean and Polar Research
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• v.43 no.2
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• pp.65-72
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• 2021

In order to evaluate the dissolved organic carbon (DOC) and fluorescent dissolved organic matter (FDOM), as indicators of organic matter in the coastal environments, we measured the concentrations of DOC, FDOM, and chemical oxygen demand (COD) in saline groundwater (Woljeong, Pyoseon, and Hwasun beaches) and coastal seawater (Haengwon, Gwideok, Pyoseon, and Yeongnak) in Jeju, Korea. The highest concentrations of DOC and COD in groundwater were found in Woljeong and Pyoseon, and those in coastal water were observed in Haengwon and Pyoseon, indicating that the higher concentrations of DOC and COD seem to be associated with saline groundwater-driven dissolved organic matter (DOM) and/or biogeochemical processes. According to origin and optical properties of DOM using FDOM as a tracer, proportion of humic-like FDOM, more refractory DOM, was relatively greater in the groundwater than in the coastal water. With regard to this result, there was no relationship between DOC and COD in groundwater, while DOC showed a good positive correlation (r² = 0.66) with COD in coastal water. This result indicates that COD as an indicator of assessment of DOM has a limitation in which it is difficult to quantify refractory DOM. Although DOC is a potential alternative to COD in the coastal environments, particulate organic carbon cannot be negligible due to relatively higher concentration compared to the open ocean. Therefore, the use of total organic carbon (TOC) as a replacement of COD in the coastal ocean is important, and the evaluation criterion of the TOC is necessary in order to evaluate of organic matter indicator in the various coastal environments.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.508-516
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• 2021

Although scientist have been reporting recently that changes in ocean environment influence the species composition, movements, and growth of fish in Korea waters. Previous studies on fish vulnerability owing to climate changes are insufficient to explain the effect of fluctuating ocean environments on fisheries ground. In this study, we suggested a method for the assessment of fisheries sensitivity to various factors in ocean environments in Korean waters. To evaluate the fisheries sensitivity, catch data (Chub mackerel, Hairtail, Common squid, small yellow croaker) from National federation of fisheries cooperatives in Korea (1991-2017) and oceanographic data from Korea Ocean Data Center (KODC; 1960-2017) were normalized using the z-score method. Thereafter, the fisheries sensitivity was calculated using the difference between the catch data and the oceanographic data. Finally, the fisheries sensitivity was evaluated based on evaluation grade ratings. Result revealed that in the south sea, variability in catch data was obviously higher than environmental fluctuation (evaluation grade 1), indicating that catch variability in response to environmental change is most sensitive in the south sea among Korean waters in 2017. These results would be helpful for fishery management and policy for sustainable yield in Korean waters.