• Journal of the korean society of oceanography
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• v.38 no.2
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• pp.80-86
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• 2003

The horizontal distributions of $^{224}Ra$ (half life=3.4 days) and $^{223}Ra$ (half life=11.3 days) were measured in surface seawaters of the Nakdong River estuary and the South Sea of Korea in April and October 2002. In order to determine these short-lived Ra isotopes, we used a delayed coincidence counter which is much more rapid and accurate than traditional methods. In an estuarine mixing zone (salinity, ~l6 ppt), the activities of $^{224}Ra\;and\;^{223}Ra$ were much greater than what would be expected from a mixture of freshwater and seawater in the Nakdong River estuary. This excess Ra may be a result of Ra desorption from fresh sediments originating from the river upstream. However, in the more open areas of the Nakdong River estuary (salinity>30 ppt) and the South Sea of Korea, $^{224}Ra\;and\;^{^{223}Ra$ activities decreased exponentially as a function of distance offshore. Using the decrease of $^{223}Ra$ with distance offshore in the South Sea of Korea, we estimated the apparent horizontal eddy diffusivities. The apparent eddy diffusion coefficients in South Sea of Korea are calculated to be approximately $3500-8000\;\textrm{m}^2/sec$.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.567-577
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• 2020

The infection of marine diatom Coscinodiscus wailesii by a parasitic protist from the Yongho Bay of Busan, Korea was observed during the diatom bloom events in 2017 through 2018. The morphological and molecular features suggested that the parasitic nanoflagellate Pirsonia diadema was responsible for the infection. During the study period, the parasite prevalence ranged from 0.3% to 3.3%, and infected C. wailesii cells were observed only at surface seawater temperatures ranging between 10.9 and 19.9℃, although the host population appeared at temperatures above 25℃. The parasite and host system was successfully established as cultures. Using the cultures, we determined the morphological features over the infection cycle, parasite generation time, parasite prevalence as a function of inoculum size, and zoospore infectivity and survival time. The diatom C. wailesii was readily infected by the parasite P. diadema, with a parasite prevalence reaching up to 100% and a zoospore to host inoculum ratio above 20:1. The survival and infectivity of the parasite zoospores decreased with age. While the zoospores could survive up to 88 hours, they quickly lost their ability to infect after 48 hours. These results could lead to a better understanding of the biology and ecology of the parasitoid infecting the giant-sized diatoms in coastal waters.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.423-433
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• 2020

Direct current (DC) electric fields have been used for electro-osmotic dewatering. Under DC conditions, however, the electrical contact resistance between the electrode and the dewatering material increases considerably during the process of dewatering. Such a circumstance hinders the continuation of effective electro-osmotic dewatering. To reduce this hindrance, an applied pulse electric field with periodic reversals of the electrode polarity should improve electro-osmotic dewatering. In this study, electro-osmotic dewatering under pulse conditions was experimentally investigated for electrode polarity reversals. During the dewatering process, the pulse electric field was able to reduce the hindrance caused by the DC, resulting in an increased final dewatered amount relative to that under a DC electric field. For a constant applied voltage, the reversed polarity condition, under which the electric current passing through the material was almost unchanged with time, yielded the maximum final dewatered amount. This technique can be used to enhance drainage from a water storage facility during a period of extreme drought and the seawater desalination plants using reverse osmosis in drought stricken coastal regions.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.627-637
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• 2023

Volleyball is an international sport with many fans. This sport has made significant progress in schools and clubs. Volleyball is suitable for all age groups and can be used in different environments. It has many social and physical benefits. During the game provides special physical training for the players and is considered one of the most exciting games. Another type of volleyball is beach volleyball, a beach sport and one of the Olympic sports held on the sand with the same rules as volleyball. This sport is usually played in coastal areas, especially with wide sandy beaches. Because this sport is played in open spaces, the players stay in this space for a long time and are exposed to dangerous ultraviolet radiation. It is a wavelength of light in the range of electromagnetic waves with a wavelength between 10 and 400 nm. This wavelength is shorter than visible light and more protracted than X-ray. Ultraviolet (UV) rays are naturally present in sunlight and include about 10% of all waves emitted from the sun's surface. Prolonged exposure to ultraviolet light causes acute and chronic damage to the skin and vision and even destroys the entire immune system. Different covers of the earth's surface reflect different amounts of UV rays. For example, snow cover, sand, and seawater surface reflect this radiation. Therefore, the health of volleyball players is in danger due to this harmful radiation. This work aims to introduce a type of clothing made of nanoparticles that can repel ultraviolet rays and protect beach volleyball players whose health is at risk from this radiation.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.264-264
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• 2021

해수면 상승 및 인간의 활동으로 인한 해수 침투 영향 반경의 예측 및 모의에 대한 연구는 활발히 진행되고 있으며, 해수 침투 피해를 완화하기 위한 다양한 대응 방안이 시도되고 있다. 하지만 해수 침투 피해 대응 방안 등을 효율적으로 사용하기 위해서는 해수 침투 피해가 가장 활발히 일어나는 지역을 선정하고, 지역 특성에 맞는 대응 방안을 선정하는 과정이 필요하다. 기존의 해수침투 취약성 평가의 방법은 대수층 매개변수의 불확실성, 자료의 결측이 빈번하게 발생하고 있다. 또한, 평가 인자에 대한 자료 수집이 어렵고, 대수층에 대한 매개변수의 불확실성으로 직관적인 평가가 어렵다. 본 연구에서는 서해안의 도서지역을 제외한 연안지역을 대상으로 해수침투 취약성 평가 기법을 개발하였다. 해수침투에 대한 직관적인 해석을 위해 직접적인 영향을 미치는 수문 성분 중 해수면, 지하수위, 함양량, 지하수 이용량을 지표로 선정하고, 행정구역 단위로 자료를 수집하였다. 각각의 자료에 대한 평균, 기울기를 이용하였다. 각각의 인자에 대해서 객관적 가중치 산정 방법인 엔트로피 방법을 이용하여 가중치를 결정하였다. Technique for Order Preference by Similarity to Ideal Solution(TOPSIS)를 이용하여 가장 취약한 지역을 선정하였다. 객관적 가중치 산정 방법을 이용하여 자료를 통해 직접적인 평가 가능하며, 추세 분석을 통해 앞으로의 해수침투 취약성에 대한 전망도 가능하다. 평가 결과를 이용하여 해안의 지하수자원의 지속가능한 운영 관리를 위한 자료로 활용할 수 있을 것이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.2-2
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• 2020

해안 지역은 종종 도시화, 인구 증가 및 환경 오염으로 인해 해안대수층의 지하수의 염도가 증가하는 현상인 해수침투가 발생한다. 본 연구는 국내 제주도 해안대수층을 대상으로 GIS 기법을 이용한 수리지질학적 변수의 지수화 방식으로 해안대수층의 해수침투 취약성 평가를 적용하였고 국내 해수침투 특성을 더욱 명확하게 반영할 수 있도록 취약성 평가 방식을 개선하고자 하였다. 취약성 평가를 수행하기 위해 대수층 특성, 수리전도도 특성, 지하수위, 해안으로부터의 거리, 염도분포, 대수층 깊이 등의 자료를 확보하여 취약성 평가의 주요 인자로 활용하였으며 특히 다년간에 걸친 국내 해수침투 관측망 관측 자료를 사용한 것을 특징으로 한다. 취약성 평가 인자 중 지하수위를 지수화 하는 과정에서 지하수위의 평가 구간 범위를 개선하였고, 염도 적용 방식을 해수침투 관측망 데이터 유형인 전기전도도를 이용한 새로운 평가 구간 범위를 설정하였다. 연구 결과 기존에 해수침투가 발생했던 지역에서의 취약성 지수가 높게 나타났으며 취약성 평가의 개선 작업 결과에 의해 지속적인 지하수위 하강이 발생하고 계절적 요인으로 해수침투가 발생하는 지역에서 취약 지수의 증가세를 더욱 선명하게 구분할 수 있었다.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.12a
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• pp.79-79
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• 2020

Halophyte is a plant that has evolved to grow well in salty places, and is mainly distributed in coastal wetlands, sand dunes, salt fields, and reclaimed lands in tidal flats and river estuaries. Because it grows in the soil where seawater enters and exits, it is very abound in natural minerals and produces certain metabolites to survive sustainably in the surrounding environment. In this study, anti-inflammatory studies were conducted using 15 kinds of halophyte to secure data on halophytes of infinite value as functional materials. The aim of this study was to select a group of halophytes that regulate iNOS expression, which is involved in the secretion of inflammatory cytokines and nitric oxide production in LPS-induced macrophages. Among the 15 species of halophyte, except for Triglochin maritimum, Suaeda japonica, and Carex pumila, NO production was reduced in 12 species of halophytes, and 7 species of halophyte (Suaeda asparagoides, Artemisia fukudo, Spergularia marina, Aster tripolium, Suaeda australis, Atriplex subcordata, Calystegia soldanella) significantly decreased the expression levels of TNF-α and IL-1β.

• Journal of the Institute of Convergence Signal Processing
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• v.24 no.1
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• pp.1-14
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• 2023

Underwater images carry information that is useful in the fields of aquaculture, underwater military security, navigation, transportation, and so on. In this research, we transmitted an underwater image through various underwater mediums in the presence of underwater turbulence and beam attenuation effects using a high-speed visible optical carrier signal. The optical beam undergoes scintillation because of the turbulence and attenuation effects; therefore, distorted images were observed at the receiver end. To understand the behavior of the communication media, we obtained the bit error rate (BER) performance of the system with respect to the average signal-to-noise ratio (SNR). Also, the structural similarity index (SSI) and peak SNR (PSNR) metrics of the received image were evaluated. Based on the received images, we employed suitable nonlinear filters to recover the distorted images and enhance them further. The BER, SSI, and PSNR metrics of the specific nonlinear filters were also evaluated and compared with the unfiltered metrics. These metrics were evaluated using the on-off keying and binary phase-shift keying modulation techniques for the 50-m and 100-m links for beam attenuation resulting from pure seawater, clear ocean water, and coastal ocean water mediums.

• 한국해양학회지
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• v.30 no.5
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• pp.458-466
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• 1995

To clarify the role of protozooplankton in the microbial food web of Inchon coastal ecosystem, the grazing capacities and growth rates of heterotrophic flagellated (HFL) and ciliates were investigated. We measured the growth rates of bacteria, HFL, autotrophic flagellated (AFL) and ciliates using reverse flow (RF) filter set and obtained the clearance rates and ingestion rates of HFL and dilates by fluorescent labelled bacteria (FLB) method and isolation culture method from natural seawater of Inchon coastal area. The standing crops of bacteria, HFL, AFL and ciliates in this study area were 0.7∼1.5${\times}$10/SUP 6/ cells$.$ml/SUP -1/ 1,680∼2,180 cells$.$ml/SUP -1/, 1,090∼2,180 cells$.$ml, and 3,600∼5,700 cells$.$l/SUP -1/, respectively. The mean growth rates of bacteria, HFL, AFL and ciliates were 0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/, 0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL, AFL and ciliates were0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/,0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL on bacteria was 0.055h/SUP -1/. Mean grazing rates of ciliates on HFL was relatively high of 0.057 h/SUP -1/, while the grazing rate of ciliates on AFL was low of 0.019h/SUP -1/. The clearance rates and ingestion rates of HFL on bacteria were 3.6∼61.8nl$.$HFL$.$h/SUP -1/ and 6∼52 BAC. HFL$.$h/SUP -1/ respectively. FLB grazing experiment showed low values, while natural bacteria experiment showed high value meaning high grazing pressure on total bacteria. The clearance rates and ingestion rates of Tintinnopsis sp., dominant ciliates in Inchon coastal waters, were 3.2∼4.6 ul$.$CIL/SUP -1/$.$h/SUP -1/ and 5∼6 cells$.$CIL/SUP -1/$.$h/SUP -1/ respectively, showing higher values in the high tide than low tide. The ingestion rates of ciliates implies that ciliate took up 17∼20% of total nanoflagellates of Inchon coastal waters.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.4
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• pp.327-342
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• 2021

The global coastal region is considered as a sink for atmospheric CO₂. Since most of the studies in the East Sea focused on the Ulleung Basin, the importance of coastal region for carbon cycle has been overlooked. In this study, we compared the biological pump and CO₂ absorption between the Ulleung Basin and coastal region by surface measurements of biological O₂ supersaturation (𝚫O₂/Ar) and partial pressure of CO₂ (fCO₂). Cold and less saline waters in the coastal regions were in contrast with a warm and saline water in the Ulleung Basin. The coastal waters near Samcheok and Pohang showed higher fluorescence, 𝚫O₂/Ar, and lower fCO₂ than those in the Ulleung Basin, indicating higher primary production and CO₂ absorption in the areas. The average net community production estimated by 𝚫O₂/Ar were 19 ± 6 and 60 ± 9 mmol O₂ m^-2d^-1 in the Samcheok and Pohang, respectively, 2-7 times higher than that of 8 ± 4 mmol O₂ m^-2d^-1 in the Ulleung Basin. Similarly, the average CO₂ flux between the seawater and atmosphere were -17.1 ± 8.9 and -25.8 ± 13.2 mmol C m^-2d^-1 in the Samcheok and Pohang, respectively, 4-5 times higher than that of -4.7 ± 2.5 mmol C m^-2d^-1 in the Ulleung Basin. In the Samcheok and Pohang, degrees of N₂ saturation were lower by 3% than that the ambient waters, suggesting the possibility of nitrogen fixation by primary producers.