• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.328-328
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• 2017

해운대 해변은 한국에서 가장 유명한 해변 중 하나로 국제적으로도 널리 알려져 매년 많은 관광객을 끌어들이는 부산의 대표 관광지 중 하나이다. 그러나 근래 들어 해운대에서 이안류가 자주 발생하며 관광객들이 불안해하고 있다. 해운대 해변에서 해수욕을 즐기던 관광객들이 이안류에 휩쓸려 구조된 사례가 2013년에만 500명을 넘는 것으로 보고되고 있다. 다행히 아직까지 이 지역에서 이안류로 인한 인명사고는 보고되지 않았으나 매년 발생하는 이안류에 대한 공포로 사회적인 경각심이 고조되고 있는 실정이다. 이에 따라 해운대 이안류의 발생 메커니즘을 규명하고자 하는 연구가 꾸준히 진행되고 있으며, 이안류 사고에 대비한 경보체계 구축 등의 연구도 병행되고 있다. 해운대 이안류의 발생원인을 공학적으로 규명할 수 있다면 향후 해운대 해변의 방재대책 수립을 위한 핵심자료로 사용될 수 있으며, 타 지역에서 발생하는 이안류의 원인분석 및 대책수립을 위한 참고자료로서도 중요한 역할을 할 수 있다. 본 연구에서는 최근 국내외에서 발표된 해운대 이안류 발생원인에 대한 고찰을 기초로 해저지형으로 인한 해운대 이안류 거동의 변화를 수치모델을 활용하여 분석하였다. 널리 알려진 Boussinesq 방정식 모델인 FUNWAVE-TVD를 사용하였으며, 병렬 연산을 활용하여 수치모의 시간을 단축하였다. 해운대 이안류는 해저지형의 변화에 따라 이안류 발달 장소가 달라지긴 하였으나 전체적인 양상은 크게 변하지 않는 것으로 나타났다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.219-219
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• 2012

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.186-194
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• 2000

bottom as a reference basis, some theoretical elements which form bottom echoes during acoustic survey of demersal fish were considered. A stable bottom detection method based on maximum voltage difference, which was not influenced by variable levels and waveform transformation. The method has been shown to be effective using in-situ bottom echo waveforms and computer simulation data. A comparison between near-bottom SV profiles acquired in Funka Bay, Hokkaido, of Japan, the East China Sea and the Yellow Sea, of Korea, with the threshold method and maximum differential voltage method, shows that the SV obtained with the maximum differential voltage method is 4-6 dB higher than those with threshold method within 2m from the bottom.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.1
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• pp.69-74
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• 2016

Bathymetric changes were studied in the southern sea off the Jinwoo-do Island, which is one of the deltaic barrier islands surrounding the Nakddong river estuary. In this study, 16 bathymetry data sets were obtained from June 2006 to April 2015. Two narrow channels, the one lying between Jinwoo-do and Shinja-do, and the other one lying between Nulcha-do and Jinwoo-do extended into the eastern and western parts of the study area, respectively. The eastern extension of the channel contained a passage of mixed estuarine waters of seawater and river water discharged from the Nakdong river barrier and the west Nakdong River. The western channel connected the Nakdong River estuary with the Busan New Port via a connecting pier. Total volumetric changes of sediments in study area and discharge flow of the Nakdong river barrier were analyzed. Bottom topographical changes occurred mainly in the eastern extension of the channel. These changes were initially characterized by gradual erosion or deposition followed by rapid restoration. The total volume of sediment gradually increased from June 2006 to March 2013, but experienced a sudden decrease in October 2013 because of typhoon Danas. Few fluctuations were observed from October 2013 to April 2015. Analysis of the cross-sectional bathymetry of the north-south direction showed that the deepest point of the eastern channel moved 100-130 m westward and 200 m northward between June 2006 and April 2015.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.22-40
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• 2009

Detailed bathymetry and magnetic survey data for NW Rota-1 and Esmeralda Bank obtained by R/V Onnuri of Korea Ocean Research & Development Institute in September 2007 were analyzed to investigate bathymetry and magnetic characteristics of the study area and to estimate the locations of possible hydrothermal vents. The shape of NW Rota-1 is corn type, and the depth of the summit is about 500 meter b.s.l. NW Rota-1 shows irregular topographic expression in the southeastern part. The shape of Esmeralda Bank is caldera type opened in the western part. The summit is very shallow, about 50 meter b.s.l. The western part of Esmeralda Bank is more steeper and topographic irregular than the eastern part, and have the valley made by erosion or collapse. The magnetic anomaly patterns of NW Rota-1 and Esmeralda Bank show low anomalies over the north and high anomalies over the south. The magnetic anomalies are steep over the summits and gently smooth over the deep bottom. The low magnetization zone occurs over the summit of NW Rota-1 and is surrounded by the high zones correlated with its crater. Two low magnetization zones are located in the summit and westside of Esmeralda Bank. The low magnetization zones of the summits of NW Rota-1 and Esmeralda Bank suggest the possible existence of hydrothermal vent.

• Journal of the Korean Geographical Society
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• v.48 no.6
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• pp.914-928
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• 2013

Establishment of limits and names for oceans and seas is necessary for a safety of navigation. Even if there are no national and international standard for the delimitation of sea boundaries, we can take guidelines for the delimitation of sea boundaries through the analysis of IHO official publications, Limits and Names for Oceans and Sea; S-23. This paper shows the changes of the spatial limit of seas since first edition publication, and the standards for a delimitation of oceans and seas were analyzed using S-23 4th edition draft(2002) in terms of physical geographic features. The generic terms of S-23 include Ocean, Sea, Channel, Passage, Strait, Sound, Gulf, Bay and Bight, and each generic term shows hierarchical structures. Several seas show different characteristics compared with definitions of IHO dictionary. Sea boundaries are delimited by longitude and latitude, cape, river mouth, sandbar, and so on. Undersea features such as a shelf, trench, trough, rise, bank and reef are also important features for delimitation of sea boundary. Especially, seas that are delimited by undersea feature are mainly located Arctic and Southern ocean area in S-23 4th edition. Advanced knowledge of marine science with a technical advance might affect to delimit for sea boundary.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.3
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• pp.195-201
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• 2000

This paper discusses methods for the stable bottom detection and the optimum bottom offset which enable to separate the fish echoes from the bottom echoes with echo integration of demersal fish. In preprocessing of the echo signal, the bottom detection has to be done stably against the fluctuation of echo level and the bottom offset has to be set to a minimum height such that near bottom fish echoes are included Two methods of bottom detection, namely echo level threshold method and maximum echo slope method were compared and analyzed. The echo level method works well if the ideal threshold level was given but it sometimes misses the bottom because of the fluctuation of the echo. Another method to detect the bottom which uses maximum echo slope indicates the simple and stable bottom detection. In addition, the bottom offset has to be set near to the bottom but not to include the bottom echo. Optimum bottom offset should be set a few samples before the detected bottom echo which relates the beginning of pulse shape and acoustic beam pattern to the bottom feature.

• Geophysics and Geophysical Exploration
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• v.10 no.3
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• pp.163-172
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• 2007

A seafloor curvature measurement method was developed to extract redundant topographic features from the multi-beam bathymetry data, and then applied to the data of abyssal plain area in the Pacific. Any seafloor might be modeled to a quadratic surface determined in a linear least squares sense, and its curvature could be derived from the eigen values related with quadratic model parameters. The curvature's magnitude as well as polarity showed distinct relationship with geometric characteristics of the seafloor like as ridge and valley. From the investigation of curvature's variation with the number of data in the quadratic surface, the optimal size of data aperture could be applied to real bathymetry data. The application to real data also required the determination of the accompanying threshold values to cope with corresponding topographic features. The calculation method of previous studies were reported to be sensitive to the background noise. The improved curvature measurement method, incorporating the sum of eigen values has reduced unwanted artifacts and enhanced ability to extract lineament features along strike direction. The result of application shows that the curvature measurement method is effective tool for the estimation of a possible mining area in the seamount free abyssal hill area.

• Water for future
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• v.19 no.3
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• pp.259-266
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• 1986

A numerical study of the process of wave deformation, such as reflection and transmission coefficients and wave forms with bottom change was carried out by Boundary Element Method using linear elements. It is assumed that the incident wave is normal and oblique to the bottom and the wave may be described by linear theory The accuracy of the computational scheme is investigated by comparing the results of other researchers in the following several cases. (1) Simple and sloping stepped bottom geometry (2) Submerged breakater type bottom geometry (3) Trench type bottom geometry

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.82-95
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• 2019

In this study, we analyzed the beam time series of ocean reverberation which was conducted in the eastsouthern region of East Sea, Korea during the August, 2015. The reverberation data was gathered by moving research vessel towing LFM (Linear Frequency Modulation) source and triplet receiver array. After signal processing, we analyzed the variation of ocean reverberation level according to the seafloor bathymetry, source/receiver depth and sound speed profile. In addition, we used the normalized data by using cell averaging algorithm and identified the statistical characteristics of seafloor scatterer by using moment estimation method and estimated shape parameter. Also, we analyzed the coincidence of data with Rayleigh and K-distribution probability by Kolmogorov-Smirnov test. The results show that there is range dependency of reverberation according to the bathymetry and also that the time delay and the intensity level change depend on the depths of source and receiver. In addition, we observed that statistical characteristics of similar Rayleigh probability distribution in the ocean reverberation.