• The Journal of the Acoustical Society of Korea
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• 제27권3E호
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• pp.69-76
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• 2008

Measurements of bubble size and distribution in the surface layer of the sea, wind speed, and variation of ocean environments were made continually over a four-day period in an experiment conducted in the South Sea of Korea during 17-20 September 2007. Theoretical background of bubble population model indicates that bubble population is a function of the depth, range and wind speed and bubble effects on sound speed shows that sound speed varies with frequency. Observational evidence exhibited that the middle size bubble population fit the model very well, however, smaller ones can not follow the model probably due to their short lifetime. Meanwhile, there is also a hysteresis effect of void fraction. Observational evidence also indicates that strong changes in sound speed are produced by the presence of swarms of micro bubbles especially from 7 kHz to 50 kHz, and calculation results are consistent with the measured data in the high frequency band, but inconsistent in the low frequency band. Based on the measurements of the sound speed and high frequency transmission configuration in the bubble layer, we present an estimation of underwater acoustic channel capacity in the bubble layer.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.28-41
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• 2009

We know the several construction methods for underwater tunnel, but properly submerged concrete box type tunnel was mostly good structure stability and mostly shot length of tunnels. Submerged box type tunnel was buildup the unit segments in dry dock or ship yard by 10 to 20meters. The submerged box was composed with segments was join each together. It was installing the gate and waterproofing the coupling the front hull of a box. The complete submerged box rise up to the surface water, tow in the submerged box by tugboat, going to the destination of tunnel construction site. Beforehand dredge up soil at the bottom of a underwater, sinking the submerged box, connection together complete submerged box in underwater. The research and development ILM tunneling method is receiving careful study. Biggest weakness in submerged concrete box type tunnel was pressure waterproofing, box to box connecting, complete submerged boxes navigation and installation, after operation the submerged tunnel and management concrete box structure. It was positive evidence in submerged concrete box type tunnel. We make a practical application of the principle "the ILM tunneling method in underwater construction methods."

• 한국해양공학회지
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• 제13권3B호
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• pp.73-82
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• 1999

In this research, an experimental study is presented to check the possibilities of offshore structures monitoring using AE techniques. The underwater transducer and preamplifier are fabricated. And, it is proved that this unit can be used for the detection of AE in offshore structures. Wave propagation studies have shown that supplementary attenuations due to seawater are significantly reducing the detection range of the sensors. It excludes the possibility of offshore structures monitoring with a small number of sensors. We conclude that AE waves would be correctly detected for a path of about 3m. Tubular joints have been tested in air and underwater using simulated elastic wave. Ability of AE techniques to detect and locate cracks early in their evolution has been demonstrated. Several parameters of AE generation have been set in evidence. It has also been shown that crack development goes with an increase of AE parameter. Conclusively, it is shown that AE techniques can provide practical alternatives to present methods being used for inspection of deep-water offshore structures undergoing structural degradation due to fatigue crack growth.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.137.5-137
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• 2001

This paper proposes a method that combines diverse evidence relevant to the reliability to evaluate the reliability of complicated systems such as robots. In practice, reliability experts combine diverse evidences relevant to the reliability and infer the answers by using their own way that are mostly informal. The proposed method also combines diverse evidence and performs inferences but informal and quantitative way by using the benefits of Bayesian Belief Nets (BBN). Diverse evidences could be those from dassical analysis techniques, test results, quality assurance about the process of manufacturing, and the quality of the company or development team, etc. Some of these evidences are qualitative and others are quantitative. Both are ...

• 한국전자통신학회논문지
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• 제3권4호
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• pp.204-209
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• 2008

3면이 바다로 덮여있는 해양국가인 우리나라에서 해난 사고는 다양한 원인과 결과를 보여준다. 매년 600-700건씩 발생하는 해난 사고는 소형선박인 어선이 대부분을 차지하고 있으며, 연안에서 발생하는 선박과 조업하는 어선과의 충돌, 유조선의 침몰등으로 인한 인명손실과 대규모의 환경오염에 대한 책임, 실종선박에 대한 수색 등은 반복되는 해난 사고의 유형이다. 21세기가 시작되면서 대형화된 선박과 선원들의 감소로 인하여 디지털 선박이 등장하게 되었고, 선박에 설치된 장비들에 대하여 디지털 데이터가 저장되고, 저장된 데이터 속에서 필요한 정보를 추출하고 분석하는 해상 디지털 포렌식이 필요하게 되었다. 해난 사고에 대한 원인 규명과 책임, 손해 배상 등을 다투기 위한 증거를 수집하는 방안으로 해상 디지털 포렌식을 제안하며 이를 이용하여 디지털 증거를 수집하는 방안을 제시한다.

• 한국콘텐츠학회논문지
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• 제22권10호
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• pp.733-741
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• 2022

해양범죄에서 발견되는 다양한 증거물 중 지문과 DNA(Deoxyribo nucleic acid)는 용의자를 특정할 수 있다는 점에서 매우 중요하다. 본 연구에서는 실제 해양환경에서 증거물로 많이 발견되는 비다공성 재질 5종(플라스틱, 스테인리스, 유리, 세라믹, FRP(Fiber reinforced plastic))을 선정하여 자연 및 혈액지문을 유류한 후 동해 해경서 전용부두에서 약 7일간 침지하였다. 그 후 CA(Cyanoacrylate) 훈증법과 4가지 분말법(Swedish black powder, Concentrated black powder, Supranano red powder, Dazzle orange powder)을 이용하여 지문 현출 후 DNA 추출, 정량, STR(Short tandem repeat) 프로필을 분석하였다. 지문현출방법 중 Supranano red powder를 적용하였을 때 DNA 농도가 상대적으로 높은 양이 나타났으며 STR 프로필 분석을 실시한 결과 평균 16.8~9개의 유전자좌위를 확보할 수 있었고, 유리 및 세라믹 재질에서는 20개 모두 확인할 수 있었다. 연구 결과 약 7일 동안 침지된 가상증거물에 지문 현출법을 적용 후 DNA를 추출 및 정량하여 STR 프로필을 확보할 수 있었으며, VMD(Vacuum metal deposition), SPR(Small particle reagent) 등 다양한 지문현출방법을 적용한 뒤 DNA를 분석하여 STR 프로필을 확보할 수 있는 추가적인 연구가 필요할 것으로 판단된다.

• Journal of Ship and Ocean Technology
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• 제6권4호
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• pp.19-76
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• 2002

The author was appointed by the UK Department of Transport as a fellow Assessor with R. A. Williams during Lord Donaldson's Assessment (1995) of the loss of the OBO ship DERBYSHIRE and in 1996 as a UK Assessor for the planning and surveys of the wreck. He relinquished his appointment in October 1997 and was not thereafter Involved in the review and analysis of data gathered. This paper may be considered to be complementary to the reports of the UK and EC Assessors (Williams and Torchio, 1998a and 1998b) which followed that review and analysis. The paper deals with the history and loss of the ship, Including the concept developed in 1995 of 13 possible loss scenarios in a formal safety Risk Matrix of probability and seriousness. It analyses abnormal wave effects on hatch cover collapse, on ship bending, and on flooding of bow spaces and no. 1 hold. The implosion-explosion mechanics during sinking is outlined to explain the devastation of the wreck. The 1996 and 1997 underwater surveys are outlined as are the findings of fact. Each of the final 14 loss scenarios is analysed in the light of the firm and circumstantial survey evidence, plus many other factors of survey experience, analyses and experiments. The updated Risk Matrix speaks for itself and leads to the prime conclusions and major recommendations.

• 한국해양바이오학회지
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• 제16권1호
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• pp.63-86
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• 2024

This study analyzed the distribution, diversity, and density variation of algal clusters in a freshwater reservoir from an oceanic island and a traditional inland water system to gain insights on future marine freshwater resource management. In the Paldang water system (Han River), despite the upstream Paldang Dam and the downstream Jamsil underwater reservoir being in the same meteorological zone, their algae density patterns varied inversely. The distinct algal cluster structure (diversity/dominance) of Paldang was altered in the downstream reservoir, suggesting that physical devices aid algae management in traditional water systems. In contrast, 24 out of 35 genera (63.2%) identified in the Jeolgol Reservoir (Baeknyeong Island) were unique, lacking regulatory mechanisms, and existing in a complex ecotone. The desmid Chlorophyceae Cosmarium, adapted to higher photosynthetic stress and low temperatures, dominated in January (38.04%) and August (86.45%) during the periods of extreme photosynthetic stress. Jeolgol's annual algal cluster structure (H' 2.097; D 0.259; S' 35) demonstrated higher stability than Paldang (H' 1.125; D 0.448; S' 13) and the Jamsil underwater reservoir (H' 1.078; D 0.469; S' 12), maintaining an H' above 1.5 even during midwinters. No evidence of TN/TP inflow from surrounding soils was observed, even during torrential rainfalls, with phosphorus being the limiting factor for algal growth. TOC, BOD, chlorophyll-a, and turbidity peaked during Cosmarium bloom. Future climate change is expected to cause fluctuations in algal clusters and related water quality factors. The complex transitional nature of the Jeolgol Reservoir, its algal diversity, and the interspecies interactions contribute to the high stability of its algal community.

• Fisheries and Aquatic Sciences
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• 제25권11호
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• pp.549-558
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• 2022

The Indonesian Archipelago has a very complex geological history, along with equatorial warm sea temperature, resulting in diverse types of coral reefs and high diversity of coral reef fish. Many livelihoods of the coastal community are dependent on coral reef fisheries. The present study aimed to determine which region and location in the Indonesian Archipelago has the most diverse and abundant coral reef fish. The archipelago was divided into four regions: the Indian Ocean, Sunda Shelf, Wallacea, and the Pacific Ocean. Data were obtained from a national coral reef monitoring program of the Indonesian Research Center for Oceanography (RCO)-the National Board for Research and Innovation (BRIN). The reef fish data were collected using the underwater visual census method, from 321 belt transects on 24 locations (districts) across the archipelago. The results show that coral reef fish diversity of the Pacific region was the highest across the archipelago for all three trophic levels, i.e., corallivore, herbivore, and carnivore fish. The Pacific Ocean region also had the highest fish abundance for the three trophic levels. Comparison among locations revealed that the best ten locations in reef fish diversity and abundance were Sabang, Mentawai, Makassar, Selayar, Buton, Luwuk, Ternate, Raja Ampat, Biak, and Wakatobi. Wakatobi reefs showed their supremacy in carnivore fish diversity and abundance, while Biak reefs were the best in herbivore fish. The abundance of corallivore fish was also considerably high in Sabang reefs, but it is still lower than in Raja Ampat, Biak, and Wakatobi reefs. These results provide empirical evidence that the coral reefs of Wakatobi and Biak are the hottest hotspots of coral reef fish diversity and abundance in the Indonesian Archipelago.