• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.451-466
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• 2017

Deep-sea fishing vessel No. 501 Oryong was fully flooded through its openings and sunk to the bottom of the sea due to the very rough sea weather on the way of evasion after a fishing operation in the Bearing Sea. As a result, many crew members died and/or were missing. In this study, a full-scale ship flooding sinking simulation was conducted, and the sinking process was analyzed for the precise and scientific investigation of the sinking accident using highly advanced Modeling & Simulation (M&S) system of Fluid-Structure Interaction (FSI) analysis technique. To objectively secure the weather and sea states during the sinking accident in the Bering Sea, time-based wind and wave simulation at the region of the sinking accident was carried out and analyzed, and the weather and sea states were realized by simulating the irregular strong wave and wind spectrums. Simulation scenarios were developed and full-scale ship and fluid (air & seawater) modeling was performed for the flooding sinking simulation, by investigating the hull form, structural arrangement & weight distribution, and exterior inflow openings and interior flooding paths through its drawings, and by estimating the main tank capacities and their loading status. It was confirmed that the flooding and sinking accident was slightly different from a general capsize and sinking accident according to the simple loss of stability.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.867-874
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• 2021

The IoT (Internet of Things) technology is rapidly becoming an important consideration in many engineering fields in the current 4th industrial era. In recent years, the concepts of digital shipbuilding and smart factories have been adopted as trends in shipyards. However, there is active interest in research on implementing autonomous driving in autonomous vehicles and airplanes, which is currently available in commercial form in a limited capacity. The present study is regarding the path-tracking performance of a boat to accomplish an autonomous driving mission using a flight controller (FC) and real-time kinematic (RTK) global positioning system (GPS) based on an open-source Ardupilot; an actual sea test is also performed using this system on a calm lake. The boat's mission is to evaluate the maneuverability of the self-driving process to a specific point and returning to the home position. For a given speed, the difference between the preset mission trajectory and actual operational trajectory was analyzed, and a series of studies were conducted on the applicability of the system to ships. In addition, the movements and maneuverability of the OmniX-type hull with four propellers were investigated, and the driving path-tracking performance was observed to increase by a maximum of 48%.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.3
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• pp.202-210
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• 2013

As incomes increase, interest in ocean leisure picks up. As a result, a lot of research and developments on hull form design and production of planing boats, mostly used for ocean leisure, are needed. Analysis in researches on resistance of planing boats shows that resistance characteristic of planing boats is different from resistance characteristic of general boats because the former is fast, and its wetted surface is very small. Using Savitsky formula widely used in the calculation of effective horse power in shipbuildingyards, and propulsion system and engine manufacturers, this study calculated total resistance of a research planing boat. Then it analyzed the flow characteristics of the planing boat through theoretical analysis and wind tunnel experiment, and computed air resistance and lift force by changes of speed and trim angle. It also compared and analyzed result of theoretical analysis and experiment of the ratio of air resistance to total resistance under variations of velocity and trim angle. When the study is used to estimate more accurate effective horse power, it is expected to remedy abuses of unnecessarily installing high-powered engine. As nature disasters due to abnormal changes of weather increase, interest in greenhouse gas grows. International Maritime Organization (IMO) legislated Energy Efficiency Design Index (EEDI) and Energy Efficiency Operational Indicator (EEOI) to reduce ship greenhouse gas emissions. But this index will be applied to over 400 tons ships, small ships, emitting more greenhouse gases than larege ships per unit power, will dodge the regulations. Thus, this study indicated a problem by calculating greenhouse gas emissions of an ocean leisure planning boat (a small ship), and suggested the need for EEDI of small ships.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.518-524
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• 2015

The objective of this research was to investigate the influence of various depths of expanded rice hull (ERH) medium and fixation dates of runner plantlets of 'Seolhyang' strawberry on the growths in nursery field and in plastic house soil after transplanting. The five treatments in medium depths (30, 50, 70, 90, and 110 mm) and four treatments in fixation dates (1st and 15th July and 1st and 15th August) were tested. The growths of runner plantlets were investigated before transplanting to plastic house soil. The early growth and inflorescence rates of crops after transplant to plastic house soil were also investigated. The plant height and fresh weight of runner plantlets were the highest in the medium depths of 50, 70, and 90 mm. The medium depth of 30 mm had higher numbers of first roots, but lower root fresh weight compared to those of 70, 90, and 110 mm. The treatment of 30 mm in medium depth showed poorer growth in all indexes except root length and root weight compared to those of 70, 90, and 110 mm. The runner plantlets fixed on July 1 and July 15 showed good root growth and the weights of ERH adhered to form root balls were 18.3 g and 13.9 g, respectively. The detached amount of ERH was less than 40% in the two treatments when root balls were shaken by a vibratory sieve shaker. The plant growth at 45 days after transplanting to plastic house soil were not significantly different when the runner plantlets were fixed in the period from July 1 to Aug. 1. The inflorescence rates of the first cluster were 93 to 100% when runner plantlets were fixed in the period from July 1 to Aug. 1. By contrast the runner plantlets fixed on the Aug. 15 had a 67% in florescence rate for the first cluster. These results indicate that optimum depth of ERH medium was 7 cm and the ranges of optimum fixation dates are from July 20 to 25.