• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.287-296
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• 2017

The Formal Safety Assessment (FSA) is a structured and systematic methodology developed by the IMO, aimed at assessing the risk of vessels and recommending the method to control intolerable risks, thereby enhancing maritime safety, including protection of life, health, the marine environment and property, by using risk analysis and cost-benefit assessment. While the FSA has mostly been applied to merchant vessels, it has rarely been applied to a DP vessel, which is one of the special purpose vessels in the offshore industry. Furthermore, most of the FSA has been conducted so far by using the Fault Tree Analysis tool, even though there are many other risk analysis tools. This study carried out the FSA for safe operation of DP vessels by using the Bayesian network, under which conditional probability was examined. This study determined the frequency and severity of DP LOP incidents reported to the IMCA from 2001 to 2010, and obtained the Risk Index by applying the Bayesian network. Then, the Risk Control Options (RCOs) were identified through an expert brainstorming and DP vessel simulations. This study recommends duplication of PRS, regardless of the DP class and PRS type and DP system specific training. Finally, this study verified that the Bayesian network and DP simulator can also serve as an effective tool for FSA implementation.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.655-655
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• 2002

Spatial distribution of phytoplankton pigment concentration (PPC) and sea surface temperature (SST) around the East Korean Warm Current (EKWC) was described, using both ocean color images and advanced very high resolution radiometer (AVHRR) images. Water mass in this region can be classified into five categories in the horizontal profile of PPC and SST, nLw(normalized water-leaving radiance) images: (1) coastal cold water region associated with concentrations of dissolved organic material or yellow colored substances and suspended sediments, (2) cold water region of thermal frontal occurred by a combination of phytoplankton absorption and suspended materials, (3) warm water overlay region by the phytoplankton absorption than the suspended materials; (4) warm water region occurred by the low phytoplankton absorption, and (5) offshore region occurred by the high phytoplankton absorption. In particular, the highest PPC area appeared in the ocean color and SST images with a band shaped distribution of the thermal front and ocean color front region, which is located the coastal cold waters along western thermal front of the warm streamer of the EKWC.

• Journal of Marine Bioscience and Biotechnology
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• v.8 no.2
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• pp.54-66
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• 2016

Productivity of Saccharina japonica was evaluated by water layers in Gijang and Wando sea area to find the suitable farming areas for mass production of biomass. For this, S. japonica was cultivated at various depths (0.5, 1, 2, 3 m), respectively. As the result, the growths in Gijang were 225.1-261.5 cm in length, 18.5-21.3 cm in widths, 396.0-537.7 g in weights, 14.3-17.8 kg/cluster in biomass, and those in Wando were 332.0-435.7 cm in lengths, 24.6-32.5 cm in widths, 766.0-1,232.9 g in weights, 16.4-24.3 kg/cluster in biomass. It showed that the growths of blades in Wando were faster than those in Gijang. The growth rates of blades by the depths were faster at 0.5-1 m depth from January to June. After June, however, as the growth rates of blades were lower than the shedding rates of blades, it showed that the growth of S. japonica decreased at all depth conditions except 2 m depth. Productivity of S. japonica was better in Wando which is lower in the water temperature and nutrients than Gijang.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.1
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• pp.32-39
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• 2021

Korean coastal fishery suffers from profitability degradation due to a decrease in fisheries resources, pollution in coastal waters, fuel coast increase, and market opening for aquaculture products. The next generation Korean fishing vessel aims at the improvement of energy efficiency, enhancement of crew welfare, and safety. These purposes can be accomplished by adopting a new standard hull form with improved resistance performance and a modernized residence facility on the deck. In order to improve resistance performance, this study attempts to optimize design variables for stern flaps for three kinds of fishing vessels - coastal multi-purpose, coastal trap, and dredged nets. A series of model tests for these fishing vessels was carried out in the towing tank of Pusan National University. The results indicate that for some cases, the stern flap caused the stern trim of the vessel to decrease, leading to the resistance reduction.

• Journal of Navigation and Port Research
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• v.46 no.5
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• pp.435-440
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• 2022

The development and introduction of a Maritime Autonomous Surface Ship (MASS) are some of the most important changes leading to the fourth industrial era in the maritime area. The term 'MASS' refers to a ship operating independently, without human intervention, to reduce maritime accidents caused by human errors. Recent UK findings MASS also noted that particularly the dynamic positioning system will be considered to apply as newly function to a MASS. The DP system, a ship system developed decades ago and used for specific purposes like offshore operations, provides various functions to facilitate the accurate movements of the vessel, and operators can make decisions within the DP system, in addition to the ordinary ship system. In this paper, it would like to present the connection and application method with the main technical elements of the DP system in connection with the main technology of the DP system to achieve the safe operation of a MASS. In particular, among various position reference systems, the capability plot function of DP system, and the "follow target" mode in the operation mode are attractive functions that can contribute to the safe operation of autonomous ships.

• Korean Journal of Remote Sensing
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• v.38 no.4
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• pp.355-364
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• 2022

In this study a tendency of abnormal sea surface temperature (SST) occurrence in the seas around South Korea is analyzed from daily SST data from satellite and 14 buoys from August 2020 to July 2021. As thresholds 28℃ and 4℃ are used to determine marine heatwaves(MHWs) and abnormal low water temperature (ALWT), respectively, because those values are adopted by the National Institute of Fisheries Science for the breaking news of abnormal temperature. In order to calculate frequency of abnormal SST occurrence spatially by using satellite SST, research area was divided into six areas of coast and three open seas. ALWT dominantly appeared over a wide area (7,745 km²) in Gyeonggi Bay for total 94 days and it was also confirmed from buoy temperature showing an occurrence number of 47 days. MHWs tended to be high in frequency in the coastal areas of Chungcheongdo and Jeollabukdo and the south coastal areas while in case of buoy temperature Jupo was the place of high frequency (32 days). This difference was supposed to be due to the low accuracy of satellite SST at the coasts. MHWs are also dominant in offshore waters around Korean Peninsula. Although detecting abnormal SST by using satellite SST has advantage of understanding occurrence from a spatial point of view, we also need to perform detection using buoys to increase detection accuracy along the coast.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.105-116
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• 2000

In order to investigate the seasonal variation of watermass in the central coast of the southern sea of korea, oceanographic observation on the fishing grounds were carried out by the trainingship of Yosu University on May, Aug. and Nov. in 1998 and Feb. in 1999. The resultes obtained are summerized as follows : 1). The watermass in the fishing ground were divided into the coastal water(30.0~31.6$\textperthousand$ ), mixing water(31.7~33.4$\textperthousand$) and the offshore water(33.5~35.0$\textperthousand$) according to the distribution of salinity from T-S diagram plotted all salinity data observed on May, Aug. and Nov. in 1998 and Feb. in 1999. 2) The ranges of temperature and salinity were from 14.1$^{\circ}C$ to 18.8$^{\circ}C$ and from 32.2$\textperthousand$ to 34.9$\textperthousand$ in spring(May), from 14.2$^{\circ}C$ to 27.7$^{\circ}C$ and from 29.0$\textperthousand$ to 34.7$\textperthousand$ in summer(August), from 13.4$^{\circ}C$ to 21.3$^{\circ}C$ and from 31.45$\textperthousand$ to 34.5$\textperthousand$ in autumn(November) and from 8.2$^{\circ}C$ to 14.8$^{\circ}C$ and from 33.9$\textperthousand$ to 34.6$\textperthousand$ in winter(February), respectively. 3) The distribution of watermass in the fishing ground varied largely each seasons, but a general tendency on the distribution was obtained. That is, in spring and autumm the offshore water was distributed most widely and in summer the coastal and mixing water occupied the fishing ground but in winter the offshore water prevailed. 4) Variation of temperature and salinity were appeared between the surface and 30m in the coastal region and between the surface and 50m in the open ocaen region. Therefore, in the summer the thermocline and halocline were made between surface and 30m layer with vertical gradients of 10.5$^{\circ}C$/30m and 4.0$\textperthousand$/30m in the coastal region and in the open ocean region the thermocline and halocline were made between surface and 50m layer with vertical gradients of 13.$0^{\circ}C$/50m and 3.8$\textperthousand$/50m.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.143-156
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• 2014

We reviewed investigation status on turbidity plume in the statement of marine environmental survey(2008 to 2012) associated with marine sand extraction projects. The survey statement from seven marine sand extraction sites (extraction area of Southern EEZ, extraction area of Western EEZ, relocation zone in the Western EEZ, sea area under jurisdiction of Taean-gun, sea area under jurisdiction of Ansan City, and two discrete sea areas under jurisdiction of Ongjin-gun) in the nearshore and offshore of Korea showed that in situ observations were carried out for the dispersion and transport of suspended sediments on two areas (One is a extraction area in the EEZs, the other is an area of coastal sites). However, sampling station and range have not been selected considering physical, geographical factors (tide, wave, stratification, water depth, etc.) and weather conditions (wind direction and velocity, fetch, duration, etc). Especially turbidity plumes originating from three sources, which include suspended sediments in overflow(or overspill) discharged from spillways and reject chutes of dredging vessel, and resuspended sediments from draghead at the seabed, may be transported to a far greater distance outside the boundary of the extraction site and have undesirable impacts on the marine environment and ecosystem. We address that behaviour of environmental pollutants such as suspended solids, nutrients, and metals should be extensively monitored and diagnosed during the dispersion and transport of the plume. Finally we suggest the necessity to supplement the current system of the sea area utilization consultation and establish the combined guidelines on marine sand extraction to collect basic data, to monitor cumulative effects, and to minimize environmental damages incurred by the aftermath of sand extraction.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.71-74
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• 2006

Currently offshore fisheries are one of shrinking industries and fishermen are getting older. Moreover it is difficult to work fisheries for decreasing fishermen as the time goes. Two people per a boat work together at least for proper fisheries. If the unskilled fisherman boards on boat, it will make some troubles to speak each other and diminish the efficiency of working because one person should control the boat. So it need to study the remote control system for leasure and outboard engine that can control and work at the same time. The remote control system is consisted of engine revolution, steering gear and forward reverse neutral gear controls. These three controls are made by position and speed control using DC motor, and microprocessor is used to communicate and control the engine speed This system can be controled and worked alone and we tested the system at sea and confirmed that the system works properly.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.487-495
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• 2021

The voltages mainly used in ships are 450 [V], 6.6 [kV], and 11 [kV], and an earthed system is applied to ensure the stability of the power distribution system. In general, low-voltage ships using 450 [V] apply an unearthed system, while high-voltage ships using 6.6 [kV] or 11 [kV] use a high-resistance earthed system. When an earth fault occurs in a ship's power distribution system, the voltage of the healthy phase increases to the line-to-line voltage or higher, which causes an excessive impact on the insulation of the cable. Thus, analyzing this behavior is very important. In this paper, we investigate the characteristics of the line-to-earth voltage variation according to earth faults and a recognition procedure of a faulty phase using the symmetrical coordinate method for a high-resistance earthed system and unearthed system. A mathematical model of the line-to-earth voltage was derived through the symmetric coordinate method, and the ship voltage for simulations was selected as 6.6 [kV] and 450 [V]. A MATLAB simulation proved that this method can determine the highest increase of the line-to-earth voltage, which leads by 120° on the faulty phase, and it accurately judges the faulty phase in both earthed systems.