• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.43-46
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• 2011

The noise characteristics of multi-purpose dive support vessel show the different patterns such as types of noise sources, accommodation arrangement and etc due to its operation. Especially, the tunnel and retractable thruster for the dynamic positioning should be considered at the noise analysis. The floating floor is selected as the main measure of noise reduction and is constructed at the deck near the noise sources. In this paper, the noise analysis of dive support vessel is based on the estimation of noise sources and floating floor and SEA (Statistical Energy Analysis) is used for analysis of the air-born noise and structure-borne noise. The noise analysis of air conditioning system is also carried out and the noise results of cabin room are reviewed.

• Journal of the Korean Society of Safety
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• v.34 no.4
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• pp.103-110
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• 2019

Underwater works are indispensable in the coastal and ocean engineering fields, and the reliance on manpower is higher than land works. Divers who work for a long time in a high-pressure underwater environment are always exposed to the risks of diving-related diseases. To prevent them, proper planning, operation, and management of diving by a supervisor with professional diving knowledge are required. This study provides the basic data for supervisors to plan, operate, and manage air diving for safe and efficient work in underwater construction sites. It is well-known that air diving simulations using the varying permeability model (VPM) require a longer decompression time as the water depth and the residence time in water increase. Therefore, it is crucial to have a proper surface interval through repetitive diving rather than single diving to improve the safety of the divers and the efficiency of underwater work. Furthermore, coastal and ocean engineers who manage and supervise underwater construction work must acquire expert knowledge on diving before they can plan, operate, and manage diving.

• Journal of the Korean Society of Safety
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• v.35 no.1
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• pp.70-78
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• 2020

Nitrox diving was introduced by the NOAA (National Oceanic and Atmospheric Administration) to increase the oxygen content and lower the nitrogen content in respiratory gases. The commercial diving sector specializing in underwater operations has recently introduced regulations on the use of Nitrox. Because the respiratory gas for Nitrox diving has a lower nitrogen content than the normal air, the amount of nitrogen dissolved in the body is small, which not only significantly reduces the decompression time compared to air diving, but also reduces the chance of exposure to decompression sickness. In this study, we applied the VPM (Varying Permeability Model) algorithm to virtual diving with air and Nitrox as a respiratory gas, respectively, to study the optimal Nitrox diving for the safety at the underwater works. The results showed that Nitrox diving had a longer NDL (No-Decompression Limit), a much shorter depression time. In other words, Nitrox diving in underwater works is safer from decompression sickness than commonly used air diving.

• Journal of the Korean Society of Safety
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• v.26 no.2
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• pp.42-47
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• 2011

Going underwater is supposed to begin with the history of human beings. At first it was confined to relatively shallow level, less than several meters by holding breath. Recently, deep level diving has been necessary for such purpose as construction, maritime salvage, military operations, research and sports by using SCUBA(self-contained underwater breathing apparatus) equipment. As one goes down into water, the pressure on the diver is increased due to water pressure with depth, usually 1 atm for each 10 m water level. In deep water, mixed gas or nitrox(EAN, enriched air nitrox) could be applied for the divers lest they should get disease due to high pressure. Of these, the former is usually composed of oxygen and inert gas like helium or hydrogen, the latter contains higher oxygen content than that in normal air in which the oxygen concentration is designated by the character "EAN" followed by vol. % of oxygen, for example, "EAN 40" contains 40% of oxygen. In this case, a victim was found at the 39 m below the sea surface breathing air and nitrox in cylinder wrongly marked as EAN 36, which was analyzed to contain 63% of oxygen by GC/TCD. The cause of death could not be exactly related with the oxygen content in the nitrox cylinder, because the accurate depth for the victim to dive was not known, even though the victim was just found at the depth of 39 m. However, the wrongly marked nitrox could be believed to be the main cause of the death at the depth unless there happened any other accident except that during diving.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.735-742
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• 2010

This paper reviewed the diving standards for underwater work in hostile environment and analyzed applied Navy diving technique, diving equipments and procedure for rescue operation of Navy ship Cheonan's missing crew occurred near Bak Ryung Do in March 2010. The operation was done beyond the international standards and safety practice, and by considering the nature of the mission, urgency and effectiveness as well as the detailed facts such as duration and depth of the dive, type of work to be performed, environmental conditions, time constraints of early rescue operation, it is analyzed that using air scuba diving system was adequate.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.485-493
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• 2016

Recently submarine and unmanned underwater vehicle (UUV) are equipped with a fuel cell system as an air independent propulsion system. Methanol fuel processor can efficiently supply the hydrogen to the fuel cell system to improve the ability to dive. This study investigated the optimal conditions of the methanol fuel processor that may be used in the closed environment. For this purpose, the numerical model based on Gibbs minimization equation was established for steam reformer and three exhaust gas burners. After simulating the characteristics of steam reformer according to the steam-to-carbon ratio (SCR) and the pressure change, the SCR condition was able to narrow down to 1.1 to 1.5. Considering water consumption and the amount of heat recovered from three burners, the optimum condition of the SCR can be determined to be 1.5. Nevertheless, the additional heat supply is required to satisfy the heat balance of the methanol fuel processor in the SCR=1.5. In other to obtain additional amount of heat, the combustion of methanol is better than the increased of SCR in terms of system design.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.139-149
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• 2006

This study is to analyze the kinematic variables of inward $1{\frac{1}{2}}$ somersault in platform diver. For the manner, 3 people form the national diving team in the year 2000were chosen as the subjects and two S-VHS video cameras set in 60frames/sec were used for recording their motions. Coordinated raw positions data through digitizing are smoothing by butter-worth's low-pass filterin method at a cut off frequency 6.0Hz. and the direct linear transformation(DLT) method was employed to obtain 3-D position coordinates. The conclusions were as follows. However, horizontal distance which is the change of the COG, form the point of the jump to the point of Event 3 where the player is out of the board range completely, Subject B showed 105.1cm and 71.1cm of the vertical distance which are shorter horizontal distance and higher vertical distance, thus, took a great advantage of the position to prepare for the entry. Therefore, if a player takes higher position by speeding up the vertical velocity at the moment of the jumping off the board, and stays in the air longer, the player can have more time to show his skill. Because of the use of the characteristics of the inward somersault, keeping the safe distance form the board is important but in order to higher the completeness, it is ideal to keep the horizontal distance little over 100cm. Also, the angles of shoulder and elbow from Event 1 to 4, depending on swing of the arms, motions in the air, getting ready for the entry, showed some difference individual by individual, according to the velocity of the thigh and shank showed much difference while getting ready and take-off, and it's because of the individual's different bending and straightening for horizontal and vertical distance.