• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.760-767
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• 2014

An experimental study is carried out to investigate the effect of jet stream in the gab of rectangular cylinders with different length in a parallel arrangement by using PIV method in a circulating water channel. The height(h) of the rectangular cylinder and the gap between the cylinder is 10mm, and the width(B) which is 300mm. The length of the model for flow direction was applied to 30mm, 60mm, 90mm & 120mm, The aspect ratio of a model on the basis of height(H=30mm) is 1, 2, 3 and 4. Reynolds number $Re=1.4{\times}10^4$, $Re=2.0{\times}10^4$, $Re=2.9{\times}10^4$ based on the height(H) of model for the distance of tidal distributions as of water depth have been applied during the whole experiments. The measurement area was set to 5H rear of the cylinder. As a result, Vortex size in the wake area were increased as velocity increased. and high aspect ratio increased through-flow velocity component in the near wake. Velocity deficit increased highly after near-wake area and low aspect ratio.

• Journal of Korean Theatre Studies Association
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• no.40
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• pp.5-27
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• 2010

The Korean Mask-Dance Theatre has been developed closely related to Korean Shaman rituals. As many scholars noticed, the performers of the Mask-Dance Theatre were closely related to the Shaman family. In addition, there are mask-dance performances in actual shaman rituals. and are the representative performances among them. This essay intends to compare these two mask-dance performances in the shaman rituals to the similar performance of Old Grandpa and Grandma episode in the regional Mask-Dance Theatre. This study would bring us further in proving the close relation between the shaman ritual and the Mask-Dance Theatre. is one episode, Keori, in the shaman ritual of 'Baeyeonsin-kut' and 'Taedong-kut' in the mid-west seashore area. 'Taedong-kut' is the village shaman ritual for fertility and prosperity, while 'Baeyeonsin-kut' is a private shaman ritual for a large catch of the ship. is held in the later part of the whole shaman ritual since the later part tend to be more for entertainment than actual ritual. The story of is very similar that of in Pongsan Mask-Dance Theatre of the mid-west region. In addition, some of their dialogues are very similar. Only the later part is different. These similarities indicate that the Mask-Dance Theatre, which came into being in later period than the shaman ritual, has likely taken the story motif of the shaman ritual. is also a performance in the shaman ritual of east coasts. is more elaborate and recreational than of the west coasts. is also performed near the end of the ritual, and sometimes it is not performed at all. This indicates that has little ritual meaning left. When we compare it with the regional Mask-Dance Theatres such as Keosung Okwangdae, Tongyong Okwangdae, and Suyong Yaryu, the structure and the story lines are also very similar. It is a question why only the motif of the Grandpa and Grandma isfound both in the shaman ritual and the Mask-Dance Theatre. Many other motifs of other episodes in the Mask-Dance Theatre are not found in the shaman rituals. It seems that the Grandpa and Grandma motif is related to the ur-belief in fertility. In other words, this motif seems to be originated from the old belief in the fertility couple of Chonha Taechanggun and Jiha Yeochanggun. The shaman ritual for fertility first picked up this motif, and then the mask-dance theatre also adapted this motif for its recreational purpose. When we compare with , still has more aspects of fertility ritual, while lost its ritualistic meaning and its main purpose is to develop dramatic needs. and are invaluable existent performances to prove theatre's origin in ritual. The existence of mask-dance performances in the shaman rituals shows us the transit performance between theatre and ritual.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.142-149
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• 2019

In the early 2000s, the Korean government first attempted to acquire nuclear-powered submarines as strategic assets. Acquisition of nuclear-powered submarines must overcome the challenges of the initial costs and operating costs of trillions of US dollars per ship, must be agreed to by the international community (including neighboring countries) and in a national consensus, and must have an established technical infrastructure (including manpower). The US navy has been working with governments that want to acquire nuclear propulsion warships since the 1950s, and in 1982, they enacted an executive order called the United States Naval Nuclear Propulsion Program to consolidate efforts and prepare for the future, which sets out the organizational structure, authority, and responsibilities of US governmental management, and integrates national efforts. This paper is to gain valuable wisdom from the U.S. Naval Nuclear Propulsion Program by analyzing all of its histories and contributions, thereby providing valuable lessons for a future program in Korea. It might not be possible to follow the U.S.A. one-on-one because of the scale of national and military forces, but at least we can avoid time and effort spent on trial and error.

• Korean Journal of Heritage: History & Science
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• v.39
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• pp.5-38
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• 2006

Although in Korea there are only three examples of wooden coffins being found in burial mounds - from the Daho-ri, Songhyun-dong, and Munyung tombs, in Japan data on the shape and structure of wooden coffins from the Gofun era is relatively abundant. The wooden coffins of the Gofun era of Japan can be classified into either the dugout log style or the combined boards style according to their method of manufacture. They can also be divided by shape, into such categories as the boat shape, the split bamboo shape, the box shape, and so on. The box shape category can be further divided into the assembled type and the nailed type, according to how the boards are put together. Japanese Umbrella Pine (Sciadopitys verticillata) was favored as coffin-wood in all ages, but during the later Gofun era easily obtained woods such as the Japanese cedar (Cryptomeria japonica) or the Hinoki Falsecypress (Chamaecyparis obtusa) were also used. The coffins found at Daho-ri and Songhyun-dong are similar to the Japanese dugout log style in shape and manufacture, while the king's and queen's coffins excavated at Munyung Tomb are seen to have had direct influence on the appearance of nailed coffins Japan. The coffin in Songhyun-dong 7th mound was originally a dugout log boat. It was probably used for practical reasons such as the bugproof, anti-corrosion qualities of camphor wood, not because of ideological reasons such as in a boat burial (in which the boat takes the deceased to the after world). Because the Changnyong region is inland, where camphor trees do not grow, using an already existing boat may have been the only way to procure a camphor-wood coffin. From historical circumstances, it may be inferred that the camphor trees were imported into Korea from Japan, between which there was much cultural exchange.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.203-208
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• 2022

Recently, various digital technology issues such as e-Navigation, Maritime Autonomous Surface Ship (MASS) and Smart ships have constantly emerged in the maritime industry, based on the fourth industrial revolution. The International Maritime Organization is gradually tightening regulations for marine safety and marine environmental protection, and these strengthened regulations are leading to new maritime industries. Thus, the purpose of this study was to design a suitable model to analyze the industrial competitiveness of domestic autonomous operation technology industry, based on the Porter's diamond model. Based on a total of five evaluation factors and 13 detailed factors, the industrial competitiveness of the domestic autonomous operation technology industry was evaluated qualitatively and quantitatively. This industry, which is in the early stage of industrial development, was evaluated as 16.9 points relative to indexing industrial competitiveness. Currently, it is characterized by the simultaneous development of related regulations and core technologies, from the establishment of the scope of the industry. The industrial competitiveness evaluation considering these industrial characteristics is expected to serve as the basis for strategic support and new industrial policy, and impact a wide range of related industries such as shipping, logistics, ports, and shipbuilding and equipment industries.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1267-1273
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• 2022

Although the Korea shipbuilding industry has recently been receiving most of the orders for ships in the world, production processes are being disrupted due to a shortage of manpower at the production site. This is because the workers quit the shipyard as both work and wages were reduced due to the long slump in the shipbuilding industry. The main reason for the increase in orders was the large-scale orders for Qatar LNG carriers, and the situation in which the technical specifications required for ships are becoming more complex is also working to an advantage. Because the contract delivery time is of utmost importance for ships, the dock launch plan is the most important management item among the shipyard's major processes. The structure to be built in the dock may be a hull that has left the design work or a finished vessel, and in some cases, it is often at the level of some blocks of the hull. When launching, the hull is affected by the hogging or sagging moment due to the fluid force, and securing the safety of the structural strength of the block connection is of utmost importance. In a normal process, the connecting member launches after welding has been completed, but in actual shipbuilders, quick decision-making is needed on the conditions for securing structural safety to comply with the docking schedule. In this study, a detailed analysis method and applicability using a bending stress evaluation method and finite element analysis modelling were analyzed to rationally judge the above-mentioned problems from an engineering point of view. The main contents mentioned in the thesis can be used as good examples when conducting similar structural strength evaluations in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.372-379
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• 2023

International oil prices are expected to increase from $85 a barrel this year to up to $100 a barrel in the second half of the year; this is likely to increase orders for offshore plants in the global market. One main characteristic of offshore plants is that a large helideck is located on the top side, and aluminum alloys are used as the basic material of the structure for weight reduction and corrosion resistance. Shipowners are increasing the size of helicopters to quickly evacuate lives in the event of an emergency, and the safety use load of devices that can stably secure helicopters to the deck is also required to increase. Owing to the nature of the aluminum material, the structural strength caused by welding is greatly reduced; therefore, the fixing device must be designed by embedding it in the deck and fixing it with bolts. In this study, a model applying aluminum alloy 6082-T6 was developed to develop a helicopter fastening device that can be used for large helidecks (diameter = 28 m). The developed item was verified through nonlinear structural strength calculation to satisfy the load used for the actual fastening condition. The load condition with a 45° showed a lower ultimate strength than the 90° case owing to local plastic collapse. The nonlinear structural collapse behavior showed a result similar to that of the experimental test. The main contents derived from this study are considered to be reference materials when evaluating the structural strength of similar aluminum equipment.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.127-128
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• 2021

This study suggests surface wave communication, which uses a metal surface as a medium, to provide wireless communication in the extreme environment due to surrounding metal materials on vessels. The test was conducted on a G/T 265 tons tug boat, and to confirm the possibility of surface wave communication between a bridge and each designated space in the boat. As a result, the transmission speed was 13Mbps in average. For the test case between the bridge and the engine room, transmission speed was 4.3Mbps while the engine was on, and 1.2Mbps during sailing. It was able to be overcome by partially changing the equipment installation location. Surface wave communication in a bow storage, a fully enclosed space, had 8Mbps better transmission speed than wireless communication; this confirmed the superiority of surface wave communication in confined spaces on a vessel. Additional surface wave generators were designed and applied to resolve the paint issue. It is expected to apply surface wave communication to implement the new wireless solution on vessels.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.4
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• pp.358-364
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• 2024

Type A carrier structures that support blocks or equipment gradually deform over time with load changes, reducing the area in contact with the block and changing the load pattern from distributed to concentrated during construction work in the shipyard. This phenomenon has the potential to misrepresent actual service loads. In particular, A carriers are often used by small manufacturers, who often do not have specialized engineering capabilities, necessitating the development of a method for easy calculation of carrier safe working load. This study proposes a quick evaluation method for the long-term safe working load of Type A carriers, to predict the plastic deformation and safety issues resulting from changes in load distribution. Based on the results of finite element analysis (beam and shell modeling) of the centralized load, beam-theory was modified to propose a method for determining the distributed load conditions of the A-carrier. In beam modeling, the theoretical value was multiplied by a correction factor of 0.73 for concentrated loads and 0.69 for distributed loads to obtain a safe working load. For shell modeling, a correction factor of 0.75 can be used for concentrated loads and 0.69 for distributed loads. This study can serve as a basis for improving the safety of shipbuilding, enabling quick and effective decisions for determining safe working loads in actual working environments.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.131-136
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• 1985

The calculation of the resulting fluid motion is an important problem of ship hydrodynamics. For a partially immersed body the condition of constant pressure at the free surface can be linearized. The resulting linear boundary-value problem for the velocity potential is the Neumann-Kelvin problem. The two-dimensional Neumann-Kelvin problem is studied for the half-immersed circular cylinder by Ursell. Maruo introduced a slender body approach to simplify the Neumann-Kelvin problem in such a way that the integral equation which determines the singularity distribution over the hull surface can be solved by a marching procedure of step by step integration starting at bow. In the present pater for the two-dimensional Neumann-Kelvin problem, it has been suggested that any solution of the problem must have singularities in the corners between the body surface and free surface. There can be infinitely many solutions depending on the singularities in the coroners.