• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.16-25
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• 2012

To calculate the total mass flux that change in dry and flood season in the Yeomha Channel of Gyeonggi Bay, the 13 hour bottom tracking observation was performed from the southern extremity. The value of the total mass flux(Lagrange flux) was calculated as the sum of the Eulerian flux value and stroke drift value and the tidal residual flow was harmonically analyzed through the least-squares method. Moreover, the average during the tidal cycle is essential to calculate the mass flux and the tidal residual flow and there is the need to equate the grid of repeatedly observed data. Nevertheless, due to the great differences in the studied region, the number of vertical grid tends to change according to time and since the horizontal grid differs according to the transport speed of the ship as a characteristic of the bottom tracking observation, differences occur in the horizontal and vertical grid for each hour. Hence, the present study has vertically and horizontally normalized(sigma coordinate) to equate the grid per each hour. When compared to the z-level coordinate system, the Sigma coordinate system was evaluated to have no irrationalities in data analysis with 5% of error. As a result of the analysis, the tidal residual flow displayed the flow pattern of sagging in the both ends in the main waterway direction of dry season. During flood season, it was confirmed that the tidal residual flow was vertical 2-layer flow. As a result of the total mass flux, the ebb properties of 359 cm/s and 261 cm/s were observed during dry and flood season, respectively. The total mass flux was moving the intertidal region between Youngjong-do and Ganghwa-do.

• 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.

• Journal of the Korean Institute of Navigation
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• v.4 no.2
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• pp.45-79
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• 1980

The aim of this paper is to analyze the mechanics of price formation in the tramp shipping. For the purpose of this study, the main characteristics of tramp freight rates and the market is examined, and a brief examination of the nature ofthe costs of operation is given which are essential for the understanding of the functioning of shipping firms as well as for the understanding of developments in the tramp freight market. The demand and supply relationships in the market is also analysed in detail. Tramp shipping is an industry that has a market which functions under conditions that are not dissimilar to the theoretical model of perfect competition. However, it does notmean that tramp shipping market is a perfectly competitive market. It is apparent that this realworld competitive system has its imperfections, which means that the market for tramp shipping is near to being a perfectly competitive market on an internaitonal scale and it is freight are therefore subjext to the laws of supply and demand. In theory, the minimum freight rate in the short term is that at which the lowest cost vessels will lay-up in preference to operating, and is equal to the variable costs minus lay-up costs; and this would imply that in all times except those of full employment for ships there is a tendency for newer low-cost, and, probably, faster vessels to be driving the older high-cost vessels in the breaker's yards. In this case, shipowners may be reluctant to lay-up their ships becasue of obligations to crews, or because they would lose credibility with shippers or financiers, or simply because of lost prestige. Mainly, however, the decision is made on strictly economic grounds. When, for example, the total operating costs minus the likely freight earnings are greater than the cost of taking the ship out of service, maintaining it, and recommissioning it, then a ship may be considered for laying-up; shipowners will, in other words, run the ships at freight earnings below operating costs by as much as the cost of laying them up. As described above, the freight rates fixed on the tramp shipping market are subject to the laws of supply and demand. In other words, the basic properties of supply and demand are of significance so far as price or rate fluctuations in the tramp freight market are concerned. In connection with the same of the demand for tramp shipping services, the following points should be brone in mind: (a) That the magnitude of demand for sea transport of dry cargoes in general and for tramp shipping services in particular is increasing in the long run. (b) That owning to external factors, the demand for tramp shipping services is capable of varying sharphy at a given going of time. (c) The demad for the industry's services tends to be price inelastic in the short run. On the other hand the demand for the services offered by the individual shipping firm tends as a rule to be infinitely price elastic. In the meantime, the properties of the supply of the tramp shipping facilities are that it cannot expand or contract in the short run. Also, that in the long run there is a time-lag between entrepreneurs' decision to expand their fleets and the actual time of delivery of the new vessels. Thus, supply is inelastic and not capable of responding to demand and price changes at a given period of time. In conclusion, it can be safely stated that short-run changes in freight rates are a direct result of variations in the magnitude of demand for tramp shipping facilities, whilest the average level of freight rates is brought down to relatively low levels over prolonged periods of time.

• Journal of Korean Classical Literature and Education
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• no.38
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• pp.201-238
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• 2018

As a way of enhancing the intercultural ability needed for diverse cultural eras, this study focuses on the "narration" of the Italian education scholar Maddalena De Carlo in order to determine the "diverse values" created by the "symbolic representation" based on the folktales narrated by immigrants living in Korea. Through this, it specifically presents educational elements and contents that can raise relative sensitivity. The authors of this paper have connected, empathized, and communicated with people of various cultures in order to go beyond Carlo's discussion. The paper discusses the expansion of cultural sensitivity as an element of education through narrative topics using the folktales of immigrant narrators in Korea. It also recognizes the limitations of a desire for a homogeneous union within an intercultural society and thus formulates educational contents for creating a relationship with heterogeneous ideas through the elimination of communication barriers through heterogeneity and a consideration of the surface and the back. This is systemized in six steps. Step 1: Listening to oral folktales of immigrants, Step 2: Finding heterogeneous motifs imprinted in the immigrants' memories, Step 3: Understanding the meaning of the opposing qualities symbolized by heterogeneous motifs, Step 4: Creating narrative topics containing the key motifs, Step 5: Generating the value of symbolic representation as a narrative topic, and Step 6: Expanding the value of life into a cultural symbol. In Chapter 3, this study focuses on educational contents using immigrants' folktales by applying these six steps. The class contents include the recognition of the limitations of desire for a homogeneous union within an intercultural society and the consideration of how to create a relationship with heterogeneous ideas through the elimination of communication barriers through heterogeneity and consideration of the surface and the back. This paper then compares the Indonesian folktale, The Inverted Ship Mountain and the Mom's Mountain, with the world-famous Oedipus myth, to determine what the symbolic representation of these heterogeneous motifs is. In Step 6, when the symbolic system is culturally extended, the incestuous desire that appears in the "inverted ship" is interpreted as a fixation that was created when the character sought to unite with homogenous idea. The Cambodian folktale, The Girl and the Tiger, is a story that is reminiscent of the Korean folktale, The Old Man with a Lump. Through the motif in "Tiger," this paper generates a narrative topic that will enhance the students' intercultural abilities by culturally expanding their skills in how to relate with a heterogeneous being that is usually represented as an animal. The Vietnamese folktale, The Coconut Bowl, similar to the Korean folktale, GureongDeongDeong SinSeonBi, is a story that draws a variety of considerations about the surface and theback, and it shows readers how to build a relationship with a heterogeneous idea and how to develop and grow with such a relationship. Thus, if a narrative topic is generated and readers are able to empathize using an opposing feature formed by the core motif of the folktale, it becomes possible, through immigrant folklore, to construct a possibility of a new life through the formation of a relationship with an unfamiliar and heterogeneous culture.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.1-2
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• 2011

Hybrid rockets have lately attracted attention as a strong candidate of small, low cost, safe and reliable launch vehicles. A significant topic is that the first commercially sponsored space ship, SpaceShipOne vehicle chose a hybrid rocket. The main factors for the choice were safety of operation, system cost, quick turnaround, and thrust termination. In Japan, five universities including Hokkaido University and three private companies organized "Hybrid Rocket Research Group" from 1998 to 2002. Their main purpose was to downsize the cost and scale of rocket experiments. In 2002, UNISEC (University Space Engineering Consortium) and HASTIC (Hokkaido Aerospace Science and Technology Incubation Center) took over the educational and R&D rocket activities respectively and the research group dissolved. In 2008, JAXA/ISAS and eleven universities formed "Hybrid Rocket Research Working Group" as a subcommittee of the Steering Committee for Space Engineering in ISAS. Their goal is to demonstrate technical feasibility of lowcost and high frequency launches of nano/micro satellites into sun-synchronous orbits. Hybrid rockets use a combination of solid and liquid propellants. Usually the fuel is in a solid phase. A serious problem of hybrid rockets is the low regression rate of the solid fuel. In single port hybrids the low regression rate below 1 mm/s causes large L/D exceeding a hundred and small fuel loading ratio falling below 0.3. Multi-port hybrids are a typical solution to solve this problem. However, this solution is not the mainstream in Japan. Another approach is to use high regression rate fuels. For example, a fuel regression rate of 4 mm/s decreases L/D to around 10 and increases the loading ratio to around 0.75. Liquefying fuels such as paraffins are strong candidates for high regression fuels and subject of active research in Japan too. Nakagawa et al. in Tokai University employed EVA (Ethylene Vinyl Acetate) to modify viscosity of paraffin based fuels and investigated the effect of viscosity on regression rates. Wada et al. in Akita University employed LTP (Low melting ThermoPlastic) as another candidate of liquefying fuels and demonstrated high regression rates comparable to paraffin fuels. Hori et al. in JAXA/ISAS employed glycidylazide-poly(ethylene glycol) (GAP-PEG) copolymers as high regression rate fuels and modified the combustion characteristics by changing the PEG mixing ratio. Regression rate improvement by changing internal ballistics is another stream of research. The author proposed a new fuel configuration named "CAMUI" in 1998. CAMUI comes from an abbreviation of "cascaded multistage impinging-jet" meaning the distinctive flow field. A CAMUI type fuel grain consists of several cylindrical fuel blocks with two ports in axial direction. The port alignment shifts 90 degrees with each other to make jets out of ports impinge on the upstream end face of the downstream fuel block, resulting in intense heat transfer to the fuel. Yuasa et al. in Tokyo Metropolitan University employed swirling injection method and improved regression rates more than three times higher. However, regression rate distribution along the axis is not uniform due to the decay of the swirl strength. Aso et al. in Kyushu University employed multi-swirl injection to solve this problem. Combinations of swirling injection and paraffin based fuel have been tried and some results show very high regression rates exceeding ten times of conventional one. High fuel regression rates by new fuel, new internal ballistics, or combination of them require faster fuel-oxidizer mixing to maintain combustion efficiency. Nakagawa et al. succeeded to improve combustion efficiency of a paraffin-based fuel from 77% to 96% by a baffle plate. Another effective approach some researchers are trying is to use an aft-chamber to increase residence time. Better understanding of the new flow fields is necessary to reveal basic mechanisms of regression enhancement. Yuasa et al. visualized the combustion field in a swirling injection type motor. Nakagawa et al. observed boundary layer combustion of wax-based fuels. To understand detailed flow structures in swirling flow type hybrids, Sawada et al. (Tohoku Univ.), Teramoto et al. (Univ. of Tokyo), Shimada et al. (ISAS), and Tsuboi et al. (Kyushu Inst. Tech.) are trying to simulate the flow field numerically. Main challenges are turbulent reaction, stiffness due to low Mach number flow, fuel regression model, and other non-steady phenomena. Oshima et al. in Hokkaido University simulated CAMUI type flow fields and discussed correspondence relation between regression distribution of a burning surface and the vortex structure over the surface.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.343-355
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• 2009

In order to restore the identity of sound environment and expand the sound culture of a region, the purpose of this study are to excavate the resources of soundscape and find out the plans for the preservation and promotion of soundscape resources peculiar to the region. For this purpose, this research is conducted through an interview survey of residents and an observation survey using listening walk in Hongdo, one of the southwesten island of Korea. The results of survey confirm that there are so many sounds to hear around Hongdo island, those are, natural sounds such as the song of the birds, the roar of the waves, the whistling sounds, the shriek of the seagulls, and the pebbles sounds washed away by the waves, and artificial sounds such as the steam-whistle signals, the ship's broadcasts, the voice of tourists, the sounds of church bells, lighthouse sirens etc. The results suggest that it is necessary to consider several ways for restoration of an unique soundscape in Hongdo island, those are, improvement for efficient management of a ship's broadcasts in public areas, removal of a ferry in Hongdo swimming beach, management of Dangsanje (a religious service), preservation of a lighthouse siren and a foghorn, restoration and improvement of underground stream, management and control of public fish market, restoration of brooklet, management of cooperative system for a fish market, restoration of PoongO-Gut (a ritual for a large harvest) and a skate festival, management of a Hongdo sports meeting, sound quality modification of a boat whistle, restoration of orientalia such as a funeral bier, ecosystem preservation activity of the shore and ocean, and promotion of amenity for fascination and vitality in a rural community. Also, a sound map is drawn up for many tourists so as to realize the importance of sound environment and identity of soundscape and to gain their experience at first hand in Hongdo island.

• Journal of Information Technology and Architecture
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• v.9 no.2
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• pp.177-186
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• 2012

Navy establishes the Naval Task Forces (TF) for many kinds of maritime operations. Then the TF in the maritime environment performs simultaneous component operations such as ASUW (Anti-Surface Warfare), ASW (Anti-Submarine Warfare), AAW (Anti-Aircraft Warfare), and assault operations. The TF consists of many tactical systems for the completion of missions C4I, VOIP (Voice Over Internet Protocol), DMHS (Digital Massage Handling System), and TDLs (Tactical Data Links) such as LINK-11, 16, ISDL (Inter Site Data Link). When the TF executes naval operations to complete a mission, we are interested in the kill chain for the maritime operations in the TF. The kill chain is a standard procedure for the naval operations to crush enemy defenses. Although each ship has a procedure about a manual for 'how to fight', it leave something to be desired for the TF detailed kill chain currently. Therefore, in this paper, we propose the naval TF's kill chain to perform the naval operations. Then, the operational effectiveness of the TF in the kill chain environment is determined through operation scenarios of TDL system implementation. It is to see the operational information sharing effect to a data link model based on MND-AF OV 6c (statement of tracking operational status) in the maritime operations applied to TDL and is to identify improvements in information dissemination process. We made the kill chain of maritime TF for the effective naval operations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.3
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• pp.211-217
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• 2008

Natural environment, topographical conditions and marine traffic flows were investigated and questionnaire surveys were performed for the purpose of understanding the cause of marine accidents. The frequent cases of ships' dragging have happened at the anchorages of E-1, E-2 and E-3. The anchorage area is insufficient for the accommodation of a number of ships, the dolphins at the nearby piers are located near a narrow fairway. SBMs' are positioned too close to the fairway. It shows that many crossing marine traffic flows occur in all areas of the port. Marine casualties are concentrated mainly at No. 1 fairway, M1-M7 waters close to the dolphins and Gwanjeolgot, "E" anchorage and the waters close to the fairway "come and go" areas. The marine traffic flow is mainly caused by the ships' movement at the inter-port and most of the ships are the dangerous cargo carriers. And small ships like the tug-barge are moving disorderly in the ports. Furthermore, the fairway‘s layout is crossing each other. Questionnaire surveys of the users and experts shows that the LANBY that can distinguish the fairway of "come and go" ports is required.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.678-684
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• 2016

The detection of an underwater work space boundary is very important when an underwater construction is carried out using seabed type underwater equipment, such as underwater machines for rubble mound leveling, because it can induce industrial disasters. Therefore, divers are needed to mark the underwater work space boundary. A nylon rope is used to improve the convenience during an underwater diver's work. The results showed that the work space boundary can be detected using a sonar system. Using these results, an efficient method to detect the underwater work space boundary can be obtained when an underwater construction is carried out using seabed type underwater 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.