• Journal of Welding and Joining
• /
• v.28 no.2
• /
• pp.84-90
• /
• 2010

Fillet welding accounts for about 80% of all constructing process of ship and ocean structure. T-joint is one of the typical shapes which are frequently reported to experience the fatigue damage when the marine structure meets the storm loads. The fatigue damage is affected by the magnitude of residual stresses on the weld. Recently, many shipping registers and design guidances have required that the fatigue strength assessment method should be compensated by the effect of the residual stress in case that the random loading or storm loading is applied to the marine vessels. This study suggests the computational procedure to analyze the residual stresses of T-joint specimen that is frequently reported to get damaged by the storm loading. Experiment by XRD as well as the 3-D computational welding model is presented in order to get the profile of residual stress. Throughout the comparison of experimental result with the computational result, the computational model was validated. Thereafter, characteristics of he residual stresses in the joint are discussed.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.3
• /
• pp.281-287
• /
• 2011

This paper explains the basic theory and a new development of for the residual strength prediction program of the asymmetrically damaged ships, being capable of searching moment-curvature relations considering neutral axis mobility. It is noted that moment plane and neutral axis plane should be separately defined for asymmetric sections. The validity of the new program is verified by comparing moment-curvature curves of 1/3 scaled frigate model where the results from new algorithm well coincide with experimental and nonlinear FEA results for intact condition and with nonlinear FEA results for damaged condition. Applicability of new algorithm is also verified by applying VLCC model to the newly developed program. It is proved that reduction of residual strengths is visually presented using the new algorithm when damage specifications of ABS, DNV and IMO are applied. It is concluded that the new algorithm shows very good performance to produce moment-curvature relations with neutral axis mobility on the asymmetrically damaged ships. It is expected that the new program based on the developed algorithm can largely reduce design period of FE modeling and increase user conveniences.

• The Korean Journal of Applied Statistics
• /
• v.30 no.5
• /
• pp.633-645
• /
• 2017

This study proposes a statistical procedure for analyzing container ship operation data that can help determine fuel consumption patterns. We first investigate the features that affect fuel consumption and develop the prediction model to find current fuel consumption. The ship data can be divided into two-type data. One set of operation data includes sea route, voyage information, longitudinal water speed, longitudinal ground speed, and wind, the other includes machinery data such as engine power, rpm, fuel consumption, temperature, and pressure. In this study, we separate the effects of external force on ships according to Beaufort Scale and apply a partial least squares regression to develop a prediction model.

• Journal of Korea Port Economic Association
• /
• v.35 no.4
• /
• pp.17-30
• /
• 2019

This study examines the recent business models of domestic logistics companies in Hanoi and Hai Phong, Vietnam, and suggests implications. We introduced business models (coastal shipping, distribution center and ICD transportation, cold chain, border crossing, port development, etc.) that provide logistics services through cooperation with existing logistics companies (shippers, logistics companies, local companies, etc.). If we propose a partnership plan in the short and medium term, short-term projects include warehouse, ICD, trucking business, and it is feasible to not only collaborate with Korean companies that have already entered the market, but to also invest in joint ventures with local companies (up to 51% of local companies). In the long term, we can consider coastal transportation, cross-border transportation, trucking, and investment in new deep sea ports. All of these businesses require local partnerships, so local companies require a 51% stake.

• Journal of Ocean Engineering and Technology
• /
• v.29 no.6
• /
• pp.418-426
• /
• 2015

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.39 no.1
• /
• pp.48-59
• /
• 2002

TSK(Takagi-Sugeno-Kang) fuzzy models with linear equations consequents, which represent complex nonlinear systems very well with a few rules, can be easily identified systematically by using input-output data. Many algorithms designing TSK fuzzy controllers based on TSK fuzzy models, which guarantees the stability of the closed system, have been suggested. On the contrary, singleton fuzzy models with singleton consequents can be easily understood and adjusted. In this paper, in order to utilize the merits of TSK fuzzy systems and singleton fuzzy systems, an algorithm transforming a TSK fuzzy model into a singleton fuzzy model having the same input-output relation is suggested. The suggested algorithm is applied to a fuzzy modelling example and a fuzzy controller design example.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.967-970
• /
• 2005

Ubiquitous Computing appeared, and moth researches are gone to apply this in various field. Specially, physical distribution circulation service field is intelligence enemy while alternate existent bar code and induction of RFID(Radio Frequency Identification) technology that permit various service is gone vigorously. In this treatise designed data model and schema to progress research about Core Event Type of PML(Product Markup Language) that is object information expression language that is proposed Auto-Id Lab and EPCglobal Inc. to process information of physical object and EPC-lS(Electronic Product Code Information Services) that is information services component and applies in sea transport physical logistics distribution service field.

• The Journal of Information Technology
• /
• v.3 no.3
• /
• pp.117-134
• /
• 2000

Client-server DBMS based on a data-skipping model can exploit client resources effectively by allowing inter-transaction caching. However, inter-transaction caching raises the need of transactional cache consistency maintenance(TCCM) protocol, since each client is able to cache a portion of the database dynamically. Detection-based TCCM schemes can reduce the message overhead required for cache consistency if they validate clients replica asynchronously, and thus they cm show high throughput rates. However, they tend to show high ratios of transaction abort since transactions can access invalid replica. For coping with this drawback, this paper develops a new notion of shadow transaction, which is a backup-purpose one that is kept ready to replace an aborted transaction. This paper proposes a new detection-based TCCM scheme named DL-ST on the basis of the notion of shadow transaction. Using a simulation model, this paper evaluates the effect of shadow transaction in terms of transaction through rate and abort ratio.

• Journal of Navigation and Port Research
• /
• v.44 no.6
• /
• pp.469-476
• /
• 2020

Modeling and Simulation (M&S) systems which deal with situational complexity often require human involvement due to the high-level decision-making that is necessary for ship movement, navigation, control center management, shipping company logistics, meteorological system information, and maritime transportation GIS. In order to properly simulate maritime traffic, it is necessary to accurately model the human decision-making process of the ship officer, including aspects of the ship officer's behavioral tendencies, personal navigation experience, and pattern of voyage errors, as this is the most accurate way in which to reproduce and predict realistic maritime traffic conditions. In this paper, which looks at agent-based maritime traffic simulation, we created a basic survey in order to conduct behavior analysis on ship operators' collision avoidance strategies. Using the information gathered throughout the survey, we developed an agent-based navigational behavior model which attempts to capture the behavioral patterns of a ship officer during an instance of ship collision. These results could be used in the future in further developments for more advanced maritime traffic simulation.

• Journal of Korea Port Economic Association
• /
• v.40 no.2
• /
• pp.1-20
• /
• 2024

The purpose of this study is to clarify a safety efficiency of ports in South Korea considering port casualties. The paper conducted a vector auto regression to analyze a cause-and-effect relationship between latent factors and port casualties. Subsequently, the paper evaluated safety efficiency for the ports using an undesirable outputs model. The results implied that the number of workers in the shipping union had a statistical effect on the port casualties. In contrast, the number of workers in the operators and working hours are unrelated to the port casualties. In addition, it was found that Yeosu Gwangyang Port is the most safety efficiency port in South Korea. Based on these results, this paper may provide various policy implications for port operators, developers, and managers.