• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.89-99
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• 1990

It is required to develop a hull form with low resistance and high propulsive efficiency for the improvement of the ship-board operational economy. Since the hull forms with low resistance frequently have lower propulsive efficiency and on the other hand the hull forms with higher propulsive efficiency don't show good resistance characteristics, it is always very difficult to obtain economical hull forms which require less propulsive power accordingly. Efforts have been made to pursue a stern form with excellent resistance and propulsion characteristics together by shaping the run of the so-called buttock-flow type stern, which is known to have good viscous resistance performance, like that of conventional aftbody(U-type or Hogner type) featured by high propulsive efficiency. First model tests confirmed that the above concept can be one of the alternative approaches to the design of the good stern form and by the continuing efforts thereafter for the refining of the concept, propelled by the first promising results, stern form of good resistance performance together with good propulsive efficiency has been realized to some extent. In addition, it is confirmed that the new new stern can have better cavitation and vibration characteristics due to uniform wake-fields and the compact engine room arrangement can be possible due to it's larger floor area in way of engine room double bottom as compared with usual barge stern.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.79-92
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• 2019

This study analyzes the effects of freight transportation income, capital, asset, non-operating expenses, and debt ratio on the debts of inner port freight transportation businesses through the GLS of panel regression analysis and the estimation of fixed effects model. The factors and hypotheses were established through a theoretical background review, and the financial statement and profit and loss data of inner port freight transportation businesses for 10 years from 2006 to 2015 were analyzed. The results showed that assets had positive effects on debts, and negative effects on capital, non-operating expenses, and debt ratio, but no effect on freight transportation income. This result empirically demonstrates the tendency of inner port freight transportation businesses to secure assets by increasing debts, creation of debt reduction leverage effect using non-operating expenses such as interest expenses through bank borrowing, and the adoption of management characteristics and financial operation method to lower the debt ratio by reducing capital more than debts. In future studies, it is necessary to analyze coastal port freight transportation business by industry (oil tankers, cargo ships, and barge ships), and regions such as East, West and South sea.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.93-100
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• 2022

The collision behaviors of the tripod and jacket structures, which are considered as support structures for offshore wind towers at the Southwest sea of Korea, were compared by nonlinear dynamic analysis. These structures, designed for the 3 MW capacity of the wind towers, were modeled using shell elements with nonlinear behaviors, and the tower structure including the nacelle, was modeled by beam and mass elements with elastic materials. The mass of the tripod structure was approximately 1.66 times that of the jacket structure. A barge and commercial ship were modeled as the collision vessel. To consider the tidal conditions in the region, the collision levels were varied from -3.5 m to 3.5 m of the mean sea level. In addition, the collision behaviors were evaluated as increasing the minimum collision energy at the collision speed (=2.6 m/s) of each vessel by four times, respectively. Accordingly, the plastic energy dissipation ratios of the vessel were increased as the stiffness of collision region. The deformations in the wind tower occurred from vibration to collapse of conditions. The tripod structure demonstrated more collision resistance than the jacket structure. This is considered to be due to the concentrated centralized rigidity and amount of steel utilized.

• Journal of Korea Port Economic Association
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• v.38 no.2
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• pp.11-30
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• 2022

Korean ports have some problems in the aspect of quality & quantity in the bunkering process. Quality of bunker is assessed as more higher than competing ports. However, quality of bunkering procedure is assessed as lower. Especially, supply chain from loading of bunker to the bunker barge at oil terminal, transport it, and supply it to the ship has not been secured. Furthermore, aspect of quantity of bunker is more serious rather than that of quality of bunkering process. Disputes on the quantity of bunker between seller and buyer occur frequently, and residue & theft of bunker is also popularized issue and serious problem. Low bunkering fee is recognized as major reason of that problem, however, though low fee can be solved, it can not be necessary secured that problem could be solved, Therefore, this paper investigates and suggests the scheme to solve the quality problems of bunker supplying procedure, and develop solution toward advanced bunkering ports through removal of the quantity disputes. Concretely, this paper suggests introduction of quality system of bunker supply chain in the aspect of bunker supply procedure, and diversion from conventional sounding method to innovative Mass Flow Metering System in the aspect of bunker measuring. These two innovative solutions contribute to the removal and improvement of current structural problems in bunkering procedure.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.177-187
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• 2023

The Ship Safety Act prescribes matters necessary for the maintenance of seaworthiness and safe navigation of ships. In this regard, Article 10 of this Act requires shipowner to undergo occasional survey if he/she wants to temporarily change intends to modify the details entered in a ship survey certificate. Such measures are in accordance with the maintenance of the state of the ship after the ship inspection under Article 15 of this Act, and this Act includes "harbor construction work ship" under Article 39 Paragraph (1) of the Harbor Act. However, although the harbor construction work ship originally showed the same operating system as the barge, it was not applied to the Ship Safety Act and was registered and surveyed under the Construction Machinery Management Act. Then "Seokjeong No. 36" sinking accident in Ulsan on December 14, 2012, led to the amendment of the Harbor Act in 2016, and considering the fact that it was added to the Ship Safety Act and applied, there is a realistic limit to applying all the regulations stipulated in the Ship Safety Act to the harbor construction work ship. Accordingly, this study discusses the work characteristics through concept, registration, work area, survey regulations, application case of temporary alteration etc. of harbor construction work ships and controversial issues related to the scope of application of the Ship Safety Act of actual harbor construction work ships, and also the appropriate scope of "temporary alteration" among temporary inspections prescribed in Article 10 of the Ship Safety Act in consideration of the legislative purpose of incorporating harbor construction work ships into the survey subject to the Ship Safety Act in accordance with the revision of the Harbor Act.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.85-93
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• 2024

In this paper, we propose a method for establishing a state-space equation model for the motion analysis of floating structures subjected to wave loads, by applying system-identification techniques. Traditionally, the motion of floating structures has been analyzed in the time domain by integrating the Cummins equation over time, which utilizes a convolution integral term to account for the effects of the retardation function. State-space equation models have been studied as a way to efficiently solve floating-motion equations in the time domain. The proposed approach outlines a procedure to derive the target transfer function for the load-displacement input/output relationship in the frequency domain and subsequently determine the state-space equation that closely approximates it. To obtain the state-space equation, the method employs the N4SID system-identification method and an optimization approach that treats the coefficients of the numerator and denominator polynomials as design variables. To illustrate the effectiveness of the proposed method, we applied it to the analysis of a single-degree-of-freedom model and the motion of a six-degree-of-freedom barge. Our findings demonstrate that the presented state-space equation model aligns well with the existing analysis results in both the frequency and time domains. Notably, the method ensures computational accuracy in the time-domain analysis while significantly reducing the calculation time.