• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.103-108
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• 2020

Generally, the cargo tank of LPG carriers corresponds to an independent tank Type A defined by the International Maritime Organization (IMO). The outside of the tank is insulated by polyurethane foam, and the tank is made of expensive low temperature steel that can withstand temperatures as low as -50℃. The cargo tank is composed of outer shell plates, bulkheads, stiffeners, web frames, and stringers. Among them, the outer shell plates, bulkheads, and stiffeners can be designed without structural analysis by the Classification Rules and are constructed easily through optimal design. On the other hand, optimal design, including numerous structural analysis, is not performed because web frames and stringers should be designed and approved through structural analysis. Only adequate design, which determines the design dimensions through several dozen structural analysis, is performed. In this study, for finite element analysis, eight loading conditions were applied, and the deformation of the entire ship for each loading condition was considered. The minimum weight design was performed for the web frames of cargo tanks in the 82,000 ㎥ LNG carrier through the gradient-based optimization technique, and the weight was reduced by approximately 108 tons per ship.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.2
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• pp.128-139
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• 2017

Railway is one of the public transportation systems along with shipping and aviation. With the recent introduction of high speed train, its proportion is increasing rapidly, which results in the higher risk of catastrophic failures. The wheel bearing to support the train is one of the important components requiring higher reliability and safety in this aspect. Recently, many studies have been made under the name of prognostics and health management (PHM), for the purpose of fault diagnosis and failure prognosis of the bearing under operation. Among them, the most important step is to extract a feature that represents the fault status properly and is useful for accurate remaining life prediction. However, the conventional features have shown some limitations that make them less useful since they fluctuate over time even after the signal de-noising or do not show a distinct pattern of degradation which lack the monotonic trend over the cycles. In this study, a new method for feature extraction is proposed based on the observation of relative frequency energy shifting over the cycles, which is then converted into the feature using the information entropy. In order to demonstrate the method, traditional and new features are generated and compared using the bearing data named FEMTO which was provided by the FEMTO-ST institute for IEEE 2012 PHM Data Challenge competition.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.195-202
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• 2006

Thin-walled structures are efficiently utilized an automobiles, aircraft, satellite and ship as well as needed light weight simultaneously. This paper presents new shape of automobile hood reinforcement that rotating parts as engine, transmission are protected by thin-walled structures. The automobile hood is concerned about the resonance occurs due to the frequency of the rotating parts. The hood must be designed by supporting the stiffness of design loads and considering the natural frequencies. Hence, it is sustained the stiffness and considered the vibration by resonance. It is deep related to ride. Therefore, the topology, shape and size optimization methods are used to design the automobile hood. Topology technique is applied to determine the layout of a structural component optimum size with maximized natural frequency by volume reduction. In this research, The optimal structure layout of an inner reinforcement of an automobile hood for the natural frequency of a designated mode is obtained by using topology optimization method. The optimum size and the optimum shape are determined by PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.864-867
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• 2003

GPS (Global Positioning System) made by the Department of Defense in U.S.A is positioning system to use satellite and initially it has been used only for the military forces but open to civilian in about 1987. This system has widely been used for not only surveying land, but also car navigation on the street and means to build up the data of the GIS. With GPS, recently our country is accelerating to make imbeded system and also the study on imbeded system is well under way. For example, Car navigation and the construction of the Seokang bridge between Willson Arch at Han river by using DGPS were evaluated as successful model to lead accurate location with the precision of the cm. The examples of the project performance with GPS has gradually been extended to the each department organization of the local and central government. for the example, It is true that BIS(Bus Information System) is widely spreading out. In addition, the study on the Distribution Maintenance System is expected to be well in progress to take advantage of GPS based on the data base of the NGIS(National Geography Institute System) of the NGI(National Geography Institute). This paper shows that we embodied not only the large imbeded system for car and finding the location in Korean Land Corporation but also the protype of the kinematics Wrist Held which is easily portable to pedestrian, climber and marathon runner.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.329-335
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• 2007

The eye measurement to observe the sea surface condition and estimate the wave height has been used in the open sea or the ship. The experts in the eye estimation can measure the wave height very accurately. The Beaufort wind scale is most widely used as a standard index of the eye measurement. However, more definite reference data such as the representative images by each wave heights must be necessary because the appearances and explanations in the Beaufort wind scale are not enough to understand the sea surface condition far the researcher and the public. The modern field data acquisition technique has been developed to measure wave heights, ocean weather data and even images of the sea surface in real-time. In this study, the wireless field image transmitting system for wave heights and images is installed in the real-time ocean measurement system of Chodo light tower near Sokcho city in South Korea. The wave heights and surface images acquired from the real time system in the field are compared with explanations of the Beaufort wind scale. The wave heights and images measured with the precision ultrasonic wave sensor and the scientific sea surface image transmitting system should be helpful to obtain more precise and definite information than the data from the Beaufort wind scale.

• Journal of Navigation and Port Research
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• v.33 no.1
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• pp.27-33
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• 2009

Estimation of the buckling and ultimate strength of a continuous stiffened plate subjected to combined transverse compression and lateral pressure is of high importance to ensure the safety of ship structures, particularly for the bottom plating under a deep draft condition For example, bottom plating of bulk carriers is subjected to transverse thrust caused by the bending of double bottom structure and the direct action of pressure on the side shells. Most of experimental tests, theoretical approach and numerical researches have been performed on the buckling and ultimate strength behaviour of plates or stiffened plates under combined compression and lateral pressure. With regard to stiffened panels, however, most of studies have been concerned with the load conditions of combined longitudinal thrust and lateral pressure, while fewer studies have been performed for the combined transverse thrust and lateral pressure. In addition, the previous researches are mainly concerned with an isolated rectangular plate simply supported along the all edges, whereas actual ship plating is continuous across the transverse frames and heavy girders. In the present paper, a series of elastoplastic large deflection FEA on a continuous stiffened plate is performed and then clarify the characteristic of collapse mode and explain the effect of transverse compression.

• Journal of Navigation and Port Research
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• v.44 no.3
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• pp.166-173
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• 2020

AtoN Accident causes navigation dangerous to ships and reduces the credibility of aids to navigation. The most light buoys on the sea have the highest accident rate from the influence of sea weather such as wind, current, and waves. However, in Korea, despite the different sea weather conditions in each sea area, in calculating the dynamic stability of the light buoy, there is a problem that only limit value conditions are applied to all sea areas. Thus, the purpose of this study was to analyze the dynamic stability of the LL-26(M) light buoy, the most installed buoy of its kind on the sea and suggest a stable operation plan for the LL-26(M) light buoy. To achieve this, after analyzing the weather for each sea area of the previous study related to the light buoy, the dynamic stability (inclination angle) was estimated by applying to the representative light buoys of each sea area wherein the number of accidents caused by sea weather was high. As a result of this study, the inclination angle of LL-26(M) light buoy for each sea area was different. That is, the inclination angle caused by winds was 10.329°-36.868°, the inclination angle caused by currents was 0.123°-18.834° and the inclination angle caused by waves was 4.777°-20.695°. The results of study can be used as basic data useful for installation standards for each sea area for stable operation of the LL-26(M) light buoy.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.177-198
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• 2021

Existing change detection researches have been focused on changes of land use and land cover (LULC), damaged areas, or large vegetated and water regions. On the other hands, increased temporal and spatial resolution of satellite images are strongly suggesting the feasibility of change detection of small objects such as vehicles and ships. In order to check the feasibility, this paper analyzes the performance of existing pixel-based change detection methods over small objects. We applied pixel differencing, PCA (principal component analysis) analysis, MAD (Multivariate Alteration Detection), and IR-MAD (Iteratively Reweighted-MAD) to Kompsat-3A and Google Map images taken within 10 days. We extracted ground references for changed and non-changed small objects from the images and used them for performance analysis of change detection results. Our analysis showed that MAD and IR-MAD, that are known to perform best over LULC and large areal changes, offered best performance over small object changes among the methods tested. It also showed that the spectral band with high reflectivity of the object of interest needs to be included for change analysis.

• Journal of Navigation and Port Research
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• v.45 no.3
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• pp.173-180
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• 2021

Although accounting is one of the core fields of corporate management, few studies have reported accounting phenomena involving shipping companies. In addition, although financial reporting is very important to shipping companies that use several financial tools such as ship finance and financial lease, it is difficult to identify studies investigating shipping companies' financial reporting, especially their earnings management. The purpose of this study is to analyze accrual earnings management behavior of shipping companies. Companies with high debt ratios and net losses are known to have incentives for earnings management. Due to the nature of the industry, shipping companies have a high debt ratio and often report net losses. Accordingly, shipping companies are expected to engage in substantial earnings management. Based on the analysis of KOSP I companies listed on the Korea Exchange from 2001 to 2020, it was found that shipping companies are engaged in higher levels of earnings management than non-shipping companies. Discretionary accrual was used as a proxy variable for earnings management. Discretionary accrual was measured using the modified Jones model of Dechow et al. (1995) and the performance matched model of Kothari et al.(2005). In this study, significant results were derived by comparatively analyzing the earnings management practices, which is one of the major accounting behaviors of shipping and non-shipping companies. Stakeholders such as external auditors, investors, financial institutions, analysts, and government authorities need to be aware of the earnings management behavior of listed shipping companies during their external audit, financial analysis, and supervision. Finally, listed shipping companies must conduct stricter accounting based on accounting principles.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.667-679
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• 2022

Fatigue damage analysis of ships includes parameters considering operational factors. Due to these operational variables, there is a difference between the fatigue damage estimated during the design stage and the actual accumulated fatigue damage. Likewise, there are various loading conditions for the real container ships, but at design stage the fatigue damage is calculated by applying the representative loading conditions. Moreover, although the difference in fatigue damages is expected when the actual and design loading conditions are applied, there are few studies on the contributions of the fatigue damage based on the loading conditions of container ships. In this paper, fatigue contributions were investigated from various cargo weight distributions. The hull girder loads calculated through seakeeping analysis and fatigue damages obtained by performing spectral fatigue analysis were identified under new loading conditions. As a result, it was found that the variation of cargo weight distribution in the container ship brought about changes in the hull girder loads and fatigue damage by affecting the hull girder stress.