• Journal of Power Electronics
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• v.13 no.1
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• pp.70-76
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• 2013

For high power high step-down dc-dc conversion applications, conventional three-level dc-dc converters are subject to extreme duty cycles or increased volume and cost due to the use of transformers. In this paper, a transformerless three-level dc-dc buck converter with a high step-down conversion ratio is proposed. The converter comprises two asymmetrical half bridges, which are of the neutral point clamped structures. Therefore, the output pulse voltage of the converter can be obtained in terms of the voltage difference between the two half bridges. In order to realize harmonious switching of the converter, a modulation strategy with capacitor voltages self balance is presented. According to the deduced output dc voltage function, transformerless operation without extreme duty cycles can be implemented. Experimental results from a 1kW prototype verify the validity of the proposed converter. It is suitable for ship electric power distribution systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.387-390
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• 2009

Digital devices that apply Ubiquitous-IT Convergence in ship manufacture are used as ship automation device. Need sailing data recording of ship black box that equip integrity and consecutiveness as legal confesser fare that inquire responsibility whereabouts of disaster such as fire of ship. It is research that create Forensic data from ship black box using Multidimensional networking that use ZigBee radio short distance communications division Wireless LAN with short distance RFID sensor that is used in ship in this treatise, UWB communication, GPS and artificial satellite. Sailing recording of shipping that is recorded to black box is transmited, and stores doubly by real time on ship insurance company and ship administration recording membrane using SHA-1 hash function and secure consecutiveness and integrity as Forensic data through artificial satellite encoding by 3DES 1024bit.

• Journal of Welding and Joining
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• v.27 no.2
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• pp.32-37
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• 2009

In shipyard, plate forming is widely used to form the ship hull plate in various shapes. Line heating method by using a flame torch is one of the major shipbuilding processes carried out by skilled workers. Since the forming characteristics depend upon their experiences in manual forming, there are much variations between products and difficulties in communication between engineers and workers. Hence, it needs to develop an automatic forming system which can not only reduce the working time and rework costs but also improve the working environment and hull forming productivity. One of the final goals of plate forming automation is to form a target shape from the initial plate automatically. For automated plate forming, it is required to determine where and how to heat on the plate. To realize this procedure, the inverse problem should be first solved and the effect of curvature shape formed at the heating path should be investigated. In this study, the inverse problem was solved by geometrical approach using the relationship between bending angle and radius of curvature of the curved shape. In addition, experiments of two-dimensional plate forming were performed with the distance-based method considering the curved bending with curvature. The result of the formed shape agreed considerably well with the target shape.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.1-7
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• 2012

It is necessary to construct the process automation system to improve the design efficiency and procure the higher design quality on the field of ship building. To construct this system, the shipbuilding companies should improve the 3D CAD/CAM system customized to the ship design and the software about design information management which could solve the conflict problem between the several related design division at the same time. The typical example is the Hole-plan process in the ship-building design. For the request of additional holes from outfitting division, the hull design division checks the compatibility conditions and reflects these holes to the hull panels if acceptable. if not, the requests are rejected and sent back to the outfitting division. These serial processes are not simple and require the tedious communication, discussion, and the complicated drawings. This article gives a basic introduction to the process of hole-plan system and proposes a strategy to automate its process.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.423-433
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• 2016

In this paper, we consider the cybersecurity issue of ship information system (SIS) from a new perspective which is called opacity. For a SIS, its confidential information (named as "secret") may be leaked through the working behaviors of each Distributed Control Unit (DCU) from an outside observer called an "intruder" which is able to determine ship's mission state by detecting the source of each data flow from the corresponding DCUs in SIS. Therefore we proposed a dual layer mechanism to enforce opacity by activating non-essential DCU during secret mission. This mechanism is calculated by two types of insertion functions: Safety-assured insertion function ($f_{IS}$) and Admissibility-assured insertion function ($f_{IA}$). Due to different objectives, $f_{IS}$ is designed to confuse intruder by constructing a non-secret behaviors from a unsafe one, and the division of $f_{IA}$ is to polish the modified output behaviors back to normal. We define the property of "$I_2$-Enforceability" that dual layer insertion functions has the ability to enforce opacity. By a given mission map of SIS and the marked secret missions, we propose an algorithm to select $f_{IS}$ and compute its matchable $f_{IA}$ and then the DCUs which should be activated to release non-essential data flow in each step is calculable.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.90-99
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• 1993

As the finite element method has become a considerable and effective design tool in ship structural analysis, modeling of three dimensional finite element mesh is more necessary than before. However, the unique style and complexity of a ship usually make the modeling be hard and costly. Although most pre-processor of FEM software and geometric modeler provides modeling function, the capability is quite limited for complicated structure. In order to perform FEM modeling quickly, it is necessary to extract, rearrange, and formalize data from ship design database for partially automatic mesh generation. In this paper, the process of designing relational data tables from design data is shown as a part of analysis automation with the application of engineering database concept.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.210-215
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• 2024

With increasing automation in ships and the development of autonomous ships, an IPMS (Integrated Platform Management System) in ship needs to integrate and process large amounts of real-time data from various equipment operating on different operating systems. A ship IPMS simulator based on data distribution service (DDS) was developed and its performance was evaluated to handle data processing similar in real ship environment. Errors were monitored while 1,000 topics/sec were asynchronously published and subscribed from data acquisitive units (DAUs) and an IPMS server operating on different operating systems. Except for the loss of some topics during the initial 4 seconds, topics were received without an error thereafter. The developed simulator demonstrates the feasibility of using DDS to integrate various control systems using different operating systems in actual ships.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2103-2123
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• 2018

Ships built today are larger in scale and feature more complex structures. The ever-evolving systems used on board a ship require vast amounts of data processing. In the future, with the advent of smart ships, unmanned ships and other next-generation ships, the volumes of data to be processed will continue to increase. Yet, to date, ship data has been processed using wired networks. Placed at fixed locations, the nodes on wired networks often fail to process data from mobile devices. Despite many attempts made to use Wi-Fi on ships just as on land to create wireless networks, Wi-Fi has hardly been available due to the complex metal structures of ships. Therefore, Wi-Fi on ships has been patchy as the ship-wide total Wi-Fi coverage has not properly implemented. A new ship-wide wireless network environment is part of the technology conducive to the shipbuilding industry. The wireless network environment should not only serve the purpose of communication but also be able to manage and control multiple features in real-time: fault diagnostics, tracking, accident prevention and safety management. To better understand the characteristics of wireless frequencies for ships, this paper tests the widely used TETRA, UHF and Wi-Fi and sheds light on the features, advantages and disadvantages of each technology in ship settings. The proposed deployment of a Super Wi-Fi network leveraging the legacy UHF system of TMS generates a ship-wide wireless network environment. The experimental findings corroborate the feasibility of the proposed ship-wide Super Wi-Fi network environment.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.72-79
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• 2003

This paper deals with the development of an interface program for automatic plate forming, which can exchange information between the heating line information generation program and the automatic heating apparatus. In this paper, the performance of the developed interface program has been verified from the view point of numerical position control. By applying the interface program to the operation of the automatic heating apparatus, an experiment of line heating has been conducted for several steel plate models. Based on the experimental results, a simplified relation to estimate angular distortion has keen derived as a natural characteristic of the present automatic heating apparatus. As a result of the present study, the prototype of the automatic plate forming system has been constructed, and its application to the real surface models found in the ship will be presented in the near future.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.90-96
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• 2021

The logistics market is continuously growing due to the development of technology and the growth of the online market. In addition, the social atmosphere that emphasizes non-face-to-face due to the pandemic situation is accelerating the growth of logistics. Delivery of goods ordered online requires delivery process through courier worker. In order for the courier worker to ship the product, the work of loading the product on the truck must be preceded. The accident caused by such delivery and loading work is increasing and it is emerging as a social problem. This study proposes a robot-based automated loading system to efficiently handle the increasing volume of courier service and to construct a more efficient and safe working environment by replacing the physical labor that was overloaded to courier workers. The proposed system replaces the loading of the courier worker and proposes the optimal loading function through the automation system.