• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.922-937
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• 2024

Maritime activities are on the rise, there is a growing demand for high-quality communication services that can cover larger areas. However, the transmission of high data rates to maritime users is challenging due to path loss from land base stations, which limits the transmission power. To overcome this challenge, researchers have been exploring the use of buoys in a marine environment as relays for communication technology. This paper proposes a simulation-based approach to investigate the impact of various beamwidths on communication performance when using a buoy as a relay. The objective is to determine the optimal beamwidth that yields the highest data rate for the target location. The approach is based on an offshore wave model where the direction of the buoy changes according to the height of the wave. The study investigates the performance of the relay in the downlink situation using receive beamforming, and the capacity at the user in the three-hop situation is verified using an amplify-and-forward (AF) relay that uses transmit beamforming to the user. The simulation results suggest that the beamwidth of the relay should be adjusted according to the wave conditions to optimize the data rate and relay position that satisfies a data rate superior to the direct path to the target position. Using a buoy as a relay can be a promising solution for enhancing maritime communications, and the simulation-based approach proposed in this paper can provide insights into how to optimize beamwidth for effective communication system design and implementation. In conclusion, the study results suggest that the use of buoys as relays for maritime communication is a feasible solution for expanding coverage and enhancing communication quality. The proposed simulation-based approach provides a useful tool for identifying relay beamwidths for achieving higher data rates in different wave conditions. These findings have significant implications for the design and deployment of communication systems in maritime environments.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.5
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• pp.1090-1095
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• 2014

The experimental and numerical studies of the single-phase flow pressure drop in parallel micro-channels were performed. The parallel micro-channels consisted of 15 channels with depth 0.2mm, width 0.45mm and length 60mm. The FC-72 was used as the working fluid and the mass fluxes ranged from 62.8 to $1371.6kg/m^2s$. The numerical analysis was performed iterative calculations to solve governing equations and finds the appropriate value. The experimental data was compared with the numerical data, the results showed good agreement with the numerical data.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.99-104
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• 2003

The maritime security risk has been recognized since the terrorists attacked the world trade center and the Pentagon In this paper, maritime security risk is analyzed on the basis if the data of crime in Korean sea We propose the countermeasures to prevent maritime security threats

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.1
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• pp.115-124
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• 2015

The aims of this study were to validate the Occupational Basic Competencies of Fisheries and Maritime High school. Fisheries & Maritime key competencies were defined as the abilities that include the essential knowledge, skills, attitude, and experiences required for the workforce on the fisheries and maritime job condition. This research collected preliminary data from 1,113 fisheries & maritime high school students. Data were analyzed to obtain reliability and validity analysis. The results of the study were as follows; First, fisheries & maritime key competencies were divided into 6 elements. Second, fisheries & maritime key competencies were consisted of marine vocational ethics, marine information capacity, marine elementary knowlegde, marine safety management skill, management & utilization of marine life and marine consciousness. Third, Cronbach-${\alpha}$ proves that the scale developed in the study is reliable. In consequence, the results of this study help to reconceptualize fisheries & maritime and apply the scale to measure students in high school settings.

• International Journal of Fluid Machinery and Systems
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• v.2 no.2
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• pp.156-164
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• 2009

This paper aims to describe the importance of data, data collection methods, parameters to estimate the potential of wave energy and environmental impacts. The technical and economical status in wave energy conversion is outlined. Power and energy efficiency relationships are discussed. Many different types of wave-energy converters have been detailed. The progress in wave energy conversion in Malaysia is reviewed.

• Ocean and Polar Research
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• v.33 no.1
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• pp.69-76
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• 2011

A test miner named MineRo was constructed for the purpose of shallow water test of mining performance. In June of 2009, the performance test was conducted in depth of 100 m, 5 km away from Hupo-port (Korean East Sea), to assess if the developed system is able to collect and lift manganese nodules from seafloor. In August of 2010, in-situ test of automatic path tracking control of MineRo was performed in depth of 120 m at the same site. For path tracking control, a localization algorithm determining MineRo's position on seabed is prerequisite. This study proposes an improved underwater navigation algorithm through estimation of MineRo's kinematic parameters. In general, the kinematic parameters such as track slips and slip angle are indirectly calculated using the position data from USBL (Ultra-Short Base Line) system and heading data from gyro sensors. However, the obtained data values are likely to be different from the real values, primarily due to the random noise of position data. The aim of this study is to enhance the reliability of the algorithm by measuring kinematic parameters, track slips and slip angle.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.499-509
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• 2013

Seafarers are one of the main engines driving economic growth in the maritime sector. The International Maritime (IMO) Organization estimated that there were approximately 1.5 million seafarers around the world engaged in international trade in 2012. Data have shown that human casualties in maritime accidents around Japan have shown an increasing trend over the last ten years. One cause is human error, which is inseparable from the human element that influences mariner's decisions and actions. The Personal Identification (PIN) Safe method is one way to systematically identify substandard and unsafe actions by considering the error taxonomies associated with various scenarios for a maritime system. The results are based on analysis of the role of the human element in commonly reported unsafe actions when interacting with equipment and other systems. Furthermore, patterns of influencing shaping factors were observed on the basis of data processing; the aim of this study was to promote safety culture and provide an opportunity to improve safety at sea.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.12
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• pp.3815-3835
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• 2022

Density-based outlier detection is one of the hot issues in data mining. A point is determined as outlier on basis of the density of points near them. The existing density-based detection algorithms have high time complexity, in order to reduce the time complexity, a new outlier detection algorithm DODMD (Density-based Outlier Detection in Multidimensional Datasets) is proposed. Firstly, on the basis of ZH-tree, the concept of micro-cluster is introduced. Each leaf node is regarded as a micro-cluster, and the micro-cluster is calculated to achieve the purpose of batch filtering. In order to obtain n sets of approximate outliers quickly, a greedy method is used to calculate the boundary of LOF and mark the minimum value as LOF_min. Secondly, the outliers can filtered out by LOF_min, the real outliers are calculated, and then the result set is updated to make the boundary closer. Finally, the accuracy and efficiency of DODMD algorithm are verified on real dataset and synthetic dataset respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.199-201
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• 2015

Nowadays, the issue of maritime safety is an extremely important issue in the maritime industry and Human' Stress is one of the biggest causes of maritime accidents. The purpose of this study was to research and compare the risk marine accidents analysis methods and find the methods which used to analysis data of the human' stress and obtained the relationship between it and the risk of maritime accidents.

• Journal of Navigation and Port Research
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• v.29 no.7
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• pp.619-625
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• 2005

The security vulnerabilities in Korea maritime domain were mentioned and analysed with the static data of crimes relating to maritime security. The counterterrorism and initiatives to reduce the security risk and to minimize the damage are introduced and evaluated. The maritime security strategy and the near term initiatives to enhance the non-military security at Korean sea and ports are proposed in order to response maritime security threats economically, efficiently and safely.