• Korean Journal of Remote Sensing
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• v.13 no.2
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• pp.133-150
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• 1997

The purpose of this paper is to develop an algorithm of classification and interpretation of seafloor based on side scan sonar data. The algorithm consists of mosaicking of sonar data using navigation data, correction and compensation of the acouctic amplitude data considering the charateristics of the side scan sonar system, and segmentation of the seafloor using digital image processing techniques. The correction and compensation process is essential because there is usually difference in acoustic amplitudes from the same distance of the port-side and the starboard-side and the amplitudes become attenuated as the distance is increasing. In this paper, proposed is an algorithm of compensating the side scan sonar data, and its result is compared with the mosaicking result without any compensation. The algorithm considers the amplitude characteristics according to the tow-fish's depth as well as the attenuation trend of the side scan sonar along the beam positions. This paper also proposes an image segmentation algorithm based on the texture, where the criterion is the maximum occurence related with gray level. The preliminary experiment has been carried out with the side scan sonar data and its result is demonstrated.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.665-669
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• 2018

In this paper, we design an antenna for LTE / Wi-Fi communication that operates in 2.65 GHz and 5 GHz band for small-sized broadband communication antenna that can be used in the sea. Microstrip patch antennas were chosen to improve the bandwidth. The slot width, length, and transmission line width were calculated using the theoretical formula for each step. In addition, we designed a microstrip antenna using CST Microwave Studio 2014 program that can design 3D. Simulation results show that the reflection lossis -12.712 dB at 2.65 GHz and -16.583 dB at 5 GHz. The gain was 1.738 dBi at 2.65 GHz and 3.284 dBi at 5 GHz. In this paper, we propose a dual-band antenna for LTE / Wi-Fi, which can be used in maritime environments, which is worse than terrestrial communication, because of differences in communication speed and communication stability compared with those used on land.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.122-129
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• 2019

Due to its nature the manufacturing industry faces a cyclical economy, and therefore there is an urgent need for a companion industry to cope with this cyclic pattern in the long run. The sector suitable for meeting this demand is the repair and shipbuilding industry. In order to operate a shipbuilding repair business, a floating dock is indispensable, and most obsolete floating docks were imported from overseas and operated through repair/maintenance. However, there is no precise guideline for floating dock safety, and most models have been in use for at least 30 years without being required to enter classification at the time of operation. In this study, structural strength analysis was carried out using measured thickness information of aged floating docks, and the residual structural strength of floating docks in operation was analyzed. The main results derived from this study can be referred to as guidelines for the review of the structural safety of similar equipment, and it is expected that an optimal solution will be found within a short time using this method for repair/maintenance.

• Journal of Advanced Navigation Technology
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• v.23 no.3
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• pp.251-257
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• 2019

The configuration of ultra-long optical transmission link with dispersion management and optical phase conjugation is proposed. The whole transmission link consist of 80 km (single mode fiber span) ${\times}$ 56 fiber spans. The artificial distribution of single mode fibers' lengths and residual dispersions in fiber spans, which are gradually increased/decreased as the span number is increased, is adopted to compensate for the distorted wavelength division multiplexed channels. Since the compensation effect through the artificial distribution in the previous researches is expected to decrease as the number of fiber spans are increased, three-time repetition of the artificial distribution patterns at intervals of 9 fiber spans applied into the link with dispersion management and optical phase conjugation is proposed. From the simulation results, it is confirmed that the compensation in the link configured by the special distribution pattern among 4 proposed patterns is slightly improved than the link configured by the conventional method, which is designed by the repeat-less distribution pattern.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.214-220
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• 2019

The calibration method of the initial value error obtained in the weight measurement through anchor bolt type strain gauge sensor is proposed. The strain gauge sensor is developed for preventing the overturning of forklift, which is the most frequent type of safety-accident in industry. It was confirmed that the initial value error is caused from the physical and mechanical error of anchor bolt, and the environmental problem. Since the elimination of these causes falls outside the realm of this research, we find out the calibrated values based on all the causes, and we adjust the initial values of analog-to-digital convertor (ADC) module consisted of strain gauge sensor block using the calibrated values. We use the linear interpolation method for our calibration. We confirm that four sensor modules have the different under 5% between the real weight and the measured value in the experiment applied with the calibration of initial values. The low correlation between the real weights and ADC values is also improved through the proposed calibration.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.194-199
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• 2019

Natural disasters destroy decades of human effort and investments, thereby placing new demands on society for reconstruction and rehabilitation. In most case, the natural phenomena triggering the disasters are beyond human control. In order to solve the problems that the information resources can not be shared among disaster management sectors and their work is hard to be coordinated in city, an idea of application of ubiquitous sense network and ICT technology to model the architecture of the disaster prevention system based on the analysis of characteristics of disasters. The proposed algorithm simulated that it is possible to locate the terminal by linking the direction angle and the estimated position that can be confirmed at the time of stopping, even if the movement direction of the terminal does not move in a certain direction with only a smaller number of mobile base stations. We also confirmed that the proposed algorithms analyzed through simulation are more efficient than existing algorithms.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.613-619
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• 2020

Hybrid media access control (MAC) is used in internet of things (IoT) network, because of communication feature concern with data capacity and communication interval between gateway and sensor nodes and the cost efficiency. Hybrid MAC consists of TDMA and CSMA generally. The distance between gateway and sensor node is openly changed in marine IoT network. Therefore, it is needed to control the period of timeslot of hybrid MAC used in marine IoT network. In this paper, the design rule of TDMA timeslot with the variable period depending on communication distance was proposed. It was confirmed from the analysis that 72 times communication between gateway and sensor nodes is possible in LoRa network by using the proposed TDMA variable timeslot scheme.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.84-89
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• 2021

The alternative method for symmetric configuration in optical link consisted of dispersion management and optical phase conjugation for compensating of the distorted optical signals due to chromatic dispersion and nonlinear effects of standard single mode fiber is proposed. The symmetric configuration means number of fiber spans, dispersion distribution in former half section and latter half section, etc should be symmetrical about optical phase conjugator. In dispersion-managed proposed in this research, optical phase conjugator is located after former half section consisted of 6 fiber spans and before latter half section of 14 fiber spans, and the averaged residual dispersion per span (RDPS) of each half section are consistence. The compensation effects of the distorted signals in the proposed link is analyzed by comparing with the results obtained in dispersion-managed link with the unequally averaged RDPS of each half section. From the simulation results, it is confirmed that RDPS deviation between adjacent fiber span has a grater effect on the compensation than the equivalent of the averaged RDPS.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.39-46
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• 2022

Piracy cases have been increasing globally since 2007. Recently, the waters of West Africa including the Gulf of Guinea, emerged as the most dangerous areas in the world. To prevent piracy damage to ships and crew, the Korean government amended the Piracy Damage Prevention Act on August 17, 2021 to newly define the risk area and the high-risk area for piracy. It also established the legal framework for restricting the entry of ships into such high-risk areas. This study aims to discuss and present a plan for establishing risk areas and high-risk areas for piracy to be noticed by the government in accordance with the amended Act. In this study, international piracy trends, international response measures and the status of international high-risk areas were investigated and analyzed, the matters to be considered to designate high-risk areas were identified. It is expected that the resulting information on high-risk areas for piracy can be utilized not only for the development of government policies on the prevention of piracy, but also as basic academic data.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.47-53
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• 2022

A person who intends to become a maritime pilot shall have sea experience as a master, pass the apprentice pilot test and pilot test, and obtain a license from the Minister of Oceans and Fisheries. In Korea, the government limits the number of pilot licenses, considering the demand for pilotage. An inherent problem exist in the apprentice pilot test system as it conducts a relative evaluation based on test scores without an absolute evaluation standard. The purpose of this study is to identify problems of the current pilot test system and to suggest ways to improve the pilot certification system. In this study, the history of amendments of the pilot certification system in the Pilotage Act was investigated, and implications were derived by examining international standards for pilot certification, and a survey was conducted on 77 incumbent pilots. Consequently, a plan to improve the domestic apprentice pilot test and a step-by-step implementation plan for pilot certification system improvement were presented. The results of this study are expected to be utilized not only for the development of the government policy on pilot certification and for related academic basic data.