• Journal of Navigation and Port Research
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• v.44 no.2
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• pp.119-127
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• 2020

In this study, the current state of management efficiency of ocean carriers in Korea and the factors affecting them were analyzed. The purpose of this research is to enhance global competitiveness of ocean carriers by presenting suggestions that can improve management efficiency based on the analysis results. The measurement of management efficiency was made using the DEA model. The results of testing the adequacy of the input and output variables used are as follows. Appropriate inputs are total assets, cost of goods sold, charter expenses, sales and general management expenses, and interest expenses. Appropriate variables are sales, operating income, and operating cash flow. According to the analysis results of the DEA model by these variables, inefficient carriers (78%) are nearly four times more than efficient carriers(22%). However, container carriers have the most improved management efficiency compared to 2016 and 2017. According to the panel regression analysis, the charter rate has the greatest negative impact on efficiency (CRS), and the debt rate has a significant negative impact. Thus, it appears that reducing the charter size and the debt-to-sale rate facilitate improvement of the management efficiency of ocean carriers. Additionally, the pre-sales tax return rate, value added rate, total asset turnover rate, and the scale variable and interest coverage rate have a positive (+) effect. Thus ocean carriers should restore their global competitiveness by improving management efficiency by securing stable cargoes increasing sales profitability from the cost management perspective, increasing productivity, and enhancing the efficiency of their total assets through efficient fleet management.

• Journal of Advanced Navigation Technology
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• v.24 no.1
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• pp.9-15
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• 2020

Recently, active electronically scanned array (AESA) radar, electro-optical and infrared (EO-IR) and infra-red search and track (IRST) sensors are under development in the Korean fighter experimental(KF-X) project, and AESA radar is currently undergoing preliminary research for flight testing. This paper focuses on the flying test bed (FTB) aircraft operation cases of developed countries in accordance with AESA radar development. As a result, we review domestic laws and regulations related to the airworthiness for FTB aircraft to operate in domestic environment and look for ways to operate FTB aircraft. Therefore, we propose how to selecting, airworthiness and operating FTB aircraft suitable for the domestic environment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.52-58
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• 2013

Operation Abstract : Operational cost required for navigating a ship may differ from according to type, scale, economic speed, navigation area and other factors. However, it is known that the fuel oil price ratio takes 50~60 %. It is the current trend because of the use of poor quality fuel and it is reviewed even for small to medium sized ships to save the operational costs due to the recent rise of international oil price. Furthermore, ocean carriers are taking action to low speed navigation as the alternative method of reducing fuel consumption. Hence, in this study, fuel consumption of main engine was measured by using actual operating ship data compared with sea speed at sea. It was suggested that the area of M/E's load(70 %) lower than NCR is the optimal navigating condition through the relation between speed and fuel consumption compared with advance ratio together with the load.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.238-244
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• 2020

The development and distribution rate of smartphones have progressed so rapidly that it is safe for the entire nation to use them in the smart age, and the use of smartphones has become an essential medium for the use of domestic media content, and many people are using various contents regardless of gender, age, or region. Recently, various media outlets have been consuming video content for online learning, indicating that learners utilize video content online for learning. In the previous research, satisfaction studies were conducted according to the type of content, and the improvement plan was necessary because no research was conducted on how to evaluate the learning content itself and provide it to learners. In this paper, we would like to propose a system through evaluation and review of learning content itself as a way to improve the way of providing video content for learning and quality learning content.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.329-342
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• 2020

In this paper, we analyzed the requirements for the application of UAM, a new concept to solve the traffic congestion in large cities. First, the current domestic and foreign status of research and development related to UAM was investigated and the pros and cons and the time required for each mission radius were analyzed for various configurations of aircraft being commercialized. In addition, in order to analyze the market acceptance of the UAM, the individual's consciousness and reliability requirements were identified and safety requirements were analyzed through accident rate data for each aircraft type. Because it operates in a densely populated urban area, requirement analyses on noise and exhaust, which are environmental factors that can affect the community were performed, and requirements related to aircraft performance, certification standards, and airworthiness standards of FAA and EASA were also analyzed.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.741-746
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• 2010

It is necessary to estimate more accurately the resistance of barge in still water and waves to compute the break load of towline and towing power for safety towing performance. The method proposed by government has calculated the total resistance of barge which is composed of frictional resistance, wave making resistance and air resistance considering the shape of hull and towing speed. However, the added resistance is equally applied with the significant wave height regardless of the type of vessels. In this study, we have carried out the numerical calculation to estimate the added resistance of wigley model in waves and compared with the experiment data to confirm the accuracy of the method. Then the computation was executed for the barge varying shape of the bow. As a result, added resistance of barge was differently occurred i.e. 0.3∼1.1 ton according to encounter angle, 0.4∼1.2 ton according to towing speed and 0.5∼1.1 ton according to shape of bow.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.483-491
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• 2013

By a development of car navigation systems and mobile or positioning technology, it increases interest in location based services, especially pedestrian navigation systems. Updating of digital maps is important because digital maps are mass data and required to short updating cycle. In this paper, we proposed change detection for different network data-sets based on areal feature matching. Prior to change detection, we defined type of updating between different network data-sets. Next, we transformed road lines into areal features(block) that are surrounded by them and calculated a shape similarity between blocks in different data-sets. Blocks that a shape similarity is more than 0.6 are selected candidate block pairs. Secondly, we detected changed-block pairs by bipartite graph clustering or properties of a concave polygon according to types of updating, and calculated Fr$\acute{e}$chet distance between segments within the block or forming it. At this time, road segments of KAIS map that Fr$\acute{e}$chet distance is more than 50 are extracted as updating road features. As a result of accuracy evaluation, a value of detection rate appears high at 0.965. We could thus identify that a proposed method is able to apply to change detection between different network data-sets.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.711-719
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• 2006

A series of geotechnical centrifuge model tests and numerical modelling have been performed to study engineering characteristics of the composite ground reinforced by both the Sand Compaction Piles(SCPs) and the deformation-reducing sheet piles. The research has covered several key issues such as the load-settlement relation, the stress concentration ratio and the final water content of the ground Totally three centrifuge tests have been conducted by changing configuration of the sheet piles, i.e., a test without the sheet pile, a test with the sheet pile at a single side and a test with the sheet piles at the both sides. In the model tests, a vertical load was applied in-flight on the ground surface. On the other hand, class-C type numerical modelling has been performed by using the SAGE-CRISP to compare the centrifuge test results using an elasto-plastic model for SCPs and the Modified Cam Clay model for the soft clay. It has been found that the sheet piles can restraint failure of foundation, thereby increasing yield stress of the ground. The stress concentration ratio was in the range of $2{\sim}4$. In addition, numerical analysis results showed reductions both in the ground heave($20{\sim}30%$) and in the horizontal movement($28{\sim}43%$), demonstrating the deformation-reducing effect of the sheet piles.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.307-315
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• 2023

Korea controls the departure of vessels based on the Maritime Safety Act such that only ships with seaworthiness can navigate in bad weather, but scientific evaluation results and quantitative basis for the designation of ships subject to control are insufficient. Opinions for improvement are being raised for a reasonable departure control operation. The purpose of this study is to evaluate the adequacy of the current departure control standards through actual measurement of tugboats, which are the type of vessels subject to control when a wind and wave advisory is effective, and to present quantitative grounds for improvement of controls. A sensor was installed on the tugboat to measure the ship's three-axis motion and hull acceleration, and the hull motion performance was measured by operating in the sea area with a significant wave height of 3 m. The measured values were compared and analyzed based on seaworthiness evaluation factors and limit value standards. The actual ship was excluded from the current control standard according to tonnage, but as a result of the analysis, the pitch value exceeded the operation standard, and a risk to navigation safety existed. The results of this study suggest the need for additional actual measurement studies that can represent various ship types and specifications and review ship departure control targets.