• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.4
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• pp.204-217
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• 2018

This study proposes a cost-effective method to monitor coastal environments using e-Navigation-implemented domestic and international ferries, and to analyze big data of records such as wind, temperature, salinity, waves, and currents that are gathered through e-Navigation system. First, we present the concept and architecture of e-Navigation operation system based on the General Information Center on Maritime Safety and Security. Then, the marine observation system that can be applied to ferries operating in our nation's territory is discussed. Analytical methods, such as spatio-temporal mixed effects model, ensemble method, and meshfree method, in handling real-time big data obtained by the e-Navigation observing system are then explained in detail. This study will support the implementation of the Korean e-Navigation project that focuses on the safety of small vessels such as coasters and fishing vessels.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.4
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• pp.489-497
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• 2019

A ship operating under rough sea conditions is exposed to a slamming load due owing to its motion relative to encountered waves. In the process of reentering the water, the ship's structure is temporarily subjected to an impact pressure. In particular, bow flare slamming often occurs in large container ships with a large flare angle, and can cause structural damage. Numerical simulations were performed in this study, and the results were compared with reliable experimental results. The simulation results were also used to estimate the bow flare slamming pressures on a container ship under head sea and oblique sea conditions. It was found that a maximum impact pressure of 475 kPa was generated near the 0.975 station of the container ship under a head sea condition.

• International journal of steel structures
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• v.18 no.4
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.375-388
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• 2022

This paper deals with the process of obtaining sound transmission loss of a cylindrical silencer lined with multi-layered poroelastic sound absorbing materials. The Biot model and the Johnson-Champoux-Allard-Lafarge (JCAL) model were used to deal with waves propagating in multi-layered poroelastic materials. The boundary conditions required for analysis of the silencer were obtained and the numerical process of finding modes was explained. A numerical experiment was conducted on the 2-layered silencer using the modes and the transmission loss converged with the first 12 modes. Finally, the mode matching method proposed in this research was validated by being compared with the results calculated from Finite Element Method (FEM) about different kinds of sound absorbing materials.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1070-1077
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• 2022

The International Maritime Organization has recently strengthened its marine environment regulations. The energy efficiency index has long been an important indicator of ship design, and now, energy efficiency is being enforced for existing ships as well as new ships. To increase the energy efficiency of existing ships, methods such as retrofitting the bow bulb, selecting an optimized trim during ship operation, and installing an energy saving device have been applied. In this study, the ship resistance was numerically simulated using computational fluid dynamics (CFD) under various bow and stern trim conditions. In addition, the bulb was redesigned to further improve the resistance performance under the selected trim conditions. When the improved bulb was applied, the effective horse power increased by approximately 5%. It is, however, necessary to verify whether the redesigned bulb can reduce ship resistance in waves.

• Journal of Appropriate Technology
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• v.5 no.2
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• pp.118-125
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• 2019

Climate change is one part of 17 Sustainable Development Goals (SDGs). According to the Fifth Assessment Report by the Inter- governmental Panel on Climate Change(IPCC) published in 2014, global warming is caused by greenhouse gas (GHG) emissions. The most important GHG is carbon dioxide (CO₂), which is released by the burning of fossil fuels and, to a lesser extent, by land use practices, followed by nitrous oxide and methane. IPCC predicts that global temperatures will rise 3.7℃ and sea level will rise 0.63 m by 2099 in the case of no strong restraint. According to the report, we can expect a massive species extinctions, changes in storm and drought cycles, altered ocean circulation, and redistribution of vegetation by global warming. However, climate changes, especially global warming, are the largest potential threat to human health and the source of a number of diseases globally. If climate changes are continued uncontrolled, human health will be adversely affected by the accelerating climate change and the natural disaster induced by climate change. It means we will face more serious conditions of injury, disease, and death related to natural disasters such as flood, drought, heat waves, malnutrition, more allergy, air pollution and climate change related infections related to morbidity and mortality. This review emphasizes on the relationship between global climate changes and human health and provides some suggestions for improvement.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.242-243
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• 2023

Different incident angles concerning ocean conditions and weather greatly influence small vessel navigation. Particularly for small vessels, different incident angles result in distinct motion characteristics closely related to stability. Based on actual coastal wave data, this study conducted simulations and experiments to analyze the motion characteristics of small vessels navigating in irregular waves. The analysis revealed that significant motions primarily occurred at lower speeds from the bow sea. In contrast, as the speed increased, the roll motions due to the bow sea decreased, but those due to the stern seas increased. Consequently, adjusting the incident wave angles according to vessel speed can enhance stability and navigational efficiency for small vessels.

• Atmosphere
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• v.33 no.5
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• pp.561-570
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• 2023

In order to improve the predictability of marine high-impacts weather such as typhoon and high waves, the marine observation network is an essential because it could be rapidly changed by strong air-sea interaction. In this regard, the National Institute of Meteorological Sciences, Korea Meteorological Administration (NIMS/KMA) has promoted the Argo float observation program since 2001 to participate in the International Argo program. In this study, current status and future direction of the NIMS/KMA Argo program are presented through the internal meeting and external expert forum. To date, a total of 264 Argo floats have been deployed into the offshore around the Korean Peninsula and the Northwestern Pacific Ocean. The real-time and delayed modes quality control (QC) system of Argo data was developed, and an official regional data assembling center (call-sign 'KM') was run. In 2002, the Argo homepage was established for the systematic management and dissemination of Argo data for domestic and international users. The future goal of the NIMS/KMA Argo program is to improve response to the marine high-impacts weather through a marine environment monitoring and observing system. The promotion strategy for this is divided into four areas: strengthening policy communication, developing observation strategies, promoting utilization research, and activating international cooperation.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.138-144
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• 2024

This paper presents a bistatic to monostatic conversion technique to analyze the bistatic target strength of submarines. The technique involves determining the transmission path length of acoustic waves, which are emitted from a source, scattered off an underwater target, and eventually received by a receiver. By generating a corresponding virtual scattering surface, this method effectively transforms the target strength analysis problem from bistatic to monostatic. The converted monostatic target strength problem can be assessed using a well-established monostatic numerical methods. The bistatic target strength analysis for Benchmark Target Strength Simulation (BeTTSi), a widely used target strength model were performed. The results were compared with those calculated by boundary element methods and Kirchhoff approximation, and confirmed the validity and the practical applicability of the proposed analysis technique for evaluating submarine target strength.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.848-857
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• 2018

Recently, around the world, active development of new renewable energy sources including solar power, waves, and fuel cells, etc. has taken place. Particularly, floating offshore wind farms have been developed for saving costs through large scale production, using high-quality wind power and minimizing noise damage in the ocean area. The development of floating wind farms requires an evaluation of the Maritime Safety Audit Scheme under the Maritime Safety Act in Korea. Floating wind farms shall be assessed by applying the line and area concept for systematic development, management and utilization of specified sea water. The development of appropriate evaluation methods and standards is also required. In this study, proper standards for marine traffic surveys and assessments were established and a systemic treatment was studied for assessing marine spatial area. First, a marine traffic data collector using AIS or radar was designed to conduct marine traffic surveys. In addition, assessment methods were proposed such as historical tracks, traffic density and marine traffic pattern analysis applying the line and area concept. Marine traffic density can be evaluated by spatial and temporal means, with an adjusted grid-cell scale. Marine traffic pattern analysis was proposed for assessing ship movement patterns for transit or work in sea areas. Finally, conceptual design of a Marine Traffic and Safety Assessment Solution (MaTSAS) was competed that can be analyzed automatically to collect and assess the marine traffic data. It could be possible to minimize inaccurate estimation due to human errors such as data omission or misprints through automated and systematic collection, analysis and retrieval of marine traffic data. This study could provides reliable assessment results, reflecting the line and area concept, according to sea area usage.