• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.spc
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• pp.11-17
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• 2022

In this study, we address the development of a floating platform system based on a unmanned surface vessel for wide-area sensing and monitoring of hazardous and noxious substances (HNSs). For long endurance, a movable floating platform with no mooring lines was used and modified for HNS sensing and monitoring. The floating platform was equipped with various sensors such as optical and thermal imaging cameras, marine radar, and sensors for detecting HNSs in water and air. Additionally, for experiment validation in real outdoor environments, a portable gas-exposure system (PGS) was built and installed on the monitoring system. The software for carrying out the mission was integrated with the Robot Operating System (ROS) framework. The practical feasibility of the developed system was verified through experimental tests conducted in inland water and real-sea environments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.563-572
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• 2006

In designing the coastal structures, the accurate estimation of wave forces on them is very important. Recently, the empirical formulae such as Goda formula are widely used to estimate wave forces, as well as 2-D hydraulic and numerical model tests. But, sometimes, these estimation methods mentioned above seem to be unreasonable to predict 3-D structure of wave pressure on the coastal structures with 3-D plane arrangement in the real coastal area. Especially, in case of consideration of phase difference at harbor and seaward sides of the large-sized coastal structures like a composite breakwater, it is easily expected that the real wave pressures on each section of coastal structure have 3-D distribution. A new numerical model of 3-D Large Eddy Simulation, which is applicable to permeable structure, is developed to clarify the 3-D structure of wave pressures acting on coastal structure. The calculated wave forces on 3-D structure installed on the submerged breakwater show in good agreement with the measured values. In this study, the composite breakwater is adopted as a representative structure among the large-sized coastal structures and the 3-D structure of wave pressures on it is discussed in relation to the phase difference at harbor and seaward sides of it due to wave diffraction and transmitted wave through rubble mound.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.631-638
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• 2016

A mariner cadet gains the ability to identify and avoid potential collisions with other ships through ARPA/Radar simulation education. This research surveyed first domestic and overseas's rules (e.g., MOMAF's Standard, the STCW Convention, etc.) of the simulation education, upon investigation the only content and timing of this simulation-based education are specified according to these rules, and maritime education institutions issue the related certification autonomously after a student has taken the simulation because no simulation education module exists to further guide the ARPA/Radar simulation. As a result, it is difficult for students to acquire consistent maritime ability through ARPA/Radar simulation. This paper discusses standardization of these education modules to produce more consistent mariner ability, and verify the degree of improvement of education that would be achieved by enacting the proposed education module. The simulation education system used in maritime institutions in Korea was investigated, and scenarios reflecting traffic flow in actual waterways was proposed based on marine traffic surveys so teaching modules can educate/assess more effectively based on core marine abilities. Improvements in education and training were also verified using data collected over 2 years based on a standardized module. Each education institution can enact an effective, systematic education approach using standardized ARPA/Radar education modules proposed in this paper, and this can set a foundation to contribute to safer vessel navigation by improving maritime abilities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1193-1199
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• 2015

Studies applying multiple carrier method such as OFDM(Orthogonal Frequency Division Multiplexing) or FMT(Filtered Multi-Tone) to Underwater acoustic communication(UAC) system are actively under way as UAC is utilized in the various fields and the demand of high speed data transmission increases. In the existing OFDM method, the use of virtual carrier, which is inserted not to affect the adjacent channel in the frequency domain, and the cyclic prefix, which is used to reduce the impact of Inter Symbol Interference and Inter Channel Interference, decrease the throughput. In particular, the length of cyclic prefix to be used becomes longer under water since underwater has a rapidly changing channel characteristic, and the data throughput diminishes because it has to allocate more subcarrier on virtual carrier. This study therefore suggests FMT-OFDM system, a combination of OFDM and FMT, for the purpose of enhanced throughput in the underwater channel environment. Besides, in this study, channel is modeled based on data measured in real sea and the performance is analyzed after setting system parameters.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.686-693
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• 2018

After the Sewol ferry-sinking incident in 2014, the public interest in safety at sea increased. In order to save and secure the initial response time required for sea rescues, not only the rescue organization, but also the victim needs to save and maintain golden time to secure the necessary time for rescue personnel. The purpose of this study was to investigate ways to maintain the psychological stability of victims during their rescue in the case of a mass rescue operation by using the oil boom installed on board oil spill response vessels. Through buoyancy tests and the development of oil booms in sea areas, it confirmed the buoyancy of two adults weighing 70 kg each per meter of oil boom could be maintained when a lifeline was installed on the side of the oil boom, and that it was possible to keep afloat four persons weighing 70 kg each on both sides of the oil boom. It also confirmed the buoyancy for three adults weighting 70 kg each per eight meters was maintained when riding on the top of the oil boom. As a method of rescue, it was found that the fastest and most accurate way to rescue victims was a rescue boat held at the rear end of the oil boom to lead to victims. In conclusion, the rescue team could utilize the oil boom installed on board the oil spill response vessel located near the marine accident site to save and secure the initial response time required for the rescue team to arrive. The victims in distress holding onto the lifeline or riding on the top of oil boom kept afloat at sea could maintain their psychological stability until the mass rescue operation initiated.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.208-218
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• 2012

Numerical simulation technique has been developed to calculate microwave backscattering from water surface. The simulation plays a role of a substitute for experiments. Validation of the simulation was shown by comparing with experimental results. Water area observations by microwave radar have been simulated to evaluate algorithms and systems. Furthermore, the simulation can be used to understand microwave scattering mechanism on the water surface. The simulation has applied to the various methods for water area observations, and the utilizations of the simulation are introduced in this paper. In the case of fixed radar, we show following examples, 1. Radar image with a pulse Doppler radar, 2. Effect of microwave irradiation width and 3. River observation (Water level observation). In addition, another application (4.Synthetic aperture radar image) is also described. The details of the applications are as follows. 1. Radar image with a pulse Doppler radar: A new system for the sea surface observation is suggested by the simulation. A pulse Doppler radar is assumed to obtain radar images that display amplitude and frequency modulation of backscattered microwaves. The simulation results show that the radar images of the frequency modulation is useful to measure sea surface waves. 2. Effect of microwave irradiation width: It is reported (Rheem[2008]) that microwave irradiation width on the sea surface affects Doppler spectra measured by a CW (Continuous wave) Doppler radar. Therefore the relation between the microwave irradiation width and the Doppler spectra is evaluated numerically. We have shown the suitable condition for wave height estimation by a Doppler radar. 3. River observation (Water level observation): We have also evaluated algorithms to estimate water current and water level of river. The same algorithms to estimate sea surface current and sea surface level are applied to the river observation. The simulation is conducted to confirm the accuracy of the river observation by using a pulse Doppler radar. 4. Synthetic aperture radar (SAR) image: SAR images are helpful to observe the global sea surface. However, imaging mechanisms are complicated and validation of analytical algorithms by SAR images is quite difficult. In order to deal with the problems, SAR images in oceanic scenes are simulated.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.209-218
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• 2011

The present study proposes a new estimation relationship for the transmission rate of the steel breakwater which is expected to make up for the weakness points in existing hard solution for shore protection. The steel breakwater consists of the wave dissipator of the dual horizontal plates, the supporting columns and their foundations, and thus its respective designs should also be conducted one by one. Furthermore, the breakwater has to ensure both functions of shore protection and structure stabilization. The study produced experimental data for the stability and safety investigation of the steel breakwater. The forces acting on the steel breakwater were classified into two categories, one is vertical up and down loads for the pile resistance and the other was maximum difference of the vertical load acting on horizontally different position for the torsion. The study applied the stability force produced by the summation of maximum pressure at each point and the safety force acting on each point simultaneously. The regular wave corresponding to the significant wave was utilized for measuring wave pressure and force. The study showed the method for the proper position of submerged upper plate by considering occurrence frequency of tide level. The design process finally determined by trial and error is proposed in the present study.