• Journal of Ocean Engineering and Technology
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• v.29 no.4
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• pp.300-308
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• 2015

With the increases in oil and gas prices, and energy consumption, drillship construction has increased during the last decade. A drillship using a dynamic positioning (DP) system to maintain its position and heading angle during drilling operations. In addition, a drillship is equipped with a moonpool structure to allow its drilling systems to be operated in the midship section. A drillship for the North Sea is specially designed to endure harsh environmental loads. For safe operation in the North Sea, the drillship should have good motion response and robust hull strength. A break water should be considered on the bow and side deck to prevent the green water on deck phenomenon from incoming waves. In addition, the moonpool should be designed to reduce the speed loss and resonance motion. In this study, the hydrodynamic characteristics of a drillship for the North Sea were examined in relation to the motion, wave loads, green water, and moonpool resonance in the initial design stage.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1029-1036
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• 2009

Seapage condition by sea water may appears on sea dike due to the gap of tidal, which generated by the sealevel repeatedly moves up and down result of the change of tidal level. In this study, apparatus was developed to apply similitude after setting the critical section. It was found that the soil loss was dramatically increased by increasing hydraulic gradient step by step. Also, to understand the change of seadike which considered the changes of the change of tidal level and inside sealevel, it was executed the experiments which divided the sea level condition of inside by continually changes the sealevel difference which is outside of the high tide and ebb tide.

• 한국해양학회지
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• v.20 no.1
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• pp.50-55
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• 1985

With the serial observation data of the Fisheries Research and Development Agency in Korea and Japan Meteorological Agency from 1969 to 1974, the geostrophic current and volume transport were calculated in the Korea Strait and in the middle of the East Sea (Japan Sea), in order to compare the total volume transport in summer and winter seasons. The results are as follows. The annual mean of the net volume transport of the Korea Strait is 0.19${\times}$10$\^$6/m$\^$3/sec in winter season and 1.33${\times}$10$\^$6/m$\^$3/sec in summer season. The transport through the western and eastern channel of the Korea Srait is almost same in winter season, but the transport of the western channel is much larger than that of the eastern channel in summer season. The annual mean of the net volume transport of the middle section of the East Sea (Japan Sea) is 2.61${\times}$10$\^$6/m$\^$3/sec in winter season and 2.41${\times}$10$\^$6/m$\^$3/sec in summer season. Therefore the transorts are almost same in both seasons. Comparing the transports of the two sections, the transport through the middle section of the East Sea is 13.7 times as large as that of the Korea Strait in winter season and 1.8 times in summer season.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.175-178
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• 2003

There is a case to use dredged-sea sand as a filling material because of difficulty of obtaining required filling material for tideland reclamation project from the land. At this time, side slope erosion is occurred because the precipitation falling to the top of bank acts as infiltration water when it pass through inside of the semi-permeable filling section. This study has confirmed the declining effect of permeability by conducting permeability test to the condition of mixing of bentonite to the dredged sea-sand. And also this study has confirmed that the above processed-soil could be used as a water-proof layer to protect infiltration of water through the infiltration flow analysis.

• Journal of National Security and Military Science
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• s.7
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• pp.155-231
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• 2009

Xu-Jing(徐競) an official of the Song(宋), a medieval Kingdom of China, wrote a book titled $\ll$Koryo Tu Jing(高麗圖經)$\gg$ which explains his travel to the Koryo as a member of diplomatic mission in 1123. $\ll$Koryo Tu Jing$\gg$ is the record of his personal experience in Koryo with many explanatory illustrations and especially contains 5 months' voyage record of his diplomatic fleet. His fleet set sail at a port located in the Ding Hai Xian(定海縣), Ming Zhou(明州) via a few islands of Koryo [Hyup Kye San(俠界山) , the Kun San Do(群山島) , the Ja Yon Do(紫燕島) , the Keup Su Mun(急水門) in Kang Hwa Gun(江華郡) and the Hap Gul(蛤窟) ] and finally arrived the Port Ye Song Hang(禮成港) . According to the Xu-Jing's record his fleet sailed the sea with the help of the favorable seaward winds and tides as the usual way of ancient sailing. The Xu- Jing's Fleet sailed the sea between the Mei Cen(梅岑), Ming Zhou(明州) of China and the Hyup Kye San(俠界山) of Koryo from about 5:00 a.m., May 24th(of the lunar calendar) to about 5:00 p.m., June 2nd. At this section, the average speed of the seaward winds was 19.45km/h and the average speed of the fleet which sailed only by the power of the winds was 6.29km/h. This means that 32.3% of the favorable seaward winds' speed was equal to the speed of the ancient fleet which sailed only by the power of the favorable seaward winds. The fleet sailed the sea between the Ja Yon Do(紫燕島) and the Keup Su Mun(急水門) from about 9:00 a.m., June 10th to about 1:00 p.m., the same day. At this section the fleet sailed by the power of tides in addition to the favorable seaward winds without oaring. The average speed of the winds was not different from that of former section and the average speed of the tides was 1.937km/h. And at this section the average speed of the fleet increased by 0.41km/h than that of the former section. This means that 21.1% of the speed of the tides was equal to the increased speed of the ancient fleet by virtue of the tides. The fleet sailed the sea between Keup Su Mun(急水門) and the Hap Gul(蛤窟) from about 1:00 p.m., June 10th to about 3:00 p.m., the same day. At this section, there were no seaward winds and the fleet sailed only by the powers of tides and oaring. And at this section, the tide increased the average speed of the fleet by 0.3114km/h and the fleet could sail at the speed of 4.3km/h. So we can conclude that the average speed of ancient fleet without any influences of the seaward winds and tides was 3.98 km/h. We can make use of the various sailing speeds of ancient fleets when judging their maritime activities. If we make use of the various sailing speeds of the ancient fleets as calculated in this article, we will be able to get various important informations about the certain ancient fleet's maritime maneuver. For example, we can infer the sailing routs of a certain fleet and the time when the fleet passed a certain spot by making use of the various sailing speeds of the ancient fleet. In this article I did not take account of the shapes of ships that consist of the ancient fleets and the sizes of the various ships and fleets. It was because that such factors would not change the foresaid conclusions seriously.

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.49-49
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• 2000

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.6-6
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• 2000

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.2
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• pp.97-105
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• 2020

In order to set up radar cross section(RCS) reduction factors for a target, the scattering point position of the target should be identified through inverse synthetic aperture radar(ISAR) image analysis. For this purpose, ISAR image focusing is important. Maritime ship is non-linear maneuvering in the sea, however, which blur the ISAR image. To solve this problem, translational and rotational motion compensation are essential to form focused ISAR image. In this paper, hourglass and ISAR image analysis are performed on the collected data in the sea instead of using the prediction software tool, which takes much time and cost to make computer-aided design(CAD) model of the ship.

• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.217-221
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• 2022

BACKGROUND: Gotjawal forest on Jeju Island is characterized by uneven topography that developed as a result of freezing-thawing weathering process and irregular substrates caused by numerous lava-flow collapses. Sanyang Gotjawal, located in southwest of Jeju Island, is a well-developed forest with a long history. In addition to photographs, there is a need for a good way to describe the unique features of Gotjawal, including its geology and vegetation. METHODS AND RESULTS: We illustrated the area's natural features using Clip Studio Paint 1.12.0. To reveal its complexity, we separated the vegetation and geological features in the illustrations. CONCLUSION(S): We drew a cross-section of Gotjawal's unique layers, including lava flows. In addition to an eco-geological approach, we described the dominant vegetation and geological characteristics of the three forest layers (trees, shrubs, and herbs) in Gotjawal.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.109-118
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• 2022

The data of the missing section among the vertex surface sea temperature observation data was imputed using the Bidirectional Recurrent Neural Network(BiRNN). Among artificial intelligence techniques, Recurrent Neural Networks (RNNs), which are commonly used for time series data, only estimate in the direction of time flow or in the reverse direction to the missing estimation position, so the estimation performance is poor in the long-term missing section. On the other hand, in this study, estimation performance can be improved even for long-term missing data by estimating in both directions before and after the missing section. Also, by using all available data around the observation point (sea surface temperature, temperature, wind field, atmospheric pressure, humidity), the imputation performance was further improved by estimating the imputation data from these correlations together. For performance verification, a statistical model, Multivariate Imputation by Chained Equations (MICE), a machine learning-based Random Forest model, and an RNN model using Long Short-Term Memory (LSTM) were compared. For imputation of long-term missing for 7 days, the average accuracy of the BiRNN/statistical models is 70.8%/61.2%, respectively, and the average error is 0.28 degrees/0.44 degrees, respectively, so the BiRNN model performs better than other models. By applying a temporal decay factor representing the missing pattern, it is judged that the BiRNN technique has better imputation performance than the existing method as the missing section becomes longer.