• Corrosion Science and Technology
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• v.9 no.1
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• pp.48-55
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• 2010

The many vessels are built with FRP(Fiber-Reinforced Plastic) material for small boats and medium vessels. However, FRP is impossible to be used for recyclable material owing to environmental problems and causes large proportion of collision accidents because radar reflection wave is so weak that large vessels could not detect FRP ships during the sailing. Hence, Al alloy comes into the spotlight to solve these kinds of problems as a new-material for next generation instead of FRP. Al alloy ships are getting widely introduced for fish and leisure boats to save fuel consumption due to lightweight. In this study, it was selected 6061-T6 Al alloy which are mainly used for Al-ships and carried out various electrochemical experiment such as potential, anodic/cathodic polarization, Tafel analysis, potentiostatic experiment and surface morphologies observation after potentiostatic experiment for 1200 sec by using the SEM equipment to evaluate optimum corrosion protection potential in sea water. It is concluded that the optimum corrosion protection potential range is -1.4 V ~ -0.7 V(Ag/AgCl) for 6061-T6 Al alloy, in the case of application of ICCP(Impressed current cathodic protection), which was shown the lowest current density at the electrochemical experiment and good specimen surface morphologies after potentiostatic experiment for Al-Mg-Si(6061-T6) Al alloy in seawater environment.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.85-100
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• 2002

This paper deals with a development of combined seismic methods, based on the application of Televiewer and seismic tomography, for the quantitative assessment of reclaimed body or dam at seashores in our county. The underground structure of reclaimed dam is very complex, mainly due to the unexpected exchange of rock fragments with the marine silty mud in conjunction with S.C.P. (Sand Compaction Pile) foundation, so that for several reasons only the use of Televiewer and seismic tomography for general application might not lead to a desirable resolution. Kinds of upgraded measuring and evaluation techniques for that are needed. For examples, a novel strategy for capturing the returning impulses from the outer side of casing plastic pipe is desired to be developed. For the tomograhy, one should be being more focussed on the study of raw data based on the wave propagation theory. In this paper, it is shown that such multidisciplinary approaches can be, by attempting to compare and jointly interpret the results from two methods, much efficient for understanding the reclaimed dam structure.

• Korean Journal of Remote Sensing
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• v.31 no.1
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• pp.29-38
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• 2015

The coastline influenced naturally and artificially changes dynamically. While the long-term change is influenced by the rise in the surface of the sea and the changes in water level of the rivers, the short-term change is influenced by the tide, earthquake and storm. Also, man-made thoughtless development such as construction of embankment and reclaimed land not considering erosion and deformation of coast has been causes for breaking functions of coast and damages on natural environment. In order to manage coastal environment and resources effectively, In this study is intended to analyze and predict erosion in coastal environment and changes in sedimentation quantitatively by detecting changes in coastal line from data collection for satellite images and aerial LiDAR data. The coastal line in 2007 and 2012 was extracted by manufacturing Digital Surface Model (DSM) with Aviation LiDAR materials. For the coastal line in 2009 and 2010, Normalized Difference Vegetation Index (NDVI) method was used to extract the KOMPSAT-2 image selected after considering tide level and wave height. The change rate of the coastal line is varied in line with the forms of the observation target but most of topography shows a tendency of being eroded as time goes by. Compared to the relatively monotonous beach of Taean, the gravel and rock has very complex form. Therefore, there are more errors in extraction of coastlines and the combination of transect and shoreline, which affect overall changes. Thus, we think the correction of the anomalies caused by these properties is required in the future research.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.169-175
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• 2003

In this paper, and estimation method for estimating the states of underwater vehicle systems with external unknown disturbance is proposed. First, the dynamics of underwater vehicle are induced by Taylor series expansion in the vertical plane and horizontal plane, respectively. For constructing the system model, the external efforts, i.e., the sea surface disturbances, the current, wave and etc., are regarded as external unknown disturbances. Thus the disturbance is added as external input into state-space form of underwater vehicle system. To estimate the state of systems with unknown disturbance, a disturbance observer which does not effected the external unknown input is proposed, and the existence condition for the observer is given. Finally, the effectiveness of the proposed disturbance observer for robust control of underwater vehicle systems is verified by using numerical simulation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.165-170
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• 2003

Due to the impermeability of outer wall facilities such a Breakwaters which dissipates the wave energy and keeps harbor tranquility, the water exchange can be worse and increased enclosed at the harbor. Recent trends of port development protect water quality and emphasize Water-Front, so the method which enhances the circulation of harbor waters and the dilution of the water pollutants are studied. The best improvement of water quality is a remove of pollutant source on land, but an enclosed port must be enhanced the tidal exchange. To this hence, the best improvement may be made on drain-route on the existing outer wall facilities. In this study, the numerical computations were carried out to predict the circulation of harbor waters and the tidal exchange in the polluted harbor(Samchonpo-guhang) located at the east coast of South Sea. Computational models adopting FDM(Finite Difference Method) were used here and were already verified from the previous studies and ocean survey. As a result of this study, the tidal exchange in Samchonpo-guhang before and after installation of drain-route is assessed.

• Journal of the Korean association of regional geographers
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• v.22 no.4
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• pp.875-886
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• 2016

The eastern coast of Seopo-myeon, Sancheon-si in the South Coast is a bay almost completely separated from open sea by Changseon and Namhae Islands. Marine terraces in this area can be classified into geomorphic surfaces with elevations of 10~12m, 15~18m, 20~24m, 25~28m, 30~33m, 35~38m, 40~45m, 45~50m and 54m. This marine terrace system is similar to the Boryeong area in the West Coast. The geomorphic surfaces distribute along ridges and show relatively small areas. The young and old surfaces show a mixed distributional pattern. This distributional pattern contrasts to the East Coast where the oldest surface farthest from the coastline is parallel to the coast and age of the surfaces increases with a distance from the coast. These seem to result in high energy waves by typhoon that developed wave-cut platform on hill areas with relatively complex relief in a short time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.76-85
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• 2002

The floating breakwater generally has an excellent water exchanging capability, but with some lowering harbor tranquility due to the wave transmission underneath floating body. In the initial stage of design, it is thus required to investigate several alternatives of breakwater layout for their performance of harbor tranquility. The present study aims to formulate a sort of reflection-transmission boundary condition of floating breakwater so that the existing numerical method using time dependent mild slope equation can still be applied to the case of floating breakwaters. The two and three dimensional tests were each performed to demonstrate the performance of the boundary condition. It was found that the reflection and transmission characteristics around the breakwater were well reproduced by the boundary condition. Finally, the reflection-transmission boundary condition were applied to a floating breakwater installed in an imaginary harbor with an irregular shape and bottom topography. The results surely showed that the present numerical method can effectively used in practical works related to the real sea construction of floating breakwaters.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.2
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• pp.63-71
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• 2003

The main functions of containment boom for marine floating debris are to prevent spreading of the marine floating debris and to effectively collect the trash skimmer. The design characteristics of containment boom for marine floating debris in wave, current and wind are investigated. The response of a containment boom on the current is a function of a number of parameters, such as geometric characteristics, buoyance/weight ratio and towing velocity. To understand the relationship between these design parameters more clearly, a series of tests with three models with the variation of current speed and gap ratio was conducted. The model tests results are developed to new numerical equation that is tension prediction method of containment boom for marine floating debris. Also its is compared with open sea experimental results.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.30.3-31
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• 2010

We performed a comprehensive comparison between GPS Global Ionosphere Map (GIM) and TOPEX/Jason (T-J) TEC data for the periods of 1998~2009 in order to assess the performance of GIM over the global ocean where the GPS ground stations are very sparse. Using the GIM model constructed by CODE at University of Bern, the GIM TEC values were obtained along the T-J satellite orbit at the locations and times of the measurements and then binned into various geophysical conditions for direct comparison with the T-J TECs. On the whole, the GIM model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations. However, the GIM model was not accurate enough to represent the well-known ionospheric structures such as the equatorial anomaly, the Weddell Sea Anomaly, and the longitudinal wave structure. Furthermore, there seems to be a fundamental limitation of the model showing the unexpected negative differences (i.e., GPS < T-J) in the northern high latitude and the southern middle and high latitude regions. The positive relative differences (i.e., GIM > T-J) at night represent the plasmaspheric contribution to GPS TEC, which is maximized, reaching up to 100% of the corresponding T-J TEC values in the early morning sector. In particular, the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity, which is different from what we normally anticipate. Among these results, the plasmaspheric contribution to the ionospheric GPS TEC will be presented in this talk and the rest of it will presented in the companion paper (poster presentation).

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.137-142
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• 2013

The displacement Deep-V catamaran concept was developed in Newcastle University(UNEW) through development of the systematic Deep-V catamaran series. One of the most important Deep-V catamaran launched to date is Newcastle University's own multi-purpose research vessel, The Princess Royal. The vessel was launched in 2011 and enhanced the Deep-V catamaran concept further with the successful adoption of a novel anti-slamming bulbous bow and tunnel stern for improved efficiency. It was however identified that the vessel has substantial amount of dynamic trim that limited the visibility of the captain. The dynamic trim also increased the wave-making resistance thereby preventing the vessel from attaining its maximum speed in certain sea states. This paper therefore presents the application of devices such as Trim Tabs, Interceptors, Transom Wedges and Integrated Transom Wedges-Tabs to control the dynamic trim and improvement of fuel efficiency of the vessel. All of these energy saving devices were fitted into a model for tests in Newcastle University's Towing Tank. Model test verification confirmed that the optimum appendage was the interceptors, they produced a 5% power saving and 1.2 degree trim reduction at 15 knots, and investigations of full scale trials will be scheduled with and without application of device to compare the improvement of performance.