• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.2
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• pp.3-18
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• 2002

This study has been carried out to find the water Quality in coastal sea of fungmun area, southern Jeju Island. In-situ observations and water sampling had been made every month from July 1997 to June 2000. The distributions of water temperature and salinity over the study area have been 13.8~27.0℃ and 30.0~34.7‰, respectively. Salinity is showed low salinity from June to September (rainy season) because of rain. Tsushima Warm Waters (TWW) as ≥15℃ and ≥34‰ influence the adjacent sea around Jeju Island all year round. Yangtse Coastal Waters (YCW) influence the surface layer around Jeju from June to September and so strong stratification (termocline, halocline) resulted at the depth of between 20~30m at outer-sea. However the stratification does not happen even in summer at inner-sea, which seem to be caused due to vertical mixing by wind, waves and tides. A water mass of high value of water temperature and salinity (respectively 14.1~17.7℃, 33.9~34.1‰) stayed at the lower layer in outer-sea all the year round. It is probably formed by mixing between TWW and YSBCW(Yellow Sea Bottom Cold Water). The mean value of DO was the lowest in summer and the highest in winter. COD and TH were the highest in summer and the lowest in winter. However, TP showed the lowest value in summer season, because the mean value of N/P ratio was over 16. The mean of N/P ratio was under 16 in other seasons. The phosphate would be a limiting factor in the growth of phytoplanHon in summer. Nitrate would be a limiting factor in other seasons. Distribution of chlorophyll a did not show any seasonal change in the study period, but especially increased during April and May in the first year(1998) and the second year(1999) all over the study area, which suggested that phytoplankton inhabitation distributed widely in the study area. The space averaged values were the highest for TIN in rainy season and lower for TP in rainy season than in other seasons. It suggests that river runoff influences the inner-sea.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.1
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• pp.46-52
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• 2005

A marine environmental information system (MEIS) useful for optimal route planning of ships running in the ocean was developed. Utilizing the simulated marine environmental data produced by the European Center for Medium-Range Weather Forecasts based on global environmental data observed by satellites, the real-time forecast and long-term statistics of marine environments around planned and probable ship routes are provided. The MEIS consists of a land-based data acquisition and analysis system(MEIS-Center) and a onboard information display system(MEIS-Ship) for graphic description of marine information and optimal route planning of ships. Also, it uses of satellite communication system for data transfer. The marine environmental components of winds, waves, air pressures and storms are provided, in which winds are described by speed and direction and waves are expressed in terms of height, direction and period for both of wind waves and swells. The real-time information is characterized by 0.5° resolution, 10 day forecast in 6 hour interval and daily update. The statistic information of monthly average and maximum value expected for a return period is featured by 1.5° resolution and based on 15 year database. The MEIS-Ship include an editing tool for route simulation and the forecasting and statistic information on planned routes can be displayed in graph or table. The MEIS enables for navigators to design an optimal navigational route that minimizes probable risk and operational cost.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.101-110
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• 2012

In order to understand temperature and salinity variations, and the characteristics of the seawater exchange through two channels of Gamak Bay, we conducted measurements of water temperature, salinity and current for fifteen days in the summer and winter. Based on the observational data, the current seemed to have a close relation with wind. In addition, a correlation analysis result proved that water temperature is likely to be more influenced by air temperature rather than tide. Moreover, water temperatures at the south channel varied more sensitively with the season rather than at the east channel because of its shallow depth. Seawater exchange rates were estimated to be 0.5~29.9% (mean: 11.6%) at the east channel but 1.3~62.6% (mean: 18.6%) at the south channel in summer. On the contrary, they were estimated to be 0.3~28.5% (mean: 8.9%) at the east channel but 0.1~97.9% (mean: 31.2%) at the south channel in winter. Thus, the rates of seawater exchange in Gamak Bay turned out that the south mouth is approximately three times higher than the east mouth, and it also suggested that seasonal winds affect the rates of seawater exchange in Gamak Bay.

• Korean Business Review
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• v.22 no.2
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• pp.157-179
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• 2009

This papers aims to focus on the city marketing as the green growth policy strategies using a case study of Gangneung City, Republic of Korea. In the case study it was verified the fields of urban growth including ecology, culture, alternative and recycled energy, green transportation system. The implications of the study were as follows: First, the city government had regenerated the coastal pine forest through removing unlicensed buildings which were squatted down in decades. Secondly, the city government has recognized the value of culture that possessed various types of cultural asserts. Thirdly, it is possible to use and produce the ocean energy with the tidal power plant, wind power plant and green deep water because Gangneung City has the ocean-oriented image and is located the coastal region. Lastly, the city government has been utilizing the LED traffic light using solar heat and is going to apply the green car like an electric car. This paper indicates the importance of the alternatives of the green growth-oriented policy through city marketing using the concept of culture and ecology. The city government will strive after an advanced triple bottom line with the ecological sustainability, cultural diversity and economic effectiveness in the near future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.2
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• pp.69-83
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• 2018

The South China Sea (SCS) is a typical marginal sea characterized with the deep basin, shelf break, shallow shelf, many straits, and complex bathymetry. This study investigated the tidal characteristics and propagation, and reproduced typhoon-induced storm surge in this region using the regional real-time tide-surge model, which was based on the unstructured grid, resolving in detail the region of interest and forced by tide at the open boundary and by wind and air pressure at the surface. Typhoon Haiyan, which occurred in 2013 and caused great damage in the Philippines, was chosen as a case study to simulate typhoon's impact. Amplitudes and phases of four major constituents were reproduced reasonably in general, and the tidal distributions of four constituents were similar to the previous studies. The modelled tide seemed to be within the acceptable levels, considering it was difficult to reproduce the tide in this region based on the previous studies. The free oscillation experiment results described well the feature of tide that the diurnal tide is prevailing in the SCS. The tidal residual current and total energy dissipation were discussed to understand the tidal and sedimentary environments. The storm-surge caused by typhoon Haiyan was reasonably simulated using this modeling system. This study established the regional real-time barotropic tide/water level prediction system for the South China Sea including the seas around the Philippines through the validation of the model and the understanding of tidal characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.83-91
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• 1984

The formation and structure of tidal front in the eastern part of the Yellow Sea were studied based on the oceanographic data compiled during the periods of $1982{\sim}1983$ and $1966{\sim}1970$. Well-defined fronts occurring in the Yellow Sea in summer mark the boundary between the stratified and vertically mixed regimes. The occurrence of vertically mixed regimes may be interpreted in terms of available turbulent kinematic energy of tidal currents. The tidal frontal regions were determined by horizontal gradients of temperature, salinity and dissolved oxygen, and were verified by water colour and transparency. In summer the tidal fronts were found at depths of $15{\sim}25m$ at about 20 miles from the shore. Potential energy of vortical stratification in the tidal frontal region was 10 $Joule/m^3$. The stratification parameter in the frontal region computed from the numerical tidal model was $S_p=1.0.$ Tidal front is formed in regions with $S_p=1-1.5,$ if surface heat flux are constant. Waters in the stratified region have the layer structures of wind-mixed surface layer, thermocline and tidal-mixed bottom layer. In the vertically mixed region, however, sea water is nearly homogeneous. in winter no distinctive tidal front was seen.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.137-143
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• 2016

The sedimentary environment and sediment were surveyed at the West-Northern site of Chagwi-do nearby Jeju Island for the design of the embedded suction anchor system of 10 MW-class floating wave-offshore wind hybrid power generation system. According to the classification scheme of Chough et al.[2002], the echo type of the seismic profiles using the chirp III was classified. As a results, the center and west-northern area of survey site were proved to be type I-3 where subbottom layer with thickness 5~15 m exists under the flat seafloor. On the other hands, the east-southern area were regarded to be type I-1, I-2 and III-1 where seafloor reflection is much stronger than type I-3. Also, the physical tests (unit weight, moisture content, grain size, liquid limit, specific gravity) were performed with samples taken from 8 fixed locations. It is found that the sand (SP), the sand blended with silt (SM) and the mixture of SP-SM are distributed uniformly on the survey area.

• Progress in Superconductivity
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• v.13 no.1
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1993-1999
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• 2013

Steel composite structures have been studied in various areas such as bridges, high rise buildings, and wind towers. They show excellent structural performance through overcoming of the weaknesses of steel and concrete. Although various methods were already developed to achieve full composite behavior between steel and concrete in flexural members, the number of studies regarding composite columns is quite limited. If slip occurs between concrete and steel under external loads, the performance of the composite column would be reduced significantly. Connection methods ensuring full composite action between steel and concrete must be suggested. This paper investigated about structural behavior of shear studs through a series of experimental tests. Extensive parameters were also performed to understand the effects of the diameter of stud, space of stud and height of concrete. The present study provides fundamental bases for further development of design method of shear studs in composite columns.

• Journal of Korea Water Resources Association
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• v.49 no.3
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• pp.227-239
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• 2016

This study is to estimate Surface Energy Balance Algorithm for Land (SEBAL) daily spatial evapotranspiration (ET) comparing with eddy covariance flux tower ET in Seolmacheon mixed forest (SMK) and Cheongmicheon rice paddy (CFK). The SEBAL input data of Albedo, Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI) from Terra MODIS products and the meteorological data of wind speed, and solar radiation were prepared for 2 years (2012-2013). For the annual average flux tower ET of 302.8 mm in SMK and 482.0 mm in CFK, the SEBAL ETs were 183.3 mm and 371.5 mm respectively. The determination coefficients ($R^2$) of SEBAL ET versus flux tower ET for total periods were 0.54 in SMK and 0.79 in CFK respectively. The main reason of SEBAL ET underestimation for both sites was from the determination of hot pixel and cold pixel of the day and affected to the overestimation of sensible heat flux.