• Journal of the Korean GEO-environmental Society
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• v.14 no.10
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• pp.39-47
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• 2013

Recently, there have been various domestic construction activities related to the reclamation of the dredged soils to expand the land use. However, the reclaimed grounds made of the dredged soils cause various problems due to highly compressible and low shear strength nature. Particularly, this nature induces huge problems in case of the harbor facilities and road construction on the reclaimed sites. Furthermore, in the reclamation activities, the marine dredged soils are often used instead of the well sorted sand, which induces problems of compressibilities. Therefore, in this study, the mechanical characteristics of artificial soil mixture of kaolinite representing the marine dredged soils and the pond ash. A large consolidometer is designed and manufactured to produce the artificial soil mixture. To represent various mixing ratio between the fly ash and bottom ash in the pond ash, six samples with the same stress history are made with different mixing ratio among kaolinite, bottom ash and fly ash. Isotropically consolidated and undrained compression tests are performed to investigate the shear characteristics of soil mixtures. Based on the experimental results, as the components of mixed ash increase, the friction angle increase and the cohesion values decrease. Also, the porepressure parameters at failure, Af increase with the mixing components of the pond ash. The portion of bottom ash has more impact on the shear behavior than that of fly ash.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.94-110
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• 2003

This study utilizes the dataset of Topex/Poseidon(T/P) altimeter sea surface height (1992-2000 yr., 286 cycles)to investigate the tempore-spatial variability in the East (Japan) Sea. Optimal interpolation (Ol) technique was applied to the pre-processed T/P dataset (level 2) to produce sea surface height anomaly (SSHA) map on regular grids. Spectral analyses of the timeseries of the SSHA at chosen stations and empirical orthogonal function (EOF) analysis of the SSHA in the entire East Sea were made. Distribution of the SSHA can be divided by the southern and northern regions sharply by the polar front situated in the middle of the East Sea. The southern region under the direct influence of the Tsushima Current exhibits higher amplitude of the SSHA fluctuation, while the northern region does relatively smaller one. The spatio-temporal variability of the SSHA in the East Sea can be characterized by the five modes of the EOFs accounting for more than 85% of the total variance. The first mode dominates the SSHA variation in the entire domain with strong seasonal and inter-annual periods accounting for the 72.3% of the total variance. The other modes (up to 5th account for 14%) are responsible for the SSHA variation associated with the local current system, meandering of the polar frontal axis, and mesoscale eddies. Spectral peaks with significant confluence level show semi-annual, annual and interannual (2, 3-4 years) periods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.601-610
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• 2021

The tidal current patterns at Keum River Estuary before and after the construction of coastal structures were compared according to the CASES. The depth-integrated and tidal difference treatment applied FLOW2DH numerical model was used for the tidal current predictions. The test conditions consisted of before construction of coastal structures (CASE1), after construction of coastal structures (CASE2), and the addition of watergate operation(CASE1Q and CASE2Q), and present (CASE3). CASE1 showed a stable tidal current pattern, such as a natural estuary. In CASE2, the tidal current velocities and directions of the Keum River Estuary were changed due to the installed coastal structures. In particular, the tidal current velocities of the Gaeya open channel sections (P5~P9) in CASE2 were calculated to be 10~30% larger than that of CASE1. In the case of the Gunsan Inner Harbor (P4), which is closest to the Geum River Estuary, the ebb flow rate was approximately 250~300% faster than that of other CASEs due to the discharge of the watergate operation for 2.7 hours during the ebb of CASE1Q and CASE2Q. This will affect sediment transport, and it is predicted to lead to seabed changes. CASE3 is considered to be entering the stabilization stage according to the simulation of the tidal current velocities and directions of the Keum River Estuary and the surrounding coastal area.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.270-285
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• 2018

The behavior of wave-induced pore water pressure inside the rubble mound and seabed, and the resultant structure failure are investigated, which are used in design of the composite breakwater representing the coastal and harbor structures. Numerical simulation techniques have been widely used to assess these behaviors through linear and nonlinear methods in many researches. While the combination of strongly nonlinear analytical method and turbulence model have not been applied yet, which can simulate these characteristics more accurately. In this study, olaFlow model considering the wave-breaking and turbulent phenomena is applied through VOF and LES methods, which gives more exact solution by using the multiphase flow analytical method. The verification of olaFlow model is demonstrated by comparing the experimental and numerical results for the interactions of regular waves-seabed and regular waves-composite breakwater-seabed. The characteristics of the spatial distributions of horizontal wave pressure, excess-pore-water pressure, mean flow velocity and mean vorticity on the upright caisson, and inside the rubble mound and seabed are discussed, as well as the relation between the mean distribution of vorticity size and mean turbulent kinetic energy. And the stability of composite breakwater are also discussed.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.67-76
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• 2009

The problems of bearing capacity, settlement and shear deformation occur when constructing a structure such as harbor, airport and bridge on soft ground of marine clay, silty clay or sandy soil. Various ground improvement methods are applied to obtain preceding settlement of soft ground and strength increase. In this study, to analyze the applicability of PBD method in deep soft ground, the compound drainage capacity test was operated in comparison with SD. As a result of the test, a minimum drainage capacity of drain material was estimated to be more than $10\;cm^3/sec$ at a more than $400\;kN/m^2$ and less than $5\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure in case of single core PBD. In case of double core PBD, it was estimated to be more than $10\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure.

• Journal of architectural history
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• v.32 no.3
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• pp.7-20
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• 2023

The compositions of ethnic groups in Macau vary with time. Prior to the opening of the port, the majority of the residents in Macau were Chinese people, including those living on land and at sea. After the port was opened, with the increase of Portugal businessmen and missionaries, the population was divided into Chinese people and foreigners (so-called 'Yiren' or 夷人 in Chinese). Chinese people living on land were mainly of Hakka, Fujian, and Cantonese descent. Those living at sea were referred to as 'Tanka People' (named 'Danmin' or 蜑民in Chinese). They lived on floating boats for their entire lives and were similar to the 'drifters' in Japan. Since modern times, many refugees from mainland China and Southeast Asia flooded into Macau due to warfare. The development of industrialization required a larger number of laborers, and some 'coolies' entered Macau in legal or illegal ways, making it a multi-ethnic city. However, the Tanka people were not considered a minority ethnic group under the national ethnic policy of 56 ethnic groups since they did not have an exclusive language and shared dialects in different regions. As the ports inhabited by Tanka people gradually restored foreign trade, the boats and stilt houses used by Tanka people were dismantled to expand the infrastructure area of the ports. Many Tanka people began to live on land and marry people on land, leading to the disappearance of the Tanka group in Macau. The fishing boats and stilt houses used by Tanka people have also disappeared, with only a few remaining in areas such as Pearl River Delta and Hong Kong. This paper examines the natural and social environment of Tanka people in Macau from the Ming and Qing dynasties to the Republic of China, as well as the adaptive changes they adopted for the aforementioned environment in terms of living space and architectural type, on the basis of summarizing the historical activities of Tanka people. Finally, this study provides a layout plan and interior structure of the most commonly used boat for Tanka people from the Ming and Qing dynasties to the Republic of China, with the use of CAD and other technical software, along with reference to written historical documentation, and provides a case study for further research on the architectural history of Macau's inner harbor cities, from anthropological and folklore perspectives.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.3
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• pp.149-158
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• 2015

In this study, we investigate tidal wave propagation characteristics, and classify regional tidal regime using tidal form number considered distribution of astronomical tide, overtides, and compound tides in the Han River Estuary, Gyeonggi Bay. The characteristics of the tidal wave propagation in main channels show dominance of major tidal constituents (e.g., $M_2$, $S_2$, $N_2$, $K_1$ and $O_1$) contributing to the astronomical tide however, distinct increasing of shallow water (e.g., $M_4$) and long period (e.g., $MS_f$) components toward up-estuary. Using the characteristics of tidal form number to astronomical tide, overtides, and compound tides, the regional tidal regime could be assorted into three regions. Firstly, a dominance area of astronomical tide was presented from open sea to a front of Incheon Harbor (Yeomha channel) and to north entrance of Seokmo channel. The area between south and north entrance of Yeomha channel and Ganghaw north channel classified into zone of showing strong shallow water components. It could be separated into upper estuary, upstream the Singok underwater dam, showed dominance of shallow overtides (e.g., $M_4$ and $MS_4$) water and long-term compound tides (e.g., $MS_f$) larger magnitude than astronomical tide. The shallow water components was earlier generated in lower part (south entrance) of Yeomha channel have strong bottom by effect of shallower and narrower compared with Seokmo channel. Tidal asymmetries of upper estuary cause by a development of overtides and compound tides are mainly controlled by influence of man-made structure.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.23 no.2
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• pp.91-108
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• 2018

An ecological study on subtidal macrobenthic fauna was conducted from 25 stations in the estuarine area of Wando-Doam Bay, southern coast of Korea during August 2013. A total of 186 species was collected with a mean density of $1,229ind./m^2$ and a mean biomass of $265.7g/m^2$. Polychaetes showed the richest benthic fauna comprising 43% of total fauna, whereas mollusks appeared as density- and biomass-dominant fauna accounted for 45% and 48% of the mean density and biomass, respectively. The number of species and mean faunal density were relatively higher at the stations surrounded by Sinjido, Joyakdo and Gogeumdo showing a gradual decrease toward inner bay stations. Species number and density were negatively correlated with bottom water temperature, but they were positively correlated with both the bottom salinity and DO. The most dominant species in terms of density was a semelid bivalve, Theora fragilis which showed a positive correlation with TOC content of surface sediment and its high density occurred around Gogeum-Sinji-Joyakdo area where dense aquaculture facilities exist. In the bay mouth area, an amphipod species, Eriopisella sechellensis showed its higher density at the stations with low organic content but fine grains. The combination of water temperature, salinity, pH of bottom water, water and sulfur content of the surface sediment could explain 71% of the spatial distribution of macrobenthic fauna from the Bio-Env analysis. From the cluster analysis, the study area consisted of 6 distinct station groups lineated from offshore area toward inner area. Ampharete arctica, Goniada maculata, Eriopisella sechellensis, Theora fragilis, Caprella sp. were identified as the main contributing faunas in classification by the SIMPER analysis. From the value of BPI, the benthic communities at the inner and central Wando-Doam Bay were assessed to be in a normal condition whereas those at the outer Wando harbor and Gogeum-Sinji-Joyakdo area were assessed in a poor or very poor condition due to the high concentration of particulate organic matter might be originated from the nearby dense aquaculture facilities. This study indicated that pristine inner bay has been influenced by the organic material supplied from the outer bay. Thus it is necessary to establish an ecological management plan to reduce organic enrichment of sediment from dense aquaculture facilities in the outer bay.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.369-378
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• 2018

This study was conducted to evaluate effects of dietary microbial probiotics on the growth and disease resistance of olive flounder (Paralichthys olivaceus) in a recirculating aquaculture system (RAS), and the effects of the probiotic bioaugmentation on the microbial community structure and water quality. For the analysis, 80 juvenile fish (average weight, $25.7{\pm}7.6g$; average length, $15.2{\pm}1.7cm$) were fed a basal diet containing a commercial microbial product CES-AQ1 (CES; $1{\times}10^9\;CFU/kg$ diet) in an RAS for 8 weeks. Weight gain, the specific growth rate, feed efficiency, and protein efficiency ratio of the fish fed the CES diet in the RAS were 1.5~2.5 times higher than those of fish fed the basal diet alone, or the basal diet containing oxytetracycline (OTC), yeast plus bacterium, or Bacillus subtilis in a still water system. There was no significant difference in the pathogen challenge test between fish fed the OTC diet and fish fed the CES diet in the RAS, suggesting the CES-AQ1 probiotic used in the RAS as a potential replacement for antibiotics. The RAS biofilter maintained the highest microbial diversity and appeared to harbor microbial communities with ammonium oxidation, denitrification, and fish pathogen suppression functions. Ammonia, which is hazardous to fish, was significantly decreased to < 0.5 mg/L in 19 days, indicating the effectiveness of probiotic supplementation to maintain good water quality in RAS. These results suggest that the intestinal microbial communities of fish are stabilized by a probiotic-containing diet (CES) and that bioaugmentation with probiotics may be an eco-friendly and economical supplement for aquaculture of olive flounder, promoting both good water quality and fish health in an RAS.

• Korean Journal of Environmental Biology
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• v.39 no.2
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• pp.195-206
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• 2021

In 2020, South Korea initiated research and development of a longitudinal connectivity evaluation between upstream and downstream based on stream ecosystem health. This study analyzed the migration of upstream and downstream migratory fish species, fish distribution characteristics, trophic guilds, tolerance guilds, and species composition changes from 2015 to 2020 at Songrim weir in Yeongok stream, where the cross-structure of an ice harbor-type fishway for fish movement was recently improved. A total of 5,136 fish, including 36 species, were collected and three major migratory fishes were identified, namely, Tribolodon hakonensis, Plecoglossus altivelis altivelis, and Oncorhynchus keta. According to the comparative analysis before (Pre-I) and after (Post-I) improvement of the fishway, the relative abundance of primary freshwater fish increased in the upstream section, while the number of migratory fishes decreased. The fish species that used the fishway in the Songrim weir were Tribolodon hakonensis (58.4%) and Plecoglossus altivelis altivelis(11.8%). According to the Wilcoxon Signed-Rank Test migratory fish showed a statistically significant difference (p<0.05) in the upstream and downstream, showing a biological improvement effect of the crossstructure. On the other hand, the annual change of migratory fish based on the MannKendall trend test did not significantly increase or decrease (p>0.05). Therefore, in the fish passage improvement project, it is necessary not only for physical, hydrological, and structural tests, but also for pre- and post-biological tests on the use and improvement effect of fishway.