• Ocean Systems Engineering
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• v.11 no.1
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• Journal of the Korean Chemical Society
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• v.67 no.2
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• pp.145-149
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• 2023

Talipariti hamabo is a plant growing around salt marshes in the Lava Coast region of Jeju Island, Korea. In this study, the extract of T. hamabo leaves was investigated for the anti-inflammatory, anti-oxidative and anti-bacterial activities and their active constituents were identified. In the anti-inflammatory tests using lipopolysaccharide-stimulated RAW264.7 cells, the ethyl acetate (EtOAc) fraction inhibited the nitric oxide production without causing cell toxicity. Moreover, the EtOAc fraction reduced pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-6) as well as prostaglandin E₂. In the anti-oxidative studies with DPPH and ABTS⁺ radicals, potent scavenging activities were observed in the EtOAc and n-butanol fractions. Upon the anti-bacterial tests using Staphylococcus epidermidis, EtOAc and n-butanol fractions exhibited good activities. Through the phytochemical studies on EtOAc fraction, three components were isolated by repeated column chromatography; oleic acid (1), p-hydroxyphenethyl-trans-ferulate (2), nicotiflorine (3). Based on these results, the extract of T. hamabo leaves can be developed as natural resources for cosmetic applications.

• Ocean and Polar Research
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• v.46 no.2
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• pp.105-121
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• 2024

Phytoplankton, as key primary producers, play a critical role in the dynamics of marine ecosystems. This study explores the variation in phytoplankton species appearance along the Jeju coast from spring to summer 2022, emphasizing the stratification and changes in nutrient dynamics. Through extensive field surveys at twelve points around Jeju Island, we measured a range of physical and chemical oceanographic parameters. Monthly average stratification indices displayed an abrupt increase from 22 in May to 3,196 in August, highlighting intense stratification, significantly influenced by the influx of Changjiang River Diluted Water during the summer months. Concurrently, nutrient concentrations exhibited a downward trend, with nitrate and nitrite levels decreasing from 6.7 µM in March to 1.3 µM in July, and phosphate levels declining from 0.31 µM to 0.02 µM during the same period, while silicate concentrations, ranging from 6.8 to 9.8 µM, remained consistently high throughout the study. Similarly, a reduction in monthly average phytoplankton biomass was observed, with concentrations peaking in the spring (April and May) at 406,053 to 409,139 cells L^-1 and declining to 45,546 to 118,214 cells L^-1 by summer (June to August). Diatoms (Chaetoceros spp. and Skeletonema spp.) dominated the phytoplankton community throughout the period; however, an increased proportion of dinoflagellates (Gyrodinium spp. and Heterocapsa spp.) was observed during the summer months, when stratification was most pronounced. This study confirms that variations in currents and water masses impacting the Jeju coast can significantly influence phytoplankton community dynamics, emphasizing the need for ongoing monitoring in this region.

• Korean Journal of Microbiology
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• v.51 no.1
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• pp.81-85
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• 2015

Since the banning of antibiotic growth promoters (AGPs), the death of livestock has been increased, thus there is a strong demand for AGP-alternatives. Modulation of gut microbiota has been reported to affect host physiological functions and suggested to be a novel approach for developing AGP-alternatives. However, little has been understood about livestock gut microbiota compared to that of humans. We conducted preliminary study provide fundamental information regarding to regional differences in swine gut microbiota. Swine fecal samples were obtained from farms in Jeju (n=40), Gwangju (n=28), and Haenam (n=30). MiSeq was used to sequence 16S rRNA V4 region, and Mothur pipeline (Schloss et al., 2009) was used for data processing. A total of 5,642,125 reads were obtained and 3,868,143 reads were remained after removing erroneous reads. Analysis of taxonomic composition at the phylum level indicated greater abundance of Firmicutes among Jeju swine, and cluster analysis of distribution of operational taxonomic units also showed regional differences among swine gut microbiota. In addition, correlation analysis between non-metric multidimensional scaling and abundance of phyla suggested that the phyla Actinobacter, Verrucomicrobia, Firmicutes, and Fibrobacteres were driving factors for the regional differences. Livestock gut microbiota may be affected by diet and practices in farms. Our results indicated significant regional differences in swine gut microbiota, suggesting that future livestock gut microbiota studies should be designed with the regional differences in mind.

• Journal of the Korean Regional Science Association
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• v.39 no.3
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• pp.13-34
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• 2023

Jeju is making multifaceted efforts to foster and attract businesses in order to increase its GRDP, which is only at the level of 1% nationwide. A firm's choice of location selection is such a significant decision that it can affect the growth of the firm. The concentration of firm locations in one region means that the characteristics of the region conduce to corporate profit maximization. Therefore, the analysis of the characteristics of regions preferred by firms and the reflection of the results thereof in policies for attracting firms will be helpful in inducing regional innovation and development. This study investigates the distribution of firm locations in Jeju, and analyzes the effects of regional characteristics on the determination of firm location by using the conditional logit model. The analysis results indicate that Jeju has various kinds of firms concentrated, regardless of the industry type, and a large economically active population in thinly populated areas. Additionally, firms in the knowledge-based industry tend to locate in areas where more firms in the same field are located in Jeju. This study is significant in that it is the basic analysis of the determinants of firm location in Jeju, which has never carried out, for the purpose of establishing policies for firm and industry promotion and local development in Jeju.

• Journal of Forest and Environmental Science
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• v.32 no.4
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• pp.384-391
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• 2016

In this study, regions infected by pine wilt disease were extracted by using object-based classification method (OB-infected region), and the characteristics of special distribution about OB-infected region were figured out. Scale 24, Shape 0.1, Color 0.9, Compactness 0.5, and Smoothness 0.5 was selected as the objected-based, optimal weighted value of OB-infected region classification. The total accuracy of classification was high with 99% and Kappa coefficient was also high with 0.97. The area of OB-infected region was approximately 90 ha, 16% of the total area. The OB-infected region in Age class V and VI was intensively distributed with 97% of the total. Also, The OB-infected region in Middle and Large DBH class was intensively distributed with 99% of the total. In terms of the topographic characteristics of OB-infected region, the damages occurred approximately 86% below the altitude of 200 m, and occurred 91% with a slope less than 10 degree. The damage occurred a lot in low hilly mountain and undulating slope. In addition, the accessibility to road and residential area from OB-infected region was less than 300 m in large part. Overall, it was figured out that artificial effect is stronger than natural effect with regard to the spread of pine wilt disease.

• The Korean Journal of Community Living Science
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• v.27 no.spc
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• pp.703-714
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• 2016

Dwelling environments that can help elderly farmers to live more safely, independently, and conveniently are becoming more and more important. Many rural houses are built without any particular architectural or energy-related criteria, so most of them have poor insulation. The construction technology used is also not precise, which increases the loads for heating and cooling. Therefore, rural houses need to be improved. Also, there is more and more need for plans to realize eco-friendly dwellings, so the principle of nature-oriented plans related to the direction, insulation, or landscaping of a house is being emphasized. Insulation is one of the most effective ways to save energy for heating and cooling. This preliminary study to improve the insulation of rural houses examined three regions in South Korea: the central region, the southern region, and the Jeju Island. A field investigation was conducted on a total of 18 houses, including six from each town in the selected regions. The information was used to figure out the current status of rural houses and the characteristics of the buildings. The main living spaces are the living room for the central region and the main room in the southern region and Jeju Island. The southern regions are plane shapes surrounded by rooms, and all ventilation is accomplished by windows. The studied houses were mostly masonry structures with slate rooftops. Additions and improvements included room expansions and bathroom interior installations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.255-262
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• 1982

The data of 37 oceanographic stations in the coastal sea of Jeju island are compiled in terms of temperature, salinity, dissolved oxygen, silicate, nitrate and phosphate to analyge the chelnical characteristics in this region. This work was carried out during June, 1951. The concentrations of nutrients in the layer more than 50 m are generally 0.5-3 times larger than the surface layer. Each constituents in this layer are as follows: temperature ranged 11.8 to $15.4^{\circ}C$ and salinity, 33.8 to $34.8\%_{\circ}$; and also dissolved oxygen and slicate are 5.2 to 5.6ml/l and 5.6 to $9.0{\mu}g-at/l$, respectively. And nitrate and phosphate ranged 1.0 to $6.0{\mu}g-at/l$ and 0.1 to $0.5{\mu}g-at/l$, respectively. The coastal sea of Jeju island is divided into two parts in chemical view point : one is the southeastern sea of Jeju island under the influence of the Tsushima Current, md the other is the northeastern sea of Jejo island under the influence of the Yellow Sea Bottom Cold Water and the south coastal water of Korea. The north-western sea of Jeju island had relatively a cold (about $13^{\circ}C$) and low saline water (about $34\%_{\circ}$), and dissolved oxygen was higher than in the neibouring waters. It seems that in the southern area between Moseulpo and Seogwipo of Jeju island, two different Ivater masses are complicately intermixed and a tidal front is formed.

• ALGAE
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• v.21 no.2
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• pp.209-216
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• 2006

The characteristics of Peyssonnelia capensis Montagne (Peyssonneliaceae, Rhodophyta) from Jeju Island were investigated in order to clarify the species entity and re-evaluate taxonomic position. The morphological variations of the Peyssonnelia capensis from Jeju Island were divided into two types, the thin thallus type and the thick thallus type. The thin thallus type is characterized by thin, soft, orbicular, slightly lobed thallus with entire to undulate margin, and compact rhizoids. The thick thallus type has thick and stiff thallus with sinuate margin and scattered rhizoids, and has more branches than the thin thallus type. The basal layer and the epithallium of thin thallus type are similar to those of thick thallus types in their structure. However, the hypothallial cells of the thick thallus type are longer than those of the thin thallus type. The erect filament of thick thallus type has more cells than those of the thin thallus type. Tetrasporangial nemathecia are distinctly protruded. Mature tetrasporangia of this species are divided cruciately into four spores as those of other Peyssonneliaceae. In addition to their morphological and anatomical distinctness between two types, the nucleotide sequence analyses of SSU and ITS2 region make no differences among populations from Jeju and other localities in Korea. Therefore these two morphological variation may not base on genetic variation.

• Journal of Medicine and Life Science
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• v.17 no.3
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• pp.65-73
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• 2020

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a single-gene disease of the cerebral small blood vessels caused by mutations in the NOTCH3 gene on chromosome 19. Although CADASIL was known as a rare disease, recent research has suggested that the NOTCH variants could be found frequently even in the general population. The main clinical features included recurrent stroke, migraine, psychiatric symptoms, and progressive cognitive decline. On brain magnetic resonance imaging, patients with CADASIL showed multifocal white matter hyperintensity lesions, lacunar infarcts, microbleeds, and brain atrophy. Among them, lacunar infarcts and brain atrophy are important in predicting the clinical outcomes of patients with CADASIL. In the Jeju National University Hospital, we have diagnosed 213 CADASIL patients from 2004 to 2020. Most NOTCH3 mutations were located in exon 11 (94.4%), and p.Arg544Cys was the most common mutation. The mean age at diagnosis was 61.0±12.8 years. The most common presenting symptoms were ischemic stroke (24.4%), followed by cognitive impairment(15.0%), headache (8.9%), and dizziness(8.0%). Although the exact prevalence of CADASIL in Jeju is still unknown, the disease prevalence could be as high as 1% of the population considering the prevalence reported in Taiwan. Therefore, it is necessary to discover efficient biomarkers and genetic tests that can accurately screen and diagnose patients suspected of having CADASIL in this region. Ultimately, it is urgent to explore the exact pathogenesis of the disease to identify leading substances of treatment potential, and for this, multi-disciplinary research through active support from the Jeju provincial government as well as the national government is essential.