• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.145-145
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• 2019

Groundwater and rainwater are the only sources of freshwater in small islands as many islands lack surface water sources. Groundwater occurring in the form of freshwater lens floating on denser seawater is highly dependent on natural recharge from rainfall. A sharp interface numerical model for regional and well scale modeling is selected to assess the sustainability of freshwater lens in the island of Tongatapu. In this study, 29 downscaled General Circulation Model(GCM) predictions are input to the recharge model based on water balance modelling. Three GCM predictions which represent wet, dry and medium conditions are selected for use in the groundwater flow model. Total freshwater volume and number of saltwater intruded wells are simulated under various climate scenarios with GCM predicted rainfall pattern, sea level rise and pumping. Simulations indicate that the sustainability of the freshwater lens is threatened by the frequent droughts which are predicted under all scenarios of recharge. The natural depletion of the lens during droughts and increase in water demands, leads to saltwater upconing under the pumping wells. Implementation of drought management measures is of utmost importance to ensure sustainability of freshwater lens in future.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.3
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• pp.9-18
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• 2021

This paper conducted a survey of residents and public officials for the projects to make smart-city plans of Geumsan-gun. In introduction, several domestic and foreign cases related to smart-city projects were Investigated. To initiate the smart-city project of Geumsan-gun, the local status of Geumsan-gun was investigated regarding various aspects of natural, social, urban environment and smart-city facilities. The results of this survey are as follows: Overall, more than half of survey respondents said they had satisfaction of their housing quality. Several problems in their residence areas, such as insufficient welfare systems, shortage of parking spaces, industrial infrastructure, were reported. Meanwhile, the survey result indicated that tourism and leisure facilities, health care support systems, industries promote the economy and job market of the area. An interview with public official is also important to select the relevant meaningful projects and regional issues. Three models for each spatial unit were proposed in Geumsan-gun based on the natural, agricultural, and geographical environment. In result, the three smart-city models are categorized as urban type(large area), complex city type(medium area), and smart village type(small area)

• Cross-Cultural Studies
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• v.26
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• pp.297-319
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• 2012

We all know how beautiful our wild and it's importance to our living planet Earth. But did you realise the speed at which man himself is damaging it's unique natural habitat. We are well on our way to destroy our forests, plants, wetlands. We are polluting our oceans and seas. This way, we're driving numerous animal species, plant species and many others into extinction. Everyone should be aware of the importance of our natural environment. We live in the period of echocide. Why we need nature to survive and how we can deal with the environmental problems we face. This paper has the purpose to reform city's environment. Because, Metropolis and megalopolis are the principal cause of environmental disruption. To reform the city is needed to consider digital technology in our age. In the face of economic and cultural globalization, many have argued that we live an increasingly placeless world. However, as a growing number of cities participate and compete in key marketplaces of advanced capitalism, the spectacle of the city is more than ever a significant medium of communication in its own right. In doing so, this work is focused specifically on the dimension of city's media environment. To that end, the paper examined U-City and U-Eco city. In this study, we will introduce the study on model of U-Eco City as one way for the eco-freindly future city.

• Journal of Plant Biotechnology
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• v.45 no.4
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• pp.333-339
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• 2018

The mature zygotic embryos of the Hevea brasiliensis were cryopreserved through the use of the vitrification and encapsulation/dehydration techniques. In all the experiments, the zygotic embryos were pre-cultured for three days in the MS medium supplemented with 0.3 M sucrose before they were used for the cryopreservation technique. In the vitrification procedure, the effect of the plant vitrification solutions (PVS2 and PVS3) and exposure time were studied. The highest survival rate (88.87%) and regrowth (66.33%) were achieved when the precultured zygotic embryos were incubated in a loading solution for 20 minutes at $0^{\circ}C$. They were subsequently exposed to PVS2 for 120 minutes at $0^{\circ}C$ and plunged directly into liquid nitrogen. Cryopreservation by the encapsulation-dehydration method was successfully done by leaving the encapsulated zygotic embryos in a laminar flow for 4 hours prior to plunging into a LN. The survival rate and regrowth of the encapsulated zygotic embryos were 37.50% and 27.98%, respectively. The cryopreserved zygotic embryos were able to develop into whole plants.

• Quantitative Bio-Science
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• v.37 no.2
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• pp.125-132
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• 2018

In this study, noble strains of lactic acid bacteria were isolated and identified by genetic analysis of 16s rRNA. Also, pH-dependent growth curve, cholesterol assimilation ability and sugar production efficiency were measured. Lactic acid bacteria were identified to inhabit in the milks from various animals. Results of sequence analysis showed that there were differences in 16S rRNA sequence among strains and part of gene deletion was also recognized. Growth rates were varied, too, depending on the pH of the medium. Lactobacillus rhamnosus LOCK908 isolated from cow milk showed the highest growth rate and high cholesterol assimilation ability. Results of sugar fermentation tests were relatively consistent with the sequencing results. So, we propose newly isolated Lactobacillus rhamnosus LOCK908 as useful candidate for a starter of fermented beverage and probiotics. Results of this study will contribute to the isolation and identification of noble Lactic acid bacteria and to the public health.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.529-540
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• 2018

Sand dam is a flow barrier commonly built on small or medium size sandy rivers to accumulate sand and store excess water for later use or increase the water table. The effectiveness of sand dam in increasing the water table and the amount of extractable groundwater is tested using numerical models. Two models are developed to test the hypothesis. The first model is to simulate the groundwater flow in a pseudo-natural aquifer system with the hydraulically connected river. The second model, a modified version of the first model, is constructed with a sand dam, which raises the riverbed by 2 m. In both models, the effect of groundwater abstraction is tested by varying the pumping rate. As the model results show the groundwater after the construction of the sand dam has increased significantly and the amount of extractable groundwater is also increased by many folds. Most importantly, in the second model, unlike the pseudo-natural aquifer system, the groundwater abstraction does not have a significant effect on the water table.

• International Journal of Clinical Preventive Dentistry
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• v.14 no.4
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• pp.216-221
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• 2018

Objective: In this study, we tried to investigate the antimicrobial activity of natural herbaceous plant-derived essential oils against oral disease-causing bacterial strains and establish the scientific evidences to apply them to the dentifrice, mouthwash, and other uses. Methods: We used the disk diffusion method with 23 types of 100% natural essential oils to verify the antimicrobial effect against Streptococcus mutans, Porphyromonas gingivalis, and Lactobacillus rhamnosus. After adhering to the surface of the plate culture medium, $20{\mu}l$ of the essential oil was prepared, and the diameter of the transparent ring was measured after incubation for 24 hours. All the experiments were repeated three times. Results: Among 23 types of oils, 13 were effective against all three strains: myrrh, ginger, basil, carrot seed, tea tree, patchouli, ylang ylang, cypress, lemongrass, cinnamon, peppermint, lavender, and eucalryptus. Seventeen oils were effective against S. mutans, and myrrh, basil, and carrot seed showed high antimicrobial activity. Eighteen oils were effective against P. gingivalis, and tea tree, carrot seed, and cinnamons showed high antimicrobial activity. Sixteen oils were effective against L. rhamnosus, and carrot seed and peppermint cinnamon showed high antimicrobial activity. Conclusion: Consequently, 13 essential oils showed the antimicrobial activity against three bacterial strains, which indicates these essential oils might be used as the effective materials to suppress the growth of oral-disease inducing microorganisms. Moreover, essential oils that have been analyzed activities in this study will be mixed up within the constant range and analyzed their antimicrobial effects to examine the synergistic activity among them.

• Journal of the Korea Fashion and Costume Design Association
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• v.24 no.3
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• pp.63-71
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• 2022

This paper aims to compare and verify the antibacterial effects of cotton fabrics naturally dyed with extracts of Ulmus davidiana var. japonica Nakai, Caesalpinia sappan, Saururus chinensis, and Artemisia princeps against antibiotic-resistant strains of bacteria. After natural dyeing of the test fabric, Al, Cu, Fe mordants were used. The color fastness against washing, rubbing, and perspiration of the cotton fabrics dyed with the 4 types of extracts were mostly excellent. However, the color fastness against light showed poor results for all four types. As for the antibacterial test method, MRSA (ATCC 33591) was applied to the cotton fabrics dyed with the four kinds of extracts and cultured for 24 hours. After that, the bacteria that proliferated on the fabrics were collected and spread on a solid medium. The bacteria were measured to find out the bacteriostatic reduction rate for the antibiotic-resistant strains. As a result of the analysis, all four extracts showed a high bacteriostatic reduction rate of more than 99% when the copper mordant was used. Even with the lack of a mordant, the bacteriostatic reduction rate was high, at 99.9% for Caesalpinia sappan and 94.6% for Saururus chinensis.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.82-91
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• 1995

Many kind of springs are used in the suspension of automotive vehicles and among these the leaf spring and the air spring are included. These two springs have not been generally used together in one suspension, but recently the automotive models which use these two springs together increase. This reason is due to the merit of the combination of two type springs. The merits are two. One is the character of air spring, that is, the natural frequen- cy of system is constant in spite of variable weight. The other is the character of leaf spring, that is, the suspension mechanism is simple. The combination spring is used in medium size and special purpose bus. In this paper, we formulate the condition which the leaf spring must satisfy to be optimal design in the combination spring. And experiment is performed to prove the theory. The results are that the combination spring is better than leaf spring in the ride, and that the purposed theory is good for the combination spring design.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.401-414
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• 2023

Organic clays are ideal habitat for flora and fauna. From a geotechnical perspective, organic clays are soft, weak, variable, heterogeneous and flocculated. Portland cement is a universally common stabiliser. However, some organic acids in soil inhibit full hydration and expose cementation products to rapid dissolution. This paper investigates scopes for use of C₃S cement to enable durable cementation. Prospects of using PP fibre alongside with C₃S cement, scopes for partial replacement of C₃S cement with a plant-based nanosilica and evolution of binders are then investigated. Binding mixtures here mimic the natural functions of rhizoliths, amorphous phases, and calcites. Testing sample population include natural and fibre-reinforced clays, compact mixes of clay - C₃S cement, clay - nanobiosilica, and clay, C₃S cement and nanobiosilica. Benefits and constraints of C₃S cement and fibres for retaining the naturally flocculated structure of organic clays are discussed. Nanobiosilica provides an opportunity to cut the C₃S content, and to transition of highly compressive organic clays into an engineered, open-structured medium with >0.5 MPa compressive strength across the strains spanning from peak to 1.5-times peak.