• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.832-846
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• 2020

The purpose of this research was to evaluate the vapor permeability of nine different species of domestic softwood and the vapor permeability evaluation through the production of small wall structures for the developing applications, utilizing the vapor permeability of wood. In addition, the permeability evaluation was attempted by means of the production of a small wall structure injected with a waste material, bottom ash, as a moisture absorbent for improving the permeability. Consequently, the results of the vapor permeability evaluation by means of S_d value are as follows: (1) It was observed that Abies holiphylla, Picea jezoensis, Ginkgo biloba, Pinus koraiensis and Pinus rigida are permeable to moisture among 9 species of domestic softwood in Korea. (2) By means of this, semi-permeability efficiency was evaluated when producing a small wall structure. (3) Besides, improved effects of permeability were evaluated when producing a small wall structure inserted with bottom ash. As a result, it was confirmed that the S_d value of Pinus koraiensis turned out to be 1.63, which is superior to other 8 tree species.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.535-541
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• 2013

The urbanization affects significantly on a natural water circulation system by increasing the imperviousness rate. It is also negatively affecting on urban temperature, environmental pollution, water quality, and aqua-ecosystems. The Korea MOE (Ministry of Environment) adapted a new environmental policy in order to reduce the impact of urbanization, which is the Green Stormwater Infrastructure (GSI) program. The GSI can be achieved by protecting conservable green spaces, enlarging more green spaces, and constructing more permeable pavements. The GSI is including many different techniques such as bioretention, rain garden, infiltration trench and so on. Also It is the infrastructures using natural mechanisms of soils, microorganisms, plants and animals on a water circulation system and pollutant reduction. In this research, a multi functional GSI technology with infiltration-filtration mechanisms has been developed and performed lab-scale tests to evaluate the performances about infiltration rate restoration and pollutant reduction. The most of pollutants including metals, organics and particulates were reduced about 50~90% due to water infiltration and storage functions. The clogging was found when the TSS loading rate was reached on $8.3{\sim}9.0kg/m^2$, which value is higher than the values in literatures. It means the new technology can show high performances with low maintenances.

• Membrane Journal
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• v.17 no.2
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• pp.81-92
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• 2007

Membrane-based separation processes are receiving increasing attention in the scientific community and industry since they provide a desirable alternative to processes that are not easy to achieve by conventional separation technologies. In particular, gas separation using polymeric membranes have annually grown so fast owing to advantages such as easy installation, no moving parts, small footprint and low energy process. The key element is definitely a polymer membrane exhibiting high permeability and high selectivity to compete with other gas separation technologies. Current polymer membranes used for commercial gas separation are a family of hydrocarbon polymers for hydrogen separation, air separation and carbon dioxide separation from natural gas sweetening. Relatively, gas or vapor separation properties of fluoropolymers are not known so much as compared with those of hydrocarbon polymers. Accordingly, in this study, membranes prepared from amorphous perfluoropolymers are of particular interest because of the unique properties of these polymers. The advantages offered by these amorphous perfluoropolymers for use in gas and vapor separation will be discussed. In addition, membrane properties and separation performance will be compared with other membranes available on the market.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.1-8
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• 2002

Latex modified concrete(LMC) became to be applied as a new material for newly constructed bridge deck overlays in Korea due to its excellent bond strength, flexural strength and impermeability against water and chloride. However, it could not be adopted at repair job site because of its long curing time required. Thus, a research on latex modified concrete with rapid-setting cement(RSLMC) is necessary if it could develope the sufficient strength for early opening to traffic. This study focused on the durability of latex modified concrete with rapid-setting cement mainly on water permeable resistance and freeze-thaw resistance. The main experimental variables were latex contents(0, 5, 10, 15 and 20%) and antifoamer contents (0, 1.6, 3.2, 4.8 and 6.4%). Test results show that the permeability of RSLMC is very low indicating below 100 coulombs at 15% of latex contents at all antifoamer contents. The freeze-thaw resistance of RSLMC maintains above 90% of relative dynamic modulus at 3.2% of antifoamer content until 300 freezing-thawing cycles.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.925-935
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• 2007

Water sources in volcanic Jeju Island are almost entirely dependent on groundwater because there are actually no perennial streams or rivers due to the permeable nature of surface soils derived from basaltic or trachytic rocks. Uncontrolled development of groundwater resulted in substantial water-level decline, groundwater pollution, and seawater intrusion in several places of the island. To maintain its sustainable groundwater, the provincial government has declared some parts of the island as the Special Groundwater Conservation/Management Area since 1994. Hence, all the activities for the groundwater development in the area should obtain official permit from relevant authorities. Furthermore, to acquire information on groundwater status, a network of groundwater monitoring was established to cover most of the low land and coastal areas with the installation of automatic monitoring systems since 2001. The analysis of the groundwater monitoring data indicated that the water levels had decreased at coastal area, especially in northern part of the island. Moreover, very high electrical conductivity (EC) levels and their increasing trends were observed in the eastern part, which was ascribable to seawater intrusion by intensive pumping in recent years. Water level decline and EC rise in the coastal area are expected to continue despite the present strict control on additional groundwater development.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.7-17
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• 2007

There has been an increase in rigid gas permeable contact lens prescription by the optometrists in Korea since 1995. Therefore, the aim of our study was to find out which equipment is needed for adequate RGP contact lens prescription and the level of the clinical knowledge that they have and the level of education for the patient, to seize about the extended lens education programmes for the Korean optometrist. Also, we tried to figure out the problem that they had in the RGP contact lens prescription, to develope the educational programs for students and to improve legal uncertainties, through this research. The result came out with the following through questionnaires of 400 male and female opticians who is in clinical field. The distributions of respondents are 270 male (67.5%), 130 female (32.5%), and 356 optometry major (89%). We found out the optometry-majored people had faster clinical lens prescriptions (p=0.000), 72.5% of opticians prescribe the RGP-Lenses, and 27.5% do not because of laking in experience (P=0.000). They responded that they need slit-lamp, button lamp, fluorescein dry paper, and etc,for prescription or fitting test. In regular-check-up (Follow-up), the result came out very low by 83% of respondents who are not getting it regularly. And 83.5% (334 people) of them wanted to have those Extended Educational Programs and also the Clinical Education Programs.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.18 no.1_2
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• pp.1-8
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• 2012

Kimchi, a Korean fermented vegetable is packaged without pasteurization and distributed with live bacteria actively working to produce lactic acid and carbon dioxide gas in the product. The $CO_2$ production consisting of two distinct phases of initial fast and later slow rates depends on kimchi type, salt content and storage temperature. The $CO_2$ produced from kimchi is accumulated in the product package causing volume expansion and pressure buildup. The dependence of $CO_2$ production rate on salt content and storage temperature has been published formerly and can be used for estimating the package volume and pressure under a variety of storage conditions. As methods to alleviate the problems from the produced $CO_2$, package designs with controlled diffusion pinhole, high $CO_2$ permeable film or $CO_2$ absorber have been tried by several researchers. Properly designed packages adopting the device or tool were shown to have high dissolved $CO_2$ in kimchi without volume expansion and pressure buildup, giving good sensory quality with carbonic taste. Advantages and limitations of each method have been discussed.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.121-131
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• 2020

In this paper, the transmissivities obtained from the pulse test, the slug test and the constant head test were compared each other to assess an applicability and a reliability of the hydrogeological test method, which are commonly used to derive the hydrogeological properties of a crystalline rock at un underground research facility. When comparing the results of the pulse test and the slug test, the transmissivities were very similar in the entire test section of the medium. However, there was a little discrepancy in the results in the areas where the permeability is relatively high. The results of the constant head test on the same section showed the lower transmissivity than the results of the pulse test and the slug test on the highly permeable section. This difference in permeability was considered to be due to the difference in the radius of the hydraulic effect applied in each hydraulic test. When the heterogenetic distribution of fracture affects the hydrogeological properties on crystalline rock, it is believed that the hydrogeological characteristics can be explained through a constant head test or a constant flow rate test with a large hydraulic effective radius, as well as a pulse and a slug test that can identify hydrogeological properties in a relatively short time.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.47-53
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• 2010

Purpose: This study was performed to achieve an acceptable piggyback fit utilizing each subject's own GP lenses, in subjects with regular low myopic astigmatism. Methods: A randomized, prospective study of 15 subjects with the diagnosis of low myopic astigmatism was conducted. Nine subjects were female and 6 were male, and mean age was: 23.73${\pm}$1.68 years. Subjects were evaluated before participate on this study and then also evaluated with period of at two hours and two weeks after obtaining their lenses. All subjects were submitted to the following tests: measurement of comfort level by means of the analogical visual scale, best corrected visual acuity and over-refraction at distance. contrast sensitivity and stereo acuity. After evaluating the fit of plano soft lens, we applied each subject's own GP lens on top. Results: Vision, visual performance and satisfaction of piggyback contact lens system were stable, if not improved, for the 15 subjects when the data was compared to the patients' wear of rigid gas permeable contact lenses. Fit with a piggyback system had the same or improved comfort, visual acuity and contrast sensitivity compared to previous GP lens wear alone. The visual acuity, contrast sensitivity and stereo acuity did not show differences in relation to the studied lens type. Conclusions: These results suggest that it is possible to achieve a successful piggyback lens fitting utilizing a patient's own GP lens. The piggyback lens system satisfied the visual performance and visual requirements of this subject with GP lens alone for the correction of low myopic astigmatism.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.433-452
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• 2018

The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.