• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.72-81
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• 2016

When the coatings of buried steel pipelines are damaged, corrosion could be occurred on the surface of the damaged areas. Moreover the pinhole occurred by corrosion of pipelines may cause accidents due to gas leakage. To prevent these accidents, foreign countries including UK and USA have carried out coating defect detection on the buried gas pipelines by using a DCVG or a ACVG and have conducted direct assessment of pipelines through digging the ground, and if necessary, have repaired the pipelines. That is called ECDA i.e External Corrosion Direct Assessment which is regulated by NACE standards(SP 0502) and etc. In Korea, the ECDA provisions were included in KGS FS551 in 2014 when the regulations of Safety Validation in Detail for the medium-pressure piping were introduced. We have developed the equipment which can be used to detect external corrosion of the buried gas pipelines. We have also constructed pipeline test bed for empirical test of the developed equipment. In addition, we have carried out the verification experiments of the developed equipment on the test bed to demonstrate the performance of the equipment. The experiments were conducted by comparison tests of the developed equipment and other equipments which have been introduced and used in Korea. As the result, we have found the developed equipment is easier to use and has far superior performance compared to other equipment being used in Korea.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.4
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• pp.347-353
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• 2016

The purpose of this study was to evaluate shear bond strength and microleakage of a new self-etch fissure sealant containing S-PRG filler (BeautiSealant). Fourty-five premolars were randomly divided into three groups: SEPBS group (Self-etching primer + BeautiSealant), AEBS group (Phosphoric acid etching + BeautiSealant), AECP group (Phosphoric acid etching + $Clinpro^{TM}$ sealant). For the shear bond strength test, microcylinders of fissure sealant were bonded to prepared buccal surfaces of teeth and shear bond strengths were measured by a universal testing machine. For the microleakage test, sealants were applicated on each occlusal fissure of teeth. All teeth surface were coated with finger nail varnish, with the exception of a 1.0 mm window around the sealant margins. The teeth were immersed in 2% methylene blue solution for 24 hours and then rinsed in water. The teeth were then embedded in resin and cut buccolingually along the tooth axis and observed with a stereomicroscope to determine the degree of microleakage. SEPBS group demonstrated lower bond strength in comparison with that of AEBS and AECP groups (p < 0.05). However, no significant differences were observed between AEBS and AECP groups. There was no statistically significant difference in degree of microleakage among three groups.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.5
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• pp.313-322
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• 2001

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. Rosette and pyrochlore phase are observed in PLZT (10/40/60) thin film and the (100) orientation, the grain size, and the surface roughness of PLZT thin films increase due to the increase of Ti amount in Zr/Ti concentration ratio. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10KHz decrease from 600 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kY/cm decrease from 1.64$\times$10$^{-6}$ to 1.26$\times$10$^{-7}$ A/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$ 170 ㎸/cm, the remanent polarization and the coercive field increase from 6.62 to 12.86 $\mu$C/$\textrm{cm}^2$ and from 32.15 to 56.45 ㎸/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying 10$^{9}$ square pulses with $\pm$5V, the remanent polarization of the PLZT (10/40/60) thin film decreases 50％ from the initial state while that of the PLZT (10/0/100) thin film decreases 30％. In the results of retention measurements of 10$^{5}$ s, the remanent polarization of the PLZT (10/0/100) thin film decreases only 11％ from the initial state, while that of the PLZT (10/40/60) thin film decreases 40%.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.255-264
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• 2014

This study analyzes the cause and the repairing method of water leak by parts of basement parking lot which is recorded to have a high defect frequency in apartment buildings. It has been assessed that the cause of water leakage on the first floor upper substrate is due to such factors as landscaping and weights. During construction or through other cases, it has been determined that cracks were produced in the apartment structure because the structure was weak and exposed to the effects of the substrate movement. The base floor and underground external walls are areas that are exposed to water pressure (uplife pressure), thus in normal cases the rear surface repair of the structure using sythetic rubberized polymer gel should be considered as an effective method. However, in cases where application of waterproofing layer is required in the structure due to high water pressure, using asystolic cement milk grout to form the waterproofing layer and applying water-swelling acrylic material into the cracked areas is considered to be highly effective.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.174-186
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• 1996

The purpose of this study was to evaluate the adaptability to tooth structure of composite resin and glass ionomer cement according to filling methods. In this study. two class V cavities were prepared on the buccal and lingual surface of each tooth of forty extracted human premolars. and they were randomly assigned into 4 groups with 10 teeth. The cavities of each group were filled with the CLEARFIL FII self curing resin(Control Group), Z-100 light curing resin (Group 1). $Vitremer^{TM}$ light curing glass ionomer cement(Group 2) and Z-100 light curing resin over the $Vitremer^{TM}$ liner(Group 3). The specimens underwent temperature changed from $5^{\circ}C$ to $55^{\circ}C$ five hundred times. After thermocycling. specimens were immersed in 2% methylene blue solution and stored in 100% relative humidity at $37^{\circ}C$ for 24 hours. And then. the specimens sectioned buccolingually. Degree of dye penetration at tooth-restoration interfaces were examined by Tool maker's microscope(x 200) and Image analyzer. The results were as follows : 1. On the occlusal margin. among the experimental groups. the group 2 showed the highest dye penetration($2.40{\pm}0.68$) and the group 3 showed the lowest dye penetration($1.15{\pm}0.37$). There was significant difference among the experimental groups(p<0.001). 2. On the gingival margin, among the experimental groups, the group 1 showed the highest dye penetration($3.30{\pm}0.57$) and the group 2 showed the lowest dye penetration($1.65{\pm}0.49$). There was significant difference among the experimental groups(p>0.001). 3. About total degree of dye penetration, the group 1 showed the highest dye penetration($2.25{\pm}1.17$) and the group 3 showed the lowest dye penetration ($1.43{\pm}0.55$). There was significant difference among the experimental groups(p<0.001). 4. The sum of dye penetration at occlusal margin was less than gingival margin. There was significant difference between occlusal margin and gingival margin (p<0.001). The results showed that differences were more pronounced at the gingival margin. Composite restorations inserted over the glass-ionomer liner demonstrated significantly less leakage than single restoration that used composite resin or glass-ionomer cement.

• Journal of the Korean Institute of Gas
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• v.18 no.1
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• pp.17-24
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• 2014

LNG storage tank is a facility to store liquefied natural gas (LNG) and its safety and stability to be greatly needed. When there is a LNG leakage in case of primary container problem, a special facility such as a bund wall should be constructed to store the leaked LNG. But this method makes the land usage inefficient and construction price high. So nowadays the full containment type LNG storage tank is selected instead of constructing a bund wall. In the full containment type tank, the concrete sidewall has the ability to store LNG temporarily. There are largely two methods to give the concrete sidewall the ability. In a method, rebar should be used when constructing the side wall of the LNG storage tank. In the other method, the protecting material such as sprayed polyurethane foam should be applied on the inner surface of the concrete sidewall. Sprayed PUF keeps the temperature of the sidewall above the specified temperature during the specified periods. Recently the thermal stability reinforcing method using sprayed polyurethane foam has been applied to all LNG storage tank built in Korea.

• Journal of Conservation Science
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• v.20
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• pp.89-103
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• 2007

The bedrock beneath the Chokseongnu pavilion consists of sandstone with alternate dark-gray to light-brown siltstone and dark-gray shale of the Jinju Formation, where bedding is well developed toward the Chokseongmun gate. Large to small joints and overbreak from the erosion weathering have been developed in the bedrock. Besides, water leakage from development of discontinuity planes, fragmentation of shale, crack and joint by tree roots are observed on the bedrock. While shale and siltstone showed high sensitivity in physical and chemical weathering, respectively, sandstone indicated the highest weathering sensitivity in both. As the results of structural stability analysis, the whole bedrock has high instability in wedge failures, and especially section No. II slope is more instable than section No. I. Therefore, it is necessary for the bedrock to be strengthened by improvement method for soft foundations and the surface reinforcement. The trees causing mechanical collapse of the bedrock should be also removed and a water flow prevention measure or a water exhaust are required.

• Clinical and Experimental Pediatrics
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• v.49 no.4
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• pp.455-459
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• 2006

The major pathogenesis of acute respiratory distress syndrome (ARDS) is an inflammatory process that results from a diversity of injuries to the body. Due to the various cytokines and vasoactive peptides released from the endothelium, the vascular permeability is increased; the migration of inflammatory cells and the leakage of plasma proteins then occur and edema develops in the alveolus. There is a hypothesis that the impairment of alveolar recruitment in ARDS is caused by a defect of the surfactant system and the resultant increase of alveolar surface tension. This has been studied in pediatric patients in ARDS; after the administration of surfactant, hypoxia, respiratory symptoms and survival chances were improved. To alleviate the major pathogenic mechanism in this disease, that is to say, inflammation of the lung, steroids have been used and studied as another treatment modality for ARDS, and it has been concluded that the administration of low dose methylprednisolone may improve patients' symptoms and survival rates. We report here on a case of a young infant admitted with ARDS, who, after the intratracheal administration of 120 mg/kg surfactant, on $PaO_2/FiO_2$ was elevated. Subsequent low doses of methylprednisolone were given, and the symptoms did not recur, and no fibrotic change was shown during the follow-up period of 2 months.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.15-20
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• 2005

Defects of dam body which can be induced in seepage or leakage procedure can directly affect dam safety. Therefore, a proper inspection method should be carried out in the first place to find out their positions and sizes, After that, some reinforcement works such as grouting and the corresponding assessment could be taken in a proper way. The dam(center core type earth dam) issued in this study has been in need for intensive diagnosis and reinforcement work, because a lot of slumps similar to cracks, seepage and some boggy area have been observed on the downstream slope. High resolution seismic reflection method was performed on the crest profile twice before and after grouting work(Aug. 2001 and Nov. 2004) aimed at the dam inspection and the assessment of grouting efficiency as well. To enhance the data resolution, P-beam energy radiation technique which can reduce the surface waves and hence to reinforce the reflection events was used. Strong reflection events were recognized in the stack section before grouting work, It seems that the events would be caused by e.g. horizontal cracks with a considerable aperture, Meanwhile such strong reflection events were not observed in the section after grouting. That is, the grouting work was dear able to reinforce the defects of dam body. Hence, the section showed an well arranged picture of dam inner structure. In this sense, seismic reflection method will be a desirable technique for dam inspection and for monitoring dam inner structure as well.

• Polymer(Korea)
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• v.25 no.3
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• pp.399-405
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• 2001

Poly[3-octylthiophene-co-3-(4-fluorophenyl)thiophene]s were synthesized in 2:1, 1:1, and 1:2 mole ratios, and organic electroluminescent devices were fabricated using the copolymers. The opto-electrical properties of the copolymers were studied by PL, EL spectra, I-V, and V-L curves of the organic electroluminescent devices in conjunction with the energy band diagrams which were obtained from the cyclic voltammogram and the electronic absorption spectra. The LUMO energy level of P(OT/FPT)(1:1) is the lowest as -3.35 eV. In the copolymers P(OT/FPT)(2:1) and P(OT/FPT)(1:1) the ${\lambada}_{max}$ in the PL and EL spectra red-shifted as the mole ratio of fluorophenyl group increased while in P(OT/FPT)(1:2) it showed a blue-shift. This indicates that the backbone chain is twisted due to the steric hinderance of the fluorophenyl group leading to shorter ${\pi}$-conjugation length. P(OT/FPT)(1:1) showed the highest EL intensity and the highest power efficiency among the three copolymers. In P(OT/FPT)(1:2) the roughness of the film surface causes unusually high local leakage current leading to the low efficiency of electroluminescence.