• Journal of the Korea Institute of Building Construction
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• v.13 no.6
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• pp.627-633
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• 2013

This paper presents the result of a mock-up test and field application of concrete that is black in color thanks to the application of superplasticizer containing carbon amino silica black (CASB-SP). Mock-up specimen with a size of $3000{\times}1500{\times}40$ mm was fabricated with black concrete applying 0.5% of CSAB-SP with 27 MPa. After dividing the zone in wall mock-up specimen, three different water repelling agents were applied to verify its effect of efflorescence prevention. It was found that the use of CASB-SP with 0.5% made the black concrete develop a highly clear black color, and the epoxy type water repelling agent had better performance in efflorescence prevention. Based on mock-up test, field application was conducted with bridge member. It was also found that the application of CASB-SP showed favorable results in black color development.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.31.2-31.2
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• 2010

질화물계 발광다이오드는 소비전력이 낮고 발광효율이 높은 조명용 반도체소자로서 다양한 분야에 적용되고 있으나 질화갈륨 반도체 층 및 외부 공기와의 계면에서 발생하는 전반사로 인하여 광추출특성이 매우 낮은 문제점이 있다. 이를 해결하기 위하여 다양한 연구가 진행되고 있으며 투명전극 또는 p형 질화갈륨 층에 주기적인 나노 패턴을 형성하고 이에 따른 난반사 효과를 통해 전반사를 억제시키는 연구가 주로 진행되고 있다. 현재까지의 연구에서 발광다이오드의 광추출향상을 위한 나노 패턴은 플라즈마 식각공정을 통하여 형성되었지만 플라즈마 데미지에 의해 소자의 전기적 특성이 저하되는 문제점이 있었다. 본 연구에서는 플라즈마 식각 공정이 요구되지 않는 sol-gel 임프린팅 공정을 이용하여 발광다이오드의 ITO 투명전극 위에 산화아연 나노 패턴을 직접 형성하였다. Sol 솔루션은 에탄올에 zinc acetate dihydrate와 diethanolamine을 희석하여 제작하였고 이를 스핀코팅 방법을 통해 발광다이오드의 ITO 투명전극 층 위에 도포하였다. 이 후, 고 투습성의 PDMS (Polydimethylsiloxane) 몰드를 이용하여 $190^{\circ}C$에서 임프린팅을 진행하였고 이 과정에서 대부분의 솔벤트(에탄올)는 PDMS 몰드로 흡수되어 임프린팅 후에는 나노 패턴이 형성된 산화아연 gel 박막을 얻을 수 있었다. 최종적으로 $500^{\circ}C$에서 1시간 동안 열처리 하여 발광다이오드의 ITO 투명전극 위에 산화아연 나노 패턴을 형성하였다. 나노임프린팅 기반의 직접 패터닝 공정을 통하여 형성된 산화아연 패턴 층을 XRD 측정을 통해 결정성을 분석하였고 형성된 패턴의 형상을 SEM을 통해 확인하였다. 또한, 산화아연 패턴 유무에 따른 발광다이오드 소자의 광추출효율 비교를 위해 electroluminescence를 측정하였으며, 소자의 전기적 특성은 I-V 측정을 통해 분석하였다.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.250-260
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• 1995

Bases have been used in order to prevent the leakage of bleachingagents through dentinal tubules in bleached teeth. But the proximal surfaces where the actual resorption takes place havenot been protected. The purpose of this study was to compare the conventional basing method with the basing of the labial and two proximal surfaces to the cementoenamel junction. The bases were placed after conventional root canal treatment. Group I: 2mm thickness bases were placed to the level of labial cementoenamel junction line. Group II : 2mm thickness bases were placed to the level of all c-e J lines including cervical area. Control : No bases were placed. After placement of sodium perborate and 30% hydrogen peroxide mixtureinto the teeth, the changes of pH were measured. The results were as follows. 1. Group II showed smaller leakage of bleaching agents and was statistically significant difference compared to Group I.(p<0.05) 2. Group I showed no statistically significant difference compared to the control group. (p>0.05) 3. There were no significant among the upper and lower teeth groups in each group and between the groups.(p>0.05). According to the above results, it was considered that basing of the labial and proximal surfaces to the cementoenamel junction can reduce the leakage of bleaching agents during bleaching procedure of pulplessteeth.

• Journal of Korean society of Dental Hygiene
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• v.16 no.1
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• pp.77-83
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• 2016

Objectives: This study was carried out to investigate the effect of fluoride application after dental prophylaxis by the type of dental floss. Methods: Artificial caries lesion was made on the surface of cow's permanent teeth having sound enamel surface and vickers hardness number(VHN) was measured. Specimens were classified into APF gel group and artificial saliva group. Each group was divided into waxed floss group and unwaxed flossed group. All specimens were immersed into the artificial saliva for one minute and dental flossing was applied to waxed or unwaxed floss. After washing and drying, APF gel groups were applied with fluoride for four minutes and artificial saliva groups were immersed into the artificial saliva for four minutes. After treatment, specimens were measured by VHN and surface conditions of enamel were confirmed by scanning electron microscopy(SEM). Results: VHN of waxed flossing and fluoride application group increased to $6.78{\pm}2.75$. VHN of unwaxed flossing and fluoride application group increased to $7.36{\pm}2.51$. There was no significant difference between waxed and unwaxed groups(p>0.05). VHN of waxed flossing and artificial saliva group increased to $1.07{\pm}2.84$. VHN of waxed flossing and artificial saliva group increased to $1.05{\pm}3.13$. There was no significant difference between waxed and unwaxed groups(p>0.05). There was significant increase in VHN between waxed/unwaxed flossing and fluoride application. However, waxed/unwaxed flossing with artificial saliva showed no significant VHN increase. SEM demonstrated no residue on the enamel surface in the waxed flossing groups. Conclusions: No difference was found in the remineralization of enamel by waxed flossing or unwaxed flossing.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.444-449
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• 1998

There are various shielding materials that have been considered; the use of a metallic plate or the layering of a conductive material on a plastic surface and the insertion of filler in plastics. All of these methods have shown their merits and weakness. Therefore, many studies have concentrated on developing materials that effectively cut down EMI without increase in weights of housing materials. In these respects, this study has focused on investigations of the shielding effect of materials that have electroless nickel plating on the lamella structured micro particles surface with low specific gravity. When a film of electroless nickel were plated on a micro particle surfaces and then mixed with paint, the electromagnetic shielding effects were measured as 63dB. Although these effects were less than that 90dB of the copper plate, trials in a series of 6 times increased the shielding effect by IOdB and is applicable to wide range of EMI shielding.

• Journal of Conservation Science
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• v.26 no.4
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• pp.417-427
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• 2010

This study is to examine the manufacturing technique based on scientific investigation and analysis on Steel-Plated Jewel Beetle's Adornment gilt-bronze openwork remains excavated from No. 100 site at Hwango-dong Gyeongju. As a result of the investigation on the manufacturing revealed that riveting was adopted to connect gilt-bronze openwork plates and steel plates, followed by mercury amalgam plating method and carving of the patterns by means of the dotted line engraving technique. There were some traces on the surface of Jewel Beetle wings that show the use of pins for fixing, which seems to be the result of recycling or processing. The sectional analysis shows the high possibilities that varnishing with lacquer was adopted for wing adhesion, and it was confirmed that varnishing with lacquer was used on the strap pendant plate to prevent corrosion.

• Polymer(Korea)
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• v.38 no.6
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• pp.767-773
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• 2014

Rheological and electrical properties of polystyrene (PS)/carbon nanotube (CNT) nanocomposites via coagulated precipitation were investigated. Chemical modification and surfactant wrapping of CNT to improve the dispersion of CNTs may reduce the intrinsic properties of pristine CNT. To avoid this problem, PS and CNTs were dissolved and dispersed in dimethylformamide and then PS/CNT nanocomposites were prepared by the coagulated precipitation of CNT-dispersed PS solution in water. The coagulated precipitation method was highly effective enhancing the electrical conductivity of nanocomposites. Furthermore, the effect of adding poly(styrene-co-divinylbenzene) crosslinked particles to PS matrix on the rheological and electrical properties was investigated. With the addition of the crosslinked particles, the electrical percolation threshold of CNT reduced to 0.25 wt% and electrical conductivity increased further. It is speculated that CNTs in the volume occupied by crosslinked particles helped electrical pathway formation.

• Journal of Conservation Science
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• v.25 no.1
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• pp.87-100
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• 2009

We carried out the effect verification of conservation treatment focusing on basement rock of alkali granite at the Yukjonbul (two-pairs of Buddha Triads) carved on rock cliff of Samneung valley in Namsan mountain of Gyeongju. The conservation treatments were used to ethylsilicate-type rock consolidant and epoxy-type resin. It is treatment method that the epoxy-type resin have been applied one time into the exfoliation area, after rock consolidation treatment have been worked for three times. As the result of measuring ultrasonic velocity, P-wave velocity of the exfoliation area was relatively increased after applied the conservation treatments. The ultrasonic velocity of all area was increased as 27.8%. This result has been proved with consolidation effects by consolidant and filler for stone cultural heritages. The treatment method should be worked about three time to consolidate sufficiently for rocks.

• Composites Research
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• v.22 no.6
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• pp.45-51
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• 2009

The marginal integrity at the composite resin-tooth interface has been analyzed in real time through acoustic emission (AE) monitoring during the polymerization shrinkage of composite resin subjected to the light exposure. It was found that AE signals were generated by the polymerization shrinkage. Most AE hit events showed a blast type signal having the principal frequency band of 100-200kHz. Bad bonding states were indicated by many hit events in the initial curing period of 1 minute with high contraction rate. The quantity of hit events for the human molar dentin specimen was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. The better the bonding state, the less the AE hit events. The AE characteristics were related with the tensile crack propagation occurring in the adhesive region between the composite resin and the ring substrate as well as the compressive behavior of the ring substrate, which could be used for a nondestructive characterization of the marginal disintegrative fracture of the dental restoration.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.1
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• pp.52-59
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• 2022

Decalcification of the buccal surface of the teeth often occurs during fixed orthodontic treatment. This case report describes two cases in which cervical decalcificated teeth that occurred during orthodontic treatment were treated with direct resin veneer restoration. Early lesions without caries can be remineralized through periodic fluoride application, diet control, and oral hygiene improvement. As it progresses, appropriate repair treatment is required, and it is more preferable to focus on prevention rather than treatment after the occurrence of the lesion.