• Restorative Dentistry and Endodontics
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• 제42권2호
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• pp.118-124
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• 2017

Objectives: This study aimed to evaluate the color stability of bulk-fill and nanohybrid resin-based composites polished with 3 different, multistep, aluminum-oxide impregnated finishing and polishing disks. Materials and Methods: Disk-shaped specimens (8 mm in diameter and 4 mm in thickness) were light-cured between two glass slabs using one nanohybid bulk-fill (Tetric EvoCeram, Ivoclar Vivadent), one micro-hybrid bulk-fill (Quixfil, Dentsply), and two nanohybrid incremental-fill (Filtek Ultimate, 3M ESPE; Herculite XRV Ultra, Kerr) resin-based composites, and aged by thermocycling (between $5-55^{\circ}C$, 3,000 cycles). Then, they were divided into subgroups according to the polishing procedure as SwissFlex ($Colt\grave{e}ne/Whaledent$), Optidisc (Kerr), and Praxis TDV (TDV Dental) (n = 12 per subgroup). One surface of each specimen was left unpolished. All specimens were immersed in coffee solution at $37^{\circ}C$. The color differences (${\Delta}E$) were measured after 1 and 7 days of storage using a colorimeter based on CIE Lab system. The data were analyzed by univariate ANOVA, Mann-Whitney U test, and Friedmann tests (${\alpha}=0.05$). Results: Univariate ANOVA detected significant interactions between polishing procedure and composite resin and polishing procedure and storage time (p < 0.05). Significant color changes were detected after 1 day storage in coffee solution (p < 0.05), except Quixfil/Optidisc which was color-stable after 7 days (p > 0.05). Polishing reduced the discoloration resistance of Tetric EvoCeram/SwissFlex, Tetric EvoCeram/Praxis TDV, Quixfil-SwissFlex, and all Herculite XRV Ultra groups after 7 days storage (p < 0.05). Conclusions: Discoloration resistance of bulk-fill resin-based composites can be significantly affected by the polishing procedures.

• 대한토목학회논문집
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• 제35권2호
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• pp.515-524
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• 2015

최근 궤도 접속부에서의 부등침하 및 궤도틀림으로 잦은 유지보수 및 열차운영에 지장을 초래하는 경우가 많아지고 있다. 이는 주로 궤도 접속부 시공에 사용되는 다양한 성토재료의 강우나 동결융해 같은 환경적 인자에 의한 역학적 물성들의 변화에 기인한 것으로, 본 연구에서는 궤도 접속부 성토재료에 대한 함수특성곡선을 산정하고 강우 시 포화도 변화 추이를 알아보고자 침투해석을 수행 하였다. 필터페이퍼를 이용하여 다짐 성토의 함수특성곡선을 성공적으로 산정할 수 있었고, 함수특성곡선 데이터를 이용한 강우 시 침투해석을 수행한 결과 궤도 접속부 성토재료의 포화도 분포는 강우강도, 뒤채움재 경사, 성토 및 절토 여부, 그리고 함수특성곡선에 큰 영향을 받는 것을 확인 하였다.

• 한국지반신소재학회논문집
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• 제12권1호
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• pp.63-72
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• 2013

필댐의 안정성은 댐 축조시 주재료로 활용되는 조립재료인 암석존(rock zone)의 공학적 거동에 의존하므로 조립재료인 rockfill 재료의 전단강도 뿐만 아니라 하중-변형 특성(stress-strain characteristics)을 보다 정확히 이해하여야 한다. 또한, 댐 제체의 거동을 예측하고 수치해석적으로 분석하기 위해서는 조립재료의 거동을 모사하기에 적합한 구성모델을 활용하기 위한 물성값 분석 및 모델 파라미터의 캘리브레이션 연구가 필요하다. 본 논문에서는 부항댐 제체 재료에 대한 대형삼축압축 실험결과를 분석하고 이를 기반으로 조립재료에 대한 구성모델 파라미터들을 분석하였다. 부항댐 제체 재료를 고밀도와 저밀도로 구분하여 시료를 제작하고 다양한 구속압으로 수행된 실험결과와 캘리브레이션 된 구성모델 시물레이션 결과를 상호 비교한 결과 MD 모델이 조립재료의 응력-변형률 거동을 효과적으로 모사할 수 있음을 파악하였다.

• 한국지반공학회논문집
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• 제20권2호
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• pp.97-105
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• 2004

본 연구에서는 석회부산물의 재활용 방안으로 경량성토재, 뒤채움재 및 경량블록의 활용방안을 종합적인 실험연구를 통해 수행하였다. 이를 위하여 본 연구에서는, 석회부산물, 성토용 토사 및 폐 EPS 조각을 혼합한 새로운 형태의 경량성토계 및 이에 시멘트 고화제를 첨가한 경량블록을 고안하였고, 다양한 배합비로 제작된 경량혼합토 및 경량블록에 대한 시료에 대하여 종합적인 시험을 실시하여 물리적, 지반공학적 및 환경적 특성을 분석하였다. 또한 경량블록에 대하여 국내 용출시험법(KMS Method)을 실시하여 화학성분의 농도변화에 대하여 평가하였다. 본 연구는 석회부산물 처분의 문제에 대하여 해결을 기대할 수 있으며 뿐만 아니라 성토재 및 블록에 대하여 석회부산물의 재활용 방안을 기대할 수 있다.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.303-308
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• 2022

Purpose: This technical report aims to describe and detail the use of micro-computed tomography for a reliable evaluation of the bulk-fill composite/tooth interface. Materials and Methods: Bulk-fill composite restorations in tooth cavities were scanned using micro-computed tomography to obtain qualitatively and quantitatively valuable information. Two-dimensional information was processed using specific algorithms, and ultimately a 3-dimensional (3D) specimen reconstruction was generated. The 3D rendering allowed the visualization of voids inside bulk-fill composite materials and provided quantitative measurements. The 3D analysis software VG Studio MAX was used to perform image analysis and assess gap formation within the tooth-restoration interface. In particular, to evaluate internal adaptation, the Defect Analysis addon module of VG Studio Max was used. Results: The data, obtained with the processing software, highlighted the presence and the shape of gaps in different colours, representing the volume of porosity within a chromatic scale in which each colour quantitatively represents a well-defined volume. Conclusion: Micro-computed tomography makes it possible to obtain several quantitative parameters, providing fundamental information on defect shape and complexity. However, this technique has the limit of not discriminating materials without radiopacity and with low or no filler content, such as dental adhesives, and hence, they are difficult to visualise through software reconstruction.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.261-269
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• 2021

Purpose: The aim of this study was to evaluate the radiopacities of various types of restorative materials with different thicknesses compared with enamel, dentin, and aluminum. Materials and Methods: Four bulk-fill resins, 2 hybrid ceramics, 2 micro-hybrid resin composites, 6 glass ionomer-based materials, 2 zinc phosphate cements, and an amalgam were used in the study. Twelve disk-shaped specimens were prepared from each of 17 restorative materials with thicknesses of 1 mm, 2 mm, and 4 mm (n=4). All the restorative material specimens with the same thickness, an aluminum (Al) step wedge, and enamel and dentin specimens were positioned on a phosphor storage plate and exposed using a dental X-ray unit. The mean gray values were measured on digital images and converted to equivalent Al thicknesses. Statistical analyses were performed using 2-way analysis of variance and the Bonferroni post hoc test(P<0.05). Results: Radiopacity was significantly affected by both the thickness and the material type (P<0.05). GCP Glass Fill had the lowest radiopacity value for samples of 1 mm thickness, while Vita Enamic had the lowest radiopacity value for 2-mm-thick and 4-mm-thick samples. The materials with the highest radiopacity values after the amalgam were zinc phosphate cements. Conclusion: Significant differences were observed in the radiopacities of restorative materials with different thicknesses. Radiopacity was affected by both the material type and thickness.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.299-307
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• 2009

New lake dike in Saemanguem area is 125km length and require a great amount of fill materials, but it's difficult to get the amount of materials and develop a quarry because of environment conservation. Therefore, the solution is to use the dredged soil in project area as the fill materials not to develop quarry. However, characteristic of dredged soil as a silty fined sand is very weak at seepage, sliding, erosion of dike due to infiltration of rainfall, wind etc. So, lake dike using dredged soil must be constructed safely against the unstable problem of dredged sand. The objective of research is to make safe lake dike using dereged soil on construction of Saemangeum new lake dike. So, we analyzed the characteristic of dredged soil and suggested a standard section of lake dike.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.836-841
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• 2008

CFRD (Concrete Faced Rockfill Dam) has been world-widely constructed due to a lot of advantages compared with rockfill dam and recently, sand/gravel materials, instead of crushed rock materials, are also utilized as a main rockfill material to overcome geological and environmental problems. In this paper, the process of water infiltration into the originally unsaturated sand/gravel-fill dam is studied using two-dimensional saturated-unsaturated seepage theory. According to the results of seepage analysis, if the effective drainage zone is installed in the dam, the reservoir water infiltrate into the dam along a downward flow path towards the lower drainage area. The main body constructed with sand/gravel materials, therefore, remains unsaturated.

• 지구물리
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• 제6권2호
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• pp.89-97
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• 2003

For safety evaluation of a rockfill dam, it is often necessary to investigate spatial distribution and dynamic characterization of weak zones such as fractures. For this purpose, both seismic and electric methods are adopted together in this research. The former employs the multichannel analysis of surface waves (MASW) method, and aims at the mapping of 2-D shear-wave velocity (Vs) profile along the dam axis that can be associated with dynamic properties of filled materials. The latter is carried out by DC- resistivity survey with a main purpose of mapping of spatial variations of physical properties of dam materials. Results from both methods are compared in their signature of anomalous zones. In addition, downhole seismic survey was carried out at three points within the seismic survey lines and results by downhole seismic survey are compared with the MASW results. We conclude that the MASW is an efficient method for dynamic characterization of dam-filling materials, and also that joint analyses of these two seemingly unrelated methods can lead to an effective safety evaluation of rock-fill dam.

• Journal of Periodontal and Implant Science
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• 제38권3호
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• pp.437-444
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• 2008

Purpose: A number of techniques and materials have been used for periodontal regeneration and bone graft procedures with guided tissue regeneration(GTR) have been suggested as alternatives to osseous surgery in the management of local infra-bony defects. However, the long-term stability and treatment outcome following bone graft procedure of infra-bony defects is poorly documented. The purpose of this study was to assess radiographic change in infra-bony defects over 2 years after bone graft procedures with various graft materials. Material and Methods: Patients attending the department of periodontics of Kyungpook National University Hospital were studied. Patients showed clinical and radiographic evidence of infra-bony defect(s). 44 sites of 34 patients aged 31 to 69 (mean age 48.3) were treated by bone graft procedure with a bone graft material. Baseline and 2-year follow-up radiographs were collected and evaluated for this study. Radiographic assessment includes a bone fill, bone crest change, defect resolution, and % of defect resolution. Pre- and post-treatment differences between variables (maxilla and mandible, defect depth, defect angle, bone graft materials) using the paired t-test were examined. Result: We observed $1.15{\pm}1.95\;mm$ of bone fill, $0.40{\pm}1.19\;mm$ of crestal resorption, $1.55{\pm}1.77\;mm$ of defect resolution, and $40{\pm}44%$ of percentage of defect resolution. Deeper initial defect depth, narrower initial defect angle showed significantly greater bone fill, defect resolution, and % of defect resolution. But no significant difference was observed in graft sites and graft materials. Conclusion: If good oral hygiene maintenance and periodic recall check of patients is assured, bone graft procedure using various graft materials is one of the appropriate treatment modality for regenerative therapy of infra-bony defects.