• International Journal of Reliability and Applications
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• 제8권1호
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• pp.111-124
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• 2007

In this paper, we apply insightful statistical reliability tools to manage and seek improvements in the strengths of Oriented Strand Board (OSB). As a part of the OSB manufacturing process, the product undergoes destructive testing at various intervals to determine compliance with customers' specifications. Workers perform these tests on sampled cross sections of the OSB panel to measure the tensile strength, also called internal bond (IB), in pounds per square inches until failure. Additional stiffness strength tests include parallel and perpendicular elasticity indices (EI), which are taken from cross sectional samples of the OSB panel in the parallel and perpendicular directions with respect to the orientation of the wood strands. We explore both graphically and statistically these "pressure-to-failures" of OSB. Also, we briefly comment on reducing sources of variability in the IB and EI of OSB.

• Fibers and Polymers
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• 제3권1호
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• pp.38-42
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• 2002

Polypropylene filaments were spun from a mixture of PP chips of two different Melt Flow Index (MFI) (3 MFI and 35 MFI). A significant difference was observed in the melting characteristics of the resultant filaments from either of the individual components as observed from the DSC. The main difference being in the degree of melting achieved at any temperature in the initial stages of the melting range, which was found to be higher in case of the filaments spun from the b]end. These filaments were then thermally bonded using silicon oil bath and heated roller method. Subsequently the bond strength of the filaments was measured on the Instron Tensile Tester using the loop technique. The values of the world strengths obtained from the blend were compared with those made from the individual component. It was found that the bond strength of the bonds obtained from the blended filament at a given temperature was higher than that of the bonds made from the filaments of either of the individual components, which is also suggested by the DSC curves. The difference in the bond strength was found to be as high as 25% in case of the blend with 60:40 composition ratios of the 3 MFI and 35 MFI components respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.519-526
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• 1997

The purpose of this study is to develop the analytical model for the reinforcement bar connection in group-filled steel pipe sleeve, which consists of beam elements for the reinforcement bar and shell elements for the sleeve and the mortar and spring elements for the bond stress-slip relationship. In the reinforcement bar connection using grout-filled steel pipe sleeve, the major variables are the bond stiffness between reinforcement bar and mortar($K_1$) and between sleeve and mortar($K_2$). It is nearly difficult to predict the exact bond stiffness with the experimental results. Therefore, The linearly elastic analyses using ABAQUS, FEM package show the validity of the mathematical equations for the bond stiffness and the choice of material elements in this paper. To predict the behaviour between yield and ultimate tensile strength, the nonlinear analyses must be performed henceforth.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.2279-2286
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• 2015

GFRP 판을 영구 거푸집 및 주요 인장 보강재로 활용한 GFRP-콘크리트 하이브리드 구조의 활용에 대해 최근 활발하게 연구가 이루어지고 있다. GFRP 판과 콘크리트 하이브리드 구조의 거동을 이해하기 위해서는 GFRP 판과 현장타설 고강도콘크리트 사이의 정량적인 국부 부착슬립모델이 필요하다. 본 연구에서는 이러한 하이브리드 구조에 간단하게 적용할 수 있는 2중 직선 단순 부착슬립관계를 제안하고자 한다. 본 연구에서 제안된 단순 부착슬립관계의 최대 평균 부착응력은 3.29MPa이며, 초기 기울기는 35.66MPa/mm, 총 슬립은 0.23mm이고 계면 파괴에너지는 0.37kN/m로 나타났다.

• Restorative Dentistry and Endodontics
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• 제20권1호
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• pp.113-128
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• 1995

The purpose of this study was to investigate the effect of stannous fluoride on the dentin bonding with three kinds of commercially available dentin bonding systems containing different adhesive monomers. Dentin specimens with exposed labial dentin prepared from freshly extracted bovine mandibular anterior teeth were divided into experimental and control groups. The specimens of experimental groups were bonded with dentin bonding systems and composite resins including All bond 2 ㅡ& Bisfil, Scotchbond Multi-Purpose & Z100, and Denthesive II Charisma after 2 % stannous& fluorided application for S minutes and washing for 1 minute. The specimens of control groups were bonded with the same dentin bonding systems and composite resins as used in the experimental groups. After bonded specimens were stored in $37^{\circ}C$ distilled water for 24 hours, the tensile bond strength and cohesive failure rate were measured, and then the pretreated dentin surfaces and the fractured dentin surfaces were examined under scanning electron microscope. The results were as follows : Mean bond strength of stannous fluoride applied groups of All bond 2, Scotchbond MP, and Denthesive II were 2.5MPa, 1.1MPa, and 1.1MPa respectively, and those of control groups were 7.5MPa, 8.1MPa, and 4.6MPa. Bond strength values of stannous fluoride applied groups were significantly lower than those of the control groups(p<0.05). SEM findings of dentin surfaces after stannous fluoride application demonstrated an appearance of partially remained smear layer and smear plugs inspite of pretreatment with 10 % phosphoric aicd or maleic acid solution, and an appearance of smear layer covered surface under Denthesive II priming. But those of control groups commonly showed clean dentin surfaces without smear layer and smear plugs. On SEM observation of the fractured dentin-resin interface, while most of the specimens of stannous fluoride applied groups showed adhesive failure mode, those of All bond 2 and Scotchbond MP control groups showed mainly adhesive-cohesive mixed failure mode, and mainly adhesive failure mode in Denthesive II control group.

• 한국구조물진단유지관리공학회 논문집
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• 제21권1호
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• pp.134-141
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• 2017

시멘트 생산 과정에서 생성되는 이산화탄소 배출량을 감소시키기 위하여 시멘트를 대체할 수 있는 건축 재료 개발에 많은 연구가 진행되어왔다. 시멘트 대체재로 사용될 수 있는 활성 황토는 $850^{\circ}C$에서 소성 과정을 거쳐 제작된다. Poly-Vinyl Alcohol(PVA) 섬유와 GFRP 보강근은 활성 황토 콘크리트의 균열 문제를 해결하기 위하여 사용된다. 본 논문은 PVA 섬유 보강 활성 황토 콘크리트에 대하여 인발 하중에 따른 GFRP 보강근의 부착 성능을 평가하기 위한 실험 연구를 나타내고 있다. 실험 결과, 황토가 치환된 PVA 보강 및 무보강 실험체들의 평균 부착 응력 계수가 2.27~2.48로 나타났으며, 부착 응력 계수가 PVA 섬유 보강 유무 및 황토 치환율에 크게 영향을 받지 않는 것으로 나타났다. 그리고 부착 길이가 길어질수록 부착 강도는 저하되었다.

• 구강회복응용과학지
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• 제22권2호
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• pp.193-202
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• 2006

Objective To evaluate the influence of water storage on the mechanical properties of dental adhesives over 1 and 3 months. Materials and Methods Adhesive resin sheets were prepared by pouring either All-bond 2(AB), Clearfil SE Bond(SE) into a mold measuring $15{\times}15{\times}0.9mm$. After solvent in primer evaporation, the adhesives were light-cured and removed from the mold and divided in two pieces, trimmed to hourglass shape that were used to determine the micro-tensile strength(MTS). Another hourglass shaped metal mold measuring $2.0{\times}1.5mm$ in cross-section area was made to determine the Young's modulus(E). Adhesive specimens for Young's modulus(E) were prepared in the same method. Specimens were stored at $37^{\circ}C$ in distilled water and tested after 1 and 3 months. The data were analyzed by one-way ANOVA and Tukey's test. Results Water storage significantly decreased the micro-tensile strength(MTS) of AB and SE specimens after 1 and 3 months(P<0.05). The Young's modulus(E) were also decreased after water storage for 1 and 3 months, but statistically not significant in each group of AB and SE group respectively. Conclusions Long-term exposure of adhesive resin to water can cause reduction of mechanical properties. It may compromise resin/dentin bonds and affect longevity of restorations.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.181-192
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• 1997

The difficulty of endodontic retreatment depends on various factors and it is affected by retention of post. In this experiment, root canal therapy was done in extracted human teeth and cut into 10mm length from the root apex, and then cemented by zinc phosphate cement, Vitremer$^{(R)}$(glass ionomer) luting cement and Panavia 21$^{(R)}$(resin cement). Post preparation was done by #4 Parapost drill at 6mm length and cement was inserted by lentulo spiral. After 24 hours, tensile bond strength, post removal time was measured after the ultrasonic application and the separation site was measured. The following results were obtained. 1. In measuring tensile bond strength, there is no statistical difference between zinc phosphate cement and Panavia 21$^{(R)}$, but Vitremer$^{(R)}$ showed lower value compared with those two cements. (p<0.001) 2. When the post removal time was measured after ultrasonic application, significant different value in order of Panavia 21$^{(R)}$, zinc phosphate cement and Vitremer$^{(R)}$ was shown. (p<0.001) 3. As a result of examining the separating site of each cement, all 16 of zinc phosphate cement group showed the fracture site between cement and post, Vitremer$^{(R)}$ was 13/16, and Panavia 2$^{(R)}$ was 8/16. In case of tooth restoration using Parapost, the use of Panavia 21 showed good retention property than Vitremer$^{(R)}$, but when retreatment is needed the difficulty of post removal will be increased.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 추계학술대회 논문집
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• pp.61-62
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• 2007

HVOF thermal spray coating of micron size Co-alloy powder has been studied for the durability improvement of high velocity spindle (HVS). Optimal coating process of this system for the best surface properties is hydrogen flow rate 75 FMR, oxygen flow rate 38-42 FMR, feed rate 30 g/min at spray distance 5 inch. Friction coefficient (FC) and wear trace (WT) decrease increasing coating surface temperature from 25$^{\circ}$C to 538$^{\circ}$C due to the higher lubricant effects of the oxides at the higher temperature. At the study of adhesion of T800 coating on a light metal alloy Ti-6Al-4V (Ti64) tensile bond strength (TBS) and tensile fracture location (TFL) of Ti64/T800 are 8,740 psi and near middle of T800 coating respectively. This shows that adhesion of Ti64/T800 is higher than the cohesion strength (8,740 psi) of T800 coating. Therefore T800 coating is strongly advisable for the surface coating on HVS such as high speed air-bearing spindle.

• 한국도로학회논문집
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• 제19권6호
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• pp.37-46
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• 2017

PURPOSES : A composite pavement utilizes both an asphalt surface and a concrete base. Typically, a concrete base layer provides structural capacity, while an asphalt surface layer provides smoothness and riding quality. This pavement type can be used in conjunction with rollercompacted concrete (RCC) pavement as a base layer due to its fast construction, economic efficiency, and structural performance. However, the service life and functionality of composite pavement may be reduced due to interfacial bond failure. Therefore, adequate interfacial bonding between the asphalt surface and the concrete base is essential to achieving monolithic behavior. The purpose of this study is to investigate the bond characteristics at the interface between asphalt (HMA; hot-mixed asphalt) and the RCC base. METHODS : This study was performed to determine the optimal type and application rate of tack coat material for RCC-base composite pavement. In addition, the core size effect, temperature condition, and bonding failure shape were analyzed to investigate the bonding characteristics at the interface between the RCC base and HMA surface. To evaluate the bond strength, a pull-off test was performed using different diameters of specimens such as 50 mm and 100 mm. Tack coat materials such as RSC-4 and BD-Coat were applied in amounts of 0.3, 0.5, 0.7, 0.9, and $1.1l/m^2$ to determine the optimal application rate. In order to evaluate the bond strength characteristics with temperature changes, a pull-off test was carried out at -15, 0, 20, and $40^{\circ}C$. In addition, the bond failure shapes were analyzed using an image analysis program after the pull-off tests were completed. RESULTS : The test results indicated that the optimal application rate of RSC-4 and BD-Coat were $0.8l/m^2$, $0.9l/m^2$, respectively. The core size effect was determined to be negligible because the bond strengths were similar in specimens with diameters of 50 mm and 100 mm. The bond strengths of RSC-4 and BD-Coat were found to decrease significantly when the temperature increased. As a result of the bonding failure shape in low-temperature conditions such as -15, 0, and $20^{\circ}C$, it was found that most of the debonding occurred at the interface between the tack coat and RCC surface. On the other hand, the interface between the HMA and tack coat was weaker than that between the tack coat and RCC at a high temperature of $40^{\circ}C$. CONCLUSIONS : This study suggested an optimal application rate of tack coat materials to apply to RCC-base composite pavement. The bond strengths at high temperatures were significantly lower than the required bond (tensile) strength of 0.4 MPa. It was known that the temperature was a critical factor affecting the bond strength at the interface of the RCC-base composite pavement.