• Steel and Composite Structures
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• v.20 no.3
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• pp.671-692
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• 2016

FRP stay-in-place (SIP) formworks are designed as a support for casting concrete and as a tension reinforcement when concrete is cured. Bond development between SIP formwork and concrete is critical for FRP tension element to be effective. This paper reports the bond strength between FRP formwork and concrete for different interfacial treatments. A novel experimental setup is prepared for observing the bond behaviour. Three different adhesives with varying workability have been investigated. Along with the load-deformation characteristics, bond slip and strains in the formwork have been measured. A finite element numerical simulation was conducted for the experiments to understand the underlying mechanism. The results show that the adhesive bonding has the best bond strength.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.9-16
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• 2012

In this study, the effect of metakaoline and silica fume on the bond performances of structural polyvinyl alcohol (PVA) fiber in cement mortar, including bond strength, interface toughness, and microstructure analysis are presented. Metakaoline and silica fume contents ranging from 0 % to 15 % are used in the mix proportions. Pullout tests are conducted to measure the bond performance of PVA fiber from cement mortar. Test results showed the incorporation of metakaoline and silica fume can effectively enhance the PVA fiber-cement mortar interfacial properties. Bond strength and interface toughness increased with metakaoline and silica fume content up to 10 % in cement mortar and decreased when the metakaoline and silica fume content reached 15 %. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results.

• Computers and Concrete
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• v.23 no.3
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• pp.155-160
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• 2019

The use of recycled aggregate concrete for the purpose of environmental and resource conservation has gained increasing interest in construction engineering. Nevertheless, few studies have reported on the bonding performance of the bars in recycled aggregate concrete after exposed to high temperatures. In this paper, 72 pull-out specimens and 36 cubic specimens with different recycled coarse aggregate content (i.e., 0%, 50%,100%) were cast to evaluate the bond behavior between recycled aggregate concrete and steel bar after various temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$). The results show that the recycled aggregate concrete pull-out specimens exhibited similar bond stress-slip curves at both ambient and high temperature. The bond strength declined gradually with the increase of the temperature. On the basis of a regression analysis of the experimental data, a revised bond strength mode and peak slip ratios relationship model were proposed to predict the post-heating bond-slip behavior between recycled aggregate concrete and steel bar.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.186-190
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• 1986

Effects of substituents in the nucleophile(X), the substrate(Y) and the leaving group(Z) on the structure of $S_N2$ transition states have been analyzed by considering effects of four components, electrostatic($E_{es}$), exchange repulsion ($E_{ex}$), polarization($E)_{pl}$) and charge transfer($E_{ct}$) terms, of interaction between the reactants on the degree of bond making and bond breaking. Prediction of net effects of all substituents(X, Y and Z) on the degree of bond making were found to be clearcut whereas the effect of an electron withdrawing group on the substrate (Y = EWG) on the degree of bond breaking was complex; the substituent(Y = EWG) is normally carbon-leaving group($C^{\ast}$-L) bond tightening($E_{pl}$ dominance) but becomes $C^{\ast}$-L bond loosening when the bond is strongly antibonding ($E_{ct}$ dominance). Our model calculations on the reaction of $CH_2XNH_2$ with $YCH_2COOCH_2Z$ using energy decomposition scheme have confirmed that predictions based on our analysis are correct.

• The Journal of Advanced Prosthodontics
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• v.9 no.2
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• pp.110-117
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• 2017

PURPOSE. This laboratory study assessed the effect of different dentin cleaning procedures on shear bond strength of resin cements for recementing prosthesis. MATERIALS AND METHODS. A $4{\times}4$ flat surface was prepared on the labial surface of 52 maxillary central incisors. Metal frames ($4{\times}4{\times}1.5mm$) were cast with nickel-chromium alloy. All specimens were randomly divided into 2 groups to be cemented with either Panavia F2.0 (P) or RelyX Ultimate (U) cement. The initial shear bond strength was recorded by Universal Testing Machine at a crosshead speed of 0.5 mm/min. Debonded specimens were randomly allocated into 2 subgroups (n = 13) according to the dentin cleaning procedures for recementation. The residual cement on bonded dentin surfaces was eliminated with either pumice slurry (p) or tungsten carbide bur (c). The restorations were rebonded with the same cement and were subjected to shear test. Data failed the normality test (P < .05), thus were analyzed with Mann Whitney U-test, Wilcoxon signed rank test, and two-way ANOVA after logarithmic transformation (${\alpha}=.05$). RESULTS. The initial shear bond strength of group P was significantly higher than group U (P = .001). Pc and Uc groups presented higher bond strength after recementation compared to the initial bond strength. However, it was significant only in Pc group (P = .034). CONCLUSION. The specimens recemented with Panavia F2.0 provided higher bond strength than RelyX Ultimate cement. Moreover, a tungsten carbide bur was a more efficient method in removing the residual resin cement and increased the bond strength of Panavia F2.0 cement after recementation.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.665-674
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• 2007

Purpose: The purpose of this study was to investigate the effect of sire and shape of retention element on the bond strength of indirect composite resin and metal. Material and method: The metal disk specimens, each 6mm in diameter, were cast from CrCo alloy. They were divided into 8 groups by applied retention element. retention bead group $B2\;({\phi}\;0.2mm),\;B4\;({\phi}\;0.4mm),\;B6\;({\phi}\;0.6mm),\;B8\;({\phi}\;0.8mm)$, retention crystal group C2 (0.2mm), C5 (0.5mm), C8 (0.8mm) and sandblasting group SB ($110{\mu}m\;Al_2O_3$ blasting) as control. Eighty-eight metal specimens were veneered with $TESCERA^{(R)}$ Indirect resin system. One specimen of each group was sectioned and the resin-metal bonding pattern at the interface was observed under measuring microscope. Other specimens were then tested for tensile bond strength on an Instron universal testing machine at a crosshead speed of 2mm/min. Results: 1. Compared to sandblasting, beads or crystals increased the resin-metal bond strength (P<.05). 2. 0.2mm retention crystals were most effective in improving the resin-metal bond strength (P>.05). 3. 0.2mm beads showed the highest bond strength among retention bead groups, but there was no statistically significant difference (P>.05). 4. Retention crystals tend to be higher in bond strength than retention beads due to wider surface area. 5. The larger retention element, the larger the undercut for the mechanical retention, but the gap at resin-metal interface was also increased. Conclusion: Within the limitations of this study, 0.2mm retention crystals were most effective in improving the resin-metal bond strength.

• The Journal of Advanced Prosthodontics
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• v.8 no.6
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• pp.504-510
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• 2016

PURPOSE. Polyamide polymers do not provide sufficient bond strength to auto-polymerized resins for repairing fractured denture or replacing dislodged denture teeth. Limited treatment methods have been developed to improve the bond strength between auto-polymerized reline resins and polyamide denture base materials. The objective of the present study was to evaluate the effect of surface modification by acetic acid on surface characteristics and bond strength of reline resin to polyamide denture base. MATERIALS AND METHODS. 84 polyamide specimens were divided into three surface treatment groups (n=28): control (N), silica-coated (S), and acid-treated (A). Two different auto-polymerized reline resins GC and Triplex resins were bonded to the samples (subgroups T and G, respectively, n=14). The specimens were subjected to shear bond strength test after they were stored in distilled water for 1 week and thermo-cycled for 5000 cycles. Data were analyzed with independent t-test, two-way analysis of variance (ANOVA), and Tukey's post hoc multiple comparison test (${\alpha}=.05$). RESULTS. The bond strength values of A and S were significantly higher than those of N (P<.001 for both). However, statistically significant difference was not observed between group A and group S. According to the independent Student's t-test, the shear bond strength values of AT were significantly higher than those of AG (P<.001). CONCLUSION. The surface treatment of polyamide denture base materials with acetic acid may be an efficient and cost-effective method for increasing the shear bond strength to auto-polymerized reline resin.

• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.108-114
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• 2015

PURPOSE. The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent. MATERIALS AND METHODS. Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to $55^{\circ}C$) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at ${\alpha}$=.05. RESULTS. Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between $7.07{\pm}2.11$ and $26.05{\pm}6.53$ N. The highest bond strength of $26.05{\pm}6.53$ N was obtained with Group 3. Group 5 showed the lowest value of bond strength. CONCLUSION. Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.173-178
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• 1993

In order to quantify the effect of transverse reinforcement on the bond splitting behavior of reinforcement monotonic loading tests of 8 slmply beams were carried out. The reinforcing details and material properties were so determined that the bond splitting failure proceded the shear and flexural failure. A bond splitting strength derived from the experimental data and it accounts for following parameters: 1) Concrete Strength 2) Transverse reinforcement ratio and shape 3) Thickness of concrete cover 4)Deformation of reinforcement

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2045-2050
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• 2006

The interstitial hydrogen bonding in NiTi solid and its effect on the metal-to-metal bond is investigated by means of the EH tight-binding method. Electronic structures of octahedral clusters $Ti_4Ni_2$ with and without hydrogen in their centers are also calculated using the cluster model. The metal d states that interact with H 1s are mainly metal-metal bonding. The metal-metal bond strength is diminished as the new metal-hydrogen bond is formed. The causes of this bond weakening are analyzed in detail.