• Journal of the Korean Geosynthetics Society
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• v.8 no.3
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• pp.25-34
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• 2009

Determination of design parameters of composite ground including colluvial soil layer is far difficult because the maximum particle size of such a soil is remarkably large and particle distribution may vary from area to area. The stress-strain behavior of colluvial soils is in fact dependent upon the engineering characteristics at the boundary between coarse and fine materials. However, strength parameters are in general determined based on the characteristics of fine material, which causes an underestimation of such parameters. In this study, strength parameters of colluvial soil are evaluated by means of BIMROCK model curve. In addition, limit equilibrium analysis is carried out to verify the rational shear strength evaluation.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.349-359
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• 2006

This paper presents a new block stiffness matrix for the analysis an orthogonal Cartesian coordinate system. The displacement fields are defined using the first order shear deformable beam theory. The longitudinal displacement can be expressed as the sum of the projected plane deformation of the cross-section due to Timoshenko's beam theory and axial warping deformation due to modified Vlasov's thin-waled beam theory. The derived element takes into account flexural shear deformation and torsional warping deformation. Three different types of beam elements, namely, the two-noded, three-noded, and four-noded beam elements, are developed. The quadratic and cubic elements are found to be very efficient for the flexural analysis of laminated composite beams. The versatility and accuracy of the new element are demonstrated by comparing the numerical results available in the literature.

• 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 korean academy of Pediatric Dentistry
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• v.42 no.4
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• pp.281-290
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• 2015

The aim of this study was to evaluate shear bond strength (SBS) of bulk-fill resin composites (RCs) to dentin and their micro-leakage. One high-viscosity bulk-fill RC and 2 low-viscosity bulk-fill RCs were compared with 1 conventional RC. 7thgenerationbondingagentswereused. In order to evaluate SBS values, 40 permanent molars were selected and divided into 4 groups. The bulk-fill RCs were applied in 4 mm thickness, whereas the conventional RC was applied in 2 mm thickness. In order to evaluate micro-leakage, class I cavities ($5{\times}2{\times}4mm$) were prepared in 32 permanent molars. The teeth were divided into 4 groups and restored with resin composites in an increment of 4 mm for the bulk-fill RC and in 2 horizontal increments of 2 mm for the conventional RC. The mean SBS value of conventional RC showed no statistically significant difference when compared with those of low-viscosity bulk-fill RCs. However, the mean SBS value of high-viscosity bulk-fill RC was significantly lower than that of conventional RC (p < 0.05). There were no statistically significant differences in micro-leakage between the 4 groups. For SBS and micro-leakage, the use of low-viscosity bulk-fill RCs might help clinicians simplify the procedure.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.151-160
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• 2003

The stability of the designed rock slope is analysed based on two kinds of shear strength model. Besides the deterministic analysis, a probabilistic approach on Monte Carlo simulation is proposed to deal with the uncertain characteristics of the discontinuity and the results obtained from two models are compared to each other. To carry out the research of characteristics of the discontinuity, BIPS, DOM Scanline survey data and direct shear test data are used, and chi-square test is used for determining the probability distribution function. The rock slope is evaluated to be stable in the deterministic analysis, but in the probabilistic analysis, the probability of failure is more than 5%, so, it is considered that the rock slope is unstable. In the shear strength models, the probability of the failure based on the Mohr-Coulomb model(linear model) is higher than that of the Barton model. It is supported by the fact that the Mohr-Coulomb model is more sensitive to block size than the Barton model. In fact, there is no reliable way to estimate the unit cohesion of the Mohr-Coulomb model except f3r back analysis and in the case of small block failure in the slope, Mohr-Coulomb model may excessively evaluate the factor of the safety. So, the Barton model of which parameters are easily acquired using the geological survey is more reasonable for the stability of the studied slope. Also, the selection of the proper shear strength model is an important factor for slope failure analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.41-47
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• 2016

This paper presents a bond test to find the effect of shear key and edge length from the bonded FRP in near surface-mounted(NSM) retrofit using FRP plate. Main parameters in the test are the location and size of shear key and the edge length. For the test, 10 specimens were made by embedding FRP plate of $3.6mm{\times}16mm$ into $400mm{\times}200(300)mm{\times}400mm$ concrete block and fixing it by using epoxy. Tensile load was applied to the FRP of the specimens until failure and was recorded at each load increase. In addition, the bond slip and elongation of FRP were measured during the test. From the test, it was found that the further the shear key located from the loading, the higher strength we could get. The bond strength inversely depended on the size of shear key. Especially, when the size of shear key was to be lagger than certain size, the bond strength decreased to very low value; even less than that of the case without shear key. The bond strength somewhat increased corresponding to the increase of edge length from the bonded end of FRP to loading in spite of same bond length. The bond-slip between FRP and concrete governed overall deformation in the bond test of NSM FRP so that the effect of excessive slip is necessary to be considered in the design.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.76-84
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• 2019

This study evaluated the microleakage of three restorative materials and three tricalcium silicate-based pulp capping agents. The restorative materials were composite resin (CR), resin-reinforced glass ionomer cement (RMGI), and traditional glass ionomer cement (GIC) and the pulp capping agents were TheraCal $LC^{(R)}$ (TLC), $Biodentine^{(R)}$ (BD), and $ProRoot^{(R)}$ white MTA (WMTA). Additionally, shear bond strengths between the pulp-capping agents and dentine were compared. Class V cavities were made in bovine incisors and classified into nine groups according to the type of pulp-capping agent and final restoration. After immersion in 0.5% fuchsin solution, each specimen was observed with a stereoscopic microscope to score microleakage level. The crowns of the bovine incisors were implanted into acrylic resin, cut horizontally, and divided into three groups. TLC, BD and WMTA blocks were applied on dentine, and the shear bond strengths were measured using a universal testing machine. The microleakage was lowest in TLC + GIC, TLC + RMGI, TLC + CR, and BD + GIC groups and highest in WMTA + RMGI and WMTA + CR groups. The shear bond strength of BD group was the highest and that of WMTA group was significantly lower than the others.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.59-72
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• 2022

This study employed a 3-D numerical analysis based on the distinct element method to estimate the strength and deformability of a Cretaceous biotite granitic rock mass at Gijang, Busan, Korea. A workflow was proposed to evaluate the scale effect and the representative elementary volume (REV) of mechanical properties for fractured rock masses. Directional strength and deformability parameters such as block strength, deformation modulus, shear modulus, and bulk modulus were estimated for a discrete fracture network (DFN) in a cubic block the size of the REV. The size of the mechanical REV for fractured rock masses in the study area was determined to be a 15 m cube. The mean block strength and mean deformation modulus of the DFN cube block were found to be 52.8% and 57.7% of the intact rock's strength and Young's modulus, respectively. A constitutive model was derived for the study area that describes the linear-elastic and orthotropic mechanical behavior of the rock mass. The model is expected to help evaluate the stability of tunnels and underground spaces through equivalent continuum analysis.

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.357-363
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• 2009

This study was carried out to investigate whether adhesive used in manufacturing glulam can be used to bond wood and GFRP, when considering working process and economical efficiency. The six different glulams were manufactured, changing the adhesives and the mixing ratios of the adhesives, and investigated by the block shear test and the delamination of the water soaking or boiling water soaking. The three glulams were manufactured, using the resocinol resin based adhesive, the PVAc resin based adhesive and the epoxy resin adhesive, and the other three glulams, using the adhesives mixing resocinol resin and PVAc resin. The block shear strength is higher than $7.1N/mm^2$ in all types, which is standard of KS F3021. However, in the wood failure the block shear strength was the highest as 65.9% in the PVAc. The delamination of glulams glued with PVAc adhesive, which was 1.08% in water soaking and 4.16% in boiling water soaking, was lower than 5.00% which is the standard of KS F 3021, and the adhesive strength is good. In glulams glued with only resocinol resin adhesive, the wood layers were good as 1.26% in the water soaking delamination and 0.00% in the boiling water soaking delamination. The GFRP layers were not good as 21.85% in the water soaking delamination but were good as 1.45% in the boiling water soaking delamination.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.1
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• pp.20-26
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• 2013

Purpose: The purpose of this study was to evaluate the bond strengths between the latest CAD/CAM ceramic inlay and various resin cements which are used primarily for esthetic restoration. Materials and methods: Cylindrical ceramic blocks(Height: 5 mm, diameter: 3 mm) were fabricated by using Cerec3 and bonded on the dentin of the ninety extracted caries-free molars using three different kinds of resin cement(Unicem$^{(R)}$, Biscem$^{(R)}$, and Variolink II$^{(R)}$) according to the manufacturer's instructions. Ninety specimens were divided into 3 groups according to three different kinds of resin cement. Half of each group were conducted thermocycling under the conditions of the $5-55^{\circ}C$, 5,000 cycle but the other half of them weren't. All specimens were kept in normal saline $37^{\circ}C$, for 24 hours before measuring the bond strength. The shear bond strength was measured by Universal testing machine with a cross head speed of 0.5 mm/min. The results were analyzed statistically by t-test and one-way ANOVA. Results: Unicem$^{(R)}$ group showed the highest shear bond strength despite a slight decline by thermocycling. The shear bond strength of Unicem$^{(R)}$ group and ValiolinkII$^{(R)}$ group were significantly influenced by thermocycling, whereas Biscem$^{(R)}$ group was not influenced (P<.05). There were no significant differences in the bond strength between the three groups without thermocycling, but there was significant differences between Unicem$^{(R)}$ group and Valiolink II$^{(R)}$ group with thermocycling(P<.05). Conclusion: It has been shown to be clinically effective when the self-adhesive resin cements Unicem$^{(R)}$ and Biscem$^{(R)}$ were used instead of the etch-and-rinse resin cement Valiolink II$^{(R)}$ during the bonding of CAD/CAM ceramic inlay restorations with teeth.