• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.536-539
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• 2004

This paper focues on the flexural behavior of RC beams externally reinforced using Carbon Fiber Reinforced Plastics plates. (CFRP) A non-linear finite element (FE) analysis is proposed in order to complete the experimental analysis of the flexural behaviour of the beams. This paper is a part of a complete program aiming to set up design formulate to predict the strength of CFRP strengthende beams, particularly when premature failure through plates-end shear or concrete cover delamination occurs. An elasto-plastic behaviour is assumed for reinforced concrete and interface elements are used to model the bond and slip.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.231-233
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• 2005

Laser have been utilized as a heat source for the soldering of electronic components for the their capability of localized heating and faster heating rate. Laser soldering process, especially the diode laser soldering of BGA solderball was investigated. In this study, an attempt was made to investigate the possibility of laser soldering using Sn-37Pb and Sn-3Ag-0.5Cu solderball. The laser energy absorbed on the pad raised the temperature of the solderball forming a reflowed solder bump. The result were discussed based on the measurement of pull and shear strength of the bond.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.2
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• pp.327-346
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• 1996

The purpose of this study was to evaluate the shear bond strengths, microhardness, compressive strength and contraction gap at the resin-tooth interface of two types of composite resins polymerized with visible light and argon laser sourse. The results from the present study can be summarized as follows ; 1. Resin samples polymerized either by argon laser or visible light did not show significant difference in their physical properties tested(p>.05). 2. The contraction gap at the resin tooth interface was found to be present in all samples but any significant difference between groups could not be established due to their variability. Although the superiority of argon laser over visible light in enhancing the physical properties of resin could not be elucidated in the present study, continous efforts are deemed to be worthwhile to investigate this area using different conditions and materials of experiment.

• Restorative Dentistry and Endodontics
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• v.28 no.4
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• pp.314-325
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• 2003

이 연구의 목적은 수종 상아질 접착 시스템과 복합 레진 및 resin-modified glass ionomer를 상아질 표면에 접착하여 재료 및 상아질내 위치에 따른 미세전단결합강도를 측정, 비교하는 것이다. 상아질 접착 시스템으로는, 3-step인 Scotchbond Multi-Purpose Plus, 2-step인 Single Bond와 자가 부식형 시스템인 Clearfil SE Bond를, 1-step인 Prompt L-Pop을 사용하였다. 이와 함께 hybrid type의 복합 레진인 Clearfil AP-X와 2250을 사용하였으며 resin-modified glass ionomer로는 Fuji II LC를 사용하였다. 상악 소구치를 치아의 근원심 중앙부를 절단하여 상아질면을 노출시켰다. 5개 실험군으로 분류하고 상아질면을 위치에 따라 치관부의 occlusal $\frac{1}{3}$, middle $\frac{1}{3}$, cervical $\frac{1}{3}$과 치근부로 구분지어 시편을 부착하였다. 미세전단결합강도측정는 Universal testing machine(EZ-test; Shimadzu, Japan)에서 측정하였다. Occlusal 1/3부위에서는 SE가 가장 높은 값을, SM과 SB간에는 유의차가 없었으며, PL, GI순으로, Middle 1/3부위에서는 $SM{\;}{\geq}{\;}SE{\;}{\geq}{\;}SB{\;}{\geq}{\;}PL{\;}{\geq}{\;}GI$순으로, cervical 1/3부위에서는 SM, SE, SB간에 유의차가 없었다. Root dentin에서는 SM이 가장 높은 값을 보였으며 SE, PL, GI간에 유의차가 없었다. SE만이 치관부 상아질에 비해 치근부에서 유의할만한 결합강도의 감소를 나타냈다(p<0.05). GI는 치관부 상아질에서는 다른 군에 비해 유의성 있게 낮은 결합강도를 보였으나 치근부에서는 SE, PL과 유의차가 없었다.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.106-121
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• 2007

The purpose of this study was to examine the effects of suggested etching method on the performance of pits and fissures sealant. In the first part, seventy extracted sound human permanent third molars and premolars were used. The teeth were randomly divided and performed in three different groups as follows : conventional etching, enameloplasty, and testing group. Non-pumicing, dye-guidance vigorous brushing-start etching technique was applied on the occlusal of testing group. Then the pit and fissure sealant was applied on all of the specimens. After the thermocycling and immersing in 1% methylene blue, the resin embedded sections were made. The microleakage data on the section were then recorded under the stereoscope and statistic analysis was done. Additional experiments were also performed : direct fissure surface etched pattern experiment, replica study, and micro-shear bond strength testing observation. The second part included two groups. A paired study was designed to evaluate the influence the environment has on the performance of the sealant. After etching, half of each occlusal surface received one of the two following treatments in succession: sealing in laboratory and intraoral condition (group 1), sealing in intraoral condition with and without a single-bonding agent (group 2). The results of present study can be summarized as follows: - The microleakage of testing group was significant different with conventional method (P<.05) and was not different with the enameloplasty group (P>.05). - The quality and quantity of etched enamel were improved. - Microshear bond strength of testing group was higher than control group (p<.05). - The environmental condition was influenced on the performance of the sealant. The testing etching method modified the capacity of the etching agent to penetrate into the pits and fissures, and simultaneous enhance their efficiency in vitro condition.

• Restorative Dentistry and Endodontics
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• v.42 no.3
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• pp.206-215
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• 2017

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide ($Al_2O_3$) particles at different pressures. Materials and Methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and ${\chi}^2$ tests (${\alpha}=0.05$). Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.4
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• pp.791-799
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• 1996

The purpose of this study was to compare the shear bond strength of adhesion bridge by various resin cements. One hundred and foully 1st premolars were used. The teeth were cut below 2mm from CEJ and the coronal portions were used. The coronal portions were embeded with the acrylic resin and trimmed with sic paper until the flat plane with ${\phi}$ 4mm above acrylic resin sticks in height 5mm were casted with nonprecious metal and the using surfaces were treated with sic paper from #200 to #1200 and polished with alminum oxide paste. And then, the using surfaces were sandblasted and treated with the electrochemical etching. The teeth were divided into three groups of fourty two each. In group I, teeth and specimens were cemented with Panavia 21 In group II, teeth and specimens were cemented with Superbond In group I, teeth and specimens were cemented with All-Bond & composite resin cement Each group was subdivided into three subgroups according to the storage period ; one-day storage, fifteen-day storage, and thirty-day storage. The special jig was made. Then, the specimen and jig were mounted to Instron Universal Testing Machine and the failure were measured. The results were as follows. 1. There was statisfically significant difference between the failure loads of group I and group II and III after one day storage(P<0.01), 2. There was statisfically significant difference between the failure loads of group II and group I and III and between group I and group III at fifteen day storage(P<0.01). 3. There was statisfically significant difference between the failure loads of group I and II and group III after thirty day storage(P<0.01). 4. There was statisfically significant difference between the failure loads of one day storage and fifteen and thirty days storages in group III (P<0.01).

• KCI Concrete Journal
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• v.14 no.1
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• pp.15-22
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• 2002

Stresses that develop due to differential shrinkage between polymer modified cement mortar (PM) and Portland cement concrete (PCC) in a repaired concrete beam at early ages were investigated. Interface delamination or debonding of the newly cast repair material from the base is often observed in the field when the drying shrinkage of the repair material is relatively large. This study presents results of both experimental and analytical works. In the experimental part of the study, development of the material properties such as compressive strength, elastic modulus, interface bond strength, creep constant, and drying shrinkage was investigated by testing cylinders and beams for a three-week period in a constant-temperature chamber. Development of shrinkage-induced strains in a PM-PCC composite beam was determined. In the analytical part of the study, two analytical solutions were used to compare the experimental results with the analytically predicted values. One analysis method was of an exact type but could not consider the effect of creep. The other analysis method was rather approximate in nature but the creep effect was included. Comparison between the analytical and the experimental results showed that both analytical procedures resulted in stresses that were in fair agreement with the experimentally determined values. It may be important to consider the creep effect to estimate shrinkage-induced stresses at early ages.

• Advances in aircraft and spacecraft science
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• v.1 no.1
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• pp.1-14
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• 2014

Physico-chemical changes of the plasma modified titanium alloy [Ti-6Al-4V] surface were studied with respect to their crystallographic changes by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM).The plasma-treatment of surface was carried out to enhance adhesion of high performance nano reinforced epoxy adhesive, a phenomenon that was manifested in subsequent experimental results. The enhancement of adhesion as a consequence of improved spreading and wetting on metal surface was studied by contact angle (sessile drop method) and surface energy determination, which shows a distinct increase in polar component of surface energy. The synergism in bond strength was established by analyzing the lap-shear strength of titanium laminate. The extent of enhancement in thermal stability of the dispersed nanosilica particles reinforced epoxy adhesive was studied by Thermo Gravimetric Analysis (TGA), which shows an increase in onset of degradation and high amount of residuals at the high temperature range under study. The fractured surfaces of the joint were examined by Scanning electron microscope (SEM).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.13-20
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• 2008

This paper describes the methods of spacer-fabrication for wafer-level CIS(CMOS Image Sensor) assembly. We propose three methods using SU-8, PDMS and Si-interposer for the spacer-fabrication. For SU-8 spacer, novel wafer rotating system is developed and for PDMS(poly-dimethyl siloxane) spacer, new fabrication-method is used to bond with alignment of glass/PDMS/glass structure. And for Si-interposer, DFR(Dry Film Resist) is used as adhesive layer. The spacer using Si-interposer has the strongest bonding strength and the strength is 32.3MPa with shear.