• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.452-459
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• 2006

Competition will usually develop between the opposing walls as the restorative resin shrinks during polymerization. Magnitude of this phenomenon may be depended upon cavity configuration and volume. The purpose of this sturdy was to evaluate the effect of cavity configuration and volume on microleakage of composite resin restoration that has margins on the enamel site only. The labial enamel of forty bovine teeth was ground using a model trimmer to expose a flat enamel surface. Four groups with cylindrical cavities were defined, according to volume and configuration factor(Depth x Diameter / C-factor) - Group I : 1.5 mm ${\times}$ 2.0 mm / 4.0, Group II : 1.5 mm ${\times}$ 6.0 mm / 2.0, Group III : 2.Omm ${\times}$ 1.72 mm / 5.62, Group IV : 2.0 mm ${\times}$ 5.23 mm / 2.54. After treating with fifth-generation one-bottle adhesive - BC Plus$^{TM}$ (Vericom, AnYang, Korea), cavities were bulk flted with microhybrid composite resin - Denfill$^{TM}$ (Vericom). Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Specimens were thermocycled 500 times between 5$^{\circ}$C and 55$^{\circ}$C for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (${\mu}$A) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. The results were as follows: 1. Small cavity volume showed lower microleakage score than large one, however, there was no statistically significant difference. 2. There was no relationship between cavity configuration and microleakage. Factors of cavity configuration and volume did not affect on microleakage of resin restorations with enamel margins only.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.198-198
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• 2004

압전 구동기는 여러 가지 적용에 있어서 높은 응답 속도와 큰 힘, 작은 크기 둥의 장점을 가지고 미세 구동에서 독보적인 위치를 차지하고 있다. 하지만, 히스테리시스, 크？ 등의 압전 소자 자체의 비선형성과 이의 구동을 위한 증폭기 등의 한계로 압전 소자의 동적인 특성은 비교적 열악한 것으로 알려져 있다. 특히, 구동 속도가 빨라질 수록 히스테리시스 곡선의 모양이 달라게 되어 구동 궤적의 정확한 예측이 어려우며, 증폭기의 최대 발생 전류가 충분치 않을 경우 압전 구동기가 지령치를 따르지 못하게 된다.(중략)

• Electrical & Electronic Materials
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• v.4 no.4
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• pp.293-303
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• 1991

소결 후 냉각 및 Annealing이 Bi(Pb)SrCaCuO계 초전도체의 특성에 미치는 영향에 대해 연구하였다. 소결 후 시편을 500[.deg.C]에서 5[hr] Annealing함으로써 1)미세조직이 치밀화 되었으며 고온상의 체적비가 증가하였다. 2)임계온도 및 전류밀도 특성이 향상되었다.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.85-91
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• 2004

최근 MEMS 기술의 비약적인 발달로 인해 미세 가공 기술을 이용하여 높은 종횡비를 갖는 각종 전기소자나 엑츄에이터 들의 제작에 관한 연구가 활발히 진행되고 있다. 금속 구조물을 형성하기 위해서 전해도금의 방식이 널리 쓰여지고 있는데, 이에 본 논문에서는 니켈 전해도금을 위한 장치를 제작하고, 온도, pH, 교반 및 전류밀도 등에 따른 영향을 조사하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.1027-1028
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• 2010

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.83-88
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• 2018

The electromigration (EM) tests were performed at $150^{\circ}C$ with $1.5{\times}10^5A/cm^2$ conditions in order to investigate the effect of non-conductive film (NCF) trap on the electrical reliability of Cu/Ni/Sn-Ag microbumps. The EM failure time of Cu/Ni/Sn-Ag microbump with NCF trap was around 8 times shorter than Cu/Ni/Sn-Ag microbump without NCF trap. From systematic analysis on the electrical resistance and failed interfaces, the trapped NCF-induced voids at the Sn-Ag/Ni-Sn intermetallic compound interface lead to faster EM void growth and earlier open failure.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.100-107
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• 2004

The nano or micro sized structures of conducting polymer had been prepared by synthesizing the desired polymer within the pores of template of nano or micro porous membrane filter. In this study, we had tried to fabricate conducting polymer microstructures on an electrode by using electrochemical deposition adopting template synthesis. Our attention was focused on two different things, attaching template on the electrode and fabricating microstructures only at limited areas of the electrode. A conducting polymer, PEDiTT (poly 3,4-ethylenedithi-athiophene) solution was blended with PVA(polyvinyl alcohol) solution and used as an conducting adhesive. After attaching template membrane, the electrode were immersed in 0.5M pyrrole in 0.1M KCI solution, and electrochemical polymerization was performed. The growth process of the microstructures studied by SEM. The electrochemical fabrication of conducting polymer was performed by using two-electrode system. A large working electrode and a micro scale disc electrode were used for the confined area synthesis. Polymerization potential was 4V in an electrolytic solution made of KCI in deionized water. The optimum polymerization conditions were, i.e. (4V/100sec) for $250{\mu}m$ electrode and (6V/30 sec) for $10{\mu}m$ electrode.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.137-144
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• 1998

High-temperature superconducting joints between 61 filaments of Bi-2223 tapes were fabricated by chem-ical corrosion and repeated thermomechanical process. The silver sheath of the superconducting tape was chemically removed using chemical etchant(NH4OH:H2O2=1:1) from one side of each tape without altering the form of lap joint. The joined region was formed by uniaxial pressing and a series of thermomechanical process and then subjected to properties measurement and microstructural analysis. The critical current(Ic) variation and I-V characteristics along the joint were mesured with several configuration of proble points. Ic value of the transition region of the joint inthe multifilament tape which limit the total current carring capacity of the superconducting tape was higher than that of monofilament tape. But the transition ex-ponent n-value of the multi-filament tape was lower than that of monofilament wire due to the interaction of the individual superconducting core of the multi-filament. The critical current through the joint area was improved by respeated press and reaction annealing treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.334-338
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• 1999

Porous silicon layers were fabricated with various conditions of HF concentration and current density. And their masses were measured. From these data, the porosity and fractal dimension were estimated and analyzed. We found that the porosity was proportional to the current density when the anodic reaction time was fixed and the constant values of fractal dimension could be estimated from a series of data with fixed HF concentration. The values of fractal dimension were decreased with increasing HF concentration. The obtained porosity and fractal dimension were compared with the 2-dimensional computer simulation based on diffusion limited deposition model. According to the simulation, the porosity was proportional to the diffusion length and the fractal dimension was inversely proportional to the diffusion length. Since, the diffusion length is proportional to current density and inversely proportional to base concentration, our experimental data qualitatively agreed with the results from the simulation. The porosity obtained by experiments, however, was not consistent with the results by simulation.

• Journal of Sensor Science and Technology
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• v.5 no.5
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• pp.1-10
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• 1996

Solar cells made of the edge-defined film-fed growth Si are characterized using current-voltage, surface photovoltage, electron beam induced current, electron microprobe, scanning electron microscopy, and electron backscattering. The weak temperature dependence of the I-V curves in the EFG solar cells is due to a voltage variable shunt resistance giving higher diode ideality factors than the ideal one. The voltage variable shunt resistance is modeled by a modified recombination mechanism which includes carrier tunneling to distributed impurity energy states in the band gap within the space-charge region. The junction integrity and the substrate quality are characterized simultaneously by combining I-V and surface photovoltage (SPV) measurements. The diode ideality factors and the surface photovoltages characterize the junction integrity while the SPV diffusion lengths characterizes the substrate quality. Most of the measured samples show the voltage variable shunt resistance although how serious it is depends on the solar cell efficiency. The voltage variable shunt resistance is understood as one of the most important factors of the degradation of EFG solar cells.