• 대한소아치과학회지
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• 제29권3호
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• pp.469-477
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• 2002

복합레진의 중요한 임상적 단점은 낮은 마모 저항성이며, 이와 관련된 하나의 인자로 수복물의 표면하 분해(subsurface degradation)가 고려되고 있다. 본 연구에서는 알카리성 용액(0.1N NaOH)에 현재 구치부 수복에 많이 이용되는 Z100(3M), Clearfil AP-X(Kuraray), Tetric Ceram(Vivadent)의 3종의 복합레진과 흐름성이 뛰어난 Aeliteflo(Bisco) 등 4종의 광중합형 레진을 보관하였을 때 각 제품의 분해저항성을 평가하고자 하였다. 분해저항성은 다음의 지표를 근거로 평가하였다. 1) 무게손실 - NaOH 용액에 노출 전후의 무게 측정, 2) Si 농도 - 시편을 제거한 용액은 ICF-AE분석기를 통하여 용액내로 용출된 Si 이온 정도 평가, 3) 분해층 깊이 - 용액에 보관한 시편을 연마하여 SEM을 이용하여 분해층의 깊이(${\mu}m$)를 측정하여 다음과 같은 결과를 얻었다. 1. 각 제품의 무게손실량은 Z100, TC, CL, AE 순으로 많았으며, AE, CL군과 TC, Z100군 사이에 유의한 차이가 있었다(p<0.05). 2. 각 제품의 표면하 분해층 깊이는 Z100, TC, CL, AE 순으로 깊었으며, AE. CL군과 Z100군 사이에 유의한 차이가 있었다(p<0.05). 3. 각 제품으로부터 용출된 Si 양은 Z100군이 가장 많고, AE, CL, TC순으로 많았다. 4. 무게손실량과 표면하 분해층 깊이 사이에 비교적 높은 상관관계를 보였다(r=0.71, p<0.05).

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.46-50
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• 2015

The cable degradation process is largely divided into three steps; Step 1 : Thermal degradation, Step 2 : Weibull degradation, Step 3 : Partial discharge. it is progress in step order. This article aims to explain the process of cable degradation using the method of insulation resistance and accordingly to compose and manufacture a system of measuring the life of electrical cable. Before measuring the insulation resistance, a system of measuring the temperature and current of cables was made, and the established system was installed for test on the site of a power plant to collect the measured data. The current sensor was used TFC30P80A-CL420, and temperature sensor was used the DK-1270 PT100 sensor as RTD sensor. When measured the temperature and the load current at the same position, was confirmed that in case of the load current value was high, also temperature value high. Therefore, the correlation between load currents and temperature was verified, and the analysis of diagnostic data was evaluated, which could be utilized in identifying the fault condition of cable systems.

• Journal of Microbiology and Biotechnology
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• 제8권4호
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• pp.388-398
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• 1998

A bacterium which is resistant to both mercury and cadmium, and also capable of utilizing phenol as a carbon and energy source, was isolated from the Kumho River sediments near Kangchang Bridge, Taegu, Korea. The isolate was labeled Pseudomonas sp. KM10 and characterized. The bacteria grew in 4 mM $CdCl_2$and in $70{\mu}M$ $HgCl_2$. The bacteria efficiently removed over 90% of 1 g/l phenol within 30 h. In the presence of 1.250 g/l phenol, the growth of the microorganism was slightly retarded and the microorganism could not tolerate 1.5 g/l phenol. Curing of plasmid from the bacteria was carried out to generate a plasmidless strain. Subsequent experiments localized the genes for phenol degradation in plasmid and the genes for mercury resistance and cadmium resistance on the chromosome. Dot hybridization and Southern hybridization under low stringent conditions were performed to identify the DNA homology. These results showed significant homologies between the some sequence of the chromosome of Pseudomonas sp. KM10 and merR of Shigella flexneri R 100, and between the some sequence of the chromosome of Pseudomonas sp. KM10 and cadA of Staphylococcus aureus pI258. The mechanism of cadmium resistance was efflux, similar to that of S. aureus pI258 cadA, and the mechanism of mercury resistance was volatilization, similar to that of S. flexneri R100 mer.

• 대한소아치과학회지
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• 제30권3호
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• pp.530-539
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• 2003

본 연구에서는 4종의 복합레진(Palpique Estelite, Filtek P 60, Spectrum, Charisma)을 선택하였다. 각 제품당 5개의 시편을 제작하여 무게 측정을 한 후, NaOH 용액에 2주 동안 보관하였고 1.23% HCl로 중화하고 세척, 건조시켜 무게 측정을 하였다. 주사전자현미경과 공초점 레이저 주사현미경으로 복합레진의 분해층 표면과 분해깊이를 관찰하였고, 분해 저항성은 용액내로 용출된 Si, Al, Ba의 농도를 근거로 평가하여 다음과 같은 결과를 얻었다. 1. 각 제품의 무게손실량은 Palpique Estelite가 가장 많았고, Filtek P 60, Charisma, Spectrum 순이었다. 2. 각 제품의 표면하 분해층 깊이는 Filtek P 60이 가장 깊었고, Charisma, Palpique Estelite, Spectrum 순이었다. 3. Si 용출량은 Charisma가 가장 많았고, Spectrum, Palpique Estelite, Filtek P 60 순이었다. 4. 무게손실과 분해층 깊이 사이에는 높은 상관관계를 보였다(r=0.704, p<0.05). 5. 주사전자현미경 관찰시 NaOH용액에 보관한 후 레진 기질과 충전제 사이의 결합의 파괴 양상인 분해층 표면을 관찰할 수 있었고 공초점 레이저 현미경 관찰시 레진의 분해층 깊이를 관찰할 수 있었다.

• Corrosion Science and Technology
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• 제5권5호
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• pp.177-180
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• 2006

The anticorrosive performance of epoxy coating was examined by using the hygrothermal cyclic test and the degradation mechanism of the coating was investigated by using the AC impedance method. The relationship between the results obtained from different tests was studied. It was revealed that the hygrothermal cyclic test can be used as an effective acceleration test for the degradation of organic coating. It was also found in hygrothermal cyclic test that the epoxy coatings have the resistance to stresses at some extent. The degradation of organic coating seems to be caused by the decrease of resistance of coating and the increase of both capacitance and free volume in the organic coating.

• 대한소아치과학회지
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• 제29권3호
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• pp.430-438
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• 2002

본 연구에서는 Prodigy(Kerr, USA), Vitalescence(Ultradent, USA), Z 250(3M, USA), Filtek flow(3M, USA)의 4종의 복합레진을 사용하여 각 제품의 분해저항성을 평가하고자 하였다. 무게손실, 표면하 분해층 깊이, 용출된 Si 농도를 기준으로 각 레진의 분해저항성을 평가하여 다음과 같은 결과를 얻었다. 1. 무게손실량은 Prodigy와 Vitalescence사이, Z 250과 Filtek flow사이에는 차이를 보이지 않았으며 전후 제품군 간에는 차이를 보였다(p<0.05). 2. 분해층 깊이는 Z 250, Filtek flow, Prodigy, Vitalescence순으로 감소하였으며, 네가지 제품간에는 유의한 차이를 보였다(p<0.05). 3. Si 용출량은 Filtek flow, Z 250, Prodigy, Vitalescence 순으로 감소하였으며, 각 제품 간에는 유의한 차이를 보였다(p<0.05). 4. 각 제품의 무게손실과 분해층 깊이 사이(r=0.714, p<0.05), 무게손실과 Si 용출량 사이(r=0.770, p<0.05), 분해층 깊이와 Si 용출량 사이 (r=0.930, p<0.05)에는 높은 상관관계를 보였다. 5. 주사전자현미경 관찰시 NaOH 용액에 보관한 후 레진 기질과 필러 사이의 결합의 파괴를 관찰할 수 있었다. 6. 공촛점 레이저 현미경 관찰시 NaOH용액에 보관한 후 레진의 분해층 깊이를 관찰할 수 있었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1361-1366
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• 2008

Failure mechanism of the poor contact is analyzed on the basis of used connectors and this poor contact of connectors is reappeared by the new forced fretting wear method. As the result of failure analysis and reappearance, fretting wear and corrosion of the contact interface causes the contact resistance degradation and the poor contact of connectors. The amount of degradation depends on the fretting stroke. Changes in contact resistance of static contacts are likely to be small and gradual, while motions of contact interface may result in larger and discontinuous changes in resistance and voltage. This voltage drop by fretting motions is large enough to cause the distortion of sensor signal and mis-working of electric components.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.117-120
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• 1999

The relationship between the DC degradation characteristics of the ZnO varistor and the ambient sintering-process is investigated in this study. ZnO varistors made of Matsuoka's composition were fabricated by standard ceramic techniques. The ambient sintering-process is performed at the extraordinary electrical-furnace which is equipped with the vacuum system. The Gas of sintering process was oxygen, nitrogen, argon, air respectively. The microstructure of ZnO varistors be made use of SEM equipment. The condition of DC degradation tests were conducted at $115\pm2^{\circ}C$ for periods up to 13 h. Current-voltage analysis is used to determine nonlinear coefficients($\alpha$). Resistance-frequency and capacitance-frequency analysis are accomplished to the understanding of electrical properties as DC degradation test. From above analysis, it is found that the ZnO varistor sintered in oxygen atmosphere showed superior properties at the DC degradation test.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1590-1592
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• 2000

The time to tracking breakdown of treated filled specimen is longer than untreated filled specimen. And, after the RWDT, the surface of specimen by adding untreated filler appeared heavy erosion. It was found that the addition to surface treated filler. the better tracking resistance. In the RWDT, the breakdown specimen is not affected by the dry flashover voltage. despite the fact that the surface degradation of tracking test has different state on each specimen. This suggests that wet flashover voltage play an important role in evaluating of tracking and erosion on the surface degradation in tracking test. And, the flashover voltage of specimen under wet conditions are greatly affected by the salt concentration and degree of degradation by the RWDT. Because of hydrophobicity and degree of degradation by the RWDT, the flashover voltage of treated filled specimen is higher than that of untreated filled specimen. Different types of specimen may have different hydrophobicity and their surface state under contaminated conditions may not be the same. It is assumed that this phenomenon is related to the decrease in hydrophobicity of the surface of the materials.

• Corrosion Science and Technology
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• 제8권5호
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• pp.203-207
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• 2009

Electrochemical methods have been widely used to study the performances and mechanisms for the degradation of organic and inorganic coatings. In this study, EN(Electrochemical noise) measurement was applied to the protective properties and review the parameters analyzed noise signals in the time and in the frequency domain for epoxy resin based coated steels during exposure to hot sea water($40^{\circ}C$) and salt spray for 200 days. It was also found that $R_n$(Noise resistance), $R_{sn}$($f_{min}$)(Spectral noise resistance) and 2H(Hurst exponent) represented the performance of epoxy coated steels. $R_n$ can be determined as the ratio of the standard deviations of potential and current noise signals and is decreased to exposure time. Data qualities can be easily checked by PSD(Power Spectral Density) plot and $V_{psd}$, $I_{psd}$ and $R_{sn}$($f_{min}$) is useful to research the protective performances and mechanisms of coated steels. Hurst exponent represents the degradation of coated steels. But, it is difficult to directly apply the protective criterion to the evaluation of epoxy coated steels used the shipbuilding processes.