• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.886-889
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• 2001

Silicone rubber is being used for the housing material of outdoor high voltage insulators such as composite insulator, bushing, surge arrestor and cable terminator because of good tracking and erosion resistance, good hydrophobicity and recovery of hydrophobicity and chemical stability. But, the leakge current occurs on surface of the composite polymeric insulation materials when the insulator is used for a long time with severe contaminative condition and it can lead the contamination flashover. So the leakage current is important to estimate the condition of the silicone rubber surface. In this paper, aging characteristics of silicone rubber used for outdoor insulation have been hydrophobicity of silicone rubber in salt fog chamber with average leakage current monitoring for observing the transformation of surface degradation properties of silicone rubber with different ATH(alumina trihydrate, A1$_2$O$_3$$.$3H$_2$O) filler contents. The experimental results show that a higher peak leakage current and to raise a long time for tracking with increasing amount of ATH by the salt fog and heat recycle ageing.

• 전기의세계
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• 제23권5호
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• pp.54-60
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• 1974

Proposals were mode on how to differentiate radiation effects in morphological phases of polyethylene and discussions were developed with the results obtained on a low density polyethylene, SOCAREX, specified by number average molecular weight; overbar Mn=5,400, density; 0.92, and degree of branch; 3.4/100 carbon atom, which was irradiated to Co$^{60}$ .gamma. ray at the dose rate of 0.5 Mrad/hr in ambient temperature under the pressure of 10$^{-5}$ Torr. or 1 atm. respectively. The effect to crystalline phase in possibly deduced from dose dependent variation of relative area between (110) and (200) peaks on X ray diffraction spectrum and that, the effects to amorphous phase can be understood through dose dependent relaxation behaviours of .betha. peak on internal friction characteristics of the specimen. The results obtained thus far indicate that, in crystalline phase, relative crystallinity shows a rather rapid decrease up to 20 Mrad with increasing dose, however, little change of crystallinity can be observed in the region between 20-200 Mrad, and degradation appears to be more predominant than crosslinking up to 60 Mrad. While in amorphous phase the indication also shows that degradation is only predominant up to 20 Mrad. Furthermore several correlations can be seen with amenable explanation between dose dependent behaviours observed in both phases.

• Elastomers and Composites
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• 제48권2호
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• pp.161-166
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• 2013

비등온 TGA 실험방법을 이용하여 가교 사이트가 서로 다른 chlorine cure-site ACM 고무와 carboxylic cure-site ACM 고무 두 종류에 대하여 열분해 거동을 연구하였다. 분해 반응이 최대인 점의 온도는 모든 승온 속도에서 carboxylic cure-site ACM 고무의 열분해 특성이 상대적으로 더 안정함을 보여 주었다. Kissinger의 해석 방법에 의한 활성화에너지는 chlorine cure-site ACM 및 carboxylic cure-site ACM 고무에 대하여 각각 118.6 및 105.5 kJ/mol로 나타났으며, Flynn-Wall-Ozawa의 해석방법에서의 전환율 0.1~0.2 범위의 평균과 유사한 값을 나타내었다. 반응차수 해석으로부터 두 시험편 모두 일반적인 고무와 유사한 다중 복합반응에 의하여 열분해 반응이 진행됨을 알 수 있었다.

• 한국해양공학회지
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• 제13권2호통권32호
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• pp.90-98
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• 1999

Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operationg conditions like high temperature and high pressure for an extended period time. Such material degradation lead to various component faliures causing serious accidents at the plant. Conventional measurement techniques such as replica method, electric resistance method, and hardness test method have such disadvantages as complex preparation and measurement procedures, too many control parameters, and therefore, low practicality and they were applied only to component surfaces with good accessibility. In this study, both artificial creep degradation test using life prediction formula and frequency analysis by ultrasonic tests for their preparing creep degraded specimens have been carried out for the purpose of nondestructive evaluation for creep damage which can occur in high-temperature pipelline of fossil power plant. As a result of ultrasonic tests for crept specimens, we confirmed that the high frequency side spectra decrease and central frequency components shift to low frequency bans, and bandwiths decrease as increasing creep damage in backwall echoes.

• Structural Engineering and Mechanics
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• 제49권6호
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• pp.775-792
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• 2014

Static loading tests were carried out in this study to investigate the effect of bar cutoff on the resistance of RC beam-column sub-assemblages under column loss. Two specimens were designed with continuous main reinforcement. Four others were designed with different types of bar cutoff in the mid-span and/or the beam-end regions. Compressive arch and tensile catenary responses of the specimens under gravitational loading were compared. Test results indicated that those specimens with approximately equal moment strength at the beam ends had similar peak loading resistance in the compressive arch phase but varied resistance degradation in the transition phase because of bar cutoff. The compressive bars terminated at one-third span could help to mitigate the degradation although they had minor contribution to the catenary action. Among those cutoff patterns, the K-type cutoff presented the best strength enhancement. It revealed that it is better to extend the steel bars beyond the mid-span before cutoff for the two-span beams bridging over a column vulnerable to sudden failure. For general cutoff patterns dominated by gravitational and seismic designs, they may be appropriately modified to minimize the influence of bar cutoff on the progressive collapse resistance.

• Journal of Microbiology
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• 제33권4호
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• pp.328-333
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• 1995

$\^$31/ P-NMR experiment was performed to detect phophonates (Pn) utilization and degradation in the several different C-P lyase mutants of E. coli and in E. aerogenes and the recombinants. The relative peak intensity (RPI) for the standard samples of 0.5 mM methylphosphonate (MPn) and 1.0 mM aminoethylphosphonate in glucose-MOPS medium showed 0.5 : 1.0 ratio. In the case of BW14329 (.DELTA.phnC-P, .delta.phoA), RPI did not change significantly after 24 hrs culturing, which means it nearly could not utilize Pn. In vivo $\^$31/ P-NMR spectrum of E. aerogens (BWKL 16627) during 3 hrs starvation showed two intense peaks at 0-2 ppm and at near-10 ppm which indicate intracellular orthophosphate (Pi) and pyrophosphate (PPi), respectively. Both of them might be released by degradation of inorganic polyphosphate pool. When MPn is supplied to the medium as an unique P source, Pi content in the cell has the constant, but PPi seems to be slightly decreased. Recombinants (BWKL 16954) grew slower than E. aerogenes in the glucose-MOPS media with various P sources. In vivo $\^$31/ P-NMR spectrum of recombinant did not show any intense signal in the cell. Surprisingly, under the cultivation adding with MPn, a few intense peaks in the region of Pi AND phospate monoester were detected.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.199-200
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• 2005

In this paper, the electrical characteristics and hot-carrier induced electrical performance degradations of high-voltage LDMOSFET fabricated by the existing CMOS technology were investigated. Different from the low voltage CMOS device, the only specific on-resistance was degraded due to hot-carrier stressing in LDMOS transistor. However, other electrical parameters such as threshold voltage, transconductance, and saturated drain current were not degraded after stressing. The amount of on-resistance degradation of LDMOS transistor that was implanted n-well with $1.0\times10^{13}/cm^2$ was approximately 1.6 times more than that of LDMOS transistor implanted n-well with $1.0\times10^{12}/cm^2$. Similar to low voltage CMOS device, the peak on-resistance degradation in LDMOS device was observed at gate voltage of 2.2V while the drain applied voltage was 50V. It means that the maximum impact ionization at the drain junction occurs at the gate voltage of 2.2V applying the drain voltage of 50V.

• 한국전기전자재료학회논문지
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• 제20권7호
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• pp.569-574
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• 2007

In this paper, the reliability (NBTI degradation: ${\Delta}V_{th}$) and device characteristic of nano-scale PMOSFET with plasma nitrided oxide (PNO) is characterized in depth by comparing those with thermally nitrided oxide (TNO). PNO case shows the reduction of gate leakage current and interface state density compared to TNO with no change of the $I_{D.sat}\;vs.\;I_{OFF}$ characteristics. Gate oxide capacitance (Cox) of PNO is larger than TNO and it increases as the N concentration increases in PNO. PNO also shows the improvement of NBTI characteristics because the nitrogen peak layer is located near the $Poly/SiO_2$ interface. However, if the nitrogen concentration in PNO oxide increases, threshold voltage degradation $({\Delta}V_{th})$ becomes more degraded by NBT stress due to the enhanced generation of the fixed oxide charges.

• 한국지형학회지
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• 제19권2호
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• pp.187-195
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• 2012

일본 홋카이도의 다이세츠산 국립공원은 지형 조건상 삼림한계를 넘는 고산대가 광범위하며, 지표지질은 침식에 취약한 화산쇄설물로 이루어져 있다. 또한 등산 성수기와 융설기가 시기적으로 겹치므로 답압, 융설수, 서릿발에 의한 토양침식이 등산로를 따라 활발하게 일어난다. 특히 융설수에 의한 노면 세굴과 서릿발에 의한 측벽 후퇴가 결합하여 등산로 단면이 크게 확대될 수 있으며, 세굴로 인하여 걷기 불편해진 등산로를 벗어나 걸음으로써 노면분기도 빈번하게 일어난다. 비탈면 구간에서 발생한 토사는 등산로 아래쪽으로 흘러내려와 노면뿐 아니라 주변 초지까지 매몰시키며 2차적인 훼손을 일으키고 있다.

• Advances in concrete construction
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• 제8권2호
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• pp.77-90
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• 2019

This paper aims to investigate vibration frequency decrease (vibration period elongation) of reinforced concrete (RC) structure with unreinforced infill wall and reinforced infill wall exposed to progressively increased artificial earthquake load on shaking table. For this purpose, two shaking table experiments were selected as a case study. Shaking table experiments were carried on 1:1 scaled prototype one bay one storey RC structure with infill walls. The purpose of this shaking table experiment sequence is to assess local behavior and progressive collapse mechanism. Frequency decrease and eigen-vector evolution are directly related to in-plane and out-of-plane bearing capacities of infill wall enclosure with reinforced concrete frame. Firstly, frequency decrease-damage relationship was evaluated on the base of experiment results. Then, frequency decrease and stiffness degradation were evaluated with applied Peak Ground Acceleration (PGA) by considering strength deterioration. Lastly, eigenvector evolution-local damage and eigenvector evolution-frequency decrease relationship was investigated. Five modes were considered while evaluating damage and frequency decrease of the tested specimens. The relationship between frequency decrease, stiffness degradation and damage level were presented while comparing with Unreinforced Brick Infill (URB) and Reinforced Infill wall with Bed Joint Reinforcement (BJR) on the base of natural vibration frequency.