• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.14-21
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• 2000

This paper presents the results of performance evaluation of silicone treatment technique which was developed for the insulation rehabilitation of water tree aged XLPE power cables. We treated the water tree aged 325 [$\textrm{mm}^2$] CN/CV cables with silicone, and then analyzed the degree of insulation rehabilitation as a function of time. AC breakdown test was conducted to evaluate insulation rehabilitation. The diagnosis test using relaxation current measurement and the characteristic analysis of insulation were also performed to estimate silicone treated cable. AC breakdown strength of silicone treated cable for one year was increased, resulting from the chemical reaction between silicone fluid and water. This experiment showed that the silicone treatment technique was effective for insulation rehabilitation of the water tree aged cables.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.9
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• pp.718-726
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• 1998

J-E 특성 AC 임피더스 분석 그리고 주파수- 전도 특성들을 실험하여 임펄스 전류 서지가 ZnO 바리스터의 열화(degradation)에 미치는 영향을 고찰하였다. ZnO 바리스터 시편에 임펄스 전류(300A/$cm^24, 8/50$\mu s$)를 인가시킨 결과, 입계(grain boundary) 특성을 나타내는 비선형계수 $\alpha$와 E\ulcorner\ulcorner의 값은 크게 감소하였으나, 입자 특성을 나타내는 E_{100A}, E_{300A}$ 값에서는 큰 변화가 없었다. 이러한 열화 현상은 입계의 위치한 부성 전하 밀도, $N_s$의 감소에 한 쇼트키 장벽의 변화에 기인한 것으로 나타났다. 임펄스 서지에 의해 열화된 ZnO 바리스터는 AC 임피더스 분석에서 현저한 non-Debye 특성을 보이며, 이는 병렬 RC 네트워크로 모델링한 Cole-Cole 완화 관계식으로 입계의 열화 특성을 잘 설명할 수 있었다. 주파수-전도도 관계를 검토한 결과 Zno 바리스터는 호핑 전도(hopping conduction),\$sigma(\omega)\varpropto\omega^{\eta}$ 특성을 나타내면, 임펄스 서지가 인가된 이후 n 값이 감소하였다. 이는 임펄스 서지에 의해 입RP 결합 상태(defect states)가 호핑 전도가 발생하기 쉽고 다중(multiple)호핑에 의한 전도 메커니즘을 갖는 것으로 고찰되었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.71-77
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• 2010

The concrete structure's durability and integrity is reduced owing to various deterioration phenomena. Therefore, it is important to prevent the deterioration phenomena. This study inquired into the various experimental results of specimens with different dilution concentration and impregnation time by the each solution to present the economic and efficient using method of the inorganic surface penetration agents. As a results, the reasonable dilution concentration and impregnation time of colloidal silica solutions are 15% and 5 minute and for the sodium alumina silicate solutions are 17% and 10 second.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.79-84
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• 1993

철근의 부식은 철근 콘크리트 구조물에 있어서 심각한 열화현상을 유발할 수 있으며 최근 들어 이로 인한 피해가 많이 보고되고 있다. 이와 같은 부식의 억제방안 중 철근에 직접 에폭시를 도막하는 것이 가장 효과적인 것으로 알려져 있다. 그러나 이 경우 에폭시 도막에 따른 부착성능의 저하가 우려되는 바 본 연구는 철근부식방지를 위해 에폭시를 도막한 철근의 부착특성을 고찰하기 위해 수행되었다. 주된 변수는 콘크리트 압축강도, 부착길이, 에폭시 도막두께이며 각 변수별로 부착특성의 변화를 관찰하였고 이를 통해 에폭시도막 철근의 사용성을 검토하였다. 본 실험결과에 기초하여 부착강도 예측식을 제안하였고 실험결과와 예측치를 비교하였다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.05a
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• pp.134-140
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• 2002

현재 국내에는 총 2,500개소의 철도교가 있는데, 이 중에서 강교량이 연장이 차지하는 비율은 약 48％를 차지하고 있으며, 교량별 구성비는 그림 1.1(a)와 같다 또한 강교량의 공용년수에 따른 분포양상은 그림 1.1(b)에서 나타낸 바와 같이 공용기간이 50년 이상인 교량이 전체교량의 약 46％를 차지하고 있다.(중략)

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.140-146
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• 2017

It is laser induced breakdown spectroscopy(LIBS) that enables qualitative and quantitative analysis of the elements contained in unknown specimen by comparing the wavelength characteristics of each element obtained from the spectral analysis of the standard specimen with the wavelength analysis results from unknown specimens. In this study, the applicability of LIBS to the analysis of major deterioration factors affecting concrete durability was experimentally analyzed. That is, the possibility of applying LIBS to the diagnosis of concrete deterioration by studying the quantitative detection of harmful deteriorating factors on chloride, sulfate and carbonated mortar specimens using LIBS was studied. As a result of LIBS test for each chloride and sulfate specimen, the LIBS spectral wavelength intensity of chlorine and sulfur ions increased linearly with increasing concentration. Carbon ion LIBS spectral wave intensities of carbonated specimens increased nonlinearly over the duration of carbonation exposure. From the above results, it can be partially confirmed that LIBS can be applied to the diagnosis of concrete deterioration. In case of concrete carbonation, it is presumed that carbon content is contained in the cement itself and is different from the detection of chloride and sulfate specimen. Therefore, it is considered that more various parameter studies should be performed to apply LIBS to concrete carbonation.

• Elastomers and Composites
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• v.40 no.3
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• pp.166-173
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• 2005

Effect of thermal aging on the weight loss and water absorption of epoxy adhesives was investigated in the presence of three types of different hardeners, such as D-230, G-5022, and HN-2200. Thermal and mechanical properties of the cured epoxy resins were also studied througth the glass transition temperature and shear adhesion strength measurements. Weight losses of DGEBA/D-230 and DGEBA/HN- 2200 systems were not varied. However, the weight of DGEBA/G-5022 system was significantly decreased with increasing the thermal aging time. The water absorption of the specimens was increased as the thermal aging time increased except that using G-5022. DEGBA/HN-2200 system showed higher $T_g$ value than those of other systems, due to the formation of the fine three-dimensional network structure containing aliphatic ring. Shear adhesion strength of all systems was increased with increasing the thermal aging tine, which is attributed to increased degree of cure and fine three-dimensional network structure formation. And $T_g$ values and shear adhesion strength of all specimens exposed to water was decreased as the immersion time increased.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.243-260
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• 2018

A literature review on the effects of high temperature and radiation on radiation shielding concrete in Spent Fuel Dry Storage is presented in this study with a focus on concrete degradation. The general threshold is $95^{\circ}C$ for preventing long-term degradation from high temperature, and it is suggested that the temperature gradient should be less than $60^{\circ}C$ to avoid crack generation in concrete structures. The amount of damage depends on the characteristics of the concrete mixture, and increases with the temperature and exposure time. The tensile strength of concrete is more susceptible than the compressive strength to degradation due to high temperature. Nuclear heating from radiation can be neglected under an incident energy flux density of $10^{10}MeV{\cdot}cm^{-2}{\cdot}s^{-1}$. Neutron radiation of >$10^{19}n{\cdot}cm^{-2}$ or an integrated dose of gamma radiation exceeding $10^{10}$ rads can cause a reduction in the compressive and tensile strengths and the elastic moduli. When concrete is highly irradiated, changes in the mechanical properties are primarily caused by variation in water content resulting from high temperature, volume expansion, and crack generation. It is necessary to fully utilize previous research for effective technology development and licensing of a Korean dry storage system. This study can serve as important baseline data for developing domestic technology with regard to concrete casks of an SF (Spent Fuel) dry storage system.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1702-1704
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• 1997

본 논문은 HDPE 필름의 절연성능을 평가하기 위하여 절연파괴강도의 결과를 Weibull분에 적용하였다. 각 절연파괴강도의 Weibull분포로부터 형의 모수를 구하였다. 또한 Weibull분포의 활용은 2개 및 3개의 모수법을 각각 적용시켜 절연파괴강도의 평가를 하였다. HDPE 필름을 열화시켜, 형의 모수변화를 비교하였다. 이와같은 Weibull분포의 활용은 절연성능과 수명의 평가를 통계적으로 평가코져 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.415-424
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• 2001

The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials by nondestructive evaluation is strongly desired. In this paper, the use of guided wave was suggested for the evaluation on thermally damaged 2.25Cr-1Mo steel as an alternative way to compensate for limitations of fracture tests. The observation of microstructure variations of the material including carbide precipitation increase and spheroidization near grain boundary was conducted and the correlation with the guided wave features such as energy loss ration and group velocity changes was investigated. Through this study, the feasibility of ultrasonic guided wave evaluation for thermally damaged materials was explored.