• 한국전기전자재료학회논문지
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• 제13권11호
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• pp.938-942
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• 2000

Radiation effects on dielectric properties of low density polyethylene(LDPE) were investigated using the various measurements of FT-IR, gel content and elongation at break. FT-IR spectra showed that polar groups were comprised in LDPE due to radiation treatment. It was also confirmed that the formation of polar groups on LDPE caused the increased dielectric properties such as permittivity and tan $\delta$. However, in this study, any evidence of decreasing permittivity was not found although the morphological change of LDPE could be identified from the increasing gel content and the decreasing elongation.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.978-983
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• 2014

The polymer nano composite possess good priority recently for engineering applications. Especially the electrical insulating materials attract the high performance of nano composites. In this work the ballmill synthesiation process of nano sized Alumina ($Al_2O_3$), the preparation of new nano composite material with an content of enamel and synthesized Alumina as 1wt%, 3wt% and 5wt%. Experimental investigation has been carried out for the prepared nano composites materials with respect to dielectric parameter measurements such as dielectric loss (tan ${\delta}$), dielectric constant (${\varepsilon}$), dielectric strength under various temperature. The partial discharge level also measured for all the samples and the PD inception voltage is also observed and compared. Weight loss of the material has been analyzed through TGA. It has been experimentally proved that 3wt% of Alumina nano filler added enamel has significant improvement in the dielectric and thermal properties.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.636-639
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• 1993

This paper is discribed the results of insulation characteristic tests that are DC leakage current, test, tan${\delta}$ test, AC breakdown test and observation of tree in the used 6.6kV CV cables. In the correlation of these tests, the tan${\delta}$ test stands for the main deterioration factor of cable insulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.169-172
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• 2000

In this paper, we evaluated the mechanical and dielectric properties of LDPE depend on $Co_{60}$${\gamma}$-irradiation doses. The chemical analyses for FT-IR, gel content, the mechanical properties for elongation at break and the dielectric parameters for permittivity, tan$\delta$ were discussed as a function of irradiation doses. Test result presented that elongation at break of irradiated LDPE was inversely proportional to gel content. For dielectric analyses, permittivity showed a salient characteristic for various irradiation doses, it was related to polar groups caused radiation degradation and tan$\delta$ of irradiated LDPE increased with irradiation doses.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 제4회 영호남학술대회 논문집
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• pp.64-68
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• 2002

According to the increasing power demand for the future construction of many underground cables will be required. However, construction of new ducts for power cables will be more difficult. Therefore, research work for realizing the high temperature superconducting(HTS) cable has advanced, where the development of electrical insulating system at cryogenic temperature is one of the major researches. For an electrical insulation design of HTS cable, it is important to understand not only breakdown but also partial discharge and dielectric loss($tan{\delta}$) in liquid nitrogen/paper composite insulation system. In this paper, we investigated breakdown characteristics in liquid nitrogen/paper composite insulation system for the application to HTS cable. And, we studied the breakdown characteristics of the multi-layer and butt gap of the insulation papers in liquid nitrogen. Also, we measured dielectric loss($tan{\delta}$) of the mini-model Cable made of TERLAM IPP.

• Food Science and Biotechnology
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• 제15권3호
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• pp.474-477
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• 2006

Dynamic rheological properties of commercial 0.8, 1.0, and 1.2% gums [carboxylmethylcellulose (CMC), guar gum, hydroxypropylmethylcellulose (HPMC), tara gum, and xanthan gum], which can be dissolved in cold water, were investigated by small-deformation oscillatory measurements. Magnitudes of storage (G') and loss (G") moduli increased with increasing concentration of gum solutions except for xanthan gum. Guar gum exhibited greatest G' and G" values among all gums except for G' value at 0.8% concentration. Slopes of G' and G" decreased with increasing concentration of gum solutions except for xanthan gum. Tan ${\delta}$ (G"/G') values decreased with increasing concentration of gum solutions except for xanthan gum. Tan ${\delta}$ values of xanthan gum solutions were much lower than those of other gum solutions, indicating that xanthan gum solutions were predominantly more elastic than viscous.

• 고무기술
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• 제5권2호
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• pp.94-103
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• 2004

The present work describes modification of dual phase filler by electron beam irradiation in presence of multifunctional acrylates like trimethylol propane triacrylate (TMPTA) or silane coupling agent like bis (3-triethoxysilylpropyltetrasulphide) and in-fluence of the modified fillers on the physical properties of styrene-butadiene rubber (SBR) vulcanizates. Modulus at 300 % elongation increases whereas the tensile strength decreases with increase in radiation dose for the dual phase filler loaded styrene-butadiene rubber vulcanizates (SBR). However, modulus and tensile strength significantly increase, which is more, pronounced at higher filler loadings for TMPTA modified dual phase filler loaded SBR. These changes in properties are explained by the equilibrium swelling data and Kraus plot interpreting the polymer-filler interaction. Electron beam modification of the filler results in a reduction of tan ${\delta}$ at $70^{\circ}C$, a parameter for rolling resistance and increase in tan ${\delta}$ at $0^{\circ}C$, a parameter for wet skid resistance of the SBR vulcanizates. Finally, the influence of modified fillers on the properties like abrasion resistance, tear strength and fatigue failure and the improvement in the properties have been explained in terms of polymer-filler interaction.

• Nuclear Engineering and Technology
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• 제6권1호
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• pp.14-22
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• 1974

아노다이징 전압이 탄탈양극산화피막의 주파수 특성에 미치는 영향을 다음 임피단스 식을 이용하여 분석하였다. (equation omitted) 여기서 $R_{f}$, $C_{f}$는 각각 양극산화피막의 등가직렬저항, 등가직련용량, 유전 손실이다. 파라데타 P, $\tau$$_{ο}$, $\tau$$_{\omega}$, Co는 다음과 같이 정의된다. P=(d-w)/w, $\tau$$_{ο}$=$textsc{k}$$\rho$$_{ο}$, $\tau$$_{\omega}$=$textsc{k}$$\rho$$_{\omega}$, $C_{ο}$=$textsc{k}$A/d 여기서 d는 양극산화피막의 두께, $\omega$는 화산층의 두께, $\rho$$_{ο}$는 금속과산화물의 계면에서의 산화물의 비저항, $\rho$$_{omega}$는 앙극산화피막의 진성영역에서의 비저항, A는 양극산화 피막의 면적이며, $textsc{k}$=0.0885$\times$$10^{-12}$ $\times$유전상수(in farad/cm). 등가직렬용량의 주파수에 따른 변화와 유전손실은 아노다이징전압이 증가함에 따라 감소하였다. 이 현상은 산화피막의 화산충의 두께가 아노다이징전압이 증가함에 따라 약간 증하는반면 선화피막 전체두께는 아노다이징전압에 비례하여 증가한다는 사실 때문이다. 실험측정치가 tan$\delta$$_{f}$=0.682$\Delta$ $C_{f}$ 관계식으로부터 부로 이탈하는것을 위의 임피단스식에 바탕을 두고 검토하였다. 여기서 $\Delta$ $C_{f}$는 0.1과 1KHZ 사이에서의 용량변화이다.이다.다.

• Transactions on Electrical and Electronic Materials
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• 제10권4호
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• pp.125-130
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• 2009

The clamping voltage characteristics and accelerated aging behavior of CoCrTb-doped Zn/Pr-based varistors were investigated for different sintering temperatures. The best clamping voltage characteristics were obtained for the varistors sintered at $1330^{\circ}C$, with a clamping voltage ratio (K) of 1.63 at a surge current of 5 A and 1.75 at a surge current of 10 A. The varistors sintered at $1330^{\circ}C$ exhibited the highest stability, with -0.1% in $%{\Delta}E_{1\;mA}$, -0.2% in $%{\Delta}{\alpha}$, and +15.5% in $%{\Delta}J_L$ for E-J characteristics under a stress state of 0.90 $E_{1\;mA/120^{\circ}C$ /24 h. Furthermore, it exhibited $%{\Delta}{\varepsilon}_{APP}$' of -0.7% and $%{\Delta}tan{\delta}$ of +5.7% for dielectric characteristics under the same stress state.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.29-37
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• 1996

A ductile fracture criterion, which has already proposed, namely, ($\Delta$1/1o)f at $\Delta$$\sigma$ m=(($\Delta$1/1o)f+(-1/tan$\theta$)$\Delta$$\sigma$m(where ($\Delta$1/1o)f is fracture elongation, $\Delta$$\sigma$m is mean stress variation) was made use of to study the working limit in axisymmetric extrusion. The present investigation is concerned with the application of theory on flow and fracture to the prediction of workability of materials in axisymmetric bar extrusion, with special reference to central bursting. The influenced of die geometry and manufacturing conditions on the central bursting are predicted.