• 한국전기전자재료학회논문지
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• 제15권3호
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• pp.244-252
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• 2002

The electrical and dielectric behavior fort DC accelerated aging stress of P $r_{6}$ $O_{11}$-based Zno varistors cnsisting of ZnO-P $r_{6}$ $O_{11}$-CoO-C $r_2$ $O_3$-E $r_2$ $O_3$ were investigated with sintering temperature in the range of 1325~1345$^{\circ}C$. The varistor ceramics with increasing sintering temperature were more densified. A more densified varistors leaded to high stability for DC accelerated aging stress. Furthermore, the stability for DC accelerated aging stress was increased with the leakage current and dtan $\delta$/dV decreasing in order of 1325longrightarrow1335longrightarrow1345longrightarrow134$0^{\circ}C$ in sintering temperature. It was found that the stability for DC stress is affected more greatly by the leakage current and dtan $\delta$/dV than the densification. It is considered that the stability of varistors for DC stress can be estimated by considering the factors, such as the densification, leakage current, and dtan $\delta$/dV. As a result, the varistor sintered at 134$0^{\circ}C$ exhibited the highest stability, with %$\Delta$ $V_{lmA}$=-1.54%, %$\Delta$$\alpha$=-2.49%, %$\Delta$ $I_{\ell}$=+240.68%, 5%$\Delta$tan$\delta$=+29.96%.96%.96%.%.

• 펄프종이기술
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• 제42권4호
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• pp.15-24
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• 2010

Many efforts to understand the deterioration processes of the beeswax-treated volume of "The Annals of Joseon Dynasty" have been made. However, most previous studies have focused on individual sample sheet of the beeswax-treated paper but not book volume format. In this study, humid cycling accelerated aging for duplicated beeswax-treated book volume and Hanji book volume were carried out to examine differences in the deterioration of different parts of each volume as well as between the two book volumes during the aging. As results, it is found that the deterioration rate for the beeswax-treated volume is higher than that for the Hanji book volume. Different parts in each volume show different magnitude of deterioration. In particular, outer sides in both beeswax-treated and Hanji book volumes, which are directly exposed to the air, are deteriorated more seriously than inner sides. It is also observed that inner sides are considerably deteriorated during the aging, implying that inner deterioration may have different mechanisms from outer deterioration.

• 한국염색가공학회지
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• 제29권3호
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• pp.155-161
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• 2017

In CPB(Cold-Pad-Batch) dyeing, the rubber of the padder roll is influenced by the heat, chemical and mechanical influences and thus aging of the padder roll rubber occurs. This study presents an accelerated thermal aging test of the CPB padder roll rubber with strong alkali conditions. Using Arrhenius formula of the various property values for the various aging temperatures($80^{\circ}C$, $90^{\circ}C$, $100^{\circ}C$) of the padder roll, the accelerated life predictions could be calculated. The threshold value of the property was set at different values. The hardness was set at the point where 5% degradation occurs based on the actual use conditions, and the tensile strength was set at the point where 50% degradation occurs based on the general life prediction standards. From the results of the different physical properties at differing temperatures, the Arrhenius plot could be obtained. Through the usage of the Arrhenius Equation, significant duration expectation could be predicted, and the chemical aging behavior of the CPB padder roll could be found at the arbitrary and actual temperatures.

• 한국전기전자재료학회논문지
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• 제16권9호
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• pp.783-789
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• 2003

The winding problems of traction motor are the major determinant of motor's life. The root cause of winding failure is gradual deterioration of the insulation due to thermal, electrical, mechanical and environmental stresses. The aging of the insulation reduces the electrical and mechanical strength of the insulation. At same point, a voltage surge or mechanical shock from a traction motor start will fracture or break down the insulation. To achieve the expected life usually requires extensive laboratory evaluation of the insulation systems and the use of accelerated aging tests. There are several nondestructive test available for checking, the condition of motor insulation, the probable extent of aging, and the rate of which aging is taking place. So the insulation characteristics of stator coil were each analyzed by measurement of dielectric loss(tan$\sigma$), capacitance and partial discharge. The method of diagnosis is able to analyze the insulation condition and evaluate the life of the traction motor.

• 한국전기전자재료학회논문지
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• 제15권2호
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• pp.119-126
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• 2002

The mica/epoxy composite used in generator(rated 22 kV and 500 MW) stator windings was aged at 180$\^{C}$ for up to 1000 hours in air and hydrogen. The degradation mechanism was investigated through the defect of evolution and microstructural analysis by performing SEM(Scanning Electron Microscope). As the thermal aging time increases, the number of voids per unit volume increases at the mica/epoxy interface of generator stator windings. The aged specimens in hydrogen showed retarded generation and growth of voids. Accelerated aging tests were conducted using the combination of thermal and electrical aging in air and hydrogen. The aging was carried out at a combined stress such as thermal aging at 110$\^{C}$, electrical aging at 5.5 kV/mm and frequencies 420 Hz in air, and electrical aging at 5.5 kV/mm and frequencies 420 Hz in hydrogen (pressure 4 kg/㎠). Thermal and electrical aging generates large voids at the mica/epoxy interface in air. Electrical aging in hydrogen also generates small voids, delaminations and cracks in mica tapes.

• 한국추진공학회지
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• 제23권4호
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• pp.61-69
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• 2019

세 가지 다른 온도($60^{\circ}C$, $70^{\circ}C$ 그리고 $75^{\circ}C$)에서 1년 동안 복기추진제의 가속 노화 시험을 수행하였다. 추진제의 노화 특성을 평가하기 위해 고성능 액체크로마토그래피(HPLC)와 AKTS-Thermokinetics 소프트웨어를 사용하여 안정제 함량과 속도론적 분석을 수행하였다. 그 결과, 추진제의 안정제 함량은 노화 온도 및 노화 기간에 따라서 점차적으로 감소하였다. $75^{\circ}C$에서의 안정제 감소 속도는 $70^{\circ}C$와 비교하여 약 2배 정도 빠른 것으로 나타났다. 이러한 실험값들을 속도론적 SB 모델과 2단계 모델로 모사하였고, n1=1, n2=0에서 실제데이터를 가장 잘 모사하였다.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1162-1168
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• 2015

Accelerated thermal aging of chlorosulfonated polyethylene (CSPE) was performed for 0 days, 80.82 days, and 161.63 days at 100℃, which is equivalent to 0 y, 40 y, and 80 y of aging, respectively, at 50℃. After freshwater flooding, the volume electrical resistivity of CSPE was highest after 180 days of drying, and its insulating property recovered when dried for more than 300 days. The dielectric constant of the CSPE was not measured after seawater flooding. The dielectric constant of the accelerated thermally aged CSPE was higher after freshwater flooding than that before seawater flooding. The bright, open pores of CSPE were converted into dark, closed pores after seawater flooding, and the dark, closed pores of the accelerated thermally aged CSPE samples were partly converted into bright, open pores after freshwater flooding. The apparent density of CSPE increased slightly whereas its elongation at break (EAB) decreased until 80 y of accelerated thermal aging before seawater flooding. The peak binding energies of oxygen in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y were shifted by more than 1.0 eV after seawater and freshwater flooding. The CH2 content in the non-accelerated and accelerated thermally aged CSPE for 40 y and 80 y after seawater flooding for 5 days was lower than that before seawater flooding whereas atoms such as Cl, O, Pb, Al, Si, Sb, and S that are related to conducting ions such as Na⁺, Cl^-, Mg²⁺, SO4 ^2-, and K⁺ were relatively increased.

• Journal of Korean Dental Science
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• 제8권2호
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• pp.49-56
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• 2015

Purpose: The effect of accelerated aging on color stability of various dual-cured self-adhesive resin cements were evaluated in this study. Materials and Methods: Color stability was examined using three different brands of dual-cured self-adhesive resin cements: G-CEM LinkAce (GC America), MaxCem Elite (Kerr), and PermaCem 2.0 (DMG) with the equivalent color shade. Each resin cement was filled with Teflon mold which has 6 mm diameter and 2 mm thickness. Each specimen was light cured for 20 seconds using light emitting diode (LED) light curing unit. In order to evaluate the effect of accelerated aging on color stability, color parameters (Commission Internationale de l'Eclairage, CIE $L^*$, $a^*$, $b^*$) and color differences (${\Delta}E^*$) were measured at three times: immediately, after 24 hours, and after thermocycling. The $L^*$, $a^*$, $b^*$ values were analyzed using Friedman test and ${\Delta}E^*$ values on the effect of 24 hours and accelerated aging were analyzed using t-test. These values were compared with the limit value of color difference (${\Delta}E^*=3.7$) for dental restoration. One-way ANOVA and Scheff's test (P<0.05) were performed to analyze each ${\Delta}E^*$ values between cements at each test period. Result: There was statistically significant difference in comparison of color specification ($L^*$, $a^*$, $b^*$) values after accelerated aging except $L^*$ value of G-CEM LinkAce (P<0.05). After 24 hours, color difference (${\Delta}E^*$) values were ranged from 2.47 to 3.48 and $L^*$ values decreased and $b^*$ values increased in all types of cement and MaxCem Elite had high color stability (P<0.05). After thermocycling, color change's tendency of cement was varied and color difference (${\Delta}E^*$) values were ranged from 0.82 to 2.87 and G-CEM LinkAce had high color stability (P<0.05). Conclusion: Color stability of dual-cured self-adhesive resin cements after accelerated aging was evaluated and statistically significant color changes occurred within clinically acceptable range.

• 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.

• 펄프종이기술
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• 제41권5호
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• pp.38-43
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• 2009

A conservation corrugated box for storing document archives was developed. The specifications of the double-walled E-flute corrugated conservation box were modified from those of the Library of Congress, USA. The Photographic activity test (PAT) of ISO 18916 was used to ensure protection of the archival contents from adverse effects of the container itself. Accelerated aging was conducted to evaluate the conservative properties of the box components. Atomic force microscopy was also used to evaluate changes in the cellulose surface due to accelerated aging.