• 한국지반공학회논문집
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• 제19권2호
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• pp.7-14
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• 2003

본 연구는 광양만 지역과 목포 남악지역의 점토를 이용하여 양생온도를 20$\times$, 50$\times$ , 80$\times$로 달리하고 각각의 온도에서 양생기간을 1일, 7일 14일, 40일로 하여 재성형.재압밀 시료를 제작하여 양생온도.양생기간이 연대효과 재현에 어떤 영향이 있는지를 밝히고, 불교란시료와 재압밀된 점토의 역학적 특성과 연대효과의 특성을 알아보기 위하여 1축압축시험, 3축압축시험 그리고 표준압밀시험을 실시하였다. 그 결과 압축지수비는 원지반점토의 연대효과를 나타내는데 유용한 지수임을 확인할 수 있었으며 또한 고온으로 양생한 점토가 연대효과를 잘 표현하고 연대효과의 재현에 필요한 최적의 양생온도는 80$\times$ 정도 부근이고 양생기간은 27일정도 임을 알 수 있었다.

• 청정기술
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• 제29권1호
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• pp.39-45
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• 2023

To investigate the effects of Mg addition at different aging times and temperatures, Cu/MgO/Al₂O₃ catalysts were synthesized for the low-temperature water gas shift (LT-WGS) reaction. The co-precipitation method was employed to prepare the catalysts with a fixed Cu amount of 30 mol% and varied amounts of Mg/Al. Synthesized catalysts were characterized using XRD, BET, and H₂-TPR analysis. Among the prepared catalysts, the highest CO conversion was achieved by the Cu/MgO/Al₂O₃ catalyst (30/40/30 mol%) with a 60 ℃ aging temperature and a 24 h aging time under a CO₂-rich feed gas. Due to it having the lowest reduction temperature and a good dispersion of CuO, the catalyst exhibited around 65% CO conversion with a gas hourly space velocity (GHSV) of 14,089 h-1 at 300 ℃. However, it has been noted that aging temperatures greater or less than 60 ℃ and aging times longer than 24 h had an adverse impact, resulting in a lower surface area and a higher reduction temperature bulk-CuO phase, leading to lower catalytic activity. The main findings of this study confirmed that one of the main factors determining catalytic activity is the ease of reducibility in the absence of bulk-like CuO species. Finally, the long-term test revealed that the catalytic activity and stability remained constant under a high concentration of CO₂ in the feed gas for 19 h with an average CO conversion of 61.83%.

• Elastomers and Composites
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• 제44권4호
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• pp.442-446
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• 2009

충전제의 영향을 막기 위해 비보강 NR, BR, SBR 고무 가황물을 원형 변형시켜 노화시킨 후 회복 거동을 비교하였다. 시료는 상온, 50, 70, $90^{\circ}C$에서 10일간 노화시켰다. 측정 시간이 증가함에 따라 회복률은 증가하였다. 노화 후 측정 시간에 따른 회복률의 변화로부터 1.0 초 미만의 순간회복률을 구하였다. 상온 노화에서는 노화 기간이 짧아 고무 간의 회복률 차이가 거의 나타나지 않았다. 하지만 50, 70, $90^{\circ}C$에서의 가속 노화 실험 결과에서는 각 고무 간의 회복률 차이가 뚜렷하게 나타났다. BR의 회복률이 가장 우수하였고, SBR의 회복률이 가장 적었다. 그러나 $90^{\circ}C$ 가속 노화 에서는 NR의 회복률이 BR보다 높게 나타났다. 노화 온도가 높아 질수록 초기 회복률이 감소하였으며, 그 감소 폭은 SBR이 가장 크게 나타났다. 실험 결과는 고무의 반발 특성과 노화에 의한 가교밀도 변화로 설명하였다.

• 한국정보통신학회논문지
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• 제22권6호
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• pp.861-866
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• 2018

OLED(Organic Light-Emitting Diode) 제조에서 에이징(aging) 공정은 제조 효율을 높이고 에이징 보정을 위한 보정 값을 측정한다. OLED의 에이징 보정을 위한 보정 값은 구동 신호에 적용할 수 있다. OLED 에이징 공정은 미리 설정된 구동신호와 온도에 의해 정해진 시간 동안 빛을 출력한 후 전류를 측정한다. OLED 제조 공정에서 증착 및 기온에 의해 균일하지 않은 것에 대해 에이징을 가하는 것이다. 이 시간이 OLED 효율 감소에 미치는 영향은 거의 없다. 에이징을 위해 필요한 조건을 만들기 위해 가열장치와 신호 생성 시스템이 요구된다. 가열장치와 신호 생성 시스템에 의해 측정된 결과값은 OLED 제조에서 전력 요구사항, 균일성, 효율성을 평가하는 근거로 사용할 수 있다. 이에 본 논문에서는 실용적인 OLED 에이징 보정을 위한 구동 신호 생성 및 가열 시스템의 연동을 위한 구성을 제안하고 이를 구현하였다.

• 열처리공학회지
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• 제22권2호
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• pp.101-107
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• 2009

Effect of isochronic aging on transformation behavior of Ti-50.85at%Ni alloy were investigated by differential scanning calorimeter (DSC). The martensitic transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with further increasing annealing temperature. This can be rationalized by interaction between the distribution of $Ti_3Ni_4$ precipitates and Ni content in the matrix. The R-phase transformation temperature increases with increasing annealing temperature until reaching a maximum, and then decreases with a further increase of annealing temperature. This is attributed to the change of Ni content in the matrix caused by precipitation of $Ti_3Ni_4$. The occurrence of the multiple-stage martensitic and R-phase transformation is attributed to precipitation-induced inhomogeneity of the matrix, both in terms of composition and of internal stress fields.

• 한국전기전자재료학회논문지
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• 제27권1호
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• pp.27-32
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• 2014

In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in $Pb(Zr,Ti)O_3$ system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at $200^{\circ}C$. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti= 53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechanical coupling factor k31 was (-) in the tetragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to increase as temperature increase in the interval $-20{\sim}80^{\circ}C$.

• Composites Research
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• 제30권1호
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• pp.7-14
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• 2017

In this paper, the inter-lamina shear strength (ILSS) of multi-wall carbon nanotube (MWNT) reinforced carbon fiber reinforced plastics (CFRP) and thin-ply composites were verified under low earth orbit (LEO) space environment. CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP were tested after aging by using accelerated ground simulation equipment. The used ground simulation equipment can simulate high vacuum ($2.5{\times}10^{-6}torr$), atomic oxygen (AO, $9.15{\times}10^{14}atoms/cm^2{\cdot}s$), ultraviolet light (UV, 200 nm wave length) and thermal cycling ($-70{\sim}100^{\circ}C$) simultaneously. The duration of aging experiment was twenty hours, which is an equivalent duration to that of STS-4 space shuttle condition. After the aging experiment, ILSS were measured at room temperature ($27^{\circ}C$), high temperature ($100^{\circ}C$) and low temperature ($-100^{\circ}C$) to verify the effect of operation temperature. The MWNT and thin-ply shows good improvement of ILSS at ground condition especially with the thin-ply. And after LEO exposure large degradation of ILSS was observed at MWNT added composite due to the thermal cycle. And the degradation rate was much higher under the high temperature condition. But, at the low temperature condition, the ILSS was largely recovered due to the matrix toughening effect.

• 한국재료학회지
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• 제26권5호
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• pp.281-286
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• 2016

In the present study, the tensile properties and dynamic strain aging of an Fe-24.5Mn-4Cr-0.45C alloy were investigated in terms of strain rate. During tensile testing at room temperature, all the stress-strain curves exhibited serrated plastic flows related to dynamic strain aging, regardless of the strain rate. Serration appeared right after yield stress at lower strain rates, while it was hardly observed at high strain rates. On the other hand, strain-rate sensitivity, indicating a general relationship between flow stress and strain rate at constant strain and temperature, changed from positive to negative as the strain increased. The negative strain-rate sensitivity can be explained by the Portevin Le Chatelier effect, which is associated with dynamic strain aging and is dependent on the strain rate because it is very likely that the dynamic strain aging phenomenon in high-manganese steels is involved in the interaction between moving dislocations and point-defect complexes.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.43-49
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• 2005

Temperature stabilities of resonance frequencies of the substrates are very important in piezoelectric ceramics oscillators and fitters. In this study, it was investigated thermal resisting property of the length-extensional vibration mode of PZT ceramics. The mode can be utilized in fabricating ultra-small 55 kHz IF devices. We fabricated the ceramic specimens with x = 0.51, 0.52, 0.53, 0.54, and 0.55 in the Pb(Zr$\sub$x/Ti$\sub$1-x/)O$_3$ system. And their resonance frequencies were measured before 1st thermal aging, after 1st and 2nd thermal aging. In order to investigate the influence of thermal aging on thermal resisting properties, thermally aged specimens were once mote thermally aged. Before 1st thermal aging, the specimens of the compositions with morphotropic phase, x = 0.53 and rhombohedral phase, x = 0.54 have weak thermal resisting property of resonance frequency, while tetragonal phase, x = 0.51 has robust thermal resisting property of resonance frequency. 1st thermal aging improved thermal resisting property of resonance frequency in all specimens.

• 한국식품영양학회지
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• 제31권2호
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• pp.258-263
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• 2018

To assess a potential possibility of Deoduck as functional food resources, this study was performed to determine the changes in chemical components and antioxidant activities on Deoduck with various aging conditions; aging temperatures were 60, 70, and $80^{\circ}C$, and aging periods were 5, 10, 15, 30, and 50 days. We determined pH, total acidity, browning index, 5-hydroxymethyl-furfural, total phenolic contents, DPPH and ABTS radical scavenging activities of aged Deoduck. Total acidity of aged samples increased during aging treatment, at higher temperature and longer time. The pH value of aged Deoduck ranged from 4.97 to 3.76. Aged Deoduck at $60^{\circ}C$ decreased slowly than 70 and $80^{\circ}C$, and these results were similar in total acidity. 5-HMF and total phenolic contents increased when increased aging temperature and periods. The DPPH and ABTS radical scavenging activities of Deoduck were ranged from 0.374 to 1.560 mg TEAC eq/g and from 0.302 to 1.745 mg trolox eq/g, respectively.