• 한국전기전자재료학회논문지
• /
• 제15권10호
• /
• pp.858-864
• /
• 2002

Aging stabilities of the operating frequency of piezoelectric devices such as filter, oscillator and discriminator are very important. In this study it was studied aging stabilities of the length-extensional vibration mode of Pb(Zr$\^$y/O$_3$+ x[wt%]Cr$_2$Co$_3$ ceramics. PZT ceramics in morphotropic phase boundary have higher aging rates of k$\_$31/ and resonance frequency than those in tetragonal phase or rhombohedral phase. Thermal aging moves the composition with maximum aging rate to Zr-rich side in Cr$_2$O$_3$ not added PZT system. In the PZT system, aging rates of k$\_$31/ and resonance frequency for first 30 days are bigger than those for the following 90 days. Thermal aging decrease those for first 30 days. Aging rate of resonance frequency of the ceramics with x=0.1, y=0.53 and x=0.3, y=0.53 increased by thermal aging.

• Journal of Animal Science and Technology
• /
• 제60권9호
• /
• pp.23.1-23.9
• /
• 2018

Background: Aging trials are conducted to determine characteristics associated with dry- and wet-aging processes of beef from delivered cows grown in Okinawa, i.e., dams that have finished giving birth (Okinawan delivered cow beef). Changes in free amino acids, hardness, and other factors were analyzed in round of Okinawan delivered cow beef during dry- and wet-aging processes along with a comparison with characteristics of beef imported from Australia. Results: Functional amino acids did not increase during both dry- and wet-aging processes. However, proteinogenic amino acids increased significantly (P < 0.05) and hardness tended to decrease during both dry- and wet-aging processes. On comparison between dry- and wet-aging processes by analysis of variance, drip and cooking losses were significantly lower during the dry-aging process than during the wet-aging process. However, there was no significant difference in free amino acids or hardness in this comparison. Conclusion: There was no significant difference between dry- and wet-aging methods for all studied variables related to free amino acids or hardness in this study.

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

• Macromolecular Research
• /
• 제16권6호
• /
• pp.561-566
• /
• 2008

NR composites with different curing systems were aged thermally at 60, 70, 80, and $90^{\circ}C$ for 2-185 days in a convection oven, and the changes in the crosslink density were investigated as a function of the accelerated thermal aging. The overall crosslink densities increased with increasing aging time irrespective of the aging temperatures and curing systems. The changes in crosslink density were enhanced by increasing the aging temperature. The degree of the increased crosslink density was in the following order: "the conventional cure system > the semi-EV system > the EV system". For short term thermal aging, the change in crosslink density with the aging time was complicated, particularly for low temperature aging. The activation energies of the change in crosslink density with thermal aging using the conventional and semi-EV cure systems increased and then remained relatively constant with increasing aging time, whereas that of the specimen with an EV cure system tended to increase linearly. The experimental results were explained by the dissociation of the existing polysulfidic linkages and the formation of new cross links through the crosslinking-related chemicals remaining in the sample.

• 열처리공학회지
• /
• 제36권5호
• /
• pp.285-297
• /
• 2023

The effects of aging treatment sequence, specifically pre-aging and post-aging, on the microstructure and mechanical properties of Al-Zn-Mg-Cu aluminum alloys has been studied in comparison to symmetrically rolled specimens. In symmetrically rolled specimens, a straight-band precipitation distribution was observed, whereas asymmetrically rolled specimens exhibited a curved-band microstructure of fine precipitates. Notably, the asymmetrically rolled specimens displayed higher strengths. In the case of post-aging, the aging process occurred after rolling, and the dislocations generated during rolling acted as nucleation sites for precipitates during aging. This resulted in the formation of fine precipitates, contributing to improved mechanical properties compared to symmetric rolling. To enhance strength of the Al-Zn-Mg-Cu aluminum alloys, asymmetric rolling proves to be more effective than symmetric rolling, with post-aging showing greater efficacy than pre-aging.

• 농업과학연구
• /
• 제43권1호
• /
• pp.61-71
• /
• 2016

The effect of postmortem aging on the quality of Semimembranosus muscle (SM) from Hanwoo was investigated. The quality of SM was compared with that of Longissimus dorsi muscle (LD). SM contained higher moisture, protein, and ash, and lower fat than LD (p<0.05). The $a^*$ and $b^*$ values of SM were significantly decreased after 21 days of aging. SM showed higher $a^*$ values than LD at 1 and 7 day of aging (p<0.05). The cooking loss of SM was not affect by aging. SM had higher cooking loss than that of LD throughout the aging period. Although the shear force of SM was significantly decreased by aging, SM showed high shear force compared to LD during aging period (p<0.05). Aging increased lipid oxidation in both muscles (p<0.05). However, TBARS value of SM was significantly lower than that of LD throughout the aging period (p<0.05). There was no effect of aging on the betaine and L-carnitine contents of SM. SM contained higher betaine and L-carnitine than LD in all aging days (p<0.05). Therefore, we concluded that consumer acceptability of SM could be increased by aging based on the increase of tenderness in addition to its high nutritional properties.

• 한국심리학회지 : 문화 및 사회문제
• /
• 제13권3호
• /
• pp.65-87
• /
• 2007

본 연구에서는 고령화 사회의 주요문제로 부각되고 있는 노인문제와 나이듦에 대한 이해의 틀을 마련하고자 성공적 노화의 통합적 개념화를 시도하였다. 이를 위해, 나이듦의 의미를 규명하고, 나이듦과 관련된 부정적 변화와 나이듦에 따른 성장과 발달 등 긍정적 변화를 구분하여 개관하였다. 특히, 긍정적 변화와 관련하여 지혜가 성공적 노화의 중요한 요인이 될 수 있음을 확인하였다. 기존의 성공적 노화 이론과 주요 연구 결과들을 제시하였고, 기존의 이론이 가지고 있는 한계에 대한 논의를 바탕으로 지혜를 포함하는 성공적 노화의 통합적 개념화를 제시하였다. 성공적 노화의 통합적 개념화의 주요내용 및 특징을 설명하고 성공적 노화의 통합적 개념화가 갖는 시사점에 대해 논의하였다.

• Journal of Animal Science and Technology
• /
• 제58권5호
• /
• pp.20.1-20.11
• /
• 2016

The present review has mainly focused on the specific parameters including aging (aging days, temperature, relative humidity, and air flow), eating quality (flavor, tenderness and juiciness), microbiological quality and economic (shrinkage, retail yields and cost) involved beef dry aging process. Dry aging is the process where beef carcasses or primal cuts are hanged and aged for 28 to 55 d under controlling environment conditions in a refrigerated room with $0^{\circ}$ to $4^{\circ}C$ and with relative humidity of 75 to 80 %. However there are various opinions on dry aging procedures and purveyors of such products are passionate about their programs. Recently, there has been an increased interest in dry aging process by a wider array of purveyors and retailers in the many countries. Dry aging process is very costly because of high aging shrinkage (6 to 15 %), trims loss (3 to 24 %), risk of contamination and the requirement of highest grades meat with. The packaging in highly moisture-permeable bag may positively impact on safety, quality and shelf stability of dry aged beef. The key effect of dry aging is the concentration of the flavor that can only be described as "dry-aged beef". But the contribution of flavor compounds of proteolysis and lipolysis to the cooked dry aged beef flavor is not fully known. Also there are limited scientific studies of aging parameters on the quality and palatability of dry aged beef.

• 한국축산식품학회지
• /
• 제40권2호
• /
• pp.286-296
• /
• 2020

This study investigates the utilization of an electric-field-induced super cooling system in long-term dry aging of beef loin. Analyzed quality properties of dry-aged beef loin applied with electric field refrigeration (EFR) versus commercial refrigeration (CR). Quality properties was including aging loss, pH, water holding capacity (WHC), cooking loss, color, warner-bractzler shear force (WBSF), total plate count (TPC), and thiobarbituric acid reactive substances (TBARS). Aging loss of wk 1 EFR was significantly lower than CR (p<0.05). pH of EFR was slow change tendency compared CR. WHC of both aging methods were higher with increase in aging duration. Cooking loss of wk 1, 2, 4, and 10 EFR were significantly lower than CR (p<0.05). Lightness and redness of EFR was slow change tendency compared CR. However, yellowness of EFR was increased until wk 2, 3, and significantly decreased at wk 10 (p<0.05), but yellowness of CR was decreased until wk 3 and significantly increased with an increasing aging weeks (p<0.05). Both aging methods of WBSF was decreased with increase in aging weeks; however, wk 10 of CR was significantly lower than EFR (p<0.05). TPC after wk 3 EFR groups were significantly lower than CR groups (p<0.05), and TBARS of EFR groups were significantly lower than CR (p<0.05). The present results show that application of the EFR system for dry aging beef loin can extends its shelf life and induce changes of several aging properties in similar to commercial aging.

• 한국지반공학회논문집
• /
• 제20권6호
• /
• pp.137-150
• /
• 2004

모래의 aging 현상은 점성토에 비하여 무시할 정도로 매우 작아서 최근까지 연구되지 않았다. 그러나 퇴적이나 교란 후 시간경과에 따라 관입저항치의 증가가 관찰되면서 현장시험을 중심으로 모래의 aging 효과에 대하여 활발한 조사가 이루어졌고, 최근에는 현장시험뿐만 아니라 실내시험에서도 여러 연구자들에 의해 모래의 aging 효과가 규명 되어지고 있다. 본 연구에서는 모래의 비배수 정적전단거동에 대한 aging 효과를 살펴보기 위해 낙동강 모래를 이용하여 상대밀도 $(D_r)$, 압밀응력비$(K_c)$ 그리고 압밀시간을 달리하여 비배수 정적삼축압축시험을 실시하였다. 그 결과 응력-변형률의 탄성구간내 탄성계수가 압밀시간 경과에 따라 증가하는 것으로 나타났으며, 또한 상전이점 강도$(S_{PT})$와 한계응력비점 강도$(S_{CSR})$도 압밀시간 경과에 따라 증가하였다. 그러나 간극수압비$(u/{p_c}')$는 압밀시간에 비례하게 감소하는 등 모래의 정적전단에서 나타나는 aging 효과를 관찰할 수 있었다.