• 한국염색가공학회지
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• 제13권6호
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• pp.435-440
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• 2001

This study investigates the rheological properties of in-situ polymerized solutions of polyacrylonitrile(PAN) and acrylonitrile(AN) -itaconic acid(IA) in dimethyl sulfoxide(DMSO) in terms of temperature, concentration, and time. The complex viscosity and storage modulus of the solutions were generally increased with elapsing time, which is ascribable to the three-dimensional pseudostructures formed by strong inter- or Intra-molecular attractions through Polar -CN and -COOH groups. The three-dimensional pseudonetworks would lead to relation of the acrylic solutions in long term. This was more noticeable at higher temperature within the temperature range examined. In the case of 20% solutions one can not observe lower Newtonian flow region in the viscosity curve. Disappearance of lower Newtonian flow region is indicative of heterogeneity of the solution system. Casson Plot of the viscosity data revealed that 20% solutions of PAN and AN-IA copolymer in DMSO clearly demonstrated positive yield stress, ascertaining formation of pseudostructures in the solution systems.

• 한국염색가공학회지
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• 제13권6호
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• pp.77-77
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• 2001

This study investigates the rheological properties of in-situ polymerized solutions of polyacrylonitrile(PAN) and acrylonitrile(AN)-itaconic acid(IA) in dimethyl sulfoxide(DMSO) in terms of temperature, concentration, and time. The complex viscosity and storage modulus of the solutions were generally increased with elapsing time, which is ascribable to the three-dimensional pseudostructures formed by strong inter- or intra-molecular attractions through Polar -CN and -COOH groups. The three-dimensional pseudonetworks would lead to gelation of the acrylic solutions in long term. This was more noticeable at higher temperature within the temperature range examined. In the case of 20% solutions one can not observe lower Newtonian flow region in the viscosity curve. Disappearance of lower Newtonian flow region is indicative of heterogeneity of the solution system. Casson Plot of the viscosity data revealed that 20% solutions of PAN and AN-IA copolymer in DMSO clearly demonstrated positive yield stress, ascertaining formation of pseudostructures in the solution systems.

• 대한기계학회논문집
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• 제17권9호
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• pp.2271-2279
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• 1993

In the case of life prediction on the structures and machines after long service, it is natural to consider a degradation problems. Most of degradation data form practical structures are isolated data obtained at the time of periodical inspection or repair. From such data, it may be difficult to obtain the degradation curve available and necessary for life prediction. In this paper, for the purpose of obtaining a degradation curves, developed the simulate degradation method and fatigue test and Charpy impact test were conducted on the degraded, simulate degraded and recovered materials. Fatigue life prediction were conducted by using the relationship between fracture transition temperature (DBTT : vTrs) obtained from the Charpy impact test through the degradation process and fatigue crack growth constants of m and C obtained from the fatigue test.

• Journal of the Korean Wood Science and Technology
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• 제26권3호
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• pp.1-8
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• 1998

Western redcedar timber, 26 by 26cm in cross section and by 200cm long, was dried in a laboratory radio-frequency/vacuum kiln under 65torr of ambient pressure and a fixed frequency of 6.78MHz for the potential rapidly dry large timber. All process data were collected and saved in a computer through a data acquisition system. The temperature in the middle of timber was higher than temperature at the quarter point of timber length and thickness. Temperature gradients developed in the longitudinal and transverse direction of timber. The pressure in the middle of timber was higher than pressure at the quarter point of timber length. The pressure in the middle of timber was lower in the early stage of drying, and higher in the latter stage of drying than pressure at the quarter point of timber thickness. Power density was very highest during heating period and then gradually decreased. The drying curve was approximately linear and the total drying time was 27 hours from an initial moisture content(MC) of 48.6 percent to a final Me of 19.2 percent with only a few mild internal checks in the middle location of timber.

• 한국대기환경학회지
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• 제15권2호
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• pp.191-199
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• 1999

This study evaluated the availability as an alternative adsorbent which is cheaper and more efficient than CuO/${\gamma}$-$Al_2O_3$ which have been studing vigorously to remove $SO_2$. Five adsorbents (CuO/${\gamma}$-$Al_2O_3$, Iron ore, Slag, LD slag, $Fe_2O_3$) was employed in a fixed bed reactor. $SO_2$ breakthrough curves were obtained as a function of temperature, initial gas velocity and particle size. Saturation capacities calculated by the numerical integration of breakthrough curves of $SO_2$ increased with increasing reaction temperature. $SO_2$ breakthrough curve equation of $Fe_2O_3$ for this system can be expressed as Kr=3,914,000 exp(-37,329.86/RT). By means of the breakthrough curve, the influence of bed height on breakthrough time was also estimated.

• 대한토목학회논문집
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• 제33권2호
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• pp.465-473
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• 2013

본 연구에서는 터널에서 발생되는 화재로부터 구조물을 보호하기 위해 내화패널이 부착된 프리캐스트 PSC 슬래브의 내화성능을 조사하기 위해 내화실험이 수행되었다. 내화실험은 독일의 RABT(Richtlinien fur die Ausstatung und den Betrieb von stra${\beta}$entunneln) 화재시간-온도곡선을 적용하여 내화성능을 평가하는 것으로 하였다. ITA(2004)에서 제시하는 기준에 따라 내화성능 시험을 수행한 결과, 콘크리트의 손상을 판단하는 위치인 t=0mm의 최대온도는 $367^{\circ}C$로서 손상한계온도 $380^{\circ}C$(ITA 2004)이하였으며, 철근의 손상을 판단하는 위치인 t=25mm의 최대온도는 $239^{\circ}C$로서 손상 한계온도인 $250^{\circ}C$이하로 나타났다. 실험결과로부터, 25mm두께의 내화패널이 부착된 프리스트레스 슬래브 시험체는 내화성능을 가진 것으로 입증되었다.

• Composites Research
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• 제30권3호
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• pp.188-192
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• 2017

The mechanical properties of composites are significantly affected by external environment. It is essential to understand the degradation of material performance and judge the material's lifetime in advance. In the current research, changes in mechanical properties of glass fiber and unsaturated polyester composite materials (GFRP, Glass fiber reinforced plastic) were investigated under different bending stress and submerged in hot water at a temperature of $80^{\circ}C$. Loading time of 100 H (hours), 200 H, 400 H, 600 H, 800 H for testing under stresses equal to 0% (stress-free state), 30%, 50% and 70% of the ultimate strength was applied on the GFRP specimens. From the values of bending stress, obtained from three-point bending test, fracture energy, failure time, and life curve were analysed. Moreover, a normalized strength degradation model for this condition was also developed. It was observed that within 100 H, the decline rate of the bending strength was proportional to the pressure.

• 한국추진공학회지
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• 제23권1호
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• pp.108-115
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• 2019

고온 고압의 연소가스로부터 구조물을 보호하는 탄성내열재는 재료 조성 및 열환경 조건에 따라 열반응에 차이를 보인다. 본 논문에서는 탄성내열재의 배합 환경 변화에 따른 열반응 특성을 비교하였다. 탄성내열재의 내열 성능 시험은 내열고무성능평가장치(TPREM)를 이용하였으며, 연소실 압력 1,000 psig에서 연소가스속도를 각각 20 m/s과 100 m/s로 시험하였다. 연소실 압력-시간 선도, 재료 내부 온도-시간 선도, 탄성내열재 시편의 잔류 두께 및 열파괴두께를 획득하였다. 배합 환경에 따른 탄성내열재의 내열 성능은 유사하였다.

• 한국식품과학회지
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• 제17권5호
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• pp.345-349
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• 1985

$3^{3}$ 요인배치법에 의하여, 농도 저장시간 저장온도의 차이에 따를 도토리묵의 물리적 특성 변화를, Instron Universal Testing Machine을 사용하여 측정 비교하였다. 도토리묵의TPA curve는 첫 번째 압착에서 두개의 peak를 보이고, negative peak는 나타나지 않았다. 견고성과 절단성은 농도 저장시간 저장온도의 세 인자들의 변화에 대해 매우 유의적인 차이를 보이고, 두 peak의 높이 차이는 농도와 저장온도의 변화에 의해 특히 영향을 받으며 저장시간의 효과도 무시할 수 없었다. Bend는 농도의 변화에 대해서는 민감하게 대응하나 저장온도의 영향은 다소 약하게 작용하며 저장시간에 따른 변화는 무시할 수 있었다. 탄성은 농도의 변화에 대해서만 유의적인 차이를 보였다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.551-559
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• 1998

Evaporation and ignition characteristics of fuel droplet have major influences on the efficiency and performance of engine. In the present study the experiment of evaporation and self-ignition of single fuel was performed under the various ambient conditions. An individually suspended droplet of n-heptane n-hexadecane ethyl-alcohol and light oil were employed as a liquid droplet. Evaporation and ignition characteristics were measured by using the video-camera and image processing technique under the various ambient temperatures (up to 1000310 OC)and partial pressure of oxigen(up to 60%) The evaporation curve shows that the droplet life time ignition delay time decreases as the ambient temperature and partial pressure of oxigen increase, The temperature variations of droplet were also reported for various fuel and ambient temperatures. The numerical simulations were carried out to predict droplet diameter and temperature with favorable agreement.