• Food Science and Biotechnology
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• 제17권1호
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• pp.90-94
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• 2008

Dynamic rheological properties of honey samples with 3 different moisture contents (17.2, 19.0, and 21.0%) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer. The honey samples displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency ($\omega$). The magnitudes of G' and G" decreased with an increase in temperature and water content while a predominant increase of G' was noticed at $-15^{\circ}C$. The time-temperature superposition (TTS) principle was applied to bring G" values for honeys at various temperatures together into a master curve. The G" over the temperature range of -15 to $0^{\circ}C$ obeyed the Arrhenius relationship with a high determination coefficient ($R^2=0.98-0.99$). Activation energy value (Ea=112.4 kJ/mol) of honey with a moisture content of 17.2% was higher than those (Ea=98.8-101.1 kJ/mol) of other honey samples with higher moisture contents.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.163-167
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• 2016

Inverter surge resistant enameled wire was prepared with an organic/inorganic hybrid nanocomposite, and the effect of ambient temperature on the insulation lifetime of the enameled wire in the form of twisted pair was studied by a withstanding voltage tester. The organic polymer was Polyesterimide-polyamideimide (EI/AI) and the inorganic material was a Nano-sized silica (average particle size : 15 nm). The enamel thickness was 50 μm and the ambient temperature was 100, 150, 200, and 250, respectively. Transmission electron microscopy (TEM) observation showed that Nano-sized Silica were evenly dispersed in EI/AI. There were many air gaps in a twisted pair, therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge accordi, ng to Paschen’s law. As ambient temperature increased, insulation lifetime decreased according to Arrhenius relationship, which was explained by the increasing mobility of polymer chains in EI or AI. And insulation breakdown voltage value at 10 kHz was 1,864.5 sec (31.1 min), which is 1.9 times higher than at 20 kHz, 981.6 sec (16.4 min).

• 대한화학회지
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• 제48권1호
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• pp.12-16
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• 2004

에탄올-산소-아르곤 혼합기체의 점화 과정을 반사 충격파를 이용 1281-1625 K의 온도 범위 및 0.69-1.06 bar 압력 범위에서 고찰하였다. 점화지연시간은 급격한 압력변화와 광 방출 스펙트럼으로부터 측정하였으며, 에탄올 및 산소 기체의 농도 그리고 반응온도에 따른 점화지연시간의 의존관계를 나타내는 실험식을 구할 수 있었다. 실험결과 에탄올 점화 과정에서 연료인 에탄올의 농도가 커지면 점화지연시간이 길어지는 경향을 보였으며, 이는 메탄올 점화 과정에서 메탄올의 농도가 증가하면 점화 과정이 짧아지는 것과는 다른 경향이었다. 그리고 에탄올 점화 과정에 관하여 보다 자세히 고찰하기 위해 다양한 에탄올 연소반응 메카니즘을 이용하여 모델 연구를 수행하였다.

• 한국미생물·생명공학회지
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• 제21권4호
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• pp.342-347
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• 1993

It was proved that the cell growth followed a photo-inhibition model in light-limited turbidostat cultivation, having 1.06 (1/h) of maximum specific growth rate and 0.00094(kcal/$cm^2$/h) and 0.063 (kcal/$cm^2$/h) as half saturation and light inhibition constants, repectively. ${\beta}$-carotene production showed a growth related porcess. And the activation energy of Dunaliella salina was roughly estimated as 12.36 (kcal/mole) in employing Arrhenius relationship. It should also point out that relatively much porduction of ${\beta}$-carotene was observed at hight light intensity with yieding 1.04 (mg-carotene/g-dry cell/day) of specific product production rate while the cell growth was decreased. The optimal conditions of producing ${\beta}$-carotene in turbiodostat cultivation were as follows: $7.5{\times}10^{-3}$(kcal/$cm^2$/h)of light intensity, 2 (mM) and 50(mM) of nitrate and sodium bicarbonate concentrations and 100(ml/h) of $CO_2$ flow rate.

• 한국응용과학기술학회지
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• 제3권2호
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• pp.41-47
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• 1986

The transesterification reaction between diethanolamine and methyl-methacrylate was kinetically investigated in the presence of various metal acetate catalysts at $120^{\circ}C$. The quantity of methylmethacrylate reacted in the reaction flask was measured by gas chromatography and liquid chromatography, and the reaction rate was investigated by measuring of the quantity of products and reactnts under various catalysts. The transesterification reaction was carried out in the first order reaction kinetics with respect to the concentration of diethanolamine and methylmethacrylate, respectively. The apparent rate constant was found to obey first-order kinetics with respect to the concentration of catalyst. The linear relationship was shown between apparent rate constant and reciprocal absolute temperature, and by the Arrhenius plot, the activation energy has been calculated as 11.08 Kcal with zinc acetate catalyst, 17.99 Kcal without catalyst. The maximum reaction rate was appeared at the range of 1.4 to 1.6 of electronegativity of metal ions and instability constant of metal acetates.

• 품질경영학회지
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• 제28권4호
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• pp.16-28
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• 2000

Recently days, High Accelerated Life Test of electrical and electronic parts is increasing its importance. This study set the hypothesis to develop the method that was analysis and application of HALT for the automotive electrical and electronic parts, it used Arrhenius's Model and Eyring's Model, and ESS theory. Validity of application is proved by other test data. Especially, this study emphasis on utility of acceleration to temperature, humidity, voltage, mechanical stress and other stress. In this study set the pattem of practical application. Therefore, this study emphasis on the application of the HALT and the use of other parameter by acceleration reliability test data. The result of this study is as follows. 1) There is relationship between molar weight and material constant. 2) Characteristic of material is operating acceleration factor as well as parts failure factors. Of course, according to the characteristic of material, activation energy is often more important than molar weight. But it will be defined by more testing and improvements in practical application.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권3호
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• pp.180-191
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• 2016

Purpose: The purpose of this study was to develop the accelerated life test method for Constant Electrical Potential Electrolysis gas sensor (CEPE gas sensor). Methods: The parts and modules of CEPE gas sensor were analyzed by using Reliability Block Diagram (RBD). Failure Mode and Effect Analysis (FMEA) and Quality Function Deployment (QFD) methods were performed for each part to determine the most affecting stress factor in its life cycle. The long term testing was conducted at three different dry heat levels and the acceleration factor was developed by using Arrhenius relationship. Conclusion: The acceleration factor for CEPE gas sensor was developed by using FMEA, QFD, and statistical analysis for its failure data. Also qualification tests were designed to meet the target life.

• Food Science and Biotechnology
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• 제15권6호
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• pp.871-876
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• 2006

Rheological behavior of commercial hot pepper-soybean paste (HPSP) was evaluated in small amplitude oscillatory and steady shear tests. Storage modulus (G'), loss modulus (G"), and complex viscosity (${\eta}^*$) as a function of angular frequency (${\omega}$), and shear stress (${\sigma}$) as a function of shear rate (${\gamma}$) data were obtained for 5 commercial HPSP samples. HPSP samples at $25^{\circ}C$ exhibited a non-Newtonian, shear-thinning flow behavior with high yield stresses and their flow behaviors were described by power law, Casson, and Herschel-Bulkley models. Time-dependent flow properties were also described by the Weltman, Hahn, and Figoni & Shoemaker models. Apparent viscosity over the temperature range of $5-35^{\circ}C$ obeyed the Arrhenius temperature relationship with activation energies (Ea) ranging 18.3-20.1 kJ/mol. Magnitudes of G' and G" increased with an increase in ${\omega}$, while ${\eta}^*$ decreased. G' values were higher than G" over the most of the frequency range (0.63-63 rad/sec), showing that they were frequency dependent. Steady shear viscosity and complex viscosity of the commercial HPSP did not fit the Cox-Merz rule.

• Food Science and Biotechnology
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• 제14권2호
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• pp.233-237
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• 2005

Rheological properties of acorn flour-guar gum mixtures (4% w/w) at different guar gum concentrations (0, 0.2, 0.4, 0.6, and 0.8% w/w) were evaluated in steady and dynamic shear. The acorn flour-guar gum mixtures at $25^{\circ}C$ showed high shear-thinning flow behavior (n= 0.20-0.27). Consistency index (K), apparent viscosity (${\eta}_{a,100}$), and Casson yield stress (${\sigma}_{oc}$) increased with the increase in guar gum concentration. Within the temperature range of $25-70^{\circ}C$, the {\eta}_{a,100}$ of mixtures obeyed the Arrhenius relationship with high determination coefficient ($R^2=\;0.974-0.994$). Activation energy values (5.37-6.77 kJ/mole) of acorn flour dispersions in the mixtures with guar gum (0.2-0.8%) were much lower than that (12.5 kJ/mole) of acorn flour dispersion (0% guar gum). Storage modulus (G'), loss modulus (G"), and complex viscosity (${\eta}^*$) increased with the increase in guar gum concentration. Dynamic rheological data of 1n (G', G") versus ln frequency (w) of guar gum-acorn flour mixtures had positive slopes with G' greater than G" over most of the frequency range, indicating that they exhibited weak gel-like behavior.

• Asian Journal of Atmospheric Environment
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• 제8권2호
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• pp.96-107
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• 2014

Extreme recovery of the thermal energy from the combustion of flue gas may bring about early gas condensation resulting in the increased formation of nitric acid vapor. The behavior of the nitric acid formed inside the stack and in the atmosphere was investigated through a computer-aided simulation in this study. Low temperatures led to high conversion rates of the nitrogen oxide to nitric acid, according to the Arrhenius relationship. Larger acid plumes could be formed with the cooled flue gas at $40^{\circ}C$ than the present exiting gas at $115^{\circ}C$. The acid vapor plume of 0.1 ppm extended to 25 m wide and 200 m high. The wind, which had a seasonal local average of 3 m/s, expanded the influencing area to 170 m along the ground level. Its tail stretched 50 m longer at $40^{\circ}C$ than at $115^{\circ}C$. The emission concentration of the acid vapor in the summer season was a little lower than in the winter. However, a warm atmosphere facilitated the Brownian motion of the discharged flue gas, finally leading to more vigorous dispersion.