• Food Science and Biotechnology
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• 제17권2호
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• pp.330-335
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• 2008

Water vapor adsorption kinetics of 3 different types of chitosan-based films, i.e., control chitosan, chitosan/montmorillionite (Na-MMT), and chitosan/silver-zeolite (Ag-Ion) nanocomposite films, were investigated at temperature range of $10-40^{\circ}C$. In all the films, water vapor is initially adsorbed rapidly and then it comes slowly to reach equilibrium condition. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs. l/t. It was found that water vapor adsorption kinetics of chitosan-based films was accurately described by a simple empirical model and the rate constant of the model followed temperature dependence according to Arrhenius equation. Arrhenius kinetic parameters ($E_a$ and $k_o$) for water vapor adsorption by chitosan-based films showed a kinetic compensation effect between the parameters with the isokinetic temperature of 315.52 K.

• 청정기술
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• 제7권3호
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• pp.187-194
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• 2001

석탄가스화 복합발전(IGCC)의 탈황공정에 사용되는 비아연계 탈황제 중 경제성이 우수한 천연망간광석을 이용하여 황화수소 제거반응에 대한 특성을 연구하였다. $H_2S$와 천연망간광석 탈황제 사이의 반응에 대한 초기 반응 속도를 $400{\sim}800^{\circ}C$의 온도범위에서 열중량 분석기로 실험하였다. 그 결과로 황화수소 제거반응 시 초기 반응은 1차 반응이었고, 반응속도상수는 Arrhenius 식에 잘 적용할 수 있었다. 또한 황화반응이 확산에 의해 제어되는 조건에서 농도 구배가 선형을 나타내었으며, 이를 통하여 유효 확산 계수를 온도에 따른 Arrhenius식으로 나타내었다. 이 결과를 통하여 황화 반응 시 확산에 대한 활성화 에너지와 반응 빈도 인자를 구하였다.

• Food Science and Biotechnology
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• 제15권2호
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• pp.264-269
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• 2006

Basic rheological data of dandelion leaf concentrates were determined to predict processing aptitude and usefulness of dandelion leaf concentrates as functional food materials. Hot water and 70% ethanol extracts of dandelion leaves were concentrated at 5, 20, and 50 Brix, and their static and dynamic viscosities, and Arrhenius plots were investigated. Most concentrated dandelion leaves extracted with hot water and 70% ethanol showed flow behaviors close to Newtonian fluid based on power law model evaluation. Apparent viscosity of concentrated dandelion leaves extracted with hot water and 70% ethanol decreased with increasing temperature. Yield stresses of concentrated dandelion leaves extracted with hot water and 70% ethanol by Herschel-Bulkley model application were 0.020-0.641 and 0.017-0.079 Pa, respectively. Activation energies of concentrated dandelion leaves extracted with hot water and 70% ethanol were $2.102-32.669{\times}10^3$ and $1.657-5.382{\times}10^3\;J/mol{\cdot}kg$ with increasing concentration, respectively. Loss modulus (G") predominated over storage modulus (G') at all applied frequencies, showing typical flow behavior of low molecular solution. G' and G" of concentrated dandelion leaves extracted with hot water slowly increased with increasing frequency compared to those of concentrated dandelion leaves extracted with 70% ethanol.

• 한국식품저장유통학회지
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• 제24권4호
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• pp.505-509
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• 2017

Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to $40^{\circ}C$ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of $1/(m-m_0)$ vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters ($E_a$ and $k_0$) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

• Food Science and Biotechnology
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• 제15권1호
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• pp.33-38
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• 2006

This study was performed to provide basic rheological data of dandelion root concentrates in order to predict their processing aptitude and usefulness as functional foods material. The hot water and 70% ethanol extracts of dandelion root were concentrated at 5, 20, and 50 Brix, and their static viscosity, dynamic viscosity, and Arrhenius plots were investigated. Almost all hot water concentrates showed the typical flow properties of a pseudoplastic fluid, but evaluation using the power law model indicated that the 70% ethanol concentrates showed a flow behavior close to a Newtonian fluid. The apparent viscosity of hot water and 70% ethanol concentrates decreased with increasing temperature. Yield stresses of hot water and 70% ethanol concentrates by Herschel-Bulkley model application were in the range of 0.026 - 1.368 Pa and 0.022 - 0.238 Pa, respectively. The effect of temperature and concentration on the apparent viscosity was examined by Arrhenius equation. The activation energies of hot water and 70% ethanol concentrates were in the range of $8.762-23.778{\times}10^3\;J/mol{\cdot}kg$ and $3.217-20.384{\times}10^3\;J/mol{\cdot}kg$ with increasing concentration, respectively. Storage (G') and loss (G") moduli were generally increased with increasing frequency. For the 70% ethanol concentrates, G" predominated over G' at all applied frequencies and so they showed the typical flow behavior of a low molecular solution. However, for the hot water concentrates, G' predominated over G" at more than 1.9 rad/sec (cross-over point) and so they showed the typical flow behavior of a macromolecular solution.

• 한국식품과학회지
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• 제35권2호
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• pp.188-194
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• 2003

천마식품가공시 기초자료로 활용될 수 있는 천마 추출농축액의 리올로지 특성을 조사하였다. 천마의 열수 및 50% 에탄올 추출물운 각각 5, 10, 15, 및 20 Brix와 10, 20, 30, 40 및 50 Brix로 농축하여 제조하였다. 열수 및 50% 에탄올 농축액의 정상유동특성과 동적점탄성을 조사하였다. Power law model로 구한 n에 의하면 모든 열수 농축액들은 전형적인 의가소성$(n=0.484{\sim}0.802)$유체의 흐름특성을 보였고, 50% 에탄올 농축액들은 뉴튼유체$(n=0.875{\sim}1.078)$에 가까운 흐름특성을 나타내었다. 열수 및 50% 에탄올 농축액의 ${\eta}_{app}$는 온도가 증가함에 따라 감소하는 경향을 나타내었다. Herschel-Bulkley model에 의한 열수 및 50% 에탄올 농축액의 C는 각각 $0.030{\sim}1.255$ Pa와 $0.007{\sim}0.065$ Pa이었다. ${\eta}_{app}$에 대한 온도 및 농도의 영향은 arrhenius식으로 해석하였다. 열수 및 50% 에탄올 농축액의 $E_a$는 농도가 증가함에 따라 각각 $3.340{\sim}4.620{\times}10^3\;J/mol{\cdot}kg$과 $1.6289{\sim}18.6699{\times}10^3\;J/mol{\cdot}kg$의 범위로 나타났다. 진동수(angular frequency, ${\omega}$)가 증가할수록 저장탄성률(storage modulus, G#)과 손실탄성률(loss modulus, G@)은 일반적으로 증가하는 경향을 나타냈다. 50% 에탄올 농축액의 경우 모든 진동수에서 G#이 G@보다 높게 나타나 전형적인 저분자용액의 흐름특성을 보였다. 그러나 열수농축액의 경우 G@이 G#보다 높았고 0.5 rad/sec에서 교차점을 형성하였으며 전형적인 고분자 용액의 흐름특성을 나타내었다.

• Preventive Nutrition and Food Science
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• 제13권1호
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• pp.28-32
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• 2008

Water vapor sorption by sodium alginate-based films may result in swelling and conformational changes in the molecular structure and affecting the water vapor barrier properties. Sodium alginate film specimens were dried in a vacuum freeze dryer and their moisture content was determined by an air-oven method. The water vapor absorption was determined at two different levels of water activities (0.727 and 0.995) and at three temperatures (10, 20, and $30^{\circ}C$), and kinetics were analyzed using a simple empirical model. Reasonably good straight lines were obtained with plotting of 1/($m-m_0$) vs 1/t. It was found that water vapor absorption kinetics of sodium alginate films were accurately described by a simple empirical model. The rate of water vapor sorption increased with increase in temperature and it showed temperature dependency following the Arrhenius equation. The activation energies varied from 49.18$\sim$149.55 kJ/mol depending on the relative humidity.

• Bulletin of the Korean Chemical Society
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• 제5권3호
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• pp.104-108
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• 1984

The self-diffusion experiment of THO was performed across a series of copolymer hydrogel membranes at different temperatures. Copolymer hydrogel membranes were prepared by copolymerizing 2-hydroxyethyl methacrylate (HEMA) and 2-aminoethyl methacrylate (AEMA) in the presence of the solvent and the crosslinker, ethylene glycol dimethacrylate (EGDMA). By changing the crosslinker content and the ratio of HEMA and AEMA monomer, two series of copolymer hydrogel membranes were synthesized. The tagging material was THO and efflux of THO was counted on a Liquid Sc-intillation Counter. The experimental data show that the permeability decreases as the amount of EGDMA and the mole fraction of HEMA increase, and the permeability is proportional to the temperature. The partition coefficient shows a parallel trend with permeability. Using the relationship between viscosity and diffusivity, the viscosity of water within the membrane was obtained. According to the result, the viscosity of watler within the membrane has the same value with those of supercooling water. And we obtained the activation energy of THO for transport in the membrane by using Arrhenius plotting.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 추계종합학술대회
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• pp.995-998
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• 2003

MOCVD 법을 이용하여 TiO$_2$ 박막을 제작하여, 투과곡선을 비교적 간단하게 분석할 수 있는 포락선방법을 사용하여 기판온도에 따른 TiO$_2$ 박막의 굴절률, 소광계수 등의 광학적 상수들을 구하였다. 투과곡선의 모사를 실시하여 포락선방법으로 구한 값들이 매우 신뢰도가 높음을 입증하였다. TiO$_2$ 박막은 35$0^{\circ}C$ 에서 부터 결정화가 되기 시작하여, 40$0^{\circ}C$ 이상에서 tetragonal structure 를 갖는 anatase 상으로 완전히 결정화됨을 알 수 있다. 기판온도에 따른 증착률을 Arrhenius plot 하여 구한 활성화에너지는 reaction limited 단계에서 17.8 kcal/mol 이었다. 포락선방법을 이용하여 구한 TiO$_2$ 박막의 굴절률 (λ=632.8 nm) 은 기판온도가 40$0^{\circ}C$ 에서 $600^{\circ}C$ 로 증가함에 따라 2.19 에서 2.32 로 증가하는 추세를 나타내었고, 소광계수는 0.021 에서 0.007로 감소하는 경향을 나타내었다.