• 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.

• 한국환경보건학회지
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• 제30권2호
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• pp.133-139
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• 2004

The objective of this study was to investigate the destruction efficiency and to determine the fundamental parameters of oxidation kinetics under the supercritical water(SCW) condition. Target material was cephradine, toxic and antibiotic material, in the pharmaceutical wastewater. For this purpose, the effect of reaction temperature and oxidant were investigated on the destruction efficiency of cephradine. And the oxidation kinetics of cephradine was derived by using a empirical power-law model. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 which was endurable high temperature and pressure. The destruction efficiency of cephradine increased with increment of the temperature and reaction time. Also the type of oxidants was effected and oxidants(Air and $H_2O$$_2$) were enhanced the destruction efficiency. The global oxidation kinetics for cephradine has led to two rate expressions according to type of oxidant. - In the presence of air oxidant: Rate=k. $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ( $O_2$)$^{0.51}$$\pm$0.05(k=3.27${\times}$$10^{5}$ sec. Ea=63.25 kJ/mole) - In the presence of $H_2O$$_2$ oxidant : Rate=kㆍ $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ($H_2O$$_2$)$^{0.62}$$\pm$0.02(k=2.76${\times}$$10^4$/sec. Ea=47.65 kJ/mole)ole))

• 폴리머
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• 제35권3호
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• pp.196-202
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• 2011

비즈페놀 A 에폭시 수지와 폴리옥시프로필렌 디아민 경화제계의 경화 반응속도를 시차주사열량계을 이용하여 승온 및 등온 경화조건에서 조사하였다. 승온실험에서는 Ozawa와 Kissinger법을 이용하여 다양한 가열속도에서 얻어진 발열피크의 이동으로부터 활성화 에너지를 구하였다. 또한 등온실험에서 얻어진 데이터는 자촉매 효과를 고려한 Kamal의 속도모델로 분석하였으며, 그 결과 경화반응 초기의 속도우세 구간에서 실험데이터와 잘 맞았다. 반응 후기의 확산우세 구간에서는 확산효과를 적용하여 경화의 전체과정을 기술하였다. 또한 동역학분석을 이용하여 경화 후 저장 탄성률과 가교점간의 평균분자량을 측정하였다.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1175-1184
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• 2022

The pore structure of uranium-bearing sandstone is one of the critical factors that affect the uranium leaching performance. In this article, uranium-bearing sandstone from the Yili Basin, Xinjiang, China, was taken as the research object. The fractal characteristics of the pore structure of the uranium-bearing sandstone were studied using mercury intrusion experiments and fractal theory, and the fractal dimension of the uranium-bearing sandstone was calculated. In addition, the effect of the fractal characteristics of the pore structure of the uranium-bearing sandstone on the uranium leaching kinetics was studied. Then, the kinetics was analyzed using a shrinking nuclear model, and it was determined that the rate of uranium leaching is mainly controlled by the diffusion reaction, and the dissolution rate constant (K) is linearly related to the pore specific surface fractal dimension (D_S) and the pore volume fractal dimension (D_V). Eventually, fractal kinetic models for predicting the in-situ leaching kinetics were established using the unreacted shrinking core model, and the linear relationship between the fractal dimension of the sample's pore structure and the dissolution rate during the leaching was fitted.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.149-154
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• 1998

A subcritical reactor driven by a linear proton accelerator has been considered as a nuclear waste incinerator at Korea Atomic Energy Research Institute(KAERI). Since the multiplication factor of a subcritical reactor is less than unity, to compensate exponentially decreasing fission neutrons from spallation reactions are essentially required for operating the reactor in its steady state. furthermore, the profile of accelerator beam currents is very important in controlling a subcritical reactor, because the reactor power varies in accordance of the profile of external neutrons. We have developed a code system to find numerical solutions of reactor kinetics equations, which are the simplest dynamic model for controlling reactors. In a due course of our previous numerical study of point kinetics equations for critical reactors, however, we learned that the same code system can be used in studying dynamic behavior of the subcritical reactor. Our major motivation of this paper is to investigate responses of subcritical reactors for small changes in thermal hydraulic parameters. Building a thermal hydraulic model for the subcritical reactor dynamics, we performed numerical simulations for dynamic responses of the reactor based on point kinetics equations with a source term. Linearizing a set of coupled differential equations for reactor responses, we focus our research interest on dynamic responses of the reactor to variations of the thermal hydraulic parameters in transient phases.

• 공업화학
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• 제24권4호
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• pp.375-381
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• 2013

상업용 니켈 촉매를 사용하여 메탄과 천연가스의 수증기 개질 반응을 각각 수행하였다. 수증기 개질 반응의 변수는 반응 온도와 반응물의 분압이었다. Kinetic data로부터 Power law rate model과 Langmuir-Hinshelwood model의 매개변수를 구하였다. 순수한 메탄을 수증기 개질 반응 실험의 원료로 사용한 경우에는 Langmuir-Hinshelwood model 식은 물론이고 Power law rate model을 사용하여 반응 속도를 적절하게 표현할 수 있었다. 그러나 천연가스 중의 메탄의 수증기개질 반응 속도를 표현하는데 있어서는 Power law rate model보다 Langmuir-Hinshelwood model이 훨씬 더 적합한 것을 확인하였다. 이러한 거동은 천연가스 중에 포함되어있는 메탄, 에탄, 프로판 및 부탄이 동일한 촉매 활성점에 경쟁적으로 흡착하기 때문으로 해석할 수 있었다.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.110-115
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• 2010

본 연구 목적은 두가지 종류의 국내 수입탄에 대한 열분해 반응율을 구하고 이를 비교하는 것이다. 이를 위해 TGA를 통하여 열분해 실험을 수행하였으며, 반응상수 분석은 New DAEM 방법을 이용하였다. 서로 다른 가열속도에서 각각 얻어진 TGA 질량변화 곡선으로부터, 활성화 에너지의 분포함수를 구한 후 최고빈도를 나타내는 활성화 에너지를 평균 활성화 에너지로 결정하였다. 그 결과 석탄의 종류에 따라 상기 반응에 대한 반응속도상수가 확실한 차이를 보였다. 이 같은 New DAEM 분석기법을 통해 얻은 반응상수를 적용시킨 CPD 모델을 가지고 예측한 결과가 TGA 실험치와 비교할 때보다 더 잘 일치함도 확인할 수 있었다.

• 대한환경공학회지
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• 제33권11호
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• pp.804-811
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• 2011

본 연구는 흡착제의 흡착특성을 이해하는데 이용되는 각종 흡착모델의 적용성을 평가하는데 목적이 있다. 이를 위해 상용의 음이온교환수지(PA-308)를 이용하여 질산성질소에 대한 흡착특성을 회분식 실험을 통해 조사하였다. 음이온교환수지에 의한 질산성질소의 속도실험 결과는 초기의 빠른 흡착과정과 후기의 느린 흡착 과정의 두 가지 단계의 과정으로 이원화되는 경향을 나타내었다. 1차 속도식과 2차 속도식 모두 전체 반응시간에서의 질산성질소에 대한 음이온교환수지의 흡착속도를 수식화 할 수 없었다. 초기의 빠른 흡착반응($t\leq$ 20분)은 1차 속도식에 따르고 외부확산에 의해 거의 지배되는 거동을 보이는 반면, 후기 느린 흡착반응(t > 20분)은 2차 속도 화학반응과 내부확산, 즉 세공 내 확산에 의해서 일어남을 알 수 있었다.

• Membrane and Water Treatment
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• 제9권2호
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• pp.95-104
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• 2018

Copper pollution around the world has caused serious public health problems recently. The heavy metal adsorption on traditional membranes from wastewater is limited by material properties. Different adsorptive materials are embedded in the membrane matrix and act as the adsorbent for the heavy metal. The carbonized leaf powder has been proven as an effective adsorbent material in removing aqueous Cu(II) because of its relative high specific surface area and inherent beneficial groups such as amine, carboxyl and phosphate after carbonization process. Factors affecting the adsorption of Cu(II) include: adsorbent dosage, initial Cu(II) concentration, solution pH, temperature and duration. The kinetics data fit well with the pseudo-first order kinetics and the pseudo-second order kinetics model. The thermodynamic behavior reveals the endothermic and spontaneous nature of the adsorption. The adsorption isotherm curve fits Sips model well, and the adsorption capacity was determined at 61.77 mg/g. Based on D-R model, the adsorption was predominated by the form of physical adsorption under lower temperatures, while the increased temperature motivated the form of chemical adsorption such as ion-exchange reaction. According to the analysis towards the mechanism, the chemical adsorption process occurs mainly among amine, carbonate, phosphate and copper ions or other surface adsorption. This hypothesis is confirmed by FT-IR test and XRD spectra as well as the predicted parameters calculated based on D-R model.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.49-52
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• 2001

The investigation of cure kinetics, morphology, and fracture toughness studies on epoxy resin/amine terminated PEI/Anhydride system were performed by differential scanning calorimetry and scanning electron microscopy. Modified autocatalystic kinetics model was applied by isothermal scan test. The fracture toughness for the neat epoxy resin was 2.15 MPa m0.5 and the fracture toughness was improved 45% as neat epoxy resin system. The generation of secondary phase of AT-PEI was observed and its size was grown up by increasing contents of PEI.