• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.41-44
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• 2007

Steam reforming reaction of natural gas is an important process for fuelcell commercialization. In this paper, steam reforming reaction is studied by numerical method. Pseudo-homogeneous model is incorporated for chemical reactions and one medium approach is used to take into account thermally equilibrium phenomena between catalyst and bulk gas. The model is validated with our experimental results under the same operating conditions. Because performance of reformer has relation to heat flux from wall, heat flux profiles was investigated by using Nusselt number. Value of Nusselt number in steam reformer is larger than one in channel, which does not have chemical reaction because steam reforming reaction is an endothermic reaction. When the difference of Nusselt number at the front and the rear is larger, performance is improved.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.839-841
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• 2008

The mutagenicity after heating of different sugars (glucose, fructose, galactose, and tagatose) on the non-enzymatic browning reaction in different sugars and glycine model system was investigated. The model system containing 0.2 M glycine and 0.2 M of different sugars in 10 mL water was heated at $150{\pm}5^{\circ}C$ for 30 min. After heating, degree of non-browning reaction intensity and mutagenicity using Salmonella typhimurium TA 98 were examined. Heated glycine model systems containing different sugars increased their mutgenicity ranged from 30 to 372 revertant colonies. After heating for 40 min, mutagenicity was achieved with glycine model systems containing 4 different sugars with by 145, 356, 206, and 369 revertants per plate, respectively. The glycine model systems containing fructose or tagatose were significantly (p<0.05) higher mutagenic activity than glycine model systems containing glucose or galactose after 40 min of heating. The linear regression between Maillard reaction intensity and mutagenic activities (slope=32.38, $R^2=0.93$) indicates that mutagenicity could be fully ascribed to Maillard reaction products.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.1051-1054
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• 2008

The entropy production in a non-equilibrium state based on the reversible Oregonator model of the Belousov-Zhabotinskii (BZ) reaction system has been studied. The reaction affinity and the reaction rate for the individual steps have been calculated by varying the concentrations of key variables in the system. The result shows a linear relationship between the reaction affinity and the reaction rate in the given concentration range. However, the overall entropy calculated on the basic assumption that the entropy in a reaction system corresponds to the summation of a product of reaction affinity and reaction rate of individual steps shows a nonlinearity of the reaction system. The results well agrees with the fact that the entropy production is not linear or complicated function in a non-linear reaction system.

• Polymer(Korea)
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• v.26 no.4
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• pp.422-430
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• 2002

The kinetics of polycondensation of bishydroxyethyl naphthalate has been studied in the range of 241 -$260^{\circ}C$ using antimony trioxide catalyst. The reaction was performed in a batch reactor and the concentration of reaction mixture was measured with HPLC. The activation energy values of forward and reverse reaction determined from molecular species model were found to be 19.7 and 31.4 kcal/mole, respectively, and the equilibrium constants were in the range of 1.4-2.0, which were larger than that of polycondensation of PET and varied to some degree with temperature. It was confirmed by applying the Flory's distribution function that the reaction rate of the hyroxyethyl group does not depend on the molecular size. By applying functional group model, we observed that there was few difference between the activation energy of the forward reaction and that of reverse reaction, therefore the equilibrium constant has almost constant value of 1.4. The rate constants obtained from functional group model was about 3-4 times larger than that from molecular species model, which showed that both model explains the reaction system well. Although the molecular species model should predict the concentration of as many as ten molecules, it fits for the experimental results well.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.56-61
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• 2016

In this study, the effect of natural minerals on the reaction kinetics for lignite-$CO_2$ gasification was investigated. After physical mixing of lignite from Meng Tai area with 5 wt% of each natural mineral catalysts among Dolomite, Silica sand, Olivine and Kaolin, $CO_2$ gasification was performed using TGA at each 800, $850^{\circ}C$ and $900^{\circ}C$. The experimental data was analyzed with volumetric reaction model (VRM), shrinking core model (SCM) and modified volumetric reaction model (MVRM). MVRM was the most suitable among three models. As increasing the reaction temperature, the reaction rate constant became higher. With natural mineral catalysts, the reaction rate constant was higher and activation energy was lower than that of without catalysts. The lowest activation energy, 114.90 kJ/mol was obtained with silica sand. The highest reaction rate constant at $850^{\circ}C$ and $900^{\circ}C$ and lower reaction rate constant at $800^{\circ}C$ were obtained with Kaolin. Conclusively, the better catalytic performance could be observed with Kaolin than that of using other catalysts when the reaction temperature increased.

• Resources Recycling
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• v.30 no.1
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• pp.14-25
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• 2021

As a demand of high-end steel raises, the importance of secondary refinement process also increases. However, the content of each component in molten steel, slag and inclusions change with the time, meaning the secondary refinement process is not an equilibrium state. Furthermore, many reactions occur between molten steel, slag, inclusion, refractory and alloying element during secondary refinement process. In order to consider the above complex reactions with non-equilibrium state, a few researchers developed kinetic models in secondary refinement process based on the experimental numerical equations. It is important to analyze and review to the previously reported models to develop a precise model. Therefore, in present study, the complex reaction models based on kinetic in secondary refinement process were analyzed, reviewed, and introduced. Moreover, the single reaction models also introduced which would be applied to the complex reaction models.

• Advances in aircraft and spacecraft science
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• v.1 no.4
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• pp.379-398
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• 2014

This article discusses the microvibration analysis of a cantilever configured reaction wheel assembly. Disturbances induced by the reaction wheel assembly were measured using a previously designed platform. Modelling strategies for the effect of damping are presented. Sine-sweep tests are performed and a method is developed to model harmonic excitations based on the corresponding test results. The often ignored broadband noise is modelled by removing spikes identified in the raw signal including a method of identifying spikes from energy variation and band-stop filter design. The validation of the reaction wheel disturbance model with full excitations (harmonics and broadband noise) is presented and flaws due to missing broadband noise in conventional reaction wheel assembly microvibration analysis are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.857-862
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• 2011

3 dimensional turbine exhaust gas flow was simplified to an axisymmetrical flow and calculated with detailed chemistry models. GRI 35 species-217 reaction step model and simplified 11 species 15 reaction model was applied to the secondary reaction of the turbine exhaust gas and compared. All the model captured the secondary combustion on the base region, and the temperature was 600K higher than that without turbine exhaust gas. This means the local temperature of the base can be higher in the case of real 3 dimensional flow. The simplified model show the similar results to the GRI detailed chemistry model although the former affected the engine plume structure slightly.

• Industry Promotion Research
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• v.3 no.2
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• pp.1-8
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• 2018

In this study, the reaction mechanism of ethane and the reaction rate equation suitable for hydrocarbon reforming were studied. Through the reaction mechanism analysis, it was confirmed that three reactions (CO2 + H2, C2H6 + H2, C2H6 + H2O) proceed during the reforming reaction of ethane, each reaction rate (CO2+H2($r=3.42{\times}10-5molgcat.-1\;s-1$), C2H6+H2($r=3.18{\times}10-5mol\;gcat.-1s-1$), C2H6+H2O($r=1.84{\times}10-5mol\;gcat.-1s-1$)) was determined. It was confirmed that the C2H6 + H2O reaction was a rate determining step (RDS). And the reaction equation of this reaction can be expressed as r = kS * (KAKBPC2H6PH2O) / (1 + KAPC2H6 + KBPH2O) (KA = 2.052, KB = 6.384, $kS=0.189{\times}10-2$) through the Langmuir-Hinshelwood model. The obtained equation was compared with the derived power rate law without regard to the reaction mechanism and the power rate law was relatively similar fitting in the narrow concentration change region (about 2.5-4% of ethane, about 60-75% of water) It was confirmed that the LH model reaction equation based on the reaction mechanism shows a similar value to the experimental value in the wide concentration change region.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.4
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• pp.328-339
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• 2010

A new gasification model for coal char was developed considering the effects of pore structure and solid reaction product (ash) and compared with conventional models. Among various parameters reflecting microscopic pore structure, initial pore surface per unit volume of char was found to have the largest effect on carbon conversions. Reaction studies showed that the proposed model can predict carbon conversion more accurately over a broader range of reaction degree compared to the conventional models. Therefore the model proposed in this study would be useful for the design of pilot or commercial scale gasifiers.