• Elastomers and Composites
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• v.53 no.1
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• pp.1-5
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• 2018

In the current research, the curing kinetics of a mixture system consisting of a Bisphenol-A type vinyl ester resin and styrene monomer was studied. Methylethylketone peroxide and cobalt octoate were used as the polymerization initiator and accelerator respectively. Thermograms with several different heating rates were obtained using non-isothermal differential scanning calorimetry. Activation energy values analyzed by the Flynn-Wall-Ozawa isoconversional method showed a three-step change with conversion ${\alpha}$: a slight decrease initially for ${\alpha}$ < 0.1, a constant value of 47.9 kJ/mol in the range 0.1 < ${\alpha}$ < 0.7, and a slow increase for 0.7 < ${\alpha}$. When assuming a constant activation energy of 47.9 kJ/mol, an autocatalytic model of the Sestak-Berggren equation was considered as the proper mathematical model of the conversion function, indicating an overall order of 1.2.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.99.1-99.1
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• 2011

Reactant mixing has a critical role in ensuring reformate quality and an important design objective is to achieve sufficiently complete mixture of reactants. For that purpose it is required to understand the coupled transport-kinetics phenomena in the mixing region. Three-dimensional computational fluid dynamics model was developed and validated in previous works. The mixing characteristics in various alternatives of a prototype mixing chamber were compared, and then a reduced reaction kinetics was applied to two extreme designs for investigating the impact of gas-phase reactions. Both designs did not reach threshold ethylene mole fraction of 0.001, but surprisingly more ethylene was generated in the design having better mixing characteristics. The presentation will deliver the development process of coupled transport and kinetics model briefly and the detailed information about the mixing characteristics and gas-phase reactions in two mixer designs.

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.380-386
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• 2010

We have investigated the growth kinetics of Al oxide film by anodization in sulfuric acid solution and the electronic properties of this film using electrochemical impedance spectroscopy. Al oxide film consisted $Al_2O_3$ was grown based on the point defect model and shown the eclctronic properties of n-type semiconductor.

• Journal of Environmental Science International
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• v.20 no.11
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• pp.1437-1445
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• 2011

The adsorption performance of lead ion was studied using five zeolites (Na-P1, sodalite (SOD), analcime (ANA), nepheline hydrate (JBW), cancrinite (CAN)) synthesized from Jeju scoria. The adsorption performances of lead ion decreased in the order of Na-P1 > SOD > ANA > JBW > CAN. These results showed that the synthetic zeolite with a higher cationic exchange capacity showed a higher adsorption performance. The uptake of lead ion by synthetic zeolites were described by Freundlich model better than Langmuir model. The adsorption kinetics of lead ion by synthetic zeolites fitted the pseudo 2nd order kinetics better than pseudo 1st order kinetics. The effective diffusion coefficients of lead ion by synthetic zeolites were ten times higher than the zeolite A synthesized from coal fly ash.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1277-1288
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• 2018

In this work, the reactor kinetics capability is used to compute the design safety parameters in a PWR due to complete loss of coolant flow during protected and unprotected accidents. A thermal-hydraulic code coupled with a point reactor kinetic model are used for these calculations; where kinetics parameters have been developed from the neutronic SRAC code to provide inputs to RELAP5-3D code to calculate parameters related to safety and guarantee that they meet the regulatory requirements. In RELAP5-3D the reactivity feedback is computed by both separable and tabular models. The results show the importance of the reactivity feedback on calculating the power which is the key parameter that controls the clad and fuel temperatures to maintain them below their melting point and therefore prevent core melt. In addition, extending modeling capability from separable to tabular model has nonremarkable influence on calculated safety parameters.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2877-2883
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• 2010

The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2399-2408
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• 2002

A prediction procedure has been developed to evaluate the microtructures and material properties of heat affected zone (HAZ) in pressure vessel steel weld, based on temperature analysis, thermodynamics calculation and reaction kinetics model. Temperature distributions in HAE are calculated by finite element method. The microstructures in HAZ are predicted by combining the temperature analysis results with the reaction kinetics model for austenite grain growth and austenite decomposition. Substituting the microstructure prediction results into the previous experimental relations, the mechanical material properties such as hardness, yielding strength and tensile strength are calculated. The prediction procedure is modified and verified by the comparison between the present results and the previous study results for the simulated HAZ in reactor pressure vessel (RPV) circurnferential weld. Finally, the microstructures and mechanical material properties are determined by applying the final procedure to real RPV circumferential weld and the local weak zone in HAZ is evaluated based on the application results.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.78-86
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• 2002

A metallurgical model for the prediction of prior austenite grain size considering the dissolution kinetics of M$_3$C precipitates at the heat affected zone of SA508-cl.3 was proposed. The isothermal kinetics of grain growth and dissolution were respectively described by well-known equation, $dD/dT=M({\Delta}F_{eff})^M$ and Whelan's analytical model. The isothermal grain growth experiments were carried out for measure the kinetic parameters of grain growth. The precipitates of the base metal and the specimens exposed to thermal cycle were examined by TEM-carbon extraction replica method. The model was assessed by the comparison of BUE simulation experiments and showed good consistencies. However, there was no difference between the model considering and ignoring $M_3C$ precipitates. It seems considered that pinning force exerted by $M_3C$ Precipitates was lower than driving force for grain growth due to large size and small fraction of precipitates, and mobility of grain boundary was low in the lower temperature range.

• Advances in environmental research
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• v.1 no.3
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• pp.223-236
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• 2012

Biosorption of methylene blue (MB) from aqueous solution was studied with respect to the point of zero charge of coconut husk, dye concentration, particle size, pH, temperature, as well as adsorbent and NaCl concentration using coconut husk biomass. Amongst Langmuir and Freundlich adsorption isotherms studied, Langmuir adsorption isotherm showed better agreement. Pseudo second order kinetics model was found to be more suitable for data presentation as compared to pseudo first order kinetics model. Also, involvement of diffusion process was studied using intraparticle diffusion, external mass transfer and Boyd kinetic model. Involvement of intraparticle diffusion model was found to be more relevant (prominent) as compared to external mass transfer (in) for methylene blue biosorption by the coconut husk. Moreover, thermodynamic properties of MB biosorption by coconut husk were studied. Desorption of methylene blue from biomass was studied with different desorbing agents, and the highest desorption achieved was as low as 7.18% with acetone, which indicate stable immobilization. Under the experimental conditions MB sorption was not significantly affected by pH, temperature and adsorbent concentration but low sorption was observed at higher NaCl concentrations.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.251-259
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• 2023

Immobilizing microalgae cells in a hyphal matrix can simplify harvest while producing novel mycoalgae products with potential food, feed, biomaterial, and renewable energy applications; however, limited quantitative information to describe the process and its applicability under various conditions leads to difficulties in comparing across studies and scaling-up. Here, we demonstrate the immobilization of both active and heat-deactivated marine diatom Phaeodactylum tricornutum (UTEX 466) using different loadings of fungal pellets (Aspergillus sp.) and model the process through kinetics and equilibrium models. Active P. tricornutum cells were not required for the fungal-assisted immobilization process and the fungal isolate was able to immobilize more than its original mass of microalgae. The Freundlich isotherm model adequately described the equilibrium immobilization characteristics and indicated increased normalized algae immobilization (g algae removed/g fungi loaded) under low fungal pellet loadings. The kinetics of algae immobilization by the fungal pellets were found to be adequately modeled using both a pseudo-second order model and a model previously developed for fungal-assisted algae immobilization. These results provide new insights into the behavior and potential applications of fungal-assisted algae immobilization.