• Korean Journal of Materials Research
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• v.31 no.8
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• pp.471-479
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• 2021

The electrochemical reaction between lead borate glass frit doped with Sn metal filler and Ni-Cr wire of a J-type resistor during a term of Joule heating is investigated. The fusing behavior in which the Ni-Cr wire is melted is not observed for the control group but measured for the Sn-doped specimen under 30 V and 500 mA. The Sn-doped lead borate glass frit shows a fusing property compared with other metal-doped specimens. Meanwhile, the redox reaction significantly contributes to the fusing behavior due to the release of free electrons of the metal toward the glass. The electrons derived from the glass, which used Joule heat to reach the melting point of Ni-Cr wire, increase with increasing corrosion rate at interface of metal/glass. Finally, the confidence interval is 95 ± 1.95₉ %, and the adjusted regression coefficient, R in the optimal linear graph, is 0.93, reflecting 93% of the data and providing great potential for fusible resistor applications.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.2
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• pp.1-10
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• 2021

Lithium-ion batteries with high energy density, long cycle life and other advantages, have been widely used to energy storage systems(ESS). But as ESS fires frequently occur, the safety concern has become the main obstacle that hinders the large-scale applications of lithium-ion batteries. Especially, thermal runaway is the key scientific problem in battery safety research. Therefore, in this study, we performed a numerical analysis on the thermal runaway phenomenon of NCM111, NCM523 and NCM622 batteries using a two-dimensional analysis model. The results show that the two-dimensional simulation results are generally matched with three-dimensional simulation. Also, In the case of NCM111 with a low Ni content in the temperature range used in this study, thermal runaway phenomenon does occurred very slowly, but as the Ni content is increased, the thermal runaway phenomenon occurs rapidly and the thermal stability tends to be decreased. And, in NCM523 and NCM622 batteries, chain reactions occur almost simultaneously, but in the case of NCM111 battery, it is found that after the SEI(Solid Electrolyte Interface) layer decomposition reaction, the cathode-electrolyte reaction is appeared sequentially. After that, the anodic decomposition reaction is increased and leads to the thermal runaway reaction.

• Structural Engineering and Mechanics
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• v.83 no.1
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• pp.79-92
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• 2022

In this paper, the impact of a vernacular pozzolanic kaolinite mine on concrete alkali-silica reaction and strength has been evaluated. For making the samples, kaolinite powder with various levels has been used in the quality specification test of aggregates based on the ASTM C1260 standard in order to investigate the effect of kaolinite particles on reducing the reaction of the mortar bars. The compressive strength, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) experiments have been performed on concrete specimens. The obtained results show that addition of kaolinite powder to concrete will cause a pozzolanic reaction and decrease the permeability of concrete samples comparing to the reference concrete specimen. Further, various machine learning methods have been used to predict ASR-induced expansion per different amounts of kaolinite. In the process of modeling methods, optimal method is considered to have the lowest mean square error (MSE) simultaneous to having the highest correlation coefficient (R). Therefore, to evaluate the efficiency of the proposed model, the results of the support vector machine (SVM) method were compared with the decision tree method, regression analysis and neural network algorithm. The results of comparison of forecasting tools showed that support vector machines have outperformed the results of other methods. Therefore, the support vector machine method can be mentioned as an effective approach to predict ASR-induced expansion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.65-73
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• 2005

The compressible flow of reactive fluid is investigated by using the transonic small-disturbance (TSD) model and the one-step first-order Arrhenuis chemical reaction. The fluid flow is restricted to dilute premixed reactions with small heat release. The effects of channel shape and Mach number on transonic combustion are studied by numerical analysis. The results show that the channel divergence increases the chemical reaction within the given channel length whereas the channel convergence inhibits the chemical reaction near the outlet and that increasing the inlet flow Mach number at a fixed reaction rate causes the flow acceleration in a diverging channel and the appearance of weak shock waves which do not show in the inert flow case. It also helps to increase the pressure and temperature near the diverging channel outlet and to consume the reactant within the given channel length.

• Journal of Environmental Science International
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• v.25 no.12
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• pp.1717-1726
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• 2016

In this study, the reductive decolorization of three acid and basic dyes using modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium coated iron (Pd/Fe)) at various pH conditions (pH 3~5) was experimentally investigated and the decolorization characteristics were evaluated by analyzing the absorbance spectra and reaction kinetics. In the case of acid dyes such as methyl orange and eriochrome black T, color removal efficiencies increased as initial pH of the dye solution decreased. However, the color removal of methylene blue, a basic dye, was not affected much by the initial pH and more than 70% of color was removed within 10 min. During the decolorization reaction, the absorbance of methyl orange (${\lambda}_{max}=464nm$) and eriochrome black T (${\lambda}_{max}=528nm$) decreased in the visible range but increased in the UV range. The absorbance of methylene blue (${\lambda}_{max}=664nm$) also decreased gradually in the visible range. Pseudo-zero order, pseudo-first order, and pseudo-second order kinetic models were used to analyze the reaction kinetics. The pseudo-second order kinetic model was found to be the best with good correlation. The decolorization reaction rate constants ($k_2$) of methylene blue were relatively higher than those of methyl orange and eriochrome black T. The reaction rate constants of methyl orange and eriochrome black T increased with a decrease in the initial pH.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.3
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• pp.52-58
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• 2011

Proton-NMR spectroscopic method was applied to kinetic study of concentrated sulfuric acid hydrolysis reaction, especially focused on 2nd step of acid hydrolysis with deferent reaction time and temperature as main variables. Commercial xylan extracted from beech wood was used as model compound. In concentrated acid hydrolysis, xylan was converted to xylose, which is unstable in 2nd hydrolysis condition, which decomposed to furfural or other reaction products. Without neutralization steps, proton-NMR spectroscopic analysis method was valid for analysis of not only monosaccharide (xylose) but also other reaction products (furfural and formic acid) in acid hydrolyzates from concentrated acid hydrolysis of xylan, which was the main advantages of this analytical method. Higher temperature and longer reaction time at 2nd step acid hydrolysis led to less xylose concentration in xylan acid hydrolyzate, especially at $120^{\circ}C$ and 120 min, which meant hydrolyzed xylose was converted to furfural or other reaction products. Loss of xylose was not match with furfural formation, which meant part of furfural was degraded to other undetected compounds. Formation of formic acid was unexpected from acidic dehydration of pentose, which might come from the glucuronic acid at the side chain of xylan.

• Korean Journal of Food Science and Technology
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• v.20 no.3
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• pp.453-458
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• 1988

This research was carried out to investigate the effects of Maillard reaction products and nondialyzable melanoidins on the nitrite-scavenging. Nitrite-scavenging reactions were done at the different pH conditions(pH 1.2, 4.2 and 6.0). Maillard reaction products and nondialyzable melanoidins, produced from the glucose-amino acids(lys., gly., arg., his.)model systems, had a great of nitrite-scavenging effects. Nitrite-scavenging effects of Maillard reaction products and nondialyzable melanoidins were also pH dependent, being higher at pH 1.2 and lower at pH 6.0. By the treatment of Maillard reaction products and nondialyzable melanoidins with sodium borohydride, nitrite-scavenging effects were remarkably decreased at pH 1.2.

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.499-504
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• 2009

Metals have often played important roles to some enzymatic reactions that are essential to biological processes. Therefore many scientists have studied the reaction mechanisms of catalytic reactions in metaloenzymes for many years. Methane MonoOxygenase (MMO) is an enzyme that oxidize methane to methyl alcohol. Recently Tolman et al. studied a model reaction for MMO, which is a hydroxide transfer reaction in Bis-($\mu$-oxo)-dicopper complex, and suggested several possible mechanisms. Later a two-step mechanism, which is hydrogen transfer followed by hydroxide rebound, was proposed from theoretical studies. In this study we calculated the reactant, product, and the transition state structures, and energetics of the first hydrogen transfer reaction using various DFT methods including recently developed the MO6 family of DFT, namely, MO6, MO6L, and MO6-2X. We found that the M06/6-31G(d,p)/LANL2DZ method reproduce the experimental XRD structure of reactants very well. The TS structures, barrier heights, and reaction energies depend very much on the size of the basis sets.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.37-43
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• 2015

This paper presents a detailed procedure for a nonlinear soil-structure interaction of a seismically isolated NPP(Nuclear Power Plant) structure using the boundary reaction method (BRM). The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. For the purpose of calculating the boundary reaction forces at the base of the isolator, the KIESSI-3D program is employed in this study to solve soil-foundation interaction problem subjected to vertically incident seismic waves. Wave radiation analysis is also employed, in which the nonlinear structure and the linear soil region are modeled by finite elements and energy absorbing elements on the outer model boundary using a general purpose nonlinear FE program. In this study, the MIDAS/Civil program is employed for modeling the wave radiation problem. In order to absorb the outgoing elastic waves to the unbounded soil region, spring and viscous-damper elements are used at the outer FE boundary. The BRM technique utilizing KIESSI-3D and MIDAS/Civil programs is verified using a linear soil-structure analysis problem. Finally the method is applied to nonlinear seismic analysis of a base-isolated NPP structure. The results show that BRM can effectively be applied to nonlinear soil-structure interaction problems.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.285-293
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• 2000

Age-related changes in the geometry of human lumbar spine would lead to changes of its mechanical behaviors. To investigate the effects of the geometric changes, no age-related changes in the material/mechanical properties were considered. Using the finite element method. two age-related models of lumbar spine segments (L3-L4) were constructed. The annulus of the models was modeled as laminate composite elements with 16 layers and 6 materials. The spinal stiffness and facet reaction of the lumbar spine increased with the age-related geometric changes in various combined loadings. Fiber and transverse tensile strains of the inner annulus. cancellous bone stress and end-plate stress decreased with the age-related geometric changes whereas fiber/layer compressive strains of the annulus. facet reaction. ligament reaction and end-plate rigidity increased. Consequently, it appears that in the normal age-related deterioration of discs, the age-related geometric change contributes to the increase of spinal stiffness (the decrease in range of the motion segment), preventing an excessive deformation of the disc.