• Fire Science and Engineering
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• v.27 no.3
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• pp.47-51
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• 2013

The explosion limit is one of the major combustion properties used to determine the fire and explosion hazards of the flammable substances. The explosion limit of organic acids have been shown to be correlated the heat of combustion and the chemical stoichiometric coefficients. In this study, the lower explosion and upper explosion limits of organic acids were predicted by using the heat of combustion and chemical stoichiometric coefficients. The values calculated by the proposed equations agreed with literature data within a few percent. From the given results, using the proposed methodology, it is possible to predict the explosion limits of the other organic acids.

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.5-11
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• 2015

The explosion limit is one of the major combustion properties used to determine the fire and explosion hazards of the flammable substances. The explosion limit of aldehydes have been shown to be correlated the heat of combustion and the chemical stoichiometric coefficients. In this study, the lower explosion and upper explosion limits of aldehydes were predicted by using the heat of combustion and chemical stoichiometric coefficients. The values calculated by the proposed equations agreed with literature data above determination coefficient 0.99. From the given results, using the proposed methodology, it is possible to predict the explosion limits of the aldehydes.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.121-127
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• 2004

It is necessary to supply external carbon source for enhancement of biological nitrogen removal from domestic wastewater with low influent C/N ratio. Sulfide was chosen as a cost effective electron donor and reaction stoichiometry for autotrophic denitrification was investigated by conducting bench-scale experiments in this study. Higher sulfur to nitrogen (S/N) ratio than the calculated value from theoretical reaction stoichiometry was required when the anoxic reactor was operated at open condition because dissolved oxygen introduced by surface aeration reacted with sulfide with ease. In addition, higher sulfate production and lower yield of microorganism could be observed under the same condition. It was possible to obtain reliable reaction stoichiometry for autotrophic denitrification by establishing pure anoxic condition. Linear relationship between bacterial growth and consumption of nitrate, sulfide, alkalinity, and sulfate production enabled to derive a relatively correct reaction stoichiometry for autotrophic denitrification when sulfide was used as an electron donor.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.33-39
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• 1986

The x-values of nonstoichiometry chemical formulas, Sm$O_{1.5+x}$ and Zr$O_{2+x}$, have been measured in temperature range from 500$^{\circ}$C to 1000$^{\circ}$C under oxygen pressure of 2 ${\times}10^{-1}$ to 1 ${\times}10^{-5}$ atm by gravimetric method. The enthalpies of formation of defect in samarium sesquioxide and zirconium dioxide decrease with decreasing oxygen pressure and are all positive. The 1/n values calculated from the slopes of the plots of log x vs. log $PO_2$ increase with temperature and are positive values which mean the higher oxygen pressure dependence at higher temperature. From x-values and thermodynamic data, it is found out that the nonstoichiometric defect is fully ionized metal vacancy. The conduction mechanisms of the systems are also discussed with respect to the nonstoichiometric compositions.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.44-50
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• 2011

Explosion limit is one of the major combustion properties used to determine the fire and explosion hazards of the flammable substances. In this study, the lower explosion limit(LEL) and upper explosion limit(UEL) of ethers were predicted by using the heat of combustion and stoichiometric coefficients. The values calculated by the proposed equations agreed with literature data within a few percent. From the given results, using the proposed methodology, it is possible to predict the explosion limits of the other flammable ethers.

• Journal of the Korean Chemical Society
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• v.28 no.4
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• pp.231-237
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• 1984

The x-values in the nonstoichiometric chemical formulas $YO_{1.5+x}\;and\;HoO_{1.5+x}$, have been measured in the temperature range from 700$^{\circ}$C to 1000$^{\circ}$C under oxygen pressures from $2{\times}l0^{-1}\;to\;1{\times}10^{-6}$ atm by gravimetric method. The observed x-values increase with increasing temperature and oxygen pressure. The enthalpies of formation of excess oxygen in yttrium oxide and holmium oxide decrease with decreasing oxygen pressure and are all positive values representing an endothermic process. The 1/n values calculated from the slopes of the plots of log x vs. log $P_{O2}$ increase with temperature and are positive values which means the higher oxygen pressure dependence at higher temperature. We have examined the nonstoichiometric defect and conduction mechanism from x-values and thermodynamic data.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.636-643
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• 2006

Supercritical water oxidation of DMMP using continuous flow reactor was studied at temperature ranging from 440 to $540^{\circ}C$ and a fixed pressure of 242 bar. The range of residence times in the reactor was from 10 to 26 s, and oxygen excess value varied from -40 to 200%. Destruction efficiencies (DE) of DMMP were greater than 99.7% at $540^{\circ}C$, and increased as the DMMP concentrations were increased. DE of DMMP were significantly affected by oxygen concentration under stoichiometric amount, but showed little difference over stoichiometric amount. On the basis of 30 data with conversions greater than 85%, kinetic correlations for the DE of DMMP were developed. The pre-exponential factor was $(1.10{\pm}0.76){\times}10^6$, and the activation energy was $90.66{\pm}3.87kJ/mol$, and the reaction orders for DMMP and oxygen were $1.02{\pm}0.03$, $0.32{\pm}0.03$, respectively. The model predictions agreed well with the experimental data.

• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.511-516
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• 1992

The x-values of the nonstoichiometric compound YbO$_x$ have been measured in a temperature range of 600 to 1150$^{\circ}C$ under oxygen partial pressure of 1.00 ${\times}$ 10$^{-2}$ atm∼atmospheric air pressure. The values are varied between 1.55453 and 1.60794 in the conditions. The enthalpy of the formation for x' in YbO$_{1.5＋x'}$(${\Delta}$H$_f$) was 1.55, 1.18, and 1.05 kJ/mol under the above conditions, respectively. The electrical conductivities of the oxides or ${\sigma}$ have been measured in the temperature range from 600 to 1100$^{\circ}C$ under oxygen partial pressure of 1.00 ${\times}$ 10$^{-5}$ ∼ 2.00 ${\times}$ 10$^{-1}$ atm. They varied from 10$^{-9}$ to 10$^{-5}$ ohm$^{-1}$ cm$^{-1}$ within the semiconductor range. The Arrhenius plots of the electrical conductivities show a linearity and the activation energy for the conduction was about 1.7eV. The oxygen partial pressure dependence of the conductivity or 1/n value increases with the pressure. The nonstoichiometric conduction mechanism of the oxide was discussed in terms of the x values, ${\sigma}$ values, and the thermodynamic data.

• Analytical Science and Technology
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• v.30 no.6
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• pp.405-410
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• 2017

High energetic materials (HEMs) have been used in fuels, civil engineering and architecture as well as military purposes such as explosives and propellants. The essential process for the development of new energetic compounds is to accurately calculate its detonation performances. The most typical equation for calculating the explosive performance is the Kamlet-Jacobs (K-J) equation. In the K-J equation, the parameter such as the number of moles of gaseous products at the explosion, the average molar mass of gas products, and the explosion heat greatly affect the explosion performance. These depend on the product composition for the detonation reaction. In this study, detonation products of 65 high energetic molecules (HEMs) were calculated from the various rules such as Kamlet-Jacobs, Kistiakowsky-Wilson, modified Kistiakowsky-Wilson, Springall-Roberts rules to calculate more accurate detonation velocity (Dv). In addition, they were applied to five kinds of detonation velocity equations proposed by K-J, Rothstein, Xiong, Stine and Keshavarz. The mean absolute error and root mean square error of HEMs were obtained from experimental and calculated velocity value for each method. The K-J and Xiong equation that is slightly complex showed a lower mean absolute error than the simple Rothstein and Keshavarz equation. When the mod-KW rule was applied to the Xiong equation, the detonation velocities were the most accurate. This study compared the various method of calculating the detonation velocity of HEMs to obtain accurate HEMs performance.

• Journal of the Korean Chemical Society
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• v.35 no.2
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• pp.99-104
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• 1991

Nonstoichiometric solid solutions of Sr$_{1+x}Er _{1-x} FeO _{4-y}$ system (x = 0.00, 0.25, 0.50, 0.75 and 1.00) with layered $K_2NiF_4$ type structure were prepared at 1350$^{\circ}$C under atmospheric pressure. By the analysis of X-ray diffraction, the crystallographic structures of the solid solution of all compositions were found to be pseudo-tetragonal system. Nonstoichiometric chemical formulas have been determined by Mohr salt analysis. It shows that the amount of Fe$^{4+}$ increases with increasing x up to 0.50 and then decreases, and the value of oxygen nonstoichiometry increases with increasing x value. Mixed valency states of Fe$^{3+}$ and Fe$^{4+}$ in the sample were identified again by Mossbauer spectroscopic analysis at 298 K. Electrical conductivity varied within the semiconductivity range of 10-2 ∼ 10-7(${\Omega}$-1cm-1), activation energy for electrical conduction decreased with the increment of the mole ratio of Fe$^{4+}$ or ${\tau}$ value. The conduction mechanism could be explained by the hopping model of the conduction electrons between the valency states of Fe$^{3+}$ and Fe$^{4+}$.