• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1513-1522
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• 2000

In this study, the burning velocities of LFG and LFG mixed fuels have been numerically determined. C3 reaction mechanism involving 92 species and 621 reactions was adopted in the calculation. The computed burning velocities using C3 mechanism show good agreements with experimental data. Based on numerical results, the maximum burning velocities of LFG and LFG mixed fuels were correlated as a function of CH$_4$ and LFG component percentage at stoichiometric conditions. In addition, the correlations of burning velocities of LFG and LFG mixed fuels were obtained over a wide range of the equivalence ratio. The numerical results are well agreed with the burning velocity correlations. The burning velocity correlations for LFG and LFG mixed fuels suggested in this study can be applied to the practical utilization of LFG.

• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.1-6
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• 2011

Flame extinction and the chemistry of stoichiometric methane/air mixture were investigated numerically in the PSR(perfectly stirred reactor). For the study, PSR code was modified to be possible to unsteady calculation, and the sinusoidal fluctuation was subjected to the residence time. In the region of residence time far from the extinction limit, combustion mode was strongly dependent on the frequency. The low frequency excitation provided the quasi-steady behavior on the temperature and the concentrations of related species, but small variation of temperature was observed under high frequency. In the region of residence time near the extinction limit, the mixture subjected above 1 KHz was still reacting even though extinction had to be occurred under quasi-steady concept. The attenuation of extinction limit resulted from that chemical time was comparable to the flow time. The mean mole fractions of both NO and CO were almost same regardless of imposed frequency. However, the average mole fraction of $C_2H_2$ was decreased as increasing frequency, which implies that soot yield might be reduced at the higher frequency of flow excitation. The result provides the basic concept for flame stabilization, and it will be used to design a mild combustor.

• Journal of the Korean Magnetics Society
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• v.24 no.3
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• pp.71-75
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• 2014

Ground state energy levels of the $Fe^{3+}$ paramagnetic impurity ion in stoichiometric $LiTaO_3$ and in congruent $LiTaO_3$ single crystals were calculated with electron paramagnetic resonance constants. Energy levels between six energy levels were obtained with spectroscopic splitting parameter g and zero field splitting constant D for $Fe^{3+}$ ion. The energy diagrams of $Fe^{3+}$ ion were different from different magnetic field directions ([100], [001], [111]) when magnetic field increases. The calculated ZFS energies of $Fe^{3+}$ ion in stoichiometric and congruent $LiTaO_3$ single crystals for ${\mid}{\pm}5/2$ > ${\leftrightarrow}{\mid}{\pm}3/2$ > and ${\mid}{\pm}3/2$ > ${\leftrightarrow}{\mid}{\pm}1/2$ > transitions were 12.300 GHz and 6.150 GHz, and 59.358 GHz and 29.679 GHz, respectively. It turns out that energy levels of $Fe^{3+}$ paramagnetic impurity in $LiTaO_3$ crystal are different from different crystal growing condition.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.6
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• pp.506-513
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• 2004

Spirulina produces $\gamma$-linolenic acid (GLA), an important pharmaceutical substance, in a relatively low level compared with fungi and plants, prompting more research to improve its GLA yield. In this study, metabolic flux analysis was applied to determine the cellular metabolic flux distributions in the GLA synthetic pathways of two Spiru/ina strains, wild type BP and a high­GLA producing mutant Z19/2. Simplified pathways involving the GLA synthesis of S. platensis formulated comprise of photosynthesis, gluconeogenesis, the pentose phosphate pathway, the anaplerotic pathway, the tricarboxylic cycle, the GLA synthesis pathway, and the biomass syn­thesis pathway. A stoichiometric model reflecting these pathways contains 17 intermediates and 22 reactions. Three fluxes - the bicarbonate (C-source) uptake rate, the specific growth rate, and the GLA synthesis rate - were measured and the remaining fluxes were calculated using lin­ear optimization. The calculation showed that the flux through the reaction converting acetyl­CoA into malonyl-CoA in the mutant strain was nearly three times higher than that in the wild­type strain. This finding implies that this reaction is rate controlling. This suggestion was sup­ported by experiments, in which the stimulating factors for this reaction $(NADPH\;and\;MgCl_{2})$ were added into the culture medium, resulting in an increased GLA-synthesis rate in the wild type strain.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.37-46
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• 2013

The gas jet from a coaxial porous injector for two-phase flows is discharged radially from the porous surface, which encloses the center liquid jet. Several hot-firing test using ethanol/nitrous oxide propellants was conducted to analyze the effect of oxidizer/fuel ratio on the combustion performance, and the uncertainty analysis was performed for the results. The characteristic velocity was affected by oxidizer/fuel ratio similarly with the results of CEA calculation except that the maximum characteristic velocity was appeared in the stoichiometric ratio. The characteristic velocity efficiency was increased as the oxidizer/fuel ratio increases.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.143-153
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• 2012

Mica-type minerals (illites) in the shales of the Jigunsan formation at Seokgaejae in Samchuk-City, Gangwon-do are studied using electron probe micro analysis (EPMA). The average chemical formula of the mica-type mineral obtained from the quantitative analysis is $(K_{1.17}Na_{0.04}Ca_{0.01})(Al_{2.80}Mg_{1.17}Fe_{0.78})(Si_{6.34}Al_{1.66})O_{20}(OH)_4$, which shows a chemical formula within the range of illite. These illites so called can be considered as mixed-phases among muscovite, pyrophyllite and chlorite due to the low contents of interlayer cations and high Mg, Fe. The formula of illite is separated into those three minerals and the method for the separation is newly formulated and proposed in this study. From the formula of illite, the content of muscovite is estimated from K (Na and Ca included), the content of chlorite by Mg+Fe, and the rest remains as pyrophyllite. The chemical formula of muscovite can be calculated by subtracting the compositions of pyrophyllite and chlorite from the analyzed composition of illite using an ideal formula for pyrophyllite and analyzed average formula for chlorite. The calculated formula of muscovite is supposed to be stoichiometric in principle. The result of the separation of analyzed illite is 61% muscovite, 27.3% chlorite and 11.7% pyrophyllite and the calculated formula of muscovite after separation is $(K,Na,Ca)_{2.00}Al_{3.69}(Si_{6.75}Al_{1.25})O_{20}(OH)_4$. The calculated formula of muscovite slightly low in Al content can be considered to be reasonable in general when the low content of Al in the rock and the uncertainties of chlorite compositions used in the calculation are counted. This supports that the method of separation proposed in this study is also applicable.