• Journal of the Korean Chemical Society
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• v.53 no.4
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• pp.427-431
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• 2009

The thermodynamical mechanism of the extraction of soybean isoflavones from soybean residuals using organic solvent method has been studied. On the basis of experiments, a simple model for determining the distribution coefficients in organic solvent extraction was employed to calculate the thermodynamical functions between $K,\;{\Delta}H^0,\;{\Delta}S^0\;and\;{\Delta}G^0$ in the soybean isoflavones extraction process. The results show that the soybean isoflavones extraction is an endothermic and an entropy-increasing process: the ${\Delta}G^0$ decreases when the temperature arises.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1195-1204
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• 2002

We calculated dose rate using radiative transfer equations to consider radiative processes distinctly. The dose rate at Pohang(36°02'N, 129°23'E) was calculated using measured ozone and meteorological data and two-stream approximations(quadrature, Eddington, delta Eddington, PIFM(practical improved flux method), discrete ordinate, delta discrete ordinate) are used in solving equation. The purpose of this study is to determine the most compatible radiative transfer approximation for simulating the radiative and photochemical processes of atmosphere through comparision between calculated and measured values. Dose rate of the biologically effective irradiance in the region 0.28-0.32 U m showed the highest value when quadrature and Eddington was used and lower value on condition that delta scaling was applied. Correlation coefficient between dose rate at surface using radiation transfer equation and measured UV-B at Pohang was 0.78, 0.79 and 0.81 when delta Eddington, PIFM and delta discrete ordinate were used. Also, in case of above approximations were used, MBE(Mean Bias Error) was within -0.3MED/30min and RMBE(Relative Mean Bias Error) was below 10% between 1200 LST and 1400 LST Approximations which are compatible in estimating radiative process are delta Eddington, PIFM and delta discrete ordinate. Especially, in case that radiative process is considered more detail, delta discrete ordinate increased the number of stream is proper.

• Journal of the Korean Society of Safety
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• v.6 no.4
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• pp.81-87
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• 1991

We propose the crack growth rate equation which will model fatigue crack growth rate behavior such that constant stress amplitude fatigue crack growth behavior can be predicted. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R＝0.2, R＝0.4 and R＝0.6. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. Through constant stress amplitude fatigue test by using unloading elastic compliance method, it is confirmed that crack closure is a close relationship with fatigue crack propagation. We describe simply fatigue crack propagation behavior as a function of the effective stress intensity factor range ($\Delta$ $K_{eff}$＝U .$\Delta$K) for all three regions (threshold region, stable region). The fatigue crack growth rate equation is given by da / dN＝A($\Delta$ $K_{eff}$­$\Delta$ $K_{o}$ )$^{m}$ / ($\Delta$ $K_{eff}$­$\Delta$K) Where, A and m are material constants, and $\Delta$ $K_{o}$ is stress intensity factor range at low $\Delta$K region. $K_{cf}$ is critical fatigue stress intensity factor.actor.

• Journal of the Korean Mathematical Society
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• v.32 no.3
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• pp.541-551
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• 1995

The nonlinear Klein Gordon equation $$ (1) \frac{\partial t^2}{\partial^2 u} - \Delta u + V_u(u) = f $$ where $\Delta$ is the Laplacian operator in $R^d (d = 1, 2, 3), V_u(u)$ is the derivative of the "potential function" V, and f is a source term independent of the solution u, in various areas of mathematical physics.l physics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.263-268
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• 2001

The constant .DELTA. K fatigue tests are performed in SS41 and its weldment. The LASER ISDG method is used in determination of crack opening ratio. This method is more precise than indirect measurement method, faster and easier than other direct measurement method. And obtained results are followed 1) Crack opening ratio U is proportional to fatigue crack growth rate da/dN at constant .DELTA. K 2) Fatigue crack growth rate da/dN in weldment increases in weld metal and heat affected zone, decreases in base metal as crack grows.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.428-433
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• 2009

Dissolved oxygen is considered as one of the important water-quality constituents in streams from one century ago and fishes perish in low dissolved oxygen concentration. Environmental scientists and engineers have introduced the deterministic model to estimate dissolved oxygen concentration of streams and recommended the use of the Delta Method (DM), Approximate Delta Method (ADM), Extreme Value Method (EVM) and Optimization Method (OPT) which can be applied in no spatial variation of dissolved oxygen. The diurnal or annual variation of dissolved oxygen is mainly determined from the parameters such as reaeration rate, 1st production rate and respiration rate which are related to dissolved oxygen. Each method was briefly introduced and applied to two sampling sites of Anseong Stream watershed in this paper. The limitation, advantages and disadvantages of each method were reviewed and analyzed after running the each method. From these analyses, the benefit-cost approach to estimate dissolved oxygen effectively in streams was recommended.

• Journal of the Korean Chemical Society
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• v.44 no.3
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• pp.177-183
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• 2000

The interaction of phenoxide anion with .the mixed micelles of CTAB(Cetyl-trimethylammonium bromide) and TTAB(Tetradecyltrimethylammonium bromide) was studied by UV/Vis spectrophotometric method. The solubilization constants($K_s$) of phenoxide anion into the mixed micellar phase and the critical micellar concentrations(CMC) of those mixed surfactant systems have been measured and analyzed with the change of overall mole fraction of CTAB($\alpha_{CTAB}$) The effects of additives(n-pentanol and NaBr) on the solubilization of phenoxide anion by those mixed surfactant systems have been also measured. There was a great decrease on the values of solubilization constant and CMC with these additives. For the thermodynamic study, the dependence of $K_s$ values on temperature has been measured and various thermodynamic parameters(${\Delta}G^0_s$, ${\Delta}H^0_s$ and ${\Delta}S^0_s$) have been also calculated. The results show that all the values of ${\Delta}G^0_s$ and ${\Delta}H^0_s$ are negative within the measured temperature region but the values of ${\Delta}S^0_s$ are positive.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.517-523
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• 2014

The micellization of TTAB(tetradecyltrimethylammonium bromide) and the solubilization of 4-halogenated phenol isomers in aqueous solution of that surfactant in water have been studied by the UV-Vis spectrophotometric method. Those properties in aqueous solutions of NaCl and n-butanol have been also measured to determine the interactions between the micelle and 4-halogenated phenols and the solubilized sites of those molecules in the micelle. The results show that the values of ${\Delta}G^o_m$ and ${\Delta}G^o_s$ are all negative and the trends of those values depend on both the kinds and the concentrations of additives. Namely, by adding NaCl both ${\Delta}G^o_m$ and ${\Delta}G^o_s$ values are all decreasing, but by adding n-butanol the ${\Delta}G^o_m$ value decreases and the ${\Delta}G^o_s$ value increases.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.337-342
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• 2010

The interaction of monochlorophenol isomers with the micellar system of TTAB (tetradecyltrimethylammonium bromide) was studied by the UV/Vis spectrophotometric method. The solubilization constants ($K_s$) of monochlorophenol isomers into this micellar system have been measured with the change of temperature. Various thermodynamic parameters (${\Delta}G^{\circ}_s$, ${\Delta}H^{\circ}_s$, and ${\Delta}S^{\circ}_s$) have been calculated and analyzed from the dependence of $K_s$ values on the temperature. The results show that the values of ${\Delta}G^{\circ}_s$ and ${\Delta}H^{\circ}_s$ are all negative but the values of ${\Delta}S^{\circ}_s$ are all positive for the solubilizations of all isomers within the measured temperature range. The effects of additives (n-butanol and NaCl) on the solubilization of monochlorophenol isomers by the same surfactant system have been also measured. There was a great change on the values of $K_s$ and CMC simultaneously with these additives. From these changes we can postulate the solubilization sites of each isomer in the micellar system of TTAB.

• Journal of the Korean Chemical Society
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• v.57 no.6
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• pp.665-671
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• 2013

The solubilization of p-bromophenol by the micellar system of TTAB(tetradecyltrimethylammonium bromide) and the micellization of TTAB were studied by the UV-vis spectrophotometric method simultaneously. And the effects of temperature on these properties have been measured for the thermodynamic study. The results show that the ${\Delta}G_s{^o}$ and ${\Delta}H_s{^o}$ values are negative and the ${\Delta}S_s{^o}$ values are positive for the solubilization of p-bromophenol within the measured range. On the other hand, the ${\Delta}G_m{^o}$ values are negative and the ${\Delta}H_m{^o}$ and ${\Delta}S_m{^o}$ values are positive for the micellization of TTAB. The effects of additives such as n-butanol and NaCl have been studied also for both properties and the relationship between these two properties has been also studied. From the results, we can postulate the solubilization site of p-bromophenol in the micelle.