• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.147-155
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• 1996

This study investigated the characteristics of ultrasonic-energy-added diesel fuel. We compared the characteristics used H-NMR spectrum, FT-IR spectrum, viscosity and surface tension between conventional diesel fuel and ultrasonic-energy-added diesel fuel. The result are obtained as follow : We knew that ultrasonic energy result to reduce BI and weaken viscosity and surface tension. Also, the ultrasonic energy caused to reduce aromatics Ha and increase Alkanes Hγ. The effect of ultrasonic-energy-added dieselfuel was principally caused by change of chemical structures and a physical characteristics.

• Journal of the Korean Chemical Society
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• v.28 no.1
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• pp.26-33
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• 1984

The rate constants for the following vibration-to-vibration energy exchange reactions have been calculated theoretically for the temperature range from 300 to 800K and for n = 2 to 5. HF(v=n) + DF(v=0) ${\to}$ HF(v=n-l) + DF(v=l) + ${\Delta}E$(a) DF(v=n) + HF(v=0) ${\to}$ DF(v=n-l) + HF(v=l) + ${\Delta}E$(b) In calculation the loosely-held, non-rigid dimer collision model and semiclassical method have been employed. The results show that the rate constants for the processes (a) are much greater than those for the processes (b). Also, it is found that the rate constants for the processes (a) increase with decreasing temperature and with increasing quantum number, while those for the processes (b) show the opposite tendencies. These findings are explained in terms of the sign and magnitude of the energy mismatch, ${\Delta}E$.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.626-633
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• 2006

Bucheon city has been rapidly urbanized and steadily enlarged. Also, the city depends on groundwater as an alternative water resource. The objective of this study is to characterize the hydrogeology in this city including the recharge of groundwater and hydraulic property of an aquifer in order to investigate the chemical characteristics and contamination of groundwater in the Bucheon area. Eleven groundwater wells in the Bucheon area were selected for applying certain hydraulic tests, such as pumping and recovery tests. Theis method and Theis recovery method were used to obtain hydraulic parameters, such as hydraulic conductivity, transmissivity by applying recovery tests. The playground of school and uncovered areas layed a major function of recharging areas. The groundwater well in these areas showed high recharge, transmissivity, and hydraulic conductivity. In a downtown area, groundwaier wells showed low pumping capacity and hydraulic parameters. Groundwater samples were collected from 48 different locations in the Bucheon area and that showed very various chemical composition in groundwater Their electrical conductivity showed various ranges from 70.4 to $1,287{\mu}S/cm$. The composition more significantly affected the groundwater due to the land use and urbanization than that of the aquifer rock type.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.70-74
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• 1999

The electrode kinetic parameters at the Pd/0.5 M LiOH electrolyte interface have been qualitatively studied using the phase-shift method. The phase shift $(\phi)$ depends on both the cathode potential (E>0) and frequency (f), and $\theta$ is inversely proportional to the fractional surface coverage $\theta$. At an intermediate frequency (10 Hz), the phase-shift profile $(\phi\;vs.\;E)$ can be related to the fractional surface coverage $(\theta\;vs.\;E)$. The phase-shift method can be used to estimate or plot the Frumkin adsorption isotherm. The rate (r) of change of the free energy of adsorption with $({\theta})$ is 22.3 kJ/mol. The equilibrium constant (K) for adsorption and the standard free energy $({\Delta}G_{\theta})$ of the adsorbed hydrogen atom $(H_{ads})$ are $3.7\times10^{-3}{\Delta}G_{\theta}>-8.4kJ/mol$, respectively. For 1$0.38>\theta>0$, the energy liberation or the exothermic reaction for hydrogen adsorption at the Pd cathode can be occurred. The electrode kinetic parameters $(r,\;K,\;{\Delta}G_{\theta}$ depend on the fractional surface coverage $({\theta})$ or the phase shift $(\phi)$.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.227-231
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• 1999

Disposable, amperometric glucose sensor was constructed using platinised carbon paste electrode. The sensor response was studied by amperometry and cyclic voltammetry applying sample solutions on the strip-type electrode. Platinization of screen-printed carbon paste electrode effectively improved the electrochemical reversibility of a mediator and the analytical characteristics of the sensor. The heterogeneous rate constant for $[Fe(CN)_6]^{4-/3-}$ was $1.45\times10^{-2}cm{\cdot}s^{-1}$. An applied potential of 0.3V vs. Ag/AgCl resulted in the best selectivity for glucose. The apparent Michaelis-Menten constant for glucose on the strip sensor, $K_m^{app}$, was 24.5 mM. To evaluate the analytical performance of the glucose sensor strip, a correlation study was performed with the NOVA S.P, Ultra M analyzer for 30 serum samples containing $80\~297mg/dL$ of glucose: the correlation coefficient value was 0.983. It can be seen that the strip sensor has satisfactory precision and accuracy.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.4
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• pp.199-205
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• 2015

Nitrogen and phosphorus are the limiting elements for growth of phytoplankton, which is a major primary producer of marine ecosystem. Incidentally the stoichiometry of N/P of ocean waters, measured by the (nitrate + nitrite)/phosphate ratio converges to a constant of 16. This characteristic ratio has been used widely for the understanding the ecosystem dynamics and biogeochemical cycles in the ocean. In the East Sea, several key papers were issued in recent years regarding the climate change and its impact on ecosystem dynamic and biogeochemical cycles using N/P ratio because the East Sea is a "miniature ocean" having her own meridional overturning circulation with the appropriate responding time and excellent accessibility. However, cited N/P values are different by authors that we tried to propose a single representative value by reanalyzing the historical nutrient data. We present N/P of the East Sea as $12.7{\pm}0.1$ for the year 2000. The ratio reveals a remarkable consistency for waters exceeding 300m depth (below the seasonal thermocline). We recommend to use this value in the future studies and hope to minimize confusion for understanding ecosystem response and biogeochemical cycles in relation to future climate change until new N/P value is established from future studies.

• Journal of the Korean Applied Science and Technology
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• v.38 no.4
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• pp.994-1002
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• 2021

The solubilization constants (K_s) of 4-halogenated aniline derivatives by cationic surfactants (DTAB, TTAB, and CTAB) were measured by the UV-Vis method. As a result, the K_s values decreased as the temperature increased for all the aniline derivatives and showed a tendency to increase as the radius of the halogen substituent and the hydrophobic length of surfactant increased. The calculated values of ΔG^o and ΔH^o for these solubilizations all showed negative values within the measured range, but all the ΔS^o values showed positive values. For all the 4-halogenated anilines, the ΔG^o values all tended to decrease as the temperature increased, but both values of ΔH^o and ΔS^o showed a tendency to increase. In addition, as the radius of the halogen substituent increased, the values of ΔH^o and ΔS^o tended to decrease in general. However, when the hydrophobic group length of the surfactant was increased, the values of these thermodynamic functions showed a tendency to increase in general, although it differed depending on the type of aniline derivative. From the changes of such functions, it was possible to estimate the type and strength of interactions between 4-halogenated aniline and micelle, and the location at which they were solubilized in the micelle.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.843-849
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• 2012

When we use NiO based particle as an oxygen carrier in a chemical looping combustion system, the fuel conversion and the $CO_2$ selectivity decreased with increasing reaction temperature within high temperature range (> $900^{\circ}C$) due to the increment of exhaust CO concentration from reduction reactor. To improve reduction reactivity at high temperature, the applicable metal oxide component was selected by calculation of the equilibrium CO concentration of metal oxide components. After that, feasibility of reduction reactivity improvement at high temperature was checked by using solid mixture of the selected metal oxide particle and NiO based oxygen carrier. The reactivity was measured and investigated using batch type fluidized bed. The solid mixture of $Co_3O_4/CoAl_2O_4$(10%) and OCN706-1100(90%) showed higher fuel conversion, higher $CO_2$ selectivity and lower CO concentration than OCN706-1100(100%) cases. Consequently, we could conclude that improvement of reduction reactivity at high temperature range by adding some $Co_3O_4$ based oxygen carrier was feasible.