• Journal of the Korean Chemical Society
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• v.50 no.5
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• pp.355-361
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• 2006

The critical micelle concentration (CMC) and the counterion binding constant (B) in a mixed micellar state of the sodium dodecylbenzenesulfonate (DBS) with the polyoxyethylene(23) lauryl ether (Brij 35) at 25oC in water and aqueous solutions of n-butanol (0.1M, 0.2M, and 0.3M) were determined as a function of a1 (the overall mole fraction of DBS) by the use of electric conductivity method and surface tensiometer method. Various thermodynamic parameters (Xi, i, Ci, aiM, , and Hmix) were calculated by means of the equations derived from the nonideal mixed micellar model. The effect of n-butanol on the micellization of the DBS/Brij 35 mixtures has been also studied by analyzing the measured and calculated thermodynamic parameters.

• Journal of the Korean Chemical Society
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• v.41 no.1
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• pp.12-17
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• 1997

The critical micelle concentrations(CMC*) and the counterion binding constants(B) in a micellar state of the mixed surfactant systems of sodium dodecylsulfate(SDS) with sodium dodecylbenzenesulfonate(DBS) at 25℃ in pure water and in aqueous solutions of n-butanol were determined as a function of α1 (the overall mole fraction of SDS) by the use of electric conductivity method. Various thermodynamic parameters(Xi, γi, Ci, aiM, β, ΔHmix and ΔGm0 for the micellization of SDS/DBS mixtures were calculated and analyzed by means of the equations derived from the nonideal mixed micelle model. The effect of n-butanol on the mixed micellization of SDS/DBS mixtures have been measured and analyzed by comparing the values of the thermodynamic parameters in pure water with those in aqueous solutions of n-butanol(0.1 M, 0.2 M, and 0.3 M).

• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.519-525
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• 1998

The critical micelle concentration $(CMC^{\ast})$ and the counterion binding constant (B) in a micellar state of the mixed surfactant systems of dodecylpyridinium chloride (DPC) with dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyldimethylethylammonium bromide (CDEAB) were determined at $25^{\circ}C$ as a function of ${\alpha}_1$ (the overall molc fraction of DPC) by the use of electric conductivity method. Various thermodynamic parameters $(X_{i},\;{\gamma}_{I},\;C_{i},\;a^{M}_{i}, \beta,\;{\Delta}H_{mix}, \;and\; {\Delta}G^{o}_{m})$ for the micellization of DPC/DTAB, DPC/TTAB, and DPC/CDEAB mixtures were calculated and analyzed for each system by means of the equations derived from the pseudophase separation model. The results show that the DPC/DTAB mixed system has the greatest deviation and the DPC/CDEAB mixed system has the smallest deviation from the ideal mixed micellar model.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.642-647
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• 2000

Nanocrystalline NiAl alloy containing 36at.%Al was synthesized by mechanical alloying (MA). Synthesized powder was sintered by a pulse electric current sintering (PECS) facility. Effecting parameters on the phase transformation were discussed in terms of cooling rate and time spent on heat treatment. The behavior of phase transformation for sintered parts was examined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) method. Microstructure was observed by scanning electron microscopy (SEM). Martensitic lattice parameter and volume fraction was calculated by direct comparison method in X-ray diffraction analysis.

• Resources Recycling
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• v.7 no.5
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• pp.13-18
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• 1998

This study was carried out to understand the properties of the E.A.F. steel-making dusts for stabilization processing. The properties are related to mincral composition, shape, particle size, magnetism, density, porosity and leaching characteristic. the dust particles, the size of which ranges from sub-micron to tens-micron, were mainly spherical like balls that were agglomerated each other: the large particles were generally Fe-rich and the small particles were spherical like balls that were agglomerated each other: the large particles were franklinite (ZnFe$_{2}O_{4}$), magnetite (Fe$_{3}O_{4}$) and zincite (ZnO) by XRD analysis. When the dusts were sieved by a wet process, the particle fraction over 200 mesh had 1.5 wt.% with magnetite and quartz. The particles in the size range of 200-500 mesh consisted of magnetite, franklinite. The 82 wt.% of the steel-making dusts were occupied by the particles finer than 500 mesh and contained franklinite and zincite as main mineralogical compositions. When the dusts of around 78% porosity compressed under the load of approximately 1 KPa, the porosity decreased to 68% and to 535 under around 13 KPa. When the E.A.F. dusts were leached according to the Korea standard leaching procedure on the waster, the heavy metals exceeding the leaching criteria were cadmium, lead and mercury.

• Journal of the Korean Applied Science and Technology
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• v.26 no.2
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• pp.117-123
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• 2009

Caprylic/Capric triglyceride-in-water emulsions stabilized by Nikkol HCO-60 and HCO-10 were prepared using emulsion inversion point method at different HLB values. Emulsions with various droplet sizes were formed, and emulsion inversion point was detected by electrical conductivity. The change in emulsion droplet sizes and long term stability were monitored using laser scattering method and visual method. The droplet sizes and stability of emulsions were affected by HLB of surfactant. At emulsion inversion point, the water volume fraction increased as the HLB of surfactants decreased. According to our analysis, this resulted from a tendency of forming the W/O (water-in-oil) emulsion as the HLB of surfactants was decreased. The emulsion inversion point was clearly detected by the microscope and the electric conductivity meter. Nanometer-sized emulsion was obtained at the optimum HLB by using emulsion inversion point method. The main pattern of instability of emulsions in HLB 12 and 13 systems was Ostwald ripening. However, The patterns of instability of emulsions below 11 of HLB systems were Ostwald ripening and coalescence. All emulsions produced with surfactants in the range of HLB 8-13, creaming caused by density difference between water phase and oil phase.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.555-566
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• 1999

The rainwater samples were collected from the 1100 Site of Mt. Halla and Cheju city during the period of March in 1997 to August in 1998, and the major soluble ions were analyzed. The confidence of analytical data was confirmed by using the comparison methods such as ino-balance, electric conductivity and acid fraction, all of which correlation coefficients were above 0.94. The ionic strengths lower than $10^{-4}$ M, the basis for the pure rainwater, were found in 47% and 38% at 1100 Site and Cheju city, respectively. The precipitations in Cheju city were more influenced by the oceanic effect than those in 1100 Site. The acidity contribution was mainly by $SO_4^{2-}$ and $NO_3^-$ in both areas, and the organic acids have contributed to the acidity with only 5~7%. The neutralization factors by $NH_3$ were about 46% at both 1100 site and Cheju city, whereas those by $CaCO_3$ were 11% and 15% at 1100 site and Cheju city respectively, and the free acidity were both about 35% in average. From the MSA analysis, it was found that the air in Cheju island has been influenced by the pollution from the other areas. The sources of the rainwater components in 1100 Site and Cheju city were also studied with a factor analyzing way, and the most probable factors were found to be anthropotgenic, oceanic, and soil-sourced. The results of multiple regression analysis have shown that $SO_4^{2-}$ was dissolved mostly in the form of $H_2SO_4, CaSO_4 and (NH_4)_2SO_4$, and $NO_3^-$ was in the form of $HNO_3, Ca(NO_3)_2 and NH_4NO_3$.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.3
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• pp.197-210
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• 2000

Suppressive role of $Na^+-Ca^{2+}$ exchange in myocardial tension generation was examined in the negative frequency-force relationship (FFR) of electric field stimulated left atria (LA) from postnatal developing rat heart and in the whole-cell clamped adult rat ventricular myocytes with high concentration of intracellular $Ca^{2+}$ buffer (14 mM EGTA). LA twitch amplitudes, which were suppressed by cyclopiazonic acid in a postnatal age-dependent manner, elicited frequency-dependent and postnatal age-dependent enhancements after $Na^+-reduced,\;Ca^{2+}-depleted$ (26 Na-0 Ca) buffer application. These enhancements were blocked by caffeine pretreatment with postnatal age-dependent intensities. In the isolated rat ventricular myocytes, stimulation with the voltage protocol roughly mimicked action potential generated a large inward current which was partially blocked by nifedipine or $Na^+$ current inhibition. 0 Ca application suppressed the inward current by $39{\pm}4%$ while the current was further suppressed after 0 Na-0 Ca application by $53{\pm}3%.$ Caffeine increased this inward current by $44{\pm}3%$ in spite of 14 mM EGTA. Finally, the $Na^+$ current-dependent fraction of the inward current was increased in a stimulation frequency-dependent manner. From these results, it is concluded that the $Ca^{2+}$ exit-mode (forward-mode) $Na^+-Ca^{2+}$ exchange suppresses the LA tension by extruding $Ca^{2+}$ out of the cell right after its release from sarcoplasmic reticulum (SR) in a frequency-dependent manner during contraction, resulting in the negative frequency-force relationship in the rat LA.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.92-97
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• 1999

The mechanical and electrical properties of the hot-pressed and annealed $\beta-Sic$+39vol.%$ZrB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of $Al_2O_3+Y_2O_3(6:4wt%)$. In this microstructures, no reactions and elongated $\alpha$-SiC grains with equiaxed $ZrB_2$, gains were observed between $\beta-SiC$ and $ZrB_2$, and the relative density was over 97.6% of the theoretical density. Phase analysis of the composites by XRD revealedmostly of $\alpha$-SiC(6H, 4H), $ZrB_2$, and weakly $\beta-SiC$(15R) phase. The fracture toughness decreased with increasing $Al_2O_3+Y_2O_3$ contents and showed the highest of $6.37MPa.m^{\fraction ane-half}$ for composite added with 4wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity increased with increasing $Al_2O_3+Y_2O_3$contents and showed the lowest of $1.51\times10^{-4}\Omega.cm$ for composite added with $Al_2O_3+Y_2O_3$ additives at $25^{\circ}C$. This reason is the increasing tendency of pore formation according to amount of liquid forming additives $Al_2O_3+Y_2O_3$. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) against temperature up to $700^{\circ}C$.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.50-55
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• 2011

Energy resistance welding (ERW) is a pipe-producing process that has high productivity and low manufacturing cost. However, the high heat input of ERW degrades the mechanical property of the pipe. This study investigates the effect of heat input and alloying elements on microstructure and mechanical properties of ERW pipes. As the heat input increased, the ferrite amount increased. The ferrite amount in the weld centerline was larger than t at in the weld boundary. Medium carbon steels (S45C and K55) having 0.3~0.4wt.% carbon yielded a significant difference of ferrite amount in the weld centerline and weld boundary. High alloyed steels (DP780 and K55) having 1.5~1.6wt.% Mn showed a ferrite rich zone in the weld centerline. These phenomena are probably due to decarburization and demanganisation in the weld centerline. As the ferrite fraction increased, the hardness decreased a little for the S45C steels. In addition, DP780 steels and K55 steels showed that the hardness drops when those steels have a ferrite rich zone. But we demonstrated the good tensile property of the DP780 steels and K55 steels in which Mn is included.