• The Korean Journal of Ceramics
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• 제4권2호
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• pp.122-127
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• 1998

Conductivities of polycrystalline ceria doped with several rare earth oxides were measured by AC admittance and DC four probe method. The conductions were separated into grain and grain boundary contributions using the complex admittance technique as well as grain size dependence of conductivity. The grain size dependence of polycrystalline conductivity, which can be adequately described by the so-called brick layer model, appears to give a more reliable measure of the grain conductivity compared to the complex admittance method. Polycrystalline resistivity(1/conductivity) increases linearly with the reciprocal of grain size. The intercept of resistivity vs. inverse grain size plot gives a measure of the grain resistivity and the slope gives a measure of the grain boundary resistivity. It was also noted that errors involved in the analysis of experimental data may be different between the complex admittance method and the impedance method. A greater resolution of the spectra was found in the complex admittance method, insofar as the present work is concerned, suggesting that the commonly used equivalent circuit may require re-evaluation.

• Bulletin of the Korean Chemical Society
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• 제20권11호
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• pp.1329-1334
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• 1999

The curing characteristics of diglycidyl ether of bisphenol A (DGEBA) with diaminodiphenylmethane (DDM) as a curing agent were studied using differential scanning calorimetry (DSC), rheometrics mechanical spectrometry (RMS), and dielectric analysis (DEA). The isothermal curing kinetics measured by DSC were well represented with the generalized auto-catalytic reaction model. With the temperature sweep, the inverse relationship between complex viscosity measured by RMS and ionic conductivity obtained from DEA was established indicating that the mobility of free ions represented by the ionic conductivity in DEA measurement and the chain segment motion as revealed by the complex viscosity measured from RMS are equivalent. From isothermal curing measurements at several different temperatures, the ionic conductivity contribution was shown to be dominant in the dielectric loss factor at the early stage of cure. The contribution of the dipole relaxation in dielectric loss factor became larger as the curing further proceeded. The critical degrees of cure, at which the dipolar contribution in the dielectric loss factor starts to appear, increases as isothermal curing temperature is increased. The dielectric relaxation time at the same degree of cure was shorter for a sample cured at higher curing temperature.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.495-500
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• 1989

The ionic conductivity of polycrystalline, glass, and glass-ceramic silicates was measured using two-terminal AC method with blocking electrode over a frequency range of 100 Hz to 100 KHz in the temperature range of $200^{\circ}C$ to $320^{\circ}C$. Analysing the capacitance (C), susceptance (B), impedance (Z), and conductance (G) under the given conditions, an equivalent circuit containing temperature and frequency dependent component is proposed. Higher capacitance could be observed in the low frequency region and on the improved ionic migration conditions i.e., at higher temperature in a better ionic conductor. Also the electrode polarization built up at the electrode-specimen interface could be sorted out above 10 KHz. However, grain boundary contribution couldn't be extracted from the bulk resistance over the frequency range measured here.

• 원예과학기술지
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• 제16권3호
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• pp.352-354
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• 1998

정밀 양액제어를 위하여 양액재배시스템 및 고정도의 양액의 계측/제어가 가능한 시스템을 제작하였고, EC 제어하에서 양액중의 각 이온이 EC에 기여하는 비율을 추정하였다. 양액재배시스템에 별도의 측정조를 사용하여 센서의 세척 및 측정이 가능하도록 설계하였고, 1대의 본체로 복수의 양액재배 시스템의 정밀 계측이 가능하였다. 또한 정량조를 이용한 Overflow 방식의 양액공급장치에 의하여 양액제어 결과, $EC{\pm}0.05mS/cm$, $pH{\pm}0.05$ 이하의 범위에서 양액의 정밀 제어가 가능하였다. EC 제어상태에서 양액중의 2가이온의 증가와 활동도계수의 감소가 나타났고, 활동도계수와 당량이온전 도도를 이용한 양액중의 각 이온의 EC기여도의 변화 내용이 확인되었다.

• 한국환경보건학회지
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• 제14권1호
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• pp.33-38
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• 1988

Natural mineral water is generally quite different from ordinary drinking water due to its original nature and various properties. The complexity of natural mineral water requires, therefore, not only to identify its nature and proper characteristics, but also to classify them by a reasonable scientific basis of comparison. The study was concentrated on a possible classification technique to natural mineral waters by their constitutions and physico-ehemical properties. The classification was carried out by the computation of such numerical parameters as ionic equivalent percentage, electrolytic conductance or mobility, ionic molecular weight, molecular concentration, equivalent conductivity and degree of ionization in consideration of the determinative criteria as follows -particular single element or molecule -major components of natural waters as bicarbonate, sulphate, chloride,caloride, calcium, magnesium, and sodium -moleculat concentration related to blood osmotic pressure -water temperature at emergence from spring -contents of free carbon dioxide (CO2) -pH value of water -total dissolved solids or salts (NaCl) The results obtained proved out to be clearly distinguhhable from ordinary drinking water as far as concern natural mineral water as an example on the subject -simple water -bicarbonate-predominating water -cold spring -carbonated-non gaseous water -weak alkaline water -non saline water Putting these various results together, the sample turned out to be a kind of natural mineral water that can be used as a drinking water if microbiologically safe.

• 한국응용과학기술학회지
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• 제23권2호
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• pp.160-168
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• 2006

The conductances of trimethyltetradecylammonium bromide (TTAB) plus triphenyltetradecyl phosphonium bromide (TTPB) and TTAB plus trimethylhexadecylammonium bromide (HTAB) over the entire mole fraction range of TTAB were measured in water and in cyclodextrin plus water mixtures at fixed 4 and 8 mM of cyclodextrin at $30^{\circ}C$. The conductivity plot for both binary mixtures shows a single break from which the mixed critical micelle concentration and degree of micelle ionization were computed. From the slope of the conductivity curve, the equivalent ionic conductivities of the monomeric, associated, and the micelle states were calculated and discussed with respect to the surfactant-cyclodextrin complexation in the whole mole fraction range of both surfactant binary mixtures. The association constant K between the respective monomeric surfactant and cyclodextrin cavity of fixed 4 mM cyclodextrin was computed by considering 1:1 association from the surface tension measurement. A comparison among the K values for HTAB-cyclodetrin, TTAB-cyclodextrin, and TTPB-cyclodextrin shows that the former complexation is significantly stronger in comparison to the other ones due to the longer hydrophobic tail.

• 한국환경과학회지
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• 제23권1호
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• pp.69-79
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• 2014

The seasonal variation of pH and ion components in precipitation were investigated from January to December 2009 at Busan, Korea. The precipitation was acidic with a volume-weighted mean pH concentration of 5.32, which ranged from 3.79 to 8.66. The volume-weighted mean conductivity showed 86.77 ${\mu}S/cm$ and indicated higher concentration about 96.69 ${\mu}S/cm$ in summer. The volume-weighted mean equivalent concentration of components followed the order: $K^+$ > $Ca^{2+}$ > $nss-Ca^{2+}$ > $NH_4^+$ > $Mg^{2+}$ > $Na^+$ > $Li^+$ in cations and $Cl^-$ > $SO_4^{2-}$ > $nss-SO_4^{2-}$ > $NO_3^-$ > $NO^{2-}$ > $F^-$ > $Br^-$ in anions. Particularly, concentration of $K^+$ and $Cl^-$ showed 56 and 78 % in cations and anions. The higher concentration in $K^+$, $Na^+$, $Mg^{2+}$ and $Cl^-$ were shown in Busan city as compared to the other cities. The neutralization factors have been found to have higher value for potassium ion in winter compared with different seasons, indicating significant neutralization of acidic components over the region by potassium. Therefore, the precipitation characteristics at Busan had both continental and coastal as consequence of pH, conductivity and ionic analyses.

• 한국세라믹학회지
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• 제48권6호
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• pp.549-558
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• 2011

Application of a generalized equivalent circuit including the electrode condition for the Hebb-Wagner polarization in the frequency domain proposed by Jamnik and Maier can provide a consistent set of material parameters, such as the geometric capacitance, partial conductivities, chemical capacitance or diffusivity, as well as electrode characteristics. Generalization of the shunt capacitors for the chemical capacitance by the constant phase elements (CPEs) was applied to a model mixed conducting system, $Ag_2S$, with electron-blocking AgI electrodes and ion-blocking Pt electrodes. While little difference resulted for the electron-blocking cell with almost ideal Warburg behavior, severely non-ideal behavior in the case of Pt electrodes not only necessitates a generalized transmission line model with shunt CPEs but also requires modelling of the leakage in the cell approximately proportional to the cell conductance, which then leads to partial conductivity values consistent with the electron-blocking case. Chemical capacitance was found to be closer to the true material property in the electron-blocking cell while excessively high chemical capacitance without expected silver activity dependence resulted in the electron-blocking cell. A chemical storage effect at internal boundaries is suggested to explain the anomalies in the respective blocking configurations.

• 한국지구과학회지
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• 제35권2호
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• pp.104-114
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• 2014

주풍에 따른 강수의 산성도, 전기전도도, 이온 성분의 변화를 알아보기 위하여 2009년 부산지역 강수를 분석하였다. 부산지역에서는 남서풍과 북동풍이 우세하게 나타났다. 주풍이 서풍인 경우, 강수의 산성도는 약 pH 7로 중성으로 나타났으나 전기전도도는 약 200 ${\mu}scm^{-1}$로 다른 풍향에 비해 월등히 높게 나타나 강수에 이온성분이 많이 함유된 것을 알 수 있었다. 양이온 $K^+$와 음이온 $Cl^-$가 다른 이온에 비해 높게 나타났으며, 북풍과 남서풍이 불 때 다른 풍향에 비해 전체적으로 높은 농도로 나타났다. 산성비의 주 원인물질인 $NO{_3}^-/SO{_4}^{2-}$의 구성비는 북풍에서 3 이상으로 월등히 높은 값이 나타났다. 다른 풍향에 비해 북동풍, 동풍, 남서풍, 서풍에서의 $K^+$의 중화기여도는 전체적으로 1 이상으로 높은 값을 나타내었는데, 이는 산성이온을 중화시키는데 있어서 알카리성 이온인 $K^+$의 중화기여도가 크게 작용하였음을 알 수 있다. 또한 해염입자는 북풍, 북동풍, 남서풍에서 800 ${\mu}sm^{-3}$ 이상으로 다른 풍향에 비해 상대적으로 많은 양을 나타내었다. 역궤적 분석 결과, 북풍, 서풍, 북서풍계열에서는 봄, 가을, 겨울철에 만주, 내몽골 고원, 중국, 러시아 지역으로부터 공기덩어리의 이동을 볼 수 있었다. 반면, 동풍, 북동풍, 남서풍계열에서는 여름철에 해양으로부터 공기덩어리의 이동을 볼 수 있었다. 따라서 부산지역의 강수중 산성도, 전기전도도, 이온 성분 농도는 내륙과 연안해역의 특성을 가진 주풍에 의한 변동 특성을 잘 나타내고 있음을 알 수 있었다.

• 한국대기환경학회지
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• 제13권1호
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• pp.9-18
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• 1997

Precipitation samples were collected by the wet- only event sampling method from Seoul during September 1991 to April 1995. These samples were analyzed for the concentrations of the major ionic components (N $O_3$$^{[-10]}$ , N $O_2$$^{[-10]}$ , S $O_4$$^{2-}$, C $l^{[-10]}$ , $F^{[-10]}$ , N $a^{＋}$, $K^{+}$, $Ca^{2＋}$, $Mg^{2＋}$, and N $H_4$$^{＋}$), pH, and electric conductivity. During the study period, a total of 182 samples were collected, but only 163 samples were used for the data analysis via quality assurance of precipitation chemistry data. The volume-weighted pH was found to be 4.7. The major acidifying species from our precipitation studies were identified to be non-seasalt sulfate (84$\pm$9 $\mu$eq/L) and nitrate (24$\pm$2 $\mu$eq/L) except for chloride. Because the Cl/Na ratio in the precipitation was close to the ratio in seawater. If all of the non-seasalt sulfate and nitrate were in the form of sulfuric and nitric acids, the mean pH in the precipitation could have been as low as 3.7 lower than the computed value. Consequently, the difference between two pH values indicate that the acidity of precipitation was neutralized by alkaline species. The equivalent concentration ratio of sulfate to nitrate was 3.5, indicating that sulfuric and nitric acids can comprise 78％ and 22％ of the precipitation acidity, respectively. Analysis of temporal trend in the measured acidity and ionic components were also performed using the linear regression method. The precipitation acidity generally showed a significantly decreasing trend, which was compatible with the pattern of the ratio (N $H_4$$^{＋}$＋C $a^{2＋}$)/ (nss-S $O_4$$^{2-}$＋N $O_3$$^{[-10]}$ ).).