• Korean Architects
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• v.4 no.14 s.14
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• pp.74-79
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• 1969

As we all know a large number of thin shell with the shape of E.P and H.P have been constructed. In this paper, we will be interested to the bending problem of thin translational shell. Two basic differential equations of shallow shell are to be used to derive approximate solution of it. Stress analysis of E.P. translational shell with constant thickness under uniform surface oad is to be given as an example. More exact solution formulated by K. Apeland can be found in the proceeding, Journal of the Engineering Mechanics Division, A.S.C.E., Feburary, 1961.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.1028-1034
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• 1989

A method of analysis of the steady-state performance of induction motor with supply voltage controlled by cyclically-triggered inline thyristors is presented. Phase-variable model and asymmetrical components are not used in this analysis. Instead, Fast Fourier Transform technique and the method of multiple reference frames are employed to obtain the constant-speed performance of I.M. easily.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.3
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• pp.463-470
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• 2010

If P(f, r) is the set of endpoints of radii which have length greater than or equal to r > 0 under a conformal mapping f of the unit disc. Then for large r, the logarithmic capacity of P(f, r), $\frac{1}{\sqrt[2]{r}}{\leq}cap(P(f,r)){\leq}\frac{k}{\sqrt{r}}$. Where k is the positive constant.

• Journal of Ecology and Environment
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• v.37 no.3
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• pp.131-137
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• 2014

To investigate the solute pattern of salt marsh plants in Suncheon Bay in Korea, plants and soil samples were collected at three sites from July to September 2011. The soil pH around the investigated species was weakly alkaline, 6.9-8.1. The total ion and Cl- content of site 1 gradually increased, while those of site 2 and site 3 were lowest in August and highest in September. The exchangeable $Ca^{2+}$, $Mg^{2+}$ and $K^+$ in the soil were relatively constant during the study period, but the soil exchangeable $Na^+$ content was variable. Carex scabrifolia and Phragmites communis had constant leaf water content and very high concentrations of soluble carbohydrates during the study period. However, Suaeda malacosperma and S. japonica had high leaf water content and constant very low soluble carbohydrate concentrations. Carex scabrifolia accumulated similar amounts of $Na^+$ and $K^+$ ions in its leaves. Phragmites communis contained a high concentration of $K^+$ ions. Suada japonica and S. malacosperma had more $Na^+$ and $Cl^-$ ions than $K^+$ ions in their leaves. Suaeda japonica had higher levels of glycine betaine in its leaves under saline conditions than C. scabrifolia and P. communis. Consequently, the physiological characteristics of salt marsh chenopodiaceous plants (S. japonica and S. malacosperma) were the high storage capacity for inorganic ions (especially alkali cations and chloride) and accumulation of glycine betaine, but monocotyledonous plant species (C. scabrifolia and P. communis) showed high $K^+$concentrations, efficient regulation of ionic uptake, and accumulation of soluble carbohydrates. These characteristics might enable salt marsh plants to grow in saline habitats.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.771-775
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• 2010

In this study, piezoelectric and dielectric properties of the $(Na_{0.5}K_{0.5})NbO_3-(1-x)(Bi_{0.5}Na_{0.5})TiO_3-xBaTiO_3$ [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of $BaTiO_3$ significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased at the morphotropic phase boundary (MPB). The $d_{33}$=184 pC/N, $k_p$=0.38, dielectric constant=1455 with dielectric loss value of less than 1% were obtained for the NKN-0.95BNT-0.05BT ceramics sintered at $1150^{\circ}C$ for 2h. These results demonstrate that the NKN-(1-x)BNT-xBT ceramics is an attractive candidate for lead-free piezoelectric materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.297-299
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• 1999

Effects of additives on the ceramic and electrical properties of Pb(Y$_{1}$2/Ta$_{1}$2/)O$_3$-PbZrO$_3$-PbTiO$_3$ceramics in a perovskite type structure were investigated. The dielectric and piezoelectric properties of the base composition were improved markedly through selection of Fe$_2$O$_3$ additives in proper amounts. The composition Pb(Y$_{1}$2/Ta$_{1}$2/)O$_3$-PbZrO$_3$-PbTiO$_3$ obtained the dielectric constant ($\varepsilon$$_{r}$=1,425). Also, electromechanical couping factors for planar(k$_{p}$) and piezoelectric constant(d$_{33}$) were obtained 0.50 and 294[pC/N] at the additives 0wt% Fe$_2$O$_3$ respectively. The mechanical quality facor(Q$_{m}$) of Pb(Y$_{1}$2/Ta$_{1}$2/)O$_3$-PbZrO$_3$-PbTiO$_3$+Fe$_2$O$_3$(0.3 wt%) is about 510.510.510.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.241-246
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• 2012

Cr(VI)-heterocyclic complex (2,2'-bipyridinium dichromate) was synthesized by the reaction between of 2,2'-bipyridine and chromium trioxide in $H_2O$, and characterized by IR and ICP. The oxidation of benzyl alcohol using 2,2'-bipyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexene < chloroform < acetone < N,N-dimethylformamide. In the presence of DMF solvent with acidic catalyst such as $H_2SO_4$ solution, 2,2'-bipyridinium dichromate oxidized the benzyl alcohol and its derivatives (p-$p-OCH_3$, $m-CH_3$, H, $m-OCH_3$, m-Cl, $m-NO_2$). Electron-donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant was -0.66 (303 K). The observed experimental data was used to rationalize the hydride ion transfer in the rate-determining step.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.25-33
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• 2000

The new ion exchange resin was synthesized from chloromethylated styrene-1,4-divinylbenzene(DVB) with 1-aza-15-crown-5 macrocyclic ligand by substitution reaction. The effect of pH, time, dielectric constant of solvent and cross-linked of the matrix on the adsorption for $UO_2^{2+}$, $Ca^{2}$ and $Lu^{3+}$ was investigated. The metal ion was not adsorbed on the resins below pH 3 but above pH 4 fast adsorption behavior was showed. The optimum equilibrium time for adsorption of metallic ions was two hours. The adsorption selectivity determined in ethanol matrix was in increasing order $UO_2^{2+}>Ca^{2}>Lu^{3+}$. The adsorption power was in the order of 1%, 2%, 10% and 20% -crosslinked resin, but adsorption properties of resins decreased in proportion to the order of dielectric constant of solvents used. In addition, these metal ions could be separated in the column packed with 1% crosslinked resin by pH2.5 $HNO_3$ as an eluent.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.50-58
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• 1996

In the presence of metal ions(Co(Ⅱ), Ni(Ⅱ), Sr(Ⅱ), Cu(Ⅱ), Fe(Ⅲ), U(Ⅵ)), the sedimentation of humic acid was increased at constant pH with increasing metal concentration and the strength was increased in the following order: Sr < Ni < Co < Cu < Fe < U. At constant metal concentration, Cu(Ⅱ), Ni(Ⅱ), and Co(Ⅱ) ions caused an increase in sedimentation of humic acid as the solution pH increased, whereas Fe(Ⅲ) and U(Ⅵ) ions caused a decrease. Sr(Ⅱ) ions did not affect the sedimentation even with the variation of pH. The analysis of FT-IR spectra for the sediments prepared from the reaction between humic acid and metal ions showed that metal ions were bound to humic acid to form complexes, suggesting that the metal complexation plays an important role in the sedimentation of humic acid.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.24-30
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• 2002

The laboratory adsorption batch tests were performed to investigate the adsorption characteristics of Pb on kaolinite. The characteristics such as adsorption equilibrium time, adsorption capacity, adsorption isotherm were studied, and also the effects of pH and the mixing ratio on the adsorption of Pb on kaolinite were investigated. Test results show that the adsorption equilibrium state was reached within 24 hours, and the adsorbed amount of Pb increased, but the adsorption efficiency over the initial concentration of 198 mg/l decreased, with increasing the initial concentration of Pb. And the adsorption constant, 1/n was obtained 0.9584 by Freundlich isotherm equation. Regardless of the initial concentration of Pb. the adsorbed amount of Pb as well as the adsorption efficiency were increased with increasing pH values and converged to a certain constant value above 8 of pH values. And also the adsorbed amount of Pb increased with the mixing ratio, but its efficiency increased with the mixing ratio up to 8 and then showed the decreasing tendency above that.