• Journal of the Korean Applied Science and Technology
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• v.22 no.1
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• pp.15-20
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• 2005

$Na_2CO_3$. Sodium orthosilicate (Na-OSi), Tetronix T-701 (T-701), Na-dioctyl sulfosuccinate (303C), Newpol PE-68 (PE-68), MJU-100A, and tetrasodium pyrophosphate were blended to prepare high performance alkaline cleaning agents (ACASs). The results of cleaning test with steel specimen showed that ACAS-6 ($Na_2CO_3$ 50g/Na-OSi 35g/T-701 20g/303C 18g/PE-68 17g/MJU-100A 10g/TSPP 20g/ water 180g mixture) had a good cleaning power. The cleaning power for press-rust preventing oil was 98% and 99% degreasing at 4wt%, $70^{\circ}C$ and $90^{\circ}C$, respectively ; for quenching oil, the cleaning power of ACAS-6 was 91% degreasing at 4wt% and $70^{\circ}C$. The foam heights measured immediately after foaming by Ross & Miles method and Ross & Clark method at 6wt%, $60^{\circ}C$ were 18mm and 65mm, respectively. It was concluded that ACAS-6 had a good low foaming cleaning agent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.665-670
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• 2009

Lead-free piezoelectric ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO and $MnO_2$ were fabricated using the conventional oxide-mixing technique. With increasing content of CuO and $MnO_2$, the dielectric constant(${\varepsilon}_{33}$) and mechanical quality factor($Q_m$) value increased, while electromechanical coupling factor($K_p$) and piezoelectric constant($d_{33}$) decreased. The piezoelectric and dielectric properties ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO 2.461 wt% and $MnO_2$ 0.538 wt% at sintered temperature $1050\;^{\circ}C$ were attained ${\varepsilon}_{33}$ = 403, $K_p$ = 15, $Q_m$ = 122 and $d_{33}$ = 36 pC/N. Based on response surface methodology results using design of experiment, it was concluded that ($Na_{1/2}K_{1/2}$)$NbO_3$ doped with CuO 0.477 wt% and $MnO_2$ 0.269 wt% has possibility composition of being used for piezoelectric transformer.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.243-248
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• 2012

ZrN nanoparticles were prepared by an exothermic reduction of $ZrCl_4$ with $NaN_3$ in the presence of NaCl flux in a nitrogen atmosphere. Using a solid-state combustion approach, we have demonstrated that the zirconium nitride nanoparticles synthesis process can be completed in only several minutes compared with a few hours for previous synthesis approaches. The chemistry of the combustion process is not complex and is based on a metathesis reaction between $ZrCl_4$ and $NaN_3$. Because of the low melting and boiling points of the raw materials it was possible to synthesize the ZrN phase at low combustion temperatures. It was shown that the combustion temperature and the size of the particles can be readily controlled by tuning the concentration of the NaCl flux. The results show that an increase in the NaCl concentration (from 2 to 13 M) results in a temperature decrease from 1280 to $750^{\circ}C$. ZrN nanoparticles have a high surface area (50-70 $m^2/g$), narrow pore size distribution, and nano-particle size between 10 and 30 nm. The activation energy, which can be extracted from the experimental combustion temperature data, is: E = 20 kcal/mol. The method reported here is self-sustaining, rapid, and can be scaled up for a large scale production of a transition metal nitride nanoparticle system (TiN, TaN, HfN, etc.) with suitable halide salts and alkali metal azide.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.671-677
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• 2011

A hyperthermophilic archaeon, $Thermococcus$ $onnurineus$ NA1 was studied to investigate its fermentation characteristics using various carbon sources including formate, maltose and carbon monoxide during the anaerobic batch cultivation at $80^{\circ}C$. Formate was the best carbon source for cell growth and hydrogen production among others. In the batch culture on formate, it was found that the cell concentration increased exponentially by 12 hrs of culture, after which the cell growth and formate consumption was retarded. Hydrogen production was continued more than 24 hrs although the cell growth was ceased at 18 hrs. Hydrogen production rate was directly correlated with the cell growth and formate degradation up to 18 hrs, and the average hydrogen production yield was 1.05 mole-$H_2$/mole-formate. Cell growth and hydrogen production were optimized at the initial pH 6-7, while inhibited at the initial pH lower than 5 and higher than 9.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.930-934
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• 2009

In this study, in order to develop excellent lead-free composition ceramics for piezoelectric transformer, ($K_4CuNb_8O_{23}$) added $(K_{0.5}Na_{0.5})(Nb_{0.96}Sb_{0.04})O_3$ ceramics were fabricated using conventional mixed oxide method and their piezoelectric and dielectric properties were investigated as a fu+EY50nction of the amount of KCN addition. With increasing the amount of KCN addition, density and mechanical quality factor(Qm), electromechanical coupling factor (Kp) were increased up to 1.2 mol% and then decreased. At the 1.2 mol% KCN added specimen, mechanical quality factor (Qm), electromechanical coupling factor (Kp), density and dielectric constant (${\varepsilon}r$) showed the optimal values of 781, 0.445, $4.42\;g/cm^3$ and 443, respectively, for piezoelectric transformer application.

• Journal of the Korean Applied Science and Technology
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• v.22 no.1
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• pp.50-55
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• 2005

A comparison of alkali metal cation and alkaline earth cation solvent extraction was made for three additional monoionizable crown ethers and one diionizable crown ether. sym-(n-Octyldibenzo)-16-crown-5-oxyacetic acid $\underline{1}$ exhibited high efficiency and selecvity in solvent extraction of alkali metal cations with respect to that observed with alkaline earth cations. Sizes of $Na^+$ and $Ca^{2+}$ appropriately match with the cavity size of monoethyl sym-bis[4(5)-tert-butylbenzo]-16-crown-5-oxymethylphosphonic acid $\underline{3}$. As the result, $Na^+$ and $Ca^{2+}$ are the best extracted. sym-(n-Octyldibenzo)-16-crown-5-oxymethyldiphosphonic acid $\underline{4}$was found to be somewhat selective for $Na^+$ over $Li^+$ and other alkaline earth metal cations. In the complexation of alklaine earth cations by crown ether diphosphonic acid $\underline{4}$, $Ca^{2+}$ and $Sr^{2+}$ are the appropriate sizes, but lager $Ba^{2+}$ may be due to favorable formation of a sandwich type complex between the crown ether cavity and the dianion of the deprotonated crown ether phoaphonic acid moiety.

• Journal of Environmental Science International
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• v.22 no.8
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• pp.999-1007
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• 2013

Electrochemical degradation of phenol was evaluated at DSA (dimensionally stable anode), JP202 (Ru, 25%; Ir, 25%; other, 50%) electrode for being a treatment method in non-biodegradable organic compounds such as phenol. Experiments were conducted to examine the effects of applied current (1.0~4.0 A), electrolyte type (NaCl, KCl, $Na_2SO_4$, $H_2SO_4$) and concentration (0.5~3.0 g/L), initial phenol concentration (12.5~100.0 mg/L) on phenol degradation and $UV_{254}$ absorbance as indirect indicator of by-product degraded phenol. It was found that phenol concentration decreased from around 50 mg/L to zero after 10 min of electrolysis with 2.5 g/L NaCl as supporting electrolyte at the current of 3.5 A. Although phenol could be completely electrochemical degraded by JP202 anode, the degradation of phenol COD was required oxidation time over 60 min due to the generation of by-products. $UV_{254}$ absorbance can see the impact of as an indirect indicator of the creation and destruction of by-product. The initial removal rate of phenol is 5.63 times faster than the initial COD removal rate.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.205-209
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• 2009

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)$NaNbO_{3-x}BaTiO_3-0,09LiNbO_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $BaTiO_3$ substitution. All the specimens showed orthorhombic phase structure without secondary phase, $BaTiO_3$ substitution enhanced density, dielectric constant(${\epsilon}_r$) and electromechanical coupling factor($k_p$), However, mechanical quality factor was deteriorated. Curie temperature of specimens was observed as about $380^{\circ}C$. At the $BaTiO_3$ substitution of 4 mol%, density, electromechanical coupling factor($k_p$), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.493g/cm^3$, 0.236, 175, 70 pC/N, respectively.

• YAKHAK HOEJI
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• v.41 no.5
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• pp.547-553
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• 1997

The purpose of this investigation was to determine the inhibition on $Na^+,\;K^+$-ATPase, cyclic AMP phosphodiesterase and platelet activation by marine sterols isolated from octocorals. Three marine polyhydroxysterols, 7${\alpha},\;8{\alpha}-epoxy-3b{\beta},\;5{\alpha},\;6{\alpha}-trihydroxycholestane (1),\;24-methyl-7{\alpha},\;8{\alpha}-epoxy-3{\beta},\;5{\alpha},\;6{\alpha}-trihydroxycholest-22-ene (2),\;and\;7{\alpha},\;8{\alpha}-epoxy-3{\beta},\;5{\alpha},\;6{\alpha}-trihydroxycholest-22-ene (3)$, were isolated from the Gorgonian Acabaria undulata. Five marine sterols(compound 4, 5, 6, 7, 8) were isolated from the soft coral Alcyonium gracillimum. Three marine polyhydroxysterols (1, 2, 3) and pregna-1. 20-diene-3-one (8) exhibit a potent inhibitory effect on rabbit platelet aggregation induced by collagen and thrombin. Those polyhydroxysterols also exhibit a potent inhibitory effect on cyclic AMP phosphodiesterase. Compound 6 with an unusual cyclic enolether exhibit a inhibitory effect on $Na^+,\;K^+$-ATPase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.484-488
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• 2009

In this study, in order to develop the lead-free piezoelectric ceramics with high piezoelectric and dielectric properties, $[(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}(Nb_{0.96}Sb_{0.04})]O_3$ ceramics were fabricated using $Ag_2O$ as sintering aid and a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $SrTiO_3$ substitution. $SrTiO_3$ substitution enhanced density, dielectric constant(${\varepsilon}_r$) and electromechanical coupling factor($k_p$). However, mechanical quality factor was deteriorated. And also, Curie temperature ($T_c$), and phase transition temperature($T_p$) were rapidly decreased. At the 0.5 mol% $SrTiO_3$ substitution, density, electromechanical coupling factor($k_p$), dielectric constant(${\varepsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.437\;g/cm^3$, 0.457, 1294, 265 pC/N, respectively.