• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.118-119
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• 2006

The development of Fe-based metal matrix composites (MMCs) with high content of hard phase has been approached by combining the use of advanced powder metallurgy techniques like high-energy milling (HEM), cold isostatic pressing (CIP) and vacuum sinterings. A 30% vol. of NbC particles was mixed with Fe powder by HEM in a planetary mill during 10h, characteristing the powder by the observation of morphology and microstructure by scanning electron microscopy (SEM). After of sintering process the variation of density, hardness,carbon content and the microstructural changes observed, permits to find the optimal conditions of processing. Afterwards, a heat treatment study was performed to study the hardenability of the composite.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.4
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• pp.211-226
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• 2015

Membrane type Mark III cargo containment system (CCS) is considered in this study to investigate its strength capability under applied loads due to liquefied natural gas (LNG) cargo. A rectangular plated structure supported by inner hull structure is exemplified from Mark III CCS according to classification society's guidance and it is assumed as multi-layered structure by stacking plywood, triplex, reinforced polyurethane (PU) foam and series of mastic upon inner hull structure. Commercially available general purpose finite element analysis package is used to have reliable FE models of Mark III CCS plate. The FE models and anisotropic failure criteria such as maximum stress, Hoffman, Hill, Tsai-Wu and Hashin taking into account the direction dependent material properties of Mark III CCS plate components and their material properties considering a wide variation of temperature due to the nature of LNG together form the strength analysis procedure of Mark III CCS plate. Strength capability of Mark III CCS plate is understood by its initial failure and post-initial failure states. Results are represented in terms of failure loads and locations when initial failure and post-initial failures are occurred respectively. From the results the basic design information of Mark III CCS plate is given.

• Journal of the Korean Chemical Society
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• v.43 no.6
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• pp.651-655
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• 1999

Xylenol Orange was bonded on an anion-exchange resin (Amberlite lRA 400, in $Cl^-$form) by batch equilibration. The resin was proved to be stable in acidic solutions of about 0.1 M HCl, $HNO_3$ or $H_2SO_4$. Sorption capacities for the metal ions on the Amberlite IRA 400 bonded with xylenol orange have been measured by batch method. The result showed that Fe(III) is higher than any other metals for sorption capacity. The preconcentration and the separation of Fe(lll) from the mixture soIution, therefore, were carried out with the 0.1 M sulfosalicylic acid as an eluent.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.172-176
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• 2006

Fe(III)-Coated Star Fish (ICSF) was prepared by reaction of calcined Star Fish (SF) with Fe(III) solution at an elevated temperature. To investigate the stability of ICSF at acidic condition, dissolution of Fe was studied at pH 2 as a function of time. Extracted iron was negligible over the entire reaction time. This stability test suggests the applicability of ICSF in the treatment of wastewater even at low pH. Adsorption capacity of Cu(II) onto SF and ICSF was investigated in a batch and a column test. In the pH-edge adsorption, adsorption of copper onto SF and ICSF was quite similar over the entire pH range due to the presence of an important amount of Fe in SF itself. From the adsorption isotherm obtained with variation of the concentration of Cu(II), ICSF showed 1.6 times greater adsorption capacity than SF. Also, ICSF showed a greater removal capacity of Cu(II) in the column test.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1251-1254
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• 2005

It has been proposed that oxidation of L-3,4-dihydroxyphenylalanine (DOPA) may contribute to the pathogenesis of neurodegenerative disease. In this study, L-DOPA-Fe(III)-mediated DNA cleavage and the protection by carnosine and homocarnosine against this reaction were investigated. When plasmid DNA was incubated with L-DOPA in the presence of Fe(III), DNA strand was cleaved. Radical scavengers and catalase significantly inhibited the DNA breakage. These results suggest that $H_2O_2$ may be generated from the oxidation of DOPA and then $Fe^{3+}$ likely participates in a Fenton’s type reaction to produce hydroxyl radicals, which may cause DNA cleavage. Carnosine and homocarnosine have been proposed to act as anti-oxidants in vivo. The protective effects of carnosine and homocarnosine against L-DOPA-Fe(III)-mediated DNA cleavage have been studied. Carnosine and homocarnosine significantly inhibited DNA cleavage. These compounds also inhibited the production of hydroxyl radicals in L-DOPA/$Fe^{3+}$ system. The results suggest that carnosine and homocarnosine act as hydroxyl radical scavenger to protect DNA cleavage. It is proposed that carnosine and homocarnosine might be explored as potential therapeutic agents for pathologies that involve damage of DNA by oxidation of DOPA.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.283.2-283
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• 2002

• Economic and Environmental Geology
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• v.36 no.1
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• pp.39-48
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• 2003

The removal of chromate from aqueous solution using finely ground pyrite and biotite was investigated by batch experiments and the kinetics and the mechanism of chromate reduction were discussed. The chromate reduction by pyrite was about hundred times faster than that by biotite and was also faster at pH 3 than at pH 4. When pyrite was used, more than 90% of initial chromate was reduced within four hours at pH 4 and within 40 min. at pH 3. However, more than 400 hours was taken for the reduction of 90% of initial chromate by biotite. The results indicate that the rate of chromate reduction was strongly depending on the amount of Fe(II) in the minerals and on the dissolution rate of Fe(II) from the minerals. The reduction of chromate at pH 4 resulted in the precipitation of (Cr, Fe)(OH))$_3$$_{ (s)}$, which is believed to have limited the concentrations of dissolved Cr(III) and Fe(III) to less than expected values. When biotite was used, amounts of decreased Fe(II) and reduced Cr(Ⅵ) did not show stoichiometric relationship, which implying there was not only chromate reduction by ferrous ions in the acidic solution but also heterogeneous reduction of ferric ions by the structural ferrous iron in biotite. However, the results from a series of the experiments using Pyrite showed that concentrations of the decreased Fe(II) and the reduced Cr(Ⅵ) were close to the stoichiometric ratio of 3:1. It was because the oxidation of pyrite rapidly created ferrous ions even in oxygenated solutions and the chromate reduction by the ferrous ions was significantly faster than ferrous ion oxygenation.

• Journal of the Korean Chemical Society
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• v.28 no.6
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• pp.384-392
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• 1984

Reaction of the Fe(II) complex of a fully saturated tetradentate macrocyclic ligand [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$, where [14]ane$N_4$ represents 1,4,8,11-tetraazacyclotetradecane, with $O_2$ has been investigated in acetonitrile solutions. [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$ reacts with oxygen to yield low spin Fe(III) species, [Fe([14]aneN$_4)(CH_3CN)_2]^{3+}$, which undergoes metal ion assisted oxidative dehydrogenation of the macrocyclic ligand to produce low spin Fe(II) complex, [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$. The macrocyclic ligand in [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$ is highly unsaturated and its double bonds are conjugated. [Fe([14]dieneN$_4)(CH_3CN)_2]^{2+}$ and [Fe([14]dieneN$_4)(CH_3CN)_2]^{3+}$ are isolated as the intermediates of the reaction. The Fe(II) complexes involved in this oxidative dehydrogenation reaction react with carbon monoxide to give respective carbon monoxide derivatives, [FeL$(CH_3CN)(CO)]^{2+}$ (where L = macrocyclic ligand). The values of $v_{CO}$ of [FeL$(CH_3CN)(CO)]^{2+}$, and the electrochemical oxidation potentials of Fe(II) ${\to}$ Fe(III) and the qualitative stability toward air-oxidation for [FeL(CH$_3CN_2)^{2+}$ increase as the degree of unsaturation of the macrocyclic ligands increase.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1293-1296
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• 2006

In this study, a solid phase extraction method has been developed for the preconcentration and separation of the elements Cr(III), Fe(III), Co(II) and Pb(II) at trace levels by using a column packed with Amberlite XAD-1180 resin loaded with 4-(2-pyridylazo)-resorcinol (PAR) reagent. After preconcentrating, the metals retained on the column were eluted with 20 mL of 3 mol/L $HNO_3$ and then determined by flame atomic absorption spectrometry (FAAS). The factors affecting the recovery of the elements, such as pH, type and concentration of eluent, volume of sample and elution solution, and matrix components, were also ascertained. The recoveries of Cr(III), Fe(III), Co(II) and Pb(II) were found to be $99\;{\pm}\;4,\;97\;{\pm}\;3,\;95\;{\pm}\;3$ and $98\;{\pm}\;4$%, respectively, under the optimum conditions at 95% confidence level and the relative standard deviations found by analyzing of nine replicates were $\leq4.4$%. The preconcentration factors for Cr(III), Fe(III), Co(II) and Pb(II) were found as 75, 125, 50 and 75 respectively. The detection limits (DL, 3s/b) were 3.0 $\mu g/L$ for Cr(III), 1.25 $\mu g/L$ for Fe(III), 3.3 $\mu g/L$ for Co(II), and 7.2 $\mu g/L$ for Pb(II). The recoveries achieved by adding of metals at known concentrations to samples and the analysis results of Buffalo river sediment (RM 8704) show that the described method has a good accuracy. The proposed method was applied to tap water, stream water, salt and street dust samples.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.48-54
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• 2012

The $[Fe_4S_4]^{2+}$ clusters with 2-, 3-, and 4-pyridinemethanethiolate (S2-Pic, S3-Pic, and S4-Pic, respectively) terminal ligands have been synthesized from the ligand substitution reaction of the $(^nBu_4N)_2[Fe_4S_4Cl_4]$ (I) cluster. The new $(^nBu_4N)_2[Fe_4S_4(SR)_4]$ (R = 2-Pic; II, 3-Pic; III, 4-Pic; IV) clusters were characterized by FTIR and UV-Vis spectroscopy. Cluster II was crystallized in the monoclinic space group C2/c with a = 24.530 (5) $\AA$, b = 24.636(4) $\AA$, c = 21.762(4) $\AA$, ${\beta}=103.253(3)^{\circ}$, and Z = 8. The X-ray structure of II showed two unique 2:2 site-differentiated $[Fe_4S_4]^{2+}$ clusters due to the bidentate-mode coordination by 2-pyridinemethanethiolate ligands. Cluster III was crystallized in the same monoclinic space group C2/c with a = 26.0740(18) $\AA$, b = 23.3195(16) $\AA$, c = 22.3720(15) $\AA$, ${\beta}=100.467(2)^{\circ}$, and Z = 8. The 3-pyridinemethanethiolate ligand of III was coordinated to the $[Fe_4S_4]^{2+}$ core as a terminal mode. Cluster IV with 4-pyridinemethanethiolate ligands was found to have a similar structure to the cluster III. Fully reversible $[Fe_4S_4]^{2+}/[Fe_4S_4]^+$ redox waves were observed from all three clusters by cyclic voltammetry measurement. The electrochemical potentials for the $[Fe_4S_4]^{2+}/[Fe_4S_4]^+$ transition decreased in the order of II, III and IV, and the reduction potential changes by the ligands were explained based on the structural differences among the complexes. The complex III was reacted with sulfonium salt of $[PhMeSCH_2-p-C_6H_4CN](BF_4)$ in MeCN to test possible radical-involving reaction as a functional model of the [$Fe_4S_4$]-SAM (S-adenosylmethionine) cofactor. However, the isolated reaction products of 3-pyridinemethanethiolate-p-cyanobenzylsulfide and thioanisole suggested that the reaction followed an ionic mechanism and the products formed from the terminal ligand attack to the sulfonium.