• Journal of the Korean Chemical Society
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• 제23권6호
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• pp.349-357
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• 1979

A non-Boltzman equilibrium population of $Cl(^2P_{1/2})$ atoms has been observed in a flow discharge-atomic absorpion experiment. The rates of reactions of $Cl(^2P_{3/2})$ atoms with various substrates are in reasonable agreement with reported values determined by competition methods. The similar reactivities of both $Cl(^2P_{1/2})$ and $Cl(^2P_{3/2})$ atoms indicate that the contribution of $Cl(^2P_{1/2})$ atoms to the rate measurements in the competition experiment is small, and this negligible contribution may be the reason why the rate constants obtained by assuming single reactive species (in competition method) agree well with our direct measurement.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.1951-1955
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• 2009

A Thermodynamic study on the interaction of bovine calf thymus DNA with new designed Pd(II) complex (Ethylendiamine- 8-hydroxyquinolinato Palladium(II) chloride) was studied by using isothermal titration calorimetry (ITC) at 27 ${^{\circ}C}$ in Tris buffer solution at pH = 7.5. The enthalpies of Pd(II) complex + DNA interaction are reported and analysed in terms of the new solvation theory. It was indicated that there are three identical and non-cooperative sites for Pd(II) complex. The binding of a Pd(II) complex is endothermic with association equilibrium constants of 428.03 m$M^{-1}$ at 27 ${^{\circ}C}$. The binding of Pd(II) complex can cause some changes in the stability of the DNA at low and high Pd(II) complex concentrations. Our results suggested that this complex might interact with DNA as an intercalator, thus interfering with DNA replication and cell proliferation.

• Membrane and Water Treatment
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• 제8권1호
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• pp.19-34
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• 2017

Boron exists in dilute concentrations in sea water, ground water and waste waters. Reactive liquid extraction can be used for removing boron to make the treated water suitable for drinking and irrigation, with its final concentration less than 0.5 ppm. The results of equilibrium experiments are reported on the removal of boron using 2-butyl-2-ethyl-1, 3-propanediol (BEPD as a nonionic carrier) in sunflower oil, a non-traditional solvent. The results of removal of boron from aqueous solutions in the concentration range 0.5-20 ppm are presented. It is shown that this new liquid membrane system, is able to remove boron from ground waters at their natural pH of 6-8 (without any chemical addition for pH adjustments). The removal efficiency is good when the process is upgraded to a hollow-fibre membrane contactor and approximately 45% boron can be removed in a single-stage contact. There are additional advantages of this new approach that includes reduced operational health and safety and environmental issues. The results reported here provide guidelines to the development of boron removal process using renewable, biodegradable, safe and cheap solvent system such as sunflower oil.

• Transactions of the Korean hydrogen and new energy society
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• 제18권4호
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• pp.391-398
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• 2007

The covalently cross-linked sulfonated polyetheretherketone (CL-SPEEK) membrane was prepared by four-step synthesis of sulfonation-sulfochlorination, partial reduction, lithiation, and cross-linking, and its electrochemical and mechanical properties were investigated for water electrolysis application. The prepared ion exchange membranes showed good electrochemical and mechanical properties; proton conductivity of 0.116 S/cm at $80^{\circ}C$, water uptake of 44.6%, ion exchange capacity of 1.75 meq/g-dry-memb., tensile strength of 64.25 MPa and elongation of 61.11%. The membrane electrode assembly (MEA) with homemade membranes were prepared by non-equilibrium impregnation-reduction (I-R) method. Especially, the electrochemical surface area (ESA) and roughness factor of CL-SPEEK electrolyte by cyclic voltammetry method were 23.46 $m^2/g$ and 307.3 $cm^2-Pt/cm^2$, respectively. The prepared MEA was used in the unit cell of water electrolysis and the cell voltage was 1.81 V at 1 A/$cm^2$ and $80^{\circ}C$, with platinum loadings of 1.31 mg/$cm^2$.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.453-458
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• 2009

Recently, new methods to synthesize and process polymers without toxic organic solvents are needed in order to solve environmental problems. The use of supercritical carbon dioxide as a solvent for the polymer synthesis is attractive since it is non-toxic, non-flammable, naturally abundant, and the product may be easily separated from the solvent. In this study, we developed the method using super critical $CO_2$ to prepare P(MAA-co-EGMA) hydrogel nanoparticles as an intelligent drug delivery carrier. The effects of concentrations of PtBuMA-PEO as a dispersion stabilizer and AIBN as an initiator on the particle synthesis were investigated. When PtBuMA-PEO concentration increased, the particle size decreased. However, there was no significant difference in the particle size according to the AIBN concentration. There was a drastic change of the equilibrium weight swelling ratio of P(MAA-co-EGMA) hydrogel nanoparticles at a pH of around 5, which is the $pK_a$ of PMAA. At a pH below 5, the hydrogels were in a relatively collapsed state but at a pH higher than 5, the hydrogels swelled to a high degree. In release experiments using Rh-B as a model solute, the P(MAA-co-EGMA) hydrogel nanoparticles showed a pH-sensitive release behavior. At low pH(pH 4.0) a small amount of Rh-B was released while at high pH(pH 6.0) a relatively large amount of Rh-B was released from the hydrogels.

• Transactions of the Korean hydrogen and new energy society
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• 제20권3호
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• pp.194-201
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• 2009

The e1ectrocatalytic properties of heteropolyacids(HPAs) entrapped in covalently cross-linked sulfonated polyetheretherketone(CL-SPEEK/HPA) membranes have been studied for water electrolysis. The HPAs, including tungstophosphoric acid(TPA), molybdophosphoric acid(MoPA), and tungstosilicic acid(TSiA) were used as additives in the composite membranes. The MEA was prepared by a non-equilibrium impregnation-reduction(I-R) method, using reducing agent, sodium borohydride(NaBH4) and tetraamineplatinum(II) chloride(pt(NH$_3$)$_4$Cl$_2$). The electrocatalytic properties of composite membranes such as the cell voltage were in the order of magnitude CL-SPEEKlMoPA40 (wt%) > /TPA30 > /TSiA40. In the optimum cell applications for water electrolysis, the cell voltage of PtlPEM/Pt-Ru MEA with CL-SPEEKlTPA30 membrane was 1.75 V at 80$^{\circ}$C and I A/cm$^2$ and this voltage carried lower than that of 1.81 V of Nafion 117. Consequently, in regards of electrochemical and mechanical characteristics and oxidation durability, the newly developed CL-SPEEKITPA30 composite membrane exhibited a better performance than the others, but CLSPEEKlMoPA40 showed the best electrocatalytic activity (1.71 Vat 80$^{\circ}$C and 1 A/cm$^2$) among the composite membranes.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2125-2130
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• 2013

A new nickel(II) complex $[NiL^1]^{2+}$ ($L^1$ = 1-(2-aminoethyl)-3-(N-{2-aminoethyl}aminomethyl-1,3-diazacyclohexane) containing one 1,3-diazacyclohexane ring has been prepared selectively by the metal-template condensation of formaldehyde with N-(2-aminoethyl)-1,3-propanediamine and ethylenediamine at room temperature. The complex reacts with nitroethane and formaldehyde to yield the pentaaza macrocyclic complex $[NiL^2]^{2+}$ ($L^2$ = 8-methyl-8-nitro-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one C-$NO_2$ pendant arm. The reduction of $[NiL^2]^{2+}$ by using Zn/HCl produces $[NiL^3(H_2O)]^{2+}$ ($L^3$ = 8-amino-8-methyl-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one coordinated C-$NH_2$ pendant arm that is readily protonated in acid solutions. The hexaaza macrocyclic complex $[NiL^4]^{2+}$ ($L^4$ = 8-phenylmethyl-8-nitro-1,3,6,8,10,13-hexaazabicyclo[13.3.1]heptadecane) bearing one N-$CH_2C_6H_5$ pendant arm has also been prepared by the reaction of $[NiL^1]^{2+}$ with benzylamine and formaldehyde. The nickel(II) complexes of $L^1$, $L^2$, and $L^4$ have square-planar coordination geometry in the solid states and in nitromethane. However, they exist as equilibrium mixtures of the square-planar $[NiL]^{2+}$ (L = $L^1$, $L^2$, or $L^4$) and octahedral $[NiL(S)_2]^{2+}$ species in various coordinating solvents (S); the proportion of the octahedral species $[NiL(S)_2]^{2+}$ is strongly influenced by the ligand structure and the nature of the solvent. Synthesis, spectra, and chemical properties of the nickel(II) complexes of $L^1-L^4$ are described.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1135-1139
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• 2017

Spatial distribution of chemical species in flame is a important indicator understanding the flame structure and combustion characteristics, and optical emission spectroscopy has been widely used for the measurement because of its simple and non-intrusive methodology. In this study, we suggest the feasibility of the measurement of chemical species (OH radical) distribution in rocket plume using optical emission spectrometer which was developed for the spatially resolved measurement along the line-of-sight. In order to predict the ground state concentration of species from the measured emission intensity by optical emission spectrometer, we consider thermal and chemical excitation mechanisms in flame, and assume thermodynamic equilibrium for the thermally excited species. We also present the spatial resolution and the correction of collection characteristics of the optical emission spectrometer depending on object distance.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제13권1호
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• pp.213-220
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• 1993

The problem of disposing of huge quantities of used tires is of growing concern to every country. As an economical solid waste management, a gasification followed by incineration process was applied to scrap tires to recover heat and to reduce waste volume for final landfill disposal. The gasification temperature, combustible and non-combustible gasified products and possibly produced air pollutants were predicted by changing equivalent mole ratios of carbon to oxygen by a chemical equilibrium model. For a risk assessment of ash toxic pollutants including heavy metals and toxic organics were thoroughly analyzed. Gasification bottom ash contained much more toxic organic compounds than fly ash, whereas fly ash contained higher concentration of heavy metals such as Pb and Cd. Pretreatment or secure landfill technology is suggested for a safe management of ash produced from the gasification incinerators.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제29권7호
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• pp.983-989
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• 2005

The effects of mechanical parameters on the characteristics of chemical mechanical polishing(CMP) can be directly evaluated by friction force. The piezoelectric quartz sensor for friction force measurement was installed, and friction force could be detected during CMP process. Furthermore, friction energy can be calculated by multiplying relative velocity by integration of the friction force throughout the polishing time. $SiO_2$ slurry for interlayer dielectric(ILD) CMP was used in this experiment to consider the relation of frictional characteristics and polishing results. From this experiment, it is proven that the friction energy is an essential factor of removal rate. Also, the friction force is related to removal amount per unit length(dH/ds) and friction energy has corelation to the removal rate(dH/dt) and process temporature. Moreover, within wafer non-unifornity(WIWNU) is related to coefficient of friction because of the mechanical moment equilibrium. Therefore, the prediction of polishing result would be possible by measuring friction force.