• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.371-373
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.833-841
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• 1998

ZnO thin films on glass substrate were deposited by on RF mangetron reaction sputter with various grgon/oxygen gas ratios and sbustrate temperatures. Crystallinities, surface morphologies, chemical compositions, and electrical properties of the films were investigated by XRD, AFM, XPS, RBS, and electrometer(keithley 617). All films showed a strong perferred orientation along the x-axis on glass substrate, and the chemical stoichiometry of Zn/)=1/1.0 was obtained at Ar/$O_2$ =50/50. Surface roughness and resistivity depended on the argon/oxygen gas ratio. The minimum surface roughness of 20$\AA$ and maximum resistivity of $10^8$ $\Omega$ cm were achieved at Ar/$O_2$=10/90.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.491-493
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• 1998

The SmBa$_2$Cu$_3$O$\sub$x/ single crystals were used as seeds to induced YBCO growth in MTG process. As the result, the large bulk oriented YBCO superconductors were prepared with dimension of plane 21mm and 32mm in diameter and 10mm in height. The typical Jc value of the sample is 6.5${\times}$10$^4$A/$\textrm{cm}^2$ and its flux float force is 4.6N/$\textrm{cm}^2$. The oxygen absorption in large bulk textured YBCO samples in pure oxygen was studied at several constant temperatures. It can be divided into two steps: a chemical reaction step and a diffusion step.

• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.146-149
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• 1980

Oxodipyrromethene was degraded by a self-photosensitized reaction, similar to the degradation of bilirubin by other investigators. Photodegradation of oxodipyrromethene was faster in methanol-d4, in which the life time of singlet oxygen is longer, than in methanol. It was slower in a solvent which contained a singlet oxygen quencher. Moreover, the products from sensitized and unsensitized reactions are same.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.336-338
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• 2016

Recent multifunctional two-dimensional material research has triggered huge interests in various modifications for substitution of atoms. Instead of novel metals used as the most popular catalysts, nonprecious transition metals are promising candidates for efficient oxidation-reduction transfers. The recent discovery of $Co@C_2N$ has an alternate possiblity as catalysts for the ORR(Oxygen Reduction Reaction) in DSSc(Dye Sensitized Solar Cell) and OER(Oxygen evolution cobalt oxides). Here we report spin-polarized DFT calculations of the structure doped Iron that is one of ferromagnetism atoms like Co to provide a basic desciption of the ferromagnetism of the elemental metals. The spin-density-funtional results present the most stable state energetically is when having pairwise up/down spin.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.829-836
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• 2006

The reaction rate of denitrification is primarily affected by the utilization of organics that are usually limited in the anoxic period in a sequencing batch reactor. It is necessary to add an extemal carbon source for sufficient denitrification. An adaptive model of state-space based on the extended Kalman filter is applied to manipulate the dosage rate of extemal carbon automatically. Control strategies for denitrification have been studied to improve control performance through simulations. The normal control strategy of the constant set-point results in the overdosage of external carbon and deterioration of water quality. To prevent the overdosage of external carbon, improved control strategies such as the constrained control action, variable set-point, and variable set-point after dissolved oxygen depletion are required. More stable control is obtained through the application of the variable set-point after dissolved oxygen depletion. The converging value of the estimated denitrification coefficient reflects conditions in the reactor.

• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.417-422
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• 1998

The electrocatalytic reduction of molecular oxygen was investigated with a Co(II)-glyoxal bis(2-hydroxyanil) complex coated-glassy carbon (GC) electrode in aqueous media. The reduction of $O_2$ at the modified electrode was an irreversible and diffusion-controlled reaction. The complex coated-GC electrode demonstrated an excellent electrocatalytic effect for $O_2$ reduction in an acetate buffer solution of pH 3.2. The coated electrode made the $O_2$ reduction potential shift of 60-510 mV in a positive direction compared to the bare GC electrode depending on pH. The Co(II)-glyoxal bis(2-hydroxyanil) coated electrode converted about 51% of the $O_2$ to $H_2O_2$ via a two-electron reduction pathway, with the balance converted to H_2O$.

• Bulletin of the Korean Chemical Society
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• v.16 no.7
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• pp.619-624
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• 1995

Oxidation of triphenylphosphine to triphenylphosphine oxide by [(tpy)(bpy)Ru(O)]2+ (tpy is 2,2':6',2"-terpyridine and bpy is 2,2'-bipyridine) in CH3CN has been studied. Experiments with the 18O-labeled oxo complex show that transfer of oxygen from [(tpy)(bpy)RuⅣ=O]2+ to triphenylphosphine is quantitative within experimental error. The reaction is first order in each reactant with k (25.3 ℃)=1.25 × 106 M-1s-1. The inital product, [(tpy)(bpy)RuⅡ-OPPh3]2+, is formed as an observable intermediate and undergoes slow k (25 ℃)=6.7 × 10-5 s-1 solvolysis. Activation parameters for the oxidation step are ΔH≠=3.5 kcal/mol and ΔS≠=-23 eu. The geometry at ruthenium in the complex cation, [(tpy)(bpy)RuⅡ(OH2)]2+, is approximately octahedral with the ligating atoms being the three N atoms of the tpy ligand, the two N atoms of the bpy ligand, and the oxygen atom of the aqua ligand. The Ru-O bond length is 2.136(5) Å.

• Environmental Engineering Research
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• v.24 no.2
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• pp.318-323
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• 2019

Paper focuses on comparison between two different orifice plate configurations (plate number 1 and plate number 2) used as cavitating device in the hydrodynamic cavitation reactor for improving pollutant removal efficiencies. Effect of four different parameters such as hydraulic characteristics (in terms of range of flow rates, orifice velocities, cavitation number at different inlet pressures); cavitation number (in range of 5.76-0.35 for plate number 1 and 1.20-0.35 for plate number 2); inlet pressure (2-8 bars) and reaction time (0 to 60 min) in terms of chemical oxygen demand (COD) removal and chlorpyrifos degradation has been studied and compared. Optimum inlet pressure of 5 bars exists for degradation of pollutants for both the plates. It is found that geometry of orifice plate plays important role in removal efficiencies of pollutant. Results obtained confirmed that orifice plate 1 with configuration of 1.5 mm 17 holes; cavitational number of 1.54 performed better with around 60% COD and 98% chlorpyrifos removal as compared to orifice plate 2 having configuration of 2 mm single hole; cavitational number of 0.53 with 40% COD and 96% chlorpyrifos in 2 h duration time.

• Membrane Journal
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• v.22 no.2
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• pp.113-119
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• 2012

$YBaCo_2O_{5+{\delta}}$ oxide was synthesized by solid state reaction and a typical dense membrane has been prepared using as-prepared powder by unilateral pressing and sintering at $1,180^{\circ}C$. The $YBaCo_2O_{5+{\delta}}$ membraneswas analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD analysis showed the double layered perovskite structure was observed over $1,150^{\circ}C$ without impurities. Oxygen permeation was measured in the temperature range from 750 to $950^{\circ}C$ according to oxygen partial pressure difference between feed and permeation side. The oxygen permeation flux increased with increasing temperature and oxygen partial pressure and the maximum oxygen flux of $YBaCo_2O_{5+{\delta}}$ membrane with 1.0 mm thickness was about 0.15 mL/$cm^2{\cdot}min$ at $950^{\circ}C$ and $PO_2$ = 0.42 atm. The activation energy for oxygen permeation decreased with decreasing oxygen partial pressure to be 76.0 kJ/mol at the condition of $PO_2$ = 0.21 atm.