• Korean Journal of Food Science and Technology
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• v.51 no.4
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• pp.404-409
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• 2019

This study was performed to determine the optimum conditions for the production of gaseous chlorine dioxide ($ClO_2$) from aqueous $ClO_2$ (HCl+$NaClO_2$). When 1 N HCl was reacted with various concentrations of $NaClO_2$ (50,000-500,000 mg/mL), the highest concentration (695 mg/L) of gaseous $ClO_2$ was obtained from the aqueous $ClO_2$ containing $100,000{\mu}g/mL$ $NaClO_2$. Next, the effects of relative humidity (RH; 43, 85, and 100%) and temperature (4, 12, and $25^{\circ}C$) on the production of gaseous $ClO_2$ were investigated. It was observed that the concentration of gaseous $ClO_2$ was increased as RH was decreased, or the temperature was increased. Finally, it was confirmed that the amount of gaseous $ClO_2$ was highly correlated ($R^2=0.9546-0.9992$) with the volume of aqueous $ClO_2$. The results of this study provide useful information for designing a sanitization program using gaseous $ClO_2$ under various environmental conditions.

• Food Engineering Progress
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• v.15 no.1
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• pp.28-33
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• 2011

UV-C and -B types of lamps, and $H_2O_2$ as a photocatalytic material were applied to optimize processing conditions for pesticides removal in Mandarine orange peel. Factors to affect the removal of pestrcides were arranged as a function of irradiation temperature, irradiation time, and $H_2O_2$ spray concentration. The optimum processing conditions for the chloropyrifos and the EPN removals in Mandarine orange peel were irradiation time of 60 min, irradiation temperature of $45^{\circ}C$ and $H_2O_2$ spray concentration of 1000 ppm. However, the optimum processing conditions for methidathion removal were 60 min of irradiation time, $40^{\circ}C$ of irradiation temperature and 1000 ppm of $H_2O_2$ spray concentration. The residual percentages of chloropyrifos, EPN and methidathion were 46, 49 and 28% after above irradiation processing, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.2
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• pp.75-78
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• 2009

Si-doped GaAs single crystals were grown by vertical gradient freeze using PBN crucibles. The amount of oxide layer $B_{2}O_{3}$ in PBN crucible was changed($0{\sim}0.2wt%$) and measured the concentration of carriers. The segregation coefficients of Si in GaAs melt decreased rapidly from initial 0.1 to 0.01 as the amount of $B_{2}O_{3}$ increases. At the same time, concentration of carriers was shown to decrease. It is likely that the reaction between dopant Si and $B_{2}O_{3}$ in GaAs melt results in the reduction of Si dopants(donor) while increase in the amount of boron(acceptor). The thin layer of $B_{2}O_{3}$ glass in PBN crucible was proved to be a better way to reduce defect formation rather than the total amount of $B_{2}O_{3}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.452-455
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• 2000

Diamond thin films were synthesized on WC-Co substrate at various experimental parameters using 13.56MHz RF PACVD(radio frequency plasma-assisted chemical vapor deposition). In order to increase the nucleation density, the WC-Co substrate was polished with 3$\mu\textrm{m}$ diamond paste. And the WC-Co substrate was pretreated in HNO$_3$: H$_2$O = 1:1 and O$_2$ plasma. In H$_2$-CH$_4$gas mixture, the crystallinity of thin film increased with decreasing CH$_4$concentration at 800W discharge power and 20torr reaction pressure. In H$_2$-CH$_4$-O$_2$gas mixture, the crystallinity of thin film increased with increasing O$_2$concentration at 800W discharge power, 20torr reaction pressure and 4% CH$_4$concentration.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.75-79
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• 1980

The effect of the additive on the dielectric property of $TiO_2$ containing 0-2.5wt %. $Sb_2O_3$ was investigated as a function of frequency from $5{\times}10^4$ to $6.3{\times}10^7$ cps and temperature from 25 to 375$^{\circ}C$. The dielectric constant increased with increasing $Sb_2O_3$ concentration from 0.25 to 0.5wt.% It is due to space charge polarization caused by increasing anion vacanices. The dielectric constant decreased for further increase in $Sb_2O_3$ concentration. It can be explained by increasing grain size effect rather than space charge polarization.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.102-105
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• 2004

ZnO-In$_2$O$_3$ films were fabricated on Corning 1737 glass substrate by an electron beam evaporation technique and their characteristics were investigated. The composition of ZnO-In$_2$O$_3$ films had a marked effect on the electrical properties of the films. The ZnO-In$_2$O$_3$ films showed superior transparent-conducting characteristics with increase of Zn content. The resistivity and carrier concentration of the film having Zn content of 45 at% are 4.45${\times}$10$^{-3}$ cm and 3.1${\times}$10$^{19}$ cm$^{-3}$ , respectively. Also, the transmittance was higher than 80% throughout the visible range. The average roughness of the film was 14.6 $\AA$ in terms of root mean square.

• Journal of Environmental Science International
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• v.2 no.3
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• pp.207-216
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• 1993

The concentrations of $SO_2$ and $SO_3$ were measured to estimate a new developed long time exposure $SO_2$ sampler at Onsan industrial area considering the meteorological factors from June to October, 1992. The mean concentration of $SO_3$ by $PbO_2$ method was 0.924 mg $SO_3 / 10cm^2$ $PbO_2$/day and their high values were shown in the center of the industrial area, which show potential pollution due to the increase of industrial activities and micrometeorological factors in and around the sites. As a result of statistical correlation between $SO_2$ concentration by new sampling method and $SO_3$ concentration by $PbO_2$ method in July and August, 1992, correlation coefficients were high (r=0.87, 0.91) and shown more than 0.83 value in the high concentration data set, which was arbitrarily divided into 7~10${\mu}l$$SO_2$ concentration in an attempt to further investigate these relationships. Therefore, use of new developed long time exposure TEX>$SO_2$ sampler is good for TEX>$SO_2$ measurement and valuable for estimation of air quality in the urban and industrial area. Key Words : a new developed long time exposure TEX>$SO_2$ sampler, correlation coefficients, high, $SO_2$ measurement, estimation of air Quality.

• Journal of Korea Water Resources Association
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• v.38 no.2
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• pp.133-142
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• 2005

The settling concentration of fine suspended solid particles(alumina(Al$_2$O$_3$) and quartz(SiO$_2$)) is investigated with the physico-chemical effects(initial concentration, pH and NaCl). Laboratory tests have confirmed the significant influence of increasing initial concentration and salinity which can lead to flocculation due to the intermolecular attraction. Furthermore, the influence of the pH value on the concentration-time corves of alumina has been on firmed. Besides a numerical model to predict the behaviour of cohesive deposit under still water is analyzed by solving the unsteady one-dimensional diffusion-advection equation with a explicit, implicit, Crank-Nicolson and finite difference scheme. The model predicts the existence of an equilibrium concentration. Application of the model with implicit centered difference to data from settling experiments shows a similar distribution.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.95-101
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• 1995

Experiments have been conducted to investigate the characteristics of formaldehyde and nitrous oxide formation from the catalytic reaction of methane. Catalysts used in the experiment were Pd. Pd/Pt/Rh loaded on ${\gamma}-Al_2O_3$ and ${\gamma}-Al_2O_3-La_2O_3$ monolith. In the catalytic reaction of methane. as the concentration of NO, $O_2$ and $CH_4$ increased, the formaldehyde emission was increased. The concentration of $N_2O$ increased as NO and CO increased. It was also found that the formaldehyde emission was produced by the gas reaction of methane in high temperature above 950K.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.495-500
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• 2007

The inside wall of a coal gasifier is lined with refractory, and the corrosion of the refractory is an important factor affecting the refractory lifetime and the replacement period. This paper examines the changes in microstructure of a chromia refractory due to chemical reactions with slag having varying amounts of $Fe_2O_3$. Slag samples were prepared by adding $Fe_2O_3$ to KIDECO slag, and static corrosion experiments were carried out at $1550^{\circ}C$. The layer of $(Fe,Cr)_3O_4$ formation and the depth of Fe depletion in the infiltrating slag were determined. In addition, FactSage equilibrium calculations were carried out in order to determine the conditions of formation, and to compare with the experimental observations. In the sample exposed to KIDECO slag, which has about 10 wt% $Fe_2O_3$, the formation of $(Fe,Cr)_3O_4$ was not observed. As the $Fe_2O_3$ concentration in slag increased, $(Fe,Cr)_3O_4$ formation and Fe depletion depth increased. Increasing $Fe_2O_3$ concentration also made the slag/refractory interface indistinguishable. Equilibrium calculations predicted that higher $Fe_2O_3$ concentrations favor chromite formation at gasification temperatures. The chromite formation was most favorable when the amount of $Cr_2O_3$ was limited, as in the case of dissolved $Cr_2O_3$ in slag. When the concentration of $Fe_2O_3$ in slag was less than 20%, the formation of chromite was least favorable in the system with equal amounts of slag and refractory.