• Journal of Food Hygiene and Safety
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• v.13 no.2
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• pp.149-154
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• 1998

The authors attempted utilization of fatty acid composition of vibrios as a tool for identification of the strains. Fatty acid of 49 strains of Vibrio cholerae non-O1, V. cholerae O1, V mimicus, V vulinificus and V parahaemolyticus was analyzed by gas-liquid chromatography column. According to the statistical analysis of the fatty acid data, the relationship between the Vibrio species and serotypes of the strains was discussed. Forty one kinds of fatty acid were detected from the tested strains and 35 kinds of fatty acids among the detected fatty acids were significant factors to identify the vibrios. The predominant fatty acids were 16:0, 16:1 cis 9, 18:1 trans 9/6/cis 11 and 15:0 iso 2OH/16:1 cis 9 as above about 20% in total. Fatty acid compositions of the Vibrio species were an important factor in identifying their subspecies either predominant fatty acids or minor ones. According to the analysed results by a conventional statistical processing method (UPGMA) and prepared dendrogram, V cholerae non-01 had more closer relationship with V. mimicus compared with V. cholerae 01. Moreover, the distribution of hydroxy acid was a significant factor for identifying V cholerae subspecies. Comprising all the 10 serotypes detected from V. cholerae non-01 examined such as O2, O5, O8, O10, O14, O27, O37, O39, O45 and O69, we could group them into seven subspecies by cluster analysis with the similarity value of fatty acid composition as above 92%. It means that there is a significant relationship between serotypes and fatty acid composition of V. cholerae. These results indicated that numerical analysis of fatty acid composition data of V cholerae non-01 could classifY them into subspecies, and also which may provide a useful epidemiologic information or a basis for further analysis such as PCR and DNA probe analysis.

• Journal of the Korean Ceramic Society
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• v.27 no.4
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• pp.567-573
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• 1990

Solidification condition for preparing transparent ${\gamma}$-6Bi2O3.GeO2 polycrystals by unidirectional solidification of melt, were investigaetd and the properties of the polycrystals prepared were measured. The ${\gamma}$-6Bi2O3.GeO2 polycrystals showing transparency like a single crystal were obtained by the unidirectional solidification of ${\gamma}$-6Bi2O3.GeO2 melt at a solidification rate of 0.5mm/h under a thermal gradient of 12$0^{\circ}C$/cm. The transparent polycrystals obtained showed the same photoconduction and optical activity as the ${\gamma}$-6Bi2O3.GeO2 single crystals grown by Czochralski method. But the electro-optic effect of polycrystals was heterogeneous because the colummar ${\gamma}$-6Bi2O3.GeO2 crystals were not oriented to the particular crystallographic direction.

• Journal of the Korean Vacuum Society
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• v.9 no.1
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• pp.24-29
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• 2000

MgO thin films were deposited on soda lime glass substrates by rf magnetron sputtering using a MgO target at various oxygen flow ratios in order to probe the relationship between MgO film properties and discharge characteristics. MgO films have a tendency to form microstructures with a preferred growth orientation of (200) with increasing oxygen flo ration up to 0.1 $O_2$/(Ar+$O_2$). MgO film obtained at 0.1[$O_2$/(Ar+$O_2$)] was found to be fully stoichiometric. The stoichiometric MgO film was observed to have relatively very clean surface and grains of large size and contain almost no hydroxyl group. The AC PDP with fully stoichiometric MgO film showed lower firing and sustain voltages than those with magnesium-rich or oxygen-rich MgO films, being largely attributed to the larger grain size and the minimized hydroxyl group.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.613-618
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• 2009

We designed new compositions for lead free and low temperature sealing glass frit of $ZnO-V_2O_5-P_2O_5$ system, which can be used for PDP (Plasma Display Panel) or other electronic devices. The $ZnO-V_2O_5-P_2O_5$ system can be used as a sealing material at temperatures even lower than 430$^{\circ}C$. This system, however, showed lower bonding strength with glass substrate compared to commercialized Pb based sealing materials. So, we added $TiO_2$ as a promoter for bonding strength. We examined the effect of $TiO_2$ addition on sealing behaviors of $ZnO-V_2O_5-P_2O_5$ glasses with the data for flow button, wetting angle, temporary & permanent residual stress of glass substrate, EPMA analysis of interface between sealing materials and glass substrate, and bonding strength. As a result, sealing characteristics of $ZnO-V_2O_5-P_2O_5$ system glasses were improved with $TiO_2$ addition, but showed a maximum value at 5 mol% $TiO_2$ addition. The reason for improved bonding characteristics was considered to be the chemical interaction between glass substrate and sealing glass, and structural densification of sealing glass itself.

• Electrical & Electronic Materials
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• v.10 no.8
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• pp.819-829
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• 1997

The microwave dielectric materials of the BaO-Nd$_2$O$_3$-TiO$_2$and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system were synthesized by conventional ceramic processing and sintered 1220 to 140$0^{\circ}C$ for 2 hours respectively. Their crystallization and dielectric properties were examined. In the BaO-Nd$_2$O$_3$-TiO$_2$ and BaO-(Sm, Nd)$_2$O$_3$-TiO$_2$system. Nd$_2$Ti$_2$O$_{7}$ and (Sm, Nd)$_2$Ti$_2$O$_{7}$ were observed as a second phase respectively. The maximum relative dielectric constant were 79,99 for the BaO-Nd$_2$O$_3$-TiO$_2$system and 105.07 for the BaO-(Sm,Nd)$_2$O$_3$-TiO$_2$system and their Q-value were over 2000 at 3GHz.GHz.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1670-1672
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• 2000

The stability of ZnO-$Pr_{6}O_{11}$-CoO-$Cr_{2}O_{3}-Dy_{2}O_3$ based varistors with d.c. stress were investigated. ZnO varistor doped with 4.0 mol% $Dy_{2}O_3$ exhibited the highest nonlinear exponet, but stability was very poor because of low density. In particular, the varistor containing 0.5 mol% $Dy_{2}O_3$ showed very excellent V-I characteristic, which the nonlinear exponent was 67.39 and leakage current was 1.18 ${\mu}A$, and high stability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.551-554
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• 2000

The stability of $Pr_6$$O_{11}$-based ZnO varistors doped with $Y_2$$O_3$ was investigated under various d.c. stresses. The varistors were sintered at $1350^{\circ}C$ for 1h in the addition range of 0.0 to 4.0 mol% $Y_2$$O_3$. The varistors doped with $Y_2$$O_3$ exhibited much higher nonlinearity than that without $Y_2$$O_3$. In Particular, the varistors containing 0.5 mol% $Y_2$$O_3$ showed very excellent V-I characteristics, which the nonlinear exponent was 51.19 and the leakage current was 1.32 $\mu\textrm{A}$. And these varistors also showed an excellent stability, which the variation rate of the varistor voltage and the nonlinear exponent were -0.80% and -2.17%, respectively, under 4th d.c. stress, such as (0.80 $V_ {1mA}$/$90^{\circ}C$/12h)+(0.85 $V_{1mA}$/$115^{\circ}C$/12h)+(0.90 $V_{1mA}$/$120^{\circ}C$/12h)+(0.95 $V_{1mA}$/$125^{\circ}C$/12h). Consequently, since $Pr_ 6$$O_{11}$-based ZnO varistors doped with 0.5 mol% $Y_2$$O_3$ have an excellent stability as well as good nonlinearity, it is expected to be usefully used to develop the superior varistors in future.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.11
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• pp.1297-1308
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• 2011

This research investigates the application of ZnO (zinc oxide) nanoparticles and $TiO_2$ (titanium dioxide) nanoparticles to polypropylene nonwoven fabrics via an electrospinning technique for the development of textile materials that can decompose harmful gases. To fabricate uniform ZnO nanocomposite fibers, two types of ZnO nanoparticles were applied. Colloidal $TiO_2$ nanoparticles were chosen to fabricate $TiO_2$ nano- composite fibers. ZnO/poly(vinyl alcohol) (PVA) and $TiO_2$/PVA nanocomposite fibers were electrospun under a variety of conditions that include various feed rates, electric voltages, and capillary diameters. The morphology of electrospun nanocomposite fibers was examined with a field-emission scanning electron micro- scope and a transmission electron microscope. Decomposition efficiency of gaseous materials (formaldehyde, ammonia, toluene, benzene, nitrogen dioxide, sulfur dioxide) by nanocomposite fiber webs with 3wt% nano-particles (ZnO or $TiO_2$) and 7$g/m^2$ web area density was assessed. This study shows that ZnO nanoparticles in colloid were more suitable for fabricating nanocomposite fibers in which nanoparticles are evenly dispersed than in powder. A heat treatment was applied to water-soluble PVA nanofiber webs in order to stabilize the electrospun nanocomposite fibrous structure against dissolution in water. ZnO/PVA and $TiO_2$/PVA nanofiber webs exhibited a range of degradation efficiency for different types of gases. For nitrogen dioxide, the degradation efficiency was 92.2% for ZnO nanocomposite fiber web and 87% for $TiO_2$ nanocomposite fiber web after 20 hours of UV light irradiation. The results indicate that ZnO/PVA and $TiO_2$/PVA nano- composite fiber webs have possible uses in functional textiles that can decompose harmful gases.

• Journal of the Korean institute of surface engineering
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• v.50 no.5
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• pp.345-351
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• 2017

A double-layered anti-reflective coating with hydrophilic/abrasion-resistant properties was studied using anatase titanium dioxide($TiO_2$) and silicon oxycarbide($SiO_xC_y$) thin film. $TiO_2$ and $SiO_xC_y$ thin films were sequentially deposited on a glass substrate by DC sputtering and PECVD, respectively. The optical properties were measured by UV-Vis-NIR spectrophotometer. The abrasion-resistance and the hydrophilicity were observed by a taber abrasion tester and a contact angle analyzer, respectively. The $TiO_2/SiO_xC_y$ double-layer thin film had an average transmittance of 91.3%, which was improved by 10% in the visible light region (400 to 800 nm) than that of the $TiO_2$ single-layer thin film. The contact angle of $TiO_2/SiO_xC_y$ film was $6.9^{\circ}$ right after UV exposure. After 9 days from the exposure, the contact angle was $10.2^{\circ}$, which was $33^{\circ}$ lower than that of the $TiO_2$ single-layer film. By the abrasion test, $SiO_xC_y$ film showed a superior abrasion-resistance to the $TiO_2$ film. Consequently, the $TiO_2/SiO_xC_y$ double-layer film has achieved superior anti-reflection, hydrophilicity, and abrasion resistance over the $TiO_2$ or $SiO_xC_y$ single-layer film.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.80-88
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• 1980

The sintering phenomena and piezoelectric properties of PZT ceramics of composition $Pb(Zr_{0.54} Ti_{0.46})O_3$ were investigated when a small quantity of $La_2O_3$ , $LaMnO_3$, $LaCrO_3$ were added. The unwanted chemical composition change in PZT during sinterin porces du to PbO evaporation poses a severe problem in PZt manufacturinig. It is observed tat an addition of small amount of $LaMnO_3$ to PZT markedly decreases the evaporation of PbO during sintering . The green compact of (1-x) PZT.xLaMnO3(x=0.02~0.10) could be sintered of under O2 atmosphere alone with no significant loss of PbO. The planar coupling factor kp of the sintered $0.98Pb(Zr_{0.54} Ti_{0.46})O_{3.0.02}LaMnO}3$ is similar to that of commercial PZT 6A. Microstructure investigation shows that part of sintering process of $Pb(Zr, Ti)O_3$.$LaMnO_3$ system progresses via liquid phase sintering. It is believed that the evaporation of PbO in PZT sintering is restricted by the addition of $LaMnO_3$ due to the above phenomena. Furthermore the solid solution of $LaMnO_3$ in PZT causes diffuses phase transition.