• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.150-156
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• 2009

Plasma Display Panels(PDPs) require to have improved luminous efficiency, low manufacturing cost, and high image quality to compete with other flat display devices such as Liquid Crystal Displays(LCDs) and organic light-emitting diodes(OLEDs). In addition, the diversity of product line-up may be needed for high market share. In this paper, the optical characteristics of typical green phosphor for PDP application are reviewed and the problem-based solution will be proposed. We also shortly describe the principle of 3D-PDPs which are promising. Then, the requirement of green phosphor for 3D-PDP application is summarized and research achievement, as of now, is described. The typical problems of $Zn_2SiO_4:Mn$ phosphor, which is the most well-known, are the negatively charged surface property and the long decay time, which leads to unstable discharge in green cell and afterimage. These problems were solved by coating the phosphor surface with metallic oxide. It was found that $Al_2O_3$ would be the best material for $Zn_2SiO_4:Mn$ phosphor. It gives longevity as well as low operating voltage due to the charging effect in green cells. Also, new phosphors, $(Y,\;Gd)Al_3(BO_3)_4:Tb$ and $(Mg,\;Zn)Al_2O_4:Mn$ phosphor are proposed for increasing the luminance and reducing the decay time, which are capable to apply for 3D-PDP application.

• Toxicological Research
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• v.11 no.2
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• pp.315-327
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• 1995

Diverse neurotoxic insults result in proliferation and hypertrophy of astrocytes, a subtype of glia in central nervous system. The hallmark of this response, often terms "reactive gliosis", is the enhanced expression of the major intermediate filament protein of castrocytes, glial fibrillary acidic protein (GFAP). These changes in the astrocytes suggest that GFAP may be a useful biochemical indicator of neurotoxicity. To investigate this possibility, we administered intra-peritoneally prototype nerotoxicants, metharnphetamine (MAP, 5 mg/kg), cocaine (30 mg/kg), N-buthyl benzenesulfonamide (NBBS, 300 mg/kg) and trimethytin (TMT, 8 mg/kg) to Wistar Rats and then assessed the effects of these agents on content of GFAP, which were determined by Sandwish ELISA and evaluated with neurotoxic symptoms, and quantitative changes of imrnunoreactivity of GFAP by light microscopic image analysis in specific regions. We found that assay of GFAP revealed time- and region-dependant patterns of neurotoxicity. The GFAP immunoreactivity of rat brain was increased in substantia nigra and hippocampus by MAP, NBBS and TMT; in roedial septal nucleus and nucleus accurnbens, it was also increased by RrBBS. Sandwich ELISA showed that GFAP levels of cerebrum in all groups on days 3 and 7 and that of brainstem(including cerebellum) in MAP, NBBS groups on day 1 and 3 were increased. A review of the background, design and results of these experiments are presented in this paper. Our findings indicate that GFAP is a sensitive and specific biomarker of neurotoxicity.otoxicity.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.29-39
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• 2020

A series of struvite (MgNH₄PO₄·6H₂O) was synthesized and dried at various temperatures (15-60℃). Crystallization of struvite and its structural properties were significantly influenced by synthetic and drying temperature. Struvite was favorably formed at synthetic temperatures ≤30℃ with an inverse relationship between the crystallinity and synthetic temperature. The crystallinity of struvite was also significantly reduced by an increase in drying temperature from 45℃ to 60℃ due to the loss of structural water molecules and ammonium ions by the facilitated thermal decomposition. However, struvite formed at lower synthetic temperature showed higher crystallinity, and its amorphization by thermal decomposition was inhibited. These results demonstrate that struvite formed at low temperature with an stable condition thermodynamically through favorable crystallization shows high crystallinity and stability with respect to the structural and thermal resistance.

• Journal of the Korean Vacuum Society
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• v.19 no.1
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• pp.10-13
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• 2010

We studied the effect of $O_2$ plasma treatments on the electrical property of Ti / Al ohmic contacts to N-face n-type GaN. The surface of N-face, n-type GaN has been treated with $O_2$ plasma for 120 s before the deposition of bilayered electrodes, Ti (50 nm) / Al (35 nm), and its contact resistance was compared with that of the reference sample without $O_2$ plasma. As a result, we found that the ohmic contact was reduced from $4.3\;{\times}\;10^{-1}\;{\Omega}cm^2$ to $1.25\;{\times}\;10^{-3}\;{\Omega}cm^2$ by applying $O_2$ plasma on the surface of n-type GaN, which was attributed to the reduction in the Schottky barrier height (SBH), caused by nitrogen vacancies formed during the $O_2$ plasma process.

• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.501-508
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• 1996

The base-catalysed carbonato or oxalato ring opening of cis-${\beta}-[Co(3,2,3,-tet))CO_3\;or\;C_2O_4)]^+$(3,2,3-tet=4,7-diazadecane-1,10-diamine, $C_2O_4$=oxalate) has been investigated in aqueous solution and in mixed aqueous-organic solvent. The rearrangement of 3,2,3-tet and carbonato or oxalato ring opening of cis-${\beta}-[Co(3,2,3,-tet))CO_3\;or\;C_2O_4)]^+$ occurred via the dissociation of one of the two coordinating carbonato or oxalato oxygen atoms. The resulting product was cis-${\alpha}-[Co(3,2,3-tet)(OH)(OCO_2\;or\;OC_2O_3)_3].$ It has been suggested that the base-catalysed reaction of cis-${\beta}-[Co(3,2,3,-tet))CO_3\;or\;C_2O_4)]^+$ takes place via the Dcb(dissociative conjugated base) mechanism. The other oxygen atom of carbonato or oxalato was dissociated continuously to give cis-${\alpha}-[Co(3,2,3-tet)(OH)_2]^+.$ Cis-${\alpha}-[Co(3,2,3-tet)(OH)_2]^+$ was isomerized to cis-${\beta}-[Co(3,2,3-tet)(OH)_2]^+.$

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.1
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• pp.16-29
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• 1991

The occurrence of thrombotic occlusion & endothelial injuries at the site of anastomosis have been considered as major problems in microvascular surgery. The purpose of this study was to ascertain whether a end-in-end(sleeve, telescope) anastomosis compared favorably with end-to-end anastomosis in healing procedures on the endothelium and to study the possibility of clinical application in end-in-end method. The microvascular anastomoses have been performed with end-in-end method in the femoral arteries of 20 rats group, also with end-to-end method on the same arteries of another 20 rats group, and then the four anastomosed vessels in subdivided groups on each group were taken after period of 1, 3, 7, 14, 21 days following by anastomoses for scanning electron microscope observation. The results were as following: 1. The patency rate was 90% in the end-in-end group and 85%in the end-to-end group and late thrombus occurred at 7, 14 days on both groups, which suggested -consistent monitoring of patency was required for two weeks at least. 2. Platelet aggregates at the site of anastomosis began to organize on post-operation 3 days and in the end-in-end group, the initially decreased lumen of inserted vessel was gradually increasing on 7 days due to atrophy of the medial layers. 3. Re-endothelialization was completed between 7 and 14 days in end-in-end group, whereas between 14 and 21 days in end-to-end group.

• Journal of Korea Soil Environment Society
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• v.3 no.1
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• pp.11-20
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• 1998

Inorganic nitrogens resulting from fertilizers are possible contaminants of bank-filtered ground water, which is an alternative source of safe drinking water. We conducted a laboratory study to determine the fate of inorganic nitrogens in the near field of bank filtration sites and we consequently illustrated the effects of these possible contaminants on the water quailty of bank filtration. Soil properties were found to be well equivalent to those of other cultivated field soils in Korea. Surface soil pH was about 4.3 which is slightly lower than average level. Overall, diverse concentrations of $NO_3$-N and $NH_3$-N were measured, and $NO_2$-N was nearly undetected. $NH_3$-N level in the field decreased, while $NO_3$-N increased along with increasing depth of unsaturated zone. Numbers of viable and nitrifying bacteria ranged from 6.73$\times$$10^{6}$to 10.7$\times$$10^{6}$ and 0.44$\times$$10^{4}$ to 5.21$\times$$10^{4}$ respectively, and both of them were highly correlated ($R^{2}$=0.992). Nitrifying potential assayed by batch test showed relatively lower than other reported results. The oxygen uptake potential of surface and subsurface soil was measured in the presence of ${(NH_4)_2}$$SO_4$. The results demonstrated that surface soil required shorter lag period and uptaked more oxygen than subsurface's.

• Resources Recycling
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• v.8 no.1
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• pp.23-28
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• 1999

Firing characteristics, transverse rupture strength, and heat capacity were studied of the heat-reservoir refractory materials made of red-firing clay, mill scale, and water glass. The firing shrinkage increased with increase of the clay proportion in samples. The volume of fired bodies showed shrinkage by drying up to $300^{\circ}C$, steady expansion in the 300-$700^{\circ}C$ range due to phase transition of iron oxides. and drastic expansion above $1200^{\circ}C$. Flexural strength decreased from 5.6 Mpa to 2.35 Mpa with the decrease of the ratio of clay to mill scale from 1:1 to 1:3 Heat capacities changed from 1.1 Joul/g$^{\circ}$C to 1.35 Joul/g$^{\circ}$C with the ratio of millscale to clay ratio from 1:1 to 1:3. Mill scale in the specimen appears to exist as liquid phase during firing. Firing the specimens in air leads to the eruption of the molten mill scale to the sample surfaces. Contrarily, firing samples in a refractory sagger with a cover suppressed the eruption of the molten mill scale to the surfaces. The addition of mill scale gave rise to porous sintered bodies which would delay cooling rates of heat-reservoir brick.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.113-117
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• 2016

Recently, hydrogen is regarded as important energy in the future, because it is clean and renewable. The photoelectrochemical (PEC) system, which produce hydrogen using water splitting by solar energy, is one of the most promising energy systems because it has abundant energy sources and good theoretical efficiency. GaN has recently been regarded as suitable photoelectrode that could be used to split water to generate hydrogen without extra bias because its band edge position include water redox potential ($V_{redox}=1.23$ vs. SHE). GaN also shows considerable corrosion resistance in aqueous solutions and it is possible to control its properties, such as structure, band gap, and catalyst characteristics, in order to improve solar energy conversion efficiency. But, even if the band edge position of GaN make PEC reaction facilitate without bias, the overpotential of oxygen evolution reaction could reduce the efficiency of system. One of the ways to decrease overpotential is introduction of co-catalyst on photoelectrode. In this paper, we will investigate the effect of manganese dioxide ($MnO_2$) as a co-catalyst. $MnO_2$ particles were dispersed on GaN photoelectrode by spincoater and analyzed properties of the PEC system using potentiostat (PARSTAT4000). After coating $MnO_2$, the flat-band potential ($V_{fb}$) and the onset voltage ($V_{onset}$) were moved negatively by 0.195 V and 0.116 V, respectively. The photocurrent density increased on $MnO_2$ coated sample and time dependence was also improved. These results showed $MnO_2$ has an effect as a co-catalyst and it would enhance the efficiency of overall PEC system.