• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.10-15
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• 1999

White emission thin film electroluminescent device was fabricated using ZnS for phosphor layer and BST ferroelectric thin film for insulating layer. For fabrication conditions of BST thin film, stoichiometry of target was $Ba_{0.5}Sr_{0.5}TiO_3$, substrate temperature was $400^{\circ}C$, working pressure was 30 mTorr, and A:$O_2$ ratio was 9:1. At this time, dielectric constant was 209 at 1kHz frequency. For phosphor layer ZnS:Mn, ZnS:Tb, and ZnS:Ag were used. Mixing rates of activators were respectively 0.8, 0.8, and 1 wt%. Total thickness of phosphor tapers was 500 nm, thickness of lower insulating layer was 200 nm, and thickness of upper insulating layer was 400 nm. In this conditions, luminescence threshold voltage of thin film electroluminescent device was $95\;V_{rms}$, maximum brightness was $3,000\;cd/m^2$ at $150\;V_{rms}$. Luminescence spectrum peak was observed at region of blue(450 nm), green(550 nm), and red(600 nm).

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.212-217
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• 2000

Dielectric thin films for TFT(thin film transistor)s, such as silicon nitride$(Si_3N_4)$ and silicon oxide$(SiO_2)$, are usually deposited at $200~300^{\circ}C$. In this study, authors have tried to form dielectric films not by deposition but by oxidation with ECR(Electron Cyclotron Resonance) oxygen plasma, to improve the interface properties was not intensionally heated during oxidation. THe oxidation was performed consecutively without breaking vacuum after the deposition of a-Si: H films on the substrate to prevent the introduction of impurities. In this study, especially pulse mode of microwave power has been firstly tried during FCR oxygen plasma formation. Compared with the case of the continuous wave mode, the oxidation with the pulsed ECR results in higher quality silicon oxide$SiO_X$ films in terms of stoichiometry of bonding, dielectric constants and surface roughness. Especially the surface roughness of the pulsed ECR oxide films dramatically decreased to one-third of that of the continuous wave mode cases.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.580-584
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• 2001

We have investigated the deposition characteristics of Ti-Si-N films obtained by rf magnetron sputtering with ratios of Ti/Si targets in an $Ar/N_2$ gas mixture. The growth rate and stoichiometry dependence of the Ti-Si-N films on the ratio of Ti/Si and $N_2$ flow rate ratio were found to be due to the different nitriding rate of Ti and Si targets. Additionally, their different sputtering yield of nitrified Ti and Si make a reason as well. Lowering Si content in the film favored the formation of crystalline TiN, leading to the low resistivity. Increasing N content led to the Ti-Si-N films having a higher density and compressive stress, suggesting that the N content in the film is one of the most important factors determining the diffusion barrier characteristics. In the current work, the optimum process conditions for the formation of efficient diffusion barrier of Ti-Si-N film has successfully obtained by manipulating the Ti/Si ratio of target and $N_2$ flow rate ratio.

• Journal of the Korean Electrochemical Society
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• v.11 no.2
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• pp.89-94
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• 2008

We synthesized and investigated $(La_{0.75}Sr_{0.25})_{1-x}FeO_{3-\delta}$ perovskite oxides having different stoichiomety (x = 0, 0.02, 0.04, 0.06, 0.08) as cathode materials. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The electrochemical performances of the synthesized powders were investigated by AC impedance spectroscopy. Both the electric conductivity and the electrochemical performance showed the highest properties at the stoichiometry x = 0.02. Finally, we concluded that the variation of A-site deficiency results in the variation of the amount of oxygen vacancy and micro structure, which leads to the variation of electric conductivity and polarization resistance.

• Resources Recycling
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• v.13 no.6
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• pp.31-36
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• 2004

This experiment was carried out to examine the effects of morphology on properties of La-Co substituted SrM ferrite. The magnetic properties of calcined and sintered materials were varried with the substitutional amount of La and Co elements in Sr-ferrite. In the substituted SrM ferrite, the atomic fraction x of La is directly related to the mole ratio n of iron oxide and the atomic fraction y of Co by equation x=2ny. The Hcj values of the calcined powder were about 270 kA/m and 240 kA/m with x=0.3 and x=0.2, respectively at stoichiometry, n=6.0. Crystallites of the sintered material were grown with a plate shape, and their size decreased with increasing mole ratios. Such a shape was caused by the initial state of crystallite formed after calcination. In case of x=0.3 and n=6.0, Br was 415 mT and Hcj was 355 kA/m, and in x=0.2 and n=6.0, Br was 410 mT and Hcj was 370 kA/m. The squareness in 2nd quarter of BH curve with x=0.2 was smoothly improved to compared with x=0.3.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.994-1001
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• 2001

An easier way of understanding the BNR system was proposed from the study on substrate, nutrient removal tendency, microbial community and its metabolic function by applying the municipal settled sewage. During the anaerobic period, the phosphorus release rate per VFACOD we varied depending on the phosphorus content in the sludge. When the phosphorus content in the sludge was $6\%$ VSS, according to influent VFACOD, the phosphorus release rate and PHA production were $0.35 gPO_4P/gVFACOD$ and 1.0 gPHA/gVFACOD, respectively. The $NO_3N$ requirement for the phosphorus uptake as an electron acceptor was about $0.5 gNO_3N/gPO_4P_{uptake}$ based on the proposed equation with PHA, biomass, production, and the concentration of phosphorus release/uptake. Bacterial-community analysis of the sludge, as determined by FISH and 16SrDNA characterization FISH, revealed that the beta-subclass proteobacteria were the most abundant group ($27.9\%$ of the proteobacteria-specific probe EUB338), and it was likely that representative of the beta-subclass played key roles in activated sludge. The next dominant group found was the gamma-protebacteria ($15.4\%$ of probe EUB338). 16S rDNA clone library analysis showed that the members of${\beta}$- and ${\gamma}$-proteobacteria were also the most abundant groups, and $21.5\%$ (PN2 and PN4) and $15.4\%$ (PN1 and PN5) of total clones were the genera of denitrifying bacteria and PAO, respectively. Prediction of the microbial community composition was made with phosphorus content (Pv, $\%$ P/VSS) in wasted sludge and profiles of COD, PHA, $PO_4P,\;and\;NO_3N$ in an anaerobic-anoxic SBR unit. Generally, the predicted microbial composition based upon metabolic function, i.e., as measured by stoichiometry, is fairly similar to that measure by the unculturable dependent method. In this study, a proposal was made on he microbial community composition that was more easily approached to analyze the reactor behavior.

• The Korean Journal of Pharmacology
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• v.24 no.1
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• pp.111-123
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• 1988

Neutrophil elastases were purified by a three step procedure consiting of one Sephadex G-75 and two HPLC elutions. The elastases cross-reacted with antibodies to human neutrophil elastase. Three bands with molecular weights between 26,000 and 29,700 were observed by gel electrophoresis. At each stage of purification the quantity of Zn increased, reaching molar ratio of 2:1 with elastase in the most purified samples. Calcium content. was seletively elevated during the earlier stages of purification but decreased to a ratio of 0.25 to 1 with elastase at the final step of purfication. Neutrophil elastase could be inhibited by EDTA, EGTA and 1,10-phenanthroline. EGTA inhbition was noncompetitive inhibition and reversible only if the time of preincubation was relatively short, indicating the instability of the apoenzyme. The concentration of chelator required to show significant inhibition of elastase was also dependent upon the stage of purity and the ionic strength of the reaction mixture. Inhibition by EGTA, followed by the removal of EGTA, could be reversed by Zn. In the presence of EGTA the enzyme could be returened to full activity by the addition of Zn, Mn and Ca, but not Mg or Na. All of the above evidence strongly supports human neturophil elastase could be a metalloenzyme as well as a serine protease.

• Korean Journal of Microbiology
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• v.43 no.4
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• pp.250-255
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• 2007

The RecA protein of Deinococcus radiodurans is essential for the extreme radiation resistance of this organism. The central steps involved in recombinational DNA repair require DNA-dependent ATP hydrolysis by recA protein. Key feature of RecA protein-mediated activities is the interactions with ssDNA and dsDNA. The ssDNA is the site where RecA protein filament formation nucleates and where initiation of DNA strand exchange takes place. The effect of sequence heterogeneity of ssDNA was examined in this experiment. The rate of homopolymeric synthetic ssDNA-dependent ATP hydrolysis was constant or nearly so over a broader range of pHs. For poly(dT)-dependent ATP or dATP hydrolysis, rates were generally faster, with a broader optimum between pH 7.0 and 8.0. Activities of RecA protein were affected by the ionic environment. The ATPase activity was shown to have different sensitivity to anionic species. The presence of glutamate seemed to slimulate the hydrolytic activity. Dr RecA protein was shown to require $Mg^{2+}$ ion greater than 2 mM for binding to etheno ssDNA and the binding stoichiometry of 3 nucleotide for RecA protein monomer.

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.17-24
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• 1991

Laves phases of $NdFe_2$, $Nd{(Fe_{0.5})}_2$, $SmCo_2$ and $Sm{(Fe_{0.5}Co_{0.5})}_2$ stoichiometry were prepared using a rapid solidification technology. Low temperature magnetic properties show ferromagnetic behaviors for the $Nd{(Fe_{0.5}Co_{0.5})}_2$, $SmCo_2$ and $Sm{(Fe_{0.5}Co_{0.5})}_2$Nd(Feo,Coo,) Laves compounds while a sort of spin reorientation has been suggested for the supposed composition of $NdFe_2$ alloy. This rapidly solidified $NdFe_2$ alloy is believed to consist of metastable rhombohedral $NdFe_7$ phase plus fine particles of Nd-rich phase. Some evidence of phase transition from the mixture of unstable $NdFe_7$ compound plus Nd-rich to $Nd_2Fe_{17}$ plus Fe-Nd-O phase was obtained after annealing the $NdFe_2$, alloy. The pseudo-binary Laves compound, $Sm{(Fe_{0.5}Co_{0.5})}_2$ exhibits a high coercivityof 4 kOe at room temperature with Curie temperature of $400^{\circ}C$ while the $Nd{(Fe_{0.5}Co_{0.5})}_2$ compound shows a magnetic moment of $2.8\;{\mu}_B/f.u.$.

• Journal of the Korean Magnetics Society
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• v.10 no.3
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• pp.123-132
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• 2000

Cerium substituted YIG thin films were grown by rf magnetron sputter techniques. We investigated the effects of post-deposition heat-treatment as well as various deposition parameters such as substrate materials, substrate temperature. sputter power, and sputter gas types on the crystallinity, chemical composition, microstructure and magnetic characteristics of the films. Post-deposition heat treatment over 750 $\^{C}$ was applied to crystallize as-prepared amorphous films, and a strong tendency of particular crystallographic planes tying parallel to substrate surface was observed for the post-deposition heat-treated films on GGG substrate. The chemical composition of the films exhibited a wide range of chemical stoichiometry depending on the oxygen fraction of sputter gas, and in particular the composition of the film deposited in sputter gas with an oxygen fraction of R = 10% was Ce$\_$0.23/Y$\_$1.30/Fe$\_$3.50/O$\_$12/. With raising the temperature of post-deposition heat-treatment from 900 $\^{C}$ to 1100 $\^{C}$, the surface roughness of the film on GGG substrates increased from about 3 nm to 40 nm, but their coercive force and ferromagnetic resonance line width decreased from 0.477 kA/m to 0.369 kA/m and from 12.5 kA/m to 8.36 kA/m, respectively.