• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.158-162
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• 1997

In this paper, the electrical and dielectrical properties were investigated in Pb(Zr,Ti)O$_3$-Pb(Mn,Nb)O$_3$ ceramics which are manufactured with the substitution of Ba in site Pb. In older to increase the del and Kp , Ba was substitued to site Pb from 0 to 0.1 by 0.02 mol%. As the Ba substitution is increased, dielectric constant is increased and electricmachanical coupling factor showed the maximum value at Ba 0.06mol% and the mechanical qualify factor is decreased and the tetragonality and the grain size are decreased as the Ba substitution.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.2
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• pp.95-102
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• 2000

Methane combustion over perovskite-type oxides prepared using the malic acid method was investigated. To enhance the catalytic activity, the perovskite oxides were modified by the substitution of metal into their A or B site. In addition, the reaction conditions, such as the temperature, space velocity, and partial pressure of the methane were varied to understand their effect on the catalytic performance. With the LaCoO3-type catalyst, the partial substitution of Sr or Ba into site A enhanced the catalytic activity in the methane combustion. With the LaBO3(B=Co, Fe, Mn, Cu)-type catalyst, the catalytic activities were exhibited in the order of Co>Fe Mn>Cu. Futhermore, the partial substitution of Co into site B enhanced the catalytic activity, whereas an excess amount of Co decreased the activity. The surface area and catalytic activity of the perovskite catalysts prepared using the malic acid method showed higher values than those prepared using the solid reaction method. The catalytic activity was enhanced with decreased methane concentration and with a decrease in the space velocity.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.40-43
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• 1999

In order to investigate Sn substitution sites and interstitial O atoms in tin-doped indium oxide, molecular dynamics (MD) simulations were carried out. There are two kinds of cation sites in $In_2O_3$, namely b-site and d-site. NTP-MD simulations under the condition of 300 K and 0 GPa were performed with two kinds of cells substituted by Sn atoms at each site. The excess oxygen atom accompanied with Sn doping was also taken into consideration. According to the calculations of Sn potential energies in each site, it was revealed that Sn atoms were substituted for b-sites rather than for d-sites. It was also revealed that the interstitial excess oxygen atoms tend to be connected with the Sn atoms substituted for the d-sites Sn rather than for the b-site. There MD simulation results well agreed with the experimental results.

• Korean Journal of Microbiology
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• v.29 no.5
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• pp.278-283
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• 1991

Two amino acid residues ($Ala^{494}$ and $Ser^{495}$ of E. coli .gamma.-glutamylcysteine synthetase have been investigated whether they are the site of feedback inhibition by site specific mutagenesis. Single substitution of $serine^{495}$ (S495F), and double substitutions of alanine$^{494}$ and $serine^{495}$ (A494G-S495F) resulted in the inactivation of the .gamma.-glutamylcysteine synthetase activity. Substitution of $alanine^{494}$ with $glycine^{494}$ resulted in a higher level of feedback inhibition. These results suggest that $serine^{495}$ in .gamma.-glutamylcysteine synthetase is required for its catalytic acitvity and $alanine^{494}$ is presumably related to the feeback inhibition site.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.471-478
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• 2011

Investigations of crystal structure and phase transition of $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramics doped with A-site substitution impurity (La, Nd) or B-site substitution impurity (Sb, Nb) at 2 mol% concentration were carried out. X-ray diffraction patterns of impurities doped $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramics have been measured at pressures up to ~5 GPa with diamond anvil cell and synchrotron radiation. The patterns were obtained at room temperature using methanol-ethanol mixture as pressure-transmitting media. In order to refine the crystal structure, Rietveld analysis has been performed. The structures of impurities doped $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramics are tetragonal in space group P4mm at ambient pressure and are transformed into a cubic phase in space group Pm$\bar{3}$m as the pressure increases. In this study, when A-site substitution donor $La^{3+}$ or $Nd^{3+}$ ion was added to $Pb(Zr_{0.52}Ti_{0.48})O_3$ ceramics, the phase transition phenomena showed up at the pressure of 2.5~4.6 GPa, but when B-site substitution donor $Nb^{5+}$ or $Sb^{5+}$ ion was added to it, the phase transition appeared at relatively lower pressure of 1.7~2.6 GPa.

• Journal of KIISE:Software and Applications
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• v.34 no.7
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• pp.595-602
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• 2007

This paper proposes a method that discriminates signal peptide and predicts the cleavage site of the secretory proteins cleaved by the signal peptidase I. The preprocessing stage uses hydrophobicity scales of amino acids in order to predict the presence of signal sequence and the cleavage site. The preprocessing enhances the performance of the prediction method by eliminating the non-secretory proteins in the early stage of prediction. for the effective use of support vector machine for the signal sequence prediction, the biologically relevant distance between the amino acid sequences is defined by using the hydrophobicity and substitution matrix; the hydrophobicity can be used to Predict the location of amino acid in a cell and the substitution matrix represents the evolutionary relationships of amino acids. The proposed method showed 98.9% discrimination rates from signal sequences and 88% correct rate of the cleavage site prediction on Swiss-Prot release 50 protein database using the 5-fold-cross-validation. In the comparison tests, the proposed method has performed significantly better than other prediction methods.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1369-1373
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• 1999

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.245-250
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• 1999

The effect of cation substitution on the inonic conductivity was studied in $(Li_{0.5}La_{0.5})_{1-y}Sr_yTi_{1-x}Mn_xO_3$ system. In case of Sr substitution, the ionic conductivity abrubtly decreased over y=0.05. This may be caused by the decrease of lithium contents which contribute to lithium inonic conductivity. Jahn-Teller distortion as well as lattice parameter variation influenced the inonic conductivity in case of Mn substitution. A and B-site cations effects on the conductivities were found to be independent, and the ionic conductivity as high as $2.8{\times}10^{-2}$S/cm was obtained in x=0.0006 and y=0.05.

• Biomedical Science Letters
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• v.14 no.2
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• pp.119-122
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• 2008

The baculovirus/insect cell expression system is of great value in the study of structure-function relationships in mammalian glucose-transport proteins by site-directed mutagenesis and for the large-scale production of these proteins for mechanistic and biochemical studies. In order to exploit this, the effects of substitution at the highly conserved residue glutamine 282 of the human erythrocyte-type glucose transporter have been examined by in vitro site-directed mutagenesis. The modified human transport protein has been expressed in Spodoptera frugiperda 21 cells by using the recombinant baculovirus AcNPV-GTL. To assess the functional integrity of the expressed transporter, measurements of the transport inhibitor cytochalasin B binding were performed, involving the membranes prepared from 4 days post infection with no virus, with wild-type virus or AcNPV-GTL virus. Data obtained showed that there was little or no D-glucose-inhibitable binding in cells infected with the wild type or no virus. Only the recombinant virus infected cells exhibited specific binding, which is inhibitable by D- but not by L-glucose. However, there was a notable reduction in the affinity for the potent inhibitor cytochalasin B when binding measurements of AcNPV-GTL were compared with those of AcNPV-GT, which has no substitution. It is thus suggested that although the modified and unmodified human transporters differed slightly in their affinity for cytochalasin B, the glutamine substitution did not interfere the heterologous expression of the human transporter in the insect cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.12
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• pp.847-851
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• 2015

The effects of Al-substitution on thermoelectric and charge transport properties of BiCuOSe compounds were investigated. The compounds were prepared by a solid-state reaction and consolidated by SPS (spark plasma sintering). In spite of the increase in the hole concentration with increasing Al amounts in BiCuOSe compound, the electrical conductivity at room temperature was kept constant due to the reduction of mobility. However, electrical conductivities of Al-substituted BiCuOSe compounds at elevated temperature (> 600 K) were higher than those of BiCuOSe, and this result was discussed in terms of it's the band gap energy. The Seebeck coefficient was drastically reduced when Al was substituted in Bi site, which indicated that the electronic structure was influenced by the Al-substitution into Bi-site.