• BMB Reports
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• v.31 no.2
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• pp.144-148
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• 1998

A bifunctional catalase-peroxidase, designated catalase-2, of a UV resistant Deinococcus radiophilus was purified to electrophoretic homogeneity by both chromatographic and electrophoretic methods. Its molecular weight was 310 kDa and composed of a tetramer of 80 kDa subunits. The catalase-2 exerted its optimal activity at $30^{\circ}C$ and around pH 9. Its $K_m$ value for $H_{2}0_{2} $ was about 10 mM. It showed the typical ferric heme spectrum with maximum absorption at 403 nm which shifted to 419 nm in the presence of cyanide. The ratio of A40i' A2S0 was 0.48. Fifty percent inhibition of the enzyme activity was observed at $4.6{\times}10^{-6}$, $7.7{\times}10^{-6}$, and $3.0{\times}10^{-6}$ M of NaCN, $NaN_3$, and $NH_{2}OH$, respectively. The enzyme was thermostable and not sensitive to 3-amino-1,2,4-triazole. Treatment of the enzyme with ethanol-chloroform caused a partial loss (30%) of its activity. The catalase-2 was distinct from the Deinococcal bifunctional catalase-3 in a number of properties, particularly in its molecular structure and substrate affinity.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.970-974
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• 2007

A mixer is a key component in the wireless communication systems. In this paper, we design a mixer which is used in a frequency modulated continuous wave(FMCW) radar system. The frequency sweep range of the radar is from 10 GHz to 11 GHz. The transmitted and received signals of the FMCW radar are applied to LO and RF ports of the mixer, respectively, but the frequency difference between the two signals, which is called "a beat frequency" is under a few KHz and depending on the distance to target. Thus the isolation between the LO and RF ports is very important factor to design this mixer. In this paper we propose a single balanced resistive mixer using GaAs MESFET for this application. We first design a single-ended type resistive mixer using a simulation tool, then design a balanced type to increase the LO-to-RF isolation of the mixer. We fabricated the mixer on the substrate of dielectric constant 10 and thickness 0.635 mm. The measured results show that the isolation and conversion loss of the mixer over the frequency band is 20dB and 10.5dB, respectively. The LO input power for operating the proposed mixer is +3dBm, which is lower than a general conventional mixer's LO power. The 1 dB compression point is 6dBm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.2
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• pp.164-168
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• 2005

Piezoelectric ZnO thin films were for the first time formed on SiO$_2$/Si(100) substrate using 2-step deposition, atomic layer deposition(ALD) and RF magnetron sputtering deposition, for film bulk acoustic resonator(FBAR) applications. The ZnO buffer layer by ALD was deposited using alternating diethyl zinc(DEZn)/$H_2O$ exposures and ultrahigh purity argon gas for purging. The ZnO films by 2-step deposition revealed stronger c-axis-preferred orientation and smoother surface than those by the conventional RF sputtering method. The solidly mounted resonator(SMR)-typed FBAR fabricated by using 2-step deposition method revealed higher quality factor of 580 and lower return loss of -17.35dB. Therefore the 2-step deposition method in this study could be applied to the FBAR device fabrication.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.260-261
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• 2005

The heterolayered thick/thin structure consisting of $Pb(Zr_{0.52}Ti_{0.48})O_3$ and $BaTiO_3(BT)$ were fabricated by a sol-gel process. PZT powders, prepared by the sol-gel method, were mixed with an organic vehicle and the PZT thick films were fabricated by the screen printing techniques on alumina substrate with Pt electrodes. The microstructural and dielectric characteristics of the stacked heterolayered PZT/BT/PZT films were investigated by varying the number of coating $BaTiO_3$ layers. The existence of a $BaTiO_3$ layer between the PZT thick films of the tri-layer $Pb(Zr_xTi_{1-x})O_3/BaTiO_3/Pb(Zr_xTi_{1-x})O_3$thick/thin/thick film can greatly improve the leakage current properties of the PZT thick films. The average thickness of a PZT(5248)/$BaTiO_3$ heterolayered thick/thin film was 25$\mu$m. The relative dielectric constant and dielectric loss of the PZT(5248)/$BaTiO_3$-3 heterolayered thin film coated three times were 1087 and 1.00% at 1[MHz].

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.53-58
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• 2003

It is well known that the anode substrate of anode-supported type SOFC should have high electrical conductivity and high gas permeability to minimize the polarization loss of the cell performance during operation. In this study, we made anode substrates of SOFC with two different methods, which gave different anode microstructures, especially different pore structures with each other. We performed electrical and microstructural characterization of Ni/YSZ cermet anode via extensive measurements of its electrical conductivity and gas permeability combined with adequate image analysis based on quantitative stereological theory

• Proceedings of the Korean Society of Applied Pharmacology
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• 1995.04a
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• pp.75-75
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• 1995

Succinic semialdehyde reductase, one of key enzyme of GABA shunt in CNS, is inactivated by o-phthalaldehyde, The inactivation followed pseudo first-order kinetics, and the second-order rate constant for the inactivation process was 28 M$\^$-1/s$\^$-1/ at pH 7.4 and 25$^{\circ}C$. The absorption spectrum(λ$\_$max/=377nm), fluorescence exitation(λ$\_$max/=340nm) and fluorescence emission spectra (λ$\_$max/=409nm) were consistent with the formation of an isoindole derivative in the catalytic site between a cysteine and a lysine residues about 3${\AA}$ apart. The substrate, succinic semialdehyde, did not protect the enzymatic activity against inactivation, whereas the coenzyme, NADPH, protected against o-phthalaldehyde induced inactivation of the enzyme. About 1 isoindole group per moi of the enzyme was formed following complete loss of the enzymatic activity. These results suggest that the amino acid residues of the enzyme participating in reaction with o-phthalaldehyde more likely residues at or near the coenzyme binding site.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.81.2-81.2
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• 2011

The gas diffusion layer (GDL) consists of two main parts, the GDL backing layer, called as a substrate and the micro porous layer (MPL) coated on the GDBL. In this process, carbon particles of MPL penetrates to the GDBL consequently forms MPL penetration part. In this study, the micro porous layer (MPL) penetration thickness is determined as a design parameter of the GDL which affect pore size distribution profile through the GDL inducing different mass transfer characteristics. The pore size distribution and water permeability characteristics of the GDL are investigated and the cell performance is evaluated under fully/low humidification conditions. Transient response and voltage instability are also studied. In addition, to determine the effects of MPL penetration on the degradation, the carbon corrosion stress test is conducted. The GDL that have deep MPL penetration thickness shows better performance in high current density region because of enhanced water management, however, loss of penetrated MPL parts is shown after aging and it induces worse water management characteristics.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.254-258
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• 2002

To realize channel cross-connecting in optical communications systems, a high speed optical matrix switch was fabricated using z-cut $LiNbO_3$. For switch fabrication was design bending structure and coupling length and four $2{\times}2$ directional couplers were integrated on one substrate far construction of a $4{\times}4$ switch. Single-mode optical waveguides were formed by Ti-diffusion at a wet $O_2$ atmosphere. Ti-diffusion profile, refractive index variation and waveguide morphology were analyzed by Prism coupler and optical microscopy, respectively.

• Journal of Microbiology and Biotechnology
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• v.15 no.2
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• pp.296-301
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• 2005

The effect of aqueous methanol on the catalytic properties of porcine pancreatic lipase has been investigated. The k$_{CAT}$, values for the hydrolysis of N$^{alpha}$-benzyloxycarbonyl-L­lysine p-nitrophenyl ester at 0$^{circ}$C increased in a linear manner with increasing methanol concentration. However, the K$_{M}$ values were not influenced at methanol concentrations lower than $30\%$ and then began to increase at higher concentrations in an exponential fashion. Based on product analysis, the increase in k$_{CAT}$, with increasing methanol concentration can be accounted for by nucleophilic competition of methanol for the acyl enzyme intermediate, indicating that the rate-limiting step of the porcine pancreatic lipase-catalyzed reaction is deacylation under current experimental conditions. The exponential increase in K$_{M}$ at methanol concentrations higher than $30\%$ is attributed to the hydrophobic partitioning effect on substrate binding. There was no loss of lipase activity over a 4 h period in $60\%$ methanol concentration at pH$^{circ}$ 5.5 and 0$^{circ}$C. By monitoring the intrinsic fluorescence and absorbance, no evidence for structural changes by methanol was observed.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.108-114
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• 1999

Surface acoustic wave (SAW) device is very attractive for gas sensor applications because of their small size, low cost, high sensitivity, and good reliability. A dual delay line surface acoustic wave $NO_2$ gas sensors have been designed and fabricated on the $LiTaO_3$ piezoelectric single crystal substrate. The capacitance of the fabricated IDTs was 326.34pF at the frequency of 79.3MHz. The maximum reflection loss of the impedence-matched IDTs was -16.74dB at the frequency of 79.3MHz. The SAW oscillator was constructed and the stable oscillation was obtained by controlling the gain of rf amplifier properly. The oscillation frequency shift of the SAW oscillator to the $NO_2$ gas was 28Hz/ppm.