• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.234-239
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• 2007

Crystallographically {h00}-oriented $0.94(Bi_{0.5}Na_{0.5})TiO_{3}-0.06BaTiO_{3}$ (0.94BNT-0.06BT) ceramics was prepared by the Reactive Templated Grain Growth (RTGG) method using the $Bi_{4}Ti_{3}O_{12}$ template. The sheets prepared by tape-casting of slurries containing the templates and starting materials are cut, laminated, and pressed. Then burn-out and sintering was conducted. Also, to compare with the 0.94BNT-0.06BT ceramics prepared by the RTGG method another 0.94BNT-0.06BT ceramics was prepared by the solid-state method. In the optimum of this experiments range, the degree of orientation of the 0.94BNT-0.06BT ceramics prepared by the RTGG method was texture fraction${\approx}92%$ and the piezoelectric constant($d_{33}$) and coupling factor($k_{p}$) was obtained to $d_{33}{\approx}205{\;}pC/N$, $k_{p}{\approx}0.33%$, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3C
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• pp.251-256
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• 2009

In this paper, we propose a new method with the improved continuity performance of overlap and add speech signal synthesis method using damping harmonic amplitude parameter. The existing method uses the average value of past and current parameters for the sinusoidal amplitude used as the weight of phase error function. But, the proposed method extracts the more accurate sinusoidal amplitude by using a correlation between the original signals and the synthesized signals for the sinusodal amplitude used as the weights. To verify the performance of the proposed method, we observed the average differential error value between the synthesized signals.

• Archives of Pharmacal Research
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• v.21 no.4
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• pp.440-444
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• 1998

A series of 6-(N-arylamino)-7-methylthio-5,8-quinolinedione derivatives 4a-4l was newly synthesized for the evaluation of antifungal activity. 6-(N-Arylamino)-7-methylthio-5,8-quinolinediones were prepared by regioselective nucleophilic substitution of 6,7-dichloro-5,8-quinolinediones with arylamines in the presence of $Ce^{3+}$, and $Na_2$S/dimethylsulfate. The MIC values of 4a-4l were determined for antifungal susceptibility in vitro against Candida species by agar streak method. The derivatives 4a-4l had generally potent antifungal activities against all human pathogenic fungi. Especially they had the most potent activity against C. krusei at 12.5-0.8 $\mu\textrm{g}$/ml. Compounds 4d, 4g, 4h, 4j and 4k had more potent antifungal activities than fluconazole. Compounds 4g and 4h completely inhibited the fungal growth at 0.8-6.3 $\mu\textrm{g}$/ml against all Candida species, while fluconazole inhibited the growth at 25 $\mu\textrm{g}$/ml. The compounds such as 4g and 4h containing an N-(4-bromo-2-methylphenyl)- or N-(4-bromo-3methylphenyl)amino substituent exhibited the most potent antifungal activities.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.131-138
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• 1995

The broad beam ion sources of hot filament plasma type have widely used for modifications of materials and thin films, and the new type intensive current broad beam metal ion source including reactive gaseous ion beams is needed for preparing the hard coating films such as DLC, $\beta-C_3N_4$ Carbides, Nitrides, Borides etc. Now a electorn beam evaporation(EBE) broad beam metal ion source has been developed for this purpose in our lab. CN film has been formed by the EBE ion source. Study of the CN film shows that it has high hardness(HK=5800kgf/$\textrm {mm}^2$)and good adhesion. This method can widely changes the ratio of C/N atom's concentrations from 0.14 to 0.6 and has high coating rate. The low energy pocket ion source which was specially designed for surface texturing of medical silicon rubber was also developed. It has high efficiency and large uniform working zone. Both nature texturing and mesh masked texturing of silicon rubbers were performed. The biocompatibility was tested by culture of monocytes, and the results showed improved biocompatibility for the treated silicon rubbers. In addition, the TiB2 film synthesized by IBED is being studied recently in our lab. In this paper, the results which include the hardness, thickness of the films and the AES, XRD analysis as well as the tests of the oxidation of high temperature and erosion will be presented.

• Applied Biological Chemistry
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• v.14 no.3
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• pp.191-200
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• 1971

As a series on the soy-bean protein and their related substances 9 samples were collected from 9 places such as straws (Rice) to obtain bacterial strains which produce protease. From these samples total of 23 strains were isolated by the use of dilution pour plate method. For all isolated strains primary screening of productivity of protease was performed and useful straines with regard to protease productivities were identified. Optimum conditions for enzyme action of protease from isolates $D_9$, $F_{20}$ strains were pH 7.5 and $40^{\circ}C$. Chung-Kook-Jang is one of the characteristic foods in Korea made from soy-bean by fermentation. The chief bacterium is Bacillus subtilis and the chief change which takes place in soy-bean during fermentation is degradation of protein. Three kinds of Chung-Kook-Jang were prepared using three different strains of Bacillus natto, $D_9\;and\;F_{20}$ from isolated. Water soluble-N, TCA soluble-N, amino-N and peptide-N were measured about the steamed soybean, Chung-Kook-Jang prepared with three strains of bacteria. Water soluble-N decreased very largely in steamed soybean, but in Chung-Kook-Jang it increased to 85% of raw soy-bean.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.679-684
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• 2000

The Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 compounds, both with Ruddlesden-Popper structures, have been synthesized by the ceramic method at $1150^{\circ}C$ under atmospheric pressure. The crystallographic structure of the compounds was assigned to the tetr agonal system with space group 14/mmm by X-ray diffraction(XRD) Rietveld refinement. The reduced lattice volume and lattice parameters increased as the Ta with 5d substitutes for the Nb with 4d in the compounds. The Co/Nb(Ta)O bond length has been determined by X-ray absorption spectroscopic(EXAFS/XANES) analysis and the XRD refinement. The CoO6,octahedra were tetragonally distorted by elongation of Co-O bond along the c-axis. The magnetic measurement shows the compounds Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 have paramagnetic properties and the Co ions with intermediate spin sates between high and low spins in D4h symmetry. All the compounds showed semiconducting behavior whose electrical conductivity increased with temperature up to 1000 K. The electrical conductiviy increased and the activation energy for the conduction decreased as the number of perovskite layers increased in the compounds with chemical formula An+1BnO3n+1.

• Macromolecular Research
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• v.17 no.10
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• pp.776-784
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• 2009

N,N-dimethyldodecylamine (tertiary amine)-modified MMT (DDA-MMT) was prepared as an organically modified layered silicate (OLS), after which styrene-butadiene rubber (SBR) nanocomposites reinforced with the OLS were manufactured via the latex method. The layer distance of the OLS and the morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By increasing the amount of N,N-dimethyldodecylamine (DDA) up to 2.5 g, the maximum values of torque, tensile strength and wear resistance of the SBR nanocomposites were increased due to the increased dispersion of the silicate layers in the rubber matrix and the increased crosslinking of the SBR nanocomposites by DDA itself. When SBR nanocomposites were manufactured by using the ternary filler system (carbon black/silica/OLS) to improve their dynamic properties as a tire tread compound, the tan $\delta$(at $0^{\circ}C$ and $60^{\circ}C$) property of the compounds was improved by using metal stearates instead of stearic acid. The mechanical properties and wear resistance were increased by direct substitution of calcium stearate for stearic acid because the filler-rubber interaction was increased by the strong ionic effect between the calcium cation and silicates with anionic surface. However, as the amount of calcium stearate was further increased above 0.5 phr, the mechanical properties and wear resistance were degraded due to the lubrication effect of the excessive amount of calcium stearate. Consequently, the SBR/organoclay nanocomposites that used carbon black, silica, and organoclay as their ternary filler system showed excellent dynamic properties, mechanical properties and wear resistance as a tire tread compound for passenger cars when 0.5 phr of calcium stearate was substituted for the conventionally used stearic acid.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.3
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• pp.110-113
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• 2011

In this paper, we propose a new method for the fabrication of GaN microstructures formed only on the vertex of GaN pyramid by using of metal catalysts. GaN pyramidal structures were selectively grown on 3 ${\mu}m$ $SiO_2$ dot patterns followed by thin film deposition of Au and Cr only on the vertex area of the GaN pyramids with precisely controlled photolithography. After the metal deposition, the samples were loaded in the MOVPE reactor for the growth of GaN microstructures for 10 minutes. Temperature for the growth of the GaN microstructures was changed from $650^{\circ}C$ to $750^{\circ}C$. Rod type GaN microstructures were grown in the direction of vertical to the six {1-101} facets and the shape of the GaN microstructures was changed depend on the type of metal.

• Journal of the Korean Statistical Society
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• v.20 no.2
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• pp.162-176
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• 1991

The problem of determining the number of clusters, K. is the main objective of this study. Attention is focused on the use of Rand(1971)'s $C_{k}$ statistic with some agglomerative clustering algorithms(ACA) defined in the ($\beta$, $\pi$) plane in predicting the number of clusters within the given set of data. The (k, $C_{k}$) plots for k=1, 2, …, N are explored by a Monte Carlo study. Based on its performance, the use of $C_{k}$ with the pair of ACA, (-.5, .75) and (-.25, .0), is recommended for predicting the number of clusters present within a set of data. data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.8
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• pp.496-500
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• 2017

$Pb(Mn_{1/3}Nb_{2/3})_{0.07}(Ni_{1/3}Nb_{2/3})_{0.10}(Zr_{0.5}Ti_{0.5})_{0.83}O_3$ composition ceramics with high piezoelectric properties were fabricated by the columbite precursor method for ultrasonic generators, and the effects of sintering temperature on microstructure and piezoelectric properties were systematically investigated. It was found that the tetragonality of the ceramics decreased with increase in sintering temperature. Moreover, excellent physical properties such as $d_{33}=447pC/N$, ${\varepsilon}_r=1,843$, $k_p=0.641$, and $Q_m=1,207$ were obtained for an ultrasonic generator when the second calcination temperature and sintering temperature were $720^{\circ}C$ and $920^{\circ}C$, respectively.