• 조명전기설비학회논문지
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• 제23권7호
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• pp.57-66
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• 2009

Microturbines system (MTS) are currently being deployed as small scale on-site distributed generators for microgrids and smart grids. In order to fully exploit DG potentialities, advanced integrated controls that include power electronics facilities, communication technologies and advanced modeling are required. Significant expectations are posed on gas microturbines that can be easily installed in large commercial and public buildings. Modeling, control, simulation of microturbine generator based distributed generation system in smart grid application of buildings for both grid-connected and islanding conditions are presented. It also incorporates modeling and simulation of MT with a speed control system of the MT-permanent magnet synchronous generator to keep the speed constant with load variation. Model and simulations are performed using MATLAB, Simulink and SimPowerSystem software package. The model is built from the dynamics of each part with their interconnections. This simplified model is a useful tool for studying the various operational aspects of MT and is also applicable with building cooling, heating and power (BCHP) systems

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.288-291
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• 2008

Recently, the importance and necessity of engineering analysis has shown a steady growth. However, researchers working in small and medium enterprises know little about the usefulness of engineering analysis and suffer from lack of technical knowledge. Axial fan is air fluid machinery in various fields of industry such as automobile, electric appliance, and heavy machinery. It is also a time and budget consuming equipment to develop the axial fan through physical experiments. In order to overcome this problem, we have designed and developed a web-base automated simulator for axial fan's fluid analysis using supercomputer. Automated simulator means that all of processes for engineering analysis including pre-process, solving, and post-process can be performed automatically without user intervention after transferring fan model(CAD files) made by user. After executing the simulator with some parameters, user can receive the report including pressure P and flow rate Q. In this paper, we introduce the architecture of our easy and efficient automated engineering analysis simulator, related techniques and result of development.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.193-195
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• 2005

[ $0.96[Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3]+0.04SrTiO_3+0.3wt%Nb_2O_5+0.2wt%La_2O_3+xwt%ZnO$ ], were studied in order to develope the superior piezoelectric properties of Lead-free piezoelectric ceramics. With increasing amount of ZnO addition, density showed the maximum value of 5.79(g/$cm^3$) at 0wt% ZnO addition, and electromechanical coupling factor($k_p$) and dielectric constant decreased, and mechanical quality factor($Q_m$) increased and showed the maximum value of 280 at 0.4wt% ZnO addition.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1195-1199
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• 2003

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, dielectric and piezoelectric properties of PSN-PZT[0.91Pb(Sb$\sub$1/2/Nb$\sub$1/2/)$\sub$0.03/(Zr$\sub$0.495/Ti$\sub$0.505/)$\sub$0.97/O$_3$-0.04Pb(Ni$\sub$1/2/W$\sub$1/2/)O$_3$+0.05BiFeO$_3$+0.3wt％MnO$_2$+0.6wt％CuO〕 ceramics were investigated according to Zr/Ti ratio. As Zr/Ti ratio is increased, electromechanical coupling factor(k$\sub$p/) and dielectric constant increased and then decreased after the ratio of Zr/Ti=50/50. Also, mechanical qualify factor(Q$\sub$m/) decreased and then increased after the ratio of Zr/Ti=50/50.

• Journal of Applied Biological Chemistry
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• 제43권3호
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• pp.141-146
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• 2000

Glycosidase activities were tested from the grape berries, Vitis labruscana B. Takasumi. Among various glycosidases, $\alpha$-D-galactosidase was found to be the most active in the flesh and other glycosidases were considerably active in the order of the following: $\alpha$-D-mannosidase>$\alpha$-D-glucosidase>$\beta$-D-glucosidase>$\beta$-D-galactosidase. In the seeds, $\alpha$-D-glucosidase activity was the highest and other glycosidases such as $\alpha$-D-galactosidase, $\beta$-D-glucosidase, and $\beta$-D-galactosidase were still significantly active. The $\alpha$-D-galactosidase in the grape flesh was purified over 83-folds through salting-out with $(NH_4)_2SO_4$ and a series of chromatographies employing Sephadex G-50, Octyl-Sepharose, Q-Sepha- rose, and Biogel P-100. The enzyme was a monomer of 45 kDs as determined through SDS-PAGE and Sephacryl S-200 chromatography. The purified enzyme showed a preference of $\alpha$-D-galactose to $\beta$-D-galactose as a substrate about 5.4 times. Sulfhydryl specific reagents such as N-ethylmaleimide and iodoacetamide significantly inhibited the enzyme activity to the extents of 48 and 52% of its initial activity, respectively. The optimumpH range of $\alpha$-D-galactosidase was around 6.5-7.0. The enzyme activity increased by 46% in the presence of 1mM $Fe^{2+}$.

• 약학회지
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• 제41권6호
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• pp.756-764
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• 1997

Ile-224 in I269S mutant horse liver alcohol dehydrogenase isoenzyme S (HLADH-S) was mutated to serine by site-directed mutagenesis in order to study the role of the residue in c oenzyme binding to the enzyme. The specific activity of the I269S and I224S mutant enzyme to ethanol was increased 6-fold and all Michaelis constants($K_a,\;K_b,\;K_p,\;and\;K_q$,/TEX>) were larger than those for the wild-type and I269S enzyme. The substitution decreased the afffinity to coenzymes and increased the specific activity of the enzyme. The mutant enzyme showed the highest catalytic efficiency for octanol among the primary alcohols. But it didn`t have activities on retinoids and 5${\beta}$-cholanic acid-3-one. From these results, it was confirmed that the hydrophobic interaction of Ile-224 residue with coenzyme was related to coenzyme affinity in ADH reaction. The substitution also affected the substrate affinities to the enzyme.

• Journal of Communications and Networks
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• 제14권1호
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• pp.21-26
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• 2012

As electrocardiogram (ECG) signals are generally sampled with a frequency of over 200 Hz, a method to compress diagnostic information without losing data is required to store and transmit them efficiently on a wireless personal area network (WPAN). In this paper, an ECG signal compression method for communications onWPAN, which uses feature points based on curvature, is proposed. The feature points of P, Q, R, S, and T waves, which are critical components of the ECG signal, have large curvature values compared to other vertexes. Thus, these vertexes were extracted with the proposed method, which uses local extrema of curvatures. Furthermore, in order to minimize reconstruction errors of the ECG signal, extra vertexes were added according to the iterative vertex selectionmethod. Through the experimental results on the ECG signals from Massachusetts Institute of Technology-Beth Israel hospital arrhythmia database, it was concluded that the vertexes selected by the proposed method preserved all feature points of the ECG signals. In addition, it was more efficient than the amplitude zone time epoch coding method.

• 한국전기전자재료학회논문지
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• 제13권3호
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• pp.220-226
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• 2000

The piezoelectric material for piezoelectric transformer needs the high electromechanical coupling factor( $k_{p}$) the piezoelectric constant( $d_{33}$) and the mechanical quality factor( $Q_{m}$)in order to obtain high voltage step-up ratio and low temperature rising. In this study the piezoelectric transformers were fabricated using Pb［$Zr_{0.45}$/ $Ti_{0}$48//L $u_{0.02}$(M $n_{1}$3//S $b_{2}$3/)$_{0.05}$］ $O_3$(PMS-PZT) and Pb［Z $r_{0.25}$/ $Ti_{0.375}$(M $g_{1}$3//N $b_{2}$3/)$_{0.375}$］ $O_3$+0.5wt%Mn $O_2$(PMN-PZT) ceramics. The piezoelectric properties of PMS-PZT and PMN-PZT were measured. The voltage set-up ratios of the piezoelectric transformers using PMS-PZT and PMN-PZT were the value of 15, 20 respectively under 100$_{KΩ}$ in Rosen type transformer.r.ormer.r.r.r.r.r.r.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.797-799
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• 1996

This paper presents a simple method for evaluating of voltage stability using the line flow equation. Line flow equations($P_{ij}$, $Q_{ij}$) are comprised of state variable, $V_i$, ${\delta}_i$, $V_j$ and ${\delta}_j$, and line parameter, r and x. Using the feature of polar coordinate, these equations become one equation with two variables, $V_i$ and $V_j$. Moreover, if bus j is slack bus or generator bus, which is specified voltage magnitude, it becomes One equation with one variable $V_i$, that is, may be formulated with the second-order equation for $V_i^2$. Therefore, solutions are obtained with simple computation. Solutions obtained are used for evaluating of voltage stability through sensitivity analysis. Also, considering of reactive power source, method for evaluating the voltage stability is introduced. The proposed method was validated to 2-bus and IEEE 6-bus system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.82-85
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• 2004

In this study, in order to increase piezoelectric properties of the low temperature sintering ceramics for multilayer piezoelectric transformer, PCW-PMN-PZT ceramics added with $Li_2CO_3$, $Bi_2O_3$ and CuO as sintering aids were manufactured according to the amount of $MnO_2$ addition, and their microstructural, dielectric and piezoelectric properties were investigated. When the sintering aids was added, specimens could be sintered at $950^{\circ}C$. However, sintering aids added specimens showed lower piezoelectric properties than those of non-added specimens. $0.1wt%MnO_2$ added specimen at $950^{\circ}C$ showed ${\varepsilon}_r$, of 1503, $k_p$ of 0.57 and $Q_m$ of 1502 were shown, respectively, and showed optimum properties for multilayer piezoelectric transformer.