• The Journal of the Korea institute of electronic communication sciences
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• v.1 no.1
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• pp.49-55
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• 2006

Applied by periodic Stimulating Currents in Bonhoeffer -Van der Pol(BVP) model, chaotic and periodic phenomena occured at specific conditions. The conditions of the chaotic motion in BVP comprised 0.7182< $A_1$ <0.792 and 1.09< $A_1$ <1.302 proved by the analysis of phase plane, bifurcation diagram, and lyapunov exponent. To control the chaotic motion, two methods were suggested by the first used the amplitude parameter A1, $A1={\varepsilon}((x-x_s)-(y-y_s))$ and the second used the temperature parameterc, $c=c(1+{\eta}cos{\Omega}t)$ which the values of ${\eta},{\Omega}$ varied respectlvly, and $x_s$, $y_s$ are the periodic signal. As a result of simulating these methods, the chaotic phenomena was controlled with the periodic motion of periodisity. The feasibilities of the chaotic and the periodic phenomena were analysed by phase plane Poincare map and lyapunov exponent.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.285-287
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• 1997

An AC shunt with low phase angle has been designed for an AC current measurement, such as currents with harmonics. This $0.2\;{\Omega}$ shunt of 5 A rated current is composed of fifty $10\;{\Omega}$ metal film resistors and applicable to the frequency band of DC to 1 kHz.

• Journal of the Korean Applied Science and Technology
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• v.18 no.1
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• pp.67-77
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• 2001

In search for several fatty acid with unusual structure in vegetable oils, we have found that unknown peaks were shown on GLC in the analysis of fatty acids of the lipids from the pulp of ripened jujube (Zizypus jujuba var. inermis) fruits. These fatty acids were identified as a series of cis-monoenoic acids with ${\omega}-5$ double bond system such as $C_{14:1{\omega}5}$, $C_{16:1{\omega}5}$ and $C_{18:1{\omega}5}$, including ${\omega}-7$ fatty acid as $C_{16:1{\omega}7}$ and $C_{18:1{\omega}7}$, by GLC, solid-phase extraction silver ion-column chromatographic, GLC-mass spectrometric and IR techniques. First of all, total fatty acid methyl esters were resolved into saturated and branched fatty acid, monoenoic acid, dienoic acid, and trienoic acid fraction, respectively, with 100% dichloromethane (DCM), DCM/acetone (9:1, v/v) 100% acetone, and acetone/ acetonitrile (97:3, v/v) solvent system. Unknown fatty acids were included in the monoenoic fraction and were confirmed to have cis-configuration by IR. Picolinyl esters of monoenoic fatty acids gave distinct molecular ion peak and dominant diagnostic peaks, for example, m/z 317, 220 and 260 fragment for $cis-C_{14:1{\omega}5}$, m/z 345, m/z 248 and 288 fragment for $cis-C_{16:1{\omega}5}$ and m/z 373, m/z 276 and 316 fragment for $cis-C_{18:1{\omega}5}$. In this way the occurrence of $cis-C_{16:1{\omega}7}$ and $cis-C_{18:1{\omega}7}$ could be deduced from the appearance of prominent fragments as m/z 345, 220 and 260, and m/z 373, 248 and 280. Level of total ${\omega}-5$ fatty acids amounted to about 30% in the fatty acid composition with the predominance of $C_{16:1{\omega}5}$ $ (18.7{\sim}25.0%)$, in the semi-ripened and/or ripened samples collected in September 14 ($C_{16:1{\omega}5}$ ; 18.7%, $C_{14:1{\omega}5}$ ; 3.6% and $C_{18:1{\omega}5}$ ; 3.0%), September 22 ($C_{16:1{\omega}5}$ ; 25.0%, $C_{14:1{\omega}5}$ ; 1.4% and $C_{18:1{\omega}5}$ ; 2.6%), and October $7 (C_{16:1{\omega}5}$ ; 24.7%, $C_{14:1{\omega}5}$ ; 7.7% and $C_{18:1{\omega}5}$ ; 2.5%). However, the lipids extracted from unripened jujube in July and August contain these unusual fatty acids as low as negligible. It could be observed that the level of ${\omega}-5$ fatty acids in the pulps increased sharply with an elapse of ripening time of jujube fruits. Other monoenoic fatty acids with ${\omega}-7$ series, $C_{16:1{\omega}7}$ (palmitoleic acid) and $C_{18:1{\omega}7}$ (cis-vaccenic acid) could be detected. And in the lipids of the kernel and leaf of jujube, none of ${\omega}-5$ fatty acids could be detected.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.629-637
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• 2008

We report several experimental data capable of evaluating the amorphous-to-crystalline (a-c) phase transformation in $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ (x = 0, 0.05, 0.1) thin films prepared by a thermal evaporation. The isothermal a-c structural phase changes were evaluated by XRD, and the optical transmittance was measured in the wavelength range of $800{\sim}3000$ nm using a UV-vis-IR spectrophotometer. A speed of the a-c transition was evaluated by detecting the reflection response signals using a nano-pulse scanner with 658 nm laser diode (power P = $1{\sim}17$ mW, pulse duration t = $10{\sim}460$ ns). The surface morphology and roughness of the films were imaged by AFM. It was found that the crystallization speed was so enhanced with an increase of Ag content. While the sheet resistance of c-phase $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ was similar to that of c-phase $Ge_2Sb_2Te_5$ (i.e., $R_c{\sim}10{\Omega}/{\square}$), the sheet resistance of a-phase $(Ag)_x(Ge_2Sb_2Te_5)_{1-x}$ was found to be lager than that of a-phase $Ge_2Sb_2Te_5$, $R_a{\sim}5{\times}10^6{\Omega}{/\square}$. For example, the ratios of $R_a/R_c$ for $Ge_2Sb_2Te_5$ and $(Ag)_{0.1}(Ge_2Sb_2Te_5)_{0.9}$ were approximately $5{\times}10^5$ and $5{\times}10^6$, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.109-115
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• 2008

A design criterion of grounding systems is commonly based on the ground resistance measured with low frequency in Korea. When lightning surges which have high frequency components are injected into the grounding system, the grounding impedance is great]y different from the static grounding resistance. In order to investigate the effect of water resistivity on the high frequency performance of grounding systems, this paper presents the frequency-dependent admittance using water tank simulating the grounding system in different water resistivities. As a result, because of capacitive effect admittances and conductance are increased with increasing frequency in higher water resistivity of greater than 500[${\Omega}{\cdot}m$]. On the other hand, admittances and conductances are decreased with increasing frequency due to inductive effect in lower water resistivity of less than 500[${\Omega}{\cdot}m$]. The phase difference between the current and voltage increases in the range of 200[kHz] to 5[MHz]. Consequently, frequency-dependent performance of grounding systems is closely related to the soil resistivity, it is necessary to consider the effect of grounding system performance on the frequency and soil resistivity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.358-366
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• 2014

This paper proposes a quasi Z-source AC-AC converter with the low DC voltage distribution capability operating as a power electronic transformer. The proposed system has configuration that the input terminals of two quasi Z-source AC-AC converters are connected in parallel, also their output terminal are connected in series. Simple control method of duty ratio was proposed for the in phase buck-boost AC voltage mode and the DC output voltage control. DSP based experiment and PSIM simulation were performed. As a result, the PSIM simulation results were same with the measured results. By controlling the duty ratio under the condition of 100 [${\Omega}$] load, quasi Z-source AC-AC converter could buck and boost the AC output voltage in phase with the AC input voltage, and the same time, the constant DC voltage could be output without affecting the AC output characteristics. And, the DC output voltage 48[V] was constantly controlled in dynamic state in case while the load is suddenly changed ($50[\Omega]{\rightarrow}100[\Omega]$). From the above result, we could know that the quasi Z-source AC-AC converter can act as a power electronic transformer with a low DC voltage distribution capability.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.943-946
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• 1988

A simple method is proposed for determining the frequency response function G(j.omega.) of a system using a pair of characteristic M-sequences (maximum length linear feed back shift register sequence). When a characteristic M-sequence is sampled with q$_{1}$ and q$_{2}$ both of which are coprime with N, where N is the period of the M-sequence, the obtained pair of sequences have conjugate complex frequency spectrum. Making use of this fact, two charcteristic M-sequences having conjugate complex frequency spectrum are applied to a system to be measured. Since the magnitude of spectrium of M-sequence is known, the gain of G(j.omega.) is directly obtained from the Fourier transform of the system output. The phase of G(j.omega.) is obtained simply by taking the average of the two phases of output spectrum.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.154-156
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• 1995

The effect of a periodic and a chaotic' behaviour in the Bonhoeffer-Van der Pol(BVP) oscillation of the nerve membrane driven by a periodic stimulating current $A_1=cos\;{\omega}\;t$ are investigated by numeric analysis and hardware Implementation. To control the chaotic motion, we are suggested by temperature parameter c, $c=c(1+\eta\;cos\;{\Omega}\;t)$ which the values of $\eta,\;Omega$ varied respectively. The feasibilities of chaotic and periodic phenomena were analysed by phase plane and time series.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.2
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• pp.48-56
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• 1995

The operating characteristics, such as, the threshold gain, lasing frequency, and longitudinal intensity profile, etc., of 1.55$\mu$m DFB laser diode with index and/or gain grating structures and with one side AR-coated mirror have been analyzed. From this analysis, the optimum design parameters have been shown that ${\Delta}{\Omega}$ (the phase difference between index grating and gain grating) is 0 or ${\pi}$, (xL)$_{r}$=1~3 and (xL)$_{i}$=0.5~0.9. It has been also shown that the modal selectivity and intensity uniformity of the DFB lasers with .DELTA..OMEGA.=0 are ~1.2 times better thatn those of the DFB lasers with ${\Delta}{\Omega}$= ${\pi}$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.2
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• pp.97-100
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• 1982

The phase differences of the omega were observed continuously for the A-C pair and the A-E pair from Sept. 1, 1980 to Feb. 28, 1981 and from Sept. 20, 1981 to Feb. 82, 1982 at Fisheries University of Busan350$^{\circ}$ 07'.9N, 129$^{\circ}$ 06'.3E)In this paper we deal with the reappearance of these phase differences by annual, month, day As a results, annual eappearance are in good condition both pairs and daily reappearance in day and night are better than an hour around the sunset, and very bad reappearance is found by month.