• 조명전기설비학회논문지
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• 제21권1호
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• pp.28-34
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• 2007

본 연구에서는 새로 고안된 방전 논리 게이트 PDP의 논리 게이트 입력인 DC 방전특성에 대해 고찰하였다. 새로 고안된 방전 논리 게이트는 방전 경로에 따른 전극사이의 전위차를 제어하여 논리 출력을 유도한다. 실험결과 이 DC 방전들의 안정성을 위해 프라이밍 방전을 인가한 경우가 인가하지 않은 경우에 비해 방전지연시간이 1/3로 단축되며 방전개시전압은 1/2로 감소하였다. 또한 이 프라이밍 방전에서 발생한 공간전하는 방전종료 후 $30[{\mu}s]$ 정도까지 영향을 미친다. 그리고 시간적, 공간적 거리변화에 파라 공간전하가 DC 방전에 미치는 영향을 측정한 결과, 주 방전에서부터 시간적으로 멀어지는 것보다 공간적으로 멀어지는 것이 주 방전의 영향에서 쉽게 벗어날 수 있음을 알았다. 그러므로 각 주사전극 마다 방전 논리 게이트들을 독립적으로 동작시킬 수 있다는 결론을 얻었다.

• 한국정보통신학회논문지
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• 제20권3호
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• pp.577-582
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• 2016

전류 컨베이어를 사용하는 카운터 타입의 동기형 시간-디지털 변환기를 공급전압 3volts에서 $0.18{\mu}m$ CMOS 공정을 이용하여 설계하였다. 비동기 시간-디지털 변환기의 단점을 보완하기 위해 클록은 시작신호가 인가되면 시작신호와 동기화되어 생성된다. 비동기형 시간-디지털 변환기에서 디지털 출력 값의 에러는 클록주기인 $-T_{CK}$에서 $T_{CK}$이다. 그러나 동기형 시간-디지털 변환기의 경우 에러는 0에서 $T_{CK}$이다. 시작신호와 클록의 동기화로 인하여 시간간격 신호를 디지털 값으로 변환할 때 출력 값의 에러 범위는 감소한다. 또한 고주파의 외부 클럭을 사용하지 않음에 따라 회로의 구성이 간단하다. 설계된 시간-디지털 변환기의 동작은 HSPICE 시뮬레이션을 통하여 확인하였다.

• 한국대기환경학회지
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• 제34권5호
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• pp.639-650
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• 2018

Identification of the major sources contributing to PM is of importance in order to understand their quantitative contributions to atmosphere. In the viewpoint of the meat cooking in Korea, only a few analyses of organic molecular markers have been conducted due to analytical difficulties. In this study, ten different parts of meat (i.e., blade shoulder, belly, and arm shoulder of pork; ribeye roll, top blade muscle, and short plate of beef; leg quarter, breast, and wing of chicken; duck; mackerel) were pyrolyzed to generate the cooked PM using an electronic heating plate. Generated PM were collected by the pyrolysis sampling system to identify total carbon (TC) using a carbon analyzer and cholesterol using a Liquid chromatography tandem-mass spectrometry (LC-MSMS) based on fragmentor voltage (FV), precursor ion, collision energy, product ion. In addition, oxydative potential (OP) analysis using dithiothreitol (DTT) method were discussed to investigate the toxicity relates. Highly correlated pairwise scatterplots between the cholesterol and TC indicate that oxydative potential was highly associated with different parts of meat. This study provides insight into the meat cooking components of PM, which could be drivers of the oxidative potential relates.

• The Korean Journal of Physiology and Pharmacology
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• 제4권3호
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• pp.197-210
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• 2000

Suppressive role of $Na^+-Ca^{2+}$ exchange in myocardial tension generation was examined in the negative frequency-force relationship (FFR) of electric field stimulated left atria (LA) from postnatal developing rat heart and in the whole-cell clamped adult rat ventricular myocytes with high concentration of intracellular $Ca^{2+}$ buffer (14 mM EGTA). LA twitch amplitudes, which were suppressed by cyclopiazonic acid in a postnatal age-dependent manner, elicited frequency-dependent and postnatal age-dependent enhancements after $Na^+-reduced,\;Ca^{2+}-depleted$ (26 Na-0 Ca) buffer application. These enhancements were blocked by caffeine pretreatment with postnatal age-dependent intensities. In the isolated rat ventricular myocytes, stimulation with the voltage protocol roughly mimicked action potential generated a large inward current which was partially blocked by nifedipine or $Na^+$ current inhibition. 0 Ca application suppressed the inward current by $39{\pm}4%$ while the current was further suppressed after 0 Na-0 Ca application by $53{\pm}3%.$ Caffeine increased this inward current by $44{\pm}3%$ in spite of 14 mM EGTA. Finally, the $Na^+$ current-dependent fraction of the inward current was increased in a stimulation frequency-dependent manner. From these results, it is concluded that the $Ca^{2+}$ exit-mode (forward-mode) $Na^+-Ca^{2+}$ exchange suppresses the LA tension by extruding $Ca^{2+}$ out of the cell right after its release from sarcoplasmic reticulum (SR) in a frequency-dependent manner during contraction, resulting in the negative frequency-force relationship in the rat LA.

• Journal of Information Display
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• 제9권4호
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• pp.21-29
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• 2008

We studied both the wavelength and intensity dependent photo-responses (photofield-effect) in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs). During the a-IGZO TFT illumination with the wavelength range from $460\sim660$ nm (visible range), the off-state drain current $(I_{DS_off})$ only slightly increased while a large increase was observed for the wavelength below 400 nm. The observed results are consistent with the optical gap of $\sim$3.05eV extracted from the absorption measurement. The a-IGZO TFT properties under monochromatic illumination ($\lambda$=420nm) with different intensity was also investigated and $I_{DS_off}$ was found to increase with the light intensity. Throughout the study, the field-effect mobility $(\mu_{eff})$ is almost unchanged. But due to photo-generated charge trapping, a negative threshold voltage $(V_{th})$ shift is observed. The mathematical analysis of the photofield-effect suggests that a highly efficient UV photocurrent conversion process in TFT off-region takes place. Finally, a-IGZO mid-gap density-of-states (DOS) was extracted and is more than an order of magnitude lower than reported value for hydrogenated amorphous silicon (a-Si:H), which can explain a good switching properties observed for a-IGZO TFTs.

• Transactions on Electrical and Electronic Materials
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• 제17권2호
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• pp.57-68
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• 2016

In this study, we present the modern hybrid system based power generation for electric vehicle applications. We describe the hybrid structure of modified current source based DC - DC converters used to extract the maximum power from Photovoltaic (PV) and Fuel Cell system. Due to reduced dc-link capacitor requirement and higher reliability, the current source inverters (CSI) better compared to the voltage source based inverter. The novel control strategy includes Distributed Maximum Power Point Tracking (DMPPT) for photovoltaic (PV) and fuel cell power generation system. The proposed DC - DC converters have been analyzed in both buck and boost mode of operation under duty cycle 0.5>d, 0.5<d<1 and 0.5<d for capable electric vehicle applications. The proposed topology benefits include one common DC-AC inverter that interposes the generated power to supply the charge for the sharing of load in a system of hybrid supply with photovoltaic panels and fuel cell PEM. An improved control of Direct Torque and Flux Control (DTFC) based induction motor fed by current source converters for electric vehicle.In order to achieve better performance in terms of speed, power and miles per gallon for the expert, to accepting high regenerative braking current as well as persistent high dynamics driving performance is required. A simulation model for the hybrid power generation system based electric vehicle has been developed by using MATLAB/Simulink. The Direct Torque and Flux Control (DTFC) is planned using Xilinx ISE software tool in addition to a Modelsim 6.3 software tool that is used for simulation purposes. The FPGA based pulse generation is used to control the induction motor for electric vehicle applications. FPGA has been implemented, in order to verify the minimal error between the simulation results of MATLAB/Simulink and experimental results.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.260-260
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• 1999

We compared c-axis tunneling characteristics of small stacked intrinsic Josephson junctions prepared on the surface of pristine, I-, and HgI$_2$-intercalated Bi$_2Sr_2CaCu_2O_{8+x}$ (Bi2212) single crystals. The R(T) curves are almost metallic in I-Bi2212 specimens, but semiconducting in HgI$_2$-Bi2212 ones.· The transition temperatures were 82.0 K, 73.0 K, and 76.8 K for pristine Bi2212, I-Bi2212, and HgI2-Bi2212 specimens, respectively, consistent with p-T$_c$ phase diagram. Current-voltage (IV) characteristics of both kinds of specimens show multiple quasiparticle branches with well developed gap features, indicating Josephson coupling is established between neighboring CuO$_2$ planes. The critical current I$_c$ of I-Bi2212 is almost the same as of that of pristine crystals, but I$_c$ is much reduced in Hgl$_2$-Bi2212. In spite of expanded interlayer distances, the interlayer coupling is not significantly affected in I-Bi2212due to holes generated by iodine atoms. The coupling in HgI$_2$-Bi2212 is, however, weakened due to inertness of HgI$_2$ molecules and the expansion of interlayer distance. Relation between the superconducting transition temperature T$_c$ and the critical current I$_c$ seems to contradict Anderson's interlayer-pair-tunneling theory but agree with a modified version of it.

• 대한기관식도과학회지
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• 제12권2호
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• pp.19-25
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• 2006

There have been numerous modalities to recover blink function of orbicularis oculi muscle in patients with facial paralysis. However, there is still no optimal method for reanimation of eyelid. In this study, we tried to recover blink function of paralyzed rabbit's eyelid with the ion polymer metal composite (IPMC) which is one of the electroactive polymers that is spotlighted as artificial muscle. We manufactured IPMC by plating the platinum over perfluorosulphonic acid polymer ($Nafion^{(R)}$). IPMC was coated by Norland optical adhesive for the purpose of insulation and keeping it from dry. IPMC modifications by roughening the surface of Nafion, repetitive plating (maximum 4 times) with platinum, and lengthening the width of IPMC were done. The facial paralysis was induced in the rabbit by sectioning of facial nerve at the main trunk. After minimum period of 4 weeks, IPMC was inserted in the paralyzed rabbit's eyelid. By modification, the force generated by IPMC was enhanced. Restoration of blink function in paralyzed rabbit was achieved on electrical stimulation of the IPMC by 5 voltage direct current. IPMC can be promising option for facial reanimation, but further studies are needed to enhance the efficiency of IPMC.

• Macromolecular Research
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• 제17권12호
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• pp.1032-1038
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• 2009

A polypyrrole (PPy)/alumina composite filler prepared via in-situ polymerization of pyrrole on alumina particles was incorporated into $Nafion^{(R)}$ to improve the performance of ionic polymer-metal composite (IPMC) actuators. The IPMCs with the pristine PPy without alumina support did not show bending displacements superior to that of the bare Nafion-based IPMC, except at a high PPy content of 4 wt%. This result was attributed to the low redox efficiency of the PPy alone in the IPMC and may have also been related to the modulus of the IPMC. However, at the optimized filler contents, the cyclic displacement of the IPMCs bearing the PPy/alumina filler was 2.2 times larger than that of the bare Nafion-based IPMC under an applied AC potential of 3 Vat 1 Hz. Even under a low AC potential of 1.5 V at 1 Hz, the displacement of the PPy/alumina-based IPMCs was a viable level of performance for actuator applications and was 2.7 times higher than that of the conventional Nafion-based IPMC. The generated blocking force was also improved with the PPy/aiumina composite filler. The greatly enhanced performance and the low-voltage-operational characteristic of the IPMCs bearing the PPy/alumina filler were attributed to the synergic effects of the neighboring alumina moiety near the PPy moiety involving electrochemical redox reactions.

• 한국재료학회지
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• 제14권11호
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• pp.764-768
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• 2004

Perovskite Pb(Mn_{1/3}Sbu_{2/3})O_2-Pb(Zr,Ti)O_3\;(PMS-PZT) was prepared and ZnO doping effects on its piezoelectric properties were investigated. Pyrochlore phase was not identified in the PMS-PZT ceramics with $0\sim5\;mol\%$ ZnO sintered at $1100^{\circ}C$ for 2 hrs, and maximum sintered density of $7.92 g/cm^3$ was obtained. Piezoelectric charge constant and voltage constant increased to $359{\times}10^{-12}\;C/N\;and\;22.5{\times}10^{-13}\;Vm/N$, respectively, with increasing ZnO content. Mechanical quality factor reduced considerably with increasing ZnO content. When the ZnO content was 3 $mol\%$, electromechanical coupling factor and relative dielectric constant showed maximum values of $56\%$ and 1727, respectively. This should be evaluated by complicated variations of sintered density, tetragonality of lattice, grain size, and A-site vacancy generated by ZnO addition and $Zn^{2+}$ substitution.