• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.471-474
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• 1997

Recently, many studies have shown clinically the detection of proximal arterial stenosis through evaluation of a Doppler waveform alternation, the so-called pulsus tardus and parvus, that often occurs distal to the stenosis. However the cause of the tardus-parvus phenomenon remains obscure. To analyze its cause, we modeled the blood-flow circuit as simple electrical circuit. This shows that pulsus tardus-parvus effect is caused as a result of high-frequency waveform component attenuation from low-pass filtering by capacitance(complience of the poststenotic vessel wall) and resistance(stenosis). As a result, the degree of pulsus tardus-parvus increased as the complience of the poststenotic segment of vessel increased, as well as increasing stenosis.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1463-1466
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• 2007

Single phases of multi-component oxides films, ZrTiO4 and Ta2Zr6O17, could be synthesized by using the combinatorial approach through surface sol-gel route, coating the appropriate mole ratio of 100 mM zirconium butoxide, tantalum butoxide and titanium butoxide precursors on Pt/Ti/SiO2/Si (100) substrate, following pyrolysis at 450 oC, and annealing them at 770 oC. Both the films and bulks of ZrTiO4 and Ta2Zr6O17 showed very stable dielectric properties in temperature range, ?140 to 60 oC, and frequency range, 100 Hz to 1 MHz, promising their applications in wide range of temperatures and frequencies. The dielectric constants of the films were lower and a little more dependent on frequency than those of the bulks. The reduction of dielectric property in the film was mainly due to the interfacial effects that worked as series and parallel-connected capacitances toward the substantial film capacitance.

• 전기학회논문지P
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• 제64권1호
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• pp.29-34
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• 2015

DC bus electrolytic capacitors are used in variety of equipments as smoothing element of the power converters because it has high capacitance for its size and low price. It is responsible for frequent breakdowns of many static converters and inverter drive systems. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure of power converter. In this paper, the on-line remote diagnosis monitoring system for DC BUS electrolytic capacitors of power converter using low-cost type Zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using AC coupling method of DC link ripple voltage/current. The Zigbee communication-based experimental results show that the proposed remote DC capacitor diagnosis monitoring system can be applied to DC/DC converter and UPS successfully.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.380-384
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• 2005

Plasma display panel (PDP) has a serious thermal problem, because the luminance efficiency of the conventional PDP is about 1.5 lm/W and it is less than $3{\sim}5$ lm/W of cathode ray tube (CRT). Thus there is a need for improving the luminance efficiency of the PDP There are several approaches to improve the luminance efficiency of the PDP and we adopt the driving PDP at high frequency range from 400 kHz up to over 700 kHz. Since a PDP is regarded as an equivalent inherent capacitance, many types of sustaining drivers have been proposed and widely used to recover the energy stored in the PDP. However, these circuits have some drawbacks for driving PDP at high frequency range. In this paper, we investigate the effect of the parasitic components of PDP itself and driver when the reactive energy of panel is recovered. Various drivers are classified and evaluated whether it is suitable for high frequency driver, and finally current-fed type with do input voltage biased is proposed. This driver overcomes the effect of parasitic component in panel and driver and fully achieves ZVS of all full-bridge switches and reduces the transition time of the panel polarity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.3124-3126
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• 2000

The application of IR(Infrared) communication is very wide and IR receiver has become a standard of home entertainment. A preamplifier with single 5V supply was designed for IR receiver IC. To operate at long distance, receiver IC should have high gain and low noise characteristic. To provide constant output signal magnitude, independent of transciever distance, gain limiting stage is needed. And to cut-off DC noise component effectively, large resistance and capacitance are required. Transimpedance type preamplifier, and diode limiting amplifier, and current limiting amplifier were designed. It is another function of current limiting amplifier that transforms single input signal to differential output signal. Using AMS BiCMOS model, both BJT version and MOS version was designed. Total power consumption is O.lmW, and IC size is $0.3mm^2$

• 한국공작기계학회논문집
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• 제17권2호
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• pp.110-113
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• 2008

Embedded capacitor technology is one of the effective packing technologies for further miniaturization and higher performance of electric packaging system. In this paper, the embedded capacitors were simulated and fabricated in 8-layered printed circuit board employing standard PCB processes. The composites of barium titanante($BaTiO_3$) powder and epoxy resin were employed for the dielectric materials in embedded capacitors. Theoretical considerations regarding the embedded capacitors have been paid to understand the frequency dependent impedance behavior. Frequency dependent impedance of simulated and fabricated embedded capacitors was investigated. Fabricated embedded capacitors have lower self resonance frequency values than that of the simulated embedded capacitors due to the increased parasitic inductance values. Frequency dependent capacitances of fabricated embedded capacitors were well matched with those of simulated embedded capacitors from the 100MHz to 10GHz range. Quality factor of 20 was observed and simulated at 2GHz range in the 10 pF embedded capacitors. Temperature dependent capacitance of fabricated embedded capacitors was presented.

• 한국광학회지
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• 제4권1호
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• pp.57-65
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• 1993

용량 이행형 방전여기에 의한 소형 XeCl레이저를 제작하고, 가스 혼합비에 따른 출력특성을 조사하였다. 내자형 capacitor에 의한 자동 예비전리 방식과 2.7 cm 간격의 Chang형상으로 가공된 전극구조의 레이저를 구성하여 2.7cm${\times}$1.5cm 크기의 출력 빔을 얻었고, Xe과 HC1의 농도 변화 및 완충 기체의 종류에 따른 최대 출력 에너지 및 최대 효율 조건을 조사하였다. 최대 레이저 펄스 에너지는 Ne 완충기체를 사용시 230mJ이며, 단위 방전 체적당 1.1 J/l의 에너지를 얻었으며, 최대 에너지 효율은 1.6%이었다. 1:3의 낮은 비율의 피-킹 캐패시턴스의 구성에 의해 레이저 펄스폭은 장펄스 효과를 나타내 foot-to-foot 200 ns로 측정되었다.

• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.20-27
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• 2018

We describe a redox-enhanced electric double-layer capacitor (EDLC) that turns the electrolyte in a conventional EDLC into an integral, active component for charge storage-charge is stored both through faradaic reactions with soluble redox-active molecules in the electrolyte, and through the double-layer capacitance in a porous carbon electrode. The mixed-redox electrolyte, composed of vanadium and iodides, was employed to achieve high power density. The electrochemical reaction in a supercapacitor with vanadium and iodide was studied to estimate the charge capacity and energy density of the redox supercapacitor. A redox supercapacitor with a mixed electrolyte composed of 0.75 M NaI and 0.5 M $VOSO_4$ was fabricated and studied. When charged to a potential of 1 V, faradaic charging processes were observed, in addition to the capacitive processes that increased the energy storage capabilities of the supercapacitor. The redox supercapacitor achieved a specific capacity of 13.44 mAh/g and an energy density of 3.81 Wh/kg in a simple Swagelok cell. A control EDLC with 1 M $H_2SO_4$ yielded 7.43 mAh/g and 2.85 Wh/kg. However, the relatively fast self-discharge in the redox-EDLC may be due to the shuttling of the redox couple between the polarized carbon electrodes.

• 대한전기학회논문지
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• 제40권2호
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• pp.162-172
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• 1991

In proportion to the capacity enlargement of the induction motor system controlled by current source inverter, the capacitance of the commutating capacitor is enlarged and then the spike value of output voltage is increased at the moment of charge and discharge. Moreover, the output currnet includes a number of harmonic components. Such voltage spike and harmonics generate the torque ripple and lead to bad effects on the performance of the induction motor. In this study, all the harmonics excluding 17th and 19th harmonics were mostly elimunated by adopting 18-phase Triple High Frequency Current Source Inverter(HFCSI), and the spike component of output voltage was reduced by adding the Voltage Clamping Circuit(VCC). As a result, the torque ripple and the commutation loss were reduced and the performance of the system was improved. Experiments for speed control were carried out in the tripple current source inverter system for induction motor drive. Overall system was controlled by ONE CHIP MICROCOMPUTER(INTEL 8751). Control circuits were simplified and good experimental results in the constant V/F control were obtained due to the flexibility of the microcomputer.

• Journal of Power Electronics
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• 제14권3호
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• pp.413-420
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• 2014

The conventional Phase-Shift Full-Bridge (PSFB) converter has a serious voltage spike because of the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches. To overcome this problem, an asynchronous active clamp technique employing an auxiliary DC/DC converter has been proposed. However, an exact analyses for designing the auxiliary DC/DC converter has not been presented. Therefore, the amount of power that is supposed to be handled in the auxiliary DC/DC converter is calculated through a precise mode analyses in this paper. In addition, this paper proposes a lossy snubber circuit with hysteresis characteristics to reduce the burden that the auxiliary DC/DC converter should take during the starting interval. This technique results in optimizing the size of the magnetic component of the auxiliary DC/DC converter. The operational principles and the theoretical analyses are validated through experiments with a 48V-to-30V/15A prototype.