• 전기화학회지
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• 제13권4호
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• pp.223-234
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• 2010

본 총설에서는 캐패시터적인 특성을 가지는 다공성 전극의 전기화학특성 분석에 활용되는 임피던스의 복소캐패시턴스 분석법(complex capacitance analysis)의 이론 및 응용에 대해 정리하였다. 이론적으로 캐패시터적인 특성을 갖는 전기화학시스템에 대해 캐패시턴스허수부 도시를 활용하면 효과적인 해석이 가능함이 제시되었다. 또한, 복소캐패시턴스 분석법은 다공성 탄소 재료/전극의 EDLC 특성, 미세기공 내부의 이온전도 특성, 고분자전해질연료전지의 촉매층 이온저항 등의 분석에 효과적으로 적용될 수 있음이 검증되었다.

• 한국전산유체공학회지
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• 제15권1호
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• pp.31-36
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• 2010

In the present study, computations for flow fields inside the CDI unit cells with electrodes and spacers have been made to evaluate their performance. Three types of unit cells that include a planar type, a serpentine channel type, and a spiral wound type were considered and their flow characteristics were compared. From the computational results, it is found that the serpentine channel type has a large flow resistance and can not guarantee the outflow flux for industrial applications. On the other hand, the planar type can sustain a large enough outflow flux but it's efficiency is low for the electrode-use because of the non-uniform velocity distribution inside the cell and dead zones in every corner. Finally, The spiral wound type has not only a large outflow flux as much as the planar type has, but also a high efficiency for the electrode-use because of uniform velocity distribution. From this comparison, we can expect that the spiral wound type of CDI unit cell would have a high performance deionization capability.

• 센서학회지
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• 제23권5호
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• pp.326-331
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• 2014

In this study, a MEMS microphone that uses $Si_3N_4$ as the vibration membrane was produced for application as an auditory device using a sound visualization technique (sound visualization) for the hearing impaired. Two sheets of 6-inch silicon wafer were each fabricated into a vibration membrane and back plate, after which, wafer bonding was performed. A certain amount of charge was created between the bonded vibration membrane and the back plate electrodes, and a MEMS microphone that functioned through the capacitive method that uses change in such charge was fabricated. In order to evaluate the characteristics of the prepared MEMS microphone, the frequency flatness, frequency response, properties of phase between samples, and directivity according to the direction of sound source were analyzed. The MEMS microphone showed excellent flatness per frequency in the audio frequency (100 Hz-10 kHz) and a high response of at least -42 dB (sound pressure level). Further, a stable differential phase between the samples of within -3 dB was observed between 100 Hz-6 kHz. In particular, excellent omnidirectional properties were demonstrated in the frequency range of 125 Hz-4 kHz.

• Journal of Electrochemical Science and Technology
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• 제11권4호
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• pp.406-410
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• 2020

Despite a simple preparation of manganese oxide (MnO₂) nanowires by electrodeposition, the improvement in specific capacitance (C_sp) and voltammetric response of the MnO₂ nanowire-based electrodes has been quite limited. This is attributed to the poor electrical conductivity of MnO₂ and its dense bulk morphology due to the aggregation of the nanowires. This study investigated the capacitive performance of MnO₂ nanowires electrodeposited on agarose thin films. The good ionic conductivity and porous network of the agarose film provided favorable growth conditions for the MnO₂ nanowires with suppressed aggregation. A maximum C_sp value of 686 F/g measured at a scan rate of 10 mV/s was obtained, which was significantly larger than that of 314 F/g for the agarose-free MnO₂ electrode at the same scan rate. The rate capability was also improved. The C_sp measured at a high scan rate of 100 mV/s retained 74.0% of the value measured at 10 mV/s, superior to the retention of 71.1% for the agarose-free MnO₂ electrode.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.793-799
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• 2016

A multi-purpose sensor interface that provides dual-mode operation of fingerprint sensing and physiological signal detection is presented. The dual-mode sensing capability is achieved by utilizing inter-pixel shielding patterns as capacitive amplifier's input electrodes. A prototype readout circuit including a fingerprint panel for feasibility verification was fabricated in a $0.18{\mu}m$ CMOS process. A single-channel readout circuit was implemented and multiplexed to scan two-dimensional fingerprint pixels, where adaptive calibration capability against pixel-capacitance variations was also implemented. Feasibility of the proposed multi-purpose interface was experimentally verified keeping low-power consumption less than 1.9 mW under a 3.3 V supply.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.845-846
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• 2006

In this paper, we describe a capacitive position sensing and motion control scheme of a MEMS scanner used for laser display application. The laser displays can be made by scanning laser beams much the same way a CRT scans electron beams. So the accuracy of the scanner motion determines the quality of the displayed image. The MEMS scanner under consideration is composed of electrostatic comb electrodes with initial gap and requires large driving voltage. Due to the under-damping and nonlinear driving characteristics, the scanner motion is subject to be an unwanted oscillation. For the linear scanner motion, we devise a differential charge amplifier and phase compensator. The experimental results show that the implemented feedback control system provides sufficient electrical damping and improves the dynamic performance of the scanner.

• 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:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.717-723
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• 1999

The transient characteristics of grounding systems play a major role in the protection of power equipments, electronic circuits and info-communication facilities against surges which arise from lightning or ground faults. Electronic devices are very weak against lightning surges injected from grounding systems and can be damaged. The malfunction and damage of electronic circuits bring about bad operation performances, a lot of economical losses, and etc. Therefore, in order to obtain the effective protection measure of electronic devices from overvoltages and lightning surges, the analysis of the transient grounding impedances in essential. One of this work is to examine the transient behaviors of grounding impedances under steplike currents for various grounding systems. And the other of this work is to evaluate the transient behaviors of a grid with rods under impulse currents and to investigate the effect of grounding lead wire. Transient grounding impedances of a grid with rods under impulse current waves have been measured as a parameter of the length of the grounding leads. Z-t, Z-i and V-i curves of transient grounding impedance under impulse current waveforms have been measured and analyzed. It was found that the grounding impedance gives the inductive, resistive and capacitive aspects under steplike current. Transient grounding impedance characteristics were very different with shapes, geometries of ground electrodes. Also, they were dependent on the waveform and magnitude of impulse current.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1184-1187
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• 2003

Electrochemical capacitors are becoming attractive energy storage systems particularly for applications involving high power requirements such as hybrid systems consisting of batteries and electrochemical capacitors for electric vehicle propulsion. A new type electric double layer capacitor (EDLC) was constructed by using carbon nanofibers (CNFs) and DAAQ(1,5-diaminoanthraquinone) electrode. Carbonaceous materials are found in variety forms such as graphite, diamond, carbon fibers etc. While all the carbon nanofibers include impurities such as amorphous carbon, nanoparticles, catalytic metals and incompletely grown carbons. We have eliminated of Ni particles and some carbonaceous particles in nitric acid. Nitric acid treated CNFs could be covered with very thin DAAQ oligomer from the results of CV and TG analyses and SEM images. DAAQ oligomer film exhibited a specific capacity as 45-50 Ah/kg in 4M $H_2SO_4$. We established Process Parameters of the technique for the formation of nano-structured materials. Furthermore, improved the capacitive properties of the nano structured CNFs electrodes using controlled solution chemistry. As a result, CNFs coated by DAAQ composite electrode showed relatively good electrochemical behaviors in acidic electrolyte system with respect to specific capacity and scan rate dependency.

• 지질공학
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• 제34권2호
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• pp.295-315
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• 2024

최근 도심지의 발달과 전기비저항 탐사 적용 분야 및 현장의 확대에 따라, 포장된 지표에서 토양이나 지하 구조를 조사하기 위한 탐사의 필요성이 증가하고 있다. 과거에는 포장된 표면에서의 탐사는 포장재를 천공하거나 그 주변의 토양에서의 탐사로 대체하였다. 최근 포장재를 손상하지 않고 포장된 지표에서 탐사하는 방법 및 연구 사례들이 늘어남에 따라, 이 논문에서는 이에 대해 분석하고자 한다. 포장 지표에서의 전기비저항 탐사 방법을 기존의 천공 후 전극 삽입 방법, 평판 접지 전극 사용을 포함한 갈바닉 방법과 용량성 결합 방식으로 나누어 각 방법의 적용 사례를 조사하였다. 이를 통해 각 탐사 방법의 장단점과 탐사 현장의 특성을 고려하여 적절한 탐사 방법을 선택할 수 있음을 시사하였다. 마지막으로, 전기비 저항 탐사의 적용 가능성과 한계를 다양한 사례를 통해 분석하였습니다.