• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.153-157
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• 2003

A hybrid electrochemical capacitor having both characteristics of electric double layer capacitance and pseudo-capacitance was studied throughout cell tests. Asymmetric electrodes with $Ni(OH)_2/activated$ carbon based positive electrode and activated carbon based negative electrode were used in preparing test cells of $5\times5cm^2$. Cyclic voltammetry measurements and impedance measurements were conducted to understand electrochemical behavior of each electrode. To find an optimal mass ratio of negative to positive electrode, charge-discharge cycle tests were also performed.

• Journal of the Korean Electrochemical Society
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• v.3 no.4
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• pp.241-245
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• 2000

The objective of this work Is to design, fabricate, and characterize pseudo-capacitor using amorphous $MnO_2\;nH_2O$ electrode material. The cyclic voltammogram under 100mV/s scan rate of the material shows the electrochemically stable potential window of 1V and the specific capacitance of 250F/g. The TDMA pulse test result indicates that the TDMA system (2 parallel-pseudo-capacitor systems) has the ohmic voltage drop of 0.22V and the capacitor voltage drop of 0.38V. The total voltage drop of the TDMA system is 0.60V and less than 1V of which value is the maximum voltage drop requirement or the TDMA satellite phone. Also, the TDMA system had the ESR of $55m{\Omega}$ and the capacitance of 105mF. Therefore, it is confirmed that the TDMA system has the application feasibility as load-leveling capacitor for the satellite phone.

• Carbon letters
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• v.23
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• pp.9-16
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• 2017

This paper introduces a nitrogen-doped ordered mesoporous carbon (NOMC) derived from glucosamine with hybrid capacitive behaviors, achieved by successfully combining electrical double-layer capacitance with pseudo-capacitance behaviors. The nitrogen doping content of the fabricated NOMC reached 7.4 at% while its specific surface area ($S_{BET}$) and total pore volume reached $778m^2g^{-1}$ and $1.17cm^3g^{-1}$, respectively. A dual mesoporous structure with small mesopores centered at 3.6 nm and large mesopores centered at 9.9 nm was observed. The specific capacitance of the reported materials reached up to $328Fg^{-1}$, which was 2.1 times higher than that of pristine CMK-3. The capacitance retention rate was found to be higher than 87.9% after 1000 charge/discharge cycles. The supplementary pseudocapacitance as well as the enhanced wettability and conductivity due to the incorporation of nitrogen heteroatoms within the carbon matrixes were found to be responsible for the excellent capacitive performance of the reported NOMC materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.70-78
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• 2004

This paper presents study of efficiency of wavelet transformation for on-line chatter detection during hard fuming process. From comparison with other time series and statistical methods such as fast fourier transformation (FFT), Kurtosis and standard deviation (STD), wavelet transform is better than others in on-line chatter detection. With using wavelet function with pseudo frequency corresponding to chatter frequency, chatter could be detected more sensitively. And for both force signal from dynamometer and displacement signal from capacitance type cylindrical sensor (CCS), wavelet transform with DB2 function on level 4 could be well used for chatter detection in hard turning process.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.443-450
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• 2014

This paper presents a 20-Gb/s optical receiver circuit fabricated with standard 65-nm CMOS technology. Our receiver circuits are designed with consideration for parasitic inductance and capacitance due to bonding wires connecting the photodetector and the circuit realized separately. Such parasitic inductance and capacitance usually disturb the high-speed performance but, with careful circuit design, we achieve optimized wide and flat response. The receiver circuit is composed of a transimpedance amplifier (TIA) with a DC-balancing buffer, a post amplifier (PA), and an output buffer. The TIA is designed in the shunt-feedback configuration with inductive peaking. The PA is composed of a 6-stage differential amplifier having interleaved active feedback. The receiver circuit is mounted on a FR4 PCB and wire-bonded to an equivalent circuit that emulates a photodetector. The measured transimpedance gain and 3-dB bandwidth of our optical receiver circuit is 84 $dB{\Omega}$ and 12 GHz, respectively. 20-Gb/s $2^{31}-1$ electrical pseudo-random bit sequence data are successfully received with the bit-error rate less than $10^{-12}$. The receiver circuit has chip area of $0.5mm{\times}0.44mm$ and it consumes excluding the output buffer 84 mW with 1.2-V supply voltage.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.12
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• pp.1458-1467
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• 1999

VLSI 공정 기술이 발달하면서 이웃한 전선 간의 간격이 점점 더 가까워 지고 있으며, 그에 따라 인접 전선 간의 혼신 문제가 심각해지고 있다. 본 논문에서는 3층 그리드 채널 배선에 적용 가능한 혼신을 최소화시키는 배선층 할당 방법을 제안한다. 이 방법은 선형 의사 불린 최적화 기법에 맞도록 고안되었으며, 적절한 변수 선택 휴리스틱과 상한값 추정 방법을 통하여 최적의 결과를 짧은 시간 안에 찾아낸다. 실험 결과를 통하여, 일반적인 0/1 정수 선형 프로그래밍 기법과 비교하여 성능과 수행시간 면에서 우수함을 보인다. Abstract Current deep-submicron VLSI technology appears to cause crosstalk problem severe since it requires adjacent wires to be placed closer and closer. In this paper, we deal with a horizontal layer assignment problem for three layer HVH channel routing to minimize coupling capacitance, a main source of crosstalk. It is formulated in a 0/1 integer linear programming problem which is then solved by a linear pseudo boolean optimization technique. Experiments show that accurate upper bound estimation technique effectively reduces crosstalk in a reasonable amount of running times.

• Carbon letters
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• v.13 no.3
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• pp.157-160
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• 2012

In this work, iron oxide ($Fe_3O_4$) nanoparticles were deposited on multi-walled carbon nanotubes (MWNTs) by a simple chemical coprecipitation method and $Fe_3O_4$-decorated MWNTs (Fe-MWNTs)/polypyrrole (PPy) nanocomposites (Fe-MWNTs/PPy) were prepared by oxidation polymerization. The effect of the PPy on the electrochemical properties of the Fe-MWNTs was investigated. The structures characteristics and surface properties of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The electrochemical performances of MWNTs, Fe-MWNTs, and Fe-MWNTs/PPy were determined by cyclic voltammetry and galvanostatic charge/discharge characteristics in a 1.0 M sodium sulfite electrolyte. The results showed that the Fe-MWNTs/PPy electrode had typical pseudo-capacitive behavior and a specific capacitance significantly greater than that of the Fe-MWNT electrode, indicating an enhanced electrochemical performance of the Fe-MWNTs/PPy due to their high electrical properties.

• Journal of the Korean Electrochemical Society
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• v.10 no.2
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• pp.141-144
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• 2007

Polypyrrole(PPy) was composite with MWNT to attain cycle stable by chemical method. We have been considered PPy is the ideal material for high energy density electrochemical capacitor due to pseudo capacitor reaction. In this study we found that increase in cycle life due to composite MWNT. Also PPy/MWNT composite material have resulted larger capacitance and exhibits better electrochemical behavior. The structural feature was investigated by using SEM and TEM. The PPy/CNT composite is not only a promising ultracapacitor material for energy storages but also has a good possibility because of its great capacitive properties, simple preparation and low cost.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1365-1366
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• 2007

Cobalt oxide was composite with MWNT to attain cycle stable by chemical method. We have been considered CoOx is the ideal material for high energy density electrochemical capacitor due to pseudo capacitor reaction. In this study we found that decrease in resistance due to composite MWNT. Also CoOx/MWNT composite material have resulted larger capacitance and exhibits better electrochemical behavior. The structural feature was investigated by using SEM. The CoOx/MWNT composite is not only a promising ultracapacitor material for energy storages but also has a good possibility because of its great capacitive properties, simple preparation and low cost.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.425-431
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• 2005

New type of supercapacitor using high surface area activated carbons mixed with high conductivity polypyrrole (Ppy) has been prepared in order to achieve low impedance and high energy density. Mixed carbons of BP-20 and MSP-20 were used as the active electrode material, and polypyrrole doped with 2-naphthalenesulfonic acid (2-NSA) and carbon black (Super P) as conducting agents were added to activated carbons in order to enhance good electric conductivity. Electrodes prepared with the activated electrode materials and the conducting agents were added to a solution of organic binder [P(VdF-co-HFP) / NMP]. The ratio of optimum electrode composition was 78 : 17 : 5 wt.％ of (MSP20 : BP-20=1 : 1), (Super P : Ppy=10 : 7) and P(VdF-co-HFP) respectively. The performance of unit cell with addition of 7 wt％ Ppy have shown specific capacitance of 28.02 F/g, DC-ESR of $1.34{\Omega}$, AC-ESR of $0.36{\Omega}$, specific energy of 19.87 Wh/kg and specific power of 9.77 kW/kg. With addition of Ppy, quick charge-discharge of unit cell was possible because of low ESR, low charge transfer resistance and quick reaction rate. And good stability up to 500 chargedischarge cycles were retained about 80％ of their original capacity. It was concluded that the specific capacitance originated highly from compound phenomena of the pseudocapacitance by oxidation-reduction of polypyrrole and the nonfaradaic capacitance by adsorption-desorption of activated carbons.