• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.4
• /
• pp.571-583
• /
• 1996

The electrochemical behavior on electrographite and graphite foil electrode with porous surface in 0.5 M $K_{2}SO_{4}$ solution with 1 mM $[Fe(CN)_{6}]^{3-}/[Fe(CN)_{6}]^{4-}$ have been characterized by impedance spectroscopy. In cyclic voltammograms, relative high current according to structure of porous surface for graphite materials was represented, and indicated hgih double layer capacitance on graphite foil. The faraday-impedance and the change of impedance spectrum on both graphite materials were not remarkable during polarization by reaction of field transport. Chemical adsorption was represented on electrographite and was depended highly at anodic polarization.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.4
• /
• pp.648-662
• /
• 1996

Electrode surface reaction on glassy carbon and synthesized graphite (PVDF mixed graphite) in sulfuric acid solution is investigated by impedance spectroscopy at cyclic polarization. The redox peak, which may be due to the change of chemical adsorped functional group on electrode surface or oxidation and reduction of oxygen, is represented on glassy carbon and graphite electrode in potentio-dynamic current curve. The oxidation and reduction of these surface functional group on glassy carbon and PVDF mixed graphite have a major affect on the impedance spectrum and Faraday impedance parameter at cyclic polarization.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1893-1896
• /
• 2003

This research aimed to fabricate a micro structure using micro electrochemical machining (${\mu}$-ECM). with a view to that the theory of ${\mu}$-ECM is established accurately in a different way of conventional electrochemical machining. In details, if the impedance is existed in the system, it is difficult to analyze the micro electrochemical reaction efficiently in polarization curve using a potentiodynamic test. Hence, this research investigates the relationships between impedance and electric current measuring with a potentiostatic test applying to a pair or electrode as a constant potential. And this paper examines the influence of temperature of electrolyte on polarization curve for the quantitative analysis of electrochemical reactions.

• Proceedings of the KIPE Conference
• /
• 2017.11a
• /
• pp.77-78
• /
• 2017

본 논문에서는 온라인 업데이트 상황에서의 배터리 용량 감소상태를 추정하기 위해 사용되는 전압변동곡선(Differential Voltage; DV)을 실시간으로 추정하는 알고리즘을 개발한다. 동적 전류 특성으로 인한 오차의 최소화를 위해 내부 임피던스 성분에 의한 전압 변동을 고려하는 방법론을 제안하며, 이는 필터링 기법을 통한 파라미터 추정 과정을 포함한다. 본 연구의 타당성은 단전지 전류 프로파일 실험 결과를 기반으로 시뮬레이션을 통하여 검증한다.

• Proceedings of the IEEK Conference
• /
• 2000.11a
• /
• pp.321-324
• /
• 2000

본 논문은 전력증폭기 정합회로 설계시 주어진 임피던스를 가지고 Ansoft사의 Ensemble을 이용해 기본적인 정합회로를 설계하였다. MHL21336 , MRF21030 ,MRF21125로 대전력 증폭기를 설계 및 제작하여 측정해본 결과 전체 이득이 52㏈, 대역폭 안에서 이득 평탄도는 ±0.37㏈ 정도, 출력이 PEP 5l㏈m에서 -30㏈c의 결과를 얻었다. Bias 전류에 대한 5㎒ Tone-space IMD 특성곡선을 측정해 본 결과 기지국용 대전력 증폭기로 사용할 수 있음을 보였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2011.05a
• /
• pp.116-116
• /
• 2011

AZ31과 AZ80의 마그네슘합금 소재를 이용하여 분극곡선과 전기화학적 임피던스를 측정하였고, 다른 금속과 접촉하여 대기환경에 노출시킨 부식시험을 하였다. 그 결과 AZ31보다는 AZ80의 부식저항이 더 큰 것을 확인할 수 있었고, 마그네슘 모재가 이종금속과 접촉된 상황에서 Cu>Fe>Al의 접촉재 순으로 부식이 진행되었다.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.4
• /
• pp.315-324
• /
• 2004

In eddy current testing(ECT), differential probes have been frequently used since they .an reduce the number of parameters that influence ECT signals. However, differential signal is actually the difference of the two coils' impedance so that signal prediction and interpretation are not easy, On the other hand, absolute coil signal is rather straightforward to predict and analyze. Therefore, combined use of the two types of signals would increase the test reliability. In this paper, absolute coil signals from Inconel plate and tubes are predicted by the finite element analysis and efforts of lift-off, fill-factor, conductivity, operating frequency, test specimen thickness, inner diameter defects, and outer diameter defects are investigated. As a result, various impedance plane diagrams are drawn and analyzed. Significant practical knowldege about absolute signals is accumulated and similar characteristics of the two types of signal could be understood. Finally, slope angle versus defect depth calibration corves are prepared for three different frequencies.

• Journal of the Korean Magnetics Society
• /
• v.8 no.1
• /
• pp.21-26
• /
• 1998

The temperature dependence of the magnetoimpedance (MI) effect is important both for scientific study and for thermal stability of MI sensor. We have performed the measurement of MI effect in amorphous $Co_{66}Fe_1Ni_1B_{14}Si_{15}$ (Metglas 2714 A) ribbon from a cryogenic chamber where the temperature of the sample can vary from 10 K to 300 K. The ac current was fixed at 10 mA for all measured frequencies ranging from 100 KHz to 10 MHz. The magnetoimpedance ratio (MIR) was revealed the drastic increment as a function of MIR (T) = MIR (0) exp(cT$^2$) where c is a constant. The measured MIR values at room temperature are usually 2-3 times larger than the data measured at 10 K for all measured frequencies. However, the shapes of the MIR curves are remained. This result shows the potential application of the MI effect for a temperature sensor. The frequency dependence of MIR has shown the typical tendency where the maximum values of MIR are increasing ans also the shapes of MIR curves are getting broader as the measured frequency increases.

• Journal of the Korean Magnetics Society
• /
• v.19 no.6
• /
• pp.191-196
• /
• 2009

Magnetic bias phenomena of field-annealed CoFeSiB amorphous ribbons showing asymmetric giant magnetoimpedance was investigated by MOKE method. The specimens removed the crystalline layer at one surface side by chemical etching were prepared and measured magnetization curves by MOKE to investigate the effect of the crystalline layer on magnetization of inner soft amorphous phase. We observed the shift of hysteresis loop, and concluded that the crystalline layer exerts bias field effect on inner soft amorphous phase and the direction of bias filed is opposite to the magnetization direction of surface crystalline layer.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.1
• /
• pp.7-13
• /
• 2006

Fisheries policy change from catching to farming requires more intensive consideration for aquaculture industry. The oceanic farm is a desirable cost effective aquaculture method. However. in odor to gather fish in the oceanic farm, eating sound or any attracting sound should be radiated through underwater loudspeaker. In this Paper, it has been found in literature that the frequency range responding to fish is about 16Hz to 13kHz but sensitive frequency range is about 150Hz to 2kHz and sound pressure level is about 100dB to 150dB reference $1{\mu}Pa$. Therefore, frequency range and output sound level of designed underwater loudspeaker has been specified as 150Hz to 3kHz and 100dB to 145dB reference $1{\mu}bar$. respectively To verify the stability and the endurance to the pressure of 40m water depth, manufactured underwater loudspeaker was examined before sea trial in manufactured water pressure tank which gives a maximum of 10 atmospheric Pressure. We experimented on acoustic characteristic with manufactured underwater loudspeaker under water depth of 10m.