• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.106-114
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• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.1059-1066
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• 2011

The micro-perforated panel absorber(MPPA) is one of promising noise control elements because of its applicability to extreme environments where general porous materials cannot be used. Since the MPPA is inherently non-porous sound absorber, it can be a good candidate of acoustic protection system of a space launcher. The overall sound pressure level inside payload fairings of commercial launch vehicles is so high(around 140 dB OASPL) that the conventional linear impedance model cannot be directly applied to the design of the acoustic protection systems. In this paper an acoustic impedance models of a micro-perforated panel absorber at high sound pressure environment were reviewed and the use of the impedance on the practical design of MPPAs was addressed. The variation of absorption characteristics of MPPA was discussed according to the design parameters, e.g., perforation ratio, the minute hole diameter, the thickness of MPP and the incident sound pressure level.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.184-197
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• 1995

In this paper, high speed IC package-to-package interconnections are modeled as lossless multiconductor transmission lines operating in the TEM mode. And, three mathematical algorithms for computing electrical parameters of the lossless multiconductor transmission lines are described. A semi-analytic Green's function method is used in computing per unit length capacitance and inductance matrices, a matrix square root algorithm based on the QR algorithm is used in computing a characteristic impedance matrix, and a matrix algorithm based on the theory of M-matrix is used in computing a diagonally matched load impedance matrix. These algorithms are implemented in a computer program DIME (DIagonally Matched Load Impedance Extractor) which computes electrical parameters of the lossless multiconductor transmission lines. Also, to illustrate the concept of design database for high speed IC package-to-package interconnection, a database for the multi conductor strip transmission lines system is constructed. This database is constructed with a sufficiently small number of nodes using the multi-dimensional cubic spline interpolation algorithm. The maximum interpolation error for diagonally matched load impedance matrix extraction from the database is 1.3 %.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.178-185
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• 2011

The micro-perforated panel absorber (MPPA) is one of promising noise control elements because of its applicability to extreme environments where general porous materials cannot be used. Since the MPPA is inherently non-porous sound absorber, it can be a good candidate of acoustic protection system of a space launcher. The overall sound pressure level inside payload fairings of commercial launch vehicles is so high (around 140 dB OASPL) that the conventional linear impedance model cannot be directly applied to the design of the acoustic protection systems. In this paper an acoustic impedance models of a micro-perforated panel absorber at high sound pressure environment were reviewed and the use of the impedance on the practical design of MPPAs was addressed. The variation of absorption characteristics of MPPA was discussed according to the design parameters, e.g., perforation ratio, the minute hole diameter, the thickness of MPP and the incident sound pressure level.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.8-12
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• 2003

Characteristics of optical transceiver module in radio frequency(RF) band were investigated with TO-can packaged Fabry-Perot laser diode(FP-LD). R-L-C parameters for equivalent circuit model of the LD were extracted with an impedance analyzer. With this model, impedance matching to the packaged LD could be performed by eliminating inductive components of the leads in the package by using lumped chip capacitors that have opposite reactance, while it shows resonance dip in low frequency band. The resonance dip could be removed using lumped elements for impedance matching by shifting the resonance frequency to the region out of interest.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.122-129
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• 2001

A characterization procedure for analyzing symmetric coupled MIS(Metal-Insulator-Semiconductor) transmission line is used the same procedure as a general single layer symmetric coupled line with perfect dielectric substrate from the extraction of the characteristic impedance and propagation constant for even- and odd-mode. In this paper, an analysis for a new substrate shielding symmetric coupled MIS structure consisting of grounded crossbar at the interface between Si and SiO2 layer using the Finite- Difference Time-Domain(FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded crossbar lines over time-domain signal has been examined. Symmetric coupled MIS transmission line parameters for even- and odd-mode are investigated as the functions of frequency, and the extracted distributed frequency- dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor for the new MIS crossbar embedded structure are also presented. It is shown that the quality factor of the symmetric coupled transmission line can be improved without significant change in the characteristic impedance and effective dielectric constant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.105-108
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• 2005

The radiated noise from the automotive intake system should be predicted at the design stage. To this end, the precise measurement of in-duct acoustic source parameters of the intake system, i.e., the source strength and source impedance, is essential. Most of previous works on the measurement of acoustic source parameters were performed under a fixed engine speed condition. However, the requirement of vehicle manufacturer is the noise radiation pattern as a function of engine speed. In this study, the direct method was employed to measure the source parameters of engine intake system under a fixed engine speed and engine run-up condition. It was noted that the frequency spectra of source impedance hardly changes with varying the engine speed. Thus, it is reasonable to calculate the source strength under the engine run-up condition by assuming that source impedance is invariant with engine speed. Measured and conventional source models, i.e., constant pressure source, constant velocity source, and non-reflective source, were utilized to predict insertion loss and radiated sound pressure level. A reasonable prediction accuracy of radiated sound pressure level spectra from the intake system was given in the test vehicle when using the measured source characteristics which were acquired under the operating condition.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1668-1671
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• 2003

A novel dual-frequency microstrip printed-dipole antenna operating at 5 GHz and 10 GHz is presented. This antenna is designed for wireless and mobile communication. The balance step coplanar strip is used to be a transmission line at the center of dipole with matching impedance at 50 ohm. Using the conductor strip align on the other side of antenna and adjust the width of step coplanar strip line to improved input impedance matching. By modification for matching impedance of dual frequency antenna are not affected to the radiation patterns. The Finite Difference Time Domain (FDTD) technique is applying to analyze the basic characteristic properties such as $S_{11}$ , input impedance , VSWR and radiation patterns. And these parameters are discussed. The analyze problem space are $51{\times}197{\times}175$ cells and cell dimension are ${\Delta}x=0.3\;mm$ and ${\Delta}y={\Delta}z=0.15\;mm$.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.149-156
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• 2018

In this technical note, I report the analysis of electrochemical impedance data measured with potential sweeping. Even though the instruments for voltammetric impedance measurements have been developed for decades using different approaches, their applications are limited due to the lack of well-established protocols to easily analyze voltammetry data. To fill this gap, the singular point of the specific potential is considered that is only determined by the standard/formal potential and the transfer coefficient and is independent of the kinetics and experimental parameters (including revertability) of faradaic reactions. Taking the advantage of its inertness, I suggest an approach employing the singular point as a reference to obtain general electrochemical information. As all the concepts and methods are verified with numerical simulations, this technique is expected to be applied for complex reactions involving electrochemical and chemical reaction mechanisms.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.137-140
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• 2002

The frequency response analysis of complex impedance spectra using small perturbation ac impedance spectroscopy is an informative method of OLED performance characterization and lifetime analysis. Using simple RC equivalent circuit mode,l macroscopic nonliniear transport properties of semiconductive emission/transport layers can be analyzed and parameterized. We present the bias voltage dependence and aging effect in impedance spectra measured from an ITO/CuPC/TPD/$Alq_3$/LiF/Al OLED device, and discuss possible failure mechanism based on impedance model parameters.