• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.6
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• pp.12-15
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• 1976

This paper presents the realization method of 90$^{\circ}$ constant phase shifter in the VHF band, constructed by the entirely differens idea from the conventional method of the realization of constant phase shifter in the audio frequency range. The construction of 90$^{\circ}$ constant phase shifter is. simple and can be easily realized by using the distributed constant element, transmission line, and the lumped constant elements, R,C,L.

• Journal of Electrochemical Science and Technology
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• v.11 no.3
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• pp.318-321
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• 2020

Here I present a formula which converts a constant phase element (CPE) to its equivalent capacitor. Electrochemical impedance spectroscopy is capable of resolving a complex electrochemical processes into its faradaic and non-faradaic elements, and the non-faradaic process is frequently described as a CPE in place of a capacitor due to the non-ideality. Being described as a capacitor, the non-faradaic element provides information by its capacitance, but a CPE cannot provide a physical meaning. In order to solve the problem, the CPE has been dealt with as an equivalent capacitor of which the capacitance provides practical information. Succeeding the two methods previously suggested, a new conversion method is suggested in this report. While the previous ones manipulate only the CPE, the new method takes both the CPE and its related resistor into account for conversion. By comparing the results obtained by the three methods, we learn that the results are nearly the same within tolerable ranges, and conclude that any of the method choices is acceptable depending on the conditions of the system of interest.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.2
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• pp.182-188
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• 1986

A method of wideband constant phase control is proposed. This can be applied to reflection type phase shifter with p-i-n diode. Using the proposed method, a microwave phase network which consists of a transmission line and reactive circuit element is suggested. By determining theproper values of design parameters, the desired wideband constant phase with different specification can easily be designed. Also, using the proposed method, the parameters variation, and 1.1 dB of insertion loss in the range of 12% bandwidth.

• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.479-485
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• 2022

The power of energy storage devices is characterized by capacitance and the internal resistance. The capacitance is measured on an assumption that the charges are stored at the electrode interface and the electric double layer behaves like an ideal capacitor. However, in most cases, the electric double layer is not ideal so a constant phase element (CPE) is used instead of a capacitor to describe the practical observations. Nevertheless, another problem with the use of the CPE is that CPE does not give capacitance directly. Fortunately, a few methods were suggested to evaluate the effective capacitance in the literature. However, those methods may not be suitable for supercapacitors which are modeled as an equivalent circuit of a CPE and resistor connected in series because the time constant of the equivalent circuit is not clearly studied. In this report, in order to study the time constant of the CPE and find its equivalent capacitor, AC and DC methods are utilized in a complementary manner. As a result, the time constants in the AC and DC domains are compared with digital simulation and a proper equation is presented to calculate the effective capacitance of a supercapacitor, which is extended to an electrochemical system where faradaic and ohmic processes are accompanied by imperfect charge accumulation process.

• Journal of Electrochemical Science and Technology
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• v.15 no.3
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• pp.427-435
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• 2024

Here we introduce a new method for characterizing the constant phase element (CPE) in electrochemical systems using cyclic voltammetry (CV), presenting an alternative to the conventional electrochemical impedance spectroscopy (EIS) approach. While CV is recognized for its diagnostic capabilities in electrochemical analysis, it traditionally encounters difficulties in accurately measuring CPE systems due to a lack of clear linearity with scan rates, unlike capacitors. Our research demonstrates a linear relationship between current and scan rate on a log-log plot, enabling the calculation of n and Y₀ values for CPE from the slopes of these linear relationships. For validation of our method, it is applied to two kinds of capacitors and the results agree with those measured by EIS. Although EIS is known to be accurate in measuring CPE systems, our alternative approach offers a timely and reasonably precise diagnostic tool, balancing between ease of use and accuracy, especially beneficial for preliminary assessments before conducting further in-depth analysis.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.26-33
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• 2001

This article involves the application of the fractal geometry to interfacial electrochemistry. Especially, we gave our attention to impedance behaviour of the fractal electrode. First, this article briefly explained the constant phase element (CPE) in electrochemical impedance and the do Levie's transmission line model. Second, we introduced the Nyikos and Pajkossy's theoretical works to approach the CPE phenomena using the fractal geometry. Finally this article presented other various fractal models for analysing the ac response of the rough electrodes.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.894-895
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• 2007

This paper presents coupled analysis between finite element method and analytic technique for predicting temperature rise of 25.8kV 25kA three-phase GIS bus bar. The power losses and temperature distribution of three-phase GIS bus bar model are analyzed by magneto-thermal finite element method. The heat transfer coefficients on the boundaries are analytically calculated by applying Nusselt number considering material constant and model geometry for the natural convection. And these are used as the input data to predict the temperature rise of three-phase GIS bus bar model by coupled magneto-thermal F.E.A. The predicted temperature of 25.8kV 25kA three-phase GIS bus bar model shows good agreement with the experimental data.

• Journal of Power Electronics
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• v.12 no.1
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• pp.113-119
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• 2012

This paper describes the design and control of a phase shift full bridge converter with a current doubler, which can be used for the on-board charger for the lead-acid battery of electric forklifts. Unlike the common resistance load, the battery has a large capacitance element and it absorbs the entire converter output ripple current, thereby shortening the battery life and degrading the system efficiency. In this paper a phase shift full bridge converter with a current doubler has been adopted to decrease the output ripple current and the transformer rating of the charger. The charge controller is designed by using the small signal model of the converter, taking into consideration the internal impedance of the battery. The stability and performance of the battery charger is then verified by constant current (CC) and constant voltage (CV) charge experiments using a lead-acid battery bank for an electric forklift.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1249-1255
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• 2009

Cord-rubber composites widely used in tires show very complicated mechanical behavior such as nonlinearity and large deformation. Three-phase(cord, rubber and the interface) modeling has been used to analyze the stress distribution in the cord-rubber composites more accurately. In this study, finite element methods were performed using two-dimensional generalized plane strain element and plane strain element to investigate the stress distribution and effective modulus of cord-rubber composites. Neo Hookean model was used for rubber property and several interface properties were assumed for various loading directions. It was found that the interface properties affect the effective modulus and the distributions of shear stress.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.1
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• pp.38-44
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• 2004

An experimental study for a crane hook was performed to investigate the stress distribution along a certain line where the maximum and minimum stresses to be developed. On this line, the isoclinic fringe and/or principal stress direction is constant. The crane hook was modeled into a 2-dimensional plate made of urethane rubber called 'Photoflex' The Photoflex is very sensitive to a load and has low photoelastic fringe constant. The Tardy compensation method with the fringe sharpening process and the 4-step phase shifting method, was used for the photoelastic technique. Experimental results by photoelasticity were compared with the calculated stresses from the simple curved beam theory and tile finite element analysis. Ail the results were close to each other.