• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.167-176
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• 2006

In this paper we show that solutions of the nonlinear Nernst-Planck equation possesses the quadruple-layer structure near the interface when the electrolyte receives a high frequency forcing such as a high-frequency alternating current. Very near to the interface wall, the well-known, classical Stern layer exists. Near to the Stern layer we have the secondly thin layer (to be called inner layer in this paper) where the ion concentrations behave under the same frequency as the external forcing. However, in this layer, the positive and negative ion concentrations develop with the time phase 180-degree different from each other. Next to this second layer, we have the third layer (called middle layer) in which two ion concentrations change with the time period double the forcing, and both concentrations behave in the same time phase. In the outermost layer, i.e. the forth layer, (called outer layer) the ion concentrations show the same-phase development as the third one but decaying very slowly in time. Our assertion is mostly based on the 1-D numerical simulation for the Nernst-Planck equation under a high frequency AC field assuming that the quadruple layer is very thin compared with the length scale representative of the bulk region.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.8
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• pp.52-63
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• 2002

In this paper, we developed a numerical analysis model by using ADI-FDTD method to analyze three-dimensional interconnect structure. We discretized maxwell's curl equation by using ADI-FDTD. We introduced PML(Perfectly Matched Layer) absorbing boundary condition to solve the effect of the reflected wave at the interface. Evaluating the numerical model of PML and ADI-FDTD, we simulated the electric field distribution in time domain. We compare standard FDTD with ADI-FDTD, and analysis the result.

• Journal of Astronomy and Space Sciences
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• v.39 no.2
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• pp.67-77
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• 2022

The elements that impact the dynamics and collaborations of waves and particles in the magnetosphere of planets have been considered here. Saturn's internal magnetosphere is determined by substantiated instabilities and discovered to be an exceptional zone of wave activity. Interchanged instability is found to be one of the responsible events in view of temperature anisotropy and energization processes of magnetospheric species. The generated active ions alongside electrons that constitute the populations of highly magnetized planets like Saturn's ring electron current are taken into consideration in the current framework. The previous and similar method of characteristics and the perturbed distribution function have been used to derive dispersion relation. In incorporating this investigation, the characteristics of electromagnetic ion cyclotron wave (EMIC) waves are determined by the composition of ions in plasmas through which the waves propagate. The effect of ring distribution illustrates non-monotonous description on growth rate (GR) depending upon plasma parameters picked out. Observations made by Cassini found appropriate for modern study, have been applied to the Kronian magnetosphere. Using Maxwellian ring distribution function of ions and detailed mathematical formulation, an expression for dispersion relation as well as GR and real frequency (RF) are evaluated. Analysis of plasma parameters shows that, proliferating EMIC waves are not developed much when propagation is parallelly aligned with magnetosphere as compared to waves propagating in oblique direction. GR for the oblique case, is influenced by temperature anisotropy as well as by alternating current (AC) frequency, whereas it is much affected only by AC frequency for parallel propagating waves.

• Transactions on Electrical and Electronic Materials
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• v.14 no.6
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• pp.308-311
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• 2013

The effect of an electric field on the ac electrical treeing in various epoxy/reactive diluent systems was studied in a needle-plate electrode geometry. Diglycidyl ether of bisphenol A (DGEBA) type epoxy was used as a base resin, and 1,4-butanediol diglycidyl ether (BDGE) or polyglycol (PG) as a reactive diluent was introduced to the DGEBA system, in order to decrease the viscosity of the DGEBA epoxy system. BDGE was acted as a chain extender, and PG acted as a flexibilizer, after the curing reaction. To measure the treeing initiation time and the propagation rate, three constant alternating currents (ac) of 10, 13 and 15 kV/4.2 mm (60 Hz) were applied to the specimen, in a needle-plate electrode arrangement, at $30^{\circ}C$ of insulating oil bath. When 10 kV/4.2 mm (60 Hz) was applied, the treeing initiation time and the propagation rate in the DGEBA system were 356 min and $1.10{\times}10^{-3}$ mm/min, respectively, those in the DGEBA/BDGE system were 150 min and $1.14{\times}10^{-3}$ mm/min, respectively. Those in the DGEBA/PG system were 469 min and $1.05{\times}10^{-3}$ mm/min, respectively. As 15 kV/4.2 mm (60 Hz) was applied, the propagation rate in the DGEBA system was $5.41{\times}10^{-3}$ mm/min, and that in the DGEBA/PG system was $1.42{\times}10^{-3}$ mm/min. These values meant that PG could be used as a reactive diluent in the DGEBA system, without the deterioration of the insulation breakdown property.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.679-685
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• 2004

Although the electrophoretic deposition method has the advantage of simple processing procedure, less fabrication facilities, and easier control for deposition thickness and wire length, providing economical and technical merits, it also has the disadvantages of cracking and porosity phenomena, requiring an improved processing method for higher particle density and constant particle orientation. we have developed an optimization method to increase the particle density and to unify its orientation, and have performed a study to overcome the cracking and porosity problems in the fabricated superconductor. In order to improve the surface uniformity and the conduction properties of the fabricated YBCO thick films, a system that applies alternate voltage vertically has been developed for the first time and applied to the electrophoretic deposition process. The applied alternate electric field caused a force to be exerted on each YBCO particle and resulted in a rotation of the particle in the direction of applied electric field, accomplishing a uniform particle orientation. We name this process as the shaky-aligned electrophoretic deposition method. For commercial utilization and efficiency, in this dissertation, alternating voltage of 60 Hz and 25 ∼ 120 V/cm was proposed to apply it as a subsidiary source for shaky-flow deposition so that the fabricated thin film showed uniform surface morphology with less voids and cracks and Tc,zero of 90 K and the critical current density of 3419 A/$cm^2$.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.155-161
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• 2010

Recently, the electromagnetic techniques of the eddy current testing(ECT), alternating current field testing, magnetic flux leakage testing and remote field testing have been used as a nondestructive evaluation method based on the electromagnetic induction. The eddy current testing is now widely accepted as a NDE method for the heat exchanger tube in the electric power industry, chemical, shipbuilding, and military. The ECT system mainly consists of the synthesizer module, analog module, analog-to-digital converter, power supplier, and data acquisition and analysis program. In this study, the synthesizer module and the analog module which are essential to the ECT system were primarily developed. The developed ECT system is basically a multifrequency type which is able to inject the maximum four frequencies based on the frequency and time domain multiplexing method. Conclusively, we confirmed that the EC signal was processed appropriately in each circuit modules, and the Lissajous EC signal was displayed in the impedance plane.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1231-1236
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• 2007

This study presents the static and dynamic actuating performances of a bending piezoelectric actuator with a thin sandwiched PZT plate under a static load. The stored elastic energy within the actuators which occurs during a curing process is obtained through a flexural bending test. An actuating performance is evaluated in terms of an actuating displacement at the simply supported condition. The results reveal that an actuator that consists of a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at the alternating current voltage, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling their performances.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.283-292
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• 2020

Current sensors that use a Hall element and Hall IC to measure the magnetic fields generated in steel silicon core gaps do not distinguish between direct and alternating currents. Thus, they are primarily used to measure direct current (DC) in industrial equipment. Although such sensors can measure the DC when installed in expensive equipment, ascertaining problems becomes difficult if the equipment is set up in an unexposed space. The control box is only opened during scheduled maintenance or when anomalies occur. Therefore, in this paper, a method is proposed for facilitating the safety management and maintenance of equipment when necessary, instead of waiting for anomalies or scheduled maintenance. A Bluetooth 4.0 low-energy current-sensor system based on near-field communication is used, which compensates for the nonlinearity of the current-sensor output signal using a piecewise linear model. The sensor is controlled using its generic attribute profile. Sensor nodes and cell phones used to check the signals obtained from the sensor at 50-A input currents showed an accuracy of ±1%, exhibiting linearity in all communications within the range of 0 to 50 A, with a stable output voltage for each communication segment.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.24-27
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• 1998

Electroluminescence (EL) comes from the light emission obtained by the electrical excitation energy passing through a phosphor layer undo. an applied high electrical field $(10^6 V/cm)$. The preparation of white and blue phosphors and characterizations of light emitting alternating current powder electroluminescent devices (ACPELDs) were investigated. In this work, we fabricated two kinds of ELDs, that is, yellow electroluminescent device (B-ELD), blue electroluminescent device (B-ELD). The basic st.uctures of Y-ELD and B-ELD are ITO (Indium Tin Oxide)/phosphor layer/Insulator layer/Carbon electrode and ITO/Phosphor layer/Insulating layer/carbon electrode, respectively. Another structures of ITO/Phosphor and Insulator mixture layer/Backelectrode are introduced. EL spectra and luminance of two types of ELDs were measured by changing voltage at fixed frequency 0.4kHz, 1.5kHz. Blue and yellow phosphors prepared in this work show $50cd/m^2\;and\;30cd/m^2$ of luminance at 400Hz, 150V.

• Journal of Korea Foundry Society
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• v.25 no.3
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• pp.115-122
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• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.