• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.78-84
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• 2009

This paper presents measurement results of transient impedance for small-sized ground electrodes in a discharge region of soil. For a realistic analysis of ionization characteristics near the ground electrode, three types of ground rod installed outdoors and high voltage impulse generator were used for injecting test current. From the analysis of response voltage and current flowing ground electrode to earth, it is verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively in high resistivity soil. As a threshold electric field density for ionization is small in low resistivity soil, the shape of ground electrode rarely contributes to the transient impedance. And, from the experiment result with shape of ground electrode, the rod with needles is more effective to reduce the transient impedance than the plate electrode in the voltage range including with ionization regions of soil.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.49-54
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• 2009

This paper presents the numerical simulation results on the moving type electrodynamic suspension (EDS) simulator and static type EDS simulator using high-Tc superconducting (HTS) levitation magnet. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible two ways to simulate the EDS system were simulated in this paper by using finite element method (FEM). The first way was the moving type simulator which consists of the fixed HTS magnet and the moving ground conductor. The second way was the static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.

• Journal of information and communication convergence engineering
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• v.14 no.3
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• pp.184-190
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• 2016

We present experimental demonstrations of electromagnetic bandgap (EBG) structures for the wideband suppression of radiated emissions from a power bus in high-speed printed circuit boards (PCBs). In most of the PCB designs, a parallel plate waveguide (PPW) structure is employed for a power bus. This structure significantly produces the wideband-radiated emissions resulting from parallel plate modes. To suppress the parallel plate modes in the wideband frequency range, the power buses based on the electromagnetic bandgap structure with a defected ground structure (DGS) are presented. DGSs are applied to a metal plane that is connected to a rectangular EBG patch by using a via structure. The use of the DGS increases the characteristic impedance value of a unit cell, thereby substantially improving the suppression bandwidth of the radiated emissions. It is experimentally demonstrated that the DGS-EBG structure significantly mitigates the radiated emissions over the frequency range of 0.5 GHz to 2 GHz as compared to the PPW.

• Asian Journal of Atmospheric Environment
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• v.5 no.3
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• pp.196-203
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• 2011

The main aim of this study is to establish methods of morphological preservation and elemental quantification for individual snow crystals. Individual snow crystals were collected at a height of 20 m above ground level. To stabilize and preserve the original morphologies of the snow crystals, cyanoacrylate, which has been used to fix liquid droplets, was applied (Kasahara et al., 2000). Several different kinds of snow crystals (dendrite, sectored plate, quasi-sectored plate, and hexagonal plate) were successively stabilized using this method. The stabilized snow crystals were pretreated with acetone, and then the elemental components contained in a whole snow crystal were quantified with the Particle Induced X-ray Emission (PIXE) analytical technique. The snow crystal residual composition determined in the present study was dominated by sulfur and mineral components, and the elemental mass showed an apparent crystal size dependence, where the elemental mass gradually decreased as the crystal size increased.

• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.105-109
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• 2009

The problem of electromagnetic coupling between a slit fed by a flanged parallel-plate waveguide(PPW) and a slit in an infinite nearby conducting screen parallel to the flanged ground conductor is studied as a simplified problem for a near-field scanning microscopy(NSM). The method of moments isused to solve the coupled integral equations for the electric field distributions over the slits. The performance of the proposed apparatus as an NSM is tested by examining the effects of some geometrical parameters on the equivalent slit admittance and coupled powers through the slits.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1950-1953
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• 1996

A $1\;{\times}\;4$ micro mirror array is designed and fabricated. In contrast to other micro mirrors which utilize torsional flexure hinges or cantilevers for restoring torque and supporting purpose, we have placed a substrate hinge structure under each mirror. Each micro mirror consists of address electrode, substrate hinge consisting of pin and staple, supporter post, and mirror plate. Electrical connection between mirror plate and ground electrode is established by substrate hinge. Mirror undergoes a rotational motion due to electrostatic force when voltage difference is applied between address electrode and mirror plate. Micro mirrors with two different types of staple shape and two different pin sizes are designed and fabricated. Each mirror is designed to have ${\pm}\;10^{\circ}$ of deflection angle and have $100\;{\times}\;110\;{\mu}m^2$ of size.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.448-452
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• 2004

The micromachined variable optical attenuator(VOA) was presented in the paper. The VOA has two single mode fiber(SMF) aligned with free space and symmetric parallel plate actuator with microshutter, which can control a amount of light by driving the actuator. In the paper, analysis on driving performances of the VOA was performed and can be reduced threshold voltage through the decreasing displacement actuating range. This paper presents a VOA that is fabricated using bosch deep silicon etching process with silicon on insulator(SOD wafer. The VOA consists of driving electrode, ground electrode, actuating microshutter, and mechanical stopper. In this VOA, actuating shutter is driven by electrostatic force and the threshold voltage is close to 28V, 46V come along with the spring width of 5${\mu}{\textrm}{m}$, 7${\mu}{\textrm}{m}$ respectively. Attenuation range is measured from 2.4㏈ to 16.7㏈.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.565-579
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• 2014

The pullout capacity of plate anchors has been studied extensively over the past 40 years. However, very few studies have attempted to calculate the pullout capacity of anchors in sandy slopes. In this paper, three upper bound approaches are used to study the effect of a sloping ground surface and friction angle on pullout capacity and failure of plate anchors. This includes the use of; simple upper bound mechanisms; the block set mechanism approach; and finite element upper bound limit analysis. The aim of this research is to better understand the various failure mechanisms and to develop a simple methodology for estimating the pullout capacity of anchors in sandy slopes.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.4
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• pp.22-32
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• 2022

To reduce energy consumption and CO₂ emission in building sector, a ground source heat pump system has been highly adopted due to its high efficient by many regulation. A certification system has been operated to distribute reliable and high-efficient heat pump units. In this study, the performance status of the recently certified ground source heat pump unit with components was investigated. All heat pump units certified from 2015 to 2020 were water to water heat pump types. Compared to the past, higher capacity systems over 400 kW have been certificed. The cooling COP of the heat pump unit based on certification criteria showed higher value than the heating COP. It is highly recommended to revise the certified criteria values considering operating conditions individually. Most of ground source heat pump units have employed scroll type compressors and plate type heat exchangers with HFC refrigerant.

• Analytical Science and Technology
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• v.11 no.5
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• pp.386-393
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• 1998

A new analytical luminescence method for the $Dy^{3+}$ ion was studied using the luminescence enhancement by the treatment of the o-phenanthroline on the TLC plate. Compared to the specific emission intensities of the ion in water solution, if the ion solution is spotted on the TLC plate, the luminescence intensities were extremely enhanced. There was additional enhancement effect of the luminescence intensities of the ions on the TLC plate, if the ion on the TLC plate is treated with o-phenanthroline. Based on the luminescence enhancement, the detection limit was improved by more than 4 order of magnitude compared to that of solution sample. The dynamic ranges and correlation coefficients of the calibration curves near the detection limit were 102 order and ~0.99, respectively. The energy-transfer mechanism was explained for the theoretical back ground of the luminescence enhancement.