• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.161-164
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• 1989

When an electric (or a magnetic) line source is located near the surface, surface wave type field is generated and the energy associated with this field is guided very close to the impedance surface. In this paper, field strength is calculated by the exact modal and ray methods for a line source excited parallel plate waveguide. The surface wave contribution to the modal and ray solutions is anticipated very strong and must be included in both solutions.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.211-216
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• 2008

Gap fillar antennas are needed for serving the high quality of DMB through the cellular phone by eliminating the shadow regions among buildings or underground. We implement Quadrifilar Helical Antenna using phase difference with PCB feeding lines without coaxial cables and four impedance matching circuits. It is shown that the antenna characteristics is affected by the size and diameter through the simulation process using MicroWave Studio and it is applied for implementing QHA. Experiment results confirm that the performance can be gained as same as the simulation data by using the phase difference with PCB feeding lines without additional impedance matching circuits.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.41-46
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• 2008

This paper conducts the research on the variation in the characteristics of the resonance and impedance of the metallic parallel plates due to the replacement of the normal dielectric substrate by the metamaterial. The ENG(${\epsilon}<0$), MNG(${\mu}<0}$) and DNG(${\epsilon},{\mu}<0$) types of metamaterial as well as the DPS(Double Positive) material are taken into consideration a full-wave modal analysis method known for accurate computation, as the SRR-kind of Lorentz model for permittivity and metal wire-periodic array-kind of Drude model for permeability, and the behaviors of parallel plates' resonance mode and impedance are observed. Based upon the observation, the design guidelines for the substrate can be addressed regrading how to suppress the parallel plates' spurious resonance modes that degrade the quality of the electronic equipment.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1870-1872
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• 2005

In this study, an ultrasonic level limit sensor with a new structure utilizing the acoustic impedance matching is proposed to be able to check it out a change of water-level. 2 PZT resonators with the same property are bonded directly on the polyethylene plate. One resonator is for transmitter as an ultrasonic transducer, the other one is for receiver. In this case, a polyethylene plate will operate as an acoustic guider to transmit a transverse wave between 2 PZT resonators in air. While in the water, a polyethylene plate having a similar acoustic impedance with the water will be emitted an acoustic energy into the water as a longitudinal wave. According to this mechanism, there was a wide difference of acoustic signal output between underwater and in air. As a summary, this proposed level limit sensor could be used as a strong candidate with low cost and more stable one.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1744-1746
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• 1996

Surface impedance boundary condition(SIBC) concepts are introduced into the finite-difference time-domain(FDTD) method. Lossy conductors are replaced by surface impedance boundary computations reducing the soluton space and producing significant computational savings. Specifically, a surface impedance boundary condition is developed to reduce a lossy dielectric half-space. Since Maxwell's eqations are solved directly, the reflected and transmitted pulse amplitude demonstrate how the reflection and transmision coefficient determine reflected wave amplitude. In this paper, two implementations of reflection coefficient are presented. One implementation is a standard FDTD technique and the other is a FDTD using surface impedence boundary condition(FDTD-SIBC) that are applicabIe over a very large frequency bandwidth. Particulary, an efficient way to transform the time domain results to frequency domain is presented. Thus, frequency domain results are presented in one dimension and are compared with exact results.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.438-440
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• 1995

The impedance characteristics and plasma parameters were experimentally studied in a weakly magnetized planar type, inductively coupled plasma (ICP) system. Compared with non-magnetized for system higher power transfer efficiency, stable impedance matching, enhancement of plasma density and higher electron temperature can be obtained. Such improvements are mainly due to the excitation of deeply penetrating electromagnetic wave and reduction of radial loss of electrons. In particulary, $SF_6$ (sulfur hexafluride) plasma shows unstable impedance matching in non-magnetized ICP because electronegativity of $SF_6$ effects on plasma characteristics. But, magnetized inductively coupled $SF_6$ plasma shows enough impedance matching stability to be applicable to the polysilicon etching in semiconductor process.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.395-400
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• 2002

Epoxy coating and sealing used in nuclear plants for the protection of radiation degrades with aging and hazardous atmosphere. In order to evaluate the degradation of the epoxy, dependence of the acoustic impedance on the change of mechanical properties has been used. Unlike metals, the surface of the epoxy coating on a concrete liner is so wavy that the acoustic impedance is difficult to measure by using the reflectivity of the ultrasound on the interface surface because of the irregular reflection and propagation from the epoxy surface. SA(simulated annealing) algorithm is applied to calculate the acoustic impedance using a reflection wave from the rough epoxy surface. The surface waviness and acoustic impedance are taken into account and determined by SA method to evaluate the state of degradation quantitatively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.870-874
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• 2004

This work presents a study on development of a practical and quantitative technique for assessment of the structural health condition by Piezoelectric impedance-based technique associated with longitudinal wave propagation method. The bolt fastening condition is adjusted by torque wrench. In order to estimate the damage condition numerically, three damage indices, impedance peak frequency shift ${\Delta}F$, peak amplitude ratio $\delta$ and quality factor ratio $\gamma$, are proposed in this paper. Furthermore, an assessment method is described for estimation of the damage by using these three damage indices.

• Journal of Multimedia Information System
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• v.9 no.2
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• pp.161-170
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• 2022

Under General anesthesia with isoflurane, we insert a chicken's esophageal catheter into the near the left atrium. 1MHz radio wave was added to electrocardiogram electrodes of the esophagus, and the change of impedance (phase) was obtained by amplitude synchronous detection technique. At the same time, a thin tube is surgically inserted into the axillary artery to continuously measure blood pressure. The correlation between impedance (phase) and blood pressure was obtained. Both showed a very high correlation (R²=0.9665). It was also observed the waveform flowing from the left atrium into the left ventricle. When an individual infected with the avian influenza virus develops, the cytokine storms lead to hypotension earlier than the test for antigen-antibody reaction. In order to detect this, in the future, this impedance technique will be useful for screening individuals infected with avian influenza virus by measuring the blood pressure of chickens in cages in a non-contact manner using microwaves.

• Structural Engineering and Mechanics
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• v.83 no.3
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• pp.377-386
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• 2022

This paper considers dynamic impedance functions and presents a detailed analysis of the soil plasticity influence on the pile-group foundation dynamic response. A three-dimensional finite element model is proposed, and a calculation method considering the time domain is detailed for the nonlinear dynamic impedance functions. The soil mass is modeled as continuum elastoplastic solid using the Mohr-Coulomb shear failure criterion. The piles are modeled as continuum solids and the slab as a structural plate-type element. Quiet boundaries are implemented to avoid wave reflection on the boundaries. The model and method of analysis are validated by comparison with those published on literature. Numerical results are presented in terms of horizontal and vertical nonlinear dynamic impedances as a function of the shear soil parameters (cohesion and internal friction angle), pile spacing ratio and frequencies of the dynamic signal.