• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.316-321
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• 2002

In this Paper, the channel characteristics of the medium voltage(22.9kV) power line to analysis the broadband power line communication in the frequency range up to 30MHz was measured. With the sideband electrical coupler in the operating frequency range from DC to 30MHz, we measured characteristic impedance, noise and attenuation of the medium voltage power line, and then characteristic impedance was measured at the state of unloaded medium voltage power line by Scattering parameter method of Vector Network Analyzer. As a measurement result, Channel impedance shows 100~380$\Omega$ at the less than 15MHz and 70~230$\Omega$ at the more than 15 MHz. Noise characteristics of power line shows -75dBm at 20MHz and Narrowband interference noise was from 3 MHz to 7MHz.

• 한국한의학연구원논문집
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• 제4권1호통권4호
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• pp.139-148
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• 1998

Measurement of different skin parameters are widely used in the practices and researches of the modern acupuncture. The most important parameter is conductance or impedance. For measurement, some researchers used D.C. and others used A.C. It has been experimentally shown that the acupuncture points and meridian lines have the characteristics of high potential, low electrical resistance, high capacitance, spontaneous sound production, spontaneous light production, and high temperature. The Purpose of this study was to examine the effect of Hapkok(LI-4, 合谷) on experimental frequency characteristics in Hapkok. The result of data analyses indicated that significant differences arise at frequency under 100Hz. We propose that development of Meridian detecting system or Meridian diagnosis system should be done using frequency under 100Hz.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1348-1349
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• 2008

Grounding impedance depends on the frequency of current flowing into a grounding system. Especially, the lightning gives a broad frequency spectrum from low frequency up to 1 MHz. So the grounding impedance related to high frequency current like lightning should be measured with high frequency source. In this paper, we described the grounding impedances of deeply-driven ground rods of 10 $\sim$ 48 m long with respect to the frequency of injected currents. For the experiments, we used the wideband power amplifier which can produce sinusoidal voltages with the frequency ranges of DC $\sim$ 250 MHz. As a result, the longer the ground rod is, the lower the ground resistance is. However the grounding impedance of deeply-driven ground rod in the range of higher frequency is significantly increased. As a consequence, it is important to evaluate the high frequency performance of grounding systems for lightning protection.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2004년도 하계학술대회
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• pp.211-214
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• 2004

The measurement system of ground impedance is based on a computer aided technique. The magnitude and phase of ground impedance were determined by the novel measurement and analysis using the revised fall-of-potential method. The ground impedances of the ground rod of 30 m long are considerably dependent on the frequency. The ground impedance is mainly resistive in the frequency range of 3-20 kHz. At higher frequencies, the reactive components of the ground impedances are no longer negligible and the inductance of the ground rod was found to be the core factor deciding the ground impedance.

• Smart Structures and Systems
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• 제15권2호
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• pp.375-393
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• 2015

In this study, local dynamic characteristics of mountable PZT interfaces are numerically analyzed to verify their feasibility on impedance monitoring of the prestress-loss in tendon anchorage subsystems. Firstly, a prestressed tendon-anchorage system with mountable PZT interfaces is described. Two types of mountable interfaces which are different in geometric and boundary conditions are designed for impedance monitoring in the tendon-anchorage subsystems. Secondly, laboratory experiments are performed to evaluate the impedance monitoring via the two mountable PZT interfaces placed on the tendon-anchorage under the variation of prestress forces. Impedance features such as frequency-shifts and root-mean-square-deviations are quantified for the two PZT interfaces. Finally, local dynamic characteristics of the two PZT interfaces are numerically analyzed to verify their performances on impedance monitoring at the tendon-anchorage system. For the two PZT interfaces, the relationships between structural parameters and local vibration responses are examined by modal sensitivity analyses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.281-283
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• 1994

The impedance characteristics of planar ICP have been measured and compared with the theoretical results obtained by the field equation. The resistance of the total impedance had a maximum point and the inductance decreased monotonically as the electron density increased from $2.5{\times}10^{10}cm^{-3}$ to $7{\times}10^{11}cm^{-3}$ and the Pressure from 1mT to 50mT. The impedance characteristics were also dependent on the profile of the electron density. The effective collision frequency, ${\nu}_{eff}$ was $9.0{\times}10^6Hz$ at 5mT and $.5{\times}10^7Hz$ at 100mT. The effective collision frequency at 5mT was not so different from that at 100mT and it is doe to the reduction of the discharge channel cross-section at high pressure. The estimated effective collision frequency from the simulation data was of the same order as the measured one.

• 전기학회논문지
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• 제60권7호
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• pp.1427-1433
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• 2011

This study describes a conductive fabric sensor and determines an optimum excitation frequency of the sensor to evaluate knee joint movements. Subjects were composed of 15 males (age: $30.7{\pm}5.3$) with no known problems with their knee joints. The upper side of subjects' lower limbs was divided into two areas and the lower side of subjects' lower limbs was divided into three areas. The sensors were attached to 1 for 3 spot from a hip joint and to 3 for 4 spot from a knee joint which are the optimum conductive fabric sensor configuration to evaluate knee joint movements. As a result, the optimum excitation frequency for evaluating knee joint movements using conductive fabric sensors was 25 kHz. Average and standard deviation of bio-impedance changes from 15 subjects were $92.1{\pm}137.2{\Omega}$ at 25 kHz. The difference of bio-impedance changes between 25 kHz and 50 kHz was statistically significant (p<0.05) and the difference of bio-impedance changes between 25 kHz and 100 kHz was also statistically significant (p<0.001). These results showed that conductive fabric sensors are more sensitive to measure bio-impedance for evaluating knee joint movements as an excitation frequency decreases.

• 한국소음진동공학회논문집
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• 제14권7호
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• pp.604-611
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• 2004

It is well known that wall impedance essentially determines how sound wave transmits from one place to another. The wall impedance is related with its dynamic properties : for example, the mass, stiffness, and damping characteristics. It is noteworthy, however, that the wall impedance is also function of spatial characteristics of two spaces that is separated by the wall. This is often referred that the wall is not locally reacting. In this paper, we have attempted to see how the acoustic characteristics of the two spaces is affected by various structure parameters such as density, applied tension, and a normalized length of the wall. Calculations are conducted for two different modally reacting boundary conditions by modal expansion method. The variation of the Helmholtz mode and the structural-dominated mode are analyzed as the structure parameters vary. The displacement distribution of the structure, pressure and active intensity of the inside and outside cavity are presented at the Helmholtz mode and the structure-dominated mode. It is shown that the frequency characteristics are governed by both structure-and fluid-dominated mode. The results exhibit that the density of the structure is the most sensitive design parameter on the frequency characteristics for the coupling system as we could imagine in the beginning. The Helmholtz mode frequency decrease as density increases. However. it increases as applied tension and an opening size increase. The bandwidth of the Helmholtz mode is mainly affected by density of the structure and its opening size.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.694-696
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• 2005

Although DC ground resistance is a good index of grounding performance for grounding electrodes, it does not reflect the grounding performance during transient state. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute index due to its dependence on impulse current shape. In this paper, ground impedance characteristics of ground electrodes has been measured in frequency domain ranging from 1 Hz to hundreds of kHz. Equivalent circuit models and transfer function models of the ground rod have been identified from the measured values of ground impedance in frequency domain.

• 한국컴퓨터정보학회논문지
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• 제9권4호
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• pp.93-97
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• 2004

본 논문에서는 수분센서용으로 적합한 구조의 안테나로 소형 도체면 구조의 개루우프 안테나를 모델로 제시하고, 그 동작특성을 모멘트법을 이용하여 수치해석하였다. 수치해석 결과 동작주파수 $300{\sim}500[MHz]$ 대역에서 안테나의 파라미터 값들의 변화에 따라 입력임피던스는 $50[{\Omega}]$으로 정합시킬 수 있었으며, 또한 개루우프 반경, 높이, 폭은 안테나의 공진주파수를 변화시키는 파라미터로 작용하였으며, 부하로 사용되는 인덕턴스 값은 안테나의 입력임피던스를 조절할 수 있는 파라미터로 작용하고 있음을 알 수 있었다.