• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.205-207
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• 2003

The line impedance is important data that is applied in all analysis fields of electric power system like power flow, fault current, stability and relay calculation etc. Usually, impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding wires, and earth resistance. Therefore, if there is a fault in cable system, these terms will severely be caused much error to calculation of impedance. Therefore, the line impedance were measured for this study in an actual power system of underground cables, and were analyzed by a generalized circuit analysis program EMTP for comparison with the measured value. These analysis result is considered to become foundation of impedance calculation for underground cable.

• Journal of Magnetics
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• 제21권1호
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• pp.29-34
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• 2016

Nd-doped $BiFeO_3$ materials were synthesized via a sol-gel method. The crystal structure, magnetic properties, and complex impedance spectroscopy of multiferroic $Bi_{1-x}Nd_xFeO_3$ (BNFO) materials were investigated by X-ray diffraction (XRD), Raman scattering, vibrating sample magnetometer (VSM), and complex impedance spectroscopy. Our results show that the lattice crystal constants (a, c) and the ratio c/a of BNFO materials decreased with increasing Nd concentration. All samples exhibited weak ferromagnetism at room temperature, and the magnetization of samples was enhanced by the presence of $Nd^{3+}$ ions. There was an enhancement in the spontaneous magnetization of BFO with increasing Nd concentration, which is attributable to the collapse of the spin cycloid structure.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권4호
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• pp.158-163
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• 2002

The pulsed Power system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNOx/DeSOx power system, often generator, etc. In this paper, we study EMTP analysis and characteristics of critical voltage and load in impedance on various electrode length of pulse corona. To obtain a stable pulse voltage, we designed a compact pulse generator switched MOSFET and tested their characteristics by adjusting electrode length and pulse repetition. As a re sult, critical voltage of pulse corona and load impedance on increasing electrode length were decreased. These results indicate we can control critical voltage of pulse corona and suppress arc discharging between two electrodes.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권2호
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• pp.74-80
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• 2000

In this paper, we present a control method of mobile power assist systems. Most of mobile power assist systems have a heavy base for preventing easy tumbling, so continual movement of the base during operations causes high energy consumption and gives the high risk of human injury. Furthermore, the slow dynamics of the base limits the frequency bandwidth of the whole system. Thus we propose a cooperation control method of the mobile base and manipulator, which removes the unnecessary movements of the base. In our scheme, the mobile base does not move until the center of gravity(C.G) of the system goes outside a safety region. When C.G. reaches the boundary of the safety region, the base starts moving to recover the manipulator's initial configuration. By varying the parameters of a human impedance controller, the operator is warned by a force feedback that C.G. is on the marginal safety region. Our scheme is implemented by assigning a nonlinear mass-damper-spring impedance to the tip of the manipulator. Our scheme is implemented by a nonlinear mass-spring impedance to the tip of the manipulator. The experimental results show the efficacy of the proposed control method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1873-1875
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• 1999

The effects of electrode and matrix in the PAFC were investigated using AC-impedance spectroscopy. The performance of PAFC was determined by changing external electronic load. AC impedance measurement was carried out as functions of phosphoric acid impregnation temperature. operating temperature and matrix coating method using various cathodes ; 20%Pt/C, 20%Pt-Ni/C, 20%Pt-Co-Ni/C, 10%Pt-Fe-Co/C, and 20%Pt-Fe-Co/C From the analysis of measured impedance data, the interfacial resistance decreased with increasing operating temperature. and with decreasing impregnation temperature. As compared with the alloy catalysts, Pt catalyst showed a lower interfacial resistance. This consist with the cell performance.

• 대한의용생체공학회:의공학회지
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• 제31권5호
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• pp.375-384
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• 2010

The purpose of this study is to determine whether there is a correlation between the segmental bio-impedance measurement with the frequency modulations and the life-style disease of obesity. An obesity is not simply the factor for estimating the life-style disease of obesity, but also the risk factor occurring. There are many methods (BMI, WHR, Waist, CT, DEXA, BIA, etc.) for measuring a degree of obesity; the bio-impedance measurement is more economic and more effective than others. The physical examination, the blood test, the medical imaging diagnosis and the bio-impedancemeasurementswithmultiple frequencies for each body parts have been conducted for 77 people. The estimated value has been calculated through a segmental bio-impedance model based on multi-frequency that was created to reflect the highest correlation by analyzing correlation with linear regression analysis method for the measured bio-impedance and the risk factors. Then we compared with the clinical diagnosis. In case of high level cholesterol, low HDL-C and high LDL-C for life-style disease, the sensitivity is 80~100%and the specificity is 83~100%. This study has shown conclusively that bio-impedance can be a possible predictor to analyze the disease risk rate of population and individual health maintenance. And also the multi-frequency segmental bio-impedance can be used as early predictor to estimate the life-style disease of obesity.

• 한국전자파학회논문지
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• 제10권5호
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• pp.663-671
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• 1999

본 연구에서는 GaAs MESFET의 게이트-소오스 캐패시턴스($C_{gs}$)와 드레인-소오스 전류($I_{ds}$)의 비션형성에 의한 이득감소(Gain Compression) 및 위상왜곡(Phase Distortion)특성을 알아보고, 이를 최소화 할 수 있 는 소오스 및 부하 임피던스의 조건에 대해 조사하였다. 먼저 Volterra - Series 분석을 통하여, $C_{gs}(V_{gs})$와 $I_{ds}(V_{gs})$의 비선형특성을 조사하고, 각각의 비선형성분이 상호 소멸되는 소오스 및 부하 임피던스의 조건에서, 전체소자의 비선형성이 최소화 됨을 얄아보았다. 그리고 소오스 및 부하측정(Source, Load Pull)을 통하여 출 력전력값에 따라 최적의 선형성이 나오는 입출력 임피던스값을 찾고, Volterra-Series에서 구한 이론적인 결과와 비교 및 분석을 행하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 추계학술대회 논문집
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• pp.26-26
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• 2007

To attest zinc electrodeposition mechanism, electric circuit models for zinc electro reaction on Pt electrode are analyzed from the a.c. impedance data. Electrochemical reactions of zinc deposition are composed of the three electrochemical reactions on the cathode layer and of the induced electrode layers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.461-461
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• 2010

For a low dielectric constant inter-metal dielectric application, the low-k SiCOH film with a dielectric constant of 2.8-3.2 has been deposited by plasma-enhanced chemical vapor deposition with decamethylcyclopentasiloxane, cyclohexane, and helium which is carrier gas. In this work, we investigated chemical deposition rate, dielectric constant, characterization of plasma polymer films according to temperature(25C-200C) of substrate and change of component concentration. We measured impedance by using V-I prove during process. From experimental result, deposition rate decrease with increasing temperature. Through real time impedance analysis of chamber, we find corelation between film thickness and impedance by assuming equivalent circuit.

• 한국항해항만학회지
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• 제46권3호
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• pp.179-190
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• 2022

본 연구에서는 실리콘 기판 상에 제작된 3D 결합구조를 가지는 코프레너 선로인 CWP3DCS(coplanar waveguide employing periodic 3D coupling structures) 구조에 대한 특성임피던스와 대역폭특성을 연구하였으며 이를 통해 완전집적형 해양무선통신 반도체 SoC(System on Chip)를 구현하기 위한 수동소자의 개발가능성을 검토하였다. CWP3DCS에 대한 특성임피던스와 대역폭특성을 추출하기 위해서 삽입손실에 대한 측정값을 반영한 measurement-based equation을 유도하였으며, 이 방법의 유효성을 검증하기 위해 전송상수 β와 특성임피던스에 대한 측정값과 measurement-based equation으로부터 추출된 계산값을 비교하였다. 비교 결과에 의하면 특성임피던스와 전송상수 β에 대한 계산값과 측정값의 최대오차는 각각 3.9%와 6.4%의 값을 보여주었다. 본 논문의 연구결과에 의하면, CWP3DCS 구조는 주기적 구조의 길이 LT = 30 ~ 150 ㎛의 범위에서 통과대역이 121 GHz인 광대역 특성을 보여주었으며, 특성임피던스 역시 주파수 의존성이 매우 적은 광대역 특성을 보여주었다. 그리고, 20 ㎛의 선로 폭으로도 20 Ω이하의 낮은 임피던스를 가지는 전송선로의 구현이 가능하였으며, 동일한 임피던스를 가지는 기존 전송선로의 선로 폭 3mm에 비해 선로 폭이 크게 감소하였다. 그리고, 주기적 구조의 길이 LT값을 조정함으로써 원하는 특성임피던스 값을 가지는 구조를 반도체 기판 상에 용이하게 구현할 수 있음을 알 수 있었다. 상기 결과로부터 CWP3DCS 구조는 완전집적형 무선통신 반도체 SoC용 정합 및 수동소자로써 유용하게 사용될 수 있음을 알 수 있었다. 본 논문은 3D 결합구조를 가지는 코프레너 선로인 CWP3DCS의 대역폭에 대한 최초의 연구이다.