• Journal of Power Electronics
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• 제16권1호
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• pp.319-328
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• 2016

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

• 반도체디스플레이기술학회지
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• 제10권4호
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• pp.25-29
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• 2011

Emerging demands for rechargeable battery for various applications needs more effective battery management system such as the prediction of the usable time about a battery. Many prediction methods have been suggested but none of them come into bounds of reliability. In this paper, we proposed a new prediction algorithm for the remaining capacity of a rechargeable battery by using the transformed curve based on its impedance. Hardware for monitoring a battery was designed and made. Through a series of experiment, we showed the effectiveness of the proposed prediction algorithm of a battery's remaining capacity.

• 대한의용생체공학회:의공학회지
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• 제23권5호
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• pp.413-418
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• 2002

본 연구에서는 변기에 앉아 있을 때 체성분을 효과적으로 측정할 수 있는 체임피던스 측정기(Bioelectrical Impedance Analyzer, BIA)를 개발하고, 이 시스템으로 정확한 체성분 값을 구할 수 있는 방정식을 도출하였다. 이를 위해 설계한 하드웨어고 건강한 한국인 남·여 181명의 체임피던스 값을 변기에 적합한 전극 부착 위치(손목, 허벅지)에서 획득였다. 같은 피험자를 대상으로 기존의 한국인에게 적용시 정확도의 문제를 내포하는 수중체중법의 Siri 방정식을 modified-Siri 방정식으로 적용함으로서 한국인의 제지방량 표준값을 산출하였다. 이 표준값을 기준으로 임피던스 지수, 체중, 성별로 한국인의 제지방을 예측하는 추정식을 얻었다. 제지방량의 추정값과 표준값 사이의 상관계수(r)는 0.977로 높은 관련성을 나타냈으며, SEE(Standard Error of Estimation)은 2.47kg으로 낮은 오차를 나타냈다(p<0.05). 이는 기존의 전극 부착위치인 손목과 발목을 같은 피험자에 적용하여 체임피던스에 의한 제지방량 추정식을 세울 때, 추정값과 표준값 사이의 상관계수(r = 0.978) 및 SEE(2.43kg)와 큰 차이가 없는 것으로 나타났다. 또한. 이중교차검증(Double Cross Validation)을 통해 실험에 참가하지 않은 피검자에 대한 적용 가능성도 유효한 것으로 나타나 본 논문에서 설계한 체임피던스 분석기와 추정식은 한국인의 제지방량을 산출하는데 적합한 것으로 평가되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.106-109
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• 2008

In this paper, impedance of the chiller foundation for ships is studied by using FEM and prediction is compared to measurements. Small and medium weight hammer are used to cover high and low frequency ranges in impedance measurements. Comparison shows that measurement and prediction is in good agreement in which coherence is higher than 0.98 for the frequency ranges of 40-50 Hz to 1600 -2000 Hz.

• Journal of Chest Surgery
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• 제28권11호
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• pp.973-976
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• 1995

The assessment method of human body composion by bioelectrical impedance is very simple, safe, rapid and noninvasive. Based on prediction formulas for total body water from bioelectrical impedance, the observed weight loss should be associated with an increase in impedance. However in edematous patients for dialysis, the calculated total body water loss as calculated from impedance were overestimated and significantly higher than the weight loss after dialysis. So determination of impedance were made in 50 edematous patients before, during and after dialysis. Mean weight loss, which was assumed to be only loss of water was 1719$\pm$ 866 gr and mean impedance change was 71.0 $\pm$ 23.0 Ohm under 50kHz. Body weight loss was highly correlated [r>0.81 with the increase in body impedance under variable frequencies[1, 10, 20, 30, 40, 50 kHz . But there were no differences between frequences. In conclusion, clinical application of bioelectrical impedance method is useful for individual edematous patients with new correlation equation[Y=230+26.8X, X;Impedance change, Y;Calculated total body water loss .

• 한국콘텐츠학회논문지
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• 제17권10호
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• pp.94-101
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• 2017

본 연구는 뇌졸중 편마비 환자 24명을 대상으로 마비측과 비마비측의 바이오 임피던스 값을 비교 분석하고자 하는 것이다. 본 연구에서는 2015년 10월부터 11월 까지 뇌졸중으로 진단 받은 편마비환자 24명을 대상으로 하였다. MultiScan 5000을 이용하여 바이오임피던스를 측정하였고 프래딕션마커(Prediction mark), 저항성분(resistance), 리액턴스(reactance), 위상각(phase angle)을 비교분석하였다. 뇌졸중 편마비 환자와 바이오임피던스 값의 비교분석을 위해 뇌졸중 편마비 가 아닌 일반인 6명의 오른쪽과 왼쪽을 비교분석하였다. 뇌졸중 편마비 환자의 마비측과 비마비측 부위에서 임피던스 값을 측정하여 정량화된 수치로 나타낸 결과 뇌졸중 편마비 환자의 마비측과 비마비측의 프래딕션마커(Prediction mark), 리액턴스(reactance), 위상각(phase angle)의 값의 유의한 차이를 보였다(p<0.05). 일반인을 대상으로 오른쪽과 왼쪽의 프래딕션마커(Prediction mark), 리액턴스(reactance), 위상각(phase angle)의 값의 유의한 차이를 보이지 않았다(p>0.05). 본 연구 결과를 통해 뇌졸중 편마비 환자의 마비측과 비마비측의 임피던스값의 유의한 차이가 있다는 것을 알 수 있었고 또한, 이를 통해 임상의 재활치료를 받는 뇌졸중 환자의 치료에 정량화된 수치로 측정할 수 있는 유용한 평가도구로서의 가능성을 제시하였다. 향후 연구에서는 임피던스 분석을 이용하여 뇌졸중환자의 마비측과 비마비측의 분석뿐만 아니라 다양한 대상군, 다양한 신체부위 그리고 재활치료 중재의 효과 등을 측정하는 연구가 필요할 것으로 보인다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1353-1355
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• 1996

This paper presents classification of high impedance fault pattern using linear prediction coefficients. A feature of neutral phase current is extracted by the linear predictive coding. This feature is classified into faults by a multilayer perceptron neural network. Neural network successfully classifies test data into three faults and one normal state.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.344-348
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• 2007

The acoustic liner has been used for the suppression of noise. The impedance characteristics of the acoustic liner are increased by the incident pressure. For the estimation of the acoustic liner on the incident acoustic pressure effect, the modified impedance model is suggested on the basis of the GE impedance prediction model. The modified impedance model is originated from the 3 parameter impedance model, and extended to the incident pressure parameter. The modified model is applied on the simple duct analysis with variant source pressure. Through the computation, it is observed that the fore directivity patterns of the duct are varied by the incident SPL level.

• Corrosion Science and Technology
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• 제5권1호
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• pp.33-38
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• 2006

Current coating practice requires the thickness of anti-corrosion organic coatings to be over $250{\mu}m$ for immersion parts of ships and offshore structures and the corrosion resistance of these coatings has been evaluated by destructive and qualitative analysis. Recently, Electrochemical Impedance Spectroscopy(EIS) method has been employed, as an alternative, to evaluate corrosion resistance of organic coatings. This method is characterized as being nondestructive, reproducible, and quantitative in evaluating aging of organic coatings. In this study, EIS method was adopted to quantitatively and effectively select the coating systems having optimized protective performance. Evaluations of several epoxy and epoxy/polyurethane coating systems typically used for ships and offshore structures were carried out in wet($50^{\circ}C$, $90^{\circ}C$) and dry(room temp.) environments to accelerate the degradation of the organic coatings. These results were compared with the conventional scribed(scratched) test results. The plausible prediction model for determining the remaining life-time of coating systems was also proposed based on variations of impedance data, FT-IR and $T_g$ measurements results.

• Smart Structures and Systems
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• 제5권1호
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• pp.81-94
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• 2009

A vibration-impedance-based monitoring method is proposed to predict the loss of prestress forces in prestressed concrete (PSC) girder bridges. Firstly, a global damage alarming algorithm using the change in frequency responses is formulated to detect the occurrence of damage in PSC girders. Secondly, a local damage detection algorithm using the change in electro-mechanical impedance features is selected to identify the prestress-loss in tendon and anchoring members. Thirdly, a prestress-loss prediction algorithm using the change in natural frequencies is selected to estimate the extent of prestress-loss in PSC girders. Finally, the feasibility of the proposed method is experimentally evaluated on a scaled PSC girder model for which acceleration responses and electro-mechanical impedances were measured for several damage scenarios of prestress-loss.