• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.113-122
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• 2015

Objectives: The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). Materials and Methods: The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results: Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions: Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.

• Journal of information and communication convergence engineering
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• 제15권2호
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• pp.123-130
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• 2017

The early detection of intravenous (IV) infiltration is necessary to minimize the injury caused by the infiltration, which is one of the most important tasks for nurses. For detecting early infiltration in patients receiving invasive vein treatment, bioelectrical impedance was measured using multi-frequency bioelectrical impedance. The impedance decreased significantly at infiltration, and then decreased gradually over time after infiltration. The relative impedance at 20 kHz decreased remarkably at infiltration, and then gradually decreased thereafter. In addition, the impedance ratio increased temporarily at infiltration and then gradually decreased over time. Furthermore, the impedance at each frequency decreased quantitatively over time. This indicates that IV solution leaking from the vein due to infiltration accumulates in the subcutaneous tissues. Moreover, slopes of log Z vs. log f differently decreased with increasing log f, indicating that the impedance exhibits different responses depending on the frequency.

• Journal of Power Electronics
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• 제18권6호
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• pp.1751-1759
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• 2018

This paper presents parallel-connected inverters to achieve accurate proportional power sharing. Due to line impedance mismatch, reactive power cannot be distributed proportionally when using the conventional $P-{\omega}$ and $\mathcal{Q}-E$ droop. In order to realize reactive proportional power sharing, the ratio of the droop coefficients should be inversely proportional to their power-sharing ratios. Meanwhile, the ratio of the line impedance should be inversely proportional to the desired power-sharing ratio, which is very difficult to be met in practice. In order to deal with this issue, a practical control strategy is presented. By measuring the PCC voltage and using the virtual impedance, the output impedance of individual inverters is reconstructed to counteract the line impedance effect. In order to guarantee system stability, a low pass filter is designed to suppress the bandwidth of the line compensation. Finally, the simulation and experimental results are given to verify the effectiveness of the proposed control strategy.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.603-604
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• 2005

A precise ratio transformer which is used to a ratio arm of a precise impedance measurement bridge at low frequencies was developed. The developed ratio transformer has the ratio taps of 1:1, 2:1, $\cdots$, to 10:1 in order to measure the primary impedance standards by substitution and special winding techniques for 10:1 ratio that is used frequently for impedance build up/down. The calibration results of the transformer has inphase and quadrature error of $0.073\times10^{-6}$ and $0.14\times10^{-6}$ respectively at 1.6 kHz.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.51-52
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• 2022

The electro-mechanical impedance(EMI) behavior of piezoelectric sensor embedded in cement mortar was investigated to assess the setting times. EMI signal was continuously measured for 12 hours by the PZT sensor embedded in cement mortar with different ratio of sand. As a result, the setting times by the penetration resistance test were accelerated as the sand ratio increased. However, the setting times by EMI sensing technique were delayed as the sand ratio increased.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.423-430
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• 2002

A feasibility of a trial test method was evaluated analytically, in which the elastic modulus of a soil deposit was tried to estimate by analyzing dynamic signals measured during conducting the SPT. If there existed a reliable relationship between the impedance ratio of a rod to a soil and the amplitude ratio of a reflected to an incident wave signal at the tip of steel rod contacting the soil surface, it was expected that one could determine the impedance of soil, and then roughly estimate the elastic modulus from the impedance. For a simple rod-soil system, the existence of the relevant relationship was verified in this study by analyzing computed wave signals propagating up and down through the rod. On the basis of these results, thus, a potential of the test method to practical applications could be seen. However, apparent theoretical shortcomings possessed in this approach were also realized since the soil part had an unconfined contact area where contacted with the rod. Therefore, it was concluded that further studies needed to be conducted, in which the reliable theoretical relationship between the impedance and the amplitude ratio as well as the effective contacting soil area contributing to wave reflection should be justified.

• 한국ITS학회 논문지
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• 제11권5호
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• pp.97-102
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• 2012

본 논문에서는 다양한 초고주파 시스템에서 SIR의 다양한 응용을 위해 반파장 공진기로 등가되는 다단 SIR의 입력 임피던스를 통해 각 단의 전기적 길이 및 고차 하모닉 주파수를 계산하였다. 다단 SIR의 크기 감소율은 단수의 증가에 따라 다소 감소하고 임피던스 비에 의해 지배적으로 영향을 받으며, 하모닉 특성은 단수에 따른 변화가 미미하며 임피던스 비가 작아질수록 기본 공진주파수에서 멀어지게 된다. 또한, 다단 SIR의 등가 임피던스는 가장 낮은 특성 임피던스와 가장 높은 특성 임피던스의 기하평균 값을 가지며 Q 값은 반파장 공진기와 유사한 특성을 보였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권5호
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• pp.217-221
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• 2005

A inductive voltage divider(IVD) is widely used as a ratio arm of precise impedance measurement bridges at low frequencies of audio frequency range and a well fabricated IVD has ratio error of $10^{-7}$ order without any calibration. Recently, the order of $10^{-8}$ of the best measurement uncertainty is needed for calibration and maintenance of impedance standards as national standards. In order to achieve that uncertainty, the IVD which is used for a ratio arm of precise impedance measurement bridge should be calibrated within the uncertain of order of $10^{-8}$ For this purpose, a ratio calibration bridge for IVDs has been developed. The measurement uncertainties of both inphase and quadrature of the bridge are analyzed less then $3{\times}10^{-8}$ respectively at 1 kHz and 25 V.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1067-1070
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• 2002

We have examined the impedance characteristics and the battery characteristics of PLI bicell. As results, the impedance of PLI bicell with 62 wt% cathode active material were lower than the other cathode active material content. And the specific resistances of PLI bicell increased with N/P ratio until 1.85. And the impedance of PLI bicell decreased with increased adding amounts of binder. But the rate capability of PLI bicell were not increased with increased adding amounts of binder. PLI bicell with 9.9 wt% binder content were the best rate capability. but the cycleability were not the same results as the rate capability. PLI bicells with cathode with more than 11 wt% binder, their cycleability were almost same, nevertheless they were better cycleability than 9.9 wt% binderl content.

• Journal of Magnetics
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• 제13권2호
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• pp.65-69
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• 2008

The magneto impedance (MI) behaviors of patterned $Co_{30}Fe_{34}Ni_{36}$ microwire were investigated with respect to its shape variation. After preparing $Co_{30}Fe_{34}Ni_{36}$ microwires using electrodeposition and photolithography methods, impedance measurements were conducted to compare the MI ratios of the devices with different aspect ratios. As a result, the anisotropy field and transverse permeability were found to be strongly affected by the aspect ratio of the device. The external field value at the maximum impedance and maximum sensitivity of the device was found to increase with increasing device width, which was attributed to the increased transverse anisotropy with decreasing aspect ratio. While an increase in the thickness also contributed to an increase in the MI ratio, a variation in the thickness not only increased the anisotropic field, but the variation in the MI ratio was as also affected by the skin effect. Conversely, the MI ratios of the present devices were hardly affected by variations in the length. Considering the typical aspect ratios of our devices, it was expected that the length effect would emerge when the aspect ratio was reduced to less than 10. Nevertheless, our results show that for the practical application of MI devices, the MI characteristics can be optimized by tailoring the aspect ratio of the devices.