• 소음진동
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• 제7권5호
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• pp.781-787
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• 1997

A new method is presented to determine two fundamental acoustic quantities of sound-absorbing materials such as characteristic impedance and propagation constant. In this study, the surface acoustic impedances of sound-absorbing materials are measured using the impedance tube and the anechoic chamber to determine the above acoustic quantities. The measured results are given for two typical sound-absorbing materials(glass wool and urethane foam) int the frequency range between 150 and 1, 600 Hz. The results are verified by other two known methods, which are Smith & Parrott method and Utsuno et al. method. The absorption coefficients calculated from the empirical models(Miki model for glass wool and Jung model for urethane foam) and two quantities by present method are in good agreement with the measured values.

• 한국건설순환자원학회논문집
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• 제5권4호
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• pp.474-480
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• 2017

본 연구에서는 전기 임피던스 분광법을 이용하여 시멘트계 재료의 응결 시점을 평가하였다. 시멘트 페이스트 시편을 제작한 후 전기노드를 매립하여 전기 임피던스 응답 스펙트럼의 변화를 연속적으로 모니터링하였으며, 이와 동시에 간이단열시험을 통한 수화온도측정과 비카트침 시험을 함께 수행하였다. 전기 임피던스 분광법에서는 시멘트 페이스트의 수화와 동시에 컨덕턴스가 서서히 증가하는 경향을 나타냈다. 이후, 특정시점에 이르러 컨덕턴스는 급격히 감소하는 경향을 나타냈으며, 이후 또다른 특정시점에서 완만하게 감소하는 경향을 나타냈다. 이러한 특정 시점은 간이단열시험 및 비카트침 시험에 의해 측정된 응결시점과 부합하는 것으로 나타났다. 이를 통해 전기 임피던스 분광법을 이용하여 시멘트계 재료의 응결을 효과적으로 모니터링하는 것이 가능하리라 판단된다.

• 한국안전학회지
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• 제29권5호
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• pp.116-122
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• 2014

Assessment of setting process of concrete is important as it provides useful information to schedule concreting work in construction site. Electrical impedance measurement method, which utilizes the change of electrical resistance of concrete, has been applied to assess setting process of cement-based materials. However, the applicability of the method has been demonstrated only for cement paste and mortar. The main purpose of this research is to develop the electrical impedance based setting process assessment for concrete. To this end, electrical impedance response model for concrete should be developed in advance since it is essential to estimate the electrical resistance of concrete from measured impedance response. The electrical resistance of concrete is a key parameter for the setting process assessment. In this study electrical impedance responses of the concrete in setting process are measured and analyzed. Thereby, an electrical impedance response model of the liquid state concrete is developed and schematically validated.

• 전력전자학회논문지
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• 제20권6호
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• pp.526-533
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• 2015

A new algorithm is proposed for the estimation of equivalent grid impedance at the point of common coupling of a grid-tie inverter output. The estimated impedance parameter can be used for the improvement of the performance and the stability of the distributed generation system. The estimation error is inevitable in the conventional estimation method because of the axis rotation due to PLL. In the conventional estimation error, the d-q voltage and current are used for the calculation of the impedance with active and reactive current injections. Conversely, in the proposed algorithm, the negative sequence current is injected, and then the negative sequence voltage is measured for the impedance estimation. As the positive and negative sequence current controller is independent and the PLL is based on the positive sequence component only, the estimation of the equivalent impedance can be achieved with high accuracy. Simulation and experimental results are compared to validate the proposed algorithm.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권8호
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• pp.426-432
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• 2004

This paper presents a systematic approach of measurement, modeling and analysis of grounding system impedance in the field of lightning protection system and intelligent power equipments. The measurement and analysis 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 50 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. Although the steady-state ground resistance of the ground rod of 50 m was less than that of the ground rod of 10 m, the ground impedances of the ground rod of 50 m over the frequency range of more than 60 kHz were much greater than those of the ground rod of 10 m. Furthermore, the equivalent circuit model based on the measured data was proposed. and the calculated results were in approximately agreement with the measured data.

• Smart Structures and Systems
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• 제28권6호
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• pp.761-777
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• 2021

This study presents a numerical investigation on the sensitivity of electromechanical (EM) impedance responses to inner damaged concrete of a prestressed anchorage zone. Firstly, the Ottosen yield criterion is selected to simulate the plasticity behavior of the concrete anchorage zone under the compressive loading. Secondly, several overloading cases are selected to analyze inner damage formations in the concrete of the anchorage zone. Using a finite element (FE) model of the anchorage zone, the relationship between applied forces and stresses is analyzed to illustrate inner plasticity regions in concrete induced by the overloading. Thirdly, EM impedance responses of surface-mounted PZT (lead-zirconate-titanate) sensors are numerically acquired before and after concrete damage occurrence in the anchorage zone. The variation of impedance responses is estimated using the RMSD (root-mean-square-deviation) damage metric to quantify the sensitivity of the signals to inner damaged concrete. Lastly, a novel PZT skin, which can measure impedance signatures in predetermined frequency ranges, is designed for the anchorage zone to sensitively monitor the EM impedance signals of the inner damaged concrete. The feasibility of the proposed method is numerically evaluated for a series of damage cases of the anchorage zone. The results reveal that the proposed impedance-based method is promising for monitoring inner damaged concrete in anchorage zones.

• International Journal of Internet, Broadcasting and Communication
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• 제15권3호
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• pp.129-134
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• 2023

Although the use of batteries is rapidly increasing worldwide to improve carbon neutrality and energy efficiency, performance degradation due to the increase in the number of uses is inevitable as it is a finite resource that can be applied according to capacity and specifications. Deterioration and failure of batteries are recognized as important problems in various applications using batteries, including electric vehicles. In order to solve these problems, a diagnostic technology capable of accurately predicting battery life and grasping state information is required, but it is difficult in a non-linear form due to internal structure or chemical change. In this paper, the factors that generally cause battery performance change are directly applied to check whether there are external changes and impedance changes in the battery, and to analyze whether they affect battery life. Impedance change trends and result values were confirmed using a universal impedance spectroscopy method and a self-developed internal impedance measurement method. The results did not significantly affect the impedance change trend. It was confirmed that the increase in the number of times of battery use was prominent in the impedance change trend.

• 대한전자공학회논문지
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• 제19권6호
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• pp.1-8
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• 1982

이 논문은 하중나무에 의한 래더형 회로의 새로운 해석 방법을 제안한다. 종래의 정보 구조를 나타내는 나무와는 달리 가지의 하중를 임피이던스 Z와 어드미턴스 Y로 하고, 그의 양단의 마디를 전압과 전류의 짝으로 표시하여 Z와 Y집합의 계층 구조의 나무를 구성한다. 다음에 나무에서 생성 레벨을 정의하고 기준 레벨과 임의의 레벨간을 path함으로써, 구동점 임피이던스, 전달함수, 전달 임피이던스를 계산에 의하지 않고 시각적으로 동시에 구한다. 본 방법에 의하여 가역정리를 유도함으로써 타당성을 입증하고 4단자 정수 및 피이드백, Tr결합 텐덤 회로에도 적용된다. In this paper a new analytic method for Ladder networks by weighted tree is proposed. In contrast to conventional tree concept that represents only information structure, in this paper, a tree with hierarchical structure is established by giving wei체t of impedance Z and admittance Y to branch and representing each node of its branch as a pair of voltage and current. Then, by defining generation level from tree structure and by parsing between standand level and arbitrary level, driving point impedance, transfer function and transfer impedance are simultaneously obtained instead of complex calculation method by inspection. The validity of this method is proved by the reciprocal theorem and this method is applied to four-terminal constants and the feedback network.

• 전기학회논문지
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• 제56권6호
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• pp.1170-1176
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• 2007

The conventional urodynamic monitoring is fulfilled by artificially filling a bladder with saline. Generally. it is difficult to evaluate the physiological functions of the storage and voiding of a bladder. With this aim, we constructed an ambulatory urodynamic monitoring (AUM) system and proposed a novel method estimating abdominal pressure by measuring bio-impedance variations. Our system was clinically evaluated for 10 patients. It turned out to be that as the intensity of the abdomen contraction increased, the amplitude of bio-impedance signal and the RMS value of EMG increased more as compared to those who observed during the rest mode. Also, we determined the optimum electrode pair for estimating the abdominal pressure using bio-impedance method and consequently compared with the conventional methods. Because impedance changes differ from a weight, a height, contractile force, volume of muscle and blood other or whatever of individuals, it was quantified in terms of impedance change, correlation coefficient and SNR Our results showed the optimum electrode pair (1,9) which could detect impedance changes due to the increase of the intensity in the abdominal pressure. The correlation coefficient and quadratic function between the RMS values of EMG and the impedance changes were 0.87 and $y=0.0014x^2+0.0620x+0.6958$, respectively. Thus, our system demonstrated that the abdominal pressure could be measured noninvasively and conveniently by simply estimating bio-impedance values. We propose that this optimum electrode configuration would be useful for the future studies involving the handy measurements of abdominal pressure with our suggested ambulatory urodynamics monitoring system.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.693-696
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• 2006

본 연구에서는 생체 임피던스의 변화를 계측하여 혈류량의 변화를 추정하기 위한 시스템을 구현하였다. 구현된 시스템은 인위적인 압력을 가하여 압력의 변화에 따른 임피던스의 변화량을 측정할 수 있도록 구성하였으며, 크게 압력 측정부와 4 전극법을 이용한 임피던스 측정부로 구분할 수 있다. 압력 측정부는 반도체식 압력센서와 센서의 출력신호를 처리하기 위한 전자회로부로 구성하였고, 임피던스 측정부는 교류 정전류원 회로와 임피던스 신호의 검출을 위한 락인 증폭기로 시스템을 구성하였다. 구현된 시스템의 성능평가를 위하여 표준저항을 이용한 임피던스 측정부의 특성조사 실험을 수행 하였다. 그리고 실제 실험군을 대상으로 임피던스의 계측을 통한 혈류량 변화 추정실험을 수행하였고, 혈류량 변화와 평균 동맥압을 이용한 혈류 저항비를 추정하였다 그 결과 혈류저항비와 혈류량의 변화는 반비례관계를 명확하게 보여 주었으며, 상관분석을 수행한 결과 상관계수가 -0.96776으로 강한 음의 상관관계를 나타내었다.