• Journal of the Korean Society of Safety
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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.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1370-1376
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• 2015

Generally, an autotransformer(AT) feeding system consists of double tracks, up and down, with the trolley wire and feeder wire of the up and down tracks connected in the sectioning post(SP). Consequently, load current or fault current flows on two tracks based on catenary impedance characteristics, making it difficult to estimate catenary impedance accurately. This paper presents a technique for the estimation of catenary impedance using boosting current compensation based on the current division characteristics of an AT feeding system to improve the operation performance of impedance relay. To verify the technique, we model an AT feeding system through a power analysis program (PSCAD/EMTDC) and simulate various operation and fault conditions. Through the simulation, we confirmed that the proposed technique has estimated catenary impedance with a similar degree of accuracy to the actual catenary impedance

• Structural Monitoring and Maintenance
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• 제4권3호
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• pp.237-253
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• 2017

Among various structural health monitoring technologies, impedance-based damage detection has been recognized as a promising tool for diagnosing critical members of civil structures. Since the piezoelectric transducers used in the impedance-based technique should be bonded to the surface of the structure using bonding layers (e.g., epoxy layer), it is hard to maintain the as-built condition of the bonding layers and to reconfigure the devices if needed. This study presents an experimental investigation by using magnetically attached PZT-interface for the impedance-based damage detection in bolted girder connections. Firstly, the principle of the impedance-based damage detection via the PZT-interface device is outlined. Secondly, a PZT-interface attachment method in which permanent magnets are used to replace the conventional bonding layers is proposed. Finally, the use of the magnetic attraction for the PZT-interface is experimentally evaluated via detecting the bolt-loosening events in a bolted girder connection. Also, the sensitivity of impedance signatures obtained from the PZT-interface is analyzed with regard to the interface's material.

• Proceedings of the KIEE Conference
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.399-402
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• 2002

In this study, we constructed a four-channel impedance measurement system including a two-channel goniometer to analyze human arm movement. Impedances and joint angles were simultaneously measured for wrist and elbow movements. As the impedance changes resulting from wrist and elbow movements depended heavily on electrode placement, we determined the optimal electrode configurations for those movements by searching for high correlation coefficients, large impedance changes, and minimum interferences in ten subjects (age: 29+6). Our optimal electrode configurations showed very strong relationships between the wrist joint angle and forearm impedance (correlation coefficient = 0.95+0.04), and between the elbow joint angle and upper arm impedance (correlation coefficient = -0.98+0.02). Although the measured impedances changes of the wrist (1.1+1.5 ohm) and elbow (-5.0+2.9 ohm) varied among individuals, the reproducibilities of wrist and elbow impedance changes of five subjects were 5.8+1.8 % and 4.6+1.4 % for the optimal electrode pairs, respectively. We propose that this optimal electrode configuration would be useful for future studies involving the measurement of accurate arm movements by impedance method.

• Smart Structures and Systems
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• 제15권1호
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• pp.41-55
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• 2015

This study proposes a laser based impedance measurement system and impedance based pipe corrosion and bolt-loosening monitoring techniques under temperature variations. For impedance measurement, the laser based impedance measurement system is optimized and adopted in this paper. First, a modulated laser beam is radiated to a photodiode, converting the laser beam into an electric signal. Then, the electric signal is applied to a MFC transducer attached on a target structure for ultrasonic excitation. The corresponding impedance signals are measured, re-converted into a laser beam, and radiated back to the other photodiode located in a data interrogator. The transmitted impedance signals are treated with an outlier analysis using generalized extreme value (GEV) statistics to reliably signal off structural damage. Validation of the proposed technique is carried out to detect corrosion and bolt-loosening in lab-scale carbon steel elbow pipes under varying temperatures. It has been demonstrated that the proposed technique has a potential to be used for structural health monitoring (SHM) of pipe structures.

• 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.

• Proceedings of the KIPE Conference
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.53-56
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• 2000

An Electrical equipment is the noise source which makes a noise. So the optimally designed filter should be inserted in the equipment in order to reduce the noise. The noise source impedance is varied according to the frequency It effects on the CE noise. Knowing the magnitude of its impedance and inserting an EMI filter in the equipment we can estimate the insertion loss of the filter. SO it helpful in designing the EMI filter. The measurement method of a noise source impedance is proposed and verified by experiment.

• Proceedings of the KSR Conference
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1308-1312
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• 2004

Transmission line impedance calculation has been tried for obtaining exact value. The method proposed by Carson contains indefinite complex integral. Although the Carson solution is proposed with power series, the solution is limited and valid at special range of frequency. In this paper, we proposed a simplified Carson solution by analytical method using ground transmission line return current. This method calculate the transmission line impedance easily.

• Journal of the Korean Institute of Telematics and Electronics A
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• 제29A권2호
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• pp.24-32
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• 1992

The impedance matching properties of infinite planar arrays of rectangular waveguides with dielectric plug loading and sheath covering are studied here. The effects of several involved parameters on the impedance matching of the phased array antenna are investigated by calculating the reflection coefficients numerically. The improvement of impedance matching and the appearance of forced surface wave resonances are also discussed.