• The Journal of the Acoustical Society of Korea
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• v.28 no.2E
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• pp.51-59
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• 2009

Mutual radiation impedance becomes more important in the design and analysis of acoustic transducers for higher power, better beam pattern, and wider bandwidth at low frequency sonar systems. This review paper focused on literature survey about the researches of mutual radiation impedance in the acoustic transducer arrays over 60 years. The papers of mutual radiation impedance were summarized in terms of transducer array structures on various baffle geometries such as planar, cylindrical, spherical, conformal, spheroidal, and elliptic cylindrical arrays. Then the computation schemes of solving conventional quadruple integral in the definition of mutual radiation impedance were surveyed including spatial convolution method, which reduces the quadruple integral to a double integral for efficient computation.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1617-1618
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• 2015

This paper analyzed catenary impedance characteristics of relays installed in substation and sectioning post to protect power feeding circuit in the extended power feeding conditions. For this, we modelled AT feeding system using PSCAD/EMTDC and calculated catenary impedance. The relay installed in substation calculated catenary impedance of the extended power feeding area adding catenary impedance of self protection zone. But, the relay installed in sectioning post calculated catenary impedance of the only protection area. Therefore, we confirmed that the more reliable protection way can be utilized using the relay installed in sectioning post.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.21-26
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• 2007

This paper presents an impedance-based structural health monitoring (SHM) technique considering temperature effects. The temperature variation results in a significant impedance variation, particularly both horizontal and vertical shifts in the frequency domain, which may lead to erroneous diagnostic results of real structures. A new damage detection strategy has been proposed based on the correlation coefficient (CC) between the reference impedance data and a concurrent impedance data with an effective frequency shift which is defined as the shift causing the maximum correlation. The proposed technique was applied to a lab-sized steel truss bridge member under the temperature varying environment. From an experimental study, it has been demonstrated that a narrow cut inflicted artificially to the steel structure was successfully detected using the proposed SHM strategy.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1251-1255
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• 2015

The purpose of this study is to measurement the cardiac output using hand to hand impedance method to provide convenience to user when measuring SV(stroke volume) with the use of ICG(Impedance Cardiography). We suggest the optimized modified formula, which can be applied when using impedance with the use of hand to hand Impedance. To verify this formula, a SV from transthoracic approach and hand to hand approach are compared for the 36 subjects, respectively. The acquired data was analyzed by using LabVIEW 8.6, analysis was implemented by SPSS 12.0. Fine difference was shown by individual. We showed that as a result of analyzing the ICG measurement value on thoracic and hand to hand, the correlation with SV was r=0.716, thereby having indicated the results of regression model in relatively high correlation.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.940-942
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• 2003

This paper describes the possibility of analyzing gait pattern from the variation of the lower leg electrical impedance. This impedance is measured by the four-electrode method. Two current electrodes are applied to the thigh and foot, and two potential electrodes are applied to the lateral aspect, medial aspect, and posterior position of lower leg. We found the optimal electrode position for knee and ankle joint movements based on high correlation coefficient, least interference, and maximum magnitude of impedance change. From such features of the lower leg impedance, it has been made clear that different movement patterns exhibit different impedance patterns and impedance level.

• Structural Monitoring and Maintenance
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• v.9 no.3
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• pp.221-235
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• 2022

Among nondestructive damage detection methods, impedance-based methods have been recognized as an effective technique for damage identification in many kinds of structures. This paper proposes a method to detect cracks in metal structures by combining electro-mechanical impedance (EMI) responses and artificial neural networks (ANN). Firstly, the theories of EMI responses and impedance-based damage detection methods are described. Secondly, the reliability of numerical simulations for impedance responses is demonstrated by comparing to pre-published results for an aluminum beam. Thirdly, the proposed method is used to detect cracks in the beam. The RMSD (root mean square deviation) index is used to alarm the occurrence of the cracks, and the multi-layer perceptron (MLP) ANN is employed to identify the location and size of the cracks. The selection of the effective frequency range is also investigated. The analysis results reveal that the proposed method accurately detects the cracks' occurrence, location, and size in metal structures.

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.6
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• pp.717-729
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• 2013

Bioelectrical Impedance Analysis (BIA) is a non-invasive and low-cost technique that estimates body composition based on the distribution of water and electrolytes in the body by analyzing body's electrical responses to source voltages. In this work, we carried out a systematic literature review on BIA researches in traditional East Asian medicine (TEAM). For comparison, firstly we introduced the concept and principle of BIA, and offered a general overview of research trends in western medical perspectives. We searched through the databases of Oriental Medicine Advanced Searching Integrated System and DataBase Periodical Information Academic for the articles published between 1994 and 2013, with keywords such as 'BIA', 'bioelectrical impedance' and 'impedance'. Among the rough-searched 274 articles, we finally selected 21 articles appropriate to the intended research field. The selected articles were categorized into diagnosis in Sasang medicine, impedance analysis in meridian system, and change of body composition after taking herbal medicine. We found that most of BIA researches in TEAM were preliminary and remained in the peripheral levels which is far behind the western medical research activities. Therefore, more efforts are needed to study BIA in association with major subjects such as pattern identification or physiological/pathological phenomena. In addition, methodological breakthrough of BIA is possible by applying the diagnostic concepts of the TEAM in relation to the balance of Qi and Blood.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.472-477
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• 2013

This paper carried out the comparative analysis on ground impedance of a carbon block and a copper rod. Two types of grounding electrode were compared ; a carbon block (L : 1 m, ${\Phi}$ : 245 mm) buried at a depth of 0.8 m and a three-linked copper rod (L : 1 m, ${\Phi}$ : 10 mm) of equilateral triangles with 1 m spacing. Ground impedance depending on applied current source was evaluated by the application of a sine wave current with 60 Hz ~ 3.5 MHz, a fast-rise pulse with rising time of 200 ns, a standard lightning impulse of $8/20{\mu}s$ and a 600 Hz square wave. Ground impedance for both electrodes were almost the same value below 100 kHz, and increased rapidly afterwards. The maximum ground impedance appeared $400{\Omega}$ at around 1.5 MHz. Ground impedance of the carbon block was lower at the square wave and was higher at fast-rise pulse than that of the copper rod. Also, ground impedance as ages showed no difference for the last 8 months. From the results, it is likely that ground performance for both electrodes shows no difference against commercial frequency and lightning impulse current, while the copper rod shows better performance against a fast-rise pulse with rise-time of a few hundred ns.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.99-105
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• 2012

This paper deals with the experimental results of the frequency-dependent resultant ground impedance of vertical ground electrodes installed with a regular n-polygon. In order to propose an effective method of installing the vertically-driven multiple ground electrodes used to obtain the low ground impedance, the resultant ground impedance of ground electrodes installed with a regular n-polygon were measured as functions of the number of ground electrodes and the frequency of test currents and the results were discussed based on the potential interferences among ground electrodes. As a consequence, the effect of potential interference on the resultant ground impedance of vertical ground electrodes is frequency-dependent and it is significant in the low frequency of a few hundreds [Hz]. The resultant ground impedance of multiple vertical ground electrodes is not decreased in linearly proportion to the number of ground electrodes due to the overlapped potential interferences. Also the distributed-parameter circuit model considering the potential interference, the frequency-dependent relative permittivity and resistivity of soil was proposed. The simulated results of the frequency-dependent resultant ground impedance of multiple vertical ground electrodes are in good agreement with the measured data.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.227-230
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• 2007

In this paper, we have analyzed the change characteristics of induced noise due to the impedance change of the ground in both ends of telecommunication line. As what affects the induced noise, there are power influence or longitudinal transverse voltages and its weighted filtered voltage. In the result of measurement, we can see the noise level change due to the change of the ground impedance, that is, as the ground impedance at either end of the telecommunication line become grower, the noise level is increased, and as the ground impedance at either end of the telecommunication line become smaller, the noise level is decreased. However, we can't define the relation between ground impedance size and PIF in these measurement results, so we will have to carry out the measurement more deeply and more practically with various conditions in environmental viewpoint and/or experimental viewpoint to establish the definition between ground impedance size and PIF.