• Title/Summary/Keyword: Surface Admittance

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Identification of Interior Noise Sources by Using Reconstruction of Active Sources and Surface Admittance (능동음원 및 벽면 어드미턴스의 재구성을 통한 실내 소음원의 정확한 규명 방법)

  • 김영기;김양한
    • Journal of KSNVE
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    • v.8 no.3
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    • pp.435-440
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    • 1998
  • The main objective of this study is to estimate location and strength of sound sources distributed on the surface of an enclosure. Acoustic holography method has been used to identify the sources in an interior sound field. However, it can not completely distinguish between the direct sound field from sources and the reflections from surfaces. The method just reconstructs the entire sound field based on the sound pressure at the finite number of measurement points. In this stduy, a method which estimates only the active sources by using measurements of field pressure and surface admittance is proposed. An in-situ technique to estimate the general boundary condition is also proposed by using acoustic holography, assuming the surfaces are locally reacting.

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System identification and admittance model-based nanodynamic control of ultra-precision cutting process (다이아몬드 터닝 머시인의 극초정밀 절삭공정에서의 시스템 규명 및 제어)

  • 정상화;김상석;오용훈
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10b
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    • pp.1352-1355
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    • 1996
  • The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surface. However, as the accuracy requirement gets tighter and desired surface contours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in addition to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamometer. Based on the parameter estimation of cutting dynamics and the admittance model-based nanodynamic control scheme, simulation results are shown.

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Simulation of PZT monitoring of reinforced concrete beams retrofitted with CFRP

  • Providakis, C.P.;Triantafillou, T.C.;Karabalis, D.;Papanicolaou, A.;Stefanaki, K.;Tsantilis, A.;Tzoura, E.
    • Smart Structures and Systems
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    • v.14 no.5
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    • pp.811-830
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    • 2014
  • A numerical study has been carried out to simulate an innovative monitoring procedure to detect and localize damage in reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) unidirectional laminates. The main novelty of the present simulation is its ability to conduct the electromechanical admittance monitoring technique by considerably compressing the amount of data required for damage detection and localization. A FEM simulation of electromechanical admittance-based sensing technique was employed by applying lead zirconate titanate (PZT) transducers to acquire impedance spectrum signatures. Response surface methodology (RSM) is finally adopted as a tool for solving inverse problems to estimate the location and size of damaged areas from the relationship between damage and electromechanical admittance changes computed at PZT transducer surfaces. This statistical metamodel technique allows polynomial models to be produced without requiring complicated modeling or numerous data sets after the generation of damage, leading to considerably lower cost of creating diagnostic database. Finally, a numerical example is carried out regarding a steel-reinforced concrete (RC) beam model monotonically loaded up to its failure which is also retrofitted by a CFRP laminate to verify the validity of the present metamodeling monitoring technique. The load-carrying capacity of concrete is predicted in the present paper by utilizing an Ottosen-type failure surface in order to better take into account the passive confinement behavior of retrofitted concrete material under the application of FRP laminate.

Design of multi-layered surface plasmon resonance sensors using optical admittance method and evolution algorithm (광학 어드미턴스 기법과 진화 알고리즘 기법을 이용한 다층 표면 플라즈몬 공명 센서의 설계)

  • Jung, Jae-Hoon;Lee, Seung-Ki
    • Journal of Sensor Science and Technology
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    • v.14 no.6
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    • pp.402-408
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    • 2005
  • This paper describes the optimal design of a multi-layered surface plasmon resonance sensors to meet various specifications and improve some physical parameters. Dip 3 dB bandwidth and depth were chosen as design parameters and the objective function was the norm of the difference between design parameters and target values. The design variables are thicknesses of each layer and to obtain the design parameters, the optical admittance method was employed. The (1+1) evolution strategy was employed as an optimization tool. By applying the proposed optimization procedure to a 3-layered sensor, the optimized design variables considerably improved the 3 dB bandwidth by 4.8 nm and the dip depth by 1.1 dB.

Study of surface state density of hydrogenated amorphous silicon thinfilm transistors by admittance spectroscopy

  • Hsieh, Ming-Ta;Chang, Chan-Ching;Chen, Jenn-Fang;Zan, Hsiao-Wen;Yen, Kuo-Hsi;Shih, Ching-Chieh;Chen, Chih-Hsien;Lee, Yeong-Shyang;Chiu, Hsin-Chih
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08a
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    • pp.904-907
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    • 2007
  • We reported a simplified circuit model to investigate the interface states and the quality of a-Si film based on a MIS structure using admittance spectroscopy. The model can be employed easily to monitor the fabrication process of thin-film transistor and to obtain the important parameters.

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Admittance Model-Based Nanodynamic Control of Diamond Turnning Machine (어드미턴스 모델을 이용한 다이아몬드 터닝머시인의 극초정밀 제어)

  • 정상화;김상석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1996.04a
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    • pp.49-52
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    • 1996
  • The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface contours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining processprohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normalto the face of the workpice can be filterd through an appropriate admittance transfer function to result in the estimated depth of cut. This can be compared to the desired depth of cut to generate the adjustment cotnrol action in addition to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. Based on the empirical data of the cutting dynamics, simulation results are shown.

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Measurement Technique of Membrane Fouling in Processes Utilizing Ion-Conducting Polymer Membranes (이온전도성 고분자막 활용 공정에서의 막 오염 현상 측정 기술)

  • Han, Soo-Jin;Park, Jin-Soo
    • Membrane Journal
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    • v.27 no.5
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    • pp.434-440
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    • 2017
  • Electrical impedance spectroscopy is used to detect membrane fouling in-situ in reverse electrodialysis. The impedance data for the AMX membrane being fouled in the reverse electrodialysis are plotted and analyzed by Nyquist and admittance method. The meaningful graphical analyses for the fouling phenomena could be done by both Nyquist and admittance method. In addition, the unstable initial fouling stage was identified by the admittance data with high standard deviation, and the structural change of the fouling layer formed at the surface of anion-exchange membranes with the operation time of reverse electrodialysis was also detected.

320-Channel Multi-Frequency Trans-Admittance Scanner(TAS) for Anomaly Detection (도전율 및 유전율이 다른 병소의 검출을 위한 320-채널 다주파수 Trans-Admittance Scanner(TAS))

  • Oh, Tong-In;Lee, Min-Hyoung;Kim, Hee-Jin;Woo, Eung-Je
    • Journal of Biomedical Engineering Research
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    • v.28 no.1
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    • pp.84-94
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    • 2007
  • In order to collect information on local distribution of conductivity and permittivity underneath a scan probe, we developed a multi-frequency trans-admittance scanner (TAS). Applying a sinusoidal voltage with variable frequency on a chosen distal part of a human body, we measure exit currents from 320 grounded electrodes placed on a chosen surface of the subject. The electrodes are packaged inside a small and light scan probe. The system includes one voltage source and 17 digital ammeters. Front-end of each ammeter is a current-to-voltage converter with virtual grounding of a chosen electrode. The rest of the ammeter is a voltmeter performing digital phase-sensitive demodulation. Using resistor loads, we calibrate the system including the scan probe to compensate frequency-dependent variability of current measurements and also inter-channel variability among multiple. We found that SNR of each ammeter is about 85dB and the minimal measurable current is 5nA. Using saline phantoms with objects made from TX-151, we verified the performance of the lesion estimation algorithm. The error rate of the depth estimation was about 19.7%. For the size estimate, the error rate was about 15.3%. The results suggest improvement in lesion estimation algorithm based on multi-frequency trans-admittance data.

Electric Properties of LB Films using Impedance Analysis of Quartz Crystal (수정진동자의 임피던스 해석에 의한 LB막의 전기적 특성)

  • Jin, Cheol-Nam;Kim, Gyeong-Hwan;Yu, Seung-Yeop;Gwon, Yeong-Su
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.7
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    • pp.503-507
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    • 1999
  • Quartz crystal in contact with viscoelastic medium was described directly in terms of the electrical equivalent circuit of the system. Stearic acid was used as viscoelastic medium and deposited on the surface of quartz crystal using the Langmuir-Blodgett(LB) method. Impedance properties of quartz crystal coated with LB films which were investigated by using admittance diagram and $Ζ-\theta$ plot a method of impedance analysis. When stearic acid LB film was deposited on the surface of quartz crystal, resonant frequency of quartz crystal was changed about 100 Hz/layer. This result illustrates the ability of the sensor system to detect small amounts of special gas in air.

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Dielectric relaxation properties in the lead scandium niobate

  • Yeon Jung Kim
    • Journal of the Korean institute of surface engineering
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    • v.56 no.4
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    • pp.227-232
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    • 2023
  • In this study, complex admittance as a function of temperature and frequency was measured to analyze the important relaxation properties of lead scandium niobate, which is physically important, although it is not an environmentally friendly electrical and electronic material, including lead. Lead scandium niobate was synthesized by heat treating the solid oxide, and the conductance, susceptance and capacitance were measured as a function of temperature and frequency from the temperature dependence of the RLC circuit. The relaxation characteristics of lead scandium niobate were found to be affected by contributions such as grain size, grain boundary characteristics, space charge, and dipole arrangement. As the temperature rises, the maximum admittance and susceptance increase in one direction, but the resonance frequency decreases below the transition temperature but increases after the phase transition.