• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.147-153
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• 2008

Improvement of the selectivity of nonenzymatic glucose based on mesoporous platinum ($H_1$-ePt) by using A.C. impedance is reported. The idea of the present work is based on the novel effect of the mesoporous electrode that the apparent exchange current due to glucose oxidation remarkably grows although the reaction kinetics on the surface is still sluggish. It is expected that the enlarged apparent exchange current on the mesoporous electrode can raise the sensitivity of admittance in A.C. impedance to glucose concentration. At a low frequency, A.C. impedance could become more powerful. The admittance at 0.01 Hz is even more sensitive to glucose than to ascorbic acid while amperometry exhibits the inverse order of sensitivity. This is the unique behavior that is neither observed by A.C. impedance on flat platinum electrode nor obtained by amperometry. The study shows how the combination of A.C. impedance and nano-structured surface can be applied to the detection of sluggish reaction such as electrochemical oxidation of glucose.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.154-160
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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 cnotours 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 dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn 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 dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.188-191
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• 2005

Taguchi method is used to determine the optimal configuration of PZT (Lead Zirconate-Titanate) patch on the host structure for improving the performance of piezoelectric shunt system. The charges generated on the surface of PZT patch are selected to be the objective function in the Taguchi method. Full three dimensional finite element models are used to simulate vibration of smart panel and to obtain the admittance of the piezoelectric shunt system. Using Taguchi method in Minitab, the optimal model is obtained. The experiment with piezoelectric shunt circuit is performed to verify the validity of the optimal model comparing with initial model.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1522-1524
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• 1997

In this paper, we measured the impedence |Z| and phase angle $\theta$ using the Impedence Analyzer (Hp 4192A). When frequency is varied to produce resonance, the curves(admittance diagram) are obtained. The resonant frequency is obtained also. We analyzed the operating characteristics of quartz crystal coated with sensitive LB films. That is the size of circle in the admittance diagram is decreased as to coat sensitive LB films on the quartz crystal. The resonant frequency and resistance is changed with coating on the surface.

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.59-66
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• 1991

Resonance angle and optimum thinckness of various thin metal films for surface plasmon resonance were calculated using an admittance diagram and optical constants and thickness of thin Ag films and Al films were determined by fitting the measured reflectance of surface plasmon resonance. Two wavelengths of an Ar ion laser were employed to select the unique optical constants which have the same thickness at two wavelengths. Also, when these films were exposed to the air, the shift of surface plasmon resonance was measured and the optical constants of modified thin films were determined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1061-1066
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• 2002

This study proposes an analytic method that determines an optimal arrangement of absorptive materials on an enclosure surface. Under the optimal arrangement, a quiet zone in the enclosure has the minimum $\varepsilon$$\sub$p/ (acoustic potential energy density). The proposed method has been implemented by using a BEM simulation and a genetic algorithm. The BEM simulation evaluates the $\varepsilon$$\sub$p/ under the prescribed arrangement of the absorptive materials. The genetic algorithm searches the optimal arrangement by referring the ep evaluated from the BEM simulation. In the BEM simulation, the absorptive material arrangement is expressed as a vector, which is denoted as in absorptive material arrangement (AMA) vector. Besides, an admittance vector of which elements are admittances of available absorptive materials and an AMA matrix that transforms the admittance vector into the AMA vector are defined. The AMA matrix is also used as a chromosome in the genetic algorithm so that it functions to relate the BEM simulation to the genetic algorithm. As a verification example, the proposed method is applied to make the quiet zone in a parallelepiped enclosure.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.501-508
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• 2007

This paper presents the feasibility of using electromechanical impedance based active sensing technique for nondestructive strength gain monitoring of early-age concrete by employing piezoelectric lead-zirconate-titanate (PZT) patches on concrete surface. The strength development of early age concrete is actively monitored by performing a series of experiments on concrete specimens under moist curing condition. The electrical admittance signatures are acquired for five different curing ages and compared with each other. The resonant frequency shifts of PZT patches with increasing days is observed which is on account of additional stiffening due to strength gain of concrete during curing and level of stiffening being related to strength obtained from compression tests on companion cylinder specimens. The proposed approach is found to be suitable for monitoring the development of compressive strength in early-age concrete. It is also observed in this study that root mean square deviation (RMSD) in admittance signatures of the PZT patches can also be used as an indicator of concrete strength development.

• Smart Structures and Systems
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• v.4 no.1
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• pp.35-46
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• 2008

In this paper the authors address the problem of comparing two different smart damping techniques using the numerical modelling of the electro-mechanical impedance for plate structures partially treated with active constrained layer damping treatments. The paper summarizes the modelling procedures including a finite element formulation capable of accounting for the observed behaviour. The example used is a smart cantilever plate structure containing a viscoelastic material (VEM) layer sandwiched between a piezoelectric constrained layer and the host vibrating plate. Comparisons are made between active constrained layer and active damping only and based on the resonance frequency amplitudes of the electrical admittance numerically evaluated at the surface of the piezoelectric model of the vibrating structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.171-174
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• 1998

Quartz crystal in contact with viscoelastic medium is described directly in terms of the electrical equivalent circuit of the system. Stearic acid is 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 and the possibility of applying the technique to chemical sensing introduced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.688-692
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• 2003

For high voltage operation, a new type of piezoelectric transformer using radial vibration of disk, poled with the same direction was proposed. The piezoelectric ceramics was composed to PZT-PMN-PSN. The diameter and thickness of a disk type piezoelectric transformer were 45［mm］and 4［mm］, respectively The surface ratio of driving electrode and generating electrode of the piezoelectric transformer was 2 : 1. The resonance characteristics of input admittance, step-up voltage ratio and power transmission efficiency of the piezoelectric transformer were measured by varying the load resistance(0.1∼70［kΩ］). As a result, both resonance frequency and step-up voltage ratio increased with increasing load resistance. The step-up voltage ratio was reached more than 60 times under no load resistance. The maximum efficiency of 97% at load resistance of 2kΩ was obtained.