• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.111-111
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• 2009

In this work, we discuss simulation of surface acoustic wave device using Comsol Multiphysics. The structure SAW device based on piezoelectric thin film aluminum-nitride (AlN) on silicon was simulated. Some parameters of SAW device such as surface velocity, displacement of piezoelectric thin film were evaluated by software. Many modes and shapes of wave are also discussed in this paper. For evaluation physical parameters of AlN piezoelectric layer, the SAW resonator was modeled and simulation results were also compared with experiment results. we simulated arid evaluated the surface Rayleigh wave of AlN thin film on silicon substrate. Results simulation and experiment showed the surface velocity of AlN thin film was about 5200 m/s and shape of surface wave was also displayed. This paper has also proposed as method to study SAW characteristic of piezoelectric thin film and found out measurement values accurately of film such as stiffness matrix, piezoelectric matrix. These values are very important in calculation and design SAW device or MEMS device based on AlN piezoelectric layer.

• ETRI Journal
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• v.31 no.6
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• pp.680-687
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• 2009

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)$O_3$ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm${\times}$20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well-designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.

• Electrical & Electronic Materials
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• v.9 no.2
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• pp.138-145
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• 1996

A multilayer piezoelectric transformer (MPT) which generates a high voltage dc power with low driving voltage and high voltage setup ratio was made by the tape casting method. The measured electrical characteristics of the MPT agreed with the results simulated from the equivalent circuit of the MPT. With increasing the number of layer in the MPT, the resonance curve of the input cur-rent revealed an asymmetry due to the increasing input capacitance, while that of output dc voltages revealed symmetry. The MPT which has very thin layer was excellently characterized as low driving voltage and high voltage setup ratio. The output dc voltage is nonlinearly influenced by the number of layer in the MPT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.740-745
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• 2014

ZnO nanowires were grown by hydrothermal synthesis process and piezoelectric poly vinylidene fluoride (PVDF) was then coated on top of the ZnO-nanowires by spray-coating technique. The composite layer of ZnO-nanowires/PVDF was applied to an energy harvesting device based on piezoelectric-conversion mechanism. A defined mechanical force was given to the nanogenerator device to evaluate their electric power generation characteristics, where output current density and voltage were examined. Electric power generation property of the ZnO-nanowires/PVDF based nanogenerator device was compared to that of the nanogenerator device with ZnO-nanowires as single active layer. Effect of the ZnO-nanowires on improvement of power generation was discussed to examine its feasibility for the nanogenerator device.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.21-28
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• 2006

Structural health monitoring (SHM) is a new technology that will be increasingly applied at the industrial field as a potential approach to improve cost and convenience of structural inspection. Recently, the development of smart sensor is very active for real application. This study has focused on preparation and application study of SAL sensor. In order to detect elastic wave, smart piezoelectric sensor, SAL, is fabricated by using a piezoelectric element, shielding layer and protection layer. This protection layer plays an important role in a patched network of distributed piezoelectric sensor and shielding treatment. Four types of SAL sensor are designed/prepared/tested, and these details will be discussed in the paper. In this study, SAL sensor can be feasibly applied to perform structural health monitoring and to detect damage sources which result in elastic waves.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.924-927
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• 2004

Measurements of fluctuating wall pressures were made with a linear array of 16 piezo-electric transducers beneath a fully-developed turbulent boundary layer. The piezoelectric bimorph actuator applied in this experiment has bonding structures of each polarity to make out-of-plane displacements rather than in-plane ones by using piezoelectric effect To specify the boundary layer characteristics at the location where the actuation was applied, the wall friction coefficients and $Re_\theta$ were measured by using the CPM method. The actuating frequency for the bimorph film was determined according to the priori bursting frequency from boundary layer parameters. The reduction of convecting energies in wave-number space was clearly observed at the specified actuating frequencies.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.81-88
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• 2002

An interface crack of a piezoelectric medium bonded between an elastic layer and a half-space is analyzed using the theory of linear piezoelectricity. Both out-of-plane mechanical and in-plane electrical loads are applied to the piezoelectric laminate. By the use of courier transforms, the mixed boundary value problem is reduced to a singular integral equation which is solved numerically to determine the stress intensity factors. Numerical analyses for various material combinations are performed and the results are discussed.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.1-17
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• 2014

An interfacial penny-shaped crack between piezoelectric layer and elastic half-space subjected to mechanical and electric loads is investigated. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric loadings and material parameters of composite on crack propagation and growth. The results seem useful for design of the piezoelectric composite structures and devices of high performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.189-192
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• 1996

In this paper ZnO Piezoelectric transducers were fabricated as follows, counter electrode (pt 99.9%) was deposited on the sapphire substrates by DC sputter method, and then piezoelectric layer (ZnO 99.999%) was deposited on the counter electrode according to the sputtering parameters, and then top electrode (pt 99.9%) was deposited on the piezoelectric layer by Electron Beam Gun Evaporator. Structural characteristic of deposited ZnO thin film was measured by XRD, SEM. Also, Frequency characteristic of ZnO transducer was analyzed theoretically and practically for input frequencies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.711-714
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• 2000

In this study, the physical properties of the acoustic element and case with metal-piezoelectric ceramics were analyzed. The dielectric and piezoelectric properties of 0.5 wt% MnO$_2$and NiO doped 0.1Pb(Mg$\_$1/3Nb$\_$2/3)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. Also, the acoustic characteristics for the geometrical form of case have been investigated. The design and fabrication method worked in this paper can be utilized in development of actuator and acoustic device.