• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.942-945
• /
• 2000

Recently, electret applications have placed the focus on polymer thin film because electrical properties of a blend are studied. In this paper, we hale measured the infra sonic frequency by using Electret Sensor. Electret is formed by appling the voltage range of -4[kV] to -8[kV] to PTFE film and the sensor is manufactured by moment method to detect the infra-sonic signal. Electret Infrasonic Transducer, which is designed and manufactured by using of the moment method according to the potential and electric field simulation , shows its promising result, since the average rising rate of sensitivity is 7.68 [dB/oct] under 1[Hz], and the average values are within ${\pm}$ 1 [dB/oct]. As a result, it is believed that the characteristics of acquired transducer can be applied to the medical treatment, the industry, and the animal life researches, and also the study on noise elimination is required.

• Electrical & Electronic Materials
• /
• v.8 no.5
• /
• pp.572-579
• /
• 1995

Most of conventional ultrasonic transducers are constructed to generate either longitudinal or shear waves, but not both of them. We investigate the mechanism of dual mode transducers that generate both of the longitudinal and shear waves simultaneously with single PZT element. The study is aimed to find the optimally desired cut by examining the anisotropic piezoelectric properties. Theory predicts that a mixed P/S mode transducer can be constructed using a rotated Z-cut of PZT piezoelectric ceramics. We study the performance of a PZT element as a function of its rotation angle so that its efficiency is optimized to excite the two waves as much as equally strong. The results are verified by the waveform in pulse-echo computer simulation and experiments. When the transducer is subjected to impedance analysis, it shows two thickness mode resonances, each of which being a mixed P/S thickness mode. By examining wave speeds on E transmitter delay line receiver setup, it is confirmed that the transducer can transmit and detect both longitudinal and shear wave simultaneously.

• Smart Structures and Systems
• /
• v.24 no.4
• /
• pp.435-446
• /
• 2019

The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.

• Journal of the Korean Society of Radiology
• /
• v.11 no.5
• /
• pp.353-359
• /
• 2017

The sonophoresis, a representative low-intensity ultrasonic therapy, is a technique for delivering the drugs into the epidermis, dermis and skin appendages by using physical vibration and heat effects of the ultrasonic waves. Sonophoresis could increases the delivering and absorption efficiency of the drugs usually consisting of hydrophilic molecules and macromolecules. In addition, it has the advantage of being effective in delivering drugs with relatively large molecular sizes such as insulin or lipid. In this study, we proposed a multi-structure ultrasonic transducer assembly with a large-size single piezoelectric element and a drug delivery function at the treatment site for efficient sonophoresis treatment. Futhermore, a transducer assembly structure capable of raising and maintaining the temperature of the treatment site was proposed and evaluated for effectiveness. The transducer assembly proposed in this study is expected to improve the efficiency of sonophoresis by providing a constant amount of drug, and assisting drug delivery through heating the treatment site.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.5
• /
• pp.185-190
• /
• 2018

The Tonpilz transducer was implemented using the structural module of COMSOL which is a FEM simulation tool. In order to compare the sound pressure characteristics of the transducer with the simulated results, the spacial distribution of the sound pressure level (SPL) was simulated by the acoustic module of COMSOL and then compared with the SPL distribution measured by a microphone. As a result, the resonance frequency and the peak in SPL for the simulation were predicted to be 28 kHz and 163.5 dB, respectively. And the resonance frequency and the peak in SPL for the actual transducer were measured to be 28.84 kHz and 137.8 dB, respectively. It is also confirmed that the simulated SPL distribution and the actually measured one are formed in a similar pattern.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.5
• /
• pp.475-479
• /
• 2003

Traditional ultrasonic evaluation to detect micro/small surface cracks is the pulse-echo technique using the normal immersion transducer with high frequency, or the angle beam transducer with surface wave. It is difficult to make the automatic ultrasonic system that is to detect micro and small surface crack and position on the large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of transducer. The aim of this study using the high precision scanning acoustic microscope with 10MHz large aperture transducer was to display the real time A, B, C-scan for the automatic ultrasonic system in order to detect the existence and position of surface crack. The ultrasonic method with large aperture transducer was improved the scanning time and speed over 10times faster than traditional methods.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.2
• /
• pp.142-150
• /
• 2004

A preliminary study of the behavior of ultrasonic guided wave mode in a pipe using a comb transducer for maintenance inspection of power plant facilities has been verified experimentally. The mode identification has been carried out in a pipe using the time-frequency analysis methods such as the wavelet transform(WT) and the short time Fourier transform (STFT), compared with theoretically calculated group velocity dispersion curves for longitudinal and flexural modes. The results are in good agreement with analytical predictions and show the effectiveness of using the time-frequency analysis method to identify the individual modes. It was found out that the longitudinal mode(0,1) is less affected by mode conversion compared with the other modes. Therefore, L(0,1) is selected as an optimal mode for the evaluation of the surface defect in a pipe.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.2
• /
• pp.180-185
• /
• 2004

Conventional ultrasonic examination to detect micro and small surface cracks is based on the pulse-echo technique using a normal immersion focused transducer with high frequency, or an angle-beam transducer generating surface waves. It is difficult to make an automatic ultrasonic system that can detect micro and small surface cracks and position in a large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of the transducer. In this study, a high-precision scanning acoustic microscope with a 10MHz large-aperture transducer has been used to assess the existence, position and depth of a surface crack from the real-time A, B, C scans obtained by exploiting the ultrasonic diffraction. The ultrasonic method with large aperture transducer has improved the accuracy of the crack depth assessment and also the scanning speed by ten times, compared with the conventional ultrasonic methods.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.8
• /
• pp.637-644
• /
• 2003

In this study, with the FEM we analyzed the variation of the resonance frequency, bandwidth, and sound pressure of the Tonpilz transducer in relation to its design variables. Through statistical multiple regression analysis of the results, we derived functional forms of the resonance frequency, bandwidth, and sound pressure in terms of the design variables. By applying the constrained optimization technique, SQP-PD, to the derived function, we determined the optimal structure of the transducer that could provide the highest sound pressure level at the resonance frequency of 30,000 Hz and having the -3 dB bandwidth more than 10%, The validity of the optimized results was confirmed through comparison of the optimal performance with that of the FEA. The optimal design method proposed could reflect all the cross-coupled effects of multiple structural variables, and could determine the detailed geometry of the transducer with great efficiency and rapidity.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.1
• /
• pp.159-165
• /
• 2018

In this paper, a low-loss wideband waveguide transducer is proposed for millimeter-wave communication and radar applications. A conventional E-plane probe transducer is generally designed using thin and flexible substrate at millimeter-wave frequencies, considering the very small waveguide size. However, it results in serious performance degradation caused by the bending of the substrate. In order to alleviate this problem and provide a reliable performance, we propose an extended E-plane probe transducer where the probe substrate is extended to and fix ed in the slit area formed in the waveguide wall. It is fabricated using $127{\mu}m$-thick substrate with dielectric constant of 2.2. The measurement in the back-to-hack configuration shows the excellent insertion loss of 1.35 dB (${\pm}0.35dB$) including the loss of 3 cm-long thru waveguide and return loss better than 13.8 dB over entire W-band (75-110 GHz). Therefore, it can be effectively applied for millimeter-wave high-speed communications and high-sensitivity radars.