• Journal of Biomedical Engineering Research
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• v.7 no.1
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• pp.41-44
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• 1986

The objective of tissue characterization is to provide quantitative information about the physical state of tissue interrogated by an ultrasound beam. In the computer simulation, it was found that the echoes were composed of the interferences of the ultrasonic waves reflected from both sides of the thin object, and could be separated by the spectral correlation method. Also, the phantom study demonstrates that thickness of the thin acryl layer beyond the resolution of common ultrasonic imaging systems can be measured- using this method.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• v.10 no.1
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• pp.274-280
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• 2005

• Journal of Soil and Groundwater Environment
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• v.19 no.6
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• pp.72-79
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• 2014

Cavitation generated by ultrasonic irradiation can enhance the diffusional transport of organic contaminants from soil surfaces or pores. Therefore, ultrasound soil washing can be an alternative of traditional soil washing process. In this study, soil was artificially contaminated with n-tetradecane, n-hexadecane and phenanthrene. A plate type ultrasonic reactor at 25 kHz frequency and 1000W power was used for laboratory soil washing experiments. Ultrasonic soil washing efficiency was compared with those of traditional soil washing using mechanical mixing. Various operational parameter such as soil/liquid ratio, irradiation time, particle size, and soil organic matter content was tested to find out the optimum condition. It was found that ultrasonic soil washing demonstrates better performance than mechanical soil washing. Optimum soil:liquid ratio for ultrasonic soil washing was 1 : 5. Desorption of organic contaminants from soils by ultrasonic irradiation was relatively fast and reached equilibrium within 10 minute. However, decrease in the soil particle sizes by ultrasonic irradiation results in re-adsorption of contaminants to soil phase. It was also observed that soil particle size distribution and soil organic matter content have significant effects on the efficiency of ultrasonic soil washing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.471-479
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• 2022

Recently, piezoelectric devices, such as ultrasonic surgery, ultrasonic atomizer, and ultrasonic speaker, are analyzed and designed by finite element simulation methods. However, the discrepancy between the design and the experiment results of the device typically occurs due to the inaccuracy of the piezoelectric material properties. To improve the simulation accuracy, the material properties of the PZT ceramics were better refined using parameter estimation method. The material parameters are elastic stiffness c^E_ij and piezoelectric constant e_ij of PZT ceramics. The impedance curve characteristics for the LTE mode of PZT ceramics were calculated. The mismatch between the simulation and the experimental data were compared and minimized by a least square method. Finally, the simulated impedance data were compared with the experimental data for the various vibration modes of PZT ceramics and the optimized material properties of PZT ceramics were verified. To further verify the accuracy, this method was also applied to piezoelectric PMN-PT single crystals.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.276-283
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• 2012

In this paper, a practical quasi-optimal DOA(direction of arrival) estimator is proposed in order to develop a one-axis gimbaled ultrasonic source tracker for mobile robot applications. With help of the gimbal structure, the ultrasonic moving source tracking problem can be simply reduced to the DOA estimation. The DOA estimation is known as one of the representative long-pending nonlinear filtering problems, but the conventional nonlinear filters might be restrictive in many actual situations because it cannot guarantee the reliable performance due to the use of nonlinear signal model. This motivates us to reformulate the DOA estimation problem in the linear robust state estimation setting. Based on the assumption that the received ultrasonic signals are noisy sinusoids satisfying linear prediction property, a linear uncertain measurement model is newly derived. To avoid the DOA estimation performance degradation caused by the stochastic parameter uncertainty contained in the linear measurement model, the recently developed NCRKF (non-conservative robust Kalman filter) scheme [1] is utilized. The proposed linear DOA estimator provides excellent DOA estimation performance and it is suitable for real-time implementation for its linear recursive filter structure. The effectiveness of the suggested DOA estimation scheme is demonstrated through simulations and experiments.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.187-190
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• 2002

In contrast to conventional electromagnetic motor, USM(Ultrasonic Motor), as piezoelectric ceramic applying ultrasonic mechanical vibration and as frictional-movement type motor, get rotational torque by elastic friction between stator and rotator, The USM, which is small motor without iron cores and coil as a simple structure, has little load weight, has character of high torque at low speed, and can apply a direct drive type without deceleration gear as low speed type. A response of USM from control input is satisfactory, and also generates much torque in low speed driving, and holding torque is much without supplying power. In this study, I designed and made Ultrasonic motor-digital multi controller(USM- DMC) using FPGA chip, A54SX72A made in Actel Corporation. By the minute, USM-DMC can control frequency, duty ratio, and phase difference of USM by llbit digital input from Pc. Therefore, when we use this controller, we can apply to typical parameter, frequency, phase difference, and voltage parameter, to control as well as we can do mixing control like phase-frequency, phase-voltage, frequency-voltage, frequency-phase-voltage, What is more, the strongest point is that it can trace frequency based on optimized frequency because we can input optimized resonant frequency while in motoring.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.4
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• pp.251-257
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• 2015

In ultrasonic nonlinear parameter measurement using the fast Fourier transform(FFT) of tone-burst signals, the side lobe and leakage on spectrum because of finite time and non-periodicity of signals makes it difficult to measure the harmonic magnitudes accurately. The window function made it possible to resolve this problem. In this study, the effect of the Hanning and Turkey window functions on the experimental measurement of nonlinear parameters was analyzed. In addition, the effect of changes in tone burst signal number with changes in the window function on the experimental measurement was analyzed. The result for both window functions were similar and showed that they enabled reliable nonlinear parameter measurement. However, in order to restore original signal amplitude, the amplitude compensation coefficient should be considered for each window function. On a separate note, the larger number of tone bursts was advantageous for stable nonlinear parameter measurement, but this effect was more advantageous in the case of the Hanning window than the Tukey window.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.726-730
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• 1997

One approach to testing the suitability of an adhesive joint for a particular application is to build and test to destruction a representativc, sample of the joini. The noncdestructive test will not measure strength directly but will measure a parameter which can be correlated to strength. It is thercforc, essential that a suitable nondestructive rest is chosen and that its results are correctly intcrpreted. In this paper, typical Ultrasonic Signal Analysis in adhesive joints are cvaluatcci together with Interface Stress from the result of Finite Elenlent Method.

• Journal of Biomedical Engineering Research
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• v.11 no.2
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• pp.227-232
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• 1990

As a part of the study on ultrasonic tissue characterization, conventional ultrasonic imaging system is interfaced to the personal computer to acquire raw ultrasonic signal. One approach for tissue charaterization is performed using the attenuation map to the conventional images and the resulting attenuation map images are compared and inspected inside the region of interest from the viewpoint of pattern analysis. Currently, these methods are applied and modified to effectively find out the differences between the normal control and the patients with liver cirrhosis.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.113-120
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• 1990

In this paper, the deconvolution method utilizing a modified Wiener filter is applied for the enhancement of lateral resolution of ultrasonic B-scan Images. For this purpose, a phantom composed of wires which are 0.6mm of diameter and apart in the range between 3 to 9mm is constructed. The modified Wiener filter with optimal parameter is applied to the phantom for the analysis of ultrasonic image. The results obtained are as follows'When all parameters of the modified Wiener filter are optimal, the resolution of B-scan images is enhanced by 50 percent : Othenrise, the images are blurred, spilt at peak points, or noises are strengthened severely. When the point-spread function representing the characteristic function of the system is determined, the selection ranges of op- timum parameters may be narrowed. It is expected that the proposed method may be able to apply to clinic situations for more accurate image analysis by means of reducing the loss of important information.