• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.41-47
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• 2012

In this paper, we proposed a new method which analyzes and eliminates errors occurring by multi-reflection of ultrasonic firing in mobile robot application. This new method allows ultrasonic sensors to fire at rates that are three times faster than those customary in conventional applications readings due to ultrasonic noise disturbance. It is possible them to collect and predict sensor data much faster than conventional methods. Furthermore, this method's capability allows mobile robot to navigate in a complex and unknown environment and to collaborate in the same environment with multiple mobile robot, even if their ultrasonic sensors operate. And it's usefulness to avoid moving obstacles by capability of rapid collecting data. Finally, we present experimental results that demonstrate the performances of the new proposed method by experiments in a multi-reflective environment.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.151-157
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• 2004

Ultrasonic testing is a kind of nondestructive test to detect a crack or discontinuity in materials or on material surfaces by sending ultrasound to it. This conventional ultrasonic technique has some limitations in reliably detecting crack or accurately assessing materials in the case of complex-shaped power plant components such as a turbine blade root. An alternative method for such a difficult inspection is highly needed. In this study, application of a phased array ultrasonic testing (UT) system to a turbine blade, one of the critical power plant components, has been considered, and the particular incident angle has been determined so that the greatest track detectability and the most accurate crack length evaluation nay be achieved. The response of ultrasonic phased array was also analyzed to establish a special method to determine the track )ength without moving the transducer. The result showed that the developed method for crack length assessment is a more accurate and effective method, compared with the conventional method.

• Journal of Internet Computing and Services
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• v.23 no.4
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• pp.1-9
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• 2022

Recently, the functions of smart speakers have diversified, and the penetration rate of smart speakers is increasing. As it becomes more widespread, various techniques have been proposed to cause anomalous behavior against smart speakers. Dolphin Attack, which causes anomalous behavior against the Voice Controllable System (VCS) during various attacks, is a representative method. With this method, a third party controls VCS using ultrasonic band (f>20kHz) without the user's recognition. However, since the method uses the ultrasonic band, it is necessary to install an ultrasonic speaker or an ultrasonic dedicated device which is capable of outputting an ultrasonic signal. In this paper, a smart speaker is controlled by generating an audio signal modulated at a frequency (18 to 20) which is difficult for a person to hear although it is in the human audible frequency band without installing an additional device, that is, an ultrasonic device. As a result with the method proposed in this paper, while humans could not recognize voice commands even in the audible band, it was possible to control the smart speaker with a probability of 82 to 96%.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.5
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• pp.107-116
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• 1992

Recently, it is gradually raised necessity that interface is measured accurately and managed in industrial circle and medical world. An Ultrasonic wave transmitted from a focused beam tranducer is being expected as a powerful tool for NDE of the delamination. The Ultrasonic NDE of the delamination is based on the form of the wave reflected from the interface. In this study results, automatically repeated discrimination analysis method can be devided in the category of all kinds of defects on semiconductor package, and also can be possible to have a sampling of partial delamination.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1303-1308
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• 2000

Detection of square shape voids with size 30$\times$20$\times$5cm and 20$\times$20$\times$20cm in concrete were carried out by ultrasonic image processing technique. The advantages and limitations of this technique for non-destructive inspection of square shape voids in concrete are investigated. In this study, it has been verified that the semi-direct measurement method is more effective than the other methods for detecting the voids in concrete using ultrasonic image processing method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.300-302
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• 1999

The standing waves of the fourth bending mode of vibration and first longitudinal mode of vibrator were utilized to construct a ultrasonic linear motor. The geometrical dimensions of the vibrator were determined by Euler-Bernoulli theoty. FEM(finite element method) employed to calculate the vibration mode of the metal-piezoceramic composite thin plate vibrator. ANSYS was used to design positions of the projections and calculate displacement of vibrator.

• Journal of the Korea Society of Computer and Information
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• v.7 no.1
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• pp.80-87
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• 2002

In this papers, It was researched Automatic frequency detection which need using ultrasonic utmost effort. As far as ultrasonic Automatic frequency detection, It was analog method, In more dedicated field, to solve a limit. It was needed a new method detection instrument.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.77-83
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• 2020

The Linear system analysis for physical system is very powerful tool for system diagnostic utilizing relationship between the input signal and output signal. This method utilized generally to investigate physical properties of system and the nondestructive test by ultrasonic signals. This method can be explained by linear system theory. In this paper the Continuous Wavelets Transform is utilized to search the relation between the linear system and continuous wavelets transform.

• International Journal of Control, Automation, and Systems
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• v.6 no.5
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• pp.767-775
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• 2008

Methods used for exploring marine resources and spaces include positioning a probe under water and then recalling it after a specified time. Hydro-acoustic Releasers are commonly used for positioning and retrieving of such exploration equipment. The most important factor in this kind of system is the reliability for recalling the instruments. The frequently used ultrasonic signal detection method can detect ultrasonic signals using a fixed comparator, but because of increased rates of errors due to outside interferences, information is repetitively acquired. This study presents an effective ultrasonic signal detection algorithm using the characteristics of a resonance and adaptive comparator Combined with the FSK+ASK modulator. As a result, approximately 8.8% of ultrasonic wave communication errors caused by background noise and transmission losses were reduced for effectively detecting ultrasonic waves. Furthermore, the resonance circuit's quality factor was enhanced (Q = 120 to 160). As such, the bias voltage of the transistor (Vb= 3.3 to 6.8V) was increased thereby enhancing the frequency's selectivity.

• The KSFM Journal of Fluid Machinery
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• v.6 no.1 s.18
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• pp.57-65
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• 2003

The measurement uncertainties of an ultrasonic flowmeter were analyzed to evaluate its applicability to the measurement of the steam generator feedwater flow-rate in a nuclear power plant. The analyses of measurement uncertainties of a reactor power were also performed with the analyses of feedwater flow measurement uncertainties. Two ultrasonic flowmeters based on a cross-correlation technique and a transit time method were used in this study. The ultrasonic flowmeters were installed on a feedwater pipe line of a typical 1000 MWe Korea-standardized nuclear power plant to take the necessary data. The results have shown that the measurement uncertainties of the ultrasonic flowmeters are adequately smaller than those or a venturi meter. The research has also indicated that the measurement uncertainties of the reactor power based on the ultrasonic flowmeter uncertainties are sufficiently bounded by the uncertainty range usually assumed in nuclear safety analyses.