• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.82-88
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• 2003

The nondestructive internal quality evaluation of agricultural products has been strongly required from the needs for individual inspection. Recently, the ultrasonic wave has been considered as a solution fur this problem, and an ultrasonic system was constructed for the ultrasonic NDE of fruits and vegetables in our previous work. In this paper, the practical applicability of our ultrasonic system is tested fur the inspection of internal defects (central cavity) in Atlantic potato. Sound speed and RMS of transmitted ultrasonic wave signal were measured and classification algorithm using 2 dimensional stochastic analysis. was presented. Experimental results showed greater value of sound speed and RMS (root mean square) of transmitted signal in normal samples than in abnormal samples with cavity. Also a stochastic method to distinguish normal and abnormal showed fault detection rate less than 5%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.107-111
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• 2010

The damage of tire by damage material classification method is researched as used ultrasonic wave signal to occur at a tire during vehicle driving. Auto-correlation function after having passed through an envelope detecting preprocess is used for detecting periodicity because of occurring periodic ultrasonic waves signal with tire revolution. One revolution cycle time of a damaged tire and period that calculated auto-correlation function appeared equally in experiment. The result that can classification whether or not there was a tire damage is established.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.32-39
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• 1999

Digital signal processor (DSP) is used to obtain the peak value and the time difference of ultrasonic signals, to make digital filter, and to derive mathematical transformation from analog circuit. In this study, C-scan system and control program have been developed to high speed data acquisition. This system consists of signal processing parts (DSP, oscilloscope, pulser/receiver, digitizer), scanner, and control program. The developed system has been applied to a practical ultrasonic testing in overlay weld, and demonstrated high speed with precision

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.541-546
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• 2001

Application of bonding by adhesives can be found in many industries, particularly in advanced technological domains such as the aeronautical and space industries, automobile manufacture, and electronics. Periodic inspection with conventional ultrasonic NDE techniques is capable of indicating the presence and possible location of crack. Continuous ultrasonic attenuation monitoring has potential to supply information. This study used adhesive-bonded single-lap joints specimen to evaluate such possibility by ultrasonic signal processing method.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1995.11a
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• pp.184-192
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• 1995

Although ship's draught information onboard is substantial for both the safety of navigation and the estimation of loaded cargoes its accuracy depends in traditional surveying method on the skillfulness of observers and the condition of the sea surface round the vessel. To obtain more accurate information accessibly measuring instruments with sophisticated sensors such as mechanical electronic and ultrasonic transducers have been developed. however they have still limitation in accuracy and in making up a system due to the complexity of processing signal. In this paper we propose a he technique for analyzing ultrasonic pulse signal in order to improve the measurement accuracy and simplify a remote sensing system of draught by ultrasonic waves. This technique is useful for measuring draught being considered the influence of sea surface fluctuation and for transferring its data briefly to required equipment in integrated bridge system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.36-43
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• 2004

In this paper, the frequency spectra from respective mechanical noise signals detected using ultrasonic wave and AE(Acoustic Emission) sensor were analysed to under spark generation between brush and commutator side with arbitrarily 15$^{\circ}$ rotation for brush from the DC motor in operation. Also, the frequency spectra from respective magnetizing noise signals detected using ultrasonic wave and AE sensor were analysed to under neutral point for brush from the DC motor in normal operation. And the analyses and comparison between the mechanical noise signal and magnetizing noise signal of ultrasonic wave with brush location change from the DC motor in operation. As the experimental results, tile mechanical noise signal of ultrasonic wave under spark generation between brush and commutator side with brush location change from the DC motor in operation were increased about 2.5∼3.0 times than magnetizing noise signal of ultrasonic wave form the DC motor in normal operation. Also, the main frequency band for mechanical noise signals of AE under spark generation between brush and commutator side with brush location change from the DC motor in operation, appeared about 1.3[MHz]∼l.5[MHz] by the fast fourier transform.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.124-132
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• 2017

With the growth of interest in the UAVs, the study of the UAV collision avoidance is in progress. Lidar, Video camera, laser sensor, and ultrasonic sensor may be utilized for collision avoidance of UAV. In this paper, the characteristics of MB 1230 ultrasonic sensor is analyzed through the experiment. When concurrently using multitudinous ultrasonic sensors, ultrasonic sensors do not generate correct measurement values. To solve ultrasonic sensor interference, sequentially transmitting ultrasonics signal is suggested by using 'Enable' signal input of ultrasonic sensor, so by activating each ultrasonic sensor gradually. This proposed solution is also verified by experimentation.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1996.11a
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• pp.122-124
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• 1996

This paper describes a diagnosis of distribution cable splices by analysis of ultrasonic signals which are generated by partial discharge. A method of ultrasonic signal was used to detect internal defects in distribution cable splices. It is possible that analysis of ultrasonic signal predicts failure by partial discharge generated in distribution cable splices.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.7
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• pp.583-589
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• 2008

For the purpose of monitoring by ultrasonic test of the ball bearing conditions in rotating machinery, a system for their diagnosis was developed. ultrasonic technique is used to detect abnormal conditions in the bearing system. And various data such as frequency spectrum, energy and amplitude of ultrasonic signals, and ultrasonic parameters were acquired during experiments with the simulated ball bearing system. Based on the above results and practical application for power plant, algorithms and judgement criteria for diagnosis system was established. Bearing diagnosis system is composed of four parts as follows : sensing part for ultrasonic sensor and preamplifier, signal processing part for measuring frequency spectrum, energy and amplitude, interface part for connecting ultrasonic signal to PC using A/D converter, graphic display and software part for display of bearing condition and for managing of diagnosis program.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1544-1553
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• 1999

Recently, ultrasonic testing techniques have been widely used in the evaluation of the quality of metal. In this experiment, six heat-treated temperature of specimen have been considered : 0, 1200, 1250, 1300, 1350 and 1387$^{\circ}C$. As heat-treated temperature increases, the grain size of stainless steel also increases and then, eventually make it destroy. In this paper, a pattern recognition method is proposed to identify the heat-treated temperature of metals by evidence accumulation based on artificial intelligence with multiple feature parameters; difference absolute mean value(DAMV), variance(VAR), mean frequency(MEANF), auto regressive model coefficient(ARC), linear cepstrum coefficient(LCC) and adaptive cepstrum vector(ACV). The grain signal pattern recognition is carried out through the evidence accumulation procedure using the distances measured with reference parameters. Especially ACV is superior to the other parameters. The results (96% successful pattern classification) are presented to support the feasibility of the suggested approach for ultrasonic grain signal pattern recognition.