• Journal of Welding and Joining
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• v.16 no.3
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• pp.64-73
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• 1998

This paper is concerned with defects detection and evaluation of heat affected zone (HAZ) in austenitic stainless steel type 304 by ultrasonic wave and neural network. In experiment, the reflected ultrasonic defect signals from artificial defects (side hole, vertical hole, notch) of HAZ appears as beam distance of prove-defect, distance of probe-surface, depth of defect-surface on CRT. For defect classification simulation, neural network system was organized using total results of ultrasonic experiment. The organized neural network system was learned with the accuracy of 99%. Also it could be classified with the accuracy of 80% in side hole, and 100% in vertical hole, 90% in notch about ultrasonic pattern recognition. Simulation results of neural network agree fairly well with results of ultrasonic experiment. Thus were think that the constructed system (ultrasonic wave - neural network) in this work is useful for defects dection and classification such as holes and notches in HAZ of austenitic stainless steel 304.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1512-1517
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• 2003

Augmentation of CHF by ultrasonic is experimentally studied under subcooling pool boiling condition. Experiment is carried out for downward-facing plate with and without the ultrasonic. The working fluid is distilled water. Experimental apparatus is composed of a bath, power supply, test section, ultrasonic generator, DAQ system. Experiment is performed with the subcooling temperature of $5^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$ and the inclined angle of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $45^{\circ}$, 90. From the experimental results, it is found that ultrasonic effect enhances CHF of the downward-facing plate. As increasing the degree of subcooling, the rate of CHF increase is enhanced. As increasing the inclined angle, the rate of CHF increase decreases. Also, we can see that the heat transfer mechanism of CHF augmentation is closely connected with the dynamic behavior of bubble generation and departure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.321-324
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• 1997

In this study, Efficiency estimation of ultrasonic sensor fabricated with porous piezoelectric resonator by experiment of 3-D underwater object recognition are presented. The sensor was satisfied with requirement of ultrasonic sensor. The recognition rates for the fixed objects and the translation-rotation objects are 95.3 and 92.7[%], respectively using porous piezoelectric ultrasonic sensor and SOFM neural network. According to the experimental results, It is believed that the self-made ultrasonic sensor can be applied as underwater ultrasonic sensor.

• 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.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.2
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• pp.121-129
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• 2016

As the lifespan of concrete structures increases, their load carrying capacity decreases owing to cyclic loads and long-term effects such as creep and shrinkage. For these reasons, there is a necessity for stress state monitoring of concrete members. Particularly, it is necessary to evaluate the concrete structures for behavioral changes by using a technique that can overcome the measuring limitations of usual ultrasonic nondestructive evaluation methods. This paper proposes the use of a nonlinear ultrasonic method, namely, nonlinear resonant ultrasonic spectroscopy (NRUS) for the measurement of nonlinearity parameters for stress monitoring. An experiment compared the use of NRUS method and a linear ultrasonic method, namely, ultrasonic pulse velocity (UPV) to study the effects of continuously increasing loads and cyclic loads on the nonlinearity parameter. Both NRUS and UPV methods found a similar direct relationship between load level and that parameter. The NRUS method showed a higher sensitivity to micro-structural changes of concrete than UPV method. Thus, the experiment confirms the possibility of using the nonlinear ultrasonic method for stress state monitoring of concrete members.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.529-531
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• 2004

For localization, it is very important for an autonomous mobile robot to be able to recognize indoor environment and match an object it detect to an object within a map developed either online or offline. Given the map defining the locations of geometric beacons like wall and comer existing in the robot operation environment, this paper presents a stereo ultrasonic sensor based method that can be conveniently used in recognizing the geometric beacons. The stereo ultrasonic sensor used in the experiment consists of an ultrasonic transmitter and two ultrasonic receivers placed symmetrically about the transmitter. Experiment shows that the proposed method is more efficient in recognizing wall and coner than the conventional method of using multiple number of transmitter-receiver pairs.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.1-7
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• 2004

This experiment was undertaken to investigate the atomization characteristics of the low viscosity biodiesel blended fuel and ultrasonic energy added one. Test fuels were conventional diesel fuel and biodiesel fuel. We compared to the characteristics of viscosity and surface tension, SMD between low viscosity biodiesel blended fuel and ultrasonic energy added one. Sauter mean diameter was measured under the variation of the spray distance. Viscosity and surface tension was measured under the variation of the time trace. To measure the droplet size, we used the Malvern system 2600C. Droplet size distribution was analyzed from the result data of Malvern system. Through this experiment, we found that the condition of the ultrasonic energy added situation had smaller Sauter mean diameter of droplet, viscosity and surface tension than that of the conventional situation.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.795-800
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• 2008

The paper presents research for the established experiment environment of multi vehicle robot, localization algorithm that is based on vehicle control, and path tracking. The established experiment environment consists of ultrasonic positioning system, vehicle robot, server and wireless module. Ultrasonic positioning system measures positioning for using ultrasonic sensor and generates many errors because of the influence of environment such as a reflection of wall. For a solution of this fact, localization algorithm is proposed to determine a location using vehicle kinematics and selection of a reliable location data. And path tracking algorithm is proposed to apply localization algorithm and LOS, finally, that algorithms are verified via simulation and experimental

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.5 s.98
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• pp.564-570
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• 2005

This paper presents some results of research for applying ultrasonic cleaning to an interior wall of cylindrical pipe. As the cleaning is achieved better for higher sound pressure, ultrasonic sound field in a cylindrical container is considered. The paper identifies nonuniform sound field established by the radiation of a cylindrical transducer driven at resonant frequency, Numerical analysis predicts the sound pressure distribution, and experiment verifies the trend of analysis results. Experiment observes the cleaning effect, and this paper suggests the possibility of using a cylindrical ultrasonic cleaning device.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.157-164
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• 2003

The pulse-echo method is one of the most widely used ultrasonic techniques for application of nondestructive evaluation. Particularly, quantitative nondestructive evaluation of defects has been considered more important to assure the reliability and the safety of structure. Frequency energy in adhesive joints is based on the ultrasonic wave analysis. The attenuation coefficient upon wave amplitude and the frequency energy that is expressed in the term of wave pressure amplitude were utilized for the primary wave experiment. By means of a control experiment, it was confirmed that the variation of the frequency energy in adhesive joints depends on transition by stress variation. In this paper, the ultrasonic characteristics were measured for single lap joint and Double Cantilever Beam specimen with different fracture modes that was subjected to stress. Consequently, the data that was obtained from the adhesive specimen was analytically compared to the fracture mechanics parameter