• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.16-23
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• 2013

By carrying out numerical analyses and model experiments, this paper presents the attenuation characterization of an L(0,2) guided ultrasonic wave propagating in a buried steel pipe. From this investigation, we first find that the L(0,2) mode has a better attenuation property. Second, it is shown from the numerical analyses that the attenuation increases with increases in the soil embedment length (0, 500, 1000, and 1500 mm) and degrees of saturation (0, 50, 99, and 100%). Third, it is also shown from the model experiment that the attenuation increases as the embedment lengths and soil moisture quantities (0, 10, 20, and 30 kg) increase. Finally, we find that an exponential extrapolation gives a better attenuation prediction because the extrapolation gives similar attenuation patterns between the numerical and experimental results.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.540-543
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• 2003

There are many stone monuments which are weathered by natural or artificial factors in Korea. The partly weathering in stone could accelerate the rate of weathering, so it is demanded to keep them from the further weathering. Consolidation is evaluated as one of the efficient treatments which have a good effectiveness in stone monuments. But following the former researches, the effectiveness of consolidation could be different, related to the kinds of stone or consolidants. Therefore, in this study, the change of properties was monitored in the long term for the exact evaluation of the stability of the consolidated stone. It is estimated that the pore structure of consolidated stone was filled by consolidant, according to the measurements of ultrasonic velocity, and the digital image analysis of the sample was shown that the color property of stone surface has varied during the curing.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.159-162
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• 2000

This paper addresses the design and implementation problem of the mobile robot with the synchronous driving mechanism that consists of modular control systems based on the Universal Serial Bus (USB). Recently, the USB have attracted the hardware developers'interests due to its low cost, compatibility, and extenability. In particular, the USB enables us to organize the whole system in the modular manner very easily, and this property plays a very important role in shortening the developing time in implementing the target system, for example, the mobile robot system. In this paper, we implement the USB motion controller and the USB ultrasonic sensor system and verified the validity and the effectiveness of the proposed system through the real experiments including the mobile robot navigation and the environment recognition.

• Transactions on Electrical and Electronic Materials
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• v.4 no.1
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• pp.29-33
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• 2003

Europium doped yttrium oxide submicron-sized particles were prepared by ultrasonic aerosol pyrolysis. To examine the size effect of submicron-sized-particle, the photoluminescence of the particles was investigated. The particle size was controlled by pH, reaction temperature, molar concentration of yttrium in precursor solution. The PL intensity of submicron-sized particles was decreased with particles size. When the particle size is above about 150 times of Bohr radius of Y$_2$O$_3$, the optical property of the particles shows the bulk characteristics.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.563-566
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• 1997

In this paper, several bandwidth sampling methods were compared in which contains "multi-order sampling", which was proposed or envelope detections in RF ultrasonic signals by a computer simulation and on experiment quadrature sampling method. The second-order sampling method were compared with it. As a conclusion, a multi-order sampling method, especially 5th order sampling method showed quite good envelope detection property. This means that more economical and quite good performance digital beamforming system can be built by adopting this new bandwidth sampling method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.510-512
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• 2015

Recently, people fear is growing because of the various crimes that may occur when you go out. The growing is interest in security systems for the protection of an individual's property. In this paper, to establish a single central server based on the home network when intruders access to city, such as image processing values obtained through the IP camera and distance values disciplined use an ultrasonic sensor the user for an attacker city that will connect to the server the surveillance system provides the information that is received and implemented.

• Journal of the Korea Institute of Building Construction
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• v.7 no.3
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• pp.107-113
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• 2007

This study is to investigate adhesive properties depending on the temperature, humidity, and freeze-thraw of the Steel plate adhesive strengthening method by the epoxy resin. The results are summarized as following. For the temperature variation, the debonding failure appear only after 1 cycle of temperature varoation because the coefficient of thermal expansion of the epoxy resin is comparatively large, and the bonding strength is decreased. The deformation properties and ultrasonic pulse velocity on each materials are similar until 4 cycles on the dry and moisture test. As the freeze-thraw test, the epoxy resin is degraded easily subjected to freeze-thaw cycle, comparatively easy, so the debonding failure may occur in short term because of the freeze-thaw repeatition.p

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.433-442
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• 1996

Since one texture property(i.e coarseness, orientation, regularity, granularity) for ultrasound liver ages was not sufficient enough to classify the characteristics of livers, we used multi texture vectors tracted from ultrasound liver images and a statistical classifier. Multi texture vectors are selected among the feature vectors of the normal liver, fat liver and cirrhosis images which have a good separability in those ultrasound liver images. The statistical classifier uses multi texture vectors as input vectors and classifies ultrasound liver images for each multi texture vector by the Bayes decision rule. Then the decision of the liver disease is made by choosing the maximum value from the averages of a posteriori probability for each multi texture vector In our simulation, we obtained higtler correct ratio than that of other methods using single feature vector, for the test set the correct ratio is 94% in the normal liver, 84% in the fat liver and 86% in the cirrhosis liver.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.105-112
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• 1998

In this paper, several bandwidth sampling methods were compared using experimental result in which contains "multi-order sampling", which was proposed for envelope detections in RF ultrasonic signals. A "Quadrature sampling method" and "Second-order sampling method" were compared with it. The resultant image of second-order sampling method introduces too much error as compared with the result of quadrature sampling. But Multi-order sampling method, specialy 5-th sampling method showed quite good envelope detection property. This means that more economical and quite good performance digital beamforming system can be built by adopting this multi-order sampling method.s multi-order sampling method.

• Journal of the Korean institute of surface engineering
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• v.51 no.4
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• pp.202-206
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• 2018

Permalloy($Ni_{80}-Fe_{20}$) which is known for its soft magnetic properties is a well-known material that has been studied intensively. Permalloy nanoflakes were fabricated with the combination of electrodeposition and sonication process. Ultrasonic power was applied to the deposited alloy which produced nanoflakes in forms of sheet. High internal stress created cracks which helped the peeling of permalloy into nanosheets. Because of shape anisotropy, flakes could be aligned by magnetic field. The magnetic properties of the nanosheets were observed, and the variation of magnetic properties with the alignment of flake was also investigated.