• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.307-314
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• 2004

A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the $S_0$ and $A_0$ mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.

• Journal of Korean Society of Disaster and Security
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• v.17 no.1
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• pp.27-35
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• 2024

This paper presents experimental research results to evaluate the applicability of chemical neutralization reaction and ultrasonic wave to remove cement paste and mortar attached to the surface of recycled aggregate. In order to derive optimal ultrasonic cleaning efficiency and chemical neutralization reaction, experiments were conducted using variables such as ultrasonic frequency and type of chemical solution. As a result, the optimal frequency was found to be 24 kHz, and immersion in a 15% hydrochloric acid solution for 30 minutes of stimulation showed the highest efficiency. In addition, the specific gravity, absorption rate, and wear rate of the quality-improved recycled coarse aggregate were similar to those of general aggregate and were found to satisfy all KS F 2527 standards. Therefore, it is believed that the recycled aggregate whose quality has been improved through the method proposed in this study can be used for concrete.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.792-796
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• 2006

In recent years, the semiconductor industry and the optical industry is developed rapidly. The recent demand has expanded for optical components such as a optical lens, a optical semiconductor and a measuring instrument. Object transport systems are driven typically by the magnetic field and the conveyer belt. Recent industry requires more faster and efficient transport system. However, conventional transport systems are not adequate for transportation of optical elements and semiconductors. Because conveyor belts can damage precision optical elements by the contact force and magnetic systems can destroy the inner structure of semiconductor by the magnetic field. In this paper, the levitation transport system using ultrasonic wave is developed for transporting precision elements without damages. This transport system is using 2-mode ultrasonic wave excitation and flexural beam modes shapes are evaluated. It compared simulation results with experimental results

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.146-146
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• 2009

최근에 광도전체와 형광체를 기반으로 평판형 디지털 방사선 검출기의 상업적 발전가능성에 많은 관심을 가지고 있다. 본 연구는 기존의 직접변환방식에 널리 사용되었던 비정질 셀레늄 (amorphous selenium) 기반의 디지털 방사선 검출기보다 높은 전기적신호 및 동작특성을 가지는 물질층을 제작하기 위해 High Purity (99.99%)의 상용화된 $PbI_2$를 특수용매에 담가두었다가 약 1시간동안 Biology 초음파 처리한 후 농축기를 사용하여 건조된 $PbI_2$를 3Roll-milling을 사용하여 미세크기의 Powder를 얻어내었다. 합성된 $PbI_2$ Powder를 PIB(Particle-in-Binder)법을 이용하여 전도성을 가진 ITO(Indium-tin-oxide)코팅된 유리판에 제작된 필름의 상부에 Magnetron sputtering system 을 사용하여 전극을 $1cm{\times}1cm$의 크기로 증착하였다. I-V 테스트를 통하여 X선 조사시 $PbI_2$필름의 Sensitivity, Dark current, SNR(signal-to-noise ratio)을 측정하여 필름의 전기적 검출 특성을 정량적으로 평가하였고 SEM(scanning electron microscope)을 통하여 입자의 크기를 관찰하였다.

• Journal of Veterinary Clinics
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• v.30 no.2
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• pp.111-114
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• 2013

A 4-year-old spayed female Miniature Pinscher was presented with a 3.5-year history of elevated liver enzymes level. Continuous elevation of liver enzymes was found on repeated blood examinations and the dog was referred for further evaluation. The abdominal ultrasonography revealed that the gallbladder could not be visualized in any plane. The absence of gallbladder was suspected on ultrasonography. Computed tomography (CT) confirmed gallbladder agenesis (GBA). This is the first reported case of diagnosis of GBA in Miniature Pinscher by using CT.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1069-1074
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• 2004

This study investigated the effect of pressure variations on augmentation of heat transfer when the ultrasonic waves were applied. The augmentation ratio of heat transfer was experimentally investigated and was compared with the profiles of pressure distributions calculated applying a coupled finite element-boundary element method (coupled FE-BEM). As the ultrasonic intensities increase from 70W to 340W, the velocity of the liquid paraffin is found to increase as well as kinetic energy, This physical behavior known as quasi-Eckart streaming results from acoustic pressure variations in the liquid. Especially, the higher acoustic pressure distribution near two ultrasonic transducers develops more intensive flow (quasi-Eckart streaming), destroying the flow instability. Also, the profile of acoustic pressure variation is consistent with that of augmentation of heat transfer. This mechanism is believed to increase the ratio of hear transfer coefficient.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.149-154
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• 2004

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the relationship of transporting speed according to the change of flexural beam shape and the effect of transporting speed according to the change of weight and amplification voltage are verified. The vibration behavior of flexural beam in the ultrasonic transport system is experimented using Laser Scanning Vibrometer.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.365-368
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• 2004

유리 전단용 스크라이빙(Scribing) 장치에 있어서 초음파 진동에 의한 절단특성의 제어 원리를 해석하고 주어진 시료에 대한 최적진동수의 판별에 대한 실험적 고찰을 수행하였다. 그 결과 가진 주파수에 따른 크랙의 깊이는 매우 큰 차이를 보이고 있었으며 최대 크랙을 생성시키는 최적 주파수 역시 시료의 길이에 따라 크게 변화함을 확인하였다.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.17-22
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• 2005

An experimental study was carried out to investigate the effect of local ultrasonic forcing on a turbulent boundary layer. Stereoscopic particle image velocimetry (SPIV) was used to probe the characteristics of the flow. A ultrasonic forcing system was made by adhering six ultrasonic transducers to the local flat plate. Cavitation which generates uncountable minute air-bubbles having fast wall normal velocity occurs when ultrasonic was projected into water. The SPIV results showed that the wall normal mean velocity is increased in a boundary layer dramatically and the streamwise mean velocity is reduced. The skin friction coefficient ($C_{f}$) decreases $60\%$ and gradually recovers at the downstream. The ultrasonic forcing reduces wall-region streamwise turbulent intensity, however, streamwise turbulent intensity is increased away from the wall. Wall-normal turbulent intensity is almost the same near the wall but it increases away from the wall, In tile vicinity of the wall, Reynold shear stress, sweep strength and production of turbulent kinetic energy were decreased. This suggests that the streamwise vortical structures are lifted by ultrasonic forcing and then skin friction is reduced.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.6
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• pp.1281-1290
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• 2001

A study on the fluid flow with ultrasonic forcing is carried out to obtain data for the turbulence enhancement. A large water tank is made of the transparent acrylic plates and a horizontal flow field is given by setting two acrylic tubes to face mutually on a horizontal line. A 2-dimensional PlV system which is composed of a continuous-output 4W Argon-ion laser, a high-speed video camera, a PC based by an image grabber and a high resolution monitor is used to investigate characteristics of the complex turbulence flow field. And a 2MHz ultrasonic transducer is used fur ultrasonic vibration forcing. Some experiments are carried out at Reynolds numbers of 2,000 and 4,000 and at 7 angles of ultrasonic incidence. In results, the flew velocity vector distribution, kinetic energy and turbulence intensity in both cases of with and without ultrasonic forcing are examined, compared and discussed by using PIV measurement. It is clarified that the ultrasonic forcing into flow field is valid to obtain the turbulence enhancement.