• 센서학회지
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• 제14권2호
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• pp.101-108
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• 2005

The research on the avoidance of the large-obstacles such as a wall, a large box, etc. using ultrasonic sensors has been generally progressed up to now. But the mobile robot could meet a small-obstacle such as a small plastic bottle, a small sphere, and so on in its designated path, and could be disturbed by them in the locomotion of the mobile robot. So, it is necessary to research on the avoidance of a small-obstacle. In this paper, a robot's small-obstacle perceiving system was designed and fabricated by arranging four ultrasonic sensors on the plastic plate to avoid small-obstacles. The system was installed on the upper part of the mobile robot with the slope angles between $40.7^{\circ}$ and $23.3^{\circ}$ to a horizontal line and the dynamic characteristic test of the robot was performed. As the result, it was confirmed that the mobile robot with the system could avoid small-obstacles in indoor environment safely.

• 비파괴검사학회지
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• 제21권1호
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• pp.1-21
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• 2001

It will be shown how models can simulate all the elements of an ultrasonic NDE measurement system, including the pulser/receiver, cabling, transducer(s), and the acoustic/elastic waves fields. When combined, these models form what is called the electroacoustic measurement model. It will be demonstrated how this electroacoustic measurement model can be used to conduct parametric transducer and system studies and how the model can form the basis for experimentally characterizing all the elements of the ultrasonic measurement system, using purely electrical measurements.

• 한국통신학회논문지
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• 제42권2호
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• pp.413-423
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• 2017

본 논문은 실내에서 위치를 측정하기 위해 초음파와 RF 기반의 실내 측위 시스템을 제안한다. 기존의 실내 측위 방안은 시간 동기화, 시스템의 복잡도, 측위의 정확성 등의 문제가 있다. 이러한 문제를 해결하기 위해 초음파와 무선주파수(RF)를 이용한 송수신 시스템을 제안한다. 송신시스템은 한 쌍의 초음파 송신기와 RF 송신기로 구성하고, 수신시스템은 복수의 초음파 수신기들과 하나의 RF 수신기로 구성한다. 또한, 제안된 시스템이 가질 수 있는 성능의 한계를 수학적으로 분석하였다. 제안된 시스템은 시뮬레이션뿐만 아니라 아두이노 모듈을 이용하여 실제 시스템을 제작하여 측위 성능을 평가하였다. 실내 공간 $2m{\times}2m{\times}2m$에서 25개 지점의 위치를 측정한 결과, 평균 6.1cm, 표준편차 1.6cm의 성능을 보였다.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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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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• 제25권6호
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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.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.344-353
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• 1996

A fundamental study was conducted to obtain the basic data involved in nondestructive quality evaluation of the fruit and vegetables. An experimental equipment for ultrasonic propagation characteristics of the fruit and vegetables such as radish , carrot , potato, and apple was set up and also power spectrum analysis system of an ultrasonic wave through the fruit and vegetables was set up. The velocity and attenuation of ultrasonic wave through the tissue specimens from the fruit and vegetables were measured and analyzed. The elastic modulus and density by the mechanical method currently used were compared with those using by ultrasonic method. The ultrasonic tranit time was almost linearly increased with the length of the specimens and attenuation of ultrasonic was mainly affected by the internal flbrous structure of the products. The regression equation was derived from the highly correlated experimental variables.

• Journal of Forest and Environmental Science
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• 제23권2호
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• pp.73-78
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• 2007

Ultrasonic deinkings of white ledger were carried out to confirm whether the ink removal efficiency and pulp qualities can be improved by the ultrasonic deinking. The effects of conventional pulping and ultrasonic treatment of white ledger on the ink particle size distribution and ink removal coefficient were compared. The physical properties of paper, energy consumption and effluent qualities were measured. The ultrasonic treatment of white ledger resulted in the ink particle size distribution suitable for flotation. The ink removal efficiency, brightness, breaking length and effluent quality were improved by the ultrasonic deinking. It is expected that the competitiveness of ultrasonic deinking system can be improved by the optimization of treatment condition.

• 한국산학기술학회논문지
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• 제11권12호
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• pp.4735-4741
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• 2010

초음파 금속 용착은 신소재, 도금 구조물 등과 같은 다양한 재료의 용착에 대한 가능성 때문에 광범위한 분야에서 사용되고 있으며 용착 조건도 다양하다. 본 연구에서는, 이종 금속 박판의 초음파 금속 용착을 위해 설계된 단부가형 한파장 혼은 유한요소해석 하였다. 유한유소해석은 초음파 혼의 최적 설계와 초음파 공구혼의 고유 주파수를 예상하기 위해 사용되었다. 그리고 설계된 한파장 스텝 혼은 고유 주파수 분석 시스템을 사용하여 실험적으로 검증하였다.

• 한국소음진동공학회논문집
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• 제22권9호
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• pp.845-852
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• 2012

Recently, wireless power transfer technology is ready to be commercialized in consumer electronics. It draws attention from not only experts but also public because of its convenience and huge market. However, previous technologies such as magnetic resonance and induction coupling have limited applications because of its short transfer distance compared to device size and magnetic intensity limitation on the safety of body exposure. As an alternative, ultrasonic wireless power transfer technology is proposed. The ultrasonic wireless power transfer system is composed of transmitter which converts electrical energy to ultrasonic energy and receiver which converts the ultrasonic energy to the electrical energy again. This paper is focused on the development of high energy conversion efficiency of ultrasonic transmitter. Optimal transfer frequency is calculated based on the acoustic radiation and damping effect. The transmitter is designed through numerical analysis, and is manufactured to match the optimal transfer frequency with the size of 100 mm diameter, 12.2 mm thickness plate. The energy conversion efficiency of about 13.6 % at 2 m distance is obtained, experimentally. This result is quite high considered with the device size and the power transfering distance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.771-776
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• 2012

Recently, wireless power transfer technology is ready to be commercialized in consumer electronics. It draws attention of not only experts but also public because of its convenience and huge market. However, previous technologies such as magnetic resonance and induction coupling have limited applications because of its short transfer distance compared to device size and magnetic intensity limitation for the safety of body exposure. As an alternative, ultrasonic wireless power transfer technology is proposed. The ultrasonic wireless power transfer system is composed of transmitter which converts electrical energy to ultrasonic energy and receiver which converts the ultrasonic energy to the electrical energy again. This paper is focused on the development of high energy conversion efficiency of ultrasonic transmitter. Optimal transfer frequency is calculated based on the acoustic radiation and damping effect. The transmitter is designed through numerical analysis, and is manufactured to match the optimal transfer frequency with the size of 100mm diameter, 12.2 mm thickness plate. The energy conversion efficiency of about 13.6% at 2m distance is obtained, experimentally. This result is quite high considered with the device size and the power transfer distance.