• Nuclear Engineering and Technology
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• 제52권4호
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• pp.776-783
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• 2020

As the refueling of a sodium-cooled fast reactor is conducted by rotating part of the reactor head without opening it, the monitoring of existing obstacles that can disturb the rotation of the reactor head is one of the most important issues. This paper deals with the ultrasonic ranging technique that directly monitors the existence of possible obstacles located in a lateral gap between the upper internal structure and the reactor core in a prototype generation IV sodium-cooled fast reactor (PGSFR). A 10 m long plate-type ultrasonic waveguide sensor, whose feasibility has been successfully demonstrated through preliminary tests, was employed for the ultrasonic ranging technique. The design of the sensor's wave radiating section was modified to improve the radiation performance, and the radiated field was investigated through beam profile measurements. A test facility simulating the lower part of the upper internal structure and the upper part of the reactor core with the same shapes and sizes as those in the PGSFR was newly constructed. Several under-water performance tests were then carried out at room temperature to investigate the applicability of the developed ranging technique using the plate-type ultrasonic waveguide sensor with the actual geometry of the PGSFR's internal structures.

• Environmental Engineering Research
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• 제11권2호
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• pp.99-105
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• 2006

A digital ultrasonic image construction system was developed for the nondestructive detection of cracks in water distribution pipes. The system consists of PC based ultrasonic testing system and a scanning device. The PC based ultrasonic system has an ultrasonic pulse/receive board for the generation and reception of ultrasonic signals, an analogue to digital conversion board for the digitization of the received ultrasonic signals, and transducers for the ultrasonic sensors. Using this system, the digitized ultrasonic signals were properly constructed in accordance with the position information obtained by scanning device that moves an ultrasonic transducer along the outer surface of pipes. In the construction of the ultrasonic signals, signal processing concepts, such as spatial average and array concept, were considered to enhance the resolution of ultrasonic images of pipe wall. Using the developed system, crack detection experiments were performed in both laboratory and field, which shows promise for crack detection in the water distribution system.

• Smart Structures and Systems
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• 제22권2호
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• pp.223-230
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• 2018

This study examines a non-contact laser scanning-based ultrasound system, called an angular scan pulse-echo ultrasonic propagation imager (A-PE-UPI), that uses coincided laser beams for ultrasonic sensing and generation. A laser Doppler vibrometer is used for sensing, while a diode pumped solid state (DPSS) Q-switched laser is used for generation of thermoelastic waves. A high-speed raster scanning of up to 10-kHz is achieved using a galvano-motorized mirror scanner that allows for coincided sensing and for the generation beam to perform two-dimensional scanning without causing any harm to the surface under inspection. This process allows for the visualization of longitudinal wave propagation through-the-thickness. A pulse-echo ultrasonic wave propagation imaging algorithm (PE-UWPI) is used for on-the-fly damage visualization of the structure. The presented system is very effective for high-speed, localized, non-contact, and non-destructive inspection of aerospace structures. The system is tested on an aluminum honeycomb sandwich with disbonds and a carbon fiber-reinforced plastic (CFRP) honeycomb sandwich with a layer overlap. Inspection is performed at a 10-kHz scanning speed that takes 16 seconds to scan a $100{\times}100mm^2$ area with a scan interval of 0.25 mm. Finally, a comparison is presented between angular-scanning and a linear-scanning-based pulse-echo UPI system. The results show that the proposed system can successfully visualize defects in the inspected specimens.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.846-851
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• 2004

In this paper, we propose a global ultrasonic system for the self-localization and autonomous navigation of indoor mobile robots. The ultrasonic sensor is regarded as the most cost-effective ranging system among the possible alternatives, and it is widely used for general purpose, since it requires simple electronic drivers and has relatively high accuracy. The global ultrasonic system presented in this paper consists of four or more ultrasonic generators fixed at reference positions in the global coordinates of an indoor environment and two receivers mounted on the mobile robots. By using the RF (Radio Frequency) modules added to the ultrasonic sensors, the robot is able to control the ultrasonic generation and to obtain the critical distances from the reference positions, which are required in order to localize is position in the global coordinates. A kalman filter algorithm designed for the self-localization using the global ultrasonic system and the experimental results of the autonomous navigation are presented in this paper.

• 비파괴검사학회지
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• 제29권4호
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• pp.283-292
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• 2009

Laser-based ultrasonic sensing requires the probe with fixed fecal length, but this requirement is not essential in laser-based ultrasonic generation. Based on this fact, we designed a pulsed laser-based ultrasonic wave propagation imaging (UWPI) system with a tilting mirror system for rapid scanning of target, and an in-line band-pass filtering capable of ultrasoaic mode selection. 1D-temporal averaging, 2D-spatial averaging, and 3D-data structure building algorithms were developed far clearer results allowing fur higher damage detectability. The imaging results on a flat stainless steel plate were presented in movie and snapshot formats which showed the propagation of ultrasound visible as a concentric wavefield emerging from the location of an ultrasonic sensor. A hole in the plate with a diameter of 1 mm was indicated by the scattering wavefields. The results showed that this robust UWPI system is independent of focal length and reference data requirements.

• 한국건축시공학회지
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• 제24권1호
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• pp.67-75
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• 2024

한국은 주택 난방 방식으로 대부분 온돌 파이프라인을 이용한 방법을 채택하고 있으나 콘크리트 속에 매설되어 있는 특성으로 인해 설치 후 배관 내부의 지속적인 관리를 하기가 쉽지 않다. 온돌 배관은 장기간 사용을 하면 슬러지나 부식 산화물, 미생물 등이 배관 내벽에 퇴적되면서 난방의 효율이 나빠져서 심한 경우에는 열화에 의한 부식, 스케일 등의 문제를 일으키기도 한다. 따라서 본 연구는 온돌 파이프라인의 유지관리를 위하여 초음파 발생 방식을 제안하고 그 가능성을 실험으로 확인하는데 그 목적이 있다. 본 연구를 위한 초음파 발생 장치는 3가지로 제시되며, 표면 진동형, 외부 발생형, 내부 발생형이 그것이다. 관내 오염물은 분말형 가루, 슬러지형 가루, 액상 물질로 선정하였다. 초음파 발생 이후 시간에 따른 세척 효과를 확인하였으며, 세척 결과는 이미지 분석 방법을 통해 산출하였다. 실험 결과, 배관 외부에서 발생시킨 초음파가 효과적임을 알 수 있었으나 배관 내부에서 발생시킨 초음파 역시 유사한 세척 결과를 얻었다. 온돌 배관의 특성 상 외부 발생이 불가능하므로 내부의 발생을 통한 세척 효과가 있을 것으로 기대된다. 향후 배관 내부 발생 장치의 개발을 통해 온돌 파이프라인의 유지관리를 위한 새로운 방식의 제시가 가능할 것으로 기대된다.

• 동력기계공학회지
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• 제17권6호
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• pp.142-148
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• 2013

High-power ultrasonic promotes a chemical reaction by its own energy, thus it has been used for sonochemistry applications. For example, it has been mostly used for mixing, reaction catalyst, dispersion and disintegration. High-power ultrasonic transducer is made with structure based on a Bolt-clamped Langevin type Transducer (BLT), But it has difficulty in the development because degradation of piezoelectric ceramic by the heat generation of BLT. In this study, for a development of the transducer of 25 kHz and 1000 W used in sonochemistry and industrial cleaning, BLT with a hole in its center and tubular type waveguide of the transducer were designed based on finite element method (FEM). The transducer was fabricated based on the design parameter, and the impedance characteristics are measured experimentally and compared with the numerical results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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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.

• 오토저널
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• 제15권3호
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• pp.47-54
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• 1993

This paper describes briefly the effect of ultrasonic fuel supply device on the performance of four stroke cycle gasoline engine. Experiments were carried out to clarify the effect of ultrasonic fuel supply device on the engine output, traveling fuel consumption ratio, exhaust emissions. The results were obtained as follows: 1.Engine output was increased 9-14% in comparison with that of the conventional injector. 2.Travelling fuel consumption ratio was improved 17-29% in comparison with that of the conventional injector. 3. CO, HC exhaust emissions was decreased compared to the value of the conventional injector. 4.Fuel consumption ratio in highway driving test was improved about 10% in comparison with that of the conventional injector.

• Composites Research
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• 제29권5호
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• pp.288-292
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• 2016

본 연구에서는 전영역 초음파전파영상화 시스템이라 불리는 새로운 초음파전파영상화 장치를 소개한다. 본 시스템은 비파괴적으로 구조를 2 축 선형 이동 스테이지 기반으로 검사한다. 일치된 초음파 센싱과 가진 레이저 빔이 구조를 스캔하며 동시에 펄스-에코 모드 레이저 초음파를 수집한다. 이 과정은 스캔영역만큼 큰 두께 방향의 전영역 초음파를 생성하는 것을 가능하도록 한다. 본 시스템을 사용하여 실제로 운용 중인 알루미늄 허니콤 구조 기반의 CN-235의 도색된 샌드위치 조종면를 검사 및 평가하고 구조 검사 결과로써 전영역 초음파전파 영상을 소개하였으며 기존 초음파 탐상 기법의 결과와 비교하여 성능 및 민감도를 검증하였다.