• Nuclear Engineering and Technology
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• 제36권1호
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• pp.12-23
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• 2004

In the present study a new measurement technique has been developed, which uses an ultrasonic transmission signal in order to identify the vertical two phase flow pattern. The ultrasonic measurement system developed in the present study not only provides the information required for the identification of vertical two phase flow patterns but also makes real time identification possible. Various vertical two phase flow patterns such as bubbly, slug, churn, annular flow etc. have been accurately identified with the present ultrasonic measurement system under atmospheric condition. In addition, the present test apparatus can practically simulate the ultrasonic propagation characteristics under high temperature and high pressure systems. Therefore, it is expected that the present ultrasonic flow pattern identification technique could be applicable to the vertical two phase flow systems under high temperature and high pressure conditions.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.953-958
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• 2007

In this paper, multilayer actuator structured-ultrasonic nozzle and resonant inverter driving circuit were manufactured, respectively. Its electrical properties were investigated. Multilayer actuator structured ultrasonic nozzle was fabricated using PMN-PNN-PZT ceramics showing excellent piezoelectric characteristics. In order to drive ultrasonic nozzle, resonant PWM inverter was used. The purpose of this study is to find the optimal driving condition of ultrasonic nozzle. Accordingly, electrical and temperature characteristic of multilayer ultrasonic driving system were investigated by experiments as a function of the series resonance inductance. The driving current of ultrasonic nozzle showed the maximum current of 27 mA. Also, the surface temperature of ceramic vibrator showed $44^{\circ}C$ at driving time for 20 min. The ultrasonic nozzle was stably operated in the case of driving for more than 20 min.

• 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.

• 한국정밀공학회지
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• 제24권8호통권197호
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• pp.41-49
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• 2007

In this paper, we proposed a new ultrasonic distance measurement system with high accuracy and long range. To improve accuracy and enlarge range, the time of flight of ultrasonic is calculated by the period detecting method. In the proposed ultrasonic distance measurement system, the ultrasonic transmitter and receiver are separated but synchronized by RF(Radio frequency) module. The experiment has been implemented from short distance 1m to maximum available distance 30m. And the period detecting method is compared with the conventional threshold level method. Experimental results show the accuracy and range of the distance measurement are improved by this period detecting method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1014-1020
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• 2003

We have developed the ultrasonic polishing system to get super finishing that consist of machine part that can rotate and travel the main shaft with power 1.5kW, ultrasonic generator with frequency 20kHz. By using this system we were investigated the characteristics of ultrasonic polishing and deduced the major facters which affect the surface roughness by the experimental plans for three different materials such as ceramic, glass, and wafer, and so could be obtained following results. We could be obtained the excellent surface for hard-to-difficult cutting materials. The rotating speed could be found to be major factor influencing the surface roughness. In the case of ceramic and wafer, we were able to obtain good surface roughness when the feed rate and ultrasonic output is higher. In the case of glass, the surface roughness becames worse when ultrasonic output is higher because of increasing of load affacting on the particles in slurry.

• 제어로봇시스템학회논문지
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• 제9권12호
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• pp.1009-1018
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• 2003

In a park or street, we can see many people Jogging or walking with their dogs chasing their masters. In the previous study, an entertainment robot, CARTRI that imitates the dog's behavior was created. The robot's task was chasing a moving goal that was recognized as the master. The physical structure of the CARTRI robot was three-wheel type locomotion system. The sensor system which could detect the position of the master in the outdoor space, was consists of a signal transmitter which was held by the master and five ultrasonic receivers which were mounted on the robot. In the experiment, the robot could chase a human walking in outdoor space like a park. But it could not avoid obstacles and its behavior was only goal-chasing behavior because of the limit of the sensor system. In this study, an improved RF-ultrasonic sensor system which can detect both goal and obstacle is developed in order to enable the CARTRI robot to carry out various behavior. The sensor system has increased angle resolution by using eight ultrasonic receivers instead of five in the previous study. And it can detect obstacle by using reflective type ultrasonic sensors. The sensor system is designed so that detection of goal and obstacle could be conducted in one sampling period. The Performance of the developed sensor system is evaluated through experiments.

• 제어로봇시스템학회논문지
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• 제14권7호
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• pp.647-655
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• 2008

This paper presents real-time algorithm for an ultrasonic Local Positioning System(LPS). An ultrasonic LPS consists of 4 transmitters and n receivers. Each transmitter transmits an sequential ultrasonic signal to avoid interference of ultrasonic signal. This method is a noneffective application for a fast object. Because receiver detects four sequential transmissive ultrasonic signal and calculates a position. This paper proposes the method which 4 transmitters transmit simultaneous ultrasonic signal and each transmitter distinguished by frequencies and codes. And Auto-Correlation Function(ACF) method separates codes from an ultrasonic echo signal which is interference of each transmitter's code. If the receiver uses only ACF method, it is difficult to implement real time application for increased computation. This paper implements LPS using dual frequencies and ACF method. Using dual frequencies reduces codes length. The reduced codes length save computation in ACF. To prove this algorithm by experiment, high performance DSP(digital signal processor) used. The result shows the performance of the designed system is good enough positioning.

• 한국융합학회논문지
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• 제11권1호
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• pp.175-180
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• 2020

본 연구에서는 미세패턴 성형이 가능하도록 개발된 초음파 미세패턴 제조시스템을 이용하여 RFID TAG 안테나 형상의 미세패턴 성형기술을 개발하였다. 미세패턴 제조시스템에 종진동 모드의 초음파 공구 혼을 설치하여 절연시트 표면에 RFID TAG 안테나 형상의 미세패턴 안테나 형상을 초음파 압입 성형공정 기술을 개발하였다. 초음파 성형기술은 60kHz 공구 혼을 공진설계 기법을 적용하여 제작하였고, 미세패턴 제조시스템을 이용하여 200㎛ 이하의 절연 시트지에 두께가 25㎛의 코일 와이어를 초음파 압입 성형을 할 수 있다. 초음파 압입 성형 시 코일 와이어의 단선, 박리 및 꼬임 현상 없이 최소선폭 150㎛인 안테나 형상을 성형할 수 있었다.

• 동력기계공학회지
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• 제9권4호
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• pp.5-10
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• 2005

The effect of ultrasonic energy for diesel fuel and blend oil has been revealed in this paper. The experimental setup consisted of a high speed diesel engine with 4 cylinder, dynamometer and ultrasonic fuel feeding system. Ultrasonic energy was added to diesel fuel and blend oil, which is a blend of diesel fuel and rape-seed oil. As engine speed was changed, engine torque and power, brake specific fuel consumption and thermal efficiency were measured in detail. As the results, by adding ultrasonic energy to diesel fuel and blend oil, the engine performance was improved in range of the experiment. The effect of improvement on brake specific fuel consumption and thermal efficiency for blend oil is higher than that for diesel fuel. When ultrasonic energy was added to diesel fuel or blend oil, a rise in engine torque for diesel fuel was higher than that for blend oil, but the effect of ultrasonic energy was small. From these results, it may be desirable to add ultrasonic energy to blend oil for the use of blend oil to diesel engine.

• Journal of the Optical Society of Korea
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• 제17권4호
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• pp.323-327
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• 2013

A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.