• Journal of the Korea Institute of Building Construction
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• v.24 no.1
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• pp.67-75
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• 2024

In the context of Korean residential heating systems, Ondol pipelines are a prevalent choice. However, the maintenance of these pipelines becomes a complex task once they are embedded within concrete structures. As time progresses, the accumulation of sludge, corrosive oxides, and microorganisms on the inner surfaces of these pipelines diminishes their heating efficiency. In extreme scenarios, this accumulation can induce corrosion and scale formation, compromising the system's integrity. Consequently, this research introduces an ultrasonic generation system tailored for the upkeep of Ondol pipelines, with the objective of empirically assessing its practicality. This investigation delineates three variants of ultrasonic generating apparatuses: those employing surface vibration, external generation, and internal generation techniques. To emulate the presence of contaminants within the pipelines, substances in powder, slurry, and liquid forms were employed. The efficacy of the cleaning process post-ultrasonic wave application was scrutinized over time, with image analysis methodologies being utilized to evaluate the outcomes. The findings indicate that ultrasonic waves, whether generated externally or internally, exert a beneficial effect on the cleanliness of the pipelines. Given the inherent characteristics of Ondol pipelines, external generation proves impractical, thereby rendering internal generation a more viable solution for pipeline maintenance. It is anticipated that future endeavors will pave the way for innovative maintenance strategies for Ondol pipelines, particularly through the advancement of internal generation technologies for pipeline applications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.151-154
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• 1993

지동 및 음향분야의 발달과 더불어 가청주파수 이상의 초음파에대한 연구가 여러분야에 걸쳐 다양하게 많은 학 자들에 의해진전되어 왔다. 이중에서 실용적인 초음파 장치가 처음으로 등장한 것은 1921년경 프랑스의 랑지방 (P. Langevin)에 의해 만들어진 초음파측심기라고 전해지고 있다. 당시 사용된 진동자는 두 장의 금속원판 사이에 수정을 샌드위치 형태로 만든것으로써 랑지방형 진동자라고 한다. 최근 각종기계의 경량화, 고도화, 고성능화가 요구 되면서 고인성, 고내열성, 고경도 등의 특성을 갖는 재료를 가공함에 있어서 저동력 및 고정밀도가 요구되고 있다. 본 연구에서는 선삭가공에서 초음파발생기에서 보낸 초음파신호를 초음파 진동혼의 설계에 의한 진폭을 증가시켜 사각형 단면을 갖는 양단자유지지 굽힘진동 공구홀더의 공진조건을 초음파 진동절삭 가공시스템에 적용시키는데 목표를 두며 또한 초음파 진동절삭을 적용시켰을 때의 절삭 특성을 규명하기 위하여 선정된 절삭조건으로 선삭할 때 발생하는 절삭분 력 및 표면거칠기를 측정하고 분석하여 그 결과로부터 절삭특성을 해석코자 본 연구를 수행하였다.

• 전기의세계
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• v.39 no.9
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• pp.27-34
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• 1990

초음파 구동장치는 기존 액츄에이터나 전동기의 우너리나 구조와는 전혀 다른 형태로, 여자전류를 흘리는 권선과 자성체로 이루어진 자기회로등의 기존 전동기에서의 필수 구성요소가 전혀 없이도 필요한 구동 토오크를 발생시키는 가장 구조가 간단한 형태이다. 즉, 압전재료에 교류전원을 인가하면 진동하는 성질을 이용하는 것으로 압전재료를 고정자로 하고 회전자 또는 이동자(리니어 액츄에이터의 경우)를 접촉시켜 놓고 고정자에 초음파 전원을 인가하면 상호간의 마찰에 의하여 힘을 받게 되어 회전자/이동자가 운동하게 되는 원리를 이용한 것이다.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.2
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• pp.84-89
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• 2006

A laser ultrasonic inspection system is a non-contact inspection device which generates and measures ultrasounds by using laser beams. A laser ultrasonic inspection system provides a high measurement resolution because the ultrasonic signal generated by a pulse laser beam has a wide-band spectrum and the ultrasonic signal is measured from a small focused spot of a measuring laser beam. In this paper, we have investigated the detection techniques of a surface-breaking crack by using the laser ultrasonic surface waves. A crack acts as a low pass filter whose cut-off frequency is lowered in proportion to the depth of a crack. And, the center frequency value of a spectrum is decreased in proportion to the depth of a crack. In this paper, we extracted the crack information by using the frequency attenuation from the normalized transfer function spectrum of a surface-breaking crack. Also, we effectively measured the crack depth by using the decreasing value of the center frequency from a crack passed ultrasonic signal. The proposed measuring techniques of crack depths provided more precise information than the amplitude measuring technique.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.30-37
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• 2003

In order to replace the manual ultrasonic testing(UT) with an automated UT(AUT), a scanner which enables us to control the positions of a transducer is essential. Encoders have been commonly used to obtain the position information from the conventional scanners controlled by motor. Encoders have various advantages in many aspects. However, if the slip of motor wheel occurs during scanning, various errors are involved in the position accuracy. Thus, the position information of encoders becomes meaningless in case of slip. The reliability of AUT results nay become serious problem. Hence, slip must be avoided, but it can not be completely avoided at present time. In this paper, a new idea that surface wave is used to solve this problem and replace encoders has been proposed. It is shown that this idea can be employed in AUT scanner without encoders. That is, one transducer transmitting surface wave is fixed and the other transducer attached to the scanner receives UT signal. Then, computer calculates the present position of scanner based on the information given by surface wave. Thus, the movement of a scanner can be controlled by the amount of input based on the information obtained.

• 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 Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1241-1246
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• 2007

In recent years, the semiconductor industry and the optical industry are developed rapidly. The recent demands have expanded for optical components such as the optical lens, the optical semiconductor and the 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. The 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. The steady state flexural vibration of the beam is expressed using Euler-Bernoulli beam theory. The transport direction of an object is examined according to phase difference and frequency. The theoretical results are verified by experiments.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.155-158
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• 2003

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 vibration behavior of flexural beam in the ultrasonic transport system is verified using Laser Scanning Vibrometer. The experiments for verifying vibration are performed in three conditions such as in the maximum transport speed, in the zero speed, and in the change of transport direction.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.151-158
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• 2005

In the semiconductor and the optical industry, a new transport system which can replace the conventional sliding systems is required. The sliding systems are driven by the magnetic field and conveyer belts. The magnetic field nay damage semiconductor and the contact force may scratch the optical lens. The ultrasonic wave driven system can solve these problems. In this paper, an object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal progressive frequency and the phase-differences between two ultrasonic wave generators are performed. The relationships between transportation speed and the excitation frequency, flexural beam shapes and amplification voltage are investigated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.371-375
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• 2003

In recent years, as the semiconductor and the optical industry grows, the necessity of the transporting system for semiconductor and precision optical lens without damage increases. The transport system using ultrasonic wave is very suitable for this area. In this paper the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The effect of transporting speed according to the change of weight and amplification voltage are verified. In addition, the system performance for actual use is evaluated.