• Title/Summary/Keyword: acoustic transducer

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Development of a split beam transducer for measuring fish size distribution (어체 크기의 자동 식별을 위한 split beam 음향 변환기의 재발)

  • 이대재;신형일
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.37 no.3
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    • pp.196-213
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    • 2001
  • A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

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Fabrication of 1-3 Piezo-composites with a "Dice & Fill" Method and Characterization of Their Piezoelectric Properties as a Function of Lateral Spatial Scale ("Dice와 fill" 방식을 이용한 1-3 압전복합재의 제조와 횡방향 단위 크기에 따른 압전특성 평가)

  • Kim, Young-Deog;Kim, Kwang-Il;Jeong, Woo-Cheol;Kim, Heung-Rak;Kim, Dong-Su
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.4
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    • pp.354-360
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    • 2002
  • The piezoelectric composites had many advantages in comparison with conventional piezoelectric ceramics and piezopolymers for ultrasonic transducers used in NDT and in medical ultrasionic imaging. The electromechanical coupling coefficient should be high and the acoustic impedance should be low in these applications. However, the cross-coupling with spurious oscillations caused by laterally running plate waves exhibited complex motions in the surface of piezoelectric composites with coarse lateral spatial scale. The thickness mode electromechanical coupling coefficient of 1-3type of piezoelectric compoistes were 0.36 to 0.64, and the acoustic impedance of them were 9.8 to 22.7 MRayl. The lateral resonance frequency of 1-3 type piezoelectric composites shifted to high frequency region with decreasing lateral spatial scale.

Experimental Study on Effect of Boiling Heat Transfer by Ultrasonic Vibration (초음파 진동이 비등열전달 과정에 미치는 영향에 관한 실험적 연구)

  • Na Gee-Dae;Oh Yool-Kwon;Yang Ho-Dong
    • Journal of Energy Engineering
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    • v.15 no.1 s.45
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    • pp.35-44
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    • 2006
  • This study experimentally investigates effect of boiling heat transfer when ultrasonic vibration was applied. Under the wall temperature condition, temperature distribution in a cavity was measured during the boiling process and heat transfer coefficient of convection, sub-tooled boiling and saturated boiling states were measured with and without ultrasonic vibration, respectively. Also, the profiles of the pressure distribution in acoustic field measured by a hydrophone were compared with the augmentation ratios of heat transfer calculated by local heat transfer coefficient. Result of this study, heat transfer coefficient and augmentation ratio of heat transfer is higher with ultrasonic waves than without one. Especially, augmentation ratio of heat transfer is more increased the convection state than sub-cooled boiling and saturated boiling states. Acoustic pressure is relatively higher near ultrasonic transducer than other points where is no installed it and affects the augmentation ratio of heat transfer.

Structural Integrity Evaluation of Nozzle Assembly using Acoustic Emission Technique (음향방출법을 응용한 노즐 조립체의 구조건전성 평가)

  • 설창원;이기범
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.10
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    • pp.32-39
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    • 2006
  • An acoustic emission technique was applied to the structural strength test for the structural integrity evaluation of the nozzle assembly. These AE results were compared with data from the strain gages and displacement transducer. NDT using X-ray technique was performed to improve the test reliability before and after each test. In this structural integrity evaluation of the nozzle assembly, the internal crack initiation in the structure could not be precisely revealed by the strain and displacement results but the location and load level of the initiated crack could be precisely evaluated by using AE technique. From this test, it was proven that some new cracks can be generated in composite liner of nozzle assembly under the unexpected load due to interference between obturator and nozzle and these can be a cause of the unexpected abnormal failure.

Analysis of Acoustic Emission Signal Sensitivity to Variations in Thin-film Material Properties During CMP Process (CMP 공정중 박막 종류에 따른 AE 신호 분석)

  • Park, Sun Joon;Lee, Hyun Seop;Jeong, Hae Do
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.8
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    • pp.863-867
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    • 2014
  • In this study, an acoustic emission (AE) sensor was used for measuring the abrasive and molecular-scale phenomena in chemical mechanical polishing (CMP). An AE sensor is a transducer that converts a mechanical wave into an electrical signal, and is capable of acquiring high-level frequencies from materials. Therefore, an AE sensor was installed in the CMP equipment and the signals were measured simultaneously during the polishing process. In this study, an AE monitoring system was developed for investigating the sensitivity of the AE signal to (a) the variations in the material properties of the pad, slurry, and wafer and (b) the change in conditions during the CMP process. This system was adapted to Oxide and Cu CMP processes. AE signal parameters including AE raw frequency, FFT, and amplitude were analyzed for understanding the abrasive and molecular-level phenomena in the CMP process. Finally, we verified that AE sensors with different bandwidths could function in complementary ways during CMP process monitoring.

A Study on the Protocol Design and Implementation for an Underwater Acoustic Multi-channel Digital Communication (수중 초음파 디지탈 이동통신을 위한 프로토콜 설계 및 구현에 관한 연구)

  • 박연식;임재홍
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.4 no.1
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    • pp.179-189
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    • 2000
  • Recently, due to the increasing interests in deep sea development, all possible efforts to the development of underwater unmanned working vehicles such as AUV(Autonomous Underwater Vehicle) or underwater robot are exerted. This paper proposes a new efficient acoustic-based underwater image data communication system, which ensures a certain level of maximum throughput regardless of the propagation delay of ultrasonic and allowsfast data transmission through the multiple ultrasonic communication channel. Proposed system consists of an acoustic transducer which operates at 136kHz center frequency and it's 10kHz bandwidth, pre-amplifier, $\pi/4 QPSK$(Quadrature Phase Shift Keying) modulation/demodu-lation method, image compressing method using JPEG technique and modified Stop & Wait protocol. The experimental result of the system make it possible to transfer the underwater image as a high throughput at the basin test. The results of test are also verified which allows to desirable transmission performance compared with the existing developed system and the possibility to put the practical use of survey and investigation in the water.

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Liquid Film Thickness Measurement by An Ultrasonic Pulse Echo Method (초음파 Pulse-echo 방법에 의한 액체막 두께 측정)

  • Jong Ryul Park;Jong-Ryul Park;Se Kyung Lee
    • Nuclear Engineering and Technology
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    • v.17 no.1
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    • pp.25-33
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    • 1985
  • The main purpose of this work is to investigate the effects of the wall thickness, the ultrasonic frequency, and the acoustic impedance of wall material on the liquid-film thickness measurement by an ultrasonic pulse echo method. A series of liquid-film thickness measurements in a horizontal air-water stratified system was performed employing a plate-type and a tube-type test sections. Measurements were repeated changing (1) the wall thickness of the test section and (2) the transducer frequency. Also, in an effort to improve the accuracy of the measurement and to exam me the effect of acoustic impedance of wall material on the measurement by an ultrasonic technique, two different stand-off rods, one made of stainless steel and the other polyacrylate, were used in the liquid-film thickness measurement. These experimental results are discussed and compared with the actual film thicknesses.

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A Study on Development of Acoustic Tweezer System Using Standing Waves and Very High Frequency Focused Beams (정상파와 초고주파 집속 빔을 이용한 음향집게시스템의 개발에 관한 연구)

  • Yang, Jeong-Won;Ha, Kang-Lyeol;Kim, Moo-Joon;Lee, Jung-Woo;Shung, K.K.
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.7
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    • pp.357-364
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    • 2008
  • For the purpose of possibility study on development of an acoustic tweezer using standing waves and very high frequency ultrasound focused beams, a system which can manipulate the position of particles in water has been constructed. It can move the particles to near focal point of a focused beam by the radiation force of standing waves, and then the particles would be trapped by the radiating force of the focused beam. The results show that micro sphere particles were trapped well at nodes of the standing waves and their position can be easily manipulated by frequency control. And, even though the radiation force by single focused beam pushes a particle away from the transducer, two focused confronted beams can trap it at near center.

Development of Ultrasonic-Optical Fiber Sensor and its Applications (초음파-광섬유 센서의 개발과 그 응용)

  • Oh, Il-Kwon;Lim, Seung-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.169-174
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    • 2006
  • The outstanding mechanical property of optical fiber and the merits of acoustic emission sensing technique are unified for novel sensor system. The generated ultrasonic wave from piezoelectric generator are propagated along the optical fiber and also sensed. The propagated wave can be influence by external pressure on the optical fiber or environmental circumstance. The optical fiber sensor using ultrasonic wave has advantages compare with existing sensor system. In this study, the sensitivity of the optical fiber sensor is experimentally investigated. As the applications of the optical fiber sensor system using piezoelectric ultrasonic waves, the point load on the optical fiber is measured and the monitoring system for the void fraction of two phase flows is developed. The experimental results show the linear relationship between sensed voltage and void fraction.

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Development of a Wireless, Battery-free SAW-based Temperature and Humidity Sensor incorporating a Bidirectional Reflective Delay Line (양방향 반사 지연선을 이용한 무선, 무전원 SAW 기반 온, 습도 센서 개발)

  • Lim, Chun-Bae;Lee, Kee-Keun
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.1515_1516
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    • 2009
  • A 440MHz wireless and passive surface acoustic wave (SAW) based micro-sensor was developed for simultaneous measurement of temperature and humidity. The developed sensor is composed of a SAW reflective delay lines structured by an IDT (Inter-Digital Transducer), four reflectors and humidity sensitive film (polyimide). Polyimide was dry-ecthed by RIE (Reactive Ion Etching) to obtain high roughness, which gives the large reaction area resulting in high sensitivity. In wireless testing using a network analyzer, sharp reflection peaks with high S/N ratio, small signal attenuation, and few spurious peaks were observed in the time domain. High sensitivity towards the temperature and humidiy were also observed in the large concentration range. The obtained sensitivity was $16.8^{\circ}/^{\circ}C$ for temperature sensor and $15.8^{\circ}$/%RH for humidity sensor.

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