• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.554-560
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• 1998

Acoustic performance of the absorptive mufflers used in air-conditioning and ventilating ducts, gas turbines, industrial fans influenced by the design parameters such as the length of mufflers, lining thickness, properties of the acoustic lining, and so forth. So we predicted the acoustic performance according to the design parameters. For the analysis, we assumed the radial propagation constant is locally reacted to the acoustic lining, and analyzed the acoustic performance based on the plane wave theory by using four-pole parameters.

• 한국해양공학회지
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• 제20권1호
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• pp.48-54
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• 2006

In this paper, flowfield and acoustic-field around moving bodies are simulated by the Arbitrary Lagrangian Eulerian (ALE) formulation in the finite difference lattice Boltzmann method. Some effects are checked by comparing flaw about a square cylinder in ALE formulation and that in the fixed coordinates, and both agree very well. Matching procedure between the moving grid and fixed grid is also considered. The applied method in which the both grids are connected through buffer region is shown to be superior to moving overlapped grid. Dipole-like emissions of sound wave from harmonically vibrating bodies in two- and three-dimensional cases are simulated.

• Journal of electromagnetic engineering and science
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• 제7권1호
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• pp.12-16
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• 2007

A UHF band wireless identification system based on passive surface acoustic wave(SAW) devices is presented in this paper. SAW ID tags were fabricated on Y-Z $LiNbO_3$ piezoelectric substrate with a good electro-mechanical coupling property. To reduce degradation of the antenna performance associated with the piezoelectric materials, an efficient design of the SAW RFID antenna is introduced. By measuring the parameters of the SAW ID tag, the performance of the antenna was tested by experimentation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.223-225
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• 2008

In this study. we propose a wide bandwidth surface acoustic wave (SAW) motor by design of Inter Digital Transducer (IDT). SAW motor has several benefits compared with preexisted actuator. But it has narrow bandwidth, which causes the lower performance. To widen the bandwidth, the change of IDT structure was proposed, which is slanted IDT and since function apodization. The frequency responses were compared original uniform IDT and changed IDT. And the time responses were compared original uniform IDT and changed IDT. As a result, the feasibility of wide bandwidth SAW motor was certified.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1100-1105
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• 2007

In the gas supply duct, the gas leakage caused by the impact of the construct equipment is serious problem. The identification of the impact position is an important issue and an engineering work. For the basic research of this problem, the principle studies for the acoustic wave propagation in a gas duct are proceeded in this paper. This principal work is based on the identification of the cut-off frequency associated with major modes of the gas duct theoretically and experimentally. The cut-off frequency is confirmed by STFT and cross-correlation function is used to identify the leakage position.

• 한국소음진동공학회논문집
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• 제21권3호
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• pp.206-211
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• 2011

In this paper, we report a high-precision wireless gap sensor based on a surface acoustic wave (SAW) device. The sensing element is a parallel-plate capacitor whose dimensions are $3{\times}3\;mm^2$, and is attached to the SAW device as an external load. The SAW device, equipped with an RF antenna, serves simultaneously as a signal conditioner and an RF transponder. The center frequency of the SAW device is 450 MHz. The wireless gap sensor prototype exhibits a resolution of 100 nm and a sensing range of $50{\mu}m$. The proposed sensor system can be used for remote, high-precision gap measurement in hard-to-reach environments.

• Smart Structures and Systems
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• 제4권5호
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• pp.565-582
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• 2008

This paper presents a feasibility study of flexible piezoelectric paint for use in wide-band low-profile surface-mount or embeddable ultrasonic sensor for in situ structural health monitoring. Piezoelectric paint is a piezoelectric composite with 0-3 connectivity. Because of its ease of application, piezoelectric paint can be readily fabricated into sensing element with complex pattern. This study examines the characteristics of piezoelectric paint in acoustic emission signal and ultrasonic guided wave sensing. A series of ultrasonic tests including pitch catch and pencil break tests were performed to validate the ultrasonic wave sensing capability of piezoelectric paint. The results of finite element simulation of ultrasonic wave propagation, and acoustic emission generated by a pencil lead break on an aluminum plate are also presented in this paper along with corresponding experimental data. Based on the preliminary experimental results, the piezoelectric paint appears to offer a promising sensing material for use in real-time monitoring of crack initiation and propagation in both metallic and composite structures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.156-159
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• 2002

Film Bulk Acoustic wave Resonator (FBAR) using thin piezoelectric films can be fabricated as monolithic integrated devices with compatibility to semiconductor process, leading to small size, low cost and high Q RF circuit elements with wide applications in communications area. This paper presents a MMIC compatible Suspended FBAR using surface micromachining. It is possible to make Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$membrane by using surface micromachining and its good effect is to remove the substrate silicon loss. FBAR was made on 2$\mu\textrm{m}$ multi-layered membrane using CVD process. According to our result, Fabricated film bulk acoustic wave resonator has two adventages. First, in the respect of device Process, our Process of the resonator using surface micromachining is very simple better than that of resonator using bull micromachining. Second, because of using the multiple layer, thermal expansion coefficient is compensated, so, the stress of thin film is reduced.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.673-676
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• 2003

This paper describes the modeling and experimental results for Bulk Acoustic Wave(BAW) Resonator using PolyVinyliDene Fluoride(PVDF). We measured the input reflection coefficient ($S_{11}$) of resonators using vector network analyzer and experimental results were measured fundamental resonance at 2.3 GHz with a return loss of -29 dB. Because of fabricated resonator without etching process, we can confirm a possibility of resonator application as using a PVDF.

• 대한기계학회논문집
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• 제18권2호
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• pp.251-259
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• 1994

Nearfield acoustic holography is known as a powerful tool to study sound radiation from a structure. In this work, the so called backward propagation of sound pressure field is studied to obtain the structure velocity distribution. The results, which were obtained using FFT algorithms, are presented for a finite plate excited at the frequencies above and below coincidence. These results illustrate the effect of stand-off distance and noise. An optimum cutoff frequency in wavenumber domain was suggested to reduce the effects of evanescent wave in the backward propagation. The experimental results were also included for a plate to demonstrate the effectiveness of the suggested cutoff frequency. The optimum cutoff frequency to exclude the unwanted noise in the process of reconstruction of the velocity field gives the good results in both simulations and experiments.