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Simulation of magnetostrictive Terfenol-D rod dynamics using a coupled FE-BEM
장순석 한국센서학회 1999 센서학회지 Vol.8 No.4
This paper describes the application of the coupled FE-BEM (finite element-boundary element method) for the numerical harmonic analysis of the linear dynamic behaviour of a magnetostrictive Terfenol-D rod in water. The magnetostrictive rod is three-dimensionally simulated to transduce applied electric current in a helical coil around the rod to mechanical displacement. The theoretical derivation of the magnetostrictive matrix equation is described in detail. The steady-state resonance response of the displacement is shown. In addition, the directivity pattern and the radiation impedance are also shown.
64채널 디지털 보청기의 In-situ에 의한 휘팅 실험 연구
장순석,Jarng, Soon-Suck 한국음향학회 2012 韓國音響學會誌 Vol.31 No.5
본 논문에서는 64채널 디지털 보청기의 주파수 채널 별 비선형 압축을 위한 휘팅 기법을 연구하였다. 청력 검사 결과로부터 수행되는 기존의 휘팅 포뮬라 기법과 달리, 귓속형 보청기를 사용자가 외이도에 착용한 상태에서 고막에서의 청력 역치를 측정하여 이를 휘팅에 적용하였다. 또한 외부 음성 음압의 주파수 별 분포도를 활용하여 입력 음압 대비 출력 음압 압축 곡선을 구현하였다. FFT-iFFT 방식의 이론적 압축 연구 결과를 실험적으로도 검증하였으며, 입력음압 레벨이 각각 50 dB, 70 dB, 90 dB일 때의 증폭 이득 곡선을 보여주었다. In this thesis, a nonlinear compression fitting method was studied for each frequency channel of a 64 channel digital hearing aid. Unlike conventional fitting formula method done from the result of the hearing loss test, the present fitting method uses the auditory threshold of sound pressure measured near the tympanic membrane while ITE (In-The-Ear) hearing aid is fitted into the user's ear canal. Also, the spectral distribution of the voice sound pressure was used for realizing of output sound pressure compression curves against input sound pressure level. Theoretical research results of FFT-iFFT compression algorithm has been evaluated by experimental gain measurements at each different input sound pressure level 50 dB, 70 dB, 90 dB respectively.
광학적 비접촉 측정에 의한 구조물에 해석의 화상처리 계측 시스템 개발에 관한 연구
장순석,김경석,양승필,정현철,강기수,김종수,최지은 한국공작기계학회 1999 한국생산제조학회지 Vol.8 No.6
This study discusses a non-contact optical technique, electronic speckle pattern interferometry(ESPI), that is well suited for in-plane and out-of-plane deformation measurement. However, the existing ESPI methods that are based on dual-exposure, real-time and time-average method have difficulties for accurate measurement of structure, due to irregular intensity and shake of phase. Therefore, phase shifting method has been proposed in order to solve this problem. About the method, the pah of reference light in interferometry is shifted and added to least square fitting method to make the improvement in distinction and precision. This proposed method is applied to measure in-plane displacement, that is compared with the previous method. Also, Used as specimen, AS4/PEEK [30/-30/90]s was analyzed by ESPI based on real-time to determine the characteristics of vibration under no-load and tension. These results are quantitatively compared with those of FEM analysis in mode shapes.
두 개의 정현 신호를 이용한 속도 측정용 고전력 쏘나 시스템 개발
장순석,안흥구,이제형 한국소음진동공학회 1999 소음 진동 Vol.9 No.5
This paper aims for the development of the high power sonar system for measuring the velocity of a moving object. The high power sonar system transmits two gated 190 kHz sinusoidal signals with 1.6 [ms] time interval to the moving object. Then the sonar system detects and calculates the changed time delay of the reflected ultrasonic signals in order to derive the velocity of the moving object. The transmission part uses a high power amplifier so that 250 W gated sinusoidal signals can be transmitted to the transmitter. 1M RAM is utilized for transmitting and storing of the ultrasonic signals. The time delay is calculted by the cross-correlation technique between the transmitted signals and the received signals. The measured value from the high power sonar system is compared with directly measured values by photo diodes. The result confirms the adjacency to 0.3% error.