• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.763-767
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• 1994

The measured vibration on a machine or a structure is shaped by the excitation waveform and the path transfer function. Mechanism diagnostics tends to focus on retrieving source featurce by minimzing the effects of the structural path, while in structural diagnostics we are more interested in minimizing source effects and retrieving path parameters. In structural diagnostics, therefore, there are experimental issues of gathering data that are independent source effects and finding a transfer function signature that reveals structural defects. This paper describes how the transfer function can be obtained more accurately by experiment using the compatibility relationship which is newly discovered.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.375-382
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• 2016

This paper presents the results for the performance improvement of underwater communication in a passive time reversal mirror (PTRM) using ray-based blind deconvolution (RBD). In conventional PTRM, the signal to be recovered is found from matched-filtering the received probe signal. However, the communication performance is degraded because the time-varying impulse response for each data frame is not reflected in the received probe signal. In this study, the time-variant transfer function is estimated from each received data frame using RBD, and the estimated time-variant transfer function is then used to recover the data signal using PTRM. The results from the experimental data show that the suggested method improves the communication performance when comparing with the conventional PTRM.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.741-746
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• 2007

In this study, transfer path identification and output estimation are simulated by multi-dimension spectral analysis method (MDSA). Multi -input/single-output system give expression the vehicle suspension which each inputs are correlated reciprocally. In case of correlating with inputs, the system needs separating the each input signal by MDSA. Main simulations are about finding effective input by coherent output spectrum and selecting optimal input's number by multiple coherence function. Also, by shielding transfer path of each input, transfer path characteristic is identified in terms of overall integrated contribution level.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.330-337
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• 2010

This paper shows an algorithm for identifying track irregularities using wavelet transfer function along the railway. An equivalent SISO wavelet transfer function is defined using continuous wavelet transform by the measured track geometry and acceleration at a bogie of a train. The estimated track geometry is made by inverse continuous wavelet transform from the regressed signals of measured acceleration signal and the pre-defined wavelet transfer function. The estimated rail irregularity geometry is evaluated by the coherence function and comparison of FRF(Frequency Response Function). As a result of evaluated outcome, This algorithm is regarded as appropriate for estimation of rail irregularity.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2793-2795
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• 2005

고장검출식별시스템의 성능을 좌우하는 가장 중요한 요소는 잔차발생알고리즘이다. 잔차발생기구는 측정된 입출력변수 정보에 근거하여 설계되며 고장의 검출 및 식별이 가능하도록 감결합(decoupling) 특성을 가져야 한다. 본 논문에서는 전달함수 접근 방법 중 최근 제안된 최소차 다항식 기저(minimal polynomial basis)를 이용한 잔차발생기구 설계기법을 소개하고, 이를 VTOL의 센서 및 구동장치고장 검출에 적용하여 그 성능을 검토하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.335-338
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• 2004

효과적인 가상음장 재현을 위한 머리전달함수(Head Related Transfer Function: HRTF) 측정 시도는 1994년에 이루어진 MIT의 Bill Gardner에 의한 KEMAR 머리전달 함수 측정 이후 이미 여러 차례에 걸쳐 이루어졌다. 그러나 대부분의 시도는 음원이 머리중심점에서 1 m 이 후에 위치한 원거리에 국한되었고 음원이 1 m나 그 이내에 위치한 근거리에서의 측정은 스피커에서 반사된 음파가 dummy head 나 피험자의 귀에 다시 들어가는 것을 막기 어려워 시도된바가 적으며 data 도 공개되지 않은 것이 현 실정이다. 음원이 머리중심점에서 1 m 보다 가까운 거리에 있는 경우 머리전달함수의 특성은 고도와 방위뿐만 아니라 거리에도 영향을 받는 것으로 알려져 있으며, 이를 알아보기 위해 무향실에 B&K HATS (Head and Torso Simulator)를 설치하고 단극음원에 가까우며 반사가 적은 스피커를 따로 제작하여 근거리 머리 전달함수를 측정하였고 이를 분석하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.340-341
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• 2010

Noise reduction is an important factor to design low noise sensor array. In this paper three layers of the de-coupler in the conformal sensor array were used to investigate noise reduction. Conformal sensor array is positioned in the layers and the distance from the layer is 0.25cm~1.5cm. Transfer function in the frequency density function is investigated according to the three different positions. When increasing the embedded distance the flow noise decreased in the region of the kx>10.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.122-132
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• 2000

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in 'Free Vibration of Car seat and Mannequin System' nonlinear and linear equations of motions were rederived for forced vibration and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests mannequin's head had a lot of problems and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints linear analyses were performed. New sets of linear spring and damping coefficients and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance indicating that this is a feasible method of modeling seated occupants.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.398-403
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• 2001

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in previous paper. Nonlinear and linear equations of motions were rederived for forced vibration, and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests, mannequin's head had a lot of problems, and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints, linear analyses were performed. New sets of linear spring and damping coefficients, and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance, indicating that this is a feasible method of modeling seated occupants.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.992-998
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• 1992

This paper presents a method for dynamic analysis of golf club. In the analysis, the sweet spot of golf club is defined based on the magnitude of torsional vibration, and transfer matrix method is employed for numerical calculations. It is shown that the calculated natural frequencies, mode shapes and transfer function agree well with the experimental results.