• 한국자동차공학회논문집
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• 제4권3호
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• pp.40-49
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• 1996

With the advance of the standard of living, the demand on automobile goes beyond the simple transportion equipment, therefore the interior noise reduction has been the important factor for improvement of the ride quality. Idling noise is a major vehicle characteristic determining occupant comfort. In the present research two approaches for noise source identification based on theory for multi-input system have been investigated. The concept of the frequency response function and the multi-dimensional spectral analysis were used to estimated the spectra of the noise source.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.199-207
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• 1999

For the stress and vibration analysis of vehicle component by computer simulation, it is necessary to find the forces acting on the vehicle components due to the road profile undulation. A precise modeling of tires is not easy due to nonlinear effects between tire-ground. In this study, a new method is proposed to regenerate road profiles that preserves the same PSD of wheel with a linear tire model. Using the frequency response function between road-wheel , the digital signal processing method, and DADS program , road profile is regenerated from the computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.180-183
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• 2005

2 axis gimbals systems are extensively used in various tracking devices for attaining the system's objective. Designers are sometimes passing over the dynamic characteristics of system in vibrating condition In this paper, 2 axis gimbals systems including interface elements is modeled with finite elements. To verify this model, the finite element model is refined by using the experimental model data. The refined model is simulated with I-DEAS and MSC.NATRAN's FRF(Frequency response Function) and RRA(Random vibration Response Analysis) function to get dynamic characteristics of 2 axis gimbals system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.173-176
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• 1996

The transient behavior of the complex-LMS adaptive filter is studied when the adaptive filter is operating on a fixed or sweeping complex frequency sine-wave signal. The first-order difference equation is derived for the mean weights and its closed form solution is obtained. The transient response is represented as a function of the eigenvectors and eigenvalues of input correlation matrix. The mean-square error of the algorithm is evaluated as well. An optimal convergence parameter and filter length can be determined for sweeping frequency sine-wave signals as a function of frequency change rate and signal and noise powers.

• 소음진동
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• 제13권6호
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• pp.377-383
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• 2003

실험적 모드 해석이란 측정된 주파수응답함수(frequency response function , FRF)로부터 시스템의 모드변수(고유진동수, 감쇠비, 진동모드)를 구하는 과정이라 할 수 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.268-271
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• 2006

고체추진 로켓엔진의 자발성 음향불안정 특성 예측 및 평가를 위해 대상 고체추진제의 연소응답함수를 측정하였다. Pulsed DB/AB 방법에 기초한 T-버너 실험을 통해 특정 주파수에서의 연소응답함수를 구하였다. 연소응답함수 계산식은 근사해석법에 기초한 연소불안정 이론으로부터 유도 적용하였다. 추진제 동시점화 및 시편 동시점화 등 연소응답의 측정에 관련된 문제들에 대해 해결방안을 제시하였다.

• 한국연소학회지
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• 제14권4호
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• Journal of Communications and Networks
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• 제1권3호
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• pp.166-181
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• 1999

The object of this paper is to investigate the influence of antenna pattern on indoor radio channel characteristics. Different from previous works where this analysis was carried out at a fixed frequency using different antennas, in the present paper (where measurements were taken in a wide frequency range) the variation of the radiation pattern was caused by two factors: the change of the radiation pattern when the same antenna was used at different frequenicies and the use of different type of antennas. To carry out this analysis, frequency domain measurements of the indoor radio channel at 1 GHz, 5.5 GHz, 10 GHz and 18 GHz were collected. Measurements were taken using a network analyzer. Serveral re-alizations of the channel transfer function were obtained varying, for each measurement, the positon of the transmitter and keep-ing the receiver fixed. Estimate of the channel impulse response was obtained from the Inverse Fourier Transform (IFT) of the fre-quency response. The measurements were performed in an office enviroment with mostly metallic walls and inner separations. The obtained data were elaborated to obtain the power versus distance relationship, the Cummulative Distribution Functions(CDFs) of rms Delay Spread(DS) and of the 3 dB frequency correlation band-width. Finally, the 3 dB width of the frequency correlation func-tion has been empirically related to the inverse of the rms DS of the impulse response.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.782-785
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• 2006

The Power Flow Analysis(PFA) can be effectively used to predict structural vibration in medium-to-high frequency range. In this paper, Power Flow Finite Element Method (PFFEM) based on PFA has been used to predict the vibration of an automobile door. The predicted results for the frequency response function of the door have been compared with corresponding experimental results. In the experiment, the automobile door has been divided into several subsystems and the loss factor of each subsystem has been measured. The input mobility at a source point has been also measured. The data for the loss factors and the input mobility have been used as the input data to predict the vibration of the automobile door with PFFEM. The frequency response functions have been measured over the surface of the door. The comparison between the experimental results and the predicted results for the frequency response functions showed that PFFEM could be an effective tool to predict the structural vibration.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.139-144
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• 2008

In this study, damage detection method using harmony search method and frequency response is proposed. In order to verify this method, the following approaches are implemented. Firstly, damage detection method using harmony search is developed. To detect damage, objective function that minimize difference with natural frequency and modal strain energy from undamaged and damaged model is used. Secondly, finite element model for beam structure is created. And damage scenario is determined. Lastly, damage detection is performed by proposed method and utility of proposed method is verified.