• 한국소음진동공학회논문집
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• 제15권3호
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• pp.266-271
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• 2005

Although time-frequency analysis is useful for dispersive wave analysis, conventional methods such as the short-time Fourier transform do not take the dispersion phenomenon into consideration in the tiling of the time-frequency domain. The objective of this paper is to develop an adaptive time-frequency analysis method whose time-frequency tiling is determined with the consideration of signal dispersion characteristics. To achieve the adaptive time-frequency tiling, each of time-frequency atoms is rotated in the time-frequency plane depending on the local wave dispersion. To carry out this adaptive time-frequency transform, dispersion characteristics hidden in a signal are first estimated by an iterative scheme. To examine the effectiveness of the present method, the flexural wave signals measured in a plate were analyzed.

• 한국소음진동공학회논문집
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• 제15권9호
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• pp.1108-1117
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• 2005

A robust damage detection method using short-time Fourier transform and beating phenomena is presented as an estimating tool of the healthiness of large structures. The present technique makes use of beating phenomena that manifest themselves when two signals of similar frequencies are added or subtracted. Unlike most existing methods based on vibration signals, the present approach does not require an analytic model for target structures. Furthermore, the main advantage of the proposed method compared to the competing diagnostic method using vibration data is its robustness. The proposed method is not affected by the amplitude of exciting signals and the location of exciting points. From a measuring view point. the location of sensing point have no influence on the performance of the present method. With a view to verifying the effectiveness of this method. a series of experiments are made and the results show its possibility as a robust damage diagnostic method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.606-610
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• 2004

Although time-frequency analysis is useful for dispersive wave analysis, conventional methods such as the short-time Fourier transform do not take the dispersion phenomenon into consideration in the tiling of the time-frequency domain. The objective of this paper is to develop an adaptive time-frequency analysis method whose time-frequency tiling is determined with the consideration of signal dispersion characteristics. To achieve the adaptive time-frequency tiling, each of time-frequency atoms is rotated in the time-frequency plane depending on the local wave dispersion. To carry out this adaptive time-frequency transform, dispersion characteristics hidden in a signal are first estimated by an iterative scheme. To examine the effectiveness of the proposed method, the flexural wave signals measured in a plate were analyzed.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 2002년도 춘계학술대회 논문집
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• pp.114-117
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• 2002

뇌-컴퓨터 인터페이스로 활용하기 위한 시도로서, 인간의 가장 간단한 의사 표시인 긍/부정 의사와 관련한 뇌파를 측정하고 시간-주파수 분석(단시간 푸리에 변환)을 수행하였다. 반응 동작과 관련한 $\mu$파와 $\beta$파, 그리고 인지 정보 처리와 관련한 ${\gamma}$파의 시간에 따른 변화를 살펴보고 선행 결과들과 비교, 토론하였다.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.2170-2178
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• 2014

본 연구에서는 작업수행시의 집중상태 변화를 검출하기 위하여 2011년 1~2월 동안 집중을 유발하는 시각유발자극에 대하여 생체신호를 측정한 피험자들 중 한명의 뇌파신호를 분석하였다. 두피에서 측정한 뇌파신호로부터 집중관련 뇌 안에서의 발원 신호와 안구운동잡음 신호를 분리하기 위하여 독립성분 분석기법을 측정뇌파 신호에 적용하였다. 안구운동잡음신호가 제거된 집중관련 신호원을 단시간 푸리에 변환하여 주파수 성분 신호를 연속적으로 축적함으로서 시변 특징 형태를 나타내는 에포크 그래프와 스펙트럴 칼라 맵에서의 도식 표현상 규칙성을 향상 시킬 수 있었다. 추출한 감각운동리듬 (SMR: 12-15Hz)과 세타파 리듬 (4-7Hz)관련 집중 지표는 집중시험시간이 경과함에 따라 증가 하였다. 실험을 통하여 단시간 푸리에 변환과 결합한 독립성분 분석기법은 참여자의 집중상태 변화를 분석하는데 사용 할 수 있을 것이다.

• 한국정보통신학회논문지
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• 제14권11호
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• pp.2548-2554
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• 2010

본 논문에서는 의료 서비스를 위한 뇌전기파(EEG: electroencephalogram) 신호 분석용 FFT(Fast Fourier Transform) 프로세서를 구현하였다. 실시간으로 발생하는 EEG 신호를 블록으로 나누어 short-time FFT 처리하기 위해 Hamming 창 함수를 사용하였으며, 이로 인해 감소되는 양끝의 값은 1/2 오버랩 시켜 보완하였다. 0~100 [Hz] 사이의 주파수 특성을 갖는 뇌전기파의 효율적인 대역 분석을 위해 256-point FFF 프로세서를 radix-4 알고리듬을 적용하여 구현하였으며, 단일 메모리 뱅크 구조를 사용하여 집적도를 높였다. 설계된 FFT 프로세서는 FPGA 구현을 통해 가능을 검증하였으며, 연산오차가 2% 이내로 높은 연산 정밀도를 갖는다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.428-433
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• 2002

There have been many studies to visualize the vibration and noise of rotary compressor. Most of these studies assumed that the signal is stationary and the time-averaged signal is used for visualization. However, the noise and vibration signals generated during one cycle of crank shaft vary continuously. In this paper, the noise and vibration of rotary compressor which vary continuously are visualized by short time fourier transform method. The location of source and the transfer path of vibration and noise at arbitrary frequencies, which can not be visualized by averaged signal, can be visualized clearly.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.106-115
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• 2000

This paper presents the measuring technique of time and velocity when rocket motor is burnt out for 2.751" rocket. This technique use doppler effect, frequency spectrum analysis and curve fitting. In this study, we use muzzle velocity radar for doppler signal acquisition, short-time fourier transform for spectrum analysis and curve fitting for smoothing.

• 한국정밀공학회지
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• 제26권11호
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• pp.47-54
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• 2009

Spin coaters are the essential instruments in micro-fabrication processes, which apply uniform thin films to flat substrates. In this research, a spin coater diagnosis system is developed to detect the abnormal operation of TFT-LCD process in real time. To facilitate the real-time data acquisition and analysis, the circular-buffered continuous data transfer and the short-time Fourier transform are applied to the fault diagnosis system. To determine whether the system condition is normal or not, a steady-state detection algorithm and a frequency spectrum comparison algorithm using confidence interval are newly devised. Since abnormal condition of a spin coater is rarely encountered, algorithm is tested on a CD-ROM drive and the developed program is verified by a function generator. Actual threshold values for the fault detection are tuned in a spin coater in process.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.346.1-346
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• 2002

There have been many studies to visualize the vibration and noise of rotary compressor. Most of these studies assumed that the signal is stationary and the time-averaged signal is used for visualization. However, the noise and vibration signals generated during one cycle of crank shaft vary continuously. In this paper, the noise and vibration of rotary compressor which vary continuously are visualized by short time fourier transform method. (omitted)