• Title/Summary/Keyword: 푸리에스펙트럼

Search Result 98, Processing Time 0.025 seconds

A Real Time Parameter Estimation of Low Frequency Oscillation in Discrete Signal Part I : Theory (이산신호에서 실시간 저주파 진동 파라미터 추정 Part I : 이론)

  • Kim, Eui-Sun;Shim, Kwan-Shik;Moon, Chae-Joo
    • Proceedings of the KIEE Conference
    • /
    • 2008.07a
    • /
    • pp.217-218
    • /
    • 2008
  • 이 논문은 이산신호에 고속푸리에 변환을 적용하여 신호에 포함되어 있는 저주파수의 진동 파라미터를 추정하는 새로운 방법에 대해서 기술하고 있다. 제안한 방법은 지수감쇠 정현파함수의 푸리에 변환에 기초를 두고 푸리에스펙트럼으로부터 직접 파라미터를 추정하는 방법이다. 푸리에스펙트럼의 첨두치와 첨두주파수 사이에 일정한 수학적 관계에서 모드를 추정하고 추정한 모드를 이용하여 모드의 크기와 위상을 추정하는 방법을 제안하고 있다. 이 논문에서 제안한 파라미터 추정방법은 수식에 기반을 둔 매우 단순한 알고리즘으로 계산속도가 매우 빠르고 작은 기억장소를 필요로 하므로 DSP 수준의 실시간 연산에 매우 적합한 알고리즘이다. 제안한 알고리즘을 간단한 시험함수에 적용한 결과, 정확하게 파라미터를 추정하여 알고리즘의 정확성을 검증하였다.

  • PDF

Application of the modified fast fourier transformation weighted with refractive index dispersion far an accurate determination of film thickness (굴절률 분산을 반영한 고속 푸리에 변환 및 막두께 정밀결정)

  • 김상준;김상열
    • Korean Journal of Optics and Photonics
    • /
    • v.14 no.3
    • /
    • pp.266-271
    • /
    • 2003
  • The reflectance spectrum of optical films thicker than a few microns shows an intensity oscillation due to interference. Since the spectral period of the oscillation is inversely related to film thickness, the thickness of an optical film can be determined from the spectral frequency of the oscillation. For rapid data processing, the spectral frequency is obtained by use of a Fast Fourier Transformation technique. The conventional method of applying a Fast Fourier Transformation to the reflectance spectrum versus photon energy is modified so as to clear the ambiguity in choosing the proper effective refractive index value and to prevent the broadening of the Fourier transformed peak due to the refractive index dispersion. This technique of modified Fast Fourier Transformation is suggested by the authors for the first time to their knowledge. From the analysis of the calculated reflectance spectrum of a 30-${\mu}{\textrm}{m}$-thick dielectric film. it is shown to improve the accuracy in determining film thickness by a great amount. The improved accuracy of the modified Fast Fourier Transformation is also confirmed from the analysis of the reflectance spectra of a sample with 80-${\mu}{\textrm}{m}$-thick cover layer and 13-${\mu}{\textrm}{m}$-thick spacer layer on a PC substrate.

Distortion Correction Method Using Spectral Characteristics of Integral Images (집적영상의 스펙트럼 특성을 이용한 왜곡 교정 방법)

  • Jin, Zhengju;Lee, Byung-Ju;Kang, Hyun-Soo
    • The Journal of the Korea Contents Association
    • /
    • v.13 no.10
    • /
    • pp.1-8
    • /
    • 2013
  • In this paper, we propose a new method to correct the perspective distortion that occurs in the process of acquiring the integral images. In the proposed method, the distortion correction is based on the spectral characteristics of integral images. As element images of an integral image are repeated nearly periodically, its Fourier spectrum is given as an impulse train. On the contrary, the impulse train do not appear in the spectra of distorted images. In the proposed method, therefore, the perspective distortion parameters are detected by using the characteristics of the spectrum obtained through the Fourier transform, and then the distorted images are corrected by using the parameters. Through experiments, we verify that the proposed method effectively works for the perspective distortion correction.

The Behavior of Grinding Wheel Wear Using Spectrum Analysis (스펙트럼 해석을 이용한 연삭숫돌 마멸거동)

  • 사승윤
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.8 no.5
    • /
    • pp.20-24
    • /
    • 1999
  • Grinding System is very difficult to examine closely wear phenomenon or dynamic characterastic because it is very complex and different from a general cutting system, Considering automatization and precision it is very important to examine closely grinding system. In this study grinding wheel surface is acquired by using computer vision system in order to explain wear and loading phenomenon. We investigate the relationship between wear and Fourier spectrum of acquired image and observe the entropy variation in the process of manufacturing.

  • PDF

잡음억제 신경회로망에 의한 스펙트럼의 추정 기법

  • Choe, Jae-Seung
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2012.10a
    • /
    • pp.597-599
    • /
    • 2012
  • 음성인식 및 음성신호처리 분야에서 신경회로망은 음성인식의 카테고리 분류에 주로 이용되고 있다는 점에 착안하여, 본 논문에서는 신경회로망의 입력신호로 음성의 진폭 스펙트럼 및 위상 스펙트럼을 사용한 잡음억제를 위한 신경회로망을 제안한다. 본 논문에서 제안한 알고리즘은 고속 푸리에 변환(Fast Fourier Transform, FFT)에 의한 진폭 스펙트럼 및 위상 스펙트럼을 사용한 잡음억제 신경회로망을 이용하여 각 프레임에서 FFT 스펙트럼을 추정한다.

  • PDF

A Basic Study on the Improvement of Leakage Error of the Acoustic Intensity (음향 인텐시티의 누설오차 개선에 관한 기초적 연구)

  • 정의봉;정호경;안세진;윤상돈
    • The Journal of the Acoustical Society of Korea
    • /
    • v.22 no.5
    • /
    • pp.345-350
    • /
    • 2003
  • Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent microphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidably have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional FFT analyzer will show distorted value. In this paper, the expression of the Fourier transformed data of a harmonic signal with a single frequency is formulated when there is leakage error. The method to eliminate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.

Section Detection Algorithm using Multi-layer Perceptron Neural Network (다층 퍼셉트론 신경회로망을 사용한 구간 검출 알고리즘)

  • Choi, Jae-Seung
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2010.10a
    • /
    • pp.274-277
    • /
    • 2010
  • 본 논문에서는 다층 퍼셉트론 신경회로망을 사용하여 각 프레임에서 유성음, 무성음, 그리고 묵음 구간을 검출하는 구간검출 알고리즘을 제안한다. 신경회로망의 입력으로는 고속 푸리에변환에 의한 전력스펙트럼 및 고속 푸리에변환 계수가 사용되어 네트워크가 학습된다. 본 실험에서는 원 음성에 백색잡음이 중첩된 음성을 신경회로망에 입력함으로서 각 프레임에서의 유성음, 무성음, 묵음 구간의 검출성능 결과를 나타낸다.

  • PDF

Wavelet Analysis of Swells in the East Sea (동해 너울에 대한 웨이블릿 분석)

  • Kim, Tae-Rim;Lee, Dong-Young
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.20 no.6
    • /
    • pp.583-588
    • /
    • 2008
  • Swell data observed in the East Sea in February, 2008 were analyzed using wavelet method. The wavelet analyzed results show detailed time series variation of wave group, peak frequency and spectrum. The comparison of time averaged wavelet spectrum with fourier spectrum turn out to be very similar in terms of spectrum shape and peak frequency evolution but the peak frequency wave energy and the significant wave height show discrepancies. Wavelet analysis can detect the change of spectrum in time as well as in frequency and very efficient to study transient and irregular phenomena such as freak waves and abnormal swells in the ocean. More analysis with more wave data are needed for future application.

Correction Method of Wiener Spectrum (WS) on Digital Medical Imaging Systems (디지털 의료영상에서 위너스펙트럼(Wiener spectrum)의 보정방법)

  • Kim, Jung-Min;Lee, Ki-Sung;Kim, You-Hyun
    • Journal of radiological science and technology
    • /
    • v.32 no.1
    • /
    • pp.17-24
    • /
    • 2009
  • Noise evaluation for an image has been performed by root mean square (RMS) granularity, autocorrelation function (ACF), and Wiener spectrum. RMS granularity stands for standard deviation of photon data and ACF is acquired by integration of 1 D function of distance variation. Fourier transform of ACF results in noise power spectrum which is called Wiener spectrum in image quality evaluation. Wiener spectrum represents noise itself. In addition, along with MTF, it is an important factor to produce detective quantum efficiency (DQE). The proposed evaluation method using Wiener spectrum is expected to contribute to educate the concept of Wiener spectrum in educational organizations, choose the appropriate imaging detectors for clinical applications, and maintain image quality in digital imaging systems.

  • PDF