• Title/Summary/Keyword: Power spectrum

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Diagnosis of Chatter Vibration using Frequency Domain in a Milling Process (밀링 공정시 주파수 영역을 이용한 채터 진동의 진단)

  • 김문기
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.10 no.3
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    • pp.12-18
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    • 2001
  • Frequency domain has been used to detect chatter vibration and to decide commencing point of chatter for the milling processes. For this, power spectrum of accelerations signal is analyzed in the frequency domain. Also, the power spectrum and surface roughness are measured, compared, and evaluated according to the depth of cut by experimental works. As a results, it is known that the commencing point of chatter can be decided the behavior of the maximum amplitude of the power spectrum of acceleration signal and there is a correlation between the power spectrum of acceleration signal and the surface roughness. In conclusion, the power spectrum of acceleration signal can be used as a useful information for detec-tion and estimation of chatter vibration in machining.

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POWER SPECTRUM ANALYSIS OF THE OMC1 IMAGE AT 1.1MM WAVELENGTH

  • Youn, So-Young;Kim, Sung-Eun
    • Journal of The Korean Astronomical Society
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    • v.45 no.4
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    • pp.93-99
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    • 2012
  • We present a 1.1mm emission map of the OMC1 region observed with AzTEC, a new large-format array composed of 144 silicon-nitride micromesh bolometers, that was in use at the James Clerk Maxwell Telescope (JCMT). These AzTEC observations reveal dozens of cloud cores and a tail of filaments in a manner that is almost identical to the submillimeter continuum emission of the entire OMC1 region at 450 and $850{\mu}m$. We perform Fourier analysis of the image with a modified periodogram and the density power spectrum, which provides the distribution of the length scale of the structures, is determined. The expected value of the periodogram converges to the resulting power spectrum in the mean squared sense. The present analysis reveals that the power spectrum steepens at relatively smaller scales. At larger scales, the spectrum flattens and the power law becomes shallower. The power spectra of the 1.1mm emission show clear deviations from a single power law. We find that at least three components of power law might be fitted to the calculated power spectrum of the 1.1mm emission. The slope of the best fit power law, ${\gamma}{\approx}-2.7$ is similar to those values found in numerical simulations. The effect of beam size and the noise spectrum on the shape and slope of the power spectrum are also included in the present analysis. The slope of the power law changes significantly at higher spatial frequency as the beam size increases.

CONVERGENCE AND POWER SPECTRUM DENSITY OF ARIMA MODEL AND BINARY SIGNAL

  • Kim, Joo-Mok
    • Korean Journal of Mathematics
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    • v.17 no.4
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    • pp.399-409
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    • 2009
  • We study the weak convergence of various models to Fractional Brownian motion. First, we consider arima process and ON/OFF source model which allows for long packet trains and long inter-train distances. Finally, we figure out power spectrum density as a Fourier transform of autocorrelation function of arima model and binary signal model.

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Improvement of Power Spectrum in Ultrashort Pulse Reflectometry Signals Using Three Chirp Configuration

  • Roh, Young-Su
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.3
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    • pp.51-56
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    • 2014
  • The flat power spectrum of the transmitter output signal for the desired frequency range is ideal to achieve the best performance of ultrashort pulse reflectometry. However, the power spectrum of a typical pulse generator decreases significantly as frequency increases. A configuration of three chirped waveforms was employed to improve the power spectrum of the transmitter signal at higher frequencies. To determine the amplification gain required for higher frequency components, three chirped waveforms were theoretically generated and their power spectra were measured using numerical band-pass filters. Based on the results of numerical computations, the three chirp configuration was successfully applied to the design of the transmitter for a broadband system.

Vocal Tract Normalization Using The Power Spectrum Warping (파워 스펙트럼 warping을 이용한 성도 정규화)

  • Yu, Il-Su;Kim, Dong-Ju;No, Yong-Wan;Hong, Gwang-Seok
    • Proceedings of the KIEE Conference
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    • pp.215-218
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    • 2003
  • The method of vocal tract normalization has been known as a successful method for improving the accuracy of speech recognition. A frequency warping procedure based low complexity and maximum likelihood has been generally applied for vocal tract normalization. In this paper, we propose a new power spectrum warping procedure that can be improve on vocal tract normalization performance than a frequency warping procedure. A mechanism for implementing this method can be simply achieved by modifying the power spectrum of filter bank in Mel-frequency cepstrum feature(MFCC) analysis. Experimental study compared our Proposal method with the well-known frequency warping method. The results have shown that the power spectrum warping is better 50% about the recognition performance than the frequency warping.

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A New Power Spectrum Warping Approach to Speaker Warping (화자 정규화를 위한 새로운 파워 스펙트럼 Warping 방법)

  • 유일수;김동주;노용완;홍광석
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.41 no.4
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    • pp.103-111
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    • 2004
  • The method of speaker normalization has been known as the successful method for improving the accuracy of speech recognition at speaker independent speech recognition system. A frequency warping approach is widely used method based on maximum likelihood for speaker normalization. This paper propose a new power spectrum warping approach to making improvement of speaker normalization better than a frequency warping. Th power spectrum warping uses Mel-frequency cepstrum analysis(MFCC) and is a simple mechanism to performing speaker normalization by modifying the power spectrum of Mel filter bank in MFCC. Also, this paper propose the hybrid VTN combined the Power spectrum warping and a frequency warping. Experiment of this paper did a comparative analysis about the recognition performance of the SKKU PBW DB applied each speaker normalization approach on baseline system. The experiment results have shown that a frequency warping is 2.06%, the power spectrum is 3.06%, and hybrid VTN is 4.07% word error rate reduction as of word recognition performance of baseline system.

Analysis on the Power Spectrum of Electromagnetic Waves Radiating from the Distributorless Spark Ignition System (무배전기식 불꽃 점화 시스템에서 복사되는 전자파의 전력 스펙트럼 분석)

  • Choe, Gwang-Je;Jho, Shi-Gie;Jeung, Weol-Rark;Jang, Sung-Kuk;Kang, Shin-Han
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.1
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    • pp.45-51
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    • 2008
  • This paper presents theoretical and experimental analysis on the characteristics of the power spectrum of electormagnetic waves radiating from the spark plug and their cables of a distributorless ignition system. The theoretical study was conducted applying the microwave transmission line theory and the antenna theory. The experimental works were carried out to measure the standing wave ratio(SWR) and the radiation power spectrum of this system. As a result, it has been found that a spark plug and its cable is working as a monopole antenna radiating elelctromagnetic waves. Because of its similar structure to a monopole antenna, the envelope of radiation power spectrum distribution has a bell shape which can be obtained from a monopole antenna operating as a series resonant circuit. The frequency characteristics from the SWR measurements show a similar frequency characteristics of power spectrum of the system studied. Also, it has been found that the density of the power spectrum of the system fitting a long time used spark plug is higher than that of fitting a new spark plug.

Organ Recognition in Ultrasound images Using Log Power Spectrum (로그 전력 스펙트럼을 이용한 초음파 영상에서의 장기인식)

  • 박수진;손재곤;김남철
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.9C
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    • pp.876-883
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    • 2003
  • In this paper, we propose an algorithm for organ recognition in ultrasound images using log power spectrum. The main procedure of the algorithm consists of feature extraction and feature classification. In the feature extraction, as a translation invariant feature, log power spectrum is used for extracting the information on echo of the organs tissue from a preprocessed input image. In the feature classification, Mahalanobis distance is used as a measure of the similarity between the feature of an input image and the representative feature of each class. Experimental results for real ultrasound images show that the proposed algorithm yields the improvement of maximum 30% recognition rate than the recognition algorithm using power spectrum and Euclidean distance, and results in better recognition rate of 10-40% than the recognition algorithm using weighted quefrency complex cepstrum.

Power Spectrum of Jittered Random Pulse Train (불규칙 Pulse 신호의 전력 Spectrum)

  • 최양희;김재경
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.17 no.1
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    • pp.10-13
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    • 1980
  • The power spectrum of jittered pulse train is derived for the independent stationary pulse sequence with a stationary Gaussian phase jitter. For the unipolar pulse train signal, it is shown that as the phase jitter increases, the continuous Part of the power spectrum increases chile the discrete part decreases.

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Power Spectrum Performance Analysis of Digital M/W Transmission System in Non-Selective Rayleigh Fading Channel (비선택성 레일리 페이딩 채널 환경에서 디지털 M/W 전송 시스템의 전력 스펙트럼 성능 분석)

  • Park, Ki-Sik
    • Journal of the Korea Society of Computer and Information
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    • v.16 no.10
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    • pp.137-145
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    • 2011
  • In this paper, we modeled digital M/W transmission channel by frequency non-selective fading channel and analyzed the power spectrum magnitude of digital M/W transmission systems adopting OFDM modulation scheme through simulation. From the simulation results, it was found that deep does not appear in the specified fixed bandwidth under the AWGN environment. Also, lower power spectrum magnitude was shown in frequency non-selective fading channel than that in AWGN channel. Futhermore, the power spectrum magnitude value became more lowered when carrier frequency and vehicle speed became higher.