• Title/Summary/Keyword: Power spectrum

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Reevaluation of Seismic Fragility Parameters of Nuclear Power Plant Components Considering Uniform Hazard Spectrum

  • Park, In-Kil;Choun, Young-Sun;Seo, Jeong-Moon;Yun, Kwan-Hee
    • Nuclear Engineering and Technology
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    • v.34 no.6
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    • pp.586-595
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    • 2002
  • The Seismic probabilistic risk assessment (SPRA) or seismic margin assessment (SMA) have been used for the seismic safety evaluation of nuclear power plant structures and equipments. For the SPRA or SMA, the reference response spectrum should be defined. The site-specific median spectrum has been generally used for the seismic fragility analysis of structures and equipments in a Korean nuclear power plant Since the site-specific spectrum has been developed based on the peak ground motion parameter, the site-specific response spectrum does not represent the same probability of exceedance over the entire frequency range of interest. The uniform hazard spectrum is more appropriate to be used in seismic probabilistic risk assessment than the site- specific spectrum. A method for modifying the seismic fragility parameters that are calculated based on the site-specific median spectrum is described. This simple method was developed to incorporate the effects of the uniform hazard spectrum. The seismic fragility parameters of typical NPP components are modified using the uniform hazard spectrum. The modification factor is used to modify the original fragility parameters. An example uniform hazard spectrum is developed using the available seismic hazard data for the Korean nuclear power plant (NPP) site. This uniform hazard spectrum is used for the modification of fragility parameters.

Adaptive Power Control Strategy based on Spectrum Sensing for Cognitive Relay Networks (CR 넷워크를 위한 주파수 감지에 기번한 적응적인 전력 제어 전략)

  • HU, SIYUAN;Joe, Inwhee
    • Proceedings of the Korea Information Processing Society Conference
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    • 2019.05a
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    • pp.82-85
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    • 2019
  • An adaptive power control scheme is proposed for the cognitive relay networks with joint overlay and underlay spectrum sharing model. The transmit power of the secondary user is adjusted adaptively according to the spectrum sensing results and the interference channel condition. The outage probability of the secondary user is compared by Monte - Carlo simulations between the fixed power control scheme and pure overlay or underlay spectrum sharing schemes. The results show that, by employing the adaptive power control strategy, the interference probability of the secondary user to the primary user is decreased by 70 % ~ 80 % under the same outage probability. Also, the outage probability of the secondary user is reduced by 1 ~ 2 orders of magnitude under the same interference probability. Thus, the performance of the spectrum sharing is improved effectively.

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.

Deviations from power-law primordial spectrum

  • Gong, Jinn-Ouk
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.58.3-58.3
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    • 2019
  • We discuss theoretical motivations for deviations from standard power-law primordial power spectrum and possible mechanism to provide non-trivial scale dependence for the primordial power spectrum.

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Spectrum Sensing Scheme Using the Ratio of the Maximum and the Minimum of Power Spectrum (전력 스펙트럼의 최대 최소 비율을 이용한 스펙트럼 감지 방식)

  • Lim, Chang Heon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.6
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    • pp.3-8
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    • 2014
  • Recently, a spectrum sensing technique employing the maximum value of a received power spectrum as a test statistic has been presented in the literature for the purpose of detecting a wireless microphone signal in TV bands This detects the presence of a primary user by comparing the test statistic with some threshold, which depends on the background noise power level as well as a target false alarm rate. Therefore its performance may deteriorate when the noise power uncertainty occurs. As a means to mitigate this difficulty, we present a spectrum sensing strategy adopting the ratio of the maximum and the minimum value of the power spectrum as a test statistic and analyze its performance of spectrum sensing.

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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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 and Spectrum Efficiencies Considering the HPA Nonlinearity in OFDM Communication System (OFDM 통신 시스템에서 비선형 증폭기 특성을 고려한 전력 효율과 대역 효율)

  • 이재은;윤기후;이준서;유흥균
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.6
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    • pp.543-549
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    • 2003
  • It is important to consider the nonlinear effects of the HPA(High Power Amplifier) in the OFDM communication systems and other digital communication systems as well. In this paper, we investigate a new performance figure-of$.$merit(D) that reflects both power and spectrum efficiencies. The performance figure-of-merit is expressed to include the spectrum and power efficiencies that depend on the magnitude of IBO(Input Backoff) and the number of subcarriers. So, we analyze the variation characteristics of the power efficiency and spectrum efficiency which has the tradeoff relationship.

A Fast Parameter Estimation of Time Series Data Using Discrete Fourier Transform (이산푸리에변환과 시계열데이터의 고속 파라미터 추정)

  • Shim, Kwan-Shik;Nam, Hae-Kon
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.55 no.7
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    • pp.265-272
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    • 2006
  • This paper describes a method of parameter estimation of time series data using discrete Fourier transform(DFT). DFT have been mainly used to precisely and rapidly obtain the frequency of a signal. In a dynamic system, a real part of a mode used to learn damping characteristics is a more important factor than the frequency of the mode. The parameter estimation method of this paper can directly estimate modes and parameters, indicating the characteristics of a dynamic system, on the basis of the Fourier transform of the time series data. Real part of a mode estimates by subtracting a frequency of the Fourier spectrum corresponding to 0.707 of a magnitude of the peak spectrum from a peak frequency, or subtracting a frequency of the power spectrum corresponding to 0.5 of the peak power spectrum from a peak frequency, or comparing the Fourier(power) spectrum ratio. Also, the residue and phase of time signal calculate by simple equation with the real part of the mode and the power spectrum that have been calculated. Accordingly, the proposed algorithm is advantageous in that it can estimate parameters of the system through a single DFT without repeatedly calculating a DFT, thus shortening the time required to estimate the parameters.