• Title/Summary/Keyword: Power Spectrum Density

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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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Density distributions and Power spectra of outflow-driven turbulence

  • Kim, Jongsoo;Moraghan, Anthony
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.1
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    • pp.57.2-57.2
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    • 2014
  • Protostellar jets and outflows are signatures of star formation and promising mechanisms for driving supersonic turbulence in molecular clouds. We quantify outflow-driven turbulence through three-dimensional numerical simulations using an isothermal version of the total variation diminishing code. We drive turbulence in real space using a simplified spherical outflow model, analyze the data through density probability distribution functions (PDFs), and investigate density and velocity power spectra. The real-space turbulence-driving method produces a negatively skewed density PDF possessing an enhanced tail on the low-density side. It deviates from the log-normal distributions typically obtained from Fourier-space turbulence driving at low densities, but can provide a good fit at high densities, particularly in terms of mass-weighted rather than volume-weighted density PDF. We find shallow density power-spectra of -1.2. It is attributed to spherical shocks of outflows themselves or shocks formed by the interaction of outflows. The total velocity power-spectrum is found to be -2.0, representative of the shock dominated Burger's turbulence model. Our density weighted velocity power spectrum is measured as -1.6, slightly less that the Kolmogorov scaling values found in previous works.

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Ultra-Wide Bandwidth Systems Using a Non-Binary Pulse Position Modulation with Preferable Line Spectrum Properties (개선된 선 스펙트럼 특성을 갖는 비이진 PPM 기반 초광대역 무선전송 시스템)

  • Hong Yun-Pyo;Song Hong-Yeop
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.6C
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    • pp.569-574
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    • 2006
  • We derive the general power spectral density of functions of ultra-wide bandwidth (UWB) systems using a pulse position modulation. We propose a new UWB system with a preferable line spectrum properies and a good bit error rate performance.

Spectral Analysis of Heart Rate Variability in ECG and Pulse-wave using autoregressive model (AR모델을 이용한 심전도와 맥파의 심박변동 스펙트럼 해석)

  • Kim NagHwan;Lee EunSil;Min HongKi;Lee EungHyuk;Hong SeungHong
    • Journal of the Institute of Convergence Signal Processing
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    • v.1 no.1
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    • pp.15-22
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    • 2000
  • The analysis of power spectrum based on linear AR model is applied widely to quantize the response of autonomic nerve noninvasively, In this paper, we estimate the power spectrum density for heartrate variability of the electrocadiogram and pulse wave for short term data(less than two minute), The time series of heart rate variability is obtained from the time interval(RRI, PPI) between the feature point of the electrocadiogram and pulse wave for normal person, The generated time series reconstructed into new time series through polynomial interpolation to apply to the AR mode. The power spectrum density for AR model is calculated by Burg algorithm, After applying AR model, the power spectrum density for heart rate variability of the electrocadiogram and the pulse wave is shown smooth spectrum power at the region of low frequence and high frequence, and that the power spectrum density of electrocadiogram and pulse wave has similar form for same subject.

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PARAMETER ESTIMATION AND SPECTRUM OF FRACTIONAL ARIMA PROCESS

  • Kim, Joo-Mok;Kim, Yun-Kyong
    • Journal of applied mathematics & informatics
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    • v.33 no.1_2
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    • pp.203-210
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    • 2015
  • We consider fractional Brownian motion and FARIMA process with Gaussian innovations and show that the suitably scaled distributions of the FARIMA processes converge to fractional Brownian motion in the sense of finite dimensional distributions. We figure out ACF function and estimate the self-similarity parameter H of FARIMA(0, d, 0) by using R/S method. Finally, we display power spectrum density of FARIMA process.

ESTIMATION OF HURST PARAMETER AND MINIMUM VARIANCE SPECTRUM

  • Kim, Joo-Mok
    • Korean Journal of Mathematics
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    • v.26 no.2
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    • pp.155-166
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    • 2018
  • Consider FARIMA time series with innovations that have infinite variances. We are interested in the estimation of self-similarities $H_n$ of FARIMA(0, d, 0) by using modified R/S statistic. We can confirm that the $H_n$ converges to Hurst parameter $H=d+\frac{1}{2}$. Finally, we figure out ARMA and minimum variance power spectrum density of FARIMA processes.

THREE-DIMENSIONAL CORE DESIGN OF A SUPER FAST REACTOR WITH A HIGH POWER DENSITY

  • Cao, Liangzhi;Oka, Yoshiaki;Ishiwatari, Yuki;Ikejiri, Satoshi;Ju, Haitao
    • Nuclear Engineering and Technology
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    • v.42 no.1
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    • pp.47-54
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    • 2010
  • The SuperCritical Water-cooled Reactor (SCWR) pursues high power density to reduce its capital cost. The fast spectrum SCWR, called a super fast reactor, can be designed with a higher power density than thermal spectrum SCWR. The mechanism of increasing the average power density of the super fast reactor is studied theoretically and numerically. Some key parameters affecting the average power density, including fuel pin outer diameter, fuel pitch, power peaking factor, and the fraction of seed assemblies, are analyzed and optimized to achieve a more compact core. Based on those sensitivity analyses, a compact super fast reactor is successfully designed with an average power density of 294.8 W/$cm^3$. The core characteristics are analyzed by using three-dimensional neutronics/thermal-hydraulics coupling method. Numerical results show that all of the design criteria and goals are satisfied.

A Proposal of Reference Power Spectral Density Functions Compatible with Highway Bridge Design Specta (도로교 내진설계 스펙트럼에 부합하는 표준 PSD함수의 제안)

  • Choi, Dong Ho;Lee, Sang Hoon;Koh, Jung Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.59-67
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    • 2008
  • Acceleration time history used in the seismic analysis of nuclear power plant structures should envelop a target power spectral density (PSD) function in addition to the design response spectrum in order to have sufficient energy at each frequency for the purpose of ensuring adequate load. The safety for complex long-span highway bridges cannot be over-emphasize. An alternative method to improve the seismic capacity is to ensure the minimum PSD function of the applied seismic load. This study proposes a technical scheme to obtain the reference power spectral density function by using artificial earthquakes which are compatible with the highway bridge design spectrum.

Retrieval of Radial Velocity and Moment Based on the Power Spectrum Density of Scattered 1290 MHz Signals with Altitude (1290 MHz 산란 신호의 고도별 파워 스펙트럼 밀도에 기반한 시선 속도와 모멘트 산출)

  • Jo, Won-Gi;Kwon, Byung-Hyuk;Yoon, Hong-Joo
    • The Journal of the Korea institute of electronic communication sciences
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    • v.13 no.6
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    • pp.1191-1198
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    • 2018
  • The wind profiler radar provides a standing profile of the wind vector and the atmospheric physical signal for the fixed point. Since the wind vector is calculated by the manufacturer's data processing program, the quality control of the date is limited. Therefore, understanding and exploiting the raw spectrum data need to improve the quality of the wind vector. The raw data of the wind vector is the power spectral density stored in binary form. In this study, an algorithm was completed to transform the raw data into the real spectral density, and the use of raw data was evaluated by retrieving zero-order and first-order moments of the spectral based on the spectrum quality control.

Raw Spectrum Analysis of operated UHF-Wind Profiler Radar in South Korea (국내 운용 UHF-윈드프로파일러 레이더의 원시 스펙트럼 분석)

  • Lee, Kyung-Hun;Kwon, Byung-Hyuk;Kim, Yu-Jin;Lee, Geon-Myeong
    • The Journal of the Korea institute of electronic communication sciences
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    • v.17 no.5
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    • pp.767-774
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    • 2022
  • In this paper raw spectrum data were analyzed to suggest the moving forward of performance evaluation and quality control of wind profilers of four manufacturers operating in South Korea. For the analysis, the profile of the spectrum averaged by season and the profile of four statistical values (minimum, average, median, and maximum) calculated by Power Spectrum Density (PSD) were used. The quality of spectrum data was the best for LAP-3000, followed by YKJ3, PCL-1300, and CLC-11-H. In Cheorwon and Chupungnyeong, where PCL-1300 was installed, the variability of the spectrum due to ground clutter and non-meteorological signals was large, so ground clutter removal and signal processing such as moving average and multi-peak were required. In Gunsan and Paju, where CLC-11-H was installed, DC (Direct Current) bias and propagation folding were found, so it is necessary to remove the DC bias and limit the effective altitude for observation.