• Title/Summary/Keyword: Spectrum Estimation

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Simultaneous estimation of the temporal and spatial spectrum using circular array (원형어레이를 이용한 시.공간 스펙트럼 동시추정)

  • 황성준;주경환;성하종;김영수;윤대희
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.2
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    • pp.347-356
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    • 1996
  • In this paper, we present the circular array structure for estimating the temporal and spatial specturm of multiple narrowband incoherent signals which have different frequencies. The conventional linear array is computationally demanding for simultaneously estimating the spatial and temporal spectrum since it requires the tapped delay line filer. The statistical performance of the circular array is never deteriorated eve though it requires much less computational load than the uniform linear array. Especially, it is shown that the circular array resolves the direction-of-arrivals of the multiple signals without the spatial and temporal aliasing the fundamental nonuniform-sampling property prossessed by it. Computer simulation results are shown to demonstrate the better performance achieved with the circular array geometry relative to that obtained with a uniform linear array with taps.

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The Estimation of Early Health Effects for Different Combinations of Release Parameters and Meteorological Data

  • Jeong, Jongtae;Jung, Wondea
    • Nuclear Engineering and Technology
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    • v.33 no.6
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    • pp.557-565
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    • 2001
  • Variations in the number of early health effects resulting from the severe accidents of the YGN 3&4 nuclear power plants were examined for different combinations of release parameters and meteorological data . The release parameters and meteorological data were selected in combination to define a limited number of basic spectra characterized by release height, heat content, release time, warning time, wind speed, rainfall rate, and atmospheric stability class. Variant seasonal spectra were also defined in order to estimate the potential significance of seasonal variations as a factor determining the incidence or number of early health effects. The results show that there are large differences in consequences from spectrum to spectrum, although an equal amount and mix of radioactive material is released to the atmosphere in each case. Also, there are large differences in the estimated number of health effects from season to season due to distinct seasonal variations in meteorological combinations in Korea. Therefore, it is necessary to consider seasonal characteristics in developing optimum emergency response strategies.

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The Characteristics of Muscle Fatigue of EMG Signal Using the AR Model (AR 모델을 이용한 EMG 신호의 근육피로 특성)

  • 김홍래;왕문성
    • Journal of Biomedical Engineering Research
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    • v.10 no.1
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    • pp.11-16
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    • 1989
  • This paper describes the AR model of EMG signal during maximum voluntary contraction. By comparing the AR coefficients and the reflection coefficients of the AR model with the median frequency of power spectrum, it is proved that muscle fatigue can be measured by the AR and the reflection coefficients. In the estimation procedure of AR model parameter, the autocorrelation method is superior to the covariance method, and it is determined that the optimal order is six. As the muscle becomes fatigue, the median frequency of power spectrum is declined, and the AR coefficient [$a_1$] and the reflection coefficient [$k_1$] are also decreased. Therefore the muscle fatigue can be measured by the AR parameter.

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On-line partial discharge measurement techniques of hydro-generator windings (수력 발전기 권선에서의 운전중 부분방전 측정기법)

  • 황동하;김진봉;김용주;박명수;김택수
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.45 no.2
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    • pp.294-300
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    • 1996
  • In hydro-generator, a groundwall insulation of stator windings gradually deteriorates due to mechanical, thermal, electrical and environmental stresses. These stresses combine to result in loose windings, delamination of the stator insulation and/or electrical tracking of the endwinding, all of which can lead to stator insulation failures. Conventionally, off-line tests such as partial discharge measurement, DC/AC current and .DELTA.tan.delta. tests has been used for estimation of winding condition. However, off-line test requires large power supply and generator outage. In addition, major cause of insulation problems such as loose wedges and slot dischages may not be found with off-line diagnoses. This paper introduces the on-line partial discharge measurement techniques using frequency spectrum analyzer(FSA) for the generator stator windings. The experimental results from the UIAM #1 hydro-generator confirms a optimistic application of on-line generator diagnosis method as a reliable tool for evaluation of winding condition.

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Estimating Mass and Radius of a Neutron Star in Low-Mass X-ray Binary

  • Kwak, Kyujin;Sung, Kwang Hyun;Kim, Young-Min;Kim, Myungkuk;Lee, Chang-Hwan
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.48.1-48.1
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    • 2019
  • Mass and radius of a neutron star in low-mass X-ray binary (LMXB) can be estimated simultaneously when the observed light curve and spectrum show the photospheric radius expansion feature. This method has been applied to 4U 1746-37 and the mass and radius were found to be unusually small in comparison with typical neutron stars. We re-estimate the mass and radius of this target by considering that the observed light curve and spectrum can be affected by other X-ray sources because this LMXB belongs to a very crowded globular cluster NGC 6441. The new estimation increases the mass and radius but they do not reach the typical values yet.

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Using the Topology of Large Scale Structure for Cosmological Parameter Estimation

  • Appleby, Stephen
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.41.2-41.2
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    • 2018
  • The Minkowski Functionals of the matter densityeld, as traced by galaxies, contain information regarding the nature of dark energy and the fraction of dark matter in the Universe. In particular, the genus is a statistic that provides a clean measurement of the shape of the linear matter power spectrum. As the genus is a topological quantity, it is insensitive to galaxy bias and gravitational collapse. Furthermore, as it traces the linear matter power spectrum, it is a conserved quantity with redshift. Hence the genus amplitude is a standard population that can be used to test the distance-redshift relation. In this talk, I show how we can extract the genus from galaxy catalogs, and how we can use its properties to constrain the equation of state of dark energy and the energy content of the Universe.

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Cosmological Parameter Estimation from the Topology of Large Scale Structure

  • Appleby, Stephen
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.53.2-53.2
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    • 2019
  • The genus of the matter density eld, as traced by galaxies, contains information regarding the nature of dark energy and the fraction of dark matter in the Universe. In particular, this topological measure is a statistic that provides a clean measurement of the shape of the linear matter power spectrum. As the genus is a topological quantity, it is insensitive to galaxy bias and gravitational collapse. Furthermore, as it traces the linear matter power spectrum, it is a conserved quantity with redshift. Hence the genus amplitude is a standard population that can be used to test the distance-redshift relation. In this talk, I present measurements of the genus extracted from the SDSS DR7 LRGs in the local Universe, and also slices of the BOSS DR12 data at higher redshift. I show how these combined measurements can be used to place cosmological parameter constraints on m, wde.

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Estimation of Nitrate Nitrogen Concentration in Liquid Fertilizer Contaminated Areas using Hyperspectral Images (초분광 영상을 이용한 액비 오염지역의 질산성질소 농도 추정)

  • Lim, Eun Sung;Kim, I Seul;Han, Soo Jeong;Lim, Tai Yang;Song, Wonkyong
    • Journal of the Society of Disaster Information
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    • v.16 no.3
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    • pp.542-549
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    • 2020
  • Purpose: As nitrate nitrogen produced during fermentation of liquid fertilizer is a pollution indicator of water, in this study, four research areas where liquid fertilizer was sprayed were selected, and a model was designed to estimate the concentration of nitrate nitrogen pollution. Method: Prior to shooting on site, a spectrum library was constructed by dividing the ratio of liquid fertilizer into 5 groups: 0%, 25%, 50%, 75%, and 100%. PLSR (Partial least squares regression) method was applied to hyperspectral images acquired in the study area based on the aspect of spectrum. Result: The behavior of nitrate nitrogen was confirmed by 1st and 2nd differentiation of the spectrum of the constructed liquid fertilizer. PLSR concentration estimation modeling was implemented using images from field experiments and compared with actual concentration of nitrate nitrogen. Conclusion: When comparing the PLSR concentration estimation model with the actual concentration of nitrate nitrogen, it was measured that the detection is possible in high concentration areas where the concentration of nitrate nitrogen is 70mg/kg or more.

Packet-Reduced Ranging Method with Superresolution TOA Estimation Algorithm for Chirp-Based RTLS

  • Oh, Daegun;Go, Seungryeol;Chong, Jong-Wha
    • ETRI Journal
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    • v.35 no.3
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    • pp.361-370
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    • 2013
  • In this paper, a packet-reduced ranging method using a superresolution time of arrival estimation algorithm for a chirp-based real-time locating system is presented. A variety of ranging methods, such as symmetric double-sided two-way ranging (SDS-TWR), have been proposed to remove the time drift due to the frequency offset using extra ranging packets. Our proposed method can perform robust ranging against the frequency offset using only two ranging packets while maintaining almost the same ranging accuracy as them. To verify the effectiveness of our proposed algorithm, the error performance of our proposed ranging method is analyzed and compared with others. The total ranging performance of TWR, SDS-TWR, and our proposed TWR are analyzed and verified through simulations in additive white Gaussian noise and multipath channels in the presence of the frequency offset.

Low Cost Rotor Fault Detection System for Inverter Driven Induction Motor

  • Kim, Nam-Hun;Choi, Chang-Ho
    • Journal of Electrical Engineering and Technology
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    • v.2 no.4
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    • pp.500-504
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    • 2007
  • In this paper, the induction motor rotor fault diagnosis system using current signals, which are measured using axis-transformation method, and speed, which is estimated using current information, are presented. In inverter-fed motor drives unlike line-driven motor drives the stator currents have numerous harmonics components and therefore fault diagnosis using stator currents is very difficult. The current and speed signal for rotor fault diagnosis needs to be precise. Also, high resolution information, which means the diagnosis system, demands additional hardware such as low pass filter, high resolution ADC, encoder and etc. Therefore, the proposed axis-transformation and speed estimation method are expected to contribute to low cost fault diagnosis systems in inverter-fed motor drives without the need for an encoder and any additional hardware. In order to confirm validity of the developed algorithms, various experiments for rotor faults are tested and the line current spectrum of each faulty situation using Park transformation and speed estimation method are compared with the results obtained from fast Fourier transforms.