共查询到20条相似文献,搜索用时 31 毫秒
1.
为提高脉冲星辐射脉冲到达时间的测量精度,提出了基于双谱的脉冲星累积脉冲轮廓时间延迟测量算法.理论上,双谱可以完全抑制加性高斯白噪声.通过进行自双谱与互双谱的比对及求解极值点,推导出时间延迟测量公式.实验结果表明,基于双谱的时间延迟测量算法可以有效抑制高斯白噪声,当累积脉冲轮廓观测值存在噪声项时,基于双谱的累积脉冲轮廓时间延迟测量精度优于泰勒提出的功率谱算法.
关键词:
脉冲星
脉冲到达时间
累积脉冲轮廓时间延迟
双谱 相似文献
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Experimental study is performed of optical diffractions by two-dimensional, self-similar mass and surface fractal apertures as well as mass fractal apertures bounded by surface fractals. Self-similar intensity distributions are observed in the Fraunhofer diffraction fields from surface and mass fractal apertures. Power law decays in average intensities of the diffraction patterns are also investigated for the mass, surface and combined fractal apertures in connection with the fractal dimensions of the objects. 相似文献
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FAN Chengyu 《中国光学快报(英文版)》1999,8(2)
The effects of light wave propagating in atmospheric turbulence are investigated experimentally, it is essential to measure the physical variable with time. In order to analyze appropriately these data, it is utilized the fractal function auto-correlative method to describe the fractal dimension of function graph of image-space. The fractal dimension Dg=1.47 of function graph is derived from the power spectral analysis of measuring data. It shows that the Kolmogorov' turbulent model is not completely in accord with actual atmospheric turbulence. 相似文献
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FAN Chengyu 《Chinese Journal of Lasers》1999,8(2):149-152
1IntroductionThehypothesisofastatisticalylocalyisotropichomogeneousturbulentfieldwasthebaseofKolmogorov’smodel[1].Thesecondo... 相似文献
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Minghua Han Naichang Yuan 《International Journal of Infrared and Millimeter Waves》1998,19(8):1131-1140
Estimation of transient signal in additive noise is very important in radar object detection and recognition. This paper presents a new method for transient signal reconstruction based on bispectrum estimation techniques. The third-order cumulants of the received noisy ultra-wide band echoes are acquired first and an ARMA model is then fitted. The bispectrum of the output signal of the ARMA model will be used to reconstruct the transient signal. Simulation results show that the effect is very good even in lower signal-to-noise (SNR) situation. 相似文献
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Application of the bispectrum for detection of small nonlinearities excited sinusoidally 总被引:1,自引:0,他引:1
C.R.P. Courtney S.A. Neild P.D. Wilcox B.W. Drinkwater 《Journal of sound and vibration》2010,329(20):4279-4293
The nonlinear behaviour of damaged systems excited by vibration or ultrasound offers potential as a technique for damage detection in machine condition monitoring and non-destructive testing applications. The bispectrum, a third-order spectrum, has properties that lend themselves to the measurement of nonlinearities in systems. The properties of interest are insensitivity to Gaussian noise and ability to detect quadratic phase coupling. However, thus far analysis of the statistics of bispectrum estimation has been mainly aimed at stochastic systems. Many applications to vibration and ultrasound involve primarily deterministic, periodic excitations in the presence of stochastic noise. This paper considers the properties of a bispectrum estimate when applied to a system with weak quadratic nonlinearity excited by the superposition of two sinusoids in the presence of additive Gaussian noise. This is compared, using signal-to-noise ratios, to the powerspectrum, with the results validated using numerical data. Also addressed is the effect of quadratic phase coupling on such a system (in the absence of noise). 相似文献
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Minghua Han Naichang Yuan 《International Journal of Infrared and Millimeter Waves》1998,19(8):1141-1149
According to the features of the echoes of the ultra-wide band radar, this paper analyses the estimating effects of choosing the AR model, MA model and ARMA model based on bispectrum. It shows that ARMA model is much better than others. Simulations verify this result, also demonstrate the estimation precision has been improved. ARMA model parametric bispectrum estimation is very efficient to echoes of ultra-wide band radar. 相似文献
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Santos MG Balbi A Borrill J Ferreira PG Hanany S Jaffe AH Lee AT Magueijo J Rabii B Richards PL Smoot GF Stompor R Winant CD Wu JH 《Physical review letters》2002,88(24):241302
We use the measurement of the cosmic microwave background taken during the MAXIMA-1 flight to estimate the bispectrum of cosmological perturbations. We propose an estimator for the bispectrum that is appropriate in the flat sky approximation, apply it to the MAXIMA-1 data, and evaluate errors using bootstrap methods. We compare the estimated value with what would be expected if the sky signal were Gaussian and find that it is indeed consistent, with a chi(2) per degree of freedom of approximately unity. This measurement places constraints on models of inflation. 相似文献
13.
A large fraction of the information collected by cosmological surveys is simply discarded to avoid length scales which are difficult to model theoretically. We introduce a new technique which enables the extraction of useful information from the bispectrum of galaxies well beyond the conventional limits of perturbation theory. Our results strongly suggest that this method increases the range of scales where the relation between the bispectrum and power spectrum in tree-level perturbation theory may be applied, from k(max) ~ 0.1 to ~0.7 hMpc(-1). This leads to correspondingly large improvements in the determination of galaxy bias. Since the clipped matter power spectrum closely follows the linear power spectrum, there is the potential to use this technique to probe the growth rate of linear perturbations and confront theories of modified gravity with observation. 相似文献
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Susumu Kuwamura Yuuki Yoshinoya Noriaki Miura Fumiaki Tsumuraya Makoto Sakamoto Naoshi Baba 《Optical Review》2011,18(1):19-26
A bispectral method for astronomical speckle imaging utilizes an average speckle bispectrum of an object to derive its Fourier
phase. There has been, however, a problem in conventional bispectral algorithm owing to difficulty in processing bispectral
data in a four-dimensional (4D) space. In this paper, we propose an implementation to overcome this problem, where a one-dimensional
(1D) object projection is reconstructed from a two-dimensional (2D) average bispectrum of speckle projections, and object
projections so obtained at various angles are then tomographically combined into a 2D object image. In this tomographic approach,
processes are separable into those for individual projection angles, implying that bispectral data required to be stored at
a time are from 4D to 2D and computation time can be substantially reduced by parallelizing angle-by-angle processes. We have
performed experiments using simulated and observed data, and have demonstrated the feasibility of the present approach with
an achievable accuracy comparable to that of a conventional approach. 相似文献
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This work derives the expressions for the bispectrum and bicoherence functions for multi-degree-of-freedom spring-mass systems with quadratic nonlinearities subject to inputs described by a wide class of random processes. The derivation uses a Volterra series model for the system response and yields expressions for both “homogeneous spectra”, where the output of only one degree of freedom is used, and “mixed spectra” where the bispectral density contains multiple response time series. This expression is then used to determine the optimal probability distribution of the input and the optimal bispectrum to compute for the goal of maximizing the probability of detecting the nonlinearity. 相似文献
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大幅度、快速光变是BL Lac天体的重要特征之一,光变研究对探索BL Lac天体内部的物理过程和机理具有特殊的意义.从大量文献中收集了BL Lac天体S5 0716+714光学V,R,I 3个波段从1994年到2008年的有效观测数据,并将这些数据30天平均后进行自回归模型(AR)的双谱估计. 双谱的等高线图和对角切片图表明,双谱估计能消除噪声的干扰来提取有用信息,抑制了噪声、提高了信噪比,有很高的分辨率,避免了伪峰的出现,能准确地认证BL Lac天体的光变周期值.由V,R,I 3个波段的双谱等高线图和对 相似文献
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We extend the deltaN formalism so that it gives all of the stochastic properties of the primordial curvature perturbation zeta if the initial field perturbations are Gaussian. The calculation requires only the knowledge of some family of unperturbed universes. A formula is given for the normalization f(NL) of the bispectrum of zeta, which is the main signal of non-Gaussianity. Examples of the use of the formula are given, and its relation to cosmological perturbation theory is explained. 相似文献
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A. A. Zelensky V. F. Kravchenko V. V. Pavlikov V. I. Pustovoit A. V. Totsky 《Doklady Physics》2014,59(7):304-308
The methods of smoothing of the bispectral density estimate when solving the problems of restoration of signals with an unknown shape in the interference environment and random signal delay are considered for the first time. The performed analysis of statistical characteristics of noise that presents in the bispectrum estimate shows that these statistical characteristics have a rather complex unsteady behavior. An ambiguous selection of a filter optimal by the criterion of the minimum of the root-mean-square error and the minimum of dynamic distortions introduced by the filter seems to be problematic because of the unsteady behavior of counts of the bispectral density estimate and the absence of a priori data on the parameters of the restored signal. Therefore, statistic investigations were performed with the use of linear and nonlinear digital filters with variations of the sliding window sizes. It is shown that the advantages of the proposed approach most pronouncedly manifest themselves with the use of the nonlinear digital filtration and small signal/noise ratios at the input and/or with a small sampling volume of observed implementations. The Kravchenko weight functions are proposed to smooth the bispectrum of the multifrequency signal with a large dynamic range of variations in amplitudes of spectral components. The presented results are of practical interest for use in applications such as radiolocation, hydrolocation, and digital communication. 相似文献
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The model of fractal continuum accounting the topological, metric, and dynamic properties of deformable physical fractal medium is suggested. The kinematics of fractal continuum deformation is developed. The corresponding geometric interpretations are provided. The concept of stresses in the fractal continuum is defined. The conservation of linear and angular momentums is established. The mapping of mechanical problems for physical fractal media into the corresponding problems for fractal continuum is discussed. 相似文献