نتایج جستجو برای: fourier power spectrum
تعداد نتایج: 740695 فیلتر نتایج به سال:
Quasi-periodic conductance fluctuations are observed in the low-temperature magneto-conductance of a bilayer graphene sample. The quasi-periodic nature of the fluctuations is confirmed by their Fourier power spectrum, which consists of just a small number of dominant frequency components. From an experimental study of these features, which are highly reminiscent of those reported previously for...
We present a power spectrum analysis of the final 2dF Galaxy Redshift Survey, employing a direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection, improving on previous treatments in a number of respects. A new angular mask is derived, based on revisions to the photometric calibration. The redshift...
This paper relates uniform α-Hölder continuity, or α-dimensionality, of spectral measures in an arbitrary interval to the Fourier transform of the measure. This is used to show that scaling exponents of exponential sums obtained from time series give local upper bounds on the degree of Hölder continuity of the power spectrum of the series. The results have applications to generalized random wal...
We propose a general approach to the question of how biological rhythms spontaneously self-regulate, based on the concept of "stochastic feedback". We illustrate this approach by considering at a coarse-grained level the neuroautonomic regulation of the heart rate. The model generates complex dynamics and successfully acounts for key characteristics of cardiac variability, including the l/f pow...
We report on selection and stabilization of transverse optical patterns in a feedback mirror experiment. Amplitude filtering in the Fourier plane is used to select otherwise unstable spatial patterns. Optical turbulence observed for nonlinearities far above the pattern formation threshold is stabilized by low-pass filtering of the optical power spectrum. Experimental observations obtained with ...
Abslrnrf This paper aim to consider using the Wavelel Transform ( WT), WignerVille Distribution ( W O ) and ChoiWilliams Distribution (CWD) applied for spectrum estimution of non-stationary signals in power sysfems. The main goal is lo emphasize advantage and disadvantage of mentioned methods in comparison with Shun-Tinu Fourier Transform (STFT). Especial& the aspect offrequency resolution are ...
A method to test for nonlinearity in time series, without the need to apply the Fourier transform, is proposed. This method therefore avoids the drawbacks of previously proposed surrogate techniques associated with the estimation of the signal's power spectrum. The test addressed by this algorithm is that the data are generated by a stationary linear system. To achieve this, the algorithm takes...
We consider the question of how the cardiac rhythm spontaneously self-regulates and propose a new mechanism as a possible answer. We model the neuroautonomic regulation of the heart rate as a stochastic feedback system and find that the model successfully accounts for key characteristics of cardiac variability, including the 1/f power spectrum, the functional form and scaling of the distributio...
Abstruct-A universal lower hound technique for the size and other implementation characteristics of an arbitrary Boolean function as a decision tree and as a two-level ANDDR circuit is derived. The technique is based on the power spectrum coefficients of the n-dimensional Fourier transform of the function. The bounds wry from constant to exponential and are tight in many cases. Several examples...
The most commonly applied technique to obtain an estimated power spectrum ) ( ˆ f S of a sampled time series ) (t x of finite length N, is to compute the Fourier transform ) 2 ( f j X , followed by multiplication by its complex conjugate and scaling by the length of the finite observation, i.e. N f j X f j X f S / ) 2 ( ) 2 ( ) ( ˆ * (see Chapter 7 in van Drongelen, 2007). The reliabi...
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