Sleep as a random walk - A superstatistical analysis of EEG data across sleep stages

In clinical practice, human sleep is classified into stages, each associated with different levels of muscular activity and marked by characteristic patterns in the EEG signals. It is however unclear whether this subdivision into discrete stages with sharply defined boundaries is truly reflecting the dynamics of human sleep. To address this question, we consider one-channel EEG signals as heterogeneous random walks: stochastic processes controlled by hyper-parameters that are themselves time-dependent. We first demonstrate the heterogeneity of the random process by showing that each sleep stage has a characteristic distribution and temporal correlation function of the raw EEG signals. Next, we perform a superstatistical analysis by computing 'hyper-parameters', such as the standard deviation, kurtosis and skewness of the raw signal distributions, within subsequent 30-second epochs. It turns out that also the hyper-parameters have characteristic, sleep-stage-dependent distributions, which can be exploited for a simple Bayesian sleep stage detection. Moreover, we find that the hyper-parameters are not piece-wise constant, as the traditional hypnograms would suggest, but show rising or falling trends within and across sleep stages, pointing to an underlying continuous rather than subdivided process that controls human sleep.

Analysis and Simulation of Radar Clutter Using Spherically Invariant Random Processe

Non-Gaussian probability distribution radar clutter not only is temporal correlated between different pulses, but also is spatial correlated between different range bins. In this paper, the method of simulation and validation of radar clutter is proposed using spherically invariant random processes (SIRP). The amplitude probability function and temporal correlation function of radar clutter can be controlled respectively, and the spatial correlation function can be also specified. The computer simulation of K-distribution and CHI-distribution radar clutter is used to validate the method, and is to validate the amplitude probability function, temporal-spatial 2D correlation function.

Simulation and Validation of Temporal-Spatial 2-Dimensional Correlated Radar Clutter Based on SIRP

Non-Gaussian probability distribution radar clutter not only is temporal correlated between different pulses, but also is spatial correlated between different range bins. In this paper, the method of simulation and validation of radar clutter is proposed using spherically invariant random processes (SIRP). The amplitude probability function and temporal correlation function of radar clutter can be controlled respectively, and the spatial correlation function can be also specified. The computer simulation of K-distribution and CHI-distribution radar clutter is used to validate the method, and is to validate the amplitude probability function, temporal-spatial 2D correlation function.

PSEUDOSCALAR MESON TEMPORAL CORRELATION FUNCTION FOR FINITE MOMENTA IN HTL APPROACH

The temporal pseudoscalar meson correlation function in a QCD plasma is investigated in a range of temperatures exceeding Tc and first time for a finite momenta which is of the experimental interest. The imaginary time formalism is employed for the finite temperature calculations. The behavior of the meson spectral function and of the temporal correlator is studied in the HTL approximation, where one replaces the free thermal quark propagators with the HTL resumed ones.

Monte Carlo simulation of coherent effects in multiple scattering

Using a combination of the stochastic Monte Carlo technique and the iteration procedure of the solution to the Bethe–Salpeter equation, it has been shown that the simulation of the optical path of a photon packet undergoing an n th scattering event directly corresponds to the n th–order ladder diagram contribution. In this paper, the Monte Carlo technique is generalized for the simulation of the coherent back–scattering and temporal correlation function of optical radiation scattered within the randomly inhomogeneous turbid medium. The results of simulation demonstrate a good agreement with the diffusing wave theory and experimental results.