arXiv subjects

Yosef Ashkenazy

Publications and source records attributed to Yosef Ashkenazy.

41 records · Page 3Linked to original sources

arXiv2001

Noise Effects on the Complex Patterns of Abnormal Heartbeats

Patients at high risk for sudden death often exhibit complex heart rhythms in which abnormal heartbeats are interspersed with normal heartbeats. We analyze such a complex rhythm in a single patient over a 12-hour period and show that the rhythm can be described by a theoretical model consisting of two interacting oscillators with stochastic elements. By varying the magnitude of the noise, we show that for an intermediate level of noise, the model gives best agreement with key statistical features of the dynamics.

cond-mat.stat-mech↗

arXiv2001

A Stochastic Model of Human Gait Dynamics

We present a stochastic model of gait rhythm dynamics, based on transitions between different ``neural centers'', that reproduces distinctive statistical properties of normal human walking. By tuning one model parameter, the hopping range, the model can describe alterations in gait dynamics from childhood to adulthood --- including a decrease in the correlation and volatility exponents with maturation. The model also generates time series with multifractal spectra whose broadness depends only on this parameter.

cond-mat.stat-mech↗

arXiv2001

Magnitude and Sign Correlations in Heartbeat Fluctuations

We propose an approach for analyzing signals with long-range correlations by decomposing the signal increment series into magnitude and sign series and analyzing their scaling properties. We show that signals with identical long-range correlations can exhibit different time organization for the magnitude and sign. We find that the magnitude series relates to the nonlinear properties of the original time series, while the sign series relates to the linear properties. We apply our approach to the heartbeat interval series and find that the magnitude series is long-range correlated, while the sign series is anticorrelated and that both magnitude and sign series may have clinical applications.

cond-mat.stat-mech↗

arXiv1999

Chaotic enhancement of decay. The effect of classical phase space structure

We investigate the decay process from a time dependent potential well in the semiclassical regime. The classical dynamics is chaotic and the decay rate shows an irregular behavior as a function of the system parameters. By studying the weak-chaos regime we are able to connect the decay irregularities to the presence of nonlinear resonances in the classical phase space. A quantitative analytical prediction which accounts for the numerical results is obtained.

chao-dyn↗

arXiv1998

The Use of Generalized Information Dimension in Measuring Fractal Dimension of Time Series

An algorithm for calculating generalized fractal dimension of a time series using the general information function is presented. The algorithm is based on a strings sort technique and requires $O(N \log_2 N)$ computations. A rough estimate for the number of points needed for the fractal dimension calculation is given. The algorithm was tested on analytic example as well as well-known examples, such as, the Lorenz attractor, the Rossler attractor, the van der Pol oscillator, and the Mackey-Glass equation, and compared, successfully, with previous results published in the literature. The computation time for the algorithm suggested in this paper is much less then the computation time according to other methods.

chao-dyn↗