Nonlinear time series analysis of the ionospheric measurements

The applications of the tools of nonlinear time-series analysis to measurements obtained by digital ionosonde PARUS, created at IZMIRAN, is considered. Small-scale structure of the electron density Ne at F-region of ionosphere is examined by exploring observables of reflected high-frequency radio wave.Time series corresponding to given transmitter frequency f and virtual height h and conforming to usual, not perturbed, day ionogram are examined. Using the standard correlation algorithm, we have determined that for an embedding dimension n = 15, computed correlation dimension D2(n) reaches its saturation, D2 4.Reliability of the estimation of the correlation dimension was confirmed by applying to our sets of measurements J. Theiler's modification of standard algorithm. The test of time difference, smoothing procedure, calculation of the largest Liapounov exponent, and analysis of the surrogate data were employed in our study of data sets. Although our sets of measurements contain a significant random noise, nonlinear time-series analysis clear up, that the dynamics of unperturbed ionosphere, generating this time series, exhibits low-dimensional behavior.     

河冰湖突发洪水的分形和混沌特征研究

本文利用天山北坡四棵树河冰湖突发洪水洪峰流量时间序列,从吸引子分维数Ｄ２和Ｋｏｌｏｍｏｇｏｒｏｖ熵等方面分析了洪峰流量变化的混沌性质,初步结果表明,河冰湖突发洪水时序分布具有分形特征,且洪峰流量的变化是一个稳定性的低维混沌吸引子。     

Qualitative analysis of two-fluid FRW cosmological models

This paper focuses attention on a qualitative analysis of the evolution of two-fluid flat FRW cosmological models.In the first model one of the fluid represents matter content of the universe comoving with respect to the another fluid that is the cosmic microwave background radiation (CMBR), these two fluids are interacting.The first model is most relevant to describe the scenario before the recombination epoch when matter and radiation were in an interactive phase and the photons was bound to electron through Thomson scattering. The second model describe two noninteracting fluids where the matter is comoving to the space-time coordinates and the CMBR is moving axially, relative to the matter thus modeling the relative velocity between galaxies and the CMBR (Phys. Rev. Lett. 39:898–901, 1977). This model portray the cosmic evolution in the postrecombination epoch when the two-fluid are noninteracting.In this epoch the photons got themselves free to form the CMBR being observed presently.      

The Evolution of Dilatonic Universe with a Double Exponential Potential

In this paper, dilaton in Weyl-Scaled induced gravitational theory is regarded as a candidate of dark energy. When the potential of dilaton field is taken as the form of a double exponential , we find that there exist attractor solutions in dilatonic dark energy model, and these attractors correspond to an equations of state and a cosmic density parameter , which are important features for a dark energy model that can meet the current observations. We find out the sufficient condition of the existence of a late time de Sitter attractor.