arXiv subjects

E. B. Postnikov

Publications and source records attributed to E. B. Postnikov.

30 records · Page 2Linked to original sources

arXiv2016

Isobaric heat capacity, isothermal compressibility and fluctuational properties of 1-bromoalkanes

We present results of the experimental measurements of the isobaric heat capacity for 1-bromohexane, 1-bromoheptane, 1-bromooctane, 1-bromononane, 1-bromodecane, 1-bromoundecane, 1-bromododecane and 1-bromo-tetradecane at normal pressure and the speed of sound and the density for 1-bromotetradecane within the temperature range 298.15--423.15~K. These data on the isobaric heat capacity and the literature-based reference data for the density and the speed of sound were used to calculate the isothermal compressibility and the inverse reduced fluctuations. Based on the comparison of the results for pure n-alkanes and $α,ω$-dibromoalkanes, we discuss the influence of bromine atom on the volume fluctuations.

physics.chem-ph↗

arXiv2016

On the speed of sound and heat capacity of liquid neon in the subcritical region

The data (the speed of sound, the isobaric and isochoric heat capacities as well as the heat capacity ratio) for liquid neon presented in NIST Chemistry WebBook are analyzed. It has been shown, basing on the representation of the inverse reduced volume fluctuations, that they consist of sufficient discrepancies in the subcritical region. The correction of data in this region of the coexistence curve is evaluated using the fluctuation approach and the theory of thermodynamic similarity.

physics.class-ph↗

arXiv2015

Analytical properties of a three-compartmental dynamical demographic model

The three-compartmental demographic model by Korotaeyv-Malkov-Khaltourina, connecting population size, economic surplus, and educational level, is considered from the point of view of dynamical systems theory. It is shown that there exist two integrals of motion, which enable the system to be reduced to one non-linear ordinary differential equation. The study of its structure provides analytical criteria for the dominance ranges of the dynamics of Malthus and Kremer. Additionally, the particular ranges of parameters enable the derived general ordinary differential equations to be reduced to the models of Gompertz and Thoularis-Wallace.

q-bio.PE↗

arXiv2014

Tait equation revisited from the entropic and fluctuational points of view

We consider the possibilities for prediction of liquids' density under pressure basing on the inverse reduced fluctuations parameter, which is directly connected with the isothermal compressibility. This quantity can be determined basing on the thermodynamical properties of saturated liquid and it consists of only two constant parameters within a relatively wide region close to the melting points. It is confirmed by the comparison with the experimental data on n-alkanes that the derived expression is a quite reasonable estimator without a necessity to fit data along some parts of isotherms for different temperatures. At the same time the obtained formula: i) can be reduced to the form of the Tait equation and ii) the resulting Tait's parameters in this representation have a clear physical meaning as functions of the excess entropy, which determines the mentioned reduced fluctuations.

cond-mat.stat-mech↗

arXiv2014

Limits of structure stability of simple liquids revealed by study of relative fluctuations

We analyse the inverse reduced fluctuations (inverse ratio of relative volume fluctuation to its value in the hypothetical case where the substance acts an ideal gas for the same temperature-volume parameters) for simple liquids from experimental acoustic and thermophysical data along a coexistence line for both liquid and vapour phases. It has been determined that this quantity has a universal exponential character within the region close to the melting point. This behaviour satisfies the predictions of the mean-field (grand canonical ensemble) lattice fluid model and relates to the constant average structure of a fluid, i.e. redistribution of the free volume complementary to a number of vapour particles. The interconnection between experiment-based fluctuational parameters and self-diffusion characteristics is discussed. These results may suggest experimental methods for determination of self-diffusion and structural properties of real substances.

cond-mat.stat-mech↗

arXiv2013

Non-spectral relaxation in one dimensional Ornstein-Uhlenbeck processes

The relaxation of a dissipative system to its equilibrium state often shows a multiexponential pattern with relaxation rates, which are typically considered to be independent of the initial condition. The rates follow from the spectrum of a Hermitian operator obtained by a similarity transformation of the initial Fokker-Planck operator. However, some initial conditions are mapped by this similarity transformation to functions which grow at infinity. These cannot be expanded in terms of the eigenfunctions of an Hermitian operator, and show different relaxation patterns. Considering the exactly solvable examples of Gaussian and generalized Lévy Ornstein-Uhlenbeck processes (OUPs) we show that the relaxation rates belong to the Hermitian spectrum only if the initial condition belongs to the domain of attraction of the stable distribution defining the noise. While for an ordinary OUP initial conditions leading to non-spectral relaxation can be considered exotic, for generalized OUPs driven by Lévy noise these are the rule.

cond-mat.soft↗

arXiv2011

Possible structure in the cosmic ray electron spectrum measured by the ATIC-2 and ATIC-4 experiments

A strong excess in a form of a wide peak in the energy range of 300-800 GeV was discovered in the first measurements of the electron spectrum in the energy range from 20 GeV to 3 TeV by the balloon-borne experiment ATIC (J. Chang et al. Nature, 2008). The experimental data processing and analysis of the electron spectrum with different criteria for selection of electrons, completely independent of the results reported in (J. Chang et al. Nature, 2008) is employed in the present paper. The new independent analysis generally confirms the results of (J. Chang et al. Nature, 2008), but shows that the spectrum in the region of the excess is represented by a number of narrow peaks. The measured spectrum is compared to the spectrum of (J. Chang et al. Nature, 2008) and to the spectrum of the Fermi/LAT experiment.

astro-ph.HE↗

arXiv2010

Analysis of patterns formed by two-component diffusion limited aggregation

We consider diffusion limited aggregation of particles of two different kinds. It is assumed that a particle of one kind may adhere only to another particle of the same kind. The particles aggregate on a linear substrate which consists of periodically or randomly placed particles of different kinds. We analyze the influence of initial patterns on the structure of growing clusters. It is shown that at small distances from the substrate, the cluster structures repeat initial patterns. However, starting from a critical distance the initial periodicity is abruptly lost, and the particle distribution tends to a random one. An approach describing the evolution of the number of branches is proposed. Our calculations show that the initial patter can be detected only at the distance which is not larger than approximately one and a half of the characteristic pattern size.

cond-mat.other↗

arXiv2006

Analysis of Saturn main rings by continuous wavelet transform with the complex Morlet wavelet

A new method based on continuous wavelet transform with the complex Morlet wavelet to analyze Saturn main rings is presented. It allows to investigate in detail the resonance zones and reveal the coexistence of waves with stable periods and the wave trains with a variable instant period. This method is based on the replacing the integration of the fast--oscillation function by the solution of the partial differential equations. It is shown that such an approach is an effective tool for the study the radial structure of Saturn's A, B, and C rings. All the analyzed images were obtained from the Cassini spacecraft during 2004--2005 years.

astro-ph↗

arXiv2005

Wavelet transform and diffusion equations: applications to the processing of the "Cassini" spacecraft observations

We show that continuous transform with the complex Morlet wavelet is easily performed if we replace the integration of the fast-oscillation function by the solution of the diffusion differential equations. The most important advantage of this approach is that the initial data can be represented by non-uniform sample of an arbitrary node number. We apply the proposed method to the processing of the image of the Saturn A-ring obtained from the Cassini spacecraft. Also we have got via the wavelet transform using PDE, the local correlation coefficient of the signal and the harmonic function.

astro-ph↗

arXiv2004

Application of the Wavelet Transform with a Piecewise Linear Basis to the Evaluation of the Hankel Transform

A method for computing the Hankel transform is proposed whereby the letter is reduced to a sum by representing the integrand as a smooth function times a Bessel function. The smooth function is replaced by its wavelet decomposition with a basis such that its scalar product with the Bessel function is calculated analytically. The result is represented as a series, with the coefficients strongly depending on the local behavior of the function being transformed. The application of the method is demonstrated by an example illustrated with plots.

math.NA↗

arXiv2003

About Calculation of the Hankel Transform Using Preliminary Wavelet Transform

The purpose of this paper is to present an algorithm for evaluating Hankel transform of the null and the first kind. The result is the exact analytical representation as the series of the Bessel and Struve functions multiplied by the wavelet coefficients of the input function. Numerical evaluation of the test function with known analytical Hankel transform illustrates the proposed algorithm.

math.NA↗