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I. H. Umirzakov

Publications and source records attributed to I. H. Umirzakov.

15 recordsLinked to original sources
arXiv2019

Comments on "Mixed Bose-Fermi statistics Kinetic equation and navigation through network" by S.F. Chekmarev, Phys. Rev. E 82, 026106 (2010)

The paper shows that the kinetic equations considered in [1], equilibrium distribution obtained in [1], and results and conclusions obtained on the basis of the kinetic equation derived in [1] do not correspond to the mixed Bose-Fermi statistics. Moreover, it is shown that the kinetic equation corresponding to the case when the copies of the system are characterized by different values of the fraction of the Fermi-like moves is incorrect. We present a correct kinetic equation for the mixture of the Bose and Fermi moves and obtained the equilibrium distribution for the case when the probability of the Fermi moves is higher or equal to that of the Bose moves.

cond-mat.other↗
arXiv2018

Van der Waals equation of state and PVT properties of real fluid

It is shown that: in the case when two parameters of the Van der Waals equation of state are defined from the critical temperature and pressure the exact parametrical solution of the equations of the liquid-vapor phase equilibrium of the Van der Waals fluid quantitatively describes the experimental dependencies of the saturated pressure of argon on the temperature and reduced vapor density, and it gives the quantitative description of the temperature dependencies of the reduced densities near critical point. When the parameters are defined from the critical pressure and density the parametric solution describes quantitatively the experimental dependencies of the saturated pressure of argon on the density and reduced temperature, it can describe qualitatively the dependencies of the vapor and liquid densities on the reduced temperature, and it gives the quantitative description of the dependencies of the densities on the reduced temperature near critical point. If the parameters are defined from the critical temperature and density then the exact solution describes quantitatively the experimental dependencies of the reduced saturated pressure of argon on the density and temperature, it describes qualitatively the temperature dependencies of the vapor and liquid densities of argon, and it gives the quantitative description of the temperature dependencies of the vapor and liquid densities near critical point. It is also shown that the Van der Waals equation of state describes quantitatively the reference experimental PVT- data for the gas and supercritical fluid states for the under-critical densities of argon, the dependencies of the saturation pressure on the temperature and vapor density, and the dependence of the vapor density of argon on temperature if the parameters are defined from the critical pressure and temperature.

cond-mat.other↗
arXiv2018

Comments on Model free temperature scaling for heat capacity (V.A. Drebushchak, Journal of Thermal Analysis and Calorimetry, 2017 130, 5)

It is shown that the isobaric heat capacity of chalcogenides , , , and can be described by the Debye and Einstein models for the phonon frequency spectrum within their uncertainties; the models give the results for the isochoric heat capacity which are close to each other; the models give the close results for the difference between the isobaric and isochoric heat capacities; the isobaric heat capacities of the isostructural , , and as the functions of the temperature reduced to the Debye (Einstein) temperature are described by single Debay (Einstein) equation for the isobaric heat capacity; the isochoric heat capacities of , , , and (which has another structure than , , and [1]) as the functions of the temperature reduced to the Debye (Einstein) temperature are described by the Debye (Einstein) equation for the isochoric heat capacity. It is shown also that the Debye and Einstein equations for the isochoric heat capacity of , , , and give the same results if the means of the squares of the frequencies of the Debye and Einstein spectra are equal to each other, and the Debye and Einstein equations for the isobaric heat capacity of , , and as the functions of the temperature reduced to the Debye or Einstein temperature give the same results.

cond-mat.other↗
arXiv2018

Failures of meso-phase hypothesis near vapor-liquid critical point

It is shown that the meso-phase hypothesis of Woodcock L. V. fails to describe quantitatively and qualitatively the isochoric and isobaric heat capacities, speed of sound, long wavelength limit of the structural factor, isothermal compressibility, density fluctuations, Joule-Thompson coefficient and isothermal throttling coefficient of argon in the meso-phase region. It is also shown that VdW-EOS can describe qualitatively the excess Gibbs energy and rigidity of argon near critical point.

cond-mat.stat-mech↗
arXiv2018

Comments on Generalization of thermodynamics in of fractional-order derivatives and calculation of heat transfer properties of noble gases, Journal of Thermal Analysis and Calorimetry 2018 133, 1189 1194

It is shown that the equations for pressure, entropy and the isochoric heat capacity obtained by using generalization of the equilibrium thermodynamics in fractional derivatives in the paper mentioned above are approximate, the comparison of the equations with the experimental (tabulated) data for Neon and Argon made in the paper is incorrect, and the conclusions of the paper made on the basis of the comparison could be incorrect. The conditions for validity of the equations are established. It is also established that the question about a physical sense of the exponent of the derivative of a fractional order is still open.

cond-mat.stat-mech↗
arXiv2018

Comments on Failures of van der Waals Equation at the Gas Liquid Critical Point, L. V. Woodcock, International Journal of Thermophysics 2018 39 120

These comments are a response to the discussion presented in the above paper concerning the New comment on Gibbs Density Surface of Fluid Argon, Revised Critical Parameters by Umirzakov. Here we show that Woodcocks results obtained for the dependencies for the isochoric heat capacity, excess Gibbs energy and coexisting difference functional of argon, and coexisting densities of liquid and vapor of the van der Waals fluid and presented in all Figures are incorrect, his Table includes incorrect values of coexisting difference functional, his paper includes many incorrect equations, mathematical and logical errors and physically incorrect assertions concerning the temperature dependences of the isochoric heat capacity and entropy of real fluids, most of the his conclusions are based on the above errors, incorrect data, incorrect comparisons and incorrect dependencies; and most of his conclusions are invalid. We also show that the van der Waals equation of state quantitatively describes the dependencies of saturation pressure on vapor density and temperature near critical point, and the equation of state can describe qualitatively the reduced excess Gibbs energy, rigidity and densities of coexisting liquid and vapor of argon, including the region near critical point.

cond-mat.stat-mech↗
arXiv2016

Comments on "Thermic and Caloric Equations of State with Small Number of Parameters"

It is shown that the potential of Keesom which depends on temperature cannot be used for calculate the second virial coefficient of polar molecules and the formulae for second virial coefficient of [2] have no molecular statistical mechanical base for water and carbon dioxide. The contradictions and errors of [2] are discussed.

cond-mat.other↗
arXiv2016

Comments on the behaviour of some thermodynamic characteristics of single component substance in the region defined by the line of liquid vapor equilibrium

It is shown that in general case may be not correct the statements of [1,2,6-8] that 1) the isochoric heat capacity on the entire thermodynamic surface, including the metastable region of states and the region defined by the spinodal, remains positive and finite except for the critical point, and 2) the isobaric heat capacity becomes negative in the region defined by spinodal.

cond-mat.other↗
arXiv2013

Some comments on `Equation for the second virial coefficient`

The second viral coefficient calculated using the equation suggested in the paper of Kaplun A.B., Meshalkin A.B. Equation for the second virial coefficient published in High temperature high pressure, 1999, Volume 31, pages 253-258 is compared with experimental data for helium, hydrogen, neon, argon, krypton, xenon, carbon dioxide, water, ammonia, methane, ethylene. It is shown the formula cannot describe the temperature dependence of the experimental data on the second virial coefficient for the all above substances within the experimental error over the investigated temperature interval. The latter is in controversy with the derivations of the paper mentioned above. It is also shown the formula cannot describe the recommended data for the second virial coefficient within their uncertainties for helium, hydrogen, neon, argon, krypton and methane.

cond-mat.stat-mech↗
arXiv2013

Equilibrium size distribution function of clusters in finite system

The equilibrium size distribution function of clusters (nanoparticles) in the system of finite number of molecules (atoms) in finite closed volume with constant total energy (isolated system) is found using methods of statistical thermodynamics. The distribution function is found from kinetic equation of nucleation using one-drop approximation for both isothermal and isolated systems. The results obtained are compared with computer simulation data of finite two-dimensional system.

cond-mat.stat-mech↗
arXiv2013

The relation of the parameters of the critical point of liquid-gas transition with the Boyle temperature

It is shown that the ratio of the Boyle temperature to the product of critical temperature and critical compressibility factor is equal to the number 9 with high accuracy for 21 real substances as predicted from Van-der-Waals equation of state. The relation is suggested to find the critical volume via the ratio of the Boyle temperature to the critical pressure. The formula is suggested also to define the critical volume via the critical temperature and the parameters of the linear line of unite compressibility.

cond-mat.other↗
arXiv2013

Microcanonical ensembles of systems with mechanical constraints

We have obtained an exact expression for the phase-space volume corresponding to a microcanonical ensemble of systems under center of mass, total linear and angular momenta conservation constraints, and arbitrary constraints on the coordinates of particles of the system. Methods are suggested to calculate the phase-space volume and density of states from the mean kinetic energy and mean inverse kinetic energy. Methods to control equilibrium in simulations are also presented. We have derived exact formulae for several thermodynamic response functions. It is shown how to obtain the phase-space volume corresponding to other ensembles when one or several of the constraints are removed. It is shown that the phase-space volume of a system at positive values of the energy is a polynomial function of the energy if the potential energy of interaction between particles of the system consists of a hard-core potential and an arbitrary negative potential. We have also shown that the coefficients of the polynomial function can be determined from simulations.

cond-mat.stat-mech↗