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Gorshenin P.A.,Moscow State University of Technology and Management
Izvestiya Vysshikh Uchebnykh Zavedenii, Seriya Teknologiya Tekstil'noi Promyshlennosti | Year: 2012

The results of the research of the processes of heat exchange in the heat exchanger with a jet stream of the heat-carrier (gas-gas) are presented in the article. On the basis of an experimental research and introduction of the concept of effective temperature the semiempirical model of calculation of the processes of heat transfer in such heat exchangers has been offered.

Zarubin D.P.,Moscow State University of Technology and Management
Journal of Chemical Thermodynamics | Year: 2011

Potentiometric measurements on cells with liquid junctions are sometimes used for calculations of single-ion activity coefficients in electrolyte solutions, the incidence of this being increased recently. As surmised by Guggenheim in the 1930s, such coefficients (of ions i), γi, are actually complicated functions of mean ionic activity coefficients, γ±, and transport numbers of ions, ti. In the present paper specific functions γi(γ ±, ti) are derived for a number of cell types with an arbitrary mixture of strong electrolytes in a one-component solvent in the liquid-junction system. The cell types include cells with (i) identical electrodes, (ii) dissimilar electrodes reversible to the same ions, (iii) dissimilar electrodes reversible to ions of opposite charge signs, (iv) dissimilar electrodes reversible to different ions of the same charge sign, and (v) identical reference electrodes and an ion-selective membrane permeable to ions of only one type. Pairs of functions for oppositely charged ions are found to be consistent with the mean ionic activity coefficients as would be expected for pairs of the proper γi quantities by definition of γ±. The functions are tested numerically on some of the reported γi datasets that are the more tractable. A generally good agreement is found with data reported for cells with single electrolytes HCl and KCl in solutions, and with binary mixtures in the liquid-junction systems of KCl from the reference solutions and NaCl and HCl from the test solutions. It is found that values of γi(γ ±, ti) functions, in general, do depend on the reference solution composition, which is at variance with the recent claim by Lladosa et al. [E. Lladosa, A. Arce, G. Wilczek-Vera, J.H. Vera, J. Chem. Thermodyn. 42 (2010) 244-250] that "the ionic activity coefficients are independent of the nature and concentration of the reference solution". The results of the present study validate Guggenheim's interpretation and afford to amplify it by stating that such coefficients are misnomers in the sense that they do not represent thermodynamic properties of ions, and ought not to be called activity coefficients. © 2011 Elsevier Ltd. All rights reserved.

Zarubin D.P.,Moscow State University of Technology and Management
Journal of Solid State Chemistry | Year: 2014

Theoretical calculations of the structure and Brønsted acidity of SiOH groups in silica clusters have never addressed the question if these vary with the degree of SiOH deprotonation. In this connection, a statistical analysis is presented of Si-OH bond lengths in crystalline hydrogen silicates with well-determined structures with a special emphasis placed on effects of the silicate composition. It is found that among hydrogen silicates of large cations with low charges the Si-OH bonds are always longer than terminal Si-O bonds in the same anion and correlate in length with the anionic charge per tetrahedron. The findings are explained by steric limitations on charge balancing at oxygen atoms by hydrogen bonds and/or cations. It is suggested that similar limitations and imbalances may underlie the well-known trends in the Brønsted acidity of silicic acids and silicas in aqueous media: decreased acidity with increased SiOH deprotonation and increased acidity with increased tetrahedra connectivity. © 2014 Elsevier Inc.

Zarubin D.P.,Moscow State University of Technology and Management
Fluid Phase Equilibria | Year: 2013

Single-ion activity coefficients reported in literature for 10 ternary common-ion liquid-junction systems with KCl(aq) in the reference solutions and MX(aq) electrolytes in the test solutions at 25°C are reproduced in the present work numerically over wide MX molality ranges by functions of mean activity coefficients and transport numbers of ions in the liquid junction, the MX being BaCl2, CaCl2, CsCl, HCl, KF, K2SO4, LiCl, MgCl2, NaCl and SrCl2. The activity coefficients of solutes in the ternary systems are represented in the calculations by Scatchard's Neutral Electrolyte Model, and the transport numbers by a molality-based version of Van Rysselberghe's rule. An analysis is given of factors affecting the magnitudes of the functions, among them composition profiles in the liquid junction, formulation of Van Rysselberghe's rule, concentration dependence of ion mobilities, and non-ideality of electrolyte mixing. Most importantly, it is found that the exact functions can be approximated reasonably closely by a product of the mean activity coefficients in binary MX and KCl solutions, both at molality of the test solution, raised to powers that can be understood as related to effective transport numbers of the respective non-common ions in the liquid junction. Advantage is taken of the simple formulas to interpret the observed concentration dependences of single-ion activity coefficients in terms of the mean activity coefficients and effective transport numbers. © 2013 Elsevier B.V.

Dementyeva O.B.,Moscow State University of Technology and Management
2013 9th International Conference on Antenna Theory and Techniques, ICATT 2013 | Year: 2013

Studied are the antenna properties of the UHF discharge plasma at the threshold of the resonance of the electron Langmuir frequency with the pump second harmonic. The results of experimental measurements of some characteristics of a plasma antenna-amplifier at the LF range are shown. A mathematical model of a similar antenna, which allows proceeding to a physical model of the distributed parametric amplifier, is built. © 2013 IEEE.

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