First-order virial expansion of short-time diffusion and sedimentation coefficients of permeable particles suspensions

For suspensions of permeable particles, the short-time translational and rotational self-diffusion coefficients, and collective diffusion and sedimentation coefficients are evaluated theoretically. An individual particle is modeled as a uniformly permeable sphere of a given permeability, with the internal solvent flow described by the Debye-Bueche-Brinkman equation. The particles are assumed to interact non-hydrodynamically by their excluded volumes. The virial expansion of the transport properties in powers of the volume fraction is performed up to the two-particle level. The first-order virial coefficients corresponding to two-body hydrodynamic interactions are evaluated with very high accuracy by the series expansion in inverse powers of the inter-particle distance. Results are obtained and discussed for a wide range of the ratio, x, of the particle radius to the hydrodynamic screening length inside a permeable sphere. It is shown that for x >= 10, the virial coefficients of the transport properties are well-approximated by the hydrodynamic radius (annulus) model developed by us earlier for the effective viscosity of porous-particle suspensions

Разработка системы автоматизированного управления установкой комплексной подготовки нефти

Выпускная квалификационная работа 97 с., 20 рис., 38 табл., 17 источников, 9 прил. Ключевые слова: УКПН, установка комплексной подготовки нефти, насосная, сырьевой резервуар, подогреватель, клапана с электроприводом, автоматизированная система управления, ПИД-регулятор, локальный программируемый логический контроллер, коммутационный программируемый логический контроллер, протокол, SCADA-система. Объектом исследования является: система автоматизированного управления УКПН. Цель работы – разработка САУ УКПН, а именно насосной подогревателя и резервуара с использованием ПЛК, на основе SCADA-системы INFINITY. В процессе исследования проводился подбор средств КИПиА, программного и алгоритмического обеспечения. В результате исследования разработана САУ подогревателя. Область применения: разрабоFinal qualification work of 97 pages, 20 fig., 38 tab., 17 sources, 9 enc. Keywords: UKPN, installation of complex preparation of oil, pump, the raw tank, a heater, the valve with the electric drive, an automated control system, the PID-regulator, the local programmable logical controller, the switching programmable logical controller, the protocol, SCADA system. Object of research is: system of automated management of UKPN. The work purpose – development of SAU UKPN, namely pump a heater and the tank with use of PLK, on the basis of SCADA-системы INFINITY. In the course of research selection of means of instrumentation and automated control systems, program and algorithmic providing was carried out. As a result of research heater SAU is developed. Scope: the developed system can be appli

Linear response of partially ionized, dense plasmas

We propose a new formalism to electronic polarizability of dense, partially ionized plasmas. This formalism is based upon the density functional theory for the electronic equilibrium, the random phase approximation for the density response of electrons, and the cluster expansion in the averaging over ionic configurations. The first term in the final cluster expansion for the imaginary part of electron polarizability corresponds to the Lindhard dielectric function formula. The second term contains the electronic states of the average atom. The additional effects that result from this theory are: channel mixing (screening), "inverse Bremstrahlung” corrections, and free-bound electronic transitions. Our approach allows the plasma (collective) and atomic physics phenomena to be treated in the frame of one formalism. The theory can be applied for stopping power and opacity calculation

Surfactant-induced migration of a spherical drop in Stokes flow

In Stokes flows, symmetry considerations dictate that a neutrally-buoyant spherical particle will not migrate laterally with respect to the local flow direction. We show that a loss of symmetry due to flow-induced surfactant redistribution leads to cross-stream drift of a spherical drop in Poiseuille flow. We derive analytical expressions for the migration velocity in the limit of small non-uniformities in the surfactant distribution, corresponding to weak-flow conditions or a high-viscosity drop. The analysis predicts that the direction of migration is always towards the flow centerline.Comment: Significant extension with additional text, figures, equations, et

Comparison between the Torquato-Rintoul theory of the interface effect in composite media and elementary results

We show that the interface effect on the properties of composite media recently proposed by Torquato and Rintoul (TR) [Phys. Rev. Lett. 75, 4067 (1995)] is in fact elementary, and follows directly from taking the limit in the dipolar polarizability of a coated sphere: the TR ``critical values'' are simply those that make the dipolar polarizability vanish. Furthermore, the new bounds developed by TR either coincide with the Clausius-Mossotti (CM) relation or provide poor estimates. Finally, we show that the new bounds of TR do not agree particularly well with the original experimental data that they quote.Comment: 13 pages, Revtex, 8 Postscript figure

Self-diffusion coefficients of charged particles: Prediction of Nonlinear volume fraction dependence

We report on calculations of the translational and rotational short-time self-diffusion coefficients $D^t_s$ and $D^r_s$ for suspensions of charge-stabilized colloidal spheres. These diffusion coefficients are affected by electrostatic forces and many-body hydrodynamic interactions (HI). Our computations account for both two-body and three-body HI. For strongly charged particles, we predict interesting nonlinear scaling relations $D^t_s\propto 1-a_t\phi^{4/3}$ and $D^r_s\propto 1-a_r\phi^2$ depending on volume fraction $\phi$, with essentially charge-independent parameters $a_t$ and $a_r$. These scaling relations are strikingly different from the corresponding results for hard spheres. Our numerical results can be explained using a model of effective hard spheres. Moreover, we perceptibly improve the known result for $D^t_s$ of hard sphere suspensions.Comment: 8 pages, LaTeX, 3 Postscript figures included using eps