576 research outputs found
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 and 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 and depending on volume fraction
, with essentially charge-independent parameters and . 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 of
hard sphere suspensions.Comment: 8 pages, LaTeX, 3 Postscript figures included using eps
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