241 research outputs found
Enhacement in the dymanic response of a viscoelastic fluid flowing through a longitudinally vibrating tube
We analyzed effects of elasticity on the dynamics of fluids in porous media
by studying a flow of a Maxwell fluid in a tube, which oscillates
longitudinally and is subject to oscillatory pressure gradient. The present
study investigates novelties brought about into the classic Biot's theory of
propagation of elastic waves in a fluid-saturated porous solid by inclusion of
non-Newtonian effects that are important, for example, for hydrocarbons. Using
the time Fourier transform and transforming the problem into the frequency
domain, we calculated: (A) the dynamic permeability and (B) the function
that measures the deviation from Poiseuille flow friction as a
function of frequency parameter . This provides a more complete theory
of flow of Maxwell fluid through the longitudinally oscillating cylindrical
tube with the oscillating pressure gradient, which has important practical
applications. This study has clearly shown transition from dissipative to
elastic regime in which sharp enhancements (resonances) of the flow are found
Composition, Structure and Tribotechnical Properties of TiN, MoN Single-Layer and TiN/MoN Multilayer Coatings
Results of comprehensive investigations of nanostructed TiN and MoN single layer coatings as well as multilayer coatings consisting of TiN/MoN alternating layers have beenconsidered. The coatings have been deposited by a promising modern method of cathode-arc evaporation (vacuum-arc method). The elemental and phase compositions of coatings, their tribological and physico mechanical properties: friction coefficient, wear, adhesion, hardness, and elastic modulus have been studied and the mechanisms of the coatings fracture have been discussedyesBelgorod State Universit
Nanostructured coatings based on amorphous carbon and gold nanoparticles obtained by the pulsed vacuum-arc method
Nanostructured coatings based on diamond-like carbon and gold-doped carbon with a thickness of 100-300 nm were obtained by a pulsed vacuum-arc method on silicon substrates. The structure of the coatingswas studied by high-resolution transmission electron microscopy, the elemental composition was studied by X-ray microanalysi
The effect of magnetophoresis and Brownian diffusion on the levitation of bodies in a magnetic fluid
New aspects related to the redistribution of magnetic particles concentration in a magnetic fluid caused by magnetophoresis and Brownian diffusion in a nonuniform magnetic field are considered. These aspects deal with the influence of these processes on pressure redistribution and levitation of bodies in a magnetic fluid. It is shown that due to these processes the pressure force acting on bodies changes significantly with time and can be reduced dozens of percent if compared to a homogenous flui
(TiZr)N/(TiSi)N Maitilayer nanostructured coatings obtained by vacuum arc deposition
The paper investigates the structure and properties of nanoscale multilayer coatings based on (TiZr)N and (TiSi)N produced by vacuum arc technique. Also, it provides an analysis of the impact of partial pressure of nitrogen on structural and phase state of coating
The use of plasma-based deposition with ion implantation technology to produce superhard molybdenum-based coatings in a mixed (C₂H₂+N₂) atmosphere
The influence of the pressure of a mixed gaseous atmosphere (80%C₂H₂+20%N₂) and the supply of a high-voltage negative potential in a pulsed form on the elemental and phase composition, structure and physico-mechanical characteristics of the vacuum-arc molybdenum-based coating
Effect of surface pre-treatment on adhesive strength of multi-component vacuum-arc coatings
The results of investigations of multi-component nanostructured coatings of (TiAlSiY)N/CrN type are presented. The influence of different variants of substrate surface pretreatment on adhesive strength and hardness of coatings was studied. Pre-treatment of samples was carried out in plasma of two-stage gas discharge according to various technological schemes. Except for ion-plasma purification, some samples were pretreated with a sublayer of chromium within 5 minutes. The coatings were formed by a vacuumarc deposition method at simultaneous spraying of two cathode target
One-step heterylation at the upper rim of calix[4]arene with 1,2,4-triazin-5(2H)-ones
A convenient way to modify calix[4]arenes based on the direct C-C coupling reaction of their phenol moiety with 1,2,4-triazines has been advanced, and the ability of modified calixarenes to provide transport of La3+ and Ga3+ cations through organic membranes has been examined. © 2006 American Chemical Society
Optical determination of flexoelectric coefficients and surface polarization in a hybrid aligned nematic cell
A. Mazzulla, F. Ciuchi, and J. Roy Sambles, Physical Review E, Vol. 64, article 021708 (2001). "Copyright © 2001 by the American Physical Society."We present an optical study of the influence of both the flexoelectric effect and surface polarization on a hybrid-aligned nematic cell using the half-leaky guided mode technique. Tilt angle profiles, obtained from fits of experimental data (reflectivity curves) taken under applied voltages, are compared with the ones derived by a complete theoretical model. Measurements with an applied alternating voltage allow the evaluation of the anchoring energy by solving the torque balance equation at the planar surface. From measurements with static fields, the sum of flexoelectric coefficients and the surface polarization are determined by numerical solution of Euler-Lagrange equations
Experimental Observation of Differences in the Dynamic Response of Newtonian and Viscoelastic Fluids
In this paper we present an experimental study of the dynamic responses of a
Newtonian fluid and a Maxwellian fluid under an oscillating pressure gradient.
We use laser Doppler anemometry in order to determine the velocity of each
fluid inside a cylindrical tube. In the case of the Newtonian fluid, the
dissipative nature is observed and the response obeys the Zhou and Sheng
universality (PRB 39, 12027 (1989)). In the dynamic response of the Maxwellian
fluid an enhancement at the frequencies predicted by the corresponding theory
(PRE 58, 6323 (1998)) is observed.Comment: 5 pages, 4 Figures, paper to be published in Phys. Rev.
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