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Characterization of a purified thermostable xylanase from caldicoprobacter algeriensis sp. nov. strain TH7C1T
No full textA simple transformation from lowpass to bandpass filter using a new quasi-arrow head defected ground structure resonator and gap-J-inverter
No full textTheoretical calculation of cathodoluminescence: Influence of surface and bulk parameters on the depletion region of p-type CdTe
No full textAnalytical and numerical analysis of bifurcations in thermal convection of viscoelastic fluids saturating a porous square box
Full text linkWe report theoretical and numerical results on bifurcations in thermal instability for a
viscoelastic fluid saturating a porous square cavity heated from below. The modified
Darcy law based on the Oldroyd-B model was used for modeling the momentum
equation. In addition to Rayleigh number ℜ, two more dimensionless parameters
are introduced, namely, the relaxation time λ1 and the retardation time λ2. Temporal
stability analysis showed that the first bifurcation from the conductive state may be
either oscillatory for sufficiently elastic fluids or stationary for weakly elastic fluids.
The dynamics associated with the nonlinear interaction between the two kinds of
instabilities is first analyzed in the framework of a weakly nonlinear theory. For
sufficiently elastic fluids, analytical expressions of the nonlinear threshold above
which a second hysteretic bifurcation from oscillatory to stationary convective pattern
are derived and found to agree with two-dimensional numerical simulations of the
full equations. Computations performed with high Rayleigh number indicated that
the system exhibits a third transition from steady single-cell convection to oscillatory
multi-cellular flows. Moreover, we found that an intermittent oscillation regime may
exist with steady state before the emergence of the secondary Hopf bifurcation. For
weakly elastic fluids, we determined a second critical value ℜOsc
2 (λ1, λ2) above
which a Hopf bifurcation from steady convective pattern to oscillatory convection
occurs. The well known limit of ℜOsc
2 (λ1 = 0, λ2 = 0) = 390 for Newtonian fluids is
recovered, while the fluid elasticity is found to delay the onset of the Hopf bifurcation.
The major new findings were presented in the form of bifurcation diagrams as
functions of viscoelastic parameters for ℜ up to 420. Published by AIP Publishin
Contribution à l'élaboration de Nano-composites à Base de Polymère Conducteur
No full text138 p. :ill.; 30 cmL'objectif du présent travail est la synthèse et caractérisation des nanocomposites polymères conducteurs (transducteurs partie sensible de biocapteurs) à base de poly(aniline) dopée par un acide solide (zéolithe HY) greffé avec différent
Experimental assessment of performance and emissions maps for biodiesel fueled compression ignition engine
No full textPhysico-mechanical properties and thermal behavior of firebrick-based mortars in superplasticizer presence
No full textPotential of sawdust materials for the removal of dyes and heavy metals : examination of isotherms and kinetics
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