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31.
The natural convection boundary layer on a horizontal plate with suction is investigated. The similar solutions of the boundary layer equations require suction to vary as a power law. The similarity equations have been integrated for various values of suction parameter and Prandtl number =0.72 and 6.8. For non-similar flow situation, a large suction approximation has been developed using the asymptotic approach. It is shown that large suction approximation is surprisingly good even for moderate values of suction parameter.
Einflüsse großer Wirkung auf die Grenzschicht bei freier Konvektion an einer horizontalen Platte
Zusammenfassung Es wird die Grenzschicht bei freier Konvektion auf einer horizontalen Platte unter Saugwirkung untersucht. Die Ähnlichkeitslösungen der Grenzschichtgleichungen machen es erforderlich, die Saugwirkung in Form eines Exponentialansatzes zu variieren. Die Ähnlichkeitsgleichungen wurden für verschiedene Werte des Saugparameters und für Prandtl-Zahlen zwischen 0,72 und 6,8 integriert. Für nicht-ähnliche Strömungszustände wurde eine Lösung für die Saugwirkung auf der Basis der asymptotischen Näherung entwickelt. Es wird gezeigt, daß die Näherungslösung für große Saugwirkung auch erstaunlich gute Ergebnisse für geringe Werte von Saug-Parametern liefert.相似文献
32.
Prabhakar K Afzal SM Kumar PU Rajanna A Kishan V 《Colloids and surfaces. B, Biointerfaces》2011,86(2):305-313
Indinavir, an antiretroviral protease inhibitor used in treatment of HIV infection has limited penetration into brain due to efflux of P-glycoprotein. The aim of this work was to develop transferrin coupled submicron lipid emulsions (SLEs) containing indinavir for delivery to brain. Stearylamine containing SLEs were prepared, characterized, tested for stability and optimized formulation (SLE-4) was developed. Transferrin was coupled to get SLE-6 by water soluble EDC method and purified by gel filtration. The coupled transferrin was quantified by modified Bradford dye assay method. The fluorescent dye (DiD oil) incorporated SLEs were used to check the brain specific delivery of SLEs. The in vivo pharmacokinetic and tissue distribution were conducted in mice. During pharmacokinetic studies, there was no significant difference in the serum levels of indinavir from SLE-1, SLE-4 and SLE-6 formulations at all time points. In tissue distribution studies the therapeutic availability (TA) of indinavir in brain from SLE-6 was 4.69, 3.1 and 1.7 times higher than drug solution, SLE-1 and SLE-4 respectively whereas, the TA of indinavir from SLE-4 was 2.76 and 1.82 times the drug solution and SLE-1. The brain to serum ratios with SLE-6 were above one indicates the brain specific delivery. The brain delivery of indinavir was improved with transferrin ligand attachment to SLEs by receptor mediated transcytosis. 相似文献
33.
Latif U Mujahid A Afzal A Sikorski R Lieberzeit PA Dickert FL 《Analytical and bioanalytical chemistry》2011,400(8):2507-2515
Polymers as coating materials were combined with quartz crystal microbalances (QCMs) to design sensor devices for the detection
of both ionic and neutral analytes in liquid phase. The design and geometry of dual and tetraelectrode QCMs have been optimized
to reduce electric field interferences. An unusual Sauerbrey effect was observed while exposing potassium salt solution to
10- and 20-MHz QCMs, i.e. increase in the frequency shifts by a factor of seven, which is attributed to electro-acoustic phenomena.
Non-functionalized sol-gel materials were synthesized by templating with hydrophobic salt such as tetraethyl ammonium picrate.
Imprinting with these ions of low charge density leads to sensitive layers, and UV–Vis spectroscopy was used to check re-inclusion
of this analyte. In the next strategy, functionalized polyurethane for potassium ions and sol-gel materials with aminopropyl
group as ligand were generated to tune selectivity and sensitivity towards Ni2+ and Cu2+. Methacrylic acid polymers were optimized for the detection of atrazine by hydrogen bonding; double molecular imprinted polyurethane
approach was followed for pyrene recognition. Finally, these imprinted polymers were combined with tetraelectrode QCM to develop
sensor platform. 相似文献
34.
The present study investigates the microchannel heat sinks (MCHSs) with smooth and wavy wall for pure electroosmotic flow
(EOF), pressure-driven flow (PDF) and combined electroosmotic and pressure-driven flow (PDF + EOF). A three-dimensional numerical
analysis was performed for EOF, PDF and combined flow (PDF + EOF) through finite volume analysis. The EOF was combined with
the PDF to enhance the flow rate and to reduce the thermal resistance of the MCHS. The effect of wall waviness on electroosmosis
and thermal performance of the MCHS was critically investigated for flow rate, friction factor, Nusselt number, thermal resistance
and pumping power. The design variables related to the wavelength and amplitude and width of microchannel were investigated
for their effect on the overall thermal performance and pumping power. The electroosmosis not only increases the flow rate
but also suppresses the secondary flow developed due to the topology of the microchannel walls. The non-uniformity of the
velocity and temperature is reduced due to the application of the EOF in a PDF and combined flow (PDF + EOF). 相似文献
35.
Heat and Mass Transfer - Effects of dissipation on heat transfer due to second order effects of longitudinal curvature, transverse curvature, displacement speed, external vorticity and stagnation... 相似文献
36.
Noor Afzal 《Applied mathematics and computation》2010,217(6):2724-2736
The simultaneous effects of suction and injection on tangential movement of a nonlinear power-law stretching surface governed by laminar boundary layer flow of a viscous and incompressible fluid beneath a non-uniform free with stream pressure gradient is considered. The self-similar flow is governed by Falkner-Skan equation, with transpiration parameter γ, wall slip velocity λ and stretching sheet (or pressure gradient) parameter β. The exact solution for β = −1 and three closed form asymptotic solutions for β large, large suction γ, and λ → 1 have also been presented. Dual solutions are found for β = −1 for each value of the transpiration parameter, including the non-permeable surface, for each prescribed value of the wall slip velocity λ. The large β asymptotic solution also dual with respect to wall slip velocity λ, but do not depend on suction and blowing. The critical values of γ, β and λ are obtained and their significance on the skin friction and velocity profiles is discussed. An approximate solution by integral method for a trial velocity profile is presented and results are compared with the exact solutions. 相似文献
37.
Adeel Afzal 《光谱学快报》2013,46(6):411-416
The structural and morphological features influencing the glass transition temperature of epoxy/silica nanohybrid and nanocomposite materials containing 25–30 phr of nanoscale silica phases are discussed in this letter to answer the questions related to the processing–structure–property relationships. X-ray photoelectron spectroscopy and atomic force microscopy are used to study the surface chemical structure and morphology of epoxy/silica nanohybrids and nanocomposites. Nanohybrids are synthesized via in situ sol-gel process, while the respective nanocomposites are prepared by mechanical blending of preformed silica nanoparticles into epoxy resin. Differential scanning calorimetry is used to determine glass transition temperature of different materials. The surface analytical characterizations reveal that in situ sol-gel process is more suitable for producing organic–inorganic hybrid materials with superior glass transition temperature owing to the achievement of stronger interfacial compatibility and greater crosslink density. A number of other factors affecting glass transition temperature are explored and discussed with reference to surface chemistry, microstructure, and morphology of epoxy/silica nanohybrids and nanocomposites, respectively. 相似文献
38.
39.
Meccanica - The present research focuses on dynamic flow control management using tiny jets with three combinations; the first one located at 90° intervals of the base, the second one located... 相似文献
40.
Afzal Hafiz Muhammad Shehzad Farrukh Zubair Mukarram Bakather Omer Yahya Al-Harthi Mamdouh A. 《Journal of Thermal Analysis and Calorimetry》2020,139(1):353-365
Journal of Thermal Analysis and Calorimetry - This article discusses the effect of microwave irradiation on the thermal properties of poly(vinyl alcohol)/graphene nanocomposites, prepared using a... 相似文献