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991.
Liang Luo Nehad Ali Shah Ibrahim M. Alarifi Dumitru Vieru 《Mathematical Methods in the Applied Sciences》2020,43(3):1337-1348
Unsteady one-dimensional flows of two incompressible and immiscible generalized second grade fluids in a rectangular channel are studied. A constant pressure gradient acts in the flow direction, while the channel walls have oscillating translational motions in their planes. The generalization considered in this paper consists into a mathematical model based on constitutive equations of second grade fluid with Caputo time-fractional derivative in which the history of the shear stress influences the velocity gradient. The velocity and shear stress fields in the Laplace transform domain are obtained. Numerical solutions for the real velocity and shear stress have been found by employing the Stehfest numerical algorithm for the inverse Laplace transform. The influence of the fractional parameters on the velocity and shear stress has been studied by numerical simulations and graphical illustrations. It is found that the memory effects are significant only for small values of the time t. 相似文献
992.
The global weak solution of an initial-boundary value problem for a compressible non-Newtonian fluid is studied in a three-dimensional bounded domain. By the techniques of artificial pressure, a solution to the initial-boundary value problem is constructed through an approximation scheme and a weak convergence method. The existence of a global weak solution to the three-dimensional compressible non-Newtonian fluid with vacuum and large data is established. 相似文献
993.
Cahn-Hilliard vs Singular Cahn-Hilliard equations in simulations of immiscible binary fluids
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Lizhen Chen 《Journal of Applied Analysis & Computation》2018,8(4):1050-1060
An efficient semi-implicit spectral method is implemented to solve the Cahn-Hilliard equation with a variable mobility in this paper. We compared the kinetics of bulk-diffusion-dominated and interface-diffusion-dominated coarsening in two-phase systems. As expected, the interface-diffusion-controlled coarsening evolves much slower. Also we find that the velocity field will be caused different greatly by using Singular Cahn-Hilliard equation and using Cahn-Hilliard in the simulation of immiscible binary fluids. 相似文献
994.
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996.
Dinesh Rangappa Dr. Koji Sone Dr. Mingsheng Wang Dr. Ujjal K. Gautam Dr. Dmitri Golberg Prof. Hiroshi Itoh Dr. Masaki Ichihara Dr. Itaru Honma Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(22):6488-6494
Graphene has attracted a great deal of attention in recent years due to its unusual electronic, mechanical, and thermal properties. Exploiting graphene properties in a variety of applications requires a chemical approach for the large‐scale production of high‐quality, processable graphene sheets (GS), which has remained an unanswered challenge. Herein, we report a rapid one‐pot supercritical fluid (SCF) exfoliation process for the production of high‐quality, large‐scale, and processable graphene for technological applications. Direct high‐yield conversion of graphite crystals to GS is possible under SCF conditions because of the high diffusivity and solvating power of SCFs, such as ethanol, N‐methyl‐pyrrolidone (NMP), and DMF. For the first time, we report a one‐pot direct conversion of graphite crystals to a high yield of graphene sheets in which about 90–95 % of the exfoliated sheets are <8 layers with approximately 6–10 % monolayers and the remaining 5–10 % are ≥10 layers. 相似文献
997.
Ana Rita C. Duarte João F. Mano Rui L. Reis 《Polymer Degradation and Stability》2010,95(10):2110-2117
Starch-based polymers have been proposed for different tissue engineering applications due to their inherent properties. In this work, a polymeric blend of starch-poly-(?-caprolactone) (SPCL) was processed using supercritical fluid technology, namely, by supercritical assisted phase inversion. As SPCL is a biodegradable polymer, the matrices produced are susceptible of undergoing enzymatic degradation upon implantation in the human body. In vitro assessment of the enzymatic degradation of SPCL was carried out in different buffer solutions containing α-amylase and/or lipase. The effect of the presence of these enzymes was studied by monitoring different parameters in order to characterise both bulk and the surface of the scaffolds. As regards to bulk analysis, weight loss of the samples incubated for 1, 3, 7, 14 and 21 days was determined, further differential scanning calorimetry was carried out. The morphology of the scaffolds after these periods was analysed by micro-computed tomography (μ-CT) and surface chemistry was characterised by infra-red spectroscopy and contact angle measurements. Results suggest that SPLC scaffolds undergo bulk degradation, which is typically characterised by hydrolysis of chemical bonds in the polymer chain at the centre of the matrix, resulting in a highly porous material. 相似文献
998.
Extraction of lanthanides from aqueous solution by using room-temperature ionic liquid and supercritical carbon dioxide in conjunction 总被引:2,自引:0,他引:2
Mekki S Wai CM Billard I Moutiers G Burt J Yoon B Wang JS Gaillard C Ouadi A Hesemann P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(6):1760-1766
For the first time, the study of a three-step extraction system of water/ionic liquid/supercritical CO2 has been performed. Extraction of trivalent lanthanum and europium from an aqueous nitric acid solution to a supercritical CO2 phase via an imidazolium-based ionic liquid phase is demonstrated, and extraction efficiencies higher than 87 % were achieved. The quantitative extraction is obtained by using different fluorinated beta-diketones with and without the addition of tri(n-butyl)phosphate. The complexation phenomenon occurring in the room-temperature ionic-liquid (RTIL) phase was evidenced by using luminescence spectroscopy. 相似文献
999.
The oxidation of cycloalkanes or alkylarenes with molecular oxygen and acetaldehyde as sacrificial co-reductant occurs efficiently in compressed (supercritical) carbon dioxide (scCO2) under mild multiphase conditions. No catalyst is required and high-pressure ATR-FTIR online measurements show that a radical reaction pathway is heterogeneously initiated by the stainless steel of the reactor walls. For secondary carbon atoms, high ketone to alcohol ratios are observed (3.5-7.9), most probably due to fast consecutive oxidation of alcoholic intermediates. Since C--C scission reactions are detected only to a very small extent, tertiary carbon atoms are transformed into the corresponding alcohols with high selectivity. Detailed analysis of the product distributions and other mechanistic evidence suggest that acetaldehyde acts not only as the sacrificial oxygen acceptor, but also as an efficient H-atom donor for peroxo and oxo radicals and as a crucial reductant for hydroperoxo intermediates. In comparison to other inert gases such as compressed N2 or Ar, the use of carbon dioxide was shown to increase the yields of alkane oxygenates under identical reaction conditions. 相似文献
1000.
We report on the rheology of a lyotropic lamellar surfactant solution (SDS/dodecane/pentanol/ water), and identify a discontinuous
transition between two shear thinning regimes which correspond to the low-stress lamellar phase and the more viscous shear-induced
multilamellar vesicle, or “onion” phase. We study in detail the flow curve, stress as a function of shear rate, during the
transition region, and present evidence that the region consists of a shear-banded phase where the material has macroscopically
separated into bands of lamellae and onions stacked in the vorticity direction. We infer very slow and irregular transformations
from lamellae to onions as the stress is increased through the two-phase region, and identify distinct events consistent with
the nucleation of small fractions of onions that coexist with sheared lamellae. 相似文献