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71.
72.
Stefan Kopecz Andreas Meister Abderrahim Ouazzi Stefan Turek Olaf Wünsch 《PAMM》2008,8(1):10845-10846
We consider the numerical solution of the non–isothermal incompressible Navier–Stokes equations using a discrete projection method. The computation of velocity and temperature subproblems is carried out on different meshes chosen with respect to the physical behavior of these quantities. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
73.
The diffusion process in the molten state at a polymer/polymer interface of symmetrical and model bilayers has been investigated using a small-amplitude oscillatory shear measurement. The polymers employed in this study were poly (vinylidene fluoride) (PVDF) and poly (methyl methacrylate) (PMMA) of varying molecular weights and polydispersities. The measurements were conducted in the linear viscoelastic regime (small deformations) so as to decouple the effect of flow from the diffusion. The focus of this paper has been to investigate the effects of healing time, angular frequency (ω), temperature, and molecular weight on the inter-diffusion and the triggered interphase between the neighboring layers. The kinetics of diffusion, based on the evolution of the apparent diffusion coefficient (D a) versus the healing time, was experimentally obtained. The transition from the non-Fickian to the normal Fickian region for the inter-diffusion at the interface was clearly observed, qualitatively consistent with the reptation model, but it occurred at a critical time greater than the reptation time (τ rep). In non-Fickian region, effects of frequency and temperature were studied with regard to the ratio of the apparent diffusion coefficient to the self-diffusion coefficient (D a/D s). The D s determined in the Fickian region was found to be consistent with Graessley’s model as well as with the literatures. And the dependence of the Ds on the frequency agreed well with the Doi–Edwards theory, in particular, scaling as $D_{\rm s} \sim \omega^{1/2}$ at ω?>?1/τ e and $D_{\rm s} \sim \omega^{0}$ at ω?<?1/τ rep. Our experimental results also confirmed that the dependence of the D s on the temperature for PMMA and PVDF can be well described by the Arrhenius law. Moreover, blends of PMMAs have been proposed in order to be able to change the $\overline M_\emph{w} $ . The rheological investigations of these corresponding bilayers rendered it possible to monitor the effect of $\overline M_\emph{w} $ on the diffusion process. The obtained results gave $D_{\rm s} \sim \overline M_\emph{w}^{-1}$ , thus corroborating some earlier studies and some experimental results recently reported by Time-Resolved Neutron Reflectivity Measurements. Lastly, the thickness of the interphase and its corresponding viscoelastic properties could be theoretically determined as a function of the healing?time. 相似文献
74.
Ahmed Chaambi Gülbin Kurtay Raoudha Abderrahim Frdric Robert Yannick Landais 《Helvetica chimica acta》2019,102(8)
The free‐radical alkenylation of a range of alkyl iodides with a vinyldisulfones has been carried out, leading to the desired vinylsulfones in moderate to good yields under mild conditions. The process is initiated by an aryl radical which abstracts the iodine atom from the alkyl iodide to form a C‐centered radical intermediate, the addition of which onto the vinyldisulfone providing the final vinylsulfone. The aryl radical is generated in situ through a single‐electron transfer from an electron donor‐acceptor complex (EDA) formed between a diaryliodonium salt (Ph2I+ PF6?) and triethylamine. 相似文献
75.
We describe the synthesis and characterization of novel molecules containing head with precise shape, spacer, and label moieties. The protocol is based on a Pd(0)-catalyzed cross-coupling reaction between ethynylphenyl/bromide to obtain a rigid head followed by the attachment of a flexible spacer possessing two reactive functional groups on the termini. The final step consists of forming a covalent bond between spacer and label. In addition, monosubstituted soluble labels were synthesized in good yields. 相似文献
76.
[reaction: see text] The reaction of symmetrical diols and oligo(ethylene glycol)s with a stoichiometric amount of p-toluenesulfonyl chloride in the presence of silver(I) oxide and a catalytic amount of potassium iodide led selectively to the monotosylate derivatives in high yields. Polysubstituted cyclic ethers were obtained readily upon treatment of the corresponding diols with an excess of silver oxide. The high selectivity was explained on the basis of the difference in acidity between the two hydroxy groups, which undergo an intramolecular hydrogen bonding. 相似文献
77.
Adly Samir Hantoute Abderrahim Nguyen Bao Tran 《Set-Valued and Variational Analysis》2020,28(2):345-368
Set-Valued and Variational Analysis - We give new criteria for weak and strong invariant closed sets for differential inclusions in $\mathbb {R}^{n}$ , and which are simultaneously governed by... 相似文献
78.
Mathematical Programming - In this work we give an extension of the Brøndsted–Rockafellar Theorem, and some of its important consequences, to proper convex lower-semicontinuous... 相似文献
79.
Serdar Serdas Alexander Schwarz Jörg Schröder Stefan Turek Abderrahim Ouazzi Masoud Nickaeen 《PAMM》2013,13(1):301-302
The focus of this contribution is the examination of the influence of different interpolation orders (especially for the pressure field) by solving the stationary incompressible Navier-Stokes equations with least-squares finite elements. We consider two different div-grad first-order systems which result in a three-field formulation with stresses, velocitites and pressure, see e.g. SCHWARZ & SCHRÖDER [1] and BOCHEV & GUNZBURGER [2]. Additionally, a numerical example is presented to show the performance of the considered formulations. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
80.
Ahmed El Akkaoui Marie-Aude Hiebel Abderrahim Mouaddib Sabine Berteina-Raboin Gérald Guillaumet 《Tetrahedron》2012,68(44):9131-9138
A two-step sequence is reported giving access to diverse 5H-pyrido[2′,1′:2,3]imidazo[4,5-b]indoles and analogues via a Bienaymé multicomponent reaction followed by N-arylation. The desired polycylic scaffolds were obtained in high yield using copper iodide in association with TMEDA in aqueous or dioxane media. 相似文献