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排序方式: 共有491条查询结果,搜索用时 15 毫秒
91.
In this article, a numerical study of swirling flows with heat transfer generated by two rotating end disks (co- and counter-rotating) inside a cylindrical enclosure having an aspect ratio equal to 2, filled with a liquid metal, and submitted to a vertical temperature gradient and an axial magnetic field is studied. The governing Navier-Stokes, energy, and potential equations along with appropriate boundary conditions are solved by using the finite-volume method. The flow and temperature fields are presented by stream function and isotherms, respectively. This flow is very unstable and reveals a great richness of structures. In an oscillatory regime, results are presented for various values of the Hartmann number, Ha = 5, 10, 20 and 30, and Richardson numbers, Ri = 0, 0.5, 1, 2 and 4, in order to see their effects on the value of the critical Reynolds number, Recr. Stability diagrams are established according to the numerical results of this investigation. These diagrams show the dependence of Recr with the increase of Ha for various values of Ri. The flow between co-rotating end disks is very different from the flow between counter-rotating end disks. Finally, this study confirms the possibility of stabilization of a liquid metal flow by application of an axial magnetic field. 相似文献
92.
García-Hernández Margarita Chadeyron Geneviève Boyer Damien García-Murillo Antonieta Carrillo-Romo Felipe Mahiou Rachid 《纳微快报(英文)》2013,5(1):57-65
Nano-Micro Letters - Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite BaTiO3... 相似文献
93.
Rachid Baati Dris Ihiawakrim Rodrigue R. Mafouana Ovidiu Ersen Céline Dietlin Guy Duportail 《Advanced functional materials》2012,22(19):4009-4015
While a hexahistidine affinity tag can be introduced at protein termini or internal sites by standard molecular biology procedures for purification, immobilization, or labeling of proteins, here the versatility of this concept is exploited for the chemical preparation of novel hexahistidine‐tagged single‐walled carbon nanotubes (His6‐tagSWNTs), a novel hard template useful for solubilizing, assembling, processing, and interfacing SWNTs in aqueous conditions. Water‐soluble and exfoliated His6‐tagSWNTs are prepared and fully characterized. This functional molecular module is able to interact via robust physisorption (π?π stacking) with the sidewall of SWNTs and combines the versatility of small, water‐soluble reporters (His6) for hierarchical directed self‐assembly (HDSA) and construction of nanocomposites. It is demonstrated that metal coordination bonds with Ni(II) can be used for the supramolecular self assembly of His6‐tagSWNTs, generating complex reticulated networks and architectures. The His6‐tagSWNTs hard template nanohybrid is further utilized for directed self‐assembly with silica nanoparticles. The versatility of the novel hybrids opens a new era for the rational design, smart (bio)functionalization, processing, interfacing, and self assembling of carbon nanotubes for the construction of multicomposites and more complex systems with controllable spatial organization and programmable properties for a wide range of applications in biology, nanoelectronics, and catalysis. 相似文献
94.
95.
Rachid S Huo L Herrmann J Stadler M Köpcke B Bitzer J Müller R 《Chembiochem : a European journal of chemical biology》2011,12(6):922-931
The cinnabaramides and salinosporamides are mixed PKS/NRPS natural products isolated from a terrestrial streptomycete and a marine actinomycete, respectively. They interfere with the proteasome and thus potentially inhibit the growth of cancer cells. The compounds exhibit a γ-lactam-β-lactone bicyclic ring structure attached to a cyclohexenyl unit and a PKS side chain. As a first step towards improving anticancer activity and permitting genetic approaches to novel analogues, we have cloned and characterized the cinnabaramide biosynthetic genes from Streptomyces sp. JS360. In addition to the expected PKS and NRPS genes, the cluster encodes functionalities for the assembly of the hexyl side chain precursor. The corresponding enzymes exhibit relaxed substrate specificities towards a number of synthesized precursors, enabling production of novel chlorinated cinnabaramides. These were isolated and analyzed for activity, revealing that derivatives bearing a chlorine atom in the PKS side chain show higher inhibitory potentials towards the proteasome's proteolytic subunits (especially the trypsin and chymotrypsin units) and higher cytotoxicities towards human tumor cell lines than the parent cinnabaramide A. Although their activities towards the proteasome were weaker than that of salinosporamide A, the cinnabaramides were found to inhibit the growth of various fungi with greater potency. 相似文献
96.
Rachid Chebbi 《Journal of Adhesion Science and Technology》2013,27(16):1655-1660
The dynamics of viscous slug fall in vertical dry capillaries is investigated by extending a published model (perfect wetting case) accounting for the film left behind the slug as it falls, and Laplace pressures at both ends of the slug in the momentum balance. The present investigation provides and uses an advancing contact-angle correlation determined based on a published theoretical work. The results are found in excellent agreement with published experimental values for falling slugs. The present model does not require any fitting parameter in the perfect wetting case, and is extended to include the non-perfect wetting case along with the unsteady-state dynamics using the quasi-steady-state approximation. 相似文献
97.
There are various factors that influence yarn strength. Yarn breaking is due to fiber breakages and fiber’s slippages. In reality, a part of the fibers slip while the other part breaks. In this study, we have shown that fatigue yarn, resulting in a fundamental way impact on the number of breaks on the weaving machine, and sometimes on the physical properties of fabrics. Given the importance of the issue and the very limited directed research number in this direction, a tests series were carried out with the aim to highlight the changes to the physical characteristics of the yarn resulting from mechanical treatment comparable to that which they are subjected on the weaving machine. In the first part of our investigation, the residual deformation, tensile strength, and elongation at break of combed and carded threads were measured. In the second part, the influence of the extensions number, their amplitudes, and frequencies were analyzed. In order to examine the influence of these parameters, carded and combed yarns, with different characteristics were prepared. Therefore, based on the separate treatment results of three test series, it appears that: the warp yarns subjected to repeated extensions undergo the phenomenon of fatigue. Yarns fatigue reduces their elasticity and resistance and it is the cause for break yarn during weaving. The fatigue of wool yarns is very low compared to other textile materials. 相似文献
98.
Rachid Essehli Brahim El Bali Ingrid Svoboda Hartmut Fuess 《Materials Research Bulletin》2009,44(4):817-2294
The new titanium oxyphosphate Co0.5TiPO5 has been prepared by solid state reaction. Its structure has been determined by single crystal X-ray diffraction and was further investigated by FT-IR spectroscopy and magnetic measurements. The compound crystallizes in the monoclinic system, S.G: P21/c [a = 7.358(1) Å, b = 7.378(2) Å, c = 7.383(3) Å, β = 119.66(3)°, Z = 4, R1 = 0.0142, wR2 = 0.0429]. The structure can be described as a network of very distorted TiO6 octahedra, in which the Ti4+ ions are displaced from the centres of the octahedra, and slightly distorted PO4 tetrahedra. Half of the octahedral cavities are occupied by Co atoms. The other half of octahedral sites is vacant and favourable for the electrochemical insertion of lithium. The insertion of lithium was studied by galvanostatic charging and discharging between different voltage limits. 相似文献
99.
Thermodynamic properties of the mixed aqueous electrolyte systems of the lithium and cesium chlorides and sodium and cesium chlorides have been studied by the hygrometric method at 298.15 K. The water activities of these systems were measured at total molalities from 0.3 mol kg−1 to saturation for different ionic strength fractions y of CsCl for the systems CsCl–LiCl(aq) and CsCl–NaCl(aq) with y=0.33, 0.50 and 0.67. The results allow the deduction of osmotic coefficients. The experimental results are compared with calculations made using the Zdanovskii–Stokes–Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LSII), Reilly, Wood and Robinson (RWR) rules, and the Pitzer model. From these measurements, the Pitzer mixing ionic parameters are determined and used to obtain the solute activity coefficients of the mixture for different ionic strength fractions y. 相似文献
100.
In this article we develop a new method to segment high angular resolution diffusion imaging (HARDI) data. We first estimate
the orientation distribution function (ODF) using a fast and robust spherical harmonic (SH) method. Then, we use a region-based
statistical surface evolution on this image of ODFs to efficiently find coherent white matter fiber bundles. We show that
our method is appropriate to propagate through regions of fiber crossings and we show that our results outperform state-of-the-art
diffusion tensor (DT) imaging segmentation methods, inherently limited by the DT model. Results obtained on synthetic data,
on a biological phantom, on real datasets and on all 13 subjects of a public NMR database show that our method is reproducible,
automatic and brings a strong added value to diffusion MRI segmentation.
相似文献
Rachid DericheEmail: |