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51.
Zusammenfassung V2C kristallisiert je nach Art der Entstehung in einer orthorhombischen Form (-Fe2N-Typ) oder mit der bekannten hexagonalen Struktur.
Mit 2 Abbildungen 相似文献
The subcarbide V2C crystallizes with an orthorhombic cell (-Fe2N) as well as with the known hexagonal cell depending on the mode of formation.
Mit 2 Abbildungen 相似文献
52.
Summary We present a method for the numerical approximation of Navier-Stokes equations with one direction of periodicity. In this direction a Fourier pseudospectral method is used, in the two others a standard F.E.M. is applied. We prove optimal rate of convergence where the two parameters of discretization intervene independently.
Approximation des équations de Navier-Stokes par une méthode éléments finis-spectrale Fourier
Resumé On présente une méthode d'approximation numérique des équations de Navier-Stokes possédant une direction de périodicité. Dans cette direction une méthode pseudospectrale basée sur des développements en série de Fourier est utilisée, dans les deux autres on applique une méthode d'éléments finis standard. On montre que la convergence est optimale et que les deux paramètres de discrétisation peuvent être choisis de façon indépendante.相似文献
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Pascale Urizzi Jean‐Pierre Souchard Ginette Ratovo Yvon Coulais Franoise Nepveu Etienne Hollande 《应用有机金属化学》2003,17(4):212-217
The present study was designed to evaluate the potential of labeled low‐density lipoprotein with 111In using a lipid chelating agent (bis(stearylamide) of diethylenetriaminepentaacetic acid: L) to detect pancreatic tumors and melanoma in mice by gamma‐scintigraphy. We compare the biodistribution of radioactivity and scintigraphic images in nude mice heterotransplanted with human cancerous pancreatic duct cells (Capan‐1) and in mice transplanted with murine tumor cells (B16 melanoma). Biodistribution studies showed that radioactivity was twice as high in the Capan‐1 xenograft after injection of the radiolabel than after injection of radiometal alone, and 34‐fold higher in the B16 tumor. On gamma‐scintigraphic imaging, the Capan‐1 tumor was just visible, whereas the B16 melanoma was clearly imaged. The lack of contrast of the Capan‐1 tumor compared with the B16 melanoma could be due to a poor vascularization. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Reduced basis methods are particularly attractive to use in order to diminish the number of degrees-of-freedom associated with the approximation to a set of partial differential equations. The main idea is to construct ad hoc basis functions with a large information content. In this Note, we propose to develop and analyze reduced basis methods for simulating hierarchical flow systems, which is of relevance for studying flows in a network of pipes, an example being a set of arteries or veins. We propose to decompose the geometry into generic parts (e.g., pipes and bifurcations), and to construct a reduced basis for these generic parts by considering representative geometric snapshots. The global system is constructed by gluing the individual basis solutions together via Lagrange multipliers. To cite this article: Y. Maday, E.M. Rønquist, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 195–200. 相似文献
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In this Note we present a model for an unsteady pure traction problem in large displacement and small perturbation for an elastic body in dimension 2, and we show the existence of a solution to the associated problem. The weak formulation of this nonlinear problem involves test-functions depending on the solution, which is not standard. We then study the dynamic of the translation, of the rotation, and of the perturbation associated to the deformation of the body. We prove the existence of a weak solution using a Galerkin method. To cite this article: C. Grandmont et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 521–526. 相似文献
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Pyrochlore solid solutions Cd2Nb2−2xMIV2xO7−2xF2x are studied with M = Ge and Sn; the domain of existence is 0 ? x ? 0.5. We can observe two cubic domains for different values of the position parameter u. With M = Zr we obtain a pyrochlore solid solution varying between 0 ? x ? 0.875. It offers a rhomboedric distortion for 0.25 < x < 0.55 due to an ordered distribution of Nb and Zr in the (111) plans of the cell. 相似文献
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Kohlmann H Werner F Yvon K Hilscher G Reissner M Cuello GJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(15):4178-4186
Binary SmH(3) (trigonal, a=656.7(3), c=680.1(3) pm, P$\bar 3$c1, Z=6), ternary SmMg2H7 (tetragonal, a=626.47(6), c=937.2(2) pm, P4(1)2(1)2, Z=4) and the corresponding deuterides SmD3 (a=653.9(1)m, c=676.7(2) pm) and SmMg2D7 (a=624.10(1), c=934.81(2) pm) have been prepared by hydrogenation (deuteration) of elemental samarium and the Laves phase SmMg2, respectively, and investigated by X-ray and neutron powder diffraction and SQUID and vibration magnetometry. The problem of the enormous neutron absorption of the natural isotopic mixture (natSm) is circumvented by carefully choosing the neutron wavelength (approximately 50 pm) and the use of double-walled cylindrical sample holders and a high-intensity neutron diffractometer (D4c at ILL). SmD3 crystallises with a tysonite-type structure and has three independently ordered deuterium atom sites with trigonal-planar, trigonal-pyramidal and tetrahedral metal environments and Sm--D bond lengths in the range 220(1)-258(1) pm (average: 235 pm). SmMg2D7 is a new deuteride that crystallises with an LaMg2D7-type structure. It displays four fully occupied deuterium sites having triangular and tetrahedral metal environments and Sm--D bond lengths in the range 227.6(5)-246.8(8) pm (average: 239 pm). These are the first samarium-deuterium bond lengths to be reported. Both deuterides are paramagnetic down to 2 K (SmD3: mueff=0.63(1) muB, thetap approximately -4 K; SmMg2D7: mueff=0.57(2) muB, thetap approximately -4 K). Their crystal structures and chemical and physical properties suggest mainly ionic bonding according to the limiting ionic formulae Sm3+(H-)3 and Sm3+(Mg2+)2(H-)7. 相似文献