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Past studies that have compared LBB stable discontinuous‐ and continuous‐pressure finite element formulations on a variety of problems have concluded that both methods yield solutions of comparable accuracy, and that the choice of interpolation is dictated by which of the two is more efficient. In this work, we show that using discontinuous‐pressure interpolations can yield inaccurate solutions at large times on a class of transient problems, while the continuous‐pressure formulation yields solutions that are in good agreement with the analytical solution. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Synthesis of niobocene imido cations: X-ray crystal structure of [Nb(NBu)(η-C5H4SiMe3)2(CNBu)][BPh4]
Andrés Garcés Santiago Gómez-Ruiz Antonio Antiñolo Carmen López-Mardomingo Sanjiv Prashar 《Journal of organometallic chemistry》2006,691(17):3652-3658
The reduction of [Nb(NBut)(η5-C5H4SiMe3)2Cl] by sodium amalgam followed by oxidation by [Fe(η5-C5H5)2][BPh4] in the presence of CNBut gave [Nb(NBut)(η5-C5H4SiMe3)2(CNBut)][BPh4] (1). In a similar manner, [Nb(NPh)(η5-C5H4SiMe3)2(CNBut)][BPh4] (2), [Nb(NPh)(η5-C5H4SiMe3)2(CO)][BPh4] (3) and [Nb(NBut){Me2Si(η5-C5Me4)(η5-C5H4)}(CNBut)][BPh4] (4), were prepared. The reduction of [Nb(NBut){Me2Si(η5-C5H4)2}Cl] gave, depending on the experimental conditions, either the d1-d1 dimer [(Nb{Me2Si(η5-C5H4)2}(μ-NBut))2] (5) or the hydride derivative [Nb(NBut){Me2Si(η5-C5H4)2}H] (6). The reaction of 5 with I2 led to the formation of [Nb(NBut){Me2Si(η5-C5H4)2}I] (7). The molecular structure of 1 was determined by single-crystal X-ray diffraction studies. 相似文献
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C. S. Jog 《Journal of Elasticity》2006,82(2):175-192
We present a solution for the tensor equation TX + XT
T
= H, where T is a diagonalizable (in particular, symmetric) tensor, which is valid for any arbitrary underlying vector space dimension n. This solution is then used to derive compact expressions for the derivatives of the stretch and rotation tensors, which in turn are used to derive expressions for the material time derivatives of these tensors. Some existing expressions for n = 2 and n = 3 are shown to follow from the presented solution as special cases. An alternative methodology for finding the derivatives of diagonalizable tensor-valued functions that is based on differentiating the spectral decomposition is also discussed. Lastly, we also present a method for finding the derivatives of the exponential of an arbitrary tensor for arbitrary n. 相似文献
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C. S. Jog 《Journal of Elasticity》2008,93(2):141-148
The logarithm of a tensor is often used in nonlinear constitutive relations of elastic materials. Here we show how the logarithm
of an arbitrary tensor can be explicitly evaluated for any underlying space dimension n. We also present a method for the explicit evaluation of the derivatives of the logarithm of a tensor.
相似文献
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C. S. Jog 《国际流体数值方法杂志》2011,66(7):852-874
This work presents a mixed three‐dimensional finite element formulation for analyzing compressible viscous flows. The formulation is based on the primitive variables velocity, density, temperature and pressure. The goal of this work is to present a ‘stable’ numerical formulation, and, thus, the interpolation functions for the field variables are chosen so as to satisfy the inf–sup conditions. An exact tangent stiffness matrix is derived for the formulation, which ensures a quadratic rate of convergence. The good performance of the proposed strategy is shown in a number of steady‐state and transient problems where compressibility effects are important such as high Mach number flows, natural convection, Riemann problems, etc., and also on problems where the fluid can be treated as almost incompressible. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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C. S. Jog 《Journal of Elasticity》2006,85(2):119-124
We present a new proof of the representation theorem for fourth-order isotropic tensors that does not assume the tensor to have major or minor symmetries at the outset. 相似文献
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The preparation and properties of poly(1‐butene) (PB)/clay nanocomposites are described for the first time. Nanocomposites were prepared with the melt‐intercalation technique, using organically modified clay. The X‐ray diffraction patterns portrayed well‐defined diffraction peaks at higher d‐spacing than pristine clay, confirming the intercalation of polymer in silicate layers. Because PB exhibits time‐dependent polymorphism, the effect of clay on the phase transformation of PB was examined with thermal analysis. The phase transformation from a metastable tetragonal form to a stable hexagonal form was enhanced because of incorporation of layered silicates in the polymer matrix. The nanocomposites exhibited about a 40–140% increase in storage modulus depending on the clay content and significantly lower coefficient of thermal expansion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1014–1021, 2003 相似文献
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