A multigrid method for steady incompressible navier-stokes equations based on flux difference splitting

The steady Navier–Stokes equations in primitive variables are discretized in conservative form by a vertex-centred finite volume method Flux difference splitting is applied to the convective part to obtain an upwind discretization. The diffusive part is discretized in the central way. In its first-order formulation, flux difference splitting leads to a discretization of so-called vector positive type. This allows the use of classical relaxation methods in collective form. An alternating line Gauss–Seidel relaxation method is chosen here. This relaxation method is used as a smoother in a multigrid method. The components of this multigrid method are: full approximation scheme with F-cycles, bilinear prolongation, full weighting for residual restriction and injection of grid functions. Higher-order accuracy is achieved by the flux extrapolation method. In this approach the first-order convective fluxes are modified by adding second-order corrections involving flux limiting. Here the simple MinMod limiter is chosen. In the multigrid formulation the second-order discrete system is solved by defect correction. Computational results are shown for the well known GAMM backward-facing step problem and for a channel with a half-circular obstruction.     

The effect of nuclear and Coulomb interactions on the nuclear shapes of two colliding208Pb nuclei

Using a complex energy density functional derived from the Reid soft-core potential, the changes in nuclear shapes of two colliding²⁰⁸Pb are investigated. At each separation distanceR, the total binding energy of the Pb + Pb system is minimized w.r.t. the quadrupole deformation and diffuseness parameters of nuclear densities. It is found that the nuclear shapes are strongly affected by the nuclear and Coulomb interactions. A sudden transition occurs from oblate to prolate shapes around R16.8fm and a smooth one from prolate to oblate shapes aroundR?11.76 fm.     

The formation of mixed copper sulfide-silver sulfide membranes for coppers(II)-selective electrodes : Part IV. Selectivity Coefficients and Complexhnetric Titrations

The analytical applicability of a mixed sulfide copper-selective electrode has been evaluated, with special attention given to end-point indication in compleximetric titrations. In acidic medium, several metals can be titrated satisfactorily. The determination of calcium and magnesium in alkaline medium is discussed briefly. Selectivity coefficients are presented for several metal ions in acidic medium.     

Nickelmodifiedlarge poremesoporoussilicas ascatalysts for methanol decomposition

Summary Ni-modifiedlarge poremesoporous silicasarecharacterized by XRD, N₂physisorption and TPR with H₂. Theeffectof the supportpore structure on their catalytic behaviorin methanol decomposition to H₂, CO and CH₄is studied.     

Behaviour of solid electrodes in normal and differential pulse voltammetric methods

In order to investigate the behaviour of solid electrodes in normal and differential pulse voltammetry, step functions have been applied to the electrochemical cell containing the electrodes to be tested, in the absence of electroactive species. The large residual current observed could be attributed to electrochemical reactions of the electrode material.     

Crystal structure of an NPNA-repeat motif from the circumsporozoite protein of the malaria parasite Plasmodium falciparum

A crystal structure is reported of the peptide Ac-Ala-Asn-Pro-Asn-Ala-NH2, representing the immunodominant region of the major surface protein on the malaria parasite; the NPNA motif adopts a type-I beta-turn, which is stabilized by hydrogen bonding between the CO of Asn2 and the NH of Ala5 as well as between the O(delta) of Asn2 and the NH of Asn4.     

Event excess in the MiniBooNE search for ¯νμ→¯νe oscillations

The MiniBooNE experiment at Fermilab reports results from a search for ˉν_{μ}→ˉν_{e} oscillations, using a data sample corresponding to 5.66×102? protons on target. An excess of 20.9±14.0 events is observed in the energy range 475相似文献   

Near-field optical experiments on low-symmetry split-ring-resonator arrays

Effective symmetric and antisymmetric eigenmodes of coupled plasmonic resonances play a crucial role in many photonic metamaterials. Recently, we discussed a particular arrangement of metallic split-ring resonators that is planar, hence enabling direct experimental access to the different eigenmodes via near-field optical microscopy. In this Letter, corresponding optical experiments are presented and compared with simple theoretical modeling, providing a direct confirmation of our previous, more indirect conclusions.