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31.
32.
In the five-dimensional Kaluza–Klein (KK) theory there is a well known class of static and electromagnetic-free KK-equations
characterized by a naked singularity behavior, namely the Generalized Schwarzschild solution (GSS). We present here a set
of interior solutions of five-dimensional KK-equations. These equations have been numerically integrated to match the GSS
in the vacuum. The solutions are candidates to describe the possible interior perfect fluid source of the exterior GSS metric
and thus they can be models for stars for static, neutral astrophysical objects in the ordinary (four-dimensional) spacetime. 相似文献
33.
34.
Back Cover: Formal Total Synthesis of Diazonamide A by Indole Oxidative Rearrangement (Chem. Eur. J. 31/2016)
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35.
Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field u when the system is segregated into two phases (at low temperatures) with a sharp interface between them. u satisfies the incompressible Navier-Stokes equations together with a jump boundary condition for the pressure across the interface which, in turn, moves with a velocity given by the normal component of u. Numerical simulations of the Vlasov-Boltzmann equations for shear flows parallel and perpendicular to the interface in a phase segregated mixture support this analysis. We expect similar behavior in real fluid mixtures. 相似文献
36.
Raffaele Battistuzzi 《Polyhedron》1985,4(6):933-941
Contrary to earlier reports in which no adducts of Co(II) metal ion with 4,6-dimethylpyrimidine-2(1H)-thione(HL) could be isolated starting from Co(ClO4)2 · 6H2O, we now report bis- and tris-ligand Co(II) complexes of the type [Co(HL)2(H2O)2]X2 · H2O (X = ClO4, BF4), [Co(HL)2NO3]NO3, [Co(HL)2SO4] · 0.5H2O and [Co(HL)3]X2 · 0.5H2O (X = ClO4, BF4). They have been synthesized by refluxing 2:1 and 3:1 mixtures of HL and CoX2 · nH2O in ethanol-triethyl orthoformate. We also describe new Co(HL)2X2 · nH2O complexes in which for X2 = ClBr, ClI and BrI, n = 2; for X2 = I2, n = 1 and for X2 = (SCN)2, n = 0. Structural characterization of the complex species is made from electronic and vibrational spectra, magnetic susceptibility measurements in the solid state and conductivity measurements in DMF solution. The magnetic and electronic spectral data together with ligand-field parameters suggest a pseudo-octahedral environment for all the Co(II) complexes, with the exception of Co(HL)2SO4 · 0.5H2O in which the Co(II) ion appears to be pentacoordinated. The IR spectra are consistent with a coordination involving N,S-chelation of the ligand through the non-protonated ring nitrogen atom and the exocyclic sulphur atom. 相似文献
37.
Synthesis of Pseudocyphellarins A and B, Two Depsides from the Lichen Pseudocyphellaria endochrysea The total synthesis of the depsides pseudocyphellarin A (= 3-hydroxy-4-methoxycarbonyl-2,5,6-trimethyl-phenyl 3-formyl-2,4-dihydroxy-5,6-dimethylbenzoate; 11 ) and pseudocyphellarin B (3-hydroxy-4-methoxycarbonyl-2,5,6-trimethylphenyl 2,4-dihydroxy-3-hydroxymethyl-5,6-dimethyl benzoate; 12 ) is described. 相似文献
38.
Raffaele Cerulli Paola Festa Giancarlo Raiconi 《Computational Optimization and Applications》2003,26(2):191-208
In this paper, the problem of finding a shortest path tree rooted at a given source node on a directed graph (SPT) is considered. A new efficient algorithm based on a primal-dual approach is presented, which improves both the convergence and the complexity of the best known auction-like algorithm. It uses the virtual source (VS) concept based on the following consideration: when a node i is visited for the first time by any algorithm which preserves verified the dual admissibility conditions, then the shortest path (SP) from the source node to i is found. Therefore, the SP from the source to the remaining nodes may be computed by considering i as a virtual source.We propose a very efficient implementation of an auction-like algorithm that uses this concept and enables us to obtain a computational cost of O(n
2), where n is the number of nodes.Numerical experimentsare reported showing that the new method outdoes previously proposed auction-like algorithms and is highly competitive with other state-of-art SP approaches. 相似文献
39.
Defining and optimizing algorithms for neighbouring particle identification in SPH fluid simulations
Lagrangian particle methods such as smoothed particle hydrodynamics (SPH) are very demanding in terms of computing time for large domains. Since the numerical integration of the governing equations is only carried out for each particle on a restricted number of neighbouring ones located inside a cut‐off radius rc, a substantial part of the computational burden depends on the actual search procedure; it is therefore vital that efficient methods are adopted for such a search. The cut‐off radius is indeed much lower than the typical domain's size; hence, the number of neighbouring particles is only a little fraction of the total number. Straightforward determination of which particles are inside the interaction range requires the computation of all pair‐wise distances, a procedure whose computational time would be unpractical or totally impossible for large problems. Two main strategies have been developed in the past in order to reduce the unnecessary computation of distances: the first based on dynamically storing each particle's neighbourhood list (Verlet list) and the second based on a framework of fixed cells. The paper presents the results of a numerical sensitivity study on the efficiency of the two procedures as a function of such parameters as the Verlet size and the cell dimensions. An insight is given into the relative computational burden; a discussion of the relative merits of the different approaches is also given and some suggestions are provided on the computational and data structure of the neighbourhood search part of SPH codes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
40.
Raffaele Cimmino 《Fresenius' Journal of Analytical Chemistry》1899,38(7):429-431
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