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991.
992.
M. Van De Vel 《Topology and its Applications》1983,16(2):181-206
It is shown that two-dimensional convex structures with certain natural properties are join-hull commutative. The main intermediate step is the computation of the so-called exchange number. We also give two examples of three-dimensional convexities which are not join-hull commutative. The second one has certain additional properties showing that the main theorem is sharp in many other respects. These properties are obtained from a study of convex hyperspaces. 相似文献
993.
G. A. Margulis 《Combinatorica》1982,2(1):71-78
We give an explicit construction of regular graphs of degree 2r withn vertices and girth ≧c logn/logr. We use Cayley graphs of factor groups of free subgroups of the modular group. An application to low density codes is given. 相似文献
994.
Marc Prevost 《Journal of Computational and Applied Mathematics》1983,9(4):333-346
The interpolation of the function x → 1/(1 ? xt) generating the series f(t) = ∑∞i = 0citi at the zeros of an orthogonal polynomial with respect to a distribution d α satisfying some conditions will give us a process for accelerating the convergence of fn(t) = ∑ni = 0citi. Then, we shall see that the polynomial of best approximation of x → 1/(1 ? xt) over some interval or its development in Chebyshev polynomials Tn or Un are only particular cases of the main theorem.At last, we shall show that all these processes accelerate linear combinations with positive coefficients of totally monotonic and oscillating sequences. 相似文献
995.
996.
Denote by σ the subspace of Hilbert space {(xi)?l2:xi=0 for all but finitely many i}. Examples of cell-like decompositions of σ are constructed that have decomposition spaces that are not homeomorphic to σ. At one extreme is a cell-like decomposition G of σ produced using ghastly finite dimensional examples such that the decomposition space σ?G contains no embedded 2-cell but (σ?G)× is homeomorphic to σ. At the other extreme is a cell-like decomposition G of σ satisfying: (a) the nondegeneracy set NG={g?G:g≠point} consists of countably many arcs (necessarily tame); (b) the nondegeneracy set NG is a closed subset of the decomposition space σ?G; (c) each map f:B2→σ?G of a 2-cell into σ?G can be approximated arbitrarily closely by an embedding; (d) σ?G is not homeomorphic to σ but (σ?G)× is homeomorphic to σ. The fact that both conditions (a) and (b) can be satisfied (and have (d) hold) is directly attributable to σ’s incompleteness as a topological space. 相似文献
997.
This paper is concerned with large- error estimates concerning convergence in distribution as well as norm convergence for Banach space-valued martingale difference sequences. Indeed, two general limit theorems equipped with rates of convergence for such difference sequences are established. Applications of these lead to the central limit theorem and the weak law of large numbers with rates for Banach space-valued martingales. 相似文献
998.
Yeinzon?RodríguezEmail author Carlos?QuimbayEmail author 《Foundations of Physics Letters》2005,18(7):581-602
No Heading Several works analyzing the new physics contributions from the Left-Right Symmetric Model to the CP violation phenomena in
the neutral B mesons can be found in the literature. These works exhibit interesting and experimentally sensible deviations
from the Standard Model predictions but at the expense of considering a low right scale υR around 1 TeV. However, when we stick to the more conservative estimates for υR, which say that it must be at least 107 GeV, no experimentally sensible deviations from the Standard Model appear for indirect CP violation. This estimate for υR arises when the generation of neutrino masses is considered. In spite of the fact that this scenario is much less interesting
and says nothing new about both the CP violation phenomenon and the structure of the Left-Right Symmetric Model, this possibility
must be taken into account for the sake of completeness and when considering the see-saw mechanism that provides masses to
the neutrino sector.
1 Associate researcher of the Centro Internacional de Física, Ciudad
Universitaria, Bogotá D.C., Colombia. 相似文献
999.
Fawaz?S.?Al-AnziEmail author Ali?Allahverdi 《Journal of Mathematical Modelling and Algorithms》2005,4(4):435-453
This research addresses the scheduling problem of multimedia object requests, which is an important problem in information
systems, in particular, for World Wide Web applications. The performance measure considered is the variance of response time
which is crucial as end users expect fair treatment to their service requests. This problem is known to be NP-hard. The literature
survey indicates that two heuristics have been proposed to solve the problem. In this paper, we present a new heuristic, a
hybrid evolutionary heuristic, which is shown to perform much better than the two existing ones, e.g., the overall average
errors of the existing ones are 1.012 and 2.042 while the error of the proposed hybrid evolutionary heuristic is 0.154. 相似文献
1000.
J.-F. Ripoll A.A. Wray 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,93(4):473-519
We present in this paper a new 3D half-moment model for radiative transfer in a gray medium, called the model, which uses maximum entropy closure. This model is a generalization to 3D of the 1D version recently proposed in (J. Comp. Phys. 180 (2002) 584). The direction space Ω is divided into two pieces, Ω+ and Ω-, in a dynamical way by the plane perpendicular to the total radiative flux, and the half moments are defined from these subspaces. The model closure and the integrations of the radiative transfer equation performed on the moving Ω± spaces are detailed. 1D planar results, which have motivated the extension of the model of (J. Comp. Phys. 180 (2002) 584) to multi-dimensions, are shown. These results are very good. The model is thereafter derived for 3D spherically symmetric geometry, where the correctness of the non-trivial border terms can be checked. Two 3D spherically symmetric problems are numerically solved in order to show the accuracy of the closure and the role of the border terms. Once again, compared to the solution obtained with a ray tracing solver, results are very good. From the 3D half-moment model, a new moment model, called , is derived for the particular case of a 3D hot and opaque source radiating into a cold medium, for applications such as simulations of stellar atmospheres and fires. Two-dimensional numerical results are presented and compared to those obtained solving the RTE and with other moment models. They demonstrate the very good accuracy of the model, its good convergence properties, and better prediction compared to all other existing moment models in its domain of applicability. 相似文献