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21.
Chepoi showed that every breadth first search of a bridged graph produces a cop-win ordering of the graph. We note here that Chepoi's proof gives a simple proof of the theorem that G is bridged if and only if G is cop-win and has no induced cycle of length four or five, and that this characterization together with Chepoi's proof reduces the time complexity of bridged graph recognition. Specifically, we show that bridged graph recognition is equivalent to (C4,C5)-free graph recognition, and reduce the best known time complexity from O(n4) to O(n3.376). 相似文献
22.
本文运用信息保存法对低速二维的流动现象进行模拟,考察了低速条件下的有限平板绕流以及微槽道气体流动问题。研究表明:在对低速流动的模拟过程中,运用IP法在能够获得较好的结果的同时,具有比DSMC方法更高的计算效率。 相似文献
23.
Johann Guilleminot Christian Soize Djimedo Kondo Christophe Binetruy 《International Journal of Solids and Structures》2008,45(21):5567-5583
Many engineering materials exhibit fluctuations and uncertainties on their macroscopic mechanical properties. This randomness results from random fluctuations observed at a lower scale, especially at the meso-scale where microstructural uncertainties generally occur. In the present paper, we first propose a complete theoretical stochastic framework (that is, a relevant probabilistic model as well as a non-intrusive stochastic solver) in which the volume fraction at the microscale is modelled as a random field whose statistical reduction is performed using a Karhunen–Loeve expansion. Then, an experimental procedure dedicated to the identification of the parameters involved in the probabilistic model is presented and relies on a non-destructive ultrasonic method. The combination of the experimental results with a micromechanical analysis provides realizations of the volume fraction random field. In particular, it is shown that the volume fraction can be modelled by a homogeneous random field whose spatial correlation lengths are determined and may provide conditions on the size of the meso-volumes to be considered. 相似文献
24.
The frequency or dispersion relation for the least‐squares mixed formulation of the shallow‐water equations is analysed. We consider the use of different approximation spaces corresponding to co‐located and staggered meshes, respectively. The study includes the effect of Coriolis, and the dispersion properties are compared analytically and graphically with those of the mixed Galerkin formulation. Numerical solutions of a test problem to simulate slow Rossby modes illustrate the theoretical results. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
25.
The reactions of IO radicals with CH3SCH3, CH3SH, C2H4, and C3H6 have been studied using the discharge flow method with direct detection of IO radicals by mass spectrometry. The absolute rate constants obtained at 298 K are the following: IO + CH3SCH3 → products (1): k1 = (1.5 ± 0.2) × 10?14; IO + CH3SH → products (2): k2 = (6.6 ± 1.3) × 10?16; IO + C2H4 →products (3): k3 < 2 × 10?16; IO + C3H6 → products (4): k4 < 2 × 10?16 (units are cm3 molecule?1 s?1). CH3S(O)CH3 and HOI were found as products of reactions (1) and (2), respectively. The present lower value of k1 compared to our previous determination is discussed. 相似文献
26.
We consider some boundary value problems in self-similar ramified domains, with Laplace and Helmholtz equations. We discuss transparent boundary conditions. These conditions permit computing the restriction of the solutions to domains obtained by stopping the geometric construction after a finite number of steps. To cite this article: Y. Achdou et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
27.
Christophe Cuny 《Journal of multivariate analysis》2006,97(8):1842-1869
Let (Xm,n)(m,n)∈Z2 be a Cp-valued wide sense stationary process. We study the prediction theory of such processes according to different total orders on Z2. In the case of a “rational order”, we give the spectral distribution of the resulting evanescent component and prove that for two different rational orders, the resulting evanescent components are mutually orthogonal. 相似文献
28.
29.
J. -F. Le Gall 《Probability Theory and Related Fields》1988,78(3):389-402
Summary We consider the following heat conduction problem. Let K be a compact set in Euclidean space 3. Suppose that K is held at the temperature 1, while the surrounding medium is at the temperature 0 at time 0. Following Spitzer we investigate the asymptotic behaviour of the integral E
K
(t) which represents the total energy flow in time t from the set K to the surrounding medium 3–K. An asymptotic expansion is given for E
K
(t) which refines a theorem due to Spitzer. This expansion also verifies and improves a formal calculation of Kac. Similar results are proved in higher dimensions. Up to the constant m(K), the quantity E
K
(t) can be interpreted as the expected value of the volume of the Wiener sausage associated with K and a d-dimensional Brownian motion. This point of view both plays a major role in the proofs and leads to a probabilistic interpretation of the different terms of the expansion. 相似文献
30.