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91.
V. A. Levin I. S. Manuylovich V. V. Markov 《Computational Mathematics and Mathematical Physics》2016,56(6):1102-1117
Numerical simulation of three-dimensional structures of gas detonation in circular section channels that emerge due to the instability when the one-dimensional flow is initiated by energy supply at the closed end of the channel is performed. It is found that in channels with a large diameter, an irregular three-dimensional cellular detonation structure is formed. Furthermore, it is found that in channels with a small diameter circular section, the initially plane detonation wave is spontaneously transformed into a spinning detonation wave, while passing through four phases. A critical value of the channel diameter that divides the regimes with the three-dimensional cellular detonation and spinning detonation is determined. The stability of the spinning detonation wave under perturbations occurring when the wave passes into a channel with a greater (a smaller) diameter is investigated. It is found that the spin is preserved if the diameter of the next channel (into which the wave passes) is smaller (respectively, greater) than a certain critical value. The computations were performed on the Lomonosov supercomputer using from 0.1 to 10 billions of computational cells. All the computations of the cellular and spinning detonation were performed in the whole long three-dimensional channel (up to 1 m long) rather than only in its part containing the detonation wave; this made it possible to adequately simulate and investigate the features of the transformation of the detonation structure in the process of its propagation. 相似文献
92.
93.
The immersion of a cylindrical solid in an undisturbed fluid is numerically investigated. Wave formation accompanying this process and the dependence of the wave parameters on those of the body are studied. The shallow water model in a cylindrical coordinate system is used. A total variation diminishing (TVD) scheme is applied on a C-type difference grid, according to Arakawa’s classification. 相似文献
94.
95.
F. Bartumeus P. Fernández M. G.E. da Luz J. Catalan R. V. Solé S. A. Levin 《The European physical journal. Special topics》2008,157(1):157-166
Rate limitation due to encounters is fundamental to many ecological
interactions. Since encounter rate governs reaction rates, and thus,
dynamics of systems, it deserves systematic study. In classical
population biology, ecological dynamics rely on the assumption of
perfectly mixed interacting entities (e.g., individuals, populations,
etc.) in a spaceless world. The so-called mean field assumption
assumes that encounter rates are driven exclusively by changes in the
density of the interacting entities and not on how they are
distributed or move in space. Therefore, the mean field assumption
does not give any insight into relevant spatiotemporal statistical
properties produced by the trajectories of moving entities through
space. In the present study, we develop spatially explicit
simulations of random walking particles (i.e., Lévy walkers) to
evaluate encounter rate constraints beyond the mean field
assumption. We show that encounter rate fluctuations are driven not
only by physical aspects such as the size or the velocity of the
interacting particles, but also by different motion patterns. In
particular, superdiffusion phenomena might be relevant at low
densities and/or low spatial dimensionality. Finally, we discuss
potential adaptive responses of living organisms that may allow
individuals to control how they diffuse through space and/or the
spatial dimensions employed in the exploration process. 相似文献
96.
An iterative method for the minimization of convex functions f :n , called a Newton Bracketing (NB) method, is presented. The NB method proceeds by using Newton iterations to improve upper and lower bounds on the minimum value. The NB method is valid for n = 1, and in some cases for n > 1 (sufficient conditions given here). The NB method is applied to large scale Fermat–Weber location problems. 相似文献
97.
Let be a polynomial whose Julia set is locally connected. Then a non-preperiodic non-precritical vertex of must have the limit set which coincides with the limit set of an appropriately chosen recurrent critical point of . In particular, if all critical points of are non-recurrent then all vertices of are preperiodic or precritical.
98.
99.
100.
Slowly convergent infinite products
are considered, where
is a sequence of numbers, or a sequence of linear operators. Using an asymptotic expansion for the “remainder” of the infinite
product a method for convergence acceleration is suggested. The method is in the spirit of the d-transformation for series. It is very simple and efficient for some classes of sequences
. For complicated sequences
it involves the solution of some linear systems, but it is still effective.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献