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91.
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
92.
93.
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
94.
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
95.
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.
96.
97.
98.
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
99.
Oversteegen and Tymchatyn proved that homeomorphism groups of positive dimensional Menger compacta are -dimensional by proving that almost -dimensional spaces are at most -dimensional. These homeomorphism groups are almost -dimensional and at least -dimensional by classical results of Brechner and Bestvina. In this note we prove that almost -dimensional spaces for are -dimensional. As a corollary we answer in the affirmative an old question of R. Duda by proving that every hereditarily locally connected, non-degenerate, separable, metric space is -dimensional.
100.
We consider the problems of three-particle scattering and annihilation in a system of three strongly interacting charged particles
(
pn). We propose a model for the elastic scattering and the breakup process in the nucleon channel as well as for the annihilation
into mesons. The mathematical foundation of the model is the extension theory of symmetrical operators. In the framework of
this model, we construct the modified integral Faddeev equations with energy-dependent interactions taking the annihilation
processes into account. These equations are uniquely resolvable for suitable classes of functions. On this basis, we deduce
the corresponding differential Faddeev equations, construct asymptotic boundary conditions for wave function components, and
formulate boundary problems for a system composed of nucleonic and mesonic channels. The results obtained are applied to scattering
and annihilation processes in the three-particle system
.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 118, No. 1, pp. 74–94, January, 1999. 相似文献