814 research outputs found
Cucker–Smale Type Dynamics of Infinitely Many Individuals with Repulsive Forces
No full textWe study the existence and uniqueness of the time evolution of a system of infinitely many individuals, moving in a tunnel and subjected to a Cucker–Smale type alignment dynamics with compactly supported communication kernels and to short-range repulsive interactions to avoid collisions
Time Evolution of Concentrated Vortex Rings
No full textWe study the time evolution of an incompressible fluid with axisymmetry without swirl when the vorticity is sharply concentrated. In particular, we consider N disjoint vortex rings of size ε and intensity of the order of | log ε| - 1. We show that in the limit ε→ 0 , when the density of vorticity becomes very large, the movement of each vortex ring converges to a simple translation, at least for a small but positive time
At most single-bend embeddings of cubic graphs
No full textThis paper provides the complete proof of the fact that any planar cubic graph is at most single-bend embeddable except for the tetrahedron. An O(n) amortized time algorithm for drawing an at most single-bend embedding of a cubic graph is also presented, where n is the number of vertices of the graph. Furthermore, it is proved that the minimum of the total number of bends in an at most single-bend embedding of a cubic graph of order n is less than or equal to 0.5 n+1. This result is the best possible. © 1994 Editorial Committee of Applied Mathematics-A Journal of Chinese Universities
Global time evolution of concentrated vortex rings
No full textWe study the time evolution of an incompressible fluid with axial symmetry without swirl, assuming initial data such that the initial vorticity is very concentrated inside N small disjoint rings of thickness ε and vorticity mass of the order of | log ε| - 1. When ε→ 0 , we show that the motion of each vortex ring converges to a simple translation with constant speed (depending on the single ring) along the symmetry axis. We obtain a sharp localization of the vorticity support at time t in the radial direction, whereas we state only a concentration property in the axial direction. This is obtained for arbitrary (but fixed) intervals of time. This study is the completion of a previous paper [5], where a sharp localization of the vorticity support was obtained both along the radial and axial directions, but the convergence for ε→ 0 worked only for short times
A parallel on-line algorithm for deriving all logical conclusions implied by a set of binary relations
No full text
On the dynamics of infinitely many charged particles with magnetic confinement
No full textWe study the time evolution of a system of infinitely many charged particles confined by an external magnetic field in an unbounded cylindrical conductor and mutually interacting via the Coulomb force. We prove the existence, uniqueness and quasi-locality of the motion. Moreover, we give some nontrivial bounds on its long time behavior
Adamant digraphs
No full textAbstractIn this paper we introduce the class of adamant digraphs. These are the digraphs with the property that for any two vertices x and y, the set of successors of x and the set of successors of y are either disjoint or (inclusionwise) comparable. Those adamant digraphs whose inverse digraph is also adamant are called inflexible. This subclass includes many previously known classes, e.g. minimal series-parallel digraphs and Ferrers digraphs. For both adamant and inflexible digraphs we give alternative characterizations and linear-time recognition algorithms. The special case of symmetric adamant digraphs is investigated
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