30,307 research outputs found
Finite State Machine Synthesis for Evolutionary Hardware
This article considers application of genetic algorithms for finite machine
synthesis. The resulting genetic finite state machines synthesis algorithm
allows for creation of machines with less number of states and within shorter
time. This makes it possible to use hardware-oriented genetic finite machines
synthesis algorithm in autonomous systems on reconfigurable platforms
Triangulating the Square and Squaring the Triangle: Quadtrees and Delaunay Triangulations are Equivalent
We show that Delaunay triangulations and compressed quadtrees are equivalent
structures. More precisely, we give two algorithms: the first computes a
compressed quadtree for a planar point set, given the Delaunay triangulation;
the second finds the Delaunay triangulation, given a compressed quadtree. Both
algorithms run in deterministic linear time on a pointer machine. Our work
builds on and extends previous results by Krznaric and Levcopolous and Buchin
and Mulzer. Our main tool for the second algorithm is the well-separated pair
decomposition(WSPD), a structure that has been used previously to find
Euclidean minimum spanning trees in higher dimensions (Eppstein). We show that
knowing the WSPD (and a quadtree) suffices to compute a planar Euclidean
minimum spanning tree (EMST) in linear time. With the EMST at hand, we can find
the Delaunay triangulation in linear time.
As a corollary, we obtain deterministic versions of many previous algorithms
related to Delaunay triangulations, such as splitting planar Delaunay
triangulations, preprocessing imprecise points for faster Delaunay computation,
and transdichotomous Delaunay triangulations.Comment: 37 pages, 13 figures, full version of a paper that appeared in SODA
201
NGC 4654: gravitational interaction or ram pressure stripping?
The Virgo cluster spiral galaxy NGC 4654 is supposed to be a good candidate
for ongoing ram pressure stripping based on its very asymmetric HI
distribution. However, this galaxy also shows an asymmetric stellar
distribution. Numerical simulations using ram pressure as the only perturbation
can produce a tail structure of the gas content, but cannot account for its
kinematical structure. It is shown that a strong edge-on stripping event can
produce an asymmetric stellar distribution up to 800 Myr after the stripping
event, i.e. the galaxy's closest passage to the cluster center. Simulations
using a gravitational interaction with the companion galaxy NGC 4639 can
account for the asymmetric stellar distribution of NGC 4654, but cannot
reproduce the observed extended gas tail. Only a mixed interaction,
gravitational and ram pressure, can reproduce all observed properties of NGC
4654. It is concluded that NGC 4654 had a tidal interaction ~500 Myr ago and is
continuing to experience ram pressure.Comment: 16 pages with 19 PS figures. Accepted for publication in A&
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