Matched Field Processing on the Connection Machine

AbstractThe interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.

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Robust matched-field processing using a coherent broadband white noise constraint processor

The Journal of the Acoustical Society of America ◽

10.1121/1.2769830 ◽

2007 ◽

Vol 122 (4) ◽

pp. 1979-1986 ◽

Cited By ~ 30

Author(s):

Claire Debever ◽

W. A. Kuperman

Keyword(s):

White Noise ◽

Matched Field Processing

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Recent Developments in the Evolution of Morphologies and Controllers for Physically Simulated Creatures

Artificial Life ◽

10.1162/106454601300328034 ◽

2001 ◽

Vol 7 (1) ◽

pp. 77-87 ◽

Cited By ~ 39

Author(s):

Tim Taylor ◽

Colm Massey

Keyword(s):

Recent Work ◽

Original Work ◽

Three Dimensional ◽

Parallel Computer ◽

Connection Machine ◽

Recent Developments ◽

Body Shapes

Karl Sims' work [25, 26] on evolving body shapes and controllers for three-dimensional, physically simulated creatures generated wide interest on its publication in 1994. The purpose of this article is threefold: (a) to highlight a spate of recent work by a number of researchers in replicating, and in some cases extending, Sims' results using standard PCs (Sims' original work was done on a Connection Machine CM-5 parallel computer). In particular, a re-implementation of Sims' work by the authors will be described and discussed; (b) to illustrate how off-the-shelf physics engines can be used in this sort of work, and also to highlight some deficiencies of these engines and pitfalls when using them; and (c) to indicate how these recent studies stand in respect to Sims' original work.

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