Hiroshi Daisaka

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We investigate the formation of spatial structure in dense, self-gravitating particle systems such as Saturn’s B-ring through local N -body simulations to clarify the intrinsic physics based on individual particle motion. In such a system, Salo (1995) showed that the formation of spatial structure such as wake-like structure and particle grouping (clump)(More)
As an entry for the 2002 Gordon Bell performance prize, we report the performance achieved on the GRAPE-6 system for a simulation of the early evolution of the protoplanet-planetesimal system of the Uranus-Neptune region. GRAPE-6 is a special-purpose computer for astrophysical N-body calculations. The present configuration has 2048 custom pipeline chips,(More)
In this paper, we describe the design and performance of GRAPE-8 accelerator processor for gravitational N -body simulations. It is designed to evaluate gravitational interaction with cutoff between particles. The cutoff function is useful for schemes like TreePM or Particle-Particle Particle-Tree, in which gravitational force is divided to short-range and(More)
We investigated the evolution of interacting disk galaxies using high-resolution N -body/SPH simulations, taking into account the multiphase nature of the interstellar medium (ISM). In our high-resolution simulations, a large-scale starburst occurred naturally at the collision interface between two gas disks at the first encounter, resulting in the(More)
In this paper, we describe the design and performance of GRAPE-8 accelerator processor for gravitational <i>N</i>-body simulations. It is designed to evaluate gravitational interaction with cutoff between particles. The cutoff function is useful for schemes like TreePM or Particle-Particle Particle-Tree, in which gravitational force is divided to(More)
We describe the design and performance of the GRAPE-MPs, a series of SIMD accelerator boards for quadruple/hexuple/octuple-precision arithmetic operations. Basic design of GRAPE-MPs is that it consists of a number of processing elements (PE) and memory components which handle data with quadruple/hexuple/octuple-precision. A GRAPE-MPs processor is(More)
Introduction: One of the most striking features of the Uranian ring system is that some of rings, at least 6, 5, 4, , , -rings, are eccentric (e.g., reviewed by French et al. [1]). The existence of the eccentric rings is truly surprising, because it requires the pericenter of ring particles with different orbital periods to behave in exactly the same way(More)