A5041411730- Scientific Research and Discoveries
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Parallel Computing and Optimization Techniques
- Astrophysics and Star Formation Studies
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Computational Physics and Python Applications
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Distributed and Parallel Computing Systems
- Advanced Data Storage Technologies
- Electromagnetic Scattering and Analysis
- Gamma-ray bursts and supernovae
- Particle accelerators and beam dynamics
- Cosmology and Gravitation Theories
- Fluid Dynamics Simulations and Interactions
- Planetary Science and Exploration
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Numerical methods for differential equations
- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Advanced Thermodynamics and Statistical Mechanics
- Magnetic confinement fusion research
Tokyo Metropolitan Bokutoh Hospital
2005-2025
Meiji Pharmaceutical University
2025
Kobe University
2015-2024
Preferred Networks (Japan)
2024
Osaka University
1983-2023
RIKEN Center for Computational Science
2013-2022
Saitama Medical University
2022
Social Insurance Saitama Chuo Hospital
2022
Naval Hospital Yokosuka Japan
2019-2021
Japan Research Institute
2020
We report the results of a large set N-body calculations aimed at studying evolution multimass star clusters in external tidal fields. Our start with same initial mass functions, but varying particle numbers, orbital types and density profiles. main focus is to study how stellar function other cluster parameters change under combined influence evolution, two-body relaxation field. find that lifetimes moving on similar orbits scale as T∼Txrh, where Trh time, exponent x depends concentration...
The evolution of star clusters is studied using N-body simulations in which the single stars and binaries taken self-consistently into account. Initial conditions are chosen to represent relatively young Galactic open clusters, such as Pleiades, Praesepe Hyades. calculations include a realistic mass function, primordial external potential parent Galaxy.
We know from observations that globular clusters are very efficient catalysts in forming unusual short-period binary systems or their offspring, such as low-mass X-ray binaries (LMXBs; neutron stars accreting matter stellar companions), cataclysmic variables (white dwarfs and millisecond pulsars (rotating with spin periods of a few milliseconds). Although there has been little direct evidence, the overabundance these objects attributed by numerous authors to high densities cores, which leads...
view Abstract Citations (135) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Building a Better Leapfrog Hut, Piet ; Makino, Jun McMillan, Steve In stellar dynamical computer simulations, as well other types of simulations using particles, time step size is often held constant in order to guarantee high degree energy conservation. many applications, allowing the change can offer great saving computational cost, but variable-size steps usually...
view Abstract Citations (174) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optimal Order and Time-Step Criterion for Aarseth-Type N-Body Integrators Makino, Junichiro How the selection of time-step criterion order integrator change efficiency Aarseth-type N-body integrators is discussed. An alternative to Aarseth's scheme based on direct calculation time derivative force using Hermite interpolation compared scheme, which uses Newton...
Observations of stellar kinematics, gasdynamics, and masers around galactic nuclei have now firmly established that many galaxies host central supermassive black holes (SMBHs) with masses in the range ~106-109 M☉. However, how these SMBHs formed is not well understood. One reason for this situation lack observations intermediate-mass BHs (IMBHs), which could bridge gap between mass SMBHs. Recently, missing link (i.e., an IMBH) has been found made by ASCA Chandra region starburst galaxy M82....
We show that the smoothed particle hydrodynamics (SPH) method, used with individual time-steps in way described literature, cannot handle strong explosion problems correctly. In time-step scheme, particles determine their essentially from a local Courant condition. Thus they respond to shock, if pre-shock timescale is too long compared shock timescale. This problem not severe SPH simulations of galaxy formation temperature cutoff cooling function at $10^4 {\rm K}$, while it very dangerous...
It has been believed that spirals in pure stellar disks, especially the ones spontaneously formed, decay several galactic rotations due to increase of velocity dispersions. Therefore, some cooling mechanism, for example dissipational effects interstellar medium, was assumed be necessary keep spiral arms. Here we show disks can maintain features tens without help cooling, using a series high-resolution three-dimensional $N$-body simulations disks. We found if number particles is sufficiently...
Occult nodal metastases increase the risk of cancer recurrence, demoting prognosis and quality life patients. While targeted drug delivery by using systemically administered nanocarriers can potentially control metastatic disease, lymph node have been mainly dealt locally injecting nanocarriers, which may not always be applicable. Herein, we demonstrated that sub-50 nm polymeric micelles incorporating platinum anticancer drugs could target in a syngeneic melanoma model after systemic...
The standard formulation of the smoothed particle hydrodynamics (SPH) assumes that local density distribution is differentiable. This assumption used to derive spatial derivatives other quantities. However, this breaks down at contact discontinuity. At discontinuity, low-density side overestimated while high-density underestimated. As a result, pressure (high-density) (underestimated). Thus, unphysical repulsive force appears resulting in effective surface tension. tension suppresses fluid...
Abstract We present the basic idea, implementation, measured performance, and performance model of FDPS (Framework for Developing Particle Simulators). is an application-development framework which helps researchers to develop simulation programs using particle methods large-scale distributed-memory parallel supercomputers. A particle-based program computers needs perform domain decomposition, exchange particles are not in each computing node, gathering information other nodes necessary...
The numerical simulations of massive collisional stellar systems, such as globular clusters (GCs), are very time-consuming. Until now, only a few realistic million-body GCs with small fraction binaries (5%) have been performed by using the NBODY6++GPU code. Such models took half year computational time on GPU based super-computer. In this work, we develop new N-body code, PeTar, combining methods Barnes-Hut tree, Hermite integrator and slow-down algorithmic regularization (SDAR). code can...
Abstract M87 is the best target for studying black hole accretion and jet formation. Reanalysis of Event Horizon Telescope (EHT) public data at 230 GHz shows a core–knots structure center features. We here compare this with new results GMVA 86 showing spatially resolved central core. There are similarities differences between two. At GHz, “two bright regions” seen on ring in The “core–knot–west knot” triple image apparent appearance two peaks similar to when convolved beam. This similarity...
Observed cusps with density profiles ρ ∝ r-1 or shallower in the central regions of galaxies cannot be reproduced standard cold dark matter picture hierarchical clustering. Previous claims to contrary were based on simulations relatively few particles and substantial softening. We present particle numbers 1 order magnitude higher essentially no softening, we show that typical are clearly steeper than r-1. The observed may have formed through smoothing effect spiral-in black holes previous...
We investigate the structure of dark matter halo formed in cold scenario using N-body simulations. simulated 12 halos with masses 6.6 × 1011-8.0 1014 M☉. In all runs, have density cusps proportional to r-1.5 developed at their centers, which is consistent results recent high-resolution calculations. The evolves a self-similar way and universal sense that it independent mass initial random realization fluctuation. profile good agreement proposed by Moore et al., has central slope an outer...
Abstract In this paper, we describe the architecture and performance of GRAPE-6 system, a massively-parallel special-purpose computer for astrophysical $N$-body simulations. is successor GRAPE-4, which was completed in 1995 achieved theoretical peak speed 1.08 Tflops. As case with primary application simulations collisional systems, though it can also be used collisionless systems. The main differences between GRAPE-4 are (a) processor chip integrates 6 force-calculation pipelines, compared...
In this paper, we describe the architecture and performance of GRAPE-4 system, a massively parallel special-purpose computer for N-body simulation gravitational collisional systems. The calculation cost self-gravitating system is O(N3). Thus, even with present-day supercomputers, number particles one can handle still around 10,000. simulations, almost all computing time spent calculating force between particles, since interactions proportional to square particles. Computational rest...
We performed three-dimensional $N$-body/SPH simulations to study how mass resolution and other model parameters, such as the star-formation efficiency parameter, $C_*$ threshold density for star formation, $n_{\rm th}$ affect structures of galactic gaseous/stellar disk. employed $10^6$–$10^7$ particles resolve a cold ($T \lt$ 100 K) dense ($n_{\rm H} \gt$ cm$^{-3}$) phase well diffuse, hot phases. found that interstellar medium (ISM) distribution young stars were sensitive assumed values...