scholarly journals petar: a high-performance N-body code for modelling massive collisional stellar systems

2020 ◽  
Vol 497 (1) ◽  
pp. 536-555 ◽  
Author(s):  
Long Wang ◽  
Masaki Iwasawa ◽  
Keigo Nitadori ◽  
Junichiro Makino
Keyword(s):  
Globular Clusters ◽  
High Performance ◽  
Computational Time ◽  
Stellar Systems ◽  
Processing Unit ◽  
Desktop Computer ◽  
Multiple Systems ◽  
Hybrid Parallelization ◽  
Good Agreement

ABSTRACT 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 simulations of GCs with a small fraction of binaries ($5{{\ \rm per\ cent}}$) have been performed by using the nbody6++gpu code. Such models took half a year computational time on a Graphic Processing Unit (GPU)-based supercomputer. In this work, we develop a new N-body code, petar, by combining the methods of Barnes–Hut tree, Hermite integrator and slow-down algorithmic regularization. The code can accurately handle an arbitrary fraction of multiple systems (e.g. binaries and triples) while keeping a high performance by using the hybrid parallelization methods with mpi, openmp, simd instructions and GPU. A few benchmarks indicate that petar and nbody6++gpu have a very good agreement on the long-term evolution of the global structure, binary orbits and escapers. On a highly configured GPU desktop computer, the performance of a million-body simulation with all stars in binaries by using petar is 11 times faster than that of nbody6++gpu. Moreover, on the Cray XC50 supercomputer, petar well scales when number of cores increase. The 10 million-body problem, which covers the region of ultracompact dwarfs and nuclear star clusters, becomes possible to be solved.

Long Term Dynamic Simulation of a Stem Cell Nucleus

2020 ◽  
Vol 15 (11) ◽  
Author(s):  
Manoochehr Rabiei ◽  
Andrew McColloch ◽  
Parisa Rabbani ◽  
Michael Cho ◽  
Alan Bowling
Keyword(s):  
Stem Cell ◽  
High Speed ◽  
Multiple Scales ◽  
Adipogenic Differentiation ◽  
Computational Time ◽  
Desktop Computer ◽  
Biological Phenomena ◽  
Time Histories ◽  
Biomolecular Simulations

Abstract Biomolecular simulations are computationally expensive. Simulating time histories larger than seconds remain elusive even with the help of supercomputers. Biological phenomena are multiscale in nature. The dynamics range from atomistic to microscale. Herein a recently developed scaling approach, based on the method of multiple scales (MMS), is used to accomplish a long term simulation of a subcellular system. The first key advantage of this approach is the drastic reduction in computational time. This approach is illustrated using a mesenchymal stem cell (MSC) as it undergoes adipogenic differentiation, a process that takes 15 days, which was simulated in less than 1.5 h on a typical desktop computer. The second key advantage of the high-speed simulation is that it facilitates the study of mechanical properties, such as nucleus membrane stiffness, that are difficult to measure experimentally with certainty.

scholarly journals Evolutionary models of rotating dense stellar systems: challenges in software and hardware

2014 ◽  
Vol 10 (S312) ◽  
pp. 239-240
Author(s):  
Jose Fiestas
Keyword(s):  
Black Hole ◽  
Globular Clusters ◽  
High Performance ◽  
Stellar Systems ◽  
Evolutionary Models ◽  
The Galaxy ◽  
Black Hole Growth ◽  
Galaxy Cores ◽  
Hole Growth ◽  
Gravitating Systems

AbstractWe present evolutionary models of rotating self-gravitating systems (e.g. globular clusters, galaxy cores). These models are characterized by the presence of initial axisymmetry due to rotation. Central black hole seeds are alternatively included in our models, and black hole growth due to consumption of stellar matter is simulated until the central potential dominates the kinematics in the core. Goal is to study the long-term evolution (~ Gyr) of relaxed dense stellar systems, which deviate from spherical symmetry, their morphology and final kinematics. With this purpose, we developed a 2D Fokker-Planck analytical code, which results we confirm by detailed N-Body techniques, applying a high performance code, developed for GPU machines. We compare our models to available observations of galactic rotating globular clusters, and conclude that initial rotation modifies significantly the shape and lifetime of these systems, and can not be neglected in studying the evolution of globular clusters, and the galaxy itself.

scholarly journals Neutron Stars in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 316-320 ◽  
Author(s):  
N. Ivanova ◽  
C. O. Heinke ◽  
F. Rasio
Keyword(s):  
Neutron Stars ◽  
Numerical Simulations ◽  
Globular Clusters ◽  
Stellar Systems ◽  
Large Scatter ◽  
X Ray ◽  
Dynamical Properties ◽  
X Ray Binaries ◽  
Collision Number ◽  
Good Agreement

AbstractDynamical interactions that occur between objects in dense stellar systems are particularly important for the question of formation of X-ray binaries. We present results of numerical simulations of 70 globular clusters with different dynamical properties and a total stellar mass of 2×107M⊙. We find that in order to retain enough neutron stars to match observations we must assume that NSs can be formed via electron-capture supernovae. Our simulations explain the observed dependence of the number of LMXBs on “collision number” as well as the large scatter observed between different globular clusters. For millisecond pulsars, we obtain good agreement between our models and the numbers and characteristics of observed pulsars in the clusters Terzan 5 and 47 Tuc.

scholarly journals A Survey on Parallel Computing and its Applications in Data-Parallel Problems Using GPU Architectures

2014 ◽  
Vol 15 (2) ◽  
pp. 285-329 ◽  
Author(s):  
Cristóbal A. Navarro ◽  
Nancy Hitschfeld-Kahler ◽  
Luis Mateu
Keyword(s):  
Parallel Computing ◽  
High Performance ◽  
Gpu Computing ◽  
Computational Physics ◽  
Processing Unit ◽  
Desktop Computer ◽  
Important Place ◽  
Massive Parallelism ◽  
Data Parallel ◽  
Physics Problems

AbstractParallel computing has become an important subject in the field of computer science and has proven to be critical when researching high performance solutions. The evolution of computer architectures (multi-coreandmany-core) towards a higher number of cores can only confirm that parallelism is the method of choice for speeding up an algorithm. In the last decade, the graphics processing unit, or GPU, has gained an important place in the field of high performance computing (HPC) because of its low cost and massive parallel processing power. Super-computing has become, for the first time, available to anyone at the price of a desktop computer. In this paper, we survey the concept of parallel computing and especially GPU computing. Achieving efficient parallel algorithms for the GPU is not a trivial task, there are several technical restrictions that must be satisfied in order to achieve the expected performance. Some of these limitations are consequences of the underlying architecture of the GPU and the theoretical models behind it. Our goal is to present a set of theoretical and technical concepts that are often required to understand the GPU and itsmassive parallelismmodel. In particular, we show how this new technology can help the field ofcomputational physics,especially when the problem isdata-parallel.We present four examples of computational physics problems;n-body, collision detection, Potts modelandcellular automatasimulations. These examples well represent the kind of problems that are suitable for GPU computing. By understanding the GPU architecture and its massive parallelism programming model, one can overcome many of the technical limitations found along the way, design better GPU-based algorithms for computational physics problems and achieve speedups that can reach up to two orders of magnitude when compared to sequential implementations.

Creep Behavior of High-Performance Concrete

2014 ◽  
Vol 919-921 ◽  
pp. 1885-1889
Author(s):  
Xue Yu Xiong ◽  
Li Jun Wang ◽  
Rong Jun Xue ◽  
Sen Zhang
Keyword(s):  
High Performance ◽  
Prediction Models ◽  
High Performance Concrete ◽  
Creep Tests ◽  
Conventional Concrete ◽  
Data Points ◽  
Improved Model ◽  
Realistic Prediction ◽  
Good Agreement

Realistic prediction of concrete creep is of crucial importance for the safety, durability and long term serviceability of concrete structures. High performance concrete (HPC) contains combinations of various components, such as aggregate, cement, water-reducing agent and other ingredients which affect the properties of the HPC including creep. This paper reviews the accuracy of the conventional concrete (CC) creep prediction models, including B3,GL2000 and CEB-FIP(2010). Further, a new creep prediction model based on the comprehensive analysis is proposed. The improved model was calibrated through a joint optimization of laboratory creep tests. Comparisons of the results of the proposed methold with 76 data points of creep coefficient showes good agreement.

scholarly journals Eclipsing Binaries in Dynamically Interacting Close, Multiple Systems

Galaxies ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Tamás Borkovits
Keyword(s):  
Orbital Period ◽  
Eclipsing Binaries ◽  
Detection Methods ◽  
Stellar Systems ◽  
Short Term ◽  
Multiple Star ◽  
Multiple Systems ◽  
History Of ◽  
Dynamical Information

Close, compact, hierarchical, and multiple stellar systems, i.e., multiples having an outer orbital period from months to a few years, comprise a small but continuously growing group of the triple and multiple star zoo. Many of them consist of at least one eclipsing pair of stars and, therefore, exhibit readily observable short-term dynamical interactions among the components. Thus, their dynamical and astrophysical properties can be explored with high precision. In this paper we present an overview of the history of the search for additional components around eclipsing binaries from the first serendipitous discoveries to more systematic recent studies. We describe the different observational detection methods and discuss their connections to the different kinds of astrophysical and dynamical information that can be mined from different datasets. Moreover, the connection amongst the observable phenomena and the long-term dynamics of such systems is also discussed.

A High Performance Image Processing Unit for On-orbit Servicing

2006 ◽  
Author(s):  
Hiroshi Yamamoto ◽  
Yasufumi Nagai ◽  
Shinichi Kimura ◽  
Hiroshi Takahashi ◽  
Satoko Mizumoto ◽  
...  
Keyword(s):  
Image Processing ◽  
High Performance ◽  
Processing Unit

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

2019 ◽  
Author(s):  
Zhao-Yang Zhang ◽  
Tao LI
Keyword(s):  
Energy Density ◽  
Solar Energy ◽  
High Performance ◽  
High Energy ◽  
Solar Thermal ◽  
High Energy Density ◽  
Low Grade ◽  
Thermal Battery ◽  
Low Grade Heat

Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

2019 ◽  
Author(s):  
Zhao-Yang Zhang ◽  
Tao LI
Keyword(s):  
Energy Density ◽  
Solar Energy ◽  
High Performance ◽  
High Energy ◽  
Solar Thermal ◽  
High Energy Density ◽  
Low Grade ◽  
Thermal Battery ◽  
Low Grade Heat

Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

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