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Performance analysis of parallel gravitational N-body codes on large GPU clusters

research in Astronomy and Astrophysics 2016年第1期16卷 89-100页

作者： Si-Yi Huang rainer Spurzem Peter Berczik National Astronomical Observatories and Key Laboratory of Computational Astrophysics Chinese Academy of Sciences Beijing 100012 China Kavli institute for Astronomy and Astrophysics Peking University Beijing 100871 China Main Astronomical Observatory Ukrainian National Academy of Sciences 03680 Kiev Ukraine astronomisches rechen-institut Zentrum fur Astronomie Universitat Heidelberg 69120 Heidelberg Germany

We compare the performance of two very different parallel gravitational N-body codes for astrophysical simulations on large Graphics Processing Unit（GPU） clusters, both of which are pioneers in their own fields as well as on certain mutual scales- NBODY6＋＋ and Bonsai. We carry out benchmarks of the two codes by analyzing their performance, accuracy and efficiency through the modeling of structure decomposition and timing measurements. We find that both codes are heavily optimized to leverage the computational potential of GPUs as their performance has approached half of the maximum single precision performance of the underlying GPU cards. With such performance we predict that a speed-up of200- 300 can be achieved when up to 1k processors and GPUs are employed simultaneously. We discuss the quantitative information about comparisons of the two codes, finding that in the same cases Bonsai adopts larger time steps as well as larger relative energy errors than NBODY6＋＋, typically ranging from10- 50 times larger, depending on the chosen parameters of the codes. Although the two codes are built for different astrophysical applications, in specified conditions they may overlap in performance at certain physical scales, thus allowing the user to choose either one by fine-tuning parameters accordingly.

关键词： methods: analytical -- methods: data analysis -- methods: numerical

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Interaction of diabatic processes, large-scale eddies and the mean atmospheric circulation over the Atlantic, Arctic and Eurasia

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Advances in Polar Science 2019年第2期30卷 81-92页

作者： ralf JAISEr D?rthe HANDOrf Klaus DETHLOff Alfred-Wegener-institut Helmholtz-Zentrum für Polar-und Meeresforschung

In the last decade, the atmospheric part of the climate system experienced a shift from pronounced zonal to stronger meridional flow configurations and regionally diverse changes and trends. The climate system shows complex interactions and nonlinear behavior, manifested in global warming, rising ocean temperatures and the retreat of Arctic sea ice. Although atmospheric trends and changes are observed, underlying processes are not well understood. In this study we diagnose the interaction of large-scale atmospheric eddies and the mean flow with respect to diabatic heating and cooling processes that impact on the atmospheric advection of heat. for this purpose, three-dimensional Eliassen-Palm flux theory is used in combination with an analysis of the thermodynamic equation, diabatic heating and cooling and heat advection. The most recent decades of observed winter climate are evaluated in terms of climatology and trends over the Atlantic, Arctic and Eurasia. The change of the atmospheric circulation and related processes differ between early and late winter. In early winter, the interaction of macro-turbulent eddies with the mean flow is inhibited at the Atlantic jet stream entrance region and atmospheric heat is meridionally advected into the Arctic, both related to strong high pressure anomalies. In late winter, these anomalies are inverted and a negative phase of the Arctic Oscillation with a more wavy mean flow and a tendency towards stronger meridionalization is observed.

关键词： diabatic heating heat advection wave-mean flow interactions North Atlantic Oscillation Arctic Oscillation sea ice climate change Arctic Amplification polar-mid-latitude linkages

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LIU TUNGSHENG'S PALAEOMAGNETIC LOESS rESEArCH IN SWITZErLAND

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第四纪研究 2009年第5期29卷 847-850页

作者： friedrich Heller institut für Geophysik ETH-zentrum CH-8092 Zürich

11月22日是刘东生先生的生日,在先生离开我们的一年多时间里,我们时刻在怀念他。这里我们刊登了刘先生的密友之一、瑞士的Heller教授的短文,怀念与刘先生一起研究黄土磁学的点点滴滴。本文是Heller教授为刘先生的纪念文集撰写的,但因故... 详细信息

11月22日是刘东生先生的生日,在先生离开我们的一年多时间里,我们时刻在怀念他。这里我们刊登了刘先生的密友之一、瑞士的Heller教授的短文,怀念与刘先生一起研究黄土磁学的点点滴滴。本文是Heller教授为刘先生的纪念文集撰写的,但因故未及在文集中刊出。现在本刊补登,除了表示对先生的深切怀念,也表示对Heller教授的感谢和歉意。

关键词：黄土磁学研究刘东

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Coordination of Schwann cell myelination and node formation at the transcriptional level

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Neural regeneration research 2022年第6期17卷 1269-1270页

作者： franziska fröb Michael Wegner institut für Biochemie Emil-Fischer-ZentrumFriedrich-Alexander-Universität Erlangen-NürnbergErlangenGermany

formation of the node of ranvier as a highly coordinated event:Saltatory conduction ensures that information in the vertebrate nervous system is rapidly transmitted over large distances and efficiently processed in complex *** requires the insulation of axonal segments by myelin and the formation of highly structured nodes of ranvier that are interspersed at regular intervals between successive myelin sheaths and regenerate the action potential as it propagates along the nerve(rasband and Peles,2021).

关键词： successive insulation conduction

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GalevNB:a conversion from N-body simulations to observations

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research in Astronomy and Astrophysics 2016年第3期16卷 1-10页

作者： Xiao-Ying Pang Christoph Olczak Di-feng Guo rainer Spurzem ralf Kotulla National Astronomical Observatories and Key Laboratory of Computational Astrophysics Chinese Academy of SciencesBeijing 100012China Shanghai institute of Technology Shanghai 201418China astronomisches rechen-institut Zentrum für Astronomie der Universitat HeidelbergMonchhofstr.12-1469120 HeidelbergGermany Kavli institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China Key Lab for Astrophysics Shanghai Normal UniversityShanghai 200234China Key Laboratory of frontiers in Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China Department of Astronomy University of Wisconsin-Madison475 N Charter StMadison WI 53706USA

We present GalevNB （Galev for N-body simulations）, a utility that converts fundamental stellar properties of N-body simulations into observational properties using the GALEV （GAlaxy EVolutionary synthesis models） package, and allowing direct comparisons between observations and N-body simulations. It works by converting fundamental stellar properties, such as stellar mass, temperature, luminosity and metallicity into observational magnitudes for a variety of filters used by mainstream instruments/telescopes, such as HST, ESO, SDSS, 2MASS, etc., and into spectra that span the range from far-UV （90 A） to near-Ir （160 ~tm）. As an application, we use Ga 1 evNB to investigate the secular evolution of the spectral energy distribution （SED） and color magnitude diagram （CMD） of a simulated star cluster over a few hundred million years. With the results given by GalevNB we discover a UV-excess in the SED of the cluster over the whole simulation time. We also identify four candidates that contribute to the fUV peak： core helium burning stars, second asymptotic giant branch （AGB） stars, white dwarfs and naked helium stars.

关键词： stars kinematics and dynamics -- stars C-M diagrams -- stars AGB and post-AGB -- stars white dwarf

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Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

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Journal of Magnesium and Alloys 2023年第2期11卷 543-552页

作者： Sang Kyu Woo risheng Pei Talal Al-Samman Dietmar Letzig Sangbong Yi institute of Materials and Process Design Helmholtz-Zentrum hereon21502 GeesthachtGermany institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany

Plastic instability, called Portevin-Le-Chatelier(PLC) effect, manifests itself as an unstable plastic flow during tensile tests of structural materials. This phenomenon has a strong influence on diverse properties, leading to unexpected vulnerabilities in the service *** various magnesium-based alloys, PLC phenomenon is most prominently observed in the Mg-Mn-Nd alloy under elevated temperature and low strain rate conditions. An important aim of the study is to clarify and compare the significance of the rE and Ca addition, which are known to cause a formation of a largely weakened non-basal type texture, in the occurrence of plastic instability. Due to the PLC phenomenon, there is a risk of weakening texture and formability improvement by the addition of rE and Ca elements in Mg alloys. Based on the understanding of the role of Nd to the PLC phenomenon in Mg-Mn alloy identified in previous studies, the PLC characteristics according to alloying elements and deformation conditions were compared and analyzed. To identify the micromechanical mechanisms of the PLC phenomenon, varies in the microstructure and mechanical properties during deformation of Mg-Mn binary and Ca or Nd-containing Mg-Mn-based ternary alloys in various conditions were systemically analyzed. The addition of Ca did not show a marked PLC effect due to the formation of low number density Mn-Ca and Ca-Ca solute clusters and an unbalanced Mn:Ca ratio. In contrast, the addition of Nd leads to the formation of a higher number density of Nd-Nd and Mn-Nd solute clusters than that of Ca-Ca and Mn-Ca solute clusters of the Mg-Mn-Ca alloy, resulting in a stable solute-dislocation interaction atmosphere under specific ranges of deformation temperature and strain rate. The deformation in the regime of PLC phenomenon, results in a decrease in ductility and an increase in strength, despite deformation at elevated temperatures with maintaining the weakened texture.

关键词： Magnesium Plastic instability Portevin-Le Chatelier effect Solute cluster Neodymium Calcium

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Type Ia Supernova Explosions in Binary Systems:A review

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research in Astronomy and Astrophysics 2023年第8期23卷 10-52页

作者： Zheng-Wei Liu friedrich K.röpke Zhanwen Han Yunnan Observatories Chinese Academy of Sciences(CAS)Kunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects CASKunming 650216China International Centre of Supernovae Yunnan Key LaboratoryKunming 650216China University of Chinese Academy of Sciences Beijing 100049China zentrum für astronomie der Universität Heidelberg Institut für Theoretische AstrophysikPhilosophenweg 12D-69120 HeidelbergGermany Heidelberger institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35D-69118 HeidelbergGermany

Type Ia supernovae(SNe Ia)play a key role in the fields of astrophysics and *** is widely accepted that SNe Ia arise from thermonuclear explosions of white dwarfs(WDs)in binary ***,there is no consensus on the fundamental aspects of the nature of SN Ia progenitors and their actual explosion *** fundamentally flaws our understanding of these important astrophysical *** this review,we outline the diversity of SNe Ia and the proposed progenitor models and explosion *** discuss the recent theoretical and observational progress in addressing the SN Ia progenitor and explosion mechanism in terms of the observables at various stages of the explosion,including rates and delay times,pre-explosion companion stars,ejecta–companion interaction,early excess emission,early radio/X-ray emission from circumstellar material interaction,surviving companion stars,late-time spectra and photometry,polarization signals and supernova remnant *** the efforts from both the theoretical and observational sides,questions of how the WDs reach an explosive state and what progenitor systems are more likely to produce SNe Ia remain *** single published model is able to consistently explain all observational features and the full diversity of SNe *** may indicate that either a new progenitor paradigm or an improvement in current models is needed if all SNe Ia arise from the same *** alternative scenario is that different progenitor channels and explosion mechanisms contribute to SNe *** the next decade,the ongoing campaigns with the James Webb Space Telescope,Gaia and the Zwicky Transient facility,and upcoming extensive projects with the Vera *** Observatory's Legacy Survey of Space and Time and the Square Kilometre Array will allow us to conduct not only studies of individual SNe Ia in unprecedented detail but also systematic investigations for different subclasses of SNe *** will advance theory and observation

关键词： (stars:)binaries(including multiple) close-methods numerical-(stars )supernovae general

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Sox9 in the developing central nervous system:a jack of all trades?

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Neural regeneration research 2021年第4期16卷 676-677页

作者： Julia K.Vogel Michael Wegner institut für Biochemie Emil-Fischer-ZentrumFriedrich-Alexander-Universität Erlangen-NürnbergErlangenGermany

Sox9–gliogenesis and beyond:Neurons and glial cells are the major neuroectodermal cell types of the vertebrate central nervous system(CNS).Their generation from common progenitor cells takes place mostly during embryonic and early postnatal *** closure of the neural tube,neural epithelial progenitor cells(NEPs)establish the ventricular zone(VZ).By asymmetrical cell division,NEPs first give rise to neuronal precursor cells(NPs)that then differentiate into various types of ***,NEPs predominantly produce glial precursor cells that become either astroglia or oligodendroglia.

关键词： development. mostly closure

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Analysis of opposing left-turn conflicts based on traffic conflict technology

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Journal of Beijing institute of Technology 2012年第4期21卷 487-491页

作者：毛琰王武宏郭伟伟丁晨曦夏塽辰 School of Mechanical Engineering Beijing Institute of Technology institut für Verkehssystemtechnik Deutsche Zentrum für Luft-und RaumfahrtLilienthalplatz 738108 BraunschweigGermany

The relationship between the opposing left-turn conflict and the traffic participants was analyzed in this study. Based on the traffic conflict technology, the image data were collected in a real traffic situation. The relationship was investigated under two different conditions. The number of opposing left-turn conflicts was positively correlated with the number of left-turn vehicles while the ratio of left-turn vehicles to opposing vehicles was less than 1, and showed a positive correlation with the number of opposing-through vehicles when the ratio of left-turn vehicles to opposing vehi- cles was more than 1. In other words, the opposing left-turn risk was positively correlated with the number of the minor traffic participants, which had a negative effect on the whole traffic system op- eration.

关键词： intersection traffic safety opposing left-turn conflict traffic conflicts technology

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Putting faces to Names： Snapshots of Two Committee Meetings, 95 Years Apart, Emphasize Continuous International Cooperation in the Atmospheric Sciences

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Advances in Atmospheric Sciences 2017年第5期34卷 571-575页

作者： Hans VOLKErT Deutsches zentrum für Luft- und raumfahrt lnstitut für Physik der Atmosphare 82234 Oberpfaffenhofen Germany

*** Spectacular advances have been made in the atmospheric sciences on a global level during a period of one hundred years or more,which is arguably most evident through"the quiet revolution of numerical weather predi... 详细信息

关键词： Co work Putting faces to Names:Snapshots of Two Committee Meetings,95 Years Apart,Emphasize Continuous International Cooperation in the Atmospheric Sciences

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