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Multi-Agent Deep Reinforcement Learning-Based Resource Allocation in HPC/AI Converged Cluster

Computers, Materials & Continua 2022年第9期72卷 4375-4395页

作者： Jargalsaikhan Narantuya jun-Sik Shin sun Park JongWon kim Department of Cloud Kakao Enterprise CorpSeongnam13494Korea AI Graduate School Gwangju Institute of Science and Technology(GIST)Gwangju61005Korea

As the complexity of deep learning(DL)networks and training data grows enormously,methods that scale with computation are becoming the future of artificial intelligence(AI)*** this regard,the interplay between machine learning(ML)and high-performance computing(HPC)is an innovative paradigm to speed up the efficiency of AI research and ***,building and operating an HPC/AI converged system require broad knowledge to leverage the latest computing,networking,and storage ***,an HPC-based AI computing environment needs an appropriate resource allocation and monitoring strategy to efficiently utilize the system *** this regard,we introduce a technique for building and operating a high-performance AI-computing environment with the latest ***,an HPC/AI converged system is configured inside Gwangju Institute of Science and Technology(GIST),called GIST AI-X computing cluster,which is built by leveraging the latest Nvidia DGX servers,high-performance storage and networking devices,and various open source ***,it can be a good reference for building a small or middlesized HPC/AI converged system for research and educational *** addition,we propose a resource allocation method for DL jobs to efficiently utilize the computing resources with multi-agent deep reinforcement learning(mDRL).Through extensive simulations and experiments,we validate that the proposed mDRL algorithm can help the HPC/AI converged cluster to achieve both system utilization and power consumption *** deploying the proposed resource allocation method to the system,total job completion time is reduced by around 20%and inefficient power consumption is reduced by around 40%.

关键词： Deep learning HPC/AI converged cluster reinforcement learning

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Estimation of deformed laser heat sources and thermal analysis on laser assisted turning of square member

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Journal of Central South University 2012年第2期19卷 402-407页

作者： kim Jae-hyun kim Kwang-sun CHOI jun-young LEE Choon-man Department of Mechanical Design and Manufacturing Engineering Changwon National University

Laser assisted machining （LAM） has difficulties in estimating temperature after applying a LAM process due to its very small heat input area, large energy and movement. In particular, in the case of laser assisted turning （LAT） process, it is more difficult to estimate the temperature after preheating because it has a shape of ellipse when a laser heat source is rotated. A prediction method and thermal analysis method for heat source shapes were proposed as a square shaped member was preheated. The temperature distribution was calculated according to the rotation of the member. Compared with the results of the former study, the maximum temperature of the calculation results, 1 407.1 ℃, is 8.5 ℃ higher than that of the square member, which is 1 398.6 ℃. In a LAT process for a square member, the maximum temperature is 1 850.8 ℃. It is recognized that a laser power control process is required because square members show a maximum temperature that exceeds a melting temperature at around a vertex of the member according to the rotation.

关键词： laser assisted machining laser assisted turning laser preheating laser power control

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A novel hybrid method for aerodynamic noise prediction of high-lift devices

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Chinese Journal of Aeronautics 2023年第9期36卷 151-161页

作者： jun TAO Gang sun Department of Aeronautics&Astronautics Fudan UniversityShanghai 200433China Key Laboratory of Aerodynamic Noise Control China Aerodynamics Research and Development CenterMianyang 621000China

Aerodynamic noise of High-Lift Devices(HLDs)is one of the main sources of airframe noise,and has immediate impacts on the airworthiness certification,environmental protection and security of commercial *** this study,a novel hybrid method is proposed for the aerodynamic noise prediction of HLD.A negative Spalart-Allmaras(S-A)turbulence model based Improved Delayed Detached Eddy Simulation(IDDES)method coupling with AFT-2017b transition model is developed,in order to elaborately simulate the complex flow field around the HLD and thus obtain the information of acoustic sources.A Farassat-Kirchhoff hybrid method is developed to filter the spurious noise sources caused by the vortex motions in solving the Ffowcs Williams-Hawkings(FW-H)equation with permeable integral surfaces,and accurately predict the far-field noise radiation of the *** results of the 30P30N HLD indicate that,the computational Sound Pressure Levels(SPLs)obtained by the Farassat-Kirchhoff hybrid method conform well with the experimental ones in the spectrum for the given observation point,and are more accurate than those obtained by the Farassat 1A *** on the hybrid method,the acoustic directivity of the HLD of a commercial aircraft is obtained,and the variation of the SPLs in the spectrum with the deflection angle of the slat is analyzed.

关键词： Aerodynamic noise Farassat-Kirchhoff hybrid method High-lift devices IDDES Negative S-A turbulence model

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How Many Pathways We Have for the Marine Carbon Neutrality

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Journal of Earth Science 2023年第5期34卷 1621-1623页

作者： jun sun Institute for Advanced Marine Research CUG Guangzhou 511462China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430078China College of Marine Science and Technology China University of GeosciencesWuhan 430074China

Global warming is one of the major challenges that the international community is currently *** Intergovernmental Panel on Climate Change(IPCC)has indicated that if the concentration of greenhouse gases in the atmosphere continues to rise,global warming is expected to pose risks to future food security,as well as to human health and wealth in the 21st *** became the world’s largest emitter of greenhouse gases in *** 2018,the global emission of greenhouse gases was 33.1 billion metric tons of CO_(2),with China accounting for 28%of the total global emission,ranking first *** to estimates by the Chinese Academy of Engineering,China will reach its peak carbon dioxide emissions in 2027 at 12.2 billion metric tons of CO_(2),making it imperative to achieve carbon neutrality and achieve harmony between humans and nature as soon as possible.

关键词： gases Marine harmony

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ENERGY ABSORPTION CONTROL CHARACTERISTICS OF AL THIN-WALLED TUBES UNDER IMPACT LOAD

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Acta Mechanica Solida Sinica 2008年第4期21卷 383-388页

作者： Kil-Stmg Lee Yong-jun Yang sun-Kyu kim In-Young Yang Department of Mechanical Design Engineering Chostrn University 375 Seosuk-dong Dong-gu Gwangju 501-759 Korea Department of Advanced Parts and Materials Engineering Graduate School Chosun University 375 Seosuk-dong Dong-gu Gwangju 501-759 Korea Department of Automobile Engineering Iksan National College 194-5 Ma-dong Iksan Chonbuk 570-752 Korea

An experimental investigation was carried out to study the energy absorption characteristics of thin-walled square tubes subjected to dynamic crushing by impact loading to develop the optimum structural members. Here, the controller is introduced to improve and control the absorbed energy of thin-walled square tubes in this paper. When the controller were used, the experimental results of crushing of square tubes controlled by the controller＇s elements showed a good candidate for a controllable energy absorption capability in impact crushing.

关键词： impact load Al thin-walled tubes energy absorption controller

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An artificial neural network approach for aerodynamic performance retention in airframe noise reduction design of a 3D swept wing model

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Chinese Journal of Aeronautics 2016年第5期29卷 1213-1225页

作者： Tao jun sun Gang School of Information Science and Technology Fudan University Shanghai 200433 China Department of Aeronautics & Astronautics Fudan University Shanghai 200433 China

With the progress of high-bypass turbofan and the innovation of silencing nacelle in engine noise reduction, airframe noise has now become another important sound source besides the engine noise. Thus, reducing airframe noise makes a great contribution to the overall noise reduction of a civil aircraft. However, reducing airframe noise often leads to aerodynamic performance loss in the meantime. In this case, an approach based on artificial neural network is introduced. An established database serves as a basis and the training sample of a back propagation （BP） artificial neural network, which uses confidence coefficient reasoning method for optimization later on. Then the most satisfactory configuration is selected for validating computations through the trained BP network. On the basis of the artificial neural network approach, an optimization pro- cess of slat cove filler （SCF） for high lift devices （HLD） on the Trap Wing is presented. Aerody- namic performance of both the baseline and optimized configurations is investigated through unsteady detached eddy simulations （DES）, and a hybrid method, which combines unsteady DES method with acoustic analogy theory, is employed to validate the noise reduction effect. The numerical results indicate not merely a significant airframe noise reduction effect but also excellent aerodynamic performance retention simultaneously.

关键词： Aerodynamic performanceretention Airframe noise Artificial neural network Noise reduction Slat cove filler

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Daily extreme precipitation and trends over China

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Science China Earth Sciences 2017年第12期60卷 2190-2203页

作者： sun jun ZHANG FuQing National Meteorological Center China Meteorological Administration Department of Meteorology and Atmospheric Sciences and Center for Advanced Data Assimilation and Predictability TechniquesPennsylvania State UniversityUniversity Park

Based on daily precipitation data of more than 2000 Chinese stations and more than 50 yr, we constructed time series of extreme precipitation based on six different indices for each station: annual and summer maximum(top-1) precipitation,accumulated amount of 10 precipitation maxima(annual, summer; top-10), and total annual and summer ***, we constructed the time series of the total number of stations based on the total number of stations with top-1 and top-10 annual extreme precipitation for the whole data period, the whole country, and six subregions, respectively. Analysis of these time series indicate three regions with distinct trends of extreme precipitation:(1) a positive trend region in Southeast China,(2) a positive trend region in Northwest China, and(3) a negative trend region in North China. Increasing(decreasing)ratios of 10–30% or even >30% were observed in these three regions. The national total number of stations with top-1 and top-10 precipitation extremes increased respectively by 2.4 and 15 stations per decade on average but with great inter-annual *** have been three periods with highly frequent precipitation extremes since 1960:(1) early 1960 s,(2) middle and late 1990 s,and(3) early 21 st century. There are significant regional differences in trends of regional total number of stations with top-1 and top-10 precipitation. The most significant increase was observed over Northwest China. During the same period, there are significant changes in the atmospheric variables that favor the decrease of extreme precipitation over North China: an increase in the geopotential height over North China and its upstream regions, a decrease in the low-level meridional wind from South China coast to North China, and the corresponding low moisture content in North China. The extreme precipitation values with a50-year empirical return period are 400–600 mm at the South China coastal regions and gradually decrease to less than 50

关键词： Extreme precipitation(EP) Extreme precipitation event(EPE) Time series Total annual number of stations Extreme event return level

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Long-lasting,reinforced electrical networking in a high-loading Li_(2)S cathode for high-performance lithium–sulfur batteries

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Carbon Energy 2023年第8期5卷 1-14页

作者： Hun kim Kyeong-jun Min Sangin Bang Jang-Yeon Hwang jung Ho kim Chong SYoon Yang-Kook sun Department of Energy Engineering Hanyang UniversitySeoulRepublic of Korea Department of Materials Science and Engineering Chonnam National UniversityGwangjuRepublic of Korea Institute for Superconducting&Electronic Materials(ISEM) Australian Institute of Innovative Materials(AIIM)University of WollongongNew South WalesNorth WollongongAustralia Department of Materials Science and Engineering Hanyang UniversitySeoulRepublic of Korea

Realizing a lithium sulfide(Li_(2)S)cathode with both high energy density and a long lifespan requires an innovative cathode design that maximizes electrochemical performance and resists electrode ***,a high-loading Li_(2)S-based cathode with micrometric Li_(2)S particles composed of two-dimensional graphene(Gr)and one-dimensional carbon nanotubes(CNTs)in a compact geometry is developed,and the role of CNTs in stable cycling of high-capacity Li–S batteries is *** a dimensionally combined carbon matrix,CNTs embedded within the Gr sheets create robust and sustainable electron diffusion pathways while suppressing the passivation of the active carbon *** a unique point,during the first charging process,the proposed cathode is fully activated through the direct conversion of Li_(2)S into S_(8) without inducing lithium polysulfide *** direct conversion of Li_(2)S into S_(8) in the composite cathode is ubiquitously investigated using the combined study of in situ Raman spectroscopy,in situ optical microscopy,and cryogenic transmission electron *** composite cathode demonstrates unprecedented electrochemical properties even with a high Li_(2)S loading of 10 mg cm^(–2);in particular,the practical and safe Li–S full cell coupled with a graphite anode shows ultra-long-term cycling stability over 800 cycles.

关键词： carbon nanotubes electrical network high energy high loading Li_(2)S cathode lithium-sulfur batteries

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Accelerated precipitation behavior of cast Mg-Al-Zn alloy by grain refinement

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Journal of Materials Science & Technology 2018年第2期34卷 265-276页

作者： Sang-Hoon kim Jong Un Lee Ye Jin kim jun Ho Bae Bong sun You sung Hyuk Park School of Materials Science and Engineering Kyungpook National University Implementation Research Division Korea Institute of Materials Science

This study demonstrates that the precipitation behavior of 13-Mg17Al12 phase during aging and the resultant variation in hardness and mechanical properties of cast Mg-Al-Zn alloy are strongly dependent on initial grain size. Grain size reduction accelerates discontinuous precipitation at the early stage of aging treatment by increasing the area fraction of grain boundaries that can act as nucleation sites for discontinuous precipitates （DP）, but it does not influence DP growth rate. Grain refinement also prematurely terminates continuous precipitation because the formation of a large number of DP reduces the amount of AI dissolved in the matrix, which is required for the formation of continuous precipitates （CP）. This promotion of DP formation and early termination of CP formation significantly decrease the peak-aging time to one-third. The enhanced precipitation behavior also leads to an additional hardness improvement in the aged alloy, along with an increase in hardness owing to grain boundary strengthening by grain refinement. The amount of increase in hardness changes with aging time, which is determined by the variation of three variables with aging time： DP fraction difference between refined and nonrefined alloys, hardness difference between DP and matrix, and matrix hardness difference between the two alloys. Grain refinement improves both tensile strength and ductility of the homogenized alloy owing to grain boundary strengthening and suppression of twinning activation, respectively. However, the loss of ductility after peak-aging treatment is greater in the refined alloy because of the larger amount of DP acting as a crack source in this alloy.

关键词： Magnesium Grain refinement Aging Precipitation Tensile properties

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Mechanical properties of molybdenum products prepared by using molybdenum powders with different micro-morphologies

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Rare Metals 2015年第4期34卷 276-281页

作者： Geng An jun sun Ren-Zhi Liu Jing Li Yuan-jun sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University Technical Center Jinduicheng Molybdenum Co. Ltd

Using two kinds of molybdenum （Mo） powders with different micro-morphologies as raw materials, the Mo wires with a diameter of 0.18 mm and Mo sheets with thickness of 0.5 and 0.2 mm were prepared at the same process of pressing, sintering, drawing, or rolling, respectively. By comparative analysis on the microstructure and mechanical properties of Mo wires and Mo sheets, the effect of Mo powder micro-morphology on properties and quality of Mo products was studied. The results show that, compared with that prepared by traditional Mo powder with inhomogeneous particle size and aggregation, the Mo wires prepared by specific Mo powder with homogeneous particle sizes, less agglomeration, and better dispersion exhibit higher yield, higher tensile strength, and lower elongation at room temperature, and the Mo sheets also show excellent high-temperature performances and better isotropy. The essential reason for those is the difference of Mo powder micro-morphology. Inhomogeneous particle size and aggregation of Mo powder greatly influence the microstructure of Mo sintered compacts and mechanical properties of Mo products.

关键词： Molybdenum powder Micro-morphology Aggregation Molybdenum product Mechanical property

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