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Influences of Hot-Isostatic-Pressing Temperature on the Microstructure, Tensile Properties and Tensile Fracture Mode of 2A12 Powder Compact

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Acta Metallurgica Sinica(English Letters) 2016年第10期29卷 963-974页

作者： gang wang Li-hui Lang Wen-Jun Yu Xi-Na Huang Fei Li School of Mechanical Engineering and Automation Beihang University Beijing 100191 China Avic Chengdu Aircraft Industrial (Group) Co. Ltd Chengdu 610000 China

2A12 aluminum alloy powders were hot-isostatic-pressed （HIPed） at representative temperatures for investi- gating the variation in microstructure, tensile property and fracture mode of the powder compact. It was found that the microstructure of raw powders changed from a dendrite structure to an equiaxed structure from room temperature to 600 ℃. The liquid phase produced by the eutectic reaction in the powder was gradually increased and finally formed a liquid pathway that ran through the entire powder from 490 to 600℃. Prior particle boundaries were observed in the powder compacts HIPed at 490 and 520℃. The liquid phase in the powder compacts was squeezed into the powder boundaries and the triple points of powder when HIPed at 580℃. However, the liquid phase located at the triple points of the powder was forced out and moved toward a small powder particle by HIP pressure under an HIPing temperature of 600℃, which led to a decrease in the mechanical properties and relative density. Better comprehensive properties were obtained at HIPing temperatures of 490 and 580℃. The low ductility exhibited by the P/M aluminum alloy HIPed at different temperatures was believed to arise from a combination of the existence of oxide film on the powder particle surface and the distribution characteristics of the liquid phase. Finally, three typical types of de-cohesion were classified.

关键词： Powder metallurgy Hot-isostatic-pressing Microstructural evolution Fracture mode Aluminum alloy Mechanical properties

Effect of solution treatment on the martensitic transformation behavior of a Ni_(43)Co_7Mn_(39)Sn_(11) polycrystalline alloy

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International Journal of Minerals,Metallurgy and Materials 2015年第6期22卷 620-626页

作者： Zhi-gang Wu hui-ying Li Frontier Institute of Science and Technology Xi'an Jiaotong University

The effect of solution treatment on the martensitic transformation behavior of a Ni43Co7Mn39Sn11 polycrystalline alloy fabricated by an arc melting method was investigated by scanning electron microscopy（SEM）, energy-dispersive X-ray spectroscopy（EDS）, and differential scanning calorimetry（DSC）. The examination indicates the presence of severe chemical segregation in the dendritic as-cast structure because of solidification. This chemical segregation completely impedes the intrinsic martensitic transformation. Annealing at 1223 K for 24 h is identified as the threshold annealing condition to eliminate the microstructural segregation and begin the martensitic transformation, as indicated by a broad and obscure feature. Annealing at 1273 K for 24–48 h is found to be effective at promoting notably the martensitic transformation, but the martensitic transformation exhibits a multiple-step feature. Complete homogeneity is achieved by annealing at 1273 K for 72 h, which produces a sharp, single-step martensitic transformation. The microstructural evolution and the valence electron concentrations of alloys（e/a ratio） are evaluated, which are reflective of the degree of compositional homogeneity of alloys, confirming that high annealing temperature and long holding time are vital to reveal the intrinsic martensitic behavior of this alloy. The adequately homogenized alloy displays a martensitic transformation at 292 K and an enthalpy of 11.2 J/g.

关键词： shape memory alloys annealing martensitic transformations homogeneity

RepoLike: a multi-feature-based personalized recommendation approach for open-source repositories

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Frontiers of Information Technology & Electronic Engineering 2019年第2期20卷 222-237页

作者： Cheng YANG Qiang FAN Tao wang gang YIN Xun-hui ZHANG Yue YU Hua-min wang Key Laboratory of Parallel and Distributed Computing National University of Defense Technology

With the deep integration of software collaborative development and social networking, social coding represents a new style of software production and creation paradigm. Because of their good flexibility and openness,a large number of external contributors have been attracted to the open-source communities. They are playing a significant role in open-source development. However, the open-source development online is a globalized and distributed cooperative work. If left unsupervised, the contribution process may result in inefficiency. It takes contributors a lot of time to find suitable projects or tasks from thousands of open-source projects in the communities to work on. In this paper, we propose a new approach called "RepoLike," to recommend repositories for developers based on linear combination and learning to rank. It uses the project popularity, technical dependencies among projects, and social connections among developers to measure the correlations between a developer and the given projects. Experimental results show that our approach can achieve over 25% of hit ratio when recommending 20 candidates, meaning that it can recommend closely correlated repositories to social developers.

关键词： Social coding Open-source software Personal recommendation GitHub

Schedulability analysis for linear transactions under fixed priority hybrid scheduling

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第6期9卷 776-785页

作者： Zhi-gang GAO Zhao-hui WU School of Computer Science and Technology Zhejiang University Hangzhou 310027 China

In hard real-time systems, schedulability analysis is not only one of the important means of guaranteeing the timelines of embedded software but also one of the fundamental theories of applying other new techniques, such as energy savings and fault tolerance. However, most of the existing schedulability analysis methods assume that schedulers use preemptive scheduling or non-preemptive scheduling. In this paper, we present a schedulability analysis method, i.e., the worst-case hybrid scheduling (WCHS) algorithm, which considers the influence of release jitters of transactions and extends schedulability analysis theory to timing analysis of linear transactions under fixed priority hybrid scheduling. To the best of our knowledge, this method is the first one on timing analysis of linear transactions under hybrid scheduling. An example is employed to demonstrate the use of this method. Experiments show that this method has lower computational complexity while keeping correctness, and that hybrid scheduling has little influence on the average worst-case response time (WCRT), but a negative impact on the schedulability of systems.

关键词： Real-time systems Hybrid scheduling Linear transactions Worst-case response time (WCRT) Schedulability analysis

Activation and pumping characteristics of Ti-Zr-V films deposited on narrow tubes

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Nuclear Science and Techniques 2021年第5期32卷 63-70页

作者： Bang-Le Zhu Xiao-Qin Ge Si-hui wang Wei Wei Yi-gang wang Gong-Fa Liu Yong wang National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China

Non-evaporable getter(NEG)films are an integral part of many particle *** films provide conductance-free evenly distributed pumping,a low thermal outgassing rate,and a low photon-and electron-stimulated *** characteristics make it an ideal solution for resolving the non-uniform pressure distribution in conductance-limited narrow vacuum *** this study,ternary Ti-Zr-V films were deposited on Si substrates and Ag-Cu(Ag 0.085 wt%)tubes with an inner diameter of 22 *** Ti-Zr-V films were prepared from an alloy target using the same DC magnetron sputtering *** compositions and corresponding chemical bonding states were analyzed by X-ray photoelectron spectroscopy after activation at different *** test particle Monte Carlo(TPMC)method was used to measure the sticking probability of the Ti-Zr-V film based on pressure readings during gas *** results indicate that activation commences at temperatures as low as 150℃and Ti~0,Zr~0,and V~0 exist on the surface after annealing at 180℃for 1 ***-Zr-V films can be fully activated at 180℃for 24 *** CO sticking probability reaches 0.15,with a pumping capacity of 1 monolayer.

关键词： Non-evaporable getter(NEG) Accelerator vacuum TPMC Activation temperature

Zoonotic origins of human coronavirus 2019(HCoV-19/SARS-CoV-2):why is this work important?

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Zoological Research 2020年第3期41卷 213-219页

作者： Gary Wong Yu-Hai Bi Qi-hui wang Xin-Wen Chen Zhi-gang Zhang Yong-gang Yao CAS Key Laboratory of Molecular Virology&Immunology Institut Pasteur of ShanghaiChinese Academy of SciencesShanghai 200031China Department of Microbiology-Infectiology and Immunology Laval UniversityQuebec G1V 4G2Canada CAS Key Laboratory of Pathogenic Microbiology and Immunology Institute of MicrobiologyCenter for Influenza Research and Early-warning(CASCIRE)CAS-TWAS Center of Excellence for Emerging Infectious Diseases(CEEID)Chinese Academy of SciencesBeijing 100101China State Key Laboratory of Virology Wuhan Institute of VirologyChinese Academy of SciencesWuhanHubei 430071China State key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan School of Life SciencesYunnan UniversityKunmingYunnan 650091China Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences and Yunnan Province Kunming Institute of ZoologyChinese Academy of SciencesKunmingYunnan 650223China Kunming College of Life Science University of Chinese Academy of SciencesKunmingYunnan 650204China KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases Kunming Institute of ZoologyChinese Academy of SciencesKunmingYunnan 650223China

The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by infection with human coronavirus 2019 (HCoV-19/SARS-CoV-2/2019-nCoV), is a global threat to the human population. Here, we briefly summarize the available data for the zoonotic origins of HCoV-19, with reference to the other two epidemics of highly virulent coronaviruses, SARSCoV and MERS-CoV, which cause severe pneumonia in humans. We propose to intensify future efforts for tracing the origins of HCoV-19, which is a very important scientific question for the control and prevention of the pandemic.

关键词： origin why is this work important HCoV-19/SARS-CoV-2 Zoonotic origins of human coronavirus 2019

Control strategy of maglev vehicles based on particle swarm algorithm

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Journal of Modern Transportation 2014年第1期22卷 30-36页

作者： hui wang gang Shen Jinsong Zhou Institute of Railway and Urban Mass Transit Tongji University

Taking a single magnet levitation system as theobject, a nonlinear numerical model of the vehicle–guidewaycoupling system was established to study the levitationcontrol strategies. According to the similarity in dynamics,the single magnet-guideway coupling system was simplifiedinto a magnet-suspended track system, and the correspondinghardware-in-loop test rig was set up usingdSPACE. A full-state-feedback controller was developedusing the levitation gap signal and the current signal, andcontroller parameters were optimized by particle swarmalgorithm. The results from the simulation and the test rigshow that, the proposed control method can keep the systemstable by calculating the controller output with the fullstateinformation of the coupling system, Step responsesfrom the test rig show that the controller can stabilize thesystem within 0.15 s with a 2 % overshot, and performswell even in the condition of violent external *** the linear quadratic optimal method, the particleswarm algorithm carries out the optimization with thenonlinear controlled object included, and its optimizedresults make the system responses much better.

关键词： Maglev control Vehicle–guideway couplingvibration Particle swarm algorithm Full-state feedback

Experimental study of temperature dependence of single-event upset in SRAMs

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Nuclear Science and Techniques 2016年第1期27卷 93-97页

作者： Li Cai gang Guo Jian-Cheng Liu hui Fan Shu-Ting Shi hui wang Gui-Liang wang Dong-Jun Shen Ning hui An-Lin He China Institute of Atomic Energy Beijing 102413China

We report on the temperature dependence of single-event upsets in the 215–353 K range in a 4M commercial SRAM manufactured in a 0.15-lm CMOS process,utilizing thin film transistors. The experimental results show that temperature influences the SEU cross section on the rising portion of the cross-sectional curve(such as the chlorine ion incident). SEU cross section increases 257 %when the temperature increases from 215 to 353 K. One of the possible reasons for this is that it is due to the variation in upset voltage induced by changing temperature.

关键词：温度依赖性单粒子翻转 SRAM 实验截面曲线薄膜晶体管工艺制造 CMOS

Effects of Shot Peening Process on Thermal Cycling Lifetime of TBCs Prepared by EB-PVD

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Chinese Journal of Aeronautics 2007年第2期20卷 145-147页

作者： ZHOU Zhao-hui GONG Sheng-kai LI He-fei XU hui-bin ZHANG Chun-gang wang Lu School of Materials Science and Engineering Beij＇ing University of Aeronautics and Astronautics Beij＇ing 100083 China Shenyang Liming.4ero-Engine Group Corporation Shenyang 110043 China

Conventional two-layered thermal barrier coatings （TBCs） are prepared by electron beam physical vapor deposition （EB-PVD） with ZrO2-8 wt% Y2O3 （8YSZ） as top coat and CoCrAlY as bond coat on disk-shaped Ni based super-alloy. In this paper, three kinds of shot peening process with different lengths of operating time were adopted for bond coating. As a result, changes took place in its surface roughness and the surface micro-hardness. A thermal cycling test at 1 273 Kx55 rain and another at room temperature for 5 min were performed to study the effects of shot peening process on the thermal cycling lifetime of TBCs. It is found that a moderate shot peening process will be able to prolong the life time. The oxidation dynamic of the as-processed TBCs basically accords with the parabolic rule, and the oxidation test also attests to the spallation between YSZ and thermal growth oxide （TGO） responsible mainly for the failure of TBCs.

关键词： thermal cycling lifetime shot peening thermal barrier coatings (TBCs)