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Einstein Probe discovery of EP240408a: A peculiar X-ray transient with an intermediate timescale

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 222-240页

作者： Wenda zhang Weimin Yuan Zhixing Ling Yong Chen Nanda Rea Arne Rau Zhiming Cai Huaqing Cheng Francesco Coti Zelati Lixin Dai Jingwei Hu Shumei Jia Chichuan Jin Dongyue Li Paul O’Brien Rongfeng Shen Xinwen Shu Shengli Sun Xiaojin Sun Xiaofeng Wang Lei Yang Bing zhang Chen zhang Shuang-Nan zhang Yonghe zhang Jie An David Buckley Alexis Coleiro Bertrand Cordier Liming Dou Rob Eyles-Ferris Zhou Fan Hua Feng Shaoyu Fu Johan P.U.Fynbo Lluis Galbany Saurabh W.Jha Shuaiqing Jiang Albert Kong Erik Kuulkers Weihua Lei Wenxiong Li Bifang Liu Mingjun Liu Xing Liu Yuan Liu Zhu Liu Chandreyee Maitra Alessio Marino Itumeleng Monageng Kirpal Nandra Jeremy Sanders Roberto Soria Lian Tao Junfeng Wang Song Wang Tinggui Wang Zhongxiang Wang Qingwen Wu Xuefeng Wu Dong Xu Yanjun Xu Suijian Xue Yongquan Xue zijian zhang Zipei Zhu Hu Zou Congying Bao Fansheng Chen Houlei Chen Tianxiang Chen Wei Chen Yehai Chen Yifan Chen Chenzhou Cui Weiwei Cui Yanfeng Dai Dongwei Fan Ju Guan Dawei Han Dongjie Hou Haibo Hu Maohai Huang Jia Huo Zhenqing Jia Bowen Jiang Ge Jin Chengkui Li Junfei Li Longhui Li Maoshun Li Wei Li Zhengda Li Tianying Lian Congzhan Liu Heyang Liu Huaqiu Liu Fangjun Lu Laidan Luo Jia Ma Xuan Mao Haiwu Pan Xin Pan Liming Song Hui Sun Yunyin Tan Qingjun Tang Yihan Tao Hao Wang Juan Wang Lei Wang Wenxin Wang Yilong Wang Yusa Wang Qinyu Wu Haitao Xu Jingjing Xu Xinpeng Xu Yunfei Xu Zhao Xu Changbin Xue Yulong Xue Ailiang Yan Haonan Yang Xiongtao Yang Yanji Yang Juan zhang Mo zhang Wenjie zhang Zhen zhang Zhen zhang Ziliang zhang Donghua Zhao Haisheng Zhao Xiaofan Zhao zijian Zhao Hongyan Zhou Yilin Zhou Yuxuan Zhu Zhencai Zhu National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Sciences University of Chinese Academy of Sciences Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Institute of Space Sciences (ICE) CSIC Institut d’Estudis Espacials de Catalunya (IEEC) Max Planck Institute for Extraterrestrial Physics Innovation Academy for Microsatellites Chinese Academy of Sciences Department of Physics University of Hong Kong School of Physics and Astronomy University of Leicester School of Physics and Astronomy Sun Yat-sen University Department of Physics Anhui Normal University Shanghai Institute of Technical Physics Chinese Academy of Sciences Physics Department Tsinghua University Nevada Center for Astrophysics University of Nevada Las Vegas Department of Physics and Astronomy University of Nevada Las Vegas South African Astronomical Observatory Department of Astronomy University of Cape Town Department of Physics University of the Free State Université Paris Cité CNRS Astroparticule et Cosmologie Université Paris Cité CEA Paris-Saclay IRFU/DAp-AIM Department of Astronomy Guangzhou University Cosmic Dawn Center (DAWN) Niels Bohr Institute University of Copenhagen Department of Physics and Astronomy Rutgers the State University of New Jersey Institute for Cosmic Ray Research The University of Tokyo ESA/ESTEC Department of Astronomy School of Physics Huazhong University of Science and Technology INAF-Osservatorio Astrofisico di Torino Sydney Institute for Astronomy School of Physics The University of Sydney Department of Astronomy Xiamen University Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Department of Astronomy University of Science and Technology School of Astronomy and Space Sciences University of Science and Technology of China Institute of Deep Space Sciences Deep Space Exploration Laboratory Department of Astronomy School of Physics and Astronomy Yunnan University Shanghai Astronomical Observatory Chi

We report the discovery of a peculiar X-ray transient,EP240408a,by Einstein Probe （EP） and follow-up studies made with EP,Swift,NICER,GROND,ATCA and other ground-based multiwavelength *** new transient was first detected with Wide-field X-ray Telescope （WXT） on board EP on April 8th,2024,manifested in an intense yet brief X-ray flare lasting for *** flare reached a peak flux of 3.9×10-9erg cm-2s-1in 0.5-4 ke V,～300 times brighter than the underlying X-ray emission detected throughout the *** and more precise follow-up observations by EP/FXT,Swift and NICER confirmed the finding of this new *** X-ray spectrum is non-thermal in 0.5-10 ke V,with a power-law photon index varying *** X-ray light curve shows a plateau lasting for ～4 d,followed by a steep decay till becoming undetectable ～10 d after the initial *** on its temporal property and constraints from previous EP observations,an unusual timescale in the range of 7-23 d is found for EP240408a,which is intermediate between the commonly found fast and long-term *** counterparts have been found in optical and near-infrared,with the earliest observation at 17 h after the initial X-ray detection,suggestive of intrinsically weak emission in these *** demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far,by comparison with,in particular,jetted tidal disruption events,gamma-ray bursts,X-ray binaries and fast blue optical *** nature of EP240408a thus remains an *** suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of～10 *** detection and follow-ups of more of such objects are essential for revealing their origin.

关键词： X-ray transients ${\bm~{Einstein~~Probe}}$

Joint Beamforming Design for RIS-Assisted Cell-Free Network with Multi-Hop Transmissions

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Tsinghua Science and Technology 2023年第6期28卷 1115-1127页

作者： Decai Shen zijian zhang Linglong Dai Department of Electronic Engineering Tsinghua UniversityBeijing 100084China Beijing National Research Center for Information Science and Technology(BNRist) Beijing 100084China

The collaboration of multiple Reconfigurable Intelligent Surfaces(RISs)and Access Points(APs)enjoys advantages of capacity enhancement,power saving,etc.,making the RIS-assisted cell-free network an important architecture for future *** to most existing works on RIS-assisted communications,the multi-hop link among RISs,i.e.,the reflecting link including more than one RISs,is usually ignored in RIS-assisted cell-free *** these scenarios,however,since multiple RISs are closely deployed,we find that the multi-hop channels should not be simply ignored due to their potential for capacity ***,to the best of our knowledge,there is no work exploring the multi-hop transmission of RIS-assisted cell-free *** fill in this blank,we investigate the multi-hop transmission of RIS-assisted cell-free networks,including the multi-hop channel model and the corresponding beamforming ***,we propose a general multi-hop transmission model,which takes the direct links,single-reflecting links,and multi-hop links into *** on this model,we formulate a beamforming design problem in an RIS-assisted cell-free network,which allows us to maximize the multi-user sum-rate with considering the impact of multi-hop *** address the non-convexity of the formulated problem,a joint active and passive beamforming scheme is proposed to solve the ***,by utilizing fractional programming,we decouple the coupled beamforming parameters in the problem,and then these parameters are alternately optimized until the convergence of the *** results verify that the consideration for multi-hop links is necessary,and the capacity performance of the proposed scheme is 20%higher than those of the existing schemes.

关键词： Reconfigurable Intelligent Surface(RiS) cell-free network multi-hop transmissions beamforming

Fine-tuning cell organelle dynamics during mitosis by small GTPases

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Frontiers of Medicine 2022年第3期16卷 339-357页

作者： zijian zhang Wei zhang Quentin Liu Sun Yat-sen University Cancer Center State Key Laboratory of Oncology in South ChinaCollaborative Innovation Center for Cancer MedicineGuangzhou 510060China Department of Clinical Immunology The Third Affiliated HospitalSun Yat-sen UniversityGuangzhou 510630China Institute of Cancer Stem Cell Dalian Medical UniversityDalian 116044China

During mitosis,the allocation of genetic material concurs with organelle transformation and *** coordination of genetic material inheritance with organelle dynamics directs accurate mitotic progression,cell fate determination,and organismal *** GTPases belonging to the Ras superfamily regulate various cell organelles during *** the key regulators of membrane dynamics,the dysregulation of small GTPases is widely associated with cell organelle disruption in neoplastic and non-neoplastic diseases,such as cancer and Alzheimer’s *** discoveries shed light on the molecular properties of small GTPases as sophisticated modulators of a remarkably complex and perfect adaptors for rapid structure *** review collects current knowledge on small GTPases in the regulation of cell organelles during mitosis and highlights the mediator role of small GTPase in transducing cell cycle signaling to organelle dynamics during mitosis.

关键词： small GTPase cell organelle mitosis

Irradiation behaviors of two novel single-phase bcc-structure high-entropy alloys for accident-tolerant fuel cladding

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Journal of Materials Science & Technology 2021年第25期84卷 230-238页

作者： zijian zhang En-Hou Han Chao Xiang Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China School of Materials Science and Engineering Northeastern UniversityShenyang110819China

High-entropy alloys(HEAs)are potential alternative materials for accident-tolerant fuel cladding due to their excellent irradiation resistance and high-temperature corrosion *** this work,two novel body-centered cubic(bcc)structured Mo_(0.5)Nb Ti VCr_(0.25)and Mo_(0.5)Nb Ti V_(0.5)Zr_(0.25)HEAs were ***-ion irradiation was performed on the two HEAs to simulate neutron irradiation,and the crystal structure,hardness,and microstructure evolution were *** crystal structure of the Mo_(0.5)NbTiVCr_(0.25)HEA remained stable at low fluences,while amorphization may occur at high fluences in the two *** irradiation hardening value of the Mo_(0.5)NbTiVCr_(0.25)was 0.77 GPa at fluences of 1×10^(17)ions/cm^(2)and 1.49 GPa at fluences of 5×10^(17)ions/cm^(2),while the hardening value of the Mo_(0.5)NbTiV_(0.5)Zr_(0.25)was 1.36 GPa at ion fluences of 5×10^(17)ions/cm^(2).In comparison with most of the conventional alloys,the two HEAs showed slight irradiation *** helium bubbles and dislocation loops with small size were observed in the two HEAs after *** is the first time to report the formation of a dislocation loop in bcc-structure HEAs after ***,voids and precipitates were not observed in the two HEAs which could be ascribed to the high lattice distortion and compositional complexity of *** research revealed that the two HEAs show outstanding irradiation resistance,which may be promising accident-tolerant fuel cladding materials.

关键词： High-entropy alloy Accident-tolerant fuel cladding Helium-ion irradiation Microstructure Irradiation hardening

Effect of Nb Content on Microstructure and Mechanical Properties of Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nbx High-Entropy Alloys

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Acta Metallurgica Sinica(English Letters) 2022年第10期35卷 1641-1652页

作者： Fengqi zhang Chao Xiang En-Hou Han zijian zhang Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang110016China Institute of Corrosion Science and Technology Guangzhou510530China

High-entropy alloys(HEAs)have significant application prospects as promising candidate materials for nuclear industry due to their excellent mechanical properties,corrosion resistance and irradiation *** this work,the Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x)(x=0,0.25,0.5,0.75 and 1.0)HEAs were designed and *** alloys were prepared by vacuum arc melting,and all the ingots were annealed at 1200℃ for 24 *** microstructures,crystal structures,hardness and mechanical properties of Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x) HEAs were *** as-cast alloys are composed of single BCC ***,the single BCC phase is retained after annealing at 1200℃ for 24 *** compressive and microhardness tests show that the strength and hardness of the alloys decrease gradually with the increase of Nb content,while the plasticity increases and the fracture mode of the alloy changes from brittle fracture to ductile fracture,which is mainly owing to the decrease of grain *** addition of Nb significantly improves the plasticity of the Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x) *** particular,Nb1.0 alloy can reach 28.32%strain without fracture,which exhibits promising potential in industrial application.

关键词： High-entropy alloy CALPHAD Microstructure Hardness Mechanical properties

A theoretical method for solving shock relations coupled with chemical equilibrium and its applications

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Chinese Journal of Aeronautics 2022年第6期35卷 47-62页

作者： zijian zhang Chihyung WEN Wenshuo zhang Yunfeng LIU Zonglin JIANG Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic UniversityHong KongChina Institute of Mechanics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

In this study,a theoretical method is proposed to solve shock relations coupled with chemical *** only shock waves in dissociated flows but also detonation waves in combustive mixtures can be *** global iterative solving process is specially designed to mimic the physical and chemical process in reactive shock waves to ensure good stability and fast convergence in the proposed *** each global step,the single-variable equations of normal and oblique shock relations are derived and solved with the Newton iteration method to reduce the complexity of the problems,and the minimization of free energy method of NASA(National Aeronautics and Space Administration)is adopted to solve equilibrium *** is demonstrated that the convergent process is stable and very close to the real chemical-kinetic process,and high accuracy is achieved in the solutions of normal and oblique reactive shock ***,the proposed theoretical method has also been applied to many problems associated with reactive shocks,including the stability of oblique detonation wave,bow detonation over a sphere,and shock reflection in dissociated *** great importance of using chemical equilibrium to theoretically predict the theoretical range of the wedge angle for a standing oblique detonation wave(the standing window of the oblique detonation wave),the stand-off distance of bow detonation wave and the transition criterion of shock reflection in dissociated air with high accuracy have been addressed.

关键词： Chemical equilibrium Detonation Dissociated air Shock relation Theoretical solution

Mission-oriented cooperative 3D path planning for modular solar-powered aircraft with energy optimization

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Chinese Journal of Aeronautics 2022年第1期35卷 98-109页

作者： Xiangyu WANG Yanping YANG Dong WANG zijian zhang The Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Army Academy of Artillery and Air Defense Hefei 230031China

Modular Solar-Powered Aircraft(M-SPA)is a kind of High-Altitude Long-Endurance(HALE)aircraft which exploits the mission advantage of swarm UAV and the HALE advantage of large aspect-ratio SPA.M-SPA’s separated mode and combined mode give it the potential to maximize the mission efficiency with limited solar *** this paper,firstly,oriented by the mission of maximizing the cruise area,the overall design of the M-SPA is modeled,including the energy model,the aerodynamic model and the flight environment ***,by analyzing the energy consumption of the flight modes,we design a multi-phase flight mission ***,a 24-hour three-dimensional(3D)flight profile of the M-SPA is optimized,including the sub-SPA cooperative path planning in the separation ***,inspired by the Traveling Salesman Problem(TSP),an improved Ant Colony Algorithm(ACA)is exploited to find the optimal path for each sub-SPA,which is further developed into a dynamic separation and combination scheme for the *** simulation results show that the mission performance of the M-SPA outperforms that of the conventional SPA,and explicitly,the mission coverage of the M-SPA is slightly less than a linear increase under comparable simulation conditions.

关键词： 3D path planning Ant colony optimization Energy optimization Modular Solar-Powered Aircraft(M-SPA) Separated and combined strategy

Integrated batteries layout and structural topology optimization for a solar-powered drone

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Chinese Journal of Aeronautics 2021年第7期34卷 114-123页

作者： zijian zhang Ruitong zhang Jihong ZHU Tong GAO Fei CHEN Weihong zhang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China State IJR Center of Aerospace Design and Additive Manufacturing School of Mechanical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Institute of Intelligence Material and Structure Unmanned System TechnologiesNorthwestern Polytechnical UniversityXi’an 710072China

The purpose of this paper is to demonstrate an integrated optimization scheme for a solar-powered drone *** a primary beam in the wing of large aspect ratio,where 100 lithium batteries are *** the proposed integrated optimization,the batteries are considered here as parts of the load-carrying *** corresponding mechanical behaviors are simulated in the structural design and described with *** batteries layout and the structural topology are then introduced as mixed design variables and optimized simultaneously to achieve an accordant load-carrying *** nonlinearity is considered due to the large *** periodic structural configurations are tested in the optimization in order to meet the structural manufacturing and assembly *** optimized designs are rebuilt and tested in different load *** the same structural weight,the global mechanical performances are improved greatly compared with the initial design.

关键词： Geometrical nonlinearity Integrated optimization Lithium batteries layout Periodic structural configuration Solar-powered drone Wing beam structure

Meter Reading Aggregation Scheme with Universally Symbolic Analysis for Smart Grid

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Chinese Journal of Electronics 2019年第3期28卷 577-584页

作者： QIU Hailing zhang zijian WANG Weiping zhang Rui ZHOU Yongbin ZHU Liehuang Institute of Information Engineering Chinese Academy of Sciences School of Computer Science Beijing Institute of Technology University

Millions of smart meters have been installed all around the world so far. The reported meter readings are conducive for utility companies to provide high quality of service. To efficiently and securely make use of those readings, data aggregation has been widely studied. Lu et al. proposed an Efficient and privacypreserving aggregation(EPPA) scheme for secure smart grid communications in recent years. Unfortunately, we found a man-in-the-middle attack to the EPPA scheme in this paper. We then propose a new meter reading aggregation scheme, namely Universally composable meter reading aggregation(UCMRA) scheme, in order to resist against that attack. Moreover, we give a universally composable symbolic analysis to prove the security for UCMRA scheme. This proof also enables the UCMRA scheme to adopt an alternative cryptographic primitive arbitrarily, as long as the primitive meets the requirements of the corresponding ideal functionality. Finally, the experiment results show that the performance of the UCMRA scheme is almost as good as that of the EPPA scheme.

关键词： Data aggregation Universally symbolic analysis Smart grid