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

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 ${\bm~{Einstein~~Probe}}$

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Hierarchical closed form solutions for plates bent by localized transverse loadings

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第7期8卷 1026-1037页

作者： CARRERA E. GIUNTA G. BRISCHETTO S. aeronautical and space department Politecnico di Torino c.so Duca degli Abruzzi 24 10129 Torino Italy

3D and 2D closed form plate models are here applied to static analysis of simply supported square isotropic plates. 2D theories are hierarchically classified on the basis of the accuracy of the displacements and stresses obtained by comparison to the 3D exact results that could be assumed by the reader as benchmark for further analyses. Attention is mainly paid on localized loading conditions, that is, piecewise constant load. Also bi-sinusoidal and uniformly distributed loadings are taken into account. All of those configurations are considered in order to investigate the behavior of the 2D models in the case of continu- ous/uncontinuous, centric or off-centric loading conditions. The ratio between the side length a and the plate thickness h has been assumed as analysis parameter. Higher order 2D models yield accurate results for any considered load condition in the case of moderately thick plates, a/h=10. In the case of thick plates, a/h=5, and continuous/uncontinuous centric loading conditions high accuracy is also obtained. For the considered off-centric load condition and thick plates good results are provided for some output quantities. A better solution could be achieved by simply increasing the polynomial approximation order of the axiomatic 2D displacement field.

关键词： Exact 3D model Hierarchical 2D models Principle of Virtual Displacements (PVD) Localized loading Simply supported square isotropic plate

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Maximal capacity nonorthogonal pulse shape modulation

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Chinese Journal of Aeronautics 2015年第6期28卷 1699-1708页

作者： Chen Zhaonan Wang Hongxing Liu Xiguo Zhong Peilin department of Electrical and Information Engineering Naval Aeronautical and Astronautical University department of Basic Experiment Naval Aeronautical and Astronautical University

To improve spectral utilization of communication system, a novel nonorthogonal pulse shape modulation （NPSM） based on prolate spheroidal wave function （PSWF） is proposed. The modulation employs nonorthogonal PSWF pulses to transmit information and it shows a higher capacity than traditional orthogonal modulations. The NPSM capacity under the constraint of finite input alphabet, which is determined by parameters of PSWF pulse, is derived. An optimiza- tion model for maximal capacity of NPSM is constructed and an exhaustive self-adapting gradient search algorithm for the model is proposed. A practical NPSM scheme with the maximal capacity is obtained by this search algorithm and it is proved to be superior to orthogonal signaling in the capacity. Our theoretical analysis is validated by numerical simulations and practical tests, and the results show that NPSM outperforms orthogonal modulations in the capacity and has a lower Peak-to-Average Power Ratio.

关键词： capacity Modulation Orthogonality Prolate spheroidal wave function Quadrature amplitude modulation

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Turbulence modelling of the aerodynamic interaction ofOGV wakes and diffuser flow

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航空动力学报 2011年第10期26卷 2302-2312页

作者： Page Gary McGuirk Jim department of aeronautical and Automotive Engineering Loughborough University

Different turbulence closures were used to predict the flow interaction between the wakes created by compressor outlet guide vanes(OGVs) and a downstream annular *** statistical turbulence models were tested based on the classical Reynolds-averaged Navier-Stokes(RANS) *** high-Re and low-Re(Launder-Sharma) versions of the k-ε model were applied to a selected test problem for OGV wake/diffuser *** test problem was specifically chosen because experimentally determined inlet conditions and both profile and performance data were available to validate predictions.A preliminary study was also reported of the more advanced large eddy simulation(LES) *** LES sub-grid-scale(SGS) model was the basic Smagorinsky eddy viscosity assumption,with a Van-Driest damping function for improved capture of near-wall viscous *** between the two RANS models showed little difference in terms of velocity contours at OGV trailing edge and diffuser *** terms of overall diffuser performance(static pressure recovery and total pressure loss coefficients),the high-Re model was shown to agree well with experimental *** preliminary LES study indicates the highly unsteady character of the OGV wake flow,but requires improved treatment of inlet conditions.

关键词： outlet guide vane(OGV) wakes diffuser flow interaction Reynolds-averaged Navier-Stokes(RANS) modelling large eddy simulation(LES) modelling

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Design concepts of an aircraft wing： composite and morphing airfoil with auxetic structures

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Frontiers of Structural and Civil Engineering 2016年第4期10卷 394-408页

作者： P R BUDARAPU Sudhir Sastry Y B R NATARAJAN department of Aerospace Engineering Indian Institute of Science Bangalore 560 012 India department of aeronautical Engineering College of Engineering Defence University Ethiopia department of aeronautical Engineering Institute of Aeronautical Engineering Hyderabad India

This paper is categorized into two parts. （1） A frame work to design the aircraft wing structure and （2） analysis ofa morphing airfoil with auxetic structure. The developed design frame work in the first part is used to arrive at the sizes of the various components of an aircraft wing structure. The strength based design is adopted, where the design loads are extracted from the aerodynamic loads. The aerodynamic loads acting on a wing structure are converted to equivalent distributed loads, which are further converted point loads to arrive at the shear forces, bending and twisting moments along the wing span. Based on the estimated shear forces, bending and twisting moments, the strength based design is employed to estimate the sizes of various sections of a composite wing structure. A three dimensional numerical model of the composite wing structure has been developed and analyzed for the extreme load conditions. Glass fiber reinforced plastic material is used in the numerical analysis. The estimated natural frequencies are observed to be in the acceptable limits. Furthermore, the discussed design principles in the first part are extended to the design of a morphing airfoil with auxetic structure. The advantages of the morphing airfoil with auxetic structure are （i） larger displacement with limited straining of the components and （ii） unique deformation characteristics, which produce a theoretical in-plane Poisson＇s ratio of -1. Aluminum Alloy AL6061-T651 is considered in the design of all the structural elements. The compliance characteristics of the airfoil are investigated through a numerical model. The numerical results are observed to be in close agreement with the experimental results in the literature.

关键词： wing design aerodynamic loads morphing airfoil auxetic structures negative Poisson's ratio

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Rapid transfer alignment for SINS of carrier craft

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Journal of Systems Engineering and Electronics 2013年第2期24卷 303-308页

作者： Jingshuo Xu Yongjun Wang Zhicai Xiao Qingdao Campus of Naval aeronautical and Astronautical University department of Control Engineering Naval Aeronautical and Astronautical University

In order to improve the survival ability and rapid response ability of the carrier craft,a new rapid transfer alignment method of the strapdown inertial navigation system（SINS） on a rocking base is put *** the method,the aircraft carrier does not need any form of ***,interfering motions such as rolling,pitching,and yawing motions caused by sea waves are effectively ***,the deck flexure deformation model is ***,the state space model of transfer alignment is ***,the feasibility of this method is validated by the *** results show that the misalignment angle error can be estimated and reach an anticipated precision-0.2 mrad in 5 s,while the deck deformation angle error can be estimated and reach a better precision- 0.1 mrad in 20 s.

关键词： strapdown inertial navigation system(SINS) transfer alignment carrier aircraft carrier moored.

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A numerical optimization of high altitude testing facility for wind tunnel experiments

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Chinese Journal of Aeronautics 2015年第3期28卷 636-648页

作者： J.Bruce Ralphin Rose G.R.Jinu C.J.Brindha department of aeronautical Engineering Regional Centre of Anna University department of Mechanical Engineering University College of EngineeringNagercoil department of aeronautical Engineering The Raajas Engineering College

Abstract High altitude test facilities are required to test the high area ratio nozzles operating at the upper stages of rocket in the nozzle full flow conditions. It is typically achieved by creating the ambient pressure equal or less than the nozzle exit pressure. On average, air/GN2 is used as active gas for ejector system that is stored in the high pressure cylinders. The wind tunnel facilities are used for conducting aerodynamic simulation experiments at/under various flow velocities and operating conditions. However, constructing both of these facilities require more laboratory space and expensive instruments. Because of this demerit, a novel scheme is implemented for conducting wind tunnel experiments by using the existing infrastructure available in the high altitude testing （HAT） facility. This article presents the details about the methods implemented for suitably modifying the sub-scale HAT facility to conduct wind tunnel experiments. Hence, the design of nozzle for required area ratio A/A＊, realization of test section and the optimized configuration are focused in the present analysis. Specific insights into various rocket models including high thrust cryogenic engines and their holding mechanisms to conduct wind tunnel experiments in the HAT facility are analyzed. A detailed CFD analysis is done to propose this conversion without affecting the existing functional requirements of the HAT facility.

关键词： CFD Enclosed free-jet section Ground testing High altitude testing (HAT)facility Optimization

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A distributed cooperative guidance law for salvo attack of multiple anti-ship missiles

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Chinese Journal of Aeronautics 2015年第5期28卷 1438-1450页

作者： Zhang Youan Wang Xingliang Wu Huali department of Control Engineering Naval Aeronautical and Astronautical University

The consensus problem of impact time is addressed for multiple anti-ship missiles. A new distributed cooperative guidance law with the form of biased proportional navigation guidance （BPNG） is presented. The proposed guidance law employs the available measurements of relative impact time error as the feedback information to achieve the consensus of impact time among mis- siles and, by exploiting the special structure of the biased cooperative control term, it can handle the seeker＇s field-of-view （FOV） constraint. The proposed scheme ensures convergence to consensus of impact time under either fixed or switching sensing/communication network, and the topological requirements are less restrictive than those in the existing results. Numerical examples are provided to illustrate the effectiveness of the proposed guidance law.

关键词： Cooperative Distributed Field-of-view constraint Missile guidance Missile trajectory control

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Isothermal study of effusion cooling flows using a large eddy simulation approach

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航空动力学报 2009年第4期24卷 729-739页

作者： W.P.Bennett J.J.Mc Guirk aeronautical and Automotive Engineering department Loughborough University

An isothermal numerical study of effusion cooling flow is conducted using a large eddy simulation(LES) *** main types of cooling are considered,namely tangential film cooling and oblique patch effusion *** represent tangential film cooling,a simplified model of a plane turbulent wall jet along a flat plate in quiescent surrounding fluid is *** contrast to a classic turbulent boundary layer flow,the plane turbulent wall jet possesses an outer free shear flow region,an inner near wall region and an interaction region,characterised by substantial levels of turbulent shear stress *** shear stress characteristics hold significant implications for RANS modelling,implications that also apply to more complex tangential film cooling flows with non-zero free stream *** LES technique used in the current study provides a satisfactory overall prediction of the plane turbulent wall jet flow,including the initial transition region,and the characteristic separation of the zero turbulent shear stress and zero shear strain *** effusion patch cooling is modelled using a staggered array of 12 rows of effusion holes,drilled at 30° to the flat plate *** effusion holes connect two channels separated by the flat ***,these comprise of a channel representing the combustion chamber flow and a cooling air supply channel.A difference in pressure between the two channels forces air from the cooling supply side,through the effusion holes,and into the combustion chamber *** from successive effusion rows coalesces to form an aerodynamic film between the combustion chamber main flow and the flat *** practical applications,this film is used to separate the hot combustion gases from the combustion chamber *** numerical model is shown to be capable of accurately predicting the injection,penetration,downstream decay,and coalescence of the effusion *** addition,the numerical model captures entrainmen

关键词： effusion cooling large eddy simulation isothermal analysis film cooling turbulent wall jet

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Highly maneuvering target tracking using multi-parameter fusion Singer model

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Journal of Systems Engineering and Electronics 2017年第5期28卷 841-850页

作者： Shuyi Jia Yun Zhang Guohong Wang Research Institute of Information Fusion Naval Aeronautical and Astronautical University department of Aircraft Engineering Naval Aeronautical and Astronautical University

An algorithm of highly maneuvering target tracking is proposed to solve the problem of large tracking error caused by strong maneuver. In this algorithm, a new estimator, named as multi-parameter fusion Singer (MF-Singer) model is derived based on the Singer model and the fuzzy reasoning method by using radial acceleration and velocity of the target, and applied to the problem of maneuvering target tracking in strong maneuvering environment and operating environment. The tracking performance of the MF-Singer model is evaluated and compared with other manuevering tracking models. It is shown that the MF-Singer model outperforms these algorithms in several examples.

关键词： maneuvering target multi-parameter fusion Singer (MF-Singer) fuzzy reasoning Singer model

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