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

Annual-perennial plant relationships and species selection for desert restoration

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Journal of Arid Land 2013年第3期5卷 298-309页

作者： Scott R ABELLA Stanley D SMITH department of Environmental and Occupational Health University of Nevada Las VegasLas VegasNevada 89154-3064USA School of Life Sciences University of Nevada Las VegasLas VegasNevada 89154-4004USA

Exotic plant invasion is a growing concern in the conservation and management of indigenous arid land ecosystems. By creating areas of ameliorated microclimates and fertile soil below their canopies, perennial plants might influence exotic annual plant invasions. We conducted a quantitative literature review of studies that compared exotic annual plant abundance among native perennial plant species and interspace （open areas） microsites in North America＇s Mojave Desert, where exotic plant invasion has corresponded with increasing extent of wildfire and broad-scale ecosystem transformation. Ten studies compared exotic annual plant abundance between inter- spaces and below a total of 36 native perennial species. These studies revealed that：（1） With few exceptions, most native perennial species supported a greater abundance of exotic annuals than interspaces, indicating overall facilitation of exotic species by native perennials. （2） Exotic species abundance varied by orders of magnitude among native perennial species, with some perennial species harboring amounts of exotics similar to interspaces. （3） Distributions of dominant exotic species varied, where Bromus rubens displayed a greater affinity for below-perennial microsites than did Schismus spp. and Erodium cicutarium that often were most abundant in interspaces. Results suggest that the degree of facilitation of exotic plants warrants consideration when selecting native perennial species for revegetation and restoration projects.

关键词： Bromus rubens exotic fertile island invasive nurse plant positive plant interaction Schismus

Geologic field evidence for non-lithostatic overpressure recorded in the North American Cordillera hinterland,northeast nevada

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geoscience Frontiers 2022年第2期13卷 471-490页

作者： Andrew V.Zuza Drew A.Levy Suzanne R.Mulligan nevada Bureau of Mines and Geology University of NevadaRenoNV 89557USA department of geoscience University of NevadaLas VegasNV 89154USA

There is a long-standing discrepancy for numerous North American Cordillera metamorphic core complexes between geobarometric pressures recorded in the exhumed rocks and their apparent burial depths based on palinspastic reconstructions from geologic field *** particular,metamorphic core complexes in eastern nevada are comprised of well-documented~12-15 km thick Neoproterozoic-Paleozoic stratigraphy of Laurentia’s western passive margin,which allows for critical characterization of field *** this contribution we focus on the Ruby Mountain-East Humboldt Range-Wood Hills-Pequop Mountains(REWP)metamorphic core complex of northeast nevada to explore reported peak pressure estimates versus geologic field relationships that appear to prohibit deep *** high pressure estimates of 6-8 kbar(23-30 km depth,if lithostatic)from the lower section of the Neoproterozoic-Paleozoic passive margin sequence require burial and or repetition of the passive margin sequence by 2-3×stratigraphic *** observations from the least migmatized and/or mylonitized parts of this complex,including field observations,a transect of peak-temperature(T_(p))estimates,and critical evaluation of proposed thickening/burial mechanisms cannot account for such deep *** Neoproterozoic-Cambrian(€)rocks part of a continuous stratigraphic section that transitions~8 km upsection to unmetamorphosed Permian strata that were not buried,we obtained new quartz-in-garnet barometry via Raman analysis that suggest pressures of~7 kbar(~26 km).A T_(p)traverse starting at the same basal€rocks reveals a smooth but hot geothermal gradient of≥40℃/km that is inconsistent with deep *** observation is clearly at odds with thermal gradients implied by high P-T estimates that are all≤25℃/*** similar discrepancies between pressure estimates and field observations have been discussed for the northern Snake Range metamorphic core complex,~200 km to the *** argue that

关键词： Non-lithostatic pressure Tectonic overpressure North American Cordillera Ruby Mountain-East Humboldt Range Peak temperature Geothermal gradient

Constraining Galactic pγ Interactions with Cosmic Ray Electron and Positron Spectra

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Chinese Journal of Astronomy and Astrophysics 2008年第2期8卷 153-158页

作者： Nayantara Gupta department of Physics university of nevada las vegas

High energy protons produced by various sources of cosmic rays, e.g., supernova remnants, pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, participate in pγ and pp interactions. Although pp interactions may be the dominant mechanism in our Galaxy, it is unclear how important Pγ process is. We show that the upper bound on the fraction of total number of protons participating in pγ interactions inside all Galactic astrophysical sources of cosmic rays is 10%.

关键词： Cosmic rays protons, electrons, positrons

SOLUTE TRANSPORT IN NATURAL FRACTURES BASED ON DIGITAL IMAGE TECHNOLOGY

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Journal of Hydrodynamics 2009年第2期21卷 219-227页

作者： TAN Ye-fei ZHOU Zhi-fang HUANG Yong College of Civil Engineering Hohai University Nanjing 210098 China The department of geoscience College of Science University of Nevada Las Vegas 89154 USA

A method of fracture boundary extraction was developed using the Gaussian template and Canny boundary detection on the basis of the collected digital images of natural fractures. The roughness and apertures of the fractures were briefly discussed from the point of view of digital image analysis. The extracted fractured image was translated into a lattice image which can be directly used in numerical simulation. The lattice Boltzmann and modified moment propagation mixed method was then applied to the simulation of solute transport in a natural single fracture, and this mixed method could take the advantages of the lattice Boltzmann method in dealing with complex physical boundaries. The obtained concentrations was fitted with the CXTFIT2.1 code and compared with the results obtained with the commercial software Feflow. The comparison indicates that the simulation using the mixed method is sound.

关键词： fracture solute transport digital image transaction boundary detection lattice Boltzmann method modified moment propagation method

The effects of exhaust air vent location on thermal comfort inside a residential building equipped with an evaporative cooling system

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Building Simulation 2021年第4期14卷 1063-1075页

作者： rmin Saraei Samir Farid Moujaes department of Mechanical Engineering College of EngineeringUniversity of Nevada Las VegasLas VegasNV89154USA

The location of exhaust air vents of an evaporative cooling system can have significant effects on providing thermal comfort and controlling humidity, temperature and air distribution in buildings. In the current study, four different strategies have been evaluated for exhaust air vent locations to provide the optimum thermal comfort inside a typical residential house. This study provides a numerical solution for temperature and relative humidity profiles in the residential house and within the living space in each room typically at a height of 1.8 m or less. By evaluating different exhaust air vent locations in a room, the best strategy(ies) to provide more appropriate thermal comfort condition and obtained and as a conclusion, the exhaust vents should be located on furthest wall away from the entrance of the room and in the middle. The results provided in the current study can eventually be applied in the design of evaporative cooler exhaust vent systems in residential buildings and lead to improve the performance of these systems.

关键词： thermal comfort CFD evaporative cooling system exhaust air vents

Simulation of the fluidic features for diffuser/nozzle involved in a PZT-based valveless micropump

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仪器仪表学报 2008年第1期29卷 1-4页

作者： HouWensheng Zheng Xiaolin Biswajit Das Jiang Yingtao Qian Shizhi Wu Xiaoying Zheng Zhigao department of Biomedical Engineering Chongqing University Chongqing 400044 China nevada Nanotechnology Center University of Nevada Las Vegas NV 89154 USA department of Electrical and Computer Engineering University of Nevada Las Vegas NV 89154 USA department of Mechanical Engineering University of Nevada Las Vegas NV 89154 USA

PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific *** this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with *** the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of *** L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/*** mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or *** simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.

关键词：流体系统模拟无阀微型泵散流器喷嘴

Evaluation of different Krylov subspace methods for simulation of the water faucet problem

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Nuclear Science and Techniques 2021年第5期32卷 1-16页

作者： Hong-Yang Wei Kevin Briggs Victor Quintanilla Yi-Tung Chen department of Mechanical Engineering University of NevadaLas VegasNV 89154USA

In this study,a one-dimensional two-phase flow four-equation model was developed to simulate the water faucet *** performance of six different Krylov subspace methods,namely the generalized minimal residual(GMRES),transpose-free quasi-minimal residual,quasi-minimal residual,conjugate gradient squared,biconjugate gradient stabilized,and biconjugate gradient,was evaluated with and without the application of an incomplete LU(ILU)factorization preconditioner for solving the water faucet *** simulation results indicate that using the ILU preconditioner with the Krylov subspace methods produces better convergence performance than that without the ILU *** the GMRES demonstrated an acceptable convergence performance under the Krylov subspace methods without the *** velocity and pressure distribution in the water faucet problem could be determined using the Krylov subspace methods with an ILU preconditioner,while GMRES could determine it without the need for a ***,there are significant advantages of using an ILU preconditioner with the GMRES in terms of *** different Krylov subspace methods showed similar performance in terms of computational efficiency under the application of the ILU preconditioner.

关键词： Water faucet problem Krylov subspace methods ILU preconditioner

Wireless actuation and control of ionic polymer-metal composite actuator using a microwave link

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International Journal of Smart and Nano Materials 2012年第4期3卷 244-262页

作者： J.S.Lee W.Yim C.Bae K.J.Kim department of Mechanical Engineering University of NevadaLas VegasUSA department of Chemistry University of NevadaLas VegasUSA department of Mechanical Engineering University of NevadaRenoUSA

The ionic polymer–metal composite(IPMC),a type of electroactive polymer(EAP)actuator,has created a unique opportunity to design robots that mimic the motion of biological systems due to its soft structure and operation at a low *** this polymer actuator has strong potential for a next-generation artificial muscle actuator,it has been observed by many researchers that supplying actuation voltages in multiple locations is *** robotic applications,a tethered operation is prohibited and the battery weight can be critical for actual *** this research,the remote unit can provide necessary power and control signals to the target mobile robot units actuated by *** research addresses a novel approach of using a wireless power link between the IPMC and a remote unit using microstrip patch antennas designed on the electrode surface of the IPMC for transmitting the *** modulation of the microwave is proposed to selectively actuate a particular portion of the IPMC where the matching patch antenna pattern is *** approach can be especially useful for long-term operation of small-scale locomotion units and avoids problems caused by complex internal wiring often observed in various types of biologically inspired robots.

关键词： ionic polymer-metal composite actuator microwave link wireless actuation robotic application biomimetic robot