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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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Evaluating current ethical values of OpenStreetMap using value sensitive design

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Geo-Spatial Information Science 2023年第3期26卷 362-378页

作者： Ruba Jaljolie Talia Dror David N.Siriba Sagi Dalyot Engineering Civil and Environmental EngineeringThe TechnionMapping and Geo-InformationTechnion CityIsrael department of geospatial and space technology University of NairobiNairobiKenya

The crowdsourced OpenStreetMap mapping platform is utilized by countless stakeholders worldwide for various purposes and ***,researchers,governments,commercial,and humanitarian organizations,in addition to the engineers,professionals,and technical developers,use OpenStreetMap both as data contributors and *** storage,usage,and integration of volunteered geographical data in software applications often create complex ethical dilemmas and values regarding the relationships between different categories of *** is therefore common for moral preferences of stakeholders to be *** paper investigates the integration of ethical values in OpenStreetMap using the value sensitive design methodology that examines technical,empirical,and conceptual aspects at each design *** use the Humanitarian OpenStreetMap Team,an existing volunteered geographic information initiative,as a case *** investigation shows that although OpenStreetMap does integrate ethical values in its organizational structure,a deeper understanding of its direct and indirect stakeholders’perspectives is still *** study is expected to assist organizations that contribute to or use OpenStreetMap in recognizing and preserving existing and important ethical *** the best of our knowledge,this is the first attempt to evaluate ethical values methodically and comprehensively in the design process of the OpenStreetMap platform.

关键词： Value Sensitive Design(VSD) OpenStreetMap(OSM) ethical values Volunteered Geographic Information(VGI) crowdsourcing geographic data contributors and consumers

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Modeling relationships between the network distance and travel time dynamics for assessing equity of accessibility to urban parks

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Geo-Spatial Information Science 2021年第3期24卷 509-526页

作者： Tahereh Ghaemi Rad Abbas Alimohammadi GIS department Faculty of Geomatics EngineeringCenter of Excellence in Geospatial Information TechnologyK.N.Toosi University of TechnologyTehranIran

Static models of accessibility are usually based on the fixed distance or Average Travel Time(ATT)*** of ignoring the traffic as a dynamic process affecting the accessibility through the change of Travel Time(TT),these models lead to unperceived temporal *** contrast to the consideration of the temporal Variation of TT(VTT)in the previous studies,the variation of traffic-related TT and its relations with network distance has not been *** this study,relations between VTT and network distance to access urban parks in Tehran megacity has been *** maps at five times of day are used to produce TT maps of Traffic Analysis Zones(TAZs)to their 3-closest *** of the Gini coefficients of accessibility show significant inequities of accessibility at different times of *** between the distance,ATT,and TT_(max) are modeled by statistical *** show both TT and TTmax have significant positive relations with distance and traffic and reach their maximum at 6 *** of significant relations between distance,ATT,TT_(max),and VTT provides interesting knowledge for the conversion of temporal measures of equity(TT)to a physical measure of equity(distance).A simple application of these findings for effective management of the spatiotemporal inequities is the definition of critical distances from public *** an example,to decrease the TT_(max) of TAZs to less than 12 min,their maximum distance to the closest parks should be less than 4 *** developed approach can be adopted for the accessibility evaluation of the other public services,particularly the health and education centers.

关键词： Spatiotemporal equity accessibility travel time variability Gini coefficient Lorenz curve urban parks Tehran megacity

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Effect of multiple rings on side force over an ogive-cylinder body at subsonic speed

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Chinese Journal of Aeronautics 2018年第6期31卷 1181-1188页

作者： Priyank KUMAR J.K.PRASAD department of space Engineering & Rocketry Birla Institute of Technology

Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of attack for the case without a ring. This increase was mainly due to the increase in the asymmetry of the existing vortex pair in the wake of the body. Attempts were made to completely reduce the existing side force at the angle of attack ranging from 35° to 45°.Three rectangular cross-sectioned circumferential rings having a height of 3% of the local diameter were placed at axial distances of 2.5, 3.5 and 4.5 times the base diameter from the tip of the body so as to reduce the side force. The results obtained indicate that inclusion of three rings completely alleviated the side force on the slender body at the angle of attack ranging from 0° to 45°. The presence of rings was found to alter the growth of the vortices that helped in the reduction of the side force. Computations performed were in reasonable agreement with the experiments.

关键词： Asymmetric vortex High angle of attack Ogive Side force Slender body Vortex lift

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Catalytic effects of Cu-Co~* on the thermal decomposition of AN and AN/KDN based green oxidizer and propellant samples

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Defence technology（防务技术） 2018年第3期14卷 250-260页

作者： Pratim Kumar Puran Chandra Joshi Rajiv Kumar Shelly Biswas department of space Engineering & Rocketry Birla Institute of Technology department of Mechanical Engineering Vidya Vihar Institute of Technology

This paper presents the catalytic effects of Cu-Co~* catalyst on the decomposition of AN and AN/KDN based oxidizer and propellant samples. Ozawa-Flynn-Wall(OFW) iso-conversional method was used for the kinetic studies and to compute the activation energy(Ea) values for various decomposition steps of the prepared oxidizer and propellant samples in the temperature range of 50 e500C. TG-DTG experiments were carried out for both oxidizer and propellant samples at the heating rates of 3, 5, and 10C/min. AN/KDN based oxidizer samples were prepared by an evaporative co-crystallization method. Citric acid sol-gel method was used for the synthesis of Cu-Co~* catalyst. The propellant sample contains HTPB as the fuel binder along with other ingredients such as TDI, DOA, and Glycerol. The Cu-Co~* catalyst was used as 2% by weight to the total weight of catalyzed oxidizer and propellant samples. It was observed from the present study that, Cu-Co~* catalyst helps in reducing the Ea values for AN and AN based propellant samples. However, with the percentage increment of KDN in the AN crystals, Ea value ***, it was observed that Cu-Co~* catalyst stabilizes the initial partial decomposition of KDN.

关键词：催化氧化剂催化效果热分解 Cu 燃料取样 TG-DTG 催化剂

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Using geospatial technologies to delineate Ground Water Potential Zones(GWPZ)in Mberengwa and Zvishavane District,Zimbabwe

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Journal of Groundwater Science and Engineering 2023年第4期11卷 317-332页

作者： Nyasha Ashleigh Siziba Pepukai Chifamba department of geospatial Science and Earth Observation Zimbabwe National Geospatial and Space Agency(ZINGSA)630 Churchill AveMount PleasantHarare Zimbabwe

The main objective of the study was to delineate Ground Water Potential Zones(GWPZ)in Mberengwa and Zvishavane districts,Zimbabwe,utilizing geospatial technologies and thematic *** factors,including geology,soil,rainfall,land use/land cover,drainage density,lineament density,slope,Terrain Ruggedness Index(TRI),and Terrain Wetness Index(TWI),were incorporated as thematic *** Multi Influencing Factor(MIF)and Analytical Hierarchical Process(AHP)techniques were employed to assign appropriate weights to these layers based on their relative significance,prioritizing GWPZ *** integration of these weighted layers resulted in the generation of five GWPZ classes:Very high,high,moderate,low,and very *** MIF method identified 3%of the area as having very high GWPZ,19%as having high GWPZ,40%as having moderate GWPZ,24%as having low GWPZ,and 14%as having very low *** AHP method yielded 2%for very high GWPZ,14%for high GWPZ,37%for moderate GWPZ,37%for low GWPZ,and 10%for very low GWPZ.A strong correlation(ρof 0.91)was observed between the MIF results and groundwater *** study successfully identified regions with abundant groundwater,providing valuable target areas for groundwater exploitation and highvolume water harvesting *** identification of these crucial regions is essential for effective decision-making,planning,and management of groundwater resources to alleviate water shortages.

关键词： Groundwater resources Analytical Hierarchical Process Multi Influence Factor Lineaments density Terrain Wetness Index Ground Water Potential Zone

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Evaluation of GNSS Signal-in-space Continuity:A Weibull-Distribution-Based Method

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Chinese Journal of Electronics 2018年第3期27卷 634-640页

作者： LI Rui ZHENG Shuaiyong WANG Zhipeng TANG Yang SUN Si HUANG Zhigang School of Electronic and Information Engineering Beihang University Collaborative Innovation Center of geospatial technology

Signal-in-space(SIS) continuity is an important performance index of Global navigation satellite system(GNSS). However, the studies on the continuity of GNSS SIS are limited both at home and abroad, and are mainly based on the exponential distribution method. We first employ this method to analyze SIS failures of GPS and BDS, finding that this method is not flexile when describing the characteristic of GNSS SIS failures and the fitting characteristic of this method is not well. Therefore, we propose a method based on Weibull distribution to evaluate the performance of GNSS SIS continuity. Our method is compared with the models of exponential distribution, normal distribution, and Gamma distribution regarding the fitting characteristics of the interruption time interval of GPS SIS, the critical parameter of continuity. Results show that the fitting characteristic of the Weibull-distributionbased method is the best and can be used in various forms to describe reliability problem. Then our method is used to evalute the SIS continuity of BDS and GLONASS and its effectiveness and rationality are validated again. The contributions of our study lie in the development of a practical method for evaluating GNSS SIS continuity and a reference for GNSS performance.

关键词： GNSS SIS continuity Evaluation Exponential distribution Weibull distribution

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Cartography and the others-aspects of a complicated relationship

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Geo-Spatial Information Science 2020年第1期23卷 52-60页

作者： Wolfgang Kainz department of Geography and Regional Research University of ViennaWienAustria Collaborative Innovation Center of geospatial technology Wuhan UniversityWuhanChina

Cartographic visualizations have been known for thousands of years and have brought forth a wealth of different map projections and cartographic ***,cartography as an independent science has been established only about 100 years ago and sometimes its position among the spatial disciplines is challenged by the scientific *** this respect it is a young science based on a very long tradition of map making,globe production,and the development of map *** and map related visualizations play an important and indispensable role in many other spatial disciplines such as geography and *** has many overlaps with these traditional disciplines as well as with the more recent ones of photogrammetry and remote *** paper reviews fundamental aspects of the conception of space and time throughout human history,the historic development of cartography from a technique of map making to a spatial science,highlighting major milestones in the history of the *** a young science and confronted with major technological developments in the late 20^(th)century cartography underwent several crises as to what exactly is cartography and how it relates to other spatial sciences,in particular to geographic information *** pitfalls and misconceptions are discussed and the three major scientific pillars of cartography are *** relationships of cartography with neighboring disciplines are discussed and the position of cartography vis a vis the others is ***,desirable future developments of scientific cartography are discussed.

关键词： Cartography GIS geodesy photogrammetry remote sensing

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Testing Procedure for Laboratory Scale Semi Cryogenic Combustion Chamber of LPRE with Problems Faced and Lessons Learned

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Journal of Thermal Science 2022年第6期31卷 2171-2177页

作者： KHAN Taj Wali QAMAR Ihtzaz department of Aeronautics and Astronautics Institute of Space TechnologyIslamabad 44000Pakistan

Design, development, and testing of LPRE(Liquid Propellant Rocket Engine) are difficult and expensive tasks. Prior to full-scale design, it is indispensable to optimize important parameters at sub-scale. Propellants flow rates are low for a sub-scale or laboratory scale combustion chambers. It is hard to satisfy chamber cooling and chill feed lines quickly with low flow rates of propellants. This paper proposes a detailed procedure for testing of a laboratory scale semi-cryogenic combustion chamber. Many tests were conducted with a small scale adjustable length combustion chamber. The injection head of the chamber was interchangeable. Liquid-liquid pressure swirl injector and like impinging injectors were used with two different injection heads. Liquid oxygen and kerosene were used as oxidizer and fuel, respectively. Oxidizer to fuel mixing ratio was 0.29-0.45 and the total propellant mass flow rate was 0.06-0.1 kg/s. Problems were faced during testing, including, explosion in the combustion chamber, fuel injector blockage, unstable combustion, incomplete chilling and blockage of cooling water channel, etc. A detailed procedure is designed on the basis of the lessons learned which was experimentally proved.

关键词： LPRE cryogenic testing procedure combustion chamber

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Developing a GIS Audit Framework in the Context of Information technology though a Reductive Model Approach

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Journal of Geographic Information System 2023年第2期15卷 196-222页

作者： Fausta Mbura Njiru David N. Siriba Faith N. Karanja department of geospatial and space technology University of Nairobi Nairobi Kenya

A GIS audit framework is necessary considering the diverse nature of GIS with regard to components, applications and industry. In practice, checklists are generated during the audit process based on specific objectives. There is no standardized list of items that can be used as a reference. The purpose of this study was to develop a GIS audit framework as a foundation for GIS audits. The framework provides that comprehensive approach to various GIS aspects during the audit process. The design builds on a developed conceptual framework where most significant categories of GIS audit parameters namely data quality, software utilization, GIS competency and procedures (work flows) were identified. The study adopted a reductive model approach to simplify the complexity associated with each category of GIS audit parameter. The resultant audit elements for each category are organized in a matrix that forms an integral part of the framework. The columns comprise audit goal, audit questions and audit subjects as indicators which are qualitatively measured. The rows comprise the parameters (data quality, software utilization, personnel competency and procedure (workflows)). To use the framework, an auditor only needs to create an audit checklist that consists of particular parameters and indicators from the framework depending on audit objective. As part of an on-going research, the next step will involve validating the framework through a mock testing process.

关键词： GIS Audit Framework GIS Complexity Reductive Model GIS Monitoring and Evaluation Audit Checklist

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