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X-Ray Source Classification Using Machine Learning:A Study with EP-WXT Pathfinder LEIA

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Research in Astronomy and Astrophysics 2024年第8期24卷 175-195页

作者： Xiaoxiong Zuo Yihan Tao yuan Liu Yunfei Xu Wenda Zhang Haiwu Pan Hui Sun Zhen Zhang Chenzhou Cui Weimin yuan National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China university of chinese academy of sciences Beijing 100049China National Astronomical Data Center Beijing 100101China

X-ray observations play a crucial role in time-domain *** Einstein Probe(EP),a recently launched X-ray astronomical satellite,emerges as a forefront player in the field of time-domain astronomy and high-energy *** a focus on systematic surveys in the soft X-ray band,EP aims to discover high-energy transients and monitor variable sources in the *** achieve these objectives,a quick and reliable classification of observed sources is *** this study,we developed a machine learning classifier for autonomous source classification using data from the EP-WXT Pathfinder—Lobster Eye Imager for Astronomy(LEIA)and EP-WXT *** proposed Random Forest classifier,built on selected features derived from light curves,energy spectra,and location information,achieves an accuracy of approximately 95%on EP simulation data and 98%on LEIA observational *** classifier is integrated into the LEIA data processing pipeline,serving as a tool for manual validation and rapid classification during *** paper presents an efficient method for the classification of X-ray sources based on single observations,along with implications of most effective features for the *** work facilitates rapid source classification for the EP mission and also provides valuable insights into feature selection and classification techniques for enhancing the efficiency and accuracy of X-ray source classification that can be adapted to other X-ray telescope data.

关键词： methods data analysis-X-rays binaries-stars variables general-X-rays bursts

Rapidly growing primordial black holes as seeds of the massive high-redshift JWST Galaxies

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Science china(Physics,Mechanics & Astronomy) 2024年第10期67卷 139-146页

作者： Guan-Wen yuan Lei Lei yuan-Zhu Wang Bo Wang Yi-Ying Wang Chao Chen Zhao-Qiang Shen Yi-Fu Cai Yi-Zhong Fan Key Laboratory of Dark Matter and Space Astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China institute of high {2. Physics Chinese Academy of SciencesBeijing 100049China Deep Space Exploration Laboratory/Department of Astronomy School of Physical SciencesUniversity of Science and Technology of ChinaHefei 230026China Jockey Club institute for Advanced Study The Hong Kong University of Science and TechnologyHong KongChina

A group of massive galaxies at redshifts of z■7 have been recently detected by the James Webb Space Telescope(JWST),which were unexpected to form at such an early time within the standard Big Bang *** this work,we propose that this puzzle can be explained by the presence of some primordial black holes(PBHs)with a mass of~1000M_(⊙).These PBHs act as seeds for early galaxy formation with masses of~10^(8)-10^(10)M_(⊙)at high redshift,hence accounting for the JWST *** use a hierarchical Bayesian inference framework to constrain the PBH mass distribution models,and find that the Lognormal model with the M_(c)~750M_(⊙)is preferred over other *** rapidly growing BHs are expected to have strong radiation and may appear as high-redshift compact objects,similar to those recently discovered by *** we focused on PBHs in this work,the bound on the initial mass of the seed black holes remains robust even if they were formed through astrophysical channels.

关键词： primordial black hole dark matter halo black hole accretion primordial galaxies

Coupling interface constructions of hollow Co-mo mixed multiple oxidation states heterostructure for high-performance aprotic Li-O_(2. battery

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Nano Research 2024年第5期17卷 4100-4107页

作者： Xingzi Zheng Mengwei yuan Jingshen Xu Zihan Li Caiyun Nan Genban Sun beijing Key Laboratory of energy Conversion and Storage Materials College of ChemistryBeijing Normal UniversityBeijing 100875China Center for Advanced Materials Research Beijing Normal UniversityZhuhai 519087China

Constructing interfaces in heterostructures is effective for modulating the electronic properties of *** hollow ComoO_(4)-Co_(3)O_(4) heterostructure(HCMCH)was prepared as a bifunctional electrocatalyst for Li-O_(2. *** different components in ComoO_(4)-Co_(3)O_(4) heterostructure presented the efficient coupling and enhanced the electrocatalytic activity for aprotic oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),in which it improved the obviously reduced overpotential of 300 mV(compared with the pure Ketjen black(KB)electrode),enhanced reversibility of 80%capacity retention after 6 full cycles and the superior cyclability of more than 2.0 cycles with an optimized *** battery performance of the HCMCH was not only associated with the unique hollow structure and rich active sites but also with coupling interface constructions synergetic effects attaching to the improving conductivity and optimized the discharge *** results suggested that this HCMCH electrocatalyst was a promising candidate for the Li-O_(2. battery and it gave a novel insight for high performance electrocatalyst designing.

关键词： Li-oxygen battery heterostructure electrocatalyst coupling interface

Dynamical Dark energy in Light of Cosmic Distance Measurements.Ⅰ.A Demonstration Using Simulated Datasets

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Research in Astronomy and Astrophysics 2024年第6期24卷 7-14页

作者： Gan Gu Xiaoma Wang Xiaoyong Mu Shuo yuan Gong-Bo Zhao National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China university of chinese academy of sciences Beijing 100049China institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China

We develop methods to extract key dark energy information from cosmic distance measurements including the BAO scales and supernova(SN) luminosity *** using simulated data sets of the complete DESI,LSST and Roman surveys designed for BAO and SN distance measurements,we show that using our method,the dynamical behavior of the energy,pressure,equation of state(with its time derivative) of dark energy and the cosmic deceleration function can all be accurately recovered from high-quality data,which allows for robust diagnostic tests for dark energy models.

关键词： (cosmology:)dark energy (cosmology:)large scale structure of universe (cosmology:)cosmic background radiation (cosmology:)cosmological parameters

Dissolving of Nb and Ti Carbonitride Precipitates in Microalloyed Steels

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Dissolving of Nb and Ti Carbonitride Precipitates in Microal...

Transverse mode-coupling instability with longitudinal impedance

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作者： YANG Shanwu~1, yuan Shaoqiang~2. NIE Wenjin~1, HE Xinlai~1 (1.School of Materials Science and Engineering, university of Science and Technology {2., beijing 100083, china 2. Tangshan College, Hebei 063000, china)

＜正＞Transmission electron microscopy （TEM） and energy dispersion x-ray spectrum （EDX） have been carried out to investigate dissolving behaviour of Nb and Ti carbonitride precipitates in microalloyed steels during isothermal holding at 1300℃. It has been found that all precipitates in Nb-Ti microalloyed steel were （Nb, Ti）（C, N）. With holding time increasing, the atomic ratio of Nb/Ti in precipitates decreased gradually. These precipitates still existed even after holding for 48h at 1300℃while Nb（C, N） precipitates dissolved away in Nb microalloyed steel only after 4h at the same temperature. These results shows that formation and thermostability of precipitates are considerably influenced by interaction between Nb and Ti.

关键词： Dissolving (Nb Ti)(C N) TEM-EDX

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Nuclear Science and Techniques 2024年第6期35卷 40-53页

作者： Hai-Sheng Xu Chun-Tao Lin Na Wang Jing-Ye Xu yuan Zhang Key Laboratory of Particle Acceleration Physics and Technology Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China university of chinese academy of sciences Beijing 100049China institute of Advanced Science Facilities Shenzhen 518107GuangdongChina

Transverse mode-coupling instability(TMCI)is a dangerous transverse single-bunch instability that can lead to severe par-ticle *** mechanism of TMCI can be explained by the coupling of transverse coherent oscillation modes owing to the transverse short-range wakefield(i.e.,the transverse broadband impedance).Recent studies on future circular colliders,e.g.,FCC-ee,showed that the threshold of TMCI decreased significantly when both longitudinal and transverse impedances were *** performed computations for the circular electron-positron collider(CEPC)and observed a similar *** studies on the influence of longitudinal impedance on the TMCI threshold were *** concluded that the imaginary part of the longitudinal impedance,which caused a reduction in the incoherent synchrotron tune,was the primary reason for the reduction in the TMCI ***,the real part of the longitudinal impedance assists in increasing the TMCI threshold.

关键词： Transverse mode-coupling instability Longitudinal impedance

In situ reconstruction induced oxygen-deficient multiphase Cu based species hybridized with Ni single atoms as tandem platform for CO_(2. electroreduction

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Nano Research 2024年第5期17卷 3888-3894页

作者： Juzhe Liu Yuheng Wang Pengpeng mo Feng Yang Kaiqi Jiang Zhixiang Cheng Yuxuan Liu Zhiyi Sun Zheng Liu Yimei Zhang Wenxing Chen The Key Laboratory of Resources and Environmental System Optimization Ministry of EducationCollege of Environmental Science and EngineeringNorth China Electric Power UniversityBeijing 102206China energy&Catalysis Center School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental SciencesBeijing 100012China SEPA Key Laboratory of Eco-Industry Chinese Research Academy of Environmental SciencesBeijing 100012China

Tandem catalysis,capable of decoupling individual steps,provides a feasible way to build a high-efficiency CO_(2. electro-conversion system for multicarbons(C_(2.)).The construction of electrocatalytic materials is one of focusing ***,we fabricated a single atom involved multivalent oxide-derived Cu composite material and found it inclined to reconstruct into oxygen-deficient multiphase Cu based species hybridized with monatomic Ni on N doped C *** this prototype,rapid CO generation and C-C coupling are successively achieved on NiN4 sites and surface amorphized Cu species with defects,resembling a micro-production *** this way,the in situ formed tandem catalyst exhibited a high Faradaic efficiency(FE)of~78%for C_(2.)products along with satisfactory durability over 50 ***,the reconstruction-induced amorphous layer with abundant asymmetric sites should be favorable to improve the ethanol selectivity(FE:63%),which is about 10 times higher than that of the non-tandem Cu-based contrast *** work offers a new approach for manipulating tandem catalyst systems towards enhancing C_(2.)products.

关键词： tandem catalysis single atom reconstruction amorphous CO_(2.reduction reaction

Advanced 3D ordered electrodes for PEMFC applications: From structural features and fabrication methods to the controllable design of catalyst layers

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Green energy & Environment 2024年第9期9卷 1336-1365页

作者： Kaili Wang Tingting Zhou Zhen Cao Zhimin yuan Hongyan He Maohong Fan Zaiyong Jiang School of Chemistry & Chemical Engineering and Environmental Engineering Weifang University beijing Key Laboratory of Ionic Liquids Clean Process State Key Laboratory of Multiphase Complex Systems CAS Key Laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences College Engineering and Physical sciences and School of Energy Resources University of Wyoming

The catalyst layers(CLs) electrode is the key component of the membrane electrode assembly(MEA) in proton exchange membrane fuel cells(PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future.

关键词： PEMFC 3D ordered electrode Structural features Preparation technology Ultralow Pt loading

Alkyl chain modulation of asymmetric hexacyclic fused acceptor synergistically with wide bandgap third component for high efficiency ternary organic solar cells

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1713-1719页

作者： Shufang Li Huilan Guan Can Zhu Chaoyuan Sun Qingya Wei Jun yuan Yingping Zou College of Chemistry and Chemical Engineering Central South UniversityChangsha 410083China beijing National Laboratory for molecular sciences CAS Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China institute of Carbon Neutrality and New energy School of Electronics and InformationHangzhou Dianzi UniversityHangzhou 310018China

Herein,two asymmetric hexacyclic fused small molecule acceptors(SMAs),namely BP4F-HU and BP4F-UU,were *** elongated outside chains in the BP4F-UU molecule played a crucial role in optimizing the morphology of blend film,thereby improving charge mobility and reducing energy loss within the corresponding ***,the PM6:BP4F-UU device exhibited a higher open-circuit voltage(V_(oc))of 0.878 V compared to the PM6:BP4F-HU device with a V_(oc)of 0.863 ***,a new wide bandgap SMA named BTP-TA was designed and synthesized as the third component to the PM6:BP4F-UU host binary devices,which showed an ideal complementary absorption spectrum in PM6:BP4F-UU *** addition,BTP-TA can achieve efficient intermolecular energy transfer to BP4F-UU by fluorescence resonance energy transfer(FRET)pathway,due to the good overlap between the photoluminescence(PL)spectrum of BTP-TA and the absorption region of ***,ternary devices with 15wt%BTP-TA exhibits broader photon utilization,optimal blend morphology,and reduced charge recombination compared to the corresponding binary ***,PM6:BP4F-UU:BTP-TA ternary device achieved an optimal power conversion efficiency(PCE)of 17.83%with simultaneously increased V_(oc)of 0.905 V,short-circuit current density(J_(sc))of 2..14 mA/cm^(2.,and fill factor(FF)of 75.38%.

关键词： asymmetric hexacyclic acceptor outside chain wide bandgap acceptor ternary organic solar cells