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Disk evolution of the M87’s nucleus observed in 2008

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Research in Astronomy and Astrophysics 2020年第7期20卷 103-111页

作者： Fei xiang cheng cheng Department of Astronomy Yunnan UniversityKunming 650091China Chinese Academy of Sciences South America Center for Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China

We report the discovery of year-scale x-ray variation in the nuclear region of the M87 by reanalyze the eight Chandra observations from 2007 to 2008. The x-ray spectra are fitted and decomposed into disk and flaring components. This year-scale x-ray variability can be explained quite well by a simple clumpy accretion model. We conclude that the central super-massive black hole of M87 was accreting a cloud of ~ 0.5 M⊙at that time.

关键词： galaxies:active x-ray:individual:M87

Relationship and Discrepancies Among Typical Interatomic Potential Functions

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Chinese Physics Letters 2004年第11期21卷 2167-2170页

作者： LIMTeik-cheng FhcultyofEngineering NanoscienceandNanotechnologyInitiativeNationalUniversityofSingapore9EngineeringDrive1S117576RepublicofSingapore

We develop a simultaneous relationship among parameters of the generalized version of the Lennard-Jones, Morse, Rydberg and Buckingham pair potentials, and the two-body portion of the Kaxiras–Pandey potential function by introducing a set of scaling factors. These potential functions are selected according to their frequent adoption in condensed matter and molecular computation. In addition to verifying the parametric relations, theoretical plots of these potential curves show that each of these potential functions is unique in terms of their characteristic shape. However, gaps between these potential functions are narrowed for interatomic interactions possessing lower separation energy and longer interatomic equilibrium distance. Finally, comparison with the ab initio results shows that the extended-Rydberg potential energy curve gives the best agreement among the five empirical potential functions, for the specific case of hydrogen molecule.

关键词： Condensed matter physics

Ultracold atomic gases going strong

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National Science Review 2016年第2期3卷 168-170页

作者： cheng Chin James Franck Institute Enrico Fermi InstituteUniversity of Chicago

The year 2015 marks the 20th anniversary of the achievement of Bose-Einstein condensation(BEC)in atomic *** BEC,realized by Eric Cornell,Carl Wieman and Wolfgang Ketterle in1995,commenced an exciting wave to explore quantum few-and many-body *** from solid state matter and helium superfluids,atomic condensates in the gas phase come with

关键词： body BEC Ultracold atomic gases going strong length

New paradigms on hematopoietic stem cell differentiation

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Protein & Cell 2020年第1期11卷 34-44页

作者： Hui cheng Zhaofeng Zheng Tao cheng State Key Laboratory of Experimental Hematology Chinese Academy of Medical Sciences and Peking Union Medical CollegeTianjin 300020China Institute of Hematology and Blood Disease Hospital Chinese Academy of Medical Sciences and Peking Union Medical CollegeTianjinChina Center for Stem Cell Medicine Chinese Academy of Medical SciencesTianjinChina Department of Stem Cell and Regenerative Medicine Peking Union Medical CollegeTianjinChina

Ever since hematopoietic stem cells(HSCs)were first identified half a century ago,their differentiation roadmap has been extensively *** classical model of hematopoiesis has long held as a dogma that HSCs reside at the top of a hierarchy in which HSCs possess self-renewal capacity and can progressively give rise to all blood lineage ***,over the past several years,with advances in single cell technologies,this developmental scheme has been *** this review,we discuss the evidence supporting heterogeneity within HSC and progenitor populations as well as the hierarchical models revised by novel approaches mainly in mouse *** evolving views provide further understanding of hematopoiesis and highlight the complexity of hematopoietic differentiation.

关键词： hematopoietic stem cell hierarchy heterogeneity differentiation

Design of a micrometer-long superconducting nanowire perfect absorber for efficient high-speed single-photon detection

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Photonics Research 2020年第8期8卷 1260-1267页

作者： RISHENG cheng SIHAO WANG CHANG-LING ZOU HONG x.TANG Department of Electrical Engineering Yale UniversityNew HavenConnecticut 06511USA Department of Optics University of Science and Technology of ChinaHefei 230026China

Despite very efficient superconducting nanowire single-photon detectors(SNSPDs)reported recently,combining their other performance advantages such as high speed and ultralow timing jitter in a single device still remains *** this work,we present a perfect absorber model and the corresponding detector design based on a micrometer-long NbN nanowire integrated with a 2D photonic crystal cavity of ultrasmall mode volume,which promises simultaneous achievement of near-unity absorption,gigahertz counting rates,and broadband optical response with a 3 dB bandwidth of 71 *** to previous stand-alone meandered and waveguideintegrated SNSPDs,this perfect absorber design addresses the trade space in size,efficiency,speed,and bandwidth for realizing large on-chip single-photon detector arrays.

关键词： absorber perfect high

Comparative studies of adsorbed CO and methanol electrooxidation on carbon supported Pt and PtRu catalysts in acid solution

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Rare Metals 2006年第3期25卷 274-280页

作者： PENG cheng ZHANG Zhen cheng xuan ZHANG Ying Department of Applied Chemistry South China University of Technology Guangzhou 510641 China Department of Chemistry State Key Laboratory for Physical Chemistry of Solid Surfaces Xiamen University Xiamen 361005 China Department of Materials Science and Engineering Xiamen University Xiamen 361005 China

Physicochemical characterization of commercial Pt/C and PtRu/C catalysts was carried out by x-ray diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy. Comparative studies of methanol electrooxidation on carbon supported Pt and PtRu catalysts in acid solution were performed by means of an electrochemical method. The experimental results showed that PtRu/C not only had a higher electrocatalytic activity for the electrocatalytic oxidation of methanol than Pt/C, but also for the electrocatalytic oxidation of adsorbed CO. Alloy formation of Ru with Pt modified not only the characteristics of H2 adsorption on the surface of catalyst but also the characteristics of CO adsorption on the sur face of catalyst. The interaction of CHaOH with Ru was a temperature-activated process requiring elevated temperature.

关键词： electrochemistry methanol oxidation cyclic voltammetry electrocatalyst

Densification of Mxene films by sequential bridging

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National Science Review 2022年第1期9卷 10-11页

作者： Hui-Ming cheng Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenzhen Institute of Advanced Technology Chinese Academy of Sciences

Voids are an essential scientific issue when it comes to traditional composite materials, because they greatly degrade the laer’s properties and usually cause catastrophic failure [1].

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Towards a Medium/High Load-Bearing Scaffold Fabrication System

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Tsinghua Science and Technology 2009年第S1期14卷 13-19页

作者： GIBSON Ian SAVALANI Monica M LAM Christopher x F OLKOWSKI Radoslow EKAPUTRA Andrew K TAN Kim cheng HUTMACHER Dietmar W Faculty of Engineering National University of Singapore Department of Biophysics and Human Physiology Medical University of Warsaw Warsaw 02-091 Poland Temasek Engineering School Temasek Polytechnic Institute of Health and Biomedical Innovation Queensland University of Technology Brisbane QL-4000 Australia

This paper describes fabrication of scaffolds for load-bearing applications, with primary consideration from the manufacturing perspective. An extrusion device, inspired by the FDM process, was used to create scaffolds from a variety of different polymeric materials and mixtures. The effectiveness of these scaffolds to host cells for bone regeneration has been investigated. This ongoing work has generated significant insight into the future direction of research and the possibilities of developing scaffolds for medium/high load-bearing applications.

关键词： tissue engineering load-bearing bone engineering scaffolds

Improved concept models for straight thin-walled columns with box cross section

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第11期9卷 1473-1479页

作者： Yu-cheng LIU Department of Mechanical Engineering University of Louisville Louisville KY40292 USA

This paper focuses on developing improved concept models for straight thin-walled box sectional columns which can better predict the peak crushing force that occurs during crashworthiness analyses. We develop a nonlinear translational spring based on previous research and apply such a spring element to build the enhanced concept models. The work presented in this article is developed on the basis of the publication of the author (Liu and Day, 2006b) and has been applied in a crashworthiness design issue, which is presented by the author in another paper (Liu, 2008).

关键词： Concept model Peak crushing force Box section Nonlinear translational springs Crashworthiness analysis Thin-walled column