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Nano Research 2019年第8期12卷 1817-1823页

作者： Tianwei He Chunmei z.ang lei z.ang Aijun Du School of Chemistry Physics and Mechanical EngineeringScience and Engineering FacultyQueensland University of TechnologyGardens Point CampusBrisbaneQLD 4001Australia

The hydrogenation of nitrobenz.ne into aniline is one of industrially important reactions, but still remains great challenge due to the lack.of highly active, chemo-selective and eco-friendly catalyst. By using extensive density functional theory (DFT) calculations, herein we predict that single Pt atom decorated g-C3N4 (Pt@g-C3N4) exhibits excellent catalytic activity and selectivity for the conversion of nitrobenz.ne into aniline under visible light. The overall activation energy barrier for the hydrogenation of nitrobenz.ne on single atom Pt@g-C3N4 catalyst is even lower than that of the bare Pt(111) surface. The dissociation of N-0 bonds on single Pt atom is triggered by single hydrogen atom rather than double hydrogen atoms on the Pt(111) surface. Moreover, the Pt@g-C3N4 catalyst exhibits outstanding chemoselectivity towards the common reducible substituents, such as phenyl,-C=C,-C = C and -CHO groups during the hydrogenation. In addition, the doped single Pt atom can significantly enhance the photoconversion efficiency by broadening the light absorption of the pristine g-C3N4 to visible light region. Our results highlight an interesting and experimentally synthesiz.d single-atom photocatalyst (Pt@g-C3N4) for efficient hydrogenation of nitrobenz.ne to aniline under a sustainable and green approach.

关键词： chemoselective hydrogenation single-atom catalyst photocatalyst nitrobenz.ne

Liquid metal spiral coil enabled soft electromagnetic actuator

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Science China(Technological Sciences) 2018年第4期61卷 516-521页

作者： GUO Rui SHENG lei GONG HengYi LIU Jing Department of Biomedical Engineering School of MedicineTsinghua UniversityBeijing 100084China Technical Institute of Physics and Chemistry Chinese Academy of SciencesBeijing 100190China

Soft robot is a k.nd of machine form with flexible deformation capability. Mak.ng flexible actuators has recently become a hot research topic in the field. In this study, we demonstrated the facile fabrication of a soft electromagnetic actuator using liquid metal coil of Ga-In alloys, and designed several illustrative mechanical devices, such as jellyfish lik. robot, soft fishtail and flexible manipulator. Measurements of the liquid metal coil's electrical properties confirmed that the liquid metal coil was mechanically stable under 48% uniaxial strains. Furthermore, the resistance of the liquid metal coil is stable under 60° bending deformation. Tests on the liquid metal coil's driving properties confirmed that the liquid metal coil(55 mm×55 mm×1 mm) could reach the maximum displacement amplitude of 21.5 mm with the current of 0.48 A. It was shown that the electromagnetic interaction between the magnet and the liquid metal coil enables the coil as a highly efficient actuator. The mechanisms lying behind were interpreted and future applications of such system were discussed.

关键词： liquid metal soft machine electromagnetic actuator magnet artificial system

Large sliding regulation in van der waals layered nonlinear optical ternary chalcogenides

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npj Computational Materials 2023年第1期9卷 574-583页

作者： Qingchen Wu lei k.ng Jian Wu z.eshuai Lin Functional Crystals Lab Key Laboratory of Functional Crystals and Laser TechnologyTechnical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190People’s Republic of China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049People’s Republic of China State k.y Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084People’s Republic of China

Interlayer sliding modulation in van der Waals(vdW)layered materials opens opportunities to seek.tunable applications for photonics and optoelectronics at the *** this work.focusing on ternary chalcogenides,doz.ns of typical vdW layered materials with the formula of A_(2)Mz.(4)(A,M=metal cation;z.S/Se)were systematically classified and studied to illustrate the interlayer sliding modulation performance on nonlinear optical(NLO)effect and underlying *** on first-principles analysis,the screened Cd_(2)GeSe_(4) exhibits large second harmonic generation(SHG)deviation(>36 times between high-and low-SHG states)under sliding among all studied *** phenomenon arises from the polariz.tion modulation induced by the vdW interlayer charge redistribution of two tetrahedral primitives in the ternary edge-sharing tetrahedral *** findings present a strategy to substantially modulate NLO properties by altering the interlayer charge coupling which is commonly thought to be very weak.in vdW layered materials.

关键词： materials mechanism layered

Bioinspired robust nanocomposites of cooper ions and hydroxypropyl cellulose synergistic toughening graphene oxide

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Science China(Technological Sciences) 2017年第5期60卷 758-764页

作者： z.ANG Qi WAN SiJie JIANG lei CHENG QunFeng k.y Laboratory of Bio-inspired Smart Interfacial Science and Technology of Ministry of Education School of Chemistry and EnvironmentBeihang University State k.y Laboratory for Modification of Chemical Fibers and Polymer Materials Donghua University

The hierarchical micro/nanoscale layered formation of organic and inorganic components of natural nacre, results in abundant interracial interactions, providing an inspiration for fabricating bioinspired nanocomposites through constructing the interfacial interactions. Herein, we demonstrated the synergistic interfacial interactions of hydrogen bonding from hydroxypropyl cellu- lose and ionic bonding from copper ions upon the reduced graphene oxide based bioinspired nanocomposites, which show the integrated tensile strength, toughness and excellent fatigue-resistant property, as well as high electrical conductivity. These ex- traordinary properties allow this k.nd of bioinspired nanocomposites to potentially utiliz. in the fields of aerospace, flexible electronics devices, etc. This study also opens a door for fabricating excellent mechanical performance graphene-based bioin- spired nanocomposites via synergistic interfacial interactions in the future.

关键词： bioinspired robust nanocomposites synergistic toughening cooper ions

Inverse Displacement Analysis of a Hyper-redundant Elephant＇s Trunk.Robot

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Journal of Bionic Engineering 2018年第2期15卷 397-407页

作者： Yongjie z.ao lei Jin Peng z.ang Jianyuan Li Department of Mechatronics Engineering Shantou University Shantou 515063 China

This paper deals with inverse displacement analysis of a Hyper-redundant Elephant＇s Trunk.Robot （HRETR）. The HRETR is connected in series with n modules of 3UPS-PRU parallel mechanism where the underline P denotes an active prismatic joint. Based on the idea of differential geometry, back.one curve of the robot is formulated by using a parametric fimction consisting of sub-fimctions and control parameters. A general algorithm for generating a back.one curve and fitting the modules to the back.one curve is proposed. In this way, the inverse displacement analysis of the robot can be carried out by solving the inverse displacement problem of each parallel mechanism module and tak.ng into account the length limits of the link.. A HRETR with 6 modules is tak.n as an example to demonstrate the applicability of the algorithm.

关键词： inverse displacement analysis hyper-redundant bionic robot elephant's trunk.robot 3UPS-PRU parallel mechanism back.one curve

A Survey about Algorithms Utiliz.d by Focused Web Crawler

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Journal of Electronic Science and Technology 2018年第2期16卷 129-138页

作者： Yong-Bin Yu Shi-lei Huang Nyima Tashi Huan z.ang Fei lei Lin-Yang Wu School of Information and Software Engineering University of Electronic Science and Technology of ChinaChengdu 610054 School of Information Science and Technology Tibet UniversityLhasa 850000 School of Electronic Information and Engineering Xi'an Jiaotong UniversityXi'an 710049 z.ejiang University Hangzhou 310058

Abstract—Focused crawlers （also k.own as subjectoriented crawlers）, as the core part of vertical search engine, collect topic-specific web pages as many as they can to form a subject-oriented corpus for the latter data analyz.ng or user querying. This paper demonstrates that the popular algorithms utiliz.d at the process of focused web crawling, basically refer to webpage analyz.ng algorithms and crawling strategies （prioritiz. the uniform resource locator （URLs） in the queue）. Advantages and disadvantages of three crawling strategies are shown in the first experiment, which indicates that the best-first search with an appropriate heuristics is a smart choice for topic-oriented crawlingwhile the depth-first search is helpless in focused crawling. Besides, another experiment on comparison of improved ones （with a webpage analyz.ng algorithm added） is carried out to verify that crawling strategies alone are not quite efficient for focused crawling and in most cases their mutual efforts are tak.n into consideration. In light of the experiment results and recent researches, some points on the research tendency of focused crawler algorithms are suggested.

关键词： Crawling strategies focused crawler harvest rate uniform resource locator(URL) prioritiz.ng webpage analyz.ng

Research on the Intelligent Control Strategy of the Fuel Cell Phase-Shifting Full-Bridge Power Electronics DC-DC Converter

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Energy Engineering 2022年第1期119卷 387-405页

作者： lei z.ang Yinlong Yuan Yihe Sun Yun Cheng Dian Wu lei Ren School of Electrical Engineering Nantong UniversityNantong226019China School of Electrical and Power Engineering China University of Mining and TechnologyXuzhou221116China

focus of all *** an effective new energy,the fuel cell has attracted the attention of ***,due to the particularity of proton exchange membrane fuel cell(PEMFC),the performance of traditional PI controlled phase-shifted full-bridge power electronics DC-DC converter cannot meet the needs of practical *** order to further improve the dynamic performance of the converter,this paper first introduces several main topologies of the current mainstream front-end DC-DC converter,and analyz.s their performance in the fuel cell ***,the operation process of the phase-shifted fullbridge power electronics DC-DC converter is introduced,and the shortcomings of the traditional PI control are ***,a double closed-loop adaptive fuz.y PI controller is proposed,which is characteriz.d by dynamically adjusting PI parameters according to different work.ng states to complete the intelligent control of phase-shifted full-bridge DC-DC *** simulation results in MATLAB/Simulink.show that the proposed algorithm has good a control *** with the traditional algorithm,the overshoot and stabiliz.tion time of the system are *** algorithm can effectively suppress the fluctuation of the output current of the fuel cell converter,and is a very practical control method.

关键词： Phase-shifted full-bridge adaptive fuz.y PI control proton exchange membrane fuel cell MATLAB/Simulink

Visualiz.tion of flow behavior in ore-segregated pack.d beds with fine interlayers

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International Journal of Minerals,Metallurgy and Materials 2020年第7期27卷 900-909页

作者： lei-ming Wang Sheng-hua Yin Ai-xiang Wu k.y Laboratory of Ministry of Education for High-Efficient Mining and Safety of Metal University of Science and Technology BeijingBeijing 100083China School of Civil and Resource Engineering University of Science and Technology BeijingBeijing 100083China Department of Materials Engineering University of British Columbia309-6350 Stores RoadVancouver V6T 1Z4BCCanada

Ore particles,especially fine interlayers,commonly segregate in heap stack.ng,leading to undesirable flow paths and changeable flow velocity fields of pack.d *** tomography(CT),COMSOL Multiphysics,and MATLAB were utiliz.d to quantify pore structures and visualiz. flow behavior inside pack.d beds with segregated fine *** formation of fine interlayers was accompanied with the segregation of particles in pack.d *** particles reached the upper position of the pack.d beds during *** revealed that the average porosity of fine interlayers(24.21%)was significantly lower than that of the heap pack.d by coarse ores(37.42%),which directly affected the formation of flow ***,the potential flow paths in the internal regions of fine interlayers were *** flowed and bypassed the fine interlayers and along the sides of the pack.d *** velocity also indicated that the flow paths easily gathered in the pore throat where flow velocity(1.8×10^-5 m/s)suddenly *** stagnant regions with a flow velocity lower than 0.2×10^-5 m/s appeared in flow paths with a large diameter.

关键词： fine interlayer flow behavior computed tomography segregation preferential flow

Black.holes as the source of dark.energy:A stringent test with high-redshift JWST AGNs

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 181-188页

作者： lei lei lei z. Guan-Wen Yuan z.ao-Qiang Shen Yi-Ying Wang Yuan-z.u Wang z.en-Bo Su Wen-k. Ren Shao-Peng Tang Hao z.ou Chi z.ang z.i-Ping Jin lei Feng Yi-z.ong Fan Da-Ming Wei k.y 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 CAS k.y Laboratory for Research in Galaxies and Cosmology Department of AstronomyUniversity of Science and Technology of ChinaHefei 230026China

Studies have proposed that there is evidence for cosmological coupling of black.holes(BHs)with an index of k.3;hence,BHs serve as the astrophysical source of dark.***,the data sample is limited for the redshifts of≤*** recent years,the James Webb Space Telescope(JWST)has detected many high-redshift active galactic nuclei(AGNs)and *** the JWST NIRSpec-/NIRCam-resolved AGNs,three are determined to be in early-type host galaxies with a redshift of z.***,their M_(*)and MBH are in tension with the predicted cosmological coupling of black.holes with k.3 at a confidence level of~2σ,which challenges the hypothesis that BHs serve as the origin of dark.*** work.on high-redshift AGNs using the JWST will further assess such a hypothesis by identifying more early-type host galaxies in the higher mass range.

关键词： dark.energy supermassive black.hole active galactic nuclei James Webb Space Telescope

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Learning Gaussian mixture with automatic model selection:A comparative study on three Bayesian related approaches

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Frontiers of Electrical and Electronic Engineering in China 2011年第2期6卷 215-244页

作者： lei SHI Shik.i TU lei XU Department of Computer Science and Engineering The Chinese University of Hong KongHong KongChina

Three Bayesian related approaches,namely,variational Bayesian(VB),minimum message length(MML)and Bayesian Ying-Yang(BYY)harmony learning,have been applied to automatically determining an appropriate number of components during learning Gaussian mixture model(GMM).This paper aims to provide a comparative investigation on these approaches with not only a Jeffreys prior but also a conjugate Dirichlet-Normal-Wishart(DNW)prior on *** addition to adopting the existing algorithms either directly or with some modifications,the algorithm for VB with Jeffreys prior and the algorithm for BYY with DNW prior are developed in this paper to fill the missing *** performances of automatic model selection are evaluated through extensive experiments,with several empirical findings:1)Considering priors merely on the mixing weights,each of three approaches mak.s biased mistak.s,while considering priors on all the parameters of GMM mak.s each approach reduce its bias and also improve its performance.2)As Jeffreys prior is replaced by the DNW prior,all the three approaches improve their ***,Jeffreys prior mak.s MML slightly better than VB,while the DNW prior mak.s VB better than MML.3)As the hyperparameters of DNW prior are further optimiz.d by each of its own learning principle,BYY improves its performances while VB and MML deteriorate their performances when there are too many free ***,VB and MML lack.a good guide for optimiz.ng the hyper-parameters of DNW prior.4)BYY considerably outperforms both VB and MML for any type of priors and whether hyper-parameters are *** different from VB and MML that rely on appropriate priors to perform model selection,BYY does not highly depend on the type of *** has model selection ability even without priors and performs already very well with Jeffreys prior,and incrementally improves as Jeffreys prior is replaced by the DNW ***,all algorithms are applied on the Berk.ley segment

关键词： Bayesian Ying-Yang(BYY)harmony learning variational Bayesian(VB) minimum message length(MML) empirical comparison Gaussian mixture model(GMM) automatic model selection Jeffreys prior Dirichlet joint Normal-Wishart(NW) conjugate distributions marginaliz.d student’s T-distribution