检索结果-南通市图书馆

A-STC: auction-based spanning tree coverage algorithm for motion planning of cooperative robots

在线全文

学校读者我要写书评

暂无评论

Frontiers of Information Technology & Electronic Engineering 2019年第1期20卷 18-31页

作者： guan-qiang GAO Bin XIN School of Automation Beijing Institute of Technology Key Laboratory of Intelligent Control and Decision of Complex Systems Beijing Advanced Innovation Center for Intelligent Robots and Systems

The multi-robot coverage motion planning(MCMP) problem in which every reachable area must be covered is common in multi-robot systems. To deal with the MCMP problem, we propose an efficient, complete, and off-line algorithm, named the "auction-based spanning tree coverage(A-STC)" algorithm. First, the configuration space is divided into mega cells whose size is twice the minimum coverage range of a robot. Based on connection relationships among mega cells, a graph structure can be obtained. A robot that circumnavigates a spanning tree of the graph can generate a coverage trajectory. Then, the proposed algorithm adopts an auction mechanism to construct one spanning tree for each robot. In this mechanism, an auctioneer robot chooses a suitable vertex of the graph as an auction item from neighboring vertexes of its spanning tree by heuristic rules. A bidder robot submits a proper bid to the auctioneer according to the auction vertexes' relationships with the spanning tree of the robot and the estimated length of its trajectory. The estimated length is calculated based on vertexes and edges in the spanning tree. The bidder with the highest bid is selected as a winner to reduce the makespan of the coverage task. After auction processes, acceptable coverage trajectories can be planned rapidly. Computational experiments validate the effectiveness of the proposed MCMP algorithm and the method for estimating trajectory lengths. The proposed algorithm is also compared with the state-of-the-art algorithms. The comparative results show that the A-STC algorithm has apparent advantages in terms of the running time and the makespan for large crowded configuration spaces.

关键词： Coverage motion planning Multi-robot system Auction algorithm Spanning tree coverage algorithm

A Review on Grain Refinement of Aluminum Alloys:Progresses,Challenges and Prospects

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2017年第5期30卷 409-432页

作者： Ren-Guo guan Di Tie School of Materials Science and Engineering Northeastern UniversityShenyang 110819China

Aluminum becomes the most popular nonferrous metal and is widely used in many fields such as packaging,building transportation and electrical materials due to its rich resource, light weight, good mechanical properties, suitable corrosion resistance and excellent electrical conductivity. Grain refinement, which is obtained by changing the size of grain structure by different techniques, is a preferred method to improve simultaneously the strength and plasticity of metallic materials. Therefore, grain refining of aluminum is regarded as a key technique in aluminum processing *** to now, there have been a number of techniques for aluminum grain refining. All the techniques can be classified as four categories as follows： grain refining by vibration and stirring during solidification, rapid solidification, the addition of grain refiner and severe plastic deformation. Each of them has its own merits and demerits as well as applicable conditions, and there are still some arguments in the understanding of the mechanisms of these techniques. In this article, the research progresses and challenges encountered in the present techniques and the future research issues and directions are summarized.

关键词： Aluminum Grain refinement Vibration and stirring Rapid solidification Grain refiner Severe plastic deformation

Study of the mechanics of progressive collapse of FPB isolated beam-pier substructures

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2022年第6期16卷 718-728页

作者： Jingcai ZHANG Yong DING Xinchun guan Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disasters of the Ministry of Industry and Information Harbin Institute of TechnologyHarbin 150090China

The horizontal stiffness of the isolated layer is reduced substantially by a friction pendulum bearing(FPB)toprotectthe structure from potential damages caused by ***,horizontal stiffness is essential to progressive collapse resistance of *** paper presents a simplified model to assess the progressive collapse response of beam-pier substructure isolated by *** collapse resistance by flexural action of the beam and additional resistance owing to the horizontal restraining force was *** influences of the equivalent radius and friction coefficient of the FPB,the applied axial force on the FPB,and span-depth ratio of the beam on the additional resistance were *** were conducted to verify the proposed *** results show that progressive collapse resistance provided by horizontal restraining can be reduced as large as 46%and 88%during compressive arching action(CAA)and catenary action(CA),*** equivalent radius of the FPB shows limited effect on the progressive collapse response of FPB isolated structures,but friction coefficient and applied axial force,as well as depth ratio of the beam,show significant influences on the additional progressive collapse resistance *** element method(FEM)results are in good agreement with the result obtained by the proposed method.

关键词： friction pendulum bearing progressive collapse horizontal stiffness compressive arching action catenary action

Non-isothermal Kinetic Analysis on the Thermal Decomposition of the Phase 517 from Hydration Product of Magnesium Sulfide Cement

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2023年第2期38卷 374-380页

作者： CUI Baodong guan Yan BI Wanli School of Materials and Metallurgy University of Science and TechnologyLiaoningAnshan110325China School of Materials Science and Engineering Shenyang Ligong UniversityShenyang110159China

In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was *** of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa *** to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal *** DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide *** three stages correspond to different activation ***,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.

关键词： magnesium sulfide cement comprehensive thermal analysis nonisothermal dynamics 517 phase

Semi-Global Leaderless Consensus of Linear Multi-agent Systems with Actuator and Communication Constraints

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2020年第4期33卷 882-902页

作者： WANG Jian SHI Liangren guan Xinping Department of Automation and Key Laboratory of System Control and Information Processing of Ministry of EducationShanghai Jiao Tong UniversityShanghai 200240China Shanghai Key Laboratory of Navigation and Location-based Services and Academy of Information Technology and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

This paper studies the leaderless consensus problems of multi-agent systems with input saturation and intermittent communication over directed networks. Both the state feedback and the output feedback consensus algorithms are developed based on low gain feedback approach. The convergence of the trajectories of all agents can be achieved by these proposed algorithms, if the communication topology has a directed spanning tree, and the intermittent communication period T and time rate ρ are larger than their associated threshold values. Simulation examples are provided to verify the theoretical results.

关键词： agent directed communication

Metal bioaccumulation in plant leaves from an industrious area and the Botanical Garden in Beijing

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2005年第2期17卷 294-300页

作者： LIUYan-ju DINGHui ZHUYong-guan BeijingCentreforPhysicalandChemicalAnalysis Beijing100089China／／ResearchCenterforEco-EnvironmentalSciencesChineseAcademyofSciencesBeijing100085China BeijingCentreforPhysicalandChemicalAnalysis Beijing100089China ResearchCenterforEco-EnvironmentalSciences ChineseAcademyofSciencesBeijing100085China

The concentrations of Fe, Mn, Al, Zn, Pb, Ni, Cr, and As were measured in soils and leaves from 21 plant species growing on hills near the Beijing Steel Factory(BSF) and 17 plant species in the Beijing Botanical Garden(BBG). The results showed that soils from BSF were Zn contaminated according to the threshold of natural background of China. There was a metal contamination of the soils by Ni, and Cr in BSF comparing with those in BBG. The comparison between concentrations of metals in leaves from both sites indicated that, in general, accumulation of metals in the leaves of the same species was significantly different between the two sites. Even within the same locality each species accumulation of metals was significantly variable. The study aimed to screen landscape plants for the capacity to clean-up toxic metals in soils, and developed an overall metal accumulation index(MAI) for leaves and then categorized the MAI that can be applied broadly in the selection of species in polluted areas. To do this, the spectrum of MAI values were divided into four classes: strongly accumulated(SA or grade I), moderately accumulated(MA or grade II), intermediately accumulated(IA or grade III), and weakly accumulated(WA or grade IV). The results showed that elemental association between Fe, Al, Ni, and As was generally highly correlated with each other in the sampling sites. This may suggest their common biochemical characteristics. Generally, those species containing strong and moderate accumulation in both sites are considered including Vitex negundo, Broussonetia papyrifera, Ulmus pumila, and Rubia cordifolia. At BSF and other industrial sites with a similar ecosystem, strong and moderate accumulation species include Sophora japonica, Ampelopsis aconitifolia var. glabra, Platycladus orientalis, Wikstroemia chamaedaphne, Cleistogenes squarrosa, Grewia biloba, and in BBG, in addition Setaria viridis, Cotinus coggygria, Lespedeza floribunda, Rhamnus parvifolia, Lespedeza tomento

关键词： Fe Mn Al Zn Pb Ni As metal accumulation index(MAI)

Rare-earth mediated dihydrogen activation and catalytic hydrogenation

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2021年第9期39卷 1017-1023页

作者： Yiwen guan Erli Lu Xin Xu Key Laboratory of Organic Synthesis of Jiangsu Province College of ChemistryChemical Engineering and Materials ScienceSoochow UniversitySuzhou 215123China School of Natural and Environmental Sciences Newcastle UniversityKing's RoadNewcastle Upon TyneNE17RUUK

This review covers H-H bond cleavage of dihydrogen(H2)mediated by structurally well-defined rareearth metal(scandium,yttrium and lanthanides)complexes,and their applications in homogenous catalysis,such as catalytic hydrogenation of unsaturated organic *** on the mechanism of the H-H bond cleavage,this review is organized in two parts:(1)σ-bond metathesis,and(2)non-σ-metathesis H2 *** latter is a new trend in this research field and is the emphasis of this *** H2 into inorganic rare-earth polyhydride complexes,albeit their potential applications as hydrogen-storage materiel,is not in the scope of this review.

关键词： Rare earths Dihydrogen activation Hydrogenation Homogeneous catalysis Cooperative effect

Condensation behavior of gaseous phase during transported in the near-substrate boundary layer of plasma spray-physical vapor deposition

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第8期67卷 127-134页

作者： Mei-Jun Liu guan-Jun Yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an fiaotong UniversityXi’anShaanxi710049PR China

Plasma spray-physical vapor deposition(PS-PVD)has exhibited the potential ability to prepare columnar structures for advanced thermal barrier coatings(TBCs).The coating structure is nominally affected by operating parameters,but it is controlled by the type of deposition unit actually and *** order to realize the columnar structure deposited by gaseous phase units,the transition behavior of gaseous phase units to clusters must be fundamentally *** work investigated the transport process of gaseous phase units in the PS-PVD near-substrate boundary layer along with the condensation *** Monte Carlo method was used to examine the transport process and condensation behavior of gaseous phase units under different scale boundary *** results show that it is easier to form more numerous larger clusters at the edge of the plasma jet than at the *** on the understanding of the changes in deposition unit caused by the condensation of gaseous phase in the near-substrate boundary layer of PS-PVD,an outlook towards TBCs with different structures is *** it is in good agreement with the experimental data.

关键词： Condensation behavior Transport process Cluster Boundary layer PS-PVD

A low-frequency and broadband wave-insulating vibration isolator based on plate-shaped metastructures

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2024年第7期45卷 1171-1188页

作者： Wei WEI Feng guan Xin FANG College of Intelligent Science National University of Defense TechnologyChangsha410073China Naval Research Academy Beijing100161China

A metamaterial vibration isolator,termed as wave-insulating isolator,is proposed,which preserves enough load-bearing capability and offers ultra-low and broad bandgaps for greatly enhanced wave *** consists of plate-shaped metacells,whose symmetric and antisymmetric local resonant modes offer several low and broad mode bandgaps although the complete bandgap remains high and *** bandgap mechanisms,vibration isolation properties,effects of key parameters,and robustness to complex conditions are *** experimentally demonstrated,the wave-insulating isolator can improve the vibration insulation in the ranges of[50 Hz,180 Hz]and[260 Hz,400 Hz]by 15 dB and 25 dB,respectively,in contrast to the conventional isolator with the same first resonant frequency.

关键词： metamaterial and metastructure vibration isolation bandgap wave insulation plate