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Tracked robot with underactuated tension-driven RRP transformable mechanism:ideas and design

Frontiers of Mechanical Engineering 2024年第1期19卷 85-104页

作者： ran xu Chao LIU School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control Technology(Ministry of Education)Beijing Jiaotong UniversityBeijing 100044China

Robots with transformable tracked mechanisms are widely used in complex terrains because of their high adaptability,and many studies on novel locomotion mechanisms have been conducted to make them able to climb higher *** underactuated transformable mechanisms for tracked robots could decrease the number of actuators used while maintaining the flexibility and obstacle-crossing capability of these robots,and increasing their cost ***,the underactuated tracked robots have appreciable research *** this paper,a novel tracked robot with a newly proposed underactuated revolute‒revolute‒prismatic(RRP)transformable mechanism,which is inspired by the sit-up actions of humans,was *** newly proposed tracked robot has only two actuators installed on the track pulleys for moving and does not need extra actuators for ***,it could concentrate the track belt’s tension toward one side,and the unbalanced tension would drive the linkage mechanisms to change its *** this method,the proposed underactuated design could change its external shape to create support points with the terrain and move its center of mass actively at the same time while climbing obstacles or crossing other kinds of terrains,thus greatly improving the climbing capability of the *** geometry and kinematic relationships of the robot and the crossing strategies for three kinds of typical obstacles are *** the basis of such crossing motions,the parameters of links in the robot are designed to make sure the robot has sufficient stability while climbing ***-crossing dynamic simulations were run and analyzed to prove the feasibility of the robot.A prototype was built and *** show that the proposed robot could climb platforms with heights up to 33.3%of the robot’s length or cross gaps with widths up to 43.5%of the robot’s length.

关键词： mechanical design tracked robot underactuated mechanisms RRP mechanism obstacle crossing strategy

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What happened during domestication of wild to cultivated rice

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The Crop Journal 2021年第3期9卷 564-576页

作者： ran xu Chuanqing Sun State Key Laboratory of Plant Physiology and Biochemistry China Agricultural UniversityBeijing 100193China

Domestication of crops is one of the greatest inventions of the human race and has played a vital role in the progress of human *** the genetic mechanisms of crop domestication could shed light on its history and would advance crop *** rice species,which were domesticated from wild rice species,are important food crops *** traits,physiological characteristics,and ecological adaptability of cultivated rice are very different from those characters of wild *** this review,we summarize current knowledge of the genetic mechanisms underlying these differences between wild and cultivated rice and discuss the application of wild rice species in modern breeding.

关键词： Oryza genus Wild rice Cultivated rice Domestication

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INVESTIGATION ON APPLICABILITY OF VARIOUS STRESS DEFINITIONS IN ATOMISTIC SIMULATION

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Acta Mechanica Solida Sinica 2009年第6期22卷 644-649页

作者： ran xu Bin Liu AML Department of Engineering Mechanics Tsinghua University Beijing 100084 China

How to correctly extract Cauchy stress from the atomistic simulations is a crucial issue in studying the mechanical behaviours of atomic systems, but is still in controversy. In this paper, three typical atomistic simulation examples are used to validate various existing stress definitions. It is found that the classical virial stress fails in predicting the stresses in these examples, because the velocity depends on the choice of the local average volume or the reference frame velocity and other factors. In contrast, the Lagrangian cross-section stress and Lagrangian virial stress are validated by these examples, and the instantaneous Lagrangian atomic stress definition is also proposed for dynamical problems.

关键词： atomic stress virial stress atomistic simulation

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Effect of strain rate on tensile strength of defective silicon nanorods

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Acta Mechanica Solida Sinica 2015年第2期28卷 133-144页

作者： Tao Chen ran xu Qingbin Li Beijing MTR Construction Administration Corporation AML Department of Engineering Mechanics Tsinghua University State Key Laboratory of Hydroscience and Engineering Tsinghua University

The effect of strain rate on the tensile strength of defective monocrystalline silicon （Si） nanorods is studied with the molecular dynamics method. The strain rate applied to the nanorods is varied from l0T to 1014 s-1, and the atomic interactions among the Si atoms are described by the Stillinger-Weber （SW） potential functions. The tensile strength of the ideal Si nanorod is shown to be strongly strain rate dependent and increasing with the strain rate. The failure pattern also shows strain rate dependence, indicating that increased strain rates gradually suppress unsuitable relaxation and dissipation mechanisms because of the accompanying larger external loadings. Furthermore, the effects of intrinsic material parameters （i.e., the cutoff radius of SW potential function） and defects （i.e., inevitable surface defects and internal preinstalled defects） are investigated. It is revealed that the effect of strain rate on the tensile strength of Si nanorod is influenced by both the intrinsic physical properties of the material and the distribution of the initial defects, with specific surface defects appearing to be more important to nanostructure design.

关键词： strain rate defect Si nanorod tensile strength molecular dynamics

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Trade Destruction and Trade Deflection:A Quasi-Natural Experiment Based on the US Additional Tariffs

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Journal of Systems Science & Complexity 2023年第6期36卷 2467-2496页

作者： ZHANG Yu GAO Xiang xu ran YANG Cuihong Yangtze Industrial Economic Institute Nanjing UniversityNanjing210093China Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing100190China School of Management Engineering Qingdao University of TechnologyQingdao266520China

This paper adopts the DID approach to investigate the trade destruction effects and trade deflection effects of the US additional *** authors find that the US additional tariffs significantly reduce China's exports of tariffed products to the US(i.e.,trade destruction effect),especially intermediate and labor-intensive *** the other hand,they significantly increase China's exports of tariffed products to the third market(i.e.,trade deflection effect).For the$50 billion list,both the trade destruction effect and trade deflection effect are concentrated on processing exports,and the US additional tariffs significantly increase China's exports of tariffed products to ASEAN,Japan and *** the$200 billion list,the US additional tariffs boost China's exports of chemicals,textiles,wood,metal products,furniture and other products to the EU,Australia,Japan,South Africa and Hong Kong,***,most trade deflections are not realized by lowering export prices,indicating that the trade deflections could compensate for the profit losses caused by the US additional tariffs to a certain *** proposed results suggest that searching for substitutions of export markets and a more open trade policy is an important way to avoid profit losses and reduce risks for enterprises and economies suffering from trade frictions.

关键词： DID approach trade deflection trade destruction US additional tariffs

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Control of grain size by G protein signaling in rice

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Journal of Integrative Plant Biology 2019年第5期61卷 533-540页

作者： ran xu Na Li Yunhai Li State Key Laboratory of Plant Cell and Chromosome Engineering CAS Center for Excellence in Molecular Plant SciencesInstitute of Genetics and Developmental Biologythe Chinese Academy of SciencesBeijing 100101China The University of Chinese Academy of Sciences Beijing 100039China

Heterotrimeric G proteins are involved in multiple cellular processes in eukaryotes by sensing and transducing various signals. G protein signaling in plants is quite different from that in animals, and the mechanisms of plant G protein signaling are still largely unknown. Several recent studies have provided new insights into the mechanisms of G protein signaling in rice grain size and yield control. In this review,we summarize recent advances on the function of G proteins in rice grain size control and discuss the potential genetic and molecular mechanisms of plant G protein signaling.

关键词： Heterotrimeric G proteins cellular processes in eukaryotes G protein signaling

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Coupling relationships between brachiopods and Girvanella during the Late Devonian F-F transition in Guilin, South China

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Science China Earth Sciences 2008年第11期51卷 1581-1588页

作者： xu ran GONG YiMing ZENG JianWei Key Laboratory of Biogeology and Environmental Geology of Ministry of Education State Key Laboratory of Geological Processes and Mineral ResourcesChina University of GeosciencesWuhan 430074China Institute of Resources and Environment Key Laboratory of Biogenic Traces&Sedimentary Minerals of Henan ProvinceHenan Polytechnic UniversityJiaozuo 454003China

The abundance curves derived from area proportions of brachiopods and Girvanella in the thin sections from the Yangdi section, South China, exhibits complex relationships during the Late Devonian Frasnian-Famennian transition. The living activity of brachiopods such as grazing and borrowing did great damage to the growth of Girvanella. However, there was more to just a mere a survival competing relationship between them, Girvanella actually improved marine environments by oxygenating the dysoxic ambient sea-water through photosynthesis in the lower Kellwasser Horizon. Profited from this improvement brachiopods' abundance increased subsequently and suppressed Girvanella again. Nonetheless, without Girvanella's photosynthesis, brachiopods were wiped out by the farther anoxic environments in the upper Kellwasser Horizon. The complex relationships between Girvanella and brachiopods may be a key to unlocking the relationships between geomicrobes and metazoans in the geological overturn periods.

关键词： brachiopods Girvanella anoxia Late Devonian F-F mass extinction South China

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Hydrothermal activities and seawater acidification in the Late Devonian F-F transition:Evidence from geochemistry of rare earth elements

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Science China Earth Sciences 2011年第4期54卷 540-549页

作者： ZENG JianWei xu ran GONG YiMing Key Laboratory of Biogeology and Environmental Geology of Ministry of Education & State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Wuhan 430074 China Institute of Resources and Environment Key Laboratory of Biogenic Traces & Sedimentary Minerals of Henan Province Henan Polytechnic University Jiaozuo 454003 China

Rare-earth dements （REE） in limestones were measured by ICP-MS from the Yangdi section across the Frasnian-Famennian （F-F） transition in Guilin, Guangxi of South China. The average EREE contents of measured samples are 33.32 ppm. The average LREE/HREE ratio is 6.35. Data show LREE-enriched REE distribution pattern in the Yangdi section. Most of samples are characterized by positive Eu anomaly with average of 1.13, and there are two maxima of Eu anomaly just below the F-F boundary. Almost all analytical samples show obvious tetrad effects. Remarkable M-shaped tetrad effects are observed in these samples with positive Eu anomaly. The characters of REE and some relative elements （Fe, Mn, Al, etc.） indicate that hydro- thermal activities occurred and resulted in seawater acidification in Upper and Lower Kellwasser horizons of the Late Devonian. The changes of marine environment caused by hydrothermal activities, such as seawater acidification, heavy metal pollution, and eutrophication, would destroy the neritic ecosystem and finally result in the F-F mass extinction.

关键词： Devonian mass extinction REE hydrothermal activities tetrad effects seawater acidification

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Temporally Consistent Depth Map Prediction Using Deep Convolutional Neural Network and Spatial-Temporal Conditional random Field

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Journal of Computer Science & Technology 2017年第3期32卷 443-456页

作者： xu-ran Zhao xun Wang Qi-Chao Chen School of Computer and Information Engineering Zhejiang Gongshang University Hangzhou 310018 China

Deep convolutional neural networks （DCNNs） based methods recently keep setting new records on the tasks of predicting depth maps from monocular images. When dealing with video-based applications such as 2D （2-dimensional） to 3D （3-dimensional） video conversion, however, these approaches tend to produce temporally inconsistent depth maps, since their CNN models are optimized over single frames. In this paper, we address this problem by introducing a novel spatial-temporal conditional random fields （CRF） model into the DCNN architecture, which is able to enforce temporal consistency between depth map estimations over consecutive video frames. In our approach, temporally consistent superpixel （TSP） is first applied to an image sequence to establish the correspondence of targets in consecutive frames. A DCNN is then used to regress the depth value of each temporal superpixel, followed by a spatial-temporal CRF layer to model the relationship of the estimated depths in both spatial and temporal domains. The parameters in both DCNN and CRF models are jointly optimized with back propagation. Experimental results show that our approach not only is able to significantly enhance the temporal consistency of estimated depth maps over existing single-frame-based approaches, but also improves the depth estimation accuracy in terms of various evaluation metrics.

关键词： depth estimation temporal consistency convolutional neural network conditional random fields

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Multi-objective Hierarchical Optimization of Interior Permanent Magnet Synchronous Machines Based on Rotor Surface Modification

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CES Transactions on Electrical Machines and Systems 2022年第4期6卷 352-358页

作者： ran xu Wenming Tong School of Electrical Engineering Shenyang University of TechnologyShenyang 110870China IEEE the National Engineering Research Center for Rare Earth Permanent Magnet Machines Shenyang University of TechnologyShenyang 110870China

To solve the problem of large torque ripple of interior permanent magnet synchronous motor(IPMSM),the rotor surface notch design method was used for V-type *** order to accurately obtain the optimal parameter values to improve the torque performance of the motor,this paper takes the output torque capacity and torque ripple as the optimization objectives,and proposes a multi-objective layered optimization method based on the parameter hierarchical design combined with Taguchi method and response surface method(RSM).The conclusion can be drawn by comparing the electromagnetic performance of the motor before and after optimization,the proposed IPMSM based on the rotor surface notch design can not only improve the output torque,but also play an obvious inhibition effect on the torque ripple.

关键词： Interior permanent magnet synchronous machine Torque ripple Rotor surface modification RSM Multi-objective hierarchical optimization

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