This paper proposes a design and control scheme for a vision-based tri-pedal crawling robot system for collaborative on-orbit assembly tasks of modular large space structures,aiming to achieve efficient and universal ...This paper proposes a design and control scheme for a vision-based tri-pedal crawling robot system for collaborative on-orbit assembly tasks of modular large space structures,aiming to achieve efficient and universal precise assembly.Firstly,a kinematic model for the dual-robot system is established to describe their pose states,and a linear interpolation method is employed to calculate their motion trajectories.Then,a visual recognition system platform is developed to monitor the pose states in real-time,providing error compensation data to enhance the motion control accuracy of the robots.Furthermore,a synchronous clock and heartbeat packet protocol are integrated into the electromechanical system to ensure the real-time performance and reliability of information interaction.The truss design adopts a hybrid approach combining a central main magnet with four peripheral pin interfaces,which improves the connection stability and assembly fault tolerance.Finally,ground-based experiments demonstrate that the proposed on-orbit assembly system can complete the dual-robot collaborative assembly task under simplified laboratory conditions.The experimental results confirm the effectiveness and feasibility of the proposed system,as well as its potential for further development toward on-orbit assembly applications.展开更多
High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation ba...High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation based on HLA/RTI, which extends HLA in various aspects like functionality and efficiency. However, related study on the load balancing problem of HLA collaborative simulation is insufficient. Without load balancing, collaborative simulation under HLA/RTI may encounter performance reduction or even fatal errors. In this paper, load balancing is further divided into static problems and dynamic problems. A multi-objective model is established and the randomness of model parameters is taken into consideration for static load balancing, which makes the model more credible. The Monte Carlo based optimization algorithm(MCOA) is excogitated to gain static load balance. For dynamic load balancing, a new type of dynamic load balancing problem is put forward with regards to the variable-structured collaborative simulation under HLA/RTI. In order to minimize the influence against the running collaborative simulation, the ordinal optimization based algorithm(OOA) is devised to shorten the optimization time. Furthermore, the two algorithms are adopted in simulation experiments of different scenarios, which demonstrate their effectiveness and efficiency. An engineering experiment about collaborative simulation under HLA/RTI of high speed electricity multiple units(EMU) is also conducted to indentify credibility of the proposed models and supportive utility of MCOA and OOA to practical engineering systems. The proposed research ensures compatibility of traditional HLA, enhances the ability for assigning simulation loads onto computing units both statically and dynamically, improves the performance of collaborative simulation system and makes full use of the hardware resources.展开更多
Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(...Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(BRI countries)as the research areas and using collaborated Web of Science(WOS)core collection papers to construct an international scientific collaboration matrix,the paper explores the spatial structure,hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road.The results show that:1)Beyond the Belt and Road regions(BRI regions),Central&Eastern Europe,China and West Asia&North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions.China has the dominant role over other BRI countries in generating scientific links.The overall spatial structure has changed to a skeleton structure consisting of many dense regions,such as Europe,North America,East Asia and Oceania.2)Within the Belt and Road regions,Central&Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries.The spatial structure of scientific collaboration networks has transformed from the‘dual core’composed of China and the Central&Eastern Europe region,to the‘multi-polarization’composed of‘one zone and multi-points’.3)The hierarchical structure of scientific collaboration networks presents a typical‘core-periphery’structure,and changes from‘single core’to‘double cores’.4)Among the formation mechanisms of scientific collaboration networks,scientific research strength and social proximity play the most important roles,while geographical distance gradually weakens the hindrance to scientific collaboration.展开更多
Carbon fibers have excellent properties,including high strength,light weight,corrosion resistance,andhigh durability;therefore,they are widely used in various fields.Carbon fibers possess excellent electricalconductiv...Carbon fibers have excellent properties,including high strength,light weight,corrosion resistance,andhigh durability;therefore,they are widely used in various fields.Carbon fibers possess excellent electricalconductivity and electrochemical stability,and they can be used as electrode materials for functionalizedapplications in civil engineering.This study explores the evolution mechanism of the electrochemicalproperties of carbon fibers and carbon fiber composites used as anodes.This study further focuses onthe collaborative intervention technique of impressed current cathodic protection and structuralstrengthening(ICCP-SS)for reinforced concrete structures,as well as the non-destructive recycling of car-bon fibers based on their electrochemical evolution mechanism.This study aims to provide new ideas forthe functionalization of carbon fiber composites in civil engineering.展开更多
Inspired that the neck structure can stabilize the head from body movements and external dynamic vibration by the role of intervertebral disc and surrounding muscles,a novel multi-layer structure with nonlinear elasti...Inspired that the neck structure can stabilize the head from body movements and external dynamic vibration by the role of intervertebral disc and surrounding muscles,a novel multi-layer structure with nonlinear elastic components is proposed in this paper.The proposed structure is expected for loading the weight of the end effector and isolating bending vibration with lowfrequency in the range of 0.1 Hz to 1 Hz.First,considering the loading,the potential energy,restoring force,and structural configuration in axial direction are defined.Then,the dynamical restoring force and stiffness for bending are modelled for different structural parameters and configurations after the axial weight.According to the functions of the proposed structure required in applications including loading capacity and bending vibration isolation effectiveness,design criteria are carried out.Due to the realization of high-order quasi-zero stiffness property,the effective isolation band for bending vibration can be extended from about 0.08 Hz.In addition,based on the proposed design criteria,the constructed multi-layer structure displays remarkable dynamical stabilization effectiveness in ultralow frequency band.The proposed structure not only provides the biological explanations for car sickness,nausea,and airsickness of humans,but also solves the bottleneck techniques in bioinspired nonlinear isolation structural design for transverse dynamical stabilization,which has remarkable potential applications in the fields of mechanical arm,sensors in satellite etc.展开更多
Ni-rich layered oxides(Ni>80%)with high energy density have become a mainstream cathode material for Li-ion batteries.However,irreversible phase transitions and interface instability are deep-seated challenges in c...Ni-rich layered oxides(Ni>80%)with high energy density have become a mainstream cathode material for Li-ion batteries.However,irreversible phase transitions and interface instability are deep-seated challenges in commercializing Ni-rich materials.This study used a collaborative modification strategy involving doping and coating with quadrivalent elements to construct Ni-rich materials.In particular,introducing tetravalent Zr makes the valence change of Ni(2+to 4+)more accessible to complete spontaneously during the charging and discharging processes,which significantly suppresses the cationic mixing and irreversible phase transition(H2?H3).Combining the strategy of constructing CeO2 coatings on the surface and interfacial spinel-like phases improves the Li+diffusion kinetics and interfacial stability.Simultaneously,part of the strongly oxidizing four-valence Ce4+diffuses to the surface layer,further increasing the average valence state of Ni.Therefore,LiNi0.83Co0.11Mn0.06O2(NCM)-Zr@Ce achieves 78.5%outstanding retention at1.0C after 200 cycles within 3.0-4.3 V compared to unmodified NCM with 41.4%retention.The improved cyclic stability can be attributed to the collaborative modification strategy of the quadrivalent elements,which provides an effective synergistic modification strategy for developing high-performance Li-ion battery cathode materials.展开更多
Taking autonomous driving and driverless as the research object,we discuss and define intelligent high-precision map.Intelligent high-precision map is considered as a key link of future travel,a carrier of real-time p...Taking autonomous driving and driverless as the research object,we discuss and define intelligent high-precision map.Intelligent high-precision map is considered as a key link of future travel,a carrier of real-time perception of traffic resources in the entire space-time range,and the criterion for the operation and control of the whole process of the vehicle.As a new form of map,it has distinctive features in terms of cartography theory and application requirements compared with traditional navigation electronic maps.Thus,it is necessary to analyze and discuss its key features and problems to promote the development of research and application of intelligent high-precision map.Accordingly,we propose an information transmission model based on the cartography theory and combine the wheeled robot’s control flow in practical application.Next,we put forward the data logic structure of intelligent high-precision map,and analyze its application in autonomous driving.Then,we summarize the computing mode of“Crowdsourcing+Edge-Cloud Collaborative Computing”,and carry out key technical analysis on how to improve the quality of crowdsourced data.We also analyze the effective application scenarios of intelligent high-precision map in the future.Finally,we present some thoughts and suggestions for the future development of this field.展开更多
The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables,such as applied load,working temperature,geometrical dimensions and material properties.In order to am...The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables,such as applied load,working temperature,geometrical dimensions and material properties.In order to ameliorate reliability analysis efficiency without loss of reliability,the distributed collaborative response surface method(DCRSM) was proposed,and its basic theories were established in this work.Considering the failure dependency among the failure modes,the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables.Then,the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion.Finally,the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method.Through the comparison of DCRSM,Monte Carlo method(MCM) and the traditional response surface method(RSM),the results show that the computational precision for DCRSM is more consistent with MCM than RSM,while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions.Thus,DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables,and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.展开更多
The lattice Boltzmann method (LBM) is coupled with the multiple-relaxation- time (MRT) collision model and the three-dimensional 19-discrete-velocity (D3Q19) model to resolve intermittent behaviors on small scal...The lattice Boltzmann method (LBM) is coupled with the multiple-relaxation- time (MRT) collision model and the three-dimensional 19-discrete-velocity (D3Q19) model to resolve intermittent behaviors on small scales in isotropic turbulent flows. The high- order scaling exponents of the velocity structure functions, the probability distribution functions of Lagrangian accelerations, and the local energy dissipation rates are investi- gated. The self-similarity of the space-time velocity structure functions is explored using the extended self-similarity (ESS) method, which was originally developed for velocity spatial structure functions. The scaling exponents of spatial structure functions at up to ten orders are consistent with the experimental measurements and theoretical results, implying that the LBM can accurately resolve the intermittent behaviors. This valida~ tion provides a solid basis for using the LBM to study more complex processes that are sensitive to small scales in turbulent flows, such as the relative dispersion of pollutants and mesoscale structures of preferential concentration of heavy particles suspended in turbulent flows.展开更多
This paper compares the effectiveness of one-semester-long instruction of teacher-student collaborative assessment(TSCA)and trained peer review assessment(TPRA).Dependent variables include occurrence of structural ele...This paper compares the effectiveness of one-semester-long instruction of teacher-student collaborative assessment(TSCA)and trained peer review assessment(TPRA).Dependent variables include occurrence of structural elements of the simplified Toulmin model,and improvement of argumentation substance which refers to the quality of reasoning reflected in Toulmin structural elements.Eighty-one sophomore English majors from TSCA group(n=41)and TPRA group(n=40)were asked to construct two argumentative essays at both the beginning and the end of the semester.The results reveal that the TSCA group produced significantly more counterargument claims and rebuttal data.Additionally,the TSCA group significantly outperformed TPRA group in constructing stronger counterargument claim,rebuttal claim and rebuttal data.展开更多
Motivated by state estimation and adaptive control of large-scale complex power systems,this paper proposes a cascaded sliding-mode observer for high-order systems with lower-triangular structure and not necessarily i...Motivated by state estimation and adaptive control of large-scale complex power systems,this paper proposes a cascaded sliding-mode observer for high-order systems with lower-triangular structure and not necessarily in Byrnes-Isidori Normal Form.Key information about the known nonlinear terms of the system is integrated into different blocks of the proposed observer.Under appropriate parameter design rules,the states of the proposed observer will quickly reach and slide on the intersection of sliding surfaces.During this sliding phase,the estimation errors rapidly converge to negligibly small values,determined by a parameter of the observer.Compared with standard high-gain observers and classical high-gain parameter embedded sliding-mode observers,the proposed observer achieves similar estimation error convergence speed with smaller gain coefficients.Moreover,the peaking phenomenon of the proposed observer is less severe.Besides,the structure of the proposed observer is more flexible than that of some well-known cascaded high-gain observers as there is no restriction on the dimension of the blocks of the proposed observer.Simulation studies are carried out on a fifth-order nonlinear system and a 10-machine 48-bus power system to further demonstrate the features of the proposed observer and its application on adaptive transient stability control of wind farms penetrated power systems.展开更多
The health monitoring for large-scale structures need to resolve a large number of difficulties,such as the data transmission and distributing information handling.To solve these problems,the technology of multi-agent...The health monitoring for large-scale structures need to resolve a large number of difficulties,such as the data transmission and distributing information handling.To solve these problems,the technology of multi-agent is a good candidate to be used in the field of structural health monitoring.A structural health monitoring system architecture based on multi-agent technology is proposed.The measurement system for aircraft airfoil is designed with FBG,strain gage,and corresponding signal processing circuit.The experiment to determine the location of the concentrate loading on the structure is carried on with the system combined with technologies of pattern recognition and multi-agent.The results show that the system can locate the concentrate loading of the aircraft airfoil at the accuracy of 91.2%.展开更多
基金supported by the Basic Science Center Pro-gram of the National Natural Science Foundation of China(62388101).
摘要This paper proposes a design and control scheme for a vision-based tri-pedal crawling robot system for collaborative on-orbit assembly tasks of modular large space structures,aiming to achieve efficient and universal precise assembly.Firstly,a kinematic model for the dual-robot system is established to describe their pose states,and a linear interpolation method is employed to calculate their motion trajectories.Then,a visual recognition system platform is developed to monitor the pose states in real-time,providing error compensation data to enhance the motion control accuracy of the robots.Furthermore,a synchronous clock and heartbeat packet protocol are integrated into the electromechanical system to ensure the real-time performance and reliability of information interaction.The truss design adopts a hybrid approach combining a central main magnet with four peripheral pin interfaces,which improves the connection stability and assembly fault tolerance.Finally,ground-based experiments demonstrate that the proposed on-orbit assembly system can complete the dual-robot collaborative assembly task under simplified laboratory conditions.The experimental results confirm the effectiveness and feasibility of the proposed system,as well as its potential for further development toward on-orbit assembly applications.
基金supported by National Science and Technology Support Program of China (Grant No. 2012BAF15G00)
摘要High level architecture(HLA) is the open standard in the collaborative simulation field. Scholars have been paying close attention to theoretical research on and engineering applications of collaborative simulation based on HLA/RTI, which extends HLA in various aspects like functionality and efficiency. However, related study on the load balancing problem of HLA collaborative simulation is insufficient. Without load balancing, collaborative simulation under HLA/RTI may encounter performance reduction or even fatal errors. In this paper, load balancing is further divided into static problems and dynamic problems. A multi-objective model is established and the randomness of model parameters is taken into consideration for static load balancing, which makes the model more credible. The Monte Carlo based optimization algorithm(MCOA) is excogitated to gain static load balance. For dynamic load balancing, a new type of dynamic load balancing problem is put forward with regards to the variable-structured collaborative simulation under HLA/RTI. In order to minimize the influence against the running collaborative simulation, the ordinal optimization based algorithm(OOA) is devised to shorten the optimization time. Furthermore, the two algorithms are adopted in simulation experiments of different scenarios, which demonstrate their effectiveness and efficiency. An engineering experiment about collaborative simulation under HLA/RTI of high speed electricity multiple units(EMU) is also conducted to indentify credibility of the proposed models and supportive utility of MCOA and OOA to practical engineering systems. The proposed research ensures compatibility of traditional HLA, enhances the ability for assigning simulation loads onto computing units both statically and dynamically, improves the performance of collaborative simulation system and makes full use of the hardware resources.
基金Under the auspices of Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA20010103)。
摘要Scientific collaboration has become an important part of the people-to-people exchanges in the Belt and Road initiative,and remarkable progress has been made since 2013.Taking the 65 countries along the Belt and Road(BRI countries)as the research areas and using collaborated Web of Science(WOS)core collection papers to construct an international scientific collaboration matrix,the paper explores the spatial structure,hierarchy and formation mechanisms of scientific collaboration networks of 65 countries along the Belt and Road.The results show that:1)Beyond the Belt and Road regions(BRI regions),Central&Eastern Europe,China and West Asia&North Africa have formed a situation in which they all have the most external links with other countries beyond BRI regions.China has the dominant role over other BRI countries in generating scientific links.The overall spatial structure has changed to a skeleton structure consisting of many dense regions,such as Europe,North America,East Asia and Oceania.2)Within the Belt and Road regions,Central&Eastern Europe has become the largest collaboration partner with other sub-regions in BRI countries.The spatial structure of scientific collaboration networks has transformed from the‘dual core’composed of China and the Central&Eastern Europe region,to the‘multi-polarization’composed of‘one zone and multi-points’.3)The hierarchical structure of scientific collaboration networks presents a typical‘core-periphery’structure,and changes from‘single core’to‘double cores’.4)Among the formation mechanisms of scientific collaboration networks,scientific research strength and social proximity play the most important roles,while geographical distance gradually weakens the hindrance to scientific collaboration.
基金the support provided by the Key-Area Research and Development Program of Guangdong Province(2019B111107002).
摘要Carbon fibers have excellent properties,including high strength,light weight,corrosion resistance,andhigh durability;therefore,they are widely used in various fields.Carbon fibers possess excellent electricalconductivity and electrochemical stability,and they can be used as electrode materials for functionalizedapplications in civil engineering.This study explores the evolution mechanism of the electrochemicalproperties of carbon fibers and carbon fiber composites used as anodes.This study further focuses onthe collaborative intervention technique of impressed current cathodic protection and structuralstrengthening(ICCP-SS)for reinforced concrete structures,as well as the non-destructive recycling of car-bon fibers based on their electrochemical evolution mechanism.This study aims to provide new ideas forthe functionalization of carbon fiber composites in civil engineering.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.12122208 and 11972254)。
摘要Inspired that the neck structure can stabilize the head from body movements and external dynamic vibration by the role of intervertebral disc and surrounding muscles,a novel multi-layer structure with nonlinear elastic components is proposed in this paper.The proposed structure is expected for loading the weight of the end effector and isolating bending vibration with lowfrequency in the range of 0.1 Hz to 1 Hz.First,considering the loading,the potential energy,restoring force,and structural configuration in axial direction are defined.Then,the dynamical restoring force and stiffness for bending are modelled for different structural parameters and configurations after the axial weight.According to the functions of the proposed structure required in applications including loading capacity and bending vibration isolation effectiveness,design criteria are carried out.Due to the realization of high-order quasi-zero stiffness property,the effective isolation band for bending vibration can be extended from about 0.08 Hz.In addition,based on the proposed design criteria,the constructed multi-layer structure displays remarkable dynamical stabilization effectiveness in ultralow frequency band.The proposed structure not only provides the biological explanations for car sickness,nausea,and airsickness of humans,but also solves the bottleneck techniques in bioinspired nonlinear isolation structural design for transverse dynamical stabilization,which has remarkable potential applications in the fields of mechanical arm,sensors in satellite etc.
基金financially supported by the Department of Science and Technology of Guangxi Province (Nos.2022JBGS004,AB21220027,AD19110090 and AD19110077)the National Natural Science Foundation of China (Nos.21805055 and12172096)+2 种基金Guangxi Natural Science Foundation (Nos.2020GXNSFAA159059 and 2020GXNSFAA159037)Guangxi Key Laboratory of Manufacturing Systems Foundation (No.20-065-40-005Z)the Engineering Research Center Foundation of Electronic Information Materials and Devices (No.EIMD-AA202005)。
摘要Ni-rich layered oxides(Ni>80%)with high energy density have become a mainstream cathode material for Li-ion batteries.However,irreversible phase transitions and interface instability are deep-seated challenges in commercializing Ni-rich materials.This study used a collaborative modification strategy involving doping and coating with quadrivalent elements to construct Ni-rich materials.In particular,introducing tetravalent Zr makes the valence change of Ni(2+to 4+)more accessible to complete spontaneously during the charging and discharging processes,which significantly suppresses the cationic mixing and irreversible phase transition(H2?H3).Combining the strategy of constructing CeO2 coatings on the surface and interfacial spinel-like phases improves the Li+diffusion kinetics and interfacial stability.Simultaneously,part of the strongly oxidizing four-valence Ce4+diffuses to the surface layer,further increasing the average valence state of Ni.Therefore,LiNi0.83Co0.11Mn0.06O2(NCM)-Zr@Ce achieves 78.5%outstanding retention at1.0C after 200 cycles within 3.0-4.3 V compared to unmodified NCM with 41.4%retention.The improved cyclic stability can be attributed to the collaborative modification strategy of the quadrivalent elements,which provides an effective synergistic modification strategy for developing high-performance Li-ion battery cathode materials.
基金National Key Research and Development Program(No.2018YFB1305001)Major Consulting and Research Project of Chinese Academy of Engineering(No.2018-ZD-02-07)。
摘要Taking autonomous driving and driverless as the research object,we discuss and define intelligent high-precision map.Intelligent high-precision map is considered as a key link of future travel,a carrier of real-time perception of traffic resources in the entire space-time range,and the criterion for the operation and control of the whole process of the vehicle.As a new form of map,it has distinctive features in terms of cartography theory and application requirements compared with traditional navigation electronic maps.Thus,it is necessary to analyze and discuss its key features and problems to promote the development of research and application of intelligent high-precision map.Accordingly,we propose an information transmission model based on the cartography theory and combine the wheeled robot’s control flow in practical application.Next,we put forward the data logic structure of intelligent high-precision map,and analyze its application in autonomous driving.Then,we summarize the computing mode of“Crowdsourcing+Edge-Cloud Collaborative Computing”,and carry out key technical analysis on how to improve the quality of crowdsourced data.We also analyze the effective application scenarios of intelligent high-precision map in the future.Finally,we present some thoughts and suggestions for the future development of this field.
基金Project(51335003)supported by the National Natural Science Foundation of ChinaProject(20111102110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
摘要The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables,such as applied load,working temperature,geometrical dimensions and material properties.In order to ameliorate reliability analysis efficiency without loss of reliability,the distributed collaborative response surface method(DCRSM) was proposed,and its basic theories were established in this work.Considering the failure dependency among the failure modes,the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables.Then,the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion.Finally,the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method.Through the comparison of DCRSM,Monte Carlo method(MCM) and the traditional response surface method(RSM),the results show that the computational precision for DCRSM is more consistent with MCM than RSM,while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions.Thus,DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables,and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.
基金Project supported by the Science Challenge Program(No.TZ2016001)the National Natural Science Foundation of China(Nos.11472277,11572331,11232011,and 11772337)+2 种基金the Strategic Priority Research Program,Chinese Academy of Sciences(CAS)(No.XDB22040104)the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-SYS002)the National Basic Research Program of China(973 Program)(No.2013CB834100)
摘要The lattice Boltzmann method (LBM) is coupled with the multiple-relaxation- time (MRT) collision model and the three-dimensional 19-discrete-velocity (D3Q19) model to resolve intermittent behaviors on small scales in isotropic turbulent flows. The high- order scaling exponents of the velocity structure functions, the probability distribution functions of Lagrangian accelerations, and the local energy dissipation rates are investi- gated. The self-similarity of the space-time velocity structure functions is explored using the extended self-similarity (ESS) method, which was originally developed for velocity spatial structure functions. The scaling exponents of spatial structure functions at up to ten orders are consistent with the experimental measurements and theoretical results, implying that the LBM can accurately resolve the intermittent behaviors. This valida~ tion provides a solid basis for using the LBM to study more complex processes that are sensitive to small scales in turbulent flows, such as the relative dispersion of pollutants and mesoscale structures of preferential concentration of heavy particles suspended in turbulent flows.
基金supported by China Foreign Language Education Fund(10th Batch)granted by Beijing Foreign Studies University,directed by Prof.Xiaoyan XU[Grant Number:ZGWYJYJJ10A130]Sichuan Research Center of Foreign Languages and LiteratureHigher Education Press,directed by Yuexin ZHONG[Grant Number:SCWYGJ21-10]。
摘要This paper compares the effectiveness of one-semester-long instruction of teacher-student collaborative assessment(TSCA)and trained peer review assessment(TPRA).Dependent variables include occurrence of structural elements of the simplified Toulmin model,and improvement of argumentation substance which refers to the quality of reasoning reflected in Toulmin structural elements.Eighty-one sophomore English majors from TSCA group(n=41)and TPRA group(n=40)were asked to construct two argumentative essays at both the beginning and the end of the semester.The results reveal that the TSCA group produced significantly more counterargument claims and rebuttal data.Additionally,the TSCA group significantly outperformed TPRA group in constructing stronger counterargument claim,rebuttal claim and rebuttal data.
摘要Motivated by state estimation and adaptive control of large-scale complex power systems,this paper proposes a cascaded sliding-mode observer for high-order systems with lower-triangular structure and not necessarily in Byrnes-Isidori Normal Form.Key information about the known nonlinear terms of the system is integrated into different blocks of the proposed observer.Under appropriate parameter design rules,the states of the proposed observer will quickly reach and slide on the intersection of sliding surfaces.During this sliding phase,the estimation errors rapidly converge to negligibly small values,determined by a parameter of the observer.Compared with standard high-gain observers and classical high-gain parameter embedded sliding-mode observers,the proposed observer achieves similar estimation error convergence speed with smaller gain coefficients.Moreover,the peaking phenomenon of the proposed observer is less severe.Besides,the structure of the proposed observer is more flexible than that of some well-known cascaded high-gain observers as there is no restriction on the dimension of the blocks of the proposed observer.Simulation studies are carried out on a fifth-order nonlinear system and a 10-machine 48-bus power system to further demonstrate the features of the proposed observer and its application on adaptive transient stability control of wind farms penetrated power systems.
基金supported by the Key Program of the National Science Foundation of China(50830201)Aviation Research Foundation(20060952)+1 种基金the National High Technology Research and Development of China(2007AA03Z117)the Natural Science Foundation of Jiansu Province(08kjd560009)
摘要The health monitoring for large-scale structures need to resolve a large number of difficulties,such as the data transmission and distributing information handling.To solve these problems,the technology of multi-agent is a good candidate to be used in the field of structural health monitoring.A structural health monitoring system architecture based on multi-agent technology is proposed.The measurement system for aircraft airfoil is designed with FBG,strain gage,and corresponding signal processing circuit.The experiment to determine the location of the concentrate loading on the structure is carried on with the system combined with technologies of pattern recognition and multi-agent.The results show that the system can locate the concentrate loading of the aircraft airfoil at the accuracy of 91.2%.