Collective cell groups are organized to form specific patterns that play an important role in various physiological and pathological processes,such as tissue morphogenesis,wound healing,and cancer invasion.Compared to...Collective cell groups are organized to form specific patterns that play an important role in various physiological and pathological processes,such as tissue morphogenesis,wound healing,and cancer invasion.Compared to the behaviors of single cells that have been studied intensively from many aspects(cell migration,adhesion,polarization,proliferation,etc.)and at various length scales(molecular,subcellular,and cellular),the behaviors of multiple cells are less well understood,particularly from a quantitative perspective.In this talk,we present our recent studies of collective polarization and orientation of multiple cells through both experimental measurement and theoretical modeling,including cell behavior on/in 2D and 3D substrate/tissue.We find that collective cell behavior,including polarization,alignment,and migration,is closely related to local stress states in cell layers or tissue,which demonstrates the crucial role of mechanical forces in living organisms.Specifically,cells demonstrate preferential polarization and alignment along the maximum principal stress in the cell layer,and the cell aspect ratio increases with in-plane maximum shear stress,suggesting that the maximum shear stress is the underlying driving force of cell polarization and orientation.This theory of stress-driven cell behaviors of polarization and orientation provides a new perspective for understanding cell behaviors in living organisms and a guideline for tissue engineering in potential biomedical applications.Strikingly,we note that with regard to the polarization and alignment of collective cells,a typical feature of cell morphology is that the cells generally align along the edge of the pattern,which was called edge effect or boundary effect by assuming that the edge plays a role in cell alignment due to a phenomenon of chemistry.However,the edge effect is an obscure explanation.Here we showed that the edge effect could be explained by the theory of stress-driven cell behavior,i.e.,inplane stress-driven cell polarization and alignment.That is,the cell layer has a stress-free boundary condition at the edge,and thus the direction of the maximum principal stress should be precisely along the edge.According to the theory of stress-driven cell polarity,the cells then preferentially align with the edge of the cell layer,independently of the geometry of the pattern.Once there is a force-free condition at the edge or the boundary,the cells align along the edge of the pattern.Otherwise,the cell may not align with the edge;for example,the cells preferentially align in the radial direction of the wound because of the presence of the contractile force by the actin ring at the wound edge,which is in contradiction with the so-called edge effect but consistent with our theory of stress-driven cell polarity.展开更多
The dynamic behaviors of collective cells play a significant role in many physiological and pathological processes,e.g.,embryonic development and cancer metastasis.In this talk,theoretical models,numerical simulations...The dynamic behaviors of collective cells play a significant role in many physiological and pathological processes,e.g.,embryonic development and cancer metastasis.In this talk,theoretical models,numerical simulations,and experimental measurements are combined to investigate the dynamics of collective cells[1-5].First,cell division is the most fundamental process in embryonic development,tissue morphogenesis,and tumor growth.Experiments have suggested that mitotic cell division is regulated by intercellular cues.However,it remains unclear how cell-cell junctions affect the spindle machinery that determines the dividing orientation of cells.We establish a dynamic cell division model to explore the coupling of mechanical and chemical mechanisms,including cortical cell polarity,microtubule kinetics,cellular stiffness,internal osmotic pressure,and cell-cell junctions[2].The model reveals that the distributed forces of astral microtubules play a key role in encoding the instructive cell-cell junctional cues to orient the division of a rounded mitotic cell.By comparing with relevant experimental observations,we show that the model can not only predict the spindle orientation and positioning,but also capture the physical mechanisms of cell rounding.This work sheds light on the biophysical linkage between the cell cortex and the mitotic spindle,and holds potential applications in regulating cell division and sculpting tissue morphology.Second,collective cell migration occurs in a diversity of physiological processes such as wound healing,cancer metastasis,and embryonic morphogenesis.In the collective context,cohesive cells may move as a translational solid,swirl as a fluid,or even rotate like a disk,with scales ranging from several to dozens of cells.An active vertex model is presented to explore the regulatory roles of social interactions of neighboring cells and environmental confinements in collective cell migration in a confluent monolayer[2,3].It is found that the competition between two kinds of intercellular social interactions-local alignment(LA)and contact inhibition of locomotion(CIL)——drives the cells to self-organize into various dynamic coherent structures with a spatial correlation scale.The interplay between this intrinsic length scale and the external confinement dictates the migration modes of collective cells confined in a finite space.We also show that the LA-CIL coordination can induce giant density fluctuations in a confluent cell monolayer without gaps,which triggers the spontaneous breaking of orientational symmetry and leads to phase separation.Third,migrating cells constantly experience geometrical confinements in vivo,as exemplified by cancer invasion and embryo development.We investigate how intrinsic cellular properties and extrinsic channel confinements regulate the two-dimensional migratory dynamics of collective cells dynamics.We find that besides external confinement,active cell motility and cell crowdedness also shape the migration modes of collective cells.Further,the effects of active cell motility,cell crowdedness,and confinement size on collective cell migration can be integrated into a unified dimensionless parameter,defined as the cellular motility number(CMN),which mirrors the competition between active motile force and passive elastic restoring force of cells.A low CMN favors laminar-like cell flows,while a high CMN destabilizes cell motions,resulting in a series of mode transitions from a laminar phase to an ordered vortex chain,and further to a mesoscale turbulent phase.These findings not only explain recent experiments but also predict dynamic behaviors of cell collectives,such as the existence of an ordered vortex chain mode and the mode selection under non-straight confinements,which are experimentally testable across different epithelial cell lines.Fourth,self-organization of cells ordinarily displays collective dynamics that are crucial in biological processes such as embryogenesis and tumor invasion.We combine experiments and theory to investigate the energy landscape of self-sustained mesoscale cell turbulence emerging in confluent two-dimensional(2D)cell monolayers.We find that the enstrophy ofcollective cell flows scales linearly with the kinetic energy as the monolayer matures,defining a characteristic length scale of vortices.The kinetic energies of cells over time collapse to a family of probability distributions,which deviate from the classic Boltzmann distribution.The energy spectra for large wavenumbers exhibit a power-decaying law,with a scaling exponent markedly different from that in the classic 2D Kolmogorov-Kraichnan turbulence.It is found that these energetic features are near-universal for all different types of cells and substrates experimentalized.Our findings provide physical insights into fundamental aspects of self-organization in biological tissues.Fifth,periodic oscillations of collective cells occur in the morphogenesis and organogenesis of various tissues and organs.An oscillating cytodynamic model is presented by integrating the chemomechanical interplay between the RhoA effector signaling pathway and cell deformation [4,5].We show that both an isolated cell and a cell aggregate can undergo spontaneous oscillations as a result of Hopf bifurcation,upon which the system evolves into a limit cycle of oscillations.The dynamic characteristics are tailored by the mechanical properties of cells(e.g.,elasticity,contractility,and intercellular tension)and the chemical reactions involved in the RhoA effector signaling pathway.External forces are found to modulate the oscillation intensity of collective cells in the monolayer and to polarize their oscillations along the direction of external tension.The proposed cytodynamic model can recapitulate the prominent features of cell oscillations observed in a variety of experiments,including both isolated cells(e.g.,spreading mouse embryonic fibroblasts,migrating amoeboid cells,and suspending 3T3fibroblasts)and multicellular systems(e.g.,Drosophila embryogenesis and oogenesis).展开更多
In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave pow...In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.展开更多
为了将模糊推理纳入逻辑的框架并从语构和语义两个方面为模糊推理奠定严格的逻辑基础,通过将模糊推理形式化的方法移植到经典命题逻辑系统中,把FMP(fuzzy modus ponens)问题转化为GMP(generalized modus ponens)问题,并基于公式的真度...为了将模糊推理纳入逻辑的框架并从语构和语义两个方面为模糊推理奠定严格的逻辑基础,通过将模糊推理形式化的方法移植到经典命题逻辑系统中,把FMP(fuzzy modus ponens)问题转化为GMP(generalized modus ponens)问题,并基于公式的真度概念提出了公式之间的支持度,进一步利用支持度的思想引入了GMP问题以及CGMP(collective generalized modus ponens)问题的一种新型最优求解机制.证明了最优解的存在性,同时指出,在经典命题逻辑系统中存在着与模糊逻辑完全相似的推理机制.该方法是一种程度化的方法,这就使得求解过程从算法上实现成为可能,并对知识的程度化推理有所启示.展开更多
Collective pitch control and individual pitch control algorithms were present for straight-bladed vertical axis wind turbine to improve the self-starting capacity.Comparative analysis of straight-bladed vertical axis ...Collective pitch control and individual pitch control algorithms were present for straight-bladed vertical axis wind turbine to improve the self-starting capacity.Comparative analysis of straight-bladed vertical axis wind turbine(SB-VAWT)with or without pitch control was conducted from the aspects of aerodynamic force,flow structure and power coefficient.The computational fluid dynamics(CFD)prediction results show a significant increase in power coefficient for SB-VAWT with pitch control.According to the aerodynamic forces and total torque coefficient obtained at various tip speed ratios(TSRs),the results indicate that the blade pitch method can increase the power output and decrease the deformation of blade;especially,the total torque coefficient of blade pitch control at TSR 1.5 is about 2.5 times larger than that of fixed pitch case.Furthermore,experiment was carried out to verify the feasibility of pitch control methods.The results show that the present collective pitch control and individual pitch control methods can improve the self-starting capacity of SB-VAWT,and the former is much better and its proper operating TSRs ranges from 0.4 to 0.6.展开更多
In general-sum games, taking all agent＇s collective rationality into account, we define agents＇ global objective, and propose a novel multi-agent reinforcement learning（RL） algorithm based on global policy. In eac...In general-sum games, taking all agent＇s collective rationality into account, we define agents＇ global objective, and propose a novel multi-agent reinforcement learning（RL） algorithm based on global policy. In each learning step, all agents commit to select the global policy to achieve the global goal. We prove this learning algorithm converges given certain restrictions on stage games of learned Q values, and show that it has quite lower computation time complexity than already developed multi-agent learning algorithms for general-sum games. An example is analyzed to show the algorithm＇ s merits.展开更多
Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a c...Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.展开更多
2024年1月4日,在Web of Science网站以“cotton”或“Gossypium”为“Title”(文题)检索词查询“Web of Science Core Collection”和“Chinese Science Citation DatabaseSM”数据库中2023年发表文章,选择被引次数5及其以上文章68篇。
根据轨道交通网络存在大量换乘路径的特点,改进深度优先搜索算法得出站点间换乘路径的有效出行时间。基于自动票务收集系统(automatic fare collection system,AFC)数据得到的乘客进出闸机时刻,利用仿真方法确定乘客与列车在时间和路径...根据轨道交通网络存在大量换乘路径的特点,改进深度优先搜索算法得出站点间换乘路径的有效出行时间。基于自动票务收集系统(automatic fare collection system,AFC)数据得到的乘客进出闸机时刻,利用仿真方法确定乘客与列车在时间和路径的接续关系,同时考虑始发乘客和换乘乘客路径选择行为的差异,将二者区分配流。动态更新先到乘客利用换乘路径的出行时间,并以更新后的时间作为后续出发乘客的路径选择依据。结果表明,该仿真方法可以有效反映乘客的出行过程,具有较高的配流精度。展开更多
Unmanned aerial vehicle(UAV)was introduced as a novel traffic device to collect road traffic information and its cruise route planning problem was considered.Firstly,a multi-objective optimization model was proposed a...Unmanned aerial vehicle(UAV)was introduced as a novel traffic device to collect road traffic information and its cruise route planning problem was considered.Firstly,a multi-objective optimization model was proposed aiming at minimizing the total cruise distance and the number of UAVs used,which used UAV maximum cruise distance,the number of UAVs available and time window of each monitored target as constraints.Then,a novel multi-objective evolutionary algorithm was proposed.Next,a case study with three time window scenarios was implemented.The results show that both the total cruise distance and the number of UAVs used continue to increase with the time window constraint becoming narrower.Compared with the initial optimal solutions,the optimal total cruise distance and the number of UAVs used fall by an average of 30.93% and 31.74%,respectively.Finally,some concerns using UAV to collect road traffic information were discussed.展开更多
With comprehensive considerations of the operational safety and collection efficiency for the tracked miner collecting the seafloor poly-metallic nodules, two new improved mining paths for the miner on the deep seaflo...With comprehensive considerations of the operational safety and collection efficiency for the tracked miner collecting the seafloor poly-metallic nodules, two new improved mining paths for the miner on the deep seafloor were proposed. Compared to the conventional mining path, the design principles and superiorities of the two new paths are that the miner turning with relative long radius should avoid large sinkage and high slip, so as to ensure its operational safety, while the space between its straight-line trajectories before and after the turning is optimum, which is designed as the total width of the miner, and collect nodules as more as possible, so as to ensure its collection efficiency. To realize the new mining paths, theoretical designs and quantitative calculations were carried out to determine the exact positions for the speed controls of the miner during its whole operation process. With the new dynamic model of the miner, and through regulations of the speeds of the left and right tracks of the miner on the exact motion positions according to the theoretical calculations, the two new improved mining paths for the miner on the seafloor were successfully simulated, thus the turning radius of the miner in the simulation is about 21.8 m, while the distance between the straight-line trajectories before and after the turning is about 5.2 m. The dynamic simulation results preliminarily prove the feasibility of these two new mining paths, and further can provide important theoretical guidance and useful technical reference for the practical tracked miner operation and control on the seafloor.展开更多
To improve the dust removal performance of the wet electrostatic precipitator(WESP), a flow field optimization scheme was proposed via CFD simulation in different scales. The simplified models of perforated and collec...To improve the dust removal performance of the wet electrostatic precipitator(WESP), a flow field optimization scheme was proposed via CFD simulation in different scales. The simplified models of perforated and collection plates were determined firstly. Then the model parameters for the resistance of perforated and collection plates, obtained by small-scale flow simulation, were validated by medium-scale experiments. Through the comparison of the resistance and velocity distribution between simulation results and experimental data, the simplified model is proved to present the resistance characteristics of perforated and collection plates accurately. Numerical results show that after optimization, both the flow rate and the pressure drop in the upper room of electric field regions are basically equivalent to those of the lower room, and the velocity distribution in flue inlet of WESP becomes more uniform. Through the application in practice, the effectiveness and reliability of the optimization scheme are proved, which can provide valuable reference for further optimization of WESP.展开更多
基金supported by the National Natural Science Foundation of China ( 11772055,11532009)
文摘Collective cell groups are organized to form specific patterns that play an important role in various physiological and pathological processes,such as tissue morphogenesis,wound healing,and cancer invasion.Compared to the behaviors of single cells that have been studied intensively from many aspects(cell migration,adhesion,polarization,proliferation,etc.)and at various length scales(molecular,subcellular,and cellular),the behaviors of multiple cells are less well understood,particularly from a quantitative perspective.In this talk,we present our recent studies of collective polarization and orientation of multiple cells through both experimental measurement and theoretical modeling,including cell behavior on/in 2D and 3D substrate/tissue.We find that collective cell behavior,including polarization,alignment,and migration,is closely related to local stress states in cell layers or tissue,which demonstrates the crucial role of mechanical forces in living organisms.Specifically,cells demonstrate preferential polarization and alignment along the maximum principal stress in the cell layer,and the cell aspect ratio increases with in-plane maximum shear stress,suggesting that the maximum shear stress is the underlying driving force of cell polarization and orientation.This theory of stress-driven cell behaviors of polarization and orientation provides a new perspective for understanding cell behaviors in living organisms and a guideline for tissue engineering in potential biomedical applications.Strikingly,we note that with regard to the polarization and alignment of collective cells,a typical feature of cell morphology is that the cells generally align along the edge of the pattern,which was called edge effect or boundary effect by assuming that the edge plays a role in cell alignment due to a phenomenon of chemistry.However,the edge effect is an obscure explanation.Here we showed that the edge effect could be explained by the theory of stress-driven cell behavior,i.e.,inplane stress-driven cell polarization and alignment.That is,the cell layer has a stress-free boundary condition at the edge,and thus the direction of the maximum principal stress should be precisely along the edge.According to the theory of stress-driven cell polarity,the cells then preferentially align with the edge of the cell layer,independently of the geometry of the pattern.Once there is a force-free condition at the edge or the boundary,the cells align along the edge of the pattern.Otherwise,the cell may not align with the edge;for example,the cells preferentially align in the radial direction of the wound because of the presence of the contractile force by the actin ring at the wound edge,which is in contradiction with the so-called edge effect but consistent with our theory of stress-driven cell polarity.
基金supported by National Natural Science Foundation of China ( 11620101001,11672161, 11672227,11432008)the Thousand Young Talents Program of China
文摘The dynamic behaviors of collective cells play a significant role in many physiological and pathological processes,e.g.,embryonic development and cancer metastasis.In this talk,theoretical models,numerical simulations,and experimental measurements are combined to investigate the dynamics of collective cells[1-5].First,cell division is the most fundamental process in embryonic development,tissue morphogenesis,and tumor growth.Experiments have suggested that mitotic cell division is regulated by intercellular cues.However,it remains unclear how cell-cell junctions affect the spindle machinery that determines the dividing orientation of cells.We establish a dynamic cell division model to explore the coupling of mechanical and chemical mechanisms,including cortical cell polarity,microtubule kinetics,cellular stiffness,internal osmotic pressure,and cell-cell junctions[2].The model reveals that the distributed forces of astral microtubules play a key role in encoding the instructive cell-cell junctional cues to orient the division of a rounded mitotic cell.By comparing with relevant experimental observations,we show that the model can not only predict the spindle orientation and positioning,but also capture the physical mechanisms of cell rounding.This work sheds light on the biophysical linkage between the cell cortex and the mitotic spindle,and holds potential applications in regulating cell division and sculpting tissue morphology.Second,collective cell migration occurs in a diversity of physiological processes such as wound healing,cancer metastasis,and embryonic morphogenesis.In the collective context,cohesive cells may move as a translational solid,swirl as a fluid,or even rotate like a disk,with scales ranging from several to dozens of cells.An active vertex model is presented to explore the regulatory roles of social interactions of neighboring cells and environmental confinements in collective cell migration in a confluent monolayer[2,3].It is found that the competition between two kinds of intercellular social interactions-local alignment(LA)and contact inhibition of locomotion(CIL)——drives the cells to self-organize into various dynamic coherent structures with a spatial correlation scale.The interplay between this intrinsic length scale and the external confinement dictates the migration modes of collective cells confined in a finite space.We also show that the LA-CIL coordination can induce giant density fluctuations in a confluent cell monolayer without gaps,which triggers the spontaneous breaking of orientational symmetry and leads to phase separation.Third,migrating cells constantly experience geometrical confinements in vivo,as exemplified by cancer invasion and embryo development.We investigate how intrinsic cellular properties and extrinsic channel confinements regulate the two-dimensional migratory dynamics of collective cells dynamics.We find that besides external confinement,active cell motility and cell crowdedness also shape the migration modes of collective cells.Further,the effects of active cell motility,cell crowdedness,and confinement size on collective cell migration can be integrated into a unified dimensionless parameter,defined as the cellular motility number(CMN),which mirrors the competition between active motile force and passive elastic restoring force of cells.A low CMN favors laminar-like cell flows,while a high CMN destabilizes cell motions,resulting in a series of mode transitions from a laminar phase to an ordered vortex chain,and further to a mesoscale turbulent phase.These findings not only explain recent experiments but also predict dynamic behaviors of cell collectives,such as the existence of an ordered vortex chain mode and the mode selection under non-straight confinements,which are experimentally testable across different epithelial cell lines.Fourth,self-organization of cells ordinarily displays collective dynamics that are crucial in biological processes such as embryogenesis and tumor invasion.We combine experiments and theory to investigate the energy landscape of self-sustained mesoscale cell turbulence emerging in confluent two-dimensional(2D)cell monolayers.We find that the enstrophy ofcollective cell flows scales linearly with the kinetic energy as the monolayer matures,defining a characteristic length scale of vortices.The kinetic energies of cells over time collapse to a family of probability distributions,which deviate from the classic Boltzmann distribution.The energy spectra for large wavenumbers exhibit a power-decaying law,with a scaling exponent markedly different from that in the classic 2D Kolmogorov-Kraichnan turbulence.It is found that these energetic features are near-universal for all different types of cells and substrates experimentalized.Our findings provide physical insights into fundamental aspects of self-organization in biological tissues.Fifth,periodic oscillations of collective cells occur in the morphogenesis and organogenesis of various tissues and organs.An oscillating cytodynamic model is presented by integrating the chemomechanical interplay between the RhoA effector signaling pathway and cell deformation [4,5].We show that both an isolated cell and a cell aggregate can undergo spontaneous oscillations as a result of Hopf bifurcation,upon which the system evolves into a limit cycle of oscillations.The dynamic characteristics are tailored by the mechanical properties of cells(e.g.,elasticity,contractility,and intercellular tension)and the chemical reactions involved in the RhoA effector signaling pathway.External forces are found to modulate the oscillation intensity of collective cells in the monolayer and to polarize their oscillations along the direction of external tension.The proposed cytodynamic model can recapitulate the prominent features of cell oscillations observed in a variety of experiments,including both isolated cells(e.g.,spreading mouse embryonic fibroblasts,migrating amoeboid cells,and suspending 3T3fibroblasts)and multicellular systems(e.g.,Drosophila embryogenesis and oogenesis).
文摘In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.
文摘为了将模糊推理纳入逻辑的框架并从语构和语义两个方面为模糊推理奠定严格的逻辑基础,通过将模糊推理形式化的方法移植到经典命题逻辑系统中,把FMP(fuzzy modus ponens)问题转化为GMP(generalized modus ponens)问题,并基于公式的真度概念提出了公式之间的支持度,进一步利用支持度的思想引入了GMP问题以及CGMP(collective generalized modus ponens)问题的一种新型最优求解机制.证明了最优解的存在性,同时指出,在经典命题逻辑系统中存在着与模糊逻辑完全相似的推理机制.该方法是一种程度化的方法,这就使得求解过程从算法上实现成为可能,并对知识的程度化推理有所启示.
基金Project(E201216)supported by Heilongjiang Provincial Natural Science Foundation,China
文摘Collective pitch control and individual pitch control algorithms were present for straight-bladed vertical axis wind turbine to improve the self-starting capacity.Comparative analysis of straight-bladed vertical axis wind turbine(SB-VAWT)with or without pitch control was conducted from the aspects of aerodynamic force,flow structure and power coefficient.The computational fluid dynamics(CFD)prediction results show a significant increase in power coefficient for SB-VAWT with pitch control.According to the aerodynamic forces and total torque coefficient obtained at various tip speed ratios(TSRs),the results indicate that the blade pitch method can increase the power output and decrease the deformation of blade;especially,the total torque coefficient of blade pitch control at TSR 1.5 is about 2.5 times larger than that of fixed pitch case.Furthermore,experiment was carried out to verify the feasibility of pitch control methods.The results show that the present collective pitch control and individual pitch control methods can improve the self-starting capacity of SB-VAWT,and the former is much better and its proper operating TSRs ranges from 0.4 to 0.6.
文摘In general-sum games, taking all agent＇s collective rationality into account, we define agents＇ global objective, and propose a novel multi-agent reinforcement learning（RL） algorithm based on global policy. In each learning step, all agents commit to select the global policy to achieve the global goal. We prove this learning algorithm converges given certain restrictions on stage games of learned Q values, and show that it has quite lower computation time complexity than already developed multi-agent learning algorithms for general-sum games. An example is analyzed to show the algorithm＇ s merits.
基金supported by the National Natural Science Fundation of China(61074031)
文摘Distributed stereoscopic rotating formation control of networks of second-order agents is investigated. A distributed control protocol is proposed to enable all agents to form a stereoscopic formation and surround a common axis. Due to the existence of the rotating mode, the desired relative position between every two agents is time-varying, and a Lyapunov-based approach is employed to solve the rotating formation control problem. Finally, simulation results are provided to illustrate the effectiveness of the theoretical results.
文摘2024年1月4日,在Web of Science网站以“cotton”或“Gossypium”为“Title”(文题)检索词查询“Web of Science Core Collection”和“Chinese Science Citation DatabaseSM”数据库中2023年发表文章,选择被引次数5及其以上文章68篇。
文摘根据轨道交通网络存在大量换乘路径的特点,改进深度优先搜索算法得出站点间换乘路径的有效出行时间。基于自动票务收集系统(automatic fare collection system,AFC)数据得到的乘客进出闸机时刻,利用仿真方法确定乘客与列车在时间和路径的接续关系,同时考虑始发乘客和换乘乘客路径选择行为的差异,将二者区分配流。动态更新先到乘客利用换乘路径的出行时间,并以更新后的时间作为后续出发乘客的路径选择依据。结果表明,该仿真方法可以有效反映乘客的出行过程,具有较高的配流精度。
基金Project(2009AA11Z220)supported by the National High Technology Research and Development Program of China
文摘Unmanned aerial vehicle(UAV)was introduced as a novel traffic device to collect road traffic information and its cruise route planning problem was considered.Firstly,a multi-objective optimization model was proposed aiming at minimizing the total cruise distance and the number of UAVs used,which used UAV maximum cruise distance,the number of UAVs available and time window of each monitored target as constraints.Then,a novel multi-objective evolutionary algorithm was proposed.Next,a case study with three time window scenarios was implemented.The results show that both the total cruise distance and the number of UAVs used continue to increase with the time window constraint becoming narrower.Compared with the initial optimal solutions,the optimal total cruise distance and the number of UAVs used fall by an average of 30.93% and 31.74%,respectively.Finally,some concerns using UAV to collect road traffic information were discussed.
基金Project(DYXM-115-04-02-01) supported by the National Deep-sea Technology Project of Development and Research, ChinaProject(2011QNZT058) supported by the Fundamental Research Funds for the Central Universities, ChinaProject(51105386) supported by the National Natural Science Foundation of China
文摘With comprehensive considerations of the operational safety and collection efficiency for the tracked miner collecting the seafloor poly-metallic nodules, two new improved mining paths for the miner on the deep seafloor were proposed. Compared to the conventional mining path, the design principles and superiorities of the two new paths are that the miner turning with relative long radius should avoid large sinkage and high slip, so as to ensure its operational safety, while the space between its straight-line trajectories before and after the turning is optimum, which is designed as the total width of the miner, and collect nodules as more as possible, so as to ensure its collection efficiency. To realize the new mining paths, theoretical designs and quantitative calculations were carried out to determine the exact positions for the speed controls of the miner during its whole operation process. With the new dynamic model of the miner, and through regulations of the speeds of the left and right tracks of the miner on the exact motion positions according to the theoretical calculations, the two new improved mining paths for the miner on the seafloor were successfully simulated, thus the turning radius of the miner in the simulation is about 21.8 m, while the distance between the straight-line trajectories before and after the turning is about 5.2 m. The dynamic simulation results preliminarily prove the feasibility of these two new mining paths, and further can provide important theoretical guidance and useful technical reference for the practical tracked miner operation and control on the seafloor.
文摘To improve the dust removal performance of the wet electrostatic precipitator(WESP), a flow field optimization scheme was proposed via CFD simulation in different scales. The simplified models of perforated and collection plates were determined firstly. Then the model parameters for the resistance of perforated and collection plates, obtained by small-scale flow simulation, were validated by medium-scale experiments. Through the comparison of the resistance and velocity distribution between simulation results and experimental data, the simplified model is proved to present the resistance characteristics of perforated and collection plates accurately. Numerical results show that after optimization, both the flow rate and the pressure drop in the upper room of electric field regions are basically equivalent to those of the lower room, and the velocity distribution in flue inlet of WESP becomes more uniform. Through the application in practice, the effectiveness and reliability of the optimization scheme are proved, which can provide valuable reference for further optimization of WESP.
