The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal rad...The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal radiation,viscous dissipation,and internal heat generation.The system is subjected to a time-periodic boundary temperature condition.The Laplace and finite Hankel transforms are used to derive the exact solutions for the velocity and temperature distributions.The effects of various key physical parameters,including the Richardson number,the Eckert number,the radiation parameter,the heat source parameter,and the nanoparticle volume fraction,are considered.The numerical results reveal that increasing the volume fraction significantly enhances the thermal conductivity and temperature,while the magnetic field intensity and viscous dissipation strongly influence the fluid motion and heat transport.Additionally,the pulsating boundary conditions produce distinct oscillatory behaviors in both the velocity and temperature fields.These findings provide important insights into optimizing the heat transfer performance in cylindrical systems such as electronic cooling modules and energy storage devices operating under dynamic thermal conditions.展开更多
Higher vocational colleges are important institutions for cultivating skilled talents.With the development of new-quality productive forces,these colleges need to meet the requirements of digital transformation and im...Higher vocational colleges are important institutions for cultivating skilled talents.With the development of new-quality productive forces,these colleges need to meet the requirements of digital transformation and improve the effectiveness of talent cultivation.In the process of higher vocational education,it is essential to emphasize teaching innovation and enhance the level of digital teaching.From the perspective of new-quality productive forces,this paper analyzes the new requirements put forward for higher vocational education and proposes specific digital transformation strategies.The purpose is to improve the effectiveness of talent cultivation and accumulate experience for the subsequent digital transformation of higher vocational education.展开更多
Digital-intelligent technologies represent the advanced direction of new quality productive forces and are becoming a driving force for the digital transformation and high-quality development of the cultural industry....Digital-intelligent technologies represent the advanced direction of new quality productive forces and are becoming a driving force for the digital transformation and high-quality development of the cultural industry.Empowered by new quality productive forces,the digital cultural industry has demonstrated diverse characteristics,including the innovation of cultural production subjects,the intelligentization of production tools,the digitization of production objects,the systematization of production methods,and the diversification of production factors.Leveraging technologies such as AIGC,virtual-physical integration,and DAOs based on Web 3.0,the digital cultural industry has established an innovative paradigm,fostering a new method of AIGC production in the digital cultural industry,a new business format of virtual-physical integration,and a new collaborative ecosystem characterized by co-creation,co-building,and co-governance.Meanwhile,the innovative paradigm of the digital cultural industry also faces a series of new challenges,such as the adaptability issues with AIGC algorithm models,creative bottlenecks,and content quality control problems.Additionally,there are obstacles like the immaturity of international development channels for new business formats,the lack of cultural connotations in creative products,and the lag of the digital-intelligent governance of the industry ecosystem behind digital practices.In light of this,there is an urgent need to establish an optimization mechanism for the high-quality development of digital cultural industries driven by new quality productive forces.This includes optimizing the content production mechanism for AIGC-led high-quality innovation in the digital cultural industry;improving the leapfrog development mechanism for new digital cultural business formats through global-regional collaboration;and enhancing the accurate,high-quality governance mechanism for the digital cultural industry that is aligned with the goals of Chinese modernization.展开更多
As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The...As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.展开更多
Each joint of a hydraulic-driven legged robot adopts a highly integrated hydraulic drive unit(HDU),which features a high power-weight ratio.However,most HDUs are throttling-valve-controlled cylinder systems,which exhi...Each joint of a hydraulic-driven legged robot adopts a highly integrated hydraulic drive unit(HDU),which features a high power-weight ratio.However,most HDUs are throttling-valve-controlled cylinder systems,which exhibit high energy losses.By contrast,pump control systems offer a high efficiency.Nevertheless,their response ability is unsatisfactory.To fully utilize the advantages of pump and valve control systems,in this study,a new type of pump-valve compound drive system(PCDS)is designed,which can not only effectively reduce the energy loss,but can also ensure the response speed and response accuracy of the HDUs in robot joints to satisfy the performance requirements of robots.Herein,considering the force control requirements of energy conservation,high precision,and fast response of the robot joint HDU,a nonlinear mathematical model of the PCDS force control system is first introduced.In addition,pressure-flow nonlinearity,friction nonlinearity,load complexity and variability,and other factors affecting the system are considered,and a novel force control method based on quantitative feedback theory(QFT)and a disturbance torque observer(DTO)is designed,which is denoted as QFT-DTOC herein.This method improves the control accuracy and robustness of the force control system,reduces the effect of the disturbance torque on the control performance of the servo motor,and improves the overall force control performance of the system.Finally,experimental verification is performed using the PCDS performance test platform.The experimental results and quantitative data show that the QFT-DTOC proposed herein can significantly improve the force control performance of the PCDS.The relevant force control method can be used as a bottom-control method for the hydraulic servo system to provide a foundation for implementing the top-level trajectory planning of the robot.展开更多
Carbon fiber composites,characterized by their high specific strength and low weight,are becoming increasingly crucial in automotive lightweighting.However,current research primarily emphasizes layer count and orienta...Carbon fiber composites,characterized by their high specific strength and low weight,are becoming increasingly crucial in automotive lightweighting.However,current research primarily emphasizes layer count and orientation,often neglecting the potential of microstructural design,constraints in the layup process,and performance reliability.This study,therefore,introduces a multiscale reliability-based design optimization method for carbon fiber-reinforced plastic(CFRP)drive shafts.Initially,parametric modeling of the microscale cell was performed,and its elastic performance parameters were predicted using two homogenization methods,examining the impact of fluctuations in microscale cell parameters on composite material performance.A finite element model of the CFRP drive shaft was then constructed,achieving parameter transfer between microscale and macroscale through Python programming.This enabled an investigation into the influence of both micro and macro design parameters on the CFRP drive shaft’s performance.The Multi-Objective Particle Swarm Optimization(MOPSO)algorithm was enhanced for particle generation and updating strategies,facilitating the resolution of multi-objective reliability optimization problems,including composite material layup process constraints.Case studies demonstrated that this approach leads to over 30%weight reduction in CFRP drive shafts compared to metallic counterparts while satisfying reliability requirements and offering insights for the lightweight design of other vehicle components.展开更多
The latest CPC Central Committee plenum laid out measures to foster new and quality productive forces in pursuit of high-quality development.HIGH-quality development is China’s primary task in building a modern socia...The latest CPC Central Committee plenum laid out measures to foster new and quality productive forces in pursuit of high-quality development.HIGH-quality development is China’s primary task in building a modern socialist country in all respects.For this purpose,at its third plenary session in July this year,the 20th Central Committee of the Communist Party of China(CPC)declared its resolve to“improve the institutions and mechanisms for fostering new quality productive forces in line with local conditions…Relevant rules and policies will be improved to accelerate the formation of relations of production that are more compatible with new quality productive forces,and to channel various types of advanced production factors toward the development of new quality productive forces.These steps will help realize a significant increase in total factor productivity.”展开更多
Achieving a reduction in global greenhouse gas(GHG)emissions requires collaborative efforts from the international community;however,a comprehensive understanding of the spatiotemporal characteristics(i.e.,complex emi...Achieving a reduction in global greenhouse gas(GHG)emissions requires collaborative efforts from the international community;however,a comprehensive understanding of the spatiotemporal characteristics(i.e.,complex emission networks and driver patterns)and the mutual influence of gross domestic product(GDP)and GHG emissions remains limited at a global level in the 21st century,which is not conducive to forming a consensus in global climate change negotiations and formulating relevant policies.To fill these gaps,this study comprehensively analyzes the complex network and driver pattern of GHG emissions,as well as the corresponding mutual influence with GDP for 185 countries during 2000-2021,based on social network analysis,the logarithmic Divisia decomposition approach,and panel vector autoregression model at global and regional levels.The results indicate that significant heterogeneity and inequality exist in terms of GHG emissions among regions and countries in different geographical areas and economic income levels.Additionally,GDP per capita and GHG emission intensity are the largest positive and negative drivers,respectively,affecting the increase in global GHG emissions.Furthermore,key countries,such as Germany and Canada,that could serve as coordinating bridges to strengthen collaboration in the global emission network are identified.This study highlights the need to encourage key participants in the emission network and foster international cooperation in governance,energy technology,and economic investment to address climate change.展开更多
Sustainable development,underpinned by robust systemic driving forces,is central to the growth of high-quality tourism.Therefore,identifying these forces at the regional level is crucial for advancing China’s goal of...Sustainable development,underpinned by robust systemic driving forces,is central to the growth of high-quality tourism.Therefore,identifying these forces at the regional level is crucial for advancing China’s goal of becoming a leading nation for tourism.This study accordingly constructs a new evaluation system that covers tourism market demand,industry supply,and structural transformation,and analyzes data from 31 Chinese provincial regions(2010–2019).The entropy method and spatial autocorrelation analysis were applied to examine the driving forces for sustainable regional tourism development.The results revealed that:First,at the national level,the driving forces for sustainable regional tourism development exhibited a clear upward trend from 2010 to 2019,with an acceleration in growth after 2015.However,there was significant regional heterogeneity:The eastern region displayed the highest levels of driving forces,followed by the central and western regions.Second,high-value clusters of these driving forces expanded from the eastern to the western regions,while the central provinces remained relatively balanced.Specifically,provincial regions such as Guangdong,Beijing,and Zhejiang were able to successively enter the high-value clusters,whereas the Xinjiang Uygur autonomous region,Gansu,and Qinghai consistently remained in the low-value clusters.Third,the driving forces exhibited a significant spatial agglomeration effect.The degree of clustering followed an inverted“U”trend over the study period,while the spatial patterns of the provincial regions remained relatively stable.展开更多
Model predictive control(MPC)has been deemed as an attractive control method in motor drives by virtue of its simple structure,convenient multi-objective optimization,and satisfactory dynamic performance.However,the s...Model predictive control(MPC)has been deemed as an attractive control method in motor drives by virtue of its simple structure,convenient multi-objective optimization,and satisfactory dynamic performance.However,the strong reliance on mathematical models seriously restrains its practical application.Therefore,improving the robustness of MPC has attained significant attentions in the last two decades,followed by which,model-free predictive control(MFPC)comes into existence.This article aims to reveal the current state of MFPC strategies for motor drives and give the categorization from the perspective of implementation.Based on this review,the principles of the reported MFPC strategies are introduced in detail,as well as the challenges encountered in technology realization.In addition,some of typical and important concepts are experimentally validated via case studies to evaluate the performance and highlight their features.Finally,the future trends of MFPC are discussed based on the current state and reported developments.展开更多
Nowadays,force sensors play an important role in industrial production,electronic information,medical health,and many other fields.Two-dimensional material-based filed effect transistor(2D-FET)sensors are competitive ...Nowadays,force sensors play an important role in industrial production,electronic information,medical health,and many other fields.Two-dimensional material-based filed effect transistor(2D-FET)sensors are competitive with nano-level size,lower power consumption,and accurate response.However,few of them has the capability of impulse detection which is a path function,expressing the cumulative effect of the force on the particle over a period of time.Herein we fabricated the flexible polymethyl methacrylate(PMMA)gate dielectric MoS_(2)-FET for force and impulse sensor application.We systematically investigated the responses of the sensor to constant force and varying forces,and achieved the conversion factors of the drain current signals(I_(ds))to the detected impulse(I).The applied force was detected and recorded by I_(ds)with a low power consumption of~30 nW.The sensitivity of the device can reach~8000%and the 4×1 sensor array is able to detect and locate the normal force applied on it.Moreover,there was almost no performance loss for the device as left in the air for two months.展开更多
To solve problems of poor security guarantee and insufficient training efficiency in the conventional reinforcement learning methods for decision-making,this study proposes a hybrid framework to combine deep reinforce...To solve problems of poor security guarantee and insufficient training efficiency in the conventional reinforcement learning methods for decision-making,this study proposes a hybrid framework to combine deep reinforcement learning with rule-based decision-making methods.A risk assessment model for lane-change maneuvers considering uncertain predictions of surrounding vehicles is established as a safety filter to improve learning efficiency while correcting dangerous actions for safety enhancement.On this basis,a Risk-fused DDQN is constructed utilizing the model-based risk assessment and supervision mechanism.The proposed reinforcement learning algorithm sets up a separate experience buffer for dangerous trials and punishes such actions,which is shown to improve the sampling efficiency and training outcomes.Compared with conventional DDQN methods,the proposed algorithm improves the convergence value of cumulated reward by 7.6%and 2.2%in the two constructed scenarios in the simulation study and reduces the number of training episodes by 52.2%and 66.8%respectively.The success rate of lane change is improved by 57.3%while the time headway is increased at least by 16.5%in real vehicle tests,which confirms the higher training efficiency,scenario adaptability,and security of the proposed Risk-fused DDQN.展开更多
A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which ca...A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which can accurately describe the strain and stress states in IF.Based on strain analysis,the model can predict the material thickness distribution and neck height after IF.By considering contact area,strain characteristics,material thickness changes,and friction,the model can predict specific moments and corresponding values of maximum axial forming force and maximum horizontal forming force during IF.In addition,an IF experiment involving different tool diameters,flanging diameters,and opening hole diameters is conducted.On the basis of the experimental strain paths,the strain characteristics of different deformation zones are studied,and the stable strain ratio is quantitatively described through two dimensionless parameters:relative tool diameter and relative hole diameter.Then,the changing of material thickness and forming force in IF,and the variation of minimum material thickness,neck height,maximum axial forming force,and maximum horizontal forming force with flanging parameters are studied,and the reliability of the analytical model is verified in this process.Finally,the influence of the horizontal forming force on the tool design and the fluctuation of the forming force are explained.展开更多
Forced imbibition,the invasion of a wetting fluid into porous rocks,plays an important role in the effective exploitation of hydrocarbon resources and the geological sequestration of carbon dioxide.However,the interfa...Forced imbibition,the invasion of a wetting fluid into porous rocks,plays an important role in the effective exploitation of hydrocarbon resources and the geological sequestration of carbon dioxide.However,the interface dynamics influenced by complex topology commonly leads to non-wetting fluid trapping.Particularly,the underlying mechanisms under viscously unfavorable conditions remain unclear.This study employs a direct numerical simulation method to simulate forced imbibition through the reconstructed digital rocks of sandstone.The interface dynamics and fluid–fluid interactions are investigated through transient simulations,while the pore topology metrics are introduced to analyze the impact on steady-state residual fluid distribution obtained by a pseudo-transient scheme.The results show that the cooperative pore-filling process promoted by corner flow is dominant at low capillary numbers.This leads to unstable inlet pressure,mass flow,and interface curvature,which correspond to complicated interface dynamics and higher residual fluid saturation.During forced imbibition,the interface curvature gradually increases,with the pore-filling mechanisms involving the cooperation of main terminal meniscus movement and arc menisci filling.Complex topology with small diameter pores may result in the destabilization of interface curvature.The residual fluid saturation is negatively correlated with porosity and pore throat size,and positively correlated with tortuosity and aspect ratio.A large mean coordination number characterizing global connectivity promotes imbibition.However,high connectivity characterized by the standardized Euler number corresponding to small pores is associated with a high probability of non-wetting fluid trapping.展开更多
Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical...Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical arms.The performance of the servo drive,which encompasses the response to the torque,efficiency,control bandwidth and the steady-state positioning accuracy,significantly influences the performance of the aviation actuation.Consequently,enhancing the control bandwidth and refining the positioning accuracy of aviation electro-mechanical actuation servo drives have emerged as a focal point of research.This paper investigates the multi-source disturbances present in aviation electro-mechanical actuation servo systems and summarizes recent research on high-performance servo control methods based on active disturbance rejection control(ADRC).We present a comprehensive overview of the research status pertaining to servo control architecture,strategies for suppressing disturbances in the current loop,and ADRC-based strategies for the position loop.We delineate the research challenges and difficulties encountered by aviation electro-mechanical actuation servo drive control technology.展开更多
Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the de...Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the degradation behavior and failure mechanism of various overcharged states(100%SOC,105%SOC,110%SOC,and 115%SOC),multiple advanced in-situ characterization techniques(accelerating rate calorimeter,electrochemical impedance spectroscopy,ultrasonic scanning,and expansion instrument)were utilized.Additionally,re-overcharge-induced thermal runaway(TR)tests were conducted,with a specific emphasis on the evolution of the expansion force signal.Results indicated significant degradation at 110%SOC including conductivity loss,loss of lithium inventory,and loss of active material accompanied by internal gas generation.These failure behaviors slow down the expansion force rate during reovercharging,reducing the efficacy of active warnings that depend on rate thresholds of expansion force.Specifically,the warning time for 115%SOC battery is only 144 s,which is 740 s shorter than that for fresh battery,and the time to TR is advanced by 9 min.Moreover,the initial self-heating temperature(T1)is reduced by 62.4℃compared to that of fresh battery,reaching only 70.8℃.To address the low safety of overcharged batteries,a passive overcharge warning method utilizing relaxation expansion force was proposed,based on the continued gas generation after stopping charging,leading to a sustained increase in force.Compared to active methods that rely on thresholds of expansion force rate,the passive method can issue warnings 115 s earlier.By combining the passive and active warning methods,guaranteed effective overcharge warning can be issued 863-884 s before TR.This study introduces a novel perspective for enhancing the safety of batteries.展开更多
Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and ev...Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.展开更多
Sine-wave drive and square-wave drive are two common motor control strategies.This study constructs a mathematical model capable of predicting the distribution of electromagnetic force waves in synchronous reluctance ...Sine-wave drive and square-wave drive are two common motor control strategies.This study constructs a mathematical model capable of predicting the distribution of electromagnetic force waves in synchronous reluctance motors(SynRMs)under these two drive methods,and comparatively analyzes the vibration phenomena induced by electromagnetic forces under different drive methods.It aims to provide an effective tool for predicting the distribution of electromagnetic force waves in SynRMs,while exploring the influence of drive modes on their vibration characteristics.The study focuses on a 4-pole,36-slot 5.5 kW SynRM.Based on the magnetomotive force(MMF)-permeance method,incorporating the special rotor structure and the characteristics of current harmonics under square-wave drive,an air-gap flux distribution function is established.Meanwhile,Maxwell’s stress tensor method is adopted to analyze how the air-gap flux density relates to electromagnetic excitation force waves.Subsequently,this analysis is applied to forecast the spatiotemporal distribution features of radial electromagnetic force waves.Finite element simulations are conducted to compute the modal and vibration responses of the SynRM,followed by a comparative analysis of the vibration characteristics under the two drive methods.Additionally,a 6-pole,36-slot SynRM is used for additional comparative verification.Ultimately,the effectiveness of the simulation results is verified through experiments.展开更多
基金Project supported by the National Natural Science Foundation of China(No.12250410244)the Jiangsu Funding Program for Excellent Postdoctoral Talent of China(No.2023ZB884)+2 种基金the Foreign Expert Project funding of China(No.WGXZ2023017L)the Shuang-Chuang(SC)Doctor Program of Jiangsu Provincethe Longshan Scholar Program of Nanjing University of Information Science&Technology。
文摘The unsteady magnetohydrodynamical(MHD)free convection flow of an incompressible,electrically conducting hybrid nanofluid within a vertical cylindrical geometry is investigated,incorporating the effects of thermal radiation,viscous dissipation,and internal heat generation.The system is subjected to a time-periodic boundary temperature condition.The Laplace and finite Hankel transforms are used to derive the exact solutions for the velocity and temperature distributions.The effects of various key physical parameters,including the Richardson number,the Eckert number,the radiation parameter,the heat source parameter,and the nanoparticle volume fraction,are considered.The numerical results reveal that increasing the volume fraction significantly enhances the thermal conductivity and temperature,while the magnetic field intensity and viscous dissipation strongly influence the fluid motion and heat transport.Additionally,the pulsating boundary conditions produce distinct oscillatory behaviors in both the velocity and temperature fields.These findings provide important insights into optimizing the heat transfer performance in cylindrical systems such as electronic cooling modules and energy storage devices operating under dynamic thermal conditions.
基金Research on High-Quality Development Pathways for Vocational Human Resource Management Programs in Higher Vocational Education under the Perspective of Modernization(Project No.:SGYJG2024B02)。
文摘Higher vocational colleges are important institutions for cultivating skilled talents.With the development of new-quality productive forces,these colleges need to meet the requirements of digital transformation and improve the effectiveness of talent cultivation.In the process of higher vocational education,it is essential to emphasize teaching innovation and enhance the level of digital teaching.From the perspective of new-quality productive forces,this paper analyzes the new requirements put forward for higher vocational education and proposes specific digital transformation strategies.The purpose is to improve the effectiveness of talent cultivation and accumulate experience for the subsequent digital transformation of higher vocational education.
基金funded by Research on Policy Design and Implementation Path for High-Quality Development of Digital Cultural Industry(23&ZD087),a major project of the National Social Science Foundation of China.
文摘Digital-intelligent technologies represent the advanced direction of new quality productive forces and are becoming a driving force for the digital transformation and high-quality development of the cultural industry.Empowered by new quality productive forces,the digital cultural industry has demonstrated diverse characteristics,including the innovation of cultural production subjects,the intelligentization of production tools,the digitization of production objects,the systematization of production methods,and the diversification of production factors.Leveraging technologies such as AIGC,virtual-physical integration,and DAOs based on Web 3.0,the digital cultural industry has established an innovative paradigm,fostering a new method of AIGC production in the digital cultural industry,a new business format of virtual-physical integration,and a new collaborative ecosystem characterized by co-creation,co-building,and co-governance.Meanwhile,the innovative paradigm of the digital cultural industry also faces a series of new challenges,such as the adaptability issues with AIGC algorithm models,creative bottlenecks,and content quality control problems.Additionally,there are obstacles like the immaturity of international development channels for new business formats,the lack of cultural connotations in creative products,and the lag of the digital-intelligent governance of the industry ecosystem behind digital practices.In light of this,there is an urgent need to establish an optimization mechanism for the high-quality development of digital cultural industries driven by new quality productive forces.This includes optimizing the content production mechanism for AIGC-led high-quality innovation in the digital cultural industry;improving the leapfrog development mechanism for new digital cultural business formats through global-regional collaboration;and enhancing the accurate,high-quality governance mechanism for the digital cultural industry that is aligned with the goals of Chinese modernization.
基金the funding support from the Taihang Laboratory,China(No.D2024-1-0201).
文摘As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.
基金Supported by National Excellent Natural Science Foundation of China(Grant No.52122503)Hebei Provincial Natural Science Foundation of China(Grant No.E2022203002)+2 种基金The Yanzhao’s Young Scientist Project of China(Grant No.E2023203258)Science Research Project of Hebei Education Department of China(Grant No.BJK2022060)Hebei Provincial Graduate Innovation Funding Project of China(Grant No.CXZZSS2022129).
文摘Each joint of a hydraulic-driven legged robot adopts a highly integrated hydraulic drive unit(HDU),which features a high power-weight ratio.However,most HDUs are throttling-valve-controlled cylinder systems,which exhibit high energy losses.By contrast,pump control systems offer a high efficiency.Nevertheless,their response ability is unsatisfactory.To fully utilize the advantages of pump and valve control systems,in this study,a new type of pump-valve compound drive system(PCDS)is designed,which can not only effectively reduce the energy loss,but can also ensure the response speed and response accuracy of the HDUs in robot joints to satisfy the performance requirements of robots.Herein,considering the force control requirements of energy conservation,high precision,and fast response of the robot joint HDU,a nonlinear mathematical model of the PCDS force control system is first introduced.In addition,pressure-flow nonlinearity,friction nonlinearity,load complexity and variability,and other factors affecting the system are considered,and a novel force control method based on quantitative feedback theory(QFT)and a disturbance torque observer(DTO)is designed,which is denoted as QFT-DTOC herein.This method improves the control accuracy and robustness of the force control system,reduces the effect of the disturbance torque on the control performance of the servo motor,and improves the overall force control performance of the system.Finally,experimental verification is performed using the PCDS performance test platform.The experimental results and quantitative data show that the QFT-DTOC proposed herein can significantly improve the force control performance of the PCDS.The relevant force control method can be used as a bottom-control method for the hydraulic servo system to provide a foundation for implementing the top-level trajectory planning of the robot.
基金supported by the S&T Special Program of Huzhou(Grant No.2023GZ09)the Open Fund Project of the ShanghaiKey Laboratory of Lightweight Structural Composites(Grant No.2232021A4-06).
文摘Carbon fiber composites,characterized by their high specific strength and low weight,are becoming increasingly crucial in automotive lightweighting.However,current research primarily emphasizes layer count and orientation,often neglecting the potential of microstructural design,constraints in the layup process,and performance reliability.This study,therefore,introduces a multiscale reliability-based design optimization method for carbon fiber-reinforced plastic(CFRP)drive shafts.Initially,parametric modeling of the microscale cell was performed,and its elastic performance parameters were predicted using two homogenization methods,examining the impact of fluctuations in microscale cell parameters on composite material performance.A finite element model of the CFRP drive shaft was then constructed,achieving parameter transfer between microscale and macroscale through Python programming.This enabled an investigation into the influence of both micro and macro design parameters on the CFRP drive shaft’s performance.The Multi-Objective Particle Swarm Optimization(MOPSO)algorithm was enhanced for particle generation and updating strategies,facilitating the resolution of multi-objective reliability optimization problems,including composite material layup process constraints.Case studies demonstrated that this approach leads to over 30%weight reduction in CFRP drive shafts compared to metallic counterparts while satisfying reliability requirements and offering insights for the lightweight design of other vehicle components.
文摘The latest CPC Central Committee plenum laid out measures to foster new and quality productive forces in pursuit of high-quality development.HIGH-quality development is China’s primary task in building a modern socialist country in all respects.For this purpose,at its third plenary session in July this year,the 20th Central Committee of the Communist Party of China(CPC)declared its resolve to“improve the institutions and mechanisms for fostering new quality productive forces in line with local conditions…Relevant rules and policies will be improved to accelerate the formation of relations of production that are more compatible with new quality productive forces,and to channel various types of advanced production factors toward the development of new quality productive forces.These steps will help realize a significant increase in total factor productivity.”
基金supported by the Humanities and Social Sciences Youth Foundation,Ministry of Education of China[Grant No.24YJC630248]Sichuan Office of Philosophy and Social Science,China[Grant No.SCJJ24ND299].
文摘Achieving a reduction in global greenhouse gas(GHG)emissions requires collaborative efforts from the international community;however,a comprehensive understanding of the spatiotemporal characteristics(i.e.,complex emission networks and driver patterns)and the mutual influence of gross domestic product(GDP)and GHG emissions remains limited at a global level in the 21st century,which is not conducive to forming a consensus in global climate change negotiations and formulating relevant policies.To fill these gaps,this study comprehensively analyzes the complex network and driver pattern of GHG emissions,as well as the corresponding mutual influence with GDP for 185 countries during 2000-2021,based on social network analysis,the logarithmic Divisia decomposition approach,and panel vector autoregression model at global and regional levels.The results indicate that significant heterogeneity and inequality exist in terms of GHG emissions among regions and countries in different geographical areas and economic income levels.Additionally,GDP per capita and GHG emission intensity are the largest positive and negative drivers,respectively,affecting the increase in global GHG emissions.Furthermore,key countries,such as Germany and Canada,that could serve as coordinating bridges to strengthen collaboration in the global emission network are identified.This study highlights the need to encourage key participants in the emission network and foster international cooperation in governance,energy technology,and economic investment to address climate change.
基金funded by the Ministry of Education’s Humanities and Social Sciences Research Planning Project(23YJA790070).
文摘Sustainable development,underpinned by robust systemic driving forces,is central to the growth of high-quality tourism.Therefore,identifying these forces at the regional level is crucial for advancing China’s goal of becoming a leading nation for tourism.This study accordingly constructs a new evaluation system that covers tourism market demand,industry supply,and structural transformation,and analyzes data from 31 Chinese provincial regions(2010–2019).The entropy method and spatial autocorrelation analysis were applied to examine the driving forces for sustainable regional tourism development.The results revealed that:First,at the national level,the driving forces for sustainable regional tourism development exhibited a clear upward trend from 2010 to 2019,with an acceleration in growth after 2015.However,there was significant regional heterogeneity:The eastern region displayed the highest levels of driving forces,followed by the central and western regions.Second,high-value clusters of these driving forces expanded from the eastern to the western regions,while the central provinces remained relatively balanced.Specifically,provincial regions such as Guangdong,Beijing,and Zhejiang were able to successively enter the high-value clusters,whereas the Xinjiang Uygur autonomous region,Gansu,and Qinghai consistently remained in the low-value clusters.Third,the driving forces exhibited a significant spatial agglomeration effect.The degree of clustering followed an inverted“U”trend over the study period,while the spatial patterns of the provincial regions remained relatively stable.
基金supported in part by the National Natural Science Foundation of China under Grant 52077002。
文摘Model predictive control(MPC)has been deemed as an attractive control method in motor drives by virtue of its simple structure,convenient multi-objective optimization,and satisfactory dynamic performance.However,the strong reliance on mathematical models seriously restrains its practical application.Therefore,improving the robustness of MPC has attained significant attentions in the last two decades,followed by which,model-free predictive control(MFPC)comes into existence.This article aims to reveal the current state of MFPC strategies for motor drives and give the categorization from the perspective of implementation.Based on this review,the principles of the reported MFPC strategies are introduced in detail,as well as the challenges encountered in technology realization.In addition,some of typical and important concepts are experimentally validated via case studies to evaluate the performance and highlight their features.Finally,the future trends of MFPC are discussed based on the current state and reported developments.
基金financially supported by the National Natural Science Foundation of China(Nos.52272160,U2330112,and 52002254)Sichuan Science and Technology Foundation(Nos.2020YJ0262,2021YFH0127,2022YFH0083,2022YFSY0045,and 2023YFSY0002)+1 种基金the Chunhui Plan of Ministry of Education,Fundamental Research Funds for the Central Universities,China(No.YJ201893)the Foundation of Key Laboratory of Lidar and Device,Sichuan Province,China(No.LLD2023-006)。
文摘Nowadays,force sensors play an important role in industrial production,electronic information,medical health,and many other fields.Two-dimensional material-based filed effect transistor(2D-FET)sensors are competitive with nano-level size,lower power consumption,and accurate response.However,few of them has the capability of impulse detection which is a path function,expressing the cumulative effect of the force on the particle over a period of time.Herein we fabricated the flexible polymethyl methacrylate(PMMA)gate dielectric MoS_(2)-FET for force and impulse sensor application.We systematically investigated the responses of the sensor to constant force and varying forces,and achieved the conversion factors of the drain current signals(I_(ds))to the detected impulse(I).The applied force was detected and recorded by I_(ds)with a low power consumption of~30 nW.The sensitivity of the device can reach~8000%and the 4×1 sensor array is able to detect and locate the normal force applied on it.Moreover,there was almost no performance loss for the device as left in the air for two months.
基金Supported by National Key Research and Development Program of China(Grant No.2022YFE0117100)National Science Foundation of China(Grant No.52102468,52325212)Fundamental Research Funds for the Central Universities。
文摘To solve problems of poor security guarantee and insufficient training efficiency in the conventional reinforcement learning methods for decision-making,this study proposes a hybrid framework to combine deep reinforcement learning with rule-based decision-making methods.A risk assessment model for lane-change maneuvers considering uncertain predictions of surrounding vehicles is established as a safety filter to improve learning efficiency while correcting dangerous actions for safety enhancement.On this basis,a Risk-fused DDQN is constructed utilizing the model-based risk assessment and supervision mechanism.The proposed reinforcement learning algorithm sets up a separate experience buffer for dangerous trials and punishes such actions,which is shown to improve the sampling efficiency and training outcomes.Compared with conventional DDQN methods,the proposed algorithm improves the convergence value of cumulated reward by 7.6%and 2.2%in the two constructed scenarios in the simulation study and reduces the number of training episodes by 52.2%and 66.8%respectively.The success rate of lane change is improved by 57.3%while the time headway is increased at least by 16.5%in real vehicle tests,which confirms the higher training efficiency,scenario adaptability,and security of the proposed Risk-fused DDQN.
基金supported in part by financial support from the National Key R&D Program of China(No.2023YFB3407003)the National Natural Science Foundation of China(No.52375378).
文摘A new analytical model for geometric size and forming force prediction in incremental flanging(IF)is presented in this work.The complex deformation characteristics of IF are considered in the modeling process,which can accurately describe the strain and stress states in IF.Based on strain analysis,the model can predict the material thickness distribution and neck height after IF.By considering contact area,strain characteristics,material thickness changes,and friction,the model can predict specific moments and corresponding values of maximum axial forming force and maximum horizontal forming force during IF.In addition,an IF experiment involving different tool diameters,flanging diameters,and opening hole diameters is conducted.On the basis of the experimental strain paths,the strain characteristics of different deformation zones are studied,and the stable strain ratio is quantitatively described through two dimensionless parameters:relative tool diameter and relative hole diameter.Then,the changing of material thickness and forming force in IF,and the variation of minimum material thickness,neck height,maximum axial forming force,and maximum horizontal forming force with flanging parameters are studied,and the reliability of the analytical model is verified in this process.Finally,the influence of the horizontal forming force on the tool design and the fluctuation of the forming force are explained.
基金supported by the National Natural Science Foundation of China(Grant Nos.42172159 and 42302143)the Postdoctora Fellowship Program of the China Postdoctoral Science Foundation(CPSF)(Grant No.GZB20230864).
文摘Forced imbibition,the invasion of a wetting fluid into porous rocks,plays an important role in the effective exploitation of hydrocarbon resources and the geological sequestration of carbon dioxide.However,the interface dynamics influenced by complex topology commonly leads to non-wetting fluid trapping.Particularly,the underlying mechanisms under viscously unfavorable conditions remain unclear.This study employs a direct numerical simulation method to simulate forced imbibition through the reconstructed digital rocks of sandstone.The interface dynamics and fluid–fluid interactions are investigated through transient simulations,while the pore topology metrics are introduced to analyze the impact on steady-state residual fluid distribution obtained by a pseudo-transient scheme.The results show that the cooperative pore-filling process promoted by corner flow is dominant at low capillary numbers.This leads to unstable inlet pressure,mass flow,and interface curvature,which correspond to complicated interface dynamics and higher residual fluid saturation.During forced imbibition,the interface curvature gradually increases,with the pore-filling mechanisms involving the cooperation of main terminal meniscus movement and arc menisci filling.Complex topology with small diameter pores may result in the destabilization of interface curvature.The residual fluid saturation is negatively correlated with porosity and pore throat size,and positively correlated with tortuosity and aspect ratio.A large mean coordination number characterizing global connectivity promotes imbibition.However,high connectivity characterized by the standardized Euler number corresponding to small pores is associated with a high probability of non-wetting fluid trapping.
基金supported by the National Natural Science Foundation of China(Nos.52177059 and 52407064).
文摘Permanent magnet synchronous motor based electro-mechanical actuation servo drives have widespread applications in the aviation field,such as unmanned aerial vehicle electric servos,electric cabin doors,and mechanical arms.The performance of the servo drive,which encompasses the response to the torque,efficiency,control bandwidth and the steady-state positioning accuracy,significantly influences the performance of the aviation actuation.Consequently,enhancing the control bandwidth and refining the positioning accuracy of aviation electro-mechanical actuation servo drives have emerged as a focal point of research.This paper investigates the multi-source disturbances present in aviation electro-mechanical actuation servo systems and summarizes recent research on high-performance servo control methods based on active disturbance rejection control(ADRC).We present a comprehensive overview of the research status pertaining to servo control architecture,strategies for suppressing disturbances in the current loop,and ADRC-based strategies for the position loop.We delineate the research challenges and difficulties encountered by aviation electro-mechanical actuation servo drive control technology.
基金supported by the National Natural Science Foundation of China(52476200,52106244)the Guangdong Basic and Applied Basic Research Foundation(2024A1515030124)+1 种基金the Science and Technology Project of China Southern Power Grid under Grant GDKJXM20230246(030100KC23020017)the Fundamental Research Funds for the Central Universities。
文摘Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the degradation behavior and failure mechanism of various overcharged states(100%SOC,105%SOC,110%SOC,and 115%SOC),multiple advanced in-situ characterization techniques(accelerating rate calorimeter,electrochemical impedance spectroscopy,ultrasonic scanning,and expansion instrument)were utilized.Additionally,re-overcharge-induced thermal runaway(TR)tests were conducted,with a specific emphasis on the evolution of the expansion force signal.Results indicated significant degradation at 110%SOC including conductivity loss,loss of lithium inventory,and loss of active material accompanied by internal gas generation.These failure behaviors slow down the expansion force rate during reovercharging,reducing the efficacy of active warnings that depend on rate thresholds of expansion force.Specifically,the warning time for 115%SOC battery is only 144 s,which is 740 s shorter than that for fresh battery,and the time to TR is advanced by 9 min.Moreover,the initial self-heating temperature(T1)is reduced by 62.4℃compared to that of fresh battery,reaching only 70.8℃.To address the low safety of overcharged batteries,a passive overcharge warning method utilizing relaxation expansion force was proposed,based on the continued gas generation after stopping charging,leading to a sustained increase in force.Compared to active methods that rely on thresholds of expansion force rate,the passive method can issue warnings 115 s earlier.By combining the passive and active warning methods,guaranteed effective overcharge warning can be issued 863-884 s before TR.This study introduces a novel perspective for enhancing the safety of batteries.
基金Supported by the National Natural Science Foundation of China (11161027)。
文摘Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.
基金supported by the Science and Technology Project of State Grid Corporation of China Headquarters under Grant 5500-202416156A-1-1-ZN.
文摘Sine-wave drive and square-wave drive are two common motor control strategies.This study constructs a mathematical model capable of predicting the distribution of electromagnetic force waves in synchronous reluctance motors(SynRMs)under these two drive methods,and comparatively analyzes the vibration phenomena induced by electromagnetic forces under different drive methods.It aims to provide an effective tool for predicting the distribution of electromagnetic force waves in SynRMs,while exploring the influence of drive modes on their vibration characteristics.The study focuses on a 4-pole,36-slot 5.5 kW SynRM.Based on the magnetomotive force(MMF)-permeance method,incorporating the special rotor structure and the characteristics of current harmonics under square-wave drive,an air-gap flux distribution function is established.Meanwhile,Maxwell’s stress tensor method is adopted to analyze how the air-gap flux density relates to electromagnetic excitation force waves.Subsequently,this analysis is applied to forecast the spatiotemporal distribution features of radial electromagnetic force waves.Finite element simulations are conducted to compute the modal and vibration responses of the SynRM,followed by a comparative analysis of the vibration characteristics under the two drive methods.Additionally,a 6-pole,36-slot SynRM is used for additional comparative verification.Ultimately,the effectiveness of the simulation results is verified through experiments.
