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
Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pell...Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pellets.Addressing the gap in the application of organically-intercalated modified bentonite in the pelletizing field,this study introduces an innovative modification process for bentonite that employs the synergistic effect of mechanical force and dimethyl sulfoxide to enhance the intercalation of organic compounds within bentonite,thus significantly enhancing its binding performance.The colloid value and swell capacity of modified bentonite(98.5 m L/3g and 55.0 m L/g)were much higher than the original bentonite(90.5 m L/3g and 17.5 m L/g).With the decrease of bentonite dosage from1.5wt%to 1.0wt%,the drop number of green pellets from a height of 0.5 m and the compressive strengths of roasted pellets using the modified bentonite(6.0 times and 2916 N per pellet)were significantly higher than those of the original bentonite(4.0 times and 2739 N per pellet).This study provides a comprehensive analysis of the intercalation modification mechanism of bentonite,offering crucial technical insights for the development of high-performance modified bentonite as iron ore pellet binders.展开更多
Using path analysis, correlation analysis, partial correlation analysis and system dynamics method to study the driving force of cultivated land in Qinghai Lake Area, and using gradually regression analysis to establi...Using path analysis, correlation analysis, partial correlation analysis and system dynamics method to study the driving force of cultivated land in Qinghai Lake Area, and using gradually regression analysis to establish the driving force model of utilized change of cultivated land. Driving factors, action mechanism and process of utilized change of cultivated land were analyzed, and the differences during all factors were compared. The study provides some decision basis for sustainable utilization and management of land resources in Qinghai Lake Area.展开更多
Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pi...Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pin-hole can be calculated more accurately in the wholedriving process.展开更多
Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit(HDU),and the contacting between the robot foot end and the ground is complex and variable,which increases the difficulty of force con...Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit(HDU),and the contacting between the robot foot end and the ground is complex and variable,which increases the difficulty of force control inevitably.In the recent years,although many scholars researched some control methods such as disturbance rejection control,parameter self-adaptive control,impedance control and so on,to improve the force control performance of HDU,the robustness of the force control still needs improving.Therefore,how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper.The force control system mathematic model of HDU is established by the mechanism modeling method,and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived,considering the dynamic characteristics of the load stiffness and the load damping under different environment structures.Then,simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform,which provides the foundation for the force control compensation experiment research.In addition,the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping,under which the force control compensation method is introduced,and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment.The research results indicate that if the load characteristics are known,the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation,i.e.,this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters,thereby,the online PID parameters tuning control method which is complex needs not be adopted.All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.展开更多
Deformation of the flexspline is the basis of analyzing tooth trajectory and designing tooth profile.Considering the tooth influence on the position of equivalent neutral layer,a piecewise method for calculating the d...Deformation of the flexspline is the basis of analyzing tooth trajectory and designing tooth profile.Considering the tooth influence on the position of equivalent neutral layer,a piecewise method for calculating the deformation of flexspline assembled with a cam wave generator is presented in this paper.Firstly,a mechanic model of a ring of uniform thickness in contact with a rigid cam is established.The displacements of the ring inside and outside an unknown wrapping angle are determined by the geometric constraints of the cam profile and the equilibrium rela-tionship,respectively.Meanwhile,the wrapping angle is solved according to the boundary conditions.The assembly forces are derived to investigate the circumferential elongation and strain.Then,considering the tooth effects on the neutral layer of flexspline,the tooth is positioned on the equivalent neutral layer,which is the non-elongation layer within one gear pitch but offset from the geometric mid-layer.The equivalent neutral layer is positioned by the empirical formula of the offset ratio,which is summarized by the orthogonal simulation on finite element models of racks.Finally,finite element models of a ring-shaped and a cup-shaped flexspline assembled with elliptical cam are established to verify the effectiveness and accuracy of the piecewise method.The results show that,compared with the geometric method,the tooth positioning deviation calculated by the piecewise method can be reduced by about 70%with a more accurate deformation description from the geometric condition and mechanic condition inside and outside the wrapping angle.展开更多
Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have th...Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeo simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeo simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The e ectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeo simulation.展开更多
The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhi...The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.展开更多
In this paper, the practicality and feasibility of Active Force Control （AFC） integrated with Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is inves...In this paper, the practicality and feasibility of Active Force Control （AFC） integrated with Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is investigated. The study emphasizes on the application and control of PAM actuators which may be considered as the new generation of actuators comprising fluidic muscle that has high-tension force, high power to weight ratio and high strength in spite of its drawbacks in the form of high nonlinearity behaviour, high hysteresis and time varying parameters. Fuzzy Logic （FL） is used as a technique to estimate the best value of the inertia matrix of robot arm essential for the AFC mechanism that is complemented with a conventional Propor- tional-Integral-Derivative （PID） control at the outermost loop. A simulation study was first performed followed by an experi- mental investigation for validation. The experimental study was based on the independent joint tracking control and coordinated motion control of the arm in Cartesian or task space. In the former, the PAM actuated arm is commanded to track the prescribed trajectories due to harmonic excitations at the joints for a given frequency, whereas for the latter, two sets of trajectories with different loadings were considered. A practical rig utilizing a Hardware-In-The-Loop Simulation （HILS） configuration was developed and a number of experiments were carried out. The results of the experiment and the simulation works were in good agreement, which verified the effectiveness and robustness of the proposed AFCAFL scheme actuated by PAM.展开更多
The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fu...The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fuel burn,and noise when taxiing on the ground at airports.There is an urgent need to reduce aircraft taxiing time on the ground.However,it is too expensive for airports and aircraft carriers to build and maintain more runways,and it is space-limited to tow the aircraft fast using tractors.Autonomous drive capability is currently the best solution for aircraft,which can save the maneuver time for aircraft.An idea is proposed that the wheels are driven by APU-powered(auxiliary power unit)motors,APU is working on its efficient point;consequently,the emissions,fuel burn,and noise will be reduced significantly.For Front-wheel drive aircraft,the front wheel must provide longitudinal force to tow the plane forward and lateral force to help the aircraft make a turn.Forward traction effects the aircraft’s maximum turning ability,which is difficult to be modeled to guide the controller design.Deep reinforcement learning provides a powerful tool to help us design controllers for black-box models;however,the models of related works are always simplified,fixed,or not easily modified,but that is what we care about most.Only with complex models can the trained controller be intelligent.High-fidelity models that can easily modified are necessary for aircraft ground maneuver controller design.This paper focuses on the maneuvering problem of front-wheel drive aircraft,a high-fidelity aircraft taxiing dynamic model is established,including the 6-DOF airframe,landing gears,and nonlinear tire force model.A deep reinforcement learning based controller was designed to improve the maneuver performance of front-wheel drive aircraft.It is proved that in some conditions,the DRL based controller outperformed conventional look-ahead controllers.展开更多
In this work,Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface.The critical a...In this work,Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface.The critical adsorption temperature Tc decreases linearly with increasing F,indicating that the driving force suppresses the adsorption of polymer.The conformation of polymer is also affected by the driving force.However,the effect of F is dependent on the competition between the driving force and temperature.Under strong force or at low temperature,the polymer is stretched along the direction of the force,while under weak force or at high temperature,the polymer is not stretched.When the force is comparable to the temperature,the polymer may be stretched perpendicular to the driving force,and below Tc,we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature.We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force.Moreover,the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature.展开更多
Based on the natural exponential pair potential, the interaction potential between curved surface body and on surface particle is studied. Firstly, the interaction potential is written as a function of curvatures thro...Based on the natural exponential pair potential, the interaction potential between curved surface body and on surface particle is studied. Firstly, the interaction potential is written as a function of curvatures through the differential geometry. Secondly, idealized numerical experiments are designed to test the accuracy of curvature-based potential. Then, the driving forces induced by curvatures are analyzed, which confirms that micro/nano curved surface body can induce driving forces, curvatures and the gradient of curvatures are the essential elements forming the driving forces. Finally, by combing with the curvature based potential and driving forces, the movements of on surface particles and the evolution of surface morphology of curved surface body are predicted.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
The discovery of the essential difference of maximum ion energy for TW-pslaser plasma interaction compared with, the 100 ns laser pulses led to the theory of a skin layermodel where the control of prepulses suppressed...The discovery of the essential difference of maximum ion energy for TW-pslaser plasma interaction compared with, the 100 ns laser pulses led to the theory of a skin layermodel where the control of prepulses suppressed the usual relativistic self-focusing. The subsequentgeneration of two nonlinear force driven blocks has been demonstrated experimentally and inextensive numerical studies where one block moves against the laser light and the other block intothe irradiated target. These blocks of nearly solid state density DT plasma correspond to ion beamcurrent densities exceeding 10^(10) A/cm^2 where the ion velocity can be chosen up to highlyrelativistic values. Using the results of the expected ignition of DT fuel by light ion beams, aself-sustained fusion reaction front may be generated even into uncompressed solid DT fuel similarto the Nuckolls-Wood scheme where 10 kJ laser pulses produce 100 MJ fusion energy. This new andsimplified scheme of laser-ICF needs and optimisation of the involved parameters.展开更多
A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single elec...A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single electrode panel,the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage.The actuation principle is proposed and verified by the experiment.The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases.The driving voltage for a 3µL deionized(DI)water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top.The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner,and the maximum transport speed reaches 96 mm/s.The droplets of normal saline,a solution of 0.9 wt%NaCl,are also successfully manipulated on the chip.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financial support by the National Key Research and Development Program of China(No.2023YFC2907801)the Hunan Provincial Natural Science Foundation of China(No.2023JJ40760)the Scientific and Technological Project of Yunnan Precious Metals Laboratory,China(No.YPML-2023050276)。
文摘Bentonite is a necessary binder in producing pellets.Its excessive use reduces the iron grade of pellets and increases production costs.Minimizing bentonite dosage is essential for producing high-quality iron ore pellets.Addressing the gap in the application of organically-intercalated modified bentonite in the pelletizing field,this study introduces an innovative modification process for bentonite that employs the synergistic effect of mechanical force and dimethyl sulfoxide to enhance the intercalation of organic compounds within bentonite,thus significantly enhancing its binding performance.The colloid value and swell capacity of modified bentonite(98.5 m L/3g and 55.0 m L/g)were much higher than the original bentonite(90.5 m L/3g and 17.5 m L/g).With the decrease of bentonite dosage from1.5wt%to 1.0wt%,the drop number of green pellets from a height of 0.5 m and the compressive strengths of roasted pellets using the modified bentonite(6.0 times and 2916 N per pellet)were significantly higher than those of the original bentonite(4.0 times and 2739 N per pellet).This study provides a comprehensive analysis of the intercalation modification mechanism of bentonite,offering crucial technical insights for the development of high-performance modified bentonite as iron ore pellet binders.
基金Supported by The Regional Sustainable Development of the Qing-TibetPlateau(2004)~~
文摘Using path analysis, correlation analysis, partial correlation analysis and system dynamics method to study the driving force of cultivated land in Qinghai Lake Area, and using gradually regression analysis to establish the driving force model of utilized change of cultivated land. Driving factors, action mechanism and process of utilized change of cultivated land were analyzed, and the differences during all factors were compared. The study provides some decision basis for sustainable utilization and management of land resources in Qinghai Lake Area.
基金National Natural Science Foundation of China(No.59075230).
文摘Based on the analysis of the pin-hole-output mechanism in the cycloid drive,a more accurate force analysis method is provided, in which the manufacture error is considered, bywhich the contact force between pin and pin-hole can be calculated more accurately in the wholedriving process.
基金Supported by National Key Basic Research Program of China(973 Program,Grant No.2014CB046405)State Key Laboratory of Fluid Power and Mechatronic Systems(Zhejiang University)Open Fund Project(Grant No.GZKF-201502)Hebei Military and Civilian Industry Development Funds Projects of China(Grant No.2015B060)
文摘Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit(HDU),and the contacting between the robot foot end and the ground is complex and variable,which increases the difficulty of force control inevitably.In the recent years,although many scholars researched some control methods such as disturbance rejection control,parameter self-adaptive control,impedance control and so on,to improve the force control performance of HDU,the robustness of the force control still needs improving.Therefore,how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper.The force control system mathematic model of HDU is established by the mechanism modeling method,and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived,considering the dynamic characteristics of the load stiffness and the load damping under different environment structures.Then,simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform,which provides the foundation for the force control compensation experiment research.In addition,the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping,under which the force control compensation method is introduced,and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment.The research results indicate that if the load characteristics are known,the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation,i.e.,this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters,thereby,the online PID parameters tuning control method which is complex needs not be adopted.All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.
基金Supported by National Natural Science Foundation of China(Grant No.51575390)Tianjin Municipal Natural Science Foundation of China(Grant Nos.19JCZDJC38700,18JCZDJC39000).
文摘Deformation of the flexspline is the basis of analyzing tooth trajectory and designing tooth profile.Considering the tooth influence on the position of equivalent neutral layer,a piecewise method for calculating the deformation of flexspline assembled with a cam wave generator is presented in this paper.Firstly,a mechanic model of a ring of uniform thickness in contact with a rigid cam is established.The displacements of the ring inside and outside an unknown wrapping angle are determined by the geometric constraints of the cam profile and the equilibrium rela-tionship,respectively.Meanwhile,the wrapping angle is solved according to the boundary conditions.The assembly forces are derived to investigate the circumferential elongation and strain.Then,considering the tooth effects on the neutral layer of flexspline,the tooth is positioned on the equivalent neutral layer,which is the non-elongation layer within one gear pitch but offset from the geometric mid-layer.The equivalent neutral layer is positioned by the empirical formula of the offset ratio,which is summarized by the orthogonal simulation on finite element models of racks.Finally,finite element models of a ring-shaped and a cup-shaped flexspline assembled with elliptical cam are established to verify the effectiveness and accuracy of the piecewise method.The results show that,compared with the geometric method,the tooth positioning deviation calculated by the piecewise method can be reduced by about 70%with a more accurate deformation description from the geometric condition and mechanic condition inside and outside the wrapping angle.
基金Supported by National Natural Science Foundation of China(Grant No.51405024)
文摘Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeo simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeo simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The e ectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeo simulation.
基金Supported by National Natural Science Foundation of China(Grant Nos.51505335,51275106)National Basic Research Program of China(973Program,Grant No.2013CB035502)
文摘The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.
文摘In this paper, the practicality and feasibility of Active Force Control （AFC） integrated with Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is investigated. The study emphasizes on the application and control of PAM actuators which may be considered as the new generation of actuators comprising fluidic muscle that has high-tension force, high power to weight ratio and high strength in spite of its drawbacks in the form of high nonlinearity behaviour, high hysteresis and time varying parameters. Fuzzy Logic （FL） is used as a technique to estimate the best value of the inertia matrix of robot arm essential for the AFC mechanism that is complemented with a conventional Propor- tional-Integral-Derivative （PID） control at the outermost loop. A simulation study was first performed followed by an experi- mental investigation for validation. The experimental study was based on the independent joint tracking control and coordinated motion control of the arm in Cartesian or task space. In the former, the PAM actuated arm is commanded to track the prescribed trajectories due to harmonic excitations at the joints for a given frequency, whereas for the latter, two sets of trajectories with different loadings were considered. A practical rig utilizing a Hardware-In-The-Loop Simulation （HILS） configuration was developed and a number of experiments were carried out. The results of the experiment and the simulation works were in good agreement, which verified the effectiveness and robustness of the proposed AFCAFL scheme actuated by PAM.
基金Funded by National Natural Science Foundation of China(No.51775014)Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems of China(No.GZKF-202010)+1 种基金National Key R&D Program of China(No.2019YFB2004503)the Science and Technology on Aircraft Control Laboratory of China。
文摘The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fuel burn,and noise when taxiing on the ground at airports.There is an urgent need to reduce aircraft taxiing time on the ground.However,it is too expensive for airports and aircraft carriers to build and maintain more runways,and it is space-limited to tow the aircraft fast using tractors.Autonomous drive capability is currently the best solution for aircraft,which can save the maneuver time for aircraft.An idea is proposed that the wheels are driven by APU-powered(auxiliary power unit)motors,APU is working on its efficient point;consequently,the emissions,fuel burn,and noise will be reduced significantly.For Front-wheel drive aircraft,the front wheel must provide longitudinal force to tow the plane forward and lateral force to help the aircraft make a turn.Forward traction effects the aircraft’s maximum turning ability,which is difficult to be modeled to guide the controller design.Deep reinforcement learning provides a powerful tool to help us design controllers for black-box models;however,the models of related works are always simplified,fixed,or not easily modified,but that is what we care about most.Only with complex models can the trained controller be intelligent.High-fidelity models that can easily modified are necessary for aircraft ground maneuver controller design.This paper focuses on the maneuvering problem of front-wheel drive aircraft,a high-fidelity aircraft taxiing dynamic model is established,including the 6-DOF airframe,landing gears,and nonlinear tire force model.A deep reinforcement learning based controller was designed to improve the maneuver performance of front-wheel drive aircraft.It is proved that in some conditions,the DRL based controller outperformed conventional look-ahead controllers.
基金financially supported by the Research Fund of Zhejiang Provincial Education Department(No.Y201738867)the National Natural Science Foundation of China(Nos.11775161,11875205,and 11974305)。
文摘In this work,Monte Carlo simulations are used to study the critical adsorption behaviors of flexible polymer chains under the action of an external driving force F parallel to an attractive flat surface.The critical adsorption temperature Tc decreases linearly with increasing F,indicating that the driving force suppresses the adsorption of polymer.The conformation of polymer is also affected by the driving force.However,the effect of F is dependent on the competition between the driving force and temperature.Under strong force or at low temperature,the polymer is stretched along the direction of the force,while under weak force or at high temperature,the polymer is not stretched.When the force is comparable to the temperature,the polymer may be stretched perpendicular to the driving force,and below Tc,we observe conformational transitions from parallel to perpendicular and again to parallel by decreasing the temperature.We found that the perpendicular stretched conformation leads the polymer chain to synchronously move along the direction of the driving force.Moreover,the conformational transitions are attributed to the competition and cooperation between the driving force and the temperature.
基金the Natural Science Foundation of Jiangsu Province (Grants BK2018041 1 and BK20180429)start-up funding awarded by the Nanjing University of Aeronautics and Astronautics (Grants 56SYAH 17065 and 90YAH17065)the Fundamental Research Funds for the Central Universities (Grant NS2018004).
文摘Based on the natural exponential pair potential, the interaction potential between curved surface body and on surface particle is studied. Firstly, the interaction potential is written as a function of curvatures through the differential geometry. Secondly, idealized numerical experiments are designed to test the accuracy of curvature-based potential. Then, the driving forces induced by curvatures are analyzed, which confirms that micro/nano curved surface body can induce driving forces, curvatures and the gradient of curvatures are the essential elements forming the driving forces. Finally, by combing with the curvature based potential and driving forces, the movements of on surface particles and the evolution of surface morphology of curved surface body are predicted.
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.
文摘The discovery of the essential difference of maximum ion energy for TW-pslaser plasma interaction compared with, the 100 ns laser pulses led to the theory of a skin layermodel where the control of prepulses suppressed the usual relativistic self-focusing. The subsequentgeneration of two nonlinear force driven blocks has been demonstrated experimentally and inextensive numerical studies where one block moves against the laser light and the other block intothe irradiated target. These blocks of nearly solid state density DT plasma correspond to ion beamcurrent densities exceeding 10^(10) A/cm^2 where the ion velocity can be chosen up to highlyrelativistic values. Using the results of the expected ignition of DT fuel by light ion beams, aself-sustained fusion reaction front may be generated even into uncompressed solid DT fuel similarto the Nuckolls-Wood scheme where 10 kJ laser pulses produce 100 MJ fusion energy. This new andsimplified scheme of laser-ICF needs and optimisation of the involved parameters.
基金by the National Basic Research Program of China under Grant No 2011CB309501the Fund for Creative Research of NSFC under Grant No 61021064+1 种基金the Key Project of NSFC under Grant No 60936001the National Natural Science Foundation of China under Grant No 60876037.
文摘A low-voltage-driven digital-droplet-transporting chip with an open structure is designed,fabricated and characterized.The digital microfluidic chip is fabricated by the silicon planar process.Using only a single electrode panel,the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage.The actuation principle is proposed and verified by the experiment.The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases.The driving voltage for a 3µL deionized(DI)water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top.The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner,and the maximum transport speed reaches 96 mm/s.The droplets of normal saline,a solution of 0.9 wt%NaCl,are also successfully manipulated on the chip.
