The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques. A novel hyperstatic six-component force/torque sensor based on...The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques. A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure, which can be used for the force measurement of the robot wrist, is proposed, and its structural optimal design, finite element analysis and calibration experimentation is presented. The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor. The mathematical expression of the sensor＇s force mapping matrix is introduced. The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively. The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy. The sensor prototype is fabricated, and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS. The calibration device is manufactured, and the data acquisition and processing system is developed. The theoretical and experimental study of the static calibration of the sensor prototype is carried out. The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure, and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.展开更多
This paper presents the isotropic optimization of a Stewart-type six-component force sensor. First,the static model of the sensor is built by the screw theory and the forward isotropy indexes and the inverse isotropy ...This paper presents the isotropic optimization of a Stewart-type six-component force sensor. First,the static model of the sensor is built by the screw theory and the forward isotropy indexes and the inverse isotropy indexes are further presented. Second,a comprehensive evaluation function is established to evaluate the isotropic performance of the sensor. By compromising all the isotropy indexes and solving the extreme value of the function,the sensor optimization process is completed and an optimal solution of a set of sensor structure parameters is obtained. Finally,the design of the components and the assembly of the prototype are established by 3D modeling software Pro-E. The verification of the isotropic performance of the sensor is conducted by the finite element analysis software ANSYS. The results obtained by our research can provide useful reference to the isotropic performance evaluation and structure design of the stewart-type six-component force sensor.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
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
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
Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high ene...Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high energy state of matter expanding outwards by spin jets from the two poles of an astronomical black hole, the new high energy state of matter in a funnel-shaped vortex showed a meteorological tornado expanding downwards from a rotated disk of cumulonimbus clouds, the new high energy state of matter in a tropical cyclone and the new high energy state of a nebulae system converging celestial materials are phenomena across disciplines and multiple time-space scales that have not yet been physically explained. In this paper, the theory of orthogonal collision in the rotational contraction continuum is used to unify the understanding of diverse extreme events or phenomena through a single dynamical mechanism, offering insights into natural processes across disciplines. In the field of astronomy, the orthogonal collision of two-beam rotating and contracting particles or stars associated with centripetal forces forms a new high-energy state of matter at the collision point and the new high-energy particles have expanding forces outward to both sides of the collision plane. In the field of meteorology, the orthogonal collision of multiple horizontally rotating and contracting airflows associated with centripetal forces forms a new high energy state of matter at the collision point as well as an updraft force and a downdraft force vertically. The updraft force and downdraft force formed by the collision of anomalous wet airflows in the lower atmosphere can well indicate tornado, thunderstorm and extreme precipitation. The orthogonal collision theory can be applied to explain new states of matter in disciplines from the astronomical scale to the meteorological scale and the Planck scale.展开更多
The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusio...The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.展开更多
Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to th...Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.展开更多
Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail ...Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.展开更多
Objective: To compare the stress distribution in the periodontal ligament under different orthodontic forces during canine distalization using long-arm brackets, and to determine the optimal force value for this devic...Objective: To compare the stress distribution in the periodontal ligament under different orthodontic forces during canine distalization using long-arm brackets, and to determine the optimal force value for this device in orthodontic treatment. Methods: A finite element model was constructed after extracting the mandibular first premolar, and a long-arm bracket with a traction height of 6 mm was placed on the labial side of the mandibular canine. Three working conditions of 50 g, 100 g, and 150 g were simulated, and the magnitude and distribution of von Mises stress in the periodontal ligament were compared for each condition. Results: The maximum von Mises stress in the periodontal ligament was 0.013281 MPa in the 50 g condition, 0.02536 MPa in the 100 g condition, and 0.035549 MPa in the 150 g condition. As the orthodontic force increased, the stress distribution area in the periodontal ligament also expanded. Conclusion: A 100 g orthodontic force is the most suitable when using long-arm brackets, providing a relatively uniform stress distribution in the periodontal ligament and keeping the stress within a reasonable range.展开更多
In a recent article, we have corrected the traditional derivation of the Schwarzschild metric, thus obtaining the formulation of the correct Schwarzschild metric, which is different from the traditional Schwarzschild ...In a recent article, we have corrected the traditional derivation of the Schwarzschild metric, thus obtaining the formulation of the correct Schwarzschild metric, which is different from the traditional Schwarzschild metric. Then, in another article by starting from this correct Schwarzschild metric, we have corrected also the Reissner-Nordstrøm, Kerr and Kerr-Newman metrics. On the other hand, in a third article, always by starting from this correct Schwarzschild metric, we have obtained the formulas of the correct gravitational potential and of the correct gravitational force in the case described by this metric. Now, in this article, by starting from these correct Reissner-Nordstrøm, Kerr and Kerr-Newman metrics and proceeding in a manner analogous to this third article, we obtain the formulas of the correct gravitational potential and of the correct gravitational force in the cases described by these metrics. Moreover, we analyze these correct results and their consequences. Finally, we propose some possible crucial experiments between the commonly accepted theory and the same theory corrected according to this article.展开更多
With the intensification of lunar exploration,the failure risk caused by the adsorption of lunar dust on the spacecraft surface cannot be ignored.Therefore,three types of typical spatial solid lubrication films,namely...With the intensification of lunar exploration,the failure risk caused by the adsorption of lunar dust on the spacecraft surface cannot be ignored.Therefore,three types of typical spatial solid lubrication films,namely polytetrafluoroethylene(PTFE),amorphous carbon(a-C)and molybdenum disulfide(MoS2),were prepared as test samples.Firstly,the surface free energy parameters of the material were measured using a contact Angle measuring instrument.At the same time,atomic force microscopy(AFM)was used to quantify the adhesion of the film samples based on the lunar dust micro-adsorption model.In order to investigate the influence of the test environment,the environmental pressure was adjusted to normal pressure environment and high vacuum environment with a vacuum degree of 10−6 Pa for testing.The results indicate a positive correlation between surface energy and adhesion.As surface energy increases,molecules tend to move closer,forming a stronger attraction and thus enhancing surface adhesion.In addition,AFM was used to measure the adhesion force under atmospheric pressure and vacuum conditions,revealing that parameters measured in atmospheric environment were generally higher than those measured in vacuum,which effectively verified the existence of capillary force in the microscopic adsorption model and its influence on the adhesion effect.Through the test comparison of three groups of typical solid lubricating films,it is found that MoS2 has a lower adhesion effect than the other two groups of films,which can effectively reduce the adhesion phenomenon of lunar dust on the surface of the material,and provide suitable materials for future lunar exploration and manned lunar missions.展开更多
The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic fi...The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic field,initiated only by this field.It is shown that the moment of force applied to any closed body surface S,corresponding to the asymmetric part TAof the stress tensor T(denoted as the force pA),balances the mass magnetic moment Lmagacting in the volume V bounded by the surface S.The emergence of the asymmetric part TAof the stress tensor arises as a consequence of a special case within the moment theory of elasticity,the use of which is necessary for accurately describing the behavior of a ferromagnetic material in a magnetic field.The force pa acts in a plane tangential to the surface S at any point,while,in addition to this force,the normal force pn also acts on the body surface.It is shown in the article that the latter force arises as a result of a jump in the normal component of the magnetic field strength appearing at the body surface,and its expression is defined by the mass' s(ponderomotive) magnetic forces Fmag.Usually,this force is introduced based on the Maxwell stress tensor,which is used in the classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum.However,as we believe and justify this in the article,such an approach is unacceptable in deformable solid mechanics.展开更多
Driven by technological innovation and the innovative allocation of production factors,new quality productive forces(NQPFs)are a key breakthrough and core element propelling China’s transition from a major agricultur...Driven by technological innovation and the innovative allocation of production factors,new quality productive forces(NQPFs)are a key breakthrough and core element propelling China’s transition from a major agricultural country to an advanced agricultural nation.At its core,agricultural modernization represents a frontier shift in agricultural development-a dynamic evolution of productive forces across technological forms,farmer demographics,industrial structures,and urban-rural relations.NQPFs drive the high-quality,integrated development of agricultural modernization through agricultural technological innovation,green and low-carbon practices,and the enhancement of all production factors.As NQPFs evolve and agricultural modernization advances,we must address constraints stemming from gaps in technology,models,resources,and talent.Furthermore,we must foster deep integration among industry,research,and education to develop new pathways for industrial upgrading,promote green and efficient agricultural development,and bridge existing technological gaps.These collective efforts are crucial for accelerating the high-quality development of agricultural modernization.展开更多
Force control merged with motion control represent the fundamental low level requirements for the most complex tasks to be performed by any robot.In particular,robust motion and force controllers allow robots to deal ...Force control merged with motion control represent the fundamental low level requirements for the most complex tasks to be performed by any robot.In particular,robust motion and force controllers allow robots to deal with real-world uncertainties among other disturbances.In this paper,an admittance-based force controller using the Active Disturbance Rejection Control approach is proposed,which allows to perform robot force control without a force sensor.In addition,a theoretical synthesis of the control law including an extended state observer for the estimation of the robot–surface force interaction and their formal stability analysis is presented.The validation of the proposal is depicted by numerical simulations using the dynamical model of a two degrees of freedom robot manipulator,for both a constant and a time-varying force control tasks with an unknown curved surface,while considering joint measurement noise and force sensors noise and an external disturbance force.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50575192)Hebei Provincial Natural Science Foundation of China (Grant No. E2007000349)
文摘The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques. A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure, which can be used for the force measurement of the robot wrist, is proposed, and its structural optimal design, finite element analysis and calibration experimentation is presented. The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor. The mathematical expression of the sensor＇s force mapping matrix is introduced. The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively. The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy. The sensor prototype is fabricated, and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS. The calibration device is manufactured, and the data acquisition and processing system is developed. The theoretical and experimental study of the static calibration of the sensor prototype is carried out. The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure, and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.
基金supported by the Fundation of Graduate Innovation Center in Nanjing University of Aeronautics and Astronautics(No.kfjj20190308)the Fundamental Research Funds for the Central Universities
文摘This paper presents the isotropic optimization of a Stewart-type six-component force sensor. First,the static model of the sensor is built by the screw theory and the forward isotropy indexes and the inverse isotropy indexes are further presented. Second,a comprehensive evaluation function is established to evaluate the isotropic performance of the sensor. By compromising all the isotropy indexes and solving the extreme value of the function,the sensor optimization process is completed and an optimal solution of a set of sensor structure parameters is obtained. Finally,the design of the components and the assembly of the prototype are established by 3D modeling software Pro-E. The verification of the isotropic performance of the sensor is conducted by the finite element analysis software ANSYS. The results obtained by our research can provide useful reference to the isotropic performance evaluation and structure design of the stewart-type six-component force sensor.
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 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(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.
文摘Astronomical extreme events or phenomena include black holes as well as nebulae systems that resemble the Milky Way. Meteorological extreme events or phenomena include tornadoes and tropical cyclones. The new high energy state of matter expanding outwards by spin jets from the two poles of an astronomical black hole, the new high energy state of matter in a funnel-shaped vortex showed a meteorological tornado expanding downwards from a rotated disk of cumulonimbus clouds, the new high energy state of matter in a tropical cyclone and the new high energy state of a nebulae system converging celestial materials are phenomena across disciplines and multiple time-space scales that have not yet been physically explained. In this paper, the theory of orthogonal collision in the rotational contraction continuum is used to unify the understanding of diverse extreme events or phenomena through a single dynamical mechanism, offering insights into natural processes across disciplines. In the field of astronomy, the orthogonal collision of two-beam rotating and contracting particles or stars associated with centripetal forces forms a new high-energy state of matter at the collision point and the new high-energy particles have expanding forces outward to both sides of the collision plane. In the field of meteorology, the orthogonal collision of multiple horizontally rotating and contracting airflows associated with centripetal forces forms a new high energy state of matter at the collision point as well as an updraft force and a downdraft force vertically. The updraft force and downdraft force formed by the collision of anomalous wet airflows in the lower atmosphere can well indicate tornado, thunderstorm and extreme precipitation. The orthogonal collision theory can be applied to explain new states of matter in disciplines from the astronomical scale to the meteorological scale and the Planck scale.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+3 种基金the Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(No.JSKL2223K01)the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Henan Science and Technology Public Relations Project(No.212102210445).
文摘The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.
文摘Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.
基金supported by Natural Science Foundation of China(52178441)the Scientific Research Projects of the China Academy of Railway Sciences Co.,Ltd.(Grant No.2022YJ043).
文摘Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways.They can cause significant wheel-rail dynamic interactions,leading to wheel-rail noise,component damage,and deterioration.Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities.However,the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape.In this study,novel theoretical models were developed for three categories of rail weld irregularities,based on measurements of the high-speed railway from Beijing to Shanghai.The vertical dynamic forces in the time and frequency domains were compared under different running speeds.These forces generated by the rail weld irregularities that were measured and modeled,respectively,were compared to validate the accuracy of the proposed model.Finally,based on the numerical study,the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network(ANN),and the optimum combination of parameters for this model is found.The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature.The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.
文摘Objective: To compare the stress distribution in the periodontal ligament under different orthodontic forces during canine distalization using long-arm brackets, and to determine the optimal force value for this device in orthodontic treatment. Methods: A finite element model was constructed after extracting the mandibular first premolar, and a long-arm bracket with a traction height of 6 mm was placed on the labial side of the mandibular canine. Three working conditions of 50 g, 100 g, and 150 g were simulated, and the magnitude and distribution of von Mises stress in the periodontal ligament were compared for each condition. Results: The maximum von Mises stress in the periodontal ligament was 0.013281 MPa in the 50 g condition, 0.02536 MPa in the 100 g condition, and 0.035549 MPa in the 150 g condition. As the orthodontic force increased, the stress distribution area in the periodontal ligament also expanded. Conclusion: A 100 g orthodontic force is the most suitable when using long-arm brackets, providing a relatively uniform stress distribution in the periodontal ligament and keeping the stress within a reasonable range.
文摘In a recent article, we have corrected the traditional derivation of the Schwarzschild metric, thus obtaining the formulation of the correct Schwarzschild metric, which is different from the traditional Schwarzschild metric. Then, in another article by starting from this correct Schwarzschild metric, we have corrected also the Reissner-Nordstrøm, Kerr and Kerr-Newman metrics. On the other hand, in a third article, always by starting from this correct Schwarzschild metric, we have obtained the formulas of the correct gravitational potential and of the correct gravitational force in the case described by this metric. Now, in this article, by starting from these correct Reissner-Nordstrøm, Kerr and Kerr-Newman metrics and proceeding in a manner analogous to this third article, we obtain the formulas of the correct gravitational potential and of the correct gravitational force in the cases described by these metrics. Moreover, we analyze these correct results and their consequences. Finally, we propose some possible crucial experiments between the commonly accepted theory and the same theory corrected according to this article.
基金Supported by National Nature Science Foundation of China(Grant Nos.52205225,U2330202)The Foundation Project of China(Grant No.2023-JCJQ-JJ-0958).
文摘With the intensification of lunar exploration,the failure risk caused by the adsorption of lunar dust on the spacecraft surface cannot be ignored.Therefore,three types of typical spatial solid lubrication films,namely polytetrafluoroethylene(PTFE),amorphous carbon(a-C)and molybdenum disulfide(MoS2),were prepared as test samples.Firstly,the surface free energy parameters of the material were measured using a contact Angle measuring instrument.At the same time,atomic force microscopy(AFM)was used to quantify the adhesion of the film samples based on the lunar dust micro-adsorption model.In order to investigate the influence of the test environment,the environmental pressure was adjusted to normal pressure environment and high vacuum environment with a vacuum degree of 10−6 Pa for testing.The results indicate a positive correlation between surface energy and adhesion.As surface energy increases,molecules tend to move closer,forming a stronger attraction and thus enhancing surface adhesion.In addition,AFM was used to measure the adhesion force under atmospheric pressure and vacuum conditions,revealing that parameters measured in atmospheric environment were generally higher than those measured in vacuum,which effectively verified the existence of capillary force in the microscopic adsorption model and its influence on the adhesion effect.Through the test comparison of three groups of typical solid lubricating films,it is found that MoS2 has a lower adhesion effect than the other two groups of films,which can effectively reduce the adhesion phenomenon of lunar dust on the surface of the material,and provide suitable materials for future lunar exploration and manned lunar missions.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(No.075-15-2024-535)。
文摘The purpose of this article is to provide,from the perspective of deformable solid mechanics,a correct justification for the expressions of all forces acting on the surface of a ferromagnetic material in a magnetic field,initiated only by this field.It is shown that the moment of force applied to any closed body surface S,corresponding to the asymmetric part TAof the stress tensor T(denoted as the force pA),balances the mass magnetic moment Lmagacting in the volume V bounded by the surface S.The emergence of the asymmetric part TAof the stress tensor arises as a consequence of a special case within the moment theory of elasticity,the use of which is necessary for accurately describing the behavior of a ferromagnetic material in a magnetic field.The force pa acts in a plane tangential to the surface S at any point,while,in addition to this force,the normal force pn also acts on the body surface.It is shown in the article that the latter force arises as a result of a jump in the normal component of the magnetic field strength appearing at the body surface,and its expression is defined by the mass' s(ponderomotive) magnetic forces Fmag.Usually,this force is introduced based on the Maxwell stress tensor,which is used in the classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum.However,as we believe and justify this in the article,such an approach is unacceptable in deformable solid mechanics.
基金funded by grants from the General Project of the National Social Science Fund:“Research on the Interactive Mechanism of Migrant Workers Returning to Their Hometowns for Entrepreneurship and Rural Revitalization in the Major Labor Export Provinces”(20BJY136)General Project of Sichuan Provincial Philosophy and Social Science Fund:“The Era Significance,Growth Constraints,and Path Optimization of the New Agricultural Laborers from the Perspective of the New Quality Productive Forces”(SCJJ24ND065)Key Project of the Sichuan Academy of Social Sciences:“The Era Significance,Current Concerns,and Action Prospects of the New Agricultural Laborers from the Perspective of the New Quality Productive Forces”(24XD02).
文摘Driven by technological innovation and the innovative allocation of production factors,new quality productive forces(NQPFs)are a key breakthrough and core element propelling China’s transition from a major agricultural country to an advanced agricultural nation.At its core,agricultural modernization represents a frontier shift in agricultural development-a dynamic evolution of productive forces across technological forms,farmer demographics,industrial structures,and urban-rural relations.NQPFs drive the high-quality,integrated development of agricultural modernization through agricultural technological innovation,green and low-carbon practices,and the enhancement of all production factors.As NQPFs evolve and agricultural modernization advances,we must address constraints stemming from gaps in technology,models,resources,and talent.Furthermore,we must foster deep integration among industry,research,and education to develop new pathways for industrial upgrading,promote green and efficient agricultural development,and bridge existing technological gaps.These collective efforts are crucial for accelerating the high-quality development of agricultural modernization.
基金Julio Antonio Caballero-Mora acknowledges the CONAHCYT Scholarship number 828530。
文摘Force control merged with motion control represent the fundamental low level requirements for the most complex tasks to be performed by any robot.In particular,robust motion and force controllers allow robots to deal with real-world uncertainties among other disturbances.In this paper,an admittance-based force controller using the Active Disturbance Rejection Control approach is proposed,which allows to perform robot force control without a force sensor.In addition,a theoretical synthesis of the control law including an extended state observer for the estimation of the robot–surface force interaction and their formal stability analysis is presented.The validation of the proposal is depicted by numerical simulations using the dynamical model of a two degrees of freedom robot manipulator,for both a constant and a time-varying force control tasks with an unknown curved surface,while considering joint measurement noise and force sensors noise and an external disturbance force.
