In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process ...In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.展开更多
The strain jump across the Austenite-Martensite (A-M) interface in single crystal Cu-14wt%Al-4.12wt%Ni Shape Memory Alloys (SMAs) under uniaxial tension was studied in this paper. A crystallographic-based mechanics an...The strain jump across the Austenite-Martensite (A-M) interface in single crystal Cu-14wt%Al-4.12wt%Ni Shape Memory Alloys (SMAs) under uniaxial tension was studied in this paper. A crystallographic-based mechanics analysis on the formation and microstructure of the interface was performed. By using the high sensitive Moiré interference technique, the full-field deformation patterns during the transformation process were successfully recorded. The orientation of the habit plane (A-M interface) and the magnitude of the shape strain were determined precisely from the Moiré fringe patterns. The theoretical predictions on the habit plane normal and the shape strain were compared with the measured results and good agreements were obtained.展开更多
The paper firstly gives a brief introduction of the credit focus as a result of the competition among the branch banks of the Commercial Bank. Then from the viewpoint of the performance of the branch bank, an analysis...The paper firstly gives a brief introduction of the credit focus as a result of the competition among the branch banks of the Commercial Bank. Then from the viewpoint of the performance of the branch bank, an analysis is made on the mechanism of the formation of the credit focus. Based on the analysis, the paper points out that the Commercial Bank branches, under competition of the deposit restrain, have brought about excessive credit, which exceeds the finance required by the normal business. And finally the paper forms the credit risk of the bank.展开更多
In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stag...In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.展开更多
In order to effectively cope with exponent increase of the complexity faced to the rock mechanics analysis problems and the large incompatibility existing between the information level required to model the rock mass ...In order to effectively cope with exponent increase of the complexity faced to the rock mechanics analysis problems and the large incompatibility existing between the information level required to model the rock mass and engineering and our obtainable information level at hand,the integrated approaches with intelligent characters are proposed. Many previous standard methods,such as precedent type analysis,rock classification,analytic method stress-based,basic numerical methods (BEM,FEM,DEM,hybrid),and their extended numerical methods (fully coupled) to be developed,can be selected respectively or integrated accordingly. It is alternative to develop basic/fully integrated system,and internet-based approaches. These novel methods can also be selected or integrated each other or with the standard methods to perform rock mechanics analysis. Some key techniques to develop these alternative methods are discussed. It may focus in future on developing fully integrated systems and internet-based approaches. Developing an environmental,virtual facility/space shall be firstly done for this collaborative research on internet.展开更多
The strength and endurance of human limbs can be enhanced through equipping exoskeletons or other types of wearabledevices. However, long-time use of such devices may cause musculoskeletal disorders (MSDs) or potentia...The strength and endurance of human limbs can be enhanced through equipping exoskeletons or other types of wearabledevices. However, long-time use of such devices may cause musculoskeletal disorders (MSDs) or potential injuries due toexternal shocks and vibrations. Consequently, preventing potential risks and enhancing comfortability are crucial to the designof exoskeleton. This research introduces a novel hybrid rigid-soft knee joint exoskeleton, which is well flexible and supportedby two curved beams. This design is friendly and comfortable for wearers. The stiffness of the curved beam is meticulouslycalibrated to match the natural need of the knee joint, which provides appropriate support under vibration and impact. Weemploy the analytical modeling, finite element method (FEM), numerical analysis, and experimental approaches to analyze thestatic and dynamic properties of the knee exoskeleton system. The results confirm that the exoskeleton system exhibits reducedvibration transmissibility in low-frequency environments, and present a new methodology for the design and mechanicalanalysis of exoskeleton systems.展开更多
In the realm of slope monitoring and reinforcement,traditional prestressing anchor cables are extensively used.However,these conventional methods often face limitations when applied to loess slopes,such as potential i...In the realm of slope monitoring and reinforcement,traditional prestressing anchor cables are extensively used.However,these conventional methods often face limitations when applied to loess slopes,such as potential issues with stress concentration and insufficient adaptability to the unique mechanical properties of loess,which may lead to challenges in ensuring long-term stability and effective reinforcement.Negative Poisson's ratio(NPR)anchor cables with constant resistance have emerged as a promising alternative,which can better match the engineering demands of loess slopes by providing more uniform stress distribution and adaptive deformation characteristics.The NPR cable's ability to maintain a constant resistance during deformation offers a distinct advantage over traditional methods as it can more effectively accommodate the complex and variable conditions of loess slopes.To investigate the anchoring performance of NPR cables in loess slope,the stress characteristics of NPR cable in loess medium were simulated and analysed by ABAQUS finite element software.First,static and general quasi-static analysis methods were used to simulate the NPR cable under static tensile conditions.The consistency of the simulated constant resistance deformation characteristics with experimental results found in the literature was verified.Second,the interaction model between the NPR cable coupled with the loess medium was established.Its constant resistance was calculated to be about 24.08%larger than that of NPR anchor cable while its plastic deformation was reduced by about 37.14%.The compressive stress on the contact surface between NPR cable and loess was concentrated near the free end of the sleeve,which indicated that the loess was prone to severe damage at the free end.The research results reveal the typical shear failure mechanism of NPR cable in loess medium,which provides an important theoretical basis for prevention of landslides and monitoring of loess slopes.展开更多
This study determines whether industrial agglomeration can solve energy poverty(ENPO)by applying a provincial dataset(2002-2019)to assess the potential effect of industrial agglomeration on ENPO.Additionally,this stud...This study determines whether industrial agglomeration can solve energy poverty(ENPO)by applying a provincial dataset(2002-2019)to assess the potential effect of industrial agglomeration on ENPO.Additionally,this study conducts an in-depth exploration of provincial heterogeneity and its influence mechanisms.The conclusions are as follows:①Industrial agglomeration is negatively correlated with ENPO;by implication,enhancing industrial agglomeration is a driving force for reducing ENPO.②The alleviating effect of industrial agglomeration on ENPO in the midwestern region is considerably higher than that in the eastern region,and the ENPO alleviation effect of the high agglomeration region is better than that in the low agglomeration region.③Foreign investment and energy efficiency have a mediating role,that is,they are valid transmission pathways for industrial agglomeration to solve the ENPO issue.Relevant policy suggestions for reducing ENPO by accelerating industrial agglomeration are proposed by drawing on the above three conclusions.展开更多
This study exploits China's"Pilot Program for the Integration of Science and Technology with Finance"as a quasi-natural experiment to investigate the effect of Sci-Tech Finance on corporate financial res...This study exploits China's"Pilot Program for the Integration of Science and Technology with Finance"as a quasi-natural experiment to investigate the effect of Sci-Tech Finance on corporate financial resilience and its underlying mechanisms.Using panel data of A-share firms listed on the Shanghai and Shenzhen stock exchanges from 2000 to 2024 and using a staggered difference-in-differences(DID)model,we find that corporate financial resilience significantly improved after the Sci-Tech Finance policy,as evidenced by reduced earnings volatility and more sustainable profit growth.Heterogeneity analyses show that the effect is more pronounced during periods of high economic policy uncertainty(EPU)and in regions with less developed traditional banking systems.Mechanism analyses suggest that Sci-Tech Finance strengthens firm financial resilience by alleviating financing constraints,mitigating information asymmetry,optimizing investment efficiency,and promoting green innovation.We provide novel evidence on the role of Sci-Tech Finance in stabilizing firm performance and fostering long-term value creation,thereby contributing to the broad literature on high-quality economic development.展开更多
Wall-climbing robots can stably ascend vertical walls and even ceilings,making them suitable for specialized tasks in high-risk,confined,and harsh conditions.Therefore,they have excellent application prospects and sub...Wall-climbing robots can stably ascend vertical walls and even ceilings,making them suitable for specialized tasks in high-risk,confined,and harsh conditions.Therefore,they have excellent application prospects and substantial market demand.However,several challenges remain,including limited load-carrying capacity,short operational duration,a high risk of detachment,and the lack of standardized physical and control interfaces for carrying auxiliary equipment to complete missions.This study analyzes the macro and micro structures and movement mechanisms of typical organisms in terms of negative pressure adsorption,hook-and-claw adhesion,dry adhesion,and wet adhesion.The exploration of biological wall-climbing mechanisms is integrated with the adhesion techniques used in practical wall-climbing robots.Additionally,the mechanisms,properties,and typical wall-climbing robots associated with adhesion technologies were investigated,including negative pressure adsorption,hook-and-claw adhesion,bionic dry adhesion,bionic wet adhesion,electrostatic adhesion,and magnetic adhesion.Furthermore,the typical gaits of quadruped and hexapod robots are analyzed,and bionic control techniques such as central pattern generators,neural networks,and compliant control are applied.Finally,the future development trends of wall-climbing robots will be examined from multiple perspectives,including the diversification of bionic mechanisms,the advancement of mechanical structure intelligence,and the implementation of intelligent adaptive control.Moreover,this paper establishes a solid foundation for the innovative design of bionic wall-climbing robots and provides valuable guidance for future advancements.展开更多
Single crystal Ni-rich cathode materials(SCNCM)are a good supplement in the market of nickel-based materials due to their safety and excellent electrochemical performance.However,the challenges of cation mixing,phase ...Single crystal Ni-rich cathode materials(SCNCM)are a good supplement in the market of nickel-based materials due to their safety and excellent electrochemical performance.However,the challenges of cation mixing,phase change during charge/discharge,and low thermal stability remain unresolved in single crystal particles.To address these issues,SCNCM are rationally modified by incorporating transition metal(TM)oxides,and the influence of metal ions with different valence states on the electrochemical properties of SCNCM is methodically explored through experimental results and theoretical calculations.Enhanced structural stability is demonstrated in SCNCM after the modifications,and the degree of improvement in the matrix materials varies depending on the valence state of doped TM ions.The highest structural stability is found in WO_(3)-modified SCNCM,due to the smaller effective ion radii,higher electro-negativity,stronger W-O bond,and efficient suppression of oxygen vacancy generation.As a result,WO_(3)-modified SCNCM have outstanding cycle performance,with a capacity retention rate of90.2%after 200 cycles.This study provides an insight into the design of advanced SCNCM with enhanced reversibility and cyclability.展开更多
Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation ...Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation to microscopic mechanisms,remains relatively sparse.This study utilizes microscopic visualization experiments to investigate the mechanisms of residual oil mobilization under various IPC scenarios,complemented by mechanical analysis at different stages.The research quantitatively assesses the degree of microscopic oil recovery and the distribution of residual oil across different injection-production methods.Findings reveal that during the initial phase of continuous gas injection(CGI),the process closely mimics miscible displacement,gradually transitioning to immiscible displacement as CO_(2)extraction progresses.Compared to CGI,the asynchronous injection-production(AIP) method improved the microscopic oil recovery rate by 6.58%.This enhancement is mainly attributed to significant variations in the pressure field in the AIP method,which facilitate the mobilization of columnar and porous re sidual oil.Furthermo re,the synchronous cycle injection(SCI) method increased microscopic oil recovery by 13.77% and 7.19% compared to CGI and AIP,respectively.In the SCI method,membrane oil displays filame ntary and Karman vo rtex street flow patterns.The dissolved and expanded crude oil te nds to accumulate and grow at the oil-solid interface due to adhesive forces,thereby reducing migration resistance.The study findings provide a theoretical foundation for improving oil recovery in lowpermeability reservoirs.展开更多
In response to the challenges of sand production and high water cut during the exploitation of oil reservoirs in unconsolidated sandstones,a novel sand-water dual-control functional polymer,PDSM,was synthesized using ...In response to the challenges of sand production and high water cut during the exploitation of oil reservoirs in unconsolidated sandstones,a novel sand-water dual-control functional polymer,PDSM,was synthesized using acrylamide(AM),methacryloxyethyltrimethyl ammonium chloride(DMC),and styrene monomer(SM)as raw materials.The chemical structure and thermal stability of PDSM were verified by1H-NMR,FT-IR,and TGA analyses.To evaluate its performance,functional polymers PDM and PSM,containing only DMC or SM,respectively,were used as control groups.The study systematically investigated the static adsorption,sand production,sand leakage time,standard water-oil resistance ratio,and water cut reduction performance of PDSM.The results demonstrated that,due to the synergistic effect of functional monomers DMC and SM,PDSM exhibited superior dual-control over sand and water compared to PDM and PSM.PDSM enhanced wettability properties reduce the contact angle of the water phase on oil-wet rock surfaces to 64.0°,facilitating better adsorption of polymer molecules on the rock surface and achieving a static adsorption capacity of 14.6 mg/g.PDSM effectively bridges/bundles sand grains through SM and DMC,increasing resistance to fluid erosion.At a flow rate of 100 mL/min,sand production was only 0.026 g/L,surpassing the"Q/SH 10202377-2020"standard for sand inhibitors,which defines"excellent"performance as having a sand production rate of≤0.05 g/L.PDSM forms an adsorption layer(polymer concentrated layer)on the rock surface,expanding when in contact with water and shrinking when in contact with oil,thereby significantly reducing the permeability of the water layer without affecting the permeability of the oil layer.The standard water-oil resistance ratio was measured at 5.41,and the watercut of produced fluid was reduced by 18.6%.These findings provide new theoretical insights and technical guidance for developing dual-function sand-water control agents.展开更多
To address the limitations of traditional manual highway guardrail inspections,this paper proposes an obstacle-crossing and collaborative tracking control method for a rail-mounted robot.Static and dynamic analyses ve...To address the limitations of traditional manual highway guardrail inspections,this paper proposes an obstacle-crossing and collaborative tracking control method for a rail-mounted robot.Static and dynamic analyses verify the robot's structural reliability and driving feasibility.Based on the leader-follower model,a triangular collaborative tracking model is developed,and a linear time-varying model predictive controll(LTV-MPC)is designed to achieve smooth and precise collaborative control.For obstacle crossing,an acceleration reference model and a gradient-based adaptive law are proposed,leading to a model reference adaptive controll(MRAC)that effectively suppresses vibrations and ensures synchronous control.Simulation results show that the MPC achieves a 0.415%overshoot and a 0.344 m steady-state accuracy,while also reducing the intensity of speed fluctuations by 35%.The MRAC ensures smooth obstacle-crossing speeds and adaptive strategy switching,validating the reliability and practicality of the rail-mounted robot under complex working conditions.展开更多
Fluidized solidified soil(FSS)is an innovative backfill material that offers benefits such as easy pumping and straightforward construction.This study examined how varying the water-soil ratio and the curing agent dos...Fluidized solidified soil(FSS)is an innovative backfill material that offers benefits such as easy pumping and straightforward construction.This study examined how varying the water-soil ratio and the curing agent dosage affect the properties and microstructure of FSS.The strength development mechanism was investigated when composite solidification agents were used.The findings show that both the water-solid ratio and the curing agent dosage can affect the microstructure of FSS,thereby affecting its performance.When the water-solid ratio increases from 0.52 to 0.56,the unconfined compressive strength(UCS)and flexural strength of the FSS decrease by 34.1% and 39.3% after 28 d.Conversely,the curing agent dosage increasing from 10% to 30% will increase both UCS and flexural strength by 11.2 times and 11.1 times.As the curing age increases,the number of cracks at failure point in the FSS will increase and lead to a more complete failure.Numerous needle-like AFt,C-S-H gel,and C-(A)-S-H gel create a three-dimensional network by adhering to soil particles.展开更多
Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of an...Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.展开更多
The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the k...The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the key strata is established given the structural characteristics and the mechanical properties of the roof rock layers of the working face in a particular coal mine. Four other models were derived from this model by rearranging the order of the layers in the key strata. The distribution characteristics of stress, deformation, pore pressure and the flow vector of all the models are computed using the analytical module of fluid-structure interaction in the FLAC software and the corresponding risks of a water-burst are analyzed. The results indicate that the water-insulating ability of the key strata is related to the arrangement of soft and hard rocks. The water-insulating ability of the compound water-resisting key strata (CWKS) with a hard-hard-soft-hard-soft compounding order is the best under the five given simulated conditions.展开更多
To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal p...To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.展开更多
A fully superconducting electron cyclotron resonance （ECR） ion source （SECRAL ID is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconductin...A fully superconducting electron cyclotron resonance （ECR） ion source （SECRAL ID is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconducting solenoids （Nb-Ti/Cu） and six superconducting sextupoles （Nb-Ti/Cu）. Different from the conventional supercon- ducting ECR magnetic structure, the SEC17AL Ⅱ includes three superconducting solenoid coils＇ that are located inside the superconducting sextupoles. The SECRAL Ⅱ can significantly reduce the interaction forces between the sextupole and the solenoids, and the magnets can also be more compact in size. For this multi-component SECRAL Ⅱ generating its self field of -8 T and being often exposed to the high self field, the mechanical analysis has become the main issue to keep their stress at 〈200 MPa on coils. The analytical and experimental results in mechanics are presented in the SECRAL Ⅱ structure. To improve the accuracy and efficiency of analysis, according to the composite rule of micromechanics, the equivalent uniform windings are used to simulate the epoxy-impregnated Nb-Ti/Cu coils. In addition, using low temperature strain gauges and a wireless fast strain acquisition system, a fundamental experiment on the based on our analysis, the stresses and deformations optimized. strains developments of a sextupole is reported. Finally, for its assembly of each SECRAL Ⅱ coil will be further展开更多
A new spherical mobile robot BHQ-1 is designed. The spherical robot is driven by two internally mounted motors that induce the ball to move straight and turn around on a fiat surface. A dynamic model of the robot is d...A new spherical mobile robot BHQ-1 is designed. The spherical robot is driven by two internally mounted motors that induce the ball to move straight and turn around on a fiat surface. A dynamic model of the robot is developed with Lagrange method and factors affecting the driving torque of two motors are analyzed. The relationship between the turning radius of the robot and the length of two links is discussed in order to optimize its mechanism design. Simulation and experimental results demonstrate the good controllability and motion performance of BHQ-1.展开更多
基金The Doctoral Program of Central South University (No. 2010ybfz048)the National High Technology Research and Development Program of China (863 Program) (No. 2007AA021908)
文摘In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.
基金The project supported by the National Natural Science Foundation of China (19891180(3))Hong Kong Research Grant Committee (DAG 96/97. EG15)
文摘The strain jump across the Austenite-Martensite (A-M) interface in single crystal Cu-14wt%Al-4.12wt%Ni Shape Memory Alloys (SMAs) under uniaxial tension was studied in this paper. A crystallographic-based mechanics analysis on the formation and microstructure of the interface was performed. By using the high sensitive Moiré interference technique, the full-field deformation patterns during the transformation process were successfully recorded. The orientation of the habit plane (A-M interface) and the magnitude of the shape strain were determined precisely from the Moiré fringe patterns. The theoretical predictions on the habit plane normal and the shape strain were compared with the measured results and good agreements were obtained.
文摘The paper firstly gives a brief introduction of the credit focus as a result of the competition among the branch banks of the Commercial Bank. Then from the viewpoint of the performance of the branch bank, an analysis is made on the mechanism of the formation of the credit focus. Based on the analysis, the paper points out that the Commercial Bank branches, under competition of the deposit restrain, have brought about excessive credit, which exceeds the finance required by the normal business. And finally the paper forms the credit risk of the bank.
基金funded by the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant Agreement(Grant No.101026104)by the National Natural Science Foundation of China(Grant No.U20A6004)in part by the State Key Laboratory of Precision Electronics Manufacturing Technology and Equipment(Grant No.JMDZ202314).
文摘In semiconductor precision packaging and other applications involving alignment of automated equipment,the nonlinear motion caused by structural characteristics and friction effects on torque-type rotating motion stages seriously affects output accuracy and stability.To solve this problem,the motion characteristics of a rotating stage and the mechanism by which friction nonlinearity influences accuracy are analyzed in detail.In addition,a compound control strategy based on a kinematic model and the Stribeck friction model is designed.A friction disturbance observer based on output position feedback is improved for simple parameter tuning.Finally,an experimental system is constructed to carry out validation tests,including identification of nonlinear characteristics and performance comparisons.The experimental results show that the linear tracking error of the torque-type rotating stage is less than 1.47µm after adoption of the proposed model-based composite control strategy,and the corresponding rotary angle deviation is less than 0.0153°.The linearity of output motion is increased to 97.59%and the error compensation effect is improved by 51.6%compared with the PID control method.The experimental results confirm that the analysis method adopted here and the proposed compensation strategy can effectively reduce frictional nonlinearity and improve motion accuracy.The proposed method can also be applied to other precision electromechanical systems.
基金Nature Science Foundation of China under Grant no.50179034.
文摘In order to effectively cope with exponent increase of the complexity faced to the rock mechanics analysis problems and the large incompatibility existing between the information level required to model the rock mass and engineering and our obtainable information level at hand,the integrated approaches with intelligent characters are proposed. Many previous standard methods,such as precedent type analysis,rock classification,analytic method stress-based,basic numerical methods (BEM,FEM,DEM,hybrid),and their extended numerical methods (fully coupled) to be developed,can be selected respectively or integrated accordingly. It is alternative to develop basic/fully integrated system,and internet-based approaches. These novel methods can also be selected or integrated each other or with the standard methods to perform rock mechanics analysis. Some key techniques to develop these alternative methods are discussed. It may focus in future on developing fully integrated systems and internet-based approaches. Developing an environmental,virtual facility/space shall be firstly done for this collaborative research on internet.
基金supported by Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(Grant No.CX2024001).
文摘The strength and endurance of human limbs can be enhanced through equipping exoskeletons or other types of wearabledevices. However, long-time use of such devices may cause musculoskeletal disorders (MSDs) or potential injuries due toexternal shocks and vibrations. Consequently, preventing potential risks and enhancing comfortability are crucial to the designof exoskeleton. This research introduces a novel hybrid rigid-soft knee joint exoskeleton, which is well flexible and supportedby two curved beams. This design is friendly and comfortable for wearers. The stiffness of the curved beam is meticulouslycalibrated to match the natural need of the knee joint, which provides appropriate support under vibration and impact. Weemploy the analytical modeling, finite element method (FEM), numerical analysis, and experimental approaches to analyze thestatic and dynamic properties of the knee exoskeleton system. The results confirm that the exoskeleton system exhibits reducedvibration transmissibility in low-frequency environments, and present a new methodology for the design and mechanicalanalysis of exoskeleton systems.
基金the State Key Laboratory of Deep Geotechnical Mechanics and Underground Engineering(SKLGDUEK2124)of China University of Mining and Technology(Beijing)for its support for this research。
文摘In the realm of slope monitoring and reinforcement,traditional prestressing anchor cables are extensively used.However,these conventional methods often face limitations when applied to loess slopes,such as potential issues with stress concentration and insufficient adaptability to the unique mechanical properties of loess,which may lead to challenges in ensuring long-term stability and effective reinforcement.Negative Poisson's ratio(NPR)anchor cables with constant resistance have emerged as a promising alternative,which can better match the engineering demands of loess slopes by providing more uniform stress distribution and adaptive deformation characteristics.The NPR cable's ability to maintain a constant resistance during deformation offers a distinct advantage over traditional methods as it can more effectively accommodate the complex and variable conditions of loess slopes.To investigate the anchoring performance of NPR cables in loess slope,the stress characteristics of NPR cable in loess medium were simulated and analysed by ABAQUS finite element software.First,static and general quasi-static analysis methods were used to simulate the NPR cable under static tensile conditions.The consistency of the simulated constant resistance deformation characteristics with experimental results found in the literature was verified.Second,the interaction model between the NPR cable coupled with the loess medium was established.Its constant resistance was calculated to be about 24.08%larger than that of NPR anchor cable while its plastic deformation was reduced by about 37.14%.The compressive stress on the contact surface between NPR cable and loess was concentrated near the free end of the sleeve,which indicated that the loess was prone to severe damage at the free end.The research results reveal the typical shear failure mechanism of NPR cable in loess medium,which provides an important theoretical basis for prevention of landslides and monitoring of loess slopes.
基金sponsored by the National Social Science Fund of China[Grant No.23VMG006].
文摘This study determines whether industrial agglomeration can solve energy poverty(ENPO)by applying a provincial dataset(2002-2019)to assess the potential effect of industrial agglomeration on ENPO.Additionally,this study conducts an in-depth exploration of provincial heterogeneity and its influence mechanisms.The conclusions are as follows:①Industrial agglomeration is negatively correlated with ENPO;by implication,enhancing industrial agglomeration is a driving force for reducing ENPO.②The alleviating effect of industrial agglomeration on ENPO in the midwestern region is considerably higher than that in the eastern region,and the ENPO alleviation effect of the high agglomeration region is better than that in the low agglomeration region.③Foreign investment and energy efficiency have a mediating role,that is,they are valid transmission pathways for industrial agglomeration to solve the ENPO issue.Relevant policy suggestions for reducing ENPO by accelerating industrial agglomeration are proposed by drawing on the above three conclusions.
文摘This study exploits China's"Pilot Program for the Integration of Science and Technology with Finance"as a quasi-natural experiment to investigate the effect of Sci-Tech Finance on corporate financial resilience and its underlying mechanisms.Using panel data of A-share firms listed on the Shanghai and Shenzhen stock exchanges from 2000 to 2024 and using a staggered difference-in-differences(DID)model,we find that corporate financial resilience significantly improved after the Sci-Tech Finance policy,as evidenced by reduced earnings volatility and more sustainable profit growth.Heterogeneity analyses show that the effect is more pronounced during periods of high economic policy uncertainty(EPU)and in regions with less developed traditional banking systems.Mechanism analyses suggest that Sci-Tech Finance strengthens firm financial resilience by alleviating financing constraints,mitigating information asymmetry,optimizing investment efficiency,and promoting green innovation.We provide novel evidence on the role of Sci-Tech Finance in stabilizing firm performance and fostering long-term value creation,thereby contributing to the broad literature on high-quality economic development.
基金supported by the National Natural Science Foundation of China(No.52405317)the Special Funds for Science and Technology Programs in Jiangsu Province(BZ2024021)+3 种基金the Natural Science Foundation of Jiangsu Province(BK20241407)the Talent Startup Funding of Chaohu University(KYQD-2023035)the Natural Science Research Projects of Chaohu University(XLZ-202205,XLZ202301)the Horizontal Projects of School-Enterprise Cooperation(No.hxkt20230267).
文摘Wall-climbing robots can stably ascend vertical walls and even ceilings,making them suitable for specialized tasks in high-risk,confined,and harsh conditions.Therefore,they have excellent application prospects and substantial market demand.However,several challenges remain,including limited load-carrying capacity,short operational duration,a high risk of detachment,and the lack of standardized physical and control interfaces for carrying auxiliary equipment to complete missions.This study analyzes the macro and micro structures and movement mechanisms of typical organisms in terms of negative pressure adsorption,hook-and-claw adhesion,dry adhesion,and wet adhesion.The exploration of biological wall-climbing mechanisms is integrated with the adhesion techniques used in practical wall-climbing robots.Additionally,the mechanisms,properties,and typical wall-climbing robots associated with adhesion technologies were investigated,including negative pressure adsorption,hook-and-claw adhesion,bionic dry adhesion,bionic wet adhesion,electrostatic adhesion,and magnetic adhesion.Furthermore,the typical gaits of quadruped and hexapod robots are analyzed,and bionic control techniques such as central pattern generators,neural networks,and compliant control are applied.Finally,the future development trends of wall-climbing robots will be examined from multiple perspectives,including the diversification of bionic mechanisms,the advancement of mechanical structure intelligence,and the implementation of intelligent adaptive control.Moreover,this paper establishes a solid foundation for the innovative design of bionic wall-climbing robots and provides valuable guidance for future advancements.
基金financially supported by the National Natural Science Foundation of China,China(52004103,51974137,52274229,22350410378 and 52304328)the China Postdoctoral Science Foundation,China(2020M671361 and 2023M733189)+4 种基金the Natural Science Foundation of Jiangsu Province,China(BK20220534)the Jiangsu Postdoctoral Science Foundation,China(2020Z090)the Senior Talents Fund of Jiangsu University,China(5501220014)the Key Research and Development Project of Ningxia Province,China(2024BEE02001)the Open Project of Key Laboratory of Advanced Battery Materials of Yunnan Province,China(KLABM-2024092403).
文摘Single crystal Ni-rich cathode materials(SCNCM)are a good supplement in the market of nickel-based materials due to their safety and excellent electrochemical performance.However,the challenges of cation mixing,phase change during charge/discharge,and low thermal stability remain unresolved in single crystal particles.To address these issues,SCNCM are rationally modified by incorporating transition metal(TM)oxides,and the influence of metal ions with different valence states on the electrochemical properties of SCNCM is methodically explored through experimental results and theoretical calculations.Enhanced structural stability is demonstrated in SCNCM after the modifications,and the degree of improvement in the matrix materials varies depending on the valence state of doped TM ions.The highest structural stability is found in WO_(3)-modified SCNCM,due to the smaller effective ion radii,higher electro-negativity,stronger W-O bond,and efficient suppression of oxygen vacancy generation.As a result,WO_(3)-modified SCNCM have outstanding cycle performance,with a capacity retention rate of90.2%after 200 cycles.This study provides an insight into the design of advanced SCNCM with enhanced reversibility and cyclability.
基金supported by the National Natural Science Foundation of China (Nos.52374064,51974347,52474072)the Shandong Provincial Universities Youth Innovation and Technology Support Program (2022KJ065)。
文摘Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation to microscopic mechanisms,remains relatively sparse.This study utilizes microscopic visualization experiments to investigate the mechanisms of residual oil mobilization under various IPC scenarios,complemented by mechanical analysis at different stages.The research quantitatively assesses the degree of microscopic oil recovery and the distribution of residual oil across different injection-production methods.Findings reveal that during the initial phase of continuous gas injection(CGI),the process closely mimics miscible displacement,gradually transitioning to immiscible displacement as CO_(2)extraction progresses.Compared to CGI,the asynchronous injection-production(AIP) method improved the microscopic oil recovery rate by 6.58%.This enhancement is mainly attributed to significant variations in the pressure field in the AIP method,which facilitate the mobilization of columnar and porous re sidual oil.Furthermo re,the synchronous cycle injection(SCI) method increased microscopic oil recovery by 13.77% and 7.19% compared to CGI and AIP,respectively.In the SCI method,membrane oil displays filame ntary and Karman vo rtex street flow patterns.The dissolved and expanded crude oil te nds to accumulate and grow at the oil-solid interface due to adhesive forces,thereby reducing migration resistance.The study findings provide a theoretical foundation for improving oil recovery in lowpermeability reservoirs.
基金supported by the National Natural Science Foundation of China(General Program)(Grant No.52474071)the financial support from the China Scholarship Council(TM.Lei,No.202406450004)。
文摘In response to the challenges of sand production and high water cut during the exploitation of oil reservoirs in unconsolidated sandstones,a novel sand-water dual-control functional polymer,PDSM,was synthesized using acrylamide(AM),methacryloxyethyltrimethyl ammonium chloride(DMC),and styrene monomer(SM)as raw materials.The chemical structure and thermal stability of PDSM were verified by1H-NMR,FT-IR,and TGA analyses.To evaluate its performance,functional polymers PDM and PSM,containing only DMC or SM,respectively,were used as control groups.The study systematically investigated the static adsorption,sand production,sand leakage time,standard water-oil resistance ratio,and water cut reduction performance of PDSM.The results demonstrated that,due to the synergistic effect of functional monomers DMC and SM,PDSM exhibited superior dual-control over sand and water compared to PDM and PSM.PDSM enhanced wettability properties reduce the contact angle of the water phase on oil-wet rock surfaces to 64.0°,facilitating better adsorption of polymer molecules on the rock surface and achieving a static adsorption capacity of 14.6 mg/g.PDSM effectively bridges/bundles sand grains through SM and DMC,increasing resistance to fluid erosion.At a flow rate of 100 mL/min,sand production was only 0.026 g/L,surpassing the"Q/SH 10202377-2020"standard for sand inhibitors,which defines"excellent"performance as having a sand production rate of≤0.05 g/L.PDSM forms an adsorption layer(polymer concentrated layer)on the rock surface,expanding when in contact with water and shrinking when in contact with oil,thereby significantly reducing the permeability of the water layer without affecting the permeability of the oil layer.The standard water-oil resistance ratio was measured at 5.41,and the watercut of produced fluid was reduced by 18.6%.These findings provide new theoretical insights and technical guidance for developing dual-function sand-water control agents.
基金Supported by the Shaanxi Provincial Key Research and Development Program(2024GX-YBXM-288)the Science and Technology Project of Shaanxi Provincial Transportation Department(21-20K)the National Natural Science Foundation of China(52172324)。
文摘To address the limitations of traditional manual highway guardrail inspections,this paper proposes an obstacle-crossing and collaborative tracking control method for a rail-mounted robot.Static and dynamic analyses verify the robot's structural reliability and driving feasibility.Based on the leader-follower model,a triangular collaborative tracking model is developed,and a linear time-varying model predictive controll(LTV-MPC)is designed to achieve smooth and precise collaborative control.For obstacle crossing,an acceleration reference model and a gradient-based adaptive law are proposed,leading to a model reference adaptive controll(MRAC)that effectively suppresses vibrations and ensures synchronous control.Simulation results show that the MPC achieves a 0.415%overshoot and a 0.344 m steady-state accuracy,while also reducing the intensity of speed fluctuations by 35%.The MRAC ensures smooth obstacle-crossing speeds and adaptive strategy switching,validating the reliability and practicality of the rail-mounted robot under complex working conditions.
基金Funded by the China Construction Shares Technology Research and Development Project(No.CSCEC-2023-Z-07)CSCEC Strait Major Scientific and Technological Project(No.ZJHX2023C001)+1 种基金Engineering Research Center of Prevention and Control of Geological Disasters in the Mountainous Areas of Northern Fujian,Fujian Province University,China(No.WYERC2024-3)Science s of Fujian Province(No.2023J01476)。
文摘Fluidized solidified soil(FSS)is an innovative backfill material that offers benefits such as easy pumping and straightforward construction.This study examined how varying the water-soil ratio and the curing agent dosage affect the properties and microstructure of FSS.The strength development mechanism was investigated when composite solidification agents were used.The findings show that both the water-solid ratio and the curing agent dosage can affect the microstructure of FSS,thereby affecting its performance.When the water-solid ratio increases from 0.52 to 0.56,the unconfined compressive strength(UCS)and flexural strength of the FSS decrease by 34.1% and 39.3% after 28 d.Conversely,the curing agent dosage increasing from 10% to 30% will increase both UCS and flexural strength by 11.2 times and 11.1 times.As the curing age increases,the number of cracks at failure point in the FSS will increase and lead to a more complete failure.Numerous needle-like AFt,C-S-H gel,and C-(A)-S-H gel create a three-dimensional network by adhering to soil particles.
基金Project(20050532021) supported by the Research Fund for the Doctoral Program of Higher Education
文摘Based on the fact that the shear stress along anchorage segment is neither linearly nor uniformly distributed, the load transfer mechanism of the tension type anchor was studied and the mechanical characteristic of anchorage segment was analyzed. Shear stress?strain relationship of soil surrounding anchorage body was simplified into three-folding-lines model consisting of elastic phase, elasto-plastic phase and residual phase considering its softening characteristic. Meanwhile, shear displacement method that has been extensively used in the analysis of pile foundation was introduced. Based on elasto-plastic theory, the distributions of displacement, shear stress and axial force along the anchorage segment of tension type anchor were obtained, and the formula for calculating the elastic limit load was also developed accordingly. Finally, an example was given to discuss the variation of stress and displacement in the anchorage segment with the loads exerted on the anchor, and a program was worked out to calculate the anchor maximum bearing capacity. The influence of some parameters on the anchor bearing capacity was discussed, and effective anchorage length was obtained simultaneously. The results show that the shear stress first increases and then decreases and finally trends to the residual strength with increase of distance from bottom of the anchorage body, the displacement increases all the time with the increase of distance from bottom of the anchorage body, and the increase of velocity gradually becomes greater.
基金Projects 50490270 supported by the National Natural Science Foundation of China, 50634050 the National Natural Science Foundation of China and 2006A038 SR Foundation of China University of Mining & Technology
文摘The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the key strata is established given the structural characteristics and the mechanical properties of the roof rock layers of the working face in a particular coal mine. Four other models were derived from this model by rearranging the order of the layers in the key strata. The distribution characteristics of stress, deformation, pore pressure and the flow vector of all the models are computed using the analytical module of fluid-structure interaction in the FLAC software and the corresponding risks of a water-burst are analyzed. The results indicate that the water-insulating ability of the key strata is related to the arrangement of soft and hard rocks. The water-insulating ability of the compound water-resisting key strata (CWKS) with a hard-hard-soft-hard-soft compounding order is the best under the five given simulated conditions.
文摘To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite (CFRC) wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.
基金Supported by the National Natural Science Foundation of China under Grant No 11302225the China Postdoctoral Science Foundation under Grant Nos 2014M560820 and 2015T81071
文摘A fully superconducting electron cyclotron resonance （ECR） ion source （SECRAL ID is currently being built in the Institute of Modern Physics, Chinese Academy of Sciences. Its key components are three superconducting solenoids （Nb-Ti/Cu） and six superconducting sextupoles （Nb-Ti/Cu）. Different from the conventional supercon- ducting ECR magnetic structure, the SEC17AL Ⅱ includes three superconducting solenoid coils＇ that are located inside the superconducting sextupoles. The SECRAL Ⅱ can significantly reduce the interaction forces between the sextupole and the solenoids, and the magnets can also be more compact in size. For this multi-component SECRAL Ⅱ generating its self field of -8 T and being often exposed to the high self field, the mechanical analysis has become the main issue to keep their stress at 〈200 MPa on coils. The analytical and experimental results in mechanics are presented in the SECRAL Ⅱ structure. To improve the accuracy and efficiency of analysis, according to the composite rule of micromechanics, the equivalent uniform windings are used to simulate the epoxy-impregnated Nb-Ti/Cu coils. In addition, using low temperature strain gauges and a wireless fast strain acquisition system, a fundamental experiment on the based on our analysis, the stresses and deformations optimized. strains developments of a sextupole is reported. Finally, for its assembly of each SECRAL Ⅱ coil will be further
基金This project is supported by National Hi-tech Research and Development Program of China(863 Program, No.2003AA404190).
文摘A new spherical mobile robot BHQ-1 is designed. The spherical robot is driven by two internally mounted motors that induce the ball to move straight and turn around on a fiat surface. A dynamic model of the robot is developed with Lagrange method and factors affecting the driving torque of two motors are analyzed. The relationship between the turning radius of the robot and the length of two links is discussed in order to optimize its mechanism design. Simulation and experimental results demonstrate the good controllability and motion performance of BHQ-1.
