Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was c...Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was constructed based on microfluidics.A microscopic and mesoscopic observation technique was proposed to simultaneously capture gas-liquid interface morphology of pores and throat and the two-phase flow characteristics in entire cleat system.The local contact characteristics of cleats reduced absolute permeability,which resulted in a sharp increase in the starting pressure.The reduced gas flow capacity narrowed the co-infiltration area and decreased water saturation at the isotonic point in a hydrophilic environment.The increased local contact area of cleats weakened gas phase flow capacity and narrowed the co-infiltration area.Jumping events occurred in methane-water flow due to altered porosity caused by local contact in cleats.The distribution of residual phases changed the jumping direction on the micro-scale as well as the dominant channel on the mesoscale.Besides,jumping events caused additional energy dissipation,which was ignored in traditional two-phase flow models.This might contribute to the overestimation of relative permeability.The work provides new methods and insights for investigating unsaturated flow in complex porous media.展开更多
In this study,we present a small,integrated jumping-crawling robot capable of intermittent jumping and self-resetting.Compared to robots with a single mode of locomotion,this multi-modal robot exhibits enhanced obstac...In this study,we present a small,integrated jumping-crawling robot capable of intermittent jumping and self-resetting.Compared to robots with a single mode of locomotion,this multi-modal robot exhibits enhanced obstacle-surmounting capabilities.To achieve this,the robot employs a novel combination of a jumping module and a crawling module.The jumping module features improved energy storage capacity and an active clutch.Within the constraints of structural robustness,the jumping module maximizes the explosive power of the linear spring by utilizing the mechanical advantage of a closed-loop mechanism and controls the energy flow of the jumping module through an active clutch mechanism.Furthermore,inspired by the limb movements of tortoises during crawling and self-righting,a single-degree-of-freedom spatial four-bar crawling mechanism was designed to enable crawling,steering,and resetting functions.To demonstrate its practicality,the integrated jumping-crawling robot was tested in a laboratory environment for functions such as jumping,crawling,self-resetting,and steering.Experimental results confirmed the feasibility of the proposed integrated jumping-crawling robot.展开更多
Bio-inspired jumping robots have emerged as a promising solution for traversing complex terrains inaccessible to conventional locomotion systems.Drawing upon the exceptional jumping kinematics observed in insects,rese...Bio-inspired jumping robots have emerged as a promising solution for traversing complex terrains inaccessible to conventional locomotion systems.Drawing upon the exceptional jumping kinematics observed in insects,researchers have developed multiple robotic prototypes mimicking biological propulsion mechanisms.However,the principal technological barrier resides in actuator systems,where current energy storage technologies suffer from inadequate energy density,fundamentally limiting takeoff velocity and jumping height.To overcome these limitations,we present a novel combustion-explosive propulsion system exhibiting high mass-specific energy release and rapid acceleration characteristics.By integrating this propulsion mechanism with a unique jumping leg structure,experimental validation through prototype testing demonstrated vertical leaps reaching 20 cm(1.67 times body length)under laboratory conditions,accompanied by comprehensive thermodynamic modeling using ABAQUS simulations that validated the effectiveness of this actuation system.The integrated design approach combines bionic structural design with combustible fuel formulations to offer new possibilities for the development of highly flexible robotic systems capable of negotiating obstacles in disaster response scenarios.展开更多
Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditi...Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditional approaches rely heavily on sophisticated algorithms and electronic sensor feedback systems to ensure landing stability,which increases the implementation complexity.Inspired by the process by which humans complete jumps and achieve stable landings in complex environments,this study proposes a novel landing control method for jumping robots.By designing a mechanically coupled perception-control structure based on mechanical logic computing,the robot simulates the real-time transmission of neural signals triggered by the ground reaction force(GRF)in human reflex loops,thereby simplifying traditional control approaches.Through the collaboration of a flexible mechanical spine and a bistable foot module,the robot achieves an average height of 16.8 cm and a distance of 25.36 cm in consecutive stable jumps.It also demonstrates reliable landing performance on challenging terrain including slopes and cobblestone surfaces.This paper proposes a novel landing control method for jumping robots that simplifies traditional control approaches.The method enables stable landings on complex terrain through a mechanically coupled perception-control structure.This approach has potential applications in tasks requiring mobility over uneven terrain,such as search and rescue.展开更多
Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding ...Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding of the trade-offs between accuracy,cost,and practicality.This comprehensive technical review synthesizes the current state of vertical jump instrumentation.We systematically analyze four primary methodologies:direct measurement,motion capture(kinematic),force platform(kinetic),and flight time-based systems.The underlying technical principles,error sources,and practical limitations of each are detailed.Our analysis reveals a clear hierarchy:force platforms and motion capture systems provide gold-standard accuracy(e.g.,±0.3 cm for force platforms)but are constrained by high cost and laboratory environments.Conversely,flight time-based systems and smartphone applications offer excellent portability and accessibility but are subject to systematic errors(1-4 cm overestimation)and lower temporal resolution.Furthermore,we examine how emerging technologies,including artificial intelligence and wearable sensors,are poised to bridge the gap between laboratory-grade accuracy and field-based utility.This review provides engineers and sports scientists with a consolidated framework to guide instrument selection,data interpretation,and future innovation in athletic performance assessment.展开更多
Using conventional mathematical statistics,linear regression and the standard deviation,the quantitative analysis was made on the climate changes in Shenyang.The results showed that the trend of precipitation reduced ...Using conventional mathematical statistics,linear regression and the standard deviation,the quantitative analysis was made on the climate changes in Shenyang.The results showed that the trend of precipitation reduced 155 mm,which was made the greatest contribution by summer and autumn.It decreased 43 mm on the average after the climate jump.The precipitation variability in spring increased and drought risk in spring increased.The first soaking rain limited the spring planting time.The temperature trend raised 1.3℃,mainly in spring and winter.The frost-free period extended about 13 d.The accumulated temperature trends in crop growing season increased 290℃ and it had an average increase of 178℃ after the climate jump.This trend of climate warming made the end of last frost advanced.Early sowing of crops suitably was possible,which was beneficial for agricultural production.The precipitation decrease,the time delay and instability of the first soaking rain were unfavorable for crop growth and seeding.And they became the factors that constrained the normal growth and stabile yield raise of crops.展开更多
This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-offphase, aerial phase an...This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-offphase, aerial phase and landing phase. We find the similar trajectories of hindlimb joints during jump, the important effect of foot during take-off and the role of forelimb in supporting the body. Based on the observation, the frog jump is simplified and a mechanical model is put forward. The robot leg is represented by a 4-bar spring/linkage mechanism model, which has three Degrees of Freedom （DOF） at hip joint and one DOF （passive） at tarsometatarsal joint on the foot. The shoulder and elbow joints each has one DOF for the balancing function of arm. The ground reaction force of the model is analyzed and compared with that of frog during take-off. The results show that the model has the same advantages of low likelihood of premature lift-off and high efficiency as the frog. Analysis results and the model can be employed to develop and control a robot capable of mimicking the jumping behavior of frog.展开更多
To reveal climatic variation over North China, the climatic jumps in summer in Beijing are analyzed using the data of precipitation of summer (June, July, August) during the period of 1841-1993, in which those missed ...To reveal climatic variation over North China, the climatic jumps in summer in Beijing are analyzed using the data of precipitation of summer (June, July, August) during the period of 1841-1993, in which those missed before 1950 were reconstructed by the stepwise regression method with minimum forecast error. The climatic jumps at different scales are analyzed using different diagnostic methods with different decade (10-100 years) windows. Some new methods and ideas are proposed. The variance difference, the linear tendency difference, and the difference of power spectral distribution between the samples before and after the period at the moving point in the center of the series are compared with other methods (for example, Mann—Kendall test, t— test, and accumulative anomaly etc.). Considering the differences among the statistics above, a synthetic jump index is also proposed in order to get the definite jump points in the moving series. The results show that the climatic jumps in the area occurred in the 1890s, the 1910s and the 1920s, and mostly in the 1920s, which suggests that the local climatic jumps in North China have a simultaneous response to the global warming in the hundred-year scales. Key words Climatic jump - New diagnostic statistics - Synthetic jump index - Response to global warming This Study was supported by the “ National Key Programme for Developing Basic Sciences” G1998040901-1.展开更多
In this paper, we consider the two-sided first exit problem for jump diffusion processes having jumps with rational Laplace transforms. We investigate the probabilistic property of conditional memorylessness, and driv...In this paper, we consider the two-sided first exit problem for jump diffusion processes having jumps with rational Laplace transforms. We investigate the probabilistic property of conditional memorylessness, and drive the joint distribution of the first exit time from an interval and the overshoot over the boundary at the exit time.展开更多
基金the financial support from the National Natural Science Foundation of China (No.42102127)the Postdoctoral Research Foundation of China (No.2024 M751860)。
文摘Cleat serves as the primary flow pathway for coalbed methane(CBM)and water.However,few studies consider the impact of local contact on two-phase flow within cleats.A visual generalized model of endogenous cleats was constructed based on microfluidics.A microscopic and mesoscopic observation technique was proposed to simultaneously capture gas-liquid interface morphology of pores and throat and the two-phase flow characteristics in entire cleat system.The local contact characteristics of cleats reduced absolute permeability,which resulted in a sharp increase in the starting pressure.The reduced gas flow capacity narrowed the co-infiltration area and decreased water saturation at the isotonic point in a hydrophilic environment.The increased local contact area of cleats weakened gas phase flow capacity and narrowed the co-infiltration area.Jumping events occurred in methane-water flow due to altered porosity caused by local contact in cleats.The distribution of residual phases changed the jumping direction on the micro-scale as well as the dominant channel on the mesoscale.Besides,jumping events caused additional energy dissipation,which was ignored in traditional two-phase flow models.This might contribute to the overestimation of relative permeability.The work provides new methods and insights for investigating unsaturated flow in complex porous media.
基金supported by the National Natural Science Foundation of China(Nos.51375383).
文摘In this study,we present a small,integrated jumping-crawling robot capable of intermittent jumping and self-resetting.Compared to robots with a single mode of locomotion,this multi-modal robot exhibits enhanced obstacle-surmounting capabilities.To achieve this,the robot employs a novel combination of a jumping module and a crawling module.The jumping module features improved energy storage capacity and an active clutch.Within the constraints of structural robustness,the jumping module maximizes the explosive power of the linear spring by utilizing the mechanical advantage of a closed-loop mechanism and controls the energy flow of the jumping module through an active clutch mechanism.Furthermore,inspired by the limb movements of tortoises during crawling and self-righting,a single-degree-of-freedom spatial four-bar crawling mechanism was designed to enable crawling,steering,and resetting functions.To demonstrate its practicality,the integrated jumping-crawling robot was tested in a laboratory environment for functions such as jumping,crawling,self-resetting,and steering.Experimental results confirmed the feasibility of the proposed integrated jumping-crawling robot.
基金supported by the National Natural Science Foundation of China(No.32270460).
文摘Bio-inspired jumping robots have emerged as a promising solution for traversing complex terrains inaccessible to conventional locomotion systems.Drawing upon the exceptional jumping kinematics observed in insects,researchers have developed multiple robotic prototypes mimicking biological propulsion mechanisms.However,the principal technological barrier resides in actuator systems,where current energy storage technologies suffer from inadequate energy density,fundamentally limiting takeoff velocity and jumping height.To overcome these limitations,we present a novel combustion-explosive propulsion system exhibiting high mass-specific energy release and rapid acceleration characteristics.By integrating this propulsion mechanism with a unique jumping leg structure,experimental validation through prototype testing demonstrated vertical leaps reaching 20 cm(1.67 times body length)under laboratory conditions,accompanied by comprehensive thermodynamic modeling using ABAQUS simulations that validated the effectiveness of this actuation system.The integrated design approach combines bionic structural design with combustible fuel formulations to offer new possibilities for the development of highly flexible robotic systems capable of negotiating obstacles in disaster response scenarios.
基金Supported by New Chongqing Innovative Young Talent Project(Grant No.2024NSCQ-qncxX0468)Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX1283)Dreams Foundation of Jianghuai Advanced Technology Center(Grant No.2023-ZM01Z007).
文摘Jumping robots are highly capable of overcoming obstacles.However,their explosive force,short duration,and variable trajectories pose significant challenges in achieving stable landings in complex environments.Traditional approaches rely heavily on sophisticated algorithms and electronic sensor feedback systems to ensure landing stability,which increases the implementation complexity.Inspired by the process by which humans complete jumps and achieve stable landings in complex environments,this study proposes a novel landing control method for jumping robots.By designing a mechanically coupled perception-control structure based on mechanical logic computing,the robot simulates the real-time transmission of neural signals triggered by the ground reaction force(GRF)in human reflex loops,thereby simplifying traditional control approaches.Through the collaboration of a flexible mechanical spine and a bistable foot module,the robot achieves an average height of 16.8 cm and a distance of 25.36 cm in consecutive stable jumps.It also demonstrates reliable landing performance on challenging terrain including slopes and cobblestone surfaces.This paper proposes a novel landing control method for jumping robots that simplifies traditional control approaches.The method enables stable landings on complex terrain through a mechanically coupled perception-control structure.This approach has potential applications in tasks requiring mobility over uneven terrain,such as search and rescue.
文摘Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding of the trade-offs between accuracy,cost,and practicality.This comprehensive technical review synthesizes the current state of vertical jump instrumentation.We systematically analyze four primary methodologies:direct measurement,motion capture(kinematic),force platform(kinetic),and flight time-based systems.The underlying technical principles,error sources,and practical limitations of each are detailed.Our analysis reveals a clear hierarchy:force platforms and motion capture systems provide gold-standard accuracy(e.g.,±0.3 cm for force platforms)but are constrained by high cost and laboratory environments.Conversely,flight time-based systems and smartphone applications offer excellent portability and accessibility but are subject to systematic errors(1-4 cm overestimation)and lower temporal resolution.Furthermore,we examine how emerging technologies,including artificial intelligence and wearable sensors,are poised to bridge the gap between laboratory-grade accuracy and field-based utility.This review provides engineers and sports scientists with a consolidated framework to guide instrument selection,data interpretation,and future innovation in athletic performance assessment.
文摘Using conventional mathematical statistics,linear regression and the standard deviation,the quantitative analysis was made on the climate changes in Shenyang.The results showed that the trend of precipitation reduced 155 mm,which was made the greatest contribution by summer and autumn.It decreased 43 mm on the average after the climate jump.The precipitation variability in spring increased and drought risk in spring increased.The first soaking rain limited the spring planting time.The temperature trend raised 1.3℃,mainly in spring and winter.The frost-free period extended about 13 d.The accumulated temperature trends in crop growing season increased 290℃ and it had an average increase of 178℃ after the climate jump.This trend of climate warming made the end of last frost advanced.Early sowing of crops suitably was possible,which was beneficial for agricultural production.The precipitation decrease,the time delay and instability of the first soaking rain were unfavorable for crop growth and seeding.And they became the factors that constrained the normal growth and stabile yield raise of crops.
基金the National High Technology Research and Development Program of China (No.2006AA04Z245)Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) (IRT0423)
文摘This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-offphase, aerial phase and landing phase. We find the similar trajectories of hindlimb joints during jump, the important effect of foot during take-off and the role of forelimb in supporting the body. Based on the observation, the frog jump is simplified and a mechanical model is put forward. The robot leg is represented by a 4-bar spring/linkage mechanism model, which has three Degrees of Freedom （DOF） at hip joint and one DOF （passive） at tarsometatarsal joint on the foot. The shoulder and elbow joints each has one DOF for the balancing function of arm. The ground reaction force of the model is analyzed and compared with that of frog during take-off. The results show that the model has the same advantages of low likelihood of premature lift-off and high efficiency as the frog. Analysis results and the model can be employed to develop and control a robot capable of mimicking the jumping behavior of frog.
基金the l' National Key Programme for Developing Basic Seiences"!G 1998040901-1.
文摘To reveal climatic variation over North China, the climatic jumps in summer in Beijing are analyzed using the data of precipitation of summer (June, July, August) during the period of 1841-1993, in which those missed before 1950 were reconstructed by the stepwise regression method with minimum forecast error. The climatic jumps at different scales are analyzed using different diagnostic methods with different decade (10-100 years) windows. Some new methods and ideas are proposed. The variance difference, the linear tendency difference, and the difference of power spectral distribution between the samples before and after the period at the moving point in the center of the series are compared with other methods (for example, Mann—Kendall test, t— test, and accumulative anomaly etc.). Considering the differences among the statistics above, a synthetic jump index is also proposed in order to get the definite jump points in the moving series. The results show that the climatic jumps in the area occurred in the 1890s, the 1910s and the 1920s, and mostly in the 1920s, which suggests that the local climatic jumps in North China have a simultaneous response to the global warming in the hundred-year scales. Key words Climatic jump - New diagnostic statistics - Synthetic jump index - Response to global warming This Study was supported by the “ National Key Programme for Developing Basic Sciences” G1998040901-1.
文摘In this paper, we consider the two-sided first exit problem for jump diffusion processes having jumps with rational Laplace transforms. We investigate the probabilistic property of conditional memorylessness, and drive the joint distribution of the first exit time from an interval and the overshoot over the boundary at the exit time.
基金Supported by the National Natural Science Foundation of China(11271312,11261056)the China Postdoctoral Science Foundation(20110491750,2012T50836)the Natural Science Foundation of Xinjiang(2011211B08)
