This study examines the spatiotemporal evolution of Tibetan villages in western Sichuan through state transition models and predictive simulations to understand their complex dynamics and key driving factors.Using a c...This study examines the spatiotemporal evolution of Tibetan villages in western Sichuan through state transition models and predictive simulations to understand their complex dynamics and key driving factors.Using a combination of multivariate time-series analysis and chaotic attractor identification,the research identifies forest cover,economic growth,employment rates,road density,and communication network coverage as critical determinants of village trajectories.For instance,Molo Village recovers rapidly with a 10%increase in regional economic growth,while Xisuo Village becomes unstable with employment rate fluctuations above 2%.Shenzuo Village benefits from improved road density,and Minzu Village’s stability depends on forest cover.Jiangba Village relies on the growth of irrigated farmland and communication network coverage,whereas Kegeyi Village exhibits periodic dynamics and high sensitivity to employment variations.The findings underscore the inherent complexity and nonlinearity of rural systems,revealed through chaotic attractor analysis,which highlights the system’s sensitivity to initial conditions and external shocks.The article provides actionable insights into resilience mechanisms and offers practical recommendations for the sustainable development of culturally and ecologically sensitive regions.Emphasis on tailored management strategies is essential to meet the challenges faced by these unique systems in the face of modernization and environmental change.展开更多
The ion channel in neurons is the basic component of signal transmission in the nervous system.The ion channel has important effects on the potential of neuron release and dynamic behavior in neural networks.Ion chann...The ion channel in neurons is the basic component of signal transmission in the nervous system.The ion channel has important effects on the potential of neuron release and dynamic behavior in neural networks.Ion channels control the flow of ions into and out of the cell membrane to form an ion current,which makes the excitable membrane produce special potential changes and become the basis of nerve and muscle activity.The blockage of ion channels has a significant effect on the dynamics of neurons and networks.Therefore,it is very meaningful to study the influence of ion channels on neuronal dynamics.In this work,a hybrid ion channel is designed by connecting a charge-controlled memristor(CCM)with an inductor in series,and a magnetic flux-controlled memristor(MFCM),capacitor,and nonlinear resistor are connected in parallel with the mixed ion channel to obtain the memristor neural circuit.Furthermore,the oscillator model with a hybrid ion channel and its energy function are calculated,and a map neuron is obtained by linearizing the neuron oscillator model.In addition,an adaptive regulation method is designed to explore the adaptive regulation of energy on the dynamic behaviors of the map neuron.The results show that the dynamics of a map neuron with a hybrid ion channel can be controlled by parameters and external magnetic fields.This study is also used to research synchronization between map neurons and collective behaviors in the map neurons network.展开更多
A rotor system supported by roller beatings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces ...A rotor system supported by roller beatings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces of a roller bearing under four-dimensional loads and establishes 4-DOF dynamics equations of a rotor roller bearing system. The methods of Newmark-β and of Newton-Laphson are used to solve the nonlinear equations. The dynamics behaviors of a rigid rotor system are studied through the bifurcation, the Poincar è maps, the spectrum diagrams and the axis orbit of responses of the system. The results show that the system is liable to undergo instability caused by the quasi-periodic bifurcation, the periodic-doubling bifurcation and chaos routes as the rotational speed increases. Clearances, outer race waviness, inner race waviness, roller waviness, damping, radial forces and unbalanced forces-all these bring a significant influence to bear on the system stability. As the clearance increases, the dynamics behaviors become complicated with the number and the scale of instable regions becoming larger. The vibration frequencies induced by the roller bearing waviness and the orders of the waviness might cause severe vibrations. The system is able to eliminate non-periodic vibration by reasonable choice and optimization of the parameters.展开更多
In this article, we consider positive steady state solutions and dynamics for a spatially heterogeneous predator-prey system with modified Leslie-Gower and Holling-Type II schemes. The heterogeneity here is created by...In this article, we consider positive steady state solutions and dynamics for a spatially heterogeneous predator-prey system with modified Leslie-Gower and Holling-Type II schemes. The heterogeneity here is created by the degeneracy of the intra-specific pressures for the prey. By the bifurcation method, the degree theory, and a priori estimates, we discuss the existence and multiplicity of positive steady states. Moreover, by the comparison argument, we also discuss the dynamical behavior for the diffusive predator-prey system.展开更多
The beer game model is a typical paradigm used to study complex dynamics behaviours in production–distribution systems. The model, however, does not accord with current practical supply chain system models in discret...The beer game model is a typical paradigm used to study complex dynamics behaviours in production–distribution systems. The model, however, does not accord with current practical supply chain system models in discrete?type manufacturing industry, which are generally composed of retailers, distributors, manufacturers with internal sup?ply chain, and suppliers. To describe how ordering policies influence the complex dynamics behaviour modes and operating cost in a general discrete?type manufacturing industry supply chain system, a high dimension piecewise?linear dynamics model is built for the supply chain system. Five kinds of ordering policy combination are considered. The distribution of both the largest Lyapunov exponent of e ective inventory and average operating cost per cycle is obtained by simulation in a policy space. The simulation shows that for the general discrete?type manufacturing industry supply chain system, the upper chaotic corners emerge besides the lower chaotic corners in the policy space expressing the distribution of system behaviour mode, and that the ordering policies at each supply chain node as well as their combination have very significant e ect on the topology of the distribution of both system behaviour mode and operating cost in the policy space. We find that chaos is not always corresponding to high cost, and the "chaos amplification" is not completely relevant to the "cost amplification".展开更多
With rapid economic and social development in China, high-rise buildings have continuously sprung up since 2006. However, several big fire accidents in high-rise buildings such as the Beijing Television Cultural Cente...With rapid economic and social development in China, high-rise buildings have continuously sprung up since 2006. However, several big fire accidents in high-rise buildings such as the Beijing Television Cultural Center fire in 2009 and the Shanghai Jing＇an District fire in 2010 etc. have claimed people＇s lives and caused huge amounts of economic and property losses,展开更多
Consider an initial-boundary problem vt - ux=0,u, + （）x + f（u） = （）x,θt+ux=（）ux=（）x+ （E） v（x,0） = v0（x）,u（x,0） = u0（x）,θ（0,x） = θ0（x）, （I） u（t,0） = u（t,1） = θx（t,0） = θx（t,1） （J...Consider an initial-boundary problem vt - ux=0,u, + （）x + f（u） = （）x,θt+ux=（）ux=（）x+ （E） v（x,0） = v0（x）,u（x,0） = u0（x）,θ（0,x） = θ0（x）, （I） u（t,0） = u（t,1） = θx（t,0） = θx（t,1） （J） Sufficient and necessary conditions for （E）, （I） and （J） to have asymptotic stability of the gobal smooth solution are given by means of the elemental L2 energy method.展开更多
Understanding the proton dynamic behavior in inorganic materials has long been a topic of intense fascination[1],especially in the field of electrochemical energy storage[2].One of the examples is the research of prot...Understanding the proton dynamic behavior in inorganic materials has long been a topic of intense fascination[1],especially in the field of electrochemical energy storage[2].One of the examples is the research of proton transport in transition metal oxides,which dates back to 1971[3]when RuO_(2) was discovered to be capable of storing protons via reversible redox reactions[4].In aqueous electrolytes,the thin film RuO_(2) electrode exhibits a surface pseudocapacitive behavior[5],which could be modified by the structural water in its hydrated form due to the facile Grotthuss hopping mode of protons along the established hydrogen bonds inside the bulk phase[6].Soon later,Goodenough et al.reported the capacitor-like behavior of amorphous MnO_(2)·xH_(2)O electrode in an aqueous KCl electrolyte[7],and further studies on the hydrated MnO_(2) electrodes prepared by sol-gel processes have soon discovered that the intercalation of protons from aqueous electrolytes plays an indispensable role in the charge storage mechanism[8].In recent years,the research interest on rechargeable aqueous batteries has fueled the renaissance of mechanistic study of proton transport in transition metal oxides[9],which can operate as cathodes or anodes via a topotactic insertion mechanism similar to that in Li-ion batteries[10].However,due to the challenges for experimental detection of local chemical environments of the inserted protons,a comprehensive understanding of proton dynamic behavior in these electrodes remains largely lacking.展开更多
A high-density tungsten-zirconium-titanium(W-Zr-Ti)reactive alloy was prepared by powder metallurgy.This alloy exhibits high density,high strength,and violent energy release characteristics,resulting in outstanding pe...A high-density tungsten-zirconium-titanium(W-Zr-Ti)reactive alloy was prepared by powder metallurgy.This alloy exhibits high density,high strength,and violent energy release characteristics,resulting in outstanding penetration and ignition abilities.Dynamic impact experiment demonstrated its strain rate hardening effect,and the energetic characteristics were investigated by digital image processing technique and thermal analysis experiment.The results show that W-Zr-Ti reactive alloy performs compressive strength of 2.25 GPa at 5784 s^(-1)strain rate,and its exothermic reaction occurs at about 961 K.Based on the explosion test and shock wave theory,thresholds of enhanced damage effect are less than 35.77 GPa and 5.18×10^(4)kJ/m^(2)for shock pressure and energy,respectively.Furthermore,the transformation of fracture behavior and failure mechanism is revealed,which causes the increase in compressive strength and reaction intensity under dynamic loading.展开更多
Based on a new bilinear equation,we investigated some new dynamic behaviors of the(2+1)-dimensional shallow water wave model,such as hybridization behavior between different solitons,trajectory equations for lump coll...Based on a new bilinear equation,we investigated some new dynamic behaviors of the(2+1)-dimensional shallow water wave model,such as hybridization behavior between different solitons,trajectory equations for lump collisions,and evolution behavior of multi-breathers.Firstly,the N-soliton solution of Ito equation is studied,and some high-order breather waves can be obtained from the N-soliton solutions through paired-complexification of parameters.Secondly,the high-order lump solutions and the hybrid solutions are obtained by employing the long-wave limit method,and the motion velocity and trajectory equations of high-order lump waves are analyzed.Moreover,based on the trajectory equations of the higher-order lump solutions,we give and prove the trajectory theorem of 1-lump before and after interaction with nsoliton.Finally,we obtain some new lump solutions from the multi-solitons by constructing a new test function and using the parameter limit method.Meanwhile,some evolutionary behaviors of the obtained solutions are shown through a large number of three-dimensional graphs with different and appropriate parameters.展开更多
This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split-Hopkinson pressure bar testing,focusing on factors like grain size and flaw dimensions.By means of digital image proces...This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split-Hopkinson pressure bar testing,focusing on factors like grain size and flaw dimensions.By means of digital image processing and the discrete element method,Particle Flow Code 2D(PFC2D)models were constructed based on real granite samples,effectively overcoming the limitations of prior studies that mainly relied on randomized parameters.The results illustrate that the crack distribution of granite is significantly influenced by grain size and flaw dimensions.Tension cracks predominate and mineral boundaries,such as between feldspar and quartz,become primary crack sites.Both flaw length and width critically affect the crack density,distribution,and dynamic strength of granite.Specifically,dynamic strength tends to decrease with the enlargement of flaws and increase with an increase in flaw angles up to 90°.展开更多
The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,wi...The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,with applications such as the gravity-only aerial deployment of high-aspect-ratio solar-powered UAVs,and aerial takeoff of fixed-wing drones in Mars research.However,the significant morphological changes during deployment are accompanied by strong nonlinear dynamic aerodynamic forces,which result in multiple degrees of freedom and an unstable character.This hinders the description and analysis of unknown dynamic behaviors,further leading to difficulties in the design of deployment strategies and flight control.To address this issue,this paper proposes an analysis method for dynamic behaviors during aerial deployment based on the Variational Autoencoder(VAE).Focusing on the gravity-only deployment problem of highaspect-ratio foldable-wing UAVs,the method encodes the multi-degree-of-freedom unstable motion signals into a low-dimensional feature space through a data-driven approach.By clustering in the feature space,this paper identifies and studies several dynamic behaviors during aerial deployment.The research presented in this paper offers a new method and perspective for feature extraction and analysis of complex and difficult-to-describe extreme flight dynamics,guiding the research on aerial deployment drones design and control strategies.展开更多
The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynami...The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynamic behavior of human skin tissue under micro-particle impact in transdermal drug delivery.The numerical model was developed based on a coupled smoothed particle hydrodynamics(SPH)and FEM method via commercial FE software RADIOSS.Analytical analysis was conducted applying the Poncelet model and was used as validation data.A hyperelastic one-term Ogden model with one pair of material parameters(μ,α)was implemented for the skin tissue.Sensitivity studies reveal that the effect of parameter α on the penetration process is much more significant than μ.Numerical results correlate well with the analytical curves with various particle diameters and impact velocities,its capability of predicting the penetration process of micro-particle impacts into skin tissues.This work can be further investigated to guide the design of transdermal drug delivery equipment.展开更多
Biological neurons exhibit a double-membrane structure and perform specialized functions.Replicating the doublemembrane architecture in artificial neurons to mimic biological neuronal functions is a compelling researc...Biological neurons exhibit a double-membrane structure and perform specialized functions.Replicating the doublemembrane architecture in artificial neurons to mimic biological neuronal functions is a compelling research challenge.In this study,we propose a multifunctional neural circuit composed of two capacitors,two linear resistors,a phototube cell,a nonlinear resistor,and a memristor.The phototube and charge-controlled memristor serve as sensors for external light and electric field signals,respectively.By applying Kirchhoff's and Helmholtz's laws,we derive the system's nonlinear dynamical equations and energy function.We further investigate the circuit's dynamics using methods from nonlinear dynamics.Our results show that the circuit can exhibit both periodic and chaotic patterns under stimulation by external light and electric fields.展开更多
Dielectric barrier discharges(DBDs)are primarily utilized as efficient sources of large-volume diffuse plasmas.However,the synergistic interaction of certain key plasma factors limits their broader application.In the ...Dielectric barrier discharges(DBDs)are primarily utilized as efficient sources of large-volume diffuse plasmas.However,the synergistic interaction of certain key plasma factors limits their broader application.In the present paper,we report numerical investigations of the effects of voltage amplitude in dual-frequency excitation on atmospheric DBDs using a 50 kHz/5 MHz frequency combination.Our results indicate that varying the voltages for low frequency(LF)and radio frequency(RF)significantly influences the electron dynamics during discharge,resulting in distinct spatio-temporal distributions of electron and metastable particle densities.These findings contribute to the regulation of discharges under atmospheric pressure conditions and facilitate the attainment of non-equilibrium and nonlinear plasma parameters.展开更多
This study investigates the dynamic compressive behavior of three periodic lattice structures fabricated from Ti-6Al-4V titanium alloy,each with distinct topologies:simple cubic(SC),body-centered cubic(BCC),and face-c...This study investigates the dynamic compressive behavior of three periodic lattice structures fabricated from Ti-6Al-4V titanium alloy,each with distinct topologies:simple cubic(SC),body-centered cubic(BCC),and face-centered cubic(FCC).Dynamic compression experiments were conducted using a Split Hopkinson Pressure Bar(SHPB)system,complemented by high-speed imaging to capture real-time deformation and failure mechanisms under impact loading.The influence of cell topology,relative density,and strain rate on dynamic mechanical properties,failure behavior,and stress wave propagation was systematically examined.Finite element modeling was performed,and the simulated results showed good agreement with experimental data.The findings reveal that the dynamic mechanical properties of the lattice structures are generally insensitive to strain rate variations,while failure behavior is predominantly governed by structural configuration.The SC structure exhibited strut buckling and instability-induced fracture,whereas the BCC and FCC structures displayed layer-by-layer crushing with lower strain rate sensitivity.Regarding stress wave propagation,all structures demonstrated significant attenuation capabilities,with the BCC structure achieving the greatest reduction in transmitted wave amplitude and energy.Across all configurations,wave reflection was identified as the primary energy dissipation mechanism.These results provide critical insights into the design of lattice structures for impact mitigation and energy absorption applications.展开更多
Video action recognition(VAR)aims to analyze dynamic behaviors in videos and achieve semantic understanding.VAR faces challenges such as temporal dynamics,action-scene coupling,and the complexity of human interactions...Video action recognition(VAR)aims to analyze dynamic behaviors in videos and achieve semantic understanding.VAR faces challenges such as temporal dynamics,action-scene coupling,and the complexity of human interactions.Existing methods can be categorized into motion-level,event-level,and story-level ones based on spatiotemporal granularity.However,single-modal approaches struggle to capture complex behavioral semantics and human factors.Therefore,in recent years,vision-language models(VLMs)have been introduced into this field,providing new research perspectives for VAR.In this paper,we systematically review spatiotemporal hierarchical methods in VAR and explore how the introduction of large models has advanced the field.Additionally,we propose the concept of“Factor”to identify and integrate key information from both visual and textual modalities,enhancing multimodal alignment.We also summarize various multimodal alignment methods and provide in-depth analysis and insights into future research directions.展开更多
Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a ser...Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.展开更多
Poly(phthalazinone ether sulfone ketone)(PPESK)is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties.However,its damage and failure mechanisms und...Poly(phthalazinone ether sulfone ketone)(PPESK)is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties.However,its damage and failure mechanisms under high-temperature and high-strain-rate coupling conditions remain unclear,significantly limiting the engineering applications of PPESK-based composites in extreme environments such as aerospace.To address this issue,in this study,a temperature-controlled split Hopkinson pressure bar experimental platform was developed for dynamic tensile/compressive loading scenarios.Combined with scanning electron microscopy and molecular dynamics simulations,the thermomechanical behavior and failure mechanisms of PPESK were systematically investigated over the temperature range of 293-473 K.The study revealed a novel"dynamic hysteresis brittle behavior"and its underlying"segmental activation±response lag antagonistic mechanism".The results showed that the strain-rate-induced response lag of polymer chain segments significantly weakened the viscous dissipation capacity activated by thermal energy at elevated temperatures.Although high-strain-rate conditions led to notable enhancement in the dynamic strength of the material(with an increase of 8%-233%,reaching 130%-330%at elevated temperatures),the fracture surface morphology tended to become smoother,and brittle fracture characteristics became more pronounced.Based on these findings,a temperature±strain rate hysteresis antagonistic function was constructed,which effectively captured the competitive relationship between temperature-driven relaxation behavior and strain-rateinduced hysteresis in thermoplastic resins.A multiscale damage evolution constitutive model with temperature±rate coupling was subsequently established and numerically implemented via the VUMAT user subroutine.This study not only unveils the nonlinear damage mechanisms of PPESK under combined service temperatures and dynamic/static loading conditions,but also provides a strong theoretical foundation and engineering guidance for the constitutive modeling and parametric design of thermoplastic resin-based materials.展开更多
In order to research the concrete archaized buildings with lintel-column joint,2 specimens were tested under dynamic experiment.The failure characteristics,skeleton curves,mechanical behavior such as the load-displace...In order to research the concrete archaized buildings with lintel-column joint,2 specimens were tested under dynamic experiment.The failure characteristics,skeleton curves,mechanical behavior such as the load-displacement hysteretic loops,load carrying capacity,degradation of strength and stiffness,ductility and energy dissipation of the joints were analyzed.The results indicate that comparies with the lintel-column joints,the loading capacity and energy dissipation of the concrete archaized buildings with dual lintel-column joints are higher,and the hysteretic loops is in plump-shape.However,the displacement ductility coefficient is less than that of lintel-column joints.Both of them of the regularity of rigidity degeneration are basically the same.Generally,the joints have the good energy dissipation capacity.And the concrete archaized buildings with lintel-column joints exhibit excellent seismic behavior.展开更多
文摘This study examines the spatiotemporal evolution of Tibetan villages in western Sichuan through state transition models and predictive simulations to understand their complex dynamics and key driving factors.Using a combination of multivariate time-series analysis and chaotic attractor identification,the research identifies forest cover,economic growth,employment rates,road density,and communication network coverage as critical determinants of village trajectories.For instance,Molo Village recovers rapidly with a 10%increase in regional economic growth,while Xisuo Village becomes unstable with employment rate fluctuations above 2%.Shenzuo Village benefits from improved road density,and Minzu Village’s stability depends on forest cover.Jiangba Village relies on the growth of irrigated farmland and communication network coverage,whereas Kegeyi Village exhibits periodic dynamics and high sensitivity to employment variations.The findings underscore the inherent complexity and nonlinearity of rural systems,revealed through chaotic attractor analysis,which highlights the system’s sensitivity to initial conditions and external shocks.The article provides actionable insights into resilience mechanisms and offers practical recommendations for the sustainable development of culturally and ecologically sensitive regions.Emphasis on tailored management strategies is essential to meet the challenges faced by these unique systems in the face of modernization and environmental change.
基金supported by the National Science Basic Research Program of Shaanxi(Grant No.2023-JC-QN-0087)。
文摘The ion channel in neurons is the basic component of signal transmission in the nervous system.The ion channel has important effects on the potential of neuron release and dynamic behavior in neural networks.Ion channels control the flow of ions into and out of the cell membrane to form an ion current,which makes the excitable membrane produce special potential changes and become the basis of nerve and muscle activity.The blockage of ion channels has a significant effect on the dynamics of neurons and networks.Therefore,it is very meaningful to study the influence of ion channels on neuronal dynamics.In this work,a hybrid ion channel is designed by connecting a charge-controlled memristor(CCM)with an inductor in series,and a magnetic flux-controlled memristor(MFCM),capacitor,and nonlinear resistor are connected in parallel with the mixed ion channel to obtain the memristor neural circuit.Furthermore,the oscillator model with a hybrid ion channel and its energy function are calculated,and a map neuron is obtained by linearizing the neuron oscillator model.In addition,an adaptive regulation method is designed to explore the adaptive regulation of energy on the dynamic behaviors of the map neuron.The results show that the dynamics of a map neuron with a hybrid ion channel can be controlled by parameters and external magnetic fields.This study is also used to research synchronization between map neurons and collective behaviors in the map neurons network.
基金National Natural Science Foundation of China(50575054)973Program(2007CB607602)
文摘A rotor system supported by roller beatings displays very complicated nonlinear behaviors due to nonlinear Hertzian contact forces, radial clearances and bearing waviness. This paper presents nonlinear bearing forces of a roller bearing under four-dimensional loads and establishes 4-DOF dynamics equations of a rotor roller bearing system. The methods of Newmark-β and of Newton-Laphson are used to solve the nonlinear equations. The dynamics behaviors of a rigid rotor system are studied through the bifurcation, the Poincar è maps, the spectrum diagrams and the axis orbit of responses of the system. The results show that the system is liable to undergo instability caused by the quasi-periodic bifurcation, the periodic-doubling bifurcation and chaos routes as the rotational speed increases. Clearances, outer race waviness, inner race waviness, roller waviness, damping, radial forces and unbalanced forces-all these bring a significant influence to bear on the system stability. As the clearance increases, the dynamics behaviors become complicated with the number and the scale of instable regions becoming larger. The vibration frequencies induced by the roller bearing waviness and the orders of the waviness might cause severe vibrations. The system is able to eliminate non-periodic vibration by reasonable choice and optimization of the parameters.
基金supported by the National Natural Science Foundation of China(11361053,11201204,11471148,11471330,145RJZA112)
文摘In this article, we consider positive steady state solutions and dynamics for a spatially heterogeneous predator-prey system with modified Leslie-Gower and Holling-Type II schemes. The heterogeneity here is created by the degeneracy of the intra-specific pressures for the prey. By the bifurcation method, the degree theory, and a priori estimates, we discuss the existence and multiplicity of positive steady states. Moreover, by the comparison argument, we also discuss the dynamical behavior for the diffusive predator-prey system.
基金Supported by National Natural Science Foundation of China(Grant No.11072192)Shaanxi Provincial Industrial Technology Research Projects of China(Grant No.2015GY118)
文摘The beer game model is a typical paradigm used to study complex dynamics behaviours in production–distribution systems. The model, however, does not accord with current practical supply chain system models in discrete?type manufacturing industry, which are generally composed of retailers, distributors, manufacturers with internal sup?ply chain, and suppliers. To describe how ordering policies influence the complex dynamics behaviour modes and operating cost in a general discrete?type manufacturing industry supply chain system, a high dimension piecewise?linear dynamics model is built for the supply chain system. Five kinds of ordering policy combination are considered. The distribution of both the largest Lyapunov exponent of e ective inventory and average operating cost per cycle is obtained by simulation in a policy space. The simulation shows that for the general discrete?type manufacturing industry supply chain system, the upper chaotic corners emerge besides the lower chaotic corners in the policy space expressing the distribution of system behaviour mode, and that the ordering policies at each supply chain node as well as their combination have very significant e ect on the topology of the distribution of both system behaviour mode and operating cost in the policy space. We find that chaos is not always corresponding to high cost, and the "chaos amplification" is not completely relevant to the "cost amplification".
文摘With rapid economic and social development in China, high-rise buildings have continuously sprung up since 2006. However, several big fire accidents in high-rise buildings such as the Beijing Television Cultural Center fire in 2009 and the Shanghai Jing＇an District fire in 2010 etc. have claimed people＇s lives and caused huge amounts of economic and property losses,
文摘Consider an initial-boundary problem vt - ux=0,u, + （）x + f（u） = （）x,θt+ux=（）ux=（）x+ （E） v（x,0） = v0（x）,u（x,0） = u0（x）,θ（0,x） = θ0（x）, （I） u（t,0） = u（t,1） = θx（t,0） = θx（t,1） （J） Sufficient and necessary conditions for （E）, （I） and （J） to have asymptotic stability of the gobal smooth solution are given by means of the elemental L2 energy method.
基金financial support from the National Natural Science Foundation of China(22109003)the Basic and Applied Basic Research Foundation of Guangdong Province(2023A1515011391)+1 种基金Soft Science Research Project of Guangdong Province(No.2017B030301013)the Major Science and Technology Infrastructure Project of Material Genome Big-science Facilities Platform supported by Municipal Development and Reform Commission of Shenzhen.
文摘Understanding the proton dynamic behavior in inorganic materials has long been a topic of intense fascination[1],especially in the field of electrochemical energy storage[2].One of the examples is the research of proton transport in transition metal oxides,which dates back to 1971[3]when RuO_(2) was discovered to be capable of storing protons via reversible redox reactions[4].In aqueous electrolytes,the thin film RuO_(2) electrode exhibits a surface pseudocapacitive behavior[5],which could be modified by the structural water in its hydrated form due to the facile Grotthuss hopping mode of protons along the established hydrogen bonds inside the bulk phase[6].Soon later,Goodenough et al.reported the capacitor-like behavior of amorphous MnO_(2)·xH_(2)O electrode in an aqueous KCl electrolyte[7],and further studies on the hydrated MnO_(2) electrodes prepared by sol-gel processes have soon discovered that the intercalation of protons from aqueous electrolytes plays an indispensable role in the charge storage mechanism[8].In recent years,the research interest on rechargeable aqueous batteries has fueled the renaissance of mechanistic study of proton transport in transition metal oxides[9],which can operate as cathodes or anodes via a topotactic insertion mechanism similar to that in Li-ion batteries[10].However,due to the challenges for experimental detection of local chemical environments of the inserted protons,a comprehensive understanding of proton dynamic behavior in these electrodes remains largely lacking.
基金National Natural Science Foundation of China(12002045)Supported by State Key Laboratory of Explosion Science and Safety Protection,Beijing Institute of Technology(QNKT22-09)。
文摘A high-density tungsten-zirconium-titanium(W-Zr-Ti)reactive alloy was prepared by powder metallurgy.This alloy exhibits high density,high strength,and violent energy release characteristics,resulting in outstanding penetration and ignition abilities.Dynamic impact experiment demonstrated its strain rate hardening effect,and the energetic characteristics were investigated by digital image processing technique and thermal analysis experiment.The results show that W-Zr-Ti reactive alloy performs compressive strength of 2.25 GPa at 5784 s^(-1)strain rate,and its exothermic reaction occurs at about 961 K.Based on the explosion test and shock wave theory,thresholds of enhanced damage effect are less than 35.77 GPa and 5.18×10^(4)kJ/m^(2)for shock pressure and energy,respectively.Furthermore,the transformation of fracture behavior and failure mechanism is revealed,which causes the increase in compressive strength and reaction intensity under dynamic loading.
基金Project supported by the National Natural Science Foundation of China(Grant No.12461047)the Scientific Research Project of the Hunan Education Department(Grant No.24B0478).
文摘Based on a new bilinear equation,we investigated some new dynamic behaviors of the(2+1)-dimensional shallow water wave model,such as hybridization behavior between different solitons,trajectory equations for lump collisions,and evolution behavior of multi-breathers.Firstly,the N-soliton solution of Ito equation is studied,and some high-order breather waves can be obtained from the N-soliton solutions through paired-complexification of parameters.Secondly,the high-order lump solutions and the hybrid solutions are obtained by employing the long-wave limit method,and the motion velocity and trajectory equations of high-order lump waves are analyzed.Moreover,based on the trajectory equations of the higher-order lump solutions,we give and prove the trajectory theorem of 1-lump before and after interaction with nsoliton.Finally,we obtain some new lump solutions from the multi-solitons by constructing a new test function and using the parameter limit method.Meanwhile,some evolutionary behaviors of the obtained solutions are shown through a large number of three-dimensional graphs with different and appropriate parameters.
基金National Natural Science Foundation of China,Grant/Award Number:52274131General Project of China Postdoctoral Science Foundation,Grant/Award Number:2023M742141Talent Introduction Project of Shandong University of Science and Technology,Grant/Award Number:0104060540171。
文摘This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split-Hopkinson pressure bar testing,focusing on factors like grain size and flaw dimensions.By means of digital image processing and the discrete element method,Particle Flow Code 2D(PFC2D)models were constructed based on real granite samples,effectively overcoming the limitations of prior studies that mainly relied on randomized parameters.The results illustrate that the crack distribution of granite is significantly influenced by grain size and flaw dimensions.Tension cracks predominate and mineral boundaries,such as between feldspar and quartz,become primary crack sites.Both flaw length and width critically affect the crack density,distribution,and dynamic strength of granite.Specifically,dynamic strength tends to decrease with the enlargement of flaws and increase with an increase in flaw angles up to 90°.
基金co-supported by the Natural Science Basic Research Program of Shaanxi,China(No.2023-JC-QN-0043)the ND Basic Research Funds,China(No.G2022WD).
文摘The aerial deployment method enables Unmanned Aerial Vehicles(UAVs)to be directly positioned at the required altitude for their mission.This method typically employs folding technology to improve loading efficiency,with applications such as the gravity-only aerial deployment of high-aspect-ratio solar-powered UAVs,and aerial takeoff of fixed-wing drones in Mars research.However,the significant morphological changes during deployment are accompanied by strong nonlinear dynamic aerodynamic forces,which result in multiple degrees of freedom and an unstable character.This hinders the description and analysis of unknown dynamic behaviors,further leading to difficulties in the design of deployment strategies and flight control.To address this issue,this paper proposes an analysis method for dynamic behaviors during aerial deployment based on the Variational Autoencoder(VAE).Focusing on the gravity-only deployment problem of highaspect-ratio foldable-wing UAVs,the method encodes the multi-degree-of-freedom unstable motion signals into a low-dimensional feature space through a data-driven approach.By clustering in the feature space,this paper identifies and studies several dynamic behaviors during aerial deployment.The research presented in this paper offers a new method and perspective for feature extraction and analysis of complex and difficult-to-describe extreme flight dynamics,guiding the research on aerial deployment drones design and control strategies.
基金supported by the Nanjing Institute of Technology(Grant No.YKJ202301).
文摘The understanding of the impact of high-velocity microparticles on human skin tissue is important for the ad-ministration of drugs during transdermal drug delivery.This paper aims to numerically investigate the dynamic behavior of human skin tissue under micro-particle impact in transdermal drug delivery.The numerical model was developed based on a coupled smoothed particle hydrodynamics(SPH)and FEM method via commercial FE software RADIOSS.Analytical analysis was conducted applying the Poncelet model and was used as validation data.A hyperelastic one-term Ogden model with one pair of material parameters(μ,α)was implemented for the skin tissue.Sensitivity studies reveal that the effect of parameter α on the penetration process is much more significant than μ.Numerical results correlate well with the analytical curves with various particle diameters and impact velocities,its capability of predicting the penetration process of micro-particle impacts into skin tissues.This work can be further investigated to guide the design of transdermal drug delivery equipment.
基金Project supported by the Gansu Provincial Department of Education University Teacher Innovation Fund Project(Grant No.2024A-168)the Qingyang Science and Technology Plan Project(Grant No.QY-STK-2024B-193)the Horizontal Research Project of Longdong University(Grant No.HXZK2422)。
文摘Biological neurons exhibit a double-membrane structure and perform specialized functions.Replicating the doublemembrane architecture in artificial neurons to mimic biological neuronal functions is a compelling research challenge.In this study,we propose a multifunctional neural circuit composed of two capacitors,two linear resistors,a phototube cell,a nonlinear resistor,and a memristor.The phototube and charge-controlled memristor serve as sensors for external light and electric field signals,respectively.By applying Kirchhoff's and Helmholtz's laws,we derive the system's nonlinear dynamical equations and energy function.We further investigate the circuit's dynamics using methods from nonlinear dynamics.Our results show that the circuit can exhibit both periodic and chaotic patterns under stimulation by external light and electric fields.
基金supported by National Natural Science Foundation of China (Nos.52377141 and 92371105)。
文摘Dielectric barrier discharges(DBDs)are primarily utilized as efficient sources of large-volume diffuse plasmas.However,the synergistic interaction of certain key plasma factors limits their broader application.In the present paper,we report numerical investigations of the effects of voltage amplitude in dual-frequency excitation on atmospheric DBDs using a 50 kHz/5 MHz frequency combination.Our results indicate that varying the voltages for low frequency(LF)and radio frequency(RF)significantly influences the electron dynamics during discharge,resulting in distinct spatio-temporal distributions of electron and metastable particle densities.These findings contribute to the regulation of discharges under atmospheric pressure conditions and facilitate the attainment of non-equilibrium and nonlinear plasma parameters.
基金supported by the National Natural Science Foundations of China(No.11972267 and 11802214)the Fundamental Research Funds for the Central Universities(No.104972024JYS0022)the Open Fund of the Hubei Longzhong Laboratory(No.2024KF-30).
文摘This study investigates the dynamic compressive behavior of three periodic lattice structures fabricated from Ti-6Al-4V titanium alloy,each with distinct topologies:simple cubic(SC),body-centered cubic(BCC),and face-centered cubic(FCC).Dynamic compression experiments were conducted using a Split Hopkinson Pressure Bar(SHPB)system,complemented by high-speed imaging to capture real-time deformation and failure mechanisms under impact loading.The influence of cell topology,relative density,and strain rate on dynamic mechanical properties,failure behavior,and stress wave propagation was systematically examined.Finite element modeling was performed,and the simulated results showed good agreement with experimental data.The findings reveal that the dynamic mechanical properties of the lattice structures are generally insensitive to strain rate variations,while failure behavior is predominantly governed by structural configuration.The SC structure exhibited strut buckling and instability-induced fracture,whereas the BCC and FCC structures displayed layer-by-layer crushing with lower strain rate sensitivity.Regarding stress wave propagation,all structures demonstrated significant attenuation capabilities,with the BCC structure achieving the greatest reduction in transmitted wave amplitude and energy.Across all configurations,wave reflection was identified as the primary energy dissipation mechanism.These results provide critical insights into the design of lattice structures for impact mitigation and energy absorption applications.
基金supported by the Zhejiang Provincial Natural Science Foundation of China(No.LQ23F030001)the National Natural Science Foundation of China(No.62406280)+5 种基金the Autism Research Special Fund of Zhejiang Foundation for Disabled Persons(No.2023008)the Liaoning Province Higher Education Innovative Talents Program Support Project(No.LR2019058)the Liaoning Province Joint Open Fund for Key Scientific and Technological Innovation Bases(No.2021-KF-12-05)the Central Guidance on Local Science and Technology Development Fund of Liaoning Province(No.2023JH6/100100066)the Key Laboratory for Biomedical Engineering of Ministry of Education,Zhejiang University,Chinain part by the Open Research Fund of the State Key Laboratory of Cognitive Neuroscience and Learning.
文摘Video action recognition(VAR)aims to analyze dynamic behaviors in videos and achieve semantic understanding.VAR faces challenges such as temporal dynamics,action-scene coupling,and the complexity of human interactions.Existing methods can be categorized into motion-level,event-level,and story-level ones based on spatiotemporal granularity.However,single-modal approaches struggle to capture complex behavioral semantics and human factors.Therefore,in recent years,vision-language models(VLMs)have been introduced into this field,providing new research perspectives for VAR.In this paper,we systematically review spatiotemporal hierarchical methods in VAR and explore how the introduction of large models has advanced the field.Additionally,we propose the concept of“Factor”to identify and integrate key information from both visual and textual modalities,enhancing multimodal alignment.We also summarize various multimodal alignment methods and provide in-depth analysis and insights into future research directions.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.52225904 and 52039007)the Natural Science Foundation of Sichuan Province(Grant No.2023NSFSC0377)supported by the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Exploring dynamic mechanical responses and failure behaviors of hot dry rock(HDR)is significant for geothermal exploitation and stability assessment.In this study,via the split Hopkinson pressure bar(SHPB)system,a series of dynamic compression tests were conducted on granite treated by cyclic thermal shocks at different temperatures.We analyzed the effects of cyclic thermal shock on the thermal-related physical and dynamic mechanical behaviors of granite.Specifically,the P-wave velocity,dynamic strength,and elastic modulus of the tested granite decrease with increasing temperature and cycle number,while porosity and peak strain increase.The degradation law of dynamic mechanical properties could be described by a cubic polynomial.Cyclic thermal shock promotes shear cracks propagation,causing dynamic failure mode of granite to transition from splitting to tensile-shear composite failure,accompanied by surface spalling and debris splashing.Moreover,the thermal shock damage evolution and coupled failure mechanism of tested granite are discussed.The evolution of thermal shock damage with thermal shock cycle numbers shows an obvious S-shaped surface,featured by an exponential correlation with dynamic mechanical parameters.In addition,with increasing thermal shock temperature and cycles,granite mineral species barely change,but the length and width of thermal cracks increase significantly.The non-uniform expansion of minerals,thermal shock-induced cracking,and water-rock interaction are primary factors for deteriorating dynamic mechanical properties of granite under cyclic thermal shock.
基金supported by National Key Research and Development Program"Advanced Structures and Composite Materials"Special Project[Grant No.2024YFB3712800]the Fundamental Research Funds for the Central Universities[Grant No.DUT22-LAB605]Liaoning Province's"Unveiling the List and Leading the Way"Science and Technology Research and Development Special Project[Grant No.2022JH1/10400043]。
文摘Poly(phthalazinone ether sulfone ketone)(PPESK)is a new-generation high-performance thermoplastic resin that exhibits excellent thermal stability and mechanical properties.However,its damage and failure mechanisms under high-temperature and high-strain-rate coupling conditions remain unclear,significantly limiting the engineering applications of PPESK-based composites in extreme environments such as aerospace.To address this issue,in this study,a temperature-controlled split Hopkinson pressure bar experimental platform was developed for dynamic tensile/compressive loading scenarios.Combined with scanning electron microscopy and molecular dynamics simulations,the thermomechanical behavior and failure mechanisms of PPESK were systematically investigated over the temperature range of 293-473 K.The study revealed a novel"dynamic hysteresis brittle behavior"and its underlying"segmental activation±response lag antagonistic mechanism".The results showed that the strain-rate-induced response lag of polymer chain segments significantly weakened the viscous dissipation capacity activated by thermal energy at elevated temperatures.Although high-strain-rate conditions led to notable enhancement in the dynamic strength of the material(with an increase of 8%-233%,reaching 130%-330%at elevated temperatures),the fracture surface morphology tended to become smoother,and brittle fracture characteristics became more pronounced.Based on these findings,a temperature±strain rate hysteresis antagonistic function was constructed,which effectively captured the competitive relationship between temperature-driven relaxation behavior and strain-rateinduced hysteresis in thermoplastic resins.A multiscale damage evolution constitutive model with temperature±rate coupling was subsequently established and numerically implemented via the VUMAT user subroutine.This study not only unveils the nonlinear damage mechanisms of PPESK under combined service temperatures and dynamic/static loading conditions,but also provides a strong theoretical foundation and engineering guidance for the constitutive modeling and parametric design of thermoplastic resin-based materials.
基金supported by Crosswise Tasks of Enterprise Entrusted(JG-ZH-A-202411-003)High-level Talents Program of Hainan Basic and Applied Basic Research Program of China(520RC543)。
文摘In order to research the concrete archaized buildings with lintel-column joint,2 specimens were tested under dynamic experiment.The failure characteristics,skeleton curves,mechanical behavior such as the load-displacement hysteretic loops,load carrying capacity,degradation of strength and stiffness,ductility and energy dissipation of the joints were analyzed.The results indicate that comparies with the lintel-column joints,the loading capacity and energy dissipation of the concrete archaized buildings with dual lintel-column joints are higher,and the hysteretic loops is in plump-shape.However,the displacement ductility coefficient is less than that of lintel-column joints.Both of them of the regularity of rigidity degeneration are basically the same.Generally,the joints have the good energy dissipation capacity.And the concrete archaized buildings with lintel-column joints exhibit excellent seismic behavior.
