The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-domin...The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-dominated grids.Conventional classifica-tions,which decouple voltage,frequency,and rotor angle stability,fail to address the emerging strong voltage‒angle coupling effects caused by RES dynamics.This coupling introduces complex oscillation modes and undermines system robustness,neces-sitating novel stability assessment tools.Recent studies focus on eigenvalue distributions and damping redistribution but lack quantitative criteria and interpretative clarity for coupled stability.This work proposes a transient energy-based framework to resolve these gaps.By decomposing transient energy into subsystem-dissipated components and coupling-induced energy exchange,the method establishes stability criteria compatible with a broad variety of inverter-interfaced devices while offering an intuitive energy-based interpretation for engineers.The coupling strength is also quantified by defining the relative coupling strength index,which is directly related to the transient energy interpretation of the coupled stability.Angle‒voltage coupling may induce instability by injecting transient energy into the system,even if the individual phase angle and voltage dynamics themselves are stable.The main contributions include a systematic stability evaluation framework and an energy decomposition approach that bridges theoretical analysis with practical applicability,addressing the urgent need for tools for managing modern power system evolving stability challenges.展开更多
Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show ...Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show significant characteristic differences and couple each other.This paper designs and conducts experiments with shaped charges to analyze the complicated process.The effects of liner angle and weight of shaped charge on the characteristics of metal jets,waves,and bubbles are discussed.It is found that in underwater explosions,the shaped charge generates the metal jet accompanied by the ballistic wave.Then,the shock wave propagates and superimposes with the ballistic wave,and the generated bubble pulsates periodically.It is revealed that the maximum head velocity of the metal jet versus the liner angle a and length-to-diameter ratio k of the shaped charge follows the laws of 1/(α/180°)^(0.55)andλ^(0.16),respectively.The head shape and velocity of the metal jet determine the curvature and propagation speed of the initial ballistic wave,thus impacting the superposition time and region with the shock wave.Our findings also reveal that the metal jet carries away some explosion products,which hinders the bubble development,causing an inward depression of the bubble wall near the metal jet.Therefore,the maximum bubble radius and pulsation period are 5.2%and 3.9%smaller than the spherical charge with the same weight.In addition,the uneven axial energy distribution of the shaped charge leads to an oblique bubble jet formation.展开更多
Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coup...Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coupled micromechanical resonators,highlighting the latest advancements in four key areas:internal resonance,synchronization,frequency combs,and mode localization.The origin,development,and potential applications of each of these dynamic phenomena within mode-coupled micromechanical systems are investigated,with the goal of inspiring new ideas and directions for researchers in this field.展开更多
We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin ...We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.展开更多
A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored fac...A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.展开更多
In the aerospace sector,the soft magnetic materials of Hermetically Sealed Electromagnetic Relays(HSERs)are critical in forming magnetic circuits.Conventional soft magnetic materials,primarily magnetic iron,have been ...In the aerospace sector,the soft magnetic materials of Hermetically Sealed Electromagnetic Relays(HSERs)are critical in forming magnetic circuits.Conventional soft magnetic materials,primarily magnetic iron,have been unable to meet the development trend of fast-response,miniaturized,and lightweight aerospace and aviation systems.This paper applies circuit theory and electromagnetics theory to establish a Field-Circuit Coupling Mathematical Model(FCCMM)for dynamic response analysis of HSERs.This model centers on inductance calculation,with the core's permeability and saturation magnetic flux density as critical parameters.Based on this model,for a specific type of HSER,this paper introduced three alloys with key parameters different from magnetic iron,then tested the magnetic characteristic curves of these four soft magnetic materials,followed by simulations to obtain the electromagnetic characteristics of digital mock-ups corresponding to these four materials,compared and validated the dynamic responses corresponding to these four soft magnetic materials finally.Based on the theoretical model analysis results,this paper designed a lightweight coil to minimize response time,made prototypes,set up test systems,and tested dynamic characteristics.The experimental results indicate that the nanocrystalline alloy1K107B exhibits the most significant optimization,reducing the closing time by 40.48%and achieving a weight reduction of 6.53%.展开更多
The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations ...The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.展开更多
This study examined the mechanisms for improving the adhesion performance of the asphalt-aggregate interface with two anti-stripping agents and two coupling agents.The investigation of contact behavior between various...This study examined the mechanisms for improving the adhesion performance of the asphalt-aggregate interface with two anti-stripping agents and two coupling agents.The investigation of contact behavior between various asphalt-aggregate surfaces was conducted using molecular dynamics(MD)simulations.The interaction energy and the relative concentration distribution were employed as the parameters to analyze the enhancement mechanisms of anti-stripping agents and coupling agents on the asphalt-aggregate interface.Results indicated that the adhesion at the asphalt-aggregate interface could be strengthened by both anti-stripping agents and coupling agents.Anti-stripping agents primarily improve adhesion through the reinforcement of electrostatic attraction,while coupling agents primarily upgrade adhesion by strengthening the van der Waals.Hence,the molecular dynamics modeling and calculation techniques presented in this study can be utilized to elucidate the development mechanism of the asphalt-aggregate interface through the use of anti-stripping agents and coupling agents.展开更多
Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics...Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics simulation,we have studied the spin dynamics induced by spin–orbit coupling(SOC)in Co and Fe using both spin-diabatic and spin-adiabatic representations.In Co system,it is found that the Fermi surface(E_(F))is predominantly contributed by the spin-minority states.The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the E_(F),and the spin-minority electrons tend to relax to the EFwith the same spin through the electron–phonon coupling(EPC).The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within100 fs.By contrast,in Fe system,the E_(F) is dominated by the spin-majority states.In this case,the SOC induced spin flip occurs for the photo-excited spin-minority electrons,which leads to a magnetization enhancement.If we move the E_(F) of Fe to higher energy by 0.6eV,the E_(F) will be contributed by the spin-minority states and the demagnetization will be observed again.This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems.展开更多
The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the ...The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.展开更多
The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carr...The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.展开更多
Plasma as the fourth state of matter has attracted great attention for material surface modification,which could induce changes in material microscopic factors,such as defects,phase transitions,crystallinity,and so on...Plasma as the fourth state of matter has attracted great attention for material surface modification,which could induce changes in material microscopic factors,such as defects,phase transitions,crystallinity,and so on.However,the interactions among those microscopic factors and regulation mechanism of macroscopic properties have rarely been investigated.Two-dimensional(2D)transition metal dichalcogenide with tunable structure and phase is one of the most promising electromagnetic wave(EMW)absorbers,which provides a favorable platform for systematically studying the dynamic coupling of its microscopic factors.Herein,we constructed a NaBH_(4) solution-assisted Ar plasma method to modify the 2H-MoS_(2)and 1T-WS_(2)for exploring the regulation mechanism of microscopic factors.For MoS_(2)and WS_(2),NaBH_(4) solution-assisted Ar plasma treatment behaves with different effects on dielectric responses,realizing dynamic coupling of material microscopic factors to collaboratively promote EM losses coupling.Consequently,the MS-D3-0.5(MoS_(2),3 kV voltage,0.5 mol L^(-1)NaBH_(4) solution)displays an optimum effective absorption bandwidth of 8.01 GHz,which is 319.4%more than that of MS-raw sample.This study not only reveals the novel mechanism of plasma induced dynamic coupling of microscopic factors for EMW dissipation,but also presents a new method of plasma-dominated surface modification to optimize the EMW absorption performance.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
The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varyin...The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varying dynamics,making the exact solutions challenging to obtain.As a result,numerical integration methods are typically employed.However,conventional methods often suffer from low computational efficiency.To address this,this paper explores the application of the parameter freezing precise exponential integrator to vehicle-road coupling models.The model accounts for road roughness irregularities,incorporating all terms unrelated to the linear part into the algorithm's inhomogeneous vector.The general construction process of the algorithm is detailed.The validity of numerical results is verified through approximate analytical solutions(AASs),and the advantages of this method over traditional numerical integration methods are demonstrated.Multiple parameter freezing precise exponential integrator schemes are constructed based on the Runge-Kutta framework,with the fourth-order four-stage scheme identified as the optimal one.The study indicates that this method can quickly and accurately capture the dynamic system's vibration response,offering a new,efficient approach for numerical studies of high-dimensional vehicle-road coupling systems.展开更多
Optical tweezers technology utilizes the optical potential well generated by a focused laser beam to achieve precise manipulation of micro and nanoparticles.Based on the optical tweezers platform,the motion behavior a...Optical tweezers technology utilizes the optical potential well generated by a focused laser beam to achieve precise manipulation of micro and nanoparticles.Based on the optical tweezers platform,the motion behavior and dynamic laws of particles are deeply studied,which can reveal the transport mechanism of complex systems.Based on summarizing the principles and experimental methods of optical tweezers technology,this article systematically summarizes the typical force characteristics of particles in optical tweezers,focusing on the dynamic research progress of single particle non-equilibrium state,double particle coupling,and multi-particle cluster system,laying a theoretical foundation for expanding the application of optical tweezers technology in physics,chemistry,biology,and other fields.展开更多
The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead...The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.展开更多
It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling st...It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling strength.In this paper,we study the quantum Rabi model with A-square terms using the Bogoliubov operator approach.After a unitary transformation,the A-square terms can be eliminated,resulting in a modified quantum Rabi model with renormalized parameters.A transcendental function responsible for the exact solution is then derived.The presence of the A-square terms is found to significantly alter the energy spectrum.The dynamics are also studied using the obtained exact wave function,which is sensitive to the strength of the A-square terms at strong coupling.We believe that these results could be observed in future light–matter interaction systems in the ultra-strong and deep strong coupling regimes.展开更多
Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was...Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was used to study the dynamics of nonequilibrium charge carriers in both textured and non-textured GaAs substrates.Our findings show that the textured surface acts as an antireflective layer, greatly boosting the infrared pump laser's coupling efficiency into the semi-insulating GaAs substrate. Additionally, texturing introduces a trapassisted recombination pathway, speeding up carrier relaxation and thus reducing Joule heating. Under the same pumping and bias field conditions, the coarse-textured GaAs photoconductive antenna shows nearly 7.85 times stronger THz emission amplitude than the non-textured device, along with improvement in signal-to-noise ratio.At a fixed bias field, higher pump power increases photogenerated carrier density, causing bias field screening and subsequent saturation of THz emission. At fixed pump power, when the bias field reaches ~2.5 kV/cm, both THz emission and photocurrent spectra show a clear kink, signaling intervalley scattering from the Γ valley to the L(X) valleys under high electric fields.展开更多
The integrated systems of unmanned surface vehicles(USVs) and remotely operated vehicles(ROVs) have been extensively applied in marine exploration and seabed coverage. However, the simultaneous navigation of USV-ROV s...The integrated systems of unmanned surface vehicles(USVs) and remotely operated vehicles(ROVs) have been extensively applied in marine exploration and seabed coverage. However, the simultaneous navigation of USV-ROV systems is frequently limited by strong disturbances induced by waves or currents. This paper develops a novel rigidflexible coupling multibody dynamic model that incorporates disturbances of variable-length marine cables with geometrically nonlinear motion. A hybrid Lagrangian-Eulerian absolute nodal coordinate formulation(ANCF) element is developed to accurately model subsea cables which undergo significant overall motion, substantial deformation,and mass flow during the deployment of underwater equipment. Furthermore, the governing equations of the coupled USV-umbilical-ROV system are derived, considering wave-induced forces and current disturbances. A numerical solver based on the Newmark-beta method is proposed, along with an adaptive meshing technique near the release point. After validating three experimental cases, the cable disturbances at both the USV and ROV ends—caused by ocean currents, heave motion, and simultaneous navigation—are comprehensively compared and evaluated. Finally,it is demonstrated that a PD controller with disturbance compensation can enhance the simultaneous navigation performance of USV-ROV systems.展开更多
Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states an...Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states and use the non-Markovian stochastic Schrödinger equation(NMSSE)to simulate the photo-in-duced dynamics processes.The re-sults show that aggregation effects have a significant impact on the interfacial exciton dissociation process.After photo-excita-tion,the excitons first preferentially delocalize and perform the charge transfer(CT)states in the pure ZnPc or F_(8)ZnPc aggregates within 100 fs.These‘intramolecular’CT states can easi-ly evolve into interfacial CT states by hopping electrons and holes in the intramolecular CT states across the interface.Compared with these exciton dissociation processes,the direct ex-citon dissociation into interfacial CT state is relatively slow due to the small electronic cou-pling and vibrational coherence between the locally excited state and the interfacial CT state.As the temperature rises and the vibronic coherence weakens,the direct dissociation rates are significantly enhanced.This investigation provides valuable insights for the design and opti-mization of high-performance organic photovoltaic devices.展开更多
基金supported by the Science and Technology Project of China Southern Power Grid Co.,Ltd under Grant 036000KC23090004(GDKJXM20231026).
文摘The integration of renewable energy sources(RESs)with inverter interfaces has fundamentally reshaped power system dynamics,challenging traditional stability analysis frameworks designed for synchronous generator-dominated grids.Conventional classifica-tions,which decouple voltage,frequency,and rotor angle stability,fail to address the emerging strong voltage‒angle coupling effects caused by RES dynamics.This coupling introduces complex oscillation modes and undermines system robustness,neces-sitating novel stability assessment tools.Recent studies focus on eigenvalue distributions and damping redistribution but lack quantitative criteria and interpretative clarity for coupled stability.This work proposes a transient energy-based framework to resolve these gaps.By decomposing transient energy into subsystem-dissipated components and coupling-induced energy exchange,the method establishes stability criteria compatible with a broad variety of inverter-interfaced devices while offering an intuitive energy-based interpretation for engineers.The coupling strength is also quantified by defining the relative coupling strength index,which is directly related to the transient energy interpretation of the coupled stability.Angle‒voltage coupling may induce instability by injecting transient energy into the system,even if the individual phase angle and voltage dynamics themselves are stable.The main contributions include a systematic stability evaluation framework and an energy decomposition approach that bridges theoretical analysis with practical applicability,addressing the urgent need for tools for managing modern power system evolving stability challenges.
基金funded by the National Natural Science Founda-tion of China(52071109).
文摘Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show significant characteristic differences and couple each other.This paper designs and conducts experiments with shaped charges to analyze the complicated process.The effects of liner angle and weight of shaped charge on the characteristics of metal jets,waves,and bubbles are discussed.It is found that in underwater explosions,the shaped charge generates the metal jet accompanied by the ballistic wave.Then,the shock wave propagates and superimposes with the ballistic wave,and the generated bubble pulsates periodically.It is revealed that the maximum head velocity of the metal jet versus the liner angle a and length-to-diameter ratio k of the shaped charge follows the laws of 1/(α/180°)^(0.55)andλ^(0.16),respectively.The head shape and velocity of the metal jet determine the curvature and propagation speed of the initial ballistic wave,thus impacting the superposition time and region with the shock wave.Our findings also reveal that the metal jet carries away some explosion products,which hinders the bubble development,causing an inward depression of the bubble wall near the metal jet.Therefore,the maximum bubble radius and pulsation period are 5.2%and 3.9%smaller than the spherical charge with the same weight.In addition,the uneven axial energy distribution of the shaped charge leads to an oblique bubble jet formation.
基金supported by the National Key Research and Development Program of China(No.2022YFB3203600)the National Natural Science Foundation of China(Nos.12202355,12132013,and 12172323)the Zhejiang Provincial Natural Science Foundation of China(No.LZ22A020003)。
文摘Due to scale effects,micromechanical resonators offer an excellent platform for investigating the intrinsic mechanisms of nonlinear dynamical phenomena and their potential applications.This review focuses on mode-coupled micromechanical resonators,highlighting the latest advancements in four key areas:internal resonance,synchronization,frequency combs,and mode localization.The origin,development,and potential applications of each of these dynamic phenomena within mode-coupled micromechanical systems are investigated,with the goal of inspiring new ideas and directions for researchers in this field.
文摘We consider matter-wave solitons in spin-orbit coupled Bose-Einstein condensates embedded in an optical lattice and study the dynamics of the soliton within the framework of Gross-Pitaevskii equations.We express spin components of the soliton pair in terms of nonlinear Bloch equations and investigate the effective spin dynamics.It is seen that the effective magnetic field that appears in the Bloch equation is affected by optical lattices,and thus the optical lattice influences the precessional frequency of the spin components.We make use of numerical approaches to investigate the dynamical behavior of density profiles and center-of-mass of the soliton pair in the presence of the optical lattice.It is shown that the spin density is periodically varying due to flipping of spinors between the two states.The amplitude of spin-flipping oscillation increases with lattice strength.We find that the system can also exhibit interesting nonlinear behavior for chosen values of parameters.We present a fixed point analysis to study the effects of optical lattices on the nonlinear dynamics of the spin components.It is seen that the optical lattice can act as a control parameter to change the dynamical behavior of the spin components from periodic to chaotic.
文摘A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.
基金supported by the National Natural Science Foundation of China(No.52177134)。
文摘In the aerospace sector,the soft magnetic materials of Hermetically Sealed Electromagnetic Relays(HSERs)are critical in forming magnetic circuits.Conventional soft magnetic materials,primarily magnetic iron,have been unable to meet the development trend of fast-response,miniaturized,and lightweight aerospace and aviation systems.This paper applies circuit theory and electromagnetics theory to establish a Field-Circuit Coupling Mathematical Model(FCCMM)for dynamic response analysis of HSERs.This model centers on inductance calculation,with the core's permeability and saturation magnetic flux density as critical parameters.Based on this model,for a specific type of HSER,this paper introduced three alloys with key parameters different from magnetic iron,then tested the magnetic characteristic curves of these four soft magnetic materials,followed by simulations to obtain the electromagnetic characteristics of digital mock-ups corresponding to these four materials,compared and validated the dynamic responses corresponding to these four soft magnetic materials finally.Based on the theoretical model analysis results,this paper designed a lightweight coil to minimize response time,made prototypes,set up test systems,and tested dynamic characteristics.The experimental results indicate that the nanocrystalline alloy1K107B exhibits the most significant optimization,reducing the closing time by 40.48%and achieving a weight reduction of 6.53%.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604200)the National Natural Science Foundation of China(Grant No.12261131495)Institute of Systems Science,Beijing Wuzi University(Grant No.BWUISS21).
文摘The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.
文摘This study examined the mechanisms for improving the adhesion performance of the asphalt-aggregate interface with two anti-stripping agents and two coupling agents.The investigation of contact behavior between various asphalt-aggregate surfaces was conducted using molecular dynamics(MD)simulations.The interaction energy and the relative concentration distribution were employed as the parameters to analyze the enhancement mechanisms of anti-stripping agents and coupling agents on the asphalt-aggregate interface.Results indicated that the adhesion at the asphalt-aggregate interface could be strengthened by both anti-stripping agents and coupling agents.Anti-stripping agents primarily improve adhesion through the reinforcement of electrostatic attraction,while coupling agents primarily upgrade adhesion by strengthening the van der Waals.Hence,the molecular dynamics modeling and calculation techniques presented in this study can be utilized to elucidate the development mechanism of the asphalt-aggregate interface through the use of anti-stripping agents and coupling agents.
基金support of Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0450101)the National Natural Science Foundation of China(Grant Nos.12125408 and 11974322)+1 种基金the Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF-0105)the support of the National Natural Science Foundation of China(Grant No.12174363)。
文摘Understanding the photoexcitation induced spin dynamics in ferromagnetic metals is important for the design of photo-controlled ultrafast spintronic device.In this work,by the ab initio nonadiabatic molecular dynamics simulation,we have studied the spin dynamics induced by spin–orbit coupling(SOC)in Co and Fe using both spin-diabatic and spin-adiabatic representations.In Co system,it is found that the Fermi surface(E_(F))is predominantly contributed by the spin-minority states.The SOC induced spin flip will occur for the photo-excited spin-majority electrons as they relax to the E_(F),and the spin-minority electrons tend to relax to the EFwith the same spin through the electron–phonon coupling(EPC).The reduction of spin-majority electrons and the increase of spin-minority electrons lead to demagnetization of Co within100 fs.By contrast,in Fe system,the E_(F) is dominated by the spin-majority states.In this case,the SOC induced spin flip occurs for the photo-excited spin-minority electrons,which leads to a magnetization enhancement.If we move the E_(F) of Fe to higher energy by 0.6eV,the E_(F) will be contributed by the spin-minority states and the demagnetization will be observed again.This work provides a new perspective for understanding the SOC induced spin dynamics mechanism in magnetic metal systems.
基金supported by the National Key R&D Program of China(No.2021YFB2011300)the National Natural Science Foundation of China(Nos.52275044,U2233212)。
文摘The Electro–Hydrostatic Actuator(EHA)is applied to drive the control surface in flightcontrol system of more electric aircraft.In EHA,the Oil-Immersed Motor Pump(OMP)serves asthe core as a power assembly.However,the compact integration of the OMP presents challenges inefficiently dissipating internal heat,leading to a performance degradation of the EHA due to ele-vated temperatures.Therefore,accurately modeling and predicting the internal thermal dynamicsof the OMP hold considerable significance for monitoring the operational condition of the EHA.In view of this,a modeling method considering cumulative thermal coupling was hereby proposed.Based on the proposed method,the thermal models of the motor and the pump were established,taking into account heat accumulation and transfer.Taking the leakage oil as the heat couplingpoint between the motor and the pump,the dynamic thermal coupling model of the OMP wasdeveloped,with the thermal characteristics of the oil considered.Additionally,the comparativeexperiments were conducted to illustrate the efficiency of the proposed model.The experimentalresults demonstrate that the proposed dynamic thermal coupling model accurately captured thethermal behavior of OMP,outperforming the static thermal parameter model.Overall,thisadvancement is crucial for effectively monitoring the health of EHA and ensuring flight safety.
基金National Natural Science Foundation of China(60475039)
文摘The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.
基金support was provided by the National Science Foundation of China(Grants nos.51872238,52074227 and 21806129)the Fundamental Research Funds for the Central Universities(Nos.3102018zy045 and 3102019AX11)the Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2017JQ5116 and 2020JM-118).
文摘Plasma as the fourth state of matter has attracted great attention for material surface modification,which could induce changes in material microscopic factors,such as defects,phase transitions,crystallinity,and so on.However,the interactions among those microscopic factors and regulation mechanism of macroscopic properties have rarely been investigated.Two-dimensional(2D)transition metal dichalcogenide with tunable structure and phase is one of the most promising electromagnetic wave(EMW)absorbers,which provides a favorable platform for systematically studying the dynamic coupling of its microscopic factors.Herein,we constructed a NaBH_(4) solution-assisted Ar plasma method to modify the 2H-MoS_(2)and 1T-WS_(2)for exploring the regulation mechanism of microscopic factors.For MoS_(2)and WS_(2),NaBH_(4) solution-assisted Ar plasma treatment behaves with different effects on dielectric responses,realizing dynamic coupling of material microscopic factors to collaboratively promote EM losses coupling.Consequently,the MS-D3-0.5(MoS_(2),3 kV voltage,0.5 mol L^(-1)NaBH_(4) solution)displays an optimum effective absorption bandwidth of 8.01 GHz,which is 319.4%more than that of MS-raw sample.This study not only reveals the novel mechanism of plasma induced dynamic coupling of microscopic factors for EMW dissipation,but also presents a new method of plasma-dominated surface modification to optimize the EMW absorption performance.
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 the National Natural Science Foundation of China(No.U22A20246)the Key Project of Natural Science Foundation of Hebei Province of China(Basic Research Base Project)(No.A2023210064)the Science and Technology Program of Hebei Province of China(Nos.246Z1904G and 225676162GH)。
文摘The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varying dynamics,making the exact solutions challenging to obtain.As a result,numerical integration methods are typically employed.However,conventional methods often suffer from low computational efficiency.To address this,this paper explores the application of the parameter freezing precise exponential integrator to vehicle-road coupling models.The model accounts for road roughness irregularities,incorporating all terms unrelated to the linear part into the algorithm's inhomogeneous vector.The general construction process of the algorithm is detailed.The validity of numerical results is verified through approximate analytical solutions(AASs),and the advantages of this method over traditional numerical integration methods are demonstrated.Multiple parameter freezing precise exponential integrator schemes are constructed based on the Runge-Kutta framework,with the fourth-order four-stage scheme identified as the optimal one.The study indicates that this method can quickly and accurately capture the dynamic system's vibration response,offering a new,efficient approach for numerical studies of high-dimensional vehicle-road coupling systems.
文摘Optical tweezers technology utilizes the optical potential well generated by a focused laser beam to achieve precise manipulation of micro and nanoparticles.Based on the optical tweezers platform,the motion behavior and dynamic laws of particles are deeply studied,which can reveal the transport mechanism of complex systems.Based on summarizing the principles and experimental methods of optical tweezers technology,this article systematically summarizes the typical force characteristics of particles in optical tweezers,focusing on the dynamic research progress of single particle non-equilibrium state,double particle coupling,and multi-particle cluster system,laying a theoretical foundation for expanding the application of optical tweezers technology in physics,chemistry,biology,and other fields.
基金support by the National Key R&D Program of China(Nos.2020YFA0714603 and 2020YFA0714604)。
文摘The heavy-atom effect of halogen(Br and I)has been widely employed for boosting spin-crossover in organic molecules,while recent investigation indicated halogen-substitution can also enhance fluorescence and even lead to aggregation-induced emission(AIE).In this work,we investigated ultrafast excited state dynamics of a halogen-substituted model system,i.e.squaryliums NSQ-R(R=H,Cl,Br,I),by using femtosecond spectroscopy and theoretical approach.Fast external reorganization(Ex-re,~3 ps)and slow internal reorganization(In-re,5-20 ps)were observed,while quantitative fitting indicated halogen-substitution leads to a slower non-radiative S1→S0 decay(k_(NR)^(s))and subsequently enhanced fluorescence emitting.By analyzing the extracted k_(NR)^(s)within theoretical framework of non-radiative transition in the strong coupling regime,a plausible AIE mechanism of NSQs was revealed.Our work provides a clear picture on non-radiative dynamics of halogen-substituted squaryliums,which might be useful for future development of organic dyes.
基金supported by the National Science Foundation of China under Grant Nos.12305009(XYC)and 11834005(QHC)the China Postdoctoral Science Foundation under Grant No.2022M720387(XYC).
文摘It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling strength.In this paper,we study the quantum Rabi model with A-square terms using the Bogoliubov operator approach.After a unitary transformation,the A-square terms can be eliminated,resulting in a modified quantum Rabi model with renormalized parameters.A transcendental function responsible for the exact solution is then derived.The presence of the A-square terms is found to significantly alter the energy spectrum.The dynamics are also studied using the obtained exact wave function,which is sensitive to the strength of the A-square terms at strong coupling.We believe that these results could be observed in future light–matter interaction systems in the ultra-strong and deep strong coupling regimes.
基金supported by the National Key Research and Development Program of China (Grant No.2023YFF0719200)the National Natural Science Foundation of China (Grant Nos.62322115,U24A20226,62588201,62435010,and 62335012)+2 种基金the 111 Project (Grant No.D18014)the Key project supported by Science and Technology Commission Shanghai Municipality (Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality (Grant Nos.22JC1400200 and 21S31907400)。
文摘Surface states are expected to play a key role in broadband terahertz(THz) emitters, where photoexcited carrier distributions are confined within about 1 μm of the surface. Optical pump and THz probe spectroscopy was used to study the dynamics of nonequilibrium charge carriers in both textured and non-textured GaAs substrates.Our findings show that the textured surface acts as an antireflective layer, greatly boosting the infrared pump laser's coupling efficiency into the semi-insulating GaAs substrate. Additionally, texturing introduces a trapassisted recombination pathway, speeding up carrier relaxation and thus reducing Joule heating. Under the same pumping and bias field conditions, the coarse-textured GaAs photoconductive antenna shows nearly 7.85 times stronger THz emission amplitude than the non-textured device, along with improvement in signal-to-noise ratio.At a fixed bias field, higher pump power increases photogenerated carrier density, causing bias field screening and subsequent saturation of THz emission. At fixed pump power, when the bias field reaches ~2.5 kV/cm, both THz emission and photocurrent spectra show a clear kink, signaling intervalley scattering from the Γ valley to the L(X) valleys under high electric fields.
基金financially supported in part by the General Program of the National Natural Science Foundation of China (Grant No.12272221)the State Key Laboratory of Ocean Engineering (Shanghai Jiao Tong University)(Grant No. GKZD010087)。
文摘The integrated systems of unmanned surface vehicles(USVs) and remotely operated vehicles(ROVs) have been extensively applied in marine exploration and seabed coverage. However, the simultaneous navigation of USV-ROV systems is frequently limited by strong disturbances induced by waves or currents. This paper develops a novel rigidflexible coupling multibody dynamic model that incorporates disturbances of variable-length marine cables with geometrically nonlinear motion. A hybrid Lagrangian-Eulerian absolute nodal coordinate formulation(ANCF) element is developed to accurately model subsea cables which undergo significant overall motion, substantial deformation,and mass flow during the deployment of underwater equipment. Furthermore, the governing equations of the coupled USV-umbilical-ROV system are derived, considering wave-induced forces and current disturbances. A numerical solver based on the Newmark-beta method is proposed, along with an adaptive meshing technique near the release point. After validating three experimental cases, the cable disturbances at both the USV and ROV ends—caused by ocean currents, heave motion, and simultaneous navigation—are comprehensively compared and evaluated. Finally,it is demonstrated that a PD controller with disturbance compensation can enhance the simultaneous navigation performance of USV-ROV systems.
基金supported by the National Natural Science Foundation of China(Nos.22033006,22173074,22473091, 92372105).
文摘Focusing on the mechanism of interfa-cial exciton dissociation in edge-on stacked ZnPc-F_(8)ZnPc aggregate,we employ the fragment particle-hole densities(FPHD)method to con-struct the Hamiltonian of diabatic states and use the non-Markovian stochastic Schrödinger equation(NMSSE)to simulate the photo-in-duced dynamics processes.The re-sults show that aggregation effects have a significant impact on the interfacial exciton dissociation process.After photo-excita-tion,the excitons first preferentially delocalize and perform the charge transfer(CT)states in the pure ZnPc or F_(8)ZnPc aggregates within 100 fs.These‘intramolecular’CT states can easi-ly evolve into interfacial CT states by hopping electrons and holes in the intramolecular CT states across the interface.Compared with these exciton dissociation processes,the direct ex-citon dissociation into interfacial CT state is relatively slow due to the small electronic cou-pling and vibrational coherence between the locally excited state and the interfacial CT state.As the temperature rises and the vibronic coherence weakens,the direct dissociation rates are significantly enhanced.This investigation provides valuable insights for the design and opti-mization of high-performance organic photovoltaic devices.
