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
In this paper,we investigate the dynamical stability of transonic shock solutions for the full compressible Euler system in a two dimensional nozzle with a symmetric divergent part.Building upon the existence and uniq...In this paper,we investigate the dynamical stability of transonic shock solutions for the full compressible Euler system in a two dimensional nozzle with a symmetric divergent part.Building upon the existence and uniqueness results for steady symmetric transonic shock solutions to the nonisentropic Euler system established in[Z.P.Xin and H.C.Yin,The transonic shock in a nozzle,2-D and 3-D complete Euler systems,J.Differential Equations 245(2008)],we prove the dynamical stability of the transonic shock solutions under small perturbations.More precisely,if the initial unsteady transonic flow is located in the symmetric divergent part of the nozzle and the flow is a symmetric small perturbation of the steady transonic flow,we use the characteristic method to establish the dynamical stability.展开更多
To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under...To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under the action of bidirectional earthquakes is proposed.First,the mass viscoelasticity model is used to simulate two main control surfaces of toppling perilous rock,the seismic dynamic response model and motion equation of toppling perilous rock are established based on the D'Alembert principle,and the Newmark-β method is used to solve the dynamic motion equation.Then,the instability event of toppling perilous rock is considered a fuzzy event,the membership function expression of the stability coefficient of toppling perilous rock is determined based on the fuzzy failure criterion,the calculation equations of the toppling perilous rock dynamic stability coefficient and fuzzy reliability are established,and the fuzzy reliability evaluation method based on the probability distribution of reliability is proposed.Finally,the influence of different superposition modes of seismic excitation on the fuzzy reliability of toppling perilous rock is analyzed.The calculation results of toppling perilous rock in the engineering case show that the fuzzy reliability calculated after considering the fuzzy failure criterion is reduced by 10.73% to 25.66% compared with the classical reliability.Considering the bidirectional seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 5.46% to 14.89%.Compared with using the acceleration peak time encounter mode to superpose the seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 3.4% when the maximum action effect time encounter mode is adopted.展开更多
Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting gro...Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.展开更多
Dynamic soaring,which harvests energy from the wind,can enhance Unmanned Aerial Vehicles'(UAVs')range and endurance.However,energy harvesting efficiency issues hinder UAV applications,which can be addressed by...Dynamic soaring,which harvests energy from the wind,can enhance Unmanned Aerial Vehicles'(UAVs')range and endurance.However,energy harvesting efficiency issues hinder UAV applications,which can be addressed by wing morphing.Therefore,this study investigates the influence of albatross wing morphing during dynamic soaring.By constructing a parametric model,the shape of the albatross wing can be modeled and achieve morphing based on joints.From the video data,this paper summarizes the typical wing morphing patterns of the albatross and notices that changes primarily occur during the leeward descent phase.This paper first analyzes the aerodynamic performance of different wing morphing patterns and finds that the drag coefficient can be reduced by 7.75%with a suitable morphing pattern.This paper also explores the drag coefficient reduction mechanism and finds that downwash airflow decreases by 30.32%after wingtip anhedral.Interestingly,the lift-to-drag ratio shows minimal variation under different morphing patterns,within 2%.From the stability perspective,this study finds that the neutral point position changes after morphing.The maximum longitudinal static margin change is 4.9%,enhancing longitudinal stability by increasing the restorative moment arm.The lateral neutral point is 4.87%closer to the center of gravity,decreasing the roll and yaw moments.It can be observed that wingtip anhedral significantly increases the stability of the albatross.Moreover,a flight simulation is carried out to study the morphing influence on trajectory and energy harvesting.The results show that maximum energy gained is improved by 47.99%,and endurance is increased by 13.05%.The results also indicate that the effects of wing morphing are global rather than limited to the phase of morphing occurrence.Finally,based on the results,this paper proposes wing morphing regularity about the wingtip for UAVs.Wingtip bends downward can significantly increase the UAVs'stability and reduce drag,but the overall trajectory needs to be reconsidered after introducing wing morphing.展开更多
Sc and Zn were introduced into O3-NaMn_(0.5)Ni_(0.5)O_(2)(NaMN)using the combination of solution combustion and solid-state method.The effect of Sc and Zn dual-substitution on Na^(+) diffusion dynamics and structural ...Sc and Zn were introduced into O3-NaMn_(0.5)Ni_(0.5)O_(2)(NaMN)using the combination of solution combustion and solid-state method.The effect of Sc and Zn dual-substitution on Na^(+) diffusion dynamics and structural stability of NaMN was investigated.The physicochemical characterizations suggest that the introduction of Sc and Zn broaden Na^(+) diffusion channels and weaken the Na—O bonds,thereby facilitating the diffusion of sodium ions.Simulations indicate that the Sc and Zn dual-substitution decreases the diffusion barrier of Na-ions and improves the conductivity of the material.The dual-substituted NaMn_(0.5)Ni_(0.4)Sc_(0.04)Zn_(0.04)O_(2)(Na MNSZ44)cathode delivers impressive cycle stability with capacity retention of 71.2%after 200 cycles at 1C and 54.8%after 400 cycles at 5C.Additionally,the full cell paired with hard carbon anode exhibits a remarkable long-term cycling stability,showing capacity retention of 64.1%after 250 cycles at 1C.These results demonstrate that Sc and Zn dual-substitution is an effective strategy to improve the Na^(+) diffusion dynamics and structural stability of NaMN.展开更多
For real-time dynamic substructure testing(RTDST),the influence of the inertia force of fluid specimens on the stability and accuracy of the integration algorithms has never been investigated.Therefore,this study prop...For real-time dynamic substructure testing(RTDST),the influence of the inertia force of fluid specimens on the stability and accuracy of the integration algorithms has never been investigated.Therefore,this study proposes to investigate the stability and accuracy of the central difference method(CDM)for RTDST considering the specimen mass participation coefficient.First,the theory of the CDM for RTDST is presented.Next,the stability and accuracy of the CDM for RTDST considering the specimen mass participation coefficient are investigated.Finally,numerical simulations and experimental tests are conducted for verifying the effectiveness of the method.The study indicates that the stability of the algorithm is affected by the mass participation coefficient of the specimen,and the stability limit first increases and then decreases as the mass participation coefficient increases.In most cases,the mass participation coefficient will increase the stability limit of the algorithm,but in specific circumstances,the algorithm may lose its stability.The stability and accuracy of the CDM considering the mass participation coefficient are verified by numerical simulations and experimental tests on a three-story frame structure with a tuned liquid damper.展开更多
Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by ...Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by increasing the chatter free material removal rate （CF-MRR） and surface finish. The method is hased on the theory of the chatter stability and the semi-bandwidth of the resonant region. The objective function of the method is material removal rate（MRR）,the constraints are chatter stability and surface finish, and the optimizing variables are cutting and structural parameters. The optimization procedure is stated. The method is applied to a milling system and CF-MRR is increased 18.86%. It is shown that the influences of the chatter stability and the resonance are simultaneously considered in the dynamic optimization of the milling system for increasing CF-MRR and the surface finish.展开更多
Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the fle...Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.展开更多
Defects at the grain boundaries(GBs)of perovskite film highly restrict both the efficiency and stability of perovskite solar cells(PSCs).Herein,organic small molecules of butanedioic acid(BA)and acetylenedicarboxylic ...Defects at the grain boundaries(GBs)of perovskite film highly restrict both the efficiency and stability of perovskite solar cells(PSCs).Herein,organic small molecules of butanedioic acid(BA)and acetylenedicarboxylic acid(AA),containing two carbonyl(C=O)groups and different core-units,were incorporated into perovskite as additives for PSCs application.Thanks to the strong coordination interaction between C=O group and under-coordinated Pb^(2+),the additives can effectively passivate film defects and regulate the perovskite crystallization,yielding high-quality perovskite films with lower defect densities.More importantly,the additives can efficiently regulate the charge transport behaviors in PSCs.Benefiting from the defects passivation and the regulation of charge carrier dynamics,the BA and AA-treaded PSCs show the power conversion efficiencies of 21.52%and 20.50%,which are higher than that of the control device(19.41%).Besides,the optimal devices exhibit a remarkable enhanced long-term stability and moisture tolerance compared to the pristine devices.Furthermore,the transient absorption spectrum reveals the mechanism of enhanced photovoltaic performances,attributing to the improvement of charge transport capability at the perovskite/Spiro-OMeTAD interfaces.This work affords a promising strategy to improve the efficiency and stability of PSCs through regulating the charge-carrier dynamic process in perovskite film.展开更多
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj...In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.展开更多
Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimati...Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimating settling-time function (STF) of the hybrid systems.When switching dynamics are FTS and impulsive dynamics involve destabilizing delay-dependent impulses, the FTS is retained if the impulses occur infrequently.展开更多
For strapdown stabilized platform used in automatic vertical drilling system,a new dynamic measurement algorithm based on three-axis accelerometer and three-axis fluxgate measurement signals is proposed and simulated ...For strapdown stabilized platform used in automatic vertical drilling system,a new dynamic measurement algorithm based on three-axis accelerometer and three-axis fluxgate measurement signals is proposed and simulated under the condition of small inclination dynamic rotation.The error compensation algorithm is also proposed.The bench test of strapdown stabilized platform is designed and carried out.The results show that:When the azimuth angle is the same,the larger the inclination angle is,the greater the error of the measurement results will be.When the inclination angle is the same,the measurement error is the largest when the azimuth angle is 90°and 270°,and the measurement error curve presents a sinusoidal change with the change of azimuth angle.After the error function compensation,the error curve between the calculation results and the true value is basically not affected by the inclination angle and the azimuth angle,and the calculation accuracy is signifi cantly improved.Under the random rotating speed of 0-180 rpm,the minimum error of the measured well inclination value was no more than 0.03°and the maximum was no more than 1.58°.The feasibility of the proposed dynamic azimuth measurement algorithm is verifi ed.This article provides a technical reference for the strapdown automatic drilling system.展开更多
The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of t...The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of this methodology are to decouple a system of ODEs of second order into a set of uncoupled ODEs of second order;next,an eigen-dependent method is proposed to approximate the solution of each uncoupled ODE of second order.It is vital to transform all eigen-dependent methods to a problem-dependent method to bypass an Eigen analysis.The development of an eigen-dependent method plays a key role in this methodology so that slow eigenmodes can be accurately integrated while there is no instability or excessive amplitude growth in fast eigenmodes.This can explain why a problem-dependent method can simultaneously combine the explicitness of each step and A-stability.Consequently,huge computational efforts can be saved for solving nonlinear stiff problems.A new family of problem-dependent methods is developed in this work so that the feasibility of the proposed methodology can be affirmed.It has almost the same performance as that of the HHT-αmethod.However,it can save more than 99.5%of CPU demand in approximating a solution for a system of 1000 nonlinear second order ODEs.展开更多
Controlling terahertz(THz)polarization with high stability and tunability is essential for achieving further progress in ultrafast spectroscopy,structured-light manipulation,and quantum information processing.Here,we ...Controlling terahertz(THz)polarization with high stability and tunability is essential for achieving further progress in ultrafast spectroscopy,structured-light manipulation,and quantum information processing.Here,we propose a magnetized plasma platform for dynamic THz polarization control by exploiting the intrinsic birefringence between extraordinary and ordinary modes.We identify a strong-magnetization,zero-group-velocity-mismatch regime where the two modes share matched group velocities while retaining finite phase birefringence,enabling robust,phase-stable spin angular momentum control.By tuning the plasma length and magnetic field,we realize programmable phase retardation and demonstrate universal single-qubit gates through parameterized unitary operations.Full-wave particle-in-cell simulations validate high-fidelity polarization transformations across the Poincarésphere and demonstrate the potential for generating structured vector beams under spatially varying magnetic fields.The platform offers ultrafast response,resilience to extreme THz intensities,and in situ tunability,positioning magnetized plasmas as a versatile and damage-resilient medium for next-generation THz polarization control and structured-wave applications.展开更多
The evolution of China-ASEAN relations ranks among the most significant geopolitical and economic dynamics of the 21st Century.Comprising 10 Southeast Asian nations,ASEAN has held the position of China’s largest trad...The evolution of China-ASEAN relations ranks among the most significant geopolitical and economic dynamics of the 21st Century.Comprising 10 Southeast Asian nations,ASEAN has held the position of China’s largest trading partner since 2020.This partnership is underpinned by sustained economic growth,political stability,security cooperation,and vibrant socio-cultural exchanges.Over the past two decades,the China-ASEAN relationship has emerged as a main axis in Asia’s geopolitical and economic landscape.By 2025,this partnership has entered a more intricate and strategic phase marked by deeper economic collaboration,expanded multilateral diplomacy,and mounting challenges stemming from global developments such as tari"wars and South China Sea tensions.展开更多
Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous wor...Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous works,this letter is based on the designed threshold function to dynamically trigger and gives the upper bound conditions for intersampling intervals with attack and attack-free scenarios to converge.展开更多
Covalent organic frameworks(COFs)are two-(2D)or threedimensional(3D)crystalline,porous networks generated by reversible polymerization of organic building blocks[1,2].The structures and functionalities of COFs are pre...Covalent organic frameworks(COFs)are two-(2D)or threedimensional(3D)crystalline,porous networks generated by reversible polymerization of organic building blocks[1,2].The structures and functionalities of COFs are precisely controlled via appropriately selected organic building blocks.This design imparts unique properties to COFs,including exceptional structural stability,tunable pore structure,and surface chemical activity,making them promising for gas separation,catalysis,optoelectronics,and sensing applications.Since Yaghi et al.'s seminal report on COFs in 2005[2],these frameworks have swiftly emerged as a hotspot in the field of materials.Originally,the focus was on fabricating rigid frameworks with static structures and optoelectronic properties.However,the inherently static nature of these frameworks hinders their responsiveness to external stimuli,potentially constraining their functionality in specific applications.Hence,an increasing number of researchers are now directing their attention toward the development of dynamic COFs capable of modifying their structures in response to external stimuli[3].Specifically,dynamic 2D COFs exhibiting enhanced structural responsiveness are of particular interest due to their capability to integrate switchable geometries and porosities with semiconductor building blocks,as well as electron conjugation across COF layers and π-stacked columns,which may enable stimuli-responsive electronic and spin properties[4].展开更多
During cellular proliferation DNA undergoes frequent rep-lication cycles in which errors inevitably accumulate.DNA simultaneously faces continuous damage from endogenous sources[e.g.,reactive oxygen species(ROS)]and e...During cellular proliferation DNA undergoes frequent rep-lication cycles in which errors inevitably accumulate.DNA simultaneously faces continuous damage from endogenous sources[e.g.,reactive oxygen species(ROS)]and environmen-tal stressors,such as ultraviolet(UV)and ionizing radiation(IR).Such lesions compromise genomic stability and may escalate into DNA double-strand breaks(DSBs).Failure to repair DSBs can ultimately trigger cell death1.展开更多
BACKGROUND Hepatic ischemia-reperfusion(I/R)injury related to liver transplantation and hepatic resection remains a challenge in clinical practice.Accumulating evidence indicates that mitochondrial dysfunction is a cr...BACKGROUND Hepatic ischemia-reperfusion(I/R)injury related to liver transplantation and hepatic resection remains a challenge in clinical practice.Accumulating evidence indicates that mitochondrial dysfunction is a critical cause of I/R injury.The protein 4-nitrophenylphosphatase domain and non-neuronal SNAP25-like protein homolog 1(NIPSNAP1)is involved in the regulation of mitophagy and the recruitment of autophagy receptor proteins independent of PTEN induced putative kinase 1.AIM To clarify the protective mechanism of NIPSNAP1 against hepatic I/R,with a focus on mitophagy and mitochondrial dynamics,as well as the potential mechanism by which n6-methyladenosine(m6A)modification regulates NIPSNAP1.METHODS Mice were administered an adeno-associated virus in vivo and a hepatic I/R model was established via portal vein interruption followed by reperfusion to explore the effect of NIPSNAP1 on hepatic I/R.HepG2 cells were subjected to hypoxia/reoxygenation treatment in vitro.RESULTS We observed a significant downregulation of both NIPSNAP1 and insulin-like growth factor 2 mRNA-binding protein 2(IGF2BP2)expression in vivo and in vitro.NIPSNAP1 knockdown impaired mitophagy and disrupted mitochondrial dynamics;in contrast,NIPSNAP1 overexpression resulted in the opposite effects.Further studies revealed that IGF2BP2 functions as an m6A reader that targets and binds NIPSNAP1,thereby regulating its mRNA stability.CONCLUSION NIPSNAP1 prevents hepatic I/R injury by promoting mitophagy and maintaining mitochondrial homeostasis,serving as a novel target of the m6A reader IGF2BP2.Therefore,targeting the IGF2BP2/NIPSNAP1 axis may facilitate the development of better therapeutics for hepatic I/R.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supported in part by NSFC(Grant Nos.12271205,12171498).
文摘In this paper,we investigate the dynamical stability of transonic shock solutions for the full compressible Euler system in a two dimensional nozzle with a symmetric divergent part.Building upon the existence and uniqueness results for steady symmetric transonic shock solutions to the nonisentropic Euler system established in[Z.P.Xin and H.C.Yin,The transonic shock in a nozzle,2-D and 3-D complete Euler systems,J.Differential Equations 245(2008)],we prove the dynamical stability of the transonic shock solutions under small perturbations.More precisely,if the initial unsteady transonic flow is located in the symmetric divergent part of the nozzle and the flow is a symmetric small perturbation of the steady transonic flow,we use the characteristic method to establish the dynamical stability.
基金financially supported by the National Key Research and Development Program of China(Nos.2021YFB2600604 and 2021YFB2600600)the General Program of Natural Science Foundation of Chongqing(No.cstc2020jcyj-msxm X0218)the Research and Innovation Program for Graduate Students in Chongqing Jiaotong University(No.2022S0021)。
文摘To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under the action of bidirectional earthquakes is proposed.First,the mass viscoelasticity model is used to simulate two main control surfaces of toppling perilous rock,the seismic dynamic response model and motion equation of toppling perilous rock are established based on the D'Alembert principle,and the Newmark-β method is used to solve the dynamic motion equation.Then,the instability event of toppling perilous rock is considered a fuzzy event,the membership function expression of the stability coefficient of toppling perilous rock is determined based on the fuzzy failure criterion,the calculation equations of the toppling perilous rock dynamic stability coefficient and fuzzy reliability are established,and the fuzzy reliability evaluation method based on the probability distribution of reliability is proposed.Finally,the influence of different superposition modes of seismic excitation on the fuzzy reliability of toppling perilous rock is analyzed.The calculation results of toppling perilous rock in the engineering case show that the fuzzy reliability calculated after considering the fuzzy failure criterion is reduced by 10.73% to 25.66% compared with the classical reliability.Considering the bidirectional seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 5.46% to 14.89%.Compared with using the acceleration peak time encounter mode to superpose the seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 3.4% when the maximum action effect time encounter mode is adopted.
基金the National Natural Science Foundation of China(NSFC,Nos.22071247,92156010,22101283,and 22101284)the Key Research Program of Frontier Sciences(No.QYZDBSSW-SLH030)of the CAS+1 种基金Natural Science Foundation of Fujian Province(Nos.2020J06035 and 2022J05085)Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(No.2021ZR112)for support.
文摘Imine bonds are among the most explored building motifs in dynamic chemistry,polymers,and materials,and yet,their acid-resistance remains a longstanding issue.Herein we demonstrate a concept of internal protecting groups for improving the kinetic stability of dynamic imine bonds and polymers.Systematic examination of structure-reactivity relationship of a series of aldehydes/imines bearing a neighboring carboxyl allowed uncovering of required structural features for dynamically masking imine bonds with cyclic structures.Mechanistic studies indicated that noncovalent interactions along with sterics control the ringchain equilibrium and the stability of imine bonds.The incorporation of internal protecting groups into imine polymers further enabled their controlled stability in acidic media.Moreover,a combination of dynamic covalent network and coordination supramolecular network provided a facile means for the modulation of luminescent and mechanical properties of polymers.The strategies and results reported should be beneficial to molecular assemblies,dynamic polymers,biological delivery,and intelligent materials.
基金sponsored by Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2024037)。
文摘Dynamic soaring,which harvests energy from the wind,can enhance Unmanned Aerial Vehicles'(UAVs')range and endurance.However,energy harvesting efficiency issues hinder UAV applications,which can be addressed by wing morphing.Therefore,this study investigates the influence of albatross wing morphing during dynamic soaring.By constructing a parametric model,the shape of the albatross wing can be modeled and achieve morphing based on joints.From the video data,this paper summarizes the typical wing morphing patterns of the albatross and notices that changes primarily occur during the leeward descent phase.This paper first analyzes the aerodynamic performance of different wing morphing patterns and finds that the drag coefficient can be reduced by 7.75%with a suitable morphing pattern.This paper also explores the drag coefficient reduction mechanism and finds that downwash airflow decreases by 30.32%after wingtip anhedral.Interestingly,the lift-to-drag ratio shows minimal variation under different morphing patterns,within 2%.From the stability perspective,this study finds that the neutral point position changes after morphing.The maximum longitudinal static margin change is 4.9%,enhancing longitudinal stability by increasing the restorative moment arm.The lateral neutral point is 4.87%closer to the center of gravity,decreasing the roll and yaw moments.It can be observed that wingtip anhedral significantly increases the stability of the albatross.Moreover,a flight simulation is carried out to study the morphing influence on trajectory and energy harvesting.The results show that maximum energy gained is improved by 47.99%,and endurance is increased by 13.05%.The results also indicate that the effects of wing morphing are global rather than limited to the phase of morphing occurrence.Finally,based on the results,this paper proposes wing morphing regularity about the wingtip for UAVs.Wingtip bends downward can significantly increase the UAVs'stability and reduce drag,but the overall trajectory needs to be reconsidered after introducing wing morphing.
基金financial support from the National Natural Science Foundation of China(No.52377220)the Natural Science Foundation of Hunan Province,China(No.kq2208265)。
文摘Sc and Zn were introduced into O3-NaMn_(0.5)Ni_(0.5)O_(2)(NaMN)using the combination of solution combustion and solid-state method.The effect of Sc and Zn dual-substitution on Na^(+) diffusion dynamics and structural stability of NaMN was investigated.The physicochemical characterizations suggest that the introduction of Sc and Zn broaden Na^(+) diffusion channels and weaken the Na—O bonds,thereby facilitating the diffusion of sodium ions.Simulations indicate that the Sc and Zn dual-substitution decreases the diffusion barrier of Na-ions and improves the conductivity of the material.The dual-substituted NaMn_(0.5)Ni_(0.4)Sc_(0.04)Zn_(0.04)O_(2)(Na MNSZ44)cathode delivers impressive cycle stability with capacity retention of 71.2%after 200 cycles at 1C and 54.8%after 400 cycles at 5C.Additionally,the full cell paired with hard carbon anode exhibits a remarkable long-term cycling stability,showing capacity retention of 64.1%after 250 cycles at 1C.These results demonstrate that Sc and Zn dual-substitution is an effective strategy to improve the Na^(+) diffusion dynamics and structural stability of NaMN.
基金National Natural Science Foundation of China under Grant Nos.51978213 and 51778190the National Key Research and Development Program of China under Grant Nos.2017YFC0703605 and 2016YFC0701106。
文摘For real-time dynamic substructure testing(RTDST),the influence of the inertia force of fluid specimens on the stability and accuracy of the integration algorithms has never been investigated.Therefore,this study proposes to investigate the stability and accuracy of the central difference method(CDM)for RTDST considering the specimen mass participation coefficient.First,the theory of the CDM for RTDST is presented.Next,the stability and accuracy of the CDM for RTDST considering the specimen mass participation coefficient are investigated.Finally,numerical simulations and experimental tests are conducted for verifying the effectiveness of the method.The study indicates that the stability of the algorithm is affected by the mass participation coefficient of the specimen,and the stability limit first increases and then decreases as the mass participation coefficient increases.In most cases,the mass participation coefficient will increase the stability limit of the algorithm,but in specific circumstances,the algorithm may lose its stability.The stability and accuracy of the CDM considering the mass participation coefficient are verified by numerical simulations and experimental tests on a three-story frame structure with a tuned liquid damper.
基金Supported by the National Key Basic Research Program of China("973"Project)(2009CB724401)the China Postdoctoral Science Foundation(20070420208)the Postdoctoral Innovation Foundation of Shandong Province(200702023)~~
文摘Considering the self-excited and forced vibrations in high-speed milling processes, a novel method for dynamic optimization of system stability is used to determine the cutting parameters and structural parameters by increasing the chatter free material removal rate （CF-MRR） and surface finish. The method is hased on the theory of the chatter stability and the semi-bandwidth of the resonant region. The objective function of the method is material removal rate（MRR）,the constraints are chatter stability and surface finish, and the optimizing variables are cutting and structural parameters. The optimization procedure is stated. The method is applied to a milling system and CF-MRR is increased 18.86%. It is shown that the influences of the chatter stability and the resonance are simultaneously considered in the dynamic optimization of the milling system for increasing CF-MRR and the surface finish.
基金Supported by the National Natural Science Foundation of China under Grant No.51965032the Natural Science Foundation of Gansu Province of China under Grant No.22JR5RA319+2 种基金the Excellent Doctoral Student Foundation of Gansu Province of China under Grant No.23JRRA842the Sichuan Province Engineering Technology Research Center of General Aircraft Maintenance under Grant No.GAMRC2023YB05the Key Research and Development Project of Lanzhou Jiaotong University under Grant No.LZJTUZDYF2302.
文摘Currently,the cranes used at sea do not have enough flexibility,efficiency,and safety.Thus,this study proposed a floating multirobot coordinated towing system to meet the demands for offshore towing.Because of the flexibility of rope-driven robots,the one-way pulling characteristics of the rope,and the floating characteristics of the base,towing robots are easily overturned.First,the spatial configuration of the towing system was established according to the towing task,and the kinematic model of the towing system was established using the coordinate transformation.Then,the dynamic model of the towing system was established according to the rigid-body dynamics and hydrodynamic theory.Finally,the stability of the towing system was analyzed using the stability cone method.The simulation experiments provide a reference for the practical application of the floating multirobot coordinated towing system,which can improve the stability of towing systems by changing the configuration of the towing robot.
基金National Natural Science Foundation of China(No.22065038)High-Level Talents Introduction in Yunnan Province(No.C619300A010)+3 种基金the Fund for Excellent Young Scholars of Yunnan(No.202001AW070008)Spring City Plan:the Highlevel Talent Promotion and Training Project of Kunming(No.2022SCP005)for financial supportthe support from the Postdoctoral Research Foundation of Yunnan University(No.W8223004)the Postdoctoral Foundation of Department of Human Resources and Social Security of Yunnan Province(No.C615300504046)。
文摘Defects at the grain boundaries(GBs)of perovskite film highly restrict both the efficiency and stability of perovskite solar cells(PSCs).Herein,organic small molecules of butanedioic acid(BA)and acetylenedicarboxylic acid(AA),containing two carbonyl(C=O)groups and different core-units,were incorporated into perovskite as additives for PSCs application.Thanks to the strong coordination interaction between C=O group and under-coordinated Pb^(2+),the additives can effectively passivate film defects and regulate the perovskite crystallization,yielding high-quality perovskite films with lower defect densities.More importantly,the additives can efficiently regulate the charge transport behaviors in PSCs.Benefiting from the defects passivation and the regulation of charge carrier dynamics,the BA and AA-treaded PSCs show the power conversion efficiencies of 21.52%and 20.50%,which are higher than that of the control device(19.41%).Besides,the optimal devices exhibit a remarkable enhanced long-term stability and moisture tolerance compared to the pristine devices.Furthermore,the transient absorption spectrum reveals the mechanism of enhanced photovoltaic performances,attributing to the improvement of charge transport capability at the perovskite/Spiro-OMeTAD interfaces.This work affords a promising strategy to improve the efficiency and stability of PSCs through regulating the charge-carrier dynamic process in perovskite film.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2141254 and U23B6009)。
文摘In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.
基金supported by the National Natural Science Foundation of China(61833005)
文摘Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimating settling-time function (STF) of the hybrid systems.When switching dynamics are FTS and impulsive dynamics involve destabilizing delay-dependent impulses, the FTS is retained if the impulses occur infrequently.
基金The financial supports from National key plan project for research and development of China (2019YFA0708300) and (2023YFC3009200)。
文摘For strapdown stabilized platform used in automatic vertical drilling system,a new dynamic measurement algorithm based on three-axis accelerometer and three-axis fluxgate measurement signals is proposed and simulated under the condition of small inclination dynamic rotation.The error compensation algorithm is also proposed.The bench test of strapdown stabilized platform is designed and carried out.The results show that:When the azimuth angle is the same,the larger the inclination angle is,the greater the error of the measurement results will be.When the inclination angle is the same,the measurement error is the largest when the azimuth angle is 90°and 270°,and the measurement error curve presents a sinusoidal change with the change of azimuth angle.After the error function compensation,the error curve between the calculation results and the true value is basically not affected by the inclination angle and the azimuth angle,and the calculation accuracy is signifi cantly improved.Under the random rotating speed of 0-180 rpm,the minimum error of the measured well inclination value was no more than 0.03°and the maximum was no more than 1.58°.The feasibility of the proposed dynamic azimuth measurement algorithm is verifi ed.This article provides a technical reference for the strapdown automatic drilling system.
文摘The feasibility of using a problem-dependent method to solve systems of second order ODEs is corroborated by an eigen-based theory and a methodology to develop such a numerical method is constructed.The key steps of this methodology are to decouple a system of ODEs of second order into a set of uncoupled ODEs of second order;next,an eigen-dependent method is proposed to approximate the solution of each uncoupled ODE of second order.It is vital to transform all eigen-dependent methods to a problem-dependent method to bypass an Eigen analysis.The development of an eigen-dependent method plays a key role in this methodology so that slow eigenmodes can be accurately integrated while there is no instability or excessive amplitude growth in fast eigenmodes.This can explain why a problem-dependent method can simultaneously combine the explicitness of each step and A-stability.Consequently,huge computational efforts can be saved for solving nonlinear stiff problems.A new family of problem-dependent methods is developed in this work so that the feasibility of the proposed methodology can be affirmed.It has almost the same performance as that of the HHT-αmethod.However,it can save more than 99.5%of CPU demand in approximating a solution for a system of 1000 nonlinear second order ODEs.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12175058 and 11921006)the National Grand Instrument Project (No. 2019YFF01014402)the Beijing Distinguished Young Scientist Program and National Grand Instrument Project No. SQ2019YFF01014400
文摘Controlling terahertz(THz)polarization with high stability and tunability is essential for achieving further progress in ultrafast spectroscopy,structured-light manipulation,and quantum information processing.Here,we propose a magnetized plasma platform for dynamic THz polarization control by exploiting the intrinsic birefringence between extraordinary and ordinary modes.We identify a strong-magnetization,zero-group-velocity-mismatch regime where the two modes share matched group velocities while retaining finite phase birefringence,enabling robust,phase-stable spin angular momentum control.By tuning the plasma length and magnetic field,we realize programmable phase retardation and demonstrate universal single-qubit gates through parameterized unitary operations.Full-wave particle-in-cell simulations validate high-fidelity polarization transformations across the Poincarésphere and demonstrate the potential for generating structured vector beams under spatially varying magnetic fields.The platform offers ultrafast response,resilience to extreme THz intensities,and in situ tunability,positioning magnetized plasmas as a versatile and damage-resilient medium for next-generation THz polarization control and structured-wave applications.
文摘The evolution of China-ASEAN relations ranks among the most significant geopolitical and economic dynamics of the 21st Century.Comprising 10 Southeast Asian nations,ASEAN has held the position of China’s largest trading partner since 2020.This partnership is underpinned by sustained economic growth,political stability,security cooperation,and vibrant socio-cultural exchanges.Over the past two decades,the China-ASEAN relationship has emerged as a main axis in Asia’s geopolitical and economic landscape.By 2025,this partnership has entered a more intricate and strategic phase marked by deeper economic collaboration,expanded multilateral diplomacy,and mounting challenges stemming from global developments such as tari"wars and South China Sea tensions.
文摘Dear Editor,This letter deals with the stabilization of a resilient model predictive control(MPC)algorithm with a dynamic event-triggered mechanism subject to Denial-of-Service(Do S)attacks.Different from previous works,this letter is based on the designed threshold function to dynamically trigger and gives the upper bound conditions for intersampling intervals with attack and attack-free scenarios to converge.
基金supported by the National Natural Science Foundation of China(Nos.51902121 and 22372067)。
文摘Covalent organic frameworks(COFs)are two-(2D)or threedimensional(3D)crystalline,porous networks generated by reversible polymerization of organic building blocks[1,2].The structures and functionalities of COFs are precisely controlled via appropriately selected organic building blocks.This design imparts unique properties to COFs,including exceptional structural stability,tunable pore structure,and surface chemical activity,making them promising for gas separation,catalysis,optoelectronics,and sensing applications.Since Yaghi et al.'s seminal report on COFs in 2005[2],these frameworks have swiftly emerged as a hotspot in the field of materials.Originally,the focus was on fabricating rigid frameworks with static structures and optoelectronic properties.However,the inherently static nature of these frameworks hinders their responsiveness to external stimuli,potentially constraining their functionality in specific applications.Hence,an increasing number of researchers are now directing their attention toward the development of dynamic COFs capable of modifying their structures in response to external stimuli[3].Specifically,dynamic 2D COFs exhibiting enhanced structural responsiveness are of particular interest due to their capability to integrate switchable geometries and porosities with semiconductor building blocks,as well as electron conjugation across COF layers and π-stacked columns,which may enable stimuli-responsive electronic and spin properties[4].
基金supported by grants fromthe Shenzhen Medical Research Fund(Grant No.A2302040).
文摘During cellular proliferation DNA undergoes frequent rep-lication cycles in which errors inevitably accumulate.DNA simultaneously faces continuous damage from endogenous sources[e.g.,reactive oxygen species(ROS)]and environmen-tal stressors,such as ultraviolet(UV)and ionizing radiation(IR).Such lesions compromise genomic stability and may escalate into DNA double-strand breaks(DSBs).Failure to repair DSBs can ultimately trigger cell death1.
基金Supported by the National Natural Science Foundation of China,No.82200658.
文摘BACKGROUND Hepatic ischemia-reperfusion(I/R)injury related to liver transplantation and hepatic resection remains a challenge in clinical practice.Accumulating evidence indicates that mitochondrial dysfunction is a critical cause of I/R injury.The protein 4-nitrophenylphosphatase domain and non-neuronal SNAP25-like protein homolog 1(NIPSNAP1)is involved in the regulation of mitophagy and the recruitment of autophagy receptor proteins independent of PTEN induced putative kinase 1.AIM To clarify the protective mechanism of NIPSNAP1 against hepatic I/R,with a focus on mitophagy and mitochondrial dynamics,as well as the potential mechanism by which n6-methyladenosine(m6A)modification regulates NIPSNAP1.METHODS Mice were administered an adeno-associated virus in vivo and a hepatic I/R model was established via portal vein interruption followed by reperfusion to explore the effect of NIPSNAP1 on hepatic I/R.HepG2 cells were subjected to hypoxia/reoxygenation treatment in vitro.RESULTS We observed a significant downregulation of both NIPSNAP1 and insulin-like growth factor 2 mRNA-binding protein 2(IGF2BP2)expression in vivo and in vitro.NIPSNAP1 knockdown impaired mitophagy and disrupted mitochondrial dynamics;in contrast,NIPSNAP1 overexpression resulted in the opposite effects.Further studies revealed that IGF2BP2 functions as an m6A reader that targets and binds NIPSNAP1,thereby regulating its mRNA stability.CONCLUSION NIPSNAP1 prevents hepatic I/R injury by promoting mitophagy and maintaining mitochondrial homeostasis,serving as a novel target of the m6A reader IGF2BP2.Therefore,targeting the IGF2BP2/NIPSNAP1 axis may facilitate the development of better therapeutics for hepatic I/R.
