We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the p...We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.展开更多
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
Ring polymers are ubiquitous in various fields including biomaterials,drug release and gene therapy.All of these applications involve the dynamics and diffusion process of ring polymers in a confined environment.By us...Ring polymers are ubiquitous in various fields including biomaterials,drug release and gene therapy.All of these applications involve the dynamics and diffusion process of ring polymers in a confined environment.By using dynamic light scattering(DLS),we discovered a dynamical transition for charged ring polymers with increasing ring concentration in the gel matrix from a diffusive state to a non-diffusive topological frustrated state with a more compact conformation.When the ring polymer size is smaller than the mesh size of the gel matrix,the rings are diffusive at low concentration of 5 g/L.The ring diffusion coefficient in the gel matrix is an order of magnitude smaller than that of rings in solution,obeying the Ogston's model.At high ring concentration of 40 g/L,the collective dynamical behavior of the charged rings exhibits a topologically frustrated non-diffusive state,which may originate from the inter-ring threading with the external confinement from the gel matrix.Based on our previous theoretical work,we also conjectured that in such a non-diffusive state,the ring polymers might adopt a more compact conformation with the overall size exponentν=1/3.展开更多
With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our resu...With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.展开更多
Molecular dynamics simulations were performed to investigate the sliding dynamics of a small charged ring chain along rigid cyclic diblock polyelectrolyte in catenane immersed in salt solution.We found that both the m...Molecular dynamics simulations were performed to investigate the sliding dynamics of a small charged ring chain along rigid cyclic diblock polyelectrolyte in catenane immersed in salt solution.We found that both the mean-square displacement g_(3)(t)and diffusion coefficient D of ring are influenced by the salt type,electrostatic interaction strength A and salt concentration cs.D first decreases and then increases as A increases when Ais not large.At large A,D decreases with an increase in A owing to the polyelectrolyte charge reversal caused by the aggregation of ions near it.Meanwhile,g_(3)(t)exhibited intermediate oscillating behavior at moderate A in monovalent cation salt solution.The sliding dynamics of ring can be attributed to the free energy landscape for diffusion.According to the potential of mean force(PMF)of ring chain,we found that our simulation results agreed well with the theoretical results of Lifson-Jackson formula.This study can provide a practical model for the diffusion of charged particles in different dielectric and periodic media,and provides a new perspective for regulating the sliding dynamics of mechanically interlocked molecules in electrolyte solutions.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
Portal vein stenosis is one of the common complications after liver transplantation in children.Accurate hemodynamic assessment is crucial for predicting the risk of complications after liver transplantation.In order ...Portal vein stenosis is one of the common complications after liver transplantation in children.Accurate hemodynamic assessment is crucial for predicting the risk of complications after liver transplantation.In order to predict the location of portal vein thrombosis after liver transplantation surgery,single-outlet and three-outlet vascular models were reconstructed from computed tomography images by commercial software MIMICS.The velocity field was measured using a 9.4 T magnetic resonance imaging scanner.Based on the experiment data of magnetic resonance velocimetry,computational fluid dynamics was verified,validated and then used to study the pressure and shear stresses on the wall of the two portal vein models.The simulation results can serve for the clinical prediction of early thrombosis after liver transplantation in portal vein.展开更多
Background Hexafluoropropylene oxide dimer acid(GenX),a substitute for per-and polyfluoroalkyl substances,has been widely detected in various environmental matrices and foods recently,attracting great attention.Howeve...Background Hexafluoropropylene oxide dimer acid(GenX),a substitute for per-and polyfluoroalkyl substances,has been widely detected in various environmental matrices and foods recently,attracting great attention.However,a systematic characterization of its reproductive toxicity is still missing.This study aims to explore the male reproductive toxicity caused by GenX exposure and the potential cellular and molecular regulatory mechanisms behind it.Results Normally developing mice were exposed to GenX,and testicular tissue was subsequently analyzed and validated using single-cell RNA sequencing.Our results revealed that GenX induced severe testicular damage,disrupted the balance between undifferentiated and differentiated spermatogonial stem cells,and led to strong variation in the cellular dynamics of spermatogenesis.Furthermore,GenX exposure caused global upregulation of testicular somatic cellular inflammatory responses,increased abnormal macrophage differentiation,and attenuated fibroblast adhesion,disorganizing the somatic-germline interactions.Conclusions In conclusion,this study revealed complex cellular dynamics and transcriptome changes in mouse testis after GenX exposure,providing a valuable resource for understanding its reproductive toxicity.展开更多
Revealing the structure evolution of interfacial active species during a dynamic catalytic process is a challenging but pivotal issue for the rational design of high-performance catalysts.Here,we successfully prepare ...Revealing the structure evolution of interfacial active species during a dynamic catalytic process is a challenging but pivotal issue for the rational design of high-performance catalysts.Here,we successfully prepare sub-nanometric Pt clusters(~0.8 nm)encapsulated within the defects of CeO_(2)nanorods via an in-situ defect engineering methodology.The as-prepared Pt@d-CeO_(2)catalyst significantly boosts the activity and stability in the water-gas shift(WGS)reaction compared to other analogs.Based on controlled experiments and complementary(in-situ)spectroscopic studies,a reversible encapsulation induced by active site transformation between the Pt^(2+)-terminal hydroxyl and Pt^(δ+)-O vacancy species at the interface is revealed,which enables to evoke the enhanced performance.Our findings not only offer practical guidance for the design of high-efficiency catalysts but also bring a new understanding of the exceptional performance of WGS in a holistic view,which shows a great application potential in materials and catalysis.展开更多
The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic e...The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic elucidation of the occurrence characteristics,flow behavior,and enhanced oil recovery(EOR)mechanisms of shale oil within commonly developed nanopores.Molecular dynamics(MD)technique can simulate the occurrence,flow,and extraction processes of shale oil at the nanoscale,and then quantitatively characterize various fluid properties,flow characteristics,and action mechanisms under different reservoir conditions by calculating and analyzing a series of MD parameters.However,the existing review on the application of MD simulation in shale oil reservoirs is not systematic enough and lacks a summary of technical challenges and solutions.Therefore,recent MD studies on shale oil res-ervoirs were summarized and analyzed.Firstly,the applicability of force fields and ensembles of MD in shale reservoirs with different reservoir conditions and fluid properties was discussed.Subsequently,the calculation methods and application examples of MD parameters characterizing various properties of fluids at the microscale were summarized.Then,the application of MD simulation in the study of shale oil occurrence characteristics,flow behavior,and EOR mechanisms was reviewed,along with the elucidation of corresponding micro-mechanisms.Moreover,influencing factors of pore structure,wall properties,reservoir conditions,fluid components,injection/production parameters,formation water,and inorganic salt ions were analyzed,and some new conclusions were obtained.Finally,the main challenges associated with the application of MD simulations to shale oil reservoirs were discussed,and reasonable prospects for future MD research directions were proposed.The purpose of this review is to provide theoretical basis and methodological support for applying MD simulation to study shale oil reservoirs.展开更多
This paper addresses urban sustainability challenges amid global urbanization, emphasizing the need for innova tive approaches aligned with the Sustainable Development Goals. While traditional tools and linear models ...This paper addresses urban sustainability challenges amid global urbanization, emphasizing the need for innova tive approaches aligned with the Sustainable Development Goals. While traditional tools and linear models offer insights, they fall short in presenting a holistic view of complex urban challenges. System dynamics (SD) models that are often utilized to provide holistic, systematic understanding of a research subject, like the urban system, emerge as valuable tools, but data scarcity and theoretical inadequacy pose challenges. The research reviews relevant papers on recent SD model applications in urban sustainability since 2018, categorizing them based on nine key indicators. Among the reviewed papers, data limitations and model assumptions were identified as ma jor challenges in applying SD models to urban sustainability. This led to exploring the transformative potential of big data analytics, a rare approach in this field as identified by this study, to enhance SD models’ empirical foundation. Integrating big data could provide data-driven calibration, potentially improving predictive accuracy and reducing reliance on simplified assumptions. The paper concludes by advocating for new approaches that reduce assumptions and promote real-time applicable models, contributing to a comprehensive understanding of urban sustainability through the synergy of big data and SD models.展开更多
In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not ...In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.展开更多
Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization proces...Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization processes lead to different order of crystallization dynamics within the perovskite thin film,resulting in the differences of additive distribution.We then tailor-designed an additive molecule named 1,3-bis(4-methoxyphenyl)thiourea to obtain films with fewer defects and holes at the buried interface,and prepared perovskite solar cells with a certified efficiency of 23.75%.Furthermore,this work also demonstrates an efficiency of 20.18%for the large-area perovskite solar module(PSM)with an aperture area of 60.84 cm^(2).The PSM possesses remarkable continuous operation stability for maximum power point tracking of T_(90)>1000 h in ambient air.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
Efficient and stable photocathodes with versatility are of significance in photoassisted lithium-ion batteries(PLIBs),while there is always a request on fast carrier transport in electrochemical active photocathodes.P...Efficient and stable photocathodes with versatility are of significance in photoassisted lithium-ion batteries(PLIBs),while there is always a request on fast carrier transport in electrochemical active photocathodes.Present work proposes a general approach of creating bulk heterojunction to boost the carrier mobility of photocathodes by simply laser assisted embedding of plasmonic nanocrystals.When employed in PLIBs,it was found effective for synchronously enhanced photocharge separation and transport in light charging process.Additionally,experimental photon spectroscopy,finite difference time domain method simulation and theoretical analyses demonstrate that the improved carrier dynamics are driven by the plasmonic-induced hot electron injection from metal to TiO_(2),as well as the enhanced conductivity in TiO2 matrix due to the formation of oxygen vacancies after Schottky contact.Benefiting from these merits,several benchmark values in performance of TiO2-based photocathode applied in PLIBs are set,including the capacity of 276 mAh g^(−1) at 0.2 A g^(−1) under illumination,photoconversion efficiency of 1.276%at 3 A g^(−1),less capacity and Columbic efficiency loss even through 200 cycles.These results exemplify the potential of the bulk heterojunction strategy in developing highly efficient and stable photoassisted energy storage systems.展开更多
The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechan...The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.展开更多
The charge carrier transport and recombination dynamics in the quantum dots-based light-emitting diodes(QLEDs)featuring multiple emitting layers(M-EMLs)has a great impact on the device performance.In this work,QLEDs b...The charge carrier transport and recombination dynamics in the quantum dots-based light-emitting diodes(QLEDs)featuring multiple emitting layers(M-EMLs)has a great impact on the device performance.In this work,QLEDs based on M-EMLs separated by polyethyleneimine ethoxylated(PEIE)layer with different stacking sequences of blue(B),green(G),and red(R)QDs layer were used to intuitively explore the injection,transportation and recombination processes of the charge carriers in QLEDs by using the time-resolved electroluminescence(TrEL)spectra.From the TrEL spectra mea-surements,green and red emissions were obtained first in the QLEDs with the EMLs sequences of G/PEIE/B/PEIE/R and B/PEIE/R/PEIE/G along the direction of light emission,respectively.While the QLEDs adopt EMLs sequences of B/PEIE/G/PEIE/R,the blue,green and red emissions were obtained nearly at the same time.The above phenomenon can be attributed to different charge carrier transmission and radiation recombination process in the EMLs due to different valence band offsets and conduction band offsets between R-,G-and B-QDs by using different sequences of EMLs.White emission with coordi-nates of(0.31,0.31)and correlated color temperature(CCT)of 5916 K was obtained in the QLEDs with the EMLs se-quences of B/PEIE/G/PEIE/R,which can be attributed to the relative uniform emission of B-,G-and R-QDs due to the effec-tive injection and radiation recombination of charge carriers in each of the EMLs.The above results have great significance for further understanding and improving the performance of QLEDs with M-EMLs.展开更多
The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-do...The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-domain impulse theory for subcavitating flow(σ=8.0)and cavitating flow(σ=3.0),and to quantify the distinct impact of individual vortex structures on the transient lift to appreciate the interplay among cavitation,flow structures,and vortex dynamics.The motion of the hydrofoil is set to pitch up clockwise with an almost constant rate from 0°to 15°and then back to 0°,for the Reynolds number,7.5×105,and the frequency,0.2 Hz,respectively.The results reveal that the presence of cavities delays the migration of the laminar separation bubble(LSB)from the trailing edge(TE)to the leading edge(LE),consequently postponing the hysteresis in the inflection of lift coefficients.The eventual stall under the sub-cavitation regime is the result of LSB bursting.While the instabilities within the leading-edge LSB induce the convection of cavitation-dominated vortices under the cavitation regime instead.Having validated the lift coefficients on the hydrofoil through the finite-domain impulse theory using the standard force expression,the Lamb vector integral emerges as the main contribution to the generation of unsteady lift.Moreover,the typical vortices’contributions to the transient lift during dynamic stall are accurately quantified.The analysis indicates that the clockwise leading-edge vortex(−LEV)contributes positively,while the counterclockwise trailing-edge vortex(+TEV)contributes negatively.The negative influence becomes particularly pronounced after reaching the peak of total lift,as the shedding of the concentrated wake vortex precipitates a sharp decline due to a predominant negative lift contribution from the TEV region.Generally,the vortices’contribution is relatively modest in sub-cavitating flow,but it is notably more significant in the context of incipient cavitating flow.展开更多
The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove vario...The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.展开更多
Dear Editor,This letter focuses on how an attacker can design suitable improved zero-dynamics (ZD) attack signal based on state estimates of target system. Improved ZD attack is to change zero dynamic gain matrix of a...Dear Editor,This letter focuses on how an attacker can design suitable improved zero-dynamics (ZD) attack signal based on state estimates of target system. Improved ZD attack is to change zero dynamic gain matrix of attack signal to a matrix with determinant greater than 1.展开更多
基金supported by the National Key R&D Program of China (Grant No. 2024YFA1408502)the National Natural Science Foundation of China (Grant Nos. 92365102, 62027807, 12474107, and 12174383)+1 种基金the Chinese Academy of Sciences project for Yong Scientists in Basic Research (Grant No. YSBR-030)the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2024A1515011600)。
文摘We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.
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 by the National Natural Science Foundation of China(No.22273114)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0770101)+1 种基金the National Key R&D Program of China(No.2023YFE0124500),the National Key R&D Program of China(No.2023YFC2411203)International Partnership Program of the Chinese Academy of Sciences(No.027GJHZ2022061FN)。
文摘Ring polymers are ubiquitous in various fields including biomaterials,drug release and gene therapy.All of these applications involve the dynamics and diffusion process of ring polymers in a confined environment.By using dynamic light scattering(DLS),we discovered a dynamical transition for charged ring polymers with increasing ring concentration in the gel matrix from a diffusive state to a non-diffusive topological frustrated state with a more compact conformation.When the ring polymer size is smaller than the mesh size of the gel matrix,the rings are diffusive at low concentration of 5 g/L.The ring diffusion coefficient in the gel matrix is an order of magnitude smaller than that of rings in solution,obeying the Ogston's model.At high ring concentration of 40 g/L,the collective dynamical behavior of the charged rings exhibits a topologically frustrated non-diffusive state,which may originate from the inter-ring threading with the external confinement from the gel matrix.Based on our previous theoretical work,we also conjectured that in such a non-diffusive state,the ring polymers might adopt a more compact conformation with the overall size exponentν=1/3.
基金supported by the National Natural Science Foundation of China (Grant No. 12074329)Nanhu Scholars Program for Young Scholars of Xinyang Normal University。
文摘With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.
基金supported by the National Natural Science Foundation of China(Nos.22173080,22403062,and22363005)the Jiangxi Provincial Natural Science Foundation(No.20202BABL203015)。
文摘Molecular dynamics simulations were performed to investigate the sliding dynamics of a small charged ring chain along rigid cyclic diblock polyelectrolyte in catenane immersed in salt solution.We found that both the mean-square displacement g_(3)(t)and diffusion coefficient D of ring are influenced by the salt type,electrostatic interaction strength A and salt concentration cs.D first decreases and then increases as A increases when Ais not large.At large A,D decreases with an increase in A owing to the polyelectrolyte charge reversal caused by the aggregation of ions near it.Meanwhile,g_(3)(t)exhibited intermediate oscillating behavior at moderate A in monovalent cation salt solution.The sliding dynamics of ring can be attributed to the free energy landscape for diffusion.According to the potential of mean force(PMF)of ring chain,we found that our simulation results agreed well with the theoretical results of Lifson-Jackson formula.This study can provide a practical model for the diffusion of charged particles in different dielectric and periodic media,and provides a new perspective for regulating the sliding dynamics of mechanically interlocked molecules in electrolyte solutions.
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.
基金the Interdisciplinary Program of Shanghai Jiao Tong University(No.YG2021QN36)the National Natural Science Foundation of China(Nos.82000615 and 52106050)the Natural Science Foundation of Shanghai(No.21ZR1431800)。
文摘Portal vein stenosis is one of the common complications after liver transplantation in children.Accurate hemodynamic assessment is crucial for predicting the risk of complications after liver transplantation.In order to predict the location of portal vein thrombosis after liver transplantation surgery,single-outlet and three-outlet vascular models were reconstructed from computed tomography images by commercial software MIMICS.The velocity field was measured using a 9.4 T magnetic resonance imaging scanner.Based on the experiment data of magnetic resonance velocimetry,computational fluid dynamics was verified,validated and then used to study the pressure and shear stresses on the wall of the two portal vein models.The simulation results can serve for the clinical prediction of early thrombosis after liver transplantation in portal vein.
基金supported by the Guangdong Provincial Key Area Research and Development Program[grant number 2022B0202090002]China Postdoctoral Science Foundation[grant number 2024M760977].
文摘Background Hexafluoropropylene oxide dimer acid(GenX),a substitute for per-and polyfluoroalkyl substances,has been widely detected in various environmental matrices and foods recently,attracting great attention.However,a systematic characterization of its reproductive toxicity is still missing.This study aims to explore the male reproductive toxicity caused by GenX exposure and the potential cellular and molecular regulatory mechanisms behind it.Results Normally developing mice were exposed to GenX,and testicular tissue was subsequently analyzed and validated using single-cell RNA sequencing.Our results revealed that GenX induced severe testicular damage,disrupted the balance between undifferentiated and differentiated spermatogonial stem cells,and led to strong variation in the cellular dynamics of spermatogenesis.Furthermore,GenX exposure caused global upregulation of testicular somatic cellular inflammatory responses,increased abnormal macrophage differentiation,and attenuated fibroblast adhesion,disorganizing the somatic-germline interactions.Conclusions In conclusion,this study revealed complex cellular dynamics and transcriptome changes in mouse testis after GenX exposure,providing a valuable resource for understanding its reproductive toxicity.
文摘Revealing the structure evolution of interfacial active species during a dynamic catalytic process is a challenging but pivotal issue for the rational design of high-performance catalysts.Here,we successfully prepare sub-nanometric Pt clusters(~0.8 nm)encapsulated within the defects of CeO_(2)nanorods via an in-situ defect engineering methodology.The as-prepared Pt@d-CeO_(2)catalyst significantly boosts the activity and stability in the water-gas shift(WGS)reaction compared to other analogs.Based on controlled experiments and complementary(in-situ)spectroscopic studies,a reversible encapsulation induced by active site transformation between the Pt^(2+)-terminal hydroxyl and Pt^(δ+)-O vacancy species at the interface is revealed,which enables to evoke the enhanced performance.Our findings not only offer practical guidance for the design of high-efficiency catalysts but also bring a new understanding of the exceptional performance of WGS in a holistic view,which shows a great application potential in materials and catalysis.
基金supported by the National Natural Science Foundation of China(52304021,52104022,52204031)the Natural Science Foundation of Sichuan Province(2022NSFSC0205,2024NSFSC0201,2023NSFSC0947)the National Science and Technology Major Projects of China(2017ZX05049006-010).
文摘The global energy demand is increasing rapidly,and it is imperative to develop shale hydrocarbon re-sources vigorously.The prerequisite for enhancing the exploitation efficiency of shale reservoirs is the systematic elucidation of the occurrence characteristics,flow behavior,and enhanced oil recovery(EOR)mechanisms of shale oil within commonly developed nanopores.Molecular dynamics(MD)technique can simulate the occurrence,flow,and extraction processes of shale oil at the nanoscale,and then quantitatively characterize various fluid properties,flow characteristics,and action mechanisms under different reservoir conditions by calculating and analyzing a series of MD parameters.However,the existing review on the application of MD simulation in shale oil reservoirs is not systematic enough and lacks a summary of technical challenges and solutions.Therefore,recent MD studies on shale oil res-ervoirs were summarized and analyzed.Firstly,the applicability of force fields and ensembles of MD in shale reservoirs with different reservoir conditions and fluid properties was discussed.Subsequently,the calculation methods and application examples of MD parameters characterizing various properties of fluids at the microscale were summarized.Then,the application of MD simulation in the study of shale oil occurrence characteristics,flow behavior,and EOR mechanisms was reviewed,along with the elucidation of corresponding micro-mechanisms.Moreover,influencing factors of pore structure,wall properties,reservoir conditions,fluid components,injection/production parameters,formation water,and inorganic salt ions were analyzed,and some new conclusions were obtained.Finally,the main challenges associated with the application of MD simulations to shale oil reservoirs were discussed,and reasonable prospects for future MD research directions were proposed.The purpose of this review is to provide theoretical basis and methodological support for applying MD simulation to study shale oil reservoirs.
基金sponsored by the U.S.Department of Housing and Urban Development(Grant No.NJLTS0027-22)The opinions expressed in this study are the authors alone,and do not represent the U.S.Depart-ment of HUD’s opinions.
文摘This paper addresses urban sustainability challenges amid global urbanization, emphasizing the need for innova tive approaches aligned with the Sustainable Development Goals. While traditional tools and linear models offer insights, they fall short in presenting a holistic view of complex urban challenges. System dynamics (SD) models that are often utilized to provide holistic, systematic understanding of a research subject, like the urban system, emerge as valuable tools, but data scarcity and theoretical inadequacy pose challenges. The research reviews relevant papers on recent SD model applications in urban sustainability since 2018, categorizing them based on nine key indicators. Among the reviewed papers, data limitations and model assumptions were identified as ma jor challenges in applying SD models to urban sustainability. This led to exploring the transformative potential of big data analytics, a rare approach in this field as identified by this study, to enhance SD models’ empirical foundation. Integrating big data could provide data-driven calibration, potentially improving predictive accuracy and reducing reliance on simplified assumptions. The paper concludes by advocating for new approaches that reduce assumptions and promote real-time applicable models, contributing to a comprehensive understanding of urban sustainability through the synergy of big data and SD models.
基金supported by the Guangdong Basic and Applied Basic Research Foundation (No.2023A1515010093)the Shenzhen Fundamental Research Program (Stable Support Plan Program)(Nos.JCYJ20220809170611004, 20231121110828001 and 20231121113641002)the National Taipei University of Technology-Shenzhen University Joint Research Program (No.2024001)。
文摘In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.
基金supported by National Natural Science Foundation of China(62104082)Guangdong Basic and Applied Basic Research Foundation(2022A1515010746,2022A1515011228,and 2022B1515120006)the Science and Technology Program of Guangzhou(202201010458).
文摘Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method.In this work,we found these two pre-crystallization processes lead to different order of crystallization dynamics within the perovskite thin film,resulting in the differences of additive distribution.We then tailor-designed an additive molecule named 1,3-bis(4-methoxyphenyl)thiourea to obtain films with fewer defects and holes at the buried interface,and prepared perovskite solar cells with a certified efficiency of 23.75%.Furthermore,this work also demonstrates an efficiency of 20.18%for the large-area perovskite solar module(PSM)with an aperture area of 60.84 cm^(2).The PSM possesses remarkable continuous operation stability for maximum power point tracking of T_(90)>1000 h in ambient air.
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.
基金supported by the project of the National Natural Science Foundation of China(52202115 and 52172101)Guangdong Basic and Applied Basic Research Foundation(2024A1515012325)+2 种基金the Natural Science Foundation of Chongqing,China(CSTB2022NSCQ-MSX1085)the Shaanxi Science and Technology Innovation Team(2023-CXTD-44)the Fundamental Research Funds for the Central Universities(G2022KY0604).
文摘Efficient and stable photocathodes with versatility are of significance in photoassisted lithium-ion batteries(PLIBs),while there is always a request on fast carrier transport in electrochemical active photocathodes.Present work proposes a general approach of creating bulk heterojunction to boost the carrier mobility of photocathodes by simply laser assisted embedding of plasmonic nanocrystals.When employed in PLIBs,it was found effective for synchronously enhanced photocharge separation and transport in light charging process.Additionally,experimental photon spectroscopy,finite difference time domain method simulation and theoretical analyses demonstrate that the improved carrier dynamics are driven by the plasmonic-induced hot electron injection from metal to TiO_(2),as well as the enhanced conductivity in TiO2 matrix due to the formation of oxygen vacancies after Schottky contact.Benefiting from these merits,several benchmark values in performance of TiO2-based photocathode applied in PLIBs are set,including the capacity of 276 mAh g^(−1) at 0.2 A g^(−1) under illumination,photoconversion efficiency of 1.276%at 3 A g^(−1),less capacity and Columbic efficiency loss even through 200 cycles.These results exemplify the potential of the bulk heterojunction strategy in developing highly efficient and stable photoassisted energy storage systems.
基金Foundation of Northwest Institute for Nonferrous Metal Research(ZZXJ2203)Capital Projects of Financial Department of Shaanxi Province(YK22C-12)+3 种基金Innovation Capability Support Plan in Shaanxi Province(2023KJXX-083)Key Research and Development Projects of Shaanxi Province(2024GXYBXM-351,2024GX-YBXM-356)National Natural Science Foundation of China(62204207,12204383)Xi'an Postdoctoral Innovation Base Funding Program。
文摘The extraordinary strength of metal/graphene composites is significantly determined by the characteristic size,distribution and morphology of graphene.However,the effect of the graphene size/distribution on the mechanical properties and related strengthening mechanisms has not been fully elucidated.Herein,under the same volume fraction and distribution conditions of graphene,molecular dynamics simulations were used to investigate the effect of graphene sheet size on the hardness and deformation behavior of Cu/graphene composites under complex stress field.Two models of pure single crystalline Cu and graphene fully covered Cu matrix composite were constructed for comparison.The results show that the strengthening effect changes with varying the graphene sheet size.Besides the graphene dislocation blocking effect and the load-bearing effect,the deformation mechanisms change from stacking fault tetrahedron,dislocation bypassing and dislocation cutting to dislocation nucleation in turn with decreasing the graphene sheet size.The hardness of Cu/graphene composite,with the graphene sheet not completely covering the metal matrix,can even be higher than that of the fully covered composite.The extra strengthening mechanisms of dislocation bypassing mechanism and the stacking fault tetrahedra pinning dislocation mechanism contribute to the increase in hardness.
文摘The charge carrier transport and recombination dynamics in the quantum dots-based light-emitting diodes(QLEDs)featuring multiple emitting layers(M-EMLs)has a great impact on the device performance.In this work,QLEDs based on M-EMLs separated by polyethyleneimine ethoxylated(PEIE)layer with different stacking sequences of blue(B),green(G),and red(R)QDs layer were used to intuitively explore the injection,transportation and recombination processes of the charge carriers in QLEDs by using the time-resolved electroluminescence(TrEL)spectra.From the TrEL spectra mea-surements,green and red emissions were obtained first in the QLEDs with the EMLs sequences of G/PEIE/B/PEIE/R and B/PEIE/R/PEIE/G along the direction of light emission,respectively.While the QLEDs adopt EMLs sequences of B/PEIE/G/PEIE/R,the blue,green and red emissions were obtained nearly at the same time.The above phenomenon can be attributed to different charge carrier transmission and radiation recombination process in the EMLs due to different valence band offsets and conduction band offsets between R-,G-and B-QDs by using different sequences of EMLs.White emission with coordi-nates of(0.31,0.31)and correlated color temperature(CCT)of 5916 K was obtained in the QLEDs with the EMLs se-quences of B/PEIE/G/PEIE/R,which can be attributed to the relative uniform emission of B-,G-and R-QDs due to the effec-tive injection and radiation recombination of charge carriers in each of the EMLs.The above results have great significance for further understanding and improving the performance of QLEDs with M-EMLs.
基金supported by the National Science Foundation of China (Grant Nos.52279081,and 51839001).
文摘The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-domain impulse theory for subcavitating flow(σ=8.0)and cavitating flow(σ=3.0),and to quantify the distinct impact of individual vortex structures on the transient lift to appreciate the interplay among cavitation,flow structures,and vortex dynamics.The motion of the hydrofoil is set to pitch up clockwise with an almost constant rate from 0°to 15°and then back to 0°,for the Reynolds number,7.5×105,and the frequency,0.2 Hz,respectively.The results reveal that the presence of cavities delays the migration of the laminar separation bubble(LSB)from the trailing edge(TE)to the leading edge(LE),consequently postponing the hysteresis in the inflection of lift coefficients.The eventual stall under the sub-cavitation regime is the result of LSB bursting.While the instabilities within the leading-edge LSB induce the convection of cavitation-dominated vortices under the cavitation regime instead.Having validated the lift coefficients on the hydrofoil through the finite-domain impulse theory using the standard force expression,the Lamb vector integral emerges as the main contribution to the generation of unsteady lift.Moreover,the typical vortices’contributions to the transient lift during dynamic stall are accurately quantified.The analysis indicates that the clockwise leading-edge vortex(−LEV)contributes positively,while the counterclockwise trailing-edge vortex(+TEV)contributes negatively.The negative influence becomes particularly pronounced after reaching the peak of total lift,as the shedding of the concentrated wake vortex precipitates a sharp decline due to a predominant negative lift contribution from the TEV region.Generally,the vortices’contribution is relatively modest in sub-cavitating flow,but it is notably more significant in the context of incipient cavitating flow.
基金the National Natural Science Foundation of China(Nos.11832005,12372042,12232011)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)+1 种基金the Fundamental Research Funds for the Central Universities(No.NS2023002)State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(No.MCAS-S-0223K04).
文摘The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.
基金supported in part by the National Natural Science Foundation of China(61873106,62303109)Start-Up Research Fund of Southeast University(RF1028623002)Shenzhen Science and Technology Program(JCYJ20230807114609019)
文摘Dear Editor,This letter focuses on how an attacker can design suitable improved zero-dynamics (ZD) attack signal based on state estimates of target system. Improved ZD attack is to change zero dynamic gain matrix of attack signal to a matrix with determinant greater than 1.
