Accurate navigation is important for long-range rocket projectile＇s precise striking. To obtain stable and high-per- formance navigation result, a ultra-tight global positioning system/inertial navigation system （GP...Accurate navigation is important for long-range rocket projectile＇s precise striking. To obtain stable and high-per- formance navigation result, a ultra-tight global positioning system/inertial navigation system （GPS/INS） integration based nav- igation approach is proposed. The accurate short-time output of INS is used by GPS receiver to assist in acquisition of signal, and output information of INS and GPS is fused based on federated filter. Meanwhile, the improved cubature Kalman filter with strong tracking ability is chosen to serve as the local filter, and then the federated filter is enhanced based on vector sharing theory. Finally, simulation results show that the navigation accuracy with the proposed method is higher than that with traditional methods. It provides reference for long-range rocket projectile navigation.展开更多
With the improvement of the accuracy of the inertial system,the influence of the disturbing gravity field on the accuracy of long-range rocket has become increasingly prominent.However,in actual engineering,there are ...With the improvement of the accuracy of the inertial system,the influence of the disturbing gravity field on the accuracy of long-range rocket has become increasingly prominent.However,in actual engineering,there are problems of low accuracy and being time-consuming for disturbing gravity field compensation.In view of this,this paper proposes a set of online comprehensive solutions combining disturbing gravity reconstruction and stellar correction.According to the pre-launch binding parameters,the net function assignment method is used in the navigation system to calculate disturbing gravity in the boost phase online.In the guidance system,a closed-loop guidance online compensation method is proposed based on the state-space perturbation method for the disturbing gravity in the coast phase.At the same time,the vertical deflection can also be corrected by stellar guidance.The calculation results are simulated and verified under different circumstances.Simulation results show that the proposed online compensation algorithm has an accuracy improvement compared with the element compensation algorithm on ground.And the stellar guidance algorithm can further correct the impact deviation.The impact deviation after comprehensive compensation does not exceed 50 m,and the compensation percentage is greater than 65%.展开更多
In the field of intelligent air combat,real-time and accurate recognition of within-visual-range(WVR)maneuver actions serves as the foundational cornerstone for constructing autonomous decision-making systems.However,...In the field of intelligent air combat,real-time and accurate recognition of within-visual-range(WVR)maneuver actions serves as the foundational cornerstone for constructing autonomous decision-making systems.However,existing methods face two major challenges:traditional feature engineering suffers from insufficient effective dimensionality in the feature space due to kinematic coupling,making it difficult to distinguish essential differences between maneuvers,while end-to-end deep learning models lack controllability in implicit feature learning and fail to model high-order long-range temporal dependencies.This paper proposes a trajectory feature pre-extraction method based on a Long-range Masked Autoencoder(LMAE),incorporating three key innovations:(1)Random Fragment High-ratio Masking(RFH-Mask),which enforces the model to learn long-range temporal correlations by masking 80%of trajectory data while retaining continuous fragments;(2)Kalman Filter-Guided Objective Function(KFG-OF),integrating trajectory continuity constraints to align the feature space with kinematic principles;and(3)Two-stage Decoupled Architecture,enabling efficient and controllable feature learning through unsupervised pre-training and frozen-feature transfer.Experimental results demonstrate that LMAE significantly improves the average recognition accuracy for 20-class maneuvers compared to traditional end-to-end models,while significantly accelerating convergence speed.The contributions of this work lie in:introducing high-masking-rate autoencoders into low-informationdensity trajectory analysis,proposing a feature engineering framework with enhanced controllability and efficiency,and providing a novel technical pathway for intelligent air combat decision-making systems.展开更多
Sluggish sulfur conversion kinetics pose an ongoing challenge in lithium-sulfur batteries(LSBs).Here,we present a solution through far-reaching long-range electronic regulation(LRER)on single-atom active sites.N-doped...Sluggish sulfur conversion kinetics pose an ongoing challenge in lithium-sulfur batteries(LSBs).Here,we present a solution through far-reaching long-range electronic regulation(LRER)on single-atom active sites.N-doped carbons(Co-NC)are implanted with densely-distributed Co single atoms,and supported on Ti_(3)C_(2)T_(x)MXene substrates to assemble 3D Co-NC/MXene catalyst.MXene effectively mediates interlayer charge transfer(~0.70|e|)contrasted with popular carbon materials(~0.06|e|)to produce LRER through surrounding carbon atoms.The synergy of LRER with near-range electronic regulation(NRER)tunes electronic structures,and enhances heterostructural stability,thus provoking desirous catalytic kinetics of Co single atoms in sulfur reduction.Thereby,the Co-NC/MXene/S cathodes exhibit impressive rate performance and excellent cycling stability(only 0.015%capacity decay per cycle over 600 cycles at 4 C)in LSBs,surpassing state-of-the-art sulfur cathodes.This work reveals the importance of LRER for improved catalysis,and provides new guidance to tailor heterostructures to achieve high-efficient catalysts in various process.展开更多
Catalysts with asymmetric coordination exhibit excellent electrocatalytic activity due to changes in the active sites,which affect the arrangement of reactants and catalytic activity/selectivity.Hence,the exploration ...Catalysts with asymmetric coordination exhibit excellent electrocatalytic activity due to changes in the active sites,which affect the arrangement of reactants and catalytic activity/selectivity.Hence,the exploration of the inherent characteristics of active sites within diverse coordination environments holds great significance for the experimental design of catalytic structures.Single-atom catalysts(SACs)characterized by high coordination with four carbons(26 candidates)and low coordination with dinitrogen(27candidates)are constructed using nitrogen-doped graphdiyne derivatives(NGDY)as the substrate.Additionally,5 species of dual-atom catalysts(DACs)with coexistence of both high and low coordination sites are also developed and their nitrogen reduction reaction(NRR)activities are systematically investigated by density functional theory.The results indicate that metals with low coordination exhibit superior catalytic performance,such as Mo^(L)-NGDY(U_(L)=-0.30 V)and Nb^(L)-NGDY(U_(L)=-0.32 V).Furthermore,machine learning(ML)methods have deeply analyzed and elucidated the primary intrinsic characteristics that influence catalytic performance.These results not only unveil the underlying mechanisms behind the exceptional catalytic performance exhibited by low-coordination metal atoms,but also provide relevant and significant descriptors.More importantly,based on an investigation of the catalytic activity of a series of DACs,the“buffer and low-coordination accumulate”asymmetric coordination mechanism is proposed to unveil the long-range interactions between low and high coordination atoms.Due to this remote communication,MoNb-NGDY(U_(L)=-0.09/-0.37 V)exhibits the best NRR activity.This mechanism provides valuable insights into the origin of long-range bipartite interactions and inspires the design and synthesis of NRR catalysts with different coordination environments.展开更多
A Hamiltonian mean-field model with long-range four-body interactions is proposed.The model describes a long-range mean-field system in which N unit-mass particles move on a unit circle.Each particleθi interacts with...A Hamiltonian mean-field model with long-range four-body interactions is proposed.The model describes a long-range mean-field system in which N unit-mass particles move on a unit circle.Each particleθi interacts with any three other particles through an infinite-range cosine potential with an attractive interaction(ε>0).By applying a method that remaps the average phase of global particle pairs onto a new unit circle,and using the saddle-point technique,the partition function is solved analytically after introducing four-body interactions,yielding expressions for the free energy f and the energy per particle U.These results were further validated through numerical simulations.The results show that the system undergoes a second-order phase transition at the critical energy Uc.Specifically,the critical energy corresponds to U_(c)=0.32 when the coupling constantε=5,and U_(c)=0.63 whenε=10.Finally,we calculated the system’s largest Lyapunov exponentλand kinetic energy fluctuationsΣthrough numerical simulations.It is found that the peak of the largest Lyapunov exponentλoccurs slightly below the critical energy Uc,which is consistent with the point of maximum kinetic energy fluctuationsΣ.And there is a scaling law ofΣ/N^(1/2)∝λbetween them.展开更多
We investigate the parity-time(PT)symmetry-breaking quantum phase transition in a one-dimensional(1D)bosonic lattice featuring cavity-mediated long-range interactions and spatially staggered dissipation.By mapping the...We investigate the parity-time(PT)symmetry-breaking quantum phase transition in a one-dimensional(1D)bosonic lattice featuring cavity-mediated long-range interactions and spatially staggered dissipation.By mapping the system to an effective spin chain under the constraints of hard-core bosons and integrating the mean-field decoupling approach with biorthogonal basis formalism,we derive a self-consistency equation.Numerical simulation results validate that the derived equation quantitatively captures thePT-symmetry order parameter’s phase diagram.Our findings reveal that coherent hopping maintainsPTsymmetry through quantum fluctuations.Conversely,cavity-engineered long-range interactions,in synergy with staggered dissipation,act in opposition to drive symmetry breaking.This competitive interplay can inspire further exploration of tunable quantum phase transitions in non-Hermitian systems.展开更多
Consecutive stresses,such as initial submergence during germination followed by water deficit during the seedling stage,pose significant challenges to direct-seeded rice cultivation.By Linkage disequilibrium analysis,...Consecutive stresses,such as initial submergence during germination followed by water deficit during the seedling stage,pose significant challenges to direct-seeded rice cultivation.By Linkage disequilibrium analysis,Sub1 and Dro1(Δbp:10 Mb),as well as Sub1 and TPP7(Δbp:6 Mb)were identified to exhibit long-range linkage disequilibrium(LRLD).Meta-QTL analysis further revealed that Sub1 and TPP7 co-segregated for tolerance to submergence at the germination and seedling stages.Based on this,we hypothesized that LRLD might influence plant responses to consecutive stresses.To test this hypothesis,we developed a structured recombinant inbred line population from a cross between Bhalum 2 and Nagina 22,with alleles(Sub1 and TPP7)in linkage equilibrium.Mendelian randomization analysis validated that the parental alleles,rather than the recombinant alleles of Sub1 and TPP7,significantly influenced 13 out of 41 traits under consecutive stress conditions.Additionally,16 minor additive effect QTLs were detected between the genomic regions,spanning Sub1 and TPP7 for various traits.A single allele difference between these genomic regions enhanced crown root number,root dry weight,and specific root area by 11.45%,15.69%,and 33.15%,respectively,under flooded germination conditions.Candidate gene analysis identified WAK79 and MRLK59 as regulators of stress responses during flooded germination,recovery,and subsequent water deficit conditions.These findings highlight the critical role of parental allele combinations and genomic regions between Sub1 and TPP7 in regulating the stress responses under consecutive stresses.Favourable haplotypes derived from these alleles can be utilized to improve stress resilience in direct-seeded rice.展开更多
A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effect...A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effects of helium injection on the burning rate and combustion of AP/HTPB propellant are analyzed in details,and the characteristics of motor performance are obtained.The numerical simulation results demonstrate that helium injection enhances the combustion chamber pressure,thereby increasing the burning rate of propellant.However,the primary combustion reaction of the AP/HTPB propellant takes place within a thin layer on the burning surface,so the low-temperature helium has minimal impact on the gasphase combustion.Ultimately,the helium not only elevates the nozzle exit velocity,resulting in specific impulse gain,but also reduces the exhaust plume temperature.With an increase of helium mass flow rate,the area of the velocity increase zone at the nozzle exit continuously decreases,but the average velocity in the motor exit continuously increases.Overall,when the helium flow rate is 2.5 kg/s,the specific impulse can reach 10.5%.Reducing the helium injection hole diameter enhances mixing of helium and combustion gas and expands the velocity increase zone,thereby maximizing the exit velocity gain in average velocity at the nozzle exit.When the injection hole diameter is reduced from 100 mm to 20 mm,the specific impulse gain increases from 3.1%to 10.6%.Furthermore,increasing helium injection temperature greatly boosts the velocity of the mixed gas with the same helium mass fraction ultimately improving specific impulse.展开更多
Prelaunch rolling of maritime rockets threatens the reliability of launch in rough sea conditions.In order to suppress the prelaunch rolling,this study introduces advanced smart prediction designed especially for mari...Prelaunch rolling of maritime rockets threatens the reliability of launch in rough sea conditions.In order to suppress the prelaunch rolling,this study introduces advanced smart prediction designed especially for maritime rockets.The suggested approach introduces a hybrid model that combines random forest(RF)and Adaptive boosting(Ada Boost)methods to describe the coupling mechanism of factors affecting rocket rolling and to suppress the rolling.This combination improves forecast accuracy.Thereafter,the dimensionality reduced response surfaces are used to visually present the coupling between rocket rolling and influencing factors,which reveals the prelaunch rolling mechanism.When angle between the launch device and the ship's bow is within 80°-100°,the dynamic friction coefficient between adapters and guideways is 0.4,and the dynamic friction coefficient between the rocket and launchpad is within 0-0.15 or0.5-0.7,the prelaunch rolling of rocket during one motion cycle of the ship is less than 0.065°,originally 0.27°,reduced by 75.93%,effectively suppressing the prelaunch rolling.This study improves the prelaunch stability of maritime rockets in rough sea conditions and establishes a mapping relationship between the factors affecting rocket rolling and the structure of the sea launch system,guiding the optimization of future sea launch systems.展开更多
Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this stud...Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.展开更多
The effects of random long-range connections （shortcuts） on the transitions of neural firing patterns in coupled Hindmarsh-Rose neurons are investigated, where each neuron is subjected to an external current. It is ...The effects of random long-range connections （shortcuts） on the transitions of neural firing patterns in coupled Hindmarsh-Rose neurons are investigated, where each neuron is subjected to an external current. It is found that, on one hand, the system can achieve the transition of neural firing patterns from the fewer-period state to the multi-period one, when the number of the added shortcuts in the neural network is greater than a threshold value, indicating the occurrence of in-transition of neural firing patterns. On the other hand, for a stronger coupling strength, we can also find the similar but reverse results by adding some proper random connections. In addition, the influences of system size and coupling strength on such transition behavior, as well as the internality between the transition degree of firing patterns and its critical characteristics for different external stimulation current, are also discussed.展开更多
This study proposes a novel general image fusion framework based on cross-domain long-range learning and Swin Transformer,termed as SwinFusion.On the one hand,an attention-guided cross-domain module is devised to achi...This study proposes a novel general image fusion framework based on cross-domain long-range learning and Swin Transformer,termed as SwinFusion.On the one hand,an attention-guided cross-domain module is devised to achieve sufficient integration of complementary information and global interaction.More specifically,the proposed method involves an intra-domain fusion unit based on self-attention and an interdomain fusion unit based on cross-attention,which mine and integrate long dependencies within the same domain and across domains.Through long-range dependency modeling,the network is able to fully implement domain-specific information extraction and cross-domain complementary information integration as well as maintaining the appropriate apparent intensity from a global perspective.In particular,we introduce the shifted windows mechanism into the self-attention and cross-attention,which allows our model to receive images with arbitrary sizes.On the other hand,the multi-scene image fusion problems are generalized to a unified framework with structure maintenance,detail preservation,and proper intensity control.Moreover,an elaborate loss function,consisting of SSIM loss,texture loss,and intensity loss,drives the network to preserve abundant texture details and structural information,as well as presenting optimal apparent intensity.Extensive experiments on both multi-modal image fusion and digital photography image fusion demonstrate the superiority of our SwinFusion compared to the state-of-theart unified image fusion algorithms and task-specific alternatives.Implementation code and pre-trained weights can be accessed at https://github.com/Linfeng-Tang/SwinFusion.展开更多
Analyses of the soil moisture evolution trend and the influence of different types of radiation on soil moisture are of great significance to the simulation and prediction of soil moisture.In this paper,soil moisture(...Analyses of the soil moisture evolution trend and the influence of different types of radiation on soil moisture are of great significance to the simulation and prediction of soil moisture.In this paper,soil moisture(2–60 cm) and various radiation data from 2014–2015 at the A’rou superstation were selected.The radiation data include the net radiation(NR),shortwave and longwave radiation(SR and LR).Using adaptive fractal analysis(AFA),the long-range correlation(LRC) of soil moisture and long-range cross correlation(LRCC) between moisture and three types of radiation were analyzed at different timescales and soil depths.The results show that:(1) Persistence of soil moisture and consistency between soil moisture and radiation mutate at 18-d and 6-d timescales,respectively.The timescale variation of soil moisture persistence is mainly related to the influence process of radiation on soil moisture;(2) Both the soil moisture persistence and soil moisture-radiation consistency vary substantially with soil depth.The soil depth variation of soil moisture persistence is related to the influence intensity of radiation;(3) From 2–6 day timescales,LR displays the strongest influence on soil moisture at depths of 2–10 cm through negative feedback of radiation on the soil temperature.The influence intensity decreases with depth from 2–15 cm.Therefore,the soil moisture persistence is weak and increases with depth from 2–15 cm;and(4) At more than 6 day timescales,SR and NR display a stronger influence on the soil moisture persistence at depths of 2–40 cm through positive feedback of radiation on the soil temperature,especially at depths of 2–10 cm.This influence also weakens with depth.The soil moisture persistence at depths of 2–10 cm is the weakest and increases with depth from 2–40 cm.The research results are instructive for determining timescales and soil depths related to soil water in hydrological models.展开更多
Air temperature(AT) is a subsystem of a complex climate.Long-range correlation(LRC) is an important feature of complexity.Our research attempt to evaluate AT’s complexity differences in different land-use types in th...Air temperature(AT) is a subsystem of a complex climate.Long-range correlation(LRC) is an important feature of complexity.Our research attempt to evaluate AT’s complexity differences in different land-use types in the Heihe River Basin(HRB) based on the stability and LRC.The results show the following:(1) AT’s stability presents differences in different land-use types.In agricultural land,there is no obvious variation in the trend throughout the year.Whereas in a desert,the variation in the trend is obvious: the AT is more stable in summer than it is in winter,with Ta ranges of [8,20]°C and SD of the AT residual ranges of [0.2,0.7],respectively.Additionally,in mountainous areas,when the altitude is beyond a certain value,AT’s stability changes.(2) AT’s LRC presents differences in different land-use types.In agricultural land,the long-range correlation of AT is the most persistent throughout the year,showing the smallest difference between summer and winter,with the Hs range of [0.8,1].Vegetation could be an important factor.In a desert,the long-range correlation of AT is less persistent,showing the greatest difference between summer and winter,with the Hs range of [0.54,0.96].Solar insolation could be a dominant factor.In an alpine meadow,the long-range correlation of AT is the least persistent throughout the year,presenting a smaller difference between summer and winter,with the Hs range of [0.6,0.85].Altitude could be an important factor.(3) Usually,LRC is a combination of the Ta and SD of the AT residuals.A larger Ta and smaller SD of the AT residual would be conducive to a more persistent LRC,whereas a smaller Ta and larger SD of the AT residual would limit the persistence of LRC.A larger Ta and SD of the AT residual would create persistence to a degree between those of the first two cases,as would a smaller Ta and SD of the AT residual.In addition,the last two cases might show the same LRC.展开更多
The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.He...The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.展开更多
The long-range transport of oxidized sulfur（sulfur dioxide（SO2） and sulfate） and oxidized nitrogen（nitrogen oxides（NOx ） and nitrate） in East Asia is an area of increasing scientific interest and political con...The long-range transport of oxidized sulfur（sulfur dioxide（SO2） and sulfate） and oxidized nitrogen（nitrogen oxides（NOx ） and nitrate） in East Asia is an area of increasing scientific interest and political concern. This paper reviews various published papers, including ground- and satellite-based observations and numerical simulations. The aim is to assess the status of the anthropogenic emissions of SO2 and NOx and the long-range transport of oxidized S and N pollutants over source and downwind region. China has dominated the emissions of SO2 and NOx in East Asia and urgently needs to strengthen the control of their emissions, especially NOx emissions. Oxidized S and N pollutants emitted from China are transported to Korea and Japan, due to persistent westerly winds, in winter and spring.However, the total contributions of China to S and N pollutants across Korea and Japan were not found to be dominant over longer time scales（e.g., a year）. The source–receptor relationships for oxidized S and N pollutants in East Asia varied widely among the different studies. This is because：（1） the nonlinear effects of atmospheric chemistry and deposition processes were not well considered, when calculating the source–receptor relationships;（2） different meteorological and emission data inputs and solution schemes for key physical and chemical processes were used; and（3） different temporal and spatial scales were employed. Therefore, simulations using the same input fields and similar model configurations would be of benefit, to further evaluate the source–receptor relationships of the oxidized S and N pollutants.展开更多
In order to explore the possible diffusion distance of carbon during proeutectoid ferrite transformation, a slow cooling test of low carbon steel was carried out under vacuum of the thermal simulator. The microstructu...In order to explore the possible diffusion distance of carbon during proeutectoid ferrite transformation, a slow cooling test of low carbon steel was carried out under vacuum of the thermal simulator. The microstructure and thermal expansion curve were discussed and the carbon concentration inside the sample was measured. The ferrite layer of about 450 μm thickness was obtained without pearlite on the surface of the sample in the microstructure. The thermal expansion curve shows that the ferrite layer without pearlite is formed during the local phase transformation, which is followed by the global transformation. The carbon concentration in the core of the sample (0.061%) is significantly higher than that of the bulk material (0.054%). All results show that carbon has long-range diffusion from the outer layer to the inner layer of the sample. The transformation is predominantly interface-controlled mode during local transformation, and the interface migration rate is about 2.25 μm/s.展开更多
In recent years,it has been proposed to use satellite-mounted radio-frequency(RF)accelerators to produce high-current relativistic electron beams to complete debris removal tasks.However,when simulating the long-range...In recent years,it has been proposed to use satellite-mounted radio-frequency(RF)accelerators to produce high-current relativistic electron beams to complete debris removal tasks.However,when simulating the long-range propagation(km-range)process of the electron beam,it is difficult to directly use the particle-in-cell method to simultaneously consider the space charge effect of beam and the influence of the geomagnetic field.Owing to these limitations,in this paper,we proposed a simplified method.The ps-range electronic micropulses emitted by the RF accelerator were transmitted and fused to form a ns-range electron beam;then,combined with the improved moving window technology,the model was constructed to simulate the long-range propagation process of the relativistic electron beam in near-Earth environment.Finally,by setting the direction of movement of the beam to be parallel,perpendicular and at an inclination of 3°to the magnetic field,we analyzed and compared the effects of the applied magnetic fields in different directions on the quality of the beam during long-range propagation.The simulation results showed that the parallel state of the beam motion and magnetic fields should be achieved as much as possible to ensure the feasibility of the space debris removal.展开更多
基金Project Funded by Chongqing Changjiang Electrical Appliances Industries Group Co.,Ltd
文摘Accurate navigation is important for long-range rocket projectile＇s precise striking. To obtain stable and high-per- formance navigation result, a ultra-tight global positioning system/inertial navigation system （GPS/INS） integration based nav- igation approach is proposed. The accurate short-time output of INS is used by GPS receiver to assist in acquisition of signal, and output information of INS and GPS is fused based on federated filter. Meanwhile, the improved cubature Kalman filter with strong tracking ability is chosen to serve as the local filter, and then the federated filter is enhanced based on vector sharing theory. Finally, simulation results show that the navigation accuracy with the proposed method is higher than that with traditional methods. It provides reference for long-range rocket projectile navigation.
基金supported by National Basic Research Program of China(No.613222)。
文摘With the improvement of the accuracy of the inertial system,the influence of the disturbing gravity field on the accuracy of long-range rocket has become increasingly prominent.However,in actual engineering,there are problems of low accuracy and being time-consuming for disturbing gravity field compensation.In view of this,this paper proposes a set of online comprehensive solutions combining disturbing gravity reconstruction and stellar correction.According to the pre-launch binding parameters,the net function assignment method is used in the navigation system to calculate disturbing gravity in the boost phase online.In the guidance system,a closed-loop guidance online compensation method is proposed based on the state-space perturbation method for the disturbing gravity in the coast phase.At the same time,the vertical deflection can also be corrected by stellar guidance.The calculation results are simulated and verified under different circumstances.Simulation results show that the proposed online compensation algorithm has an accuracy improvement compared with the element compensation algorithm on ground.And the stellar guidance algorithm can further correct the impact deviation.The impact deviation after comprehensive compensation does not exceed 50 m,and the compensation percentage is greater than 65%.
文摘In the field of intelligent air combat,real-time and accurate recognition of within-visual-range(WVR)maneuver actions serves as the foundational cornerstone for constructing autonomous decision-making systems.However,existing methods face two major challenges:traditional feature engineering suffers from insufficient effective dimensionality in the feature space due to kinematic coupling,making it difficult to distinguish essential differences between maneuvers,while end-to-end deep learning models lack controllability in implicit feature learning and fail to model high-order long-range temporal dependencies.This paper proposes a trajectory feature pre-extraction method based on a Long-range Masked Autoencoder(LMAE),incorporating three key innovations:(1)Random Fragment High-ratio Masking(RFH-Mask),which enforces the model to learn long-range temporal correlations by masking 80%of trajectory data while retaining continuous fragments;(2)Kalman Filter-Guided Objective Function(KFG-OF),integrating trajectory continuity constraints to align the feature space with kinematic principles;and(3)Two-stage Decoupled Architecture,enabling efficient and controllable feature learning through unsupervised pre-training and frozen-feature transfer.Experimental results demonstrate that LMAE significantly improves the average recognition accuracy for 20-class maneuvers compared to traditional end-to-end models,while significantly accelerating convergence speed.The contributions of this work lie in:introducing high-masking-rate autoencoders into low-informationdensity trajectory analysis,proposing a feature engineering framework with enhanced controllability and efficiency,and providing a novel technical pathway for intelligent air combat decision-making systems.
基金supported by the National Natural Science Foundation of China(Nos.21573059,12274118 and 22208088)Henan Center for Outstanding Overseas Scientists(No.GZS2023007)Special Project for Fundamental Research in University of Henan Province(No.22ZX013)。
文摘Sluggish sulfur conversion kinetics pose an ongoing challenge in lithium-sulfur batteries(LSBs).Here,we present a solution through far-reaching long-range electronic regulation(LRER)on single-atom active sites.N-doped carbons(Co-NC)are implanted with densely-distributed Co single atoms,and supported on Ti_(3)C_(2)T_(x)MXene substrates to assemble 3D Co-NC/MXene catalyst.MXene effectively mediates interlayer charge transfer(~0.70|e|)contrasted with popular carbon materials(~0.06|e|)to produce LRER through surrounding carbon atoms.The synergy of LRER with near-range electronic regulation(NRER)tunes electronic structures,and enhances heterostructural stability,thus provoking desirous catalytic kinetics of Co single atoms in sulfur reduction.Thereby,the Co-NC/MXene/S cathodes exhibit impressive rate performance and excellent cycling stability(only 0.015%capacity decay per cycle over 600 cycles at 4 C)in LSBs,surpassing state-of-the-art sulfur cathodes.This work reveals the importance of LRER for improved catalysis,and provides new guidance to tailor heterostructures to achieve high-efficient catalysts in various process.
基金supports by the National Natural Science Foundation of China(NSFC,Grant No.52271113)the Natural Science Foundation of Shaanxi Province,China(2020JM 218)the Fundamental Research Funds for the Central Universities(CHD300102311405)。
文摘Catalysts with asymmetric coordination exhibit excellent electrocatalytic activity due to changes in the active sites,which affect the arrangement of reactants and catalytic activity/selectivity.Hence,the exploration of the inherent characteristics of active sites within diverse coordination environments holds great significance for the experimental design of catalytic structures.Single-atom catalysts(SACs)characterized by high coordination with four carbons(26 candidates)and low coordination with dinitrogen(27candidates)are constructed using nitrogen-doped graphdiyne derivatives(NGDY)as the substrate.Additionally,5 species of dual-atom catalysts(DACs)with coexistence of both high and low coordination sites are also developed and their nitrogen reduction reaction(NRR)activities are systematically investigated by density functional theory.The results indicate that metals with low coordination exhibit superior catalytic performance,such as Mo^(L)-NGDY(U_(L)=-0.30 V)and Nb^(L)-NGDY(U_(L)=-0.32 V).Furthermore,machine learning(ML)methods have deeply analyzed and elucidated the primary intrinsic characteristics that influence catalytic performance.These results not only unveil the underlying mechanisms behind the exceptional catalytic performance exhibited by low-coordination metal atoms,but also provide relevant and significant descriptors.More importantly,based on an investigation of the catalytic activity of a series of DACs,the“buffer and low-coordination accumulate”asymmetric coordination mechanism is proposed to unveil the long-range interactions between low and high coordination atoms.Due to this remote communication,MoNb-NGDY(U_(L)=-0.09/-0.37 V)exhibits the best NRR activity.This mechanism provides valuable insights into the origin of long-range bipartite interactions and inspires the design and synthesis of NRR catalysts with different coordination environments.
基金supported by the National Natural Science Foundation of China(Grant No.11962002)the Innovation Project of the Guangxi Graduate Education(Grant Nos.YCBZ2021021 and YCSW2022070).
文摘A Hamiltonian mean-field model with long-range four-body interactions is proposed.The model describes a long-range mean-field system in which N unit-mass particles move on a unit circle.Each particleθi interacts with any three other particles through an infinite-range cosine potential with an attractive interaction(ε>0).By applying a method that remaps the average phase of global particle pairs onto a new unit circle,and using the saddle-point technique,the partition function is solved analytically after introducing four-body interactions,yielding expressions for the free energy f and the energy per particle U.These results were further validated through numerical simulations.The results show that the system undergoes a second-order phase transition at the critical energy Uc.Specifically,the critical energy corresponds to U_(c)=0.32 when the coupling constantε=5,and U_(c)=0.63 whenε=10.Finally,we calculated the system’s largest Lyapunov exponentλand kinetic energy fluctuationsΣthrough numerical simulations.It is found that the peak of the largest Lyapunov exponentλoccurs slightly below the critical energy Uc,which is consistent with the point of maximum kinetic energy fluctuationsΣ.And there is a scaling law ofΣ/N^(1/2)∝λbetween them.
基金supported by the National Natural Science Foundation of China(Grant No.12375025).
文摘We investigate the parity-time(PT)symmetry-breaking quantum phase transition in a one-dimensional(1D)bosonic lattice featuring cavity-mediated long-range interactions and spatially staggered dissipation.By mapping the system to an effective spin chain under the constraints of hard-core bosons and integrating the mean-field decoupling approach with biorthogonal basis formalism,we derive a self-consistency equation.Numerical simulation results validate that the derived equation quantitatively captures thePT-symmetry order parameter’s phase diagram.Our findings reveal that coherent hopping maintainsPTsymmetry through quantum fluctuations.Conversely,cavity-engineered long-range interactions,in synergy with staggered dissipation,act in opposition to drive symmetry breaking.This competitive interplay can inspire further exploration of tunable quantum phase transitions in non-Hermitian systems.
基金supported by the Director General,Indian Council of Agricultural Research(ICAR),New Delhithe Director,ICAR-National Rice Research Institute,Cuttack.
文摘Consecutive stresses,such as initial submergence during germination followed by water deficit during the seedling stage,pose significant challenges to direct-seeded rice cultivation.By Linkage disequilibrium analysis,Sub1 and Dro1(Δbp:10 Mb),as well as Sub1 and TPP7(Δbp:6 Mb)were identified to exhibit long-range linkage disequilibrium(LRLD).Meta-QTL analysis further revealed that Sub1 and TPP7 co-segregated for tolerance to submergence at the germination and seedling stages.Based on this,we hypothesized that LRLD might influence plant responses to consecutive stresses.To test this hypothesis,we developed a structured recombinant inbred line population from a cross between Bhalum 2 and Nagina 22,with alleles(Sub1 and TPP7)in linkage equilibrium.Mendelian randomization analysis validated that the parental alleles,rather than the recombinant alleles of Sub1 and TPP7,significantly influenced 13 out of 41 traits under consecutive stress conditions.Additionally,16 minor additive effect QTLs were detected between the genomic regions,spanning Sub1 and TPP7 for various traits.A single allele difference between these genomic regions enhanced crown root number,root dry weight,and specific root area by 11.45%,15.69%,and 33.15%,respectively,under flooded germination conditions.Candidate gene analysis identified WAK79 and MRLK59 as regulators of stress responses during flooded germination,recovery,and subsequent water deficit conditions.These findings highlight the critical role of parental allele combinations and genomic regions between Sub1 and TPP7 in regulating the stress responses under consecutive stresses.Favourable haplotypes derived from these alleles can be utilized to improve stress resilience in direct-seeded rice.
基金co-supported by the Fundamental Research Funds for Central Universities,China(No.3072024XX0206)the Natural Science Foundation of Heilongjiang Province,China(No.LH2024E069)。
文摘A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effects of helium injection on the burning rate and combustion of AP/HTPB propellant are analyzed in details,and the characteristics of motor performance are obtained.The numerical simulation results demonstrate that helium injection enhances the combustion chamber pressure,thereby increasing the burning rate of propellant.However,the primary combustion reaction of the AP/HTPB propellant takes place within a thin layer on the burning surface,so the low-temperature helium has minimal impact on the gasphase combustion.Ultimately,the helium not only elevates the nozzle exit velocity,resulting in specific impulse gain,but also reduces the exhaust plume temperature.With an increase of helium mass flow rate,the area of the velocity increase zone at the nozzle exit continuously decreases,but the average velocity in the motor exit continuously increases.Overall,when the helium flow rate is 2.5 kg/s,the specific impulse can reach 10.5%.Reducing the helium injection hole diameter enhances mixing of helium and combustion gas and expands the velocity increase zone,thereby maximizing the exit velocity gain in average velocity at the nozzle exit.When the injection hole diameter is reduced from 100 mm to 20 mm,the specific impulse gain increases from 3.1%to 10.6%.Furthermore,increasing helium injection temperature greatly boosts the velocity of the mixed gas with the same helium mass fraction ultimately improving specific impulse.
文摘Prelaunch rolling of maritime rockets threatens the reliability of launch in rough sea conditions.In order to suppress the prelaunch rolling,this study introduces advanced smart prediction designed especially for maritime rockets.The suggested approach introduces a hybrid model that combines random forest(RF)and Adaptive boosting(Ada Boost)methods to describe the coupling mechanism of factors affecting rocket rolling and to suppress the rolling.This combination improves forecast accuracy.Thereafter,the dimensionality reduced response surfaces are used to visually present the coupling between rocket rolling and influencing factors,which reveals the prelaunch rolling mechanism.When angle between the launch device and the ship's bow is within 80°-100°,the dynamic friction coefficient between adapters and guideways is 0.4,and the dynamic friction coefficient between the rocket and launchpad is within 0-0.15 or0.5-0.7,the prelaunch rolling of rocket during one motion cycle of the ship is less than 0.065°,originally 0.27°,reduced by 75.93%,effectively suppressing the prelaunch rolling.This study improves the prelaunch stability of maritime rockets in rough sea conditions and establishes a mapping relationship between the factors affecting rocket rolling and the structure of the sea launch system,guiding the optimization of future sea launch systems.
基金financial support from the National Key Research and Development Program(Grant No.2024YFA1209801)the National Natural Science Foundation of China(Grant Nos.12302140,12325204)+4 种基金the China Postdoctoral Science Foundation(Grant No.2023M732794)the Fundamental Research Funds for the Central Universities of China(Grant No.sxzy012023213)the Scientific Research Program of Shaanxi Province(Grant No.2023JC-XJ-02)the Young Talent Support Program of Xi'an Science and Technology Association(Grant No.959202413069)Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(Grant No.GZB20230575)。
文摘Hypervelocity rocket sled systems are critical for testing advanced military technologies,yet track damage at speeds exceeding Mach 5 remains a significant challenge for system reliability and performance.In this study,we investigated the hypervelocity impact response and protection for highstrength U71 Mn or bainitic steel used in rocket sled tracks.Flyer plate impact experiments using a two-stage light-gas gun were conducted to study the hypervelocity collision response,followed by the microstructural characterization via optical microscope,scanning electron microscopy equipped with electron backscatter diffraction to reveal underlying damage mechanisms.Then,the calibrated thermalmechanical coupled finite element simulations using the Johnson-Cook constitutive model and MieGrüneisen equation of state were carried out.Results indicated that bainitic steel exhibits superior impact resistance with predominantly smooth scratch-dominated damage due to its higher ductility.In contrast,U71 Mn suffered significant material spallation and crack propagation arising from brittle fracture mechanisms.Zinc-rich epoxy primer coatings effectively mitigated stress concentration and temperature rise in the substrate at impacting velocities below 2.4 km/s,so as to suppress the microstructural damage such as adiabatic shear bands and dynamic recrystallization.However,coating protection diminished at ultra-high-speed impacts due to the coating failure.Dimensional analysis established quantitative relationships of the gouge damage size to projectile mass,impact velocity,and material yield strength.This study provides in-depth insights into damage mechanisms in hypervelocity rail systems,demonstrating that bainitic steel combined with protective coatings can significantly enhance impact resistance and system reliability,offering valuable guidance for the design and optimization of hypervelocity testing platforms.
文摘The effects of random long-range connections （shortcuts） on the transitions of neural firing patterns in coupled Hindmarsh-Rose neurons are investigated, where each neuron is subjected to an external current. It is found that, on one hand, the system can achieve the transition of neural firing patterns from the fewer-period state to the multi-period one, when the number of the added shortcuts in the neural network is greater than a threshold value, indicating the occurrence of in-transition of neural firing patterns. On the other hand, for a stronger coupling strength, we can also find the similar but reverse results by adding some proper random connections. In addition, the influences of system size and coupling strength on such transition behavior, as well as the internality between the transition degree of firing patterns and its critical characteristics for different external stimulation current, are also discussed.
基金This work was supported by the National Natural Science Foundation of China(62075169,62003247,62061160370)the Key Research and Development Program of Hubei Province(2020BAB113).
文摘This study proposes a novel general image fusion framework based on cross-domain long-range learning and Swin Transformer,termed as SwinFusion.On the one hand,an attention-guided cross-domain module is devised to achieve sufficient integration of complementary information and global interaction.More specifically,the proposed method involves an intra-domain fusion unit based on self-attention and an interdomain fusion unit based on cross-attention,which mine and integrate long dependencies within the same domain and across domains.Through long-range dependency modeling,the network is able to fully implement domain-specific information extraction and cross-domain complementary information integration as well as maintaining the appropriate apparent intensity from a global perspective.In particular,we introduce the shifted windows mechanism into the self-attention and cross-attention,which allows our model to receive images with arbitrary sizes.On the other hand,the multi-scene image fusion problems are generalized to a unified framework with structure maintenance,detail preservation,and proper intensity control.Moreover,an elaborate loss function,consisting of SSIM loss,texture loss,and intensity loss,drives the network to preserve abundant texture details and structural information,as well as presenting optimal apparent intensity.Extensive experiments on both multi-modal image fusion and digital photography image fusion demonstrate the superiority of our SwinFusion compared to the state-of-theart unified image fusion algorithms and task-specific alternatives.Implementation code and pre-trained weights can be accessed at https://github.com/Linfeng-Tang/SwinFusion.
基金National Key R&D Program of China,No.2017YFB0504102National Natural Science Foundation of China No.41771537
文摘Analyses of the soil moisture evolution trend and the influence of different types of radiation on soil moisture are of great significance to the simulation and prediction of soil moisture.In this paper,soil moisture(2–60 cm) and various radiation data from 2014–2015 at the A’rou superstation were selected.The radiation data include the net radiation(NR),shortwave and longwave radiation(SR and LR).Using adaptive fractal analysis(AFA),the long-range correlation(LRC) of soil moisture and long-range cross correlation(LRCC) between moisture and three types of radiation were analyzed at different timescales and soil depths.The results show that:(1) Persistence of soil moisture and consistency between soil moisture and radiation mutate at 18-d and 6-d timescales,respectively.The timescale variation of soil moisture persistence is mainly related to the influence process of radiation on soil moisture;(2) Both the soil moisture persistence and soil moisture-radiation consistency vary substantially with soil depth.The soil depth variation of soil moisture persistence is related to the influence intensity of radiation;(3) From 2–6 day timescales,LR displays the strongest influence on soil moisture at depths of 2–10 cm through negative feedback of radiation on the soil temperature.The influence intensity decreases with depth from 2–15 cm.Therefore,the soil moisture persistence is weak and increases with depth from 2–15 cm;and(4) At more than 6 day timescales,SR and NR display a stronger influence on the soil moisture persistence at depths of 2–40 cm through positive feedback of radiation on the soil temperature,especially at depths of 2–10 cm.This influence also weakens with depth.The soil moisture persistence at depths of 2–10 cm is the weakest and increases with depth from 2–40 cm.The research results are instructive for determining timescales and soil depths related to soil water in hydrological models.
基金Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA23100303
文摘Air temperature(AT) is a subsystem of a complex climate.Long-range correlation(LRC) is an important feature of complexity.Our research attempt to evaluate AT’s complexity differences in different land-use types in the Heihe River Basin(HRB) based on the stability and LRC.The results show the following:(1) AT’s stability presents differences in different land-use types.In agricultural land,there is no obvious variation in the trend throughout the year.Whereas in a desert,the variation in the trend is obvious: the AT is more stable in summer than it is in winter,with Ta ranges of [8,20]°C and SD of the AT residual ranges of [0.2,0.7],respectively.Additionally,in mountainous areas,when the altitude is beyond a certain value,AT’s stability changes.(2) AT’s LRC presents differences in different land-use types.In agricultural land,the long-range correlation of AT is the most persistent throughout the year,showing the smallest difference between summer and winter,with the Hs range of [0.8,1].Vegetation could be an important factor.In a desert,the long-range correlation of AT is less persistent,showing the greatest difference between summer and winter,with the Hs range of [0.54,0.96].Solar insolation could be a dominant factor.In an alpine meadow,the long-range correlation of AT is the least persistent throughout the year,presenting a smaller difference between summer and winter,with the Hs range of [0.6,0.85].Altitude could be an important factor.(3) Usually,LRC is a combination of the Ta and SD of the AT residuals.A larger Ta and smaller SD of the AT residual would be conducive to a more persistent LRC,whereas a smaller Ta and larger SD of the AT residual would limit the persistence of LRC.A larger Ta and SD of the AT residual would create persistence to a degree between those of the first two cases,as would a smaller Ta and SD of the AT residual.In addition,the last two cases might show the same LRC.
基金the support of the National Natural Science Foundation of China (22002118,22208262,52271228,52202298,52201279,51834009,51801151)the Natural Science Foundation of Shaanxi Province (2021JQ-468,2020JZ-47)+2 种基金the Natural Science Foundation of Shaanxi Provincial Department of Education (21JP086)the Postdoctoral Research Foundation of China (2020 M683528,2020TQ0245,2018M633643XB)the Hundred Talent Program of Shaanxi Province。
文摘The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.
基金supported by the National Natural Science Foundation of China (Nos. 41175105, 41175018, 41405121,41475113, 41505091, 41575124, and 91544221)the Key Project of the Chinese Academy of Sciences (No. XDB05030301)the Carbon and Nitrogen Cycle Project of the Institute of Atmospheric Physics, Chinese Academy of Sciences
文摘The long-range transport of oxidized sulfur（sulfur dioxide（SO2） and sulfate） and oxidized nitrogen（nitrogen oxides（NOx ） and nitrate） in East Asia is an area of increasing scientific interest and political concern. This paper reviews various published papers, including ground- and satellite-based observations and numerical simulations. The aim is to assess the status of the anthropogenic emissions of SO2 and NOx and the long-range transport of oxidized S and N pollutants over source and downwind region. China has dominated the emissions of SO2 and NOx in East Asia and urgently needs to strengthen the control of their emissions, especially NOx emissions. Oxidized S and N pollutants emitted from China are transported to Korea and Japan, due to persistent westerly winds, in winter and spring.However, the total contributions of China to S and N pollutants across Korea and Japan were not found to be dominant over longer time scales（e.g., a year）. The source–receptor relationships for oxidized S and N pollutants in East Asia varied widely among the different studies. This is because：（1） the nonlinear effects of atmospheric chemistry and deposition processes were not well considered, when calculating the source–receptor relationships;（2） different meteorological and emission data inputs and solution schemes for key physical and chemical processes were used; and（3） different temporal and spatial scales were employed. Therefore, simulations using the same input fields and similar model configurations would be of benefit, to further evaluate the source–receptor relationships of the oxidized S and N pollutants.
基金Project(16PJ1430200)supported by Shanghai Pujiang Program,China
文摘In order to explore the possible diffusion distance of carbon during proeutectoid ferrite transformation, a slow cooling test of low carbon steel was carried out under vacuum of the thermal simulator. The microstructure and thermal expansion curve were discussed and the carbon concentration inside the sample was measured. The ferrite layer of about 450 μm thickness was obtained without pearlite on the surface of the sample in the microstructure. The thermal expansion curve shows that the ferrite layer without pearlite is formed during the local phase transformation, which is followed by the global transformation. The carbon concentration in the core of the sample (0.061%) is significantly higher than that of the bulk material (0.054%). All results show that carbon has long-range diffusion from the outer layer to the inner layer of the sample. The transformation is predominantly interface-controlled mode during local transformation, and the interface migration rate is about 2.25 μm/s.
基金supported by National Natural Science Foundation of China (Nos. 61372050, U1730247)
文摘In recent years,it has been proposed to use satellite-mounted radio-frequency(RF)accelerators to produce high-current relativistic electron beams to complete debris removal tasks.However,when simulating the long-range propagation(km-range)process of the electron beam,it is difficult to directly use the particle-in-cell method to simultaneously consider the space charge effect of beam and the influence of the geomagnetic field.Owing to these limitations,in this paper,we proposed a simplified method.The ps-range electronic micropulses emitted by the RF accelerator were transmitted and fused to form a ns-range electron beam;then,combined with the improved moving window technology,the model was constructed to simulate the long-range propagation process of the relativistic electron beam in near-Earth environment.Finally,by setting the direction of movement of the beam to be parallel,perpendicular and at an inclination of 3°to the magnetic field,we analyzed and compared the effects of the applied magnetic fields in different directions on the quality of the beam during long-range propagation.The simulation results showed that the parallel state of the beam motion and magnetic fields should be achieved as much as possible to ensure the feasibility of the space debris removal.
