T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection met...T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection methods face challenges owing to surface oxide scales,and conventional high-precision magnetic sensors are ineffective at high temperatures.To overcome these limitations,a small coil sensor was employed to measure the residual magnetism strength in oscillation traces,using metal magnetic memory and electromagnetic induction methods,which can carry out detection without an external excitation source.Using this technology,the proposed scheme successfully detects defects at high tempe-ratures(up to 670℃)without a cooling device.The key findings include the ability to detect both surface and near-surface defects,such as cracks and oscillation marks,with an enhanced signal-to-noise ratio(SNR)of 7.2 dB after signal processing.The method’s practicality was validated in a steel mill environment,where testing on casting slabs effectively detected defects,providing a foundation for improving industrial quality control.The proposed detection scheme offers a significant advancement in nondestructive testing(NDT)for high-temperature applications,contributing to more efficient and accurate monitoring of ferromagnetic material integrity.展开更多
In manganese electrolysis,electrochemical oscillations and manganese dendrite growth are typical nonlinear phenomena critical for energy consumption reduction.Nonetheless,existing research lacks a deep understanding o...In manganese electrolysis,electrochemical oscillations and manganese dendrite growth are typical nonlinear phenomena critical for energy consumption reduction.Nonetheless,existing research lacks a deep understanding of their underlying mechanisms.In this study,we systematically explored the evolution of anode electrochemical oscillations during manganese electrolysis and designed a square wave circuit to effectively suppress oscillations and dendrite growth while reducing energy consumption.A novel four-dimensional differential equation was introduced to explore the internal dynamic mechanisms of typical nonlinear behaviors.The experimental results showed that while the evolutionary patterns of current and potential oscillation signals were consistent,their waveform directions were opposite.The square wave current effectively suppressed both electrochemical oscillations and the growth of manganese dendrites.Furthermore,compared to direct current electrolysis,the square wave current improved the current efficiency by 3.6%and reduced the energy consumption by 0.32 kW·h·kg^(−1).展开更多
In this paper,we study the asymptotic behavior of the micropolar fluid flow through a thin domain,assuming zero Dirichlet boundary condition on the top boundary,which is rapidly oscillating,and non-standard boundary c...In this paper,we study the asymptotic behavior of the micropolar fluid flow through a thin domain,assuming zero Dirichlet boundary condition on the top boundary,which is rapidly oscillating,and non-standard boundary conditions on the flat bottom.Assuming“Reynolds roughness regime”,in which the thickness of the domain is very small compared to the wavelength of the roughness(i.e.a very slight roughness),we rigorously derive a generalized Reynolds equation for pressure,clearly showing the roughness-induced effects.Moreover,we give expressions for the average velocity and microrotation.展开更多
The influence of oscillation amplitude on molten pool thermal history,weld morphology characteristics,microstructural evolution,and mechanical properties during laser oscillating welding of QP980 steel was systematica...The influence of oscillation amplitude on molten pool thermal history,weld morphology characteristics,microstructural evolution,and mechanical properties during laser oscillating welding of QP980 steel was systematically investigated.Results show that laser beam oscillation significantly regulates molten pool thermomechanical behavior through optimized spatial energy distribution,thereby enabling microstructural reconstruction and joint performance enhancement.As the oscillation amplitude increases from 0 to 0.8 mm,the molten pool duration extends to 1.7 times the original value,while peak temperature and average cooling rate decrease by 19%and 39%,respectively.This thermal regulation promotes weld surface width expansion from 0.72 to 1.07 mm.The welding mode undergoes a progressive transition from keyhole mode→transitional mode→conduction mode.This transformation effectively suppresses porosity defects,substantially reducing porosity from 1.8%to 0.15%.Microstructural analysis indicates that oscillation modifies the maximum temperature gradient direction within the molten pool,facilitating preferential growth of coarse columnar grains along the welding centerline to establish load-transfer-favorable crystallographic orientations.The synergistic effects of these factors substantially improve joint mechanical properties:lap joint shear load increases by 81.5%(7.6→13.8 kN),and fracture elongation is enhanced by 135%(0.98→2.3 mm).The operational principles of laser oscillation parameters on the welding quality of QP980 steel were elucidated,providing theoretical foundations for joining process optimization.展开更多
Male sexual behaviors,including mounting,intromission,and ejaculation,are not only critical for reproduction but also serve as a model for understanding how the brain orchestrates sequential motor and motivational pro...Male sexual behaviors,including mounting,intromission,and ejaculation,are not only critical for reproduction but also serve as a model for understanding how the brain orchestrates sequential motor and motivational processes.While previous studies have identified key brain regions involved in sexual behaviors,such as the medial preoptic area(MPOA)and the nucleus accumbens(NAc)[14],the neural mechanisms governing the transitions between different phases of male sexual behavior remain poorly understood.展开更多
Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchroniza...Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.展开更多
Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity ...Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity in PD and LID has frequently been reported in recent cross-sectional studies.We aimed to investigate the temporal features of beta and gamma activity in the hyper-direct pathway during the development of PD and LID in rats,as well as the regulatory role of the dopamine receptors DI(D1Rs)and DIII(D3Rs)in these disorders.We recorded motor behavior and electrophysiological data during the development of PD and LID,and after interventions with D1R and D3R antagonists and agonists.We demonstrated exaggerated beta-band activity in the PD state and excessive gamma-band activity during on-state dyskinesia.Subsequently,process-dependent increased beta activity correlated with bradykinesia during PD modeling,while process-dependent increased gamma activity correlated with dyskinesia under the cumulative effects of levodopa during on-state dyskinesia.Finally,both D1Rs and D3Rs were found to be involved in regulating dyskinesia and gamma activity.Dynamic oscillations are closely associated with motor behavior,and mapping dynamic oscillations may be associated with optimizing deep brain stimulation parameters and developing personalized neurotherapeutic targeting.Moreover,D1Rs and D3Rs may ameliorate dyskinesia by mediating gamma oscillations.展开更多
Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium all...Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium alloy plates.To address these issues,circular oscillating laser welding combined with post-weld heat treatment was employed to improve the formation quality and mechanical properties of the welds.The effects of the frequency of circular oscillating laser on the forming quality,microstructure,and properties of the welds were analyzed.At an oscillation frequency of 200 Hz,the grain size in the weld zone was reduced compared to single laser welding,and the maximum tensile strength of the weld was observed to reach(264.96±1.33)MPa,representing approximately 61.19%of the base metal.Following the post-weld heat treatment of"solid solution and artificial aging",the grain boundary segregation was diminished.Nanoscale precipitated phases are present in the weld zone.Furthermore,the tensile strength was augmented to(386.35±5.65)MPa,representing approximately 89.23%of the strength of the base metal.The results of this study can provide a theoretical basis and technological reference for the circular oscillating laser welding of medium-thickness 2219-T 6 aluminium alloy plates.展开更多
Tunable mid-infrared and far-infrared laser output was demonstrated based on BaGa_(4)Se_(7)crystals and an optical parametric oscillator(OPO).With a 1.06μm Nd:YAG laser and a double-pass singly resonant OPO cavity,a ...Tunable mid-infrared and far-infrared laser output was demonstrated based on BaGa_(4)Se_(7)crystals and an optical parametric oscillator(OPO).With a 1.06μm Nd:YAG laser and a double-pass singly resonant OPO cavity,a laser energy output of 2.2 mJ at 10μm was obtained.By tuning the angle and temperature,a tunable laser output covering the wavelength range from 6μm to 17μm was obtained with a tuning precision better than 3 nm.The corresponding optical-to-optical conversion efficiency was 2.8%,and the slope efficiency was 4.4%.The damage effect of the output laser on detectors was also investigated,and point damage to the detector occurred at an output energy of 16.4μJ.The laser system has the advantages of miniaturization,a wide tuning range,high energy and high tuning resolution.Its broadband laser characteristics make it highly valuable for applications in atmospheric detection,infrared spectroscopy and electro-optical countermeasures.展开更多
Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this fie...Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this field has focused on systems in equilibrium or steady states.In this work,we demonstrate a room-temperature Rydberg atomic platform where the unidirectional propagation of light acts as a switch to mediate time-crystalline-like collective oscillations through atomic synchronization.展开更多
We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parame...We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.展开更多
Various factors,including weak tie-lines into the electric power system(EPS)networks,can lead to low-frequency oscillations(LFOs),which are considered an instant,non-threatening situation,but slow-acting and poisonous...Various factors,including weak tie-lines into the electric power system(EPS)networks,can lead to low-frequency oscillations(LFOs),which are considered an instant,non-threatening situation,but slow-acting and poisonous.Considering the challenge mentioned,this article proposes a clustering-based machine learning(ML)framework to enhance the stability of EPS networks by suppressing LFOs through real-time tuning of key power system stabilizer(PSS)parameters.To validate the proposed strategy,two distinct EPS networks are selected:the single-machine infinite-bus(SMIB)with a single-stage PSS and the unified power flow controller(UPFC)coordinated SMIB with a double-stage PSS.To generate data under various loading conditions for both networks,an efficient but offline meta-heuristic algorithm,namely the grey wolf optimizer(GWO),is used,with the loading conditions as inputs and the key PSS parameters as outputs.The generated loading conditions are then clustered using the fuzzy k-means(FKM)clustering method.Finally,the group method of data handling(GMDH)and long short-term memory(LSTM)ML models are developed for clustered data to predict PSS key parameters in real time for any loading condition.A few well-known statistical performance indices(SPI)are considered for validation and robustness of the training and testing procedure of the developed FKM-GMDH and FKM-LSTM models based on the prediction of PSS parameters.The performance of the ML models is also evaluated using three stability indices(i.e.,minimum damping ratio,eigenvalues,and time-domain simulations)after optimally tuned PSS with real-time estimated parameters under changing operating conditions.Besides,the outputs of the offline(GWO-based)metaheuristic model,proposed real-time(FKM-GMDH and FKM-LSTM)machine learning models,and previously reported literature models are compared.According to the results,the proposed methodology outperforms the others in enhancing the stability of the selected EPS networks by damping out the observed unwanted LFOs under various loading conditions.展开更多
The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The obj...The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The objective is to test the sensitivity of unsteady behaviors of shock waves in the ED nozzle to backpressure changing rate,and to further elucidate the thrust evolution mechanism and mode transition hysteresis.The movement of shock reflection points on the nozzle wall follows two flow mechanisms,namely,shock self-excited oscillations and rapid backpressure changes.A low backpressure changing rate enables shock self-excited oscillations,leading to a reciprocating motion of the shock waves accompanied by thrust oscillations,while a high backpressure changing rate suppresses the shock self-excited oscillations,leading to a unidirectional motion of the wave system on the nozzle shroud wall.A criterion for distinguishing ED nozzle operation modes is proposed,which relies on the loading inflection points of the nozzle pintle base and exhibits a fast and user-friendly feature.A dual-wake mode hysteresis region is defined to quantify the hysteresis in nozzle mode transition,with the span of the region decreasing as the backpressure changing rate slows down.The present work helps in understanding the unsteady flow mechanism and thrust evolution in ED nozzles.展开更多
Numerical models are crucial for quantifying the ocean-atmosphere interactions associated with the El Niño-Southern Oscillation(ENSO)phenomenon in the tropical Pacific.Current coupled models often exhibit signifi...Numerical models are crucial for quantifying the ocean-atmosphere interactions associated with the El Niño-Southern Oscillation(ENSO)phenomenon in the tropical Pacific.Current coupled models often exhibit significant biases and inter-model differences in simulating ENSO,underscoring the need for alternative modeling approaches.The Regional Ocean Modeling System(ROMS)is a sophisticated ocean model widely used for regional studies and has been coupled with various atmospheric models.However,its application in simulating ENSO processes on a basin scale in the tropical Pacific has not been explored.For the first time,this study presents the development of a basin-scale hybrid coupled model(HCM)for the tropical Pacific,integrating ROMS with a statistical atmospheric model that captures the interannual relationships between sea surface temperature(SST)and wind stress anomalies.The HCM is evaluated for its capability to simulate the annual mean,seasonal,and interannual variations of the oceanic state in the tropical Pacific.Results demonstrate that the model effectively reproduces the ENSO cycle,with a dominant oscillation period of approximately two years.The ROMS-based HCM developed here offers an efficient and robust tool for investigating climate variability in the tropical Pacific.展开更多
Deep learning(DL)has become a crucial technique for predicting the El Niño-Southern Oscillation(ENSO)and evaluating its predictability.While various DL-based models have been developed for ENSO predictions,many f...Deep learning(DL)has become a crucial technique for predicting the El Niño-Southern Oscillation(ENSO)and evaluating its predictability.While various DL-based models have been developed for ENSO predictions,many fail to capture the coherent multivariate evolution within the coupled ocean-atmosphere system of the tropical Pacific.To address this three-dimensional(3D)limitation and represent ENSO-related ocean-atmosphere interactions more accurately,a novel this 3D multivariate prediction model was proposed based on a Transformer architecture,which incorporates a spatiotemporal self-attention mechanism.This model,named 3D-Geoformer,offers several advantages,enabling accurate ENSO predictions up to one and a half years in advance.Furthermore,an integrated gradient method was introduced into the model to identify the sources of predictability for sea surface temperature(SST)variability in the eastern equatorial Pacific.Results reveal that the 3D-Geoformer effectively captures ENSO-related precursors during the evolution of ENSO events,particularly the thermocline feedback processes and ocean temperature anomaly pathways on and off the equator.By extending DL-based ENSO predictions from one-dimensional Niño time series to 3D multivariate fields,the 3D-Geoformer represents a significant advancement in ENSO prediction.This study provides details in the model formulation,analysis procedures,sensitivity experiments,and illustrative examples,offering practical guidance for the application of the model in ENSO research.展开更多
In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the syste...In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the system is analyzed by Poincar´e mapping,a time series diagram,and a bifurcation diagram.The results show that the new system has several significant characteristics.First,the new system has a constant Lyapunov exponent,transient chaos and one complete Feigenbaum tree.Second,the system has the phenomenon of bifurcation map shifts that depend on the initial conditions.In addition,we find periodic bursting oscillations,chaotic bursting oscillations,and the transition of chaotic bursting oscillations to periodic bursting oscillations.In particular,when the system parameters take different discrete values,the system generates a bubble phenomenon that varies with the initial conditions,and this bubble can be shifted with the initial values,which has rarely been seen in the previous literature.The implementation by field-programmable gate array(FPGA)and analog circuit simulation show close alignment with the MATLAB numerical simulation results,validating the system’s realizability.Additionally,the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.展开更多
The hook formation mechanism in continuously cast slabs of ultra-low carbon steel was analyzed in detail through numerical calculations and experimental observations using optical microscopy,and its distribution chara...The hook formation mechanism in continuously cast slabs of ultra-low carbon steel was analyzed in detail through numerical calculations and experimental observations using optical microscopy,and its distribution characteristics were determined.Numerical simulations confirmed that the freezing–overflow mechanism is the primary cause of hook formation.They also revealed that the freezing event occurs unpredictably,while the overflow event takes place during the positive strip time.The average pitch of oscillation marks(OMs)on the slab surface was 8.693 mm,while the theoretical pitch was 8.889 mm,with a difference of approximately 2%.This discrepancy primarily results from varying degrees of overflow,which affects the morphology of the OMs and the positions of their deepest points.Notably,this result further confirmed that the freezing and overflow in the meniscus were indeed caused by the periodic oscillation of the mold.Higher superheat hindered hook formation,leading to a negative correlation between the hook depth distribution around the slab and the temperature distribution within the mold.Therefore,the depth of the corner hook was greater than that of other positions,which was caused by the intensified cooling effect of the corner.Moreover,key factors influencing hook development were analyzed,providing insights into transient fluid flow and heat transfer characteristics within the mold.Transient fluid flow and heat transfer contributed to the randomness and tendency of hook formation.This randomness was reflected in the varying angles of the hooks,whereas the tendency was evident in the negative correlation between superheat and hook length.Based on the randomness and tendency of hook formation and its profile characteristics,a new method for controlling hook depth based on“sine law”is proposed.展开更多
Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.Thi...Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.展开更多
Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibrat...Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure.To reveal the oscillation mechanism of gas explosion load,the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m,and the explosion process was numerically analyzed using FLACS.The results show that the essential cause of oscillation effect is the reflection of the pressure wave.In addition,due to the difference in the propagation path of the pressure wave,the load oscillation frequency at the middle position of the tunnel is twice that at the end position.The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately,and the error is less than 15%.The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude.The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7%and 34.7%lower than the numerical results,respectively.The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load,and the difference between the theoretical and numerical results is only 4.6%.In the theoretical derivation of the overpressure model,an improved model of dynamic turbulence factor is established,which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence.Based on the one-dimensional propagation theory of pressure wave,the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation.The average error of amplitude and frequency is less than 20%.展开更多
文摘T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection methods face challenges owing to surface oxide scales,and conventional high-precision magnetic sensors are ineffective at high temperatures.To overcome these limitations,a small coil sensor was employed to measure the residual magnetism strength in oscillation traces,using metal magnetic memory and electromagnetic induction methods,which can carry out detection without an external excitation source.Using this technology,the proposed scheme successfully detects defects at high tempe-ratures(up to 670℃)without a cooling device.The key findings include the ability to detect both surface and near-surface defects,such as cracks and oscillation marks,with an enhanced signal-to-noise ratio(SNR)of 7.2 dB after signal processing.The method’s practicality was validated in a steel mill environment,where testing on casting slabs effectively detected defects,providing a foundation for improving industrial quality control.The proposed detection scheme offers a significant advancement in nondestructive testing(NDT)for high-temperature applications,contributing to more efficient and accurate monitoring of ferromagnetic material integrity.
基金support from the Fundamental Research Funds for the Central Universities(2022CDJQY-005,2024CDJXY010)the Guangxi Science and Technology Program(AB24010229)is greatly acknowledged.
文摘In manganese electrolysis,electrochemical oscillations and manganese dendrite growth are typical nonlinear phenomena critical for energy consumption reduction.Nonetheless,existing research lacks a deep understanding of their underlying mechanisms.In this study,we systematically explored the evolution of anode electrochemical oscillations during manganese electrolysis and designed a square wave circuit to effectively suppress oscillations and dendrite growth while reducing energy consumption.A novel four-dimensional differential equation was introduced to explore the internal dynamic mechanisms of typical nonlinear behaviors.The experimental results showed that while the evolutionary patterns of current and potential oscillation signals were consistent,their waveform directions were opposite.The square wave current effectively suppressed both electrochemical oscillations and the growth of manganese dendrites.Furthermore,compared to direct current electrolysis,the square wave current improved the current efficiency by 3.6%and reduced the energy consumption by 0.32 kW·h·kg^(−1).
文摘In this paper,we study the asymptotic behavior of the micropolar fluid flow through a thin domain,assuming zero Dirichlet boundary condition on the top boundary,which is rapidly oscillating,and non-standard boundary conditions on the flat bottom.Assuming“Reynolds roughness regime”,in which the thickness of the domain is very small compared to the wavelength of the roughness(i.e.a very slight roughness),we rigorously derive a generalized Reynolds equation for pressure,clearly showing the roughness-induced effects.Moreover,we give expressions for the average velocity and microrotation.
基金supported by the National Natural Science Foundation of China(Grant Nos.51805084 and 52474401)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2023B1515120086 and 2025A1515012873).
文摘The influence of oscillation amplitude on molten pool thermal history,weld morphology characteristics,microstructural evolution,and mechanical properties during laser oscillating welding of QP980 steel was systematically investigated.Results show that laser beam oscillation significantly regulates molten pool thermomechanical behavior through optimized spatial energy distribution,thereby enabling microstructural reconstruction and joint performance enhancement.As the oscillation amplitude increases from 0 to 0.8 mm,the molten pool duration extends to 1.7 times the original value,while peak temperature and average cooling rate decrease by 19%and 39%,respectively.This thermal regulation promotes weld surface width expansion from 0.72 to 1.07 mm.The welding mode undergoes a progressive transition from keyhole mode→transitional mode→conduction mode.This transformation effectively suppresses porosity defects,substantially reducing porosity from 1.8%to 0.15%.Microstructural analysis indicates that oscillation modifies the maximum temperature gradient direction within the molten pool,facilitating preferential growth of coarse columnar grains along the welding centerline to establish load-transfer-favorable crystallographic orientations.The synergistic effects of these factors substantially improve joint mechanical properties:lap joint shear load increases by 81.5%(7.6→13.8 kN),and fracture elongation is enhanced by 135%(0.98→2.3 mm).The operational principles of laser oscillation parameters on the welding quality of QP980 steel were elucidated,providing theoretical foundations for joining process optimization.
基金supported by the National Natural Science Foundation of China(32525031,32500896,32571210,and 32171233)the China Postdoctoral Science Foundation(2025M772776 and BX20250148)+2 种基金the Sanqin Talent Special Support Program(2024STD04)the Natural Science Foundation of Shandong Province of China(ZR2025MS1180)the Natural Science Foundation of Shaanxi Province of China(2019JC-07,2021TD-37,2023-ZDLSF-23,and 2024JC-YBMS-146).
文摘Male sexual behaviors,including mounting,intromission,and ejaculation,are not only critical for reproduction but also serve as a model for understanding how the brain orchestrates sequential motor and motivational processes.While previous studies have identified key brain regions involved in sexual behaviors,such as the medial preoptic area(MPOA)and the nucleus accumbens(NAc)[14],the neural mechanisms governing the transitions between different phases of male sexual behavior remain poorly understood.
文摘Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.
基金supported by the Non-profit Central Research Institute Fund of the Chinese Academy of Medical Sciences(2020-PT310-01).
文摘Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity in PD and LID has frequently been reported in recent cross-sectional studies.We aimed to investigate the temporal features of beta and gamma activity in the hyper-direct pathway during the development of PD and LID in rats,as well as the regulatory role of the dopamine receptors DI(D1Rs)and DIII(D3Rs)in these disorders.We recorded motor behavior and electrophysiological data during the development of PD and LID,and after interventions with D1R and D3R antagonists and agonists.We demonstrated exaggerated beta-band activity in the PD state and excessive gamma-band activity during on-state dyskinesia.Subsequently,process-dependent increased beta activity correlated with bradykinesia during PD modeling,while process-dependent increased gamma activity correlated with dyskinesia under the cumulative effects of levodopa during on-state dyskinesia.Finally,both D1Rs and D3Rs were found to be involved in regulating dyskinesia and gamma activity.Dynamic oscillations are closely associated with motor behavior,and mapping dynamic oscillations may be associated with optimizing deep brain stimulation parameters and developing personalized neurotherapeutic targeting.Moreover,D1Rs and D3Rs may ameliorate dyskinesia by mediating gamma oscillations.
基金Projects(E2024203001,E2024203049,E2024203071)supported by the Hebei Natural Science Foundation of ChinaProject(236Z1805G)supported by the S&T Program of Hebei,China。
文摘Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium alloy plates.To address these issues,circular oscillating laser welding combined with post-weld heat treatment was employed to improve the formation quality and mechanical properties of the welds.The effects of the frequency of circular oscillating laser on the forming quality,microstructure,and properties of the welds were analyzed.At an oscillation frequency of 200 Hz,the grain size in the weld zone was reduced compared to single laser welding,and the maximum tensile strength of the weld was observed to reach(264.96±1.33)MPa,representing approximately 61.19%of the base metal.Following the post-weld heat treatment of"solid solution and artificial aging",the grain boundary segregation was diminished.Nanoscale precipitated phases are present in the weld zone.Furthermore,the tensile strength was augmented to(386.35±5.65)MPa,representing approximately 89.23%of the strength of the base metal.The results of this study can provide a theoretical basis and technological reference for the circular oscillating laser welding of medium-thickness 2219-T 6 aluminium alloy plates.
基金supported by Independent Innovation Science Foundation of National University of Defense Technology(Grant No.23-ZZCX-JDZ-44)。
文摘Tunable mid-infrared and far-infrared laser output was demonstrated based on BaGa_(4)Se_(7)crystals and an optical parametric oscillator(OPO).With a 1.06μm Nd:YAG laser and a double-pass singly resonant OPO cavity,a laser energy output of 2.2 mJ at 10μm was obtained.By tuning the angle and temperature,a tunable laser output covering the wavelength range from 6μm to 17μm was obtained with a tuning precision better than 3 nm.The corresponding optical-to-optical conversion efficiency was 2.8%,and the slope efficiency was 4.4%.The damage effect of the output laser on detectors was also investigated,and point damage to the detector occurred at an output energy of 16.4μJ.The laser system has the advantages of miniaturization,a wide tuning range,high energy and high tuning resolution.Its broadband laser characteristics make it highly valuable for applications in atmospheric detection,infrared spectroscopy and electro-optical countermeasures.
基金supported by the National Natural Science Foundation of China (Grant No.12274131)the Innovation Program for Quantum Science and Technology (Grant No.2024ZD0300101)。
文摘Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this field has focused on systems in equilibrium or steady states.In this work,we demonstrate a room-temperature Rydberg atomic platform where the unidirectional propagation of light acts as a switch to mediate time-crystalline-like collective oscillations through atomic synchronization.
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFC2201504)the National Natural Science Foundation of China (Grant Nos.12588101 and 12535002)。
文摘We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.
基金supported by the Deanship of Research at the King Fahd University of Petroleum&Minerals,Dhahran,31261,Saudi Arabia,under Project No.EC241001.
文摘Various factors,including weak tie-lines into the electric power system(EPS)networks,can lead to low-frequency oscillations(LFOs),which are considered an instant,non-threatening situation,but slow-acting and poisonous.Considering the challenge mentioned,this article proposes a clustering-based machine learning(ML)framework to enhance the stability of EPS networks by suppressing LFOs through real-time tuning of key power system stabilizer(PSS)parameters.To validate the proposed strategy,two distinct EPS networks are selected:the single-machine infinite-bus(SMIB)with a single-stage PSS and the unified power flow controller(UPFC)coordinated SMIB with a double-stage PSS.To generate data under various loading conditions for both networks,an efficient but offline meta-heuristic algorithm,namely the grey wolf optimizer(GWO),is used,with the loading conditions as inputs and the key PSS parameters as outputs.The generated loading conditions are then clustered using the fuzzy k-means(FKM)clustering method.Finally,the group method of data handling(GMDH)and long short-term memory(LSTM)ML models are developed for clustered data to predict PSS key parameters in real time for any loading condition.A few well-known statistical performance indices(SPI)are considered for validation and robustness of the training and testing procedure of the developed FKM-GMDH and FKM-LSTM models based on the prediction of PSS parameters.The performance of the ML models is also evaluated using three stability indices(i.e.,minimum damping ratio,eigenvalues,and time-domain simulations)after optimally tuned PSS with real-time estimated parameters under changing operating conditions.Besides,the outputs of the offline(GWO-based)metaheuristic model,proposed real-time(FKM-GMDH and FKM-LSTM)machine learning models,and previously reported literature models are compared.According to the results,the proposed methodology outperforms the others in enhancing the stability of the selected EPS networks by damping out the observed unwanted LFOs under various loading conditions.
基金the National Natural Science Foundation of China(No.12002102)。
文摘The characteristics of flow and thrust evolution of an annular Expansion-Deflection(ED)nozzle are numerically investigated under varying backpressure changing rates during ascending and descending trajectories.The objective is to test the sensitivity of unsteady behaviors of shock waves in the ED nozzle to backpressure changing rate,and to further elucidate the thrust evolution mechanism and mode transition hysteresis.The movement of shock reflection points on the nozzle wall follows two flow mechanisms,namely,shock self-excited oscillations and rapid backpressure changes.A low backpressure changing rate enables shock self-excited oscillations,leading to a reciprocating motion of the shock waves accompanied by thrust oscillations,while a high backpressure changing rate suppresses the shock self-excited oscillations,leading to a unidirectional motion of the wave system on the nozzle shroud wall.A criterion for distinguishing ED nozzle operation modes is proposed,which relies on the loading inflection points of the nozzle pintle base and exhibits a fast and user-friendly feature.A dual-wake mode hysteresis region is defined to quantify the hysteresis in nozzle mode transition,with the span of the region decreasing as the backpressure changing rate slows down.The present work helps in understanding the unsteady flow mechanism and thrust evolution in ED nozzles.
基金Supported by the Laoshan Laboratory(No.LSKJ 202202404)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB 42000000)+1 种基金the National Natural Science Foundation of China(NSFC)(No.42030410)the Startup Foundation for Introducing Talent of NUIST,and the Jiangsu Innovation Research Group(No.JSSCTD 202346)。
文摘Numerical models are crucial for quantifying the ocean-atmosphere interactions associated with the El Niño-Southern Oscillation(ENSO)phenomenon in the tropical Pacific.Current coupled models often exhibit significant biases and inter-model differences in simulating ENSO,underscoring the need for alternative modeling approaches.The Regional Ocean Modeling System(ROMS)is a sophisticated ocean model widely used for regional studies and has been coupled with various atmospheric models.However,its application in simulating ENSO processes on a basin scale in the tropical Pacific has not been explored.For the first time,this study presents the development of a basin-scale hybrid coupled model(HCM)for the tropical Pacific,integrating ROMS with a statistical atmospheric model that captures the interannual relationships between sea surface temperature(SST)and wind stress anomalies.The HCM is evaluated for its capability to simulate the annual mean,seasonal,and interannual variations of the oceanic state in the tropical Pacific.Results demonstrate that the model effectively reproduces the ENSO cycle,with a dominant oscillation period of approximately two years.The ROMS-based HCM developed here offers an efficient and robust tool for investigating climate variability in the tropical Pacific.
基金Supported by the Laoshan Laboratory(No.LSKJ202202402)the National Natural Science Foundation of China(No.42030410)+2 种基金the Startup Foundation for Introducing Talent of Nanjing University of Information Science&Technology,and Jiangsu Innovation Research Group(No.JSSCTD 202346)supported by the China National Postdoctoral Program for Innovative Talents(No.BX20240169)the China Postdoctoral Science Foundation(No.2141062400101)。
文摘Deep learning(DL)has become a crucial technique for predicting the El Niño-Southern Oscillation(ENSO)and evaluating its predictability.While various DL-based models have been developed for ENSO predictions,many fail to capture the coherent multivariate evolution within the coupled ocean-atmosphere system of the tropical Pacific.To address this three-dimensional(3D)limitation and represent ENSO-related ocean-atmosphere interactions more accurately,a novel this 3D multivariate prediction model was proposed based on a Transformer architecture,which incorporates a spatiotemporal self-attention mechanism.This model,named 3D-Geoformer,offers several advantages,enabling accurate ENSO predictions up to one and a half years in advance.Furthermore,an integrated gradient method was introduced into the model to identify the sources of predictability for sea surface temperature(SST)variability in the eastern equatorial Pacific.Results reveal that the 3D-Geoformer effectively captures ENSO-related precursors during the evolution of ENSO events,particularly the thermocline feedback processes and ocean temperature anomaly pathways on and off the equator.By extending DL-based ENSO predictions from one-dimensional Niño time series to 3D multivariate fields,the 3D-Geoformer represents a significant advancement in ENSO prediction.This study provides details in the model formulation,analysis procedures,sensitivity experiments,and illustrative examples,offering practical guidance for the application of the model in ENSO research.
基金Project supported by the Natural Science Foundation of Hubei Province(Grant No.2024AFD068).
文摘In recent years,the phenomenon of multistability has attracted wide attention.In this paper,a memristive chaotic system with extreme multistability is constructed by using a memristor.The dynamic behavior of the system is analyzed by Poincar´e mapping,a time series diagram,and a bifurcation diagram.The results show that the new system has several significant characteristics.First,the new system has a constant Lyapunov exponent,transient chaos and one complete Feigenbaum tree.Second,the system has the phenomenon of bifurcation map shifts that depend on the initial conditions.In addition,we find periodic bursting oscillations,chaotic bursting oscillations,and the transition of chaotic bursting oscillations to periodic bursting oscillations.In particular,when the system parameters take different discrete values,the system generates a bubble phenomenon that varies with the initial conditions,and this bubble can be shifted with the initial values,which has rarely been seen in the previous literature.The implementation by field-programmable gate array(FPGA)and analog circuit simulation show close alignment with the MATLAB numerical simulation results,validating the system’s realizability.Additionally,the image encryption algorithm integrating DNA-based encoding and chaotic systems further demonstrates its practical applicability.
基金financially supported by the National Natural Science Foundation of China(No.52174306)the Fundamental Research Funds for the Central Universities(Nos.N2225023 and N2425006)the Basic Research Projects of Liaoning Provincial Department of Education(No.LJ212410148027)。
文摘The hook formation mechanism in continuously cast slabs of ultra-low carbon steel was analyzed in detail through numerical calculations and experimental observations using optical microscopy,and its distribution characteristics were determined.Numerical simulations confirmed that the freezing–overflow mechanism is the primary cause of hook formation.They also revealed that the freezing event occurs unpredictably,while the overflow event takes place during the positive strip time.The average pitch of oscillation marks(OMs)on the slab surface was 8.693 mm,while the theoretical pitch was 8.889 mm,with a difference of approximately 2%.This discrepancy primarily results from varying degrees of overflow,which affects the morphology of the OMs and the positions of their deepest points.Notably,this result further confirmed that the freezing and overflow in the meniscus were indeed caused by the periodic oscillation of the mold.Higher superheat hindered hook formation,leading to a negative correlation between the hook depth distribution around the slab and the temperature distribution within the mold.Therefore,the depth of the corner hook was greater than that of other positions,which was caused by the intensified cooling effect of the corner.Moreover,key factors influencing hook development were analyzed,providing insights into transient fluid flow and heat transfer characteristics within the mold.Transient fluid flow and heat transfer contributed to the randomness and tendency of hook formation.This randomness was reflected in the varying angles of the hooks,whereas the tendency was evident in the negative correlation between superheat and hook length.Based on the randomness and tendency of hook formation and its profile characteristics,a new method for controlling hook depth based on“sine law”is proposed.
基金supported by the National Natural Science Foundation of China(Nos.U23B6009 and 12272050)。
文摘Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.
基金financial support from National Natural Science Foundation of China(Grant No.52378488)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0222).
文摘Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure.To reveal the oscillation mechanism of gas explosion load,the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m,and the explosion process was numerically analyzed using FLACS.The results show that the essential cause of oscillation effect is the reflection of the pressure wave.In addition,due to the difference in the propagation path of the pressure wave,the load oscillation frequency at the middle position of the tunnel is twice that at the end position.The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately,and the error is less than 15%.The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude.The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7%and 34.7%lower than the numerical results,respectively.The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load,and the difference between the theoretical and numerical results is only 4.6%.In the theoretical derivation of the overpressure model,an improved model of dynamic turbulence factor is established,which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence.Based on the one-dimensional propagation theory of pressure wave,the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation.The average error of amplitude and frequency is less than 20%.
