A method for correlating thermal light over a wide spectral range is proposed.A multi-wavelength pseudothermal source,prepared by projecting laser beams of multiple wavelengths(650 nm,635 nm,532 nm,and 473 nm)onto a m...A method for correlating thermal light over a wide spectral range is proposed.A multi-wavelength pseudothermal source,prepared by projecting laser beams of multiple wavelengths(650 nm,635 nm,532 nm,and 473 nm)onto a moving thin ground glass plate,is employed in a double-slit interference experiment.The ground glass plate induces random phase differences between light beams of different wavelengths passing through it.This initial random phase difference significantly influences the high-order intensity correlation functions of multi-wavelength thermal beams.Experimentally,second-order correlated interference patterns,including subwavelength interference,of pseudothermal beams with different wavelengths are observed in the intensity correlation measurements.This method facilitates applications of correlated thermal photons in quantum information processing and quantum imaging.展开更多
Discriminative region localization and efficient feature encoding are crucial for fine-grained object recognition.However,existing data augmentation methods struggle to accurately locate discriminative regions in comp...Discriminative region localization and efficient feature encoding are crucial for fine-grained object recognition.However,existing data augmentation methods struggle to accurately locate discriminative regions in complex backgrounds,small target objects,and limited training data,leading to poor recognition.Fine-grained images exhibit“small inter-class differences,”and while second-order feature encoding enhances discrimination,it often requires dual Convolutional Neural Networks(CNN),increasing training time and complexity.This study proposes a model integrating discriminative region localization and efficient second-order feature encoding.By ranking feature map channels via a fully connected layer,it selects high-importance channels to generate an enhanced map,accurately locating discriminative regions.Cropping and erasing augmentations further refine recognition.To improve efficiency,a novel second-order feature encoding module generates an attention map from the fourth convolutional group of Residual Network 50 layers(ResNet-50)and multiplies it with features from the fifth group,producing second-order features while reducing dimensionality and training time.Experiments on Caltech-University of California,San Diego Birds-200-2011(CUB-200-2011),Stanford Car,and Fine-Grained Visual Classification of Aircraft(FGVC Aircraft)datasets show state-of-the-art accuracy of 88.9%,94.7%,and 93.3%,respectively.展开更多
Ice lens initiation is the core issue in understanding the dynamic process of frost heave.However,there are still limitations to find an adequate criterion for describing the formation of ice lens.A series of one-dime...Ice lens initiation is the core issue in understanding the dynamic process of frost heave.However,there are still limitations to find an adequate criterion for describing the formation of ice lens.A series of one-dimensional freezing tests is designed using the particle image velocimetry(PIV)method to monitor the frost heave and ice lens formation.The results show that the conventional parameters,such as displacement and velocity,cannot be used to track the ice lens formation,while the strain can be employed to detect the ice lens formation and investigate the freezing change patterns.This study proposes strain as a new criterion for assessing ice lens initiation,applicable across various soil types and freezing conditions(constant freezing and ramped freezing).The strain change in the region where the ice lens forms is the largest during the freezing process.Additionally,strain curves at the top of the soil samples can reveal different freezing patterns and distinguish the first and second frost heave stages.This newly developed technology enables continuous,non-destructive monitoring of ice lens initiation across diverse conditions and soil types,enhancing data visualization and three-dimensional modeling of freezing parameters while improving traditional methods by directly measuring velocity and strain in frost heave investigations.The study is expected to enhance the research of ice lens criterion and provide a new perspective for monitoring the freezing process.展开更多
The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated....The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated.By adjusting the furnace cooling time after solution treatment and the aging temperature,Ti6422 alloy samples were developed with a multi-level lamellar microstructure,in-cluding microscaleαcolonies and α_(p) lamellae,as well as nanoscale α_(s) phases.Extending the furnace cooling time after solution treatment at 920℃ for 1 h from 240 to 540 min,followed by aging at 600℃ for 6 h,increased the α_(p) lamella content,reduced the α_(s) phase content,expanded theαcolonies and α_(p) lamellae size,and improved the impact toughness from 22.7 to 53.8 J/cm^(2).Additionally,under the same solution treatment,raising the aging temperature from 500 to 700℃ resulted in a decrease in the α_(s) phase content and a growth in the thickness of the α_(p) lamella and α_(s) phase.The impact toughness increased significantly with these changes.Samples with high α_(p) lamellae content or large α_(s) phase size exhibited high crack initiation and propagation energies.Impact deformation caused severe kinking of the α_(p) lamellae in crack initiation and propagation areas,leading to a uniform and high-density kernel average misorientation(KAM)distribu-tion,enhancing plastic deformation coordination and uniformity.Moreover,the multidirectional arrangement of coarserαcolonies and α_(p) lamellae continuously deflect the crack propagation direction,inhibiting crack propagation.展开更多
The stability of rock slopes is frequently controlled by the initiation and propagation of inherent dominant cracks.This study systematically investigated these processes in valley slopes by combining fracture-mechani...The stability of rock slopes is frequently controlled by the initiation and propagation of inherent dominant cracks.This study systematically investigated these processes in valley slopes by combining fracture-mechanics analysis with transparent soil model tests.An analytical expression for the stress field at the dominant crack tip was derived from the slope stress distribution by superposing the corresponding stress intensity factors(SIFs).The theoretical predictions were then validated against observations from transparent soil model tests.The influences of slope angle(β),crack inclination angle(α),crack position parameter(b),and crack length parameter(h)on crack initiation and propagation were quantified.The results indicated that:(1)cracks at the slope crest tended to propagate in shear mode,and the shear crack initiation angle(θ_(s))was approximately 8°.Cracks at the slope toe might propagate in either tensile or shear mode.(2)θ_(s) at the slope crest increased withβ,b,and l,and decreased withα.The maximum change inθ_(s) induced by the considered parameters was approximately 30°.(3)The tensile crack initiation angle(θ_(t))at the slop toe decreased withβ,α,and l,while the influence of b was comparatively minor.The maximum change inθ_(t) caused by individual parameters ranged approximately from 25°to 60°.Predicted crack propagation modes and directions showed good agreement with experimental results.These findings provide theoretical guidance for stability assessments of valley slopes controlled by dominant crack propagation.展开更多
Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fa...Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fatigue tests on Ti-6Al-3Nb-2Zr-1Mo alloy with bimodal microstructure to reveal its microstructural characteristics and crack initiation mechanisms.The study demonstrated that the faceted primaryα nodules located near the specimen surface acted as crack initiation sites during both fatigue and dwell fatigue tests.Slip trace analysis revealed that faceted cracking occurred at(0001)basal plane with the maximum Schmid factor value through a special cracking mode referred to as(0001)twist boundary cracking.Innovative criteria of parameters C1 and C2 were proposed based on experimental observation and molecular dynamics simulations,which well identify candidates for(0001)twist boundary crack nucleation.It demonstrated that grain pairs combining a moderately high Schmid factor for basal slip and a well-orientated Burgers vector in the out-of-surface plane was the preferable location for surface(0001)twist-boundary crack initiation,and grain pairs combining a high Schmid factor for basal slip and a high normal stress on basal plane are perfect candidates for subsurface cracking.Based on this,phenomeno-logical models are proposed to explain the surface(0001)twist-boundary cracking mechanism from the perspective of surface extrusion-intrusion-induced micro-notches.展开更多
In recent years,the study of higher-order topological states and their material realizations has become a research frontier in topological condensed matter physics.We demonstrate that twisted bilayer graphene with sma...In recent years,the study of higher-order topological states and their material realizations has become a research frontier in topological condensed matter physics.We demonstrate that twisted bilayer graphene with small twist angles behaves as a second-order topological insulator possessing topological corner charges.Using a tight-binding model,we compute the topological band indices and corner states of finite-sized twisted bilayer graphene flakes.It is found that for any small twist angle,whether commensurate or incommensurate,the gaps both below and above the flat bands are associated with nontrivial topological indices.Our results not only extend the concept of second-order band topology to arbitrary small twist angles but also confirm the existence of corner states at acute-angle corners.展开更多
Continuous control protocols are extensively utilized in traditional MASs,in which information needs to be transmitted among agents consecutively,therefore resulting in excessive consumption of limited resources.To de...Continuous control protocols are extensively utilized in traditional MASs,in which information needs to be transmitted among agents consecutively,therefore resulting in excessive consumption of limited resources.To decrease the control cost,based on ISC,several LFC problems are investigated for second-order MASs without and with time delay,respectively.Firstly,an intermittent sampled controller is designed,and a sufficient and necessary condition is derived,under which state errors between the leader and all the followers approach zero asymptotically.Considering that time delay is inevitable,a new protocol is proposed to deal with the time-delay situation.The error system’s stability is analyzed using the Schur stability theorem,and sufficient and necessary conditions for LFC are obtained,which are closely associated with the coupling gain,the system parameters,and the network structure.Furthermore,for the case where the current position and velocity information are not available,a distributed protocol is designed that depends only on the sampled position information.The sufficient and necessary conditions for LFC are also given.The results show that second-order MASs can achieve the LFC if and only if the system parameters satisfy the inequalities proposed in the paper.Finally,the correctness of the obtained results is verified by numerical simulations.展开更多
This paper reviews the latest advancements in artificial intelligence-assisted R&D project initiation,aiming to provide intelligent solutions for R&D management.It thoroughly examines the value of artificial i...This paper reviews the latest advancements in artificial intelligence-assisted R&D project initiation,aiming to provide intelligent solutions for R&D management.It thoroughly examines the value of artificial intelligence technologies in four core areas:intelligent requirement analysis,technical feasibility assessment,market prospect forecasting,and automated risk identification.Furthermore,it proposes three forward-looking trends—enhanced intelligence,the establishment of industry standards,and deeper human-machine collaboration.These insights are expected to improve project approval success rates and shorten initiation timelines,driving a paradigm shift in R&D management from experience-based to data-driven decision-making.The review highlights how artificial intelligence,through machine learning,natural language processing,and data mining,effectively addresses chronic challenges in traditional initiation processes such as inefficiency,delayed decisions,and resource misallocation.It also identifies critical hurdles,including data quality,model interpretability,and organizational transformation,offering a vital reference framework for the future of intelligent R&D development.展开更多
Back-arc basins are key sites for oceanic lithosphere formation and consumption at convergent plate boundaries,and their formation and subduction processes can be highly variable.The tectonic setting and evolution of ...Back-arc basins are key sites for oceanic lithosphere formation and consumption at convergent plate boundaries,and their formation and subduction processes can be highly variable.The tectonic setting and evolution of the Meso-Tethys Shiquanhe-Jiali ophiolite sub-belt(SJO sub-belt)within BangongNujiang Suture Zone(BNSZ),central xizang,are disputed for the complex rock composition and ages.In this paper,we present geochronology,geochemistry and field observations on the Shiquanhe ophiolite,providing a representative ophiolite example in the western end of SJO.Based on investigation of the petrogenesis and tectonic setting of different rock types,combined with the U-Pb dating,we propose a twostage subduction model for explaining the tectonic evolution of SJO as well as the wither away of a backarc basin.Geochemical and geochronological data indicate that the ca.183 Ma LAN(north of Lameila)gabbros formed in the forearc setting and represent the early-stage subduction of the Bangong MesoTethys.This subduction induced the back-arc spreading recorded in the ca.170 Ma gabbros and lower pillow basalts of PL-SDN(Pagelizanong-Shiquanhe Dam Nan)ophiolitic fragments in the Shiquanhe ophiolite.The basaltic lavas overlying the lower basalts,represented by the ca.168–164 Ma diabasic and boninite dikes have forearc characteristics,and they represent the back-arc basin subduction initiation at a late stage.This work thus recovered the multiple tectonic evolution of SJO sub-belt and emphasise the importance of the back-arc basin subduction in the evolution of ancient oceans.展开更多
The conventional view suggests that the subduction of the South China Sea plate beneath Luzon occurred due to the oceanic lithosphere’s high density,facilitating subduction initiation.However,before the South China S...The conventional view suggests that the subduction of the South China Sea plate beneath Luzon occurred due to the oceanic lithosphere’s high density,facilitating subduction initiation.However,before the South China Sea opened,a continental margin likely existed,meaning that Luzon was directly adjacent to the continental margin rather than the oceanic basin.This would make subduction initiation more challenging.Here,we propose a new model suggesting that during the formation of the South China Sea,extensive mafic magmatic underplating occurred along its continental margin.The high-density magmatic additions may have increased the overall density of the continental margin,potentially exceeding that of Luzon,thereby enabling subduction to proceed.展开更多
In this paper,we investigate the phenomena of electromagnetically induced transparency and the generation of second-order sideband in a Laguerre–Gaussian cavity optorotational system with a Kerr nonlinear medium.Usin...In this paper,we investigate the phenomena of electromagnetically induced transparency and the generation of second-order sideband in a Laguerre–Gaussian cavity optorotational system with a Kerr nonlinear medium.Using the perturbation method,we analyze the first-and second-order sideband generations in the output field from the system under the actions of a strong control field and a weak probe field.Numerical simulations show that the Kerr nonlinearity can lead to the occurrence of the asymmetric line shape in the transmission of the probe field.Comparing with traditional scheme for generating the second-order sideband,our spectral shape of the second-order sideband is amplified and becomes asymmetric,which has potential applications in precision measurement,high-sensitivity devices,and frequency conversion.展开更多
The stabilization problem of second-order bilinear systems with time delay is investigated.Feedback controls are chosen so that the strong and exponential stabilization of the system is ensured.The obtained results ar...The stabilization problem of second-order bilinear systems with time delay is investigated.Feedback controls are chosen so that the strong and exponential stabilization of the system is ensured.The obtained results are illustrated by wave and beam equations with simulation.展开更多
0 INTRODUCTION Initial subduction involves the complex process of oceanic lithosphere first inserting beneath oceanic or continental lithosphere(Chen et al.,2024;Yang et al.,2022;Stern and Gerya,2018).The modern Izu-B...0 INTRODUCTION Initial subduction involves the complex process of oceanic lithosphere first inserting beneath oceanic or continental lithosphere(Chen et al.,2024;Yang et al.,2022;Stern and Gerya,2018).The modern Izu-Bonin-Mariana(IBM)initial subduction system suggests that identifying the earliest ophiolites,arc igneous and metamorphic complexes(e.g.,blueschist,eclogites)can reconstruct ancient initial subduction systems(Yao et al.,2021;Ishizuka et al.,2011).However,knowledge of ancient subduction initiation is often limited due to poor exposures of rocks formed during the earliest stages of subduction(Chen et al.,2024;Cawood et al.,2009).展开更多
In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated i...In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.展开更多
In this work,the effect of high angle grain boundaries(HAGBs),including prior austenite grain boundaries(PAGB),packet grain boundaries(PGB)and block grain boundaries(BGB),on the priority of pitting and microcrack init...In this work,the effect of high angle grain boundaries(HAGBs),including prior austenite grain boundaries(PAGB),packet grain boundaries(PGB)and block grain boundaries(BGB),on the priority of pitting and microcrack initiation for 10Cr13Co13Mo5Ni3W1VE ultra-high strength stainless steel(UHSS)has been clarified.PAGB had the highest carbide distribution coefficient and was the main location where pitting preferentially initiated for the UHSS in 3.5 wt.%NaCl solution without strain.It was shown that nanocarbides were the key factor of pitting initiation for the UHSS without strain.However,BGB was the key factor of pitting/microcrack initiation for the UHSS with strain,which was attributed to the high-density dislocations accumulated at BGB and then enhanced the local electrochemical activity of the UHSS surface.The change of the key factor for the pitting initiation in the UHSS was the result of the synergy between strain and corrosion environment.This study provides guidance for designing advanced UHSS with high service stability and safety.展开更多
Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic a...Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic and whole-rock geochemical data,we report the first discovery of a latest Cambrian–Early Ordovician forearc-arc rock sequence in the Eastern Alps.This sequence includes granitic gneisses,amphibolites,and amphibole plagiogneisses from the ophiolitic Speik Complex and Gleinalpe Complex.These rocks exhibit geochemical affinities with typical oceanic plagiogranites,forearc basalts(FABs),and island arc basalts,respectively.The latest Cambrian plagiogranitic protoliths(491±2 Ma)are shearing-type plagiogranites that were formed in the tectonic setting of forearc spreading.The latest Cambrian FABs(496–489 Ma)have similar geochemical compositions and positiveεHf(t)values(+2.5 to+14.9)to the depleted mid-ocean ridge basalts.However,they show depletion in high field strength elements(HFSEs;e.g.,Nb,Ta,and Zr)and have relatively low Ti/V ratios.These features suggest that they were derived from a depleted mantle source modified by subducting slab-released components in a forearc environment.The Early Ordovician basaltic protoliths(476–472 Ma)of amphibole plagiogneisses show enrichment in large ion lithophile elements and depletion in HFSEs(e.g.Nb,Ta,Zr,and Hf),implying a mature island arc environment.These metaigneous rocks,along with the coeval boninite-like high-Mg amphibolites near the study area,form a typical rock sequence resembling that of the Izu–Bonin–Mariana(IBM)arc system.The Speik and Gleinalpe complexes document a complete magmatic evolution from subduction initiation to mature arc development within the West Proto-Tethys Ocean.Integrating our new data with published work,we reconstruct the late Ediacaran–early Paleozoic tectonic evolution of the northern Gondwana.During the late Ediacaran–early Cambrian,the rollback of the West Proto-Tethys oceanic plate triggered the separation of the Wechsel-Silvretta-Gleinalpe continental arc from the northern Gondwana.This process led to the formation of the Speik back-arc oceanic basin,a southwestern branch of the West Proto-Tethys Ocean.In the latest Cambrian–Early Ordovician,subduction initiation occurred in the Speik Ocean,which subsequently developed into an intra-oceanic arc system.During the Early Devonian,the Speik Ocean closed and the Wechsel-Silvretta-Gleinalpe continental arc reattached to the Gondwana,as evidenced by the metamorphic event at ca.400 Ma.展开更多
The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditi...The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions.In this work,considering the different combinations of confining pressure and bedding plane inclination angle(α),biaxial mechanical loading experiments were conducted on shale containing circular holes.The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes.The instability of shale containing circular holes can be classified into five types:tensile failure along the bedding planes,tensile failure through the bedding planes,shear slip along the bedding planes,shear failure through the bedding planes,and block instability failure.Furthermore,the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks.The crack initiation criterion for shale containing circular hole was established,providing a new method for evaluating the trajectory of shale hole wall fractures.This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.展开更多
This research,based on Mason's formula,proposes a novel design for a second-order transconductance-mode universal filter with the operational transconductance amplifier(OTA)as the core and the second-generation cu...This research,based on Mason's formula,proposes a novel design for a second-order transconductance-mode universal filter with the operational transconductance amplifier(OTA)as the core and the second-generation current-controlled conveyor(CCCⅡ)as the auxiliary.The circuit incorporates two OTAs,one CCCⅡ,two grounded capacitors,and one grounded resistor.The quality factor Q and natural frequency fo of the filter can be electronically tuned and are not sensitive to temperature.The input and output terminals of the cir-cuit exhibit no loading effect,and the sensitivity of the circuit is low.At last,alternating frequency analysis,parameter scanning analysis,and temperature scanning analysis have been carried out by using Multisim software,confirming the correctness and effectiveness of the designed circuit.展开更多
Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can...Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can respond immediately to the threat.Therefore,when an animal detects a threat through its visual system,it must quickly direct its gaze and attention toward the source of danger,assess the threat level,and take appropriate action.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62105278 and 11674273)the Natural Science Foundation of Shandong Province(Grant No.ZR2023MA015)。
文摘A method for correlating thermal light over a wide spectral range is proposed.A multi-wavelength pseudothermal source,prepared by projecting laser beams of multiple wavelengths(650 nm,635 nm,532 nm,and 473 nm)onto a moving thin ground glass plate,is employed in a double-slit interference experiment.The ground glass plate induces random phase differences between light beams of different wavelengths passing through it.This initial random phase difference significantly influences the high-order intensity correlation functions of multi-wavelength thermal beams.Experimentally,second-order correlated interference patterns,including subwavelength interference,of pseudothermal beams with different wavelengths are observed in the intensity correlation measurements.This method facilitates applications of correlated thermal photons in quantum information processing and quantum imaging.
基金supported,in part,by the National Nature Science Foundation of China under Grant 62272236,62376128 and 62306139the Natural Science Foundation of Jiangsu Province under Grant BK20201136,BK20191401.
文摘Discriminative region localization and efficient feature encoding are crucial for fine-grained object recognition.However,existing data augmentation methods struggle to accurately locate discriminative regions in complex backgrounds,small target objects,and limited training data,leading to poor recognition.Fine-grained images exhibit“small inter-class differences,”and while second-order feature encoding enhances discrimination,it often requires dual Convolutional Neural Networks(CNN),increasing training time and complexity.This study proposes a model integrating discriminative region localization and efficient second-order feature encoding.By ranking feature map channels via a fully connected layer,it selects high-importance channels to generate an enhanced map,accurately locating discriminative regions.Cropping and erasing augmentations further refine recognition.To improve efficiency,a novel second-order feature encoding module generates an attention map from the fourth convolutional group of Residual Network 50 layers(ResNet-50)and multiplies it with features from the fifth group,producing second-order features while reducing dimensionality and training time.Experiments on Caltech-University of California,San Diego Birds-200-2011(CUB-200-2011),Stanford Car,and Fine-Grained Visual Classification of Aircraft(FGVC Aircraft)datasets show state-of-the-art accuracy of 88.9%,94.7%,and 93.3%,respectively.
基金supported by the National Natural Science Foundation of China(Grant No.52178376)National Key R&D Program of China(Grant No.2022YFB2603301)Science and Technology Research and Development Program of China Railway Group Limited(Grant No.2022-ZD-13).
文摘Ice lens initiation is the core issue in understanding the dynamic process of frost heave.However,there are still limitations to find an adequate criterion for describing the formation of ice lens.A series of one-dimensional freezing tests is designed using the particle image velocimetry(PIV)method to monitor the frost heave and ice lens formation.The results show that the conventional parameters,such as displacement and velocity,cannot be used to track the ice lens formation,while the strain can be employed to detect the ice lens formation and investigate the freezing change patterns.This study proposes strain as a new criterion for assessing ice lens initiation,applicable across various soil types and freezing conditions(constant freezing and ramped freezing).The strain change in the region where the ice lens forms is the largest during the freezing process.Additionally,strain curves at the top of the soil samples can reveal different freezing patterns and distinguish the first and second frost heave stages.This newly developed technology enables continuous,non-destructive monitoring of ice lens initiation across diverse conditions and soil types,enhancing data visualization and three-dimensional modeling of freezing parameters while improving traditional methods by directly measuring velocity and strain in frost heave investigations.The study is expected to enhance the research of ice lens criterion and provide a new perspective for monitoring the freezing process.
基金supported by the National Natural Science Foundation of China(No.52090041).
文摘The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated.By adjusting the furnace cooling time after solution treatment and the aging temperature,Ti6422 alloy samples were developed with a multi-level lamellar microstructure,in-cluding microscaleαcolonies and α_(p) lamellae,as well as nanoscale α_(s) phases.Extending the furnace cooling time after solution treatment at 920℃ for 1 h from 240 to 540 min,followed by aging at 600℃ for 6 h,increased the α_(p) lamella content,reduced the α_(s) phase content,expanded theαcolonies and α_(p) lamellae size,and improved the impact toughness from 22.7 to 53.8 J/cm^(2).Additionally,under the same solution treatment,raising the aging temperature from 500 to 700℃ resulted in a decrease in the α_(s) phase content and a growth in the thickness of the α_(p) lamella and α_(s) phase.The impact toughness increased significantly with these changes.Samples with high α_(p) lamellae content or large α_(s) phase size exhibited high crack initiation and propagation energies.Impact deformation caused severe kinking of the α_(p) lamellae in crack initiation and propagation areas,leading to a uniform and high-density kernel average misorientation(KAM)distribu-tion,enhancing plastic deformation coordination and uniformity.Moreover,the multidirectional arrangement of coarserαcolonies and α_(p) lamellae continuously deflect the crack propagation direction,inhibiting crack propagation.
基金financially supported by the National Nature Science Foundation of China(Nos.52379110 and 42207222)the Key Technologies for Accurate Diagnosis and Intelligent Prevention and Control of Slope Hazards in Open Pit Mines,181 Major R&D projects of Metallurgical Corporation of China Ltd。
文摘The stability of rock slopes is frequently controlled by the initiation and propagation of inherent dominant cracks.This study systematically investigated these processes in valley slopes by combining fracture-mechanics analysis with transparent soil model tests.An analytical expression for the stress field at the dominant crack tip was derived from the slope stress distribution by superposing the corresponding stress intensity factors(SIFs).The theoretical predictions were then validated against observations from transparent soil model tests.The influences of slope angle(β),crack inclination angle(α),crack position parameter(b),and crack length parameter(h)on crack initiation and propagation were quantified.The results indicated that:(1)cracks at the slope crest tended to propagate in shear mode,and the shear crack initiation angle(θ_(s))was approximately 8°.Cracks at the slope toe might propagate in either tensile or shear mode.(2)θ_(s) at the slope crest increased withβ,b,and l,and decreased withα.The maximum change inθ_(s) induced by the considered parameters was approximately 30°.(3)The tensile crack initiation angle(θ_(t))at the slop toe decreased withβ,α,and l,while the influence of b was comparatively minor.The maximum change inθ_(t) caused by individual parameters ranged approximately from 25°to 60°.Predicted crack propagation modes and directions showed good agreement with experimental results.These findings provide theoretical guidance for stability assessments of valley slopes controlled by dominant crack propagation.
基金supported by the National Natural Science Foundation of China(Nos.52074231,52274396 and 52001258)the Chongqing Natural Science Foundation(No.cstc2020jcyj-msxmX1056).
文摘Crack initiation mechanism of dwell fatigue has always been a key problem in rationalizing the dwell effect,and it is not completely understood yet.This study conducted stress-controlled low-cycle fatigue and dwell fatigue tests on Ti-6Al-3Nb-2Zr-1Mo alloy with bimodal microstructure to reveal its microstructural characteristics and crack initiation mechanisms.The study demonstrated that the faceted primaryα nodules located near the specimen surface acted as crack initiation sites during both fatigue and dwell fatigue tests.Slip trace analysis revealed that faceted cracking occurred at(0001)basal plane with the maximum Schmid factor value through a special cracking mode referred to as(0001)twist boundary cracking.Innovative criteria of parameters C1 and C2 were proposed based on experimental observation and molecular dynamics simulations,which well identify candidates for(0001)twist boundary crack nucleation.It demonstrated that grain pairs combining a moderately high Schmid factor for basal slip and a well-orientated Burgers vector in the out-of-surface plane was the preferable location for surface(0001)twist-boundary crack initiation,and grain pairs combining a high Schmid factor for basal slip and a high normal stress on basal plane are perfect candidates for subsurface cracking.Based on this,phenomeno-logical models are proposed to explain the surface(0001)twist-boundary cracking mechanism from the perspective of surface extrusion-intrusion-induced micro-notches.
基金supported by the National Natural Science Foundation of China(Grant Nos.12104232 and 12074156).
文摘In recent years,the study of higher-order topological states and their material realizations has become a research frontier in topological condensed matter physics.We demonstrate that twisted bilayer graphene with small twist angles behaves as a second-order topological insulator possessing topological corner charges.Using a tight-binding model,we compute the topological band indices and corner states of finite-sized twisted bilayer graphene flakes.It is found that for any small twist angle,whether commensurate or incommensurate,the gaps both below and above the flat bands are associated with nontrivial topological indices.Our results not only extend the concept of second-order band topology to arbitrary small twist angles but also confirm the existence of corner states at acute-angle corners.
基金supported by the National Natural Science Foundation of China under Grants 62476138 and 42375016.
文摘Continuous control protocols are extensively utilized in traditional MASs,in which information needs to be transmitted among agents consecutively,therefore resulting in excessive consumption of limited resources.To decrease the control cost,based on ISC,several LFC problems are investigated for second-order MASs without and with time delay,respectively.Firstly,an intermittent sampled controller is designed,and a sufficient and necessary condition is derived,under which state errors between the leader and all the followers approach zero asymptotically.Considering that time delay is inevitable,a new protocol is proposed to deal with the time-delay situation.The error system’s stability is analyzed using the Schur stability theorem,and sufficient and necessary conditions for LFC are obtained,which are closely associated with the coupling gain,the system parameters,and the network structure.Furthermore,for the case where the current position and velocity information are not available,a distributed protocol is designed that depends only on the sampled position information.The sufficient and necessary conditions for LFC are also given.The results show that second-order MASs can achieve the LFC if and only if the system parameters satisfy the inequalities proposed in the paper.Finally,the correctness of the obtained results is verified by numerical simulations.
文摘This paper reviews the latest advancements in artificial intelligence-assisted R&D project initiation,aiming to provide intelligent solutions for R&D management.It thoroughly examines the value of artificial intelligence technologies in four core areas:intelligent requirement analysis,technical feasibility assessment,market prospect forecasting,and automated risk identification.Furthermore,it proposes three forward-looking trends—enhanced intelligence,the establishment of industry standards,and deeper human-machine collaboration.These insights are expected to improve project approval success rates and shorten initiation timelines,driving a paradigm shift in R&D management from experience-based to data-driven decision-making.The review highlights how artificial intelligence,through machine learning,natural language processing,and data mining,effectively addresses chronic challenges in traditional initiation processes such as inefficiency,delayed decisions,and resource misallocation.It also identifies critical hurdles,including data quality,model interpretability,and organizational transformation,offering a vital reference framework for the future of intelligent R&D development.
基金supported by the Guangdong Basic and Applied Basic Research Foundation,China(Grant Nos.2024A1515010439,2025A1515010724)National Nature Science Foundation of China(Grant Nos.41972049,41472054,42072229,41977231)+4 种基金Young Innovative Talent Project of Department of Education of Guangdong Province(Natural ScienceGrant No.2022KQNCX184)Natural Research Project of Guangdong Polytechnic of Industry&Commerce(Grant No.2022-ZKT-01)China State Scholarship Fund of visiting scholar(Grant No.20170638507)High-level Talent Special Support Program of Guangdong Polytechnic of Industry&Commerce(Grant No.2023-gc-03).
文摘Back-arc basins are key sites for oceanic lithosphere formation and consumption at convergent plate boundaries,and their formation and subduction processes can be highly variable.The tectonic setting and evolution of the Meso-Tethys Shiquanhe-Jiali ophiolite sub-belt(SJO sub-belt)within BangongNujiang Suture Zone(BNSZ),central xizang,are disputed for the complex rock composition and ages.In this paper,we present geochronology,geochemistry and field observations on the Shiquanhe ophiolite,providing a representative ophiolite example in the western end of SJO.Based on investigation of the petrogenesis and tectonic setting of different rock types,combined with the U-Pb dating,we propose a twostage subduction model for explaining the tectonic evolution of SJO as well as the wither away of a backarc basin.Geochemical and geochronological data indicate that the ca.183 Ma LAN(north of Lameila)gabbros formed in the forearc setting and represent the early-stage subduction of the Bangong MesoTethys.This subduction induced the back-arc spreading recorded in the ca.170 Ma gabbros and lower pillow basalts of PL-SDN(Pagelizanong-Shiquanhe Dam Nan)ophiolitic fragments in the Shiquanhe ophiolite.The basaltic lavas overlying the lower basalts,represented by the ca.168–164 Ma diabasic and boninite dikes have forearc characteristics,and they represent the back-arc basin subduction initiation at a late stage.This work thus recovered the multiple tectonic evolution of SJO sub-belt and emphasise the importance of the back-arc basin subduction in the evolution of ancient oceans.
基金support from the National Natural Science Foundation of China (Grant No. 42276049)。
文摘The conventional view suggests that the subduction of the South China Sea plate beneath Luzon occurred due to the oceanic lithosphere’s high density,facilitating subduction initiation.However,before the South China Sea opened,a continental margin likely existed,meaning that Luzon was directly adjacent to the continental margin rather than the oceanic basin.This would make subduction initiation more challenging.Here,we propose a new model suggesting that during the formation of the South China Sea,extensive mafic magmatic underplating occurred along its continental margin.The high-density magmatic additions may have increased the overall density of the continental margin,potentially exceeding that of Luzon,thereby enabling subduction to proceed.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174344 and 12175199)Foundation of Department of Science and Technology of Zhejiang Province(Grant No.2022R52047)。
文摘In this paper,we investigate the phenomena of electromagnetically induced transparency and the generation of second-order sideband in a Laguerre–Gaussian cavity optorotational system with a Kerr nonlinear medium.Using the perturbation method,we analyze the first-and second-order sideband generations in the output field from the system under the actions of a strong control field and a weak probe field.Numerical simulations show that the Kerr nonlinearity can lead to the occurrence of the asymmetric line shape in the transmission of the probe field.Comparing with traditional scheme for generating the second-order sideband,our spectral shape of the second-order sideband is amplified and becomes asymmetric,which has potential applications in precision measurement,high-sensitivity devices,and frequency conversion.
文摘The stabilization problem of second-order bilinear systems with time delay is investigated.Feedback controls are chosen so that the strong and exponential stabilization of the system is ensured.The obtained results are illustrated by wave and beam equations with simulation.
基金supported by the special fund of the State Key Laboratory of Deep Earth and Mineral Exploration(No.KFDM2025203)the Natural Science Foundation of Liaoning Province(No.2025-MS-037)+2 种基金the National Natural Science Foundation of China(No.41972234)support provided by the China Scholarship Council(No.202306080045)the Geological Society Research Grants-Mike Coward Fund.
文摘0 INTRODUCTION Initial subduction involves the complex process of oceanic lithosphere first inserting beneath oceanic or continental lithosphere(Chen et al.,2024;Yang et al.,2022;Stern and Gerya,2018).The modern Izu-Bonin-Mariana(IBM)initial subduction system suggests that identifying the earliest ophiolites,arc igneous and metamorphic complexes(e.g.,blueschist,eclogites)can reconstruct ancient initial subduction systems(Yao et al.,2021;Ishizuka et al.,2011).However,knowledge of ancient subduction initiation is often limited due to poor exposures of rocks formed during the earliest stages of subduction(Chen et al.,2024;Cawood et al.,2009).
基金financially supported by the National Natural Science Foundation of China(No.U21A2050)support of the Chinese Scholarship Council(No.202006290165).
文摘In recent years,(0001)twist grain boundaries(BTGBs)located in primary α grain clusters were identified as fatigue crack nucleation sites in different Ti alloys.In the present study,crack initiation was investigated in a bimodal Ti-5Al-4 V alloy subjected to low-cycle fatigue and dwell-fatigue loadings at room temperature.The low fraction of primary α grains was not associated with a lack of sensitivity to BTGB cracking.Transmission electron microscopy and electron back-scattered diffraction were used to characterize BTGBs in the initial microstructure.The fatigue mechanisms were then analyzed with a focus on dislocation activity.α_(p) grains adjacent to cracked BTGBs contained a high dislocation density.It was primarily composed of planar slip bands of dislocations.In addition,<c+a>dislocations were noticed in the vicinity of cracked BTGBs.They supposedly pertain to crack tip plasticity during growth,and no evidence of a role of an incoming slip event in crack nucleation was obtained.Also,basal slip bands extending across adjacent grains were found to emerge from BTGBs.This feature provides an easier path for crack extension when growth along the grain boundary becomes difficult owing to a deviation from the basal plane.Atom probe tomography analyses evidenced V and Fe segregation at a grain boundary with a significant deviation from the BTGB configuration.This suggests a possible contribution of local solute segregation to the high cracking resistance of general α_(p)/α_(p) grain boundaries.This work provides new insights into the mechanisms involved in cracking of BTGB in Ti alloys subjected to cyclic loadings.
文摘In this work,the effect of high angle grain boundaries(HAGBs),including prior austenite grain boundaries(PAGB),packet grain boundaries(PGB)and block grain boundaries(BGB),on the priority of pitting and microcrack initiation for 10Cr13Co13Mo5Ni3W1VE ultra-high strength stainless steel(UHSS)has been clarified.PAGB had the highest carbide distribution coefficient and was the main location where pitting preferentially initiated for the UHSS in 3.5 wt.%NaCl solution without strain.It was shown that nanocarbides were the key factor of pitting initiation for the UHSS without strain.However,BGB was the key factor of pitting/microcrack initiation for the UHSS with strain,which was attributed to the high-density dislocations accumulated at BGB and then enhanced the local electrochemical activity of the UHSS surface.The change of the key factor for the pitting initiation in the UHSS was the result of the synergy between strain and corrosion environment.This study provides guidance for designing advanced UHSS with high service stability and safety.
基金supported by the National Natural Science Foundation of China(Grant Nos.42272244 and 91755212)Taishan Scholars(Grant No.ts20190918).
文摘Subduction initiation is a critical part of the plate tectonic system,but its geodynamic process is still poorly understood due to the lack of well-preserved geological records.Based on new zircon U–Pb–Hf isotopic and whole-rock geochemical data,we report the first discovery of a latest Cambrian–Early Ordovician forearc-arc rock sequence in the Eastern Alps.This sequence includes granitic gneisses,amphibolites,and amphibole plagiogneisses from the ophiolitic Speik Complex and Gleinalpe Complex.These rocks exhibit geochemical affinities with typical oceanic plagiogranites,forearc basalts(FABs),and island arc basalts,respectively.The latest Cambrian plagiogranitic protoliths(491±2 Ma)are shearing-type plagiogranites that were formed in the tectonic setting of forearc spreading.The latest Cambrian FABs(496–489 Ma)have similar geochemical compositions and positiveεHf(t)values(+2.5 to+14.9)to the depleted mid-ocean ridge basalts.However,they show depletion in high field strength elements(HFSEs;e.g.,Nb,Ta,and Zr)and have relatively low Ti/V ratios.These features suggest that they were derived from a depleted mantle source modified by subducting slab-released components in a forearc environment.The Early Ordovician basaltic protoliths(476–472 Ma)of amphibole plagiogneisses show enrichment in large ion lithophile elements and depletion in HFSEs(e.g.Nb,Ta,Zr,and Hf),implying a mature island arc environment.These metaigneous rocks,along with the coeval boninite-like high-Mg amphibolites near the study area,form a typical rock sequence resembling that of the Izu–Bonin–Mariana(IBM)arc system.The Speik and Gleinalpe complexes document a complete magmatic evolution from subduction initiation to mature arc development within the West Proto-Tethys Ocean.Integrating our new data with published work,we reconstruct the late Ediacaran–early Paleozoic tectonic evolution of the northern Gondwana.During the late Ediacaran–early Cambrian,the rollback of the West Proto-Tethys oceanic plate triggered the separation of the Wechsel-Silvretta-Gleinalpe continental arc from the northern Gondwana.This process led to the formation of the Speik back-arc oceanic basin,a southwestern branch of the West Proto-Tethys Ocean.In the latest Cambrian–Early Ordovician,subduction initiation occurred in the Speik Ocean,which subsequently developed into an intra-oceanic arc system.During the Early Devonian,the Speik Ocean closed and the Wechsel-Silvretta-Gleinalpe continental arc reattached to the Gondwana,as evidenced by the metamorphic event at ca.400 Ma.
基金Projects(52104143,52109135,52374099)supported by the National Natural Science Foundation of ChinaProject(2025YFHZ0323)supported by the Natural Science Foundation of Sichuan Province,China。
文摘The evolution of cracks in shale directly affects the efficient production of shale gas.However,there is a lack of research on the characteristics of crack initiation in deep dense shale under different stress conditions.In this work,considering the different combinations of confining pressure and bedding plane inclination angle(α),biaxial mechanical loading experiments were conducted on shale containing circular holes.The research results indicate that the confining pressure and inclination angle of the bedding planes significantly influence the failure patterns of shale containing circular holes.The instability of shale containing circular holes can be classified into five types:tensile failure along the bedding planes,tensile failure through the bedding planes,shear slip along the bedding planes,shear failure through the bedding planes,and block instability failure.Furthermore,the evolution of strain and stress fields around the circular holes was found to be the fundamental cause of variations in the initiation characteristics and locations of shale cracks.The crack initiation criterion for shale containing circular hole was established,providing a new method for evaluating the trajectory of shale hole wall fractures.This study holds significant importance for evaluating the evolution and stability of fracture networks within shale reservoirs.
基金Supported by the Natural Science Foundation of Shaanxi Province(2017JM6087)。
文摘This research,based on Mason's formula,proposes a novel design for a second-order transconductance-mode universal filter with the operational transconductance amplifier(OTA)as the core and the second-generation current-controlled conveyor(CCCⅡ)as the auxiliary.The circuit incorporates two OTAs,one CCCⅡ,two grounded capacitors,and one grounded resistor.The quality factor Q and natural frequency fo of the filter can be electronically tuned and are not sensitive to temperature.The input and output terminals of the cir-cuit exhibit no loading effect,and the sensitivity of the circuit is low.At last,alternating frequency analysis,parameter scanning analysis,and temperature scanning analysis have been carried out by using Multisim software,confirming the correctness and effectiveness of the designed circuit.
基金supported by the National Natural Science Foundation of China(32471055 and 82171090)Shanghai Municipal Science and Technology Major Project(2018SHZDZX01)ZJLab,Shanghai Center for Brain Science and Brain-Inspired Technology,the Lingang Laboratory(LG-QS-202203-12).
文摘Throughout the lifespan,an animal can encounter predators frequently,thus the ability to avoid attacks from predators is crucial for its survival.The chances of evading danger can be greatly improved if the animal can respond immediately to the threat.Therefore,when an animal detects a threat through its visual system,it must quickly direct its gaze and attention toward the source of danger,assess the threat level,and take appropriate action.
