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
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
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,(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
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
Recessive resistance mediated by mutations in the eukaryotic translation initiation factor 4E(eIF4E),has proven effective against diverse potyviruses and is extensively utilized in breeding programs.However,the rise o...Recessive resistance mediated by mutations in the eukaryotic translation initiation factor 4E(eIF4E),has proven effective against diverse potyviruses and is extensively utilized in breeding programs.However,the rise of resistance-breaking(RB)strains and emerging potyviral species necessitates the development of more durable and broad-spectrum resistance strategies.In this study,our field survey in Yunnan,China,identified potato virus Y(PVY)RB isolates,as well as the prevalence of tobacco vein banding mosaic virus(TVBMV)and chilli veinal mottle virus(ChiVMV),in tobacco carrying the recessive va locus,which lacks the eIF4E1-S susceptibility gene,due to a chromosomal deletion.Protein interaction and viral infection assays demonstrated that both eIF4E1-S and eIFiso4E-T are used by PVY RB as susceptibility factors for infection,with the combined inactivation of these genes confering durable resistance.Similarly,the knockout of eIFiso4E-S,in the va genetic background,provided effective resistance to TVBMV and reduced susceptibility to ChiVMV.Notably,pyramiding mutations in eIFiso4E-S and eIFiso4E-T,in va tobacco,generated plants exhibiting robust,broad-spectrum resistance,to all three viruses,without compromising plant development.These findings underscore the potential of stacking eIF4E mutations to engineer durable,broad-spectrum resistance to potyviruses in tobacco,offering a promising strategy for crop improvement.展开更多
Hydrogen has emerged as a promising clean energy source,leading to numerous recent efforts to integrate hydrogen into turbine engine applications[1].This integration has the potential to significantly enhance engine e...Hydrogen has emerged as a promising clean energy source,leading to numerous recent efforts to integrate hydrogen into turbine engine applications[1].This integration has the potential to significantly enhance engine efficiency while reducing carbon dioxide emissions[2].However,the degradation of nickel alloys induced by hydrogen has been well documented[3-7].Consequently,hydrogen-assisted failure of nickel alloys poses a critical concern for the design and safe operation of hydrogen-powered turbine engines.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
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
The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 ...The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 and frequency （f） is 40 Hz. Microstructure observations were examined by optical microscopy, transmission electron microscopy, scanning electron microscopy and electron back scattered diffusion, in order to investigate the relationship between microstructure and fatigue crack initiation and early propagation behavior of 2A97 alloy. The results show that the fatigue cracks are predominantly initiated at inclusions and coarsen secondary phases on the surface of 2A97 alloy. The fatigue crack early propagation behavior of 2A97 alloy is predominantly influenced by the interactions between grain structure and dislocations or persistent slip bands （PSBs）. When the misorientation of two neighbouring grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary severely hinders the PSBs passing through, and thus leads to crack bifurcation and deflection.展开更多
The time course of the initiation of different types of apical primordia on the stem of wheat (Triticum aestivum L.) was investigated to establish a comprehensive pattern of apical primordium development and quantitat...The time course of the initiation of different types of apical primordia on the stem of wheat (Triticum aestivum L.) was investigated to establish a comprehensive pattern of apical primordium development and quantitative dynamic relationships among different primordium initiation. The results showed that the initiation of leaf and bracteal primordia took the S shape, and that of spikelet and floret took the rise stage of parabolic shape in relation to GDD (growing degree days after sowing) in wheat. The bracteal was much like vegetative rather than reproductive organ in terms of the dynamic pattern of primordium initiation. The progress of spikelet and floret primordium initiation could well reflect the characteristics of different genotypes and the impact of different ecological environments on wheat apical development. The integrated model of different primordium initiation in shoot of wheat was an S_shaped curvilinear, and could be divided into three sub_models. The number of leaf primordia was affected by both genotype and environment, while the numbers of bracteal, spikelet and floret primordia were affected mainly by environmental factors. Measured with mean thermochron, the rates of initiation of leaf, bracteal and spikelet primordia in normal planting were the highest among all the sowing date treatments. In contrast to the relationships among leaf, bracteal, spikelet and their initiation duration, the correlation between the number of floret and its initiation duration was highly significant.展开更多
The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A...The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.展开更多
In order to study the relationship between charge size and thermal initiation critical temperature of explosive in defined conditions,cook-off test about JH explosive was carried out at a heating rate of 1 ℃/min usin...In order to study the relationship between charge size and thermal initiation critical temperature of explosive in defined conditions,cook-off test about JH explosive was carried out at a heating rate of 1 ℃/min using self-designed cook-off experiment setup based on thermostatic control technology.Numerical simulation was conducted to study the effects of different charge sizes on thermal initiation critical temperature of explosives with FLUENT software.Experiment results show that there is a thermal initiation critical temperature in cook-off bomb.Simulation results show that when the ratio of the length to diameter of explosives grains is a fixed value,the thermal initiation critical temperature of explosives decreases with the increase of the diameter of explosives grains.When the grains diameter of explosives increase up to a certain value,the influence of charge size on thermal initiation critical temperature tends to be weakened.Charge size has no influence on the ignition point of explosives.The ignition point is always in the center of the grain.展开更多
The structure of loess is loose,and the shear strength of loess drops sharply after contact with water.Therefore,loess mudflows have become a common geological disaster on the Chinese Loess Plateau.In order to study t...The structure of loess is loose,and the shear strength of loess drops sharply after contact with water.Therefore,loess mudflows have become a common geological disaster on the Chinese Loess Plateau.In order to study the initiation mode and mechanism of loess mudflows,in this study,seven sets of flume experiments were designed by controlling the slope angle and rainfall intensity.The results show that(1)when the slope angle is between 10°and 20°,there are two initiation mechanisms of loess mudflows:mudflow(large scale)and retrogressive toe sliding,and mudflow(small-scale)and retrogressive toe sliding.(2)The main method by which water infiltrates into the soil accumulation is mainly vertical infiltration,which is not affected by the slope angle and the seepage direction of the accumulation soil.(3)The liquefaction of loess is the root cause of loess mudflows.Water infiltrates into the area with an uneven density and a large amount of water accumulates in this area.Thus,the water content of the loess increases and the pore water pressure increases quickly and cannot dissipate in time,so the loess liquefies and the liquefacted area continues to spread and become larger.Thus,loess mudflows(large scale)occur.The increase in pore water pressure was captured in the seven sets of experiments.However,the order of the rising positions in the accumulation were different.This requires us to carry out tracking of the particle displacement inside the soil and the spatial changes in the internal structure of the soil in future research.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
The maximum Mode Ⅰ and Mode Ⅱ stress intensity factors(SIFs), KI,kmax(θ) and KII,kmax(θ)(0°<θ<360°), of inclined parallel multi-crack varying with relative positions(including horizontal and verti...The maximum Mode Ⅰ and Mode Ⅱ stress intensity factors(SIFs), KI,kmax(θ) and KII,kmax(θ)(0°<θ<360°), of inclined parallel multi-crack varying with relative positions(including horizontal and vertical spacings) are calculated by the complex function and integration method to analyze their interacting mechanism and determine the strengthening and weakening zone of SIFs. The multi-crack initiation criterion is established based on the ratio of maximum tension-shear SIF to predict crack initiation angle, load, and mechanism. The results show that multi-crack always initiates in Mode Ⅰ and the vertical spacing is better not to be times of half crack-length for crack-arrest, which is in good agreement with test results of the red-sandstone cube specimens with three parallel cracks under uniaxial compression. This can prove the validity of the multi-crack initiation criterion.展开更多
In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests ...In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests were implemented in the drop plate impact device.Strain gauges were employed to measure impact loads and crack initiation time.The corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the crack.Using experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading rate.For the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.展开更多
The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and...The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and resultant peak particle velocity(PPV)generates.With the orientation sequence of holes blasts on site,the superimposition angle of wave changes and hence results in significant variation in resultant PPV.The orientation with respect to the initiation of blasts resulting in lowest PPV needs to be identified for any site.By knowing the PPV contour of vibration waves in mine sites,it is possible to reduce the vibration on the structures by changing the initiation sequence.In this paper,experimental blasts were conducted at two different mine sites and the PPV values were recorded at different ori-entations from the blast site and its initiation sequence.The PPV contours were drawn to identify the orientation with least and highest PPV generation line.It was found that by merely changing the initi-ation sequence of blasts with respect to the sensitive structure or point of interest,the PPV values can be reduced significantly up to 76.9%.展开更多
Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in G...Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in Garai et al.,2022),there are contours of measured vibration velocities in 4 directions(every 90?)and an incorrect interpretation between them.By placing all measured vibration velocity values(Gerai et al.,2022)at well-defined points on a single figure,it was not possible to precisely determine the type of vibration velocity,such as radial,tangential and vertical vibration velocities,with their different shapes.An incorrect conclusion was also drawn about the direction of the highest vibration velocity.The paper by Garai et al.(2022)measured the vibrational velocity of the medium through which the seismic wave passed,but used the incorrect term shock wave.The shock wave would have destroyed the seismic measuring instruments.A superposition of the vibrational velocity was considered,but not combined with the vibrational frequency of the seismic wave.This paper presents a method for selecting the time delay between successively initiated explosive charges to the measured frequency of the seismic wave,so that the direction of initiation of the explosive charges does not affect the vibration velocity of the ground through which the seismic wave passes.The theoretical and measured shapes and waveforms of radial velocity and tangential velocity in an opencast lignite mine are then presented.Moreover,the conditions for the formation of shock wave,transition wave and seismic waves are presented.展开更多
Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Ove...Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution.Tracking the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316F, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.展开更多
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.
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.
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supported by National Natural Science Foundation of China(31860490)YNTC funds(2023530000241007 and 2017YN02)+1 种基金Yunnan Daguan Lab(YNDG202302ZY01)CLZ is supported by the Postdoctoral Fellowship Program of CPSF under grant number GZC20241527。
文摘Recessive resistance mediated by mutations in the eukaryotic translation initiation factor 4E(eIF4E),has proven effective against diverse potyviruses and is extensively utilized in breeding programs.However,the rise of resistance-breaking(RB)strains and emerging potyviral species necessitates the development of more durable and broad-spectrum resistance strategies.In this study,our field survey in Yunnan,China,identified potato virus Y(PVY)RB isolates,as well as the prevalence of tobacco vein banding mosaic virus(TVBMV)and chilli veinal mottle virus(ChiVMV),in tobacco carrying the recessive va locus,which lacks the eIF4E1-S susceptibility gene,due to a chromosomal deletion.Protein interaction and viral infection assays demonstrated that both eIF4E1-S and eIFiso4E-T are used by PVY RB as susceptibility factors for infection,with the combined inactivation of these genes confering durable resistance.Similarly,the knockout of eIFiso4E-S,in the va genetic background,provided effective resistance to TVBMV and reduced susceptibility to ChiVMV.Notably,pyramiding mutations in eIFiso4E-S and eIFiso4E-T,in va tobacco,generated plants exhibiting robust,broad-spectrum resistance,to all three viruses,without compromising plant development.These findings underscore the potential of stacking eIF4E mutations to engineer durable,broad-spectrum resistance to potyviruses in tobacco,offering a promising strategy for crop improvement.
基金supported by the Science Center for Gas Turbine Project(No.P2022-B-IV-009-002).
文摘Hydrogen has emerged as a promising clean energy source,leading to numerous recent efforts to integrate hydrogen into turbine engine applications[1].This integration has the potential to significantly enhance engine efficiency while reducing carbon dioxide emissions[2].However,the degradation of nickel alloys induced by hydrogen has been well documented[3-7].Consequently,hydrogen-assisted failure of nickel alloys poses a critical concern for the design and safe operation of hydrogen-powered turbine engines.
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.
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.
文摘The fatigue crack initiation and early propagation behavior of 2A97 Al-Li alloy was studied. The smooth specimens were fatigued at room temperature under constant maximum stress control when stress ratio （R） is 0.1 and frequency （f） is 40 Hz. Microstructure observations were examined by optical microscopy, transmission electron microscopy, scanning electron microscopy and electron back scattered diffusion, in order to investigate the relationship between microstructure and fatigue crack initiation and early propagation behavior of 2A97 alloy. The results show that the fatigue cracks are predominantly initiated at inclusions and coarsen secondary phases on the surface of 2A97 alloy. The fatigue crack early propagation behavior of 2A97 alloy is predominantly influenced by the interactions between grain structure and dislocations or persistent slip bands （PSBs）. When the misorientation of two neighbouring grains is close to the orientations of the favorable slip plane within these two grains, high-angle grain boundary severely hinders the PSBs passing through, and thus leads to crack bifurcation and deflection.
文摘The time course of the initiation of different types of apical primordia on the stem of wheat (Triticum aestivum L.) was investigated to establish a comprehensive pattern of apical primordium development and quantitative dynamic relationships among different primordium initiation. The results showed that the initiation of leaf and bracteal primordia took the S shape, and that of spikelet and floret took the rise stage of parabolic shape in relation to GDD (growing degree days after sowing) in wheat. The bracteal was much like vegetative rather than reproductive organ in terms of the dynamic pattern of primordium initiation. The progress of spikelet and floret primordium initiation could well reflect the characteristics of different genotypes and the impact of different ecological environments on wheat apical development. The integrated model of different primordium initiation in shoot of wheat was an S_shaped curvilinear, and could be divided into three sub_models. The number of leaf primordia was affected by both genotype and environment, while the numbers of bracteal, spikelet and floret primordia were affected mainly by environmental factors. Measured with mean thermochron, the rates of initiation of leaf, bracteal and spikelet primordia in normal planting were the highest among all the sowing date treatments. In contrast to the relationships among leaf, bracteal, spikelet and their initiation duration, the correlation between the number of floret and its initiation duration was highly significant.
基金Project(11102224)supported by the National Natural Science Foundation of ChinaProject(201206370124)supported by the China Scholarship Council,China
文摘The ratio of crack initiation stress to the uniaxial compressive strength(SCI,B/SUC,B) and the ratio of axial strain at the crack initiation stress to the axial strain at the uniaxial compressive strength(B,UCB,CI,A,A/SSSS) were studied by performing numerical stress analysis on blocks having multi flaws at close spacing's under uniaxial loading using PFC3 D. The following findings are obtained: SCI,B/SUC,B has an average value of about 0.5 with a variability of ± 0.1. This range agrees quite well with the values obtained by former research. For joint inclination angle, β=90°,B,UCB,CI,A,A/SSSS is found to be around 0.48 irrespective of the value of joint continuity factor, k. No particular relation is found betweenB,UCB,CI,A,A/SSSS and β; however, the average B,UCB,CI,A,A/SSSS seems to slightly decrease with increasing k. The variability ofB,UCB,CI,A,A/SSSS is found to increase with k.Based on the cases studied in this work,B,UCB,CI,A,A/SSSS ranges between 0.3 and 0.5. This range is quite close to the range of 0.4to 0.6 obtained for SCI,B/SUC,B. The highest variability of ± 0.12 forB,UCB,CI,A,A/SSSS is obtained for k=0.8. For the remaining k values the variability ofB,UCB,CI,A,A/SSSS can be expressed within ± 0.05. This finding is very similar to the finding obtained for the variability of SCI,B/SUC,B.
文摘In order to study the relationship between charge size and thermal initiation critical temperature of explosive in defined conditions,cook-off test about JH explosive was carried out at a heating rate of 1 ℃/min using self-designed cook-off experiment setup based on thermostatic control technology.Numerical simulation was conducted to study the effects of different charge sizes on thermal initiation critical temperature of explosives with FLUENT software.Experiment results show that there is a thermal initiation critical temperature in cook-off bomb.Simulation results show that when the ratio of the length to diameter of explosives grains is a fixed value,the thermal initiation critical temperature of explosives decreases with the increase of the diameter of explosives grains.When the grains diameter of explosives increase up to a certain value,the influence of charge size on thermal initiation critical temperature tends to be weakened.Charge size has no influence on the ignition point of explosives.The ignition point is always in the center of the grain.
基金financially supported by the Program of National Natural Science Foundation of China(Nos.42090053,42041006,4210071970)Central University Fundamental Research Fund(No.300102262907)。
文摘The structure of loess is loose,and the shear strength of loess drops sharply after contact with water.Therefore,loess mudflows have become a common geological disaster on the Chinese Loess Plateau.In order to study the initiation mode and mechanism of loess mudflows,in this study,seven sets of flume experiments were designed by controlling the slope angle and rainfall intensity.The results show that(1)when the slope angle is between 10°and 20°,there are two initiation mechanisms of loess mudflows:mudflow(large scale)and retrogressive toe sliding,and mudflow(small-scale)and retrogressive toe sliding.(2)The main method by which water infiltrates into the soil accumulation is mainly vertical infiltration,which is not affected by the slope angle and the seepage direction of the accumulation soil.(3)The liquefaction of loess is the root cause of loess mudflows.Water infiltrates into the area with an uneven density and a large amount of water accumulates in this area.Thus,the water content of the loess increases and the pore water pressure increases quickly and cannot dissipate in time,so the loess liquefies and the liquefacted area continues to spread and become larger.Thus,loess mudflows(large scale)occur.The increase in pore water pressure was captured in the seven sets of experiments.However,the order of the rising positions in the accumulation were different.This requires us to carry out tracking of the particle displacement inside the soil and the spatial changes in the internal structure of the soil in future research.
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The authors are grateful for the financial supports from the National Natural Science Foundation of China(51874351,51474251)Hunan Provincial Innovation Foundation For Postgraduate,China(CX2018B047)the Open Sharing Fund for the Large-scale Instruments and Equipments of Central South University,China(CSUZC201923).
文摘The maximum Mode Ⅰ and Mode Ⅱ stress intensity factors(SIFs), KI,kmax(θ) and KII,kmax(θ)(0°<θ<360°), of inclined parallel multi-crack varying with relative positions(including horizontal and vertical spacings) are calculated by the complex function and integration method to analyze their interacting mechanism and determine the strengthening and weakening zone of SIFs. The multi-crack initiation criterion is established based on the ratio of maximum tension-shear SIF to predict crack initiation angle, load, and mechanism. The results show that multi-crack always initiates in Mode Ⅰ and the vertical spacing is better not to be times of half crack-length for crack-arrest, which is in good agreement with test results of the red-sandstone cube specimens with three parallel cracks under uniaxial compression. This can prove the validity of the multi-crack initiation criterion.
基金Projects(U19A2098,1210021843)supported by the National Natural Science Foundation of ChinaProject(2021SCU12130)supported by Fundamental Research Funds for the Central Universities,China+1 种基金Project(2021YJ0511)supported by the Sichuan Science and Technology Program,ChinaProjects(DESEYU202205,DESE202005)supported by the Open Fund of Key Laboratory of Deep Earth Science and Engineering,China。
文摘In order to simultaneously measure the initiation toughness of pure mode Ⅰ and mode Ⅱ cracks in one specimen,a large-size double-cracked concave-convex plate(DCCP)specimen configuration was proposed.Impacting tests were implemented in the drop plate impact device.Strain gauges were employed to measure impact loads and crack initiation time.The corresponding numerical model was established by using the dynamic finite difference program AUTODYN,and the experimental-numerical method and ABAQUS code were utilized to obtain the initial fracture toughness of the crack.Using experiments and numerical research,we concluded that the DCCP specimen is suitable for measuring the initial fracture toughness of pure mode Ⅰ and mode Ⅱ cracks at the same time;the dynamic initiation toughness increases with the increase of loading rate and the crack initiation time decreases with increasing loading rate;the initiation toughness of mode Ⅱ crack is 0.5 times that of mode Ⅰ crack when subjected to the same loading rate.For the pre-crack in the vicinity of the bottom of a sample,when its length increases from 20 to 100 mm,the dynamic initiation toughness of the pure mode Ⅰ crack gradually decreases,and the longer the lower crack length is,the easier the crack would initiate,but the dynamic initiation toughness of pure mode Ⅱ crack varies little.
文摘The blast-induced ground vibrations can be significantly controlled by varying the location and orien-tation of point of interest from blast site.The blast waves generated due to individual holes get super-imposed and resultant peak particle velocity(PPV)generates.With the orientation sequence of holes blasts on site,the superimposition angle of wave changes and hence results in significant variation in resultant PPV.The orientation with respect to the initiation of blasts resulting in lowest PPV needs to be identified for any site.By knowing the PPV contour of vibration waves in mine sites,it is possible to reduce the vibration on the structures by changing the initiation sequence.In this paper,experimental blasts were conducted at two different mine sites and the PPV values were recorded at different ori-entations from the blast site and its initiation sequence.The PPV contours were drawn to identify the orientation with least and highest PPV generation line.It was found that by merely changing the initi-ation sequence of blasts with respect to the sensitive structure or point of interest,the PPV values can be reduced significantly up to 76.9%.
文摘Recently,Garai et al.(2022)published a paper on the impact of orientation of blast initiation on ground vibrations.However,some of the claims are not supported by the results of the given tests.In Fig.1(see Fig.8 in Garai et al.,2022),there are contours of measured vibration velocities in 4 directions(every 90?)and an incorrect interpretation between them.By placing all measured vibration velocity values(Gerai et al.,2022)at well-defined points on a single figure,it was not possible to precisely determine the type of vibration velocity,such as radial,tangential and vertical vibration velocities,with their different shapes.An incorrect conclusion was also drawn about the direction of the highest vibration velocity.The paper by Garai et al.(2022)measured the vibrational velocity of the medium through which the seismic wave passed,but used the incorrect term shock wave.The shock wave would have destroyed the seismic measuring instruments.A superposition of the vibrational velocity was considered,but not combined with the vibrational frequency of the seismic wave.This paper presents a method for selecting the time delay between successively initiated explosive charges to the measured frequency of the seismic wave,so that the direction of initiation of the explosive charges does not affect the vibration velocity of the ground through which the seismic wave passes.The theoretical and measured shapes and waveforms of radial velocity and tangential velocity in an opencast lignite mine are then presented.Moreover,the conditions for the formation of shock wave,transition wave and seismic waves are presented.
基金supported financially by the National Natural Science Foundation of China (Nos. 51771212 and 11327901)the Innovation Fund in IMR (No. 2017-ZD05)
文摘Passive metals have superior resistance to general corrosion but are susceptible to pitting attack in certain aggressive media, leading to material failure with pronounced adverse economic and safety consequences. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution.Tracking the accurate sites where initial dissolution occurs as well as the propagation of the dissolution by means of multi-scale characterization is key to deciphering the link between microstructure and corrosion at the atomic scale and clarifying the pitting initiation mechanism. Here, we review our recent progresses in this issue by summarizing the results in three representative materials of 316F, and Super 304H stainless steel as well as 2024-Al alloy, using in situ ex-environmental TEM technique.
