This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches tha...This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches that descended from the analyzed gully,as reported in the literature from the 1900s until now.However,only the data collected in recent years,our field studies,combined with modern LIDAR data and GIS-based modeling,allowed us to perform a detailed analysis.The GIS-based approach effectively uses spatial data to address snow avalanche modeling challenges.Although the study area lies within Tatra National Park,no official services carry out systematic avalanche monitoring or measurements.The impact of hazardous events,such as snow avalanches,on the most famous Polish mountain lake,Morskie Oko,has been poorly described in the literature and has yet to be discovered.Therefore,to analyze the selected avalanche parameters,we mainly used our ground and additional aerial photographs taken by local mountain services and related field measurements.Our analysis resulted in figurative estimates of the extent and volume of avalanche snow and its weight,both on the surface of the ice sheet and the part of the avalanche that did not reach the lake's shore and remained on the slope of Marchwiczny Gully.For example,the values for the mighty avalanche on February 3,2023,are 23,500 m~3 and 4,700 tons on the ice surface and 20,000 m~3 and 4,000 tons on the slope.It was determined that avalanches that descend onto the studied lake's surface result in its shallowing.This process occurs because of sedimentation of slope material carried by avalanches,especially during the final phase of ice cover melting.When openings appear in the solid ice cover in spring,floating ice can migrate,driven by wind pressure,and deposit avalanche material in various parts of the lake bottom.Thus,avalanches contributed to the gradual disappearance of the lake.展开更多
Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events...Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events that occurred in the NQM.However,there is a lack of systematic discussion on the genetic dynamics of these rock avalanches.Hence,taking Earth system scientific research as a starting point,this paper systematically summarizes and discusses development characteristics,formation times and genetic dynamic mechanisms of granitic rock avalanches in the NQM based on geological investigations,high-precision remote sensing interpretations,geomorphological dating,geophysical exploration,and a large-scale shaking table model test.We identified 53 granitic rock avalanches in this area,with a single collapse area ranging from 0.01×10~6 to 1.71×10~6 m^(2).Their development time can be divided into six stages,namely,107000 years BP,11870–11950 years BP,11000 years BP,2300 years BP,1800 years BP,and 1500 years BP,which were closely related to multiple prehistoric or ancient earthquakes.We suggest that long-term coupling of internal and external earth dynamics was responsible for the granitic rock avalanches in the NQM;the internal dynamics were mainly related to subduction,collision and extrusion of different plates under the Qinling terrane,leading to the formation and tectonic uplift of the Qinling orogenic belt;and the external dynamics were closely associated with climate changes resulting in mountain denudation,freeze-thaw cycles and isostatic balance uplift.In this process,the formation and evolution of the Qinling orogenic belt play a geohazard-pregnant role,structural planes,including faults and joints,play a geohazard-controlled role,and earthquakes play a geohazard-induced role,which jointly results in the occurrence of large-scale granitic rock avalanches in the NQM.This research can not only decipher the genetic dynamic mechanism of large hard granitic rock avalanches but also reveal temporal and spatial patterns of the evolution of breeding and the generation of large-scale rock avalanches in the margins of orogenic belts.展开更多
Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors ...Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors than Earth,and interestingly,a pyrolitic mantle composition under warmer conditions is predicted to have a distinctly different mantle transition zone compared to the present-day Earth(Hirose,2002;Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014;Dannberg et al,2022).Instead of olivine primarily transforming into its higher-pressure polymorphs such as wadsleyite and then ringwoodite,at pressures corresponding to 410 km and 520 km depth in Earth,respectively,it instead transforms into a mineral assemblage of wadsleyite,majorite,and ferropericlase(WMF),and then to majorite+ferropericlase(MF),before finally transforming into bridgmanite at pressures corresponding to 660 km depth in Earth(Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014).Convective motions in stagnant lid planets are dominated by small-scale instabilities(cold drips)forming within the mobile rheological sublayer under the rigid lid.Using ASPECT and a thermodynamic model of a pyrolitic mantle composition generated by HeFESTo,we show that under certain conditions,the small drips can pond atop the WMF-MF mineral phase transition.The barrier to convective flow arises from the WMF mineral phase assemblage having an effective negative thermal expansivity(Stixrude and Lithgow-Bertelloni,2022).Although large-scale downwellings that typically occur within mobile lid planets are able to pass through the WMF zone without difficulty(Dannberg et al.,2022;Li RP et al.,2024),the smaller and less negatively buoyant nature of downwelling drips in stagnant lid planets are more susceptible to these effects,which leads to an ephemeral layering of the mantle.Our numerical models show that in stagnant lid planets with mantle potential temperatures that exceed 1900 K,the smaller,cold drips from the lid continue to pile up until enough of them have coalesced that they collectively avalanche as a larger instability into the deeper interior.展开更多
As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge ...As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains lacking.We summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st century.The distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to September.We highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing factors.The failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure type.Finally,we deliver recommendations concerning the risk assessment and prediction of IAs.The results provide important scientific value for addressing climate change and resisting glacier-related hazards.展开更多
Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in ...Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in high altitude mountainous regions.Specifically,the extreme glaciated slope failures often transform into extraordinarily large and mobile debris flows,resulting in disastrous consequences such as sedimentation and desertification.Due to a dearth of on-site observation data and experimental data collection,our comprehension of the geomorphic and kinematic characteristics of rock-ice avalanches remains poor.Here we report a cluster of ancient rock-ice avalanches spreading along the Chomolhari range of the China-Bhutan Himalayas.By integrating remote sensing image interpretation with detailed field investigations,we demonstrate the geomorphic and sedimentary characteristics of four events among the avalanches.The estimated volumes of the four are 23.73 Mm³,39.69 Mm³,38.43 Mm³,and 38.25 Mm³,respectively.The presence of pre-existing moraines or alluvial fans constrained their movement,resulting in deposition features such as marginal digitated lobes at higher elevations and large depressed areas in the interior.Applying the Savage-Hutter theory,we calculate the basal friction angle and travel angle of these ancient rock-ice avalanches that are both less than 10°,affirming the similarity of these avalanches in the study area to those occurring in other regions.Our study significantly contributes to understanding the geomorphic and kinematic characteristics of rock-ice avalanches in high-altitude mountainous regions,providing valuable insights into their response to the disproportionate growth of Himalayan peaks.展开更多
Arrays of baffles are usually installed in front of protection site to attenuate the flow energy of rock avalanches in mountainous areas. Optimization design is crucial for efficiency promotion in hazard energy dissip...Arrays of baffles are usually installed in front of protection site to attenuate the flow energy of rock avalanches in mountainous areas. Optimization design is crucial for efficiency promotion in hazard energy dissipation engineering. In this study, a deceleration strip was added in the baffles protection system to optimize the traditional baffles system. The effects of the "baffles-deceleration strip" hybrid protection system was discussed in detail with the nails number and nails angle. This study presents details of numerical experiments using the discreteelement method(DEM). The effect of the optimization of hybrid protection system(nail angle and nail number) were investigated specifically, especially the impact force that avalanches exerted on structures. The results show that the maximum impact forces and kinetic energy of the rock avalanches decreases with the increase of the number and angle of the nail. Moreover, the distance between the toe and the bearing structure(L_m) is also a key factor. The shorter the distance L_m(30 m) is, the higher the maximum impact force are. The longer the distance L_m(70 m) is, the lower the maximum impact force are. Under the same size of the nails, increasing the numbers can enhance the dissipation ability of the hybrid protection system. Meanwhile, increasing itsangle can also enhance the dissipation ability. There are three key ways for nails attenuate rock avalanches:(i) block the fine particles directly;(ii) form the particles bridge between nails and baffles;(iii) dissipate the coarse particles energy directly. The effect of segregation in rock avalanches is crucial for the energy dissipation mechanism, which is a key factor to optimize the traditional baffle system.展开更多
In mountainous areas,rock avalanches swarm downslope leading to large impact forces on structures.Baffle systems are usually set up in torrent channels to dissipate the flow energy and reduce the destructive effects.I...In mountainous areas,rock avalanches swarm downslope leading to large impact forces on structures.Baffle systems are usually set up in torrent channels to dissipate the flow energy and reduce the destructive effects.In this paper,a crown-like baffle system is proposed to better dissipate the flow energy.The energy dissipation mechanism of this system was investigated based on DEM.The results reveal more than 90%of the kinetic energy of the granular flow was dissipated by particleparticle interaction.Two effects,the impedance effect and the deflection effect,were identified.The influence of these effects leads to the formation and growth of cushions behind the baffles,and these cushions enhance the particle-particle interaction.Two crown-like baffle systems were compared with a conventional baffle system based on the typical avalanche model.The results reveal the cumulative residual kinetic energy of the crown-like baffle system with square baffles decreased by 18.75%with the same concrete consumption as the conventional baffle system.For the crown-like baffle system with triangular baffles,the cumulative residual kinetic energy decreased by 6.22%with 83.94%of the concrete consumption of the conventional baffle system.Hence,the proposed baffle system is more cost-effective compared with the conventional baffle system.展开更多
In the current research, serrated flow is investigated under tensile and compressive loading in a ZrCubased bulk metallic glass composite (BMGC) that is well known for its plastic deformability, which is higher than t...In the current research, serrated flow is investigated under tensile and compressive loading in a ZrCubased bulk metallic glass composite (BMGC) that is well known for its plastic deformability, which is higher than that of metallic glasses. Statistical analysis on serrations shows a complex, scale free process, in which shear bands are highly correlated. The distribution of the elastic-energy density stored in each serration event follows a power-law relationship, showing a randomly generated serrated event under both tension and compression tests. The plastic deformation in the temporal space is explored by a timeseries analysis, which is consistent with the trajectory convergent evolution in critical dynamic behavior even in the low strain rate regime in both tests. The results demonstrate that the secondary phase in the BMGC can stabilize the shear band extension and facilitate the critical behavior in the low strain rate regime. This study provides a strong evidence of serrated flow phenomenon in BMGC under tension test, and offers a deep understanding of the correlation between serrations and shear banding in temporal space.展开更多
Scientific research on snow avalanches is relatively modem, yet in constant and rapid evolution, as the multiple disciplines involved in its development will, in turn, become more specialized and more technical. Paten...Scientific research on snow avalanches is relatively modem, yet in constant and rapid evolution, as the multiple disciplines involved in its development will, in turn, become more specialized and more technical. Patents are part of research and knowledge production. The scientific community and policy makers are increasingly interested in production of knowledge collaboratively. Almost all of the research being conducted on snow avalanches uses technology, technique or instrumentation. One main objective of this study is to draw from the literature the many technologies, techniques and instrumentations that are being used in research related to avalanches. Thus, a textual analysis of the most significant literature in the field of snow avalanches was done. In this analysis, techniques, technologies and instrumentations have emerged. A patent search has been done in databases. Subsequently, patents were conceptualized. The proportion of applicants for patents is higher in industry than in universities. The measure of exploration of the ongoing sociocognitive transformations of science and technology systems presents a useful tool to conduct a study to explore these transformations. It would be interesting for the scientific community, but also for the industry, to elaborate concept mapping when applied to avalanche research, which would help in determining referents.展开更多
A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby...A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby the hillside are taken for analysing the weather situation. The meteorological parameters air temperature, wind intensity and wind speed, relative humidity, precipitation and snow depth are investigated for similarities short before and during an avalanche. The avalanches are grouped into three categories and meteorological characteristics are found for each category. Thereby the avalanche hazard for the observed hillside is better assessed and an infrastructure safety by avalanche control due to concerted avalanche blasts is more effective. The result of the analysis shows three kinds of hazard weather conditions, which increase the avalanche hazard： warm air temperatures cause a settlement of the snow pack, but in the beginning of the process a weakening in the snow pack happens. Rapidly decreasing of the air temperature cause cracks in the snow pack and the combination of fresh snow and strong wind speed leads to accumulation of snow on sheltered slopes.展开更多
Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are di...Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are displayed during stable plastic flows at strain rates of 2×10-4 s-1 and 5×10-5 s-1,respectively,which means that serration behavior depends on the strain rate.However,the remarkable agreement between measured slip-avalanche magnitudes and the scaling behavior,i.e.a universal complementary cumulative distribution function（CCDF）predicted by mean-field theory（MFT）model,indicates that the plasticity of the present Fe-based BMGs can be tuned by imposed strain rates：Smax^6）ε-λ.This tuned plasticity is elucidated with expended free-volume model.Moreover,the scaling behavior of serrated flows for other strain rates can be predicted as well.展开更多
The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat co...The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat contraction index(T)is introduced to quantify variations in throat topography,and 96 numerical simulation experiments with varying T and slope angles(δ)are conducted.The findings indicate that granular flows experience transient obstructions when traversing throat topographies,primarily due to the periodic formation and breaking of the arch structure.Observations suggest that the acceleration of velocity in the tails of granular flows is restrained by the throat region,potentially altering the dynamics of related geohazards.In this study,the impact of throat topography is quantitatively assessed,demonstrating a reduction in peak flowrates of granular materials by 20%-80% and extending the flowduration up to six times.The present study proposes the throat-induced hazard index(Φ)to evaluate the influenceof throat topography on the risk of rockslides and avalanches characterized by granular flows,which may provide insights for the design of mitigation structures in topographic regions.展开更多
Flux avalanches,prevalently existing in superconducting thin films,can cause catastrophic breakdowns of electromagnetic properties and even irreversible damage to superconducting materials.Metal coating is an effectiv...Flux avalanches,prevalently existing in superconducting thin films,can cause catastrophic breakdowns of electromagnetic properties and even irreversible damage to superconducting materials.Metal coating is an effective way to suppress the flux avalanches in superconducting thin films.Nevertheless,it is difficult to reveal the suppression mechanisms due to the challenge of effectively separating the simultaneous eddy currents and heat exchange in the metal coating.In this work,the eddy currents and heat exchange in the Ag metal coating are separated by setting a thermal insulation layer,and its inhibiting effect on the flux avalanches of the YBCO superconducting thin films is elucidated.The results indicate that eddy currents play an important part in suppressing magnetic flux avalanches,and their effect strengthens with increasing Ag thickness.Meanwhile,employing the double-exposure method,the flux avalanche velocity of YBCO superconducting thin films was measured,revealing a significant decrease in the magnetic flux avalanche velocity due to suppression by eddy currents.Moreover,a theoretical model was established to investigate the influence of eddy currents on the motion of a single vortex,and the calculated results showed good agreement with the experiments.These findings provide a better understanding of the flux avalanches and their suppression in YBCO superconducting thin films.展开更多
Photon avalanche occurring in lanthanide-doped materials exhibits a giant optical nonlinear response of the emission intensity to the excitation intensity,which holds great potential in the applications of optical sen...Photon avalanche occurring in lanthanide-doped materials exhibits a giant optical nonlinear response of the emission intensity to the excitation intensity,which holds great potential in the applications of optical sensing,super-resolution imaging,quantum detection,and other techniques.However,strategies for developing photon avalanches in nanoparticles are limited,and many widely used lanthanide ions have not yet been able to generate high-efficiency avalanching emissions.A general strategy named cascade migrating photon avalanche was proposed to achieve efficient avalanching emissions with huge optical nonlinearities from a large number of emitters at the nanoscale and at room temperature.Specifically,the optical nonlinearity order of bright avalanched Tm^(3+)-emission was achieved at 63rd order by utilizing the Yb^(3+)∕Pr^(3+)-codoped nano-engine.By further incorporating a Gd^(3+)sublattice migrating network,its avalanching energy can propagate over a long distance to arouse avalanching emission with extreme optical nonlinearities up to 45th order among various emitters(Tb^(3+),Eu^(3+),Dy^(3+),Sm^(3+))in multilayered nanostructures.By achieving abundant avalanching full-spectrum emissions,it would be highly conducive to applications in various fields.For instance,our strategy demonstrated its applicability in multi-color super-resolution microscopic imaging with single-nanoparticle sensitivity and resolution up to 48 nm,utilizing a single low-power 852 nm excitation beam.展开更多
Disordered ferromagnets with a domain structure that exhibit a hysteresis loop when driven by the external magnetic field are essential materials for modern technological applications.Therefore,the understanding and p...Disordered ferromagnets with a domain structure that exhibit a hysteresis loop when driven by the external magnetic field are essential materials for modern technological applications.Therefore,the understanding and potential for controlling the hysteresis phenomenon in thesematerials,especially concerning the disorder-induced critical behavior on the hysteresis loop,have attracted significant experimental,theoretical,and numerical research efforts.We review the challenges of the numerical modeling of physical phenomena behind the hysteresis loop critical behavior in disordered ferromagnetic systems related to the non-equilibriumstochastic dynamics of domain walls driven by external fields.Specifically,using the extended Random Field Ising Model,we present different simulation approaches and advanced numerical techniques that adequately describe the hysteresis loop shapes and the collective nature of the magnetization fluctuations associated with the criticality of the hysteresis loop for different sample shapes and varied parameters of disorder and rate of change of the external field,as well as the influence of thermal fluctuations and demagnetizing fields.The studied examples demonstrate how these numerical approaches reveal newphysical insights,providing quantitativemeasures of pertinent variables extracted from the systems’simulated or experimentally measured Barkhausen noise signals.The described computational techniques using inherent scale-invariance can be applied to the analysis of various complex systems,both quantum and classical,exhibiting non-equilibrium dynamical critical point or self-organized criticality.展开更多
Analytical expressions for scaling of brain wave spectra derived from the general nonlinear wave Hamiltonian form show excellent agreement with experimental“neuronal avalanche”data.The theory of the weakly evanescen...Analytical expressions for scaling of brain wave spectra derived from the general nonlinear wave Hamiltonian form show excellent agreement with experimental“neuronal avalanche”data.The theory of the weakly evanescent nonlinear brain wave dynamics[Phys.Rev.Research 2,023061(2020);J.Cognitive Neurosci.32,2178(2020)]reveals the underlying collective processes hidden behind the phenomenological statistical description of the neuronal avalanches and connects together the whole range of brain activity states,from oscillatory wave-like modes,to neuronal avalanches,to incoherent spiking,showing that the neuronal avalanches are just the manifestation of the different nonlinear side of wave processes abundant in cortical tissue.In a more broad way these results show that a system of wave modes interacting through all possible combinations of the third order nonlinear terms described by a general wave Hamiltonian necessarily produces anharmonic wave modes with temporal and spatial scaling properties that follow scale free power laws.To the best of our knowledge this has never been reported in the physical literature and may be applicable to many physical systems that involve wave processes and not just to neuronal avalanches.展开更多
The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for t...The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for testing the dynamic avalanche capability of FS-IGBTs.Numerous studies have demonstrated that factors such as device structure,avalanche-generating current filaments,and electrical parameters influence the dynamic avalanche effect of the FS-IGBT.However,few studies have focused on enhancing the avalanche reliability of the FS-IGBT by adjusting circuit parameters during operation.In this paper,the dynamic avalanche effect of the FS-IGBT under UIS conditions is comprehensively investigated through a series of comparative experiments with varying circuit parameters,including bus voltage V_(DC),gate voltage V_(G),gate resistance R_(g),load inductance L,and temperature TC.Furthermore,a method to enhance the dynamic avalanche reliability of the FS-IGBT under UIS by optimizing circuit parameters is proposed.In practical applications,reducing gate voltage,increasing load inductance,and lowering temperature can effectively improve the dynamic avalanche capability of the FS-IGBT.展开更多
The precise mathematical method was adopted to simulate the breakdown process of 5 mm rod and plate electrode gap,which was filled with supercritical nitrogen at the condition of 127 K,4 MPa and seed electron density ...The precise mathematical method was adopted to simulate the breakdown process of 5 mm rod and plate electrode gap,which was filled with supercritical nitrogen at the condition of 127 K,4 MPa and seed electron density 1×10^(6) m^(-3) under 29 kV DC voltage.The result shows that the discharge process was completed within 11.8 ns from seed electron triggering,avalanche bulking to streamer extending until gap eventually breakdown.The entire gap breakdown process was divided into three discharge stages,namely,the initial discharge triggered(0-4 ns),avalanche(4-7 ns)and streamer phase(7-11.8 ns).At the same time,the facts were also revealed that the discharge evolution,electric field distribution,and electron density had different values,and also showed different temporal and spatial distribution characteristics along the axis of the discharge gap.Specifically,the discharge characteristics of SCN2 under 1,2,3,4,4.5,and 5 MPa at 127 K were theoretically analyzed respectively,and the microscopic mechanisms of the breakdown process were also detailed.The results indicate that the gas discharge law remained applicable within the 1-3 MPa range.However,the discharge characteristics of supercritical nitrogen at 3.4-5 MPa differed significantly from those at lower pressures,likely attributable to the unique state of matter exhibited by supercritical nitrogen.This study contributes to understanding the discharge mechanism of supercritical nitrogen and offers theoretical guidance for its practical application in the power industry.展开更多
Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in re...Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in regional temperatures and the occurrence of extreme snowfall events,the frequency and intensity of avalanches have escalated,resulting in more severe incidents and higher casualty rates.As natural archives of environmental changes,tree rings offer valuable proxies for avalanche hazard assessments in regions where direct observation data is scarce,particularly in high-altitude regions.The dendrogeomorphology has been gradually being applied in avalanche hazard evaluation,however,it remains limited in China.To address this gap,this study systematically investigates the principles and methodologies for reconstructing avalanche histories and evaluates their applications in avalanche hazard assessments through a literature review and field observations.It provides a comprehensive overview of recent advancements in key areas,including the impact of avalanches on forest ecosystems,the reconstruction of avalanches,and the analysis of avalanche events(i.e.,the spatiotemporal distribution,the historical recurrence intervals,magnitudes,and triggering conditions of avalanches).Considering the current limitations in avalanche hazard assessments and the urgent need for such research in China,we outline key priorities and future directions,including refining reconstruction methodologies,developing a comprehensive tree-ring-based avalanche database for high-altitude regions,and establishing an advanced hazard assessment framework based on dendrochronological evidence.展开更多
This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with...This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with temperature-dependent elastoplastic behavior.The primary objective of the proposed method is to prevent crack propagation during pressure surges from operational to critical levels.This study examines the“Beineu-Bozoy-Shymkent”steel gas conduit,examining its performance across a temperature range of−40 to+50℃.This work builds on prior research on extended avalanche destruction in steel gas conduits and crack propagation prevention techniques.Theanalysis was conducted using a dynamic finite-element approach with the ANSYS-19.2/ExplicitDynamics software.Simulations of unprotected conduits revealed that increasing gas-dynamic pressure can convert a partial-depth crack into a through-crack,extending longitudinally to approximately seven times its initial length.Notably,at T=+50℃,the developed crack length was 1.2%longer than that at T=−40℃,highlighting the temperature sensitivity of crack progression.The modeling results indicate that crack propagation can be effectively controlled using a circular composite overlay with a thickness between 37.5%and 50%of the crack depth and a length approximately five times that of the initial crack,centered symmetrically over the crack.In addition,preliminary stress analysis indicated that limiting the overlay-induced pressure to 5%of the operational pressure effectively arrested crack growth without generating significant stress concentrations near the overlay boundaries,thereby preventing conduit integrity.展开更多
文摘This study represents a pioneering effort to analyze the impact of avalanches descending into Morskie Oko from Marchwiczny Gully,the most active avalanche path around the lake.It focuses on catastrophic avalanches that descended from the analyzed gully,as reported in the literature from the 1900s until now.However,only the data collected in recent years,our field studies,combined with modern LIDAR data and GIS-based modeling,allowed us to perform a detailed analysis.The GIS-based approach effectively uses spatial data to address snow avalanche modeling challenges.Although the study area lies within Tatra National Park,no official services carry out systematic avalanche monitoring or measurements.The impact of hazardous events,such as snow avalanches,on the most famous Polish mountain lake,Morskie Oko,has been poorly described in the literature and has yet to be discovered.Therefore,to analyze the selected avalanche parameters,we mainly used our ground and additional aerial photographs taken by local mountain services and related field measurements.Our analysis resulted in figurative estimates of the extent and volume of avalanche snow and its weight,both on the surface of the ice sheet and the part of the avalanche that did not reach the lake's shore and remained on the slope of Marchwiczny Gully.For example,the values for the mighty avalanche on February 3,2023,are 23,500 m~3 and 4,700 tons on the ice surface and 20,000 m~3 and 4,000 tons on the slope.It was determined that avalanches that descend onto the studied lake's surface result in its shallowing.This process occurs because of sedimentation of slope material carried by avalanches,especially during the final phase of ice cover melting.When openings appear in the solid ice cover in spring,floating ice can migrate,driven by wind pressure,and deposit avalanche material in various parts of the lake bottom.Thus,avalanches contributed to the gradual disappearance of the lake.
基金financially supported by the National Natural Science Foundation of China(Nos.42207197,42293355,41672285,42293350,42341101)the Fundamental Research Funds for the Central Universities(Nos.300102264917,300102262908,590123008)。
文摘Massive granitic rock avalanches are extensively developed in the middle section of the northern Qinling Mountains(NQM),China.The current consensus is that their formation could have been connected with seismic events that occurred in the NQM.However,there is a lack of systematic discussion on the genetic dynamics of these rock avalanches.Hence,taking Earth system scientific research as a starting point,this paper systematically summarizes and discusses development characteristics,formation times and genetic dynamic mechanisms of granitic rock avalanches in the NQM based on geological investigations,high-precision remote sensing interpretations,geomorphological dating,geophysical exploration,and a large-scale shaking table model test.We identified 53 granitic rock avalanches in this area,with a single collapse area ranging from 0.01×10~6 to 1.71×10~6 m^(2).Their development time can be divided into six stages,namely,107000 years BP,11870–11950 years BP,11000 years BP,2300 years BP,1800 years BP,and 1500 years BP,which were closely related to multiple prehistoric or ancient earthquakes.We suggest that long-term coupling of internal and external earth dynamics was responsible for the granitic rock avalanches in the NQM;the internal dynamics were mainly related to subduction,collision and extrusion of different plates under the Qinling terrane,leading to the formation and tectonic uplift of the Qinling orogenic belt;and the external dynamics were closely associated with climate changes resulting in mountain denudation,freeze-thaw cycles and isostatic balance uplift.In this process,the formation and evolution of the Qinling orogenic belt play a geohazard-pregnant role,structural planes,including faults and joints,play a geohazard-controlled role,and earthquakes play a geohazard-induced role,which jointly results in the occurrence of large-scale granitic rock avalanches in the NQM.This research can not only decipher the genetic dynamic mechanism of large hard granitic rock avalanches but also reveal temporal and spatial patterns of the evolution of breeding and the generation of large-scale rock avalanches in the margins of orogenic belts.
基金The authors are thankful for support from NASA Award 80NSSC22K0100U.S.Department of Energy Computational Science Graduate Fellowship under Award Number DESC0022158+1 种基金Computational resources were provided by Extreme Science and Engineering Discovery Environment(XSEDE),which is supported by National Science Foundation grant number ACI-1053575This research used resources of the National Energy Research Scientific Computing Center(NERSC),a Department of Energy Office of Science User Facility using NERSC award ASCRERCAP0026889.
文摘Stagnant lid planets are characterized by a globe-encircling,conducting lid that is thick and strong,which leads to reduced global surface heat flows.Consequently,the mantles of such planets can have warmer interiors than Earth,and interestingly,a pyrolitic mantle composition under warmer conditions is predicted to have a distinctly different mantle transition zone compared to the present-day Earth(Hirose,2002;Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014;Dannberg et al,2022).Instead of olivine primarily transforming into its higher-pressure polymorphs such as wadsleyite and then ringwoodite,at pressures corresponding to 410 km and 520 km depth in Earth,respectively,it instead transforms into a mineral assemblage of wadsleyite,majorite,and ferropericlase(WMF),and then to majorite+ferropericlase(MF),before finally transforming into bridgmanite at pressures corresponding to 660 km depth in Earth(Stixrude and Lithgow-Bertelloni,2011;Ichikawa et al.,2014).Convective motions in stagnant lid planets are dominated by small-scale instabilities(cold drips)forming within the mobile rheological sublayer under the rigid lid.Using ASPECT and a thermodynamic model of a pyrolitic mantle composition generated by HeFESTo,we show that under certain conditions,the small drips can pond atop the WMF-MF mineral phase transition.The barrier to convective flow arises from the WMF mineral phase assemblage having an effective negative thermal expansivity(Stixrude and Lithgow-Bertelloni,2022).Although large-scale downwellings that typically occur within mobile lid planets are able to pass through the WMF zone without difficulty(Dannberg et al.,2022;Li RP et al.,2024),the smaller and less negatively buoyant nature of downwelling drips in stagnant lid planets are more susceptible to these effects,which leads to an ephemeral layering of the mantle.Our numerical models show that in stagnant lid planets with mantle potential temperatures that exceed 1900 K,the smaller,cold drips from the lid continue to pile up until enough of them have coalesced that they collectively avalanche as a larger instability into the deeper interior.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0201)the National Natural Science Foundation of China(Grant No.42377199,No.41941019)+1 种基金State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(Grant No.SKLGP2021Z005)Chengdu University of Technology Postgraduate Innovative Cultivation Program(Grant No.CDUT2023BJCX008).
文摘As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains lacking.We summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st century.The distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to September.We highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing factors.The failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure type.Finally,we deliver recommendations concerning the risk assessment and prediction of IAs.The results provide important scientific value for addressing climate change and resisting glacier-related hazards.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0902)the National Natural Science Foundation of China(91747207,41790434)。
文摘Large-scale rock-ice avalanches resulting from the interaction of tectonics and climate are characterized with high mobility,huge volumes of sediment,and rapid denudation,being a major agent of landscape evolution in high altitude mountainous regions.Specifically,the extreme glaciated slope failures often transform into extraordinarily large and mobile debris flows,resulting in disastrous consequences such as sedimentation and desertification.Due to a dearth of on-site observation data and experimental data collection,our comprehension of the geomorphic and kinematic characteristics of rock-ice avalanches remains poor.Here we report a cluster of ancient rock-ice avalanches spreading along the Chomolhari range of the China-Bhutan Himalayas.By integrating remote sensing image interpretation with detailed field investigations,we demonstrate the geomorphic and sedimentary characteristics of four events among the avalanches.The estimated volumes of the four are 23.73 Mm³,39.69 Mm³,38.43 Mm³,and 38.25 Mm³,respectively.The presence of pre-existing moraines or alluvial fans constrained their movement,resulting in deposition features such as marginal digitated lobes at higher elevations and large depressed areas in the interior.Applying the Savage-Hutter theory,we calculate the basal friction angle and travel angle of these ancient rock-ice avalanches that are both less than 10°,affirming the similarity of these avalanches in the study area to those occurring in other regions.Our study significantly contributes to understanding the geomorphic and kinematic characteristics of rock-ice avalanches in high-altitude mountainous regions,providing valuable insights into their response to the disproportionate growth of Himalayan peaks.
基金supported by the Major Program of the National Natural Science Foundation of China(Grant No.41790433 Grant No.41772312+4 种基金 Grant No.41472325)the NSFC-ICIMOD Collaborative Project(Grant No.41661144041)Key Research and Development Projects of Sichuan Province(2017SZ0041)Scientific Research Foundation of Graduate School of Southeast University(YBJJ 1844)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX17_0130)
文摘Arrays of baffles are usually installed in front of protection site to attenuate the flow energy of rock avalanches in mountainous areas. Optimization design is crucial for efficiency promotion in hazard energy dissipation engineering. In this study, a deceleration strip was added in the baffles protection system to optimize the traditional baffles system. The effects of the "baffles-deceleration strip" hybrid protection system was discussed in detail with the nails number and nails angle. This study presents details of numerical experiments using the discreteelement method(DEM). The effect of the optimization of hybrid protection system(nail angle and nail number) were investigated specifically, especially the impact force that avalanches exerted on structures. The results show that the maximum impact forces and kinetic energy of the rock avalanches decreases with the increase of the number and angle of the nail. Moreover, the distance between the toe and the bearing structure(L_m) is also a key factor. The shorter the distance L_m(30 m) is, the higher the maximum impact force are. The longer the distance L_m(70 m) is, the lower the maximum impact force are. Under the same size of the nails, increasing the numbers can enhance the dissipation ability of the hybrid protection system. Meanwhile, increasing itsangle can also enhance the dissipation ability. There are three key ways for nails attenuate rock avalanches:(i) block the fine particles directly;(ii) form the particles bridge between nails and baffles;(iii) dissipate the coarse particles energy directly. The effect of segregation in rock avalanches is crucial for the energy dissipation mechanism, which is a key factor to optimize the traditional baffle system.
基金supported by the National Natural Science Foundation of China(No.41831291)。
文摘In mountainous areas,rock avalanches swarm downslope leading to large impact forces on structures.Baffle systems are usually set up in torrent channels to dissipate the flow energy and reduce the destructive effects.In this paper,a crown-like baffle system is proposed to better dissipate the flow energy.The energy dissipation mechanism of this system was investigated based on DEM.The results reveal more than 90%of the kinetic energy of the granular flow was dissipated by particleparticle interaction.Two effects,the impedance effect and the deflection effect,were identified.The influence of these effects leads to the formation and growth of cushions behind the baffles,and these cushions enhance the particle-particle interaction.Two crown-like baffle systems were compared with a conventional baffle system based on the typical avalanche model.The results reveal the cumulative residual kinetic energy of the crown-like baffle system with square baffles decreased by 18.75%with the same concrete consumption as the conventional baffle system.For the crown-like baffle system with triangular baffles,the cumulative residual kinetic energy decreased by 6.22%with 83.94%of the concrete consumption of the conventional baffle system.Hence,the proposed baffle system is more cost-effective compared with the conventional baffle system.
基金financially supported by National Natural Science Foundation of China (Nos. 51671067, 51761135125 and 11771407)the Plan for Scientific Innovation Talent of Henan Province (No. 164200510011)the Innovative Research Team of Science and Technology in Henan Province (No. 17IRTSTHN007)
文摘In the current research, serrated flow is investigated under tensile and compressive loading in a ZrCubased bulk metallic glass composite (BMGC) that is well known for its plastic deformability, which is higher than that of metallic glasses. Statistical analysis on serrations shows a complex, scale free process, in which shear bands are highly correlated. The distribution of the elastic-energy density stored in each serration event follows a power-law relationship, showing a randomly generated serrated event under both tension and compression tests. The plastic deformation in the temporal space is explored by a timeseries analysis, which is consistent with the trajectory convergent evolution in critical dynamic behavior even in the low strain rate regime in both tests. The results demonstrate that the secondary phase in the BMGC can stabilize the shear band extension and facilitate the critical behavior in the low strain rate regime. This study provides a strong evidence of serrated flow phenomenon in BMGC under tension test, and offers a deep understanding of the correlation between serrations and shear banding in temporal space.
文摘Scientific research on snow avalanches is relatively modem, yet in constant and rapid evolution, as the multiple disciplines involved in its development will, in turn, become more specialized and more technical. Patents are part of research and knowledge production. The scientific community and policy makers are increasingly interested in production of knowledge collaboratively. Almost all of the research being conducted on snow avalanches uses technology, technique or instrumentation. One main objective of this study is to draw from the literature the many technologies, techniques and instrumentations that are being used in research related to avalanches. Thus, a textual analysis of the most significant literature in the field of snow avalanches was done. In this analysis, techniques, technologies and instrumentations have emerged. A patent search has been done in databases. Subsequently, patents were conceptualized. The proportion of applicants for patents is higher in industry than in universities. The measure of exploration of the ongoing sociocognitive transformations of science and technology systems presents a useful tool to conduct a study to explore these transformations. It would be interesting for the scientific community, but also for the industry, to elaborate concept mapping when applied to avalanche research, which would help in determining referents.
文摘A set of detected avalanches from January to April 2012 on a hillside southeast of lschgl, Austria is given. The avalanches are off-the-cut or caused by blast. The meteorological data of two monitoring stations nearby the hillside are taken for analysing the weather situation. The meteorological parameters air temperature, wind intensity and wind speed, relative humidity, precipitation and snow depth are investigated for similarities short before and during an avalanche. The avalanches are grouped into three categories and meteorological characteristics are found for each category. Thereby the avalanche hazard for the observed hillside is better assessed and an infrastructure safety by avalanche control due to concerted avalanche blasts is more effective. The result of the analysis shows three kinds of hazard weather conditions, which increase the avalanche hazard： warm air temperatures cause a settlement of the snow pack, but in the beginning of the process a weakening in the snow pack happens. Rapidly decreasing of the air temperature cause cracks in the snow pack and the combination of fresh snow and strong wind speed leads to accumulation of snow on sheltered slopes.
基金the financial support of National Natural Science Foundation of China(No.51371122)the financial support of National Natural Science Foundation of China(No.51501220)+1 种基金the Youth Natural Science Foundation of Shanxi Province,China(No.2015021005)the Natural Science Foundation of Jiangsu Province(BK20150170)
文摘Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics analysis.Peak and clutter distribution of slip-avalanche magnitudes are displayed during stable plastic flows at strain rates of 2×10-4 s-1 and 5×10-5 s-1,respectively,which means that serration behavior depends on the strain rate.However,the remarkable agreement between measured slip-avalanche magnitudes and the scaling behavior,i.e.a universal complementary cumulative distribution function（CCDF）predicted by mean-field theory（MFT）model,indicates that the plasticity of the present Fe-based BMGs can be tuned by imposed strain rates：Smax^6）ε-λ.This tuned plasticity is elucidated with expended free-volume model.Moreover,the scaling behavior of serrated flows for other strain rates can be predicted as well.
基金supported by the National Natural Science Foundation of China(Grant Nos.42307194 and 42120104002)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2024QNRC001).
文摘The impact of cross-sectional topographic variability on the kinetic properties of granular flows has been underexplored,which hinders the understanding of the kinematics of rock avalanches.In this study,the throat contraction index(T)is introduced to quantify variations in throat topography,and 96 numerical simulation experiments with varying T and slope angles(δ)are conducted.The findings indicate that granular flows experience transient obstructions when traversing throat topographies,primarily due to the periodic formation and breaking of the arch structure.Observations suggest that the acceleration of velocity in the tails of granular flows is restrained by the throat region,potentially altering the dynamics of related geohazards.In this study,the impact of throat topography is quantitatively assessed,demonstrating a reduction in peak flowrates of granular materials by 20%-80% and extending the flowduration up to six times.The present study proposes the throat-induced hazard index(Φ)to evaluate the influenceof throat topography on the risk of rockslides and avalanches characterized by granular flows,which may provide insights for the design of mitigation structures in topographic regions.
基金National Natural Science Foundation of China(No.12325205,No.12232005,U2241267,12272155)Major Scientific and Technological Special Project of Gansu Province(23ZDKA0009)Natural Science Foundation of Gansu Province of China(No.23JRRA1118).
文摘Flux avalanches,prevalently existing in superconducting thin films,can cause catastrophic breakdowns of electromagnetic properties and even irreversible damage to superconducting materials.Metal coating is an effective way to suppress the flux avalanches in superconducting thin films.Nevertheless,it is difficult to reveal the suppression mechanisms due to the challenge of effectively separating the simultaneous eddy currents and heat exchange in the metal coating.In this work,the eddy currents and heat exchange in the Ag metal coating are separated by setting a thermal insulation layer,and its inhibiting effect on the flux avalanches of the YBCO superconducting thin films is elucidated.The results indicate that eddy currents play an important part in suppressing magnetic flux avalanches,and their effect strengthens with increasing Ag thickness.Meanwhile,employing the double-exposure method,the flux avalanche velocity of YBCO superconducting thin films was measured,revealing a significant decrease in the magnetic flux avalanche velocity due to suppression by eddy currents.Moreover,a theoretical model was established to investigate the influence of eddy currents on the motion of a single vortex,and the calculated results showed good agreement with the experiments.These findings provide a better understanding of the flux avalanches and their suppression in YBCO superconducting thin films.
基金supported by the National Natural Science Foundation of China(Grant Nos.62122028 and 62335008)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2023B1515040018 and 2018B030306015)+1 种基金National Key Research and Development Program of China(Grant No.2023YFF0722600)Scientific Research Cultivation Fund for Young Faculty of South China Normal University(Grant Nos.23KJ01 and 22KJ30).
文摘Photon avalanche occurring in lanthanide-doped materials exhibits a giant optical nonlinear response of the emission intensity to the excitation intensity,which holds great potential in the applications of optical sensing,super-resolution imaging,quantum detection,and other techniques.However,strategies for developing photon avalanches in nanoparticles are limited,and many widely used lanthanide ions have not yet been able to generate high-efficiency avalanching emissions.A general strategy named cascade migrating photon avalanche was proposed to achieve efficient avalanching emissions with huge optical nonlinearities from a large number of emitters at the nanoscale and at room temperature.Specifically,the optical nonlinearity order of bright avalanched Tm^(3+)-emission was achieved at 63rd order by utilizing the Yb^(3+)∕Pr^(3+)-codoped nano-engine.By further incorporating a Gd^(3+)sublattice migrating network,its avalanching energy can propagate over a long distance to arouse avalanching emission with extreme optical nonlinearities up to 45th order among various emitters(Tb^(3+),Eu^(3+),Dy^(3+),Sm^(3+))in multilayered nanostructures.By achieving abundant avalanching full-spectrum emissions,it would be highly conducive to applications in various fields.For instance,our strategy demonstrated its applicability in multi-color super-resolution microscopic imaging with single-nanoparticle sensitivity and resolution up to 48 nm,utilizing a single low-power 852 nm excitation beam.
基金Djordje Spasojevic and Svetislav Mijatovic acknowledge the support from the Ministry of Science,TechnologicalDevelopment and Innovation of the Republic of Serbia(Agreement No.451-03-65/2024-03/200162)S.J.ibid.(Agreement No.451-03-65/2024-03/200122)Bosiljka Tadic from the Slovenian Research Agency(program P1-0044).
文摘Disordered ferromagnets with a domain structure that exhibit a hysteresis loop when driven by the external magnetic field are essential materials for modern technological applications.Therefore,the understanding and potential for controlling the hysteresis phenomenon in thesematerials,especially concerning the disorder-induced critical behavior on the hysteresis loop,have attracted significant experimental,theoretical,and numerical research efforts.We review the challenges of the numerical modeling of physical phenomena behind the hysteresis loop critical behavior in disordered ferromagnetic systems related to the non-equilibriumstochastic dynamics of domain walls driven by external fields.Specifically,using the extended Random Field Ising Model,we present different simulation approaches and advanced numerical techniques that adequately describe the hysteresis loop shapes and the collective nature of the magnetization fluctuations associated with the criticality of the hysteresis loop for different sample shapes and varied parameters of disorder and rate of change of the external field,as well as the influence of thermal fluctuations and demagnetizing fields.The studied examples demonstrate how these numerical approaches reveal newphysical insights,providing quantitativemeasures of pertinent variables extracted from the systems’simulated or experimentally measured Barkhausen noise signals.The described computational techniques using inherent scale-invariance can be applied to the analysis of various complex systems,both quantum and classical,exhibiting non-equilibrium dynamical critical point or self-organized criticality.
基金supported by NSF grant ACI-1550405UCOP MRPI grant MRP17454755NIH grant R01 AG054049.
文摘Analytical expressions for scaling of brain wave spectra derived from the general nonlinear wave Hamiltonian form show excellent agreement with experimental“neuronal avalanche”data.The theory of the weakly evanescent nonlinear brain wave dynamics[Phys.Rev.Research 2,023061(2020);J.Cognitive Neurosci.32,2178(2020)]reveals the underlying collective processes hidden behind the phenomenological statistical description of the neuronal avalanches and connects together the whole range of brain activity states,from oscillatory wave-like modes,to neuronal avalanches,to incoherent spiking,showing that the neuronal avalanches are just the manifestation of the different nonlinear side of wave processes abundant in cortical tissue.In a more broad way these results show that a system of wave modes interacting through all possible combinations of the third order nonlinear terms described by a general wave Hamiltonian necessarily produces anharmonic wave modes with temporal and spatial scaling properties that follow scale free power laws.To the best of our knowledge this has never been reported in the physical literature and may be applicable to many physical systems that involve wave processes and not just to neuronal avalanches.
基金supported in part by the National Natural Science Foundation of China under Grant 62071073in part by the Fundamental Research Funds for Central Universities under Grant 2023CDJXY-041in part by the Foundation from Guangxi Key Laboratory of Optoelectronic Information Processing under Grant GD20201.
文摘The dynamic avalanche effect is a critical factor influencing the performance and reliability of the field-stop insulated gate bipolar transistors(FS-IGBT).Unclamped inductive switching(UIS)is the primary method for testing the dynamic avalanche capability of FS-IGBTs.Numerous studies have demonstrated that factors such as device structure,avalanche-generating current filaments,and electrical parameters influence the dynamic avalanche effect of the FS-IGBT.However,few studies have focused on enhancing the avalanche reliability of the FS-IGBT by adjusting circuit parameters during operation.In this paper,the dynamic avalanche effect of the FS-IGBT under UIS conditions is comprehensively investigated through a series of comparative experiments with varying circuit parameters,including bus voltage V_(DC),gate voltage V_(G),gate resistance R_(g),load inductance L,and temperature TC.Furthermore,a method to enhance the dynamic avalanche reliability of the FS-IGBT under UIS by optimizing circuit parameters is proposed.In practical applications,reducing gate voltage,increasing load inductance,and lowering temperature can effectively improve the dynamic avalanche capability of the FS-IGBT.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51077032).
文摘The precise mathematical method was adopted to simulate the breakdown process of 5 mm rod and plate electrode gap,which was filled with supercritical nitrogen at the condition of 127 K,4 MPa and seed electron density 1×10^(6) m^(-3) under 29 kV DC voltage.The result shows that the discharge process was completed within 11.8 ns from seed electron triggering,avalanche bulking to streamer extending until gap eventually breakdown.The entire gap breakdown process was divided into three discharge stages,namely,the initial discharge triggered(0-4 ns),avalanche(4-7 ns)and streamer phase(7-11.8 ns).At the same time,the facts were also revealed that the discharge evolution,electric field distribution,and electron density had different values,and also showed different temporal and spatial distribution characteristics along the axis of the discharge gap.Specifically,the discharge characteristics of SCN2 under 1,2,3,4,4.5,and 5 MPa at 127 K were theoretically analyzed respectively,and the microscopic mechanisms of the breakdown process were also detailed.The results indicate that the gas discharge law remained applicable within the 1-3 MPa range.However,the discharge characteristics of supercritical nitrogen at 3.4-5 MPa differed significantly from those at lower pressures,likely attributable to the unique state of matter exhibited by supercritical nitrogen.This study contributes to understanding the discharge mechanism of supercritical nitrogen and offers theoretical guidance for its practical application in the power industry.
基金supported by National Natural Science Foundation of China(NO.42371085)the Tibet Science and Technology Program(XZ202201ZY0011G)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0906).
文摘Snow avalanches present a significant threat to infrastructure,affecting buildings,roads,railways,and power lines,and frequently leading to massive economic losses in livelihoods and production.With the increase in regional temperatures and the occurrence of extreme snowfall events,the frequency and intensity of avalanches have escalated,resulting in more severe incidents and higher casualty rates.As natural archives of environmental changes,tree rings offer valuable proxies for avalanche hazard assessments in regions where direct observation data is scarce,particularly in high-altitude regions.The dendrogeomorphology has been gradually being applied in avalanche hazard evaluation,however,it remains limited in China.To address this gap,this study systematically investigates the principles and methodologies for reconstructing avalanche histories and evaluates their applications in avalanche hazard assessments through a literature review and field observations.It provides a comprehensive overview of recent advancements in key areas,including the impact of avalanches on forest ecosystems,the reconstruction of avalanches,and the analysis of avalanche events(i.e.,the spatiotemporal distribution,the historical recurrence intervals,magnitudes,and triggering conditions of avalanches).Considering the current limitations in avalanche hazard assessments and the urgent need for such research in China,we outline key priorities and future directions,including refining reconstruction methodologies,developing a comprehensive tree-ring-based avalanche database for high-altitude regions,and establishing an advanced hazard assessment framework based on dendrochronological evidence.
基金supported by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘This research presents a numerical simulation methodology for optimizing circular composite overlays’dimensions and pressure characteristics with orthotropic mechanical properties,specifically,for metal conduits with temperature-dependent elastoplastic behavior.The primary objective of the proposed method is to prevent crack propagation during pressure surges from operational to critical levels.This study examines the“Beineu-Bozoy-Shymkent”steel gas conduit,examining its performance across a temperature range of−40 to+50℃.This work builds on prior research on extended avalanche destruction in steel gas conduits and crack propagation prevention techniques.Theanalysis was conducted using a dynamic finite-element approach with the ANSYS-19.2/ExplicitDynamics software.Simulations of unprotected conduits revealed that increasing gas-dynamic pressure can convert a partial-depth crack into a through-crack,extending longitudinally to approximately seven times its initial length.Notably,at T=+50℃,the developed crack length was 1.2%longer than that at T=−40℃,highlighting the temperature sensitivity of crack progression.The modeling results indicate that crack propagation can be effectively controlled using a circular composite overlay with a thickness between 37.5%and 50%of the crack depth and a length approximately five times that of the initial crack,centered symmetrically over the crack.In addition,preliminary stress analysis indicated that limiting the overlay-induced pressure to 5%of the operational pressure effectively arrested crack growth without generating significant stress concentrations near the overlay boundaries,thereby preventing conduit integrity.
