Many bird species are known to differ in their vocal repertoires between populations across a range of geographic scales.This is generally assumed to be caused by acoustic drift and social learning of small difference...Many bird species are known to differ in their vocal repertoires between populations across a range of geographic scales.This is generally assumed to be caused by acoustic drift and social learning of small differences in songs among individuals in separate populations.To determine the extent to which vocal repertoire is structured in a highly nomadic species with a low degree of isolation among populations,we characterized the vocalizations of the'Apapane(Himatione sanguinea)and described the variations in its songs on a microgeographic scale.'Apapane had significant shifts in their songs in both fragmented and non-fragmented forest habitats,with little to no overlap in song meme structure within distances as short as 2 km,despite birds moving freely between areas with distinct songs.Forest fragments had unique song compositions and shared more syllables with closer fragments than with the ones further apart.Furthermore,microgeographic variation was relatively stable at a given recording location even over multiple years.This pattern of song differentiation in a highly mobile species at the microgeographic scale may be a consequence of their ability to learn new vocalizations over their life and of intraspecific mimicry,or“vocal matching”by individuals visiting other populations.展开更多
Conservationists have long debated whether fragmented habitats are best conserved by protecting a single large patch(SL)or several small patches(SS),i.e.,the SLOSS debate.Although this SLOSS debate has provided import...Conservationists have long debated whether fragmented habitats are best conserved by protecting a single large patch(SL)or several small patches(SS),i.e.,the SLOSS debate.Although this SLOSS debate has provided important insights into biodiversity conservation,research has predominantly focused on only one dimension of diversity(i.e.,taxonomic),failing to consider how phylogenetic and functional diversity might inform conservation strategies.In this study,we determined whether grasslands in the agro-pastoral ecotone of the Tabu River Basin,Inner Mongolia should be conserved by protecting a single large patch or several small patches.For this purpose,we quantified the relationships between three dimensions of biodiversity(taxonomic,phylogenetic,and functional diversity)and grassland patch area.We found species richness and the standardized effect size of phylogenetic diversity increased with patch area,whereas the standardized effect size of functional diversity decreased.Taxonomic measures of diversity indicated that the best strategy for conserving Tabu River Basin grasslands is to protect several small habitat patches;in contrast,phylogenetic and functional measures of diversity indicated that conserving a single large habitat patch was best.Our study emphasizes the necessity of considering multiple dimensions of diversity when designing conservation strategies for fragmented landscapes to achieve comprehensive biodiversity conservation.展开更多
A phase-field model including magnetic field induced dendrite fragmentation was established and applied to the cases with different initial crystal nuclear positions for AA5754 aluminum alloy electromagnetic laser bea...A phase-field model including magnetic field induced dendrite fragmentation was established and applied to the cases with different initial crystal nuclear positions for AA5754 aluminum alloy electromagnetic laser beam welding.Compare the calculated results that include dendrite fragmentation caused by the thermal electromagnetic Lorentz force with the results that consider only the thermal electromagnetic Lorentz force,without fragmentation,at the characteristic time instants.Both in the early and late stages,the small fragmentation at the dendrite tip promotes the number of higher-order branches and their growth,especially in the direction perpendicular to the solidification.The later stage fragmentation has the possibility of breaking one grain into several,which verifies the possibility of grain refinement caused by dendrite fragmentation.The fracture surface caused by fragmentation also makes more solid-liquid interfaces and their growth.In addition,the cases with different initial nuclear positions were compared.The grain growth in the low-temperature zone can be inhibited by the equiaxed grains'fragmentation at the high-temperature area(179.8μm^(2) and 14.7% start at the center,115.4μm^(2) and 9.4% start at the high-temperature corner,134.3μm^(2) and 10.9%start at the low-temperature corner),which is another kind of grain refinement by the dendrite fragmentation.This kind of inhibition effect on grain growth in the low-temperature region will be enhanced with the increasing time interval between the two crystal nuclei’appearance(179.8μm^(2) and 14.7%when virtual grains appear at t=4.3803 s and t=4.3803 s,134.3μm^(2) and 10.9%at t=4.0977 s and t=3.9564 s,and 115.4μm^(2) and 9.4%at t=3.8151 s and t=3.5325 s).展开更多
Fragment velocity distribution is an important parameter affecting the terminal effects of warheads.The rarefaction wave,end cap,and its confinement state can significantly affect the fragmentation of the cylindrical ...Fragment velocity distribution is an important parameter affecting the terminal effects of warheads.The rarefaction wave,end cap,and its confinement state can significantly affect the fragmentation of the cylindrical charge casing.Most of the existing studies have performed experiments and simulations considering the rarefaction wave and unfixed end caps;research on fixed end caps and sufficient theoretical explanations are limited.In this work,the effects of rarefaction waves,end caps,and their fixed states,on the fragment velocity distribution,were studied via experimentation and simulation,and reasonable theoretical explanations were provided.The results show that the rarefaction wave and end caps affect the fragment velocity by changing the pressure states of the detonation products.At the initiation end,the fragment velocities of casings with unfixed initiation ends are 33.3%(300 m/s)greater than that of casings without end caps,because of the weakening of the attenuation effect of the rarefaction wave.The fragment velocities of the casings with fixed initiation ends are 8.3%(100 m/s)greater than that of casings with unfixed initiation ends.At the non-initiation end,the fragment velocities are 24.8%(297 m/s)greater than that of a casing without end caps,and the reflecting shock wave generated by the fixed non-initiation end increases the fragment velocity by 7.3%(113 m/s),compared to the theoretical velocity.This work provides a basis for the structural design and analysis of the terminal effects of warheads.展开更多
Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of ...Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of gangue deformation,saturation,and goaf geometry.This study investigates the deformation and void evolution of fragmented gangue with varying lithologies,particle sizes,and water contents through an independent-developed testing system and theoretical model.A planar micro-unit model and a three-dimensional spatial structure model are proposed to quantify the storage coefficient and total reservoir capacity of underground water storage structures.These models incorporate the effects of stratified lithologies,saturation-induced softening,and spatially distributed stress conditions.The methodology is applied to the underground reservoir in Chahasu coal mine,and the results show that under increasing stress,storage coefficients decline exponentially,with pronounced differences between single-and double-lithology structures.The storage coefficient in the spatial model demonstrate greater resilience to stress concentration compared to planar models,and further analysis identifies critical thresholds in roof fracture distances and stress-recovery times affecting long-term storage performance.This research provides a comprehensive framework for evaluating underground reservoir storage potential,offering theoretical support and engineering guidance for the sustainable utilization of mine water.展开更多
Floodplain wetlands are invaluable ecosystems providing numerous ecological benefits,yet they face a global crisis necessitating sustainable preservation efforts.This study examines the depletion of floodplain wetland...Floodplain wetlands are invaluable ecosystems providing numerous ecological benefits,yet they face a global crisis necessitating sustainable preservation efforts.This study examines the depletion of floodplain wetlands within the Hastinapur Wildlife Sanctuary(HWLS)in Uttar Pradesh.Encroachment activities such as grazing,agriculture,and human settlements have fragmented and degraded critical wetland ecosystems.Additionally,irrigation projects,dam construction,and water diversion have disrupted natural water flow and availability.To assess wetland inundation in 2023,five classification techniques were employed:Random Forest(RF),Support Vector Machine(SVM),artificial neural network(ANN),Spectral Information Divergence(SID),and Maximum Likelihood Classifier(MLC).SVM emerged as the most precise method,as determined by kappa coefficient and index-based validation.Consequently,the SVM classifier was used to model wetland inundation areas from 1983 to 2023 and analyze spatiotemporal changes and fragmentation patterns.The findings revealed that the SVM clas-sifier accurately mapped 2023 wetland areas.The modeled time-series data demonstrated a 62.55%and 38.12%reduction in inundated wetland areas over the past 40 years in the pre-and post-monsoon periods,respectively.Fragmentation analysis indicated an 86.27%decrease in large core wetland areas in the pre-monsoon period,signifying severe habitat degradation.This rapid decline in wetlands within protected areas raises concerns about their ecological impacts.By linking wetland loss to global sustainability objectives,this study underscores the global urgency for strengthened wetland protection measures and highlights the need for integrating wetland conservation into broader sustainable development goals.Effective policies and adaptive management strategies are crucial for preserving these ecosystems and their vital services,which are essential for biodiversity,climate regulation,and human well-being.展开更多
Efficient hard-rock fragmentation remains a critical challenge in mechanized mining.This study designed an adjustable-spacing mold and conducted double cutting pick indentation tests on granite.Mechanical responses an...Efficient hard-rock fragmentation remains a critical challenge in mechanized mining.This study designed an adjustable-spacing mold and conducted double cutting pick indentation tests on granite.Mechanical responses and fragmentation characteristics under varying horizontal stresses,pick spacings,and groove depths were systematically analyzed.Unidirectional stress concentration altered the rock fragmentation modes,exhibiting a dual effect on the fragmentation process.The maximum indentation force(F_(max)),indentation hardness index(IHI),indentation modulus(IM),and indentation energy(W)initially increased and then decreased with rising horizontal stress.Appropriate spacing promoted radial crack coalescence,whereas too small a spacing(20 mm)caused repetitive re-fragmentation of rock chips,and too large a spacing(50 mm)resulted in unbroken ridges.Pre-cut grooves weakened the rock,reducing F_(max) and specific energy(SE),thus improving fragmentation efficiency,although the improvement slowed beyond a 10-mm groove depth.Based on the results and rock-mass conditioning assisted fragmentation mechanism,a“stress-structure dual control”assisted fragmentation mechanism was proposed,and a“pre-drilling unloading−alternate stopping”mining scheme was exploratorily designed.This approach creates favorable conditions for rock fragmentation by reducing stress levels and rock mass integrity in target zones,providing theoretical support and an engineering paradigm for mecheanized mining of deep resources.展开更多
Integrated land and resource planning is critical for achieving global sustainability goals,yet a persistent chasm separates policy ambition from on-the-ground outcomes.The review article undertakes a comparative eval...Integrated land and resource planning is critical for achieving global sustainability goals,yet a persistent chasm separates policy ambition from on-the-ground outcomes.The review article undertakes a comparative evaluation across the world to diagnose the systemic gaps of the policy that is leading to this implementation failure.We come up with a general typology of 5 categories of gaps that are interconnected:spatial-temporal mismatches,institutional fragmentation,the knowledge-action divide,lack of equity and justice,and broken monitoring and feedback loops.In a comparative study of the High-Income Countries,Rapidly Developing Economies,and Low-Income Countries,we show how these universal gaps are reflected in specific contextual syndromes,which are defined by the political economy,state capacity,and global integration.As can be seen in the analysis,these failures are not stand-alone but exist in a vicious,self-perpetuating cycle that is based on power asymmetries,institutional path dependency,and scale mismatches.In order to break this cycle,we suggest a revolutionary structure of action,which is structured around integration,adaptive management,and justice.The framework identifies the specific operation strategies,such as developing meta-governance formations and establishing community tenure to implement participatory monitoring,and aligning a multi-scale agenda.We infer that the implementation gap must be bridged by going beyond technical solutions to ensure a virtuous circle of legitimate learning-oriented governance that can address the complexity of socio-ecological conditions of the Anthropocene.展开更多
The peripheral immune system has emerged as a regulator of neurodegenerative diseases such as Alzheimer’s disease.Microglia are resident immune cells in the brain that may orchestrate communication between the centra...The peripheral immune system has emerged as a regulator of neurodegenerative diseases such as Alzheimer’s disease.Microglia are resident immune cells in the brain that may orchestrate communication between the central nervous system and peripheral immune system,though the mechanisms are unclear.Here,we found that gamma-type immunoglobulin,a product originating from peripheral blood B cells,localized in the brain parenchyma of multiple mouse models with amyloid pathology,and was enriched on microglia but not on other brain cell types.Further experiments showed that gamma-type immunoglobulin bound to microglial cell membranes and led to diverse transcriptomic changes,including upregulation of pathways related to phagocytosis and immunity.Functional assays demonstrated that gamma-type immunoglobulin enhanced microglial phagocytic capacity for amyloid-beta fibrils via its Fc fragment,but not Fab fragment,fragment.Our data indicate that microglia,when exposed to gamma-type immunoglobulin,exhibit an enhanced capacity for clearing amyloid-beta fibrils,potentially via the gamma-type immunoglobulin Fc fragment signaling pathway.This suggests that parenchymal gamma-type immunoglobulin should be further investigated to determine whether it may play a beneficial role against Alzheimer’s disease by enhancing microglial function.展开更多
The global mining industry,particularly deep high-stress hard-rock mining,confronts prominent challenges of massive energy consumption and low crushing/grinding efficiency.Optimized blasting,as an alternative to grind...The global mining industry,particularly deep high-stress hard-rock mining,confronts prominent challenges of massive energy consumption and low crushing/grinding efficiency.Optimized blasting,as an alternative to grinding,effectively reduces energy usage and improves transportation efficiency.Despite extensive research on the effects of confining stress to cut blasting,studies focusing on fragmentation characteristics of deep confined blasting remain scarce.This study integrates theoretical analysis,similarity model tests,and SPH-FEM simulations to investigate fragmentation size distribution and energy dissipation under varying confining stresses.Results show that the Swebrec(SWE)function achieves superior fitting to fragmentation data(goodness-offit>0.95).With increasing confining stress,the fractal dimension of specimens increases(ranging from 2.16 to 2.42 in model tests),while fragmentation energy decreases—55.23% lower under high confining stress than no confining stress in tests,and 50.61%lower at 40 MPa than 0 MPa in simulations.The ratio of fragmentation energy to blasting energy is 2%-10%.Distinct from previous studies emphasizing confining stress macroeffects on cut blasting,this work explores fragmentation distribution functions and energy under biaxial confining stress,providing valuable insights for blasting efficiency evaluation and promoting energy conservation and emission reduction in post-mineral processing.展开更多
Alzheimer’s disease(AD)is the most common origin of sporadic dementia.Rare familial forms have identified a central role for toxicity based on aggregation of peptide fragments generated from amyloid precursor protein...Alzheimer’s disease(AD)is the most common origin of sporadic dementia.Rare familial forms have identified a central role for toxicity based on aggregation of peptide fragments generated from amyloid precursor protein(APP),named amyloid-beta(Aβ),which exists in two common forms,Aβ_(1-40)(Aβ_(40))and Aβ_(1-42)(Aβ_(42)).The latter is more neurotoxic.A common clinical biomarker measured in blood is the ratio Aβ_(42)/Aβ_(40).展开更多
Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon ...Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon dioxide upon electron-impact.Through fragment ions and electron coincidence momentum imaging,we unambiguously determine the ionization mechanism by measuring the projectile energy loss in association with the C^(+) +O_(2)^(+) channel.Further potential energy and trajectory calculations enable us to elucidate the dynamical details of this fragmentation process,in which a bond rearrangement pathway is found to proceed via the structural deformation to a triangular intermediate.Moreover,we demonstrate a further roaming pathway for the formation of O_(2)^(+) from CO_(2)^(+) 2,in which a frustrated C-O bond cleavage leaves the O atom without sufficient energy to escape.The O atom then wanders around varied configuration spaces of the flat potential energy regions and forms a C-O-O_(2)^(+) intermediate prior to the final products C^(+) +O_(2)^(+).Considering the large quantities of free electrons in interstellar space,the processes revealed here are expected to be significant and should be incorporated into atmospheric evolution models.展开更多
Deep rock engineering is affected by coupled thermo-hydro-mechanical(THM)-dynamic fields,necessitating the elucidation of the dynamic mechanical behavior and failure mechanisms.This study utilized a Multi-field Couple...Deep rock engineering is affected by coupled thermo-hydro-mechanical(THM)-dynamic fields,necessitating the elucidation of the dynamic mechanical behavior and failure mechanisms.This study utilized a Multi-field Coupled Controlled Split Hopkinson Pressure Bar(MCC-SHPB)system to elucidate the cross-scale dynamic responses of rocks and the boundaries of failure modes under THM coupling.Impact tests were conducted on green sandstone under coupled conditions of temperature(25℃-80℃),confining pressure(0-15 MPa),and seepage water pressure(0-15 MPa).Scanning electron microscopy(SEM)microstructural characterization and COMSOL Multiphysics numerical simulations were conducted,and a dynamic constitutive theoretical framework and failure-prediction methodology were established.We investigated the impact toughness index(I_(t)),dynamic modulus(E_(d)),dynamic triaxial compressive strength(TCS_(d)),fragmentation degree(W),and failure modes of green sandstone under thermo-confining pressure-seepage-impact loading conditions.The key findings reveal that the(I_(t))reflects different energy regulation mechanisms across different confining pressure regimes.Thermal-microcrack interactions dominate at low pressure,and energy absorption prevails at high pressure.A triphasic dynamic modulus model captures stiffness evolution under energy-driven conditions,revealing cross-scale crack nucleation-propagation and fragment reorganization.The TCSd inflection point signifies energy dissipation shifts,causing nonlinear skeleton bearing-capacity degradation.A critical criterion based on the W was established to distinguish between the two failure modes and predict the unstable failure initiation.Numerical simulations were used to elucidate the effects of inertia-dominated crack propagation and stress wave interference,validating the critical criterion and the predictive accuracy of the theoretical model during cross-scale failure.This study provides a theoretical foundation for assessing the dynamic stability of rock masses subjected to multi-field coupling during deep resource exploitation.展开更多
To establish practical,evidence-based strategies for noninvasive assessment and referral of patients with metabolic dysfunction-associated steatotic liver disease(MASLD)in Japan,we must address the urgent clinical nee...To establish practical,evidence-based strategies for noninvasive assessment and referral of patients with metabolic dysfunction-associated steatotic liver disease(MASLD)in Japan,we must address the urgent clinical need for accurate risk stratification and timely specialist intervention.A panel of 11 Japanese hepatology experts conducted a modified Delphi process to evaluate consensus recommendations regarding the use of noninvasive tests(NITs),including the fibrosis-4 index,enhanced liver fibrosis test,Mac-2-binding protein glycosylation isomer,type IV collagen 7S,cytokeratin-18 fragments,and imaging modalities such as ultrasound elastography and magnetic resonance elastography,for MASLD assessment and clinical referral.Practical algorithms were developed based on current Japanese data and panel consensus.The expert panel validated the utility of NITs as reliable tools for identifying patients with MASLD at risk for advanced fibrosis.Sequential use of NITs improved diagnostic accuracy and referral appropriateness while minimizing unnecessary specialist consultations.The proposed algorithms offer stepwise guidance for primary care physicians,supporting efficient,evidence-based decisionmaking.However,prospective longitudinal studies remain necessary for full prognostic validation of NITs in MASLD management.Noninvasive testing algorithms enable effective risk stratification and referral for MASLD in real-world Japanese practice with anticipated benefit for patient outcomes and healthcare systems.Broader adoption and further validation are warranted.展开更多
This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key de...This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key design parameters including casing dimensions and detonation positions.The paper details the finite element analysis for fragmentation,the characterizations of the dynamic hardening and fracture models,the generation of comprehensive datasets,and the training of the ANN model.The results show the influence of casing dimensions on fragment velocity distributions,with the tendencies indicating increased resultant velocity with reduced thickness,increased length and diameter.The model's predictive capability is demonstrated through the accurate predictions for both training and testing datasets,showing its potential for the real-time prediction of fragmentation performance.展开更多
Rock fragmentation is an important indicator for assessing the quality of blasting operations.However,accurate prediction of rock fragmentation after blasting is challenging due to the complicated blasting parameters ...Rock fragmentation is an important indicator for assessing the quality of blasting operations.However,accurate prediction of rock fragmentation after blasting is challenging due to the complicated blasting parameters and rock properties.For this reason,optimized by the Bayesian optimization algorithm(BOA),four hybrid machine learning models,including random forest,adaptive boosting,gradient boosting,and extremely randomized trees,were developed in this study.A total of 102 data sets with seven input parameters(spacing-to-burden ratio,hole depth-to-burden ratio,burden-to-hole diameter ratio,stemming length-to-burden ratio,powder factor,in situ block size,and elastic modulus)and one output parameter(rock fragment mean size,X_(50))were adopted to train and validate the predictive models.The root mean square error(RMSE),the mean absolute error(MAE),and the coefficient of determination(R^(2))were used as the evaluation metrics.The evaluation results demonstrated that the hybrid models showed superior performance than the standalone models.The hybrid model consisting of gradient boosting and BOA(GBoost-BOA)achieved the best prediction results compared with the other hybrid models,with the highest R^(2)value of 0.96 and the smallest values of RMSE and MAE of 0.03 and 0.02,respectively.Furthermore,sensitivity analysis was carried out to study the effects of input variables on rock fragmentation.In situ block size(XB),elastic modulus(E),and stemming length-to-burden ratio(T/B)were set as the main influencing factors.The proposed hybrid model provided a reliable prediction result and thus could be considered an alternative approach for rock fragment prediction in mining engineering.展开更多
Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains com...Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains complex and not fully understood.This study aims to gain a further understanding of the energy transfer mechanism during rockfall impact and fragmentation by impact tests using a variety of rock-like sphere specimens.The experiments mainly focus on the quantitative correlation between fragmentation degree and influence factors,i.e.impact angle and velocity on steel and granite slabs.The analysis focuses on the energy distribution characteristics,energy dissipation mechanisms,and the energy conversion rate of the fragments during impact and fragmentation.The results show that there is a significant correlation between the energy conversion rate and the fragmentation degree.In normal impact tests,elasto-plastic deformation energy and fracture energy are found to be two primary categories of energy dissipation.The proportion of total kinetic energy after impact is inversely proportional to the initial energy.A comparative analysis between normal and inclined slab impact tests reveals that the impact angle significantly influences the energy conversion rate,which controls the fragmentation degree as well.In addition,the fragmentation degree is inversely proportional to the restitution coefficient.These findings contribute to a better understanding of the energy conversion mechanism during rockfall impact and fragmentation,providing valuable insight for the development of effective strategies to mitigate such rockfall hazards.展开更多
Percussion drilling is a promising approach for hot dry rock(HDR)fragmentation.However,understanding of HDR fragmentation mechanism under multi-dimensional percussion remains limited and hinders the corresponding dril...Percussion drilling is a promising approach for hot dry rock(HDR)fragmentation.However,understanding of HDR fragmentation mechanism under multi-dimensional percussion remains limited and hinders the corresponding drilling performance.Herein,an innovative true triaxial multi-dimensional percussion device was developed for the study of HDR fragmentation mechanism under in-situ temperature and stress conditions.Multi-dimensional percussion,involving both axial and torsional components,was applied to drilling in granite and carbonatite rocks sampled from the typical HDR target areas.Multiscale visualization techniques and a whale optimization-variational mode decomposition algorithm were employed to investigate the rock failure patterns and drilling energy characteristics.Results indicated that multi-dimensional percussion enhances brittle-ductile mixed failure in granite,characterized by transgranular,intergranular,and combined fracture patterns that promote rock cracking.In contrast,carbonatite drillhole displays enhanced brittle fragmentation and tortuous failure surface dominated by transgranular fracture pattern.Frequency-domain characteristics of penetration force signals for multidimensional percussion,especially the significant dominant frequency,amplitude,and high-frequency dissipation,indicate an increase in net energy for drilling into HDR and intensified rock fragmentation.Further,the effect of impact frequency on rock fragmentation performance was emphasized to maximize drilling efficiency.The optimal regulation schemes between axial and torsional impact frequencies are identified as 15 Hz+15 Hz for granite and 30 Hz+15 Hz for carbonatite.The reliability of the optimization approach was validated through a field test that employed a novel impactor in the geothermal well Fushen-1.展开更多
In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Ther...In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.展开更多
基金supported by the Spanish Ministry of ScienceInnovation and Universities(MCIN/AEI/10.13039/501100011033,grant number:RYC2019-027216-I)by ESF Investing in your future。
文摘Many bird species are known to differ in their vocal repertoires between populations across a range of geographic scales.This is generally assumed to be caused by acoustic drift and social learning of small differences in songs among individuals in separate populations.To determine the extent to which vocal repertoire is structured in a highly nomadic species with a low degree of isolation among populations,we characterized the vocalizations of the'Apapane(Himatione sanguinea)and described the variations in its songs on a microgeographic scale.'Apapane had significant shifts in their songs in both fragmented and non-fragmented forest habitats,with little to no overlap in song meme structure within distances as short as 2 km,despite birds moving freely between areas with distinct songs.Forest fragments had unique song compositions and shared more syllables with closer fragments than with the ones further apart.Furthermore,microgeographic variation was relatively stable at a given recording location even over multiple years.This pattern of song differentiation in a highly mobile species at the microgeographic scale may be a consequence of their ability to learn new vocalizations over their life and of intraspecific mimicry,or“vocal matching”by individuals visiting other populations.
基金supported by the Natural Science Foundation of Inner Mongolia Key Project(2023ZD24)the Erdos City Major Science and Technology Special Project(ZD20232305)+3 种基金the Inner Mongolia Autonomous Region Science and Technology Plan Project(2025KYPT0012)the Inner Mongolia Autonomous Region Science and Technology Plan Project(2022ZD007)the Inner Mongolia Autonomous Region Education Department Project(NMGIRT2409)the Inner Mongolia First-Class Disciplines Scientific Research Special Project(YLXKZX-ND-047).
文摘Conservationists have long debated whether fragmented habitats are best conserved by protecting a single large patch(SL)or several small patches(SS),i.e.,the SLOSS debate.Although this SLOSS debate has provided important insights into biodiversity conservation,research has predominantly focused on only one dimension of diversity(i.e.,taxonomic),failing to consider how phylogenetic and functional diversity might inform conservation strategies.In this study,we determined whether grasslands in the agro-pastoral ecotone of the Tabu River Basin,Inner Mongolia should be conserved by protecting a single large patch or several small patches.For this purpose,we quantified the relationships between three dimensions of biodiversity(taxonomic,phylogenetic,and functional diversity)and grassland patch area.We found species richness and the standardized effect size of phylogenetic diversity increased with patch area,whereas the standardized effect size of functional diversity decreased.Taxonomic measures of diversity indicated that the best strategy for conserving Tabu River Basin grasslands is to protect several small habitat patches;in contrast,phylogenetic and functional measures of diversity indicated that conserving a single large habitat patch was best.Our study emphasizes the necessity of considering multiple dimensions of diversity when designing conservation strategies for fragmented landscapes to achieve comprehensive biodiversity conservation.
基金supported by the Alexander von Humboldt Foundation,and Deutsche Forschungsgemeinschaft(DFG,German Research Foundation,Project No.506270597 and No.466939224).
文摘A phase-field model including magnetic field induced dendrite fragmentation was established and applied to the cases with different initial crystal nuclear positions for AA5754 aluminum alloy electromagnetic laser beam welding.Compare the calculated results that include dendrite fragmentation caused by the thermal electromagnetic Lorentz force with the results that consider only the thermal electromagnetic Lorentz force,without fragmentation,at the characteristic time instants.Both in the early and late stages,the small fragmentation at the dendrite tip promotes the number of higher-order branches and their growth,especially in the direction perpendicular to the solidification.The later stage fragmentation has the possibility of breaking one grain into several,which verifies the possibility of grain refinement caused by dendrite fragmentation.The fracture surface caused by fragmentation also makes more solid-liquid interfaces and their growth.In addition,the cases with different initial nuclear positions were compared.The grain growth in the low-temperature zone can be inhibited by the equiaxed grains'fragmentation at the high-temperature area(179.8μm^(2) and 14.7% start at the center,115.4μm^(2) and 9.4% start at the high-temperature corner,134.3μm^(2) and 10.9%start at the low-temperature corner),which is another kind of grain refinement by the dendrite fragmentation.This kind of inhibition effect on grain growth in the low-temperature region will be enhanced with the increasing time interval between the two crystal nuclei’appearance(179.8μm^(2) and 14.7%when virtual grains appear at t=4.3803 s and t=4.3803 s,134.3μm^(2) and 10.9%at t=4.0977 s and t=3.9564 s,and 115.4μm^(2) and 9.4%at t=3.8151 s and t=3.5325 s).
基金the support of the Youth Scientific Research Projects of the Basic Research Program of Shanxi Province(Grant Nos.202303021222111,202303021222113)the China Postdoctoral Science Foundation(Grant No.2025M770001).
文摘Fragment velocity distribution is an important parameter affecting the terminal effects of warheads.The rarefaction wave,end cap,and its confinement state can significantly affect the fragmentation of the cylindrical charge casing.Most of the existing studies have performed experiments and simulations considering the rarefaction wave and unfixed end caps;research on fixed end caps and sufficient theoretical explanations are limited.In this work,the effects of rarefaction waves,end caps,and their fixed states,on the fragment velocity distribution,were studied via experimentation and simulation,and reasonable theoretical explanations were provided.The results show that the rarefaction wave and end caps affect the fragment velocity by changing the pressure states of the detonation products.At the initiation end,the fragment velocities of casings with unfixed initiation ends are 33.3%(300 m/s)greater than that of casings without end caps,because of the weakening of the attenuation effect of the rarefaction wave.The fragment velocities of the casings with fixed initiation ends are 8.3%(100 m/s)greater than that of casings with unfixed initiation ends.At the non-initiation end,the fragment velocities are 24.8%(297 m/s)greater than that of a casing without end caps,and the reflecting shock wave generated by the fixed non-initiation end increases the fragment velocity by 7.3%(113 m/s),compared to the theoretical velocity.This work provides a basis for the structural design and analysis of the terminal effects of warheads.
基金supported by the National Natural Science Foundation of China(Nos.52404153,52504157 and 52504156)the Natural Science Foundation of Jiangsu Province(No.BK20241649).
文摘Coal mine underground reservoirs help address the severe water imbalance in ecologically fragile mining regions of western China,but evaluating their storage capacity remains challenging due to the coupled effects of gangue deformation,saturation,and goaf geometry.This study investigates the deformation and void evolution of fragmented gangue with varying lithologies,particle sizes,and water contents through an independent-developed testing system and theoretical model.A planar micro-unit model and a three-dimensional spatial structure model are proposed to quantify the storage coefficient and total reservoir capacity of underground water storage structures.These models incorporate the effects of stratified lithologies,saturation-induced softening,and spatially distributed stress conditions.The methodology is applied to the underground reservoir in Chahasu coal mine,and the results show that under increasing stress,storage coefficients decline exponentially,with pronounced differences between single-and double-lithology structures.The storage coefficient in the spatial model demonstrate greater resilience to stress concentration compared to planar models,and further analysis identifies critical thresholds in roof fracture distances and stress-recovery times affecting long-term storage performance.This research provides a comprehensive framework for evaluating underground reservoir storage potential,offering theoretical support and engineering guidance for the sustainable utilization of mine water.
基金support through the“Trans-Disciplinary Research”Grant(No.R/Dev/IoE/TDRProjects/2023-24/61658),which played a crucial role in enabling this research endeavor.
文摘Floodplain wetlands are invaluable ecosystems providing numerous ecological benefits,yet they face a global crisis necessitating sustainable preservation efforts.This study examines the depletion of floodplain wetlands within the Hastinapur Wildlife Sanctuary(HWLS)in Uttar Pradesh.Encroachment activities such as grazing,agriculture,and human settlements have fragmented and degraded critical wetland ecosystems.Additionally,irrigation projects,dam construction,and water diversion have disrupted natural water flow and availability.To assess wetland inundation in 2023,five classification techniques were employed:Random Forest(RF),Support Vector Machine(SVM),artificial neural network(ANN),Spectral Information Divergence(SID),and Maximum Likelihood Classifier(MLC).SVM emerged as the most precise method,as determined by kappa coefficient and index-based validation.Consequently,the SVM classifier was used to model wetland inundation areas from 1983 to 2023 and analyze spatiotemporal changes and fragmentation patterns.The findings revealed that the SVM clas-sifier accurately mapped 2023 wetland areas.The modeled time-series data demonstrated a 62.55%and 38.12%reduction in inundated wetland areas over the past 40 years in the pre-and post-monsoon periods,respectively.Fragmentation analysis indicated an 86.27%decrease in large core wetland areas in the pre-monsoon period,signifying severe habitat degradation.This rapid decline in wetlands within protected areas raises concerns about their ecological impacts.By linking wetland loss to global sustainability objectives,this study underscores the global urgency for strengthened wetland protection measures and highlights the need for integrating wetland conservation into broader sustainable development goals.Effective policies and adaptive management strategies are crucial for preserving these ecosystems and their vital services,which are essential for biodiversity,climate regulation,and human well-being.
基金National Major Science and Technology Project for Deep Earth Exploration(No.2025ZD1008301)National Natural Science Foundation of China(No.52374153)for the financial supportthe support of the China Scholarship Council.
文摘Efficient hard-rock fragmentation remains a critical challenge in mechanized mining.This study designed an adjustable-spacing mold and conducted double cutting pick indentation tests on granite.Mechanical responses and fragmentation characteristics under varying horizontal stresses,pick spacings,and groove depths were systematically analyzed.Unidirectional stress concentration altered the rock fragmentation modes,exhibiting a dual effect on the fragmentation process.The maximum indentation force(F_(max)),indentation hardness index(IHI),indentation modulus(IM),and indentation energy(W)initially increased and then decreased with rising horizontal stress.Appropriate spacing promoted radial crack coalescence,whereas too small a spacing(20 mm)caused repetitive re-fragmentation of rock chips,and too large a spacing(50 mm)resulted in unbroken ridges.Pre-cut grooves weakened the rock,reducing F_(max) and specific energy(SE),thus improving fragmentation efficiency,although the improvement slowed beyond a 10-mm groove depth.Based on the results and rock-mass conditioning assisted fragmentation mechanism,a“stress-structure dual control”assisted fragmentation mechanism was proposed,and a“pre-drilling unloading−alternate stopping”mining scheme was exploratorily designed.This approach creates favorable conditions for rock fragmentation by reducing stress levels and rock mass integrity in target zones,providing theoretical support and an engineering paradigm for mecheanized mining of deep resources.
文摘Integrated land and resource planning is critical for achieving global sustainability goals,yet a persistent chasm separates policy ambition from on-the-ground outcomes.The review article undertakes a comparative evaluation across the world to diagnose the systemic gaps of the policy that is leading to this implementation failure.We come up with a general typology of 5 categories of gaps that are interconnected:spatial-temporal mismatches,institutional fragmentation,the knowledge-action divide,lack of equity and justice,and broken monitoring and feedback loops.In a comparative study of the High-Income Countries,Rapidly Developing Economies,and Low-Income Countries,we show how these universal gaps are reflected in specific contextual syndromes,which are defined by the political economy,state capacity,and global integration.As can be seen in the analysis,these failures are not stand-alone but exist in a vicious,self-perpetuating cycle that is based on power asymmetries,institutional path dependency,and scale mismatches.In order to break this cycle,we suggest a revolutionary structure of action,which is structured around integration,adaptive management,and justice.The framework identifies the specific operation strategies,such as developing meta-governance formations and establishing community tenure to implement participatory monitoring,and aligning a multi-scale agenda.We infer that the implementation gap must be bridged by going beyond technical solutions to ensure a virtuous circle of legitimate learning-oriented governance that can address the complexity of socio-ecological conditions of the Anthropocene.
基金supported by the National Natural Science Foundation of China,Nos.82171082(to ZX),32000727(to TZ),32370731(to YZ)Guangdong Basic and Applied Basic Research Foundation,No.2024A151501069(to ZX)+1 种基金Shenzhen Science and Technology Program,Nos.JCYJ20210324101603009(to ZX),GJHZ20220913142807015(to TZ),JCYJ20220531100204010(to TZ),JCYJ20230807091308018(to YZ)Shenzhen Medical Research Funds,No.A2303068(to TZ).
文摘The peripheral immune system has emerged as a regulator of neurodegenerative diseases such as Alzheimer’s disease.Microglia are resident immune cells in the brain that may orchestrate communication between the central nervous system and peripheral immune system,though the mechanisms are unclear.Here,we found that gamma-type immunoglobulin,a product originating from peripheral blood B cells,localized in the brain parenchyma of multiple mouse models with amyloid pathology,and was enriched on microglia but not on other brain cell types.Further experiments showed that gamma-type immunoglobulin bound to microglial cell membranes and led to diverse transcriptomic changes,including upregulation of pathways related to phagocytosis and immunity.Functional assays demonstrated that gamma-type immunoglobulin enhanced microglial phagocytic capacity for amyloid-beta fibrils via its Fc fragment,but not Fab fragment,fragment.Our data indicate that microglia,when exposed to gamma-type immunoglobulin,exhibit an enhanced capacity for clearing amyloid-beta fibrils,potentially via the gamma-type immunoglobulin Fc fragment signaling pathway.This suggests that parenchymal gamma-type immunoglobulin should be further investigated to determine whether it may play a beneficial role against Alzheimer’s disease by enhancing microglial function.
基金supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology(No.2024yjrc71)State Key Laboratory of Precision Blasting,Jianghan University(No.PBSKL25B15)+2 种基金Foundation of Anhui Engineering Research Center of New Explosive Materials and Blasting Technology(No.AHBP2024B11)National Natural Science Foundation of China(No.52208384)Auhui Provincial Key Laboratory of Urban Rail Transit Safety and Emergency Management,Hefei University(No.2024GD003)。
文摘The global mining industry,particularly deep high-stress hard-rock mining,confronts prominent challenges of massive energy consumption and low crushing/grinding efficiency.Optimized blasting,as an alternative to grinding,effectively reduces energy usage and improves transportation efficiency.Despite extensive research on the effects of confining stress to cut blasting,studies focusing on fragmentation characteristics of deep confined blasting remain scarce.This study integrates theoretical analysis,similarity model tests,and SPH-FEM simulations to investigate fragmentation size distribution and energy dissipation under varying confining stresses.Results show that the Swebrec(SWE)function achieves superior fitting to fragmentation data(goodness-offit>0.95).With increasing confining stress,the fractal dimension of specimens increases(ranging from 2.16 to 2.42 in model tests),while fragmentation energy decreases—55.23% lower under high confining stress than no confining stress in tests,and 50.61%lower at 40 MPa than 0 MPa in simulations.The ratio of fragmentation energy to blasting energy is 2%-10%.Distinct from previous studies emphasizing confining stress macroeffects on cut blasting,this work explores fragmentation distribution functions and energy under biaxial confining stress,providing valuable insights for blasting efficiency evaluation and promoting energy conservation and emission reduction in post-mineral processing.
文摘Alzheimer’s disease(AD)is the most common origin of sporadic dementia.Rare familial forms have identified a central role for toxicity based on aggregation of peptide fragments generated from amyloid precursor protein(APP),named amyloid-beta(Aβ),which exists in two common forms,Aβ_(1-40)(Aβ_(40))and Aβ_(1-42)(Aβ_(42)).The latter is more neurotoxic.A common clinical biomarker measured in blood is the ratio Aβ_(42)/Aβ_(40).
基金supported by the National Natural Science Foundation of China (Grant Nos.12325406,92261201,12404305,and W2512072)the Shaanxi Province Natural Science Fundamental Research Project (Grant Nos.2023JC-XJ-03 and23JSQ013)the China Postdoctoral Science Foundation (Grant Nos.BX20240286 and 2024M7625)。
文摘Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon dioxide upon electron-impact.Through fragment ions and electron coincidence momentum imaging,we unambiguously determine the ionization mechanism by measuring the projectile energy loss in association with the C^(+) +O_(2)^(+) channel.Further potential energy and trajectory calculations enable us to elucidate the dynamical details of this fragmentation process,in which a bond rearrangement pathway is found to proceed via the structural deformation to a triangular intermediate.Moreover,we demonstrate a further roaming pathway for the formation of O_(2)^(+) from CO_(2)^(+) 2,in which a frustrated C-O bond cleavage leaves the O atom without sufficient energy to escape.The O atom then wanders around varied configuration spaces of the flat potential energy regions and forms a C-O-O_(2)^(+) intermediate prior to the final products C^(+) +O_(2)^(+).Considering the large quantities of free electrons in interstellar space,the processes revealed here are expected to be significant and should be incorporated into atmospheric evolution models.
基金supported by the National Natural Science Foundation of China(Grant Nos.12272411 and 42007259).
文摘Deep rock engineering is affected by coupled thermo-hydro-mechanical(THM)-dynamic fields,necessitating the elucidation of the dynamic mechanical behavior and failure mechanisms.This study utilized a Multi-field Coupled Controlled Split Hopkinson Pressure Bar(MCC-SHPB)system to elucidate the cross-scale dynamic responses of rocks and the boundaries of failure modes under THM coupling.Impact tests were conducted on green sandstone under coupled conditions of temperature(25℃-80℃),confining pressure(0-15 MPa),and seepage water pressure(0-15 MPa).Scanning electron microscopy(SEM)microstructural characterization and COMSOL Multiphysics numerical simulations were conducted,and a dynamic constitutive theoretical framework and failure-prediction methodology were established.We investigated the impact toughness index(I_(t)),dynamic modulus(E_(d)),dynamic triaxial compressive strength(TCS_(d)),fragmentation degree(W),and failure modes of green sandstone under thermo-confining pressure-seepage-impact loading conditions.The key findings reveal that the(I_(t))reflects different energy regulation mechanisms across different confining pressure regimes.Thermal-microcrack interactions dominate at low pressure,and energy absorption prevails at high pressure.A triphasic dynamic modulus model captures stiffness evolution under energy-driven conditions,revealing cross-scale crack nucleation-propagation and fragment reorganization.The TCSd inflection point signifies energy dissipation shifts,causing nonlinear skeleton bearing-capacity degradation.A critical criterion based on the W was established to distinguish between the two failure modes and predict the unstable failure initiation.Numerical simulations were used to elucidate the effects of inertia-dominated crack propagation and stress wave interference,validating the critical criterion and the predictive accuracy of the theoretical model during cross-scale failure.This study provides a theoretical foundation for assessing the dynamic stability of rock masses subjected to multi-field coupling during deep resource exploitation.
基金Supported by Japan Society for the Promotion of Science KAKENHI,No.25K11274.
文摘To establish practical,evidence-based strategies for noninvasive assessment and referral of patients with metabolic dysfunction-associated steatotic liver disease(MASLD)in Japan,we must address the urgent clinical need for accurate risk stratification and timely specialist intervention.A panel of 11 Japanese hepatology experts conducted a modified Delphi process to evaluate consensus recommendations regarding the use of noninvasive tests(NITs),including the fibrosis-4 index,enhanced liver fibrosis test,Mac-2-binding protein glycosylation isomer,type IV collagen 7S,cytokeratin-18 fragments,and imaging modalities such as ultrasound elastography and magnetic resonance elastography,for MASLD assessment and clinical referral.Practical algorithms were developed based on current Japanese data and panel consensus.The expert panel validated the utility of NITs as reliable tools for identifying patients with MASLD at risk for advanced fibrosis.Sequential use of NITs improved diagnostic accuracy and referral appropriateness while minimizing unnecessary specialist consultations.The proposed algorithms offer stepwise guidance for primary care physicians,supporting efficient,evidence-based decisionmaking.However,prospective longitudinal studies remain necessary for full prognostic validation of NITs in MASLD management.Noninvasive testing algorithms enable effective risk stratification and referral for MASLD in real-world Japanese practice with anticipated benefit for patient outcomes and healthcare systems.Broader adoption and further validation are warranted.
基金supported by Poongsan-KAIST Future Research Center Projectthe fund support provided by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(Grant No.2023R1A2C2005661)。
文摘This study presents a machine learning-based method for predicting fragment velocity distribution in warhead fragmentation under explosive loading condition.The fragment resultant velocities are correlated with key design parameters including casing dimensions and detonation positions.The paper details the finite element analysis for fragmentation,the characterizations of the dynamic hardening and fracture models,the generation of comprehensive datasets,and the training of the ANN model.The results show the influence of casing dimensions on fragment velocity distributions,with the tendencies indicating increased resultant velocity with reduced thickness,increased length and diameter.The model's predictive capability is demonstrated through the accurate predictions for both training and testing datasets,showing its potential for the real-time prediction of fragmentation performance.
基金National Natural Science Foundation of China,Grant/Award Number:52374153。
文摘Rock fragmentation is an important indicator for assessing the quality of blasting operations.However,accurate prediction of rock fragmentation after blasting is challenging due to the complicated blasting parameters and rock properties.For this reason,optimized by the Bayesian optimization algorithm(BOA),four hybrid machine learning models,including random forest,adaptive boosting,gradient boosting,and extremely randomized trees,were developed in this study.A total of 102 data sets with seven input parameters(spacing-to-burden ratio,hole depth-to-burden ratio,burden-to-hole diameter ratio,stemming length-to-burden ratio,powder factor,in situ block size,and elastic modulus)and one output parameter(rock fragment mean size,X_(50))were adopted to train and validate the predictive models.The root mean square error(RMSE),the mean absolute error(MAE),and the coefficient of determination(R^(2))were used as the evaluation metrics.The evaluation results demonstrated that the hybrid models showed superior performance than the standalone models.The hybrid model consisting of gradient boosting and BOA(GBoost-BOA)achieved the best prediction results compared with the other hybrid models,with the highest R^(2)value of 0.96 and the smallest values of RMSE and MAE of 0.03 and 0.02,respectively.Furthermore,sensitivity analysis was carried out to study the effects of input variables on rock fragmentation.In situ block size(XB),elastic modulus(E),and stemming length-to-burden ratio(T/B)were set as the main influencing factors.The proposed hybrid model provided a reliable prediction result and thus could be considered an alternative approach for rock fragment prediction in mining engineering.
基金financially supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U23A2047)the General Project of the Natural Science Foundation of Sichuan Province,China(Grant No.2023NSFSC0264).
文摘Rockfall represents a significant geological hazard in mountainous regions,characterized by a sudden and unpredictable feature.The process of dynamic fragmentation and energy conversion in a rockfall event remains complex and not fully understood.This study aims to gain a further understanding of the energy transfer mechanism during rockfall impact and fragmentation by impact tests using a variety of rock-like sphere specimens.The experiments mainly focus on the quantitative correlation between fragmentation degree and influence factors,i.e.impact angle and velocity on steel and granite slabs.The analysis focuses on the energy distribution characteristics,energy dissipation mechanisms,and the energy conversion rate of the fragments during impact and fragmentation.The results show that there is a significant correlation between the energy conversion rate and the fragmentation degree.In normal impact tests,elasto-plastic deformation energy and fracture energy are found to be two primary categories of energy dissipation.The proportion of total kinetic energy after impact is inversely proportional to the initial energy.A comparative analysis between normal and inclined slab impact tests reveals that the impact angle significantly influences the energy conversion rate,which controls the fragmentation degree as well.In addition,the fragmentation degree is inversely proportional to the restitution coefficient.These findings contribute to a better understanding of the energy conversion mechanism during rockfall impact and fragmentation,providing valuable insight for the development of effective strategies to mitigate such rockfall hazards.
基金supported by the Major Program of National Natural Science Foundation of China(No.52192624)the Innovative Research Group Project of National Natural Science Foundation of China(No.52421002)+3 种基金Major Science and Technology Project of Yunnan Province(No.202302AF080001)NSFC Key International(Regional)Cooperative Research Projects(No.52020105001)General Program of National Natural Science Foundation of China(Nos.52204019 and 52274016)the Foundation of State Key Laboratory of Petroleum Resources and Prospecting(No.PRE/DX-2402)。
文摘Percussion drilling is a promising approach for hot dry rock(HDR)fragmentation.However,understanding of HDR fragmentation mechanism under multi-dimensional percussion remains limited and hinders the corresponding drilling performance.Herein,an innovative true triaxial multi-dimensional percussion device was developed for the study of HDR fragmentation mechanism under in-situ temperature and stress conditions.Multi-dimensional percussion,involving both axial and torsional components,was applied to drilling in granite and carbonatite rocks sampled from the typical HDR target areas.Multiscale visualization techniques and a whale optimization-variational mode decomposition algorithm were employed to investigate the rock failure patterns and drilling energy characteristics.Results indicated that multi-dimensional percussion enhances brittle-ductile mixed failure in granite,characterized by transgranular,intergranular,and combined fracture patterns that promote rock cracking.In contrast,carbonatite drillhole displays enhanced brittle fragmentation and tortuous failure surface dominated by transgranular fracture pattern.Frequency-domain characteristics of penetration force signals for multidimensional percussion,especially the significant dominant frequency,amplitude,and high-frequency dissipation,indicate an increase in net energy for drilling into HDR and intensified rock fragmentation.Further,the effect of impact frequency on rock fragmentation performance was emphasized to maximize drilling efficiency.The optimal regulation schemes between axial and torsional impact frequencies are identified as 15 Hz+15 Hz for granite and 30 Hz+15 Hz for carbonatite.The reliability of the optimization approach was validated through a field test that employed a novel impactor in the geothermal well Fushen-1.
基金supported by National Natural Science Foundation of China (No.U23A20597)National Major Science and Technology Project of China (No.2024ZD1003803)+1 种基金Chongqing Science Fund for Distinguished Young Scholars of Chongqing Municipality (No.CSTB2022NSCQ-JQX0028)Natural Science Foundation of Chongqing (No.CSTB2024NSCQ-MSX0503)。
文摘In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still unclear.Therefore,the fluid evolution characteristics and rock fracture behavior during jet impingement were studied.The results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration stage.With the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet impact.In addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was established.These findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.
