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
Industrial wastes such as steel slag and coal gangue etc.were chosen as raw materials for preparing ceramic via the conventional solid-state reaction method.With steel slag and coal gangue mixed in various mass ratios...Industrial wastes such as steel slag and coal gangue etc.were chosen as raw materials for preparing ceramic via the conventional solid-state reaction method.With steel slag and coal gangue mixed in various mass ratios,from 100%steel slag to 100%coal gangue at 10%intervals,microstructure and possible phase evolution of the coal gangue-steel slag ceramics were investigated using X-ray powder diffraction,scanning electron microscopy,mercury intrusion porosimetry and Archimedes boiling method.The experimental results suggest that the phase compositions of the as-prepared ceramics could be altered with the increased amount of coal gangue in the ceramics.The anorthite-diopside eutectic can be formed in the ceramics with the mass ratios of steel slag to coal gangue arranged from 8:2 to 2:8,which was responsible for the melting of the steel slag-coal gangue ceramics at relatively high temperature.Further investigations on the microstructure suggested that the addition of the proper amount of steel slag in ceramic compositions was conducive to the pore formation and further contributed to an increment in porosity.展开更多
Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the micros...Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the microscopic morphology of the bonding interface.At the same time,combined with finite element calculations,the evolution mechanism of the interface of the hot melt explosion welded W/CuCrZr composite plate was explored.The results show that the interface bonding of the hot melt explosion welded W/CuCrZr composite plate is good and there is a cross-melting zone with 3–8μm in thickness,but cracks are developed on the W side.The numerical simulation reproduces the changes of pressure,stress,strain and internal energy at the bonding interface in the process of hot melt explosion welding.The location of the crack generated in the experiment coincides with the high stress position calculated by numerical simulation.The high pressure and high temperature near the hot melt explosion welding interface further promote the bonding of the interface.展开更多
This study selected the Sino-US route data from the top 30 global container liner companies between December 1,2019,and December 29,2019,as the data source utilizing the complex network research methodology.It constru...This study selected the Sino-US route data from the top 30 global container liner companies between December 1,2019,and December 29,2019,as the data source utilizing the complex network research methodology.It constructs a Sino-US container shipping network through voyage weighting and analyzes the essential structural characteristics to explore the network’s complex structural fea-tures.The network’s evolution is examined from three perspectives,namely,time,space,and event influence,aiming to comprehens-ively explore the network’s evolution mechanism.The results revealed that:1)the weighted Sino-US container shipping network exhib-its small-world and scale-free properties.Key hub ports in the United States include NEW YORK NY,SAVANNAH GA,LOS ANGELES CA,and OAKLAND CA,whereas SHANGHAI serving as the hub port in China.The geographical distribution of these hub ports is uneven.2)Concerning the evolution of the weighted Sino-US container shipping network,from a temporal perspective,the evolution of the regional structure of the entire Sino-US region and the Inland United States is in a stage of radiative expansion and de-velopment,with a need for further enhancement in competitiveness and development speed.The evolution of the regional structure of southern China and Europe is transitioning from the stage of radiative expansion and development to an advanced equilibrium stage.The shipping development in Northern China,the Western and Eastern United States,and Asia is undergoing significant changes but faces challenges of fierce competition and imbalances.From a spatial perspective,the rationality and effectiveness of the improved weighted Barrat-Barthelemy-Vespignani(BBV)model are confirmed through theoretical derivation.The applicability of the improved evolution model is verified by simulating the evolution of the weighted Sino-US container shipping network.From an event impact per-spective,the Corona Virus Disease 2019(COVID-19)pandemic has not fundamentally affected the spatial pattern of the weighted Sino-US container shipping network but has significantly impacted the network’s connectivity.The network lacks sufficient resilience and stability in emergency situations.3)Based on the analysis of the structural characteristics and evolution of the weighted Sino-US con-tainer shipping network,recommendations for network development are proposed from three aspects:emphasizing the development of hub ports,focusing on the balanced development of the network,and optimizing the layout of Chinese ports.展开更多
"Carbon neutrality movies"are movies that focus on carbon neutrality as the object of expression and dissemination.Using carbon neutrality as an element,it influences the development of the plot,reflects env..."Carbon neutrality movies"are movies that focus on carbon neutrality as the object of expression and dissemination.Using carbon neutrality as an element,it influences the development of the plot,reflects environmental changes,and focuses on climate change caused by carbon emissions.At the same time,it focuses on offsetting carbon emissions through carbon neutrality behavior,showcasing the impact of carbon neutrality.From the perspective of ecological movies,the evolution of carbon neutrality movies at three stages can be explored.The first stage is high-carbon movies that reflect the high conflict between humans and the natural environment.The second stage is low-carbon movies,reflecting humanity's pursuit of a harmonious coexistence between humans and nature,thus adopting green and low-carbon behaviors.The third stage is carbon neutrality movies,which awaken or guide the public to pay attention to carbon emissions,promote low-carbon living,guide life practice in a carbon neutrality way,and create a better life.There are three characteristics of"carbon neutrality movies",including scientific reflection on global warming,advocating energy conservation and emission reduction in daily life,and promoting clean energy in policies.展开更多
In this study,a comprehensive rolling mill vibration test program was designed,including specific test conditions and a test system.The analysis of measured signals reveals the vibration response characteristics and t...In this study,a comprehensive rolling mill vibration test program was designed,including specific test conditions and a test system.The analysis of measured signals reveals the vibration response characteristics and their evolution at different gauge points in the finishing mill.This is particularly evident during abnormal rolling,where the signals highlight the characteristics of abnormal responses and vibration intensities.Abnormal vibrations during the rolling process mainly occur when the strip thickness is less than 2.5 mm,and at the rolling speed-up stage,the strong abnormal vibration occurs at each measuring point on the F2 transmission side.The maximum vibration intensity of the backup roll’s bearing seat is 17 mm/s.As the rolling progresses,the stress on the bolts changes.The strip thickness is negatively correlated with the peak values of bite and tail-flick impacts.The vibration characteristics vary with the strip thickness and the process state.展开更多
The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal agin...The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal aging at 150 ℃ was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn-8Zn-3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn-8Zn-3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn-Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound （IMC） layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn-8Zn-3Bi solder/Cu joint.展开更多
[Objective] The paper aimed to reflect the spatial pattern and temporal and spatial evolution characteristics, the differences between inter-regional tourism economy was measured from the quality aspect, which provide...[Objective] The paper aimed to reflect the spatial pattern and temporal and spatial evolution characteristics, the differences between inter-regional tourism economy was measured from the quality aspect, which provided a reference for the local governments in the future tourism development. [Method] Using the location entropy methods, three time periods side of tourism-related date of 2000, 2005, 2007 were selected, from the angle of the spatial pattern and the evolution of the differences within the different scales, the spatial and temporal evolution characteristics of the economic development level of Jiangsu were analysed. [Result] The results showed that from the aspect of spatial evolution pattern, as time goes on, the economic development of Jiangsu tourism has experienced morphological evolution of concentration- dispersion decrease-stability; when it comes to the development of the tourism economy, in recent years, the overall gap between the tourism economy in Jiangsu did not widen, the gap mainly led by the region one after another. According to their volatility, it will be divided into four categories: A Stable type (Wuxi, Xuzhou, Lianyungang and Taizhou), B Increasing type (Huai’an), C Fluctuations type (Nanjing, Changzhou, Suzhou and Yangzhou) and D Depression type (Nantong, Yancheng, Zhenjiang and Suqian). [Conclusion] Location entropy was quoted into tourism economic analysis, the method was simple and easy to understand, the result was accurate and convincing, which provided a reference for travel economic development and investment decision-making of Jiangsu.展开更多
To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unload...To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path,the initial confining pressure,and the energy conversion rate.The results show that(1)before the peak stress,the elastic energy increases with an increase in deviatoric stress,while the dissipated energy slowly increases first.After the peak stress,the elastic energy decreases with the decrease of deviatoric stress,and the dissipated energy suddenly increases.The energy release intensity during rock failure is positively correlated with the axial stress.(2)When the initial confining pressure is below a certain threshold,the stress path is the main factor influencing the total energy difference.When the axial stress remains constant and the confining pressure is unloading,the total energy is more sensitive to changes in the confining pressure.When the axial stress remains constant,the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure.The initial confining pressure is positively correlated with the rock's energy storage limit.(3)The initial confining pressure increases the energy conversion rate of the rock;the initial confining pressure is positively correlated with the energy conversion rate;and the energy conversion rate has a high confining pressure effect.The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure.(4)When the deviatoric stress is small,the confining pressure mainly plays a protective role.Compared with the case of triaxial compression paths,the rock damage is more severe under unloading paths,and compared with the case of constant axial stress,the rock damage is more severe under increasing axial stress.展开更多
Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in differen...Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in different regions.The findings reveal a significant increase in heatwaves since the 2000s,with the average occurrence rising from approximately 3 to 5 times,and their duration increasing from 15 to around 30 days,nearly doubling.An increasing trend of“early onset and late withdrawal”of heatwaves has become more pronounced each year.In particular,eastern regions experience heatwaves that typically start earlier and tend to persist into September,exhibiting greater interannual variability compared to western areas.The middle and lower reaches of the Yangtze River and Xinjiang are identified as high-frequency heatwave areas.Complex network analysis reveals the dynamics of heatwave propagation,with degree centrality and synchronization distance indicating that the middle and lower reaches of the Yangtze River,Northeast China,and Xinjiang are key nodes in heatwave spread.Additionally,network divergence analysis shows that Xinjiang acts as a“source”area for heatwaves,exporting heat to surrounding regions,while the central region functions as a major“sink,”receiving more heatwave events.Further analysis from 1994 to 2023 indicates that heatwave events exhibit stronger network centrality and more complex synchronization patterns.These results suggest that complex networks provide a refined framework for depicting the spatiotemporal dynamics of heatwave propagation,offering new avenues for studying their occurrence and development patterns.展开更多
In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepa...In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.展开更多
Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material ...Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material toughness is not sufficient to meet the requirements of mine disaster prevention.Based on this,in order to find the optimal-ratio material that combines strength and toughness,the synergistic mechanism of lithium slag(LS),ethylene-vinyl acetate(EVA)copolymer,and polyvinyl alcohol(PVA)fiber mixtures in improving the mechanical properties of cement concrete,as well as the mechanism of microscopic phase evolution,was analyzed through macroscopic experiments,mesoscopic characterization,microscopic analysis,theoretical calculations,and comprehensive evaluation.The stress-strain curves obtained from the uniaxial compressive strength tests of specimens with different admixtures and fibers were investigated,and the characteristics of different stages were analyzed.The mechanical properties of different admixtures and fiber-reinforced materials,including their advantages and disadvantages,were compared through weighted comprehensive evaluation.The entire process of material failure,ranging from pore compaction,crack initiation,crack propagation,specimen instability to crack penetration,was explained via macroscopic fracture morphology,and the mechanical mechanism of how different admixtures affect the mechanical properties of concrete materials was revealed.The microscopic mechanism and the phase-evolution process of how the admixture affects concrete properties were elucidated using X-ray diffraction(XRD),hydration reaction theory,and Fourier transform infrared spectroscopy(FTIR).Furthermore,scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS)was used to reveal the interfacial pore state and element distribution of the internal microstructure of concrete.The results show that PVA fiber bars can play the role of a“skeleton bridge”to improve the toughness of materials.LS can effectively promote the hydration process and cooperate with PVA fiber bars to enhance the mechanical properties of the material.EVA will inhibit the hydration reaction and degrade the material’s mechanical properties through the“organic isolation”effect.In addition,the on-site application has proven that the R3-group materials in this study can effectively inhibit the deformation of the roadway and possess strong reliability.Finally,the advantages and feasibility of LS-and-fiber-reinforced concrete were discussed from four perspectives:environmental protection,economy,disaster prevention,and development.This paper is expected to provide technical reference for the large-scale disposal of solid waste LS,the performance-optimization direction of concrete materials,and the prevention and control of coal and rock dynamic disasters.展开更多
The Cambrian platform margin in the Tarim Basin boasts favorable source-reservoir-cap assemblages,making it a significant target for hydrocarbon exploration in ultra-to extra-deep facies-controlled for-mations.Of the ...The Cambrian platform margin in the Tarim Basin boasts favorable source-reservoir-cap assemblages,making it a significant target for hydrocarbon exploration in ultra-to extra-deep facies-controlled for-mations.Of the three major basins in western China,Tarim is the only basin with large-scale platform margin where no exploration breakthrough has been achieved yet.This study determines the vertical and lateral differential evolution of the platform margin(in the Manxi area hereafter referred to as the Cambrian Manxi platform margin)through fine-scale sequence stratigraphic division and a segmented analysis.The platform margin can be divided into the Yuqi,Tahe,Shunbei,and Gucheng segments,from north to south,based on the development of different ancient landforms and the evolutionary process of the platform.The Yuqi and Shunbei segments exhibit relatively low-elevation ancient landforms.Both segments were in a submarine buildup stage during the Early Cambrian,resulting in overall limited scales of their reservoirs.The Gucheng segment features the highest-elevation ancient landforms and accordingly limited accommodation spaces.As a result,the rapid lateral migration of high-energy facies zones leads to the development of large-scale reservoirs with only limited thicknesses.In contrast,the Tahe segment,exhibiting comparatively high-elevation ancient landforms,is identified as the most favorable segment for the formation of large-scale reservoirs.The cap rocks of the platform margin are dominated by back-reef dolomitic flats and tight carbonate rocks formed in transgressive periods.A comprehensive evaluation of source rocks,reservoirs,and cap rocks indicates that the Tahe segment boasts the optimal hydrocarbon accumulation conditions along the platform margin.In this segment,the Shayilike Formation transgressive deposits and the high-energy mound-shoal complexes along the platform margin of the Wusonggeer Formation constitute the optimal reservoir-cap rock assemblage,establishing this segment as the most promising target for hydrocarbon exploration in the platform margin.展开更多
Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structur...Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structure.Based on measured data,a thermal-mechanical coupling model of the track was established.The deformation characteristics and interfacial damage behavior of joints under typical temperature fields were studied.The findings indicate that the annual extreme temperature range of the slab track,fluctuates from−1.4 to 49.8℃.The annual temperature gradient within the vertical depth range of 0 to 0.2 m of the track varies between−16.19℃/m and 30.15℃/m.The vertical deformation of joints is significantly influenced by high temperatures,with a maximum measured deformation of 0.828 mm.The joint seams are primarily affected by low temperatures,which lead to a separation of 0.9 to 1.0 mm.Conversely,interlayer damage of joints is predominantly influenced by elevated temperatures.In summer,the maximum ratio of interface damage area in the joint can reach up to 95%,with the maximum debonding area ratio can be as high as 84%.The research results can provide help for joint damage regularity and deformation control of CRTS II slab track.展开更多
To conduct a comprehensive analysis of the current status of water environment quality in Yilong Lake,a systematic study was undertaken to characterize the evolution of water quality.This study utilized monthly data o...To conduct a comprehensive analysis of the current status of water environment quality in Yilong Lake,a systematic study was undertaken to characterize the evolution of water quality.This study utilized monthly data on water quality indicators collected from three monitoring sections of Yilong Lake between 2016 and 2023,employing the Mann-Kendall trend test and ArcGIS spatial interpolation technique.The results indicated that the five-day biochemical oxygen demand(BOD5),total nitrogen(TN),and chlorophyll a(Chla)exhibited an overall increasing trend,whereas other indicators demonstrated a decreasing trend.The permanganate index(PI),chemical oxygen demand(COD),TN,and Chla were observed in the following order:east of the lake>middle of the lake>west of the lake.In contrast,the BOD5 and total phosphorus(TP)were ranked as west of the lake>east of the lake>middle of the lake.Additionally,ammonia nitrogen(NH3-N)was found to be in the order of east of the lake>west of the lake>middle of the lake,while transparency was ranked as west of the lake>middle of the lake>east of the lake.Urban domestic sewage,effluent from industrial parks,domestic waste generated by rural residents’production and daily activities,agricultural waste,wastewater from decentralized farming,domestic sewage,and point source discharges from the soybean processing industry are the primary contributors to the exceedance of water quality standards.The enhancement of a precise pollution control system,along with the regulation of pollution sources and the interception of pollutants,can significantly diminish the pollution load entering the lake.This approach is essential for the protection and restoration of river and lake ecosystems,thereby facilitating the gradual recovery of their ecological functions.Additionally,the implementation of ecological water replenishment and the recycling of water resources can improve the capacity of the water environment.Furthermore,bolstering scientific and technological support,as well as comprehensive supervision and assurance measures,is crucial to ensuring that water quality remains stable and adheres to established standards.展开更多
The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the Sout...The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the South Yellow Sea is located at the convergence of these plates,it becomes a pivotal area for understanding the tectonic evolution of East Asia.The characteristics and provenance of clastic rocks of the Middle Permian-the Early Triassic were analyzed and the strata in the Central Uplift including the Qinglong Formation(T_(1)q)and Talung Formation(P_(3)d),consisting of various mudstones and sandstones,were anatomized.Results show that quartz and feldspar are the main diagenetic minerals,while illite and chlorite show signs of secondary alterations.Geochemical imprints indicate a gradual shift in provenance from ancient sedimentary and mafic igneous rocks to intermediate igneous rocks.In the meantime,the tectonic background transformed from continent to continental island arc from the Middle Permian to the Early Triassic.Therefore,we inferred that a soft collision between the North China Plate and the Yangtze Plate likely occurred during the Late Permian,resulted in intensified collision between two plates in the Early Triassic,and shaped the South Yellow Sea.This study provided valuable information on the timing of plate collisions in the South Yellow Sea.展开更多
Pygmy lorises are arboreal primates primarily found in forest environments across Southeast Asia(Nekaris 2014).Theyhave a diverse diet,including plant secretions,nectar,fruits,invertebrates,tree bark,and bird eggs.All...Pygmy lorises are arboreal primates primarily found in forest environments across Southeast Asia(Nekaris 2014).Theyhave a diverse diet,including plant secretions,nectar,fruits,invertebrates,tree bark,and bird eggs.All 9 known speciesof pygmy lorises are listed as globally endangered species(Nekaris 2014).Pygmy lorises exhibit a range of unique phenotypic characteristics rarely seen among primates.展开更多
The size of mineral grain has a significant impact on the initiation and propagation of microcracks within rocks.In this study,fine-,medium-,and coarse-grained granites were used to investigate microcrack evolution an...The size of mineral grain has a significant impact on the initiation and propagation of microcracks within rocks.In this study,fine-,medium-,and coarse-grained granites were used to investigate microcrack evolution and characteristic stress under uniaxial compression using the acoustic emission(AE),digital image correlation(DIC),and nuclear magnetic resonance(NMR)measurements.The experimental results show that the characteristic stress of each granite decreased considerably with increasing grain sizes.The inflection points of the b-value occurred earlier with an increase in grain sizes,indicating that the larger grains promote the generation and propagation of microcracks.The distribution characteristics of the average frequency(AF)and the ratio of rise time to amplitude(RA)indicate that the proportion of shear microcracks increases with increasing grain size.The NMR results indicate that the porosity and the proportion of large pores increased with increasing grain size,which may intensify the microcrack evolution.Moreover,analysis of the DIC and AE event rates suggests that the high-displacement regions could serve as a criterion for the degree of microcrack propagation.The study found that granites with larger grains had a higher proportion of high-displacement regions,which can lead to larger-scale cracking or even spalling.These findings are not only beneficial to understand the pattern of microcrack evolution with different grain sizes,but also provide guidance for rock monitoring and instability assessment.展开更多
Cryptocrystalline basalt is one of the two major types of rocks exposed in the super large-scale underground powerhouse in Baihetan hydropower station in China.The rock of this type shows various sitespecific mechanic...Cryptocrystalline basalt is one of the two major types of rocks exposed in the super large-scale underground powerhouse in Baihetan hydropower station in China.The rock of this type shows various sitespecific mechanical responses(e.g.fragmentation,fracturing,and relaxation)during excavation.Using conventional triaxial testing facility MTS 815.03,we obtained the stressestrain curves,macroscopic failure characteristics,and strength characteristics of cryptocrystalline basalt.On this basis,evolution of crack initiation and propagation was explored using the finite-discrete element method(FDEM)to understand the failure mechanism of cryptocrystalline basalt.The test results showed that:(1)under different confining stresses,almost all the pre-peak stressestrain curves of cryptocrystalline basalt were linear and the post-peak stresses decreased rapidly;(2)the cryptocrystalline basalt showed a failure mode in a form of fragmentation under low and medium confining stresses while fragmentation-shear coupling failure dominated at high confining stresses;and(3)the initial strength ratio(sci/sf,where sci and sf are the crack initiation strength and peak strength,respectively)ranged from 0.45 to 0.55 and the damage strength ratio(scd/sf,where scd is the crack damage strength)exceeded 0.9.The stressestrain curve characteristics and failure modes of cryptocrystalline basalt could be reflected numerically.For this,FDEM simulation was employed to reveal the characteristics of cryptocrystalline basalt,including high scd/sf values and rapid failure after scd,with respect to the microscopic characteristics of mineral structures.The results showed that the fragmentation characteristics of cryptocrystalline basalt were closely related to the development of tensile cracks in rock samples prior to failure.Moreover,the decrease in degree of fragmentation with increasing confining stress was also correlated with the dominant effect of confining stress on the tensile cracks.展开更多
There are several basins with high sediment yield in the Pisha-sandstone covering area of the east wing of the Ordos Plateau. Due to the lack of targeted research on the dynamical characteristics of geomorphic evoluti...There are several basins with high sediment yield in the Pisha-sandstone covering area of the east wing of the Ordos Plateau. Due to the lack of targeted research on the dynamical characteristics of geomorphic evolution that plays an important role in the sand production, this paper analyzed the tectonic activity intensity and erosion characteristics of the area. The results show that the intensity of tectonic activities in the area is generally moderateweak and shows an unconspicuous increase from north to south. Tectonic activity is manifested mainly in the form of uplift. The uplift rate in the lower reaches of each basin is greater than the erosion rate,which is prominent in the Kuyehe and the Tuweihe rivers. During the uplift of the regional topography,the most serious parts under erosion are generally concentrated in the upstream and midstream of basins. All longitudinal profiles of the basins have a shape close to an exponential function, which indicates that they are in the early stage of erosion evolution. The mechanisms of geomorphologic evolution of these basins have a great similarity. The conservative estimate of historical average erosion rate was less than 182–520 t/(km^2·yr), much less than that of the modern times. The average stream power values are typically distributed between 4 and102 W/m, with the larger being in the Kuyehe and the Tuweihe rivers and the smallest being in the Qinshuihe River. The maximum stream power value appears in the downstream reach, which should be the main reason for the particles being directly injected into the Yellow River. From the perspective of geomorphological evolution, the current soil and water conservation measures can hardly cure the erosion of these basins in the long run.展开更多
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.
基金Funded by the Scientific and Technological Innovation Project of Carbon Emission Peak and Carbon Neutrality of Jiangsu Province(No.BE2022028-4)。
文摘Industrial wastes such as steel slag and coal gangue etc.were chosen as raw materials for preparing ceramic via the conventional solid-state reaction method.With steel slag and coal gangue mixed in various mass ratios,from 100%steel slag to 100%coal gangue at 10%intervals,microstructure and possible phase evolution of the coal gangue-steel slag ceramics were investigated using X-ray powder diffraction,scanning electron microscopy,mercury intrusion porosimetry and Archimedes boiling method.The experimental results suggest that the phase compositions of the as-prepared ceramics could be altered with the increased amount of coal gangue in the ceramics.The anorthite-diopside eutectic can be formed in the ceramics with the mass ratios of steel slag to coal gangue arranged from 8:2 to 2:8,which was responsible for the melting of the steel slag-coal gangue ceramics at relatively high temperature.Further investigations on the microstructure suggested that the addition of the proper amount of steel slag in ceramic compositions was conducive to the pore formation and further contributed to an increment in porosity.
基金National Natural Science Foundation of China(12072363,12272374,12372373)Special Fund for Fundamental Research of the Central Universities(WK2480000008,WK2480000007,WK2320000049)Anhui Provincial Science and Technology Major Project(202003A05020035)。
文摘Explosion welding was carried out on the basis of vacuum hot melt W/CuCrZr composite plate.Metallurgical microscope,scanning electron microscope and energy dispersive X-ray spectroscope were used to observe the microscopic morphology of the bonding interface.At the same time,combined with finite element calculations,the evolution mechanism of the interface of the hot melt explosion welded W/CuCrZr composite plate was explored.The results show that the interface bonding of the hot melt explosion welded W/CuCrZr composite plate is good and there is a cross-melting zone with 3–8μm in thickness,but cracks are developed on the W side.The numerical simulation reproduces the changes of pressure,stress,strain and internal energy at the bonding interface in the process of hot melt explosion welding.The location of the crack generated in the experiment coincides with the high stress position calculated by numerical simulation.The high pressure and high temperature near the hot melt explosion welding interface further promote the bonding of the interface.
基金Under the auspices of National Natural Science Foundation of China(No.41201473,41371975)。
文摘This study selected the Sino-US route data from the top 30 global container liner companies between December 1,2019,and December 29,2019,as the data source utilizing the complex network research methodology.It constructs a Sino-US container shipping network through voyage weighting and analyzes the essential structural characteristics to explore the network’s complex structural fea-tures.The network’s evolution is examined from three perspectives,namely,time,space,and event influence,aiming to comprehens-ively explore the network’s evolution mechanism.The results revealed that:1)the weighted Sino-US container shipping network exhib-its small-world and scale-free properties.Key hub ports in the United States include NEW YORK NY,SAVANNAH GA,LOS ANGELES CA,and OAKLAND CA,whereas SHANGHAI serving as the hub port in China.The geographical distribution of these hub ports is uneven.2)Concerning the evolution of the weighted Sino-US container shipping network,from a temporal perspective,the evolution of the regional structure of the entire Sino-US region and the Inland United States is in a stage of radiative expansion and de-velopment,with a need for further enhancement in competitiveness and development speed.The evolution of the regional structure of southern China and Europe is transitioning from the stage of radiative expansion and development to an advanced equilibrium stage.The shipping development in Northern China,the Western and Eastern United States,and Asia is undergoing significant changes but faces challenges of fierce competition and imbalances.From a spatial perspective,the rationality and effectiveness of the improved weighted Barrat-Barthelemy-Vespignani(BBV)model are confirmed through theoretical derivation.The applicability of the improved evolution model is verified by simulating the evolution of the weighted Sino-US container shipping network.From an event impact per-spective,the Corona Virus Disease 2019(COVID-19)pandemic has not fundamentally affected the spatial pattern of the weighted Sino-US container shipping network but has significantly impacted the network’s connectivity.The network lacks sufficient resilience and stability in emergency situations.3)Based on the analysis of the structural characteristics and evolution of the weighted Sino-US con-tainer shipping network,recommendations for network development are proposed from three aspects:emphasizing the development of hub ports,focusing on the balanced development of the network,and optimizing the layout of Chinese ports.
文摘"Carbon neutrality movies"are movies that focus on carbon neutrality as the object of expression and dissemination.Using carbon neutrality as an element,it influences the development of the plot,reflects environmental changes,and focuses on climate change caused by carbon emissions.At the same time,it focuses on offsetting carbon emissions through carbon neutrality behavior,showcasing the impact of carbon neutrality.From the perspective of ecological movies,the evolution of carbon neutrality movies at three stages can be explored.The first stage is high-carbon movies that reflect the high conflict between humans and the natural environment.The second stage is low-carbon movies,reflecting humanity's pursuit of a harmonious coexistence between humans and nature,thus adopting green and low-carbon behaviors.The third stage is carbon neutrality movies,which awaken or guide the public to pay attention to carbon emissions,promote low-carbon living,guide life practice in a carbon neutrality way,and create a better life.There are three characteristics of"carbon neutrality movies",including scientific reflection on global warming,advocating energy conservation and emission reduction in daily life,and promoting clean energy in policies.
文摘In this study,a comprehensive rolling mill vibration test program was designed,including specific test conditions and a test system.The analysis of measured signals reveals the vibration response characteristics and their evolution at different gauge points in the finishing mill.This is particularly evident during abnormal rolling,where the signals highlight the characteristics of abnormal responses and vibration intensities.Abnormal vibrations during the rolling process mainly occur when the strip thickness is less than 2.5 mm,and at the rolling speed-up stage,the strong abnormal vibration occurs at each measuring point on the F2 transmission side.The maximum vibration intensity of the backup roll’s bearing seat is 17 mm/s.As the rolling progresses,the stress on the bolts changes.The strip thickness is negatively correlated with the peak values of bite and tail-flick impacts.The vibration characteristics vary with the strip thickness and the process state.
基金Project(50675234)supported by the National Natural Science Foundation of China
文摘The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal aging at 150 ℃ was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn-8Zn-3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn-8Zn-3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn-Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound （IMC） layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn-8Zn-3Bi solder/Cu joint.
文摘[Objective] The paper aimed to reflect the spatial pattern and temporal and spatial evolution characteristics, the differences between inter-regional tourism economy was measured from the quality aspect, which provided a reference for the local governments in the future tourism development. [Method] Using the location entropy methods, three time periods side of tourism-related date of 2000, 2005, 2007 were selected, from the angle of the spatial pattern and the evolution of the differences within the different scales, the spatial and temporal evolution characteristics of the economic development level of Jiangsu were analysed. [Result] The results showed that from the aspect of spatial evolution pattern, as time goes on, the economic development of Jiangsu tourism has experienced morphological evolution of concentration- dispersion decrease-stability; when it comes to the development of the tourism economy, in recent years, the overall gap between the tourism economy in Jiangsu did not widen, the gap mainly led by the region one after another. According to their volatility, it will be divided into four categories: A Stable type (Wuxi, Xuzhou, Lianyungang and Taizhou), B Increasing type (Huai’an), C Fluctuations type (Nanjing, Changzhou, Suzhou and Yangzhou) and D Depression type (Nantong, Yancheng, Zhenjiang and Suqian). [Conclusion] Location entropy was quoted into tourism economic analysis, the method was simple and easy to understand, the result was accurate and convincing, which provided a reference for travel economic development and investment decision-making of Jiangsu.
基金Anhui Natural Science Foundation Youth Program,Grant/Award Number:2208085QE142National Natural Science Foundations of China,Grant/Award Numbers:52004003,52304073Opening Foundation of Anhui Province Key Laboratory of Building Structure and Underground Engineering,Grant/Award Number:KLBSUE-2022-04。
文摘To study the energy evolution and failure characteristics of saturated sandstone under unloading conditions,rock unloading tests under different stress paths were conducted.The energy evolution mechanism of the unloading failure of saturated sandstone was systematically explored from the perspectives of the stress path,the initial confining pressure,and the energy conversion rate.The results show that(1)before the peak stress,the elastic energy increases with an increase in deviatoric stress,while the dissipated energy slowly increases first.After the peak stress,the elastic energy decreases with the decrease of deviatoric stress,and the dissipated energy suddenly increases.The energy release intensity during rock failure is positively correlated with the axial stress.(2)When the initial confining pressure is below a certain threshold,the stress path is the main factor influencing the total energy difference.When the axial stress remains constant and the confining pressure is unloading,the total energy is more sensitive to changes in the confining pressure.When the axial stress remains constant,the compressive deformation ability of the rock cannot be significantly improved by the increase in the initial confining pressure.The initial confining pressure is positively correlated with the rock's energy storage limit.(3)The initial confining pressure increases the energy conversion rate of the rock;the initial confining pressure is positively correlated with the energy conversion rate;and the energy conversion rate has a high confining pressure effect.The increase in the axial stress has a much greater impact on the elastic energy than the confining pressure.(4)When the deviatoric stress is small,the confining pressure mainly plays a protective role.Compared with the case of triaxial compression paths,the rock damage is more severe under unloading paths,and compared with the case of constant axial stress,the rock damage is more severe under increasing axial stress.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFE0136000 and 2024YFC3013100)the Joint Meteorological Fund(Grant No.U2342211)+1 种基金the Joint Research Project for Meteorological Capacity Improvement(Grant No.22NLTSZ004)the National Meteorological Information Center(Grant No.NMICJY202301)。
文摘Using complex network methods,we construct undirected and directed heatwave networks to systematically analyze heatwave events over China from 1961 to 2023,exploring their spatiotemporal evolution patterns in different regions.The findings reveal a significant increase in heatwaves since the 2000s,with the average occurrence rising from approximately 3 to 5 times,and their duration increasing from 15 to around 30 days,nearly doubling.An increasing trend of“early onset and late withdrawal”of heatwaves has become more pronounced each year.In particular,eastern regions experience heatwaves that typically start earlier and tend to persist into September,exhibiting greater interannual variability compared to western areas.The middle and lower reaches of the Yangtze River and Xinjiang are identified as high-frequency heatwave areas.Complex network analysis reveals the dynamics of heatwave propagation,with degree centrality and synchronization distance indicating that the middle and lower reaches of the Yangtze River,Northeast China,and Xinjiang are key nodes in heatwave spread.Additionally,network divergence analysis shows that Xinjiang acts as a“source”area for heatwaves,exporting heat to surrounding regions,while the central region functions as a major“sink,”receiving more heatwave events.Further analysis from 1994 to 2023 indicates that heatwave events exhibit stronger network centrality and more complex synchronization patterns.These results suggest that complex networks provide a refined framework for depicting the spatiotemporal dynamics of heatwave propagation,offering new avenues for studying their occurrence and development patterns.
基金Projects(12072102,12102129)supported by the National Natural Science Foundation of ChinaProject(DM2022B01)supported by the Key Laboratory of Safe Mining of Deep Metal Mines,Ministry of Education,ChinaProject(JZ-008)supported by the Six Talent Peaks Project in Jiangsu Province,China。
文摘In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.
基金supported by the National Natural Science Foundation of China(Nos.U23B2093 and 52034009)the National Key R&D Program of China(No.2024YFC3013801)the Fundamental Research Funds for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMTB)(No.BBJ2025001).
文摘Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material toughness is not sufficient to meet the requirements of mine disaster prevention.Based on this,in order to find the optimal-ratio material that combines strength and toughness,the synergistic mechanism of lithium slag(LS),ethylene-vinyl acetate(EVA)copolymer,and polyvinyl alcohol(PVA)fiber mixtures in improving the mechanical properties of cement concrete,as well as the mechanism of microscopic phase evolution,was analyzed through macroscopic experiments,mesoscopic characterization,microscopic analysis,theoretical calculations,and comprehensive evaluation.The stress-strain curves obtained from the uniaxial compressive strength tests of specimens with different admixtures and fibers were investigated,and the characteristics of different stages were analyzed.The mechanical properties of different admixtures and fiber-reinforced materials,including their advantages and disadvantages,were compared through weighted comprehensive evaluation.The entire process of material failure,ranging from pore compaction,crack initiation,crack propagation,specimen instability to crack penetration,was explained via macroscopic fracture morphology,and the mechanical mechanism of how different admixtures affect the mechanical properties of concrete materials was revealed.The microscopic mechanism and the phase-evolution process of how the admixture affects concrete properties were elucidated using X-ray diffraction(XRD),hydration reaction theory,and Fourier transform infrared spectroscopy(FTIR).Furthermore,scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS)was used to reveal the interfacial pore state and element distribution of the internal microstructure of concrete.The results show that PVA fiber bars can play the role of a“skeleton bridge”to improve the toughness of materials.LS can effectively promote the hydration process and cooperate with PVA fiber bars to enhance the mechanical properties of the material.EVA will inhibit the hydration reaction and degrade the material’s mechanical properties through the“organic isolation”effect.In addition,the on-site application has proven that the R3-group materials in this study can effectively inhibit the deformation of the roadway and possess strong reliability.Finally,the advantages and feasibility of LS-and-fiber-reinforced concrete were discussed from four perspectives:environmental protection,economy,disaster prevention,and development.This paper is expected to provide technical reference for the large-scale disposal of solid waste LS,the performance-optimization direction of concrete materials,and the prevention and control of coal and rock dynamic disasters.
基金funded by SINOPEC Science and Technology Research Program (project Nos:P24226, P24077)Northwest Oil Field Company,SINOPEC.
文摘The Cambrian platform margin in the Tarim Basin boasts favorable source-reservoir-cap assemblages,making it a significant target for hydrocarbon exploration in ultra-to extra-deep facies-controlled for-mations.Of the three major basins in western China,Tarim is the only basin with large-scale platform margin where no exploration breakthrough has been achieved yet.This study determines the vertical and lateral differential evolution of the platform margin(in the Manxi area hereafter referred to as the Cambrian Manxi platform margin)through fine-scale sequence stratigraphic division and a segmented analysis.The platform margin can be divided into the Yuqi,Tahe,Shunbei,and Gucheng segments,from north to south,based on the development of different ancient landforms and the evolutionary process of the platform.The Yuqi and Shunbei segments exhibit relatively low-elevation ancient landforms.Both segments were in a submarine buildup stage during the Early Cambrian,resulting in overall limited scales of their reservoirs.The Gucheng segment features the highest-elevation ancient landforms and accordingly limited accommodation spaces.As a result,the rapid lateral migration of high-energy facies zones leads to the development of large-scale reservoirs with only limited thicknesses.In contrast,the Tahe segment,exhibiting comparatively high-elevation ancient landforms,is identified as the most favorable segment for the formation of large-scale reservoirs.The cap rocks of the platform margin are dominated by back-reef dolomitic flats and tight carbonate rocks formed in transgressive periods.A comprehensive evaluation of source rocks,reservoirs,and cap rocks indicates that the Tahe segment boasts the optimal hydrocarbon accumulation conditions along the platform margin.In this segment,the Shayilike Formation transgressive deposits and the high-energy mound-shoal complexes along the platform margin of the Wusonggeer Formation constitute the optimal reservoir-cap rock assemblage,establishing this segment as the most promising target for hydrocarbon exploration in the platform margin.
基金Projects(U23A20666,52178405)supported by the National Natural Science Foundation of ChinaProject(K2022G038)supported by the Science and Technology Research and Development Program of China State Railway Group Co.,Ltd.Project(2021B03)supported by the Science and Technology Plan of Shandong Provincial Department of Transportation,China。
文摘Arching and cracking of joints between slabs have become a problem in China Railway Track System(CRTS)II slab track.The slab track is susceptible to complex temperature variations as a longitudinal continuous structure.Based on measured data,a thermal-mechanical coupling model of the track was established.The deformation characteristics and interfacial damage behavior of joints under typical temperature fields were studied.The findings indicate that the annual extreme temperature range of the slab track,fluctuates from−1.4 to 49.8℃.The annual temperature gradient within the vertical depth range of 0 to 0.2 m of the track varies between−16.19℃/m and 30.15℃/m.The vertical deformation of joints is significantly influenced by high temperatures,with a maximum measured deformation of 0.828 mm.The joint seams are primarily affected by low temperatures,which lead to a separation of 0.9 to 1.0 mm.Conversely,interlayer damage of joints is predominantly influenced by elevated temperatures.In summer,the maximum ratio of interface damage area in the joint can reach up to 95%,with the maximum debonding area ratio can be as high as 84%.The research results can provide help for joint damage regularity and deformation control of CRTS II slab track.
文摘To conduct a comprehensive analysis of the current status of water environment quality in Yilong Lake,a systematic study was undertaken to characterize the evolution of water quality.This study utilized monthly data on water quality indicators collected from three monitoring sections of Yilong Lake between 2016 and 2023,employing the Mann-Kendall trend test and ArcGIS spatial interpolation technique.The results indicated that the five-day biochemical oxygen demand(BOD5),total nitrogen(TN),and chlorophyll a(Chla)exhibited an overall increasing trend,whereas other indicators demonstrated a decreasing trend.The permanganate index(PI),chemical oxygen demand(COD),TN,and Chla were observed in the following order:east of the lake>middle of the lake>west of the lake.In contrast,the BOD5 and total phosphorus(TP)were ranked as west of the lake>east of the lake>middle of the lake.Additionally,ammonia nitrogen(NH3-N)was found to be in the order of east of the lake>west of the lake>middle of the lake,while transparency was ranked as west of the lake>middle of the lake>east of the lake.Urban domestic sewage,effluent from industrial parks,domestic waste generated by rural residents’production and daily activities,agricultural waste,wastewater from decentralized farming,domestic sewage,and point source discharges from the soybean processing industry are the primary contributors to the exceedance of water quality standards.The enhancement of a precise pollution control system,along with the regulation of pollution sources and the interception of pollutants,can significantly diminish the pollution load entering the lake.This approach is essential for the protection and restoration of river and lake ecosystems,thereby facilitating the gradual recovery of their ecological functions.Additionally,the implementation of ecological water replenishment and the recycling of water resources can improve the capacity of the water environment.Furthermore,bolstering scientific and technological support,as well as comprehensive supervision and assurance measures,is crucial to ensuring that water quality remains stable and adheres to established standards.
基金Supported by the National Natural Science Foundation of China(No.U 2344221)。
文摘The Yangtze Plate(YP)and the North China Plate(NCP)are key components of the East Asian continent,and their collision significantly influences the tectonic evolution of the eastern Asian continental margin.As the South Yellow Sea is located at the convergence of these plates,it becomes a pivotal area for understanding the tectonic evolution of East Asia.The characteristics and provenance of clastic rocks of the Middle Permian-the Early Triassic were analyzed and the strata in the Central Uplift including the Qinglong Formation(T_(1)q)and Talung Formation(P_(3)d),consisting of various mudstones and sandstones,were anatomized.Results show that quartz and feldspar are the main diagenetic minerals,while illite and chlorite show signs of secondary alterations.Geochemical imprints indicate a gradual shift in provenance from ancient sedimentary and mafic igneous rocks to intermediate igneous rocks.In the meantime,the tectonic background transformed from continent to continental island arc from the Middle Permian to the Early Triassic.Therefore,we inferred that a soft collision between the North China Plate and the Yangtze Plate likely occurred during the Late Permian,resulted in intensified collision between two plates in the Early Triassic,and shaped the South Yellow Sea.This study provided valuable information on the timing of plate collisions in the South Yellow Sea.
基金supported by the Shaanxi FundamentalScience Research Project for Chemistry&Biology(grant no.22JHQ049)Basic Research Program of Natural Sciencesof Shaanxi Province(2019JM-339).
文摘Pygmy lorises are arboreal primates primarily found in forest environments across Southeast Asia(Nekaris 2014).Theyhave a diverse diet,including plant secretions,nectar,fruits,invertebrates,tree bark,and bird eggs.All 9 known speciesof pygmy lorises are listed as globally endangered species(Nekaris 2014).Pygmy lorises exhibit a range of unique phenotypic characteristics rarely seen among primates.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51927808,11972378 and 52174098).
文摘The size of mineral grain has a significant impact on the initiation and propagation of microcracks within rocks.In this study,fine-,medium-,and coarse-grained granites were used to investigate microcrack evolution and characteristic stress under uniaxial compression using the acoustic emission(AE),digital image correlation(DIC),and nuclear magnetic resonance(NMR)measurements.The experimental results show that the characteristic stress of each granite decreased considerably with increasing grain sizes.The inflection points of the b-value occurred earlier with an increase in grain sizes,indicating that the larger grains promote the generation and propagation of microcracks.The distribution characteristics of the average frequency(AF)and the ratio of rise time to amplitude(RA)indicate that the proportion of shear microcracks increases with increasing grain size.The NMR results indicate that the porosity and the proportion of large pores increased with increasing grain size,which may intensify the microcrack evolution.Moreover,analysis of the DIC and AE event rates suggests that the high-displacement regions could serve as a criterion for the degree of microcrack propagation.The study found that granites with larger grains had a higher proportion of high-displacement regions,which can lead to larger-scale cracking or even spalling.These findings are not only beneficial to understand the pattern of microcrack evolution with different grain sizes,but also provide guidance for rock monitoring and instability assessment.
基金supported by the Key Projects of the Yalong River Joint Fund of the National Natural Science Foundation of China (Grant No.U1865203)the National Natural Science Foundation of China(Grant No.51279201)The partial support from the Youth Innovation Promotion Association of Chinese Academy of Science (CAS) is gratefully acknowledged
文摘Cryptocrystalline basalt is one of the two major types of rocks exposed in the super large-scale underground powerhouse in Baihetan hydropower station in China.The rock of this type shows various sitespecific mechanical responses(e.g.fragmentation,fracturing,and relaxation)during excavation.Using conventional triaxial testing facility MTS 815.03,we obtained the stressestrain curves,macroscopic failure characteristics,and strength characteristics of cryptocrystalline basalt.On this basis,evolution of crack initiation and propagation was explored using the finite-discrete element method(FDEM)to understand the failure mechanism of cryptocrystalline basalt.The test results showed that:(1)under different confining stresses,almost all the pre-peak stressestrain curves of cryptocrystalline basalt were linear and the post-peak stresses decreased rapidly;(2)the cryptocrystalline basalt showed a failure mode in a form of fragmentation under low and medium confining stresses while fragmentation-shear coupling failure dominated at high confining stresses;and(3)the initial strength ratio(sci/sf,where sci and sf are the crack initiation strength and peak strength,respectively)ranged from 0.45 to 0.55 and the damage strength ratio(scd/sf,where scd is the crack damage strength)exceeded 0.9.The stressestrain curve characteristics and failure modes of cryptocrystalline basalt could be reflected numerically.For this,FDEM simulation was employed to reveal the characteristics of cryptocrystalline basalt,including high scd/sf values and rapid failure after scd,with respect to the microscopic characteristics of mineral structures.The results showed that the fragmentation characteristics of cryptocrystalline basalt were closely related to the development of tensile cracks in rock samples prior to failure.Moreover,the decrease in degree of fragmentation with increasing confining stress was also correlated with the dominant effect of confining stress on the tensile cracks.
基金supported by the National Natural Science Foundation of China(Grant No.41671004)
文摘There are several basins with high sediment yield in the Pisha-sandstone covering area of the east wing of the Ordos Plateau. Due to the lack of targeted research on the dynamical characteristics of geomorphic evolution that plays an important role in the sand production, this paper analyzed the tectonic activity intensity and erosion characteristics of the area. The results show that the intensity of tectonic activities in the area is generally moderateweak and shows an unconspicuous increase from north to south. Tectonic activity is manifested mainly in the form of uplift. The uplift rate in the lower reaches of each basin is greater than the erosion rate,which is prominent in the Kuyehe and the Tuweihe rivers. During the uplift of the regional topography,the most serious parts under erosion are generally concentrated in the upstream and midstream of basins. All longitudinal profiles of the basins have a shape close to an exponential function, which indicates that they are in the early stage of erosion evolution. The mechanisms of geomorphologic evolution of these basins have a great similarity. The conservative estimate of historical average erosion rate was less than 182–520 t/(km^2·yr), much less than that of the modern times. The average stream power values are typically distributed between 4 and102 W/m, with the larger being in the Kuyehe and the Tuweihe rivers and the smallest being in the Qinshuihe River. The maximum stream power value appears in the downstream reach, which should be the main reason for the particles being directly injected into the Yellow River. From the perspective of geomorphological evolution, the current soil and water conservation measures can hardly cure the erosion of these basins in the long run.
