This study investigates the low-velocity impact and post-impact flexural properties of 3D integrated woven spacer composites,focusing on their orthotropic behavior when tested along two principal directions,i.e.,warp(...This study investigates the low-velocity impact and post-impact flexural properties of 3D integrated woven spacer composites,focusing on their orthotropic behavior when tested along two principal directions,i.e.,warp(X-type)and weft(Y-type)directions.The same composite material was tested in these orientations to evaluate the differences in impact resistance and residual bending strength.Specimens were fabricated via vacuum-assisted molding and tested at 2,3,5,and 7 J impact energies using an Instron Ceast 9350 drop-weight impact testing machine,in accordance with ASTM D7136.Post-impact flexural tests were performed using a four-point bending method in accordance with ASTM D7264.The absorbed energy increased from 1.97 to 6.98 J,and the panel damage area ranged from 121 to 361 mm^(2) as impact energy roses.Specimens tested in the weft direction(Y-type)showed greater residual strength(up to 15.83 N)and displacement(up to 0.538 mm)than those tested in the warp direction(X-type).Ultrasonic C-scan imaging revealed localized matrix cracking and fiber failure damage patterns.Results emphasize the directional differences in impact resistance and residual bending properties,highlighting the importance of material orientation in structural applications.This study provides a foundation for utilizing 3D woven spacer composites in lightweight,damage-tolerant structural components.展开更多
[Objective]As hydrogen energy has gained new momentum recently,analyzing the economic and social impacts of developing a hydrogen energy sector can inform further policy formation and investment decision making in thi...[Objective]As hydrogen energy has gained new momentum recently,analyzing the economic and social impacts of developing a hydrogen energy sector can inform further policy formation and investment decision making in this regard.[Method]Considering the increasingly important role of East Asia Summit(EAS)region in both economic growth and green energy transition,this paper developed a demand-driven model for the hydrogen energy supply chains to comprehensively and quantitatively evaluate the economic and social impacts hydrogen energy development in the EAS region.[Result]This model provides estimates of the capital investment required,the number of new jobs created,the potential carbon emissions reduction,the subsidies needed in the early stages of development,and the impacts on key energy security indicators.[Conclusion]This study find that hydrogen energy development has a significant job creation effect,and that the total investment and the fiscal burden appear to be manageable for countries in the EAS region.In addition to substantial carbon emissions reduction,positive social impacts also include general improvements in energy security indicators.展开更多
At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to i...At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to incomplete statistics,as of 2023,80%of coal mine rock bursts accidents in China occur in mining roadway.In view of this phenomenon,the cyclic impact test of post-peak sandstone is designed,focusing on the post-peak stress state of sandstone,and exploring the post-peak dynamic response of sandstone.The post-peak sandstone specimens were prepared by a uniaxial compressor,and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment.The results show that:1)The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure,indicating that the impact tendency of sandstone after peak decreased under lower axial pressure.On the contrary,the post-peak sandstone had strong impact tendency under higher axial pressure;2)The higher the axial pressure,the lower the dynamic strength of the post-peak sandstone,indicating that the axial pressure promoted the failure process of the post peak sandstone;3)It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure;4)Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure,and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level.The research shows that when the roadway surrounding rock was in the post-peak stress state,reducing the static stress was the key to prevent the secondary ground pressure disaster.The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment,and promote the research and exploration of post-peak mechanical properties of coal and rock.展开更多
Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate...Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate the impact resistance of PMI foam sandwich structures,the dynamic response and energy absorption characteristics of PMI foam sandwich structures with different core layers under various water impact loads were investigated using combined experimental and numerical methods.A fluid-structure interaction device with a diffusion angle was used for water impact testing of the PMI foam sandwich structures.The 3D-DIC technique was employed to process the deformation images of the sandwich-structure back panel captured by the high-speed cameras.Numerical simulations were performed to analyze the dynamic deformation process of the PMI foam core.The results indicated that the maximum deformation of the back panel exhibited a nonlinear relationship with the impulse.Below the critical impulse,the maximum deformation of the back panel plateaued,which was determined by the core density.Beyond the critical impulse,the rate of deformation increased with the impulse was governed by the core thickness.Compared with different sandwich panels,PMI foam sandwich struc-tures demonstrate significant advantages in terms of impact resistance under high-impulse conditions.展开更多
To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with...To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with varying gangue thicknesses and positions.The response patterns of compressive strength,elastic modulus,pre-peak accumulated energy,elastic energy index,and impact energy index were systematically analyzed.Furthermore,a new index for evaluating the impact tendency of gangue-containing coal was proposed,and its effectiveness was verified.The findings are as follows:(1)As the gangue thickness increases,both the compressive strength and the pre-peak energy of the combined structure decrease,whereas the elastic modulus increases accordingly.When the gangue is located in the lower middle position,the combined structure exhibits the lowest compressive strength and elastic modulus but the highest pre peak energy.(2)As the gangue shifts toward the middle position of the combined structure,the failure mode gradually transitions from comple te“crushing”failure to an incomplete“point-type”failure.As gangue thickness further increases,the failure region evolves from overall failure to localized failure,with the degree of failure shifting from complete to incomplete.The K_(crc)value corresponding to“crushing”complete failure is higher and has a stronger impact tendency compared to“point-type”incomplete failure.(3)The proposed comprehensive impact instability evaluation index K_(crc)for the gangue-coal combined structure has shown a significant positive correlation with compressive strength(R_(c))and impact energy index(K_(E)),further verifyi ng its rationality in comprehensively assessing the impact tendency of gangue-containing coal bodies.Applying this index to the evaluation of gangue-containing coal seams provides a more accurate reflection of their impact tendency compared with the residual energy index,which has a wide range of potential applications and practical significance.展开更多
CNKI has published the ＂Annual Report for International Citation of Chinese Academic Journals＂ since 2012. In the past three years, it has provided comprehensive data on the international impact of Chinese academic ...CNKI has published the ＂Annual Report for International Citation of Chinese Academic Journals＂ since 2012. In the past three years, it has provided comprehensive data on the international impact of Chinese academic journals. Using the clout index （CI） to rank the Chinese academic journals, ＂the Highest International Impact Academic Journals of China＂ and ＂ the Excellent International Impact Academic Journals of China＂ are announced every year. By introducing the rating criteria of the ＂Annual Report for International Citation of Chinese Academic Journals＂, the characteristics of high impact journals are discussed. Especially, the status of the pharmaceutical journals is discussed. We found that there are increasing numbers of Chinese journals that are included in the SCI, and some of them are high impact journals. However, journals published in Chinese are still facing difficulties to be included in SCI, even though they show higher impact than journals published in other non-English languages. The Chinese Pharmaceutical journals need to enhance their international impact, but Journals on Chinese Medicine show high impact.展开更多
The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstru...The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstructural characterization,analysis of worn surface morphology,and measurement of key performance like impact toughness and surface hardening.The findings demonstrate that increasing C content and tempering temperature both has a positive effect on wear resistance,with C content exhibiting a more pronounced influence compared to the tempering temperature.The improved wear resistance of the steel with higher C content and tempering at a higher temperature can be attributed to its enhanced impact toughness.This increase in impact toughness is primarily a result of microstructural refinement and alterations in carbide morphology.Moreover,cyclic impact loading induces surface hardening due to dislocation strengthening within the martensite and the retained austenite,leading to an increase in surface hardness.The combination of surface hardening and excellent impact toughness synergistically contributes to the overall improved wear resistance observed in the experimental steel with higher C content after tempering at a higher temperature.Additionally,the dominant features observed on the worn surface are scratches and substrate delamination,indicative of a wear mechanism of the experimental steels characterized by micro-cutting/ploughing and fatigue wear.展开更多
The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils we...The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils were evaluated for each scenic spots by calculating its soil impact indexes （SII） in the park. The results indicated that visitors＇ activities caused a serious influence on the soil in the park, especially in the two most used scenic spots-- Yellowstone Village and Gold Whip Stream. The impact of tourism on soil mainly occurred within 3 m along the trails. The impact shapes are classified into six type as single-sided node type, double-sided node type, cross node type, single-sided linkage type, double-sided linkage type and short-cut linkage type. Of six types of impact shapes, the single-sided node type and double-sided type were dominant. The average water contents of soil for six scenic spots at sample areas of 1 m, 2 m and 3 m from trial is 36.6%, 24.5% and 2.2% lower than that of the control area, respectively. The average soil hardness for six scenic spots at 1m, 2 m, and 3m from the trails tramped increased 167.9%, and 122.2%, and 15.8%, respectively, compared with the control area. Soil bulk density increased 26.5% at 1 m and 20.9% at 2 m from the trails. The main countermeasures for reducing the range and extent of tourism impact on soil are discussed.展开更多
The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological feat...The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological features of deposits within the impact crater using drilled sedimentary cores(23HIC01,20CR05,20CR09,and 20CR10),which consisted of an ascending order of impact breccias,lake sediments,and subaerial(e.g.,wetland)sediments.The impact breccia deposits in the 20CR05 and 23HIC01 cores contain shatter cones,which are a macroscopic indication of a meteorite impact.The overlying lake sediments were divided into three stages.The early stage of the post-impact lake environment corresponded to the lowermost lake sediments with frequent microfaults and slump-turbidite events.This stage is characterized by high calcite content of up to 13%.The middle stage showed a stable depositional environment,with silty to sandy lamination and bedding,and fewer microfaults.The final stage of the post-impact lake environment appears to have been very short and dramatic.This ended with the final slumping event,which appears to have been triggered by an abrupt outburst of lake water.This study demonstrates early post-impact lake sedimentation processes and crater instability in terms of soft-sediment deformation structures(e.g.,microfaults and slumps).展开更多
Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as ...Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as exploring how to obtain materials with desired properties remains a long-term challenge.Machine learning with its ability to solve complex tasks and perform robust data processing can reveal the relationship between performance and descriptive indicators,potentially accelerating the development process of energetic materials.In this background,impact sensitivity,detonation performances,and 28 physicochemical parameters for 222 energetic materials from density functional theory calculations and published literature were sorted out.Four machine learning algorithms were employed to predict various properties of energetic materials,including impact sensitivity,detonation velocity,detonation pressure,and Gurney energy.Analysis of Pearson coefficients and feature importance showed that the heat of explosion,oxygen balance,decomposition products,and HOMO energy levels have a strong correlation with the impact sensitivity of energetic materials.Oxygen balance,decomposition products,and density have a strong correlation with detonation performances.Utilizing impact sensitivity of 2,3,4-trinitrotoluene and the detonation performances of 2,4,6-trinitrobenzene-1,3,5-triamine as the benchmark,the analysis of feature importance rankings and statistical data revealed the optimal range of key features balancing impact sensitivity and detonation performances:oxygen balance values should be between-40%and-30%,density should range from 1.66 to 1.72 g/cm^(3),HOMO energy levels should be between-6.34 and-6.31 eV,and lipophilicity should be between-1.0 and 0.1,4.49 and 5.59.These findings not only offer important insights into the impact sensitivity and detonation performances of energetic materials,but also provide a theoretical guidance paradigm for the design and development of new energetic materials with optimal detonation performances and reduced sensitivity.展开更多
In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and compreh...In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.展开更多
Purpose:For a set of 1,561 Open Access(OA)and non-OA journals in business and economics,this study evaluates the relationships between four citation metrics-five-year Impact Factor(5IF),CiteScore,Article Influence(AI)...Purpose:For a set of 1,561 Open Access(OA)and non-OA journals in business and economics,this study evaluates the relationships between four citation metrics-five-year Impact Factor(5IF),CiteScore,Article Influence(AI)score,and SCImago Journal Rank(SJR)-and the journal ratings assigned by expert reviewers.We expect that the OA journals will have especially high citation impact relative to their perceived quality(reputation).Design/methodology/approach:Regression is used to estimate the ratings assigned by expert reviewers for the 2021 CABS(Chartered Association of Business Schools)journal assessment exercise.The independent variables are the four citation metrics,evaluated separately,and a dummy variable representing the OA/non-OA status of each journal.Findings:Regardless of the citation metric used,OA journals in business and economics have especially high citation impact relative to their perceived quality(reputation).That is,they have especially low perceived quality(reputation)relative to their citation impact.Research limitations:These results are specific to the CABS journal ratings and the four citation metrics.However,there is strong evidence that CABS is closely related to several other expert ratings,and that 5IF,CiteScore,AI,and SJR are representative of the other citation metrics that might have been chosen.Practical implications:There are at least two possible explanations for these results:(1)expert evaluators are biased against OA journals,and(2)OA journals have especially high citation impact due to their increased accessibility.Although this study does not allow us to determine which of these explanations are supported,the results suggest that authors should consider publishing in OA journals whenever overall readership and citation impact are more important than journal reputation within a particular field.Moreover,the OA coefficients provide a useful indicator of the extent to which anti-OA bias(or the citation advantage of OA journals)is diminishing over time.Originality/value:This is apparently the first study to investigate the impact of OA status on the relationships between expert journal ratings and journal citation metrics.展开更多
A series of transparent,intrinsically flame-retardant,and impact-resistant poly(carbonates-b-siloxanes)were synthesized by incorporating Schiff-base modified polysiloxanes(DMS-Schiff)and naphthalene-sulfonate units in...A series of transparent,intrinsically flame-retardant,and impact-resistant poly(carbonates-b-siloxanes)were synthesized by incorporating Schiff-base modified polysiloxanes(DMS-Schiff)and naphthalene-sulfonate units into the polycarbonate(PC)chain.In addition to high transparency,the resultant copolymers(SS-co-PC5,SS-co-PC9,SS-co-PC14,and SS-co-PC20)exhibited remarkable improvements in fire safety and mechanical performance.Compared to pure PC,these copolymers demonstrated significantly enhanced limiting oxygen index(LOI,up to 34.5%)and a UL-94 V-0 rating under a thickness of only 1.6 mm.The incorporation of the polysiloxane blocks not only improved flame retardancy but also enhanced the impact strength,with SS-co-PC9 showing a 48%increase in elongation at break and a 38%rise in impact toughness compared to pure PC.In addition,SS-co-PC9 presented high mechanical strength.The synergistic effects between the naphthalene-sulfonate and polysiloxane blocks,along with the well-controlled polysiloxane phase separation(sulfonate units enabled lower processing viscosity of copolymers),led to superior comprehensive performance.These findings provide a promising pathway to create high-performance copolycarbonates for real-world applications.展开更多
Land use transformations in Sonipat District,Haryana,driven by urbanization,industrialization,and land acquisitions,have posed significant ecological and socio-economic challenges,particularly concerning food security...Land use transformations in Sonipat District,Haryana,driven by urbanization,industrialization,and land acquisitions,have posed significant ecological and socio-economic challenges,particularly concerning food security.This study investigates the interplay between these land use changes and their environmental implications at macro(district)and micro(village)levels,focusing on agricultural productivity and resource sustainability.The study employs a mixed-method approach,integrating secondary data from official datasets and primary data gathered through structured household surveys,focus group discussions,and visual analysis techniques.Data from 20 villages,selected based on predominant land use characteristics,were analysed using statistical and geospatial tools,including ArcGIS and STATA,to quantify food grain losses and evaluate environmental degradation.Findings of this study reveal a 19%reduction in agricultural land over two decades(2000-2024),correlating with increased residential and industrial areas.Groundwater resources face severe overexploitation,with pollution from industrial clusters further degrading water and soil quality.The study estimates a total food grain loss of 1.5 million kilograms across surveyed villages due to land acquisitions.A strong positive correlation(R^(2)=0.98)between land acquisition and food loss underscores the direct impact of urbanization on agricultural output.The research underscores the urgency of sustainable land management practices,including preserving agricultural lands,optimizing groundwater usage,and enhancing community involvement in planning.By addressing these challenges,the study advocates for balanced urban expansion and food security to ensure ecological and economic resilience in the region.展开更多
As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their ...As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.展开更多
The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains lar...The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains largely unexplored,as existing research focuses mainly on static stability.Energy dissipation and instability evolution under impact loading require further study.To address this gap,this study conducts drop-weight impact experiments on specimens with circular perforations,complemented by numerical simulations.By integrating dimensional analysis,cusp catastrophe theory,and strength reduction techniques,the dynamic instability mechanism of goaf roofs with varying thickness-to-span ratios is revealed.Results show that the thickness-to-span ratio significantly influences energy accumulation and dissipation during roof failure.A higher ratio increases both the magnitude and rate of energy dissipation,particularly during crack initiation and stable propagation,while its impact diminishes in the final failure stage.Optimizing the thickness-to-span ratio within a critical range enhances structural stability,improving the safety factor by up to 83%.However,beyond a certain threshold,additional thickness yields diminishing benefits.This study provides new insights into the energy-based instability mechanism of goaf roofs under impact loads,establishing a theoretical foundation for early warning systems and optimized safety design.展开更多
Based on the investigation of mechanical response and microstructure evolution of a commercial 7003 aluminum alloy under high-speed impact,a new simple and effective method was proposed to determine the critical strai...Based on the investigation of mechanical response and microstructure evolution of a commercial 7003 aluminum alloy under high-speed impact,a new simple and effective method was proposed to determine the critical strain required for the nucleation of adiabatic shear band(ASB).The deformation results of cylindrical and hat-shaped samples show that the critical strain required for ASB nucleation corresponds to the strain at the first local minimum after peak stress on the first derivative curve of true stress−true strain.The method of determining the critical strain for the nucleation of ASB through the first derivative of the flow stress curve is named the first derivative method.The proposed first derivative method is not only applicable to the 7003 aluminum alloy,but also to other metal materials,such as commercial purity titanium,WY-100 steel,and AM80 magnesium alloy.This proves that it has strong universality.展开更多
Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an...Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.展开更多
基金funded by Open Foundation of the State Key Laboratory of Advanced Inorganic Fibers and Composites(Grant No.KF2024SYS02)the Jiangsu Province Special Fund for Carbon Peaking and Carbon Neutrality Technology Innovation(Grant No.BE2022008)the Prioritized Academic Program Development for Higher Education Institutions in Jiangsu.
文摘This study investigates the low-velocity impact and post-impact flexural properties of 3D integrated woven spacer composites,focusing on their orthotropic behavior when tested along two principal directions,i.e.,warp(X-type)and weft(Y-type)directions.The same composite material was tested in these orientations to evaluate the differences in impact resistance and residual bending strength.Specimens were fabricated via vacuum-assisted molding and tested at 2,3,5,and 7 J impact energies using an Instron Ceast 9350 drop-weight impact testing machine,in accordance with ASTM D7136.Post-impact flexural tests were performed using a four-point bending method in accordance with ASTM D7264.The absorbed energy increased from 1.97 to 6.98 J,and the panel damage area ranged from 121 to 361 mm^(2) as impact energy roses.Specimens tested in the weft direction(Y-type)showed greater residual strength(up to 15.83 N)and displacement(up to 0.538 mm)than those tested in the warp direction(X-type).Ultrasonic C-scan imaging revealed localized matrix cracking and fiber failure damage patterns.Results emphasize the directional differences in impact resistance and residual bending properties,highlighting the importance of material orientation in structural applications.This study provides a foundation for utilizing 3D woven spacer composites in lightweight,damage-tolerant structural components.
文摘[Objective]As hydrogen energy has gained new momentum recently,analyzing the economic and social impacts of developing a hydrogen energy sector can inform further policy formation and investment decision making in this regard.[Method]Considering the increasingly important role of East Asia Summit(EAS)region in both economic growth and green energy transition,this paper developed a demand-driven model for the hydrogen energy supply chains to comprehensively and quantitatively evaluate the economic and social impacts hydrogen energy development in the EAS region.[Result]This model provides estimates of the capital investment required,the number of new jobs created,the potential carbon emissions reduction,the subsidies needed in the early stages of development,and the impacts on key energy security indicators.[Conclusion]This study find that hydrogen energy development has a significant job creation effect,and that the total investment and the fiscal burden appear to be manageable for countries in the EAS region.In addition to substantial carbon emissions reduction,positive social impacts also include general improvements in energy security indicators.
基金Projects(U23B2093,52034009)supported by the National Natural Science Foundation of ChinaProject(2022YFC3004602)supported by the National Key Research and Development Program of ChinaProject(BBJ2024009)supported by the Fundamental Research Funds for the Central Universities,China。
文摘At present,the surrounding rock of the deep mine roadway is prone to post-peak stress under the action of high stress,and secondary rock burst disaster is prone to occur under complex stress disturbance.According to incomplete statistics,as of 2023,80%of coal mine rock bursts accidents in China occur in mining roadway.In view of this phenomenon,the cyclic impact test of post-peak sandstone is designed,focusing on the post-peak stress state of sandstone,and exploring the post-peak dynamic response of sandstone.The post-peak sandstone specimens were prepared by a uniaxial compressor,and then cyclic impact tests were carried out on the post-peak sandstone under different coaxial pressure conditions by an improved separated Hopkinson equipment.The results show that:1)The number of impact times required for sandstone failure after peak decreased with the increase of axial pressure,indicating that the impact tendency of sandstone after peak decreased under lower axial pressure.On the contrary,the post-peak sandstone had strong impact tendency under higher axial pressure;2)The higher the axial pressure,the lower the dynamic strength of the post-peak sandstone,indicating that the axial pressure promoted the failure process of the post peak sandstone;3)It was a nonlinear evolution of a quadratic polynomial function between the dissipation-energy release rate and axial pressure;4)Shear failure occurred mainly in post-peak impact sandstone with the increased axial pressure,and the composite failure of intergranular failure and transgranular failure changed to single intergranular failure at the microscopic level.The research shows that when the roadway surrounding rock was in the post-peak stress state,reducing the static stress was the key to prevent the secondary ground pressure disaster.The research results provide a theoretical basis for the prevention and control of roadway rock burst disaster under high ground stress environment,and promote the research and exploration of post-peak mechanical properties of coal and rock.
文摘Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate the impact resistance of PMI foam sandwich structures,the dynamic response and energy absorption characteristics of PMI foam sandwich structures with different core layers under various water impact loads were investigated using combined experimental and numerical methods.A fluid-structure interaction device with a diffusion angle was used for water impact testing of the PMI foam sandwich structures.The 3D-DIC technique was employed to process the deformation images of the sandwich-structure back panel captured by the high-speed cameras.Numerical simulations were performed to analyze the dynamic deformation process of the PMI foam core.The results indicated that the maximum deformation of the back panel exhibited a nonlinear relationship with the impulse.Below the critical impulse,the maximum deformation of the back panel plateaued,which was determined by the core density.Beyond the critical impulse,the rate of deformation increased with the impulse was governed by the core thickness.Compared with different sandwich panels,PMI foam sandwich struc-tures demonstrate significant advantages in terms of impact resistance under high-impulse conditions.
基金Project(52274130)supported by the National Natural Science Foundation of ChinaProject(ZR2024ZD22)supported by the Major Basic Research Project of the Shandong Provincial Natural Science Foundation,China+1 种基金Project(2023375)supported by the Guizhou University Research and Innovation Team,ChinaProject(LH[2024]-026)supported by the Guizhou Science and Technology Plan Project,China。
文摘To investigate the mechanical response during failure and the impact tendency characteristics of gangue-coal combined structure,uniaxial compression tests were conducted on nine groups of combined structures,each with varying gangue thicknesses and positions.The response patterns of compressive strength,elastic modulus,pre-peak accumulated energy,elastic energy index,and impact energy index were systematically analyzed.Furthermore,a new index for evaluating the impact tendency of gangue-containing coal was proposed,and its effectiveness was verified.The findings are as follows:(1)As the gangue thickness increases,both the compressive strength and the pre-peak energy of the combined structure decrease,whereas the elastic modulus increases accordingly.When the gangue is located in the lower middle position,the combined structure exhibits the lowest compressive strength and elastic modulus but the highest pre peak energy.(2)As the gangue shifts toward the middle position of the combined structure,the failure mode gradually transitions from comple te“crushing”failure to an incomplete“point-type”failure.As gangue thickness further increases,the failure region evolves from overall failure to localized failure,with the degree of failure shifting from complete to incomplete.The K_(crc)value corresponding to“crushing”complete failure is higher and has a stronger impact tendency compared to“point-type”incomplete failure.(3)The proposed comprehensive impact instability evaluation index K_(crc)for the gangue-coal combined structure has shown a significant positive correlation with compressive strength(R_(c))and impact energy index(K_(E)),further verifyi ng its rationality in comprehensively assessing the impact tendency of gangue-containing coal bodies.Applying this index to the evaluation of gangue-containing coal seams provides a more accurate reflection of their impact tendency compared with the residual energy index,which has a wide range of potential applications and practical significance.
基金Project for Enhancing International Impact of China STM Journals(2013–2015)the High Quality Scientific Journals Project(2014–2015Chinese Association for Science and Technology)
文摘CNKI has published the ＂Annual Report for International Citation of Chinese Academic Journals＂ since 2012. In the past three years, it has provided comprehensive data on the international impact of Chinese academic journals. Using the clout index （CI） to rank the Chinese academic journals, ＂the Highest International Impact Academic Journals of China＂ and ＂ the Excellent International Impact Academic Journals of China＂ are announced every year. By introducing the rating criteria of the ＂Annual Report for International Citation of Chinese Academic Journals＂, the characteristics of high impact journals are discussed. Especially, the status of the pharmaceutical journals is discussed. We found that there are increasing numbers of Chinese journals that are included in the SCI, and some of them are high impact journals. However, journals published in Chinese are still facing difficulties to be included in SCI, even though they show higher impact than journals published in other non-English languages. The Chinese Pharmaceutical journals need to enhance their international impact, but Journals on Chinese Medicine show high impact.
基金supported by Science and Technology Project of Guangzhou(2023A04J0297)Guangdong Basic and Applied Basic Research Foundation(2024A1515011622)+3 种基金National Natural Science Foundation of China(52301040)GDAS’Project of Science and Technology Development(2023GDASQNRC-0205 and 2022GDASZH-2022010107)Evaluation Project of Guangdong Provincial Key Laboratory(2023B1212060043)Young Elite Scientists Sponsorship Program by CAST(2022QNRC001).
文摘The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstructural characterization,analysis of worn surface morphology,and measurement of key performance like impact toughness and surface hardening.The findings demonstrate that increasing C content and tempering temperature both has a positive effect on wear resistance,with C content exhibiting a more pronounced influence compared to the tempering temperature.The improved wear resistance of the steel with higher C content and tempering at a higher temperature can be attributed to its enhanced impact toughness.This increase in impact toughness is primarily a result of microstructural refinement and alterations in carbide morphology.Moreover,cyclic impact loading induces surface hardening due to dislocation strengthening within the martensite and the retained austenite,leading to an increase in surface hardness.The combination of surface hardening and excellent impact toughness synergistically contributes to the overall improved wear resistance observed in the experimental steel with higher C content after tempering at a higher temperature.Additionally,the dominant features observed on the worn surface are scratches and substrate delamination,indicative of a wear mechanism of the experimental steels characterized by micro-cutting/ploughing and fatigue wear.
基金This study was supported by the National Natural Science Foundation of China (NSFC30200040) and the Thousand-hundred-ten Talent Engineering project of Guangdong Province, P. R. China (03130401)
文摘The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils were evaluated for each scenic spots by calculating its soil impact indexes （SII） in the park. The results indicated that visitors＇ activities caused a serious influence on the soil in the park, especially in the two most used scenic spots-- Yellowstone Village and Gold Whip Stream. The impact of tourism on soil mainly occurred within 3 m along the trails. The impact shapes are classified into six type as single-sided node type, double-sided node type, cross node type, single-sided linkage type, double-sided linkage type and short-cut linkage type. Of six types of impact shapes, the single-sided node type and double-sided type were dominant. The average water contents of soil for six scenic spots at sample areas of 1 m, 2 m and 3 m from trial is 36.6%, 24.5% and 2.2% lower than that of the control area, respectively. The average soil hardness for six scenic spots at 1m, 2 m, and 3m from the trails tramped increased 167.9%, and 122.2%, and 15.8%, respectively, compared with the control area. Soil bulk density increased 26.5% at 1 m and 20.9% at 2 m from the trails. The main countermeasures for reducing the range and extent of tourism impact on soil are discussed.
基金supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources(GP2022-006[24-3111-3]and GP2022-005[24-3807])。
文摘The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological features of deposits within the impact crater using drilled sedimentary cores(23HIC01,20CR05,20CR09,and 20CR10),which consisted of an ascending order of impact breccias,lake sediments,and subaerial(e.g.,wetland)sediments.The impact breccia deposits in the 20CR05 and 23HIC01 cores contain shatter cones,which are a macroscopic indication of a meteorite impact.The overlying lake sediments were divided into three stages.The early stage of the post-impact lake environment corresponded to the lowermost lake sediments with frequent microfaults and slump-turbidite events.This stage is characterized by high calcite content of up to 13%.The middle stage showed a stable depositional environment,with silty to sandy lamination and bedding,and fewer microfaults.The final stage of the post-impact lake environment appears to have been very short and dramatic.This ended with the final slumping event,which appears to have been triggered by an abrupt outburst of lake water.This study demonstrates early post-impact lake sedimentation processes and crater instability in terms of soft-sediment deformation structures(e.g.,microfaults and slumps).
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2682024GF019)。
文摘Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials.Exploring the underlying factors that affect impact sensitivity and detonation performances as well as exploring how to obtain materials with desired properties remains a long-term challenge.Machine learning with its ability to solve complex tasks and perform robust data processing can reveal the relationship between performance and descriptive indicators,potentially accelerating the development process of energetic materials.In this background,impact sensitivity,detonation performances,and 28 physicochemical parameters for 222 energetic materials from density functional theory calculations and published literature were sorted out.Four machine learning algorithms were employed to predict various properties of energetic materials,including impact sensitivity,detonation velocity,detonation pressure,and Gurney energy.Analysis of Pearson coefficients and feature importance showed that the heat of explosion,oxygen balance,decomposition products,and HOMO energy levels have a strong correlation with the impact sensitivity of energetic materials.Oxygen balance,decomposition products,and density have a strong correlation with detonation performances.Utilizing impact sensitivity of 2,3,4-trinitrotoluene and the detonation performances of 2,4,6-trinitrobenzene-1,3,5-triamine as the benchmark,the analysis of feature importance rankings and statistical data revealed the optimal range of key features balancing impact sensitivity and detonation performances:oxygen balance values should be between-40%and-30%,density should range from 1.66 to 1.72 g/cm^(3),HOMO energy levels should be between-6.34 and-6.31 eV,and lipophilicity should be between-1.0 and 0.1,4.49 and 5.59.These findings not only offer important insights into the impact sensitivity and detonation performances of energetic materials,but also provide a theoretical guidance paradigm for the design and development of new energetic materials with optimal detonation performances and reduced sensitivity.
基金supported by the Chongqing Youth Talent Support Program(Cstc2022ycjh-bgzxm0079)the Chinese National Natural Science Foundation(52379128,51979152)+2 种基金Science Fund for Distinguished Young Scholars of Hubei Proivnce(2023AFA048)Educational Commission of Hubei Province of China(T2020005)the Young Top-notch Talent Cultivation Program of Hubei Province.
文摘In rock drilling and blasting,the misfire of electronic detonators will not only affect the rock fragmentation result but also bring serious potential safety hazards to engineering construction.An accurate and comprehensive understanding of the failure mechanisms of electronic detonators subjected to impact loading is of great significance to the reliability design and field safety use of electronic detonators.The spatial distribution characteristics and failure modes of misfired electronic detonators under different application scenarios are statistically analysed.The results show that under high impact loads,electronic detonators will experience failure phenomena such as rupture of the fuse head,fracture of the bridge wire,falling off of the solder joint,chip module damage and insufficient initiation energy after deformation.The lack of impact resistance is the primary cause of misfire of electronic detonators.Combined with the underwater impact resistance test and the impact load test in the adjacent blasthole on site,the formulas of the impact failure probability of the electronic detonator under different stress‒strength distribution curves are deduced.The test and evaluation method of the impact resistance of electronic detonators based on stress‒strength interference theory is proposed.Furthermore,the impact failure model of electronic detonators considering the strength degradation effect under repeated random loads is established.On this basis,the failure mechanism of electronic detonators under different application environments,such as open-pit blasting and underground blasting,is revealed,which provides scientific theory and methods for the reliability analysis,design and type selection of electronic detonators in rock drilling and blasting.
文摘Purpose:For a set of 1,561 Open Access(OA)and non-OA journals in business and economics,this study evaluates the relationships between four citation metrics-five-year Impact Factor(5IF),CiteScore,Article Influence(AI)score,and SCImago Journal Rank(SJR)-and the journal ratings assigned by expert reviewers.We expect that the OA journals will have especially high citation impact relative to their perceived quality(reputation).Design/methodology/approach:Regression is used to estimate the ratings assigned by expert reviewers for the 2021 CABS(Chartered Association of Business Schools)journal assessment exercise.The independent variables are the four citation metrics,evaluated separately,and a dummy variable representing the OA/non-OA status of each journal.Findings:Regardless of the citation metric used,OA journals in business and economics have especially high citation impact relative to their perceived quality(reputation).That is,they have especially low perceived quality(reputation)relative to their citation impact.Research limitations:These results are specific to the CABS journal ratings and the four citation metrics.However,there is strong evidence that CABS is closely related to several other expert ratings,and that 5IF,CiteScore,AI,and SJR are representative of the other citation metrics that might have been chosen.Practical implications:There are at least two possible explanations for these results:(1)expert evaluators are biased against OA journals,and(2)OA journals have especially high citation impact due to their increased accessibility.Although this study does not allow us to determine which of these explanations are supported,the results suggest that authors should consider publishing in OA journals whenever overall readership and citation impact are more important than journal reputation within a particular field.Moreover,the OA coefficients provide a useful indicator of the extent to which anti-OA bias(or the citation advantage of OA journals)is diminishing over time.Originality/value:This is apparently the first study to investigate the impact of OA status on the relationships between expert journal ratings and journal citation metrics.
基金financially supported by the National Natural Science Foundation of China(Nos.52403117,52173083,51991355,and 52173082)the 2024 Ningbo Yongjiang Talent Programme,the Natural Science Foundation of Zhejiang Province(No.LY24E030007)the Australian Research Council(No.DE230100616).
文摘A series of transparent,intrinsically flame-retardant,and impact-resistant poly(carbonates-b-siloxanes)were synthesized by incorporating Schiff-base modified polysiloxanes(DMS-Schiff)and naphthalene-sulfonate units into the polycarbonate(PC)chain.In addition to high transparency,the resultant copolymers(SS-co-PC5,SS-co-PC9,SS-co-PC14,and SS-co-PC20)exhibited remarkable improvements in fire safety and mechanical performance.Compared to pure PC,these copolymers demonstrated significantly enhanced limiting oxygen index(LOI,up to 34.5%)and a UL-94 V-0 rating under a thickness of only 1.6 mm.The incorporation of the polysiloxane blocks not only improved flame retardancy but also enhanced the impact strength,with SS-co-PC9 showing a 48%increase in elongation at break and a 38%rise in impact toughness compared to pure PC.In addition,SS-co-PC9 presented high mechanical strength.The synergistic effects between the naphthalene-sulfonate and polysiloxane blocks,along with the well-controlled polysiloxane phase separation(sulfonate units enabled lower processing viscosity of copolymers),led to superior comprehensive performance.These findings provide a promising pathway to create high-performance copolycarbonates for real-world applications.
文摘Land use transformations in Sonipat District,Haryana,driven by urbanization,industrialization,and land acquisitions,have posed significant ecological and socio-economic challenges,particularly concerning food security.This study investigates the interplay between these land use changes and their environmental implications at macro(district)and micro(village)levels,focusing on agricultural productivity and resource sustainability.The study employs a mixed-method approach,integrating secondary data from official datasets and primary data gathered through structured household surveys,focus group discussions,and visual analysis techniques.Data from 20 villages,selected based on predominant land use characteristics,were analysed using statistical and geospatial tools,including ArcGIS and STATA,to quantify food grain losses and evaluate environmental degradation.Findings of this study reveal a 19%reduction in agricultural land over two decades(2000-2024),correlating with increased residential and industrial areas.Groundwater resources face severe overexploitation,with pollution from industrial clusters further degrading water and soil quality.The study estimates a total food grain loss of 1.5 million kilograms across surveyed villages due to land acquisitions.A strong positive correlation(R^(2)=0.98)between land acquisition and food loss underscores the direct impact of urbanization on agricultural output.The research underscores the urgency of sustainable land management practices,including preserving agricultural lands,optimizing groundwater usage,and enhancing community involvement in planning.By addressing these challenges,the study advocates for balanced urban expansion and food security to ensure ecological and economic resilience in the region.
基金supported by the National Natural Science Foundation of China(Nos.U24A2088,42177130,42277174,and 42477166).
文摘As coal mining depth increases,the combined effects of high stress,mining stress,and fault structures make dynamic impact hazards more frequent.The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms.Physical simulation test represents an efficacious methodology.However,there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena,including high stress and fault slip dynamic impact.To solve aforementioned issues,the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact.The phenomena of high stress and fault slip dynamic impact are reproduced successfully.A comparative analysis is conducted on dynamic phenomena,stress evolution,roadway deformation,and support force.The high stress dynamic impact roadway instability mode,which is characterized by the release of high energy accompanied by symmetric damage,and the fault slip dynamic impact roadway instability mode,which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage,are clarified.On the basis,the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.
基金support from the Natural Science Foundation of Jiangsu Province(Grant No.BK20242059)the Collaborative Innovation Center for Prevention and Control of Mountain Geological Hazards of Zhejiang Province(PCMGH-2023-02)the opening fund of State Key Laboratory of Coal Mine Disaster Dynamics and Control(2011DA105827-FW202209)are gratefully acknowledged.
文摘The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains largely unexplored,as existing research focuses mainly on static stability.Energy dissipation and instability evolution under impact loading require further study.To address this gap,this study conducts drop-weight impact experiments on specimens with circular perforations,complemented by numerical simulations.By integrating dimensional analysis,cusp catastrophe theory,and strength reduction techniques,the dynamic instability mechanism of goaf roofs with varying thickness-to-span ratios is revealed.Results show that the thickness-to-span ratio significantly influences energy accumulation and dissipation during roof failure.A higher ratio increases both the magnitude and rate of energy dissipation,particularly during crack initiation and stable propagation,while its impact diminishes in the final failure stage.Optimizing the thickness-to-span ratio within a critical range enhances structural stability,improving the safety factor by up to 83%.However,beyond a certain threshold,additional thickness yields diminishing benefits.This study provides new insights into the energy-based instability mechanism of goaf roofs under impact loads,establishing a theoretical foundation for early warning systems and optimized safety design.
基金National Natural Science Foundation of China (No. U20A20275)Natural Science Foundation of Hunan Province,China (No. 2021JJ40096)。
文摘Based on the investigation of mechanical response and microstructure evolution of a commercial 7003 aluminum alloy under high-speed impact,a new simple and effective method was proposed to determine the critical strain required for the nucleation of adiabatic shear band(ASB).The deformation results of cylindrical and hat-shaped samples show that the critical strain required for ASB nucleation corresponds to the strain at the first local minimum after peak stress on the first derivative curve of true stress−true strain.The method of determining the critical strain for the nucleation of ASB through the first derivative of the flow stress curve is named the first derivative method.The proposed first derivative method is not only applicable to the 7003 aluminum alloy,but also to other metal materials,such as commercial purity titanium,WY-100 steel,and AM80 magnesium alloy.This proves that it has strong universality.
基金The authors would like to acknowledge the support of the National Natural Science Foundation of China(No.52279097,No.51779264)Blue and Green Project of Jiangsu Province.
文摘Natural cemented calcareous sand and limestone are highly complex and not well understood in terms of the me-chanical behavior due to the difficulty of obtaining undisturbed samples from far sea.This paper proposes an artificial method in a laboratory setting using microbial-induced carbonate precipitation(MICP)to simulate the natural process of cementation of limestone.The artificially cemented sand has a high degree of similarity with the natural weakly limestone in three aspects:(1)the mineral composition of the cemented material is also granular calcite and acicular aragonite;(2)the microstructure in interconnected open pore network can be gradually closed and contracted with cementation.The porosity reaches to approximately 9.2%;(3)both the stress-strain relationship and the unconfined strength closely resemble that of natural weakly limestone.Furthermore,both static and dynamic behaviors of artificial limestone were studied by quasi-static compression tests and Split Hopkinson Pressure Bar(SHPB)tests,finding that the unconfined strength of weakly artifical limestone exponentially increases with increasing strain rate.A rate-dependent bond strength was proposed and implemented in software to reveal the mechanism of strain rate effects.It is found that the loading velocity is too high to keep in sync with the initiation and propagation of cracks under impact loading.This delay-induced viscosity may restrict the movement of the surrounding balls,thus increasing resistance.
