The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction ...The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse actuator.The impact point easily deviates from the target,and thus the correction result cannot be readily evaluated.However,the cost of shooting tests is considerably high to conduct many tests for data collection.To address this issue,this study proposes an aiming method for shooting tests based on small sample size.The proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion center.The experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.展开更多
In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to c...In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to create the hollow centers of the tapering tubes,with and without corrugations.The results demonstrate that the energy absorption(EA)and specific energy absorption(SEA)of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher,respectively,than those of the conical tube sandwich.Furthermore,the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency.Additionally,the tapered corrugated tubes'resistance to oblique impacts was studied.Compared to a straight tube,the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force(PCF),according to numerical simulations.After conducting a parametric study,it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude,number of corrugations,and wall thickness.EA and SEA of DTS with corrugation number of 8 increased by 17.4%and 29.6%,respectively,while PCF decreased by 9.2% compared to DTS with corrugation number of 10.展开更多
This paper presents the first-ever investigation of Menger fractal cubes'quasi-static compression and impact behaviour.Menger cubes with different void ratios were 3D printed using polylactic acid(PLA)with dimensi...This paper presents the first-ever investigation of Menger fractal cubes'quasi-static compression and impact behaviour.Menger cubes with different void ratios were 3D printed using polylactic acid(PLA)with dimensions of 40 mm×40 mm×40 mm.Three different orders of Menger cubes with different void ratios were considered,namely M1 with a void ratio of 0.26,M2 with a void ratio of 0.45,and M3with a void ratio of 0.60.Quasi-static Compression tests were conducted using a universal testing machine,while the drop hammer was used to observe the behaviour under impact loading.The fracture mechanism,energy efficiency and force-time histories were studied.With the structured nature of the void formation and predictability of the failure modes,the Menger geometry showed some promise compared to other alternatives,such as foams and honeycombs.With the increasing void ratio,the Menger geometries show force-displacement behaviour similar to hyper-elastic materials such as rubber and polymers.The third-order Menger cubes showed the highest energy absorption efficiency compared to the other two geometries in this study.The findings of the present work reveal the possibility of using additively manufactured Menger geometries as an energy-efficient system capable of reducing the transmitting force in applications such as crash barriers.展开更多
The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and...The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and proposes four different configurations of concave hexagonal honeycomb structures.The structures'macroscopic deformation behavior,stress-strain relationship,and energy dissipation characteristics are evaluated through quasi-static compression and Hopkinson pressure bar impact experiments.The study reveals that,under varying strain rates,the structures deform starting from the weak layer and exhibit significant interlayer separation.Additionally,interlayer shear slip becomes more pronounced with increasing strain rate.In terms of quasi-static compression,symmetric gradient structures demonstrate superior energy absorption,particularly the symmetric negative gradient structure(SNG-SMS)with a specific energy absorption of 13.77 J/cm~3.For dynamic impact,unidirectional gradient structures exhibit exceptional energy absorption,particularly the unidirectional positive gradient honeycomb structure(UPG-SML)with outstanding mechanical properties.The angle gradient design plays a crucial role in determining the structure's stability and deformation mode during impact.Fewer interlayer separations result in a more pronounced negative Poisson's ratio effect and enhance the structure's energy absorption capacity.These findings provide a foundation for the rational design and selection of seismic protection structures in different strain rate impact environments.展开更多
The three common genetic models(or modes of inheritance)in association analysis are the dominant,additive,and recessive models.It is known that the Cochran-Armitage trend test(CATT)which correctly incorporates informa...The three common genetic models(or modes of inheritance)in association analysis are the dominant,additive,and recessive models.It is known that the Cochran-Armitage trend test(CATT)which correctly incorporates information from genetic models,is more powerful than the commonly used Pearson’s chi-square test.However,the true genetic model is usually unknown in practice,and the power of the CAT test could be substantially reduced with a wrongly specified genetic model.To achieve a power that is close to that of a correctly specified CAT test,it is natural to apply trend tests under different possible genetic models and to report the most significant test result.This results in a MAX-type testing procedure,and it was found that this test is usually more powerful than the Pearson’s chi-square test.Although the signi-ficance(i.e.,p value)of the MAX-type test can be accessed by either large sample approximation or permutation methods,requirements for sample size or simulation replicates are demanding with respect to accuracy and efficiency.This paper proposes an approach to calculate the exact p values of MAX-type tests based on the combinatorial counting method.The simulation results show that the exact method is more accurate than the large sample approximation methods and more computationally efficient than the permutation method,and our method can be readily applied to genome-wide association studies(GWASs).The proposed methodis built in an R package,MaXact,which is available at the https://github.com/Myuan 2019/MaXact/.展开更多
This paper explores the performances of a finite element simulation including four concrete models applied to a full-scale reinforced concrete beam subjected to blast loading. Field test data has been used to compare ...This paper explores the performances of a finite element simulation including four concrete models applied to a full-scale reinforced concrete beam subjected to blast loading. Field test data has been used to compare model results for each case. The numerical modelling has been, carried out using the suitable code LS-DYNA. This code integrates blast load routine(CONWEP) for the explosive description and four different material models for the concrete including: Karagozian & Case Concrete, Winfrith, Continuous Surface Cap Model and Riedel-Hiermaier-Thoma models, with concrete meshing based on 10, 15, and 20 mm. Six full-scale beams were tested: four of them used for the initial calibration of the numerical model and two more tests at lower scaled distances. For calibration, field data obtained employing pressure and accelerometers transducers were compared with the results derived from the numerical simulation. Damage surfaces and the shape of rupture in the beams have been used as references for comparison. Influence of the meshing on accelerations has been put in evidence and for some models the shape and size of the damage in the beams produced maximum differences around 15%. In all cases, the variations between material and mesh models are shown and discussed.展开更多
The study of the charge conjugation and parity(CP)violation of hyperon is the precision frontier for probing possible new CP violation sources beyond the standard model(SM).With the large number of quantum entangled h...The study of the charge conjugation and parity(CP)violation of hyperon is the precision frontier for probing possible new CP violation sources beyond the standard model(SM).With the large number of quantum entangled hyperonantihyperon pairs to be produced at Super Tau-Charm Facility(STCF),the CP asymmetry of hyperon is expected to be tested with a statistical sensitivity of 10^(−4) or even better.To cope with the statistical precision,the systematic effects from various aspects are critical and need to be studied in detail.In this paper,the sensitivity effects on the CP violation parameters associated with the detector resolution,including those of the position and momentum,are studied and discussed in detail.The results provide valuable guidance for the design of STCF detector.展开更多
Plant roots are widely known to provide mechanical reinforcement to soils against shearing and further increase slope stability.However,whether roots provide reinforcement to loess cyclic re-sistance and how various f...Plant roots are widely known to provide mechanical reinforcement to soils against shearing and further increase slope stability.However,whether roots provide reinforcement to loess cyclic re-sistance and how various factors affect roots reinforcement during seismic loading have rarely been studied.The objective is to conduct a series of cyclic direct simple shear tests and DEM numerical simulation to investigate the cyclic behaviour of rooted loess.The effects of initial static shear stress and loading frequency on the cyclic resistance of root-soil composites were first investigated.After that,cyclic direct simple shear simulations at constant volume were carried out based on the discrete element method(PFC^(3D))to investigate the effects of root geome-try,mechanical traits and root-soil bond strength on the cyclic strength of rooted loess.It was discovered that the roots could effectively improve the cyclic resistance of loess.The cyclic resistance of the root-soil composite decreases with the increase of the initial shear stress,then increases,and improves with the increase of the frequency.The simulation result show that increases in root elastic modulus and root-soil interfacial bond strength can all enhance the cyclic resistance of root-soil composites,and the maximum cyclic resistance of the root-soil composite was obtained when the initial inclination angle of the root system was 90°.展开更多
The lack of systematic and scientific top-level arrangement in the field of civil aircraft flight test leads to the problems of long duration and high cost.Based on the flight test activity,mathematical models of flig...The lack of systematic and scientific top-level arrangement in the field of civil aircraft flight test leads to the problems of long duration and high cost.Based on the flight test activity,mathematical models of flight test duration and cost are established to set up the framework of flight test process.The top-level arrangement for flight test is optimized by multi-objective algorithm to reduce the duration and cost of flight test.In order to verify the necessity and validity of the mathematical models and the optimization algorithm of top-level arrangement,real flight test data is used to make an example calculation.Results show that the multi-objective optimization results of the top-level flight arrangement are better than the initial arrangement data,which can shorten the duration,reduce the cost,and improve the efficiency of flight test.展开更多
With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and...With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and using them in contemporary warfare.An electric probe-type cylinder test measured the displacement-time behavior of NEPE high-energy solid propellant,and the parameters of the Jones-Wilkins-Lee(JWL)equation of state(EOS)were derived using particle swarm optimization(PSO)with the Gurney energy model.Further,the parameters of JWL-Miller EOS,determined through AUTODYN simulations,were validated by comparing airburst process simulations with experimental overpressure data.The study established a method for determining EOS parameters of high-energy propellants,achieving a high degree of accuracy.The derived parameters ensure precise modeling of propellant behavior,offering a reliable foundation for future applications in solid rocket motor performance optimization and safety assessment.展开更多
In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain ...In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain rate by using an Instron servo hydraulic axial testing machine with the testing temperature from 218K to 393K. The results show that the mechanical property of acrylic polymers depends heavily on the testing temperature. The yield stress and Young's modulus were found to decrease with increasing temperature at low strain rate. At very low temperature, the materials display typical brittle fracture; however their plasticity improves remarkably at high temperatures. The predictions of the mechanical behavior including the effect of temperature and strain rate using a proposed theoretical model have a good agreement with experimental results.展开更多
The lithology of fracture zone which was developed at the dam foundation of a hydropower station is weak sandstone with poor integrity and pore cementation contact.Its creep properties have a significant impact on the...The lithology of fracture zone which was developed at the dam foundation of a hydropower station is weak sandstone with poor integrity and pore cementation contact.Its creep properties have a significant impact on the deformation and stability of the dam.Based on the characteristics of loose organizational structure,high moisture content and poor mechanical properties,the triaxial compression tests and creep tests were carried out,respectively.The results show significant non-linear,low strength and no obvious strength peaks.Both axial and lateral strains are achieved more than 3%when the tests are failed.The weak sandstone has a significant creep property,but only transient and steady state appear under low stress.Increased stress causes creep intensified and lateral strain gradually exceeds axial strain.In the failure stage,it has characteristics of large axial plastic deformation,obvious volumetric ductility dilation and large steady creep rate.The accelerated creep appears shortly after transient loading under confining of pressures 1.0 MPa and 1.5 MPa.Therefore,an improved Burgers creep model considering the non-linear characteristics of weak sandstone is built based on hyperbolic equation and the creep parameters are identified.This model can well describe the creep properties of weak sandstone.展开更多
The complex systems are often in the structure of multi-operating modes, and the components implementing system functions are different under different operation modes, which results in the problems that components of...The complex systems are often in the structure of multi-operating modes, and the components implementing system functions are different under different operation modes, which results in the problems that components often fail in different operating modes, faults can be only detected in specified operating modes, tests can be available in specified operating modes,and the cost and efficiency of detecting and isolating faults are different under different operating modes and isolation levels. Aiming at these problems, an optimal test selection method for fault detection and isolation in the multi-operating mode system is proposed by using the fault pair coding and rollout algorithm. Firstly,the faults in fault-test correlation matrices under different operating modes are combined to fault-pairs, which is used to construct the fault pair-test correlation matrices under different operating modes.Secondly, the final fault pair-test correlation matrix of the multioperating mode system is obtained by operating the fault pair-test correlation matrices under different operating modes. Based on the final fault pair-test correlation matrix, the necessary tests are selected by the rollout algorithm orderly. Finally, the effectiveness of the proposed method is verified by examples of the optimal test selection in the multi-operating mode system with faults isolated to different levels. The result shows that the proposed method can effectively mine the fault detection and isolation ability of tests and it is suitable for the optimal test selection of the multi-operating mode system with faults isolated to the replacement unit and specific fault.展开更多
With the gradual depletion of available ore at shallow depth,deep mines have been widely operated around the world and therefore need a longer distance to transport the backfill to the underground stope.In this case,t...With the gradual depletion of available ore at shallow depth,deep mines have been widely operated around the world and therefore need a longer distance to transport the backfill to the underground stope.In this case,the determination of pressure drop is more important in the pipeline transportation system design.As the pilot loop systems require a large amount of capital and manual investment,even its results are reliable,there is an urgent need to find an alternative simple and cost-saving method to determine the pressure drop.Hence,laboratory L-pipe and a pilot-loop tests were employed to study the flow properties of cemented paste backfill cured at various solid and binder content.The results indicate that the L-pipe test presented a similar trend to the loop test,but the L-pipe was characterized by higher pressure drop values for various solid and cement contents.As cement content increased beyond 0%,the paste in the L-pipe showed a slighter difference in pressure drop evolution compared to the paste in the loop-pipe.These results suggest that the simple L-pipe is a workable substitute for semi-industrial loop tests and can provide guidance for designing practical CPB pipeline systems in deep mines.展开更多
In order to study the rheological properties of red stone granular soil,a series of rheological experiments were executed on large tri-axial rheological apparatus.Under 100,200 and 300 kPa confining stress conditions,...In order to study the rheological properties of red stone granular soil,a series of rheological experiments were executed on large tri-axial rheological apparatus.Under 100,200 and 300 kPa confining stress conditions,the rheological tests were carried out.These experiment results showed that the stress conditions,especially the stress level were the critical influencing factors of the rheological deformation properties.Under the low stress level(S=0.1),the granular soil showed the elastic properties,and there was no obvious rheological deformation.Under the middle stress level(0.2<S≤0.6),creep curves showed the linear viscoelastic rheological properties.However,under the high stress level(S>0.8) creep curves showed the non-linear viscous plastic rheological properties.Especially,under the stress level of S=1.0,the accelerated rheological phase of creep curves occurred at early time with a trend of failure.The stress level had obvious effects on the final rheological deformation of the soil sample,and the final rheological deformation increments nonlinearly increased with stress level.The final rheological deformation increment and step was little under low stress level,while it became large under high stress level,which showed the nonlinearly rheological properties of the granular soil.The confining pressure also had direct effects on final rheological deformation,and the final rheological deformation linearly increased with confining pressure increments.展开更多
The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures hav...The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.展开更多
In order to investigate the influence of intermediate principal stress on the stress-strain and strength behaviour of a coarse-grained soil, a series of true triaxial tests were performed. The tests were conducted in ...In order to investigate the influence of intermediate principal stress on the stress-strain and strength behaviour of a coarse-grained soil, a series of true triaxial tests were performed. The tests were conducted in a recently developed true triaxial apparatus with constant minor principal stress σ3 and constant value of intermediate principal stress ratio b=（σ2-σ3）/（σ1-σ3） （al is the vertical stress, and % is the horizontal stress）. It is found that the intermediate principal strain, ε2, increases from negative to positive value with the increase of parameter b from zero to unity under a constant minor principal stress. The minor principal strain, ε3, is always negative. This implies that the specimen exhibits an evident anisotropy. The relationship between b and friction angle obtained from the tests is different from that predicted by LADE-DUNCAN and MATSUOKA-NAKAI criteria. Based on the test results, an empirical equation of g（b） that is the shape function of the failure surface on re-plane was presented. The proposed equation is verified to be reasonable by comparing the predicted results using the equation with true triaxial test results of soils, such as coarse-grained soils in this study, sands and gravels in other studies.展开更多
基金the National Natural Science Foundation of China(Grant No.61973033)Preliminary Research of Equipment(Grant No.9090102010305)for funding the experiments。
文摘The longitudinal dispersion of the projectile in shooting tests of two-dimensional trajectory corrections fused with fixed canards is extremely large that it sometimes exceeds the correction ability of the correction fuse actuator.The impact point easily deviates from the target,and thus the correction result cannot be readily evaluated.However,the cost of shooting tests is considerably high to conduct many tests for data collection.To address this issue,this study proposes an aiming method for shooting tests based on small sample size.The proposed method uses the Bootstrap method to expand the test data;repeatedly iterates and corrects the position of the simulated theoretical impact points through an improved compatibility test method;and dynamically adjusts the weight of the prior distribution of simulation results based on Kullback-Leibler divergence,which to some extent avoids the real data being"submerged"by the simulation data and achieves the fusion Bayesian estimation of the dispersion center.The experimental results show that when the simulation accuracy is sufficiently high,the proposed method yields a smaller mean-square deviation in estimating the dispersion center and higher shooting accuracy than those of the three comparison methods,which is more conducive to reflecting the effect of the control algorithm and facilitating test personnel to iterate their proposed structures and algorithms.;in addition,this study provides a knowledge base for further comprehensive studies in the future.
基金the grants from the National Natural Science Foundation of China(Nos.52078152 and 12002095)Guangzhou Government-University Union Fund(No.202201020532)。
文摘In this article,the experimental and finite element analysis is utilized to investigate the quasi-static compression features of sandwich constructions built with tapered tubes.3D printing technology was utilized to create the hollow centers of the tapering tubes,with and without corrugations.The results demonstrate that the energy absorption(EA)and specific energy absorption(SEA)of the single corrugated tapered tube sandwich are 51.6% and 19.8% higher,respectively,than those of the conical tube sandwich.Furthermore,the results demonstrate that energy absorbers can benefit from corrugation in order to increase their efficiency.Additionally,the tapered corrugated tubes'resistance to oblique impacts was studied.Compared to a straight tube,the tapered tube is more resistant to oblique loads and has a lower initial peak crushing force(PCF),according to numerical simulations.After conducting a parametric study,it was discovered that the energy absorption performance of the sandwich construction is significantly affected by the amplitude,number of corrugations,and wall thickness.EA and SEA of DTS with corrugation number of 8 increased by 17.4%and 29.6%,respectively,while PCF decreased by 9.2% compared to DTS with corrugation number of 10.
文摘This paper presents the first-ever investigation of Menger fractal cubes'quasi-static compression and impact behaviour.Menger cubes with different void ratios were 3D printed using polylactic acid(PLA)with dimensions of 40 mm×40 mm×40 mm.Three different orders of Menger cubes with different void ratios were considered,namely M1 with a void ratio of 0.26,M2 with a void ratio of 0.45,and M3with a void ratio of 0.60.Quasi-static Compression tests were conducted using a universal testing machine,while the drop hammer was used to observe the behaviour under impact loading.The fracture mechanism,energy efficiency and force-time histories were studied.With the structured nature of the void formation and predictability of the failure modes,the Menger geometry showed some promise compared to other alternatives,such as foams and honeycombs.With the increasing void ratio,the Menger geometries show force-displacement behaviour similar to hyper-elastic materials such as rubber and polymers.The third-order Menger cubes showed the highest energy absorption efficiency compared to the other two geometries in this study.The findings of the present work reveal the possibility of using additively manufactured Menger geometries as an energy-efficient system capable of reducing the transmitting force in applications such as crash barriers.
基金financially supported by National Natural Science Foundation of China,China (Grant No.52022012)National Key R&D Program for Young Scientists of China,China (Grant No.2022YFC3080900)。
文摘The high variability of shock in terrorist attacks poses a threat to people's lives and properties,necessitating the development of more effective protective structures.This study focuses on the angle gradient and proposes four different configurations of concave hexagonal honeycomb structures.The structures'macroscopic deformation behavior,stress-strain relationship,and energy dissipation characteristics are evaluated through quasi-static compression and Hopkinson pressure bar impact experiments.The study reveals that,under varying strain rates,the structures deform starting from the weak layer and exhibit significant interlayer separation.Additionally,interlayer shear slip becomes more pronounced with increasing strain rate.In terms of quasi-static compression,symmetric gradient structures demonstrate superior energy absorption,particularly the symmetric negative gradient structure(SNG-SMS)with a specific energy absorption of 13.77 J/cm~3.For dynamic impact,unidirectional gradient structures exhibit exceptional energy absorption,particularly the unidirectional positive gradient honeycomb structure(UPG-SML)with outstanding mechanical properties.The angle gradient design plays a crucial role in determining the structure's stability and deformation mode during impact.Fewer interlayer separations result in a more pronounced negative Poisson's ratio effect and enhance the structure's energy absorption capacity.These findings provide a foundation for the rational design and selection of seismic protection structures in different strain rate impact environments.
基金This work was supported by the Natural Science Foundation of Anhui Province(2008085MA09)the National Natural Science Foundation of China(11671375).
文摘The three common genetic models(or modes of inheritance)in association analysis are the dominant,additive,and recessive models.It is known that the Cochran-Armitage trend test(CATT)which correctly incorporates information from genetic models,is more powerful than the commonly used Pearson’s chi-square test.However,the true genetic model is usually unknown in practice,and the power of the CAT test could be substantially reduced with a wrongly specified genetic model.To achieve a power that is close to that of a correctly specified CAT test,it is natural to apply trend tests under different possible genetic models and to report the most significant test result.This results in a MAX-type testing procedure,and it was found that this test is usually more powerful than the Pearson’s chi-square test.Although the signi-ficance(i.e.,p value)of the MAX-type test can be accessed by either large sample approximation or permutation methods,requirements for sample size or simulation replicates are demanding with respect to accuracy and efficiency.This paper proposes an approach to calculate the exact p values of MAX-type tests based on the combinatorial counting method.The simulation results show that the exact method is more accurate than the large sample approximation methods and more computationally efficient than the permutation method,and our method can be readily applied to genome-wide association studies(GWASs).The proposed methodis built in an R package,MaXact,which is available at the https://github.com/Myuan 2019/MaXact/.
基金This research has been conducted under SEGTRANS project,funded by the Centre for Industrial Technological Development(CDTI,Government of Spain).
文摘This paper explores the performances of a finite element simulation including four concrete models applied to a full-scale reinforced concrete beam subjected to blast loading. Field test data has been used to compare model results for each case. The numerical modelling has been, carried out using the suitable code LS-DYNA. This code integrates blast load routine(CONWEP) for the explosive description and four different material models for the concrete including: Karagozian & Case Concrete, Winfrith, Continuous Surface Cap Model and Riedel-Hiermaier-Thoma models, with concrete meshing based on 10, 15, and 20 mm. Six full-scale beams were tested: four of them used for the initial calibration of the numerical model and two more tests at lower scaled distances. For calibration, field data obtained employing pressure and accelerometers transducers were compared with the results derived from the numerical simulation. Damage surfaces and the shape of rupture in the beams have been used as references for comparison. Influence of the meshing on accelerations has been put in evidence and for some models the shape and size of the damage in the beams produced maximum differences around 15%. In all cases, the variations between material and mesh models are shown and discussed.
基金supported by the National Key R&D Program of China(2022YFA1602200)the International Partnership Program of the Chinese Academy of Sciences(211134KYSB20200057).
文摘The study of the charge conjugation and parity(CP)violation of hyperon is the precision frontier for probing possible new CP violation sources beyond the standard model(SM).With the large number of quantum entangled hyperonantihyperon pairs to be produced at Super Tau-Charm Facility(STCF),the CP asymmetry of hyperon is expected to be tested with a statistical sensitivity of 10^(−4) or even better.To cope with the statistical precision,the systematic effects from various aspects are critical and need to be studied in detail.In this paper,the sensitivity effects on the CP violation parameters associated with the detector resolution,including those of the position and momentum,are studied and discussed in detail.The results provide valuable guidance for the design of STCF detector.
文摘Plant roots are widely known to provide mechanical reinforcement to soils against shearing and further increase slope stability.However,whether roots provide reinforcement to loess cyclic re-sistance and how various factors affect roots reinforcement during seismic loading have rarely been studied.The objective is to conduct a series of cyclic direct simple shear tests and DEM numerical simulation to investigate the cyclic behaviour of rooted loess.The effects of initial static shear stress and loading frequency on the cyclic resistance of root-soil composites were first investigated.After that,cyclic direct simple shear simulations at constant volume were carried out based on the discrete element method(PFC^(3D))to investigate the effects of root geome-try,mechanical traits and root-soil bond strength on the cyclic strength of rooted loess.It was discovered that the roots could effectively improve the cyclic resistance of loess.The cyclic resistance of the root-soil composite decreases with the increase of the initial shear stress,then increases,and improves with the increase of the frequency.The simulation result show that increases in root elastic modulus and root-soil interfacial bond strength can all enhance the cyclic resistance of root-soil composites,and the maximum cyclic resistance of the root-soil composite was obtained when the initial inclination angle of the root system was 90°.
基金supported by the National Natural Science Foundation of China(62073267,61903305)the Fundamental Research Funds for the Central Universities(HXGJXM202214).
文摘The lack of systematic and scientific top-level arrangement in the field of civil aircraft flight test leads to the problems of long duration and high cost.Based on the flight test activity,mathematical models of flight test duration and cost are established to set up the framework of flight test process.The top-level arrangement for flight test is optimized by multi-objective algorithm to reduce the duration and cost of flight test.In order to verify the necessity and validity of the mathematical models and the optimization algorithm of top-level arrangement,real flight test data is used to make an example calculation.Results show that the multi-objective optimization results of the top-level flight arrangement are better than the initial arrangement data,which can shorten the duration,reduce the cost,and improve the efficiency of flight test.
基金supported by"the Fundamental Research Funds for the Central Universities",No.30924010503.
文摘With the development of high energy solid propellants,it is critical to evaluate the safety and power performance of solid propellants in the face of threats such as unmanned aerial vehicles(UAVs)when transporting and using them in contemporary warfare.An electric probe-type cylinder test measured the displacement-time behavior of NEPE high-energy solid propellant,and the parameters of the Jones-Wilkins-Lee(JWL)equation of state(EOS)were derived using particle swarm optimization(PSO)with the Gurney energy model.Further,the parameters of JWL-Miller EOS,determined through AUTODYN simulations,were validated by comparing airburst process simulations with experimental overpressure data.The study established a method for determining EOS parameters of high-energy propellants,achieving a high degree of accuracy.The derived parameters ensure precise modeling of propellant behavior,offering a reliable foundation for future applications in solid rocket motor performance optimization and safety assessment.
文摘In this paper, the mechanical behavior of acrylic polymers at elevated temperature was investigated. Four acrylic polymers were tested at high strain rate by using compression Hopkinson bar and at quasi-static strain rate by using an Instron servo hydraulic axial testing machine with the testing temperature from 218K to 393K. The results show that the mechanical property of acrylic polymers depends heavily on the testing temperature. The yield stress and Young's modulus were found to decrease with increasing temperature at low strain rate. At very low temperature, the materials display typical brittle fracture; however their plasticity improves remarkably at high temperatures. The predictions of the mechanical behavior including the effect of temperature and strain rate using a proposed theoretical model have a good agreement with experimental results.
基金Project(2011CB013504)supported by the National Basic Research Program of ChinaProject(11172090)supported by the National Natural Science Foundation of China
文摘The lithology of fracture zone which was developed at the dam foundation of a hydropower station is weak sandstone with poor integrity and pore cementation contact.Its creep properties have a significant impact on the deformation and stability of the dam.Based on the characteristics of loose organizational structure,high moisture content and poor mechanical properties,the triaxial compression tests and creep tests were carried out,respectively.The results show significant non-linear,low strength and no obvious strength peaks.Both axial and lateral strains are achieved more than 3%when the tests are failed.The weak sandstone has a significant creep property,but only transient and steady state appear under low stress.Increased stress causes creep intensified and lateral strain gradually exceeds axial strain.In the failure stage,it has characteristics of large axial plastic deformation,obvious volumetric ductility dilation and large steady creep rate.The accelerated creep appears shortly after transient loading under confining of pressures 1.0 MPa and 1.5 MPa.Therefore,an improved Burgers creep model considering the non-linear characteristics of weak sandstone is built based on hyperbolic equation and the creep parameters are identified.This model can well describe the creep properties of weak sandstone.
基金supported by the Natural Science Foundation of Shannxi Province(2017JQ5016)the Joint Laboratory for Sea Measurement and Control of Aircraft(DOM2016OF011)
文摘The complex systems are often in the structure of multi-operating modes, and the components implementing system functions are different under different operation modes, which results in the problems that components often fail in different operating modes, faults can be only detected in specified operating modes, tests can be available in specified operating modes,and the cost and efficiency of detecting and isolating faults are different under different operating modes and isolation levels. Aiming at these problems, an optimal test selection method for fault detection and isolation in the multi-operating mode system is proposed by using the fault pair coding and rollout algorithm. Firstly,the faults in fault-test correlation matrices under different operating modes are combined to fault-pairs, which is used to construct the fault pair-test correlation matrices under different operating modes.Secondly, the final fault pair-test correlation matrix of the multioperating mode system is obtained by operating the fault pair-test correlation matrices under different operating modes. Based on the final fault pair-test correlation matrix, the necessary tests are selected by the rollout algorithm orderly. Finally, the effectiveness of the proposed method is verified by examples of the optimal test selection in the multi-operating mode system with faults isolated to different levels. The result shows that the proposed method can effectively mine the fault detection and isolation ability of tests and it is suitable for the optimal test selection of the multi-operating mode system with faults isolated to the replacement unit and specific fault.
基金Project(51904055)supported by the National Natural Science Foundation of ChinaProject(N2001010)supported by the Fundamental Research Funds for the Central Universities of China。
文摘With the gradual depletion of available ore at shallow depth,deep mines have been widely operated around the world and therefore need a longer distance to transport the backfill to the underground stope.In this case,the determination of pressure drop is more important in the pipeline transportation system design.As the pilot loop systems require a large amount of capital and manual investment,even its results are reliable,there is an urgent need to find an alternative simple and cost-saving method to determine the pressure drop.Hence,laboratory L-pipe and a pilot-loop tests were employed to study the flow properties of cemented paste backfill cured at various solid and binder content.The results indicate that the L-pipe test presented a similar trend to the loop test,but the L-pipe was characterized by higher pressure drop values for various solid and cement contents.As cement content increased beyond 0%,the paste in the L-pipe showed a slighter difference in pressure drop evolution compared to the paste in the loop-pipe.These results suggest that the simple L-pipe is a workable substitute for semi-industrial loop tests and can provide guidance for designing practical CPB pipeline systems in deep mines.
基金Project(200413) supported by Communication Science and Technology Fund of Hunan Province,China
文摘In order to study the rheological properties of red stone granular soil,a series of rheological experiments were executed on large tri-axial rheological apparatus.Under 100,200 and 300 kPa confining stress conditions,the rheological tests were carried out.These experiment results showed that the stress conditions,especially the stress level were the critical influencing factors of the rheological deformation properties.Under the low stress level(S=0.1),the granular soil showed the elastic properties,and there was no obvious rheological deformation.Under the middle stress level(0.2<S≤0.6),creep curves showed the linear viscoelastic rheological properties.However,under the high stress level(S>0.8) creep curves showed the non-linear viscous plastic rheological properties.Especially,under the stress level of S=1.0,the accelerated rheological phase of creep curves occurred at early time with a trend of failure.The stress level had obvious effects on the final rheological deformation of the soil sample,and the final rheological deformation increments nonlinearly increased with stress level.The final rheological deformation increment and step was little under low stress level,while it became large under high stress level,which showed the nonlinearly rheological properties of the granular soil.The confining pressure also had direct effects on final rheological deformation,and the final rheological deformation linearly increased with confining pressure increments.
文摘The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress-strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carded out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.
基金Project(50639050) supported by the National Natural Science Foundation of China and Er-Tan Hydraulicpower Limited CompanyProject(50579014) supported by the National Natural Science Foundation of China+3 种基金Project(09KJD560003) supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of ChinaProject(BK2007582) supported by Jiangsu Provincial Natural Science Foundation of ChinaProject(20070294002) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(GH200904) supported by Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,China
文摘In order to investigate the influence of intermediate principal stress on the stress-strain and strength behaviour of a coarse-grained soil, a series of true triaxial tests were performed. The tests were conducted in a recently developed true triaxial apparatus with constant minor principal stress σ3 and constant value of intermediate principal stress ratio b=（σ2-σ3）/（σ1-σ3） （al is the vertical stress, and % is the horizontal stress）. It is found that the intermediate principal strain, ε2, increases from negative to positive value with the increase of parameter b from zero to unity under a constant minor principal stress. The minor principal strain, ε3, is always negative. This implies that the specimen exhibits an evident anisotropy. The relationship between b and friction angle obtained from the tests is different from that predicted by LADE-DUNCAN and MATSUOKA-NAKAI criteria. Based on the test results, an empirical equation of g（b） that is the shape function of the failure surface on re-plane was presented. The proposed equation is verified to be reasonable by comparing the predicted results using the equation with true triaxial test results of soils, such as coarse-grained soils in this study, sands and gravels in other studies.
