Data compression plays a vital role in datamanagement and information theory by reducing redundancy.However,it lacks built-in security features such as secret keys or password-based access control,leaving sensitive da...Data compression plays a vital role in datamanagement and information theory by reducing redundancy.However,it lacks built-in security features such as secret keys or password-based access control,leaving sensitive data vulnerable to unauthorized access and misuse.With the exponential growth of digital data,robust security measures are essential.Data encryption,a widely used approach,ensures data confidentiality by making it unreadable and unalterable through secret key control.Despite their individual benefits,both require significant computational resources.Additionally,performing them separately for the same data increases complexity and processing time.Recognizing the need for integrated approaches that balance compression ratios and security levels,this research proposes an integrated data compression and encryption algorithm,named IDCE,for enhanced security and efficiency.Thealgorithmoperates on 128-bit block sizes and a 256-bit secret key length.It combines Huffman coding for compression and a Tent map for encryption.Additionally,an iterative Arnold cat map further enhances cryptographic confusion properties.Experimental analysis validates the effectiveness of the proposed algorithm,showcasing competitive performance in terms of compression ratio,security,and overall efficiency when compared to prior algorithms in the field.展开更多
With the increase in the quantity and scale of Static Random-Access Memory Field Programmable Gate Arrays (SRAM-based FPGAs) for aerospace application, the volume of FPGA configuration bit files that must be stored ha...With the increase in the quantity and scale of Static Random-Access Memory Field Programmable Gate Arrays (SRAM-based FPGAs) for aerospace application, the volume of FPGA configuration bit files that must be stored has increased dramatically. The use of compression techniques for these bitstream files is emerging as a key strategy to alleviate the burden on storage resources. Due to the severe resource constraints of space-based electronics and the unique application environment, the simplicity, efficiency and robustness of the decompression circuitry is also a key design consideration. Through comparative analysis current bitstream file compression technologies, this research suggests that the Lempel Ziv Oberhumer (LZO) compression algorithm is more suitable for satellite applications. This paper also delves into the compression process and format of the LZO compression algorithm, as well as the inherent characteristics of configuration bitstream files. We propose an improved algorithm based on LZO for bitstream file compression, which optimises the compression process by refining the format and reducing the offset. Furthermore, a low-cost, robust decompression hardware architecture is proposed based on this method. Experimental results show that the compression speed of the improved LZO algorithm is increased by 3%, the decompression hardware cost is reduced by approximately 60%, and the compression ratio is slightly reduced by 0.47%.展开更多
This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performe...This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performed on saturated expansive soil specimens with varying compaction conditions and soil structures under different stress states.Experimental results demonstrate that the specimens expand during freezing and contract during thawing.All specimens converge to the same residual void ratio after seven FT cycles,irrespective of their different initial void ratio,stress state,and soil structure.The compression index of the expansive soil specimens increases with the initial void ratio,whereas their swelling index remains nearly constant.A model extending the disturbed state concept(DSC)is proposed to predict the 1D compression behaviors of FT-impacted soils.The model incorporates a parameter,b,to account for the impacts of FT cycles.Empirical equations have been developed to link the key model parameters(i.e.the normalized yield stress and parameter b)to the soil state parameter(i.e.the normalized void ratio)in order to simplify the prediction approach.The proposed model well predicts the results of the tested expansive soil.In addition,the model’s feasibility for other types of soils,including low-and high-plastic clays,and high-plastic organic soils,has been validated using published data from the literature.The proposed model is simple yet reliable for predicting the compression behaviors of soils subjected to FT cycles.展开更多
Basic life support for cardiac arrest associates cardiopulmonary resuscitation(CPR)and defibrillation.CPR relies on chest compressions(CC)and ventilation.Current guidelines on CPR recommend a depth of 5-6 cm at a rhyt...Basic life support for cardiac arrest associates cardiopulmonary resuscitation(CPR)and defibrillation.CPR relies on chest compressions(CC)and ventilation.Current guidelines on CPR recommend a depth of 5-6 cm at a rhythm of 100-120 times/min for CC.[1,2]Interruptions of the CC must be as short as possible and are related to ventilation,defibrillation and turnover of the rescuers.Most of the automated external defibrillators(AEDs)require interruptions of the CC to perform rhythm analysis.Among the numerous marketed models of AEDs,some provide real-time feedback about the quality of the CC.展开更多
The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics ...The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.展开更多
The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compressio...The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.展开更多
The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at c...The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at current density of 60 A/mm^(2) and strain rate of 0.1 s^(−1),the ultimate tensile stress shows a significant decrease from approximately 3000 MPa to 1900 MPa with reduction ratio of about 36.7%.However,as current density increases,elongation decreases due to intermediate temperature embrittlement.This is because the current induces Joule effect,which then leads to stress concentration and more defect formation.Moreover,the flow stress is decreased with the increase in strain rate at constant current density.展开更多
Steel cylindrical shells are widely used in engineering structures due to their high strength-to-weight ratio,but they are vulnerable to buckling under axial loads.To address this limitation,fiber-reinforced polymer(F...Steel cylindrical shells are widely used in engineering structures due to their high strength-to-weight ratio,but they are vulnerable to buckling under axial loads.To address this limitation,fiber-reinforced polymer(FRP)composites have emerged as promising materials for structural reinforcement.This study investigates the buckling behavior of steel cylindrical shells reinforced with inner and outer layers of polymer composite materials under axial compression.Using analytical and numerical modeling methods,the critical buckling loads for different reinforcement options were evaluated.Two-sided glass fiber reinforced plastic(GFRP)or carbon fiber reinforced plastic(CFRP)coatings,as well as combined coatings with layers of different composites,were considered.GFRP+CFRPIn the calculations,the coatings were treated as homogeneous orthotropic materials with equivalent averaged elastic characteristics.The numerical analysis revealed that CFRP reinforcement achieved the highest increase in buckling load,with improvements ranging from 9.84%to 47.29%,depending on the composite thickness and steel shell thickness.GFRP reinforcement,while beneficial,demonstrated a lower effectiveness,with buckling load increases between 5.89%and 19.30%.The hybrid reinforcement provided an optimal balance,improving buckling resistance by GFRP+CFRP6.94%to 43.95%.Statistical analysis further identified composite type and thickness as the most significant factors affecting buckling performance.The findings suggest that CFRP is the preferred reinforcement material,especially when applied to thin-walled cylindrical shells,while hybrid reinforcements can be effectively utilized for structures requiring a balance between stiffness and ductility.These insights provide a foundation for optimizing FRP reinforcement strategies to enhance the structural integrity of steel shells in engineering applications.展开更多
During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomen...During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomenon,a numerical simulation framework of the finite volume method and transient embedded discrete fracture model is proposed to establish a new constitutive model that links poroelastoplastic deformation,adsorption-induced swelling,and aperture compression.From this model,anisotropic permeability tensors were derived to further achieve the simulation of coevolution.Meanwhile,our permeability model was verified against the measured permeability data,and the history match of the numerical model showed better results where the mismatch was less than 5%.The results indicate that(1)the long-term permeability evolution clearly showed the competitive effects of multiple deformation mechanisms,which involves three stages:compaction-dominated decline,adsorption-dominated rebound,and creep-controlled loss.(2)The increased number of compressible cleats/fractures accelerated the initial permeability decline,while the increased desorption-induced strain promoted faster rebound and enhancement and higher viscosity coefficients enhanced the creep effect,which led to significant long-term permeability loss.(3)Massive hydraulic fracturing created a larger drainage area,accelerating methane desorption and causing sharp permeability rebound with reduced residual gas,which shows that the permeability remained higher than the initial values even after the extensive extraction via the fractured horizontal wells.The permeability evolution mechanisms displayed varying properties,such as coal rank and burial depth,and distinct characteristics.A precise understanding of multiple competitive stress effects is crucial for optimizing coalbed methane extraction techniques and improving recovery efficiency.展开更多
Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accur...Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accurate overpressure prediction remains challenging in offshore Northwest Borneo despite several decades of drilling experience.This paper focuses on two exploration wells drilled by Brunei Shell Petroleum 40 years apart that faced similar challenges with overpressure prediction and well control.An integrated lookback study is attempted using seismic and well-log data to explore the causes of the unsatisfactory Pore Pressure Prediction(PPP)outcome in pre-drill and real-time operation settings for thesewells.Our study indicates that the misprediction of overpressures is due to real differences in shale pressure(basis of pre-drill work and monitoring)and sand pressure(source of drill kick and well control chal-lenges)due to large-scale vertical leak or expulsion of deep-seated fluids into pre-compacted normally pressured overlying sediments in several regions through a mix of shear and tensile failure mechanisms.Such migrated fluids inflate the sand pressure in the normally compacted shallower sequences with the shale pressure remaining low.A predictive framework for upward fluid expulsion was attempted but found impracticable due to complex spatial and temporal variations in the horizontal stress field responsible for such leakage.As such,it is proposed that these migratory overpressures are essentially'unpredictable'from conventional PPP workflows viewed in the broad bucket of compaction disequi-librium(undercompaction)and fluid expansion(unloading)mechanisms.Further study is recommended to understand if such migrated overpressures in the sand can produce a discernible and predictable geophysical or petrophysical signature in the abutting normally compacted shales.The study highlights the possibility of large lateral variability in the sand overpressure within the same stratigraphic unit in regions with complex tectonostratigraphic evolution like Northwest Borneo.展开更多
Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in...Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in the impact load mitigation where an external kinetic energy is absorbed by the deformation/crushing of lattice cells.This has motivated a growing number of experimental and numerical studies,recently,on the crushing behavior of additively produced lattice structures.The present study overviews the dynamic and quasi-static crushing behavior of additively produced Ti64,316L,and AlSiMg alloy lattice structures.The first part of the study summarizes the main features of two most commonly used additive processing techniques for lattice structures,namely selective-laser-melt(SLM)and electro-beam-melt(EBM),along with a description of commonly observed process induced defects.In the second part,the deformation and strain rate sensitivities of the selected alloy lattices are outlined together with the most widely used dynamic test methods,followed by a part on the observed micro-structures of the SLM and EBM-processed Ti64,316L and AlSiMg alloys.Finally,the experimental and numerical studies on the quasi-static and dynamic compression behavior of the additively processed Ti64,316L,and AlSiMg alloy lattices are reviewed.The results of the experimental and numerical studies of the dynamic properties of various types of lattices,including graded,non-uniform strut size,hollow,non-uniform cell size,and bio-inspired,were tabulated together with the used dynamic testing methods.The dynamic tests have been noted to be mostly conducted in compression Split Hopkinson Pressure Bar(SHPB)or Taylor-and direct-impact tests using the SHPB set-up,in all of which relatively small-size test specimens were tested.The test specimen size effect on the compression behavior of the lattices was further emphasized.It has also been shown that the lattices of Ti64 and AlSiMg alloys are relatively brittle as compared with the lattices of 316L alloy.Finally,the challenges associated with modelling lattice structures were explained and the micro tension tests and multi-scale modeling techniques combining microstructural characteristics with macroscopic lattice dynamics were recommended to improve the accuracy of the numerical simulations of the dynamic compression deformations of metallic lattice structures.展开更多
With the rapid development of digital communication and the widespread use of the Internet of Things,multi-view image compression has attracted increasing attention as a fundamental technology for image data communica...With the rapid development of digital communication and the widespread use of the Internet of Things,multi-view image compression has attracted increasing attention as a fundamental technology for image data communication.Multi-view image compression aims to improve compression efficiency by leveraging correlations between images.However,the requirement of synchronization and inter-image communication at the encoder side poses significant challenges,especially for constrained devices.In this study,we introduce a novel distributed image compression model based on the attention mechanism to address the challenges associated with the availability of side information only during decoding.Our model integrates an encoder network,a quantization module,and a decoder network,to ensure both high compression performance and high-quality image reconstruction.The encoder uses a deep Convolutional Neural Network(CNN)to extract high-level features from the input image,which then pass through the quantization module for further compression before undergoing lossless entropy coding.The decoder of our model consists of three main components that allow us to fully exploit the information within and between images on the decoder side.Specifically,we first introduce a channel-spatial attention module to capture and refine information within individual image feature maps.Second,we employ a semi-coupled convolution module to extract both shared and specific information in images.Finally,a cross-attention module is employed to fuse mutual information extracted from side information.The effectiveness of our model is validated on various datasets,including KITTI Stereo and Cityscapes.The results highlight the superior compression capabilities of our method,surpassing state-of-the-art techniques.展开更多
Plastometric experiments,supplemented with numerical simulations using the finite element method(FEM),can be advantageously used to characterize the deformation behavior of metallic materials.The accuracy of such simu...Plastometric experiments,supplemented with numerical simulations using the finite element method(FEM),can be advantageously used to characterize the deformation behavior of metallic materials.The accuracy of such simulations predicting deformation behaviors of materials is,however,primarily affected by the applied rheology law.The presented study focuses on the characterization of the deformation behavior of AISI 1045 type carbon steel,widely used e.g.,in automotive and power engineering,under extreme conditions(i.e.,high temperatures,strain rates).The study consists of two main parts:experimentally analyzing the flow stress development of the steel under different thermomechanical conditions via uniaxial hot compression tests and establishing the rheology law via numerical simulations implementing the experimentally acquired flow stress curves.The numerical simulations then not only serve to establish the rheology law but also to verify the reliability of the selected experimental process.The results of the numerical simulations showed that the established rheology law characterizes the behavior of the investigated steel with sufficient accuracy also at high temperatures and/or strain rates,and can,therefore,be used for practical purposes.Last but not least,supplementary microstructure analyses performed for the samples subjected to the highest deformation temperature provided a deeper insight into the effects of the applied(extreme)thermomechanical conditions on the behavior of the investigated steel.展开更多
The accurate prediction of battery pack capacity in electric vehicles(EVs)is crucial for ensuring safety and optimizing performance.Despite extensive research on predicting cell capacity using laboratory data,predicti...The accurate prediction of battery pack capacity in electric vehicles(EVs)is crucial for ensuring safety and optimizing performance.Despite extensive research on predicting cell capacity using laboratory data,predicting the capacity of onboard battery packs from field data remains challenging due to complex operating conditions and irregular EV usage in real-world settings.Most existing methods rely on extracting health feature parameters from raw data for capacity prediction of onboard battery packs,however,selecting specific parameters often results in a loss of critical information,which reduces prediction accuracy.To this end,this paper introduces a novel framework combining deep learning and data compression techniques to accurately predict battery pack capacity onboard.The proposed data compression method converts monthly EV charging data into feature maps,which preserve essential data characteristics while reducing the volume of raw data.To address missing capacity labels in field data,a capacity labeling method is proposed,which calculates monthly battery capacity by transforming the ampere-hour integration formula and applying linear regression.Subsequently,a deep learning model is proposed to build a capacity prediction model,using feature maps from historical months to predict the battery capacity of future months,thus facilitating accurate forecasts.The proposed framework,evaluated using field data from 20 EVs,achieves a mean absolute error of 0.79 Ah,a mean absolute percentage error of 0.65%,and a root mean square error of 1.02 Ah,highlighting its potential for real-world EV applications.展开更多
Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving en...Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving engineering safety.Although extensive studies have been conducted on the uniaxial compressive properties of CTB,damage constitutive models that effectively capture its damage evolution process remain underdeveloped,and its failure mechanisms are not yet fully clarified.To address these gaps,this study conducted systematic uniaxial compression tests on CTB specimens prepared with varying cement-tailings ratios.The results revealed distinct compaction and softening phases in the stress−strain curves.A lower cement-tailings ratio significantly reduced the strength and deformation resistance of CTB,along with a decrease in elastic energy accumulation at peak stress and dissipation energy in the post peak stage.Based on these findings,a modified damage constitutive model was developed by introducing a correction factor,enabling accurate simulation of the entire uniaxial compression process of CTB with different cement-tailings ratios.Comparative analysis with classical constitutive models validated the proposed model’s accuracy and applicability in describing the compressive behavior of CTB.Furthermore,particle size distribution and acoustic emission tests were employed to investigate the influence of cement-tailings ratio on failure mechanisms.The results indicated that a lower cement-tailings ratio leads to coarser particle sizes,which intensify shear-related acoustic emission signals and ultimately result in more pronounced macroscopic shear failure.This study provides theoretical support and practical guidance for the optimal design of CTB mix ratios.展开更多
An additional hot compression process was applied to a dilute Mg−Mn−Zn alloy post-extrusion.The alloy was extruded at 150℃ with an extrusion ratio of 15:1 and subsequently hot-compressed at 180℃ with a true strain o...An additional hot compression process was applied to a dilute Mg−Mn−Zn alloy post-extrusion.The alloy was extruded at 150℃ with an extrusion ratio of 15:1 and subsequently hot-compressed at 180℃ with a true strain of 0.9 along the extrusion direction.The microstructure,mechanical properties and thermal conductivity of as-extruded and as-hot compressed Mg−Mn−Zn alloys were investigated using optical microscopy,scanning electron microscopy,electron backscattering diffraction,and transmission electron microscopy.The aim was to concurrently enhance both strength and thermal conductivity by fostering uniform and refined microstructures while mitigating basal texture intensity.Substantial improvements were observed in yield strength(YS),ultimate tensile strength(UTS),and elongation(EL),with increase of 77%,53% and 10%,respectively.Additionally,thermal conductivity demonstrated a notable enhancement,rising from 111 to 125 W/(m·K).The underlying mechanism driving these improvements through the supplementary hot compression step was thoroughly elucidated.This study presents a promising pathway for the advancement of Mg alloys characterized by superior thermal and mechanical properties.展开更多
Analyzing the fatigue damage characteristics of hot dry rock(HDR)affected by seawater thermal shock cycles is required for the efficient exploitation of HDR and the conservation of freshwater resources.Mechanical and ...Analyzing the fatigue damage characteristics of hot dry rock(HDR)affected by seawater thermal shock cycles is required for the efficient exploitation of HDR and the conservation of freshwater resources.Mechanical and acoustic emission(AE)monitoring tests were conducted during the triaxial compression of HDR at different confining pressures,temperatures,and numbers of seawater thermal shocks to investigate the seawater damage of HDR.The test results indicated an increase in the cumulative AE counts with increasing temperature and number of seawater thermal shocks,and a decrease in AE counts with increasing confining pressure.The effect of the number of seawater thermal shocks was significant.The AE counts were 276% higher at 15 than at 0 seawater thermal shocks.The b-value increased with the number of thermal shocks and stabilized after 5 shocks.Most of the damage was small fractures,which reduced the rock’s damage resistance.The AE time series under HDR triaxial compression exhibited multifractal features.High energy AE events dominated the damage mechanism of HDR,indicating shear damage to the HDR.Therefore,this study can provide a reference for seawater as a heat transfer fluid in the design of geothermal energy resource extraction.展开更多
The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase...The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.展开更多
The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot...The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot provide information on the structure evolution during deformation.In order to investigate the failure mechanism of Al alloy foam under quasi-static compression,by utilizing X-ray imaging technology,in situ CT image data were obtained during the loading process.A geometric model characterizing the real structure of Al alloy foam was reconstructed from the initial CT images and used for finite element simulation.Besides,based on the digital volume correlation(DVC)method,the displacement and strain fields of Al alloy foam were calculated.The results show that the in situ experimental observation based on X-ray imaging can effectively obtain the failure information of Al alloy foam.The simulation results for deformation and failure behavior of Al alloy foam are consistent with experimental results.During the quasi-static compression,a shear band can be observed diagonally across the profile of Al alloy foam,with weak regions occurring in the cells with larger volume and higher aspect ratios.Using these weak regions as boundaries,the relative displacement of cell structures on one side compared to another side was identified as the intrinsic cause of shear band formation.The high-strain regions identified by DVC closely match the crack locations on the cell walls,validating the accuracy of DVC on localizing cracks on cell walls and predicting their propagation trends.展开更多
Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mec...Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mechanical behavior and failure mechanisms of CAC under multiaxial stress conditions.This paper employs a 3D mesoscale model that considers the actual size,shape,and spatial distribution of aggregates.The reliability of the model and material parameters is verified through comparison with existing experimental data.Subsequently,the model is used to systematically study the mechanical properties,failure modes,and failure processes of C40 CAC under the biaxial compression.The numerical results are compared with the experimental results of CAC and ordinary portland concrete(OPC).The results indicate that the failure modes of CAC under the biaxial compression are diagonal shear failure.The biaxial compressive strength and elastic modulus of CAC are greater than those under uniaxial stress and exhibit a significant intermediate principal stress effect.The biaxial compressive strength reaches its maximum value when the stress ratio is 0.5,which is consistent with the conclusions for OPC.Finally,failure criteria and strength envelopes for CAC under the biaxial compression are established in order to provide a reference for analyzing the strength characteristics and structural design of CAC.展开更多
基金the Deanship of Graduate Studies and Scientific Research at Qassim University for financial support(QU-APC-2025).
文摘Data compression plays a vital role in datamanagement and information theory by reducing redundancy.However,it lacks built-in security features such as secret keys or password-based access control,leaving sensitive data vulnerable to unauthorized access and misuse.With the exponential growth of digital data,robust security measures are essential.Data encryption,a widely used approach,ensures data confidentiality by making it unreadable and unalterable through secret key control.Despite their individual benefits,both require significant computational resources.Additionally,performing them separately for the same data increases complexity and processing time.Recognizing the need for integrated approaches that balance compression ratios and security levels,this research proposes an integrated data compression and encryption algorithm,named IDCE,for enhanced security and efficiency.Thealgorithmoperates on 128-bit block sizes and a 256-bit secret key length.It combines Huffman coding for compression and a Tent map for encryption.Additionally,an iterative Arnold cat map further enhances cryptographic confusion properties.Experimental analysis validates the effectiveness of the proposed algorithm,showcasing competitive performance in terms of compression ratio,security,and overall efficiency when compared to prior algorithms in the field.
基金supported in part by the National Key Laboratory of Science and Technology on Space Microwave(Grant Nos.HTKJ2022KL504009 and HTKJ2022KL5040010).
文摘With the increase in the quantity and scale of Static Random-Access Memory Field Programmable Gate Arrays (SRAM-based FPGAs) for aerospace application, the volume of FPGA configuration bit files that must be stored has increased dramatically. The use of compression techniques for these bitstream files is emerging as a key strategy to alleviate the burden on storage resources. Due to the severe resource constraints of space-based electronics and the unique application environment, the simplicity, efficiency and robustness of the decompression circuitry is also a key design consideration. Through comparative analysis current bitstream file compression technologies, this research suggests that the Lempel Ziv Oberhumer (LZO) compression algorithm is more suitable for satellite applications. This paper also delves into the compression process and format of the LZO compression algorithm, as well as the inherent characteristics of configuration bitstream files. We propose an improved algorithm based on LZO for bitstream file compression, which optimises the compression process by refining the format and reducing the offset. Furthermore, a low-cost, robust decompression hardware architecture is proposed based on this method. Experimental results show that the compression speed of the improved LZO algorithm is increased by 3%, the decompression hardware cost is reduced by approximately 60%, and the compression ratio is slightly reduced by 0.47%.
基金support from the Natural Sciences and Engineering Research Council of Canada(NSERC)through the Discovery Grant(Grant No.5808)received in 2019 for his research programsThe third author appreciates the funding from the National Natural Science Foundation of China(Grant No.52378365)Hubei Key Research&Development Program(Grant No.2023BCB112).
文摘This study investigates the volumetric behaviors of various soils during freeze-thaw(FT)cycles and subsequent one-dimensional(1D)compression from experimental and theoretical studies.Experimental studies were performed on saturated expansive soil specimens with varying compaction conditions and soil structures under different stress states.Experimental results demonstrate that the specimens expand during freezing and contract during thawing.All specimens converge to the same residual void ratio after seven FT cycles,irrespective of their different initial void ratio,stress state,and soil structure.The compression index of the expansive soil specimens increases with the initial void ratio,whereas their swelling index remains nearly constant.A model extending the disturbed state concept(DSC)is proposed to predict the 1D compression behaviors of FT-impacted soils.The model incorporates a parameter,b,to account for the impacts of FT cycles.Empirical equations have been developed to link the key model parameters(i.e.the normalized yield stress and parameter b)to the soil state parameter(i.e.the normalized void ratio)in order to simplify the prediction approach.The proposed model well predicts the results of the tested expansive soil.In addition,the model’s feasibility for other types of soils,including low-and high-plastic clays,and high-plastic organic soils,has been validated using published data from the literature.The proposed model is simple yet reliable for predicting the compression behaviors of soils subjected to FT cycles.
文摘Basic life support for cardiac arrest associates cardiopulmonary resuscitation(CPR)and defibrillation.CPR relies on chest compressions(CC)and ventilation.Current guidelines on CPR recommend a depth of 5-6 cm at a rhythm of 100-120 times/min for CC.[1,2]Interruptions of the CC must be as short as possible and are related to ventilation,defibrillation and turnover of the rescuers.Most of the automated external defibrillators(AEDs)require interruptions of the CC to perform rhythm analysis.Among the numerous marketed models of AEDs,some provide real-time feedback about the quality of the CC.
基金supported by the National Natural Science Foundation of China(Grant Nos.42372312,and 42172299)the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20220807).
文摘The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.
基金financially supported by the National Natural Science Foundation of China(Nos.52174092,51904290,and 52374147)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the National Key Research and Development Program of China(No.2023YFC3804204)the Major Program of Xinjiang Uygur Autonomous Region S cience and Technology(No.2023A01002)。
文摘The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
基金National Natural Science Foundation of China(52305349)Heilongjiang Touyan Team(HITTY-20190036)+2 种基金Heilongjiang Provincial Natural Science Foundation of China(LH2023E033)CGN-HIT Advanced Nuclear and New Energy Research Institute(CGN-HIT202305)Natural Science Basic Research Program of Shaanxi Province(2023-JC-QN-0518)。
文摘The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at current density of 60 A/mm^(2) and strain rate of 0.1 s^(−1),the ultimate tensile stress shows a significant decrease from approximately 3000 MPa to 1900 MPa with reduction ratio of about 36.7%.However,as current density increases,elongation decreases due to intermediate temperature embrittlement.This is because the current induces Joule effect,which then leads to stress concentration and more defect formation.Moreover,the flow stress is decreased with the increase in strain rate at constant current density.
文摘Steel cylindrical shells are widely used in engineering structures due to their high strength-to-weight ratio,but they are vulnerable to buckling under axial loads.To address this limitation,fiber-reinforced polymer(FRP)composites have emerged as promising materials for structural reinforcement.This study investigates the buckling behavior of steel cylindrical shells reinforced with inner and outer layers of polymer composite materials under axial compression.Using analytical and numerical modeling methods,the critical buckling loads for different reinforcement options were evaluated.Two-sided glass fiber reinforced plastic(GFRP)or carbon fiber reinforced plastic(CFRP)coatings,as well as combined coatings with layers of different composites,were considered.GFRP+CFRPIn the calculations,the coatings were treated as homogeneous orthotropic materials with equivalent averaged elastic characteristics.The numerical analysis revealed that CFRP reinforcement achieved the highest increase in buckling load,with improvements ranging from 9.84%to 47.29%,depending on the composite thickness and steel shell thickness.GFRP reinforcement,while beneficial,demonstrated a lower effectiveness,with buckling load increases between 5.89%and 19.30%.The hybrid reinforcement provided an optimal balance,improving buckling resistance by GFRP+CFRP6.94%to 43.95%.Statistical analysis further identified composite type and thickness as the most significant factors affecting buckling performance.The findings suggest that CFRP is the preferred reinforcement material,especially when applied to thin-walled cylindrical shells,while hybrid reinforcements can be effectively utilized for structures requiring a balance between stiffness and ductility.These insights provide a foundation for optimizing FRP reinforcement strategies to enhance the structural integrity of steel shells in engineering applications.
基金support of the National Natural Science Foundation of China(U23B6004 and 52404045)the CAST Young Talent Support Program,Doctoral Student Special Project.
文摘During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomenon,a numerical simulation framework of the finite volume method and transient embedded discrete fracture model is proposed to establish a new constitutive model that links poroelastoplastic deformation,adsorption-induced swelling,and aperture compression.From this model,anisotropic permeability tensors were derived to further achieve the simulation of coevolution.Meanwhile,our permeability model was verified against the measured permeability data,and the history match of the numerical model showed better results where the mismatch was less than 5%.The results indicate that(1)the long-term permeability evolution clearly showed the competitive effects of multiple deformation mechanisms,which involves three stages:compaction-dominated decline,adsorption-dominated rebound,and creep-controlled loss.(2)The increased number of compressible cleats/fractures accelerated the initial permeability decline,while the increased desorption-induced strain promoted faster rebound and enhancement and higher viscosity coefficients enhanced the creep effect,which led to significant long-term permeability loss.(3)Massive hydraulic fracturing created a larger drainage area,accelerating methane desorption and causing sharp permeability rebound with reduced residual gas,which shows that the permeability remained higher than the initial values even after the extensive extraction via the fractured horizontal wells.The permeability evolution mechanisms displayed varying properties,such as coal rank and burial depth,and distinct characteristics.A precise understanding of multiple competitive stress effects is crucial for optimizing coalbed methane extraction techniques and improving recovery efficiency.
文摘Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accurate overpressure prediction remains challenging in offshore Northwest Borneo despite several decades of drilling experience.This paper focuses on two exploration wells drilled by Brunei Shell Petroleum 40 years apart that faced similar challenges with overpressure prediction and well control.An integrated lookback study is attempted using seismic and well-log data to explore the causes of the unsatisfactory Pore Pressure Prediction(PPP)outcome in pre-drill and real-time operation settings for thesewells.Our study indicates that the misprediction of overpressures is due to real differences in shale pressure(basis of pre-drill work and monitoring)and sand pressure(source of drill kick and well control chal-lenges)due to large-scale vertical leak or expulsion of deep-seated fluids into pre-compacted normally pressured overlying sediments in several regions through a mix of shear and tensile failure mechanisms.Such migrated fluids inflate the sand pressure in the normally compacted shallower sequences with the shale pressure remaining low.A predictive framework for upward fluid expulsion was attempted but found impracticable due to complex spatial and temporal variations in the horizontal stress field responsible for such leakage.As such,it is proposed that these migratory overpressures are essentially'unpredictable'from conventional PPP workflows viewed in the broad bucket of compaction disequi-librium(undercompaction)and fluid expansion(unloading)mechanisms.Further study is recommended to understand if such migrated overpressures in the sand can produce a discernible and predictable geophysical or petrophysical signature in the abutting normally compacted shales.The study highlights the possibility of large lateral variability in the sand overpressure within the same stratigraphic unit in regions with complex tectonostratigraphic evolution like Northwest Borneo.
基金the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 101034425 for the project titled A2M2TECHThe Scientific and Technological Research Council of Türkiye (TUBITAK) with grant No 120C158 for the same A2M2TECH project under the TUBITAK's 2236/B program
文摘Recent advances in additive manufacturing have enabled the construction of metallic lattice structures with tailored mechanical and functional properties.One potential application of metallic lattice struc-tures is in the impact load mitigation where an external kinetic energy is absorbed by the deformation/crushing of lattice cells.This has motivated a growing number of experimental and numerical studies,recently,on the crushing behavior of additively produced lattice structures.The present study overviews the dynamic and quasi-static crushing behavior of additively produced Ti64,316L,and AlSiMg alloy lattice structures.The first part of the study summarizes the main features of two most commonly used additive processing techniques for lattice structures,namely selective-laser-melt(SLM)and electro-beam-melt(EBM),along with a description of commonly observed process induced defects.In the second part,the deformation and strain rate sensitivities of the selected alloy lattices are outlined together with the most widely used dynamic test methods,followed by a part on the observed micro-structures of the SLM and EBM-processed Ti64,316L and AlSiMg alloys.Finally,the experimental and numerical studies on the quasi-static and dynamic compression behavior of the additively processed Ti64,316L,and AlSiMg alloy lattices are reviewed.The results of the experimental and numerical studies of the dynamic properties of various types of lattices,including graded,non-uniform strut size,hollow,non-uniform cell size,and bio-inspired,were tabulated together with the used dynamic testing methods.The dynamic tests have been noted to be mostly conducted in compression Split Hopkinson Pressure Bar(SHPB)or Taylor-and direct-impact tests using the SHPB set-up,in all of which relatively small-size test specimens were tested.The test specimen size effect on the compression behavior of the lattices was further emphasized.It has also been shown that the lattices of Ti64 and AlSiMg alloys are relatively brittle as compared with the lattices of 316L alloy.Finally,the challenges associated with modelling lattice structures were explained and the micro tension tests and multi-scale modeling techniques combining microstructural characteristics with macroscopic lattice dynamics were recommended to improve the accuracy of the numerical simulations of the dynamic compression deformations of metallic lattice structures.
基金supported by the National Natural Science Foundation of China(Key Program)(No.11932013)the Tianjin Science and Technology Plan Project(No.22PTZWHZ00040)。
文摘With the rapid development of digital communication and the widespread use of the Internet of Things,multi-view image compression has attracted increasing attention as a fundamental technology for image data communication.Multi-view image compression aims to improve compression efficiency by leveraging correlations between images.However,the requirement of synchronization and inter-image communication at the encoder side poses significant challenges,especially for constrained devices.In this study,we introduce a novel distributed image compression model based on the attention mechanism to address the challenges associated with the availability of side information only during decoding.Our model integrates an encoder network,a quantization module,and a decoder network,to ensure both high compression performance and high-quality image reconstruction.The encoder uses a deep Convolutional Neural Network(CNN)to extract high-level features from the input image,which then pass through the quantization module for further compression before undergoing lossless entropy coding.The decoder of our model consists of three main components that allow us to fully exploit the information within and between images on the decoder side.Specifically,we first introduce a channel-spatial attention module to capture and refine information within individual image feature maps.Second,we employ a semi-coupled convolution module to extract both shared and specific information in images.Finally,a cross-attention module is employed to fuse mutual information extracted from side information.The effectiveness of our model is validated on various datasets,including KITTI Stereo and Cityscapes.The results highlight the superior compression capabilities of our method,surpassing state-of-the-art techniques.
文摘Plastometric experiments,supplemented with numerical simulations using the finite element method(FEM),can be advantageously used to characterize the deformation behavior of metallic materials.The accuracy of such simulations predicting deformation behaviors of materials is,however,primarily affected by the applied rheology law.The presented study focuses on the characterization of the deformation behavior of AISI 1045 type carbon steel,widely used e.g.,in automotive and power engineering,under extreme conditions(i.e.,high temperatures,strain rates).The study consists of two main parts:experimentally analyzing the flow stress development of the steel under different thermomechanical conditions via uniaxial hot compression tests and establishing the rheology law via numerical simulations implementing the experimentally acquired flow stress curves.The numerical simulations then not only serve to establish the rheology law but also to verify the reliability of the selected experimental process.The results of the numerical simulations showed that the established rheology law characterizes the behavior of the investigated steel with sufficient accuracy also at high temperatures and/or strain rates,and can,therefore,be used for practical purposes.Last but not least,supplementary microstructure analyses performed for the samples subjected to the highest deformation temperature provided a deeper insight into the effects of the applied(extreme)thermomechanical conditions on the behavior of the investigated steel.
基金supported in part by the Science and Technology Department of Sichuan Province(No.2025ZNSFSC0427,No.2024ZDZX0035)the Open Project Fund of Vehicle Measurement,Control and Safety Key Laboratory of Sichuan Province(No.QCCK2024-004)the Industrial and Educational Integration Project of Yibin(No.YB-XHU-20240001)。
文摘The accurate prediction of battery pack capacity in electric vehicles(EVs)is crucial for ensuring safety and optimizing performance.Despite extensive research on predicting cell capacity using laboratory data,predicting the capacity of onboard battery packs from field data remains challenging due to complex operating conditions and irregular EV usage in real-world settings.Most existing methods rely on extracting health feature parameters from raw data for capacity prediction of onboard battery packs,however,selecting specific parameters often results in a loss of critical information,which reduces prediction accuracy.To this end,this paper introduces a novel framework combining deep learning and data compression techniques to accurately predict battery pack capacity onboard.The proposed data compression method converts monthly EV charging data into feature maps,which preserve essential data characteristics while reducing the volume of raw data.To address missing capacity labels in field data,a capacity labeling method is proposed,which calculates monthly battery capacity by transforming the ampere-hour integration formula and applying linear regression.Subsequently,a deep learning model is proposed to build a capacity prediction model,using feature maps from historical months to predict the battery capacity of future months,thus facilitating accurate forecasts.The proposed framework,evaluated using field data from 20 EVs,achieves a mean absolute error of 0.79 Ah,a mean absolute percentage error of 0.65%,and a root mean square error of 1.02 Ah,highlighting its potential for real-world EV applications.
基金Project(52374153)supported by the National Natural Science Foundation of ChinaProject(kq2502150)supported by the Natural Science Foundation of Changsha,China。
文摘Cemented tailings backfill(CTB)is a crucial support material for ensuring the long-term stability of underground goafs.A comprehensive understanding of its compressive mechanical behavior is essential for improving engineering safety.Although extensive studies have been conducted on the uniaxial compressive properties of CTB,damage constitutive models that effectively capture its damage evolution process remain underdeveloped,and its failure mechanisms are not yet fully clarified.To address these gaps,this study conducted systematic uniaxial compression tests on CTB specimens prepared with varying cement-tailings ratios.The results revealed distinct compaction and softening phases in the stress−strain curves.A lower cement-tailings ratio significantly reduced the strength and deformation resistance of CTB,along with a decrease in elastic energy accumulation at peak stress and dissipation energy in the post peak stage.Based on these findings,a modified damage constitutive model was developed by introducing a correction factor,enabling accurate simulation of the entire uniaxial compression process of CTB with different cement-tailings ratios.Comparative analysis with classical constitutive models validated the proposed model’s accuracy and applicability in describing the compressive behavior of CTB.Furthermore,particle size distribution and acoustic emission tests were employed to investigate the influence of cement-tailings ratio on failure mechanisms.The results indicated that a lower cement-tailings ratio leads to coarser particle sizes,which intensify shear-related acoustic emission signals and ultimately result in more pronounced macroscopic shear failure.This study provides theoretical support and practical guidance for the optimal design of CTB mix ratios.
基金financially supported by the National Key Research and Development Program of China(No.2022YFE0109600)the National Natural Science Foundation of China(No.52150710544)。
文摘An additional hot compression process was applied to a dilute Mg−Mn−Zn alloy post-extrusion.The alloy was extruded at 150℃ with an extrusion ratio of 15:1 and subsequently hot-compressed at 180℃ with a true strain of 0.9 along the extrusion direction.The microstructure,mechanical properties and thermal conductivity of as-extruded and as-hot compressed Mg−Mn−Zn alloys were investigated using optical microscopy,scanning electron microscopy,electron backscattering diffraction,and transmission electron microscopy.The aim was to concurrently enhance both strength and thermal conductivity by fostering uniform and refined microstructures while mitigating basal texture intensity.Substantial improvements were observed in yield strength(YS),ultimate tensile strength(UTS),and elongation(EL),with increase of 77%,53% and 10%,respectively.Additionally,thermal conductivity demonstrated a notable enhancement,rising from 111 to 125 W/(m·K).The underlying mechanism driving these improvements through the supplementary hot compression step was thoroughly elucidated.This study presents a promising pathway for the advancement of Mg alloys characterized by superior thermal and mechanical properties.
基金Projects(2024ZD1003903,2024ZD1003906)supported by the National Science and Technology Major ProjectProjects(U22A20166,52304097)supported by the National Natural Science Foundation of China+1 种基金Project(DUSE202301)supported by the Open Foundation of Key Laboratory of Deep Earth Science and Engineering(Sichuan University),Ministry of Education,ChinaProjects(2025A1515010049,2023A1515012654)supported by the Guangdong Basic and Applied Basic Research Foundation,China。
文摘Analyzing the fatigue damage characteristics of hot dry rock(HDR)affected by seawater thermal shock cycles is required for the efficient exploitation of HDR and the conservation of freshwater resources.Mechanical and acoustic emission(AE)monitoring tests were conducted during the triaxial compression of HDR at different confining pressures,temperatures,and numbers of seawater thermal shocks to investigate the seawater damage of HDR.The test results indicated an increase in the cumulative AE counts with increasing temperature and number of seawater thermal shocks,and a decrease in AE counts with increasing confining pressure.The effect of the number of seawater thermal shocks was significant.The AE counts were 276% higher at 15 than at 0 seawater thermal shocks.The b-value increased with the number of thermal shocks and stabilized after 5 shocks.Most of the damage was small fractures,which reduced the rock’s damage resistance.The AE time series under HDR triaxial compression exhibited multifractal features.High energy AE events dominated the damage mechanism of HDR,indicating shear damage to the HDR.Therefore,this study can provide a reference for seawater as a heat transfer fluid in the design of geothermal energy resource extraction.
基金Project(2021YFB3400900)supported by the National Key R&D Program of ChinaProjects(51905551,52205435)supported by the National Natural Science Foundation of China Youth Foundation+1 种基金Project(2022ZZTS0196)supported by the Fundamental Research Founds for the Central Universities,ChinaProject(CX20220282)supported by the Hunan Provincial Innovation Foundation for Postgraduate,China。
文摘The asymmetric creep aging behaviors of a pre-treated Al-Zn-Mg-Cu alloy under high and low stresses have been investigated for high precision creep age forming application of aluminum integral panels.With the increase of applied stress,the creep strains under the tensile stresses are higher than those of compressive stresses and the asymmetry of creep strain is more obvious.However,the mechanical properties of tensile stress creep aged samples are lower than those of compressive stress creep aged samples.Dislocation density,dislocation moving velocity and the proportion of precipitates directly lead to the asymmetry of creep strain and mechanical properties after tensile-compressive creep aging process.In addition,the tensile and compressive stresses have little effect on the width of the precipitate-free zone(PFZ).It indicates that in the high stress creep age forming process of the pretreated Al-Zn-Mg-Cu alloy,the tensile stress promotes the dislocation motion to obtain a better creep strain but weakens its mechanical properties compared with the compressive stress.In the field of civil aviation aircraft component manufacturing,the introduction of tension and compression stress asymmetry into the creep constitutive model may improve the accuracy of creep age forming components.
基金supported by the National Natural Science Foundation of China(Nos.12072105,11932006,and 52474388).
文摘The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot provide information on the structure evolution during deformation.In order to investigate the failure mechanism of Al alloy foam under quasi-static compression,by utilizing X-ray imaging technology,in situ CT image data were obtained during the loading process.A geometric model characterizing the real structure of Al alloy foam was reconstructed from the initial CT images and used for finite element simulation.Besides,based on the digital volume correlation(DVC)method,the displacement and strain fields of Al alloy foam were calculated.The results show that the in situ experimental observation based on X-ray imaging can effectively obtain the failure information of Al alloy foam.The simulation results for deformation and failure behavior of Al alloy foam are consistent with experimental results.During the quasi-static compression,a shear band can be observed diagonally across the profile of Al alloy foam,with weak regions occurring in the cells with larger volume and higher aspect ratios.Using these weak regions as boundaries,the relative displacement of cell structures on one side compared to another side was identified as the intrinsic cause of shear band formation.The high-strain regions identified by DVC closely match the crack locations on the cell walls,validating the accuracy of DVC on localizing cracks on cell walls and predicting their propagation trends.
基金supported by the National Science Foundations of China(Nos.52078250,51878350,11832013,51678304,51508272)。
文摘Studies on coral aggregate concrete(CAC)mainly focus on uniaxial stress conditions.However,concrete structures often experience complex stress conditions in practical engineering.It is essential to investigate the mechanical behavior and failure mechanisms of CAC under multiaxial stress conditions.This paper employs a 3D mesoscale model that considers the actual size,shape,and spatial distribution of aggregates.The reliability of the model and material parameters is verified through comparison with existing experimental data.Subsequently,the model is used to systematically study the mechanical properties,failure modes,and failure processes of C40 CAC under the biaxial compression.The numerical results are compared with the experimental results of CAC and ordinary portland concrete(OPC).The results indicate that the failure modes of CAC under the biaxial compression are diagonal shear failure.The biaxial compressive strength and elastic modulus of CAC are greater than those under uniaxial stress and exhibit a significant intermediate principal stress effect.The biaxial compressive strength reaches its maximum value when the stress ratio is 0.5,which is consistent with the conclusions for OPC.Finally,failure criteria and strength envelopes for CAC under the biaxial compression are established in order to provide a reference for analyzing the strength characteristics and structural design of CAC.
