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
A complex rubber foam under quasi-static compression is simulated using the finite element method （FEM）, The present work sets up the phenomenological constitutive model for the silicon rubber, The computerized tomo...A complex rubber foam under quasi-static compression is simulated using the finite element method （FEM）, The present work sets up the phenomenological constitutive model for the silicon rubber, The computerized tomography （CT） technique is utilized to reconstruct the real complex foam geometries, The quasi-static uniaxial compression on the foam is simulated in ABAQUS. The present work obtains the stress response as the nominal strain nearly reaches 80% and the foam exhibits hyper-elastic behavior, The FEM results achieve good agreements with the data obtained from the multi-scale simulation and the tests as the nominal strain is less than 60%.展开更多
The sandwich structure of cushioning packaging has an important influence on the cushioning performance.Mathematical fractal theory is an important graphic expression.Based on Hilbert fractal theory,a new sandwich str...The sandwich structure of cushioning packaging has an important influence on the cushioning performance.Mathematical fractal theory is an important graphic expression.Based on Hilbert fractal theory,a new sandwich structure was designed.The generation mechanism and recurrence formula of theHilbert fractal were expressed by Lin’s language,and the second-orderHilbert sandwich structure was constructed fromthermoplastic polyurethane.The constitutive model of the hyperelastic body was established by using the finite element method.With the unit mass energy absorption as the optimization goal,the fractal sandwich structure was optimized,and the best result was obtained when the order was 2.5 and the unit layer thickness was 0.75 mm.TheHilbert sandwich structure was compared with the rice-shaped sandwich structure commonly used in industry,and the Hilbert fractal structure had better energy absorption.This has practical significance for the development and application of newcushioning packaging structures.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
Based on the rigid plastic theory; the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parall...Based on the rigid plastic theory; the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parallel rigid plates. The non-dimensional load-deflection responses predicted by the present theory and the finite element simula- tions are compared, and the favorable agreement is found. The results show that strain hardening may have a noticeable influence on the load-deflection curves of an elliptical tube under quasi-static compression. Compared with the circular counterpart, the ellip- tical tube exhibits different energy absorption behavior due to the difference between the major axis and the minor axis. When loaded along the major axis of a slightly oval tube, a relative even and long plateau region of the load-deflection curve is achieved, which is especially desirable for the design of energy absorbers.展开更多
In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equi...In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equilibriums numerically obtained using the Grad–Shafranov equation solver NIMEQ.Based on the new scaling for the elongation and the magnetic fields at the separatrix and the wall,the empirically stable limits for the compression ratio,the fusion gain,and the neutron yield are evaluated,which may serve as a more accurate estimate for the upper ceiling of performance from the magnetic compression of FRC plasma as a potential fusion energy as well as neutron source devices.展开更多
Zn-22 Al alloy closed-cell foams were fabricated by melt foaming process using hydride foaming agent. The compressive properties were investigated under quasi-static condition. The structure of the foamed material was...Zn-22 Al alloy closed-cell foams were fabricated by melt foaming process using hydride foaming agent. The compressive properties were investigated under quasi-static condition. The structure of the foamed material was analyzed during compression test to reveal the relationship between morphology and compressive behavior. The results show that the stress-strain behavior is typical of closed-cell metal foams and mostly of brittle type. Governing deformation mechanism at plateau stage is identified to be brittle crushing. A substantial increase in compressive strength of Zn-22 Al foams was obtained. The agreement between compressive properties and Gibson-Ashby model was also detected.展开更多
To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a ...To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a strain rate from 10-4 to 104/s, and the fracture surfaces and damage morphology were observed. The results show that the dynamic failure strength of 2D-SiC1/SiC obeys the Weibull distribution, and the Weibull modulus is 5,66. Meanwhile, 2D-SiC1/SiC presents a transition from brittle to tough with a decrease of strain rate, and 2D-SiC1/SiC has a more significant strain rate sensitivity compared to the 2D-C/SiC composites. The failure mode of 2D-SiC1/SiC depends upon the strain rate.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 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
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
AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the...AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the interface was investigated.Moreover,the interface bonding mechanisms of the AZ31/Al/Ta composites during the VHCB process were explored.The results demonstrate that as the VHCB temperature increases,the phase composition of the interface between Mg and Al changes from the Mg-Al brittle intermetallic compounds(Al_(12)Mg_(17)and Al_(3)Mg_(2))to the Al-Mg solid solution.Meanwhile,the width of the Al/Ta interface diffusion layer at 450℃increases compared to that at 400℃.The shear strengths are 24 and 46 MPa at 400 and 450℃,respectively.The interfacial bonding mechanism of AZ31/Al/Ta composites involves the coexistence of diffusion and mechanical meshing.Avoiding the formation of brittle phases at the interface can significantly improve interfacial bonding strength.展开更多
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
Robotics plays an increasingly important role in all areas of human activity.Teleoperation robots can effectively ensure the safety of operators when operating in difficult and high‐risk industrial scenarios,which ob...Robotics plays an increasingly important role in all areas of human activity.Teleoperation robots can effectively ensure the safety of operators when operating in difficult and high‐risk industrial scenarios,which obviously requires instant and efficient signal compression and transmission in the system.However,most of the existing algorithms cannot fully explore the correlation within the signal,which mostly limits the compression efficiency.In this paper,a novel prediction‐aided kinaestheticsignal compression framework is proposed,which uses semantic communication methods to explore the temporal and spatial correlations of signals and employs neural network predictions to uncover their internal correlations.Specifically,the signal is first divided into two groups:the base part and the predictable part,and then a series of transformation matrices are introduced to establish the correlation between the two groups of the signal,which can be automatically optimised by a well‐designed neural network.This strategy of using learnable transformation matrices for prediction can not only accurately construct the correlation within the signal through massive data mining but also efficiently execute inference in a simple matrix multiplication computing form.Experimental results demonstrate that the proposed method outperforms the existing traditional tactile codecs and the latest tactile semantic communication methods.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
We demonstrate few-cycle pulse generation based on double-stage all-fiber nonlinear pulse compression from a thulium-doped fiber laser at a repetition rate of∼199.74 MHz.The homemade laser provides an average power o...We demonstrate few-cycle pulse generation based on double-stage all-fiber nonlinear pulse compression from a thulium-doped fiber laser at a repetition rate of∼199.74 MHz.The homemade laser provides an average power of 130 mW,serving as the seed for subsequent amplification.After amplification,significant spectral broadening to an octave-spanning bandwidth(1.2 to 2.4μm)is attained through self-phase modulation-dominated nonlinear effects in an ultrahigh numerical aperture fiber and a highly nonlinear fiber.Followed by a two-stage nonlinear compressor,the system directly delivers near transform-limited pulses with a pulse duration of 19.8 fs(2.9 cycles at a central wavelength of 2000 nm)and a pulse energy of 3.37 nJ.To the best of our knowledge,this result is the shortest pulse duration directly generated from a thulium-doped fiber laser.This robust and simplified all-fiber system provides a promising route toward practical mid-infrared frequency comb generation and mid-infrared spectroscopy.展开更多
In recent years,video coding has been widely applied in the field of video image processing to remove redundant information and improve data transmission efficiency.However,during the video coding process,irrelevant o...In recent years,video coding has been widely applied in the field of video image processing to remove redundant information and improve data transmission efficiency.However,during the video coding process,irrelevant objects such as background elements are often encoded due to environmental disturbances,resulting in the wastage of computational resources.Existing research on video coding efficiency optimization primarily focuses on optimizing encoding units during intra-frame or inter frame prediction after the generation of coding units,neglecting the optimization of video images before coding unit generation.To address this challenge,This work proposes an image semantic segmentation compression algorithm based on macroblock encoding,called image semantic segmentation compression algorithm based on macroblock encoding(ISSC-ME),which consists of three modules.(1)The semantic label generation module generates interesting object labels using a grid-based approach to reduce redundant coding of consecutive frames.(2)The image segmentation network module generates a semantic segmentation image using U-Net.(3)The macroblock coding module,is a block segmentation-based video encoding and decoding algorithm used to compress images and improve video transmission efficiency.Experimental results show that the proposed image semantic segmentation optimization algorithm can reduce the computational costs,and improve the overall accuracy by 1.00%and the mean intersection over union(IoU)by 1.20%.In addition,the proposed compression algorithm utilizes macroblock fusion,resulting in the image compression rate achieving 80.64%.It has been proven that the proposed algorithm greatly reduces data storage and transmission,and enables fast image compression processing at the millisecond level.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
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
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 Natural Science Foundation of China(No.11272300)the NSAF(No.U1530259)
文摘A complex rubber foam under quasi-static compression is simulated using the finite element method （FEM）, The present work sets up the phenomenological constitutive model for the silicon rubber, The computerized tomography （CT） technique is utilized to reconstruct the real complex foam geometries, The quasi-static uniaxial compression on the foam is simulated in ABAQUS. The present work obtains the stress response as the nominal strain nearly reaches 80% and the foam exhibits hyper-elastic behavior, The FEM results achieve good agreements with the data obtained from the multi-scale simulation and the tests as the nominal strain is less than 60%.
基金supported by the Natural Science Foundation of Tianjin Munici-pality[21YDTPJC00480]the Science and Technology Project of Tianjin[20YDTPJC00830].
文摘The sandwich structure of cushioning packaging has an important influence on the cushioning performance.Mathematical fractal theory is an important graphic expression.Based on Hilbert fractal theory,a new sandwich structure was designed.The generation mechanism and recurrence formula of theHilbert fractal were expressed by Lin’s language,and the second-orderHilbert sandwich structure was constructed fromthermoplastic polyurethane.The constitutive model of the hyperelastic body was established by using the finite element method.With the unit mass energy absorption as the optimization goal,the fractal sandwich structure was optimized,and the best result was obtained when the order was 2.5 and the unit layer thickness was 0.75 mm.TheHilbert sandwich structure was compared with the rice-shaped sandwich structure commonly used in industry,and the Hilbert fractal structure had better energy absorption.This has practical significance for the development and application of newcushioning packaging structures.
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Project supported by the National Natural Science Foundation of China(No.11472035)
文摘Based on the rigid plastic theory; the load-deflection functions with and without considering the effect of strain hardening are respectively derived for an elliptical tube under quasi-static compression by two parallel rigid plates. The non-dimensional load-deflection responses predicted by the present theory and the finite element simula- tions are compared, and the favorable agreement is found. The results show that strain hardening may have a noticeable influence on the load-deflection curves of an elliptical tube under quasi-static compression. Compared with the circular counterpart, the ellip- tical tube exhibits different energy absorption behavior due to the difference between the major axis and the minor axis. When loaded along the major axis of a slightly oval tube, a relative even and long plateau region of the load-deflection curve is achieved, which is especially desirable for the design of energy absorbers.
基金supported by the National Magnetic Confinement Fusion Program of China (No. 2017YFE0301805)National Natural Science Foundation of China (No. 51821005)+3 种基金the Fundamental Research Funds for the Central Universities at Huazhong University of Science and Technology (No. 2019kfy XJJS193)the U.S. Department of Energy (Nos. DE-FG02-86ER53218 and DE-SC0018001)the supports from the NIMROD teamthe support from the Chinese Government Scholarship.
文摘In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equilibriums numerically obtained using the Grad–Shafranov equation solver NIMEQ.Based on the new scaling for the elongation and the magnetic fields at the separatrix and the wall,the empirically stable limits for the compression ratio,the fusion gain,and the neutron yield are evaluated,which may serve as a more accurate estimate for the upper ceiling of performance from the magnetic compression of FRC plasma as a potential fusion energy as well as neutron source devices.
文摘Zn-22 Al alloy closed-cell foams were fabricated by melt foaming process using hydride foaming agent. The compressive properties were investigated under quasi-static condition. The structure of the foamed material was analyzed during compression test to reveal the relationship between morphology and compressive behavior. The results show that the stress-strain behavior is typical of closed-cell metal foams and mostly of brittle type. Governing deformation mechanism at plateau stage is identified to be brittle crushing. A substantial increase in compressive strength of Zn-22 Al foams was obtained. The agreement between compressive properties and Gibson-Ashby model was also detected.
基金Funded by the Scientific and Technological Development Project of Yantai(No.2013JH020)
文摘To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a strain rate from 10-4 to 104/s, and the fracture surfaces and damage morphology were observed. The results show that the dynamic failure strength of 2D-SiC1/SiC obeys the Weibull distribution, and the Weibull modulus is 5,66. Meanwhile, 2D-SiC1/SiC presents a transition from brittle to tough with a decrease of strain rate, and 2D-SiC1/SiC has a more significant strain rate sensitivity compared to the 2D-C/SiC composites. The failure mode of 2D-SiC1/SiC depends upon the strain rate.
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.
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(52275308,52301146)Fundamental Research Funds for the Central Universities(2023JG007)Supported by Shi Changxu Innovation Center for Advanced Materials(SCXKFJJ202207)。
文摘AZ31/Al/Ta composites were prepared using the vacuum hot compression bonding(VHCB)method.The effect of hot compressing temperature on the interface microstructure evolution,phase constitution,and shear strength at the interface was investigated.Moreover,the interface bonding mechanisms of the AZ31/Al/Ta composites during the VHCB process were explored.The results demonstrate that as the VHCB temperature increases,the phase composition of the interface between Mg and Al changes from the Mg-Al brittle intermetallic compounds(Al_(12)Mg_(17)and Al_(3)Mg_(2))to the Al-Mg solid solution.Meanwhile,the width of the Al/Ta interface diffusion layer at 450℃increases compared to that at 400℃.The shear strengths are 24 and 46 MPa at 400 and 450℃,respectively.The interfacial bonding mechanism of AZ31/Al/Ta composites involves the coexistence of diffusion and mechanical meshing.Avoiding the formation of brittle phases at the interface can significantly improve interfacial bonding strength.
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supported in part by the National Natural Science Foundation of China(NSFC)(Grants 62302128 and 624B2049)supported by Shenzhen Science and Technology Innovation Committee(Grant RCBS20231211090749086).
文摘Robotics plays an increasingly important role in all areas of human activity.Teleoperation robots can effectively ensure the safety of operators when operating in difficult and high‐risk industrial scenarios,which obviously requires instant and efficient signal compression and transmission in the system.However,most of the existing algorithms cannot fully explore the correlation within the signal,which mostly limits the compression efficiency.In this paper,a novel prediction‐aided kinaestheticsignal compression framework is proposed,which uses semantic communication methods to explore the temporal and spatial correlations of signals and employs neural network predictions to uncover their internal correlations.Specifically,the signal is first divided into two groups:the base part and the predictable part,and then a series of transformation matrices are introduced to establish the correlation between the two groups of the signal,which can be automatically optimised by a well‐designed neural network.This strategy of using learnable transformation matrices for prediction can not only accurately construct the correlation within the signal through massive data mining but also efficiently execute inference in a simple matrix multiplication computing form.Experimental results demonstrate that the proposed method outperforms the existing traditional tactile codecs and the latest tactile semantic communication methods.
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supported by the National Natural Science Foundation of China(Grant Nos.62227821 and 42461050)the Key Project of the National Institute of Metrology,China(Grant Nos.AKYZD2411 and AKYZD2511-2).
文摘We demonstrate few-cycle pulse generation based on double-stage all-fiber nonlinear pulse compression from a thulium-doped fiber laser at a repetition rate of∼199.74 MHz.The homemade laser provides an average power of 130 mW,serving as the seed for subsequent amplification.After amplification,significant spectral broadening to an octave-spanning bandwidth(1.2 to 2.4μm)is attained through self-phase modulation-dominated nonlinear effects in an ultrahigh numerical aperture fiber and a highly nonlinear fiber.Followed by a two-stage nonlinear compressor,the system directly delivers near transform-limited pulses with a pulse duration of 19.8 fs(2.9 cycles at a central wavelength of 2000 nm)and a pulse energy of 3.37 nJ.To the best of our knowledge,this result is the shortest pulse duration directly generated from a thulium-doped fiber laser.This robust and simplified all-fiber system provides a promising route toward practical mid-infrared frequency comb generation and mid-infrared spectroscopy.
文摘In recent years,video coding has been widely applied in the field of video image processing to remove redundant information and improve data transmission efficiency.However,during the video coding process,irrelevant objects such as background elements are often encoded due to environmental disturbances,resulting in the wastage of computational resources.Existing research on video coding efficiency optimization primarily focuses on optimizing encoding units during intra-frame or inter frame prediction after the generation of coding units,neglecting the optimization of video images before coding unit generation.To address this challenge,This work proposes an image semantic segmentation compression algorithm based on macroblock encoding,called image semantic segmentation compression algorithm based on macroblock encoding(ISSC-ME),which consists of three modules.(1)The semantic label generation module generates interesting object labels using a grid-based approach to reduce redundant coding of consecutive frames.(2)The image segmentation network module generates a semantic segmentation image using U-Net.(3)The macroblock coding module,is a block segmentation-based video encoding and decoding algorithm used to compress images and improve video transmission efficiency.Experimental results show that the proposed image semantic segmentation optimization algorithm can reduce the computational costs,and improve the overall accuracy by 1.00%and the mean intersection over union(IoU)by 1.20%.In addition,the proposed compression algorithm utilizes macroblock fusion,resulting in the image compression rate achieving 80.64%.It has been proven that the proposed algorithm greatly reduces data storage and transmission,and enables fast image compression processing at the millisecond level.
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.
